一种新的板状构件无损检测方法

对于板、壳构件的无损检测，提出了一种新的数字层析方法。采用射线相对于构件长宽表面倾斜入射、构件绕旋转轴回转的扫描方式，以采集的二维数字投影序列，通过相应的预处理和重建算法，重构出该扫描区域的断层图像。计算机模拟和实验结果表明，该方法能较好地解决此类结构的层析检测，与传统的二维CT相比，它不受被检测板壳长、宽尺寸的限制，可通过一次扫描获得投射数据，并完成对扫描区域的数字层析，但是，由于该重建方法属于不完全数据重建，所以存在着相邻层之间的图像“混叠”现象，从而降低了厚度方向上的分辨力。     

基于FDK反投影权重的锥束DSA重建算法

针对锥束数字减影血管造影成像系统(DSA)锥角增大而导致锥束伪影严重的问题,提出了一种基于FDK的反投影权重锥束DSA重建算法.分析了圆扫描轨迹远端伪影的成因,针对短扫描阴影区域导致的Radon空间数据缺失,提出了一种距离变量的反投影权重函数,并将其作为约束条件引入到FDK算法中,实现扫描轨迹远端区域的数据补偿,扩大图像重建区域.应用该算法对无噪声和有噪声的模拟投影数据,及自行研发的锥束DSA的实际扫描数据分别进行了重建试验.结果表明,文中算法较FDK类算法(Parker-FDK)对大锥角投影数据可明显抑制锥角伪影,其归一化均方距离判据和归一化平均绝对距离判据比Parker-FDK均降低了5％.     

CT投影变换理论及其在圆轨道锥束重建中的应用

为了精确地获得计算机断层成像(CT)图像重建所需的平行束X射线投影,提出了CT投影变换理论,得到了一种精确地由锥束投影计算平行束投影的算法.该算法可以适用于任意形式的扫描轨道.在此基础上,分别提出了针对完整物体和物体感兴趣区域进行CT投影变换的投影数据完备性条件.将CT投影变换方法应用于圆轨道CT图像重建,有效地改善了FDK算法的重建结果,特别是在远离扫描轨道的平面内,改进后的重建图像CT值更加接近真实值.数值模拟实验证明了上述CT投影变换理论和方法的有效性.     

利用投影数据重排进行锥形束体积重建的改进算法

针对锥顶轨迹为单圆的锥形束体积重建问题,提出了一种基于平板检测器的T-FDK算法．不同于传统的FDK算法,该算法首先将锥形束投影数据重排为倾斜平行投影数据,然后再经过加权滤波和反投影重建,最后重建出待测物体的三维结构．数据仿真实验结果表明,该算法在保持与传统FDK算法有相同的计算复杂度的同时,重建图像的质量有了明显的提高,可以确保在较大的锥角范围内获得满意的重建图像．因而该算法在医学成像和无损探伤等领域具有重要的实用价值．     

锥束CT的分区短扫描FDK重建算法

圆轨道锥束CT(computed tomography)重建中,随着锥角增大,锥角伪影和数据缺失伪影越来越严重,影响FDK算法(由Feldkamp-Davis-Kress名字命名)重建区域的大小和图像质量。本文分析了短扫描FDK算法(short scanFDK,SS-FDK)重建时的数据完整性,提出了根据重建切片高度自适应地将重建切片分成若干区域,对每个区域采用SS-FDK算法进行重建的分区短扫描FDK重建算法。理论分析及试验仿真表明,该方法虽然计算复杂度有所增加,但充分利用了锥束CT投影数据,较大地增大了重建区域,完全重建区域高度达到扫描高度的1-sin2δ倍(δ为射线源半张角),且重建精度和图像质量与FDK算法相当。     

锥束CT的分区短扫描FDK重建算法

圆轨道锥束CT(computed tomography)重建中,随着锥角增大,锥角伪影和数据缺失伪影越来越严重,影响FDK算法(由Feldkamp-Davis-Kress名字命名)重建区域的大小和图像质量。本文分析了短扫描FDK算法(short scanFDK,SS-FDK)重建时的数据完整性,提出了根据重建切片高度自适应地将重建切片分成若干区域,对每个区域采用SS-FDK算法进行重建的分区短扫描FDK重建算法。理论分析及试验仿真表明,该方法虽然计算复杂度有所增加,但充分利用了锥束CT投影数据,较大地增大了重建区域,完全重建区域高度达到扫描高度的1-sin2δ倍(δ为射线源半张角),且重建精度和图像质量与FDK算法相当。     

基于转角增量关系的FDK锥束重建改进算法

单圆形轨迹不能满足锥束投影精确重建的充要条件是经典FDK算法出现锥向衰减伪像的根本原因.通过斜平面转角增量关系的分析,推导出同锥角斜平面间转角及其增量的计算关系,进而得出FDK算法是对同锥角斜平面族上有限视角的投影数据进行重建,并且在滤波反投影重建过程中存在转角关系不匹配问题.针对上述两个问题,提出了一种利用转角及其增量关系对FDK算法进行改进的新方法,改进思路也进一步推广到T-FDK算法中.Shepp-Logan模型的仿真实验结果表明在适中或较大锥角情况下,改进算法显著改善了FDK算法所存在的锥向衰减伪像.     

GPU加速实现的锥束CT高精度正投影算法

CT的正投影计算是对CT数据采集过程的模拟,不仅可用于生成投影数据,而且是CT图像迭代重建算法的一个关键组成部分.在CT的锥束扫描方式下,正投影计算量大,计算时间长.为此,提出了一种GPU加速实现的锥束CT正投影算法.该算法通过并行计算各条X射线在探测器上投影,实现了锥束CT正投影的快速计算.由于该算法支持全浮点运算精度计算,且采用三线性插值方式,因此计算精度高.通过对Shepp-Logan模型的正投影计算实验以及与其他正投影算法的比较,验证了作者算法的优点.     

基于相机模型的锥束CT重建误差校正

该文对存在几何误差的锥束计算机层析成像(CT)的图像重建校正方法进行了研究。该文将锥束CT系统看做针孔相机,因此相机的成像模型可以用来修正三维体素与二维投影之间的映射关系。将该映射关系带入到重建算法中,就可以对存在误差的锥束CT进行有效的重建,提高重建图像的质量。计算机视觉中的相机标定技术被用来构建成像模型。该技术的可靠性保证了本文方法的精度和鲁棒性。仿真和实际系统实验表明:本方法可以在图像重建过程中对锥束CT中的几何误差进行有效的校正。     

基于图形处理器的锥束CT快速迭代重建算法

提出了一种基于图形处理器实现的锥束CT图像迭代重建算法.该算法将三维纹理作为被重建物体的离散模型,基于射线投射方法实现了锥束CT的正投影计算;通过反向逐层映射到三维纹理实现了反投影计算;采用多纹理融合等技术完成了图像校正和投影校正.与经典的TMA-SART算法比较,作者算法运算速度快,占用显存少,支持全浮点精度运算,且易于在算法中添加先验知识和约束条件.通过对Shepp-Logan模型的图像迭代重建实验,验证了该算法的优势.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to