Table of Content

30 June 1991, Volume 9 Issue 2

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Articles

SIMILARITY OF NONLINEAR RLC CIRCUITS TO THE INTRINSIC OPTICAL BISTABLE SYSTEM

LIU CUIHONG, WU TINGWAN, ZHANG XIAODONG, OU FA

1991, 9(2):  95-103. 

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This paper reveals in dynamical equations the similarity of the nonlinear ELC circuits to the intrinsic optical bistable system (OBS) The bistability and the related transient behaviors of the RLC circuits of ferromagnetics are studied, through the imitative permeability function which is obtained by the least-square method according to some experimental data.

MÖSSBAUER SPECTROSCOPIC STUDIES OF THE OXIDATION OF IRON IMMERSED IN HYDROCHLORIC ACID AND ANTI-OXIDATION OF CORROSION INHIBITOR

ZHOU SUNXUAN, ZHENG JIAXIN

1991, 9(2):  104-108. 

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The oxides of iron immersed in hydrochloric acid and the antioxidation of the inhibitor have been studied by the Conversion Electron Mössbauer Spectroscopy (OEMS). The oxides of iron immersed in hydrochloric acid are β-FeOOH and γ-FeOOH, the latter being the dominant composition. The inhibitor in hydrochloric acid slows down the oxidation progress of iron immersed in hydrochloric acid. Furthermore, the better the inhibition ability of the inhibitor for iron in bydrochloric acid, the slower the oxidation progress of iron in the air. At the end of this paper, the anti-oxidation mechanism of the inhibitor is discussed.

STUDIES ON THE BLENDING OF POLYCARBONATE WITH STYRENE-MALEIC ANHYDRIDE COPOLYMER

YE JINYONG, LUO HUIZIONG

1991, 9(2):  109-116. 

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The compatibility of polycarbonate (PC) with styrene-maleic anhydride copolymer (SMa) varies according to the Ma content of SMa, good compatibility being achieved when the Ma content of SMa is about 26-28 mole%.
Results from DSC, FTIR, ¹³C-NMR and SEM studies indicate a graft copolymerization takes p]aoe between PC and SMa during the process of melt blending.

INVESTIGATION OF ALUMINIUM NITRIDE THIN FILMTRANSDUCERS

LIUFU De, LIANG ZINAN

1991, 9(2):  117-122. 

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A one-dimension longitudinal model microwave transducer made with high quality piezoele otric aluminium nitride thin films is reported in this paper. These films are deposited by d. o. planar magnetron sputtering on a z-LiNbO₃ propagation medium. With these films, a microwave bulk acoustic wave delay line is fabricated which has a time delay of 1.83 μs, insertion loss of 22 dB, and bandwidth (3 dB) of 13% under the central frequency of 2.21 GHz. For such piezoelectric films used in the microwave frequency, the electromechanical coupling coefficient (kt) of 0.13 is obtained by the comparison of theoretical input admittance values of the transducer with the measured values. This kt is smaller than that of the bulk material which may be mainly caused by the derivation and inversion of c-axis orientation in crystallites. The experimental results also show that there is an equivalent series resistance in the, transducer that may illustrate why the tuned and matched transducer has losses.

SUPERLOW-PASS FILTER FREQUENCY RESPONSE TEST BY MICROCOMPUTER

XU CHENGTANG

1991, 9(2):  123-128. 

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This paper introduces how to best the frequency response of a superlow-pass filter by a microcomputer. The customary signal exciting the filter is a slowly swept sine. Due to the development of digital signal processing algorithms and especially the efficient implementation of the discrete Fourier transform (DFT) with the fast Fourier transform (FFT), it becomes possible to use more complex input signals. Instead of exciting the filter under test frequency by frequency, it is possible to generate arbitrary waveform with a broadband spectrum, using a digital-to-analog (D/A) converter, to gather all the spectral information in one measurement. In many applications, the prescribed spectral shape is a flab spectrum. One waveform that has such a flat spectrum is a sharp impulse, but in this case all the power is concentrated at one point in time, leading to a maximum peak power. This results in an important reduction of the measurement time, bub also in an undesired accuracy loss of the measurement results if no spacial precautions were taken. According to Schroeder's method a waveform that is the sum of a number of harmonically related cosine waves with equal amplitudes and with modulated phases for reducing the peak-factor has been generated. The data file, which is discretely calculated by the microcomputer according to one period of the waveform, has been created. While the filter is tested, the data file will be read into the memory of the microcomputer. By interrupting the CPU of the microcomputer at regular intervals, the waveform is sent to the filter through the digital-to-analog converter.At the same time, the output of the filter is collected by the microcomputer through an analog-to-digital converter. The frequency response of the filter can be obtained by FFT for the output. Thus the test can be performed in a shorter time with better accuracy.

