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Use of geopolymer-derived leucite as a reinforcement in dental bioceramic composites
Cengiz Bagci 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.4
Leucite (K2O·Al2O3·4SiO2) converted from geopolymers as a sustainable approach, was used as an alternative to feldspar, oneof the three components of dental ceramics. Leucite crystals were obtained from a dried potassium geopolymer of thecomposition K2O·Al2O3·4SiO2·11H2O by heating at 1200 oC for 3 h in an open-air furnace. Produced leucite was crushed intosmall parts, powdered in a planetary mill and then sieved to sub-63 micron size. Leucite crystals were then replaced byfeldspars at a range from 0-100 (wt.%) in all three parts of dental ceramic slurries. The slurries were molded to 1 cm3 andsubsequently heat-treated at 1300 oC-1450 ºC/4.5 h with a heating rate of 10 ºC/min. Final products were microstructurallycharacterized with XRD, SEM-EDS and mechanically based on Weibull analysis of compressive tests. Due to the phasetransformation occurring in leucite, it was determined that the amount of leucite had a significant effect on the structuralintegrity and therefore the mechanical properties of the final dental material. Results of the statistical analysis showed that thereplacement of 50% leucite exhibited the highest compressive strength of (49.3±10.5 MPa) compared to the other samplesconsistent with microstructural analysis.
Cengiz Tatar,Dilek Bagci,Omer Kaygili 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
In the present study, the effects of high amounts of Al and Zn additives on the crystal structure, phase composition andmicrostructure of hydroxyapatite (HAp) samples synthesized by sol-gel route were investigated by X-ray diffraction (XRD),Fourier transformation infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The values of thecrystallinity percent, crystallite size, lattice parameter of a and volume of the unit cell decrease gradually with increasingamount of the co-additives. The formation of the new phases is observed and these phases become dominant with increasingamount of Al and Zn. The morphology of HAp, shape and size of the particles are also affected by the amount of Al and Zn. As expected, a gradual decrease in the Ca/P molar ratio is observed.
Comparison of Controllable Photovoltaic Emulation Methods for Real-Time Hardware Experiments
Darsana Deo,F. Selin Bagci,Katherine A. Kim 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
Emulating photovoltaic (PV) modules in a controllable lab environment to interface with power electronics hardware is challenging but vital as it enables more realistic experiments to be conducted in real-time. However, the emulation methods often require nonlinear PV modeling, which may have long computational times. Hence, an effective real-time emulation method should minimize the computation time while maintaining high accuracy. This work compares different PV emulation techniques to investigate the advantages and disadvantages of various methods for real-time hardware testing. First, a literature survey compares the type of PV model, interface used, controller, and real-time technique adopted to emulate a PV model’s current-voltage characteristics. Then, the PV model emulation methods are compared using a low-cost real-time emulator (RT Box 1), and computational cycle times are measured. The target application is to emulate a PV panel over various days and test the system control algorithm in real time for a PV microinverter with an integrated battery.
Dual-Band Double-Cylindrical-Ring 3D Frequency Selective Surface
Sultan Can,Emrullah Karakaya,Fulya Bagci,Asim Egemen Yilmaz,Baris Akaoglu 한국전자통신연구원 2017 ETRI Journal Vol.39 No.1
This study presents a dual-band 3D frequency selective surface that provides a large degree of freedom in frequency and bandwidth adjustability. The proposed structure is evaluated in terms of its structural parameters, and prototypes were fabricated. The radius of the copper rings and the height of the cylinders are considered, and are shown through full-wave electromagnetic simulations to have a significant effect on the frequency characteristics of the frequency selective surface. The measurement results of the fabricated samples are compared with the simulation results, and a satisfactory agreement was obtained.
Strengthening of RC beams with prefabricated RC U cross-sectional plates
Demir, Ali,Tekin, Muhammed,Turali, Tezcan,Bagci, Muhiddin Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.6
The topic of this study is to strengthen cracked beams with prefabricated RC U cross-sectional plates. The damaged beams were repaired by epoxy based glue. The repaired beams were strengthened using prefabricated plates. The strengthening plates were bonded to the bottom and side faces of the beams by anchorage rods and epoxy. The strengthened beams were incrementally loaded up to maximum load capacities. The experimental results were satisfactory since the load carrying capacities of damaged beams were increased approximately 76% due to strengthening. It was observed that strengthening plates had a dominant effect on the performance of beams in terms of both the post-elastic strength enhancement and the ductility. The experimental program was supported by a three-dimensional nonlinear finite element analysis. The experimental results were compared with the results obtained from the beam modeled with ANSYS finite element program.
