Biased Reduced Sampling: Detectability of an Attribute and Estimation of Prevalence

In surveilling a population, detection of systems with an attribute of interest and estimation of the prevalence of the attribute in the population are two main goals. Due to cost constraints, only a subset of all components of sampled systems may be fully tested. Biasing the sampling to increase the probability of choosing a component with an attribute of interest ameliorates the impact of reduced sampling. In this paper, we consider the impact of biased reduced sampling on detection and propose an approach for estimating the prevalence of the attribute in the population which properly accounts for the biasing. The proposed method is illustrated with a simulated example. Copyright © 2005 John Wiley & Sons, Ltd.     

A Novel Auto-Annotation Technique for Aspect Level Sentiment Analysis

In machine learning, sentiment analysis is a technique to find and analyze the sentiments hidden in the text. For sentiment analysis, annotated data is a basic requirement. Generally, this data is manually annotated. Manual annotation is time consuming, costly and laborious process. To overcome these resource constraints this research has proposed a fully automated annotation technique for aspect level sentiment analysis. Dataset is created from the reviews of ten most popular songs on YouTube. Reviews of five aspects—voice, video, music, lyrics and song, are extracted. An N-Gram based technique is proposed. Complete dataset consists of 369436 reviews that took 173.53 s to annotate using the proposed technique while this dataset might have taken approximately 2.07 million seconds (575 h) if it was annotated manually. For the validation of the proposed technique, a sub-dataset—Voice, is annotated manually as well as with the proposed technique. Cohen's Kappa statistics is used to evaluate the degree of agreement between the two annotations. The high Kappa value (i.e., 0.9571%) shows the high level of agreement between the two. This validates that the quality of annotation of the proposed technique is as good as manual annotation even with far less computational cost. This research also contributes in consolidating the guidelines for the manual annotation process.     

轴承盖冲压工艺分析及模具设计

通过对轴承盖零件冲压成形工艺进行了分析,介绍了零件的工艺参数的计算及设备的选择,同时介绍了模具结构及模具的工作过程,分析了零件引伸过程中产生拉裂现象的原因,并给出了解决措施,实现了该零件引伸的顺利进行,得出了垫旧报纸可以解决零件拉裂现象的方法。     

一种新型电涡流阻尼器及阻尼性能研究

基于电涡流原理提出一种新型的可用于航天器振动被动抑制的电涡流阻尼器。首先,依托数值仿真建立阻尼器的磁场和力学有限元分析模型,对阻尼器的性能进行分析计算。其次,在振动测试实验台上进行阻尼特性测试,获得了小位移0.1 mm、大位移1 mm下的1 Hz～50 Hz频率范围内正弦激励作用工况下的阻尼系数。然后根据Bouc-Wen滞回模型建立了阻尼器的力学模型,研究了负载、阻尼器结构、交变洛仑兹力之间的关系。研究结果表明这种新型的电涡流阻尼器在外载激励作用下能够输出与仿真结果较为接近的阻尼力,且阻尼系数随激励频率变化具有明显的规律性,根据仿真和实验结果建立的阻尼力力学模型可以很好地用于电涡流阻尼器的力学特性仿真分析。     

一种新型三维微位移工作台的设计和分析

为了解决微位移工作台的三维耦合问题,设计了一种驱动器固定的三维无耦合微位移工作台.本文介绍了它的结构和工作原理,通过有限元分析计算和样机实测验证,分别在X方向,X、Y方向和X、Y、Z方向施加载荷时,三维微位移工作台在X方向的位移不变,解决了三维空间运动耦合问题;分别在X、Y、Z方向施加不同载荷时,得到了工作台X、Y、Z方向的刚度,验证了工作台的位移、最大等效应力与载荷成正比.样机实测结果与有限元计算结果相吻合,工作台符合设计要求.     

车载平台刚体动力学模型分析

车载火控系统平台装置主要包括光束控制系统、激光器和支撑平台。将整个系统视为刚体，建立刚体动力学模型，并主要对平台在地基的各种振动激励，激光器的脉冲振动以及光束控制系统在力矩、加速度的荷载下进行计算分析．     

笔记本电脑的动力学分析与减振设计

对某型笔记本电脑的显示屏结构系统建立有限元模型，基于模态分析和瞬态响应分析结果．找到了影响显示屏余振的主要因素，通过修改相关结构参数，使余振得到有效抑制。动态测试与分析的结果与数值计算结果符合得很好。     

动态不确定度的估算方法和应用实例

提出动态校准结果的动态不确定度,并说明其物理意义、估算方法和步骤。并给出对压力和力两种传感器的多次动态校准结果以及估算其动态不确定度的应用实例。     

基于图像印刷技术的滤波器分析与设计

依据数字图像处理基本原理,针对现实中高斯噪声、椒盐噪声和乘性噪声,设计了一个基于FPGA的专用数字滤波器系统.该系统能对3种典型噪声进行有效滤除,同时该滤波器的性能可通过修改相应参数予以实时调整,通过实验和仿真证明该方案行之有效.     

Dynamic Plastic Deformation （DPD）： A Novel Technique for Synthesizing Bulk Nanostructured Metals

While some superior properties of nanostructured materials （with structural scales below 100 nm） have attracted numerous interests of material scientists, technique development for synthesizing nanostructured metals and alloys in 3-dimensional （3D） bulk forms is still challenging despite of extensive investigations over decades. Here we report a novel synthesis technique for bulk nanostructured metals based on plastic deformation at high Zener-Hollomon parameters （high strain rates or low temperatures）, i.e., dynamic plastic deformation （DPD）. The basic concept behind this approach will be addressed together with a few examples to demonstrate the capability and characteristics of this method. Perspectives and future developments of this technique will be highlighted.     

