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    20 February 2017 Volume 36 Issue 2
      
    Resistance resolution method and its applications
    CHEN Nan-xian
    College Physics. 2017, 36(2):  1-4.  doi:10.16854 /j.cnki.1000-0712.2017.02.001
    Abstract ( 1144 )   PDF (1024KB) ( 855 )  
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    The present work shows a new method for circuit analysis,that is resistance resolution method with several applications,which may enrich imagination for college students.This work can be considered as an example of inverse problems in electricity.
    What does“virtual”mean in the virtual displacement?
    LIU Tian-gui,LIU Quan-hui
    College Physics. 2017, 36(2):  5-7.  doi:10.16854 /j.cnki.1000-0712.2017.02.002
    Abstract ( 2312 )   PDF (173KB) ( 1457 )  
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    Virtual displacement is an important physical concept in physics.For exaggerating the role of the non-reality in applications of the virtual displacement,we analyze how the virtual displacement is applied,which can be divided into three steps: 1) for a given physical problem,the definition of virtual displacement of a variable is introduced; 2) the variation of a mathematical function along the change of the virtual displacement is given,which is not necessarily compatible with physics principles; 3) with imposing physical conditions on the mathematical function,the physics consequence is resulted.
    The fourth cosmic speed of the Moon
    YU Feng-jun
    College Physics. 2017, 36(2):  8-10.  doi:10.16854 /j.cnki.1000-0712.2017.02.003
    Abstract ( 1723 )   PDF (397KB) ( 888 )  
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    The minimum speed,required for an object escaping from the gravity of the solar system launched from the lunar surface,is calculated. The result is 11.6 km/s,its direction is along the one of the full moon’s orbital motion.
    Transformation and simulation of Gaussian beams   through spherical refractive surfaces
    QIN Hua,ZHANG Shuang,LI Wen-rui,WEI Gong-xiang,LIU Yun-yan
    College Physics. 2017, 36(2):  11-17.  doi:10.16854 /j.cnki.1000-0712.2017.02.004
    Abstract ( 1348 )   PDF (1530KB) ( 1461 )  
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    In order to study Gaussian beam propagation in the spherical refractive surfaces,the relationship between the location and radius of the object beam waist and ones of the image beam waist are deduced theoretically by using the paraxial ray tracing in geometrical optics. By hypothesis that Gaussian beam ray is the rectilinear generatrices of hyperboloid of one sheet,we simulate the Gaussian beam propagation through lens systems with the ray tracing method. Simulation results show that when the distance between the Gaussian beam waist and the object focus of a lens system is much larger than the confocal parameter of the Gaussian beam,the simulation results for the waist location and the waist radius are consistent with the theoretical results obtained from the paraxial approximation, otherwise,the simulation results will be inconsistent with theoretical results.
    Application of coherent state in the normal ordering of quantum operators
    REN Gang,DU Jian-ming,YU Hai-jun,ZHANG Wen-hai
    College Physics. 2017, 36(2):  18-23.  doi:10.16854 /j.cnki.1000-0712.2017.02.005
    Abstract ( 1305 )   PDF (244KB) ( 573 )  
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    By using the over-completeness of coherent state and the technique of integration within an ordered product of operators,we derive some new normal ordering forms of quantum operators. Compared with other methods, this method is easier and clearer in theory and application.
    The study of conserved quantities and symmetries for microvibration of three coupled pendulums
    LOU Zhi-mei
    College Physics. 2017, 36(2):  20-23.  doi:10.16854 /j.cnki.1000-0712.2017.02.006
    Abstract ( 1218 )   PDF (411KB) ( 549 )  
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    The kinematic differentiation equations of microvibration of three coupled pendulums are obtained by using Lagrangian equations,we decouple the Lagrangian by transforming coordinates and obtain directly four conserved quantities from uncoupled Lagrangian. The Noether symmetries and Lie symmetries of four conserved quantities are studied by using inverse Noether theorem and Lie symmetry theorem.
