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Table of Content

    20 January 2020 Volume 39 Issue 01
      
    Energy and Wigner functions of the Dirac oscillator in noncommutative phase space
    LV Tengbo, LIU Li, LIU Weihua, LI Xin, WANG Xiaoli,
    College Physics. 2020, 39(01):  1-4.  doi:10.16854 / j.cnki.1000-0712.190294
    Abstract ( 1008 )   PDF (253KB) ( 338 )  
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    With the development of noncommutative geometry,string theory and loop quantum gravity theory,he noncommutative space has been made more and more concerned. The noncommutative quantum theory is different from the ordinary quantum theory,which is a special physical effect under the string scale. Therefore,special methods are needed to deal with noncommutative quantum mechanics problems. In this paper,the Moyal equationand Wigner function first are introduced. Starting from Moyal-Weyl multiplication and Bopp transformation,H(x,p)is transformed into H^ (x^ ,p^ )by considering the noncommutability of coordinate-coordinate,momentum-momen tum to realize the star-multiplication eigenequation in the non-commutative phase space. The algebraic relationship of noncommutative phase space quantum mechanics is used to discuss the Wigner functions and energy levels of Dirac oscillator in noncommutative phase space. The results show that the energy level of the Dirac oscillator in the non-commutative phase space is obviously dependent on non-commutative parameters.
    Bohr hypothesis to luminescent mechanism
    ZHAO Lijuan
    College Physics. 2020, 39(01):  5-8.  doi:10.16854 / j.cnki.1000-0712.190166
    Abstract ( 1149 )   PDF (800KB) ( 691 )  
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    Light is an electronicmagnific radiation in the range of violet to infrared.Luminescence is light radiation except thermal radiation.Luminescence is the theoretical fundation for design luminescent materials and its applications.In this work,based on Bohr hypothesis,energy levels and transition of isolated atom in vacuum and inantivacuum are analysized and the luminescent mechanism is induced.Quantum cutting and up-conversion lumines cence of non-isolated atoms are investigated by energy transfer of atom at excited state.And it is found that the atomic excieted state energy transfer is a key for understanding luminescence.The students follow the advance of lumines cent physics by introducing Nobel prize that is relative with luminescence.We get overstep from fundament knowl edge to science border in the college physics.
    The moment of inertia of ring and torsional ring with elliptic cross section
    YU Feng-jun, TIAN Jun-long, TANG Zhen-jie, ZHANG Xi-wei
    College Physics. 2020, 39(01):  9-11.  doi:10.16854 / j.cnki.1000-0712.190067
    Abstract ( 1376 )   PDF (512KB) ( 534 )  
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    The mathematical models of rings and torsional rings with elliptical cross section are established.According to the definition,the moment of inertia and the product of inertia about three coordinate axes are calculated. The calculation process is simplified by making full use of the symmetry of the section figure. Some useful conclusions and results are obtained.
    Clearing up the misunderstanding about the principle of relativity and covariance of equations
    ZHAO Kai-hua
    College Physics. 2020, 39(01):  12-13.  doi:10.16854 / j.cnki.1000-0712.190405
    Abstract ( 1203 )   PDF (338KB) ( 702 )  
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    Some authors confirm that the energy of a physical system conserves in an inertial frame of referencemust do so in any other frames. Actually they have confused the covariance of equations with the principle of relativity. The present article attempts to clear up this misunderstanding.
    Thinking about a typical mechanical problem
    WANG Xiao-ying, WANG Ming-li, HOU Yan-xue
    College Physics. 2020, 39(01):  14-17.  doi:10.16854 / j.cnki.1000-0712.190014
    Abstract ( 1083 )   PDF (554KB) ( 395 )  
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    A typical mechanical problem is analyzed in this paper. A heavy ball is hanged below the ceiling by a rope,and another rope is tied at the bottom of the ball. If the end of the rope moves at a certain velocity,which rope will snap first. The results show that when the moving speed v is less than a certain critical speed Vc,the rope above the ball snaps first. Which rope snaps first when the speed exceeding Vc is decided by the maximum tensile force that the rope can sustain. The rope under the ball snaps first when the speed v>>Vc .

    Teaching application of dimensional analysis in the thermodynamics part of college physics
    LAN Shan-quan, CHEN Jian-ming
    College Physics. 2020, 39(01):  18-22.  doi:10.16854 / j.cnki.1000-0712. 190205
    Abstract ( 929 )   PDF (193KB) ( 384 )  
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    This paper briefly introduces the homogeneous theorem and the Π theorem in dimensional analysis,

    and then specifically cites the teaching application of dimensional analysis in the thermodynamics part of college

    physics. Our solution process is:analyzing and listing the possible physical quantities;writing a dimension table of

    all physical quantities;analyzing the dimension table,determining the relevant physical quantities and independent

    dimension;setting the dimensionless quantity equation;listing and solving the dimension index equations.

