Table of Content

30 June 1990, Volume 8 Issue 2

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Articles

“ZOU MODEL” OF EL2 DEFECT IN GaAs in memory of Prof. Zou Yuanxi

WANG GUANGYU

1990, 8(2):  95-102. 

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Prof. Zou Yuanxi had explored the nature of some native derects in compound semiconductors by means of physicochemical method over 20 years. We sincerely introduce his science ideas and profound fruits in the identification of EL2 (the most important deep level in GaAs) in this paper,and express to cherish our deep memory of him.

THE PRESSURE EFFECT OF THE NiCr-NiSi THERMOCOUPLE AT LOW TEMPERATURE

HUANG TONGKAI, GU JINMO, JIN BIANJIN

1990, 8(2):  103-106. 

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We measured (1) the thermo-emf of the NiCr-NiSi thermocouple at various temperatures and (2) the pressure effect on the thermo-emf of this thermocouple at room and liquid nitrogen temperature up to 18 kilobar. A method of pressure-emfcorrection was given.

LASER SELECTED IONIZATION OF Rb AND MEASUREMENT OF ISOTOPE SHIFT ON Rb

LU YIQUN

1990, 8(2):  107-111. 

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In a heat pipe furnace, Rb atoms, pumped by two-photon Doppler tree absorption (760.1 nm), are excited from the ground state 5S_1/2 to state 7S. Then the atoms are excited to the ionization state by Nd·YAG laser. The signals of the ions of Rb are amplified by the look-in amplifier and then enter the x-y record. Selected ionization signals of Rb⁸⁵ and Rb⁸⁷ are observed, and the isotope shift of Rb(7S) is obtained. The super-fine structure of Rb (5S→7S) has also been observed.

NEW Q ENHANCED SWITCHED-CAPACITOR FILTERS

WU JIE

1990, 8(2):  112-116. 

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A new Q enhanced technique is presented, and two new switched-capacitor filters based on the technique are proposed. Design equations and optimal solutions for capacitor spread are obtained. Computation shows that the capacitor spread for the proposed circuits can be significantly reduced.

SURFACE LATERAL ELECTRIC FIELD FOR LDD MOSFET AND ITS APPLICATION

CHEN XIAO, EUAN GANG, ZHANG QIANLING

1990, 8(2):  117-125. 

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In this paper, an analytical model of the surface lateral electric field for LDD MOSFET is presented. This model contains geometric and doping parameters of LDD MOSFET. It can be used to calculate the surface lateral electric field of LDD MOSFET which has lightly doped drain regions of different lengths, junction depths and doping concentrations, Using this model, the electric field of the conventional and graded drain MOSFET can also be calculated. The result obtained from this model is identical with the numerical result of FD-MINIMOS. This model can also be applied to calculate the substrate current and breakdown voltage. According to this model, the optimal geometric and doping parameters can be easily determined. The present model provides a fast method for extracting the related parameters and is a convenient tool for the LDD MOSFET design.

A METHOD FOR THE DETERMINATION OF ENERGY GAP IN Si TRANSISTOR

ZHEN JIANG, FONG YAOLAN, WEI TONGLI

1990, 8(2):  126-130. 

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Energy gap is one of the most important physical parameters in Si transisitors. Based on the temperature dependence of the part of the reverse diffusion current in the emitter and the forward voltage of the collector-base PN junction, a new method for the determination of energy gap in regions of the Si transistor is presented in this paper. Because of the heavy doping effect, the carrier's Femi-Dirac statistical distribution is considered. The method only requires measurement of the temperature dependence of the DO parameter; therefore the result is accurate.

THE PRECIPITATION OF γ' PHASE IN ELINVAR ALLOY BY MOSSBAUER EFFECT

QIAN XIANGRONG, CHEN FUSHI, JIN HUIJUAN

1990, 8(2):  131-137. 

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The Mössbauer spectra of Ni42CrTi Elinvar alloy in quenching, aged and cold-working states are measured respectively. On the basis of the spectra, the distributions of internal fields are calculated. The experimental P(H) curves spread widely and are decomposed into three Gaussian curves, which represent three preferential configurations of iron atoms. The variation in internal fields can be referred to the precipitation of γ' phase in the alloys, which results in the variation in the neighbouring environment of iron atoms. Comparing the relative areas under the probability peaks at different internal fields in P(H) curves, the relative amounts of γ phases in different states of alloys can be deduced. In addition, the intensity ratio of the components of Mössbauer spectrum indicates the extent of preferential orientation of magnetic moments.

SYNTHESIS, PROPERTIES AND BIOMEDICAL APPLICATION OF SEGMENTED POLYETHER URETHANE EXTENDED WITH DIOL

HUANG ZUXIU, FENG XINDB

1990, 8(2):  138-144. 

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A series of segmented polyether urethanes (SPEU) were synthesized from 4, 4-diphenylemthane diisocyanate (MDI), polytetramethylene glycol (PTMG) and low molecular weight diols as the chain extender by the two-step solution polymerization with a mixture of dimethyl sulfoxide (DMSO) and methyl isobutyl ketone (MIBK) as the solvent. The effect of the reaction temperature on the intrinsic viscosity of the SPEU was studied. There was a slight change in viscosity of the polymers in the reaction temperature range of 60~110℃. The high molecular weight polymers without crosslinking were obtained by using a lower reaction temperature (at about 60℃). The effects of the structure and amount of the chain extender on the mechanical properties of the SPEU were discussed. Some of them can be used in the balloon of the Intra Aortic Balloon Pump (IABP) which exhibited excellent mechanical properties and blood compatibility.

