Bible Project Essay Example for Free

Bible Project Essay 1. The difference between self-interest and selfishness could perhaps be best described as the difference between a desire to be monetarily successful and voracious greed for every last penny. Self-interest is when someone wants more for themselves, regardless of what it is they desire. A person could want more money, a bigger television, faster computers, or just better health with six pack abs. Selfishness is much more like when someone is willing to do anything, including hurt others, to get what they want. The difference is subtle, but it is there. Now, in terms of a competitive market economy, selfishness will lead to eventual collapse, while self-interest could potentially increase the general good, even if inadvertently. Selfishness is corrupting and businesses that are so will seek to draw as much profit out of their employees and customers as is possible, heedless of economic survival. 2. In my reading so far, I do believe the text will discuss normative economics. On page 178, the text has a section discussing unemployment. This set-aside section discusses the problem of unemployment, and the question of whether or not unemployment would exist at all if the market were functioning perfectly. This theory is completely untestable as the market will never function perfectly, and/or unemployment will never cease to exist to test whether the market is functioning perfectly at the time. 3. Adam Smith believes that people at heart desire others to approve of them, so their selfish attributes are restrained just enough that people don’t think less of them for it. 4. In keeping with God’s plan, a person can take part of the democratic capitalistic society, but without becoming corrupted by it. A person keeping true to faith and prayer will be more capable of sympathy, of doing more for the good will, and of creating an abundance of good will (worth far more than its weight in gold). Keeping God in one’s heart will keep selfishness out. - 1. Reparation for historical acts is a very difficult issue to discuss, let alone decide upon. Honestly, while I feel for the countries and peoples that have suffered throughout history for the malicious and greedy acts of others, I think that offering reparations of any sort to anyone would do little more knock over the first domino in a very long series of requests for reparations. It becomes a question of when to draw the line, and in that it would be unfair to say that this person doesn’t deserve reparations over that one. If we are going to discuss the sins of one, we must admit to the same sinful traits of the other. The same greed that motivated the historical acts is likely to affect those coming forward to ask for reparation. Rather than looking back, we should look forward and consider how best to aid these same affected peoples and countries in the future. 2. Benefits: 1) There are plenty of jobs to go around. 2) The quality of life improves, both through the proliferation of jobs and innovation in trade markets, whether agricultural or technological or other change. 3) People generally live longer and debatably healthier lives, through medical innovations, having more money to spend on healthcare, and better quality goods in their lives. 4) People and companies and churches and other charitable organizations are more capable of doing good in the world. More money does equal more charitable giving. 5) People can grow closer through technological improvements (the phone, computer, internet) and through changes in transportation (one day there will hopefully be some form of instantaneous transportation, making it possible to be closer to friends and family who are very far away). Costs: 1) As people come closer together, they are also driven apart. Currently technology binds people together, but also isolates people in different rooms, on different computers, and practically living on different planets. The internet is the one place where you can be with millions of people and still completely alone. 2) Environmental damage is a serious issue, as we are entrusted with the stewardship of the planet and economic growth usually means that some company somewhere is taking shortcuts and likely making profit to the detriment of everyone. 3) As much as there are jobs created, there are also many jobs lost. For example, the growing crop of future employees will be far more computer capable and technologically innovative and skilled then the current set of employees. No doubt in the future companies will fire their current older and less qualified employees to hire someone younger, more skilled, but willing to take less pay. 4) When it comes to the now plentiful state of food in most countries, there is a steep price to pay all on its own. Economic growth is usually best defined by a growth in profits, and where a lot of food companies see a growth in profits is by spreading the meal as thinly and cheaply as possible. Food has become an amalgamation of processed chemicals with a little dash of real nutrition thrown in, both to suit the profit margin and to make meals easier for people to prepare in their increasingly busy lives. This is in stark contrast to a time when people used to buy food in its whole, natural state and cook it for themselves. Health is simultaneously going up and going down. People are living longer, but the quality of their health is one that is always up for discussion. 5) Values are sometimes lost in a growing economy. As others prosper, even more see their success and covet it for themselves, losing sight of the real point of economic growth – making lives better so that everyone can better partake in their faith and therefore please God. 3. The United States can maintain its trade deficit because of an inflow of capital. Foreign markets bring in money, making it possible for the country to accept more imports. 4. In the times past, have the winners shared? Not really. But today, I would say I think that nobody is really losing as long as the trade system is working. In most cases both sides are going to benefit in some manner, although there will undoubtedly be one side gaining more than the other. But if the system isn’t resulting in the complete destruction or abuse of a people or culture as it has in the past, there isn’t a real â€Å"loser.†

Different Power Factor Correction Engineering Essay

Different Power Factor Correction Engineering Essay Different power-factor correction methods are reviewed, as well as the back ground to the power-factor. Problem is arising in modern electrical distribution systems due to the connection of rapidly increasing numbers of non-linear electronic loads. The basic principles of harmonic generation and limitation in power systems are first discussed. The main part presents a critical review of commonly used power-factor correction techniques that have been identified in a literature review, and highlights the advantages and disadvantages of these techniques. After the analysis of methods and their working principles, the development of the most promising systems such as the boost-type PFC converters is considered. Finally, a project plan is proposed for the next phase of the dissertation work. This will involve investigating the operation, dynamic control and performance of the most promising systems by conducting a theoretical study and setting up and running a number of simulation models using the MATLAB/SIMULINK software tools. Key-words: Power factor correction, harmonic mitigation, PFC converters Contents List of Abbreviations and Principle Symbols Abbreviations: AC Alternating Current APF Active Power Filter CCM Continuous Conduction Mode DC Direct Current DCM Discontinuous Conduction Mode DF Distortion Factor FFT Fast-Fourier analysis IGBT Insulated Gate Bipolar Transistor PF Power Factor PFC Power Factor Correction PWM Pulse Width Modulation RMS Root Mean Square THD Total Harmonic Distortion TDD Total Demand Distortion Principle Symbols: Power Factor Distortion Factor Displacement Factor h Harmonic contents RMS value of the line-current fundamental component RMS value of the line-current harmonic components Total RMS value of the line-current 1. Introduction It is now clearly visible from power systems journals and general literatures that power-factor correction is now an important research topic in the power systems area. As non-linear power electronic systems are increasingly being connected to power systems in greater quantities as well as capacities for such applications as power quality control, adjustable speed drives, uninterruptible power supplies, renewable energy-source interfacing, and so on [1] [2]. The power quality regulators of those systems are highly concerned now, because some of their drawbacks, such as harmonics generation and reduced power factor can spoil their advantages [3]. Power electronic systems are effective because their high efficiency and rapidly adjustable output. However, when processing and controlling the input electric energy suitable for users [4], power electronic systems often operate at a low power-factor, and that may cause serious problems to power system operators by reducing distribution comp onent RMS current capacity and to other users on the same network by distorting the sinusoidal supply voltage seen by other user connected at the same point of common coupling as a heavy electronic or power electronic load.. Of all power line disturbances, harmonics are probably the most serious one for power users because they exist under steady state conditions. This literature review considers harmonic generation prediction of power electronic systems and examines the effectiveness of harmonic mitigation methods. The boost-type power factor correction converters will be taken as the core power factor correction method for future research. The existing publications arising from research in this area and their conclusions have set a good foundation for this report. Results in this report will be based on a theoretical study and simulation studies using software MATLAB/SIMULINK power-factor correction system models which be developed. 