Failure Rate Estimation Research Articles

A hybrid maintenance approach for key components of the train bogie to optimize fleet availability

In the context of intelligent transport systems and the rapid development of the global economy, railways face increasing demand to become safer, more efficient, and more sustainable. As a critical structure of the railway vehicle, the bogie, designed to support the vehicle body and transmit dynamic loads through the wheels, houses several components that are vital for the reliability and safety of the train. The maintenance of such a structure is complex and can greatly benefit from hybrid approaches that leverage the potential of condition-monitoring data in proactively identifying faults or irregularities whilst ensuring appropriate intervals that maximize the availability of resources. This paper proposes a hybrid maintenance approach that combines preventive maintenance, condition-based monitoring, and predictive maintenance for the key components of the bogie, aiming to optimize costs while exploiting potential economic savings of maintenance decisions for different grouping strategies, therefore, maximizing fleet availability. The model aims to study the feasibility and measure the expected economic returns of shifting from a complete preventive maintenance program to a hybrid program incorporating predictive maintenance tasks in selected components of the bogie. A deterioration model, along with failure rate estimation, is proposed and integrated into the optimization formulation. A case study of a railway company operating in Catalonia, Spain, is presented. The framework demonstrates flexibility in tackling current maintenance practices, including hierarchy and periodicity of maintenance tasks according to the intervention type and flexible hazard rates with three stages to mimic the bathtub curve behaviour. The results show that shifting to a hybrid maintenance plan has great potential to reduce costs.

A Unique Failure Mode of SiC MOSFETs under Accelerated HTRB

Device lifetime under reverse bias conditions is an important reliability concern for SiC devices. Provided that the termination structure is well designed, device failure in the active cell is driven by gate oxide breakdown due to the high field in the semiconductor and gate dielectric. For planar MOSFETs, the largest field occurs in the JFET region [1,2]. Standard HTRB testing is insufficient to estimate failure rates under operating conditions and hence testing under accelerated off-state conditions (ALT-HTRB) is required. This paper provides data, statistical analysis, failure analysis and finally a Weibull statistics-based temperature, Vd and stress time dependent model.

Dynamic risk assessment of natural gas transmission pipelines with LSTM networks and historical failure data

In the realm of energy infrastructure, ensuring the security of gas transmission pipelines is critical. This research introduces an advanced dynamic risk assessment framework that leverages the predictive capabilities of LSTM networks, presenting an improvement over conventional failure prediction models. Unlike traditional approaches that rely on averaging historical failure records, this framework dynamically processes historical pipeline failure incidents into sequential time series analysis, facilitating and improving the accuracy of the current failure rate. The model refines the failure rate estimation for individual pipelines by incorporating unique characteristics and modification factors, resulting in a highly precise failure likelihood estimation. Additionally, this study introduces a quantifiable linkage between mortality risk and the fatality probit value across various accident scenarios, enhancing consequence evaluation. A sensitivity analysis is then performed to assess the impact of various input parameters on the model's performance. The practical application of the model on a U.S. pipeline confirms its effectiveness. This proposed methodology substantially enhances the understanding of incident causation in gas pipeline systems, paving the way for superior safety management strategies. It is instrumental in enhancing pipeline safety, refining infrastructure planning, and optimizing safety resource allocation. The methodology offers benefits for pipeline operators, industry professionals, and regulatory agencies, contributing to improved operational safety and resource management in the pipeline industry.

