Permeability Prediction of Well Log Responses Using a Local Linear Model Tree Based on a TSK-fuzzy System

Abstract

A learned model obtained from a data set can be used for prediction, simulation, optimization, and analysis of the system. The local linear model tree used for the TSK-fuzzy system has been successful in predicting the permeability of a typical Iranian oilfield rock. The methodology involves the heuristic search to choose the space of the input partitions by axis-orthogonal splits and also automatic permeability estimation from digitized data (well logs) obtained from oil wells. The results show that the local linear model tree is incurred to the smallest error on the unseen data when compared to similar algorithms. On the other hand, the limited flexibility of the local estimation reduces the variance error due to the bias/variance dilemma. Consequently, the local estimation approach has a regularization effect on the estimation.     

正电子发射计算机断层扫描、医用回旋加速器在地下室的安装要点

正电子发射计算机断层扫描是一种先进的核医学影像设备，医用回旋加速器主要为正电子发射计算机断层扫描检查提供所需示踪剂中的放射性核素。上述设备涉及放射物理、放射化学、医学工程、药物学等各方面知识，且机器结构比较复杂，环境条件要求高。本文针对在大型地下室安装正电子发射计算机断层扫描设备和医用回旋加速器需供应商、专业使用部门及工程建设部门协调和解决的相关问题，将笔者在负责安装该设备时所获得的一些经验总结出来，与各位同行探讨。     

Local power of likelihood‐based tests for cointegrating rank: Comparative analysis of full and partial systems

This note investigates local power properties of likelihood‐based cointegrating rank tests for partial and full vector autoregressive systems. The asymptotic distributions of partial likelihood‐based tests under local alternatives are derived, depending on various specifications of deterministic terms. A simulation study is then performed using both the full and partial systems. It is demonstrated that the rank tests based on the partial system, if a required parametric condition is fulfilled, can be more powerful than those based on the full system. This finding encourages testing cointegrating rank using a partial system as well as a full system, in such circumstances as the parametric condition could be satisfied.     

Navigating gendered labor and local food: A tale of working mothers in Vermont

Over the past several decades, the state of Vermont has become a national leader in the local food movement. Located along the banks of Lake Champlain, Chittenden County is a hub for the local food movement and innovative food security efforts. This article presents qualitative data from a collaborative research project examining the multiple ways that Chittenden County residents access, prepare, and share food. Following the model of “critical case studies,” I focus in on the narratives of six working mothers from diverse cultural backgrounds to examine the work of these mothers related to accessing, preparing, and sharing food and how this work is shaped by intersections of cultural identity and gendered obligations. I argue that narratives of food and family are a meaningful site for examining the lived dimensions of local food systems and shared values related to food that are culturally familiar and embedded in social relationships.     

A model of fatigue crack propagation in metals

A model of the formation and evolution of a local plastic deformation zone at the crack tip is proposed based on the analysis of the main physical processes taking place in a metallic material under the action of cyclic loads. An equation of fatigue crack growth rate curves, which explicitly accounts for the loading frequency, was derived. The equation applies to the whole range of crack lengths from short cracks to macroscopic ones. __________ Translated from Problemy Prochnosti, No. 1, pp. 35–43, January–February, 2009.     

Bootstrap prediction intervals in state–space models

Abstract.  Prediction intervals in state–space models can be obtained by assuming Gaussian innovations and using the prediction equations of the Kalman filter, with the true parameters substituted by consistent estimates. This approach has two limitations. First, it does not incorporate the uncertainty caused by parameter estimation. Second, the Gaussianity of future innovations assumption may be inaccurate. To overcome these drawbacks, Wall and Stoffer [ Journal of Time Series Analysis (2002) Vol. 23, pp. 733–751] propose a bootstrap procedure for evaluating conditional forecast errors that requires the backward representation of the model. Obtaining this representation increases the complexity of the procedure and limits its implementation to models for which it exists. In this article, we propose a bootstrap procedure for constructing prediction intervals directly for the observations, which does not need the backward representation of the model. Consequently, its application is much simpler, without losing the good behaviour of bootstrap prediction intervals. We study its finite-sample properties and compare them with those of the standard and the Wall and Stoffer procedures for the local level model. Finally, we illustrate the results by implementing the new procedure to obtain prediction intervals for future values of a real time series.     

含有纯滞后特性的PI(D)—VGAC系统的稳定性和鲁棒性

应用Fenandez等人对含有纯滞后特性的自适应系统的理论分析方法,针对由一阶惯性环节加纯滞后特性所构成的PI(D)—VGAC系统的稳定性及鲁棒性进行了分析,得出了一些结论,并将其推广到高阶系统。数字仿真结果验证了这些结论是正确的。     

循环代数迭代松驰法在全息层析术测量三维温度场中的应用

本文通过计算机模拟运算并结合温度场（折射率场）的先验知识。考查了用循环代数迭代松驰法重建三维温度场时不同视角范围、视角方向和松驰系数对重建精度的影响。得出了该算法的六个特点。作为实例，计算了二个截面火焰温度场分布。     

理想可压弹塑性介质中Ⅰ型准静态扩展裂纹端的局部场渐近分析

Gao(1982)和 Drugan(1983)曾分别给出了可压(v<1/2)理想弹塑性介质中Ⅰ型定常扩展裂纹平面应变问题的渐近解,然而高玉臣(1986)又提出 Gao 和 Drugan 给出的结果导致应变率一级渐近协调方程产生矛盾,因此是不恰当的。本文在高玉臣(1986)给出的应力函数渐近展开级数的基础上,给出了不同的渐近解。发现表征材料可压特性的函数 Q 的零级渐近近似值不为零,从而裂纹邻域局部应力场和应变率场与 Gao 和 Dru-gan 的结果具有不同的形式。特别地塑性应变率在均匀应力区具有r~(-1)(1nR/r)~(-1)阶奇异性,在中心扇形区有 r~(-1)阶奇异性。在整个裂尖邻域应变率具有r~(-1)阶奇异性。本文所给的结果不会导致应变率一级渐近协调方程产生矛盾。     

用等参元方法计算弹丸结构特征数

本文利用有限元分析中的等参元和高斯积分法建立了计算弹丸结构特征数的公式,这种方法数据准备少,计算精度高。更重要的是利用这种方法使得繁琐的计算弹丸结构特征数的工作,无单独存在的必要。在利用有限元程序进行结构强度分析的同时附带就把弹丸结构特征数计算完毕,大大节省了时间,加快了设计进度。