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Investigation of the compressibility and sinterabilty of AZ91 powder production and particle production by gas atomisation method

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Journal of Magnesium and Alloys 2019年第3期7卷 400-413页

作者： mehmet Akkas Mustafa Boz Faculty of Engineering and Architecture Department of Mechanical EngineeringKastamonu UniversityTurkey Faculty of Technology Department of Manufacturing EngineeringKarabiik UniversityKarabiikTurkey

This study intends to determine the pressability and sinterability of AZ91 powder production by gas atomisation method and that of the produced powder for partial ***,first,a gas atomisation unit has been designed and manufactured in the laboratories of the Karabiik University,Department of Manufacturing *** powder production has been achieved at a temperature of 795℃,with nozzle diameters of 2 and 4 mm and four different gas pressures(5,15,25,35 bars).Argon gas has been used for atomisation and as a protective gas *** electron microscope(SEM)is used to determine the shape of the produced AZ91 powder,and a laser particle size analyzer is used to analyze the powder ***,a microhardness(HV0.025)measurement has been conducted to determine the hardness of the produced *** achieve a homogeneous distribution,the produced powders are mixed in a three-dimensional moving turbulator for 30 *** powders have been pressed at 300,400,500 and 600 MPa and have been sintered at 500℃,550℃and 600℃.Additionally,the density values have been determined before and after sintering of the *** images have been obtained from the fractured surfaces of the samples before and after *** and EDX analyses have been performed to determine the chemical ***,microhardness(HV0.5)is obtained from the pressure surfaces of the samples to determine the effects of the pressing pressure and the sintering temperature on the *** a result of the experimental studies,it has been observed that the powder size decreases with the increase in gas pressure and that the powder shape generally changes from ligament and complex shape to droplet and spherical *** the XRD,XRF and EDX results,it has been determined that the structure comprises an a phase(Mg main matrix)and Mg17Al12 interphase,which isβphase,and very small amounts of MgO have been *** hardness of the produced powders increas

关键词： Gas atomisation AZ91 alloy powder Gas pressure Nozzle diameter Pressing Sintering

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Wear and mechanical properties of carburized AISI 8620 steel produced by powder metallurgy

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 430-439页

作者： mehmet Akif Erden Fatih Aydın Department of Biomedical Engineering Karabuk UniversityKarabuk 78050Turkey Department of Metallurgical and Materials Engineering Karabuk UniversityKarabuk 78050Turkey

The effect of carburization on the tensile strength and wear resistance of AISI 8620 steel produced via powder metallurgy was *** 1 and 2(with 0.2wt%C and 0.25wt%C,respectively)were first pressed at 700 MPa and then sintered at 1300,1400,or 1500℃for 1 *** ideal sintering temperature of 1400℃was ***,Alloys 1 and 2 sintered at 1400℃were carburized at 925℃for 4 *** microstructure characterization of alloys was performed via optical microscopy and scanning electron *** mechanical and wear behavior of carburized and noncarburized alloys were investigated via hardness,tensile,and wear *** carburization,the ultimate tensile strength of Alloys 1 and 2 increased to 134.4%and 138.1%,***,the elongation rate of Alloys 1 and 2 decreased to 62.6%and 64.7%,*** wear depth values of Alloy 2 under noncarburized and carburized conditions and a load of 30 N were 231.2 and 100.1μm,*** wear changed to abrasive wear when the load transitioned from 15 to 30 N.

关键词： powder metallurgy steels carburization microstructure wear mechanical properties

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RULES-IT： incremental transfer learning with RULES family

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Frontiers of Computer Science 2014年第4期8卷 537-562页

作者： Hebah ELGIBREEN mehmet Sabih AKSOY Information Technology Department College of Computer and Information Sciences King Saud University Riyadh 11415 Saudi Arabia Information Sysytem Department College of Computer and Information Sciences King Saud University Riyadh 11543 Saudi Arabia

