Similarity solutions to the second boundary value problem of unsaturated flow through porous media

Similarity solutions to the second boundary value problem of unsaturated flow are studied in one-dimensional, semi-infinite porous media with the soil-water diffusivity proportional to some power of the water content. The existence and uniqueness of two types of similarity solutions to the problem are investigated and the properties of these solutions are presented. It is shown that these two types of similarity solutions exist and that they may not be unique for every parameter range studied. The use of the similarity solutions is discussed for the experimental determination of soil-water diffusivity.     

Response of selected binomial coefficients to varying degrees of matrix sparseness and to matrices with known data interrelationships

Numerous departures from ideal relationships are revealed by Monte Carlo simulations of widely accepted binomial coefficients. For example, simulations incorporating varying levels of matrix sparseness (presence of zeros indicating lack of data) and computation of expected values reveal that not only are all common coefficients influenced by zero data, but also that some coefficients do not discriminate between sparse or dense matrices (few zero data). Such coefficients computationally merge mutually shared and mutually absent information and do not exploit all the information incorporated within the standard 2 × 2 contingency table; therefore, the commonly used formulae for such coefficients are more complicated than the actual range of values produced. Other coefficients do differentiate between mutual presences and absences; however, a number of these coefficients do not demonstrate a linear relationship to matrix sparseness. Finally, simulations using nonrandom matrices with known degrees of row-by-row similarities signify that several coefficients either do not display a reasonable range of values or are nonlinear with respect to known relationships within the data. Analyses with nonrandom matrices yield clues as to the utility of certain coefficients for specific applications. For example, coefficients such as Jaccard, Dice, and Baroni-Urbani and Buser are useful if correction of sparseness is desired, whereas the Russell-Rao coefficient is useful when sparseness correction is not desired.     

辅助模型辨识方法(2):输入非线性输出误差系统

针对具有已知基的输入非线性输出误差系统,提出了基于过参数化模型的辅助模型递推辨识方法和辅助模型递阶辨识方法,提出了基于关键项分离的辅助模型递推辨识方法、基于关键项分离的辅助模型两阶段辨识方法和辅助模型三阶段辨识方法,提出了基于双线性参数模型分解的辅助模型随机梯度算法和基于双线性参数模型分解的辅助模型递推最小二乘算法,并给出了几个典型辨识算法的计算量、计算步骤.这些算法的收敛性分析都是需要研究的辨识课题.     

Degree of Geochemical Similarity (DOGS): a simple statistical method to quantify and map affinity between samples from multi-element geochemical data sets

The 42 element, 1190 sample Mobile Metal Ion subset of the National Geochemical Survey of Australia database was used to develop and illustrate the concept of Degree of Geochemical Similarity of soil samples. Element concentrations were unified to parts per million units and log(10)-transformed. The degree of similarity of pairs of samples of known provenance in the Yilgarn Craton was obtained using least-squares linear regression analysis and demonstrated that the method successfully assessed the degree of similarity of soils related to granitoid and greenstone lithologies. Exploratory Data Analysis symbol maps of all remaining samples in the database against various reference samples were used to obtain correlation maps not only for granitoid- and greenstone-related soil types but also to distinguish between, for example, samples derived from marine vs regolith carbonate. Likewise, the distribution of soil samples having a geochemical fingerprint similar to mineralised provinces (e.g. Mount Isa) can be mapped, and this can be used as a first-order prospection tool.     

A grid-search inversion method looking for the best classification of polyphase fault/slip data

A novel, grid search-based stress inversion method is developed in this paper to find the global minima in the solution region for the classification of fault/slip data into many single-phase subsets. Exhaustively repetitious grid searches are taken to deal with possible local minima, in a departure from existing grid search-based inversion methods. Two stopping rules, to stop at the abrupt change of the objective function or at the least change of the classification, are adopted in the method to look for the best classification. Much calculation time is saved by using a modified version of conventional grid search. The feasibility of this proposed method is demonstrated by applying it to two artificial examples and two real examples. However, enormous time in calculation is still needed in the case of a data set either with a large number of data or for a large number of assigned subsets.     

机载干涉SARDEM绝对定向技术研究

机载干涉SAR产生的未经地理编码的DEM有较高的相对高程精度,但因其是基于斜距表达的,且干涉几何定标存在误差,需要利用控制点来进行绝对定向。本文首先改正由地形起伏引起的像点位移,将斜距DEM转换成地距DEM,然后根据空间相似变换,将地距DEM视为刚体,利用控制点求模型平移偏量、缩放因子及旋转角,达到绝对定向的目的。     

The exemplar‐aided constructor of hyper‐rectangles learning algorithm for stream flow estimation

The exemplar‐aided constructor of hyper‐rectangles (EACH) model which simulates human intelligence by learning from experience and adjusting in time, proposed by Salzberb (1991), is presented and modified to strengthen its performance in variable stream flow extension. The modification is intended to resolve the contradiction between building hyper‐rectangles and predictive accuracy in which the number of hyper‐rectangles becomes too large if higher accuracy is required. To explore the feasibility of the modified EACH, a mathematical function is simulated by the model. It is then applied to extend the 10‐day stream flow records according to the nearby rainfall and/or stream flow gauges. The results show that the modified EACH achieves the goal of saving memory space and promoting predictive accuracy, and its performance is better than those of the original EACH and traditional methods. This research suggests that the modified EACH shows considerable promise in stream flow estimation. Copyright © 2000 John Wiley & Sons, Ltd.     

Optimal damper placement for building structures including surface ground amplification

A systematic method for optimal added damper placement in building structures is developed, taking into account the response amplification due to the surface ground. Non-linear amplification of the surface ground is described by an equivalent linear model. Hysteretic damping of the surface ground and radiational damping into the semi-infinite visco-elastic ground are included in the model. An original steepest direction search algorithm is applied to the interaction model. Closed-form expressions of the inverse of the coefficient matrix (tri-diagonal matrix) enable one to compute the transfer function and its derivative with respect to design variables very efficiently. It is shown that the ratio of the fundamental natural period of the structure to that of the surface ground is a key parameter for characterizing the optimal damper placement. Several examples for different soil conditions are presented to demonstrate the effectiveness and validity of the present method.