Table of Content

31 March 1986, Volume 4 Issue 1

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Articles

THE PRINCIPLE OF FEL OPERATION IN A LONGITUDINAL UNIFORM MAGNETIC FIELD

CHENG GANZHEN

1986, 4(1):  1-7. 

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This article discusses the principle of FEL operation in a longitudinal uniform magnetic field for the main problems in the development of FEL. A new approach of energy compensation is presented as a new basis for the development of FELresearch.

THEORY AND COMPUTATIONS FOR 3-DIMENSIONAL PROBLEMS OF MULTI-CRACKS (Ⅱ) NUMERICAL COMPUTATIONS AND EXAMPLES

OUYANG CHANG, XU LINLIN

1986, 4(1):  8-15. 

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This is Sec. Ⅱ of the paper "Theory and Computations for 3-Dimensional Problems of Multi-Cracks",[1]. With the method and formulations given in[1], here we give numerical results for examples of two parallel oraoks with the same radius but in different planes. Detailed results are ghiven for various oases which indicate the interaction between cracks. It is shown that the method proposed here is quite workable, and the results obtained enlarge the contents of "Handbook of Stress Intensity Factors"[2, 3].

A STUDY ON THE SPACE CHARGE SCATTERING CENTERS IN UNDOPED VPE GaAs

SHAO JIUAST, ZHOU YUAKXI, PENG RUIWU

1986, 4(1):  16-21. 

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In this paper, the product of space charge density and scattering cross section has been calculated from the measured room temperature mobility by the use of Matthiessen's rule. A linear relationship between N_SCA and N_D has been found. On the basis of this relationship, the space charge center presented in undoped VPE GaAs epilayers is postulated to be a complex of the SiGa (O₁, V₁) type.
Besides, an in site sulpher remover has been designed and used in the AsCl₃-Ga-H₂ epitaxial system for the first time, and found to be quite effective in depressing the carrier concentration of the epilayers.

THE EFFECT OF PRESSURES ON THE DIFFUSE PHASE TRANSITIONS OF POLYCRYSTAL FERROELECTRIC PbMg_1/3Nb_2/3O₃

JIN BIANJUN, ZHONG FAN, WANG XIANGQTJAN, SHEN JIAQI

1986, 4(1):  22-27. 

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The behaviour of the dielectric constant s of polyerystal ferroelectric PbMg_1/3 Nb_2/3O₃ was measured in the temperature range -196℃-50℃ at the different pressures and the ε-P relation was obtained. The results were analysed by the statistical model of diffuse phase transition and the effect of pressures on diffuse phase transitions was discussed.

THE INPUT IMMITTANCES OF COUPLED ANTENNAS OF ARBITRARY-SHAPED WIRES

ZHANG WENXUN

1986, 4(1):  28-35. 

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In this paper the simultaneous integro-differential equations of two arbitrary-shaped thin-wire antennas with point-exitation are given. The formulas to determine the input self-and mutual-immittances are derived using the moment method. These formulas can be simplified by means of rational selection of basis functions and weighting functions. The mutual impedances of parallel circular-loops and coplanar dipoles are calculated as examples respectively, which are found to agree with the experimental data.

COUPLING COEFFICIENTS FOR DISTRIBUTED FEEDBACK LASERS

CAO ZHANGQI, FANG JUNXIN

1986, 4(1):  36-42. 

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We have analysed and calculated the coupling coefficients for TE mode of the periodic structure in distributed feedback lasers by the method of characteristic matrix. Simple analytic results of coupling coefficients expressed as functions of film corrugation shape, height and film thickness are here presented. Equations for various corrugation shapes such as rectangular, sinusoidal, symmetrical-triangular and sawtooth are evaluated. It is shown that the accuracy of the formulae we derived is quite good.

SINGLE-MODE FIBER DISPERSION MEASUREMENTS AT 1.3μm WAVELENGTH REGION

YAO HUIHAI, CHEN JUNFU

1986, 4(1):  43-48. 

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The principle of operation, design, construction and measured results of time-domain measurement system using pulse spreading are presented in this paper. All of the elements and devices used in this system are made in China. The system can be used to measure single-mode fiber dispersion at longer wavelength (1.3μm). It is shown by the measured results and analyses that the system is applicable to multi-mode fiber dispersion measurement and photodeteotor response time measurement with high accuracy. For single-mode[fiber dispersion measurement, the relative error can be better than 3% if the test fiber is longer than 10km. When the test fiber is shorter, the relative error becomes worse. However, it is still applicable to identify whether a single-mode fiber meets the dispersion specification of 6ps, kru-nm at 1.3μm wavelength region.

IMPULSE RESPONSE MEASUREMENT THE ELECTROMECHANICAL COUPLING FACTOR k_t OF THICKNESS MODE PIEZOELECTRIC RESONATOR

WANG XIAOGUANG

1986, 4(1):  49-53. 

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The pulse response voltage of a piezoelectric circular disk resonator excited by an external voltage is discussed. The voltage is the superposition of a pulse exponential decay resulted principally from the discharging of the clamped capacity of the resonator through R, the resistance of the circuit, and a decaying high frequency oscillation resulted from the piezoelectric effect of the resonator by the applied pulse voltage.lt is shown that the amplitude of the high frequency oscillation is dependent on the electromechanical coupling factor K of the resonator when adequately adjusting the width of the initial pulse voltage and R, the resistance of the circuit. A new method for measuring thickness model electromechanical coupling factor k_t of the piezoelectric resonator is presented.The advantages of this method are simpler equipments and exact results. It is found that the measuring results of some samples using this method are in good agreement with the data obtained from measuring with the conventional method.

