Calculate Failure Rates Research Articles

Providing an approach to analyze the risk of central oxygen tanks in hospitals during the COVID-19 pandemic

The central oxygen unit of hospitals is considered a high-risk unit, requiring high safety standards to maintain the integrity of the system during the COVID-19 pandemic. The linear reasoning assumption of conventional risk analysis methods cannot adequately describe these modern systems, which are characterized by tight connections and complex interactions between technical, human, and organizational aspects. Therefore, this study presents a new and comprehensive approach to oxygen tanks in hospitals during the COVID-19 pandemic. In this study, trapezoidal fuzzy numbers were used to calculate failure rates. After determining the probability of basic events (BEs), intermediate events (IE), and top event (TE) with fuzzy logic and transferring it into Bayesian Network (BN), deductive and inductive reasoning, and sensitivity analysis were performed using RoV in GeNIe software. The results of the case study showed that the IE of “Human Error” had the highest probability of fuzzy fault tree (FFT) and the probability of oxygen leakage was lower using FBN than FFT. According to the results, BE16 (failure to use standard and updated instructions) and BE12 (defects in the inspection and testing program of tank devices) had the highest posterior probability, while based on the FFT results, BE4 (defects in the external coating system of the tank) and, BE3 (Corrosive environment (acidity state)) had the least probability. According to the sensitivity analysis, basic events 10, 11, and 16 were the most important in the oxygen leakage event with a very small difference, which was almost in line with the results of posterior FBN (FBNPO). Updating the existing guidelines, fixing defects in the inspection of all types of tank gauges, and testing related equipment can greatly help the reliability of these tanks. Root cause analysis of these events provides opportunities for prevention and emergency response in critical situations, such as the COVID-19 pandemic.

A Mission Profile-Based Reliability Modeling Framework for Fault-Tolerant Electric Propulsion

This article proposes a thermally enhanced reliability modeling framework which works from the mission profile of an electrified aviation propulsion system, incorporating known fault-tolerant power electronics, motor drives, control, and their pre and postfault behaviors. The reliability framework is presented in a hierarchical fashion. Multiphysics modeling is used, incorporating electromechanical states, power losses, and thermal behaviors. The approach includes the device thermal stress in healthy and postfault operating states in the failure rate calculations. Markov chain models are then used with the calculated failure rates to form system level reliability models. A case study of an electric vertical takeoff and landing urban aerial vehicle (eVTOL UAV) walks through the proposed method, modeling multiple versions of the propulsion system, with various levels of fault tolerance and redundancy. The proposed reliability modeling framework captures the operating temperatures and thermal swings seen by the components due to the flight mission, enhancing the failure rate calculation. Further, since the postfault operating mode of the fault tolerant system causes higher component currents and temperatures, different component failure rates are calculated for postfault operation. Finally, the Markov chain modeling allows for a reliability comparison between various UAV propulsion systems, including the effect of combining fault tolerance at the subsystem level, with redundancy at the system level.

Variability in Contraceptive Clinical Trial Design and the Challenges in Making Comparisons Across Trials.

Clinical trials of contraceptives have often differed in their study designs, making cross-trial comparisons difficult. This brief report outlines some of the technical design features that can vary from trial to trial. For example, the overall number of menstrual cycles in a study has substantial impact on the final efficacy determination; however, the rules related to qualifying cycles can differ based on the length of the study and the statistical analysis plan. In two commonly used methods of calculating efficacy, the Pearl Index and the time-to-event analysis, inclusion of fewer menstrual cycles results in higher calculated failure rates. Statistical analysis plans for contraceptive trials have sometimes excluded menstrual cycles because of an absence of documented vaginal intercourse and the concomitant use of another birth control method. Other design features that have varied between contraceptive trials relate to body mass index inclusion/exclusion criteria and the definition of “on-treatment” pregnancy. In addition, study designs of non-hormonal products can differ from those of hormonal products in their length and rules for qualifying cycles. The Draft Guidance for Hormonal Contraception, published in 2019 by the US Food and Drug Administration (FDA), will hopefully lead to more uniform trial design in the future, particularly for hormonal products. In the meantime, health care providers and patients should be aware of the nuances in trial design that make direct comparisons about relative efficacy challenging.

