Risk Of System Failure Research Articles

Preventive replacement policies with multiple missions and maintenance triggering approaches

For the mission-oriented systems, it is not feasible to do any preventive maintenance when the mission is executing. However, the replacement time obtained by traditional replacement policies might be planned during the mission duration. The planned number of missions derived by traditional methods may overestimate the actual value. It would fail to complete the missions or increase the risk of system failure during the mission durations. And the major accident and unimaginable economic losses might occur. Therefore, an appropriate preventive maintenance policy with mission durations should be proposed to guarantee the required reliability and maintainability of the systems. To maintain the large and complex systems, we firstly extend the periodic replacement with minimal repair for systems which are designed to perform multiple missions. Then, two maintenance triggering approaches, i.e., the replacement first and replacement last are discussed, respectively. The optimum replacement time and number of missions are presented analytically and numerically. Finally, the comparison of above replacement policies in maintaining the reconnaissance system of unmanned aerial vehicle is given based on assumed data. The suggested models in this paper can provide better guidance The suggested models in this paper can provide better guidance for maintaining the systems which should implement the periodic replacement policies with minimal repair.

CAN Controller Design for Diagnosing Automation System Failure

This paper proposes a controller area network (CAN) controller design for monitoring the state of a programmable logic controller (PLC) system and predicting its failure. The PLC system is the main device used in production automation equipment based on a large amount of sensor data. The proposed controller collects and stores the status data of multiple PLCs and sensors, and sends the collected data to the host system through the CAN interface. Then, the host system analyzes the transmitted data and predicts whether the PLC system will fail. Moreover, the host system informs the user of the risk of system failure. The proposed controller is composed of a processor block and CAN communication module. It was tested by connecting a PLC device. Consequently, a diagnostic message was received per a period of 500 ms.

Prognostic index to assess the risk of systemic right ventricular failure after atrial switch operation for transposition of the great arteries

Background:Diabetic patients with Non ST Elevated Myocardial Infarction (NSTEMI) are at high risk for subsequent cardiovascular events. But, early Percutaneous Coronary Intervention (PCI) in high risk group of NSTEMI patients significantly prove the primary outcomes.

A Model‐Based Assessment of Controllable Phase Change Materials/Liquid Coupled Cooling System for the Power Lithium‐Ion Battery Pack

An excellent battery cooling system is required not only to control the battery temperature within a reasonable range, but also to minimize the parasitic power consumption and the failure risk. A simplified thermal model for a pouch battery pack with three cooling schemes is developed in this work, where the battery heat generation rate is calculated by a semi‐empirical equation and the reliability of the thermal model is validated by the battery discharge experiments. Finally, an improved phase change materials (PCM)/liquid coupled cooling system is proposed, and its cooling effects are compared with the traditional liquid cooling scheme, where the start–stop control and the hysteresis phenomenon of the cooling system are considered in the simulations. Compared to the traditional liquid cooling scheme, the phase change materials (PCM)/liquid coupled system decreases the start–stop frequency by less than half (which can reduce the risk of system failure effectively) and reduces the pumping power consumption by at least 60%. In addition, the PCM/liquid coupled cooling system exhibits a higher reliability, whereas the battery temperature usually exceeds the upper limit when cooled with the traditional liquid cooling scheme due to the hysteresis problem of the cooling system.

Quantifying the automated vehicle safety performance: A scoping review of the literature, evaluation of methods, and directions for future research

