How DVDs Work Introduction:- It was the VHS tapes that conquered the residence in the video market, but now it was a time of DVDs that fully occupy the position of a VHS tapes.. Departing from tape to disc gave the pleasure of home theater to a major extent, and filled the world with a feature of exsiting home video at the home too. Here are the article which help you to learn about the following topics in a brief. 1.What a DVD consists of. 2.In what way a DVD player reads a disc. 3.What are the major thing to look for when you are going to buy a DVD player. 4.Some history about DVD player. DVD Disks DVD is a very interesting invention of modern technology and is very parallel to a CD, but as we compare DVD with a CD it has a much bigger data capacity. When we take a typical DVD it hold about seven times more data than a CD contain. When we see the huge capacity on DVD it means that a DVD has sufficient room to store a full-length movies, MPEG-2-programmed movie, as well as we store a lot of other information too. Now we see the some of the typical contents of a DVD movie:- It contain Upto 135 minutes of high-quality video, in a format of letterbox or pan-and-scan format, with a 720 dot of horizontal resolution (When we discuss about the compression ratio of video it is about 40:1 using MPEG-2 compression.) When we discuss about the audio capability it was obtainable in up to eight languages using 5.1 channel Dolby digital surround music and Subtitles upto 32 languages. In case of DVD it can be used to store approximately eight hours of CD-worth music per side. The format of DVD is very different as we compare to the VHS tapes: 1.The picture quality of DVD is better as compare to VHS tapes. 2.Almost all the DVDs have a Dolby Digital or DTS sound of best quality, which is very similar to the sound you are going to experience in a theater. One of the interesting feature of DVD that it has an on-screen index,Means the maker of the DVD has paste many of the important parts of the movie, manytime with a picture icon. And when you use the remote and you select the part of the movie you want to view on DVD player, the DVD player will catch you exact to that part,and you does not need to rewind or fast-forward. DVD players are also compatible with audio CDs. Some of the DVD movies have both the option of letterbox format, which are going to fits wide-screen TVs, and the standard TV size format, In that case you can select in which way you want to see the movie. The movies on DVD have a number of soundtracks on them, so they can make available subtitles in different languages. The movies in english language may give you the option between the version dubbed into your own language, and provide the creative soundtrack with subtitles in your own language. DVD Layers As CDs DVDs have same diameter and thickness as CDs, and DVDs are prepared using some of the identical materials and manufacturing methods. As we see a data on a CD the data is encoded in the form of small pits and bumps in the track of CDs,in the same way the data on a DVD is also encoded in the form of small pits and bumps in the track of the DVDs. A perfect DVD is collection of several layers of plastic, calculating about 1.2 millimeters thick. Each layer of DVD is created by injecting the molding polycarbonate plastic. And the whole process forms a disc that contain a microscopic bumps which are arranged as a continuous, single and very long spiral track of data. When the clear and plain pieces of polycarbonate are formed, then the thin reflective layer is sputtered on top of the disc, by wrapping the bumps. Now the Aluminum is used at the back of inner layers,and the semi-reflective gold layer is used for the external layers of the disc, then we allowing the laser light to spotlight through the external and toward the inner layers. And when all the layers are made,the each layer is covered with lacquer, squeezed collectively and cured below infrared light.When we take a one-sided discs, the label is silk-screened on top of the nonreadable surface. On the other hand when we take a two-sided discs are printed only on the nonreadable region near the hole in the middle.Now we see the Cross sections of the a variety of completed DVDs is look like this way: Each one of the writable layer of a DVD contain a spiral track of data. On one-layer DVDs, the track provided are always circles from the inside of the DVD to the outside of the DVD. When the spiral track begin at the center It means that a one-layer DVD can be lesser than 12 centimeters. When you see the image to the right cannot make an impression upon us is how unbelievably tiny the data track is.It was only 740 nanometers that separate one track from the next (nanometer is avery small it was billionth of a meter).Now the lengthened bumps that are used to make a track are each 320 nanometers wide only, the dimension is only a minimum of 400 nanometers long and 120 nanometers high. The following figure give you the clear look through the polycarbonate layer at the bumps. Now you will learn about the "pits" on a DVD instead of bumps. Pits appear on the aluminum side, but on the other side that the laser reads , they are known as bumps. It was the microscopic dimensions of the bumps that make the spiral track on a DVD extremely long. If you are able to raise the data track off a one layer of a DVD, and extend it out into a straight line, then the size is almost 7.5 miles long. It means that the two-sided, two-layer DVD would have 30 miles of data that is almost 48 kilometres. When you try to read bumps then you an amazingly accurate disc-reading mechanism. DVD Storage Capacity There was a some reason that make DVDs better than CDs as respect to storage. 1. It has a higher-density data storage. 