THE AB INITIO CALCULATION FOR THE BONDING STATE OF THE Hn CTUSTERS

The equilibrium geometries of several Hn（n=4,5,6,7,9,13) clsters with certain symmetry have been optimized by the ab inito Murtaug-Sargent(MS) method.We find that the stability of a centered cluster depends on the structure,the spin symmetry and the coordinate number,and the latter plays a more important role.     

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

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ON THE IRREDUCIBLE REPRESENTATIONS OF THE SIMPLE LIE GROUPS I——THE TENSOR BASIS FOR THE INFINITESIMAL GENERATORS OF THE CLASSICAL SIMPLE LIE GROUPS

In this paper, we analyse the commutation relations of the infinitesimal generatorsof all simple classical Lie groups and establish a new basis for these generators, calledthe tensor basis. In tensor basis, the infinitesimal, generators can be written as somescalar operators, some sets of angular momentum operators and some sets of irreducibletensor operators. The commutation relations, of these operators are very simple andhave many regularities. By means of the method that has been used in the earlier papers, "On the irre-ducible representations of the compact simple Lie groups of rank 2, I,II,III" and thetensor basis, all the irreducible representations of the classical simple Lie groups canbe calculated systematically.     

THE MACQM CALCULATION OF THE TOTAL ENERGY CURVE FOR THE ICOSAHEDRAL CENTRAL STRUCTURE OF THE CLUSTER H_13~-

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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     

THE ι-E PUZZLE AND THE GENERALIZED MOMENT ANALYSIS

We have introduced the photon angular distribution for moments of the process e⁺e^－→J/ψ→γB,B→P₁P₂P₃ to discuss the ι-E puzzle and got an effective criterion to distinguish whether there exist E(1⁺⁺) component in the peak for the process e⁺e^－→J/ψ→γKKπ.     

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 TWO-BOSON SCATTERING PHASE SHIFTS IN THE GENERAL φ6 THEORY WITH THE GAUSSIAN WAVE-FUNCTIONAL APPROACH

The two-particle scattering phase shifts with a λφ⁴ +ξφ⁶ interaction are com-puted in (1 + 1) and (2 + 1) dimensions using the Gaussian wave-functional approach.Through numerical analysis, we give the phase-shift curves with respect to the scat-tering energy for most cases of this theory. In (1 + 1) and (2 + 1 ) dimensions, for the symmetry vacuum the phase shifts are positive or negative depending on the signs of the renormalized parameter, while for the asymmetric vacuum the phase shifts are negative.     

THE BOUND STATES OF THE ISOBAR △ (1236)

We have discussed the single particle energies and wave functions of a boundisobar in O¹⁶ by using the O¹⁶ equation.     

DOES PARISI'S SOLUTION OF THE SHERRINGTON-KIRKPATRICK MODEL LOCATE ON THE ABSOLUTEMAXIMUM OF THE FREE ENERGY?

In the spin glass phase near the critical temperature we find in aparticular replica symmetry breaking pattern an order parameter with free energy greater than that of the Parisi's.     

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.     

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

Based on the ultrasonic measurements of an isotropic NdFeB magnet in the temperature range of 77 -300 K, it was found that the elastic parameters, such as Young's modulus E, and Poisson ratio v, change abruptly near the spin reorientation temperature T_sr. This indicates that soft mode emerges in the process of spin reorientation. Thermal hysteresis was observed during heating-up and cooling-down processes. Both Debye temperature and heat capacity were calculated, which suggests that the magnetic entropy of the Nd-sublattice is larger in easy-cone state than in easy-axis state.     

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

Based on the ultrasonic measurements of an isotropic NdFeB magnet in the temperature range of 77 - 300 K, it was found that the elastic parameters, such as Young's modulus E, and Poisson ratio v, change abruptly near the spin reorientation temperature Tsr. This indicates that soft mode emerges in the process of spin reorientation. Thermal hysteresis was observed during heating-up and cooling-down processes. Both Debye temperature and heat capacity were calculated, which suggests that the magnetic entropy of the Nd-sublattice is larger in easy-cone state than in easy-axis state.     

