Introduction to Rocket Propulsion

Introduction to Rocket Propulsion tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập lớn về tất cả các lĩn...

CAMERAPhân tíchảnhNhận dạngThu nhận ảnhSố hoáHệ thốngThu nhận ảnhChương Một: NHẬP MÔN XỬ LÝ ẢNH NHẬP MÔN XỬ LÝ ẢNH INTRODUCTION TO DIGITAL IMAGE PROCESSING1.1 TỔNG QUAN VỀ MỘT HỆ THỐNG XỬ LÝ ẢNHXử lý ảnh là một khoa học còn tương đối mới mẻ so với nhiều ngành khoa học khác, nhất là trên qui mô công nghiệp, song trong xử lý ảnh đã bắt đầu xuất hiện những máy tính chuyên dụng. Để có thể hình dung cấu hình một hệ thống xử lý ảnh chuyên dụng hay một hệ thống xử lý ảnh dùng trong nghiên cứu, đào tạo, trước hết chúng ta sẽ xem xét các bước cần thiết trong xử lý ảnh.Trước hết là quá trình thu nhận ảnh. Ảnh có thể thu nhận qua camera. Thường ảnh thu nhận qua camera là tín hiệu tương tự (loại camera ống kiểu CCIR), nhưng cũng có thể là tín hiệu số hoá (loại CCD - Charge Coupled Device). Lưu trữ SENSOR Lưu trữ Hệ Q.Định Hình 1.1.a. Các giai đoạn chính trong xử lý ảnhẢnh cũng có thể thu nhận từ vệ tinh qua các bộ cảm ứng (sensor), hay ảnh, tranh được quét trên scanner. Chi tiết về quá trình thu nhận ảnh sẽ được mô tả trong chương 2. Tiếp theo là quá trình số hoá (Digitalizer) để biến đổi tín hiệu tương tự sang tín hiệu rời rạc (lấy mẫu) và số hoá bằng lượng hoá, trước khi chuyển sang giai đoạn xử lý, phân tích hay lưu trữ lại.Qúa trình phân tích ảnh thực chất bao gồm nhiều công đoạn nhỏ. Trước hết là công việc tăng cường ảnh để nâng cao chất lượng ảnh. Do những nguyên nhân khác nhau: có thể do chất lượng thiết bị thu nhận ảnh, do nguồn sáng hay do nhiễu, ảnh có thể bị suy biến. Do vậy cần phải tăng cường và khôi phục lại ảnh để làm nổi bật một số đặc tính chính của ảnh, hay làm cho ảnh gần giống nhất với trạng thái gốc- trạng thái trước khi ảnh bị biến dạng. Giai đoạn tiếp theo là phát hiện các đặc tính như biên, phân vùng ảnh, trích chọn các đặc tính, v.v .Nhập môn xử lý ảnh số - ĐHBK Hà nội 11 Chương Một: NHẬP MÔN XỬ LÝ ẢNH Cuối cùng, tuỳ theo mục đích của ứng dụng, sẽ là giai đoạn nhận dạng, phân lớp hay các quyết định khác. Các giai đoạn chính của quá trình xử lý ảnh có thể mô tả ở hình 1.1.a.Với các giai đoạn trên, một hệ thống xử lý ảnh (cấu trúc phần cứng theo chức năng) gồm các thành phần tối thiểu như hình 1.1.b. Đối với một hệ thống xử lý ảnh thu nhận qua camera-camera như là con mắt của hệ thống. Có 2 loại camera: camera ống loại CCIR và camera CCD. Loại camera ứng với chuẩn CCIR quét ảnh với tần số 1/25 và mỗi ảnh gồm 625 dòng. Loại CCD gồm các photo điốt và làm tương ứng một cường độ sáng tại một điểm ảnh ứng với một phần tử ảnh (pixel). Như vậy, ảnh là tập hợp các điểm ảnh. Số pixel tạo nên một ảnh gọi là độ phân giải (resolution). Bộ xử lý tương tự (analog processor). Bộ phận này thực hiện các chức năng sau:- Chọn camera thích hợp nếu hệ thống có nhiều camera.- Chọn màn hình hiển thị tín hiệu- Thu nhận tín hiệu video thu nhận bởi bộ số hoá(digitalizer). Thực hiện lấy mẫu và mã hoá.- Tiền xử lý Introduction to Rocket Propulsion Introduction to Rocket Propulsion Bởi: OpenStaxCollege Rockets range in size from fireworks so small that ordinary people use them to immense Saturn Vs that once propelled massive payloads toward the Moon The propulsion of all rockets, jet engines, deflating balloons, and even squids and octopuses is explained by the same physical principle—Newton’s third law of motion Matter is forcefully ejected from a system, producing an equal and opposite reaction on what remains Another common example is the recoil of a gun The gun exerts a force on a bullet to accelerate it and consequently experiences an equal and opposite force, causing the gun’s recoil or kick Making Connections: Take-Home Experiment—Propulsion of a Balloon Hold a balloon and fill it with air Then, let the balloon go In which direction does the air come out of the balloon and in which direction does the balloon get propelled? If you fill the balloon with water and then let the balloon go, does the balloon’s direction change? Explain