scholarly journals Reliability and Sensitivity Analysis of a Repairable System with Warranty and Administrative Delay in Repair

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mohamed S. El-Sherbeny ◽  
Zienab M. Hussien
Keyword(s):  
Performance Metrics ◽  
Failure Time ◽  
Relative Sensitivity ◽  
Sensitivity Analyses ◽  
Inspection Time ◽  
Industrial Systems ◽  
Negative Exponential Distribution ◽  
Product Warranty ◽  
Negative Exponential ◽  
The Cost

The purpose of this study is to analyze the behavior of some industrial systems in light of the cost-free warranty policy. According to this policy, we assume that the repairman is not always present in the system. When the active unit fails, the repairman will be called to visit the system; however, administrative procedures may delay the visit for some time. Once on the system, the repairman first inspects whether the fault is caused by the user or not and whether it is repairable or not. According to product warranty laws, the repairman carries out the repair or replacement of the faulty unit. The failure time, administrative delay time, inspection time, and repair time are assumed taken as a negative exponential distribution. The system model is analyzed by the supplementary variable technique and Laplace transform, as various performance metrics of system efficiency have been obtained. The sensitivity and relative sensitivity analyses for the system parameters have also been performed. Finally, an illustrative example is taken to illustrate the efficiency of the system.

scholarly journals Profit Analysis of a Standby Repairable System with Priority to Preventive Maintenance and Rest of Server Between Repairs

2021 ◽  
Author(s):  
Chhama Aggarwal ◽  
Nitika Ahlawat ◽  
S.C. Malik
Keyword(s):  
Preventive Maintenance ◽  
Failure Time ◽  
Random Variable ◽  
Productivity Level ◽  
Reliability Characteristics ◽  
Profit Analysis ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
The Cost ◽  
Efficiency And Productivity

The paper aims to bring out the profit analysis of a system with cold standby redundancy of two identical units. In the system, we keep one unit productive and the other is to backup the operation. The system requires preventive maintenance after a specific time. In addition to that, the server is allowed to rest between two consecutive repairs. The repairs are done to increase the efficiency and productivity level of the system. The repair and rest times follow arbitrary distributions while the random variable related to failure time of the unit follows negative exponential distribution. The provision of priority has been made for the preventive maintenance over repairs. Some important reliability characteristics are studied in steady state by using the approach of stochastic processes. The revenue per unit time and the cost per unit time for which server is busy in repairs and maintenances are considered for determining the profit incurred to the system.  The results are shown graphically and numerically to highlight the effect of different parameters on some significant reliability characteristics.

scholarly journals Censored Negative Exponential Distribution as a Mixed Distribution and Derivation of Its Moments

2013 ◽  
Vol 14 (1) ◽  
pp. 167-176
Author(s):  
Srijan Lal Shrestha
Keyword(s):  
Exponential Distribution ◽  
Failure Time ◽  
Three Dimensional ◽  
Time Data ◽  
Exponential Distributions ◽  
Discrete Random Variables ◽  
Negative Exponential Distribution ◽  
Doubly Censored ◽  
Mean And Variance ◽  
Negative Exponential

Censored negative exponential distribution is treated as a mixed type distribution having two distinct types of components. These components give arise to continuous as well as discrete random variables. Moments (mean and variance) are derived for the doubly censored, right censored, and left censored negative exponential distributions (NEDs) along with separations of continuous and discrete components and their respective means and variances. Moments obtained for the censored NEDs are then compared to the corresponding values of the uncensored NEDs and the changes in the proportions of the moments due to censoring are examined and assessed. Plots of moments of the censored distributions including a three dimensional scatter plot are presented considering different hypothetical values at which censoring may occur. These distributions are widely applied in fitting and modeling failure time data in survival and reliability analyses. Nepal Journal of Science and Technology Vol. 14, No. 1 (2013) 167-176 DOI: http://dx.doi.org/10.3126/njst.v14i1.8937

scholarly journals Mixed Topology of DF Relayed Terrestrial Optical Wireless Links with Generalized Pointing Errors over Turbulence Channels

