合金碳化物M23 C6的磁性及磁致磁性

利用第一性原理研究了碳化物M23 C6 (M=Fe,Cr)的晶胞结构、磁矩和态密度,并结合魏氏分子场理论分析了磁场作用下一些碳化物的磁致磁性.结果 显示:Fe20 Cr3 C6碳化物中的Fe3和Fe4原子连接组成稳定的晶格框架,Cr1、Cr2和C原子位于框架中心;Fe20 Cr3 C6的磁性主要来源于Fe和Cr原子的3...     

Investigation of charge loss characteristics of HfO2 annealed in N2 or 02 ambient

The retention characteristics of electrons and holes in hafnium oxide with post-deposition annealing in a N2 or 02 ambient were investigated by Kelvin probe force microscopy. The KFM results show that compared with the N2 PDA process, the O2 PDA process can lead to a significant retention improvement. Vertical charge leakage and lateral charge spreading both played an important role in the charge loss mechanisms. The retention improvement is attributed to the deeper trap energy. For electrons, the trap energy of the HOS structure annealed in a N2 or 02 ambient were determined to be about 0.44 and 0.49 eV, respectively. For holes, these are about 0.34 and 0.36 eV, respectively. Finally, the electrical characteristics of the memory devices are demonstrated from the experiment, which agreed with our characterization results. The qualitative and quantitative determination of the charge retention properties, the possible charge decay mechanism and trap energy reported in this work can be very useful for the characterization of hafnium charge storage devices.     

Q值正演模拟约束下的零偏移距VSP资料Q值估算

随着油气勘探目的层逐步走向深部,球面扩散、透射损失、环境噪声等使得VSP资料的初至子波发生改变,导致常规的Q值估算方法质量难以得到保证。为此,利用塔里木盆地托甫台地区TP327井零偏移距VSP资料,综合考虑透射损失和球面扩散的影响,提出一种Q值正演模拟约束下的零偏移距VSP资料Q值估算方法。该方法通过研究区的纵波速度、横波速度和密度建立层状地质模型,利用射线追踪的方法,用大地吸收介质模型的Q值正演模拟结果,对频谱比法和经验公式估算的初始Q值进行修正,使得Q值正演模拟结果与实际地震波的衰减记录在频谱特征上吻合,从而得到更为精确的Q模型。TP327井Q值估算结果表明,该方法与李庆忠经验公式得到的结果在浅层比较接近,但在中层和深层,两者差异较大;Q值正演模拟结果约束的子波与实际VSP资料子波的频谱比较吻合,证实用Q值正演模拟约束得到的层间Q值更为可靠。利用Q值正演模拟约束方法得到的Q模型对研究区地震资料进行反Q滤波能显著提高地震资料分辨率,有助于提高碳酸盐岩地层中缝洞的识别精度。     

高强度厚壁H型钢桩轧制工艺优化研究

针对莱钢高强度厚壁H型钢桩存在屈服强度波动较大以及性能不合的现象,通过对加热、轧制、冷却工艺进行优化改进,解决了高强度H型钢桩生产中的技术难题,使钢材的性能检验合格率由95%提升至97%,吨钢煤气消耗减少了0.1 GJ/t,保证了生产的顺行。     

MPI通信代码自动生成算法

对于高性能并行计算机而言，如何由给出的计算、数据划分信息及精确数组数据流分析信息自动生成并行化代码是实现串行程序并行化的一个重要问题。根据Saman P.Amarasinghe和Lam的定理，实现了一种并行化识别工具中MPI（Message Passing Interface）并行化代码自动生成技术的算法，并对该算法的性能进行分析。     

Computer-based learning of neuroanatomy: A longitudinal study of learning, transfer, and retention.

