Work Bibliography Paper Research Example | Topics and Well Written Essays - 1500 words

Work Bibliography - Research Paper Example The fist is an official document that served as an imperial record of the confiscation of church property, and reveals the depth to which persecution took place, and the Roman Empire re-embraced the persecution of Christians. It also points to an even more systematic persecution than had happened before, where persecutions would only be carried out in cases where Christians were overt in their worship, and would refuse to deal with Roman authorities, or when a local Roman Official was incredibly intent in the persecution. The acceptance of the Church in the decades before Julian’s reign, however, pushed Christianity into public life. This meant that the rise of persecution struck more deeply at the now open Christianity than previous persecutions had at closeted Christianity. This article also outlines a letter from a man to his wife that indicates the kinds of small personal resistances that Christians attempted to undertake in the face of this new brutal oppression. Though t hey would not often stand openly against the state, according to this article, they also did not bend to that oppression, and attempted to resist in the small ways that were available to them. Harrison, J. R. 2002. Paul and the Imperial Gospel at Thessaloniki.  Journal for the Study of the New Testament  25 (1): 71-96. ... the creation of Bishops who would preside over a certain area, and made the travel of Christians from one area to another easier, as well as allowing the birth of Christian communities in areas where there had not been ones previously easier, because they had a mold and a model to follow. Furthermore, it indicates that this administrative copying of the Roman Empire also had a profound impact on the theology of the Christian Church, allowing for the deciding of theological issues through councils of Bishops, but also reducing the populism of the earliest church in favor of a more top-down, authoritarian religious practice. den Boeft, J., and D. H. Williams. 1996. Ambrose of Milan and the end of the Arian-Nicene conflicts.  Vigiliae Christianae  50 (3): 315. This text outlines the role of one of the most important early Bishops, Ambrose of Milan, in bringing to a close the Arian-Nicene conflict. Though the council of Nicene decided on an orthodoxy, declaring the Arian beliefs hete rodox or heretical, this did not stop the continuation of Arian practices. This was a pattern that emerged though many church councils, where the losing side would continue to act in the ways they had previously, especially if, as was the case with the Arian heresy, the heresy was geographically concentrated. The article argues that without strong defense of orthodoxy, as was provided by Ambrose of Milan, it is quite possible that Arian beliefs would have continued to flourish for many years after the Nicean council. It outlines the steps Ambrose took to defend orthodoxy as decided by the Council of Nicene. But it also complicates the historical memory of Ambrose of Milan somewhat, by demonstrating that he had substantial investment in defending the orthodoxy for reasons other than theological

Platos Apology Essay Example for Free

Platos Apology Essay Platos The Apology is an account of the speech Socrates makes at the trial in which he is charged with not recognizing the gods recognized by the state, inventing new deities, and corrupting the youth of Athens. Socrates speech, however, is by no means an apology in our modern understanding of the word. The name of the dialogue derives from the Greek apologia, which translates as a defense, or a speech made in defense. Thus, in The Apology, Socrates attempts to defend himself and his conductcertainly not to apologize for it. For the most part, Socrates speaks in a very plain, conversational manner. He explains that he has no experience with the law courts and that he will instead speak in the manner to which he is accustomed: with honesty and directness. He explains that his behavior stems from a prophecy by the oracle at Delphi which claimed that he was the wisest of all men. Recognizing his ignorance in most worldly affairs, Socrates concluded that he must be wiser than other men only in that he knows that he knows nothing. In order to spread this peculiar wisdom, Socrates explains that he considered it his duty to question supposed wise men and to expose their false wisdom as ignorance. These activities earned him much admiration amongst the youth of Athens, but much hatred and anger from the people he embarrassed. He cites their contempt as the reason for his being put on trial. Socrates then proceeds to interrogate Meletus, the man primarily responsible for bringing Socrates before the jury. This is the only instance in The Apology of the elenchus, or cross-examination, which is so central to most Platonic dialogues. His conversation with Meletus, however, is a poor example of this method, as it seems more directed toward embarrassing Meletus than toward arriving at the truth. In a famous passage, Socrates likens himself to a gadfly stinging the lazy horse which is the Athenian state. Without him, Socrates claims, the state is liable to drift into a deep sleep, but through his influenceirritating as it may be to someit can be wakened into productive and virtuous action. Socrates is found guilty by a narrow margin and is asked to propose a penalty. Socrates jokingly suggests that if he were to get what he deserves, he should be honored with a great meal for being of such service to the state. On a more serious note, he rejects prison and exile, offering perhaps instead to pay a fine. When the jury rejects his suggestion and sentences him to death, Socrates stoically accepts the verdict with the observation that no one but the gods know what happens after death and so it would be foolish to fear what one does not know. He also warns the jurymen who voted against him that in silencing their critic rather than listening to him, they have harmed themselves much more than they have harmed him.

