TR Dizin İndeksli Yayınlar Koleksiyonu / TR Dizin Indexed Publications Collections

Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/4

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Citation - WoS: 5
Citation - Scopus: 4
12th June 2017 Offshore Karaburun-Lesvos Island Earthquake Coseismic Deformation Analysis Using Continuous Gps and Seismological Data
(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2021) Yıldız, Hasan; Çırmık, Ayça; Pamukçu, Oya; Özdağ, Özkan Cevdet; Gönenç, Tolga; Kahveci, Muzaffer
Understanding the tectonic mechanism generated by the earthquakes and faults is possible only if the preseismic, coseismic and postseismic crustal deformation related to the earthquakes is determined properly. By the analysis of continuous GPS (CGPS) coordinate time series, it is possible to estimate the crustal deformation. Besides, accelerometer records at strong motion stations (SMSs) may support the CGPS-based estimates. In this study, CGPS coordinate time series were analyzed in comparison with the accelerometer records for clarifying the coseismic deformation caused by the earthquake occurred in the surrounding of Lesvos fault located in the northern part of Karaburun within the active mechanism that controls the area where the earthquakes occurred during June 2017 on the offshore Karaburun. The activity of this fault continued throughout June 2017 until the time when the main shock (12th June 2017, M-W = 6.2) occurred. We analyzed CGPS coordinate time series of AYVL and CESM and DEUG stations to determine the coseismic deformation due to the offshore Karaburun-Lesvos Island earthquake using the empirical mode decomposition (EMD) method. Besides, the EMD method results were compared with the accelerometer records obtained from the SMSs close to the CGPS stations and CGPS-based results were found to be consistent with the accelerometer records. Additionally, the horizontal displacements were calculated by Coulomb 3.3 software using different focal plane solutions and compared with CGPS-based results. Consequently, it is suggested an integrated use of CGPS and strong motion accelerometer networks for the joint assessment of the crustal deformation and for the cost-effective use of existing observation networks as well as for the establishment of future observation networks at lower cost.
Citation - WoS: 11
Citation - Scopus: 19
Artificial Intelligence in Healthcare Competition (teknofest-2021): Stroke Data Set
(AVES, 2022) Koç, U.; Sezer, E.A.; Özkaya, Y.A.; Yarbay, Y.; Taydaş, O.; Ayyıldız, V.A.; Bahadır, Murat
Objective: The artificial intelligence competition in healthcare was organized for the first time at the annual aviation, space, and technology festival (TEKNOFEST), Istanbul/Türkiye, in September 2021. In this article, the data set preparation and competition processes were explained in detail; the anonymized and annotated data set is also provided via official website for further research. Materials and Methods: Data set recorded over the period covering 2019 and 2020 were centrally screened from the e-Pulse and Teleradiology System of the Republic of Türkiye, Ministry of Health using various codes and filtering criteria. The data set was anonymized. The data set was prepared, pooled, curated, and annotated by 7 radiologists. The training data set was shared with the teams via a dedicated file transfer protocol server, which could be accessed using private usernames and passwords given to the teams under a non-disclosure agreement signed by the representative of each team. Results: The competition consisted of 2 stages. In the first stage, teams were given 192 digital imaging and communications in medicine images that belong to 1 of 3 possible categories namely, hemorrhage, ischemic, or non-stroke. Teams were asked to classify each image as either stroke present or absent. In the second stage of the competition, qualifying 36 teams were given 97 digital imaging and communications in medicine images that contained hemorrhage, ischemia, or both lesions. Among the employed methods, Unet and DeepLabv3 were the most frequently observed ones. Conclusion: Artificial intelligence competitions in healthcare offer good opportunities to collect data reflect-ing various cases and problems. Especially, annotated data set by domain experts is more valuable. © 2022, AVES. All rights reserved.
