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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. 相似文献
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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 总被引:9,自引:2,他引:7
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。 相似文献
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Sarita Yadav Vinita Yadav Sudha Yadav Kapil D.S. Yadav 《International Journal of Food Science & Technology》2012,47(2):290-298
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. 相似文献
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Aula Alwattar Athir Haddad Quan Zhou Tatiana Nascimento Ryan Greenhalgh Eliton Medeiros Jonny Blaker Adam Parry Peter Quayle Stephen Yeates 《Polymer International》2019,68(3):360-368
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 相似文献
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Lijuan Zhan Jinqiang Hu Lingyun Pang Yu Li Jianfeng Shao 《International Journal of Food Science & Technology》2014,49(2):347-353
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. 相似文献