Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article A Coupled Modelling and Simulation Approach to Electromagnetic Sheet Metal Forming(Taylor & Francis Ltd, 2025) Aslan, Ozgur; Kabakci, Gamze Cakir; Sait, Ferit; Camalan, Caner; Baranoglu, Besim; Bayraktar, Emin; Cakir Kabakci, GamzeThis study presents a coupled numerical and experimental investigation of electromagnetic forming (EMF) for aluminium sheets. A custom simulation framework is developed in ABAQUS/Standard using user-defined material (UMAT) and load (DLOAD) subroutines. The magnetic pressure exerted on the workpiece is computed through a finite difference-based solution of Maxwell's equations and applied to the mechanical solver. The mechanical response of the material is modelled using a strain-rate-sensitive plasticity law calibrated for aluminium 7075-O. Experimental forming trials are performed using a custom-built EMF setup, and the results are compared with numerical predictions to validate the model. The comparison shows strong agreement in deformation profiles, confirming the predictive capability of the proposed simulation strategy. This work offers a reliable computational tool for optimising EMF processes and provides insights into material behaviour under high strain rate electromagnetic loading.Article An Innovative Showcase of Similarity Methods for Accelerated Turbine Design Processes and Cost-Effective Solutions(Taylor & Francis Ltd, 2025) Kantar, Ece Nil; Ayli, Ece; Celebioglu, KutayThis study aims to design a containerized Francis-type turbine for installation on drinking water pipelines equipped with pressure-reducing equipment, enabling energy recovery from untapped hydraulic resources. The turbine, designed to operate unmanned and housed within a container, represents an innovative approach to harnessing residual energy in drinking water pipelines. The research methodology leverages similarity laws derived from a previously developed high-efficiency turbine facility as a foundation for the preliminary design. This approach diverges from conventional turbine design methods, offering significant time and cost efficiencies. It should be noted that similarity laws were used only for the preliminary dimensioning of the scale turbine. Following this initial design, design optimizations were carried out based on CFD, focusing on components such as the runner, to enhance performance and achieve the required power output without cavitation at the specified flow rate and head. The results demonstrate that the application of similarity laws expedites the design process while maintaining high efficiency, effectively addressing the unique constraints of the operational environment. Additionally, the study provides a comprehensive analysis of the advantages and limitations of employing similarity in turbine design. In conclusion, this research not only exemplifies a novel turbine design methodology that ensures operational similarity but also serves as a practical guide for reducing costs and design timelines in small hydropower applications.This now clearly states that similarity was used for the preliminary dimensioning, followed by optimization based on CFD.Article Citation - WoS: 4Citation - Scopus: 4Microstructure and Mechanical Properties of Al-Co High Entropy Alloys(Taylor & Francis Ltd, 2022) Ayrenk, A.; Kalay, IThe structure and mechanical properties of non-equiatomic Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 high entropy alloys (HEAs) were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness and tensile testing. TEM and XRD analyses revealed the formation of gamma''-Ni3Nb/gamma (FCC), double FCC and gamma'-Ni3Al/gamma (FCC) structure for as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs, respectively. The hardness and yield strength values were found to increase with the addition of Nb while the ductility of alloys increased with the increase in Ti concentration, significantly. The as-cast Al8Co30Cr18Fe9Ni31Ti4 alloy exhibited an excellent combination of ultimate tensile strength of 844 MPa and an elongation of 29.8% due to the coherent phase relation between gamma' precipitates and gamma matrix. The fractured surfaces of as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs showed typical dimple type ductile fracture under tension test.Article Citation - WoS: 3Citation - Scopus: 4Towards an Earthquake-Resistant Architectural Design With the Image Classification Method(Taylor & Francis Ltd, 2024) Akan, Asli Er; Bingol, Kaan; Ormecioglu, Hilal Tugba; Er, Arzu; Ormecioglu, Tevfik Oguz; Er Akan, AslıArchitectural design is an interdisciplinary process which involves multiple stages that are interconnected. In this process, it is common for major decisions to be changed during the final stage, the analysis of the structural system. After making substantial