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Determinants Of Contraceptive Practice In Oman By Using Multilevel Modeling, Moza S. Al-Balushi, Mohammed S. Ahmed, M. Mazharul Islam Apr 2025

Determinants Of Contraceptive Practice In Oman By Using Multilevel Modeling, Moza S. Al-Balushi, Mohammed S. Ahmed, M. Mazharul Islam

Sultan Qaboos University Journal For Science

In this paper, multilevel logistic regression models are developed for examining the hierarchical effects of contraceptive use and its selected determinants in Oman using the 2008 Oman National Reproductive Health Survey (ONRHS). Comparison between single level and multilevel logistic regression models has been made to examine the plausibility of multilevel effects of contraceptive use. From the multilevel logistic regression model analysis, it was found that there is real multilevel variation among contraceptive users in Oman. The results indicate that a multilevel logistic regression model is the best fit over ordinary multiple logistic regression models. Generally, this study revealed that women’s …

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Some Improved Estimators In Double Sampling Using Two Auxiliary Variables, Mohammad S. Ahmed Apr 2025

Some Improved Estimators In Double Sampling Using Two Auxiliary Variables, Mohammad S. Ahmed

Sultan Qaboos University Journal For Science

Dash and Mishra [1] suggested an improved class of estimators without defining the optimum estimator. However, they gave the wrong Taylor’s series expression of their class of estimator and their minimum mean squared error expressions are also incorrect. Here we show that Ahmed et al.’s [2] class of chain estimators is more efficient than Dash and Mishra’s [1], with minimum mean squared error.

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Hydromagnetic Boundary Layer Flow And Heat Transfer Characteristics Of A Nanofluid Over An Inclined Stretching Surface In The Presence Of A Convective Surface: A Comprehensive Study, Mohammad M. Rahman, Mohammed M. Al-Hatmi Apr 2025

Hydromagnetic Boundary Layer Flow And Heat Transfer Characteristics Of A Nanofluid Over An Inclined Stretching Surface In The Presence Of A Convective Surface: A Comprehensive Study, Mohammad M. Rahman, Mohammed M. Al-Hatmi

Sultan Qaboos University Journal For Science

In this paper we investigate numerically the hydromagnetic boundary layer flow and heat transfer characteristics of a nanofluid using three types of nanoparticles (copper, aluminium oxide and titanium dioxide) having various shapes (spherical, cylindrical, arbitrary, etc) by considering three kinds of base fluids (water, ethylene glycol and engine oil) over a nonlinear inclined stretching surface, taking into account the effect of convective surface condition. Using similarity transformations, the governing nonlinear partial differential equations of the physical model are transformed into non-dimensional ordinary differential equations which are solved for local similar solutions using the very robust computer algebra software, Maple 13. …

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Projection Of Polyhedra Onto Coxeter Planes Described With Quaternions, Mudhahir Al-Ajmi, Mehmet Koca, Hashima Bait Bu Salasel Apr 2025

Projection Of Polyhedra Onto Coxeter Planes Described With Quaternions, Mudhahir Al-Ajmi, Mehmet Koca, Hashima Bait Bu Salasel

Sultan Qaboos University Journal For Science

3-dimensional convex uniform polyhedra have been projected onto their corresponding Coxeter planes defined by the simple roots of the Coxeter diagram ,

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A Test For Dominance, Atsu S.S. Dorvlo Apr 2025

A Test For Dominance, Atsu S.S. Dorvlo

Sultan Qaboos University Journal For Science

In some selection situations a simple majority is not enough to indicate that one item dominates the others. In this paper we develop a simple procedure for testing the dominance of one item with respect to others in a multi option situation. Expressions are given for computing the relevant p-values. The procedure is illustrated.

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Homotopy Perturbation Method For Fractional Shallow Water Equations, Kamel Al-Khaled, M. K. Al-Safeen Apr 2025

Homotopy Perturbation Method For Fractional Shallow Water Equations, Kamel Al-Khaled, M. K. Al-Safeen

Sultan Qaboos University Journal For Science

In this paper, the homotopy perturbation method is adopted to find explicit and numerical solutions for systems of non-linear fractional shallow water equations. The fractional derivatives are described in the Caputo sense. We apply both the homotopy perturbation method and the homotopy analysis method, to solve certain shallow water equations with time-fractional derivatives, and explicitly construct convergent power series solutions. The results obtained reveal that these methods are both very effective and simple for finding approximate solutions. Some numerical examples and plots are presented to illustrate the efficiency and reliability of these methods.

