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1.
王雷 《大学物理》2022,(1):24-26+72
本文讨论了相对论教学中几个方面的问题,包括常见例子的问题,洛伦兹变换的方便形式,同时相对性例子在另一参考系的讨论,长度测量在另一参考系看到的现象,时间延缓及运动参考系各点时间不同和光的多普勒效应的简单推导.通过不同过程在不同参考系中的讨论,掌握在运动系讨论问题的方法,以及同一过程在不同惯性系内的不同表现,而所有现象的测量结论在洛伦兹变换下保持不变.  相似文献   
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Aluminum pigments were coated with Fe2O3 and CuO by solution-based thermal decomposition of the urea nitrate compounds hexakisureairon(III)nitrate and tetrakisureacopper(II)nitrate. The deposition process was optimized to obtain homogeneously coated aluminum pigments. The growth of the surface coatings was controlled by investigation with scanning electron microscopy, energy dispersive X-ray spectroscopy and static light scattering as well as infrared, X-ray diffraction and thermogravimetric analysis. The iron precursor showed an incomplete decomposition in solution, incorporating traces of urea molecules inside the coatings while the copper precursor showed complete dissociation accompanied by in situ formation of amine complexes. The amount of organic residues resulting from ligand fragments in the final oxide coatings could be reduced to 22 % for the iron oxide and 12 % for the copper oxide by further temperature treatment in solution (259 °C). Colorimetric investigations of the obtained pigments revealed an excellent hiding power, outperforming the pigments used in current state-of-the-art formulations.  相似文献   
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计算了在两个假想的星际航行方案中,与"双子佯谬"相关的时间差别.这种差别体现了惯性与非惯性参考系经历的时间有绝对差异,而不再是"相对"效应.  相似文献   
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Using an operator ordering method for some commutative superposition operators, we introduce two new multi-variable special polynomials and their generating functions, and present some new operator identities and integral formulas involving the two special polynomials. Instead of calculating complicated partial differential, we use the special polynomials and their generating functions to concisely address the normalization, photocount distributions and Wigner distributions of several quantum states that can be realized physically, the results of which provide real convenience for further investigating the properties and applications of these states.  相似文献   
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黄绍书  冯俊杰 《大学物理》2021,40(5):5-7,27
在电子线路工程及其教学过程中,都需要对电容器的直流电阻进行计算.然而,对一些特殊形状的电容器的直流电阻计算,普遍采用的电流密度法是比较麻烦的.本文根据电阻定义式,结合电阻的串联和并联的简洁关系,简单明了地对球冠形电容器、柱冠形电容器和正多棱柱形电容器等的直流电阻进行了计算,并给出相应的定量表达式.  相似文献   
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The self-excited oscillation of a large aspect ratio planar jet impinging on a flat plate is investigated experimentally at a single transonic jet velocity to clarify the effect of varying the jet thickness on pattern of jet oscillation and frequency of resulting acoustic tone. The study has been performed for a series of jet thicknesses, 1 mm to 4 mm, each of which is tested for the complete range of plate position, i.e. impingement distance, over which acoustic tones are generated. The results reveal that the jet oscillation is controlled by a fluid-dynamic mechanism for small impingement distances, where the hydrodynamic flow instability controls the jet oscillation without any coupling with local acoustic resonances. At larger impingement distances, a fluid-resonant mechanism becomes dominant, in which one of the various hydrodynamic modes of the jet couples with one of the resonant acoustic modes occurring between the jet nozzle and the impingement plate. Within the fluid-resonant regime, the acoustic tones are found to be controlled by the impingement distance, which is the length scale of the acoustic mode, with the jet thickness having only minor effects on the tone frequency. Flow visualization images of the jet oscillation pattern at a constant impingement distance show that the oscillation occurs at the same hydrodynamic mode of the jet despite a four-fold increase in its thickness. Finally, a feedback model has been developed to predict the frequency of acoustic tones, and has been found to yield reasonable predictions over the tested range of impingement distance and nozzle thickness.  相似文献   
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This paper deals with the ancient origin of matrices, and the system of linear equations. Included are algebraic properties of matrices, determinants, linear transformations, and Cramer’s Rule for solving the system of algebraic equations. Special attention is given to some special matrices, including matrices in graph theory and electrical networks. It contains a wide variety of important materials accessible to college and even high school students and teachers at all levels.  相似文献   
10.
We classify all the closed 3‐dimensional orbifolds with Sol‐geometry. These are aspherical orbifolds and so their fundamental groups determine the orbifolds completely. Thus we will classify all the crystallographic groups of Sol, together with all the Bieberbach groups, up to isomorphism.  相似文献   
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