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Objective: The evidence base for the use of space maintainers is relatively sparce despite being used for decades after the premature loss of primary molars. This study aims to increase the dental evidence base via investigating retrospectively the success rates of prefabricated fixed and removable space maintainers inserted from 2019 to 2021 and followed up until February 2023 at a specialized university clinic and to identify reasons for any reported minor and major failure. The authors hypothesized that there is no significant difference in failure rates between fixed and removable space maintainers inserted after the premature loss of a single primary molar per quadrant. Method and materials: Patients' digital records were searched yielding 645 space maintainers. After the application of inclusion criteria, 157 (67%) fixed prefabricated space maintainers in 112 children and 77 (33%) removable space maintainers in 61 children were analyzed for an average of 18.4 ± 9.5 months. Results: Kaplan-Meier survival analysis with Mantel-Cox statistics showed an overall cumulative survival time of 31.6 months (SE = 1.15, 95% CI = 29.4 to 33.9). Major failure occurred significantly more in removable maintainers (n = 40/67, 59.7%), mostly due to loss of the appliance, compared to fixed space maintainers (n = 27/67, 40.3%; P < .001). The present study indicates that space maintainers were mainly placed in young children with high caries experience, where treatment was mostly possible using advanced behavior management. Conclusions: Fixed space maintainers had a significantly lower failure rate than their removable counterpart. However, both require continual repairs, preservation, or even replacement till the eruption of the permanent tooth. [ABSTRACT FROM AUTHOR]

A maintenance model is specially developed for the work rolls equipped in the hot finishing mill group, with the purpose to decrease the total maintenance cost for the roll group under the constraint of the production batches and the roll thermal character. During the maintenance modelling at roll level, the impacts of the surface wear of the work roll on its failure rate state, the production quality and the preventive maintenance cost are deeply discussed. Then, a preventive maintenance grouping method is further proposed at roll group level, with the mutual restriction between the adjustable replacement time of the roll group and the optimal maintenance time of each work roll involved. The case study shows that the proposed maintenance model is practical for the maintenance scheduling of the work rolls in the real rolling production scenario. The total maintenance cost under the proposed maintenance method is always lower that the ones under the individual OM method and the maintenance window-based OM method. [ABSTRACT FROM AUTHOR]

In this article, we consider a particular type of coherent systems, in which, when the coherent system fails, either no active component remains or the remaining active components are connected in parallel. This work studies two coherent systems of such type with two components, four coherent systems with three components, and seven coherent systems with four components as examples. Lifetime as well as system signature of each of these coherent systems is given. We investigate the restart of such a coherent system using a single cold standby component. The reliability of a system is studied through the (reliability) characteristics such as reliability function, mean time to failure, mean residual life functions of the system. We compute signature-based exact expression for the reliability function of the considered coherent system, which is equipped with a cold standby component. Also, we obtain three different mean residual life functions of the system. So far, no attempt has been made to study such coherent systems in cold standby sparing; therefore, we have provided some new results. We illustrate the theoretical results by considering three particular coherent systems as examples. [ABSTRACT FROM AUTHOR]

The present study explored district-wise monthly rainfall of two climatic regimes (1960–1990 and 1991–2020) of the West Bengal state of India, which receives an annual rainfall of about 1500 mm with huge seasonal rainfall variability. A simple time series analysis does not show any noticeable trend. However, decomposing rainfall parameters into several indicators may explore the change. From this perspective, the present paper intends to explore the nature, degree, and direction of rainfall alteration. The range of variability approach (RVA) considered 29 indicators was adopted for unveiling it. RVA explored that in the 1991–2017 phase, the rainfall failure rate above the upper threshold (75th percentile) is 33% which is 10% greater than in 1961–1990. Seasonal variation in failure rate was detected, but overall larger area of the state recorded failure rate (FR) above the threshold. This result leads to increasing wetness conditions. Very low to moderate (< 0.4) degree of impact of rainfall alteration (DIRA) was found in the recent period. The areal occupation of moderate DIRA was considerable in pre-monsoon, post-monsoon, and winter seasons. Time series rainfall data-based flow duration curves (FDCs) indicated the dominance of the eco-surplus rainfall state over greater parts of the state (72–84%) in all the seasons except winter (49%). Such surplus rainfall may be beneficial to the ecological and agricultural perspective of the state. [ABSTRACT FROM AUTHOR]

The double sampling plan (DSP) is a generalized version of the single sampling plan (SSP) that provides several advantages, such as reduced sample size, increased discriminatory power, and better communication between producers and consumers. This study proposes a DSP for truncated life tests (TLT-DSP) using a two-parameter Lindley distribution. The proposed TLT-DSP's parameters are determined by a mathematical model designed to minimize the average sample number while fulfilling two constraints related to predefined quality levels and tolerated risks. Performance measures of the sampling plans are investigated to evaluate and compare their efficiency and effectiveness. Our results demonstrate that the proposed DSP is more efficient than the traditional SSP, especially in cases where the lot's quality is excellent or poor, and provides necessary protection to both parties involved. Additionally, two examples are presented, discussed and illustrated through a graphical user interface designed to validate the practicability of the proposed approach. [ABSTRACT FROM AUTHOR]

Temporary anchorage devices (TADs) address challenges in traditional orthodontic anchorage like patient compliance and precision, showing significantly improved clinical outcomes, particularly for cases requiring maximum anchorage. A systematic electronic search was performed in five research databases, focusing on studies published between 2015 and 2023. The ROBINS-I tool from the Cochrane Bias Methods Group assessed the risk of bias. Data analysis included categorical and numerical variables, with categorical variables analyzed using Cohen's method in a random effects model to account for variability. Sensitivity and heterogeneity were evaluated using a 'leave-one-out' approach and the I 2 statistic, respectively. At the same time, publication bias was checked using Egger's test, with findings presented through Forest and Funnel plots. Numerical variables were subjected to weighted regression analysis. Examination of 15 studies involving 1981 patients and 3272 orthodontic mini-implants identified key factors affecting implant stability. Failure rates varied significantly, influenced by factors such as the characteristics and insertion site of the orthodontic mini-implants (OMIs), patient-specific variables, and operator experience. Notably, the insertion site and implant characteristics like size did not significantly affect failure rates, but there was a negative correlation between the magnitude of force applied and failure rates. The success of orthodontic mini-implants is broadly consistent across patient demographics and is not significantly impacted by gender or age, though failure rates were higher in males and when implants were placed in the maxilla. These findings suggest that higher applied forces might reduce failure rates. This review underlines mini-implant efficacy across varied patient demographics, emphasizing the importance of site selection, jaw location, and force application in enhancing success rates and guiding tailored treatment strategies. PROSPERO ID CRD42023411955. [ABSTRACT FROM AUTHOR]

