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Koleksiyondaki öğeler
- MakaleAçık Erişim2019Scopus SJRQ2Optical and surface properties of ZnN thin films manufactured by radio frequency reactive magnetron sputtering
Şenay, Volkan; Özen, Soner; Aydoğmuş, Tuna
ZnN is a relatively new material and its physical properties are not yet well studied. In this research, ZnN thin films having different thickness values were deposited on glass substrates by means of radio frequency (RF) reactive magnetron sputtering technique at room temperature and some physical properties of ZnN thin films were investigated by several techniques. UV–vis spectrophotometer and reflectometer were employed to investigate the optical properties of the produced thin films. The surface properties were investigated by using tensiometer and atomic force microscope (AFM). The effects of film thickness on the optical and surface properties of ZnN thin films were discussed. The refractive index and band gap values were found to be dependent on thickness of ZnN thin films. The AFM investigations indicated that the surfaces of the films are compact and smooth. From the wetting experiments, it was found that the surfaces of the films are hydrophobic and surface free energy values are low as reported in literature.
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İncele - Derleme MakaleYalnız künye2016Scopus SJRQ4Influence of oxygen partial pressure on the metastable copper oxide thin films
Geçici, Birol; Korkmaz, Šadan; Özen, Soner; Šenay, Volkan; Pat, Suat
Paramelaconite (Cu4O3) is a metastable copper oxide. Metastable copper oxide thin films were deposited on glass substrates by reactive RF magnetron sputtering in argon (Ar) and oxygen (O2) gas mixture atmospheres. Ar/O2 gas ratios in the sputtering ambient were chosen as 1/1 and 1/9. The surface and optical properties were determined by X-ray diffractometer (XRD), atomic force microscope (AFM) and UV-Vis spectrophotometer. The XRD patterns of the samples exhibited single strong diffraction peaks at 35.39° and 35.49° , corresponding to the (202) peak of Cu4O3. The mean thickness values were measured as 100 nm and 80 nm for the films deposited at 1/1 and 1/9 Ar/O2 gas ratios, respectively. The samples showed low transmittance and high absorbance in the high frequency region.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2018Scopus SJRQ2X-ray CT monitoring of macro void development in mortars exposed to sulfate attack
Tekin, Ilker; Birgul, Recep; Aruntas, Huseyin Y.
This study reports the results of nondestructive monitoring of macro void developments in mortars manufactured with both ordinary Portland cement and sulfate resistant cement. Two types of curing were utilized; tap water curing and another curing environment that contains 5% Na2(SO4) solution. Being the primary objective of this study, macro void developments of the mortar specimens were monitored by X-ray Medical Computerized Tomography. Compressive strength tests and water absorption tests were conducted on specimens that were kept in both curing environments for a duration of 560 days. Data analyses yielded consistent results among the three tests used in this experimental study. Macro void ratios of mortars decreased at the beginning of experiments for a certain period; afterwards, macro void ratios increased. The objective of this study was accomplished as anticipated since X-CT image analysis was able to nondestructively monitor macro void development process in cement mortars.
AtıfScopus6WoS6OpenAlex1İncele - MakaleYayıncıda açık erişim2016Scopus SJRQ2The influence of voltage applied between the electrodes on optical and morphological properties of the InGaN thin films grown by thermionic vacuum arc
Özen, Soner; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan
The aim of this research is to investigate the optical and morphological properties of the InGaN thin films deposited onto amorphous glass substrates in two separate experiments with two different voltages applied between the electrodes, i.e. 500 and 600 V by means of the thermionic vacuum arc technique. This technique is original for thin film deposition and it enables thin film production in a very short period of time. The optical and morphological properties of the films were investigated by using field emission scanning electron microscope, atomic force microscope, spectroscopic ellipsometer, reflectometer, spectrophotometer, and optical tensiometer. Optical properties were also supported by empirical relations. The deposition rates were calculated as 3 and 3.3 nm/sec for 500 and 600 V, respectively. The increase in the voltage also increased the refractive index, grain size, root mean square roughness and surface free energy. According to the results of the wetting experiments, InGaN samples were low-wettable, also known as hydrophobic. SCANNING 38:14-20, 2016.
