基于启发式策略的最短路径算法

在讨论经典Dijkstra算法和启发式策略算法（A^＊，矩形算法等）的基础上，提出一种基于Dijkstra算法的动态方向限制搜索算法用于求解道路网络中两节点之间最短路径．该算法结合人类的搜索思路和动态灵活的处理方式，对最短路径算法的搜索策略进行改进，动态改变搜索限制区域，减少计算时间．该算法不仅可以单独提高计算最短路径的效率，而且与其他算法结合起来还可取得更好的效果．实际结果证明动态方向限制搜索算法比经典Dijkstra算法减少近50％的搜索节点数和搜索时间．     

复杂路网下多客户间最短路径的扇面Dijkstra算法

复杂路网模型下多客户之间最短路径的计算,直接影响市区集送货问题的求解效率。该文提出多客户间最短路径扇面Dijkstra算法。该算法首先由客户在路网的分布确定出最小扇形区域及扇面搜索区域,并将路网节点分为拓展点集、邻节点集。然后在搜索过程中通过优化到达邻节点的通行代价来确定新的拓展点集、邻节点集。算法通过限制搜索区域、减少遍历节点的数量来缩短搜索时间。100个分布于北京市的客户间最短路径的计算表明,相对于Dijkstra算法,扇面Dijkstra算法能够在保证精度的前提下,降低15%的最短路径求解时间。     

基于改进Dijkstra算法的最短路径搜索仿真

提出基于Dijkstra算法的最短路径搜索改进算法,通过设置高效的优先目标搜索区域,减少大量无意义运算,达到提高搜索效率的目的.以淄博市交通道路图(局部)为例建立系统仿真模型,分别以两点间距离系数和拥堵系数作为权值进行系统仿真,得出了基于不同权值的最短路径求解结果,并对算法改进前后测试数据进行对比分析.结果表明,基于改进Dijkstra算法实际运行时间均值仅占Dijkstra算法运行时间均值的23%以下.     

动态速度和代价约束的最短路径算法

Dijkstra算法是计算有向图中一个节点到其余各个节点最短路径的著名多项式时间算法,在交通规划、地理信息系统等方面有重要的应用。本文改进Dijkstra算法用于计算带有动态速度和代价约束的有向图中节点之间的最短路径,即有向图的节点之间除了静态的距离外,还有动态的速度和代价,例如城市交通中的高峰与非高峰时段影响速度/时间,收费与非收费路段影响代价;时间和代价在最短路径中由一个比例因子控制,通过调节该比例因子可计算节点间的最短时间/距离和最少代价的路径。该改进的算法被证明是可靠的,实验结果也表明了该算法的有效性。     

两种改进的最优路径规划算法

在对经典Dijkstra算法和A*算法分析的基础上对它们分别进行了改进.在经典Dijkstra算法中,针对当前不相连节点间路径长度为无穷大这一特点,首先对两个节点是否相连进行判断;若发现两个节点并不相连时,则舍去相应计算,从而减小计算量.针对A*算法在实际应用中搜索效率低的缺点,将经典A*算法搜索出的原始最优路径中的节点依次进行封堵后,再按照经典A*算法搜索出相应的新最优路径,最后再将原始最优路径与这些新最优路径进行对比,以便确定最终的最优路径.仿真研究表明:改进的Dijkstra算法可以减少大量的无关节点计算,提高运算的效率;改进的A*算法则可以提高搜索到最优路径的成功率.     

基于权值的Dijkstra停车路径规划算法的优化与实现

基于用户自由选择车位,以停车时间最短为准则,结合权值的计算方法及停车场的内部结构特点,对Dijkstra算法进行改进,设计并实现符合实际的最优停车路径规划算法,并对武汉某公园的大型停车场进行应用验证.结果表明,相对于传统算法,改进后的Dijkstra算法降低时间的复杂度,减少节点的搜索量,提高搜索效率,在停车场引导系统中有一定的实际应用价值.     

应急资源配送中Dijkstra改进算法的研究

路径规划问题是应急资源配送中的核心问题,最短路径算法在路径规划过程中起着决定性的作用,在众多路径规划算法中最经典且最具代表性的就是Dijkstra算法。以传统的Dijkstra算法分析为基础,从存储结构和算法过程两个方面进行一定程度的改进,目的是在节点数和边数较多的情况下,提高网络模型的处理效率。以真实道路交通数据为基础进行相关实验,结果证明,改进后的Dijkstra算法可以有效减少节点的计算量,提高算法的运行效率。     

基于GIS 的最短路径算法研究

针对单源最短路径Dijkstra 算法效率低的问题, 基于地理信息系统(GIS: Geographic Information System),提出距离均衡的社区分析网络分割方法。将GIS 中道路网络分割降解为距离均衡的社区网络, 再利用限制分层算法, 通过淘汰不太可能出现在最短路径上的节点, 限制GIS 中最短路径的搜索区域, 以降低算法的复杂度。实验结果表明, 优化后的算法可有效减少搜索节点数, 与经典算法相比, 其运行效率有所提高。     

网络最短路径算法的改进及实现

从节约存储空间和提高运算速度方面对Dijkstra最短路径算法进行了改进.定义新的节点类来高效存储网络的拓扑信息,节省了计算机存储空间;采用满二叉堆数据结构对节点进行排序并选取最短路径节点,大大提高算法效率.仿真例子表明,对于某些网络结构,改进算法能把传统Dijkstra算法的时间复杂度由原来的O(N2)近似降至O(N).     

Dijkstra改进算法在车辆导航系统中的应用与仿真

车辆导航系统的最基本功能是最短路径的搜索,车载导航是单源单目标的最短路径算法的重要应用之一.传统的Dijkstra算法是一种典型的单源最短路径算法,因为实际系统的实时要求,有必要改进Dijkstra算法.基于对时间和空间复杂度的分析,提出一种新型的Dijkstra改进算法,具有高效性.其改进分3个方面:采用邻接表作为道路网络拓扑的存储结构;利用二叉堆实现优先队列;根据节点的分布情况将搜索过程分为几个阶段,引入了动态限制搜索区域机制.最后在实际道路网络中的测试及仿真结果表明了改进算法的可行性和优越性.     

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.     

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.     

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)

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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.