Agreement on success following surgical treatment for periprosthetic joint infection (PJI) is important for comparing the efficacy of different surgical approaches with varying consequences and outcomes and setting patient expectations. We compared success rates following two-stage exchange arthroplasty for knee PJI using two expert-consensus definitions of success. Prospectively documented data for 57 knees treated by a single surgeon at an academic tertiary care center were retrospectively reviewed. Treatment outcomes were quantified using the Delphi Consensus Criteria and the Musculoskeletal Infection Society Outcome Reporting Tool (MSIS ORT). Success rates were 81% using the Delphi Consensus Criteria and 56% using the MSIS ORT (P =.008). The MSIS ORT success rates increased to 76% when aseptic revisions and deaths unrelated to PJI were not penalized as failures of treatment. Predicted probabilities of successful treatment in a hypothetical case scenario were lowest based on the MSIS ORT and similarly higher using Delphi Consensus Criteria and MSIS ORT modified for both women (53.0, 90.8, and 88.7%) and men (29.1, 89.1, and 89.3%). Study observations underscore the need for a uniformly accepted single definition of surgical treatment success. [ABSTRACT FROM AUTHOR]

Background: Soft tissue defects of the lower limbs pose significant challenges in reconstructive surgery, accounting for approximately 10% of all reconstructive free flaps performed. These reconstructions often encounter higher complication rates due to various factors such as inflammation, infection, impaired blood flow, and nerve injuries. Methods: A systematic review was conducted following PRISMA guidelines, reviewing literature from 2017 to 2024. Eligible studies included those on free flap reconstruction of lower limb defects in living human subjects, with more than three cases and reported rates of flap failure and return to the operating room. Systematic reviews and metanalysis were excluded. Results: A total of 17 studies comprising 5061 patients and 5133 free flap reconstructions were included. The most common defects were in the lower leg (52.19%) due to trauma (79.40%). The total flap necrosis rate was 7.78%, the partial necrosis rate was 9.15%, and the rate of return to the operating room for suspected vascular compromise was 13.79%. Discussion: Lower limb reconstruction presents challenges due to diverse etiologies and variable tissue requirements. Factors such as recipient vessel availability, flap selection, and multidisciplinary approaches influence outcomes. Muscle and fasciocutaneous flaps remain common choices, each with advantages and limitations. This systematic review underscores the importance of individualized treatment planning. Conclusions: Microsurgical reconstruction of lower limb defects demonstrates safety and reliability, with overall favorable outcomes. Flap selection should be tailored to specific patient needs and defect characteristics, emphasizing meticulous surgical techniques and multidisciplinary collaboration. This systematic review provides valuable insights into current standards and encourages adherence to best practices in lower limb reconstruction. [ABSTRACT FROM AUTHOR]

Objective: To compare between lower permanent retainers placed in the middle of the incisal third and retainers placed in the middle of lower incisors in terms of gingival condition, lower incisors stability and retainers’ failure rate. Materials and methods: This is a split-mouth clinical trial. Fifty patients finished fixed orthodontic treatment and required fixed permanent retainer in the lower arch were recruited. A multistranded (0.0215 inch) retainer, with a vertical step in the midline placing half of the retainer in the incisal third and the other half in the middle of the lower incisors was attached to all the teeth in the lower labial segment. After one year, all the subjects were recalled. The primary outcome was to evaluate the plaque index (PI) and the gingival index (GI) of the lower labial segment teeth. The secondary outcome was to assess retainers’ failure rate and the relapse in lower labial segment alignment. Results: The GI and the PI scores were significantly smaller on the side where the retainer was placed incisally (P = 0.004, P < 0.001, respectively). There was no statistical difference in the average Irregularity Index (IRI) and the retainer’s failure rate between the two sides (P = 0.52, P = 0.76, respectively). Conclusion: Placing lower fixed retainers in the incisal third will improve the lower labial segment oral hygiene and gingival health in the lingual area without affecting the efficiency or the integrity of the retainers. This trial was not registered Null Hypothesis: Placing the lower permanent retainer in the middle of the lingual surfaces of the lower labial segment’ teeth or in the incisal third will not affect the gingival health of the lower incisors. [ABSTRACT FROM AUTHOR]

Allograft prosthetic composite (APC) reconstruction is performed after resection of proximal humerus tumors or failure of arthroplasty implants. There is limited literature on the postoperative outcomes of this technique. We sought to assess implant survival, failure rates, and postoperative functional outcomes after APC reconstruction of the proximal humerus. A systematic review of the PubMed and Embase databases was conducted. The study was registered on PROSPERO (ID: 448,663). The Strengthening of the Reporting of Observational Studies in Epidemiology checklist was used for quality assessment. Implant failure was determined using the Henderson classification for biological reconstruction. Functional outcome was primarily assessed using the Musculoskeletal Tumor Society score at last follow-up. Twenty-five studies with a total of 488 patients were included. Mean follow-up in reporting studies ranged from 2.5 to 10 years. Five-year revision-free survival for implants ranged from 41% to 92%. Overall implant failure rate ranged from 9% to 54%, and reoperation rate ranged from 0% to 55%. Graft host nonunion (type 2) was the most common mode of failure, with rates ranging from 0% to 75%. The mean Musculoskeletal Tumor Society scores at last follow-up ranged from 57% to 90% across studies. A trend towards better functional outcomes was seen in patients having an APC with a reverse total shoulder arthroplasty (rTSA) compared with those with hemiarthroplasty. APCs show promise in proximal shoulder reconstruction, with heterogeneous functional outcomes that are noninferior to other reconstruction techniques. Graft host nonunion is a common mode of failure and remains a concern in this type of prosthesis. Future studies should compare rTSA-APCs and rTSA endoprostheses while controlling for potential confounders. [ABSTRACT FROM AUTHOR]

• Alveolar ridge miniscrews are an excellent choice of anchorage in an edentulous site. • Their survival rate was (62.0%) over a mean follow-up duration of 35.84 ± 19.47 months. • Clinical and demographical variables had minimal effects on their clinical efficacy. • Splinting adjacent miniscrews had a reported survival rate of 100%. An uncommon location for placing miniscrews, used to provide anchorage control in various tooth movements, is the alveolar ridge. This study aimed to provide an evaluation of the success rate of alveolar ridge miniscrews and examine variables that might impact their success. Charts for 295 patients who had miniscrews were screened. Twenty patients (5 male and 15 female: average age = 38.15 ± 15.10 years) with a total of 50 alveolar ridge miniscrews were analyzed. A customized data form was used to collect patients' and miniscrews' related variables. Kaplan–Meier estimator was used for the survival function, whereas Cox proportional hazards regression models were used to associate collected variables with alveolar ridge miniscrew survival. In total, 31 (62.0%) miniscrews were stable and 19 (38.0%) failed. The survival time for those that failed was 6.03 ± 7.08 months. The follow-up period for those that survived was 35.84 ± 19.47 months. Male gender versus female (hazard ratio [HR] 2.46; 95% confidence interval [CI] 1.35–4.48; P = 0.003), and if the miniscrew was a replacement versus non-replacement (HR 0.27; 95% CI 0.07–0.99; P = 0.048) influenced the survival. Additionally, miniscrews that were used for both indirect and direct or indirect anchorage alone plus those with evidence of splinting showed a 100% survival rate, which led to an HR 0 (P < 0.001). When the previously mentioned variables were modeled, none seemed to have a significant effect on failure except for splinting and type of anchorage (P < 0.001), because none of the splinted miniscrews failed. The failure rate of alveolar ridge miniscrews was (38.0%) over 6.03 ± 7.08 months. The survival rate was (62.0%) over 35.84 ± 19.47 months. The evidence of splinting and the type of anchorage had a significant effect on survival probability. [ABSTRACT FROM AUTHOR]

