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Life Tests (life + test)
Selected AbstractsShelf Life Prediction of Bread Sticks Using Oxidation Indices: A Validation StudyJOURNAL OF FOOD SCIENCE, Issue 2 2008S. Calligaris ABSTRACT:, The aim of this study was to apply the protocol for the shelf life prediction of bakery products proposed by Calligaris and others (2007a) on bread sticks. The methodology comprises 4 steps: (1) evaluation of the physical properties of fat; (2) performing the accelerated shelf life test; (3) evaluation of sensory acceptance limit and the relevant chemical index limit; (4) setting up the shelf life prediction model. The results allow validating the shelf life prediction methodology proposed. In fact, the peroxide number was found to be a representative index of the quality depletion of bread sticks during their shelf life. In addition, once again by accounting for the changes in the fat physical state, it is possible to set up a modified Arrhenius equation able to describe the temperature dependence of peroxide formation. Finally, a mathematical model to simply and quickly calculate the shelf life of bread sticks has been developed. [source] Failure Mechanism of a Low-Temperature-Cofired Ceramic Capacitor with an Inner Ag ElectrodeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Yi-Ting Shih Failure mechanism of a multilayer ceramic capacitor (MLCC) made of a low-fire BaNd2Ti4O12(BNT)+ZnO,B2O3 (ZB) dielectric with an inner pure silver electrode at elevated temperatures and voltages has been investigated. A nonlinear current,voltage leakage characteristic is found when the degradation of MLCC occurs, and the time to failure decreases with increasing either the temperature or the voltage. Results of microstructure, composition, and impedance analyses reveal that the failure is caused by silver diffusion in the ZB glass during sintering and highly accelerated life test. [source] Optimum step-stress accelerated life test plans for log-location-scale distributionsNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 6 2008Haiming Ma Abstract This article presents new tools and methods for finding optimum step-stress accelerated life test plans. First, we present an approach to calculate the large-sample approximate variance of the maximum likelihood estimator of a quantile of the failure time distribution at use conditions from a step-stress accelerated life test. The approach allows for multistep stress changes and censoring for general log-location-scale distributions based on a cumulative exposure model. As an application of this approach, the optimum variance is studied as a function of shape parameter for both Weibull and lognormal distributions. Graphical comparisons among test plans using step-up, step-down, and constant-stress patterns are also presented. The results show that depending on the values of the model parameters and quantile of interest, each of the three test plans can be preferable in terms of optimum variance. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 [source] Study on constant stress: Accelerated life tests of fouling thermal resistanceHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2006Yang Shan-rang Abstract To shorten the time of fouling tests, fouling life was defined. The statistical analysis method for type II-censored exponential life data under constant-stress accelerated life testing models and the accelerated coefficients a and b were obtained. By using an accelerated model, the estimators of the fouling life under usual stress could be obtained. A computing example was given. Results indicated that it is credible and feasible to perform accelerated life tests of asymptotic fouling thermal resistance, and will be of important value to experimental research of fouling. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 110,114, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20105 [source] Designing an accelerated degradation experiment by optimizing the estimation of the percentileQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 3 2003Hong-Fwu Yu Abstract Degradation tests are widely used to assess the reliability of highly reliable products which are not likely to fail under traditional life tests or accelerated life tests. However, for some highly reliable products, the degradation may be very slow and hence it is impossible to have a precise assessment within a reasonable amount of testing time. In such cases, an alternative is to use higher stresses to extrapolate the product's reliability at the design stress. This is called an accelerated degradation test (ADT). In conducting an ADT, several decision variables, such s the inspection frequency, sample size and termination time, at each stress level are influential on the experimental efficiency. An inappropriate choice of these decision variables not only wastes experimental resources but also reduces the precision of the estimation of the product's reliability at the use condition. The main purpose of this paper is to deal with the problem of designing an ADT. By using the criterion of minimizing the mean-squared error of the estimated 100th percentile of the product's lifetime distribution at the use condition subject to the constraint that the total experimental cost does not exceed a predetermined budget, a nonlinear integer programming problem is built to derive the optimal combination of the sample size, inspection frequency and the termination time at each stress level. A numerical example is provided to illustrate the proposed method. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||