corrections, the architect has to revisit the early stages, the preliminary project. This back-and-forth process can result in significant losses in time and cost. The proposed Irregularity Control Assistant (IC-Assistant) aims to provide architects with feedback on the conformity of structural system decisions to the irregularities defined in the Turkish Building Earthquake Code (TBEC-2018), using image processing methods at the early stages of the design process. The IC-Assistant was preliminarily created to evaluate the torsional irregularity of plan organization using deep learning methods. In this study, the results of the IC-Assistant were verified by structural analysis with the Prota-Structure program. The novelty of this study is the use of the image-classification method in earthquake-resistant architectural design. Up to this point, the method has been mainly used in facial recognition systems. This method minimizes time, human error, and cost losses and includes awareness of load bearing and earthquake resistance as inputs in the early stages of architectural design.Article Citation - WoS: 19Citation - Scopus: 20Bioglass-Polymer Composite Scaffolds for Bone Tissue Regeneration: a Review of Current Trends(Taylor & Francis Ltd, 2024) Motameni, Ali; Cardakli, Ismail Seckin; Gurbuz, Riza; Alshemary, Ammar Z. Z.; Razavi, Mehdi; Farukoglu, Omer CanBiocompatible and bioactive composite scaffolds are essential in bone tissue regeneration because of their bioactivity and multilevel porous assemblies. There is a high demand for three-dimensional (3D) scaffolds to treat bone regeneration defects, trauma, and congenital skeletal abnormalities in the current scenario. The main objective of this review is to collect all the possible information concerning synthetic and natural polymer-Bioglass (BG)-based scaffold materials and systematically present them to summarize the importance and need for these materials. The importance of the bone tissue engineering field has been highlighted. Given the current challenges, a comprehensive description of materials fabrication and patterns in scaffold structures is required. This review also includes the most crucial aspect of this study: why are polymeric materials mixed with BG materials? Individually, both BG and polymeric materials lack specific essential characteristics to enhance the scope of these materials. However, preparing the composites of both ensures the researchers that composites of polymers and BG have improved properties that make them versatile materials for bone tissue engineering applications. This study deals with the individual drawbacks of the inorganic BGs, synthetic polymers, and the deficiencies of natural polymers. This study has also included a brief description of various scaffold fabricating techniques. Finally, this study revealed that by manufacturing and developing novel composite materials-scaffolds bearing the capability to repair, heal, and regenerate accidentally damaged or badly injured bones, many occasional problems can be solved in vivo and in vitro. Moreover, this review demonstrated that natural polymeric materials present many advantages over synthetic bone grafts. Yet, synthetic biomaterials have one additional attractive feature, as they have the flexibility to be designed according to the desired demands. These features make them the best choice for a wide range of bone tissue engineering projects for orthopedic surgeons.Article Citation - WoS: 2Citation - Scopus: 2Wetting Behavior and Reaction Layer Formation in C/Sic Composite-Titanium Alloy Joints(Taylor & Francis Ltd, 2022) Esen, Ziya; Dericioglu, Arcan F.; Saltik, SimgeThe present study investigates the effect of brazing parameters on reaction layer formation, and mechanical properties of C/SiC composite-Ti6Al4V alloy joints produced by brazing technique. The wetting mechanism of the C/SiC composite surface by the Ag-CuTi-based active brazing filler alloy has also been studied and correlated with the reaction layer formation. The strength of C/SiC composite/Ti6Al4V alloy joints increased at first and then decreased with increasing reaction layer thickness. The joints with 1-mu m-thick reaction layer, which were obtained by brazing at 915 degrees C for 15 min, had the highest shear strength of 33 MPa. Brazing filler alloy presented a minimum contact angle of 15 degrees on the C/SiC composite surface at 915 degrees C during the wetting experiments. 