Vehicle automation safety must be evaluated not only for market success but also for more informed decision-making about Automated Vehicles' (AVs) deployment and supporting policies and regulations to govern AVs’ unintended consequences. This study is designed to identify the AV safety quantification studies, evaluate the quantification approaches used in the literature, and uncover the gaps and challenges in AV safety evaluation. We employed a scoping review methodology to identify the approaches used in the literature to quantify AV safety. After screening and reviewing the literature, six approaches were identified: target crash population, traffic simulation, driving simulator, road test data analysis, system failure risk assessment, and safety effectiveness estimation. We ran two evaluations on the identified approaches. First, we investigated each approach in terms of its input (required data, assumptions, etc.), output (safety evaluation metrics), and application (to estimate AVs' safety implications at the vehicle, transportation system, and society levels). Second, we qualitatively compared them in terms of three criteria: availability of input data, suitability for evaluating different automation levels, and reliability of estimations. This review identifies four challenges in AV safety evaluation: (a) shortcomings in AV safety evaluation approaches, (b) uncertainties in AV implementations and their impacts on AV safety, (c) potential riskier behavior of AV passengers as well as other road users, and (d) emerging safety issues related to AV implementations. This review is expected to help researchers and rulemakers to choose the most appropriate quantification method based on their goals and study limitations. Future research is required to address the identified challenges in AV safety evaluation.

A copula-based stochastic fractional programming method for optimizing water-food-energy nexus system under uncertainty in the Aral Sea basin

Abstract A copula-based stochastic fractional programming (CSFP) method is developed for optimizing water-food-energy nexus (WFEN) system, which can tackle random variables under conflicting objectives and analyze the interrelationship between marginal benefit and system-failure risk. Then, a CSFP-WFEN model is formulated for the Aral Sea basin and multiple scenarios with individual- and joint-probabilistic risks related to water resources, arable land, and hydropower generation are examined. Synthesizing the results under all scenarios, hydropower generation would decrease by 11.9% and crop area would increase by 12.4% by 2035 under severe water scarcity. Agricultural water would decrease with time (from 69.1% in 2021 to 53.9% in 2035), and the share of wheat farmland would increase by 16.4% for food security. Compared with the traditional stochastic fractional programming (SFP) and copula-based stochastic programming (CSP) methods, the marginal benefit from CSFP would be improved 1.7% and water would be saved 9.2%. To support sustainable development of the study basin, some suggestions can be derived from the results: (i) since agriculture is still the largest water user in the future, it is desired to reduce its water consumption through improving irrigation efficiency and adjusting crop planting structure; (ii) effectively reducing Uzbekistan’s water consumption can improve water allocations to other countries and relieve regional conflicts caused by water shortage; (iii) compared to the single management pattern, the integrated optimization of water, food and energy nexus not only has higher efficiency of resources allocation and utilization, but also allows an increased robustness in controlling system-failure risk under joint probabilistic constraints.

Condition-based inspection policies for boiler heat exchangers

This study considers the inspection and maintenance of boiler heat exchangers, which are examples of a system composed of degrading, non-repairable components in series whose operation can be restored by removing failed components from service (albeit at a performance loss). For such systems, the increased failure risk due to component degradation may be managed through inspections and preventive removal of high failure risk components from service (again at a performance loss for remaining life of systems). In this study, a new joint inspection and preventive maintenance policy is developed, which uses condition information obtained at an inspection to optimize decisions regarding maintenance and future inspections to optimally balance the risks of system failure, future performance losses, and maintenance costs. The policy is optimized using the Markov Decision Process paradigm and is applied to a case study of a boiler heat exchanger operating in an Australian sugar factory. The results show that the proposed policy yields significant savings compared to benchmark policies that represent the factory's current practice.

Optimization of Ecological Water Supplement Scheme for Improved Suitable Habitat Area for Rare Migratory Birds in Nature Reserves Using Interval-Parameter Fuzzy Two-Stage Stochastic Programming Model.