2. Background This section provides discussion on the fundamental principles of power-factor correction, including definitions of power-factor terms and a consideration of the common standards which affect how harmonics controlled in power system. Also, the harmonic generation prediction of ideal power electronic systems is discussed at the end of this section 2.1 Important definitions and objective of power-factor correction The power factor (PF) is the ratio of the real power to the apparent power [5] and gives a measure of AC supply utilization on how efficient that the energy is supplied and can be converted into effective work output. The definition of power factor is as shown below: (2.1) In the definition, the value of the power factor is always between 0 and 1, and can be either inductive or capacitive. That means average power is always lower than apparent power. The reason is harmonic components and phase-displacement angle,. Hence, the power factor equivalent can be described as below: (2.2) is termed the (current) distortion factor (DF) and represent the harmonic components in the current and relative to wave shape [6]. DF is defined as the ratio of the fundamental current component to the RMS current value [4]. is termed the displacement factor and defined as the current and voltage waveform phase angle [6]. Displacement factor has unity value for in-phase current and voltage. The increase of displacement angle will cause larger reactive current in the power system [4]. Hence, the objective of power-factor correction is to decrease the current distortion or harmonic content and increase the displacement factor or bring the current in phase with the voltage. The closer power factor is to the unity value, the higher efficiency and lower energy loss. And the power system will operate at a lower supply voltage. Another commonly used index for measuring the harmonic content of a waveform applied for current distortion level is total harmonic distortion, THD. THD is the distortion current as a percentage of the fundamental current. The equation of THD is given by: or (2.3) In AC supply utilizations, power factor,, can be expressed in terms of THD and the displacement factor: (2.4) With these equations, it is easy to see that high THD leads to low power factor and even damaging of the power network. THD and power factor will be used together in the following work as important index in measuring performance of the harmonic mitigation techniques. 2.2 Effects and limitation of harmonic distortion on power system In any power conversion process, to get high efficiency and low power loss are important for two reasons: the cost of the wasted energy and the difficulty in removing the heat generated due to dissipated energy [4]. The performance of power output efficient is defined by several factors. The power factor and harmonic distortion are the most important ones. References [8] [9] show the main issues of harmonics within the power system include the possibility of them exciting series and parallel resonances which cause a further increase of harmonic levels, low efficiency caused in generation, transmission, and utilization of electric energy, increasing thermal losses in the electrical components and shortening their useful life and causing malfunction of motors and other components in the power system. Those effects can be divided into three general categories: Thermal stress, Insulation stress and Load disruption [10]. Those represent effects on increasing equipment losses and thermal losses, increased value of current drawn from the power system and insulation stress and failure to action and malfunction of some electrical devices and systems. The IEEE Standard 519-1992 recommended harmonic current limits with an additional factor, TDD. This is very same as THD except the distortion factor is expressed by load current instead of fundamental current magnitude [11]. Hence, the equation of TDD is given by: (2.5) Therefore, IEEE Standard 519-1992 limitation for harmonic current in power system expressed with TDD is shown below: Maximum harmonic current distortion in percent of Individual harmonic order (Odd harmonics) TDD 4.0 2.0 1.5 0.6 0.3 5.0 20 7.0 3.5 2.5 1.0 0.5 8.0 50 10.0 4.5 4.0 1.5 0.7 12.0 100 12.0 5.5 5.0 2.0 1.0 15.0 >1000 15.0 7.0 6.0 2.5 1.4 20.0 Even harmonics are limited to 25% of the odd harmonics limits above. Table 2.1 IEEE 519-1992 Standard for harmonic current limits [12]. Also, there are limitations for power system harmonic voltage and power factor regulation, like IEC 61000-3-2 standard. The methods for power factor correction should not cause disturbances for other aspects of performance. 2.3 Harmonics generation in power electronic systems Power electronic systems may naturally operate at low power-factor due to large harmonic generation and phase shifting in controlled devices like controlled rectifiers. Understanding characteristics of the harmonic current is essential for harmonic mitigation research. Based on the form on the two sides, converters can be divided into four categories [4] including: 1. AC to DC (rectifier) 2. DC to AC (inverter) 3. DC to DC 4. AC to AC Power electronic systems always draw high quality of low frequency harmonic current from the utility and hence cause problems for other users. Take an ideal single-phase diode bridge rectifier as example, the total harmonic distortion can be up to 48.43% [4] and the 3rd harmonic current can be as large as one third of the fundamental current. If a non-linear load is considered, the displacement factor will fall down from unity value and cause a decrease of power factor. This is surely over the harmonic standards limitation and needs to be corrected. Theoretically, Rectifiers and choppers output DC and draw a fundamental AC source current and large low frequency harmonic content. On the other hand, inverters output low frequency AC and supply fundamental current and harmonic content usually at higher frequency. Harmonic contents can be reduced by harmonic mitigation techniques and hence increase power factor. Take Fourier analysis result diagram of single-phase diode bridge rectifier and PWM control Buck converter as example. (a) (b) Figure 2.1 Fourier analysis diagram for input current of (a) single-phase diode bridge rectifier and (b) PWM control Buck converter. 2.4 Software tools for harmonic mitigation evaluation To filtering harmonic current in the power system, the frequency of harmonic contents is essential. However, in practice, the harmonic frequency is not absolutely equal to the theoretical value and that makes analysis of harmonic frequencies very difficult. The reason is stray inductance and capacitance in the system and reverse recovery time and forward voltage drop of non-ideal devices [1]. To analyze harmonic contents, appropriate software can be helpful. In this project, the software chosen to help analyzing harmonic current drawn by power electronic systems is MATLAB/SIMULINK. Taking the three-phase diode bridge rectifier as an example, a simulation model can be established as shown below. In the model, a three-phase 50Hz AC power supply is used for a resistive load and most devices are not ideal. The model is followed by the diagram of input current waveform and frequency spectrum of AC input current. Values of each order harmonic content and total THD are given by Fast-Fourier (FFT) analysis in powergui analysis tools. With the help of Fourier analysis, the performance of harmonic mitigation techniques can be evaluated and compared quickly. Figure 2.2 Simulation model for three-phase diode bridge rectifier. Figure 2.3 Waveform of rectifier input current (phase A). Figure 2.4 Frequency spectra of AC input current of three-phase rectifier. 