life tests
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Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 95
Author(s):  
Chu-Chin Hsieh ◽  
Jyong-Sian Tsai ◽  
Hwo-Shuenn Sheu ◽  
Jen-Ray Chang

V2O5/NaY-SiO2 adsorbents were prepared by soaking up vanadium oxalate precursors into pellet NaY-SiO2. The NaY-SiO2 supports were prepared from NaY-SiO2 dough followed by extrusion and calcination at 450 °C. Ethanol was used as a model adsorbate to test the performance of the adsorbents. The regeneration efficacy, defined as the ratio of the adsorption capacity of a regenerated adsorbent to that of the fresh adsorbent, was investigated through the dynamics of fixed-bed adsorption (breakthrough curve). TPO, DSC, and FT-IR were used to characterize carbonaceous species on the adsorbents; meanwhile, synchrotron XRPD, XAS, and the N2 isotherm were used to characterize the zeolite, vanadia structure, and surface area, respectively. The results indicated that in low temperature (300 °C) regeneration, adsorption sites covered by alkylated aromatic coke formed during regeneration, causing adsorbent deactivation. In contrast, during regeneration at a high temperature (450 °C), the deactivation was caused by the destruction of the NaY framework concomitant with channel blockage, as suggested by the BET surface area combined with Rietvelt XRPD refinement results. In addition, the appearance of V-O-V contribution in the EXAFS spectra indicated the aggregation of isolated VO4, which led to a decrease in the combustion rate of the carbonaceous species deposited on the adsorbents. For regeneration at 350 and 400 °C, only trace coke formation and minor structural destruction were observed. Long-term life tests indicated that regeneration at 400 °C presents a higher maintenance of stability.


Author(s):  
Н.В. Сушкевич ◽  
Л.А. Казаковцев

В качестве оборудования ресурсных испытаний аккумуляторных батарей используется зарядно-разрядное устройство (ЗРУ). В данной статье проведен анализ статической погрешности ЗРУ, определена методическая ошибка, а также предложена методика определения коэффициентов разомкнутых контуров. The charging and discharging device (CDD) is used as the equipment for carrying out service life tests of accumulator batteries. In this article, we perform the analysis of the static error of the CDD, determine the methodological, and propose a method for determining the coefficients of open contours.


Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3206
Author(s):  
Yuan Ma ◽  
Wenhao Gui

In many survival analysis studies, the failure of a product may be attributed to one of several competing risks. In addition, if survival time is long, researchers can adopt accelerated life tests, causing devices to fail more quickly. One popular type of accelerated life tests is the step-stress test, and in this test, the stress level changes at a predetermined point time. The manner that stress levels change abruptly and increase discontinuously has been studied extensively. This paper considers a more realistic situation where the effect of stress increases cannot be achieved all at once, but with a lag time, and we propose a step-stress model consisting of two independent competing risks with a lag period in which the failure time caused by different risks at different stress levels obey Gompertz distribution, and the range of lag period is predetermined. The unknown parameters are estimated by maximum likelihood estimation and least squares estimation. For comparison, asymptotic confidence intervals and percentile bootstrap confidence intervals are constructed. By using Monte-Carlo simulations, we obtain the means and mean square errors of the maximum likelihood estimates and the least squares estimates, as well as the mean lengths and coverage rates of the two confidence intervals, which show the performance of various methods. Finally, in order to illustrate the model and proposed methods, we analyze a dataset from a solar energy experiment.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ayten Yiğiter ◽  
Canan Hamurkaroğlu ◽  
Nazan Danacıoğlu

PurposeAcceptance sampling plans are a decision-making process on the basis of a randomly selected sampling from a party, where it is not possible to completely scan the products for reasons such as time and cost being limited or the formation of damaged products during the inspection. For some products, the life span (time from beginning to failure) may be an important quality characteristic. In this case, the quality control adequacy of the products can be checked with an acceptance sampling plan based on the truncated life test with a censored scheme for the lifetime of the products. In this study, group acceptance sampling plans (GASPs) based on life tests are studied under the Type-I censored scheme for the compound Weibull-exponential (CWE) distribution.Design/methodology/approachGASPs based on life tests under the Type-I censored scheme for the CWE distribution are developed by using both the producer's risk and the consumer's risk.FindingsIn this study, optimum sample size, optimum number of groups and acceptance number are obtained under the Type-I censored scheme for the CWE distribution. Real data set illustration is given to show GASPs how to be used for the industry applications.Originality/valueDifferent from acceptance sampling plans with just considering the producer's risk, GASPs are constructed by using two-point approach included both the producer's risk and the consumer's risk for CWE distribution.


2021 ◽  
Vol 2144 (1) ◽  
pp. 012025
Author(s):  
I V Blinkov ◽  
A P Demirov ◽  
D S Belov ◽  
A V Chernogor

Abstract The paper presents results of life tests in machining titanium alloy with cutting carbide tool with Ti-Mo-Al-Ni-Si-N, (Ti, Al) N coatings and without it. Shown, that tool life with first coatings is 1.8 and 3.6 times higher than tool with second coatings and simple carbide tool,respectively.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2041
Author(s):  
Mansour Shrahili ◽  
Amer I. Al-Omari ◽  
Naif Alotaibi

In this paper, acceptance sampling plans (ASPs) are proposed for the new Weibull-Pareto distribution (NWPD) percentiles assuming truncated life tests at a pre-determined time. The minimum sample sizes essential to assert the specified percentile are calculated for a given consumer’s risk. The operating characteristic function values of the developed ASPs and producer’s risk are provided. A real data set related to the breaking stress of carbon fibers data are presented for illustration.


Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2112
Author(s):  
Ahmed Elshahhat ◽  
Berihan R. Elemary

Censoring mechanisms are widely used in various life tests, such as medicine, engineering, biology, etc., as they save (overall) test time and cost. In this context, we consider the problem of estimating the unknown xgamma parameter and some survival characteristics, such as reliability and failure rate functions in the presence of adaptive type-II progressive hybrid censored data. For this purpose, the maximum likelihood and Bayesian inferential approaches are used. Using the observed Fisher information under s-normal approximation, different asymptotic confidence intervals for any function of the unknown parameter were constructed. Using the gamma flexible prior, Bayes estimators against the squared-error loss were developed. Two procedures of Bayesian approximations—Lindley’s approximation and Metropolis–Hastings algorithm—were used to carry out the Bayes estimates and to construct the associated credible intervals. An extensive simulation study was implemented to compare the performance of the different methods. To validate the proposed methodologies of inference—two practical studies using datasets that form engineering and chemical fields are discussed.


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