"电压和电压表的使用"教学设计创新

随着时代的发展,人们的日常生活、学习和工作已越来越离不开信息技术．信息化环境越来越成为学生生活和学习的环境,也将成为学生将来踏上社会工作的环境．让信息技术进入中学物理课程,成为物理课程的组成部分,可以帮助学生熟悉信息化环境,加强物理课程内容与现实世界的联系,     

虚功原理与广义坐标

指出所选广义坐标使平衡点成为虚位移,进而成为广义力的奇点是导致"广义力"在平衡点上不为零的原因,而不是虚功原理本身的问题.     

宇宙中的暗物质

 十多年来,宇宙中暗物质的研究已成为天体物理、粒子物理和宇宙学的交叉热点,其中的冷暗物质的观测研究也已成为当今非加速器物理实验最热门的课题之一.     

初中物理中考复习的几个着重点

如何激发初中学生对于物理知识的求知欲,并将这种动机转化成为他们对物理知识的兴趣,从而进一步成为这些即将毕业的初中学生对物理知识复习的动力,是非常重要的.     

MATLAB在工科物理教学中的应用

 信息技术对当今社会的发展产生了深远的影响,它不仅大大提高了社会生产力的发展速度,而且对社会生活方式与社会结构都产生了深层的影响,加快了人类进入信息化社会的步伐。信息、知识成为社会中的基本资源,信息产业成为社会中的核心产业之一,信息技术渗透到社会生活与工作的方方面面,无处不在,无孔不入。信息素养成为信息社会每个公民必须具备的一种基本素养.     

完整力学系统的广义梯度表示

将梯度系统推广到包含时间的情形,称之为广义梯度系统.给出完整力学成为梯度系统的条件.如果广义梯度系统的势函数可以成为Lyapunov函数,那么可用Lyapunov定理来研究系统的稳定性.     

手机电源新家族——当代高能化学电源

 手机已成为当代一种时尚文化,发短信息、打游戏、上网、下载铃声、查看当天的新闻和电子邮件,正在迅速成为新一代中青年的精神宠儿。因为手机不再仅仅被当做联络信息的工具,它已成为交友娱乐,追求时尚,甚至是治疗孤独的爱物。因此,信息消费年轻化将是一个不可逆转的潮流。未来5年,中青年消费将更加趋于享受生活,追逐前卫和展示个性。随着信息技术的发展,通讯技术产品开发的日新月异,高能化学电源成为电子产品的原动力,是须臾也离不开的开路电压高、高比能量、工作温度范围宽、放电平稳、自放电小、长寿命的化学电源。     

相对论的协变场是虚构

基于洛伦兹电子论和洛伦兹磁力,否定法拉第定律和相对论电磁学,暨揭示广义洛伦兹磁力的科学研究之五:相对论的协变场是荒唐。本文基于洛伦兹电子论和洛伦兹磁力,论证表明:协变换出来的磁力线成为直线,它违背客观事实;协变换出来的环形电力线更荒唐;协变换出来的电磁场成为无穷大,广义洛伦兹磁力才是真谛;两电荷对撞时协变换出来的排斥力成为虚数,它违背客观事。     

事件空间中完整力学系统的梯度表示

本文研究事件空间中完整力学系统的梯度表示和分数维梯度表示, 建立系统的微分方程并将其表示为一阶形式, 给出系统成为梯度系统的条件以及成为分数维梯度系统的条件. 最后, 举例说明结果的应用.     

冰封木卫二将成为人类最大科研仪器

 冰封的木星卫星--木卫二将会成为人类最大的科学研究仪器之一,它将成为飞向太阳系遥远太空带电粒子的传感器。木卫二是研究中微子的理想靶场,在地球上利用水探测器来捕获中微子,具有高能量的中微子在地球上很难成功发现而在与探测器相互作用时仍相当罕见。     

光纤传感阵列用于智能复合材料状态监测的研究

以光纤智能材料与结构中的损伤估计为目的,提出了一种新颖的、利用多模光纤缠绕尼龙筋式的传感器,由这种传感器组成的传感阵列可以对智能材料与结构的受力、应变等参量进行检测,并采用ＯＴＤＲ 技术实时处理其输出的并行分布式传感信号,给出了测试数据、识别结果。在复合材料构件上的初步实验表明此系统能够对结构的状态进行在线监测和估计,在航空航天、船舶工业和土木建筑等领域有着潜在的实用价值。     

Micro-vibration suppression of equipment supported on a floor incorporating magneto-rheological elastomer core

In this study, magneto-rheological elastomers (MREs) are adopted to construct a smart sandwich beam for micro-vibration control of equipment. The micro-vibration response of a smart sandwich beam with MRE core which supports mass-concentrated equipment under stochastic support-motion excitations is investigated to evaluate the vibration suppression capability. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. A frequency-domain solution method for the stochastic micro-vibration response of the smart sandwich beam supporting mass-concentrated equipment is developed based on the Galerkin method and random vibration theory. First, the displacements of the beam are expanded as series of spatial harmonic functions and the Galerkin method is applied to convert the partial differential equations of motion into ordinary differential equations. With these equations, the frequency-response function matrix of the beam–mass system and the expression of the velocity response spectrum are then obtained, with which the root-mean-square (rms) velocity response in terms of the one-third octave frequency band can be calculated. Finally, the optimization problem of the complex modulus of the MRE core is defined by minimizing the velocity response spectrum and the rms velocity response of the sandwich beam, through altering the applied magnetic fields. Numerical results are given to illustrate the influence of MRE parameters on the rms velocity response and the response reduction capacity of the smart sandwich beam. The proposed method is also applicable to response analysis of a sandwich beam with arbitrary core characterized by a complex shear modulus and subject to arbitrary stochastic excitations described by a power spectral density function, and is valid for a wide frequency range.     

