Izmir Institute of Technology
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Article Article ANASTILOSIS: ANTIK TAPINAK KALINTILARININ AYAGA KALDIRILMASININ OZGUNLUK BAGLAMINDA DEGERLENDIRILMESI(IEEE, 2024) Yılmaz, Ahmet...Article Article Article Article Effect of Geometry and Fiber Type on Energy Absorption in Polymer Based Composite Crash Boxes: An Experimental Study(Wiley, 2025) Kosedag, Ertan; Araz, Zumray; Erkek, BaranVehicle crash boxes, mounted on the chassis before the bumper, absorb impact energy to protect passengers, but their metal construction adds weight, prompting increased research into lightweight composite alternatives with comparable strength. In this study, energy absorption values (EA), specific energy absorption (SEA), peak forces (PF) and crashing force efficiency (CFE) of carbon fiber, glass fiber, and aramid fiber reinforced composite crash boxes with epoxy resin matrix were compared. Composite crash boxes with different geometries were fabricated using vacuum infusion method in three different geometries: hexagonal, circle, and square. Unlike hand lay-up and prepreg winding methods, vacuum infusion method was chosen because it provides homogeneous distribution of epoxy resin. The crashworthiness of the samples was evaluated through quasi-static compression tests. The best energy absorption performance was obtained with the hexagonal carbon fiber-reinforced composite crash box (246.17 J), corresponding to a specific energy absorption of 8.57 J/g. Although aramid fiber-reinforced specimens showed lower energy absorption, they exhibited the highest crash force efficiency among all tested configurations. These results confirm the significant influence of both fiber type and geometry on the crashworthiness of polymer-based composite crash boxes. The study highlights that hexagonal geometry consistently provided superior energy absorption across all fiber types, while carbon fiber-reinforced composites demonstrated the best overall mechanical performance, making them strong candidates for lightweight crashworthiness applications.Article Effect of Geometry and Fiber Type on Energy Absorption in Polymer Based Composite Crash Boxes: An Experimental Study(Wiley, 2025) Kosedag, Ertan; Araz, Zumray; Erkek, BaranVehicle crash boxes, mounted on the chassis before the bumper, absorb impact energy to protect passengers, but their metal construction adds weight, prompting increased research into lightweight composite alternatives with comparable strength. In this study, energy absorption values (EA), specific energy absorption (SEA), peak forces (PF) and crashing force efficiency (CFE) of carbon fiber, glass fiber, and aramid fiber reinforced composite crash boxes with epoxy resin matrix were compared. Composite crash boxes with different geometries were fabricated using vacuum infusion method in three different geometries: hexagonal, circle, and square. Unlike hand lay-up and prepreg winding methods, vacuum infusion method was chosen because it provides homogeneous distribution of epoxy resin. The crashworthiness of the samples was evaluated through quasi-static compression tests. The best energy absorption performance was obtained with the hexagonal carbon fiber-reinforced composite crash box (246.17 J), corresponding to a specific energy absorption of 8.57 J/g. Although aramid fiber-reinforced specimens showed lower energy absorption, they exhibited the highest crash force efficiency among all tested configurations. These results confirm the significant influence of both fiber type and geometry on the crashworthiness of polymer-based composite crash boxes. The study highlights that hexagonal geometry consistently provided superior energy absorption across all fiber types, while carbon fiber-reinforced composites demonstrated the best overall mechanical performance, making them strong candidates for lightweight crashworthiness applications.Article Effects of Escitalopram and Bupropion on Oxidative Stress Parameters and Blood Count Findings in Female Rats(Yuzuncu Yil Universitesi Tip Fakultesi, 2025) Arihan, Okan; Ergül Erkeç, Ozlem; Doǧan, Abdulahad; Yıldırım, AbdullahIn this study, the effects of two antidepressants with different mechanisms on rat blood oxidative stress parameters and blood count findings were studied. Escitalopram is a selective serotonin reuptake blocker (SSRI) derivative and bupropion has a mechanism of action