Basic Events Research Articles

Reliability evaluation of the Chinese Train Control System Level 3 using a fuzzy approach

The Chinese Train Control System Level 3 (CTCS-3) has been developed to ensure the safe and efficient operation of high-speed railway networks in China. Failure of the CTCS-3 may result in serious accidents, causing damage to assets and risking the safety of passengers. In this paper, the reliability evaluation of the CTCS-3, comprising an onboard and trackside subsystem, is conducted using the fault tree analysis where the basic events are divided into known failure rate basic events and unknown failure rate basic events. The probabilities of the occurrence of the known basic events are obtained from field data, while those of the unknown failure rate basic events are estimated by expert judgment. The fuzzy set theory is then adopted to deal with the imprecise expert judgment. Considering a specific operational scenario, to accomplish one mission, the failure probability of the CTCS-3 is calculated. Importance analysis is carried out not only to identify the critical basic events but also to provide suggestions on the improvement of preventive maintenance. Sensitivity analysis shows that hardware factors have the most significant effect on the reliability of the CTCS-3.

Deep learning of system reliability under multi-factor influence based on space fault tree

For the fault tree analysis, a basic event probability is often complicated. The probability is not constant and even can be represented by function. In order to analyze the system reliability and related characteristics, we represent the probabilities of the basic events by functions. The variables of the function are n influencing factors on the basic events. We extend the top event probability from the constant value to n + 1-dimensional space considering n influencing factors, and the probability is n + 1th dimension. Further research the n + 1-dimensional space with related mathematical methods, and then, transform the system probability analysis into the problem of mathematic. The above ideas are the space fault tree (SFT). In SFT, component fault probability distribution replace basic event probability and system fault probability distribution replace top event probability. In this paper, we research the electrical system fault probability distribution and explain the related construction process. The main factors influencing the system are working temperature c and working time t. This paper constructs the three-dimensional fault probability distribution of the components and the system, and the probability importance and criticality importance of the components. With partial derivation of the system fault probability distribution by the c and t, we study the change trend of the fault probability. The optimal replacement schemes of components and the scheme considering the cost are obtained. The results show SFT is feasible and reasonable to analyze the fault probability of system under multi-factor influence and suitable for deep learning of the characteristics of the system reliability change.

Efficient response modelling for performance characterisation and risk assessment of ship-iceberg collisions

Unique features of the Arctic region, such as sub-zero temperatures and glacial activities, pose serious risk to ships. The potential for ship accidents requires tailored guidelines for ship-ice interactions which justify the need for a suitable performance and risk assessment model for ships navigating in the Arctic waters. Research on the development of such model is currently limited. In this paper, a conceptual framework is proposed for performance characterisation and quantitative risk assessment of ships in iceberg collisions. The framework focusses on the components required for asset risk computation, such as probabilistic performance measures and ship-iceberg collision probability. The computationally intensive ship-iceberg collision models are captured by efficient surrogate models in performance estimation, while the basic events are linked by a fault tree representation to identify collision probability. The interaction between a double-hull oil tanker and a spherical iceberg is chosen as the reference collision scenario to demonstrate the applicability of the framework. The crushable foam plasticity model for the iceberg material is validated and the response computations are performed using the non-linear finite element software Abaqus®. The presented computation model underlines the significance of different risk components, providing valuable guidance for improving risk-based ship designs.

Risk Analysis of Propulsion System based on Similarity Measure and Weighted Fuzzy Risk Priority Number in FMEA

Abstract Due to the epistemic uncertainty, it is difficult for the experts to give precise parameter values in Risk Priority Number (RPN) evaluations. To overcome this drawback, a hybrid method is proposed by integrating the concepts of fuzzy set theory, weight analysis and similarity value measure of fuzzy numbers. The analysis process is divided into two phases to identify the hazard source. The first phase uses fuzzy Fault Tree Analysis (FTA) and Failure Mode and Effect Analysis (FMEA), then the main potential failure modes can be determined. The importance analysis of basic events can be calculated using fuzzy set theory and weight analysis. In the second phase, the multiple failure modes and component correlations are modelled using the Fuzzy Risk Priority Number (FRPN) evaluation and the Similarity Measure Value Method (SMVM). The proposed method has been applied to the risk analysis of a satellite propulsion system to show the effectiveness and applicability.

