抢渡长江模型

本模型对抢渡长江问题的研究 ,根据江面水流速度的各种情况 ,给出了若干个抢渡长江的模型 ,根据问题中所提供的具体数据 ,利用Mathematica对数值问题解的精确性、正确性、有效性 ,得出在各种情况下渡过长江所需的最小时间Tmin。首先给了长江流速呈离散分布 ,且游泳者的速度大小不变 (方向可变 )的情况下从起点游到终点所需时间的模型 ,模型如下 :MinT(d) =2×t1+t2s.t.v2 x1+v2 y1=v2v2 x2 +v2 y2 =v2(vx1+1.4 7)×t1=d(vx2 +2 .11)×t2 =10 0 0 - 2×dvy1×t1=2 0 0vy2 ×t2 =76 0t1>0 ,t2 >0 ,vx1<0 ,vx2 <0 ,vy1>0 ,vy2 >00 0 ,t2 >0 ,vx1<0 ,vx2 <0 ,vy1>0 ,vy2 >00 相似文献   

GLONASS卫星星座最新状态

系统编号卫星编号轨道面 /卫星星位 发射日期开始运行日期状态停止使用日期7782 32 4 2 / 15 1995 .12 .14 1999.4 .2 6停用 2 0 0 1.1.2 97792 3641/ 11998.12 .30 1999.2 .18使用784 2 3631/ 81998.12 .30 1999.1.2 9使用7862 362 1/ 71998.12 .30 1999.1.2 9使用7832 374 3/ 182 0 0 0 .10 .132 0 0 1.1.5使用7872 375 3/ 172 0 0 0 .10 .132 0 0 0 .11.4使用7882 3763/ 2 4 2 0 0 0 .10 .132 0 0 0 .11.2 1使用7892 3811/ 0 32 0 0 1.12 .1未用790 2 380 1/ 0 62 0 0 1.12 .1未用7112 382 1/ 0 5 2 0 0 1.12 .1未用　　　　　　注 :所示…     

GLONASS卫星星座最新状态

至 2 0 0 1年 8月 1 7日为止的 GLNASS卫星星座状态列于下表。系统编号 卫星编号 轨道面/卫星星位 发射日期开始运行日期状态停止使用日期781宇宙 2 3172 / 10 1995 .7.2 4 1995 .8.2 2停用 2 0 0 1.4 .2 4778宇宙 2 32 4 2 / 15 1995 .12 .141999.4 .2 6停用 2 0 0 1.1.2 9782宇宙 2 32 5 2 / 13 1995 .12 .141996.1.18停用 2 0 0 1.7.2 3779宇宙 2 3641/ 11998.12 .30 1999.2 .18使用784宇宙 2 363 1/ 81998.12 .30 1999.1.2 9使用786宇宙 2 362 1/ 71998.12 .30 1999.1.2 9使用783宇宙 2 374 3/ 182 0 0 0 .10 .13 2 0 0 1.1.5使用787…     

以色列计划研制新型卫星

继 2 0 0 0年 1 2月 5日发射分辨率为 1 .8ｍ的ＥｒｏｓＡ1商业高分辨率遥感卫星之后 ,以色列的ＩｍａｇｅＳａｔ国际公司可能取消原定 2 0 0 1年晚些时候的Ａ2卫星发射计划 ,转而研制将耗资 1亿美元的更高分辨率的新型ＥｒｏｓＢ系列卫星。由于采用以色列电子光学公司新的光学技术 ,ＥｒｏｓＢ系列性能更优 (分辨率为 0 .8ｍ) ,寿命更长 (设计寿命 1 0年 ,Ａ1系列为 6年 )。ＥｒｏｓＢ可能于 2 0 0 3年早些时候发射。以色列计划研制新型卫星@张晓岚     

2000年欧洲遥测会议(ETC2000)举行

20 0 0年欧洲遥测会议 ( ETC2 0 0 0 )于 2 0 0 0年 5月 2 2日至 2 5日 ,在德国南部小城加米施-帕滕基兴 ( Garmisch- Partenkirchen )举行。会议的主要内容有两部分 :学术交流和产品展示。学术交流设置了七个专业小组和一个论坛。七个专业小组分别是 :1 .数据记录和储存 ;2 .数据获取和处理 ;3.数据传输 ;4.生物遥测 ;5 .计算机与接口技术 ;6 .航天遥测 ;7.卫星与导航。一个论坛是 :FQPSK论坛。我国有两篇文章参加了数据传输小组和计算机与接口技术小组的交流。产品展示与学术交流同时进行 ,约 70家厂商参加了展示。厂商主要来自美国、…     

