声纳隔振模块性能分析

拖曳线声纳在海洋资源勘探、水下反潜战争中一直起着非常重要的作用。为了提高声纳的隔振性能,必须在声阵模块前、后插入性能优良的隔振模块。文章在建立声纳隔振模块有限元模型的基础上,对隔振模块的隔振性能进行了理论计算,得到了一些有价值的结论。这些结论对于进一步改进和提高隔振模块性能具有参考价值。     

SDG故障诊断决策表的粒约简算法

为了减少故障特征集的维数,降低流程系统故障诊断知识库的复杂程度,本文将基于二进制粒矩阵的粒约简算法引入到基于SDG模型的故障诊断中.以离心泵与液位系统为例,用粒语言来描述和表达SDG故障诊断模型中的元素,建立反映故障-征兆因果关系的决策表,进而对冗余属性及属性值进行约简,有效地约简了SDG诊断规则,提高了故障诊断的效率.     

Time-varying performance prediction and system identification of internal combustion engines

Design for life-time performance and proper maintenance measures are usually needed to prolong the mean-time-between-failures of complex equipments such as internal combustion engines. To reach this, it is important to obtain the information of time-varying system performance in design stage and to identify the structural change at each moment. So a multidisciplinary model based method is studied in this paper to unify the time-varying performance(TVP) prediction and system identification(SI) of equipments. The related multidisciplinary model in this paper should be not only precise to give simulation results but also sensitive to the variation of system parameters. So the varying history of system performance along with the structural change can be obtained from the model. Then the value of system parameters can be identified by seeking roots with given detected responding data and relationship between system responding data and system parameters. A case study on a low power gasoline engine shows that the method presented in this paper can provide useful information for the development and maintenance of complex equipments.     

Robust intelligent control design for marine diesel engine

This work deals with the nonlinear control of a marine diesel engine by use of a robust intelligent control strategy based on cerebellar model articulation controller （CMAC）. A mathematical model of diesel engine propulsion system is presented. In order to increase the accuracy of dynamical speed, the mathematical model of engagement process based on the law of energy conservation is proposed. Then, a robust cerebellar model articulation controller is proposed for uncertain nonlinear systems. The concept of active disturbance rejection control （ADRC） is adopted so that the proposed controller has more robustness against uncertainties. Finally, the proposed controller is applied to engine speed control system. Both the model of the diesel engine propulsion system and of the control law are validated by a virtual detailed simulation environment. The prediction capability of the model and the control efficiency are clearly shown.     

基于Lyapunov理论的交流传动系统建模和稳定性分析

为完整分析PWM整流器-逆变器-电机串联交流传动系统的稳定性跟随主要系统参数变化的规律,基于各子系统的开关函数模型,结合空间矢量脉宽调制算法的开关函数在dq坐标系下的等效表达式,建立整个系统的状态空间模型,采用偏微分法进行线性化处理,得到系统的增量方程;基于Lyapunov第一法,采用MATLABMAT语言对系统的稳定性进行分析．仿真结果表明：在传动系统全速度范围内,增大PWM整流器滤波参数和电机定转子电阻有利于增加系统的稳定性,电机定转子电感的变化对系统稳定性的影响呈双极性变化．因此,合理选择系统设计参数,能够使系统保持较大的稳定区域,避免系统振荡现象的发生．     

光纤非线性偏振耦合引起偏振态抖动的研究

研究了光纤非线性偏振耦合引起的偏振态抖动的现象，从理论上导出了基于NRZ码的偏振复用系统中偏振度降低与两路调制信号的时域波形及他们的初始相位差之间的关系．对于100Gb／s的偏振复用系统进行了理论仿真，结果表明：只有当二路调制信号的光功率相等且初相位差为零或者π/2时，所引起的偏振态抖动最小．     

基于灰色残差GM（1，1）模型的道路交通量预测的研究

道路交通体系是一个多因素、多层次、多目标的复杂系统。其中交通量信息系统具有明显的层次复杂性,结构关系的模糊性,动态变化的随机性,指标数据的不完全和不确定性。由于技术方法、人为因素、自然环境变化的影响,造成各种数据误差、短缺甚至虚假现象,系统的作用机制不明确,系统的状态、结构、边界关系难以精确描述,属于典型的灰色系统。在作量化、模型化、实体化研究时,能作为反映系统主要动态特征的数据是很少的。由于环境对系统的干扰,系统信息中原始数据序列往往呈现离乱情况,离乱数列即为灰色数列或称灰色过程,灰色理论利用那些较少的或不确切的表示系统行为特征的原始数据序列作生成变换后建立微分方程,对灰色过程建立的模型称为灰色模型（Greymodel）,简称GM模型。本文从理论上介绍了GM（1,1）模型和灰色残差GM（1,1）模型建立的一般过程,然后将其应用于交通量预测的实际例子中。预测结果表明,该方法是可行的。     

