ELECTRON-STATES OF A STACKING-FAULT RIBBON IN SILICON

The electronic structure of a bounded intrinsic stacking fault in silicon is calculated. The method used is an LCAO-scheme (Linear Combinations of Atomic Orbitals) taking ten atomic orbitals of s-, p-, and d-type into account. The levels in the band gap are extracted using Lanczos' algorithm and a continued fraction representation of the local density of states. We find occupied states located up to 0.3 eV above the valence band maximum (E(v)). This significantly differs from the result obtained for the ideal infinite fault for which the interface state is located at E(v)+ 0.1 eV.

New observation on the luminescence of CdS clusters in zeolite-Y

The excitation spectrum of CdS dusters in zeolite-Y is consistent with their absorption spectrum, both showing two absorption bands that are assigned to the Is-is and Is-lp transitions, respectively. A new emission at 400 nn is considered to be the recombination of the bounded excitons. The emission firstly increases then decreases with increasing cluster size or loading. The emission by excitation into the Is-is band is stronger and sharper than that by excitation into the Is-lp band. This phenomenon is attributed to the size inhomogeneity and the strong electron-phonon interaction of the dusters. Copyright (C) 1996 Elsevier Science Ltd

沉积物重要矿物成份及腐植酸结合的镉对文蛤的生物有效性研究

沉积物中Cd的赋存形态对其生物有效性的影响十分显著。在水生环境中，Cd究竟结合于沉积物中的何种组分在很大程度上决定了它能否被生物所吸收。本文利用颗粒物悬浮系统研究了沉积物中Cd的赋存形态对其在文蛤体内富集速率的影响。 对沉积物中三种典型矿物上附着的Cd（氢氧化铁结合态，氢氧化铝结合态，二氧化锰结合态）的生物有效性进行了比较，结果表明，在Cd浓度为70 mg/kg时，22 d富集实验中氢氧化铁结合态和氢氧化铝结合态Cd在文蛤体内均没有明显的积累，而二氧化锰结合态Cd在文蛤体内有明显的富集，其富集速率为0.0094±0.0010 μg /g d (r2 = 0.8539, p<0.0001)。在Cd浓度为140mg/kg时，氢氧化铁结合态Cd仍然无法被文蛤吸收，氢氧化铝和二氧化锰结合态Cd则可以被文蛤富集，其富集速率分别为0.0166±0.0017 μg/gd和0.0248±0.0017 μg/gd。不同赋存形态Cd的生物有效性表现为：Cd-MnO2> Cd-Al(OH)3> Cd-Fe(OH)3。对于不同赋存形态的Cd，吸收效率（AE）和摄食率（IR）的差异导致了其生物有效性的不同。 本文进一步考察了作为沉积物中Cd生物有效性的两种主要控制组分——氢氧化铁和颗粒态腐殖酸上赋存的Cd在文蛤体内的富集规律。实验结果表明，氢氧化铁（Fe(OH)3）和腐殖酸（HA）上附着的Cd在文蛤体内的富集规律存在显著差异。在实验设置的低Cd浓度组中（如70mg/kg和140 mg/kg），Cd-HA的生物有效性高于Cd-Fe(OH)3，而在高镉浓度组中（280 mg/kg），Cd-Fe(OH)3更易于在文蛤体内富集。生物对于污染物的响应（如及时的调整摄食消化策略）对于污染物在生物体内的富集影响十分显著，而这种“生物响应”在一定程度上可能在生物体内污染物浓度达到一定阈值后才会被引发。实验进一步表明Cd在腐殖酸不同组分之间的分配对其在文蛤体内的积累规律具有显著影响。相比于溶解态的腐殖酸-Cd污染物，文蛤对颗粒态腐殖酸上结合的Cd的富集具有更强的控制作用。 与无机颗粒物相比，双壳类生物对有机颗粒物的消化更为剧烈，通常认为有机物质上结合的污染物生物有效性较高。然而，本实验结果显示，当体内污染物浓度达到一定水平时，双壳类生物可以通过调节颗粒物在体内的消化过程控制重金属在生物体内的富集。在长期暴露过程中，结合与无机颗粒物上的污染物可能更容易在生物体内富集到比较高的水平

FLOW STRUCTURES IN THREE-DIMENSIONAL FISH-LIKE SWIMMING

The swimming of a fish-like body is numerical simulated. The wake structures consist of a series of hairpin-like vortices braided together. The caudal fins generated vorticity interacts constructively with the body-bounded vorticity.

两井条件下圆形封闭煤层中压力场分布研究

煤层气开采方式的本质是排水降压采气,了解煤层的降压效果对排采制度的确定有着积极的意义。通过建立圆形封闭煤层中考虑煤层气解吸作用的两井不定常渗流模型,利用有限元方法求得了其数值解,分析解吸作用对理论特征曲线的影响。计算结果表明,煤层气解吸具有减缓压力传播的作用;分析不同性质邻井对理论曲线特征的影响,给出存在邻井影响时的压力场发展规律。提出压力场的4种描述方法,分析邻井性质、邻井流量变化,以及外边界性质对煤层压力场分布的影响,得到不同条件下煤层气压力场的变化规律。

Characteristics of electroosmotic flow and migration of neutral solutes under stepwise gradient elution of capillary electrochromatography

A theoretical study on the velocity of electroosmotic flow (EOF) and the retention times of neutral solutes under multiple-step gradient of capillary electrochromatography (CEC) was carried out, focusing on that with three kinds of mobile phases. Through the model computations, the detaining time of the second kind of mobile phase in the column was proved to play an important role in affecting EOF. The variation speed of EOF was shown to be determined by the differences among dead times in different steps. In addition, the prediction of the retention times of 13 aromatic compounds under gradient mode was performed with the deduced equations. A relative error below 3.3% between the calculated and experimental values was obtained, which demonstrated the rationality of the theoretical deduction. Our study could not only improve the comprehension of stepwise gradient elution, but also be of significance for the further optimization of separation conditions in the analysis of complex samples.

