气液耦合系统中固有频率的实验研究

流体砰击现象广泛存在于海洋环境、航空航天等自然界与工程中.流体砰击大尺度结构过程中,自由液面破碎时会包裹气体进入流场,气液混合易导致局部砰击荷载增大,引起结构破坏的危险.砰击过程中,气室压力对自由液面固有模态的影响尚未有系统的研究报道.该文采用物理模型实验方法在二维储舱内设计并开展一系列实验,系统研究了两种不同的气室压力对耦合系统的固有频率和阻尼的影响.实验中采用高速摄影机记录了自由液面振荡过程,通过自主研制的图像处理软件提取自由液面波高.结果表明:在低气室压力下,晃荡能量主要集中于一阶固有频率;在高气室压力下,晃荡能量主要集中于二阶固有频率.随着气室压强的增大,影响液体晃荡的主要固有频率提高,而对应的阻尼比却随之降低.因此,气体可压缩性是研究流体晃荡的一个重要因素.     

利用遗传算法对生物质发电集料处理系统优化研究

遗传算法是一种基于生物选择与遗传机理的随机搜索与优化的方法,近年来解决了许多不同领域不同类型的优化难题.采用此方法就生物质发电过程中集料处理作业系统优化问题进行了研究.文中以获取最小生物质发电集料处理系统成本为目标,利用遗传算法对集料处理系统工序进行了优化设计,通过输入实际案例数据,得到的输出结果与试验结果一致,证明了设计的有效性.同时,通过测试不同参数取值对输出结果的影响,得到了最佳参数值.研究对于企业优化生产工艺、降低生产成本,对于政府审核生物质发电项目具有重大意义.     

用于铁磁谐振过电压故障辨识的VMD参数优化方法研究

准确辨识铁磁谐振故障可为启动消谐装置提供重要的依据,针对单相接地、弧光接地和铁磁谐振三种过电压故障频率混叠导致数据特征提取困难的问题,提出变分模态分解(Variational Mode Decomposition,VMD,VMD)的优化方法:首先分析各过电压故障信号的特征与区别,指出VMD参数对故障信号分解的影响;再利用NSGA-Ⅲ(Non-dominated Sorting Genetic AlgorithmⅢ,NSGA-Ⅲ)优化算法对VMD分量个数、惩罚因子等参数组合进行搜索,并依此确定变分模态分解算法的关键参数,利用参数优化变分模态分解算法对故障信号进行处理;最后,利用实际电网参数搭建过电压故障仿真模型,获得各种工况下的故障数据,并对故障信号进行提取,结果表明,利用NSGA-Ⅲ算法进行优化后的VMD在对故障信号进行特征提取,能够清晰的反映不同类型故障的特征,且对数据采样频率不敏感,与原有的VMD算法效果相比,能够更有效应用于各类故障的辨识.     

复杂物流系统订货点量建模与仿真优化

复杂物流系统是一个由若干个制造商、若干个批发商和若干个零售商组成的网状物流链.讨论了在不确定性环境下,采取周期性盘点策略的复杂物流系统中各实体订货点量的建模与仿真问题.作者认为,在分散控制策略和以零售商为核心的控制策略这两种情况下,可以通过建立基于模糊集合理论的复杂物流系统模糊分析模型来确定各实体的最佳订货点量,在此基础上运用作者所开发的复杂物流系统仿真工具CLSim对订货点量进行仿真优化,可以得到在物流链集成控制策略下的订货点量.文章的最后,通过一个实例对作者的上述观点进行了说明.     

多收费方式收费系统资源配置优化方法

随着ETC技术的发展,高速公路收费系统从单人工收费方式逐渐向多收费方式格局演变.同时高速公路收费系统的设计涉及到政府、道路管理者、道路使用者及道路非使用者之间利益的协调发展,因此研究在多收费方式情况下,满足不同利益层面需求的系统资源的优化配置问题具有重要意义.通过建立收费系统资源优化配置模型,在收费制式既定的情况下,利用遗传算法对收费站位置与数量进行寻优,并利用非集计方法对多收费方式情况下的车道配置进行均衡求解,可定量计算出最佳系统资源配置方案,包括确定收费制式、收费站位置与数量、收费方式、各收费站不同收费方式车道组合情况.最后我们进行算例研究,并对优化结果进行了分析比较,可为收费制式的选择及收费站的车道布设提供理论依据.     

