Time stepping schemes for coupled displacement and pore pressurē analysis

 The paper investigates the performance of various time stepping schemes for coupled displacement and pore pressure analysis. A number of alternative forms of the automatic time stepping method proposed by Sloan and Abbo (1999a) are also presented. These alternative schemes use different updates for the displacements and pore pressures and also adopt different starting conditions for the iterations. The automatic schemes are compared with an implicit θ-method, as well as an explicit method, through analysis of a variety of problems involving undrained loading, drained loading, and consolidation for Mohr-Coulomb and critical state models. As expected, the numerical results confirm that the explicit scheme is neither accurate nor robust. Although the implicit θ-method is accurate and fast, it fails to give a solution in a number of cases where the time step is large. The automatic schemes are shown to be accurate, fast and generally robust. Two of the automatic schemes proposed never fail to furnish a solution for the cases considered. In addition, all the automatic schemes are able to constrain the time-stepping (temporal integration) error in the displacements and pore pressures to lie near a prescribed tolerance, provided the iteration error tolerance is properly chosen. For complex soil models, it is important that the latter is set sufficiently small in order for the schemes to be able to constrain the time-stepping error to lie within a prescribed tolerance. Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many years.     

Robustness issues in optimal control of unstable plants

This paper presents a robustness analysis of the optimal solution of the step tracking problem in a one-degree of freedom control architecture, for the discrete-time multivariable (MIMO) case. It is shown that the resulting closed loop becomes arbitrarily fragile, i.e. the sensitivity peak becomes arbitrarily large, for certain reference directions. The cause of this problem is that the optimal controller depends on the reference direction. The paper shows that this dependence can be eliminated with an alternative formulation of the optimal problem where the cost is averaged over all reference directions.     

中国大油田的分布特征与发现前景

大油田在石油储量增长和产量构成中占有重要位置.截至2004年底,中国大油田的可采储量占总探明储量的77%,2004年大油田产量占全国石油产量的70%.中国大油田的储集层主要是白垩系和第三系的陆相碎屑岩,圈闭以背斜圈闭和混合圈闭为主,20世纪70年代是中国大油田发现的高峰期.中国的大油田主要分布在富油气凹陷中;凹陷的资源丰度越大,发现大油田所需的时间越短;凹陷的资源量越大,发现的大油田规模也越大.中国目前整体勘探程度比较低,未来在中西部地区和海域都可能有大油田发现.图6表1参10     

A Detection-Theoretic Model of Echo Inhibition.

A detection-theoretic analysis of the auditory localization of dual-impulse stimuli is described, and a model for the processing of spatial cues in the echo pulse is developed. Although for over 50 years "echo suppression" has been the topic of intense theoretical and empirical study within the hearing sciences, only a rudimentary understanding of its mechanisms has emerged. In this article, psychometric functions and results from matching studies are used in developing a model that specifies the perceived position of the echo pulse as a normal deviate, with an expectation that is a logistic function of the echo delay and a variance that depends on interaural time difference. Loss of information in the echo event is quantified as a decline in the efficiency with which the binaural system receives information from the lag impulse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction of spectral reflectance factor distribution of automotive paint finishes

It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125     

具有未知时滞的线性连续系统的辨识

本文给出了一种频域方法,它能用来辨识具有未知时滞的连续过程.     

一种新的混合相位反褶积方法

在地震资料处理中,常用预测反褶积方法提高地震资料的分辨率,它具有两个基本的假设条件:①地震子波是最小相位;②反射系数序列是随机过程。上述假设条件与实际地震子波的混合相位存在较大差别。为此,笔者在借鉴前人研究的基础上,提出了一种新的混合相位反褶积方法。其实现过程为:①根据地震记录的自相关和地震子波自相关之间的关系,由最小二乘法拟合出地震子波的振幅谱,进而计算出地震子波的自相关;②利用计算出来的地震子波自相关设计一个最小相位滤波器,然后加一个延迟量于自相关函数的主对角线上,将最小相位反滤波器分解为一个长度很短的滤波器,再与一个长度较长的滤波器进行褶积,可得到一系列的混合相位子波和混合相位滤波器;③将得到的混合相位滤波器和原始地震道进行褶积,选取一定的判别准则,以选出最佳的混合相位滤波器以及相应的混合相位子波。通过模型试算和实际资料处理可知,分时窗反褶积的效果要好于单时窗反褶积,混合相位反褶积效果好于最小相位反褶积。在分时窗求取地震子波时,为了得到更好的反褶积效果,要注意时窗宽度与算子长度之间的关系。     

利用地震属性钻前预测井壁稳定性

钻前准确预测井壁稳定性是防止钻进过程中井壁失稳的有效手段。声波时差和地层密度是井壁稳定分析的两个关键参数。根据地震记录与地层声波时差及密度之间存在的非线性关系，提出了利用地震属性钻前预测井壁稳定性的方法。从井旁地震记录中提取地震属性，通过RBF神经网络在已钻井段的地震属性与声波时差及密度之间建立起映射模型，以此为基础预测待钻地层的声波时差和密度。运用预测结果结合井壁稳定力学模型，确定岩石力学参数和地应力状态，计算井壁坍塌压力和破裂压力，确定安全钻井液密度窗口，实现钻前井壁稳定预测。该方法在塔里木油田的应用中取得了良好的预测效果。     

复杂不规则刚体转动惯量的测试原理和方法

为了测量复杂不规则刚体转动惯量，采用时间常数法，通过A/D卡PS2129的定时/计数器8253高精度测速、计时，能较好地应用于测量转动惯量。     

Stability of formal thought disorder and referential communication disturbances in schizophrenia.

This study examined the degree to which different types of communication disturbances in the speech of 48 schizophrenia patients and 28 controls were variable and state related versus stable and traitlike. Clinically rated formal thought disorder and 5 types of referential disturbance showed substantial stability within participants over time. The sixth type of referential disturbance, the vague reference, was not stable over time. Formal thought disorder was associated with the severity of core psychotic symptoms in patients, whereas referential disturbances showed little or no association with positive or negative symptom severity. Furthermore, changes in psychotic symptoms over time were accompanied by corresponding changes in formal thought disorder but not referential disturbances. These results support the idea that some types of referential disturbances are traitlike and may be reflective of vulnerability as well as manifest illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)