ENERGY BAND STRUCTURES OF CsC₈

Guo JIANQING, Lu DONG

1991, 9(2):  129-134. 

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The band structures of cesium graphite intercalation compound CsC₈ is calculated with the method put forward by Ohno, Nakao and Kamimura. The band bottom of 6S electrons of cesium lies 3.6eV above the Fermi level. Hence all the valence electrons of the cesium atom layer transfer to the antibonding π band of graphite carbon layers. The obtained band structure is in good agreement with that of other calculations.

THE PHONON DISPERSION CURVES OF DIAMOND, Si, Ge and α-Sn

Zi JIAN, ZHANG KAIMING

1991, 9(2):  135-139. 

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The phonon dispersion curves of diamond, Si, Ge and α-Sn are calculated using the six-parameter Born-von Karman model. Except for the TA modes of Si, Ge and αSn, the calculated results are in good agreement with the experimental data.

A REAL TIME STATISTICAL ANALYSIS METHODOLOGY AND APPLICATION FOR INTEGRATED CIRCUIT PROCESS

He YIE

1991, 9(2):  140-144. 

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A real time statistical analysis methodology of IC manufacturing process in combination with an experimental design is presented. The modelling analysis results of the real CMOS and NMOS IC indi cate that the most possible process step which is responsible for the unusual device or circuit performance stribution can be found using the methodology to analyze the measurementl diresults obtained from chips in the process line.

FINITE DIFFERENCE METHODS FOR ENHANCED OIL RECOVERY SIMULATION OF CHEMICAL FLOODING

YUAN YIRANG, WANG WBNQIA

1991, 9(2):  145-153. 

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A two-dimensional, multiphase, compressible, compositional reservoir simulator has been developed, and applied to micellar/polymer flooding. The mathematical model for the two-dimensional enhanced oil recovery simulation can be described by a system of nonlinear partial differential equations. We put forward a class of finite difference scheme. The estimates obtained are the best possible.

CALCULATION OF BEST AFFINE APPROXIMATIONS OF SYMMETRIC FUNCTIONS

Wu CHUANKuN

1991, 9(2):  154-160. 

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This paper presents an efficient algorithm for calculating the best affine approximations of symmetric functions by using spectral techniques.

A CLASS OF INVERSE PROBLEMS OF ORDINARY DIFFERENTIAL EQUATION IN MECHANICS

WU XlNYUAN

1991, 9(2):  161-168. 

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This paper puts forward a class of inverse problems of ordinary differential equations in mechanics, and gives a numerical method for dealing with them.

BOOLEAN METHOD FOR SOLVING DECI SION PROCESSES

LIU YONGCAI

1991, 9(2):  169-176. 

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In the enormous number of decision processes of scientific experiments, engineering tests, medical diagnoses, environment monitoring, etc., we usually meet, such problems:how can the objective laws be deduced from the limited number of trials and how onn the inherent cause-effect relationships be revealed? In this paper, a Boolean method for solving such problems is given.

DECOMPOSITION OF RECOGNIZABLE STRONG CODES

QIU WEIDE, ZHANG LING

1991, 9(2):  177-181. 

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In this paper we give the following results:(1)Every group is a syntactic monoid of language X^* with X being a maximal strong code; (2) Recognizable strong code X can decompose into two recognizable strong codes iff there is a proper congruence in the minimal automaton recongnizing X^*; (3)the maximal strong code, whose syntactic monoid is a simple group, is called a simple maximal strong code. Any recognizable strong code can decompose into a finite number of simple recognizable strong codes.

Research Notes

GROWTH AND OPTICAL PROPERTIES OF SCINTILLATION CRYSTAL CdWO₄

Xu JUN, MA XIAOSHAN, Wu GUANGZHAO, SHEN YAFANG, ZHANG XINMIN, Gu JI

1991, 9(2):  182-184. 

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Large size crystal CdWO₄ has been successfully grown with the CZ method heated by a high-frequency inducing generator. We find that the oxygen vacancy and Fe³⁺ impurities are the main reasons for crystal colouration. The luminescence spectra of crystal CdWO₄ have also been measured.

X-RAY DIFFRACTOMETRY OF THE STRUCTURE OF In_xGa_1-xAs/GaAs SUPERLATTICE

CHONG FUMIN, CHEN JINGYI

1991, 9(2):  185-188. 

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A conventional X-ray diffractometer is used to analyse the structure of In_xGa_1-x As/GaAs superlattice. Kinematical approximation is employed in the analysis. The results are similar to those got by double-crystal diffractometry The differences between the two methods are also discussed.