A novel method for fault tree uncertainty analysis using error propagation methods

2020 ◽  
Author(s):  
Raymond “Randy” Freeman
1999 ◽  
Vol 26 (6) ◽  
pp. 523-532 ◽  
Author(s):  
Antonio C.F. Guimarẽes ◽  
Nelson F.F. Ebecken

Author(s):  
S. M. Orel ◽  
O. V. Ivashchenko

Military activities resulting in chemical pollution of the environment could produce a long-term impact on human health, whereas under certain conditions even ultra-low concentrations of some substances might provoke cancer, without noticeable toxic effect. According to modern views on carcinogenesis, the effect of carcinogens on human health does not have a threshold level of concentration. With the current deplorable state of the environment and an urgent need to improve it in view, we argue that there is a critical need for the mechanism that could assess the real state of the environment and would be instrumental for optimal decision-making process aimed at reducing environmental costs. The paper reports a case-study and exemplifies that a stepped health risk assessment is appropriate and helpful in case of environmental pollution following military actions. It also highlights the results of the risk assessment for life of the population living in the vicinity of hostilities. The results of the possible risk calculations concerning the damage non-carcinogenic and carcinogenic compounds could cause to the people living in the vicinity of hostilities were obtained in stages; the simple Monte Carlo error propagation methods and the two-dimensional Monte Carlo procedure were used to estimate the probability of different outcomes due to the intervention of random variables. It is shown that, in comparison with the simple Monte Carlo error propagation methods, the two-dimensional Monte Carlo procedure for estimating the probability of different outcomes provides additional information for the decision-making process, concerning either taking some specific measures or not. The findings of the study are the following: the assessment and subsequent analysis of environmental risk provide much more relevant information for taking an environmental decision, as compared to the threshold concentration methodology. The risk assessment should be carried out in stages, starting from simple (deterministic) to more complex ones (first the simple Monte Carlo error propagation methods, and later, two-dimensional Monte Carlo method), whenever there arise any of the following needs: if it is necessary to establish priorities among the areas, polluters, pollutants, pollutant transfer routes, categories of population and other risk factors; if resources for environmental conservation are limited; if mistaken decisions could generate destructive results; if there is a lack of information necessary to take a competent decision.


Safety ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 26 ◽  
Author(s):  
Victor Bolbot ◽  
Gerasimos Theotokatos ◽  
Evangelos Boulougouris ◽  
George Psarros ◽  
Rainer Hamann

Cyber-Physical Systems (CPSs) represent a systems category developed and promoted in the maritime industry to automate functions and system operations. In this study, a novel Combinatorial Approach for Safety Analysis is presented, which addresses the traditional safety methods’ limitations by integrating System Theoretic Process Analysis (STPA), Events Sequence Identification (ETI) and Fault Tree Analysis (FTA). The developed method results in the development of a detailed Fault Tree that captures the effects of both the physical components/subsystems and the software functions’ failures. The quantitative step of the method employs the components’ failure rates to calculate the top event failure rate along with importance metrics for identifying the most critical components/functions. This method is implemented for an exhaust gas open loop scrubber system safety analysis to estimate its failure rate and identify critical failures considering the baseline system configuration as well as various alternatives with advanced functions for monitoring and diagnostics. The results demonstrate that configurations with SOx sensor continuous monitoring or scrubber unit failure diagnosis/prognosis lead to significantly lower failure rate. Based on the analysis results, the advantages/disadvantages of the novel method are also discussed. This study also provides insights for better safety analysis of the CPSs.


2013 ◽  
Vol 62 (3) ◽  
Author(s):  
W. Priharti ◽  
S. B. Samat ◽  
A. B. A. Kadir

The Hp(10) of an ideal TLD is independent of photon energy. This is to say that at any photon energy, the ratio R of the measured dose Hp(10)meas to the delivered dose Hp(10)del is always 1. In practice however the Hp(10) is dependent on the energy and R is not equal to 1. For this reason, ICRP has set the lower limit LL and upper limit UL for R as 0.55≤R≤1.63 for detection limit of 0.1 mSv and Hp(10)del=1 mSv. As R is the quantity arises from the measurement processes, the existence of uncertainty of R, i.e. ΔR is inevitable. In the boundary cases, such as when R is slightly lower than LL or slightly larger than UL, ΔR would serve a useful quantity in decision making either to accept or to reject the value of R. The purpose of the present work is to estimate ΔR for the TLD–100H for photon energy of 24–1250 keV. The estimation of ΔR is based on the error propagation method. For the eleven photon energies, this work obtained (a) R in the range of 0.77 to 1.16, (b) ΔR in the range of ± 0.02 to ± 0.04. The values of R were satisfactory as they complied the ICRP limit. The determined ΔR is considered very small as it is in the order of 3% in comparison of R.


Author(s):  
Lei Wang ◽  
Zhiqiang Lin ◽  
Yongjun Peng

Disturbing gravity field is becoming an important factor leading to impact error of long-range rockets. In this paper, the influence mechanism of deflection of the vertical and spatial disturbing gravity on inertial navigation and guidance system are firstly introduced, respectively. Then, the navigation error propagation methods due to disturbing gravity field are reviewed. The fast assignment models of disturbing gravity field, which are available for compensating navigation errors in engineering, are also summarized. After that, the unpowered trajectory error propagation methods and the corresponding guidance correction strategies, as well as potential directions for future efforts, are discussed.


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