Comparative Analysis of Fuzzy Dagum Hazard Function Approaches for Estimating Failure Rates

Comparative Analysis of Fuzzy Dagum Hazard Function Approaches for Estimating Failure Rates

Quantitative assessment of charging ports in EV charging stations from reliability and economic perspective in the distribution system

With the emerging development of electrical vehicles (EVs) in transportation, the utilization manufacturing companies are concentrating on the development of charging facilities for customers. Maintaining the reliability of charging ports is a difficult task for the intermediate charging conditions of EVs, even though the charging station industries are installing the charging stations as per the specifications of the distribution system. To improve the reliability of the charging station for the distribution system, the 12 and 24-ported configurations have been proposed and systems have been designed with the individual batch structure. The performance analysis of the proposed non-uniform configurations has been estimated in terms of reliability as per the failure rate of the individual port in batch. The proposed 12 and 24-ported configuration’s failure rate has been evaluated with the standards of MILHBK-217 F. According to the failure rate of the port, the evaluation process has been introduced to find the success rate of the charging station. The maintenance cost has been estimated based on the failure and success rate of the proposed 12 and 24 systems. Finally, the performance analysis of the proposed 12 and 24-port configurations comparison has been estimated in terms of failure rate, success rate and maintenance cost. In this work, the binomial distribution probability technique has been implemented for the appropriate failure rate estimation of the charging station. The proposed 12 and 24-port non-uniform configurations are capable of providing reliable operation and are implementable for the low area of the plinth for EV charging stations.

Serious Failure Modes After EVAR Are Device Specific.

Type I and III endoleaks following endovascular aneurysm repair (EVAR) can lead to catastrophic events that require major re-interventions. We reviewed our experience with aortic endograft re-interventions for type I and III endoleaks and other serious failures among different devices. We retrospectively reviewed patients with a prior EVAR who underwent open conversion (OC) or major endovascular intervention (MEI) (re-lining, cuff/limb extension, parallel graft) for type I/III endoleaks at our institution from 2002 to 2019. Baseline characteristics, procedural details, re-interventions, and outcomes were collected. A total of 229 patients (194 men) underwent re-interventions for type I and III endoleaks after EVAR (90 OC, 139 MEI) for devices implanted between 1997 and 2019. Average age at re-intervention was 78±8.5 years. A total of 135 (59%) were implanted at our institution, whereas 93 (41%) were referred. Median time to re-intervention was 4 years with 25% to 75% interquartile range (IQR) of 2.2-6.6 years. There was no significant difference in baseline demographics or type of re-interventions (OC/MEI) between device types. 42/229 (18%) presented with ruptured aneurysms, 20/229 (9%) were symptomatic, whereas the rest presented with asymptomatic radiographic findings. Type 1A endoleak was present in 146/229 (63.8%-72 with proximal migration), type IB in 46/229 (20.1%), type IIIA in 37/229 (16.6%), type IIIB in 15/229 (6.5%), and persistent aneurysm sac growth with no radiographic evidence of an endoleak in 6/229 (2.6%). Devices included most commercial products: AFX, Excluder, AneuRx, Ancure, Endurant, and Zenith. A smaller number of investigational devices accounted for the rest. Type 1A endoleak was the most common indication for re-intervention among all devices except for AFX and ancure devices, proximal migration was a frequent presentation with AneuRx. AFX devices more frequently presented with a type III and ancure devices more frequently presented with a type IB endoleak. Serious failure modes after EVAR differ between endografts and occur throughout the follow-up period. This is important to guide targeted interrogation of surveillance studies and follow-up schedules, even for discontinued devices, as well as comparisons between various series and estimation of EVAR failure rates. Surveillance after EVAR is critical for long term success of the repair, understanding of the differential modes of failure of every graft available is important in the longitudinal evaluation of these endografts. Equally important is the understanding of the modes of failure of legacy endografts that are no longer on the market but still being followed, in order to be able to tailor a surveillance regiemn and the evntual repair if needed.

