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The Effect Of Starvation On The Liver Of Aphanius Dispar (Pisces; Cyprinodontidae): A Microscopic Study, Taher A. Ba-Omar, Mariam Al-Amri, Jameela Al-Belushi, Reginald Victor Apr 2025

The Effect Of Starvation On The Liver Of Aphanius Dispar (Pisces; Cyprinodontidae): A Microscopic Study, Taher A. Ba-Omar, Mariam Al-Amri, Jameela Al-Belushi, Reginald Victor

Sultan Qaboos University Journal For Science

Stress due to starvation is not an uncommon phenomenon in fresh-and brackish water fish living in arid environments. This study, a part of a larger investigation on the effects of stress due to starvation on the organ systems of Aphanius dispar, a cyprinodont fish in Oman, reports on the histopathological changes in the liver, using light and transmission electron microscopy. The hepatocytes showed structural and ultrastructural changes in response to 24, 48, 72 and 96 hours of starvation. The hepatocytes of the starved fish groups were characterized by a reduction in the size of their cells and their nuclei, chromatin …

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Ferrocenylethynyl - A Versatile Platform For New Molecules To Novel Materials, Hakikulla H. Shah, Rayya A. Al-Belushi, Muhammad S. Khan Apr 2025

Ferrocenylethynyl - A Versatile Platform For New Molecules To Novel Materials, Hakikulla H. Shah, Rayya A. Al-Belushi, Muhammad S. Khan

Sultan Qaboos University Journal For Science

Ferrocenylethynyl is a key starting material for the synthesis of fascinating new molecules and novel functional materials. It combines the robust and redox-active ferrocene moiety with the rigid-rod ethynyl unit. The ferrocene center provides chemically and electrochemically switchable material properties whereas the ethynyl backbone facilitates electron delocalization along the molecule, yielding materials with the potential for a wide range of applications from sensors to bio-organometallics and pharmaceuticals, from catalysts to nonlinear optical materials, and from fuel additives to chelating agents. However, lifetime performances and costs still need to be optimized to make ferrocenylethynyl-based materials commercially competitive. Efficient synthetic methods are …

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Late Cretaceous Sub-Marine Fan System In Batain Mélange Zone, The Fayah Formation In Northeastern Oman, Iftikhar Ahmed Abbasi, Abdulrahman Al-Harthy, Yahya Khalifa Al-Subhi Apr 2025

Late Cretaceous Sub-Marine Fan System In Batain Mélange Zone, The Fayah Formation In Northeastern Oman, Iftikhar Ahmed Abbasi, Abdulrahman Al-Harthy, Yahya Khalifa Al-Subhi

Sultan Qaboos University Journal For Science

The Batain coast along the northeastern margin of Oman between Ra’s Al-Hadd and Ra’s Jibsch, is comprised of Permian to Late Cretaceous complex stratigraphy in a tectonically deformed area recording Permian rifting to late Cretaceous Tethys closure events. These rocks are thrust over Mesozoic and older autochthonous sedimentary cover in the form of a major nappe structure known as the Batain Nappe. The uppermost part of the Batain nappe is comprised of isolated outcrops of early Maastrichtian siliciclastic Fayah Formation dominated by gravity flow deposits. The Fayah Formation in the Jabal Fayah area is over four hundred meters thick and …

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Synthesis And Spectroscopic Properties Of A Fluorosensor For Zn2+ Ions, Nawal K. Al-Rasbi, Bushra Alwihibi, Nada Alnofali Apr 2025

Synthesis And Spectroscopic Properties Of A Fluorosensor For Zn2+ Ions, Nawal K. Al-Rasbi, Bushra Alwihibi, Nada Alnofali

Sultan Qaboos University Journal For Science

The new Schiff base ligand L: (E)-N'-(pyridin-2-ylmethylene)acetohydrazide, was synthesized, and its reaction with Zn(II) ions form the complex: [ZnL2](ClO4)2, as confirmed by X-ray crystallography. This complex is stable in polar and non-polar solvents as proven by NMR. A significant enhancement in the fluorescence was observed from L upon coordination to Zn(II) ions over other transition metals such as Fe(II), Co(II), Ni(II), Cu(II), Cd(II) and Ag(I). These results suggest that L can be used as a selective flourosensor for the detection of Zn(II) ions.

