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### Assiment

1. 1. What is Digital Electronics A description of what we mean by digital electronics is, strangely, best approached froma description of what it is not. It is not analogue. Analogue electronics are designed andused to process analogue signals. An analogue signal is a fluctuating voltage which canhave any numerical value. i.e it may be tiny fractions of a volt or it may be hundreds ofvolts. It may be a constant voltage or rapidly changing. The key feature that separates itfrom digital electronics is this ability to assume any value within a continuous range. Inmany ways this is a more true reflection of the real world than digital signals. Nnnnext Ifyou consider the amplification of a singers voice via a microphone it is obvious that theresulting signal from the microphone will have a voltage continuously varying inamplitude from the quietest to the loudest note. The processing of this signal must takeaccount of this to accurately reproduce it when amplified. In sharp contrast to this is digital electronics. A digital signal can only have one of twopossible values. The exact value of these voltages depends on the particular type ofdigital circuit but one of the most common systems uses +5 volts and 0 volts. In thissystem the +5v is referred to as the digital High (or simply HI) and the 0v as digital Low(or LO). At first glance this may seem a little restrictive. After all what real world signalscan be represented (and then processed) by two states, except perhaps a simple switchwhich is either on or off ? The true power of digital representation becomes apparent when we start to considerpatterns of these two states rather than just the one. If you take two signals , each capableof being either HI or LO then the combination can have four different patterns i.e. LOLO, LO HI, HI LO, HI HI. By considering the pattern rather than just the individualsignal we have increased the range of what can be represented from two to four. Similarlywe can use three digital signals to represent a range of 8 and four signals for a range of16. More generally, if we use N signals we can represent 2N possible patterns. Lets give these patterns a name. Conventionally we use the BINARY number system toname these patterns of HI and LO, although you should be aware that this is not alwaysthe case. Below you can see a table of the first few binary number patterns. The HI isrepresented as 1 and the LO as 0Using patterns of these "two state" signals we are getting back to the ability that analoguesignals have in representing a bigger range of values. However, representing real worldsignals using these discrete values is a bit like using an approximation. It gives youroughly what you had but not exactly. If we take the example of the singer and theamplified microphone and assume the microphone signal varied from, say, 0.1 volts to3.2 volts, then we could use 5 digital signals to represent each 0.1 volt level (i.e. 32different binary patterns). We could then process this and generate bigger numbers whichcould be used to generate correspondingly larger voltages (i.e amplification). The onlything wrong with this is quality. We would be ignoring, or actually rounding off, theintermediate values of signal between these discrete values. Trust me on this; the singerwould not sound so good. If however we had used 32 digital signals then theRESOLUTION of the representation would be much better and, in fact , you wouldprobably not be able to distinguish the resultant amplified signal from the analogueprocessed type. The binary representation of real world signals is important, but , by no means, the
2. 2. only use of digital electronics. In the next section we will look at the use of theseBINARY patterns to represent numbers which are manipulated as numbers without anyrequirement to represent an analogue signal. We will also show how these HI/LO patternscan be used to represent the logical decision making process we all take for grantedWhy is digital electronics important to modern technology and information processing?Digital electronics leads to fewer mistakes in sending and receiving information. Also theamount of information is greater than when using analogue electronics. Also simple tasksand basic mathematics become much easier.The principles of digital electronicsThe circuits and components we have discussed are very useful. You can build a radio ortelevision with them. You can make a telephone. Even if that was all there was toelectronics, it would still be very useful. However, the great breakthrough in the last fiftyyears or so has been in digital electronics. This is the subject which gave us the computer.The computer has revolutionised the way business, engineering and science are done.Small computers programmed to do a specific job (called microprocessors) are now usedin almost every electronic machine from cars to washing machines. Computers have alsochanged the way we communicate. We used to have telegraph or telephone wires passingup and down a country — each one carrying one telephone call or signal. We now haveoptic fibres each capable of carrying tens of thousands of telephone calls using digitalsignals.So, what is a digital signal? Look at Figure 1. A normal signal, called an analogue signal,carries a smooth wave. At any time, the voltage of the signal could take any value. Itcould be 2,00 V or 3,53 V or anything else. A digital signal can only take certain voltages.The simplest case is shown in the figure — the voltage takes one of two values. It iseither high, or it islow. It never has any other value.These two special voltages are given symbols. The low voltage level is written 0, whilethe high voltage level is written as 1. When you send a digital signal, you set the voltageyou want (0 or 1), then keep this fixed for a fixed amount of time (for example 0.01 μs),then you send the next 0 or 1. The digital signal in Figure 1 could be written 01100101. Figure 1: The difference between normal (analogue) signals and digital signals.Why are digital signals so good?
