The Mental Health Risk Associated With The Tiger Mom...

The debate is on: The Mental Health risk associated with the Tiger Mom parenting style versus Western parenting style and how it affects the education of their kids. Recently we have been overwhelmed with the comments of strict parenting techniques used to enforce respect and discipline, education, and success. Attention has been focused on the 2011 book Battle Hymn of the Tiger Mother by Amy Chua. The Chinese culture Tiger Moms has made child rearing a mental Health issue, which could lead to the development of low self-esteem and school adjustment difficulties in their children and leave them vulnerable to depression and problem behaviors, stated by Cixin Wang, an assistant professor at UC Riverside s Graduate School of Education. Our research shows that Tiger Mother type of parenting, specifically controlling, punitive, and less supportive type of parenting is really not working in this sample of Chinese adolescents, said Cixin Wang. This research was based on data from a youth survey in Hangzhou, China. The sample included 589 middle and high school children (C. Wang, September 22, 2014). In comparison to Tiger Moms, do the western parent ing style exhibits Mental Health issue focused towards their kids? Although, experts has taken a stand, that the Tiger mom parenting style is mentally unhealthy for the rearing of children. We can also look at the western parenting style and scrutinize the liberty that kids have which make them lazy, defiant, and lackShow MoreRelated Parenting Styles: What They Are and Why They Matter Essay2804 Words   |  12 Pagesyou to the right path of knowledge and teaching you how to stay on the right path independently. A parent does not need to have any biological associations to the child in order to be a parent to them. A parent must have certain characteristics to be rightfully called a parent. For many years psychologists have defined ways to correctly support a child to adulthood for parents all over the world. Some people conclude their practice of parenting their children after the child reaches the age of 18Read Morepreschool Essay46149 Words   |  185 PagesCalifornia Preschool Learning Foundations Volume 2 CALIFORNIA DEPAR TMENT OF EDUCATION †¢ SACRAMENTO, 2010 California Preschool Learning Foundations Volume 2 Visual and Performing Arts Physical Development Health Publishing Information The California Preschool Learning Foundations (Volume 2) was developed by the Child Development Division, California Department of Education. This publication was edited by Faye Ong, working in cooperation with Laura Bridges and DesireeRead MoreStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesPearson Education, Inc., publishing as Prentice Hall. All rights reserved. Manufactured in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission(s) to use material from this work, please submit a written request to Pearson Education, Inc

Drinking Age - 1395 Words

In almost all scenarios an argument can occur that debates whether one thing or another is good or bad, helpful or hurtful. Some debates are simple with no major side effects such as would drinking gatorade or water better maximize the performance of athletes. Other debates involving drinking are not as simple, these debates involve alcohol drinking age. Both arguments can have different viewpoints, the difference is the significance in the argument. What should the legal drinking age in the United States be? Consuming alcohol has been done for many years. Unlike a typical beverage that hydrates the body alcohol is consumed for its positive side effects, but the negative effects are forgotten. Often these so called positive side†¦show more content†¦A college report showed that most kids are drinking to get drunk. In college a large sum and the majority of students are under twenty one. This fact is showing the immaturity of the students and more reasons the age should be tw enty-one to drink. Drinking to get drunk and binge drinking are irresponsible which those under twenty-one are continually showing that they are. Yes there are adults who drink irresponsibly but the majority handle alcohol maturily. Some argue that there are children who drink responsibly, how can a minor drink responsibly when drinking at all is illegal. Binge drinking does more than harm the body , thsi is another reason the drinking age at eighteen would harm college students. Binge drinking increases academic struggles in students and while eveyone may not believe this, the actual reason for college is an education. By binge drinking obtaining this goal can be a challenge. While the college life is a large part of the legal drinking age there are other reasons it should stay at twenty-one. Drinking and driving is not acceptable by any age group and effects many lives every day. A vehicle is a weapon and operating this such weapon while intoxicated, or under the influence of any substance that will decrease your ability to operate the vehicle is foolish and dangerous for the driver, its passengers, and anyone who may be unfortunate enough toShow MoreRelatedLowering the Drinking Age1523 Words   |  7 Pages According to Andrew Herman, â€Å"Each year, 14,000 die from drinking too much. 600,000 are victims of alcohol related physical assault and 17,000 are a result of drunken driving deaths, many being innocent bystanders† (470). These massive numbers bring about an important realization: alcohol is a huge issue in America today. Although the problem is evident in Americans of all ages, the biggest issue is present in young adults and teens. In fact, teens begin to feel the effects of alcohol twice asRead MoreNot Lowering The Drinking Age989 Words   |  4 PagesLowering the Drinking Age There are many different views on drinking alcohol, especially underage drinking. Everyone has different views on the drinking age. Some think it should be lowered and others believe that it should be raised. Then some believe that it should remain the same at the age of twenty-one years old. Keeping the alcohol consumption age at twenty-one limits the dangers of not only those under twenty-one, but other people in the community. Lowering the drinking age will cause moreRead MoreDrinking Age1012 Words   |  5 PagesDrinking Age The drinking age was moved from 18 to 21 for a reason. The higher drinking age of 21 has saved many lives, helped reduce the amount of underage drinking, and therefore should not be lowered. Many studies from a large variety of sources have proven higher drinking ages have a positive effect on society. Alcohol is harmful to the development of younger people. Research has shown that an adult is less likely to bingeRead MoreDrinking Age Essay677 Words   |  3 PagesDrinking Age When teen-agers turn 18, they are told that they are adults and are sent into the world. They go to college, get a job, marry or join the military. They do grown-up things like vote, pay taxes and become parents. But they cant go to the pub for a beer because when it comes to liquor, they are still just kids. Wheres the fairness in the 21-and-older drinking law? First, it is necessary to question this law. Why is 21 the magical age that makes one intelligent and matureRead MoreLowering the Drinking Age1223 Words   |  5 Pagesâ€Å"What we’re doing now to prevent underage drinking isn’t working; it’s time to try something else.† Although many people argue that the National Minimum Drinking Age Act of 1964, which lowed the drinking age from eighteen to twenty one, was a good idea. David J Hanson a professor in the State University of New York believed that something needs to be done to make the United States a safer place to live. Is it fair that people in the United States can serve in the military, vote in elections, serveRead MoreThe Debate Of The Drinking Age959 Words   |  4 PagesThe drinking age has always been twenty-one in the United States, whenever it has been questioned on why twenty-one and not eighteen. The scientific answer has always been because the eighteen-year-old brain is not fully develo ped yet. See what I have a hard time understanding is why eighteen-year-olds are considered adults at the age of eighteen, but we can’t have a drink. At eighteen you are allowed to buy cigarettes, join the army, change your name. I just don’t understand why at eighteen youRead MoreMilitary Drinking Age1983 Words   |  8 PagesDrinking Age of the Military: Should it be Lowered Jason M. Stoudt DeVry University The drinking age in the military is currently set at 21 years old as it is set for the rest of the country. There has been an age old statement widely used by those in the military, â€Å"If I am old enough to fight and die for my country, I