Evaluation of Reliability and Financial Feasibility of Various EV Charging Station Layouts

As the popularity of electric vehicles (EVs) continues to rise, companies are increasingly focusing on expanding charging infrastructure to meet growing consumer demand. Despite attempts to design charging stations that align with distribution system requirements, ensuring reliable performance for EV charging ports remains a complex challenge. To address this issue, a unique design featuring 56 ports, comprising both uniform and non-uniform arrangements, has been introduced. These configurations underwent testing across distribution systems ranging from 50 to 500 kW. Reliability assessments were carried out using established standards for failure rate estimation and Monte Carlo simulations to evaluate port probability functions in terms of failure rate and reliability. By scrutinizing the failure rates of individual ports, a systematic evaluation method was established to gauge the overall performance of the charging station. The failure rate of the proposed 56-ported charging station was further assessed using the binomial distribution method. Also, cost estimation procedures were developed, taking into account the maintenance costs associated with the failure and success rates of individual ports for the proposed design. The research findings suggest that by enhancing port arrangement reliability and improving voltage stability, it is possible to achieve lower failure rates and maintenance costs, thereby enhancing overall system performance

Assessing Reliability and Economic Viability of Different EV Charging Station Configurations

With the increasing popularity of electric vehicles (EVs) as a mode of transportation, companies are prioritizing the development of charging infrastructure to cater to customer needs. Despite efforts to align charging station designs with distribution system requirements, maintaining reliability for EV charging ports remains challenging. To enhance reliability, a novel 56-ported design incorporating both uniform and non-uniform port arrangements has been proposed. These configurations have been tested with distribution systems ranging from 50 to 500 kW. Reliability assessments were conducted using standards outlined failure rate estimation and monte-carlo functions for evaluating port probability functions in terms of failure rate and reliability. By analyzing the failure rates of individual ports, an evaluation process was introduced to determine the overall success rate of the charging station. The failure rate of the proposed 56-ported charging station was further evaluated using the binomial distribution method. Additionally, cost estimation procedures were implemented considering the failure and success rates of individual port maintenance for the proposed configuration. The findings indicate that achieving lower failure rates and maintenance costs is possible through improved port arrangement reliability and enhanced voltage stability.

Clinical Outcomes of Maxillary Sinus Floor Perforation by Dental Implants and Sinus Membrane Perforation during Sinus Augmentation: A Systematic Review and Meta-Analysis.

The aim of the present systematic review was to investigate the clinical outcomes after the perforation of the maxillary sinus by dental implants, or after maxillary sinus membrane perforation during sinus lift procedure. Twenty-nine publications were included. Failure rates of implants in cases where perforation of sinus floor had happened (11 studies) was generally low, and only one case of transient sinusitis was reported. The estimated failure rate of these implants was 2.1% (SE 1.0%, p = 0.035). There were 1817 implants (73 failures) placed in augmented sinuses in which the sinus membrane was perforated and 5043 implants (274 failures) placed in sinuses with no perforated membrane, from 18 studies. The odds of implant failure difference between the groups were not significant (OR 1.347, p = 0.197). log OR of implant failure between perforated and non-perforated membrane groups did not significantly change with the follow-up time (-0.004/month; p = 0.500). In conclusion, implant failure rate is generally low either for implants penetrating in the floor of the maxillary sinus or implants placed in augmented sinuses in which the sinus membrane was perforated. The prevalence of postoperative infection/sinusitis is low, and it may depend either on the dimensions of the perforation or on the anatomical predisposition.

Reasons for Crown Failures in Primary Teeth: Protocol for a Systematic Review and Meta-Analysis