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İncele - MakaleAçık Erişim2016Scopus SJRQ3A multi-criteria neutrosophic group decision making method based TOPSIS for supplier selection
Şahin, Ridvan; Yigider, Muhammet
The process of multi-criteria group decision making (MCGDM) is of determining the best choice among all of the probable alternatives. The problem of supplier selection on which decision maker has usually vague and imprecise knowledge is a typical example ofmulti criteria group decision-making problem. The conventional crisp techniques has notmuch effective for solvingMCDMproblems because of imprecise or fuzziness nature of the linguistic assessments. To find the exact values for MCGDM problems is both difficult and impossible in more cases in real world. So, it is more reasonable to consider the values of alternatives according to the criteria as single valued neutrosophic sets (SVNS). This paper deal with the technique for order preference by similarity to ideal solution (TOPSIS) approach and extend the TOPSIS method to MCGDM problem with single valued neutrosophic information. The value of each alternative and the weight of each criterion are characterized by single valued neutrosophic numbers. Here, the importance of criteria and alternatives is identified by aggregating individual opinions of decision makers (DMs) via single valued neutrosophic weighted averaging (SVNWA) operator. The proposed method is, easy use, precise and practical for solving MCGDM problem with single valued neutrosophic data. Finally, to show the applicability of the developed method, a numerical experiment for supplier choice is given as an application of single valued neutrosophic TOPSIS method at end of this paper.
AtıfScopus42OpenAlex50İncele - MakaleYalnız künye2015Scopus SJRQ3Biodiversity and Landscape Use of Sea Buckthorn (Hippophae rhamnoides L.) in the Coruh Valley of Turkey; [Sanddorn (Hippophae rhamnoides L.) im Coruh-Tal (Türkei): Biologische Vielfalt und Landschaftsnutzung]
Sezen, Isik; Ercisli, Sezai; Cakir, Ozlem; Koc, Aysen; Temim, Elma; Hadziabulic, Alisa
The Sea buckthorn, one of the most important wild edible fruits widely grown in Northeastern part of Turkey, is characterized by resistance to hard environmental conditions and looks spectacular, especially in autumn and winter when it is decorated with orange berries. Climatic conditions in Northern Anatolia are suitable for the growing of the Sea buckthorn, which can be encountered in various dry areas as well as by riversides. Local people traditionally processed or preserved sea buckthorn fruits (berries). The decorative sea buckthorn shrubs/trees and berries are an important element of natural landscape in Northeastern Anatolia. The aim of the study was to define the biodiversity among trees/shrubs, berries and leaves of the Sea buckthorn accessions based on morphological and biochemical data. Results showed a high diversity among accessions in terms of plant, leaf and berry characteristics. Berry diameter, length and 100 berry weight ranged from 5.48 to 7.18 mm; 6.64 to 9.14 mm and 15 to 26 g, respectively. A wide variability of berry skin colour was observed to be yellow, light yellow, dark yellow, yellow orange, orange and dark orange. The anthocyanin content varied from 7 to 38 mg/l berry juice.
AtıfScopus14WoS11OpenAlex14İncele - MakaleAçık Erişim2014Scopus SJRQ1Simultaneous separation and preconcentration of Ni(II) and Cu(II) ions by coprecipitation without any carrier element in some food and water samples
Duran, Celal; Tumay, Sureyya O.; Ozdes, Duygu; Serencam, Huseyin; Bektas, Hakan
A simple and highly sensitive separation and preconcentration procedure, which has minimal impact on the environment, has been developed. The procedure is based on the carrier element-free coprecipitation of Ni(II) and Cu(II) ions by using 2-{4-[2-(1H-Indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-(pyrrol-2-ylmethyliden)acetohydrazide (ICOTPA), as an organic coprecipitant. The levels of analyte ions were determined by flame atomic absorption spectrometry. The detection limits for Ni(II) and Cu(II) ions were found to be 0.27 and 0.58 μg L-1, respectively, and the relative standard deviations for the analyte ions were lower than 4.0%. Spike tests and certified reference material analyses were performed to validate the method. The method was successfully applied for the determination of Ni(II) and Cu(II) ions levels in sea and stream water as liquid samples and red lentil and rice as solid samples.
