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Search Results: 1 - 10 of 372895 matches for " 王建鹏 "
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中国股票市场的多分形波动率测度及其有效性研究
,
中国管理科学 , 2008,
Abstract: ?由多分形分析出发,提出了一种新型的金融市场多分形波动率测度Sα。与传统测度Δα相比,Sα更为充分地利用了多分形分析过程中产生的对描述金融市场波动有益的统计信息。以上证综指和深证成指1354个交易日内5个不同抽样频率的高频数据为例,通过运用具有bootstrap特性的SPA检验法,检验了Sα测度和Δα测度对中国股票市场真实波动率估计的有效性差异。实证研究表明,Sα测度对市场真实波动率的估计较Δα测度更为准确。
采动覆岩“三带”高度相似模拟及实证研究
张军,
采矿与安全工程学报 , 2014,
Abstract: 基于采动覆岩破坏、断裂机理及其裂隙分布、发育特性,采用相似材料模拟实验方法,对杜儿坪矿68303工作面采动覆岩“三带”进行了研究;通过分析采空区顶板断裂、离层、下沉、裂隙分布及延伸特性,得出冒落带高度12.5m,裂隙带高度37.5m,弯曲下沉带高度大于80m;采用仰斜钻孔分段注水及钻孔参数分析法现场实测了冒落带、裂隙带高度,与相似模拟实验结果进行了对比,分别相差0.8,2.5m。表明基于采动覆岩裂隙分布特性的相似模拟实验研究结果合理、可靠,可以作为工作面顶板“三带”高度研究的有效手段。
急倾斜煤层围岩活动规律及煤柱合理宽度研究
,张军
煤炭科学技术 , 2014,
Abstract: 为解决七台河新铁矿煤柱宽度留设不合理的问题,基于对该矿采场围岩变形特征的研究,采用数值模拟方法对急倾斜煤层区段煤柱宽度进行研究。结果表明:工作面下端头是受围岩运动影响的集中区域,影响范围30.5m,应力峰值23.12MPa;不同煤柱宽度对巷道支护影响较大,工程实践表明采用15m护巷煤柱,巷道顶板变形量最大值87mm,底鼓量最大值231mm,上帮变形量最大值52mm,15m宽护巷煤柱能有效控制巷道变形。
拱上恒载调整的石拱桥加固改造研究
,
重庆交通大学学报(自然科学版) , 2006,
Abstract: :?结合工程实践,通过原理分析,恒载调整内容、幅度和调整工序的介绍,提出了基于拱上恒载调整的石拱桥加固改造技术.加固前后桥梁实测拱轴线变化及加固前后的理论分析比较结果表明,该加固改造技术实用、可靠,可望为我国同类桥梁的加固改造起到积极的借鉴作用.
期望效用理论的发展历程及最新动态
栾大,
天府新论 , 2012,
Abstract: 系列悖论的出现,使得传统期望效用理论对于现实问题的解释力度不断下降.近年来,学者们不断对传统期望效用理论模型进行修正和完善.特别是本世纪以来,借助于实验经济学的分析工具,对期望效用理论的研究取得了诸多成果.如何将期望效用理论从实验室搬到现实之中,继而解释和分析现实中面临不确定性问题所出现的各种经济行为,是期望效用理论今后发展过程中所应重点解决的问题.
NaX/NaF催化剂的制备及其应用于催化合成脱氢乙酸
Preparation of NaX/NaF Solid Alkaline Catalyst and Synthesis of Dehydroacetic Acid Catalyzed by Solid Base
 [PDF]

, 何丹丹, 韩兵营, 宋成盈, 留成,, 建设
Hans Journal of Chemical Engineering and Technology (HJCET) , 2013, DOI: 10.12677/HJCET.2013.31005
Abstract: 以NaX分子筛为载体,负载前驱体NaF,采用浸渍法制备环境友好负载型固体碱NaF/NaX催化剂,并用于催化乙酰乙酸乙酯合成脱氢乙酸。探讨了NaF负载量、煅烧温度、煅烧时间对催化剂活性的影响;考查了催化剂用量、反应温度和反应时间对脱氢乙酸收率的影响。实验结果表明,固体碱催化剂NaF/NaX的最佳制备条件为NaF负载量20%,600℃下煅烧7 h;最适的脱氢乙酸合成条件为催化剂用量0.02%(以乙酰乙酸乙酯质量计),反应温度210℃,反应时间7 h,该条件下脱氢乙酸产率达81%。
The solid base catalyst NaF/NaX was prepared by impregnation. Dehydroacetic acid was synthesized from ethylacetoacetate in those friendly environmental solid base. Effects of the calcination temperature, calcination time, loading amount, mass fraction of catalyst, reaction temperature and time on the reaction were studied. The results showed that, the optimal catalyst were prepared under the conditions of loading amount 20%, calcination temperature 600°C and calcination time 7 h. Under the conditions of the mass fraction of catalyst 0.02%, reaction temperature 210°C and reaction time 7 h, the yield of dehydroacetic acid reached 81%.
石英挠性加速度计表头行为模型研究
Study of Behavior Model of Quartz Flexible Accelerometer Header
 [PDF]

