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ABAQUS 子程序断裂模型

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abaqus fortran 子程序断裂模拟相关还有inp模型文件

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Qt 自绘波形图心电图的实时显示
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2020-12-07下载

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2021-05-06下载

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2020-12-05下载

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2021-11-18 00:48:52下载

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我的C++自动化测试程序.zip
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2021-11-24 00:46:15下载

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2020-11-07下载

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2020-12-12下载

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利用Hilbert变换提取信号瞬时特征的算法实现
研究了在工程中如何通过算法来实现利用 Hilbert 变换提取信号的瞬时特征。深入地分析了如何利用数值微分法提高提取瞬时频率特征的精度。最后,给出了一种可行的算法,并通过实验验证了这种方法可以在工程中有效地提取信号的瞬时频率特征。84微机发展第13卷①H(x)=y;H(x)=y;(i=0,1,…n)(j=0,1(11)②在每个小区间/x1,x1+17i=0,1,…,n-1)上由相关定理知:当划分的小区间的长度趋于零时H(x)是三次多项式。s(x)及其一至三阶导数分别一致收敛到f(x)及其一至可以写出分段三次 Hermite插值函数的分段表达式:三阶导数。所以用三次样条插值函数去近似表达用离散值(x)=(1+2x-x过+)2v;+表示的原函数,具有较高的可靠性。3)两种插值的比较挨尔米特 Hermite插值较三次样I-i,1+2条插值具有较好的稳定性与收敛性,但它只能休让各段曲线在连接点上的连续性,而不能保证整条曲线在这些点上y+1Ditl的光滑性。而有时不仅要求曲线连续,而且要求曲线的曲X/(i=0,18)率也连续即要求分段插值函数具有连续的一阶导数,埃H(x)的导数为尔米特 Hermite插值此时就不能满足上述要求6次样条插值较埃尔米特 Hermite插值具有较好的H(x光滑程度,用三次样条插值函数求数值导数比用埃尔米特+2(x-x2(xHermite插值可靠性大,但计算比较复杂,二者的区别见图h2yV+17, h(i-0,12)三次样条插值。已知函数y=f(x)在区间/a,b上的n+1个节点上的值y=f(x;)(i=0,1,…m),求插值函数s(x),使(i=0,1图4 Hermite插值与三次样条插值的比较图2在每个小区间x,x+1(=0.1.…n-1)上利用埃尔米特 Hermite插值得到的2FSK信号的瞬时s(x是三次多项式,记为s(x频率见图5,利用二次样条插值得到的该信号的瞬时频率③3(x)在la,b/上二阶连续可徵。见图6。数s(x)称为f(x)的三次样条插值函数可以利用节点处的二阶导数值为参数,也可以利用节点处的导数值为参数求三次样条插值涵数的表达式。若利用节点处的一阶导数值为参数,求得的三次样条插值函数的表达式为(x)=M-1x-x-)36 h6 hMihi5 DEMeN5a亩pai66hx∈[x;,x+17,b-x+1-x,S"(x)=M图5由 Hermite插值提取图6由三次样条插值提取(j=0,1的2FSK信号的瞬时频率的2FSK信号的瞬时频率对s(x)进行求导,利用S(x)在节点处一阶导数连从图5、图6可以看出利用三次样条插值得到的瞬时续的性质结合边界条件求解出参数M,把求得的参数代频率可以准确反映出信号具有的的摒时频率特征而利用入公式(10),即得三次样条插值函数的s(x)分段表示式。