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30 September 1988, Volume 6 Issue 3
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Articles
THE CHINESE CONTRIBUTION TO THE STUDY OF FIELDS AND WAVES IN MEMORY OF 100TH ANNIVERSARY OF HEINRICH HERTZ DISCOVERY OF ELECTROMAGNETIC WAVES
HUANG HUNGCHIA
1988, 6(3): 189-196.
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In this paper, the author attempts to review the Chinese contribution to the study of fields and waves, with some special reference to microwaves and optics of the electromagnetic spectrum. Like Maxwell, who accomplished at one blow the theoretical prediction of the existence of electromagetic waves and the identification of light and electromagnetic waves, Hertz discovered experimentally electromagnetic waves and simultaneously, the identity of electromagnetic waves and light. The Chinese are known to have observed the phenomena associated with magnetism, electricity and light, and found their applications, since remote antiquity. Interestingly enough, a long history of two thousand years had elapsed before man began to understand electromagnetism and optics as a unified science at the time of Faraday-Maxwell-Hertz. Some aspects of the Chinese study of fields and waves during recent decades, which are related to the impact of Heinrich Hertz' discovery, are sketched in this paper according to the above theme.
DEVELOPMENT IN THE RESEARCH ON PLASTIC BENDING OF PLATES
YU TONGXI, ZHANG LIANGCHI
1988, 6(3): 197-202.
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Taking the plastic forming processes of strips and plates, which, are widely applied in modern manufacturing, as background, this paper presents a systematic introduction to the research methods and results on the elastic-plastic bending, springback and wrinkling of plates, made by the authors in recent years. The calculation of the springback of strips and shaped beams after their elastic-plastic bending has been solved completely. The so-called Plastica equations, which describe the large elastic-plastic deflection of flexible stripe, have both theoretical and practical significances. The work on the double-curvature bending and stamping of plates, especially the investigation on the role of membrane forces in the large elastic-plastic deformation of plates, is creative. In the new research field of the elastic-plastic wrinkling of plates during forming processes, energy method and other semi-analytical methods have been developed and successfully applied to solving particular problems; the results obtained are in good agreement with those of the experiment.
INVERSION OF TWO-DIMENSIONAL ELASTIC WAVE EQUATION WITH TWO VARIABLES WITHIN BORN APPROXIMATION
CHENG JIANCHUN, WEI YU
1988, 6(3): 203-208.
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In this paper, the P-wave scattering equation of a weak inhomogeneous elastic medium is derived from the elastic wave equation of an isotropic medium. The inversion procedure of P-wave velocity and density distributions of the elastic medium within Born approximation is presented, by using the extrapolating field methods developed in Refs.[1]and[2].
ANALYSIS OF SINGULARITIES ARISING IN EM FIELD COMPUTATION
HONG WEI
1988, 6(3): 209-214.
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Some singularities encountered in the EM field computation are discussed in this paper. Several approaches for dealing with the singularities and their error estimations are given.
THEORETICAL ANALYSIS FOR THE LATERALMODE OF SECTIONAL CONSTRICTED PLANAR COMPOSITE CAVITY DH LASERS
DU GUOTONG, LIU ZHONGYU, GAO DINGSAN
1988, 6(3): 215-221.
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In this paper, the theoretical analysis for the improvement of lateral mode selectivity and stability in sectional constricted planar composite cavity lasers (SCP) is made, and the effects of structural parameters on lateral mode selectivity and stability are numerically calculated. The calculated results indicate that, if the structural parameters and the ratio between CDH section and OS section cavity lengths are selected appropriately, the output power of the fundamental lateral mode in SCP lasers is more than 3-4 times that in ridge-guide CDH lasers.
EFFECTS OF SEVERAL KINDS OF ANISOTROPY ONMAGNETIC COERCIVITY
H
c
OF IRONOXIDES DURING PHASE CHANGES
YAO KANYI, YANG ZHIJUN
1988, 6(3): 222-226.
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The variations of magnetic coercivity (
H
c
) during the phase changes between Fe
3
O
4
and
γ
-Fe
2
O
3
for granular powders and continous thin films are investigated. Whether during the oxidation from Fe
3
O
4
to
γ
-Fe
2
O
3
or during the reduction from
γ
-Fe
2
O
3
to Fe
3
O
4
, the increases in
H
c
of the spherical particles and the continous thin films are mainly caused by the stress anisotropy, and the decreases in
H
c
of the acicular particles are affected with the shape anisotropy related to the changes in particle size.
