College Physics

Study on quantum tunneling of one-dimensional triple square potential barriers

LI Hai-feng, CHEN Kang-kang, WANG Xin-mao

College Physics. 2024, 43(02): 1. doi:10.16854/j.cnki.1000-0712.230189

Abstract ( 514 )

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In this paper, the quantum tunneling characteristics of onedimensional symmetric triplesquarepotential barriers are studied by solving the stationary state Schrdinger equation in different areas. Moreover, the exact expression of the transmission coefficient is analytically attained, and the dependence of the transmission coefficient on the barrier width, barrier spacing, and the incident energy of the particle is numerically simulated. Furthermore, the results show that when different potential barrier widths or different incident energies of the particle are taken, the periodic oscillation phenomenon of the transmission coefficient with the increasement of the barrier spacing is exhibited. Comparing with one-dimensional symmetric double barriers, the periods of the transmission coefficient oscillating with the barrier spacing increases are the same. However, the oscillation of the triple square potential barriers is more intense and the amplitude is larger. At a period, it is a bimodal curve for the triplesquare potential barriers, while it is a unimodal curve for the double-square potential barriers. This characteristic provides theoretical guidance for designing novel nanodevices and resonant tunneling quantum devices.

Analyzing the system with rheonomic constraint from various perspectives

ZHU Ren-gui, HUANG Wan-xia

College Physics. 2024, 43(02): 5. doi:10.16854/j.cnki.1000-0712.230081

Abstract ( 237 )

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Compared with scleronomic constraint, rheonomic constraint brings more complication, however, it can be dealed with by more means. Through transforming the reference frame, and selecting smartly the proper form of Lagrange equation or energy integral, we can solve the rheonomic constraint problem by various ways. From the comparison among different perspectives, we can verify some results that often neglected by textbooks, such as the ideal constraint does not depend on the reference frame, and the ideal constraint force has no influence on the application conditions of the Lagrange equation for conservative system, even if it does the real work. Through analyzing the rheonomic constraint problem from various perspectives, we can promote efficiently the ability of students to comprehend and apply the important knowledge of analytical mechanics.

Discussion on eigenfunction orthogonality for analytical solution of unsteady heat conduction problem

JIN Wan-long1, SHI Wan-yuan2, CHE De-fu1

College Physics. 2024, 43(02): 8. doi:10.16854/j.cnki.1000-0712.230085

Abstract ( 211 )

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The analytical solution of the unsteady heat conduction problem is one of the critical contents of heat transfer. However, the explanations of eigenfunction orthogonality in most heat transfer textbooks are relatively simple, which hinders the understanding of solving process. Taking the analytical solution procedure of the large plane wall unsteady heat conduction problem for example, the meaning of eigenfunction orthogonality, the proof of eigenfunction orthogonality and the application of eigenfunction orthogonality were discussed emphatically. Several teaching suggestions for keeping the solution process coherent and helping students understand were given. It provides a reference for the teaching of the analytical solution and mathematical analysis of the unsteady heat conduction problem.

Discuss more about half-wave loss and the interference of thin film

LIU Jia-ming

College Physics. 2024, 43(02): 16. doi:10.16854 /j.cnki.1000-0712.230052

Abstract ( 592 )

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There are four parts in this paper. First, more discussions about the formulas and the physical situations are presented to the article “Condition of half-wave loss when light is emitted from optically denser medium to optically thinner medium”, which was published in this magazine not long ago. Second, some views about half-wave loss in that article are discussed. It is pointed out that there is usually no half-wave loss when the light with polarization parallel to the plane of incidence shooting on the medium with small refractive index from the medium with large refractive index and the ratio between their refractive indexes is huge. Third, the quantitative analysis of the interference of thin film is presented. It is shown that the results from the formulas in the textbook are usually close to the results from the Fresnel formula. Fourth, it is pointed out that the formula of the interference of thin film for the dark lines in the textbook is right, but to the bright lines, it will be absolutely wrong in some cases.

Response of a uniformly accelerated Unruh-DeWitt particle detector near a boundary

ZHOU Wen-ting

College Physics. 2024, 43(02): 23. doi:10.16854/j.cnki.1000-0712.230084

Abstract ( 178 )

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With the time-dependent perturbation theory, we calculate the response rate of an Unruh-DeWitt particle detector, which is uniformly accelerated in vacuum along a trajectory parallel to a perfectly reflecting boundary. By comparing the results with their counterparts of a detector being inertial or uniformly accelerated in an unbounded vacuum, we discover that the uniformly accelerated motion may induce spontaneous excitation for a detector initially in its ground state, and the presence of the boundary may bring in significant revisions to the transition rates of the detector.