should be old enough to drink†. The debate is out there that the drinking age should be lowered for all young adults from 18 years old to 21 years old. The idea behind the factRead MoreLowering The Drinking Age Of The Age981 Words   |  4 PagesHowever, there are those who remain persistent in their requests to drop the drinking age to a slightly lower option. Opposition to the legal drinking age of twenty-one has shown to have some support from mostly younger groups of people, without much validation as to why a lowered drinking age would be beneficial to our country as a whole. Yet, there are still some interesting arguments for those in favor of dropping the age at which it is legal to drink to eighteen. Consider how many young adults chooseRead MoreBinge Drinking vs the Drinking Age Essays829 Words   |  4 PagesEnglish 101 March 13, 2013 Binge Drinking VS the Drinking Age Presidents of college campuses around the nation face issues of underage drinking and binge drinking on a regular basis and realizes that it is a danger and a problem. â€Å"Alcohol consumption is the third leading cause of death in the U.S., a major contributing factor to unintentional injuries, the leading cause of death for youths and young adults, and accounts for an estimated 75,000 or more deaths in the United States annually† (WechslerRead MoreBinge Drinking And The Minimum Legal Drinking Age3264 Words   |  14 PagesKarzhova Marina Erin Beaver English Composition II 5 November 2014 Binge Drinking and the Minimum Legal Drinking Age In the year 1984, President Ronald Reagan enacted a law that increased the minimum drinking Age all U.S states to 21 years. As a result, it is believed that the mortality rates due to road accidents reduced from 5,000 in the 80’s to 2, 000 in 2005 (Dean-Mooney). However, the issue of binge drinking remains unsolved with learning institutions having to deal with it every semester. In

Electronic Health Record Free Essays

Introduction Hospitals and other health care providers increasingly rely on cutting-edge technology to provide medical treatments to patients, and a growing number also realize the benefits of technological advances in administration and record-keeping. In the recent past, most health care providers maintained patient records in paper files, eventually transferring the completed records to microfilm for safekeeping. Many providers now, however, use computers and computer networks, microwave technology, facsimile machines, and optical scanning and storage equipment in the creation, transmission, storage and retrieval of medical records. We will write a custom essay sample on Electronic Health Record or any similar topic only for you Order Now Although a computer based patient record system can improve efficiency and the quality of care rendered by a provider, it may also increase a health care facilities exposure to liability under many of the legal theories or causes of action traditionally associated with health information management. It generates unique confidentiality and integrity concerns; for example, it increases the risk of improper disclosure of personal health information and computer sabotage of persons gaining unauthorized access to a computerized record system. There are a number of issues, more of an ethical rather than technological concern regarding electronic health records. An EHR is defined as a longitudinal collection of electronic health information that provides immediate electronic access by authorized users. (HIMSS) An EHR may involve knowledge and decision support tools that enhance safety and efficiency as well as support of efficient processes for health care delivery. As new advances in technology occur and the value of large databases of clinical data continues to grow, the conversion of records from paper to a computerized format will remain a dominating trend in health information management in the decade to come. Health care reform initiatives and the increasing penetration of managed care into the health care delivery system have further heightened the need for comprehensive automation and the automated need for health care information. Whether it is to monitor costs, improve patient care, or evaluate participating health care professionals, the basis is in gathering and sharing health care information. In a managed care setting, confidential patient information is frequently linked through databases that allow participating providers to access all the clinical data about a patient who may have received treatment at a variety of points of service within an integrated delivery system. In this environment, paper record systems that were provided based are being replaced with electronic medical records. Computerization of a provider’s records can enhance quality of care by permitting quick capture of information in a patient’s record and by improving access to a patient’s records by the many health professionals who may be involved in his care. In addition, quality improvement and quality assurance programs can be strengthened with the help of automated record systems. One basic risk prevention technique involves determining who has access to what information for what purpose at which times. (McWay, 2003). Automated record systems create the possibility of linking the patient record to expert diagnostic systems and other electronic decision support tools to further enhance the quality of patient care. A fully integrated computer based record system can also increase efficiency by reducing the volume of paperwork required for admissions, order entry, reporting of results of radiological examinations and laboratory tests, pharmacy dispensing. This in turn diminishes the overall time spent on updating and filing the records. In addition a computerized record system can assist with patient scheduling. Although a computer based patient record system can improve efficiency and the quality of care rendered by a provider, it may also increase a health care facility’s exposure to liability under many of the legal theories or causes of action traditionally associated with health information management. Inadequate system security reflects the potential for large-scale breaches of data security in a computerized medical record system. Electronic data exchange has also opened the door to new kind of health care fraud, arising from the growing number of computer links to claims information and the addition of electronic fund transfer capabilities. According to Forty percent of surveyed U. S. adults think that electronic health records will have a â€Å"somewhat negative† effect on the privacy of personal information and health data, while 20% believe EHRs will have a â€Å"somewhat positive† impact on the privacy of personal data, according to a new survey from CDW Healthcare. Moehrke, 2011). Conclusion Millions of individual medical records float around these days in a vast electronic network that serves both commerce and scientific research. The information navigates around the country, speeded by computers. Computers help diagnose patients; enhance quality of care; improve access; increase efficiency; and conserves time. One of the main reasons that there is such a big national movement toward elect ronic medical records is the increasing evidence that they improve patient safety. Preserving the confidentiality, integrity, accessibility, accuracy, and durability of records on an automated system should be prioritized. Finally, it is vital that computerized record systems be designed, installed, and maintained in a manner that preserves the reliability of records created and stored on such systems. Whether the health care provider chooses a traditional paper-based patient record or electronic record, the same legal requirements apply: the record must be kept secure and guarded from unauthorized access. Works Cited HIMSS. (n. d. ). EHR Electronic Health Record. Retrieved April 28, 2011, from www. himss. org: http://www. himss. org/ASP/index. asp McWay, D. C. (2003). Legal Aspects of Health Information Management, Second Edition. In D. C. McWay. Clifton Park: Thomson Delmar Learning. Moehrke, J. (2011, March 13). Healthcare Security/Privacy. Retrieved April 28, 2011, from www. healthcaresecprivacy. blogspot. com: http://healthcaresecprivacy. blogspot. com/2011/03/ healthcare-privacy-why-are-patients. html How to cite Electronic Health Record, Essay examples Electronic Health Record Free Essays Abstract Electronic health records (EHR) is more and more being utilized in organizations offering healthcare to enhance the quality and safety of care. Understanding the advantages and disadvantaging of EHR is essential in the nursing profession as nurses would learn its strengths and