超长并列斜拉索尾流驰振及其控制风洞试验研究

通过气动弹性模型风洞试验,测试了不同风攻角及索间距下,并列超长拉索间的风致振动特性,研究了拉索尾流驰振的运动轨迹及其控制措施.研究表明,拉索发生尾流驰振时,其运动轨迹通常为椭圆轨道,振动主轴与来流方向成一定倾角;运动方向为靠近尾流外侧时,向下游运动,靠近尾流中心时,向上游运动;尾流驰振发生时,拉索从来流中吸收能量,振幅缓慢增大;随着风速增加,振幅增加较快直至出现明显的、振动主轴近似沿来流方向的极限环为止;采用分隔架可以有效抑制尾流驰振的发生,研究结果对并列拉索的抗风设计与振动控制具有指导意义.     

探空湿度传感器空间飞行姿态和加热模型研究

为计算出探空湿度传感器随气球上升过程中在空间的飞行姿态和测量周期,应用了一种计算流体动力学方法.首先,建立五种传感器间距模型,获得最优的传感器间距.其次,建立四种飞行姿态,通过观察传感器的壁面剪切应力大小,确定最优的飞行姿态角.最后,利用瞬态分析,仿真出0 ～32 km高空的加热时间和冷却时间,从而确定测量周期.仿真结果表明:在入口风速8 m/s,次流入口为10 m/s时,最优的间距为3.5 ～6 mm.传感器的俯仰角为45°时,壁面剪切应力较大,故较为理想的俯仰角为43°～48°.传感器的测量周期采用0.53 W的加热功率和温度降幅为超环境温度12℃所对应的时间.     

水平轴风力机串联工况尾流效应影响

为减小尾流效应对风力机输出功率的影响,基于CFX模拟实验研究8D串联间距风力机尾流场和不同方向速度场的变化规律.结果 表明,上游风力机的尾流叠加作用使下游风力机产生复杂的湍流和涡流现象,造成不同方向上速度差异.随着轴向距离增加,轴向速度先减小后增加,5D处轴向速度亏损最严重,而径向速度高速区在叶尖区迎风面,切向速度叶尖区影响最大.随着不同方向速度的恢复,8D截面处尾流影响基本消失.     

几何布局对掘进机位姿检测精度的影响分析

为实现综掘工作面悬臂式掘进机位姿无人化、高精度检测,提出了一种基于超宽带测距技术的掘进机位姿检测系统,推导了基于该系统的掘进机定位坐标及机身姿态角计算方法,通过Matlab仿真分析了基站布局间距、角度对定位精度的影响及机身定位点间距对姿态角检测精度的影响。仿真结果表明:随着基站至掘进机机身定位点的测量距离增大,系统定位精度降低;基站布局间距越大,系统定位精度越高;基站布局角度在yoz平面呈60°时系统定位精度优于基站布局角度呈0°及90°时;基站至掘进机机身定位点的测量距离对姿态角检测精度没有显著影响;机身定位点间距越小,系统姿态角检测精度越高。     

考虑速度对期望间距影响的车辆跟驰模型研究

为了真实地反映驾驶员在道路行驶中的车辆跟驰机理,使用相关性分析方法找出影响期望间距的关键因素,从而提出改进的基于期望间距的车辆跟驰模型(improved desired distance model,IDDM).利用NGSIM数据对IDDM和经典的Gipps车辆跟驰模型的参数进行了标定,之后对标定的模型进行评价.研究结果表明,前后两车的速度以及相对速度主要影响跟驰过程中驾驶员采用的期望间距;IDDM与传统Gipps模型相比,其加速度、速度与位置的仿真精度分别提高了0.24 m/s2、0.72 m/s、0.53 m,可以为车辆跟驰行为分析提供参考.     

66kV覆冰导线的舞动仿真分析

针对偏心覆冰导线在风的激励下极易诱发舞动对输电线路造成损坏,对整个供电系统的安全运行造成严重危害的问题,采用Fluent软件中的SSTk-ω模型对覆冰导线的空气动力参数进行了仿真,得到了各攻角下不同冰厚的升力、阻力系数以及邓哈托系数,并依据此结果判定覆冰导线是否发生舞动。仿真结果表明:在风速相同的情况下,覆冰厚度大的易发生驰振,在冰厚度相同的情况下,风速变大气动力系数变得平稳,不易发生驰振;6mm以下的覆冰导线不会发生驰振。仿真验证了覆冰导线模型的有效性,其数据结果对覆冰导线防舞工具的设计和安装都具有重要的参考价值。     

漂浮式斜拉桥全局模态对CFRP索的敏感性研究

斜拉桥复杂动力学问题中的一个关键问题是局部模态频率与全局模态频率成倍数匹配关系时可能导致的斜拉索大幅振动.本文针对这个问题,基于传递矩阵法,研究CFRP索对斜拉桥全局模态频率的敏感性.将斜拉桥的桥面梁和桥塔分别视为多离散弹性支承欧拉伯努利梁,建立其动力学控制微分方程,基于传递矩阵法对其特征频率进行求解.以长沙某独塔斜拉桥作为算例,对结构主要构件:斜拉索、塔和桥面梁的刚度变化对全局模态频率变化的敏感性问题进行了分析.结果表明,桥面梁和桥塔全局模态频率对斜拉索刚度变化非常敏感,并且用CFRP索替换钢质拉索可能避开拉索局部模态与斜拉桥全局模态的倍频关系,从而控制斜拉索的大幅振动.     

