Modelling of temperature effects on the characteristics of mid-infrared quantum cascade lasers

The effect of temperature on the characteristics of GaAs/AlGaAs quantum cascade lasers operating in the mid-infrared range is theoretically investigated and compared with reported experimental results. We have included the dependence of the phonon scattering rate, linewidth variations and thermionic lifetime on temperature. It is found that the characteristics depend strongly on temperature. Our model yields threshold current densities in good agreement with the experiments. The effect of injection efficiency on the unsaturated modal gain is also considered.     

香菇代料开放式两步法栽培技术研究

该项研究，第一步根据香菇菌丝所产生的酶能分离大分子物质的生理特性。采用该项技术收到了克服杂菌危害，补足基质养分，保证香菇产量和节省能源的效果。     

非英语专业大学生语言输入现状调查与研究

基于Krashen的可理解性输入假设与Swain的输出假设，文章对非英语专业大学生语言输入现状进行了调查研究。结果显示，目前制约大学英语学习者表达能力和交际能力的原因并不单单是忽视语言输出造成的，语言输入的质量不高，来源单一等因素也严重制约了学习者语言应用能力的发展。在分析目前我国大学英语教学现状的基础上，本文探讨了相应的对策及启示。     

A framework for incremental generation of closed itemsets

Association rule mining from a transaction database (TDB) requires the detection of frequently occurring patterns, called frequent itemsets (FIs), whereby the number of FIs may be potentially huge. Recent approaches for FI mining use the closed itemset paradigm to limit the mining effort to a subset of the entire FI family, the frequent closed itemsets (FCIs). We show here how FCIs can be mined incrementally yet efficiently whenever a new transaction is added to a database whose mining results are available. Our approach for mining FIs in dynamic databases relies on recent results about lattice incremental restructuring and lattice construction. The fundamentals of the incremental FCI mining task are discussed and its reduction to the problem of lattice update, via the CI family, is made explicit. The related structural results underlie two algorithms for updating the set of FCIs of a given TDB upon the insertion of a new transaction. A straightforward method searches for necessary completions throughout the entire CI family, whereas a second method exploits lattice properties to limit the search to CIs which share at least one item with the new transaction. Efficient implementations of the parsimonious method is discussed in the paper together with a set of results from a preliminary study of the method's practical performances.     

Reconstruction of bandlimited signal from its non-uniform integral samples

In this article, we discuss the problem of reconstructing a bandlimited signal f from the samples of the integral of the signal. We first apply the trigonometric polynomials to approximate the integral of the signal and then reconstruct instantaneous samples from the signal integral.     

格式化输出语句在解题中的应用

以一类ＦＯＸＢＡＳＥ＋考题为例，找出这类问题的内在联系，由此得出规律性的结论     

一种单向卫星网络中冗余递增的数据分发机制

为了解决单向数据分发系统存在的问题,设计了一种新的数据分发机制.一方面,分组级FEC机制被用来恢复接收端的误码.另一方面,发送端采用冗余递增的方式发送分组级FEC编码生成冗余信息.发送端将冗余信息分层传输,接收端通过加入一个或多个发送层次以接收不同冗余度的数据,从而有效地解决了接收端异质性引起的系统效率降低.仿真结果表明,新的数据分发机制可以使误码率低的接收端尽快接收到需要的数据,在保证数据可靠传输的同时提高了系统的发送效率.     

二语习得理论在多媒体网络化大学英语听说教学中的应用

二语习得过程中，只有将Krashen的输入假设和Swain的输出假设相互配合应用，学习者才能流利、准确地掌握和运用目标语。对Krashen和Swain的假设进行了批判性反思分析，结合大学英语多媒体网络化听说教学改革现状，从教学原则、情景设想、教学手段等几方面探讨了多媒体网络化大学英语听说教学设计，以期对研究、建立多媒体网络化英语听说教学新模式起到借鉴作用。     

由半导体激光器端面输出谱确定自发辐射谱

利用射线法和平均载流子分布近似，从理论上预言了用阈值以下半导体激光器的端面输出谱来确定自发辐射谱的可能性。在此基础上，通过实验测得的阈值以下半导体激光器的端面输出谱确定了自发辐射谱，并且对自发辐射谱和增益谱进行了比较和分析。     

HL－1装置热脉冲传播的傅里叶分析

本文采用一种新提出的数值方法［１］，即傅里叶变换分析法，研究了ＨＬ－１装置中用软Ｘ射线测量得到的锯齿振荡诱导的热脉冲传播行为。此方法不仅可以计算扰动调制的热传导系数，而且可以分析各次谐波的幅值和相位随频率及空间的演变，并与热脉冲峰值时间延迟分析法进行了比较，两者推算的热传导系数符合较好。所得结果和稳态能量平衡方法的推测值也为同一量级。在相似条件下，氘放电的热传导系数比氢小，即同位素效应能改善约束。大量运算结果表明，傅里叶分析法和峰值时间延迟分析法都可用于ＨＬ－１装置热脉冲传播的常规数值分析，并可应用于ＨＬ－１Ｍ的数据处理。