Enhanced spontaneous emission factor for microcavity lasers

The microcavity and the influence of nonradiative recombination can control spontaneous emission. An analytic resolution of rate equation is studied for microcavity lasers. The relationship between output prop- erties and structural parameters of multi-quantum wells (MQWs) is obtained. One of the most important consequences of the incrcased spontaneous emission factor is the reduction of laser threshold. It is found that the characteristic curve of a "thresholdless" laser is strongly nonradiative depopulation-dependent. The light output is increased by the enhanced well number and the reduced width. In particular, there is an optimal well number corresponding to the lowest threshold current density for MQW structure in the microcavity lasers.     

位移测量中真空室偶极涡流的影响及其扣除

一、真空室上偶极涡流对测量的影响 在托卡马克放电中,出现宏观不稳定性时,等离子体电流会出现小的正尖峰,并在整个大环上沿水平方向向内快速收缩。这时真空室(薄不锈钢壳)上会感应出很大偶极涡流,如图1所示,真空室上偶极电流分布为     

强直流场介质表面次级电子倍增效应的数值模拟研究

通过粒子模拟方法,实现了强直流场下介质表面击穿过程中次级电子倍增效应的数值模拟.具体研究了强直流场场强、介质表面光滑度和次级电子产生率等对次级电子倍增的影响,以及倾斜直流场和外加磁场对次级电子倍增的抑制.结果表明,选择次级电子产生率较低的介质材料和倾斜强直流场可以有效降低次级电子倍增效应的强度,而外加磁场必须超过一定值时才可以有效降低次级电子倍增强度. 关键词： 次级电子倍增 强直流场 介质表面击穿 数值模拟     

反射式Sagnac干涉光纤电流互感器的传感头误差研究

阐述了反射式Sagnac干涉型电流传感器的原理,对Sagnac型光纤电流传感器进行了深入的理论研究,建立了完整的系统理论模型。采用偏振系统的Jones矩阵对反射式Sagnac干涉型电流传感器的偏振误差进行了研究,并对光纤传感头中的线性双折射、圆双折射对测量准确度的影响进行了模拟分析,从理论上得到了反映影响规律的曲线。仿...     

An example of applications of the elementary catastrophe theory in Hamiltonian systems

The convection in atmosphere discussed in ref. [1] is rigorously treated by considering the variation of environmental temperature with the height. This represents an example of applications of the elementary catastrophe theory in Hamiltonian systems.     

磁过滤器电流对非晶碳薄膜摩擦学特性影响的研究

研究了过滤阴极真空电弧技术中,不同的磁过滤器电流下(5—13 A),制备的四面体非晶碳(ta-C)薄膜对摩擦学特性的影响.通过对薄膜厚度,薄膜结构以及薄膜表面粗糙度随磁过滤电流的变化结果进行了测试,结果表明,随着磁过滤器电流的增大,薄膜的sp³键含量逐渐减少,表面粗糙度从0.13增大到0.38.磁过滤器电流在5 A时,薄膜的摩擦系数最小约为0.08,当电流增大到7 A时,摩擦系数显著增大,磁过滤器电流从7 A增大到13 A时,薄膜的摩擦系数再次减小约为0.1. 关键词： 四面体非晶碳 过滤阴极真空电弧 磁过滤器电流 摩擦系数     

Uniqueness of the standard model neutral current predictions

In view of an excellent agreement between the recently determinedv _μ-hadron couplings and predictions of the standard model, the basic question discussed is how far its neutral current predictions can be mimiced in going either from the isodoublet to an isotriplet (or an even higher isospin) left-handed representation or from SU _L (2) × U(1) toG × U(1), whereG is a simple group of rank two. This question is addressed with reference to a sufficiently broad class of schemes. Their most distinctive properties are: in the higher isospin scheme, neutrino couplings are precisely in the form obtainable with standard l.h. representation; the higher g.g. scheme isL+R type in which, to each light fermion of evenRU parity, a superheavy fermion of the same charge and oddRU parity is associated, parity conservation forbidding their mixing. Reasons for excluding theL-type andG ₂ higher g.g. schemes are given. Their neutral current predictions are compared with those of the standard model. A higher isospin representation can mimic the predictions of the standard model in inclusive and semi-inclusivev _μ-hadron reactions but is conclusively discriminated from the isodoublet representation by elasticv _μ ⁽⁻ p scattering. TheG × U(1) scheme can mimic standard model neutrino sector but is conclusively discriminated from minimal scheme by parity violating effects.     

新型书写方式—化学书写术

应用化学原理发明了化学书写术,它比现行的书写方式具有突出的优点。     

三维回旋自共振微波放大器的理论计算

给出了三维回旋自共振微波放大器（ＣＡＲＭ）的电于运动方程和光场演化方程，并在忽略束流空间电荷效应的前提下，编制了单模放大器程序。利用数值模拟详细考察了电子束束流质量对微波输出功率的影响，模拟结果与实验值符合得很好。     

A modified electron bombardment type ion source for the study of solids

A modified electron bombardment type ion source suitable for use with mass spectrometer is described. Ion formation occurs throughout a relatively large volume in the ionisation box, since no magnetic field is used to collimate the ionising electrons. A sensitivity of 2 × 10⁻⁵ amp/torr is obtained for an ion extraction energy of 2 keV and 200 mass resolution. Trajectory tracing has been used to study the operation of the ion source. Capability of the ion source to analyse solid samples in microgram quantity was tested by studying evaporation of BaO from tungsten.