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Table of Content

    20 May 2018 Volume 37 Issue 5
      
    Feynman’s invesgation of Challanger dizaster
    ZHAO Kai-hua
    College Physics. 2018, 37(5):  1-4.  doi:10.16854 /j.cnki.1000-0712.180097
    Abstract ( 2346 )   PDF (214KB) ( 1285 )  
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    The American space shuttle Challanger had an accident in 1986,R. Feynman took part of the investigation. As a great scientist by his wisdom and honesty he found out all the reason,both technical and in management.
    Another side of Mr.Feynman
    CHENG Hung
    College Physics. 2018, 37(5):  5-6.  doi:10.16854 /j.cnki.1000-0712.180056
    Abstract ( 1809 )   PDF (99KB) ( 841 )  
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    When studying the parton model,Feynman discussed with me several times and even invited me to his home,spending a whole day listening to me the details of the works done by T.T.Wu and me,including those published and not yet.In a later Stony Brook conference (1969),he gave a talk in which my name and Wu’s name were mentioned more than ten times.However,in the published papers,he never mentioned our names,never cited our works,and in private he never explained to us.
    Ten years experience of Feynman physics teaching
    RUAN Dong
    College Physics. 2018, 37(5):  7-10.  doi:10.16854 /j.cnki.1000-0712.180031
    Abstract ( 1810 )   PDF (176KB) ( 1092 )  
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    Since 2008,we have opened a new three-semester General Physics course with the Feynman lectures on physics as the text books for junior students in physics department of Tsinghua University.In this paper,we introduce the background and purpose of this course,teaching practice and experience,as well as the preliminary achievement.
    Feynman’s education idea and molecular motor
    BAO Jing-dong
    College Physics. 2018, 37(5):  11-13.  doi:10.16854 /j.cnki.1000-0712.180061
    Abstract ( 1546 )   PDF (153KB) ( 758 )  
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    Feynman used often the unique approach to study the main current problems,although he published only 48 papers,one needs to learn his artifice idea.In order to prove the second thermodynamics law,he designed a well-known ideal experiment for the ratchet and paw,which induced the studies of molecular motors hereafter.
    Feynman and quantum computer
    HUANG An-ping,ZHANG Xin-jiang,WANG Wen-ling,XIAO Zhi-song
    College Physics. 2018, 37(5):  14-15.  doi:10.16854 /j.cnki.1000-0712.180041
    Abstract ( 2089 )   PDF (145KB) ( 746 )  
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    In this paper,we introduce Feynman’s insights on computer science and the progress of quantum technology in Beihang University.In the lectures on computer science,Feynman described the feasibility of realizing quantum mechanism based universal computer at atomic level,and pioneered the field of quantum computers and nanotechnology.
    The Feynman lectures on physics in eyes of an atmospheric scientist
    LU Jian-hua
    College Physics. 2018, 37(5):  16-18.  doi:10.16854 /j.cnki.1000-0712.180090
    Abstract ( 3006 )   PDF (143KB) ( 753 )  
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    Some personal views on the Feynman lectures on physics (FLP) are presented by focusing on the relationship between physics and meteorology and also on the way how Feynman taught fluid mechanics in the FLP.The FLP is still very helpful for developing students’ ability of creative thinking.
    Calculating the ground state of hydrogen molecule by Bohr’s quantum theory
    HOU Ji-xuan
    College Physics. 2018, 37(5):  19-20.  doi:10.16854 /j.cnki.1000-0712.170392
    Abstract ( 2011 )   PDF (309KB) ( 610 )  
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    By using Bohr’s quantum theory that dealt with the ground states of hydrogen successfully,a semiclassical model of the ground state of hydrogen molecule is presented and its energy and radius are calculated.The results are comparable to the experimental results and the results of quantum variational method,and thus our model should have potential pedagogical value.
    Equivalent parameters and Fano resonances for graphene-coated nanowires
    ZHANG Kai,SANG Zhi-fang,GAO Lei
    College Physics. 2018, 37(5):  21-25.  doi:10.16854 /j.cnki.1000-0712.170388
    Abstract ( 1113 )   PDF (851KB) ( 457 )  
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    Based on the full wave scattering theory,we establish the effective media theory for the composite system,where graphene-coated nanowires are parallel to each other and randomly embedded in the host medium.Under the long-wave limit,we achieve the equivalent (EQ) permittivity and permeability of the graphene-coated dielectric (GCD) nanowire,and we demonstrate that the far-field scattering spectrum of the electromagnetic structure with equivalent parameters matches well with the one of the composite system. Besides,we find that it is possible to realize tunable invisibility and resonance by varying the permittivity of the dielectric nanowires or the chemical potential of the coated graphene. With further study,we prove that there also exists tunable Fano-resonance in such composite system.