Raman and brillouin scattering in a single crystal of K2Hg(CN)4

The temperature dependence of the elastic constants of cubic K₂Hg(CN)₄ has been measured by optical Brillouin spectroscopy in the temperature range from 300-110 K. A decrease of all three elastic constants was found in agreement with the results of ultrasonic measurements. Raman measurements in the temperature range from 300-4 K revealed a splitting of the F_2g modes corresponding to a trigonal distortion of the Hg(CN)₄-tetrahedra in the low temperature phase.     

非晶态快离子导体(AgI)x(Ag4P2O7)1-x的声学性质

用液氮骤冷方法制备了(AgI)_x(Ag₄P₂O₇)_1-x系列非晶态快离子导体。对AgI摩尔浓度x=0.50,0.60,0.67,0.75,0.80的样品,在77—300K温度范围及2,5,10,15MHz的频率上测量了纵波和横波的超声衰减和声速。发现在200—240K附近存在一个异常强的弛豫型超声吸收峰,随AgI含量的增加,该峰的位置向低温方向移动,且峰的高度增大。在实验的温度范围内,观察到纵波和 关键词：     

Rfe10.5V1.5Nx化合物的结构和内禀磁性研究

系统地研究了Rfe_10.5V_1.5N_x（Ｒ＝Ｙ，Ｃｅ，Ｎｄ，Ｓｍ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ）化合物的结构和内禀磁性，并与相应的Rfe_10.5V_1.5N_x化合物进行了比较。同Rfe_10.5V_1.5N_x化会物相比，由于ｖ含量低，Rfe_10.5V_1.5N_{x关键词：}     

Anelastic effects in (AgI)x(Ag2O·B2O3)1−x superionic glasses

We present here the first measurements of acoustic absorption in (AgI)_x(Ag₂O·B₂O₃)_1?x superionic glasses at ultrasonic frequencies (5–45 MHz) and in the 80–434 K temperature range. The attenuation shows, at decreasing temperature, an unusually high peak which seems to be attributed to a thermally activated relaxation process. A possible microscopic explanation of this anomaly is proposed, in connection with the presence of mobile ions in those materials.     

Magnetization and torque measurements on Nd2Fe14B single crystals

Magnetization and torque measurements on single crystal specimens of Nd₂Fe₁₄B have been carried out. The magnetization values measured always in the direction of easy magnetization and those in the [001] direction have been precisely determined at temperatures from 4.2K to 600K with a superconducting magnet up to 52.65 kOe. Below the spin reorientation temperature 135K, the magnetization value of the direction of easy magnetization increases anomalously with decreasing temperature. The direction of easy magnetization tilts from the [001] axis to the [110] axis and this tilt angle has been also precisely determined by torque measurement in the temperature range below the spin reorientation temperature. The four-fold symmetry in torque curve for the (001) plane is continously observed at even up to near room temperature and the [110] direction of easy magnetization and the [100] direction of hard magnetization do not change below and above the spin reorientation temperature.     

Study of high-coercivity sintered NdFeB magnets

Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of _jH_c=25.6 kOe, B_r=13.2 kG and (BH)_max=39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 °C) is –0.53%/°C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors.     

Effect of process on the magnetic properties of bonded NdFeB magnet

The effects of magnetic separation, coupling treatment, lubricating treatment, preform and biaxial molding on the density and magnetic properties of bonded NdFeB magnet were investigated. The results demonstrate that magnetic separation separates the powders with low coercive force; coupling treatment improves the interfaces between the powders and the binders; decrease in volume fraction of the binder increases magnetic properties of the magnet; granular arrangement improves both the magnetic and mechanical properties when powders are arranged in certain size; lubricating treatment improves the formability of the magnet and preform and biaxial molding improves both density and magnetic properties greatly. Combining these methods, the density of the bonded NdFeB magnet can reach 6.52 g/cm³ and the maximum energy product can reach 114 kJ/m³.