The optimization of ecological water supplement scheme in Momoge National Nature Reserve (MNNR), using an interval-parameter two-stage stochastic programming model (IPTSP), still experiences problems with fuzzy uncertainties and the wide scope of the obtained optimization schemes. These two limitations pose a high risk of system failure causing high decision risk for decision-makers and render it difficult to further undertake optimization schemes respectively. Therefore, an interval-parameter fuzzy two-stage stochastic programming (IPFTSP) model derived from an IPTSP model was constructed to address the random variable, the interval uncertainties and the fuzzy uncertainties in the water management system in the present study, to reduce decision risk and narrow down the scope of the optimization schemes. The constructed IPFTSP model was subsequently applied to the optimization of the ecological water supplement scheme of MNNR under different scenarios, to maximize the recovered habitat area and the carrying capacity for rare migratory water birds. As per the results of the IPFTSP model, the recovered habitat areas for rare migratory birds under low, medium and high flood flow scenarios were (14.06, 17.88) × 103, (14.92, 18.96) × 103 and (15.83, 19.43) × 103 ha, respectively, and the target value was (14.60, 18.47) × 103 ha with a fuzzy membership of (0.01, 0.83). Fuzzy membership reflects the possibility level that the model solutions satisfy the target value and the corresponding decision risk. We further observed that the habitat area recovered by the optimization schemes of the IPFTSP model was significantly increased compared to the recommended scheme, and the increases observed were (5.22%, 33.78%), (11.62%, 41.88%) and (18.44%, 45.39%). In addition, the interval widths of the recovered habitat areas in the IPFTSP model were reduced by 17.15%, 17.98% and 23.86%, in comparison to those from the IPTSP model. It was revealed that the IPFTSP model, besides generating the optimal decision schemes under different scenarios for decision-makers to select and providing decision space to adjust the decision schemes, also shortened the decision range, thereby reducing the decision risk and the difficulty of undertaking decision schemes. In addition, the fuzzy membership obtained from the IPFTSP model, reflecting the relationship among the possibility level, the target value, and the decision risk, assists the decision-makers in planning the ecological water supplement scheme with a preference for target value and decision risk.

Response of semi-rigid steel frames to sequential earthquakes

In a seismic event, large number of aftershocks are generally triggered due to the complex interaction within and between tectonic plates. Even though aftershocks are typically smaller in magnitude than mainshocks, their ground-motion intensity, measured by peak ground acceleration, is not always smaller. Moreover, mainshocks can result in permanent damage to structural components. As a result, the vulnerability of structures to extensive damage and complete collapse due to aftershocks could increase. Despite their importance in evaluating the true risk of system failure and collapse, the inclusion of aftershocks in code provisions and guidelines for seismic risk assessment and performance-based engineering is lacking. In this study, three semi-rigid frames, with connection capacities of 50%, 60%, and 70% of the plastic moment of the beam, were designed and their performance under mainshock-aftershock sequences assessed. The objective of this study, pertaining to the seismic performance of the frames, is twofold. First, is to develop fragility functions for the subject frames under sequential mainshock-aftershock events. Second, is to evaluate the extent of spread of inelasticity and period elongation in the investigated frames as a result of the sequential events. A new method for selection and scaling of mainshock-aftershock sequences is proposed and non-linear time history analysis of the frames is conducted. The results show that the inclusion of the aftershocks increases the probability of reaching or exceeding a particular damage limit state in the frames, primarily due to the considerable period elongation resulting from the induced permanent damages.

A roadmap investment strategy to reduce carbon intensive refrigerants in the food retail industry

High global warming potential (GWP) refrigerant leakage is the second-highest source of carbon emissions across UK supermarket retailers and a major concern for commercial organisations. Recent stringent UN and EU regulations promoting lower GWP refrigerants have been ratified to tackle the high carbon footprint of current refrigerants. This paper introduces a data-driven modelling framework for optimal investment strategies supporting the food retail industry to transition from hydrofluorocarbon (HFC) refrigeration systems to lower GWP systems by 2030, in line with EU legislation. Representative data from a UK food retailer is applied in a mixed integer linear model, making simultaneous investment decisions across the property estate. The model considers refrigeration-system age, capacity, refrigerant type, leakage and past performance relative to peer systems in the rest of the estate. This study proposes two possible actions for high GWP HFC refrigeration systems: a) complying with legislation by retrofitting with an HFO blend (e.g. R449-A) or b) installing a new natural refrigerant system (e.g. R744). Findings indicate that a standard (i.e. business-as-usual) investment level of £6 m/yr drives a retrofitting strategy enabling significant reduction in annual carbon emissions of 71% by the end of 2030 (against the 2018 baseline), along with meeting regulatory compliance. The strategy is also highly effective at reducing emissions in the short term as total emissions during the 12-year programme are 59% lower than would have been experienced if the HFC emissions continued unabated. However, this spending level leaves the business at significant risk of refrigeration system failures as necessary investments in new systems are delayed resulting in an ageing, poorly performing estate. The model is further tested under different budget and policy scenarios and the financial, environmental, and business-risk implications are analysed. For example, under a more aggressive investment approach of £50 m/yr carbon reductions are at 93% by the end of 2030, whilst also ensuring compliance with the legislative cut-off four years early in 2026 and substantially enhancing the reliability of the refrigeration systems in the portfolio. Alternatively, when emissions are minimised instead of cost with a £50 m/yr investment level, 99% decarbonisation is achieved by 2030. Overall, the study highlights the trade-offs between capital investment and system resilience requiring a careful balance of priorities and the need to have up to date information so decision makers can reliably drive a successful strategy towards more sustainable operation of refrigeration systems.