校企合作,构建应用性人才培养模式

为把学生培养成为适应 2 1世纪社会生产、服务、建设、管理第一线需要的、基础理论够用、实践动手能力强的应用性人才 ,构建校企合作的应用性人才培养模式是深化教学改革的关键。从 2 0 0 0年开始 ,我校根据教育部《关于加强高职高专教学人才培养工作的意见》的文件精神 ,在部分专业探索实施“2 .5 + 0 .5”人才培养模式取得经验的基础上 ,及时修订了 99级各专业教学计划 ,重新安排第三、四、五学期课程 ,将安排在第六学期的课程全部取消 ,第六学期全部安排顶岗实训和综合实践训练。1　突出高职高专教育特色 ,构建“2 .5+ 0 .5”人才培养模…     

OH-58D轻型武装观察直升机将装备瞄准装置

美陆军 2 0 0 3年 1 2月宣布 ,DRS公司技术部(位于新泽西州Parsippany)已得到两份总价值为5 .2 1亿美元的合同 ,以对约有 370架OH 5 8D直升机的整个飞行机队提供红外瞄准系统。为期 5年、价值 5 .1 4亿美元的主合同将于2 0 0 4年 1月开始执行 ,其内容包括为OH 5 8D直升机桨毂上方的桅式瞄准器 (MMS)提供光电部件、备件、支援和站上维修服务。在主合同生效之前的三个月内 ,另有一份价值为 7百万美元的过渡合同。美陆军航空与导弹司令部的发言人BobHunt说 ,这些合同基本上是以前合同的延续 ,不包含任何技术升级。据DRS公司透露 ,MMS…     

双通道反射式强度调制型光纤位移测量系统

对双通道反射式强度调制型光纤位移传感器测量系统进行优化设计。测量结果表明 ,所构成的系统重复性误差小于 0 .5 % ,测量范围为 2 .0 mm。该测量系统使用单片机处理测得数据 ,用查表插值的方法得到输出位移量     

俄罗斯发射GLONASS系统补网卫星

格林威治时间 2 0 0 1年 1 2月 1日 1 8时 0 4分 ,俄罗斯使用质子号 K/DM- 2运载火箭从哈萨克斯坦境内的拜科努尔发射场成功发射了 3颗 GL ONASS系统补网卫星 ,卫星编号分别为宇宙号 2 380、2 381和 2 382 ,其中包括 2颗旧型 GLONASS卫星和 1颗改进型 GLONASS- M卫星 ,前者重 1 4 1 5千克 ,后者重 1 50 0千克。质子号 K/DM- 2火箭将这 3颗卫星送入了远地点距离为 1 91 0 0公里 ,倾角为 6 4 .8°的椭圆轨道。此后 ,每颗卫星将使用自带的推进系统进入GL ONASS网络中的最终轨道星位。目前 ,这 3颗卫星还未投入使用。俄罗斯应用力…     

锂离子电池用正极材料LiNi_(1-x)Co_xO_2的研究

采用高温固相法分别在空气和氧气气氛下合成锂离子电池正极材料LiNi1-xCoxO2 (x =1 ,0 .8,0 .5,0 .2 ,0 ) ,用X射线衍射 (XRD)测定晶格结构和晶胞参数 ,并用CR2 0 2 5扣式电池及 1 8650型电池对材料充放电性能进行测试。试验结果表明 ,随着LiNi1-xCoxO2 中钴含量增加 ,晶胞参数a和c值依次减小 ,晶胞体积收缩。同时烧结气氛对材料结构和电化学性能影响极大 ,氧气气氛有助于LiNi1-xCoxO2 (x >0 )的生成     

怀念恩师钱学森

作者从初见钱学森的印象、在工程力学研究班学习、从事早期卫星准备工作、合作进行远程星际航行后续研究、航天名词规范及航天科普宣传等多方面,回忆了钱学森对自己的引导、指导和教导。     

How the science and engineering of spaceflight contribute to understanding the plasticity of spinal cord injury.

Space programs support experimental investigations related to the unique environment of space and to the technological developments from many disciplines of both science and engineering that contribute to space studies. Furthermore, interactions between scientists, engineers and administrators, that are necessary for the success of any science mission in space, promote interdiscipline communication, understanding and interests which extend well beyond a specific mission. NASA-catalyzed collaborations have benefited the spinal cord rehabilitation program at UCLA in fundamental science and in the application of expertise and technologies originally developed for the space program. Examples of these benefits include: (1) better understanding of the role of load in maintaining healthy muscle and motor function, resulting in a spinal cord injury (SCI) rehabilitation program based on muscle/limb loading; (2) investigation of a potentially novel growth factor affected by spaceflight which may help regulate muscle mass; (3) development of implantable sensors, electronics and software to monitor and analyze long-term muscle activity in unrestrained subjects; (4) development of hardware to assist therapies applied to SCI patients; and (5) development of computer models to simulate stepping which will be used to investigate the effects of neurological deficits (muscle weakness or inappropriate activation) and to evaluate therapies to correct these deficiencies.     

