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Table of Content

    20 December 2020 Volume 39 Issue 12
      
    Some thoughts on teaching solid state physics I:the tight-binding approximation with multiple orbitals
    YUAN Zhe
    College Physics. 2020, 39(12):  1-4.  doi:10.16854 / j.cnki.1000- 0712.200278
    Abstract ( 2126 )   PDF (570KB) ( 3768 )  
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    The tight binding approximation is one of the most important parts in the teaching of energy band theory,which contains many key concepts of solid state physics and intuitive pictures.Most of the popular textbooks only illustrate the tight-binding approach by using single-band examples.Then it becomes difficult for students to comprehend the Hamiltonian,energy bands,Bloch wave functions and the related concepts.Here a one-dimensional diatomic linear chain is solved with a detailed elucidation for how to obtain the energy bands with multiple orbitals using the tight-binding approximation.The perturbation of atomic energy level and overlap integral of neighboring atomic orbitals are illustrated in the mathematical derivation of the tight-binding Hamiltonian.The energy band dispersion with the relationship to the Bloch wave functions is discussed as well as the factors that determine the number of bands and band widths.
    General method and example analysis on orthogonalization for pure quantun state
    XU Xuexiang, YUAN Hongchun
    College Physics. 2020, 39(12):  5-7.  doi:10.16854 / j.cnki.1000-0712.200069
    Abstract ( 1221 )   PDF (510KB) ( 336 )  
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    General method and some skill are introduced in this paper.Taking coherent state as example,an orthogonal state is constructed based on the creation operator.Three properties of the orthogonal state,including mean photon number,photon number distribution and Wigner function,are studied.Moreover,we compare these properties with those of original coherent state and photon-added coherent state.
    Quantum uncertainty relation
    ZHENG Xiao, MA Shaoqiang, ZHANG Guofeng
    College Physics. 2020, 39(12):  8-12.  doi:10.16854 / j.cnki.1000-0712.190541
    Abstract ( 1692 )   PDF (284KB) ( 414 )  
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    Quantum uncertainty relations,the foundational difference between classical and quantum mechanics,are divided into variance-based uncertainty relations and entropic uncertainty relations.Here,we mainly review the development of two types of uncertain relationships and introduce the application of uncertainties in quantum information science.We hope that our review is helpful for the future study of the quantum uncertainty.
    Using Igor Pro to solve the brachistochrone problem
    JIA Xiaowen, HE Xiuliang, FAN Haiying
    College Physics. 2020, 39(12):  13-19.  doi:10.16854 / j.cnki.1000- 0712.200038
    Abstract ( 1243 )   PDF (1105KB) ( 448 )  
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    Using a scientific data visualization and data processing software-Igor Pro,this paper introduces the numerical solution method of the brachistochrone problem in detail from the three aspects of analytical expression, differential equation and numerical method.By using the numerical method,the time of the ball sliding along different curves is calculated by using the analytic function.The solution process and application scope of each method are discussed in detail,and graphs and tables are used to show the whole process of numerical solution.
    Study of the application physics problem of pumping work in infinitesimal calculus
    PANG Guoying, LIU Jun, GUO Yan, LIU Jia
    College Physics. 2020, 39(12):  20-27.  doi:10.16854 / j.cnki.1000-0712.200025
    Abstract ( 3766 )   PDF (1621KB) ( 1524 )  
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    Considering the physical problem of pumping power,infinitesimal method and triple integral are used in this paper,combined scenes of real life and engineering background. Considering the container placed vertically and tilted,the model of vertical condition and the different positions of the straw,the model of tilted condition and liquid not flowing out,and the model of tilted condition and liquid flowing out of the container are established. Through numerical simulation,the strong practical application and the value of theoretical reference are pointed out.

    Analysis of magnetic force and magnetic moment in medium
    LUO Chaoyi
    College Physics. 2020, 39(12):  28-31.  doi:10.16854 / j.cnki.1000-0712.200101
    Abstract ( 1291 )   PDF (362KB) ( 365 )  
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    Problems of calculating magnetic force by existing method are pointed out. The calculation formulas of magnetic force and magnetic moment acting on the medium are derived,which can be used to analyze the deformation and movement trend of the medium under the action of magnetic field,and examples are given. In this paper,the Maxwell stress formula is further improved. To some extent,the formulas in this paper make up for the deficiency of virtual displacement method,and provide theoretical verification for Faraday’s point of view and equivalent magnetic charge method.

