Signal generators also know as function generator or test oscillator The WritePass Journal

Signal generators also know as function generator or test oscillator ABSTRACT Signal generators also know as function generator or test oscillator ABSTRACTINTRODUCTION ­SIGNAL GENERATOR (Outline and types)ARBITRARY WAVEFORM GENERATORFUNCTION SIGNAL GENERATORDESIGN OF SIGNAL GENERATORSOPERATING PRINCIPLES OF SIGNAL GENERATORFUNCTIONS AND APPLICATIONSVERIFICATIONCHARACTERIZATIONSTRESS AND MARGING TESTINGCONCLUSIONREFERENCESRelated ABSTRACT Signal generators also know as function generator or test oscillator, have come to be more popular and most used testing device for the engineers especially and also for the medical sector. Signal generator delivers an accurate calibrated range. It provides a signal that can be adjusted according to the frequency, output voltage, impendence, waveform and modulation. It has been in existence and they are used in so many ways before time till present. An American inventor Nikola Tesla has conveyed electricity from one location to another in the form of signal and uses the same frequency. This report talks about the overview of a signal generator, how they do function using their applications and also describe to us their operating principles using the direct digital synthesis DDS, their types and designs. The Next page gives you a brief introduction about the early days of signal generator and how they are been used in those days. INTRODUCTION Before the Initiation of this device called signal generator which is around 1906 to 1920 are regarded to be the early days of radio, the only way for testing of new apparatus or electronic instrument was to use another similar device to create the signal, which was the case of new tools and modulation format in radio. During that time, this basic method of testing worked excellently with minimum percentage errors, but problem arises when there is a circumstance whereby they might be diverse devices under test. To solve this problem, there must be need for so many reference devices. One radio’s was picked which was used as a performance parameter and was measured which was now used as the standard or â€Å"golden radio† as it has been called. Even if they are expensive,   a regular change in their functioning features either during a short time as a result of warming up or during a long time as an effect of continued use, and for this reason their will be reduction in their accuracy. The need for signal generator that can effectively used to test devices as the field of engineers must be to reduce this flow. However, we are going to explain the device â€Å"signal generator† in this report and also we will discuss about the operating principles, and also the things I have already mention in the abstract area. In this next page, we will be looking at the overview of this device signal generator.  ­SIGNAL GENERATOR (Outline and types) A signal generator also called a function generator or a text signal generator is an electronic device designed to perform a variety of operations which includes band pass filter characteristics, the response of amplifiers to frequency or fault tracing in many electronic equipment and circuits. â€Å"Signal generator is a tool widely used in fields such as industrial electronic instrumentation, medicine, production, communication and research†, (Alloca and Stuart, 1983). A signal generator is the stimulus source that pairs with an acquisition instrument to create the two elements of a complete measurement solution. In its various configurations, signal generator can provide stimulus signals in the form of analog waveforms, digital data patterns, modulation, noise and it may add known, repeatable amount and types of error (distortion) to the signal it delivers. Signal generator can produce the most types of waveforms or signal which are square waves, sine waves and triangular waves over a wide range of frequency. Coombs, (1972) declares that the frequency range of a signal generator maybe less than 1Hzto at least 1MHz. Some other type of signal generators, have the ability to produce pulse, trapezoid and ramp waveforms including the ones mention above. Therefore, there are many types of signal generator designed to a variety of uses which has much possible application meaning that one particular type of signal generator may not be suitable for all pur poses. Here are the two main type of signal generator Arbitrary waveform generator Function signal generator Below is a picture example of a typical function generator: ARBITRARY WAVEFORM GENERATOR Arbitrary waveform generators (AWG) are complicated playback system that delivers waveforms based on stored digital data that describes the regularly changing voltage levels of an AC signal. The arbitrary waveform generator can produce any kind of waveform you can think of. You can use many methods to create the needed