Trovan Essay Example | Topics and Well Written Essays - 500 words

Trovan - Essay Example Trovan of Pfizer, an unapproved drug, was administered in children at the hospital of Kano in 1996, which came to the public attention only in December 2000. Pfizer picked approximately 200 children for their clinical trial, of which 100 children were administered with Trovan whereas the other half was treated with the standard anti-meningitis drug Ceftriaxone that also acted as the control group. The children who were treated with Ceftriaxone, a cephalosporin antibiotic, were given an initial dosage level of 100 mg/kg dose which was subsequently reduced to 33 mg/kg to reduce the pain caused by intramuscular injection. These children, who had reached the hospital for their treatment of meningitis, were hand-picked randomly by the doctors of Pfizer. These children were also given tags to identify the drug they received. These two batches of children continued their treatment with Trovan and Ceftriaxone for five consecutive days and were monitored either in the hospital or out-patient clinics, depending on their health. Those children who required additional care were transferred to another hospital at the expense of Pfizer. The study was concluded after four weeks and a follow-up exam was conducted by Pfizer. The results at the end of the trial conducted at Kano IDH recorded a survival rate of 94.4% at Kanos IDH against the overall survival rate in Nigeria of 90%. However, this anti-meningitis trial treatment was not devoid of mortality issues. Five children out of 100 children treated with Trovan and six out of 100 children treated with the standard drug Ceftriaxone died after the treatment. Though the follow-up conducted by the Pfizer team reported that there were no unusual side-effects, unrelated to meningitis, the children treated with Trovan did develop symptoms of arthritis, though no evidence relating the drug to this development is available. Trovan was being developed for its

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

Education Essay -- essays research papers

Education   Ã‚  Ã‚  Ã‚  Ã‚  In many different ways, American cultural life during the Jeffersonian Era began to appear as a reflection of the Republican vision of the future. The Republicans had observed many modernizing trends, some of them favorable and others detrimental to their view of an ideal society. American religion began to adjust to the spread of Enlightenment philosophies. However, one of the most notable alterations was the new emphasis placed upon education. As more and more opportunities for learning arose, the nations literary and artistic life began to digress from the European influences which had governed early colonial society for years. In many respects, the new culture was the antithesis of many Republican ideals, and the new education system fell into that category.   Ã‚  Ã‚  Ã‚  Ã‚  The foundation of the Republican conception of America was based upon a virtuous and educated population; Jefferson himself called for a â€Å"crusade against ignorance.† Unmistakably, the Republicans believed that a nationwide system of schools should be created to produce the first wave of an educated populace, which they believed was necessary to the advancement of society. Under the Republican view, all white male citizens would receive a free education. Nonetheless, they were unable to actualize that ideal. However, many of the Republican efforts to better education would in turn spur a movement later on in which an erudite society would thrive...