Delta Modulation And Demodulation Computer Science Essay

Delta Modulation And Demodulation Computer Science Essay A modem to improve communication system performance that uses multiple modulation scheme comprising modulation technique and encoder combinations. As communication system performance and objective change, different modulation schemes may be selected. Modulation schemes may also be selected upon the communication channel scattering function estimate and the modem estimates the channel scattering function from measurements of the channels frequency (Doppler) and time (multipath) spreading characteristics. An Adaptive sigma delta modulation and demodulation technique, wherein a quantizer step size is adapted based on estimates of an input signal to the quantizer, rather than on estimates of an input signal to the modulator. A technique for digital conferencing of voice signals in systems using adaptive delta modulation (ADM) with an idle pattern of alternating 1s and 0s has been described. Based on majority logic, it permits distortion-free reception of voice of a single active subscriber by all the other subscribers in the conference. Distortion exists when more than one subscriber is active and the extent of this distortion depends upon the type of ADM algorithm that has been used. An LSI oriented system based on time sharing of a common circuit by a number of channels has been implemented and tested. This technique, with only minor changes in circuitry, handles ADM channels that have idle patterns different from alternating single 1s and 0s. This method used for noise reduction. The modulator factor does not require a large amount of data to be represented. Representation is based upon a frequency domain function having particular characteristics. A preferred embodiment of the invention incorporates transform or sub band filtered signals which are transmitted as a modulated analog representation of a local region of a video signal. The modulation factor reflects the particular characteristic. Side information specifies the modulation factor 1.2. Aim: Digital techniques to wirelessly communicate voice information. Wireless environments are inherently noisy, so the voice coding scheme chosen for such an application must be robust in the presence of bit errors. Pulse Coded Modulation (PCM) and its derivatives are commonly used in wireless consumer products for their compromise between voice quality and implementation cost. Adaptive Delta Modulation (ADM) is another voice coding scheme, a mature technique that should be considered for these applications because of its bit error robustness and its low implementation cost. Bandpass modulation techniques encode information as the amplitude, fre ­quency, phase, or phase and amplitude of a sinusoidal carrier. These band ­pass modulation schemes are known by their acronyms ASK (amplitude shift keying), FSK (frequency shift keying), PSK (phase shift keying), and QAM (qua ­ternary amplitude modulation), where keying or modulation is used to indicate that a carrier signal is modified in some manner. The carrier is a sinusoidal signal that is initially devoid of any information. The purpose of the carrier is to translate essentially a baseband information signal to a frequency and wavelength that can be sent with a guided or propagating electro ­magnetic (EM) wave. Bandpass ASK is similar to baseband pulse amplitude modulation (PAM) in Chapter 2, Baseband Modulation and Demodulation, but FSK, PSK, and DM are new non-linear modulation techniques. ASK, FSK, and PSK can be readily extended to multiple level (M-ary) signaling and demodulated coherently or non-coherently. The optimum receiver for bandpass symmetrical or asymmetrical sig ­nals is the correlation receiver, which is developed for baseband signals in Chapter 2. Coherent demodulation uses a reference signal with the same frequency and phase as the received signal. No coherent demodulation of bandpass signaling may use differential encoding of the information to derive the reference signal in the correlation receiver. The observed bit error rate (BER) for a single, in a MATLAB simulation for several bandpass digital communication systems with coherent and non coherent correlation receivers is compared to the theoretical probability of bit error (Pb). Digital communication systems are subject to performance degrada ­tions with additive white Gaussian noise (AWGN). MATLAB simulations of bandpass communication systems are used to investigate the effect upon BER of the performance of the correlation receiver, the reduction in BER with Gray-coding of M-ary data, and binary and quaternary differential signaling. MATLAB simulations of such bandpass digital communication systems and investigations of their characteristics and performance are provided here. These simulations confirm the theoretical expectation for Pb and are the starting point for the what-ifs of bandpass digital communication system design. Finally, the constellation plot depicts the demodulated in-phase and quadra ­ture signals of complex modulation schemes in the presence of AWGN. The opti ­mum decision regions are shown, and the observed BER performance of the bandpass digital communication system can be qualitatively assessed. Delta Modulation: Delta modulation is also abbreviated as DM or Ά-modulation. It is a technique of conversion from an analog-to-digital and digital-to-analog signal. If we want to transmit the voice we use this technique. In this technique we do not give that much of importance to the quality of the voice. DM is nothing but the simplest form of differential pulse-code modulation (DPCM). But there is some difference between these two techniques. In DPCM technique the successive samples are encoded into streams of n-bit data. But in delta modulation, the transmitted data is reduced to a 1-bit data stream. Main features: * The analog signal is similar as a series of segments. * To find the increase or decrease in relative amplitude, we should compare each and every segment of the approximated signal with the original analog wave. * By this comparison of original and approximated analog waves we can determine the successive bits for establishing. * only the change of information is sent, that is, only an increase or decrease of the signal amplitude from the previous sample is sent whereas a no-change condition causes the modulated signal to remain at the same 0 or 1 state of the previous sample. By using oversampling techniques in delta modulation we can get large high signal-to-noise ratio. That means the analog signal is sampled at multiple higher than the Nyquist rate. Principle In delta modulation, it quantizes the difference between the current and the previous step rather than the absolute value quantization of the input analog waveform, which is shown in fig 1. Fig. 1 Block diagram of a Ά-modulator/demodulator The quantizer of the delta modulator converts the difference between the input signal and the average of the previous steps. The quantizer is measured by a comparator with reference to 0 (in 2- level quantizer), and its output is either 1 or 0. 