College Physics

Some definitions of quantum entropy based on Wigner function

LIN Bing-sheng, HENG Tai-hua

College Physics. 2019, 38(3): 1-3. doi:10.16854 /j.cnki.1000-0712.180498

Abstract ( 1906 )

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Some quantum entropy，such as von Neumann entropy，linear entropy，Rényi entropy，Tsallis entropy，

and several different definitions of them based on Wigner functions in phase space，are introduced respectively.

Through some theoretical deductions and numerical calculations，the definitions of quantum entropy in phase

space using the absolute value of Wigner function in the literatures are proved to be inappropriate. The quantum entropy

defined in this paper by the Moyal star product of Wigner function is consistent with that defined by density

　　matrices.

Application of Gaussian integration in quantum representation theory

REN Gang, DU Jian-ming, ZHANG Wen-hai

College Physics. 2019, 38(3): 4. doi:10.16854 /j.cnki.1000-0712.180450

Abstract ( 1279 )

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At first，the normal product form of the vacuum projection operator is proved and then the Gaussian

integral in mathematics is extended to the integral form of the quantum operator. Using the completeness and symmetry

of quantum representation，the concrete forms of the coordinate representation，momentum representation，intermediate

representation and coherent state representation are given.

Hysteresis loop characteristic quantities of Stoner-Wohlfarth model

XUE De-sheng, MIAO Yu

College Physics. 2019, 38(3): 7. doi:10.16854 /j.cnki.1000-0712.180281

Abstract ( 3042 )

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This paper focuses on the Stoner-Wohlfarth model which describes a coherent rotation of magnetiza-tion. Characteristic quantities such as remanence，coercivity and saturation field，of hysteresis loop are obtained ex-actly even though the model cannot be solved generally. Based on the analysis of the coherent rotation of magnetiza-tion，we find not only the criterions to obtain the characteristic quantities but also derive the relationships between these technical magnetization quantities and intrinsic saturation magnetization as well as anisotropic effective field of magnetic materials. Further，we verify the correctness of the relationships by using the exact solutions of three spe-cial hysteresis loop and the numerical solutions of general case. These results are of important reference for the judg-ment of the magnetic reversal magnetization process and inside understanding of the coherent rotation of magnetic materials.

The unexpected harvest of solving static magnetic field with two kinds of views of magnetization of the magnetic medium theory

JING Yi-lin

College Physics. 2019, 38(3): 11. doi:10.16854 /j.cnki.1000-0712.180414

Abstract ( 1508 )

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In this paper，the magnetic charge molecular current view of magnetization of the magnetic medium

theory is used to solve a static magnetic field，then the polarized magnetic charge distribution of the static magnetic

field is calculated. On this basis，we has calculated equal amounts of heterogeneous magnetic ( electric) charge in

the vacuum and in a straight line bounded by magnetic ( electric) be inversely proportional to the load distribution

and point to a straight line distance of infinite planar magnetic ( electric) board of magnetic ( electric) field. This

paper points out a new way of solving static magnetic field and electrostatic field generated by static magnetic

charge.

Study of electric properties of an 2×n Fan network

TAN Zhi-zhong, YU Qing-yi , WANG Yi-xiao

College Physics. 2019, 38(3): 14. doi:10.16854 /j.cnki.1000-0712.180376

Abstract ( 1095 )

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We achieve the innovation in theory and method on the research of the electrical properties ( including

the branch current，voltage of any node，and equivalent resistance) of an arbitrary 2×n Fan resistor network

by the Recursion-Transform ( RT) method. In this paper，the matrix equation model and the boundary condition equation

model are established by using the branch current as the variable in terms of applying Kirchhoff’s law. We

study the general solution and special solution of the matrix equation by the matrix transform，thus the branch currents

　　of the 2×n Fan network are obtained，and derived the voltage formula of arbitrary node，at the same time，the

　　equivalent resistance formula between any two nodes is obtained as well. The special situation of the conclusion is

　　analyzed and discussed.

