Yıldız Technical University Research Information System
Not a member yet
91324 research outputs found
Sort by
Synthesis and investigation of dielectric properties of a hydrogen-bonded chalcone aniline monomer and its polymer
No full textA tertiary amine-substituted chalcone-based monomer was synthesized via a Claisen-Schmidt reaction between 3-aminoacetophenone and 4-(dimethylamino) benzaldehyde, using KOH as a base catalyst and ethanol as the solvent under ambient conditions for 24 h. The chalcone-modified aniline monomer was subsequently polymerized oxidatively using ammonium persulfate as an initiator and HBr as a doping agent in an aqueous medium for 24 h at room temperature. Additionally, a hydrogen-bonded liquid crystalline (LC) compound, 11-(4-cyanobiphenyl-4(-oxy)undekan-1-ol (LC11), was synthesized as per the literature and employed as an H-bond donor mesogen. Both the tertiary amine-substituted chalcone monomer (Ch-ANI) and its polymer (Ch-PANI) served as hydrogen bond acceptors. The liquid crystalline behavior of the materials was investigated using DSC (Differential Scanning Calorimetry), dielectric and AC conductivity measurements, spectroscopic methods, and POM (Polarized Optical Microscopy). To elucidate the hydrogen bonding mechanism between LC11 and the synthesized materials, computational methods were employed
Revealing the Bright Soliton Solution of the Perturbed Fourth-Order SchröDinger-Hirota Equation Having Cubic-Quintic-Septic Laws and Modulation Instability
No full textThis paper aims to explore the bright soliton solutions of the perturbed fourth-order Schrödinger-Hirota equation with cubic-quintic-septic nonlinearities, a model relevant for understanding complex wave dynamics in nonlinear media. Bright solitons are indispensable in optics, particularly for applications that benefit from stable, long-distance transmission with minimal signal degradation. Their usage spans from telecommunications to medical imaging and sensing, where their ability to maintain shape and resist interference makes them highly valuable. Using the addendum to the Kudryashov's method, we systematically derive the bright soliton solutions, including both bright and singular forms, and conduct a modulation instability analysis to identify stability regions and parameter conditions that influence soliton persistence. The methodology involves addendum to the Kudryashov's method through additional analytical steps, tailored to accommodate the equation's complex terms, enabling the extraction of explicit solutions. Findings reveal that the parameters significantly impact soliton amplitude, displacement and stability, as illustrated through 2D and 3D plots. The modulation instability analysis further clarifies the effect of these parameters on soliton stability, underscoring the balance between dispersive and nonlinear influences. This study's limitations include focusing on analytical solutions within specific parameter ranges, which may not fully capture the behavior under extreme conditions. Nonetheless, the originality lies in the integration of Kudryashov-based techniques with a high-order nonlinear model, offering benchmark solutions and insights that support future theoretical and experimental research in nonlinear optics and other wave-propagating media
A second-law analysis-based analytical method for insulation thickness optimization in a space with constant insulation volume
No full textThis paper develops the first closed-form analytical model for optimizing insulation thickness distribution in enclosures with non-uniform thermal boundaries (e.g., 10 °C and −5 °C), under a fixed insulation volume or cost constraint. Unlike prior second-law-based studies (e.g., Keçebaş, Ucar, Arslan) that required iterative or numerical optimization, our approach derives explicit algebraic relations by equating marginal exergy destruction rates across all walls. This contribution fills a clear research gap by providing a non-iterative solution applicable to refrigerators, building envelopes, and industrial systems where unequal boundary conditions exist. A case study shows that the second-law-based optimum differs significantly from the first-law: the colder wall requires 150 mm insulation versus 124 mm by the first-law. This reduces exergy destruction by 15 %, and although total heat transfer rises slightly (7.84 vs. 7.4 W/m2), the overall system energy consumption decreases by 3.3 % thanks to improved COP. These results highlight the practical importance of exergy-based allocation, which prioritizes preserving work potential over merely reducing heat loss. The proposed closed-form formulas also provide a benchmark for validating numerical/CFD models and can be extended in future work to include life-cycle cost and environmental impact
KR12 peptide-modified ECM coating for enhanced osteogenic and antimicrobial activity of titanium surfaces
No full textKENT KİMLİĞİNİ YANSITACAK VE İKLİM DEĞİŞİKLİĞİNE UYUM SAĞLAYABİLECEK ODUNSU BİTKİLER: ÇORUM
No full textComprehending the internal– external mode of participatory urban regeneration practice: Learning lessons from the sanitation programme of the Orangi Pilot Project, Karachi, Pakistan
No full textSignificant issues including dilapidated housing, poor sanitation systems and inadequate provision, operation and maintenance of utility services are underlying factors in the depletion of informal settlements in Pakistan. Furthermore, these issues are exacerbated by institutional inefficiencies in dealing with them. To address the challenges, the Orangi Pilot Project (OPP) was launched in Orangi Town, Karachi, by a non-governmental organisation (NGO) in collaboration with local residents and government agencies, using an internal–external model of participation. The aim of the study discussed in this paper was to better comprehend the methodology used in the internal–external model, as well as to review the sanitation programme implemented as part of the OPP and how it affected urban infrastructure and quality of life. This article is also included in The Business & Management Collection which can be accessed at https://hstalks.com/business/
Hydrodynamic cavitation-assisted tissue ablation using a continuum robotic device with heat and mass transfer considerations