INVESTIGATION OF OHMIC CONTACT ON HIGH RESISTIVITY SILICON SINGLE CRYSTAL
CHEN CUNLI, CHEN ZHENGFU, CHEN YIPING, ZHONG XINQUN
1988, 6(3): 227-232.
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By appropriately controlling the surface quality of a silicon wafer and using the electrical sparking technique, high boron-alloy (BAlNiIn) and high phosphorus-alloy (PSbAuIn) can simply be used to make good ohmic contacts on silicon materials of resistivity as high as 20000Ωcm and 4000Ωcm for the P-type and N-type, respectively. Even after 30 times of temperature circulation from 300 K to 77 K, the linear I-V property of the ohmic contacts still remains. The ohmic contact formations and carrier transport characteristics are discussed, based on the current-voltage and specific contact resistance measurements at different temperatures, the ion microprobe analysis, and the calculation of specific contact resistance of metal to silicon as a function of doping concentration. This method has been successfully applied to the measurements of impurity compensation and carrier mobility on high resistivity silicon materials.
THE ELECTRICAL EFFECTS OF GOLD AND PLATINUM AT THE Si-Al
2
O
3
INTERFACE
LI SIYUAN, YIN CHIPING, ZHANG TONGJUN, WANG YUZHEN, JIA XIAOTIAN
1988, 6(3): 233-240.
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In this paper, the electrical effects of gold (Au) and platinum (Pt) at the Si-Al
2
O
3
interface and the annealing behaviour of these effects tinder different annealing conditions are studied. The results of the photoelectron spectroscopy of the Si-Al
2
O
3
system are presented also. Further, the action mechanism of Au and Pt at the interface is discussed.
STUDIES IN MAGNETIC PROPERTIES OF NdFeB ALLOYS WITH LOW PURITY NEODYMIUM
GONG WEI, WANG YIZHONG, FENG MINYING, WANG ZHENXI, HUANG YONGCHBNG, CAO YONGJING
1988, 6(3): 241-244.
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By substituting low purity neodymium for the high purity one, NdFeB permanent magnets of (BH)
max
=41 MGOe were prepared by powder metallurgy. Several properties of NdFeB alloys were measured by means of x-ray diffraction, the differential thermal analyzer, magnetic balance, extracting sample magnetometer and pulse high magnetic field apparatus respectively. The results show that there is a peak of phase transition at 1439K, and the abnormal phenomenon on the magnetic hysteresis loop at low temperature originates from the conical magneto-crystalline anisotropy of the major phase Nd
2
Fe
14
in the NdFeB alloys.
TEMPERATURE DEPENDENCE OF MAGNETIZATION FOR AMORPHOUS Fe
90-
x
Co
x
Zr
10
ALLOYS
ZHAN WENSHAN, SHEN BAOGEN, ZHAO JIANGAO, ZHENG XIAONIAN
1988, 6(3): 245-248.
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Amorphous Fe
90-
x
Co
x
Zr
10
(0 ≤
x
≤ 90) alloys were prepared by melt-spinning under argon atmosphere. The temperature dependence of the magnetization of samples was studied. Experiments show that the Curie temperature increases with increasing Co content, but the crystallization temperature decreases. The magnetization
σ
(
RT
) at 300K exhibits a maximal value of 161 emu/g. The Co content dependence of
σ
(
RT
) is discussed.
THE GROWTH OF CADMIUN TELLURIDE SINGLECRYSTAL FROM THE MELT UNDER A VAPOR PHASE WITH CONTROLLED Cd PARTIAL PRESSURE
SANG WENBIN, YU MEIYUN, WU WENHAI
1988, 6(3): 249-254.
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On the basis of the equilibrium Cd partial pressure over the cadmium telluride melt determined by means of optical absorbance measurement, cadmium telluride single crystals were grown from the melt under a vapor phase with controlled Cd partial pressure. The deviation of the crystal composition from the stoichiometric was effectively controlled; The crystal perfection, electrical properties and optical properties were improved obviously. The values of some properties were of the same order of magnitude or better than the best data reported in the literature.
The tentative use of our cadmium telluride single crystals to fabricate the temperature sensor and Liquid junction optochemical cell, and to act as the substrate for the hot wall epitaxial growth of cadmium telluride film yielded very satisfactory results.
EQUILIBRIUM CALCULATIONS ON THE HYDROGEN PARTITION OF SOCl
2
AND CF
4
IN MCVD SILICA SYSTEM
YAN YIMIN, KUO CHUKUN, ZHANG YINGHUA
1988, 6(3): 255-259.
