Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Günaydin, Murat(6)
- Ak, Muammer(5)
- Akinoglu, Bulent G.(5)
- Akpinar, Muhammet Vefa(5)
- Genç, Ali Fuat(5)
- Kahraman, Yakup(5)
- Takaoğlu, Zeynep Başkan(5)
- Acet, Tuba(4)
- Aliyazicioglu, Yuksel(4)
- Altunişik, Ahmet Can(4)
- Ashyralyyev, Charyyar(4)
- Bölükbaş, Mehmet(4)
- Dağ, Serhat(4)
- Demir, Selim(4)
- Kaygusuz, Abdullah(4)
- Kayikçioglu, Temel(4)
- Okur, Fatih Yesevi(4)
- Ozden, Talat(4)
- Topal, Mehmet Hanefi(4)
- Turan, Ibrahim(4)
- Adanur, Süleyman(3)
- Akdu, Uğur(3)
- Aksakal, Vecihi(3)
- Aktaş, Ibrahim(3)
- Arslan, Mehmet(3)
- Ashyralyev, A.(3)
- Aslan, Emre Ş(3)
- Aydin, Orhan(3)
- Duran, Celal(3)
- Düzgün, Azer Özad(3)
- Gul, Fatih(3)
- Güllüpunar, Hasan(3)
- Karahasan, Olguhan Şevket(3)
- Kaya, Yusuf(3)
- Lukashov, A.(3)
- Nizetic, S(3)
- Orhan, Halit(3)
- Ozcan, Kadriye(3)
- Paksoy, Zahid(3)
- Papadopoulos, A(3)
Yayınlar
- MakaleYalnız künye2018Automatic Building Extraction from Image and LiDAR Data with Active Contour Segmentation
Akbulut, Zeynep; Özdemir, Samed; Acar, Hayrettin; Karsli, Fevzi
Automatic building extraction is an important topic for many applications such as urban planning, disaster management, 3D building modeling and updating GIS databases. Its approaches mainly depend on two data sources: light detection and ranging (LiDAR) point cloud and aerial imagery both of which have advantages and disadvantages of their own. In this study, in order to benefit from the advantages of each data sources, LiDAR and image data combined together. And then, the building boundaries were extracted with the automated active contour algorithm implemented in MATLAB. Active contour algorithm uses initial contour positions to segment an object in the image. Initial contour positions were detected without user interaction by a series of image enhancements, band ratio and morphological operations. Four test areas with varying building and background levels of detail were selected from ISPRS’s benchmark Vaihingen and Istanbul datasets. Vegetation and shadows were removed from all the datasets by band ratio to improve segmentation quality. Subsequently, LiDAR point cloud data was converted to raster format and added to the aerial imagery as an extra band. Resulting merged image and initial contour positions were given to the active contour algorithm to extract building boundaries. In order to compare the contribution of LiDAR to the proposed method, the boundaries of the buildings were extracted from the input image before and after adding LiDAR data to the image as a layer. Finally extracted building boundaries were smoothed by the Awrangjeb (Int J Remote Sen 37(3): 551–579. https://doi.org/10.1080/01431161.2015.1131868, 2016) boundary regularization algorithm. Correctness (Corr), completeness (Comp) and accuracy (Q) metrics were used to assess accuracy of segmented building boundaries by comparing extracted building boundaries with manually digitized building boundaries. Proposed approach shows the promising results with over 93% correctness, 92% completeness and 89% quality.
- MakaleAçık Erişim2018A nutritional evaluation of the berry of a new grape: 'Karaerik' (Vitis vinifera L.)
