Yayınlar
Koleksiyondaki öğeler
- MakaleAçık Erişim2017Scopus SJRQ3Influence of Duplex Treatment on Structural and Tribological Properties of Commercially Pure Titanium
Çelik, Ilhan
Titanium and its alloys are widely used in many fields, including aerospace and the chemical and biomedical industries. This is due to their mechanical properties, excellent corrosion resistance, and biocompatibility although they do have poor wear resistance. In this study, a duplex layer was successfully formed on the commercially pure titanium surface by duplex treatments (plasma nitriding and physical vapor deposition (PVD)). In the initial treatment, plasma nitriding was performed on the pure titanium samples and in the second treatment, the nitrided samples were coated with CrN by PVD. The friction and wear properties of the duplex-treated samples were investigated for tribological applications. Surface morphology and microstructure of the duplex-treated samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the tribological properties were investigated using pin-on-disc tribometer. A compound layer composed of ϵ-Ti2N and δ-TiN phases and a diffusion layer formed under the compound layer were obtained on the surface of pure titanium after the nitriding treatments. CrN coated on the nitrided surface provided an increase in the surface hardness and in the wear resistance.
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İncele - MakaleAçık Erişim2018Scopus SJRQ3Bounds for radii of starlikeness and convexity of some special functions
Aktaş, Ibrahim; Baricz, Árpád; Orhan, Halit
In this paper we consider some normalized Bessel, Struve, and Lommel functions of the first kind and, by using the Euler-Rayleigh inequalities for the first positive zeros of a combination of special functions, we obtain tight lower and upper bounds for the radii of starlikeness of these functions. By considering two different normalizations of Bessel and Struve functions we give some inequalities for the radii of convexity of the same functions. On the other hand, we show that the radii of univalence of some normalized Struve and Lommel functions are exactly the radii of starlikeness of the same functions. In addition, by using some ideas of Ismail and Muldoon we present some new lower and upper bounds for the zeros of derivatives of some normalized Struve and Lommel functions. The Laguerre-Pólya class of real entire functions plays an important role in our study.
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İncele - MakaleYalnız künye2016Scopus SJRQ2Indoor radon and gamma spectrometric measurements for the Erzincan Basin on North Anatolian Fault Zone, Turkey
Kucukomeroglu, B.; Ozturk, E.; Damla, N.; Celik, N.; Duran, S. Uzun; Cevik, U.; Taskin, H.; Albayrak, N.
Indoor radon and soil radioactivity levels were determined for Erzincan province in Turkey. Indoor radon concentrations were determined in 89 dwellings using CR-39 passive Solid State Nuclear Track Detectors (SSNTDs) for four seasons. The mean annual 222Rn activity concentration was found to be 119 Bq.m-'3. In the winter season, indoor radon concentrations showed the highest values while the lowest values were observed in the summer season. A model was used to predict the number of lung cancer incidences due to inhalation of radon. The findings have indicated that radon is responsible for 13% of lung cancer incidences occurring in the Erzincan province. Since indoor radon concentration correlates with 226Ra content in soil beneath the dwellings, soil samples were collected near the houses where indoor radon measurements were performed in order to seek a correlation. The 226Ra, 232Th, 40K and 137Cs activity concentration values were 52, 26, 649 and 9 Bq.kg-'1, respectively. The annual effective dose due to naturally occurring radionuclides was around 82 μSv.y-'1 which is higher than the world average value of 70 μSv.y-'1. The results of the present study are expected to be a useful baseline data for future studies.
