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Computer Modeling in Engineering & Sciences 2019年第7期120卷 63-81页

作者： mustafa Turkyilmazoglu Department of Mathematics Hacettepe University06532-BeytepeAnkaraTURKEY

A ratio approach based on the simple ratio test associated with the terms of homotopy series was proposed by the author in the previous *** was shown in the latter through various comparative physical models that the ratio approach of identifying the range of the convergence control parameter and also an optimal value for it in the homotopy analysis method is a promising alternative to the classically used h-level curves or to the minimizing the residual(squared)error.A mathematical analysis is targeted here to prove the equivalence of both the ratio approach and the traditional residual approach,especially regarding the root-finding problems via the homotopy analysis *** are provided to further justify ***,it is conjectured that every nonlinear differential equation can be considered as a root-finding problem by plugging a parameter in it from a physical *** examples from the boundary and initial and value problems are provided to verify this ***,besides the advantages as deciphered in the previous publications,the feasibility of the ratio approach over the traditional residual approach is made clearer in this paper.

关键词： Homotopy analysis method convergence control parameter optimum value ratio approach residual approach

Statistical and Geometrical Way of Model Selection for a Family of Subdivision Schemes

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Chinese Annals of Mathematics,Series B 2017年第5期38卷 1077-1092页

作者： Ghulam mustafa Department of Mathematics The Islamia University of BahawalpurBahawalpur 63100Pakistan

The objective of this article is to introduce a generalized algorithm to produce the m-point n-ary approximating subdivision schemes(for any integer m, n ≥ 2). The proposed algorithm has been derived from uniform B-spline blending functions. In particular, we study statistical and geometrical/traditional methods for the model selection and assessment for selecting a subdivision curve from the proposed family of schemes to model noisy and noisy free data. Moreover, we also discuss the deviation of subdivision curves generated by proposed family of schemes from convex polygonal curve. Furthermore, visual performances of the schemes have been presented to compare numerically the Gibbs oscillations with the existing family of schemes.

关键词： Approximating subdivision schemes B-spline blending function Convex polygon Statistical and geometrical methods Model selection andassessment

Nonlinear Problems via a Convergence Accelerated Decomposition Method of Adomian

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Computer Modeling in Engineering & Sciences 2021年第4期127卷 1-22页

作者： mustafa Turkyilmazoglu Department of Mathematics Hacettepe UniversityAnkara06532Turkey Department of Medical Research China Medical University HospitalChina Medical UniversityTaichung40447Taiwan

The present paper is devoted to the convergence control and accelerating the traditional Decomposition Methodof Adomian (ADM). By means of perturbing the initial or early terms of the Adomian iterates by adding aparameterized term, containing an embedded parameter, new modified ADM is constructed. The optimal value ofthis parameter is later determined via squared residual minimizing the error. The failure of the classical ADM is alsoprevented by a suitable value of the embedded parameter, particularly beneficial for the Duan–Rach modification ofthe ADM incorporating all the boundaries into the formulation. With the presented squared residual error analysis,there is no need to check out the results against the numerical ones, as usually has to be done in the traditional ADMstudies to convince the readers that the results are indeed converged to the realistic solutions. Physical examplesselected from the recent application of ADM demonstrate the validity, accuracy and power of the presented novelapproach in this paper. Hence, the highly nonlinear equations arising from engineering applications can be safelytreated by the outlined method for which the classical ADM may fail or be slow to converge.

关键词： Nonlinear equations Adomian decomposition method modification convergence acceleration

Comparison of a commercial powder and a powder produced from Ti–6Al–4V chips and their effects on compacts sintered by the sinter-HIP method

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International Journal of Minerals,Metallurgy and Materials 2019年第7期26卷 878-888页

作者： mustafa Ustundag Remzi Varol Department of Mechanical Engineering Suleyman Demirel University