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Velocity Profiles For Flow Of Omani Crude Oils And Other Liquids, Sayyadul Arafin, S. M. Mujibur Rahman Apr 2025

Velocity Profiles For Flow Of Omani Crude Oils And Other Liquids, Sayyadul Arafin, S. M. Mujibur Rahman

Sultan Qaboos University Journal For Science

Velocity profiles of Newtonian immiscible liquids undergoing laminar flow between two horizontal plates under pressure gradient are investigated using a momentum balance equation. The differential equation describing the flow has been solved and equations for the velocity profiles of a two-layer and three-layer liquid systems are presented. As examples, we show flow patterns of two-layer water-crude oil system and three-layer system involving water, tetrachloromethane, xylene, cyclopentane and hexane. A distinctive pattern is noticeable between the velocity profiles of heavy (API 19.19) and light (API 40.89) Omani crude oils.

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Dihedral Groups As Epimorphic Images Of Some Fibonacci Groups, Abdullahi Umar, Bashir Ali Apr 2025

Dihedral Groups As Epimorphic Images Of Some Fibonacci Groups, Abdullahi Umar, Bashir Ali

Sultan Qaboos University Journal For Science

The Fibonacci groups are defined by the presentation where , and all subscripts are assumed to be reduced modulo . In this paper we give an alternative proof that for , , and are all infinite by establishing a morphism (or group homomorphism) onto the dihedral group for all .

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Superstatistics In Random Matrix Theory, A.Y. Abul-Magd Apr 2025

Superstatistics In Random Matrix Theory, A.Y. Abul-Magd

Sultan Qaboos University Journal For Science

Random matrix theory (RMT) provides a successful model for quantum systems, whose classical counterpart has chaotic dynamics. It is based on two assumptions: (1) matrix-element independence, and (2) base invariance. The last decade witnessed several attempts to extend RMT to describe quantum systems with mixed regular-chaotic dynamics. Most of the proposed generalizations keep the first assumption and violate the second. Recently, several authors have presented other versions of the theory that keep base invariance at the expense of allowing correlations between matrix elements. This is achieved by starting from non-extensive entropies rather than the standard Shannon entropy, or by following …

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The Induction Of Electric Currents In A Conducting Spherical Cap With Geomagnetic Applications: A Semi-Analytical Approach For The Axisymmetric Case, A.A. Ashour, M.S. Abou-Dina, A.F. Ghaleb Apr 2025

The Induction Of Electric Currents In A Conducting Spherical Cap With Geomagnetic Applications: A Semi-Analytical Approach For The Axisymmetric Case, A.A. Ashour, M.S. Abou-Dina, A.F. Ghaleb

Sultan Qaboos University Journal For Science

The objective is to introduce a semi-analytical method for solving axisymmetric problems of electromagnetic induction in thin spherical caps placed in a time-varying magnetic field due to an axial magnetic dipole or in a time-varying uniform axial magnetic field. This method provides approximate solutions to mathematically difficult mixed boundary-value problems governing the induction of electric currents in thin sheets, for arbitrary angles of the cap. Numerical results are given and discussed. The best approximations were obtained for sheets with integrated conductivity decreasing to zero towards the edge of the sheet. The case of uniform conductivity, characterized by weak singularities of …

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A Galerkin Method For A Gaseous Ignition Model, M. Salman, Jintae Kim Apr 2025

A Galerkin Method For A Gaseous Ignition Model, M. Salman, Jintae Kim

Sultan Qaboos University Journal For Science

We consider a Galerkin procedure to solve a parabolic integrodifferential equation that arises in a gas combustion model. This model has been proposed by Kassoy and Poland, and subsequently analyzed by Bebernes, Eberly and Bressan. The problem is formulated in the variational form. In order to estimate the error, some intermediate projection has been employed. Under certain conditions on the given data, the error estimate has been obtained. A fully descretized version by using an extrapolated Crank-Nicolson method has been applied and the order of convergence derived.

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Local Projection Stabilization Method For Incompressible Flow Problems, A.M. Essefi, K. Nafa Apr 2025

Local Projection Stabilization Method For Incompressible Flow Problems, A.M. Essefi, K. Nafa

Sultan Qaboos University Journal For Science

We analyze Local Projection Stabilization (LPS) methods for the solution of Stokes problem using equal order finite elements. We investigate their convergence, stability and accuracy properties. The resulting stabilized method is shown to lead to optimal rates of convergence for both velocity and pressure approximations. We distinguish two classes of LPS methods: one-level and two-level methods. Numerical examples using bilinear interpolations are presented to validate the analysis and assess the accuracy of both approaches.

