Detecting chaotic and ordered motion in barred galaxies

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基于相空间重构的神经网络风暴潮增水预测方法

基于相空间重构的神经网络风暴潮增水预测方法尤成;于福江;原野【摘要】风暴潮增水的准确预测对于国民生产、防灾减灾有重大意义.本文提出一种基于相空间重构的神经网络风暴潮增水预测方法,即使用单站风暴潮增水数据重构出与之相关的相空间,然后使用BP神经网络模型拟合该相空间的空间结构.将该模型用于库克斯港风暴潮增水预测,结果表明:该模型应用在风暴潮增水时间序列的预测中是合理、可行的,并具有较高的精度.此外,使用dbl0小波函数对原始余水位数据进行降噪处理可以显著地提高模型的预测精度.【期刊名称】《海洋预报》【年(卷),期】2016(033)001【总页数】6页(P59-64)【关键词】相空间重构;BP神经网络;风暴潮增水预测;小波降噪【作者】尤成;于福江;原野【作者单位】国家海洋环境预报中心国家海洋局海洋灾害预报技术研究重点实验室,北京100081;国家海洋环境预报中心国家海洋局海洋灾害预报技术研究重点实验室,北京100081;国家海洋环境预报中心国家海洋局海洋灾害预报技术研究重点实验室,北京100081【正文语种】中文【中图分类】P731.23Packard等[1]提出了重构相空间的思想。

随后Takens等[2]提出嵌入定理，建立起观测资料与动力系统空间特征之间的桥梁，使得深入分析时间序列的背景和动力学机制成为可能。

Lyapunov指数、G-P关联维算法、虚假近邻法、Cao方法、自相关法、互信息法、C-C方法等对各种参数的计算，使得相空间重构技术日趋成熟。

Farmer等[3]第一次提出使用相空间重构的方法预测时间序列。

这个方法后来被称作k-NN方法。

许多学者讨论K-NN方法中权重系数ωi该如何取值[4-6]。

为了尽量避免k的选取引起预测误差，Yankov等[7]以一组k取值不同的k-NN方法为成员，进行集合预报，发现预报效果有一定的改进。

此外，人们在天气预报、水文预报等方面应用相空间重构的理论进行了研究取得了相当的成果。

底部钻具规则涡动轨迹的内摆线描述方法

底部钻具规则涡动轨迹的内摆线描述方法2011年第35卷第3期中国石油大学(自然科学版)JournalofChinaUniversityofPetroleumV o1.35No.3Jun.20l1文章编号:1673—5005(2011)03-0076-03底部钻具规则涡动轨迹的内摆线描述方法马汝涛,纪友哲,贾涛,韩飞,朱英杰(1.中国石油勘探开发研究院研究生部,北京100083;2.中国石油集团钻井工程技术研究院机械所,北京100195)摘要:为了认识和控制钻井过程中的钻柱涡动,基于几何学原理提出内摆线描述方法.该方法将涡动视为规则运动,从分析钻柱外缘固定点的运动特性入手,求解底部钻具(BHA)与井壁的摩擦接触的运动轨迹方程,确定轨迹上各点的速度,分析钻柱自转和公转速度对底部钻具运动轨迹的影响.结果表明:底部钻具的涡动可能造成钻柱以远高于其自转速度的角速度沿着井壁快速公转,导致井下工具过早失效;钻柱规则涡动引起BHA外缘某点沿井壁的运动轨迹可用几何方法进行描述,轨迹方程证实线速度是影响井下工具磨损的重要参数;根据现场测试与室内试验所获得的钻柱规则运动轨迹可以反推涡动方程,从而掌握BHA的运动状态;利用内摆线描述法所得结果与文献试验数据吻合较好.关键词:底部钻具;钻柱涡动;内摆线;运动轨迹;过程监测中图分类号:TE243文献标志码:Adoi:10.3969/j.issn.1673-5005.2011.03.015 HypocycloidmethodfordescribingregularwhirlingofbottomholeassemblyMARu.tao,JIY ou.zhe,JIATao,HANFei,ZHUYing-jie(1.PostGraduateSchoolofResearchInstituteofPetroleumExploration&Developmen t,PetroChina,Beijing100083,China;2.DepartmentofDrillingMachineryofDrillingResearchInstitute,CNPC,Beijing100195, China)Abstract:Onthebasisofgeometry,ahypocycloidmethodwasproposedtoidentifyandcontro ldrillstringwhirling.Treatingthewhirlingasaregularpattern,thismethodwasusedtodescribemotioncharacteristicsofafi xedpointondrillstringcirc—umference,tosolveequationsrepresentingbottomholeassembly(BHA)motiontrajectories ,todefinevelocitiesofeachpointOilthetrajectory,andtoanalyzetheimpactsofrotationandrevolutionspeedsonBHAwh irling.Theresultsshowthat whirlingmightcausedrillstringrollingaroundboreholewallwitharevolutionspeedmuchhi gherthanrotating,inducingdownholetoolsprematurefailures.TheregularmotionpatternsofafixedpointonBHAcircu mferencecanbeexpressedbygeometrymeasures,andthetrajectoryequationindicatesthatthelinearvelocityplaysanimpo rtantroleintoolwear.The whirlingequationsrepresentingBHAmotioncanbeworkedoutfrominversionsoffieldandla boratorytestsandtheresultsproperlymatchdocumentedtests.Keywords:bottomholeassembly;drillstringwhirling;hypocycloid;motiontrajectories;pr ocessmonitoring底部钻具(BHA)的涡动现象普遍存在于钻井过程中¨,可能引起钻铤偏磨,钻头磨蚀,随钻测量工具损坏等破坏性后果.为了认识BHA的涡动机制,须建立描述钻柱运动的合理方法.常见的方法有3类:基于机械振动原理建立BHA动力学模型,分析横向力对钻柱振动的影响规律'";通过室内试验测得特定结构BHA的运动参数,给出其轴线及外边缘的运动轨迹'";在钻井过程中采集钻压,转速,钩载等数据,根据运动学和动力学理论分析BHA涡动状态_2'B..第1类方法难以体现BHA外缘与井壁的摩擦状况;第2类方法过程复杂且成本较高;第3类方法不能直观显示BHA运动状况.笔者将BHA涡动视为规则运动,引入内摆线方程直观,简洁地求解BHA外缘某一固定点的运动轨迹,收稿日期:2010—08—30基金项目:国家"863"高技术研究发展计划项目(2006AA06A107)作者简介:马汝涛(1982一),男(汉族),山东青岛人,博士研究生,从事套管钻井工作机制研究和井下工具研发工作.第35卷第3期马汝涛,等:底部钻具规则涡动轨迹的内摆线描述方法-77?通过分析轨迹特点了解钻柱涡动状况.1内摆线描述法基本方程l-1模型简化考虑BHA与井壁发生接触的情况,如图1所示.图1中外圆为井壁,内圆为BHA截面的外壁.以井眼中心O为圆心建立平面直角坐标系oxy,o轴与内圆交于点P,而P点同时也是内圆与外圆的接触点.将点P固定于内圆上,分析P点在oxy坐标系中的运动即可实现对钻铤的横向运动的描述.BHA的剖面可以选在任一位置,区别只是最终表达式相应的加入一项钻柱偏心量.图1BHA涡动示意图Fig.1SketchmapofBHAwhirling1.2几何内摆线方程对于图1所示的几何模型,假定小圆沿大圆内侧做无滑动滚动,那么由小圆上一固定点P所形成的轨迹就称为内摆线,其参数方程为f=(R—r)c.s+rc.s[(-1)],,.,尼吖)si哪rsin[(式中,尺为外圆半径,m;r为内圆半径,m;0为大圆中心O与小圆中心0t的连线沿逆时针方向摆动时与OX轴之间的夹角,rad.若令∥r=k,则当k为整数时内摆线为封闭曲线,且曲线带有k个尖角;若k为有理数,令k=m/n为其最简形式,则内摆线具有m个尖角.1.3BHA涡动轨迹方程BHA旋转过程中可能发生正向涡动(顺时针公转)或负向涡动(逆时针公转),现以负向涡动为例求解固定点P的轨迹方程(图1).为保证方程的合理性,假设:井壁为刚性,与BHA相互作用后不发生变形;井壁与BHA接触类型为点接触;BHA与井壁相对运动过程中始终保持相互接触.固定点P的参数方程为f%=(R-r)cos(f)"4-/'COS(∞￡),,,【y=(R—r)sin()+rsin(∞f).,式中,为公转角速度,rad/s;to为钻柱自转角速度,rad/s,自钻头上部向下看为顺时针方向,本文中取逆时针方向为正向,故∞前添加了负号;和Y分别为点P的横坐标和纵坐标.对比分析方程(1)和方程(2)发现,如果令∞=R/r一1,则方程(2)即为标准内摆线方程.实际上,这种情况相当于钻铤沿井眼内壁做无滑动滚动, 称为"负向纯滚动".除去这种特殊情况,涡动都将伴随钻柱与井筒的相对滑动并磨损钻具.若将和作为变量处理,并考虑两者作用时间不一致,可引入参数t.和t将方程(2)改写为,t2rt1f=Rc0s(I(t)dt)+rcos(I一(t)dt),{.(3)I一2一l【Y=Rfsin(J(t)dt)+rsin(I一(t)dt).0J0其中R科=R—r—h(t),h(t)是考虑到BHA可能脱离井壁的情况而引入的函数,其含义为BHA截面外缘到井壁的最短距离.实际应用中,可在钻铤的适当位置装人加速度计和位移计,测得BHA旋转和位移参数,代人方程(3),即能描绘出合理的BHA运动轨迹图.2典型轨迹曲线方程(2)是内摆线描述法的理论依据.根据方程特点可以判断当to//2为某些特殊值时,P点轨迹应表现出与内摆线相似的性质.图2为R=120.65 mm,r=88.9mm,=一12.56rad/s时力取不同值对应的BHA外缘涡动轨迹.图2(a)中BHA只是围绕自身轴线旋转,旋转同时与井壁的一侧发生接触, 此时的轨迹就是BHA的外缘轮廓.图2(b)为D=to时P点的运动轨迹,这种运动称为"正向同步涡动",其特点是P点始终与井壁保持接触,沿井壁划出完整的圆形曲线.运动过程中, 钻铤上除P点之外其他各点均未接触井壁.图2(C)为=to/(R/r一1)=58.61rad/s时P点的运动轨迹,此时力是的数倍,即钻柱以大大高于其自转速度的角速度沿着井壁快速公转.Johnson…通过试验认为,PDC钻头出现负向纯滚动的几率比正向涡动高许多;章扬烈J,Kesaven等也在模拟试验中得出类似结论,说明这种运动状态较为常见.图2(c)的轨迹为标准内摆线,容易发现,函数在每个尖角处不可导,其物理意义表示尖角78?中国石油大学(自然科学版)2011年6月处P点线速度为0,而尖角之外的曲线上速度不为度已经完成了多次周期性变化.BHA内应力的周0,即在完成一条完整的内摆线时,BHA截面各点速期性变化势必对井下工具造成损伤.+井眼内壁十涡动轨迹_t-井眼内壁十涡动轨迹_t-井眼内壁十涡动轨迹42一2-4/m(a)f005—505/m/Ⅲ(b)I~=-12.56rad/s(c)I1=58.61rad/s图2BHA外缘涡动轨迹Fig.2TrajectoriesofBHAwhirling根据方程(2)求得轨迹上各点的速度为:~/(R—r)+r+.(4)其中=2r(R-r)axOcos((∞一)t).由表达式可以发现,为周期函数,其周期=I21T/(一)l.需要指出,式(4)中(cJ恒为正,不再考虑其方向,而需考虑方向,当为正向时取正值,负向时取负值.考虑特例,令t=0,此时P点刚好与井壁接触,则V=(R-r)+.(5)实际上,如果BHA发生了负向纯滚动,则不仅P点,其他所有与井壁接触的点的速度都可用式(4)计算.Shyu_l钊也得到了与方程(5)相同的结果并将该速度作为关键参数分析了钻铤涡动对其磨损程度的影响.3内摆线描述方法的应用JohnsonL1提出了一种提高PDC钻头横向稳定性的设计方法,为检验该方法的可靠性试制了多种专用钻头并进行室内试验.其中一种钻头用于校验涡动对钻进的影响,试验结果给出了一种典型的涡动轨迹(图3).Johnson指出发生负向纯滚动时钻头切削齿外缘将生成瓣状切削痕迹,且瓣状曲线出现频率很高,但并未说明曲线的成因.由图3可以看出,钻头滚动轨迹主要有如下特征:单一封闭曲线,自身没有交叉;具有15个波瓣;波瓣之间光滑连接.根据内摆线描述法可以作如下推理:曲线处于稳定状态,则公转与自转角速度之比O/to为整数;波瓣数量说明井眼半径与钻头外径之比可以表示为R/r=15/n,其中n为与15互质的整数;波瓣中未出现尖角,严格来说并非达到无滑动的滚动效果,但考虑到实际试验条件对轨迹的影响,可以认为已经形成标准的内摆线.,I图3典型的钻头负向纯滚动轨迹(由Jonhson原图修改)Fig.3Typicallocusofbitwhirling(afterJonhson)不妨验证一下给出的推理,令=一12.56rad/S,则O=rto/(R-r)=175.84rad/s,而/2,'to=14为整数,合乎推理.按上述参数绘制轨迹如图4所示,与图3有很大的相似性.十井眼内壁+涡动轨迹42一2-4一b0b/m图4推理得到标准内摆线Fig.4DeducedhypoeycloidcuIe4结论(1)底部钻具的涡动可能造成钻柱以远高于其自转速度的角速度沿井壁快速公转,导致井下工具过早失效.(下转第83页)第35卷第3期郭辛阳,等:固井封固系统初始作用力及其影响?83? (上接第78页)(2)钻柱规则涡动引起BHA外缘某点沿井壁的运动轨迹可以用几何方法进行描述,线速度是影响井下工具磨损的重要参数.(3)根据现场测试与室内试验所获得的钻柱规则运动轨迹可以反推该点的涡动方程,从而掌握BHA的运动状态.参考文献:[2][3][4][5][6]JANSENJD.Whir】andchaoticmotionofstabilizeddrillcollars『R].SPE20930,1992.REY—FABRETI,OUDINN.Detectingwhirlingbehaviour ofthedrillstringfromsurfacemeasurements[R].SPE38587,1997.章扬烈.钻柱运动学与动力学[M].北京:石油工业出版社,2001:1-5.高德利,高宝奎.水平井段管柱屈曲与摩阻分析[J].石油大学:自然科学版,2000,24(2):1-3.GAODe.1i.GAOBaokui.Bucklingandfractionalanaly. sisofdrillstringinhorizontalwell[J].JournaloftheUni—versityofPetroleum,China(EditionofNaturalSci?ence),2000,24(2):1—3.KESHAV ANB.Jarringdynamicsofdrillstrings[D].Cambridge:MassachusettsInstituteofTechnology,1993.V ANDLVERJK,NLCHOLS0NWJ,SHYUR.J.Casestudiesofthebendingvibrationandwhirlingmotionof drillcollars[R].SPE18452,1990.[7]MANSUREAJ,FINGERJT,KNDSENSD.Interpreta—tionofdiagnostics—while—drillingdata[R].SPE84244, 2003.[8]HEISIGG,teraldrillstringvibrationsin extended—reachwells[R].IADC/SPE59235.2000.[9]wuSX,PAEZL,PARTINU.Decouplingstick?slip andwhirltoachievebreakthroughindrillingperformance [R].IADC/SPE128767,2010.[10]DUPRIESTEF,SOWERSFS.Maintainingsteerability whileextendinggaugelengthtomanagewhirl[R].SPE/IADC119625,2009.[11]JOHNSONS.Anewmethodofproducingl~erallystable PDCdrillbits[R].SPE98986,2006.[12]LANGEVELDCJ.PDCbitdynamics[R].SPE/IADC 23867,1992.[13]MASONJS,SPRAWLSM.AddressingBHAwhirl—the culpritinmobilebay[R].IADC/SPE35034,1996.[14]MENANDS,SELLAMIH,SIMONC.Howdrillstring rotationaffectscriticalbucklingload?[R].IADC/SPE 112571,2008.[15]NEUBERTM,HEISIGG,FORSTNERI.V erification ofanadvancedanalysismodelwithdownholebending momentmeasurements[R].SPE93864,2005.[16]SHYUR-J.Bendingvibrationofrotatingdrillstrings[D].Cambridge:MassachusettsInstituteofTechnolo-gY,1989.(编辑李志芬)●。

