氮化硅/石墨激光合金化涂层的组织结构与性能研究

为获得金属表面特别是高副接触金属表面含自润滑特性且具有高硬度耐磨特性的功能材料 ,研究了 45 # 钢表面激光合金化氮化硅 /石墨复合涂层的工艺方法、组织特征、界面形态及其形成机制 ,利用光学显微镜、扫描电镜和X射线能谱对所形成合金化层的元素分布和含量进行了分析 ,并对试样硬度进行了测定。结果表明 ,合金化层中元素Fe ,Co ,Si,C分布均匀 ;C含量达到了 15 6 9%,大部分以石墨的形式存在 ,具有一定的自润滑性能 ;但在形成合金化层的温度条件下 ,氮化硅分解严重 ;合金化层硬度提高的主要原因是Si Fe ,Co Fe固溶体的强化作用及高碳马氏体的生成和高硬度碳化物的存在。     

Magnetic Properties of Fe-Doped Rutile

Ball-milling method was applied to dissolve Fe into titanium dioxide (TiO₂). X-ray diffraction indicated the starting anatase changed to a rutile-type structure with oxygen deficiency after ball milling. Transmission electron microscopy and X-ray absorption experiments were conducted to examine the possible existence of magnetic impurities in the ball-milled powders after they were leached in HCl solutions. Temperature dependence of the resistivity shows semiconducting behavior and the magnetic hysteresis loops at 5 and 300 K exhibit ferromagnetic characteristics. Fe-doped TiO₂ films were also prepared by pulsed laser deposition. The magnetic properties of the films are discussed.     

On the convergence of the inverses of Toeplitz matrices and its applications

Many issues in signal processing involve the inverses of Toeplitz matrices. One widely used technique is to replace Toeplitz matrices with their associated circulant matrices, based on the well-known fact that Toeplitz matrices asymptotically converge to their associated circulant matrices in the weak sense. This often leads to considerable simplification. However, it is well known that such a weak convergence cannot be strengthened into strong convergence. It is this fact that severely limits the usefulness of the close relation between Toeplitz matrices and circulant matrices. Observing that communication receiver design often needs to seek optimality in regard to a data sequence transmitted within finite duration, we define the finite-term strong convergence regarding two families of matrices. We present a condition under which the inverses of a Toeplitz matrix converges in the strong sense to a circulant matrix for finite-term quadratic forms. This builds a critical link in the application of the convergence theorems for the inverses of Toeplitz matrices since the weak convergence generally finds its usefulness in issues associated with minimum mean squared error and the finite-term strong convergence is useful in issues associated with the maximum-likelihood or maximum a posteriori principles.     

浅谈东深供水改造工程的设计监理工作

施工图阶段设计监理工作的内容归纳起来主要是对设计质量进行控制.依据<水利建设工程招标、施工图阶段设计监理试行规定>,其具体工作内容仅限于设计成果的合法性和安全性,没有充分发挥设计监理作用,对施工图阶段设计质量的理解是不全面的.施工图阶段的设计质量不仅仅是提交合法和安全的图纸,而且图纸的提交时限性、可实施性及经济性也应是考核设计质量的重要组成部分,为此东深供水改造工程的设计监理工作内容确定为"五项控制"和"两项权利",全面地对施工图阶段的设计质量进行控制.     

论建立动态勘探目标评价体系的迫切必要性

从国际上通行的油气勘探评价工作重点,中国石油所面临的"已逐步进入一个不断在老区范围内开展精细勘探、在老区范围内开展新区块、新层系勘探以获得主要的储量增长"的新的勘探形势,现有地质研究中各专题研究与具体勘探目标评价脱节等多个方面,论述了在中国石油内部建立一套动态勘探目标评价体系的迫切必要性;并在此基础上阐述了一个完整的动态勘探目标评价体系应包括的主要内容;最后对该体系的建设进行了可行性分析。     

大坝监测自动化中的人工比测研究

阐述了人工比测的概念、方式和数据分析方法,对人工比测及数据分析中应注意的问题也进行了深入研究。     

时频域自动识别与压制高频噪声

本文在分析张宇等及钱忠平等提出的高频噪声判别准则基础上,利用夏洪瑞等根据在窄档等频距小波分频之后识别、压制高频噪声的思路,提出在时频域将代表地震道主要能量的几个频带的平均振幅绝对值作为正常子波的平均振幅绝对值,以此来识别和压制高频噪声的异常振幅。实际处理结果表明,此法不仅可以压制高频谐振及高频突发噪声,而且可以保护弱地震反射信号不受损害。     

工程设计仿真网络环境的信息安全技术架构研究

研究意义和应用前景信息系统的安全威胁成为日益受到关注的严重问题。涉密内网虽然与因特网物理隔离,仍同样面临着漏洞、蠕虫、病毒、木马和后门等威胁。涉密信息可以通过文件共享、木马、邮件等方式被泄露,也可能被非授权用户登录访问,还可能通过外设(如:USB、光     

两两NQD列乘积和的Jamison型强稳定性的一个注记

讨论了不同分布两两NQD列的Jamison型加权乘积和的强稳定性。推广了不同分布独立列部分和和同分布NQD列部分和情形相类似的结论，得到了一些新的结果。     

Wavelet-based Rayleigh background removal in MRI

Rayleigh distribution governs noise in 'no signal' regions of magnetic resonance magnitude images. Large areas of background noise in MRI images will seriously affect their effective utilisation. A new wavelet-based algorithm is presented that can work efficiently either as a standalone procedure or couple with existing denoising algorithms to significantly improve their effectiveness.