Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Densification-Induced Chemical Reorganization and Mechanical Enhancement in Amorphous Si2BC3N(Elsevier, 2026-02) Durandurdu, MuratThe atomistic mechanisms that govern the mechanical performance of amorphous silicon-boron carbonitride (SiBCN) ceramics remain insufficiently understood, particularly regarding the role of density. Here, we employ ab initio molecular dynamics simulations to elucidate the structural evolution and mechanical response of low-density (LDA, 2.20 g/cm3) and high-density (HDA, 2.53 g/cm3) amorphous Si2BC3N prepared via melt-quench. The HDA phase exhibits markedly higher atomic packing and network connectivity, accompanied by a nontrivial chemical reorganization. Densification significantly enhances heteronuclear bonding-especially Si-C coordination-while suppressing C-C and Si-Si homopolar bonds. These changes yield substantial mechanical strengthening: the HDA phase exhibits a 48% increase in bulk modulus (130 GPa vs. 88 GPa), along with elevated Young's (266 GPa) and shear (112 GPa) moduli. Our findings reveal a clear density-structure-property relationship in amorphous SiBCN, demonstrating that densification suppresses weak self-bonded motifs and promotes a robust, interconnected atomic network. This insight provides a pathway for designing high-performance amorphous SiBCN ceramics for extreme-environment applications.Article Supervised Learning-Driven Dead Band Control of Occupant Thermostats for Energy-Efficient Residential HVAC(Elsevier, 2026-03) Savasci, Alper; Ceylan, Oguzhan; Paudyal, SumitHeating, ventilation, and air conditioning (HVAC) systems play a crucial role in demand-side management (DSM) by shaping residential electricity consumption and enabling flexible, grid-responsive operation. Thermostats in HVAC systems regulate indoor temperature as part of a closed-loop control framework, typically incorporating a fixed temperature dead band-a range around the setpoint where no action is taken-to reduce energy use and prevent frequent cycling of the HVAC system. Although essential for efficiency and equipment longevity, fixed dead bands limit adaptability, as dynamically adjusting them under varying environmental conditions remains challenging for occupants. To address this limitation, we propose a machine learning (ML)-based dead band tuning framework that optimally adjusts thermostat settings in real time. The method integrates conventional optimization with data-driven modeling: a mixed-integer linear programming (MILP) model is first used to gen erate optimal dead band values under measured outdoor temperature records (diverse seasonal weather scenarios) which are then employed to train the ML-based predictor to learn a real-time discrete dead band decision policy that approximates the MILP-optimal hysteresis-aware decisions. Among the evaluated models, Random Forest demonstrates superior predictive performance, achieving a mean squared error (MSE) of 0.0399 and a coefficient of determination (R2) of 95.75 %.Article Tuning Properties of Amorphous Boron Via Hydrogenation: An Ab Initio Study(Elsevier, 2026-01) Durandurdu, MuratAb initio simulations are employed to investigate the structural, mechanical, and electronic properties of hydrogenated amorphous boron (a-B:H) across a range of hydrogen concentrations (approximate to 6-21 at.%). The results indicate that pentagonal-like boron clusters constitute the primary structural motifs. The bonding environment consists of both B-H terminal bonds and B-H-B bridging bonds, with the fraction of bridging bonds ranging from 10 % to 16 %. Increasing the hydrogen content leads to a reduction in density and bulk modulus, accompanied by a systematic widening of the electronic band gap. These results demonstrate that hydrogen incorporation profoundly modifies the atomic structure, softens the network, and enhances the semiconducting character of a-B:H, highlighting the tunability of properties in boron-based amorphous materials.Article Citation - WoS: 7Citation - Scopus: 7Unveiling the Multifaceted Properties of a 3D Covalent-Organic Framework: Pressure-Induced Phase Transition, Negative Linear Compressibility and Auxeticity(Elsevier, 2023-08) Erkartal, MustafaHigh-pressure behavior and mechanical properties of a three-dimensional covalent-organic framework (NPN-1) were investigated by using different types of first principles molecular simulations. An irreversible pressureinduced first-order isosymmetric phase transition was predicted at 0.14 GPa. The subunit of NPN-1 retains its rigidity under pressure thanks to the strong covalent bonds. However, compression leads to significant tilting of the nitrophenyl groups. The mechanical properties of frameworks are highly anisotropic. Remarkably, both phases exhibit not only negative linear compressibility along the c-axis but also negative Poisson's ratio in certain directions. Detailed structural analysis revealed that the origin of the phase transition and anomalous mechanical properties of both phases are the wine-rack motif and strut-hinge mechanism. To the best of our knowledge, this study is the first report of such behavior in COFs, opening up new avenues for the exploration of COFs as materials for many promising applications.Article The Ground State Properties of Two Dimensional Fermi Gas System Confined in a Potential Composed of Harmonic and a Gaussian Terms(Elsevier, 2019-01) Gulveren, Berna; Sahin, Mehmet; Atav, UlfetIn this work, the ground state properties of two dimensional Fermi gas system interacting in a potential con- sisting of harmonic and Gaussian terms are investigated in the frame of Thomas-Fermi approximation. The depth and the curvature of the potential are changed by varying confinement parameters and the influence of the constraining conditions on the system properties like the density profile, the kinetic and the potential energy of