    Some notes on the explicit formula for the parity operator
    LIN Qiong-gui
    College Physics. 2018, 37(5):  26-27.  doi:10.16854 /j.cnki.1000-0712.170544
    Abstract ( 1506 )   PDF (133KB) ( 1007 )  
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    It is pointed out that the explicit formula for the parity operator published in this journal in recent years had been given in the literature several decades ago. Some notes are presented for that formula,including improvement of the derivation,its classical limit,and extension to the Dirac equation.
    The instantaneous center of a sphere in collision with a homogeneous free rod
    REN Cai- gui
    College Physics. 2018, 37(5):  28-29.  doi:10.16854 /j.cnki.1000-0712.170315
    Abstract ( 1434 )   PDF (335KB) ( 728 )  
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    Combining with the complete elastic collision,completely inelastic collision and general inelastic collision results of the ball and the homogeneous free rod,we point out the existence of the instantaneous center of the rod in the collision of the ball and the rod and prove the uniqueness of the instantaneous position.The instantaneous center used in the principle of mechanics is explained,too.
    The depolarization factors of dielectric ellipsoid and other shapes
    WANG Ben-yang,MAO Xiao-qin,WANG Xin-Shun,ZHANG Li-bin
    College Physics. 2018, 37(5):  30-34.  doi:10.16854 /j.cnki.1000-0712.170300
    Abstract ( 1822 )   PDF (498KB) ( 1276 )  
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    The scattering efficiency factors or internal electric fields of the representative ellipsoid,cylinder, cube and other five kinds of particle shapes are investigated by discrete dipole approximation and electrostatic approximation methods,and the depolarization factors under external electric field in different directions are calculated. Furthermore,a simple method to obtain the depolarization factor of a dielectric particle in different shape is given. The results can help students understand the relationship between the shape of medium and the intensity of depolarization field,and it also provides some references for the study of depolarization factor.
    Solving eigenvalues of nonlinear harmonic oscillators by parameter perturbation method
    WU Feng,Huang Bei-bing,MENG Li-juan
    College Physics. 2018, 37(5):  35-38.  doi:10.16854 /j.cnki.1000-0712.170390
    Abstract ( 1728 )   PDF (385KB) ( 918 )  
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    Eigenvalues of one-dimensional and two-dimensional nonlinear harmonic oscillators are computed by using the parameter perturbation method. The calculated first-level approximate results are shown to be significantly superior to the corresponding first-level and even higher-level results obtained from the parameter-free perturbation method.
    Goos-Hanchen shift modified bymonolayer and multilayer MoS2
    JIA Guang-yi,HUO Yi-qi,LIU Yu-huan,ZHANG Xue-hua
    College Physics. 2018, 37(5):  39-43.  doi:10.16854 /j.cnki.1000-0712.170484
    Abstract ( 1638 )   PDF (1379KB) ( 535 )  
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    As one of graphene analogues,monolayer or multilayer MoS2 is one kind of new two-dimensional materials. It has many tunable optical properties due to its layer-dependent dielectric constants. According to transfer matrix method,we derive the Goos-Hänchen(GH) shift in the structure of Al2O3 /MoS2 /air by the phase angle of reflection coefficient,and analyze the influence of layer number of MoS2 on the GH shift. The results reveal that the GH shift exhibits different dependent behaviors on the layer number of MoS2 in different incident-angle ranges.
    Influence of white light source spectrum on interference signal
    HU Yan-min,CHENG Si-han,NIE Ping,MA Long,QIN Zhe
    College Physics. 2018, 37(5):  44-48.  doi:10.16854 /j.cnki.1000-0712.170578
    Abstract ( 1786 )   PDF (1083KB) ( 746 )  
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    Traditional white light sources are typically modeled by a pure Gaussian function,which adjust the interference signal by changing the center wavelength and bandwidth. In this paper,the Gaussian model and the Lorentzian model are used to discuss the white light interference signals,respectively. The larger the ratio of the central wavelength to the coherence length is,the higher the visibility of the zero-order fringes. The reliable range of the Gaussian model is also obtained. In view of the difference between modern white light source and traditional light source,the white LED is used as an example to simulate the influence of modern white light source on white light interference signal. When the Lorentz model is used,the interference signal has a depression. Furthermore,by adjusting the distance between the peaks of the LED fitting light properly,the influence of the depression on the zero order fringes is reduced in order to acquire a better white light source spectrum with interference properties in practical application.
    Einstein’s ring of a distant star formed by the sun’s gravity
    ZHAO Fan2,HE Feng2,REN Wen-hui3
    College Physics. 2018, 37(5):  49-51.  doi:10.16854 /j.cnki.1000-0712.170546
    Abstract ( 1328 )   PDF (156KB) ( 432 )  
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    When a distant star,the sun and the observer are in a line,the Einstein’s ring can be viewed. Ignoring rotation of the sun,the gravitational field of solar system is described by Schwarzschild metric and then the null geodesic equation is solved exactly by elliptic integral.It must be apart from the sun at least 547.7 AU to observe the Einstein’s ring. However,the diameter of Einstein’s ring and the sun’s edge almost overlap each other so that it is very difficult to distinguish them under current technology.
