THE AVERAGE FIELD OF THE ISOBAR △(1232) IN NUCLEI

The one boson exchange nuclear force is applied to the discussion of the nucleon-△ interaction. The coupling constant is determined by the straton model. Assuming that the wave function is unaltered by the presence of △, we are able to obtain the average field of the isobar in the nuclei approximately. The qualitative feature obtained is that the average field of △ is shallower then that of nueleon by an amount of～15 MeV.     

A STUDY ON ABSORPTION OF Na ATOMS ON Si(100) 2×1 SURFACES WITH DV-Xα METHOD

The Na absorption on Si(100) 2×1 surface is studied with quantum chemistry molecular cluster method. The calculated results show that the most favourable absorption site of Na is the cave site and the charge transfer of Na atom to Si is large when the Na coverage is smaller than 0.5 monolayer (ML). A Na chain is formed along the cave sites at the 0.5 ML Na coverage, the charge transfer then becomes small. The calculated density of states show that the Na atoms are metallic along the chain. At 1 ML coverage, the Na atoms occupy both the cave and pedestal sites and form a double-layer. There is a charge transfer of 0.5e from each Na atom to the Si surface. The calculated surface energy shows that the saturation absorption of Na on Si surface is 1 ML.     

A STUDY ON ABSORPTION OF Na ATOMS ON Si(100) 2×1 SURFACES WITH DV-Xα METHOD

The Na absorption on Si(100) 2×1 surface is studied with quantum chemistry molecular cluster method. The calculated results show that the most favourable absorption site of Na is the cave site and the charge transfer of Na atom to Si is large when the Na coverage is smaller than 0.5 monolayer (ML). A Na chain is formed along the cave sites at the 0.5 ML Na coverage, the charge transfer then becomes small. The calculated density of states show that the Na atoms are metallic along the chain. At 1 ML coverage, the Na atoms occupy both the cave and pedestal sites and form a double-layer. There is a charge transfer of 0.5e from each Na atom to the Si surface. The calculated surface energy shows that the saturation absorption of Na on Si surface is 1 ML.     

THE STUDY OF HORIZONTAL DIRECTIVITY OF CYLINDRICAL(ARC)ARRAYS WITH BAFFLE

The influence of baffle on horizontal directivity and the frequency response of elements is analysedin detail in this paper.Some formulas of calculating the received response and the horizontal directi-vity of the cylindrical(arc)array are given.The influence of parameters of arrays on the performanceof the array is discussed.A comparison between the theoretical values and a part of the experimentalresults is shown.     

ON THE PROBLEM OF THE DUAL CHARGE (MAGNETIC MONOPOLE) OF NON-ABELLAN GROUPS (Ⅱ)

The method of relating the gauge potential to the connection on a spherical surface developed in a previous paper is generalized to the discussion of the potential of an SU(2) magnetic monopole with O(5) symmetry. Expressions for the potential of the monopole with double string singularity or single string singularity are obtained. Finally, by a combined coordinate-gauge transformation, we obtain a string free expression for an SU(2) magnetic monopole with O(5) symmetry.     