Failure Occurrence Probability Assessment of Claus Furnace Package in Sulfur Recovery Unit Using Fault Tree Analysis Based on Conventional and Fuzzy-Based Approach

Background: If shutdown scenario of burner of the sulfur recovery unit takes place, toxic release, fire, and explosion accident can easily occur. Therefore, it is essential to assess the basic causes of burner shutdown scenario. Fault Tree Analysis (FTA) could be used to assess the occurrence probabilities of burner shutdown scenario and its basic causes/events. The failure occurrence probability of these Basic Events (BE) are often not available in lack of data and uncertain conditions. Objectives: This study was done to provide a comprehensive approach for analyzing and calculating BE failure occurrence probability affecting the shutdown scenario, using combined fuzzy logic, expert judgment, and FTA. Methods: The study was carried out from June to December, 2016. In this study, a fuzzy-based approach based on expert judgment was proposed to calculate the occurrence probability of burner shutdown scenario in lack of data and uncertain conditions. The brainstorming and FMEA, and HAZOP study were first used to identify fault events of the fault tree. Then, based on these methods, the fault tree was constructed. Subsequently, the failure occurrence probabilities of BE and shutdown scenario were calculated using the fuzzy-based approach and a conventional approach. Finally, the Fussell-Vesely importance analysis was used to rank the BE in FTA. Results: Results showed that the occurrence probability of shutdown scenario was 4.76E-04 per year. Since the failure occurrence probabilities of some BEs were not available, using failure probability functions in the conventional approach cannot provide failure occurrence probabilities of those BE. Therefore, the occurrence probability of shutdown scenario based on the conventional approach was not available. Based on the Fussell-Vesely importance measure analysis, it was determined that the blower failure while running, air pre-heater blockage, and shut-off valve fail close were 3 major causes of “burner shutdown scenario”. Conclusions: The fuzzy-based approach could derive a failure occurrence probability of BE based on expert subjective judgments using the failure possibility distributions (FPDs) in lack of data conditions. This study overcame the weaknesses of the conventional approach, to calculate BE failure occurrence probabilities via fuzzy logic.

Uncertainty Handling in the Safety Risk Analysis: An Integrated Approach Based on Fuzzy Fault Tree Analysis

Chemical process plants, especially the oil and gas plants operating under severe processing conditions and dealing with hazardous materials, are susceptible to catastrophic accidents. Thus safety risk assessment is vital in designing effective strategies for preventing and mitigating potential accidents. Fault tree analysis (FTA) is a well-known technique to analyze the risks related to a specific system. In the conventional FTA, the ambiguities and uncertainties of basic events (BEs) cannot be handled effectively. Therefore, employing fuzzy set theory helps probabilistic estimation of BEs and subsequently the top event (TE). This study presents an integrated approach to fuzzy set theory and FTA for handling uncertainty in the risk analysis of chemical process plants. In this context, the worst case scenario based on a qualitative risk analysis is selected first and then the fuzzy FTA is established. Finally, different fuzzy aggregation and defuzzification approaches are employed to obtain the probability of each BE and TE, the output of each approach is compared to the occurrence probability of TE, and the critical BEs are ranked. The proposed methodology is applied to the fuzzy probabilistic analysis of hydrocarbon release in the BP tragic accident of March 2005. The results indicate that the proposed approach is very effective in risk analysis considering uncertainty reduction or handling.

The Role of Grb2 in Cancer and Peptides as Grb2 Antagonists.

