铜-铝扩散焊及拉伸的分子动力学模拟

采用分子动力学方法模拟了铜-铝扩散焊过程,分析了理想平面铜-铝试件(001)晶面间扩散焊的过渡层厚度,并利用径向分布、键对分析方法分析了在不同的降温速率下过渡层的结构变化.降温速率大时,过渡层保持原有无序结构,降温速率小时,过渡层从无序结构向面心立方结构转变.还对扩散焊后的铜-铝试件进行了拉伸模拟,并与尺寸大小相近的单晶铜和单晶铝的拉伸模拟结果进行比较.结果发现焊接后的强度比单晶铝和单晶铜的强度都要小,最大应变值也小.

宏观深度测量压入仪器的研制

基于深度测量压入方法,以材料试验机Instron 5848 Microtester作为加载平台,外接高分辨力位移传感器,设计专用夹具,开发出该材料试验机的宏观压入功能.研究发现:对于机架柔度,无需再进行修正;对于压针接触面积,可用相关的方法计算.采用Oliver-Pharr方法处理测试数据,可获得材料的硬度和弹性模量.为了验证试验的可靠性,选用5种典型金属材料,将宏观压入测试结果与MTS Nano Indenter(R) XP测试结果进行对比,二者基本一致,其分散性均在10%以内.显示了开发传统材料试验机宏观压入测试功能的可行性

生物黏附与仿生黏附力学的进展

介绍了动物及昆虫黏附能力及黏附系统的实验研究,重点介绍了力学仿生动物及昆虫的黏附能力及黏附系统的研究工作.还简单介绍实验室仿生制备及仿生黏附潜在的用途,并对仿生黏附力学新的研究方向提出建议.

Low temperature growth of c-axis oriented AlN films on gamma-LiAlO2 by radio frequency magnetron sputtering

Aluminum nitride (AlN) films were prepared on gamma-LiAlO2 substrates by radio frequency (rf) magnetron sputtering. The influence of substrate temperature (T-s) and nitrogen (N-2) concentration on film growth was investigated. The X-ray diffraction (XRD) results reveal that highly c-axis oriented AlN films can be obtained in the temperature range from room temperature (RT) to 300 degrees C. A smoother surface and a crystalline quality decrease with increasing N-2 concentration have been observed by XRD and atomic force microscopy (AFM) for the films deposited at lower substrate temperature. On the contrary, the degradation of the surface smoothness and the higher crystalline quality can be observed for the films deposited at a higher substrate temperature with N-2-rich ambient. The growth mechanism which leads to different crystalline quality of the films is discussed. (C) 2008 Elsevier B.V. All rights reserved.