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The equilibria of the systems O
2
-H
2
O-CH
4
-SOCl
2
-SiO
2
and O
2
-H
2
O-CH
4
-CF
4
-SiO
2
for compositions of interest to the MCVD silica fibre process have been calculated. The equilibrating hydroxyl concentration in the resulting SiO
2
glass at 1073-2573K is given and the ability of SOCl
2
and CF
4
to remove hydrogen from the chemical deposition system is discussed.
STUDY ON UNCYCLIZED AND UNDEGRADED PROCESS OFPHOTOCROSSLINKING REACTION OF BENZOPHENONE-SENSITIZED 3, 4-POLYISOPRENE
HUANG JUNLIAN, YU TONGYIN
1988, 6(3): 260-264.
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It was found that the photocrosslinking reaction of benzophenone-sensitized 3, 4-polyisoprene was an uncyclized process by means of IR, NMR and chemical analysis.
The measurement of GPC proved that the molecular weight distribution of benzophenone-sensitized 3, 4-polyisoprene which was irradiated by an 80 W high pressure Hg lamp was the same as unsensitized 3, 4-polyisoprene.
The conclusion therefore, is that the photocrosslinking reaction of this system was an uncyclized and undegraded process.
A STUDY ON ADHESIVES FOR RETORTABLE POUCH
ZHOU QINGLI, CAO YONGXING, ZHOU JIANHUA
1988, 6(3): 265-270.
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The laminated film of the retortable pouch is made up of PET, Al and PP films. It is known that the types of adhesives for laminating the films have strong influences on the properties of the retortable pouch. The adhesive studied for laminating the PET-Al film was a polyether type of polyurethane adhesive. whose peel strength of adhesion amounted to 6.3N/2cm. The adhesive for laminating Al-PP films was a maleic acid modified PP; its preparation and properties were well studied; the peel strength of adhesion amounted to 8.1N/2cm. These PP adhesives have been proved to be poisonless through animals' toxicity test. Both adhesives have been applied to the manufacture of retortable pouches in Wuhan Printing House, Hubei Province.
SIMS INVESTIGATION OF ION CLUSTERS ON MAGNESIUM
WANG NAILI, GAO PEIDE, LIU HONGLIN, CHEN NIANYI
1988, 6(3): 271-274.
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The constructure and isotope abundance of atom clusters on clean magnesium surface were measured by SIMS. The experimental results of their constructure types agreed with those calculated by the ab initio method of quantum chemistry. Therefore, it was obtained from both experiment and theoretical computation that Mg
+
and Mg
2
+
should be stable than Mg
2
2+
.
MODEL STUDY OF THE EFFECTS OF THE FINITE ENERGY RESOLUTION IN THE EXAFS DATA ANALYSIS
ZHENG YU, HUA ZHONGYI
1988, 6(3): 275-277.
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The effects of the finite energy resolution of the spectrometer on the EXAFS structural determination of the material having two types of neighboring atoms have been investigated by model calculations. And the solutions to overcoming the effects have been also discussed.
A STUDY ON THE CHANGE OF CHEMICAL STRUCTUREOF THREE POLYACRYLONITRILE FIBRES DURING LOW TEMPERATURE PYROLYSIS
ZHAO GENXIANG, CHEN BANGJIE
1988, 6(3): 278-282.
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The chemical structure changes of three polyacrylonitrile fibres used for making carbon fibres were measured continuously during low temperature (350℃) pyrolysis in air atmosphere by the in-situ Fourier transform infrared spectroscopic method. From the information of the qualitative and quantitative spectra, it was obtained that the dehyrogenation and oxidation reactions proceeded mainly after the cyclization reaction for the British fibre, the dehyrogenation reaction occurred mainly after cyclization and oxidation reactions for the Jilin fibre, but the cyclization and dehyrogenation reactions occurred mainly before the oxidation reaction for the Lanzhou fibre. It was shown that the maximum length of cycloforming sequence for the British fibre was obtained at 260℃, for the Lanzhou fibre at 300℃, and for the Jilin fibre at 320℃. The length of cycloforming sequence of the Lanzhou fibre was the shortest. Wherefore, the results are valuable, and it may be expected that high performance PAN-carbon fibres can be obtained by improving the operation conditions of carbonization.
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Bimonthly, Founded in 1983
Editor-in-Chief:Wang Tingyun
ISSN 0255-8297
CN 31-1404/N