Growth factor receptor-bound protein 2 (Grb2) is a 25 kDa adaptor protein, which was originally discovered to accomplish basic cellular events such as cell growth, cell proliferation, and metabolism. However, recent studies evidenced that Grb2 was largely involved in multiple tumor malignancies. The mature Grb2 is a 217 amino acid sequence, which consists of one Src homology 2 (SH2) domain flanked by two Src homology 3 (SH3) domains. Using these binding motives, the ubiquitously expressed Grb2 acts as an intermediate between cell-surface activated receptors and downstream targets. Consequently, the Grb2 becomes the key element of this oncogenesis and launched a number of defected signaling cascades. Therefore, vast concern of the Grb2 in multiple cancer patterns makes it an attractive therapeutic target. In this review, we have compiled the maximum tumor conformations caused by the involvement of the Grb2, the central role of Grb2 in numerous oncogenic pathways and particular approaches that can be useful to downregulate the Grb2 overexpression. We will discuss in details the activity of different types of novel peptides, their high affinity for the Grb2 protein and blockade of Grb2 mediated signaling pathways by targeting the SH2/SH3 binding sites. There is a three-fold aspect to this review: Grb2 protein introduction, Grb2 protein involvement in cancer, and the role of peptides as Grb2 antagonists. First, Grb2 and compiled maximum tumor conformations induced by Grb2 involvement were introduced. Secondly, several oncogenic pathways of Grb2 involvement and particular approaches potentially useful to downregulate Grb2 overexpression were outlined. The activity of different types of novel peptides for the Grb2 protein was also detailed. Last but not least, the blockade of Grb2-mediated signaling pathways by targeting SH2/SH3 binding sites were summarized. We have epitomized the utmost cancer malignancies caused by abnormal signaling of the Grb2 adaptor molecule. Indeed, Grb2's enormous involvement in the progression and development of different cancers broaden our tactics to build anticancer drug candidates. Depending on the high affinity and increased specificity we have described the major potent peptides which may efficiently target and block the SH2 or SH3 arms of the Grb2. It may be of benefit for developing novel anticancer peptides. However, further work is needed to pinpoint more binding motives of Grb2 to generate efficacious anticancer agents for diverse human cancers in the near future.

Generalized Theory for the Timescale of Molecular Electronic Decoherence in the Condensed Phase.

We introduce a general theory of electronic decoherence for molecules in the condensed phase that captures contributions coming from pure dephasing effects, electronic transitions among diabatic states, and their interference. The theory is constructed by taking advantage of a recently developed [ J. Phys. Chem. Lett. 2017 , 8 , 4289 - 4294 ] general expression for decoherence times that is based on an early time expansion of the purity dynamics and extends early electronic decoherence models based on pure dephasing ideas. Using this theory, we construct the decoherence time for the displaced harmonic oscillator model amended with constant and linear diabatic couplings, which is a widely used model of the photoexcited dynamics of molecules. The validity of the short-time expansion is demonstrated by the quantitative agreement of the theory with exact numerical computations of the decoherence dynamics obtained using the hierarchical equation of motion method. These developments offer a rigorous understanding of early time electronic decoherence processes that accompany basic molecular events and demonstrate that electronic transitions among diabatic states play a major role in the decoherence dynamics.

Reliability Analysis of RSG-GAS Primary Cooling System to Support Aging Management Program

Multipurpose Research Reactor G.A. Siwabessy (RSG-GAS) which has been operating since 1987 is one of the main facilities on supporting research, development and application of nuclear energy programs in BATAN. Until now, the RSG-GAS research reactor has been successfully operated safely and securely. However, because it has been operating for nearly 30 years, the structures, systems and components (SSCs) from the reactor would have started experiencing an aging phase. The process of aging certainly causes a decrease in reliability and safe performances of the reactor, therefore the aging management program is needed to resolve the issues. One of the programs in the aging management is to evaluate the safety and reliability of the system and also screening the critical components to be managed.One method that can be used for such purposes is the Fault Tree Analysis (FTA). In this papers FTA method is used to screening the critical components in the RSG-GAS Primary Cooling System. The evaluation results showed that the primary isolation valves are the basic events which are dominant against the system failure.

