Search

Abstract.Frailty and resilience models provide a way to introduce random effects in hazard and reversed hazard rate modeling by random variables, called frailty and resilience random variables, respectively, to account for unobserved or unexplained heterogeneity among experimental units. This article investigates the effects of frailty and resilience random variables on the baseline random variables using some shifted stochastic orders based on some ageing properties of the baseline random variables. Relevant examples are presented to illustrate the findings, and the applicability of the results is demonstrated with real-world data, highlighting their relevance in practical scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we establish some stochastic comparison results for largest claim amounts of two sets of independent and also for interdependent portfolios under the setup of the proportional odds model. We also establish stochastic comparison results for aggregate claim amounts of two sets of independent portfolios. Further, stochastic comparisons for largest claim amounts from two sets of independent multiple-outlier claims have also been studied. The results we obtained apply to the whole family of extended distributions, also known as the Marshall–Olkin family of distributions. We have given many numerical examples to illustrate the results obtained. [ABSTRACT FROM AUTHOR]

In this paper, we consider two finite mixture models (FMMs) with inverted-Kumaraswamy distributed components' lifetimes. Several stochastic ordering results between the FMMs are obtained. Mainly, we focus on three different cases in terms of the heterogeneity of parameters. The usual stochastic order between the FMMs is established when heterogeneity presents in one parameter as well as two parameters. In addition, we also study ageing faster order in terms of the reversed hazard rate between two FMMs when heterogeneity is in two parameters. For the case of heterogeneity in three parameters, we obtain the comparison results based on reversed hazard rate and likelihood ratio orders. The theoretical developments are illustrated using several examples and counterexamples. [ABSTRACT FROM AUTHOR]

An effective way to increase system reliability is to use redundancies (spares) into the systems either in component level or in system level. In this prospect, it is a significant issue that which set of available spares providing better system reliability in some stochastic sense. In this paper, we derive sufficient conditions under which a coherent system with a set of active redundancy at the component level or the system level provide better system reliability than that of the system with another set of redundancy, with respect some stochastic orders. We have derived the results for the component lifetimes following accelerated life (AL) model. The results obtained help us to design more reliable systems by allocating appropriate redundant components from the set of available options for the same. Various examples satisfying the sufficient conditions of the theoretical results are provided. Some results are illustrated with real‐world data. [ABSTRACT FROM AUTHOR]

This paper investigates stochastic comparisons of largest claim amounts of two sets of independent or interdependent portfolios in the sense of some stochastic orders. Let random variable Xi$$ {X}_i $$ (i=1,...,n$$ i=1,\dots, n $$) with distribution function F(x;αi)$$ F\left(x;{\alpha}_i\right) $$, represents the claim amount for ith risk of a portfolio. Here two largest claim amounts are compared considering that the claim variables follow a general semiparametric family of distributions having the property that the survival function F‾(x;α)$$ \overline{F}\left(x;\alpha \right) $$ is increasing in α$$ \alpha $$ or is increasing and convex/concave in α$$ \alpha $$. The results obtained in this paper apply to a large class of well‐known distributions including the family of exponentiated/generalized distributions (e.g., exponentiated exponential, Weibull, gamma and Pareto family), Rayleigh distribution and Marshall–Olkin family of distributions. As a direct consequence of some main theorems, we also obtained the results for scale family of distributions. Several numerical examples are provided to illustrate the results. [ABSTRACT FROM AUTHOR]

Dispersive order is a type of variability order for comparing the variability in probability distributions. Star order compares the skewness of probability distributions. This work considers dispersive and star orders of extreme order statistics from dependent random variables following the proportional odds (PO) model. The joint distribution of the random variables is modeled with Archimedean copula. Numerical examples are provided to illustrate the findings. [ABSTRACT FROM AUTHOR]

A fail-safe system is a (n − 1) -out-of-n system whose lifetime is represented by the second-order statistic. This work studies stochastic comparisons of lifetimes of fail-safe systems with dependent and heterogeneous components, where the components are subjected to random shocks instantaneously. The results are derived for a general semiparametric family of distributions of the component lifetimes. We derive sufficient conditions for the comparison results under the usual stochastic order, and we provide counterexamples to show that under those conditions, similar comparisons cannot be made under the hazard rate order. [ABSTRACT FROM AUTHOR]

This paper investigates medical device selection problem in healthcare organizations. As compared to numerous research works on supplier/equipment selection problems in diverse areas of applications, surprisingly, the number of works is less in case of the healthcare industry. In this paper, as a case study, we consider MRI (Magnetic Resonance Imaging) system selection problem in private hospitals. Because of non-radiation and advanced technology, MRI has emerged as the imaging modality of choice in diagnostic and monitoring treatment. In this study, we identify 16 brands (alternatives) of MRI systems and select 10 selection criteria that are chosen with the consultation of a group of experts in the field of hospital management. Methodological framework as suggested to deal with the device selection problem includes an integrated MCGDM (multi-criteria group decision-making) approach which is a combination of fuzzy PSI (preference selection index) method and fuzzy MARCOS (measurement of alternatives and ranking according to compromise solution) method. To cope with the vagueness in linguistic evaluation done by the decision makers, fuzzy numbers have been used in the representation of linguistic terms. The integrated fuzzy MCGDM method is applied to evaluate and rank the alternatives, and the results are analyzed through a comprehensive sensitivity analysis. Total 100 scenarios are created by changing the weight of each criterion as computed using fuzzy PSI technique to examine the effects of change of the weights of the criteria on the ranking results. It is observed that out of 100 scenarios, alternative 8 (A8) remains the best option for 96 scenarios, and it is the second-best option only for the remaining 4 scenarios. Also, the results of the hybrid fuzzy MCGDM technique have been compared with the results obtained by using other MCGDM methods. [ABSTRACT FROM AUTHOR]

