声矢量阵列波达方向估计的四元数空间稀疏分解

针对稀疏分解(sparse decomposition)类算法在恢复矢量阵列信号时收敛速度慢的问题,本文将稀疏分解理论推广到四元数空间,提出了一种声矢量阵列波达方向估计的四元数正交匹配追踪算法。首先,建立声矢量阵列的四元数模型,然后将方向矢量矩阵在四元数空间展开作为冗余字典,最后利用正交匹配追踪算法恢复原始信号得到目标方位信息。实验结果表明:在四元数空间建立的冗余字典强化了声矢量传感器各输出分量间正交性,与长矢量模型即在复数域的冗余字典相比恢复性能更好。具体表现为:冗余字典原子长度降为长矢量方法的1/3,并有效去除长矢量方法在DOA估计角度真值附近1°范围内的偏差。仿真结果验证了算法的有效性。     

基于增广矩阵束的方向角与仰角估计

基于最小冗余线阵提出了基于增广矩阵束（MEMP）的方向角与仰角的联合估计算法。采用2个垂直的有约束最小冗余线阵构造一个类L型阵列,首先,利用四阶累积量虚拟阵列扩展的性质,计算2个线阵输出的互累积量矩阵,对此矩阵构造增广矩阵,然后,运用2D ESPRIT算法实现二维角度的估计,并采用一种新的配对算法,实现方向角与仰角的自动配对。该算法增加了阵列的分辨能力,提高了阵列的利用率,无需进行谱峰搜索,计算量小。仿真实验证明了算法的有效性。     

应用分数低阶循环相关估计单电磁矢量传感器的波达方向和极化参数

提出了一种在α和高斯混合噪声以及循环平稳干扰并存背景下基于分数低阶循环相关(FLOCC)联合估计单电磁矢量传感器波达方向(DOA)和极化参数的多重信号分类(MUSIC)方法。该方法利用信号的循环平稳特性,采用分数低阶循环相关函数抑制α和高斯混合噪声以及循环平稳干扰信号;然后利用MUSIC方法对单电磁矢量传感器的DOA和极化参数进行联合估计,并利用DOA参数与极化参数的相互独立性,将传统MUSIC方法的四维搜索简化为两次二维搜索,从而有效地减少该算法的计算量。对所提算法与基于分数低阶矩的MUSIC算法进行了实验对比。结果显示:提出的方法可充分地抑制与待测信号循环频率相异的任意循环平稳干扰信号;在α和高斯混合信噪比为0dB,信干比为3dB时,估计得到的DOA和极化参数的均方根误差分别为0.3°和0.7°,明显优于基于分数低阶矩的MUSIC方法。     

利用隔离小生境混合蛙跳方法联合估计波达方向和多普勒频率

为了高效准确地联合估计波达方向（DOA）和多普勒频率,提出了基于二维MUSIC谱和隔离小生境混合蛙跳算法的联合谱估计方法。首先,利用状态空间模型构造包含DOA和多普勒频率信息的广义可观测矩阵。 然后,利用MUSIC算法和广义可观测矩阵构造联合估计的二维谱函数,将参数估计问题转化为多峰函数优化问题。最后,引入混合蛙跳算法（SFLA）并利用隔离小生境技术对混合蛙跳算法进行改进,使其适应于二维MUSIC谱多个极值的优化搜索,降低搜索计算量,得到DOA和多普勒频率的估计值。实验结果表明：在考虑信噪比为0 dB的两个独立信号源的情况下,利用本文方法估计得到的DOA和多普勒频率的均方根误差分别为0.23°和0.005 5 rad。该方法具有控制参数少、计算量小、参数自动配对等特点。     

基于任意声矢量传感器阵列的角度和频率估计算法

提出了一种基于任意声矢量传感器阵列下联合角度和频率估计新方法.将矢量传感器阵输出的信号进行建模分析表明此信号具有平行因子四线性模型特征.利用四线性分解的唯一性条件,从分解得到的矩阵中联合估计出声源的参数.该算法首先应用平行因子四线性分解算法估计出频率矩阵和方位矩阵,然后根据频率矩阵和方位矩阵的结构特点及最小二乘方法进行声源参数的计算.该方法与传统算法相比,无需多维谱峰搜索及参数配对,并具有更高的估计精度,在工程上有一定的应用价值.计算机仿真和实验结果验证了该方法的有效性.     

