College Physics

Introduction to the virtual simulation experiment of spin dynamics of quantum materials

College Physics. 2024, 43(9): 1. doi:10.16854/j.cnki.1000-0712.230347

Abstract ( 66 )

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The virtual simulation experiment of spin dynamics of quantum materials is based on the research content of the secondary discipline of condensed matter physics, combined with the background of undergraduate solid state physics and quantum mechanics courses. New contents and technologies in cutting-edge research are introduces into experimental teaching in a timely manner so as to stimulate undergraduates’ keen perception and exploration awareness of cutting-edge new physical phenomena, theories and technologies. The whole process of extremely low temperature neutron scattering experiment was highly simulated by 3D simulation technology. Through two solid state physics experiments, the methods of neutron elastic and inelastic scattering experimental research problems is mastered, and the interaction mechanism of microscopic particles in solids is understood. Through the study of three cutting-edge research experiments, the research methods and ideas of the microscopic mechanism of quantum materials is mastered. By independently setting experimental conditions, completing data collection and analyzing experimental data, students’ professional practice ability can be improved. This experimental course combines digital highquality resources with undergraduate experimental teaching projects, which is high-order, innovative and challenging. It was selected as the “second batch of national first-class undergraduate courses”.

Squeezed state representation of angular momentum operators in quantum mechanics

ZHAN De-hui1, FAN Hong-yi2

College Physics. 2024, 43(9): 9. doi:10.16854/j.cnki.1000-0712.230237

Abstract ( 54 )

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We notice that the angular momentum raising and lowering operators exhibit squeezing transformation property under rotating around the third axis, so we compare this with two-mode squeezing operator to find new Bose realization of angular momentum operators. By observing the quantum mechanical bipartite entangled state representation，we find the new Bose realization of angular momentum operators, which enables us to view quantum rotation as squeezing. We also study the new raising and lowering operators’ character in the entangled state representation. This shows that the entangled state representation is of necessity to teaching quantum mechanics. We expect that new multi-partite entangled state representation can be constructed and multi-mode Bose realization of angular momentum operator can be found.

Different definitions of virtual displacement and ideally constrained system

ZHANG Jiu-zhu

College Physics. 2024, 43(9): 12. doi:10.16854/j.cnki.1000-0712.230456

Abstract ( 39 )

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For ideal, general first-order nonholonomic constrained systems, this paper argues that the relation satisfied by the virtual displacement, namely Chetaev relation, can be derived, but the virtual displacement in the relation should refer to the Gauss variation. Similarly, in order to derive the Lagrange equation with multipliers from the general equations of dynamics using Chetaev relations, it is necessary to first determine whether the system is an ideal constrained system, and the virtual displacement in the ideal constraint conditions should also refer to the Gauss variation. For an ideal, first-order linear nonholonomic constrained system, in the relation and ideal constraint conditions satisfied by the virtual displacement, the virtual displacement can be either Gauss variation or Jourdain variation.

Solution of dynamic matrix equation of phonon dispersion relations in one-dimensional to three-dimensional lattice

LU Yong

College Physics. 2024, 43(9): 15. doi:10.16854/j.cnki.1000-0712.230447

Abstract ( 50 )

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In this paper, the phonon dispersion relation of lattice vibrations from one-dimension to three-dimension is solved by constructing dynamic matrix equation. Compared to traditional method of solving one-dimensional atomic chain classical model using Hamilton’s canonical equations in solid state physics courses, constructing a dynamic matrix provides a more unified and universal form for solving phonon dispersion relation from one-dimensional to three-dimensional lattice. It is helpful to establish a continuous physical picture of one-dimensional to three-dimensional lattice vibration from the way of thinking. In terms of numerically solving three-dimensional lattice vibrations and considering the effects of anharmonicity, this method also offers greater convenience.

Discussion and analysis on the approximate formula for the period of a large-angle pendulum

YUAN Qing-xin, ZHANG Xin-yue, SHAO Li

College Physics. 2024, 43(9): 20.

Abstract ( 57 )

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A comprehensive analysis and discussion have been conducted on the approximate formula for the period of a large-angle pendulum in the literature. In terms of analytical form, the arithmetic-geometric mean recursive method is used. Although it has the highest accuracy, other simple approximate formulas can be selected when considering the convenience of calculation, simplicity of the formula, and the need for experimental measurement accuracy.

A proof of e=1 in fully elastic collisions of rigid bodies

CHEN Yi-ling, TANG Peng

College Physics. 2024, 43(9): 24. doi:10.16854/j.cnki.1000-0712.230434

Abstract ( 60 )

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This article provides a proof that the non loss of kinetic energy is equivalent to the recovery coefficient e=1 in a fully elastic collision between three-dimensional rigid bodies. This article extended the applicability of previous results which obtained in collisions between particles, and collisions between particle and rigid body. This proof avoids the calculation of rotational energy of rigid bodies, and completes a simple proof by starting with impulse and work done.