改进的以SMT为基础的实时系统限界模型检测

基于SAT的限界模型检测在处理实时系统时具有很高的复杂度.SMT求解器在计算可满足性的同时,还能处理算术和其他可判定性理论.在对实时系统进行检测时,用SMT求解器代替SAT求解器,系统里的时钟就可以用整型或实型变量表示,时钟约束则可以直接表示成线性算术表达式,从而使整个检测过程更加高效.带时间参数的计算树逻辑(timed computation tree logic,简称TCTL)被用来描述实时系统里的性质.同时,还对检测方法作了相应的改进.

基于Yices对时间自动机的有界模型检测

为了避免在有界模型检测过程中对变量进行布尔编码以及对时间自动机模型中的时钟进行预处理,给出一个利用SMT(satisfiability modulo theories)工具进行的对时间自动机进行有界模型检测的方法。该方法将时间自动机模型直接转换成SMT工具可识别的逻辑公式,利用SMT工具可求解包含有整数型和实数型变量逻辑公式的能力来进行模型检测。实验结果表明,对于某些可达性性质的验证,该方法的效率有一定的优势。

基于一阶迁移系统的限界模型检测工具实现

为了简化在限界模型检测过程中模型的建立过程,给出了一种采用基于一阶迁移系统语言的模型建立方法,并在此一阶迁移系统语言中加入了通道的功能,增强了描述能力。然后在此基础上完成了一个以基于插值和k步归纳的限界验证算法为核心的模型检测工具(BMCF),最后利用该工具对常见的互斥协议,简单数据传输协议的性质进行了分析与验证。结果表明,利用该工具对系统进行建模具有方便直观的特点,并借助实现的验证算法能高效的检验性质的正确性,如果性质不成立工具还会给出反例提示。

Synthesis of gold nanoplates by aspartate reduction of gold chloride

Single crystal nanoplates with thickness less than 30 nm, characterized by hexagonal and truncated triangular shapes bounded mainly by {111} facets, were obtained in large quantities by aspartate reduction of gold chloride.

X-ray crystal structure and molecular mechanics calculations of (2,6-iso-dipropyl-phenylamide) dimethyl (tetra-methylcyclopenta-dienyl) silane titanium dichloride

Crystal and molecular structure of (2.6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic. with a = 12.658 (3) Angstrom. b = 16.62 (3) Angstrom. c = 11.760 (2) Angstrom. V = 2474.2 (9) Angstrom(3). Z = 4, space group Pnma. R = 0.0399; Componud I compose of the pi-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed.

Characteristics and Formation Mechanism of Polygonal Faults in Qiongdongnan Basin, Northern South China Sea

Based on high-resolution 3D seismic data, we document the polygonal faults within the Miocene Meishan (sic) Formation and Huangliu (sic) Formation of the Qiongdongnan (sic) basin, northern South China Sea. Within the seismic section and time coherent slice, densely distributed extensional faults with small throw and polygonal shape were identified in map view. The orientation of the polygonal faults is almost isotropic, indicating a non-tectonic origin. The deformation is clearly layer-bounded, with horizontal extension of 11.2% to 16%, and 13.2% on average. The distribution of polygonal faults shows a negative correlation with that of gas chimneys. The development of polygonal faults may be triggered by over-pressure pore fluid which is restricted in the fine-grained sediments of bathyal facies when the sediments is compacted by the burden above. The polygonal faults developed to balance the volumetric contraction and restricted extension. The product of hydrocarbon in the Meishan Formation may have contributed to the development of the polygonal faults. In the study area, it was thought that the petroleum system of the Neogene post-rift sequence is disadvantageous because of poor migration pathway. However, the discovery of polygonal faults in the Miocene strata, which may play an important role on the fluid migration, may change this view. A new model of the petroleum system for the study area is proposed.

网络控制系统稳定性的图理论

针对具有有界时延和数据包丢失的网络控制系统,提出了一种新的稳定性判据.基于Lyapunov方法和图论理论,给出非线性离散和连续网络控制系统渐近稳定的充分条件,获得保持这两类系统稳定的最大允许时延界,得到控制器设计方法.并且,利用区间矩阵的谱特征,给出网络控制系统区间稳定的充分条件.设计算法,获得比例积分反馈控制器增益.算例表明所提方法的有效性。

一种输电线路巡检机器人控制系统的设计与实现

介绍了一种超高压输电线路巡检机器人控制系统的设计与实现方法.根据巡检作业任务的要求,采用遥控与局部自主相结合的控制模式实现巡检机器人沿线行走及跨越障碍.设计了巡检机器人有限状态机模型,实现了机器人遥控与局部自主控制的有机结合.采用基于激光传感器定位的方法实现了巡检机器人的自主越障控制.实验结果表明,该机器人可实现沿线行走及自主跨越障碍,从而验证了控制系统设计的有效性与合理性.

基于AFM的机器人化纳米操作中纳观力的初步研究

针对基于原子力显微镜(AFM)的机器人化纳米操作,对探针作用下探针—基片—微粒之间纳观力的作用规律进行了初步分析.指出起主要作用的纳观力为范德华力、接触斥力、纳米摩擦力、毛细作用力以及纳米静电力等五种,并初步推导了各种纳观力的表达形式.通过力—距离曲线仿真与实验验证了所进行分析的合理性;该分析有助于进行纳米操作的精确控制.