公平偏好信息非对称下的信号传递博弈模型

采用信号传递模型来研究公平偏好信息非对称下零售商的甄选与合作问题.首先,对零售商公平偏好信息对称和非对称下供应商收益进行比较,得出零售商公平偏好信息非对称会引起逆向选择问题并损坏供应商收益.然后,分别设计了不同类型零售商信号传递成本相同、不同情况下的信号传递博弈模型来揭示零售商的真实公平偏好类型.最后,通过模型推理发现只有当不同类型零售商的信号传递成本不同时,信号传递模型才能起到揭示零售商类型的作用,从而解决公平偏好信息非对称引起的逆向选择问题.     

基于粒子群算法的太阳能热水器倾角优化设计

研究了带有辅助电加热的太阳能热水器的最优安装角度.对于真空管下方不带反射镜的热水器,通过分析其倾角和方向角与每天吸收的光能以及电加热器的耗电量之间的关系,将电加热器全年的用电量最小作为优化目标,解得最佳的安装倾角和方向角;对于带有反射镜的太阳能热水器,采用临界法并结合几何知识,求出真空管背面吸收的太阳能.基于粒子群算法计算得到山西省大同市不带反射镜的太阳能热水器的最佳安装倾角为53.49°,方向角为10.26°,用电量为149.80度;带有反射镜的太阳能热水器的最佳安装倾角为49.32°,方向角为10.33°,用电量为50,16度.结果说明带反射镜的太阳能热水器具有明显的节能效果.比较发现基于粒子群算法求得的两种情况下的用电量比应用两阶段搜索法求得的用电量分别减少了6.60度和8.59度.     

基于果蝇算法优化广义回归神经网络的矢量水听器的DOA估计

为了提高矢量水听器阵列对窄带信号的DOA估计精度,运用果蝇算法优化广义回归神经网络,通过对阵列协方差矩阵实值化,并提取信号子空间的基作为样本特征进行网络训练,构建了果蝇算法优化下的广义回归神经网络,实现了基于矢量水听器阵列的水下声源的DOA估计.仿真实验结果表明,方法泛化性能较好,能解决输入维数过大的问题,且运行时间短,DOA估计精度高,具有较强的工程应用价值.     

一个新混沌系统及错位投影同步通讯方案

提出了一个新的混沌系统,该系统含有五个参数,每个状态方程均含有非线性乘积项.通过理论推导,数值仿真,Lyapunov指数、Lyapunov维数、分岔图研究其基本的动力学特性,并分析了改变参数时系统的动力学行为的变化.本文研究了该系统的错位投影同步,设计了非线性控制器,实现了两个初值不同的新系统的错位投影同步.另外,将该系统及错位投影同步方法应用到保密通信中,基于改进的混沌掩盖通讯原理,在发送端使用新系统信号对信息信号进行加密及传送,最后在同步后的接收端不失真地恢复出有用信号.数值仿真表明所设计的新的混沌系统具有复杂的动力学特性,适用于保密通讯.     

基于改进小波阈值去噪算法的心电信号处理及仿真

为更好地滤除心电信号处理过程中基线漂移、肌电以及工频干扰等噪声,提出了一种新阈值函数去噪算法.通过仿真确定了最佳的小波函数类型和分解层数;改进算法克服了传统的阈值函数在信号处理中存在不连续性或恒定偏差的问题;利用双曲线函数实现向原函数的快速逼近,避免了去噪后的波形失真和振荡现象的发生;具有更少的参数,调节方便,计算量小;注重对较小系数的处理,提高重构信号的精度.利用MIT-BIH心律失常数据库中的105号数据进行验证.算法能有效地滤除噪声干扰,相比于其他方法,其重构信号的信噪比和均方误差均有极大的改善,去噪效果更好.     