on noradrenaline and dopamine and increases their synaptic amount by inhibiting their uptake. Adult, female, Wistar-albino rats were divided into 3 different groups with a total of 24 animals. Rats in escitalopram group were administered with 20 mg/kg/day escitalopram and rats in the bupropion group were administered with 20 mg/kg/day bupropion for 28 days via gastric gauge. The rats in the control group were given tap water via gastric gauge. Hematocrit and hemoglobin parameters were significantly higher in Escitalopram and Bupropion than control group. No significant difference was observed in weight gain at the end of 28 days. In this experimental model, 28 days of 20 mg/kg escitalopram or bupropion use did not cause a significant increase in total oxidant status or a significant decrease in total antioxidant status. Oxidative stress index which combines these two findings imply a possible oxidative stress in female rat blood due to Escitalopram treatment. © 2025 Elsevier B.V., All rights reserved.Article Effects of Escitalopram and Bupropion on Oxidative Stress Parameters and Blood Count Findings in Female Rats(Yuzuncu Yil Universitesi Tip Fakultesi, 2025) Arihan, Okan; Ergül Erkeç, Ozlem; Doǧan, Abdulahad; Yıldırım, AbdullahIn this study, the effects of two antidepressants with different mechanisms on rat blood oxidative stress parameters and blood count findings were studied. Escitalopram is a selective serotonin reuptake blocker (SSRI) derivative and bupropion has a mechanism of action on noradrenaline and dopamine and increases their synaptic amount by inhibiting their uptake. Adult, female, Wistar-albino rats were divided into 3 different groups with a total of 24 animals. Rats in escitalopram group were administered with 20 mg/kg/day escitalopram and rats in the bupropion group were administered with 20 mg/kg/day bupropion for 28 days via gastric gauge. The rats in the control group were given tap water via gastric gauge. Hematocrit and hemoglobin parameters were significantly higher in Escitalopram and Bupropion than control group. No significant difference was observed in weight gain at the end of 28 days. In this experimental model, 28 days of 20 mg/kg escitalopram or bupropion use did not cause a significant increase in total oxidant status or a significant decrease in total antioxidant status. Oxidative stress index which combines these two findings imply a possible oxidative stress in female rat blood due to Escitalopram treatment. © 2025 Elsevier B.V., All rights reserved.Conference Paper Fourier analysis-based automatic test pattern generation for combinational circuits(Ieee, 2015) Ayav, Tolga; Ayav, Tolga; Bilgisayar Mühendisliği BölümüFourier analysis of boolean functions has attracted great attention from computer scientists in the last decade but it still has few application areas. This work presents a Fourier analysis-based automatic test pattern generation method for combinational circuits.Article Green Synthesis of Silver Nanoparticles From Melanoleuca Grammopodia: Changes in Bioactive Components, Antidiabetic Properties and Bioaccessibility(TUBITAK, 2025) Acar, İsmail; Okumus, Emine; Karatas, ArzuGreen synthesis of silver nanoparticles (AgNPs) using plant materials allows the production of low-cost and biocompatible nanoparticles without the use of toxic compounds or solvents. In this study, biogenic AgNP/Mg nanoparticles were synthesized using the Melanoleuca grammopodia mushroom. Vitamin C and E contents of the mushroom were 42.6 mg/g and 26.82 mg/g, respectively. FTIR analysis revealed the reducing and stabilizing effects of bioactive components present in M. grammopodia mushroom extract. SEM micrographs showed that the nanoparticles were spherical in form and the EDX spectrum confirmed the presence of the characteristic metallic silver peak at 3.0 keV. A significant reduction in the amounts of phenolic compounds in the mushroom extract and nanoparticles was observed after in vitro gastrointestinal digestion (p < 0.05). The bioaccessibility values of nanoparticles for gallic acid, caffeic acid, syringic acid and protocatechuic acid were determined as 33.46%, 43.25%, 32.18% and 41.49%, respectively. A significant increase in thermal resistance, antioxidant activity (22.50 mg/mL), antilipid peroxidation (4.41 mg/mL), antidiabetic properties (6.02 mg/mL) and bioaccessibility of AgNP/Mg compared to the mushroom extract was