your answer [link] shows a rocket accelerating straight up In part (a), the rocket has a mass m and a velocity v relative to Earth, and hence a momentum mv In part (b), a time Δt has elapsed in which the rocket has ejected a mass Δm of hot gas at a velocity ve relative to the rocket The remainder of the mass (m − Δm) now has a greater velocity (v + Δv) The momentum of the entire system (rocket plus expelled gas) has actually decreased because the force of gravity has acted for a time Δt, producing a negative impulse Δp = −mg Δt (Remember that impulse is the net external force on a system multiplied by the time it acts, and it equals the change in momentum of the system.) So, the center of mass of the system is in free fall but, by rapidly expelling mass, part of the system can accelerate upward It is a commonly held misconception that the rocket exhaust pushes on the ground If we consider thrust; that is, the force exerted on the rocket by the exhaust gases, then a rocket’s thrust is greater in outer space than in the atmosphere or on the launch pad In fact, gases are easier to expel into a vacuum 1/9 Introduction to Rocket Propulsion By calculating the change in momentum for the entire system over Δt, and equating this change to the impulse, the following expression can be shown to be a good approximation for the acceleration of the rocket a= ve Δm m Δt −g “The rocket” is that part of the system remaining after the gas is ejected, and g is the acceleration due to gravity Acceleration of a Rocket Acceleration of a rocket is a= ve Δm m Δt − g, where a is the acceleration of the rocket, ve is the escape velocity, m is the mass of the rocket, Δm is the mass of the ejected gas, and Δt is the time in which the gas is ejected (a) This rocket has a mass m and an upward velocity v The net external force on the system is −mg , if air resistance is neglected (b) A time Δt later the system has two main parts, the ejected gas and the remainder of the rocket The reaction force on the rocket is what overcomes the gravitational force and accelerates it upward 2/9 Introduction to Rocket Propulsion A rocket’s acceleration depends on three major factors, consistent with the equation for acceleration of a rocket First, the greater the exhaust velocity of the gases relative to the rocket, ve, the greater the acceleration is The practical limit for ve is about 2.5 × 103 m/s for conventional (non-nuclear) hot-gas propulsion systems The second factor is the rate at which mass is ejected from the rocket This is the factor Δm / Δt in the equation The quantity (Δm / Δt)ve, with units of newtons, is called "thrust.” The faster the rocket burns its fuel, the greater its thrust, and the greater its acceleration The third factor is the mass m of the rocket The smaller the mass is (all other factors being the same), the greater the acceleration The rocket mass m decreases dramatically during flight because most of the rocket is fuel to begin with, so that acceleration increases continuously, reaching a maximum just before the fuel is exhausted Factors Affecting a Rocket’s Acceleration • The greater the exhaust velocity ve of the gases relative to the rocket, the greater the acceleration • The faster the rocket burns its fuel, the greater its acceleration • The smaller the rocket’s mass (all other factors being the same), the greater the acceleration Calculating Acceleration: Initial Acceleration of a Moon Launch A Saturn V’s mass at liftoff was 2.80 × 106 kg, its fuel-burn rate was 1.40 × 104 kg/s, and the exhaust velocity was 2.40 × 103 m/s Calculate its initial acceleration Strategy This problem is a straightforward application of the expression for acceleration because a is the unknown and all of the terms on the right side of the equation are given Solution Substituting the given values into the equation for acceleration yields a = = = ve Δm m Δt −g 2.40 × 103 m/s 2.80 × 10 1.40 × 104 kg/s) − 9.80 m/s2 ( kg ...An introduction to disk drivemodelingChris Ruemmler and John WilkesHewlett-Packard