output (from mathematical formulae to drawing the waveform). FUNCTION SIGNAL GENERATOR Function generators are more simple compare to arbitrary waveform generator. They generate simple signal in wave form and this signals are been produce by a circuit which creates the repeating wave which is usually a sine wave. They are most often use in process of designing or repair simples electronics. DESIGN OF SIGNAL GENERATORS Before the modern waveform generators were initiated, analog was the mode of operation. In some industries, analog refers both to the circuit technique used to generate signals and to the signal themselves. Functionality, economic feasible, and types of waveform needed have really change the design of signal generator in period of times, although the traditional analog signal generators still exist till date. The analog is a means to represent a material measure, for instance an indicator on a current meter (regulator), by a quantity whose measurement is known. Such measurements, do not really give the accurate result of a particular tool or device under test, as they are prone to having drifts in their working parts. Most modern signal generators are based on the digital technologies such as the modern function generators which uses a technology known as Direct Digital Synthesis (DDS) which are able to provide a wide range of signal or waveform. The DDS device are more like to generate analog signals via creating a digital output signal that is continuously pulsed by a clock signal and at last translating the digital signal to form an analog signal. Below is the experimental diagram of this process. The Method above, illustrate that the input is supplied into the 8bit counter which evaluate the input with an analog, (Q5 to Q0). The matching analog now is been verified with an already stored address which is the ROM (Read Only Memory) 256 x 8. As the counter cycles through the 256 different addresses, which the ROM has for each analog, the ROM counter now picks out a digital value corresponding to that address which sequentially represents the input. This information is then processed and outputs the 256 data points to the DAC (Digital to Analog Converter) which is the 8bit converter. The analog signal obtain is then shown as a waveform. An example of a generator that uses this method illustrated above is the 20MHz sweep function generator from BK Precision (model 4040DDS) image is shown below. According to BK Precision (2010), this sweep generator is a full featured DDS generator, the unit generate superb quality waveforms with a high signal precision and stability and it provides sine and square wave outputs over the frequency range from 0.1Hz to 20 MHz in one extended range. Most of the DDS generator today are dedicated instrument, simple and comfortable, and are at low cost from a few tens of dollars to tens of thousand of dollars. In the next section, we are going to look at how this device operates. OPERATING PRINCIPLES OF SIGNAL GENERATOR In this 21st century, most of the modern function generators use Direct Digital Synthesis (DDS) technology to generate output wave forms. BK Precision sweep function generator (model 4040DDS) happens to be among one of this generators. This section describes how DDS technology works. There are two fundamental ideas of DDS technology which includes: Producing an arbitrary waveform that can be in various waveforms or not assigned a particular value from a periodic ramp signals. Producing a digital ramp. First, consider producing wave function that can be in various waveforms or not assigned a particular value from a periodic ramp signal. To make this explanation more simple and understandable, imagine the ramp period (t) is greater than or equal to 0s (t ≠¥ 0), then lets call the recurring ramp function R(t) as shown in the diagram below. This ramp function R(t) as shown in figure 1 differs linearly or oscillate between 0 and 1 with period T. Now, suppose their is a new function F(t) that is defined on the interval 0≠¤ t ≠¥1, in mathematical terminology, the domain of the function which is the values assigned to the independent variables of F(t) is the half-closed interval. Imagine to construct another wave function of period T which is similar to R(t) with the shape of F(t) and assuming again that the period is 4s using the diagram shown in figure 4, we will notice that as the time increases from t0 to t4, which is equal to one period, there is a sequence which implies that their will be a gradual rise in the function until t4, therefore calculating the corresponding value of each time and removing the integer part of it. For instance, tn=  Ã¢â‚¬â€œ . The calculation for t0 to t8 is shown in the table below using the figure 4 diagram. The illustration shows that there is a rise in the time value, in the sense that when one period is reach, it will start over again until another period is reached. This