The present paper is related to the conversion of Ti–6Al–4V chips into powder and investigates the usability of the produced powder in powder metallurgy applications. In this regard, a disc-milling process was applied to Ti–6Al–4V chips and the obtained powder was subsequently compacted. The compacted samples were sintered by the sinter hot isostatic pressing (sinter-HIP) method at 1200°C under high vacuum, their mechanical properties and microstructure were investigated and compared with those of commercial powder compacts subjected to the same preparation processes. The results showed that the produced powder exhibits greater flowability and higher apparent density than the commercial powder. However, the sintered products prepared from the commercial powder exhibited a higher relative density, lower porosity, and, as a result, greater flexural strength compared with the sintered compacts prepared from the produced powder. In addition, transgranular fracture was greater in the sintered products of the commercial powder. The microstructural studies revealed that the sintered products made from both the commercial and the produced powders consisted of α- and β-phase but contained more α-phase. All of the examined properties were found to be substantially affected by the particle size of the powders.

关键词： Ti-6Al-4V chips sinter hot isostatic pressing flexural strength porosity

Effect of ZrSiO_4 on the Friction Performance of Automotive Brake Friction Materials

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Journal of Materials Science & Technology 2007年第6期23卷 843-850页

作者： mustafa BOZ Adem KURT Metallurgy Department Z.K.U.Karabük Technical Education Faculty78200 KarabükTurkey Metallurgy Department Gazi UniversityTechnical Education Faculty06500 AnkaraTurkey

Friction-wear properties of the ZrSiO4 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested. Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy （SEM）, and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820℃. Density of the final samples decreased with increasing the amount of reinforcing elements （ZrSiO4） before pre-sintering. However after sintering, there is no change in density of the samples including reinforcing elements （ZrSiO4）. With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0. 5% reinforced ZrSiO4. The SEM images of the sample indicated that while bronze-based break lining material without ZrSiO4 showed abrasive wear behaviour, increasing the amount of ZrSiO4 resulted a change in abrasive to adhesive wear mechanism. All samples exhibited friction-wear values, which were within the values shown in SAE-J661 standard. With increasing the amount of reinforcing ZrSiO4, wear resistance of the samples was increased. However samples reinforced with 5% and 6% ZrSiO4 showed the best results.

关键词： Friction materials ZrSiO4 Wear Friction Brake lining

Characterization of Microstructural and Morphological Properties in As-deposited Ta/NiFe/IrMn/CoFe/Ta Multilayer System

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Journal of Materials Science & Technology 2014年第4期30卷 359-364页

作者： Ramis mustafa ksoglu Umut Sarac mustafa Yildirm Hakan inar Department of Materials Sciences and Engineering University of Anadolu Department of Elementary Education University of Bartin

Surface morphology and its relationship with microstructure in Ta/NiFe/IrMn/CoFe/Ta multilayer system deposited by pulsed DC magnetron sputtering have been investigated in dependence of Ta buffer and NiFe seed layer thicknesses using atomic force microscopy. The structural parameters such as grain size, dislocation density, texture and strain were calculated. For each surface, a self-affinity behavior with mean fractal dimensions in the range of 2.03-2.18 was found. Additionally, it was also observed that the surface of all samples has locally smooth textured surface structure in the short range. The texture aspect parameter and texture direction index have been obtained for isotropy/anisotropy surface texture. A significant relationship between the surface texture and the strength of the 〈111〉 texture in IrMn layer has been found. The analysis indicated that the surface roughness is strongly affected by the thicknesses of the NiFe seed and Ta buffer layers.

关键词： Pulsed DC magnetron sputtering Surface roughness Strain and texture

ESTIMATING ERROR BOUNDS FOR TERNARY SUBDIVISION CURVES/SURFACES

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Journal of Computational Mathematics 2007年第4期25卷 473-484页

作者： Ghulam mustafa Jiansong Deng Department of Mathematics Islamia University Bahawalpur Pakistan Department of Mathematics University of Science and Technology of China Hefei 230026 China Department of Mathematics University of Science and Technology of China Hefei 230026 China

We estimate error bounds between ternary subdivision curves/surfaces and their control polygons after k-fold subdivision in terms of the maximal differences of the initial control point sequences and constants that depend on the subdivision mask. The bound is independent of the process of subdivision and can be evaluated without recursive subdivision. Our technique is independent of parametrization therefore it can be easily and efficiently implemented. This is useful and important for pre-computing the error bounds of subdivision curves/surfaces in advance in many engineering applications such as surface/surface intersection, mesh generation, NC machining, surface rendering and so on.

