Powered Limb Prostheses: Their Clinical Significance

The clinical importance of existing powered prosthetic devices is investigated. In this regard, several powered prosthetic systems that are in practical use are reviewed and put in perspective with respect to body-powered systems. The unique problems of delivery and maintenance of these systems are discussed as are practical design limitations. An appraisal is made of development trends in the field and the author's viewpoint on the optimal environment for practical advances in the field is presented.     

Wireless Robotics: A History,an Overview,and the Need for Standardization

The field of Robotics is one of the most fascinating areas of research in the world. Right now, hundreds of universities, corporations, and governments are spending billions researching and developing intelligent robotic systems for use in automation, military, medicine, electronics, food and beverage, service and a host of other industries. There is no doubt that robotic systems will play a major role in shaping the future of the world and as research and industry merge, progress in robotics technology will advance several times beyond the current level. This progress will be driven by a need to not only make life easier for consumers, but also to improve communities and even nations as a whole. The market for wireless robots and robotic systems far exceeds the current utilization and as technology advances, the use of robots will be incorporated primarily or indirectly in almost all fields. Of course the most interesting application is use of mobile and communicative robotic systems in everyday life. The possibilities are limited only by human creativity and intellect—the driving force that can turn this industry into the forerunner for an autonomous robot assisted future. Two of the most important areas for furthering the wide scale adaption of robotics are “autonomous mobility” and “wireless communications”. The field of endeavor by which robotic systems communicate wirelessly is known as Wireless Robotics. Advances in the field of Wireless Robotics are necessary to further the growth of robotic systems and their use in everyday life. Research and development in this field needs to progress more rapidly in order to see faster adoption of robots in everyday life. One way to stimulate this growth is by leveraging expertise on a global scale. But for people to cooperate in a global environment and be able to design systems without running into compatibility issues, standards are necessary. In this paper, we shall provide a brief background on the origin of robots and our fascination with them, discuss various use cases in current life, and provide the motivation for standardization in the field of Wireless Robotics.     

移动信道场强预测系统的分析与设计

移动信道场强预测系统在实际应用中具有重要意义。本文论述了基于OM模型的智能型场强预测系统，介绍了系统的总体设计和实现方法。并用计算实例验证了系统的使用价值。他将计算机辅助设计和可视化技术结合起来，从而使繁琐的专业设计成为易于操作的简单过程。     

偏转线圈彗差校正系统分析

本文对彩色显像管偏转线圈用两种六极场彗差校正系统进行了分析讨论，对垂直偏转场参量Ｖｏ，Ｖｚ的测量结果表明六极场校正系统的引入在偏转线圈颈部形成垂直枕形场有利于彗差的校正。同时，文中还对磁八极场对彗差的校正作用进行了分析。     

On Electromagnetics and Information Theory

Some connections are described between electromagnetic theory and information theory, identifying some unavoidable limitations imposed by the laws of electromagnetism to communication systems. Starting from this result, the role of the degrees of freedom of the field in radiating systems is investigated. Different classes of antennas use the available degrees of freedom in different ways. In particular, a multiple-input multiple-output antenna is a radiating system conveying statistically independent information on more than one degree of freedom of the field. Applications of the theory to antenna synthesis and antenna characterization in complex environments are shown.     

自由曲面在离轴光学系统中的应用

针对自由曲面能提升成像光学系统的性能和校正像差的特点,分析了自由曲面在离轴光学系统中的应用优势。光学系统选用视场角为30°×11°、焦距为150 mm、F数为3的Cook-TMA。本设计中,离轴三反光学系统的主反射镜采用自由曲面设计。分析了使用Zernike多项式曲面在大视场离轴反射式光学系统中对离轴光学系统性能的提升效果,并与使用常规非球面的情况进行了比较,分析了自由曲面的优缺点。结果表明,自由曲面在提高离轴光学系统的成像质量方面具有更大的优势,系统的平均传递函数比常规非球面提升了15.9%以上,系统接近衍射极限。Zernike多项式曲面在离轴三反系统中的应用效果良好,系统的成像性能得到了较大的提升。     

红外成像导引头双视场光学系统小型化技术

红外成像导引头越来越广泛地采用双视场光学系统,但光学系统性能与体积之间的矛盾非常突出。通过分析导引头红外变倍光学系统和一般红外系统的区别,阐明了导引头双视场光学系统的特点,在保证性能指标的前提下,介绍了通过采取出瞳与冷屏合适的匹配方式、优化变焦结构、采取红外新技术等有效减小红外变倍系统体积的几种方法,并对其进行了公式推导和证明,给出了计算实例,同时阐明了优化总体指标,使导引头总体性能最优的观点。     

