不断创新的巴黎

在此提出的是可供您选择的有关巴黎的一种想像的滋味,它自我凝思、自我伪装而又自我显露出来。两座国际机场、六个国际火车站将巴黎与世界相连,今天巴黎也因此成为地处欧洲中心的令人心动不已的旅游目的地之一。与往年一样,众多文化场馆、旅游景点的开放或重新开放     

持久专注不断创新——BMEI新品迭出

北京机电院高技术股份有限公司(BMEI)是一家在数控机床方面技术领先,集科研、设计、生产、销售于一体的高技术公司。     

罗—罗持续发展发动机"全面维护"服务

罗—罗公司曾经只是单纯的原设备制造商(OEM),生产航空发动机并为其产品提供技术支持.10年来,罗—罗公司不断地扩展服务范围,以提升航空公司的价值.     

Optimum Realizable Continuous Range Estimation

The ability to detect the presence or absence of a target is no longer the fundamental design criterion when the vehicle to be tracked is cooperative. In spacecraft tracking or navigation systems, for example, emphasis is placed on post-acquisition performance. Therefore, classical radar theory and design techniques are not specifically applicable. On the other hand, there are optimization techniques for extracting the tracking data from noise that are more to the point. In particular, optimum demodulation theory is directed specifically to the problem of continuously extracting data from a nonlinear modulation process. In this paper, the tracking properties of a multitone PM ranging signal are reviewed and are shown to be nearly optimum for cooperative vehicles. An optimum, but nonrealizable, maximum a posteriori (MAP) continuous estimator of range is derived for this signal. The linearized model of this receiver is the optimum nonrealizable Wiener filter for the data. Interpretation of this optimum nonrealizable estimator leads to a receiver design that is both practical and intuitively satisfying. With the aid of post-detection processing in the Wiener-Hopf sense, almost optimum performance is obtained from the resulting receiver, above threshold.     

横向裂纹对转子动力特性的影响

选取转子支承系统为研究对象，利用传递矩阵方法计算转子系统的动力特性，目的在于探求裂纹对转子动力特性的影响。计算结果表明：裂纹对转子的各种动力特性都有影响，但影响很小。这对于发动机的正常工作是非常有利的。但从故障检测方面考虑，若想通过振动特性的变化来检测裂纹故障是相当困难的。     

拓扑线性空间上连续线性泛函的延拓

本文在线性空间中给出了线性球的定义，由此我们得出：拓朴线性空间中连续线性泛函延拓定理成立的主要条件为当其任意子空间中的线性球为开集时，存在原拓扑上的凸邻域，使此凸邻域限制在子空间上时属于线性球。     

罗-罗持续发展发动机"全面维护"服务

罗-罗公司曾经只是单纯的原设备制造商(OEM),生产航空发动机并为其产品提供技术支持.10年来,罗-罗公司不断地扩展服务范围,以提升航空公司的价值.2005年,罗-罗公司的总销售额为65亿英镑,其中3 5亿英镑来自售后服务.现在,罗-罗公司在航空发动机领域的多数业务都是通过"全面维护"(Total Care)协议而展开的.     

推陈出新问鼎一流——打造世界一流数控重型机床品牌

武汉重型机床集团有限公司(简称武重)是我国一五时期156项重点建设项目之一,目前是我国研发、设计和制造重型、超重型机床的大型骨干企业,以生产重型机床产品规格最大、品种最全而闻名遐迩.武重为国家机床装备制造业的发展以及推动重型机床行业技术进步所做出的贡献得到了国家的充分肯定和行业的认同.     

连续凸偏好的一个性质

偏好与效用是联系在一起的。如果一种商品对于消费者没有效用，消费者就不会产生对这种商品的偏好，对偏好的研究为人们对效用进行定量的描述与研究奠定了基础。本文给出连续凸偏了的一个性质的严格证明。     

社会技术与自然技术的和谐图景

技术是人的本质存在形式。技术范畴已发生本体论上的外延,除自然技术外,还必然涵括社会技术范畴。社会技术的存在毋庸置疑,自学界提出社会技术的概念后,社会技术与自然技术的关系便成为技术哲学研究的崭新视角。和谐技术观是社会技术与自然技术关系之基。社会技术和自然技术在消解与融合、界限、可逆性等诸方面显现出和谐图景。     

Security technology

Security requirements and capabilities have changed dramatically over the past fifty years. Personal identification and detection of illegal substances including explosives have come to the forefront. With the proliferation of computers the security of information has also become a major concern. Substantial advances have been made over the last three decades in entry control, counter-terrorism, cryptology and airport protection. The utilization of technology has become an irreversible trend. Electronic devices and systems are capable of automatically and tirelessly monitoring and reporting breaches of security. For example, airport security began with physical protection of the facility with fences and area surveillance. The most recent concern is detecting explosives in both checked and early-on baggage, Other techniques relate to monitoring passengers for weapons as they transit the terminal building, especially crowds gathered at the metal detectors and X-ray machines. The application of electronics has produced reliability improvements and cost savings in systems that protect against unauthorized entry and numerous other threats. PCs have become the heart of security command and control systems. Most PC platforms rely on the proven software stability of Windows NT and present data in human-friendly, graphic format. It is expected that in the near future security monitoring will be consolidated in a central location, possibly to be integrated with other command and control functions     

