金属掺杂对In2O3薄膜光学性质的影响

研究了射频溅射法制备的金属／半导体类型颗粒膜的光学特性。通过样品透射谱分析，发现金属Fe的掺杂使半导体In2O3的带间跌迁由直接跃迁变为间接跃迁；随Fe所占体积份数的增加，局域态尾变宽，带隙变窄。这是由于掺入Fe颗粒后。母体材料与金属颗粒的界面处表面态增多，以及母体材料的非晶化引起的。     

Evaluation of Two Homogenization Techniques for Modeling the Elastic Behavior of Granular Materials

This paper discusses the capabilities of two homogenization techniques to accurately represent the elastic behavior of granular materials considered as assemblies of randomly distributed particles. The stress-strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations, using two different homogenization methods, namely the kinematic method and the static method. The numerical predictions obtained by these two homogenization techniques are compared to results obtained during experimental studies on different granular materials. Relations between elastic constants of the assembly, interparticle properties, and fabric parameters are discussed, as well as the capabilities of the models to take into account inherent and stress-induced anisotropy for different stress conditions.     

Dynamic Spar Elements and Discrete Element Methods in Two Dimensions for the Modeling of Soil-Inclusion Problems

Discrete element methods (DEMs) provide new numerical means to study the behavior of soil-inclusion systems. In some cases, however, the classic DEM fails to model specific aspects of the inclusions. That is why a model based on spar elements is introduced, designed specifically for inclusions. In this model, the movement of the inclusion is considered as a dynamic process and is computed step by step in the same way as in the DEM. The model can be coupled with a DEM code, thus enabling one to simulate the interaction between an inclusion and a disk assembly. Contact laws at the contacts between disks and spar elements describe the interface constitutive behavior. Finally, the results obtained by simulating a geosynthetic anchorage in two different ways are reported. In the first case the inclusion is represented by disks, while in the last case it is represented by spar elements. The comparison shows that spar elements are much more versatile and can simplify the calibration of the discrete models used to simulate soil-inclusion systems.     

钙钛矿氧化物La0.3Ca0.7MnO3的磁性质

采用固相反应法制备了样品La0.3Ca0.7MnO3. 通过测量样品的M-T曲线、 M-H曲线和ESR曲线, 研究了La0.3Ca0.7MnO3的磁性质. 结果表明 在262 K时形成电荷有序相(CO相). 当T＞262 K时, 表现为顺磁;当T＜190 K时, 表现为长程反铁磁(在AFM本底中存在少量FM成分);从262～190 K(TCO), 随温度降低在电荷有序态下从顺磁向反铁磁转变.     

基于AHP法的信息熵模糊物元模型在地基处理方案评价中的应用

将信息论和模糊物元分析理论相结合 ,建立地基处理方案评价的信息熵模糊物元分析模型 ,运用层次分析法建立指标层次结构 ,确定指标权重 ,消除了专家权重分配困难的缺陷 ,提高了方案评价的可信度 ,并通过具体实例说明了模型的实际应用 .     

有色酒类中色素对还原糖测定影响的消除

在葡萄酒的发酵生产和产品质量检验方面，还原糖测定是一个重要指标。本文采用手工直接测定法与原糖测定仪测定两种方法对红葡萄酒及干红酒中还原糖进行测定，结果表明手工直接测定时色素对测定结果影响较大。将样品利用活性炭脱色处理和原样品用仪器测定都可提高测定的准确度。     

Fast Collision Detection Algorithms with Applications to Particle Flow

In this paper, we present efficient algorithms for collision detection of arbitrarily shaped rigid moving objects in a variety of interactive as well as non-interactive environments. The algorithms primarily consist of two stages. The first stage involves finding candidate objects for possible collisions. The second stage involves detecting exact (within a prespecified tolerance) collision between these candidates. The primary data structure used in the algorithms is an octree. In the first stage, we build an octree for the enclosure containing the objects, which is used to detect possible collisions. Assuming spatial/temporal coherence i.e., that the particles move slowly or that the time sampling is fast enough, the average time complexity of this stage can be shown to be O(n) (excluding the time complexity for a one time octree construction), where n is the number of particles. In the second stage, we build a surface-octree for each object. If the objects are convex and assuming coherence, the expected time complexity to detect precise (within a prespecified tolerance) collision for each pair is a constant (excluding the time complexity for a one time surface-octree construction). Therefore, the overall expected time complexity for convex object collision detection is linear with respect to n. For the concave objects, complexity analysis is nontrivial to perform and instead we provide a very practical (almost linear time) algorithm. We apply our algorithms to particle flow simulations by simulating flow density conditions often arising in granular flows.     

长期轮作施肥对土壤有机质及其组分的影响

研究了长期轮作施肥对土壤有机质及其组分的影响，结果表明：在不施肥耕种条件下，通过粮豆轮作，基本可以维持土壤有机质的平衡，但其活性有机质含量、腐殖酸总量及胡敏酸含量却在不断下降，单施化肥，开始时土壤有机质含量降低，以后随耕种年限的延长，基本可以维持在较低水平，活性有机质、腐殖酸总量、胡敏酸和胡敏素含量降低，富里酸含量提高；施用有机肥处理，特别是施用高量有机肥，有利于提高胡敏酸和胡敏素比例，而减少富里酸的生成，培肥作用较为明显。     

试论我党对所有制结构理论的探索与创新

多年来,我党在不断深化对社会主义认识的基础上,对传统所有制结构理论进行了大胆的探索与创新,丰富和发展了马克思主义关于所有制问题的理论.党的十六大在此基础上进一步强调,要把坚持公有制的主体地位和促进非公有制经济发展统一于社会主义现代化建设的进程中.同时提出理顺收入分配关系,"完善保护私人财产的法律制度".显示了党和政府坚持现阶段"基本经济制度"这一政策的长期性、连续性和稳定性.对引导我国多种所有制经济的健康发展,必然产生深远影响.     

Stress transmission through three-dimensional granular crystals with stacking faults

We explore the effect of stacking fault defects on the transmission of forces in three-dimensional face-centered-cubic granular crystals. An external force is applied to a small area at the top surface of a crystalline packing of granular beads containing one or two stacking faults at various depths. The response forces at the bottom surface are measured and found to correspond to predictions based on vector force balance within the geometry of the defects. We identify the elementary stacking fault as a boundary between two pure face-centered-cubic crystals with different stacking orders. Other stacking faults produce response force patterns that can be viewed as resulting from repetitions of this basic defect. As the number of stacking faults increases, the intensity pattern evolves toward that of an hexagonal-close-packed crystal. This leads to the conclusion that the force pattern of that crystal structure can be viewed as the extreme limit of a face-centered-cubic crystal with a stacking fault at every layer.This work was supported by NSF-CTS 0090490 and by the NSF MRSEC Program under DMR-0213745. MJS acknowledges support by the University of Chicago MRSEC Summer 2002 REU program.