2.it contain Less overhead, and more area. 3.It has a multi-layer storage It has a higher-density data storage. When we talk about one-sided, one-layer DVDs it can store about eight times more data than from CDs. This larger area come on DVDs because pits and tracks on DVDs are very smaller in size. Now its time to learn how much extra data can be stored due to the presence of pits on a DVD. The track pitch on the DVDs is 2.16 times smaller, and the minimum length of the pits of a one-layer DVD is 2.08 times smaller than on a CDs.When we multiplying these two numbers given above then we find that there is room for about 4.5 times as many pits on a DVDs. Now where the rest of the increase come from? In the case of a CD,we find a lot of extra information that was encoded on the disc which permit for error correction .This information is only the reappearance of information that is already presence on the disc. The error correction method that is used on CD uses is very old and inefficient as compare to the method that are used on DVDs. In the case of DVD it doesn't waste as much space on error correction, It enable the DVD to store much more genuine information. There is one other way that DVDs attain higher capacity by encoding data on a slightly larger area of the disc than is made on a CD. Multi-Layer Storage When we increase the storage capacity of a DVD To a large extent , Then we increase layer of DVD up to four layers, two on each side of DVDs. On the DVD the laser that are used to reads the disc can mainly focus on the second layer through the first layer. Now see the list of the capacities of various forms of DVDs: It is amazing to see that the capacity of a DVD does not double when you plus a whole second layer to the disc. This reason behind this that when a disc is made with two layers, Then the pits have to be a slight longer, on each layers, than when a one- layer is used. This helps to neglect interference between the layers, this may cause errors when the disc is played in DVD player. DVD Video DVD Fact When you use a normal DVD movie that was not compressed, then it will take at least one year to download it from a normal phone line. Although the storage capacity of DVDs is very huge, and the video data that was not compressed would never fit on a DVD. If you want to make video movie fit to DVD, then you must need a video compression. There was a group called the Moving Picture Experts Group (MPEG).It established the principles for compressing of the moving pictures. When the video movies are going to put on the DVDs, they must encoded in MPEG-2 format and then they are stored on the disc and the compression format is a broadly accepted international standard. The DVD player contains an MPEG-2 decoder, which are not compressed this data as quickly as soon as you can watch it. The MPEG-2 Format and Data Size Reduction All the movie that are generally filmed at a rate of 24 frame/ second. This line we means that every second, there are accurately 24 complete images display on the movie screen. NTSC is a format that was used by American and Japanese television. Which display a total of 30 frames per second; but it does this in a series of 60 fields, every of which contains alternating lines of the picture. On the other hand other countries use PAL format, which display at 50 fields per second, but at the cost of higher resolution. Due to the differences in frame rate and resolution, an MPEG movie desires to be converted either the NTSC or the PAL system. The MPEG encoder that are responsible for the creation of the compressed movie file analyzes each frame and they decides how to encode it. This compression uses several of the technology as still image compression are used to eliminate redundant or irrelevant data. It may uses information from different frames to shrink the overall size of the file. Now each of the frame can be encoded in one of three ways given below: 1. As an intraframe It contain the entire image data for that frame. And this is the method of encoding provides the least compression. 2.As a predicted frame This frame contain a basic information which tell the DVD player how to show the frame based on the most freshly displayed intraframe or predicted frame. It means that the frame contains simply the data that relate in which way the picture has changed from the previous frame. 3. As a bidirectional frame When you want to display this kind of frame, then the DVD player must have the sufficient information from the neighboring intraframe or predicted frames.and by using this data from the nearby surrounding frames, it uses interpolation which calculate the exact position and exact color of each pixel. DVD Audio Now the DVD audio and DVD video both are different formats.Today the DVD audio discs and players are comparatively very less right now, and they will become more regular, and the difference in sound quality can be easily visible. If you want to take advantage of superior-quality DVD audio, then you need a DVD player that has a 192kHz/24-bit digital-to-analog converter (DAC). In market most of the DVD players are 96kHz/24-bit digital-to-analog converter. So in that case if you want to hear a DVD audio, then you like to have a DVD player with a 192kHz/24-bit digital-to-analog converter. As compare to CDs a DVD audio recordings can give better sound. Below are the chart that give the lists of the sampling rate and accuracy for CD recordings and the maximum sampling rate and accuracy for DVD recordings. In case of CDs it can hold 74 minutes of music. On the other hand DVD audio discs can hold 74 minutes of music at the rate of highest quality level, 192kHz/24-bit audio. When you try to lower either the sampling rate or the accuracy,Then the capacity of DVD increase and hold more music. In case of DVD audio disc it can store up to two hours of 6-channel,which is better than CD quality, 96kHz/24-bit music.When we Lower the specifications further, then the DVD audio disc can occupy roughly seven hours of CD-quality audio.  