Panasonic WV-S1131 高质量的自动对焦摄像头说明书

Lens not includedPanasonic WV-S1131 captures the highest quality images automatically even in very challenging and fast-changingsurveillance environments. Intelligent Auto (iA) allows the camera to automatically adjust the key settings in real-time depending on the scenery and movement, reducing distortion such as motion blur and moving objects. New industry-leading 144dB dynamic range delivers balanced scene exposure in dynamic and extreme-backlit lighting environments. In addition, color night vision provides outstanding low-light performance with accurate color rendition and saturation from i-Pro's 1/3" sensor, rivaling the performance of costlier 1/2" sensor cameras in the market. The adopted H.265 Smart Coding technology, intelligently reduces bandwidth efficiency of up to 95%* more than H.264 for longer recording and less storage. Cameras out-of-the-box, support full data encryption streaming and is compliant to FIPS 140-2 Level 1 standards to keep your video secured.*Value in Advanced mode with Smart Facial Coding. It depends on the scene.Extreme image quality allows evidence to be captured even under challenging conditions-Auto Shutter speed control for fast moving vehicles -Sharp and clear images of a walking person day & night-Outstanding low light performance in true color with low noise for night time applications-Super Dynamic 144dB for backlit situations involving headlights and shadows on night streetsExtreme H.265 compression with new Smart Coding-Longer recording and less storage compared to any H.264 based compression techniques-New self-learning ROI* encoding (Auto VIQS) detects movement within the image and compresses the areas with little motion in order to reduce transmitted data while maintaining the quality of the image.-New “Smart Facial Coding” adds more bandwidth reduction for ID camera applications mainly capturing faces*Region of InterestExtreme Data Security-Full encryption SD card edge recording to keep your data safe -FIPS 140-2 Level 1 compliant-Full end-to-end system encryption with supported VMS and devices to protect from IP snooping/spoofing and detect data alterationiA (intelligent Auto) H.265 Network Camera•Full HD 1080p 60fps •iA (intelligent Auto)•Extreme Super Dynamic 144dB •Color night vision (0.0007 to 0.01 lx)•H.265 Smart Coding•FIPS 140-2 Level 1 compliantKey Features•Public safety (City / Road / Highway / Port)•Transportation (Airport / Train / Subway)•Retail / Bank / Education / Hospital / BuildingApplicationsWV-S1131PJ(Made in JAPAN)DISTRIBUTED BY :https:///PanasonicNetworkCamera(2A-170DA)Trademarks and registered trademarks– iPad and iPhone are registered trademarks of Apple Inc.– Android is a trademark of Google Inc.– ONVIF and the ONVIF logo are trademarks or registered trademarks of ONVIF Inc.– All other trademarks identified herein are the property of their respective owners.• Masses and dimensions are approximate. • Specifications are subject to change without notice.Important– Safety Precaution : Carefully read the Important Information, Installation Guide and operating instructions before using this product.– Panasonic cannot be responsible for the performance of the network and/or other manufacturers' products used on the network.Specifications*2 Super Dynamic function is automatically set off on 60 fps mode.*3 Stabilizer, Smart Facial Coding, i-VMD can not be used at the same time.*4 When “3 mega pixel [4 : 3](30fps mode)” is selected for “Image capture mode”, “90 °” and “270 °” cannot be selected.*5 Used by super resolution techniques*6 Transmission for 4 streams can be individually set.*7 Only use AAC-LC (Advanced Audio Coding - Low Complexity) when recording audio on an SD memory card.*8 Including alarms from Plug-in SoftwareAppearanceOptional AccessoryUnit : mm (inches)Notification sent to the monitoring screen。

海康威视 30X 高清鱼眼网络摄像机用户手册说明书

Copyright ©1993- 2017 Infinova. All rights reserved. Appearance and specifications are subject to change without prior notice.• Inbuilt 30X HD integrated camera module• 1/1.9" large area progressive scanning CMOS sensor• ICR infrared filter type automatic switch to realize true day/nightsurveillance• Starlight ‐level ultra ‐low illumination: 0.0005 lux• Supports multi ‐frame composite pattern wide dynamic and the maximumdynamic range is 120dB• Inbuilt efficient infrared lamps, wave length 850nm, ensure stablelong-term use and reduce maintenance cost • Night vision distance up to 200m• The ways of turning on the infrared lamps can be flexible to meetdiversified surveillance environment demands• The infrared power is adjusted automatically based on dome drive zoomingor manually to optimize the night vision fill ‐in light effects • HD network video output: 1920×1080@60fps• Features smart functions to achieve border protection (wire cross,intrusion) • Three Simultaneous Video Streams: Dual H.265 & M-JPEG or Dual H.264 &Scalable M-JPEG• Supports embedded storage/NAS storage• Supports alarm recording and alarm snapshots• Bi ‐directional audio, G.711a/G.711u/AAC standard optional • Two alarm inputs and one alarm output• Supports motion detection, 4 detecting areas dividable• Supports servo feedback mechanism and multiple alarm-triggered ways,such as IO input, network disconnected, motion detection, smart detection, etc.; supports flexible alarm associated configurations, such as I/O output, email, FTP picture-uploading, audio and TF card recording • Supports Local Recording• Supports Region of Interest (ROI), 8 regions dividable• Allows multiple users to perform live access and parameters settings viaWeb Server• Supports preset, autopan, pattern, autoscan, time tour, normal tour, power‐on return, etc.• Supports Auto-Flip and Image overlapping • Manual Consumption adjustment• Compatible with Infinova digital video surveillance software and convenient to integrate with other video surveillance software • Supports ONVIF Profile S & G standards• Standard SDK, easy to integrate with other digital system• Supports RS485 control and analog video output for easy debugging • IP67 protection rate, inbuilt a heater and air circulation system to avoid icing• Supports remote network upgrade•Adopts hydrophobic lens, lens self-cleanVT231-A230-A series is our newly introduced high definition infrared network dome camera that supports 1920×1080@60fps HDnetwork video output. It adopts H.265/H.264/M ‐JPEG encoding and its output provides excellent definition and color revivificationdegree which enables the acquisition of rich and accurate details so as to effectively guarantee smart analysis accuracy.This product adopts large power LED infrared lamps, infrared wave length 850nm, long night vision distance up to 200m, strongillumination. The IR lamps can turn on or off automatically based on environmental lighting conditions or can be adjusted manually. The IR illumination allows flexible adjustment so as to reduce IR lamp calorific value and extend its service life.User ‐friendly GUI interface design allows users to perform dome PTZ control easily via network and to configure detailed camera parameters settings. At Web interface users can perform dome camera settings and operations by using a mouse which is more convenient than the traditional keyboard control. It also supports area zoom and image PTZ function.VT231-A230-A series dome cameras also feature general dome functions such as preset, pattern, autopan, autoscan, time tour and normal tour .5E232008-A53VT231-A230-A061HD IR IP dome cameras, 2.0M, 30X, 1/1.9" CMOS, day/night, H.265/H.264/MJPEG, with audio alarm, outdoor, bracket mount, 24VDC/24VAC/PoEIf select POE power source, LAS60-57CN-RJ45-F is must.AccessoriesV1761K Wall Mount, bayonet, 10 inches V1762K Corner Mount, bayonet, 10 inches V1763K Pole-side Mount, bayonet, 10 inchesLAS60-57CN-RJ45-F PoE power sourcing equipment, 100-240VAC inputs, 60W output(Unit: inch, in the parentheses is mm)MountingWall Mounting Corner MountingPole Mounting。

不确定曲面上非完整移动机器人的鲁棒镇定

水平面上运动．实际情况却并非总是如此，尤其是当轮式移动器人被用于野外环境作业以及星际探测等任务时，它们将不可避免的运动在不平坦的支撑面上．当轮式移动机器人在曲面上运动时，重力将会对系统的运动产生影响，因此在系统的拉格朗
日方程中需要考虑机器人的势能．Ｔ程角度而从
Ｔｙｒａｌ线性化系统不可控，ｏ使得经典的线性控制技
术也不适用．了克服这些困难，究者提ｌ了三为研ｑＪ
种其他类型的镇定控制律，即光滑时变控制律ｌ、２Ｊ不连续控制律以及混合控制律．比于不连Ｊ相续控制律，光滑时变控制律的主要缺点是收敛速率慢．实际上，这类控制律最多只能实现多项式衰减．不过，光滑控制律的优势在于所得到的闭环系统仍
引言
近二十年来，完整动力学系统的控制问题一非
满解决．但实际上，在该领域仍然存在着值得更深
入研究的问题．比如，滑控制律的过渡过程性能光
需要进一步提高，以及镇定和跟踪的统一控制设计问题，等等Ｊ．此外，一个经常被研究者忽略的议题是如何对运动在曲面上的轮式移动机器人进行控
维普资讯
动
力
学
与
控
制
学
报
２００６年第４卷
氏群Ｓ（）Ｅ２上的系统时对于标准群运算的左不变性，设计过程中使用了横截函数方法¨ 、积分器
ｂｃｓｐｉｇ以及Ｌａｕｏａｋｔｐｎｅｙｐｎｖ重设计方法 ¨ 具体而．
动机器人动力学模型为对象，设计鲁棒实际镇定控

