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    20 June 2017 Volume 36 Issue 6
      
    The Anomaly Frullani Integrals
    WU Chong-shi
    College Physics. 2017, 36(6):  1-5.  doi:10.16854 /j.cnki.1000-0712.2017.06.001
    Abstract ( 1461 )   PDF (254KB) ( 474 )  
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    A series of improper integrals,anomaly Frullani integrals,are discussed. They cannot be ascribed to the famous Frullani integrals,although they are in the form similar to the Frullani integrals,but fail to meet the requirements for the latter. Many anomaly Frullani integrals are deduced from two typical ones.
    Interference of two-dimensional superconducting induced current in vector potential A field
    LI Yuan-jie,JIA Wen-chuan
    College Physics. 2017, 36(6):  6-8.  doi:10.16854 /j.cnki.1000-0712.2017.06.002
    Abstract ( 1008 )   PDF (2052KB) ( 424 )  
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    When a two-dimensional superconducting mental surface is passed through by two infinite straight magnetic flux,it is shielded by superconductivity.It is supposed that the change rate of flux is not equal to zero at the beginning,which induces two opposite and equal currents on the two - dimensional superconducting mental surface.In this situation,when the change rate of flux is changed to zero and both magnetic fluxes remain constant,a new physical interference effect appears. In this paper, the interference streamline distribution on the two-dimensional superconducting mental surface is calculated and simulated. We named the new interference phenomenon L-J effect considered as a two-dimensional A-B effect.
    Monotonic and non-monotonic increase of the energy for a 1D simple harmonic oscillator on action of exponentially-decaying-on-time perturbation
    LI Zhao,YANG Zi-qian,ZHANG Meng-nan,ZHOU Xiao-yu,LI Yong-ping,LIU Quan-hui
    College Physics. 2017, 36(6):  9-14.  doi:10.16854 /j.cnki.1000-0712.2017.06.003
    Abstract ( 1313 )   PDF (846KB) ( 491 )  
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    When a 1D simple harmonic oscillator is under the action of the perturbation that decays exponentially with the increase of time,the energy of the system can increase monotonically or non-monotonically,depends mainly on the ratio of the period of the oscillation and the characteristic time of the perturbation. Once the ratio is small,i.e.,it is much less than 1,the increasing is monotonic; however,which is large,i.e.,it is much greater than 1,the increasing is oscillating with diminishing amplitudes. The physical mechanism is proposed in the following. That the ratio is small means that the perturbation ends practically within one period of the unperturbed system,so the probability of the system in the every energy level cannot change any more. That the ratio is large means that the perturbation needs many periods of the unperturbed system before it ends practically,so the probability of the unperturbed system in the every energy level can change alternatively. Since this physical mechanism holds universally for the perturbation decays on time,the system studied in present paper serves as an illustration. In addition,we have found that once the perturbation acts,the system starts to deviate from the initial state in such a manner that is independent of the characteristic time of the perturbation at very short time of the action.
    Calculation and analysis of background magnetic fields in relativistic heavy-ion collisions
    AI Xin,FENG Sheng-qin,ZHONG Yang
    College Physics. 2017, 36(6):  15-20.  doi:10.16854/j.cnki.1000-0712.2017.06.004
    Abstract ( 1179 )   PDF (993KB) ( 506 )  
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    The magnetic field formula of a point charge in relativistic form is derived by using the Lorentz transformation. On this basis,we estimate the background magnetic field in relativistic heavy - ion collisions by aking consideration in the longitudinal thickness of nucleus. The numerical calculations of Au -Au collisions in RHIC energy regions and Pb-Pb collisions in LHC energy regions are carried out.Then,we discuss mainly the energy dependence of the magnetic field at original point and give an intuitive,qualitative theory explanation.
    Calculation of rotational inertia of a circle tire uniform rigid body
    WANG Yong-chao
    College Physics. 2017, 36(6):  21-22.  doi:10.16854 /j.cnki.1000-0712.2017.06.005
    Abstract ( 1377 )   PDF (314KB) ( 928 )  
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    According to the definition of rotational inertia,the mass projection method is used to calculate the rotational inertia.The rotational inertia of a circle tire uniform rigid body is calculated.
    Calculating the eccentricity of the Earth's orbit by approximate orbital equation
    YU Feng-jun
    College Physics. 2017, 36(6):  23-24.  doi:10.16854 /j.cnki.1000-0712.2017.06.006
    Abstract ( 1329 )   PDF (248KB) ( 742 )  
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    The elliptic orbit equation of the Earth is treated approximately,and then the eccentricity of the orbit is calculated by the Kepler area law and the season length.
    An apprehensible geometrical approach to analyze the acceleration at the instantaneous center of rotation
    CHEN Kui-fu,HE Wei
    College Physics. 2017, 36(6):  25-27.  doi:10.16854 /j.cnki.1000-0712.2017.06.007
    Abstract ( 1575 )   PDF (367KB) ( 1119 )  
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    An apprehensible geometrical approach is presented to analyze the acceleration at the instantaneous center of rotation. This approach only involves the method of instantaneous center of rotation,the definitions of acceleration and curvature for a rigid body in planar motion.
