ACOUSTICAL PROPERTIES OF THE YONGLE BELL

the Yongle Bell is the largest bell in china.Experimenta study on the bell has been carriedout in two aspects:modal analysis and characterstics of bell sound.A method for modal analysisunder transient state is presented in this paper.The lowest natural frequency is 16 Hz.The soundof bell is harmonious.Frequences of some partial tones which are important in sensation are inconformity with the standard pitches.     

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     

NUMERICAL APPLICATION OF THE RECURSION METHOD TO THE ELECTRONIC STRUCTURE OF C_(60)

采用Ｒｅｃｕｒｓｉｏｎ方法计算了Ｃ６０分子的能态密度，所得的能隙、能级的简并度及顺序与ＬＤＡ方法或者解析方法得到的结果吻合。     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

RESEARCH AND TECHNICAL NOTES ACOUSTIC PROPERTIES OF RIGID CLOSED-CELL PLASTIC FOAMS

Acoustic properties of typical rigid c1osed-cll plastic foams have been studied experimentallyas functions of skeleton materials and cells.Longitudinal sound speed perpendicular to the rise direc-tion for PAPI polyurethane foam can be related to foam density by an equation C_l=aρ~b.Polyurethanefoams present acoustic orthotropy as a result of elongated cells in rise direction.For an air-backedfoam layer in a water-filled pulse tube,phase angles of complex reflection coefficients are always near180°when cell sizes are about 0.5mm.Frequency and temperature dependences of sound speed,as wellas attenuation at audiofrequencies in foams,are governed primarily by properties of skeleton materials.     

STOCHASTIC CONVERGENCE PROPERTIES OF THE TWO-PARAMETER ADAPTIVE LATTICE FILTERS

In this paper,the perturbation theory of the matrix eigenvalues,the operator spectral norm and a fixed-point theorem are used to research on the stochastic convergence properties of the two-parameter adaptivelattice filters.The relative difference value between the two parameters is a important factor.We obtainsome results:1.The singular values of the mean of elementary operator vary in a circle which has the radiusproportionated to ,they vary not only in magnitude,but also in direction due to; 2.Theeigenvalues of the mean square of elementary operator vary in a circle,its radius is proportional to also;3.The limits of stepsize are stricker than the ones of the one-parameter lattice filters;4.Zero-misadjustment can not be obtained.The misadjustment varys in the range where the center is equal to themisadjustment of the one-parameter lattice filters and the length is propertional to 5.The relationsbetween the misadjustment and order Nare neither linear nor exponential,but are in some conditions betweenthe     

CALCULATION ON A CLUSTER MODEL FOR THE ELECTRONIC CHARGE DENSITY AT NUCLEAR SITE AND THE ELECTRONIC STRUCTURE PARAMETERS OF α IRON

In order to investigate the M6ssbauer isomer shifts and its related electronic charge densities for some substances, the electronic charge density at nuclear site of a iron have been computed for an octahedral cluster Fe₆ with SCF MS-X_α method. Some other electronic structure parameters of the cluster have also been obtained, such as the orbital energy distri- bution, the electron density of states, the Fermi level and various kinds of electron energies, etc. The cohesive energy of α iron have also been calculated and discussed.     

EFFECT OF THE INERTIAL TERM ON THE CDW TRANSPORT PROPERTIES Ⅱ. NUMERICAL SOLUTIONS

Using the classical particle model with an inertial term, we have numerically analyzed the effect on the nonlinear transport properties of the CDW system,e.g., the hysteresis effect, the interference phenomena between the dc and ac applied fields. Our calculations demonstrate the importance of the inertial effect on the sliding CDW states. Some results are probably new, and important to experimental observations; for example, the zero step width region exists for the 1/2 subharmonic step in its variation with amplitude of the ac driving field.     

INFLUENCE OF Pb ON THE STRUCTURAL PROPERTIES OF 2212 SINGLE CRYSTALS IN Bi-Sr-Ca-Cu-O SYSTEM

The effect of Pb on the structural properties is studied in PbxBi2Sr2CaCu2Oy single crystals by electron diffraction and EDX elemental analysis. Results show: a/b increases with increasing Pb content, and the structural modulation changes following 4,7b-mixed (4. 7b, 8. 556)-disappeared. There is a phase transition happened at Pb content about 10% (Elemental percentage calculation only contains four elements of Bi, Sr, Ca, Pb. The content is in atom percentage. ) A new phase which has 2a and 1. 5b superstructure is observed in high Pb concentration region.     

ACOUSTICAL PROPERTIES OF QING

The qing was an important percussion musical instrument in ancient China.Qing is a stone plate withspecial form.The vibration of qing is studied both theoretically and experimentally in this paper.Thevibrational modes of a qing have been calculated by using finite element method in accordance with the ex-perimental results.As compared with a rectangular plate,the frequency relations between the overtones arevaried with the changes of shape of the qing.From the analysis,it is possible to speculate upon the idea ofdesign of the qing in ancient time.In order to confirm the idea,the sound of qing has been simulated bycomputer and judged subjectively.An empirical formula for the calculation of the pitch frequency of qingsound is given.     

ACOUSTICAL PROPERTIES OF CMME BELLS

The acoustic characteristics of chime bells have been studied by the measurements of vibrationalmodes and the power spectra of bell sound.Each of the chime bell has two tones depending on thestriking positions on the bell.At the tone frequencies,the modes of vibration are similar,but thepositions of nodal lines are different.The short-time sound spectra of chime bells were measured bythe use of FFT.The sound of chime bell can also be analyzed by the method of linear predictionused in signal processing.     

