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Table of Content
20 August 2012 Volume 31 Issue 8
著者文摘
The relation between nonequilibrium work and free-energy difference
. 2012, 31(8): 1-1.
Abstract
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875
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(333KB) (
513
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The relation between nonequilibrium work and free-energy difference, i. e. , the Jarzynski equality is proved by using a forced harmonic oscillator, in wich the free-energy difference between two equilibrium states can be calculated by the exponential averaging of generalized work. This process is performed during a finite time. Moreover, we find a dynamical resonance of average work or dissipative energy can become maximum if the external driving force is regarded as a periodic signal.
A new simple approach for disentangling some exponential operators
. 2012, 31(8): 4-4.
Abstract
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857
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(247KB) (
782
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We recommend a new convenient method for disentangling some exponential operators, which can lead us to a set of new operator identities.
The length of rotating spring
. 2012, 31(8): 6-6.
Abstract
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728
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(164KB) (
594
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The model of circular spring encircling a rotating smooth metal rod is established. The differential e- quation of displacement is derived by infinitesimal analysis method and the solution is given. The theoretical expres- sion of total length of spring in rotation frame is given, which is in good agreement with the experiment data.
Tension in a string with circular plate
. 2012, 31(8): 8-8.
Abstract
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1086
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(233KB) (
498
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A string system is discussed, in which the circular plate goes through the circular plate. The formula of calculating the tension in of both objects and the friction between them being factored in. rotates around a fixed axis and the string the string is given in the case of the mass
The electric capacity of a confocal elliptic cylindrical capacitor
. 2012, 31(8): 11-11.
Abstract
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855
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(292KB) (
776
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By mean of the eonfoeal elliptic cylindrical coordinate, we calculate capacitance of a confocal ellip- soid-shaped capacitor and hyperbolic cylindrical capacitor, and show the general expression of capacitance for a confocal ellipsoid-shaped capacitor. It makes the calculation results of so kinds of capacitors become richer.
A way of deducing two-level atom＇ s spontaneous emission
. 2012, 31(8): 15-15.
Abstract
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934
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(164KB) (
494
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An equation for describing interaction of atom and vacuum fluctuation is proposed, because the en- ergy of vacuum fluctuation is negative. It can get the probability of atoms in the excited state changing with time. The relation between the atom＇ s spontaneous emission and the strength of vacuum fluctuation is discussed.
An approximate solution of two-dimensional coupling nonlinear harmonic oscillator
. 2012, 31(8): 17-17.
Abstract
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748
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PDF
(248KB) (
527
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Two-dimensional coupling nonlinear harmonic oscillator is analyzed and the basic eigenvalue is ob- tained by using the approximation method of self-consistent averaging. The result is very close to the one derived from the perturbation method.
An alternative derivation of the relativistic mass-velocity and mass-energy relations
. 2012, 31(8): 19-19.
Abstract
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995
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(254KB) (
783
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An alternative derivation of the mass-velocity and mass-energy relations in the relativistic mechan- ics is presented, in which the well-known Lorentz transformation is not used. The mass-velocity and mass-energy relations are not necessarily related to the speed of light, but to more general upper limit of speed vm.
Research on the method for measuring viscosity coefficient by rotating cylinder viscometer
. 2012, 31(8): 21-21.
Abstract
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754
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(359KB) (
703
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Based on the theory of viscous fluid mechanics, the formula regarding the radial velocity gradient of rotating liquids in the measuring device is obtained, and the more accurately calculation formula of viscosity coeffi- cient for rotating cylinder viseometer is further worked out, the errors of approximate formula used in the derivation in textbooks and documents nationwide are put forward, and the torque of frictional drag in the measuring device is calculated by using the parameter estimation method, which makes the measuring results calibrated be accurately. The experimental results show that the difference of the radial velocity gradient and the liquid viscous coefficient calculated by the approximate and exact formula are 13.1% and 28.6% , respectively; the torque of frictional drag in the measuring device is 9. 482×10-5N · m when temperature of the castor oil is 25.5 ℃ , which is equivalent to the torque caused by 0. 540 grams of weight.