3. Power Factor Correction Techniques After tens of years developing and improving, various types of power factor correction techniques or harmonic mitigation techniques can be chosen to solve power factor problem. Those techniques can be divided into five categories [11] [13] as shown below: 1. Passive filters Passive filters can improve power factor with low cost and reduce high frequency harmonics effectively. However, they are always in large size and cannot vary flexibly with system changes [4] [14]. If tuning reactors are not used, parallel resonance may occur in operation [15]. 2. Active filters Active filters improve power factor and provide stable output even under varying supply condition, and reduce harmonics in the output current effectively and efficiently [4] [16]. These, however, always requires much higher costs and the harmonic currents they injected may flow into other system components [13] [14]. 3. Hybrid systems Hybrid active filters combine active and passive filters together in various forms [17]. Hence they can reduce initial and running costs and improve performance of the filter [11] [13]. Smaller filter inductor, smaller dimension, light weight and better filter performance hybrid system take advantages of both passive and active filters [18]. However, the complexity of operation is the main drawback of hybrid systems. 4. Phase multiplication Increasing the pulse number of power converters can raise the lowest harmonic order generated by the converter [2]. Typically, 6-pulse converter has the lowest harmonic order of 5 [1]. When rising pulse number to 12, the lowest harmonic order can increase to 11. As value of harmonic current are ideally proportional to fundamental current value [4], the amount distortion of the power system can de reduce to a low level. On the other hand, the effectiveness of this technique is based on balanced load [13] which rarely happens in practice. 5. PWM PWM converters have much better performance compared to traditional converters like diode rectifiers and square-wave control inverters [4]. As a control strategy improvement, PWM harmonic mitigation technique can even used with some devices for traditional converters and hence get broad application prospect [11]. However, the topology complexity and difficult on designing controllers [19] makes the use of PWM is limited. The objective of these techniques is to make the input current nearly a pure sinusoidal waveform and hence to improve the power factor in electrical supply system. All these five techniques are discussed separately in the following work. 3.1 Passive filters Passive filters have widely been used to absorb harmonics generated by the power electronic systems, primarily due to their simplicity, low cost and high efficiency [20]. Passive filters are always consists inductors, capacitors and damping resistors [21]. The objective of the passive filter is to stop the flow of the harmonic current from disturbing power system, either by preventing them with the usage of series filters or diverting them to a shunt path [9] [11]. That is the different between series filter and shunt filter, too. Series filters can be tuned LC system or only a single inductor in the system. Parallel inductance and capacitance are tuned to provide low impedance for fundamental frequency current and high impedance for a selected frequency current, always high level harmonic current. The series tuned filters are simple and reliable to use. The circuit configuration can be shown as below. Figure 3.1 Series LC tuned filter. The series tuned filters are always used as input filter for power electronic systems. However, a big drawback limits the using. If the series tuned filter is used in a VSI system as the input filter for the inverter, several order harmonic current need to be filtered, 5th, 7th, and so on. Each order harmonic current required an individual filter, and hence the size of the system can be intolerable. On the other hand, shunt filter have much more types including shunt-tuned filter, double-band pass filter and 1st, 2nd and 3rd -order damped filters. Also, broadband filters are good solution for filtering wide range of harmonics [22]. The circuit configurations of these widely used passive filters are like shown below. (a) (b) (c) (d) Figure 3.2 Typical harmonic filters: (a) Single-tuned filter (b) Double tuned filter (c) High-pass parallel filter (d) C-type high-pass filter [5] [27]. A few single tuned filters cope with large level harmonic contents and a high-pass (2nd order) filter filtering high frequency harmonics is the typical model for shunt passive filters and can get better characteristic than series filters [24]. Take the single tuned filter as example, single-tuned filter also called the band-pass filter as only a selected frequency of current can pass in low impedance. The tuning frequency of the single-tuned filter could be: (3.1) And at this frequency, the impedance of the filter is: (3.2) where s is the Laplace operator, L represents value of inductance and C represents the capacitance value. However, mostly passive filters can only filtering 30% of harmonic current in the power system [23] and can not match IEEE 519-1992 standard well. Even the broadband filter, which can filter a range of harmonic contents and reduce system THD to approximately 10%, the resonance caused by the filter and the big size of inductor and capacitor still limit the usage of the filter. So we can get the list of advantages and disadvantages for passive filters shown in table 3.1. Advantages Disadvantages Effectively for filtering high frequency harmonics Low availability for low frequency harmonic filtering Very low cost and reliable Bulky devices and inflexible devices parameters Simple structure Individual branch is necessary for each dominant harmonics in the system High probability resonance Table 3.1 List of passive filter performances [4] [14] [25] [29]. 3.2 Active power filters (APF) The basic idea of an active filter is to compensate current or voltage disturbance so as to reduce the reactive power electronic systems drawn from the power system [23]. The active filters using in power system are not the same as what we use in electronic circuits. The active filters conventional means combined operational amplifiers and passive components like inductors and capacitors, and always been used in electronic circuits operating under low voltage. That is the beginning of the active compensation applications and came out earlier than active filters using in power systems. The active filters which are used in power system for active power compensation and harmonic compensation are always called Active Power Filter (APF) [30]. The active in APF means the filters are act as power sources or generators and provide compensation currents which have opposite phase angle with the harmonic currents in power system [30]. Similarity between electronic circuit active filters and pow er system active filters are the requirement of external power supply. The active filters which are talked in the following parts are all means APF. With the active power filters, the compensation for reactive power and for harmonic current can de done at the same time, hence efficiency on harmonic compensation and also dynamic response are all be improved [23]. The trend of active power filters began in 1970s and was introduced by Mr. Akagi. The incentive for active filters is the inductor is not appropriate to use under high frequency, so the trend is to replace the inductor with active components. As the harmonic contents in the power system various frequently, fast response of active filters required a good control strategy to make active filters smarter and faster. But more complex devices and sophisticated control strategy are required, that all makes active filters more expensive and hard to use [26]. Active filters can also be classified by converter type as shunt-type active filters and series-type active filters. The diagrams of two basic types of active filters are shown below. The other way to classify active filters is the phase number of filters which will be discussed later. (a) (b) Figure 3.3 Diagrams of (a) Shunt-type active filter and (b) Series-type active filter [11] [28]. Series active filters are good at compensate voltage harmonics and capacitive, voltage-source loads. When applied to an inductive or current-source load, a low impedance parallel branch is necessary. Similarly, shunt active filters are always used with inductive, current-source loads and high current distortion conditions. Sometimes over current condition occurs with the use of shunt-type active filters [31]. Typical working principle of the active power filter is: 1. Detection. The sensor detects the waveform of the instantaneous load current and feedback to the controller, which is typically a digital processing block. 