weaknesses. This would help the nursing profession know how to deal with the weak areas of the system. We will write a custom essay sample on Electronic Health Record or any similar topic only for you Order Now The topic on advantages and disadvantages of EHR has been widely researched on with different researchers coming up with different opinions. Nurses ought to have knowledge on the advantages and disadvantages of EHR systems for them to use systems efficiently. This would transform the operations of health systems and benefit patients with quality service. The advantage and disadvantage of Electronic Health Records Electronic health records are designed for offering national access to selected information amassed from data found in medical records created by various providers irrespective of whether providers are in a similar healthcare system or in the event of patients of accident in a different healthcare facility (Devine, Hansen, Wilson-Norton, et al 2010). EHR is essential to nurses because it increases their efficiency hence undertake their mandate to offer care to patients effectively. Recently most of the sectors have made heavy investments in computerization of their services. The nursing practice is impacted significantly by the use EHR systems. There are both positive and negative impacts in the use of EHR systems. Some researchers have associated EHR with increased efficiency and high quality of care while others cite negative effects like high start of cost and confidentiality of health information. Understanding the advantages of EHR encourages nurses to make greater use of them, while understanding their disadvantages enables nurses to determine areas in which they ought to take caution when using them. Advantages of Electronic Health Records EHR and organizational outcomes These organizational outcomes of EHR are mostly comprised of increased revenue and cost containment, together with other less tangible benefits like enhanced regulatory and legal compliance, increased job satisfaction, and improved ability to undertake research. Various authors have made the ssertion that EHRs help care givers in capturing patient charges accurately and at the right time (Devine, Hansen, Wilson-Norton, et al, 2010). Use of EHR ensures elimination of billing errors together with erroneous coding; this in turn increases the cash flow of the provider and enhancement of revenue. Appointment reminders by EHR to patients increases visits by these patients hence increasing revenue. Majority of ave rted costs linked to EHRs result from efficiencies which result from storing the information of patients electronically (Fleming, Culler, McCorkle, et al. 2011). These comprise of increased test utilization, reduction in resources of staff used in management of patients, reduction of cost of supplies required for maintenance of paper folders decrease in cost of transcription and costs linked to pulling of charts. Other less tangible benefits include that there is increased operational performance and compliance to legal and regulatory requirements is improved. Additionally, researchers who use EHR experience less malpractice claims. EHRs Clinical outcomes The majority of clinical outcomes been focused relate to care quality and safety of patient. Care quality is defined as doing the appropriate action to the right person at the right time and in the appropriate manner and obtaining optimal results. Similarly safety of the patient is defined as avoiding injuries to patients from care aimed at helping them. Most of the research on EHR is focused on efficiency, effectiveness and patient safety. Weinger, (2010) made the assertion that computerized alerts directed at physicians enhanced the use of prophylactic care for patients hospitalized with the condition of deep vein thrombosis. There was a 19 percent increase in use of anticoagulation prophylaxis when computer alerts are used. This meant that there was 41 percent reduction in the risk of pulmonary embolism or deep vein thrombosis ninety days following discharge. In addition, researchers have established that there is a relation between efficiency and EHRs in the delivery of healthcare. EHRs societal benefits Improved ability to conduct research is another less tangible benefit associated with EHR. When the data for patients is electronically stored, makes the data easily accessible hence more quantitative analysis can be undertaken for identification of evidence-based best practices with ease. In addition, public health researchers use electronic clinical data more actively which have been amassed from a huge population hence coming up with research that benefits the society (Mitka, 2011). Clinical data availability is limited but this form of data will increase. Probable EHRs disadvantages Irrespective of the findings regarding the advantages of various functionalities of EHRs, some probable drawbacks on EHR have been identified by researchers. These comprise of financial concerns, temporal loss in productivity linked with adoption of EHR, change in workflow, security and confidentiality concerns and several unintentional consequences. Financial concerns comprise of costs of adoption and implementation, cost of maintenance, revenue loss due to temporal low productivity, and revenue declination. These factors act as deterrent for physicians together with hospitals in adopting and implementing an EHR. The purchase and installation of software and hardware, conversion of paper files to electronic forms and training of end-users are major costs. Irrespective of the associated costs, EHR technology has become common recently, as the cost has gone down significantly. The cost of maintenance for EHR can as well be high; there ought to be replacement of hardware and upgrading of software regularly. Other costs include fees for support, vendor software maintenance, external contractors’ payments and information systems staff payment. The majority of EHR financial benefits are not linked with the provider, but to the payers of third party in form of averted errors, and enhanced efficiencies; these translate into reduced payment of claims (DesRoches, Campbell, Vogeli, et al. 2010). Poor alignment of incentives for healthcare organizations and towering direct costs are an obstacle. Another probable disadvantage is the risk of violating the privacy of patients. Some of these concerns have been relieved by having policy makers take actions to ensure that patient data privacy is maintained (DesRoches, Campbell, Vogeli, et al. 2010). Recent legislation enforces stringent requirements which prevent unauthorized entities from accessing the data. Topic availability The topic on advantages and disadvantages of EHR is widely available both online and on printed sources. Searching the topic online a wide range of information was obtained. Google search engine had considerable information on the topic. In the search the keywor ds used were ‘Electronic Health Records’ and ‘EHR. ’ With these keywords, the information obtained was on general knowledge on electronic health records. On adding advantages and disadvantages to the EHR, more refined results on the positive and negative impacts of EHR were obtained. On adding ‘EHR effect on nursing’ the results obtained showed how EHR has positively and negatively affected the functionality of the healthcare system and nursing profession. Nursing and medical journals were mostly used to get this information. In the search, online libraries like EBCOHOST and Apollo library were used. When conducting the search only peer reviewed materials were chosen by selecting that option and the sources selected were not older than five years. For this case sources were chosen to be from 2010 up to 2013. On EBSCOHOST, with the above mentioned criteria and keywords the search results were 485. Apollo online library had search results of 502. This indicates that the topic is widely researched and there is adequate information online to be used for research and practical nursing practice. This search criterion was also used on Google scholar and relevant information was obtained. Information availability On conducting search online with various search engines, information was accessible in various formats. The information obtained showed articles written by researchers regarding the advantages and disadvantages of electronic health records. While some articles presented challenges, others presented benefits of the EHR system. Files were found in PDF PowerPoint and Word document formats. The obtained results on this topic could be used for a wide range of reasons. Some on the information touched on how professionals could use this information in their work. For instance, the