Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
36 results
Search Results
Now showing 1 - 10 of 36
Article Geothermal Drying in Agricultural Sector - Worldwide Examples(Elsevier Ltd, 2026) Tomaszewska, B.; Baba, A.; Akkurt, G.G.; Mukti, M.; Helvaci, H.U.; Bielec, B.; Operacz, A.Agricultural drying is traditionally used to preserve fruits and vegetables which mostly relied on energy-intensive processes usually powered by fossil fuels. In this review, we explore an innovative and sustainable alternative: using geothermal energy to dry produce. The paper reviews the main technical aspects related to the use of geothermal energy in drying fruits and vegetables. We delve into the technical details of two leading methods, hot air drying and refractive window drying, highlighting their advantages, drawbacks, and the critical factors that influence the quality of the final product. By examining real-world applications from countries as diverse as Iceland, the USA, Greece, Turkey, Macedonia, Kenya, Serbia, El Salvador, Guatemala, Mexico, Thailand, Poland, and the Philippines, this paper showcases how geothermal energy can be directly applied in drying operations—whether through standalone systems operating between 60 °C and 97 °C or integrated cascade systems wherever geothermal resources are used for power generation and in the form of the waste heat for drying purposes, can be considered as important direction. Due to a lack of actual information on the economic aspects of geothermal drying, in addition to outlining the technical merits of geothermal drying, we also discuss economic considerations and potential challenges to provide a roadmap for future projects. Moreover, the authors underlined several aspects that can contribute to the failure or limited success of geothermal drying projects. Ultimately, adopting geothermal drying not only reduces greenhouse gases (GHS) emissions but also lessens dependence on costly, polluting fossil fuels, paving the way for a greener, more energy-efficient future in food preservation. © 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Article Floating Pontoons to Reduce Wave Overtopping at a Vertical Seawall: An Experimental Study(Elsevier Ltd, 2026) Eroglu, N.; Ozbahceci, B.Coastal flooding caused by extreme wind, wave and water level conditions is an increasing concern, particularly for historical coastal cities where conventional flood defenses may be unsuitable due to aesthetic and cultural constraints. Floating structures have gained attention for their adaptability to sea level rise, yet previous studies have mainly examined wave transmission rather than their capacity to reduce wave overtopping. This study presents the first experimental investigation to directly measure wave overtopping for floating pontoons placed in front of a vertical seawall. Tests were conducted in a controlled wave flume environment to evaluate the effects of pontoon geometry, mooring type, and distance from the seawall on overtopping performance. The results show that floating pontoons can significantly reduce wave overtopping. Overtopping reductions of 75–98 % was achieved, with the most effective configuration combining high freeboard and large draft (1.5 m prototype scale). Wave transmission was also measured and compared with existing prediction formulas. When the transmitted wave height is used in EurOtop (2018) formula, overtopping rate is overestimated particularly when the relative crest freeboard exceeds 0.75 as differences in wave steepness, spectral period and directional spreading induced by the floating pontoon are not captured by the formula. To improve predictive capability, a new influence coefficient (γ<inf>fp</inf>) is proposed to modify Eq. 7.5 in EurOtop (2018) for cases involving pile-guided floating pontoons. These findings provide new experimental evidence on wave–structure interaction and highlight the potential of floating pontoons as effective, adaptable, and visually compatible flood mitigation solutions for vulnerable coastal regions. © 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Article Scattering of Water Waves by a Truncated Vertical Cylinder of Arbitrary Cross Section: Asymptotic Analysis(Elsevier Ltd, 2025) Disibuyuk, N.B.; Yilmaz, O.Scattering of water waves by a vertical truncated cylinder of arbitrary cross-section is investigated using the linear theory and asymptotic analysis. The flow domain is divided into the exterior and interior regions. The linearized boundary value problem is solved by the method of matched eigenfunctions and in an asymptotic manner that deals with the arbitrary geometry of the cross section. The cross-section shape is expanded in a Fourier series involving a small parameter that represents the deviation of the geometry from a circle. The advantage of this method is that the wave forces on the cylinder are obtained in terms of the coefficients of the Fourier series of the cylinder shape. For the case of a circular cylinder, exact analytical results are recovered. Cylinders with cross-section geometries of cosine-type radial perturbations and of a quasi-ellipse are considered for validation of the present method. Good agreement with the published results is obtained with the first and second-order asymptotic orders. New graphical analyses based on the problem parameters are presented for a vertical elliptical cylinder. Long-wave approximations of wave forces are obtained for cylinders whose cross-sections are not too different from a circle. © 2025 Elsevier LtdArticle Citation - WoS: 3Citation - Scopus: 3Nonlocal Static Modeling of Laminated Composite Shells Using Peridynamic Differential Operator in a Higher-Order Shear Deformation Framework(Elsevier Ltd, 2025) Bab, Yonca; Dorduncu, Mehmet; Kutlu, Akif; Markert, BerndThis study investigates the flexural behaviour of the laminated composite shells in the