Using ANN to error compensation and analysis for experiment of measuring the metal linear expansion coefficient
. 2012, 31(8): 25-25.
Abstract
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818
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(347KB) (
451
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This paper analyzes the factors that influence the measure of the metal linear coefficient of expansion in light lever experiment and finds that calibration is nonlinear variation with temperature changing. Artificial neural network （ANN） has more abilities to learning and highly nonlinear reflecting than other traditional method. It is used to error compensation and analysis for experiment, and the simulation result obtained shows that the method is feasible and the calculation is precise.
Research on value relation between scanning field and horizontal field in optical magnetic resonance experiment
. 2012, 31(8): 29-29.
Abstract
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1076
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(287KB) (
727
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In the experiment of optical magnetic resonance, there are simultaneously pumping signal and reso- nance signal constantly, which seriously affect the experimental observation and measurement. Based on the influ- ence of the scanning field and horizontal field on the pumping signal, as well as the theoretical analysis and experi- mental measurement, we find the relationship between the scanning field and the horizontal field, while pumping signal and resonance signal do not exist at the same time. The interference of the pumping signal on the resonance signal and misjudging the direction of the total magnetic field is avoided, so a smooth and accurate experimental measurement is assured.
The important contributions of Geiger to physics
. 2012, 31(8): 32-32.
Abstract
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1111
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1257
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The brief biography of Hans Geiger is outlined. His research of the radioactivity under the guidance of Ernest Rutherford, especially the alpha-particle scattering experiment which he made with Marsden is reviewed. How he developed and improved his counters and how he researched the Compton effect with Bothe by coincidence method are introduced. Geiger＇s outstanding style of work is discussed.
Promoting college physics teaching through introduction of scientific research works
. 2012, 31(8): 39-39.
Abstract
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752
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(522KB) (
733
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In this paper, we take physics teaching. Promoting college p college physics, but also stimulate the physics teaching. an example of introducing submillimeter astronomy research work in hysics teaching can not only guide interest and love for college physic students to understand the effective s. thus contributes to the effects of college ness of college
Computational analysis of influential factors on optical tweezers trapping force
. 2012, 31(8): 44-44.
Abstract
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953
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(427KB) (
1036
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Optical tweezers are powerful tools for optical trapping, micromanipulation and force transduction. The calculations of three factors have significantly influences on optical tweezers trapping force including particle size, the refractive index and beam type have been carried out. The result shows that the trapping efficiency is opti- mized for a particle with a size closing to the wavelength and a relatively large refractive index in a trap formed with properly-chosen beam type.
Study on measuring system of velocity based on PASCO device
. 2012, 31(8): 49-49.
Abstract
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811
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1052
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An instrument for measuring velocity of system based on the Doppler effect of light using PASCO system to acquire signal are made. We have succeeded in measuring the velocity of liquid and solid （fiber） and an- alyzed the data and signal spectrum acquired.
Study on visualization of the electronic probability density in hydrogen atom
. 2012, 31(8): 53-53.
Abstract
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1309
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(993KB) (
727
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According to the characteristics of abstract and hard to understand of electronic probability density in hydrogen atom in quantum physics, this paper suggests the distributed function of electronic probability density in hydrogen atom including the radial distribution function and angular distribution function. We investigate the distri- bution law of electronic probability density for visualization by using powerful drawing function of Matlab. The re- sults show that the method reveals the distribution of electronic probability density in hydrogen atom intuitively and vividly. It provides a new way in physics teaching.
Exploration of influence factors and efficiency of the driving car powered by balloon
. 2012, 31(8): 57-57.
Abstract
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981
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(392KB) (
473
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Starting from the internal pressure of the balloon and considering friction comprehensively, this arti- cle does research on the state of motion of balloons jet-powered car. We define and study the efficiency of the bal- loon car to explore influencing factors of the efficiency of the car. At last we combine with experiments and use rea- sonable theory correction to determine the range of maximum efficiency.
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