the fermionic system is analyzed comprehensively. The deviations of the results due to the Gaussian potential are also determined by comparing the results with those obtained for pure harmonic potential. Calculations are also performed analytically for non-interacting case for comparative purposes. The results show that the confinement parameters play crucial role on the ground state properties of confined system.Article Citation - WoS: 8Citation - Scopus: 9Synthesis of Benzotriazole Functionalized ZIF-8 by Postsynthetic Modification for Enhanced CH4 and CO2 Uptakes(Elsevier, 2022-08) Erkartal, Mustafa; Incekara, Kaan; Sen, UnalIn this work, a series of functionalized ZIF-8 were synthesized via incorporation of benzotriazole ligands into the framework with a post-synthetic method. The crystal structure and porosity were preserved for all functionalized samples. Although a relatively low percentage of ligand exchange (approximately 10-22%) was observed due to steric and kinetic effects, a remarkable improvement was found in CO2 and CH4 uptake capacities due to the incorporation of more polar N sites into the structure and the change in pore size of the frameworks. The resulting ZIF-8-S5 exhibited 45.17(CO2) and 15.08 (CH4) cm(3) g(-1) at 273 K under 1.2 bar, which corresponds to an enhancement of 20 and 35% compared to pristine ZIF-8. Further, all functionalized samples showed the significant improvement of selective CO2 over N-2.Article Citation - WoS: 16Citation - Scopus: 15Role of AHR, NF-kB and CYP1A1 Crosstalk With the X Protein of Hepatitis B Virus in Hepatocellular Carcinoma Cells(Elsevier, 2023-02) Celik-Turgut, Gurbet; Olmez, Nazmiye; Koc, Tugba; Ozgun-Acar, Ozden; Semiz, Asli; Dodurga, Yavuz; Sen, AlaattinIn this study, it was aimed to elucidate the interaction between aryl hydrocarbon receptor (AHR), nuclear factor -kappa B (NF-kB), and cytochrome P4501A1 (CYP1A1) with hepatitis B virus X protein (HBX) in a human liver cancer cell line (HepG2) transfected with HBX. First, AHR, NF-kB, and CYP1A1 genes were cloned into the appropriate region of the CheckMate mammalian two-hybrid recipient plasmids using a flexi vector system. Renilla and firefly luciferases were quantified using the dual-luciferase reporter assay system to measure the interactions. Secondly, transient transfections of CYP1A1 and NF-kB (RelA) were performed into HBX-positive and HBX-negative HepG2 cells. The mRNA expression of CYP1A1 and NF-kB genes were confirmed with RT-PCR, and cell viability was measured by WST-1. Further verification was assessed by measuring the activity and protein level of CYP1A1. Additionally, CYP1A1/HBX protein-protein interactions were performed with co-immunoprecipitation, which demonstrated no interaction. These results have clearly shown that the NF-kB and AHR genes interact with HBX without involving CYP1A1 and HBX protein-protein interactions. The present study confirms that AHR and NF-kB interaction plays a role in the HBV mechanism mediated via HBX and coordinating the carcinogenic or inflammatory responses; still, the CYP1A1 gene has no effect on this interaction.Article Pressure-Driven Structural Evolution of Amorphous InN(Elsevier, 2025-02) Durandurdu, MuratThrough constant-pressure ab initio simulations, we have uncovered high-pressure phase transformations in amorphous indium nitride for the first time. Our results reveal a distinct two-step progression under compression. Initially, a polyamorphic transition occurs, where the low-density amorphous (LDA) phase transforms into a high-density amorphous (HDA) phase. This HDA structure remains stable in some pressure range and then crystallization initiates, leading to a rocksalt configuration. Upon decompression, the HDA phase reverts to an amorphous network with a slightly higher density and coordination number than the initial LDA state.Article Citation - WoS: 5Citation - Scopus: 5Optimization of High Efficiency Blue Emissive N-, S-Doped Graphene Quantum Dots(Elsevier, 2025-02) Tiras, Kevser Sahin; Soheyli, Ehsan; Sharifirad, Zeynab; Mutlugun, EvrenGraphene quantum dots (GQDs) with bright emission at short wavelengths have attracted much attention due to their importance in various applications such as light-emitting diodes. During or after synthesis, several parameters can significantly improve the optical properties of GQDs. This study presents a facile solvothermal method with low-cost precursors using glutamic acid as the carbon source to realize blue emitting GQDs. The positive effects of urea and 1-octanethiol as nitrogen and sulfur dopants on the photoluminescence quantum yield (PLQY) of the prepared GQDs were demonstrated and optimized. The results confirmed the formation of 2.2 nm nanoparticles with a bright emission around 381 nm with a full width at half maximum of 58 nm and a PLQY approaching 70 %. The decay lifetime of the emission also showed a tri-exponential profile with an average lifetime of 2.4 ns. The simplicity of the preparation method without any post-treatment process, together with a high PLQY of 70 % at short wavelengths, nominates the prepared GQDs for optoelectronics and UV light-driven biological purposes.Article Citation - WoS: 1Magnus Series Expansion Method for Solving Nonhomogeneous Stiff Systems of Ordinary Differential Equations(Elsevier, 2016) Atay, Mehmet T.; Eryilmaz, Aytekin; Komez, Sure; Köme, SureIn this paper, Magnus Series Expansion Method, which is based on Lie Groups and Lie algebras is proposed with different orders to solve nonhomogeneous stiff systems of ordinary differential equations. Using multivariate Gaussian quadrature, fourth (MG4) and sixth (MG6) order method are presented. Then, it is applied to nonhomogeneous stiff systems using different step sizes and stiffness ratios. In addition, approximate and exact solutions are demonstrated with figures in detail. Moreover, absolute errors are illustrated with detailed tables.