埃尔米特 Hermite插值得到的瞬时频率与信号具有的瞬s;(x)的导数为时频率特征不符。这是因为利用数值微分法求瞬时频率插值以后喫进行求导。三次样条插值函数具有连续的二阶M2 hiM; 2 hj导数,因而具有较好的光滑程度,符合求导条件,所以可以J+1-h(M2+1-M/)准确求出信号的瞬时频率;而埃尔米特 Hernite插值.不够光滑,虽能保证插值多项式收敛于原函数,但不能保证插x Elx,x;+1 h,=xi+I-x, S(xj )=M;值多顷式的导数收敛于原函数的导数,所以求得的值与信o1994-2010ChinaAcademicJournalElectronicPublishingHouse.Allrightsreservedhttp://www.cnki.net第6期刘慧婷等:利用 Hilbert变提取信号瞵时特征的算法实现号实际的瞬时频率值不符。实验结果和理论分析结果是(1) Hilbert变换只能近似应用于窄带信号,即形如纹的(t)=a(1)cosu+6(1)),其中>>B(B为信号带2.3.3结论宽)的信号。但实际应用中,存在许多非窄带信号, Hilbcrt利用数值微分法求瞬时频率ω(t)的步骤可以归纳变换对这些信号无能为力为:首先通过三次样条插值得到分段多项式p(1),(2)对于任意给定时刻,通过 Hilbert变换运算后的结pp(抄);然后分别对分段多项式p(t),Pp()关于变量t果只能存在一个频率值,即只能处理任何时刻为单一频率进行求导,得到pd(,ppd(t);最后求出每一时刻t所对的信号。这显然不合理,因为在实东中同一信号会含有多应的导数值,即求得t(t,u(t)。再把求得的值代入公种频率成分式(6)就完成了提取瞬时频率ω(1)的过程。求解结果见(3)对信号进行 Hilbert变换时,信号的两端会出现严图7重的端点效应。提取某些信号瞬时特征所得的瞬时频率在局部出现了负数,端点效应是造成负频率的一个原因而端点效应可以通过利用特征波对原有数据序列进行延拓的方法来解决,具体解决办法将在今后讨论。尽管目前出现了EMD担论4,其目的是将不满足Hibt变换的信号进行分解得到若干个IMF( intrinsic mode function),然后进行 Hilbert运算,达到提取信号瞬时特征的目的。该理论开辟了信号处理的新空间。但它还不够成熟还需喫进一步的完善和研究图7利用数值微分法提取信号的瞬时频率特征参考文献从图7可以看出,以三次烊条指值进行的数值微分可[]黄长蓉. Hilbert变换及其应用[J].成都气象学院学报以准确岀提取岀信号的瞬时频率特征。199,14(3):273-276.[2]杨小牛,楼A义,徐建良.软件无线电原理与应用[M].北3结束语京:电子工业出版社,2001在工程中, Hilbert变换使得我们对短信号和复杂信号[3]丁丽妤.数值计算方法[M].北京:北京理工大学出版社,的摒时特征的提取成为可能特别是对瞬时频率特征提1997取,在工程中具有十公重要的意义。文中讨论的利用三次[4] Huang N e. The empirical mode decomposition and the hilbert样条插值进行数值徵分以提取瞬时特征的方法是可行的,spectrum for nonlinear and nor stationary time series anal ysis但还存在着如下问题。[].Proc.R.soc.Lond.A,1998,454:903-995(上接第81页)218994。例22(x)=(1-2siny=223101075一般的(A算法计算了120代,求到的最大值为454176.219。154370083改进的α算法计算了34代,求到的最大值为1048575.875。改进后的αA算法收敛速度(指迭代次数)比一般GA算法几乎快了一个数量级,精度也提高了不少,特别是例2的最大值提高一倍多,速度提高这么快是未曾料到的y=74958参考文献+4X Axl Thla[1]陈国良.遗传算法及其应用[M]·北京:人民邮电出版社,图2函数2的图像1996一般GA算法计算了20代,求到的最大值为[2]袁亚湘,孙文瑜.最优化理沦与方法[M]北京:科学出版社,19991.218983[3]张铃,张钹·遗传算法杋理的硏究[J]·软件学报,改进(A算法计算了5代,求到的最大值为2000,11(7):945952o1994-2010ChinaacAdemicJournalElectronicPublishingHouse.Allrightsreservedhttp://www.cnki.net

