Ultrasonic investigation of amorphous carbon in various frequencies at low temperatures from 2.1 to 300 K

Using pulse echo overlap measurement, the elastic behavior of amorphous carbon has been studied at ambient and low temperatures. The smaller ratio B/G of the bulk modulus to shear modulus and smaller Poisson's ratio σ at room temperature indicate that there is an intrinsic stiffening of transverse acoustic phonons in the amorphous carbon. The acoustic velocity and attenuation for longitudinal modes have been measured between 2.1 and 300 K at three frequencies of 7, 21 and 35 MHz, respectively. Their frequency and temperature dependence are observed. The elastic constant C₁₁ increases with decreasing temperature and show enhanced stiffening at low temperatures. In the 130-220 K region, the abnormal change and effect of longitudinal velocity and attenuation with temperature and frequency, and a phase transition associated with structure relaxations are discussed.     

AGS能量下π~－π~－的Bose—Einstein关联

全同粒子间的玻色－爱因斯坦关联可以用来研究相对论性核碰撞中次级粒子源分布及有关的物理问题．本文用强子级联模型（ＨＣＭ）模拟２８Ｓｉ（１４．６ＡＧＣＶ／ｃ）＋Ａｕ反应，得到π－粒子的ｆｒｅｅｚｅ－ｏｕｔ状态，进而计算了π－π－关联函数，取得与实验一致的结果．还计算了ｆｒｅｅｚｅ—ｏｕｔπ－源的均方根线度，并讨论了它与拟合方法抽取的源参数间的关系．     

Temperature anomaly of the Cd hyperfine field in a trivacancy complex in Ni

The temperature dependence of the Cd hyperfine field in a trivacancy complex in Ni between 25 and300 K is reported. It was found that, unlike the Cd substitutional field in Ni which follows the temperature dependence of the magnetization, the Cd hyperfine field in a trivacancy complex is essentially temperature independent. This temperature anomaly is compared with other temperature anomaly of impurity hyperfine fields in ferromagnetic hosts.     

Unique edge structure and stability of fabricated dimer islands on Si(001)

The edge structure and stability of monolayer-high islands fabricated on Si(001) surfaces by scanning tunneling microscopy have been analyzed theoretically. In contrast to the edges of similar islands grown by depositing Si, the properties of edges of fabricated islands are determined by the length of the trench of dimers that are removed to create the island. We demonstrate the possibility of controlling the edge structure, and thus the stability, through a selective process of atom removal.     

The proportional hazards regression model with staggered entries: A strong martingale approach

The proportional hazards regression model, when subjects enter the study in a staggered fashion, is studied. A strong martingale approach is used to model the two-time parameter counting processes. It is shown that well-known univariate results such as weak convergence and martingale inequalities can be extended to this two-dimensional model. Strong martingale theory is also used to prove weight convergence of a general weighted goodness-of-fit process and its weighted bootstrap counterpart.     

Angular momentum effect in prescission particle multiplicities for a light system by diffusion model

The effect of angular momentum on the competition between fission and particle emission during light system fission process was studied via fission diffusion model. The prescission particle multiplicities were found to increase with decreasing angular momentum. The experimental prescission proton and α particle multiplicities can be fitted for 10.6 MeV/nucleon ⁸⁴Kr(²⁷Al,binary fission) reaction with this model. Entrance channel effect found in [1] is proved to be angular momentum effect.     

Interference Diagnosis of the Initial Stage of Laser-Produced-Plasma in Air

By using a Q-switched YAG Laser and a optical path delay set-up, we study the process in whith a laser induces breakdown to produce plasma in air, and obtain time-resolved Mach-Zehnder interferograms and optical shadowgrams of the initial stage of the plasma and the expansion wave produced in the process for the first time     

不同倾角的脉管制冷机内自然对流影响的研究

本文通过对脉管内自然对流的数值模拟，讨论了当脉管冷端处在不同方向时，脉管内的自然对流对脉管制冷机性能的影响．数值模拟结果表明，当冷端在下时获得的制冷温度最低；当热端在下并与重力方向成３０°时制冷温度最高．结论与实验测量结果定性一致．所做的理论分析对实现脉管制冷机的良好运行有指导意义。     

非线性物理简介:8.光学孤子及其在光纤通讯中的应用

本文介绍了光学孤子的形成、特性及其在光纤通讯中的应用．     

Isolation and Structure Elucidation of Nortriterpenoids from Schisandra rubriflora

Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1.