detected. This is the first study in which the bioactive components of the M. grammopodia mushroom species were determined and changes and developments in the synthesized nanoparticles were compared with the mushroom extract. The results revealed that this mushroom species and its silver nanoparticles may be a natural and valuable resource with potential applications, especially in the fields of chemistry, pharmacology, and medicine. © 2025 Elsevier B.V., All rights reserved.Article Green Synthesis of Silver Nanoparticles From Melanoleuca Grammopodia: Changes in Bioactive Components, Antidiabetic Properties and Bioaccessibility(TUBITAK, 2025) Acar, İsmail; Okumus, Emine; Karatas, ArzuGreen synthesis of silver nanoparticles (AgNPs) using plant materials allows the production of low-cost and biocompatible nanoparticles without the use of toxic compounds or solvents. In this study, biogenic AgNP/Mg nanoparticles were synthesized using the Melanoleuca grammopodia mushroom. Vitamin C and E contents of the mushroom were 42.6 mg/g and 26.82 mg/g, respectively. FTIR analysis revealed the reducing and stabilizing effects of bioactive components present in M. grammopodia mushroom extract. SEM micrographs showed that the nanoparticles were spherical in form and the EDX spectrum confirmed the presence of the characteristic metallic silver peak at 3.0 keV. A significant reduction in the amounts of phenolic compounds in the mushroom extract and nanoparticles was observed after in vitro gastrointestinal digestion (p < 0.05). The bioaccessibility values of nanoparticles for gallic acid, caffeic acid, syringic acid and protocatechuic acid were determined as 33.46%, 43.25%, 32.18% and 41.49%, respectively. A significant increase in thermal resistance, antioxidant activity (22.50 mg/mL), antilipid peroxidation (4.41 mg/mL), antidiabetic properties (6.02 mg/mL) and bioaccessibility of AgNP/Mg compared to the mushroom extract was detected. This is the first study in which the bioactive components of the M. grammopodia mushroom species were determined and changes and developments in the synthesized nanoparticles were compared with the mushroom extract. The results revealed that this mushroom species and its silver nanoparticles may be a natural and valuable resource with potential applications, especially in the fields of chemistry, pharmacology, and medicine. © 2025 Elsevier B.V., All rights reserved.Journal Article Citation - WoS: 5Heme binding constricts the conformational dynamics of the cytochrome: Heme binding cavity(Amer Chemical Soc, 2012) Akdogan, Yasar; Anbazhagan, Veerappan; Hinderberger, Dariush; Schneider, DirkCytochrome b(559)' is a transmembrane protein formed by homodimerization of the 44-residue PsbF polypeptide and noncovalent binding of a heme cofactor. The PsbF polypeptide can dimerize in the absence and presence of heme. To monitor structural alterations associated with binding of heme to the apocytochrome, we analyzed the apo- and holo-cytochrome structure by electron paramagnetic resonance spectroscopy. Spin labeling of amino acids located close to the heme binding domain of the cytochrome revealed that the structure of the heme binding domain is unconstrained in the absence of heme. Heme binding restricts the conformational dynamics of the heme binding domain, resulting in the structurally more constricted holo-cytochrome structure.Conference Object High-Frequency Link Voltage Multiplexing for Multi-Level Inverters With Optimized Transformer Windings(Institute of Electrical and Electronics Engineers Inc., 2025) Hataş, HasanThe need for more than one voltage source in multilevel inverters (MLI) increases the system cost and circuit complexity. In this study, a voltage multiplexing method with a high frequency link (HFL) structure is proposed as a solution to the problem in question. Unlike the traditional HFL application, a half H -bridge is added to the input of the transformer and thus the obtained voltage is diversified. The output voltage is provided by a separate H-bridge circuit by preserving the isolation of the input and output voltages. The winding ratios of the transformer are determined by optimizing the total harmonic distortion (THD) of the output voltage with the NLC method. The proposed topology provides a low THD value of 1 1. 