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Table of Content

    20 October 2015 Volume 34 Issue 10
      
    著者文摘
    The practical significance of Feynman' s style in physics teaching
    . 2015, 34(10):  1-1. 
    Abstract ( 808 )   PDF (547KB) ( 693 )  
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    The Feynman' s style of melting miscellaneousness into simpleness for research and teaching is analyzed. He also tackled the key point of problem when he met a difficulty in research or teaching, and then he solved fascinatedly the problem by using the imagery method and the dramatic language.The style of this kind has the important meaning in the case of both regarding diathesis and shorting teaching time.
    A brief review on Laplace-Runge-Lenz vector
    . 2015, 34(10):  5-5. 
    Abstract ( 3011 )   PDF (352KB) ( 2281 )  
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    Applications of Laplace- Runge-Lenz vector in classical mechanics, quantum mechanics and general relativity are reviewed briefly. By using this vector conserved in classical and quantum Kepler problems, one can study some important properties, such as obit equation and eigenvalue of energy, without solving the equa- tions of motion. Although the corrections from general relativity violate the conservation, its evolution, with respect to time, will completely determine the perihelion precession and light bending. All these examples indicate that La- place-Runge-Lenz vector is a fundamental physics quantity which is dictated by basic dynamical symmetries, thus it is instructive to introduce it into general physics courses.
    The energy level splitting and degeneracy in the first order Stark effect of hydrogen atom
    . 2015, 34(10):  9-9. 
    Abstract ( 1827 )   PDF (262KB) ( 1170 )  
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    The energy level splitting and degeneracy in the first order Stark effect of hydrogen atom can quickly be obtained in a table,and the results are in agreement with the ones from the theoretical calculations. Based on the results of the first order Stark effect of hydrogen atom in the parabolic coordinate, it is proved that the space of two adjacent levels fulfill the relation 1.5neεa.
    The trajectory analysis of instantaneous center acceleration of the round of pure rolling on the fixed surface
    . 2015, 34(10):  12-12. 
    Abstract ( 2436 )   PDF (254KB) ( 1240 )  
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    The paper focuses on the deduction of the acceleration formula of any point at the round of pure roll- ing on the fixed surface. The characteristics of tracks of the acceleration instantaneous center at the wheel pure roll- ing on a fixed surface are analyzed, and the movement of the wheels pure rolling is more deeply understood. An ef- fective method of point acceleration of plane motion graphics is provided.
    Discussion on the energy of simple harmonic wave
    . 2015, 34(10):  15-15. 
    Abstract ( 943 )   PDF (261KB) ( 612 )  
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    Based on the longitudinal wave in a bar, it is shown that the kinetic and potential energy density may have different instantaneous values when the initial stress is presented in the medium.
    Calculation and symmetrical analysis of electric field of a finite line with even charge
    . 2015, 34(10):  17-17. 
    Abstract ( 1141 )   PDF (229KB) ( 824 )  
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    Based on the property of ellipse and hyperbola, we find that the equipotential surface of a finite line with even charge is ellipsoid. Using ellipsoidal coordinates, we calculate the electric field and potential with Gauss theorem by direct integral, and make some essential discussions.
    Calculation of two confocal parabolic cylinder plate between the electric field and capacitance using Gauss theorem
    . 2015, 34(10):  20-20. 
    Abstract ( 888 )   PDF (255KB) ( 646 )  
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    By using the Gauss theorem of electrostatic field in the parabolic cylindrical coordinates, two confo- cal parabolic cylinder plate between the electric field intensity, electric potential and capacitance are calculated.
    Infinite sum and asymptotic expansion
    . 2015, 34(10):  23-23. 
    Abstract ( 866 )   PDF (250KB) ( 659 )  
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    The asymptotic expansion and analytical expression of Madelung constant of circle chain are derived from the Euler-Maclaurin summation formula,
    General formula for the first level energy approximation of two-dimensional hydrogen atom in Stark effect
    . 2015, 34(10):  25-25. 
    Abstract ( 895 )   PDF (223KB) ( 527 )  
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    The general formula for perturbative matrix elements is deduced, and the general formula for the first level energy approximation of any state energy of two-dimensional hydrogen atom in Stark effect is given.
    and application of Minkowski' four-dimensional space
    . 2015, 34(10):  28-28. 
