Applications of Electrostatics

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169CHAPTER9Applications of the DFTThe Discrete Fourier Transform (DFT) is one of the most important tools in Digital SignalProcessing. This chapter discusses three common ways it is used. First, the DFT can calculatea signal's frequency spectrum. This is a direct examination of information encoded in thefrequency, phase, and amplitude of the component sinusoids. For example, human speech andhearing use signals with this type of encoding. Second, the DFT can find a system's frequencyresponse from the system's impulse response, and vice versa. This allows systems to be analyzedin the frequency domain, just as convolution allows systems to be analyzed in the time domain.Third, the DFT can be used as an intermediate step in more elaborate signal processingtechniques. The classic example of this is FFT convolution, an algorithm for convolving signalsthat is hundreds of times faster than conventional methods. Spectral Analysis of SignalsIt is very common for information to be encoded in the sinusoids that forma signal. This is true of naturally occurring signals, as well as those thathave been created by humans. Many things oscillate in our universe. Forexample, speech is a result of vibration of the human vocal cords; starsand planets change their brightness as they rotate on their axes and revolvearound each other; ship's propellers generate periodic displacement of thewater, and so on. The shape of the time domain waveform is not importantin these signals; the key information is in the frequency, phase andamplitude of the component sinusoids. The DFT is used to extract thisinformation. An example will show how this works. Suppose we want to investigate thesounds that travel through the ocean. To begin, a microphone is placed in thewater and the resulting electronic signal amplified to a reasonable level, say afew volts. An analog low-pass filter is then used to remove all frequenciesabove 80 hertz, so that the signal can be digitized at 160 samples per second.After acquiring and storing several thousand samples, what next? The Scientist and Engineer's Guide to Digital Signal Processing170The first thing is to simply look at the data. Figure 9-1a shows 256 samplesfrom our imaginary experiment. All that can be seen is a noisy waveform thatconveys little information to the human eye. For reasons explained shortly, thenext step is to multiply this signal by a smooth curve called a Hammingwindow, shown in (b). (Chapter 16 provides the equations for the Hammingand other windows; see Eqs. 16-1 and 16-2, and Fig. 16-2a). This results ina 256 point signal where the samples near the ends have been reduced inamplitude, as shown in (c). Taking the DFT, and converting to polar notation, results in the 129 pointfrequency spectrum in (d). Unfortunately, this also looks like a noisy mess.This is because there is not enough information in the original 256 points toobtain a well behaved curve. Using a longer DFT does nothing to help thisproblem. For example, if a 2048 point DFT is used, the frequency spectrumbecomes 1025 samples long. Even though the original 2048 points containmore information, the greater number of samples in the spectrum dilutes theinformation by the same factor. Longer DFTs provide better frequencyresolution, but the same noise level. Applications of Electrostatics Applications of Electrostatics Bởi: OpenStaxCollege The study of electrostatics has proven useful in many areas This module covers just a few of the many applications of electrostatics The Van de Graaff Generator Van de Graaff generators (or Van de Graaffs) are not only spectacular devices used to demonstrate high voltage due to static electricity—they are also used for serious research The first was built by Robert Van de Graaff in 1931 (based on original suggestions by Lord Kelvin) for use in nuclear physics research [link] shows a schematic of a large research version Van de Graaffs utilize both smooth and pointed surfaces, and conductors and insulators to generate large static charges and, hence, large voltages A very large excess charge can be deposited on the sphere, because it moves quickly to the outer surface Practical limits arise because the large electric fields polarize and eventually ionize surrounding materials, creating free charges that neutralize excess charge or allow it to escape Nevertheless, voltages of 15 million volts are well within practical limits 1/14 Applications of Electrostatics Schematic of Van de Graaff generator A battery (A) supplies excess positive charge to a pointed conductor, the points of which spray the charge onto a moving insulating belt near the bottom The pointed conductor (B) on top in the large sphere picks up the charge (The induced electric field at the points is so large that it removes the charge from the belt.) This can be done because the charge does not remain inside the conducting sphere but moves to its outside surface An ion source inside the sphere