DISCOVERY OF MULTIPLE,COLLECTIVE BAND STRUCTURES IN NUCLEI WITH A=60—80

Recent studies of levels in even-even ^68,70,72Ge,^70,72,74Se,^74,76,78,80Kr and ⁶⁵Ga and ⁷⁴Br have led to the discovery of a wide variety of different collective band structures.These include bands built on near spherical ground states and excited more well de-formed shapes that may include triaxial shapes,rotation-aligned bands built on thesame orbital （g_（9/2））² for both protons and neutrons,RAL negative parity bands witheven and odd spins,and ΔI=1 γ-type vibrational bands in even-even nuclei.As recent as 1974,a survey of the energy level in the even-even Ge and Se iso-topes^[1] revealed little was known above a spin of 4⁺ （see for examples Figs.1 and 2 of Ref.1）.With the exception of the unusally low-lying excited 0⁺ states in ^70,72Ge,first discovered in ⁷²Ge in 1948 at Vanderbilt^[2],the theoretical treatment of thesenuclei was limited primarily to some variation of the vibrational model.However,very recently there has been a surge of information on nuclei in this region that hasrevealed fascinating new features and also provided new insight into the excited 0^+’states.Particularly striking are the multiple,independent and highly collective bandstructures which we have discovered in our in-beam γ-ray spectroscopy studies fol-lowing heavy-ion induced reaction.Evidence for and the theoretical understandingof the richness of the collective band structures that are found in our studies of^68,70,72Ge （Refs.3—6）,^70,72,74Se （Refs.7—13） and ^74,76,78,80Kr （Refs.14—18）,as illustratedby the at least seven different bands found in our studies of the levels of ⁶⁸Ge ⁷⁴Se,and ⁷⁶Kr （Figs.1—3）,are described in this paper.These multiple structures includethe following:a) coexistence of ground bands built on near-spherical shapes andexcited bands with larger deformation built on O^+′ band heads;b) bands with 8⁺ band heads interpreted as rotation-aligned,RAL,bands built on both neutron and/orproton （g_（9/2））² quasiparticle configurations coexisting with the ground-state band;c)RAL neutron and proton odd-parity bands formed from coupling of a g_{（9/2 ）}quasipar-ticle and a p_（1/2）,p_（3/2） or f_（5/2）,quasiparticle with the core;d) ΔI=1 even-parity bands,which are best characterized as gamma-vibrational bands;and e) additional bandswhose nature are presently not known.     

A STUDY ON THE ACOUSTIC NONLINEAR PARAMETER IN BIOLOGICAL MEDIA WITH HIGR ATTENUATION

Using the comparative method with the corrections of the diffraction and attenuation,we measured thenonlinear parameter B/A of several biological media with high attenuation.The acoustic nonlinear parameterB/A of biological media such as heart,liver,spleen,kidney,and muscle is about 7,that of bile and urine about6,and about 9.6 for fat.The nonlinear parameter of the fat is more than others mainly due to high lipid contentin it.Ichida‘s result about the fat is discussed.     

STUDY ON SPECTRAL CHARACTERISTICS OF AC STARK SPLITTING IN OPTICALLY PUMPED NH_3 FIRLASER

以ＮＨ３分子作为工作物质，在ＣＯ２－１０Ｒ（６）泵浦下，利用密度矩阵方程和迭代法计算了ＮＨ３分子的Ｖ２：ａ→ｓＱ（５，４）远红外跃迁的频谱特性。理论计算表明，在一定泵浦强度下出现ＡＣＳｔａｒｋ分裂，且ＮＨ３分子工作压强对ＡＣＳｔａｒｋ分裂双峰有不同的影响，当压强达到某一临界值时，ＡＣＳｔａｒｋ分裂的偏频Ｒａｍａｎ峰消失，另外，一定长度的超辐射远红外激光器的输出光强主要受工作气压和泵浦强度的影响，其中最佳工作气压由激光器长度和泵浦强度决定，实验结果与理论计算一致     

DETERMINATION OF REFLECTION TIME DELAY AND CRITERION OF CORRECT OVERLAP IN ULTRASONIC WAVE VELOCITY MEASUREMENT WITH PEO METHOD

The Pulse-Echo-Overlap method(PEO method)has now been considered as the most adequatemethod for accurate measurement of the absolute value of ultrasonic velocity.For this accurate timemeasurement,it is essential to find the time delay and implement its corrections,e.g.the correction ofreflection time delay,the correction of diffraction time delay,etc.To overcome the inconvenience of thewidely used in practice method of reflection time delay calculation,and its imperfection in theory,a newcalculation procedure of the reflection time delay correction is worked out in this paper,and an experimentaldetermination method for its value by means of double crystal is suggested.This paper further suggests aparameter of the period increment of zero phase shift Δτ_r,and considers it as an experimental constant,whose value is about 1.7 ns in practical applications. Furthermore,this paper suggests a criterion of correct overlap.If the echoes are correctly overlapped,the slope of the curve of the ultrasonic wave tri     

Estimate of the Δ(1232) component in the 12C nucleus

The cross section for the ¹²C(γ, π⁺ p) reaction was measured in the range of the Δ(1232) isobar. The data were analyzed using the models taking into account the nucleon and isobaric degrees of freedom of the ¹²C nucleus. The conclusion is drawn that in the large-momentum transfer range the π⁺ p pairs are produced in the course of the direct knocking-out of Δ⁺⁺ isobar from the nucleus. The probability of finding the Δ isobar in the ground-state ¹²C nucleus is estimated at 0.018±0.005 Δ isobars per nucleon.     

