College Physics

Numerical calculation of energy spectrum of quantum graph

ZHANG Xue, YANG Hua-tong

College Physics. 2019, 38(9): 1. doi:10.16854 /j.cnki.1000-0712.190151

Abstract ( 1525 )

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Quantum graphs refer to the quantum mechanical problems which are defined on networks formed by some connecting one-dimensional lines. In this paper，some basic concepts as well as the mathematical formulism of the stationary state problem of the quantum graphs are introduced. From the boundary conditions satisfied by the wave functions and their derivatives at vertices，the secular equation determining the energy eigenvalues of a quantum graph is derived. It is proved that the coefficient determinant of the secular equation is real if the number of edges of the quantum graph is even，but is imaginary if the number is odd. This property makes it possible to numerically calculate all the energy levels in a finite energy range. Two typical quantum graphs are taken as examples to analyze the variation of energy eigenvalues with the change of the length of a specific edge.

Isoenergetic surface of s-state electron in cubic lattices under tight binding approximation

WANG Chun-an, FU Si-lie

College Physics. 2019, 38(9): 6. doi:10.16854 /j.cnki.1000-0712.180655

Abstract ( 1482 )

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Cubic lattice is a common crystal structure. In the teaching of solid-state physics in university，the cubic lattice is usually taken as an example to illustrate the spatial distribution characteristics of isoenergetic surface in the form of static images. However，it is lack of the detail changing of isoenergetic surface with the wave vector k. In this paper，the variation of isoenergetic surface of the s-state electron in cubic lattices with the wave vector k under the tight binding approximation is shown in detail by using the MATLAB program. The superposition，crosssection and extension graphs of the isoenergetic surface are also given visually. These images show that when the wave vector k changes from the center of Brillouin zone to the boundary，the isoenergetic surface changes from a sphere to a spherical-like surface until it breaks and concentrates near the corner of Brillouin zone. These results vividly show the changing of isoenergetic surface and it effectively assists teachers' teaching and deepens students' understanding of solid-state physics.

Study of the steady flow of ideal gas in horizontal stream tubes

ZHOU Yue, ZHANG Guo-feng

College Physics. 2019, 38(9): 11. doi:10.16854 /j.cnki.1000-0712.190070

Abstract ( 1311 )

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The fundamental properties of the compressible flow are discussed based on the steady flow of ideal gas in a horizontal stream tube，and are compared with those of ideal fluids. The condition in which the compressibility of gases is ignorable that is also analyzed.

Damping oscillation of charged particles in the electric field of four fixed points charges

ZHAO Li-qiang

College Physics. 2019, 38(9): 15. doi:10.16854 /j.cnki.1000-0712.180694

Abstract ( 1021 )

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Based on the Coulomb law and the Newton second law，the damping vibration dynamic equation of charged particles in four fixed points charge electric field is theoretically expressed and the analytical solution is obtained. The conditions of under-damp，critical damp and over-damp are analyzed and discussed. Finally，some example images are drawn by using MATLAB mathematical software.

Study of equivalent resistance of a n-step bridge network of resistors

LI Wei, TAN Zhen, WANG Ming-jun, TAN Zhi-zhong

College Physics. 2019, 38(9): 19. doi:10.16854 /j.cnki.1000-0712.180557

Abstract ( 1265 )

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The structure of resistor network model is complex and diverse，which is applied in many fields of natural science.This paper researches a kind of n-step bridge network model，which has not been solved before.The investigations show that the network model contains multiple different network types.In this paper，a simplified equivalent model is adopted and a non-linear difference equation model is established by using Kirchhoff's law to solve this problem.A concise formula of fractional equivalent resistance is obtained and several interesting special conclusions are given，where we explain the reason why this network is called bridge circuit network.

Research and simulation of wavelength measurement experiment using Michelson interference

SHI Shao-hui, FENG Shun-zhen, NIU Ping, DONG Yan-hui, LIU Ji-hong, WU Shu-hua

College Physics. 2019, 38(9): 24. doi:10.16854 /j.cnki.1000-0712.190020

Abstract ( 3507 )

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Equivalent optical path method is used to study the optical path difference，the characteristics of interference fringes of Michelson interferometer by using He-Ne laser source is also analyzed theoretically. It is found that off-center problem of the interference fringes is mainly caused by the no perpendicularity of the two mirrors or the laser and the beam expander. Based on the software of Matlab，a simulation program MIGUI for Michelson interferometer is designed. MIGUI can not only accurately simulate the process of wavelength measurement，but also simply adjust the five parameters affecting interference fringes and study the intensity distribution of fringes quantitatively. Finally，MIGUI is used to study the influence of the position of the moving mirror and the beam expander on the interference fringes. It is found that the change of the position of the moving mirror has a greater effect on the fringe radius than the latter.

Research on SPOC teaching mode of university physics experiment based on guide map

ZHANG Li

College Physics. 2019, 38(9): 29. doi:10.16854 /j.cnki.1000-0712.180625

Abstract ( 1460 )

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SPOC teaching model is a product of the post -MOOC era，which reduces the high loss rate of MOOC teaching model and avoids the maladjustment of the students caused by flipped classroom. Thus，more and more schools and teachers are trying to use SPOC teaching model which plays a more important role in experimental teaching field. In this paper，guide maps，such as preview guide，principle map，step map，report guide map，are used in the SPOC teaching reform to simplify the digestion of principle process for students，improve the interest of study，standardize the experimental procedures and promote the in-depth discussion. After practice，it is proved that this scheme improves the effect of the learning preview and the understanding of operation process. Meanwhile， part of the students’experiments is expanded and some good results are achieved. The implementation of this idea should be a reference for the other courses，especially for experimental courses.