AtıfScopus3WoS3İncele - MakaleYalnız künye2017Scopus SJRQ4Molecular docking analysis and determination of minimum inhibition concentration of VIM-38/R228S
Duzgun, Azer Ozad; Saral, Aysegul
Objective: The aim of this study was to determine the effects of residues at 228th positions of VIM-38 on minimum inhibition concentration (MIC) and molecular docking analysis. Materials and methods: blaVIM-38 gene was cloned into expression vector pET100/D-TOPO. Then pET100/D-TOPO-VIM-38 was used to generate the R228S mutation by site-directed mutagenesis. The mutant was transformed into E. coli Dh5α. Changes in the activity of mutation R228S was determined by E-test. Molecular docking analysis of the binding affinity of meropenem and imipenem with VIM-38 and VIM-38 R228S was performed using AutoDock Vina_1_1_2. Results: According to E-test results, pET100/D-TOPO-VIM-38 and pET100/D-TOPO-VIM-38/ R228S have same MIC value for amoxicillin, ticarcillin/clavulanic acid, ampicillin and ticarcillin. It was determined decrease in pET100/D-TOPO-VIM-38/ R228S of MIC for aztreonam, amikacin and cefixine. There are 3-fold deference in MIC between pET100/D-TOPO-VIM-38 and pET100/D-TOPO-VIM-38/ R228S for cefoxitin. pET100/D-TOPO-VIM-38 has 0.5 µg/ml and pET100/D-TOPO-VIM-38/ R228S has 0.125 µg/m for imipenem, we observed 4-fold deference. Also, there is about 170-fold deference between pET100/D-TOPO-VIM-38 (16 µg/ml) and pET100/D-TOPO-VIM-38/ R228S (0.094 µg/ml) for meropenem. VIM-38 and VIM-38 R228S have very close to the negative low free energies of binding of the meropenem and imipenem. Conclusion: These results showed that substitution (R228S) slightly have effect on enzyme activity.
- MakaleYalnız künye2018Scopus SJRQ2A novel OTA-based circuit model corroborated by an experimental semiconductor memristor
Gul, Fatih; Babacan, Yunus
A semiconductor memristor device based on a 300-nm ZnO thin film was fabricated by direct-current reactive sputter. The memristive behavior of this device was confirmed by time dependent current–voltage (I-V-t) measurements, and the distinctive pinched hysteresis I-V loops of the memristor were observed. Structural analysis of the ZnO memristor was carried out using both X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). After physical implementation of the memristor, an operational transconductance amplifier (OTA) based memristor circuit was designed to emulate the ZnO-based semiconductor memristor for use in memristor-based circuit applications. All simulations were in good agreement with experimental results. In addition, a comparison of the proposed circuit with other memristor emulators was presented.
AtıfScopus29WoS27OpenAlex29İncele - BildiriYalnız künye2017A day ahead hourly solar radiation forecasting by artificial neural networks: A case study for Trabzon province; [Yapay Sinir Aǧlari ile Gün Öncesi Saatlik Güneş Radyasyonu Tahmini: Trabzon İli Örneǧi]
Çevik, Sibel; Çakmak, Recep; Altaş, Ismail Hakki
The integration of renewable energy sources to the electrical grid leads to some issues in the grid because of intermittent and variable characteristics of renewable energy sources such as wind and solar. It has been predicted that the solar based electricity production will has highest annual increase rate among the other renewable sources. Due to the intermittent and volatile nature of the solar energy in an electricity grid where photovoltaic systems are intensive, load planning is essential. Therefore, day ahead solar radiation forecasting will contribute to the load planning studies. Artificial neural networks are one of the methods that are applied frequently and successfully in forecasting studies. In this study, a cause effect based artificial neural network (ANN) has been designed and performed for day ahead hourly solar radiation forecasting in Trabzon province. A similar day selection algorithm has been utilized to get more accurate forecasting by the ANN. The designed ANN has been trained and tested in MATLAB simulation environment without using ready codes of MATLAB ANN toolbox. The obtained results reveal that the designed ANN forecasts the solar radiation with acceptable error for a place such as Trabzon which has rainy and cloudy weather conditions.
AtıfScopus9OpenAlex13İncele - BildiriYalnız künye2017Gamma ray spectrometry method in detecting the low sulfidation type epithermal Au+Ag mineralization (Gümüshane, Ne Turkey)
Maden, N.; Akaryali, E.
The gamma ray spectrometry has been widely used in mineral exploration, geological mapping and environmental radiation monitoring.The Eastern Pontide orogenic belt, which constitutes an important part of the Alpine-Himalayan system, hosts various types of economic mineral deposits of massive sulfide, porphyry copper, skarn, and epithermal vein-type ore deposits. Potassium is generally the most useful pathfinder element for gold mineralization zones. High level K/eTh, K/eU and Efimov F-Parameter (KeU/eTh) anomalies showed the alteration zones transmitting hydrothermal ore solutions to the surface. As a result, the gamma ray spectrometry, which is fast and economics method, might be used for estimation of prospective Au ore zones associated with the K alteration.