2. Analysis. Load current is always high distortion current including fundamental current and many orders of harmonic current. The processor must distinguish the fundamental current with the harmonic currents and give out the information including frequency, value, and phase angle of harmonic contents, so as to control the power source inverter providing opposite phase current of harmonic current. 3. Compensation. The power source inverter draws current from individual DC voltage supply and converting to required current to cancel harmonic currents. Like the diagram shown below. Figure 3.4 Diagram of compensation characteristics [31]. Hence, we can draw a conclusion of advantages and disadvantages of active power filters shown in the table below. Advantages Disadvantages High compensation efficiency and high ability on harmonic compensation Low reliability with sophisticated control system and devices Small size components Difficult to construct a large rated current source with a rapid current Fast action on harmonic current variation makes good dynamic response High initial costs and running costs No resonance causing Complex control strategy and controllers are necessary Suitable for widely supply and load conditions, like unbalanced power supply Table 3.2 List of active power filter performances [13] [22] [30] [31]. 3.3 Hybrid systems Hybrid filters comes from the idea to combine the advantages of both passive filters and active filters together hence to get brilliant performance on harmonic mitigation [17]. Combine passive filters and active filters can significantly reduce costs and improve the compensation characteristics in the power system. Also, various types of hybrid systems of passive and active filters can get better performance than only passive or active filters. Like the reference [18] and [20], small rating active power filter and passive filter connected in serial or shunt type. Smaller filter inductor, smaller dimension, light weight and better filter performance hybrid system take advantages of both passive and active filters [18]. However, as the basement of the hybrid power filters are always active power filters, the initial costs and control complexity is still big disadvantages of hybrid systems. 3.4 Phase multiplication The purpose of phase multiplication is to increase the pulse number of the converter and hence to increase the harmonic order and frequency [4]. The low frequency harmonics can be mitigated effectively and phase multiplication technique does not cause serious resonance and other bad effects on power system performances [13]. The practical application of phase multiplication technique, the multipulse converters, have the ability to draw low distortion current from power source and generate DC current with low level ripple [32]. Typically, 6-pulse converter has the lowest harmonic order of 5 [1]. When rising pulse number to 12, the lowest harmonic order can increase to 11. As value of harmonic current are ideally proportional to fundamental current value [4], the amount distortion of the power system can de reduce to a low level. Also, the multipulse thyristor converters can output various value current by controlling the thyristor fairing angle () [32]. The drawbacks of phase multiplication technique are mostly the contradiction between the cost and output characteristic. If controlled output is required, the multipulse converter should contain at least 12 switching devices and that can be a big amount of costs. On the other hand, multipulse converter only use diodes may operate on low efficiency [11]. 3.5 PWM PWM (Pulse Width Modulation) is a modern control technique for power electronic systems. PWM converters have much better performance compared to traditional converters like diode rectifiers and square-wave control inverters [4]. Like the phase multiplication technique, PWM control can raise the frequency of harmonic contents of current so as to reduce the effect caused by harmonics. Also, converters using PWM control can have high efficiency and small size. With all these advantages, PWM control absorbed great concern in modern power conversion systems. However, the topology complexity and difficult on designing controllers [19] makes the use of PWM is limited. 3.6 Power factor correction converter Power factor correction (PFC) converter is a typical active power factor correction method. As a mature technique for power factor correction, PFC converters have been widely used in power electronic systems to achieve high power factor (PF) and low harmonic distortion [33]. PFC convener forces the input current follow the input voltage, which makes the input current drawn from power supply nearly in a unity power factor [34]. The Boost-type PFC converters are the most used topology which have many advantages, such as low level ripple in the input current, high power factor, small size and simple circuit structure [35]. A typical circuit diagram of Boost-type PFC converter is as shown below from reference [36]. Figure 3.5 Typical circuit diagram of Boost-type PFC converter [36]. As we seen in the diagram before, conventional PFC converter consists two main stages [33] [37]: Power factor correction stage. This stage is combined with a diode rectifier and a DC/DC converter and used to correct power factor of the input current drawn from the power system. The most used type of chopper is Boost chopper. Also, the new Buck and Cuk type PFC converters are increasingly being used now. The switching working principle can be divided into two types, DCM and CCM. 2. DC/DC converter The chopper here is used to convert the power output voltage and current match the users demand. Since choppers only drawn low distortion power from supply, the typical filter on the utilization end is always a passive filter. This is the working principle for conventional PFC converters, the two-stage DCM/CCM Boost-type PFC converter. However, this type of PFC converter has some disadvantages and need to be improved [33]-[39]: 1. Stage number Individual control system and switching devices are required for each stage of PFC converter, hence increasing the costs of the whole system and cause some other problems, such as power density, transmission efficiency and control response [38]. Also, the design of control system can be a challenge. A new one-stage PFC converter topology has been introduced to power factor correction research area. The circuit diagram is as shown in figure 3.6 [36]. The combination of the power factor correction converter and the forward converter may bring many advantages point as below [36]: 1. High power factor correction performance 2. Reduced value of ripple in the DC output 3. Low initial cost and running cost 4. High efficiency and easy control system And so on. Figure 3.6 Circuit diagram of single stage PFC converter [36]. 2. Converter type Like shown in figure 3.6, Buck converter is increasingly being used in PFC converters. Also, Cuk converter and other type of choppers are becoming good choice for PFC converters [36]-[39]. The Buck type PFC converter was rarely used since its high input current distortion. However, with the characteristic improving of the Buck type PFC converter, it can reach good performance with specific dual mode duty cycle control scheme [36]. The main advantage of Buck type PFC converter is easy to reduce the stage number to one stage. 3. Devices and control strategy One of the most important aims in the design of power electronic systems is the reduction of the size of the passive devices, since it allows increase on the power density and the reduction in the initial and running cost. As inductor and capacitor are still using in the PFC converter, the reduction of them can be very important [33] [37]. However, the improvement of devices must base on the developing of the control strategy [37]. With a good detect and control system, the size of the inductor and capacitor can be reduced while the harmonic content can still meet the requirement [33]. The further analysis and improvement of PFC converter based on this literature review will be an important work in the last stage of project. 4. Conclusion This literature review provides a critical study on power factor issues and power factor correction techniques. A theoretical review of power factor definitions and harmonic generation by power electronic systems are presented at the beginning of the paper. The performance of five basic types of harmonic mitigation techniques has been discussed with the support of many previous research publication and their results. The PFC converter is chosen as the promising system for power factor correction after the analysis and comparison. The simulation model establishment and simulation comparison of power factor correction techniques will be important works for the next period of the project. Also, design rules and guidance of PFC converters will be designed in the next period, too.

