Advantages and disadvantages Sample Essay Example For Students

Focal points and burdens Sample Essay An affordable way of collecting informations from a major figure of individuals. On the off chance that the survey is acceptable planned. so the results can be broke down simple. perchance by registering machine. Great surveys are difficult to assemble. There is no programmed component for development or looking at all the more significantly. despite the fact that it is conceivable to catch up with a meeting by phone or in individual if vital. Postal surveys experience the ill effects of low reaction rates. Proper condition of affairss Surveys are most utile when the positions or cognizance of a major figure of individuals should be acquired or when the individuals are topographically scattered. for delineation. in an organization with numerous regions or workplaces around the state or around the universe. Polls are other than fitting for data frameworks which will be utilized by the general people. what's more, where the examiner needs to gain a picture of the kinds of client and utilize that the framework will require to oversee. 5. 3. 6 Remembering the procedures For the individuals who like mental aides. these strategies are now and again alluded to as SQIROâ€Sampling. Polls. Meeting. Perusing ( or Research ) and Observation. This request has been decided to do it conceivable to verbalize the memory aide. Be that as it may. this is non the request wherein they are well on the way to be utilized. This will rely upon the situation and the association wherein the methods are being utilized. 5. 3. 7 Other procedures A few sorts of framework require specific truth happening strategies. Skilled frameworks are processing machine frameworks which are intended to manifest the expertness of a human master in maintain excursion sources of income. Models incorporate frameworks for clinical diagnosing. securities exchange exchanging and land examination for mineral prospecting. The strategy of catching the comprehension of the master is called discernment obtaining and. as it contrasts from set uping the requests for an ordinary data framework. a figure of explicit procedures are applied. A portion of these are utilized in simultaneousness with PC based apparatuses.

Mongolian Effects on Russia and China

In the years somewhere in the range of 1100 and 1400 the Mongol domain extended the most remote of any realm from the beginning of time. Inside the gigantic land under Mongol standard laid the grounds of China and Russia. The Mongols realized how to keep up their domain yet had various methods of doing it in each part. This lead to the different, unique methods of overseeing the two terrains. In China and Russia, the Mongol period got a colossal change political and affordable force. In China, political effect from the Mongols fell off a lot stricter than it did in Russia.The pioneer of the Mongolians, Kublai Khan guided the Mongols to overcome the Southern Song tradition. Despite the fact that the Mongols had controlled domains, which included advanced northern China for a long time, it was not until 1271 that Kublai Khan authoritatively acknowledged a customary Chinese style. When Kublai Khan built up the Yuan tradition, he for all intents and purposes vanquished the entirety of Ch ina. The Chinese weren’t as politically free as the Russians. For instance Chinese were not permitted to between wed. He likewise prohibited Chinese researchers from learning Mongolian content and kept the two militaries separate.Mongol political control in Russia was unique in relation to China. One could contend that Mongolia was marginally â€Å"looser† with the Russian government. The Russians were resoundingly a fabulous sovereign to lead under Mongolian force however they had to pay tribute. Not exclusively did the Mongol guideline hugy affect the governmental issues of China and Russia yet the economy was influenced also. During the Mongolian guideline, the China turned into a heart of exchange for the Eastern world. This gave the Mongols full oversight of the Silk Road. China had things that such a large number of different places on the planet needed, for example, silk and porcelain.With a popularity for these Chinese merchandise the occupations were made, exc hange thrived, and the Mongolians profoundly profited by the blasting economy in China. The Mongols had a totally different impact on the Russian economy than the Chinese economy. The Mongols made the Russian economy crash, which caused Russia to restart the entirety of its farming issues. This constrained Russia to depend for the most part on laborer work. Paper cash was likewise being made which caused significant expansion. Rather than turning into a problem area for exchange, Russia became more fragile do to the financial Mongol torment.

This Year Beat the Crap Out of Me and It Was Awesome

This Year Beat the Crap Out of Me and It Was Awesome I feel like a bruised thing. Tired, tattered, and threadbare, Im not entirely sure how I made it through this year. But I didâ€"we didâ€"and it was awesome. Four years ago we started a little blog and called it The Minimalists, and we never anticipated everything that would follow. Among all the successes and failures these past four years, 2014 has been our greatest year of personal growth: we published our best work, Everything That Remains, our bestselling book to date; we brought our simple-living message to tens of thousands of people in eight countries during our 100-city tour (photos); we planted 100 free local meetup groups across three continents; we spoke at TEDx, Apple, and several other conferences, organizations, and universities; we introduced a team of mentors to assist people one-on-one with their challenges; we filmed a documentary about lifes most important things; we partook in hundreds of television, radio, and newspaper interviews, including our Christmas Day appearance on the TODAY show; we taught 127 students how to write better; we watched our audience grow from 2 to 4 million as readers shared our message with th eir friends and family; and, most important, by testing and expanding our boundaries, we grew in every area of life: health, relationships, passion, contribution, creativity. It is astonishing what one can accomplish in a year. Glancing in the rearview, though, everything seems much easier now than it did through the windshield in January. Back then, had we tried to plan all this out, it would have seemed impossible.  But rather than focus on arbitrary goals and plotting every potential outcome, we avoided busywork and instead remained intensely focused through it all. Thats the only way we could have done it: not busy but focused. Because busy for the sake of busy is, by definition, unfocused, which makes it impossible to discern that which matters most amid the blur. Of course with great growth comes great growing pains. Hence the bruised feeling Im currently experiencing. So  now, after slamming on the breaks to enjoy the holidays, Ryan and I are caring for our  bruises, attempting to recover, spending time with people we love, resting before moving forward toward  the new year on the horizon. Thank you for being with us on this exciting journey, helping us spread a message we truly believe in. Looking back, here are my favorite essays from 2014: Live Like Stan (my personal favorite) Lessons from the Fall Constructing and Extraordinary Life Packing Party: Unpack a Simpler Life Stimulate the Economy Like a Minimalist Letting Go: Dealing with the Death of a Loved One A Minimalist, A Japanese Cowboy, and an Arrogant American Walk into a Museum Well see you next year. We have a lot in store, including an outstanding documentary, a new tour, and a surprise or two. The best way to stay in the loop  is to subscribe to our essays via  email  (no spam, ever). Take it simple. If you find value in The Minimalists, consider donating a dollar.

Gerontology and Gerontic Nursing Practice - 2318 Words

NRS 353 Gerontology and Gerontic Nursing Practice Assignment 2: Assignment Questions Questions and Answers about Elderly People and Patients Submitted by: Fujimi Sakai Student No: 11413992 Lecturer’s Name: Christine Haley Due date: 25 January 2010 Date of submission: 25 January 2010 Introduction Health of older people has some issues which nurses should know. Older people tend to suffer some health problems, however, some people do not know about problems of older people and may treat them wrongly. These are some questions and answers below whose topics may be well-known but misunderstood. Nurses need to know scientific truth about health and health problems of older people and should reject myths of them which may be†¦show more content†¦These ways could protect the patients from injuries if they tried to wander. She also described adapting design of the facilities for the older patients, for example, using subdued colour in order to calm down 2 the older patients who are agitated and wander. Replacing liner corridor with connected passages that encourage the patient wander around on their own pace in the facility. These ways could reduce the patients who are wandering or cases of injury from wandering. The important thing to remember is the alternatives to physical restraints are not one. The alternative ways of the restraints can be mixed for fitting the individual’s behaviour of wandering. The alternative approaches to reduce the risk of wander may not be known as wide as a means of physical restraint. So, it would be important to extend knowledge of the alternatives in the workplace. Q 5: Define the term delirium Delirium is defined as â€Å"a transient disturbance in cognitive and attentional function, characterised by a fluctuating course and an alteration in the conscious state† (Street, 2004, p. 140). According to Luggen (2004, pp. 573-574), delirium is a common clinical condition for older patients and it often caused by emergency surgery and chemotherapy. The symptoms of delirium are reducing abilities to maintain and process attention both internal and external

What Is a Block Copolymer

A block copolymer is a copolymer formed when the two monomers cluster together and form blocks of repeating units. For example, a polymer made up of X and Y monomers joined together like: -Y-Y-Y-Y-Y-X-X-X-X-X-Y-Y-Y-Y-Y-X-X-X-X-X- is a block copolymer where -Y-Y-Y-Y-Y- and -X-X-X-X-X- groups are the blocks. Block Copolymer Examples The material used to make automobile tires is a block copolymer called SBS rubber (acrylonitrile butadiene styrene). The blocks in SBS rubber are polystyrene and polybutadiene (StyreneButatineStyrene). Nitrile and ethylene-vinyl acetate are also copolymers.

Stefan’s Diaries Origins Chapter 21 Free Essays

The next morning, Damon left with the brief explanation that he was helping the militia at the camp. I wasn’t sure I believed his excuse, but the house was decidedly more peaceful in his absence. Katherine came over each night to play cribbage with Father. We will write a custom essay sample on Stefan’s Diaries: Origins Chapter 21 or any similar topic only for you Order Now Occasionally I’d join her as a two-against-one team. While playing, Katherine would tell Father stories from her past: about her father’s shipping business; about her Italian mother; about Wheat, the Scottish terrier she’d had as a girl. I wondered if any of them were true, or if it was Katherine’s plan to act as a modern- day Scheherazade, spinning stories that would eventually persuade Father to spare her. Katherine would always make a show of going back to the carriage house, and it was agony waiting for the moment when Father went to bed so that I could follow her. She never talked about her past–or her plans–with me. She didn’t tell me how she got her nourishment, and I didn’t ask. I didn’t want to know. It was far easier to pretend she was just a normal girl. One afternoon, when Father was in town with Robert, discussing business with the Cartwrights, Katherine and I decided to spend an entire day together, instead of a few stolen, dark hours. It was nearing October, but no one would know it from the high temperatures and the daily late- afternoon thunderstorms. I hadn’t gone swimming all summer, and I couldn’t wait to feel the water of the pond on my skin–and Katherine in my arms in the daylight. I stripped down and jumped in immediately. â€Å"Don’t splash!† yelled Katherine. She lifted her simple blue skirt up to her ankles and cautiously stepped toward the edge of the pond. She’d already left her muslin flats beneath the willow tree, and I couldn’t stop staring at the delicate white of her ankles. â€Å"Come in! The water’s fine!† I yelled, even though my teeth were chattering. Katherine continued to tiptoe toward the edge of the pond until she was standing on the muddy strip between the grass and the water. â€Å"It’s dirty.† She wrinkled her nose, shielding her eyes from the sun. â€Å"That’s why you have to get in. To wash off all the mud,† I said, using my fingers to flick water toward Katherine. A few droplets landed on the bodice of her dress, and I felt desire course through me. I dunked under the water to cool my head. â€Å"You’re not afraid of a little splashing,† I said as I emerged, my hair dripping on my shoulders. â€Å"Or, shall I say, you’re not afraid of splashing Stefan?† I felt a little bit ridiculous saying it, because such comments didn’t sound nearly as clever on my lips. Still, she did me the favor of laughing. I carefully sidestepped the rocks on the bottom of the pond to walk closer toward her, then flicked more water in her direction. â€Å"No!† Katherine shrieked, but she made no move to run away as I walked out of the pond, grabbed her around the waist, and carried her into the water. â€Å"Stefan! Stop!† she screamed as she clung to my neck. â€Å"At least let me take off my dress!† At that, I immediately let her go. She lifted her hands over her head, allowing me to easily pull off her dress. There she stood in her little white slip. I gaped in amazement. Of course I’d seen her body before, but it had always been in shadows and half-light. Now I saw the sun on her shoulders, and the way her stomach curved inward and I knew, for the millionth time, that I was in love. Katherine dove underwater, reemerging right next to me. â€Å"And now, revenge!† She leaned down and splashed cool water on me with all her might. â€Å"If you weren’t so beautiful, I might fight back,† I said, pulling her toward me. I kissed her. â€Å"The neighbors will talk,† murmured Katherine against my lips. â€Å"Let them talk,† I whispered. â€Å"I want everyone to know how much I love you.† Katherine kissed me harder, with more passion than I’d ever felt. I sucked my breath in, feeling so much desire that I stepped away. I loved Katherine so much that it almost hurt; it made it harder to breathe, harder to talk, harder to think. It was as if my desire was a force larger than myself, and I was simultaneously frightened and overjoyed to follow wherever it led me. I took a shaky breath and looked up at the sky. Large thunderclouds had rolled in, obscuring the sky, which had been a pure cerulean just moments before. â€Å"We should go,† I said, heading toward shore. Sure enough, as soon as we stepped onto dry land, a clap of thunder rolled off in the distance. â€Å"The storm came in fast,† Katherine observed as she wrung out her curls. She didn’t seem at all self-conscious even though her soaking-wet white slip left nothing to the imagination. Somehow, it seemed almost more illicit and erotic to see her scantily dressed than to see her naked. â€Å"One could think that it was almost a sign that our relationship is not meant to be.† Her voice was teasing, but I felt a shiver of dread go up my spine. â€Å"No,† I said loudly, to reassure myself. â€Å"I’m just teasing you!† Katherine kissed my cheek before leaning down to pick up her dress. As she stole behind the weeping willow tree, I yanked up my breeches and put on my shirt. Katherine emerged from behind the tree a moment later, her cotton dress clinging to her curves, the damp tendrils of her hair sticking to her curves, the damp tendrils of her hair sticking to her back. Her skin had a bluish quality to it. I put my arms around her and rubbed her arms vigorously, trying to warm her up, though I knew that was impossible. â€Å"I have something to tell you,† Katherine said as she tilted her face up to the open sky. â€Å"What?† I asked. â€Å"I would be honored to attend the Founders Ball with you,† she said, and then, before I could kiss her again, she broke from my embrace and ran back to the carriage house. How to cite Stefan’s Diaries: Origins Chapter 21, Essay examples

