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    20 January 2022 Volume 41 Issue 1
      
    Concerted construction of undergraduate and graduate courses of computational physics
    LU Guang-hong, LIANG Lin-yun, JIANG Yin, ZHOU Hong-bo, HU Di, ZHU Li-hua, GENG Li-sheng, MAN Xing-kun, LI Bo, ZHOU Miao, ZHANG Yu-jie, LIU Li-min, JIN Shuo, SONG Chun-yan, ZHANG Ying, SHU Xiao-lin
    College Physics. 2022, 41(1):  1.  doi:10.16854 / j.cnki.1000-0712.210162
    Abstract ( 399 )   PDF (330KB) ( 255 )  
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    Computational physics,as the third method of studying physical phenomena and laws

    alongside the- oretical and experimental physics,has become more and more important with

    the rapid development of computer technology and continuous intercross of

    disciplines. However, due to the relatively late development of computational physics

    and some of its own discipline characteristics,there is no mature teaching system for under-

    graduate and graduate courses. In this article the exploration andpractice of concerted

    construction of undergraduate and graduate computational physics courses in Beihang University

    are mainly introduced. Undergraduate course is positioned to master the basic theoretical

    knowledge of computational physics as well as the case practice to solve physics

    problems. The undergraduate course teaching is small-sized. The graduate course is positioned on

    the solid professional basis and broad knowledge structure of computational physics,highlighting

    the professional and cutting-edge of the contents,and emphasizing the importance of the practical ability and the independent

    capability in sci- entific research. The graduate course offers parallel courses based on the student’s major. The exploration and prac- tice of concerted construction are carried out mainly from the course content,teaching method,and assessment method to ensure continuity and unity of graduate and undergraduate courses.

    Attracting and repelling of matter wave solitons by external potentials
    WANG Yan
    College Physics. 2022, 41(1):  8.  doi:10.16854 / j.cnki.1000-0712.210191
    Abstract ( 333 )   PDF (311KB) ( 150 )  
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    The theoretical results are presented using the Lagrange approach for matter wave

    solitons motion in some external potentials. The focus is the solitons with zero initial

    velocity,which exhibit different behaviors in po- tential wells and barriers,and the results are

    that the barrier repels solitons and the potential well attracts solitons. These conclusions are

    verified by numerical simulation.

    The tidal force related to the moon
    JIN Xian-yi
    College Physics. 2022, 41(1):  11.  doi:10.16854 / j.cnki.1000-0712.210110
    Abstract ( 361 )   PDF (203KB) ( 574 )  
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     Starting from the simplified mechanical model of the earth-moon system,the dynamic

    equations of the surface object in different coordinate systems are derived strictly,and through

    the analysis of symmetry,the tid- al force is obtained,which is helpful to understanding of the

    tidal force and the cause of tide.

    Study and numerical simulation of quantum tunneling for one-dimensional double square potential barriers
    LI Hai-feng, WANG Xin-mao
    College Physics. 2022, 41(1):  15.  doi:10.16854 / j.cnki.1000-0712.210279
    Abstract ( 312 )   PDF (305KB) ( 115 )  
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    Quantum tunneling effect has important applications in practical technology. In

    this paper,it is shown how to calculate the transmission coefficients of one-dimensional

    asymmetric and symmetric double square potential barriers with the arbitrary boundary.

    Then we study the dependence of the transmission coefficients for symmetric double square

    potential barriers on the barrier width,the spacing between the two barriers and the ratio of the

    incident energy of microscopic particles to barrier height ( E / U₀) . Finally,the results show

    that the transmis-sion coefficient decreases from the maximum value 1 to the minimum value 0 with the increase of the

    barrier width. Moreover,the transmission coefficient oscillates periodically with the increase of

    the barrier spacing. The analytical expression of the barrier spacing corresponding to the maximum

    transmission coefficient is derived,and the period of oscillation is given,which is equal to

    the de Broglie wave length of the microscopic particle. When the barrier width is

    smaller,the transmission coefficient is easier to reach and keep the maximum value 1 with the

    increase of E / U₀. When the spacing of the double potential barriers is larger,the oscillation

    period of the transmission coeffi- cient is larger,while the oscillation amplitude becomes

    smaller,with the increase of E / U₀. Therefore,the particle is easier to realize resonant

    tunneling in this case.