This article examines the research carried out regarding the failure rate in electricity distribution systems. It introduces a comprehensive framework for managing failure rates in power distribution systems. This framework highlights that studies on failure rates in power distribution systems can be categorized into three distinct groups: modifying asset management activities in order to reduce failure rate, evaluate and control threats and risks, emergency measures after failure. In this article, all the studies conducted on the failure rate of electricity distribution systems are listed and presented, and categorized in the form of a comprehensive and conceptual framework. The relation of each category with the failure rate is explained and by studying the process of studies, the research gaps and the roadmap of future studies in the field of failure rate in electricity distribution systems are determined. [ABSTRACT FROM AUTHOR]

The present work is devoted to the analysis of the most important reliability indicators of components of electrical devices of mining dump trucks, and analytical methods of their evaluation are proposed. A mathematical model for calculating the reliability of electrical devices integrated into the electrical systems of quarry dump trucks is presented. The model takes into account various loads arising in the process of operation and their influence on reliability reduction. Optimisation of maintenance and repair schedules of electrical equipment has revealed problems for research. One of them is the classification of electrical equipment by similar residual life, which allows the formation of effective repair and maintenance cycles. The analysis of statistical data on damages revealed the regularities of their occurrence, which is an important factor in assessing the reliability of electrical equipment in mining production. For quantitative assessment of reliability, it is proposed to use the parameter of the average expected operating time per failure. This parameter characterises the relative reliability of electrical equipment and is a determining factor of its reliability. The developed mathematical model of equipment failures with differentiation of maintained equipment by repeated service life allows flexible schedules of maintenance and repair to be created. The realisation of such cycles makes it possible to move from planned repairs to the system of repair according to the actual resource of the equipment. [ABSTRACT FROM AUTHOR]

Aims: To systematically review the predominant complication rates and changes to patient-reported outcome measures (PROMs) following osteochondral allograft (OCA) transplantation for shoulder instability. Methods: This systematic review, following PRISMA guidelines and registered in PROSPERO, involved a comprehensive literature search using PubMed, Embase, Web of Science, and Scopus. Key search terms included “allograft”, “shoulder”, “humerus”, and “glenoid”. The review encompassed 37 studies with 456 patients, focusing on primary outcomes like failure rates and secondary outcomes such as PROMs and functional test results. Results: A meta-analysis of primary outcomes across 17 studies revealed a dislocation rate of 5.1% and an increase in reoperation rates from 9.3% to 13.7% post-publication bias adjustment. There was also a noted rise in conversion to total shoulder arthroplasty and incidence of osteoarthritis/osteonecrosis over longer follow-up periods. Patient-reported outcomes and functional tests generally showed improvement, albeit with notable variability across studies. A concerning observation was the consistent presence of allograft resorption, with rates ranging from 33% to 80%. Comparative studies highlighted similar efficacy between distal tibial allografts and Latarjet procedures in most respects, with some differences in specific tests. Conclusion: OCA transplantation presents a promising treatment option for shoulder instability, effectively addressing both glenoid and humeral head defects with favourable patient-reported outcomes. These findings advocate for the inclusion of OCA transplantation in treatment protocols for shoulder instability, while also emphasizing the need for further high-quality, long-term research to better understand the procedure’s efficacy profile. Cite this article: Bone Jt Open 2024;5(7):570–580.

In the current university environment, national accreditations within the field of engineering serve as a continuous improvement tool for educational programs. These accreditations contribute to increased completion rates and a reduction in school dropout rates, underscoring the utility of tutoring throughout the educational process. High school students adapting to the new pace of university work often undergo significant changes in their school performance habits. Therefore, the initial group tutoring sessions aim to address issues and undertake specific activities that help students learn about their attending university, its organization and work areas, the program they are enrolled in, and the need for psychological support and specialized counseling, among other elements. This work presents an analysis and evaluation of the application of a technique designed to reduce dropout rates in Tutoring 1 for first-semester engineering students.

The insufficiency of water resources and the need for potable water constitute a major concern for many countries, especially Morocco, which has experienced a significant increase in water demand due to population growth, economic development, and climatic conditions. To address this issue, Morocco has initiated an ambitious program to establish seawater desalination plants using reverse osmosis technology in semi-arid areas.This study addresses the pressing concern of ensuring the reliability and quality of desalinated water in the Al Hoceima seawater desalination plant, a vital initiative by Morocco to combat water scarcity in semi-arid regions. Employing the Failure Modes, Effects, and Criticality Analysis (FMECA) method, a comprehensive analysis was conducted to identify potential malfunctions compromising water quality and process reliability. Failures were ranked in descending order of criticality, and cumulative criticality was calculated to prioritize improvement actions. The Pareto diagram generated from this analysis helped identify critical failures in the studied system that require prioritized improvement actions. Notably, it was observed that 80% of the criticality corresponded to half of the failures. Consequently, an improvement plan should be developed for 12 out of the 24 predetermined failure modes, focusing on those identified as most critical. Subsequently, an improvement plan was formulated, integrating short-term corrective actions such as optimizing cleaning protocols and medium to long-term preventive measures such as upgrading equipment and implementing redundancy systems. This study contributes novel insights into enhancing process reliability in seawater desalination plants, particularly in semi-arid regions like Morocco, by providing a systematic approach to identify and prioritize potential failures, ensuring the sustainable provision of potable water.

