Cut Sets Research Articles

Risk Analysis of Instability Failure of Earth–Rock Dams Based on the Fuzzy Set Theory

Determining the anti-sliding instability risk of earth–rock dams involves the analysis of complex uncertain factors, which are mostly regarded as random variables in traditional analysis methods. In fact, fuzziness and randomness are two inseparable uncertainty factors influencing the stability of earth–rock dams. Most previous research only focused on the randomness or the fuzziness of individual variables. Moreover, dam systems present a fuzzy transition from a stable state into a failure state. Therefore, both fuzziness and randomness of the influencing factors should be considered in the same framework, where the instability of an earth–rock dam is regarded as a mixed process. In this paper, a fuzzy risk model of instability of earth–rock dams is established by considering the randomness and fuzziness of parameters and the failure criteria comprehensively. We obtained the probability threshold of instability risk of earth–rock dams by Monte-Carlo simulation after the fuzzy parameters were transformed into interval numbers by cut set levels. By applying the proposed model to the instability analysis of the Longxingsi Reservoir, the calculation results showed that the lower limits of risk probability under different cut set levels exceeded the instability risk standard of grade C for earth–rock dams. Compared with the traditional risk determination value, the risk interval obtained with the proposed methods reflects different degrees of dam instability risk and can provide reference for dam structure safety assessment and management.

Research on Site Selection Method of Battery Energy Storage System Based on Critical CutSet Identification

Under different operating conditions, the influence of energy storage battery on the power grid is different, and the location and capacity determination methods are also different. Therefore, how to scientifically and reasonably select the location is of great significance. This paper proposes a candidate set identification method for the most vulnerable branch and critical cut set of power system transient stability based on branch potential energy, and uses the improved comprehensive index to identify the critical cut set. This method does not need to wait for the end of time domain simulation to determine the most vulnerable lines and critical cut sets, thus providing the basis for the location of battery energy storage system (BESS). Through the power system comprehensive analysis program (PSASP) simulation, the accuracy of theoretical analysis and engineering practicability are verified.

Comprehensively analysis the failure evolution and safety evaluation of automotive lithium ion battery

In response to environmental pollution and the energy crisis, the number of electric vehicles (EV) has increased year by year. However, frequent EV accidents have pushed the safety of EVs to a new height of attention. The failure of lithium-ion batteries (LIBs) is the root of most accidents. Although many standards have been made, the battery system's safety still lacks scientific, comprehensive, and quantifiable assessment. Here, we innovatively put forward a comprehensive map of LIBs failure evolution combining battery tests and forward development. By analyzing the root cause of the EV fire through the Fault Tree Analysis (FTA), 20 basic events, 26 minimum cut sets, and 29 battery tests related to the accident were obtained. The result indicates that the low thermal stability materials and battery management system (BMS) failure to warn in time are the most important factors leading to EV fire. According to the test content, the battery tests are classified, and the Analytic Hierarchy Process (AHP) model of the battery test is established. By comparing the importance of every two tests with the judgment matrix, the weights of battery tests are obtained. Finally, combining with the fault tree branch structure, comprehensive forward development suggestions are put forward to improve the safety of EV.

Failure Rate Prediction of Belt Conveyor Systems using 2-parameter Weibull distribution

Abstract: The conveyor belt is one of the most operational critical equipment’s in the mining industry, they are mostly used in the transportation of crushed materials from the crushing station to where there’ll be further processed. Due to the increasing complexity of belt conveyor systems, managing their integrity has become even more difficult, as they are now used across various industries, environments and carry materials of different weight variations, leaving them susceptible to failures (1). This paper provides an industry specific knowledge on how Weibull analysis can be used to predict the failure rate of a conveyor belt system, using parameters such as the time to failure (TTF), installation and failure dates, as determinant parameters for the predictions. Several Weibull failure distributions and functions have been used to establish accuracy of results and to create comparisons on the different ways in which risk, unreliability and availability are quantified, using calculated values such as the Shape and scale parameter. The paper utilizes real world case studies in the area of mining, which sheds light on key component failures and their cut sets within the conveyor belt system (2) Keywords: TTF, TTR, Threshold parameter, Repair date, Shape parameter, B10, B15, B20, Scale parameter, ECA, CDF, PDF

Probing naturally light singlets with a displaced vertex trigger

We investigate the physics case for a dedicated trigger on a low mass, hadronic displaced vertex at the high luminosity LHC, relying on the CMS phase II track trigger. We estimate the trigger efficiency with a simplified simulation of the CMS track trigger and show that the L1 trigger rate from fake vertices, B meson decays and secondary interactions with the detector material can likely be brought down to the kHz level with a minimal set of cuts. While it would with any doubt be a severe experimental challenge to implement, we conclude that a displaced vertex trigger could open qualitatively new parameter space for exotic Higgs decays, exotic B decays and even direct production of light resonances. We parametrize the physics potential in terms of a singlet scalar mixing with the Standard Model Higgs and an axion-like particle with a coupling to gluons, and review a number or relevant models motivated by the hierarchy and strong CP problems, Dark Matter and baryogenesis.