Laboratories, Palo Alto, CAMuch research in I/O systems is based on disk drive simulation models, but howgood are they? An accurate simulation model should emphasize the performance-critical areas.This paper has been published in IEEE Computer 27(3):17–29, March 1994. Itsupersedes HP Labs technical reports HPL–93–68 rev 1 and HPL–OSR–93–29.Copyright © 1994 IEEE.Internal or personal use of this material is permitted. However, permission toreprint/republish this material for advertising or promotional purposes or forcreating new collective works for resale or redistribution must be obtained from theIEEE. To receive more information on obtaining permission, send a blank emailmessage to info.pub.permission@ieee.org.Note: this file was obtained by scanning and performing OCR on the IEEEpublished copy. As a result, it may contain typographic or other errors that are notin the published version. Minor clarifications and updates have been made to thebibliography. 1Modern microprocessor technology is advancing at an incredible rate, and speedups of 40 to 60 percentcompounded annually have become the norm. Although disk storage densities are also improvingimpressively (60 to 80 percent compounded annually), performance improvements have been occurring atonly about 7 to 10 percent compounded annually over the last decade. As a result, disk system performanceis fast becoming a dominant factor in overall system behavior.Naturally, researchers want to improve overall I/O performance, of which a large component is theperformance of the disk drive itself. This research often involves using analytical or simulation models tocompare alternative approaches, and the quality of these models determines the quality of the conclusions;indeed, the wrong modeling assumptions can lead to erroneous conclusions. Nevertheless, little work hasbeen done to develop or describe accurate disk drive models. This may explain the commonplace use ofsimple, relatively inaccurate models.We believe there is much room for improvement. This article demonstrates and describes a calibrated, high-quality disk drive model in which the overall error factor is 14 times smaller than that of a simple first-ordermodel. We describe the various disk drive performance components separately, then show how theirinclusion improves the simulation model. This enables an informed trade-off between effort and accuracy.In addition, we provide detailed characteristics for two disk drives, as well as a brief description of asimulation environment that uses the disk drive model.Characteristics of modern disk drivesTo model disk drives, we must understand how they behave. Thus, we begin with an overview of the currentstate of the art in nonremovable magnetic disk drives with embedded SCSI (Small Computer SystemsInterconnect) controllers, since these are widely available.Disk drives contain a mechanism and a controller. The mechanism is made up of the recording components(the rotating disks and the heads that access them) and the positioning components (an arm assembly thatmoves the heads into the correct position together with a track-following system that keeps it in place). Thedisk controller contains a microprocessor, some buffer memory, and an interface to the SCSI bus. Thecontroller manages the storage and retrieval of data to and from the mechanism and performs mappingsbetween incoming logical addresses and the physical disk sectors that store the information.Below, we look more closely at each of these elements, emphasizing features that need to be consideredwhen creating a disk drive model. It will become clear Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyChapter 6I/O Streams as an Introduction to Objects and Classes Slide 6- 3Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyOverview6.1 Streams and Basic File I/O 6.2 Tools for Stream I/O6.3 Character I/O6.4 Inheritance Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley6.1Streams and Basic File I/O Slide 6- 5Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyI/O