Practical surface acoustic wave devices

A tutorial discussion is presented on selected surface acoustic wave (SAW) devices for the use of engineers and electronic systems designers. Currently practical components for use in radar systems, communications systems, and as frequency domain filters are described. Emphasis is placed on nondispersive and dispersive delay lines, devices for generating and detecting various radar waveforms, devices for generating and detecting fixed and programmable biphase and multiphase codes, and broad-band and narrow-band filters. The device possibilities of several new approaches are described, including multistrip couplers, nonlinear convolvers, reflective structures, and overlay films. It is concluded that, while SAW devices have found many applications in large radar systems because of their size, cost effectiveness, and reliability, wide-scale applications, for example as frequency domain filters, will be needed to justify continued research in this field. Wide-scale applications will come as systems engineers realize the potential of these devices and confidently design them into their systems.     

Mechanical signature analysis using time-frequency signalprocessing: application to internal combustion engine knock detection

Signature analysis consists of the extraction of information from measured signal patterns. The work presented in this paper illustrates the use of time-frequency (TF) analysis methods for the purpose of mechanical signature analysis. Mechanical signature analysis is a mature and developed field; however, TF analysis methods are relatively new to the field of mechanical signal processing, having mostly been developed in the present decade, and have not yet been applied to their full potential in this field of engineering applications. Some of the ongoing efforts are briefly reviewed in this paper. One important application of TF mechanical signature analysis is the diagnosis of faults in mechanical systems. In this paper we illustrate how the use of joint TF signal representations can result in tangible benefits when analyzing signatures generated by transient phenomena in mechanical systems, such as might be caused by faults or otherwise abnormal operation. This paper also explores signal detection concepts in the joint TF domain and presents their application to the detection of internal combustion engine knock     

Calculation of Radiation Fields in Waveguides by a Principle of Power Balance

A simple formula is derived for calculating the amplitude of the field that is due to an elemental radiator which radiates into a particular waveguide mode. The method used is based on rather elementary principles, and appeals readily to physical intuition. In this technique, the field radiated into an infinite-length waveguide is obtained from the expression for the field developed by the radiator in a traveling wave resonator formed of this waveguide, where this expression is found by use of the Poynting theorem. While derived for the electromagnetic system, the method and formula can be applied to other waveguide systems, such as mechanical, mixed, or others. Several examples are given to illustrate the use of the method.     

Near-field optics: a new tool for data storage

Evanescent energy can be used to produce extremely small optical spots. Two practical implementations that use evanescent energy are aperture probes and solid immersion lenses (SILs). For data storage, the optical near field is defined in terms of evanescent coupling between the system used to read data and the recording layer. Because of the small spot size, near-field techniques are applied to optical data storage systems in order to increase recording density. Both aperture-type systems and SIL systems show good promise of achieving densities of more than 150 Gb/in/sup 2/. The characteristics and performance of several systems are compared, and future near-field technologies are discussed.     

近红外星图全天时定位技术导航应用的可行性研究

随着红外探测器和拍星技术的迅速发展,利用近红外进行全天时星光目标探测已经成为可能。对近红外全天时星光图像进行了特性分析。近红外星光目标提取、星光目标定位误差修正方法的研究与改进将会给导航系统带来新的革命,使得全天时导航的稳定性与可靠性变得更佳。根据近红外星图技术及其发展状况,结合目前典型导航平台的需求,分析了基于近红外星图全天时定位技术在导航平台上应用的可行性。对其中的典型关键技术进行了论述,为该领域的研究与应用提供了相应的依据。     

Information hiding-a survey

Information-hiding techniques have recently become important in a number of application areas. Digital audio, video, and pictures are increasingly furnished with distinguishing but imperceptible marks, which may contain a hidden copyright notice or serial number or even help to prevent unauthorized copying directly. Military communications systems make increasing use of traffic security techniques which, rather than merely concealing the content of a message using encryption, seek to conceal its sender, its receiver, or its very existence. Similar techniques are used in some mobile phone systems and schemes proposed for digital elections. Criminals try to use whatever traffic security properties are provided intentionally or otherwise in the available communications systems, and police forces try to restrict their use. However, many of the techniques proposed in this young and rapidly evolving field can trace their history back to antiquity, and many of them are surprisingly easy to circumvent. In this article, we try to give an overview of the field, of what we know, what works, what does not, and what are the interesting topics for research     