Skin Diseases Affect On Peoples Health

Skin Diseases Affect On Peoples Health In modern society, more and more people are attacked by a variety of diseases. In medicine, relevant skin diseases seriously affect peoples health. As one of the common diseases, skin diseases such as leprosy, scabies, fungal disease, bacterial skin infections appear frequently. With the form, structure and functions changing, skin (including hair and armor) is influenced by external and internal factors, which produce the pathological process, and the corresponding produce all sorts of clinical successively performance. This is the cause of skin diseases. They have a high incidence of dermatitis, but relatively the symptoms are not serious, they often do not affect health, but a few heavier are even life-threatening. As a typical kind of skin diseases, photodermatoses are among the most common skin disorders in the world. Some of them acquired a particular importance in some regions because of their high frequency, severity, and also beÂÂ ­cause of their different diagnostic and therapeutic apÂÂ ­proaches. Photo medicine is a rapidly developing subspeÂÂ ­cialty of dermatology concerned with skin diseases caused by radiation in the UV and visible spectra. Initiation or exacerbation of a rash after sun exposure that occurs in typical light-exÂÂ ­posed areas is features that point toward a sunÂÂ ­light-induced condition. The diagnosis of photosenÂÂ ­sitive conditions may be difficult, and the use of investigations such as light, patch, and photopatch testing may be necessary to confirm the diagnosis. [1] Background and history With the development of modern medicine, every Teaching Hospital Department is in treatÂÂ ­ment development dilemmas. For becoming involved in a new therapy, they still need to promise to be at the speculative stage. In the early 1990s, the problem about whether to actively become involved in the development of PDT for skin cancers was discussed by the Photobiology Unit within the Department of Dermatology in Dundee. As a new invest significant reÂÂ ­sources, its so difficult for PDT to have a fairly certain outcome. By 1998, with the position changed and enough good quality data existed, treatment outcomes justiÂÂ ­fied become involved in the development of both PDT and photodiagnosis (PD) for pre-malignant and malignant skin lesions. From a clinical reÂÂ ­search and therapeutic point of view, the skin has two huge advantages. Firstly, it can be easily exÂÂ ­amined with the naked eye, and secondly, it is the most accessible organ for investigation, biopsy an d treatment. Although PDT firmly has its roots at the beginning of the last century, it is only over the last 15 years that it has gained considerate popularity as a topical treatment of great promise for the treatment of skin cancers.[2] In 1900 a German medical student Oscar Raab famously reported the concept of cell-induced death subsequent to light interacting with chemicals. In subsequent experÂÂ ­iments he demonstrated that this effect was greater that with alcidine red alone, light alone or alcidine red exposed to light and then added to the paramecium. He postulated that in vitro toxicity occurred as a result of fluorescence caused by the transfer of energy from the light to the chemÂÂ ­ical. Professor von Tappeiner soon after predicted the future of fluorescent substances in medicine. In 1904 von Tappeiner and Jodlbauer identified that oxyÂÂ ­gen was integral component in photosensitisation reactions and termed the phrase photodynamic action in 1907. Since its incidental discovery in 1900 photodynamic therÂÂ ­apy (PDT) and all aspects relating to it from mechanism of action, differing photosensitisers through to clinically based applications have been studied. Three components are required for PDT to occur; a photosensitiser, oxygen and a light source. [3] The Photobiology Unit (photobiology = the study of tight on living systems) has the purpose in Scotland of diagnosing tight sensitive skin disease (the photodermatoses) and the development of new forms of tight therapy (phototherapy). This Centre, which has been in existence since 1973, has always combined clinical skills (photodermatology) with a strong scientific base (photophysics) and laboratory biology (photobiology). This combination of applied science and clinical service in the same unit has proÂÂ ­vided exciting research opportunities. Applied photo physics, through the Medical Physics Department, has dedicated members of staff whose only rote is optical physics. The necessary expertise in tight de-tivery and measurement is essential for predictable PDT and PD. Basic knowledge of sun and the skin Nm 254 290 320 360 X-rays UVC UVB UVA Visible light Figure 1 the place of ultraviolet radiation in the electromagnetic spectrum Figure 1 illustrates the relationship between ultraviolet radiation and the other types of non-ionizing radiation, such su natural light an infra-red radiation. It will be seen that ultraviolet radiation from the sun is divided into three different wavelengths-UVA, UVB, and UVC. The UVA waves are the longest and the UVC the shortest. At present, UVC is prevented from reaching the earths surface by the ozone layer, and is not therefore a natural hazard. There is, however, concern that the loss of the protective layer of ozone above the earths atmosphere will continue, and that in future more UVB might reach the earth. The main ultraviolet component of travel of natural that does each the earths surface is UVB. This penetrates the epidermis and reaches the more superficial layer of the dermisthe papillary dermis. UVA is also present in sunlight and ,in the early spring, a high proportion of natural sunlight in countries at latitudes 50 degrees or more north of south of the equator is composed of UVA. As the summer develops the proportion of UVA falls. UVA is the main, but not the only, wavelength found in the long tubes in UVA sunbeds. The effects of UVA go deeper into the skin than those of UVB. A very simple rule of thumb is that chronic over-exposure to UVB causes wrinkles, chronic over-exposure UVA causes saggi ng, and chronic over-exposure to both increases the risk of developing skin cancer. One of the important points of difference between UVB and UVA exposure is that acute over-exposure to UVB causes the redness and soreness recognized as sunburn. This is maximal 12-24 hours after the exposure has taken place, and is a useful warning that the skin should be protected for a few days until the redness has disappeared. The chemicals in sun-screens that protect against UVA and UVB can be divided into those that absorb ultraviolet radiation and those that reflect it away. The absorbing chemicals include para-aminobenzoic acid-PAMA- cinnamates, and salicylates, which protect against UVB alone. Benzophenones protect against both UVB and UVA and are also chemical sun-screeners.