Measuring Social Enterprise Value Creation

Question: Discuss about the Measuring Social Enterprise Value Creation. Answer: Introduction: Dodsworth and Anderson (2015) depict that sharing knowledge is the most effective procedure in the training to make every internal shareholder to develop their skills and ability. Assessments Situational question are provided to them so that their knowledge and skills can be tested after the knowledge sharing activity. Setting and launching Dates must be set for staring the training programs Evaluation of the number of internal stakeholders Formulation of Additional Materials Reviewing and revising the plan Launch the programs in the desired date Activities involved Outline of the training program for training vendors, customers and suppliers Selection of an appropriate place Formulation of organizational codes of ethics that the supplier must have to know Setting and launching Dates must be set for staring the training programs Evaluation of the number of external stakeholders Creation of a Stakeholder Partnership Plan Evaluation of time, money, material and human re Reviewing and revising the plan Launch the programs in the desired date Time line Expert Stylists Interior Decorator Color Expert Internal Stakeholders 7 weeks training 5.5 days 3 days 9thFeb-23rd Feb 2017 (Only one class per week) 20thFeb-25thFeb 2017 -12:00am-5:00pm on Weekdays 25thDec-27thDec 2017 9:30am-4:00pm 10:30am-4:00pm -10:00am-2:00pm on Weekends External Stakeholders Customers Logistics manager Suppliers Not Applicable 3 days 5 days 17thDec-19thDec 2017 25thDec-29thDec 2017 11:00am-2:00pm 12:00am-4:00pm Table 3: Time line (Source: Created by Author) Bibliography Bumgardner, M., Buehlmann, U. and Koenig, K., 2015. Woodworking housing: impacts actions. cocorepublic.com.au Default Store View., 2016.Student Types - Professionals. [online] Available at: https://www.cocorepublic.com.au [Accessed 27 Nov. 2016]. Dodsworth, S. and Anderson, S., 2015.The fundamentals of interior design. Bloomsbury Publishing. Mook, L., Chan, A. and Kershaw, D., 2015. Measuring Social Enterprise Value Creation.Nonprofit Management and Leadership,26(2), pp.189-207. Yu, Y., Hui, C.L. and Choi, T.M., 2012. An empirical study of intelligent expert systems on forecasting of fashion color trend.Expert Systems with Applications,39(4), pp.4383-4389.