AtıfScopus26WoS23OpenAlex26İncele - MakaleYalnız künye2018Scopus SJRQ1Stochastic responses of isolated bridge with triple concave friction pendulum bearing under spatially varying ground motion
Yurdakul, Muhammet; Ates, Sevket
This study aims to investigate the stochastic response of isolated and non-isolated highway bridges subjected to spatially varying earthquake ground motion model. This model includes wave passage, incoherence and site response effects. The wave passage effect is examined by using various wave velocities. The incoherency effect is investigated by considering the Harichandran and Vanmarcke coherency model. The site response effect is considered by selecting homogeneous firm, medium and soft soil types where the bridge supports are constructed. The ground motion is described by power spectral density function and applied to each support point. Triple concave friction pendulum (TCFP) bearing which is more effective than other seismic isolation systems is used for seismic isolation. To implement seismic isolation procedure, TCFP bearing devices are placed at each of the support points of the deck. In the analysis, the bridge selected is a five-span featuring cast-in-place concrete box girder superstructure supported on reinforced concrete columns. Foundation supported highway bridge is regarded as three regions and compared its different situation in the stochastic analysis. The stochastic analyses results show that spatially varying ground motion has important effects on the stochastic response of the isolated and non-isolated bridges as long span structures.
AtıfScopus13WoS13OpenAlex6İncele - MakaleYalnız künye2018Scopus SJRQ2Determining the Patient-Specific Optimum Osteotomy Line for Severe Mandibular Retrognathia Patients
Şensoy, Abdullah Tahir; Kaymaz, Irfan; Ertaş, Ümit; Kiki, Ali
Purpose: The purpose of this study is to suggest a patient-specific osteotomy line to optimize the distractor position and thus to minimize the disadvantages of conventional mandibular distraction osteogenesis (MDO) protocols. In addition, this study also aims to compare the conventional MDO protocols with the new MDO protocol proposed in this study in terms of both orthodontic outcomes and mechanical effects of osteotomy level on callus stabilization by means of the finite element method. Methods: A preoperative patient-specific 3-dimensional bone model was created and segmented by using computed tomography images of an individual patient. Virtual orthodontic set-up was applied to the segmented model prior to the virtual surgery. In order to compare the proposed osteotomy line with the conventional lines used in clinical applications, virtual surgery simulations were performed and callus tissues were modelled for each scenario. The comparison of the success of each osteotomy line was carried out based on the occlusion of the teeth. Results: The osteotomy line determined using the method proposed in this study has resulted in far less malocclusion than the conventional method. Namely, any angular deviation from the optimum osteotomy line determined in this study might result in deep-bite or open-bite. On the other hand, the finite element analysis results have indicated that this deviation also negatively affects the callus stability. Conclusion: In order to achieve a better MDO treatment in terms of occlusion of the teeth and the callus stability, the location of the osteotomy line and the distractor position can be computationally determined. The results suggest that MDO protocol developed in this study might be used in clinic to achieve a better outcome from the MDO treatment.
AtıfScopus7WoS4OpenAlex8İncele - MakaleYalnız künye2019Scopus SJRQ3Synthesis and Biological Evaluation of Novel Tricyclic Pyrrolidinyl (R)-Alcohols and Amines
Şahin, Engin; Kılıç, Hamdullah; Törnük, Fatih; Dertli, Enes
Three new tricyclic pyrrolidinyl alcohols and three tricyclic pyrrolidinyl amines were synthesized, and the antibacterial activities of these compounds were tested against Salmonella enterica subsp. enterica serovar Typhimurium, Escherichia coli O157:H7, Staphylococcus aureus, and Listeria monocytogenes. All tested pyrrolidinyl alcohols and amines showed antibacterial activity to the tested pathogens, but this activity was dependent on the final concentration of the tested compound, and the structure of these compounds were also important for this antibacterial activity. Of the tested compounds, (2R)-2-(octahydro-4,8-ethanocyclohepta[c] pyrrol2(1H)-yl)-2-phenylethanamine (2c) was the most effective compound among the tested pyrrolidinyl alcohols and amines. This study shows a good example of finding new antimicrobials in order to control pathogenic bacteria.