Virtual versus real nuclear Compton scattering in the Δ(1232) region

In this paper we calculate the cross section for Virtual Compton Scattering off nuclei in the delta resonance region. We also calculate the background for the process from Coherent Bremsstrahlung in nuclei and explore the regions where the Virtual Compton Scattering cross section dominates. The study also shows that it is possible to extract the cross section for Real Compton Scattering from the Virtual Compton one in a wide range of scattering angles.     

π+ absorption on 12C in the Δ(1232) region

A search for possible structure in the energy spectrum of forward going protons from the ¹²C(π⁺, 3p)X reaction was undertaken. The measurement was done for π⁺ momenta of 355, 375, and 405 MeV/c. No narrow (less than 20 MeV) structure was found. A broad structure corresponding to a quasi-free scattering of the pion before capture, superimposed on a continuum background, was observed. The data indicate that additional free nucleons or light products are usually present in the final state.     

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.     

ELECTRONIC STRUCTURE OF BIMETALLIC LAYERED SYSTEMS WITH RANDOMNESS IN LAYER THICKWESSESⅠ. CPA STUDY OF A SIMPLE MODEL

The influence of randomness in layer thicknesses in a blmetallic layered system, i.e., of randomness in the "modulation period" of a,bimetallic "superlattice" on its electronic structure is studied in terms of a simple model in the coherent potential approximation (CPA).Numerical examples are presented for illustration.     

Parity-violating excitation of the Δ(1232): hadron structure and new physics

We consider prospects for stydying the parity-violating (PV) electroweak excitation of the Δ(1232) resonance with polarized electron scattering. Given present knowledge of Standard Model parameters, such PV experiments could allow a determination of the N → Δ electroweak helicity amplitudes. We discuss the experimental feasibility and theoretical interpretability of such a determination as well as the prospective implications for hadron structure theory. We also analyze the extent to which a PV N → Δ measurement could constrain various extensions of the Standard Model.     

USING STATISTICAL ENERGY ANALYSIS IN STUDY OF SOUND INSULATION OF PARTITIONS

The models of Statistical Energy Analysis(SEA)of sound insulation of partitions,single wall,double wall and double panels connected by studs,are made.The evaluation of the parametersof SEA is discussed.Gypsum board walls are used as objects of study.Radiation resistance,lossfactor and sound transmission loss are measured.The sound insulations of seventeen types ofgypsum board walls are calculated by computer.Agreement between calculated results and experi-ments is found to be good.Finally,the influence of some factors,such as parameters of room,damping loss of wall,absorption material in cavity and form of stud,upon the sound insulationof walls is discussed.     

Photoproduction of pion-nucleon pairs on nuclei in the Δ(1232)-resonance region

Data from three experiments performed at the linear accelerator in Saclay, the Tomsk synchrotron, and the MAMI accelerator in Mainz and devoted to studying single pion photoproduction on light nuclei that is accompanied by nucleon emission are analyzed. The behavior of respective experimental cross sections, which is inexplicable in the impulse approximation, is interpreted within a model where the formation of an intermediate quasibound isobar-nucleus state is followed by its decay to a final state involving a pion and a nucleon.     

Coherent pion electroproduction on the deuteron in the Δ(1232) resonance region

Coherent pion electroproduction on the deuteron is studied in the ((1232) resonance region in the impulse approximation, i.e., neglecting pion rescattering and two-body effects. The elementary reaction on the nucleon is described in the framework of an effective Lagrangian approach including the dominant P₃₃(1232) resonance and the usual background terms of the Born contributions for ?⁰ production. We have studied the influence of these different contributions on the various structure functions which determine the unpolarized exclusive differential cross section in a variety of kinematic regions.     

A STUDY ON THE ULTRASONIC VELOCITY AND ATTENU-ATION IN NdFeB MAGNET WITHIN THE TEMPERATURE RANGE OF 80-300K(Ⅰ)

The ultrasonic velocity V and attenuation A of both longitudinal and shear waves in an anisotropic NdFeB magnet were measured over the temperature range from 80K to 300 K by the pulse echo method. The anisotropy of the ultrasonic wave propagating in a NdFeB magnet was observed. Anomalous changes in both V-T and A-T curves in the temperature range of 110-160 K were found, which might be due to the spin reorientation phase transition of Nd2Fe14B.