Kurt, Aynur; Colak, Nesrin; Bengu, Aydin Sükrü; Gundoğdu, Ali; Akpinar, Erdal; Hayirlioglu-Ayaz, Sema; Ayaz, Faik Ahmet
Grape berries are a good source of nutrients and nutraceuticals and have many benefits for human health. Growing interest in the export potential and consumption of a new grape (cv. Karaerik), cultivated as a table grape in Turkey, encouraged us to profile its major nutrient contents from six different locations. Due to its popularity, the nutritional value of this grape berry needs to be investigated to ascertain its potential economic and health benefits. The most abundant sugars in the grape berry were fructose and glucose (peel/whole fruit; averages 236.57 and 127.87, and 183.36 and 108.60 g kg -1 fresh weight, respectively), while the major organic acids were tartaric and malic acids (7.17 and 2.81, and 2.61 and 1.76 g kg -1 fresh weight, respectively). Linoleic acid (peel/whole fruit/seed; 37.14, 33.12 and 57.83%, respectively) was the predominant fatty acid, while potassium (peel/whole fruit/seed; 9331.5, 10226.33 and 5354 μg/g dry weight, respectively) was the predominant mineral, followed by phosphorus (1592.8, 2672 and 3072.67) in the berry. Our results demonstrate that the nutrient components and physicochemical parameters varied significantly among the sampling locations. The grape berry contains considerable quantities of potentially beneficial healthy nutrients worthy of further evaluation.
- MakaleYalnız künye2018Utilizing the sustainable livelihoods approach to evaluate tourism development from the rural host communities’ point of view: The case of Cappadocia (Turkey)
Çakir, Onur; Evren, Savaş; Tören, Emrullah; Kozak, Nazmi
The objective of this study was to contribute to and expand the limited knowledge base of the ways in which tourism development impacts rural livelihoods. It traced the process of tourism-based livelihood development in the Cappadocia region of Turkey by using The Sustainable Livelihoods Approach (SLA) framework to provide the perspectives of those who chose to incorporate tourism as a major part of their overall livelihood strategy. The results showed that tourism development had a great impact on the locals’ livelihoods. In order to enhance the locals’ livelihood and achieve an environmentally, socially, and economically sustainable outcome for tourism livelihood, the recommendation is to support and encourage small local establishments versus large scale foreign investments, increase the number of overnight stays by promoting Cappadocia as a main tourist destination, take precautions to prevent fraud and forgery in locale handicrafts and souvenir shops, and enact a protection law that prevents harm to the environment caused by traffic, shops, balloons, and hydroelectric power plants.
- MakaleAçık Erişim2018The effects of 4-vinylcyclohexene diepoxide on the testes of dogs; [Učinci 4-vinilcikloheksen diepoksida na testise pasa.]
Paksoy, Zahid; Kandemi̇r, Fatih M.; Gokhan, Nezihe; Ozkaraca, Mustafa
This study was aimed at investigating the effects of 4-vinylcyclohexene diepoxide (VCD) on testicular tissue in dogs. For this purpose, 30 mongrel male dogs were used and allocated to 5 groups randomly. The first group (n = 6), used as the control, was administered sesame oil by the intraperitoneal route (i/p). The VCD was administered i/p at doses of 80, 160, 240, 320 mg/kg to the second, third, fourth and the fifth groups (n = 6), respectively, once a day for 8 days. The dogs were surgically castrated on the day after the last VCD injection. The testes were removed immediately and fixed in 10% bouine solution. The testes were subjected to routine tissue processing and examined to determine the testicular damage in each testis. When compared to the control group, it was seen that the seminiferous tubule damage increased significantly in the treatment groups. Malondialdehyde levels reached the highest level in the fifth group, while superoxide dismutase, catalase, glutathione peroxidase activity and glutathione levels were higher in the control group (P<0.0001). Nosignificant difference was detected when all the groups were compared with respect to AST, ALT and GGT activities before and after the treatment (P>0.05). Our results showed that VCD may contribute to the sterilization of male dogs.
- MakaleYalnız künye2018Natural convection in a parallel-plate vertical channel with discrete heating by two flush-mounted heaters: effect of the clearance between the heaters
Sarper, Bugra; Saglam, Mehmet; Aydin, Orhan; Avci, Mete
In this study, natural convection in a vertical channel is studied experimentally and numerically. One of the channel walls is heated discretely by two flush-mounted heaters while the other is insulated. The effects of the clearance between the heaters on heat transfer and hot spot temperature while total length of the heaters keeps constant are investigated. Four different settlements of two discrete heaters are comparatively examined. Air is used as the working fluid. The range of the modified Grashof number covers the values between 9.6 × 105 and 1.53 × 10.7 Surface to surface radiation is taken into account. Flow visualizations and temperature measurements are performed in the experimental study. Numerical computations are performed using the commercial CFD code ANSYS FLUENT. The results are represented as the variations of surface temperature, hot spot temperature and Nusselt number with the modified Grashof number and the clearance between the heaters as well as velocity and temperature variations of the fluid.