    Application of Fermat's principle in ideal imaging at the spherical boundary for the object point outside the principal axis
    WAN Jian-jie,ZOU Jia-bing
    College Physics. 2017, 36(6):  28-30.  doi:10.16854 /j.cnki.1000-0712.2017.06.008
    Abstract ( 1477 )   PDF (326KB) ( 519 )  
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    Fermat's principle is a basic one in the geometrical optics,which means that the actual trajectory in the space depends on the extremum of the optical path.Based on the Fermat's principle,a new method is proposed to get directly the equation for the practical optical path in reflections and refractions at spherical boundary for the object point outside the principal axis,and then the object-image formula is also derived in the condition of axial ray and axial object.
    Discussion on the experiment of measuring the effective mass of spring by Jolly’s scale
    ZHANG Chun-ling,SUN Qian,CUI Xiu-mei,TANG Lei
    College Physics. 2017, 36(6):  31-35.  doi:10.16854 /j.cnki.1000-0712.2017.06.009
    Abstract ( 1292 )   PDF (402KB) ( 1141 )  
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    For the experiment of measuring the effective mass of the spring,we study the effect of the shape and mass of spring and the starting point of recording time on the effective mass of the spring. We also compare the calculations of two kinds of data processing methods and discuss the open teaching methods.
    Development of simulation experiment for Wheatstone bridge and Kelvin bridge based on LabVIEW
    YANG Tie-zhu,LAI Xiao-lei,ZHANG Zhi-qiang,SU Ming,MENG Shu-heng,PAN Feng
    College Physics. 2017, 36(6):  36-40.  doi:10.16854 /j.cnki.1000-0712.2017.06.010
    Abstract ( 1396 )   PDF (1915KB) ( 444 )  
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    Aiming at the experiment of Wheatstone bridge and Kelvin bridge,the current intensity through the alvanometer in the single bridge and double bridge is expressed by a unified formula. Based on LabVIEW,a platform of virtual simulation experiment for DC bridge with the full function of Wheatstone and Kelvin bridges is designed. The two bridges are applied to measure the middle value resistance and low value resistance separately. Inthe classroom,the virtual instrument is used for the experiment teaching,which is useful to explain the difficulty of teaching and improve the teaching quality effectively. The sharing of the application ( EXE) of the virtual simulation experiment on the campus network provides autonomous learning space for students. It is also used for informationized teaching for college physics experiment.
    The method of optical-path amplification for measuring the micro-displacement based on the Michelson interference
    HUANG Zhen-xian,LIU Yue,JIA Guang-yi
    College Physics. 2017, 36(6):  41-43.  doi:10.16854 /j.cnki.1000-0712.2017.06.011
    Abstract ( 1365 )   PDF (350KB) ( 734 )  
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    Based on the Michelson interferometer,this paper introduces a new experiment method to measure the micro-displacement. The incident and reflected light are multiply reflected by adding the parallel plane mirror group in the Michelson optical path. When the distance between the parallel plane mirrors presents a small change,the optical path difference of the two reflected light beams will be amplified such that the micro-displacement can be calculated according to the measured change of interference fringe. The design of experiment optical path as well as the corresponding experimental verification are achieved. The measurement accuracy is greatly improved by this proposed method comparing with the traditional Michelson experimental facility.
    Turning and returning: Historian of science Derek Price’s obsession for physics
    DONG Guo-hao,2,QIAN Wei
    College Physics. 2017, 36(6):  44-49.  doi:10.16854 /j.cnki.1000-0712.2017.06.012
    Abstract ( 1252 )   PDF (231KB) ( 359 )  
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    At the beginning of the creation and development of history of science,those who changed from physics to history of science have made great contributions. The young physicist Price shifted his interests to history of science in the middle of the last century,but the experience and thoughts in physics have never been away from his study,but to help him to develop many perspectives,such as the quantitative study of history of science, the concept of“big science”and the thought of “cross-fertilization”. This story not only reflects the obsession for physics of the historian of science Derek Price,but also provides another way to realize the integration of subjects.
    Mechanical analysis of the non-uniform falling chimney
    HOU Ji-xuan,LI Zhi-ang,GUO Xing,NIU Zhi-hao
    College Physics. 2017, 36(6):  50-51.  doi:10.16854 /j.cnki.1000-0712.2017.06.013
    Abstract ( 1355 )   PDF (431KB) ( 937 )  
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    It is generally known that chimney might break at a certain place before it hit the ground during a demolition blasting. However,previous models have assumed that the mass distribution of the chimney is uniform. The chimney model analyzed in this paper is a more realistic one with non-uniform mass distribution.By seeking the maximum point of the torque,the possible rupture point of the chimney is given.