framework of Higher-Order Shear Deformation Theory (HSDT) and Peridynamic Differential Operator (PDDO), namely PD-HSDT, for the first time. Laminated composite shell structures are widely used in aerospace, automotive, and marine industries due to their high strength-to-weight ratio and design flexibility. Therefore, understanding their mechanical behavior under various loading conditions is crucial for ensuring structural reliability and performance optimization. However, such structures may possess complex curvatures and highly heterogenous laminate stackings, leading to inaccurate numerical stress analyses. The HSDT successfully captures displacement and stress distributions as well as cross-sectional warping through higher-order functions exist in the kinematics. Moreover, the PDDO represents the local derivatives in their nonlocal form, making it well-suited for problems involving higher-order derivatives and discontinuities. The governing equations and boundary conditions of the HSDT are solved by using the PDDO to accurately achieve the stress and displacement fields in the laminated composite shells. The robustness of the PD-HSDT is established by considering various loading and boundary conditions. The proposed approach demonstrates high accuracy in stress and displacement predictions when validated against reference solutions available in existing literature. This indicates strong potential for extending the methodology to more complex loading scenarios and damage mechanisms in future studies.Article Citation - WoS: 3Citation - Scopus: 3A Novel Hybrid Thin Jacketing Method for Seismic Retrofitting of Substandard Reinforced Concrete Columns(Elsevier Ltd, 2025) Narlitepe, Furkan; Kian, Nima; Demir, Ugur; Demir, Cem; Ilki, AlperThis paper introduces a novel hybrid thin jacketing method for seismic strengthening of substandard reinforced concrete (RC) columns for which structural repair mortar along with carbon fiber reinforced polymer (CFRP) and longitudinal steel bars are utilized. The method involves three application phases comprising a) removing the cover concrete, b) re-forming the cover concrete with structural repair mortar just after installing extra longitudinal steel bars c) transverse wrapping of CFRP sheets. The effect of using different types of structural repair mortar and its application process are other test parameters taken into account in this study. To evaluate the efficacy of the proposed method, a comprehensive experimental program was conducted, consisting of six largescale RC column specimens with square and rectangular cross-sections. For all of the specimens tested under a simultaneous constant axial load and reversed cyclic lateral loading, three main properties representing existing substandard RC columns such as a) insufficient transverse reinforcement, b) high axial load ratio (0.75) and, c) relatively high shear force corresponding to moment capacity to shear capacity ratios between 0.60 and 0.80, were considered. The responses of specimens were specified in terms of the lateral load-displacement curves, stiffness variation, ductility ratios, damage progression, and energy dissipation. The experimental results demonstrated that in case the retrofitting method is properly applied, the strengthened columns exhibit satisfactory performance in terms of strength and ductility with a remarkable improvement with respect to the substandard columns. Furthermore, a numerical study was conducted to validate the experimental results by using the OpenSees framework.Article Citation - WoS: 1Citation - Scopus: 2Effect of Preparation Method on the Activity of Red Mud Based Catalysts in Hydrogen Production From Biomass(Elsevier Ltd, 2025) Cay, Hakan; Akbas, Nazire Merve; Duman, Gozde; Simsek, Osman; Yildiz, Guray; Wang, Weitao; Yanik, JaleBiomass gasification is a promising technology for hydrogen production. This study presents H2 production from olive tree pruning (OTP), employing a fixed dual-bed reactor that combines OPT gasification and volatile reforming. The thermal steam gasification of OTP was performed at 850 degrees C, followed by the catalytic gasification of volatiles at different temperatures. Red mud (RM) and nickel loaded red mud (Ni-RM) catalysts were used as catalytic bed material. The effects of different operating parameters, i.e. catalytic bed temperature, catalyst preparation method (thermal reduction & plasma reduction), and nickel ratios in catalyst on the yield and composition of produced gases were investigated. The catalyst prepared by reduction under non-thermal plasma showed no effect on the gasification due to the insufficient temperature for the reduction of Fe2O3 and NiO. The results indicated that the bottom bed temperature had a significant effect on the H2 yield, especially in the catalytic experiments. The RM alone shows almost the same activity with Ni-RM on the H2 yield; 1076 mL gas/g OTP and 1128 mL gas/g OTP, respectively. The results of present study showed that reduced RM had as much catalytic activity as Ni loaded reduced RM in hydrogen production.Article Advancing Nanofluid Numerical Modelling: a Novel Euler–Lagrange Method With Experimental Validation(Elsevier Ltd, 2025) Vovk, N.; Kamenik, B.; Elcioglu, E. Begum; Ozyurt, E.; Karadeniz, Z. H.; Turgut, A.; Ravnik, J.We present a novel approach to numerical modelling of thermal nanofluids based on the Euler-Lagrange method. This approach overcomes the challenge of extremely fine temporal discretization, which previous Euler-Lagrange nanofluid numerical models struggled to address, while also avoiding the need for too many Lagrangian nanoparticles. A numerical uncertainty assessment method is adapted for the proposed approach. The model is validated with a simple verification case and applied to simulate a closed natural circulation loop heat exchanger operating with heating power