学术英语(综合)U7教师用书

Unit 7 MathematicsI Teaching ObjectivesAfter learning Unit 7, students (Ss) are expected to develop the following academic skills and knowledge:II Teaching Activities and ResourcesReadingText ALead-inTeaching StepsPut Ss into pairs and ask them to do the task in Lead-in. Then choose several Ss to share their answers with the whole class.Answer Keys (Suggested Answers)•Analyzing statistics collected from questionnaires•Conducting experiments and analyzing the data•Purchasing financial productsText AnalysisTeaching Steps1.OverviewLet Ss preview Text A before class. An alternative plan is to allocate some time for Ss to read Text A quickly in class. Then invite several Ss to summarize the main idea.2.In-Depth Analysis1)Show Ss the following words and invite them to share their ownunderstandings with the class. Provide additional information in Supplementary Information when necessary.•Fibonacci sequence•decimal place•Stephen Baker and The Numerati•Acronym and Initialism2)Explain some important language points in Language Support to Ss.3)Discuss with Ss the nature and predictive function of mathematics in theauthor’s eyes by doing Task 1 in Critical reading and thinking.4)Ask Ss to work in pairs on some of the questions about mathematics bydoing Task 2 in Critical reading and thinking. Call on some Ss to report their answers to the class.Supplementary Information1.Fibonacci sequenceFibonacci sequence is often observed in the geometry of plants such as flowersand fruit with regard to their recurrent structures and forms. For instance, Fibonacci sequence is used to study and indicate the arrangement of leaves, branches, flowers or seeds in plants, highlighting the existence of regular patterns.Fibonacci sequence is also closely related to the Golden Ratio (approximately noted as 1.168), which not only frequently occurs in nature, but is widely used to achieve aesthetic perfection in artworks, such as sculptures and paintings.2.Stephen Baker and The NumeratiStephen Baker is an American journalist, non-fiction author and novelist who often explores themes concerning data and technology. The Numerati is a non-fiction book written by Stephen Baker. In this book, Baker discusses the increasing role that data-mining plays in politics, business, law enforcement, etc. on the basis of interviews with the numerati, which refers to people who are developing and using technologies to analyze and characterize our everyday actions. The book shows that data-mining can be used to predict outcomes and influence human behavior.3.Acronym and InitialismAcronym and Initialism are two types of abbreviation. Acronyms are pronounced as a whole word (e.g. NASA) while Initialisms are pronounced one letter at a time(e.g. FBI). In this text, an example of Acronym is ASCII, and CCTV is a typicalexample of Initialism.Language Support1.What if those strings of numbers are records of the things you’ve bought, placesyou’ve traveled to, websites you’ve visited, parties you’ve voted for?(Para. 3)此处作者为了引起读者注意，营造交互感，使用了偏对话体的文风。

正向运动学英文

正向运动学英文Here is an essay on the topic of "Forward Kinematics" with a word count of over 1000 words, written in English without any additional title or unnecessary punctuation marks.Forward kinematics is a fundamental concept in the field of robotics and mechanical engineering, which deals with the relationship between the joint angles or joint positions of a robot and the position and orientation of the end-effector or tool. It is the process of determining the position and orientation of a robot's end-effector based on the known values of its joint angles or joint positions.In a robotic system, the end-effector is the part of the robot that interacts with the environment, such as a gripper, a welding torch, or a painting tool. The forward kinematics problem involves finding the position and orientation of the end-effector in the robot's reference frame, given the values of the joint angles or joint positions.To understand the forward kinematics problem, consider a simple two-link robot arm, as shown in Figure 1. The robot arm has two joints, each with a single degree of freedom, and two links of lengths L1 and L2. The position and orientation of the end-effector can bedescribed by the Cartesian coordinates (x, y) and the angle θ, which represents the rotation of the end-effector around the z-axis.Figure 1: A two-link robot armThe forward kinematics problem for this robot arm can be formulated as follows: Given the joint angles θ1 and θ2, find the position (x, y) and orientation θ of the end-effector.To solve this problem, we can use the following equations:x = L1 * cos(θ1) + L2 * cos(θ1 + θ2)y = L1 * sin(θ1) + L2 * sin(θ1 + θ2)θ = θ1 + θ2These equations represent the forward kinematics of the two-link robot arm, and they can be used to calculate the position and orientation of the end-effector for any given values of the joint angles θ1 and θ2.The forward kinematics problem becomes more complex as the number of joints and links in the robot increases. For a robot with n joints, the forward kinematics equations can be expressed in matrix form using the Denavit-Hartenberg (DH) convention, which is a systematic way of assigning coordinate frames to each joint in therobot.The DH convention defines four parameters for each joint: the linkl ength (a), the link twist (α), the joint offset (d), and the joint angle (θ). These parameters are used to construct a homogeneous transformation matrix, which represents the position and orientation of the end-effector with respect to the base frame of the robot.The forward kinematics equations for an n-joint robot can be written as:T_0^n = T_0^1 * T_1^2 * ... * T_(n-1)^nwhere T_i^(i+1) is the homogeneous transformation matrix that relates the (i+1)th coordinate frame to the ith coordinate frame, and T_0^n is the final homogeneous transformation matrix that represents the position and orientation of the end-effector with respect to the base frame.The computation of the forward kinematics for a complex robot can be a challenging task, especially when the robot has a large number of joints or when the robot's structure is complex. In such cases, numerical methods and computer software are often used to solve the forward kinematics problem.One common approach is to use the Denavit-Hartenberg (DH) parameters to construct the homogeneous transformation matrices and then multiply them together to obtain the final transformation matrix. This method is widely used in robotics and is implemented in many software libraries and frameworks, such as the Robot Operating System (ROS) and the Robotics Toolbox for MATLAB.Another approach is to use symbolic computation to derive the forward kinematics equations. This method involves expressing the forward kinematics equations in terms of the joint angles and link parameters, and then simplifying and solving the resulting equations using symbolic algebra software, such as Mathematica or Maple.In addition to the mathematical formulation of the forward kinematics problem, there are also practical considerations in the implementation of forward kinematics in real-world robotic systems. These include issues such as sensor calibration, joint encoder resolution, and the effects of mechanical compliance and backlash in the robot's joints and links.Overall, the forward kinematics problem is a fundamental concept in robotics and plays a crucial role in the design, control, and programming of robotic systems. Understanding and solving the forward kinematics problem is essential for many roboticapplications, such as pick-and-place operations, assembly tasks, and trajectory planning.。

机器人发展前景作文英语

In the realm of technological advancement,robotics has emerged as a field of immense potential and rapid growth.The development of robots has not only revolutionized industries but also transformed the way we live and work.This essay will delve into the prospects of robotics,exploring its current state,potential applications,and the impact it may have on society.The inception of robotics can be traced back to the early20th century,with the concept of a programmable machine capable of performing tasks autonomously.However,it was not until the latter half of the20th century that significant strides were made in the field.Today,robots are ubiquitous, from the assembly lines of automobile factories to the exploration of space and the depths of the ocean.One of the most significant areas of development in robotics is in manufacturing.Automation has been a gamechanger for the industry, increasing efficiency and reducing the cost of production.Robots are now capable of performing repetitive tasks with precision and speed,allowing for mass production of goods at a scale previously unimaginable.This has led to an increase in productivity and a decrease in the cost of goods, benefiting consumers and businesses alike.Another area where robotics is making a significant impact is in healthcare. Surgical robots,such as the da Vinci Surgical System,have transformed the way surgeries are performed.These robots provide surgeons with enhanced dexterity and precision,leading to less invasive procedures and faster recovery times for patients.Additionally,robots are being developed to assist in elderly care,providing companionship and assistance to thosewho may require it.The field of robotics is not limited to physical machines software robots,or bots,are also making an impact.These bots are capable of performing tasks such as data entry,customer service,and even complex decisionmaking processes.The integration of artificial intelligence AI into these bots has allowed them to learn and adapt,making them increasingly efficient and capable.The development of robotics also brings with it ethical considerations.As robots become more advanced and capable,questions arise about their role in society and the potential impact on employment.While robots can perform tasks more efficiently than humans,this also means that they may replace human workers in certain industries.This raises concerns about job displacement and the need for retraining and education to prepare individuals for a changing job market.Moreover,the integration of AI into robots also raises questions about privacy and surveillance.As robots become more intelligent and capable of learning,there is a risk that they may be used to monitor and collect data on individuals without their consent.This raises ethical concerns about the balance between the benefits of robotics and the potential infringement on personal privacy.Despite these challenges,the prospects for robotics are vast.As technology continues to advance,robots are likely to become more sophisticated and capable.They may play a crucial role in addressing someof the worlds most pressing issues,such as climate change,by assisting in tasks such as environmental monitoring and clean energy production.In conclusion,the development of robotics is a testament to human ingenuity and innovation.While there are challenges and ethical considerations to be addressed,the potential benefits of robotics are immense.As we continue to push the boundaries of what is possible,it is essential to consider the implications of these advancements and strive to ensure that they are used responsibly and for the betterment of society. The future of robotics holds great promise,and it will be exciting to see how this field continues to evolve and shape our world.。

计算机期刊大全

计算机期刊大全【前言】随着计算机技术的快速发展，越来越多的人开始关注计算机期刊，以获取最新的科研成果和技术进展。

本文旨在介绍全球范围内主要的计算机期刊，帮助读者了解各期刊的主题范围、影响因子、最新收录论文等信息，以提高论文发表效率和科研成果的质量。

【一、计算机科学顶级期刊】计算机领域的顶级期刊，对于任何一位计算机科学家来说，都是非常重要的。

这些期刊的文章水平高、质量优，其发表文章往往具有一定的权威性和影响力。

以下是全球最著名的计算机科学顶级期刊：1.《ACM Transactions on Computer Systems》（ACM TOCS）主题范围：该期刊关注计算机系统的设计、分析、实现和评估等方面，特别是操作系统、网络、分布式系统、数据库管理系统和存储系统等方面的最新研究成果。

影响因子：3.612发行周期：每年4期最新收录论文：Content-Based Data Placement for Efficient Query Processing on Heterogeneous Storage Systems, A Framework for Evaluating Kernel-Level Detectors, etc.2.《IEEE Transactions on Computers》（IEEE TC）主题范围：该期刊刊登计算机科学领域的创新性研究成果，重点关注计算机系统、组件和软件的设计、分析、实现和评估等方面的最新进展。

影响因子：4.804发行周期：每月1期最新收录论文：A Comprehensive View of Datacenter Network Architecture, Design, and Operations, An Efficient GPU Implementation of Imperfect Hash Tables, etc.3.《IEEE Transactions on Software Engineering》（IEEE TSE）主题范围：该期刊涉及软件工程领域的各个方面，包括软件开发、可靠性、维护、测试等方面的最新研究成果。

