Failure Rate Analysis Research Articles

Crystal contacts as nature's docking solutions

The assumption that crystal contacts reflect natural macromolecular interactions makes a basis for many studies in structural biology. However, the crystal state may correspond to a global minimum of free energy where biologically relevant interactions are sacrificed in favor to unspecific contacts. A large-scale docking experiment was performed to assess the extent of misrepresentation of natural (in-solvent) protein dimers by crystal packing. As found, the failure rate of docking may be quantitatively interpreted if both calculation errors and misrepresentation effects are taken into account. The failure rate analysis is based on the assumption that crystal structures reflect thermodynamic equilibrium between different dimeric configurations. The analysis gives an estimate of misrepresentation probability, which suggests that weakly bound complexes with K(D) > or = 100 microM (some 20% of all dimers in the PDB) have higher than 50% chances to be misrepresented by crystals. The developed theoretical framework is applicable in other studies, where experimental results may be viewed as snapshots of systems in thermodynamic equilibrium.

Statistical analysis of structural failures of water pipes

Statistical analysis and prediction of failure rates of water distribution pipes are usually performed using parametric lifetime models. In this paper, a new probabilistic measure for the failure rate, called the ‘likelihood of number of failures’, is defined and formulated for cases where the pipe lifetimes follow parametric models. The resulting theoretical failure rates are time-invariant and, therefore, the parametric models would be useful only if the failure rates of water distribution pipes are stationary random processes. This paper then examines the stationarity of pipe failure rates in practice. For the water pipes in the western district of Melbourne (Australia), the failure rates are empirically calculated using a 4-year failure history, and it is observed that the distribution of empirical failure rates varies with time. In order to explain these variations, the pattern of rainfall in the region is compared with the pattern of failure rate variations, and in 70% of the times the two patterns are observed to be consistent. Two approaches are proposed to tackle the time-varying nature of pipe failure rate processes: regular updating of the parameters of lifetime models or developing a non-parametric technique for modelling of pipe failure rates.

Bayesian assessment of the variability of reliability measures

Population variability analysis, also known as the first stage in two-stage Bayesian updating, is an estimation procedure for the assessment of the variability of reliability measures among a group of sub-populations of similar systems. The estimated variability distributions are used as prior distributions in system-specific Bayesian updates. In this paper we present a Bayesian approach for population variability analysis involving the use of non-conjugate variability models that works over a continuous, rather than the discretized, variability model parameter space. The cases to be discussed are the ones typically encountered by the reliability practitioner: run-time data for failure rate assessment, demand-based data for failure probability assessment, and expert-based evidence for failure rate and failure probability analysis. We outline the estimation procedure itself as well as its link with conventional Bayesian updating procedures, describe the results generated by the procedures and their behavior under various data conditions, and provide numerical examples.

Measuring reliability of service systems using failure rates: variations and extensions

In a recent article in this journal, Gunes and Deveci proposed the use of failure rate analysis, a technique commonly used to determine reliability rates of products, systems and components, to determine reliability rates of service systems. They also presented an application of this concept to a student office service system. This paper first extends this idea to multi‐stage service systems. Next, it illustrates how several other concepts and techniques of reliability engineering can be applied for measuring reliability rates of services. Two case studies where such techniques were applied are presented. It will also discuss how customers view reliability of a service and how objective measures of reliability rates based on reliability engineering concepts and techniques can be combined with customer expectations and perceptions to set performance standards for a service.

Short-term emissions deterioration in the California and Phoenix I/M programs

An earlier analysis of the inspection and maintenance (I/M) program in Phoenix, Arizona [Environ. Sci. Policy 4 (2001) 377] found that fleet average emissions increased or “deteriorated” substantially between biennial I/M test cycles, and that a large fraction of the vehicles that initially failed and later passed in the first I/M cycle failed again two years later. In this paper we study vehicles that reported for a second I/M cycle well before their required biennial cycle, often because the subject vehicle was about to be sold to a new owner, in the decentralized California ASM program and the centralized Phoenix IM240 program. Because the off-cycle tests occurred at different times after the initial cycle, they allow the analysis of repeat failure rates over the shorter term (less than two years). We found that in California 20% of fail–pass vehicles, and 5% of initial-pass vehicles, failed the initial test of their next I/M cycle occurring within three months of completing the previous cycle; the failure rates were even higher in the centralized Phoenix program. This suggests that highly variable emissions, and not test fraud, were the cause of the large number of vehicles failing so soon after completing a previous I/M cycle. According to a model, as much as 74% of the vehicles that failed their initial test in Phoenix passed a retest because of emissions variability, and not because any repairs were performed. Vehicles with highly variable emissions may not only fail and pass a subsequent retest without repair, but also are likely to fail again if tested shortly thereafter. A large number of these vehicles may explain the apparent rapid increase or “deterioration” in fleet emissions observed in multiple years of I/M test result data.