Calculation method of the second and third boundary value problems of electrostatic fields in multi-conductor systems

TANG Lie-zheng1, ZHOU Guo-hua1, BIAN Qiang1, BU Fan-yun2, YU Yan-juan1

College Physics. 2024, 43(9): 26. doi:10.16854/j.cnki.1000-0712.230463

Abstract ( 40 )

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The total charges of conductors are usually given in the second and third boundary value problems of the electrostatic field, but the electric field cannot be directly solved due to the unknown charge density distribution on the conductor surface. Therefore, according to the linear relationship between the conductor charge and the electric potential in the electrostatic field, the second and third boundary value problems are transformed into the first boundary value problem, so as to realize the calculation of the above problems. On this basis, the finite element analyses of the electrostatic field are carried out to verify the effectiveness of the proposed method by taking the parallel two-wire system as the research object.

Simulation of a reflectron time-of-flight mass spectrometer using LabVIEW

XIN Jia-Qi, HOU Gao-Lei

College Physics. 2024, 43(9): 29. doi:10.16854/j.cnki.1000-0712.230262

Abstract ( 30 )

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In this work, LabVIEW is utilized to simulate a reflectron time-of-flight (TOF) mass spectrometer, and to conduct virtual experiments to investigate the main factors that affect the resolving power of the spectrometer. Such virtual experiments should be helpful for students to understand the working principles of a TOF mass spectrometer quickly. In addition, it also stimulates students’ interest in learning and cultivates their sense of creativity.

Uncertainty analysis of the curvature radius of Newton's rings#br# with replacing the diameter by chord length#br#

WEN Jun1, YANG Yang1, LIANG Zhen-yu2+, SHI Yue2+

College Physics. 2024, 43(9): 35. doi:10.16854/j.cnki.1000-0712.230405

Abstract ( 49 )

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In the experiment of Newton's ring， measuring the diameter of interference ring is the key and difficult step．It is confirmed in this paper that the type B uncertainty of the curvature radius of Newton's rings is affected when the parameter measured is the chord length rather than the diameter.The type B uncertainty can not be ignored when the linear correlation coefficient approaches to 1． In addition，the advantages are analyzed when measuring the chord length instead of the diameter on the basis of theoretical analysis，the method of calculating the type B uncertainty is also given．

Virtual simulation design of Ytterbium doped fiber laser amplifier

SU Xin-yang1, TIAN Zhao-yang1, WEI Ran1, HU Jian-guo1, FENG Jian-hui1, NIE Zi-kun1, CHI Hong-xiang1, XU Tian-jia2, ZHU Rui-xue3

College Physics. 2024, 43(9): 40.

Abstract ( 46 )

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A virtual simulation software for ytterbium doped fiber laser amplifier is designed and developed using Python programming language. By adjusting the initial input data of seed signal light, pump light, pump mode, fiber length and fiber type in the virtual simulation software, three-dimensional spectrum, two-dimensional spectrum curves of the amplified signal light, pump light, ASE can be obtained. Users can observe the output results of amplifiers through this virtual simulation program. This software can save trial and error costs, help to improve experimental efficiency and achieve excellent teaching effects in amplifier related experiments.

Simulation of imaging through scattering medium based on digital holography

CHENG Qi-luan, TAN Zuo-jun

College Physics. 2024, 43(9): 46. doi:10.16854/j.cnki.1000-0712.230402

Abstract ( 28 )

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According to the scalar diffraction theory of light, the process of generating conjugated light by digital holography has been simulated in this paper. By using the conjugated light, the disturbance of scattering media is eliminated and the object covered by scattering media is imaged clearly. The imaging process in actual application is analyzed and discussed. Imaging effects caused by different particle sizes ofscattering medium and different depths of medium are simulated. In addition, the feasibility of realtime imaging by using CCD and spatial light modulator is also discussed.

Analysis of white light interference with Michelson interferometer

Dou Ling-yu1, Ji Chao-ran2, Ren Li-qing2, Li Hong-guo3, SongXin-bing1

College Physics. 2024, 43(9): 50. doi:10.16854/j.cnki.1000-0712.230353

Abstract ( 54 )

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In the experiment of observing white light interference with a Michelson interferometer to measure refractive index of a transparent medium, a key step is to move a the moving mirror of the interferometeron the basis of observing white light interference without the introduction of the medium to be measured,so that the interference fringes appear again after the introduction of the medium. In actual experiments, interference patterns can be observed just when the moving mirror moves halfstandard distance.In this paper, the reasons for this phenomenon are theoretically analyzed, and comparative experiments are designed for experimental analysis. The theoretical and experimental results show that this phenomenon originates from the single passage of the beam through the medium which is small in size and occupies only a small part of viewfield.In addition, the interference fringes for this case appear outside the medium region, while the interference fringes for the standard case appear inside the medium region.

