共查询到20条相似文献,搜索用时 125 毫秒
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逆流检漏仪用扩散泵属于特殊用途的扩散泵。它要求扩散泵对空气的压缩比大,对氦气的最大压缩比小。为满足这样的要求,设计了 K—65F风冷金属油扩散泵。本文介绍了 K—65F的特殊结构,论述了采用这种结构的理论依据。并运用真空物理中的理论,气体动力学理论和Jaeckel理论,对K—65F泵作了性能分析,说明设计的合理性,证明这种结构的扩散泵能够满足逆流检漏仪的特殊要求。 相似文献
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分别基于平面应力型全弹性模型和三维数值模型建立了计算复合材料飞轮破坏转速的二维和三维算法。这两个算法均采用了正交各向异性材料的最大拉应力(材料主方向) 准则, 其中三维算法还采用了两种强度判据, 即基于轴向大部分区域每层应力的平均值判据和轴向边界区域每层应力的最大值判据。对张紧力缠绕的3个实验复合材料飞轮成功实施了高速旋转破坏实验, 破坏均发生在径向强度最弱的飞轮与金属芯轴的界面处。实验结果表明, 飞轮的实际破坏转速与理论破坏转速十分接近, 证实本文中建立的二维和三维算法是可靠的;二维算法得到的理论破坏转速偏高, 而飞轮的实际破坏转速落在三维算法分别按最大值判据和平均值判据得到的两个理论破坏转速之间, 说明三维算法的精度更高。 相似文献
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Results of a series of experimental tests performed to determine the influence of matrix characteristics on the leaching mechanism
of copper aluminum oxychloride immobilized into cement matrices are presented. The objective of this work was to investigate
the leaching mechanism of copper as a constituent of copper aluminum oxychloride (‘CAOX’). Transport phenomena involved in
the leaching of a waste material from a composite matrix into surrounding water were investigated using three methods based
on theoretical equations: (i) diffusion equation derived for a plane source model, (ii) rate equation for diffusion coupled
with a first-order reaction and (iii) the leaching data were also analysed by an empirical method employing a polynomial equation.
These three methods are compared with respect to their applicability to the leaching data. 相似文献
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利用显微粒子追踪测速系统(Micro-PTV)对四种不同粒径(2μm、1μm、0.71μm、0.52μm)的颗粒在纯水中的布朗运动进行了实验研究.使用波长为532nm的连续激光器、电子倍增CCD(EMCCD)相机以及放大倍率为63倍的显微物镜得到颗粒图像.对原始图像进行处理,借助于Video Spot Tracker软件获得相邻两帧图像中示踪颗粒的单步位移,在此基础上计算颗粒在纯水中的实验扩散系数,分别为0.191μm2/s,0.391μm2/s,0.579μm2/s及0.746μm2/s.将计算结果与采用Stokes-Einstein公式计算的无限大空间单个颗粒理论扩散系数进行了比对,偏差在10%以内,实验值略小.实验结果能够正确反映微米(μm)/亚微米颗粒布朗运动的特征. 相似文献
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掺稀土纳米发光材料的研究进展 总被引:5,自引:0,他引:5
概述了掺稀土纳米发光材料的理论研究价值和应用前景,介绍了此类材料的制备方法、结构测试方法及光谱研究情况,对掺稀土纳米发光材料的发展前景进行了展望. 相似文献
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标准氡室在氡浓度量值溯源和传递中起着重要作用。为了保证测氡仪量值统一、准确可靠,建立了测氡仪检定装置。针对在建立标准过程中出现的流气式氡源泄漏、氡室实验累积氡浓度值与理论值不一致和液体镭源结晶等问题,重点研究多重密封、改造洗气管路、优化洗气模式及多重过滤等技术方法,并建立氡室累积氡浓度经验曲线和质量管理措施等。按照新建立的实验方法和实验流程,氡室实验调节氡浓度和理论累积氡浓度相对偏差在±3.8%以内,液体镭源长期稳定性在0.7%以内,符合氡室建标的计量性能要求。 相似文献
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目的对人工智能在产品创意设计方法中的研究与应用现状进行了综述性地介绍,从定义、理论研究与传统设计方法的比较加以了系统阐述,对现有的设计理论与技术有所增值。方法利用文献综述的方法,从传统设计方法、基于程序的设计方法、基于数据驱动的生成设计在产品创意设计研究中的成果进行了回顾与总结,比较了不同设计方法的核心思想、优缺点以及设计应用,并分析了基于人工智能的设计方法所面临的挑战和发展趋势。结论通过智能化设计水平将设计方法分为3类,其研究结论有助于设计研究者选择合适的研究途径与合理的评价方式。 相似文献
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Boundary elements approach for solving stochastic nonlinear problems with fractional Laplacian terms
Models involving stochastic diffusion equations are utilized for describing the evolution of a number of natural phenomena and are widely discussed in the open literature. In recent years, these models have been revisited in light of experimental observations in which “anomalous” diffusion processes were identified, such as in the propagation of acoustic waves in random media. In this context, a critical characteristic of the theoretical models is the introduction of fractional derivative operators in the associated governing equations. Specifically, anomalous diffusion involves a fractional Laplacian operator replacing the classical Laplacian. Currently, solutions to equations with fractional Laplacians are available for a quite limited numbers of cases. Further, to the authors’ knowledge, no solutions are available for nonlinear equations involving fractional Laplacians. This fact creates the need of developing adequate numerical methods for estimating the response of this kind of systems. This paper proposes a Boundary Element Method (BEM)-based approach to determine the response of a system governed by a nonlinear fractional diffusion equation involving a random excitation. The approach is constructed by utilizing the integral representation of the classical Poisson equation solution, in which unknown constants are determined by the BEM. Then, based on a recently proposed representation of the fractional Laplacian operator, the value of the fractional Laplacian of the response is updated progressively by matrix transformation of these constants. Numerical results pertaining to a system exposed to white noise are presented to elucidate the mechanization of the approach. Further, parameter studies are done for examining the influence of the fractional Laplacian order on the system response. 相似文献
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Michael D. McKay 《Reliability Engineering & System Safety》1997,57(3):267-279
This paper examines the feasibility and value of using nonparametric variance-based methods to supplement parametric regression methods for uncertainty analysis of computer models. It shows from theoretical considerations how the usual linear regression methods are a particular case within the general framework of variance-based methods. Examples of strengths and weaknesses of the methods are demonstrated analytically and numerically in an example. The paper shows that relaxation of linearity assumptions in nonparametric variance-based methods comes at the cost of additional computer runs. 相似文献