information on the benefits of using EHRs could help nurses determine how well they can use the EHR systems to enhance efficiency in their operations. Professionals can also get the information of some of the negative impacts of electronic health records. As nurses get to understand this information, it can form basis for their research to unearth what has not yet been found. Some sections of information were useful for patients who want to know about the efficiency and privacy of the system. The administration would find the information useful because it shows ways in which the hospital will benefit as well as how it will be affected negatively by the EHR system. For instance, the administration of the health care facilities will ensure increase in efficiency in the provision of services and billing process would be improved (Otto Nevo, 2013). Understanding these benefits would encourage healthcare administrators to make decisions on whether to adopt EHR systems. Personal views In the nursing practice, this technology of electronic health records poses some challenges that need to be addressed before it is adopted. The major concern of this topic is the security issue, whereby the confidentiality of the information stored in these systems is under question (Weinger, 2010). It is felt that unauthorized people may get access to this information and use it maliciously. Patients wouldn’t be willing to use this system unless they are assured that their information is secure. In addition, some nurses may have inadequate skills in using the system and can easily make errors that can put patients in danger. Therefore, the nurses should be adequately trained on the use of EHR systems. Failure to do so may put patients at risk and lower the quality of the care provided which would be contrary to the intentions of EHR. Though there are cons to using the system, the pros outweigh them. Conclusion This paper has discussed the topic on advantages and disadvantages related with adoption of EHR. EHR is widely believed to ensure that there is improved efficiency in provision of healthcare, cost is contained and that accuracy is maintained by reducing medical errors. Through adoption of EHR, it will be easy to conduct research as medical data of the required population would be readily available. Some of the drawbacks associated with use of EHR are financial concerns, temporal loss in productivity linked with adoption of EHR, change in workflow, security and confidentiality concerns and several unintentional consequences. Despite having many unintentional consequences of EHR on balancing the benefits with the drawbacks, EHRs are beneficial specifically at social level. Information on this topic is readily available and can be used as a basis for deciding whether to adopt the system or not. References DesRoches, C. M. , Campbell, E. G. , Vogeli, C. , et al. (2010). Electronic health records’ limited successes suggest more targeted uses. Health Aff (Millwood) 29(4), 639–646. Devine E. B. , Hansen R. N. , Wilson-Norton J. L, et al. (2010). The impact of computerized provider order entry on medication errors in a multispecialty group practice. J Am Med Inform Assoc. 17(1):78–84. Fleming NS, Culler SD, McCorkle R, et al. (2011). The financial and nonfinancial costs of implementing electronic health records in primary care practices. Health Aff (Millwood) 30(3), 481–489. Mitka, M. (2011). Electronic health records, The Journal of the American Medical Association, 305(14), p1402 Otto, P. Nevo, D. (2013). Electronic health records, Journal of enterprise informationmanagement, 26(1/2), 165-182 Weinger, M. B. (2010). Electronic health records, The New England journal of medicine, 363(24), 2372-2374 How to cite Electronic Health Record, Papers

Should Guns Be Banned free essay sample

Data from previous decades reveals that areas within America with the most stringent gun ownership rules are generally the ones with high rates of violence. Areas where guns are most commonly found and impose little controls on guns ownership to responsible and law abiding citizens experience low homicide levels. There are many explanations to this situation, but none of them prove that enforcing gun control will reduce violence and murder. This is saying that allowing citizens to own guns does not result to more violent crimes or murders. It allows a responsible citizen to have the peace of mind by self-defense. The statement that more guns equal more death would only be true if murders only involved ordinary people who kill because they have access to a gun when they get angry. However, when people tend to get angry they do thing they will regret later. a long time researcher in gun control quotes more guns per capital do not show higher crime levels than those with lesser guns per capital. We will write a custom essay sample on Should Guns Be Banned? or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Gun ownership has been put down numerous times, with critics saying that someone who owns a gun to protect themselves from burglars is likely to use it on their spouse or other members of the family when enraged, since it is the closed weapon near hand. These comments are not put in stone by any evidence, since studies show that most people that commit murder are individuals that have pasts of violence, substance abuse, psychopathology and other dangerous behaviors in the past. Should Guns Be Banned free essay sample Guns people say that they are the main cause of homicide in america today, but are they really? There is a controversy of weither or not guns should be banned to stop the crime rate in america. People of america seem to believe that guns are the leading cause of homicide, but while guns may be taken away from law abiding citizens, criminals will still have them and they will use them to threaten Americas citizens. Data from previous decades reveals that areas within America with the most stringent gun ownership rules are generally the ones with high rates of violence. Areas where guns are most commonly found and impose little controls on guns ownership to responsible and law abiding citizens experience low homicide levels. There are many explanations to this situation, but none of them prove that enforcing gun control will reduce violence and murder. This is saying that allowing citizens to own guns does not result to more violent crimes or murders. We will write a custom essay sample on Should Guns Be Banned? or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page It allows a responsible citizen to have the peace of mind by self-defense. The statement that more guns equal more death would only be true if murders only involved ordinary people who kill because they have access to a gun when they get angry. However, when people tend to get angry they do thing they will regret later. a long time researcher in gun control quotes more guns per capital do not show higher crime levels than those with lesser guns per capital. Gun ownership has been put down numerous times, with critics saying that someone who owns a gun to protect themselves from burglars is likely to use it on their spouse or other members of the family when enraged, since it is the closed weapon near hand. These comments are not put in stone by any evidence, since studies show that most people that commit murder are individuals that have pasts of violence, substance abuse, psychopathology and other dangerous behaviors in the past.

Dc Power Supply Essay Example