Chaotic motion and ballistic ejection of gravitating shells

a r X i v :a s t r o -p h /0107051v 2 7 O c t 2004Model of ejection of matter from nonstationary dense stellarclusters and chaotic motion of gravitating shells.M.V.BarkovSpace Research Institute,84/32Profsoyuznaya Str ,Moscow,Russia,117997;barmv@sai.msu.ruV.A.BelinskiNational Institute of Nuclear physics (INFN)and International Center of Relativistic Astrophysics (ICRA),Dip.di Fisica -Universita‘degli Studi di Roma ”La Sapienza”P.leAldo Moro,5-00185Roma,Italy;volodia@vxrmg9.icra.itG.S.Bisnovatyi-KoganSpace Research Institute,84/32Profsoyuznaya Str ,Moscow,Russia,117997;gkogan@mx.iki.rssi.ruABSTRACTIt is shown that during the motion of two initially gravitationally boundspherical shells,consisting of point particles moving along ballistic trajectories,one of the shell may be expelled to inﬁnity at subrelativistic speed v exp ≤0.25c .The problem is solved in Newtonian gravity.Motion of two intersecting shells in the case when they do not runaway shows a chaotic behaviour.We hope that this toy and oversimplyﬁed model can give nevertheless a qualitative idea on the nature of the mechanism of matter outbursts from the dense stellar clustersSubject headings:black holes —ejection:active galactic nuclei:stars:chaos.1.Introduction.Dynamical processes around supermassive black holes in quasars,blazars and active galactic nuclei (AGN)are characterised by violent phenomena,leading to formation of jets and other outbursts.Jet formation is usually connected with the processes in the magnetizedaccretion disks(Lovelace,1976;Bisnovatyi-Kogan&Blinnikov,1976).Formation of qua-sispherical outbursts,which are probably observed in quasars with broad absorption lines, could be connected with another mechanism.Here we consider a possibility of a shell out-burst from a supermassive black holes(SBH)surrounded by a dense massive stellar cluster, basing on a pure ballistic interaction of gravitating shells oscillating around SBH.Ballistic ejection may be responsible for appearance of stars and observed SN in the intergalactic space,as well as the existence of stars between galaxies,suggested by many authors.Investigation of spherical stellar clusters using shell approximation was started by H´e non (1964),and than have been successfully applied for investigation of the stability H´e non (1973),violent relaxation and collapse(H´e non1964;Gott1975),leading to formation af a stationary cluster.Investigation of the evolution of spherical stellar cluster with account of diﬀerent physical processes was done on the base of a shell model in the classical serie of pa-pers of L.Spitzer and his coauthors(Spitzer&Hart1971a,b;Spitzer&Thuan1972;Spitzer &Shapiro1972;Spitzer&Chevalier1973;Spitzer&Shull1975a,b;Spitzer&Mathiew 1980).Numerical calculations of a collapse of stellar clusters in a shell approximation(Yangu-razova&Bisnovatyi-Kogan1984;Bisnovatyi-Kogan&Yangurazova1987,1988)had shown, that even if all shells are initially gravitationally bound,after a number of intersections some shells obtain suﬃcient energy to become unbound,and to be thrown to the inﬁnity.In the Newtonian gravity the remnant is formed as a stationary stellar cluster,and in general relativity SBH may be formed as a remnant.Formation of outbursts due to the ballistic interactions may happen as a result of in-tersection of shells,oscillating around SBH.In the smooth cluster with or without SBH in the centre stars evaporate,due to stellar encounters mainly with small kinetic energy,and formation of rapidly expelling stars is about100times less probable due to predominance of gravitational encounters with small momentum transfer Ambartsumian(1938).If the cluster is strongly aggregated,consisting of few compact pieces,the encounters between these pieces are quite diﬀerent,collision with large momentum transfer are becoming probable.In this case gravitational interaction between compact pieces may lead to the outburst with large velocity,and when such event happens in the vicinity of SBH the velocity could become a considerable part of the light velocity c.Such kind of situation in principle may be produced as a result of galactic collisions with close encounter of nuclei,when one of the nuclei strips the matter from the companion in the form of a collapsing shells.Interaction of such shell with the stellar cluster may leadnot only to collapse into SBH,but also to the reverse phenomena:expelling of the shell witha speed,much larger than the average speed of stars in the cluster.The shell is not fallinginto SBH due to high angular momentum of its stars.Even more important example of a quasi-spherical mass ejection is a relativistic collapseof a spherical stellar system,which is considered(Zeldovich&Podurets,1965;Lightman&Shapiro1978;Ipser1980;Rasio et al.1989)as the main mechanism of a formation of super-massive black holes in the galactic centers.Approximation of such collapse by considerationof spherical shells is the simplest approach,which reﬂects all important features of suchcollapse(Gott1975;Bisnovatyi-Kogan&Yangurazova1987,1988).Our consideration isrelated to the motion of stars(shells)which remain outside the newly formed supermassiveblack hole.Here we consider a simpliﬁed problem of a motion of two massive spherical shells,eachconsisting of stars with the same speciﬁc angular momentum and energies,around SBH.Theaim of this paper is to give an elementary treatment of the ballistic ejection,and to estimatethe maximal eﬃciency of this ejection.Note,that in a more complicated case of numerousshell intersection this elementary act is a key process of the energy exchange between starsand of matter ejection.This is also the elementary process leading to the violent relaxationof the cluster Lynden-Bell(1967),studied in the shell approximation by Gott(1975)andYangurazova&Bisnovatyi-Kogan(1984).Chaotization of the motion of two gravitatingintersecting shells appears as a by-prodiuct of our consideration.The appearence of chaos insuch a system,which is described by a set of simple algebraic equations,is a rare example.For the oversimpliﬁed case with a pure radial motion and reﬂecting inner boundary thechaotic shell motion was found by Miller and Youngkins(1997).Here we consider realisticshells consisting of stars moving along eliptical trajectories,and their chaotic propertieswould be examined in more details in another work.Weﬁnd conditions at which one of twoshells is expelling to inﬁnity taking energy from another shell.Weﬁnd a maximum of thevelocity of the outbursting shell as a function of the ratio of its mass m to the mass M ofSBH using only Newtonian theory of the shell’s motion.However we introduce cutoﬀﬁxing the minimal radius of the potentially outburstingshell r m on the level of few r g=2GM/c2.We show,that for equal masses of two shells theexpelling velocity reach the value v max≈0.3547v p at m/M=1.0,and v max≥0.3v p was obtained at the masses of shells0.25÷1.5M,where the parabolic velocity of a shell in thepoint of a smallest distance to the black hole v p may be of a considerable part of c.In sections2,3we describe outburst eﬀect and in sections4we present the evidence ofthe chaos in the system of intersecting shells.The exact solution of these problems in thecontext of General Relativity will be presented in the subsequent paper.2.Two shells around SBH.Physically the nature of the ballistic ejection is based on the following four subsequent events.The outer shell is accellerated moving to the center in a strong gravitationalﬁeld of a central body and inner shell.Somewhere near the inner minimal radius of the trajectory shells intersect.After that the former outer shell is deccellerating moving from the center in the weaker gravitationslﬁeld of only one central body.The second intersection happens somwhere far from the center.That may result in the situation when the total energy (negative)of the initially gravitationally bound outer shell is becoming positive as a result of two subsequent intersections with another shell.The quantitive analysis of this procrss is done in this section.Equation of motion of a shell with mass m and total conserved energy E in theﬁeld of a central body with mass M isE=mv2r+J2m2−Gm1(M+m1/2+m2)2r2,(2)E2(0)=m2v22(0)r+J22m22−Gm1(M+m1/2)2r2,(4)E2(1)=m2v22(1)r+J22m2The crucial point now are the matching conditions at the intersection point r=a1,t=t1 where from one can obtain the initial data to the equations(4),(5)in order to deﬁne uniquely the evolution during this new stage.In Newtonian theory these conditions are:E1(0)+E2(0)=E1(1)+E2(1);v1(0)(t1)=v1(1)(t1);v2(0)(t1)=v2(1)(t1),(6) i.e.the conservation of the total energy of the system and continuity of the velocities through the intersection point.Expressing v1(0)(t1),v2(0)(t1)from eqs.(2),(3)and v1(1)(t1),v2(1)(t1) from eqs.(4),(5)and equating them following conditions(6)we get:E1(1)=E1(0)+Gm1m2a1.(7)At some point r=a2,t=t2can happen the second intersection after which the shell”1”again becomes the outer and shell”2”becomes inner one.It is a simple task to write the equation of motion during this third stage(we designate it by the index(2))and repeat the same procedure of matching velocities but now at point r=a2,t=t2.The result is:E1(2)=E1(1)−Gm1m2a1−1a2=E2(0)−Gm1m2 1a2 .(9) Let us describe the situation,when one shell is ejected to inﬁnity after intersection of to initially bound shells.We consider a case when a2is larger then a1so,that the second term in(8)has larger absolute value,then theﬁrst one,theﬁrst shell gains a positive energy and goes to inﬁnity.Both shells have initial negative energies E1(0)and E2(0),but with small enough absolute values.Theﬁrst shell takes the energy from the second one,which is becoming more bound with larger absolute value of the negative energy E2(2),according to (8).3.Numerical solution.Let’s illustrate the foregoing scenario by an exact particular example of two shells of equal masses.We choose parameters in the following way:m1=m2=m,E1(0)=E2(0)=0,J1<J2,(10)In fact such exact solution represents theﬁrst approximation to the more general situation when E1(0)and E2(0)are nonzero(negative)but small in that sense that both modulus|E1(0)| and|E2(0)|are much less than Gm2/a1.We assume that initially both shells are moving towards the center.It follows from eqs.(2),(3)that under condition(10)such shells will intersect inescapably at the point r=a1,t=t1.After the second intersection at r=a2,t=t2the shell”1”will be thrown to inﬁnity with expelling velocity v1exp.It follows from(8)thatv1exp=v1(2) r→∞= a1−1b32(1)a1,e2(1)= (M+3m/2)2r m2mWe substitute this expression for J21into eq.(4)and again with conditions(7)and(10) obtain the following parametric form of the solution of this equation:r(ξ)=b1(1)(e1(1)coshξ−1),t(ξ)= G(M+m/2)(e1(1)sinhξ−ξ),(16) where the constant b1(1)and e1(1)are:b1(1)=M+m/2M+m/2r mb32(1)b31(1)b1(1)e1(1)(19)cosη1=b2(1)−a1b31(1)b32(1)From(14),(17)and(19)-(23)it is easy to see that all these relations determine a2/a1as a function of a1/r m and m/M.We introduce now the”parabolic”velocity v p of the any outer shell at the point of its minimal distance to the center r=r m as:v p= r m.(24) Than we havev1exp mr ma1−2and for the maximal possible runaway velocity in the family of solutions,characterized by(12),(15)we get v1exp∼0.25c.4.Chaos in the shell motion.Theﬁrst evidence that the motion of two intersecting shells can show chaotic character was given by ler&V.P.Youngkins(1997).They investigated the special case when the central body is absent and particles consisting the shells are moving only in radial direction(in our notation M=0and J1=J2=0).This situation,however,cannot model astrophysical cluster with massive nuclei,and also the problem of the inﬂuence of central Newtonian singularity arise which need some additional care.In any case a study of more physically realistic models with nonzero M,J1and J2from the point of view of possible chaotic behaviour represents essential interest.We report here some results for such more general two shells model which was investigated in the previous sections but again for the shells with equal masses.We consider now only oscillatory regime of motion without any runaway eﬀects.The shell motion in the Newton gravitationalﬁeld is completely regular,but at presence of intersections the picture changes qualitatively.The shell intersections result to chaos intheir motions.Character of chaos depends,mainly,on mass ratio of a shell and a central body.At a small shell mass the motion of the shells occurs basically in theﬁeld of the central body,and after one intersection there is a little change in a trajectory of each shell. Consider a case when angular momentum parameters J and energies of shells are close to each other,and as a result of two intersections energy is transferred to the shell”1”. Since shell parameters changes are not large,the mutual positions and speeds of shells after intersections do not change strongly.Then at the next intersection the part of energy will again be transferred to the shell”1”.After a large number of intersections,however, the mutual positions changes essentially.Then the energy starts toﬂow to the shell”2”, consequently we observe beating in oscillation of shells.In the case when the masses of the intersecting shells are large enough,the energy is transferred very intensively between them. It changes trajectories of shells essentially so that the next intersection does not resemble at all the previous one.In this case a shell’s motion at once gets properties of a randomness.Shell oscillations with mass ratio m/M=0.015are presented in Fig.5.In the case of massive shells the exchange of energy between shells occurs more intensively.As a result we have the obviously expressed chaotic behaviour of shells.Chaotic shell oscillations with m/M=0.08are presented in Fig.6.In Fig.6a full randomness of behaviour of the shells is seen obviously.Let us note,that when the exchange of energy between shells is suﬃciently large the strong randomness appears.Shells may exchange their positions during the motion.The external shell may become inner one and vice versa.One of the shells may give up practically all its energy of the orbital motion,which it may loose at constant angular momentum,i.e. the orbits of its particles become almost circular.It may be seen in Figs.6,7at those moments when the orbit of the inner shellﬁlls a narrow band by itself.Let us note that in our calculations the motion of the shells is very sensitive to initial parameters,what gives an additional evidence that intersecting shells represent a really chaotic system.When we change only precision of integrator from10−6to3×10−7,after several intersection motion of shells becomes absolutely diﬀerent from its initial behaviour in Fig.6at the same initial conditions.If we change the angular momentum parameter of one of shell from1.40to1.41,then in the same way as in previous case,motion of shells becomes absolutely diﬀerent after several intersection.We can make statement that the behaviour of shells is unstable and is strongly aﬀected by any perturbation in initial parameters of shell motion.The example of a chaotic behaviour of two intersecting selfgraviting shells,moving in their own gravitationalﬁeld,without a central mass,is represented in Fig.7.Chaotic behaviour of the intersecting selfgravitating shells in the Newton gravity is a rare example of a chaotic dynamical system,described fully analytically by algebraic relations.5.DiscussionWe have shown that pure gravitational interaction of two spherical shells and central object may lead to considerable energy exchange and ejection of one of the shell with a subrelativistic speed∼0.25c.Motion of stars around SBH may lead to similar eﬀects due to their interaction,and we may expect formation of very rapidly moving stars,which could overcome the galactic gravity and runaway into the intergalactic space.In this way very extended galactic halo may be formed.Ballistic mechanism of energy exchange between gravitating particles may be important in the evolution of spatial distribution of cold dark matter,when gravitational instabilities are developing in masses,much less than galactic ones,and gravitationally bound massive objects,consisting mainly from the dark matter interacting only due to its gravitation,may be formed.Interesting examples of ballistic interaction of satellites with planets and stars,their acceleration and ballistic control are presented in the book of V.V.Beletskyi(1977).AcknowledgementThe work of G.S.B.-K.and M.V.B.was partly supported by RFBR grant99-02-18180, and INTAS grant00-491.We are grateful to the referee,Prof.Seppo Mikkola for useful comments.REFERENCESAmbartsumian,V.A.1938,Uch.Zap.LGY22,19Beletskyi,V..1977,Sketches about the motion of celestial bodies,Nauka,M.(in Russian) Bisnovatyi-Kogan,G.S.,Blinnikov,S.I.1976,Astron.Zh.2,489Bisnovatyi-Kogan,G.S.,Yangurazova,L.R.1987,Asrtoﬁzika27,79Bisnovatyi-Kogan,G.S.,Yangurazova,L.R.1988,Ap.Sp.Sci.147,121Gott,J.P.1975,ApJ201,296H´e non,M.1964,Ann.d’Ap.27,83H´e non,M.1973,Astron.Ap.24,229Ipser,J..1980,ApJ238,1101Lightman,A.P.,Shapiro,S.L.1978,Rev.Mod.Phys.50,437Lovelace,R.V.E.1976,Nature262,649Lynden-Bell,D.1967,MNRAS136,101Miller B..and Youngkins V.1997,Chaos7,187.Rasio,F.,Shapiro,S.,Teukolsky,S.1989,ApJ336,L63Spitzer,L.Jr.,Hart,H.M.1971a,ApJ164,399Spitzer,L.Jr.,Hart,H.M.1971b,ApJ166,483Spitzer,L.Jr.,Shapiro,S.L.,1972,ApJ173,529Spitzer,L.Jr.,Thuan,T.X.1972,ApJ175,31Spitzer,L.Jr.,Chevalier,R.,1973,ApJ183,565Spitzer,L.Jr.,Shull,J.M.,1975a,ApJ200,339Spitzer,L.Jr.,Shull,J.M.,1975b,ApJ201,773Spitzer,L.Jr.,Mathieu,R.D.,1980,ApJ241,618Yangurazova,L.R.,Bisnovatyi-Kogan,G.S.1984,Ap.Sp.Sci.100,319Zeldovich,Ya.B.,Podurets,M.A.1965,AZh42,963(transl.Soviet Astron.-AJ,29,742 [1966])Figure1.Time dependence of radiuses r of two shells(in units r m)on time t(in units r m/v p,v p=r m/v p,v p=the shell mass to the mass of central body m/M.The maximum value of v1exp=0.3547 corresponds to m/M=1.0.with maximum runaway velocities.radius of the approach to the central body r m)as a function of m/M for solutions with maximum runaway velocities.Fig.6.—Chaotic shell oscillations with mass ratio m/M=0.08.ﬁeld without a central mass.。