    Improving Newton's law application———an example of Navier-Stokes equation
    MO Run-yang,WANG Cheng-hui,BIAN Xiao-bin
    College Physics. 2017, 36(2):  24-27.  doi:10.16854 /j.cnki.1000-0712.2017.02.007
    Abstract ( 1529 )   PDF (280KB) ( 891 )  
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    Navier- Stokes equation of incompressible fluid is derived according to the idea and method in classical Newtonian mechanics. This method which combines the cross-section method in mechanics of elasticity, the concept of fluid micelle and the fluid continuity equation and so on. It is an exercise for students' thinking   ability,while it improves the ability of comprehensive utilization of knowledge.
    Study of motion of string-bound two-body particles
    SHU Xin-wen,XU Xin-sheng,YAO Guan-xin,HOU Chang-jian
    College Physics. 2017, 36(2):  28-33.  doi:10.16854 /j.cnki.1000-0712.2017.02.008
    Abstract ( 1470 )   PDF (1349KB) ( 1011 )  
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    The dynamics model and the motion of string-bound two-body particles are studied.By using the Taylor series expansion method and the Runge- Kutta numerical method,the approximate and numerical solution of differential equations are obtained,respectively.Calculations of the dynamic equation give the evolution of position vector as a function of time,motion trajectory and phase diagrams. The motion of particle depends on the initial position and transverse velocity.For a larger or smaller initial transverse velocity,the motion is non-linear oscillation. There is a critical initial velocity at which the two-body system is in mechanical equilibrium,and will perform harmonic vibration under small perturbation.The results are valuable for teaching and research on the mechanics   problems of micro-vibrations.
    Solving the self-inductance of“three-dimensional conductor”in the quasi-steady circuit in the light of magnetic vector potential
    LIU Shi-ming
    College Physics. 2017, 36(2):  34-38.  doi:10.16854 /j.cnki.1000-0712.2017.02.009
    Abstract ( 1223 )   PDF (222KB) ( 486 )  
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    The self-induction electromotive force of“three-dimensional conductor”in the light of magnetic vector potential is analyzed. The solution of the self-inductance of“three dimensional conductor”unlimited length coaxial cable is given by using the formula The self-induction electromotive force of“three-dimensional conductor”in the light of magnetic vector potential is analyzed. The solution of the self-inductance of“three dimensional conductor”unlimited length coaxial cable is given by using the formula E = L| ∂l/∂t| ,then the cause of formation of the self -conductance is discussed visually.,then the cause of formation of the self -conductance is discussed visually.
    Influence of a grounding strip conductor plate on uniform electric field and its numerical simulation
    WANG Fu-qian,JIA Lan-fang,WANG Lei
    College Physics. 2017, 36(2):  36-38.  doi:10.16854 /j.cnki.1000-0712.2017.02.010
    Abstract ( 1227 )   PDF (1229KB) ( 793 )  
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    The influence of a grounding strip conductor plate on uniform electric field is studied by conformal mapping and reset function method,and electric potential distribution and electric field intensity distribution are obtained. Furthermore,the distribution of electric field is numerical simulated by using the software MATLAB.
    Improvement on measuring coefficient of surface tension by abruption
    LIN Ren-rong,QIU Zhu-qiang,CHEN Li-min,XIE Zhi
    College Physics. 2017, 36(2):  39-42.  doi:10.16854 /j.cnki.1000-0712.2017.02.011
    Abstract ( 1842 )   PDF (680KB) ( 2526 )  
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    A new method for measuring coefficient of surface tension of liquid is designed by improving equipment of the experiment. New calculation formula is proposed based on force analysis of the metal ring. It corrects the used rough method which ignoring the weight of liquid. This new method has easy operation,and experiment data show that it has high accuracy and good stability. By a careful analysis of the new experimental results, some mistakes in related literatures are corrected.