Development of Climate Impact Response Functions for highly regulated water resource systems

Climate Impact Response Functions (CIRFs) can be useful for exploring potential risks of system failure under climate change. The performance of a water resource system can be synthesized through a CIRF that relates climate conditions to system behavior in terms of a specified threshold of deliveries to demands or environmental flow requirements. However, in highly regulated water resource systems this relationship may be quite complex, depending on storage capacity and system operation. In this paper we define a CIRF for these types of systems through a multivariable logistic regression (LR) model where a binary variable (system response) is explained by two continuous variables or predictors (precipitation and temperature). The approach involves generating multivariate synthetic inflow time series and relating them to specific climate conditions. Next, these inflows are used as inputs in a water management model, and the outcome is coded as a binary variable (failure or its absence) depending on selected vulnerability criteria. To identify the time span before the failure event in which climate variables are relevant, we characterized drought development stages through relative standardized indices. Mean values of precipitation and temperature for the selected time span are computed and used as explanatory variables through a LR model, which is validated using data from several climate models and scenarios. Results show that the predictive capacity of LR models is acceptable, so that they could be used as screening tools to detect challenging climate conditions for the system which would require adaption actions.

Experimental investigation of the effect of solid-gas two-phase flow in CO2 cascade refrigeration system

ABSTRACT The dry ice sublimation process of CO2 is a unique technique in which temperature ranges below the triple point of −56 °C can be achieved in a CO2 refrigeration system. However, during the evaporation process of the actual refrigeration system, the dry-ice blockage maybe happens in the evaporator, which causes a risk of system failure in the suction of the compressor. In order to overcome this problem, in this study, an ultra-low temperature CO2 cascade refrigeration system with a novel tapered evaporator/sublimator was designed and constructed. The novel evaporator/sublimator included a swirl promoter, which induces the swirling flow of solid-gas two-phase flow. Experiments were conducted for the investigation of solid-gas two-phase flow heat transfer characteristics in the evaporator/sublimator. According to the experimental results, it is verified that the CO2 refrigeration system can operate consistently and steadily without dry ice blockage in the evaporator/sublimator. In addition, the dry ice particles are uniformly distributed along the inner wall of the evaporator/sublimator by the installation of the swirl promoter, and the heat transfer coefficient is considerably improved.

Best Suited Machine Learning Techniques for Software Fault Prediction

In this world of emerging applications of software, it is always important to provide a quality assured product to customers. Software Fault Prediction popularly abbreviated as SFP is a major field which helps to provide quality assured products to customers. It helps to recognize modules that are bug- free and bug-prone in a software module. Machine learning techniques for both classification and determination are used for the purpose of software fault prediction. Software Fault Prediction is carried out prior to testing process without executing the source code, instead vital characteristics of software is taken into consideration. This early identification of faults can help software engineers to reduce the risk of system failure. A company does not always prefer to invest more expense on testing and in those situations, software fault prediction can have an upper hand in testing. The software fault prediction model will first train the learning techniques to generate base learners and then apply these base learners to unseen projects. It is always preferred to determine the count of faults rather than classifying each software module as fault-free and fault-prone. All software fault prediction techniques depend on base learners used and also nature of fault dataset. In this paper, the major learning techniques to determine software fault, characteristics of software fault dataset, etc. are discussed.