Dc Power Supply Essay Adaptive Control of a Step-Up Full-Bridge DC-DC Converter for Variable Low Input Voltage Applications Elton Pepa Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering Approved: ____________ok_________________ Dr. Jason Lai (Chair) ____________________ Dr. Krishnan Ramu ____________________ Dr. William T. Baumann February 6, 2004 Blacksburg, Virginia Keywords: adaptive control, phase shift modulation, full bridge, converter Copyright 2004, Elton Pepa Adaptive Control of a Step-Up Full-Bridge DC-DC Converter for Variable Low Input Voltage Applications By Elton Pepa Electrical Engineering Abstract This thesis shows the implementation of a novel control scheme DC-DC converter. The converter is a phase-shifted full-bridge PWM converter that is designed to operate as a front stage of a power conversion system where the input is a variable low voltage high current source. The converter is designed to step-up the low voltage input to an acceptable level that can be inverted to a 120/240 VAC 60Hz voltage for residential power. A DSP based adaptive control model is developed, taking into account line variations introduced by the input source while providing very good load dynamics for the converter in both discontinuous and continuous conduction modes. The adaptive controller is implemented using two voltage sensors that read the input and the output voltages of the converter. The controller’s bandwidth is comparable to current mode control, without the need for an expensive current sensor, yet providing the noise immunity seen in voltage mode controllers. The intended input source was a fuel cell but in its absence a DC supply is utilized instead. We will write a custom essay sample on Dc Power Supply specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Dc Power Supply specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Dc Power Supply specifically for you FOR ONLY $16.38 $13.9/page Hire Writer The system is simulated for both discontinuous and continuous conduction modes and implemented and demonstrated for the continuous conduction mode. The test results are shown to match the simulation results very closely. Acknowledgements First and foremost, I want to express my sincere gratitude to my advisor, Dr. Jason Lai, for his guidance, encouragement, and support during my graduate studies. His practical way of teaching, his impressive knowledge, technical skills, and creative thinking have been a source of inspiration throughout the course of my work. I am grateful to my other committee members, Dr. Krishnan Ramu and Dr. William T. Baumann. Dr. Ramu has shown his cheer, support, and advice to me from the moment I considered starting my graduate studies. The lectures, long conversations with him, and the guidance he has given me are invaluable. Dr. Baumann’s teachings of control systems have been some best lectures I have ever received during my entire school studies. My work would have not been possible without the help of a number of my fellow students. I would especially like to thank Jerry Francis for his support and help with the DSP work, testing, and great friendship. I am extremely grateful to: Chris Smith, Damian Urciuoli, Andy Mclandrich, Amy Johnson, Mike Gilliom, Mike Schenck, and Joel Gouker, all of whom I spent countless late nights and early mornings working on the FEC competition; Xudong Huang, who was my partner in the Delphi project; and other FEEC students including Changrong Liu, Huijie Yu, Junhong Zhang. There are also some past and present CPES students and friends including Lincoln, Troy, Jeremy, Leonard, Carl, Daniel, Doug and Sebastian that are deserving of my appreciation. Additionally, I would like to thank my good friends from the Albanian Club at Virginia Tech, who to some extent have eased the longing I have for my family and friends back home. Most importantly, I would like to thank my parents and my brother for everything that they have done for me throughout my life and the joy they have brought to me for just having their support. I only hope that what I have accomplished can pay somewhat for the efforts for raising and making me the person that I am today. Finally, I would like to express a great amount of gratitude to my girlfriend, Carrie, for her companionship and for being the most supportive. ii Table of Contents FEC is a competition between universities around the country and abroad primarily supported by the Department of Energy (DOE) and the Department of Defense (DOD). With the energy use rising every year and as the country becomes more dependent on foreign oil, it is in the focus of DOE to develop alternative renewable sources. One of the competitions in FEC was the Fuel Cell Inverter challenge, with the objective to develop a low-cost power processing system that supports the commercialization of a 5 kW solid-oxide fuel cell (SOFC) power generation system to provide non-utility and ultra clean residential electricity. One of the objectives of the VT team was to complete a control system that would meet the requirements set by the competition. However, due to time restrictions, a complete control system design was not implemented by the time the competition was held. The focus of this study was to design a high performance controller for a frontend DC-DC converter to be used in a variable low voltage input power conversion system similar to the FEC requirements. Since at the time of FEC competition and when the work in this thesis was conducted a SOFC was not available, a variable DC supply was utilized instead. The control method presented here is an individual effort to complete the work from the FEC, surpassing the given requirements. 1 1. 2 Objective and Outline The focus of this thesis is in the conversion of an unregulated low voltage high current input source to a useful source of energy that can be used directly by consumers. As mentioned before, the intended primary energy source from the FEC [1] was a solid oxide fuel cell which in this thesis was replaced by a DC supply that can vary the input voltage in a fashion similar to a fuel cell. In the FEC, the variable DC input voltage was to be converted to two single phase 120 VAC outputs that can be combined to produce a 240VAC, 60 Hz output. Such conversion was done in two stages. First, the nominal voltage of 28VDC input from the DC source is boosted to a 200VDC bus voltage that can be inverted by a single phase inverter to the desired 120/240VAC outputs. The main requirements for the FEC competition are listed in Table 1 [2]. Table 1. Main design requirements for FEC 2003 Design Item 1. Manufacturing Cost 2. Output Power Capability-nominal 3. Output Power capability overload 4. Output Voltage 5. Input Source (SOFC) 6. Galvanic isolation Target Requirement Less then US $40/kW for the 10 kW design in high volume production 5 kW continuous 10 kW overload for 1 minute (5kW from fuel cell) 120 V/ 240 V nominal 22-41 VDC, 29 V nominal Galvanic isolation of the system. The common neutral point of the ac output phases must be earth ground gt; 90% 7. Overall Efficiency To achieve these cost and efficiency targets, the hardware had to be designed from the bottom up, eliminating expensive components with cost-effective solutions. This energy management system has three main parts: the front-end DC-DC converter, the AC inverter and energy storage elements. The system block diagram designed for the FEC 2003 is shown in Figure 1. 1. This report focuses on the front end DC-DC which is an important link between the low voltage high current unregulated input voltage source and the 60 Hz inverter. 2 Input Fuel DC Cell (SOFC) source DC-DC Converter DC link DC-AC Inverter 120/240V Load Bi-directional Converter DC Q1 I A Q3 Q4 Llk B Lf Cf Q2 DC- DC XFMR Rload Battery System Figure 1. 1. Basic block diagram of the power conversion system The solid-oxide fuel cell that was used as the basis for designing the DC-DC converter, has a voltage-current characteristic, also known as the polarization curve, given in Figure 1. 2 Figure 1. 2. Voltage to current plot of a solid oxide fuel cell (SOFC) According to the power plot Figure 1. 2 , the front end DC-DC converter is required to operate at low-voltage high-current at heavy load, and high-voltage-low current at light load conditions. In order to provide a bus voltage large enough for a 120/240V inverter, the input voltage must be boosted significantly. For this application, an isolated topology is favored for converter optimization [3]. Isolated converter topologies provide 3 advantages in applications requiring large voltage conversion ratios. Transformer isolation can reduce switch and diode device stresses and allows multiple windings or taps to be used to for multiple converter outputs. The full-bridge is a popular design for both buck and boost applications and has become a basis for numerous resonant zero voltage and zero current switching (ZVS, ZCS) schemes. Often in high power applications a phase shift modulation (PSM) switching scheme is used to achieve ZVS and/or ZCS transitions through the interaction of converter parasitic energy storage elements [4]. Another advantage for using the full bridge converter is the fact that when higher power application are requested the full bridge converter can act as a modular block and that it is possible to stack up [5]. For this purpose the chosen topology for the converter to be used in this application is a Full bridge phase shifted PWM converter. The DC-DC converter discussed herein provides a favorable method of boosting the low DC voltage high current input DC for an inverter input. For sufficient inverter input voltage margin, a 200 V converter output was desired for the entire fuel cell input voltage range. To meet these criteria, the converter consists of a switching stage, a transformer stage, and an output rectifier and filter stage Since the input source is unregulated, the DC-DC converter has to take into account these