scholarly journals Data Analysis of Step-Stress Accelerated Life Test with Random Group Effects under Weibull Distribution

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Juan Wang
Keyword(s):  
Data Analysis ◽  
Weibull Distribution ◽  
Random Effect ◽  
Accelerated Life Test ◽  
Failure Behavior ◽  
Model Parameters ◽  
Life Test ◽  
Time Data ◽  
Data Set ◽  
Mixed Effect

Step-stress accelerating life test (SSALT), aiming to predict the failure behavior under use condition by the data collected from elevated test setting, is implemented to specimen with time-varying stress levels. Typical testing protocols in SSALT, such as subsampling, cannot guarantee complete randomization and thus result in correlated observations among groups. To consider the random effects from the group-to-group variation, we build a nonlinear mixed effect model (NLMM) with the assumption of Weibull distribution for life time data analysis from SSALT. Both maximum likelihood estimation (MLE) and Bayesian inference are introduced for the estimation and prediction of model parameters as well as other statistics of interest. Gauss–Hermite (G-H) quadrature is used to obtain an accurate approximation of the likelihood for observations, and different priors of model parameters are applied in Bayesian analysis. A comprehensive simulation study and an analysis for a real data set are conducted to justify the proposed method, suggesting that the incorporation of the random effect from the underlying experimental routine ensures a more solid and practical conclusion when the heterogeneous group effect is statistically significant.

scholarly journals Design and application of accelerated life test of grating ruler based on step stress loading

2021 ◽  
Vol 336 ◽  
pp. 02027
Author(s):  
Jili Wang ◽  
Qingyu Li ◽  
Xiaocui Zhu ◽  
Cheng Gao ◽  
Yi Li ◽  
...  
Keyword(s):  
Weibull Distribution ◽  
Test Method ◽  
Accelerated Life Test ◽  
Test Scheme ◽  
Life Test ◽  
Test Device ◽  
Typical Application ◽  
Accelerated Life ◽  
Life Model ◽  
Accelerated Life Model

Combined with the actual project, a grating ruler accelerated life test device is designed, which can simulate the actual loads, including temperature, humidity and speed stress. An accelerated life test scheme based on stepped stress loading is proposed, and 6 grating rulers are tested based on time-censored test method. An accelerated life model based on Weibull distribution used for evaluating the lifetime is established. Related experimental techniques also can be typical application cases for innovative practical teaching.

scholarly journals Accelerated Life Tests under Pareto-IV Lifetime Distribution: Real Data Application and Simulation Study

Mathematics ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1786 ◽  
Author(s):  
A. M. Abd El-Raheem ◽  
M. H. Abu-Moussa ◽  
Marwa M. Mohie El-Din ◽  
E. H. Hafez
Keyword(s):  
Simulation Study ◽  
Stress Test ◽  
Real Data ◽  
Accelerated Life Test ◽  
Maximum Likelihood Estimates ◽  
Cumulative Exposure ◽  
Exposure Model ◽  
Model Parameters ◽  
Data Set ◽  
Accelerated Life

In this article, a progressive-stress accelerated life test (ALT) that is based on progressive type-II censoring is studied. The cumulative exposure model is used when the lifetime of test units follows Pareto-IV distribution. Different estimates as the maximum likelihood estimates (MLEs) and Bayes estimates (BEs) for the model parameters are discussed. Bayesian estimates are derived while using the Tierney and Kadane (TK) approximation method and the importance sampling method. The asymptotic and bootstrap confidence intervals (CIs) of the parameters are constructed. A real data set is analyzed in order to clarify the methods proposed through this paper. Two types of the progressive-stress tests, the simple ramp-stress test and multiple ramp-stress test, are compared through the simulation study. Finally, some interesting conclusions are drawn.

scholarly journals Variation of Efficacy of Filtering Face Pieces Respirators over Time in a Dental Setting: A Pilot Study

2021 ◽  
Vol 9 (4) ◽  
pp. 36
Author(s):  
Vittorio Checchi ◽  
Marco Montevecchi ◽  
Luigi Checchi
Keyword(s):  
Fixed Effects ◽  
Random Effect ◽  
Wilcoxon Test ◽  
Linear Mixed Effect Model ◽  
Clinical Activity ◽  
Time Data ◽  
Paired Data ◽  
Mixed Effect ◽  
Protective Function ◽  
Over Time

Since aerosol continuously persists in dental settings, where different procedures and patients come in succession, the use of oronasal masks is highly recommended. Among them, respirators known as Filtering Face Pieces (FFP) show a protective superiority compared to surgical masks. Even concerning respirators classified as non-reusable, it is not known how many hours of use are necessary to compromise their filtering capacity. The aim of this study is to investigate the variations of filtering capacity of an FFP2 respirator over time, in order to safely optimize the timing of its use. Five respirators were worn by the same operator during clinical activity for different usage times (8, 16, 24, 32, 40 h), and one respirator was kept unused. All respirators underwent a bacterial filtration efficacy (BFE) test. T-test for paired data with Bootstrap technique and Wilcoxon test for paired data compared BFE values of the five tested FFP2s respectively at each time, and the areas with the corresponding values of the control respirator (FFp2-F). A generalized linear mixed effect model (GLM) was applied considering type of respirator and time as fixed effects and intercept as random effect. No significant statistical differences were present in the BFE of each time. Data obtained by the present study highlight the important ability of FFP2s to maintain their BFE over time, suggesting a long lasting protective function.

