Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Synthesis of Pristine Chitosan Foams with Enhanced Pore Structure, Surface Area, and Mechanical Strength for Tissue Engineering Applications(Iop Publishing Ltd, 2025) Polat, M.; Cropper, Chelsea; Ozdamar, A. B.; Polat, H.With its excellent biocompatibility, biodegradability, and antimicrobial activity, chitosan is a promising scaffold material for hard-tissue engineering. Yet, pristine chitosan foams typically lack the strength and porosity required for such use. Here we present a simple emulsion-templating approach to fabricate pristine chitosan foams with optimized strength and porosity. Sodium dodecyl sulfate (SDS), a widely used biocompatible anionic surfactant, was employed at trace levels to aid polymerization. The foams display a dual-scale pore morphology. Cavities of 150-300 mu m are separated by around 50 mu m thick chitosan walls containing large interconnecting openings. The walls are further populated with meso- and macropores of 50-500 nm. This architecture should support cell attachment and growth, facilitate proliferation, and enhance nutrient transport and metabolic exchange. The structure yields high surface area (up to 10 m2 g-1). Mechanically, the thick-walled cavities impart both elastic recovery and high compressive resistance (255 kPa at 40% strain from foams polymerized with 4% chitosan). A preliminary drug-release study using vancomycin confirmed excellent loading and sustained release.Article Citation - WoS: 1Citation - Scopus: 1Spiral-Shaped Dual-Port Microstrip Antenna for 5G/6G Applications With Wideband-To Transition Using Shape-Memory Alloy(Iop Publishing Ltd, 2025) Atac, Enes; Karatay, AnilWe propose a compact, thermally reconfigurable dual-port microstrip antenna featuring a spiral-shaped design and shape-memory alloy (SMA) that enable switching between wideband and narrowband operation for 5G/6G communication systems. The SMA's thermally induced shape-memory behavior allows reconfiguration in response to temperature changes without the need for electronic or optical control circuits, thus avoiding issues such as self-interference problem, high costs, regular maintenance requirements, and durability concerns. In the wideband mode, measured results show that Port 1 covers 4.7-10.5 GHz and Port 2 covers 4.5-8.3 GHz, which closely agrees with simulations. When the SMA is activated by heat, the antenna switches to the narrowband mode, where Port 1 operates at 7.6 and 9.5 GHz, and Port 2 operates at 8.9 GHz. A ground-plane isolation element ensures low coupling between the ports, with the envelope correlation coefficient remaining below 0.1 across all configurations. The antenna reaches a peak gain of 5.2 dBi and maintains consistent performance through repeated switching. By combining spiral-shaped geometry with a responsive smart material, this work presents a novel and efficient approach for designing reconfigurable dual-port antennas suitable for future wireless technologies.Article Machinability Investigation on Cnc Milling of Recycled Short Carbon Fiber Reinforced Magnesium Matrix Composites(Iop Publishing Ltd, 2024) Atasoy, Sahin; Kandemir, SinanThis study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480-560-640 m min(-1)) and feed rates (0.65-0.8-0.95 mm min(-1)). The experimental design was based on the Taguchi L-9 (3(3)) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for the 5 wt% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations.Article Citation - Scopus: 1Genetic Algorithm Optimization of Langevin Thermostat and Thermal Properties of Graphene-Aluminum Nanocomposites: a Molecular Dynamics(Iop Publishing Ltd, 2024) Toprak, KasimThe thermal properties of a laminated structure of graphene-coated aluminum composite nanomaterial were investigated through non-equilibrium molecular dynamics (NEMD) simulations to address the problem of temperature deviation in the thermostat volume applied. This paper presents a new insight into the best values of timestep and Langevin thermostat damping parameters for each atom in the nanomaterial with different size configurations using the genetic algorithm (GA) method by considering the timestep and thermostat damping parameters for each atom type, as well as the thickness of the nanomaterial, the thermostat, buffer, and heat flow lengths. The initial population results indicate that the thermostat temperature deviation increases with higher thermostat damping coefficients and timestep. However, the deviation decreases significantly with increased heat flow and thermostat lengths. Variations in buffer length and aluminum thickness do not have a significant effect on temperature. The application of a GA for optimization leads to a decrease in thermostat temperature deviation. The optimized parameters resulted in better thermostat temperature deviations when analyzing the temperature, aluminum thickness, and both buffer and thermostat lengths. Additionally, the thermal conductivity of aluminum-graphene nanomaterial decreases with increasing temperature, buffer length, and aluminum thickness, but increases by up to 9.85% with increasing thermostat length.Article Citation - WoS: 3Citation - Scopus: 3Understanding Neural Network Tuned Langevin Thermostat Effect on Predicting Thermal Conductivity of Graphene-Coated Copper Using Nonequilibrium Molecular Dynamics Simulations(Iop Publishing Ltd, 2024) Toprak, KasimCopper has always been used in thermoelectric applications due to its extensive properties among metals. However, it requires further improving its heat transport performance at the nanosized applications by supporting another high thermal conductivity material. Herein, copper was coated with graphene, and the neural network fitting was employed for the nonequilibrium molecular dynamics simulations of graphene-coated copper nanomaterials to predict thermal conductivity. The Langevin thermostat that was tuned with a neural network fitting (NNF), which makes up the backbone of deep learning, generated the temperature difference between the two ends of the models. The NNF calibrated the Langevin thermostat damping constants that helped to control the temperatures precisely. The buffer and thermostat lengths were also analyzed, and they have considerable effects on the thermostat temperatures and a significant impact on the thermal conductivity of the graphene-coated copper. Regarding thermal conductivity, the four different shapes of vacancy defect concentrations and their locations in the graphene sheets were further investigated. The vacancy between the thermostats significantly decreases the thermal conductivity; however, the vacancy defect in thermostats does not have a similar effect. When the graphene is placed between two copper blocks, the thermal conductivity decreases drastically, and it continues to drop when the sine wave amplitude on the graphene sheet increases.Conference Object Citation - WoS: 6Citation - Scopus: 13A Methodology for Daylight Optimisation of High-Rise Buildings in the Dense Urban District Using Overhang Length and Glazing Type Variables With Surrogate Modelling(Iop Publishing Ltd, 2019) Ekici, Berk; Kazanasmaz, Zehra Tuğçe; Turrin, Michela; Taşgetiren, M. Fatih; Sarıyıldız, I. SevilUrbanization and population growth lead to the construction of higher buildings in the 21st century. This causes an increment on energy consumption as the amount of constructed floor areas is rising steadily. Integrating daylight performance in building design supports reducing the energy consumption and satisfying occupants' comfort. This study presents a methodology to optimise the daylight performance of a high-rise building located in a dense urban district. The purpose is to deal with optimisation problems by dividing the high-rise building into five zones from the ground level to the sky level, to achieve better daylight performance. Therefore, the study covers five optimization problems. Overhang length and glazing type are considered to optimise spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE). A total of 500 samples in each zone are collected to develop surrogate models. A self-adaptive differential evolution algorithm is used to obtain near-optimal results for each zone. The developed surrogate models can estimate the metrics with minimum 98.25% R2 which is calculated from neural network prediction and Diva simulations. In the case study, the proposed methodology improves daylight performance of the high-rise building, decreasing ASE by approx. 27.6% and increasing the sDA values by around 88.2% in the dense urban district. © Published under licence by IOP Publishing Ltd.