Visual FoxPro数据词典对数据库完整性控制的实现

本文阐述了实体完整性、参照完整性和用户定义完整性等数据库完整性的基本概念,并通过实例分析如何运用Visual FoxPro数据词典来设置字段级和记录级验证规则、触发器以及参照完整性,从而实现对数据库完整性的控制。     

网络数据库环境下的数据完整性

在一个大型的数据库管理系统中,最核心的部分是数据的操纵与管理。优良的数据库设计使系统维护容易、编程简单,并能加快开发速度。在数据库的设计开发过程中,应充分考虑分布式并发控制,力求系统协调工作,保证结果的正确性、数据库的完整性;当系统有冗余数据时,要尽可能使系统以最小的开销保证各冗余副本的一致性。 一般地说,数据完整性是指存储在数据库中的数据的一致性。主要体现在以下三个方面:实体完整性(Entity Integrity)、域完整性(Domain Integrity)、参照完整性(Referenfial     

DML触发器保持数据库完整性应用研究

对数据进行频繁的更新操作可能破坏数据库的完整性,合理设计触发器可以有效保护数据。本文讨论在SQL Serv-er 2005中通过DML触发器技术实现数据的完整性控制机制,重点论述DML触发器工作原理和实现过程,并结合实例分析设计触发器的基本步骤。测试结果表明,触发器的应用可提高系统性能,很好地维护数据库的完整性。     

面向企业级数据库管理——介绍Sybase的Adaptive Server Enterprise(四)

高度的数据可靠性 Sybase是唯一获得ISO9001认证的DBMS厂商。在ASE中,完全的联机事务处理功能保证了用户数据的高度可靠性,而磁盘镜像、自动错误渡越(Fail—over)和高速备份/恢复功能又可使硬件故障对正在运行的应用的影响达到最小。 声明参照完整性:在关系数据库中,参照完整性是控制主键及其和外键之间关系的规则,它可以保证引用表中被修改的数据在被引用表中有匹配的值。ASE支持声明参照完整性,即在建表时定义的参照完整性,这比使用触发器的参照完整     

试论Oracle数据备份与恢复

因Oracle数据库在数据安全性和完整性控制方面性能优越,且支持跨系统,跨平台操作,故越来越多的用户将其作为应用数据处理系统。文章就如何正确使用Oracle数据库的备份与恢复功能来保证其数据安全性和完整性,做了一个简单的探讨。     

软件定义网络可信连接设计与实现

软件定义网络（software defined networking,SDN）将控制层和数据转发层分离,由控制层对数据转发层进行统一管理。目前控制层及数据转发层设备间完整性认证机制尚不完善,若平台完整性损坏的设备接入网络,会给整个SDN网络带来严重的安全问题。为确保双方设备在完整可信的前提下建立连接,进而在源头上保障设备安全、网络可信,提出了一种新的SDN可信连接方案。该方案以可信网络远程设备认证技术为基础,利用可信平台模块作为可信支撑,在SDN数据转发设备与控制器的连接过程中添加完整性认证环节。测试分析表明,该方案有效可行,符合实际应用。     

地下管线管理信息系统的数据质量与质量控制

地下管线管理信息系统的数据主要为地理数据(空间数据和属性数据);数据质量内容主要包括位置精度、属性精度、逻辑一致性和完整性;影响数据质量的主要因素基本体现在数据采集、数据处理、数据应用的生产过程中;数据的质量控制应贯穿于数据生产的整个过程中,其中,源数据采集和数据处理过程中的质量控制是关键环节。     

浅谈数据库中的完整性约束

数据完整性是指数据的正确性、完备性和一致性,是衡量数据库质量好坏的标准。本文从以下三个方面分析了数据的完整性。即实体完整性、参照完整性和用户自定义完整性。     

Notes数据库中数据一致性与完整性问题的解决

数据的一致性和完整性设计在数据库开发与应用中是一个非常重要的环节。Notes非结构化数据库的特性以及提供的“继承”功能仅在创建文档时发生一次等问题容易破坏数据的一致性。本文提出了同步修改的方案，并使用了文档链指针和数据库事件的定义，充分保证了Notes数据库中数据的一致性。并在此基础上讨论Notes数据库的完整性控制问题。     

保持你的数据清洁—Access高级使用

1、简介保护你的数据的正确性是至关重要的。如果你不信任该数据,那是另一回事。为保持数据的完整,你必须控制客户修改、添加和删除数据。Microsoft Access使用“参照的完整性约束”来强制此类控制。在本文中,我们将解释此问题,并指导如何应用。     

机器人足球比赛截球策略设计

在机器人世界杯足球锦标赛(TheRobotWorldCup,简称RoboCup)中,截球效率直接影响到比赛的结果。通过足球截球模型,建立方程,从而求出截球位置。解方程的根是提高截球效率的关键,本文采用高效的弦割法来快速计算方程的根。试验发现方程曲线的变化对弦割法解方程根的效率有很大影响,曲线的形状直接影响了弦割法的收敛速度。为加速收敛性,对弦割法进行了优化。最后与优化前的弦割法以及二分法进行了比较,结果表明优化后整体性更为高效,很好地满足了比赛的要求。     

