全国短波监测网络系统的设计与实现

阐述了一种全国短波监测网络系统的设计与实现方案。该系统实现了短波监测的实时监测和非实时监测功能，实现了频谱数据、台站信息的管理和与国家无线电管理中心数据库无缝链接的功能，并具有自动控守扣报警功能。此外，还实现了与ARGUS无线电监测软件XML接口的链接，满足了异构监测数据交换的需求。系统采用模块化结构，由一系列标准模块组成,具有良好的可维护性和可扩展性。     

主流电子交易网站账户安全登录模式缺陷与安全设计

账户的使用是互联网的基础应用之一。由于传统账户登录方式存在极大的安全隐患,不少大型电子交易网站如银行、淘宝等逐步采用了安全控件登录的方式。文章对安全登录、传输以及身份认证过程进行了分析,指出了其中存在的重放攻击漏洞,提出了采用时间戳的公钥登陆安全模型来解决漏洞的方法。     

FPC市场与技术展望

该文叙述了挠性印制板在电子设备中应用,市场的重点,电子设备对挠性印制板的要求以及技术发展趋势。     

调Q脉冲YAG三波长激光诱导液相沉积Si基Ni-Pd-P纳米膜

使用脉冲三波长Nd：YAG激光实现了室温下半导体硅上化学沉积Ni-Pd-P纳米膜。SEM结果表明,激光诱导化学沉积Ni-Pd－P纳米膜具有良好的选择性。经STM测试发现,由于激光作用,镀层不仅沿表面生长,而且在厚度方向上也不断增厚。极化曲线测试表明,短时间激光诱导沉积的Ni-Pd-P纳米膜具有优异的析氢催化性能。     

Delay time in GaAs high-power photoconductive switches

The delay time defined as the time interval between the beginning of optical illumination and the onset of switching in photocurrent in gallium arsenide (GaAs) high-power photoconductivity switches is studied on the basis of electroabsorption caused by absorption edge shifting due to bandgap narrowing. The influences of the initial open-state field, the laser wavelength and the temperature are given. The results show it is the reflection and the transmission of the switch semiconductor slab indicated by the absorption fraction express the absorption rate of the illumination energy by the switch     

An Airborne Radar Clutter Tracking Algorithm Based on Multifractal and Fuzzy C-Mean Cluster

For an airborne Iookdown radar, clutter power often changes dynamically about 80 dB with wide distributions as the platform moves. Therefore, clutter tracking techniques are required to guide the selection of const false alarm rate （CFAR） schemes. In this work, clutter tracking is done in image domain and an algorithm combining multifractal and fuzzy C-mean （FCM） cluster is proposed. The clutter with large dynamic distributions in power density is converted to steady distributions of multifractal exponents by the multifractal transformation with the optimum moment. Then, later, the main lobe and side lobe are tracked from the multifractal exponents by FCM clustering method.     

Ultra-Wideband Electrostrictive Mechanical Antenna

Mechanical antennas based on piezoelectric materials can effectively reduce the size of long wave antennas down to 1/1000 of the wavelength (from km scale to mm level). However, the narrow bandwidth and weak field intensity seriously restrict its practical applications in transmission distance and channel capacity. Here, a mechanical antenna-based electrostrictive effect of relaxor ferroelectric ceramic (PMN-PT) is proposed to improve radiation capacity and achieve ultra-wideband characteristics (10 kHz–1 MHz). Due to the ultra-high dielectric constant at working temperature and the relationship between the strain and applied field intensity, the proposed antenna gets rid of the dependence on the poled materials and exhibits excellent communication properties beyond traditional mechanical antennas, which are experimentally demonstrated by a practical wireless communication system. Only using a single proposed mechanical antenna with 8 mm diameter and 3 mm thickness, the effective communication with a transmission distance of 200 m can be realized. This design offers a promising way of constructing mechanical antennas for long-wave communication.     

恶意代码分析技术综述

随着全球信息化的不断推进,整个世界越来越被连成一个整体,威胁计算机系统安全的领域也越来越广泛,其中以恶意代码最为严重。而随着计算机系统安全攻击与防御技术的不断较量,恶意代码的攻击手法、攻击形式也越来越趋于隐秘化、复杂化。因此,有必要对当下的恶意代码分析技术进行总结,从中发现新的发展方向,以应对不断变化的恶意代码形势。     

Novel last passage time based jitter model with application to low slew rate/high noise ring oscillator

In a ring oscillator, the behaviour in which the output voltage ramp (up/down) of its individual delay cell crosses the threshold, which triggers the next stage delay cell, is crucial in determining the timing jitter, and hence phase noise. Specifically, as the slew rate of the ramp decreases and/or the amount of noise contribution from the transistors in the delay cell increases, the voltage ramp (up or down) has a higher probability of crossing the threshold multiple times, before finally passing it at a time denoted as last passage time, which is more accurate than the conventional first passage time model. This multiple crossing results in a higher jitter. In the past, investigation in last passage time jitter model results in jitter expression that can only be calculated numerically and thus no design guidelines/insights are apparent. In this paper, a novel model is presented with a simple closed form formula, which shows the extra jitter, due to multiple crossing, adds a term that increases as a function of the fourth power of the noise strength/slew rate ratio. The formula is applied to a real life practical low slow rate/high noise ring oscillator which finds application, for example, in random number generator implementation. Corresponding transistor level simulation results agree reasonably well with the model. Furthermore, it is shown that, on example designs, the last passage time approach in this paper can lead to time jitter that is 100 % larger than that due to conventional first passage time model.     

Adaptive Step-Size Natural Gradient ICA Algorithm with Weighted Orthogonalization

To improve the stability of the traditional natural gradient independent component analysis (ICA) algorithm and the accuracy of its separated results, a adaptive step-size natural gradient ICA algorithm with weighted orthogonalization is proposed. First, to take advantage of the pre-whitening pre-processing and keep the equivariance property of the ICA algorithm, based on the weighted orthogonal constraint on the separating matrix without pre-whitening of observed signals, weighted orthogonalization is introduced after the traditional gradient update. Then, according to the error estimation from the smoothed distance between separated outputs and optimal outputs, we obtain two adaptive step sizes based, respectively, on an unconstrained natural gradient ICA process and a weighted orthogonalization process. Simulation experiment results show that the speed of convergence of the adaptive step-size natural gradient ICA algorithms with weighted orthogonalization are faster than the traditional one; also, the stability of the algorithms and the accuracy of the separated results are improved observably.