Probabilistic analysis on the failure of reactivity control for the PWR

The fundamental safety function of the power reactor is to control reactivity, to remove heat from the reactor, and to confine radioactive material. The safety analysis is used to ensure that each parameter is fulfilled during the design and is done by deterministic and probabilistic method. The analysis of reactivity control is important to be done because it will affect the other of fundamental safety functions. The purpose of this research is to determine the failure probability of the reactivity control and its failure contribution on a PWR design. The analysis is carried out by determining intermediate events, which cause the failure of reactivity control. Furthermore, the basic event is determined by deductive method using the fault tree analysis. The AP1000 is used as the object of research. The probability data of component failure or human error, which is used in the analysis, is collected from IAEA, Westinghouse, NRC and other published documents. The results show that there are six intermediate events, which can cause the failure of the reactivity control. These intermediate events are uncontrolled rod bank withdrawal at low power or full power, malfunction of boron dilution, misalignment of control rod withdrawal, malfunction of improper position of fuel assembly and ejection of control rod. The failure probability of reactivity control is 1.49E-03 per year. The causes of failures which are affected by human factor are boron dilution, misalignment of control rod withdrawal and malfunction of improper position for fuel assembly. Based on the assessment, it is concluded that the failure probability of reactivity control on the PWR is still within the IAEA criteria.

Master Logic Diagram: An Approach to Identify Initiating Events of HTGRs

Initiating events of a nuclear power plant being evaluated need to be firstly identified prior to applying probabilistic safety assessment on that plant. Various types of master logic diagrams (MLDs) have been proposedforsearching initiating events of the next generation of nuclear power plants, which have limited data and operating experiences. Those MLDs are different in the number of steps or levels and different in the basis for developing them. This study proposed another type of MLD approach to find high temperature gas cooled reactor (HTGR) initiating events. It consists of five functional steps starting from the top event representing the final objective of the safety functions to the basic event representing the goal of the MLD development, which is an initiating event. The application of the proposed approach to search for two HTGR initiating events, i.e. power turbine generator trip and loss of offsite power, is provided. The results confirmed that the proposed MLD is feasiblefor finding HTGR initiating events.

Lognormal Approximations of Fault Tree Uncertainty Distributions.

Fault trees are used in reliability modeling to create logical models of fault combinations that can lead to undesirable events. The output of a fault tree analysis (the top event probability) is expressed in terms of the failure probabilities of basic events that are input to the model. Typically, the basic event probabilities are not known exactly, but are modeled as probability distributions: therefore, the top event probability is also represented as an uncertainty distribution. Monte Carlo methods are generally used for evaluating the uncertainty distribution, but such calculations are computationally intensive and do not readily reveal the dominant contributors to the uncertainty. In this article, a closed-form approximation for the fault tree top event uncertainty distribution is developed, which is applicable when the uncertainties in the basic events of the model are lognormally distributed. The results of the approximate method are compared with results from two sampling-based methods: namely, the Monte Carlo method and the Wilks method based on order statistics. It is shown that the closed-form expression can provide a reasonable approximation to results obtained by Monte Carlo sampling, without incurring the computational expense. The Wilks method is found to be a useful means of providing an upper bound for the percentiles of the uncertainty distribution while being computationally inexpensive compared with full Monte Carlo sampling. The lognormal approximation method and Wilks's method appear attractive, practical alternatives for the evaluation of uncertainty in the output of fault trees and similar multilinear models.

Fuzzy-Bayesian-network-based Safety Risk Analysis in Railway Passenger Transport

This study presents a fuzzy Bayesian network (FBN) method to analyze the influence on the safety risk of railway passenger transport applying different risk control strategies. Based on the fuzzy probability of the basic event determined by the expert group decision method, the proposed FBN method can reasonably predict the probability of railway passenger safety risk. It is also proven that control the risk in the safety management of railway passenger transport will be the most effective way to reduce the risk probability of the railway passenger transport safety.