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Fabrication And Surface Characterization Of Poly(4-Aminodiphenylamine) Film Modified Electrode And Its Application For Lead And Cadmium Determination, Mohammed M. Al-Hinaai, Salim H. Al-Harthi, Emad A. Khudaish Apr 2025

Fabrication And Surface Characterization Of Poly(4-Aminodiphenylamine) Film Modified Electrode And Its Application For Lead And Cadmium Determination, Mohammed M. Al-Hinaai, Salim H. Al-Harthi, Emad A. Khudaish

Sultan Qaboos University Journal For Science

Poly(4-aminodiphenylamine), Padpa, film was synthesized electrochemically on a glassy carbon electrode by potentiodynamic repetitive cycling of 4‑aminodiphenylamine (4adpa) in 1.0 M HCl. The mechanistic steps involved the oxidation of the protonated monomer to diimine species which underwent dimerization process to form the mono-charged radical intermediate which was considered as the initiation step for the progress of polymerization. The electrochemical properties and surface morphology of the film modified electrode were characterized using electrochemical and various surface scanning techniques. The XPS data demonstrated the existence of (=N-) bonding responsible for polymer formation, while the AFM image revealed a uniform and symmetrical fiber …

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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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A Terbium Sensitized Luminescence Method For The Assay Of Flubiprofen In Pharmaceutical Formulations, Salma M.Z. Al-Kindy, Arwa Al-Ghazali, Fakhr Eldin O. Suliman, Haidar A.J. Al-Lawati Apr 2025

A Terbium Sensitized Luminescence Method For The Assay Of Flubiprofen In Pharmaceutical Formulations, Salma M.Z. Al-Kindy, Arwa Al-Ghazali, Fakhr Eldin O. Suliman, Haidar A.J. Al-Lawati

Sultan Qaboos University Journal For Science

A sensitive time-resolved luminescence method for the determination of flubiprofen (FLP) in methanol and in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb3+ ) by the formation of a ternary complex with FLP in the presence of 4,7 diphenyl 1,10 phenanthroline (DPP) as co-ligand, and Tween-20 as surfactant. The signal for Tb-FLP-DPP was monitored at λex = 285 nm and λem = 552 nm. Optimum conditions for the formation of the complex in an aqueous system were TRIS buffer, pH 8.0, DPP (2.5Å~10−7 M), Tween-20 (0.30%) and 4Å~10-5 mol L-1 of Tb3+ which …

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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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Fcc, Bcc And Sc Lattices Derived From The Coxeter-Weyl Groups And Quaternions, Nazife Özdeş Koca, Mehmet Koca, Muna Al-Sawafi Apr 2025

Fcc, Bcc And Sc Lattices Derived From The Coxeter-Weyl Groups And Quaternions, Nazife Özdeş Koca, Mehmet Koca, Muna Al-Sawafi

Sultan Qaboos University Journal For Science

We construct the fcc (face centered cubic), bcc (body centered cubic) and sc (simple cubic) lattices as the root and the weight lattices of the affine extended Coxeter groups W(A3) and W(B3)=Aut(A3). It is naturally expected that these rank-3 Coxeter-Weyl groups define the point tetrahedral symmetry and the octahedral symmetry of the cubic lattices which have extensive applications in material science. The imaginary quaternionic units are used to represent the root systems of the rank-3 Coxeter-Dynkin diagrams which correspond to the generating vectors of the lattices of interest. The group elements are written explicitly in terms of pairs of quaternions …

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An Annotated Checklist Of The Mammals Of Kuwait, Peter J. Cowan Apr 2025

An Annotated Checklist Of The Mammals Of Kuwait, Peter J. Cowan

Sultan Qaboos University Journal For Science

An annotated checklist of the mammals of Kuwait is presented, based on the literature, personal communications, a Kuwait website and a blog and the author’s observations. Twenty five species occur, a further four are uncommon or rare visitors, six used to occur whilst another two are of doubtful provenance. This list should assist those planning desert rehabilitation, animal reintroduction and protected area projects in Kuwait.

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Effects Of Pesticide Temephos On The Liver Of Aphanius Dispar (Rüppell 1828) (Pisces: Cyprinodontidae): A Microscopic Study, Taher A. Ba-Omar, Iman Al-Kharusi, Reginald Victor Apr 2025

Effects Of Pesticide Temephos On The Liver Of Aphanius Dispar (Rüppell 1828) (Pisces: Cyprinodontidae): A Microscopic Study, Taher A. Ba-Omar, Iman Al-Kharusi, Reginald Victor

Sultan Qaboos University Journal For Science

The effects of the pesticide temephos, at different concentrations, on the liver of Aphanius dispar, (Rüppell 1828) a cyprinodont fish, have been described. The changes in the liver tissue after exposure to 1 ppm, 5 ppm, 10 ppm and 25 ppm concentrations of temephos have been presented. Light and transmission electron microscopy showed that the degeneration of the liver cells commenced after exposure to 1 ppm and steadily progressed to show maximum changes at 25 ppm. Histopathological changes included the dilation of sinusoids, an increase in the number of lipid droplets and cytoplasmic vacuolation, pyknosis of the nuclei and focal …

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Optimised Methods For Quantitative Analysis Of Solasodine And Its Glycoside Solamargine By High Performance Liquid Chromatography, Sana S. Al-Sinani, Elsadig A. Eltayeb Apr 2025

Optimised Methods For Quantitative Analysis Of Solasodine And Its Glycoside Solamargine By High Performance Liquid Chromatography, Sana S. Al-Sinani, Elsadig A. Eltayeb

Sultan Qaboos University Journal For Science

Improved and simplified HPLC conditions for the determination and quantification of both the steroidal glycoalkaloid (solamargine) and its aglycone (solasodine) are described. The best isocratic conditions were developed using a C18 column and methanol in combination with an ammonium dihydrogen phosphate buffer. The isocratic conditions were shown to be more reproducible, less time consuming and to give sharper peaks (better separation). The effects of adjusting solvent: buffer ratio, buffer pH and buffer molarity were evaluated.

