基于改进非局部先验的Bayesian低剂量CT投影平滑算法

针对低剂量CT(LDCT)图像质量退化的问题,提出了一种改进的非局部先验模型,并将基于该模型的Bayesian统计算法应用于LDCT投影降噪中.首先将方向性测度引入到传统的非局部先验模型中,构建一种改进的先验模型;同时结合基于加权欧氏距离的距离测度,提高权重系数计算的准确性;然后运用基于该先验模型的Bayesian统计算法对LDCT投影进行平滑降噪;最后依据降噪后投影,利用滤波反投影(FBP)方法进行重建,得到改善的LDCT图像.实验结果表明,与典型的传统LDCT重建算法相比,该算法在抑制噪声、去除伪影的同时,较好地保留了重建图像细节信息.     

基于线过程的POCS超分辨图像重构算法

传统的凸集投影（POCS）超分辨重构算法易使图像产生边缘振荡效应问题,在研究了边缘振荡效应的成因后,提出一种基于线过程模型的POCS算法来对低分辨图像序列进行超分辨图像重构．该算法采用线过程模型检测出超分辨初始估计图像的4个方向的边缘,在传统POCS的投影过程中增加了对图像的平滑处理,实现了低分辨图像序列超分辨重建的对比实验,实验结果表明图像边缘振荡效应能得到明显改善．     

基于非局部方向性核先验的PET图像Bayesian重建

为了在抑制噪声的同时更好地保持PET重建图像中的细节结构,提出了一种基于非局部方向性核先验(NSKP)的Bayesian重建算法.为了充分利用图像中的全局信息,该算法在二阶核回归过程中估计出图像梯度,计算出相应的方向性矩阵,并根据非局部均值权值矩阵和方向性矩阵的卷积,计算先验项的权值.在重建中,该算法在高阶核回归过程中同时更新图像的梯度和先验信息,而不是单独计算图像梯度.另外,高阶核回归方法运用多自由度的参数估计提高了重建的精确度.研究结果表明,该算法通过计算引入局部结构信息的全局先验权重,更好地抑制了噪声和过平滑,保持了重建图像中细节区域的结构性和背景区域的一致性.对体模数据的模拟实验结果从视觉和数值角度验证了该算法在PET图像重建中的有效性.     

基于互反射先验的端到端沉浸式投影补偿

沉浸式投影系统中的互反射现象会导致投影质量下降，投影补偿任务通过对输入图像的修改补偿，减少互反射造成的影响从而得到更好的成像效果.投影补偿任务是研究输入原图与最终成像之间的关系，通过对输入图像的修改补偿，减少互反射造成的影响从而得到更好的成像效果.本文提出互反射先验，互反射先验是指发生互反射的区域的临近区域通道像素值十分接近最大值256，因此通过图像的区域通道像素值可以获得互反射信息.本文提出的互反射补偿网络(IRCN)，通过互反射先验生成互反射掩膜，消除沉浸式投影环境中的多余互反射.为了验证IRCN模型，使用了超过5000对投影图像数据集和曲面投影系统以及折面投影系统来完成实验.本文将IRCN对比多种现有投影补偿方法，实验结果表明IRCN在PSNR，RMSE，SSIM，均值标准差分析等客观评价指标中具有明显优势，说明本文提出的IRCN能够有效利用互反射先验信息，对沉浸式投影环境中的互反射现象进行补偿，在均衡训练时间的基础上增强了投影效果.     

结合等照度线信息的图像去噪变分模型

噪声是图像获取、传输和储存过程中不可避免的现象,去噪是图像处理的首要步骤与基本问题,也是后续的高层次图像处理的基础。基于图像梯度的PM模型能有效增强图像的轮廓信息,但同时会造成图像边缘模糊并在图像的平滑区域产生阶梯效应。图像的等照度线能有效抑制图像边缘的过度平滑,考虑到等照度线与PM模型图像梯度的互补性,提出一种同时极小化图像梯度与原图像等照度线信息的复合变分模型,并给出该模型的迭代求解过程。通过对比实验证明,提出的复合模型能有效地利用原图像的结构信息,在消除平滑区域阶梯效应的同时能增强图像的边缘,取得较高的峰值信噪比,获得较好的图像去噪性能。     

先验知识在三维折射率场重建中的应用研究

在干涉层析中，目前最大的难点仍是对非完全投影数据场的重建，非完全投影数据指观察角小于１８０°，或者折射率场中存在不透明的遮挡模型，问题的核心在于如何设计结合先验知识的可行算法，对于三维折射率场的重建，先验知识，如折射率非负，遮挡物的尺寸，几何形状，空间位置等是常用的信息。该文提出了一种有效易行的给先验知识的三维折射率场重虎法，在算法中引起属性矩阵的概念，无需对缺少的投影数据补齐，将该算法应用于高超     

基于投影加权的多能光子计数X线CT全能谱图像重建改进方法

为了提高多能光子计数X线CT全能谱重建图像的对比噪声比,提出了一种基于投影加权的图像重建改进方法.首先,针对包含不同对比材料的3种模体进行投影仿真,获得包含泊松噪声和高斯噪声的投影正弦图;然后,从投影正弦图中提取噪声信息,构造关于权重的对比噪声比优化函数;最后,求解出使对比噪声比最优的权重,利用该权重进行投影加权图像重建,并对重建图像进行评估.实验结果表明:与当前仅考虑泊松噪声的基于投影加权的图像重建方法相比,对于含钙材料的模体,利用改进方法可明显提高重建图像的对比噪声比;对于含碘材料和等效软组织材料的模体,利用改进方法重建的图像对比噪声比则无显著统计差异.     

基于三维分叉模型的血管轴重建方法

针对血管轴重建中血管段难以配准的问题，提出了一种基于先验分叉模型的血管轴重建方法。该方法利用血管走向和分叉结构的先验信息，对血管片段进行基于先验分叉模型的配准，从而更有效地将血管分支的三维结构信息提取出来。实验结果表明，该方法降低了血管片断重建的复杂度，提高了重建速度和重建精度。     

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.     

基于无监督学习的编码衍射成像方法研究

编码衍射成像旨在利用衍射强度图样重建原始图像，而现有基于人工设计先验的编码衍射成像算法大都在低信噪比下成像质量低。通过基于深度神经网络学习的深度先验能够解决上述问题，但有监督学习需要大规模样本对，不利于实际应用。针对这一问题，本文提出一种基于无监督学习的编码衍射成像方法。该方法结合双数据保真项、卷积稀疏编码模型和深度图像先验模型构建了能够融合互补先验的优化模型，并利用交替优化方法对其进行有效求解。实验结果表明，提出的方法能够在低信噪比下仅通过单幅编码衍射强度图样重建出高质量的图像。     

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