- BildiriAçık Erişim2018OBJECT BASED BUILDING EXTRACTION and BUILDING PERIOD ESTIMATION from UNMANNED AERIAL VEHICLE DATA
Comert, Resul; Kaplan, Onur; Honkavaara, E.; Komp, K.; Stilla, U.; Jiang, J.; Zhang, H.; Peled, A.; Soergel, U.; Scaioni, M.
The aim of this study is to examine whether it is possible to estimate the building periods with respect to the building heights in the urban scale seismic performance assessment studies by using the building height retrieved from the unmanned aerial vehicle (UAV) data. For this purpose, a small area, which includes eight residential reinforced concrete buildings, was selected in Eskisehir (Turkey) city center. In this paper, the possibilities of obtaining the building heights that are used in the estimation of building periods from UAV based data, have been investigated. The investigations were carried out in 3 stages; (i) Building boundary extraction with Object Based Image Analysis (OBIA), (ii) height calculation for buildings of interest from nDSM and accuracy assessment with the terrestrial survey. (iii) Estimation of building period using height information. The average difference between the periods estimated according to the heights obtained from field measurements and from the UAV data is 2.86 % and the maximum difference is 13.2 %. Results of this study have shown that the building heights retrieved from the UAV data can be used in the building period estimation in the urban scale vulnerability assessments.
- MakaleYalnız künye2018Geometric optimization of an ejector for a 4 kW SOFC system with anode off-gas recycle
Genc, Omer; Toros, Serkan; Timurkutluk, Bora
One of the important energy saving tools used in solid oxide fuel cell (SOFC) system is the anode off-gas recycling (AGR) via an ejector which allows the recirculation of the unused fuels in the anode exhaust gas including hot steam which is essential for the elimination of the carbon deposition and the initiation of the reactions in the reformer. In an ejector system developed for the SOFCs, the steam to carbon ratio (STCR) and entrainment ratio are the crucial parameters for the determination of the ejector performance. These parameters can be engineered by modifying the geometric dimensions and operation conditions. This study focuses on the determination of the maximum STCR value and entrainment ratio via numerical geometric analyses for a micro combined heat and power (μ-CHP) system based on 4 kW SOFC, utilizing methane. A detailed numerical procedure for designing an ejector is provided and the ejector performance is investigated for different critical dimensions (throat diameter, nozzle exit angle and nozzle position etc.). The results show that the nozzle position and the nozzle exit angle significantly affect STCR and the entrainment ratio. When the nozzle position increases and nozzle exit angle decreases, the entrainment ratio and STCR is found to increase. The entrainment ratio and STCR are determined as around 7.3 and 2.7, respectively for a specific design created in the study.
- MakaleYalnız künye2018Volume calculation of brain structures in migraine disease by using mristudio
Palancı, Özgür; Kalaycıoğlu, Ahmet; Acer, Niyazi; Eyüpoğlu, İlker; Çakmak, Vildan A.
Migraine is a neurological disorder that is known as headache and accompanies attacks of neurological and gastrointestinal symptoms and prevents daily life activities of the person. In the literature, the volume changes of many structures in the brain have been investigated using brain magnetic resonance images (MRI) of migraine patients, but it has not yet been investigated whether there is a comprehensive and detailed volume change involving all the structures of the brain. The purpose of this study is to examine the brain structures in a wide range and to determine in which regions the volume changes. In this study, 25 healthy subjects and 25 migraine patients were included in the study. SPSS 15.0 program was used for statistical analysis. The Mristudio was used in our study when we examined the volumes of migraine patients and brain structures of healthy individuals. Statistically significant volume changes were found in the volumes of structures found in the brain frontal, parietal, occipital, temporal lobes. Volumetric changes were assessed in terms of duration of illness and frequency of attacks. In conclusion, our study is compatible with migraine pathophysiology. Structural changes in the brain are thought to be a risk factor for migraine. The evidence on the relationship of regional gray matter volumetric change detected in migraine is unclear. We believe that this ambiguity is caused by the method used.