is how it works continuously for the defined time interval. This means that it resets after each successive cycle. On the other hand, the resetting of the time interval is carried out by a phase accumulator which is the first time interval that is the t1 = frequency. In the above example, the waveform that was created has a frequency of 0.25Hz and a phase angle of 90  that means the frequency is x360 As BK precision (2010) guild book instruct that to produce a digital ramp, as an alternative of increasing the time intervals by 1s, let the increment be in terms of ÃŽ ±, the phase angle, by the digital clock and for an N-bit counter, it will count from 0 to 2N – 1, then reset to 0 again. For example, let the value of be N = 4, which will be (24), therefore the counter result is 16 bits. When a signal is received, it will only match up to one of the bits frequencies and the waveform of that frequency will be generated. Lastly, the generated waveform might be displayed as a square or triangular signal using the control buttons on the device. This is made possible by including an operating amplifier (op-amp) in the circuit. Assume the received input signal was a sine wave, it can be converted to a square waveform; an op-amp acts as a comparator that gives and output signal of â€Å"1† only when the amplitude of the sine wave is greater than 0 and a â€Å"-1† when the amplitude is less than 0. According to Floyd (2009), this change was essential because digital data processing and transmission can be more effective and dependable than analog data and it’s of advantage when data storage is needed. FUNCTIONS AND APPLICATIONS Signal generators have hundreds of different applications and function that are suited for variety of use in many fields but in electronics measurement context, they fall into three basic types: Verifications Characterization Stress and margin testing VERIFICATION In the world of electronic and technologies, wireless equipment designers that are building new transmitter and receiver hardware must stimulate baseband I and Q signals (with or without impairments), to verify some wireless standards, a high performance arbitrary waveform generators can provide the needed low-distortion, high-resolution signals at rates up to 1GB/secs. CHARACTERIZATION This is a state whereby the newly developed digital to Analog converter (DAC) and the Analog to digital converters (ADC) must be systematically tested to determine their limits of undeviating, distortion and so on. STRESS AND MARGING TESTING Advanced signal generators, save the engineers hours of calculation by providing efficient built- in jitter editing and generation tools because engineers that works with the serial data stream architectures; commonly used in digital communications buses and disk drive amplifiers, need to stress their devices with impairment especially jitter and timing violations so engineers must characterize their emerging designs to ensure that the new hardware meets design specifications across the full range of operation and more. However, using this device, much difficulty in electronics and also field like the medicine can now be resolute easily.   To design an assorted signal and a high speed low filter data, an arbitrary waveform generator can be used. They are specifically design for it. Radio frequency signals are used to achieve tests on radio transmitters and receivers. (Theraja and Thereja, 1959)   Signal generators that are connected to oscilloscopes can be use in testing faults in electronic equipment and devices. In telecommunications today phones functions using signals, for example: the process, transmit and receive data. Devices for example: digital X-ray appliances, brain mapping system and advanced cardiology uses signal in most medical field today. CONCLUSION The modern DDS generators have some advantages and disadvantages of it depict that they help in solving solutions in various fields. Describing about the advantages of DDS, you discover that their frequency is tuneable with sub-Hertz resolution; their phase angle is digitally adjustable, as long as the clock is stable, they don’t go with the flow due to temperature changes or aging of components, addition of arbitrary waveform generator is not theoretically difficult and lastly they have simple design and low parts count which help to keep cost down. However, describing the disadvantages of this machine has to do with the negative aspect which is their output frequency is ≠¤  ½ the clock frequency, their amplitude is also fixed that is; they need external circuitry to change, sine wave is sampled and not spectrally pure; distortion is present at that moment. But this disadvantages, does not cost more harm the technology is still the best and with more careful design in future, these advantages can me minimized. REFERENCES Floyd, L. (1977) Digital Fundamentals. 