    The research of the blind navigation glasses
    LIU Xing-yun,YANG Huo-xiang,LIU Xing-hao,LU Chi-mei,MA Lang,DING Ke-yu,
    College Physics. 2017, 36(6):  52-55.  doi:10.16854 /j.cnki.1000-0712.2017.06.014
    Abstract ( 1645 )   PDF (1211KB) ( 598 )  
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    The modern society is full of skyscrapers and traffic developed,but for the blind everywhere is filled with obstacles which brings inconvenience for the blind's travel,traveling safety for blind people gradually become the focus of attention. The purpose of this navigation glasses is to assist the blind to travel,by designing two sets of ultrasonic distance measurement system to help the blind avoid obstacles in time. The data are obtained by ultrasonic measurement related algorithm which can get three aspects information about the distance,speed and direction of the obstacles to inform the blind in the form of vibration and achieve the effect of navigating to the blind. The glasses have the following characteristics: simple structure,easy operation,high integration,good accuracy,low power consumption,low cost and broad market prospects.
    FDTD analysis of the light transmission properties at the interface of discontinuous medium
    CHEN Yu,PENG Yong-yi,XIA Hui,OUYANG Fang-ping
    College Physics. 2017, 36(6):  56-60.  doi:10.16854 /j.cnki.1000-0712.2017.06.015
    Abstract ( 1010 )   PDF (1204KB) ( 568 )  
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    Based on the finite - difference time - domain ( FDTD) method and combined with Matlab programming,the characteristics of light reflection,transmission and interference at the interface of discontinuous medium are studied. Parameters such as the gradient and continuity of permittivity,which affect the intensity of reflected light at the interface,are discussed. Also,dynamic modeling of light interference is rebuilt on computer and systematically investigated by tuning the electromagnetic and structural parameters of the interference thin film. The FDTD method can achieve a time-domain and numerical solution of the electromagnetic field,which is very convenient for dynamic demonstration. Meanwhile,computer experiments can be realized by changing the structural and electromagnetic parameters of the cared medium,which makes it possible for students to do it themselves and to learn,to investigate the physical nature that is covered behind of those numerical physical phenomena.
    Constructing college physics teaching team and promoting college physics teaching
    Ci-Ren-Ni-Ma,NING Chang-chun,CHEN Tian-lu,ZHANG Hui-jie,WANG Ya-ping,
    College Physics. 2017, 36(6):  61-65.  doi:10.16854 /j.cnki.1000-0712.2017.06.016
    Abstract ( 1365 )   PDF (211KB) ( 499 )  
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    This paper introduces the meaning and practice method of college physics teaching team,as well as the function and value of college physics teaching team in college physics teaching. For the teaching reform of college physics,it is a new attempt.
    Theoretical and experimental studies of nonlinear characteristics of rubber balloon
    College Physics. 2017, 36(6):  66-72.  doi:10.16854 /j.cnki.1000-0712.2017.06.017
    Abstract ( 1211 )   PDF (1414KB) ( 1381 )  
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    According to the thermodynamic properties of rubber balloon and the theory of Mooney model,we derive the relationship between the additional pressure and the radius of rubber balloons' membrane during inflation and deflation when two balloons are connected,and the relationship between the two connected balloons' volume changes and internal pressure is also obtained. The theoretical results are in agreement with the experimental results. Applying the model into the research of the simple model of the hovercraft,we take use of the experimental results to modify the theoretical model.
    Error analysis and correction method of measured speed with strip light barrier
    College Physics. 2017, 36(6):  73-77.  doi:10.16854 /j.cnki.1000-0712.2017.06.018
    Abstract ( 1831 )   PDF (445KB) ( 423 )  
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    In all kinds of experiments using air track with accessories and spare parts,whether direct or indirect measurement,velocity is a basic physical quantity to be determined and the accurate measurement of velocity is of great significance. Universal counter MUJ-6B is often used to record the blackout time as different type of light barrier passes through the optical gate,while the vernier caliper is used to measure the blackout distance,then the value of velocity is obtained. From the viewpoint of the principle of photoelectric timing,this article analyzes the reason that there is no systematic error with U-shape light barrier using timing mode 2,while there is great systematic error with strip light barrier using timing mode 1. Moreover,the“swallowed”width of strip light barrier by photoelectric gate is deduced by using the theoretical formula of harmonic vibration model which is realized by two springs and a slider moving on the air track. Hence,the modified formula of velocity is obtained,which is tested and verified by the experiment of momentum conservation on the air track. Therefore,the proposed velocity correction method is tested to be reliable from another aspect.
    Preparation and detection of an ohmic contact electrode material Ag /Codoped amorphous carbon film for semi-insulated GaAs   
    DU Wei-jia1,ZHAI Zhang-yin1, JI Shuai,ZANG Ting-yu
    College Physics. 2017, 36(6):  78-81.  doi:10.16854 /j.cnki.1000-0712.2017.06.019
    Abstract ( 1110 )  
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    Stable ohmic contacts play the important role in the normal operation of semiconductor devices. At present,Au /AuGeNi alloy is used as the electrode material of n type GaAs. The process is complex and the cost is high.In this paper,a new type of ohmic contact electrode material Ag /Co doped amorphous carbon film for semi-insulated GaAs and its preparation process are introduced to make it easy for readers to understand the process and technology of semiconductor devices.
     
    College Physics. 2017, 36(6):  82. 
    Abstract ( 762 )   PDF (171KB) ( 329 )  
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