In today＇s world of excessive development in technologies, sustainability and adaptability of computer applications is a challenge, and future prediction became significant. Therefore, strong artificial intelligence （AI） became important and, thus, statistical machine learning （ML） methods were applied to serve it. These methods are very difficult to understand, and they predict the future without showing how. However, understanding of how machines make their decision is also important, especially in information system domain. Consequently, incremental covering algorithms （CA） can be used to produce simple rules to make difficult decisions. Nevertheless, even though using simple CA as the base of strong AI agent would be a novel idea but doing so with the methods available in CA is not possible. It was found that having to accurately update the discovered rules based on new information in CA is a challenge and needs extra attention. In specific, incomplete data with missing classes is inappropriately considered, whereby the speed and data size was also a concern, and future none existing classes were neglected. Consequently, this paper will introduce a novel algorithm called RULES-IT, in order to solve the problems of incremental CA and introduce it into strong AI. This algorithm is the first incremental algorithm in its family, and CA as a whole, that transfer rules of different domains to improve the performance, generalize the induction, take advantage of past experience in different domain, and make the learner more intelligent. It is also the first to introduce intelligent aspectsinto incremental CA, including consciousness, subjective emotions, awareness, and adjustment. Furthermore, all decisions made can be understood due to the simple representation of repository as rules. Finally, RULES-IT performance will be benchmarked with six different methods and compared with its predecessors to see the effect of transferring rules in the learning process, and to pro

关键词： incremental learning transfer learning covering algorithms RULES family inductive learning

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Orbital decompression surgery for the treatment of Graves＇ ophthalmopathy：comparison of different techniques and long-term results

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International Journal of Ophthalmology(English edition) 2018年第8期11卷 1363-1370页

作者： mehmet Ozgur Cubuk Onur Konuk mehmet Unal Istanbul Education and Research Hospital Istanbul 34098Turkey Department of Ophthalmology Gazi University School of Medicine Besevler Ankara 06500 Turkey Dunya Goz Hospital Ankara 06500 Turkey

AIM： To evaluate the long-term results of different orbital decompression techniques performed in patients with Graves＇ ophthalmopathy（GO）.METHODS： Totally 170 cases with GO underwent orbital decompression between 1994 and 2014. Patients were divided into 4 groups as medial-inferior, mediallateral（balanced）, medial-lateral-inferior, and lateral only according to the applied surgical technique. Surgical indications, regression degrees on Hertel exophthalmometer, new-onset diplopia in the primary gaze and new-onset gaze-evoked diplopia after surgery and visual acuity in cases with dysthyroid optic neuropathy（DON） were compared between different surgical ***： The study included 248 eyes of 149 patients. The mean age for surgery was 42.3±13.2 y. DON was the surgical indication in 36.6% of cases, and three-wall decompression was the most preferred technique in these cases. All types of surgery significantly decrease the Hertel values（P〈0.005）. Balanced medial-lateral, and only lateral wall decompression caused the lowest rate of postoperative new-onset diplopia in primary gaze. The improvement of visual acuity in patients with DON did not significantly differ between the groups（P=0.181）. CONCLUSION： The study show that orbital decompression surgery has safe and effective long term results for functional and cosmetic rehabilitation of GO. It significantly reduces Hertel measurements in disfiguring proptosis and improves visual functions especially in DON cases.

关键词： orbital decompression Graves' ophthalmopathy dysthyroid optic neuropathy

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Hexagonal Type Ising Nanowire with Spin-1 Core and Spin-2 Shell Structure

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Communications in Theoretical Physics 2015年第10期64卷 401-408页

作者： mehmet Ertas Ersin Kantar Department of Physics Erciyes University

Thermodynamic properties and phase diagrams of a mixed spin-(1,2) Ising ferrimagnetic system with single ion anisotropy on hexagonal nanowire are studied by using effective-field theory with correlations. The susceptibility,internal energy and specific heat of the system are numerically examined and some interesting phenomena in these quantities are found. The effect of the Hamiltonian parameters on phase diagrams are examined in detail. Besides second-order phase transition, lines of first-order transition and tricritical points are found. In particular, we found that for some negative values of single-ion anisotropies, there exist first-order phase transitions.

关键词： hexagonal Ising nanowire mixed spin-(1 2) effectiv

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NONLINEAR DYNAMIC ANALYSIS OF A LAMINATED HYBRID COMPOSITE PLATE SUBJECTED TO TIME-DEPENDENT EXTERNAL PULSES

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Acta Mechanica Solida Sinica 2012年第6期25卷 586-597页

作者： mehmet Senyer Zafer Kazanci Turkish Air Force Academy Aeronautics and Space Technologies Institute34149 Ye silyurt Istanbul Turkey Turkish Air Force Academy Aerospace Engineering Department34149 Ye silyurt Istanbul Turkey

Nonlinear dynamic responses of a laminated hybrid composite plate subjected to time-dependent pulses are investigated. Dynamic equations of the plate are derived by the use of the virtual work principle. The geometric nonlinearity effects are taken into account with the yon Karman large deflection theory of thin plates. Approximate solutions for a clamped plate are assumed for the space domain. The single term approximation functions are selected by considering the nonlinear static deformation of plate obtained using the finite element method. The Galerkin Method is used to obtain the nonlinear differential equations in the time domain and a MATLAB software code is written to solve nonlinear coupled equations by using the Newmark Method. The results of approximate-numerical analysis are obtained and compared with the finite element results. Transient loading conditions considered include blast, sine, rectangular, and triangular pulses. A parametric study is conducted considering the effects of peak pressure, aspect ratio, fiber orientation and thicknesses.