Constant-Step-Stress Accelerated Life Test of White OLED Under Weibull Distribution Case

2012 ◽  
Vol 59 (3) ◽  
pp. 715-720 ◽  
Author(s):  
JianPing Zhang ◽  
TingJun Zhou ◽  
Helen Wu ◽  
Yu Wu ◽  
WenLi Wu ◽  
...  
Keyword(s):  
Weibull Distribution ◽  
Accelerated Life Test ◽  
Life Test ◽  
Accelerated Life ◽  
White Oled

scholarly journals Phycocyanin Thermo-photostability: an Accelerated Life-test Analysis

2020 ◽  
Vol 64 (3) ◽  
Author(s):  
Froylan M. E. Escalante ◽  
Daniel A. Pérez-Rico ◽  
Jorge Luis Alarcón-Jiménez ◽  
Escarlett González-Morales ◽  
Luis Felipe Guerra-Álvarez ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Storage Conditions ◽  
Accelerated Life Test ◽  
Effect Of Temperature ◽  
Order Kinetic ◽  
Life Test ◽  
Time Data ◽  
Test Analysis ◽  
Accelerated Life ◽  
Degradation Ratio

Abstract. Phycocyanin is a natural blue colorant with antioxidant activity which can be safely used in food, however its rapid degradation is still a concern for food manufacturing. Phycocyanin is easily degraded when exposed to mid-temperatures and/or light. Several studies have been stablished the degradation kinetics of aqueous solutions evaluating temperature or light as accelerating factors using a first order kinetic model and, both factors have been studied by separate or fixing one of them to evaluate the combined effect. The aim of this work was to develop an empirical model able to predict the effect of temperature and light combined in the degradation ratio of this pigment at selected storage conditions. We have tested five correlation models to fit temperature, light and time data to the degradation ratio of the phycocyanin; these were statistically tested to select the more appropriate. This is a novelty in the study of accelerated life-test analysis of phycocyanin, since most of the models are based on one accelerating variable at the time and the relationship between accelerating variables has not been explored before. We were able to develop a methodology to evaluate the effect of two accelerating life factors at once using CPC as model which is highly precise and easy to apply. Resumen. La ficocianina es un pigmento natural color azul con actividad antioxidante que puede utilizarse de manera segura en alimentos, sin embargo, su rápida degradación sigue siendo un problema para su uso en alimentos. La ficocianina se degrada fácilmente cuando se expone a temperaturas medias o a la luz. Algunos estudios han establecido la cinética de degradación de las soluciones evaluando la temperatura o la luz como factores de aceleración usando modelos cinéticos de primer orden. Además, ambos factores han sido estudiados por separado o fijando uno de ellos para evaluar el efecto combinado. El objetivo de este trabajo fue desarrollar un modelo empírico capaz de predecir el efecto de la temperatura y la iluminación en forma combinada sobre la velocidad de degradación de la ficocianina a las condiciones de almacenamiento seleccionadas. Se probaron cinco modelos de correlación para ajustar los datos de temperatura, luz y tiempo a la velocidad de degradación de la ficocianina; dichos modelos fueron probados estadísticamente para determinar el más adecuado. Esta es una novedad en el estudio de los análisis de pruebas de vida acelerada de la ficocianina, dado que la mayoría de los modelos se basan en una sola variable acelerante a la vez y, no se han explorado las relaciones entre las variables de aceleración. Fuimos capaces de desarrollar una metodología altamente precisa y sencilla para evaluar el efecto de dos factores simultáneos de aceleración de la vida de la ficocianina C como modelo.

scholarly journals Accelerated Life Test Sampling Plans under Progressive Type II Interval Censoring with Random Removals

2017 ◽  
Vol 7 (1) ◽  
pp. 26
Author(s):  
Siu Keung Tse ◽  
Chang Ding
Keyword(s):  
Numerical Study ◽  
Interval Censoring ◽  
Accelerated Life Test ◽  
Model Parameters ◽  
Type Ii ◽  
Life Test ◽  
Sampling Plans ◽  
Accelerated Life ◽  
Progressive Type ◽  
Stress Levels

This paper investigates the design of accelerated life test (ALT) sampling plans under progressive Type II interval censoring with random removals. For ALT sampling plans with two over-stress levels, the optimal stress levels and the allocation proportions to them are obtained by minimizing the asymptotic generalized variance of the maximum likelihood estimation of model parameters. The required sample size and the acceptability constant which satisfy given levels of producer’s risk and consumer’s risk are found. ALT sampling plans with three over-stress levels are also considered under some specific settings. The properties of the derived ALT sampling plans under different parameter values are investigated by a numerical study. Some interesting patterns, which can provide useful insight to practitioners in related areas, are found. The true acceptance probabilities are computed using a Monte Carlo simulation and the results show that the accuracy of the derived ALT sampling plans is satisfactory. A numerical example is also provided for illustrative purpose.

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