3. 3. Using a computer, any information can be turned into a pattern of 0s and 1s. Pictures,recorded music, text and motion pictures can all be turned into a string of 0s and 1s andtransmitted or stored in the same way. The computer receiving the signal at the other endconverts it back again. A Compact Disc (CD) for example, can store music or text orpictures, and all can be read using a computer.The 0 and the 1 look very different. You can immediately tell if a 0 or a 1 is being sent.Even if there is interference, you can still tell whether the sender sent a 0 or a 1. Thismeans that fewer mistakes are made when reading a digital signal. This is why the bestmusic recording technologies, and the most modern cameras, for example, all use digitaltechnology.Using the 0s and 1s you can count, and do all kinds of mathematics. This will beexplained in more detail in the next section.The simplest digital circuits are called logic gates. Each logic gate makes a decisionbased on the information it receives. Different logic gates are set up to make the decisionsin different ways. Each logic gate will be made of many microscopic transistorsconnected together within a thin wafer of silicon. This tiny circuit is called an IntegratedCircuit or I.C. - all the parts are in one place (integrated) on the silicon wafer..Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel§ consisting of long-chain alkyl§ (methyl§, propyl§ or ethyl§) esters§. Biodiesel is typically made bychemically reacting lipids§ (e.g.,vegetable oil§, animal fat (tallow§[1][2])) with analcohol§ producing fatty acid esters§.Biodiesel is meant to be used in standard diesel engines and is thus distinct from thevegetable and waste oils used to fuel converted diesel engines. Biodiesel can be usedalone, or blended with petrodiesel. Biodiesel can also be used as a low carbon alternativeto heating oil§.The National Biodiesel Board§ (USA) also has a technical definition of "biodiesel" as amono-alkyl ester.[3]Blends of biodiesel and conventional hydrocarbon-based diesel are products mostcommonly distributed for use in the retail diesel fuel marketplace. Much of the worlduses a system known as the "B" factor to state the amount of biodiesel in any fuel mix:[4]  100% biodiesel is referred to as B100, while  20% biodiesel, 80% petrodiesel is labeled B20  5% biodiesel, 95% petrodiesel is labeled B5  2% biodiesel, 98% petrodiesel is labeled B2.
4. 4. Blends of 20% biodiesel and lower can be used in diesel equipment with no, or onlyminor modifications,[5] although certain manufacturers do not extend warranty coverageif equipment is damaged by these blends. The B6 to B20 blends are covered by theASTM§ D7467 specification.[6] Biodiesel can also be used in its pure form (B100), butmay require certain engine modifications to avoid maintenance and performanceproblems.[7] Blending B100 with petroleum diesel may be accomplished by:  Mixing in tanks at manufacturing point prior to delivery to tanker truck  Splash mixing in the tanker truck (adding specific percentages of biodiesel and petroleum diesel)  In-line mixing, two components arrive at tanker truck simultaneously.  Metered pump mixing, petroleum diesel and biodiesel meters are set to X total volume, transfer pump pulls from two points and mix is complete on leaving pump  APPLICATIONBiodiesel can be used in pure form (B100) or may be blended with petroleum diesel atany concentration in most injection pump diesel engines. New extreme high-pressure(29,000 psi) common rail§ engines have strict factory limits of B5 or B20, depending onmanufacturer.[citation needed] Biodiesel has different solvent§ properties thanpetrodiesel, and will degrade natural rubber§ gaskets§ and hoses§ in vehicles (mostlyvehicles manufactured before 1992), although these tend to wear out naturally and mostlikely will have already been replaced with FKM§, which is nonreactive to biodiesel.Biodiesel has been known to break down deposits of residue in the fuel lines wherepetrodiesel has been used.[8] As a result, fuel filters§ may become clogged withparticulates if a quick transition to pure biodiesel is made. Therefore, it is recommendedto change the fuel filters on engines and h AVABALITY & PRICE Global biodiesel production§ reached 3.8 million tons in 2005.Approximately 85% of biodiesel production came from the European Union.[citationneeded]In 2007, in the United States, average retail (at the pump) prices, including federal andstate fuel taxes§, of B2/B5 were lower than petroleum§ diesel by about 12 cents, and B20blends were the same as petrodiesel.[42] However, as part as a dramatic shift in dieselpricing, by July 2009, the US DOE was reporting average costs of B20 15 cents pergallon higher than petroleum diesel (\$2.69/gal vs. \$2.54/gal).[43] B99 and B100generally cost more than petrodiesel except where local governments provide a taxincentive or subsidy.BIODIESA; FEED BACKA variety of oils can be used to produce biodiesel. These include:  Virgin oil feedstock – rapeseed and soybean oils§ are most commonly used, soybean oil alone accounting for about ninety percent of all fuel stocks in the US. It also can be obtained from Pongamia§, field pennycress§ and jatropha§ and other crops such as mustard§, jojoba§, flax§, sunflower§, palm oil§, coconut§, hemp§ (see list of vegetable oils for biofuel§ for more information);  Waste vegetable oil§ (WVO);