Construction of public elective course based on physics fight

WANG Jin, LI Chuan-yong, LI Wen-hua, ZHANG Chun-ling, LIU Li-sa, CHEN Jing, YU Hua

College Physics. 2019, 38(9): 34. doi:10.16854 /j.cnki.1000-0712.180658

Abstract ( 1310 )

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This is a brief introduction of the public elective course of Nankai university based on physics fight，which includes the teaching objectives，the teaching method，the course content，the course effect，feedback of students and the improvement project of the course. Constructive summary and proposal about the laboratory construction are also discussed. Based on this course，the cross merging of physics major education and liberal education is promoted，which paves one way for the improvement of the comprehensive quality and innovation spirit the undergraduate students.

Practice and thinking of promoting higher education equity through the construction of online open excellent courses

WANG Lei, NI Mu-cui, ZHANG Han, ZHANG Han-zhuang

College Physics. 2019, 38(9): 38. doi:10.16854 /j.cnki.1000-0712.190040

Abstract ( 1008 )

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In this paper，the existing unfair phenomenon in China's higher education is analyzed from the perspective of higher education equity. Taking mechanics as an example，the construction of the resources and the running practice of the online open courses are introduced. It is shown that the construction and running of high-quality online open courses play a positive role in promoting the equity of starting point，process and result in higher education.

Reform of the multi-disciplinary integrated innovative physics experiment course under the background of emerging engineering education

WANG Li-ying, QIN Zhu, LIAO Yi, DAI Hai-tao, MI Wen-bo

College Physics. 2019, 38(9): 43. doi:10.16854 /j.cnki.1000-0712.180592.

Abstract ( 1447 )

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A reform scheme of multi-disciplinary integrated innovative physics experiment course is proposed according to the educational goal to cultivate the“emerging engineering education”undergraduate students. In this paper， the reform plan has been elaborated in three aspects: the aim and the problems planed to be solved，the investigation on these problems in various domestic and overseas universities and the specific reform ideas and measures of our reform program. The reform program combines traditional physics experiments with the multidisciplinary latest scientific researches and could also promote teachers to convert latest scientific research results into teaching. Designing such multi-disciplinary integrated innovative physics experiments and combining them with scientific research would help to establish a foundation for the cultivation of emerging engineering undergraduate students.

Study of the relationship between the flow rate of particulate matters and Beverloo formula

CHEN He-tian, NAN Jie, GAO Hong, WANG Mei

College Physics. 2019, 38(9): 49. doi:10.16854 /j.cnki.1000-0712.180687

Abstract ( 2226 )

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The hourglass has been used as a historical time-keeping tool and its physical principles are still applied in all aspects of life. In this paper，different particle materials are studied. Under the condition that the diameter of particles is extremely small and the specific surface area is sharply increased，the flow rate of particles is positively correlated with their diameters when keeping the hole of the same diameter. At the same time，the maximum stability angle is measured and the influence of factors，such as opening diameter and inclination angle on the flow velocity is further explored.

Pattern selection of Faraday waves at lower frequencies

QI Rui-shi, WANG Hai-lin, WANG Wei, ZHOU Lu-qun

College Physics. 2019, 38(9): 54. doi:10.16854 /j.cnki.1000-0712.190046

Abstract ( 1538 )

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Under certain conditions，specific nonlinear standing waves would form on the free fluid surface subjected to a vertical oscillation，termed Faraday waves. In this experiment，xanthan gum solution in a cylinder container is took as the research object，and the pattern selection problem at lower frequencies is explored. A vibration exciter is used to drive the platform where the vessel is placed and a high-speed camera is employed to catch the images of the Faraday waves. The experimental results have shown that under certain parameters，there exists a weakly nonlinear region near the onset value at which many experimental phenomena could be explained approximately by the linear vibration theory. In this region the pattern is usually located only along one of the diameters of the container. The number of antinodes increases with the frequency of the driving force increasing and the stability of the pattern changed alternately. Theoretical analysis shows that this phenomenon is resulted from the interaction of the dispersion relation and the container boundary conditions.

Mie resonance based microwave nondestructive detection for metal surface crack

WANG Ren-yu, LIANG Ge, LIN Zhe-yu, ZHU Hong-bo, LI Hai-hong, BI Ke

College Physics. 2019, 38(9): 58. doi:10.16854 /j.cnki.1000-0712.180648

Abstract ( 1793 )

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During the interaction between dielectric particles and incident electromagnetic waves，Mie resonance is generated，which results in the absorption of microwave near the resonance frequency. At this time，the energy of electromagnetic field will be gathered near the dielectric particles. If there are small perturbations around the dielectric particles，such as small cracks on the reflecting surface of metal，the resonance frequency will change

obviously. The network analyzer can measure the reflection coefficient of electromagnetic wave and record the frequency change of absorption peak to obtain the information of cracks. In the experiment，cracks of different sizes are detected，and two rules can be concluded: for cracks of the same depth ( or width) ，the resonance frequency of dielectric particles decreases with the increase of crack width ( depth) ，and the change rate of resonance frequency decreases with the increase of crack width ( depth) .

How to Teach the First Lesson in Physics———The writing structure of new form textbook“Introduction to Physics”

XIN Bei

College Physics. 2019, 38(9): 62. doi:10.16854 /j.cnki.1000-0712.190295

Abstract ( 1344 )

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The new form textbook“Introduction to Physics”published by Higher Education Press summarized current physical laws from their logic，history，and practicability. This paper introduces the textbook and helps readers understanding it well.

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