Introduction: Despite modern fixation techniques, spinopelvic fixation failure (SPFF) after adult spinal deformity (ASD) surgery ranges from 4.5 to 38.0%, with approximately 50% requiring reoperation. Compared to other well-studied complications after ASD surgery, less is known about the incidence and predictors of SPFF. Aims/objectives: Given the high rates of SPFF and reoperation needed to treat it, the purpose of this systematic review and meta-analysis was to report the incidence and failure mechanisms of SPF after ASD surgery. Materials/methods: The literature search was executed across four databases: Medline via PubMed and Ovid, SPORTDiscus via EBSCO, Cochrane Library via Wiley, and Scopus. Study inclusion criteria were patients undergoing ASD surgery with spinopelvic instrumentation, report rates of SPFF and type of failure mechanism, patients over 18 years of age, minimum 1-year follow-up, and cohort or case–control studies. From each study, we collected general demographic information (age, gender, and body mass index), primary/revision, type of ASD, and mode of failure (screw loosening, rod breakage, pseudarthrosis, screw failure, SI joint pain, screw protrusion, set plug dislodgment, and sacral fracture) and recorded the overall rate of SPF as well as failure rate for each type. For the assessment of failure rate, we required a minimum of 12 months follow-up with radiographic assessment. Results: Of 206 studies queried, 14 met inclusion criteria comprising 3570 ASD patients who underwent ASD surgery with pelvic instrumentation (mean age 65.5 ± 3.6 years). The mean SPFF rate was 22.1% (range 3–41%). Stratification for type of failure resulted in a mean SPFF rate of 23.3% for the pseudarthrosis group; 16.5% for the rod fracture group; 13.5% for the iliac screw loosening group; 7.3% for the SIJ pain group; 6.1% for the iliac screw group; 3.6% for the set plug dislodgement group; 1.1% for the sacral fracture group; and 1% for the iliac screw prominence group. Conclusion: The aggregate rate of SPFF after ASD surgery is 22.1%. The most common mechanisms of failure were pseudarthrosis, rod fracture, and iliac screw loosening. Studies of SPFF remain heterogeneous, and a consistent definition of what constitutes SPFF is needed. This study may enable surgeons to provide patient specific constructs with pelvic fixation constructs to minimize this risk of failure. [ABSTRACT FROM AUTHOR]

In Present time, the utility of the theory of reliability and lifetesting analysis attracting many workers and theory is well established in engineering and medical sciences. Now, as the area of applicability of life testing is enlarging day by day, the variety of situations and their related data are also growing up. So, it seems not logical that this variety of data can be dealt with only two or three types of the above life testing models. It seems desirable to develop more and more realistic life testing models to deal with the variety of life testing data so that the proper inferences concerning with the reliability and other aspects can be drawn with more precision. It has been observed that in a number of situations the application of the models discussed so far can be made only after imposing a number of assumptions. So, there is a requirement of a relatively larger family of life time models, so that proper justification can be done with the daya analysis. In the present paper, an attempt has been made to develop a new life-testing model to enlarge the family of life testing models. [ABSTRACT FROM AUTHOR]

The insufficiency of water resources and the need for potable water constitute a major concern for many countries, especially Morocco, which has experienced a significant increase in water demand due to population growth, economic development, and climatic conditions. To address this issue, Morocco has initiated an ambitious program to establish seawater desalination plants using reverse osmosis technology in semi-arid areas. This study addresses the pressing concern of ensuring the reliability and quality of desalinated water in the Al Hoceima seawater desalination plant, a vital initiative by Morocco to combat water scarcity in semi-arid regions. Employing the Failure Modes, Effects, and Criticality Analysis (FMECA) method, a comprehensive analysis was conducted to identify potential malfunctions compromising water quality and process reliability. Failures were ranked in descending order of criticality, and cumulative criticality was calculated to prioritize improvement actions. The Pareto diagram generated from this analysis helped identify critical failures in the studied system that require prioritized improvement actions. Notably, it was observed that 80% of the criticality corresponded to half of the failures. Consequently, an improvement plan should be developed for 12 out of the 24 predetermined failure modes, focusing on those identified as most critical. Subsequently, an improvement plan was formulated, integrating short-term corrective actions such as optimizing cleaning protocols and medium to long-term preventive measures such as upgrading equipment and implementing redundancy systems. This study contributes novel insights into enhancing process reliability in seawater desalination plants, particularly in semi-arid regions like Morocco, by providing a systematic approach to identify and prioritize potential failures, ensuring the sustainable provision of potable water. [ABSTRACT FROM AUTHOR]

More than half a century ago, it was proved that the increasing failure rate (IFR) property is preserved under the formation of k -out-of- n systems (order statistics) when the lifetimes of the components are independent and have a common absolutely continuous distribution function. However, this property has not yet been proved in the discrete case. Here we give a proof based on the log-concavity property of the function $f({{\mathrm{e}}}^x)$. Furthermore, we extend this property to general distribution functions and general coherent systems under some conditions. [ABSTRACT FROM AUTHOR]

The studies carried out address an important problem for the concrete and asphalt industry, referring to the wear phenomena that affect the elements (flights) of rotary dryers used to dry mineral aggregates. In this article, the authors propose a lifetime estimation method for rotary dryer flights. In order to benefit from greater credibility, the proposed method was applied based on the experimental results obtained, by the authors, in the laboratory, on a stand that reproduces a portion of the real equipment. Starting from these results, the authors identified the mathematical functions used to model the failure rates (wear) of the flights by referring to characteristic quantities for wear evaluation: mass loss of material; reduction in the thickness of the part; surface affected by wear. The experimental data—the input data for the proposed algorithm—correspond to six steels used in industrial applications. The wear phenomenon was modeled considering both the situation of uniform wear and the situation of differentiated wear on the flight surface. Therefore, the steel type with the highest service life values could be identified, namely, steel grades E and G. The method proposed in this paper can be extended to any category of material or part provided that the failure rate function is identified beforehand, possibly based on a laboratory experiment. [ABSTRACT FROM AUTHOR]

Focusing on Weibull failure rules, which govern the stopping of components, this work evaluates reliability metrics such as stability and the mean time to system failure (MTSF) of a structure that is parallel. These metrics' behaviour has been seen for one or two decimal random values of component failure rates, operation times, form parameters, and the total quantity of components used in the parallel structure. In order to analyze the variation in the ethics of reliability as well as MTSF, the particular case of the Weibull distribution has also been taken up. [ABSTRACT FROM AUTHOR]

Aim: Implant-supported overdenture presents failures. To minimize and avoid the occurrence of implant and prosthetic complications, a number of considerations must be taken into account. This systematic review aimed to point out variables associated with failure rates of implant-supported overdenture. Settings and Design: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented during carrying out this systematic review. Materials and Method: An automatic electronic literature search of peer-review articles was conducted on the MEDLINE database by querying its PubMed portal, the Cochrane Library and LILACS in addition to a complementary manual search. Clinical trial (CT), Randomized controlled trial (RCT) and Observational study (OS) from 2018 to 2023 were included. Two examiners, independently, selected studies based on the inclusion criteria and recorded the extracted data. The risk of bias of the included studies was evaluated via the Cochrane Collaboration's tool. Results: After the screening and eligibility assessment stages, the inclusion criteria allowed to retain 20 articles: 13 RCT, one prospective CT, three prospective studies, two retrospective studies and one cross-sectional OS. The synthesis of the articles allowed to deduct that the failures of the implant-supported overdenture are variable and related to several factors such as the general condition of the patient, the edentulous arch, the number of implants and the loading protocol, which can be considered to minimize them. Conclusion: Aptitude of the dentist and regular follow-up as well as intense patient care can minimize implant-retained overdenture failure rate. In spite of this, this denture remains the best solution suitable for most patients and providing them with comfort, satisfaction and improved quality of life.