[4] Photosensitivity The skin is our main defense against light, and in particular against ultraviolet (UV) radiation. Sometimes the skin reacts abnormally to light by becoming inflamed. This is called photosensitivity. There are many causes of photosensitivity. Some of the most important are below: Acute parts like Sunburn Xeroderma pigmentosum, Porphyria, Solar urticaria, Pellagra, and Photosensitivity disorders like Polymorphic light eruption, Juvenile spring eruption, Hydroa vacciniforme, actinic prurigo. Disorders exacerbated by light include Drug reactions, Lupus erythematosus, Rosacea Dariers disease Eczema (including actinic dermatitis and photo contact dermatitis Psoriasis Lichen planus. These reactions are either a direct toxic effect of light, or have an immunological component, either provoked by light alone or in conjunction with something else such as a drug. Diagnosis and treatment of common causes of photosensitivity The acute effects of sun on the skin are all too familiar. They are caused largely by medium wavelength UV radiation (UVB), but the dose required producing sunburn depends on: (1)An individuals skin type (2)The intensity of the radiation (greatest near the equator and around midday) (3)The length of exposure to UVB Mild sunburn causes erythema: more severe damage leads to extensive blistering and epidermal boss. Treatment makes little difference to the acute changes, but symptomatic relief can be obtained with soothing lotions, such as calamine. These include avoiding the midday sun, seeking shade, wearing appropriate clothing and eyewear, and using sunscreens, this is more important for those with skin type I and II than for those with a more radiation skin. There are several special examples which are listed and explained: (1) Porphyria: Some forms of porphyria are associated with photosensitivity. In a European child the most common is erythropoietic protoporphyria, whereas an adult presenting for the first time probably has porphyria cutanea tarda. The latter is often associated with alcoholic liver disease. Screening tests involve blood ,urine and stool samples and are best undertaken in a specialist setting. (2)Solar Urticaria: Rarely, exposure to light leads to urticarial weals. (3)Pellagra: In western societies, nicotinic acid deficiency is seen most commonly in alcoholics. It presents a triad of changes: Diarrhoea Dementia Dermatitis, which is light sensitive. (4)Polymorphic light eruption This is perhaps the most important, and certainly the commonest of the primary photosensitivity disorders. Patients often refer to their skin changes asprickly heat, but true prickly heat (or miliaria rubra)is quite different. Polymorphic light eruption presents a day or two after sun exposure, with changes on light exposed areas, for example the forearms, legs the V of the neck and the face. The lesions are itchy and morphologically variable (hence polymorphic). There may be papules, plaques, and blisters of areas resembling eczema. They increase in intensity over a week or so before subsiding. Treatment with topical steroids provides some relief, but some patients require systemic steroids to control an acute attack. Prevention is a better approach. Unfortunately, sunscreens are often not effective, but pre-season PUVA works well and can last for a whole summer. An alternative is the use of antimalarial medication (notably hydroxychloroquine) taken during sunny periods, or while abroad. A variety of polymorphic light eruption occurs almost exclusively in boys. Clusters of small blisters appear on the topes of the ears, especially in early spring. The condition settles spontaneously with age. Clinics in Photodermatosis Actinic Prurigo Actinic prurigo (AP) is a dermatosis that belongs to the group of idiopathic photodermatoses. Many names have been given to it, such as: solar dermatitis, GuaÂÂ ­temalan cutaneous syndrome, solar prurigo, light-sensitive eruption in American Indians,familial actinic prurigo, polymorphous light eruption, (prurigo type) solar prurigo of high plateaus, and hereditary polyÂÂ ­morphic light eruption of American Indians; howÂÂ ­ever, it is the term actinic prurigo, coined by Lon-dono11 in 1968, which is preferred and used by most authors today. Actinic prurigo is a chronic photodermatosis that has frequently been confused with polymorphic light erupÂÂ ­tion (PLE). However, there are now enough clinical, histologic, epidemiological, and immunogenetic data to suggest that they are two different diseases. AP begins in the first decade of life usually around ages 4 to 5, affects females more than males (ratio 2:1). The lesions are symmetrical in the sun-exposed areas of the face (eyebrows, dorsum of the nose, malar reÂÂ ­gions, upper and lower lips), V-area of the neck, dor-sum of hands and forearms. The primary lesions are erythematous papules although excoriaÂÂ ­tions, crusts, and lichenified plaques are commonly seen. Pruritus is a rule and usually very intense. One of the clinical features which distinguish this disease from PLE is the absence of vesicles as primary lesions in AP. Of course, whenever a secondary dermatosis such as eczema, impetigo, or contact dermatitis ensues, vesiÂÂ ­cles may be seen. Two other differences between AP and PLE are lip and conjunctival affection in AP. CheiÂÂ ­litis of actinic prurigo affects 84% of patients. AlÂÂ ­though lesions are usually seen in both lips, the lower one being more exposed to sun rays is affected first an d more intensely; severe cases show edema, crusts, fisÂÂ ­sures, shallow ulcerations, and hyperpigmentation, while in mild cases only dry lips with scaling may be found. Atopic dermatitis with photosensitivity where the key findings are a familial incidence, an early infancy onset, the presence of xerosis, the sparing of the tip of the nose, and a good response to topical cortico-steroids and emollients. Chronic actinic dermatitis which is quite infrequent, starts much later in life has a reduced UVB minimal erythema dose induction, and/or positive photo-patch testing. Persistent light reactors and actinic reticuloid show histologically dense lymphocytic inÂÂ ­filtrates, which especially in the latter may resemble true lymphomas. [5] Phytophotodermatitis Phytophotodermatitis is a very common skin disease in some countries. It is an acute phototoxic reaction where a substance containing psoralens comes in conÂÂ ­tact with the skin which is then exposed to UVA light. The clinical picture is that of sunburn ranging from mild erythema to severe blistering; it is usually accomÂÂ ­panied by stinging or burning sensations. A residual hyperpigmented macule is the final stage of the disease and usually persists for weeks to months; some dark-skinned individuals (skin types IV to VI) may only present with this hyperpigmentation without any preÂÂ ­vious signs or symptoms of sunburn. The most common phototoxic compounds are the furocoumarins which contained in a wide variety of plants, especially of the Umbelliferae, Rutaceae, and Moracea families. Commonly occurring photosensitizÂÂ ­ing plants include citrus fruits such as limes and orÂÂ ­anges, figs, and many vegetables such as celery, parsÂÂ ­nip, parsley, carrots, and dill32; furocoumarins in lime pulp are 13 to 182 times less concentrated than those in the peel. Treatment is only symptomatic. Topical corticoste-roids help alleviate the burning sensations but do not seem to improve skin healing. Sunscreen use helps the resolution of the hyperpigmentation, and is the most important prophylactic measure for high-risk people. Melasma Melasma (chloasma) is characterized by light or dark brown hyperchromic macules with undefined borders, affecting mainly and symmetrically, the sunlight-exÂÂ ­posed areas of the face. Melasma predominates in women, although it also affects men and has been reÂÂ ­lated to sunlight exposure as well as hormonal, racial, and hereditary factors. Melanocytes are well known to be stimulated by estrogen and other sex-related hormones. Pregnancy and the ingestion of oral contraceptives can produce or exacerbate melasma, with an increase of melanogenesis and the presence of large melanocytes. Facial melano-cytes appear to be especially sensitive to hormonal inÂÂ ­fluences but sunlight is always necessary for melasma to occur. Melasma has been reported to have a greater inciÂÂ ­dence in tan or dark-skinned persons, especially in skin types III, IV, and V, but also depends, as stated before, on sunlight exposure (including UVA and visiÂÂ ­ble light). Piquero-Martin has observed that pigment dispoÂÂ ­sition (as seen with woods light), tends to occur more superficially in lighter skins and deeper in darker skins, the latter being more difficult to treat and eradicate. In some dark-skinned patients with clinically evident melasma, under woods light, the hyperpigmentation disappears. Apparently, this can be related to melanic pigment located deep in the dermis. Differential diagnoses include Rhiel melanosis, Ashy dermatosis, Addison disease, pigmented lichen planus, and postinflammatory