College Physics

Noncommutative phase space and the motion of Dirac particle in electromagnetic field

Mamatabdulla Hekim，Nurbiya Siyit，Reyima Rashidin

College Physics. 2017, 36(5): 2-5. doi:10.16854 /j.cnki.1000-0712.2017.05.002

Abstract ( 1682 )

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In the past a few years，noncommutative space related problems are became a hot topic among a lot of researchers， and noncommutative space problems are extensively discussed in many field like quantum mechanics，quantum field theory，quantum electrodynamics，condense matter physics，astrophysics etc. In this article，we derive velocity operator and corresponding force operator thorough Hamiltonian of Dirac particle with electromagnetic field in the noncommutative space. By using the Bopp transformation，we provide Hamiltonian of Dirac particles with electromagnetic interaction in the noncommutative space and the noncommutative phase space，respectively. We also derive the expressions of velocity operator and force operator，which include correction term caused by noncommutativity. On these basis，we perform further analysis and have know that noncommutative effect　has some influences to the velocity and force operators of the Dirac particle，but the noncommutative character of momentum-momentum operator has no influence to the velocity operator of Dirac particle.

Quantum tunneling in one-dimensional time-dependent periodic potential

LUO Guo-zhong,AN Zheng

College Physics. 2017, 36(5): 6-10. doi:10.16854 /j.cnki.1000-0712.2017.05.003

Abstract ( 1172 )

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The quantum tunneling in one - dimensional time - dependent periodic potential is investigated

theoretically. Two models of the one - dimensional periodic potentials are established and discussed in different

conditions，in which the quantum tunneling problem in one-dimensional time-dependent periodic potential can be

treated as one model.

Discussions on multiple connotations of quality factor and its teaching

LI Xiang

College Physics. 2017, 36(5): 11-18. doi:10.16854/j.cnki.1000-0712.2017.05.004

Abstract ( 1447 )

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Multiple connotations of the quality factor Q associated with frequency characteristic，energy conversion，and various physical variables are analyzed. The analysis is based on the differential equation of second-order system with sinusoidal excitation，as well as the physical contexts of forced damping vibration and RLC serial /parallel resonant circuits. Then it is also discussed that how to teach the concept of quality factor Q better for engineering students.

Application of equivalent circuit method to the expression of lightning electromagnetic field

YE Gen，LIU Zhi-min

College Physics. 2017, 36(5): 15-18. doi:10.16854 /j.cnki.1000-0712.2017.05.005

Abstract ( 1039 )

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According to the lightning electromagnetic field effects on transmission line，we put the lightning electromagnetic field in the transmission line equation understood as LC series parallel circuits，to calculate and analyze quickly and accurately the influence degree of the electric field on transmission lines. This study by using the equivalent circuit method on our deep understanding of lightning electromagnetic field on transmission line coupling mechanism is of great significance.

Calculation example of the problem with variable refractive index materials in geometrical optics teaching

HE Jian

College Physics. 2017, 36(5): 19-23. doi:10.16854 /j.cnki.1000-0712.2017.05.006

Abstract ( 1589 )

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The problem of imaging discussed in the course of optics customarily is under the conditions of “paraxial approximation”. In order to enhance the effectiveness of teaching and their confidence of the theory in practice，we need to give some discussion on non-paraxial approximation of the general situation. It makes clear that directly inverse solution for the change regulation of the refractive index from Fermat’s principle is not a feasible solution. The approximate method will let the refractive index’s functional problem change as the slope of one-dimensional function problem. By using the Euler equation and numerical calculation，we obtain a set of reference parameters for material made.

The studies of energies and coherent state for harmonic oscillator by ladder operators

YU Hua-ling

College Physics. 2017, 36(5): 24-26. doi:10.16854 /j.cnki.1000-0712.2017.05.007

Abstract ( 1521 )

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Harmonic oscillator is not only the most basic but also a representative problem in the quantum mechanics. The discussion on it in the coordinate representation by the Schrdinger equation is very complicated.The dimensionless ladder operators are introduced to calculate the eigenvalues and eigenvectors of Hamiltonian dexterously. The coherent states of harmonic oscillator is investigated by translation operators. It is found that the basic-vectors in the representation of coherent states are over-complete and there is the minimum uncertainty of position and its momentum in the coherent states.

The cause and quantitative analysis of air resistance of moving objects by air resistance coefficient meter

WU Qin-chun，QIAN Yang-de

College Physics. 2017, 36(5): 27-32. doi:10.16854 /j.cnki.1000-0712.2017.05.008

Abstract ( 1195 )

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By constructing a small wind tunnel，a theoretical model for calculating the wind resistance coefficient is proposed from the perspective of energy conversion after several studies on the wind resistance of several typical shapes.The experinental results are in good agreement with the theoretical deduction after quantitatively verifying the four different shapes of objects.The air resistance theory proposed in this paper can also be applied to the study of liquid.

A teaching effort on the uncertainty calculation of indirect measurement

TAN Guo-tai，LI Ya-meng，HOU Ting-ting，CHEN Xi-yan，LI Xue

College Physics. 2017, 36(5): 33-37. doi:10.16854 /j.cnki.1000-0712.2017.05.009

Abstract ( 3244 )

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Uncertainty，as a new concept of college physics experiment，cannot be understood and applied well by freshmen due to the lack of the basic knowledge on probability distribution. In order to reduce the difficulty of learning uncertainty，a teaching effort is paid by showing how to calculate the uncertainty of the refractive index.