10th Edn. Upper Saddle River, New Jersey: Pearson Education Ifeachor, E. and Jervis, B. (2002) Digital Signal Processing. A Practical Approach. 2nd Edn. Harlow, England: Pearson Education Hill, A. (2010) What is signal generator? Available at: wisegeek.com/what-is-a-signal-generator.htm (Accessed 15 March 2011.) Nashedky, B. (1996) Electronic Devices and Circuit Theory. 6th Edn. Englewood Cliffs, New Jersey: Prentice-Hall. Peterson, D. and BK Precision (2010) Function Generator and Arbitrary Waveform Generators Guidebook. Available at: bkprecision.com/support/downloads/guides/Function_and_Arbitrary_Waveform_Generator_Guidebook/BK-Function-Generator-and-AWG-Guidebook.pdf. (Accessed: 25 March 2011) Alloca, J. and Stuart, A. (1983) Electronic Instrumentation. Reston, Virginia: Prentice-Hall. Crecratf, D. et al (1990) Analogue and Digital Electronics. Great Britain: The Open University Referencec.com (2010) Signal generators. Available at: reference.com/browse/signal+generator (Accessed: 14 April 2011) Theraja, B. And Theraja, A. (1959) A Textbook of Electrical Technology. 23rd Edn. Reprint 2003. Ram Nagar, New Delhi: S. Chand Company Ltd. Coombs, C. (1972) Handbook of Basic Instrumentation. New York: Mc Graw-Hill Yourdictionary.com (2010) Nikola Tesla Biography. Available at: http://biography.yourdictionary.com/nikola-tesla (Accessed 18 April 2011) Tektronics (2008) Signal generator fundamentals Guidebook. Available at: http://circuitslab.case.edu/manuals/Signal_Generator_Fundamentals-_Tektronix.pdf (Accessed 20 April 2011) ZTech Instruments (2010) Waveform Generator Fundamentals. Available at: ztecinstruments.com//applications/waveform-generator-fundamentals.php (Accessed: 6 April 2011)

What strategic influence does Special Operations have Research Paper

What strategic influence does Special Operations have - Research Paper Example This research aims at analyzing the nature and the characteristics of special operations and the strategic influence that they have on the target population. Special operations demand the use of special methods of employment, special techniques, tactics, procedures as well as equipment. Special operations acquire significance in harsh environments characterized by high level of hostility, denial and environments that are most sensitive politically or diplomatically. These operations are thus more time sensitive and concealed in nature. Special operations according to Derek (2006, 149) have lower visibility, work in collaboration with local forces and require greater regional point of reference as well as cultural proficiency. Special operations require very high level of intelligence and the intelligence organ must have a good understanding of the major activities. It must be capable of approving all the logistical requirements within the shortest time possible, which is usually within a span of fifteen days. The communication system has to be significantly efficient to ease collection of information from the ground as well as coordination within the staff members involved to arrive at the best solution for the prevailing situation. In operating in remote areas, according to Derek (2006, 252) special operations mostly require the use of long range and surface oriented combined firing support. With special operations, offensive actions can be either by seizing the core facilities of the people as a piece of the wide operation or utilizing a guerilla war tactic of hitting and running away to cool the chosen targets. Even though the other ordinary units are capable of carrying out such operations, special units perform with greater precision thus yielding better results. Special Forces are also capable of conducting such operations in areas where the other ordinary units cannot reach. A common characteristic of special operations is effectiveness in terms

Policy control process Essay Example | Topics and Well Written Essays - 2000 words

Policy control process - Essay Example The overall set up is termed polity. In a modern society the pivotal principle of polity specifies that power be legitimated by the reference to the consent of the governed, that is, each person must have a more or less equal voice in providing this consent. The arrangements in a society like political parties, lobby groups and social movements are the tools invented to express the consent. (Ritzer, 2000, pp579) Hence the policy makers retain the power of controlling the process in their own hands. This exhorts them to opt for elite theory and makes them politically elite. But generally elitists do not opt to get involved in politics; they get everything done through political stalwarts. They even posses complete control over the entire government. Its size, wealth, status, organizational strength, leadership, access to decision makers and internal cohesion, determine the proportionate strength of an elite group. While elitism cannot be challenged anywhere in this globe, pluralism is a supporting modality for elitists to reach their goal. Socially elite groups of Australia were trying hard for the upbringing of the aborigines, the 40000 years old primitives of the land. The Constitution of Australia prevented the federal government from directly aiding the aborigines. However with the help of the socially elite groups Australians got the clause removed in 1967. (World Book Encyclopedia, 1995, pp778). The elite theory does not compromise in its core, that is, powerful minority rules the masses. However the perseverance of the elite group in accomplishing their goal imparts them a type of immortality. 