1 means input signal is positive and 0 means negative. It is also called as a bit-quantizer because it quantizes only one bit at a time. The output of the demodulator rises or falls because it is nothing but an Integrator circuit. If 1 received means the output raises and if 0 received means output falls. The integrator internally has a low-pass filter it self. Transfer Characteristics A signum function is followed by the delta modulator for the transfer characteristics. It quantizes only levels of two number and also for at a time only one-bit. Output signal power In delta modulation amplitude it is does not matter that there is no objection on the amplitude of the signal waveform, due to there is any fixed number of levels. In addition to, there is no limitation on the slope of the signal waveform in delta modulation. We can observe whether a slope is overload if so it can be avoided. However, in transmitted signal there is no limit to change. The signal waveform changes gradually. Bit-rate The interference is due to possibility of in either DM or PCM is due to limited bandwidth in communication channel. Because of the above reason DM and PCM operates at same bit-rate. Noise in Communication Systems Noise is probably the only topic in electronics and telecommunications with which every-one must be familiar, no matter what his or her specialization. Electrical disturbances interfere with signals, producing noise. It is ever present and limits the performance of most systems. Measuring it is very contentious almost everybody has a different method of quantifying noise and its effects. Noise may be defined, in electrical terms, as any unwanted introduction of energy tending to interfere with the proper reception and reproduction of transmitted signals. Many disturbances of an electrical nature produce noise in receivers, modifying the signal in an unwanted manner. In radio receivers, noise may produce hiss in the loudspeaker output. In television receivers snow, or confetti (colored snow) becomes superimposed on the picture. In pulse communications systems, noise may produce unwanted pulses or perhaps cancel out the wanted ones. It may cause serious mathematical errors. Noise can l imit the range of systems, for a given transmitted power. It affects the sensitivity of receivers, by placing a limit on the weakest signals that can be amplified. It may sometimes even force a reduction in the bandwidth of a system. Noise is unwanted electrical or electromagnetic energy that degrades the quality of signals and data. Noise occurs in digital and analog systems, and can affect files and communications of all types, including text, programs, images, audio, and telemetry. In a hard-wired circuit such as a telephone-line-based Internet hookup, external noise is picked up from appliances in the vicinity, from electrical transformers, from the atmosphere, and even from outer space. Normally this noise is of little or no consequence. However, during severe thunderstorms, or in locations were many electrical appliances are in use, external noise can affect communications. In an Internet hookup it slows down the data transfer rate, because the system must adjust its speed to match conditions on the line. In a voice telephone conversation, noise rarely sounds like anything other than a faint hissing or rushing. Noise is a more significant problem in wireless systems than in hard-wired systems. In general, noise originating from outside the system is inversely proportional to the frequency, and directly proportional to the wavelength. At a low frequency such as 300 kHz, atmospheric and electrical noise are much more severe than at a high frequency like 300 MHz. Noise generated inside wireless receivers, known as internal noise, is less dependent on frequency. Engineers are more concerned about internal noise at high frequencies than at low frequencies, because the less external noise there is, the more significant the internal noise becomes. Communications engineers are constantly striving to develop better ways to deal with noise. The traditional method has been to minimize the signal bandwidth to the greatest possible extent. The less spectrum space a signal occupies, the less noise is passed through the receiving circuitry. However, reducing the bandwidth limits the maximum speed of the data that can be delivered. Another, more recently developed scheme for minimizing the effects of noise is called digital signal processing (DSP). Using fiber optics, a technology far less susceptible to noise, is another approach. Sources of Noise As with all geophysical methods, a variety of noises can contaminate our seismic observations. Because we control the source of the seismic energy, we can control some types of noise. For example, if the noise is random in occurrence, such as some of the types of noise described below, we may be able to minimize its affect on our seismic observations by recording repeated sources all at the same location and averaging the result. Weve already seen the power of averaging in reducing noise in the other geophysical techniques we have looked at. Beware, however, that averaging only works if the noise is random. If it is systematic in some fashion, no amount of averaging will remove it. The noises that plague seismic observations can be lumped into three categories depending on their source.  · Uncontrolled Ground Motion This is the most obvious type of noise. Anything that causes the ground to move, other than your source, will generate noise. As you would expect, there could be a wid e variety of sources for this type of noise. These would include traffic traveling down a road, running engines and equipment, and people walking. Other sources that you might not consider include wind, aircraft, and thunder. Wind produces noise in a couple of ways but of concern here is its affect on vegetation. If you are surveying near trees, wind causes the branches of the trees to move, and this movement is transmitted through the trees and into the ground via the trees roots. Aircraft and thunder produce noise by the coupling of ground motion to the sound that we hear produced by each. Adaptive Delta Modulation (ADM) Another type of DM is Adaptive Delta Modulation (ADM). In which the step-size isnt fixed. The step-size becomes progressively larger when slope overload occurs. When quantization error is increasing with expensive the slope error is also reduced by ADM. By using a low pass filter this should be reduced. The basic delta modulator was studied in the experiment entitled Delta modulation. It is implemented by the arrangement shown in block diagram form in Figure Figure: Basic Delta Modulation A large step size was required when sampling those parts of the input waveform of steep slope. But a large step size worsened the granularity of the sampled signal when the waveform being sampled was changing slowly. A small step size is preferred in regions where the message has a small slope. This suggests the need for a controllable step size the control being sensitive to the slope of the sampled signal. This can be implemented by an arrangement such as is illustrated in Figure Fig: An Adaptive Delta Modulator The gain of the amplifier is adjusted in response to a control voltage from the SAMPLER, which signals the onset of slope overload. The step size is proportional to the amplifier gain. This was observed in an earlier experiment. Slope overload is indicated by a succession of output pulses of the same sign. The TIMS SAMPLER monitors the delta modulated signal, and signals when there is no change of polarity over 3 or more successive samples. The actual ADAPTIVE CONTROL signal is +2 volt under normal conditions, and rises to +4 volt when slope overload is detected. The gain of the amplifier, and hence the step size, is made proportional to this Control voltage. Provided the slope overload was only moderate the approximation will catch up with the wave being sampled. The gain will then return to normal until the sampler again falls behind. Comparison of PCM and DM When coming to comparison of Signal-to-noise ratio DM has larger value than signal-to-noise ratio of PCM. Also for an ADM signal-to-noise ratio when compared to Signal-to-noise ratio of companded PCM. Complex coders and decoders are required for powerful PCM. If to increase the resolution we require a large number of bits per sample. There are no memories in Standard PCM systems each sample value is separately encoded into a series of binary digits. An alternative, which overcomes some limitations of PCM, is to use past information in the encoding process. Delta modulation is the one way of doing to perform source coding. The signal is first quantized into discrete levels. For quantization process the step size between adjacent samples should be kept constant. From one level to an adjacent one the signal makes a transition of transmission. After the quantization operation is done, sending a zero for a negative transition and a one for a positive transition the signal transmission is achieved. We can observe from this point that the quantized signal must change at each sampling point. The transmitted bit train would be 111100010111110 for the above case. The demodulator for a delta-modulated signal is nothing but a staircase generator. To increments the staircase in positively a one should be received. For negative increments a zero should be receive. This is done by a low pass filter in general. The main thing for the delta modulation is to make the