Table of Content

31 March 1985, Volume 3 Issue 1

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Articles

FINITE DEFORMATION ANALYSIS FOR STRESS CONCENTRATION AROUND A FREE NOTCH AND STRESS SINGULARITY AROUND A DEEP NOTCH

OUYANG CHANG, TANG GUOAN

1985, 3(1):  1-5. 

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The expressions of stresses in finite deformation of an elliptic or parabolic notch in infinite elastic plane has been obtained by incremental analysis. Such expressions are functions of loads, notch shape and material behavior. The stress singularity for a deep notch has especially been discussed, and it is found that this singularity could be related with the stress intensity factor in linear fracture mechanics, but the order of this singularity has been changed from 1/√ρ to α ln 1/√ρ, ρ being the curvature radiu of the notch root, α a material constant. The new result here explains the difference between the cases of plane strain and plane stress.

GROUND-STATE ENERGY OF A STRONG-COUPLING EXCITON IN PIEZOELECTRIC CRYSTAL

GU SHIWEI, ZHOU YUKUI

1985, 3(1):  6-12. 

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In this paper, some properties of a strong-coupling exciton in piezoelectric crystal are studied. An effective Hamiltanian of the exciton is obtained by the method of a linear-combination operator and a simple unitary transformation. The self-energy could be written as a series in α^-1, the first term being proportional to α, the coupling constant. The interaction potential induced by the interaction of the electron-hole with the phonons is related to coupling constant and sound speed etc.

AGING OF PIEZOELECTRIC CERAMIC PARAMETERS AND DETERIORATION OF TRANSDUCER PERFORMANCES

HUANG DANNI, WANG ZHICHAO, SHOD XINMIN, ZHENG ZHONGYOU, WANG HONG

1985, 3(1):  13-19. 

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The variations of parameters of piezoelectric ceramics Fe1.5 and corresponding high power transmitting transducers with the logarithm of time have been examined separately with normal specimens and a certain type of vibrator under defined temperatures (room temperatures, 60℃ and 100℃), pressure (30 kg/cm²) and electrical power densities (0.3W/cm³·KC and 0.5W/cm³·KC) in this paper. Experimental results show that the causes of aging of ε₃₃^T and k_p are not all the same. The varying tendency of the properties of ceramic elements after the cumulative action of the electrical power density of 0.3W/KC·cm³ is different from that of the normal specimens under each single condition. Both the value of k_p and ε₃₃^T are some what increased. It was considered that this aging behaviour was related to the internal bias electrical field of the ceramic material selves.
We would conclude that the aging of properties of piezoceramics under the given temperature, pressure and electrical power density is not serious enough to cause the deterioration of performances of transducer. The appropriate heat treatment will be favourable to stabilizing the performances of ceramic materials and transducers.

MICROSCOPIC QUANTUM THEORY OF THE OPTICAL WAVEGUIDE

SUN HONG, PENG QIANJUEN, FANG JUNXIN

1985, 3(1):  20-28. 

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The present article takes the Frenkel exciton in a crystalline planar waveguide as a model to set up a microscopic quantum theory of the optical waveguide.

A NEW METHOD FOR MEASURING THE BIREFRINGENCE OF SINGLE-MODE FIBERS WITH SHORT BEAT-LENGTH OR NONUNIFORMITY

HUANG SHANGYUAN, LIN ZONGQJ

1985, 3(1):  29-37. 

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A birefringence formula of single-mode optical fiber in terms of the positions of the highest peak and its adjacent valley on the curve of the measured polarization ellipticity via the fiber twist is proposed and the distortion of the measured curves for the fibers with nonuniform birefringence is discussed. The new measuring process which is based on null measurement is simple and reliable.

SOME CHARACTERISTICS OF Si-DOPED GaAs BULK CRYSTALS

MO PEIGEN

1985, 3(1):  38-45. 

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In this paper, a study has been made of the compensation ratio (θ), the minority carrier diffusion length (L_p) and the dislocation density of Si-doped GaAs crystals grown by the horizontal Bridgman method. The study on compensation ratio shows that tie donor can be self-compensated through a defect equilibrium due to the formation of the Si_GaV_Ga complex, when the carrier concentration is greater than 10¹⁷cm^-3. Some relationships between L_p, dislocation density and θhave been found. The L_p decreases with the θ increasing and changes abruptly at around θ=0.3, while the θ found for dislocation-free and low dislocated crystals is greater than 0.38 with the carrier concentration in the range of 1~2×10¹⁸cm^-3. It may be suggested that the L_p and dislocation density are related to Si_GaV_Ga in some way, which is formed through the interaction between Si_Ga and V_Ga, and with V_Ga created in turn from Si and O, by the removal of Si from Ga sites.
In general, the θ could be used as a satisfactory guide to the quality of Si-doped GaAs crystals.

