接收声基阵相位一致性校准研究

现代声纳系统中普遍采用由多个阵元组成的基阵接收信号并进行处理.在基阵的实际应用中,阵元的相位一致性是一项重要技术参数,研究基阵的相位校准方法用于相位补偿有重要的理论意义.文中主要研究了一种基于非线性最小二乘估计的相位一致性校准方法,此校准方法无需知道确切的声源位置,可在不满足远场条件的实验环境中进行,且适用于任意需要测量阵元间相位一致性的面阵或线阵.通过MATLAB对一均匀线阵进行了仿真,验证了此算法估计相位一致性和声源位置的有效性,最后应用此校准方法在水池中对一均匀线阵进行了验证性的实验,再次验证它的有效性与可行性.     

声学基阵波束性能仿真与分析

声学基阵的波束指向性函数具有统一的表达式,运用符号运算的方法,可得到任意阵型声学基阵的波束指向图.论文在仿真计算几类代表性阵型波束图的基础上,以柔性垂直阵为例进一步分析了工程实际中基阵的波束性能.在拉伸作用下和海流作用下基阵波束性能会发生变化,阵元间距与波长比可根据主旁瓣比及栅瓣控制要求进行限制,阵的配重可根据阵弯曲后波束性能的变化进行设计.     

一种被动拖曳声纳阵列信号模拟器设计

声纳基阵信号模拟器是一种实用的可仿真实际检测目标及使用环境的阵元级信号发生器。设计的被动拖曳声纳阵列信号模拟器,仿真了拖曳阵的拖船干扰时域信号和空间传播特性、目标辐射信号以及环境噪声。通过预设定拖船干扰宽带功率谱,以AR模型拟合该功率谱,利用海底、海面对声场的一次反射作用仿真了拖船干扰的空间多途信道。采用插值滤波器,解决了宽带信号阵元间延时的时延精确控制问题。     

小型化线列阵研究

介绍了一种小型化线列阵,阵结构与常规线列阵最大的不同在于阵元间距小于四分之一波长。通过理论分析和仿真计算优化了各阵元的最佳权系数,获得了良好的指向性,得到了实验的证明。小型化线列阵的指向性图具有四大特点：①单向性：仅在半空间出现一个轴对称的主波束,无栅瓣和次瓣。②端射特性：主波束出现在线阵的轴射方向。③超指向性：在阵的尺寸远小于二分之一波长条件下不仅可以获得良好的指向性图,并且波束宽度随阵元间距的减小而减小。④恒定束宽特性：在阵元间距小于八分之一波长条件下,波束宽度随频率变化非常平缓。这种小型化基阵也可用于大型基阵如拖曳阵和展开式体积阵的子基阵,进行低频宽带信号的检测。     

一种基于谱减的声纳噪声自适应消除方法

噪声自适应消除是声纳信号处理的重要研究内容之一.传统的噪声自适应抵消算法需要单独的阵列(阵元)以获得不含期望信号的参考噪声信号,这在实际工程应用中往往是不现实的.提出在不增加阵元的情况下,通过相邻两个阵元输出信号进行加权处理,合成一路不包含给定方向信号的噪声信号;同时,借鉴语音信号处理中普遍应用的谱减降噪处理方法,达到...     

声纳基阵信号模拟器实时软件的开发

声纳基阵信号模拟器是一种实用的、可近似仿真实际监测目标及使用环境的阵元级信号发生器。声纳基阵信号模拟器的使用将有效缩短数字式声纳的研制周期，大大减少湖试和海试的次数。文章中以通用信号阵列处理系统为运行环境，详细介绍了一种声纳基阵信号模拟器实时多任务系统的软件设计与开发过程，分析了该软件系统中所有基本任务的功能以及多任务之间的通信关系，并且最后给出了该实时多任务软件在通用信号处理机上的实现拓扑图。实践证明，该套软件功能完备，且具有很好的实时性和稳定性，非常适用于现代声纳工程领域。     

基于压缩感知的旋转式基阵DOA估计

提出旋转基阵方法,达到增加虚拟阵元的效果,再利用压缩感知理论进行阵列信号方位估计(DOA)。此方法可降低阵列流形矩阵相关性,提高多信号恢复算法成功率,且具有高分辨率。信源个数大于阵元个数时,该方法仍能成功对各信源方向进行估计。     