Introduction:-        

      

When you take your cold drink for the next time in a very hot day then you are thankful to a machine which is know as refrigerator.Today we have a chilled cold drink and we got a lots of enjoyment by that drink but there was a time when there is no refrigerator.Many people use to make a large amount of ice cubes and they sell them at high price and become very rich,but today is a era of refrigerator.

When there is no existence of refrigerator then at that time food preserving is very difficult job.

Refrigeration is one of the great invention that changed our life to a larher exent .Now we are not worry about the presevation of food ,we can easily preserve it by using the refrigerator. The supply of the food is very much stable now a day.As vwe see that a gallon of milk can be easily preserve for about 14-15 days with the help of refrigerator.That means you does not need a cow or buffalo in the background of your house for the regular supply of milk.

In U.S it is expected that about 5 percentage of all all electrical energy is used to keep the homes cool.This was really a amazing thing to know that when we know that the princple behind most of the refrigerator are very simple as we comapre it to other home appliances.

Now the principle of refrigerator in a easy way is that when a liqid evaporates,then this process obsorb the heat and by a some process a liquid is convert into gaseous state.

Purpose of a refrigerator

Now we talk about refrigerator but what is the real purpose of a refrigerator lets us know about this.

The most important and the fundamental needs of a refrigerator is to keep our food cool so it can last for a long time.Refrigerator play a very important role in slowing down the activity of a bacteria on our food for that reason bacteria needs a bigger time to spoil the food kept in a refrigerator.

Supose we take a example of milk when the milk is kept in a room temperature during the hot summer then bacteria attack on them very easily and it will spoil the milk as soon as in 4-5 hours but when we keep the milk in a refrigerator temperature then activity of bacteria slow down and milk last for a long time.

Parts of a general refrigerator

You all heared about the alcohal when you take little bit of alcohal and spread over your hand you feel cold means very cold .How this was possible is it a refrigerator or something else.In case of a alchol it evaporate in a room temperature.When the alcohal evaporate it work is to obsord heat from your skin and feel your skin cool.As the alchol is act as a coolant in the same way there is a coolant in refrigerator known as a refrigerant.It function is same as a alcohal but it is different only in the aspect that it is trapped in a series of coils.

A refrigerator is a collection of five main parts that is as follow:-

1.Compressor

2.Heat exchanging pipes- It is a coiled set of pipes outside the component.

3.Expansion valve..