Analytic Controlling Reorientation of a Spacecraft Using a Combined Criterion of Optimality

We consider the problem of optimally controlling the reorientation of a spacecraft (SC) from an arbitrary initial angular state into a given final angular position. We study the case when the minimized functional joins, in the given proportion, the time spent and the integral of the squared modulus of the angular momentum on the reorientation of a SC. The problem is solved in a kinematic setting. We consider two versions of the problem of the optimal rotation of a SC, with bounded and unbounded control. Using the necessary optimality conditions in the form of the Pontryagin maximum principle and the quaternion method for solving control problems on the motion of spacecrafts, we obtain an analytical solution of the posed problem. The solution of the problem is based on the quaternionic differential equation relating the angular momentum vector of a SC with the orientation quaternion of the related coordinate system. We present formalized equations and give computational expressions for constructing the optimal control program. We state the control law as an explicit dependence of the control variables on the phase coordinates. Using the transversality condition as a necessary optimality condition, we determine the maximal value of the modulus of the angular momentum for the optimal motion. For a dynamically symmetric SC, the problem of reorientation in space is solved completely: we obtain the dependences for the optimal law of the change of the angular momentum vector as explicit time functions. We give the results of the mathematical modeling of the motion for optimal control which demonstrate the practical realizability of designed algorithm for controlling the spatial orientation of a SC.     

Application of a global model to the study of Arctic basin pollution: radionuclides,heavy metals and oil hydrocarbons

The status of pollution of the Arctic basin is studied in ecological terms, and the interactions of the Arctic ecosystem with the global system are estimated. A spatial simulation model for the kinetics of pollutants in the Arctic basin is proposed in which the ecological and spatial distribution of the hydrological parameters is taken into account. The model includes blocks describing the flows of pollutants in the trophic chains, the exchange between the water–ice system and the atmosphere and the interaction of the water ecosystem with the global biosphere–climate system. A global model controls the inputs of the simulation model and makes it possible to compute the dynamics of the distribution of pollutants between the Arctic aquatories, which include the Central basin and the peripheral seas. The model uses both published data and the data of the US/Russian expedition to Siberia accomplished in the summer of 1995. Climatic and anthropogenic processes are described in the form of scenarios. The results of computer experiments are given demonstrating the advantages of the simulation model to forecast and to estimate the dynamics of radionuclides, heavy metals and oil hydrocarbons in the Arctic Seas. The total and local pictures of the spatial distribution of pollutants in the Arctic basin are given as functions of various environmental and anthropogenic parameters. It is concluded that the use of the global biospheric model enables the consideration of the interactions between the Arctic basin environment and adjoining territories. This allows estimates to be made of the consequences of the anthropogenic impact on the Arctic ecosystem.     

Calculation of the parameters of Hidden Markov models used in the navigation systems of surface transportation for map matching: A review

This article provides an overview of the mathematical methods for calculating the parameters of Hidden Markov Models (HMM) used in conjunction with the map coordinates measured by the global positioning systems (GPSs) of mobile navigation systems. These methods are analyzed and compared. There is considered an example of calculating of emission probability of observations emissions and transition probabilities for the Hidden Markov Model of a road network. The example is accompanied by the construction of a states diagram of the HMM and a trellis diagram of the Viterbi algorithm. Using the example, there is estimated the influence of the choice of the value of the standard deviation for the probability density distribution of the minimum distances and the angles difference between the direction of the road element and the direction of the velocity of the vehicle on the probability of the path on the Viterbi trellis. It is proposed to use the functional dependence of the optimal path on the standard deviations and the orthogonal distances for the correction in the process of testing and the practical application of the algorithm of map matching based on the HMM.     

A model of the functional state of participants of laboratory markets

The dynamics of psycho-physiological characteristics of participants of laboratory markets in the process of making economical decisions in the decentralized control system is analyzed. For this purpose, the method based on the comparison of stabilographic data with the history of market actions recorded in the course of the experiment is used. The key tool for data analysis is the new segmentation algorithm, which provides efficient partitioning of the stabilographic time series into homogeneous fragments. The segmentation algorithm is obtained as the solution of the problem of estimation of the parameters of the hidden Markov model. The application of this algorithm on the level of individual decision making proves the hypothesis of connection of the stabilogram segmentation time instants of the participant with the time instants of signal actions on the laboratory market. On the level of group decisions, the effect of synchronization of stabilographic time series of participants at the time instant of auction culmination connected with revelation of private information is supported. The degree of synchronization is estimated using a proximity factor calculated based on the specially aggregated canonical correlation.     