Studies and practices of ideology and politics in atomic physics teaching#br# #br#

JIN Feng-tao, GAO Cheng, WANG Xiao-wei, DAI Jia-yu

College Physics. 2024, 43(9): 54. doi:10.16854/j.cnki.1000-0712.230441

Abstract ( 32 )

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The development of atomic physics is linked to many famous physicists and stories in the history of modern physics, and is a gold mine rich for ideological and political materials. Deeply exploring these materials and integrating them into atomic physics teaching not only helps students deepen their understanding of knowledge, but also cultivates their scientific thinking mode, and plays a very important role in establishing students' correct outlook on life, world, and science. In this paper, ideological and political materials are reasonably classified and naturally integrated into classroom teaching according to their characteristics, so that physical content and ideological and political elements can be organically combined to play a role of “spring breeze turns rain, moistens things silently”, and also the depth and breadth of the course is expanded. From the practice of questionnaire surveys, extracurricular communication, and exam design, it has also been confirmed that ideological and political education can play such a role.

A teaching model design for university physics experiments under #br# the background of new engineering with integration #br# of “competition and general education”#br#

CHEN Wu-hui, ZHANG Ting, LIU Cai-xia, JING jia

College Physics. 2024, 43(9): 63. doi:10.16854/j.cnki.1000-0712.230393

Abstract ( 26 )

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To address the issues of relatively monotonous teaching content, single learning methods, and single assessment methods in university physics experimental courses, the results of China Undergraduate Physics Tournament, Chinese Undergraduate Physics Experiment Competition from 2020 to 2023 are used to integrate with university physics experiments. Then the teaching mode of university physics experiments based on new engineering disciplines is designed, including case teaching, innovative topic selection, scheme design, practical operation, and multi-dimensional assessment. These five parts enable students to apply these concepts to practical situations based on a deep understanding of core concepts of physics, enhance their ability to actively explore and independently practice, and lay a solid foundation for their development in the field of new engineering.

Construction and practice of online examination #br# of all question types for college physics#br#

YU Shu-yun, LIU Jian-qiang

College Physics. 2024, 43(9): 67. doi:10.16854/j.cnki.1000-0712.230470

Abstract ( 31 )

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Digital transformation in examination is an important part in digital transformation of higher education. It has been tried in many universities in China. At present, the main difficulty for large-scale promotion is the online input for different question types. In this paper an online test system which is developed by Shandong University and IFLYTEK is described. The input problem is effectively resolved with the help of high-speed photographic apparatus. The organization and implementation of the online final examination for college physics I in Shandong University is described in detail. The results of the examination are also discussed. It is predicted that this mode will be widely adopted in the future.

Study on the vibration modes of two leaf springs coupled with magnetic interaction

LU Jian-shi, ZHOU Wen-hao, WANG Chun-mei, ZHANG Jie, XIA Cheng-jie

College Physics. 2024, 43(9): 71. doi:10.16854/j.cnki.1000-0712.230411

Abstract ( 32 )

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Normal modes and eigen frequencies are crucial characteristics of a multi-degree-of-freedom oscillation system. The influence of the coupling interactions between different degrees of freedom on the normal modes is a fundamental mechanical research topic，and is also relevant to various engineering and application problems. Here，we study the vibration of two identical leaf springs coupled with magnetic force. We show that the magnetic coupling causes a set of coupling-dependent modes，with the springs moving in opposite directions，and another set of coupling-independent modes，with the springs moving in same directions. In addition，the lower order vibration modes are more strongly affected by the magnetic force，while the higher order modes of the two springs are barely coupled. Thus，the two springs would have distinct vibration frequency spectrums if their initial conditions are different. We have also performed experiments，to observe the vibration phenomena and measure the eigen frequencies with different key variables，including the spacing distance of the springs，spring thickness and length. The experimental results are all in accordance with our theoretical predictions.

Structural stability analysis of “3n+1” tennis tower

LIU Peng-yu1, LIU Peng-fei2, YU Gui-hua2, JIANG Wen-ke3, ZHANG Tian-yu2

College Physics. 2024, 43(9): 78. doi:10.16854/j.cnki.1000-0712.230357

Abstract ( 23 )

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The factors influencing the stability of the “3n+1” style tennis tower，constructed by stacking three tennis balls per layer with one tennis ball on top，are investigated. Under ideal conditions，the presnt study explores the relevant parameters affecting its stability from both statics and dynamics perspectives. It is found that the pressure on the bottom tennis ball is positively correlated with its height，and the static friction coefficient between the tennis balls decreases with increasing pressure. Combining these findings with the results of experiment 1，it is concluded that the energy loss is inversely proportional to the number of layers，suggesting that there is no upper limit to the number of layers in the tennis tower. Taking into account the interference factors，the experiment 2 demonstrates an exponential decrease in the success rate of constructing tennis towers with 2~8 layers. Through analysis of the contact model between tennis balls and the force chain structure，it is determined that the contact force on the bottom tennis ball increases exponentially with the length of the force chain. Ultimately，the maximum height of the tennis tower is determined to be 10 layers.

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