Browsing Mathematics, Statistics & Physics by Title
Now showing items 545-564 of 676
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Production of sensitive gas sensors using CuO/SnO2 nanoparticles
( Springer Verlag , 2019 , Article)Metal oxide nanoparticles, such as CuO and SnO2, are outstanding systems for H2S gas sensing in air. In this work, those nanoparticles were deposited with different mixing percentages on substrates to form percolating ... -
Production Of Size-selected Copper Nanoclusters For Petroleum Refinery Applications
( Hamad bin Khalifa University Press (HBKU Press) , 2014 , Conference Paper)Atomic nanoclusters exhibit large surface to volume ratio which enhances their ability to interact with external materials, thus, they can be utilized efficiently for catalysts and gas sensing applications. Copper (Cu) ... -
Proposing a Nondestructive and Intelligent System for Simultaneous Determining Flow Regime and Void Fraction Percentage of Gas-Liquid Two Phase Flows Using Polychromatic X-Ray Transmission Spectra
( Springer , 2021 , Article)Two phase flows are of particular importance in various research fields. In the current article, a novel system consists of an X-ray tube and one sodium iodide crystal detector with ability of determining type of flow ... -
Protection from previous natural infection compared with mRNA vaccination against SARS-CoV-2 infection and severe COVID-19 in Qatar: a retrospective cohort study
( Elsevier , 2022 , Article)BackgroundUnderstanding protection conferred by natural SARS-CoV-2 infection versus COVID-19 vaccination is important for informing vaccine mandate decisions. We compared protection conferred by natural infection versus ... -
Protection of Omicron sub-lineage infection against reinfection with another Omicron sub-lineage
( Nature Research , 2022 , Article)There is significant genetic distance between SARS-CoV-2 Omicron (B.1.1.529) variant BA.1 and BA.2 sub-lineages. This study investigates immune protection of infection with one sub-lineage against reinfection with the other ... -
Pt-Based Nanostructures for Electrochemical Oxidation of CO: Unveiling the Effect of Shapes and Electrolytes
( MDPI , 2022 , Article)Direct alcohol fuel cells are deemed as green and sustainable energy resources; however, CO-poisoning of Pt-based catalysts is a critical barrier to their commercialization. Thus, investigation of the electrochemical CO ... -
Pt-doped armchair graphene nanoribbon as a promising gas sensor for CO and CO2: DFT study
( Elsevier , 2021 , Article)In this work, four armchair graphene nanoribbon (AGNR) based sensor materials were built using Atomistic ToolKit Virtual NanoLab (ATK-VNL) and utilized to detect carbon monoxide (CO) and carbon dioxide (CO2) gases. First, ... -
Quadratic problems with two quadratic constraints: Convex quadratic relaxation and strong lagrangian duality
( EDP Sciences , 2021 , Article)In this paper, we study a nonconvex quadratic minimization problem with two quadratic constraints, one of which being convex. We introduce two convex quadratic relaxations (CQRs) and discuss cases, where the problem is ... -
Quantization of the Szekeres system
( Institute of Physics Publishing , 2018 , Article)We study the quantum corrections on the Szekeres system in the context of canonical quantization in the presence of symmetries. We start from an effective point-like Lagrangian with two integrals of motion, one corresponding ... -
Radioactivity levels in the marine environment along the Exclusive Economic Zone (EEZ) of Qatar
( Elsevier , 2015 , Article)A study on 137Cs, 40K, 226Ra, 228Ra, and 238U was carried out along the EEZ of Qatar. Results serve as the first ever baseline data. The level of 137Cs (mean value 1.6 ± 0.4 Bq m 3) in water filters was found to be in the ... -
Radon concentration determination in some dwellings of Doha city of Qatar
( Elsevier , 1997 , Article)Yearly average radon concentrations have not been reported yet in Qatar. Only few measurements on indoor radon concentrations have been conducted during the autumn season in 1992. To complete these measurements a determination ... -
Re-emission of slow positrons from tungsten at elevated temperatures
( Elsevier , 2002 , Conference Paper)A series of measurements have been made on the dependence of the intensity and energy spectrum of slow positrons re-emitted from polycrystalline tungsten foil held at temperatures of up to 500 °C. Irrespective of target ... -
Rectangular eigenvalue problems
( Springer , 2022 , Article)Often the easiest way to discretize an ordinary or partial differential equation is by a rectangular numerical method, in which n basis functions are sampled at m ≫ n collocation points. We show how eigenvalue problems can ... -
Refined Inference on the Scale Parameter of the Generalized Logistic Distribution Based on Adjusted Profile Likelihood Functions
( MDPI , 2022 , Article)We consider inference based on the profile likelihood function for the scale parameter of the generalized logistic distribution. This distribution is a generalization of the logistic distribution, a symmetric distribution ... -
Regression estimator under inverse sampling to estimate arsenic contamination
( John Wiley & Sons, Ltd , 2011 , Article)The fate of arsenic introduced to the environment as a result of the natural and human activities is an important issue. Surveys of arsenic typically involve sampling from a large area. Measuring arsenic concentrations in ... -
Regression-type estimators for adaptive two-stage sequential sampling
( Springer , 2013 , Article)Adaptive two-stage sequential sampling (ATSSS) design was developed to observe more rare units and gain higher efficiency, in the sense of having a smaller variance estimator, than conventional sampling designs with equal ... -
Relative infectiousness of SARS-CoV-2 vaccine breakthrough infections, reinfections, and primary infections.
( Springer , 2022 , Article)SARS-CoV-2 breakthrough infections in vaccinated individuals and in those who had a prior infection have been observed globally, but the transmission potential of these infections is unknown. The RT-qPCR cycle threshold ... -
Response Surface Methodology for Optimization of Operational Parameters to Remove Ciprofloxacin from Contaminated Water in the Presence of a Bacterial Consortium
( American Chemical Society , 2022 , Article)Ciprofloxacin (CFX) is a broad-spectrum fluoroquinolone antibiotic that is widely used to treat bacterial infections in humans and other animals. However, its unwanted occurrence in any (eco)system can affect nontarget ... -
A review on lithium recovery using electrochemical capturing systems
( Elsevier , 2021 , Article Review)Resource recovery from natural reserves is appealing and Li extraction from different brines is in the forefront. Li extraction by membranes is reviewed in the literature much more than electrochemical processes. However, ... -
Revisited carmichael's reduced totient function
( MDPI AG , 2021 , Article)The modified Totient function of Carmichael ?(.) is revisited, where important properties have been highlighted. Particularly, an iterative scheme is given for calculating the ?(.) function. A comparison between the Euler ...