'White Australia Policy' was in vogue for about 70 years since, 1901. The Immigration Restriction Act passed in 1901 excluded the entry of Asians on the basis of a dictation test on any European language. But an epochal decision by the government in 1993 that affirmed aboriginal land rights diverted the entire attention to aboriginal Australians. This made Australia close to Asia and 'White Australia Policy' was allowed to die slowly. A new official policy of multiculturalism was created, which was very similar to cultural pluralism, an offshoot of cultural diversity. (International Encyclopedia of PROPAGANDA; pp60) Pluralism has paved way for smooth running of government in the land. The power of the Governor General of Australia to appoint more than one minister for one portfolio is the indication of the effect of pluralism conceived in a healthy manner. The Cabinet ministers collectively take major decisions on government policy matters and programs. They bear the collective responsibility on the decision arrived at. If one minister is not willing to support, he resigns and the remaining ministers who made the decisions shoulder the responsibilities. The business of policy making is normally done at Cabinet meetings of the ministers only. Since a Cabinet is an unofficial body it can conduct its business with flexibility, confidentiality and informality. The Cabinet primarily concerns itself with policy rather than the form of actions and legal restraints or legal instruments. It is the part of executive council, which includes parliamentary secretaries and some ministers too to approve gover nment's subordinate legislations. Policy decisions are normally arrived at after combining three important factors. They are: resources, evidences and values. The issue

Experiment to Determine the Coefficient of Friction

Experiment to Determine the Coefficient of Friction Student Name: Ahmad Raza Summary: This experiment has two aims. The first aim of this experiment is to determine the coefficient of friction on an inclined plane by using various materials tray. Secondly, to verify that the force have already found which were required to move a body on an inclined plane. We have provided apparatus to do this experiment that include stainless steel plane, load hanger, different weights and 4 trays of different materials such as aluminium, brass, nylon and ferado. Firstly, we place tray at the middle of plane and apply weight on weight hanger until tray starts to move. Note the angle and find the coefficient of friction. For this purpose we have found the Normal force and sliding. Then, by using formula of coefficient of friction we found the value, which was approximately 0.18 at 10Â °, 20Â ° and 30Â °. Nevertheless, the additional 10N weight was added but the friction coefficient but the angle will remain same. The experiment was taken by under good circumstances. However, errors can be reduce by overlapping the mistake that was take place in this experiment. This experiment could be done exactly the same as international standard if the following conditions apply on it. CHAPTER 1 INTRODUCTION AIMS AND OBJECTIVE The aims of the friction experiment are to find the coefficient of different combination of material which is in this experiment, the steel bar. Making use of inclined plane, also to study equilibrium and non-equilibrium of a body of an incline plane under the action of the force. The objective is to understand that a coefficient of friction could be determine via incline plane, collect experiment data and calculate the corresponding results and coefficient and finally to compare the value of coefficient generated from different pairs of surface. 