曲线的非正则问题研究

鉴于数学分析和微分几何某些教科书提供的正则概念不完备．本文从讨论正则曲线的概念出发．研究曲线上各类非正则点的几何特征及判别方法。并以楔积运算为工具．通过拐点的讨论．研究有重要实用价值的平面三次参数曲线的非正则点．得到“二重拐点”是非正则点等结论．     

非共沸工质自复叠制冷技术研究现状

回顾自复叠制冷技术的发展历史,介绍其原理和特点,并与单级压缩／双级压缩及复叠式制冷进行比较。总结自复叠制冷技术目前的研究概况,指出该技术在现阶段应用中存在的问题和缺陷,以及今后研究中应该着重考虑并改进的方面。     

改进的Kullback-Leibler复非负矩阵分解语音增强算法

针对单通道非负矩阵分解语音增强算法忽略相位信息的问题,提出了一种改进的Kullback-Leibler复非负矩阵分解的语音增强算法。该算法考虑到传统非负矩阵分解算法在复频域中增强语音时目标函数的影响,构建了一种适用于复频域的Kullback-Leibler散度下的目标函数,同时采用频谱一致性约束相位谱补偿算法,使其重构出的语音数据相位谱得到进一步的调制。实验结果表明,对于不同的非平稳噪声,所提出的算法在不同信噪比下均取得了较好的语音增强效果,尤其在低信噪比条件下（0 dB以下）语音增强效果较为明显,性能评估指标的增量较高,较好地克服了由传统相位谱补偿算法造成的信源失真率较低的缺点,进一步减少失真,抑制背景噪声,实现语音增强。     

求解病态问题的一种新的正则化子与正则化算法

根据紧算子的奇异系统理论,提出了一种新的正则化子,进而建立了一类新的求解病态问题的正则化方法。证明了正则解的收敛性并得到了其最优的渐近收敛阶,数值算例说明文中建立的正则化算法是可行而有效的。     

偏导方程的解算子在Cauchy-Riemann复切方向的局部正则性

在Leray映射W(z，ξ)非全纯的严格拟凸开集上，得到了偏导方程解的局部C^1-边界正则性.推广了Chen Z在1992年所得的结果，给出了偏导闭的(p，q)-形式局部地保持实解析性到边界点．     

非径向对称随机向量的研究

本文利用过定点的Copula的最佳上、下界,构造了4个奇异Copula;证明了任意Copula与其生存Copula差的绝对值的上确界是三分之一;给出了度量随机变量非径向对称的方法;研究了最大非径向对称随机变量的性质及相关性度量的界。     

基于复小波变换和支持向量机的缺陷类型识别

 针对传统缺陷检测存在的工序繁琐、不易在线实施、准确率低、容易受人为因素影响,以及用人工神经网络对小样本事件进行缺陷类型识别时存在泛化能力差和过学习等问题,提出一种基于复小波变换和支持向量机（SVM）模式识别理论的缺陷类型识别新方法．在利用小波对超声缺陷回波信号进行消噪的基础上,采用复小波变换获得缺陷回波信号的包络并提取其特征参数,构成输入特征向量后运用支持向量机进行分类．实验结果表明,该方法具有识别准确率高、泛化能力强、容易实现在线处理等优点．     

非共沸混合工质自复叠热泵相积存实验研究

混合工质循环浓度是影响自复叠热泵循环性能的主要因素之一,而相积存导致工质循环浓度偏离充灌浓度,造成热泵性能变化.实验结果表明热泵中存在明显的相积存,最大可达充灌总量的50%以上;加热水温度对相积存的影响很大,每升高10℃,积存量减少10%～21%;工质充灌浓度一定时,积存量随充灌量的增大而增加,工质充灌量增加10%,其积存比例增加1%左右.相积存导致工质循环浓度高于充灌浓度1.6%～37%,由于工质积存量随加热水温度的升高不断降低,循环工质浓度受相积存的影响也不断减小而逐渐接近充灌浓度.     

-方程的解算子在Cauchy-Riemann复切方向的局部正则性

在Ｌｅｒａｙ映射Ｗ（ｚ，ζ）非全纯的严格拟凸开集上，得到了－－方程解的局部Ｃｋ－边界正则性。推广了ＣｈｅｎＺ在１９９２年所得的结果，给出了－－闭的（ｐ，ｑ）－形式局部地保持实解析性到边界点。     

最小二乘支持向量机的扩展及其在时间序列预测中的应用

根据时间序列近期数据较远期数据包含有更多未来信息的思想,对最小二乘支持向量机预测方法进行了扩展,得到了更具一般性的最小二乘支持向量机预测模型,给出了扩展后的预测模型具体算法。两个时间序列的预测实例表明,扩展后的预测方法获得了更好的预测效果,提升了最小二乘支持向量机预测方法的价值。     

扩展性噪声源定位的空间谱估计仿真研究

波束形成是列车噪声源定位的常用方法,但在低频条件下分辨率较差,对扩展性声源的识别效果不佳.我们以扩展性声源为研究对象,理论推导了去自谱算法的扩展源模型.信噪比分别为-5dB和5dB时,通过比较分辨率和信源间隔的关系,对CBF、MVDR、MUSIC三种算法的稳健性进行定性分析,发现MVDR算法的分辨率受信噪比影响最小、稳健性较好.还系统地比较了MVDR算法和去自谱算法对单点声源、扩展性声源的定位效果,仿真表明,去自谱算法能有效抑制旁瓣效果(最大旁瓣级比MVDR算法低7.4dB),更适用于扩展性声源的定位.     