基于杜芬振子的微弱信号检测技术及其FPGA实现研究

分类号：密级：U D C：编号：河北工业大学硕士学位论文基于杜芬振子的微弱信号检测技术及其FPGA实现研究论文作者：田晓旭学生类别：全日制学科门类：工学学科专业：通信与信息系统指导教师：高振斌职称：教授资助基金项目：国家自然科学基金(61139001)Dissertation Submitted toHebei University of TechnologyforThe Master Degree ofHere Is The Subject or Specialty You EngageThe weak signal detection technology based on Duffing oscillator and its field programmable gate array implementationbyTian XiaoxuSupervisor: Prof. Gao ZhenbinMay 2017摘要本文构建了一种在现场可编程门阵列(field programmable gate arrays，FPGA)平台实现微弱信号检测的系统。

本系统采用杜芬混沌算法对淹没在强噪声下的微弱正弦信号进行检测并采用四阶龙格库塔法对杜芬方程进行求解，通过对模块合理的划分减少运算周期，提高运算速度。

论文研究了杜芬振子微弱信号检测的可行性，实现了杜芬方程的计算、杜芬系统的状态判别、信号频率计算等一系列操作。

在系统设计过程中，采用节约存储空间的递推数列的方法计算正弦值，并将该方法与查表法进行了比较，分析了该方法的可行性；运用四阶龙格库塔对杜芬方程进行数值求解，并对计算过程中所选定点数的位数进行理论分析，并验证了所选定点数的正确性；在四阶龙格库塔法计算杜芬方程部分，根据四阶龙格库塔法的迭代原理，采用模块公用的方法节省硬件资源，利用多路选择器对计算过程进行调度，通过对乘法器、计数器、单端口ROM等IP核的调用，实现了对FPGA内部器件的合理利用；在状态判别部分，根据杜芬系统在混沌和大周期2种状态下相图的明显区别，运用基于相图分割的信号检测方法，该方法与传统方法相比实现简单，经验证可有效对混沌状态进行判决；运用zedboard中自带的OLED对状态识别单元中计算出的频率值进行显示。