changes and act appropriately without affecting the output. The output from the DC-DC converter creates the DC link bus voltage. The DC link bus voltage created by the converter needs to be stiff because it is being used by single phase inverter and a bi-directional converter. The converter’s output should respond to the load dynamics and still maintain good regulation. The rest of this chapter gives an overview of the system and different control methods that are used in power converter designs and lays some of the foundations of the adaptive control model that is developed in this thesis. Chapter 2 presents an overview of the design options and discusses in more detail the challenges that arise when a high performance controller is required for the DC-DC converter in the power conversion system application. In chapter 3 the models for the chosen converter topology and the control scheme are developed. This includes the design of a closed loop control for the full bridge converter based on an adaptive model reference scheme that has a very good disturbance rejection and bandwidths comparable to current mode control methods. In 4 his chapter, the design of the controller is simulated under different load and input voltage conditions. Next, in chapter 4 the design of the hardware and software implementation is discussed. Experimental results are taken and the performance of the converter is compared with the predicted simulation results. Finally, a summary of the design is given, the conclusions are drawn, and future work ideas are presented. 1. 3 Background Information In this section a literature review, on the basic operation of the fuel cells, converters and the control techniques most commonly used is provided. In addition a special section is dedicated to adaptive control from which much of the thesis was based upon. 1. 3. 1 Fuel Cells Fuel cells are ideal for distributed power generation applications, environmentally friendly, efficient and desirable for remote locations and developing countries as a mean of providing power at a low cost. Fuel cells are classified by the electrolyte that they employ and the temperature of operation. Solid oxide fuel cells (SOFC) [6] operate at high temperature and the oxygen from air is the oxidant (cathode fuel). SOFCs are solidstate devices operating at temperatures up to 1000 °C. They can use a wider choice of fuels and there is no requirement to manage liquid electrolytes. Current is conducted by the movement of oxygen ions through a solid electrolyte. At the cathode, oxygen is reduced to form oxygen ions; at the anode, the transported oxygen ions react with the gaseous fuel to produce water and free electrons for the external circuit. In the case of SOFCs, the temperature has to be high enough to enable oxygen ions to defuse through the electrolyte, which is made possible by the presence of oxygen vacancies in the crystalline structure of the electrolyte. The efficiency of SOFC is in the 50-60%, and although still at a relatively early stage of development, they are regarded as the most promising for generating electricity from hydrocarbon fuels [6]. A fuel cell system consists of the following main stages: †¢ †¢ †¢ †¢ Fuel Processing Water management Temperature Control Power Conditioning 5 The power conditioning that is made up of power electronics is the focus in this thesis report. The fuel cell output is in the form of direct current (DC) and the output voltage depends on the stack size. In many applications, alternating current (AC) at higher voltages is required; therefore fuel cell output is transformed from DC to AC by means of power electronics. Different circuit topologies were considered for this application and the design was done in three stages: 1. DC-DC converter 2. DC-AC inverter 3. Bidirectional battery charger Since the SOFC is used as an input source, the input voltage into the DC-DC converter is 22-31 VDC at a 28 VDC nominal voltage, and a maximum current of 275 A from the fuel cell. The whole system needs to provide galvanic isolation from the input to output for the purpose of safety [2]. Given that the input voltage is low and the required voltage of the whole system is 120V/240 VAC nominal, the main purpose of the DC-DC converter is to provide a sufficient DC link voltage which will be inverted into AC by the inverter. 1. 3. 2 Control of DC-DC Converters The structure and complexity of the converter control depends on specific application requirements. A cascaded loop control structure with an inner current loop and a superimposed voltage loop is used as a standard control in DC-DC converters to provide high performance, wide bandwidth output voltage regulation [7]. In all switching converters the output voltage v(t) is a function of input line voltage vg(t), duty cycle d(t), and the load current iload(t) as well as the converter circuit element values. In DC-DC converter applications it is desired to obtain a constant output voltage v(t) = V in spite of the disturbances in vg(t) and iload(t) (Figure 1. 3), and in spite of variations in the converter circuit element values. The unknown and unmeasurable variations of the process parameters degrade the performance of the control system. Feedback is used in conventional control systems to reject the effect of the disturbances upon the controlled variables and to bring them back to their desired values. To achieve this, first the controlled variables are measured then 6 compared with the desired values and the difference is fed into controller which will appropriately control these variables to meet the desired specifications. 1. 3. 3 Voltage Mode Control A feedback loop can be constructed for regulation of the output voltage. The output voltage v(t) is compared to a reference voltage Vref, to generate an error signal [3, 8]. This error signal is applied to the input of a compensation network, and the output of the compensator drives the control signal d(t) as shown in Figure 1. 3. In the case of a full bridge converter, the control signal d(t) is given to a full bridge controller IC which in this case is implemented by the Texas Instruments UCC3895 [9]. This control IC generates the appropriate turn on signals for all four switches in the pattern explained in chapter 2. vg (t ) Lf Q1 I DC Q3 Q2 DC-DC XFMR H(s) Q1 Q2 Q3 Q4 Sensor Gain Cf Q4 Llk v(t ) Vout load (t ) Rload Phase Shift PWM Controller (UCC3895) d(t) GC (s ) Compesator Error Signal Figure 1. 3. Voltage Mode Control In voltage mode control any change in the source or load is only detected after it has propagated to the output. This slows the control, especially when the source voltage changes as in the case when the input source is a SOFC. Vref 7 1. 3. 4 Current Mode Control Another control scheme that finds a wide application is current mode c ontrol. In this type of control the inductor current is used as a feedback state [10]. However the current and voltage reference values are not independent and this specifically requires knowledge of the load [7]. To overcome this obstacle the voltage error signal is used to generate a current error signal as shown in Figure 1. 4 [11]. Using the current creates the drawback that the knowledge of how the current affects the voltage is needed. For example, in a resistive system, v=ir, and increasing v will increase i. However, in a constant power load, increasing v will decrease i to maintain the relationship iv=p, where p is typically constant. This means that the current reference should be smaller for larger voltages. This dependency in undesired, and is a drawback of this type of control. Misrepresenting the load can lead to decreased performance, and possibly instability. Vref + kv _ + ki _ Converter IL Vout Figure 1. 4. Current Mode Control Current mode control requires knowledge of the inductor current, which is controlled via the inner loop. The outer loop manages the output voltage error by commanding the necessary current. The inner loop makes the converter act as a current source. There are many schemes that deal with current mode control. There are many methods to use to do current mode control, such as peak current mode control [12], average current mode control [13], sensorless current mode control [14]. In this thesis a brief overview of the main schemes is described. 8 1. 3. 5 Peak Current Mode Control Figure 1. 5 shows the generic inductor current of a switching converter operating in continuous conduction mode (CCM). The inductor current changes with a slope m1 during the first subinterval, and a slope –m2 during the second subinterval. At D gt; 0. 5 there is an inherent instability which is not dependent of the converter topology [3]. The controller can be made stable for all duty cycles by the addition of an artificial ramp with a slope Ma to the sensed current waveform. When M a ? 