- MakaleYalnız künye2018Scopus SJRQ1Investigation of radiation absorption coefficients of lead-zinc mine waste rock mixed heavy concrete at 662–1460 keV energy range
Çullu, Mustafa; Bakırhan, Emir
The objective of this study is to observe the radiation shielding efficiency of concrete produced by using the lead wastes that are stored in lead-zinc mines processing of which is not financially viable in the mines they are extracted from that have negative effects on the environment. Within this scope, concretes were produced to be used as radiation shield concretes. The samples were prepared by altering the amounts of heavy aggregates such as lead–zinc mine waste, Magnetite, Limonite, and Barite at 25%, 50%, and 75% ratios, and concrete samples were prepared in C16/20, C25/30, and C35/45 concrete strength grades to determine the effects of these grades on radiation absorption properties. In order to determine the radiation absorption coefficients, absorption coefficients at 662 keV, 1173 keV, 1332 keV, and 1460 keV energy levels from Cs-137, Co-60 and K-40 sources were determined by concrete slabs with dimensions of 20 × 20 × 5 cm.
AtıfScopus35WoS33OpenAlex32İncele - MakaleAçık Erişim2018Scopus SJRQ3Evaluation of enamel surface morphology and microhardness after the application of different protective agents
Simsek, Huseyin; Derelioglu, Sera; Buyuk, Suleyman Kutalmış; Sukuroglu, Ebru Emine
The aim of this in vitro study was to compare the effect of different protective agents on the surface microhardness and morphology on enamel eroded by a cola drink. Sixty sound anterior teeth were randomly divided into five groups. The baseline surface microhardness of the enamel was measured. For demineralization procedures, all teeth were immersed in cola for 8 minutes and surface microhardness was remeasured. The five groups for remineralization procedures were defined as: Group 1: Artificial saliva, Group 2: 1.23% Acidulated Phosphate Fluoride gel (APF), Group 3: 5% NaF varnish, Group 4: Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP), and Group 5: Probiotic yogurt. After each experimental procedure, a third microhardness measurement was repeated. Surface morphological changes were observed using SEM. All data were recorded for each group and statistically analyzed using two-way analysis of variance and one-way repeated-measures analysis of variance. All tests were performed at a significance level of p < 0.05. No significant differences for baseline microhardness values were found (P> 0.05). The mean surface microhardness in all groups decreased significantly after immersion in cola (P< 0.05). After remineralization, NaF varnish and APF gel significantly increased the surface microhardness values. There were no significant increases in the surface microhardness values of artificial saliva, CPP-ACP and probiotic yogurt. This study concludes that NaF varnish is more effective in re-hardening of eroded enamel.
AtıfScopus2WoS2OpenAlex5İncele - MakaleAçık Erişim2016Scopus SJRQ2Investigation of Hydroxymethylfurfural Formation in Herle
Baltacı, Cemalettin; Ilyasoglu, Huri; Gundogdu, Ali; Ucuncu, Osman
Mulberry pestil and köme are Turkish traditional foods made from herle. Browning leads to quality losses in the herle, and its products. In this study, the effect of thermal treatment on the hydroxymethylfurfural formation and color values in the herle was evaluated. The herle samples were kept at different temperatures (60–110°C) and times (2–6 h). The hydroxymethylfurfural formation was found to increase with increasing time and temperature. The legal limit for hydroxymethylfurfural in the pestil (50 mg/kg) was exceeded at temperatures above 90°C. The lightness (L* value) of the sample decreased with the thermal treatment, indicating browning.
AtıfScopus10WoS10OpenAlex12İncele - BildiriYalnız künye2016Stability estimates for solution of Bitsadze-Samarskii type inverse elliptic problem with Dirichlet conditions
Ashyralyyev, Charyyar; Akyüz, Gulzipa
In this study, we discuss well-posedness of Bitsadze-Samarskii type inverse elliptic problem with Dirichlet conditions. We establish abstract results on stability and coercive stability estimates for the solution of this inverse problem. Then, the abstract results are applied to three overdetermined problems for the multi-dimensional elliptic equation with different boundary conditions. Stability inequalities for solutions of these applications are obtained.
