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Testing Whether a Survival Distribution is Better Mean Residual Life at Age $t_0$
Alwasel Ibrahim A.,El-Bassiouny Ahmed H. The Korean Reliability Society 2006 International Journal of Reliability and Applicati Vol.7 No.1
The better mean residual life at $t_0\;(BMRL-t_0)$ class of life distribution is introduced by Kulasekara and Park (1987). They proved that the $BMRL-t_0$ class contains the DMRL class, but it is a proper subclass of the NBUE class. In this paper we develop a new family of tests for testing exponentiality against the $BMRL-t_0\;(WMRL-t_0)$ alternatives based on the goodness of fit approach. It is shown that the suggested test is better than the one introduced by Kulasekara and Park (1987) in the sense of Pitman asymptotic efficiency values.
Statistical Inference of Some Semi-Markov Reliability Models
Alwasel, I.A. The Korean Reliability Society 2008 International Journal of Reliability and Applicati Vol.9 No.2
The objective of this paper is to discuss the stochastic analysis and the statistical inference of a three-states semi-Markov reliability model. Using the maximum likelihood procedure, the parameters included in this model are estimated. Based on the assumption that the lifetime and repair time of the system are gener-alized Weibull random variables, the reliability function of this system is obtained. Then, the distribution of the first passage time of this system is derived. Many important special cases are discussed. Finally, the obtained results are compared with those available in the literature.
A Goodness of Fit Approach to Major Lifetesting Problems
Ahmad, Ibrahim A.,Alwasel, Ibrahim A.,Mugdadi, A.R. The Korean Reliability Society 2001 International Journal of Reliability and Applicati Vol.2 No.2
Lifetesting problems have been the subject of investigations for over three decades. Most suggested approaches are markedly different from those used in the related but wider goodness of fit problems. In the current investigation, it is demonstrated that a goodness of fit approach is possible in many lifetesting problems and that It results in simpler procedures that are asymptotically equivalent or better than standard ones. They may also have superior finite sample behavior. Several perennial classes are addressed here. The class of increasing failure rate (IFR) and the class of new better than used (NBU) are addressed first. In addition, we provide testing for a newer and practical class of new better than used in convex ordering (NBUC) due to Cao and Wang (1991). Other classes can be developed similarly and this point is illustrated with the classes of new better than used in expectation (NBUE) and harmonic new better than used in expectation (HNBUE).
Afsun Sujayev,Nastaran Sadeghian,Parham Taslimi,Namık Kılınç,Musa Akkuş,Burak Özçelik,Vagif Farzaliyev,Saleh H. Alwasel,İlhami Gülçin 한국고분자학회 2024 Macromolecular Research Vol.32 No.6
Phenylthiourea was synthesized for the first time with a yield of 75–80% based on thiourea, in the presence of various catalysts, and optimal conditions were identified for some reactions. At the same time, the condensation of their methylene-active molecules and various aldehydes in acidic media caused the synthesis of di-, tetra-, hexahydropyrimidinethiones, which are not known in the literature so far; the role of different catalysts in this process were comparatively studied. Synthesis of heterocyclic compounds containing phenol hydroxyl, mono-, dual-, triple-amine, -thion, and hydroxyl groups in the presence of ionic liquids, CCl3COOH CF3COOH, NiCl2.6H2O catalysts as well as in the increase of yield percentages showed that the use of environmentally and economically efficient ionic liquids among these catalysts allows to obtain purposeful compounds with the highest yield (95%). The inhibition of α-glycosidase, aldose reductase, and α-amylase enzymes by functionally substituted derivatives of thiourea and phenylthiourea (1a–1f) is then observed. Compound 1d displayed the lowest inhibitory effect against AR in these series with an IC50 value of 3.25 μM, whereas compound 1c compound displayed the highest inhibitory effect with an IC50 value of 1.46 μM. The enzymes α-amylase and α-glycosidase were also easily inhibited by these substances. All substances were examined for their capacity to inhibit the α-glycosidase enzyme, with Ki values ranging between 14.321.53 and 29.322.50 μM and IC50 values between 12.23 and 25.22 μM. Additionally, the IC50 values for the effective inhibition profile of the α-amylase, which was determined vary from 1.02 to 7.87 μM.