RELATION BETWEEN CHOOSING “GOOD” COORDINATES AND THE BEHAVIOR OF LIGHT SIGNALS

It is pointed out that the statement in Ref.[1] (Rindler, assential Relativity) claiming that "the metric coefficients are time-independent if signals tracing out the same path always take the same coordinate time" is false. A counterexample and a revised statement with its proof are given in this paper.     

RELATION BETWEEN CHOOSING “GOOD” COORDINATES AND THE BEHAVIOR OF LIGHT SIGNALS

It is pointed out that the statement in Ref.[1] (Rindler, assential Relativity) claiming that "the metric coefficients are time-independent if signals tracing out the same path always take the same coordinate time" is false. A counterexample and a revised statement with its proof are given in this paper.     

A WEIGHTED MODIFICATION FOR THE DOUBLE DISPERSIVE SAW PULSE COMPRESSION FILTERS

In this paper,an improved design approach for the double dispersive SAW pulse compressionfilters is given.Based on the computer simulation of the filter performances,by modifying the weightedenvelopes of the filter finger lengths,the approximate design formulas have been obtained. Usingthese formulas,three sorts of samples of the pulse compression filters are designed and fabricated.The experimental results indicate that the sidelobe level have achieved up to-37dB in the best situation.     

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.