The emergence of design in pedestrian dynamics

Available online at Physics of Life Reviews10(2013)168–190/locate/plrevReviewThe emergence of design in pedestrian dynamics:Locomotion, self-organization,walking paths and constructal lawAntonio F.Miguel a,b,∗a Department of Physics,Evora University,Rua Romão Ramalho59,7000-671Evora,Portugalb Geophysics Center of Evora(CGE),PO Box84,7002-554Evora,PortugalReceived25February2013;accepted7March2013Available online26March2013Communicated by J.FontanariAbstractGait is inherent to human life and hence its importance is often overlooked.But walking remains the most basic form of transportation and almost all journeys begin and end with a walk,regardless of the modes used in-between.Gaining a good under-standing of pedestrian’s dynamics is thus a crucial step in meeting the mobility and accessibility needs of people by providing safe and quick walkingﬂows.This paper presents a critical and integrative review of research on pedestrian’s dynamics and associated topics.The review focuses on comprehensive theories and models,with an emphasis on the advances made possible by the application of the con-structal law.Constructal law points out that the emergence and evolution of design in pedestrian dynamics is analogous to that of animateﬂow systems.Most importantly,it also highlights that the basic features of pedestrian dynamics and supportive walking infrastructures can be optimally envisaged with the help of a few fundamental physics laws.©2013Elsevier B.V.All rights reserved.Keywords:Human gait;Walk–run transition speed;Fundamental pedestrian diagram;Self-organization;Walking paths;Constructal law1.IntroductionAlthough there are over250species of primates,only one moves primarily on two legs.Bipedalism developed approximately4–5million years ago and it was theﬁrst major adaptation that separated hominids from other primates [1–4].Human anatomy is built on a body planned for bipedal locomotion.The two distinct gait modes of humans are walking and running,which make use of strikingly different mechanics and energetics.Currently,the fastest human being on Earth,Usain Bolt,is able to run at a speed greater than10.44m/s.Regular pedestrians,however,tend to walk rather than run,and do this mainly at a comfort walking speed of around1.3m/s[5,6].The different speeds at which humans walk or run translate themselves into varying energy costs.Keeping energy spending low is highly desirable and leads to greater mobility,given that humans must carry their energy supply with them[7,8].*Correspondence to:Department of Physics,Evora University,Rua Romão Ramalho59,7000-671Evora,Portugal.Tel.:+351266745372;fax: +351266745394.E-mail address:afm@uevora.pt.1571-0645/$–see front matter©2013Elsevier B.V.All rights reserved./10.1016/j.plrev.2013.03.007A.F.Miguel/Physics of Life Reviews10(2013)168–190169Since the middle of last century,the study of the pedestrian dynamics has become an active subject of research in science[5–8].Pedestrian dynamics has theoretical importance and a multitude of practical applications.Primary questions such as why and how human walks,or how crowd dynamics occurs based on individual interactions,along with some more practical aspects like the design of pedestrian optimized facilities,have puzzled many researchers.In-situ observational studies and time-lapseﬁlms,together with the modeling have revealed important quantitative details and have led to a unique understanding of pedestrian dynamics with important practical implications[5,6].Despite the considerable progress in understanding various aspects of pedestrian dynamics,there has been no systematic attempt to integrate what remain disconnected,because of the wide scope of the subject.Fitting the“pieces”together will contributes decisively to a uniﬁed view of the topic.This paper starts with a brief description of basic mechanics of human locomotion and its energetic cost.Factor such as gender,age and environment are important in the walking speed choice.Pedestrians react to other pedestrians and obstacles,and can only move freely when there is enough free space in front of them.Then,the relation between spatial headway(distance to the predecessor)and speed of pedestrians is analyzed.Empirical data(i.e.,the fundamental diagram)available in the literature is presented and models of pedestrian interactions are introduced.The calibration and the validation of the models using empirical data are also discussed.Finally,I turn the attention to the Constructal law which constitutes the thermodynamics law of nonequilibrium (ﬂow)systems with conﬁguration.For these systems,this law provides new physical insights,and a uniﬁed view on domains apparently foreign to each other.The Constructal law is introduced and,then,the Constructal view of pedestrian dynamics is presented and discussed.Furthermore,the design of improved pedestrian facilities,using the Constructal law,is also addressed.The objective of this Constructal section is to forge a more structured and uniﬁed view that engage a set of issues which are addressed under different frameworks and disciplinary spaces.2.Modern human anatomy and locomotion:mechanics,energetics and gait speedBipedal locomotion is the sole form of locomotion in all healthy modern humans and it sets them apart from all other living primates[1–4].A large number of anatomical features are functionally related to this type of locomotion. The human pelvis is pronouncedly bowl-shaped,with an adapted musculature which allows the thighs to be angled in, the lower limbs are lengthened and have an enlarged joint surface area to properly support body weight,the vertebral column is shortened and S-shaped,for rigidity and balance,lining up head and trunk vertically above the feet,the hole through which the column cord enters the skull is situated near the center of the cranium which allows the head to balance easily atop the column,the feet have an arched shape with the enlarged great toe brought in line with the other toes,to absorb shock and a more efﬁcient walk,are among other important evolutionary features[9,10].From an evolutionary perspective,the global impression of the human anatomy is that of a bio-cylinder shape[7,10].Although bipedalism is not the most stable and fast way of locomotion,it must clearly represent an evolutionary advantage to humans,because we still walk on two legs.Some of the advantages associated to bipedalism include the ability to carry things over longer distances,the freeing of arms and hands for other tasks(foraging and protection,for instance),the acquisition of improved long-distance perception and the improvement of body thermoregulation[1,9, 11–13].It is not uncommon to see apes such as chimpanzees walking on two legs in order to carry things.Octopuses have been also documented walking bipedally in order to camouﬂage themselves from predators[14].Placing six limbs close to their head,the octopus assumes the shape of a drifting plant,and then uses its two remaining limbs to walk away from predators.Another possible explanation for bipedalism is its lower energetic cost compared to other forms of locomotion. In a study by Taylor and Rowntree[15],chimpanzees(Pan troglodytes)and capuchin monkeys(Cebus capucinus) were trained to run on a treadmill on either two or four legs.Results showed that the energy spent by the animals on this exercise was fairly independent of the mode of locomotion they adopted.Fedak and Seeherman[16]also reported negligible differences of the scaling of energy requirements for locomotion between bipedal and quadrupedal behavior. On the other hand,Alexander[7]stated that gait of humans is distinct from the occasional bipedalism of apes because the patterns of force exerted on the ground are different,due to biomechanical differences in anatomy mentioned above.Therefore,the trajectory of the center of mass is completely different for gaits in humans and other animals [7,17].Sockol et al.[18]reported that the energy expended in human walking is approximately75%less than that expend in both quadrupedal and bipedal walking in chimpanzees.The study of Carrier et al.[8]also supported the170 A.F.Miguel/Physics of Life Reviews10(2013)168–190idea that humans are more economical when they walk.Besides,Alexander[7]stated that while the walk spends less energy than the gait pattern of quadrupedal mammals of the same body mass,running actually spends more.2.1.Forms of human gait:walking and runningPeople move across the Earth’s surface(are not be attached to one site),and this capability is called locomotion. Walking and running are the two most common forms of human gait.The increase of speed intuitively triggers the switch from a walk to a run.Walking gait is characterized by two distinct phases[19]:the stance phase,when the leg is on the ground,and the swing phase,when it is off the ground.The stance phase begins with heel-strike,as the foot strikes the ground.Most of the time just one foot is on the ground,with brief periods where both feet come in contact with the walking surface.The body vaults up and over each stiff leg in an arc.This gait pattern can be well approximated by a linear“inverted pendulum”[7,17,19,20].An ideal inverted pendulum system exhibits an optimal conversion of gravitational potential energy to kinetic energy.The energy converted by such an“inverted pendulum”mechanism can reduce the mechanical work required from the muscular system by up to70%[17].Running,in contrast,involves longer aerial phases,in which neither foot is in contact with the ground.In this case,the pendulum mechanism that characterizes gait switches to a spring-mass system,where bent legs bounce up between aerial phases [20].As feet hit the ground in a run,the leg springs compress,as a result of jointﬂexion,and the mass moves downwards.At the middle of the stance phase,the leg is maximally compressed,and the mass reaches its lowest point.The plantigrade foot posture of a runner is also very distinct of that of a walker[21],with its center of mass reaching the lowest point at the middle of the stance phase.In contrast,the center of mass of walkers is at its highest point precisely at the middle of the stance phase.Moreover,the stance limb sweeps through a larger angle during walking(∼30◦)than during running(∼19◦)[17].Finally,running involves a decrease of approximately35%in time of foot–ground contact and an increase of the peak ground reaction force by about50%,when compared to walking[17].Humans prefer changing their gait from walking to running and from running to walking at increasing and decreas-ing speeds.This switch occurs at a Froude number of0.5[22,23].For adults,it corresponds to a walking speed of about2m/s[24].Both walking and running are related to several demands that must be processed simultaneously:the propulsion of the body in the horizontal plane,the maintenance of a stable equilibrium(coordination between posture and move-ment),and a continuous and instantaneous adaptation to environmental requirements[25,26].This demands the use of the central and peripheral nervous system,the regulation of the skeletal segments and the contraction of mus-cles[27].Gait speed is therefore tightly linked to neurological development/degeneration,balance control,changes in limb length,and maturation.Studies performed by several authors[28,29]suggest that the gait speed is a quick, inexpensive,reliable measure of functional capacity.Recent studies also reported a signiﬁcant association between walking speed and life span in seniors[30,31].Others[32],ﬁnally,presented evidence that successive step durations during walking actually present a typical structure over time,one that is characterized by a long-range dependence (i.e.,a scaling relationship).It is suggested that this dependence plays an important role in the adaptability and the ﬂexibility of locomotion,since it disappears in individuals with neurodegenerative pathologies.2.2.Least energy-consuming gaitHumans carry their energy supply with them,and they are limited by the rate of production of metabolic energy in their bodies,that depends of the capacity of the cardiovascular system to absorb and distribute oxygen throughout the body.The slower energy is consumed,the less energy must be carried and greater mobility is achieved.A number of experimental studies have shown that the average metabolic energy consumption per unit distance traveled,E x,may be expressed by[33]E x=0.533M bu+0.3M b u(1)Here M b is the body mass and u is the gait speed.This equation has a minimum at a speed of∼1.33m/s,which is within the walking speed range(i.e.,below the average transition speed of∼2m/s between walking and run-ning[24]).This average speed is recurrently mentioned in the literature as the comfortable walking speed or desired walking speed[5,6,34].A.F.Miguel/Physics of Life Reviews10(2013)168–190171Fig.1.The comfortable walking speed versus decade of age:!female,"male(experimental data obtained from Bohannon[35]).Fig.2.The comfortable walking speed versus the body mass:!female,"male(experimental data obtained from[6]and[35]).Several studies[6,35]report the effect of gender and age on the comfortable walking speed of healthy humans (Fig.1).Speed is also expected to increase with the body mass due to fundamental structural reasons[36,37].The effect of the body mass on the comfortable walking speed is illustrated in Fig.2.From thisﬁgure,one can conclude that the comfortable walking speed scales sublinearly with body mass.Indeed,the power exponents depicted for females and males are0.182and0.156,respectively.3.Pedestrian’s guided locomotionPedestrians are attentive to details of the walking environment,especially those that are very close to them[38]. They feel uncomfortable if they get too close to other pedestrians(territorial effect or private“sphere”),as well as to physical obstacles.The vision(the eye)provides information about the environment,which is then cognitively interpreted and helps shape the way pedestrians evolve in space[39,40].This enables the selection of safer and straighter paths,and the circumvention of other pedestrians and obstacles.This guided behavior constitutes a primary and an essential feature in the perfecting of locomotion.To avoid other pedestrians or obstacles,pedestrians may adjust their comfortable speed to a lower self-selected speed.A number of researchers have studied the inﬂuence of pedestrian density(or interpersonal distances1)on1The concept“interpersonal distance”was introduced by Thompson and Marchant[41].The average interpersonal distance is obtained from the inverse of square root of pedestrians’density.172 A.F.Miguel/Physics of Life Reviews10(2013)168–190Fig.3.Experimental fundamental diagram of pedestrian movement:walking speed vs.pedestrian density(or interpersonal distance).Fig.4.Pedestrian density domains in the fundamental diagram of pedestrian movement.pedestrian speed[41–44].Several experimental studies have shown that pedestrians are able to walk at their com-fortable walking speed at densities up to0.2–0.8persons/m2.Beyond such values,an increase of pedestrian density leads to a pronounced reduction of walking speed.The walking speed–pedestrian density diagram depicted in Fig.3is known as the fundamental diagram of pedestrian movement[45–48].Seyfried et al.[45]suggested that this diagram can be divided into5density-domains.In alternative,Miguel[46]proposed that the array of points in this diagram may be divided into two major density-domains,as indicated in Fig.4:(i)Density-domain I:The interpersonal distance between the pedestrians is large enough(or the density of pedes-trians is small enough)and pedestrians are able to walk at their comfortable walking speed(0 δ δfs,whereδfs is the smaller interpersonal distance between the pedestrians that corresponds to the free walking speed).(ii)Density-domain II:Due to the reduction of the free available space,pedestrians adjust their speed,due to a natural desire of avoiding or reducing contact with other pedestrians.In this domain two sub-domains are identiﬁed which exhibit curves with different slopes:(a)the interpersonal distance between the pedestrians is not enough to walk at their comfortable walking speed,but is large enough to avoid contacts between them by a small reduction of walking speed;and(b)a more pronounced reduction in walking speed is required,since the space around each pedestrian is very small,and contacts with other pedestrians may hardly be avoided.A.F .Miguel /Physics of Life Reviews 10(2013)168–190173These pedestrian interactions can be cast into mathematical equations.Accordingly,pedestrians dynamics can be well approached within the framework of a Langevin-like equation of motion [49,50].The Langevin formulation is used to describe the Brownian particle’s motion as an Ornstein–Uhlenbeck process [51],and its position as the time integral of its velocity.Illustrative examples of this formulation for pedestrians are the social force and centrifugal force models.In the social force model [52,53],pedestrians’movement toward a destination results of the acceleration towards the desired walking speed,and the repulsive/attractive interactions with other pedestrians and obstacles.This model includes the concept of territorial effect (the private sphere)that leads to repulsive forces between pedestrians,as ﬁrst suggested by Gipps and Marksjös [54].In the centrifugal force model [55,56],pedestrian movement results from the driving and repulsive forces acting on each pedestrian,with the repulsive forces being described similarly to centrifugal forces.Both models are able to capture and describe important features of pedestrian movement,such the formation of lanes in counter-ﬂow,clogging at exit doors,oscillations at bottlenecks,among others [56].ngevin-like model for the pedestrian dynamicsA simple Langevin-like model can be derived from the above-present concept of density-domain II [46].At den-sity sub-domain IIa,pedestrians’interpersonal distances are still large enough,hence the deviation from the desired walking speed results from the necessary deceleration to adjust own speed to the speed of neighboring pedestrians.Therefore,M b d 2r dt=M b τ dr dt −dr ∗dt ,δrp δ δfs (2)and after integration of this equation,the walking speed within this domain,u IIa ,can be expressed asu IIa =u 0+1τ(δ−δfs ),δrp δ δfs (3)Here r is the position of the pedestrian,τis a relaxation time,(dr/dt −dr ∗/dt )is the mean relative speed to the pedestrians situated around,u 0is the free walking speed,δrt is the interpersonal distance that corresponds to the start of sub-domain IIb,and δfs is the smaller interpersonal distance between the pedestrians for whom free walking speed is still available.Pedestrians get too close to others at sub-domain IIb.The decrease of pedestrians’interpersonal distances leads to the presence of repulsive forces between them.These forces depend not only on the relative velocity of pedestrians,but also on the distance between them.Within this domain,M b d 2r dt=M b γ(r −r ∗) dr dt −dr ∗dt ,δmin <δ δrp (4)Integration of this equation yields the following walking speed,u IIb ,u IIb =u rp +γln δδrp ,δmin <δ δrp (5)where γis a coefﬁcient,r −r ∗(=δ)is the mean interpersonal distance between the pedestrians,u rp is the walking speed corresponding to the minimum interpersonal distance where “repulsive forces”start to occur,and δmin is the smallest interpersonal distance possible between pedestrians in the domain.The average interpersonal distance and the pedestrians’density are related through the equation [41]δ=1√ρ(6)Substituting Eq.(6)into Eqs.(3)and (5)gives [46]u IIa =u 0−1τ √ρ−√ρfs √ρfs ρ ,ρfs ρ ρrp (7)u IIb =u rp +γ2ln ρrp ρ ,ρrp <ρ<ρmax (8)174 A.F.Miguel/Physics of Life Reviews10(2013)168–190Empirical data available in the literature can beﬁtted with Eqs.(7)and(8),and the corresponding empirical coefﬁ-cients obtained.Pedestrian trafﬁc may be unidirectional or multidirectional by nature.An examination of the results presented in prior studies indicates that both unidirectional and multidirectional streams are consistent with these two sub-domains, but that the interpersonal distance that corresponds to the start of“repulsive”forces is different[57].Therefore, a separate analysis must be performed,which yields the following coefﬁcients[46,57]:–For unidirectional streams:τ=3.77s,u0=1.36m/s(0.3 ρ 1.4persons/m2);andγ=1.17m/s and u rp=0.995m/s(1.5 ρ 4.1persons/m2).–For multidirectional streams:τ=5.56s,u0=1.35m/s(0.14 ρ 0.88persons/m2);γ=1.10m/s and u rp=1.03m/s(0.89 ρ 5.2persons/m2).Although these results clearly support the existence of similar velocity–density domains for unidirectional and mul-tidirectional streams,the density range corresponding to each domain is actually different.Notice that neitherγnor u rp are signiﬁcantly different between both streams,because these are quantities measured in the domain with less space available to pedestrians.On the other hand,the relaxation time is higher for the multidirectional streams.As the interpersonal distances between pedestrians in this domain are still large,the existence of multidirectional stream requires that pedestrians are more attentive,and more time to adjust their motion is needed.3.2.Diffusion coefﬁcient model for the pedestrian dynamicsEinstein’s perspective of the Langevin’s approach of motion(i.e.a Wiener process)describes the penetrants mo-bility through a diffusion coefﬁcient[58,59]and may be approached by a single coefﬁcient.By analogy with kinetic theory,the pedestrian diffusion coefﬁcient is related to mean walking speed and mean free interpersonal distance via the Einstein–Smoluchowski equation.The experimental data available in the literature is bestﬁtted by taking[57] (a)For unidirectional streams:D=1.512δ−0.588,0.47<δ 4.47m(9) (b)For multidirectional streams:D=1.498δ−0.593,0.43<δ 4.47m(10)These results also provide direct evidence supporting the differences between uni-and multidirectionalﬂows of pedestrians.Additionally,these coefﬁcients are valid for the entire range of domain II.In summary,the models based on Langevin’s and Einstein’s pioneering studies in1905and1908[49,58],respec-tively,are able toﬁt well experimental data that relates walking speed to pedestrian density.The analysis of pedestrian dynamics as an Ornstein–Uhlenbeck type process,however,produces more insight into the“forces”that drive pedes-trian motion,and delivers different approaches according to pedestrian density sub-ranges(Eqs.(7)and(8)).On the other hand,a Wiener-type process,which is based on a single coefﬁcient(Eqs.(9)and(10)),provides a more compact and simples approach of pedestrian motion.Despite their different mathematical formulation,all of these approaches are physically equivalent.Gillespie[60]presents a review of the arguments that lead to the conclusion that any diffusion coefﬁcient may be linked with quantities such asτandγ.4.Constructal theory of pedestrian dynamics4.1.A new thermodynamics insight into dissipativeﬂow systemsSince Anaximenes of Miletus(585–528B.C.),laws are considered operative throughout Nature[61].This consti-tutes a magniﬁcent triumph of reason and observation:laws tell us how things operate and can guide us in the quest for news knowledge.The invariance provides a structure and coherence to the laws just as the laws provide a structure and coherence to the set of natural events.A.F .Miguel /Physics of Life Reviews 10(2013)168–190175Thermodynamics is one of the bedrocks of modern science,and is ﬁrmly grounded into laws.Different laws provide us a view of natural phenomena.The zeroth law deﬁnes a useful property “temperature”(and proposes the equality of temperature as necessary and sufﬁcient condition for thermal equilibrium).The ﬁrst law deﬁnes useful extensive property “energy”(and asserts that energy is conserved).Since it is possible to take the same amount of internal energy “forward”and “backward”,the ﬁrst law expresses symmetry.Although all processes must take place in accordance to the ﬁrst law,the principle of conservation of energy is,by itself,insufﬁcient to describe preferred directions of action in time.Both the reverse ﬂow (hot to cold and cold to hot)and the immutability of conﬁguration are not in violation of the ﬁrst law [61].The second law of thermodynamics asserts the existence of extensive property entropy and states that this property in an adiabatically isolated system never decreases in time.The entropy is a Lyapunov function of the dynamical system and the “backward”process is not allowed [61].There is a “time asymmetry“or a “direction of time”or an “arrow of time”of the state of the system.The third law deﬁnes a state known as “absolute zero”(and relates the entropy of a system to its absolute temperature).Most real systems are however not isolated and may exhibit distinct characteristics.If two mixable liquids are let to mix in a vase,diffusion takes place spontaneously and a progressive decrease of initial individual concentrations will occur with a corresponding increase of entropy.But living organisms are able to maintain the differences of liq-uid concentrations in time (by chemical reactions and active transport).Prigogine named these systems ‘dissipative structures’because they cannot exist independently of their environment [62,63].These “structures”make an effort to avoid a transition into thermodynamic equilibrium by a continuous exchange of materials and energy with the en-vironment.Therefore,they are also able to self-organize through instabilities that lead to irreversible bifurcations and new stable system states [62,63].Another of Prigogine’s contributions was the minimum entropy production principle (or Prigogine theorem),which applies to open linear nonequilibrium systems in the stationary (or approaching the stationary)state.At every instant,currents of ﬂuid,heat,mass,or information are ﬂowing through animate and inanimate,dissipative open systems.This involves a state of organizational structure intimately coupled with nodes and channels of supply and distribution.The ubiquitous generation of conﬁguration (design,organization)in these nonequilibrium systems is covered by the constructal law of Adrian Bejan,which states that “For a ﬁnite-size ﬂow system to persist in time (to live )it must evolve such that it provides greater and greater access to the currents that ﬂow through it ”[64–70].This new law asserts that for any ﬂow system there is a property “conﬁguration”and relates the generation of conﬁguration to its greater access to ﬂow.2This is possible because systems have the freedom to morph (i.e.,freedom to change the conﬁguration in time)to achieve their purpose of higher global performance under constraints.Flows occur against resistances (imperfections)that constantly cause energy dissipation and try to slow them down.Therefore,the emergence of conﬁguration (organization)with a purpose,deﬁned by the constructal law,also requires that entropy changes.For the sake of simplicity,let us consider a linear pressure–ﬂow relation (or potential–current relation).In this case,the resistance,R ,is related with the time rate of entropy generation,d ˙S g ,by R =1T V 2d ˙Sg and R =T d ˙S g 2,where V is the potential (or pressure difference),I is the current (or ﬂow),and T is the absolute temperature.Minimization of resistance in morphing conﬁgurations under constant I and constant V (constraints)corresponds not only to a minimization of the entropy generation rate but to a maximization of the entropy generation,respectively.In summary,conﬁguration emerges in systems that have a purpose and are far from equilibrium,and the emergence of this organization requires that entropy changes.The constructal law is not only connected to the entropy generation rate,but it also provides the reasons for why and how design occurs in nonequilibrium systems.4.2.Constructal view of human gaitEngines (man-made,animal,geophysical)use energy to produce the work required for driving movement.In order to induce movement,they should be able to overcome internal and external resistances (i.e.,energy input is matched by energy loss).Such thermodynamic “imperfections”cannot be avoided,and the constructal improvement of functions implies the generation of a design that distributes imperfections optimally to ﬁll the ﬂow space.Therefore,the constructal law is about both the necessity and the evolution of design to occur.2“Maximum ﬂow access”corresponds to minimum travel time or minimum transfer time [67].Therefore,“for a ﬁnite-size ﬂow system to persist in time it must evolve such that it provides a minimum travel time to currents that ﬂow through it”.。