right choice of step size and sampling period. A term overloading is occurred when a signal changes randomly fast for the steps to follow. The step size and the sampling period are the important parameters. In modern consumer electronics short-range digital voice transmission is used. There are many products which uses digital techniques. Such as cordless telephones, wireless headsets (for mobile and landline telephones), baby monitors are few of the items. This digital techniques used Wirelessly communicate voice information. Due to inherent noise in wireless environments the Voice coding scheme chosen. For such an application the presence of robust bit errors must be. In the presence of bit errors Pulse Coded Modulation (PCM) and its derivatives are commonly used in wireless consumer products. This is due to their compromise between voice quality and implementation cost, but these are not robust schemes. Another important voice coding scheme is Adaptive Delta Modulation (ADM). It is a mature technique for consideration for these types of applications due to its robustness in bit error and its low implementation cost. To quantize the difference between the current sample and the predicted value of the next Sample ADM is used. It uses a variable called step height which is used to adjustment of the prediction value of the next sample. For the reproduction of both slowly and rapidly changing input signals faithfully. In ADM, the representation of each sample is one bit (i.e. 1 or 0). It does not require any data framing for one-bit-per-sample stream to minimizing the workload on the host microcontroller. In any digital wireless application there should be Bit errors. In ideal environment most of the voice coding techniques are provided which are good in quality of audio signals. The main thing is to provide good audio signals in everyday environment, there may be a presence of bit errors. For different voice coding methods and input signals the traditional performance metrics (e.g. SNR) does not measure accurately in audio quality. . Mean Opinion Score (MOS) testing is the main important parameter which overcomes the limitations of other metrics by successfully in audio quality. For audio quality the MOS testing is used. It is a scale of 1 to 5 which tells the audio quality status. In there 1 represents very less (bad) speech quality and 5 represents excellent speech quality. A toll quality speech has a MOS score of 4 or higher than it. The audio quality of a traditional telephone call has same MOS value as above. The below graphs shows the relationship between MOS scores and bit errors for three of the most common voice coding schemes. Those are CVSD, ÃŽÂ ¼-law PCM, and ADPCM. A continuously Variable Slope Delta (CVSD) coding is a member of the ADM family in voice coding schemes. The below graph shows the resulted audio quality (i.e. MOS score). All three schemes explain the number of bit errors. As the no of bit errors increases the graph indicates that ADM (CVSD) sounds better than the other schemes which are also increase. In an ADM design error detection and correction typically are not used because ADM provides poor performance in the presence of bit errors. This leads to reduction in host processor workload (allowing a low-cost processor to be used). The superior noise immunity significantly reduced for wireless applications in voice coding method. The ADM is supported strongly by workload for the host processor. The following example shows the benefits of ADM for wireless applications and is demonstrated. For a complete wireless voice product this low-power design is used which includes all of the building blocks, small form-factor, including the necessary items. ADM voice codec Microcontroller RF transceiver Power supply including rechargeable battery Microphone, speaker, amplifiers, etc. Schematics, board layout files, and microcontroller code written in C. Delta modulation (DM) may be viewed as a simplified form of DPCM in which a two level (1-bit) quantizer is used in conjunction with a fixed first-order predictor. The block diagram of a DM encoder-decoder is shown below.   The dm_demo shows the use of Delta Modulation to approximate input sine wave signal and a speech signal that were sampled at 2 KHz and 44 KHz, respectively. The source code file of the MATLAB code and the out put can be viewed using MATLAB. Notice that the approximated value follows the input value much closer when the sampling rate is higher. You may test this by changing sampling frequency, fs, value for sine wave in dm_demo file. Since DM (Delta Modulator) approximate a waveform Sa(t) by a linear staircase function, the waveform Sa(t) must change slowly relative to the sampling rate. This requirement implies that waveform Sa(t) must be oversampled, i.e., at least five times the Nyquist rate. Oversampling means that the signal is sampled faster than is necessary. In the case of Delta Modulation this means that the sampling rate will be much higher than the minimum rate of twice the bandwidth. Delta Modulation requires oversampling in order to obtain an accurate prediction of the next input. Since each encoded sample contains a relatively small amount of information Delta Modulation systems require higher sampling rates than PCM systems. At any given sampling rate, two types of distortion, as shown below limit the performance of the DM encoder.   Slope overload distortion: This type of distortion is due to the use of a step size delta that is too small to follow portions of the waveform that have a steep slope. It can be reduced by increasing the step size. Granular noise: This results from using a step size that is too large too large in parts of the waveform having a small slope. Granular noise can be reduced by decreasing the step size. Even for an optimized step size, the performance of the DM encoder may still be less satisfactory. An alternative solution is to employ a variable step size that adapts itself to the short-term characteristics of the source signal. That is the step size is increased when the waveform has a step slope and decreased when the waveform has a relatively small slope. This strategy is called adaptive DM (ADM). Block Diagram Adaptive Delta Modulation for Audio Signals: While transmitting speech for e.g. telephony the transfer rate should be kept as small as possible to save bandwidth because of economic reason. For this purpose Delta Modulation, adaptive Delta modulation, Differential Pulse-Code modulation is used to compress the data. In this different kind of Delta modulations and Differential Pulse Code modulations (DPCM) were realized to compress audio data. At first the principal of compressing audio data are explained, which the modulations based on. Mathematical equations (e.g. Auto Correlation) and algorithm (LD recursion) are used to develop solutions. Based on the mathematics and principals Simulink models were implemented for the Delta modulation, Adaptive Delta modulation as well as for the adaptive Differential Pulse Code modulation. The theories were verified by applying measured signals on these models. Signal-to-noise ratio Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering measurement, also used in other fields (such as scientific measurement or biological cell signaling), defined as the ratio of a signal power to the noise power corrupting the signal. A ratio higher than 1:1 indicates more signal than noise. In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is. In engineering, signal-to-noise ratio is a term for the power ratio between a signal (meaningful information) and the background noise: where P is average power. Both signal and noise power must be measured at the same and equivalent points in a system, and within the same system bandwidth. If the signal and the noise are measured across the same impedance, then the SNR can be obtained by calculating the square of the amplitude ratio: where A is root mean square (RMS) amplitude (for example, typically, RMS voltage). Because many signals have a very wide dynamic range, SNRs are usually expressed in terms of the logarithmic decibel scale. In decibels, the SNR is, by definition, 10 times the logarithm of the power ratio: Cutoff rate For any given system of coding and decoding, there exists what is known as a cutoff rate R0, typically