In this paper, we establish some stochastic comparison results for two finite mixture models where the corresponding random variables follow one of the parental families of distributions, namely, proportional odds, proportional hazards, and proportional reversed hazards. The results of this paper are illustrated with numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, we investigate various stochastic orderings for series and parallel systems with independent and heterogeneous components having lifetimes following the proportional odds model. We also investigate comparisons between a system with heterogeneous components and that with homogeneous components. This paper also studies relative ageing orders for two systems in the framework of components having lifetimes following the proportional odds model. [ABSTRACT FROM AUTHOR]

Current industrial processes utilize Co/Mn bromides as catalysts to catalyze the oxidative conversion of para-xylene to terephthalic acid (TA) in acetic acid at high temperatures (>200 °C, air, 15–30 atm.). The decomposition of metallo-catalysts and solvents at high temperatures as well as a subsequent hydropurification process releases thousands of millions of tons of wastewater, global warming gas (CO2) and ozone depleting gas (CH3Br) into the global environment per year, causing global warming, ozone depletion, dramatic climate change, huge economic losses, and many other environmental problems. Herein, we report an alternative sustainable process with low energy demand for the room temperature oxidative conversion of p-xylene to terephthalic acid, with 96% TA yield and 98% selectivity, via ozone treatment and concurrent UV irradiation and without the generation and release of greenhouse gas (CO2), ozone depleting gas (CH3Br), and wastewater, or the need for a high energy-demand hydropurification process. The reaction mechanism involves the singlet O(1D)- and hydroxyl radical-mediated selective C–H functionalization of p-xylene. [ABSTRACT FROM AUTHOR]

Generally, in transportation problem, full vehicles (e.g., light commercial vehicles, medium duty and heavy duty trucks, etc.) are to be booked, and transportation cost of a vehicle has to be paid irrespective of the fulfilment of the capacity of the vehicle. Besides the transportation cost, total time that includes travel time of a vehicle, loading and unloading times of products is also an important issue. Also, instead of a single item, different types of items may need to be transported from some sources to destinations through different types of conveyances. The optimal transportation policy may be affected by many other issues like volume and weight of per unit of product, unavailability of sufficient number of certain types of vehicles, etc. In this paper, we formulate a multi-objective multi-item solid transportation problem by addressing all these issues. The problem is formulated with the transportation cost and time parameters as fuzzy variables. Using credibility theory of fuzzy variables, a chance-constraint programming model is formulated, and is then transformed into the corresponding deterministic form. Finally numerical example is provided to illustrate the problem. [ABSTRACT FROM AUTHOR]

The proportional odds model gives a method of generating new family of distributions by adding a parameter, called tilt parameter, to expand an existing family of distributions. The new family of distributions so obtained is known as Marshall–Olkin family of distributions or Marshall–Olkin extended distributions. In this paper, we consider Marshall–Olkin family of distributions in discrete case with fixed tilt parameter. We study different ageing properties, as well as different stochastic orderings of this family of distributions. All the results of this paper are supported by several examples. [ABSTRACT FROM AUTHOR]

This paper investigates multi-objective solid transportation problems (MOSTP) under various uncertain environments. The unit transportation penalties/costs are taken as random, fuzzy and hybrid variables respectively, in three different uncertain multi-objective solid transportation models and in each case, the supplies, demands and conveyance capacities are fuzzy. Also, apart from source, demand and capacity constraints, an extra constraint on the total budget at each destination is imposed. Chance-constrained programming technique has been used for the first two models to obtain crisp equivalent forms, whereas expected value model is formulated for the last. We provide an another approach using the interval approximation of fuzzy numbers for the first model to obtain its crisp form and compare numerically two approaches for this model. Fuzzy programming technique and a gradient based optimisation - generalised reduced gradient (GRG) method are applied to beget the optimal solutions. Three numerical examples are provided to illustrate the models and programming. [ABSTRACT FROM AUTHOR]

Phosgene is a very toxic gas, which was used as a chemical weapon in World War I, and is currently widely used in industrial processes. So far, no any phosgene fluorescent sensor has been reported. In this study, we report rational design of unimolecular fluorescent phosgene sensors for the first time. Phosgene was used to initiate intramolecular cyclization and convert noniluorescent molecules to highly fluorescent products. Bright blue fluorescence of phosgene reaction products can be easily visualized by naked eye. The detection limit for phosgene is as low as 1 nM in solutions at room temperature. [ABSTRACT FROM AUTHOR]

Antimony trichloride is an efficient catalyst for the cyclization of 2-amino chalcones to the corresponding 2-aryl-2,3-dihydroquinolin-4(1H)-ones under mild reaction conditions and in almost quantitative yields. [ABSTRACT FROM AUTHOR]

Indoles undergo conjugate addition with α,β-unsaturated ketones in the presence of a catalytic amount of antimony trichloride under refluxing condition to afford the corresponding Michael adduct in excellent yields. The substitution on the indole ring occurred exclusively at 3-position without a trace of any N-alkylated products. [ABSTRACT FROM AUTHOR]

Abstract: Antimony trichloride efficiently catalyses diastereoselective three-component reaction of urea, aromatic aldehydes and 2,3-dihydrofuran or 3,4-dihydro-2H-pyran leading to 4-arylhexahydrofuro[2,3-d]pyrimidin-2(3H)-ones and 4-arylhexahydro-1H-pyrano[2,3-d]pyrimidin-2(8aH)-ones, respectively in good yield. [ABSTRACT FROM AUTHOR]