produces positive ions, which are accelerated away from the positive sphere to high velocities Take-Home Experiment: Electrostatics and Humidity Rub a comb through your hair and use it to lift pieces of paper It may help to tear the pieces of paper rather than cut them neatly Repeat the exercise in your bathroom after you have had a long shower and the air in the bathroom is moist Is it easier to get electrostatic effects in dry or moist air? Why would torn paper be more attractive to the comb than cut paper? Explain your observations Xerography Most copy machines use an electrostatic process called xerography—a word coined from the Greek words xeros for dry and graphos for writing The heart of the process is shown in simplified form in [link] A selenium-coated aluminum drum is sprayed with positive charge from points on a device called a corotron Selenium is a substance with an interesting property—it is a 2/14 Applications of Electrostatics photoconductor That is, selenium is an insulator when in the dark and a conductor when exposed to light In the first stage of the xerography process, the conducting aluminum drum is grounded so that a negative charge is induced under the thin layer of uniformly positively charged selenium In the second stage, the surface of the drum is exposed to the image of whatever is to be copied Where the image is light, the selenium becomes conducting, and the positive charge is neutralized In dark areas, the positive charge remains, and so the image has been transferred to the drum The third stage takes a dry black powder, called toner, and sprays it with a negative charge so that it will be attracted to the positive regions of the drum Next, a blank piece of paper is given a greater positive charge than on the drum so that it will pull the toner from the drum Finally, the paper and electrostatically held toner are passed through heated pressure rollers, which melt and permanently adhere the toner within the fibers of the paper Xerography is a dry copying process based on electrostatics The major steps in the process are the charging of the photoconducting drum, transfer of an image creating a positive charge duplicate, attraction of toner to the charged parts of the drum, and transfer of toner to the paper Not shown are heat treatment of the paper and cleansing of the drum for the next copy Laser Printers Laser printers use the xerographic process to make high-quality images on paper, employing a laser to produce an image on the photoconducting drum as shown in [link] In its most common application, the laser printer receives output from a computer, and it can achieve high-quality output because of the precision with which laser light can be controlled Many laser printers significant information processing, such as making sophisticated letters or fonts, and may contain a computer more powerful than the one giving them the raw data to be printed 3/14 Applications of Electrostatics In a laser printer, a laser beam is scanned across a photoconducting drum, leaving a positive charge image The other steps for charging the drum and transferring the image to paper are the same as in xerography Laser light can be very precisely controlled, enabling laser printers to produce high-quality images Ink Jet Printers and Electrostatic Painting The ink jet ... Multi-Carrier Digital Communications Theory and Applications of OFDM Information Technology: Transmission, Processing, and Storage Series Editor: Jack Keil Wolf University of California at San Diego La Jolla, California Editorial Board: James E. Mazo Bell Laboratories, Lucent Technologies Murray Hill, New Jersey John Proakis Northeastern University Boston, Massachusetts William H. Tranter Virginia Polytechnic Institute and State University Blacksburg, Virginia Multi-Carrier Digital Communications: Theory and Applications of OFDM Ahmad R. S. Bahai and Burton R. Saltzberg Principles of Digital Transmission: With Wireless Applications Sergio Benedetto and Ezio Biglieri Simulation of Communication Systems, 2nd Edition: Methodology, Modeling, and Techniques Michel C. Jeruchim, Philip Balaban, and K. Sam Shanmugan A Continuation Order Plan is available for this series. A continuation order will bring delivery of each new volume immediately upon publication. Volumes are billed only upon actual shipment. For further information please contact the publisher. Multi-Carrier Digital Communications Theory and Applications of OFDM Ahmad R. S. Bahai and Burton R. Saltzberg Algorex, Inc. Iselin, New Jersey Kluwer Academic Publishers New York, Boston, Dordrecht, London, Moscow eBook ISBN: 0-306-46974-X Print ISBN: 0-306-46296-6 ©2002 Kluwer Academic Publishers New York, Boston, Dordrecht, London, Moscow Print ©1999 Kluwer Academic / Plenum Publishers New York All rights reserved No part of this eBook may be reproduced or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Kluwer Online at: http://kluweronline.com and Kluwer's eBookstore at: http://ebooks.kluweronline.com Preface Multi-carrier modulation, in