The classification and regression tree approach to pump failure rate analysis

Abstract In this article, a technique based on rule induction is suggested as non-parametric alternative to determine the expected failure rates of 143 centrifugal pumps included in a oil refinery plant and subjected to different operating conditions. At the same time, the procedure makes it possible to determine the critical operating factors influencing the reliability of the pumps. In particular, the classification and regression tree approach is used to automatically generate rules from an extended data base of the plant concerning information about failures and operating conditions of the different facilities.

An Analysis of Business Cycles and Restaurant Failure Rates

An Analysis of Business Cycles and Restaurant Failure Rates

An Analysis of Business Cycles and Restaurant Failure Rates

ABSTRACT Restaurants are thought to be high-risk businesses to operate and invest in. Specific myths about the failure rate of restaurants compared to other businesses have been examined by industry analysts and suggest industry rules-of-thumb for predicting high restaurant failure rates in their first year of operation. Analysts cite the lack of accurate data in tracking true restaurant failure rates. The purpose of this study is to examine the relationship between restaurant failure rates in 50 U.S. states and nine U.S. regions and the respective business cycles in these 50 states and nine regions. In particular, the study seeks to determine if there is a relationship between business cycles and restaurant failure rates.

Emergency repair of thoracoabdominal aortic aneurysms with immediate presentation

Objective: The objective of this report was the study of the clinical outcome of emergently repaired thoracoabdominal aortic aneurysms (TAAAs). Methods: We retrospectively reviewed our experience with TAAA repairs from 1990 to 1998. During this interval, 110 TAAA procedures were performed, 33 (30%) of which were for immediate presentations. The χ 2 test and regression analysis were used for the analysis of mortality, paraplegia, and renal failure (hemodialysis) rates and of factors that predict these complications, respectively. Results: There were no significant differences between the elective and immediate presentations with respect to the use of adjunctive procedures (lumbar drain, hypothermia, and bypass grafting). The overall mortality rate was 13%. There were no statistically significant differences between the 30-day mortality rates or the complication rates in elective versus immediate presentations. Subgroup analysis results showed a significantly higher in-hospital mortality rate in type II TAAA with immediate presentation and free rupture presentation as compared with the overall mortality rate (50% vs 13%, P < .05, and 67% vs 13%, P < .01, respectively). Multiple regression analysis results identified the use of bypass grafting (atrial-femoral or cardiopulmonary) and lumbar drain and shorter bypass grafting time as significant predictors of decreased overall mortality ( P < .05). The mortality rates were not significantly different among aneurysm types and were not significantly decreased with the use of hypothermia. Paraplegia (5%) and renal failure (9%) rates were not predicted with aneurysm type, immediate versus elective presentation, or the adjunctive use of hypothermia, lumbar drain, or bypass grafting. Conclusion: The emergency repair of TAAA with immediate presentation can be performed with mortality and morbidity rates that approach those of elective presentations, except in the setting of free rupture or symptomatic type II TAAA. Adjunctive circulatory management techniques and lumbar drains may reduce mortality in TAAA repair. (J Vasc Surg 1999;30:996-1003.)

Estimating matched filter amplitude probability functions by failure rate analysis

Performance analysis of echolocation systems requires knowledge of the probability density function (pdf) or cumulative distribution function (cdf) of a matched filter output. A method is presented to estimate these and other probability functions from data by estimating the failure rate function, a function employed in reliability theory. The method can also be used to derive approximations to closed-form probability functions. The method is demonstrated using experimental sonar and radar clutter data and a closed-form radar clutter model.

Organizational Survival in Small-Firm Clusters.

This study tests the argument that geographic clustering of firms in the same and related industries enhances organizational survival. The event-history analysis of failure rates of firms in the kn...