Railway infrastructure is generally classified as either fixed or movable infrastructure assets. Failure in any of the assets could lead to the complete shutdown and disruption of the entire system, economic loss, inconvenience to passengers and the train operating company(s), and can sometimes result in death or injury in the event of the derailment of the rolling stock. Considering the importance of the railway infrastructure assets, it is only necessary to continuously explore their behavior, reliability, and safety. In this paper, a proactive multi-criteria decision-making model that is based on an interval-valued intuitionistic fuzzy set and some reliability quantitative parameters has been proposed for the evaluation of the reliability of the infrastructure assets. Results from the evaluation show that the failure mode 'Broken and defective rails' has the most risk and reliability concerns. Hence, priority should be given to the failure mode to avoid a total system collapse. [ABSTRACT FROM AUTHOR]

Dual mobility (DM) constructs for revision total hip arthroplasty (THA) have continued to grow in popularity to mitigate instability. This benefit comes at the cost of potential unique modes of failure, and there are theoretical concerns that combining femoral and acetabular components from different manufacturers could lead to increased failure rates. We aimed to investigate rates of reoperation between matched and unmatched DM implants used in revision THA. We retrospectively reviewed 217 revision THAs performed with DM constructs between July 2012 and September 2021 at a single institution. Dual mobility (DM) constructs were classified as "matched" if the acetabular and femoral components were manufactured by the same company. They were classified as "unmatched" if the acetabular and femoral components were manufactured by different companies. The primary outcome was reoperation for any reason. There were 136 matched DM constructs and 81 unmatched constructs. Average follow-up was 4.6 years (range, 2.0 to 9.6 years). There was no difference in reoperation rate between matched and unmatched groups (11.0 versus 13.6%, P =.576). The most common reasons for reoperation in both groups were instability and periprosthetic joint infection. There was 1 revision for intraprosthetic dislocation in the matched group. The use of unmatched DM components in revision THA was common and did not increase the risk of reoperation at an average of 4.6-year follow-up. This information can be helpful in operative planning, but further research on long-term survival will be necessary. [ABSTRACT FROM AUTHOR]

Aim: Implant-supported overdenture presents failures. To minimize and avoid the occurrence of implant and prosthetic complications, a number of considerations must be taken into account. This systematic review aimed to point out variables associated with failure rates of implant-supported overdenture. Settings and Design: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented during carrying out this systematic review. Materials and Method: An automatic electronic literature search of peer-review articles was conducted on the MEDLINE database by querying its PubMed portal, the Cochrane Library and LILACS in addition to a complementary manual search. Clinical trial (CT), Randomized controlled trial (RCT) and Observational study (OS) from 2018 to 2023 were included. Two examiners, independently, selected studies based on the inclusion criteria and recorded the extracted data. The risk of bias of the included studies was evaluated via the Cochrane Collaboration's tool. Results: After the screening and eligibility assessment stages, the inclusion criteria allowed to retain 20 articles: 13 RCT, one prospective CT, three prospective studies, two retrospective studies and one crosssectional OS. The synthesis of the articles allowed to deduct that the failures of the implant-supported overdenture are variable and related to several factors such as the general condition of the patient, the edentulous arch, the number of implants and the loading protocol, which can be considered to minimize them. Conclusion: Aptitude of the dentist and regular follow-up as well as intense patient care can minimize implant-retained overdenture failure rate. In spite of this, this denture remains the best solution suitable for most patients and providing them with comfort, satisfaction and improved quality of life. [ABSTRACT FROM AUTHOR]

Background CAD/CAM (computer-aided design/computer-aided manufacturing) fixed retainers (FRs) as an alternative to multistranded FRs to maintain orthodontic treatment outcome. Objectives The primary aim was to compare CAD/CAM versus conventional multistranded FRs in terms of stability until 2 years. Secondary outcomes were failure rates, patient satisfaction, and cost-minimization. Trial design 2-arm parallel, two-centre randomized controlled trial. Methods Patients were randomized to CAD/CAM or conventional FRs in both arches, in a 1:1 ratio and blocks of four. Allocation concealment was secured by using sequentially numbered envelopes. Patients were blinded. FRs were bonded at the end of treatment, and patients were recalled after 12 and 24 months. First-time retainer failures were recorded and digital impressions were taken. Arch widths and lengths, as well as Little's Irregularity Index (LII), were measured. Additionally, patients answered satisfaction questionnaires. Linear mixed models were applied for measurements and patient satisfaction. Survival analyses were estimated with Kaplan–Meier curves, along with Cox-regression modelling. Cost-minimization analysis was undertaken. Results One hundred and eighty-one patients were randomized (98 in Centre 1, and 83 in Centre 2): 90 in CAD/CAM and 91 in conventional group. One hundred and fifty three patients attended T24 follow-up. There were no significant differences in LII and arch dimensions between groups for failure-free patients. Within 24 months, 34% maxillary CAD/CAM FRs and 38% maxillary conventional FRs failed, along with 42% mandibular CAD/CAM FRs and 40% mandibular conventional FRs, with no significant difference in survival between groups (hazard ratios conventional to CAD/CAM: maxillary arch: 1.20 [ P  = 0.46], mandibular arch: 0.98 [ P  = 0.94]). There were no significant differences in patient satisfaction between groups. No harms were observed. Cost-minimization analysis showed that CAD/CAM FRs were slightly cheaper than conventional FRs. Conclusions There were no clinically significant differences in LII, arch widths, and lengths between CAD/CAM and conventional FRs after 24 months. There were no differences in failures and patient satisfaction between groups. CAD/CAM FRs were slightly cheaper than conventional FRs. Trial registration ClinicalTrials.gov NCT04389879. [ABSTRACT FROM AUTHOR]

