基于AFM的微结构加工实验研究

本文建立了微动工作台和原子力显微镜相结合的微加工系统，在该系统上采用金刚石针尖进行微加工实验，与SPI系统本身的刻划软件刻划出的图形进行了比较分析，得出这个系统适合微结构的加工；并给出了采用该方法加工的1111面及多边形面微结构；还分析了金刚石针尖几何角度及SPM和工作台的相关参数对加工的影响。     

Numerical Study of Finite Element Method Based Solutions for Propagation of Wetting Fronts in Unsaturated Soil

The accurate prediction of the propagation of a wetting front in an unsaturated soil subjected to surficial infiltration is of practical importance to many geotechnical and geoenvironmental problems. The finite element method is the most common solution technique as the hydraulic soil properties are highly nonlinear. Two important issues are often found to create difficulties in such analyses. First, numerical oscillations are usually observed in the calculated pore pressures at the wetting front. Second, when a reasonable mesh size and time step are used, the elevation of the wetting front may be seriously overpredicted. This paper is focused on the second issue. The under-relaxation (UR) technique used in the iterative process within each time step is found to have a serious impact on rate of convergence with refinement in mesh size and time step. Two different techniques are typically used; the first evaluates the hydraulic conductivity using an average of heads calculated from the preceding time node and the most recent iteration of the current time node (UR1), and the second evaluates the hydraulic conductivity using the average of heads calculated from the two most recent iterations of the current time nodes (UR2). The study shows that UR1, which is adopted in programs such as SEEP/W, ensures that the solution converges rapidly to a stable solution within a time step, but may converge to the wrong wetting front at a given elapsed time unless a sufficiently refined mesh is used. UR2 converges much more slowly within a time step, but the error in the wetting front is smaller than that generated by UR1.     

Effects of a K+ATP channel opener, lemakalim, on systemic, coronary and regional vascular dynamics in conscious dogs: comparison with nifedipine, adenosine, nitroglycerin and acetylcholine

The systemic, coronary and regional vascular responses to the K+ATP channel opener lemakalim were compared to other potent vasodilators (i.e., nifedipine, adenosine, nitroglycerin and acetylcholine). Experiments were performed in 12 conscious dogs 2 to 4 weeks after implantation of aortic catheters and flow probes on the ascending aorta, left circumflex coronary, celiac, mesenteric, renal and iliac arteries, and solid-state miniature pressure gauges in the left ventricular cavity. Dose-response curves induced by bolus injection (i.v.) were examined. For doses that reduced total peripheral resistance by 22%, lemakalim reduced celiac (-28 +/- 2%), mesenteric (-24 +/- 3%), renal (-17 +/- 3%) and iliac (-18 +/- 3%) vascular resistances (i.e., by amounts similar to those observed with the other vasodilators, except for adenosine, which increased renal resistance). At these doses, lemakalim induced a greater decrease (-52 +/- 3%) (P < .05) in coronary resistance, as compared with nifedipine (-35 +/- 3%), adenosine (-38 +/- 3%), nitroglycerin (-25 +/- 2%) and acetylcholine (-32 +/- 3%). However, when near maximal vasodilation was elicited, adenosine elicited the greatest (P < .05) decrease in coronary resistance (-81 +/- 1%), as compared with lemakalim (-74 +/- 2%), nifedipine (-67 +/- 2%), nitroglycerin (-63 +/- 2%) and acetylcholine (-72 +/- 1%). Both the time to maximal increases in regional blood flow and the time for recovery in all vascular beds were significantly prolonged for lemakalim compared with the other vasodilators. Thus, the K+ATP channel opener lemakalim dilates the coronary bed out of proportion to other vascular beds, is relatively more potent at lower doses than other vasodilators and exhibits a delayed and more prolonged action in all regional vascular beds.     

R-Calculus for ELP:An Operational Approach to Knowledge Base Maintenance

Sme concepts used in knowledge base maintenace,such as sequence,new law,user‘s rejection and reconstructions of a knowledge base,are first introduced,and then a framework for extended logic programming(ELP)is given,where an extended logic program is equivalent to a knowledge base.A transition system called R-calculus for ELP is provided.For a given knowledge base and a user‘s rejection,the R-calculus for ELP will deduce best revisions of the base.The soundness and the completeness of the R-calculus for ELP are proved,and the R-calculus for ELP is implemented in Prolog.In addition,the research is compared with other relevant work.     

心电地图仪中工频干扰的一种滤除方法

在心电地图仪中记录到的体表心电信号往往由于电磁的影响而引进工频干扰．基于体表心电信号中工频干扰的特点，作者提出了一种滤除工频干扰的方法，即就单独—胸导联信号通过提高频谱的分辨率来估计工频干扰的频率；基于最小均方误差准则来估计各导联信号中工频干扰的幅度和相位。文中还给出了该算法的流程图和滤波性能分析。模拟结果表明了该算法的有效性。应用该算法对心电地图仪中的工频干扰进行对消，取得了满意的结果。     

对分布式数据库发展方向的分析

本文对分布式数据库的设计方法、分割与分配技术作了一些探讨，并就分布式数据库的发展方向进行了初步分析。     

Delay-dependent state estimation for delayed neural networks

In this letter, the delay-dependent state estimation problem for neural networks with time-varying delay is investigated. A delay-dependent criterion is established to estimate the neuron states through available output measurements such that the dynamics of the estimation error is globally exponentially stable. The proposed method is based on the free-weighting matrix approach and is applicable to the case that the derivative of a time-varying delay takes any value. An algorithm is presented to compute the state estimator. Finally, a numerical example is given to demonstrate the effectiveness of this approach and the improvement over existing ones.     

长江重要堤防隐蔽工程建设投资对扩大内需、拉动经济的作用和影响

长江重要堤防隐蔽工程是党中央、国务院实施积极财政政策进行长江堤防建设的重要组成部分，隐蔽工程既是重要的基础设施，也是重要的环境保护工程，隐蔽工程与其他行业的关联性很强，对众多行业具有巨大的带动作用，有效地扩大了内需，拉动了经济增长。     

Systematic characterization of Cl2 reactive ion etchingfor improved ohmics in AlGaN/GaN HEMTs

Pre-metal-deposition reactive ion etching (RIE) was performed on an Al_0.3Ga_0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs     

两种波长激光血管内照射生物效应比较

目的：研究同等照射条件的低强度532nm与633nm激光血管内照射生物效应的特点。方法：用532nm和633nm激光对健康大耳白家兔血管内照射，平均照射功率均设定在5mW左右，照射总能量约12J。两组家兔均于照前及照后1d、4d、7d、11d采集外周血，检测血浆ET、NO、MDA含量和SOD活性。结果：两组家兔上述各指标随照后时间的变化规律相似，经方差分析组间各指标都没有显著性差异。结论：同等照射条件下，低强度532nm与633nm激光照射血液的生物效应相似。