Investigation Into The Rate of Water Uptake By Transpiration Essay Example

Investigation Into The Rate of Water Uptake By Transpiration Essay The rate of water uptake in a plant is directly proportional to the surface area of the leaves on the plant. As the surface area is reduced, the time taken for the water to travel up the stem over the same distance will increase.Background Knowledge:Plants add a considerable volume of moisture to the atmosphere. After absorbing water through their roots, the water travels up the stem to the leaves where over 99% of the absorbed water is lost through the leaves by a process named transpiration. The Sun provides the energy required to turn the water in the leaves into a vapour, causing it to diffuse out of the plant and into the atmosphere. Water evaporates from the leaves and causes a force that pulls the water up the stem. The water travels through the vessels in the vascular bundles and this flow of water is called the transpiration stream.Vascular tissue is made up of xylem and phloem. These tissues are concerned with the translocation (transport) of water and nutrients around the plant. Xylem carries mainly water and mineral salts, whereas phloem carries mainly organic solutes in solution, for example sugars. As the vascular tissue forms a transport system around the plant, a large, complex body will develop.Xylem fibres are thought to have originated from tracheids (single cells that are elongated and lignified), however they are shorter and narrower than tracheids. Overlapping walls are present at the end of the xylem. Phloem resemble xylem as they also have a tubular structure that is modified for translocation. The tubes are composed of living cells, and there are five different cell types: sieve tube elements, companion cells, parenchyma, fibres and schlerids.See Figure 1a that shows how phloem and xylem play an important role in transpiration. Figure 1b shows how gaseous exchange occurs in leaves..Transpiration is the evaporation of water from leaves; therefore any change that increases or reduces evaporation will have the same effect on transpiration. The following variables can affect the rate of transpiration.Light intensity Light itself does not directly affect transpiration, but in daylight the stomata of the leaves are open. This allows the water vapour in the leaves to diffuse out of the plant into the atmosphere. At night, when the stomata are closed, transpiration rates are greatly reduced. Generally, transpiration speeds up when the light intensity increases as the stomata respond to changes in the light intensity.Humidity If the air is very humid it can accept very little from the plants and therefore transpiration slows down. In dry air, the diffusion of water vapour from the leaf to the atmosphere will be rapid.Temperature Warm air can hold more water than cool air. Thus, transpiration will take place more rapidly in warm air. When the sun shines on the leaves, they will absorb heat as well as light. This warms them up and increases the rate of transpiration.Air movements In still air, the region surrounding a tr anspiring leaf will become saturated with water vapour so that no more can escape from the leaf. In these conditions, transpiration will slow down. In moving air, the water vapour will be swept away from the leaf as fast as it diffuses out. This will increase the rate of transpiration.Leaf surface area A reduction in leaf surface area will reduce the rate of transpiration, as there will be a smaller distribution of stomatal pores.Cuticle The thinner the leaf cuticle layer, the greater the rate of cuticular transpiration. The upper surface of dicotyledonous leaves generally has a thicker cuticle compared with the lower layer. Thick, waxy cuticles can virtually eliminate cuticular transpiration and the shine reflects solar radiation.Stomata The greater the number of stomata per unit area, the greater the rate of transpiration. Plants showing xeromorphic adaptations usually have reduced numbers of stomata. In dicotyledonous plants, the lower leaf surface usually possesses more stoma ta than the upper surface.In order to make this a fair experiment, the following precautions need to be taken. My experiment will be conducted inside a science lab at school, away from the windows. The light intensity should not change during the experiment. The humidity of the air will not change within the laboratory. There is a thermostat located within the laboratories, and therefore the temperature should remain constant. There is an air conditioning unit installed in order to control the temperature, but it should not affect my experiment. I am unable to change the thickness of the cuticle, but I will use the same plant for each attempt. I will also not be able to change the number of stomata present on the leafs surface; therefore I will assume that there will be an equal spread of stomata over each and every surface.All of these are factors that may affect the experiment, but hopefully I will be able to conduct a fair test.Plan:For this experiment I will be using a simple po tometer (from pot meaning drink and meter meaning measure) to measure the rate of water uptake in a plant, and how this rate is affected by leaf surface area.Apparatus:1. Privet plant (used as it has many leaves that may be easily counted and that are about the same size)2. Capillary tubing with water used as a meniscus scale (each mm on the scale is equivalent to 1mm? of water I will use 50mm)3. Beaker of water4. Stand (this will help to support the plant)5. Stop clock (showing minutes, seconds and 1/10th second)See Figure 2 that shows how I will set up the apparatus. It must be secure on the tabletop. This is so that it is not dangerous in any way to anyone else.Method:1. I will cut a privet plant underwater about 3cm up the stem. This will remove any blockages in the xylem from when the plant was cut previously. The xylem must not be crushed, so the plant will be cut at an angle with a sharp blade. The plant will be cut underwater to prevent any air bubbles getting into the xyle m, as this may affect the final results.2. I will submerge the capillary tube in the same water bowl. It will be attached to the plant, making sure no air bubbles are inside. I must make sure the open end of the capillary tube is also underwater so that all of the apparatus can be lifted out.3. This will make sure that the whole system is completely airtight. When the plant transpires, water will be pulled along the tubing. I will allow the apparatus to equilibrate for about 5 minutes.4. I am going to introduce an air bubble into the system. Holding the tubing out of the water for a minute can do this.5. I will make sure the bubble starts at the correct place on the scale, and time how long it takes for the bubble to move 50mm. This can be achieved by allowing the bubble to pass from no.1 to no.5 on the scale. Afterwards I will move the bubble back with the water.6. I will note the times in the table.7. I am going to repeat each attempt three times. This should give me enough readin gs to be able to calculate the mean average if need be. Each measurement will be taken from the same point of the bubble.Figure 3 shows how I am going to make sure the bubble is at the correct place on the scale. The bubble can be moved backwards by opening the tap from the reservoir and allowing more water in.8. Ten leaves will be removed and the surface area of the leaves calculated. The test will be repeated again. Each time I will remove ten leaves, and the last test I conduct will have only ten leaves on the plant.9. I will be conducting a practice experiment, with just one reading for each set of leaves that I remove. This will appear in my results as 1st attempt.10. Three other readings will be taken with another branch of the same privet plant. It is the surface area of this second branch that I will record. The surface area will be used to compare how the rate of uptake will change against the number of leaves I will be removing.Safety Procedures:* I will not be using any h azardous substances, but I must be careful not to spill any water on the workbench.* The sharp blade must be used with care, as it is very sharp and fingers can be cut easily. When they are not being used, the blades must be kept inside their box so that other people will not hurt themselves if they are left lying around.* I will not break any branches off the privet hedge that I will not be using for the experiment. This means that I will not be disturbing any organisms unnecessarily that live on the plant.* The apparatus must be positioned steadily on the surface. It is quite bulky, and I must be careful not to knock it over and spill the water.Predictions:I predict that if the surface area of the plants leaves is reduced the rate of uptake will slow down. This is because the number of stomata will be reduced, and transpiration rates will be reduced. I predict that the rate will decrease in proportion to the number of leaves removed, for example if the number of leaves is reduced by 50%, the rate of uptake will be reduced by 50%. The rate of transpiration is directly proportional to the surface area of the leaves on the plant. This is assuming that all other variables will remain constant. I am assuming that there will be an equal distribution of stomata on all of the leaves, and also that the surface area of each set of 10 leaves I remove will be approximately the same. For example, each set may have a combined surface area of 50 cm?.See Figure 4 that shows how I predict the rate of uptake will change. As I am unsure of the rate at present, I have left the axis unlabelled and shown only the general trend.Method:This was carried out as stated earlier, with no changes made to the original plan. The first attempt was carried out on a different branch to the other three attempts. This was to test the experiment, and it also gave me an approximate time of the whole experiment.Results:Time of Water Uptake (seconds)Number of Leaves1st Attempt2nd Attempt3rd Attempt 4th Attempt1003623753673849042342743448580409423423409703754634234716045848548049750505561543609404046945746843040978160970420704892704735101612962862943I choose to display the rate of water uptake (mm/second) rather than the time taken to travel 50mm as this gave a more accurate indication of how quickly the bubble travelled:50mm = Rate in mm/secondTime taken (s)Rate of Water Uptake (mm/second)Number of Leaves1st Attempt2nd Attempt3rd Attempt4th Attempt1000.1380.1330.1360.130900.1180.1170.1150.103800.1220.1180.1180.122700.1330.1070.1180.106600.1090.1030.1040.101500.0990.0890.0920.082400.1240.0720.0870.073300.1220.0640.0820.071200.0710.0560.0710.068100.0310.0520.0580.053I have plotted the results graph in a conventional way, with the number of leaves starting at 10 and leading up to 100. Although I carried out the experiment from 100 downwards, it seemed logical to plot the results the other way around. This shows the pattern clearly. I did carry out an experiment for 0 leaves, but the rate was too slow, and it is for this reason that I have not displayed the results I found.Figure 5 shows the results. The rates are shown, as these are easily comparable numbers to work with. They give a more accurate view of how quickly the bubble travelled over 50mm.It is clear from the graph that there is an increase in the time taken as the number of leaves decreases. The rate slows down, and the bubble travels more slowly. This is due to the decreasing rate of transpiration. As the number of leaves decreases, the numbers of stomata decrease and the rate of transpiration slows down. As the transpiration rate slows down, the rate of uptake is slowed down to prevent further water loss.Conclusion:My results show that the rate of uptake slowed down as more leaves were removed, and as the surface area of the plant decreased.The first attempt proved very useful, as I did not anticipate that the air-conditioning unit would affect my results as much as it did. The graph that I drew with the rates of water uptake shows clearly all four attempts. From this, I can see that the mean average rate for 100 leaves was 0.134mm/second. The mean average rate for 10 leaves was 0.049mm/second.This experiment has matched my predictions, however not quite as well as I had hoped. I had predicted that when the leaf surface area was reduced by 50%, the rate of water uptake would decrease by 50%. This was not the case. The mean rate of transpiration for 50 leaves is not 50% of the mean average for 100 leaves; it is nearer to 67%. The mean rate of water uptake for 50 leaves was 0.091mm/second.The anomalies from the first attempt have been marked as A, B and C. A and B have higher rates of water uptake than expected. This was because the air conditioning unit came on and moved the air around the leaves more quickly, thus causing the plant to transpire more quickly. C also has a higher rate of water uptake than expected due to the light intensity changing. The first attempt was co nducted in front of a window, and when the Sun came out the light intensity increased. The other three attempts were not conducted directly in front of a window. The time taken to transpire increases as the leaf surface area decreases. This is due to the removal of stomatal pores that allow the plant to exchange gases and water vapour. To prevent dehydration, the pores close to prevent further water loss and the rate of transpiration slows down.There was only one other anomaly throughout the whole experiment. This has been marked on the results graph as D, and occurred on the fourth attempt for 90 leaves. Although I had moved the apparatus away from the air-conditioning unit previously, on this occasion the breeze still affected my results. It did not disturb the air surrounding the leaf, as it did previously. This would have increased the rate of uptake. The cooler air meant that transpiration slowed down, having a direct effect on the rate of water uptake.The rate of transpiration was fastest for all four attempts when there were all 100 leaves on the plant, and slowest when there were only 10 leaves on the plant. All of the conditions were kept constant; therefore it was the stomatal quantity that affected the rate of transpiration.It was important that I measured the rate of uptake and not the rate of transpiration. Transpiration is very difficult to measure. The volume of water taken up is far greater than the volume of water given out through transpiration. This is because a large volume of water is used by the plant for turgidity, photosynthesis and other biological functions such as hydrolytic processes.My results shown in Figure 5 are almost linear. This matches my predicted graph, and is due to the proportion of leaves removed at each time. Although I did not realise at the time, I was removing approximately 10% of the leaves each time. This was purely coincidental, and was only discovered when I plotted the surface area against the number of leaves in Figure 6. The trend shown in Figure 5 is mirrored in Figure 6. This pattern may also have followed my predictions for another reason. The stomatal distribution across the leaf surface area may have been equal across all 100 leaves. If this was true, the total number of stomatal pores would have decreased in proportion to the number of leaves too.Evaluation:The first attempt was affected by the air-conditioning and light intensity. However, this was my practise experiment and I decided to then use another branch, approximately the same size for the next three attempts. All of the surface area calculations shown in Figure 6 are for the second branch. I made sure that the air-conditioning would not start during the second experiment, and also that I did not set up the apparatus next to another window. When the Sun shone through the window, it was very bright and the light intensity increased. I did not realise that these two factors could affect the rate of transpiration as much as they did.I did not take into account the stomatal distribution in either of my two experiments. This would have been an interesting variable to look at, however I found that I was short on time. I would have liked to have looked at the lower epidermis underneath a microscope, and made an approximate stomatal count. I could have seen if they were evenly spread, and if not, still made an estimated rate of uptake from my other results.My results were very pleasing overall. They followed my predicted trend and I have been able to see why, due to measuring the total surface area of the second branch. I have accounted for my anomalies as the experiment was affected by factors beyond my control. I had not realised that the air-conditioning and positioning of the apparatus would affect the experiment in such an extreme fashion. Factors such as light intensity and the temperature of the surrounding air may only change slightly, but have a larger effect on the overall experiment.I would have liked to repeat the experiment again, so that I could obtain more results. This would give me a more significant mean average, and I would have been able to leave out the anomalies in the analysis. A source of error may have been counting the number of leaves rather than the surface area. Nevertheless, it turned out that I was removing the leaves by nearly 10% each time.I would improve the experiment by measuring the stomatal distribution next time. This will allow me to calculate a more significant rate of uptake by calculating how much water is taken in through each stomatal pore. I could then estimate how much water should be taken in. If I was able to calculate the transpiration rate as well, I would be able to work out how much water was being used within the plant.Generally, this experiment was conducted well. The anomalies were not large enough to change the trend in any way, and the overall results were beneficial in proving the hypothesis correct. Investigation Into The Rate of Water Uptake By Transpiration Essay Example Investigation Into The Rate of Water Uptake By Transpiration Essay The rate of water uptake in a plant is directly proportional to the surface area of the leaves on the plant. As the surface area is reduced, the time taken for the water to travel up the stem over the same distance will increase.Background Knowledge:Plants add a considerable volume of moisture to the atmosphere. After absorbing water through their roots, the water travels up the stem to the leaves where over 99% of the absorbed water is lost through the leaves by a process named transpiration. The Sun provides the energy required to turn the water in the leaves into a vapour, causing it to diffuse out of the plant and into the atmosphere. Water evaporates from the leaves and causes a force that pulls the water up the stem. The water travels through the vessels in the vascular bundles and this flow of water is called the transpiration stream.Vascular tissue is made up of xylem and phloem. These tissues are concerned with the translocation (transport) of water and nutrients around the plant. Xylem carries mainly water and mineral salts, whereas phloem carries mainly organic solutes in solution, for example sugars. As the vascular tissue forms a transport system around the plant, a large, complex body will develop.Xylem fibres are thought to have originated from tracheids (single cells that are elongated and lignified), however they are shorter and narrower than tracheids. Overlapping walls are present at the end of the xylem. Phloem resemble xylem as they also have a tubular structure that is modified for translocation. The tubes are composed of living cells, and there are five different cell types: sieve tube elements, companion cells, parenchyma, fibres and schlerids.See Figure 1a that shows how phloem and xylem play an important role in transpiration. Figure 1b shows how gaseous exchange occurs in leaves..Transpiration is the evaporation of water from leaves; therefore any change that increases or reduces evaporation will have the same effect on transpiration. The following variables can affect the rate of transpiration.Light intensity Light itself does not directly affect transpiration, but in daylight the stomata of the leaves are open. This allows the water vapour in the leaves to diffuse out of the plant into the atmosphere. At night, when the stomata are closed, transpiration rates are greatly reduced. Generally, transpiration speeds up when the light intensity increases as the stomata respond to changes in the light intensity.Humidity If the air is very humid it can accept very little from the plants and therefore transpiration slows down. In dry air, the diffusion of water vapour from the leaf to the atmosphere will be rapid.Temperature Warm air can hold more water than cool air. Thus, transpiration will take place more rapidly in warm air. When the sun shines on the leaves, they will absorb heat as well as light. This warms them up and increases the rate of transpiration.Air movements In still air, the region surrounding a tr anspiring leaf will become saturated with water vapour so that no more can escape from the leaf. In these conditions, transpiration will slow down. In moving air, the water vapour will be swept away from the leaf as fast as it diffuses out. This will increase the rate of transpiration.Leaf surface area A reduction in leaf surface area will reduce the rate of transpiration, as there will be a smaller distribution of stomatal pores.Cuticle The thinner the leaf cuticle layer, the greater the rate of cuticular transpiration. The upper surface of dicotyledonous leaves generally has a thicker cuticle compared with the lower layer. Thick, waxy cuticles can virtually eliminate cuticular transpiration and the shine reflects solar radiation.Stomata The greater the number of stomata per unit area, the greater the rate of transpiration. Plants showing xeromorphic adaptations usually have reduced numbers of stomata. In dicotyledonous plants, the lower leaf surface usually possesses more stoma ta than the upper surface.In order to make this a fair experiment, the following precautions need to be taken. My experiment will be conducted inside a science lab at school, away from the windows. The light intensity should not change during the experiment. The humidity of the air will not change within the laboratory. There is a thermostat located within the laboratories, and therefore the temperature should remain constant. There is an air conditioning unit installed in order to control the temperature, but it should not affect my experiment. I am unable to change the thickness of the cuticle, but I will use the same plant for each attempt. I will also not be able to change the number of stomata present on the leafs surface; therefore I will assume that there will be an equal spread of stomata over each and every surface.All of these are factors that may affect the experiment, but hopefully I will be able to conduct a fair test.Plan:For this experiment I will be using a simple po tometer (from pot meaning drink and meter meaning measure) to measure the rate of water uptake in a plant, and how this rate is affected by leaf surface area.Apparatus:1. Privet plant (used as it has many leaves that may be easily counted and that are about the same size)2. Capillary tubing with water used as a meniscus scale (each mm on the scale is equivalent to 1mm? of water I will use 50mm)3. Beaker of water4. Stand (this will help to support the plant)5. Stop clock (showing minutes, seconds and 1/10th second)See Figure 2 that shows how I will set up the apparatus. It must be secure on the tabletop. This is so that it is not dangerous in any way to anyone else.Method:1. I will cut a privet plant underwater about 3cm up the stem. This will remove any blockages in the xylem from when the plant was cut previously. The xylem must not be crushed, so the plant will be cut at an angle with a sharp blade. The plant will be cut underwater to prevent any air bubbles getting into the xyle m, as this may affect the final results.2. I will submerge the capillary tube in the same water bowl. It will be attached to the plant, making sure no air bubbles are inside. I must make sure the open end of the capillary tube is also underwater so that all of the apparatus can be lifted out.3. This will make sure that the whole system is completely airtight. When the plant transpires, water will be pulled along the tubing. I will allow the apparatus to equilibrate for about 5 minutes.4. I am going to introduce an air bubble into the system. Holding the tubing out of the water for a minute can do this.5. I will make sure the bubble starts at the correct place on the scale, and time how long it takes for the bubble to move 50mm. This can be achieved by allowing the bubble to pass from no.1 to no.5 on the scale. Afterwards I will move the bubble back with the water.6. I will note the times in the table.7. I am going to repeat each attempt three times. This should give me enough readin gs to be able to calculate the mean average if need be. Each measurement will be taken from the same point of the bubble.Figure 3 shows how I am going to make sure the bubble is at the correct place on the scale. The bubble can be moved backwards by opening the tap from the reservoir and allowing more water in.8. Ten leaves will be removed and the surface area of the leaves calculated. The test will be repeated again. Each time I will remove ten leaves, and the last test I conduct will have only ten leaves on the plant.9. I will be conducting a practice experiment, with just one reading for each set of leaves that I remove. This will appear in my results as 1st attempt.10. Three other readings will be taken with another branch of the same privet plant. It is the surface area of this second branch that I will record. The surface area will be used to compare how the rate of uptake will change against the number of leaves I will be removing.Safety Procedures:* I will not be using any h azardous substances, but I must be careful not to spill any water on the workbench.* The sharp blade must be used with care, as it is very sharp and fingers can be cut easily. When they are not being used, the blades must be kept inside their box so that other people will not hurt themselves if they are left lying around.* I will not break any branches off the privet hedge that I will not be using for the experiment. This means that I will not be disturbing any organisms unnecessarily that live on the plant.* The apparatus must be positioned steadily on the surface. It is quite bulky, and I must be careful not to knock it over and spill the water.Predictions:I predict that if the surface area of the plants leaves is reduced the rate of uptake will slow down. This is because the number of stomata will be reduced, and transpiration rates will be reduced. I predict that the rate will decrease in proportion to the number of leaves removed, for example if the number of leaves is reduced by 50%, the rate of uptake will be reduced by 50%. The rate of transpiration is directly proportional to the surface area of the leaves on the plant. This is assuming that all other variables will remain constant. I am assuming that there will be an equal distribution of stomata on all of the leaves, and also that the surface area of each set of 10 leaves I remove will be approximately the same. For example, each set may have a combined surface area of 50 cm?.See Figure 4 that shows how I predict the rate of uptake will change. As I am unsure of the rate at present, I have left the axis unlabelled and shown only the general trend.Method:This was carried out as stated earlier, with no changes made to the original plan. The first attempt was carried out on a different branch to the other three attempts. This was to test the experiment, and it also gave me an approximate time of the whole experiment.Results:Time of Water Uptake (seconds)Number of Leaves1st Attempt2nd Attempt3rd Attempt 4th Attempt1003623753673849042342743448580409423423409703754634234716045848548049750505561543609404046945746843040978160970420704892704735101612962862943I choose to display the rate of water uptake (mm/second) rather than the time taken to travel 50mm as this gave a more accurate indication of how quickly the bubble travelled:50mm = Rate in mm/secondTime taken (s)Rate of Water Uptake (mm/second)Number of Leaves1st Attempt2nd Attempt3rd Attempt4th Attempt1000.1380.1330.1360.130900.1180.1170.1150.103800.1220.1180.1180.122700.1330.1070.1180.106600.1090.1030.1040.101500.0990.0890.0920.082400.1240.0720.0870.073300.1220.0640.0820.071200.0710.0560.0710.068100.0310.0520.0580.053I have plotted the results graph in a conventional way, with the number of leaves starting at 10 and leading up to 100. Although I carried out the experiment from 100 downwards, it seemed logical to plot the results the other way around. This shows the pattern clearly. I did carry out an experiment for 0 leaves, but the rate was too slow, and it is for this reason that I have not displayed the results I found.Figure 5 shows the results. The rates are shown, as these are easily comparable numbers to work with. They give a more accurate view of how quickly the bubble travelled over 50mm.It is clear from the graph that there is an increase in the time taken as the number of leaves decreases. The rate slows down, and the bubble travels more slowly. This is due to the decreasing rate of transpiration. As the number of leaves decreases, the numbers of stomata decrease and the rate of transpiration slows down. As the transpiration rate slows down, the rate of uptake is slowed down to prevent further water loss.Conclusion:My results show that the rate of uptake slowed down as more leaves were removed, and as the surface area of the plant decreased.The first attempt proved very useful, as I did not anticipate that the air-conditioning unit would affect my results as much as it did. The graph that I drew with the rates of water uptake shows clearly all four attempts. From this, I can see that the mean average rate for 100 leaves was 0.134mm/second. The mean average rate for 10 leaves was 0.049mm/second.This experiment has matched my predictions, however not quite as well as I had hoped. I had predicted that when the leaf surface area was reduced by 50%, the rate of water uptake would decrease by 50%. This was not the case. The mean rate of transpiration for 50 leaves is not 50% of the mean average for 100 leaves; it is nearer to 67%. The mean rate of water uptake for 50 leaves was 0.091mm/second.The anomalies from the first attempt have been marked as A, B and C. A and B have higher rates of water uptake than expected. This was because the air conditioning unit came on and moved the air around the leaves more quickly, thus causing the plant to transpire more quickly. C also has a higher rate of water uptake than expected due to the light intensity changing. The first attempt was co nducted in front of a window, and when the Sun came out the light intensity increased. The other three attempts were not conducted directly in front of a window. The time taken to transpire increases as the leaf surface area decreases. This is due to the removal of stomatal pores that allow the plant to exchange gases and water vapour. To prevent dehydration, the pores close to prevent further water loss and the rate of transpiration slows down.There was only one other anomaly throughout the whole experiment. This has been marked on the results graph as D, and occurred on the fourth attempt for 90 leaves. Although I had moved the apparatus away from the air-conditioning unit previously, on this occasion the breeze still affected my results. It did not disturb the air surrounding the leaf, as it did previously. This would have increased the rate of uptake. The cooler air meant that transpiration slowed down, having a direct effect on the rate of water uptake.The rate of transpiration was fastest for all four attempts when there were all 100 leaves on the plant, and slowest when there were only 10 leaves on the plant. All of the conditions were kept constant; therefore it was the stomatal quantity that affected the rate of transpiration.It was important that I measured the rate of uptake and not the rate of transpiration. Transpiration is very difficult to measure. The volume of water taken up is far greater than the volume of water given out through transpiration. This is because a large volume of water is used by the plant for turgidity, photosynthesis and other biological functions such as hydrolytic processes.My results shown in Figure 5 are almost linear. This matches my predicted graph, and is due to the proportion of leaves removed at each time. Although I did not realise at the time, I was removing approximately 10% of the leaves each time. This was purely coincidental, and was only discovered when I plotted the surface area against the number of leaves in Figure 6. The trend shown in Figure 5 is mirrored in Figure 6. This pattern may also have followed my predictions for another reason. The stomatal distribution across the leaf surface area may have been equal across all 100 leaves. If this was true, the total number of stomatal pores would have decreased in proportion to the number of leaves too.Evaluation:The first attempt was affected by the air-conditioning and light intensity. However, this was my practise experiment and I decided to then use another branch, approximately the same size for the next three attempts. All of the surface area calculations shown in Figure 6 are for the second branch. I made sure that the air-conditioning would not start during the second experiment, and also that I did not set up the apparatus next to another window. When the Sun shone through the window, it was very bright and the light intensity increased. I did not realise that these two factors could affect the rate of transpiration as much as they did.I did not take into account the stomatal distribution in either of my two experiments. This would have been an interesting variable to look at, however I found that I was short on time. I would have liked to have looked at the lower epidermis underneath a microscope, and made an approximate stomatal count. I could have seen if they were evenly spread, and if not, still made an estimated rate of uptake from my other results.My results were very pleasing overall. They followed my predicted trend and I have been able to see why, due to measuring the total surface area of the second branch. I have accounted for my anomalies as the experiment was affected by factors beyond my control. I had not realised that the air-conditioning and positioning of the apparatus would affect the experiment in such an extreme fashion. Factors such as light intensity and the temperature of the surrounding air may only change slightly, but have a larger effect on the overall experiment.I would have liked to repeat the experiment again, so that I could obtain more results. This would give me a more significant mean average, and I would have been able to leave out the anomalies in the analysis. A source of error may have been counting the number of leaves rather than the surface area. Nevertheless, it turned out that I was removing the leaves by nearly 10% each time.I would improve the experiment by measuring the stomatal distribution next time. This will allow me to calculate a more significant rate of uptake by calculating how much water is taken in through each stomatal pore. I could then estimate how much water should be taken in. If I was able to calculate the transpiration rate as well, I would be able to work out how much water was being used within the plant.Generally, this experiment was conducted well. The anomalies were not large enough to change the trend in any way, and the overall results were beneficial in proving the hypothesis correct.