关键词： nonlinear vibration hybrid composite plate Newmark method dynamic loads

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Aerodynamics of non-slender delta and reverse delta wings:Wing thickness,anhedral angle and cropping ratio

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Chinese Journal of Aeronautics 2023年第4期36卷 79-91页

作者： Göktug KOCAK mehmet Metin YAVUZ Turkish Aerospace Industries Inc.Aerodynamics Chief Engineer at TF-XProjectAnkara 06980Turkey Mechanical Engineering Department Middle East Technical UniversityAnkara 06800Turkey

The effects of thickness-to-chord(t=c)ratio,anhedral angle(d),and cropping ratio from trailing-edge(Cr%)on the aerodynamics of non-slender reverse delta wings in comparison to non-slender delta wings with sweep angle of 45°were characterized in a low-speed wind tunnel using force and pressure *** measurements were conducted for total of 8 different delta and reverse delta *** different t/c ratios of 5.9%and 1.1%,and two different anhedral angles ofd=15°and 30°for non-cropped and cropped at Cr=30%conditions were *** results indicate that the reverse delta wings generate higher lift-to-drag ratio and have better longitudinal static stability characteristics compared to the delta *** wing thickness has favorable effect on longitudinal static stability for the reverse delta wing whereas longitudinal static stability is not influenced by wing thickness for the delta *** reverse delta wings,the anhe-draled wing without cropping has adverse effect on aerodynamic performance and decreases the lift-to-drag *** in anhedraled wing causes significant improvement in lift-to-drag ratio,shift in aerodynamic and pressure centers towards the trailing-edge,and enhancement in longitudi-nal static stability.

关键词： Aerodynamic coefficients Anhedral Cropping Leading-edge vortex Longitudinal static stability Non-slender delta wing Non-slender reverse delta wing Stall Three-dimensional surface separation

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Performance analysis of a distributed power control algorithm for shared and split spectrum femtocell networks

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Control Theory and Technology 2016年第4期14卷 314-322页

作者： Kamil SENEL mehmet AKAR Department of Electrical and Electronics Engineering Bogazici University Istanbul 34342 Turkey

In this paper, we study the performance of a distributed power adjustment algorithm for shared and split spectrum allocation setups. The theoretical analysis reveals that the convergence of the power control algorithm is guaranteed under different spectrum allocation schemes and the convergence rate is exponential. The performance analysis is also carried out via simulations which demonstrate the algorithm fairness under Jain＇s and Atkinkons＇ fairness indices.

关键词： Femtocell networks power control consensus

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On Gauss-Weierstrass Semigroups and Inversion of Potentials Associated with the Bessel Differential Operator

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Acta Mathematica Sinica,English Series 2009年第10期25卷 1741-1758页

作者： mehmet ZekiSARIKAYA HüseyinYILDIRIM Department of Mathematics Faculty of Science and ArtsAfyon Kocatepe University

In this paper, we define the generalized Gauss Weierstrass semigroups with Weierstrass kernel, and give some of their properties. Using them, we study the inversion formulas for the generalized Riesz and Bessel potent... 详细信息

关键词： Bessel differential operator Bessel potential Riesz potential Schwartz space convolution,semigroup Gauss-Weierstrass kernel

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Spiraea cudidaghense:a new species from south-eastern Anatolia,Turkey

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Journal of Forestry Research 2018年第6期29卷 1751-1756页

作者： mehmet Firat Necmi Aksoy Department of Biology Faculty of EducationYuzucu Yil University65080 VanTurkey Faculty of Forestry&DUOF Herbarium Duzce University81620 DuzceTurkey

A new species, Spiraea cudidaghense(sect. Spiraeoideae, Rosaceae), is described and illustrated with diagnostic characters and taxonomic comments. Its characteristics are compared with those of the type species from which it differs mainly in compound corymbs inflorescence, ovate-obovate leaves, white petals, glabrous branches and densely pilose corymbs. In addition, a map of the geographic distribution of the new species, an IUCN ranking and notes on taxonomic affinities are also provided.

关键词： Spiraea cudidaghense Taxonomy New species Turkey

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