Fast parallel algorithm for three-dimensional distance-driven model in iterative computed tomography reconstruction

The projection matrix model is used to describe the physical relationship between reconstructed object and projection.Such a model has a strong influence on projection and backprojection,two vital operations in iterative computed tomographic reconstruction.The distance-driven model(DDM) is a state-of-the-art technology that simulates forward and back projections.This model has a low computational complexity and a relatively high spatial resolution;however,it includes only a few methods in a parallel operation with a matched model scheme.This study introduces a fast and parallelizable algorithm to improve the traditional DDM for computing the parallel projection and backprojection operations.Our proposed model has been implemented on a GPU(graphic processing unit) platform and has achieved satisfactory computational efficiency with no approximation.The runtime for the projection and backprojection operations with our model is approximately 4.5 s and 10.5 s per loop,respectively,with an image size of 256×256×256 and 360 projections with a size of 512×512.We compare several general algorithms that have been proposed for maximizing GPU efficiency by using the unmatched projection/backprojection models in a parallel computation.The imaging resolution is not sacrificed and remains accurate during computed tomographic reconstruction.     

深海锰结核结壳中超微生物化石的电镜观察

深海锰结核锰结壳是富含钴、锰等金属的重要矿藏，为了更好地勘探和开采利用这些资源，许多研究工作都围绕着锰结核结壳的成因而展开。总体来说，关于锰结核结壳的成因有胶体说和生物催化说两种。     

基于新型Loyt滤波器选频的Nd∶GdVO4单频绿光微片激光器

报道了一种LD泵浦Nd∶GdVO4晶体的单频绿光微片激光器。采用Rochon棱镜与KTP倍频晶体构成的新型Loyt滤波器作为选频元件,各元件之间采用光胶的方法结合在一起,从而实现稳定的单纵模绿光输出。在600 mW,808 nm LD泵浦时获得95.3 mW稳定的单频绿光输出,光-光转换效率达15.9%。     

自组装单分子空穴传输层在反式钙钛矿太阳电池的研究进展

空穴传输层在钙钛矿太阳电池(Perovskite solar cell, PSC)中起着抽取和传输钙钛矿层产生的光生空穴、抑制电子回流等重要作用,是构成高性能器件的重要组成部分.经典的空穴传输材料,如2,2’,7,7’-四[N,N-二(4-甲氧基苯基)氨基]-9,9’-螺二芴(spiro-OMe TAD)、聚[双(4-苯基)(2,4,6-三甲基苯基)胺](PTAA)等,空穴迁移率低、价格昂贵等缺点限制了其规模化应用.近年来,在反式PSC中自组装单分子层(self-assembledmonolayers,SAM)作为空穴传输层广泛应用,提升了器件性能.SAM分子结构中含有锚定官能团,可以在衬底上形成单分子薄膜,有着材料消耗小、无需添加剂、寄生吸收低、能够兼容叠层器件和有利于大面积制造等优点,已成为PSC领域的研究热点.本综述结合PSC发展,按照SAM分子结构中锚定基团的不同,对近年来基于SAM的空穴传输层的研究进行了分类和归纳,结合分子骨架变化分析了结构变化对其特性及器件性能的影响.最后,对SAM作为空穴传输层的发展做了总结和展望.     

A new LD-pumped single frequency micro-chip green laser

A novel LD-pumped single-frequency micro-chip green laser is presented. By using the combination of short cavity and Loyt filter formed by Rochon prism and KTP crystal, a stable single t~equency green laser is obtained with 60 mW output at 500 mW LD-pump. The optical-to-optical conversion efficiency is about 12%. The optical contact between components of the laser is adopted. This laser has the advantages of a compact structure and a low cost.     

结合刚体基本运动分析三刚片体系几何构造

为探寻体系几何构造分析技巧,总结了三刚片连接的所有可能形式,在简化模型分析基础上,结合刚体的基本运动特征,针对三刚片连接形式中有无穷远瞬铰出现的特殊情况进行详细分析,获取体系构造分析中的一般规律,为学习体系几何构造分析提供帮助.     

激光二极管端面抽运高偏振比Nd∶YVO_4晶体微片绿光激光器

报道了一种激光二极管(LD)抽运高偏振比腔内倍频全固态微片激光器,采用两光轴正交的Nd∶YVO4激光晶体作为增益介质,消除单块Nd∶YVO4晶体对输出绿光的退偏作用,获得高偏振度的绿光输出,同时各晶体之间采用光学胶合的方法,实现了微片绿光激光器。在1.8 W抽运功率下,获得了偏振比为110∶1,功率为336 mW的绿光输出,光-光转换效率为18.7%。该激光器结构简单、体积小、成本低,适合于大批量生产。     

翼缘削弱型节点钢结构的抗震性能研究

采用有限元方法对翼缘削弱型节点钢结构的抗震性能进行了研究,通过模态分析和动力时程分析,详细分析了框架的周期、结构动内力、动应力以及塑性变形区的发展规律等,并和普通节点框架的计算结果进行对比. 研究结果表明：在小震下,翼缘削弱型节点的抗震性能并不理想,但在大震下,表现出了良好的抗震性能,塑性变形出现在梁端削弱处,塑性应变增加,柱底剪力和顶层位移均比普通节点框架的小,建议在强震区推广使用翼缘削弱型节点.     

东海碎屑矿物特征的研究

本文根据东海在全球构造中的位置,海底表层沉积物中碎屑矿物的组成、成因、分布特征,讨论了碎屑重矿物群、重矿物组合类型以及碎屑矿物组合分带对沉积地段古地理环境、海底矿产、沉积相及区域构造等方面的指示意义。     

苏州广播电视总台大屏宣传车

针对现有大屏展示车的不足和使用瓶颈,结合突发事件时现场处置的快速便捷要求,我们设计了一种全新的液压翻转叠加方案,并加以屏幕360°旋转,最大化增大屏幕的面积和使用便捷性。搭配小型视音频系统,在实际使用中取得了很好的效果