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介绍了第35届全国中学生物理竞赛决赛实验试题的实验内容,并给出了试题解析以及竞赛成绩分析.试题1为测量光学玻璃材料的杨氏模量和折射率,可分为3部分:利用洛埃法测量半导体激光器的波长,利用单缝衍射法测定光学玻璃条的杨氏模量,测量厚光学玻璃片的折射率.试题2为测量电学黑盒子,给出其中元件连接的结构和元件性质,利用黑盒子的电路和电容率测量仪等,测量真空电容率和给定介质的相对电容率.实验试题设计性较强,成绩区分度较好.建议学生平时注重基本实验仪器的使用训练,掌握实验技巧,并加强物理基本原理的灵活应用. 相似文献
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重庆大学数理学院物理实验中心是全国中学生物理竞赛实验培训基地之一。在该中心开办的培训班中,根据全国中学生物理竞赛实验操作要求,围绕拓展参赛者的思维空间,提高参赛者动手解决实际问题的能力,开设了热学、光学、电学、力学等内容的实验。这些实验内容各具特色,激发了受训同学对物理实验的浓厚兴趣。本文就介绍该中心为竞赛参加者开设的一种电学实验——“黑盒子”实验。 相似文献
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轨道交通箱型梁在列车荷载作用下产生的低频振动与噪声对人体健康危害很大,针对箱型梁的减振降噪研究具有重要意义。将有限元振动分析理论与声辐射分析边界元法相结合,计算列车荷载作用下箱型梁的结构噪声,并对比分析不同的腔室结构对箱型梁结构噪声辐射的影响。计算结果表明:箱型梁场点结构噪声的辐射受振动水平影响较大;对于不同的腔室结构的箱型梁,跨中场点的最大线性声压级从大到小依次为单箱单室、单箱双室、单箱三室、双箱单室箱型梁;箱型梁采用双箱单室结构形式最有利于结构噪声的控制,且随辐射距离的增加,噪声辐射衰减越快;降低翼缘和腹板振动水平能够有效降低箱型梁结构噪声。分析结果可为城市轨道交通箱型梁的结构减振降噪设计提供一定的理论参考。 相似文献
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The sound field both in the loudspeaker box and in the room is calculated by an analytical solution of three-dimensional wave equation. It is shown in theory that the amplitude response in small rooms is affected by the following positions: driver position on the front panel of the box, box position in the room, absorption material position in the box and absorption material position on the interior walls of the room. Both our computer prediction and experiments prove that the optimum positions are beneficial to the amplitude response. 相似文献
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为探讨混凝土箱梁噪声的时变特性,以京沪高铁32 m混凝土简支箱梁为原型,制作了1:10的缩尺模型,通过模态试验的方法验证箱梁模型与原型的相似关系,通过声学试验验证箱梁声学计算模型的正确性。然后,建立了箱梁缩尺模型与原型两种计算模型,利用有限元和边界元法求出两种模型的瞬态结构噪声。研究发现,箱梁缩尺模型与箱梁原型的材料参数满足一定关系,模型试验的方法能够验证箱梁模型与箱梁原型之间符合相似关系,箱梁模型的振动噪声测试结果能真实反映原型振动噪声水平。两种模型的结构噪声在时域内声压级及对应场点的声压存在一定相似关系。该研究可为箱梁缩尺模型结构噪声反演至箱梁原型提供依据,所采用的方法和得到的结果对桥梁结构振动与声辐射实验研究具有参考作用。 相似文献
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介绍了中国聚变工程实验堆(CFETR)极向场线圈馈线系统终端盒(CTB)设计,CTB由外盒体、80K内冷屏、电流引线及超导母线、内部管路系统、阀门系统等子部件组成.利用ANSYS有限元软件,在运行工况和地震工况下对CTB外盒体及内冷屏进行结构强度校核、结构热分析和地震响应分析,得到CTB外盒体的位移、应力分布云图和在地... 相似文献
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This is the second in a series of three papers in which we study a two-dimensional lattice gas consisting of two types of
particles subject to Kawasaki dynamics at low temperature in a large finite box with an open boundary. Each pair of particles
occupying neighboring sites has a negative binding energy provided their types are different, while each particle has a positive
activation energy that depends on its type. There is no binding energy between particles of the same type. At the boundary
of the box particles are created and annihilated in a way that represents the presence of an infinite gas reservoir. We start
the dynamics from the empty box and are interested in the transition time to the full box. This transition is triggered by
a critical droplet appearing somewhere in the box. 相似文献
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The integral representation of the gamma function and the Poisson summation formula are used to calculate the interaction energy of charged particles in a 3-dimensional system periodic in two directions. A parallelogram shape simulation box is considered. Calculations are carried out for interactions described by any inverse power, and analytical continuation of the energy function leads to the final expression for the Coulomb interaction energy. Summation over the simulation box replica along one or the other side of the box base is replaced by summation in reciprocal space. Therefore there are two equivalent formulas for the potential energy that offer the possibility of avoiding slowly convergent series. The energy expressions are identical to those obtained from the Lekner method. The special case is considered where the functions defining the energy are infinite, i.e. when two charges lie on a line parallel to the simulation box side that was chosen to convert real space summation into reciprocal space. 相似文献
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《Journal of Electrostatics》2007,65(7):414-422
When a charged body exists near an opening of a partially opened metal box of an electronic apparatus, a potential difference is induced between conductive objects contained in the box. If the charged body moves, the potential difference changes and is capable of causing the breakdown of microelectronic devices in the box. However, one can rarely find a thorough study of this voltage. In this study, a potential difference induced between two metal foils in the partially opened metal box is measured without electrical connections. In some experiments, a piece of foil is grounded, whereas in others, both foils are ungrounded (floating). The measured result shows that the potential difference for a piece of foil grounded in the box is approximately 80% larger than that for both foils ungrounded. The potential difference decreases linearly by increasing the logarithm of the distance between the charged body and the front of the metal box. The result will provide a basis for a design to prevent the possible malfunction and breakdown of electronic apparatuses. 相似文献
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R. H. Dicke 《Foundations of Physics》1986,16(2):107-113
An atom is confined to a box in its ground state. An attempt is made to observe it in the left half of the box by scattering photons out of a photon wave packet passing through this half of the box. If no photons are scattered, the atom is missing. It is located on the right side of the box and its wave function is changed. The expectation value of the combined atom and photon energy is increased. For the other alternative, that the atom is found on the left side, the expectation value is decreased. By including both alternatives, it is shown that the mean energy is conserved. 相似文献
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WANG Baoguang 《Chinese Journal of Lasers》1997,6(6):481-488
StudyontheLevelMonitoringSystemfortheShipcariageboxWANGBaoguang(TianjinUniversity,Tianjin300072,China)GENGShijun(HebeiIndus... 相似文献