BRDF模型观测角测量模块的研制

BRDF(双向反射分布函数)模型是多角度遥感定量解译的理论基础,观测角是模型中的重要参数,其中包括观测天顶角和观测方向角.传统的测量观测角的方法是采用机械圆盘以及在地表画圆,但这种测量方法设备笨重、精度低、效率低,不适合水域的测量.提出了一种新的电子测量方法,利用加速度计测量重力加速度的三维分量,利用磁阻传感器测量地磁场的三维分量,通过坐标投影原理得到BRDF模型中的观测角.这种测量方法设备便携、成本低、效率高.观测天顶角的测量范围为-90°～90°,观测方位角的测量范围为0°～ 360°,在测量范围内的测量精度为±1°,满足BRDF观测角的测量要求.     

舰船热尾流的测试技术研究

舰艇螺旋桨的扰动和船体引起的船壳涡等将破坏尾流区中原有的温度梯度结构,形成明显的冷的或热的温度变化,称为热尾流.本文介绍了舰船热尾流的主要特征,研制了舰船热尾流和电导尾流实验测量系统,在海上试验测量了水面舰艇热尾流和电导尾流信号.研究结果表明舰艇存在明显的温度和电导信号,海洋表层温度梯度越大,热尾流信号就越强;目标船的吨位和吃水深度越大,热尾流的信号也越强.利用高灵敏度和高分辨率的温度和电导率传感器能可靠的将舰艇热尾流识别出来,有希望作为鱼雷攻击舰艇的一种新的尾流自导手段.     

大位移传感器的设计与验证

为了研发与验证Flex无线传感器用于土体监测时的可行性,本文参考已有的土体变形监测技术后,结合3D打印技术,传感测量技术与蓝牙无线传输技术,成功制作了 Flex无线土体位移传感器.本试验首先通过3D打印封装Flex制作变形监测传感器,再由室内试验模拟基坑和边坡工况,利用Flex传感器随着土体的变形分别可以对土体水平或竖直位移进行测 量.试验结果表明:Flex在用作室内试验时有较好的精确度,单个传感器量程为0°～60°,分辨率为0.3°～0.4°,并且可以实时反映土体的变化情况,其回传到后台的数据可以进一步分析得到土体位移量.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

法律信息库系统

本文分析了法律数据库的结构和特点，介绍了采用面向对象设计方法和超文本数据库技术开发和实现法律信息库系统将作为重要网络资源之一为不同用户进行法律咨询服务。     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

International Journal of Automation and Computing Table of Contents

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Information for authors

正SCIENCE CHINA Information Sciences(Sci China Inf Sci),cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press,is committed to publishing highquality,original results of both basic and applied research in all areas of information sciences,including computer science and technology;systems science,control science and engineering(published in Issues with odd numbers);information and communication engineering;electronic science and technology(published in Issues with even numbers).Sci China Inf Sci is published monthly in both print and electronic forms.It is indexed by Academic OneFile,Astrophysics Data System(ADS),CSA,Cabells,Current Contents/Engineering,Computing and Technology,DBLP,Digital Mathematics Registry,Earthquake Engineering Abstracts,Engineering Index,Engineered Materials Abstracts,Gale,Google,INSPEC,Journal Citation Reports/Science Edition,Mathematical Reviews,OCLC,ProQuest,SCOPUS,Science Citation Index Expanded,Summon by Serial Solutions,VINITI,Zentralblatt MATH.     

Erratum to: Fast global kernel fuzzy c-means clustering algorithm for consonant/vowel segmentation of speech signal

正Erratum to:J Zhejiang Univ-Sci C(ComputElectron)2014 15(7):551-563doi:10.1631/jzus.C1300320The original version of this article unfortunately contained mistakes.Algorithm 6 should be as follows:Algorithm 6 FGKFCM-F clustering Input:(1)X={x_1,x_2,…,x_N},,x_iR~d,i=1,2,…,N,the dataset;(2)C,1C≤N,the number of clusters;(3)ε0,the stopping criterion;     

Journal of Zhejiang University-SCIENCE C (Computers & Electronics) Total contents

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A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.