尖劈吸波体的研究和微波暗室的模拟

对尖劈形状吸波体的吸波性能进行了研究,并对导弹导引仿真实验用的微波暗室的性能进行分析和仿真.首先对尖劈体的二维反射性能进行了研究,从单条波线反射的原理出发,得到波束平面反射的统计模型.单条波线的反射通过数值模拟得到;波束反射模型则通过对数值模拟的结果进行统计和拟合得到,最终用多项式表示.对于一些简单或特殊的情况,也给出了解析解.通过分析发现,三维反射和二维反射之间有明确的关系.这种关系可以由三维入射角和反射次数决定,而反射次数可以通过二维模型得到.据此将平面反射模型扩展为三维反射模型,从而得到尖劈形状吸波体的三维反射模型.无回波暗室用于模拟没有背景微波辐射的环境,其关键在于选择合适的吸波材料.基于微波反射通量平衡原理,建立了考虑暗室墙面各点之间的相互影响的耦合模型,从而可以求解出在指定的发射源照射之下墙面各点的辐射强度分布.对模型的求解精度和收敛性进行了验证.基于此模型,对一个导弹引导试验进行了数值模拟,推算出了使用两种不同吸波材料时静区接收到的微波信号的信噪比.     

光的波粒二象性探索

光具有波粒二象性,但很难从光的某一特定现象中同时看到这两种性质.如果能用粒子性解释波动性,光的两种性质就能得到完美的统一.分别对龚祖同光子模型、前进电磁场光子模型进行数学建模和MATLAB仿真,并与已有的实验结果比较.发现两个模型都存在不足,进而提出改进的光子模型,从粒子的角度,对展现光的波动性质的干涉、衍射以及偏振现象进行解释.     

Chaos time-domain reflectometry for fault location on live wires

We propose a chaos time-domain reflectometry (CTDR) for locating faults on live wires. This method uses a chaotic output of an improved Colpitts oscillator as probe signal, and detects wire faults by correlating a duplicate with the echo of the probe signal. Benefiting from the anti-jamming of the correlation function of the wideband chaos, fault location on live wires can be achieved. We experimentally demonstrate the detection for live wires in a digital communication system, in which a type of digital signal named high density bipolar of order 3 (HDB3) is transmitted. The effects of the chaotic probe signal on the bit error rate (BER) of the transmitted HDB3 at different rates are analyzed. Meanwhile, the influences of the backward HDB3 reflected by wiring faults on the signal-noise-ratio (SNR) of CTDR measurement are examined experimentally. The results show that fault detection on live wires is achieved when the power of the chaotic probe signal is about from -24.8 dB to -13.5 dB lower than that of the transmitted digital signal. In this case, the BER is kept less than 3E-10, and the SNR of CTDR is higher than 3 dB. Besides, the auto-correlation properties of the improved Colpitts oscillator at different states are investigated experimentally to explore the suitable chaotic states for the CTDR.     

Dynamic analysis and experiment investigation of a cracked dual-disc bearing-rotor system based on orbit morphological characteristics

The paper is aimed to examine dynamic behaviors of a dual-disc bearing-rotor system in multi-fault state, and the crack detection based on the orbit morphological characteristics and vibration responses is proposed. Dynamic response and vibration signal analysis are two significant studies in rotor system. Most researchers have simulated the nonlinear dynamics and analyzed the fault signal using various methods separately. However, the fault feature from vibration signal is tightly connected with the dynamic mechanism in the rotor system, especially in rotor system with coupling multi-fault. In the paper, the dynamic model of the dual-disc bearing-rotor system is established, which takes into account the effects of crack, rub-impact and nonlinear oil-film forces. The vibration responses and the effect of crack on dual-disc rotor system with multi faults are investigated. The existence of crack and the coupling effect of multi faults enrich dynamic behavior of the dual-disc bearing-rotor system, and the response near the 1/2 subcritical speed provides a criterion for crack detection. Experiment investigation is attempted for the first time, which is based on the changes of crack depth and rotation speed for multi-fault dual-disc rotor system. The analysis of the dynamic response and the orbit morphological characteristics from experiment can effectively detect the crack information.     

