去除椒盐噪声的交替方向法

传统图像去噪法基于有用信息和噪声频率特性的差别实现去噪,实际中,有用信息和噪声在频带上往往存在重叠,因此,传统去噪法在抑制噪声的同时,往往损失了细节信息,使图像变模糊. 本文引入稀疏与低秩矩阵分解模型描述图像去噪问题,基于该模型,采用交替方向法（Alternating direction method,ADM）得到复原图像. 实验证明该方法比常用的中值滤波法更有效地抑制了椒盐噪声,同时更好地保持了原始图像的细节信息.     

基于Bregman迭代的CT图像重建算法

针对大规模集成电路领域CT重建图像的特点,提出TV约束条件下采用l1范数作正则项的重建模型,并给出了基于Bregman迭代的模型求解算法.算法分为两步: 1)采用Bregman迭代求解图像的l1范数作为正则项,误差的加权l2范数作为保真项的约束极值问题;2) 采用TV约束对1)中得到的重建图像进行修正.算法对TV约束条件下采用l1作正则项的重建模型分开求解,降低了算法的复杂度,加快了收敛速度.算法在稀疏投影数据下可以快速重建CT图像且质量较好.本文采用经典的Shepp-Logan图像进行仿真实验并对实际得到的电路板投影数据进行重建,结果表明该算法可满足重建质量要求且重建速度有较大提升.     

黄酮及维生素C的抗羟基自由基的比较研究

以大豆甙和芦丁作为黄酮化合物的代表，并与维生素C比较，研究其对羟基自由基的抑制能力，并以大豆、橙皮、柑皮和青椒提取物作羟基自由基清除剂，研究这些提取物对羟基自由基的清除作用。结果表明，大豆甙对羟基自由基的清除率最高，其次是芦丁，再次是维生素C；含黄酮化合物的提取物比含维生素C的提取物对羟基自由基的清除率大，其中以大豆撮以物最优。     

TDI—PEG线型遥爪聚合物改善纸张物理性能的研究

本文研究了甲苯－2,4－二异氰酸酯（TDI）与柔性高分子聚乙二醇（PEG）生成线型遥爪聚合物对纸张物理性能的影响,分析了其遥爪聚合物中柔性链对纸张性能的作用。研究结果表明：由于线型遥爪聚合物可以使纸张中的相距较远的纤维之间产生柔性较好的氨基甲酸酯型架桥结构,所以对纸张耐折度、撕裂度、挺度、耐破度、湿强度以及表面强度等物理性能有明显改善。     

交流电动机变频调速时的谐波影响及其测量

讨论了谐波对交流电动机的不良影响。说明不同类型的逆变器其谐波对电动机的影响是不同的。分析了变频调速系统中谐波测量的实际问题。介绍了一种适用于变频调速系统中电压、电流、功率测量的新型宽带数字测量仪。     

基于平面五杆闭环结构的空间并联机构类型综合与拓扑分析

分析了五杆闭环结构的类型、拓扑描述、组成形式和运动性能 ,重点研究了基于 5R闭环结构与RPRPR闭环结构在空间并联机构中的应用 ,给出了基于五杆闭环结构的空间并联机构的类型综合方法及步骤 ,并综合出了九种空间并联机构的构型。     

Purification,characterisation and application of α‐l‐rhamnosidase from Penicillium citrinum MTCC‐8897

An α‐l ‐rhamnosidase secreted by <i>Penicillium citrinum</i> MTCC‐8897 has been purified to homogeneity from the culture filtrate of the fungal strain using ammonium sulphate precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The sodium dodecyl sulphate/polyacrylamide gel electrophoresis analysis of the purified enzyme gave a single protein band corresponding to the molecular mass 51.0 kDa. The native polyacrylamide gel electrophoresis also gave a single protein band confirming the enzyme purity. The <i>K</i><sub>m</sub> and <i>V</i><sub>max</sub> values of the enzyme for p‐nitrophenyl α‐l ‐rhamnopyranoside were 0.36 mm and 22.54 μmole min<sup>?1</sup> mg<sup>?1</sup>, respectively, and <i>k</i><sub>cat</sub> value was 17.1 s<sup>?1</sup> giving <i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub> value of 4.75 × 10<sup>4</sup> m <sup>?1 </sup>s<sup>?1</sup>. The pH and temperature optima of the enzyme were 7.0 and 60 °C, respectively. The purified enzyme liberated l ‐rhamnose from naringin, rutin, hesperidin and wine, indicating that it has biotechnological application potential for the preparation of l ‐rhamnose and other pharmaceutically important compounds from natural glycosides containing terminal α‐l ‐rhamnose and also in the enhancement of wine aroma.     

Synthesis and characterisation of fluorescent pyrene‐end‐capped polylactide fibres

Fluorescent markers are critical for tracking the position and movement of molecules both <i>in vivo</i> and <i>in vitro</i>. Conventionally, synthetic dyes are non‐covalently added to polymers for fluorescent tracking, but often diffuse away. Here we demonstrate, for the first time, a facile method for the synthesis of fluorescent poly(lactic acid) nano‐/microfibres for biomedical applications using solution spin blowing. Pyrene‐end‐capped poly(l ‐lactide) (PLLA) derivatives were synthesised using the ring‐opening polymerisation of l ‐lactide and they were characterised using spectroscopic and thermal analyses. Submicrometre‐sized fluorescent fibres were produced from these PLLA derivatives using solution blow spinning techniques generating polymer blends and core–shell fibres. Such system could be further exploited to incorporate electrically conductive carbon allotropes via the pyrene aromaticity, producing fluorescent and electrically active fibres for <i>in vitro</i> monitoring and electrical stimulation. © 2018 Society of Chemical Industry     

Effects of light exposure on chlorophyll,sugars and vitamin C content of fresh‐cut celery (Apium graveolens var. dulce) petioles

Effects of light exposure (24 μmol m<sup>?2</sup> s<sup>?1</sup>) on fresh‐cut celery nutritional quality were evaluated during 8‐day storage at 7 °C using darkness as control. Light exposure preserved 47% chlorophyll <i>a</i> and 48% chlorophyll b contents more than darkness at the end of storage. Sucrose, reducing sugar and glucose contents in light‐stored petioles were 17%, 25% and 67% higher than those in dark‐stored petioles after 8‐day storage, respectively, thus resulting in higher total soluble solids content in light condition. Moreover, l ‐ascorbic acid content increased at 2‐day storage in light condition and was 46% more than in darkness at the end of storage. The fresh weight loss significantly increased in all petioles, and this increase was markedly accelerated by light exposure with a maximum of 1.43% at the end of storage. Dry matter content was induced more by light exposure than by darkness at 2‐day storage.