915 degrees C and 15 min were determined to be the optimised brazing parameters to ensure almost complete wetting and a uniform reaction layer for effective adhesion of the C/SiC composite surface.Article Citation - WoS: 8Citation - Scopus: 8Analysis of the Specific Heat and the Free Energy of [N(ch3)4]2znbr4 Close To the Ferro-Paraelastic Phase Transition(Taylor & Francis Ltd, 2019) Kiraci, A.A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat and the Gibbs free energy of [N(CH3)(4)](2)ZnBr4 compound in the vicinity of the phase transition temperature of T-C = 287.2 K. Obtained values of the critical exponents from the Gibbs free energy were consistent with that predicted from 2-d potts model ( = 0.3), while obtained values of from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory ( = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH3)(4)](2)ZnBr4 compound undergoes a second order type phase transition. Also, the enthalpy () and the entropy () of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.Article Citation - WoS: 8Citation - Scopus: 8Localization of Metallicity and Magnetic Properties of Graphene and of Graphene Nanoribbons Doped With Boron Clusters(Taylor & Francis Ltd, 2014) Kunstmann, Jens; Quandt, Alexander; Ozdogan, CemAs a possible way of modifying the intrinsic properties of graphene, we study the doping of graphene by embedded boron clusters with density functional theory. Cluster doping is technologically relevant as the cluster implantation technique can be readily applied to graphene. We find that B-7 clusters embedded into graphene and graphene nanoribbons are structurally stable and locally metallize the system. This is done both by the reduction of the Fermi energy and by the introduction of boron states near the Fermi level. A linear chain of boron clusters forms a metallic "wire" inside the graphene matrix. In a zigzag edge graphene nanoribbon, the cluster-related states tend to hybridize with the edge and bulk states. The magnetism in boron-doped graphene systems is generally very weak. The presence of boron clusters weakens the edge magnetism in zigzag edge graphene nanoribbon, rather than making the system appropriate for spintronics. Thus, the doping of graphene with the cluster implantation technique might be a viable technique to locally metallize graphene without destroying its attractive bulk properties.Conference Object Citation - WoS: 2Citation - Scopus: 3An Extension of the Clark-Ocone Formula Under Benchmark Measure for Levy Processes(Taylor & Francis Ltd, 2012) Okur, Yeliz Yolcu; Yolcu Okur, YelizThe classical Clark-Ocone theorem states that any random variable F is an element of D-1,2(W) subset of L-2 (F-T, P) can be represented as F = E[F] + integral(T)(0) E[DtF vertical bar F-t]dWd(t), where E[.vertical bar F-t] denotes the conditional expectation, W(.) is a Brownian motion with canonical filtration {Ft}(t is an element of[0,T]) and D denotes the Malliavin derivative in the direction of W. Since many applications in financial mathematics require representation of random variables with respect to risk neutral martingale measure, an equivalent martingale measure version of this theorem was stated by Karatzas and Ocone (Stoch. Stoch. Rep. 34 (1991), 187-220). In this paper, we extend these results to be valid for square integrable pure jump Levy processes with no drift and for square integrable Ito-Levy processes using Malliavin calculus and white noise analysis. This extension might be useful for some applications in finance. As an application of our result, we calculate explicitly the closest hedge strategy for the digital option whose pay-off, F = chi([H,K))(S(T)) is not an element of D-1,2(W,(N) over tilde), is square integrable and the stock price S(.) is driven by a Levy process.Article Citation - WoS: 8Citation - Scopus: 8Reconfigurability of Behavioural Specifications for Manufacturing Systems(Taylor & Francis Ltd, 2017) Schmidt, Klaus WernerReconfigurable manufacturing systems (RMS) support flexibility in the product variety and the configuration of the manufacturing system itself in order to enable quick adjustments to new products and production requirements. As a consequence, an essential feature of RMS is their ability to rapidly modify the control strategy during run-time. In this paper, the particular problem of changing the specified operation of a RMS, whose logical behaviour is modelled as a finite state automaton, is addressed. The notion of reconfigurability of specifications (RoS) is introduced and it is shown that the stated reconfiguration problem can be formulated as a controlled language convergence problem. In addition, algorithms for the verification of RoS and the construction of a reconfiguration supervisor are proposed. The supervisor is realised in a modular way which facilitates the extension by new configurations. Finally, it is shown that a supremal nonblocking and controllable strict subautomaton of the plant automaton that fulfils RoS exists in case RoS is violated for the plant automaton itself and an algorithm for the computation of this strict subautomaton is presented. The developed concepts and results are illustrated by a manufacturing cell example.