基于改进KNN算法的AVS到H.264/AVC 快速转码方法

尽管音视频编码标准(Audio and Video Coding Standard,AVS)的编码性能可以与H.264相媲美,但是H.264的应用范围更加广泛,因此视频由AVS标准转码成H.264标准具有很大的应用前景.目前,主流的转码方法是将AVS的分块模式与H.264的分块模式映射的方式降低转码复杂度,但是技术之间的差异导致这两种标准之间的分块模式并不是一一映射的关系,因此会导致编码效率大幅度降低.提出一种基于改进KNN(K最邻近节点)算法的AVS到H.264/AVC快速转码方法.充分利用了AVS码流中的各种信息,通过改进的KNN算法建立了中间信息和H.264分块模式之间的映射模型.根据AVS中运动矢量信息的差异自适应确定H.264可能的分块模式,实验结果表明上述问题得到有效解决,该算法在保证H.264编码效率的前提下大幅降低了转码复杂度.     

多元LDPC码列分层DBC译码算法

针对多元LDPC码扩展最小和（Extended Min Sum,EMS）译码算法收敛速度慢、运算复杂度高的问题,提出一种多元LDPC码列分层动态检泡（Dynamic Bubble-Check,DBC）译码算法。首先对变量节点按不同列重进行分层处理,译码时率先更新列重较大分层的变量节点消息,不同层之间采用串行方式进行消息传递,通过并串结合的方式降低译码迭代次数。在校验节点消息更新过程中,采用动态检泡方法减少EMS算法中的运算量,降低算法复杂度。仿真结果表明,在几乎不损失性能的前提下,该算法的平均最大迭代次数仅为EMS译码算法的50%,复杂度降低为EMS算法的50%。     

基于蝗虫优化算法变论域模糊PI的PMSM矢量控制

永磁同步电机是一个多变量、强耦合、非线性和变参数的复杂控制对象,采用传统的PI控制很难满足现代工业的控制要求。为了获得较好的控制性能,在标准模糊PI控制的基础上,提出了一种蝗虫优化算法和变论域模糊PI相结合的控制方法。首先,介绍了蝗虫优化算法和变论域模糊PI控制的基本原理;然后,阐述了蝗虫优化算法变论域模糊PI转速控制器的设计过程,根据系统偏差在线调整模糊控制的论域;最后,搭建了基于dSPACE的永磁同步电机矢量控制系统的半实物平台,对提出的控制方法进行了实验验证。结果表明,相比于标准模糊PI控制,所提出的控制方法提高了系统的动态响应速度和鲁棒性。     

Pseudo‐3D RSSI‐based WSN localization algorithm using linear regression

Receiver Strength Signal Indication based Wireless Sensor Networks offer a cheap solution for location‐aware applications. For a final breakthrough these systems need fast deployment and easy auto‐configuration. In this study, we use the real‐life iMinds test bed to expand a two‐dimensional localization algorithm to the pseudo third dimension with very low additional computational time. Our experiments show that this fast three‐dimensional algorithm has no outliers and avoids manual calibration. Our algorithm has lower position errors than a maximum likelihood algorithm with a mean square error cost function. Furthermore, with non‐parametric statistical tests, we show that our previously designed two‐dimensional preprocessing performs equally well in pseudo‐three dimensions: the preprocessing reduces the position error in a statistically significant way.Copyright © 2013 John Wiley & Sons, Ltd.     

Genetic algorithm optimization in building portfolio management

A significant proportion of building investment expenditure goes to replacement expenditure for organizations owning a large building stock or portfolio. Over the years, researchers have attempted to develop asset replacement models to aid decision-making in building portfolio management, based upon' a statistical or an heuristic approach. This study attempts to use genetic algorithms to develop models for forecasting long term asset replacement strategies, aiming at smoothing fluctuations of expenditure and resource requirements, and most importantly minimizing the total maintenance and replacement costs. Scenarios are presented to demonstrate how these can be achieved. Further refinement for practical application of the models is also presented.     

