光纤连接器端面几何参量自动测量仪

报道了一种高精度测量光纤连接器端面几何参量的自动测量仪。叙述了光纤连接器的端面几何参量的测量原理。由光纤连接器端面形貌和纤芯中心坐标,可以高精度得到曲率半径、顶点偏移量、端面倾斜角和光纤高度等影响连接器性能的关键端面几何参量。该仪器体积小,自动化程度高,用户界面友好,使用方便,可测量物理接触、角度式物理接触等类型的光纤连接器端面几何参量。实际测量证明,该测量仪有很好的重复测量精度。该测量仪与美国Dorc公司ZX-1 mini PMS测量仪和Norland公司NC3000测量仪相比,测量精度水平相当。该仪器样机已通过华东国家计量测试中心的测试。     

Generalized total variation-based MRI Rician denoising model with spatially adaptive regularization parameters

Magnetic resonance imaging (MRI) is an outstanding medical imaging modality but the quality often suffers from noise pollution during image acquisition and transmission. The purpose of this study is to enhance image quality using feature-preserving denoising method. In current literature, most existing MRI denoising methods did not simultaneously take the global image prior and local image features into account. The denoising method proposed in this paper is implemented based on an assumption of spatially varying Rician noise map. A two-step wavelet-domain estimation method is developed to extract the noise map. Following a Bayesian modeling approach, a generalized total variation-based MRI denoising model is proposed based on global hyper-Laplacian prior and Rician noise assumption. The proposed model has the properties of backward diffusion in local normal directions and forward diffusion in local tangent directions. To further improve the denoising performance, a local variance estimator-based method is introduced to calculate the spatially adaptive regularization parameters related to local image features and spatially varying noise map. The main benefit of the proposed method is that it takes full advantage of the global MR image prior and local image features. Numerous experiments have been conducted on both synthetic and real MR data sets to compare our proposed model with some state-of-the-art denoising methods. The experimental results have demonstrated the superior performance of our proposed model in terms of quantitative and qualitative image quality evaluations.     

板条Nd:YAG晶体的合成盘抛光技术

针对高功率板条激光器核心工作器件——板条Nd:YAG晶体的超精密加工开展研究,分析了具有特殊构型的板条Nd:YAG晶体元件的加工性能及工艺难点,提出了一种新的基于合成盘抛光的板条Nd:YAG晶体加工工艺,并对规格为100mm×30mm×3mm的板条Nd:YAG晶体进行了加工实验。实验结果表明,合成盘抛光可以很好地控制元件的塌边现象;通过磨料的优化选择,在合成盘抛光工艺中匹配合适粒度的Al2O3磨料能够实现元件的低缺陷加工,元件下盘后的全反射面平面度达0.217λ(1λ=632.8nm),端面平面度达到0.06λ,表面粗糙度达0.55nm(RMS),端面楔角精度可达2″。     

Quantification of glutathione in plasma samples by HPLC using 4-fluoro-7-nitrobenzofurazan as a fluorescent labeling reagent

A rapid and highly sensitive high-performance liquid chromatograpy method with fluorescence detection has been developed for determination of glutathione (GSH) in human plasma. A simple pre-column derivatization procedure with 7-flouro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-F) reagent was employed. The separation of the derivatized glutathione was performed using a mobile phase consisting of phosphate buffer (0.02 mol/L, pH 6.0)-acetonitrile (77:23, v/v) at a flow rate of 1.0 mL/min with the column temperature 2°C. The eluted derivatives were fluorometrically detected at an excitation wavelength 470 nm and an emission wavelength 530 nm. Under the optimum chromatographic conditions, the calibration curve was linear over the range of 0.1 μmol/L to 10.0 μmol/L with the correlation coefficient of 0.9988. The precision of the method was satisfactory with the intra- and inter-day coefficient of variation being 6.3%, 6.9%, respectively. This method has been used to determine glutathione concentrations in plasma samples from healthy individuals.     

化学计量学用于决明子色谱指纹图谱峰纯度的鉴别

应用化学计量学方法鉴别色谱指纹图谱的峰纯度。对背景进行扣除后,用对照组分光谱构建正交投影矩阵对目标色谱峰的光谱进行投影,以目标色谱峰投影后的残余光谱与投影前的原始光谱的夹角余弦为判据鉴别目标色谱峰的峰纯度：用该方法对决明子药材色谱指纹图谱的峰纯度进行识别,鉴别出大黄素、大黄酚和大黄素甲醚三个纯色谱峰。此方法用于色谱指纹图谱峰纯度的鉴别,结果可靠。     

A Smoothing Newton-Type Algorithm of Stronger Convergence for the Quadratically Constrained Convex Quadratic Programming

In this paper we propose a smoothing Newton-type algorithm for the problem of minimizing a convex quadratic function subject to finitely many convex quadratic inequality constraints. The algorithm is shown to converge globally and possess stronger local superlinear convergence. Preliminary numerical results are also reported. Mathematics Subject Classification (1991): 90C33, 65K10 This author’s work was also partially supported by the Scientific Research Foundation of Tianjin University for the Returned Overseas Chinese Scholars and the Scientific Research Foundation of Liu Hui Center for Applied Mathematics, Nankai University-Tianjin University.     