1.2: THEORY AND BACKGROUND: Friction can be defined as the force that will resists the relative motion of solid surfaces which are sliding against each other. There are mainly three types of friction. Dry friction, Fluid friction and internal friction but this particular experiment was just examined only for dry friction. Dry friction is the encountered when two dry surfaces are in convention if there is a tendency of sliding. However this dry friction has split into two sub frictions as static and kinetic. Commonly, kinetic frictional force will be less than the absolute maximum value from the static frictional force. This static frictional force is derived as fs = ÃŽ ¼sN, while kinetic frictional force is fk =ÃŽ ¼kN, where ÃŽ ¼s is the coefficient of static friction, ÃŽ ¼k is the coefficient of kinetic friction, N is the normal force and ÃŽ ¼ is the proportionality constant and called coefficient of friction. An inclined plane can be defined as any plane surface positioned at an angle with respect to the horizontal plane. At the moment of sliding, the friction force must be the same to the element of weight acting down the plane. ÃŽ ¼W .cosÃŽ ¸ =W .sinÃŽ ¸ This leads to the concept of the angle of the friction ÃŽ ¼ = tanÃŽ ¸ CHAPTER 2 APPRATUS AND experimental procedure 2.1: APPRATUS: Adjustable stainless steel plane complete with base .5N load hanger Weights Trays of Aluminium, Brass, Nylon and Ferado Fig1.1: Wood plane and trays 2.2: experimental procedure: As we discussed above, we have two aims for this experiment. Each aim has different procedure. 2.2.1: Following procedure is to find the angle of friction on a steel plane by using different materials. We have given four trays for this experiment such as Aluminium, Brass, Nylon and Ferado. First of all set the plane of stainless steel at 0 slope by ensuring that it is in horizontal plane. Afterward, set the tray of any material at the middle of stainless steel plane then apply weight at the end of plane by weight hanger and note the angle of inclination when tray starts to slide. Take coefficient of Tan ÃŽ ¸ to evaluate static deflection (ÃŽ ¼s).Repeat the same procedure three times and take the average. Subsequently, to evaluate the angle of sliding friction (ÃŽ ¼k) , place the tray again in the middle of plane and reduce the tilt as this time tilt was increased, we keep pushing the tray till it started to move and note the angle for three times and take the average. Static deflection (ÃŽ ¼s) Measure angle ÃŽ ¸ for static deflection by using Aluminium tray Table 1.1: Aluminium tray Measure angle ÃŽ ¸ for static deflection by using Brass tray Table 1.2: Brass tray Measure angle ÃŽ ¸ for static deflection by using Nylon tray Table 1.3: Nylon tray Measure angle ÃŽ ¸ for static deflection by using Ferado tray Table 1.4: Ferado tray Sliding Friction (ÃŽ ¼k) Measure angle ÃŽ ¸ for sliding friction by using Aluminium tray Table 2.1: Aluminium tray Measure angle ÃŽ ¸ for sliding friction by using Brass tray Table 2.2: Brass tray Measure angle ÃŽ ¸ for sliding friction by using Nylon tray Table 2.3: Nylon tray Measure angle ÃŽ ¸ for sliding friction by using Ferado tray Table 2.4: Ferado tray 2.2.2: Following procedure is to verify the force required parallel to an inclined plane to move a body up the plane corresponds to the friction coefficient already found. First of all set the stainless steel plane horizontally at 10 slope. Place the towing cord and weight hanger in position to pull the tray up to the plane by placing any material tray at the lower end of plane. Add load to the hanger until the tray, given a slide push, slides slowly up the plane. Repeat the same procedure by applying 10N weight at angle 20 and 30. CHAPTER 3 CALCULATIONS AND RESULTS 3.1: Procedure 1 As we found angle above, now to find coefficient of static deflection, take tan ÃŽ ¸. For Aluminium (Tan15.8) = 0.28 For Brass (Tan14) = 0.25 For Nylon (Tan20) = 0.36 For Ferado (Tan18.8) = 0.34 Table 3.1: Coefficient of static deflection As we found angle above, now to find the coefficient of sliding friction, take tan ÃŽ ¸. For Aluminium (Tan10.8) = 0.19 For Brass (Tan15.1) = 0.27 For Nylon (Tan12.3) = 0.22 For Ferado (Tan13.7) = 0.24 Table 3.1: Coefficient of sliding friction Procedure 2: First of all find the normal force Normal Force = W.cosÃŽ ¸ Normal Force = 3.58.cos10Â ° Normal Force = 3.52 N Secondly find the Sliding force Sliding Force = p-(W.sinÃŽ ¸) Sliding Force = 1.2-(3.58.sin10Â °) Sliding Force = 0.58 N Now as we have both normal and sliding force, we can find Friction Coefficient ÃŽ ¼ Friction Coefficient = Sliding force / Normal force Friction Coefficient = 0.58 / 3.52 Friction Coefficient = 0.16 All the values were measured for angle 20Â ° and 30Â ° as shown in the table below. Table 4.1: Nevertheless, the additional 10N weight were added but the friction coefficient and angle will remain same as shown above in the table which proves that weight cannot change the angle and coefficient of friction. By converting mass of the tray into weight we can prove the experiment. W = mg W = 0.365*9.81 W = 3.58 N CHAPTER 4 ANALYSIS AND DISCUSSION Subsequently investigation in the data, we all observed that hypothesis is true, where the static along with kinetic friction is usually affected by the mass of body. The coefficient in the kinetic along with static friction is determined by materials used for each call surfaces. The coefficients will never always be bigger than 1 and the coefficient connected