- MakaleYalnız künye2018Automated Model Updating Effect on the Linear and Nonlinear Dynamic Responses of Historical Masonry Structures
Altunişik, A.C.; Okur, F.Y.; Genç, A.F.; Günaydin, M.; Karahasan, O.
Finite element models supply the simulation of the problems to obtain the structural behaviors under different loading conditions. The updating processes based on changing the uncertain parameters such as material properties, boundary conditions, meshing size etc. are made to create actual finite element models in order to represent the real conditions of the problems. This procedure can be made using two methods, namely manual model updating and global/local automatic model updating. The global/local automatic model updating procedures are very popular owing to the applicability to all kind of engineering structures, minimizing the differences nearly to zero, availability of damage localization and structural health monitoring. In this paper a historical masonry armory building selected as an application and its finite element analyses, experimental measurements and automated model updating processes are carried out. The finite element model of the structures was developed with ANSYS software and first three natural frequencies are attained. The experimental dynamic characteristics such as natural frequencies, damping ratios and mode shapes are obtained using ambient vibration method. The differences between experimental and numerical frequencies are minimized up to the range of 0–1%, by using local updating procedure. The linear and nonlinear seismic analyses of the building are conducted on initial and updated models. At the end of the analyses, maximum displacements, principal stresses and strains are given with detail. In addition, crack distributions diagrams are attained to validate the stresses accumulation points. It can be seen that there is an increasing trend in the displacement, stress and strain values after finite element model updating both linear and nonlinear analysis. In addition, linear and nonlinear analysis results are compared with each other to evaluate the nonlinear analysis effect. It is concluded that the displacement and strain values are increased after nonlinear analysis. But, there is not any agreement in stress values.
- MakaleYalnız künye2018An enhanced scanning-based MPPT approach for DMPPT systems
Başoğlu, Mustafa Engin
In this paper, an improved maximum power point tracking (MPPT) approach being low parameter dependency, simple structure and limited search interval has been presented for distributed MPPT photovoltaic (PV) systems. Basically, this approach is based on scanning of power–voltage (P-V) characteristic curve of PV modules in a limited duty ratio interval which makes tracking operation simple, fast and efficiently available in both uniform irradiance and partial shading conditions (PSCs). By limiting the scanning interval of maximum and minimum values of duty ratio via some analyses related to P-V characteristic for PSCs, global MPPT (GMPPT) is achieved in an efficient way. So as to validate performance of the proposed approach, a single-ended primary inductance converter has been used in both simulation and experimental studies. PV simulator has been used as a PV source to obtain different module characteristics with different number of bypass diodes and PV power levels. Both simulation and experimental results clarify that improved MPPT approach realises GMPPT effectively. Due to the high performance results, this approach can be an alternative technique in module-integrated converters, smart modules and PV power optimisers in which single module is used.
- MakaleAçık Erişim2018Indoor and outdoor radon measurements at lung cancer patients’ homes in the dwellings of Rize Province in Turkey
Özen, Songül Akbulut; Celik, Necati; Dursun, Emrehan; Taskın, Halim
In this study, indoor and outdoor radon (222Rn) surveys were carried out in the summer and winter seasons in homes of one hundred lung cancer patients in the year 2013–2014. The aim was to investigate the relationship between radon and cancer patients. Lung cancer patients completed a questionnaire concerning their living environment, various physical parameters and living habits. Pearson correlation and t tests revealed no meaningful results between radon concentrations, on one hand, and environmental and personal living habits, on the other hand. Consequently, the BEIR VI model was adapted and 222Rn exposure was estimated to be responsible for about 12% of the lung cancer incidences in the winter season and around 5% in the summer season in the Rize Province. However, due to the limited number of data and numerous parameters that could lead to lung cancer, the estimations done with the model should be taken very lightly. The annual effective doses due to inhalation of indoor and outdoor 222Rn were estimated to be, respectively, 1.43 and 0.94 mSv y−1. The indoor and outdoor annual effective doses were, respectively, close and below the world annual effective dose (1.3 mSv y−1). At the district level, the indoor annual effective dose equivalent in the İyidere district was 4.52 mSv y−1, which was 3.5 times greater than the world average. The number of patients in the majority of the houses in this district was more than one.