描写机器人的英语作文

Robots have become an integral part of modern technology,transforming various industries and aspects of our daily lives.Heres a detailed composition on robots, exploring their evolution,applications,and potential future developments.Introduction to RobotsRobots are machines designed to execute tasks automatically,often with the ability to interact with their environment.The concept of a robot dates back to ancient times,but it was only in the20th century that they became a reality in the form we recognize today. The term robot was first coined by Czech writer KarelČapek in his1920play R.U.R. Rossums Universal Robots,which depicted artificial beings capable of performing human tasks.Evolution of RoboticsThe evolution of robots can be traced through several key milestones.Early robots were primarily industrial,designed for repetitive tasks such as assembly line work.The first programmable robot,the Unimate,was introduced in1961and revolutionized manufacturing by automating the process of die casting and spot welding.Over time,robots have become more sophisticated,with advancements in artificial intelligence AI and machine learning allowing them to perform more complex tasks. Today,robots are capable of learning from their experiences,making decisions,and even interacting with humans in a more natural way.Applications of RobotsRobots are now used in a wide range of applications across various sectors:1.Industrial Automation:Robots continue to play a crucial role in manufacturing,where they perform tasks such as precision assembly,material handling,and quality control.2.Healthcare:In the medical field,robots assist in surgeries,deliver medication,and even help in patient rehabilitation.3.Domestic Assistance:Home robots perform tasks like cleaning,lawn mowing,and even providing companionship to the elderly.4.Space Exploration:Robots explore environments that are inhospitable to humans,such as deep space or the ocean floor.5.Disaster Response:In emergency situations,robots can enter dangerous areas to assess damage,locate survivors,and assist in rescue operations.itary:Autonomous drones and ground vehicles are used for surveillance, reconnaissance,and combat support.Technological AdvancementsThe integration of AI has been a significant factor in the advancement of robotics.Robots now have enhanced sensory capabilities,allowing them to perceive their surroundings and interact with them more effectively.They can process information,make decisions based on complex algorithms,and even exhibit a level of autonomy.Ethical ConsiderationsAs robots become more advanced,ethical considerations come to the forefront.Issues such as privacy,job displacement,and the potential for misuse of technology are important to address.Ensuring that robots are designed and used responsibly is a challenge that society must face.Future of RoboticsThe future of robotics is promising,with ongoing research and development aimed at creating more intelligent,adaptable,and interactive machines.We can expect to see robots that are capable of performing tasks with greater autonomy,learning from their environment,and even exhibiting emotional intelligence.In conclusion,robots are not just a product of science fiction but a reality that is continuously evolving and expanding.As technology progresses,the role of robots in society will only grow,offering new possibilities and challenges that we must navigate with care and foresight.。

用英语作文写自己会做的事和不会做的事

用英语作文写自己会做的事和不会做的事全文共3篇示例，供读者参考篇1Things I Can and Cannot DoAs a student, there are many things that I am capable of doing, and many things that are still out of my reach. In this essay, I will explore the skills and talents that I possess, as well as the areas where I struggle or have yet to develop proficiency.Let's start with the things that I can do. One of my strongest suits is academic work, particularly in the realm of writing. From a young age, I have had a love for words and a natural aptitude for stringing them together in a coherent and engaging manner. Whether it's crafting a persuasive essay, a creative short story, or a research paper, I find joy in the process of articulating my thoughts and ideas on paper (or, more realistically, on a computer screen).Furthermore, I am quite adept at analyzing complex texts and breaking them down into their constituent parts. I have a keen eye for detecting underlying themes, symbolism, and literary devices, which has served me well in my English andliterature classes. Not only does this ability aid me in comprehending the material, but it also allows me to formulate well-reasoned and insightful critiques and interpretations.Another area where I excel is problem-solving, particularly in the realm of mathematics and logic puzzles. I have a natural inclination towards analytical thinking, and I derive great satisfaction from unraveling intricate problems and finding elegant solutions. Whether it's tackling a challenging calculus equation or working through a mind-bending riddle, I relish the opportunity to exercise my cognitive muscles.Moving on to the extracurricular realm, I am an avid reader and have a deep appreciation for literature of all genres. From classic novels to contemporary works, I find myself constantly drawn to the rich tapestry of stories and characters that books have to offer. Reading not only fuels my imagination but also broadens my horizons and exposes me to diverse perspectives and experiences.Lastly, I have a passion for volunteering and giving back to my community. Whether it's tutoring younger students, participating in beach clean-ups, or serving meals at a local shelter, I find great fulfillment in using my time and energy to make a positive impact on the world around me.Now, let's turn our attention to the things that I cannot do, or at least the areas where I struggle or have room for improvement.One of my greatest weaknesses is public speaking. Despite my proficiency in written communication, the thought of standing in front of a crowd and delivering a speech fills me with trepidation. I tend to become flustered and lose my train of thought, which can make presentations or class discussions quite challenging for me. I am working on building my confidence and honing my oral communication skills, but it remains an area where I have significant room for growth.Another aspect that I find challenging is time management. With a seemingly endless array of assignments, extracurricular activities, and social commitments vying for my attention, it can be difficult to strike an appropriate balance and allocate my time effectively. I often find myself procrastinating or becoming overwhelmed by the sheer volume of tasks on my plate, which can lead to unnecessary stress and last-minute cramming sessions.Closely related to time management is my struggle with organization. My desk is often a chaotic jumble of papers, books, and various knick-knacks, and my digital files are no better. Ihave a tendency to misplace important documents or forget upcoming deadlines, which can be frustrating and detrimental to my productivity.In the realm of physical activities, I must admit that I am not particularly skilled or coordinated. While I enjoy the occasional game of pickup basketball or a leisurely hike, I have never excelled at organized sports or intense physical pursuits. My lack of hand-eye coordination and athletic prowess has been a source of frustration at times, but I have learned to embrace my strengths and focus my energies elsewhere.Finally, I must confess that I have a propensity for procrastination and a tendency to become easily distracted. Whether it's mindlessly scrolling through social media or indulging in yet another episode of my favorite television series, I often find myself engaging in activities that sap my productivity and derail my best-laid plans.Despite these shortcomings, I am constantly striving to improve and expand my skill set. I firmly believe that with dedication, perseverance, and a willingness to step outside of my comfort zone, I can overcome my weaknesses and develop new capabilities.In conclusion, this essay has provided a candid exploration of the things that I can and cannot do as a student. While I possess strengths in areas such as writing, analysis,problem-solving, and community involvement, I also grapple with challenges like public speaking, time management, organization, athleticism, and procrastination. However, I am committed to continuous self-improvement and personal growth, recognizing that each obstacle presents an opportunity to learn, adapt, and become a more well-rounded individual.篇2Things I Can and Cannot DoAs a student, there are many things in life that I am capable of doing and many more that I struggle with or cannot do at all. Some of my abilities come naturally, while others have been honed through years of practice and hard work. At the same time, I have numerous shortcomings and limitations that I constantly strive to overcome or find ways to work around. In this essay, I will explore the various things I can and cannot do, shedding light on my strengths, weaknesses, and the journey ofself-discovery that comes with being a student.One of the things I excel at is academic writing. From a young age, I have had a natural affinity for the written word, and I find great joy in crafting well-structured essays, research papers, and creative pieces. I can easily organize my thoughts, construct compelling arguments, and express myself clearly and eloquently on paper. This skill has served me well throughout my academic career, enabling me to produce high-quality work that has consistently earned me top grades.However, while I may be a talented writer, I cannot claim to be an exceptional public speaker. The thought of standing in front of a large audience fills me with dread, and my nervousness often gets the better of me. I struggle to articulate my thoughts coherently, my voice trembles, and I have a tendency to ramble or go off on tangents. Despite my best efforts to overcome this fear, it remains one of my greatest weaknesses, and I often find myself avoiding situations that require public speaking whenever possible.In contrast, I am quite adept at problem-solving and critical thinking. I have a natural curiosity that drives me to question everything around me, and I take great pleasure in dissecting complex issues, analyzing them from multiple angles, and arriving at well-reasoned solutions. This skill has proveninvaluable in my studies, particularly in subjects like mathematics, science, and philosophy, where I can apply my analytical mind to tackle intricate problems and unravel intricate concepts.Unfortunately, my problem-solving abilities do not extend to the realm of spatial awareness and hand-eye coordination. I am notoriously clumsy, often bumping into objects and struggling with tasks that require dexterity and precision. Sports and physical activities have never been my forte, and I have a tendency to shy away from them, preferring to spend my time engaged in more cerebral pursuits.One area where I truly shine is time management and organization. I am a master of creating schedules, setting deadlines, and prioritizing tasks. I thrive on structure and routine, and I find great satisfaction in crossing items off my to-do list. This skill has been instrumental in helping me balance the demands of my academic life with my extracurricular activities and personal commitments, ensuring that I never fall behind or miss important deadlines.However, despite my organizational prowess, I cannot claim to be a natural leader. While I am perfectly content working in a team environment, I often find myself deferring to others when it comes to taking charge or making executive decisions. I tend tobe more of a follower, preferring to support and collaborate rather than take the reins. This has sometimes held me back in group projects or team-based activities, where a strong leadership presence is required.In the realm of technology, I am a true digital native. I have grown up surrounded by computers, smartphones, and the internet, and I possess a deep understanding of how to navigate and utilize these tools effectively. From coding and web development to video editing and graphic design, I amwell-versed in a wide range of digital skills. This expertise has proven invaluable in both my academic and personal life, allowing me to stay connected, collaborate with others, and express my creativity in new and innovative ways.Yet, for all my technological prowess, I cannot claim to be musically inclined. While I deeply appreciate and enjoy music, I have never been able to master an instrument or develop a strong sense of rhythm or pitch. My attempts at singing or playing an instrument have been met with mixed results at best, and I often find myself in awe of those who possess natural musical talent.One of my greatest strengths lies in my ability to empathize and connect with others. I am a skilled listener, capable of trulyunderstanding and relating to the experiences and perspectives of those around me. This has helped me build strong relationships and foster a sense of community wherever I go. I am often sought out by my peers for advice or a sympathetic ear, and I take great pride in being able to provide emotional support and guidance when needed.Conversely, I cannot claim to be particularly skilled in the realm of sales or persuasion. While I am confident in my beliefs and opinions, I often struggle to effectively convey them in a way that sways or convinces others. I tend to be more reserved and hesitant to assert myself, which can sometimes be interpreted as a lack of conviction or passion. This has proven to be a challenge in situations where I need to pitch ideas, negotiate, or sell myself and my abilities.Despite my many strengths and weaknesses, one thing I can say with certainty is that I am a lifelong learner. I have an insatiable curiosity and a thirst for knowledge that drives me to constantly seek out new experiences, skills, and insights. I am not afraid to step out of my comfort zone or try something new, even if it means facing challenges or failures along the way.Of course, there are also countless things in this world that I cannot do, or at least not yet. I cannot speak multiple languagesfluently, I cannot perform complex mathematical calculations in my head, and I certainly cannot claim to have all the answers to life's most profound questions. But what I lack in specific abilities, I make up for in determination, resilience, and a willingness to grow and evolve.As I continue on my journey through academia and into the wider world, I am certain that the list of things I can and cannot do will change and evolve. Some weaknesses may become strengths, while new challenges and limitations will inevitably arise. But it is this constant process of self-discovery andself-improvement that makes the experience of being a student so rewarding and fulfilling.In conclusion, my abilities and inabilities are a tapestry woven from my unique experiences, talents, and shortcomings. While there are many things I excel at, such as writing, problem-solving, time management, and technological proficiency, there are also areas where I struggle, like public speaking, physical coordination, leadership, and persuasion. Yet, it is this very diversity of strengths and weaknesses that shapes who I am and drives me to continuously grow, learn, and strive for self-betterment. As a student, I embrace the journey, celebrating my victories and learning from my failures, secure inthe knowledge that each experience is an opportunity to expand the boundaries of what I can and cannot do.篇3Things I Can and Cannot DoAs a student, there are many things I'm capable of doing, as well as plenty of things that are still beyond my abilities. In this essay, I'll outline some of the key tasks and activities I'm skilled at, as well as areas where I struggle or have room for improvement.One of my biggest strengths is writing. From an early age, I discovered a love for putting pen to paper (or fingers to keyboard) and expressing my thoughts and ideas through the written word. Whether it's creative fiction, analytical essays, or persuasive arguments, I feel confident in my writing abilities. I have a strong grasp of grammar, spelling, and structuring a coherent narrative or argument. My vocabulary is extensive, allowing me to convey complex ideas with precision.I'm also skilled at research and analysis. When faced with an essay question or assignment, I know how to gather reliable sources, sift through information, identify key points and evidence, and form a well-reasoned perspective. I enjoyunpacking complex topics, considering multiple viewpoints, and arriving at my own conclusions backed by facts and logic.Academically, I tend to perform well across most subjects. My strongest areas are English literature, history, and social sciences, where my writing and analytical capabilities really shine.I have an aptitude for understanding abstract concepts, making connections between ideas, and communicating my knowledge effectively.In terms of extracurricular activities, I'm a talented artist. Drawing, painting, and digital art are hobbies I've cultivated for years. I have a good eye for color, composition, and detail, allowing me to create visually striking and expressive pieces. Art is an outlet for me to tap into my creativity and emotions in a way that transcends words.Despite my strengths, there are certainly areas where I struggle or have room for growth. Mathematics, particularly advanced calculus and statistics, has always been a challenge for me. I can grasp basic concepts and calculations, but when the problems become increasingly complex and abstract, I often find myself getting lost or making careless mistakes. Numbers and equations don't come as naturally to me as words and ideas.Similarly, I have difficulties with hard sciences like physics and chemistry. The theoretical aspects aren't too problematic, but I struggle with the practical applications and experiments that require precise measurements, calculations, and an understanding of scientific processes. My mind doesn't seem wired for the meticulous attention to detail and logical thinking required in these fields.Public speaking is another area where I face challenges. While I'm comfortable expressing myself through writing, the prospect of standing in front of an audience and delivering a speech or presentation fills me with anxiety. I tend to get flustered, lose my train of thought, and struggle to articulate my ideas clearly when put on the spot. Impromptu speaking, in particular, is a weakness of mine.Athleticism and physical activities are also not my strong suit. I'm not inherently uncoordinated or lacking in stamina, but I've never been particularly drawn to sports or exercise. Running, jumping, throwing, and catching don't come naturally to me, and I often feel self-conscious about my lack of athletic abilities compared to my more physically gifted peers.When it comes to technological skills, I'm relatively proficient with basic software and applications. I can navigateword processors, presentation tools, and spreadsheets without too much trouble. However, more advanced programming, coding, and web development are areas where I struggle. The logical thinking and problem-solving required to write effective code and understand complex algorithms is a challenge for me.Teamwork and group projects can also be difficult for me at times. While I'm generally a good listener and can contribute ideas, I sometimes have trouble compromising or deferring to others' perspectives. I tend to be quite headstrong and can get frustrated when my ideas or approaches aren't adopted. Collaborative efforts require patience, communication, and flexibility – traits I'm still working on developing.Despite my weaknesses, I'm continuously striving to improve and expand my skillset. I'm not afraid to put in the hard work and practice required to turn areas of weakness into strengths. Whether it's seeking extra tutoring, joining study groups, or dedicating more time and effort to the things I struggle with, I'm committed to personal growth and development.In conclusion, as a student, I have a diverse range of abilities and talents, as well as areas where I face challenges and limitations. Writing, analysis, art, and certain academic subjects are my strong suits, while mathematics, sciences, public speaking,athletics, and technology pose greater difficulties for me. Group work and collaboration can also be trying at times. However, I'm aware of my weaknesses and actively work to improve upon them, embracing a growth mindset and a willingness to learn and evolve. This self-awareness and dedication toself-improvement will serve me well as I continue my educational journey and strive to reach my full potential.。

