线性组合边界中煤层气井的不稳定压力数值分析

文章建立并求解了不同线性组合边界条件下的煤层气井不定常渗流模型，得到了井底压力和压力导数的理论曲线，以及压力场分布图。在不稳定流动的早期，压力和压力导数曲线都是斜率为1的直线段。当流体流动进入稳定流动状态时，在压力导数曲线上出现一个值为0．5的水平直线段。在理论曲线的晚期，理论曲线与边界性质存在密切关系。对于全封闭煤层气藏，所有压力和压力导数曲线是斜率为1的直线段。对于存在定压边界煤层气藏，压力双对数曲线的晚期是水平直线段，压力导数双对数曲线的晚期都是急剧下掉的曲线。但是混合边界的压力导数存在上翘现象，上翘程度和早晚与封闭边界的数目多少以及距离大小有关。压力场中，在靠近封闭边界的等压线垂直于边界，在靠近定压边界的等压线平行于边界。在邻近定压和封闭边界交合处，定压边界起主导作用。所得到的理论曲线可以直接应用于煤层气田的试井测试资料分析，压力场分布图对了解煤层气藏的开发状况有积极的意义。

基于广义模型和分类回归树的中国常见树种地理分布模拟研究

研究植被、物种分布与环境的关系一直是生态学中的重点。长期以来，在全球变化与陆地生态系统的研究中，主要研究重点是对大尺度植被分布的模拟和预测，并建立了大量的气候－植被分布关系模型。而对于物种潜在分布的模拟和预测，国内外相关的研究较少。近年来，随着统计技术和地理信息系统的发展，用于预测物种分布的统计模型技术得到了迅速的发展。统计模型技术已被广泛应用于生物地理分布、植物群落、生物多样性、气候变化影响评估等方面。 本论文基于当前在物种分布研究中应用广泛的广义线性模型、广义加法模型及分类回归树3种统计模型技术，对我国常见树种的地理分布进行模拟分析，并比较不同模型模拟精度的优劣，将模拟精度较高的模型应用于预测未来气候情景下我国几种主要树种的未来潜在地理分布。 基于建立的广义线性模型（GLM）、二次项逐步回归广义线性模型（SGLM）、广义加法模型（GAM）和分类回归树（CART）4个模型对我国20种常见树种地理分布进行模拟，结果表明，4个模型均有较高的模拟精度。GAM的模拟精度最高;添加二次项并进行逐步回归有效的提高了GLM的模拟精度;CART是一种基于规则的模型技术，模拟结果比GLM稍好，比GAM略差。 对不同树种的模拟分析表明，4个模型对于主要分布在暖温带落叶阔叶林区域的油松、辽东栎分布的模拟结果较差;GLM对分布在温带针阔混交林中红松、蒙古栎、胡桃楸和糠椴的模拟结果不太理想;4个模型对分布在中国亚热带常绿阔叶林区域的树种均表现出较高的模拟精度;对广布种也表现出很高的模拟精度。 结合地理信息系统，以地图形式将青冈、油松的模拟结果表示出来。结果表明：地理信息系统直观的反映出了模型模拟结果差异。4个模型均能很好模拟青冈的分布，且模拟结果接近;而对油松分布模拟结果4个模型均不甚理想，以GLM最差。这些结果与模型模拟评估结果相吻合。 在未来气候变化情景下，基于4个模型模拟结果优劣，以我国三种主要造林树种马尾松、油松、红松和两种常见树种青冈、蒙古栎为研究对象，分析其未来变化趋势。结果表明，未来气候变化情景下，对于马尾松而言，4个模型均预测马尾松在基本保持原有分布的基础上，其未来潜在分布区域均有所扩大，且有向西和向北扩展的趋势;对于油松而言，基于GLM、SGLM和GAM3个模型，油松的未来潜在分布除有北移的趋势外，其分布区还将向东北和西南两个方向扩展;对于红松而言，基于SGLM、GAM和CART3个模型的预测结果较为接近，即红松的未来潜在分布区域将有所减少;对蒙古栎而言，4个模型预测蒙古栎未来分布均将向西扩展;对青冈而言，4个模型预测青冈能基本保持其原有分布区，并向西和向北扩展，其中CART预测结果还表明，青冈在广东南部及广西南部的分布区域将消失。

Microelectrode voltammetric measurement of heterogeneous electron transfer rate constants for reduction of 7,7,8 ',8 '-tetracyanoquinodimethane in polymer electrolytes

This paper presents a microelectrode voltammetric determination of heterogeneous electron transfer rate constants (k(s)) and diffusion coefficients (D) of 7,7,8',8 '-tetracyanoquinodimethane (TCNQ) in polyelectrolytes. The diffusion coefficients are estimated using cyclic voltammetry under linear diffusion conditions, and the heterogeneous electron transfer rate constants are obtained under mixed linear and radial diffusion in the polyelectrolyte. k(s) and D increase with increasing temperature, and the activation barriers of the electrode reaction for reduction of TCNQ are obtained. On the other hand, the dependencies of D and k(s) of TCNQ on the size and charge of the counterion are compared in the polyelectrolyte. (C) 1998 Elsevier Science Ltd. All rights reserved.

