排序方式: 共有32条查询结果,搜索用时 46 毫秒
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SSL V3.0及其安全性分析 总被引:6,自引:0,他引:6
文章简述了SSL V3.0的分层结构、协议状态、握手协议和加密参数计算,并对其安全性做出分析. 相似文献
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用各向异性代数应力模型数值模拟搅拌槽中的三维全流场 总被引:4,自引:0,他引:4
In accordance to the anisotropic feature of turbulent flow, an anisotropic algebraic stress model is adopted to predict the turbulent flow field and turbulent characteristics generated by a Rushton disc turbine with the improved inner-outer iterative procedure. The predicted turbulent flow is compared with experimental data and the simulation by the standard κ-ε turbulence model. The anisotropic algebraic stress model is found to give better prediction than the standard κ-ε turbulence model. The predicted turbulent flow field is in accordance to experimental data and the trend of the turbulence intensity can be effectively reflected in the simulation. The distribution of turbulent shear rate in the stirred tanks was simulated with the established numerical procedure. 相似文献
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Stirred tanks are used extensively in process industry and one of the most commonly used impellers in stirred tanks is the R.ushton disk turbine. Surprisingly few data are available regarding flow and mixing in stirred-tank reactors with Rushton turbine in the laminar regime, in particular the laminar flow in baffled tanks.In this paper, the laminar flow field in a baffled tank stirred by a standard R.ushton turbine is simulated with the improved inner-outer iterative method. The non-inertial coordinate system is used for the impeller region, which is in turn used as the boundary conditions for iteration. It is found that the simulation results are in good agreement with previous experiments. In addition, the flow number and impeller power number calculated from the simulated flow field are in satisfactory agreement with experimental data. This numerical method allows prediction of flow structure requiring no experimental data as the boundary conditions and has the potential of being used to scale-up and design of related process equipment. 相似文献
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车辆监控系统中时空数据模型设计与实现 总被引:1,自引:2,他引:1
针对车辆监控GIS系统中车辆对象轨迹数据变化频率较高、数据量大的特点,首先分析了当前常用的几种数据存储方法,然后在时空立方体模型基础上,提出通过切分时空立方体,形成单元时空立方体,并建立轨迹版本的建模思想。对模型的实现和基于此模型的时空查询算法进行了详细阐述。验证表明该模型能满足实际应用的需要,在减少存储和时空查询性能上有较大提高。 相似文献
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根据搅拌槽内的流动呈各向异性的特点 ,引入适用于强旋转流场的各向异性k -ε湍流模型 ,用改进的内外迭代法对有挡板的Rushton桨搅拌槽进行了整体数值模拟 .利用文献中对搅拌槽内流场测定结果 ,给出了适用于Rushton桨搅拌槽的各向异性湍流黏度系数值 .模拟计算得到了搅拌槽内的流场分布和脉动速度分布 ,并同标准k -ε湍流模型计算结果及文献数据进行比较 .结果表明 ,各向异性k -ε湍流模型能成功反映Reynolds应力、湍流动能等湍流特征量 ,明显优于标准k -ε湍流模型 . 相似文献
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生物可降解聚合物/药物纳米微粒在药物靶向递送、有效成分封装和医疗诊断等领域具有突出的优势。超临界流体超细微粒制备技术具有绿色环保、制备方法种类多、粒径易调节和后续分离纯化容易等特点,得到了广泛的研究。为了得到满足使用要求的聚合物/药物纳米微粒,超临界流体制粒技术是有效的手段之一。论述了生物可降解聚合物纳米材料的特点和应用情况,简要介绍了超临界流体及特性,重点介绍了超临界溶液快速膨胀(RESS)、超临界抗溶剂沉淀(SAS)、超临界CO2辅助雾化(SAA)和超临界流体乳液萃取(SFEE)的工艺特点、制备方法、基本原理和研究进展,并对超临界流体技术制备聚合物/药物纳米微粒的发展方向进行了展望。 相似文献
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对搅拌槽内的重要参数———气泡直径进行了数值模拟。结果表明,在搅拌槽内排出流区和循环区内模拟值与实验值吻合较好。在模拟过程中仅考虑了湍流动能耗散率对气泡大小的影响,没有考虑到气泡自身的凝并和循环过程,所以在循环区中模拟值比实验值稍大。 相似文献