- MakaleYalnız künye2018Solving power transmission line routing problem using improved genetic and artificial bee colony algorithms
Eroğlu, Hasan; Aydin, Musa
In engineering studies, finding the best route from a start point to an end point on pixel-based weighted maps is a big problem for researchers. For this problem many methods and algorithms have been developed until now. The “cost distance” (CD) and “cost path” (CP) tools that are used by a modified Dijkstra’s algorithm and used by Environmental Systems Research Institute’s (ESRI) ArcGIS Desktop 10 software are very fast and most preferred solutions for route optimization problems. Despite the advantages of these tools, they have the disadvantage of making a lot of curves with big angles. Especially in some engineering studies like power transmission lines’ routing, the angle of the curves of the lines should not have big values. For overcoming this problem both genetic algorithm (GA) and artificial bee colony (ABC) algorithm that have been improved and adapted for the problem were used as powerful optimizers to find the best routes with fewer curves in those kinds of optimum route problems. New functions like smart direction sensing and improved random functions were developed for application of GA and ABC algorithms in power transmission lines routing studies. This study showed that the ABC algorithm’s performance is better than GA. The accuracy of the algorithms was proven by comparing the results with the CD–CP tools’ results. The experimental results showed that the improved algorithms gave better performance than Dijkstra’s algorithm.
- MakaleYalnız künye2018Optimization of drying parameters for chestnut fruits using central composite design
Koca, I.; Yilmaz, V.A.; Odabas, I.H.; Tekguler, B.
The chestnut drying process was optimized by Response Surface Methodology (RSM). A central composite design with two numerical factors was selected for modelling the drying process. The numerical factors were air temperature from 40 to 60°C and air velocity from 0.75 to 1.75 m s-1. The investigated responses were color values, including lightness (L*), redness (a*), yellowness (b*), total color changes (ΔE) and browning index (BI). The study revealed that the drying temperature was significantly effective on lightness, redness, total color changes and browning index. However, none of the independent variables were significant on yellowness. The L*, a*, ΔE and BI of chestnuts during drying process were adequately described by RSM models. According to desirability function, the optimum drying conditions of chestnuts were 40°C and 0.75 m s-1 air. At optimum conditions, predicted L*, a*, ΔE and BI values were 76.34, -0.20, 7.45 and 17.00, respectively. Under optimized conditions the experimental values of L* (77.46), a* (-0.36), ΔE (6.31) and BI (16.88) agreed with the predicted values. RSM was not successful to develop a satisfactory model for b* values of chestnuts during drying process.
- MakaleAçık Erişim2018Purification and selected biochemical properties of peroxidase from cress (Lepidium sativum sub sp. sativum)
Altay, Ahmet; Koktepe, Tubanur; Durmaz, Lokman; Topal, Fevzi; Gülçin, İlhami; Köksal, Ekrem
Cress (Lepidium sativum) is an annual herb from Brassicaceae family, and in some regions. It is known as peppergrass, garden cress, garden pepper-cress, pepperwort, or poor man’s pepper. Cress is an important medicinal plant in some countries including Turkey. This plant has major scientific and therapeutic significance. Peroxidase (POD, E.C.1.11.1.7) is an oxidor-eductase enzyme produced by a number of organisms. In this study, POD enzyme was purified from cress by ammonium sulphate precipitation, gel filtration, and CM-Sephadex ion-exchange chromatographies. K m and V max values were calculated from the Lineweaver-Burk graph for H 2 O 2 and guaiacol substrates and the substrate specificity of POD was investigated. The results showed that substrate specificity of H 2 O 2 is better than substrate specificity of guaiacol for this enzyme. The inhibition effects of three cations (Al 3+ , Cu 2+ , and Cr 3+ ) and one organic compound of cetyl trimethylammonium bromide were performed and their inhibition types were determined. Finally, optimum pH, optimum temperature, optimum ionic strength, and stable pH were determined.
