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Fully developed forced convection through semi-elliptic ducts

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Applied mathematics and Mechanics(English Edition) 2016年第1期37卷 37-44页

作者： R.ALASSAR department of mathematics and Statistics King Fahd University of Petroleum and Minerals

An exact solution of the problem of fully developed forced convection through semi-elliptic ducts is obtained under constant axial heat flux and peripherally uniform temperature. The solution is validated by comparing... 详细信息

关键词： convection semi-elliptic duct

Dynamic Interaction Analysis of Coupled Axial-Torsional-Lateral Mechanical Vibrations in Rotary Drilling Systems

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Structural Durability & Health Monitoring 2025年第1期19卷 77-103页

作者： Sabrina Meddah Sid Ahmed Tadjer Abdelhakim Idir Kong Fah Tee Mohamed Zinelabidine Doghmane Madjid Kidouche Applied Automation Laboratory Faculty of Hydrocarbons and ChemistryUniversity of BoumerdesBoumerdes35000Algeria Institute of Electrical and Electronic Engineering(IGEE) University of BoumerdesBoumerdes35000Algeria Laboratory of the Electrification of Industrial Enterprises University of BoumerdesBoumerdes35000Algeria Electrical Engineering department Mohamed Boudiaf University of M’silaM’sila28000Algeria department of Civil and Environmental Engineering King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Interdisciplinary Research Center for Construction and Building Materials King Fahd University of Petroleum&Minerals(KFUPM)Dhahran31261Saudi Arabia

Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and *** achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is *** study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling *** study speciﬁcally investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency *** events not only hinder the efﬁciency of drilling but also lead to exhaustion and harm to the system’s components since they are difﬁcult to be detected and controlled in real *** study investigates the dynamic interactions of these vibrations,speciﬁcally in their high-frequency modes,usingﬁeld data obtained from measurement while ***ﬁndings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem *** obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control ***,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect ***,by exploiting theseﬁndings,the assessment of structural resilience in rotary drilling systems can be ***,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efﬁciency of rotary drilling systems in the petroleum industry.

关键词： Rotary drilling systems mechanical vibrations structural durability dynamic interaction analysis ﬁeld data analysis

Energy Decay in Thermoelasticity with Viscoelastic Damping of General Type

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Acta Mathematica Sinica,English Series 2015年第2期31卷 331-344页

作者： Muhammad I.MUSTAFA King fahd university of petroleum and minerals Department of Mathematics and Statistics

In this paper we consider an n-dimensional thermoelastic system with viscoelastic damping. We establish an explicit and general decay rate result without imposing restrictive assumptions on the behavior of the relaxation function at infinity. Our result allows a larger class of relaxation functions and generalizes previous results existing in the literature.

关键词： Thermoelasticity viscoelastic damping general decay convexity

FRACTIONAL HALANAY INEQUALITY AND APPLICATION IN NEURAL NETWORK THEORY

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Acta Mathematica Scientia 2019年第6期39卷 1605-1618页

作者： Nasser-eddine TATAR King fahd university of petroleum and minerals Department of Mathematics and Statistics

The (integer order) Halanay inequality with distributed delays is extended to the fractional order case. It is proved that solutions decay to zero as a Mittag-Leffler function as time goes to infinity provided that the delay feedback are bounded by similar *** application to a problem arising in neural network theory is provided showing that the equilibrium is Mittag-Leffler stable.

关键词： Hopfield neural network Mittag-Leffler stability Caputo fractional derivative fractional Halanay inequality

Recovering of Damping Coefficients for a System of Coupled Wave Equations with Neumann Boundary Conditions:Uniqueness and Stability

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Chinese Annals of mathematics,Series B 2011年第5期32卷 669-698页

作者： Roberto TRIGGIANI department of mathematics University of Virginia department of mathematics and Statistics King Fahd University of Petroleum and Minerals

The authors study the inverse problem of recovering damping coefficients for two coupled hyperbolic PDEs with Neumann boundary conditions by means of an additional measurement of Dirichlet boundary traces of the two solutions on a suitable, explicit subportion F1 of the boundary F, and over a computable time interval T 〉 0. Under sharp conditions on Г0= Г／Г1, T 〉 0, the uniqueness and stability of the damping coefficients are established. The proof uses critically the Carleman estimate due to Lasiecka et al. in 2000, together with a convenient tactical route ＂post-Carleman estimates＂ suggested by Isakov in 2006.

关键词： Inverse problem Coupled wave equations Carleman estimate

Conformal Killing Vectors in LRS Bianchi Type Ⅴ Spacetimes

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Communications in Theoretical Physics 2016年第3期65卷 315-320页

作者： Suhail Khan Tahir Hussain Ashfaque H.Bokhari Gulzar Ali Khan department of mathematics University of Peshawar department of mathematics and Statistics King Fahd University of Petroleum and Minerals

In this note,we investigate conformal Killing vectors(CKVs)of locally rotationally symmetric(LRS)Bianchi type V *** to some integrability conditions,CKVs up to implicit functions of(t,x)are *** these integrability conditions in some particular cases,the CKVs are completely determined,obtaining a classification of LRS Bianchi type V *** inheriting conformal Killing vectors of LRS Bianchi type V spacetimes are also discussed.

