Sensitivity Analysis of Model Output with Input Constraints: A Generalized Rationale for Local Methods

In this work, we introduce a generalized rationale for local sensitivity analysis (SA) methods that allows to solve the problems connected with input constraints. Several models in use in the risk analysis field are characterized by the presence of deterministic relationships among the input parameters. However, SA issues related to the presence of constraints have been mainly dealt with in a heuristic fashion. We start with a systematic analysis of the effects of constraints. The findings can be summarized in the following three effects. (i) Constraints make it impossible to vary one parameter while keeping all others fixed. (ii) The model output becomes insensitive to a parameter if a constraint is solved for that parameter. (iii) Sensitivity analysis results depend on which parameter is selected as dependent. The explanation of these effects is found by proposing a result that leads to a natural extension of the local SA rationale introduced in Helton (1993) . We then extend the definitions of the Birnbaum, criticality, and the differential importance measures to the constrained case. In addition, a procedure is introduced that allows to obtain constrained sensitivity results at the same cost as in the absence of constraints. The application to a nonbinary event tree concludes the article, providing a numerical illustration of the above findings.     

明清徽州林木盗砍事件的社会经济与文化考察

现有关于徽州林木的研究大多注意到徽州山林经营、林木保护及地方社会应对等问题,但难见对明清徽州林木盗砍现象及原因的系统考察,对文书资料利用也很少。系统梳理了契约文书资料后,揭示了徽州文书对林木盗砍现象及原因研究的独特价值。资料显示,在明清徽州的农村社会,林木盗砍对农家经济、生态环境有深远影响,其原因值得深思。明清徽州林木盗砍既有人口激增的背景,也与人口流动趋于频繁有关,并且,在明清时期徽州逐利民俗的大背景下,徽州人的贪图小利以及棍徒横行等因素也加重了徽州林木盗砍现象。这些问题在以往研究中并未得到关注。     

论贵州侗族服饰中的审美民族性

贵州侗族服饰就是一个独特的隐喻体系,它是通过服饰的三大核心部位来完成对其民族历史、文化、精神及意识的隐喻:衣服的款式和颜色宛如一颗杉树,隐喻的是民族精神的本源,是人与自然和谐一体观念的表达;发式宛如土堆,隐喻的是始祖居所,是"萨"崇拜信仰的形式表达;头花宛如新生命,隐喻的是情爱和生殖力,是自由、快乐追求的表达,是柔性美文化的体现。贵州侗族服饰通过以上三个方面的隐喻,表现了该民族最纯真的艺术意志和审美精神。     

中国现代作家笔下的“南洋”风景:花木与建筑简

中国现代作家笔下有许多描写“南洋”风景的篇章,其中以“南洋”花木描写与“南洋”建筑描写卓为突出。诗人杜运燮的《热带三友》笔致动人地写述了“南洋”椰、蕉、木棉的尤异姿态和精神内涵。“南洋”的佛塔寺可谓“南洋”文化“超机体”的一个泛例隐喻,而新加坡的“鱼尾狮”则是“南洋”文化记忆库里最微缩典型的一个特案象征,两者分别从宏观与微观的代表性视界具体而微地诠证了“南洋”建筑风景全部文化归属性的“情感结构”。     

Gaining insight with recursive partitioning of generalized linear models

Recursive partitioning algorithms separate a feature space into a set of disjoint rectangles. Then, usually, a constant in every partition is fitted. While this is a simple and intuitive approach, it may still lack interpretability as to how a specific relationship between dependent and independent variables may look. Or it may be that a certain model is assumed or of interest and there is a number of candidate variables that may non-linearly give rise to different model parameter values. We present an approach that combines generalized linear models (GLM) with recursive partitioning that offers enhanced interpretability of classical trees as well as providing an explorative way to assess a candidate variable's influence on a parametric model. This method conducts recursive partitioning of a GLM by (1) fitting the model to the data set, (2) testing for parameter instability over a set of partitioning variables, (3) splitting the data set with respect to the variable associated with the highest instability. The outcome is a tree where each terminal node is associated with a GLM. We will show the method's versatility and suitability to gain additional insight into the relationship of dependent and independent variables by two examples, modelling voting behaviour and a failure model for debt amortization, and compare it to alternative approaches.     

New two-stage sampling designs based on neoteric ranked set sampling

Neoteric ranked set sampling (NRSS) is a recently developed sampling plan, derived from the well-known ranked set sampling (RSS) scheme. It has already been proved that NRSS provides more efficient estimators for population mean and variance compared to RSS and other sampling designs based on ranked sets. In this work, we propose and evaluate the performance of some two-stage sampling designs based on NRSS. Five different sampling schemes are proposed. Through an extensive Monte Carlo simulation study, we verified that all proposed sampling designs outperform RSS, NRSS, and the original double RSS design, producing estimators for the population mean with a lower mean square error. Furthermore, as with NRSS, two-stage NRSS estimators present some bias for asymmetric distributions. We complement the study with a discussion on the relative performance of the proposed estimators. Moreover, an additional simulation based on data of the diameter and height of pine trees is presented.     

Toward an Application Guide for Safety Integrity Level Allocation in Railway Systems

The work in the article presents the development of an application guide based on feedback and comments stemming from various railway actors on their practices of SIL allocation to railway safety‐related functions. The initial generic methodology for SIL allocation has been updated to be applied to railway rolling stock safety‐related functions in order to solve the SIL concept application issues. Various actors dealing with railway SIL allocation problems are the intended target of the methodology; its principles will be summarized in this article with a focus on modifications and precisions made in order to establish a practical guide for railway safety authorities. The methodology is based on the flowchart formalism used in CSM (common safety method) European regulation. It starts with the use of quantitative safety requirements, particularly tolerable hazard rates (THR). THR apportioning rules are applied. On the one hand, the rules are related to classical logical combinations of safety‐related functions preventing hazard occurrence. On the other hand, to take into account technical conditions (last safety weak link, functional dependencies, technological complexity, etc.), specific rules implicitly used in existing practices are defined for readjusting some THR values. SIL allocation process based on apportioned and validated THR values is finally illustrated through the example of “emergency brake” subsystems. Some specific SIL allocation rules are also defined and illustrated.     

长输管道故障树及可靠性增长对策

天然气大部分通过远距离运输和销售,管道运行的可靠性对天然气市场具有重要的影响。分析讨论了影响道运行可靠性的主要因素,并据此提出提高管道运行可靠性的对策与措施,供管道运行管理者参考。     

基于人工神经网络的在线设备状态监测系统的研究(英文)

研究了基于人工神经网络在线设备状态监测系统,简要介绍了人工神经网络的基础理论,描述了基于人工神经网络在线设备状态监测系的结构和工作过程,给出该系统对卷烟机MK9-5的状态监测和故障诊断的结果。实验结果表明,将多层前馈人工种经网络用于设备在线状态监测具有较好的效果,并可对设备故障进行可靠诊断。