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Table of Content
20 August 2009 Volume 28 Issue 8
著者文摘
Thermodynamic laws and mathematic inequalities
. 2009, 28(8): 7-7.
Abstract
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810
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489
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A general inequality is established simply and conveniently based on the first and second laws of thermodynamics, from which many familiar inequalities are directly derived. It may be expected that some new inequalities are derived from the inequality.
Study of asymptotic relationship between Bessel function and Legendre function by analyzing vibration modes
. 2009, 28(8): 11-11.
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1194
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727
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By analyzing the symmetric vibration on a disk and a sphere surface, the curves of the zero-order Bessel function and the Legendre function are compared. It is shown that there are apparent similarities between them. After transformation of amplitude, the curves of the Bessel function agree with those of the Legendre function very well. The reasons for the similarities are explained both in mathematical and physical approaches. The asymptotic relationship between the functions of two kinds and an estimating formula for zeros of the Bessel function are derived.
Some notes on space translation invariance
. 2009, 28(8): 15-15.
Abstract
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909
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405
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A generalized analysis for symmetry in quantum mechanics is presented. The associated conserved quantities are extended to time-dependent ones. It is shown that a single particle （including the relativistic case） moving in a static uniform magnetic field and a time-dependent linear potential possesses space translation invariance. The translated wave function and the time-dependent conserved quantities are obtained.
Analyses on a ball up rolling
. 2009, 28(8): 18-18.
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955
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394
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Some problems including the reasons, the conditions and the demo effect in the experiment of a ball up rolling on nonparallel double-beeline are discussed, and a geometric proposition on ellipse is given.
Study of the period of a damped single pendulum
. 2009, 28(8): 20-20.
Abstract
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861
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905
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The vibration of a weakly damped nonlinear single pendulum is studied by means of the averaging method. The expression of the ratio of the period varying with the angle amplitude and the damping coefficient are obtained.
Derivation of the restitution coefficient formula for plane-parallel motion rigid body
. 2009, 28(8): 23-23.
Abstract
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1277
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605
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The formula of restitution coefficient for the collision of plane-parallel motion rigid body is derived.
The electric potential of a line charge and a cylindroid conductor system
. 2009, 28(8): 25-25.
Abstract
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771
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(225KB) (
434
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Conformal mapping is used to transform a cylindroid conductor into a cylindrical conductor, and the electric potential of a line charge and a cylindroid conductor system is given by the mirror image method.
The magnetic field distribution of a current-carrying tightly wound solenoid with finite length
. 2009, 28(8): 28-28.
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1120
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1244
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For a steady current-carrying tightly wound solenoid with finite length, first, the expression of vector potential is derived by using the method of cylindrical function expansion and the expressions of magnetic field in the integral form are obtained by employing the relation between vector potential and magnetic induction. Next, the analytic expressions in the series form of magnetic field distribution are calculated by using the integration method directly. Finally, the magnetic field on some special positions is discussed.
The dispersion law of medium to high frequency electromagnetic wave
. 2009, 28(8): 31-31.
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1037
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896
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According to the classical dispersion theory, we derive the dispersion law of medium to high frequency electromagnetic wave. From this law we know that almost all the mediums are transparent for high frequency electromagnetic wave. Therefore, the latter can pass through the former. This conclusion is proved with copper for an example. One can understand some application about high frequency electromagnetic wave by means of this conclusion.
Derivation of spin matrix in Dirac theory
. 2009, 28(8): 33-33.
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1011
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472
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The common form of spin matrix in the Dirac theory is proven to be the general one. The proof here is independent of representation.
Analysis on the Fraunhofer diffraction of random distributed holes
. 2009, 28(8): 35-35.
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1133
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855
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The Fraunhofer diffraction of random distributed circular holes is analyzed using the Monte-Carlo method and is compared with the diffraction distribution of a single circular hole. It is shown that the diffraction pattern of the random distributed circular holes has the same geometry characters as that of a single hole with the same radius. The former has a power stronger than the latter and has a very strong point in the center. Besides, the diffraction field of multi-holes has an unsmooth distribution which is similar to be added some noises. These conclusions are in agreement with the experimental results.
A new experiment of white light interference
. 2009, 28(8): 39-39.
Abstract
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691
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(267KB) (
682
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A new experiment of white light fringes has been developed. When Lloyd＇s mirror interference is combined with grating diffraction the fringes for different colors produced by white light source can be coincident, thus the white and black fringes will be observed. The theory, apparatus and method are introduced, and the key points of observation and measurement and data resuhs also are given.
Analysis for linear fitting results in the experiment of relative pressure coefficient
. 2009, 28(8): 42-42.
Abstract
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755
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(160KB) (
321
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The type-A evaluation of measurement uncertainty should be to evaluate the quality of linear fitting results. The uncertainty will increase when the fitting equation is applied outside measuring line segment.
The history of liquefaction
. 2009, 28(8): 43-43.
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1121
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1638
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The development of liquefaction has experienced a long and tortuous process. Helium was liquefied 100 years ago, so 2008 was a historical year. By looking back the history of liquefaction, we may know the cognition of knowledge is a dialectical process. This article is for commemorating the brilliant scientists Sir James Dewar and Kamerlingh Onnes for their outstanding contribution in the liquefaction
The role of IYPT （International Young Physicists＇ Tournament） for improving the physical thinking of young students
. 2009, 28(8): 46-46.
Abstract
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828
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672
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The paper describes and analyzes the significance of IYPT on improving the physical thinking of young students by introducing China＇ s first participation of IYPT. It also provides an important approach to improve their creative thinking, team work, researching ability and presentation skill. Promotion of IYPT in China will helps training of our international physics talents with creativity.
Exploring teaching of quantum physics in engineering course
. 2009, 28(8): 51-51.
Abstract
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647
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(300KB) (
792
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Teaching of quantum physics in engineering course is a subject which we should pay more attention to. Deemphasizing early quantum theory, introducing 5 basic postulates and reducing mathematical contents, teaching of quantum physics is reinforced.
Generalization of the gravity law in an inverse n-order force field
. 2009, 28(8): 54-54.
Abstract
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765
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1346
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The gravity law in an inverse n-order force field and its inspiration are discussed.
The exact deduction of Bragg condition
. 2009, 28(8): 56-56.
Abstract
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1240
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1199
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Under the assumptions of the undulatory theory of light, especially diffraction of light, Bragg condition is deducted quantitatively.
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