Weekly Teacher Parent Communication Through Newsletters

Weekly Teacher Parent Communication Through Newsletters In the elementary classroom, parent communication is a critical part of being an effective teacher. Parents want, and deserve, to know whats going on in the classroom. And, more than that, by being proactive in your communication with families, you can avoid possible problems before they even start. But, lets be realistic. Who really has the time to write a proper newsletter each week? A newsletter about classroom happenings may seem like distant goal that will probably never happen with any regularity. Heres a simple way to send a quality newsletter home each week while teaching writing skills at the same time. From experience, I can tell you that teachers, parents, and principals love this idea! Each Friday, you and your students write a letter together, telling families about what happened in class this week and whats coming up in class. Everyone ends up writing the same letter and the content is directed by the teacher. Heres a step-by-step guide for this quick and easy activity: First, pass out a piece of paper to each student. I like to give them paper with a cute border around the outside and lines in the middle. Variation: Write the letters in a notebook and ask parents to respond to each letter over the weekend. At the end of the year youll have a diary of communication for the entire school year!Use an overhead projector or chalkboard so that the kids can see what youre writing as you do it.As you write, model to the kids how to write the date and greeting.Make sure to tell the students to address the letter to whoever they live with. Not everyone lives with a mom and a dad.Ask for input from the kids about what the class did this week. Say, Raise your hand and tell me one big thing we learned this week. Try to steer the kids away from reporting only fun things. Parents want to hear about academic learning, not just the parties, games, and songs.After each item you get, model how you write it into the letter. Add a few exclamation points to show excitem ent. Once youve written enough of past events, youll need to add a sentence or two about what the class is doing the next week. Usually, this information can only come from the teacher. This also gives you an opportunity to preview for the kids about next weeks exciting activities!Along the way, model how to indent paragraphs, use proper punctuation, vary sentence length, etc. At the end, model how to sign off the letter properly. Tips and Tricks: Early finishers can color in the border around the letter. Youll find that, after the first few weeks, the students will get quicker at this process and you wont need to set aside so much time for it.Tell the kids that theres no excuse for incorrect spelling in their letters because youve written everything for them to see.Make a copy of each letter and, at the end of the year, youll have a complete record of each weeks highlights!Perhaps as kids get used to this process, you will decide to allow them to write the letters independently.You may still want to supplement the weekly newsletters with your own monthly or bi-monthly newsletter. This teacher-produced letter can be lengthier, meatier, and of greater scope. Have fun with it! Smile because you know that this simple Guided Writing activity helps kids to hone letter-writing skills while you accomplish an important goal of effective parent-teacher communication. Plus, its a great way to recap your week. What more can you ask for? Edited by: Janelle Cox

Item Analysis Assignment Example | Topics and Well Written Essays - 1000 words

Item Analysis - Assignment Example This information needs to be interpreted in context to the principles on the basis of which the test was designed. A test that was given at the beginning of a course simply to assess which concepts a class was familiar with would be expected to have a positive skew; as there would be fewer items that students would be able to answer. On the other hand; if this test was given to assess mastery or proficiency; these scores would indicate that a number of course goals were not met. If the test were given in order to choose a few individuals who are proficient in very advanced concepts; it would be acceptable that a majority of scores are clustered towards the lower half; as only a few individuals would qualify by getting higher scores.It is also necessary to assess if these results are caused by a few erroneous or confusing items. This may be done by evaluating the trends seen for each item. A competency test typically contains a few simple items, a few difficult items and a few items w ith moderate difficulty. A speed test, on the other hand, requires all items to be similarly difficult. For a competency test; it is necessary that we choose items that not only have different levels of difficulty; but also discriminate between individuals who are able to solve it and those who are not. A good item would typically help us in understanding how well the individual test taker has mastered the individual concept while also helping us differentiate those who did master the concept from those who did not.... Also; the Alpha coefficient is affected by the length of the test; with the reliability being higher and more trusted for a longer test than a shorter one. The given test is only 10 items long; and this may compromise the reliability to some extent. The skewed scores also present other concerns. The Standard Error of Skewness for this test may be calculated by using the Tabachnick & Fidell’s (1996) formula . This provides us with a SES value of 0.245. If we define the acceptable limits within which the value of skewness may fall as being between 2 SES both sides of zero; then we may accept a value that falls between – 0.49 and + 0.49. the obtained value of + 0.78 is well outside these limits, indicating that there is a positive skew to the scores and a significant clustering of scores towards the lower side of the scale. This information needs to be interpreted in context to the principles on the basis of which the test was designed. A test that was given at the beginni ng of a course simply to assess which concepts a class was familiar with would be expected to have a positive skew; as there would be less items that students would be able to answer. On the other hand; if this test was given to assess mastery or proficiency; these scores would indicate that a number of course goals were not met. If the test were given in order to choose a few individuals who are proficient in very advanced concepts; it would be acceptable that a majority of scores are clustered towards the lower half; as only a few individuals would qualify by getting higher scores. It is also necessary to assess if these results are caused by a few erroneous or confusing items. This may be done by evaluating the trends seen for each item. A