A method of defuzzification based on the approach of areas' ratio

The new method of defuzzification of output parameters from the base of fuzzy rules for a Mamdani fuzzy controller is given in the paper. The peculiarity of the method is the usage of the universal equation for the area computation of the geometric shapes. During the realization of fuzzy inference linguistic terms, the structure changes from the triangular into a trapezoidal shape. That is why the universal equation is used. The method is limited and can be used only for the triangular and trapezoidal membership functions. Gaussian functions can also be used while modifying the proposed method. Traditional defuzzification models such as Middle of Maxima − MoM, First of Maxima − FoM, Last of Maxima − LoM, First of Suppport − FoS, Last of Support − LoS, Middle of Support − MoS, Center of Sums − CoS, Model of Height − MoH have a number of systematic errors: curse of dimensionality, partition of unity condition and absence of additivity. The above-mentioned methods can be seen as Center of Gravity − CoG, which has the same errors. These errors lead to the fact that accuracy of fuzzy systems decreases, because during the training root mean square error increases. One of the reasons that provokes the errors is that some of the activated fuzzy rules are excluded from the fuzzy inference. It is also possible to increase the accuracy of the fuzzy system through properties of continuity. The proposed method guarantees fulfilling of the property of continuity, as the intersection point of the adjustment linguistic terms equals 0.5 when a parametrized membership function is used. The causes of errors and a way to delete them are reviewed in the paper. The proposed method excludes errors which are inherent to the traditional and non- traditional models of defuzzification. Comparative analysis of the proposed method of defuzzification with traditional and non-traditional models shows its effectiveness.     

Design of characteristics of air-pressure-controlled hydraulic shock absorbers in an intercity bus

The air-pressure-controlled shock absorber is capable of changing its damping force depending on the air pressure in the air springs. Due to the possibility of improving dynamic properties of all vehicles that use the axles’ air suspensions, BRANO Inc. (the Czech producer of shock absorbers) started to develop semi-active air-pressure-controlled hydraulic telescopic shock absorbers. The SOR C 12 intercity bus is the reference vehicle for which the research and development of controlled shock absorbers is done and on which the shock absorbers are verified. Force–velocity characteristics of the controlled shock absorbers of the axles’ air suspension were designed on the basis of results of computer simulations with the bus multibody models created in the alaska simulation tool. Multibody models of an empty vehicle, a fully loaded vehicle and three variants of a partly loaded vehicle were created. For each weight of the bus two multibody models of various levels of complexity were created. Since the bus multibody models should be used especially for designing force–velocity characteristics of air-pressure-controlled shock absorbers, great attention (in the framework of the possibilities of multibody dynamics) was paid to the correct interpretation of the real behaviour of hydraulic shock absorbers and air springs of the axles’ suspension. As a criterion for the design of the optimum force–velocity characteristics of the controlled shock absorbers, the maximum similarity of the dynamic responses of multibody models of the bus of all the considered weights to dynamic response of the reference multibody model of the bus with the same load as during the experimental measurements on the real vehicle (approx. 71.5% of the maximum loaded vehicle weight) was chosen. In the course of the measurements the non-controlled shock absorbers’ characteristics were optimally tuned for that vehicle weight. Time histories of relative deflections of the axles’ air springs determined during the simulations of the vehicle running over the vertical artificial obstacle were compared. The approach based on the evaluation of the correlation coefficient of two time series was used for the evaluation of the dynamic responses accordance.     

人工免疫在未知木马检测中的应用研究*

针对传统木马检测技术比较被动这一缺陷,提出一种基于人工免疫原理的木马检测方法。利用人工免疫具有自适应以及免疫学习能力的特点,将人工免疫原理应用到木马检测中。分析了数据来源特征,给出了计算抗体与抗原或抗体与抗体之间相似度以及抗体的适应度公式,建立了一个木马检测系统模型;实验测试了利用人工免疫的方式检测木马能有效提高木马检测的检测率,减少误报率。     

Choice of optimal strategy of tumor chemotherapy in Gompertz model

A mathematical model of tumor growth dynamics based on the Gompertz model is considered. It is assumed that tumor cells are affected by a chemotherapeutical agent capable of killing these cells. The degree of action is characterized by the therapy function. Two types of therapy functions are studied: the monotonic and the threshold ones. In the first case, the action of the chemotherapeutical agent is the larger, the higher its concentration. In the second case, the degree of action decreases if the concentration exceeds some threshold value. It is assumed that the concentration of the chemotherapeutical agent is controlled using the control function; the maximum value of this function is limited. The problem of synthesis of optimal control for minimization of the number of tumor cells at the end of the process is formulated. The problem is solved using the dynamic programming method. Exact solutions to the corresponding Hamilton-Jacoby-Bellman equations, which make the synthesis of optimal control possible, are obtained. The results of calculations for optimal therapy strategies are presented.     

改进遗传算法在差分像运动图像实时处理中的应用

差分像运动图像的处理是大气相干长度测量的关键环节,而大气相干长度测量通常需要实时获取数据。因此,差分像运动图像的处理速度与测量仪器的性能有直接的联系。为提高大气相干长度仪的实时测量能力,根据差分像运动图像的特点设计一种改进的遗传算法,对目标光斑进行快速识别。改进的遗传算法为提高收敛速度,取消交叉算子,同时为避免早熟收敛,改进染色体结构,使其在仅使用变异算子的情况下仍具有全局探索能力。Schaffer函数模拟寻优实验验证该方法的可行性。使用改进遗传算法的大气相干长度仪实现实时快速测量。