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Weakly Orthogonal Spherical Harmonics In A Non-Polar Spherical Coordinates And Its Application To Functions On Cubed-Sphere, M.A.A.M. Faham, H.M. Nasir Apr 2025

Weakly Orthogonal Spherical Harmonics In A Non-Polar Spherical Coordinates And Its Application To Functions On Cubed-Sphere, M.A.A.M. Faham, H.M. Nasir

Sultan Qaboos University Journal For Science

In a recent paper (Nasir, 2007), a set of weakly orthogonal and completely orthogonal spherical harmonics in a non-polar spherical coordinate system based on a cubed-sphere was constructed. In this work, we explore some linear relations between these two sets of spherical harmonics. Moreover, a power representation for the set of weakly orthogonal spherical harmonics corresponding to a mode is presented. We also determine the norm of the orthogonal spherical harmonics and hence the inner products for the weakly orthogonal spherical harmonics. As an immediate application of these properties, we present a Fourier series formulation of spherical functions defined on …

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A Wavelet-Based Energetic Approach For The Analysis Of Electroencephalogram, Abul Hasan Siddiqi, Hulya Kodal Sevindir Apr 2025

A Wavelet-Based Energetic Approach For The Analysis Of Electroencephalogram, Abul Hasan Siddiqi, Hulya Kodal Sevindir

Sultan Qaboos University Journal For Science

Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by the firing of neurons within the brain. The main application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study. EEG signals, like many biomedical signals, are highly non-stationary by their nature. Wavelet analysis has found a prominent position in the investigation of biomedical signals for its ability to analyze such signals, in particular EEG signals. Wavelet transform is capable of separating the signal energy among different frequency bands (i.e., different scales), achieving a good compromise between …

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First Steps In Mesh Wifi Network Design By Genetic Algorithm, Martin B. Reed, Stuart Nash Apr 2025

First Steps In Mesh Wifi Network Design By Genetic Algorithm, Martin B. Reed, Stuart Nash

Sultan Qaboos University Journal For Science

Given a mesh of wireless nodes for WiFi customers covering a city district, we describe a genetic algorithm-based approach to the problem of selecting a small fixed number of nodes as gateways to the internet, and linking the remaining nodes to the gateways either directly or by 'hopping', to create an efficient mesh network structure. The algorithm uses a modification of k-means clustering to allocate nodes to gateways.

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Error Analysis Of An Explicit Finite Difference Approximation For The Space Fractional Wave Equations, N.H. Sweilam, T.A. Assiri Apr 2025

Error Analysis Of An Explicit Finite Difference Approximation For The Space Fractional Wave Equations, N.H. Sweilam, T.A. Assiri

Sultan Qaboos University Journal For Science

In this paper, the space fractional wave equation (SFWE) is numerically studied, where the fractional derivative is defined in the sense of Caputo. An explicit finite difference approximation (EFDA) for SFWE is presented. The stability and the error analysis of the EFDA are discussed. To demonstrate the effectiveness of the approximated method, some test examples are presented.

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Numerical Experience With Damped Quasi-Newton Optimization Methods When The Objective Function Is Quadratic, Mehiddin Al-Baali, Anton Purnama Apr 2025

Numerical Experience With Damped Quasi-Newton Optimization Methods When The Objective Function Is Quadratic, Mehiddin Al-Baali, Anton Purnama

Sultan Qaboos University Journal For Science

A class of damped quasi-Newton methods for nonlinear optimization has recently been proposed by extending the damped-technique of Powell for the BFGS method to the Broyden family of quasi-Newton methods. It has been shown that this damped class has the global and superlinear convergence property that a restricted class of 'undamped' methods has for convex objective functions in unconstrained optimization. To test this result, we applied several members of the Broyden family and their corresponding damped methods to a simple quadratic function and observed several useful features of the damped-technique. These observations and other numerical experiences are described in this …

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Global Search Strategies For Solving Multilinear Least-Squares Problems, Mats Andersson, Oleg Burdakov, Hans Knutsson, Spartak Zikrin Apr 2025

Global Search Strategies For Solving Multilinear Least-Squares Problems, Mats Andersson, Oleg Burdakov, Hans Knutsson, Spartak Zikrin

Sultan Qaboos University Journal For Science

The multilinear least-squares (MLLS) problem is an extension of the linear least-squares problem. The difference is that a multilinear operator is used in place of a matrix-vector product. The MLLS is typically a large-scale problem characterized by a large number of local minimizers. It originates, for instance, from the design of filter networks. We present a global search strategy that allows for moving from one local minimizer to a better one. The efficiency of this strategy is illustrated by the results of numerical experiments performed for some problems related to the design of filter networks.