How can managers assist employees with their career development Research Paper

How can managers assist employees with their career development - Research Paper Example It has also been stated that presence of a motivated workforce is very critical to the success of a firm in the market. It has been proved in various researches that job satisfaction is an essential aspect that leads to motivation among the employees. A motivated employee is known to provide the best shot at the workplace and is likely to view his or her tasks as responsibilities rather than routine work that can lead to organizational efficiency generating competitive advantage for the organization. The aspect of motivation is also directly linked to career development of the individual employees. The role of the manager or the supervisor becomes very important in this regard as their attitude can lead to considerable effects on the level of motivation and job satisfaction. The present paper would try to analyze the role of the managers in assisting employees towards their career development Analysis The concept of career development has been a matter of consistent research over the last few decades. During the era of the 80’s the focus was based on the ‘unitarist’ practices with employees extending their career options to multiple employers in an attempt to get the best of development of their personal careers. The present age has led to a situation in which employers are facing issues of high turnovers that has led to formulation of strategies that call for the need to ensure career development of the employees so as to ensure motivation and job satisfaction that can in turn help retain the best employees in the organization. The aspect of career development also calls on managers and supervisors to formulate practices that tend to encourage and improve their learning curves. The recent recession and downturn in the markets also had a very negative impact on the relationship with employees and their managers as well as on the careers of employees who were downsized in order to maintain costs. However, many organizations and managers have realized this as an opportunity to ensure a relationship based on partnerships and mutual benefits leading to a condition of greater shared responsibility that has led to generation of a positive sentiment even during times of severe crisis situations like the economic recession (Bratton & Gold, 2001, p.172-180). Figure 1: Career Development Model (Source: Bratton & Gold, 2001, p.182) The figure above shows a career development plan that combines the organizational needs along with the career development of an employee in the organization. The model proposes a session for career counseling that can be used to integrate organizational requirements with the career growth and competence of an individual employee. The model also shows a significant and important role for the manager in the entire process as the entire task of making a mutual integration with the career goals of an individual employee. The manager has a key role in making a decision about the type of training program tha t should be suitable for the employee so as to ensure organizational development as well as career development of an individual (Bratton & Gold, 2001, p.172-180). Numerous research conducted by academic and professional circles have stated the importance of the role of