Technologies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 121 ◽  
Author(s):  
GeorgeK. Varotsos ◽  
Hector E. Nistazakis ◽  
Argyris N. Stassinakis ◽  
Christos K. Volos ◽  
Vasileios Christofilakis ◽  
...  
Keyword(s):  
Performance Metrics ◽  
Cooperative Diversity ◽  
Optical Signal ◽  
Decode And Forward ◽  
Pointing Error ◽  
Pointing Errors ◽  
Mathematical Expressions ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
Signal Fading

This study investigated the outage performance of a terrestrial FSO communication system that uses mixed series and parallel decode-and-forward (DF) relay-assisted (i.e., cooperative diversity) configurations, taking into account the influence of both atmospheric turbulence and pointing error effects. Turbulence-induced optical signal fading is modeled by gamma-gamma or the negative exponential distribution for weak to strong and saturated turbulence conditions, respectively. Additionally, weak to strong non-zero boresight misalignment-induced optical signal fading is modeled by the generalized Beckmann distribution. Under these conditions, an outage analysis of the examined FSO system is performed, in terms of both outage probability and mean outage duration metrics. Thus, fairly accurate closed-form mathematical expressions for both performance metrics are derived, while their corresponding analytical results demonstrate concrete performance and availability improvements for the total FSO system, especially when the number of the connected in parallel DF relays increases. Moreover, the obtained results are verified through the corresponding simulation results.

Stroke Prevention in Non-Valvular Atrial Fibrillation

1997 ◽  
Vol 17 (03) ◽  
pp. 166-169
Author(s):  
Judith O’Brien ◽  
Wendy Klittich ◽  
J. Jaime Caro
Keyword(s):  
Atrial Fibrillation ◽  
Clinical Trials ◽  
Care Home ◽  
Relevant Literature ◽  
Clinical Trial Data ◽  
Outcome Data ◽  
Sensitivity Analyses ◽  
Bleeding Events ◽  
Discharge Data ◽  
The Cost

SummaryDespite evidence from 6 major clinical trials that warfarin effectively prevents strokes in atrial fibrillation, clinicians and health care managers may remain reluctant to support anticoagulant prophylaxis because of its perceived costs. Yet, doing nothing also has a price. To assess this, we carried out a pharmacoe-conomic analysis of warfarin use in atrial fibrillation. The course of the disease, including the occurrence of cerebral and systemic emboli, intracranial and other major bleeding events, was modeled and a meta-analysis of the clinical trials and other relevant literature was carried out to estimate the required probabilities with and without warfarin use. The cost of managing each event, including acute and subsequent care, home care equipment and MD costs, was derived by estimating the cost per resource unit, the proportion consuming each resource and the volume of use. Unit costs and volumes of use were determined from established US government databases, all charges were adjusted using cost-to-charge ratios, and a 3% discount rate was applied to costs incurred beyond the first year. The proportions of patients consuming each resource were estimated by fitting a joint distribution to the clinical trial data, stroke outcome data from a recent Swedish study and aggregate ICD-9 specific, Massachusetts discharge data. If nothing is done, 3.2% more patients will suffer serious emboli annually and the expected annual cost of managing a patient will increase by DM 2,544 (1996 German Marks), from DM 4,366 to DM 6,910. Extensive multiway sensitivity analyses revealed that the higher price of doing nothing persists except for very extreme combinations of inputs unsupported by literature or clinical standards. The price of doing nothing is thus so high, both in health and economic terms, that cost-consciousness as well as clinical considerations mandate warfarin prophylaxis in atrial fibrillation.

The Comparison Between the Bayes Estimator and the Maximum Likelihood Estimator of the Reliability Function for Negative Exponential Distribution

2018 ◽  
pp. 439
Author(s):  
Hazim Mansour Gorgees ◽  
Bushra Abdualrasool Ali ◽  
Raghad Ibrahim Kathum
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimator ◽  
Exponential Distribution ◽  
Reliability Function ◽  
Bayes Estimator ◽  
Likelihood Estimator ◽  
Monte Carlo Simulation Technique ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
Better Than

     In this paper, the maximum likelihood estimator and the Bayes estimator of the reliability function for negative exponential distribution has been derived, then a Monte –Carlo simulation technique was employed to compare the performance of such estimators. The integral mean square error (IMSE) was used as a criterion for this comparison. The simulation results displayed that the Bayes estimator performed better than the maximum likelihood estimator for different samples sizes.