关键词： conformal Killing vectors Homothetic vectors conformally flat metrics

Spark plasma and microwave sintering of Al6061 and Al2124 alloys

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International Journal of minerals,Metallurgy and Materials 2013年第2期20卷 152-159页

作者： Nouari Saheb1 department of Mechanical Engineering King Fahd University of Petroleum & Minerals Center of Excellence in Nanotechnology King Fahd University of Petroleum & Minerals

Despite the importance of aluminum alloys as candidate materials for applications in aerospace and automotive industries, very little work has been published on spark plasma and microwave processing of aluminum alloys. In the present work, the possibility was explored to process A12124 and A16061 alloys by spark plasma and microwave sintering techniques, and the microstructures and properties were compared. The alloys were sintered for 20 rain at 400, 450, and 500℃. It is found that compared to microwave sintering, spark plasma sintering is an effective way to obtain homogenous, dense, and hard alloys. Fully dense （100%） A16061 and A12124 alloys were obtained by spark plasma sintering for 20 rain at 450 and 500℃, respectively. Maximum relative densities were achieved for A16061 （92.52%） and A12124 （93.52%） alloys by microwave sintering at 500℃for 20 min. The Vickers microhardness of spark plasma sintered samples increases with the increase of sintering temperature from 400 to 500℃, and reaches the values of Hv 70.16 and Hv 117.10 for A16061 and A12124 alloys, respectively. For microwave siutered samples, the microhardness increases with the increase of sintering temperature from 400 to 450℃, and then decreases with the further increase of sintering temperature to 500~C.

关键词： aluminum alloys spark plasma sintering microwave sintering microstructure hardness density

Biogenic amino acid methionine-based corrosion inhibitors of mild steel in acidic media

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International Journal of minerals,Metallurgy and Materials 2019年第4期26卷 467-482页

作者： L.K.M.O.Goni M.A.Jafar Mazumder S.A.Ali M.K.Nazal H.A.Al-Muallem Chemistry department King Fahd University of Petroleum and Minerals

N,N-Diallyl methionine ethyl ester hydrochloride 5 underwent alternating copolymerization with SO_2 via the Butler cyclopolymerization protocol in dimethyl sulfoxide(DMSO) to give water-soluble cycloterpolymer 6 with a ～1:1 molar ratio of sulfide and sulfoxide groups as a result of oxygen transfer from DMSO. Half of the sulfide groups in 6, upon oxidation with H_2O_2, afforded polymer sulfoxide 7 and polymer sulfone 8. The solution properties of these polymers were determined via a viscometric technique. The thermal stability of these polymers was determined by thermogravimetric analysis. The inhibition efficiency obtained from gravimetric mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques agreed well with each other. The corrosion efficiencies increase with increasing concentration of the polymers. At a polymer concentration of 175 mM, the maximum inhibition efficiency of copolymer compounds 6–8 was determined to be 92%, 97%, and 95%, respectively. The synthesized polymer compounds acted as mixed-type inhibitors. Polymer compound 7 adsorbed onto the metal surface via chemisorption and physisorption and obeyed Langmuir, Temkin, and Freundlich adsorption isotherms. Analyses by X-ray photoelectron spectroscopy and scanning electron microscopy–energy-dispersive X-ray spectroscopy indicated that the adsorbed polymers formed a thin film on the metal surface and prevented further corrosive attack.

关键词： cyclopolymerization methionine methionine sulfoxide methionine sulfone diallylamine salt corrosion inhibition

IMC based robust PID controller tuning for disturbance rejection

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Journal of Central South university 2016年第3期23卷 581-597页

作者： Mohammad Shamsuzzoha department of Chemical Engineering King Fahd University of Petroleum and Minerals

It is well-known that the IMC-PID controller tuning gives fast and improved set point response but slow disturbance rejection. A modification has been proposed in IMC-PID tuning rule for the improved disturbance rejection. For the modified IMC-PID tuning rule, a method has been developed to obtain the IMC-PID setting in closed-loop mode without acquiring detailed information of the process. The proposed method is based on the closed-loop step set point experiment using a proportional only controller with gain K_(c0). It is the direct approach to find the PID controller setting similar to classical Ziegler-Nichols closed-loop method. Based on simulations of a wide range of first-order with delay processes, a simple correlation has been derived to obtain the modified IMC-PID controller settings from closed-loop experiment. In this method, controller gain is a function of the overshoot obtained in the closed loop set point experiment. The integral and derivative time is mainly a function of the time to reach the first peak(overshoot). Simulation has been conducted for the broad class of processes and the controllers were tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms, in order to obtain a reasonable comparison. The PID controller settings obtained in the proposed tuning method show better performance and robustness with other two-step tuning methods for the broad class of processes. It has also been applied to temperature control loop in distillation column model. The result has been compared to the open loop tuning method where it gives robust and fast response.

关键词： PI/PID controller step test closed-loop response IMC-PID overshoot