The management of power outages caused by severe weather disasters such as earthquakes, tornadoes, and weather disturbances is critical in power transmission and distribution systems. The transmission system is the key to any power system and can trigger severe or significant effects if it fails. Different causes of fires, extreme weather conditions, ageing components, poor maintenance and malfunctions, human error, mal-operative procedure, and high operating network variables may cause transmission components to fail. System reliability is the probability that, despite component failures, a system remains available or functional. Risk management of the failures describes it. There are several methods to predict the failure rate, including exponential and Bayesian distributions. In this study, Poisson distribution forecasted the outage patterns for transmission and distribution networks for one and five years. A probability distribution function generated this pattern. Moreover, previous data were obtained from National Electric Power Regulatory Authority (NEPRA). On comparing the acquired results with previous outage data, it was reported that the average outages in the transmission system were 567.The average outages in the distribution system stood at 37 for five years with a 100% confidence level. However, the probability of getting 620 transmission outages and 50 distribution outages was highest in the probability distribution function for five years. Poisson distribution proved to be a useful tool to assess the transmission and distribution system reliability by estimating the failure rate over the years. It would allow the risk professionals to schedule, reduce, and track the systems' risks. It would also help to improve the system's reliability. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present systematic review was to quantitatively synthesize the best literature evidence regarding osteoarthritis developing after anterior cruciate ligament reconstruction (ACLR), including only studies with a follow‐up duration of at least 20 years. Material and Methods: A systematic review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines on four electronic databases (PubMed, Scopus, EMBASE and Cochrane Library). The outcome measures extracted from the studies were failure rate, subsequent knee surgery on the same knee, radiographic development of osteoarthritis measured with Kellgren–Lawrence, International Knee Documentation Committee (IKDC) radiographic score and Ahlbäck classification. The health of both the ACLR knee and the contralateral knee was compared. Results: A total of 1552 patients were included in the study, of which 1290 (83.11%) were operated on using a patellar tendon graft, 190 (12.24%) with hamstrings, 27 (1.73%) with an iliotibial band and 45 (2.89%) with patellar tendon plus a ligament augmentation device (LAD). The mean age at the time of surgery was 25.18 ± 1.91 years, and the mean follow‐up time was 23.34 ± 2.56 years. Analysing IDKC Score at final follow‐up, ACLR Group showed a higher degree of OA compared with contralateral healthy knee (p < 0.01), but only 33.2% (324/976) of the patients showed a moderate to severe degree (Grade C or D) of osteoarthritis, while for Kellgren–Lawrence, ACLR Group showed a higher degree of OA compared with contralateral healthy knee (p < 0.01), but only 28.9% (196/678) of the patients showed a moderate to severe degree (Grade III or IV) of osteoarthritis. In total, 1552 patients were registered, 155 reruptures (9.98%) and a total of 300 (19.3%) new surgeries, of which 228 meniscectomy (14.69%), 21 (1.35%) knee arthroplasty and 17 (1.09%) hardware removal were recorded. Conclusions: ACL reconstruction appears to result in mild osteoarthritis in the long term in most of the patients and only less than 33.2% develop a moderate to severe degree of knee OA according to IKDC radiographic score. A slight degree of osteoarthritis appears to be present in ACLR knees compared with contralateral healthy knees. Level of Evidence: Level IV. [ABSTRACT FROM AUTHOR]

Electric power utilities are striving to address critical challenges such as energy consumption, material recovery, e-waste, procurement, and supplier working conditions. Currently, they are converting their old infrastructure into smart grids. The installation of smart meters is a key step in this process. Since a smart meter is an intelligent and modern measuring device that includes computer-aided measurements while also allowing intelligent management and determination of residential and industrial users' energy consumption and supply, their deployment in smart grids is of major importance. In this study, considering that the estimated number of smart meter units will be 188.12 million units by 2025, five different types of smart meters are used to estimate their failure behavior. We adopted the probability of smart meters' survival, considering the number of the components included in their PCBs, while the influence of their components follows an exponential distribution for a given lifetime. The meaning of the "fair" smart meter is introduced to solve critical concerns such as energy use, material consumption, e-waste, supplier sourcing, and labor conditions. To achieve the above targets, a circular economy chain analysis is implemented by dismantling the existing smart meters, classifying their materials into five primary groups and weighing them to obtain average values. Moreover, we calculate the average cost of the components using their equivalent market value as provided by stock markets to get the average weight of each component in terms of material cost. Finally, we introduce the "remanufacturing index" and the "reusing index" indices as procedure metrics to further quantify the circular economy chain results. The results show that the percentage of the reusing procedure in the "fair" smart meter circular economy chain is greater than the corresponding percentage of the remanufacturing procedure, while the percentage of the recycling procedure is increased as the recycling cost per unit, is also increased. [ABSTRACT FROM AUTHOR]

The ocean thermal energy conversion (OTEC) systems, as renewable energy-based power plants, have the potential to play a significant role in meeting future electricity demands due to the vast expanse of the world's oceans. These systems employ the temperature difference between surface ocean waters and deep ocean waters to drive a thermodynamic cycle and produce electricity. The temperature of deep ocean waters, approximately 1000 m below the surface, is approximately 4 °C, while surface ocean temperatures typically range between 20 and 30 °C. The generated power of OTEC systems is dependent on these temperature differences and may vary with changes in surface ocean temperatures. In this study, the main focus is to find the impact of temperature variation on the failure rates of OTEC system components and the generated power output of these plants. The findings indicate that as the demand for the power system increases, its reliability decreases. In order to improve the reliability of the power system, the integration of a new generation unit, such as the close cycle OTEC power plant under investigation, could be necessary. The findings also indicate the importance of considering temperature variation in the evaluation of the reliability of such types of power plants based on renewable energy. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the safety and efficacy of chloral hydrate in auditory brainstem response (ABR) tests. Setting and Design: In this study, the authors systematically searched both English (Embase, PubMed, and Web of Science) and Chinese (Chinese National Knowledge Infrastructure, Wanfang Data, and VIP Chinese Science) databases. Two authors independently performed data extraction and quality assessment. The pooled sedation failure rate and the pooled incidence of adverse events were calculated via a random‐effects model. Sensitivity and subgroup analyses were performed to explore the sources of heterogeneity, and the PRISMA guideline was followed. Participants: Patients with ABR tests receiving chloral hydrate sedation. Main outcome measures: The pooled sedation failure rate and the pooled incidence of adverse events. Results: A total of 23 clinical studies were included in the final analysis. The pooled sedation failure rate of patients who received chloral hydrate sedation before ABR examination was 10.0% [95% confidence interval (CI) (6.7%, 15.0%), I2 = 95%, p <.01]. There were significant differences in the prevalence of sedation failure between sample sizes greater than 200 and those less than or equal to 200 (5.6% vs. 19.6%, p <.01) and between the studies that reported sleep deprivation and those that did not report sleep deprivation (7.1% vs. 18.9%, p <.01). The pooled incidence of adverse events was 10.32% [95% CI (5.83%, 14.82%), I2 = 98.1%, p <.01]. Conclusions: Chloral hydrate has a high rate of sedation failure, adverse events, and potential carcinogenicity. Therefore, replacing its use in ABR tests with safer and more effective sedatives is warranted. [ABSTRACT FROM AUTHOR]