Densification of CuO-ZrO2 Nanocomposites by Flash Sintering
(Sakarya University, 2025) Çetinkaya, Zeynep
This study is a comprehensive investigation into CuO-doped ZrO2 nanoparticles (NPs) produced by the hydrothermal method and its conventional (CS) and flash-sintering (FS) processes. Besides this production, the effect of the differences in sintering techniques and density was investigated to prove the results. However, to the authors’ knowledge, the FS of CuO/ZrO2 nanocomposite (NC) material has yet to be studied, which is the first report on this material. The CuO/ZrO2 nanocomposite particle (NCP) pellet was sintered at 1250 oC for 1 hour using CS. The other sintering method is FS, which obtains highly dense NCs. The CuO/ZrO2 NCPs pellet was successfully produced with the lower sintering temperature (673 oC) and duration (60 seconds) by FS under a current density of 50 mA/mm2, and electric field (100 V/cm). The microstructure and density of the pellets produced from CS and FS experiments were evaluated. The SEM results showed that the CuO/ZrO2 NCPs with the FS experiment were successfully performed, and density results with 4.38 g/cm3 proved this success compared to CS pellet density (3.72 g/cm3). The FS process for CuO/ZrO2 NCPs consumes ~ 2.2 kJ (0.227 kJ/cm³), whereas CS samples require ~ 13 kJ (54 kJ/cm³), making FS approximately six times more energy-efficient. This significant reduction in energy consumption highlights FS as a promising method for future applications focused on carbon emission reduction and energy efficiency.
Citation - WoS: 2
Citation - Scopus: 2
Gan/Zno Hybrid Nanostructures for Improved Photocatalytic Performance: One-Step Synthesis
(Scientific And Technological Research Council Turkey, 2023) Üstün, Tugay; Haspulat Taymaz, Bircan; Eskizeybek, Volkan; Kamış, Handan; Avcı, Ahmet
Nanostructured semiconductor materials are considered potential candidates for the degradation of textile wastewater via the photocatalytic process. This study aims to produce hexagonal gallium nitride (GaN) nanoplates and zinc oxide (ZnO) nanoparticles in a deionized water environment utilizing a one-step arc discharge process. Detailed characterization of samples has been completed via scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV visible spectroscopy methods. The hybrid nanostructure morphologies consist of nanoplates and nanorods of different sizes. The photoperformance of GaN/ZnO hybrid nanostructures was assessed via the malachite green (MG) dye degradation under UV exposure. Under UV exposure, the degradation yield reached 98% in 60 min. Compared to individual ZnO and GaN nanoparticles, the photocatalytic reaction rate of the GaN/ZnO photocatalyst is 2.2 and 3.6 times faster, respectively. Besides, the GaN/ZnO hybrid nanostructures show excellent photocatalytic stability. The energy consumption of the photocatalytic degradation in the presence of GaN/ZnO hybrid nanostructures was 1.688 kWhL-1. These results demonstrate that the GaN/ZnO hybrid nanostructures with improved photocatalytic activity are a reasonable option for the decomposition of textile wastewater under UV light exposure.
Citation - Scopus: 7
Investigation of Optimal Designs for Concrete Cantilever Retaining Walls in Different Soils
(Tulpar Academic Publishing, 2020) Uray, E.; Çarbaş, S.; Erkan, İ.H.; Olgun, M.
