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Koleksiyondaki öğeler
- MakaleAçık Erişim2019Scopus SJRQ3A study concerning berger type deformed sasaki metric on the tangent bundle
Altunbas, Murat; Simsek, Ramazan; Gezer, Aydın
Let TM be the tangent bundle over an almost anti-paraHermitian manifold endowed with Berger type deformed Sasaki metric gBS. In this paper,first, we obtain the Levi-Civita connection of this metric and study geodesics on TM. Secondly, we construct some almost anti-paraHermitian structures on TM and search conditions for these structures to be anti-paraKähler and quasi-anti-paraKähler. Finally, we present certain Riemannian curvature properties of (TM, gBS).
AtıfScopus36OpenAlex21
İncele - MakaleAçık Erişim2017Scopus SJRQ2Chinese postman problem approach for a large-scale conventional rail network in Turkey; [Primjena pristupa "problem kineskog poštara" na široku mrežu Turske željeznice]
Yılmaz, Mustafa; Çodur, Merve Kayacı; Yılmaz, Hamid
Every year, railways are inspected periodically to examine the status of rail tracks and ensure the safety of train operations of the railroad networks in Turkey. These inspection projects must be performed by several specialized machines with large and expensive equipment. Finding the optimum route of inspection machines that control through travelling all lines is critically important in terms of cost and distance. In current practice, determining the route of these machines is largerly manual and primarily relies on the knowledge and judgment of experts. This paper proposes Chinese Postman Problem (CPP) to solve the inspection machine routing problem. The objective is to minimize the total travel distance on the railroads by finding the shortest route. The proposed model is applied to a large-scale real world problem. Compared to the current practice the proposed approach significantly outperforms the reduced objective value by 20, 76%.
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İncele - MakaleYalnız künye2015Scopus SJRQ2Effect of Er doping on the superconducting properties of porous MgB2
Erdem, O.; Yanmaz, E.
MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg1-xErx)B2, where x = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants a and c of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature (Tonsetc) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field (Bc2), the irreversibility field (Birr) and the critical current density (Jc) values are significantly enhanced in the doped samples. For the best sample (x = 0.03), at 15 K under a magnetic field of 4 T, the Jc value reaches 2.4×104 A cm-2, which is higher than that of the porous sample by an order of 103, and the Birr value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.
AtıfScopus13WoS11OpenAlex12İncele - MakaleYalnız künye2017Scopus SJRQ1Antimicrobial and functional properties of lactic acid bacteria isolated from sourdoughs
Demirbaş, Fatmanur; İspirli, Hümeyra; Kurnaz, Asena Ayşe; Yilmaz, Mustafa Tahsin; Dertli, Enes
The technological and functional properties of 15 LAB species previously isolated from sourdough were determined in terms of antifungal and antibacterial activities, production of GABA as a functional component and phytase activity. All sourdough isolates were capable of producing GABA and Weissella paramesenteroides N-7 and Lactobacillus paralimentarius E-106 showed the highest and the lowest production levels as 18,43 mM and 3,39 mM, respectively determined by HPLC analysis. The antifungal activity of these strains were tested against Aspergillus niger and Penicillium chrysogenum and two strains Lactobacillus paraplantarum N-15 and L. paralimentarius E-106 showed significant inhibitory effects to these mould species. Generally, different levels of antibacterial activity of these species were observed against food-borne pathogens but only one strain showed low levels of inhibitory effect to Salmonella typhimurium but not the other strains. The PCR detection of several bacteriocin coding genes revealed that all strains were harboured at least one bacteriocin gene among the tested genes. Finally, all strains showed phytase activity but these activity was dependant on strain specific conditions. This study revealed some important techno-functional properties of sourdough LAB strains which can play crucial roles on sourdough technology.
AtıfScopus73WoS60OpenAlex68İncele - MakaleAçık Erişim2017Scopus SJRQ3Asymmetric epoxidation of enones using cumyl hydroperoxide and in situ generated zinc complexes of chiral pyrrolidinyl alcohols
Karaman, Halide Sedef; Kılıç, Hamdullah; Şahin, Engin
The homogeneous asymmetric epoxidation of a range of enones was carried out using cumyl hydroperoxide, diethylzinc, and chiral pyrrolidinyl alcohol-containing ligands to afford the corresponding epoxy ketones with enantioselectivities of ≤97% ee. Examination of the enantioselectivities obtained in the asymmetric epoxidation of enones using a range of chiral ligands indicated that synergy between the sterically bulky bicyclo[2.2.2]octane skeleton and the substituents attached to the carbinol moiety played an important role in determining the reaction enantioselectivity. The position and nature of the substituent on the aromatic ring of the enone also had a pronounced effect on the observed enantioselectivity.