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A New Sparse Quasi-Newton Update Method, Minghou Cheng, Yu-Hong Dai, Rui Diao Apr 2025

A New Sparse Quasi-Newton Update Method, Minghou Cheng, Yu-Hong Dai, Rui Diao

Sultan Qaboos University Journal For Science

Based on the idea of maximum determinant positive definite matrix completion, Yamashita proposed a sparse quasi-Newton update, called MCQN, for unconstrained optimization problems with sparse Hessian structures. Such an MCQN update keeps the sparsity structure of the Hessian while relaxing the secant condition. In this paper, we propose an alternative to the MCQN update, in which the quasi-Newton matrix satisfies the secant condition, but does not have the same sparsity structure as the Hessian in general. Our numerical results demonstrate the usefulness of the new MCQN update with the BFGS formula for a collection of test problems. A local and …

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Preconditioning Large Indefinite Linear Systems, Giovanni Fasano, Massimo Roma Apr 2025

Preconditioning Large Indefinite Linear Systems, Giovanni Fasano, Massimo Roma

Sultan Qaboos University Journal For Science

After briefly recalling some relevant approaches for preconditioning large symmetric linear systems, we describe a novel class of preconditioners. Our proposal is tailored for large indefinite linear systems, which arise very frequently in many different contexts of numerical analysis and nonlinear optimization. Our preconditioners are built as a byproduct of the Krylov subspace method used to solve the system. We describe theoretical properties of the proposed class of preconditioners, namely their capability of both shifting some eigenvalues of the system’s matrix to controlled values, and reducing the modulus of the other ones. The results of a numerical experimentation give evidence …

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Cg Versus Minres: An Empirical Comparison, David Chin-Lung Fong, Michael Saunders Apr 2025

Cg Versus Minres: An Empirical Comparison, David Chin-Lung Fong, Michael Saunders

Sultan Qaboos University Journal For Science

For iterative solution of symmetric systems the conjugate gradient method (CG) is commonly used when A is positive definite, while the minimum residual method (MINRES) is typically reserved for indefinite systems. We investigate the sequence of approximate solutions generated by each method and suggest that even if A is positive definite, MINRES may be preferable to CG if iterations are to be terminated early. In particular, we show for MINRES that the solution norms are monotonically increasing when A is positive definite (as was already known for CG), and the solution errors are monotonically decreasing. We also show that the …

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Model Calibration In Option Pricing, Andre Loerx, Ekkehard W. Sachs Apr 2025

Model Calibration In Option Pricing, Andre Loerx, Ekkehard W. Sachs

Sultan Qaboos University Journal For Science

We consider calibration problems for models of pricing derivatives which occur in mathematical finance. We discuss various approaches such as using stochastic differential equations or partial differential equations for the modeling process. We discuss the development in the past literature and give an outlook into modern approaches of modelling. Furthermore, we address important numerical issues in the valuation of options and likewise the calibration of these models. This leads to interesting problems in optimization, where, e.g., the use of adjoint equations or the choice of the parametrization for the model parameters play an important role.

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A Superlinearly Convergent Penalty Method With Nonsmooth Line Search For Constrained Nonlinear Least Squares, Nezam Mahdavi-Amiri, Mohammad Reza Ansari Apr 2025

A Superlinearly Convergent Penalty Method With Nonsmooth Line Search For Constrained Nonlinear Least Squares, Nezam Mahdavi-Amiri, Mohammad Reza Ansari

Sultan Qaboos University Journal For Science

Recently, we have presented a projected structured algorithm for solving constrained nonlinear least squares problems, and established its local two-step Q-superlinear convergence. The approach is based on an adaptive structured scheme due to Mahdavi-Amiri and Bartels of the exact penalty method. The structured adaptation also makes use of the ideas of Nocedal and Overton for handling the quasi-Newton updates of projected Hessians and appropriates the structuring scheme of Dennis, Martinez and Tapia. Here, for robustness, we present a specific nonsmooth line search strategy, taking account of the least squares objective. We also discuss the details of our new nonsmooth line …

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A New Criterion For Optimality In Nonlinear Programming, L.M. Graña Drummond, A.N. Iusem Apr 2025

A New Criterion For Optimality In Nonlinear Programming, L.M. Graña Drummond, A.N. Iusem

Sultan Qaboos University Journal For Science

We establish a sufficient condition for the existence of minimizers of real-valued convex functions on closed subsets of finite dimensional spaces. We compare this condition with other related results.