StreamsI/O refers to program input and outputInput is delivered to your program via a stream objectInput can be fromThe keyboardA fileOutput is delivered to the output device via a streamobjectOutput can be to The screenA file Slide 6- 6Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyObjectsObjects are special variables thatHave their own special-purpose functionsSet C++ apart from earlier programming languages Slide 6- 7Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyStreams and Basic File I/OFiles for I/O are the same type of files used tostore programsA stream is a flow of data.Input stream: Data flows into the programIf input stream flows from keyboard, the program willaccept data from the keyboardIf input stream flows from a file, the program will acceptdata from the fileOutput stream: Data flows out of the programTo the screenTo a file Slide 6- 8Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesleycin And cout StreamscinInput stream connected to the keyboardcout Output stream connected to the screencin and cout defined in the iostream libraryUse include directive: #include <iostream>You can declare your own streams to use with files. Slide 6- 9Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyWhy Use Files?Files allow you to store data permanently!Data output to a file lasts after the program endsAn input file can be used over and overNo typing of data again and again for testingCreate a data file or read an output file at yourconvenienceFiles allow you to deal with larger data sets Slide 6- 10Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-WesleyFile I/OReading from a fileTaking input from a fileDone from beginning to the end (for now)No backing up to read something again (OK to start over)Just as done from the keyboardWriting to a fileSending output to a fileDone from beginning to end (for now)No backing up to write something again( OK to start over)Just as done to the screen [...]... only to the stream named in the call Slide 6- 3 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Overview 6.1 Streams and Basic File I/O 6.2 Tools for Stream I/O 6.3 Character I/O 6.4 Inheritance Slide 6- 45 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Manipulators  A manipulator is a function called TEAM LinG INTRODUCTION TODIGITAL SIGNALPROCESSING ANDFILTER DESIGN INTRODUCTION TODIGITAL SIGNALPROCESSING ANDFILTER DESIGNB. A. ShenoiA JOHN WILEY & SONS, INC., PUBLICATION Copyright © 2006 by John Wiley & Sons, Inc. 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For more information about Wiley products, visit ourweb site at www.wiley.com.Library of Congress Cataloging-in-Publication Data:ISBN-13 978-0-471-46482-2 (cloth)Printed in the United States of America.10987654321ISBN-100-471- 46482-1 (cloth) CONTENTSPreface xi1 Introduction 11.1 Introduction 11.2 Applications of DSP 11.3 Discrete-Time Signals 31.3.1 Modeling and Properties of Discrete-Time Signals 81.3.2 Unit Pulse Function 91.3.3 Constant Sequence 101.3.4 Unit Step Function 101.3.5 Real Exponential Function 121.3.6 Complex Exponential Function 121.3.7 Properties of cos(ω0n) 141.4 History of Filter Design 191.5 Analog and Digital Signal Processing 231.5.1 Operation of a Mobile Phone Network 251.6 Summary 28Problems 29References 302 Time-Domain Analysis and z Transform 322.1 A Linear, Time-Invariant System 322.1.1 Models of the Discrete-Time System 332.1.2 Recursive Algorithm 362.1.3 Convolution Sum 382.2 z Transform Theory 412.2.1 Definition 412.2.2 Zero Input and Zero State Response 49v viCONTENTS2.2.3 Linearity of the System 502.2.4 Time-Invariant System 502.3 Using z Transform to Solve Difference Equations 512.3.1 More Applications of z Transform 562.3.2 Natural Response and Forced Response 582.4 Solving Difference Equations Using the Classical Method 592.4.1 Transient Response and Steady-State Response 632.5 z Transform Method Revisited 642.6 Convolution Revisited 652.7 A Model from Other Models 702.7.1 Review of Model Generation 722.8 Stability 772.8.1 Jury–Marden Test 782.9 