Thermal conductance for single wall carbon nanotubes

We report a theoretical analysis of the phonon thermal conductance, κ(T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ(T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length is slightly varied, κ(T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior of κ(T). Received 12 June 2001     

大学物理实验教学改革的实践与思索

本主要介绍了我校近年来在大学物理实验课程体系和教学内容改革的实践及下一步改革的思路。     

炉液倾动重心近似计算的数学分析

为给转炉设计提供依据,需要计算炉液倾动的重心.利用数学方法将实际问题进行简化,通过分析炉液倾动过程中变量间的相互关系,来确定每个倾动角度对应情况下的液面位置.利用数学中三重积分的有关应用,进一步得出转炉在每个倾动角度为α∈(0,π2)时的重心计算方法及相关结论,在理论上为工程计算重心的方法提供参考.     

高温高密度Z-pinch等离子体自适应式平面丝阵负载制备技术研究

 在Z-pinch实验中，加速器两电极间距会因抽真空而发生改变从而导致平面丝阵负载的丝分布发生变化，为了解决这个问题，采用弹簧预压缩的方法，制备出了平面丝阵负载，经实验室模拟检测和物理实验的实际应用证明，平面丝阵负载不但能适应电极方向呈任何方向放置的靶室，还能自动适应靶室电极间距因抽真空而发生的变化。在实验过程中丝阵可以保持绷紧的状态，满足了物理实验的要求。     

背越式跳高教学中应用多媒体技术的实践与探讨

在背越式跳高教学中实行多媒体组合教学 ,改进传统单一的教学方式 ,加深了学生对技术本质特征的理解 ,经教学实验对比 ,教学效果明显提高 .并具体分析探讨了开展多媒体教学的优越性和重要性     

Anderson transition in dilute systems with pure exponential interactions

Summary Assuming a completely disordered lattice it is shown that all the states are localized when the disorder parameterx=a ₀/0 reachesthe value 0.31, wherea is the mean atomic separation anda ₀ is the Bohr radius.     

A numerically stable algorithm for two server queue models

In this paper, we consider a queueing system in which there are two exponential servers, each having his own queue, and arriving customers will join the shorter queue. Based on the results given in Flatto and McKean, we rewrite the formula for the probability that there are exactlyk customers in each queue, wherek = 0, 1,…. This enables us to present an algorithm for computing these probabilities and then to find the joint distribution of the queue lengths in the system. A program and numerical examples are given.     

家庭的消费行为规律

家庭是社会消费的基本单位,大多数商品都是直接供家庭购买与消费的。即使是家庭个体成员的消费,也会受到家庭各方面因素的直接或间接的影响。家庭特征与家庭消费行为规律之间存在一定联系,尤其是家庭经济收入、家庭类型、家庭生命周期、家庭消费角色对家庭消费行为有很大的影响作用。探讨家庭的消费行为规律,对工商企业制定合理的营销策略有重要的意义。     

Gauge-invariant treatment of the exponential decay of an unstable atomic state

Summary By using a self-consistent projection-operator method, developed recently by the present author, a gauge-invariant Markovian treatment of the spontaneous decay of an unstable atomic state is presented. Without ignoring retardation and electron-spin effects a gauge-invariant result for the probability amplitude of finding the atom in the unstable state is obtained.     

Infraglottic aspect of canine vocal fold vibration: Effect of increase of mean airflow rate and lengthening of vocal fold

The mucosal upheaval (MU), where the mucosal wave starts and propagates upward, appears only when the vocal fold vibrates. The location of the MU histologically and the effect of changes in mean air flow rate (MFR) and vocal fold length on occurrence of the MU were studied in twelve excised canine larynges. The lower surface of the vocal fold was marked to serve as a landmark for subsequent study. Cricothyroid approximation was performed to lengthen the vocal fold. After taking high-speed pictures or recording stroboscopic images from the tracheal side, a small cut wound was made at the mark. This wound served to compare the position of the MU with the histologically identified location of the mark. The larynx was then sectioned in the frontal plane. Before lengthening the vocal fold, the MU occurred on the area where the lamina propria became thinner and where the muscular layer neared the epithelial layer. After lengthening the vocal fold, the MU actually shifted medially compared with its original position. The subglottic area surrounded by the bilateral MUs became longer and thinner. Whether or not complete glottal closure during a vibratory cycle was achieved did not alter these findings. In contrast, with a fixed vocal fold length the MU appeared more laterally as MFR increased, but, based on the relation with the mark, its location on the vocal fold did not change from its original position before increase of MFR.