Misoprostol in second trimester termination of pregnancy

Objective: The purpose of this study is to compare misoprostol to oxytocin and prostaglandin E 2 (PGE 2) in second trimester termination of pregnancy. Methods: Patients between 14 and 24 weeks gestation scheduled for induction were asked to enroll in the study using misoprostol. Comparison was made with historical controls delivered over the last 3 years who received medical induction with (PGE 2) suppositories or received high dose oxytocin. After pretreatment with acetaminophen, lomotil, and promethazine, a PGE 2 suppository (20 mg) was placed every 4 hours until passage of fetus or treatment failure. Oxytocin was given in dosages that were sequentially infused in 500 mL of D-5 LR over 3 hours each beginning at 50 units/500 mL and increasing an additional 50 units with each subsequent infusion until a maximum of 300 units. Each infusion was followed by 60 mL NS over 1 hour. Treatment failure was defined as undelivered after completion of the 24-hour infusion regimen. Misoprostol was placed into the posterior vaginal fornix every 8 hours until passage of fetus or treatment failure, which was defined as failure to pass fetus within 48 hours. Development of maternal signs or symptoms severe enough to preclude further treatment was also considered treatment failure. Data were collected on use of analgesia, induction to delivery interval, and adverse symptoms. Results: A total of 54 subjects were analyzed. Sixteen were given misoprostol, 21 high dose oxytocin, and 18 PGE 2. Mean induction to delivery times were 1374.2 ± 1009.5 minutes, 609.2 ± 515.6 minutes, and 933.6 ± 1363.7 minutes, respectively. ANOVA with least square analysis showed no difference between groups. There were 3 misoprostol failures, 7 high dose oxytocin failures, and 1 prostin failure. χ 2 analysis of failure rates showed a difference between the 3 groups ( P < .05), attributable to the difference between PGE 2 and oxytocin. Conclusions: Induction to delivery interval was not different between the three agents using intravaginal misoprostol of 200 μg every 8 hours. More treatment failures, however, occurred with oxytocin than prostaglandin. In view of lower cost and ease of storage and administration, misoprostol may be a more useful agent.

Universal newborn hearing screenings: a three-year experience.

To perform hearing screenings on all newborns before hospital discharge, using auditory brainstem evoked responses with analysis of time, cost, and failure rates to evaluate and determine the screening practicality. Over a 3-year period from January 1, 1993 to December 31, 1995, auditory brainstem evoked response screenings were performed on 15 749 infants born at Saint Barnabas Medical Center, Livingston, New Jersey, before their hospital discharge by certified/licensed audiologists. The auditory brainstem evoked response screenings were conducted using the Nicolet Compass Evoked Potential System. A 3-year experience of testing 15 749 infants proved to be a cost-effective program with costs less than $30.00/baby. To date, 46 babies have been identified with bilateral sensorineural hearing loss and 6 babies with unilateral sensorineural hearing loss. The universal newborn hearing screening program at Saint Barnabas Medical Center has proved to be effective, beneficial, and necessary for an institution with more than 5000 births, annually. Early identification of hearing loss has resulted in infants receiving early intervention, and the screening program has provided education and follow-up services to both parents and physicians.

Reliability-Based Performance Model for Large Bridge Component Systems

A method for modeling the performance of large bridge components subjected to normal loading and deterioration effects using reliability engineering techniques is presented. Development of the method was motivated by the need to advance a practical performance model for large bridge rehabilitation decision analysis. The modeling scope includes three basic elements: performance assessment, system modeling, and failure rate analysis. Two fundamental assumptions of the developed performance model are that (a) bridge components are systems of independent critical elements and (b) each element’s failure rate is constant throughout its functional service life. The model is used to qualitatively assess the performance of bridge components with respect to reliability and enables the estimation of two important rehabilitation planning indices, functional service life and expected damage. An application of the model is illustrated in an example involving a comparative evaluation of the performance of two large bridge deck systems. The bridges selected have similar traffic, maintenance, and environmental conditions; however, they have significantly different design characteristics. It is concluded that the performance model provides a viable approach to qualitative and quantitative evaluation of bridge performance over time. The research efforts described are part of a larger, comprehensive project to develop and enhance the bridge management system of the New York State Thruway Authority.

Institutions, Intergroup Competition, and the Evolution of Hotel Populations Around Niagara Falls

Earlier versions of this paper benefited from the comments of Joel Baum, Margaret Brindle, Mark Fichman, John Freeman, Paul Goodman, Amie Yael Inman, David Loree, Victor Nee, Jerry Salancik, and Tal Simons, as well as Christine Oliver, Linda Johanson, and the anonymous ASO reviewers. Earlier versions of the paper were presented at Cornell University and the University of Toronto. This paper examines institution building and the problems of collective action that must be overcome so that institutions can regulate the self-interested activity of organizations and facilitate the production or protection of resources that collectively benefit organizations. We show that the presence of competing groups of organizations is key to institution building because it may allow cooperating organizations to gain relative competitive advantage over other organizations and because the presence of salient rivals facilitates collective action. We use the history of tourism institutions at Niagara Falls to illuminate the collective action problems, and their solutions, associated with building institutions. We propose that (1) institution building in this context was the result of collective action among competitors to solve a common problem, (2) rivalry and competition between hotels on either side of the falls enhanced collective action among locally competing hotels, and (3) the regulation provided by the institutions lowered the failure rates and increased the founding rates of hotels on both sides of the falls. We examined these propositions first through historical analysis to show the motivation and process of building institutions and then through analysis of hotel failure and founding rates to show the presence of interpopulation competition and the influence over time of the institutions on organizational populations. Our analysis of failure and founding rates indicates that Niagara Falls hotels did benefit from the institutions they helped create and that there were two competing groups of organizations, but, surprisingly, institutions helped all Niagara Falls hotels, regardless of which group created them.'