    Deriving laws of geometrical optics using symmetry principle
    NIU Dong-mei
    College Physics. 2020, 39(01):  23-25.  doi:10.16854 / j.cnki.1000-0712.190139
    Abstract ( 1282 )   PDF (497KB) ( 425 )  
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    The space and time symmetrical properties of optical wave and the medium have been analyzed. According to the symmetry principle the time translation symmetry and some of the space translation symmetry have to be preserved during light propagation,reflection and refraction processes,and the three geometrical optic laws of rectlinear propagation law,reflection law and refraction Snell’s law are derived. The symmetrical analysis here explicit that the symmetry principle is of fundamental importance and is the basement governing the optical processes.
    A further discussion on application of coherent state in the ordering of quantum operators
    XU Ye-jun, LI Chao, AN Jing
    College Physics. 2020, 39(01):  26-28.  doi:10.16854 / j.cnki.1000-0712.190038
    Abstract ( 1041 )   PDF (185KB) ( 479 )  
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    The S-ordering expansion of density operator of coherent state is obtained by means of the generalized Weyl quantization scheme. Based on this S-ordered expression and the technique of integration within S-or-dered product of operators,we derive the S - ordering forms of some quantum operators (including normally ordered,Weyl ordered and antinormally ordered product of operators). The proposed method further expands the application of the coherent state on the ordering of quantum operators.

    A simple calculationand application of the Fermi level of non-degenerated semiconductors
    HUANG Hai-meng, WANG Chang-wang, XIAO Lin-hao
    College Physics. 2020, 39(01):  29-32.  doi:10.16854 / j.cnki.1000-0712.190177
    Abstract ( 3368 )   PDF (320KB) ( 1458 )  
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    Based on the teaching practice of semiconductor device physics,a simple law between the carrier

    concentration and the Fermi level from the Boltzmann statistical law of non-degenerated semiconductor is summarized in this paper. When its carrier concentration is changed by one order of magnitude,its corresponding Fermi level should change by 60 meV. In order to understand this law deeply,this paper analyzes and calculates the important parameters,such as the quasi-Fermi level in non-equilibrium state,the work function of semiconductor,the threshold voltage of an MIS structure and the built-in potential of a PN junction. This facilitates students not only to deepen their perceptual knowledge in the process of mastering the physical knowledge of semiconductor devices,but also to develop and enhance the ability in analyzing and designing semiconductor devices.

    In-depth study of chaos in a nonlinear dynamical system
    LI Ming-da, YUAN Zhe-cheng, LUO Duan-bin
    College Physics. 2020, 39(01):  33-37.  doi:10.16854 / j.cnki.1000-0712.190009
    Abstract ( 1181 )   PDF (1772KB) ( 807 )  
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    A kind of nonlinear chaotic pendulum system is introduced into the experiment teaching.By adjusting the period of the driving force of the chaotic pendulum,the process of chaotic phenomena appearing in the nonlinear dynamic system is demonstrated so that students can understand the basic characteristics of chaotic phenomena,such as parameter sensitivity,phase diagram characteristics,spectrum characteristics and so on.In order to further under-stand the characteristics of the chaotic pendulum,a simplified dynamic equation of the nonlinear pendulum system is established and studied numerically.The numerical simulation based on dynamic equation overcame the difficulties of quantitative change of experimental parameters,difficult control of swing stability and long experimental period.In the numerical simulation,the related characteristics of the chaotic pendulum is described in detail by changing the phase diagram,spectrum diagram and bifurcation diagram obtained by different parameters,which is also helpful for students to deepen their understanding of the chaotic pendulum.
    Simulation design of the swinging ball
    MENG Yong
    College Physics. 2020, 39(01):  38-44.  doi:10.16854 / j.cnki.1000-0712.190133
    Abstract ( 1372 )   PDF (2155KB) ( 728 )  
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    The swing of the object is one of the most basic forms of motion in nature,and it is also one of the

    basic contents in the mechanics course.Under the guidance of Newtonian mechanics and Lagrangian mechanics,the

    mathematical calculation software Maple's powerful calculation and graphic functions are used to analyze and calculate the problems in the large-angle single pendulum,double pendulum and the Foucault pendulum motion under resistance.The simulating animations made by Maple are accurate and vivid,and reflected the physical laws of the pendulum movement.At the same time,it realizes the purpose of visual teaching.

    Theoretical and experimental study of the relation between refractive index and concentration of sucrose solution
    XU Fei, ZHU Jiang-zhuan, GAO Yun-jing, ZHENG Hu-lin, LI Zhong-chao, ZHU Yi-ran
    College Physics. 2020, 39(01):  45-47.  doi:10.16854 / j.cnki.1000-0712.190220
    Abstract ( 2694 )   PDF (557KB) ( 845 )  
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    The propagation of light in the medium follows Fermats principle.In homogeneous medium,lightpropagates along a straight line,and in inhomogeneous medium,the propagation trajectory of light is more complex.In this paper,taking sucrose solution as the research object,the experiment of light propagation in inhomogeneous medium is designed,the related model is established,and the relationship between the refractive index of the solution and the concentration is analyzed theoretically.The gradient expression of refractive index of solution is obtained by fitting the data.