Background There is a tendency nowadays to restore large defects in primary dentition with pediatric crowns instead of conventional restorations. Thus, understanding the factors contributing to the survival or failure of dental crowns in pediatric dentistry is essential for optimizing treatment outcomes. Objective The primary objective of this protocol is to outline the methodological approach for analyzing data from observational studies and randomized controlled trials to investigate reasons for the failure of dental crowns in primary teeth and to compute their survival and failure rates. Methods A comprehensive literature review will be performed in electronic databases, including PubMed (MEDLINE), Cochrane, Embase, and Web of Science. As per predefined inclusion criteria, we will include observational studies (prospective clinical studies) and randomized clinical trials that have an English abstract and involve children aged 1-10 years undergoing crown restorations. Two independent reviewers will independently screen all retrieved records and full-text articles and extract data. The study’s methodological quality will be appraised using suitable tools. Assessments of publication bias will be performed using funnel plots. The findings will be described qualitatively for the systematic review. If possible, a meta-analysis will be performed to estimate failure rates by dividing the number of failures by the total exposure time. A Poisson regression model, assuming constant event rates, will be used to compute 3-year and 5-year survival proportions. The Pearson goodness-of-fit statistics will be used to assess the heterogeneity of the model. A P value <.05 will be considered significant. All analyses will be performed using R Statistical software (version 4.1.2; R Core Team). Results This systematic review and synthesis aim to assess the survival and failure rates of dental crowns in pediatric dentistry. By following this rigorous methodology, we seek to provide valuable insights into the factors contributing to the success or failure of these restorations. The results of our full review will have implications for pediatric dentists, researchers, and policy makers, helping to improve dental care for children. Conclusions This systematic review protocol helps in establishing a thorough approach for reviewing failures in pediatric crowns. By following this methodology, standardization and transparency of the process as well as accountability for the stated methods and outcomes will be ensured. The findings of this review and analysis will provide useful data on the survival of crowns to pediatric dentists and researchers. Trial Registration PROSPERO CRD42023442266; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=442266 International Registered Report Identifier (IRRID) PRR1-10.2196/51505

Performance Evaluation of Data Utility for a Differential Privacy Scheme Supporting Fault Tolerance

The evolution of smart grids improves the sustainability, controllability, stability, and efficiency of traditional power grids. There is a challenging issue in smart grids with protecting users’ privacy while collecting and controlling individual fine-grained data. To ensure data integrity and address the privacy issue, differential privacy protection is an efficient method to resist differential attacks on aggregated data. However, due to differential noise and faulty smart meters, the problem of differential noise deviation has a great impact on the utility of aggregated data. In this paper, we further supplement the previous work by improving the prediction method, forming a relatively complete DP protection scheme (DPP-UFT) with fault tolerance, and providing a detailed performance evaluation process. The experimental results show that the proposed method of adding differential noise based on the estimated failure rate is related to the estimated failure rate and the noise factor. Compared with several other related literature, it has achieved a higher data utilization effect.

On the Sensitivity of Wind Turbine Failure Rate Estimates to Failure Definitions

This study presents a wind turbine reliability analysis at the turbine and assembly level. It is concerned with the uncertainties associated with data-processing for wind turbine failure rate figures. These uncertainties are prominent in discussions of failure data in the literature. In particular, the influence of different failure definitions on failure rate estimates are investigated. The baseline estimate is 9.06 failures per turbine per year. This figure changes significantly when introducing a lower downtime limit, repair limit or limit on time between subsequent downtimes of the same turbine for a downtime event to be considered a failure. It changes significantly depending on which maintenance actions are categorised as corrective and by what data points represent an intervention. From the one dataset analysed here, results show derived failure rates ranging from below 1 failures per turbine per year to over 10 failures per turbine per year using failure definitions which have previously been used in the literature. When restricting failures to those that can be attributed to a particular assembly, the failure rate estimate reduces to 7.47 failures per turbine per year. Assemblies that fail the most are the frequency converter (at around 1 failures per turbine per year) and the cooling system (at around 0.9 failure per turbine per year). The gearbox, blades, yaw system and hydraulic group were the next most frequently failing assemblies.

Novel Strategy for Optimizing the Antibacterial Activity of Psidium guajava Against Clinical Isolates of Escherichia coli, Staphylococcus aureus, Salmonella spp., and Streptococcus spp.