2020-12-05下载

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OFDMA System Analysis and Design
OFDMA系统分析与设计的国外经典教材Chapter 1 Introduction to OFDM and OFDMAChapter 2 Characterization of the Mobile Wireless ChannelChapter 3 Fundamentals of Digital Communications and NetworkingChapter 4 Fundamentals of OFDM and OFDMA: Transceiver StructureChapter 5 Physical Layer: Time and FrequencyChapter For a listing of recent titles in theArtech House Mobile Communications Library,turn to the back of this bookOFDMA System Analysis and DesignSamuel C. YangARTECHHOUSEBOSTON LONDONartechhouse. comLibrary of Congress Cataloging-in-Publication DataA catalog record for this book is available from the U.S. Library of CongressBritish Library cataloguing in Publication DataA catalogue record for this book is available from the british libraryISBN-13:978-1-60807-076-3Cover design by vicki KaneC 2010 Artech House685 Canton streetNorwood. MA 02062All rights reserved. Printed and bound in the United States of America. No partof this book may be reproduced or utilized in any form or by any means, elec-tronic or mechanical, including photocopying, recording, or by any informationstorage and retrieval system, without permission in writing from the publisherAll terms mentioned in this book that are known to be trademarks or servicemarks have been appropriately capitalized artech House cannot attest to theaccuracy of this information. Use of a term in this book should not be regardedas affecting the validity of any trademark or service mark10987654321To my beautiful wife JennyContentsPrefaceAcknowledgmentsXVCHAPTER TIntroduction to ofdm and ofdma1.1 Motivation1.2 Conventional FDm1.3 Advantages of FDm1.3.1 Intersymbol Interference(ISI)and Multipath Fading1.3.2 Modulation and Coding per Subcarrier1.3.3 Simple equalization1.4 Disadvantages of FDM1.5 Basics of ofdm1.6 Advantages of OFDM1.6.1 Low-Complexity modulation1.6.2 Spectral Efficiency1.7 Basics of ofdma1.8 Advantages of OFDMA121.9 Some Practical issues of ofdm and ofdma1.9.1 Time Domain: Interblock Interference131.9.2 Frequency Domain: Intercarrier Interference131.10 OFDM and Dsss141.11 Overview of the book14References15Selected BibliographyCHAPTER 2Characterization of the mobile wireless channel2.1 Introduction2.2 Link analysis2.3 Distance Dimension: Propagation Loss2.3.1 Path Loss2.3.2 Shadowing Loss24Contents2.3.3 Multipath Fading26Example 2.1282.3.4 Concluding Remarks292.4 Time Dimension: Multipath Delay Spread302.4.1 Delay Spread30Example 2.231Example 2.3312. 4.2 Coherence bandwidth322.4.3 Implications for OFDM352.5 Frequency Dimension: Doppler Spread362.5.1 Doppler Spread36Example 2. 4372.5.2 Coherence time2.5.3 Implications for OFDM402. 6 Conclusions41References43Selected Bibliography44ChAPTER 3Fundamentals of Digital Communications and Networking453.1 Introduction453.2 Basic Functions of a Transceiver453.3 Channel Coding473.3.1 Linear block codes473.3.2 Convolutional codes493.4 Symbol mapping and modulation3.5 Demodulation563. 5. 1 Matched Filter563.5.2 Symbol Error3.6 Adaptive Modulation and Coding603.7 Cyclic Redundancy Check(CRC)623.8 Automatic Repeat Request(arQ)643.8.1 Stop-and-Wait ARQ643.8.2 Sliding Window arQ653.9 Hybrid ARQ67References69Selected bibliographyCHAPTER 4Fundamentals of ofdm and ofdma: transceiver structure4.1 Basic Transmitter functions714.2 Time domain: guard time4.3 Frequency Domain: Synchronization744.4 Basic receiver functions754.5 Equalization764.6 OFDM Symbol79Contents4.7 OFDMA Transmitter844. 