3-（v，K4^（3）-e，λ）最小覆盖问题

考虑一种特殊类型的超图分解．证明了对任意的正整数v≥4和λ,存在具有[λv（v-1）（v-2）／18]个区组的MCλ（3,K4^（3）-e,v）,其边超越中至多含有两条边．     

双幅桥静分力系数气动干扰效应研究

采用计算流体动力学(CFD)的方法,利用F1unet软件对某双幅桥面桥梁三分力系数的气动干扰效应进行数值模拟.结果表明:由于前桥对后桥的遮挡作用,后桥的静力三分力系数受到较大影响,阻力系数与单桥相比减小了74％,升力系数减小了88％;随着前后桥间距的增大,双幅桥梁之间的气动干扰效应逐渐减小,但双幅桥面达到8b(b为梁高...     

Fast affine projection algorithm for adaptive noise canceling and its application on the fetal electrocardiogram extraction

Aimed at the problem of adaptive noise canceling (ANC), three implementary algorithms, which are least mean square (LMS) algorithm, recursive least square (RLS) algorithm and fast affine projection (FAP) algorithm, have been researched. The simulations were made for the performance of these algorithms. The extraction of fetal electrocardiogram (FECG) is applied to compare the application effect of the above algorithms. The proposed FAP algorithm has obvious advantages in computational complexity, convergence speed and steadystate error.     

Fabrication of a Novel Porous Poly（Vinylidene Fluoride） Blend Five-Bore Membrane for Wastewater Treatment

Porous poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend five-bore hollow fiber membranes are prepared by wet phase inversion methods. In spinning these PVDF hollow fibers, N, N-dimethylacetamide (DMAc) and polyvinyl pyrrolidone (PVP) are used as the solvent and the non-solvent additive, respectively. The external coagulant uses water. The internal coagulants use water and DMAc-water solutions. The membranes are characterized in terms of water flux and molecular weight cut-off for the wet membranes. The cross-sectional structures are examined by scanning electron microscopy (SEM). The effects of polymer concentration and the internal coagulant on the permeation properties and membrane structures are examined keeping the bore liquid flow and air-gap constants. Relative high flux, rejection and strengh PVDF five-bore hollow fiber membranes could be prepared from the polymer concentration in dope solution at 17% of mass fraction, the air gap distance of 14 cm, and using 10% of mass fraction of DMAc solution as the internal coagulant at 13mL/min of flow.     

Slat noise suppression using upstream mass injection

A new approach,mass injection near the slat cusp,is proposed for the suppression of slat noise.The mechanism and efciency of the slat noise suppression using upstream mass injection are numerically studied with hybrid Reynolds-averaged Navier-Stokes simulation/Large eddy simulation（RANS/LES）of a three-component high-lift model.Ffowcs-Williams and Hawking（FW-H）integration is employed to obtain far-field acoustic characteristics.Results show that with injection,aerodynamic capability of the high-lift devices is sustained.In addition,a considerable noise reduction is observed in the downward direction.With detailed analysis of the time-averaged and instantaneous flow fields,two mechanisms are identified as the reason accounting for the noise suppression：upstream mass injection significantly reduces the scale and strength of the vortices stemming from the cusp;the shear layer is lifted up,which relieves the shear layer impingement on the slat lower surface.     

Simplified model for evaluation of VIV-induced fatigue damage of deepwater marine risers

A simplified empirical model for fatigue analysis of deepwater marine risers due to vortex-induced vibration (VIV) in non-uniform current is presented. A simplified modal vibration equation is employed according to the characteristics of deepwater top tensioned risers. The response amplitude of each mode is determined by a balance between the energy feeding into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainder based on the data from self-excited oscillation and forced oscillation experiments of rigid cylinders. Multi-modal VIV fatigue loading is obtained by the square root of the sum of squares approach.Compared with previous works, this model can take fully account of the main intrinsic natures of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping. In addition, a closed form solution of fatigue damage is presented for the case of a riser with uniform mass and cross-section oscillating in a uniform flow. Fatigue analysis of a typical deepwater riser operating in Gulf of Mexico and West Africa shows that the current velocity profiles affect the riser's fatigue life significantly and the most dangerous locations of the riser are also pointed out.     