- MakaleYalnız künye2018Open source library-based 3D face point cloud generation
Bayram, Bulent; Ozkan, Taskin; Reis, Hatice Catal; Bakirman, Tolga; Cetin, Ibrahim; Seker, Dursun Zafer
Three dimensional (3D) face and body modeling is widely used in various fields such as plastic surgery, diagnosis of facial or body anomalies, 3D computer games and 3D simulation software. Since, commercial 3D face and body scanners are usually expensive, an alternative solution with lower cost is highly desirable. The objective of this study is to create 3D facial point cloud using Semi Global Image Matching method with minimum number of images utilizing a cost effective method. A non-metric Canon 600D camera with 18 megapixels resolution (3456 × 5184) and 60 mm macro lens have been used for face imaging that have been taken from a distance of 120 cm. Five faces have been modeled by the developed algorithm and scanned by David SLS-2 structured light system for accuracy assessment. Open source Cloud Compare software has been used for comparing the results of proposed method with the structured light system. The mean accuracy of five faces obtained as 90.5%. It has been observed that illumination conditions, uncontrolled movements of face or body, hair and eyebrow have negative impacts on the obtained results. The sufficiency of Semi global image matching method has been tested to create dense point cloud data from three stereo pairs for 3D facial modelling.
- MakaleYalnız künye2018Geochemistry of Çoruh River Bed Sediments in NE Turkey: Implications in Weathering-Sedimentary Cycle, Provenance, and Metal Pollution
Eker, Ç.Saydam.; Kiliç, E. Demirkol
This study defines the source area, sub-aerial weathering, and sedimentary cycle level, as well as heavy metal content and origin, of the Çoruh River bed sediments. The studied sediments are geochemically classified as litharenite based on the ratio of the major element contents. Relative to the Upper Continental Crust (UCC), trace elements Rb, Sr, Ba, Th, U, Zr, Hf, Y, Nb, and Pb are generally depleted; Co, Ni, Cu, Sc, and V are generally enriched; and Au is depleted in some places and enriched in other places. The rare earth element (REE) distributions of the samples exhibit a trend similar to that of the upper continental crust (UCC); however, low to moderate depletion occurs in the bed sediments in UCC. The analyzed samples exhibit low Chemical Index of Alteration (CIA) values, Plagioclase Index of Alteration (PIA) values (<50), CIA/WIP (Weathering Index ratios <1), and substantially high Index of Compositional Variability values (ICV) (>1). Thus, the samples are not chemically mature and are mainly derived from non-altered sources and were exposed the simple cycling history. REEs are depleted in the river bed sediments, unlike the world river average silt, world river average clay, and suspended sediment in world rivers. Minor enrichment of Zn, Sn, and Sc contents, low-to-moderate enrichment of Cu content, very severe enrichment of as content, and extremely severe enrichment of Ni content of the analyzed samples are observed. Consequently, stream bed sediments are derived from intermediate sources close to mid-continental crust rather than felsic sources Low-to-moderate degrees of chemical weathering of these sediments indicate increased tectonic activity, increased erosion, and rapid sedimentation in semiarid to arid conditions in the source regions over time. Thus, the sediments are chemically immature. These sediments are exposed to lithogenic and anthropogenic contamination.
- MakaleAçık Erişim2018The effect of energy resolution of detection instrument on mass attenuation coefficient
Çelik, N.; Özen, S.A.; Demirtaş, Ö.F.; Çevik, U.