    Experimental study of the energy measurement of the pulse laser with a calorimetric laser power meter#br#
    MIAO Xinyang, PENG Xue, LU Wanting, ZHAN Honglei, ZHAO Kun
    College Physics. 2020, 39(12):  32-35.  doi:10.16854 / j.cnki.1000-0712.200026
    Abstract ( 1141 )   PDF (920KB) ( 448 )  
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    In this paper,a method is proposed to measure the laser energy of the narrow pulses by using a thermal power meter. The laser response is measured at different repetition frequencies. The results suggest that the calorimetric laser power meter can achieve heat balance when the frequency is higher than 8 Hz and the interaction time between the laser and the probe is not less than 4 s. The average energy of a single pulse laser can be calculated by the indicator.

    A new spectrometer based on digital camera and its adjusting method
    WANG Fengpeng, LI Chenglan, LIU Daolian, YU Liangbin, LI Cheng, XIAO Yingzhen
    College Physics. 2020, 39(12):  36-40.  doi:10.16854 / j.cnki.1000-0712.200214
    Abstract ( 1215 )   PDF (820KB) ( 457 )  
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    A new scheme and adjusting method of spectrometer with digital camera are presented,and an experimental prototype is developed. The optical phenomena is observed and recorded by a digital camera instead of a telescope in a conventional spectrometer. The digital camera lens is focus to infinity for doing parallel light adjustment,the position of the slit image is used to adjust the verticality between the platform and the rotation axis,and then the digital camera and the parallel light tube are adjusted to be perpendicular to the rotation axis with the platform as a reference. The analysis and experimental results show that the new spectrometer has the characteristics of low adjustment difficulty,small measurement error and simultaneous observation of multiple spectral lines.

    Simulation design and analysis of participatory learning teaching practice———Taking the proposed gold course “College Physics”as an example
    LI Jiaojiao, ZHOU Yuqing, DONG Ke, ZHANG Zhihong, WANG Jianing
    College Physics. 2020, 39(12):  41-49.  doi:10.16854 / j.cnki.1000-0712.200028
    Abstract ( 967 )   PDF (1029KB) ( 979 )  
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    Curriculum teaching is the core way of talent training,and the construction of high-quality undergraduate courses is an important link to improve the quality of undergraduate education,so it is imperative to construct the golden course. Based on the course of college physics,this paper explores the role of the participatory learning in the construction of college physics golden course. According to the specific course content,taking the “pyramid”model as the theoretical basis,the way that students participate in the course is simulated and designed,the form,the content,the method and the expected effect of participatory learning are explored and analyzed. A demonstrative course is designed as an example to show the process design of participatory learning practice,to explore the dual subject relationship between teaching and learning,and to complete the whole process from design to implementation under the guidance of the golden course thought. A useful attempt is provided to explore the construction of the whole college physics gold course.