H.264 Video Streaming System on Embedded Platform

H.264 Video Streaming System on Embedded Platform ABSTRACT The adoption of technological products like digital television and video conferencing has made video streaming an active research area. This report presents the integration of a video streamer module into a baseline H.264/AVC encoder running a TMSDM6446EVM embedded platform. The main objective of this project is to achieve real-time streaming of the baseline H.264/AVC video over a local area network (LAN) which is a part of the surveillance video system. The encoding of baseline H.264/AVC and the hardware components of the platform are first discussed. Various streaming protocols are studied in order to implement the video streamer on the DM6446 board. The multi-threaded application encoder program is used to encode raw video frames into H.264/AVC format onto a file. For the video streaming, open source Live555 MediaServer was used to stream video data to a remote VLC client over LAN. Initially, file streaming was implemented from PC to PC. Upon successfully implementation on PC, the video streamer was ported to the board. The steps involved in porting the Live555 application were also described in the report. Both unicast and multicast file streaming were implemented in the video streamer. Due to the problems of file streaming, the live streaming approach was adopted. Several methodologies were discussed in integrating the video streamer and the encoder program. Modification was made both the encoder program and the Live555 application to achieve live streaming of H.264/AVC video. Results of both file and live streaming will be shown in this report. The implemented video streamer module will be used as a base module of the video surveillance system. Chapter 1: Introduction 1.1. Background Significant breakthroughs have been made over the last few years in the area of digital video compression technologies. As such applications making use of these technologies have also become prevalent and continue to be of active research topics today. For example, digital television and video conferencing are some of the applications that are now commonly encountered in our daily lives. One application of interest here is to make use of the technologies to implement a video camera surveillance system which can enhance the security of consumers business and home environment. In typical surveillance systems, the captured video is sent over a cable networks to be monitored and stored at remote stations. As the captured raw video contains large amount of data, it will be of advantage to first compress the data by using a compression technique before it is transferred over the network. One such compression technique that is suitable for this type of application is the H.264 coding standard. H.264 coding is better than the other coding technique for video streaming as it is more robust to data losses and coding efficiency, which are important factors when streaming is performed over a shared Local Area Network. As there is an increasing acceptance of H.264 coding and the availability of high computing power embedded systems, digital video surveillance system based on H.264 on embedded platform is hence a feasible and a potentially more cost-effective system. Implementing a H.264 video streaming system on an embedded platform is a logical extension of video surveillance systems which are still typical implemented using high computing power stations (e.g. PC). In a embedded version, a Digital Signal Processor (DSP) forms the core of the embedded system and executes the intensive signal processing algorithm. Current embedded systems typical also include network features which enable the implementation of data streaming applications. To facilitate data streaming, a number of network protocol standards have also being defined, and are currently used for digital video applications. 1.2. Objective and Scope The objective of this final year project is to implement a video surveillance system based on the H.264 coding standard running on an embedded platform. Such a system contains extensive scopes of functionalities and would require extensive amount of development time if implemented from scratch. Hence this project is to focus on the data streaming aspect of a video surveillance system. After some initial investigation and experimentation, it is decided to confine the main scope of the project to developing a live streaming H.264 based video system running on a DM6446 EVM development platform. The breakdown of the work to be progressive performed are then identified as follows: 1. Familiarization of open source live555 streaming media server Due to the complexity of implementing the various standard protocols needed for multimedia streaming, the live555 media server program is used as a base to implement the streaming of the H.264.based video data. 2. Streaming of stored H.264 file over the network The live555 is then modified to support streaming of raw encoded H.264 file from the DM6446 EVM board over the network. Knowledge of H.264 coding standard is necessary in order to parse the file stream before streaming over the network. 3. Modifying a demo version of an encoder program and integrating it together with live555 to achieve live streaming The demo encoder was modified to send encoded video data to the Live555 program which would do the necessary packetization to be streamed over the network. Since data is passed from one process to another, various inter-process communication techniques were studied and used in this project. 1.3. Resources The resources used for this project are as follows: 1. DM6446 (DaVinciâ„ ¢) Evaluation Module 2. SWANN C500 Professional CCTV Camera Solution 400 TV Lines CCD Color Camera 3. LCD Display 4. IR Remote Control 5. TI Davinci demo version of MontaVista Linux Pro v4.0 6. A Personal Workstation with Centos v5.0 7. VLC player v.0.9.8a as client 8. Open source live555 program (downloaded from www.live555.com) The system setup of this project is shown below: 1.4. Report Organization This report consists of 7 chapters. Chapter 1 introduces the motivation behind embedded video streaming system and defines the scope of the project. Chapter 2 illustrates the video literature review of the H.264/AVC video coding technique and the various streaming protocols which are to be implemented in the project. Chapter 3 explains the hardware literature review of the platform being used in the project. The architecture, memory management, inter-process communication and the software tools are also discussed in this chapter. Chapter 4 explains the execution of the encoder program of the DM6446EVM board. The interaction of the various threads in this multi-threaded application is also discussed to fully understand the encoder program. Chapter 5 gives an overview of the Live555 MediaServer which is used as a base to implement the video streamer module on the board. Adding support to unicast and multicast streaming, porting of live555 to the board and receiving video stream on remote VCL client are explained in this chapter. Chapter 6 explains the limitations of file streaming and moving towards live streaming system. Various integration methodologies and modification to both encoder program and live555 program are shown as well. Chapters 7 summarize the implementation results of file and live streaming, analysis the performance of these results. Chapter 8 gives the conclusion by stating the current limitation and problems, scope for future implementation. Chapter 2: Video Literature Review 2.1. H.264/AVC Video Codec Overview H.264 is the most advanced and latest video coding technique. Although there are many video coding schemes like H.26x and MPEG, H.264/AVC made many improvements and tools for coding efficiency and error resiliency. This chapter briefly will discuss the network aspect of the video coding technique. It will also cover error resiliency needed for transmission of video data over the network. For a more detailed explanation of the H.264/AVC, refer to appendix A. 2.1.1. Network Abstraction Layer (NAL) The aim of the NAL is to ensure that the data coming from the VCL layer is â€Å"network worthy† so that the data can be used for numerous systems. NAL facilitates the mapping of H.264/AVC VCL data for different transport layers such as: * RTP/IP real-time streaming over wired and wireless mediums * Different storage file formats such as MP4, MMS, AVI and etc. The concepts of NAL and error robustness techniques of the H.264/AVC will be discussed in the following parts of the report. NAL Units The encoded data from the VCL are packed into NAL units. A NAL unit represents a packet which makes up of a certain number of bytes. The first byte of the NAL unit is called the header byte which indicates the data type of the NAL unit. The remaining bytes make up the payload data of the NAL unit. The NAL unit structure allows provision for different transport systems namely packet-oriented and bit stream-oriented. To cater for bit stream-oriented transport systems like MPEG-2, the NAL units are organized into byte stream format. These units are prefixed by a specific start code prefix of three bytes which is namely 0x000001. The start code prefix indicates and the start of each NAL units and hence defining the boundaries of the units. For packet-oriented transport systems, the encoded video data are transported via packets defined by transport protocols. Hence, the boundaries of the NAL units are known without having to include start code prefix byte. The details of packetization of NAL units will be discussed in later sections of the report. NAL units are further categorized into two types: * VCL unit: comprises of encoded video data  · Non-VCL unit: comprises of additional information like parameter sets which is the important header information. Also contains supplementary enhancement information (SEI) which contains the timing information and other data which increases the usability of the decoded video signal. Access units A group of NAL units which adhere to a certain form is called a access unit. When one access unit is decoded, one decoded picture is formed. In the table 1 below, the functions of the NAL units derived from the access units are explained. Data/Error robustness techniques H.264/AVC has several techniques to mitigate error/data loss which is an essential quality when it comes to streaming applications. The techniques are as follows:  · Parameter sets: contains information that is being applied to large number of VCL NAL units. It comprises of two kinds of parameter sets: Sequence Parameter set (SPS) : Information pertaining to sequence of encoded picture Picture Parameter Set (PPS) : Information pertaining to one or more individual pictures The above mentioned parameters hardly changes and hence it need not be transmitted repeatedly and saves overhead. The parameter sets can be sent â€Å"in-band† which is carried in the same channel as the VCL NAL units. It can also be sent â€Å"out-of-band† using reliable transport protocol. Therefore, it enhances the resiliency towards data and error loss.  · Flexible Macroblock Ordering (FMO) FMO maps the macroblocks to different slice groups. In the event of any slice group loss, missing data is masked up by interpolating from the other slice groups.  · Redundancy Slices (RS) Redundant representation of the picture can be stored in the redundant slices. If the loss of the original slice occurs, the decoder can make use of the redundant slices to recover the original slice. These techniques introduced in the H.264/AVC makes the codec more robust and resilient towards data and error loss. 2.1.2. Profiles and Levels A profile of a codec is defined as the set of features identified to meet a certain specifications of intended applications For the H.264/AVC codec, it is defined as a set of features identified to generate a conforming bit stream. A level is imposes restrictions on some key parameters of the bit stream. In H.264/AVC, there are three profiles namely: Baseline, Main and Extended. 5 shows the relationship between these profiles. The Baseline profile is most likely to be used by network cameras and encoders as it requires limited computing resources. It is quite ideal to make use of this profile to support real-time streaming applications in a embedded platform. 2.2. Overview of Video Streaming In previous systems, accessing video data across network exploit the ‘download and play approach. In this approach, the client had to wait until the whole video data is downloaded to the media player before play out begins. To combat the long initial play out delay, the concept of streaming was introduced. Streaming allows the client to play out the earlier part of the video data whilst still transferring the remaining part of the video data. The major advantage of the streaming concept is that the video data need not be stored in the clients computer as compared to the traditional ‘download and play approach. This reduces the long initial play out delay experienced by the client. Streaming adopts the traditional client/server model. The client connects to the listening server and request for video data. The server sends video data over to the client for play out of video data. 2.2.1. Types of Streaming There are three different types of streaming video data. They are pre-recorded/ file streaming, live/real-time streaming and interactive streaming. * Pre-recorded/live streaming: The encoded video is stored into a file and the system streams the file over the network. A major overhead is that there is a long initial play out delay (10-15s) experienced by the client. * Live/real-time streaming: The encoded video is streamed over the network directly without being stored into a file. The initial play out delay reduces. Consideration must be taken to ensure that play out rate does not exceed sending rate which may result in jerky the picture. On the other hand, if the sending rate is too slow, the packets arriving at the client may be dropped, causing in a freezing the picture. The timing requirement for the end-to-end delay is more stringent in this scenario. * Interactive streaming: Like live streaming, the video is streamed directly over the network. It responds to users control input such as rewind, pause, stop, play and forward the particular video stream. The system should respond in accordance to those inputs by the user. In this project, both pre-recorded and live streaming are implemented. Some functionality of interactive streaming controls like stop and play are also part of the system. 2.2.2. Video Streaming System modules Video Source The intent of the video source is to capture the raw video sequence. The CCTV camera is used as the video source in this project. Most cameras are of analogue inputs and these inputs are connected to the encoding station via video connections. This project makes use of only one video source due to the limitation of the video connections on the encoding station. The raw video sequence is then passed onto the encoding station. Encoding Station The aim of the encoding station digitized and encodes the raw video sequence into the desired format. In the actual system, the encoding is done by the DM6446 board into the H.264/AVC format. Since the hardware encoding is CPU intensive, this forms the bottleneck of the whole streaming system. The H.264 video is passed onto the video streamer server module of the system. Video Streaming and WebServer The role of the video streaming server is to packetize the H.264/AVC to be streamed over the network. It serves the requests from individual clients. It needs to support the total bandwidth requirements of the particular video stream requested by clients. WebServer offers a URL link which connects to the video streaming server. For this project, the video streaming server module is embedded inside DM6446 board and it is serves every individual clients requests. Video Player The video player acts a client connecting to and requesting video data from the video streaming server. Once the video data is received, the video player buffers the data for a while and then begins play out of data. The video player used for this project is the VideoLAN (VLC) Player. It has the relevant H.264/AVC codec so that it can decode and play the H264/AVC video data. 2.2.3. Unicast VS Multicast There are two key delivery techniques employed by streaming media distribution. Unicast transmission is the sending of data to one particular network destination host over a packet switched network. It establishes two way point-to-point connection between client and server. The client communicates directly with the server via this connection. The drawback is that every connection receives a separate video stream which uses up network bandwidth rapidly. Multicast transmission is the sending of only one copy of data via the network so that many clients can receive simultaneously. In video streaming, it is more cost effective to send single copy of video data over the network so as to conserve the network bandwidth. Since multicast is not connection oriented, the clients cannot control the streams that they can receive. In this project, unicast transmission is used to stream encoded video over the network. The client connects directly to the DM6446 board where it gets the encoded video data. The project can easily be extended to multicast transmission. 2.3. Streaming Protocols When streaming video content over a network, a number of network protocols are used. These protocols are well defined by the Internet Engineering Task Force (IETF) and the Internet Society (IS) and documented in Request for Comments (RFC) documents. These standards are adopted by many developers today. In this project, the same standards are also employed in order to successfully stream H.264/AVC content over a simple Local Area Network (LAN). The following sections will discuss about the various protocols that are studied in the course of this project. 2.3.1. Real-Time Streaming Protocol (RTSP) The most commonly used application layer protocol is RTSP. RTSP acts a control protocol to media streaming servers. It establishes connection between two end points of the system and control media sessions. Clients issue VCR-like commands like play and pause to facilitate the control of real-time playback of media streams from the servers. However, this protocol is not involved in the transport of the media stream over the network. For this project, RTSP version 1.0 is used. RTSP States Like the Hyper Text Transfer Protocol (HTTP), it contains several methods. They are OPTIONS, DESCRIBE, SETUP, PLAY, PAUSE, RECORD and TEARDOWN. These commands are sent by using the RTSP URL. The default port number used in this protocol is 554. An example of such as URL is: rtsp://  · OPTIONS: An OPTIONS request returns the types of request that the server will accept. An example of the request is: OPTIONS rtsp://155.69.148.136:554/test.264 RTSP/1.0 CSeq: 1rn User-agent: VLC media Player The CSeq parameter keeps track of the number of request send to the server and it is incremented every time a new request is issued. The User-agent refers to the client making the request. * DESCRIBE: This method gets the presentation or the media object identified in the request URL from the server. An example of such a request: DESCRIBE rtsp://155.69.148.138:554/test.264 RTSP/1.0 CSeq: 2rn Accept: application/sdprn User agent: VLC media Player The Accept header is used to describe the formats understood by the client. All the initialization of the media resource must be present in the DESCRIBE method that it describes.  · SETUP: This method will specify the mode of transport mechanism to be used for the media stream. A typical example is: SETUP rtsp://155.69.148.138:554/test.264 RTSP/1.0 CSeq: 3rn Transport: RTP/AVP; unicast; client_port = 1200-1201 User agent: VLC media Player The Transport header specifies the transport mechanism to be used. In this case, real-time transport protocol is used in a unicast manner. The relevant client port number is also reflected and it is selected randomly by the server. Since RTSP is a stateful protocol, a session is created upon successful acknowledgement to this method.  · PLAY: This method request the server to start sending the data via the transport mechanism stated in the SETUP method. The URL is the same as the other methods except for: Session: 6 Range: npt= 0.000- rn The Session header specifies the unique session id. This is important as server may establish various sessions and this keep tracks of them. The Range header positions play time to the beginning and plays till the end of the range. * PAUSE: This method informs the server to pause sending of the media stream. Once the PAUSE request is sent, the range header will capture the position at which the media stream is paused. When a PLAY request is sent again, the client will resume playing from the current position of the media stream as specified in the range header. RSTP Status Codes Whenever the client sends a request message to the server, the server forms a equivalent response message to be sent to the client. The response codes are similar to HTTP as they are both in ASCII text. They are as follows: 200: OK 301: Redirection 405: Method Not Allowed 451: Parameter Not Understood 454: Session Not Found 457: Invalid Range 461: Unsupported Transport 462: Destination Unreachable These are some of the RTSP status codes. There are many others but the codes mentioned above are of importance in the context of this project. 2.3.2. Real-time Transport Protocol (RTP) RTP is a defined packet structure which is used for transporting media stream over the network. It is a transport layer protocol but developers view it as a application layer protocol stack. This protocol facilitates jitter compensation and detection of incorrect sequence arrival of data which is common for transmission over IP network. For the transmission of media data over the network, it is important that packets arrive in a timely manner as it is loss tolerant but not delay tolerant. Due to the high latency of Transmission Control Protocol in establishing connections, RTP is often built on top of the User Datagram Protocol (UDP). RTP also supports multicast transmission of data. RTP is also a stateful protocol as a session is established before data can be packed into the RTP packet and sent over the network. The session contains the IP address of the destination and port number of the RTP which is usually an even number. The following section will explain about the packet structure of RTP which is used for transmission. RTP Packet Structure The below shows a RTP packet header which is appended in front of the media data.s The minimum size of the RTP header is 12 bytes.. Optional extension information may be present after the header information. The fields of the header are:  · V: (2 bits) to indicate the version number of the protocol. Version used in this project is 2.  · P (Padding): (1 bit) to indicate if there padding which can be used for encryption algorithm  · X (Extension): (1 bit) to indicate if there is extension information between header and payload data.  · CC (CSRC Count) : (4 bits) indicates the number of CSRC identifiers  · M (Marker): (1 bit) used by application to indicate data has specific relevance in the perspective of the application. The setting for M bit marks the end of video data in this project  · PT (Payload Type): (7 bits) to indicate the type of payload data carried by the packet. H.264 is used for this project  · Sequence number: (16 bits) incremented by one for every RTP packet. It is used to detect packet loss and out of sequence packet arrival. Based on this information, application can take appropriate action to correct them.  · Time Stamp: (32 bits) receivers use this information to play samples at correct intervals of time. Each stream has independent time stamps.  · SSRC: (32 bits) it unique identifies source of the stream.  · CSRC: sources of a stream from different sources are enumerated according to its source IDs. This project does not involve the use of Extension field in the packet header and hence will not be explained in this report. Once this header information is appended to the payload data, the packet is sent over the network to the client to be played. The table below summarizes the payload types of RTP and highlighted region is of interest in this project. Table 2: Payload Types of RTP Packets 2.3.3. RTP Control Protocol (RTCP) RTCP is a sister protocol which is used in conjunction with the RTP. It provides out-of-band statistical and control information to the RTP session. This provides certain Quality of Service (QoS) for transmission of video data over the network. The primary functions of the RTCP are: * To gather statistical information about the quality aspect of the media stream during a RTP session. This data is sent to the session media source and its participants. The source can exploit this information for adaptive media encoding and detect transmission errors. * It provides canonical end point identifiers (CNAME) to all its session participants. It allows unique identification of end points across different application instances and serves as a third party monitoring tool. * It also sends RTCP reports to all its session participants. By doing so, the traffic bandwidth increases proportionally. In order to avoid congestion, RTCP has bandwidth management techniques to only use 5% of the total session bandwidth. RTCP statistical data is sent odd numbered ports. For instance, if RTP port number is 196, then RTCP will use the 197 as its port number. There is no default port number assigned to RTCP. RTCP Message Types RTCP sends several types of packets different from RTP packets. They are sender report, receiver report, source description and bye.  · Sender Report (SR): Sent periodically by senders to report the transmission and reception statistics of RTP packets sent in a period of time. It also includes the senders SSRC and senders packet count information. The timestamp of the RTP packet is also sent to allow the receiver to synchronize the RTP packets. The bandwidth required for SR is 25% of RTCP bandwidth.  · Receiver Report (RR): It reports the QoS to other receivers and senders. Information like highest sequence number received, inter arrival jitter of RTP packets and fraction of packets loss further explains the QoS of the transmitted media streams. The bandwidth required for RR is 75% of the RTCP bandwidth.  · Source Description (SDES): Sends the CNAME to its session participants. Additional information like name, address of the owner of the source can also be sent.  · End of Participation (BYE): The source sends a BYE message to indicate that it is shutting down the stream. It serves as an announcement that a particular end point is leaving the conference. Further RTCP Consideration This protocol is important to ensure that QoS standards are achieved. The acceptable frequencies of these reports are less than one minute. In major application, the frequency may increase as RTCP bandwidth control mechanism. Then, the statistical reporting on the quality of the media stream becomes inaccurate. Since there are no long delays introduced between the reports in this project, the RTCP is adopted to incorporate a certain level of QoS on streaming H.264/AVC video over embedded platform. 2.3.4. Session Description Protocol (SDP) The Session Description Protocol is a standard to describe streaming media initialization parameters. These initializations describe the sessions for session announcement, session invitation and parameter negotiation. This protocol can be used together with RTSP. In the previous sections of this chapter, SDP is used in the DESCRIBE state of RTSP to get sessions media initialization parameters. SDP is scalable to include different media types and formats. SDP Syntax The session is described by attribute/value pairs. The syntax of SDP are summarized in the below. In this project, the use of SDP is important in streaming as the client is VLC Media Player. If the streaming is done via RTSP, then VLC expects a sdp description from the server in order to setup the session and facilitate the playback of the streaming media. Chapter 3: Hardware Literature Review 3.1. Introduction to Texas Instrument DM6446EVM DavinciTM The development of this project based on the DM6446EVM board. It is necessary to understand the hardware and software aspects of this board. The DM6446 board has a ARM processor operating at a clock speed up to 300MHz and a C64x Digital Signal Processor operating at a clock speed of up to 600MHz. 3.1.1. Key Features of DM6446 The key features that are shown in the above are: * 1 video port which supports composite of S video * 4 video DAC outputs: component, RGB, composite * 256 MB of DDR2 DRAM * UART, Media Card interface (SD, xD, SM, MS ,MMC Cards) * 16 MB of non-volatile Flash Memory, 64 MB NAND Flash, 4 MB SRAM * USB2 interface * 10/100 MBS Ethernet interface * Configurable boot load options * IR Remote Interface, real time clock via MSP430 3.1.2. DM6446EVM Architecture The architecture of the DM6446 board is organized into several subsystems. By knowing the architecture of the DM6446, the developer can then design and built his application module on the boards underlining architecture. The shows that DM6446 has three subsystems which are connected to the underlying hardware peripherals. This provides a decoupled architecture which allows the developers to implement his applications on a particular subsystem without having to modify the other subsystems. Some of subsystems are discussed in the next sections. ARM Subsystem The ARM subsystem is responsible for the master control of the DM6446 board. It handles the system-level initializations, configurations, user interface, connectivity functions and control of DSP subsystems. The ARM has a larger program memory space and better context switching capabilities and hence it is more suited to handle complex and multi tasks of the system. DSP Subsystem The DSP subsystem is mainly the encoding the raw captured video frames into the desired format. It performs several number crunching operations in order to achieve the desired compression technique. It works together with the Video Imaging Coprocessor to compress the video frames. Video Imaging Coprocessor (VICP) The VICP is a signal processing library which contains various software algorithms that execute on VICP hardware accelerator. It helps the DSP by taking over computation of varied intensive tasks. Since hardware implementation of number cru H.264 Video Streaming System on Embedded Platform H.264 Video Streaming System on Embedded Platform ABSTRACT The adoption of technological products like digital television and video conferencing has made video streaming an active research area. This report presents the integration of a video streamer module into a baseline H.264/AVC encoder running a TMSDM6446EVM embedded platform. The main objective of this project is to achieve real-time streaming of the baseline H.264/AVC video over a local area network (LAN) which is a part of the surveillance video system. The encoding of baseline H.264/AVC and the hardware components of the platform are first discussed. Various streaming protocols are studied in order to implement the video streamer on the DM6446 board. The multi-threaded application encoder program is used to encode raw video frames into H.264/AVC format onto a file. For the video streaming, open source Live555 MediaServer was used to stream video data to a remote VLC client over LAN. Initially, file streaming was implemented from PC to PC. Upon successfully implementation on PC, the video streamer was ported to the board. The steps involved in porting the Live555 application were also described in the report. Both unicast and multicast file streaming were implemented in the video streamer. Due to the problems of file streaming, the live streaming approach was adopted. Several methodologies were discussed in integrating the video streamer and the encoder program. Modification was made both the encoder program and the Live555 application to achieve live streaming of H.264/AVC video. Results of both file and live streaming will be shown in this report. The implemented video streamer module will be used as a base module of the video surveillance system. Chapter 1: Introduction 1.1. Background Significant breakthroughs have been made over the last few years in the area of digital video compression technologies. As such applications making use of these technologies have also become prevalent and continue to be of active research topics today. For example, digital television and video conferencing are some of the applications that are now commonly encountered in our daily lives. One application of interest here is to make use of the technologies to implement a video camera surveillance system which can enhance the security of consumers business and home environment. In typical surveillance systems, the captured video is sent over a cable networks to be monitored and stored at remote stations. As the captured raw video contains large amount of data, it will be of advantage to first compress the data by using a compression technique before it is transferred over the network. One such compression technique that is suitable for this type of application is the H.264 coding standard. H.264 coding is better than the other coding technique for video streaming as it is more robust to data losses and coding efficiency, which are important factors when streaming is performed over a shared Local Area Network. As there is an increasing acceptance of H.264 coding and the availability of high computing power embedded systems, digital video surveillance system based on H.264 on embedded platform is hence a feasible and a potentially more cost-effective system. Implementing a H.264 video streaming system on an embedded platform is a logical extension of video surveillance systems which are still typical implemented using high computing power stations (e.g. PC). In a embedded version, a Digital Signal Processor (DSP) forms the core of the embedded system and executes the intensive signal processing algorithm. Current embedded systems typical also include network features which enable the implementation of data streaming applications. To facilitate data streaming, a number of network protocol standards have also being defined, and are currently used for digital video applications. 1.2. Objective and Scope The objective of this final year project is to implement a video surveillance system based on the H.264 coding standard running on an embedded platform. Such a system contains extensive scopes of functionalities and would require extensive amount of development time if implemented from scratch. Hence this project is to focus on the data streaming aspect of a video surveillance system. After some initial investigation and experimentation, it is decided to confine the main scope of the project to developing a live streaming H.264 based video system running on a DM6446 EVM development platform. The breakdown of the work to be progressive performed are then identified as follows: 1. Familiarization of open source live555 streaming media server Due to the complexity of implementing the various standard protocols needed for multimedia streaming, the live555 media server program is used as a base to implement the streaming of the H.264.based video data. 2. Streaming of stored H.264 file over the network The live555 is then modified to support streaming of raw encoded H.264 file from the DM6446 EVM board over the network. Knowledge of H.264 coding standard is necessary in order to parse the file stream before streaming over the network. 3. Modifying a demo version of an encoder program and integrating it together with live555 to achieve live streaming The demo encoder was modified to send encoded video data to the Live555 program which would do the necessary packetization to be streamed over the network. Since data is passed from one process to another, various inter-process communication techniques were studied and used in this project. 1.3. Resources The resources used for this project are as follows: 1. DM6446 (DaVinciâ„ ¢) Evaluation Module 2. SWANN C500 Professional CCTV Camera Solution 400 TV Lines CCD Color Camera 3. LCD Display 4. IR Remote Control 5. TI Davinci demo version of MontaVista Linux Pro v4.0 6. A Personal Workstation with Centos v5.0 7. VLC player v.0.9.8a as client 8. Open source live555 program (downloaded from www.live555.com) The system setup of this project is shown below: 1.4. Report Organization This report consists of 7 chapters. Chapter 1 introduces the motivation behind embedded video streaming system and defines the scope of the project. Chapter 2 illustrates the video literature review of the H.264/AVC video coding technique and the various streaming protocols which are to be implemented in the project. Chapter 3 explains the hardware literature review of the platform being used in the project. The architecture, memory management, inter-process communication and the software tools are also discussed in this chapter. Chapter 4 explains the execution of the encoder program of the DM6446EVM board. The interaction of the various threads in this multi-threaded application is also discussed to fully understand the encoder program. Chapter 5 gives an overview of the Live555 MediaServer which is used as a base to implement the video streamer module on the board. Adding support to unicast and multicast streaming, porting of live555 to the board and receiving video stream on remote VCL client are explained in this chapter. Chapter 6 explains the limitations of file streaming and moving towards live streaming system. Various integration methodologies and modification to both encoder program and live555 program are shown as well. Chapters 7 summarize the implementation results of file and live streaming, analysis the performance of these results. Chapter 8 gives the conclusion by stating the current limitation and problems, scope for future implementation. Chapter 2: Video Literature Review 2.1. H.264/AVC Video Codec Overview H.264 is the most advanced and latest video coding technique. Although there are many video coding schemes like H.26x and MPEG, H.264/AVC made many improvements and tools for coding efficiency and error resiliency. This chapter briefly will discuss the network aspect of the video coding technique. It will also cover error resiliency needed for transmission of video data over the network. For a more detailed explanation of the H.264/AVC, refer to appendix A. 2.1.1. Network Abstraction Layer (NAL) The aim of the NAL is to ensure that the data coming from the VCL layer is â€Å"network worthy† so that the data can be used for numerous systems. NAL facilitates the mapping of H.264/AVC VCL data for different transport layers such as: * RTP/IP real-time streaming over wired and wireless mediums * Different storage file formats such as MP4, MMS, AVI and etc. The concepts of NAL and error robustness techniques of the H.264/AVC will be discussed in the following parts of the report. NAL Units The encoded data from the VCL are packed into NAL units. A NAL unit represents a packet which makes up of a certain number of bytes. The first byte of the NAL unit is called the header byte which indicates the data type of the NAL unit. The remaining bytes make up the payload data of the NAL unit. The NAL unit structure allows provision for different transport systems namely packet-oriented and bit stream-oriented. To cater for bit stream-oriented transport systems like MPEG-2, the NAL units are organized into byte stream format. These units are prefixed by a specific start code prefix of three bytes which is namely 0x000001. The start code prefix indicates and the start of each NAL units and hence defining the boundaries of the units. For packet-oriented transport systems, the encoded video data are transported via packets defined by transport protocols. Hence, the boundaries of the NAL units are known without having to include start code prefix byte. The details of packetization of NAL units will be discussed in later sections of the report. NAL units are further categorized into two types: * VCL unit: comprises of encoded video data  · Non-VCL unit: comprises of additional information like parameter sets which is the important header information. Also contains supplementary enhancement information (SEI) which contains the timing information and other data which increases the usability of the decoded video signal. Access units A group of NAL units which adhere to a certain form is called a access unit. When one access unit is decoded, one decoded picture is formed. In the table 1 below, the functions of the NAL units derived from the access units are explained. Data/Error robustness techniques H.264/AVC has several techniques to mitigate error/data loss which is an essential quality when it comes to streaming applications. The techniques are as follows:  · Parameter sets: contains information that is being applied to large number of VCL NAL units. It comprises of two kinds of parameter sets: Sequence Parameter set (SPS) : Information pertaining to sequence of encoded picture Picture Parameter Set (PPS) : Information pertaining to one or more individual pictures The above mentioned parameters hardly changes and hence it need not be transmitted repeatedly and saves overhead. The parameter sets can be sent â€Å"in-band† which is carried in the same channel as the VCL NAL units. It can also be sent â€Å"out-of-band† using reliable transport protocol. Therefore, it enhances the resiliency towards data and error loss.  · Flexible Macroblock Ordering (FMO) FMO maps the macroblocks to different slice groups. In the event of any slice group loss, missing data is masked up by interpolating from the other slice groups.  · Redundancy Slices (RS) Redundant representation of the picture can be stored in the redundant slices. If the loss of the original slice occurs, the decoder can make use of the redundant slices to recover the original slice. These techniques introduced in the H.264/AVC makes the codec more robust and resilient towards data and error loss. 2.1.2. Profiles and Levels A profile of a codec is defined as the set of features identified to meet a certain specifications of intended applications For the H.264/AVC codec, it is defined as a set of features identified to generate a conforming bit stream. A level is imposes restrictions on some key parameters of the bit stream. In H.264/AVC, there are three profiles namely: Baseline, Main and Extended. 5 shows the relationship between these profiles. The Baseline profile is most likely to be used by network cameras and encoders as it requires limited computing resources. It is quite ideal to make use of this profile to support real-time streaming applications in a embedded platform. 2.2. Overview of Video Streaming In previous systems, accessing video data across network exploit the ‘download and play approach. In this approach, the client had to wait until the whole video data is downloaded to the media player before play out begins. To combat the long initial play out delay, the concept of streaming was introduced. Streaming allows the client to play out the earlier part of the video data whilst still transferring the remaining part of the video data. The major advantage of the streaming concept is that the video data need not be stored in the clients computer as compared to the traditional ‘download and play approach. This reduces the long initial play out delay experienced by the client. Streaming adopts the traditional client/server model. The client connects to the listening server and request for video data. The server sends video data over to the client for play out of video data. 2.2.1. Types of Streaming There are three different types of streaming video data. They are pre-recorded/ file streaming, live/real-time streaming and interactive streaming. * Pre-recorded/live streaming: The encoded video is stored into a file and the system streams the file over the network. A major overhead is that there is a long initial play out delay (10-15s) experienced by the client. * Live/real-time streaming: The encoded video is streamed over the network directly without being stored into a file. The initial play out delay reduces. Consideration must be taken to ensure that play out rate does not exceed sending rate which may result in jerky the picture. On the other hand, if the sending rate is too slow, the packets arriving at the client may be dropped, causing in a freezing the picture. The timing requirement for the end-to-end delay is more stringent in this scenario. * Interactive streaming: Like live streaming, the video is streamed directly over the network. It responds to users control input such as rewind, pause, stop, play and forward the particular video stream. The system should respond in accordance to those inputs by the user. In this project, both pre-recorded and live streaming are implemented. Some functionality of interactive streaming controls like stop and play are also part of the system. 2.2.2. Video Streaming System modules Video Source The intent of the video source is to capture the raw video sequence. The CCTV camera is used as the video source in this project. Most cameras are of analogue inputs and these inputs are connected to the encoding station via video connections. This project makes use of only one video source due to the limitation of the video connections on the encoding station. The raw video sequence is then passed onto the encoding station. Encoding Station The aim of the encoding station digitized and encodes the raw video sequence into the desired format. In the actual system, the encoding is done by the DM6446 board into the H.264/AVC format. Since the hardware encoding is CPU intensive, this forms the bottleneck of the whole streaming system. The H.264 video is passed onto the video streamer server module of the system. Video Streaming and WebServer The role of the video streaming server is to packetize the H.264/AVC to be streamed over the network. It serves the requests from individual clients. It needs to support the total bandwidth requirements of the particular video stream requested by clients. WebServer offers a URL link which connects to the video streaming server. For this project, the video streaming server module is embedded inside DM6446 board and it is serves every individual clients requests. Video Player The video player acts a client connecting to and requesting video data from the video streaming server. Once the video data is received, the video player buffers the data for a while and then begins play out of data. The video player used for this project is the VideoLAN (VLC) Player. It has the relevant H.264/AVC codec so that it can decode and play the H264/AVC video data. 2.2.3. Unicast VS Multicast There are two key delivery techniques employed by streaming media distribution. Unicast transmission is the sending of data to one particular network destination host over a packet switched network. It establishes two way point-to-point connection between client and server. The client communicates directly with the server via this connection. The drawback is that every connection receives a separate video stream which uses up network bandwidth rapidly. Multicast transmission is the sending of only one copy of data via the network so that many clients can receive simultaneously. In video streaming, it is more cost effective to send single copy of video data over the network so as to conserve the network bandwidth. Since multicast is not connection oriented, the clients cannot control the streams that they can receive. In this project, unicast transmission is used to stream encoded video over the network. The client connects directly to the DM6446 board where it gets the encoded video data. The project can easily be extended to multicast transmission. 2.3. Streaming Protocols When streaming video content over a network, a number of network protocols are used. These protocols are well defined by the Internet Engineering Task Force (IETF) and the Internet Society (IS) and documented in Request for Comments (RFC) documents. These standards are adopted by many developers today. In this project, the same standards are also employed in order to successfully stream H.264/AVC content over a simple Local Area Network (LAN). The following sections will discuss about the various protocols that are studied in the course of this project. 2.3.1. Real-Time Streaming Protocol (RTSP) The most commonly used application layer protocol is RTSP. RTSP acts a control protocol to media streaming servers. It establishes connection between two end points of the system and control media sessions. Clients issue VCR-like commands like play and pause to facilitate the control of real-time playback of media streams from the servers. However, this protocol is not involved in the transport of the media stream over the network. For this project, RTSP version 1.0 is used. RTSP States Like the Hyper Text Transfer Protocol (HTTP), it contains several methods. They are OPTIONS, DESCRIBE, SETUP, PLAY, PAUSE, RECORD and TEARDOWN. These commands are sent by using the RTSP URL. The default port number used in this protocol is 554. An example of such as URL is: rtsp://  · OPTIONS: An OPTIONS request returns the types of request that the server will accept. An example of the request is: OPTIONS rtsp://155.69.148.136:554/test.264 RTSP/1.0 CSeq: 1rn User-agent: VLC media Player The CSeq parameter keeps track of the number of request send to the server and it is incremented every time a new request is issued. The User-agent refers to the client making the request. * DESCRIBE: This method gets the presentation or the media object identified in the request URL from the server. An example of such a request: DESCRIBE rtsp://155.69.148.138:554/test.264 RTSP/1.0 CSeq: 2rn Accept: application/sdprn User agent: VLC media Player The Accept header is used to describe the formats understood by the client. All the initialization of the media resource must be present in the DESCRIBE method that it describes.  · SETUP: This method will specify the mode of transport mechanism to be used for the media stream. A typical example is: SETUP rtsp://155.69.148.138:554/test.264 RTSP/1.0 CSeq: 3rn Transport: RTP/AVP; unicast; client_port = 1200-1201 User agent: VLC media Player The Transport header specifies the transport mechanism to be used. In this case, real-time transport protocol is used in a unicast manner. The relevant client port number is also reflected and it is selected randomly by the server. Since RTSP is a stateful protocol, a session is created upon successful acknowledgement to this method.  · PLAY: This method request the server to start sending the data via the transport mechanism stated in the SETUP method. The URL is the same as the other methods except for: Session: 6 Range: npt= 0.000- rn The Session header specifies the unique session id. This is important as server may establish various sessions and this keep tracks of them. The Range header positions play time to the beginning and plays till the end of the range. * PAUSE: This method informs the server to pause sending of the media stream. Once the PAUSE request is sent, the range header will capture the position at which the media stream is paused. When a PLAY request is sent again, the client will resume playing from the current position of the media stream as specified in the range header. RSTP Status Codes Whenever the client sends a request message to the server, the server forms a equivalent response message to be sent to the client. The response codes are similar to HTTP as they are both in ASCII text. They are as follows: 200: OK 301: Redirection 405: Method Not Allowed 451: Parameter Not Understood 454: Session Not Found 457: Invalid Range 461: Unsupported Transport 462: Destination Unreachable These are some of the RTSP status codes. There are many others but the codes mentioned above are of importance in the context of this project. 2.3.2. Real-time Transport Protocol (RTP) RTP is a defined packet structure which is used for transporting media stream over the network. It is a transport layer protocol but developers view it as a application layer protocol stack. This protocol facilitates jitter compensation and detection of incorrect sequence arrival of data which is common for transmission over IP network. For the transmission of media data over the network, it is important that packets arrive in a timely manner as it is loss tolerant but not delay tolerant. Due to the high latency of Transmission Control Protocol in establishing connections, RTP is often built on top of the User Datagram Protocol (UDP). RTP also supports multicast transmission of data. RTP is also a stateful protocol as a session is established before data can be packed into the RTP packet and sent over the network. The session contains the IP address of the destination and port number of the RTP which is usually an even number. The following section will explain about the packet structure of RTP which is used for transmission. RTP Packet Structure The below shows a RTP packet header which is appended in front of the media data.s The minimum size of the RTP header is 12 bytes.. Optional extension information may be present after the header information. The fields of the header are:  · V: (2 bits) to indicate the version number of the protocol. Version used in this project is 2.  · P (Padding): (1 bit) to indicate if there padding which can be used for encryption algorithm  · X (Extension): (1 bit) to indicate if there is extension information between header and payload data.  · CC (CSRC Count) : (4 bits) indicates the number of CSRC identifiers  · M (Marker): (1 bit) used by application to indicate data has specific relevance in the perspective of the application. The setting for M bit marks the end of video data in this project  · PT (Payload Type): (7 bits) to indicate the type of payload data carried by the packet. H.264 is used for this project  · Sequence number: (16 bits) incremented by one for every RTP packet. It is used to detect packet loss and out of sequence packet arrival. Based on this information, application can take appropriate action to correct them.  · Time Stamp: (32 bits) receivers use this information to play samples at correct intervals of time. Each stream has independent time stamps.  · SSRC: (32 bits) it unique identifies source of the stream.  · CSRC: sources of a stream from different sources are enumerated according to its source IDs. This project does not involve the use of Extension field in the packet header and hence will not be explained in this report. Once this header information is appended to the payload data, the packet is sent over the network to the client to be played. The table below summarizes the payload types of RTP and highlighted region is of interest in this project. Table 2: Payload Types of RTP Packets 2.3.3. RTP Control Protocol (RTCP) RTCP is a sister protocol which is used in conjunction with the RTP. It provides out-of-band statistical and control information to the RTP session. This provides certain Quality of Service (QoS) for transmission of video data over the network. The primary functions of the RTCP are: * To gather statistical information about the quality aspect of the media stream during a RTP session. This data is sent to the session media source and its participants. The source can exploit this information for adaptive media encoding and detect transmission errors. * It provides canonical end point identifiers (CNAME) to all its session participants. It allows unique identification of end points across different application instances and serves as a third party monitoring tool. * It also sends RTCP reports to all its session participants. By doing so, the traffic bandwidth increases proportionally. In order to avoid congestion, RTCP has bandwidth management techniques to only use 5% of the total session bandwidth. RTCP statistical data is sent odd numbered ports. For instance, if RTP port number is 196, then RTCP will use the 197 as its port number. There is no default port number assigned to RTCP. RTCP Message Types RTCP sends several types of packets different from RTP packets. They are sender report, receiver report, source description and bye.  · Sender Report (SR): Sent periodically by senders to report the transmission and reception statistics of RTP packets sent in a period of time. It also includes the senders SSRC and senders packet count information. The timestamp of the RTP packet is also sent to allow the receiver to synchronize the RTP packets. The bandwidth required for SR is 25% of RTCP bandwidth.  · Receiver Report (RR): It reports the QoS to other receivers and senders. Information like highest sequence number received, inter arrival jitter of RTP packets and fraction of packets loss further explains the QoS of the transmitted media streams. The bandwidth required for RR is 75% of the RTCP bandwidth.  · Source Description (SDES): Sends the CNAME to its session participants. Additional information like name, address of the owner of the source can also be sent.  · End of Participation (BYE): The source sends a BYE message to indicate that it is shutting down the stream. It serves as an announcement that a particular end point is leaving the conference. Further RTCP Consideration This protocol is important to ensure that QoS standards are achieved. The acceptable frequencies of these reports are less than one minute. In major application, the frequency may increase as RTCP bandwidth control mechanism. Then, the statistical reporting on the quality of the media stream becomes inaccurate. Since there are no long delays introduced between the reports in this project, the RTCP is adopted to incorporate a certain level of QoS on streaming H.264/AVC video over embedded platform. 2.3.4. Session Description Protocol (SDP) The Session Description Protocol is a standard to describe streaming media initialization parameters. These initializations describe the sessions for session announcement, session invitation and parameter negotiation. This protocol can be used together with RTSP. In the previous sections of this chapter, SDP is used in the DESCRIBE state of RTSP to get sessions media initialization parameters. SDP is scalable to include different media types and formats. SDP Syntax The session is described by attribute/value pairs. The syntax of SDP are summarized in the below. In this project, the use of SDP is important in streaming as the client is VLC Media Player. If the streaming is done via RTSP, then VLC expects a sdp description from the server in order to setup the session and facilitate the playback of the streaming media. Chapter 3: Hardware Literature Review 3.1. Introduction to Texas Instrument DM6446EVM DavinciTM The development of this project based on the DM6446EVM board. It is necessary to understand the hardware and software aspects of this board. The DM6446 board has a ARM processor operating at a clock speed up to 300MHz and a C64x Digital Signal Processor operating at a clock speed of up to 600MHz. 3.1.1. Key Features of DM6446 The key features that are shown in the above are: * 1 video port which supports composite of S video * 4 video DAC outputs: component, RGB, composite * 256 MB of DDR2 DRAM * UART, Media Card interface (SD, xD, SM, MS ,MMC Cards) * 16 MB of non-volatile Flash Memory, 64 MB NAND Flash, 4 MB SRAM * USB2 interface * 10/100 MBS Ethernet interface * Configurable boot load options * IR Remote Interface, real time clock via MSP430 3.1.2. DM6446EVM Architecture The architecture of the DM6446 board is organized into several subsystems. By knowing the architecture of the DM6446, the developer can then design and built his application module on the boards underlining architecture. The shows that DM6446 has three subsystems which are connected to the underlying hardware peripherals. This provides a decoupled architecture which allows the developers to implement his applications on a particular subsystem without having to modify the other subsystems. Some of subsystems are discussed in the next sections. ARM Subsystem The ARM subsystem is responsible for the master control of the DM6446 board. It handles the system-level initializations, configurations, user interface, connectivity functions and control of DSP subsystems. The ARM has a larger program memory space and better context switching capabilities and hence it is more suited to handle complex and multi tasks of the system. DSP Subsystem The DSP subsystem is mainly the encoding the raw captured video frames into the desired format. It performs several number crunching operations in order to achieve the desired compression technique. It works together with the Video Imaging Coprocessor to compress the video frames. Video Imaging Coprocessor (VICP) The VICP is a signal processing library which contains various software algorithms that execute on VICP hardware accelerator. It helps the DSP by taking over computation of varied intensive tasks. Since hardware implementation of number cru