DESCRIPTION OF A CALCULATION METHOD OF ELASTIC CONSTANTS OF CRYSTALS

With the help of the decline method,a computer-aided analysis program of Christoffel equation is des-cribed which makes it possible to calculate elastic and viscous constants of crystals precisely and easily.Theelastic constants of LiNbO_3 and Bi_(12)GeO_(20)crystals are calculated with an Apple-Ⅱcomputer and theFortran program suggested,and the calculated data are compared with the values achieved by others.     

STUDY OF ULTRASONIC PROPERTIES OF THE AQUEOUS SOLUTION OF GELATIN

The experimental investigation of aqueous solution of the gelatin has been made by usingultrasound at frequency 11.4 MHz.The relation between concentration and ultrasound absorptiondoes not reach its saturated value even at the weight concentration of the solution c=8.5%. When the concentration is more than l.5%,the solution transforms into jelly under room tem-porature,but the ultrasonic absorption does not change in the whole transformation proces.Whenthe temperature of the solution is decreased to the vicinity of gelling point,the viscosity η of the solutionincreases gradually with time,making the value of sound absorption calculated from η largerthan the experimental one by several orders.But when the temperature of the solution is appropriatelyhigher than the gelling point,the calculated value of sound absorption is smaller than the experimentalone but with the same order. The temperature at which the maximum sound velocity occurs in the concentrated(c=6.4%)solution is not much different from that     

GROWTH TECHNIQUE OF MOLECULAR CRYSTAL OF NAPHTHALENE

A furnace for growing single crystal naphthalene of diameter 1-1.3cm and length up to15cm has been constructed by the Bridgman method in combination with zone-melting technique.The furnace is simple in its construction,convenient in its operation and convenient for the observa-tion of the crystal growth process.The effect of the shape of crystal growth container on crystalgrowth is discussed and the experiment in vapor growth of small naphthalene flakes is described.The preparation procedure of naphthalene samples for ultrasonic measurement,which may be alsouseful for preparation of other soft crystals,is given.     

A METHOD OF DISPLAYING COLOR SPECTROGRAM OF SPEECH BY USE OF MICROCOMPUTER

A method of drawing color spectrogram of speech by using microcomputer is described in this paper,and referred to the metod of drawing spectrogram by computer.With the software and no addition anyother aqripment.,we can draw color three-dimension spectrogram(or black-white spectrogram with-out color monitor),and it is similar to spectrogram of sonagrapher.     

MULTIDIMENSIONAL ANALYSIS OF PERCEPTIONAL CONFUSION OF CHINESE CONSONANTS

The perceptional features of Chinese consonants has been analysed in multidimensional scalingby means of optimizing the fitting to the confusion probabilities of consonants as observed in articula-tion tests.The dependence of minimum Stress as criterion for fitting on dimensions has beenobtained. In this paper,a method of multidimensional scaling is described briefly.A program for perform-ing calculations on a programmable calculator and the questions of handling the blank data as wellas setting the starting configurations are discussed.Some typical results of calculation are given.     

A METHOD OF PULSE-TO-PULSE CORRELATION FOR STUDY OF TIME-VARIANT CHARACTERISTICS OF UNDERWATER SOUND CHANNEL

A method of measuring correlation among signal pulses for investigation of random time-variantproperties of underwater sound channel is presented in this paper.The expression of correlationfunction between periodic pulses propagating in underwater sound channel is derived.The mea-sured results of the correlation coefficent of the received signal pulses in propagating channel andin fixed-target reflected channel are given.Primary analysis of measured results and a channel modelhave heen shown in this Paper.     

