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971.
通过深入地研究数据交换的通用模型,抽象数据交换的过程状态和规则,提出了一种基于数据交换的测试模型及其测试的方法,该方法能够适用于绝大多数数据交换场景的测试并有效地提高测试效率.最后给出了未来的研究方向. 相似文献
972.
M-distinct extension算法通过将数据添加、删除、更新三种情况分开处理,在删除情况下引入伪记录的概念,使得攻击者无法得出插入和删除数据之间的联系;另一方面提出事实:数据记录的不同属性在不同的发布用途中其信息权重并不相同,根据事实,引入属性权重的概念,减少算法在分配和划分两个阶段的循环次数,提高算法的效率。 相似文献
973.
在联机分析处理中,由于传统的模型无法对文本文件进行建模,因此提出了基于维概念的星系模型。该模型删除了事实的概念,消除了只能把事实作为分析主题的限制,令联机分析更加自由;而且引入了联系的概念,实现了对文本文件中的超链接进行建模。通过两种方法可以把星型模型中的事实转换成星系模型中的维,实现了星系模型与其他模型之间的转换。 相似文献
974.
For a study of the movement and deformation of coal-rock mass and low protected seams below a stope,as well as for fracture developments and rules of evolution of permeability,we designed a plane strain model test stand to carry out model tests of similar materials in order to improve the effect of gas drainage from low protected seams and to measure the movement and deformation of coal-rock mass using a method of non-contact close-range photogrammetry.Our results show that 1) using paraffin melting to take the place of coal seam mining can satisfy the mining conditions of a protective seam;2) coal-rock mass under goafs has an upward movement after the protective seam has been mined,causing floor heaving;3) low protected seams become swollen and deformed,providing a good pressure-relief effect and causing the coal-rock mass under both sides of coal pillars to become deformed by compression and 4) the evolution of permeability of low protected seams follows the way of initial values→a slight decrease→a great increase→stability→final decrease.Simultaneously,the coefficient of air permeability increased at a decreasing rate with an increase in interlayer spacing. 相似文献
975.
Mine overburden dumps have posed significant safety issues in the operations of various unit operations of open pit min-ing especially the external dumps. The external dumps are composed of a mixture of fragmented rocks and loose soil. Their charac-teristic is comparable to heavily discontinuous solid mass. The conventional approach of limit equilibrium methods provide safety factors for the slope but nothing about the stress-strain characteristics of the large dump mass. The designs of dump location and their respective geometry are integrated for the know-how of the stability characteristics of these dumps. The discrete element method uses a circular disk to represent the granular solid mass and their interactions are described by the Newton's third law of motion. The displacement is described by the sliding of the circular disk. This work is focused on the modeling efficiency of the discrete element methods to represent the behaviour of mine dump masses with the specified joint plane for the limit equilibrium method. The advantage of the work lies on the ease of information retrieval at any point at the dump mass concerning the stress and strain histories, displacement, failures etc. which when integrated produces a better understanding of the stability of the dump masses. 相似文献
976.
977.
Design and validation of wireless strain test system for bridge based on the resistance strain sensor 总被引:1,自引:0,他引:1
In order to achieve an access to strain sensor data with wireless transmission in bridge engineering structure testing, a wireless strain test system is presented based on the resistance strain sensor of networks. The wireless bridge strain test system composed of master station and substation adopts the wireless method to realize the high accuracy data acquisition between the master station and the substation under a reliable communication protocol. The system has been tested in contrast with the present strain apparatus. Results show that the wireless system is high-reliable, and has many characteristics such as high efficiency, good precision, high stability with low cost, and good flexibility, without using the present communication network. 相似文献
978.
We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60° and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field. 相似文献
979.
威布尔分布场合无失效数据的可靠性验证试验 总被引:1,自引:0,他引:1
利用Bayes方法讨论了Weibull型产品的可靠性验证问题。在产品寿命服从Weibull分布、形状参数未知且尺度参数已知、假定产品的可靠性指标达到某个给定值的情况下,给出了无失效数据的可靠性验证试验方案。 相似文献
980.
陈荣元 《上海电力学院学报》2010,(4)
针对现有图像融合方法的规则不易根据融合图像的后续使用要求进行自适应调整,并且各种方法的优点不易综合的问题,提出一种数据同化框架下的基于粒子群优化(PSD)和差分进化(DE)算法的融合方法。该方法把比率低通金字塔变换作为数据同化系统的模型算子,把非下采样的Contourlet变换(NSCT,nonsubsampled contourlet transform)作为观测算子,根据后续处理对图像各个属性指标值的依赖程度构造目标函数,再利用PSD和DE的混合算法来优化目标函数从而获取合适的影像。两组实验从视觉效果和定量指标两方面验证了方法的有效性。 相似文献