共查询到20条相似文献,搜索用时 62 毫秒
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为了提高水下结构声学计算的效率,采用有限元软件进行水下圆柱壳结构声辐射分析,建立声学分析近似代理模型,给出壳体结构几何尺寸与水下声辐射特性的显式解析表达式,简化声学计算,建立高效的结构声学优化设计模型。利用拉丁超立方取样方法进行样本点的选取,分别采用多项式响应面法、Kriging函数和径向基函数法构造水下双层圆柱壳结构的声辐射代理模型。通过比较三种代理模型的拟合精度,选择三种代理模型建立双层圆柱壳结构水下声辐射优化设计模型,并采用Matlab进行尺寸优化,减轻了结构质量。该研究为水下结构声辐射预报和声学设计提供参考。 相似文献
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无限长双层加肋圆柱壳水下声辐射解析计算 总被引:1,自引:0,他引:1
建立了无限长双层加肋圆柱壳水下声辐射解析计算方法,计算模型采用了Donnell壳体理论,考虑环肋、舱壁和实肋板对内外圆柱壳径向反作用力,利用傅氏变换和模态展开在波数域建立了这种计算模型的声弹耦合控制方程.文中推导了所有结构部件以及水介质的速度阻抗表达式,利用稳相法得到远场辐射声压.计算表明,实肋板和舷间水都是重要的声传递通道,在双层圆柱壳水下声辐射计算时必须考虑实肋板和舷间水的振动传递,双层圆柱壳水下声辐射对结构参数(壳板厚度、舷间距离等)变化不敏感. 相似文献
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为了满足水下结构振动与声学预报的需要,本文基于有限元/边界元法,采用以实测振动数据作为输入对水下结构振动与辐射噪声进行预报。预报采用大阻抗方法。使用大阻抗方法时,在建立结构有限元模型时,在振动测点建立一个虚构的单元,使得测点处具有很大的阻抗,并在测点施加一个相关的激振力,使得在该激振力的作用下测点处具有等于实测振动的响应,从而实现实测振动数据的输入。依据所测物理量的不同,大阻抗法可分为大质量方法和大刚度方法。如果测点振动响应能够完全描述测点“上游”激振源特性,则无须考虑测点“上游”的激振设备相关参数,这为水下结构振动与辐射噪声预报提供了便利。 相似文献
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为探究板壳间的振动传递机理,建立一种L型板-圆柱壳耦合结构有限元模型,并结合有限元理论给出板壳间振动传递功率的计算方法。利用ANSYS计算板-壳耦合结构的振动传递功率,分析L型板夹角、板长、板厚及激励等因素对结构振动传递的影响。研究发现,可以通过减小L型板夹角、增大板长和板厚、合理调整激励方向及位置等方式降低结构振动传递功率,减小板壳间振动传递的能量,改善结构的振动传递特性。 相似文献
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大坝升船机是利用机械装置升降船舶使之快速过坝的重要通航建筑物。承船厢是引导船舶过坝的载体,是大坝升船机的核心设备。由于承船厢的体形与质量巨大,在地震作用下将与升船机塔柱之间发生复杂的耦合振动。以三峡大坝升船机为工程背景,利用动力等效原理,将传统的升船机三维板壳有限元模型简化为三维杆系有限元模型;通过静力缩聚建立适用于升船机结构耦合振动分析的数值模型,验证对升船机塔柱和承船厢耦合振动进行控制的必要性;讨论弹簧、黏滞液体阻尼器和磁流变液阻尼器三种连接装置对地震作用下结构耦合振动的控制效果。计算结果显示,与被动控制装置相比,采用合适半主动控制策略的磁流变液阻尼器具有更好的减振效果,在实际工程中有着广阔的应用前景。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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V. T. Bublik A. I. Voronin E. A. Vygovskaya V. F. Ponomarev N. Yu. Tabachkova O. V. Toropova 《Inorganic Materials》2011,47(14):1563-1568
An analysis of anisotropy of the properties of a Bi2Se0.3Te2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal
expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological
fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained
using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied. 相似文献
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Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995. 相似文献
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O'Brien RS 《Radiation protection dosimetry》2003,105(1-4):95-100
Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides. 相似文献
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V. T. Kornienko 《Strength of Materials》1991,23(7):760-765
The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991. 相似文献
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由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。 相似文献
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M. M. Gadenin 《Inorganic Materials》2013,49(15):1352-1356
It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle. 相似文献
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