No full textPrecision and efficiency constitute the main challenges in minimally invasive surgeries. Current endoscopic robotic system limitations have been sought for innovative design and optimization strategies. Moreover, the use of flexible surgical robots in high-speed flows such as cavitation flows is a problem that needs to be solved. To address these issues, the design optimization of a tendon-driven endoscopic robot based on hydrodynamic cavitation is presented in this study. The flexible part of the robot was analyzed using the Finite Element Method (FEM), where fluid–structure interactions and material mechanical properties were considered which led to the fabrication of a prototype. Employing the shadow-graphy technique, sprays emerging from the endoscopic robot were imaged at various bending angles and fluid pressures to examine carefully flow cone angle change effects. Subsequently, the results from the experiments involving ex vivo human cervix and uterus myoma tissues were included. Thermal conditions and mass transfer rates were measured according to variations in applied pressure, bending angle enabling quantitative assessment of heat diffusion and material removal efficiency at the tissue interface. This study focuses on the continuum endoscopic robots operating at high flow rates and presents an optimal working area via a prototype. Tissue experiments demonstrated that superficial endometrial ablation increased proportionally with the bending angle of the robot in both cervix and myoma tissues, which are characterized by their dense and resilient structure. The results highlight the interconnected dynamics of cone angle, flow pressure, and tissue ablation during robot bending. In short, this study presents guidelines for future studies on the design optimization of continuum robots for high-flow rate applications
Integrating metaheuristic optimization algorithms with random forest to predict waste generation in construction and demolition projects
No full textThe construction sector is a significant source of global waste, making accurate and proactive prediction of Construction and Demolition Waste (C&DW) essential for sustainable resource management and circular economy efforts. However, estimating C&DW at the project level remains a major challenge. This paper investigates whether C&DW prediction accuracy can be enhanced by integrating the Random Forest (RF) model with two metaheuristic optimization algorithms: the Archimedes Optimization Algorithm (AOA) and Grey Wolf Optimization (GWO). Based on data from 200 real-world projects in Palestine, the GWO-RF model achieved the highest predictive accuracy using only four input variables: project type, start date, building type, and number of floors. To ensure model transparency, Shapley Additive Explanations (SHAP) analysis confirmed that project type and the number of floors were the most influential parameters. This study thus provides a practical, robust, and highly accurate model to support effective waste management strategies in the construction industry.</p
Development Study of Teachers' Digital Pedagogy Research Community Competence Perception Scales
No full textAbstractThe present study seeks to develop "Digital Pedagogy Research Community Competence Perception Scales" consisting of two scales, namely "Digital Pedagogy Competence Perception Scale in Research Community" (Scale 1) and "Digital Pedagogy Competence Perception Scale in Teaching" (Scale 2) to determine teachers' perceptions of digital pedagogical competence in professional development. Within the scope of validity studies, Exploratory Factor Analysis (EFA) was conducted with 274 teachers in Bursa (in 2024-2025 academic year), and Confirmatory Factor Analysis (CFA) was conducted with 309 different teachers. In the validity study, EFA indicated that the total variance explained was 73.03% (Scale 1) and 69.10% (Scale 2) and that the items in both scales loaded under 2 factors with eigenvalues above 1. In addition, the inter-factor correlation values were found to be r≥.75 in Scale 1 and r ≥.78 in Scale 2. According to the reliability of the scales, Cronbach's.alpha (Scale 1 and Scale 2: α ≥.95) and McDonald's omega ( Scale 1 and Scale 2: ω ≥.95) coefficients above .90 for both scales. As a result, "Digital Pedagogy Research Community Competence Perception Scales" were found to be valid and reliable in measuring teachers' digital pedagogical competencies. Factors in Scale 1 were named as "Cognitive Competence Perception" and "Social Competence Perception"; factors in Scale 2 were named as "Digital Pedagogical Orientation" and "Digital Pedagogical Practices". Scale 1 consisted of 14 items and scale 2 consisted of 15 items.</p
Efficient design, operation and control of commercial proton exchange membrane fuel cells (PEMFCs) in clean energy technology
No full textProton exchange membrane fuel cells (PEMFCs) are a promising clean energy technology with the potential to play a significant role in a sustainable energy future. Although current-voltage measurements for PEMFCs are given in manufacturer data sheets, the model parameters are unknown. The accurate and reliable identification of PEMFC model parameters is a major challenge that requires further research and advanced algorithms. Overcoming this challenge will pave the way for more efficient operation of PEMFC systems and contribute to the widespread adoption of this promising clean energy technology. With this point of view, the present study develops a novel arctic puffin optimization based on quasi-opposition-based learning and dynamic fitness-distance balance (APO-QOBL-dFDB) for more efficient design, operation, and control of PEMFC systems. The best set of seven unknown parameters (ξ1, ξ2, ξ3, ξ4, β, Rc, λ) of the Ballard Mark V, Temasek 1 kW, NedStack PS6, and BSC 500W PEMFC stacks are identified using the developed APO-QOBL-dFDB algorithm and 11 state-of-the-art metaheuristic techniques. Mean absolute error (MAE), root mean square error (RMSE), and the sum of squared error (SSE) between model predictions and experimental data are selected as objective functions. The minimum RMSE, MAE, and SSE results in 12 test cases of the PEMFC parameter identification problem were achieved by the developed APO-QOBL-dFDB algorithm. The proposed algorithm outperforms competing algorithms in 10 out of 12 PEMFC cases based on standard deviation metric results. The efficiency metric results for the APO-QOBL-dFDB are calculated to be 99.97%, 99.81%, 99.60%, and 99.94% in parameter optimization of Ballard Mark V, Temasek 1 kW, NedStack PS6, and BCS 500W PEMFC stacks, respectively. The evaluation based on the relative error (RE) metric showed that RMSE is the most suitable objective function for estimating the parameters of the examined PEMFC stacks with high accuracy. Considering all the results together, the developed APO-QOBL-dFDB algorithm comes to the fore as the best method in the PEMFC parameter identification problem with an average Friedman score of 1.1611