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2015Scopus SJRQ1Numerical modeling of cold powder compaction using multi particle and continuum media approaches
Güner, Faruk; Cora, Ömer Necati; Sofuoğlu, Hasan
Numerical analysis of powder compaction process requires multi-particle modeling approach as continuum models fail to simulate the nature of process (e.g. interparticle, and particle-die interactions), accurately. This study aimed for analyzing powder compaction process utilizing 3-D finite element modeling approach along with different material models including modified Cam-Clay, Mohr-Coulomb, Shima-Oyane and von-Mises. The finite element analyses were carried out by implementing multi-particle finite element method. Moreover, continuum modeling was also performed for comparison purposes. In both cases, the compaction of spherical copper particles was analyzed at room temperature conditions. The obtained FEA results were compared in terms of equivalent stress and strain, and deformed shape. Results showed that the FE models in which von-Mises and modified Cam-clay material models were used yielded results of similar magnitude while those of Shima-Oyane and Mohr-Coulomb material models resulted in equivalent stress and strain values are in close proximity. Effect of coefficient of friction on the results was also investigated by implementing three distinct coefficients of friction ( μ= 0.1, 0.25, 0.4). It was noted that increasing friction resulted in elevated level of deformation for the particles and harsher particle-particle, and particle-die contact interactions.
AtıfScopus72WoS67OpenAlex76İncele - MakaleYalnız künye2016Scopus SJRQ2Applicability of statistical process control for surface modification plant and properties of coated calcite
Ucurum, Metin; Malgir, Eda; Deligezen, Hamdi; Karaer, Necmettin; Avsar, Mustafa
Due to its low surface energy, easy dispersion, high homogeneity and whiteness, coated (modified) calcite has increasingly been used in many industries, particularly in the plastics. The demand for this product will most likely increase in the years to come. Surface modification of calcite with a fatty acid would lead to a great expansion of industrial applications. The color values of coated calcite products are the first quality parameter. Therefore, it is very important to monitor the variations in the color characteristics of the coated calcite products. It is well known that statistical process control (SPC) techniques have been widely used in the many industries. In the present study, the surface of micronized calcite was coated with stearic acid by a pin mill. X-R control graphics and process capability index were applied for monitoring variations in quality control based on color parameters (L*,a*and b*) for the pin mill plant. In addition, active ratio, particle size distribution, whiteness parameters, BET, FTIR, TGA-DTA and SEM were then determined on a coated calcite sample. The results show that the pin mill plant seems under control and the coating technology is very effective in modifying the surface of micronized calcite.products.
AtıfScopus3WoS2OpenAlex4İncele - MakaleYalnız künye2017Scopus SJRQ1Role of airtightness in energy loss from windows: Experimental results from in-situ tests
Cuce, Erdem
The rate of air leakage related energy loss from glazed areas is unequivocal especially in older and poorly installed windows. Therefore, in this research, a comprehensive experimental investigation is done to analyse the importance of air leakage on overall heat transfer coefficient (U-value) of conventional air filled double glazed windows. The tests are conducted in a typical UK dwelling of Nottingham fitted with traditional air filled double glazed windows. One sash of the test window is sealed internally with a special transparent cover to provide excellent airtightness whereas the second window sash is left as it is to represent the ordinary case. The experiments are conducted in April 2016, and dynamic co-heating test methodology is applied to evaluate the rate of enhancement in the U-value of airtight window sash. The results indicate that the airtight window sash has a notably lower U-value compared to the ordinary window sash due to the impact of airtightness and reverse heat flux during noon time owing to the greenhouse effect between transparent cover and internal glazing. The overall U-value of ordinary window sash is found to be 2.67 W/m2K, whereas it is 1.79 W/m2K for airtight window sash. It is observed that about 33% of reduction in heat losses can be achieved via airtight windows.