    Visualization research on the quantum properties of N-dimensional potential box functions
    ZHENG Xing-rong¹, ZHENG Yan-fei²
    College Physics. 2022, 41(1):  19.  doi:10. 16854 / j.cnki.1000-0712.210250
    Abstract ( 261 )   PDF (436KB) ( 97 )  
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    Using quantum theory derivation and numerical calculation methods,the diagram and model

    of one- dimensional potential box function are firstly obtained. Then the wave function,energy

    level and probability density of N-dimensional potential box functions in quantum mechanics are

    studied comprehensively and systematically. Fi- nally,all characteristics of the potential box

    functions are simulated using MATLAB software. We find that the ener- gy of particles is quantized

    and discontinuous in N-dimensional potential box. The quantum number n cannot be ze- ro,and the

    higher the quantum number n is,the higher the energy level is,while the higher the mass

    m is,the lower the energy level is. Generally,the larger one-dimensional potential box length a

    is,the lower the correspond- ing energy level is. The number of nodes is N-1,and the more

    the nodes are,the shorter the wavelength is,the higher the frequency is,the higher the energy

    level is. For two-dimensional potential box function,the number of peaks is nₓ ×ny ,and the

    intersection numbers of wave function and a plane of Ψ = 0 is nₓ ×ny ,too. For degeneracy, in

    general,the degeneracy of particles in the two-dimensional potential box model is uncertain. But

    for the two di- mensional square potential box function model,the energy level degeneracy of the

    particles in the box can be divid- ed into general and special cases. The degeneracy of

    three-dimensional potential box function are nx +ny +nz . The vi- sualization results are in

    complete agreement with the theoretical results. Finally,the color function of MATLAB

    software is firstly used to realize the four-dimensional representation,and the four-dimensional

    slice diagram of the three-dimensional potential box function are obtained. The results of

    this visualization are in complete agreement with the theoretical results,and it is also of

    great significance for the understanding of the abstract concept.

    Some problems in the teaching of special relativity
    WANG Lei
    College Physics. 2022, 41(1):  24.  doi:10.16854 / j.cnki.1000-0712.210190
    Abstract ( 383 )   PDF (273KB) ( 262 )  
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     This paper discusses several problems in the teaching of relativity,including

    questions in common examples,convenient form of Lorentz transformation,discussion on the example

    of simultaneous relativity in another frame of reference,the phenomenon of length measurement seen

    in another reference frame,delay of time and the time of each point in the motion reference frame

    are different,and a simple derivation of Doppler effect of light is preformed. Through the

    discussion of different processes in different reference systems,master the method of discus- sing

    problems in motion reference frame,and the different performance of the same process in

    different inertial frames,the measurement results of all phenomena remain unchanged under Lorentz

    transformation.

    Collision test of pure rolling double steel balls on wide and narrow rails
    LU Jun-ling, GU Chen, REN Nai-jing, MA Bo-yi
    College Physics. 2022, 41(1):  27.  doi:10.16854 / j.cnki.1000-0712.210184
    Abstract ( 256 )   PDF (296KB) ( 146 )  
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    A pure rolling double steel ball collision experiment is carried out on a wide

    and narrow horizontal rails,and it is found that it is significantly different from the double

    steel ball collision experiment in sliding motion; the reason is that the collision of the pure

    rolling double steel ball is the frontal and tangential collision at the colli- sion point. The

    two types of collisions obey different dynamic laws; after a collision,the motion state of the two

    steel balls is no longer pure rolling. To return to pure rolling,each steel ball must pass through

    the interaction between it- self and the guide rail. The effect is to go through a self-adjusting

    stage; the energy loss in the self-adjusting stage is related to the rolling radius of the steel

    ball and the deviation of its immediate state from pure rolling.