Ehrenfest urn models

1965 ◽  
Vol 2 (02) ◽  
pp. 352-376 ◽  
Author(s):  
Samuel Karlin ◽  
James McGregor
Keyword(s):  
Exponential Distribution ◽  
Continuous Time ◽  
Random Variables ◽  
Independent Random Variables ◽  
Urn Models ◽  
Time Intervals ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
Random Times

In the Ehrenfest model with continuous time one considers two urns and N balls distributed in the urns. The system is said to be in stateiif there areiballs in urn I, N −iballs in urn II. Events occur at random times and the time intervals T between successive events are independent random variables all with the same negative exponential distributionWhen an event occurs a ball is chosen at random (each of theNballs has probability 1/Nto be chosen), removed from its urn, and then placed in urn I with probabilityp, in urn II with probabilityq= 1 −p, (0 <p< 1).

The cost implication of primary prevention in the HOPE 3 trial

2019 ◽  
Vol 5 (3) ◽  
pp. 266-271
Author(s):  
Andre Lamy ◽  
Eva Lonn ◽  
Wesley Tong ◽  
Balakumar Swaminathan ◽  
Hyejung Jung ◽  
...  
Keyword(s):  
Developing Countries ◽  
Primary Prevention ◽  
Cost Saving ◽  
Developed Countries ◽  
Sensitivity Analyses ◽  
Clinical Trial Registration ◽  
Pressure Lowering ◽  
The Cost ◽  
Care Costs ◽  
Country Specific

Abstract Aims The Heart Outcomes Prevention Evaluation-3 (HOPE-3) found that rosuvastatin alone or with candesartan and hydrochlorothiazide (HCT) (in a subgroup with hypertension) significantly lowered cardiovascular events compared with placebo in 12 705 individuals from 21 countries at intermediate risk and without cardiovascular disease. We assessed the costs implications of implementation in primary prevention in countries at different economic levels. Methods and results Hospitalizations, procedures, study and non-study medications were documented. We applied country-specific costs to the healthcare resources consumed for each patient. We calculated the average cost per patient in US dollars for the duration of the study (5.6 years). Sensitivity analyses were also performed with cheapest equivalent substitutes. The combination of rosuvastatin with candesartan/HCT reduced total costs and was a cost-saving strategy in United States, Canada, Europe, and Australia. In contrast, the treatments were more expensive in developing countries even when cheapest equivalent substitutes were used. After adjustment for gross domestic product (GDP), the costs of cheapest equivalent substitutes in proportion to the health care costs were higher in developing countries in comparison to developed countries. Conclusion Rosuvastatin and candesartan/HCT in primary prevention is a cost-saving approach in developed countries, but not in developing countries as both drugs and their cheapest equivalent substitutes are relatively more expensive despite adjustment by GDP. Reductions in costs of these drugs in developing countries are essential to make statins and blood pressure lowering drugs affordable and ensure their use. Clinical trial registration HOPE-3 ClinicalTrials.gov number, NCT00468923.

scholarly journals Cost-effectiveness of zoledronic acid compared with sequential denosumab/alendronate for older osteoporotic women in Japan

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Takahiro Mori ◽  
Carolyn J. Crandall ◽  
Tomoko Fujii ◽  
David A. Ganz
Keyword(s):  
Health Economic ◽  
Cost Effectiveness ◽  
Zoledronic Acid ◽  
Cost Saving ◽  
Fragility Fracture ◽  
Community Dwelling ◽  
Sensitivity Analyses ◽  
Term Care ◽  
Lifetime Horizon ◽  
The Cost