自身形状优化原则:薄壁型材截面承载力的优化

为实现经济效益,已对大批量生产的钢结构产品的优化进行了广泛研究。旨在不削弱结构构件的强度和实用性的条件下,尽量减少材料的用量。当前研究主要集中于传统截面形状主要尺寸的优化,而并未考虑采用新的最佳截面。介绍了一种新的优化方法,利用遗传算法(GA)的进化和自适应特点,使截面的自身形状达到最佳效果。采用该方法对薄壁型材的截面承载力进行优化,验证了该方法的可行性和精确性。特别地,通过简单参数对截面的优化方法中,这种分析方法是众所周知的,即双轴对称闭口截面的优化。结果表明,经过几代演化,截面自身形状产生出精确的最优解。给出了影响收敛的因素。该方法可推广至冷弯型钢开口截面柱的优化。     

An investigation into the thermal transport properties of PP/EPDM/clay nanocomposites using a new combined experimental/numerical method

This research work is devoted to the study of the thermal transport properties of nanocomposites based on PP/EPDM/Clay (Polypropylene/Ethylene Propylene Diene Monomer/Clay). Six different formulations were designed and the corresponding nanocomposites (with 0, 2, 4 and 6% of clay) were prepared via melt mixing. To achieve the goals, densities, specific heat capacities and thermal conductivities were measured as function of temperature and nanocomposites compositions. A new and novel methodology was developed to determine the thermal conductivity which was based on an inverse heat transfer problem. First, assuming a linear relationship for thermal conductivity, the transient heat transfer equation in a solid specimen was numerically solved. The obtained temperature profile was used as the input to an optimisation technique based on genetic algorithm and the parameters of the thermal conductivity relationship were found. The results showed that the specific heat increases both with increasing of temperature and clay contents. It is also increased with the addition of the rubber to the blend. In all samples, the thermal conductivity decreases with increasing of temperature with a linear relationship. In addition, at relatively constant ratios of PP/EPDM, thermal conductivity of nanocomposite and its sensitivity increase with temperature rise. Moreover, at constant value of clay content, the thermal conductivity is decreased with increase of rubber content. The explanations to above findings were also presented and discussed.     

重型AT锁止阀的流量特性分析与优化

为了提高锁止阀开启中液动力的计算效率,通过动网格技术在流体动力学软件Fluent中模拟锁止阀的阀芯开启过程,在对阀口过流面积进行数值计算的基础上,分析其流量及流量系数随阀芯位移的变化情况。使用BP神经网络对随机抽样法获得的样本数据进行训练和预测,并对预测的结果进行准确性评估。最后,以BP神经网络预测的数学模型为基础,使用遗传算法对锁止阀节流槽参数进行优化。结果表明：优化后的锁止阀开启过程中流量-开度特性更加稳定,有利于提高锁止阀的工作性能。     

基于遗传算法的多级主压阀动态特性优化

多级主调压阀作为自动变速器液压控制系统的关键元件,其动态特性直接影响系统的快速性、稳定性和控制精度。在对阀进行结构参数优化时,先凭借经验对参数逐个调整再通过试验验证的方法,效率低且不能保证阀的性能最优。根据多级主压阀工作原理建立了多级主压阀数学模型;搭建多级主压阀Simulink仿真模型,通过分析多级主调压阀各结构参数对阀入口压力动态响应特性的影响,选取弹簧刚度、弹簧预压缩量和阻尼孔直径作为待优化变量;利用MATLAB优化工具箱中提供的遗传算法与Simulink结合对多级主调压阀的动态性能进行优化,并搭建试验台进行试验验证。仿真和试验结果表明：优化后多级主调压阀静态特性良好,负载流量突增时主压压力降低现象得到了改善,响应时间短,动态性能好。     

7500T大型压铸机增压阀块内流道流场仿真分析及优化

设计性能优良的阀块对提升液压系统性能具有重要意义。利用计算动力学方法对7500T大型压铸机增压阀块的流阻特性进行分析,计算得到两种不同压铸机增压阀块结构在不同流量时的压力损失。结果表明：增压阀块压力损失随着流量的增大呈现出近似线性增大的变化情况;加设倾斜流道的压力损失比没有倾斜流道的压力损失小,且减阻效果随着流量的增大而增大。利用正交试验建立了4因素5水平的正交试验数据库,对斜流道增压阀进行多参数单目标优化,然后基于遗传算法协同BP神经网络优化斜流道增压阀块之后,可使增压阀块的压力损失下降20%左右。