AtıfScopus4WoS4OpenAlex3İncele - Kitap BölümüYalnız künye2016Green development: Case of Turkey, Norway, and China
Doğru, Bülent; Beken, Hikmet Gülçin
The focus of this chapter is to assess green or sustainable development concept because of its increased importance throughout the world. Droughts, environmental degradation, air pollution, greenhouse gas emissions are important problems that the humankind have been facing since the Industrial Revolution. Renewable energy sources can be used to overcome these problems. The general tendency of modern-day societies is to transform traditional production techniques and development models to new renewable energy sources and also move towards to sustainable development path. Therefore, this study tries to explain current status of Norway, China and Turkey in terms of their renewable energy sources and policy implementations.
- MakaleAçık Erişim2019Scopus SJRQ2The Impact of Education About Cervical Cancer and Human Papillomavirus on Women's Healthy Lifestyle Behaviors and Beliefs: Using the PRECEDE Educational Model
Koç, Zeliha; Özdeş, Emel Kurtoǧlu; Topatan, Serap; Çinarli, Tuǧba; Şener, Asuman; Danaci, Esra; Palazoǧlu, Cansu Atmaca
Background Early detection of cervical cancer improves the chances of successful treatment. Objective The aim of this study was to determine the effect of education about cervical cancer and human papillomavirus on the healthy lifestyle, behavior, and beliefs of Turkish women who were without cancer, using the PRECEDE education model. Methods This qualitative and quantitative study was conducted as a prospective, randomized, 2-group (intervention and control) trial at a community training center in north Turkey. A total of 156 Turkish women who were without cancer participated in this study. The semistructured interview form, the SF-36 Health Status Questionnaire, the Health Belief Model Scale for Cervical Cancer and Pap Smear Test, and the Healthy Lifestyle Behavior Scale II were used. Results The subdimension scores of the Health Belief Model Scale for Cervical Cancer and Pap Smear Test were found to be higher among women in the study group (cervical cancer seriousness, P =.001; health motivation, P =.001) as compared with the control group after the education program. The SF-36 Health Status Questionnaire domain scores for physical role limitations, mental role limitations, and general health perceptions increased in the study group after the intervention. Conclusion The posteducation health motivation of women in the study group was improved, the women's perceptions of obstacles to Papanicolaou testing decreased, and through increased knowledge and awareness, the rate of Papanicolaou testing increased. Implications for Practice Educational programs aimed at motivating women to increase their awareness of cervical cancer, preventing cervical cancer, and having Papanicolaou testing are necessary and beneficial in this sample.
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İncele - BildiriYalnız künye2016Scheduling of domestic shiftable loads via Cuckoo search optimization algorithm
Cakmak, Recep; Altas, Ismail H.
Electrical power systems have been developed to more advanced structures called as smart grids. Among many other issues, demand side management (DSM) is one of the important instruments of the smart grids. DSM techniques increase the efficiency of the grid, and modify consumer's electrical demand via demand response (DR) programs using financial incentives. In this study, shiftable domestic loads scheduled by Cuckoo search algorithm (CSA) to ensure balanced load curve as much as possible while considering the consumers' preferences. The main motivation of this paper is scheduling the usage hours of the shiftable household appliances in a neighborhood by applying the recently developed metaheuristic CSA. This paper proposes an approach to increase the efficiency and lifetime of utility network by scheduling and operating shiftable domestic loads while considering consumer's demand in terms of financial benefits. Proposed CSA based scheduling mechanism is compared with that of Genetic algorithm (GA). The results reveal positive effects of the scheduling and the performance of the CSA over GA.