粘性对离心泵性能的换算方法的探索

在同一试验台架上，采用三种不同粘度的油以及水作为输送介质，实测了相同比转速，相同叶轮外径和出口宽度，但不同叶型的叶轮的外特性，同时，采用美国AHI、前苏联ГОСТ以及德国KSB的换算方法得到了以清水实验外特性为基准的粘性换算曲线，对比了各换算曲线与实测性能之间、叶型与粘性外特性之间的关系。结果表明：叶型对外特性影响明显，且各换算结果都和试验值具有较大的偏差，尤其是前苏联的方法偏离试验值更大。     

双单体原位接枝插层法制备聚丙烯纳米复合材料的研究Ⅰ.制备、表征及力学性能的研究

用有机插层剂处理蒙脱土原土 ,制得有机蒙脱土 (O MMT) .采用双单体 (马来酸酐和苯乙烯 )原位接枝插层法 ,制备了聚丙烯 蒙脱土纳米复合材料母料 .将母料与聚丙烯基体在双螺杆上共混挤出 ,制得聚丙烯 蒙脱土纳米复合材料 (PP Montmorillonetenanocomposites,PMNC) .这是制备聚合物纳米复合材料的一种新方法 .通过X 射线衍射测试 (XRD)表明 ,有机蒙脱土片层 0 0 1面间距从原土的 1 4 9nm扩大到 2 96nm ,复合材料中蒙脱土片层 0 0 1面间距由有机蒙脱土的 2 96nm扩大到 4 0nm .力学性能测试表明 ,复合材料的力学性能明显优于PP基体 ,在提高材料拉伸强度的同时 ,缺口冲击强度也得到很大的提高 .用扫描电镜 (SEM)对材料的冲击断面形貌进行了研究 ,并从理论上分析了断裂机理 .随着蒙脱土含量的增加 ,冲击断裂形式逐渐从脆性断裂变成韧性断裂     

Synthesis of Porous Fe3C-Based Composite Beads as Heterogeneous Oxidation Catalysts

A series of multiscale cementite/iron/porous carbon (CIPC-T) composites with extremely low nitrogen content and millimeter-size spherical morphology were prepared by simple carbothermal pyrolysis of resin spheres exchanged with ferric oxalate anions. CIPC-T materials are composed of highly disperse core–shell-structured Fe₃C/Fe@graphitic carbon (CI@GC) nanoparticles embedded in a porous amorphous carbon framework. A mechanism for the formation of the composites is proposed on the basis of the results of XRD, SEM, TEM, and thermogravimetric analysis. The Fe₃C content can be easily controlled just by using different carbothermal temperatures. The CIPC-T materials proved to be active as heterogeneous catalysts for oxidation of ethylbenzene to acetophenone and Fenton-like oxidation of methylene blue. For the first time, the role of Fe₃C in catalytic oxidation was confirmed. The spherical morphology of the composites and magnetic property facilitate separation of the catalyst from the reaction solution. More importantly, no leaching of iron active sites occurs during the reactions and the catalyst can be reused in continuous runs without obvious loss of activity. Such high stability of iron sites in the composites is ascribed to the protecting outer graphitic carbon shell of CI@GC.     

Correlation stress testing for value-at-risk: an unconstrained convex optimization approach

Correlation stress testing is employed in several financial models for determining the value-at-risk (VaR) of a financial institution’s portfolio. The possible lack of mathematical consistence in the target correlation matrix, which must be positive semidefinite, often causes breakdown of these models. The target matrix is obtained by fixing some of the correlations (often contained in blocks of submatrices) in the current correlation matrix while stressing the remaining to a certain level to reflect various stressing scenarios. The combination of fixing and stressing effects often leads to mathematical inconsistence of the target matrix. It is then naturally to find the nearest correlation matrix to the target matrix with the fixed correlations unaltered. However, the number of fixed correlations could be potentially very large, posing a computational challenge to existing methods. In this paper, we propose an unconstrained convex optimization approach by solving one or a sequence of continuously differentiable (but not twice continuously differentiable) convex optimization problems, depending on different stress patterns. This research fully takes advantage of the recently developed theory of strongly semismooth matrix valued functions, which makes fast convergent numerical methods applicable to the underlying unconstrained optimization problem. Promising numerical results on practical data (RiskMetrics database) and randomly generated problems of larger sizes are reported.