Modeling bid/no bid decisions using fuzzy fault tree

Purpose Decisions by construction contractors to bid (or not to bid) require the thorough assessment and evaluation of factors relevant to the decision, as well as the quantification of their combined impact, to produce successful bid/no-bid decisions. The purpose of this study is to present a fuzzy fault tree model to assist construction contractors to more efficiently bid for future projects. Design/methodology/Approach The proposed model consist of two stages: first, identification of the factors that affect bidding decision using a questionnaire survey after an extensive literature review, and second, usage of the identified factors to build a fuzzy fault tree model to simulate the bidding decision. Findings A list of 15 factors that affect bid/no-bid decisions was identified. Analysis of factors revealed that the highest-ranking factors were related to financial aspects of the project. A case study is presented to demonstrate the capabilities of the model, and a fuzzy important analysis is performed on the basic events to demonstrate the differences between three contractors’ bid/no-bid decisions. The results reveal that there is variation between the decisions of each contractor based on their willingness to participate. Besides, the influence of evaluation factors on the final decision for each contractor is different. Originality/value The study contributes to the body of knowledge on tendering and bidding practices. The proposed model incorporated the fuzzy set theory, which suits human subjectivity. The proposed methodology overcomes the limitations of previous models as it can, using the linear pool opinion principle, combine and weigh the evaluations of multiple experts. In addition, the model is convenient for situations where historical data are not available.

A Survey of Alternative Splicing in Allotetraploid Cotton (<i>Gossypium hirsutum </i>L.)

Allotetraploid cotton ( Gossypium hirsutum L.), accounting for more than 90% of cultivated cotton worldwide, provides textile fibers and seeds. Alternative splicing (AS) is a post-transcriptional process that generates more than one RNA isoforms from a single pre-mRNA transcript, increasing the diversity of functional proteins and RNAs. We surveyed the alternatively spliced genes in cotton using expressed sequence tag (EST) and mRNA sequences available in the public databases. A total of 56,080 AS events, including 41,150 (73.4%) basic events and 14,930 (26.6%) complex events were identified, which were generated from approximately 23,930 genes. Intron retention was the most frequent event, accounting for 34.8%, followed by alternative acceptor site events (18.8%) and alternative donor site events (11.8%), and exon skipping being the least frequent event (8.0%). Complex types, which are formed by more than one basic event, are accounted for 26.6%. The estimated AS rates of genes generating AS isoforms was 27.1% in cotton. Gene Ontology and protein family analysis showed that the products of alternatively spliced genes were involved in many biological processes with diverse molecular functions. The transcripts to cotton genome mapping information can be used to improve the predicted gene models in cotton. The annotation information of AS isoforms of these genes provides a basis for future investigation on the functions of these AS genes in cotton biology. The data can be accessed at Plant Alternative Splicing Database (http://proteomics.ysu.edu/altsplice/).

Application of Probabilistic Model for Marine Steam System Failure Analysis under Uncertainty

In ship and offshore operations, machinery systems have associated operational hazard because of the prevailing harsh environment. Therefore, the need for an overall evaluation of the associated risk and failures of these systems, such as the marine steam boiler, is crucial to the industry. The concept of probability risk model is used to model the failure mode considering the overall risk associated with the system as a whole. The rate of occurrence of the failure that described the basic events as represented by the fault tree was developed to model the marine steam system. This specific event was implemented and evaluated to estimate the failure frequencies of the overall systems, based on the available failure rate in core literatures. A risk model which is hazard severity weight with its failure frequencies, and the time of operation was applied in the analysis. The probability of failure of the boiler system was estimated at 0.323225 at 35,040 operating hours with hazard severity weight of catastrophic if it occurs. The associated failure frequency calculated for the period is 1.114 × 10-5. The over failure frequency of the marine steam system for the period of consideration is conditioned on the pre-defined minimum cut sets of the top event. This therefore agreed with the fact that the basic events with their failure frequencies will lead to the catastrophic failure of the entire system within the period if the maintenance plan is not proactive.