corresponding to an Eb/N0 about 2 dB above the Shannon capacity limit. The cutoff rate used to be thought of as the limit on practical error correction codes without an unbounded increase in processing complexity, but has been rendered largely obsolete by the more recent discovery of turbo codes. Bit error rate In digital transmission, the bit error rate or bit error ratio (BER) is the number of received binary bits that have been altered due to noise and interference, divided by the total number of transferred bits during a studied time interval. BER is a unit less performance measure, often expressed as a percentage number. As an example, assume this transmitted bit sequence: 0 1 1 0 0 0 1 0 1 1, And the following received bit sequence: 0 0 1 0 1 0 1 0 0 1, The BER is in these case 3 incorrect bits (underlined) divided by 10 transferred bits, resulting in a BER of 0.3 or 30%. The bit error probability pe is the expectation value of the BER. The BER can be considered as an approximate estimate of the bit error probability. The approximation is accurate for a long studied time interval and a high number of bit errors. Factors affecting the BER In a communication system, the receiver side BER may be affected by transmission channel noise, interference, distortion, bit synchronization problems, attenuation, wireless multipath fading, etc. The BER may be improved by choosing a strong signal strength (unless this causes cross-talk and more bit errors), by choosing a slow and robust modulation scheme or line coding scheme, and by applying channel coding schemes such as redundant forward error correction codes. The transmission BER is the number of detected bits that are incorrect before error correction, divided by the total number of transferred bits (including redundant error codes). The information BER, approximately equal to the decoding error probability, is the number of decoded bits that remain incorrect after the error correction, divided by the total number of decoded bits (the useful information). Normally the transmission BER is larger than the information BER. The information BER is affected by the strength of the forward error correction code. CHAPTER II Pulse-code modulation: Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals, which was invented by Alec Reeves in 1937. It is the standard form for digital audio in computers and various Compact Disc and DVD formats, as well as other uses such as digital telephone systems. A PCM stream is a digital representation of an analog signal, in which the magnitude of the analogue signal is sampled regularly at uniform intervals, with each sample being quantized to the nearest value within a range of digital steps. PCM streams have two basic properties that determine their fidelity to the original analog signal: the sampling rate, which is the number of times per second that samples are taken; and the bit-depth, which determines the number of possible digital values that each sample can take. Digitization as part of the PCM process In conventional PCM, the analog signal may be processed (e.g. by amplitude compression) before being digitized. Once the signal is digitized, the PCM signal is usually subjected to further processing (e.g. digital data compression). PCM with linear quantization is known as Linear PCM (LPCM). Some forms of PCM combine signal processing with coding. Older versions of these systems applied the processing in the analog domain as part of the A/D process; newer implementations do so in the digital domain. These simple techniques have been largely rendered obsolete by modern transform-based audio compression techniques. * DPCM encodes the PCM values as differences between the current and the predicted value. An algorithm predicts the next sample based on the previous samples, and the encoder stores only the difference between this prediction and the actual value. If the prediction is reasonable, fewer bits can be used to represent the same information. For audio, this type of encoding reduces the number of bits required per sample by about 25% compared to PCM. * Adaptive DPCM (ADPCM) is a variant of DPCM that varies the size of the quantization step, to allow further reduction of the required bandwidth for a given signal-to-noise ratio. * Delta modulation is a form of DPCM which uses one bit per sample. In telephony, a standard audio signal for a single phone call is encoded as 8000 analog samples per second, of 8 bits each, giving a 64 kbit/s digital signal known as DS0. The default signal compression encoding on a DS0 is either ÃŽÂ ¼-law (mu-law) PCM (North America and Japan) or A-law PCM (Europe and most of the rest of the world). These are logarithmic compression systems where a 12 or 13-bit linear PCM sample number is mapped into an 8-bit value. This system is described by international standard G.711. An alternative proposal for a floating point representation, with 5-bit mantissa and 3-bit radix, was abandoned. Where circuit costs are high and loss of voice quality is acceptable, it sometimes makes sense to compress the voice signal even further. An ADPCM algorithm is used to map a series of 8-bit  µ-law or A-law PCM samples into a series of 4-bit ADPCM samples. In this way, the capacity of the line is doubled. The technique is detailed in the G.726 standard. Later it was found that even further compression was possible and additional standards were published. Pulse code modulation (PCM) data are transmitted as a serial bit stream of binary-coded time-division multiplexed words. When PCM is transmitted, pre modulation filtering shall be used to confine the radiated RF spectrum. These standards define pulse train structure and system design characteristics for the implementation of PCM telemetry formats. Class Distinctions and Bit-Oriented Characteristics The PCM formats are divided into two classes for reference. Serial bit stream characteristics are described below prior to frame and word orient

The History of Welfare in America Essay -- Origins of Public Welfare P

Welfare has been a safety net for many Americans, when the alternative for them is going without food and shelter. Over the years, the government has provided income for the unemployed, food assistance for the hungry, and health care for the poor. The federal government in the nineteenth century started to provide minimal benefits for the poor. During the twentieth century the United States federal government established a more substantial welfare system to help Americans when they most needed it. In 1996, welfare reform occurred under President Bill Clinton and it significantly changed the structure of welfare. Social Security has gone through significant change from FDR’s signing of the program into law to President George W. Bush’s proposal of privatized accounts. The increase in industrialization in the U.S. during the 1820’s caused a rise in homelessness. Women made up the majority of the homeless population. During the beginning of the nineteenth century, private charities helped provide food and shelter for the homeless. Towards the end of the nineteenth century men became the majority of the homeless population. The federal government created â€Å"mother’s pension laws† which were protective labor laws that assisted poor women and children. Shelters required a work test for men to enter and only allowed them to stay for a limited amount of time. Charities did not help men in the nineteenth century (Homelessness in the United States). On October 29, 1929, the roaring twenties ended. The U.S. stock market crashed and the Great Depression began. Those who had invested in the stock market for retirement saw their investments disappear. President Franklin Roosevelt’s â€Å"New Deal† focused first on providing employment for the... ...for Children and Families. 6 Mar 2009. . â€Å"Medicaid Home Page.† 16 Sept 2004. Centers for Medicare & Medicaid Services. 6 Mar 2009. . Shields, Mark. â€Å"Messing with Social Security.† Cnn.com. 7 Mar 2009. . â€Å"Bill of Rights in Action.† June 1998. Constitutional Rights Foundation. 6 Mar 2009. . â€Å"Food Stamp Program.† 4 Feb 2005. Food and Nutrition Service. 6 Mar 2009. . â€Å"Women, Infants, and Children.† 1 Jan 2004. Food and Nutrition Service. 6 Mar 2009. . â€Å"The Future of Social Security.† Mar 2005. Social Security Administration. 6 Mar 2009. .