数字化可视人体的构建技术与应用研究

数字化可视人体，或称虚拟可视人体，是根据人体解剖学研究的全部数据综合构成的一系列数字化三维图像，而且可以虚拟地进行人体的一切生理活动。这种数字化可视人体可用于进行医学教学、模拟临床手术和放射治疗等，效果显著。本文阐述了制作方法和主要用途。     

车载自动码垛设备设计与动态性能分析

目的为中小型化肥厂的汽车运输设计一套自动码垛设备,并对设备工作的动态稳定性进行分析。方法应用拉格朗日运动学方程求出了大车机构和小车机构的驱动力,同时该驱动力也是提升臂产生激励振荡的激励力,运用结构动力学原理,得出了提升臂激励运动方程,并对影响方程中关键的设计参数进行了仿真分析。结果大车机构和小车机构完成一次动作的时间参数对设备动态稳定有较大影响;连接提升臂升降部件的直径d越小,设备运行动态稳定性越差;连接提升臂升降部件选用不同的钢材,对设备运行动态稳定性影响基本相同。     

Estimation and Validation of Semiparametric Dynamic Nonlinear Models

An approach for measurement-based modeling of nonlinear devices is proposed. The method that is commonly used for linear time-invariant systems, namely, parametric modeling and nonparametric verification, is hereby extended to a class of nonlinear systems. The applicability of the method is illustrated on the baseband modeling of a radio-frequency amplifier over a wide power and frequency range.     

Optimization Technique for Design of Automotive Air Filter Housings with Improved Fluid Dynamic Performance and Filtration

A filter housing design technique has been developed that computes the housing geometry required to provide a user-specified velocity distribution through the filter. Appropriate control of the flow field across the filter can improve filter efficiency. Two-dimensional computational designs have been performed specifying a uniform velocity distribution through the filter. This distribution corresponds to a uniform, constant pressure drop across the filter from the upstream to the downstream side. A computational optimization method is used to minimize the variation in the pressure drop along the filter by changing the geometry of the upper wall. Computational fluid dynamics (CFD) calculations of the viscous laminar flow upstream and downstream of the filter are performed using two-dimensional Navier-Stokes equations. As the upper wall profile is numerically changed, the CFD solution for the computations is repeated and the pressure drop variation is reevaluated until an optimum configuration is achieved. The optimization results have produced a pressure distribution that is very close to the specified uniform distribution. Experimental verifications were performed using a laser Doppler anemometer to measure the velocity distribution just upstream of the filter and a pressure transducer to measure pressure drops across the filter. The velocity distribution in this (optimized) housing is more uniform than other housing models having the same fundamental rectangular geometry.     

基于刚体与流体动力学耦合分析的太阳电池阵地面展开仿真技术

用动态网格技术进行刚体与流体动力学耦合计算,研究太阳能电池阵在地面开展的动态过程.该方法可以到捕捉电池阵展开对周围空气介质扰动复杂流场的特性,计算得到的展开时间与实测值吻合,具有较高的准确性.刚体和流体动力学计算采用通用的算法或程序,对电池阵结构形状和展开方式无特殊的假设,能适应不同类型的电池阵展开分析,具有通用性.     

基于辩证的设计动力分析

目的从哲学的角度对设计动力中的知觉与直觉进行分析。方法以条理的秩序因素以及变化的无序因素为基础,对理性的知觉和非理性的直觉动力进行分类研究。结论通过在"哲学的辩证方法如何潜移默化的影响着设计"中找到逻辑依据,发现设计动力的作用体现在方方面面,无论是人类有形的行为活动还是启迪行为的无形的思维方式,都离不开知觉与直觉的驱动,通过合理地运用这些设计的动力,可以有助于达到最佳的设计效果。     

叉车造型的视觉动力分析及其意象仿生设计研究

目的 为了提升叉车外观造型,增强市场竞争力,满足用户的感性意象需求,需要通过意象仿生设计提升叉车的情感内涵.方法 通过视觉动力分析,综合考虑理性与感性视觉意象进行设计.首先采用语义差分法获得叉车的目标意象,建立意象与叉车动力式样之间的关联,并利用层次分析法得到叉车关键造型部位的权重排序;其次利用生物特征作为意象感知介质,渲染目标意象氛围.结论 将可识别的生物特征匹配设备的关键造型部位,形成的备选方案可满足用户意象需求,评价筛选后得到最优方案.该意象仿生设计流程期望能够对相关工程车辆造型设计提供借鉴.     

差动式测量仪器动态误差分析与滤波网络设计

通过了一个动态在线测量系统实例，分析滤波网络分布位置对系统动态测量误差的影响，并提出对于差动式动态测量系统，滤波网络必须位于和差动算电路之后的设计原则。     

空间可展结构能量节点的设计和动力分析

 设计了一种用于空间可展抛物面天线的能量节点机构,并分析其展开机理,对杆件及其端部的扭簧组成的宏单元的缩减刚度矩阵进行了讨论.结果表明,在结构体系中设置能量节点可显著改善结构的共振性能,证明该设计是可靠、可行的.     

典型输电塔气弹模型设计及动力特性研究

输电塔结构受到风荷载激励,极易引起其气动弹性失稳,造成大幅振动,严重威胁着输电线路安全稳定运行。为研究高压输电塔结构风振动力特性,以某典型输电塔为原型,按照结构动力学相似准则,采用一种新型设计方法制作输电塔气弹模型,并利用有限元分析软件以及相关测试系统对其进行动力学分析,验证气弹模型的准确性。最后,进行不同风速和风向角下的气弹模型风洞试验。试验结果表明:输电塔模型的响应随风速增大而增大;输电塔横风向响应显著;通过对试验结果的对比分析,揭示了典型输电塔结构动力特性和风振响应特点,为高压输电线路抗风设计及改造提供依据。