Probability-based extensive quantitative risk analysis: collision and grounding case studies for bulk carrier and general cargo ships

ABSTRACT In this study, the risk of collision and grounding accidents on bulk carrier and general cargo ships was investigated. A comprehensive risk analysis consisting of past accident reports, fault tree analysis (FTA) and Cut sets importance measure (CS-I) methods was carried out. The failures effective in the occurrence of collision and grounding accidents were determined by examining past accident reports. In the study, the probability for each failure was derived by using real accident data. Using FTA, various potential accident occurrence combinations/scenarios, also known as minimal cut sets (MCSs), for both accident types were obtained. In addition, prioritization was conducted for the MCSs of both types of accidents using CS-I sensitivity analyses. The faults that increase the risk of collision accidents the most were found to be interpretation failure of the Convention on the International Regulations for Preventing Collisions (COLREG) and lack of situational awareness. In addition, the top failures that lead to groundings were determined to be lack of communication in bridge resource management (BRM), fatigue/sleeplessness and inappropriate voyage plan. Recommendations are made for eliminating potential risk factors, preventing the recurrence of such accidents and establishing safer maritime transport.

Systematizing the different notions of growth-coupled product synthesis and a single framework for computing corresponding strain designs.

A widely used design principle for metabolic engineering of microorganisms aims to introduce interventions that enforce growth-coupled product synthesis such that the product of interest becomes a (mandatory) by-product of growth. However, different variants and partially contradicting notions of growth-coupled production (GCP) exist. Herein, we propose an ontology for the different degrees of GCP and clarify their relationships. Ordered by coupling degree, we distinguish four major classes: potentially, weakly, and directionally growth-coupled production (pGCP, wGCP, dGCP) as well as substrate-uptake coupled production (SUCP). We then extend the framework of Minimal Cut Sets (MCS), previously used to compute dGCP and SUCP strain designs, to allow inclusion of implicit optimality constraints, a feature required to compute pGCP and wGCP designs. This extension closes the gap between MCS-based and bilevel-based strain design approaches and enables computation (and comparison) of designs for all GCP classes within a single framework. By computing GCP strain designs for a range of products, we illustrate the hierarchical relationships between the different coupling degrees. We find that feasibility of coupling is not affected by the chosen GCP degree and that strongest coupling (SUCP) requires often only one or two more interventions than wGCP and dGCP. Finally, we show that the principle of coupling can be generalized to couple product synthesis with other cellular functions than growth, for example, with net ATP formation. This work provides important theoretical results and algorithmic developments and a unified terminology for computational strain design based on GCP.

On strict-double-bound numbers of graphs and cut sets

For a poset P =( X ,≤ P ), the strict-double-bound graph of P is the graph sDB( P ) on V (sDB( P ))= X for which vertices u and v of sDB( P ) are adjacent if and only if u ≠ v and there exist elements x , y ∈ X distinct from u and v such that x ≤ P u ≤ P y and x ≤ P v ≤ P y. The strict-double-bound number ζ( G ) of a graph G is defined as min{ n ; sDB( P ) ≅ G ∪ Ǩ n {for some poset P }. We obtain an upper bound of strict-double-bound numbers of graphs with a cut-set generating a complete subgraph. We also estimate upper bounds of strict-double-bound numbers of chordal graphs.

Representing non-crossing cuts by phylogenetic trees

Phylogenetic trees are representations of the evolutionary descendency of a set of species. In graph-theoretic terms, a phylogenetic tree is a partially labeled tree where unlabeled vertices have at least degree three and labels corresponds to pairwise disjoint subsets of the set of species. A cut of a graph G = ( V , E ) is defined as bipartition { S , V \ S } of the vertex set V of G . A pair of cuts { S , S } , { T , T } is said to be crossing, if neither S ∩ T , S ∩ T , S ∩ T nor S ∩ T is empty. In this paper, we show that each set of pairwise non-crossing cuts of a graph G can be represented uniquely by a phylogenetic tree such that the set of species corresponds to the vertex set of G .