In this paper, the investigation of the optimum designs for two types of concrete cantilever retaining walls was conducted utilizing the artificial bee colony algorithm. Stability conditions like safety factors of sliding, overturning and bearing capacity and some geometric instances due to inherent of the wall were considered as the design constraints. The effect of the existence of the key in wall design on the objective function was probed for changeable properties of foundation and backfill soils. In optimization analysis, the concrete of the wall, which directly affects parameters such as carbon dioxide emission and the cost, was considered as the objective function and analyzes were performed according to different discrete design variables. The optimum concrete cantilever retaining wall designs satisfying constraints of stability conditions and geometric instances were obtained for different soil cases. Optimum designs of concrete cantilever retaining wall with the key were attained in some soil cases which were not found the feasible optimum solution of the concrete cantilever retaining wall. Results illustrate that the artificial bee colony algorithm was a favorable metaheuristic optimization method to gain optimum designs of concrete cantilever retaining wall. © 2020, Tulpar Academic Publishing. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 84
A Literature Review on Walking Strategies of Legged Robots
(GAZI UNIV, 2020) Bakırcıoğlu, Veli; Kalyoncu, Mete
In this study, previous studies on legged motion; in particular, important milestones of the legged robots' literature were referred. From the past period research, primarily, studies on the walking of the living beings and the machines that can mimic it were mentioned. Subsequently, the history of legged robots that is the subject of the study was addressed. In the studies on the legged robots, two basic approaches as the walking strategy were concerned; static gait and dynamic gait. Due to this reason, the history of the legged robots was reported in chronological order under two main topics as Static Walking Legged Robots and Dynamic Walking Legged Robots. In the Static Walking Legged Robots topic, researches on the development of techniques for controlling of the multi-legged systems to cope with more complex problems of the land adaptation such as locomotion on rough surfaces and overcoming obstacles; as for in the Dynamic Walking Legged Robots topic, researches on the improvement of dynamic control concepts and techniques to develop legged systems with highly sophisticated mobility capabilities such as running and jumping are presented.
Citation - Scopus: 3
Mechanical Strength Variation of Zeolite-Fly Ash Geopolymer Mortars With Different Activator Concentrations
(Tulpar Academic Publishing, 2021) Liban, Roble Ibrahim; Keskin, Ülkü Sultan; Öztürk, Oğuzhan
Zeolite is of a significance for geopolymers as it is a natural precursor and does not require additional heat treatment for activation. However, aluminosilicates sourced from natural sources require additional handling for the best use of exploitation. In this study, geopolymers were synthesized by binary use of zeolite and fly ash as main binding material and sodium silicate and sodium hydroxide as alkaline activator. The influence of alkaline activator ratios and sodium hydroxide concentrations on the compressive strength and flexural strength of the zeolite-fly ash based geopolymers were studied. In this research, zeolite-fly ash based geopolymer mortars were produced by using 50% of natural zeolite (clinoptilolite) and 50% of C-type fly ash. Four different activator ratios (Na2SiO3/NaOH: 1, 1.5, 2 and 2.5) and two sodium hydroxide molarities (10M and 12M) was utilized to activate zeolite and fly ash in order to determine the effect of these parameters on the mechanical strengths of the produced geopolymer mortars. The results indicated that as the alkaline activator ratio and NH molarity were increased the compressive strength of the zeolite-fly ash based geopolymers also increased. The maximum compressive and flexural strength values obtained after 28 days of curing were 20.1 MPa and 5.3 MPa respectively and corresponds when used activator ratio of 2.5 and sodium hydroxide concentration of 12 molarity. The obtained results indicated that both the alkaline activator ratio and sodium hydroxide concentration affected the compressive and flexural strengths of zeolite-fly ash based geopolymer mortar specimens. © 2021, Tulpar Academic Publishing. All rights reserved.
Citation - WoS: 4
Citation - Scopus: 4
Medical Image Fusion With Convolutional Neural Network in Multiscale Transform Domain
(TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2021) Abas, Asan İhsan; Koçer, Hasan Erdinç; Baykan, Nurdan Akhan
Multimodal medical image fusion approaches have been commonly used to diagnose diseases and involve merging multiple images of different modes to achieve superior image quality and to reduce uncertainty and redundancy in order to increase the clinical applicability. In this paper, we proposed a new medical image fusion algorithm based on a convolutional neural network (CNN) to obtain a weight map for multiscale transform (curvelet/ non-subsampled shearlet transform) domains that enhance the textual and edge property. The aim of the method is achieving the best visualization and highest details in a single fused image without losing spectral and anatomical details. In the proposed method, firstly, non-subsampled shearlet transform (NSST) and curvelet transform (CvT) were used to decompose the source image into low-frequency and high-frequency coefficients. Secondly, the low-frequency and high-frequency coefficients were fused by the weight map generated by Siamese Convolutional Neural Network (SCNN), where the weight map get by a series of feature maps and fuses the pixel activity information from different sources. Finally, the fused image was reconstructed by inverse multi-scale transform (MST). For testing of proposed method, standard gray-scaled magnetic resonance (MR) images and colored positron emission tomography (PET) images taken from Brain Atlas Datasets were used. The proposed method can effectively preserve the detailed structure information and performs well in terms of both visual quality and objective assessment. The fusion experimental results were evaluated (according to quality metrics) with quantitative and qualitative criteria.
