High-resolution imaging of dielectric profiles by using a time-domain ultra wideband radar sensor

This paper describes the development of an imaging instrument that capitalizes on high-resolution phenomenon in inverse scattering using a time-domain ultra wideband (UWB) sensor. The image reconstruction algorithm that accounts for the band-limited view of the UWB data is based upon the TM-mode wave equation, the Born approximation, and the adjoint method for computing the Fréchet derivatives. The computation of the sensitivity function requires the forward propagation of the UWB wavefield, as well as the reverse propagation of the residual wavefield. The electromagnetic and adjoint fields are calculated using the finite-difference time-domain (FDTD) method, implementing the first and second orders Mur’s absorbing boundaries. The overall performance of the instrumentation system is demonstrated using computer simulations and experimental measurements. Results indicate that the equipment can reconstruct fairly complicated dielectric profiles at near millimeter resolution even with the presence of large amount of noise.     

利用场路结合方法分析磁轴承悬浮力

针对磁轴承悬浮力分析比较复杂的问题,提出利用场路结合分析磁轴承悬浮力的方法.基于磁路法推导了径向磁轴承悬浮力的线性化模型,针对具体的磁轴承系统,利用有限元法分析了磁轴承能够满足线性化模型的偏置电流选择范围和磁轴承转子偏移范围,通过最小二乘法修正了线性化模型的电流刚度系数和位移刚度系数,并对超出线性化模型范围的悬浮力进行...     

应用电站设备宽频特性的过电压在线监测装置

过电压的监测和分析对现代电力供电系统有极其重要的意义.通过分析比较国内外现有过电压在线监测装置的特点,提出了一种新型的利用设备宽频传输特性的过电压在线监测方法,其原理是将电压互感器(TV)、二次电缆和分压器等二次设备看作相互级联的二端口网络,通过有理甬数逼近建立了其传输参数模型;基于该模型,可由二次设备输出端口的电压信...     

脂肪族硝基含能化合物撞击感度的QSPR研究

基于定量结构-性质相关性(QSPR)原理,研究脂肪族硝基化合物撞击感度与其分子结构间的内在定量关系。应用遗传函数算法筛选出与撞击感度密切相关的6个参数作为分子描述符;采用多元线性回归方法建立基于该6参数的脂肪族硝基化合物撞击感度预测模型。分别采用内部验证及外部验证的方式对模型性能进行验证,研究结果表明模型具有较高的稳定性、预测能力及泛化性能。     

数字可调中频噪声源设计

介绍了用FPGA和AD9739产生可调中频噪声源的方法.采用Combined Tausworthe方法产生均匀分布,根据均匀分布和高斯分布之间的映射关系,使用折线逼近的方法产生基带的高斯分布.采用可配置HR IP核实现中心频率和带宽可调的中频噪声.FPCA产生的中频噪声源通过LVDS接口输出给AD9739.     

Robust multi‐level partition of unity implicits from triangular meshes

This paper presents a new robust multi‐level partition of unity (MPU) method, which constructs an implicit surface from a triangular mesh via the new error metric between the mesh and the implicit surface. The new error metric employs a weighted function of inner points and vertices of a triangle to fit an implicit surface, which can control the approximation error between the surface and vertices of the triangle. Furthermore, it is applied to the MPU method by utilizing the dual graph of a triangular mesh, and the general quadric implicit surface is used for surface representation. Compared with the MPU method, the new method generates fewer subdivision cells with the same approximation error and performs more steadily especially when given triangular mesh with fewer vertices. Copyright © 2013 John Wiley & Sons, Ltd.     

航空雷达故障诊断的β上近似属性约简及规则融合

航空雷达故障诊断的一个主要目标是求出某种程度上可能发生的故障类型,为此,首先引入β上近似属性约简,定义了β上近似决策辨识集和辨识矩阵,给出了求取β上近似约简集的方法;其次,提出了一种基于包含度的规则融合方法,该方法充分挖掘属性值信息,可以得到全部属性条件下的带可信度的决策规则,有效解决了在各类型故障样本数目相差较大的情形下的规则融合问题;最后,以某型航空雷达的整机测试为例,在基于β上近似约简对其测试参数进行约简的基础上,应用基于包含度的规则融合方法,得到了全部属性取值条件下的航空雷达故障诊断规则。结果表明：该方法直观有效、计算简便,为航空雷达故障诊断提供了新的思路和途径。     

环境激励下基于信号降噪的模态参数识别研究

提出一种环境激励下基于测试信号降噪的模态参数识别方法。该方法首先对测试的随机响应数据采用自然激励技术(NEx T)获得互相关函数,进而基于结构矩阵低秩逼近(SLRA)方法得到降噪后的信号,最后通过复指数(Prony)方法识别结构的模态参数。数值算例和模型实验结果表明,该方法对测量信号有很好的降噪作用,识别精度高。     

Novel computational methods for high‐dimensional stochastic sensitivity analysis

This paper presents three new computational methods for calculating design sensitivities of statistical moments and reliability of high‐dimensional complex systems subject to random input. The first method represents a novel integration of the polynomial dimensional decomposition (PDD) of a multivariate stochastic response function and score functions. Applied to the statistical moments, the method provides mean‐square convergent analytical expressions of design sensitivities of the first two moments of a stochastic response. The second and third methods, relevant to probability distribution or reliability analysis, exploit two distinct combinations built on PDD: the PDD‐saddlepoint approximation (SPA) or PDD‐SPA method, entailing SPA and score functions; and the PDD‐Monte Carlo simulation (MCS) or PDD‐MCS method, utilizing the embedded MCS of the PDD approximation and score functions. For all three methods developed, the statistical moments or failure probabilities and their design sensitivities are both determined concurrently from a single stochastic analysis or simulation. Numerical examples, including a 100‐dimensional mathematical problem, indicate that the new methods developed provide not only theoretically convergent or accurate design sensitivities, but also computationally efficient solutions. A practical example involving robust design optimization of a three‐hole bracket illustrates the usefulness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.