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Synthesis Of Doped And Non-Doped Nano Mgo Ceramic Membranes, Shiraz Labib Apr 2025

Synthesis Of Doped And Non-Doped Nano Mgo Ceramic Membranes, Shiraz Labib

Sultan Qaboos University Journal For Science

Doped and non-doped MgO coated thin films on alumina substrates were prepared using a chelating sol-gel method under controlled conditions to prepare nanomaterials with unprecedented properties. The effect of doping of ZnO on thermal, surface and structural properties was investigated using DTA-TG, BET and XRD respectively. Also microstructural studies and coating thickness measurements of MgO thin film were conducted using SEM. An increase in the thermal stability of MgO with increasing ZnO doping percent was observed. The increase of ZnO doping percent showed a marked decrease in the average particle size of MgO powder as a result of the replacement …

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Neorotalia Omanensis And Operculina Musawaensis From The Sultanate Of Oman, Abdul Razak Siddiq Al-Sayigh Apr 2025

Neorotalia Omanensis And Operculina Musawaensis From The Sultanate Of Oman, Abdul Razak Siddiq Al-Sayigh

Sultan Qaboos University Journal For Science

Two new species of larger benthic foraminifera, Neorotalia omanensis n. sp. and Operculina musawaensis n. sp. are described and illustrated from the eastern Oman Mountains. N. omanensis n. sp. occurs in the Musawa Formation in association with the planktonic foraminifera Morozovella edgari and Truncarotaloides topilensis indicating an early to middle Eocene age (P10-P13). Operculina musawaensis n. sp. occurs in the Abat Formation in association with the planktonic foraminifera Acarinina esnaensis and A. soldadensis indicating an early Eocene age (P6). This is the first known record showing the presence of genus Neorotalia in the Middle East. Representatives of the larger foraminiferal …

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Volatile Compounds Of The Leaves And Flowers Of Lavandula Dhofarensis A.G. Miller, John R. Williams, Majekodunmi O. Fatope, Salma M.Z. Al-Kindy, Fakhr Eldin O. Suliman, Salim H. Al-Saidi Apr 2025

Volatile Compounds Of The Leaves And Flowers Of Lavandula Dhofarensis A.G. Miller, John R. Williams, Majekodunmi O. Fatope, Salma M.Z. Al-Kindy, Fakhr Eldin O. Suliman, Salim H. Al-Saidi

Sultan Qaboos University Journal For Science

The leaves and flowers of Lavandula dhofarensis were collected from the Dhofar region of Oman and hydro-distilled to give low boiling volatiles, which did not condense at 10 oC. The dichloromethane extract of the hydrosol was analyzed by GC/FID and GC/MS. Sixty four compounds were identified in the volatiles of the leaves, accounting for 78.7% of the total. The major components were caryophyllene oxide (8.0%), germacrene (7.9%), spathulenol (7.8%), and b-caryophyllene (6.6%). Eighty six compounds were also identified in the volatiles of the leaves plus flowers, comprising 94.5% of the total. The major compounds were camphor (12.9%), viridiflorol (10.5%), a-terpinyl …

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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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Preface, - Squjs Apr 2025

Preface, - Squjs

Sultan Qaboos University Journal For Science

This special issue contains selected papers presented at the Second International Conference on Numerical Analysis and Optimization: Theory, Methods, Applications and Technology Transfer (NAOII2011) held during the period January 3-6, 2011 at Sultan Qaboos University (SQU), Muscat, Oman. The conference was sponsored by SQU, The Research Council (TRC) of Oman, The International Center for Theoretical Physics (ICTP) of Italy, Microsoft (Middle East and Africa Division); and the local sponsors the British Council (Oman), Bank Muscat, the Al-Anan Press, and Al-Roya Newspaper.Following on from the success of the previous conference on Numerical Analysis and Optimization (NAO2008) also held at SQU during …

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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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The Squared Slacks Transformation In Nonlinear Programming, Paul Armand, Dominique Orban Apr 2025

The Squared Slacks Transformation In Nonlinear Programming, Paul Armand, Dominique Orban

Sultan Qaboos University Journal For Science

In this short paper, we recall the use of squared slacks used to transform inequality constraints into equalities and several reasons why their introduction may be harmful in many algorithmic frameworks routinely used in nonlinear programming. Numerical examples performed with the sequential quadratic programming method illustrate those reasons. Our results are reproducible with state-of-the-art implementations of the methods concerned and mostly serve a pedagogical purpose, which we believe will be useful not only to practitioners and students, but also to researchers.

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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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