一种基于矢量传感器阵的盲波束形成方法研究

本文针对水声环境和信号的特点，提出了一种基于矢量传感器阵的盲波束形成算法。首先建立了矢量传感器阵列接收信号模型，然后推导了基于矢量传感器阵列的波束形成最优权矢量的表达式。在此基础上，定义了接收信号的四阶累积量，进而盲估计了矢量传感器阵列的方向向量，实现了盲波束形成。该方法利用高阶累积量可消除高斯噪声干扰这一特性，有效地实现了基于矢量传感器阵列的盲波束形成。仿真实验验证了该方法的有效性和正确性。     

基于十字形阵列和2D-MUSIC算法的Lamb波检测

采用由压电传感器组成的十字形阵列进行Lamb波信号的激励和接收,提出一种二维多重信号分类（2D-MUSIC）方法对铝板中的缺陷进行定位检测。选用合适的频率激励产生单一模态信号,可避免多模态的影响,降低Lamb波的频散;利用2D-MUSIC算法对接收信号进行分段处理,并结合反射信号和二维导向矢量对铝板中的缺陷进行定位。结果表明,提出的2D-MUSIC算法对铝板中的缺陷定位比传统MUSIC算法更精准。     

基于高阶累积量的阵列式超声波传感器风速风向测量

针对现有超声波测风系统在实际应用中环境噪声抑制效果差、风速和风向测量精度不高的问题,提出了一种基于高阶累积量的阵列式超声波传感器风速风向测量方法。所提方法采用一种由一个超声波发射阵元和五个超声波接收阵元组成的阵列式超声波测风系统结构,并在此系统结构上,采用基于高阶累积量的多重信号分类(MUSIC)算法,抑制高斯白噪声及高斯色噪声的干扰,实现高斯混合噪声下风速风向的有效测量。所提方法与应用相关算法的测风方法相比,具有更高的噪声抑制能力及更高的风速风向测量精度。最后通过仿真实验与实测数据验证实验对所提方法的有效性进行了验证与分析,实验结果表明风速和风向角的测量误差分别为2.3%和-2°,基本达到了超声波测风方法的技术要求。     

适用任意平面阵列的二维宽带DOA快速估计算法

二维宽带波达方向(DOA)估计对实现水声通信定位一体化具有重要作用。双边相关变换(TCT)算法是高分辨宽带DOA估计的经典算法之一,但只适用均匀线列阵下的一维DOA估计,且计算量大。本文在对TCT简化算法(STCT)进行扩展改进的基础上,提出了一种适用于任意面阵列且具有低计算复杂度的二维宽带DOA快速估计算法。所提算法利用水声通信同步信号的已知波形对阵列输出数据进行匹配预处理,有效压缩了聚焦变换所需频点数量,从而降低了聚焦变换过程的计算量;利用余弦域加速粒子群最优化(APSO)搜索二维空间谱谱峰,在保持高搜索精度的同时显著降低了搜索计算量。相较于单纯的STCT扩展算法,所提算法保持高DOA估计精度,在信噪比为20 dB时精度约为0.02°,但计算量远低于前者。仿真和实验结果验证了所提算法的优势。     

并联式六维加速度传感器的哈密顿动力学研究

针对六维加速度传感器在解耦难度与结构复杂度之间存在矛盾的现状,通过Legende变换,并用四元数来描述旋转运动,建立并联式六维加速度传感器的哈密顿约束正则方程。依据四元数的性质,在相空间内推导出系统哈密顿变量之间隐含的正交关系式,并据此给出一种求解微分代数方程的显式递推算法。通过构建系统内的固有约束关系并求解相容线性方程组的最小范数解,对动力学方程的计算误差进行修正。通过仿真和试验对系统的动力学模型及其算法进行验证,结果相一致,且计算效率较高。研究表明:应用相空间内的哈密顿动力学理论,可以实现并联式六维加速度传感器这类多体系统在一般工作环境下的动力学解耦。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.