Essay example --

The Scarlet Letter starts off by throwing Hester Prynne into drama after being convicted for adultery in a Puritan area. Traveling from Europe to America causes complications in her travel which also then separates her from her husband, Roger Chillingworth for about three years. Due to the separation, Hester has an affair with an unknown lover resulting in having a child. Ironically, her lover, Arthur Dimmesdale, is a Reverend belonging to their church who also is part of the superiors punishing the adulterer. No matter how many punishments are administered to Hester, her reactions are not changed. Through various punishments, Hester Prynne embraces her sin by embroidering a scarlet letter â€Å"A† onto her breast. However, she is also traumatized deep within from everything she’s been through. Nathaniel Hawthorne depicts this story of sin by using rhetorical devices such as allusion, alliteration and symbolism. The first rhetorical device used is allusion. An allusion is used to make a reference to a person, place, or thing that has happened. â€Å"they marked out the first burial-ground, on Isaac Johnson's lot, and round about his grave.† After finding a new colony, they allot a portion of soil to a cemetery in King’s Chapel and another portion of land to a prison. Hawthorne uses this to hint something is going to happen later in the story and by saying the Puritans first built a prison and a cemetery before anything else basically leads the whole story to what we know. As we find out at the end, Reverend Arthur Dimmesdale develops a heart disease from stress of the sin he has committed and eventually dies confessing his love for Hester Prynne. In this allusion, a prison, one of the first marks in the town, is built. We le... ...ven symbolize the lesson taught in The Scarlet Letter is beautiful, despite its tragic ending. Nathaniel Hawthorne uses allusion, alliteration and symbolism to tell the perfect story. Anyone can infer from this novel that adultery is obviously wrong. Adultery doesn’t only affect the two people who have committed it, but also affects the townspeople. Keeping quiet causes extreme pain and suffering. The townspeople are always suspicious of each other and no one can trust anyone. Because Reverend Arthur Dimmesdale kept his secret bottled up and Hester admitted to the whole thing, he was left to suffer from guilt. If Dimmesdale came out and told the truth, maybe he would have been spared, lived a free life and survived long enough to spend time with the one he truly loved, Hester Prynne. That means the prison and cemetery wouldn’t mean anything in the future.

Global Financial Institutions Essay

This paper briefly presents the role of global financial institutions, such as the International Monetary Fund, the World Bank, and Asian Development Bank in the global financing; and examines briefly their influence on exchange rate. International Monetary Fund (IMF) Established in 1944, the IMF has a headquarters in Washington DC. , employs 2,596 staff from 146 countries, and is owned and financed by 185 member countries (IMF, 2008). Its main task is to ensure the stability of the international monetary system—â€Å"the system of exchange rates and international payments that enables countries to buy goods and services from each other† (IMF, 2008). To maintain stability in the international monetary system, it provides (1) advice on appropriate social and economic policies, (2) financing to help member countries cope with balance of payments problems when foreign exchange payments exceed foreign exchange earnings, and (3) technical assistance and training to build needed expertise and institutions to attain economic growth (IMF, 2006). To maintain exchange rate stability, member countries prior to 1971 pegged their exchange rates that could only be adjusted with the IMF’s agreement. Since 1971, member countries can freely select any type of exchange rate arrangement: â€Å"allowing the currency to float freely; pegging it to another currency or a basket of currencies; adopting the currency of another country; or participating in a currency bloc† (IMF, 2006). The World Bank (the Bank) The Bank, established in 1944, has a headquarters in Washington DC with more than 100 country offices, and employs about 10,000 staff. It is owned and financed by 187 member countries (World Bank, 2008). The Bank is made up of two development institutions: the International Bank for Reconstruction and Development (IBRD), and (2) the International Development Association (IDA). Each institution has a role in achieving the Bank’s mission of reducing global poverty and improving living standards. The IBRD is responsible for middle income poor countries, while IDA caters to the needs of the poorest countries in the world. Both provide interest-free credit and grants, and low-interest loans to developing countries for infrastructure, health, education, communications, and other purposes (World Bank, 2008). The Bank provides â€Å"local cost financing for projects in non-CFP borrowing countries† with clear indirect foreign costs and â€Å"if a specific project has too little foreign exchange cost to permit the Bank to achieve its project objectives by foreign exchange financing alone† (World Bank, 2007). It also has a project preparation facility that finances foreign exchange costs (World Bank, 2007). Asian Development Bank (ADB) Established in 1966, ADB has a headquarters in Manila with 26 country offices, and employs more than 2,400 staff. It is owned and financed by 67 members with 48 members from the region and other members from other parts of the world (ADB, 2008). As an international development finance institution, it helps its developing member countries reduce poverty and enhance people’s quality of life. It provides assistance to the public sector through grants, low-interest loans, advice, and knowledge as well as to private enterprises through loans, guarantees, and equity investments (ADB, 2008). In making direct loans, ADB assumes the foreign exchange risks involved in private sector operations, but not in public sector lending. To address the foreign exchange risks (e. g. , foreign exchange fluctuations between loan approved amount and disbursement), ADB introduced the LIBOR-based loan, which allows borrowing countries to match the procurement currencies with loan denomination currencies, or convert the loan denomination currencies at any time to match the revenue denomination currencies (ADB, 2004). ADB may also provide financing to meet the â€Å"indirect foreign exchange cost of items procured in local currency for ADB-financed projects with foreign exchange costs† (ADB, 2003). References Asian Development Bank (2008). About ADB. Retrieved June 16, 2008, from http://www. adb. org/About/default. asp. Asian Development Bank (2004, July 1). Foreign exchange risk. Retrieved June 16, 2008, from http://www. adb. org/Documents/Manuals/Operations/OMH07_1apr04. pdf. Asian Development Bank (2003, October 29). Financing indirect foreign exchange cost of projects. Retrieved June 16, 2008, from http://www. adb. org/Documents/Manuals/Operations/OMH07_1apr04. pdf. International Monetary Fund (2008, May). IMF at a glance. Retrieved June 12, 2008, from http://www. imf. org/external/np/exr/facts/glance. htm. International Monetary Fund (2006, September 30). What is IMF? Retrieved June 12, 2008, from http://www. imf. org/external/pubs/ft/exrp/what. htm/. The World Bank (2008). About us. Retrieved June 16, 2008, from http://web. worldbank. org/WBSITE/EXTERNAL/EXTABOUTUS/0,,pagePK:50004410~piPK:36602~theSitePK:29708,00. html The World Bank (2007, March 23). Specific expenditure eligibility and cost sharing requirements for investment projects in countries without approved country financing parameters. Retrieved June 16, 2008, from http://wbln0018. worldbank. org/Institutional/Manuals/OpManual. nsf/22b87a45c65c