关键词： Subdivision curve Subdivision surface Subdivision depth Error bound.

Relaxation theory of spin-3/2 Ising system near phase transition temperatures

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Chinese Physics B 2010年第8期19卷 257-269页

作者： Osman Canko mustafa Keskin Department of Physics Erciyes University

Dynamics of a spin-3/2 Ising system Hamiltonian with bilinear and biquadratic nearest-neighbour exchange interactions is studied by a simple method in which the statistical equilibrium theory is combined with the Onsager＇s theory of irreversible thermodynamics. First, the equilibrium behaviour of the model in the molecular-field approximation is given briefly in order to obtain the phase transition temperatures, i.e. the first- and second-order and the tricritical points. Then, the Onsager theory is applied to the model and the kinetic or rate equations are obtained. By solving these equations three relaxation times are calculated and their behaviours are examined for temperatures near the phase transition points. Moreover, the z dynamic critical exponent is calculated and compared with the z values obtained for different systems experimentally and theoretically, and they are found to be in good agrement.

关键词： spin-3/2 Ising system 0nsager theory

Dynamic magnetic behavior of the mixed spin (2, 5/2) Ising system with antiferromagnetic/antiferromagnetic interactions on a bilayer square lattice

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Chinese Physics B 2013年第12期22卷 160-167页

作者： Mehmet Ertas mustafa Keskin Department of Physics Erciyes University

Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions on the bilayer square lattice under a time varying （sinusoidal） magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic （FM/FM） and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions.

关键词： dynamic magnetic behavior of a bilayer Ising system mixed spins glauber-type stochastic dynamics antiferromagnetic/antiferromagnetic interactions

Effect of ultrasonic assisted KOH pretreatment on physiochemical characteristic and anaerobic digestion performance of wheat straw

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Chinese Journal of Chemical Engineering 2020年第9期28卷 2409-2416页

作者： Rashid mustafa Korai Xiujin Li Department of Environmental Science&Engineering Beijing University of Chemical TechnologyBeijing 100029China Department of Petroleum&Gas Engineering Dawood University of Engineering&TechnologyNew M-A.Jinnah RoadKarachi-74800Pakistan

In this study,ultrasonic field was applied during potassium hydroxide(KOH) pretreatment of wheat straw(WS).Three concentrations of KOH(2%,4%,and 6%) were tested during *** results showed that there was a significant influence of the ultrasonic assisted KOH pretreatment(KOH(Upt)) on physiochemical characteristics of WS during pretreatment as well as on digester *** pretreatment time was optimized to 36 h for all KOH *** highest total volatile fatty acid(TVFA) productions(3189 mg·L^-1) from 6%KOHupt samples were ***,the SEM analysis and FTIR observation revealed that KOH(Upt) effectively disrupted the physical morphology of WS and successful breaking of lignin and hemicellulose linkage between carboxyl ***,the highest biogasification(555 ml·(g VS(loaded))^-1) and biomethane productions(282 ml·(g VS(loaded))^-1) from 4%KOH(Upt) digesters,with 69% of biodegradability,indicated significant availability of organic matter from KOH(Upt).The R^2 values(0.993-0.998) in Modified Gompertz Model indicated that the model was feasible to predict methane yield for this ***,the Bo values for 4%KOH(Upt)(283.30±2.74 ml·(gVS(loaded))^-1) were also in agreement to the experimental methane *** results suggested that ultrasonic addition during KOH pretreatment of WS can effectively increase the organic yield during ***,the increase in methane production from 4% KOH(Upt) suggested that digester performance can be improved with lower KOH concentrations using this pretreatment.

关键词： Ultrasonic pretreatment Potassium hydroxide(KOH) Wheat straw Anaerobic digestion Biogasification Biomethane