Browsing Mathematics, Statistics & Physics by Title

Now showing items 553-572 of 676

    • Quantization of the Szekeres system 

      Paliathanasis A.; Zampeli A.; Christodoulakis T.; Mustafa M.T. ( 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 

      Al-Qaradawi, Ilham; Abdel-Moati, Mohamed; Al-Yafei, Mohsin Al-Ansi; Al-Ansari, Ebrahim; Al-Maslamani, Ibrahim; ... more authors ( 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 

      Arafa, W.; El-Karadawi, E. ( 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 

      Al-Qaradawi, I. Y.; Coleman, P. G. ( 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 

      Hashemi, Behnam; Nakatsukasa, Yuji; Trefethen, Lloyd N. ( 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 

      Baklizi, Ayman ( 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 

      Moradi, M.; Salehi, M.; Brown, J. A.; Karimi, N. ( 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 

      Salehi, Mohammad; Panahbehagh, Bardia; Parvardeh, Afshin; Smith, David R.; Lei, Yuancai ( 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. 

      Abu-Raddad, Laith J; Chemaitelly, Hiam; Ayoub, Houssein H; Tang, Patrick; Coyle, Peter; ... more authors ( 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 

      Shah, Syed Wajid Ali; Rehman, Mujaddad ur; Arslan, Muhammad; Abbasi, Saddam Akber; Hayat, Azam; ... more authors ( 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 

      Sifani, Zavahir; Elmakki, Tasneem; Gulied, Mona; Ahmad, Zubair; Al-Sulaiti, Leena; ... more authors ( 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 

      Belhaouari, S.B.; Hamdi, Y.; Hamdi, A. ( 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 ...

    • A rich learning lesson using the Poisson distribution 

      Al-Saleh, Mohammad Fraiwan ( Elsevier B.V. , 2007 , Article)
      In this note, we explore the rich information about inference that the Poisson distribution has. The source of this information is mainly the fact that the mean and variance of this distribution are equal.

    • Robust adaptive learning control for different classes of dissipative vehicle systems 

      Mabrok, M.A.; Tran, Vu Phi; Petersen, Ian R.; Garratt, Matthew A. ( Institute of Electrical and Electronics Engineers Inc. , 2022 , Conference Paper)
      This paper presents a methodology that leverages learning techniques and robust control theory to design an adaptive controller for a wide class of linear dynamical dissipative vehicle systems. In particular, learning ...

    • Robust Distribution-Free Hybrid Exponentially Weighted Moving Average Schemes Based on Simple Random Sampling and Ranked Set Sampling Techniques 

      Malela-Majika, Jean Claude; Shongwe, Sandile C.; Aslam, Muhammad; Abbasi, Saddam A. ( Hindawi , 2021 , Article)
      This paper proposes new nonparametric hybrid exponentially weighted moving average (HEWMA) control charts based on simple random sampling (SRS) and ranked set sampling (RSS) techniques using the Wilcoxon rank-sum W statistic. ...

    • Robust index-tracking and enhanced index-tracking in portfolio optimization 

      Khoshabar, N.A.; Salahi, M.; Lotfi, S.; Hamdi, A. ( Ascociacion Internacional de Economia Aplicada , 2020 , Article)
      We study index-tracking and enhanced index-tracking problems in portfolio optimization under interval uncertainty for returns and covariance matrix. The proposed robust counterparts for both models are in the form of second ...

    • Robust profile monitoring for phase II analysis via residuals 

      Nassar, Sara H.; Abdel-Salam, Abdel Salam G. ( Wiley , 2022 , Article)
      Many studies were conducted for fitting models using parametric and non-parametric techniques; in fact, their fits may be biased and have inflated the estimated variances when the model is misspecified, respectively. Thus, ...

    • Robust stabilization of LTI negative imaginary systems using the nearest negative imaginary controller 

      Mabrok, Mohamed; Abdelrahim, Mahmoud ( John Wiley and Sons Inc , 2023 , Article)
      This paper considers the problem of robust stabilization of linear time-invariant systems with respect to unmodelled dynamics and structure uncertainties. To that end, a methodology to find the nearest negative imaginary ...

    • Robustification of CUSUM control structure for monitoring location shift of skewed distributions based on modified one-step M-estimator 

      Abdul Rahman, Ayu; Syed Yahaya, Sharipah Soaad; Atta, Abdu Mohammed Ali ( Taylor and Francis Inc. , 2019 , Article)
      Including three existing charts, a new approach employing a modified one-step M-estimator (MOM) with Cumulative Sum (CUSUM) control structure were evaluated and compared for their Phase II performances based on the average ...

    • Rough oscillatory singular integrals on ℝⁿ 

      Al-Qassem, Hussain Mohammad; Cheng, Leslie; Pan, Yibiao ( Instytut Matematyczny , 2014 , Article)
      We establish sharp bounds for oscillatory singular integrals with an arbitrary real polynomial phase P. The kernels are allowed to be rough both on the unit sphere and in the radial direction. We show that the bounds grow ...