STUDY ON THE PHASE-SEPARATION OF EPOXY RESIN TOUGHENED BY MULTI-FUNCTIONAL RUBBER

LI SHANJUN, WANG HONGBIN, YE JINYONG

1990, 8(2):  145-150. 

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The morphology and process of phase-separation of toughening epoxy resin with epoxy-functional poly(n-butyl acrylate) (ETPnBA) and carboxy-functional poly (n-butyl acrylate) (CTPnBA) rubbers were studied by the optical microscope. The effect of curing conditions and prereact time of rubber and epoxy resin on the phase-separation were investigated. The control of the phase-separation and the mechanism of the phase-separation of the modified epoxy resin (by ETPnBA and CTPnBA rubbers) were discussed.

SEPARATION OF WATER-ETHANOL MIXTURES BY PERVAPORATION THROUGH CELLULOSE ACETATE MEMBRANES

WU BINGKUN, SHI YANQIAO, ZHANG SHIMIN, CHENG GANJU, OHEN GUANWEN

1990, 8(2):  151-157. 

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In this paper, the cellulose diacetate (CA) dense membrane, CA reverse osmosis (RO) membrane and cellulose triacetate (CTA) dense membrane were used for the separation of water-ethanol mixtures by pervaporation (PV). The effect of acetyl group contents and the membrane morphology on PV characteristics are discussed. For CA and CTA dense membranes, the total flux (J) and the water-ethanol selectivity coefficient (α) vary with feed compositions in the same way. But for all the feed compositions the J of the CTA dense membrane is slightly higher than that of the CA dense membrane. The J and α of the CA RO membrane vary with feed compositions in the opposite way as the CA dense membrane does.

THE RESEARCH ON ELECTRICAL AND HYDRAULIC CONTROL FOR A TRIAXIAL TESTING DEVICE

CHEN XIAOGUANG, XIU GUANGGENG, PAN GUODONG, WANG SHUHAI

1990, 8(2):  158-164. 

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In this paper, a multi-purpose triaxial testing device is described. The device, controlled by a computer, is able to control loads in three dimensions independently. The deformation of the specimen is monitored by the grating type displacement transducers. Their counting numbers could be sampled at the same time.

THE TEMPORAL PREDICATES-EVENTS NETS WITH CONFIDENCE The Earthquake Forecast and Decision Model

ZHANG YULI, YIN BAIWEN

1990, 8(2):  165-169. 

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According to the requirements of earthquke forecast decision, and using the survey of Petri nets and the knowledge representation of essential entities and inferences of temporal logics, we propose the model of temporal predicates-events nets with confidence. It can express, imply and verify the causality of manifold elements, and can process concurrently and dynamically also. Furthermore, this model can be applied to other forecast and decision problems, such as those in military affairs, meteorology, marketing, etc.

DIRECT METHODS FOR MONOTONE DECOMPOSITION OF BOOLEAN FUNCTIONS (Ⅱ)

LIU YONGCAI

1990, 8(2):  170-176. 

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For those Boolean functions which can be monotonically decomposed, we present two classes of direct methods for monotone decomposition again in this paper. The first class of methods is available for canonical product of sums form and the second one is available for arbitrary boolean expressions. They also can be performed on computers easily.

Research Notes

TEMPERATURE DEPENDENCE OF A POLARON IN SEMI-INFINITE POLAR CRYSTAL

ZHAO XUNJIE, GU SHIWEI

1990, 8(2):  177-180. 

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Taking into account the interaction of an electron with both Lo and So phonons as well as the image potential at finite temperature, we study the effective Hamiltonian of a polaron in a semi-infinite polar crystal. The temperature dependence on the self-induced polaron potential, the effective mass and the depth of the dead layer is given.

NUMERI CAL CALCULATION FOR STATIC PERMANENT MAGNETIC CIRCUIT

XU SHUJUN, SHI TAIHUA

1990, 8(2):  181-184. 

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Up to now, the empirical formula is usually used to design the permanent magnet design. Because of the nonlinear characteric of the material, the design formula is difficult to correct; it is only a simplified approximation. The error may be great, which will cause heavy economical less, if expensive permanent materials, such as the rare earth permanent material, are used. This paper describes the result of the numerical calculation method for such a problem. This method can select the optimum working condition, and by making a reasonable compromise, good performance can be got at a lower cost. The authors calculated a magnetic circuit used for a moving-coil meter and obtained results which agree with the measured values.

THE DETERMINATION OF PSEUDO-KOSSEL DIFFRACTION INDICES BY SIMULATION METHOD

ZHANG JIANZHONG, FAN DEPEI, ZHOU BING

1990, 8(2):  185-188. 

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The X-ray pseudo-Kossel diffraction indices of crystals can be determined on a large scale by using a simulation method, which is capable of indicating the indices of complete, incomplete or even severely broken.lines. By means of this method, the diffraction patterns could be made full use of and the standard diagrams of pseudo-Kossel diffraction can be offered.