THE EFFECT OF MULTIPLE SCATTERING ON ACOUSTIC ENERGY TRANSFER IN HIGHLY CONCENTRATED AQUEOUS SUSPENSIONS

An acoustic energy transfer equation has been set up to solve the multiple scattering problem inacoustic wave transfer in highly concentrated aqueous suspensions.This method is easier to handle than theusual one,and can be used for any values of the ratio of particle size to wave length.It has been found thatwhen the multiple scattering is considered the scattering coefficient is decreased by 5% to 14% in the case ofka=3 to 5 and the product of the coefficient and the path length less than 0.256.As the concentrationincreases the scattering coefficient becomes even less.The influence of the particle size distribution,absorption and inhomogeneity in suspensions on the scattering coefficient is discussed.     

SPIN EFFECT AND π-N OFF SHELL AMPLITUDE CORRECTION ON π-NUCLEUS DOUBLE CHARGE EXCHANGE REACTION

We study the influence. of the spin terms and off shell correction of π-N amplitudeπ-nucleus double charge exchange reaction. It is showed that both greatly reduce thecross sections and improve the theoretical result to fit the experimental data better.Spin effect is importance in the (3,3) resonance energy region, but it is less importantin the higher energy.     

DISCREPANCY IN SOUND POWER DETERMINATION AT LOW FREQUENCIES

The determination of the sound power of a source is simple in a reverberation chamber,but usuallylower valves are obtained at low frequencies than the free-space value.It is shown that the sound powerdetermined in a reverberation chamber depends not only on its free-space power,but also on the positions of the source and the reveiver,as well as the way the measurements are made and averaged.Exactand statistical formulas are derived to account for these factors.The results explain the discrepancy andagree well with earlier experiments.Based on the theory,parcticable techniques of sound power determina-tion are propesed and correct power formulas presented.     

LOW—ENERGY MOLECULAR COLLISI0NS

Ⅰ:Collision processes involved In this talk,emphasis will be put in the sub-eV energy region.Collisions of molecules with atoms,molecules,or their ions lead to elasticcollisions,rotational transitions,vibrational transitions,excitation or de-excitation of low-lying electronic states such as fine-structure levels,     

APPLICATION OF CORRELATION—POLARIZA TION POTENTIAL TO THE LOW—ENERGY ELECTRON SCATTERING WITH ATOMS AND MOLECULES

Applicability of the correlation potential,which is currently used in the local density functional theory,to the low-energy electron-atom and molecule scattering is investigated with some examples of scattering processes.     

QUASI-FREE α-α SCATTERING IN 12C AT 31.2MeV

The summed energy spectra and the angular correlation for two alpha particles from the ¹²C(α, 2α) ⁸Be reaction were measured.
The data show that the quasi-free scattering of incident alpha particle from the alpha cluster in ¹²C is probably the main mechanism of the reaction on 12C. The data are analyzed by means of PWIA. The probability of forming cluster is 0.07 which is close to the result obtained by James at high incident energy.     

2π→2K SCATTERING AND πK ELASTIC SCATTERING

The 2π→2K low energy scattering cross-section was obtained using the relation between field and current. The low energy πK elastic scattering cross-section and its scattering length were also obtained using cross symmetry.     

RESEARCH AND TECHNICAL NOTES ULTRASONIC ATTENUATION IN α-LiIO_3 SINGLE CRYSTAL AT LOW TEMPERATURES

Ultrasonic attenuation in an α-LiIO_3 single crystal has been measured in the [001],[010] and[100] directions at low temperatures by using the standard pulse echo method.It is clear thatultrasonic attenuation anisotropy exists in α-LiIO_3 above 273 K and disappears below 273 K.     

STUDIES ON LOW ENERGY ION-ATOM COLLISIONS BY MEANS OF ELECTRON-SPECTROSCOPY

We present typical results of studies on autoionizationprocesses produced by low energy ion-atom collisions bymeans of the ejected electron spectroscopy,which havebeen performed by Atomic Physics Group of SophiaUniversity.     

ON MESON RATIOS IN MULTIPARTICLE PRODUCTION AT HIGH ENERGY——A STATISTICAL QUARK MODEL

A statistical quark model is proposed which combines the quark model with the statistical thermodynamical model.The relative multiplicity of different mesons produced in the small longitudinal momentum region is calculated.The result is in agreement with the experimental data.     