基于线性预测的虚拟阵元波束形成

常规波束形成方法在信号频率一定的情况下,为提高其分辨率,需要增大基阵孔径,这在实际工程运用中受到了一定的限制。文中提出了基于线性预测技术的虚拟阵元波束形成方法。该方法在有限尺度基阵的情况下,运用线性预测技术,根据已知阵元的接收数据,估计虚拟阵元上的接收数据,使基阵孔径在虚拟的意义上得到了扩大,从而实现了高指向性窄波束,提高了基阵的指向性指数。仿真实验表明了方法的有效性。     

一种简化的平面阵波束形成方法

0引言波束形成技术是将一个多元阵经适当处理使其对某些空间方向的声波具有所需响应的方法。波束形成技术系统是现代声纳的核心部件,是声纳具有良好的战术、技术性能的基础[1]。平面阵是声纳系统常用的基阵,可以实现对目标的全空间定向,但平面阵二维波束形成运算量较大,在某些小平台上,由于功耗和系统复杂性的限制,希望能在性能没有显著降低的前提下进行简化处理。本文把平面     

稀疏矢量阵设计的模拟退火算法

对于均匀间隔线列阵,由采样定理可知,当阵元间距超过信号波长的一半时,指向性图会产生与目标等高的栅瓣。为了获得高分辨率,同时避免栅瓣出现,需要大量的传感器。为了减少设备复杂度,可以采用稀疏布阵技术,以较少的阵元获得较高的分辨力。将模拟退火算法应用到稀疏矢量水听器阵的设计中。通过优化阵元位置控制指向性图,可以获得无栅瓣的指向性图。给出了优化后的稀疏矢量阵与均匀间隔矢量阵的指向性图比较。     

A HIGHER ORDER EXPANSION METHOD FOR OPTIMUM DESIGN OF STRUCTURES FOR SPECIFIED FUNDAMENTAL EIGENVALUE

A higher order expansion method is presented for optimum design of structures for specified fundamental eigenvalue. The design function, fundamental eigenmode and total volume are expressed in terms of the Taylor series expansion with respect to the specified fundamental eigenvalue. A solution with null design function, where all the eigenvalues degenerate to null, is chosen as a trivial initial solution, and higher order terms are incorporated. By using the proposed method, a set of optimum designs for a wide range of fundamental eigenvalues is easily found. The proposed method is applied to an Euler-Bernoulli beam and expanded forms are presented analytically for a simply supported beam. The method is then extended to a plane truss, and the results are compared with those by an optimality criteria method.     

稳健的波束优化设计及FPGA实现

在分析二阶锥规划(Second-Order Cone Programming,SOCP)算法的基础上,设计了声呐阵列并采用SOCP方法对其波束图进行了优化;根据SOCP的波束优化设计方法,设计了基于FPGA的16元均匀圆阵的波束形成器。目的在于提高波束优化设计的稳健性以及信号处理系统的运算实时性、运算精度等。对FPGA波束形成器的仿真性能进行了分析,主要分析了以下两个方面:首先分析了当权值位数不同时对波束形成器输出的影响,其次分析了波束优化设计方法的抗阵列流形误差的性能。仿真设计结果和实验表明本文方法的有效性。二阶锥波束优化设计的波束图有着良好的稳健性,采用12位权值的FPGA波束形成器,抗阵元位置误差性能也比较好。     

A firefly algorithm for optimum design of new-generation beams

This research addresses the minimum weight design of new-generation steel beams with sinusoidal openings using a metaheuristic search technique, namely the firefly method. The proposed algorithm is also used to compare the optimum design results of sinusoidal web-expanded beams with steel castellated and cellular beams. Optimum design problems of all beams are formulated according to the design limitations stipulated by the Steel Construction Institute. The design methods adopted in these publications are consistent with BS 5950 specifications. The formulation of the design problem considering the above-mentioned limitations turns out to be a discrete programming problem. The design algorithms based on the technique select the optimum universal beam sections, dimensional properties of sinusoidal, hexagonal and circular holes, and the total number of openings along the beam as design variables. Furthermore, this selection is also carried out such that the behavioural limitations are satisfied. Numerical examples are presented, where the suggested algorithm is implemented to achieve the minimum weight design of these beams subjected to loading combinations.     

