高分辨率雷达二维图像的图像处理与特征提取

首先分析了雷达目标散射信号特征。在此基础上 ,根据MUSIC算法得到的雷达图像特点 ,通过平滑、量化、增强等适当的图像处理方式对F - 16、HY - 2 0 0 0两种飞机缩比模型在阶梯变频雷达上所获取的雷达图像进行处理 ,并形成雷达二维灰度图 ;最后 ,采用图像矩阵描述方示进行雷达图像的特征提取     

野生和栽培红毛五加的比较研究

为比较野生和栽培红毛五加形态、光合、光谱及生理特征差异,制定合理的红毛五加人工栽培方案提供技术支持,对野生与栽培红毛五加叶片的外部形态与解剖特征、光合气体交换参数、叶绿素荧光参数、叶片及冠层光谱特性及以刺五加苷E、绿原酸为代表的次生代谢产物含量进行比较。①与野生红毛五加叶片相比,栽培红毛五加叶片厚度、叶面积明显增加,叶片长宽比明显减少,栅栏组织较厚而海绵组织较薄;②栽培红毛五加光合速率及光能利用率较高;③野生和栽培红毛五加都具有典型的植株反射光谱特征,但同野生红毛五加相比,栽培红毛五加叶片和冠层光谱在近红外波段的反射率都较高,一阶导数光谱中的红边振幅和红边面积也较大,红边位置红移10 nm;④2009年所测的栽培红毛五加茎皮中的绿原酸、刺五加苷E含量较野生红毛五加,栽培6年后,上述两种成分含量有所上升,且刺五加苷E含量符合《四川省中药材标准》相关标准。结果表明光照条件的改变影响着红毛五加的叶片形态,充足的光照有利于红毛五加的光合作用和正常生长,研究结果将有助于指导红毛五加的人工驯化栽培工作。     

管内旗形件后掠角对油类介质对流换热的影响

实验研究了水平圆管内插入旗形件时其后掠角对３０＃透平油的对流传热及流阻特性的影响。实验圆管为φ２４ｍｍ×２ｍｍ×７００ｍｍ的紫铜圆管，后掠角为８６°，８１°，７６°，７０°，６５°五种。其它参数范围为：１４６≤Ｐｒ≤２０６，１０６７≤Ｒｅ≤６８５７，０．０７＜ｃｏｓ＜０．４２。实验范围内，换热系数首先随后掠角的增大而上升，然后又下降，在后掠角７６°左右呈现出最佳值，阻力则随后掠角的增加而增加。     

基于SD-SEM模型的消费者食品安全风险感知的信息搜寻行为

本文利用系统动力学模型和结构方程模型来研究消费者食品安全风险感知和消费者信息搜寻行为之间的关系,在总结消费者食品安全风险感知和消费者食品安全信息搜寻行为研究文献的基础上,利用结构方程确定消费者食品安全风险感知的影响因素及其之间的路径系数,进而建立系统动力学模型模拟信息搜寻行为对消费者食品安全风险感知的影响,以提出降低消费者食品安全风险感知的建议.     

基于网络关注度的大宗商品市场预测研究

随着大宗商品市场化的加快和电子信息技术的快速发展,以互联网为载体的网络信息将方便快捷地传递到市场及市场参与者.本文从海量开源数据出发,利用搜索引擎平台,提取核心信息构建网络关注度指标,并提出了基于网络关注度的大宗商品价格预测模型.通过引入具有不同核函数的支持向量回归模型,分别建立了针对单个市场(原油、铜以及玉米)的网络关注度预测模型和综合考虑市场间联动性的多市场网络关注度预测模型.实证结果表明,网络关注度对于市场价格的变动有显著的格兰杰因果关系,引入网络关注度指标和相关市场信息能显著提高预测精度.     

动态抗饱和平滑切换控制器设计方法

针对一类受饱和约束的切换系统,提出了一种动态抗饱和平滑切换控制器的设计方法。首先,基于模型依赖平均驻留时间的方法设计了平滑切换控制器,能够确保系统全局一致渐进稳定并具有一定的鲁棒性能。同时,通过引入链式切换律降低控制器设计的保守性。在此基础上,给出动态抗饱和补偿器的设计方法。将动态抗饱和补偿器设计问题转化为受线性矩阵不等式组约束的优化问题。以航天器在轨加注过程姿态控制系统为例,建立了该系统的链式平滑切换模型,上述模型能够更加准确地反映系统转动惯量的渐变特性。最后,数值仿真算例表明了所提出的控制器设计方法的有效性。     

A DEA-TOPSIS method for multiple criteria decision analysis in emergency management

A hybrid approach of DEA (data envelopment analysis) and TOPSIS (technique for order performance (preference) by similarity to ideal solution) is proposed for multiple criteria decision analysis in emergency management. Two DEA-based optimization models are constructed to facilitate identifying parameter information regarding criterion weights and quantifying qualitative criteria in TOPSIS. An emergency management case study utilizing data from the Emergency Management Australia (EMA) Disasters Database is provided to demonstrate the feasibility of the proposed analysis procedure.     

Adaptive broadband beamformer for nonuniform linear array based on second order cone programming

Adaptive broadband beamforming is a key issue in array applications. The adaptive broadband beamformer with tapped delay line (TDL) structure for nonuniform linear array (NLA) is designed according to the rule of minimizing the beamformer's output power while keeping the distortionless response (DR) in the direction of desired signal and keeping the constant beamwidth (CB) with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming (SOCP). The computer simulations are presented which illustrate the effectiveness of our bearaformer.     

DDFS spurious signals due to amplitude quantization in absence of phase-accumulator truncation

Spurious signals in direct digital frequency synthesizers (DDFSs) are partly caused by amplitude quantization and phase truncation, which affect their application to many wireless telecommunication systems. Thee signals are deterministic and periodic in the time domain, so they appear as line spectra in the frequency domain. Two types of spurious signals due to amplitude quantization are exactly formulated and compared in thetime and frequency domains respectively. Then the frequency spectra and power levels of the spurious signals due to amplitude quantization in the absence of phase-accumulator truncation are emphatically analyzed, and the effects of the DDFS parameter variations on the spurious signals are thoroughly studied by computer simulation. And several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.     

基于非线性内电位构造函数的抗伪状态联想记忆

针对传统Hopfield神经网络在联想记忆中存在的大量伪状态,设计出一种以非线性内电位函数构造为核心的抗伪状态方案,以取代传统的Hebb规则及其外积法,建立了一种抗伪状态的联想记忆网络(ASS-SSNN),并通过吸引域的变化研究抗伪状态方案的正确性和有效性.仿真结果表明:ASS-SSNN比采用传统Hebb规则及其外积法的Hopfield联想记忆网络(HNN)在容错性上更优,记忆状态的吸引域明显增大,存储容量也有所增加.