hyperpigmentation. Many treatment modalities have been used, such as mercury compounds, vitamin C, tretinoin, topical steÂÂ ­roids, glycolic acid, azelaic acid, and hydroquinone. Pytiriasis Alba Pytiriasis alba is a chronic asymptomatic dermatosis of unknown ethiology, characterized by hypochromic macules, 1 to 5 cm in diameter, covered by a very fine scale, with an ill-defined and occasionally hyperpig-mented border. The macules are mainly located on the sun-exposed areas of the face (malar areas, forehead, around the nasal and moth orifices) and extremities. The cause of this dermatosis is unknown, but many factors have been attributed to it. The main cause is sunlight exposure on a tan or dark skin, and it has been described as a reactive dermatosis to a distant staphy-loccocal or streptoccocal upper respiratory tract infection. The lesions have been attributed to postinflamma-tory hypopigmentation, with a decrease in melanosome number and size, low keratinocyte melanin uptake, and light refraction from a hyperkeratotic and parakeratotic stratum corneum. The histopathology shows an epiÂÂ ­dermis with hyperkeratosis and parakeratosis, acantho-sis, and mild spongiosis. In the papillary dermis, vaso-dilation and mild perivascular inflammatory infiltrate and occasional pigment incontinence can be seen. Sunlight radiation (UVA, UVB, and visible light) in atopic patients with tan or dark skin are the most commonly affected. Treatment of pytiriasis alba must include sunlight protection, sun filters, low potency corticosteroids with a topical antibiotic (mupirocin, vioform). If an upper respiratory tract infection is detected, specific treatment should be given. Pellagra Also named Gaspar Casals disease, pellagra is a nutriÂÂ ­tional disorder due to nicotinic acid deficiency, a B complex vitamin. Niacin is a nonessential vitamin and can be synthesized from the aminoacid tryptophan via the kynurenine pathway. It is mainly expressed on the skin, gastrointestinal and central nervous system. Pellagra is a bilateral and symÂÂ ­metrical dermatosis affecting sun-exposed areas. The avitaminosis can be caused by drugs, such as isoniazid, 6-mercaptopurine, 5-fluouracil, and chloram-fenicol. Phenytoin and sodium valproate51 have also been related to nicotinamide deficiency. Clinical findings in pellagra include dermatitis, diarÂÂ ­rhea, and dementia (the 3Ds). Pellagra is characterized by a intense red, scaly and hyperpigmented plaques on areas exposed to sun, heat, friction, or pressure. The lesions can be edematous with a burning sensation and occasional vesicules and des-quamation. In chronic lesions, the skin is thickened, hyperpig-mented with a dark brown hue. A typical finding is Casals necklace, a scaling collarette around the neck which extends down toward the sternum. Flexural fold may be macerated, and on seborrheic areas, follicular hyperkeratotic plugs are freÂÂ ­quently present. Frequently, angular cheilitis, glossitis with papillary atrophy with a tender beefy red tongue, and esophagitis are seen. Manifestations in adÂÂ ­vanced disease cases are vomiting, diarrhea, and weight loss with secondary anemia or amenorrea. CenÂÂ ­tral nervous system symptoms include irritability, headaches, insomnia, amnesia, and anxiety. Later on, patients develop tremor, movement disorders, numbÂÂ ­ness, encephalopathy, paralysis, and psycosis.[5] PDT in dermatology Photodynamic therapy (PDT) harnesses the power of light and oxygen to enact biologic change. In its infancy, the use of PDT in the treatment of dermatologic disease was limited due to the prolonged and pronounced photosensitivity resulting from systemic photosensitizing agents. HowÂÂ ­ever, in the early 1990s Kennedy and Pottier described the use of topical 5-aminolevulinic acid (ALA) to create endogÂÂ ­enous protoporphyrin IX (PpIX) from which came a limited, localized, photodynamic response. With this development, many of the early limitations of PDT were alleviated, and the treatment became much more convenient. Early application focused primarily on the treatment of dysplastic and neoplastic disease; however, during the past few years, the versatility of PDT has been more fully realized, and it is now also being used to treat a wide variety of inflammatory and infectious processes. The effectiveness of PDT depends on the photosensitizer used, its ability to selectively penetrate diseased tissue, and the duration of application; the activating light source, its ability to penetrate to the desired target, and its duration of exposure; and the type of target cells and their oxygenation status. To be effective, the damage resulting from PDT must surpass cellular repair mechanisms, a feature referred to as the minimum photodynamic dose. [6] Summary According to the lecture the Professor Moseley gave us and the materials I get from relative books and papers. We can know that the photodermatology is a huge branch of skin disease. First I give the introduction and a review of background and history, it can clear explain what is photodermatology especially photodermatosis in clinic use. Next I focus on Photosensitivity, PDT in dermatology and Clinics in Photodermatosis, which explain different parts of the whole photodermatology. In Clinics of photodermatosis, there are many kinds of photodermatosis listed and illustrated, including the principles, treatment and prevention. As new to dermatology, PDT is an effective therapy to cure dermatosis by penetrating diseased tissue.

Scarlett Letter :: essays research papers

Pearl and the Spice of Life Really good salsa has lots of zesty vegetables and spices to make it good. But what if the spiciness of the salsa was taken away? It would just be tomato sauce. Pearl is the spice of The Scarlet Letter by Nathaniel Hawthorne. If her character was not present, the book would have a completely different flavor. In his essay entitled â€Å"The Genius of The Scarlet Letter,† Anthony Trollope states, â€Å"Pearl is miraculous,-speaking, acting, thinking like an elf,-and is therefore, I think, a drawback rather than an aid. The desolation of the woman, too, would have been more perfect without the child† (Trollope 243). Trollope’s point is well made, however the absence of Pearl would have made The Scarlet Letter an entirely different story. Without Pearl there would have been no proof of Hester’s adultery, and she might have become more depressed, even sinned more. However, if Pearl had been a more normal and obedient child, she would have been more well liked by readers. The most drastic change that would have been made in the book in the absence of Pearl would be that it would no longer have been called The Scarlet Letter. The reason for this being that without Pearl, there would have been no proof that Hester had committed adultery. Therefore, no one would have known and there would have been no punishment. Instead, Hester would have gone through the same guilt and internal battle as the minister, Reverend Dimmesdale. The reason that Dimmesdale is so tortured inside is because of the incredible feeling of guilt that he has because of having never taken blame or punishment for his sin. If Hester took no punishment, she would feel that same torture inside. But Pearl is present, so she is proof of Hester’s adultery. Hawthorne says it best when he states, â€Å"God, as a direct consequence of sin which man thus punished, had given her a lovely child† (82). Hester’s punishment was the consequence of having a child. Pearl is not only the proof of Hester’s adultery, she is also the thing that keeps Hester going. Hester may have fallen into a depression and eventually died, but Hester has to keep sewing, keep getting out of bed in the morning, and keep taking care of herself because she has someone else to take care of too. Hester’s feelings about Pearl are revealed when Hawthorne states, â€Å"But she named the infant ‘Pearl,’ as being of great price,-purchased with all she had,-her mother’s only treasure!† (82).