Bio-Medical Waste Management System in Multi-Specialty Hospital Using Birnbaum's Measures-A Case Study

In the present scenario medical waste produced in health care is a special kind of waste which causes for several possible health and safety hazards to the public and environment, if inadequately treated. In general the bio-medical wastes in hospitals are accumulated everyday which is to be properly disposed or incinerated so that it won't cause pollution and harmful effects to the society. This should be carried out within the working hours every day without any delay, but there is an undesired event of time delay in the collection of BMW. The aim of this research is to identify the events which are highly influencing the time delay in BMW management in a private multi-specialty hospital, Chennai. The fault tree analysis method is used to trace out the events, which could contribute for the delay in BMW collection and it focuses on the qualitative and quantitative aspects. Finally, all the basic events were ranked based on their effects on the undesired top event related to time delay using Birnbaum's importance measures. It was found that there are ten basic factors having higher contribution over the time delay and these factors should be prevented or eliminated to avoid the time delay during BMW collection.

Study on the Cause of Car Accidents at Intersections

The accident data used in this paper are all collected from the traffic accident investigation team of Shanghai University of Engineering Science from 2008 to 2017. The analysis is based on full and detailed data. The conclusion can provide a reliable basis for the prevention of car accidents in domestic intersections. The content of this paper can be summarized as follows: The fault tree analysis method is used to analyze the traffic accident data collected and explore the deeper causes of interjunction accidents. The logical relationship between the occurrence of the intersection car accident and the factors such as human, car, road and environment is summarized from the top down to the fault tree model. Finally, the model is qualitatively analyzed and the mechanism of the accident is deduced systematically. Research shows: Drivers do not avoid or avoid effective collision for vehicles that are going to collide, which are the two basic events that cause the collision of cars at the crossroads.

Human Pre-gastrulation Development.

Understanding the progression of early human embryonic development prior to implantation is of fundamental biological importance. Greater insights into early developmental events may lead to clinical improvements, not only via the establishment of novel stem cell models with increased potential or more physiological relevance, but also by uncovering some underlying causes of infertility, miscarriages, and developmental disorders. The majority of human embryos available for study are those donated to research once they are surplus to family building following in vitro fertilization, though in some countries it is also possible to create embryos using donated gametes. As human embryo development is surprisingly inefficient, with only 40% reaching the blastocyst stage in vitro (French, Sabanegh, Goldfarb, & Desai, 2010; Gardner, Lane, Stevens, Schlenker, & Schoolcraft, 2000), many embryos may not develop to a stage suitable for study. Where legally permitted, the oversight of human embryo research is subject to either ethics approval from a local institutional review board (i.e., China and the United States) or both a national regulator as well as a regional research ethics committee (i.e., the United Kingdom). The study of human development has historically been by necessity comparative, relying on model organisms and stem cell lines to inform analyses. Preimplantation mouse and human embryos in particular exhibit remarkably similar gross morphologies at these early stages of development, although key differences have been identified in gene expression patterns and developmental timing. While recent advances in high-resolution transcriptomic analyses at the single cell level have improved our capability to interrogate expression patterns directly in the human embryo, we still lack an understanding of basic molecular events in the human embryo, including how the first cell lineages become specified. Here, we present a current overview of the major developmental events during human preimplantation development, from fertilization to delineation of the embryonic and extraembryonic lineages prior to implantation. Comparisons to both the mouse and alternative models are included where these have formed the basis for similar investigations in a human context.

Fire Safety Analysis of Nanjing Yangtze River Tunnel Based on Fault Tree and Triangle Fuzzy Theory

Abstract In order to realistic study of fire accidents in tunnel, according to the uncertainty and fuzziness of accident, the model of fault tree is established for Nanjing Yangtze River Tunnel after Nanjing Yangtze River Bridge closed, and with the triangular fuzzy theory, the estimate of base event is obtained by scoring of the relevant professional, and the probable range of top event is calculated. In addition, the fuzzy importance is obtained by the median method of triangular fuzzy theory, to find the fuzzy importance of basic event. Then the fire prevention measures are proposed for Nanjing Yangtze River Tunnel. The results show that the possibility of uncontrolled fire is small in Nanjing Yangtze River Tunnel. Among them, fire rescue no arriving in time, no knowledge of fire extinguishing, vehicle collision on fire and auto-alarm failure are main factors leading to catastrophic fire. Thus, it is of great significance to strengthen the fire-fighting knowledge of personnel and the capacity of automatic fire-fighting for the tunnel itself, to reduce the occurrence of fire in tunnel.