0. 5 ? m2 , then the controller is stable for all duty cycles. The controller now switches the transistor off when this summation crosses the reference value iref, as shown in Figure 1. 5. [12]. The relationship between the ramp, inductor and reference current is given in (1) ia (dT ) + iL (dT ) = iref (1) L iL Converter duty Clock S SET Q ? Ma iref iref ? ia ? m2 iL iref + _ Ramp m1 + _ iL ON OFF R CLR Q ON OFF ia Figure 1. 5. Peak current mode control Some benefits of peak current mode control are: †¢ †¢ †¢ Control of the peak inductor current Inherent current limiting and sharing Good dynamics and performance Some of the limitations are: †¢ Limited accuracy in controlling the average inductor current (especially in the DCM case) (The peak and average inductor current are not related) †¢ †¢ Increased sensitivity to line variations Increased switching noise problems 9 1. 3. 6 Average Current Mode Control In the average current mode control (ACM) a compensator is added to make the average inductor current track a reference as shown in Figure 1. [13] . The triangle carrier waveform in this case remains in place. In this case the variations in the duty cycle are dependent on the value of the averaged current. L iL Converter duty Clock iL iref + _ Ramp GC (s ) + _ S SET Q R CLR Q ia Figure 1. 6. Average Current Mode Control (ACM) 1. 3. 7 Sensorless Current Mode Control An alternative method for current mod e control is to use an observer method. In an observer, a model of the system to be controlled is used in place of the system to provide estimates of the control state values. In the case of sensorless current mode control an observer state is used in the place of inductor current. Since the output should match the reference, the output is a command rather than a dynamic state. So the desired output reference value replaces the output state. The SCM signal can be used as a direct substitute for peak current mode control. It shares the two key properties of the current mode controls and it provides a direct match to peak current mode control [15]: †¢ †¢ It compensates for changes in the input source It requires a stabilizing ramp to reach duty ratios above 50%. 10 This method, however, has its disadvantages: †¢ Since an integration step involves an arbitrary constant, the average DC current is not controlled †¢ †¢ For current limiting or current sharing some extra control is needed The general version requires an analog representation of the switches or other means to create the observer, as shown in Figure 1. 7. v1 q1 L v3 q4 q2 q3 Vout v2 v1 v2 q2 Switching q1 + + vL q4 Vref vI PWM Controller q3 v3 Figure 1. 7. General SCM Process In summary, the sensorless current mode (SCM) control uses the integrated inductor voltage as shown in Figure 1. in place of measured inductor current, and substitutes an intended command reference for the states intended to be fixed. The approach is based on an observer, which emulates the converter’s operation. To implement the general form, low power switches are added to the PWM IC in order to support the method. 11 L iL Converter duty Clock SET Ma VI + _ Ramp S Q m2 R Q ? m1 VI CLR ON O FF ON OFF ON Figure 1. 8. Sensorless Current Mode Control 1. 3. 8 Adaptive control In the nature of the application, the input source varies with time and its response is highly dependent on external factors. For DC-DC converter to achieve a good output control independent of the line input and load type, other types of control techniques are studied. These methods are highly beneficial in the case when the parameters of the control process are poorly known or vary during normal operation. With PCM, ACM and SCM control techniques the inductor current/voltage needs to be measured and the selection of the ramp control signal needs to be done such that the controller is stable throughout the duty cycle range. In most DC-DC converters, the inductor current is a function of the load current. The converter’s operation changes from continuous conduction mode CCM, to discontinuous conduction mode (DCM) when the inductor ripple current is higher than the average value. In DCM, the properties of the converter change radically. The conversion ratio, M, becomes load dependent and the output impedance increases. As a result the control to output transfer function (duty to output voltage) may be unknown when the load is removed. The control method used in this work is a variation of the adaptive control techniques, which provide a systematic approach for automatic adjustment of the controllers in real time [16]. This method is preferable in order to achieve or maintain a desired level of performance of the control system when the parameters of the plant dynamic model are unknown and/change with time. 12 The plant (DC-DC converter) dynamic characteristics depend upon the load and the input line. In order to achieve and maintain acceptable level of performance when changes in the model occur, adaptive control has to be considered. In order to design a good controller the following is needed: †¢ †¢ Specification of the desired control loop performances Knowledge of the dynamics model of the plant to be controlled Among various alternative methods, the technique known as adaptive model reference seems to be one of the most feasible approaches for this application [17]. It should be noted that the control system under consideration is an adjustable dynamic system in the sense that its performance can be adjusted by modifying the parameters of the controller or the control signal. The difference between the desired performance and the measured performance (the error) acts through an adaptation law to force the model to match the real system. A general block diagram of the adaptive control is shown in Figure 1. 9 Plant Vref ? + Controller d Model Ym + ? Adaptation Law Figure 1. 9. Basic configuration of an adaptive model 13 Chapter 2 FB-ZVS Converter Model in DCM CCM 2. 1 Principle of operation In order to reduce the size and the weight of magnetic components it is desirable to increase the switching frequency for DC-DC converters. When conventional PWM converters are operated at high frequencies, the circuit parasitics have negative effects on the converter performance [18]. Switching losses increase in high power applications and snubbers and/or other means of protection are required, which introduce significant losses and lower the efficiency. In the case of the conventional full bridge converter, the diagonally opposite switches (Q1 and Q2, or Q3 and Q4) are turned on and off simultaneously as shown in Figure 2. 1. In the FB-PWM converter, when all four switches are turned off, the load current freewheels through the rectifier diodes [19]. In this case the energy stored in the leakage inductance of the power transformer causes severe ringing with MOSFET junction capacitances. This creates the need for using snubbers that increase the overall losses bringing down the efficiency. If snubbers are not used, the selection of the devices becomes more difficult as the voltage rating for these switches has to be much higher. As the voltage rating goes up, so do the conduction losses and as a result the overall losses increase. At the same time the cost increases as well. In order to minimize the parasitic ringing, the gate signals of Q2 and Q4 are delayed (phase-shifted) with respect to those of Q1 and Q3 [20], as shown in Figure 2. , so that the primary of the transformer is either connected to the input voltage or shorted. The leakage inductance current is never interrupted, thus solving the problem of parasitic ringing associated with the conventional full-bridge PWM converter. The energy stored in the leakage inductance can be used to discharge the energy stored in the MOSFET junction capacitances to achieve zero voltage switching (ZVS) conditions for all fou r switches in the primary side. In this case, the converter requires no additional resonant components. 14 Lf Q1 I Q2 DC-DC XFMR Q4 Llk B DC Q3 A Cf Rload Q1 Q2 Q3 Q4 D ? TS 2 V AB Figure 2. 1. Conventional FB-PWM Converter 15 Lf Q1 I Q2 DC-DC XFMR Q4 Llk B DC Q3 A Cf Rload Q1 Q2 Q3 Q4 D ? TS 2 V AB Figure 2. 2. Phase Shifted FB-PWM Converter 2. 2 Converter Analysis The FB-ZVS-PWM converter provides ZVS for all four switches in the bridge. However the mechanism by which ZVS is achieved is different for both legs of the bridge Figure 2. 3. For transistors Q2 and Q4, the ZVS is provided by the resonance between the leakage inductance, LLK and the output capacitance of the switch. 16 Lf Q1 I Q2 Q4 Llk B Vin Q3 A + Vs DC-DC XFMR Cf Rload Ip I2 I1 I t1 t2 t3 t4 t5 t6 t7 t8 Q1 Q2 Q2 D3 D1 Q4 D1 D2 D3 D4 VAB Q3 Q4 Vs Figure 2. 