程序设计中递归思想教学方法探讨

递归思想是程序设计中一种非常重要、有效的思想。许多有趣的算法可以用几行简单的递归函数来表达。然而学生在学习递归函数由于对其执行过程不了解,对递归思想似懂非懂,难以设计正确的递归函数。本文介绍自己在教授此内容时的几点经验,希望与同行共同探讨.     

递归程序的转换技术

提出了一种实用的递归程序转换技术,它可以方便地把递归函数转换成与之等价的非递归形式,已在DPS8/49机上实现。     

自底向上记录式Hanoi塔非递归算法

Hanoi塔问题的经典递归算法虽然代码量小,但时间复杂度却是指数级的,而且难以理解。该文基于Hanoi塔问题的递归思想,构造出Hanoi塔的树模型,仔细分析递归函数的调用参数和语句执行时盘子移动的顺序,巧妙地找到两者之间的对应关系,从而提出一种新的自底向上非递归算法。该算法逐一地记录下n从1开始时盘子从源柱到目标柱时经历过的移动轨迹,进而直接应用到n+1个盘子的移动问题。实验结果表明,该算法对应的代码易读且高效,时间复杂度降为O(n),是对Hanoi塔问题的非递归算法研究的进一步实践与探讨。     

递归函数浅析

介绍了递归函数和函数的递归调用概念，分析了汉诺塔问题函数的递归调用过程，并对递归和迭代进行了简要的比较     

递归算法在C/C＋＋程序设计中的描述与实现

递归是函数实现的一个很重要的环节，对许多复杂的问题，递归能提供简单、自然的解法。本文在对递归的概念进行介绍的基础上，重点讨论了递归的程序设计方法，并分析了递归函数的调用和回溯过程。     

基于有限递归和μ-算子的α-递归论

根据Ｂｌｕｍ，Ｓｈｕｂ和Ｓｍａｌｅ定义实数环上的计算模型中将递归和μ－算子限制在自然数上这一特点，提出了基于自然数上的递归定义和μ－算子。研究了在可允许序数α－上定义的可计算函数－弱α－递归函数的弱α－递归论的基本性质及其与α－递归论的差别，证明了每个弱α－递归函数是以自然数为参量关于取值α上的变量的多项式函数，并且每个弱α－递归可枚举集与自然数集的交集是递归可枚举的。     

一般递归函数定义中极小化次数问题的研究

研究了定义递归函数过程中极小化运算的次数问题，证实了任意一个递归函数可以从初始子数出发，经有限次复合，递归和至多一次极小化运算而得到。这一结论对计算复杂性理论有明显的意义。     

递归算法非递归化的一般规律

尽管递归算法具有结构简练、清晰、可读性强、正确性容易得到证明等优点，但递归算法在执行过程中会耗费太多时间和空间。为了追求算法的时空效率，特别是使用不支持递归的程序语言的情况下，必须将递归算法转化为非递归算法，问题才能得到有效解决。为此，给出了递归算法转化为非递归算法的一般方法，并以Hanoi塔问题、二叉树的中序遍历问题为例进行了详细地分析。     

关于Grzegorczyk第九问题

本文通过引进二重递归函数类的一种分层{Y_n}_(n∈∞),证明了借助于本原函数(后继函数、零函数和投影函数)以及原始递归和复合运算,如果仅增加有限多个二重递归函数作为开始函数,则不足以产生全体二重递归函数。     

递归问题的非递归算法及效率分析

给出了程序设计中两种递归问题的非递归算法实现过程，并与递归算法进行比较，结果表明，非递归算法在时间复杂度与空间复杂度两项指标上均优于递归算法，且不使用系统栈，执行过程不依赖于函数或过程的重复调用，有更大的灵活性，可以应用在程序与软件设计中．     

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.