山区Y形河口附近桥址区地形风特性数值模拟研究

为研究在山区Y形河口影响下桥址区的桥梁风载特性,以山区峡谷大跨度悬索桥桥址区真实地形为工程背景,应用CFD(computational fluid dynamics)的方法,建立了桥址区复杂地形区域风场数值模型.通过36个工况的分组对比分析,探讨了山区Y形河口对主梁的平均风速、风攻角、风剖面以及风速放大系数在不同来流方向下的影响规律,并分析了河口处河道的导流与山体的绕流作用.研究结果表明:不同于普通深切峡谷地形风特性,在Y形河口影响下,桥址区附近的平均风速最大增幅达24 m/s,平均风攻角主要表现为负攻角,出现了最高达1.13的风速放大系数,且河道的导流及山体的绕流作用会导致主梁风速分布不均匀.      

Composition-dependent mechanical and thermal transport properties of carbon/silicon core/shell nanowires

Molecular dynamics (MD) simulations are performed to study the composition-dependent elastic modulus and thermal conductivity for carbon/silicon core/shell nanowires (NWs). For each concerned carbon/silicon core/shell NW with a specified diameter, it is found that elastic modulus is reduced with a linear dependence on cross-sectional area ratio. The fact matches well with the results of theoretical model. Analysis based on the cross-sectional stress distribution indicates that the core region of core/shell NW is capable of functioning as a mechanical support. On the other hand, thermal conductivity also relies on the cross-sectional area ratio of amorphous silicon shell. The core/shell interface plays a considerable influence on the thermal transport property. The decreasing rate of thermal conductivity is gradually decreased as the composition of amorphous silicon shell increases. In addition, by calculating the phonon density of state, we demonstrate that the reduction in thermal conductivity of the core/shell NW stems from the increase of the low frequency modes and the depression of high-frequency nonpropagating diffusion modes. These results provide an effective way to modify the properties of core/shell NWs for related application.     

新型12相多重叠加逆变器的建模与仿真

基于圆形移相变压器的12相多重叠加逆变器的工作原理,分析了在12相方波电压输入情况下,圆形移相变压器中的磁动势将近似为圆形旋转磁动势,因此在三相输出绕组中将得到近似的三相对称正弦电压.文中建立了该逆变器的数学模型,推导了参数计算公式,给出了简单的调压策略,并用Matlab对12相多重叠加的逆变过程进行了仿真.仿真结果表明,这种新型的12相多重叠加逆变器可以有效地减小输出的谐波,改善逆变器的输出性能,同时可以方便地调节输出电压.     

Electrode wear prediction in milling electrical discharge machining based on radial basis function neural network

Milling electrical discharge machining (EDM) enables the machining of complex cavities using cylindrical or tubular electrodes. To ensure acceptable machining accuracy the process requires some methods of compensating for electrode wear. Due to the complexity and random nature of the process, existing methods of compensating for such wear usually involve off-line prediction. This paper discusses an innovative model of electrode wear prediction for milling EDM based upon a radial basis function (RBF) network. Data gained from an orthogonal experiment were used to provide training samples for the RBF network. The model established was used to forecast the electrode wear, making it possible to calculate the real-time tool wear in the milling EDM process and, to lay the foundations for dynamic compensation of the electrode wear on-line. This paper demonstrates that by using this model prediction errors can be controlled within 8%.     

应急物流中基于PPSVM的应急物资分类研究

突发事件一旦发生,应急物资需求种类是纷繁复杂的,应急物流中的物资需求又是紧迫的、动态变化的. 为了提高应急物流的运作效率,救援管理人员需要对应急物资进行分级. 本文提出一种基于后验概率支持向量机的应急物资分类方法,并在此基础上建立应急物资分类模型. 把物资的重要性、时效性和缺口程度三个因素作为物资需求分级的评价标准,将模糊化后的评价值作为PPSVM的输入,选择后验概率最大所的类别作为测试样本的类别输出来完成整个分类过程,从而得到对应的分级结果. 实验结果表明,PPSVM用于应急物资分类是可行的,能够很好地解决应急物资的分类问题.     

基于拟T-S模糊模型的网络化控制系统稳定性分析

综合考虑网络化控制系统（NCS）出现时延和丢包问题,提出一种基于拟T-S模糊模型.以时延和丢包出现的概率作为隶属度,并根据丢包出现在系统中的不同环节,分别构造相应的系统模型,再利用线性矩阵不等式（LMI）方法证明系统的稳定性,并通过对一个二阶倒立摆系统的数值分析说明方法的可行性,从而为网络化控制系统的分析与设计提供了新方法.     

基于灰色关联和组合赋权法的道路交通安全评价

利用灰色关联分析法得到各决策变量（DMU）之间的关联度,通过组合数据包络分析（DEA）和层次分析法（AHP）确定关联系数的权重,同时考虑主客观因素得到相对最优的关联度,实现对评价对象的客观优先排序。建立城市道路交通安全评价体系,运用MATLAB软件进行编程,实现模型的运算,并得到评价结果。