with kinetic friction is definitely more compact as opposed to among static friction for that identical scenario. The value of coefficient of friction is 0.18.The laboratory on the other hand, we all would come up with a vibrant mistake thats produced each of our kinetic friction importance unfeasible, as the importance for we all received ended up being caused by the tension pulling on the block. However, there were some systematic error occur while doing experiment. These errors were arisen due to string and hanger as they were not straight and each group member have different value while taking reading. CHAPTER 5 CONCLUSION The experiment was taken under good circumstances. However, errors can be reduce by overlapping the mistake that was take place in this experiment. This experiment could be done exactly the same as international standard if the following conditions apply on it. First of all make sure that the hanging masses do not move while adding additional weight on load hanger. This experiment will be really useful in the future to determine the coefficient of friction for different materials. REFERENCE: John, B Carl,T.F.T.F. Ross (2002).Mechanical Engineering Principles. Oxford: Taylor Francis. APPENDIX A CHAPTER 1.. CHAPTER 2.. CHPATER 3.. CHAPTER 4. Page 1 of 11

computer architecture :: essays papers

computer architecture Computer architecture covers the design of system software, such as the operating system (the program that controls the computer), as well as referring to the combination of hardware and basic software that links the machines on a computer network. Computer architecture refers to an entire structure and to the details needed to make it functional. Thus, computer architecture covers computer systems, microprocessors, circuits, and system programs. Typically the term does not refer to application programs, such as spreadsheets or word processing, which are required to perform a task but not to make the system run. In designing a computer system, architects consider five major elements that make up the system's hardware: the arithmetic/logic unit, control unit, memory, input, and output. The arithmetic/logic unit performs arithmetic and compares numerical values. The control unit directs the operation of the computer by taking the user instructions and transforming them into electrical signals that the computer's circuitry can understand. The combination of the arithmetic/logic unit and the control unit is called the central processing unit (CPU). The memory stores instructions and data. The input and output sections allow the computer to receive and send data, respectively. Different hardware architectures are required because of the specialized needs of systems and users. One user may need a system to display graphics extremely fast, while another system may have to be optimized for searching a database or conserving battery power in a laptop computer. In addition to the hardware design, the architects must consider what software programs will operate the system. Software, such as programming languages and operating systems, makes the details of the hardware architecture invisible to the user. For example, computers that use the C programming language or a UNIX operating system may appear the same from the user's viewpoint, although they use different hardware architectures. When a computer carries out an instruction, it proceeds through five steps. First, the control unit retrieves the instruction from memory—for example, an instruction to add two numbers. Second, the control unit decodes the instructions into electronic signals that control the computer. Third, the control unit fetches the data (the two numbers). Fourth, the arithmetic/logic unit performs the specific operation (the addition of the two numbers). Fifth, the control unit saves the result (the sum of the two numbers). Early computers used only simple instructions because the cost of electronics capable of carrying out complex instructions was high. As this cost decreased in the 1960s, more complicated instructions became possible. Complex instructions can save time because they make it unnecessary for the computer to retrieve additional instructions. For example, if seven operations are combined in one instruction, then six of

The Misery in Evil

