基于集员滤波的宽带有源噪声控制算法

子带结构是提高宽带噪声控制的有效方法,归一化子带自适应滤波(NSAF)结构消除了传统子带结构在输出端产生混叠分量的问题,但由于在每个子带上采用相同的全带自适应滤波器,使得计算量高于传统子带结构,集员滤波(SMF)技术具有数据选择更新的特点,可有效降低计算量,且在收敛速度和稳态均方误差之间具有较好的折中性。在此引入集员滤波技术,建立基于NSAF结构的无延迟前馈有源噪声控制系统,降低计算量,最后仿真验证了该算法对宽带噪声具有更优的降噪效果。     

A genetic strategy to design cellular automata based block ciphers

We propose an evolutionary computation approach to design a fast and secure block cipher using non-uniform second-order cellular automata. We build a flexible block ciphering model that permit the construction of a huge space of possible instances defined each one by a finite set of elementary transition rules. The constructed space is explored using a genetic algorithms strategy in order to find an optimal solution with respect to the strict avalanche criterion used as fitness measurements. The genetically designed cipher is benchmarked experimentally using conventional statistical tests, and shown to have very admissible characteristics leading to a very acceptable level of cryptographic security. Moreover, performances analysis shows that the designed cipher permit to achieve a high encryption/decryption speed, and compete many of the existing standardized ciphers.     

入口速度分布对后台阶流动模拟的影响研究

为深入研究台阶入口速度分布情况对后台阶流动的影响,利用Fluent软件,分别使用S-A和标准κ-ε两种湍流模型,将不同的速度分布情况作为速度入口条件,对后台阶流动进行数值仿真计算,研究了入口条件差异导致的水平速度曲线在近壁面处的凸起情况,并将计算结果与试验数据和已有研究成果进行比较。结果表明,两种湍流模式下,在附着点距离和速度分布曲线上均存在普遍而明显的差异,且这种差异受入口条件影响较大,进而得出了合理的速度入口条件,能有效减小计算结果与试验结果的误差,对理论分析和工程应用均具有参考意义。     

Influence of abnormal stress under a residual bearing coal pillar on the stability of a mine entry

Mine entries close to residual bearing coal pillars(RBCPs) will suffer large deformation that may cause rock burst. To better understand the deformation mechanism and develop safe and practical guidelines for entry design, most studies focus on the absolute size of the stress field in and around the pillar. In this paper, we present a new approach to analyze the abnormal stress field close to a RBCP that uses the stress concentration coefficient(SCC), stress gradient(SG), and coefficient of lateral pressure(CLP) to describe the stress state induced by the RBCP. Based on elastic theory and a mathematical model for the abutment stress in the RBCP, an analytical solution for the abnormal stress in the strata below the RBCP was derived and the characteristics of the abnormal stress for a case study of a coal mine in China were analyzed. The results show that the abnormal stress field around the pillar is characterized by four distinct zones: a zone of high SCC, high SG, and CLP less than 1, a zone of high SCC, low SG, and CLP less than 1, a zone of low SCC, SG close to 0, and CLP greater than 1, and a zone of SCC close to 1, SC close to 0, and CLP close to 1. Based on this zoning pattern, a numerical model was established to study the combined effects of the abnormal stress on the stability of the entry. The most stable zone was determined based on a model of the Xinrui coal mine and verified by field measurements at the mine. Our conclusions can be used as guidelines for designing safe entry layouts in similar geological and mining settings.     

自悬浮定向流法制备纳米Fe微粒的粒度控制

采用自悬浮定向流技术制备了金属Fe纳米微粒，对样品平均粒度进行TEM等测试分析，研究了主要制备工艺条件对微粒粒径的影响。结果表明，自悬浮定向流技术可用以制备出不同粒度的金属Fe纳米微粒，其平均粒径随熔球温度的降低和冷却气体流速的增大而减小;在1500℃左右时，微粒平均粒径随冷却惰性气体Ar压强的增大而减小，而在1600℃时，气体压强对微粒平均粒径的影响不再具有规律性。     

A new linear time algorithm to compute the genomic distance via the double cut and join distance

The genomic distance problem in the Hannenhalli–Pevzner (HP) theory is the following: Given two genomes whose chromosomes are linear, calculate the minimum number of translocations, fusions, fissions and inversions that transform one genome into the other. This paper presents a new distance formula based on a simple tree structure that captures all the delicate features of this problem in a unifying way, and a linear time algorithm for computing this distance.     

网格GIS研究

本文概述了网格（GRID）出现的技术背景、网格（GRID）发展现状及其对地理信息服务的影响。重点阐述了GRIDGIS的关键技术。     

公路工程土石方调配及造价计算的探讨

文章分别介绍了公路工程中土石方数量的正确计算、土石方的合理调配、土石方工程数量的摘取、土石方定额套用及造价计算。     

燃气活塞式弹翼展开动力系统内弹道性能分析

为了给某型燃气活塞式弹翼展开动力系统的研制和改进提供理论依据,根据弹翼展开机构的具体结构,考虑展开动力系统与展开执行机构之间的耦合联动关系及弹翼展开过程中的气动负载等,建立了该动力系统的内弹道性能分析模型并完成了性能计算,将计算结果与试验数据进行了对比分析,两者基本吻合.研究结果表明,该模型可为工程实践提供理论支持.     

并行计算在垂直发射火箭弹转弯过程中的应用

火箭弹垂直发射转弯过程是非线性动力学过程,为解决巨型规模的最优弹道解算问题,研究了分布式并行计算方法,建立了最优弹道的并行求解模型,研制了专用仿真软件.仿真分析结果表明:在满足一定的参数精度要求的情况下,最优控制弹道问题具有极好的并行性,分布式并行计算可显著提高计算效率,问题的求解时间随并行机节点数的增加而成比例的缩短.