Objective: The primary aim of this study was to provide a review of the types and frequency of orthodontic brackets, molar bands and orthodontic auxiliaries used for patients undergoing orthognathic surgery. The secondary aim was to evaluate the risk of failure of these items during orthognathic surgery. Methods: From three Dutch hospitals, 124 adult patients were included in this prospective cohort study. Five independent researchers collected the data during surgery using a specifically created data extraction form. The type of surgery, surgeon, orthodontist and type of orthodontic bracket, molar band or auxiliary were noted for each tooth. To evaluate their failure risk, the following variables were noted: failure and site; and type and cause of failure. Results: Stainless-steel brackets were the most frequently (75.8%) used bracket type seen in patients undergoing orthognathic surgery. Ceramic brackets were seen in 24.2% of the cases and were only applied in the anterior region. Molar bands were present in 58.9% of the patients and mostly with bands on the first molars in combination with bonded tubes on the second molars. In 32.2% of all cases, one or more failures were noted. One-third of all failures were described as detachment of the molar tube on the most posterior molar. Kobayashi ligatures and powerpins showed the highest risk of failure (odds ratio [OR] 3.70, 95% confidence interval [CI] = 1.91–7.15). No significant difference in failure rate was found between stainless-steel brackets, molar bands (OR 0.34, 95% CI = 0.08–1.43) and ceramic brackets (OR 0.44, 95% CI = 0.14–1.45). Conclusion: Stainless-steel brackets, ceramic brackets, molar bands and surgical hooks are suitable for orthognathic cases. Kobayashi ligatures and powerpins had a significantly higher risk of failure so are not recommended for temporary intraoperative maxillomandibular fixation (TIO-MMF). [ABSTRACT FROM AUTHOR]

Stop production and overhaul is an annual work of LNG (Liquefied Natural Gas) plant. However, the shutdown maintenance work under different market conditions needs comprehensive allocation of resources to achieve the purpose of economy, speed and safety. In order to study the fault situation of pneumatic valve, targeted maintenance work is carried out. In this paper, a workflow of DGM(1, 1) prediction model of grey system and sampling inspection method is proposed. With the help of DGM(1, 1) to predict the universality of "poor information and small sample" and the partial detection method of sampling inspection, the expected engineering purpose is achieved. The research results are as follows: (1) The failure situation of pneumatic valve in LNG plant from 2015 to 2020 is brought into the model to compare the actual value and predicted value in 2020, and the residual error is between 0.92 and 3, which indicates that the predicted result of the model is reliable. It is predicted that the comprehensive failure rate will remain at around 18% in 2021 and 2022. Next, we can continue to use DGM(1, 1) model to analyze the redundancy of actuator measurable signals. Make full use of the field known data, construct the functional relationship of measurable variables of actuators, realize on-line real-time judgment of actuator faults, and dynamically predict the failure rate of parts. (2) For maintenance work, 130 pneumatic valves need to be dismantled, with emphasis on the inspection of three components such as drive gas filter, electromagnetic valve and actuator. If the damage number is found to be less than or equal to 4, production can continue after the spare parts are repaired and replaced, otherwise, total inspection is required. In the next step, the relationship between valve distribution position and parts damage frequency should be counted, and the damage frequency should be reduced by strengthening sealing and changing installation methods. [ABSTRACT FROM AUTHOR]

Abstract.This article focuses on a specific type of coherent system in which, when the coherent system fails, either no active component remains or the remaining active components are connected in parallel. Roy and Gupta (2023) also considered the same type of coherent systems. We observe the restart of such a coherent system using two cold standby components. In our study, standbys are not placed into action simultaneously. They are put into action one by one. We compute the reliability function of the considered coherent system, which is equipped with two cold standby components. In addition, we show that when we use a stronger standby component (in the sense of failure rate order) at first, we get a longer system lifetime. Also, we compute three different mean residual life functions of the system. We have presented a few numerical results to illustrate the importance of our analysis. [ABSTRACT FROM AUTHOR]

Reliability assessment in distribution systems done using network methods in which failure probability distributions and negative components repair or the severity of failure and repair is clear. However, in real networks and Industry, these amounts are usually not precise and it conforms a probability distribution. Fuzzy logic is a typical method to consider indecision in engineering parameters, responsible consumption and production. As an innovation, in this paper using fuzzy logic, uncertainties are considered in assessment reliability indicator. Affecting factors on the rate of line failure and distribution transformers and factors affecting load consumption is considered as membership functions and by choosing the right rules failure rate and restoration time, are gained by considering the effect of these uncertainties. [ABSTRACT FROM AUTHOR]

Transformers, as the hub equipment of the power system, are highly valued by engineering and scientific researchers in production practice and scientific research. The goal of transformer research is to ensure the safe operation of transformers while considering their economic benefits, arrange transformer inspections reasonably to reduce inspection costs, and save labor and maintenance costs reasonably. This study first provides a brief analysis of the life cycle cost of transformers. The life cycle of transformers is divided into initial cost, operating cost, maintenance cost, fault cost, and scrap cost. Based on the distribution of transformer failure rate, the corresponding life cycle cost of transformers is calculated. Taking 110 kV transformers as an example, the differences in the impact of key factors on the full life cycle cost are analyzed to achieve high quality, high reliability, economically optimal equipment procurement. [ABSTRACT FROM AUTHOR]

Background. To obtain permission to construct and commission NPP units, it is necessary to submit a probabilistic safety analysis (PSA) of the designed unit to Rostechnadzor. Estimates of component failure rates of such unit can only be obtained based on pooling operational data from operating analogues. This task requires the development of special methods that consider the non-homogeneity of the pooled data. Materials and methods. One of the possible approaches to solving this problem is the use of the empirical Bayesian method, which assumes the presence of some primary distribution of failure rates of combined groups of components, which parameters are calculated from the maximum of the unconditional likelihood function. Knowing the estimates of the distribution parameters, it is possible to obtain estimates of the parameters of the combined sample. Results. The proposed methodology and the program that implements it made it possible to consider the uncertainty factor when pooling data on the basis of the Poisson model, which assumes constant failure rates. The results of its application were used in the development of PSA of the designed units. Conclusions. Pooling the reliability data of similar type components from operating NPP units should be carried out considering their potential non-homogeneity. The proposed methodology allows to solve this problem, preventing unreasonable underestimation of the uncertainty factor, which is typical for simple summation of failure data.