4. Heat exchanging pipes- It is a coiled set of pipes inside the component.

5.Refrigerent- It is a liquid inside the refrigerator that function is to evaporate and form a cool temperature inside the refrigerator.

 

Understanding the Refrigerator

To learn about what happen inside the refrigerator let us perform a small experient which elaborate more about the refrigertor workink.

Requirement:-

1.A glass container filled with water must be a oven protected.

2.A therometer that measure up to a 480 degree Fahrenheit.

 

Process :-

Add a thermometer to a glass container that is filled with a water and place both in a oven by seting the temperature of a oven is equivalent to 420 degree Fahrenheit.

As the temperature of the oven rises it rises the temperature of the water upto the 100 degree celcius or 212 degree Fahrenheit and water start boiling.The temperature of the water remain or stick to the 100 degree celcius even when the temperature of the oven rises upto the maximum of 420 Fahrenheit.The temperature of the thermometer reach the 420 degree Fahrenheit when all the water boils.

Now we take a case of liquid nitrogen.All human being is comfortable at a temperature of 70 degree Fahrenheit but the liquid nitrogen boils at a 320 degree Fahrenheit.If you place a liquid nitrogen container at a room temperature it will boils at a 320 degree Fahrenheit.

Today is the time when all refrigerator generating a cycle to reuse a refrigent again and again.You too could generating a cycle by follow the step discuss below.

1.Again take a example of oven water boil at a 100 degree celcius even a oven produce a steam at a 420 Degree Fahrenheit temperature .According to max he told that collect all the steam in a bag.

2.When all the water boils then you give pressure the steam into the steel container.Now when the temperature reach a 800 degree Fahrenheit then he think that the steel container become very hot as a tempertaure grow up to the 800 degree Fahrenheit.

3. when max releases the steel container then it give heat to the aior in that oven.Now at that moment he slow down the temperature to a 400 degree Fahrenheit. At that point the high pressure air is condenses and form a pressurized water.

4.After that max remove all the water that is pressurized and take in a another container and again boil the water at a 100 degree celcius.

5.Now he follow all the four step again and again to reuse the same water.

 

 

Real process in refrigerator

Now you use a refrigerator that uses a cycle as the same way as that explain above.In the refrigerator the cycle is continous and it cannot stop for a moment.

Let us take a another example which explain you how refrigerator works in brief.This time we take a ammonia thjat must be pure it boils at 27 degree fahrenheit.Now come and see what happen in a refrigerator that help the refrigerator to keep cool.

1. Now we take a one of the parts of refrigertor that is the compressor that compresses the ammonia gas. Now the ammonia gas that is compressed heats up as it is going to pressurized .
2. Now the coils which is situated at the back side of the refrigerator now the hot ammonia gas dissolve its heat. At high pressure the ammonia gas condenses and converted into ammonia liquid which is dark blue in color.
3. Now the ammonia liquid that is produce by a high pressure it flows through the expansion valve. Expansion valve is a type of a small hole. Now on the both side of the hole there is a difference in pressure due to the presence of high pressure ammonia on one side and the low pressure area on the other side.
4. Now it time to boil the liquid ammonia and get vaporized nad turn into light blue in color now the temperature fall upto the 27 degree fahrenheit That is the reason which makes the inside of the refrigerator cool.
5. This process repeat as the cold ammonia gas is going to be sucked by the compressor, and the above cycle repeat.

Gas or propane Refrigerator

Another type of refrigerator that is a Gas and Propane Refrigerators.This type of refrigerator use a gas as there primary source.These type of refrigerator use the heat to produce cold inside the refrigerator.

When we discuss about a gas refrigerator uses It uses ammonia as a coolant.water,ammoia and hydrogen produce a continous cycle of ammonia.This gas refrigerator have five main parts they are:-

1.Generator – It function is to creates ammonia gas.

2.Separator – It function is to separate the ammonia gas from water.

3.Condenser – It play a major function to create liquid ammonia when hot ammonia gas is cooled and condensed .