How we put reliability tools into the hands of designers : Tyrone Jackson. Proc. A. Reliab. Maintainab. Symp., 168 (1991)

The managerial issues encountered during the development of FRATOOLS, a computerized methodology for performing failure rate analysis, are described. FRATOOLS was developed inhouse because a tool was needed for performing failure rate analysis in a concurrent engineering environment. No suitable commercial software or shareware could be found which adequately supports concurrent engineering. FRATOOLS consists of several stand-alone programs integrated together to work as a single software package. The FRATOOLS methodology complies with the methods contained in Mil-Hdbk-217E. Some of the novel elements of FRATOOLS include the use of smart software for automating the decision-making process, capability to compute the failure rates for advanced technology devices, and integrating the methodology with the design process in a manner which fully supports concurrency in the design of radar systems. >

Analysis of Gas-Fired Ceramic Radiant Tubes During Transient Heating: Part II—Thermoelastic Stress Analysis

Abstract Transient radial and axial temperature distributions based on measured external surface temperatures and finite-element calculations were used with temperature dependent elastic material properties to determine the thermoelastic stresses experienced by reaction-bonded and sintered-alpha silicon-carbide open ended radiant tubes during gas-combustion beating. The resulting stresses exhibited a dependence on the radial temperature difference and the curvature of the axial temperature distribution. A failure rate analysis using a two-parameter Weibull formulation with a polyaxial stress approximation, the calculated surface and volume principal stresses, and temperature-dependent surface and volume Weibull strength data indicated low failure rates and the viability of both materials for the transient heating conditions studied.

THE RECIDIVISM OF SEX OFFENDERS IN THE WESTERN AUSTRALIAN PRISON POPULATION

Five hundred and sixty sex offenders released from prisons over the period 1975–87 were followed for up to twelve years. A failure rate analysis (Wetbull ‘mixture’ model) provided estimates of probabilities of recidivism (re-incarceration) for any offence of 0.35 (for 95 per cent confidence interval it should lie between 0.25 and 0.46) for non-Aborigines and 0.80 (confidence interval 0.68–0.88) for Aborigines. Estimates or probabilities of committing further offences of violence, including further sex offences, were 0.21 (confidence interval 0.08–0.48) and 0.62 (confidence interval 0.13–0.95) respectively, but these figures are imprecise. A method of covariate analysis for recidivist data demonstrated that prior record, age, and race were crucial determining factors, but little evidence of specialization was found. It is argued that the evaluation of interventions should proceed on the basis of estimates of violent rather than repeat offending. The utility of incapacitation strategies and problems of crime prevention are discussed.

Comparison of Survivorship by the Logrank Test: Criticisms and Alternatives

Several recent papers have addressed the problem of making statistical comparisons of survival rates between populations or cohorts of plants (Tremlett et al. 1984, Muenchow 1986, Pyke and Thompson 1986). The non-parametric logrank test was introduced into the ecological literature for this purpose by Pyke and Thompson (1986). This test has been extensively used for the analysis of clinical trials and failure rates of industrial components, where the observations are often right-censored (i.e., data collection ceases before death or failure of all subjects in the trials has taken place). Although the logrank test can be a valuable tool in comparative demographic analysis, its uncritical use can result in a failure to identify important differences in survivorship. This problem is illustrated in this paper. Two procedures are suggested that allow more detailed comparisons to be made of the mortality risks experienced by populations as time passes. Although this paper is written to illustrate comparison of survival rates between populations of plants, the methods described can be applied to a wide range of organisms and for analysis of failure times (Muenchow 1986). Application in the analysis of plant survivorship is particularly appropriate, however, since data are often collected for cohorts of plants that all commence life within a short period of time.

Reliability diagnostics of electronic equipment

Reliability diagnostics is important in the selection and design of equipment and spare parts, and for establishing maintenance policy. Three possible methods are: failure rate analysis; failure mode, effect and criticality analysis; and fault tree analysis. The importance of reliability diagnostics in the early planning and design stages is emphasised.