8 OFDMA Receiver4.9 OFDMA4.9.1 Frequency diversity4.9.2 Multiuser diversity914.9.3 Concluding Remarks4.10 Peak-to-Average Power ratio924.11 Conclusions93References94Selected Bibliography95CHAPTER 5Physical Layer: Time and Frequency975.1 Introduction5.2 Distributed Subcarrier Permutation: Forming Subchannels onDownlink5.2.1 Full Usage of Subchannels(FUSC1005.2.2 Partial Usage of Subchannels(PUSC)1015.2.3 Tile Usage of Subchannels 1(TUSC1)1025.2.4 Tile Usage of Subchannels 2(TUSC2)1025.3 Distributed Subcarrier Permutation: Forming Subchannels on Uplink 1025.3.1 Partial Usage of Subchannels(PUSC)1035.3.2 Optional Partial Usage of Subchannels(Optional PUSC)1035.4 Adjacent Subcarrier Permutation: Downlink and Uplink1045.5 Summary of Subcarrier Permutation Modes1045.6 Bursts and Permutation Zones1055.7 Subframes and frames1075.7.1 Preamble1105.7.2 Frame Control Header(FCH)1105.7.3 Downlink MAP (DL-MAP)and Uplink MAP(UL-MAP1115. 8 TDD and FDD5. 9 System Design Issues1125.9.1 Frequency Diversity and multiuser diversity1125.9.2 Segmentation1125. 10 Adaptive burst profiles1155.10.1 Burst Profiles1155.10.2 Channel Quality Feedback116References117ChAPTER 6Physical Layer: Spatial Techniques1196.1 Introduction6.2 Spatial Diversity: Receive Diversity1206.2.1 Receive Diversity: Antenna Selection1226.2.2 Receive Diversity: Maximal Ratio Combining6.3 Spatial Diversity: Transmit Diversity123Contents6.3. 1 Transmit Diversity: Open-Loop 2 X 11246.3.2 Transmit Diversity: Open-Loop 2X 21266.3.3 Transmit Diversity: Closed-Loop Antenna Selection128Example 6.11296.3.4 Transmit Diversity: Closed-Loop precoding1306.3.5 Remarks1326.4 Spatial Multiplexing1336.5 MIMO-OFDM1366.6 Beamforming1366.7 System Design Issues139References140Selected Bibliography141CHAPTER 7Medium Access control: architecture and data plane1437.1 MAC Architecture1437.2 Convergence Sublayer1457. 2.1 Address Mapping( Classification1467. 2.2 Header Suppression1467. 3 Common Part Sublayer1477.3.1ARQ1477. 3.2 MAC SDU and MAc pdu1487.3.3 Fragmentation/Packing1497.4 Security Sublayer152References152chaPTeR 8Medium Access Control Lower Control plane1538. 1 Introduction1538.2 Scheduler1538.3 Bandwidth Request1558.3.1 Request in Existing Uplink Allocation1568.3.2 Unicast Polling1568.3.3 Multicast and Broadcast Polling1578.3.4 Contention-Based Request for OFDMA1578.4 Control Signaling1588.5 Ranging1598.5.1 Initial Ranging1598.5.2 Periodic Ranging1608.5.3 Handover ranging1618.6 Power Control1618.6.1 Uplink Power Control: Closed-Loop1648.6.2 Uplink Power Control: Open-Loop1668.6.3 Assignment of Uplink Modulation and Coding8.6.4 Concluding Remarks168References169ContentsChaPTER 9Medium Access Control: Upper Control plane1719.1 Introduction1719.2 Network Entry1719.2. 1 Synchronization with Downlink of Base Station and acquisitionof parameters1739.2.2 Initial Ranging1739. 2.3 Negotiation of Mobile Capabilities1749.2.4 Security Procedures1749.2.5 Mobile registration1759.2.6 IP Connectivity1759.2.7 Connection Setup1769.3 Mobility Management: Link Handover1769.3.1 Cell Reselection1779.3.2 Hard Handover(HHO1799.3.3 Macro Diversity Handover(MDHO)1849.3.4 Fast Base Station Switching(FBSS1879.3.5 System Design Issue: H Add and h delete1899.3.6 Concluding Remarks1919.4 Mobility management: Network handover192References192CHAPTER 10Quality of Service(Qos)19510.1 Introduction19510.2 Definitions and Fundamental Concepts19510.2.1 Service Flows and Qos Parameters19510.2.2 Connections19610.3 Object Relationship Model19710.4 Service flow transactions19910.4.1 Creating a Service Flow19910.4.2 Changing a Service Flow20010.4.3 Deleting a Service Flow20310.5 QoS Parameters20410.6 Scheduling Services20610.6.1 Unsolicited Grant Service(UGS)20610.6.2 Real-Time Polling Service(rtPS20710.6.3 Extended Real-Time Polling Service(ertPS20710.6.4 Nonreal-Time Polling Service(nrtPS20810.6.5 Best Effort(BE)20810.6.6 Remarks209References210

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ABAQUS 子程序断裂模型

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