Reliability analysis of dynamic systems by translating temporal fault trees into Bayesian networks

Classical combinatorial fault trees can be used to assess combinations of failures but are unable to capture sequences of faults, which are important in complex dynamic systems. A number of proposed techniques extend fault tree analysis for dynamic systems. One of such technique, Pandora, introduces temporal gates to capture the sequencing of events and allows qualitative analysis of temporal fault trees. Pandora can be easily integrated in model-based design and analysis techniques. It is, therefore, useful to explore the possible avenues for quantitative analysis of Pandora temporal fault trees, and we identify Bayesian Networks as a possible framework for such analysis. We describe how Pandora fault trees can be translated to Bayesian Networks for dynamic dependability analysis and demonstrate the process on a simplified fuel system model. The conversion facilitates predictive reliability analysis of Pandora fault trees, but also opens the way for post-hoc diagnostic analysis of failures

Quantification of temporal fault trees based on fuzzy set theory

© Springer International Publishing Switzerland 2014. Fault tree analysis (FTA) has been modified in different ways to make it capable of performing quantitative and qualitative safety analysis with temporal gates, thereby overcoming its limitation in capturing sequential failure behaviour. However, for many systems, it is often very difficult to have exact failure rates of components due to increased complexity of systems, scarcity of necessary statistical data etc. To overcome this problem, this paper presents a methodology based on fuzzy set theory to quantify temporal fault trees. This makes the imprecision in available failure data more explicit and helps to obtain a range of most probable values for the top event probability

A Long Time Gone: Post-conflict Rural Property Restitution under Customary Law

Mass displacement of people due to violence poses a unique set of challenges for property restitution when people return to their homes after a long absence. This is particularly evident in rural areas where the dominant form of land holding is customary tenure. Violence-induced displacement, unlike voluntary migration, challenges both customary and public legaladministrative structures. The lack of written documentation of customary holdings and the importance of the support of community leaders means that incorporating returnees back into a community can be easier for those who choose to return, while reclaiming property without physical return is nearly impossible. This article seeks to make three contributions: 1) to note the diversity of return processes after long displacements in terms of timing and demographics; 2) to demonstrate that the nature of the claims people can make on customary tenure systems is at odds with international legal norms on property restitution after displacement; and 3) to introduce a set of observations and questions on how conflict can change customary law. The article is based on fieldwork conducted in Uganda, Liberia and Timor-Leste, all countries with extended displacement

What are the living conditions and health status of those who don't report their migration status? a population-based study in Chile

BACKGROUND: Undocumented immigrants are likely to be missing from population databases, making it impossible to identify an accurate sampling frame in migration research. No population-based data has been collected in Chile regarding the living conditions and health status of undocumented immigrants. However, the CASEN survey (Caracterizacion Socio- Economica Nacional) asked about migration status in Chile for the first time in 2006 and provides an opportunity to set the base for future analysis of available migration data. We explored the living conditions and health of self-reported immigrants and respondents who preferred not to report their migration status in this survey. METHODS: Cross-sectional secondary analysis of CASEN survey in Chile in 2006. Outcomes: any disability, illness/accident, hospitalization/surgery, cancer/chronic condition (all binary variables); and the number of medical/emergency attentions received (count variables). Covariates: Demographics (age, sex, marital status, urban/rural, ethnicity), socioeconomic status (education level, employment status and household income), and material standard of living (overcrowding, sanitation, housing quality). Weighted regression models were estimated for each health outcome, crude and adjusted by sets of covariates, in STATA 10.0. RESULTS: About 1% of the total sample reported being immigrants and 0.7% preferred not to report their migration status (Migration Status - Missing Values; MS-MV). The MS-MV lived in more deprived conditions and reported a higher rate of health problems than immigrants. Some gender differences were observed by health status among immigrants and the MS-MV but they were not statistically significant. Regressions indicated that age, sex, SES and material factors consistently affected MS-MVs’ chance of presenting poor health and these patterns were different to those found among immigrants. Great heterogeneity in both the MS-MV and the immigrants, as indicated by wide confidence intervals, prevented the identification of other significantly associated covariates. CONCLUSION: This is the first study to look at the living conditions and health of those that preferred not to respond their migration status in Chile. Respondents that do not report their migration status are vulnerable to poor health and may represent undocumented immigrants. Surveys that fail to identify these people are likely to misrepresent the experiences of immigrants and further quantitative and qualitative research is urgently required

The emergence of modern statistics in agricultural science : Analysis of variance, experimental design and the reshaping of research at Rothamsted Experimental Station, 1919–1933