Strengthening of RC beams with prefabricated RC U cross-sectional plates
Ali Demir,Muhammed Tekin,Tezcan Turalı,Muhiddin Bagci 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.6
The topic of this study is to strengthen cracked beams with prefabricated RC U cross-sectional plates. The damaged beams were repaired by epoxy based glue. The repaired beams were strengthened using prefabricated plates. The strengthening plates were bonded to the bottom and side faces of the beams by anchorage rods and epoxy. The strengthened beams were incrementally loaded up to maximum load capacities. The experimental results were satisfactory since the load carrying capacities of damaged beams were increased approximately 76% due to strengthening. It was observed that strengthening plates had a dominant effect on the performance of beams in terms of both the post-elastic strength enhancement and the ductility. The experimental program was supported by a three-dimensional nonlinear finite element analysis. The experimental results were compared with the results obtained from the beam modeled with ANSYS finite element program.
Crack detection in folded plates with back-propagated artificial neural network
Oguzhan Das,Can Gonenli,Duygu Bagci Das 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.3
Localizing damages is an essential task to monitor the health of the structures since they may not be able to operate anymore. Among the damage detection techniques, non-destructive methods are considerably more preferred than destructive methods since damage can be located without affecting the structural integrity. However, these methods have several drawbacks in terms of detecting abilities, time consumption, cost, and hardware or software requirements. Employing artificial intelligence techniques could overcome such issues and could provide a powerful damage detection model if the technique is utilized correctly. In this study, the crack localization in flat and folded plate structures has been conducted by employing a Backpropagated Artificial Neural Network (BPANN). For this purpose, cracks with 18 different dimensions in thin, flat, and folded structures having 150 , 300 , 450 , and 600 folding angle have been modeled and subjected to free vibration analysis by employing the Classical Plate Theory with Finite Element Method. A Four-nodded quadrilateral element having six degrees of freedom has been considered to represent those structures mathematically. The first ten natural frequencies have been obtained regarding healthy and cracked structures. To localize the crack, the ratios of the frequencies of the cracked flat and folded structures to those of healthy ones have been taken into account. Those ratios have been given to BPANN as the input variables, while the crack locations have been considered as the output variables. A total of 500 crack locations have been regarded within the dataset obtained from the results of the free vibration analysis. To build the best intelligent model, a feature search has been conducted for BAPNN regarding activation function, the number of hidden layers, and the number of hidden neurons. Regarding the analysis results, it is concluded that the BPANN is able to localize the cracks with an average accuracy of 95.12%.
Dolen, Utku Can,Sungur, Nezih,Koca, Gokhan,Ertunc, Onur,Bosi, Ayse Tulay Bagci,Kocer, Ugur,Korkmaz, Meliha Korean Society of Plastic and Reconstructive Surge 2015 Archives of Plastic Surgery Vol.42 No.6
Background It is still difficult to prevent partial or full-thickness flap necrosis. In this study, the effects of a cream containing menthol and methyl salicylate on the viability of random-pattern skin flaps were studied. Methods Forty female Sprague-Dawley rats were divided into two equal groups. Caudally based dorsal random-pattern skin flaps were elevated, including the panniculus carnosus. In the study group, 1.5 mL of a cream containing menthol and methyl salicylate was applied to the skin of the flap, and saline solution (0.9%) was used in the control group. Upon completion of the experiment, flap necrosis was analyzed with imaging software and radionuclide scintigraphy. Histopathological measurements were made of the percentage of viable flaps, the number of vessels, and the width of the panniculus carnosus muscle. Results According to the photographic analysis, the mean viable flap surface area in the study group was larger than that in the control group (P=0.004). According to the scintigrams, no change in radioactivity uptake was seen in the study group (P>0.05). However, a significant decrease was observed in the control group (P=0.006). No statistically significant differences were observed between the groups in terms of the percentage of viable flaps, the number of vessels, or the width of the panniculus carnosus muscle (P>0.05). Conclusions Based on these results, it is certain that the cream did not reduce the viability of the flaps. Due to its vasodilatory effect, it can be used as a component of the dressing in reconstructive operations where skin perfusion is compromised.
Kun-Che Ho,Cheng-Chung Lin,F. Selin Bagci,Shun-Chung Wang,Yi-Hua Liu,Yu-Shan Cheng 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this study, three swarm intelligence (SI)-based maximum power point tracking (MPPT) techniques for photovoltaic generation systems (PGSs) operating under partially shaded conditions (PSCs) are investigated. The compared methods include particle swarm optimization (PSO), firefly algorithm (FA) and cuckoo search (CS). Simulated results for 252 different shading patterns will be provided and some conclusion will be made. This study presents reference information for scholars planning to carry out research in this field.