Reliability function of k-out-of-n system equipped with two cold standby components

In this article, we focus on reliability properties of a k-out-of-n system equipped with two cold standby components. We describe the lifetime of the system and compute the reliability function of the system, which will allow us to investigate the risk of system failure. Further, three different mean residual life functions of the system are derived. We also provide some stochastic ordering results. The theoretical results established in this article addresses a problem proposed by Eryilmaz and Wang. We have presented a few numerical results to illustrate the importance of our analysis.

A bi-level chance-constrained programming method for quantifying the effectiveness of water-trading to water-food-ecology nexus in Amu Darya River basin of Central Asia

Issues of water scarcity, food crisis, and ecological degradation pose great challenges to the sustainable development of Central Asia. In this study, a bi-level chance-constrained programming (BCCP) method is developed for planning water-food-ecology (WFE) nexus system of the Amu Darya River basin, where the efficiency of water-trading mechanism and the impact of uncertain water-availability are examined. This is the first attempt for planning WFE nexus system by incorporating chance-constrained programming (CCP) within a bi-level optimization framework. BCCP can reflect the risk of violating probabilistic constraint under uncertainty as well as balance the tradeoff between two-level decision makers in the WFE nexus system. Under trading scheme, multiple scenarios in association with different food demand, ecological-water requirement, and water availability are examined. Major findings are: (i) compared with that under non-trading, system benefits would increase [3.9, 20.4]% under trading scenarios, disclosing that water trading is an effective mechanism for the study basin; (ii) when food demand increases 10.5%, water allocated to ecological use would decrease [0.9, 2.7]% under all scenarios, revealing that agriculture can squeeze ecological water; (iii) both system benefit and water allocation would increase with p level, implying there is a tradeoff between system benefit and system-failure risk. These findings can gain insight into the interaction between two-level stakeholders and objectives as well as provide decision support for WFE nexus synergetic management.

Compliance, acute toxicity and postoperative complications of short-course radiotherapy followed by chemotherapy and surgery for high-risk rectal cancer. results of the randomized RAPIDO-trial

Background: Preoperative chemoradiotherapy (CRT) followed by total mesorectal excision is widely accepted as the standard of care for high-risk rectal cancer. Although the exact survival benefit remains unclear and compliance is poor, adjuvant chemotherapy is advised in several international guidelines. This multidisciplinary approach has led to major improvements in local control, yet the occurrence of distant metastases has not decreased accordingly. With the aim of achieving higher compliance and better effect of systemic therapy, the combination of short-course radiotherapy (SCRT) and preoperative chemotherapy prior to surgery was examined in this trial for patients diagnosed with rectal cancer with a high risk of local and systemic failure.

A Tale of Two Markets: How Lower-end Borrowers Are Punished for Bank Regulatory Failures in Nigeria

In 2009, the Nigerian banking system witnessed a financial crisis caused by elite borrowers in the financial market. Regulatory response to the Nigerian crisis closely mirrored the international response with increased capital and liquidity thresholds for commercial banks. While the rise of consumer protection on the agenda of prudential supervisors internationally was logical in that consumer debt was the main cause of the global recession, the Nigerian banking reforms of 2009 disproportionately affected access by poorer consumers, who ironically had little to do with the underlying causes of the crisis. As lending criteria become more stringent, poorer consumers of credit products are pushed into informal markets because of liquidity-induced credit rationing. Overall, consumer protection is compromised because stronger consumer protection rules for the formal sector benefits borrowers from formal institutions who constitute the minority of borrowers in all markets. While the passage of regulation establishing credit bureaux and the National Collateral Registry will, in theory, ease access to credit especially by lower-end borrowers, the vast size of the informal market continues to compound the information asymmetry problem, fiscal policies to tackle structural economic issues such as unemployment and illiteracy remain to be initiated, and bank regulators continue to pander to elite customers with policy responses that endorse too big to fail but deems lower-end consumers too irrelevant to save. The essay concluded that addressing the wide disparity in access to credit between the rich and poor through property rights reforms to capture the capital of the informal class, promoting regulation to check loan concentration, and stimulating competition by allowing Telecommunication Companies (TELCOs) and fintech companies to carry on lending activities because of their superior knowledge of lower-end markets will facilitate greater access. The risk of systemic failure deriving from consumer credit in Nigeria is insignificant compared to the consumer vulnerabilities resulting from the exposure of consumers to unregulated products in the informal market.