高一英语科学术语高级理解单选题40题

高一英语科学术语高级理解单选题40题1.The phenomenon of light bending when it passes through a prism is called _____.A.reflectionB.refractionC.diffractionD.interference答案：B。

“reflection”是反射；“refraction”是折射，光通过棱镜时发生弯曲是折射现象；“diffraction”是衍射；“interference”是干涉。

2.When two waves meet and combine to form a new wave, this is known as _____.A.reflectionB.refractionC.diffractionD.interference答案：D。

“reflection”是反射；“refraction”是折射；“diffraction”是衍射；“interference”是干涉，两波相遇并结合形成新波是干涉现象。

3.The force that pulls objects towards the center of the Earth is called _____.A.magnetic forceB.electrical forceC.gravitational forceD.nuclear force答案：C。

“magnetic force”是磁力；“electrical force”是电力；“gravitational force”是重力，把物体拉向地球中心的力是重力；“nuclear force”是核力。

4.The unit of measurement for force is _____.A.newtonB.jouleC.wattD.ampere答案：A。

“newton”是牛顿，力的单位是牛顿；“joule”是焦耳，能量单位；“watt”是瓦特，功率单位；“ampere”是安培，电流单位。

Avigilon Control Center 7软件 - 异常运动和活动检测说明书

AVIGILON CONTROL CENTER ™7 SOFTWAREUNUSUAL MOTION & ACTIVITY DETECTIONAdvanced AI technology that highlights the unanticipated byautomatically flagging unusual motion and activity. This edge-based intelligence technology distinguishes between typical and atypical events by continuously learning from observation of scenes over time. Unusual Motion Detection (UMD) detects atypical movement, while Unusual Activity Detection (UAD) is object-aware and detects the anomalous speed and location of people and vehicles.UMD is available on H5SL, H5M, H4SL, H4A and H4 Mini Dome cameras. UAD is available on our H5A camera line.FACIAL RECOGNITIONAI-powered facial recognition technology that helps organizations accelerate response times by identifying people of interest. People of interest are identified based on one or more secure watch lists managed by authorized users at the organization. Populate watch lists easily by uploading images or finding faces from recorded video. Afterwards, an Appearance Search can quickly be started for any person on a watch list.Avigilon cameras licensed for facial recognition will search theconfigured face watch lists for potential matches. If a match is found, operators can be notified either using the FoA interface or through ACC alarms using armed panels or the alarm view. ACC will display the video image that triggered the alarm along with the reference image from the watch list, enabling operators to verify the match and act quickly.Avigilon Control Center (ACC) 7, our latest and most advanced version of ACC ™video management software, is designed to revolutionize how operators interact with and gain situational awareness from their video security systems.FOCUS OF ATTENTION (FOA) INTERFACEA cutting-edge user interface for live video monitoring that leverages AI and video analytics technologies to determine what information is important and should be presented to security operators.AVIGILON APPEARANCE SEARCH ™ TECHNOLOGYSophisticated AI-powered video search engine that sorts through hours of video with ease to help quickly locate a specific person or vehicle of interest across an entire site or multiple sites running the same version of ACC software. Search for a person or vehicle of interest by entering a physical description, uploading a photo, or finding an example in recorded video.CLOUD-CONNECTED ACCAvigilon Cloud Services (ACS) connects existing ACC sites to the cloud for easy and secure remote access to video from a standard web browser. Operators can leverage centralized System Health Monitoring to assess the operational state of cameras and servers from a central location. Benefit from future enhancements of ACS by updating to the latest versions of ACC software.CYBERSECURITY & PRIVACY PROTECTIONACC security measures include strong password enforcement, connection authentication and data encryption, as well as strict user permissions to access search functionality that uses personally-identifiable information.Blurred Export helps support compliance with new data protection and privacy requirements of GDPR by allowing you to export Appearance Search results in ACC software while blurring the background of the camera view to feature only the person of interest in the video.FEDERAL GOVERNMENT COMPLIANCE WITH FIPS 140-2 CERTIFIED ENCRYPTIONFor U.S. government agencies and enterprises that require FIPS-compliant cryptography, ACC software offers an option to use Microsoft Windows’ FIPS 140-2 certified cryptographic libraries to comply with IT policies.On the camera side, ACC offers the option to turn on licensed FIPScryptography on Avigilon cameras. To establish a chain of trust between systems, ACC can be configured to require valid signed certificates from cameras before establishing a trusted connection with them and generate a report on all cameras without valid certificates.LICENSE PLATE RECOGNITION ANALYTICSAutomatically reads license plate information from vehicles, linking it to both live and recorded video. Create and import multiple vehicle license plate watch lists for instant alarm notification when a license plate match is detected, or search and quickly find specific captured license plate video for verification and investigation.COVID-19 RESPONSE TECHNOLOGYOperate safely and comply with local health and safety guidelines with the help of powerful video analytics – natively available to operators on ACC 7 software with no additional licenses required:Occupancy Counting: Automate the manual counting of people entering and exiting a facility or area. Use real-time cloud-based dashboards on mobile tablets to instruct customers on when to enter or queue.Social Distancing: Run cloud-based reports in ACS to proactively identify where and when social distancing guidelines are not being followed for corrective action.No Face Mask Detection: Automate the detection of people not wearing face masks, complete with alarms to flag violations in real-time. Run cloud-based reports in ACS to identify where corrective action is required.Avigilon H4 Thermal Elevated Temperature Detection (ETD):ACC is built to work seamlessly with the new Avigilon H4 Thermal ETD solution, which offers a low friction, contactless alternative to traditional screening methods.ACCESS CONTROL UNIFICATIONACC software works together with the Access Control Manager (ACM) system to receive and act on ACM ™door events, hardware input events and access grants, empowering operators to unlock access doors directly from a camera view. Identity Verification dynamically displays ACM credentials with ACC camera views. Identity Search can help find a person of interest using their ACM cardholder information.© 2020, Avigilon Corporation. All rights reserved. AVIGILON, the AVIGILON logo, AVIGILON CONTROL CENTER, ACC, AVIGILON APPEARANCE SEARCH, ACCESS CONTROL MANAGER, and ACM are trademarks of Avigilon Corporation. MOTOROLA, MOTO, MOTOROLA SOLUTIONS, and the Stylized M Logo are trademarks or registered trademarks of Motorola Trademark Holdings, LLC and are used under license. All other trademarks are the property of their respective owners. 11-2020For more information visit /acc*Images of product features and/or interfaces have been simulated for illustrative purposes.。

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a r X i v :a s t r o -p h /0510824v 1 29 O c t 2005SF2A 2005
F.Casoli,T.Contini,J.M.Hameury,and L.Pagani (eds)
DETECTING CHAOTIC AND ORDERED MOTION IN BARRED GALAXIES MANOS,T.1and ATHANASSOULA,E.2Abstract.A very important issue in the area of galactic dynamics is the detection of chaotic and ordered motion inside galaxies.In order to achieve this target,we use the Smaller ALignment Index (SALI)method,which is a very suitable tool for this kind of problems.Here,we apply this index to 3D barred galaxy potentials and we present some results on the chaotic behavior of the model when its main parameters vary.1Introduction The Smaller ALignment Index (SALI)(Skokos 2001;Skokos et al.2004)or,as elsewhere called,Alignment Index (AI)(Voglis et al.2002),can distinguish be-tween chaotic and ordered motion in dynamical systems.In order to compute the SALI for a given orbit,one has to follow the time evolution of the orbit itself and of two deviation vectors v 1and v 2,which initially point in two diﬀerent directions.At every time step the two deviation vectors are normalized and the SALI is then computed as:SALI (t )=min { v 1(t ) v 2(t ) , v 1(t ) v 2(t ) }.(1.1)
The SALI for a chaotic trajectory tends to zero,while for a regular one it ﬂuctuates around a positive number.
2Discussion of the applications and the results in 3dof Ferrers
We apply the method to a 3D Ferrers potential which consists of the superposition of a Miyamoto sphere,a Plummer disc and a Ferrers bar.In ﬁgure 1we present
238SF2A2005
Fig.1.Percentages of regular(ﬁrst and second bar)and chaotic(third and forth bar) orbits,for our standard model(left column of panels),a model with a thick bar(central column)and a model with a massive bar(right column).The two rows show two diﬀerent ways of choosing the orbital population.
percentages of chaotic,intermediate and regular trajectories,where we vary the mass of the bar component(panels A3-B3)and the length of the short z-axis (panels A2-B2)of the initial models A1and B1.The two rows diﬀer in the way we give the27000initial conditions.For the A1,we give initial conditions in the plane(x,p y,z)with(y,p x,p z)=(0,0,0)and for the B1,in the plane(x,p y,p z) with(y,z,p z)=(0,0,0).By comparing the results,we see that the increase of the bar mass causes more chaotic behavior in both cases(panels A3,B3).This conﬁrms the results by Athanassoula et al.(1983)in2dof.On the other hand, it is obvious that when the bar is thicker,i.e.the length of the z-axis larger,the system gets more regular.We also,investigated how the pattern speed of the bar aﬀects the system and found that the percentage of the regular orbits is greater in slow bars.
Acknowledgements.Thanos Manos was partially supported by Karatheodory graduate student fellowship No B395of the University of Patras and by Marie-Curie fellowship No HPMT-CT-2001-00338.
References
Athanassoula,E.,et al.,1983,Astr.Astroph.127,349
Skokos,Ch.,2001,J.Phys.A:Math.Gen.,34,10029
Skokos,Ch.,et al,2004,J.Phys.A,37,6269
Voglis,N.,et al.,2002,Mon.Not.R.Astr.Soc.337,619。