P-M扩散方程图像去噪方法分析

目的 对P-M扩散方程图像去噪方法的原理及参数选取问题进行分析.方法 通过傅立叶变换法和图像特征方向的正交坐标系方法.结果 该方法比从P-M扩散方程本身出发讨论其去噪原理更为直观.结论 为P-M扩散方程图像去噪的参数选取提供了理论依据.     

Riemann问题基于双激波近似的激波捕捉格式

Riem ann问题迭代求解的计算量很大 ,为了提高效率 ,减小计算量 ,提出一种 Riemann问题的近似解法。把Riem ann问题中的膨胀波看成是“膨胀激波”,认为左右状态之间存在由两个激波围成的相似解区域。该方法的优点是保留了 Riem ann问题的非线性特征 ,且保证左右波之间的自相似解区域的熵不减少。该方法在一维及多维无粘可压缩流动求解中取得了较好的结果。     

内燃机进排气管有限容积法一维非定常流模拟

应用有限容积法对发动机排气管系中的气体流动作模拟计算．该方法是以往一维非定常流动计算方法的进一步发展．与特征线法相比,具有计算稳定、质量流量误差小等优点．文中对该方法的模型作了简述,并以８Ｌ２４０Ｚ四冲程柴油机为例,进行了模拟计算,包括：发动机的性能参数、排气管系的压力波动情况、质量流量误差等．计算结果表明,该模拟方法具有较高的计算精度     

小型二冲程汽油机排气动力过程的计算机模拟

根据非定常气体流动理论,建立了二冲程汽油机排气动力过程的数学模型,并用特征线法对其进行了模拟计算,压力波的数值解析结果与实测结果比较吻合,表明所用模型和计算方法正确,可用于指导设计二冲程汽油机的排气动力效应系统.     

轴对称收-扩喷管内外流场一体化数值模拟

基于求解Navier-Stokes方程组对某航空发动机的轴对称固定几何收-扩喷管进行了六种工况的内外流场一体化数值模拟,计算出了喷管的流量系数和推力系数。结果表明,收-扩喷管超音速射流,在地面工况下表现为过膨胀特征,在高空不同工况下表现为欠膨胀特征,形成了复杂的激波系和膨胀波系。在欠膨胀状态,随着落压比的增大,喷管的流量系数无明显变化,但推力系数显著减小。另外,从理论解出发,计算了前面各种工况的喷管出口气动性能参数,并与数值模拟结果进行了对比分析,验证了数值模拟结果的可靠性。     

螺旋式气波制冷机结构参数匹配数值研究

结合理论分析和数值计算，对螺旋式气波制冷机中的核心结构——波转子，进行了结构敏感性分析.首先，根据波转子内激波与膨胀波等波系的流动，建立螺旋式波转子的理想波图，由此揭示波转子内能量传递与气体流动规律.在此基础上给出一维螺旋式波转子结构设计方法，该方法具有一定精度，可以用于指导螺旋式气波制冷机设计.接下来建立螺旋式压力振荡管的数值模型，研究波转子垂直长度、螺旋长度以及螺旋导程对其效率的影响，并提出最优螺旋导程的拟合方程.最后，建立螺旋式气波制冷机整机模型，对比不同螺旋导程下的等熵制冷效率.结果表明，对一定垂直长度的波转子来说，随着螺旋导程的增大，等熵制冷效率先增大后减小，与拟合方程结果相符.经过螺旋最优化的波转子等熵制冷效率高于同垂直长度的均直型波转子，提高值可达13%.     

Wave rotors used for expansion refrigeration technology

波转子是一种利用通道内压力气体接触时产生的各种气波运动实现能量转换的非定常流动设备.提出了一种新型的四端口返流波转子制冷机——压力交换制冷机,并利用一维非定常流动理论和计算流体力学方法分析了其工作过程和制冷原理,得到了该设备正常工作的基本限制条件;实验研究了影响压力交换制冷机的各种因素.目前该机实验室等熵效率已达68%,表明在气体膨胀制冷领域将波转子用于制冷技术前景看好.     

任意挠曲通道中正交曲线网格的构筑

运用微分几何的方法将有向正则空间的Ｆｒｅｎｅｔ标架旋转，改善中心流线ｃ－坐标系的斜交性，从而在任意挠率与曲率非零的三维通道中构造出具有严格局部正交性的ｃ－α曲线坐标系，采用该坐标系的等坐标参数线即构成正交计算网格，从而为简化流动方程、考察二次流及分析计算结果创造了条件     

膨胀波枪炮发射原理数值建模与分析

对于新近问世的膨胀波枪炮,提出了其发射过程的四阶段物理模型,采用准一维准两相流理论建立了其发射过程动力学模型,以14.5 mm膨胀波弹道枪为对象进行了数值仿真计算,将计算结果与普通闭膛枪炮的内弹道过程进行了对比,得出了膨胀波枪炮发射中的各种特征参量变化规律以及膛尾打开时刻等关键参数.计算表明:14.5 mm膨胀波弹道枪在基本不降低枪炮初速的前提下能减少59%的后坐动量.     

小型二冲程汽油机排气压力波的计算

建立小型二冲程汽油机非常排气流动的数学模型，给出用特征线法解排气压力波的计算实例。在计算过程中通过迭代不断修正特征线的位置，提高了数值解的精度。计算结果与结果相当吻合。     

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.     

A computer generator for randomly layered structures

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

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。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

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     

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

正~~     

An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.