AtıfScopus60WoS59OpenAlex75İncele - MakaleYalnız künye2016Scopus SJRQ1Properties of NaOH activated geopolymer with marble, travertine and volcanic tuff wastes
Tekin, Ilker
In this study, geopolymer composite pastes (GCM) were produced using wastes of marble, travertine and natural pozzolan, with 1 M, 5 M and 10 M NaOH as alkali-activator. Curing process were done at 20, 45 and 75 °C temperatures for 24 h in an oven. And after that GCMs were exposed to wet and dry condition separately. The strength tests were done on the 2nd, 3rd, 7th, 28th and 90th days of curing period. The compressive strengths of the specimens in the wet conditions were reduced depending on time, but in dry conditions were increased with curing time.
AtıfScopus137WoS117OpenAlex149İncele - MakaleAçık Erişim2019Impact of Managers’ Innovation Perception on Innovation Activities and Innovation Strategies in Hotel Businesses
Karakaş, Ayhan; Bilgin, Yusuf; Yildiz, Muhammed Raşit
The purpose of this study is to examine the impact of managers’ innovation perceptions on innovation activities and innovation strategies in hotel business. The research also examined the relationship between innovation types applied in hotel businesses and innovation strategies. Quantitative method was used in the research. The universe of the research constitutes hotel businesses operating in the Western Black Sea Region. Survey data were obtained using questionnaire technique. As a result of the analysis, it is determined that the innovation perceptions of the managers of the hotel businesses has an effect on the types of innovations applied in the businesses. Nevertheless, it has been determined that business managers’ perceptions of innovation have no meaningful effect on innovation strategies applied to the business. In other words, it has been reached that the innovation strategies of the businesses are determined by the variables other than the innovation perceptions of the managers. The research also find that there is a relationship between innovation types applied in hotel businesses and innovation strategies.
AtıfScopus2WoS2OpenAlex5İncele - BildiriYalnız künye2016Impedance analysis of nano thickness layered AlGaN acoustic sensor deposited by thermionic vacuum arc
Özen, Soner; Bilgiç, Eyüp; Gülmez, Gülay; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan; Mohammadigharehbagh, Reza
In this study, AlGaN acoustic sensor was deposited on aluminum metal substrate by thermionic vacuum arc (TVA) method for the first time. Gallium materials are used in many applications for optoelectronic device and semiconductor technology. Thermionic vacuum arc is the deposition technology for the variously materials and applications field. The thickness of the acoustic sensor is in deposited as nano layer. Impedance analyses were realized. Also, TVA production parameters and some properties of the deposited layers were investigated. TVA is a fast deposition technology for the gallium compounds and doped gallium compounds. Obtained results show that AlGaN materials are very promising materials. Moreover, these acoustic sensors have been produced by TVA technology.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2019Scopus SJRQ1Optimization of design parameters for heat transfer and friction factor in a heat sink with hollow trapezoidal baffles
Sahin, Bayram; Ates, Ibrahim; Manay, Eyuphan; Bayrakceken, Abdulkadir; Celik, Cafer
The aim of this study is to optimize the design parameters of a heat sink on which hollow trapezoidal baffles are mounted on the bottom surface by using Taguchi experimental-design method. The Nusselt number and the friction factor are considered as performance parameters. An orthogonal array is selected as experimental plan for the six parameters: the corner angle (α), the inclination angle (β), the baffle height (H), the baffle length (L), the baffle width (S) and Reynolds number. First of all, each goal has been optimized, separately. Then, all the goals have been optimized together, considering the priority of the goals. The length of the baffle is found to be the most influential parameter on the friction factor. This can be attributed the enhanced effect of longitudinal vortices with baffle length in flow direction. Likewise, it is demonstrated that the most effective parameter on the heat transfer is Reynolds number. The results show that the baffle width (S) and the corner angle (α) have insignificant effect on Nusselt number. The maximum heat transfer was obtained at Re = 17,000, H = 36 mm, L = 45 mm, S = 26 mm, α = 0°, β = 0°. The inclination angle (β) and the baffle height (H) have nearly no effect on the friction factor. The minimum friction factor was obtained at Re = 17,000, H = 20 mm, L = 25 mm, S = 26 mm, α = 16°, β = 0°. The inclination angle (β) and the baffle height (H) have nearly no effect on the friction factor. It can be concluded that the higher heat transfer rates can be achieved with lower pressure drop penalty with this type of vortex generator in particular configurations.