一种头盔式高亮背光显示系统设计

高亮背光显示装置在航空航天领域有着广泛的应用,结构小巧,重量轻便是其发展趋势;通过自由曲面棱镜和菲涅尔螺纹镜的引入从而使系统的光学结构简单,依据光学原件设计了显示系统的机械封装和电路系统,整个显示系统部件定位准确,组装和拆卸方便,总重量小于30g。测试结果表明整个系统可以达到如下的指标：亮度200000cd／m2,均匀度大于859／6,功耗小于6W,达到设计要求。     

Integrated design of piezoelectric damping system for flexible structure

This paper aims at developing an integrated design method of the active/passive hybrid type of piezoelectric damping system for reducing the dynamic response of the flexible structures due to external dynamic loads. The design method is based on the numerical optimization technique whose objective function is a control effort of the active damping. A vibration suppression performance, which is evaluated by the maximum value of the gain of the frequency response function of the structure, is constrained. In order to demonstrate the structural damping capability of the hybrid type of piezoelectric damping system designed by proposed method, numerical simulation and laboratory experiment will be done using a three-story flexible structure model equipped with 12 surface bonded PZT tiles pairs. Both numerical and experimental results indicate that the optimally designed hybrid piezoelectric damping system can be successfully achieving excellent performance as compared to a conventional purely active piezoelectric damping system.     

Modeling and Measurement of a Tunable Acoustoelastic System

Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal cavity. The impact of this coupling on the total dynamic response of the structure can be quite severe depending on the similarity of the modal frequencies and shapes. Typically, acoustoelastic coupling is not a design feature, but rather an unintended result that must be remedied as modal tests of structures are often used to correlate or validate finite element models of the uncoupled structure. Here, however, a test structure is intentionally designed such that multiple structural and acoustic modes are well-aligned, resulting in a coupled system that allows for an experimental investigation. First, coupling in the system is identified using a measure termed the magnification factor. Next, the structural-acoustic interaction is measured. Modifications to the system demonstrate the dependency of the coupling on changes in the mode shape and frequency proximity. This includes an investigation of several practical techniques used to decouple the system by altering the internal acoustic cavity, as well as the structure itself. These results show that acoustic absorption material effectively decoupled the structure while structural modifications, in their current form, proved unsuccessful. Readily available acoustic absorptive material was effective in reducing the coupled effects while presumably adding negligible mass or stiffness to the structure.     

Smart structures—The relevance of fiber optics

The concept of the smart structure integrates structural engineering, sensing, control systems, and actuation to provide a mechanical assembly that is capable of responding to its environment and/or loading conditions. The realization of the smart structure requires integration of skills in a variety of scientific and engineering disciplines ranging from mechanical engineering through materials science into signal processing, data analysis, sensing, and actuation. The sensing technology must have a number of key features of which the ability to take distributed measurements of various parameters throughout the structure is paramount. Therefore, fiber optics technology promises to have a significant role to play in the evolution of the smart structures concept. This article analyzes this role in detail, presents an assessment of the current state of the art in fiber optic technology related to smart structures, and presents a scenario for future developments.     

基于6LoWPAN的智慧校园空调监控系统设计

针对总线制空调监控系统存在布线施工成本高、联网结构复杂、维护难度大等问题,设计了一种基于6LoWPAN的智慧校园空调监控系统。首先给出了系统的整体功能及网络架构;然后,给出了传感器节点、系统核心模块及网关节点的硬件设计;接下来对6LoWPAN协议及简化进行了描述,给出了系统嵌入式软件的设计;最后给出了相关的空调控制策略。测试和实验结果表明,该空调监控系统具有结构简洁,扩展性高,实时在线响应,有效解决了校园空调物联网的信息互联问题,利用云平台智能管理达到节能减排目标。     

Coupled FEM/BEM for control of noise radiation and sound transmission using piezoelectric shunt damping

In this paper, we present a coupled finite element/boundary element method (FEM/BEM) for control of noise radiation and sound transmission of vibrating structure by passive piezoelectric techniques. The system consists of an elastic structure (with surface mounted piezoelectric patches) coupled to external/internal acoustic domains. The passive shunt damping strategy is employed for vibration attenuation in the low frequency range. The originality of the present paper lies in evaluating the classically used FEM/BEM methods for structural–acoustics problems when taking account smart systems at the fluid–structure interfaces.     

Using chaotic interrogation and attractor nonlinear cross-prediction error to detect fastener preload loss in an aluminum frame

Structural health monitoring is an important field concerned with assessing the current state (or "health") of a structural system or component with regard to its ability to perform its intended function appropriately. One approach to this problem is identifying appropriate features obtained from time series vibration responses of the structure that change as structural degradation occurs. In this work, we present a novel technique adapted from the nonlinear time series prediction community whereby the structure is excited by an applied chaotic waveform, and predictive maps built between structural response attractors are used as the feature space. The structural response is measured at several points on the structure, and pairs of attractors are used to predict each other. As the dynamics of the structure change due to damage, the prediction error rises. This approach is applied to detecting the preload loss in a bolted joint in an aluminum frame structure.     

Optical smart card using semipassive communication

An optical secure short-range communication system is presented. The mobile unit (optical smart card) of this system utilizes a retroreflector with an optical modulator, using light from the stationary unit; this mobile unit has very low power consumption and can be as small as a credit card. Such optical smart cards offer better security than RF-based solutions, yet do not require physical contact. Results from a feasibility study model are included.