    Systematic error analysis of period of simple pendulum
    SHAO Yun
    College Physics. 2022, 41(1):  32.  doi:10.16854 / j.cnki.1000-0712.210247
    Abstract ( 716 )   PDF (353KB) ( 160 )  
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    This paper analyzes and calculates the influence of the pendulum angle,the rotation of

    the ball,the mass of the suspension line,the air buoyancy and the air resistance on the period of

    the pendulum one by one. Tak- ing a 1 m length and 5° swing angle small amplitude pendulum as an

    example,the relative errors of the five factors are

    +0.45‰,+0.02‰,-0.45‰,+0.07‰,-0.14‰,respectively,and the total is only -0.05‰,which means that the

    five error factors almost cancel each other,and the systematic error of the small

    pendulum experiment is very small in theory. This paper gives a more detailed

    reasoning,calculation and analysis process,especially the reasoning process of air resistance

    moment,as well as charts and tables,for providing a more complete and accu- rate

    understanding. Finally,some necessary explanations are given in view of some possible deficiencies

    in people's understanding of air resistance.

    Design and simulation of fingerprint lock based on optical holography
    YAN Ai-min, HU Zhi-juan
    College Physics. 2022, 41(1):  39.  doi:10.16854 / j.cnki.1000-0712.210214
    Abstract ( 198 )   PDF (333KB) ( 56 )  
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    In this paper,we propose a fingerprint lock that combines fingerprint verification

    and optical holo- graphic encryption. It is placed in front of the IC chip of the smart card to

    pre-encrypt and authenticate the user's PIN code,and strongly enhances the protection of

    smart-card. Actually,the proposed fingerprint lock uses the fin- gerprint image as the key and

    records the angle multiplexing optical encrypted hologram in the photorefractive crystal

    material. This kind of hologram is different from the traditional angle multiplexed volume

    hologram. Its refer- ence light has both amplitude modulation of fingerprint image and random phase

    modulation. It has the advantages of good privacy,convenient carrying and high security.

    Numerical simulations confirm the validity and safety of pro- posed technique.

    Exploration and practice of student-centered college physics teaching
    GAO Lan-xiang, XU Dan-hua
    College Physics. 2022, 41(1):  43.  doi:10.16854 / j.cnki.1000-0712.210218
    Abstract ( 207 )   PDF (522KB) ( 112 )  
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    In order to solve the real problems of teaching college physics monotonously,and too much

    emphasis on knowledge itself but not the ability and quality during the assessment,our teaching

    paradigm has been changed from teacher-centered to student-centered. Based on the smart

    classroom and the Wisdom Tree platform,a new smart learning environment of internet plus

    education has been established. The physics curriculum has been inte- grated with the

    ideological and political elements,resulting in a new knowledge-application cutting-edge-contentcurriculum system,which also highlights the feature of energy and power industry. It also encourages the student to construct the knowledge system independently and learn deeply by group teaching approach based on real tasks,as well as the emphasis on the individual learning experience. A comprehensive evaluation system has been built to promote the overall development of knowledge,abilities,and qualities of students. The design of the system is result-oriented,featured with a combination of both formative and summative,and of qualitative and quantitative measures.

    Design and practice of ideological education in college physics ———taking particle mechanics as an example
    LONG Xiao-yan¹, XIE Hai-yan², WU Shi¹, ZHANG Yi-xun¹, LI Jia-ding¹
    College Physics. 2022, 41(1):  50.  doi:10.16854 / j.cnki.1000-0712.210166
    Abstract ( 437 )   PDF (563KB) ( 256 )  
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    It is of great significance and imperative to strengthen political and ideological

    education in teaching. In order to deepen the teaching reform of college physics,the teaching

    design of ideological education is carried out under the blended learning mode by using the

    effective teaching method based on the traditional teaching and aiming at knowledge goal.

    Through the design and practice of on-line,off-line and examination,combining the lec- ture of

    ideological education by famous teachers,the course mode of ideological education is formed.

    The applica- tion of this model takes the first chapter,particle mechanics,as an example. The

    practice shows that the education quality is improved.