As the core of high-voltage direct-current transmission technology, the DC converter valve and its key power device thyristor face a high risk of failure caused by atmospheric neutron when operating in high-altitude areas. The atmospheric neutron failure rate of thyristors used at high altitudes can be quantitatively evaluated by conducting accelerated irradiation tests. The accelerated irradiation experiments of 8.5 kV/5 kA thyristor for DC transmission were carried out at different temperatures by using the China spallation neutron source. The atmospheric neutron-induced single-event burnout (SEB) for thyristor was verified by experiments. It is manifested as a sudden surge in reverse bias leakage current during irradiation, and the device loses its high voltage blocking ability. The failure rates of thyristor caused by atmospheric neutrons were also evaluated based on the accelerated irradiation experimental results. The reverse bias voltages and junction temperatures of thyristor are the key factors affecting the failure rates. The atmospheric neutron-induced failure rates increase exponentially with the reverse bias voltage. The atmospheric neutron failure rate of the 8 500 V thyristor operating at 4 350 V will reach 673 FIT at room temperature at sea level; when the bias voltage drops to 4 100 V (a decrease of about 5.7%), the atmospheric neutron failure rate can be reduced to 11 FIT. In addition, the failure rate increases with the decrease of temperature. The failure rate at 5℃ is nearly 6 times higher than that at 25℃ when the device is biased at 50% of the rated voltage. Based on TCAD simulations, the failure mechanism of thyristor caused by irradiation is further verified. The simulation results show that the SEB failure is directly related to the avalanche breakdown effect-induced by the incident radiation particles. For radiation-induced SEB failure of thyristors, the sensitive region is the N-drift/P-substrate junction depletion region (corresponding to the electric field concentration region under reverse bias of thyristors). When radiation particles are incident into the sensitive region, it can cause the concentration of electric field near the incident location, resulting in additional electric field spikes. If the peak of the electric field exceeds the critical electric field Ec (about 1.64×105 V/cm), it will induce avalanche breakdown. The high voltage reverse bias high current state caused by avalanche breakdown ultimately leads to the failure of the thyristor. The avalanche breakdown effect is positively correlated with the reverse bias voltage of thyristor and negatively correlated with the junction temperature. This is consistent with the variation of atmospheric neutron failure rates with bias voltages and junction temperatures.

The pitch system is notably one of the critical subsystems of a wind turbine, supporting its effective control towards maximising wind capture and at the same time protecting its integrity in cases of excessive loads. A pitching mechanism is also responsible for operational downtime, hence its reliability performance needs to be carefully evaluated so as to ensure operational availability. This study aims to derive failure rates of two configurations of pitch systems, namely the electrical and hydraulic, based on statistical analysis of a large population of onshore assets, followed by a classification of findings by turbine rating, effect of seasonality, and reliability performance of different manufacturers. The data sets underlying the present analysis are based on maintenance reports and comprise 1847 operational years of wind turbines with electrical and 848 operational years of turbines with hydraulic pitch system. Results of this study show high failure rates in pitch systems of both types, with hydraulic systems performing slightly better than electrical (0.54 vs. 0.56 failures per turbine per year), a significant variation between turbines of different manufacturers, and a tendency for higher failure rates for larger turbines.

In this comprehensive study, we delve deeply into the concept of multivariate total positivity, defining it in accordance with a direction. We rigorously explore numerous salient properties, shedding light on the nuances that characterize this notion. Furthermore, our research extends to establishing distinct forms of dependence among the order statistics of a sample from a distribution function. Our analysis aims to provide a nuanced understanding of the interrelationships within multivariate total positivity and its implications for statistical analysis and probability theory.

AbstractSo far, a lot of work has been done on the characterization of distributions. In this article, we characterize a lifetime random variable following any distribution among two-parameter Weibull, modified Weibull, modified Weibull extension, log-logistic, modified log-logistic, power Lomax, modified power Lomax, and inverse two-parameter Weibull distributions. The functions, viz., failure rate, reversed failure rate, aging intensity, reversed aging intensity, and log odds rate, available in reliability theory, along with the recently introduced concepts of generalized aging intensity and generalized reversed aging intensity functions, are used in the analysis. [ABSTRACT FROM AUTHOR]

This paper presents a new joint production, maintenance and quality control chart for a manufacturing system subject to random failure and produces both conforming and non-conforming products. The degradation of the manufacturing unit increases with the production rate and the time of its use, which affects its reliability and the product quality. The purposed joint policy aims to establish, firstly, the optimal plan of production during finite horizon that satisfies random demand under a given service level. and secondly, to determine simultaneously the optimal number of imperfect preventive maintenance actions at each production cycle, and the optimal control chart parameters for appropriate quality monitoring in the presence of assignable causes. Furthermore, rework activity is proposed for a fraction of the non-conforming products, which are detected in the presence of assignable causes, in order to improve their quality and sold as a second-rate product. The proposed optimization model minimises the average total costs including production, reworking, storage, rejection, quality and maintenance. Numerical examples and sensitivity analyses are presented to show the effectiveness of the proposed joint approach. [ABSTRACT FROM AUTHOR]

Power systems comprise different electrical, electronic, electromechanical and electrochemical components. Adequacy, security, resilience and reliability represent essential requirements for grids functioning mode. The evaluation of such aspects can constitute a delicate task in the presence of heterogeneous components. Focusing on reliability assessment, several Reliability Prediction Models are available. They are suitably applied according to the type of component under evaluation. The lack of homogeneity of these models forbids the comparison of performance and identification of unreliable systems and grid section. This paper aims to face the mentioned issue proposing a unique reliability assessment methodology able to characterize different equipment connected to radial/meshed/ring grids and subjected to different stressing and ageing factors. It is customized for electrical lines, transformers, circuit breakers, converters and renewables plants. Component and systemic key indices are calculated. Furthermore, a novel "load feeding reliability" indicator is evaluated for providing information about the supply reliability of a specific load. This index is meaningful for the identification of unreliable grids, microgrids and systems. Such an approach can contribute to improve power systems design, planning and control. The proposed method is integrated in a software application implemented for grid reliability assessment. The obtained results are reported for an urban grid including an underground transportation area. [ABSTRACT FROM AUTHOR]

Due to the high failure rates of mechanical equipment with complex structures and numerous moving parts, devising an effective preventive maintenance (PM) plan and avoiding the influence brought by failure is crucial. However, some PM efforts are disorganized, unpractical, and unscientific, leading to prolonged downtime and significant cost losses. The challenge in creating PM plans is exacerbated by the asymmetry between maintenance and failure data. Therefore, focusing on single-unit mechanical equipment, the reliability-centered maintenance (RCM) idea is put forward to find out the key parts to implement preventive maintenance, and PM models are built to draw up a more reasonable PM plan. Such strategies aim to lower maintenance costs and enhance economic performance. Data on past maintenance and failures are analyzed to determine the life distribution and maintenance effect functions, helping to quantify the uncertainty caused by data asymmetry. Two PM optimization models considering time-varying failure rates are proposed: one focuses on minimizing costs, while the other aims to maximize availability. A PM plan example is demonstrated using a component from a tire-building machine including six parts, which proves the validity of the models. The availability results of two parts corresponding to the maintenance strategy obtained by the availability maximization model are above 0.99, and the results of total costs per unit time of the remaining four parts obtained by the cost minimization model are under 5.69. [ABSTRACT FROM AUTHOR]

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