一种适用于低信噪比条件的DOA估计方法

波达方向（Direction of Arrival,DOA）估计技术是信号处理中一个非常活跃的研究领域。但是无论传统的波束形成技术还是现代谱估计技术均适应于高信噪比的环境,当信噪比较低时,这些方法的波达方向（DOA）估计性能急剧下降。根据信号在时间上的强相关性和噪声在时间的弱相关性,提出了一种协方差矩阵的重构方法,该方法能够明显地提高协方差矩阵的信噪比。将新的协方差矩阵应用到最小方差无畸变响应（Minimum Variance Distortionless Re-sponse,MVDR）算法进行DOA估计,改善了传统MVDR算法在低信噪比条件下的DOA估计性能。计算机仿真和定向实验均表明在信噪比较低的环境中可以进行高精度的DOA估计。     

An Electronically Driven Improper Ferroelectric: Tungsten Bronzes as Microstructural Analogs for the Hexagonal Manganites

Since the observation that the properties of ferroic domain walls (DWs) can differ significantly from the bulk materials in which they are formed, it has been realized that domain wall engineering offers exciting new opportunities for nanoelectronics and nanodevice architectures. Here, a novel improper ferroelectric, CsNbW₂O₉, with the hexagonal tungsten bronze structure, is reported. Powder neutron diffraction and symmetry mode analysis indicate that the improper transition (T_C = 1100 K) involves unit cell tripling, reminiscent of the hexagonal rare earth manganites. However, in contrast to the manganites, the symmetry breaking in CsNbW₂O₉ is electronically driven (i.e., purely displacive) via the second‐order Jahn–Teller effect in contrast to the geometrically driven tilt mechanism of the manganites. Nevertheless CsNbW₂O₉ displays the same kinds of domain microstructure as those found in the manganites, such as the characteristic six‐domain “cloverleaf” vertices and DW sections with polar discontinuities. The discovery of a completely new material system, with domain patterns already known to generate interesting functionality in the manganites, is important for the emerging field of DW nanoelectronics.     

An optimal replacement policy for complex multi-component systems

Given a reward structure, this paper addresses an optimal replacement problem for complex multi-component systems. To maintain revenue stream resulting from system, the system is inspected according to a homogeneous Poisson process and certain actions are carried out in response to the system state. Decisions are based on a performance measure described by a Squared Bessel process. Given some assumption, we explore the inherent relation between the Squared Bessel process and an extended Gamma (EG) process. Since there are some flow of income and increasing costs due to inspections, the problem is to optimally stop processing the system and carrying out a renewal to maximize the reward functional. To this end, using the local characteristics of the EG process as a stopping criterion and the expected total discounted reward as a measure of policy, this paper aims at determining an optimal operating (stopping) time which truly balances both income and cost and so maximizes the expected discounted reward over a cycle. In support of the model a numerical example is provided to show feasibility of this programme in real application. Attention is restricted to perfect repair and inspection, but the paper provides the structure so that different scenarios can be explored.     

Estimation of the complex refractive index of epoxy resin phantom using EDTRM

Epoxy resin is a commonly used material in the manufacture of tissue-equivalent phantoms. The complex refractive index (RI) of a series of epoxy resin phantoms with different scattering ability was measured using a recently developed extended derivative total reflection method (EDTRM). Al₂O₃ particles were added into the epoxy resin substrate as the scattering constituent. An increase of the real and imaginary part of the RI with the amount of Al₂O₃ particles was observed. The real part of the RI values reached an impressive precision of 0.002 using EDTRM, which provides a means for the improvement in accuracy for analysis related to RI values in phantom studies.     

极坐标-直角坐标下水下目标跟踪算法及试验研究

在实际水下目标跟踪系统中,由声纳获得的速度量测是一个相对径向速度,并且量测噪声是非白的,为此提出了基于扩展量测和扩展状态的混合坐标系下水下目标跟踪算法。该方法把径向速度量测引入观测模型,提高了目标的状态估计精度和收敛时间;引入了扩充向量,克服了实际水下目标观测噪声非白的影响。提出了水下多目标跟踪水池试验方法。该方法应用静态长线阵和多目标信号源在水池实现了多目标和跟踪体之间的相对运动的模拟。水池试验结果表明所提出的方法性能明显优于基于量测转换跟踪方法(如MC方法),具有重大工程应用价值。     

提高多普勒计程仪性能的矩阵算法

文中介绍了一种精确的矩阵算法,从而使多普勒计程仪的性能有很大程度的提高。借助于高精度频率测量、载体姿态的实时输入、最小二乘方估计以及矩阵算法,从而使载体速度矢量3个分量的测量精度优于0.1%。借助于高精度时延测量、最小二乘方估计以及矩阵算法,使载体下方的局部海底参数得以建立,从而使载体高度的测量精度有望优于1%,并且能获得助航海底姿态。     

Improving performance of wavelet-based image de-noising algorithm using complex diffusion process

Abstract

Image enhancement and de-noising is an essential pre-processing step in many image processing algorithms. In any image de-noising algorithm, the main concern is to keep the interesting structures of the image. Such interesting structures often correspond to the discontinuities (edges). In this paper, we present a new algorithm for image noise reduction based on the combination of complex diffusion process and wavelet thresholding. In the existing wavelet thresholding methods, the noise reduction is limited, because the approximate coefficients containing the main information of the image are kept unchanged. Since noise affects both the approximate and detail coefficients, the proposed algorithm for noise reduction applies the complex diffusion process on the approximation band in order to alleviate the deficiency of the existing wavelet thresholding methods. The algorithm has been examined using a variety of standard images and its performance has been compared against several de-noising algorithms known from the prior art. Experimental results show that the proposed algorithm preserves the edges better and in most cases, improves the measured visual quality of the de-noised images in comparison to the existing methods known from the literature. The improvement is obtained without excessive computational cost, and the algorithm works well on a wide range of different types of noise.