The effect of energy resolution of two detection systems, HPGe and NaI(Tl), was determined by Monte Carlo (MC) calculation on mass attenuation coefficients of magnesium (Mg) and tungsten (W). In order to reveal the energy resolution effect, the detectors' collimator diameters were changed from 2 mm to 20 mm while sending collimated photon beams to the absorber material. It was observed that mass attenuation coefficients were increased with increasing collimator diameters. The performances of HPGe and NaI(Tl) detectors were quantified. The calculated results were compared with experimental results for Mg at energy of gamma rays 662 keV for different collimator diameters using both HPGe and NaI(Tl). It was observed that the MC calculation results were in a good agreement with the experimental data within the relative error from around 4% to 8%.
- MakaleYalnız künye2018Differential scanning calorimetry (DSC) and Ni+2 release analysis of NiTi-shape-memory dental alloys coated by micro-arc oxidation (MAO) method
Yeşildal, Ruhi; Karabudak, Filiz; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Zamanlou, Hamid; Bayındır, Funda; Şen, Sadri; Totik, Yaşar
This study aims to prevent the release of Ni+2 and increase the biocompatibility of NiTi-shape-memory dental alloys with the micro-arc oxidation (MAO) coating by preserving the shape-memory feature in the oral environment. The TiO2-ceramic coating and Ag-doped TiO2 coating have been grown on shape-memory, co-atoms’ dental NiTi alloys with the MAO method. Biocompatibility properties of the coating were determined by in-vitro tests. In-vitro tests have been made as retention tests in a simulated body fluid (SBF). Whether the grown surface coating impacts the shape-memory properties of the base material or not has been determined by differential scanning calorimetry (DSC) analysis. It was observed as a result of retention tests that bone-like apatite form occurred on the surface of TiO2-coated NiTi and Ag-doped TiO2-coated NiTi coating. It was determined as a result of retention tests in SBF that the Ni+2 release rate from the base material was below the limit of detection in coated samples. As a result of DSC analysis, it was not observed any significant changes in transformation temperature with the MAO coating. It was concluded that the thin-film coatings formed by MAO technique prevent the release of Ni in the oral environment and increase the biocompatibility by preserving shape memory properties of NiTi dental alloys.
- MakaleYalnız künye2018Carrier transport mechanism and bipolar resistive switching behavior of a nano-scale thin film TiO2 memristor
Gul, Fatih
A titanium dioxide (TiO2) based memristor device having an active layer thickness of 10 nm was fabricated using radio frequency (RF) reactive sputtering and its resistive switching characteristics and carrier transport mechanisms were investigated. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to confirm the structural properties of the device. Measurement of the time-dependent current-voltage (I-V-t) was used to characterize resistive switching and memristive behavior. The characteristic pinched hysteresis I-V loops of the memristor were apparent. Bipolar and homogeneous resistive switching characteristics and a forming voltage of 2 V were detected in the device. The retention time exceeded 103 s and the endurance test was reasonably acceptable. In addition, the carrier transport mechanism of the device was revealed. The linear region of the low electric field demonstrated ohmic behavior, whereas the non-linear high electric field region was dominated by a Schottky emission carrier transport mechanism. A Poole-Frenkel emission mechanism acted as a secondary conduction mechanism. It was proposed that the Poole-Frenkel and Schottky emission mechanisms were associated with oxygen vacancies in the TiO2.
- BildiriYalnız künye2018Seasonal Variation of the Monthly Efficiencies of Thin Film PV Modules
Özden, Talat; Turan, Raşit; Akmoǧlu, Bülent Gültekin; Zaz, Y.; Essaaidi, M.
Outdoor testing of solar photovoltaic (PV) modules must be carried out at different climates as PV power plants nowadays are installed and continues to be installed in many countries. Present study is outdoor testing results and analyses of 5 thin film modules in Ankara, Turkey. The analyses are carried out using monthly efficiencies of the modules that are derived using the energy yield and input. The average efficiencies of the CIS, CIGS and μc-Si/a-Si thin film modules are. We present the monthly and average efficiencies and discuss their variations with the parameter: input, ambient temperature and relative humidity. We also carried out seasonal analyses using Pearson's correlation coefficient and find out that the efficiencies are differently dependent on the above mentioned parameters. This arose a new open question on differentiation of the strength of the effect of each parameter on the monthly efficiencies.