7 3% despite different voltage steps. In addition, simulations performed under various amplitude and frequency conditions using the SPWM technique have shown that the proposed method is effective and applicable. © 2025 Elsevier B.V., All rights reserved.Conference Object High-Frequency Link Voltage Multiplexing for Multi-Level Inverters With Optimized Transformer Windings(Institute of Electrical and Electronics Engineers Inc., 2025) Hataş, HasanThe need for more than one voltage source in multilevel inverters (MLI) increases the system cost and circuit complexity. In this study, a voltage multiplexing method with a high frequency link (HFL) structure is proposed as a solution to the problem in question. Unlike the traditional HFL application, a half H -bridge is added to the input of the transformer and thus the obtained voltage is diversified. The output voltage is provided by a separate H-bridge circuit by preserving the isolation of the input and output voltages. The winding ratios of the transformer are determined by optimizing the total harmonic distortion (THD) of the output voltage with the NLC method. The proposed topology provides a low THD value of 1 1. 7 3% despite different voltage steps. In addition, simulations performed under various amplitude and frequency conditions using the SPWM technique have shown that the proposed method is effective and applicable. © 2025 Elsevier B.V., All rights reserved.Article Citation - Scopus: 1Hydrothermal Liquefaction of Sinapis Arvensis Biomass Using TiO2-Supported Metal Catalysts: A Study on Bio-Oil Yield and Composition(Elsevier, 2026) Durak, Halil; Genel, Salih; Genel, YasarThe development of catalytic systems for hydrothermal liquefaction (HTL) is crucial for transforming lignocellulosic biomass into biofuels with high energy density. This research investigates the HTL process of Sinapis arvensis biomass using TiO2-supported catalysts, specifically Fe, Al, and Fe-Al, at temperatures from 275-325 degrees C. The catalysts were synthesized through incipient wetness impregnation and characterized using techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and inductively coupled plasma optical emission spectrometry (ICP-OES) to evaluate element distribution and surface chemistry. Findings show that the Al/TiO2 catalyst boosted lighter bio-oil production via acid-catalyzed dehydration and decarboxylation, while the Fe/TiO2 catalyst favored heavier oils through redox-assisted depolymerization. The Fe-Al/TiO2 bifunctional catalyst exhibited superior biomass conversion, yielding more aliphatic hydrocarbons. Gas chromatography-mass spectrometry (GC-MS) revealed how catalysts influenced product distributions, increasing monoaromatic and aliphatic compounds and reducing oxygenated entities. Elemental analysis confirmed higher carbon content, lower oxygen levels, and improved higher heating values (HHVs) in catalyzed bio-oils, indicating enhanced fuel quality.Article Citation - Scopus: 1Hydrothermal Liquefaction of Sinapis Arvensis Biomass Using TiO2-Supported Metal Catalysts: A Study on Bio-Oil Yield and Composition(Elsevier, 2026) Durak, Halil; Genel, Salih; Genel, YasarThe development of catalytic systems for hydrothermal liquefaction (HTL) is crucial for transforming lignocellulosic biomass into biofuels with high energy density. This research investigates the HTL process of Sinapis arvensis biomass using TiO2-supported catalysts, specifically Fe, Al, and Fe-Al, at temperatures from 275-325 degrees C. The catalysts were synthesized through incipient wetness impregnation and characterized using techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and inductively coupled plasma optical emission spectrometry (ICP-OES) to evaluate element distribution and surface chemistry. Findings show that the Al/TiO2 catalyst boosted lighter bio-oil production via acid-catalyzed dehydration and decarboxylation, while the Fe/TiO2 catalyst favored heavier oils through redox-assisted depolymerization. The Fe-Al/TiO2 bifunctional catalyst exhibited superior biomass conversion, yielding more aliphatic hydrocarbons. Gas chromatography-mass spectrometry (GC-MS) revealed how catalysts influenced product distributions, increasing monoaromatic and aliphatic compounds and reducing oxygenated entities. Elemental analysis confirmed higher carbon content, lower oxygen levels, and improved higher heating values (HHVs) in catalyzed bio-oils, indicating enhanced fuel quality.Article Impact of E-Service Quality on Direct Booking Intentions