ANALYSIS OF SURFACE EXCITATION OF ELASTIC WAVE FIELD IN A HALF SPACE OF PIEZOELECTRIC CRYSTAL——GENERAL FORMULAE OF SURFACE EXCITATION OF ELASTIC WAVE FIELD

This paper developes the general theory of the surface excitation of elastic wave field in a halfspace of piezoelectric crystal for both free and metallized surfaces.It is shown that the general elas-tic wave field U is equal to the convolution of the generalized Green's functions G and the general-ized forces T, U = G Twhere symbol,expresses dot-product-convolution. The generalized Green's functions are independent of excitation conditions and only dependenton material parameters and orientation. For the piezoelectric crystal,not only a mechanical source distribution at the surface,but anelectrical source distribution can also excite the elastic wave fields.Complete expressions of thegeneralized forces representing mechanical and electrical source distribution respectively are given.Especially for the free surface,the surface electrical sources can be composed of the discontinuityof normal electric displacement at the surface,and of the discontinuity of the tangential electric fieldas well.     

DEVELOPMENT OF THE LAW OF TURBULENT JET NOISE

Lighthill's theory of aerodynamic noise is re-examined,and an equivalent of his U~8-law derived interms of pressures.The total acoustic power of jet noise is expressed as W=8KD~2(p_1-P_0)~4/(σ_0c_0P_1~2)K being the Lighthill's constant,D the diameter of the nozzle,P_1,the plenum pressure and P_0 theatmospheric pressure.This formula applies to cold-air jet at low pressures.Further development,theformula is generalized to high pressures,working material of molecular weight M at temperature T.Soundpressure level in the direction perpendicular to the jet is seen more exact to describe the field,and this at lmeter from the nozzle is found as L=80+10 log(R-1)~4/(R~2-R+0.5)+20 log(TM_0)/(T_0M)+20 log dwhere R=P_1/P_0 and d=diameter in mm.The general formula reduces to the empirical formulae uponneglecting some small terms.     

NOVEL SYSTEMATICS OF AUTOIONIZATION AND RADIATIVE DECAY RATES OF DOUBLY EXCITED STATES OF ATOMS

We discuss the novel systematics and the calculation of autoionization and radiative decay rates of doubly excited states of atoms and ions where both electrons have high principal quantum numbers.     

PRISE THE SECRET OF HETEROGENEITY OUT OF BIOPOLYMER SYSTEMS

High-resolution 13C spectra of solid polymers are often acquired with cross polarization with magic angle spinning (CP/MAS) to take advantage of the abunda ntly available protons in the polymer chains. The sequence for transferring mag netization from 1H to13C using Hartmann-Hahn spin locking in the rotating frame is now a standard in commercial solidstate NMR spectrometers.     

RECOGNITION OF SHIP OBJECTS ACCORDING TO THE SHAPE OF AVERAGE POWER SPECTRUM OF RADIATED NOISE

The methods of recognizing different types of ship objects according to the shape of average powerspectrum of the radiated noise are discussed in this paper.The pre-processing of the data is con-sidered first.After applying general correlation method,the distance method and weighted distancemethod,a new method i.e.M-m_2 plane partition method,is proposed.The basis of this methodis the shape of averaged power spectrum of ship radiated noise may be approximately described bythe Ece noise model.Such a noise model,which may be characterized by a set of three parametersf_0,f_m and K or w_0,a and K is described in detail.The approaches of extraction these parameters arealso discussed.By using of the recognition features M.which is the location of the maximum value ofaverage power spectrum curve,and m_2,which is the second central moment of normalized averagepower spectrum level and applying a piece-linear classifier,a 92% of correct recognition rateis obtained for two different types of ship objects.Compared w     

THE RESEARCH OF ELECTRONIC PROPERTIES OF HYDROGENATED а-Si

We first used Bethe lattice method and coherent potential approximation method to calculate the densities of bulk and surface states for a-Si,a-Si:H. The ideal vacancies were also studied.The results agree with experiments and other works.Dihedral disorder contributes to the submerging of a peak and sp peak of the valence band.In hydrogenated case,extra structure appears in the spectrum of densities of surface states.Doped hydrogen affects the densities of bulk states in the gap in principle,but hydrogen is not important for densities of surface states in the gap.Finally,we obtained self-energies which are in good.agreement with the empirical results from experiments and other methods^[1].     