During the twentieth century statistical methods have transformed research in the experimental and social sciences. Qualitative evidence has largely been replaced by quantitative results and the tools of statistical inference have helped foster a new ideal of objectivity in scientific knowledge. The paper will investigate this transformation by considering the genesis of analysis of variance and experimental design, statistical methods nowadays taught in every elementary course of statistics for the experimental and social sciences. These methods were developed by the mathematician and geneticist R. A. Fisher during the 1920s, while he was working at Rothamsted Experimental Station, where agricultural research was in turn reshaped by Fisher’s methods. Analysis of variance and experimental design required new practices and instruments in field and laboratory research, and imposed a redistribution of expertise among statisticians, experimental scientists and the farm staff. On the other hand the use of statistical methods in agricultural science called for a systematization of information management and made computing an activity integral to the experimental research done at Rothamsted, permanently integrating the statisticians’ tools and expertise into the station research programme. Fisher’s statistical methods did not remain confined within agricultural research and by the end of the 1950s they had come to stay in psychology, sociology, education, chemistry, medicine, engineering, economics, quality control, just to mention a few of the disciplines which adopted them

Migration Costs and Networks: household optimal investment in migration

International migration is an expensive form of investment, that only households relatively better off can afford. However poorer households have the higher incentive to migrate. Migration decision is conditional on the entry cost, expected returns and risks of migration. This paper, using data from Mexican rural and urban areas, examines the relation between household and community networks and costs and risks of migration focusing on the optimal investment in migration. To investigate an household optimal number of migrants this paper introduces a Three Step procedure to solve simultaneously for the endogeneity of network size and possible selection of migrants. The analysis confirms the inverted U-shaped relation between wealth and migration, stressing the importance of networks particularly in facilitating the migration of social strata belonging to the left tail of the income distribution. Moreover, in presence of sunk costs and/or high initial investment, household and community networks accomplish different functions

'Crawling in the Flanders mud': Samuel Beckett, war writing and scatological pacifism

This article explores the depiction of wounded soldiers in Samuel Beckett’s novel Mercier and Camier (written in French in 1946, published in 1970, and translated and published in English in 1974). This aspect of the novel is discussed from two perspectives: the Irish military history which Beckett repeatedly invokes in the novel, notably the Boer War and World War I; and the relation between the novel and the ‘war books’ which followed World War I, many of which express pacifist ideals by laying bare the suffering which combatant bodies experience. Drawing attention to the hitherto neglected context of war writing for the image of the wounded soldier in Beckett’s work, this article uses Mercier and Camier to consider the political implications of the author’s allusions to military history following World War II

Common ground in collaborative intelligence analysis: an empirical study

This paper reports an empirical exploration of how different configurations of collaboration technology affect peoples’ ability to construct and maintain common ground while conducting collaborative intelligence analysis work. Prior studies of collaboration technology have typically focused on simpler conversational tasks, or ones that involve physical manipulation, rather than the complex sensemaking and inference involved in intelligence work. The study explores the effects of video communication and shared visual workspace (SVW) on the negotiation of common ground by distributed teams collaborating in real time on intelligence analysis tasks. The experimental study uses a 2x2 factorial, between-subjects design involving two independent variables: presence or absence of Video and SVW. Two-member teams were randomly assigned to one of the four experimental media conditions and worked to complete several intelligence analysis tasks involving multiple, complex intelligence artefacts. Teams with access to the shared visual workspace could view their teammates’ eWhiteboards. Our results demonstrate a significant effect for the shared visual workspace: the effort of conversational grounding is reduced in the cases where SVW is available. However, there were no main effects for video and no interaction between the two variables. Also, we found that the “conversational grounding effort” required tended to decrease over the course of the tas

Evaluating the effectiveness of agricultural adaptation to climate change in preindustrial society

The effectiveness of agricultural adaptation determines the vulnerability of this sector to climate change, particularly during the preindustrial era. However, this effectiveness has rarely been quantitatively evaluated, specifically at a large spatial and long-term scale. The present study covers this case of preindustrial society in AD 1500–1800. Given the absence of technological innovations in this time frame, agricultural production was chiefly augmented by cultivating more land (land input) and increasing labor input per land unit (labor input). Accordingly, these two methods are quantitatively examined. Statistical results show that within the study scale, land input is a more effective approach of mitigating climatic impact than labor input. Nonetheless, these observations collectively improve Boserup's theory from the perspective of a large spatial and long-term scale.postprin

Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce

The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary–secondary amine and graphitized carbon black) and large-volume (20 μL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC–MS–MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC–MS and LC–MS–MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg−1 were achieved with both GC–MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC–MS–MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC–MS (135 compounds) and LC–MS–MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg−1 level acceptable recoveries were obtained for 93% (GC–MS) and 92% (LC–MS–MS) of pesticide–matrix combinations