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排序方式: 共有410条查询结果,搜索用时 15 毫秒
71.
扩展重要抽样法及其在平尾转轴可靠性分析中的应用 总被引:3,自引:0,他引:3
提出了扩展重要抽样法,用以计算结构系统的多个失效模式中含有不全相同基本随机变量时的系统失效概率。通过构造扩展重要抽样法的抽样密度函数,给出该方法失效概率的估计值,以及其方差和变异系数的计算公式。并将此方法用于某型飞机平尾转轴的可靠性分析,算例结果表明其优越性。 相似文献
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73.
A series of bis-quaternary ammonium compounds(bis-QACs) N,N’-hevamethylenebis(1-alkyl-4-carbamoyl pyridinium bromide)(4BCAP-6,n)(alkyl chain length,n=8,10,12,14,16 and 18) were synthesized and characterized.Their surface tensions,critical micelle concentrations(CMC),and antimicrobial activities were evaluated.4BCAP-6,10 exhibited the strongest antimicrobial activities except for that against Proteus vulgari.The activities of 4BCAP-6.n against Escherichia coli zk126 were not significantly influenced by temperature.pH and initial bacteria concentration.These results indicate that bis-QACs exhibit high antimicrobial activity regardless of the environmental conditions. 相似文献
74.
We design and analyze a novel multiband left-handed metamaterial based on a fishnet-like structure at terahertz (THz) frequencies.The metamaterial exhibits simultaneous negative refractions around the frequencies of 0.48,1.05,and 1.19 THz for the electromagnetic (EM) wave normal incidence,and around the frequencies of 0.20,0.79,and 1.13 THz for parallel incidence.The simulated results verify the left-handed properties.A particularly important observation is the capability of the proposed metamaterial with a single geometrical structure to display multifrequency operations in a unit cell.The compact metamaterial is a major step toward the miniaturization of THz materials and devices suitable for multifrequencies. 相似文献
75.
CHEN Wei & LIU PeiDe School of Mathematical Sciences Yangzhou University Yangzhou China School of Mathematics Statistics Wuhan University Wuhan 《中国科学 数学(英文版)》2011,(6)
Under appropriate conditions on Young's functions Φ1 and Φ2,we give necessary and sufficient conditions in order that weighted integral inequalities hold for Doob's maximal operator M on martingale Orlicz setting.When Φ1 = tp and Φ2 = tq,the inequalities revert to the ones of strong or weak(p,q)-type on martingale space. 相似文献
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77.
ZHANG HongPing LV HaiXia LI Min & SHI Chuang State Key Laboratory of Information Engineering in Surveying Mapping Remote Sensing Wuhan University Wuhan China GNSS Research Center Wuhan School of Geodesy Geomatics 《中国科学:物理学 力学 天文学(英文版)》2011,(6)
Ionospheric delay is one of the major error sources in GNSS navigation and positioning.Nowadays,the dual-frequency technique is the most widely used in ionospheric refraction correction.However,dual-frequency measurements can only eliminate the first-order term of ionospheric delay,while the effect of the second-order term on GNSS observations may be several centimeters.In this paper,two models,the International Reference Ionosphere (IRI) 2007 and International Geomagnetic Reference Field (IGRF) 11 are used... 相似文献
78.
针对Lennard-Jones(LJ)团簇的结构优化问题,在前人工作的基础上,提出了一个新的无偏优化算法,即DLS-TPIO(dynamic lattice searching method with two-phase local searchand interior operation)算法.对LJ2-650,LJ660,LJ665-680这666个实例进行了优化计算.为其中每个实例所找到的构型其势能均达到了剑桥团簇数据库中公布的最好记录.对LJ533与LJ536这两个算例,所达到的势能则优于先前的最好记录.在DLS-TPIO算法中,采用了内部操作,两阶段局部搜索方法以及动态格点搜索方法.在优化的前一阶段,内部操作将若干能量较高的表面原子移入团簇的内部,从而降低团簇的能量,并使其构型逐渐地变为有序.与此同时,两阶段局部搜索方法指导搜索进入更有希望的构型区域.这种做法显著地提高了算法的成功率.在优化的后一阶段,借用动态格点搜索方法对团簇表面原子的位置作进一步优化,以再一次降低团簇的能量.另外,为识别二十面体构型的中心原子,本文给出了一个简单的新方法.相比于文献中一些著名的无偏优化算法,DLS-TPIO算法具... 相似文献
79.
§ 1 IntroductionThe relationship of population and economic growth is one of the most importantproblems in modern economic growth theory.Establishing a mathematical model theoreti-cal to study the interrelation of population and economic growth becomes a fundamentalmethod in this field[1~ 7] .In the papers[8,9] ,we obtain the especial C-K models with solv-able endogenous fertility under the specified strongly additive utility function and Cobb-Douglas production function.In the models,th… 相似文献
80.
Hui Jing Zhang Yong Gang Hu Yong Qian Wanga Jie Zhangc a School of Environmental Science Engineering Huazhong University of Science Technology Wuhan China b State Key Laboratory of Agricultural Microbiology College of Life Science Technology Huazhong Agricultural University Wuhan China c College of Environmental Science & Technology Huangshi Institute of Technology Huangshi China 《中国化学快报》2010,(8)
<正>The possibility of direct analytical applications of ferrate(Ⅵ) solution,which was freshly electrogenerated in low-concentration NaOH electrolyte,was studied by a flow-injection-chemiluminescence(FI-CL) system.It was found that some inorganic ions, organic molecule and biomolecule could enhance the chemiluminescence emission caused by ferrate(Ⅵ)-luminol reaction.V(Ⅴ), Ca(Ⅱ),Mg(Ⅱ),phloroglucinol,and bovine hemoglobin(Hb) chosen as samples were successfully detected by this developed method.The analytical characteristics of the system for the analytes determination including linear ranges,correlation coefficients, limits of detection combined with FI analysis were studied. 相似文献