Analysis of comprehensive sensitivity evaluation of aircraft system based on FTA-AHP

Aiming at the lack of unified evaluation index for the sensitivity analysis of fault tree of the system, the Analytic Hierarchy Process(AHP) is introduced into Fault Tree Analysis(FTA), and an FTA-AHP method is proposed to generate the comprehensive sensitivity evaluation index of the system. Firstly, the reliability analysis model of the system fault tree is established, and three indexes including probabilistic sensitivity, relative sensitivity and structural sensitivity, are calculated by using the traditional sensitivity analysis method. Then, combined with the analytic hierarchy process, the weight coefficients were determined according to the sensitivity analysis results above and the type of the minimum cut set, and the comprehensive sensitivity evaluation and analysis of the system fault tree were carried out. Finally, the case verification shows that compared with the traditional method, the comprehensive sensitivity ranking results have less repeatability, and the factors are considered comprehensively, which is convenient for decision makers to make judgment. The synthetic sensitivity evaluation model developed provides support for system reliability analysis.

Research on Reliability Optimization Design of Mechanical Structure Based on Computational Intelligence

In order to extend the actual service life of mechanical equipment components and realize the reasonable protection of applied structural components, the reliability optimization design of mechanical structure based on computational intelligence is studied. With the help of wavelet neural network, the established reliability and reliability index are obtained, and then the basic theory of reliability and computational intelligence technology are studied through the reliability optimization of mechanical zero structure. On this basis, the application concepts of reliability design method are defined, and the final calculation result of reliability optimization value is obtained by combining fuzzy set and level cut set, so as to realize the reliability optimization design of mechanical structure based on computational intelligence. The experimental results show that, compared with the traditional design method, the optimization design method supported by computational intelligence technology can better improve the disadvantages of mechanical structure object, and has strong practical application value in extending the reliability application time.

Reliability Modeling and Analysis of Reactor Protection System Based on FPGA

In order to establish a reactor protection system reliability model based on the field programmable gate array (FPGA) to provide effective analysis and verification methods for system safety, this study adopts the fault tree and stochastic Petri net (SPN) models to perform reliability modeling and analysis for the single channel of CANDU reactor shutdown system 1 (SDS1). The analysis by fault tree model provides the minimal cut set. With the top event probability taken as the system fault probability, and in consideration of the fault detection, maintenance and periodic testing, the probability of rejection of the system is obtained by the stochastic Petri net model simulation. The results show that both the fault tree and state space representation are limited to a certain extent, while the stochastic Petri net can reflect the impact of fault detection and periodic tests on the reactor protection system, dynamically present the system reliability, and avoid the problem of state space explosion. Therefore, the stochastic Petri net model established in this study is suitable for the reliability modeling of the reactor protection system.

Applications of FFTA–HFACS for Analyzing Human and Organization Factors in Electric Misoperation Accidents

Human and organizational factors (HOFs) play an important role in electric misoperation accidents (EMAs), but research into the reliability of human factors is still in its infancy in the field of EMAs, and further investment in research is urgently required. To analyze the HOFs in EMAs, a hybrid method including the Human Factors Analysis and Classification System (HFACS) and fuzzy fault tree analysis (FFTA) was applied to EMAs for the first time in the paper. HFACS is used to identify and classify the HOFs with 135 accidents, reorganized as basic events (BEs), intermediate events (IEs), and top event (TE), and develop the architecture of fault tree (FT). Fuzzy aggregation is employed to address experts’ expressions and obtain the failure probabilities of the BEs and the minimal cut sets (MCSs) of the FT. The approach generates BEs failure probabilities without reliance on quantitative historical failure statistics of EMAs via qualitative records processing. The FFTA–HFACS model is applied for quantitative analysis of the probability of failure of electrical mishaps and the interaction between accident risk factors. It can assist professionals in deciding whether and where to take preventive or corrective actions and assist in knowledgeable decision-making around the electric operation and maintenance process. Finally, applying this hybrid method to EMAs, the results show that the probability of an EMAs is 1.0410 × 10−2, which is a risk level that is likely to occur and must be controlled. Two of the most important risk factors are habitual violations and supervisory violation; a combination of risk factors of inadequate work preparation and paralysis, and irresponsibility on the part of employees are also frequent errors.

Optimal allocation of a coherent system with statistical dependent subsystems

AbstractThis paper studies the optimal allocation policy of a coherent system with independent heterogeneous components and dependent subsystems, the systems are assumed to consist of two groups of components whose lifetimes follow proportional hazard (PH) or proportional reversed hazard (PRH) models. We investigate the optimal allocation strategy by finding out the number $k$ of components coming from Group A in the up-series system. First, some sufficient conditions are provided in the sense of the usual stochastic order to compare the lifetimes of two-parallel–series systems with dependent subsystems, and we obtain the hazard rate and reversed hazard rate orders when two subsystems have independent lifetimes. Second, similar results are also obtained for two-series–parallel systems under certain conditions. Finally, we generalize the corresponding results to parallel–series and series–parallel systems with multiple subsystems in the viewpoint of the minimal path and the minimal cut sets, respectively. Some numerical examples are presented to illustrate the theoretical findings.