Interactional misalignment in the UK NHS 111 healthcare telephone triage service

BackgroundA recent review of primary care serious incidents suggests that diagnosis and assessment problems, underpinned by communication failures, involving the UK telephone triage service, NHS 111, may contribute to patient harm. MethodsThe present study utilised conversation analysis to address the lack of evaluative research examining the NHS 111 system and in particular interactions between system components (call handler, computerized decision support system, patients/caller). ResultsAnalysis of audio recorded call interactions revealed interactional misalignment across four mapped call phases (eliciting caller details, establishing reason for call, completing the Pathways assessment, and agreeing the outcome). This misalignment has the capacity to increase the risk of system failure, particularly in relation to assessment problems and issues related to the accurate transfer of care advice. Our analysis suggests that efforts to enhance the NHS 111 system, similar telehealth services, and patient safety management more generally, should shift their focus from a limited set of individual components towards a system-specific interactionist perspective encompassing all elements. ConclusionsFurther evaluative research is required in order to build a comprehensive evidence-base concerning the multiple interacting factors influencing patient safety in the NHS 111 system.

Use “risk of system failure” rather than additive aggregation methods of indicators when assessing habitat quality

Abstract The choice of method for aggregation of ecological indicators is important for the outcome of the aggregation. We demonstrate and discuss how additive versus risk of system failure (i.e. use of one-out-all-out logic) aggregation methods can result in opposing outcomes when assessing the conservation status of habitat types under the EU-habitat directive. In additive aggregation systems, failure to meet a given ecological indicator that is required for favorable conservation status can be compensated by other indicators. The consequence is that ecosystem changes that are detrimental in the long term may be ignored when an additive aggregation method is applied. Despite this, additive aggregation systems appear to be dominant among conservationists and are frequently used to assess habitat status. We recommend the risk of system failure method when developing habitat quality assessment systems instead of only relying on additive aggregation systems.

A Nonlinear Inexact Two-Stage Management Model for Agricultural Water Allocation under Uncertainty Based on the Heihe River Water Diversion Plan

In this study, a nonlinear inexact two-stage management (NITM) model is proposed for optimal agricultural irrigation water management problems under uncertainty conditions. The model is derived from incorporating interval parameter programming (IPP), two-stage stochastic programming (TSP) and quadratic programming (QP) within the agricultural water management model. This model simultaneously handles uncertainties not only in discrete intervals, but also in probability distributions, as well as nonlinearity in the objective function. A concept of the law of diminishing marginal utility is introduced to reflect the relationship between unit benefits and allocated water, which can overcome the limitation of general TSP framework with a linear objective function. Moreover, these inexact linear functions of allocated water can be obtained by an interval regression analysis method. The model is applied to a real-world case study for optimal irrigation water allocation in midstream area of the Heihe River Basin in northwest China. Two Heihe River ecological water diversion plans, i.e., the original plan and an improved plan, will be used to determine the surface water availabilities under different inflow levels. Four scenarios associated with different irrigation target settings are examined. The results show that the entire study system can arrive at a minimum marginal utility and obtain maximum system benefits when optimal irrigation water allocations are the deterministic values. Under the same inflow level, the improved plan leads to a lower water shortage level than that of the original plan, and thus leads to less system-failure risk level. Moreover, the growth rate of the upper bound of economic benefits between each of two scenarios based on the improved plan are greater than that from the original plan. Therefore, these obtained solutions can provide the basis of decision-making for agricultural water allocation under uncertainty.