FAST ALGORITHMS FOR TRANSPOSING LARGE MATRICES USING MICROCOMPUTER OR MINICOMPUTER

YU RENKANG, LIU CHONGQING

1986, 4(1):  54-60. 

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The purpose of this paper is to present three algorithms for transposing large matrices of whnich data are larger than main memory available. The data can be stored on external storage device, such as disk or magnetic tape. The transposing operations using 128*256 matrices have been carried out on PDP11/24 minicomputer. Experimental results demonstrated that tie algorithms could realize a speed advantage.

XPS ANALYSIS OF Ag AND T₁ IN ION MIGRATION LINBO₃ OPTICAL WAVEGUIDES

ZHANG XIAOYANG, LI CHUAN, CHEN GUANGMENG, CHEN YIXIN

1986, 4(1):  61-65. 

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In this paper the X-ray Photoeleotron Spectroscopy (XPS) analysis on the LiNbO₃ waveguide samples is reported. The samples were prepared by ion migration enhanced by electric field. The elements such as Ag, Tl, Nb and O in the different mode number waveguide planes on both the positive and the negative sides were measured. The depth profile of Ag and Tl ions in the waveguide layer was analysed. The results show that the Nb⁺⁵ in the LiNbO₃ samples prepared by this method has no change of valency. The concentration of Ag⁺ on the positive guide side increases with the salt-bath time, but there isn't similar rule on the negative guide. The results of depth profile analysis show that the migration depth of Ag+ and Tl+ ions is about 500~2500Å. The ion distribution in the positive guide layer presents a step, then decreases as a complementary error function. Whereas the ion distribution in the negative guide layer is a complementary error function. Compared with the calculated results of optical measurement, the migration depth of the Ag⁺ and Tl⁺ ions is less than the 1/10 depth of the waveguide layer.

MEASUREMENT ACCURACY ANALYSIS OF THE GROUND SCATTEROMETER

YU SHUNDI, ZHU WEIZHONG, XU SAIQING

1986, 4(1):  66-71. 

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The measurement accuracy of the groud scatterometer is discussed in this article. Various factors -which can give rise to measurement error of this instrument are analysed. And it is pointed out that the stability of the following radar para-meters is very important for ensuring the measurement accuracy:transmitter power, gain of the receiver, wavelength, pointing corner of the beam, sidelobe levels, and nonlinear sweeping frequency. A method used to define the error which is caused by nonlinear sweeping frequency is developed.

AN APPROXIMATE CALCULATION OF THE CAPACITANCE OF AN IDT OVER A PIEZOELECTRIC LAYERED STRUCTURE

YUAN JINGHONG, LIU XIAOXIA

1986, 4(1):  72-78. 

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To calculate the interelectrode capacitance, two approximate formulas of an IDT on a piezoelectric layered structure are obtained by assuming a simple potential function and a simple electric charge density function on the intersurface of IDT. For the different values of the electrode width factor a, i. e. When a<3/8, S/8<a< 6/8 and a>5/8, the approximate values of the calculated capacitance are very good.

A NEW CRYSTAL BaO·Nd₂O₃·Al₂O₃·6B₂O₃ AND ITS CRYSTALLOGRAPHIC STUDY

KONG HUASHUANG, HE CHONGFAN, WANG PEILING, LI DEYU

1986, 4(1):  79-83. 

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We have found a new crystal whose composition is BaO·Nd₂O₃·Al₂O₃·6B₂O₃ while studying the miorolaser crystal NAB[NdAl₃ (BOs) ₄]. The crystal is in sheet shape and is light purple. It possesses hexogonal symmetry. The unit cell parameters are a=4.566 (2) Å, c=24.93 (1) Å. This paper describes its growth conditions and crystallographio study. Under convergent polarized light, the interference pattern of its uniaxial crystal was observed, and the crystal was determined to be positive light crystal. Fluorescence spectrum was also measured at room temperature

AN INVESTIGATION OF MBS RESIN

YE JINYONG, WANG WEI, SHEN HONG

1986, 4(1):  84-89. 

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Poly-cis-1, 4-butadiene was dissolved in methyl methacrylate and styrene, the bulk polymerization was carried out at 110℃ An impact transparent MBS resin was obtained. The relationship between the shear rate in bulk polymerization and the morphology of rubber phase, impact strength, gloss, fluidity and transparency of MBS resin had been investigated. The effect of M. W. of matrix on the impact strength was discussed. A new regulator, a-methyl styrene dimer had a similar effect as text-dodeoyl meroaptan in bulk-suspension poly-merization of MBS resin.

A NEW CHART FOR TRANSFORMATION FROM LAUE PHOTOGRAPH TO STEREOGRAPHIC PROJECTION OF CRYSTAL

WEI GOANGPU

1986, 4(1):  90-92. 

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A new char t for transformation from Laue photograph to storeographic projection of crystal and its principle were described. This chart can be used to transmission or back-reflection Laue photographs.

GLOBAL OPTIMIZATION OF A CLASS OF DISCONTINUOUS FUNCTIONS

ZHENG QUAN

1986, 4(1):  93-94. 

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In this letter the concepts of robust set and a class of discontinuous functions are introduced. The global optimality contions and algorithm for finding global minima of this kind of functions are given.