Double parton scattering in four-jet production in proton-proton collisions at the LHC

We study the contribution from double parton scattering (DPS) to four-jet production at the LHC, both at the leading order accuracy and after incorporating the effects of QCD radiation. Apart from DPS, we also include and discuss the contribution from single parton scattering (SPS). We find that the QCD radiation impacts theoretical predictions significantly, with DPS contributions more affected than the SPS. We also examine a number of observables in regard to their effectiveness for discrimination between DPS and SPS events and propose sets of kinematical cuts to improve the prospects of measuring DPS in four-jet production.

Line Failure Localization of Power Networks Part II: Cut Set Outages

Transmission line failure in power systems prop-agate non-locally, making the control of the resulting outages extremely difficult. In Part II of this paper, we continue the study of line failure localizability in transmission networks and characterize the impact of cut set outages. We establish a Simple Path Criterion, showing that the propagation pattern due to bridge outages, a special case of cut set failures, are fully determined by the positions in the network of the buses that participate in load balancing. We then extend our results to general cut set outages. In contrast to non-cut outages discussed in Part I whose subsequent line failures are contained within the original blocks, cut set outages typically impact the whole network, affecting the power flows on all remaining lines. We corroborate our analytical results in both parts using the IEEE 118-bus test system, in which the failure propagation patterns exhibit a clear block-diagonal structure predicted by our theory, even when using full AC power flow equations.

Overheat fault analysis of drillship electric winch drive system

In order to solve the problem of winch motor overheating, this paper analyzes the possible reasons of motor overheating along with the structure and principle of drillship winch. Taking the overheating fault of drillship’s driving motor as the top event, the fault tree model of the overheating problem of the driving motor is established, and the relative weak links of the winch are found out through the minimum cut set. With the result of fault tree analysis as a guide, the lifting device was inspected, the fault reason of the lifting device was found out, and the corresponding solutions were put forward. The results show that the proposed method in the paper can improve the efficiency of fault location.

Comprehensive Analysis of The Concept of Child Abuse: A Critical Appraisal

Throughout the history of mankind, children have only sometimes been spared to indignities, cruelties, and horrors that human beings so often inflict upon each other. At various times, in various places, children have been abandoned, starved, beaten, enslaved, sexually assaulted, and put to death. One such horror- child abuse – have become serious social problems in the united states and in some other industrialized societies, yet it occurs infrequently or not at all in many of the world’s societies. Child abuse seem’ s to increase in situations of rapid socio- cultural change, urban migration, family disorganization, and the like, no clear cut set of prognostic variables has been identified. Indeed, it seems that factors that predict child abuse in one society will not be predictive in another. Only active public and professional concerns led to the emergence of the truer picture of all forms of the child abuse and neglect: physical, sexual, emotional, and failure to thrive owing to maternal deprivation. The present paper is an attempt to make a comprehensive analysis and study of child abuse which is existing in different form and how they have been addressed in different existing legislation and government policies.

L-Fuzzy Sub-Effect Algebras

In this paper, the notions of L-fuzzy subalgebra degree and L-subalgebras on an effect algebra are introduced and some characterizations are given. We use four kinds of cut sets of L-subsets to characterize the L-fuzzy subalgebra degree. We induce an L-fuzzy convexity by the L-fuzzy subalgebra degree, and we prove that a morphism between two effect algebras is an L-fuzzy convexity preserving mapping and a monomorphism is an L-fuzzy convex-to-convex mapping. Finally, it is proved that the set of all L-subalgebras on an effect algebra can form an L-convexity, and its L-convex hull formula is given.

Hierarchical auxetic and isotropic porous medium with extremely negative Poisson’s ratio

We propose a novel two-dimensional hierarchical auxetic structure consisting of a porous medium in which a homogeneous matrix includes a rank-two set of cuts characterised by different scales. The six-fold symmetry of the perforations makes the medium isotropic in the plane. Remarkably, the mesoscale interaction between the first- and second-level cuts enables the attainment of a value of the Poisson’s ratio close to the minimum reachable limit of -1. The effective properties of the hierarchical auxetic structure are determined numerically, considering both a unit cell with periodic boundary conditions and a finite structure containing a large number of repeating cells. Further, results of the numerical study are validated experimentally on a polymeric specimen with appropriately arranged rank-two cuts, tested under uniaxial tension. We envisage that the proposed hierarchical design can be useful in numerous engineering applications exploiting an extreme auxetic effect.