My Worst Nightmare

As the rain hit me like a thousand knifes, I checked my disreputable, scruffy watch for the time. I had a few more minutes until I had to be at the diminutive, quiet corner shop across from the busy train station to meet Emmy before school. The rain was starting to come down heavier so I took out my incomplete tartan umbrella and covered my reddish-brown hair. Black clouds filled the sky like poisonous fumes in the clear blue sky. I could barely see the deserted phone box ahead of me because of the intense muggy fog. I started to feel worried and nervous as I hated Emmy shouting at me every time I was late. I heard a car pull up by the side of the abandoned street a few metres ahead of me. From what I could see, the old car was blue and inside it were two men. As I innocently hurried past the tatty vehicle one of the men bellowed†¦ â€Å"Scuze me, got the time darlin'?† â€Å"Sorry, I'm in a rush, can't stop.† I replied â€Å"Jump in, I'll drive you. Where you off to?† I thought about it for a few seconds then took up the offer. â€Å"Well just around the corner then, cheers.† â€Å"Hop in then, what ya waiting for?† I didn't feel scared, although I knew it was wrong. I was fine; I just concentrated on getting to the shops in time. Time passed slowly and the traffic was diabolical. â€Å"Look guys, thanks a lot but if you don't mind I'll get out here and walk, the traffics gonna take forever† â€Å"No, we'll get you there don't worry.† I unlatched my rough seat belt and attempted to open the chipped, jammed door but it just wouldn't budge. I started to panic; the two men who seemed to be nice gentlemen had now turned into my worst nightmare. Sweat poured down my delicate face like a swiftly dripping tap. â€Å"You're staying put young lady, until I say so† said the driver sternly. I was terrified, where were they taking me? I slowly pulled out my red, run down phone and started to dial in ‘999'. I trembled with fear as I keyed in the three simple digits. â€Å"What you got there hey?† I quickly slid the phone behind my stiff back as I hesitated to answer the fully-grown, evil looking man. â€Å"Nothing, I swear, nothing† † You liar, give that to me you little brat!† I started to cry, I felt scared, I wish I'd taken the sensible way out and walked to meet Emmy. We passed the bakery; I could smell the succulent sweet, freshly cooked bread, which reminded me of home. Tears ran down my cheeks like the rain on the car window They pulled up outside a desolate warehouse, fear ripped through me like a cat tearing at a cushion. I looked around to see if I recognized where I was but I could just about focus on the horse riding stables and I knew that I was close to a local bus station. They dragged me into the warehouse like a sack of rotten potatoes. The warehouse smelt of vermin and vomit. It was dark and bloodcurdling. The walls were painted dark, repulsive green and they were covered in dirt and stains. There were only two chairs in the tiny warehouse, except for a few empty cans of beer lying around the floor. Rats scattered the cold floor for the slightest bit of food. The air was misty and smelt of damp clothes. The men tied me up to a loose, rusty radiator and started to search my pockets, they pulled out a florescent green lighter. The small man laughed in my face and dashed the lighter across the floor. I felt my heart skip a beat. The tallest man slapped me across the face, I screamed with pain and trepidation. â€Å"AAAhhhhhhhhh!† I began to aggressively cry again, the small hideous man kicked me and slammed an empty Fosters can in my eye. It hurt like hell. How long would I be here? Thos questions ran back and forth through my head like a swing. As the men headed towards the door, the tall obese man called out â€Å"there's no way of escaping!† They both sneered with joy together as they left me alone in the empty warehouse. I lent back against the freezing, brittle radiator. Tears streamed down my face. ‘How could I be so stupid?' I thought of my mum, I wanted to be with her, for her to cuddle me like I was a little kid again. â€Å"Help, can anybody here me?† I gave up, nobody could here me, and so I sat there and waited, and waited. I suddenly heard a knocking at the door. â€Å"Hello?† I was desperate to here a reply. â€Å"Help me please, I can't get up, I'm tied up† Surprising there was a voice, a friendly voice. â€Å"Just give me a minute, I'm doing all I can to get in† My heart was beating faster than the speed of light. This could be my chance to get out, to escape and be free of these daunting men. The person on the other side of the door was shaking the door and from what I could here it sounded like they were hitting the door with an axe. After 20 minutes the door finally gave way, and when it opened, standing in the doorway was a tall figure. He ran over and started to untie the ropes around my arms and legs. I stood up and stared at the man, he looked so kind and gentle. I gave him the biggest hug and insisted we got out of there as quickly as possible. The man, Mathew, drove me home. In the car it was silent, I was still in great shock and he didn't know what to say to make me feel better. When we got to my road, I thanked him and got out of the car. He watched me walk to my door to make sure I got there ok. I rang the bell, and after a few seconds my mum answered the door. It was such a relief to see her; I gave her a massive hug as tears streamed down my face. She looked at me in confusion as we went into the house. We both sat down on the leather sofa, as I began to tell her the story of my worst nightmare.

Things fall apart 5

Things fall apart 5 Polygamy in Things Fall Apart It is obvious that in reading Things Fall Apart that polygamy was alive and well in the village of Umuofia. Not only was it accepted it was expected.Men's wealth was judged by their huge barns [and their] number of wives and children. The more wives a man had, usually meant more children. If a man had several wives and many offspring, he of course had to provide for all of them, hence more land [was] needed for planting crops, and more barns for storing food. Men seemed to benefit greatly from having more than one wife, but did they really? A man was not only judged by the amount of wives, children, crops, and barns that he had, but also judged on how he ruled his women and what control he had over them.Folkestone - July 2010 - Shorts Candid with Wife T...In Things Fall Apart, the tribe was preparing for the New Yam Festival. Okonkwo had three wives at the time of the festival. As Okonkwo sat in his hut, each wife sent a dish in order of importance. Wife number one sent the first dish and so on. Not a bad set up if Okonkwo did not like what his first wife prepared, he had two more meals to fall back on. If a man's first wife did not produce the sons he longed for, he had other wives to impregnate and hope they would produce the sons he desired. In Things Fall Apart, the book seems to depict men as getting all the benefits of polygamy, or do they? What about the relationships between the wives? Do they all get along? Are they jealous of one another? Can a man really live with more than one wife in total peace? For example wife number one bears...