Research on optical method for measuring pressure distribution in the airflow field

NI Min，ZHENG Yuan-ming，XU Shi-jia，HAN Wei-wei，XU Xiao-lin，CAO Zheng

College Physics. 2017, 36(5): 38-41. doi:10.16854 /j.cnki.1000-0712.2017.05.0010

Abstract ( 1417 )

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Based on the Michelson interferometer with a basic optical component，we use an optical method to measure the changes of pressure and refractive index within an area. Then synthesize the static and dynamic images by computer technology to obtain the lines of equal pressure of the air current field. Finally， the experimental phenomena is analyzed.

Analysis of Franck-Hertz experiment by spectral analysis method

WANG Yun-jie

College Physics. 2017, 36(5): 42-46. doi:10.16854 /j.cnki.1000-0712.2017.05.011

Abstract ( 1336 )

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The energy level gap in the Frank-Hertz experiment has cyclical nature. In this paper，we introduce design and verification of the approaches for analyzing the experimental data of Frank -Hertz experiment by the spectral analysis method. The results have shown that the energy level gap is revealed and the present method has high accuracy and greatly intuitive.

Physicists who have had an important influence on Otto Stern

NING Chang-chun，WANG Ya-ping，ZHANG Hui-jie，ZHOU Yi

College Physics. 2017, 36(5): 47-52. doi:10.16854 /j.cnki.1000-0712.2017.05.012

Abstract ( 1514 )

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Some physicists who have been living in the same age and having very close contacts with Otto Stern are introduced.These physicists have had an important influence on Sterns academic career.

An analysis on the characteristics of the textbook of fundamental physics experiment in America

XIONG Ze-ben，MA Shi-hong

College Physics. 2017, 36(5): 53-61. doi:10.16854 /j.cnki.1000-0712.2017.05.013

Abstract ( 1204 )

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By selecting the textbooks of fundamental physics experiments compiled by five universities in the United States，we make a comparative analysis on the arrangement of textbook contents，the scope of knowledge points，the choice of matching information resources，the characteristics and the advantages of textbooks. Furthermore，we sum up the features of textbooks in basic concepts，teaching objectives，ability cultivation and emotional goals. The purpose of the paper is to provide some references for the further advancement of the teaching reform，the reconstruction of physics experiment teaching material，and the improvement and optimization of physics experimental teaching methods and concepts.

Discussion on Kepler’s laws and the parameters of revolution of the earth

ZHAO Xian-jue，SANG Sheng-jing

College Physics. 2017, 36(5): 62-65. doi:10.16854 /j.cnki.1000-0712.2017.05.014

Abstract ( 1720 )

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Starting from Lagrangian，Runge -Lenz vector and differential equation，respectively，the Kepler’s three laws are derived from the law of gravity and Kepler' s equation and the orbital period are obtained by integration.The eccentricity and period of revolution of the earth are calculated by employing the data of perihelionand aphelion speed from two references and large inconformity is found between the calculated results and the observed values.The cause is analyzed and the corrected velocities are given resulting in self-consistency.

Model analysis based on the phase transfer mechanism of asynchronous motor

MA Peng-de，LI Yu-bo，SUN Lin， JIN Feng-tao

College Physics. 2017, 36(5): 66-69. doi:10.16854 /j.cnki.1000-0712.2017.05.015

Abstract ( 1211 )

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Electro mechanical problem has been the focus of scientists for a long time. In order to explore how　to make motor rotation speed and direction of rotation control flexibly，an economical and simplified motor model based on a new rotating mechanism is proposed. Starting from mechanism of plate rotation and combining with simulation of COMSOL， the moment of force is analyzed theoretically，and the related influence factors of rotation are discussed quantitatively. The results show that the root cause of rotation is phase difference，and the moment of force coming from an attractive power leads to rotation. In addition， the rotating speed is proportional to the area sheet metal inserts and inversely proportional to the distance between sheet metal and plate. The direction of rotation depends on the position of sheet metal.

Luminescence spectra from mobile phone，computer display and human eye health

MA Biao，WANG Ya-fang，CUI Mei-na，ZHAO Ying

College Physics. 2017, 36(5): 70-73. doi:10.16854 /j.cnki.1000-0712.2017.05.016

Abstract ( 1870 )

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Spending too much time on mobile phone， tablets and other mobile devices has become a very common phenomenon. In this paper， the screen spectra of different types of mobile phone and computers are collected by using optical fiber spectrometer and the intensity with the distance was studied as well. The result shows that the spectral emission bands of the electronic display screen are mainly on 450 nm， 530 nm and 590 nm. The intensity of blue emission varies with types of products，which means the damage of blue light to the human eye is different with products.

Zeta function regularization of partition function of free particle

CEN Zhen-hao，CHEN hao

College Physics. 2017, 36(5): 74-77. doi:10.16854 /j.cnki.1000-0712.2017.05.017

Abstract ( 1672 )

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The Zeta function regularization technique is an invaluable method in the modern physics. This paper discusses its application in college physics，namely，we use the zeta function regularization to deal with partition function of free particle and derive the corresponding thermodynamic quantities. By considering that the volume of the cubic container is finite， the first-order corrections of thermodynamic quantities are obtained.

The quantum properties of atom in Jaynes-Cummings model

BAI Zhi-da

College Physics. 2017, 36(5): 78-80. doi:10.16854 /j.cnki.1000-0712.2017.05.018

Abstract ( 1499 )

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We derive the expression for the uncertainty between atom state and spin component in large photons. It has found that the uncertainty can transfer between the spin component but hold conservation of whole uncertainty.

College Physics. 2017, 36(5): 82.

Abstract ( 564 )

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