How to build a heat engine between two black holes: Starting from the 2023 CPhO problems

MA Yu-han

College Physics. 2024, 43(02): 27. doi:10.16854/j.cnki.1000-0712.230398

Abstract ( 322 )

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The theoretical fifth problem in the final round of the 2023 Chinese Physics Olympiad (CPhO) involves black hole thermodynamics. In this paper, we provide an introduction to the background of black hole thermodynamics and further analyze the characteristics of thermodynamic cycles between black holes based on our research experience. Finally, we summarize some recent research progress in the field of finite system thermodynamics and statistical physics relevant to this topic.

Introducing the 21st Century Noble Prize Experiment into physics experiment teaching — QCSE of LED

DEND Dong-mei, ZHANG Huan

College Physics. 2024, 43(02): 33. doi:10.16854/j.cnki.1000-0712.230089

Abstract ( 221 )

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At present, Nobel experiments involved in university physics experiment teaching are mainly from the 20th century. The practical value and educational meaning of the century-old classic Nobel experiments have been verified by practice. To deeply explore the educational value of the new Nobel Prize and to keep the experimental teaching in the university in line with the times and scientific research, the Nobel Prize experiment light-emitting diodes (LED) in 2014 are introduced into physics experiment curriculum. In this experiment, students can master LEDs quantum well structure and light-emitting mechanism and follow Shuji Nakamuras in-depth research on LEDs. This experiment also introduced and showed that the quantum-confined Stark effect in LED by measuring the change of spectrum with the injection current. By combining with the theoretical model, students can understand this effect and the piezoelectric field in the quantum well can also be evaluated.

Preliminary practice in developing optical concept inventory

ZHANG Fengxuan, WU Lixiong, ZHAO Ruiqing, ZHANG Mei

College Physics. 2024, 43(02): 37. doi:10.16854 /j.cnki.1000-0712.230163

Abstract ( 206 )

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Optics is an important branch of college physics, which involves studies on the properties and phenomena of light, including knowledge of light propagation, refraction, reflection, interference, diffraction, polarization,etc. In the Fundamental physics course, optics is compulsory and students mastery of optics concepts can effect the quality of physics teaching some degree. An optics concept inventory is first developed and then distributed online to students in a top lies university.Data is collected and analysed,and accordingly assessment of the teaching and learning is done.Besides,the preliminary practice in developing the inventory is evaluated in detail.

Research on the cultivation strategy of students’ internal drive in online teaching of college physics

LI Gang, GAO Shun-qi

College Physics. 2024, 43(02): 44. doi:10.16854/j.cnki.1000-0712.230076

Abstract ( 270 )

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With the unique advantages, online teaching during the epidemic has become an inevitable choice for the normal teaching, and also a useful supplement to offline teaching in the post-epidemic era. By stimulating and cultivating students internal drive, students online learning initiative will be greatly increased, the learning efficiency and classroom teaching effectiveness will be improved. Taking the course of college physics as an example, in this paper the cultivation strategy of students internal drive in online teaching is expounded. It provides beneficial enlightenment for the development of online and offline blended teaching.

Landing uniformity Exploration of the probability of three sides of cylinder

DU Wang-yi-xin, BAI Lu-jing, ZHOU Yun

College Physics. 2024, 43(02): 49. doi:10.16854/j.cnki.1000-0712.230069

Abstract ( 302 )

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The probability of landing on the front and back of traditional coin approaches 1/2 respectively, while the probability of landing on the side is almost zero. In order to explore the factors affecting the probability of landing evenly on three sides of a new type of cylindrical dice, kinematic process of elastic collision and inelastic collision of cylindrical dice are theoretically analyzed from the perspective of mechanics, and the factors affecting the probability of landing evenly are divided into physical and geometric characteristics of cylindrical dice and external influencing factors. By establishing various types of cylindrical dice models, the control variable method is used to carry out the experiment and the software is used to carry out the simulation. The experimental and simulation results are agreement with the theoretical analysis. The results show that the thickness to diameter ratio, the hardness of contact surface material, the throwing height and the angle between the center of gravity of the cylinder and the vertical direction vector are the main factors affecting the uniformity of landing probability.