蕨类植物配子体发育及化感作用的研究

我国的蕨类植物资源十分丰富，约有2600多种，占全世界12000种的1/5强，其中许多种具有很高的观赏价值。在欧美的一些国家，蕨类植物已经成为花卉行业的一个重要组成部分，早已进入家庭居室、宾馆、商场、办公楼和其它公共场所，绿化和美化人们的生活环境。到目前为止，全世界共已栽培成功观赏蕨类植物700多种（品种），而我国仅有十多种投入花卉市场作为盆景和切花配叶，尚未形成一定的规模。繁殖技术不过关是造成蕨类植物在我国花卉市场难以迅速发展的障碍之一。目前国内对蕨类植物的需求主要靠野外采挖得以满足，对野生蕨类植物资源造成严重的破坏，再加上自然生态环境的恶化，致使许多物种濒临灭绝。因此，加强相关的基础研究、繁殖技术和外界环境对蕨类植物影响的研究，对蕨类植物资源的利用和保护具有重要的研究价值和现实意义。 作者在近五年的研究过程中，建立了蕨类植物孢子无菌培养技术，观察记录了蕨类植物配子体的形态发育，为建立蕨类植物快速有效的繁殖技术体系打下了良好的基础。在此研究基础上，探讨了对蕨类植物生长发育构成威胁的外界环境之一—外来入侵植物紫茎泽兰对蕨类植物的生长发育的化感作用。紫茎泽兰为目前国际上研究的热点入侵植物之一，对我国农业、林业等已造成很大破坏，并对蕨类植物资源构成一定威胁。蕨类植物配子体发育过程是蕨类植物生活史中相对脆弱的环节，最容易受化感作用的影响。但迄今为止，国际上尚未开展任何紫茎泽兰对蕨类植物（包括孢子体阶段和配子体阶段）的化感作用的研究。为保护蕨类植物自然资源，填补这一研究领域的空白，开展了紫茎泽兰对蕨类植物配子体发育过程的化感作用的研究。实验结果如下： （1）建立了金毛狗（已被列入《濒危野生动植物种国际贸易公约》（CITES）附录II 名单）、凤尾蕨属植物如傅氏凤尾蕨、剑叶凤尾蕨、蜈蚣草、银脉凤尾蕨、溪边凤尾蕨、疏裂凤尾蕨、西南凤尾蕨等多种蕨类植物的孢子无菌培养技术体系。 （2）采用无机培养基培养、土壤培养和滤纸培养三种培养方法，显微镜下观察傅氏凤尾蕨、剑叶凤尾蕨、蜈蚣草、银脉凤尾蕨、溪边凤尾蕨、疏裂凤尾蕨、西南凤尾蕨、三角鳞毛蕨、乌毛蕨、普通针毛蕨、金毛狗的孢子萌发及配子体形态发育的整个过程，研究了上述蕨类植物孢子萌发的类型、配子体各发育阶段的形态特征以及到达每个发育阶段所需的时间，为蕨类植物的繁殖技术提供了科学的依据，同时为蕨类植物系统进化和形态分类学研究提供了重要的基础资料。 （3）以金毛狗、普通针毛蕨、疏裂凤尾蕨为受体植物，研究了紫茎泽兰对这三种蕨类植物的配子体发育的化感作用。选择蕨类植物孢子萌发、假根生长、配子体形态、配子体发育各阶段及所占比例为测定指标，结果表明：紫茎泽兰根、茎、叶提取液可以对这三种蕨类植物的配子体发育产生不同程度的化感作用。表现为：延迟这三种蕨类植物的孢子萌发，降低其孢子萌发率，抑制假根的伸长，并且上述抑制作用随紫茎泽兰提取液浓度的升高而增强。随着紫茎泽兰叶水提液浓度的升高，金毛狗配子体发育阶段会滞后。在紫茎泽兰根提取液处理下，普通针毛蕨配子体上的假根发生畸变。随着时间的推移，这种现象削弱或基本消失。随着根和叶提取液的浓度升高，普通针毛蕨配子体发育阶段将会滞后。高浓度的紫茎泽兰根提取液能改变疏裂凤尾蕨的配子体的形态，并使疏裂凤尾蕨的配子体发育阶段滞后，浓度越高效果越显著。这三种蕨类植物在受到紫茎泽兰化感作用的影响后表现不同，推测与它们对紫茎泽兰所含有的化感物质的不同敏感度有关。

羊草（Leymus chinensis）对刈割响应的特征研究

羊草是高品质的牧草，羊草草地是优良的割草场，刈割是人类对草地的主要利用手段之一，其对羊草草地造成的影响一直受到学者和生产管理者的关注并开展了大量研究。但以往刈割的相关研究主要集中在整个草地的水平上，羊草个体对刈割的响应迄今还没有深入研究。随着畜牧业的发展对草场质量要求的不断提高，发掘耐刈割的羊草种质势在必行，而羊草在不同时期对刈割的响应状况及不同生态型羊草对刈割的响应则是其中必不可少的研究环节。 本文以羊草为实验材料，对其在不同发育时期进行了刈割研究，主要以高度作为动态研究的手段，包括四个部分： 实验1，羊草在苗期对刈割的响应，结果表明，苗期进行的刈割，对羊草第1片叶生长速率没有影响。 实验2，两种生态型羊草在三四叶期及七八叶期两次刈割的响应，表明三四叶期进行的刈割，羊草能达到85.1%的恢复，灰绿型比黄绿型多恢复8.5%。七八叶期进行的刈割，刈除茎尖使羊草停滞生长。三四叶期的刈割能导致灰绿型增加1个分株，黄绿型则减少1个分株。 实验3，四年生羊草草地对不同程度刈割的响应，表明羊草草地在重度刈割后所受影响更严重，但每株羊草分蘖数目会增加1。 实验4，赖草属十一个物种生长期刈割响应，表明羊草对刈割的恢复性明显高于所研究的赖草属其他物种，达到超补偿水平。 在对羊草草原合理利用时，适度刈割是关键的，刈割的频次及程度关系重大。羊草生态型的选择也有举足轻重的作用，选用适应性强的灰绿型羊草对于提高羊草草地具有一定的积极作用。

Theoretical analysis and experimental study of the space-charge-screening effect in uni-traveling-carrier photodiode

A new optimized structure of an UTC (uni-traveling-carrier) photodiode is developed and epitaxied by metal-organic chemical vapor deposition. We fabricated a UTC photodiode of 30 mu m in diameter. Theoretical simulation based on drift-diffusion model was used to analyze the space-charge-screening effect in UTC photodiode primarily in two aspects: the carrier concentrations and the space electric field. The simulation results were generally in agreement with the experimental data.