Development and Application of Systems Science and Systems Engineering

Systems science and systems engineering, as a new science and technology domain in modern science and technology, is developing rapidly, and showing greater and greater vitality. QIAN Xuesen is recognized as the pioneer and founder of systems science and systems engineering in China. His whole innovation process from systems thinking to systems practice has made pioneering contributions at different levels from engineering, technology, science to philosophy. These achievements and contributions have very important scientific value and practical significance. Presenting QIAN Xuesen's contribution in systems science and practice, this paper elaborates the development and application of systems science and systems engineering.     

Improving science literacy and education through space life sciences.

The National Space Biomedical Research Institute (NSBRI) encourages open involvement by scientists and the public at large in the Institute's activities. Through its Education and Public Outreach Program, the Institute is supporting national efforts to improve Kindergarten through grade twelve (K-12) and undergraduate education and to communicate knowledge generated by space life science research to lay audiences. Three academic institution Baylor College of Medicine, Morehouse School of Medicine and Texas A&M University are designing, producing, field-testing, and disseminating a comprehensive array of programs and products to achieve this goal. The objectives of the NSBRI Education and Public Outreach program are to: promote systemic change in elementary and secondary science education; attract undergraduate students--especially those from underrepresented groups--to careers in space life sciences, engineering and technology-based fields; increase scientific literacy; and to develop public and private sector partnerships that enhance and expand NSBRI efforts to reach students and families.     

科技信息研究在科技发展战略研究中的作用探讨

科技信息研究是科技发展战略研究的基础,是科学决策的依据。文章归纳了科技信息研究中涉及的几个重要方面,包括科技信息研究在科技发展战略决策各环节中的作用、科技信息研究的选题检索、成果体现与评价的基本标准以及科技信息研究人员的素质要求等,得出了有关结论和启示。     

论科技进步与党内和谐

新的时期科技进步与党的建设之间关系日益紧密,影响巨大而复杂。本文系统阐述了科技进步的内涵、功能和主要特征,并对科技进步给党的建设带来的机遇和挑战进行了初步分析。     

集大成得智慧——钱学森的系统科学成就与贡献

介绍了钱学森科学历程的三大创造高峰:创建物理力学和工程控制论;开创我国火箭、导弹和航天事业,以及系统工程管理方法与技术;建立系统科学及其体系,创建系统学,并开创复杂巨系统科学与技术领域.以钱学森建立的科学技术体系结构为基础,分析了钱学森的系统科学体系、系统学与综合集成方法,以及复杂巨系统科学技术体系.     

System design and performance of the two-gyro science mode for the Hubble Space Telescope

For 15 years, the science mission of the Hubble Space Telescope (HST) required using three of the six on-board rate gyros for attitude control. Failed gyros were eventually replaced through Space Shuttle Servicing Missions. To ensure the maximum science mission life, a two-gyro science (TGS) mode has been designed and implemented with performance comparable to three-gyro operations. The excellent performance has enabled a transition to operations with 2 gyros (by intentionally turning off a running gyro to save it for later use), and allows for an even greater science mission extension. Predictions show the gain in mission life approaching two years. In TGS mode, the rate information formerly provided by the third gyro is provided by another sensor. There are three submodes, each defined by the sensor used to provide the missing rate information (magnetometers, star trackers, and fine guidance sensors). Although each sensor has limitations, when used sequentially they provide the means to transition from relatively large, post-maneuver attitude errors of up to 10, to the arcsecond errors needed to transition to fine pointing required for science observing. Only small reductions in science productivity exist in TGS mode primarily due to more difficult target scheduling necessary to satisfy constraints imposed by the use of the star trackers. Scientists see no degradation in image quality due to the very low jitters levels that are nearly equivalent to three-gyro mode.     

Space science and applications in CSIRO: towards a strategic plan

This Australian discussion paper, developed over a period of 12 months with input from a wide selection of scientists throughout the Commonwealth Scientific and Industrial Research Organization (CSIRO) and prepared for CSIRO by C B Faudry, G P Harris and G J Huntington, recognizes that methodologies in space science are tools to be used in the support of CSIRO's science programs. It addresses the strengths and capabilities of CSIRO in the area of space science and puts forward policies, identifies roles and areas of opportunity for CSIRO. Implementation strategies are suggested. Following this step, the CSIRO Office of Space Science and Applications (COSSA) in consultation with Instiutes and Divisions will develop further the coherent strategy for space science research in CSIRO and use it to prepare a rolling strategic plan for this important area of science in the organisation. Copies of the report are available from COSSA at the address below.     

论以科技竞赛促进网络工程专业实践教学改革

本文论述了大学生科技竞赛活动对学校网络工程专业实践教学改革的促进作用。结合网络工程专业的教学实践,提出了重视科技竞赛,促进实践教学改革,提高学生学习兴趣和积极性的一些思路和做法。