AtıfScopus5WoS5OpenAlex5İncele - MakaleYalnız künye2013Scopus SJRQ3Application of carrier element free coprecipitation (CEFC) method for determination of Co(II), Cu(II) and Ni(II) ions in food and water samples
Serencam, Huseyin; Duran, Celal; Ozdes, Duygu; 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 (CEFC) of Co(II), Cu(II), and Ni(II) ions by using 2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-methylbenzyl)-5-oxo- 4,5-dihydro-1H-1,2,4-triazol- 1-yl}-N'-(pyridin-2-yl methylidene)acetohydrazide (IMOTPA), as an organic coprecipitant. The levels of analyte ions were determined by flame atomic absorption spectrometry (FAAS). The detection limits for Co(II), Cu(II) and Ni(II) ions were found to be 0.40, 0.16 and 0.17 μg L-1, respectively, and the relative standard deviations for the analyte ions were lower than 3.0%. Spike tests and certified reference material analyses were performed to validate the method. The method was successfully applied for the determination of Co(II), Cu(II) and Ni(II) ions levels in sea and stream water as liquid samples and red pepper, black pepper, and peppermint as solid samples.
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İncele - MakaleAçık Erişim2015Scopus SJRQ2The views of mathematics teachers on the factors affecting the integration of technology in mathematics courses
Kaleli-Yilmaz, Gül
The aim of this study was to determine the views of mathematics teachers on the factors that affect the integration of technology in mathematic courses. It is a qualitative case study. The sample size of the study is 10 teachers who are receiving postgraduate education in a university in Turkey. The current study was conducted in three stages. At the first stage, software and learning objects were introduced to the teachers. At the second stage, activities were performed with the teachers. At the third stage, teachers practiced a technology-assisted course in a real classroom environment. After all stages were fulfilled, a retrospective interview was conducted with all teachers individually. The content analysis of the interviews indicated that there are many factors affecting technology integration, namely, the categories of teacher-based factors, student-based factors, content-method-resource-timemanagement based factors and technical considerations.
AtıfScopus26İncele - MakaleYalnız künye2017Scopus SJRQ1Experimental determination of cohesion & internal friction angle on conventional concretes
Pul, Selim; Ghaffari, Amir; Öztekin, Ertekin; Hüsem, Metin; Demir, Serhat
Various failure criterions have been used for the nonlinear analysis of concrete and reinforced concrete structures. To get more accurate results from the analyses, the selected failure criterion must be appropriate with the characteristics of problem and the assumptions made in the criterion should comply with the characteristics of problem. In this study, an experimental investigation was carried out to determine the cohesion (c) and internal friction angle (?) values, which are in the compressive strength range of 14.4 MPa ≤ fcm cube ≤ 47.0 MPa (2.03 ksi ≤ fcm cube ≤ 6.82 ksi) that are used in failure criterions such as Mohr-Coulomb and Drucker-Prager preferred in end unit analyses for concrete and reinforced concrete structures. Tests are performed by using the direct shear test system, which is designed and produced for this study. Finally, cohesion and internal friction angle were determined between 2.94 and 12.34 MPa (0.43 and 1.79 ksi) and 29.8 and 41.7 degrees, respectively.
AtıfScopus44WoS38OpenAlex36İncele - Kitap BölümüAçık Erişim2017Cognitive approach to improve media literacy: Mind puzzles
Karadag, Zekeriya; Devecioglu-Kaymakci, Yasemin
This chapter starts with an exploration of the media literacy literature and its place in the developing 21st century. The literature suggests that media literacy should be considered as one of the capstones for the skills needed for the 21st century citizens. In terms of developing media literacy skills, scholars look at the concept from either cognitive or social perspective, and the review reveals that both of them are closely related to each other. Moreover, the study asserts that cognitive and metacognitive skills play a significant role in developing the media literacy and the skills for 21st century. Then, the chapter presents a city-wide activity done in Bayburt, Turkey. It is our assumption that the case presented here may be an inspiring example for whom may want to explore different approaches.