Research on Reliability of Grid Connected Photovoltaic Renewable Generation System

Renewable energy sources are increasingly being implemented in power systems to curb global warming and improve generation adequacy. These renewable sources include Hydro, wind, tidal, and solar power systems. Since Pakistan experiences decent solar irradiation throughout the year, the most viable renewable energy option is photovoltaic generation. Before solar systems are implemented, the proposed design is first simulated using design software such as MATLAB-Simulink to correct and adjust parameters to attain the DC voltage and current through the irradiation and environment temperature. Reliability studies and analysis are performed on the simulated systems to ascertain the success and long life before the system components’ failure. In this thesis, the grid-connected PV system’s reliability model established based on the reliability block diagram method using the MIL-HDBK-217F handbook. The handbook provides the methodology of calculating failure rates of specific physical electronics operations. The mean time to failure (MTTF) and Mean time to repair (MTTR) of the system is calculated from the overall system reliability. Photovoltaic power output varies greatly, and it is dependent on solar irradiation and temperature, resulting in intermittent and variable energy production. All of these considerations have a significant effect on the entire system adequacy of the power generation system. This study uses a probabilistic analytical methodology to develop comprehensive reliability models of grid-connected Photovoltaic generation systems.

전자장비 무기체계 고장률 기반 신뢰성 샘플링 계획의 비용 효과 최적 설계 방법

Purpose: Realization of the dynamic requirements (reliability) in time involves a higher cost compared to that for static requirements (quality) in time. Therefore, a reliability sampling plan must be designed to enable the efficient realization of reliability tests. Notably to conduct such tests, a certain number of samples and test time are required to perform the statistical analysis after the development of the electronic equipment weapon system.<BR>Methods: The failure rate of the target electronic equipment is calculated based on MIL-HDBK-217, using an electronic equipment reliability prediction model. Based on the calculated failure rate, the total time required for the reliability sampling test is calculated through MIL-STD-690. Finally, based on the calculated total test time, the correlation between the number of sampled samples and test time, considering the total number of samples, is adopted to optimally design the failure rate sampling plan for the electronic equipment weapon system.<BR>Results: The proposed model to cost-effectively design the reliability sampling plan is applied to a domestically developed military DC-DC converter. The optimal cost-effectiveness is ensured when the input is KRW 64,064,731 [Constraint condition (n: Integer > 0, t: Real number > 0): c = 0, n = 59, t = 492.37 h]/KRW 64,081,117 [Constraint condition (n: Integer > 0, t: Integer > 0): c = 0, n = 58, t = 501 h].<BR>Conclusion: The proposed model can be used to optimize the reliability sampling test plan for military electronic equipment in a cost-effective manner.

A Non-Parametric Approach for Survival Analysis of Component-Based Software

Reliability of a software or system is the probability of system to perform its functions adequately for the stated time period under specific environment conditions. In case of component-based software development reliability estimation is a crucial factor. Existing reliability estimation model falls into two broad categories parametric and non-parametric models. Parametric models approximate the model parameters based on the assumptions of fundamental distributions. Non-parametric models enable parameter estimation of the software reliability growth models without any assumptions. We have proposed a novel non-parametric approach for survival analysis of components. Failure data is collected based on which we have calculated failure rate and reliability of the software. Failure rate increases with the time whereas reliability decreases with the time.