There is a lot we can learn from infants. Infants have control over their emotions. When they feel hungry, they cry. When we feed them, they stop. They react the same way when dealing with such feelings and emotions such as nausea, sleep, and even anger. The children know how to let their emotions flow and as soon as the emotion is dealt with, they let the feelings go. As life becomes more complicated, people tend to forget how to let thing flow and then let them go. The older we get, the more we hold in the emotional baggage, allow ourselves to be possessed by them. Emily Bronte's Wuthering Heights tells a very good story of the consequences of holding emotions in without ever releasing them. The characters in the book are so deeply enveloped into their emotions that they create prisons for their minds. Their own acts of hate and unkindness create these prisons; prisons that won't let them escape from their misery. From a very early age, the seeds of hatred are planted into Hindley. When the orphan boy, Heathcliff is brought home to live with the Earnshaw family, Hindley becomes immediately jealous when the love of his father goes into Heathcliff. Along with his sister, Catherine, the two work together to ridicule the orphan child of his disabilities, mainly his illiteracy. When Hindley's father dies, he goes on to make Heathcliff's life miserable. He treats Heathcliff as one of the servants and terminates his education. The hatred is spread into Heathcliff as he vows to seek revenge on Hindley. While Hindley continued his abuse on Heathcliff, Catherine falls in love with the orphan child. However, Catherine had a personal ambition to find someone that would carry her away like an enchanted princess. She got this opportunity when she was allowed to enter the Linton house. Heathcliff, on the other hand, was told to go back home. While Catherine learned the ways of the rich, Heathcliff started his plan to seek revenge. One of the interesting aspects of the book is the fact that Heathcliff started off with the typical romantic hero. He was the orphan child, destined to rise above the standards. However, Bronte doesn't allow Heathcliff to transcend above his position in life. Throughout the novel, Heathcliff commits act of pure evil that is very hard for the reader to believe. He starts by killing a few dogs and goes on to create even more havoc. He tortures Isabella by testing her undying love for him. He even goes on to plan the use of his own child to seek revenge on his arch nemesis, Edgar Linton. All the while, the one thing that caused all of his pain, all of his misery, never stopped haunting him. Catherine died from the love she had for Heathcliff. Her acts of unkindness towards him led to her misery which would eventually lead to her death. Heathcliff could never bury Catherine and he felt like her ghost was always around watching him, waiting for him to join her. Heathcliff's ultimate revenge would take place by destroying the love between Hareton and the young Catherine. He tried to recreate a love triangle between his son Linton Heathcliff, the young Catherine, and Hareton. However, the young Catherine reminded Heathcliff of his love for her mother so much, that his desire to fulfill his act of revenge soon disappeared. When he finally realized this, his anger, his rage, turned to misery. Like his love before him, he let the misery take over, which would lead him to his own death. Heathcliff, along with many other characters in the story, were locked inside a cage they couldn't escape. The lock was composed of love, hatred, revenge and misery. For the second generation of children in the story (Heathcliff, Edgar Linton, Hindley, and Catherine), the self-made prisons made for some very miserable lives and depressing deaths.

What You Need to Know About the SAT Chemistry Subject Test

The SAT Chemistry Test or SAT Chemistry Subject Test is an optional single-subject test that you can take to showcase your understanding of chemistry. You might choose to take this test if you are applying to college to study science or engineering. The test is intended to help you with the college admission process. SAT Chemistry Test Basics Here are some important facts about the SAT Chemistry Subject Test: 60 minutes (one hour) long.85 multiple-choice questions.Offered October, November, December, January, May, and June.A calculator is not permitted.The periodic table is provided.All units are metric.Only simple numerical calculations are required.Scoring is from 200-800. (Note: You do not need to get all of the questions correct to get a perfect score.) It is expected that students will not have been exposed to every subject covered on the test. Recommended Preparation for the SAT Chemistry Test Year of algebraYear of general chemistry, college-prep level or higherSome lab experience Topics Covered by the SAT Chemistry Test The percentages given here are approximate. Structure of Matter (25%)States of Matter (16%)Types of Reactions (14%)Stoichiometry (14%)Descriptive Chemistry (12%)Laboratory (8%)Thermochemistry (6%)Equilibrium and Rates of Reactions (5%) This is not a memorization-type test. While students are expected to have an understanding of the fundamental concepts of chemistry, most of the test will involve organizing and interpreting information. With respect to the types of skills that will be needed to succeed with the SAT Chemistry Test, you can expect: 45% application of knowledge35% synthesis of knowledge20% fundamental knowledge and concepts