    Design and implementation of temperature and pressure sensing experiment system based on optical fiber interference
    PEI Shi-xin,CUI Fen-ping,XIE Xin-tong
    College Physics. 2018, 37(5):  52-56.  doi:10.16854 /j.cnki.1000-0712.170416
    Abstract ( 1761 )   PDF (914KB) ( 818 )  
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    A fiber temperature and pressure sensing system for undergraduate teaching is designed,a diode laser with 650 nm is used as light source,and the output is divided into two beams by a beam splitter,which are then coupled into two fibers by a lens,one of the fiber is wound around a PZT tube,and the other fiber by making the shape of a torus is put in a temperature controlled box,the ends of the two fibers are closely coupled to form a double fiber interference system. By measuring the movement of the interference ring caused by pressure and temperature changes,the relation between the change of the temperature and pressure and the fringe number is established. The experimental system has advantages of simple structure,low cost and easy operation and so on,the system can be set up by the students themselves,and it can effectively improve students' experimental ability and mastery of theoretical knowledge,and it is suitable for experimental teaching of optical fiber temperature sensing and optical fiber pressure sensing in photoelectric information science and engineering specialty and similar specialty in universities.
    The research-based physics experiment: Photoconductivity of the semiconducting film
    QIU Hong,ZHAO Xue-dan,YU Ming-peng,WU Ping
    College Physics. 2018, 37(5):  57-61.  doi:10.16854 /j.cnki.1000-0712.170473
    Abstract ( 1510 )   PDF (945KB) ( 432 )  
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    A measurement of the photoconductivity of the semiconducting film can be used as the researchbased physics experiment. The conductivity of the network ZnO ∶Al films with different thickness is measured. The experiment can well train students’ability to analyze and solve problem. Finally,we summarize systematically the basic characteristics of the research-based physical experiment from the real research project.
    Who wrote F=ma?An investigation on the development history of physics symbols
    LI Xi-jun,CHENG Min-xi
    College Physics. 2018, 37(5):  62-67.  doi:10.16854 /j.cnki.1000-0712.170399
    Abstract ( 3329 )   PDF (1229KB) ( 1498 )  
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    By asking a question"who wrote F =ma?" the materials from 1638 to 1960 (including physics original works,biographies,physics textbooks in college and secondary school and reports of international conferences,etc) are discussed,the development of physics symbols is reviewed£® This history is summarized into four stages (geometry,mathematic symbol,physics symbol and SI symbol)
    Physics tournament in Nankai University
    YU Hua,LI Chuan-yong,WU Qiang,BO Fang,LIU Zhi-bo,YAN Bao- yan
    College Physics. 2018, 37(5):  68-71.  doi:10.16854 /j.cnki.1000-0712.170453
    Abstract ( 1676 )   PDF (333KB) ( 379 )  
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    This paper briefly introduces the development of physics tournament in each stage of the senior high school,undergraduate stage and postgraduate stage in Nankai University,and the effective convergence of the physics tournament activities and other innovative activities in the undergraduate education stage. A sustainable and hierarchical innovative education network has been formed from senior middle school to graduate school.
    Numerical simulation and experiment of the forced vibration of hanging droplets
    ZHU Ze-bin,LIU Jing,BIAN Qi-qi,YOU Jian,CAO Sa
    College Physics. 2018, 37(5):  72-77.  doi:10.16854 /j.cnki.1000-0712.170373
    Abstract ( 1397 )   PDF (333KB) ( 463 )  
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    The numerical simulation based on finite element is used to study the vibration of liquid droplets which hang on the needle in the second mode. The results show that there is a linear relationship between the natural vibration frequency of the hanging droplets and that of the weightless free droplets. The linear relationship is related to the liquid surface tension coefficient,liquid density and needle diameter,and is independent of the liquid viscosity and“the ratio of the liquid surface tension coefficient and density”. Under the excitation of a sound field, the displacement resonance curves of the hanging droplets fit the normal velocity resonance curves of the forced vibration in shape,and the damping coefficient is positively correlated with the liquid viscosity,the liquid surface tension coefficient and the needle diameter,while negatively correlated with the liquid density and“the ratio of the liquid surface tension coefficient and density”. Finally,the simulation results are compared with the experimental data,and the two are in well agreement.
    The quantum properties of photon in single-mode dissipative cavity
    BAI Zhi-da
    College Physics. 2018, 37(5):  78-81.  doi:10.16854 /j.cnki.1000-0712.170393
    Abstract ( 1346 )   PDF (298KB) ( 649 )  
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    At absolute zero of temperature,we derive the analytic expression for the time evolution of the light  -field in the single-mode dissipative cavity under both Fock state and coherent field. Also,we present a new derivation in the presentation of the number states,which is different from textbooks.