High Al-content AlInGaN epilayers with different thicknesses grown on GaN/sapphire templates

We studied the structural and optical properties of high Al-content AlInGaN epilayers with different thicknesses grown on GaN/sapphire templates by metalorganic chemical vapor deposition (MOCVD). Direct evidences of the gradual evolution of the content of Al, Ga and In along the growth direction were obtained. When the film thickness was over a certain value, however, the AlInGaN epilayer with constant element contents began to form. These results were also supported by the blue shift and splitting of the photoluminescence (PL) peak. For the thinnest epilayer, the surface was featured with outcrops of threading dislocations (TDs) which suggested a spiral growth mode. With increase in thickness, step-flow growth mode and V-shaped pits were observed, and the steps terminated at the pits. (C) 2008 Elsevier B. V. All rights reserved.

Gap states and microstructure of microcrystalline silicon thin films

The density of states (DOS) above Fermi level of hydrogenated microcrystalline silicon (mu c-Si H) films is correlated to the material microstructure. We use Raman scattering and infrared absorption spectra to characterize the structure of the films made with different hydrogen dilution ratios. The DOS of the films is examined by modulated photocurrent measurement. The results have been accounted for in the framework of a three-phase model comprised of amorphous and crystalline components, with the grain boundary as the third phase. We observed that the DOS increases monotonically as the grain boundary volume fractions f(gb) is increased, which indicates a positive correlation between the DOS and the grain boundary volume fraction.

黄土丘陵区农业生态系统和经济系统的互动关系——以安塞县纸坊沟小流域为例

基于1938—2007年黄土丘陵区纸坊沟流域的调查资料,利用生态系统服务价值评估方法和生态足迹理论对该流域生态系统服务价值与生态足迹进行了测算,并分析了研究区农业生态系统与经济系统的互动关系.结果表明:1938—2007年,纸坊沟流域经历了3个阶段,即生态环境破坏-经济发展落后阶段(1938—1975年)、生态环境恢复-经济迅速发展阶段(1975—2000年)和生态环境保持良好-经济稳定增长阶段(2000—2007年);该区生态经济系统的互动关系表现为"生态恶化-生态、经济相互调节、适应-生态、经济良性互动"的过程.

黄土丘陵区纸坊沟流域“退耕还林”工程实施后生态足迹变化分析

以黄土丘陵区纸坊沟流域所辖3个自然村农户的调查资料为依据,利用生态足迹理论及模型对该流域生态足迹与生态承载力进行了测算。结果表明,纸坊沟流域退耕还林工程实施前(1999年)生态足迹0.9910 hm2/cap,生态承载力0.8926 hm2/cap,生态赤字0.0984 hm2/cap;退耕还林工程一期结束后(2007年)生态足迹1.0188 hm2/cap,生态承载力1.2703 hm2/cap,生态盈余0.2515 hm2/cap,说明退耕还林工程的实施已见成效;同时退耕还林一期工程实施前后3个自然村生态足迹顺序并未发生变化,这与其区位特征一致。根据该流域及其3个自然村的发展特点,为实现其可持续发展,应发展商品型生态农业,强化产业与资源的耦合。

Microarray-based kinase inhibition assay by gold nanoparticle probes

We report on the development of a new class of kinase microarray for the detection of kinase inhibition based on marking peptide phosphorylation/biotinylation events by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The alpha-catalytic subunit of cyclic adenosine 5'-monophosphate-dependent protein kinase (PKA), and its well-known substrate, kemptide, were used for the purpose of monitoring phosphorylation and inhibition. As expected, highly selective inhibition of PKA is demonstrated with the four inhibitors: H89, HA1077, mallotoxin, and KN62. Furthermore, an inhibition assay demonstrates the ability to detect kinase inhibition as well as derive IC50 (half-maximal inhibitory concentration) plots.