STATUS OF COMMUNITY NOISE IN THE PEOPLE'S REPUBLIC OF CHINA

Noise surveys have been carried out in Beijing,Tianjin and in 22 smaller towns in the generalmetropolitan area.This region has a population of about 18 million.The results of these surveys give apicture of the situation of the community noise in a typical section of China and the change in the last tenyears,showing the effectiveness of various noise control measures,both technical and legal.     

MEASUREMENT OF LOW MAGNETIC FIELD DISTRIBUTION OF A β SPECTROMETER

The low magnetic field distribution of an iron-core double-focusing low-energy β spectrometer is measured with a second harmonic magnetic flux gate magnetometer, the relative measuring precision is better than ±0.05%. The field strength of the spectrometer is about 10G. This spectrometer is used to measure the β spectrum from tritium β decay for estimating the rest mass of electron antineutrion.     

PRINCIPLE OF PIEZOELECTRIC DAMPING OF VIBRATION:AN EXPERIMENTAL INVESTIGATION

Since the vibration behaviours of a piezoelectric vibration system change with an electrical load,thevibration of such a system will be damped,when the electrical load includes a resistance component.Basedon this effect,a principle of piezoelectric damping of vibration is developed.In this paper piezoelectric damping configurations for both thickness and longitudinal vibrations areexperimentally studied.The results show that the piezoelectric material may become a new type of materialfor damping and the piezoelectric vibrator can be used as a new type of damper.The piezoelectric damping adjustment is convenient and can be carried out continuously andinstantaneously.     

EXPERIMENTAL STUDY OF IONIZATION CROSSSECTIONS OF ATOMIC IONS BY ELECTRON-IONCOLLISIONS

Worldwide demands for quantitative information on the electron-ioncollisions from both the field of the controlled thermonuclear fusion andof the space science have caused significant promotion in efforts in experi-mental study to determine cross sections for electron collisions with ions.     

THEORY OF NONLINEAR INTERACTION OF FINITE AMPLITUDE RANDOM SOUND WAVES

In this paper a theory of nonlinear interaction for finite amplitude random sound waves is devel-oped.On the basis of the assumption that the velocity amplitude of source of sound should obeyRayleigh distribution,the authors successfully extend Fenlon's theory to the case of random soundwaves.A series of interesting formulas expressed in the form of the spectral dlstribution are derived(for example,the formulas for the nonlinear distortion of random sound waves,the suppression of theweak random sound wave by the intense regular sound wave,the parametric process of random soundwaves,etc.).In this paper it is also pointed out that some important results of statisitical phenomenaof nonlinear acoustics obtained by O.V.Rudenko can be easily derived from the present theory.     

MEASUREMENT METHOD OF MATERIAL CONSTANTS OF THIN PIEZOELECTRIC CYLINDRICRL TUBES

This paper reports a new measurement method of the constants of piezoelectric ceramics.Themethod can be used for measuring the material constants of the radially polarized thin piezoelectricceramic cylindrical tubes.The mathematical formulas only contain very simple algebraic operationand the measurement equipments in use is usual electrical ones.Using developed method,we candetermine Poisson's ratio σ,the elastic compliances_(11)~E at constant electric field,the planar electrome-chanical coupling factor k_p,the transverse electromechanical coupling factor k_(31),the mass density p and the dielectric constant ε_(33)~T/ε_0 at constant stress.The material constants obtained from theradially polarezed thin cylindrical tubes by our method are in good agreement with the results ob-tained by using the method in IRE Standards on Piezoelectric Crystals.     

CALCULATION OF THE ELASTIC-SCATTERING CROSS-SECTION OF ENERGETIC ELECTRON BY 40Ca NUCLEUS IN CONSIDERATION OF THE INFLUENCE OF“PION CONDENSATION”

Using Migdal's theoretical results of "pion Condensation", the influence of "π condensation" on the distribution of charge of N=Z nucleus is determined. The elastic-scattering differential cross-section of energetic electron by ⁴⁰Ca nucleus is also calculated. The results of our calculations agree better with the experimental data.