Russian History Essay -- Vladimir Lenin, Peter the Great

The Soviet Union has had numerous leaders throughout it’s existence as a country. However, there are a few leaders that will forever be in Russian history books and lectures. Among those leaders who have had the largest influence on the Soviet Union are; Vladimir Lenin, Peter the Great, Alexander Kerensky, and Joseph Stalin to name a few. While all of the leaders are interesting and have influence on Russia, this research paper will specifically focus on Joseph Stalin. Joseph Stalin lead the Soviet Union for over 20 years and he certainly had a unique way of doing so. While Stalin did contribute to turning Russia into a world superpower, he was a murderous dictator who is among many things, responsible for millions of innocent lives, genocides, and famines. While Stalin’s birthday is printed in different places as two different dates, Iosiph Vissarionovich Djugashvili was born on December 21, 1879 in Gori, Georgia (Montefiore 2004). Stalin was born to â€Å"illiterate peasant parents†, Vissarion and Ekaterina, and his father is said to be the cause of his ruthless soul. According to the Jewish Library, he was undeservingly beaten by his father and this was reason for him to have revengeful feelings towards everyone who had power over him (Jewish Virtual Library 2011). He eventually would chang his name to Joseph Stalin, which means â€Å"Man of Steel†. Some sources say that Lenin is referenced in his name change (stal + Lenin = Stalin) (Jewish Virtual Library 2011). When Stalin was just seven years old his face was permanently scared after he acquired a case of smallpox. Iosiph attended church school when he was young and would also do so later under the preference of his mother (Radzinsky 1996). Stalin was involved in two ac... ... of tyrant reign, millions of innocent Soviet people were enduring murders, false imprisonments, famines, brainwashing, and terror. They feared constantly that they be subjected to unjustified arrest or execution. They feared for the lives of their friends and family and also for the future of their children and the future of Russia. Stalin died on March 19, 1962 in Kazan where he was banished to. It is thought that he had help, like his father, in dying. I’m sure that the Soviet people breathed a sigh of relief, they no longer had to live in such an intense fear and anxiety. However terrible he was many Russians still believed him to be a great leader. Stalin was a murderous dictator who is among many things, responsible for millions of innocent lives, genocides, and famines however, Russia has Stalin to thank for turning the country into a world superpower.

The Outsiders Essay

The Outsiders Critical Lens Essay The quote in question is  Ã¢â‚¬Å"All good is destined to be defeated. †Ã‚  The quote means,  for every good guy,  there is a bad guy. For every hero,  there is a villain. Everyone who has ever tried to do something good has been destined to be stopped. The quote not only speaks for literature,  but for everything. If you look from now, all the way back to ancient times, you will see examples of this in many works of literature. The book The Outsiders is a good representation of the quote. I agree with the quote â€Å"All good is destined to be defeated†. I can’t think of any good that hasn’t had an attempt to be stopped. In the story The Outsiders there are many examples of good being defeated. When Johnny went into a burning building to save kids, he ended up getting killed. When Darry was trying to give Ponyboy a better life, he ended up forcing him to run away. When Ponyboy attempted to make friends with Cherry and Marsha, he was jumped by their boyfriends. These are just a few of examples from the story. I feel that the story The Outsiders really showcased the quote â€Å"All good is destined to be defeated. † It was a story of how fun loving greasers turned to cold blooded killers after a gang of socs continue to attack them with violence. The story builds up to a climax, where there are many nail biting things are happening simultaneously. Johnny kills Cherry’s boyfriend Bob, The greasers are preparing for a big rumble with the socs, and Ponyboy and Johnny run away The Outsiders Essay The Outsiders Critical Lens Essay The quote in question is  Ã¢â‚¬Å"All good is destined to be defeated. †Ã‚  The quote means,  for every good guy,  there is a bad guy. For every hero,  there is a villain. Everyone who has ever tried to do something good has been destined to be stopped. The quote not only speaks for literature,  but for everything. If you look from now, all the way back to ancient times, you will see examples of this in many works of literature. The book The Outsiders is a good representation of the quote. I agree with the quote â€Å"All good is destined to be defeated†. I can’t think of any good that hasn’t had an attempt to be stopped. In the story The Outsiders there are many examples of good being defeated. When Johnny went into a burning building to save kids, he ended up getting killed. When Darry was trying to give Ponyboy a better life, he ended up forcing him to run away. When Ponyboy attempted to make friends with Cherry and Marsha, he was jumped by their boyfriends. These are just a few of examples from the story. I feel that the story The Outsiders really showcased the quote â€Å"All good is destined to be defeated. † It was a story of how fun loving greasers turned to cold blooded killers after a gang of socs continue to attack them with violence. The story builds up to a climax, where there are many nail biting things are happening simultaneously. Johnny kills Cherry’s boyfriend Bob, The greasers are preparing for a big rumble with the socs, and Ponyboy and Johnny run away

Health and Education

Health education is an essential tool of community health. Every branch of community health has a health educational aspect and every community health worker is a health educator. But health education has been defined as a process which effects changes in the health practices of people and in the knowledge and attitudes related to suet changes. A great deal of ill-health in this country and elsewhere is due to ignorance of simple rules of hygiene or of indifference to their practical application. However, health is of the greatest importance and an indispensable factor in life.Without it a man becomes burden to others and useless to himself. In other words, health is the basis of individual and social welfare. But the concept of health and practice of health-education is almost as old as the human race. Health education has been defined as â€Å"the sum of all experiences in school and elsewhere that favor ably influence habits, attitudes and knowledge, related to individual, commun ity and racial health. † At present in our country much attention is being paid to the education for total health. Good health is a pre condition for good education.There is a saying that sound mind lives in a sound body. So, education cannot be acquired without the proper frame of the mind and proper frame of mind cannot be possible without proper health and hygiene. Realizing the importance of health education Secondary Education Commission, 1952-53 stated: â€Å"Unless! Physical education is accepted as an integral part of education and the educational authorities recognize it, need in schools the youth of the country, which form its ‘most variable asset, will never be able to pull their full weigh to national welfare.The emphasis so far has been more on the academic type of education without proper consideration being given to physical welfare and the main ­tenance ‘ proper standards of health of the pupils†. Health education is the very foundation of every successful public health programme so one of the main functions educations should be to help every child deve ­lop a healthy body, an alert mind and sound emotional attitudes. Health education aims at bridging the gulf between the health knowledge and health practices of the children.