ranging from 10 W to 50 W and nanoparticle volume fractions of 0.5% to 2%, using an Al2O3-water nanofluid. Results are compared with experimental temperature measurements and an Euler-Euler implementation of the same nanofluid. The model is also applied to simulate the natural convection inside a vertical enclosure, studied experimentally by other authors. The proposed novel approach demonstrates agreement with both experimental data and the Euler-Euler implementation, effectively capturing the overall behaviour of nanofluids. We establish, that the interplay of multiple transport phenomena, that occur in nanofluid operated devices, can be difficult to completely reproduce numerically within the framework of current modelling assumptions.Article Citation - WoS: 1Citation - Scopus: 1Homodyne Detection Based Confocal Phase Diffraction Method for Thickness Characterization of Ultra-Thin Dielectric Films Coated on Optical Fibers(Elsevier Ltd, 2025) Karatay, Anil; Atac, EnesCharacterizing the thickness of thin dielectric films is crucial in fiber optic sensor technologies due to their significant impact on sensor performance. However, non-destructive thickness characterization of films in the range of tens of nanometers, particularly on non-planar surfaces, is often a challenging, complex, and tedious process. In addition, the measurements often need highly calibrated devices under the control of specialists. In this paper, we propose a novel, non-destructive, and practical method for characterizing the thickness of ultra-thin (<100 nm) curved transparent dielectric films using homodyne detection of the confocal phase diffraction. The numerical simulations and experimental results show that suppressing stray light improves the influence of thickness information in the diffracted field. This significantly enhances the system's sensitivity to nanometer-scale variations in dielectric film thickness, especially when integrated with a coherent detection scheme. According to the results, the film thickness can be precisely measured within a few nanometers, making it highly significant and promising for cost-effective optical metrology applications.Article Citation - Scopus: 1Esterase-Mediated Degradation of Dibutyl and Diethylhexyl Phthalates in Aqueous and Soil Systems(Elsevier Ltd, 2025) Balci, E.; Sanli-Mohamed, G.; Sofuoglu, A.Phthalate esters (PAEs), widely used as plasticizers, pose severe environmental and health risks. This study investigated the enzymatic hydrolysis of PAE congeners (dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP)) in aqueous and soil systems using Bacillus subtilis esterase and a new thermoalkaliphilic Geobacillus sp. esterase. A novel esterase secreted from Geobacillus sp. which was isolated from a geothermal region (Türkiye) was expressed in E.coli and purified. Geobacillus sp. esterase was able to degrade almost 30% of DBP and 40% of DEHP (100 mg/L) in the aqueous system within 336 h, while it degraded virtually 59% and 98% of DBP in agricultural area soil (soil-1) and forest area soil (soil-2), respectively, at the same time. To compare with Geobacillus sp. esterase, Bacillus subtilis esterase was used, which fully degraded DBP with 100 mg/L in the soil-1 and soil-2 for 72 h and 2 h, respectively. The performances of both esterases to degrade DEHP (100 mg/L) were similar in soil-1 (∼35%) and soil-2 (∼50%) for 336 h. Soil characteristics significantly influenced PAE degradation. Compared to that in the aqueous system, Geobacillus sp. esterase in soil systems had a higher degradation efficiency. This was likely due to its origin from a soil microorganism. Variations in the degradation ability of two enzymes most probably arose from substrate specificities and enzyme dynamics. Molecular docking results showed that DBP had a higher affinity to both enzymes than DEHP. Overall, this study offers important evidence that Bacillus subtilis esterase and Geobacillus sp. esterase are effective biocatalysts for removing the pollutants with ester bonds in the environment. © 2025 Elsevier LtdArticle Design and Performance of SiOC Foam-Silica Aerogel Composites for Hot and Cold Thermal Management Applications(Elsevier Ltd, 2025) Icin, Oyku; Vakifahmetoglu, CekdarThis study focuses on the fabrication of monolithic preceramic polymer-derived ceramic (SiOC) foam-silica aerogel composites by filling the open cells of ceramic foam with a silica aerogel solution using the sol-gel technique. The effects of different drying techniques (ambient pressure vs CO2 supercritical drying) and surface modification agents, including trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), are comprehensively investigated. These factors are analyzed for their influence on the composites' morphology, porosity, chemical structure, and thermal insulation performance. The drying technique and surface modification agents are found to play a critical role in achieving a high filling ratio of silica aerogel within the composites. Pure silica aerogels exhibit specific surface areas (SSAs) reaching similar to 1120 m(2).g(-1), while the SiOC foam-silica aerogel composites demonstrate SSAs of 385-440 m(2).g(-1). Nearly all samples achieve a total porosity of similar to 93 vol%. Surface modification effectively tailors the surface properties, imparting hydrophobicity with a water contact angle of 133 degrees. Thermal conductivity at room temperature ranges between 38 and 43 mW<middle dot>m(-1)<middle dot>K-1. The potential applications of these SiOC foam-silica aerogel composites as thermal insulators are assessed under extreme thermal conditions. For instance, a 14 mm thick composite has a temperature of -27 degrees C when subjected to a cold source at -78 degrees C. Instead, when exposed directly to a butane flame (similar to 1200 degrees C), the backside of the composite recorded only similar to 57 degrees C.