The development of a new antibiotic is a challenging task, with an estimated failure rate of 95%. Minor changes in the chemical structure of a drug, such as stereochemistry, geometry, or functional group modifications, can significantly impact its medicinal activity. In this study, we aim to devise novel strategies for optimizing the antimicrobial properties of guava leaf extract through simple reactions, either by self-reaction or combination reactions with a reagent, drug, or different plant extract. Fourier transform infrared spectroscopy analysis revealed conjugation and formation of new functional groups in the prepared sample of Guava Guava (GG) and Guava Aspirin Guava (GAG), which were further confirmed by weight analysis. The results demonstrated that the antimicrobial activity of medicinal plants can be improved or optimized through simple reactions, such as combining the plant extract with a non-antimicrobial drug like aspirins or adding a small volume of concentrated sulfuric acid to the plant extract by heating at a temperature range of 100 – 110°C. Among the two combinatory methods used, GG exhibited better performance in inhibiting the growth of all tested bacterial strains at a concentration of 0.1 mg/mL compared to GAG at the same concentration, which inhibited the growth of only two bacterial strains: Escherichia coli and Streptococcus spp. These methods can be further explored and applied in various studies, including antifungal, anti-inflammatory, antiviral, and anticancer research, leveraging the availability and diverse range of natural products found in medicinal plants.

How extreme failure‐data filtering leads to poor process safety

AbstractThis paper describes both appropriate and inappropriate practices of filtering field failure data (FFD) prior to using the resulting failure count from the failure data to estimate failure rates. The underlying causes of inappropriate (extreme) filtering of FFD are examined, and the consequences (poor process safety) are discussed. An example is presented illustrating the benefits of using all real failures discovered in the field in the estimation of failure rates based on FFD.

EPA Consensus Project Paper: Failure Rates of Direct Versus Indirect Single-Tooth Restorations. A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to evaluate and compare the failure rates of direct and indirect restorations for single-tooth restorations. A literature search was conducted by using electronic databases and relevant references for clinical studies on direct and indirect dental restorations with a follow-up of at least 3 years. The risk of bias was assessed with the ROB2 and the ROBINS- I tools. The I2 statistic was used for the assessment of heterogeneity. The authors reported summary estimates of annual failure rates of single-tooth restorations using a random-effects model. Of 1415 screened articles, 52 (18 RCTs, 30 prospective, 4 retrospective) met the inclusion criteria. No articles with direct comparisons were identified. No significant difference was found in the annual failure rates of single teeth restored with either direct or indirect restorations, which were calculated as 1% using a random-effects model. High heterogeneity was found, ranging from 80% (P⟨0.01) for studies on direct restorations to 91% (P⟨0.01) for studies on indirect restorations. Most of the studies presented some risk of bias. Annual failure rates were similar for direct and indirect single-tooth restorations. Further randomized clinical trials are needed to draw more definitive conclusions.

Statistical concepts and data requirements for valid failure rate estimation

AbstractThe distinction between point estimation and confidence interval estimation for failure rates is described. Why the upper bounds of failure rate confidence intervals are prescribed by safety standards for use in safety metric computations is explained. Statistical formulas for the failure rate upper bounds are provided. The requirements that the field failure data (FFD) must meet to ensure the validity of the failure rate estimations are discussed from both mathematical and engineering perspectives. The need to understand the underlying causes of failure in determining when FFD can be aggregated is explained. Examples illustrating the impacts on failure rate estimation when the data requirements are and are not met are presented.

Five-year surgical outcomes of transvaginal apical approaches in women with advanced pelvic organ prolapse.