A longitudinal experiment was conducted to evaluate the effectiveness of new methods for learning neuroanatomy with computer-based instruction. Using a three-dimensional graphical model of the human brain and sections derived from the model, tools for exploring neuroanatomy were developed to encourage adaptive exploration. This is an instructional method that incorporates graphical exploration in the context of repeated testing and feedback. With this approach, 72 participants learned either sectional anatomy alone or whole anatomy followed by sectional anatomy. Sectional anatomy was explored either with perceptually continuous navigation through the sections or with discrete navigation (as in the use of an anatomical atlas). Learning was measured longitudinally to a high performance criterion. Subsequent tests examined transfer of learning to the interpretation of biomedical images and long-term retention. There were several clear results of this study. On initial exposure to neuroanatomy, whole anatomy was learned more efficiently than sectional anatomy. After whole anatomy was mastered, learners demonstrated high levels of transfer of learning to sectional anatomy and from sectional anatomy to the interpretation of complex biomedical images. Learning whole anatomy prior to learning sectional anatomy led to substantially fewer errors overall than learning sectional anatomy alone. Use of continuous or discrete navigation through sectional anatomy made little difference to measured outcomes. Efficient learning, good long-term retention, and successful transfer to the interpretation of biomedical images indicated that computer-based learning using adaptive exploration can be a valuable tool in instruction of neuroanatomy and similar disciplines. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The role of classroom quality in ameliorating the academic and social risks associated with difficult temperament.

The present study examines the moderating role first grade classroom quality may have on the relations between children's difficult temperament (assessed in infancy) and their academic and social outcomes in early elementary school (first grade). Using data from the National Institute of Child Health and Human Development's Study of Early Child Care and Youth Development, 1032 children were rated by their mothers at 6 months of age on difficult temperament. The quality of first grade classroom environments were then observed and rated along three domains: emotional support, classroom organization, and instructional support. Regression analyses examined the statistical interactions between difficult temperament and classroom quality domains on children's academic and social outcomes. Results indicate high-quality classroom environments may ameliorate the academic and social risks associated with having a difficult temperament. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

三峡工程1998年防汛工作回顾

分析１９９８年汛期三峡坝址天气及水情情况，结合三峡工程挖填方量大、基坑多、高陡边坡多、地下洞室多、雷击高发区域广的特点，组织参与三峡工程建设的设计、施工、监理、通航管理、水文气象等单位，采取积极的防洪抢险措施，包括：明确工程渡汛标准；健全渡汛组织机构；充分做好渡汛准备；重视天气和水情预报．同时介绍了充分利用葛洲坝水利枢纽３次超高水位拦洪削峰支持荆江抗洪的情况，以及２００３年三峡水库初期调度运行方案．三峡工程建成后，将具有２２１５亿ｍ３的防洪库容，通过调度，可蓄洪约１５０多亿ｍ３，沙市水位可限制在４３５ｍ（１９９８年达４５２２ｍ），防洪效益十分显著．     

天然气水合物储层泥质细粉砂挡砂介质堵塞规律与微观挡砂机制

中国南海海域部分天然气水合物储层中地层砂为高泥质含量细粉砂，开采防控砂难度较大。针对高泥质细粉砂挡砂机制问题，使用粒度中值为10.13 μm的泥质细粉砂样品，模拟单向气液携砂流动条件，使用绕丝筛板、金属烧结网、金属纤维、预充填陶粒4类挡砂介质在20~80 μm挡砂精度下进行挡砂模拟实验，采用显微成像系统观察挡砂介质内部及表面砂粒沉积与堵塞动态，分析介质流通性能和挡砂性能变化，总结堵塞规律、微观挡砂机制与形态及其控制因素。研究结果表明，不同类型和精度的挡砂介质对泥质细粉砂的堵塞总体呈现堵塞开始、堵塞加剧和堵塞平衡3个阶段。随着驱替进行，挡砂介质渗透率逐渐降低，幅度会高达90%以上；同时过砂速度减缓，最终过砂率为5%~10%。根据堵塞规律和微观图像分析，提出了粗组分分选桥架、局部砂团适度挡砂、整体砂桥阻挡等挡砂介质对泥质细粉砂的3种微观挡砂机制。以粗组分分选桥架挡砂机制为主的挡砂工况下，挡砂介质堵塞渗透率较高，但过砂率超过15%，挡砂效果较差；以整体砂桥挡砂机制为主时，过砂率在10%以下，挡砂性能较好，但各类挡砂介质的堵塞渗透率不足1 D，流通性能较差。局部砂团适度挡砂机制为主时介质挡砂性能及流通性能介于两者之间。挡砂介质对天然气水合物储层泥质细粉砂的微观挡砂机制和形态受挡砂介质类型、精度、地层砂特征以及流动条件等因素控制，其规律对于水合物泥质细粉砂防控砂优化有指导意义。