基于循环前缀的OFDM同步算法研究与FPGA实现

提出了一种基于循环前缀的符号同步算法。此算法在最大似然估计的基础上加以改进,简化了符号同步中相关运算的判决方法,在保持同步效率的同时,极大地节约了硬件资源,使算法更易于硬件实现。改进算法基于IEEE 802.11a的标准提出,通过Matlab仿真分析其性能,并在FPGA硬件平台上实现,利用ChipScope观测得到波形。实验结果表明,电路系统工作可靠,满足设计要求。     

基于FPGA的单精度浮点数乘法器设计

设计了一个基于FPGA的单精度浮点数乘法器。设计中采用改进的带偏移量的冗余Booth3算法和跳跃式Wallace树型结构,并提出对Wallace树产生的2个伪和采用部分相加的方式,提高了乘法器的运算速度;加入对特殊值的处理模块,完善了乘法器的功能。本设计在AlteraDE2开发板上进行了验证。     

基于CPCI总线的测井数据采集板卡的设计

介绍了一种基于CPCI总线的测井数据采集智能IO板卡的设计,包括数据采集、数据处理、板卡自诊断等功能。板卡结合具体应用环境设计滤波电路对敏感干扰信号进行有效的滤除,使用高性能A/D、FPGA和DSP做数据采集处理,高带宽CPCI总线进行传输数据,为测井数据采集设计提供了一套可行的硬件设计方案。     

电力线通信中动态子载波组分配

针对电力线通信自适应OFDM系统的限制条件,探讨在每OFDM符号内各RT用户要求的约束下,研究系统总功率地窖注水分配后多子载波上的速率自适应子载波分配模型,提出一种新的动态子载波组分配算法。在典型电力线信道环境下对其仿真,并与另外两种分配算法进行比较,结果表明,本文动态子载波组分配算法的复杂度大大减小,能满足多用户资源分配的多目标要求。     

Analysis of maintenance policies for finite life-cycle multi-state systems

Maintenance policies for multi-state systems (MSS) are often analyzed under infinite horizon assumptions. In practice, it is important to consider maintenance policies under a finite horizon because the life cycles of most systems are finite. In this paper, we consider a finite life-cycle MSS that is subject to both degradation and Poisson failures. We study two classes of maintenance policies – preventive replacements and corrective replacements, and their effectiveness in controlling the customer’s expected discounted maintenance cost (EDMC). For both policies, replacement decisions are modelled via two control parameters – a threshold on the current system state and a threshold on the residual life cycle, which is measured as the time span from present to the end of life cycle. We derive close-to-explicit forms of the cost models under each of the policy. Methodologies for optimizing the maintenance thresholds are further proposed. Computational results verify that preventive replacements outperform corrective replacements typically when the downtime cost per failure is relatively high compared to the repair cost.     

Representation of functional micro-knowledge cell (FMKC) for conceptual design

The conceptual design process of a complex product concerns multidisciplinary design knowledge. This paper presents an approach of consistent knowledge representation for conceptual design. Firstly, the concept of functional micro-knowledge cell (FMKC) is presented, and the knowledge representation approach of FMKC is proposed. In the function layer, the functional ontology is used to provide a rich vocabulary. By constructing the mapping relationships between the function and structure layer, a systematic knowledge representation scheme is obtained. Secondly, the functional knowledge decomposition theory is proposed to unify the resolution of knowledge representation. Finally, the FMKC is applied to a hydraulic cylinder, which demonstrates the possibility in representing the multidisciplinary knowledge for conceptual design with a unified systematic representation scheme. In addition, the FMKC can be used in knowledge fusion and design reuse for our further study.     

Feedback-free rate-allocation scheme for transform domain Wyner–Ziv video coding

In most existing Wyner–Ziv video coding schemes, a feedback channel (FC) is expected at the decoder in order to allocate a proper bit rate for each Wyner–Ziv frame. However, FC not only results in additional latency but also increases decoding complexity due to the several feedback-decoding iterations. Moreover, FC may be unavailable in many practical video applications. In this paper, we propose a novel feedback-free rate-allocation scheme for transform domain Wyner–Ziv video coding (TD-WZVC), which predicts the rate for each Wyner–Ziv frame at the encoder without significantly increasing the complexity of the encoder. First, a correlation estimation model is presented to characterize the relationship between the source frame and the reference frame estimated at the encoder in TD-WZVC. Then, an efficient FC-free rate-allocation algorithm is proposed and a linear model is built to avoid both overestimation and underestimation of the real rate and obtain an optimal rate-distortion performance. Experimental results show that the proposed scheme is able to achieve a good encoder rate allocation while still maintaining consistent coding efficiency.     

反汇编过程中call指令后混淆数据的识别

恶意程序往往使用各种混淆手段来阻碍静态反汇编,call指令后插入数据便是常用的一种,对该方式的混淆进行研究,提出一种有效的识别call指令后混淆数据的方法。该方法基于改进的递归分析反汇编算法,分两阶段对混淆进行处理。经测试验证,该方法可有效地对此种混淆做出判断,提高反汇编的准确性。     

网格计算中费用约束的最优时间调度算法

在网格资源处理速度和资源价格异构的网格环境下,讨论基于用户费用约束的最优时间调度问题,提出一种相应的调度算法,将该任务调度问题转化为线性规划问题,采用单纯形算法获得近似最优解,从而获得费用约束下资源的最优执行时间以及该任务的最小完成时间。仿真结果表明,该算法的性能优于其他同类算法。     

基于绝对最小Lipschitz延拓的图像编码算法

提出一种基于图像水平集绝对最小Lipschitz延拓(AMLE)的图像编码方法。该算法在原有AMLE算法的基础上,保留图像水平集的边界数据,采用逐层处理方法实现图像重构。实验结果表明,其峰值信噪比高于原有AMLE算法,取得了更好的视觉效果。