考虑横法向热应变的Reddy型功能梯度梁理论

Reddy型高阶理论已被广泛用于功能梯度材料(FGM)结构分析,然而此理论忽略了横法向应变,难于准确分析功能梯度梁的热力行为。为提高Reddy理论分析热力响应的精度,提出了一种考虑横法向热应变的三参数Reddy型高阶功能梯度梁理论。此模型考虑了横法向热应变,但不增加额外位移变量。应用构建的模型分析了功能梯度梁的热力响应,并研究了不同体积分数对面内应力和位移的影响。数值结果表明,所提出的模型能准确分析功能梯度梁的热力响应,而忽略横法向应变的模型计算结果精度较低。     

浅谈持续适航维修方案

持续适航维修方案与平时常用的维修方案是完全不同的一个概念.本文着重介绍了持续维修方案的基本要素、维修记录的保存系统以及持续分析和监控方案.     

一种块级连续数据保护的系统设计

提出了一种基于逻辑卷的连续数据保护系统的设计方案,论述了它的系统结构以及实现方法。。该系统不依赖于具体的存储设备,能实现数据块级的连续保护,并可以实现保护时间区间内任意时间点的恢复。系统提供了独特的数据存储组织结构和相应的空间管理策略,并且具有很好的恢复技术,该系统提供了一种经济、通用的纯软件方案,能广泛推广应用。     

Adaptive Trackers Based on Continuous Learning Theory

The theory of ?continuous learning? is applied here to the design of nonlinear sampled-data trackers. This theory provides a continuous-motion approximation of the discrete or sampled motion of the actual tracker. The theory prodicts the transient-response performance of the tracker as well as the mean-square errors caused by noise and statistical fluctuations in the signal. Numerical examples of first-order and second-order trackers designed by this technique are presented. These examples illustrate the adaptive behavior predicted by the technique. In one of these examples the trade-off between transient-response performance and the suppression of noise-induced tracking errors is demonstrated.     

轴向运动粘弹性板横向振动分析的有限差分方法

研究轴向运动粘弹性矩形薄板的横向振动特性.根据牛顿第二定律建立了偏微分控制方程,采用有限差分法,计算四边简支边界条件下粘弹性板的无量纲固有复频率.重点讨论了矩形薄板的粘弹性系数、轴向无量纲运动速度对其横向振动特性的影响.     

Layerwise third-order shear deformation theory with transverse shear stress continuity for piezolaminated plates

Regarding laminated structures,an electromechanically coupled Finite Element(FE)model based on Layerwise Third-Order Shear Deformation(LW-TOSD)theory is proposed for sta-tic and dynamic analysis.LW-TOSD ensures the continuity of in-plane displacements and trans-verse shear stresses.The current LW-TOSD can be applied to arbitrary multi-layer laminated structures with only seven Degrees of Freedom(DOFs)for each element node and eliminates the use of the shear correction factors.Moreover,a shear penalty stiffness matrix is constructed to sat-isfy artificial constraints to optimize the structural shear strain.A dynamic finite element model is obtained based on LW-TOSD using the Hamilton's principle.First,the accuracy of the current model is validated by comparing with literature and ABAQUS results.Then,this study carries out numerical investigations of piezolaminated structures for different width-to-thickness ratios,length-to-width ratios,penalty stiffness matrix,boundary conditions,electric fields and dynamics.     

Iris recognition technology

IriScan Inc. has been developing an identification/verification system capable of positively identifying and verifying the identity of individuals without physical contact or human intervention. A new technology, using the unique patterns of the human iris, shows promise of overcoming previous shortcomings and providing positive identification of an individual without contact or invasion, at extremely high confidence levels. The video-based system locates the eye and iris; evaluates the degree of occlusion by eyelid and spectral reflection; determines the quality of image focus; and determines the center and boundary of the pupil and the limbus (outer edge of the iris) for processing. The iris is zoned, and the features therein measured and encoded into a 256-byte (2048 bit) IrisCode for enrollment or identification. The presented biometric is compared to an extensive database for identification, or to a referenced IrisCode for verification. Computations and decisions are accomplished at extremely high rates of speed, resulting in processing times of less than two seconds. The process is based on the unique nature and extreme richness of the human iris. The multiple features produce a non-duplicable organ with more than 400 degrees of freedom, or measurable variables. The IriScan process typically uses about 200 of these to create a code which can be compared to an entire database in milliseconds, producing a positive identification with “imposter odds” as high as 1 in 10³⁴     

PWM inverter technology

The approach used to optimize a transistorized pulsewidth-modulated inverter used in an uninterruptible power supply is detailed. Through the use of computer modeling with a space state-model, a variety of scenarios for the optimal inverter design were evaluated. The computer modeling resulted in an optimized feedback control loop, which provided the best level of response while minimizing the amount of switching losses to achieve the highest level of efficiency