Magnetic properties of high-temperature superconductors: Analysis within the framework of the impurity mechanism

The impurity mechanism proposed earlier is used to interpret the magnetic properties of hightemperature superconductors. The appearance of superconductive granules and the existence of weak bonds in grains of ceramics and in single crystals is explained. The irreversibility line is obtained and its new interpretation as the line of thresholds of appearance of infinite nonsuperconductive cluster is given. The relaxation time of the magnetic susceptibility in alternating magnetic fields is calculated. The decrease of the Meissner fraction with increase in magnetic field and decrease in doping, and other magnetic properties are explained.     

Clustering-based topical Web crawling using CFu-tree guided by link-context

Topical Web crawling is an established technique for domain-specific information retrieval. However, almost all the conventional topical Web crawlers focus on building crawlers using different classifiers, which needs a lot of labeled training data that is very difficult to label manually. This paper presents a novel approach called clustering-based topical Web crawling which is utilized to retrieve information on a specific domain based on link-context and does not require any labeled training data. In order to collect domain-specific content units, a novel hierarchical clustering method called bottom-up approach is used to illustrate the process of clustering where a new data structure, a linked list in combination with CFu-tree, is implemented to store cluster label, feature vector and content unit. During clustering, four metrics are presented. First, comparison variation （CV） is defined to judge whether the closest pair of clusters can be merged. Second, cluster impurity （CIP） evaluates the cluster error. Then, the precision and recall of clustering are also presented to evaluate the accuracy and comprehensive degree of the whole clustering process. Link-context extraction technique is used to expand the feature vector of anchor text which improves the clustering accuracy greatly. Experimental results show that the performance of our proposed method overcomes conventional focused Web crawlers both in Harvest rate and Target recall.     

Quantum states of a hydrogenic donor impurity in a cubic quantum dot by the finite difference method

The problem of a hydrogenic donor impurity in a cubic quantum dot with finite confinement potential is solved by the finite difference method. The discretized matrix equation needs to be solved for its eigenvalues and eigenfunctions. An algorithm of nonlinear programming is utilized for this problem. The results match references qualitatively in the weak regime, but introduce new problems in the strong and intermediate regimes.     

集成电路生产中成品率的有效管理

本文分析了在集成电路制造过程中,使用的基础材料、设备、工艺技术所产生的污染粒子,随机缺陷对IC产品成品率的影响。并主要介绍了从经典学习曲线概念中推导出来的成品率提高模型已被用于追踪产品成品率的提高,该模型建立在能优先迅速解决影响成品率诸多问题的基础上。实际成品率与模型化成品率的比较充分证明了成品率提高模型的实际意义。     

New techniques in SIMS analysis of HgCdTe materials

This paper presents two new approaches used in the secondary ion mass spectrometry (SIMS) for high sensitivity dopant and impurity analysis in HgCdTe materials, namely, the high mass resolution with dynamic transfer and the MCs⁺ technique. It is shown that better detection limits for As and Cu can be obtained at a level of 2–5e14 at/cm³. The MCs⁺ technique has added advantages of better measurement precision, monitoring Cd composition in the same profile, and small device area analysis capability. Advantages and trade-offs of each technique are discussed and compared. An updated detection limit table for all elements measured in HgCdTe materials using SIMS is also presented.     

硅研磨片超声波清洗技术的研究

介绍了硅研磨片清洗的重要性,分析了影响硅研磨片质量的主要因素,即金属杂质和各种污染物.重点分析了硅研磨片表面沾污的原因,并且通过大量的实验分析得到了活性剂和碱性清洗液、去离子水的最佳体积比是0.20:1.00:10.0,清洗的最佳时间为3 min～5 min和最佳温度范围为40℃～50℃.     

Deep levels in superlattices

The physics governing deep levels in superlattices and quantum wells is elucidated, with emphasis on the importance of shallow-deep transitions caused by a band edge passing through a deep level, and the accompanying change in doping character of the impurity.     

The behavior of unintentional impurities in Ga0.47 In0.53As grown by MBE

A number of factors contribute to the high n-type background carrier concentration (high 10¹⁵ to low 10¹⁶ cm⁻³) measured in MBE Ga_0.47In_0.53As lattice-matched to InP. The results of this study indicate that the outdiffusion of impurities from InP substrates into GalnAs epitaxial layers can account for as much as two-thirds of the background carrier concentration and can reduce mobilities by as much as 40%. These impurities and/or defects can be gettered at the surfaces of the InP by heat treatment and then removed by polishing. The GalnAs epitaxial layers grown on the heat-treated substrates have significantly improved electrical properties. Hall and SIMS measurements indicate that both donors and acceptors outdiffuse into the epitaxial layers during growth resulting in heavily compensated layers with reduced mobilities. The dominant donor species was identified by SIMS as Si, and the dominant acceptors as Fe, Cr and Mn.     

JWF1204A型高产梳棉机纺纯棉精梳纱的应用实践

不同型号梳棉机的结构和工艺配置略有差异,其单机产量、生条及成纱质量也不相同。在简要介绍了JWF1204A型梳棉机的主要结构和工艺配置后,通过一系列的生产试验说明了JWF1204A型高产梳棉机在纺纯棉精梳纱时的单机产量、生条及成纱质量。     

量子尺寸效应对InGaN/GaN量子点中的类氢杂质态的影响

在有效质量近似下,运用变分法研究了量子尺寸效应对闪锌矿InGaN/GaN量子点中类氢杂质的施主束缚能的影响.数值结果显示,类氢杂质的施主束缚能在很大程度上依赖于杂质位置和量子点结构参数,当杂质位于量子点中心时,施主束缚能最大;当量子点尺寸增加时,位于该量子点任一位置处的杂质束缚能均降低.