THE PHOTOELECTROCHEMICAL PROPERTIES OF LIQUID JUNCTION SOLAR CELLS COMPOSED OF N-CdTe FILM ELECTRODES

DENG XUNNAN, PANG RENDE, GAN SHAOXIN

1985, 3(1):  46-51. 

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The elementary photoelectrochemical properties of liquid junction solar cells composed of N-CdTe film electrotrodes are reported in this paper. The cell could be represented as
N-CdTe/1M Na₂S, 1M S. 1M NaOH/C
The electrode potential-current curves, voltage-current curves of the cells have been measured. The relationship between the irradiation intensity and the photovoltage, photocurrent and conversion efficiency have been determined. Under the irradiation of 60mW/cm², the energy conversion efficiency is 1~2%. The band gap of the electrode is 1.43eV. The flatband potential of -1.1~-1.2V (VS·SCE)is determined by the measurement of the differential capacitance and the maximum open-circuit photopotential. Furthermore, the influence of the counter electrodes and electrolytes on the conversion efficiency have been tested.

DETERMINATION OF DEEP LEVER CENTERS ON GaAs MESFET BY CONDUCTANCE DLTS

SHENG CHI, ZHAN QIANBAO

1985, 3(1):  52-56. 

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A conductance DLTS is developed to detect traps in epitaxial grown and ion-implanted GaAs MESFETS. The trap of E_V+0.91eV which is generally regarded as Cr level and the trap of E_V+0.52eV exist in both devices. Besides, a level of E_V 4-0.71eV exists only in ion-implanted devices with large noise. A large and wide energy band at E_V+0.2~E_V+0.5eV is attributed to interface state which exists only in epitaxial large-noise FET and degraded devices.
The trap in ion-implanted GaAs FET can be decreased to a level of the best-quality epitaxial FET.

ANALYSIS OF WEIGHTED FILTERING

ZHANG RONGXIN

1985, 3(1):  57-64. 

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In this paper, different fading memory filters have been discussed and a new technique to get weighted Sequences is given by using weight function sequence. This makes it possible to choose weight sequence according to majorization of some result functions.

AN IMPROVED PROGRAM USED FOR SEARCHING AND MATCHING OF X-RAY POWDER DIFFRACTION PATTERNS

LIN TEINHUI, ZHANG SAIZHU, CHEN LIJUN, CAIXINXING

1985, 3(1):  65-73. 

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A program used for searching and matching of X-ray powder diffraction patterns was written and a library for this purpose was built by using FORTRAN-IV language. The program has been tested by using it to sdarch tens of patterns. Generally, all the existing phases can be searched out and the number of missearchings is not so large. In comparison with other programs, briefly, two major improvements have been made in the present program:(1) a so-called 'substance-type-discrimination' was introduced into the searching process which can reduce missearching remarkably; (2) a new method for quantitative intensity-matching was proposed, based on the least square method. It can give better results than the Frevel's method and provide more information to discriminate the canditates further.

SYNTHESIS OF POLYSULFONE-(OR POLYETHERSULFONE) EPOXY RESINBLOCK COPOLYMERS

DIKG YOUJUN, LEI YUQING, WANG XINRONG

1985, 3(1):  74-81. 

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Polysulfone (or Polyethersulfone)-epoxy resin was synthesized by the interaction of dihydroxyl-terminated polysulfone (or polyethersnlfone) oligomers with epoxy resin.
The block copolymers have excellent adhesive properties with metals such as Al, Cu and Pe at high temperature (150℃).

FOCUSING METHOD FOR NONDESTRUCTIVE MEASUREMENT OF OPTICAL FIBER AND PREFORM INDEX PROFILE

XU KUODA, ZHANG ZHAONAN, HOU YUANGQINQ

1985, 3(1):  82-87. 

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The focusing method is a nondestructive one for obtaining the refractive-index profile of fibers and preforms of different sizes. An uniform incoherent collimated light beam is passed transversely through the fiber or preform immersed in an index matching oil and the light intensity distribution is directly detected by a CdS photo conductive detector, or recorded on an X-Y recorder with the aid of silicon vidicon camera and sampling line oscilloscope. The refractive-index profile is finally computed by means of a microcomputer.
This paper relates briefly the principle of the method and experimental details and also gives the quantitative results and conclusions.

DISPERSION MEASUREMENT IN SINGLE-MODE FIBERS

HUANG ZHAOMING, YAO SHOUQUAN, ZHANG GUFAN

1985, 3(1):  88-91. 

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We have measured dispersion of single-mode fibers by means of time domain and frequency domain methods at 0.82μm. Since single-mode fibers designed for longer wavelengths have 2 or 3 modes at this wavelength, it is necessary to separate ntermodal dispersion from singlemode dispersion. The two methods gave the same iresult.

THE APPLICATION OF THE BOUNDARY ELEMENT METHOD TO SOLVING FREE BOUNDARY PROBLEMS

ZHENG JIADONG

1985, 3(1):  92-94. 

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In this paper the free boundary problems are solved with boundary element method. The practical free surface of.seepage flow of an earth dam is calculated successfully.