particular Orthogonal Frequency Division Multiplexing (OFDM), has been successfully applied to a wide variety of digital communications applications over the past several years. Although OFDM has been chosen as the physical layer standard for a diversity of important systems, the theory, algorithms, and implementation techniques remain subjects of current interest. This is clear from the high volume of papers appearing in technical journals and conferences. This book is intended to be a concise summary of the present state of the art of the theory and practice of OFDM technology. The authors believe that the time is ripe for such a treatment. Particularly based on one of the author's long experience in development of wireless systems, and the other's in wireline systems, we have attempted to present a unified presentation of OFDM performance and implementation over a wide variety of channels. It is hoped that this will prove valuable both to developers of such systems and to researchers and graduate students involved in analysis of digital communications. In the interest of brevity, we have minimized treatment of more general communication issues. There exist many excellent texts on communication v vi Preface theory and technology. Only brief summaries of topics not specific to multi- carrier modulation are presented in this book where essential. We begin with a historical overview of multi-carrier communications, wherein its advantages for transmission over highly dispersive channels have long been recognized, particularly English morpheme system Luong Thuan & Kim Phuong Acknowledgment Firstly, we are deeply grateful to Ms Huyen Nguyen Thi Thanh, my supervisor for her valuable instructions, corrections and assistance during the implementation process of our graduation thesis. Secondly, we would like to give our special thanks to all lecturers and staff from the Foreign Language Faculty, English Department of Phuong Dong University for giving us opportunities and encouragement to complete our study. Finally, we also would like to express our sincere thanks to TA vu Son Tung for his support during our process to complete this essay. Group: Luong Thi Thuan Ha Kim Phuong 1 English morpheme system Luong Thuan & Kim Phuong OUTLINE Part I: Introduction. 1. Rationale (reasons of the study) .3 2. Aims of the study .3 3. Scope of the study 3 4. Methods of the study 4 Part II: Development. Chapter 1: Theoretical background. I. An overview of English morpheme I.1. Definition of Morpheme .5 I.2. Type of morpheme .6 II. An overview of Vietnamese morpheme II.1. Definition of Vietnamese morpheme .9 II.2. Derivational morphology: word formation 9 Chapter 2: Comparison with Vietnamese morphology. 1. The similarities 11 2. The difference .13 3. Some suggestion .15 Part III: Conclusion .18 Exercises 19 References .23 2 English morpheme system Luong Thuan & Kim Phuong Part I: Introduction 1. The rationale “Language is the most important social communication among countries and people in the world”, said V.I Lenin. As the world changes and develops, the global integration becomes the trend in all over the world. All countries, including Viet Nam have been cooperated with each other in many aspects of society in order to enhance development of economy. It designated international communication as an important part of all sectors. English is considered as the international language which is widely used all over the world. However, each language as well as English has its own typical features which make difficulties for learners. To learn English well, first of all, we should understand deeply about its morpheme system. Living in a community, human beings need a tool to communicate with each other, and to carry on human and social affairs. They, therefore, arbitrarily named the things and occurrences around making use of vocal sounds for the purpose of communication. After that they showed the vocal sounds and sets of vocal sounds in written signals. Because of these reasons, we decided to choose the topic “English morpheme system and some applications of learning morpheme in establishing words”. 2. Aims of the study We hope that our study is useful for English learners, for those who want to consolidate their knowledge about APPLICATIONS OF ROBOTICS AND ARTIFICIAL INTELLIGENCE Get any book for free on: www.Abika.com 1 Applications of Robotics and Artificial Intelligence to Reduce Risk and Improve Effectiveness By National Research Council Get any book for free on: www.Abika.com APPLICATIONS OF ROBOTICS AND ARTIFICIAL INTELLIGENCE Get any book for free on: www.Abika.com 2 Contents Acknowledgements and Contents 1. Background 2. Summary of the Technology 3. Criteria for Selection of Applications 4. Recommended Applications and Priorities 5. Implementation of Recommended Applications 6. Other Considerations 7. Recommendations • Appendix: State of the Art and Predictions for Artificial Intelligence and Robotics • Glossary of Acronyms APPLICATIONS OF ROBOTICS AND ARTIFICIAL