DEMAGNETIZATION EFFECT IN CRITICAL STATE IN CYLINDRICAL SUPERCONDUCTORS

This paper presents the results of field and current distribution in the critical state in a superconducting cylinder using Bean critical state model and isotropic critical current density Jc. We introduced an equivalent effective field and demagnetization factor Dc, and showed that Dc, from extremely long cylinder to very thin disks, is equal to Meissner demagnetization factor of the inscribed spheroid of the cylinder. The application of these parameters is discussed at the end of paper.     

TOMOGRAMS OF LIQUID CYLINDERS IN HOMOGENEOUS SCATTERING MEDIUM

Investigation of the tomogram of a liquid cylinder in homogeneous scattering medium is described.A model has been made and experiments on some sorts of liquid cylinders have been done.An ex-pression is derived for the brightness funotion of the tomograms while STC(Sensitivity Time Control)is used.According to this expression,the experiments on som sorts of mediums with differentacoustic properties have been simulated by computer.The resulte enable us to estimate acousticproperties of a liquid cylinder from its tomogram.     

LOW ENERGY TRIPLE DIFFERENTIAL CROSS SECTIONS FOR ELECTRON IMPACT IONIZATION OF HYDROGEN

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LONG-RANGE REVERBERATION AND BOTTOM SCATTERING STRENGTH IN SHALLOW WATER

According to the method of angular power spectrum for averaged sound field in shallow water,the transformation relation between arbitrary angle dependence of hottom scattering and the rangedependence of long-range reverberation in shallow water homogeneous layer is established.Ascompared with the conventional model of boundary reverberation at short range in deep sea,a multipath correction factor is added.By using the transformation relation,the bottombackscattering strength for the frequency band of 0.8—4.0kHz and grazing angle range of 2—10°has been derived from shallow-water reverberation data at five locations in the Yellow Sea,theBobai Sea and the East China Sea.It is shown that the bottom scattering constant(μ)and theangle index(2n)for high speed sediment of the continental shelf depend not only on sea area andfrqucncy,but also on angle range.     

RESEARCH AND TECHNICAL NOTES THE HEARING THRESHOLD AT LOW FREQUENCIES

In this paper some typical works are introduced in detail to make a review of the human hearingthreshold at low frequencies in which an identical result has not been got up to now.     

πN SCATTERING PHASE SHIFTS IN A MODIFIED SKYRME MODEL

The P-wave phase shift of πN scattering and the mass and width of the Roper resonance are computed in a modified Skyrme model.The results are better than those calculated from the original Skyrme model.     

REVIEW OF THE PARTICLE SCATTERING THEORY IN ROCKET TECHNIQUE APPLICATION

In this paper three calculation methods of scattering cross section are discussed for particles and its calcuation ,existing problems and further deveplopment.     

STUDY OF QUASI-MOLECULE RESONANCE OF CHAIN CONFIGURATION INDUCED BY 6Li(d,dd) α REACTION AT LOW ENERGY

⁶Li(d,dd) α reaction induced by 7.3—10.6MeV deuterons was studied under collinear condition.An enhancement in differential cross section beyond the well known QFS and FSI contribution was observed at incident energy of 9MeV.It is the state of quasi-molecule resonance of chain configuration.     

THE ACOUSTOELECTRIC EFFECT IN α-LiIO_3 CRYSTAL

In α-LiIO_3 crystal,the attenuation coefficient of longitudinal wave is increased by the action of anelectrostatic field,if the direction of wave propagating and the field are along the same c-axis of the crystal.The change of the attenuation coefficient with time possesses a relaxation character.We believe that thisphenomenon may be caused by the interaction between the longitudinal wave and the unilaterally moving     

ULTRASONIC INVESTIGATION OF NONLINEAR EFFECT IN BIOLOGICAL MEDIUM

The nonlinear acoustic parameter B/A and its dependence on solute concentration have beendetermined for several aqueous solutions of biological samples by using comparative method.TheB/A values for aqueous solutions of dextrose,sucrose,and ethylene glycol were found to increaselinearly with solution concentration.The B/A value for fresh whole porcine blood has been obtained tobe 5.8 at temperature 26℃.Dependence of internal pressure P_* on concentration also has beendetermined for ethylene glycol solution.