AtıfScopus23WoS9OpenAlex25İncele - MakaleYalnız künye2018Scopus SJRQ1Competitive positioning of winter tourism destinations: A comparative analysis of demand and supply sides perspectives–Cases from Turkey
Evren, Savaş; Kozak, Nazmi
This study was conducted to determine the competitive positions of five winter tourism destinations in Turkey. The explanatory sequential mixed method was used in order to compare the views of both the supply and demand sides. A questionnaire was first applied to current and potential visitors of the related destinations (n = 417), both in the field and online, followed by semi-structured interviews conducted with destination stakeholders (n = 12). It was observed that visitor perceptions positioned Uludağ with its tourism superstructure means and entertainment opportunities, Kartalkaya with its tourism superstructure quality and service quality, Erciyes, with its reasonable pricing policy and uncrowded slopes/lifts, Palandöken with its adequate number of lifts and snow quality, and Kartepe, with its beautiful scenery and accessibility. The assessments of the destination stakeholders demonstrated that strategies for strengthening the current position was not accepted at every destination and that only some destination stakeholders were inclined toward repositioning.
AtıfScopus42WoS37OpenAlex55İncele - MakaleYalnız künye2019Scopus SJRQ1An improved 0.8 V OC model based GMPPT technique for module level photovoltaic power optimizers
Basoglu, Mustafa Engin
Photovoltaic modules may experience some mismatching conditions that affect their available power capacity, causing inefficient maximum power point tracking (MPPT). Furthermore, their power-voltage (P-V) characteristic curve becomes a multi-peak structure in such conditions owing to the presence of bypass diodes included since every part of the modules may receive different solar irradiance. By taking into account these facts, this paper introduces an improved global MPPT technique comprising 0.8 V OC model and the limited and adaptive scan approach. The proposed technique eliminates the requirement of some threshold value, leading to unreliable operation which the classical 0.8 V OC model based studies suffer from. Furthermore, the tracking time has been reduced substantially with the proposed technique by limiting scanning interval. Performance of the proposed technique has been verified by experimental studies and compared with classical 0.8 V OC model and a full scanning technique, which have been already presented in the literature. Experimental results show that the proposed technique is simple to be implemented and it has better performance than classical 0.8 V OC model, full scanning, and perturb and observe algorithms. Therefore, the proposed technique is feasible and it can be used technically in module level distributed MPPT (DMPPT) applications.
AtıfScopus65WoS49OpenAlex64İncele - MakaleYalnız künye2019THE NEW SUMUDU TRANSFORM ITERATIVE METHOD FOR STUDYING THE RANDOM COMPONENT TIME-FRACTIONAL KLEIN-GORDON EQUATION
Merdan, Mehmet; Anaç, Halil; Kesemen, Tülay
In this study, the solutions of the random component time-fractional Klein-Gordon equation is obtained as approximately or exactly. The initial condition of this Klein-Gordon equation is studied by Gamma distribution. The fractional derivatives are defined in the Caputo sense. An example is shown to illustrate the influence of the solutions obtained by the new Sumudu transform iterative method (NSTIM). The expected value and variance of these solutions of this Klein-Gordon equation are obtained. The approximate analytical solution of this equation obtained by NSTIM and VIM are compared. NSTIM is applied to analyze the solution of this equation. Solution and figures are obtained by using MAPLE software. The formulas for the expected values and variances and results from the simulations of this Klein-Gordon equation are compared and the efficiency of this method is investigated.
AtıfScopus5WoS5İncele - MakaleAçık Erişim2017Scopus SJRQ1Analysis of transcriptional profiles of Saccharomyces cerevisiae exposed to bisphenol A
Bereketoglu, Ceyhun; Arga, Kazim Yalcin; Eraslan, Serpil; Mertoglu, Bulent
Bisphenol A (BPA), an endocrine disrupting chemical, is used as a monomer in the production of epoxy resins and polycarbonates, and as a plasticizer in polyvinyl chloride. As such, it is produced in large quantities worldwide and continuously leaches into the environment. To capture the genome reprogramming in eukaryotic cells under BPA exposure, here, we used Saccharomyces cerevisiae as model organism and analyzed the genome-wide transcriptional profiles of S. cerevisiae BY4742 in response to BPA, focusing on two exposure scenarios: (1) exposure to a low inhibition concentration (50 mg/L; resulting in <10 % inhibition in cell number) and (2) a high inhibition concentration (300 mg/L; resulting in >70 % inhibition in cell number). Based on the transcriptional profiling analyses, 81 genes were repressed and 104 genes were induced in response to 50 mg/L BPA. Meanwhile, 378 genes were downregulated and 606 genes were significantly upregulated upon exposure to 300 mg/L BPA. While similar processes were affected by exposure to distinct BPA concentrations, including mitochondrial processes, nucleobase-containing small molecule metabolic processes, transcription from the RNA polymerase II promoter, and mitosis and associated processes, the number and magnitude of differentially expressed genes differ between low and high inhibition concentration treatments. For example, exposure to 300 mg/L BPA resulted in severe changes in the expression levels of several genes involved in oxidative phosphorylation, the tricarboxylic acid cycle, ribosomal activity, replication, and chemical responses. Conversely, only slight changes were observed in the expression of genes involved in these processes in cells exposed to 50 mg/L BPA. These results demonstrate that yeast cells respond to BPA in a concentration-dependent manner at the transcriptional level via different genes and provide insight into the molecular mechanisms underlying the modes of action of BPA.
