A dynamic coupling model for hybrid atomistic-continuum computations

A dynamic coupling model is developed for a hybrid atomistic-continuum computation in micro- and nano-fluidics. In the hybrid atomistic-continuum computation, a molecular dynamics (MD) simulation is utilized in one region where the continuum assumption breaks down and the Navier-Stokes (NS) equations are used in another region where the continuum assumption holds. In the overlapping part of these two regions, a constrained particle dynamics is needed to couple the MD simulation and the NS equations. The currently existing coupling models for the constrained particle dynamics have a coupling parameter, which has to be empirically determined. In the present work, a novel dynamic coupling model is introduced where the coupling parameter can be calculated as the computation progresses rather than inputing a priori. The dynamic coupling model is based on the momentum constraint and exhibits a correct relaxation rate. The results from the hybrid simulation on the Couette flow and the Stokes flow are in good agreement with the data from the full MD simulation and the solutions of the NS equations, respectively. (c) 2007 Elsevier Ltd. All rights reserved.

金属粉末爆炸烧结界面能量沉积机制

本文用“绝热摩擦机制”和“微爆炸焊接模型”讨论了爆炸烧结过程中金属粉末颗粒边界局部升温以至熔融的机理。指出这种升温时间大致和激波前沿的上升时间相当,约10~(-8)秒量级 升温率高达10~(11)度/秒。其界面温度可超过常压下的金属熔点。并与McQueen等人建立的多孔隙材料的绝热压缩理论进行了比较。

Structure and magnetic properties of CoNiP nanowire arrays embedded in AAO template

Ternary CoNiP nanowire (NW) arrays have been synthesized by electrochemical deposition inside the nanochannels of anodic aluminum oxide (AAO) template. The CoNiP NWs deposited at room temperature present soft magnetic properties, with both parallel and perpendicular coercivities less than 500 Oe. In contrast, as the electrolyte temperature (T-elc) increases from 323 to 343 K, the NWs exhibit hard magnetic properties with coercivities in the range of 1000-2500 Oe. This dramatic increase in coercivities can be attributed to the domain wall pinning that is related to the formation of Ni and Co nanocrystallites and the increase of P content. The parallel coercivity (i.e. the applied field perpendicular to the membrane surface) maximum as high as 2500 Oe with squareness ratio up to 0.8 is achieved at the electrolyte temperature of 328 K. It has been demonstrated that the parallel coercivity of CoNiP NWs can be tuned in a wide range of 200-2500 Oe by controlling the electrolyte temperature, providing an easy way to control magnetic properties and thereby for their integration with magnetic-micro-electromechanical systems (MEMS). (C) 2008 Elsevier B.V. All rights reserved.

盘羊的染色体研究

盘羊(Ovis amman)又称大角羊、大头羊，为山地岩栖动物，隶属偶蹄目牛科绵羊属，国家二类保护动物。盘羊具有角大而粗的外形特征，雌雄皆有，但雌性角较小，体型粗壮有力，为亚洲中部高山代表动物，在我国主要分布于新疆、西藏、青海、内蒙、甘肃等地，有关盘羊的地理分布、食性、活动规律等的研究已有报道，但盘羊的细胞遗传学研究在国内尚属首次。

提高硅薄膜致密性的制备方法

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-06-04T08:36:34Z No. of bitstreams: 1 dspace.cfg: 33388 bytes, checksum: ac9630d3fdb36a155287a049e8b34eb7 (MD5)

可调三角形共轭振幅模板及其实现光纤光栅切趾的方法

本发明公开了一种用于光纤光栅切趾的可调三角形共轭振幅模板，其特征在于，包括一共轭振幅板(19)，上有正切趾光阑(17)和反切趾光阑(18)，该共轭振幅板(19)正面安装有上挡板(20)和下挡板(21)，上挡板(20)和下挡板(21)分别在上挡板导轨(25)和下挡板导轨(26)的导引下上下滑动，该共轭振幅板(19)背面安装有左栅长定位板(22)和右栅长定位板(23)，左栅长定位板(22)和右栅长定位板(23)在栅长定位板导轨(31)的导引下左右滑动。本发明同时公开了一种利用可调三角形共轭振幅模板实现光纤光栅切趾的方法。本发明适应性好，灵活性强，工艺简单。