In women with advanced prolapse, differences in vaginal apex anchoring sites may impact surgical outcomes over time. The primary aim was to compare 5-year surgical outcomes of uterosacral ligament suspension (ULS) versus sacrospinous ligament fixation (SSLF) in women with advanced (stage III-IV) prolapse. A secondary analysis was conducted in a subset of women with advanced prolapse from a multicenter randomized trial comparing ULS versus SSLF and its extended follow-up, using publicly accessible de-identified datasets. The primary outcome was time to failure, defined as any one of (1) apical descent > 1/3 into the vaginal canal or anterior/posterior compartment beyond the hymen, (2) bothersome vaginal bulge symptoms, or (3) re-treatment. Secondary outcomes include symptom severity measured by the Pelvic Organ Prolapse Distress Inventory (POPDI) and adverse events. Of 285 women, 90/147 (61.2%) in ULS and 88/138 (63.8%) in SSLF had advanced prolapse. Baseline characteristics did not differ between groups except for median-vaginal deliveries (3.0 [2.0, 5.0] versus 3.0 [2.0, 4.0], p < 0.01). The median time to failure was 1.7years ULS versus 2.0years SSLF (p = 0.42). Surgical failure increased over time in both groups with no intergroup difference; by year 5, the estimated failure rate was 67.7% ULS versus 71.5% SSLF (adjusted difference -3.8; 95%CI [-21.9, 14.2]). No differences were noted in individual failure components (p > 0.05). POPDI scores improved over 5years without intergroup difference (ULS -68.0 ± 61.1 versus SSLF -69.9 ± 60.3, adjusted difference -0.1 [-20.0, 19.9]). No difference in adverse events were observed (p > 0.05). In women with advanced prolapse, surgical failure, symptom severity, and adverse events did not differ between ULS and SSLF over 5years.

A restoration-clustering-decomposition learning framework for aging-related failure rate estimation of distribution transformers

A restoration-clustering-decomposition learning framework for aging-related failure rate estimation of distribution transformers

The Success Rate of the Adhesive Partial Fixed Prosthesis after Five Years: A Systematic Review

Objective: Evaluation of the success and/or survival rates of resin-bonded fixed partial dentures (RBFPDs) reported in the scientific literature with a minimum average observation time of five years. Materials and Methods: Search conducted in Pubmed, Web of Science, and Cochrane databases in free-text format and MESH terms, until May 2021. The random-effects model was used for the estimated survival rate, percentage per year of estimated failure, and existing complications for the meta-analysis. Study heterogeneity was assessed by the inconsistency test (I2) and study quality by the Downs and Black scale. Results: Eleven articles were included, with 687 participants and 783 RBFPDs, with a mean observation time of 8.2 years, with success rates mentioned in three articles and survival rates reported in nine articles. A total of 142 failures were reported for 783 prostheses, the most frequent being debonding. The estimated failure rate was between 0.53% and 5.10% per year. The studies were of sufficient quality. In the meta-analysis, the survival rates showed a significant result (p &lt; 0.001), with moderate heterogeneity (I2 = 58.76%). Conclusions: Within the limitations of this research, mainly related to the heterogeneity of the studies and their quality, it seems possible to conclude that RBFPDs are a viable clinical option for the rehabilitation of patients with single edentulous spaces, mainly when using a single retainer and a zirconia-ceramic prosthesis.

A conservative method for estimating the uncertainty for the probability of an upper-level event in a fault tree

Abstract. Aim. The aim of the paper is to construct a non-simulation method for finding the confidence interval for the probability of an upper-level event of a failure tree. Iterative Monte Carlo algorithms require very much time and computational resources, especially for large fault trees. Therefore, developing “fast” algorithms for finding uncertainty in a calculated fault tree is extremely important.Methods. The algorithm was developed using classical methods of the probability theory, mathematical statistics and dependability theory. The mathematical foundation of the algorithm is the central limit theorem and certain properties of the dispersion of a random variable from the probability theory. To simplify calculations, the confidence interval was built on the assumption of a lognormal distribution of the failure rate estimate with a certain specified error factor. The initial information consists of a set of minimal cross-sections defined for the fault tree using specialized software tools, as well as dependability parameters of the events in each of the cross-sections. The cross-sections may contain dependent events that are part of common cause failure (ССF) groups. Various ССF accounting models, including the betafactor model, alpha-factor model, etc., can be used to calculate the probability of such events. To simplify the set of cross-sections, a program code is used that groups the cross-sections that are identical in value and meaning. Results. A conservative method for constructing a confidence interval for the probability of an upper-level event in a fault tree was developed. The method is not iterative and allows identifying the uncertainty of the final result for randomly-sized fault trees.Conclusions. The algorithm for identifying the uncertainty can be used instead of the Monte Carlo method in specialized software suites that calculate fault trees.