船载光电成像三轴自主稳定平台控制回路设计

船载光电成像稳定平台为舰船在高速及恶劣海况下进行光电成像侦察提供了基础条件,近年来光电平台结构越来越复杂,要求的稳定精度越来越高,为了提高平台稳定精度,必须选择合适的结构方案并进行合理的控制回路设计;文中介绍了稳定平台的几种框架形式,从稳定原理方面分析了各自的特点,指出三轴稳定平台系统是最佳的选择方案,在此基础上对三轴自主稳定平台伺服稳定控制回路进行了设计,仿真结果表明在选择合适的超前-滞后网络后,系统的隔离度达56db,稳定性能满足使用要求。     

利用反馈的车牌字符分割算法

字符分割是车牌识别系统的重要步骤。提出一种利用反馈的车牌字符分割算法。首先,对车牌图像进行预处理;其次,根据车牌图像的垂直投影进行字符粗分割;最后,通过两级反馈进行字符精分割。第一级反馈是字符个数与字符宽度反馈,第二级反馈是字符识别反馈。实验结果表明,算法对光照不均、对比度较小、倾斜、污迹、字符粘连和断裂等严重退化的车牌图像具有很好的字符分割性能。     

Efficient and provably secure password-based group key agreement protocol

This paper considers the issue on authenticated group key agreement protocol among n users broadcasting communication over an insecure public network. Many authenticated group Diffie-Hellman key agreement protocols have been proposed to meet the challenges. However, existing protocols are either limited by the use of public key infrastructure or by their scalability, requiring O(n) rounds. To overcome these disadvantages, we propose an efficient password-based group key agreement protocol resistant to the dictionary attacks by adding password-authentication services to a non-authenticated multi-party key agreement protocol proposed by Horng. The proposed protocol is very efficient since it only requires constant rounds to agree upon a session key, and each user broadcasts a constant number of messages and only requires four exponentiations. Under the Decisional Diffie-Hellman assumption, we will show the proposed protocol is provably secure in both the ideal-cipher model and the random-oracle model.     

Design and fabrication of an electrostatically suspended microgyroscope using UV-LIGA technology

A micromachined electrostatically suspended gyroscope, with a wheel-like rotor housed by top stator and bottom stator, using UV-LIGA microfabrication technology, was presented. The designed structure and basic operating principle of the gyroscope are described. The key steps in the fabrication process, such as wet etching of Pyrex glass pits for soldering, and integration of thick nickel structures by removal of SU-8 mold, were considered in detail and well solved. Cr/Pt/photoresist was used as etching mask and the etched pits, in depth of near 30 μm, with aspect ratio (depth to undercutting) of 0.75, were obtained. With metal foundations constructed for consolidation, successful integration of the nickel structures, in thickness of 200 μm, was achieved by successful removal of the SU-8 mold using oleum. After the two stators and the rotor were fabricated separately, they were assembled and soldering bonded to form axial and radial small gaps, hence, the initial prototype of the microgyroscope was realized. The key techniques described in this paper can be applied to fabrication of other micro devices. The metal foundation method, associated with removal of SU-8 mold by oleum, is expected to make SU-8 wider applications in making integrated microstructures with fabricated circuitry on the same chip.     

Robust admissibility and admissibilisation of uncertain discrete singular time-delay systems

This paper is concerned with the characterisation of robust admissibility and admissibilisation for uncertain discrete-time singular system with interval time-varying delay. Considering the norm-bounded uncertainty and the interval time-varying delay, a new comparison model is introduced to transform the original singular system into two connected subsystems. After this transformation, a singular system without uncertainty and delay can be handled by the Lyapunov–Krasovskii functional method. By virtue of the scaled small gain theorem, an admissibility condition of the original singular system is proposed in terms of linear matrix inequalities. Moreover, the problem of robust admissibilisation of uncertain discrete singular time-varying system is also studied by iterative linear matrix inequality algorithm with initial condition optimisation. Several numerical examples are used to illustrate that the results are less conservative than existing ones.     

Multiple-mode adaptive state estimator for nonlinear switched systems

This paper deals with the issue of state estimator design for nonlinear switched systems. A multiplemode adaptive estimator is proposed under mode-dependent average dwell time (MDADT) switching, and the switching signal with MDADT constraint is also obtained to guarantee the exponential stability of estimation error dynamics, where the Lipschitz constant may be unknown since it is adaptively adjusted by designing an adaptation law. Based on both Lyapunov stable theory and the feasible solution of an optimization problem with linear matrix inequality constraint, the gain matrices and switching signals are provided, respectively. The sufficient conditions of the existence of multiple-mode adaptive switched estimator are also derived. Meanwhile, the above methods are also extended to the case of the average dwell time (ADT) switching, and an algorithm is given to summarize the implementation of the proposed estimators. Finally, the effectiveness of the designed methods is illustrated by simulation examples.     

The Ground Process Segment of SAR Altimeter

The key innovation technology of SAR Altimeter (Synthetic Aperture Radar Altimeter)are Doppler\|beam sharpen and delay/Doppler range compensation.The cooperation of these two technologies makes it has high along track resolution and high precision in height measurement.The ground processor is the key hinge to make sure that SAR altimeter could obtain these superiorities.Many key technologies for SAR altimeter processor,such as Doppler beam\|sharpen,delay/Doppler compensation and the second range correction,multilook,echo model and gradient function for retracker,are introduced in the paper.Based on the processor and related work,some simulation work and airborne experiment were tested by the processor,and both of the quantity results show that the SAR altimeter has more potential superiorities.     

Exploring the wild birds’ migration data for the disease spread study of H5N1: a clustering and association approach

Knowledge about the wetland use of migratory bird species during the annual life circle is very interesting to biologists, as it is critically important in many decision-making processes such as for conservation site construction and avian influenza control. The raw data of the habitat areas and the migration routes are usually in large scale and with high complexity when they are determined by high-tech GPS satellite telemetry. In this paper, we convert these biological problems into computational studies and introduce efficient algorithms for the data analysis. Our key idea is the concept of hierarchical clustering for migration habitat localizations, and the notion of association rules for the discovery of migration routes from the scattered location points in the GIS. One of our clustering results is a tree structure, specially called spatial-tree, which is an illusive map depicting the breeding and wintering home range of bar-headed geese. A related result to this observation is an association pattern that reveals a high possibility that bar-headed geese’s potential autumn migration routes are likely between the breeding sites in the Qinghai Lake, China and the wintering sites in Tibet river valley. Given the susceptibility of geese to spread H5N1, and on the basis of the chronology and the rates of the bar-headed geese migration movements, we can conjecture that bar-headed geese play an important role in the spread of the H5N1 virus at a regional scale in Qinghai-Tibetan Plateau.     

多现场总线接口智能仪表设计

在不同现场总线的产品共存的自动化系统中,如何使新兴智能仪表与原有现场设备或未来更新设备在通信方面相兼容,已经成为一个现实问题.为此,提出了智能仪表中多现场总线接口技术.从硬软件方面研究了智能仪表中MODBUS、PROFIBUS和CANBUS三种现场总线通信接口,重点分析了设计中的关键问题,并结合电工仪表产品实现了三种现...     

一种基于码本聚类的低复杂度用户选择算法

现有块对角化(BD)预编码系统用户选择算法较少考虑利用已选用户与剩余用户之间的关系来排除不可选用户.针对这点不足,给出了一种采用码本聚类的低复杂度用户选择算法( CodeGreedy算法).该算法采用弦距离刻画用户信道的相关性,以此为依据将用户划分到不同码本空间中,聚集在同一码本空间的用户信道具有较强的相关性,形成互斥...