Outcome of revision hip arthroplasty in patients younger than 55 years: an analysis of 1,037 revisions in the Dutch Arthroplasty Register

Background and purpose — The increasing use of hip arthroplasties in young patients will inevitably lead to more revision procedures at younger ages, especially as the outcome of their primary procedures is inferior compared with older patients. However, data on the outcome of revision hip arthroplasty in young patients are limited. We determined the failure rates of revised hip prostheses performed in patients under 55 years using Dutch Arthroplasty Register (LROI) data.Patients and methods — All 1,037 revised hip arthroplasty procedures in patients under 55 years at the moment of revision registered in the LROI during the years 2007–2018 were included. Kaplan–Meier survival analyses were used to calculate failure rates of revised hip arthroplasties with endpoint re-revision for any reason. Competing risk analyses were used to determine the probability of re-revision for the endpoints infection, dislocation, acetabular and femoral loosening, while other reasons for revisions and death were considered as competing risks.Results — Mean follow-up of revision procedures was 3.9 years (0.1–12). 214 re-revisions were registered. The most common reason for the index revision was dislocation (20%); the most common reason for re-revision was infection (35%). The 5-year failure rate of revised hip prostheses was 22% (95% CI 19–25), and the 10-year failure rate was 28% (CI 24–33). The 10-year cumulative failure rates of index revisions with endpoint re-revision for infection was 7.8% (CI 6.1–9.7), acetabular loosening 7.0% (CI 4.1–11), dislocation 3.8% (CI 2.6–5.2), and femoral loosening 2.7% (CI 1.6–4.1). The 10-year implant failure rate of index revisions for infection was 45% (CI 37–55) with endpoint re-revision for any reason.Interpretation — Failure rate of revised hip prostheses in patients under 55 years is worrisome, especially regarding index revisions due to infection. This information facilitates realistic expectations for these young patients at the time of primary THA.

Free Gracilis Muscle Transfers Compared with Nonfree Muscle Flaps for Reanimation of Elbow Flexion: A Meta-Analysis

Objectives Elbow flexion loss is a debilitating upper extremity injury. Surgical treatment options include nonfree muscle transfers (tendon transfers, nerve transfers, Steindler procedure, Oberlin transfers, and pedicled muscle transfers) or free muscle transfers. We sought to determine if free muscle transfers and nonfree muscle transfers have similar outcomes for elbow flexion reanimation.Materials and Methods A literature search for studies evaluating free and nonfree muscle transfers for elbow flexion reanimation was performed. Included studies reported on transfer failure (strength <M3, unable to flex arm against gravity), strength, range of motion (ROM), or Disabilities of the Arm, Shoulder, and Hand (DASH) score. Pooled odds ratios were used to calculate failure rate, and pooled mean differences were used to calculate differences in strength, ROM, and DASH scores.Results Six studies were included (n = 331 patients). Free muscle patients experienced lower failure rates than nonfree muscle patients. There was no significant difference in ROM. A nonsignificant trend toward better mean strength and DASH scores among free muscle patients was observed.Conclusion Free muscle transfers may be superior to nonfree muscle transfers for elbow flexion reanimation, given their lower failure rates. Well-powered future studies may reveal differences in strength and DASH scores between free and nonfree muscle transfers.

Calculation of single event burnout failure rate for high voltage devices under satellite orbit without fitting parameters

Increase of power bus voltages in spacecraft are expected with the power demand growth. Accordingly, high voltage semiconductor devices in the power supply system will be required to withstand high energy and high flux cosmic ray environment. In this paper, we propose a new formula to calculate failure rate for power semiconductor devices in space application.

Failure Rates of Base of Thumb Arthritis Surgery: A Systematic Review

The purpose of the current review was to estimate failure rates of trapeziometacarpal (TMC) implants and compare against failure rates of nonimplant techniques for surgical treatment of TMC joint (basal thumb joint) arthritis. A systematic review was conducted to identify articles reporting on thumb implant arthroplasty and on nonimplant arthroplasty techniques for treatment of base of thumb arthritis in the English literature. The collected data were combined to calculate failure rates per 100 procedure-years. Failure was defined by the requirement for a secondary salvage procedure. The failure rates between different implant and nonimplant arthroplasty groups were compared directly and implants with higher than anticipated failure rates were identified. One hundred twenty-five articles on implant arthroplasty and 33 articles on the outcome of nonimplant surgical arthroplasty of the TMC joint were included. The implant arthroplasty failure rates per 100 procedure-years were total joint replacement (2.4), hemiarthroplasty (2.5), interposition with partial trapezial resection (4.5), interposition with complete trapezial resection (1.7), and interposition with no trapezial resection (4.5). The nonimplant arthroplasty failure rates per 100 procedure-years were: trapeziectomy (0.49), joint fusion (0.52), and trapeziectomy with ligament reconstruction ± tendon interposition (0.23). Several implant designs (arthroplasties) had high rates of failure due to aseptic loosening, dislocation, and persisting pain. Furthermore, some implants had higher than anticipated failure rates than other implants within each class. Overall, the failure rates of nonimplant techniques were lower than those of implant arthroplasty. Therapeutic IV.