    Two methods for measuring grating constants in grating diffraction experiment
    JIN Fang-zhou
    College Physics. 2020, 39(01):  48-52.  doi:10.16854 / j.cnki.1000-0712.190066
    Abstract ( 2646 )   PDF (832KB) ( 571 )  
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    Diffraction gratings can separate the light of different wavelengths spatially,which have graduallyreplaced prisms for application in most areas of spectral analysis.Measuring the grating constant by grating diffraction is a typical experiment in the experiment of college physics.This paper introduces two interesting phenomena found during the grating diffraction experiment:(i)there is a minimum diffraction angle when rotating the grating angle,and (ii)when the grating is rotated to a certain angle,the diffracted spot will gradually disappear into the field of view.Then,we analyze and explain these two phenomena in theory,and we design two methods for measuring grating constants.Moreover,we verify these two methods in experiment.Compared with the traditional method of measuring the grating constant with the minimum deflection angle,this paper analyzes the influence of the position deviation of the minimum deflection angle,and proposes a method of symmetric rotation measurement to further reduce the error.
    The mathematic model and numerical simulation of swing with parametric self-excited oscillation
    YANG Bai-yu, WANG Cui-xiang, WANG Bin-ke, LI Chun-wang, FAN Qi, TIAN Chang-hui
    College Physics. 2020, 39(01):  53-56.  doi:10.16854 / j.cnki.1000-0712.190080
    Abstract ( 1091 )   PDF (880KB) ( 652 )  
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    The swing is regarded as a variable length simple pendulum. Based on the normalized Gauss function,the velocity of pendulum ball relative to pendulum rod is designed. On this basis,the nonlinear dynamic differential equation of swing is established,and the motion of swing is simulated numerically based on this mathematic model,the motion,work and energy transformation mechanism of swing are obtained.

    Exploration on the reform of basic physics experiment teaching based on professional differences—Taking the example of Anhui University of Technology
    LI Cheng-long, SHENG Zong-qiang
    College Physics. 2020, 39(01):  57-60.  doi:10.16854 / j.cnki.1000-0712.190059
    Abstract ( 883 )   PDF (474KB) ( 414 )  
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    Taking Anhui University of Science and Technology as an example,the practice of the basic physicsexperiment teaching reform based on professional differences is briefly introduced. Especially,the new measures put forward in content reform of physics experiment course in this university. These measures involve the classification of experimental contents,the supplement of experimental contents and the resolution of " divergence" of experimental contents. Through the implementation of these specific new measures,the teaching level of the physics experiment course and the students' enthusiasm for learning the physics experiment course are both improved.
    An analysis of the innovation production issued by college students in the specialties of physics,science and technology———Data based on the articles in “The Scope of Students”of “College Physics”from 2010
    WEI Hui-ling, MA Chun-wang, WU Qi-wen, SHI Ya-jie
    College Physics. 2020, 39(01):  61-65.  doi:10.16854 / j.cnki.1000-0712.190236
    Abstract ( 986 )   PDF (1890KB) ( 304 )  
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    Based on the publications issued in column of “The Scope of Students”of “College Physics”from

    2010,the articles for innovation research done by college students in specialties of physics,science and technology

    are analyzed. The main characteristics of the innovation activities have been obtained. The results are helpful to

    guide the innovation research activities for college students in the new era of higher education in China.

    Research on the chaos phenomena of Lorenz water wheel
    CHENG Nai-han, CHENG Min-xi, LI Chun-lan, LIN Mo-di, YANG Shang-zhao
    College Physics. 2020, 39(01):  66-70.  doi:10.16854 / j.cnki.1000-0712.190047
    Abstract ( 1893 )   PDF (1718KB) ( 871 )  
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    Lorenz water wheel is a model to describe the chaotic system. The movement equations are analyzed

    and a Lorenz water wheel is set up. The video analysis software tracker is used to trace the motion of the water wheel

    recorded by a mobile phone. The corresponding physical images,such as phase diagrams,are drawed quickly and

    easily. Both the chaotic attractor and the initial value sensitivity have been found. Then the system has been proved

    to be a chaotic system by analyzing several experimental images.

    Thermodynamic properties of Berthelot fluid and parametric solutions
    LI Dan-dan, MI Li-qin, CHENG Qing-cheng, LING Fang-he
    College Physics. 2020, 39(01):  71-76.  doi:10.16854 / j.cnki.1000-0712.190182
    Abstract ( 1041 )   PDF (607KB) ( 830 )  
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    This paper is devoted to the study of thermodynamic properties on the Berthelot fluid. The Helmholtz

    free energy,entropy,Gibbs function,internal energy and enthalpy of monoatomic Berthelot fluid are derived;the

    parametric solutions of the Berthelot fluid two coexisting phases are obtained,and phase diagrams,thermodynamic

    behaviors near the critical point and associated properties are discussed by using the parametric solutions. The study

    provides analytic theory of thermodynamics and phase transition for substances satisfying the Berthelot fluid.