Demand Curve and Supply Curve Essay

Demand and supply have been generalized to explain macroeconomic variables in a market economy. The Aggregate Demand-Aggregate Supply model is the most direct application of supply and demand to macroeconomics. Compared to microeconomic uses of demand and supply, different theoretical considerations apply to such macroeconomic counterparts as aggregate demand and aggregate supply. The AD-AS or Aggregate Demand-Aggregate Supply model is a macroeconomic model that explains price level and output through the relationship of aggregate demand and aggregate supply. It is based on the theory of John Maynard Keynes presented in his work â€Å"The General Theory of Employment, Interest, and Money†. It is one of the primary simplified representations in the modern field of macroeconomics and is used by a broad array of economists, from libertarian, monetarist supporters of laissez-faire, such as Milton Friedman to Post-Keynesian supporters of economic interventionism, such as Joan Robinson. Brief history of demand curve and supply curve According to Hamid S.  Hosseini, the power of supply and demand was understood to some extent by several early Muslim economists, such as Ibn Taymiyyah who illustrates- â€Å"If desire for goods increases while its availability decreases, its price rises. On the other hand, if availability of the good increases and the desire for it decreases, the price comes down†. In 1691, John Locke worked on some considerations of the consequences of the lowering of interest and the raising of the value of money. It includes an early and clear description of supply and demand and their relationship. In this description demand is rent: â€Å"The price of any commodity rises or falls by the proportion of the number of buyer and sellers† and â€Å"that which regulates the price of goods is nothing else but their quantity in proportion to their rent. † The phrase â€Å"supply and demand† was first used by James Denham-Steuart in his Inquiry into the â€Å"Principles of Political Oeconomy† which was published in 1767. Adam Smith used the phrase in his book â€Å"The Wealth of Nations† (1776) and David Ricardo titled one chapter of his work â€Å"Principles of Political Economy and Taxation† (1817) On the Influence of Demand and Supply on Price. In The Wealth of Nations, Smith generally assumed that the supply price was fixed but that its value would decrease as its â€Å"scarcity† increased, in effect what was later called the law of demand also. Ricardo, in Principles of Political Economy and Taxation, more rigorously laid down the idea of the assumptions that were used to build his ideas of supply and demand. Antoine Augustin Cournot first developed a mathematical model of supply and demand in his 1838 Researches into the Mathematical Principles of Wealth including diagrams. In1870, Fleeming Jenkin in the course of â€Å"Introducing the diagrammatic method into the English economic literature† published the first drawing of supply and demand curves including comparative statics from a shift of supply or demand and application to the labor market. The model was further developed and popularized by Alfred Marshall in the textbook â€Å"Principles of Economics† (1890). The Standard demand curve and the aggregate demand curve The standard demand curve represents the quantity of a good that a consumer will buy at a given price, holding all else constant. For example, consumer A might buy zero oranges at $1 each, one orange at 75 cents each, and two at 50 cents each, while consumer B might buy one at $1, two at 75 cents, and three at 50 cents. When charted on a grid with price on the vertical axis and quantity purchased on the horizontal axis, these points form the individual demand curves for consumers A and B. The aggregate demand curve represents the total quantity of all goods (and services) demanded by the economy at different price levels. An example of an aggregate demand curve is given in Figure 1. The vertical axis represents the price level of all final goods and services. The aggregate price level is measured by either the GDP deflator or the CPI. The horizontal axis represents the real quantity of all goods and services purchased as measured by the level of real GDP. Notice that the aggregate demand curve, AD, like the demand curves for individual goods, is downward sloping, implying that there is an inverse relationship between the price level and the quantity demanded of real GDP. The standard supply curve and the aggregate supply curve The standard supply curve is a graph showing the relationships between the price of a good and the quantity supplied. The supply curve slopes upward because other things equal, a higher price means a greater quantity supplied. The aggregate supply curve shows the relationship between the price level and the quantity of goods and services supplied in an economy. The equation for the upward sloping aggregate supply curve, in the short run, is Y = Ynatural + a (P – Pexpected). In this equation, Y is output, Ynatural is the natural rate of output that exists when all productive factors are used at their normal rates, â€Å"a† is a constant greater than zero, P is the price level, and Pexpected is the expected price level. This equation holds only in the short run because in the long run the aggregate supply curve is a vertical line, as output is dictated by the factors of production alone. An aggregate supply curve is shown in Figure 2. The aggregate supply curve equation means that output deviates from the natural rate of output when the price level deviates from the expected price level. The constant, a, shows how much output changes due to unexpected deviation in the price level. The slope of the aggregate supply curve is (1/a) which depicts the short-run aggregate supply curve and the long- run aggregate supply curve. The vertical axis is the price level. The horizontal axis is output or income. The short-run aggregate supply curve is downward sloping with slope equal to (1/a) while the long-run aggregate supply curve is vertical with no slope. The reason that the short-term aggregate supply curve is upward sloping is a bit more complex. Factors that determine the slope of AD-AS curve model The slope of AD curve