Study on the probability of final face orientation of cylindrical dice

JIANG Su-xin, SHAO Fang-na, XU Ze-lin, LOU Ci-bo, DUAN Xiang-mei, WANG Ji

College Physics. 2024, 43(02): 55. doi:10.16854 /j.cnki.1000-0712.230042

Abstract ( 288 )

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The final resting state of a falling object depends on the geometric characteristics, motion state, material properties, etc. Based on the dynamic model, this paper explores the influence of the initial velocity, angular velocity, height, mass and recovery coefficient of cylindrical dice on the final face orientation of the dice after landing, and discusses the geometric characteristics and physical conditions that should be presented to make the final orientation probability of each side of the cylinder dice equal. The results of this paper can provide ideas and reference for such research.

Theoretical analysis and experimental research of tennis-ball tower

LI Jia-rui, ZHANG Chen, DU Ru-hai, GAO Jian-zhi, WANG Heng-tong

College Physics. 2024, 43(02): 60. doi:10.16854/j.cnki.1000-0712.230045

Abstract ( 277 )

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With the help of the friction between tennis balls, the tennis balls can be formed into a multi-layer “tennis-ball tower”. The problem of “tennis-ball tower” is interesting, scientific and comprehensive, and the study of this problem is of great significance to exercise the comprehensive physical literacy of college students. In this paper, firstly, the selected tennis balls can be regarded as rigid bodies, which is proved by experiments on deformation degree and contact area. Secondly, the relationship between the static friction coefficient and the supporting force on the balls is measured considering factors like the stripes on the balls and so on, and the theoretical mechanics analysis and the solution method of the stable tennis-ball tower are given. They are proved by the Adams simulation and practical experiments. Finally, it is pointed out that when the number of balls is the same in all layers except the top layer, the structure of the tennis-ball tower can be changed by changing the stacking density of the balls or constructing the “coupling” structure, and the statically indeterminate problem in the correlated solution is discussed.

Measurement of Young's modulus of metal wires using micro-resistance measurement

TANG Jie-yang, LYU Mei-yu, WANG Yi-fan, YANG Jia-xu , ZHOU Liu-zhu

College Physics. 2024, 43(02): 68. doi:10.16854 /j.cnki.1000-0712.230086

Abstract ( 451 )

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An experimental device that can measure and display Young's modulus of metal wire online in real time was designed, based on the principle of tiny resistance measurement and based on the relationship equation between the modulus of elasticity and the amount of tiny change in the resistance of metal wire. When the metal wire is stretched and causes a small change in resistance, the magnitude of Young's modulus can be displayed in real time on the display after being amplified by a two-stage integrated operational amplifier circuit, analog/digital conversion, microcontroller acquisition and calculation. The data measured on a 0.201mm diameter steel wire and a 0.269mm diameter constantan wire show that the Young's modulus of the wire measured by this device has a relative error of no more than 0.3%, high accuracy, simple operation and short measurement time, and provides a feasible method for rapid measurement of the Young's modulus of the wire.

A review of the development of d-band center theory to study the mechanism of MoS2 electrocatalytic hydrogen reaction

LIU Shi-ping, HUANG Xiao-xiao

College Physics. 2024, 43(02): 71. doi:10.16854/j.cnki.1000-0712. 230220

Abstract ( 387 )

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Molybdenum disulfide (MoS2) nanosheets, a typical two-dimensional material,have received much attention for its unique tunable electronic structure and excellent electrocatalytic activity for hydrogen evolution reaction (HER). In order to further improve its electrocatalytic performance,in-depth investigations on microscopic HER mechanism have been conducted to elucidate the key factors influencing the electrocatalytic performance within the material's electronic structure and construct reasonable electronic descriptors. This paper reviews the origin,development and current status of the d-band center theory to probe the mechanism of MoS2 electrocatalytic HER in recent years,with a view to providing guidance for the further development of this type of catalyst.

Application of Quantum ant colony algorithm to TSP and algorithm evaluation

LI Xuan-qiu, HUANG Fei-jun, JING Peng-fei

College Physics. 2024, 43(02): 79. doi:10.16854/j.cnki.1000-0712.230129

Abstract ( 268 )

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Quantum ant colony algorithm (QACA) is an efficient biological evolutionary algorithm. It combines quantum theory with traditional ant colony optimization algorithm (ACO). It is mainly applied to the solving of fault diagnosis,path planning,image segmentation. Based on the process of ACO,this paper introduces the quantum theory foundation of QACA and how it is applied to QACA. The advantages of QACA over ACO are analyzed by applying them to several examples of traveling salesman problem. Current research often uses discrete indexes to evaluate different algorithms,and it is difficult to intuitively display the differences of algorithms. In view of that,a comprehensive evaluation method for algorithm search efficiency is proposed. It is successfully applied to the comparison between QACA and ACO.

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