AtıfScopus31WoS27OpenAlex32İncele - MakaleYalnız künye2016Scopus SJRQ1Optimum design of steel space frames including soil-structure interaction
Daloglu, Ayse T.; Artar, Musa; Özgan, Korhan; Karakas, Ali İ.
The effect of soil-structure interaction on the optimum design of steel space frames is investigated using metaheuristic algorithms. Three-parameter elastic foundation model is used to incorporate soil-structure interaction. A computer program is developed in MATLAB interacting with SAP2000-OAPI for two way data flow in all optimization procedures. Optimum design of space frames is formulated according to LRFD-AISC (Load and Resistance Factor Design, American Institute of Steel Construction) specifications. The parameters of foundation model are obtained by using soil surface displacements. It is concluded that consideration of soil-structure interaction ends up with heavier frames, and method is applicable for practical purposes.
AtıfScopus27WoS28OpenAlex31İncele - MakaleYalnız künye2014Scopus SJRQ4Fatty acid profile and quality specifications of chocolate spreads
Kara, Hasan Hüseyin; Çaǧlar, Abdullah; Mercan, Emin; Gök, Gökçen; Taşbaş, Sultan; Arslan, Merve
This study examined the characteristics of 13 samples from 10 different brands of chocolate spread that are sold in markets in Turkey. Humidity level, oil content, pH value, color values (L*, a*, b*), were determined, chocolate fat samples were tested for free fat acidity rate, peroxide value, iodine value and fat acids composition. The samples composed of 14 different fatty acids. Dominant fatty acids were palmitic acid (9.82-27.19 %), oleic acid (26.27-56.05 %) and linoleic acid (10.87-52.40 %). It was observed that saturated fatty acids (SFA) of the samples ranged between 17.01 and 32.03 %, monounsaturated fatty acids (MUFA) ranged between 19.74 and 57.00 % and polyunsaturated fatty acids (PUFA) ranged between 11.01 and 52.51 %. The analyses showed that contents of the samples complied with legal limits. The types of fatty acids used were determined to be remarkable due to their fatty acids composition.
AtıfScopus5WoS6İncele - MakaleYalnız künye2019Scopus SJRQ2Expert system application for prioritizing preventive actions for shift work: shift expert
Esen, Hatice; Hatipoğlu, Tuğçen; Cihan, Ahmet; Fiğlali, Nilgün
Introduction. Shift patterns, work hours, work arrangements and worker motivations have increasingly become key factors for job performance. The main objective of this article is to design an expert system that identifies the negative effects of shift work and prioritizes mitigation efforts according to their importance in preventing these negative effects. The proposed expert system will be referred to as the shift expert. Methods. A thorough literature review is conducted to determine the effects of shift work on workers. Our work indicates that shift work is linked to demographic variables, sleepiness and fatigue, health and well-being, and social and domestic conditions. These parameters constitute the sections of a questionnaire designed to focus on 26 important issues related to shift work. The shift expert is then constructed to provide prevention advice at the individual and organizational levels, and it prioritizes this advice using a fuzzy analytic hierarchy process model, which considers comparison matrices provided by users during the prioritization process. An empirical study of 61 workers working on three rotating shifts is performed. After administering the questionnaires, the collected data are analyzed statistically, and then the shift expert produces individual and organizational recommendations for these workers.
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