    Practice of online / in-class integrate teaching methodology for medical physics and its role under the pandemic
    LIU Hai-lan, GU Mu, NI Zhong-qiang, WU Tian-gang, SONG Zhi-huai
    College Physics. 2020, 39(12):  50-54.  doi:10.16854 /j.cnki.1000-0712.200183
    Abstract ( 993 )   PDF (1522KB) ( 314 )  
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    Due to the fewer teaching hours of medical physics course,only selective topics related to medical profession were involved in the curriculum. However,without systematic teaching,it is difficult to achieve the teaching goals required by this course. Modern technology in education has brought hope to resolve this long existing problem. In this article,SPOC Online Course in medical physics based on Chinese Universities’MOOC Platform is introduced. On this basis,an integrated teaching model of online mode and in-class mode is carried out,which provides a better solution to achieve the teaching goals and formed a set of specific teaching model for medical physics. Such exploration in teaching ultimately plays an outstanding role in supporting the continuous teaching and learning during the COVID-19 pandemic period.
    Research on the substantial equivalent measures on the quality of online and offline teaching
    LI Cui-lian
    College Physics. 2020, 39(12):  55-60.  doi:10.16854 /j.cnki.1000-0712.200259
    Abstract ( 1421 )   PDF (237KB) ( 380 )  
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    In this paper,teaching designs of a newly developed four 100% online teaching ( 100% student attendance, 100% serious attitude of learning,100% help to students with learning difficulties,100% answer rate of Wechat and Wechat group after class) and its implementation are introduced. Comparing the online teaching in 2020 with the offline teaching in 2019,it is found that the quality of online teaching based on this new online teaching design is equivalent to or greater than that of the offline teaching. However,the lack of face-to-face teacherstudent communication and student communication,the educating effect of online teaching is still unknown,and needs to be investigated in future.
    Creating online teaching of college physics with warm atmosphere
    CHENG Ming-fei, ZHOU Lin, PENG Ju, YANG Jian-hua
    College Physics. 2020, 39(12):  61-63.  doi:10.16854 /j.cnki.1000-0712.200246
    Abstract ( 1089 )   PDF (1087KB) ( 492 )  
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    As a basic course of science and engineering,college physics with complete theoretical content and diversified teaching forms let students learn basic knowledge and scientific research methods. It is introduced in this paper how to develop an effective online teaching based on optimized combination of educational technologies in face of COVID-19 epidemic. The teaching team not only creates a space for students to study independently through the MOOC platform of Chinese universities,but also makes students feel a warm online college physics class through effective implementation plan ( live interaction,asking and resolving,classroom management) and multidimensional evaluation ( preview before class,interaction in class and self-test after class) .
    Advance with the times,never forget why you started ———Revision of content in the 7th edited“Physics”
    XIE Xi-shun
    College Physics. 2020, 39(12):  64-66.  doi:10.16854 /j.cnki.1000-0712.200082
    Abstract ( 1392 )   PDF (990KB) ( 2014 )  
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    The 7th edited“Physics”( by Ma Wenwei,Xie Xishun,et al.) will be published by Higher Education Press. In the process of revision,the author of this paper revised the parts of electromagnetics,optics,thermal physics and the theory of relativity. The scientific nature,contemporaneity,applicability and teaching usability of the contents are considered seriously in the new edition of this book. Many new developments and achievements of physics and its applications achieved in recent years are added in it. On the other hand,in terms of two dimensional code,many related videos,animations and word documents are linked in this book,which can enrich the knowledge and its presentation. The new edition is hoped to be satisfied with the different readers or different needs.
    Design and analysis of single-slit diffraction simulation experiment
    CHEN Jia-fu, WANG Zhi-yong, YU Bin, LIN Dan-ying
    College Physics. 2020, 39(12):  67-74.  doi:10.16854 /j.cnki.1000-0712.200160
    Abstract ( 2682 )   PDF (1305KB) ( 1008 )  
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    In view of the lack of the detailed analysis and elaboration on the Fresnel diffraction pattern of single slit and its transition to Fraunhofer diffraction pattern in the existing textooks or reference books,a proposal is given on designing a diffraction simulation experimental section between learning the diffraction theory and conducting an experimental verification. For this purpose,the mathematic formula used to realize the simulation is deduced from the diffraction theory. Then,taking the single slit diffraction as an example,Matlab programming and its graphical user interface ( GUI) module are used,and a diffraction simulation experiment is designed. Through analyzing the results of the simulation experiments,the charateristics of the two diffraction phenomena and their transition situations are elaborated in detail. Finally,the real experiment is carried out by using actual experimental devices to verify the reliability of the simulation experiment and the advantages of introducing such a section. It is proved that the simuluation experimental section provides a useful auxiliary means for better guiding students to study the diffraction of light in depth.
    Bernard convection prediction based on dissipative structure
    LI Rui-hang, FANG Ai-ping, CHEN Zi-long, QI Hao-ran, ZHANG Xiao-ru,
    College Physics. 2020, 39(12):  75-80.  doi:10.16854 /j.cnki.1000-0712.200145
    Abstract ( 1563 )   PDF (1690KB) ( 468 )  
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    A common phenomenon of fluid self-organization named Bernard convection is often difficult to predict,

    the paper starts from the dissipative structure,then studies and simulates the Bernard convection under specific

    boundary conditions by means of hydrodynamics. First of all,according to the continuity equation,energy conservation

    equation and Navier-Stokes equation of incompressible fluid,Boussinesq approximation and flow function

    method are introduced to simplify the control equation of Bernard convection. Because of the nonlinearity of the equation,

    combined with the boundary conditions of ideal fluid,variable separation is carried out for the obtained equation,

    and Lorentz system and Rayleigh number are introduced to describe the governing equation of the fluid.

    Secondly,the finite difference method is used to solve the control equation of Bernard convection,analyze the

    phase space trajectories corresponding to different parameters,and give the transition temperature of Bernard convection

    under certain conditions. Finally,based on the lattice Boltzmann method to deal with the interaction

    between the micro elements of the fluid,combining with appropriate boundary conditions,the volume of 0.008l cubic

    meter three-dimensional container is divided into 106 small cubes according to the normal cube to verify the feasibility

    of this method by analyzing simulation of Bernard convection.