- MakaleAçık Erişim2015Scopus SJRQ3The investigation of the effects of frayer model on vocabulary knowledge in social studies; [Sosyal bilgilerde kelime hazinesinin geliştirilmesinde frayer modelinin etkisinin ıncelenmesi]
Ilter, İlhan
The purpose of the present study is to determine the effects of Frayer model on the development of vocabulary knowledge in social studies. A quasi-experimental nonequivalent control group design was used in the study. For the research, an experimental (N=19) and a control group (N=18) were randomly selected. While Frayer model as text based organizer was utilized on vocabulary instruction in the experimental group, the definitional and contextual approaches by integrating were used in the control group. This research was implemented at a state school with the 4th grade students in Bayburt, in 2013-2014 academic season. The scale, which was developed by Wesche and Paribakht (1996) and validity and reliability of which were examined and adapted to Turkish by the researcher, was used to determine the students’ vocabulary knowledge level. As for the results, it was found that the experimental group was more successful in vocabulary knowledge through the meanings of the target words by enlarging their vocabulary capacity in-depth. The data obtained from the study demonstrated that Frayer model facilitated the students to identify relevant, irrelevant attributes, examples and non-examples of the concepts and uncover the relationships and hierarchical structures between the concepts, thus guide to generate the meanings of terms by activating prior knowledge. Therefore, it helps to the students facilitate development of vocabulary knowledge and vocabulary acquisition.
AtıfScopus3OpenAlex10İncele - MakaleAçık Erişim2019Scopus SJRQ3Investigation of Stress Corrosion Cracking Behaviour of Mg-Al-Zn Alloys in Different pH Environments by SSRT Method
Catar, Recep; Altun, Hikmet
In this study, stress corrosion behaviors of AZ31, AZ61 and AZ91 Mg alloys which contain different amounts of Al were investigated under acidic, basic and neutral environments having chloride ions using Slow Strain Rate Test (SSRT) method. Stress corrosion indexes (ISCC), ultimate tensile strength (UTS) and elongation of AZ31, AZ61, and AZ91 Mg alloys were determined and compared. Slow strain rate test showed that three Mg alloys in basic environments were the least stress corrosion susceptible, while the most stress corrosion susceptible occurred in acidic environments. Also, it has been shown that the stress corrosion indexes of AZ91 Mg alloys are less than AZ31 and AZ61 Mg alloys in all environments. UTS and elongation of AZ61 Mg alloys were higher than those of AZ31 and AZ91 in all media. The fracture of surface images also examined in the scanning electron microscope (SEM) and both intergranular stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) were observed in all three alloys.
AtıfScopus16WoS13OpenAlex14İncele - Kitap BölümüYalnız künye2018Scopus SJRQ3Contribution of the cogeneration systems to environment and sustainability
Kemal, Çomakli; Uğur, Çakir; Ayşegül, Çokgez Kuş; Erol, Şahin
The kind of energy that buildings need changes, like heating energy, cooling energy, electrical energy, and thermal energy for hot top water. Usually, the processes or systems that produce thermal energy emit pollutants while they produce heat because of the fossil fuels they use. A lower consumption of thermal energy will contribute not only to a reduction in the running costs but also in the reduction of pollutant emissions that contribute to the greenhouse effect and a lesser dependence of the hospital on the external power supply. Cogeneration or CHP (combined heat and power) is the system that produces power and usable heat simultaneously. Combined production of mechanical or electrical and thermal energy using a simple energy source, such as oil, coal, natural or liquefied gas, biomass, or the sun, affords remarkable energy savings and frequently makes it possible to operate with greater efficiency when compared to a system producing heat and power separately. Because of the life standard of humanity in new age, energy sources must be continually improved and updated. For this reason, the installation of a system for the simultaneous generation of electrical, heating, and cooling energy would be one of the best solutions if we want to have qualified energy and reduce investment and operating costs and meet ecological requirements. This study aims to bring out the contributions of cogeneration systems to the environment and sustainability by saving the energy and reducing the emissions.
AtıfOpenAlex1İncele - MakaleAçık Erişim2018Scopus SJRQ1Investigation of seismic performance of in-plane aligned masonry panels strengthened with Carbon Fiber Reinforced Polymer
Can, Ömer
Masonry structures are economical, easy to construct and has important advantages such as the use of natural materials. In Turkey, these structures have been heavily built especially with traditional construction methods and nowadays they are popular as well. Therefore, the reinforcement of masonry structures and seismic safety are of paramount importance. Masonry walls are not naturally stable and cannot be considered as homogeneous structures so it is difficult to predict their behavior under load by using numerical methods. Supportive framework of the mathematical model and the data of the experimental studies are required. In this study, 36 wall blocks were prepared in 900 × 900 × 200 mm using hollow masonry brick, blend brick and aerated concrete and these blocks are reinforced with Carbon Fiber Reinforced Polymer in both directions by using three different methods. For the analysis of retrofit brick walls produced and reinforced with different materials, ASTM E591 test method was used. At the end of the experiment period; shear strength performances of the reinforcement methods of the elements, their deformation and energy dissipation capacities were evaluated. According to results, maximum shear strength performance was observed at the masonry panel strengthened by two face. Maximum load value was 172.63 Kn. Also maximum dissipation capacity was observed at the masonry wall reinforced with CFRP covered diagonally. Maximum energy dissipation capacity was 317.1 J.