基于矢量水听器阵的恒定束宽波束形成器的原理与设计

摘要：在对水下目标进行探测识别的应用中，一般要求声纳系统具备在较宽频带内形成恒定束宽波束的能力：过去对声纳恒定束宽波束形成器的研究一直针对声压水听器阵，近来随着对矢量水听器认识的深入，开展基于矢量水听器阵的恒定束宽波束形成器研究越发变得必要。本文正是体现了作者在这一方面的阶段性研究成果。文中首先介绍了单个矢量水听器的指向特性，接着提出了矢量水听器阵宽带恒定束宽波束形成器的实现原理和设汁方法，并以均匀等间距线阵为例，给出了获得实现恒定束宽算法所需频域加权矩阵的步骤，之后又进一步给出了恒定束宽算法的频域实现流程，并通过计算机仿真验证了其有效性：     

Efficient robust design via Monte Carlo sample reweighting

A novel probabilistic method for the optimization of robust design problems is presented. The approach is based on an efficient variation of the Monte Carlo simulation method. By shifting most of the computational burden to outside of the optimization loop, optimum designs can be achieved efficiently and accurately. Furthermore by reweighting an initial set of samples the objective function and constraints become smooth functions of changes in the probability distribution of the parameters, rather than the stochastic functions obtained using a standard Monte Carlo method. The approach is demonstrated on a beam truss example, and the optimum designs are verified with regular Monte Carlo simulation. Copyright © 2006 John Wiley & Sons, Ltd.     

面向定制的液压机可适应产品平台构建方法研究

基于可适应设计理论研究了汽车门盖包边液压机系列产品的可适应产品平台构建方法,构建了包括CAD和CAE模型以及工艺的液压机可适应模块,使用实验设计技术（DOE）分析了模块的各个设计变量对产品性能的贡献值;综合DOE分析结果和单机产品优化结果确定了液压机的公共设计参数和个性设计参数,在产品族优化的基础上构建可适应产品平台,并给出了汽车包边液压机上横梁可适应产品平台构建的实例．     

平面包络环面蜗杆副的参数优化设计

提出了平面包络环面蜗杆副参数优化设计的原则和目的,建立了一个优化模型,采用复合形法实现了主要参数的优化设计,并成功地编制了平面包络环面蜗杆副的优化设计程序．     

二阶镶拼圆管矢量接收换能器研究

文章介绍了一种二阶镶拼圆管矢量接收换能器的设计方法，获得了类偶极子指向性以及波束宽度更为锐化的类四极子指向性。利用理论计算以及有限元仿真分析了镶拼圆管的指向性以及接收灵敏度，并实际制作了二阶镶拼圆管矢量接收换能器。在消声水池的测试表明，灵敏度测试结果与有限元仿真计算结果吻合较好，镶拼圆管矢量接收换能器类偶极子指向性图-3 dB波束宽度在95°左右，类四极子指向性图-3 dB波束宽度在40°左右，二阶矢量指向性图波束宽度明显比一阶矢量指向性图波束宽度更加锐化。     

Application of linear buckling sensitivity analysis to economic design of cylindrical steel silos composed of corrugated sheets and columns

The paper deals with global stability of steel cylindrical silos composed of corrugated walls and vertical columns with loads imposed by a bulk solid following Eurocode 1. The optimum silo design with respect to the steel weight was based on a sensitivity analysis method. The changes of silo column profiles at each design step were performed by means of influence lines for the buckling load factor due to the unit column bending stiffness variation. The corrugated walls were simulated as an equivalent orthotropic shell and vertical thin-walled columns as beam elements. The results were compared with the Eurocode 3 approach and verified by FE results of linear buckling and non-linear analyses with geometric non-linearity carried out with the commercial finite element code ABAQUS for a 3D shell model of a perfect silo. The proposed procedure allowed for a rational silo design with an economic material use. Some recommendations for the silo optimum design were elaborated.     

Optimum detailed design of reinforced concrete frames using genetic algorithms

This article presents the application of the genetic algorithm to the optimum detailed design of reinforced concrete frames based on Indian Standard specifications. The objective function is the total cost of the frame which includes the cost of concrete, formwork and reinforcing steel for individual members of the frame. In order for the optimum design to be directly constructible without any further modifications, aspects such as available standard reinforcement bar diameters, spacing requirements of reinforcing bars, modular sizes of members, architectural requirements on member sizes and other practical requirements in addition to relevant codal provisions are incorporated into the optimum design model. The produced optimum design satisfies the strength, serviceability, ductility, durability and other constraints related to good design and detailing practice. The detailing of reinforcements in the beam members is carried out as a sub-level optimization problem. This strategy helps to reduce the size of the optimization problem and saves computational time. The proposed method is demonstrated through several example problems and the optimum results obtained are compared with those in the available literature. It is concluded that the proposed optimum design model can be adopted in design offices as it yields rational, reliable, economical, time-saving and practical designs.