College Physics

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 ( 1150 )

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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 ( 1312 )

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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 ( 1615 )

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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 ( 1349 )

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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 ( 1219 )

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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 ( 1101 )

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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 ( 1440 )

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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 ( 1174 )

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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 ( 3949 )

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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 ( 1403 )

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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 ( 1538 )

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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 ( 3245 )

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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 ( 3208 )

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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 ( 1235 )

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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 ( 1033 )

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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 ( 1099 )

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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 ( 2097 )

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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 ( 1193 )

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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.

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