نتایج جستجو برای: qra

تعداد نتایج: 104  

Journal: :Rel. Eng. & Sys. Safety 2014
Andrew Rae Rob Alexander John McDermid

Quantitative Risk Assessment (QRA) is widely practiced in system safety, but there is insufficient evidence that QRA in general is fit for purpose. Defenders of QRA draw a distinction between poor or misused QRA and correct, appropriately used QRA, but this distinction is only useful if we have robust ways to identify the flaws in an individual QRA. In this paper we present a comprehensive matu...

2008
Jelle Vlaanderen Roel Vermeulen Dick Heederik Hans Kromhout

BACKGROUND Careful evaluation of the quality of human observational studies (HOS) is required to assess the suitability of HOS for quantitative risk assessment (QRA). In particular, the quality of quantitative exposure assessment is a crucial aspect of HOS to be considered for QRA. OBJECTIVE We aimed to develop guidelines for the evaluation of HOS for QRA and to apply these guidelines to case...

2012
Andrew Rae John McDermid Rob Alexander

In safety, environmental, and financial regulation the public are often asked to accept estimates of a concept, “risk”, that they cannot directly perceive. Faith in these estimates is supported by logical reasoning but not by empirical evidence. Unfortunately, the evidence that does exist about risk phenomena indicates that human reasoning about risk is highly unreliable. In this paper we deter...

Journal: :Risk analysis : an official publication of the Society for Risk Analysis 2004
George E Apostolakis

This article discusses the use of quantitative risk assessment (QRA) in decision making regarding the safety of complex technological systems. The insights gained by QRA are compared with those from traditional safety methods and it is argued that the two approaches complement each other. It is argued that peer review is an essential part of the QRA process. The importance of risk-informed rath...

2006
Masahito Hayashi Kazuo Iwama Harumichi Nishimura Rudy Raymond Shigeru Yamashita

An (n, 1, p)-Quantum Random Access (QRA) coding, introduced by Ambainis, Nayak, Ta-shma and Vazirani in ACM Symp. on Theory of Computing 1999, is the following communication system: The sender which has n-bit information encodes his/her information into one qubit, which is sent to the receiver. The receiver can recover any one bit of the original n bits correctly with probability at least p, th...

Journal: :Risk analysis : an official publication of the Society for Risk Analysis 2011
Qiang Meng Xiaobo Qu Xinchang Wang Vivi Yuanita Siew Chee Wong

Urban road tunnels provide an increasingly cost-effective engineering solution, especially in compact cities like Singapore. For some urban road tunnels, tunnel characteristics such as tunnel configurations, geometries, provisions of tunnel electrical and mechanical systems, traffic volumes, etc. may vary from one section to another. These urban road tunnels that have characterized nonuniform p...

2008
ALEXANDER L. STOLYAR A. L. STOLYAR

We consider a model of random access (slotted-aloha-type) communication networks of general topology. Assuming that network links receive exogenous arrivals of packets for transmission, we seek dynamic distributed random access strategies whose goal is to keep all network queues stable. We prove that two dynamic strategies, which we collectively call queue length based random access (QRA), ensu...

Journal: :European heart journal 2008
Benny Drieghe Juraj Madaric Giovanna Sarno Ganesh Manoharan Jozef Bartunek Guy R Heyndrickx Nico H J Pijls Bernard De Bruyne

AIMS A ratio of distal renal pressure to aortic pressure (P(d)/P(a)) <0.90 can be considered a threshold for defining a significant renal artery stenosis (RAS). The aim of this study was to compare renal angiography (QRA) and colour duplex ultrasound (CDUS) to pressure measurements in assessing RAS. METHODS AND RESULTS In 56 RAS, percent diameter stenosis (DS(angio)), minimal luminal diameter...

2015
M.W. Wheeler R. M. Park A. J. Bailer C. Whittaker

Virtually no occupational exposure standards specify the level of risk for the prescribed exposure, and most occupational exposure limits are not based on quantitative risk assessment (QRA) at all. Wider use of QRA could improve understanding of occupational risks while increasing focus on identifying exposure concentrations conferring acceptably low levels of risk to workers. Exposure-response...

2010
Nikolaos Galatos Peter Jipsen

This paper studies generalizations of relation algebras to residuated lattices with a unary De Morgan operation. Several new examples of such algebras are presented, and it is shown that many basic results on relation algebras hold in this wider setting. The variety qRA of quasi relation algebras is defined and shown to be a conservative expansion of involutive FL-algebras. Our main result is t...

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