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反射边界条件是当前流行的处理运动固壁边界的方法,并取得了很大的成功。但应用于有强非线性波作用的情况下,这种方法被发现精度不够高而且容易产生数值过热现象。本文将处理多介质运动边界的MGFM方法推广到处理运动固壁边界。数值实验证明了MGFM方法在处理运动固壁边界上比反射边界条件更为有效。 相似文献
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音像制品作为物化形态的精神文化产品，是传播中国先进文化的载体和媒介。相对于传统的纸介质出版物，音像制品以其小、轻、薄和超级容量等特点与优势，日益成为人们普遍欢迎的不可或缺的文化传播介质，市场需求快速增长。自上世纪70年代末，音像制品被引入中国市场，在短短的二十几年中，中国的音像业有了快速的发展。据新闻出版总署统计，到2004年，全国共出版音像制品24423种，出版数量5．68亿盒（张），发行金额25.1亿元。现在，全国共有出版单位320家，音像复制单位250多家，发行单位1000多家，零售单位10多万个。产业规模迅速扩大，产业体系初步形成。事实证明，随着信息社会和知识经济时代的到来，音像、电子及网络等新型媒介的出版，正在成为我国新闻出版业新的生力军。 相似文献
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我们知道波动的产生首先需要一个处于平衡状态的介质,还需要有破坏介质平衡的扰动力和使介质恢复平衡的回复力,根据回复力的不同性质,对波浪的分类也很重要.回复力最重要的一种是重力,特别是对水自由表面的波浪,这种波浪成为表面重力波,第二种回复力是表面张力,这是由于水的表面具有表面张力的特性,水面一旦受到扰动,重力和表面张力力图使水面恢复到原来的平衡态,并形成波浪传播出去。 相似文献
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应力波反射法是一种经济实用效果显著的方法,目前已被广泛地应用到桩基动测实践之中,但是该方法并不是一种十分成熟的方法,尚有许多问题没有解决。由于工程桩的复杂性和多变性,有些问题甚至无法解决,这些没有解决的问题严重地限制了应力波反射法的应用。 相似文献
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当理想波色子气体被冷却到一个临界温度以下时将会发生相变,从而导致一种新的物质状态,这种相变称为波色-爱因斯坦凝聚,本文介绍了波色-爱因斯坦凝聚的基本理论及其最新进展。 相似文献
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Strong, Weak, and Latent Ties and the Impact of New Media 总被引：2，自引：0，他引：2
Caroline Haythornthwaite 《The Information Society》2002,18(5):385-401
This article argues that consideration of the strength of ties between communicators can help reconcile disparate results on the impact of new media on social relations. It is argued from the research literature and studies by the author that where ties are strong, communicators can influence each other to adapt and expand their use of media to support the exchanges important to their tie, but where ties are weak, communicators are dependent on common, organizationally established means of communication and protocols established by others. Due to this differential use of media, a new medium that adds means and opportunities for previously unconnected others to communicate will have positive effects on weak ties and weak-tie networks, in particular by laying an infrastructure of latent ties (ones that exist technically but have not yet been activated), and providing an opportunity for weak ties to develop and strengthen. A new medium may also have positive effects on strongly tied pairs where it adds another means of communicating and supports the communication needs and tasks of the pair. However, where a new medium replaces a former, common means of communication, the dependence of weak ties on a common medium makes weak-tie networks highly susceptible to dissolution. In contrast, strong-tie networks, with their connections via multiple relations and multiple media, can be expected to be more robust under conditions of change. 相似文献
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利用高温相变材料储热，同时用重力热管作为能量传输元件这一高效偶合装置在生产和生活中有广阔的应用前景。本文在实验基础上建立一个考虑自然对流影响的相变传热与热管传热相偶合的传热模型，并对该模型进行数值计算，通过与实验结果进行的对比，证实所建立的模型与所采用的计算方法均是合理可行的。 相似文献
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普通光学显微镜只能传递光波的振幅信息而丢失相位信息,因此用普通光学显微镜对透明和半透明的物体观察会丢失一些特征信息。植物纤维基本介于透明体与半透明体的状态,而透明物体对光只产生相位的移动而不能显著地改变光的振幅,所以在普通光学显微镜中难以观察到棉麻纤维的局部细节特征信息。而微分干涉相衬显微镜所观察的物体是位相物体,因此应用微分干涉显微镜可以明显改善这种情况。 相似文献
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Meng L Cai F Zhang Z Niu L Jin Q Yan F Wu J Wang Z Zheng H 《Biomicrofluidics》2011,5(4):44104-4410410