Research on the vibration mode and Raman vibration spectrum of phosphate ion by the group theory method

KUANG Xiang-jun

College Physics. 2019, 38(3): 20. doi:10.16854 /j.cnki.1000-0712.180385

Abstract ( 2774 )

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Based on the geometrical structure，feature table and irreducible representation of phosphate ion，

the vibration mode is analyzed. Then，according to selection rules of Raman spectroscopy，Raman activity of phosphate

ion is also discussed. Using the G matrix and F matrix of phosphate ion，we solve the prolonged equation of

simple positive vibration and got the Raman spectral frequency shift. By using the Demol3 program package under

the frame of density functional theory，the Raman vibration frequency shift for Phosphate ion are calculated and the

results are close to the data obtained above.

A review of students’misunderstanding in learning special relativity

LIAN Lin-xin, XIAO Yang, WANG Xiao-jun, BAO Lei

College Physics. 2019, 38(3): 25. doi:10.16854 /j.cnki.1000-0712.180418

Abstract ( 1398 )

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Special relativity，which sets the boundary between classical and modern physics，can deeply influence

students’understanding of the nature of the world. However，considerable students’misunderstanding related

to this topic has been identified by a numbers of empirical studies and through teaching practices. In this paper，a

systematic literature review is conducted on education research in special relativity. Students’common misunderstanding

and the corresponding reasoning on key concepts of special relativity reviewed and summarized. The implications

for future research and teaching are also discussed.

Error propagation law in measurement of the magnetic field by Zeeman effect

DONG Jian, HU Kun

College Physics. 2019, 38(3): 32. doi:10.16854 /j.cnki.1000-0712.180346

Abstract ( 2322 )

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In the Zeeman effect experiment，the diameter of the spectral line ring varies with the strength of

the magnetic field. This phenomenon can be used to measure the magnetic field. In this paper，the magnetic field

measurement formula is deduced，the law of magnetic field measurement error is found through practical measurement，

and the error propagation model is designed to simulate and demonstrate this rule，and the conclusions obtained

can guide the method of magnetic field measurement and improve the precision of measurement.

Research on the contributions of physics in Nanjing University in the first half of the 20th century

WANG Jing

College Physics. 2019, 38(3): 36. doi:10.16854 /j.cnki.1000-0712.180371

Abstract ( 1449 )

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Based on the outstanding achievements in academic development and education，the physics in

Nanjing University was one of the birth place of higher education and research in physics during the initial period of

institutionalization of modem physics in China. The contributions of Physics in Nanjing University in the first half of

the 20th century are introduced. According to the origins of the department of physics，the article describes the

great efforts on its teaching and scientific research，scientific extension and talents cultivation.

Research on the applicability of two types of photovoltaic power generation engineering model

XIAO Wen-bo, YU Xiao-peng, HE Xing-dao,

College Physics. 2019, 38(3): 41. doi:10.16854 /j.cnki.1000-0712.180477

Abstract ( 951 )

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The research of photovoltaic power generation model is of great significance for predicting and analyzing

the influence of photovoltaic power generation by the outside factors. This paper studies and analyzes the applicability

of two types of photovoltaic power generation models proposed at home and abroad in recent years. One is

called as the simplified model based on parallel resistance infinite ( referred to as the simplified model) ，the other

is called exponential model based on power law function ( referred to as exponential model) . The results show firstly

that both models can reproduce the experimental data generally accurately. However，the theoretical and experimental

errors of the two models increase obviously with the increase of bias voltage. The reason is that the cell's characteristics

under high bias have been completely changed，can not use the ideal constant current source and diode to

describe. Secondly，it was found that the errors of both models are increased when the cell's work condition is not in

the standard environments. The reasons are in two aspects，the first is that the external environment changes，the

cell has a significant nonlinear effect and the model can not adapt to the actual change of the cell. In addition，both

models predict the power generation characteristics based on the technical reference values in the case of standard

tests. As a result，the models will have obvious errors in the analysis of the case in the non standard conditions. Finally，

noting that the exponential model is better than the simplified model in any situation. The reason lies in two

aspects，on the one hand，the exponential model considers the influence of light intensity on current and voltage，

while the simplified model only considers the influence of light intensity on current. On the other hand，the exponential

model considers temperature coefficients of short - circuit current，open circuit voltage，maximum power

point current and voltage，while the simplified model only considers two temperature compensation systems.