    Abstract ( 1155 )   PDF (706KB) ( 2207 )  
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    Proposition and Geometrieal expression of Minkowski' four-dimensional space are reviewed. Born' application of the conception and his geometrical methods to analyze special theory to obtain eonelusions of spaee- time concept are introdueed.
    Illustration of collisions between a material particle and a rigid body
    . 2015, 34(10):  35-35. 
    Abstract ( 1508 )   PDF (391KB) ( 1086 )  
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    Based on the experiments of bullet-block collisions, the applicable conditions of energy conserva- tion, momentum conservation, and angular momentum conservation are analyzed. The collisions of bullet-block can be simplified as the interaction between a material particle and a rigid body. Therefore, the experimental phenomena show some features of this interaction.
    Theoretical analysis of measuring Young' s modulus using dynamic method based on Matlab
    . 2015, 34(10):  39-39. 
    Abstract ( 880 )   PDF (356KB) ( 357 )  
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    According to the idea of measuring Young' s modulus using dynamic method, we establish the partial differential equation of transverse vibration of the bar. By using variable separation method, the general solution is obtained. On the analysis of boundary conditions of free vibration, we present a transcendental equation and the coefficients of the general solution. Also, by using graphic method in Matlab 7.0 environment, we obtain the approximate solution and high precision numerical solution to the first three order natural frequencies of the transverse vibration of the bar. The first three order vibration modes and nodes location are given by graphic, which consistent with the theoretical values in the textbook.
    Improvement of measuring the sound velocity by using resonant pipe device
    . 2015, 34(10):  43-43. 
    Abstract ( 1513 )   PDF (266KB) ( 790 )  
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    In order to make a sound, one end of the straw is sealed with blowing another end of the straw. Based on the software of spectral analysis, fundamental frequency of the acoustic signal is ascertained. The differ- ence between theory and experiment is pointed out. In theory, since the corresponding tube length of fundamental frequency is a quarter of the acoustic wavelength, the sound velocity can be calculated with fundamental frequency and tube length. But in fact, the effective tube length is the combination of the real tube length and the end correc- tion which is changed by the different thickness and shape of the tube. In experiment, for the straws with the diame- ter of 1.1cm and 0.6cm, better sound velocity is achieved with the application of the end correction of 0.5d and l d respectively. Besides, if the tube length is too short, it will be hard to acquire the accurate fundamental frequency.
    Design of hydrodynamic comprehensive experimental platform
    . 2015, 34(10):  48-48. 
    Abstract ( 850 )   PDF (633KB) ( 576 )  
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    A comprehensive experimental platform is designed according to the principles of fluid mechanics. The Poiseuille law, Bernoulli principle and Torricelli law, can be quantitatively studied well. In addition, the con- version processes between laminar flow and turbulent can be figuratively demonstrated by observing Raynaud's phe- nomenon.
    The power generation speed experiment of Kelvin water dripping generator and its improving research
    . 2015, 34(10):  51-51. 
    Abstract ( 848 )   PDF (858KB) ( 1035 )  
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    Kelvin water dripping generator uses the most common water droplets to accumulate electrical charge, and applies positive feedback so that electrical charge keeps accumulating in the device and the potential difference between gets higher and higher. But the cause of the potential difference is still controversial now, and the experimental device is rough and lacks of a unified production specification, the quantitative injury of each fac- tor causing the potential difference is scarce, as well. That is why this experiment is instable and difficult to spread. In this paper, we adopt the idea of control variables to conduct quantitative injuries of each factor causing the po- tential difference, and found the best conditions to carry out this experiment, verified the cause of the potential difference, made an improved standardized Kelvin water dripping generator.
    Measurement of the activity of 60Co radioactive source by coincident method
    . 2015, 34(10):  57-57. 
    Abstract ( 1319 )   PDF (557KB) ( 826 )  
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    The gamma energy spectrum of 60Co is measured by using NaI (T1) scintillator detector. According to the peak area of the measured 1.173MeV and 1.332MeV gamma rays as well as that of their coincident peak, the activity of radioactive source is obtained, which has a (6.64±0.40)% deviation in comparison with the real value. It is shown that this method can measure the activity of radioactive source.