    Reform and exploration of college physics in architectural university under the background of new engineering education
    LIU Yan-ling¹, GU Jin-xia¹, LIANG Chun-tian¹, TIAN Wei¹, SONG Feng²
    College Physics. 2022, 41(1):  56.  doi:10.16854 / j.cnki.1000-0712.210132
    Abstract ( 295 )   PDF (467KB) ( 145 )  
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    College physics is an important public fundamental and compulsory course for students

    who major in science and engineering. In this paper,by combining the new engineering education

    with times characteristic,col- lege physics teaching of Tianjin Chengjian university is taken as an

    example. A series of exploratory teaching inno- vation reform are carried out,and the innovative

    effect and the existing problems of pain point are summarized and analyzed. An effective way is

    explored to cultivate architectural talents with solid physical skills.

    Analysis of the rotation modes of the coin under different conditions
    FANG You-le, WANG Tian-xiao
    College Physics. 2022, 41(1):  61.  doi:10.16854 / j.cnki.1000-0712.210089
    Abstract ( 263 )   PDF (424KB) ( 149 )  
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    In this paper,the basic equations of motion of coins under different

    conditions are derived. The problem of the coin's motion around a circle is analyzed,and two

    special modes of motion are discussed using the results,which are finally verified via

    experiments and numerical simulations.

    Improvement of Helmholtz coil magnetic field measurement based on electromagnetic induction
    XU Lin-chao, XIANG Wen-li
    College Physics. 2022, 41(1):  68.  doi:10.16854 / j.cnki.1000-0712.210195
    Abstract ( 360 )   PDF (457KB) ( 219 )  
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     Based on the electromagnetic induction method,the distribution of Helmholtz coil

    magnetic field under different capacitance parameters is measured by the improved method of

    achieving resonance with the Helm- holtz coil in series,and the relationship between the magnetic

    field of Helmholtz coil and the position of central axis is analyzed by using Origin software. The

    experimental results show that the accuracy of the magnetic field of Helm- holtz coil measured by

    the improved method is higher than that by the traditional electromagnetic induction method to a

    certain extent. Among the three capacitor options,when the series capacitance is 0.099×10-⁶ F,the

    accuracy is the highest. The fitted relationship between the magnetic field of Helmholtz coil and the

    position of the central ax- is is basically consistent with the theoretical formula. The experimental effect of the improved method is obvious,the accuracy is high,and it is scientifically feasible. It is an improved method for measuring the magnetic field of Helm- holtz coils that is worth popularizing.

    Improvement and analysis of optical-fiber temperature sensor experiment
    RAN Lu, LIAO Hong-bo
    College Physics. 2022, 41(1):  73.  doi:10.16854 / j.cnki.1000-0712.210258
    Abstract ( 183 )   PDF (558KB) ( 87 )  
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    In this paper,the optical-fiber temperature sensor experiment is modified by using a

    cheap commer- cial fiber splitter at 1310 nm and aluminum foil for thermal conducting. The

    temperature coefficient is measured and found to be more stable after improvement. Also,the

    conducting condition can infect the temperature coefficient a lot. At last,teaching

    suggestion is proposed.

    Monte-Carlo simulation of 2-D Ising model———application of Metropolis,Swendsen-Wang and Wolff algorithm
    XU Lin, CHEN Yu-ze, LIU Jia-hao
    College Physics. 2022, 41(1):  79.  doi:10.16854 / j.cnki.1000-0712.210101
    Abstract ( 353 )   PDF (336KB) ( 192 )  
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     Ising model is a widely used magnetic spin interaction model. It is very complicated to

    solve the ana- lytic solution in 2-D case. In practical application,Wolff algorithm is usually

    used to simulate the Ising model and it is considered to be the best clustering flipping Monte

    Carlo algorithm. Metropolis and Swendsen-Wang algorithms are similar to Wolff algorithm,and

    theoretically they are also applicable to the simulation of Ising model. So far, there

    is no paper has compared the three algorithms to show the advantages of Wolff algorithm,and there

    are few in- troductions of Monte Carlo algorithm in undergraduate courses. In this paper,we use

    these three algorithms to simu- late 2-D Ising model and introduce the principle,parameter

    selection and implementation of the algorithms. In the end,we compare the simulation effect and

    application range of the three algorithms,and summarize the reason why Wolff algorithm has better

    effect in the simulation of 2D Ising model.