3. Principle of Operation of Phase Shifted FB-PWM Converter The needed energy for achieving ZVS is given in . E= 1 4 1 2 2 2 ? LLK ? I 2 ? ? Cmos ? Vin + ? CTR ? Vin 2 3 2 (2) In equation22 (2) I 2 is the current through the primary when Q2 turns off, Vin is the input voltage CTR is the transformer winding capacitance. The factor 4/3 is the two times the energy stored in the nonlinear drain to source capacitor, whose capacitance is inversely proportional to the square root of the voltage [20]. The resonance between LLK , C mos and CTR provides a sinusoidal voltage across the capacitances that reaches a maximum at one fourth of the resonant frequency period. 17 The dead time between Q2 and Q4 has to be set at ? t max to ensure that there is sufficient time to charge and discharge the capacitances the dead time required to ensure ZVS with the maximum possible load range can be determined by the following equation (3): ? t max = Where C = C mos + CTR T ? = 4 2 LLK ? C (3) Whether ZVS can be achieved for Q2 and Q4 is dependent on the load level of the converter. For light loads, the current though LLK when Q2 and Q4 are turned off may not be enough to turn on the anti-parallel diode. For switches Q1 and Q3, ZVS is provided by a different mechanism. Before Q1 is turned off the current in the primary is reaching its peak value. The primary current is the filter inductor current reflected to the primary. When Q1 is turned off the energy available to charge the output capacitance of Q1 and discharge the output capacitance of Q3 is the energy stored in LLK and the energy in the output filter inductor. This energy in the output filter inductor is available because the filter inductor current does not freewheel through the rectifier until the voltage across the secondary has fallen to zero. Since the energy in the filter inductor is large compared to the energy stored in the switch capacitances in the primary, the charging of the switches can be approximated by a linear charging with a constant current. Consequently, the dead time dt1 required between the turn off of Q1 and turn on of Q3 can be determined from the equation (4): dt1 ? I p = 4 ? Cmos ? Vin (4) Where 4 ? Cmos ? Vin corresponds to twice the charge stored in the nonlinear output capacitance of the MOSFET and I p is the peak current in the output filter inductor reflected to the primary. The dead time can be calculated for the minimum I p chosen to achieve ZVS. If load current is further reduced the ZVS property can not be maintained. 18 -Critical Current for Zero-Voltage Switching The ZVS for Q1 and Q3 can be achieved even at light loads because D1 and D3 can always be turned on by the energy stored in the output filter inductance. However, ZVS for Q2 and Q4 can only be achieved for a load current above the critical values it is shown in equation (5): I CRIT = 2 LLK 1 ? 4 2 2? ? ? ? CMOS ? Vin + ? Ctr ? Vin ? 2 ? 3 ? (5) The available current through LLK at t2 can be calculated by: I2 = NS NP ? VOUT T? ?I ? ? I load + ? (1 ? D) ? ? 2 LLK + LF 2? ? ? (6) Finally, ZVS is achieved for a load current so that I2gt;Icrit which can be expressed as: I load ? VOUT ? I NP T ? I CRIT ? + ? (1 ? D) NS 2 LLk + LF 2 (7) The magnetizing current can only be used to achieve ZVS when the load current reflected to the primary is lower than the magnetizing current (i. . at light loads) [20]. For such light loads the energy available to charge/discharge the output capacitances of the switches Q2 and Q4 at times t2 and t6 respectively (Figure 2. 3) is the energy stored in the transformer’s leak

Apply the budget surplus to science essays

Apply the budget surplus to science essays For years, everyone has opined on what to do with the budget surplus: fund new educational programs, cut taxes, and so on. Science needs the money. In some technologies, we are beginning to fall behind other countries. We must not allow this to happen. Everyone reaps the benefits of science; increasing funding for research programs would only enhance these benefits. Where would the United States be today without science? Science is a big part of our economy, but today most research and development occur in the private sector. Why has the government cut spending? Because they know that the private sector will do the work. Money motivates the private sector to perform research; when profitability wanes in a certain area, research by the private sector also declines. Kenneth Brown asserts that private firms often focus on their own product rather than work on a broader understanding of science. Should Uncle Sam allow such a deficiency in research? Increased government spending in science would produce a greater breadth and depth of knowledge. You may ask yourself: why is this important? As the world leader in virtually everything, it is imperative for the US to lead the world in science also. Not only for defense reasons, but also to keep pace with other countries so no country can monopolize a scientific breakthrough. Would we want Japan or Russia to come up with a cure for AIDS and have to purchase the knowledge from them? The US needs to lead the world in science; to maintain this position we must apply the budget surplus to federal science research programs. ...

Close Critical Reading of Poem Inescapably Me Essay

Close Critical Reading of Poem Inescapably Me - Essay Example The poem argues that to live in the uncertainties and regrets of the past kills people’s ability to move on and live for the present and the future. The use of first person and second person makes the poem immediate and personal, wherein memories are expressed in terms of the past’s close relationship with the present and future. The second person shows that the speaker wants to be in a conversation. Readers are invited to enter his world: â€Å"†¦If you ask the little bald/clerk†¦Ã¢â‚¬  (Chan 3-4) â€Å"†¦you could slip into one of them,/so nice and cool, and see if it will fit, with your arms folded/nicely, hands over your heart†¦Ã¢â‚¬  (Chan 5-7). The speaker wants the audience to participate in the act of feeling death by asking them to enter the coffin. A personal relationship is established, where the â€Å"you† can try understanding the â€Å"I† of the poem. Moreover, the first person results to immediacy and intimacy too. Im mediacy helps readers feel that they are inside the mind of the speaker, who is argued as a male because of his relationship with a woman, although the speaker can be a lesbian too. After giving examples of conditions that do not fit, the speaker says: â€Å"It also doesn’t fit that I loved a girl, who broke my heart† (Chan 15). The speaker asserts that like the dead things in his life, it does not make any sense that he loves someone who does not love him back. He is stuck in the past and the pain of his heartbreak. The past shapes the future of the speaker too. The first and second person creates a monologue for a beloved: â€Å"†¦.Still/there is a corner of my heart I saved for you./You could come back, slip in there, and see if it will fit† (Chan 26-28). The speaker continues to wait for the past to return. He cannot imagine a future without removing this gaping emptiness in his heart. The first and second person views establish the intimacy of past mem ories. The free verse form of the poem, enjambment, and alliteration add to the conversational and intimate writing style of the poem. Free verse follows the melody of natural speech. Chan speaks in first person with a free verse form: â€Å"There are coffin shops in the old parts of Hong Kong,/empty and dark like garages, except for the bulks of smooth† (1-2). The speaker expresses himself in a usual conversation, starting with coffin shops in Hong Kong. The choice of topic and images is interesting, which the free form style emphasizes, because the effect is a storytelling rhythm about the cycle of life. Furthermore, the poem is filled with enjambment. Most of the lines are enjambed, such as lines 3 to 7: †¦If you ask the little bald/clerk, his bare arms speckled with tiny brown islands, fanning/himself with yellowed newspaper, you could slip into one of them,/so nice and cool, and see if it will fit, with your arms folded/nicely, hands over your heart. (Chan 3-7) The speaker describes the bald clerk who is in charge of the shop and enjambs this description with the experience of testing coffins. The effect is that the clerk is connected to the images and feelings of death, since he is bald and seems to be physically moldering like the â€Å"yellowed newspaper† he uses as a fan (Chan 5). The alliteration of â€Å"bald† â€Å"bare† and â€Å"brown† suggests decaying, relating it to someone who is dying. In this