商梅雪, 贺慧勇, 唐立军,, 刚煜,,
Journal of Electrical Engineering (JEE) , 2016, DOI: 10.12677/JEE.2016.41011
Abstract:
针对石英挠性加速度计PID参数整定繁琐、读出电路新方案的验证平台搭建复杂等问题,开展了对石英挠性加速度计表头的工作原理以及数学模型的分析,设计了加速度计表头的行为模型。搭建了相应的验证平台,将所得的表头行为模型的开环阶跃响应与实际表头做对比,验证了该行为模型的正确性。将该行为模型与表头的读出电路进行联合仿真,实现了表头模型和读出电路的闭环,并分析了不同PID参数对系统的调节时间等闭环动态响应特性的影响以及在特定PID参数下系统的?3 dB带宽。本表头行为模型可用于研究表头读出电路的设计、整定读出电路的PID参数以及分析读出电路的性能指标等多个方面。
For cumbersome tuning of quartz flexible accelerometer PID parameters, complex building of readout circuit’s new program verification platform and other issues, analysis of the quartz flexible accelerometer meter works and mathematical model was carried out, and accelerometers header behavioral model was designed. We set up the appropriate verification platform, compared the open loop step response of the resulting header behavior model with the actual header, and verified the correctness of the behavior of the model. A joint simulation was done combining the behavioral model with the read-out circuit header, to realize the closed loop of header model and readout circuit, and the influence of different PID parameters on the closed-loop dynamic response characteristics such as system accommodation time, and ?3dB bandwidth of particular PID parameters of the system were analyzed. The header behavior model can be used to study the meter readout circuit design, setting PID parameter of the readout circuit and analyze the performance index of the readout circuit and other aspects.
接枝丙烯酸对聚偏氟乙烯膜表面亲水改性的研究
Studies on Surface Modification of PVDF Membranes by UV Grafted Acrylic Acid
 [PDF]

, 区文仕, 吴业辉, ,, 尹忠
Hans Journal of Chemical Engineering and Technology (HJCET) , 2013, DOI: 10.12677/HJCET.2013.34023
Abstract: 为了改善传统聚偏氟乙烯(PVDF)亲水性不强的缺点,本研究以二苯甲酮(BP)为光引发剂,通过紫外光照,将亲水性单体丙烯酸接枝于PVDF膜的表面。通过测试纯水接触角和吸水率的表征值,考察PVDF膜改性前后的亲水性的变化,并且确定了引发剂浓度、辐照时间等因素对接枝率的影响。结果发现接枝后的PVDF膜的亲水性得到明显改善,而且随着光引发剂浓度的增大,丙烯酸的接枝率先增大而后在一定区间内保持稳定。本实验还通过衰减全反射光谱和扫描电子显微镜图片对接枝后PVDF膜表面化学组成和微观形貌进行了表征。
To improve the hydrophilic property for the traditional PVDF, acrylic acid was grafted onto the surface of PVDF membrane by UV irradiation grafting polymerization with benzophenone as photo-initiator. The static contact angle and water absorption ratio were used to study the changes of hydrophilic property of modified PVDF membranes, and the principal factors influenced the grating degree were discussed, such as the concentration of photo-initiator, irra-diation time. The results showed that the hydrophilic property of PVDF membranes was improved significantly, and with the increase of the concentration of photo-initiator, the degree of grafting increased first, then stayed stable in a certain range. We also used attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron mi-croscopy to characterize the chemical structure and morphological changes of the original and modified PVDF membrane.
基于属性的云存储访问控制系统的设计与实现
Design and Implementation of an Attribute Based Access Control System for Cloud Storage
 [PDF]

, 张思悦, 刘川意,
Computer Science and Application (CSA) , 2013, DOI: 10.12677/CSA.2013.38A003
Abstract:
本文针对云存储应用的安全访问需求,以及目前适用于云存储环境的基于属性的方案,设计和实现了一种基于属性的云存储系统访问控制机制:EncFSEncFS基于fuse的用户态文件系统,权限鉴别建立在Linux系统对用户的划分基础上,将用户的身份信息作为属性进行访问控制,不需要输入口令,从而简化了对身份和口令的管理和存储,实现了云存储下的细粒度访问控制,解决了大规模用户动态扩展问题。
>To satisfy the security demand of cloud storage application, this paper designed and implemented an attribute based access control mechanism named EncFS, which is suitable for cloud storage system. EncFS is a file system of user space, which is based on fuse and access control strategy for Linux operating system. It uses identity information as attributes for access control. Therefore, this system can simplify password management and storage, realize the fine-grained access control and solve the problem of dynamic expansion of large-scale users.
Ramberg-B?cklund反应在功能有机分子合成中的应用有机化学
,小龙,曹小平
有机化学 , 2006,
Abstract: 碳碳双键广泛地存在于功能有机分子中,其构筑在合成化学中具有极其重要的意义.Ramberg-B?cklund反应是构筑碳碳双键的重要方法之一,其关键步骤是砜在碱性条件下进行1,3-消除,得到环状砜,然后重排除去SO2形成双键.该方法具有良好的立体选择性,底物在不同的反应条件下得到不同构型的产物,因而可以应用于合成许多功能有机分子,具有很好的应用前景.结合自己的研究工作对Ramberg-B?cklund反应在功能有机分子合成中的应用进行了较为系统的总结,也对Ramberg-B?cklund反应的拓展进行了简要介绍.
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