    Application of K-means mean clustering algorithm in the magnetoresistance effect
    WANG Yun-jie
    College Physics. 2017, 36(2):  43-46.  doi:10.16854 /j.cnki.1000-0712.2017.02.012
    Abstract ( 1098 )   PDF (736KB) ( 654 )  
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    We introduce the action principle of magnetoresistance effect and the application of magnetroresistive elements,as well as the design and verification of the approaches of analyzing and processing the experimental data of magnetoresistance effect using curvature and K-means clustering algorithm. The results show that the present method has high accuracy and low human factors and greatly intuitive.
    Topology changes physics———2016 Nobel Prize in Physics
    SHI Yu
    College Physics. 2017, 36(2):  47-54.  doi:10.16854 /j.cnki.1000-0712.2017.02.013
    Abstract ( 1850 )   PDF (2061KB) ( 1507 )  
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    Starting with the general background of physics and condensed matter physics,the author describes he awarded achievements of 2016 Nobel Prize in Physics,as well as their scientific backgrounds and later development. After exposing the phase and phase transitions,the author explains how topological phase transitions go around the constraint of the dimension,how topology is the key to the essence of quantum Hall effect and leads to Chern insulator,as well as how topology makes the one-dimensional antiferromagnet depends on whether the spin quantum number is an integer or a half-integer.
    The effect of relativity on GPS
    ZHONG Ji-kang,HU Pan-xin
    College Physics. 2017, 36(2):  55-57.  doi:10.16854 /j.cnki.1000-0712.2017.02.014
    Abstract ( 2200 )   PDF (353KB) ( 1188 )  
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    Global positioning system ( GPS) on the accuracy of the clock makes a very high demand. Since the speed and the altitude of the satellite,this paper shows that both effects from the special relativity which make motion clock slow and from the general theory of relativity which makes the clock at higher place in a gravitational field fast be large enough,thus the influence of relativity to accuracy of satellite clocks can not be ignored. This is a very good example when we talk about the application of relativity in college physics course.
    A method of measuring viscosity of liquid by two-capillary
    ZHU Ze-bin,SUN A-ming,DAI Bi-fen
    College Physics. 2017, 36(2):  58-60.  doi:10.16854 /j.cnki.1000-0712.2017.02.015
    Abstract ( 1231 )   PDF (303KB) ( 430 )  
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    When fluid flows through a capillary,head losses will be occurred,which relates to the length of the capillary. With this principle,we make the liquid flow through two capillaries,whose inner diameters are the same while lengths are different. Controlling the same perpendicular distances from the outflow end of capillaries to liquid level,and measuring the ratio of liquid mass flowing from two capillaries in the same time,the viscosity of this liquid can be obtained theoretically by calculation.
    Study of decay characteristic by measurement of energy spectrum of β decay and internal conversion electrons of 137Cs
    REN Zan,WANG Xuan,NIU Ya-zhou,LI Pan-gen,ZHANG Ze-tao,ZHANG Gao-long
    College Physics. 2017, 36(2):  61-65.  doi:10.16854 /j.cnki.1000-0712.2017.02.016
    Abstract ( 2767 )   PDF (725KB) ( 1412 )  
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    The energy spectra of β decay and internal conversion electrons of 137Cs are measured by Si( Li) drift detector. The energy spectrum of β decay is studied by Curie plot and the internal conversion coefficients are obtained from the energy spectrum of internal conversion electron. The obtained maximum energy of β decay for 137Cs is ( 513.11±1.76) keV with an error 0.17% with respect to the reference data and the obtained internal conversion coefficients correspond to K/L = 5.712±0.217 and M/L = 0.264±0.018 with the errors 0.92% and 1. 54% with respect to the reference data,respectively. Then the transition levels of β and γ decays for 137Cs and its decayed daughter nucleus are determined. The spins and parities of 137Cs and its daughter nucleus 137Ba are obtained, then the decay scheme of 137Cs is plotted. As a result,it is indicated that the experimental technology is credible, and can be used for experimental teaching and study of nuclear structure as well as it can provide the necessary experimental data for nuclear structure.
     
    College Physics. 2017, 36(2):  66. 
    Abstract ( 758 )   PDF (171KB) ( 223 )  
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