34,596 research outputs found
The xSAP Safety Analysis Platform
This paper describes the xSAP safety analysis platform. xSAP provides several
model-based safety analysis features for finite- and infinite-state synchronous
transition systems. In particular, it supports library-based definition of
fault modes, an automatic model extension facility, generation of safety
analysis artifacts such as Dynamic Fault Trees (DFTs) and Failure Mode and
Effects Analysis (FMEA) tables. Moreover, it supports probabilistic evaluation
of Fault Trees, failure propagation analysis using Timed Failure Propagation
Graphs (TFPGs), and Common Cause Analysis (CCA). xSAP has been used in several
industrial projects as verification back-end, and is currently being evaluated
in a joint R&D Project involving FBK and The Boeing Company
Causality and Temporal Dependencies in the Design of Fault Management Systems
Reasoning about causes and effects naturally arises in the engineering of
safety-critical systems. A classical example is Fault Tree Analysis, a
deductive technique used for system safety assessment, whereby an undesired
state is reduced to the set of its immediate causes. The design of fault
management systems also requires reasoning on causality relationships. In
particular, a fail-operational system needs to ensure timely detection and
identification of faults, i.e. recognize the occurrence of run-time faults
through their observable effects on the system. Even more complex scenarios
arise when multiple faults are involved and may interact in subtle ways.
In this work, we propose a formal approach to fault management for complex
systems. We first introduce the notions of fault tree and minimal cut sets. We
then present a formal framework for the specification and analysis of
diagnosability, and for the design of fault detection and identification (FDI)
components. Finally, we review recent advances in fault propagation analysis,
based on the Timed Failure Propagation Graphs (TFPG) formalism.Comment: In Proceedings CREST 2017, arXiv:1710.0277
Effects of the electron correlation and Breit and hyperfine interactions on the lifetime of the 2p3s states in neutral neon
In the framework of the multiconfiguration Dirac-Hartree-Fock method, we
investigate the transition properties of four excited states in the
configuration of neutral neon. The electron correlation effects are taken into
account systematically by using the active space approach. The effect of
higher-order correlation on fine structures is shown. We also study the
influence of the Breit interaction and find that it reduces the oscillator
strength of the transition by 17%. It turns out that the
inclusion of the Breit interaction is essential even for such a light atomic
system. Our ab initio calculated line strengths, oscillator strengths and
transition rates are compared with other theoretical values and experimental
measurements. Good agreement is found except for the M2
transition for which discrepancies of around 15% between theories and
experiments remain. In addition, the impact of hyperfine interactions on the
lifetimes of the and metastable states is investigated for
the Ne isotope (I=3/2). We find that hyperfine interactions reduce the
lifetimes drastically. For the state the lifetime is decreased by a
factor of 630.Comment: Accepted by Phys. Rev.
Self-pain enmeshment: Future possible selves, sociotropy, autonomy and adjustment to chronic pain
The aims of this study were to replicate and extend previous observations on the relationship between enmeshment of the self and pain and measures of adjustment [Morley et al., Possible selves in chronic pain: self-pain enmeshment, adjustment and acceptance, Pain 2005;115:84–94], and to test the hypothesis that individual variation in motivational preferences interacts with enmeshment. 82 chronic pain patients completed standardized self-report measures of depression, anxiety, acceptance and the possible selves interview which generated measures of their hoped-for (own and other perspectives) and feared-for selves. They made judgments about the conditionality of each self on the continuing presence of pain as a measure of self-pain enmeshment. A series of hierarchical regression analyses, that adjusted for demographics, pain characteristics and disability, confirmed the relationship between self enmeshment and depression and acceptance. When anxiety was considered, there was no main effect for any of the self aspects but there were specific interactions between the hoped-for (own) and (other) selves and two motivational preferences – autonomy and sociotropy
A review of the state of art in applying Biot theory to acoustic propagation through the bone
Understanding the propagation of acoustic waves through a liquid-perfused porous solid framework such as cancellous bone is an important pre-requisite to improve the diagnosis of osteoporosis by ultrasound. In order to elucidate the propagation dependence upon the material and structural properties of cancellous bone, several theoretical models have been considered to date, with Biot-based models demonstrating the greatest potential. This paper describes the fundamental basis of these models and reviews their performance
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