基于定位导航系统的改进无线节点空间定位算法

提出了一套针对无线节点空间定位的修正算法.首先提出了一种抽样后求点估计的方法,消除了GPS信息误差造成的影响,然后通过分治法的策略来选取锚节点,保证锚节点的可靠性,普通节点可以通过锚节点与本身进行定位求概率分布,继而修正拓扑,最后通过一个竞争机制来进行有序的网络拓扑坐标修正.实际测试达到了预期的效果.通过该算法,可以在较低功耗下将无线传感网络的定位精度提高,使得无线传感网络能够适应高定位精度的要求.     

Optimization of gear ratio and power distribution for a multimotor powertrain of an electric vehicle

The architecture and design of the propulsion system of electric vehicles are highly important for the reduction of energy losses. This work presents a powertrain composed of four electric motors in which each motor is connected with a different gear ratio to the differential of the rear axle. A strategy to reduce energy losses is proposed, in which two phases are applied. Phase 1 uses a divide-and-conquer approach to increase the overall output efficiency by obtaining the optimal torque distribution for the electric motors. Phase 2 applies a genetic algorithm to find the optimal value of the gear ratios, in which each individual of each generation applies Phase 1. The results show an optimized efficiency map for the output torque and speed of the powertrain. The increase in efficiency and the reduction of energy losses are validated by the use of numerical experiments in various driving cycles.     

对广义映射混沌扩频序列的分割攻击

研究廖旎焕等人提出的广义映射混沌扩频序列算法（电子与信息学报,2006年第7期）,发现该算法所产生的混沌序列具有前几个值对密钥的低位比特变化不够敏感的性质,提出一个能有效降低密钥熵的分割攻击方法。在密钥长度为64bit且参数d=3,h=0时,该分割攻击方法的成功率为0．9797,平均计算复杂性约为2^43.46,可在PC上实现。     

基于分治的属性约简复杂性分析

属性约简是粗糙集理论研究的主要内容之一,该文采用了分治策略,提出了一个新的属性约简方法,将计算整个全域上的属性约简问题转化为计算相应划分的子区域上属性约简问题。将原有计算POSX0(Y)的算法复杂度O(｜A｜｜U｜2)犤4犦降为O(｜A｜(｜Y1｜2+｜Y2｜2+……+｜Yn｜2)),对于一般比较大的｜U｜来说,明显地提高了属性约简可计算性和计算效率。     

对自同步混沌密码的分割攻击方法

本文分析了自同步混沌密码的信息泄漏规律,并据此提出了对自同步混沌密码的分割攻击方法.由于能够利用所有时刻的已知明文进行攻击,因而自同步混沌密码比同步混沌密码的抗分割攻击能力更弱.本文以Hong Zhou等提出的自同步混沌密码为例,完成了对密钥规模为64比特且以混沌映射的65次迭代为自同步映射的自同步密码的分割攻击.利用1万个已知明文,在主频为2.5GHz的Pentium-4 PC上,攻击的平均时间为25小时22分,成功率为0.86.     

An Efficient Algorithm for Ray Tracing

This paper presents a new algorithm that performs more efficient ray tracing compared to existing algorithms. This algorithm is based on the divide-and-conquer technique well known from the area of lists sorting, and speeds up the intersections and light-visibility tests for the first hit. A new definition of transitive-between-relations (TBR) is introduced. A simple shooting ray guide is embedded into a conventional ray tracer to reduce the number of intersection tests and thus speed-up the first hit calculation and the associated light conditions tests. The algorithm was tested in environments made up of convex polygons (random triangles, linearly positioned pyramids) but it can be used in environments with other primitives.     

Hierarchical parallel processing of large scale data clustering on a PC cluster with GPU co-processing

This paper presents an effective scheme for clustering a huge data set using a PC cluster system, in which each PC is equipped with a commodity programmable graphics processing unit (GPU). The proposed scheme is devised to achieve three-level hierarchical parallel processing of massive data clustering. The divide-and-conquer approach to parallel data clustering is employed to perform the coarse-grain parallel processing by multiple PCs with a message passing mechanism. By taking advantage of the GPU’s parallel processing capability, moreover, the proposed scheme can exploit two types of the fine-grain data parallelism at the different levels in the nearest neighbor search, which is the most computationally-intensive part of the data-clustering process. The performance of our scheme is discussed in comparison with that of the implementation entirely running on CPU. Experimental results clearly show that the proposed hierarchial parallel processing can remarkably accelerate the data clustering task. Especially, GPU co-processing is quite effective to improve the computational efficiency of parallel data clustering on a PC cluster. Although data-transfer from GPU to CPU is generally costly, acceleration by GPU co-processing is significant to save the total execution time of data-clustering.     

改进的隐私保护关联规则挖掘算法

数据挖掘技术可以从收集到的大量数据集中挖掘出潜在的知识,这就可能把涉及到个人隐私的信息挖掘出来,从而产生了隐私保护下的数据挖掘。首先分析了国外学者Rizvi提出的隐私保护关联规则挖掘算法MASK,然后使用分治策略对MASK进行了改进。时间复杂度分析和实验结果均表明,对MASK算法的改进是有效的。     

An Efficient Algorithm to Generate Prime Implicants

In this paper, an efficient recursive algorithm is presented to compute the set of prime implicants of a propositional formula in conjunctive normal form (CNF). The propositional formula is represented as a (0,1)-matrix, and a set of 1's across its columns are termed as paths. The algorithm finds the prime implicants as the prime paths in the matrix using the divide-and-conquer technique. The algorithm is based on the principle that the prime implicant of a formula is the concatenation of the prime implicants of two of its subformulae. The set of prime paths containing a specific literal and devoid of a literal are characterized. Based on this characterization, the formula is recursively divided into subformulae to employ the divide-and-conquer paradigm. The prime paths of the subformulae are then concatenated to obtain the prime paths of the formula. In this process, the number of subsumption operations is reduced. It is also shown that the earlier algorithm based on prime paths has some avoidable computations that the proposed algorithm avoids. Besides being more efficient, the proposed algorithm has the additional advantage of being suitable for the incremental method, without recomputing prime paths for the updated formula. The subsumption operation is one of the crucial operations for any such algorithms, and it is shown that the number of subsumption operation is reduced in the proposed algorithm. Experimental results are presented to substantiate that the proposed algorithm is more efficient than the existing algorithms.