WHAT ARE REALLY THE PROPERTIES OF THE TRIPLE BAND FORKING IN 68Ge?

An analysis and discussion has been made for the properties of the triple bandforking in Ge. We also give some supports and questions for the existing explana-tions.     

RESEARCH AND TECHNICAL NOTES ON THE IMPORTANT ROLE OF CHINESE TONES IN SPEECH INTELLIGIBILITY

The role of Chinese tones played in speech perception were investigated by speech articulationtests in this paper.The first part of these tests was carried out under four different transmission con-ditions.It is shown that the tone articulation is higher than 95% although the syllable articulation ischanged from 77% to 28%,and at the sametime the initial articulation changed from 87.2% to 46.7%and the final articulation changed from 89% to 39.5 %. In order to separate the tones from the spectrum of speech sounds,a 2400 bits/s digital channelvocoder was used in the second part of the articulation tests under four different conditions of ex-citation source:1.a noise source only,2.a triangular pulse train souce with constant fundamentalfrcquency F_0=127 Hz only,3.a triangular pulse train source with normal fundamental frequencyonly and 4.both noise source and pulse source with normal fundamental frequency.It is shown thati.the rank order of the tone articulation for the four testing conditions is 4,3,1,2;ii     

A STUDY OF THERMAL DESORPTION OF HELIUM FROM HIGH-PURE α-Ti AND HYDROGENATED Ti SAMPLES

Helium ions have been implanted into highly pure α-Ti and hydrogenated Ti samples with energy of 140keV and at dose of 5.2×10¹⁷He·cm^-2. The retained amount and depth pro-files of helium in the samples were determined by means of proton-enhanced-backscattering (PEBS) at room temperature. The changes of He peaks during isochronical annealing at 100, 200, 300℃,… were monitored in-situ by PEBS for groups of samples. The process of temperature ramping was not stopped until He peaks almost disappeared and hence the release curves were obtained. It was found that ～ 60% of helium was released at 200℃ for high-pure α-Ti samples, whereas massive release occurred at 300℃ for the samples with H/Ti=0.9 and at 350℃ for the samples with H/Ti=0.2. The mechanism of He release and the effect of hydrogen were also discussed.     

THE MACQM CALCULATION OF THE TOTAL ENERGY CURVE OF THE BODY-CENTERED CUBIC STRUCTURE OF THE H_9~- CLUSTER

ＴＨＥＭＡＣＱＭＣＡＬＣＵＬＡＴＩＯＮＯＦＴＨＥＴＯＴＡＬＥＮＥＲＧＹＣＵＲＶＥＯＦＴＨＥＢＯＤＹ－ＣＥＮＴＥＲＥＤＣＵＢＩＣＳＴＲＵＣＴＵＲＥＯＦＴＨＥＨ－９ＣＬＵＳＴＥＲＧｏｕＱｉｎｇｑｕａｎＺｈａｎｇＪｉａｎｐｉｎｇＬｉＰｉｎｇＩｎｓｔｉｔｕ...     

RESEARCH ACTIVITY OF ATOMIC PHYSICS IN RIKEN

RIKEN has a long trasition of atomic physics research in the field ofatomic and molecular spectroscopy.In recent years,the research activityhas also be maintained but be a little shifted to the field of spectroscopyof highly ionized ions in plasma and of high energy atomic collision ex-     

ON THE INVESTIGATION OF THE SOUND ABSORPTION OF LINEAR TRANSITION WEDGES

In this article the reflection coefficient of linear transition wedges is discussed,and an analyticalexpression and a simple real expression of the reflection coefficient under W.K.B.approximationare derived.The approximate expression of the reflection coefficient proves to be simple and con-venient for the design of absorbers. The sound absorbent structure of rib is also computed and analyzed,with emphasis on the rela-tionship between the size of the structure and the parameters of the material. In design of two types of wedges mentioned above,for the required frequency range,the materialperameters can be chosen properly and the dependence of the Wedge length on the lower limit fre-quency can be determined easily based on the derived expression.The theoretical computationsagree well with the experimental results.     

ON THE CONTROL OF RINGING NOISE EXCITED BY IMPACT II:THE ENERGY OF RINGING NOISE AND THE BUFFERING OF THE IMPACT

In the first of these two papers,the expression for the total energy of vibration excited by impacthas been obtained.In this paper the energy equation of ringing noise was derived from the resultof the first paper.This energy equation indicates the approaches to control ringing noise.Thebuffering method was discussed here in detail.The experiment which has been conducted was describedalso.     

THE ACOUSTIC FUNCTIONS OF THE MELON OF THE CHINESE RIVER DOLPHIN(Lipotes vexillifer)

In this paper,the acoustic functions of the melon of the Chinese river dolphin(Lipotes vexillifer)are studied.Based on the comparison between the directivity patterns of the whole head and the skull,it is suggested that the melon plays an important role in beamforming.At the frequencuy of 40 kHz,the—3 dB beamwidth of the emitted vertical beam of the whole head is approximately 21.6°,withthe major axis elevated 10°above the ristrum plane;the—3 dB beamwidth of the horizontal beam ofthe whole head is approximately 20°,with the major axis deviated 12°rightward from the body axis.The vertical and horizontal—3dB beamwidths of the whole head are 9.4°and 13°,narrower than thoseof the skull respectively,and the directions of the major axes are different for both cases.It canbe seen that the melon narrows the width of the main beam and greatly reduces the side lobes of thebeam formed by the skull.The distribution of the sound velocity in the melon tissue is measured andthe distribution pattern is drawn.Fr