Canada’s federal database is inadequate for the assessment of environmental consequences of oil and gas pipeline failures

In Canada, the National Energy Board (NEB) regulates inter-provincial oil and gas pipelines and maintains historical records that contain data on oil and gas pipeline accidents; these data include information about operators, the accidents’ cause, and the resulting consequences. New inter-provincial pipelines are being built in Canada to transport fuels, but no comprehensive statistical analysis of the risk to environmental receptors exists. This study assesses the quality and quantity of NEB pipeline failure data available in Canada with a focus on environmental consequences and investigates differences between Canada and a more thoroughly studied jurisdiction, the United States, in tracking accident data. The discrepancies in agencies’ jurisdiction and regulated mileage are analyzed, along with reporting criteria and initial recording year. The level of detail provided by the two agencies is compared, identifying deficiencies in data collection. The Pipeline and Hazardous Materials Safety Administration (PHMSA) regulates 76% of pipelines in the United States, whereas the NEB only monitors 9% of pipelines in Canada. PHMSA provides four databases that include accidents from the 1980s for most pipelines and from 2011 for liquefied natural gas facilities; the NEB database includes accident data starting from 2008, which derive primarily from transmission pipelines. Information about environmental consequences is quite detailed in the US database, which reports 21 descriptive fields, whereas in Canada only two NEB database fields describe environmental outcomes. Moreover, dissimilarities in accident reporting criteria prevent the combination of data from the two agencies. Consequently, the NEB database does not allow for statistically robust and system wide analysis of the environmental consequences of pipeline failures in Canada. Furthermore, to calculate failure rates (annual number of accidents per kilometre of pipeline) for regulated pipelines, annual total mileage estimates are required. Mileage per year is provided by PHMSA for gas gathering, transmission, and distribution pipelines starting from 1984, and for hazardous liquid pipelines from 2004; the NEB provides annual mileage from 2010, a shorter period of record. The Canadian federal agencies are encouraged to improve accuracy and consistency in recording past accidents and in collecting pipeline data, with the goal of preventing and minimizing future pipeline failures.

Prolonged use of the etonogestrel implant and levonorgestrel intrauterine device: 2 years beyond Food and Drug Administration–approved duration