Abstract Summary Among hypothetical cohorts of older osteoporotic women without prior fragility fracture in Japan, we evaluated the cost-effectiveness of two treatment strategies using a simulation model. Annual intravenous zoledronic acid for 3 years was cost-saving compared with biannual subcutaneous denosumab for 3 years followed by weekly oral alendronate for 3 years. Purpose Osteoporosis constitutes a major medical and health economic burden to society worldwide. Injectable treatments for osteoporosis require less frequent administration than oral treatments and therefore have higher persistence and adherence with treatment, which could explain better efficacy for fracture prevention. Although annual intravenous zoledronic acid and biannual subcutaneous denosumab are available, it remains unclear which treatment strategy represents a better value from a health economic perspective. Accordingly, we examined the cost-effectiveness of zoledronic acid for 3 years compared with sequential denosumab/alendronate (i.e., denosumab for 3 years followed by oral weekly alendronate for 3 years, making the total treatment duration 6 years) among hypothetical cohorts of community-dwelling osteoporotic women without prior fragility fracture in Japan at ages 65, 70, 75, or 80 years. Methods Using a previously validated and updated Markov microsimulation model, we obtained incremental cost-effectiveness ratios (Japanese yen [¥] (or US dollars [$]) per quality-adjusted life-year [QALY]) from the public healthcare and long-term care payer’s perspective over a lifetime horizon with a willingness-to-pay of ¥5 million (or $47,500) per QALY. Results In the base case, zoledronic acid was cost-saving (i.e., more effective and less expensive) compared with sequential denosumab/alendronate. In deterministic sensitivity analyses, results were sensitive to changes in the efficacy of zoledronic acid or the cumulative persistence rate with zoledronic acid or denosumab. In probabilistic sensitivity analyses, the probabilities of zoledronic acid being cost-effective were 98–100%. Conclusions Among older osteoporotic women without prior fragility fracture in Japan, zoledronic acid was cost-saving compared with sequential denosumab/alendronate.

scholarly journals 503. The Misappropriation of COVID-19 Related TV Ad Expenditures

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S317-S317
Author(s):  
Kartavya J Vyas
Keyword(s):  
Cost Effectiveness ◽  
Performance Metrics ◽  
Control Measures ◽  
Mortality Data ◽  
Preventive Interventions ◽  
Social Distancing ◽  
Epidemic Curve ◽  
Incidence And Mortality ◽  
The Cost ◽  
The U.S

Abstract Background With nearly three-fourths of the U.S. population isolated in their homes between early March and the end of May, almost all of whom regularly watch television (TV), it was no surprise that companies began to purchase airtime on major television networks to advertise (ad) their brands and showcase their empathy with the populace. But how would the coronavirus disease 2019 (COVID-19) epidemic curve have changed had these same dollars been allocated to proven preventive interventions? Methods Performance and activity metrics on all COVID-19 related TV ads that have aired in the U.S. between February 26th and June 7th, 2020, were provided by iSpot.tv, Inc., including expenditures. COVID-19 incidence and mortality data were collected from the Centers for Disease Control and Prevention (CDC). Descriptive statistics were performed to calculate total TV ad expenditures and other performance metrics across industry categories. Leveraging a previously published stochastic agent-based model that was used to assess the cost-effectiveness of non-pharmaceutical interventions to control COVID-19, the number of cases that would have been prevented had these same dollars been used for preventive interventions was calculated using cost-effectiveness ratios (CERs), the cost divided by cases prevented. Results A total of 1,513 companies purchased TV airtime during the study period, totaling approximately 1.1 million airings, 215.5 billion impressions, and $2.7 billion in expenditures; most of the expenditures were spent by the restaurant (15.9%), electronics and communications (15.4%), and vehicle (13.7%) industries. The CERs for PPE and social distancing measures were $13,856 and $29,552, respectively; therefore, had all of these TV ad dollars instead been allocated to PPE or social distancing measures, approximately 194,908 and 91,386 cases of COVID-19 may have been prevented by the end of the study period, respectively. Figure 2. COVID-19 cases prevented had TV ad expenditures been reallocated for interventions. Conclusion Americans were inundated with COVID-19 related TV ads during the early months of the pandemic and companies are now showing some signs to relent. In times of disaster, however, it is paramount that the private sector go beyond showcasing their empathy and truly become socially responsible by allocating their funds to proven prevention and control measures. Disclosures All Authors: No reported disclosures

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