Exploration of whole program research teaching mode in general physics experiment

YIN Jiao-jian, XU Zhi-jie, ZHANG Ya-ping, LI Shu-guang, GUO Ya-hui

College Physics. 2019, 38(3): 46. doi:10.16854 /j.cnki.1000-0712.180365

Abstract ( 1267 )

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Based on the main problems existing in the traditional general physics experiment course system，a

trinity full program research experimental teaching model which lays solid foundation strengthens synthesis and faces

scientific research practice has been proposed. In this system，the cultivation of students' innovation ability is divided

into three stages guided by the thought of research teaching: cultivation of the basic ability，cultivation of comprehensive

ability and cultivation of the scientific research ability，the teaching content including obstacles，problems

and subject research content has designed，and the research teaching methods including heuristic，inquiry，

tutorial methods have been implemented.

The electric field intensity of a homogeneously charged cylindrical surface having limited length

College Physics. 2019, 38(3): 49. doi:10.16854 /j.cnki.1000-0712.180277

Abstract ( 5180 )

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By using the elliptic integral， the electric field intensity of a homogeneously charged cylindrical surface

with limited length is calculated in the cylindrical coordinates.

Liquid surface tension coefficient measurement based on the profile fitting of axisymmetric liquid bridge

LIU Yi-fei, WANG Jin, LI Wen-hua, HUI Wang-wei, WEN Xiao-qing, ZHANG Chun-ling

College Physics. 2019, 38(3): 54. doi:10.16854 /j.cnki.1000-0712.180330

Abstract ( 1310 )

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Based on Yang-Laplace formula and mean curvature，the relationship between the surface appearance

and surface tension of two parallel plates is studied，and the method of measuring the surface tension of the

liquid bridge by fitting profile of the liquid bridge is explored. A set of experimental platform for measuring the surface

tension coefficient by photographing the enlarged image of the liquid bridge and performing edge detection is

developed. The sobel operator is used to extract the edge information on the MATLAB platform，and the liquid

bridge profile is fitted to obtain the surface tension coefficient of liquid. Relative error is controlled within 5%.

Measurement of surface free energy based on the Laplace's equation

ZHANG Zong-kun, DONG Guo-bo, LI Si-yuan, TANG Fang, LI Hua

College Physics. 2019, 38(3): 57. doi:10.16854 /j.cnki.1000-0712.180462

Abstract ( 1362 )

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Surface free energy is meaningful as a vital characteristic of material surface energy state. As it's equal

to surface tension coefficient in value for liquid，the free energy can be got by measuring the surface tension.

Traditional methods can not guarantee both application scope and precision. As to this problem，a new method is

mentioned in this paper: Based on the Laplace's equation studying bubble films，the process of bubble gradually increasing

is considered. The data of differential pressure and related radius is dealt with by linear regression equation

to get the liquid surface tension. This method not only applies to the environment of high temperature and pressure，

but also avoids the main error source of maximum bubble pressure method without introducing new error.

A double-fiber bidirectional interference fringe counter based on Arduino singlechip

ZHENG Mei-jun, PING Cheng, YU Shu-peng, LIAO Xin

College Physics. 2019, 38(3): 62. doi:10.16854 /j.cnki.1000-0712.180354

Abstract ( 1668 )

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A double-fiber bidirectional interference fringe counter based on Arduino singlechip is presented. The device can achieve the bidirectional counting of fringes according to the gushing and the sinking of interference fringes. In the experiment of measuring the thermal expansion coefficient of metal by the interferometry，this counter is used to count the fringes. It has low cost，convenient operation，high counting accuracy，strong anti-interference ability，short reaction time and so on.

Neither position nor momentum can be accurately measured

DAI Shuo, WANG Xin, LIU Quan-hui

College Physics. 2019, 38(3): 67. doi:10.16854 /j.cnki.1000-0712.180449

Abstract ( 2043 )

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A misconception in quantum mechanics is that when the measurement of position or momentum

alone is performed，completely accurate values will be obtained. We take the measurement of position for an oscillator

in a ground state for instance，and calculations show that the oscillator must gain some energy during the measurement

and the amount of the energy increases without bound along with degree of the accuracy. Therefore，neither

position nor momentum can be accurately measured.

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