AtıfScopus32WoS26OpenAlex34İncele - MakaleAçık Erişim2017Scopus SJRQ1Concretes with synthetic aggregates for sustainability
Tekin, Ilker; Yasin Durgun, Muhammed; Gencel, Osman; Bilir, Turhan; Brostow, Witold; Hagg Lobland, Haley E.
We have used waste marble aggregates, marble dust and fly ash from thermic power plants as fillers in concretes for replacing natural aggregates. We have used two different kinds of cements. After curing, we have determined the workability (by slump tests), air content, unit weight, Schmidt hardness, ultrasound pulse velocity, compressive strength and carbonation depth. The concretes containing waste marble at least match or exceed the workability and strength of the control concrete type. Fly ash significantly improves the workability. Utilizing waste marble aggregate at the replacement ratio of 100% along with waste marble dust, fly ash and pozzolanic cements in concrete leads to lower cost – achieving at the same time environmentally friendly production process with decreased consumption of natural resources and energy. Our work also contributes to enhancement of sustainability by finding a use for marble waste and fly ash.
AtıfScopus28WoS24OpenAlex33İncele - MakaleYalnız künye2016Scopus SJRQ1A receding contact problem between a functionally graded layer and two homogeneous quarter planes
Adıyaman, Gökhan; Birinci, Ahmet; Öner, Erdal; Yaylacı, Murat
In this paper, the plane problem of a frictionless receding contact between an elastic functionally graded layer and two homogeneous quarter planes is considered when the graded layer is pressed against the quarter planes. The top of the layer is subjected to normal tractions over a finite segment. The graded layer is modeled as a non-homogeneous medium with a constant Poisson’s ratio and exponentially varying shear modules. The problem is converted into the solution of a Cauchy-type singular integral equation in which the contact pressure and the receding contact half-length are the unknowns using integral transforms. The singular integral equation is solved numerically using Gauss–Jacobi integration. The corresponding receding contact half-length that satisfies the global equilibrium condition is obtained using an iterative procedure. The effect of the material non-homogeneity parameter on the contact pressure and on the length of the receding contact is investigated.
AtıfScopus58WoS55OpenAlex42İncele - MakaleAçık Erişim2017Scopus SJRQ1Inhibition behaviours of some phenolic acids on rat kidney aldose reductase enzyme: an in vitro study
Alim, Zuhal; Kilinç, Namik; Şengül, Bülent; Beydemir, Şükrü
Aldose reductase (AR) inhibitors have vital importance in the treatment and prevention of diabetic complications. In this study, rat kidney AR was purified 19.34-fold with a yield of 3.49% and a specific activity of 0.88 U/mg using DE-52 Cellulose anion exchange chromatography, gel filtration chromatography and 2′5′ ADP Sepharose-4B affinity chromatography, respectively. After purification, the in vitro inhibition effects of some phenolic acids (tannic acid, chlorogenic acid, sinapic acid, protocatechuic acid, 4-hydroxybenzoic acid, p-coumaric acid, ferulic acid, vanillic acid, syringic acid, α-resorcylic acid, 3-hydroxybenzoic acid and gallic acid) were investigated on purified enzyme. We determined IC50, Ki values and inhibition types of these phenolic acids. As a result, tannic and chlorogenic acid had a strong inhibition effect. On the other hand, gallic acid had a weak inhibition effect. In this study, all phenolic acids except for chlorogenic acid and p-coumaric acid showed non-competitive inhibition effects on rat kidney AR.