Citation - Scopus: 24
A Review of the Effect and Optimization of Use of Nano-Tio2 in Cementitious Composites
(MIM RESEARCH GROUP, 2022) Döndüren, M. S.; Al-Hagri, M.G.
There are some problems and weaknesses related to cement-based materials, such as their very low tensile strength, low chemical resistance and the huge contribution of cement production to industrial CO2 emissions. One possible method to reduce the impacts of such problems is the partial replacement of cement in cementitious materials with nano materials. This work provides a detailed review of incorporation of one of the most widely used nano materials, namely nano-titanium dioxide, and its effect on the properties of cementitious composites. Different properties have been considered in the current study, such as fresh properties, mechanical properties (compressive strength, split tensile strength and flexural strength), durability (permeability, ultrasonic pulse velocity (UPV), electrical resistivity, carbonation resistance, freeze and thaw resistance and sulfate attack resistance) and microstructural properties. This paper also investigates the optimum content of nano-TiO2 in cement-based materials. Moreover, the cost effectiveness of use on nano-titania in cementitious composites has been discussed. Nano titania reduces the workability and setting time of cement-based materials. It can be very effective in improving the mechanical properties, durability and microstructural properties of cementitious composites. © 2022 MIM Research Group.
Citation - WoS: 3
Smart and Sustainable Supplier Selection Using Interval Type-2 Fuzzy Ahp
(Gazi Univ, 2022) Torğul, Belkız; Paksoy, Turan
Government regulations, customers' environmental awareness, quality of life-improving efforts and developments in the information and communication system have almost obliged organizations to consider smart and sustainable factors while evaluating their suppliers. Working with suitable suppliers in terms of technological, environmental and social aspects as well as economic aspects, will be the basis for smart and sustainable supply chains. An effective supplier selection running is also needed to continue the process in harmony. The issue of supplier selection is one of the multi-criteria decision- making problems that requires consideration of many qualitative and/or quantitative factors. In this study, Analytic hierarchy process (AHP) method with interval type-2 fuzzy sets, which are more flexible and successful in reflecting uncertainty for fuzzy decision-making problems with contradictory criteria, was proposed to evaluate the overall performance of suppliers. In order to demonstrate the applicability of the proposed method, an empirical study was conducted on the evaluation of material suppliers for an automotive manufacturer and a comparative scenario analysis was performed to investigate the effect of different criteria under different conditions.
Transient Heat Transfer in Pipes With Time Periodically Changing Boundary Condition
(Turk Isı Bilimi ve Teknigi Dernegi, 2018) Altun, A.H.; Ateş, A.; Atmaca, Şükrü Ulaş; Koçak, Sedat; Bilir, Şefik
Transient heat transfer in thermal entrance region of pipes with time periodically changing surface temperature is investigated. The problem is handled in a two-regional pipe for laminar, hydrodynamically developed flow by involving fluid axial conduction. The solution is made numerically by a finite-difference method. A parametric study is done to analyse the effects of Peclet number and angular frequency on heat transfer characteristics. The results show that, considerable amount of heat is diffused back towards the upstream region by axial fluid conduction, which causes preheating the fluid prior to the heated downstream region. The heat transfer characteristics, in all axial positions, including the preheated upstream and the fully developed region, are seen to change periodically in time, similar to the periodic change of the surface temperature in the downstream region. ©2018 TIBTD Printed in Turkey.

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