基于奇异值分解与KL变换的数字水印算法

数字水印是数字产品保护的一种新技术,近年来已在国内外引起了广泛的关注.本文在结合K-L变换和奇异值分解(SVD)特征的基础上,利用图像信号自身特性,提出了一种多功能水印嵌入算法,仿真实验结果表明,该方法具有较好的透明性与鲁棒性,尤其在抗图像几何操作、有损压缩方面表现出良好的稳健性.     

基于分簇的无线多媒体传感器网络数据聚合方案研究

该文提出了一种基于分簇的无线多媒体传感器网络(WMSNs)数据聚合方案(Cluster-based Data Aggregation Algorithm, CDAA)。利用新的分簇方法和数据聚合策略,CDAA可以有效延长网络生命期。根据多媒体节点数据采集的方向性和节点剩余能耗,该文提出新的无线多媒体传感器网络的分簇方法,并基于该分簇方法进行网内多媒体数据聚合。仿真结果表明,该方法能够有效减少冗余数据的传送,与LEACH, PEGASIS等传统WSNs路由协议和针对WMSNs的AntSensNet协议相比,在能耗均衡和节能方面表现出更好的性能。     

Reversible data hiding based on hybrid prediction and interleaving histogram modification with single seed pixel recovery

This paper proposes a reversible data hiding scheme for natural images. A hybrid prediction mechanism is utilized in order to produce prediction errors as many as possible. The cover image excluding a seed pixel is partitioned into four non-overlapping segments, and four predictors are tailored for each of them. As a result, most prediction errors concentrate around zero in prediction error histogram. Besides, an interleaving histogram modification mechanism is presented such that the capacity is enhanced and easier to be finely tuned in contrast to some previous approaches. Third, a single seed pixel recovery strategy is introduced. Experimental results show the effectiveness of the proposed method.     

CLTC: a cluster-based topology control for ad hoc networks

The topology of an ad hoc network has a significant impact on its performance in that a dense topology may induce high interference and low capacity, while a sparse topology is vulnerable to link failure and network partitioning. Topology control aims to maintain a topology that optimizes network performance while minimizing energy consumption. Existing topology control algorithms utilize either a purely centralized or a purely distributed approach. A centralized approach, although able to achieve strong connectivity (k-connectivity for k /spl ges/ 2), suffers from scalability problems. In contrast, a distributed approach, although scalable, lacks strong connectivity guarantees. We propose a hybrid topology control framework, cluster-based topology control (CLTC) that achieves both scalability and strong connectivity. By varying the algorithms utilized in each of the three phases of the framework, a variety of optimization objectives and topological properties can be achieved. In this paper, we present the CLTC framework; describe topology control algorithms based on CLTC and prove that k-connectivity is achieved using those algorithms; analyze the message complexity of an implementation of CLTC, namely, CLTC-A, and present simulation studies that evaluate the effectiveness of CLTC-A for a range of networks.     

A new shared AWG-based OCDMA scheme implemented with time-spreading and wavelength-group-hopping embedded M-sequence code

This paper exploits the inherent cyclic and periodic free-spectral-range (FSR) properties of arrayed-waveguide grating (AWG) routers to construct a two-dimensional (2D) time-spreading and wavelength-group-hopping embedded M-sequence code for optical multiple-access networks. In the proposed codecs (encoder/decoder), a fine arrayed-waveguide grating (AWG) is used to generate an M-sequence code pattern, which is then spread in the wavelength domain by multiple coarse AWGs. The signals produced at the output ports of the coarse AWGs are then spread in the time domain using optical delay lines. The 2D code is evaluated in terms of its correlation, bit-error-rate (BER) and cardinality characteristics. It is shown that the TS/GH embedded M-sequence code yields a significant improvement in both the BER and cardinality performance of the optical multiple-access networks compared to that obtained using conventional prime-hop code (PHC), modified prime-hop code (MPHC), Barker and Walsh-based bipolar–bipolar sequence.     

三相共补复合开关的研制

功率因素过低对电网及负载有极大负面影响,在感性负载两端并接电容是常见的无功补偿方法。针对电磁开关和电力电子开关投切电容器在无功补偿装置应用中存在的问题,从分析功率因素补偿意义入手,提出三相共补开关拓扑结构及其电路模型,分析投切过程冲击电流形成机理及其避免对策。研制了一种基于AVR单片机在电压过零时投切并应用于低压无功补偿装置的复合开关。该复合开关的优点是电压过零时投切,冲激电流小;每相过零时触发中断,响应迅速快;采用了atmega16作为主控芯片,样机测试果表明达到设计之要求。     

On delay constrained CAC scheme and scheduling policy for CBR traffic in IEEE 802.11e wireless LANs

CBR (constant bit rate) traffic is expected to be an important traffic source in wireless networks. Such sources usually have stringent jitter or delay requirements and in many cases they should be delivered exactly as they were generated. In this paper, we propose a strictly guaranteed QoS (quality‐of‐service) provisioning CAC (call admission control) scheme with a polling‐based scheduling policy for CBR traffic in IEEE 802.11e wireless LANs. Under such a scheme, the proposed transmit‐permission policy for HCCA (HCF controlled channel access) method can forecast the maximum suffered delay for each packet and derive sufficient conditions so that all the CBR sources satisfy their time constraints to provide deterministic QoS guarantees. A simple analytical model is carried out to estimate the average queueing delay of the proposed scheme. In addition to theoretical analysis, simulations are conducted to validate its promising performance. Our simulation results show that the proposed scheme maintains a high throughput with respect to the whole range of system load. Copyright © 2009 John Wiley & Sons, Ltd.     

Fuzzy working state evaluating function and its algorithm for analogue circuits

The working state(WS) evaluation is a valuable task in the process of failure diagnosis in the analogue circuits. A fuzzy evaluating algorithm was proposed to quantify the working condition of analogue circuit regarded as fuzzy system. Several familiar WS evaluating functions based on fuzzy membership functions were also proposed to calculate the local working state indexes(WSI) of each node in an analogue circuit. The decision function combined with the WS evaluating functions is used to synthesize all the local WSI to the global WSI of the whole circuit. An example was presented to verify that the working status of the analogue circuits can be described by the new WS evaluating algorithm and the global WSI objectively and accurately.     

基于信令测试数据支撑移动互联网形势下自有业务营销研究

传统通信时代,公司大抵都是围绕语音/短信进行的业务发展,支撑手段也常来自对用户自身通话行为、套餐属性等进行的分析。而进入移动互联时代之后,运营商除了继续保有原有的传统业务,更是大力发展了自有的移动互联网业务。在自有移动互联网业务的发展过程中,我们越发感觉基于传统的用户通话行为、基本套餐等数据的分析对自有互联网业务支撑乏力。最大的局限莫过于对用户在移动互联网上的行为分析,如对业务的喜好,上网规律等,这些行为是传统数据无法支撑的,而这些数据恰恰对于发展公司自有业务具有极其重要作用。通过对信令测试数据中用户的互联网行为进行了分析、建模,支撑新形势下的自有业务互联营销。     

改进的萤火虫群优化算法及其非线性盲源分离

摘要：根据萤火虫算法的特点,针对萤火虫算法较早进入局部收敛的不足进行改进,引入了“挡板效应”的方法,扩大种群多样性,并提出了BGSO算法。在分析了非线性盲源分离模型的基础上,利用系统两次遍历萤火虫群,比较评价函数,获得最优解的方式。其有效性被仿真结果所证实。