Solution Using MATLAB Functions 812.10 Summary 93Problems Wireless CommunicationsIntroduction to Wireless Communications 2Objectives•Explain how the major wireless technologies are used today•Describe various applications of wireless communications technology•Explain the advantages and disadvantages of wireless communications technology•List several different wireless technologies 3How Wireless Technology is Used•Wireless–Describes devices and technologies that are not connected by a wire•Wireless communications–Transmission of user data without the use of wires•Wireless data communications technologies include:–Bluetooth–Wireless LAN and WAN–Satellite–Cellular 4A Wireless World•Wireless devices–Distance: 300 feet (90 meters)–Bandwidth: 54 Mbps–Can also include Voice over IP (VoIP)•Wireless network interface card (Wireless NIC)–Sends and receives data over radio waves•Smartphone–Combination mobile phone and personal digital assistant (PDA) 5A Wireless World (continued) 6Bluetooth and Ultra Wide Band•Radio frequency identification device (RFID) tags–Small chips containing radio transponders•Can be used to track inventory•Bluetooth and Ultra Wide Band (UWB)–Wireless standards designed for very short ranges–Communicate using small, low-power transceivers•Link manager–Special software that helps identify other Bluetooth devices 7Bluetooth and Ultra Wide Band (continued) 8Bluetooth and Ultra Wide Band (continued)•Bluetooth–Distance: up to 33 feet (10 meters)–Bandwidth: 1 Mbps•Ultra Wide Band–Distance: 150 feet (50 meters)–Bandwidth: 100 Mbps to 2 Gbps•Piconet–Wireless personal area network (WPAN)–Consists of two or more Bluetooth devices that are exchanging data with each other 9Bluetooth and Ultra Wide Band (continued) 10Satellite Networks•Used to transmit data over very long distance•Repeater–Located in the satellite itself–Simply “repeats” the same signal to another location–Used to transmit data from one earth station to another•Transmission time is approximately 250 milliseconds [...]... heating effects • Wireless devices emit low levels of RF while being used 40 Construction • Wireless communications – Send information from the job site to the main office – Alert when maintenance operations need to be performed on equipment 50 Summary (continued) • Remote sensors – Capable of communicating using wireless technologies – Used in large manufacturing facilities • To monitor equipment... (UWB) – Wireless standards designed for very short ranges – Communicate using small, low-power transceivers • Link manager – Special software that helps identify other Bluetooth devices 8 Bluetooth and Ultra Wide Band (continued) • Bluetooth – Distance: up to 33 feet (10 meters) – Bandwidth: 1 Mbps • Ultra Wide Band – Distance: 150 feet (50 meters) – Bandwidth: 100 Mbps to 2 Gbps • Piconet – Wireless. .. (WPAN) – Consists of two or more Bluetooth devices that are exchanging data with each other 32 Education • Ideal application for colleges and schools • It frees students from having to go to a specific computer lab or the library – To get on the school’s computer network • Wireless technology translates into a cost savings for colleges as well 41 Warehouse Management • Implementing wireless technology is key... users – Transmission towers are spread throughout a geographical area – The same radio frequency channels can be reused by another tower • Located a few miles away to avoid interference • Maximizes the use of a ... from her space ship and needing to get back to it The astronaut has a few packages that she can throw away to move herself 8/9 Introduction to Rocket Propulsion toward the ship Construct a problem... The real lunar lander is very hard to control Lunar Lander 5/9 Introduction to Rocket Propulsion Section Summary • Newton’s third law of motion states that to every action, there is an equal... the remainder of the rocket The reaction force on the rocket is what overcomes the gravitational force and accelerates it upward 2/9 Introduction to Rocket Propulsion A rocket s acceleration