A Novel Terahertz Rat-Race Hybrid Coupler Based on PPDW

A novel rat-race hybrid coupler based on parallel-plate dielectric waveguide (PPDW) is proposed. PPDW has been proposed as a basic terahertz transmission line for its remarkable simple structure and comparatively low attenuation at terahertz frequency band. It can be applied to design many terahertz components. In this paper, a (3 N + 3/2) × lambda circumference PPDW rat-race hybrid coupler operating at quasi-TE₁₀ mode is studied. The investigation results show that, at 0.34 THz, the transmission losses of the two split output ports are both equals −3.2 dB; the return loss at its input port is below −20 dB; the insertion loss at each split transmission port is less than 0.2 dB; and the two isolated ports show good isolation of above 20 dB. Therefore, it will have wide potential applications at terahertz frequency band.     

一种高精度的电力巡检定位导航系统

文章介绍了利用现代通信技术和地理信息技术,针对电力巡检特殊要求开发出的一种基于气压海拔高度测量、支持通用分组无线业务(GPRS)无线双向通信与断点续传、地图可定制的高精度定位导航系统.阐述了该高精度定位导航系统的设计原则及其模块化功能,介绍了该系统相比于传统定位导航系统的优点,最后介绍了该系统的应用实例.     

Aircraft type recognition in satellite images

This paper proposes a hierarchical classification algorithm to accurately recognise aircraft in satellite images. Before recognition, a novel symmetry-based algorithm is proposed to estimate an aircraft's optimal orientation for rotation correction. Then, distinguishable features are derived from each aircraft for aircraft recognition. However, different features have different discrimination abilities to recognise the types of aircraft. Therefore, a novel booting algorithm is proposed to learn a set of proper weights from training samples for feature integration. Owing to this integration, significant improvements in terms of recognition accuracy and robustness can be achieved. Last, a hierarchical recognition scheme is proposed to recognise the types of aircraft by using the area feature, first for a rough categorisation on which detailed classifications are then achieved using several suggested features. Experiments were conducted on a wide variety of satellite images. Experimental results reveal the feasibility and validity of the proposed approach in recognising aircraft in satellite images.     

Orthogonal sets of quadriphase sequences with good correlationproperties

A general construction for orthogonal sets of quadriphase sequences based on the sequence family A discovered by Sole (1989), Boztas, Hammons, and Kumar (1992) is presented. The sequence family A is equivalent to the S(0) family that belongs to a chain of sequence families S(i),i=0,1,2,..., m with each family in the chain containing the preceding family. Therefore, a number of orthogonal subsets can be generated for an arbitrary family S(m). The algorithm for an efficient implementation of the bank of correlators corresponding to any orthogonal subset of family S(m) is derived as well     

Voltage- and temperature-dependent gate capacitance and current model: application to ZrO/sub 2/ n-channel MOS capacitor

Based on the energy-dispersion relation in each region of the gate-dielectric-silicon system, a tunneling model is developed to understand the gate current as a function of voltage and temperature. The gate capacitance is self-consistently calculated from Schrodinger and Poisson equations subject to the Fermi-Dirac statistics, using the same band structure in the silicon as used for tunneling injection. Franz two-band dispersion is assumed in the dielectric bandgap. Using a Wentzel-Kramer-Brillouin (WKB)-based approach, direct and Fowler-Nordheim (FN) tunneling and thermionic emission are considered simultaneously. The model is implemented for both the silicon conduction and valence bands and both gate- and substrate-injected currents. ZrO/sub 2/ NMOSFETs were studied through temperature-dependent C/sub g/-V/sub g/ and I/sub g/-V, simulations. The extracted band gaps and band offsets of the ZrO/sub 2/- and interfacial-Zr-silicate-layer are found to be comparable with the reported values. The gate currents in ZrO/sub 2/-NMOSCAPs are found to be primarily contributed from the silicon conduction band and tunneling appears to be the most probable primary mechanism through the dielectric. Oscillations of gate currents and kinks of gate capacitance were observed near the flat-band in the experiments. These phenomena might be caused by the interface states.     

无线基站用于海域覆盖时出现的问题及其解决方法

首先提出了用GSM900无线基站在做近海海域覆盖时会出现的一些问题，并阐述了其原因：随后给出了处理这些问题的解决方案，最后提供了一个在实际工程中对某海域覆盖型基站的测试实例。     

双服务器分组调度算法

分组调度算法对于确保分组交换系统的QoS具有重要意义。时延,公平性,计算复杂度是微量分组度算法的主要指标。本文提出了一种双服务器分组调度算法,该算法在两种不同的工作状态下分别采用两种服务规则决定分组的服务次序。其中一种服务规则用来确保分组的时延,另一种服务规则在时延得到保障的情况下对系统的公平性进行改善,这两种规则计算都不复杂。因此本文提出的算法具有时延低,公平性较好,计算复杂度低的特点。     

Design and Validation of an Efficient Authentication Scheme with Anonymity for Roaming Service in Global Mobility Networks

Designing a user authentication protocol with anonymity for the global mobility network (GLOMONET) is a difficult task because wireless networks are susceptible to attacks and each mobile user has limited power, processing and storage resources. In this paper, a secure and lightweight user authentication protocol with anonymity for roaming service in the GLOMONET is proposed. Compared with other related approaches, our proposal has many advantages. Firstly, it uses low-cost functions such as one-way hash functions and exclusive-OR operations to achieve security goals. Having this feature, it is more suitable for battery-powered mobile devices. Secondly, it uses nonces instead of timestamps to avoid the clock synchronization problem. Therefore, an additional clock synchronization mechanism is not needed. Thirdly, it only requires four message exchanges between the user, foreign agent and home agent. Further, the security properties of our protocol are formally validated by a model checking tool called AVISPA. We also demonstrate that this protocol enjoys important security attributes including prevention of various attacks, single registration, user anonymity, no password table, and high efficiency in password authentication. Security and performance analyses show that compared with other related authentication schemes, the proposed scheme is more secure and efficient.     

接入网网管在中国的应用

本论述了接入网网管的基本功能，介绍我国接入网网管发展的现状和相关协议标准，简述了建立统一接入网网管平台的重要性，以及如何将接入网网管最终纳入ＴＭＮ中。     

离子束溅射铂膜沉积速率的温度效应

实验研究了离子束溅射铂膜的沉积速率与溅射功率、基片温度之间的关系。结果表明基片温度对沉积速率有明显的影响．沉积速率随基片温度的上升而增大。利用吸附理论对此现象进行了探讨。