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Robust Resistance Network Topology Design By Conic Optimization, C. Roos, Y. Bai, D. Chaerani Apr 2025

Robust Resistance Network Topology Design By Conic Optimization, C. Roos, Y. Bai, D. Chaerani

Sultan Qaboos University Journal For Science

After a brief introduction to the field of Conic Optimization we present an application to the (robust) resistor network topology design problem, where the goal is to design an electrical network containing resistors, such that the dissipation is minimal, given the external current values at the nodes of the network and assuming that the conductance values satisfy some normalizing constraint. We present a linear model for the single-current case and semidefinite models for multi-current cases. All models are illustrated by examples.

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Solving The Flood Propagation Problem With Newton Algorithm On Parallel Systems, Chefi Triki Apr 2025

Solving The Flood Propagation Problem With Newton Algorithm On Parallel Systems, Chefi Triki

Sultan Qaboos University Journal For Science

In this paper we propose a parallel implementation for the flood propagation method Flo2DH. The model is built on a finite element spatial approximation combined with a Newton algorithm that uses a direct LU linear solver. The parallel implementation has been developed by using the standard MPI protocol and has been tested on a set of real world problems.

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Spectral Analysis Of Magnetic Anomalies Due To A 2-D Horizontal Circular Cylinder: A Hartley Transforms Technique, Mansour A. Al-Garni Apr 2025

Spectral Analysis Of Magnetic Anomalies Due To A 2-D Horizontal Circular Cylinder: A Hartley Transforms Technique, Mansour A. Al-Garni

Sultan Qaboos University Journal For Science

The spectral analysis of the vertical effect of magnetic anomalies due to a 2-D horizontal circular cylinder is presented using Hartley transform. Hartley transform is an alternative approach to the famous complex Fourier transform. The depth to the center of the horizontal cylinder can be computed by a simple equation as a function of frequency. A synthetic example has been used to illustrate this technique and the validity of this approach has been proved by applying it to real data of a narrow band of quartz-magnetite in Mangampalli near Karimnagar town, India. The noise analyses were tested on the technique …

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On The Existence Of Evolutionary Learning Equilibriums, Masudul Alam Choudhury Apr 2025

On The Existence Of Evolutionary Learning Equilibriums, Masudul Alam Choudhury

Sultan Qaboos University Journal For Science

The usual kinds of Fixed-Point Theorems formalized on the existence of competitive equilibrium that explain much of economic theory at the core of economics can operate only on bounded and closed sets with convex mappings. But these conditions are hardly true of the real world of economic and financial complexities and perturbations. The category of learning sets explained by continuous fields of interactive, integrative and evolutionary behaviour caused by dynamic preferences at the individual and institutional and social levels cannot maintain the assumption of closed, bounded and convex sets. Thus learning sets and multi-system inter-temporal relations explained by pervasive complementarities …

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Chiral Polyhedra Derived From Coxeter Diagrams And Quaternions, Mehmet Koca, Nazife Ozdes Koca, Muna Al-Shueili Apr 2025

Chiral Polyhedra Derived From Coxeter Diagrams And Quaternions, Mehmet Koca, Nazife Ozdes Koca, Muna Al-Shueili

Sultan Qaboos University Journal For Science

There are two chiral Archimedean polyhedra, the snub cube and snub dodecahedron together with their dual Catalan solids, pentagonal icositetrahedron and pentagonal hexacontahedron. In this paper we construct the chiral polyhedra and their dual solids in a systematic way. We use the proper rotational subgroups of the Coxeter groups and to derive the orbits representing the solids of interest. They lead to the polyhedra tetrahedron, icosahedron, snub cube, and snub dodecahedron respectively. We prove that the tetrahedron and icosahedron can be transformed to their mirror images by the proper rotational octahedral group so they are not classified in the class …

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Formulas For The Number Of Spanning Trees In A Chain Of Cycles, Thomas Bier Apr 2025

Formulas For The Number Of Spanning Trees In A Chain Of Cycles, Thomas Bier

Sultan Qaboos University Journal For Science

We give a formula for the number of spanning trees in a chain of cycles that have connected intersection of one edge but where the cycles have variable sizes. The formula uses basic properties of continued fractions.

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