Vol. 28, No. 2 (1979)
1979-01-20
CONTENT
1979, 28 (2): 141-151.
doi: 10.7498/aps.28.141
Abstract +
A survey of recent progress in the studies of lattice defects is presented and the trends of developement in this field are discussed.
1979, 28 (2): 152-159.
doi: 10.7498/aps.28.152
Abstract +
We adopted Hu Ning's expression of pseudo-energy-momentum tensor density for the gravitational field. From it, we obtained a regular result of the energy of a double-star system. But the distribution of this energy in space cannot be determined uniquely and its distribution laws are essentially identical to those of Schwarzschild external field of an isolated static star. If we recognize that the gravitational field produced by the source matter no longer possesses gravitational mass, then the value of n in that expression can be determined, and the distribution of field energy can also be determined consequently.
1979, 28 (2): 160-172.
doi: 10.7498/aps.28.160
Abstract +
In this paper, Nyquist diagrams of cyelotron instabilities caused by plasma streams are analysed. The calculation method on instability criterions of ns(the electron density of plasma stream), n0(the electron density of static plasma), B(the applied magnetie field strength), h(the wave number), V(the stream velocity) and T(the temperature) are developed. The numerical results of hydrogen plasma are given. Finally, the cyclotron and electrostatic instabilities caused by two plasma streams are also analysed.
1979, 28 (2): 173-182.
doi: 10.7498/aps.28.173
Abstract +
The physical behaviour of an incoherent-light illuminated optical imaging system is investigated. The result obtained is that there is a coherent region in the reference spherical surface of entrance or emergent pupil which is corresponding to a certain spatial frequency. The author explained the physical characteristics of incoherent optical transfer function sufficently, and suggested a possibility which may vary the transfer function curves of the system, thus permits a normal optical imaging system to have the ability of processing input signals in the frequency region.
1979, 28 (2): 183-200.
doi: 10.7498/aps.28.183
Abstract +
According to the principles of theoretical dynamics and the method of mathematical analysis, the mass, centroid and moment of inertia for 45° sean mirror are calculated exactly. The starting power of motor is also computed. Furthermore, The calculation of statical and dymamical equilibrium of 45° sean mirror are also conducted. The results are satisfactory.
1979, 28 (2): 201-221.
doi: 10.7498/aps.28.201
Abstract +
The multipole fields are widely used in electron-optical devices and instruments. The multipole fields are generated by several azimuthaly-arranged electrodes or pole-pieces and, are thereby not rotational symmetric. They generally possess some planes of symmetry or anti-symmetry.The Fourier-transform method is used to decompose the three dimensional potential distribution into a series of independent two dimensional potentials, which can be calculated easily by the relaxation method. For this purpose, the three dimensional boundary values must be expressed in Fourier-series with respect to the azimuth θ in eylindrical coordinates. After these treatments, the corresponding two dimensional potentials can be calculated and superimposed.A computer program has been worked out for calculation of the properties of the multipole fields and its fringe fields. Some examples of importance such as quadrupole lens or doublet, and a toroidal deflection coil have been treated in detail. The numerieal results show that the Fourier-transform method for multipole field is a useful means for analysis and design of electron-optical devices.
1979, 28 (2): 222-228.
doi: 10.7498/aps.28.222
Abstract +
The present paper has proposed a shell model to describe clad particles of superconductors. The model describes the particles as consist of two parts, i.e. a shell part and a nuclei part. According to the conclusion of the solution of Eliashberg equation in inhomogeneous systems we add the spectrum functions of the two parts together with specific weights. We have calculated the Tc of Pb, Sn, In clad particles with different sizes by the Louie and Cohen's critical temperature Tc fomula which is valid to both weak and strong coupling superconductors. The calcutated results are in agreement with experimental data which have been published so far. In contrast to other authors' calculated results, our results give conclusion which shows that the Tc of Pb clad particles decreases when the size of the particles is reduced.
1979, 28 (2): 229-233.
doi: 10.7498/aps.28.229
Abstract +
Strontium sodium lithium niobate (SNLN) single crystal possesses good electro-optical properties, but at room temperature only its metastable phase can be obtained. An eutectoidal decomposition will take place when the grown crystal is cooled slowly across the eutectoid horizontal which is about 1200℃. Single crystal up to 10 mm diameter and 15 mm in length were grown by the Czochralski method. Large temperature gradient is adopted during the growth period. The grown crystal is cooled at a higher cooling rate acress the eutectoid horizontal to avoid decomposition. The major problems in the process of growth and cause of crystal cracking are discussed.
1979, 28 (2): 234-239.
doi: 10.7498/aps.28.234
Abstract +
The electro-optic, pyroelectrie, dielectric and piezoelectric properties of single crystal strontium sodium lithium niobate which was grown by Czochralski technique have been investigated. The temperature dependence of the half-wave voltage is closely relevant to lithium content in the crystal. The measured pyroelectric coefficient (7×10-8c/cm2·k) is nearly equal to that of SBN (Ba～0.5) at room temperature. The depolarization is almost undetectable in the erystals poled previously. A pyroelectric device using this crystal has been made and its detectivity D is found to be no less than 1.7×107cm·Hz1/2/w. In addition, the dielectrie and some piezoelectric properties are described in this paper.
1979, 28 (2): 240-249.
doi: 10.7498/aps.28.240
Abstract +
In this article, starting with the depiction of the crystal structure, the relationship between the crystallization habit of the synthetic quartz and the physical and chemical conditions for its growth is described. The author puts forward a viewpoint that the simple form of the trigonal trapezohedron plays an important role during the growing period. By means of analysing the crystallization habit, an outer to inner relation between the external and the internal structures of the synthetic quartz has been established. Moreover, a correlation between the crystallization habit of the trigonal trapezohedron and the crystal defects has been studied for various seed orientations, namely the Z-cut, Y-cut, X-cut and the cut which intersects the Z-axis at 55°. The results of the experimental investigations show that the defects of synthetic quartz, usually called "facet defects", arise mainly from the growth traces of the crystal faces of the trigonal trapezohedron, while in the X-cut and Y-cut crystals there are still pyramidal growth interface defects formed between the various crystal faces concerned.
1979, 28 (2): 250-257.
doi: 10.7498/aps.28.250
Abstract +
Beyond the upper limit of the linear region of an ionization gauge, there is a falloff in the ion current with the increase of the measured pressure. This nonlinear behavior is to be expected by the theory of non-self-sutaining discharge, from which it follows that the pressure corresponding to the maxium of ion current may be expressed as p=E/C, where E is the field strength between the electrodes and C is a constant. Thus the upper limit, of the linear region will be extended as E increases.Four versions of gauge-electrodes configuration capable of giving higher field strength as well as maintaining lower sensitivity have been under test, leading to the result that the upper limit of linearity have extended from 10-1 Torr ab originc up to 1 Torr, 2 Torr, 6 Torr and 10 Torr, respeetively. There is satisfactory agreement between these experimental data and the calculated values based on the above theory.