Tips on how to be outgoing and social

Tips on how to be outgoing and social How to become more outgoing and social student Some students face some difficulties with socializing while entering the university. It can be not easy to make new friends and reveal yourself. However, there are many useful tips which can help you become more outgoing and social student. You should just practice a lot, become more confident, and present yourself to your student community. Make the eye contact It is very important to make eye contact with the people around you while being in different social situations. Eye contact establishes the connection between people. You look can be understood as invitation. Establish eye contact and give a friendly smile. It is just perfect if the person responds, but otherwise don`t force interaction on somebody who isn`t interested in you. Being outgoing means to know where and when you should approach other people. Don`t be shy to introduce yourself Of course, it is not an easy task to introduce yourself when you are somewhere on a social meeting. You can find many people who may feel the same as you. Be the first to say â€Å"hello†. Be friendly and outgoing, but not pushy. Leave the person, if he or she is disinterested. Search for a common interest Find out which things you have in common with the person you have just got acquainted with. Talk about your mutual friends, work, interests, and hobbies. Such themes should open up further topics for your conversation. Be careful and try to avoid judgmental and offensive comments. Go on working on your existing friendships Improve your relations with people you know for a very long time. Become more connected and try to gain new experiences together. You can easily introduce each other to new people and expand the circle of acquaintances. Remember that being outgoing is a skill It can take some time to learn the skill of being outgoing. Just set a goal and work persistently on yourself. Decide what exactly challenges you. Don`t be afraid to ask some outgoing people about how they managed to achieve such success in overcoming their social phobia. Change yourself for you Don`t start your inner changes only because somebody told you to do that. It should be your own initiative. You should remember that being shy and being an introvert is quite normal. In any case you have to be yourself and behave naturally. However, if your shyness bothers you, try to do something to feel yourself more comfortable. Practice your smile A real smile produces feeling of happiness, lowers stress, and brings positive emotions and joy. If your smiling is natural, the muscles around your eyes and mouth are activated. So, practice your smiling in front of the mirror. Dress for success The way you look can help you be more outgoing and confident. Dressing expresses your personality and your feeling about yourself. If you are nervous about going somewhere just wear those things that make you feel attractive and powerful. You can easily make some compliments to the person who is wearing something you really like. Join a club and master a hobby It is a good idea to join a club and interact with people who share the same interest with you. Clubs are great for shy people as they encourage socializing and make them share their experiences. Moreover, your hobby can help you become more outgoing, confident, and proud. You can always share your interests with your new acquaintances. Try talking to new people Talk to anyone and everyone. Of course, it can be quite uncomfortable to talk with strangers, but the more you try, the easier your interaction with people will be. Be an active listener It is very important to show the person that you are engaged in the conversation. Focus on the topic, look at the person, nod, repeat central ideas, use brief expressions, don`t interrupt, and don`t plan your response.

Business Plan for EuroFlorida Case Study Example | Topics and Well Written Essays - 3500 words

Business Plan for EuroFlorida - Case Study Example More and more frequently, the "grey gold" of north Europe (Scandinavia, Germany and the UK) are liquefying their assets and moving to south Europe. Their destinations are often Spain and south France. Indeed in Spain a large building industry has started up building "pensioner complexes" to cater for the market, similarly in south France, house prices are rising significantly. Smaller markets in the English-speaking Med (Gibraltar and Malta) have seen very dramatic rises in real estate value. However Apulia (the "heel" of Italy) is a relatively undiscovered region; prices are very reasonable and indeed, for a decade, Apulia was the poorest region of the (old) EU. The infrastructure, however, is excellent, with an airport at Bari, a motorway all the way to Vienna and the European net, excellent train connections within Italy and by ferry to Greece. Climatically Apulia is the second most "blessed" region of the EU, after Portugal's Algarve. Temperatures are, however, not extreme and th e landscape is lush, fertile and green. It is an area of small industry, as well as being extremely rich in culture & history. This plan sets out EuroFlorida objectives and targets for 2009 /10... The Mission and vision: EuroFlorida's contractual obligation is to be able to render Europe's finest service for promising the possession of property in addition to other assisting property business. EuroFlorida's revelation is carrying out property dealings which are unproblematic for all. In order to be able to accomplish this visualization, EuroFlorida will need to present an array of alternative selections to their clientele , this is the element that will make them capable enough to conduct a complete transaction in a way that would be most appropriate to their personal otherwise trade requirements, however be able to equalize this alongside the responsibility towards the government within the Apulia state as a major stakeholder to present a cost efficient resolution. The long term premeditated objectives: EuroFlorida's approach is looking forward towards developing as well as improving the already existing land and property. Together with initiating work over the new found property for providing services, and satisfying the needs of our clientele, along with the by and large desire of carrying out property dealings that would satisfy most of our customers. This matter to be precise will encompass carrying out sales and purchase deals, refurbishing deals, and other property deals that are included in our services. These services in total have been specified time and again within the coming pages of this paper. The management at EuroFlorida has been able to recognize the following major segments. At the same time as the customer dealing system is most likely going to be World Wide Web, the most important dare is within the supply chain.