Embryology of Swertia (Gentianaceae) relative to taxonomy

The embryological features of three species of Swertia (s.l.) - S. erythrosticta, S. franchetiana, and S. tetraptera were characterized, and the observations were used, together with previously gathered data on other species, to evaluate a recently proposed polyphyly, based on molecular data, of Swertia s.l. Comparisons of species within the genus showed that they have diversified embryologically, and there are significant between-species differences. Notable features that vary between species include the number of cell layers that form the anther locule wall, the construction of the wall of the mature anther, tapetum origin, the cell number in mature pollen grains, the structure of the fused margins of the two carpels, the ovule numbers in placental cross-sections, the shape of the mature embryo sac, the degree of ovule curvature, antipodal variation and the presence of a hypostase, and seed appendages. They share characters that are widely distributed in the tribe Gentianeae, such as a dicotyledonous type of anther wall formation, a glandular tapetum with uninucleate cells, simultaneous cytokinesis following the meiosis of the microsporocytes, tetrahedral microspore tetrads, superior, bicarpellary and unilocular ovaries, unitegmic and tenuinucellar ovules, Polygonum-type megagametophytes, progamous fertilization, nuclear endosperm, and Solanad-type embryogeny. The presence of variation in embryological characters amongst the species of Swertia s.l. strongly supports the view that Swertia s.l. is not a monophyletic group. Frasera is better separated from Swertia s.l. as an independent genus, and is only distantly related to Swertia s. s. judging from the numerous differences in embryology. Swertia tetraptera is very closely related to Halenia, as they show identical embryology. (C) 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 383-400.

裂隙/孔隙型弹性介质中地震波场模拟与叠前逆时偏移

With the development of oil/gas seismic exploration, seismic survey for fracture/porosity type reservoir is becoming more and more important. As for China, since it has over 60% store of low porosity and low permeability oil/gas reservoir, it’s more urgent to validly describe fracture/porosity type oil/gas trap and proposing the related, developed seismic technique. To achieve mapping fracture/porosity region and its development status, it demands profound understanding of seismic wave propagation discipline in complex fractured/pored media. Meanwhile, it has profound scientific significance and applied worth to study forward modeling of fracture/porosity type media and pre-stacked reverse time migration. Especially, pre-stacked reverse-time migration is the lead edge technique in the field of seismology and seismic exploration. In this paper, the author has summarized the meaning, history and the present state of numerical simulation of seismic propagation in fractured/pored media and seismic exploration of fractured/pored reservoirs. Extensive Dilatancy Anisotropy (EDA) model is selected as media object in this work. As to forward modeling, due to local limitation of solving spatial partial derivative when using finite-difference and finite-element method, the author turns to pseudo-spectral method (PSM), which is based on the global characteristic of Fourier transform to simulate three-component elastic wave-field. Artifact boundary effect reduction and simulation algorithm stability are also discussed in the work. The author has completed successfully forward modeling coding of elastic wave-field and numerical simulation of two-dimensional and three-dimensional EDA models with different symmetric axis. Seismic dynamic and kinematical properties of EDA media are analyzed from time slices and seismic records of wave propagation. As to pre-stacked reverse-time migration for elastic wave-field in fractured/pored media, based on the successful experience in forward modeling results with PSM, the author has studied pre-stacked reverse-time depth-domain migration technique using PSM of elastic wave-field in two dimensional EDA media induced by preferred fracture/pore distribution. At the same time, different image conditions will bring up what kind of migration result is detailed in this paper. The author has worded out software for pre-stacked reverse-time depth-domain migration of elastic wave-field in EDA media. After migration processing of a series of seismic shot gathers, influences to migration from different isotropic and anisotropy models are described in the paper. In summary, following creative research achievements are obtained:  Realizing two-dimensional and three-dimensional elastic wave-field modeling for fractured/pored media and related software has been completed.  Proposed pre-stacked reverse-time depth-domain migration technique using PSM of elastic wave-field.  Through analysis of the seismic dynamic and kinematical properties of EDA media, the author made a conclusion that collection of multi-component seismic data can provide important data basis for locating and describing the fracture/pore regions and their magnitudes and the preferred directions.  Pre-stacked reverse-time depth-domain migration technique has the ability to reconstruct complex geological object with steep formations and tilt fracture distribution. Neglecting seismic anisotropy induced by the preferred fracture/pore distribution, will lead to the disastrous imaging results.