On a structural acoustic model with interface a Reissner-Mindlin plate or a Timoshenko beam

This paper is concerned with a model which describes the interaction of sound and elastic waves in a structural acoustic chamber in which one “wall” is flexible and flat. The model is new in the sense that the composite dynamics of the three-dimensional structure is described by the linearized equations for a gas defined on the interior of the chamber and the Reissner-Mindlin plate equations on the two-dimensional flat wall of the chamber, while, if a two-dimensional acoustic chamber is considered, the Timoshenko beam equations describe the deflections of the one-dimensional “wall.” With a view to achieving uniform stabilization of the structure linear feedback boundary damping is incorporated in the model, viz. in the wave equation for the gas and in the system of equations for the vibrations of the elastic medium. We present the uniform stability result for the case of a two-dimensional chamber and outline the method for the three-dimensional model which shows strong resemblance with the system of dynamic plane elasticity.     

Single PON network design with unconstrained splitting stages

A Passive Optical Network (PON) is a network technology for deploying access networks based on passive optical components. In a single PON access network, the client terminals are connected to a Central Office through optical splitters and interconnecting fibers where each splitter splits in equal parts the input optical signal coming from the Central Office over its different output fibers. In this paper, we consider PON topology solutions where the splitting ratio and the number of splitting stages are not constrained to a given target design but, instead, are decided based on the cost of the solutions. We present different Integer Linear Programming formulations to model this problem and provide computational results showing that the optimal solutions can be computed for realistic problem instances. In addition, we describe how the formulations can be adapted for the traditional PON topology approaches and present computational results showing that significant cost gains are obtained with the unconstrained splitting stage approach.     

Simulation of eye deformation in the measurement of intraocular pressure

The procedure of measuring the intraocular pressure by an optical analyzer is numerically simulated. The cornea and the sclera are considered as axisymmetrically deformable shells of revolution with fixed boundaries; the space between these shells is filled with incompressible fluid. Nonlinear shell theory is used to describe the stressed and strained state of the cornea and sclera. The optical system is calculated from the viewpoint of the geometrical optics. Dependences between the pressure in the air jet and the area of the surface reflecting the light into a photodetector are obtained. The shapes of the regions on the cornea surface are found from which the reflected light falls on the photodetector. First, the light is reflected from the center of the cornea, but then, as the cornea deforms, the light is reflected from its periphery. The numerical results make it possible to better interpret the measurement data.     

A new method of digital simulation for an aircraft gas turbine engine control system

An LD-9 aircraft gas turbine engine with its control system is simulated digitally by a new method, called the ‘method of spare parts’. The computer program of simulation possesses the main capabilities of a real engine altitude test facility and is called a ‘digital engine altitude simulator’. The results of simulation show that the capabilities of this new method are much better than that of the ordinary ‘method of block diagram’. The method can be used for modelling and simulating any type of gas turbine engines or industrial process control systems.     

Monte Carlo simulation of brain sensing by optical diffuse spectroscopy

We report on development of adapted Monte Carlo based algorithm and code for simulation of light propagation in turbid media with complex geometry aimed for simulation of optical diffuse spectroscopy signal in noninvasive brain sensing. Simulation will allow to determine optimal characteristics of a prototype device for optical diffuse brain sensing. The developed Monte Carlo code can be efficiently parallelized both for SMP and distributed memory systems. We show that the speed-up of the developed algorithm almost linearly depends on the number of nodes/threads in a utilized system.     

A methodology for probabilistic model-based prognosis

This paper deals with the prognosis of complex systems using stochastic model-based techniques. Prognosis consists in this case in computing the distribution of the Remaining Useful Life (RUL) of the system conditionally to available information. In so doing, three main challenges arise from the industrial context. First, the model should unify the two classical approaches to describing complex systems: the bottom-up and the top-down approaches. The former uses elementary interacting components whilst the latter models the system’s physical behavior by means of a set of differential equations. Second, the prognosis must integrate online information to provide a specific result for each system depending on their life events. Online information can take different forms (e.g. inspections, component faults, non detection or false alarm, noisy signal) which must all be considered. Third, the prognosis must supply ready, meaningful numerical results, the error of which must also be under control. This paper proposes a method addressing those challenges. The method is illustrated with two different examples: a simplified spring-mass system and a pneumatic valve for aeronautical application.