in Hotels: The Mediating Effects of E-Satisfaction and E-Trust(Emerald Publishing, 2025) Rol, Serkan; Alaeddinoğlu, FarukPurpose Despite the increasing trend of online hotel bookings, understanding the factors that influence consumers’ intentions to book directly through hotel websites remains essential. This study aims to investigate the effect of e-service quality in hotel websites on consumers’ direct booking intention, as well as the underlying mechanism involving e-satisfaction and e-trust perceptions. Design/methodology/approach This study used a quantitative methodology using a structured online survey approach. To quantify the role of mediation, PROCESS macro was used. Since the study aimed to examine multiple mediation effects, Model 4 with a parallel mediation model was applied. Findings Based on a survey of 393 participants, this study reveals a significant relationship between e-service quality and consumers’ direct booking intention. In addition, perceptions of e-satisfaction and e-trust partially mediate the impact of e-service quality, underscoring its pivotal role in enhancing direct bookings for accommodation businesses. Practical implications Hoteliers should prioritize enhancing e-service quality and fostering positive e-satisfaction and e-trust perceptions to increase direct bookings; in doing so, they can lessen their reliance on intermediaries. Originality/value This study contributes significantly to existing knowledge of direct booking intention by examining the associations between e-service quality, e-satisfaction, e-trust and direct booking intention on hotel websites. © 2025 Elsevier B.V., All rights reserved.Article Impact of E-Service Quality on Direct Booking Intentions in Hotels: The Mediating Effects of E-Satisfaction and E-Trust(Emerald Publishing, 2025) Rol, Serkan; Alaeddinoğlu, FarukPurpose Despite the increasing trend of online hotel bookings, understanding the factors that influence consumers’ intentions to book directly through hotel websites remains essential. This study aims to investigate the effect of e-service quality in hotel websites on consumers’ direct booking intention, as well as the underlying mechanism involving e-satisfaction and e-trust perceptions. Design/methodology/approach This study used a quantitative methodology using a structured online survey approach. To quantify the role of mediation, PROCESS macro was used. Since the study aimed to examine multiple mediation effects, Model 4 with a parallel mediation model was applied. Findings Based on a survey of 393 participants, this study reveals a significant relationship between e-service quality and consumers’ direct booking intention. In addition, perceptions of e-satisfaction and e-trust partially mediate the impact of e-service quality, underscoring its pivotal role in enhancing direct bookings for accommodation businesses. Practical implications Hoteliers should prioritize enhancing e-service quality and fostering positive e-satisfaction and e-trust perceptions to increase direct bookings; in doing so, they can lessen their reliance on intermediaries. Originality/value This study contributes significantly to existing knowledge of direct booking intention by examining the associations between e-service quality, e-satisfaction, e-trust and direct booking intention on hotel websites. © 2025 Elsevier B.V., All rights reserved.Journal Article Citation - WoS: 7Citation - Scopus: 9Input contract testing of graphical user interfaces(World Scientific Publ Co Pte Ltd, 2016) Tuglular, Tugkan; Belli, Fevzi; Linschulte, Michael; Tuğlular, Tuğkan; Bilgisayar Mühendisliği BölümüUser inputs are critical for the security, safety, and reliability of software systems. This paper proposes a new concept called user input contracts, which is an integral part of a design-by-contract supplemented development process, and a model-based testing approach to detect violations of user input contracts. The approach generates test cases from an input contract integrated with graph-based model of user interface specification and applies them to the system under consideration. The paper presents a proof-of-concept tool that has been developed and used to validate the approach by experiments. The experiments are conducted on a web-based system for marketing tourist services to analyze input robustness of system under consideration with respect to user input contracts.