防护林防护成熟与更新

近一个多世纪以来，防护林科学的研究和发展，使全世界很多国家都越来越深刻地认识到防护林在人类的生活中有着与人类怎么样息息相关的重大作用（曹新孙等，1981）。随着对防护林这一特殊人工森林的研究和发展，各种功能的防护林相继分门别类地建立起来；诸如农田防护林，牧场防护林，水土保持林，水源涵养林，家畜防护林和住宅防护林等。其中以农田防护林的研究最为详尽。最早从事防护林研究的要属苏联，自1843年苏联就开始了营造干旱草原防护林（曹新孙等，1981），到1931年已建立起专门的研究机构（王广钦等，1987）中国营建防护林的历史也有一个多世纪，然而在我国正式进行科研还是从50年代开始的。在近几十年里，着重于农防林的效益、结构配置、营造技术，各种效应以及经营管理等研究，并取得了很大的成就。到目前为止，防护林具有相当水平的国家除中国外，还有苏联、美国、丹麦等（曹新孙，1983）。在国外苏联防护林的研究力量比较雄厚，从所查有关防护林的文献看（cab 文库，林业文摘）苏联关于防护林的文献占一半。

超重反冲余核时间探测器性能测试

介绍了一种铝制内椭球面反射镜闪烁薄膜探测器, 对其探测效率、光收集效率和时间性能的测试. 结果分析表明采用 1μm厚的BC498闪烁薄膜探测器测量实验中超重反冲余核, 探测效率接近 100%, 时间分辨好于 200ps, 其性能满足超重反冲余核时间测量的要求.

On configuration of exchanged La3+ on ZSM-5: A theoretical approach to the improvement in hydrothermal stability of La-modified ZSM-5 zeolite

Density functional calculations have been employed to investigate the locating and binding of lanthanum cation, i.e., La(OH)(2)(+), on HZSM-5 zeolite. Through geometry optimization, it was determined that lanthanum ions are favorably accommodated in the two 6-T rings of the straight channels (Clusters 1 and 2, see Sec. III A for details). Cluster 1 was found to exist in prior to Cluster 2 due to the preference of Al substitution in the T11 site (Cluster 1) rather than in the T8 site (Cluster 2). Geometry-optimization of Cluster 1 containing another two lanthanide ions Nd3+ and Yb3+ was also carried out and it was found that a monotonic decrease in Ln-O bond length will take place as the atomic number increases, conforming well to the rule of lanthanide contraction. Some of the optimized parameters are comparable to the corresponding experimental values in Y zeolite, which confirms that the optimized configurations are acceptable. The average frequencies of hydroxyls attached to La3+ or Yb3+ in Cluster 1 fall at 3609.16 and 3579.76 cm(-1), respectively, with the gap of these two frequencies close to that in the sodalite cage of Y zeolite. Compared to H-form zeolite, the charges on both Al and O atoms in Ln-ZSM-5 zeolite show an obvious increase, which will undoubtedly lead to a stronger mutual interaction and hence enhance the stability of the [AlO4](-) anion. Moreover, the Ln(OH)(2)(+) seem to have thickened the zeolite framework, which can effectively retard the process of dealumination. Through the evaluation of the possibility for dimer formation, it turned out that when the exchange degree arrived to approximately 0.28, lanthanum monomers began to aggregate into dimers, and were completely converted into dimers when the exchange degree approached 0.60. (C) 2003 American Institute of Physics.

LANTHANIDE-INDUCED SHIFT AND RELAXATION RATE STUDIES OF THE AQUEOUS COMPLEXATION OF CITRATE

The aqueous complexation of lanthanide ions with citrate in pH 7.4 solution has been investigated with use of the lanthanide-induced shift and paramagnetic relaxation rate enhancement methods. The results show that citrate coordinates via hydroxyl and central carboxylate groups with lanthanide ions and forms 1:2 (Ln/cit) isostructural complexes through the lanthanide series. A new possible coordination geometry deduced from our experimental data is suggested and discussed.