Roles of equatorial waves and western boundary reflection in the seasonal circulation of the equatorial Indian Ocean

An ocean general circulation model (OGCM) is used to study the roles of equatorial waves and western boundary reflection in the seasonal circulation of the equatorial Indian Ocean. The western boundary reflection is defined as the total Kelvin waves leaving the western boundary, which include the reflection of the equatorial Rossby waves as well as the effects of alongshore winds, off-equatorial Rossby waves, and nonlinear processes near the western boundary. The evaluation of the reflection is based on a wave decomposition of the OGCM results and experiments with linear models. It is found that the alongshore winds along the east coast of Africa and the Rossby waves in the off-equatorial areas contribute significantly to the annual harmonics of the equatorial Kelvin waves at the western boundary. The semiannual harmonics of the Kelvin waves, on the other hand, originate primarily from a linear reflection of the equatorial Rossby waves. The dynamics of a dominant annual oscillation of sea level coexisting with the dominant semiannual oscillations of surface zonal currents in the central equatorial Indian Ocean are investigated. These sea level and zonal current patterns are found to be closely related to the linear reflections of the semiannual harmonics at the meridional boundaries. Because of the reflections, the second baroclinic mode resonates with the semiannual wind forcing; that is, the semiannual zonal currents carried by the reflected waves enhance the wind-forced currents at the central basin. Because of the different behavior of the zonal current and sea level during the reflections, the semiannual sea levels of the directly forced and reflected waves cancel each other significantly at the central basin. In the meantime, the annual harmonic of the sea level remains large, producing a dominant annual oscillation of sea level in the central equatorial Indian Ocean. The linear reflection causes the semiannual harmonics of the incoming and reflected sea levels to enhance each other at the meridional boundaries. In addition, the weak annual harmonics of sea level in the western basin, resulting from a combined effect of the western boundary reflection and the equatorial zonal wind forcing, facilitate the dominance by the semiannual harmonics near the western boundary despite the strong local wind forcing at the annual period. The Rossby waves are found to have a much larger contribution to the observed equatorial semiannual oscillations of surface zonal currents than the Kelvin waves. The westward progressive reversal of seasonal surface zonal currents along the equator in the observations is primarily due to the Rossby wave propagation.

Deformation Of Pdms Membrane And Microcantilever By A Water Droplet: Comparison Between Mooney-Rivlin And Linear Elastic Constitutive Models

In this paper, we studied the role of vertical component Of Surface tension of a water droplet on the deformation of membranes and microcantilevers (MCLs) widely used in lab-on-a-chip and micro-and nano-electromechanical system (MEMS/NEMS). Firstly, a membrane made of a rubber-like material, poly(dimethylsiloxane) (PDMS), was considered. The deformation was investigated using the Mooney-Rivlin (MR) model and the linear elastic constitutive relation, respectively. By comparison between the numerical solutions with two different models, we found that the simple linear elastic model is accurate enough to describe such kind of problem, which would be quite convenient for engineering applications. Furthermore, based on small-deflection beam theory, the effect of a liquid droplet on the deflection of a MCL was also studied. The free-end deflection of the MCL was investigated by considering different cases like a cylindrical droplet, a spherical droplet centered on the MCL and a spherical droplet arbitrarily positioned on the MCL. Numerical simulations demonstrated that the deflection might not be neglected, and showed good agreement with our theoretical analyses. (C) 2008 Elsevier Inc. All rights reserved.

Bayesian mixed models and divergence time estimation of Chinese cavefishes (Cyprinidae : Sinocyclocheilus)

The genus Sinocyclocheilus is distributed in Yun-Gui Plateau and its surrounding region only, within more than 10 cave species showing different degrees of degeneration of eyes and pigmentation with wonderful adaptations. To present, published morphological and molecular phylogenetic hypotheses of Sinocyclocheilus from prior works are very different and the relationships within the genus are still far from clear. We obtained the sequences of cytochrome b (cyt b) and NADH dehydrogenase subunit 4 (ND4) of 34 species within Sinocyclocheilus, which represent the most dense taxon sampling to date. We performed Bayesian mixed models analyses with this data set. Under this phylogenetic framework, we estimated the divergence times of recovered clades using different methods under relaxed molecular clock. Our phyloegentic results supported the monophyly of Sinocyclocheilus and showed that this genus could be subdivided into 6 major clades. In addition, an earlier finding demonstrating the polyphyletic of cave species and the most basal position of S. jii was corroborated. Relaxed divergence-time estimation suggested that Sinocyclocheilus originated at the late Miocene, about 11 million years ago (Ma), which is older than what have been assumed.