A microfluidic device was developed to precisely transport a single cell or multiple microbubbles by introducing phase-shifts to a standing leaky surface acoustic wave (SLSAW). The device consists of a polydimethyl-siloxane (PDMS) microchannel and two phase-tunable interdigital transducers (IDTs) for the generation of the relative phase for the pair of surface acoustic waves (SAW) propagating along the opposite directions forming a standing wave. When the SAW contacts the fluid medium inside the microchannel, some of SAW energy is coupled to the fluid and the SAW becomes the leaky surface wave. By modulating the relative phase between two IDTs, the positions of pressure nodes of the SLSAW in the microchannel change linearly resulting in the transportation of a single cell or microbubbles. The results also reveal that there is a good linear relationship between the relative phase and the displacement of a single cell or microbubbles. Furthermore, the single cell and the microbubbles can be transported over a predetermined distance continuously until they reach the targeted locations. This technique has its distinct advantages, such as precise position-manipulation, simple to implement, miniature size, and noninvasive character, which may provide an effective method for the position-manipulation of a single cell and microbubbles in many biological and biomedical applications. 相似文献
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Doppler effects for time-varying inhomogeneous media are considered. The ray path is represented in terms of a two-parameter function, this takes into account its time evolution. Time dilation along the path is discussed. This provides, in a systematic way, an alternative derivation to a heuristic expression previously given by Gill. The phase function is integrated along the ray path and yields the various Doppler effects in a straightforward way. It is shown that the generalized Doppler effect is produced by the relative motion of source and receiver with respect to the medium, and the cumulative rate of change of frequency and propagation vector along the path. 相似文献
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固体中冲击波及其一维一阶非线性演化方程数值模拟 总被引：1，自引：0，他引：1
定义固体中的冲击波为冲击波阵面及其后状态物理量发生急剧变化的狭窄区域。利用前人讨论结果进一步探讨了 4种边界输入形式下的冲击波形成距离计算式。分别采用具有二阶精度的显式MacCormack差分格式和MacCormackTVD格式对黏弹性、热弹性以及非均匀性非线性固体介质中一维一阶非线性演化方程进行数值模拟研究,探讨了这些复杂介质中冲击波的形成及演化的基本性质,并较成功地避免了非物理解的产生 相似文献
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Dan Censor 《Journal of The Franklin Institute》1975,299(5):333-338
The Doppler effect for the modulation of a wave signal is investigated. This group Doppler effect is considered for rays in inhomogeneous, dispersive, absorbing, anisotropic and time-varying media. In addition, the receiver or scatterer is allowed to move with respect to the medium. It is shown that the new effects depend on the group velocity and its direction relative to the normal. 相似文献
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机械波是大学物理教学中的重点内容,本文以平面简谐波为例,阐明了波动方程所描述的物理意义,讨论了介质中两点之间的相位差,并对驻波进行了分析。 相似文献
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媒介即讯息,在对人的组合和行动的尺度和形态上,媒介发挥着塑造和控制作用,手机媒介改变人际交往行为和方式。以北京邮电大学462名90后大学生为例,分析手机媒介在维系人际关系圈中的影响力。从关系强度、信任程度和人际交往能力3个维度,分析了手机媒介维系人际关系时发挥的效用。 相似文献