4.Evaporator – Now the evaporator it function is to convert liquid ammonia to a gas which create the cool temperature inside the refrigerator.

5.Absorber – It function is to absorb the ammonia gas in which is present in water.

 

How this gas refrigerator works :-

1.First of all we apply heat to the solution of ammonia and water in a generator

2.When the mixture of ammonia and water comes to the boiling point of ammonia, then it flow into the separator

3.Now the ammonia gas will flows toward the up into the condenser, and ammonia gas is converted into liquid

4.Now the liquid ammonia takes way to the evaporator and its mixes with hydrogen gas where its evaporates and produce a cool temperatures inside the cold box of refrigerator.

5.Now its time come when the ammonia and hydrogen gases flow and come to the absorber here water is collected in the separator now it follow the step 2 again and mixes with the ammonia and hydrogen gas.

6.At last the ammonia forms a solution with the help of water and produce the hydrogen gas, this hydrogen gas again flows back to the evaporator.

7.Now the solution form by the mixting of ammonia and water flows toward the generator which repeat the cycle again and again.

Nanogenerators as the name suggests is a small chip which can be held in between our two fingers and can generate power equivalent to a typical AA size battery. We are now living in the nano-era where researches and developments are carried out at the nano scale. The problem with these nanodevices is that the powering source used,ie the battery tend to negate the size advantages of this nanodevices. So it is necessary to have power source also at the nano scale. This led to the development of nanogenerators. The basic building block of nanogenerators are nanowires. Nanowires are mainly made from zinc oxide through a process called hydrothermal synthesis. Nanowires have the same thickness as that of an average human hair. These nanowires are stacked together to form a nanogenerator. Generating electricity naturally is of prime importance nowadays and nanogenerator is a perfect example of it. It works on the principle of piezoelectric effect. Nanogeneraors mainly converts body movements, blood flow etc to useful electricity. It can also be used to power various implants made inside the human body. The manufacturing cost of nanogenerators is very small. A nanogenerator that is held between two fingers can be used to light up an LED. Nanogenerators if stacked up together, can become a potential energy source. It can convert any form of mechanical stress or energy into useful electricity. It is available in three major configurations: LING, VING and NEG. The main applications include: 1. Self powered nano devices: Devices that recharge and power themselves will be using nanogenerators in the near future. 2. Smart sensors: Smart wearable systems can use nanogenerators as a power source. 3. Implants: Implants inside human body can be powered using nanogenerators as they are free from toxic substances and are very small. 4. Flexible devices: Nanogenerators can be implemented in any flexible devices so that the device can be charged when flexed or subjected to mechanical stress. Nanogenerators, for sure will be an absolute trend in the near future. . .

Wall speakers are more common nowadays compared to their counterparts. The wall speakers function on the principle of converting the electrical signal in to audio signal. The basic difference between the wall speakers and other type of speakers is the ordinary speakers are impaled inside the cabinet while this is not the case with wall speakers where the wall speakers are impaled inside the frame and then fixed in the wall. This gives two advantages of the wall speakers over the other speakers. Firstly since the wall speakers are fixed inside the wall, there is much space left for other furniture or for other use. Moreover the cabinet of the wall speakers are also large which give a better room for sound effect.

However when you consider purchasing the wall speakers make sure that there is enough room for the wall speakers to fixed the same as per the requirement to get a better sound effect. Other points of considerations are the technical aspects such as power, frequency level etc. A speaker with 50 Hz frequency and 100 watts with proper sensitivity is ideal for most of the situations. If the room is not spacious than consider other alternatives of fixing the wall speakers.

The last and the most important part is the actual installation of the wall speakers. It is advisable to get the help of the professional in this aspect for better results. However some of the important steps which can be performed by the layman to install the wall speakers include deciding the exact location for the wall speakers, drilling holes for the speakers as required making room for the speakers in the wall, attaching wires from the speakers to the plugs and you are finally over with the installation of the wall speakers. Thus a little bit technical knowhow and proper implantation of the wall speakers will help in getting much better sound effect from the wall speakers.