Browsing Mathematics, Statistics & Physics by Title

Now showing items 564-583 of 676

    • 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 ...

    • Run Rules-Based EWMA Charts for Efficient Monitoring of Profile Parameters 

      Yeganeh, Ali; Shadman, Ali Reza; Triantafyllou, Ioannis S.; Shongwe, Sandile Charles; Abbasi, Saddam Akber ( Institute of Electrical and Electronics Engineers Inc. , 2021 , Article)
      In usual quality control methods, the quality of a process or product is evaluated by monitoring one or more quality characteristics using their corresponding distributions. However, when the quality characteristic is ...

    • Sampling of Multiple Variables Based on Partially Ordered Set Theory 

      Panahbehagh, Bardia; Bruggemann, Rainer; Salehi, Mohammad ( Iranian Statistical Society , 2021 , Article)
      We introduce a new method for ranked set sampling with multiple criteria. The method relaxes the restriction of selecting just one individual variable from each ranked set. Under the new method for ranking, units are ranked ...

    • SARS-CoV-2 antibody-positivity protects against reinfection for at least seven months with 95% efficacy 

      Laith J., Abu-Raddad; Chemaitelly, Hiam; Coyle, Peter; Malek, Joel A.; Ahmed, Ayeda A.; ... more authors ( Elsevier , 2021 , Article)
      Background Reinfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been documented, raising public health concerns. SARS-CoV-2 reinfections were assessed in a cohort of antibody-positive persons ...

    • SARS-CoV-2 infection hospitalization, severity, criticality, and fatality rates in Qatar 

      Seedat, Shaheen; Chemaitelly, Hiam; Ayoub, Houssein H.; Makhoul, Monia; Mumtaz, Ghina R.; ... more authors ( Nature Research , 2021 , Article)
      The SARS-CoV-2 pandemic resulted in considerable morbidity and mortality as well as severe economic and societal disruptions. Despite scientific progress, true infection severity, factoring both diagnosed and undiagnosed ...

    • SEIRD model for Qatar COVID-19 outbreak: A case study 

      Ghanam, Ryad; Boone, Edward L.; Abdel-Salam, Abdel Salam G. ( Intercollegiate Biomathematics Alliance , 2021 , Article)
      The COVID-19 outbreak of 2020 has required many governments to develop mathematical-statistical models of the outbreak for policy and planning purposes. This work provides a tutorial on building a compartmental model using ...

    • Selective gas sensors using graphene and CuO nanorods 

      Ayesh A.I.; Ahmed R.E.; Al-Rashid M.A.; Alarrouqi R.A.; Saleh B.; ... more authors ( Elsevier B.V. , 2018 , Article)
      This work reports on the fabrication of sensitive and selective gas sensors fabricated using graphene and/or copper oxide (CuO) nanorods. Herein, three batches of sensors were produced based on graphene/SiO2/Si, CuO nanorods, ...

    • Selective H2S sensor based on CuO nanoparticles embedded in organic membranes 

      Ayesh, Ahmad I.; Abu-Hani, Ayah F. S.; Mahmoud, Saleh T.; Haik, Yousef ( Elsevier B.V. , 2016 , Article)
      We report on H2S gas sensors based on CuO nanoparticles that are embedded within polymer membranes of poly-vinyl-alcohol (PVA) and glycerol ionic liquid (IL). The nanoparticles were fabricated by the colloid microwave ...

    • Selective hydrogen gas sensor using CuFe 2 O 4 nanoparticle based thin film 

      Haija, Mohammad Abu; Ayesh, Ahmad I.; Ahmed, Sadiqa; Katsiotis, Marios S. ( Elsevier B.V. , 2016 , Article)
      Hydrogen gas sensors based on CuFe2O4 nanoparticle thin films are presented in this work. Each gas sensor was prepared by depositing CuFe2O4 thin film on a glass substrate by dc sputtering inside a high vacuum chamber. ...

    • Self-implantation of Cz-Si: Clustering and annealing of defects 

      Abdulmalik, D. A.; Coleman, P. G.; Al-Qaradawi, I. Y. ( Elsevier , 2006 , Article)
      Observations of vacancy clusters formed in Czochralski (Cz) Si after high energy ion implantation are reported. Vacancy clusters were created by 2 MeV Si ion implantation of 1 × 10 15 ions/cm 2 and after annealing between ...

    • Semiparametric MEWMA for Phase II profile monitoring 

      Nassar, Sara H.; Abdel-Salam, Abdel-Salam G. ( John Wiley and Sons Ltd , 2021 , Article)
      A control chart is one of the statistical process techniques that is used to monitor different processes. Some processes are characterized by functions or profiles, and a profile is a functional relationship between the ...

    • Sensitive SO2 gas sensor utilizing Pt-doped graphene nanoribbon: First principles investigation 

      Salih, Ehab; Ayesh, Ahmad I. ( Elsevier Ltd , 2021 , Article)
      The objective of this work is to seek a highly sensitive gas sensor for the detection of sulfur dioxide (SO2) by investigating the impacts of passivation as well as metal doping of armchair-edge graphene nanoribbon (AGNR) ...