reflects the extent to which the real balances change the equilibrium level of spending, taking both assets and goods markets into consideration. An increase in real balances will lead to a larger increase in equilibrium income and spending, the smaller the interest responsiveness of money demand and the higher the interest responsiveness of investment demand. An increase in real balances leads to a larger level of income and spending, the larger the value of multiplier and the smaller the income response of money demand. This implies that the AD curve is flatter, smaller is the interest responsiveness of the demand for money and larger is the interest responsiveness of investment demand. Also, the AD curve is flatter; the larger is the multiplier and the smaller the income responsiveness of the demand for money. We know that aggregate demand is comprised of C(Y – T) + I(r) + G + NX(e) = Y. Thus, a decrease in any one of these terms will lead to a shift in the aggregate demand curve to the left. The first term that will lead to a shift in the aggregate demand curve is C(Y – T). This term states that consumption is a function of disposable income. If disposable income decreases, consumption will also decrease. There are many ways that consumption can decrease. An increase in taxes would have this effect. Similarly, a decrease in income–holding taxes stable–would also have this effect. Finally, a decrease in the marginal propensity to consume or an increase in the savings rate would also decrease consumption. The second term that will lead to a shift in the aggregate demand curve is I(r). This term states that investment is a function of the interest rate. If the interest rate increases, investment falls as the cost of investment rises. There are a number of ways that investment can fall. If the interest rate rises, say due to contractionary monetary or fiscal policy, investment will fall. Similarly, in the short run, expansionary fiscal policy will also cause investment to fall as crowding out occurs. Another interesting cause of a fall in investment is an exogenous decrease in investment spending. This occurs when firms simply decide to invest less without regard for the interest rate. The term variable that will lead to a shift in the aggregate demand curve is G. This term captures the whole of government spending. The only way that government spending is changed is through fiscal policy. Recall that the budgetary debate is an ongoing political battlefield. Thus, government spending tends to change regularly. When government spending decreases, regardless of tax policy, aggregate demand decrease, thus shifting to the left. The fourth term that will lead to a shift in the aggregate demand curve is NX(e). This term means that net exports, defined as exports less imports, is a function of the real exchange rate. As the real exchange rate rises, the dollar becomes stronger, causing imports to rise and exports to fall. Thus, policies that raise the real exchange rate though the interest rate will cause net exports to fall and the aggregate demand curve to shift left. Again, an exogenous decrease in the demand for exported goods or an exogenous increase in the demand for imported goods will also cause the aggregate demand curve to shift left as net exports fall. An example of this type of exogenous shift would be a change in tastes or preferences. The aggregate demand curve also can shift right as the economy expands. When the aggregate demand curve shifts right, the quantity of output demanded for a given price level rises. Therefore, a shift of the aggregate demand curve to the right represents an economic expansion. A shift of the aggregate demand curve to the right is simply affected by the opposite conditions that cause it to shift to the left. A change in one or more of the following determinants of aggregate supply will shift the aggregate supply curve in the short run. – Change in the input prices (domestic or imported resources price), change in productivity, change in legal institutional environment (business taxes and government regulation). An increase in short-run aggregate supply will shift the curve rightward; a decrease will shift the curve leftward. The long run aggregate supply curve is vertical. Similarities between the Ad-AS curve model and the standard demand-supply curve model The conventional â€Å"aggregate supply and demand† model is actually a Keynesian visualization that has come to be a widely accepted image of the theory. The Classical supply and demand model, which is largely based on Say’s Law, or that supply creates its own demand depicts the aggregate supply curve as being vertical at all times. The both demand curve and the aggregate demand curve is negatively sloped from left to right and both curves represent the law of demand. The short-run aggregate supply curve or SRAS curve has similarities the standard supply curve. Both are positively sloped. Both curves relate price and quantity. Differences between the Ad-AS curve model and the standard demand-supply curve model In aggregate demand curve, there is no substitute effect because we cannot substitute all goods. But in standard demand curve it exists. The aggregate demand curve has no income effect because a lower price level actually means less nominal income for the resource suppliers’ e. g. lower wages, rents, interests, and profits. But in standard demand curve it exists. The major differences between the standard supply curve and the aggregate supply curve are as follows- for the market supply curve, the vertical axis measures supply price and the horizontal axis measures quantity supplied. For the short-run aggregate supply curve, however, the vertical axis measures the price level (GDP price deflator) and the horizontal axis measures real production (real GDP). The positive slope of the market curve reflects the law of supply and is attributable to the law of diminishing marginal returns. In contrast, the positive slope of the short-run aggregate supply curve is attributable to: (1) inflexible resource prices that often makes it easier to reduce aggregate real production and resource employment when the price level falls, (2) the pool of natural unemployment, consisting of frictional and structural unemployment, that can be used temporarily to increase aggregate real production when the price level rises and (3) imbalances in the purchasing power of resource prices that can temporarily entice resource owners to produce more or less aggregate real production than they would at full employment. Conclusion Whereas the standard supply and demand curve model discusses on individuals, the aggregate supply and demand curve model works with the whole economy. This model is built on the assumption that prices are sticky in the short run and flexible in the long run. This model also highlights the role of monetary policy. This model shows how shocks to the economy cause output to deviate temporarily from the level implied by the standard model. By this model, we can observe the economy more efficiently than before.