AtıfScopus20WoS18OpenAlex21İncele - BildiriYalnız künye2019Scopus SJRQ3Teachers’ Resistance to Mobile Learning in Turkey and Spain: What Similarities? What Differences?
Aliagas, Cristina; Mutlu, Tugba
The aim of this paper is to present the data on secondary school teachers’ resistant attitudes towards integrating digital technologies and literacies into their classrooms. The data was gathered through qualitative interviews in the frame of two distinct one-to-one technology programs that took place in distant socio-cultural and educational contexts: the FATIH Project of Turkey and the Escuela 2.0/EduCAT1x1 of Catalonia/Spain. This comparative analysis shows that teachers mainly resist educational change and the government, although they slightly differ in the underlying assumptions supporting their resistance. Their discourses on technology in schools have settled into “discourses of uncertainty” where negative attitudes are compensated with slightly positive comments about digital artefacts and literacies as tools for learning. Findings also indicate that teachers, regardless of the educational context they work in, have assumed the “discourse of inevitability” that dominates viewpoints concerning technology and digital literacy in education.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2019Scopus SJRQ1Jurassic acidic magmatism in a back-arc setting, eastern Sakarya Zone, Turkey: Geochemical constraints and an evolutionary model
Dokuz, Abdurrahman; Sünnetçi, Kadir
The Early Jurassic in the Sakarya Zone, Turkey, was dominated by basic magmatism. The products of this magmatic episode are found as basaltic lavas and pyroclastic rocks in the Şenköy Formation, which was deposited in an extensional basin, or as intrusives cutting Variscan crystalline basement rocks. The Olur (Erzurum) region in the easternmost part of the Sakarya Zone is one of the few locations where contemporaneous acidic rocks crop out, exposed in an area of ~50 km 2 . The acidic rocks in the eastern Sakarya Zone consist of dacitic lavas, rare pyroclastic rocks, and very rare pebble dikes. Porphyries and trondhjemites are their intrusive equivalents and crop out as dikes and small stocks within the underlying Variscan basement. These Early Jurassic rocks have modal K-feldspar contents of <10% and are trondhjemitic in character. Laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of zircons from two samples yielded formation ages for these rocks of 185.3 ± 1.0 and 184.1 ± 1.1 Ma (±2σ). Geochemically, the rocks are strongly peraluminous and display a medium- to low-K affinity and sodic compositions (K 2 O/Na 2 O = 0.03–0.49). Enrichment in large-ion lithophile elements and depletion in Nb, Ta, P, and Ti are regarded as signatures of a subduction-related setting. Moderately radiogenic I Sr ratios (0.70508–0.70877) and depleted mantle-like Ɛ Nd (t) values (−0.6 to +3.0) and Pb(t) isotopes suggest that the acidic rocks were derived from juvenile lower crust. Geochemical and isotope data imply that the partial melting of juvenile mafic lithologies of the lower crust produced K-poor tonalitic melts that later fractionated to trondhjemitic melts while ascending to the surface. Considering the available data, we suggest that the Early Jurassic bimodal magmatic rocks of the eastern Sakarya Zone were formed in a back-arc setting during the southward subduction of the Paleotethys oceanic lithosphere. These rocks are a prime example of the formation of shallow subduction products following Late Triassic ridge subduction.
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