The subdermal contraceptive implant and the 52-mg levonorgestrel intrauterine device are currently Food and Drug Administration approved for 3 and 5 years of use, respectively. Limited available data suggested both of these methods are effective beyond that time. Demonstration of prolonged effectiveness will improve the cost-effectiveness of the device, and potentially patient continuation and satisfaction. We sought to evaluate the effectiveness of the contraceptive implant and the 52-mg hormonal intrauterine device in women using the method for 2 years beyond the current Food and Drug Administration-approved duration. We initiated this ongoing prospective cohort study in January 2012. We are enrolling women using the contraceptive implant or 52-mg levonorgestrel intrauterine device for a minimum of 3 and 5 years, respectively (started intrauterine device in ≥2007 or implant in ≥2009). Demographic and reproductive health histories, as well as objective body mass index, were collected. Implant users were offered periodic venipuncture for analysis of serum etonogestrel levels. The primary outcome, unintended pregnancy rate, was calculated per 100 woman-years. We analyzed baseline demographic characteristics using χ2 test and Fisher exact test, and compared serum etonogestrel levels stratified by body mass index using the Kruskal-Wallis test. Implant users (n= 291) have contributed 444.0 woman-years of follow-up. There have been no documented pregnancies in implant users during the 2 years of postexpiration follow-up. Calculated failure rates in the fourth and fifth years for the implant are calculated as 0 (1-sided 97.5% confidence interval, 0-1.48) per 100 woman-years at 4 years and 0 (1-sided 97.5% confidence interval, 0-2.65) per 100 woman-years at 5 years. Among 496 levonorgestrel intrauterine device users, 696.9 woman-years of follow-up have been completed. Two pregnancies have been reported. The failure rate in the sixth year of use of the levonorgestrel intrauterine device is calculated as 0.25 (95% confidence interval, 0.04-1.42) per 100 woman-years; failure rate during the seventh year is 0.43 (95% confidence interval, 0.08-2.39) per 100 woman-years. Among implant users with serum etonogestrel results, the median etonogestrel level was 207.7 pg/mL (range 63.8-802.6 pg/mL) at the time of method expiration, 166.1 pg/mL (range 67.9 25.0-470.5 pg/mL) at the end of the fourth year, and 153.0 pg/mL (range 72.1-538.8 pg/mL) at the end of the fifth year. Median etonogestrel levels were compared by body mass index at each time point and a statistical difference was noted at the end of 4 years of use with overweight women having the highest serum etonogestrel (195.9; range 25.0-450.5 pg/mL) when compared to normal (178.9; range 87.0-463.7 pg/mL) and obese (137.9; range 66.0-470.5 pg/mL) women (P= .04). This study indicates that the contraceptive implant and 52-mg hormonal intrauterine device continue to be highly effective for at least 2 additional years of use. Serum etonogestrel evaluation demonstrates median levels remain above the ovulation threshold of 90 pg/mL for women in all body mass index classes.

Life test of an X-band MMIC multi-function chip for active phased array radar applications

A 1000-h steady state life test at a temperature of 125°C was performed on ten X-band MMIC multifunction chips for use in active phase array radar systems. Internal switches, phase shifters, and attenuators were operated through an integrated serial-to-parallel converter under the five-second stepped external control signal for the life test period. None of the ten samples failed under the failure criteria based on the JEP118 standard. The calculated failure rate using the Chi Square Statistic was 1.6e−6 failures/h for the 90% confidence level. Maximum DC current variation was +16% for an initial value. Maximum variations of small signal gain, phase shift, and attenuation were 0.96dB, 2°, and 0.17dB, respectively, over a frequency range of 8.5–10.5GHz.

SEL Cross Section Energy Dependence Impact on the High Energy Accelerator Failure Rate

We use a single event latchup (SEL) model calibrated to heavy ion (HI) and proton data below 230 MeV to extrapolate the proton cross section to larger energies and evaluate the impact of the potential cross section increase with energy on the SEL rate in different environments. We show that in the case of devices with a large LET onset for HI and a certain amount of tungsten near the sensitive volume (SV), the calculated failure rates for energetic environments based on monoenergetic test data can significantly underestimate the real value. In addition, we show through measurements using a 480 MeV beam and an inspection of the device's architecture that the model was successful in estimating the SEL cross section and tungsten volume per cell.

Optimization of the Maintenance Program of Elevating Equipment Using Risk Assessment

Maintenance program for elevating equipments is basically done in time-based concept. Inspection periods are determined for each item which is composed of plural parts; however, this inspection interval is based on experiences and does not have clear scientific backgrounds. In order to rationalize the maintenance program, the application of available data such as failure reports given by customers, and inspection data reported at periodical maintenance is extremely important. Unfortunately, this information is not necessarily utilized sufficiently at this moment. In this research, we try to quantify a risk by calculating failure rates and harm severities of each maintenance item. When calculating the failure rate, we use a statistical method and take “interruption data” into consideration to make up for the lack of data. When defining the harm severities, we evaluate the suspension time caused by the failure of . Finally, by multiplying the failure rate and the harm severity, we quantify a risk which matches maintenance executer's sense, and develop the method of optimizing the maintenance program based on risk.