基于VHDL语言的有限域正则基乘法器设计

有限域的运算已经广泛应用于Reed—Solomon码、存储领域和各种加密算法中。乘法运算是其中最复杂的一种运算,有限域中的元素可以用各种基表示。文中在给出有限域元素自然基下的表示方法的基础上,推导出了域元素正则基下的表示方法,并给出了正则基下域元素的乘法运算,编写了乘法器的VHDL模型。用XILINX公司的ISE5．2软件对电路模型进行了仿真,结果表明乘法器的运算结果完全正确。     

lnterplex?A New Versatile Full-Resolution Single-Tube Color TV Camera System

IN RECENT YEARS several single-tube color TV camera systems have been proposed. Some of them are already on the market. However, there are some defects with these systems which restrict their application field. All these systems use stripe filters, the width and the number of the stripes determining the resolution of the tube.     

Optical componentry utilized in field trial of single-mode fiber long-haul transmission

Realization of large-capacity long-haul transmission systems is now quite promising due to rapid development in the field of optical fibers. This paper describes single-mode fiber optical components for use in the above-mentioned system. In particular, LD modules and optical connectors are most important for construction of a practical system. Thus, they are explained in detail along with their development procedures. Important field trial results of these components are also presented.     

Estimation of the reliability of computer components from field renewal data

The assessment of the performance of electronic components in actual use is important to the manufacturers of these parts for many reasons. In this paper, we discuss the complexities involved in statistically estimating the reliability of computer components from field data on systems having different operating times. We also describe the operations of a specific department of the IBM Corporation involved with measuring the field performance of locally manufacturered product. The renewal method for estimating component reliability and the corresponding assumptions are explained, and the procedure is illustrated with an application to some actual field data. In particular, the estimated cumulative distribution function, hazard rate, and lognormal and Weilbull probability plots for this field example are shown.     

Satellite Geodynamics

Satellite geodynamics concerns the use of space technology in the study of the dynamic processes and movements of the solid Earth. The study involves measurements of the Earth's gravity and magnetic fields, the distortions and relative motions of its tectonic plates and the orientation of, and rate of rotation about, its axis. These studies address fundamental questions of geophysics such as the causes of Earth movements and earthquakes, the nature of convection in the mantle, and the origin of the magnetic field. The use of space technology has helped advance our concepts and models in solid-Earth geophysics. Shortly after the dawn of the space age, tracking data were used to precisely define the pear-shaped Earth. Since that time, other data have given several up-to-date representations of the secularly changing magnetic field and global models of the gravity field. Using this technology, it is now possible to determine the contemporary rate of relative plate motion at the level of about 1 cm a year. There are exciting prospects for future missions in satellite geodynamics. The Geopotential Research Mission is designed to improve gravity and magnetic field models and new, highly portable geodetic systems based on the Global Positioning System and spaceborne laser systems should permit rapid determination of positions with 1-cm precision.     

On the wide-band CW illumination of large-scale systems. II. Therhombic illuminator

The Phillips Laboratory has designed and constructed a continuous wave illuminator for studying the responses of large-scale systems subject to vertically or horizontally polarized electromagnetic stresses incident from the horizontal. The illuminator is developed by a nonuniform two-wire transmission line oriented over the system under test. When the wires are driven from a common mode voltage with respect to the ground a vertically polarized electric field is generated and when the wires are driven from equal but opposite voltages a horizontally polarized electric field is developed. The structure is called the rhombic illuminator since the wire configuration is very similar to the rhombic antenna. In order to illustrate the use of the illuminator, data are presented for the illumination field and for the response of an illuminated aircraft recorded at the Phillips Laboratory     

Coherent multicarrier technology for implementation in the customeraccess

The use of coherent multicarrier (CMC) techniques in the integrated broadband communication network (IBCN) is proposed. Technology, implementation strategies, system engineering, system application areas, and evolution aspects are considered. The use of CMC systems for distributive and interactive services is discussed, and related CMC transmission and switching issues are considered. Details on the realization of a CMC demonstrator for a customer access and plans for implementation of the engineered equipment in field trials are presented