5. 5.  Animal fats§ including tallow§, lard§, yellow grease§, chicken fat,[56] and the by-products of the production of Omega-3 fatty acids§ from fish oil.  Algae§, which can be grown§ using waste materials such as sewage[57] and without displacing land currently used for food production.  Oil from halophytes§ such as Salicornia bigelovii§, which can be grown using saltwater in coastal areas where conventional crops cannot be grown, with yields equal to the yields of soybeans and other oilseeds grown using freshwater irrigation[58] CURRENT RESERCHThere is ongoing research into finding more suitable crops and improving oil yield. Othersources are possible including human fecal matter, with Ghana§ building its first "fecalsludge-fed biodiesel plant." [96] Using the current yields, vast amounts of land and freshwater would be needed to produce enough oil to completely replace fossil fuel usage. Itwould require twice the land area of the US to be devoted to soybean production, or two-thirds to be devoted to rapeseed production, to meet current US heating andtransportation needs.[citation needed]Specially bred mustard varieties can produce reasonably high oil yields and are veryuseful in crop rotation§ with cereals, and have the added benefit that the meal leftoverafter the oil has been pressed out can act as an effective and biodegradable pesticide.[97]The NFESC§, with Santa Barbara§-based Biodiesel Industries is working to developbiodiesel technologies for the US navy and military, one of the largest diesel fuel users inthe world.[98]A group of Spanish developers working for a company called Ecofasa§ announced a newbiofuel made from trash. The fuel is created from general urban waste which is treated bybacteria to produce fatty acids, which can be used to make biodiesel.[99]Another approach that does not require the use of chemical for the production involvesthe use of genetically modified microbes.[100][101]Sagarika (missile)[edit§]DevelopmentDevelopment of the K-15 missile started in the late 1990s with the goal of building asubmarine-launched ballistic missile for use with the Indian Navy§ nuclear-poweredArihant class submarines§.[6][7] Sagarika has a length of 10 metres (33 ft), diameter of0.74 metres (2 ft 5 in), weighs 17 tonnes and can carry a payload of up to 1,000 kilograms(2,205 lb) over 700 kilometres (435 mi). It was developed at the DRDO§’s missilecomplex in Hyderabad§.[8]The development of the underwater missile launcher, known as Project 420, wascompleted in 2001 and handed over to the Indian Navy§ for trials. The missile launcher isdeveloped at Hazira in Gujarat§.[9] The Sagarika missile began integration with Indiasnuclear-powered§ Arihant class submarine§ that began sea trials on the 26 July 2009.[10]By 2008, the missile was successfully test fired seven times, and tested to its full range up
6. 6. to four times. The tests of February 26, 2008, were conducted from a submerged pontoon50 metres (160 ft) beneath the surface off the coast of Visakhapatnam§.[6][8][11][12] Aland-based version of the K-15 Sagarika was successfully test-fired on November 12,2008.[13] A full range test of the missile was done on 11 March 2012.[14] The twelfthand final development trial of the missiles was conducted on 27 January 2013. AccordingtoV.K. Saraswat§, the missile was again tested for its full range of 7Yesterday India successfully test-fired the underwater ballistic missile, Sagarika K-15(code-named B05), off the Visakhapatnam coast, marking en end to a series ofdevelopmental trials.The trail was conducted on a day when China tested a missile defence system, aninterceptor.K-15 Sagarika is a nuclear-capable submarine-launched ballistic missile with a range of700 kilometres (435 mi).In its twelfth flight trial, the 10-metre tall Submarine-Launched Ballistic Missile (SLBM)lifted off from a pontoon, rose to an altitude of 20 km and reached a distance of about 700km as it splashed down in the waters of the Bay of Bengal near the pre-designated targetpoint.According to scientific advisor to the Defence Minister V.K. Saraswat, the missile wastested for its full range of 700 km and the mission met all its objectives. He said theimpact accuracy of the medium range strategic missile was in single digit.With the completion of developmental trials, the process of integrating K-15 missile withINS Arihant, the indigenously-built nuclear submarine, will begin soon.As many as 12 nuclear-tipped missiles, each weighing six tonnes will be integrated withArihant, which will be powered by an 80 MWt (thermal) reactor that uses enricheduranium as fuel and light water as coolant and moderator.India is only the fifth country to have such a missile — the other four nations being theUnited States, Russia, France and China.Read more: Meanwhile the reactor has been integrated with the submarine and it wasexpected to go critical in May/ June 2013. Once that was done, the harbour trials willbegin.Read more:New Delhi: India’s 700 kms range Sagarika (K-15) submarine launched ballistic missile(SLBM) tested on 16 March 2012, was unsuccessful.This was the second test within a span of five days. The first test in the last fortnight, wascarried out on 11 March which was reported to be successful. Both tests took place about10 kms off Visakhapatam on the east coast of India.In the absence of a submarines, the missile tests were carried out from a submergedpontoon, simulating a submarine. Sagarika is a DRDO project.According to sources, the second test of 16 March was not successful due to very roughsea condition. The sea condition was so rough that some Indian Navy personnel on boarda logistic support ship fell sick. The ship was positioned a few kms away from thepontoon to provide logistic support. The fire control systems was on the ship and the ship