Browsing by Author "Kumar, Upendra"

Now showing 1 - 5 of 5
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    Confidence intervals for the reliability characteristics via different estimation methods for the power Lindley model
    (Gnedenko Forum, 2022) Yadav, Abhimanyu S.; Vishwakarma, P.K.; Bakouch, H.S.; Kumar, Upendra; Chauhan, S.
    In this article, classical and Bayes interval estimation procedures have been discussed for the reliability characteristics, namely mean time to system failure, reliability function, and hazard function for the power Lindley model and its special case. In the classical part, maximum likelihood estimation, maximum product spacing estimation are discussed to estimate the reliability characteristics. Since the computation of the exact confidence intervals for the reliability characteristics is not directly possible, then, using the large sample theory, the asymptotic confidence interval is constructed using the above-mentioned classical estimation methods. Further, the bootstrap (standard-boot, percentile-boot, students t-boot) confidence intervals are also obtained. Next, Bayes estimators are derived with a gamma prior using squared error loss function and linex loss function. The Bayes credible intervals for the same characteristics are constructed using simulated posterior samples. The obtained estimators are evaluated by the Monte Carlo simulation study in terms of mean square error, average width, and coverage probabilities. A real-life example has also been illustrated for the application purpose. � 2022 Reliability: Theory and Applications. All rights reserved.
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    Copper-Catalyzed Chemoselective O-Aroylation of Phenolic Oxime Ethers with Aryl Aldehydes
    (John Wiley and Sons Inc, 2021) Kumar, Upendra; Sharma, Ajay; Kumar, Naveen; Kumar Pandey, Satyendra
    Copper-catalyzed oxidative O-aroylation of phenolic oxime ethers with a wide range of aromatic aldehydes are described. This approach offers an efficient synthesis of phenolic oxime ether esters in good to excellent yields. � 2021 Wiley-VCH GmbH
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    Copper-catalyzed chemoselective oxidative o-aroylation of 2-acetylphenols, alkyl salicylates and 1,3-dicarbonyl compounds using styrene derivatives
    (Elsevier Ltd, 2021) Kumar, Upendra; Sharma, Ajay; Kumar, Naveen; Pandey, Satyendra Kumar
    A novel copper-catalyzed chemoselective oxidative O-aroylation of 2-acetylphenols, alkyl salicylates and 1,3-dicarbonyl compounds with a wide range of styrene derivatives are described. This approach provides an efficient chemoselective preparation of phenol, alkyl salicylate and enol esters in good to excellent yields. This method represents an alternative protocol for the classical esterification reactions. � 2021 Elsevier Ltd
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    Multicomponent Reaction of CS2, Amines, and Sulfoxonium Ylides in Water: Straightforward Access to ?-Keto Dithiocarbamates, Thiazolidine-2-thiones, and Thiazole-2-thiones
    (American Chemical Society, 2023) Kumar, Naveen; Sharma, Ajay; Kumar, Upendra; Pandey, Satyendra Kumar
    Simple, versatile, and catalyst-free synthetic methods for ?-keto dithiocarbamates, thiazolidine-2-thiones, and thiazole-2-thiones via the multicomponent reaction of CS2, amines, and sulfoxonium ylides have been described. The ?-keto sulfoxonium ylides furnished ?-keto dithiocarbamates in the presence of CS2 and secondary amines, whereas primary amines afforded thiazolidine-2-thiones or thiazole-2-thiones after dehydration in an acidic environment. With simple procedures, the reaction has a wide substrate scope and excellent functional group tolerance. � 2023 American Chemical Society.
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    RIXS, XES and XAS studies for electronic structure of rare earth and alkaline earth modified manganite
    (Elsevier B.V., 2022) Abu-Samak, Mahmoud; Kumar, Upendra; Quraishi, A.M.; Kumar, Rajneesh; Kumar, Shalendra; Dalela, S.; Ahmad, M. Ayaz; Choudhary, B.L.; Alvi, P.A.
    This article reports on the RIXS (Resonant inelastic X-ray scattering), XES (X-ray emission spectroscopy), and XAS (X-ray absorption spectroscopy) of the LaSr2Mn2O7, La0.95Ba0.05MnO3, and La1.2(BaCa)1.8Mn2O7 at 40 K, 100 K and 300 K. The RIXS spectra of these samples show the presence of Mn in different valence states (Mn2+, Mn3+, and Mn4+) which is associated with the Jahn-Teller distortion due to overlapping between O2? and the unpaired electrons of transition metal Mn. It has also been noticed that the distortion observed in different valence states of Mn with O2? is found to be suppressed with dropping and the temperature. So, based on aforementioned studies, the Manganites have been considered as a strongly correlated magnetic system which would be useful in magnetic device applications. � 2021 Elsevier B.V.