INTELLIGENCE Get any book for free on: www.Abika.com 3 APPLICATIONS OF ROBOTICS AND ARTIFICIAL INTELLIGENCE TO REDUCE RISK AND IMPROVE EFFECTIVENESS A Study for the United States Army Committee on Army Robotics and Artificial Intelligence Manufacturing Studies Board Commission on Engineering and Technical Systems National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1983 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purpose of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which establishes the Academy as a private, nonprofit, self- governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences. This report represents work under contract number MDA 903-82-C-0351 between the U.S. Department of the Army and the National Academy of Sciences. A limited number of copies are available from: Manufacturing Studies Board APPLICATIONS OF ROBOTICS AND ARTIFICIAL INTELLIGENCE Get any book for free on: www.Abika.com 4 National Academy of Sciences 2101 Constitution Avenue, N.W. Washington, D.C. 20418 Printed in the Multimedia Applications of the Wavelet Transform Inauguraldissertation zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften der Universit ¨ at Mannheim vorgelegt von Dipl.–Math. oec. Claudia Kerstin Schremmer aus Detmold Mannheim, 2001 Dekan: Professor Dr. Herbert Popp, Universit¨at Mannheim Referent: Professor Dr. Wolfgang Effelsberg, Universit¨at Mannheim Korreferent: Professor Dr. Gabriele Steidl, Universit¨at Mannheim Tag der m ¨undlichen Pr¨ufung: 08. Februar 2002 If we knew what we were doing, it would not be called research, would it? — Albert Einstein Abstract This dissertation investigates novel applications of the wavelet transform in the analysis and compres- sion of audio, still images, and video. In a second focal point, we evaluate the didactic potential of multimedia–enhanced teaching material for higher education. Most recently, some theoretical surveys have been published on the potential for a wavelet–based restoration of noisy audio signals. Based on these, we have developed a wavelet–based denoising program for audio signals that allows flexible parameter settings. It is suited for the demonstration of the potential of wavelet–based denoising algorithms as well as for use in teaching. The multiscale property of the wavelet transform can successfully be exploited for the detection of semantic structures in still images. For example, a comparison of the coefficients in the transformed domain allows the analysis and extraction of a predominant structure. This idea forms the basis of our semiautomatic edge detection algorithm that was developed during the present work. A number of empirical evaluations of potential parameter settings for the convolution–based wavelet transform and the resulting recommendations follow. In the context of the teleteaching project Virtuelle Hochschule Oberrhein, i.e., Virtual University of the Upper Rhine Valley (VIROR), which aims to establish a semi–virtual university, many lectures and seminars were transmitted between remote locations. We thus encountered the problem of scalability of a video stream for different access bandwidths in the Internet. A substantial contribution of this dissertation is the introduction of the wavelet transform into hierarchical video coding and the recom- mendation of parameter settings based on empirical surveys. Furthermore, a prototype implementa- tion of a hierarchical client–server video program proves the principal feasibility of a wavelet–based, nearly arbitrarily scalable application. Mathematical transformations of digital signals constitute a commonly underestimated problem for students in their first semesters of study. Motivated by the VIROR project, we spent a considerable amount of time and effort on the exploration of approaches to enhance mathematical topics with multimedia; both the technical design and the didactic integration into the curriculum are discussed. In a large field trial on traditional teaching versus multimedia–enhanced teaching, in which the students were assigned to different learning settings, not only the motivation, but the objective knowledge gained by the students was measured. This allows us to objectively rate positive the efficiency of the teaching modules developed in the scope of this dissertation. II A BSTRACT Kurzfassung Die vorliegende Dissertation untersucht neue Einsatzm ¨oglichkeiten der Wavelet–Transformation f¨ur die Analyse ... to the length d of one 12/14 Applications of Electrostatics side of the square Determine the magnitude of q in terms of Q, m, and d, if the Coulomb force is to equal the weight of m (b) Is this... charge duplicate, attraction of toner to the charged parts of the drum, and transfer of toner to the paper Not shown are heat treatment of the paper and cleansing of the drum for the next copy... of electrostatic precipitators is seen by the absence of smoke from this power plant (credit: Cmdalgleish, Wikimedia Commons) Problem-Solving Strategies for Electrostatics 5/14 Applications of