A study of the actual failure situation of XLPE cable and the order of priority of degradation diagnosis

AbstractWe analyzed statistical data on failures due to dielectric breakdowns caused by water tree degradation in 6‐kV XLPE cables using the Hazard Analysis. The data used in this report reflect actual conditions of XLPE cables. The data are classified by the conductor size of the cables. Calculated failure rates were different for cables having different conductor sizes. In this report, the failure rates were calculated based on the information regarding conductor size, cable length, and cable age. The results obtained make it possible to quantitatively establish the order of the priority of degradation diagnosis. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 50–58, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10301

A targeted review of study outcomes with short (< or = 7 mm) endosseous dental implants placed in partially edentulous patients.

Generally, threaded root-form endosseous dental implants are thought to perform poorly in short lengths (i.e., < 10 mm). However, whether modifications in implant surface geometry will improve performance of short threaded implants is less clear. The relationship between dental implant failure rates and their surface geometry, length, and location (maxilla versus mandible) was explored in the published literature. Using a MEDLINE search (1985 through 2001), studies were sought with the following criteria: 1) data suitable to calculate failure rates of implant lengths < or = 7 mm versus > 7 mm; 2) data separable into maxillary versus mandibular results; 3) criteria for "failure" clearly defined; and 4) minimal functional period of 2 years. Twelve papers were identified as follows: eight with machined threaded implants, two with acid-treated threaded implants, and two with sintered porous-surfaced press-fit implants. The following results were found: 1) machined surface implants experienced greater failure rates than textured surface implants; 2) with the exception of sintered porous-surfaced implants, 7 mm long dental implants appear to have higher failure rates than those > 7 mm length; and 3) with textured surface implants, higher failure rates were more likely in the maxilla than in the mandible, but with machined surface implants there were no differences in failure rates between maxilla and mandible. Dental implant surface geometry is a major determinant in how well these implants perform in short lengths, defined here as lengths of < or = 7 mm. While threaded implants show higher failure rates in short versus longer lengths, sintered porous-surfaced implants perform well in the defined "short" lengths. More studies are needed to better assess the performance of short, acid-washed threaded implants.

The effects of torque control spurs in twin-block appliances.

The study compared the effects of torque control spurs on upper incisor retroclination and extrusion with two designs of a twin-block functional appliance in Class II/1 cases. The two designs were also compared with respect to anchorage loss in the lower arch and for patient compliance rates. Consecutively started cases were chosen - 90 patients with a design incorporating a labial bow (CTB group) and 110 with upper incisor 'torquing' spurs (STB group) and used to calculate failure rates. Thirty consecutive patients with satisfactory records from each group were analysed cephalometrically. The STB group experienced substantially less upper incisor retroclination, reduced upper incisor extrusion and slightly more favourable mandibular growth. The labial movement of lower incisors and the patient compliance were not significantly different in the two groups. Overall, 82.5% of patients fully reduced their overjet with 9% failing to reduce the overjet below 6 mm.Fig. 1f

Test and reliability: partners in IC manufacturing. 2

This article discusses the major gate oxide failure modes, reliability modeling, burn-in, and qualification testing. We present a typical method to calculate failure rates.

The multi-class binomial failure rate model

The impact of common cause failure (CCF) on PSA results for NPPs is in sharp contrast with the limited quality which can be achieved in their assessment. This is due to the dearth of observations and cannot be remedied in the short run. Therefore, the methods employed for calculating failure rates should be devised such as to make the best use of the few available observations on CCF. The Multi-Class Binomial Failure Rate (MCBFR) Model presented here achieves this by assigning observed failures to different classes according to their technical characteristics and applying the BFR formalism to each of these. The results are determined by a superposition of BFR type expressions for each class, each of them with its own coupling factor. The model hence integrates additional technical information on CCFs and leads to a better quality of results whenever this information is available. This is demonstrated by evaluating CCFs observed for combined impulse pilot valves in German NPPs.