AtıfScopus61WoS60OpenAlex64İncele - MakaleYalnız künye2016Scopus SJRQ2ANN based investigations of reliabilities of the models for concrete under triaxial compression
Öztekin, Ertekin
Purpose - A lot of triaxial compressive models for different concrete types and different concrete strength classes were proposed to be used in structural analyses. The existence of so many models creates conflicts and confusions during the selection of the models. In this study, reliability analyses were carried out to prevent such conflicts and confusions and to determine the most reliable model for normal- and high-strength concrete (NSC and HSC) under combined triaxial compressions. The paper aims to discuss these issues. Design/methodology/approach - An analytical model was proposed to estimate the strength of NSC and HSC under different triaxial loadings. After verifying the validity of the model by making comparisons with the models in the literature, reliabilities of all models were investigated. The Monte Carlo simulation method was used in the reliability studies. Artificial experimental data required for the Monte Carlo simulation method were generated by using artificial neural networks. Findings - The validity of the proposed model was verified. Reliability indexes of triaxial compressive models were obtained for the limit states, different concrete strengths and different lateral compressions. Finally, the reliability indexes were tabulated to be able to choose the best model for NSC and HSC under different triaxial compressions. Research limitations/implications - Concrete compressive strength and lateral compression were taken as variables in the model. Practical implications - The reliability indexes were tabulated to be able to choose the best model for NSC and HSC under different triaxial compressions. Originality/value - A new analytical model was proposed to estimate the strength of NSC and HSC under different triaxial loadings. Reliability indexes of triaxial compressive models were obtained for the limit states, different concrete strengths and different lateral compressions. Artificial experimental data were obtained by using artificial neural networks. Four different artificial neural networks were developed to generate artificial experimental data. They can also be used in the estimations of the strength of NSC and HSC under different triaxial loadings.
AtıfScopus5WoS5OpenAlex6İncele - MakaleAçık Erişim2015Scopus SJRQ1Levitation and guidance force efficiencies of bulk YBCO for different permanent magnetic guideways
Abdioglu, M.; Ozturk, K.; Gedikli, H.; Ekici, M.; Cansiz, A.
The development of superconductor Maglev systems depends on various disciplinary studies due to the inherent composition of available technologies. Because the fabrication cost is very effective on the Maglev, the requirement of the efficiency improvement focuses the researchers on the design considerations. In this study, the guidance force, the magnetic levitation force (MLF) and magnetic stiffness of different permanent magnetic guideway (PMG) arrangements were investigated in different cooling heights (CH) to enhance the efficiency of Maglev system. The single domain cylindrical bulk YBCO superconductors fabricated by top seeding method with the diameter of 45 mm and the height of 15 mm were used as HTS. Magnetic field distributions of the PMGs were calculated by finite element method to determine optimum HTS-PMG arrangements. We have used auxiliary onboard permanent magnets with YBCOs to improve the MLF of three pole Halbach PMG arrangements. It is seen that the efficiency of Maglev systems can be improved by using suitable HTS-PMG arrangements. In this study cost efficiency of the integrated levitation and guidance force ((Fz)max(Fx)max/(SPMG ∗ Cost)) was also determined. It is inferred from this study that the cooling height and PMG-HTS arrangement are key parameters for guidance force, levitation force, magnetic stiffness and efficiency of Maglev systems. It is believed that this study will supply useful references for practical application of HTS Maglev systems.
AtıfScopus60WoS59OpenAlex61İncele - MakaleYalnız künye2018Scopus SJRQ2Changes of surface properties of calcite particles with calcium stearate using conventional experimental design and properties of coated calcite
Ucurum, Metin; Bayram, Ozkan; Toraman, O. Yusuf; Kilic, Habibe; Yalcin, Seyma
Calcite is utilized as a filler mineral in the industries such as plastics, rubber, and paint, to gain products with a variety of features. In order to use a calcite ore as a filler, some specific physical and physico-chemical properties are required such as ultra-fine sizes and conversion of hydrophilic to hydrophobic structure. In the present study, for these purposes, surfaces of the ultra-fine calcite powder (d50=2.94 μm) were coated by a mechano-chemical process with calcium stearate [Ca(C17H35COO)2] in a stirred ball mill. The influence of operating parameters such as calcite filling-ratio, ball-filling ratio, operation speed, grinding time and chemical dosage on the active ratio (%) was systematically examined. Then, the properties of modified calcite product were measured and evaluated by contact angle, TGA, DTA, FTIR, and SEM. The results showed that the mechano-chemical technology is very effective for modifying the surface of micronized calcite products using calcium stearate chemical.
AtıfScopus20WoS18İncele - MakaleYalnız künye2018Scopus SJRQ3Width, length, and height conceptions of students with learning disabilities
Güven, N. Dilşad; Argün, Ziya
Teaching responsive to the needs of students with learning disabilities (LD) can be provided through understanding students’ conceptions and their ways of learning. The current research, as a case study based on qualitative design, aimed to investigate the conceptions of students with learning disabilities with regard to the different representations of length (width, length, and height). The participants were 3 Turkish students at 4th, 5th and 6th grades recognised by the local Counselling and Research Centre (CRC) as having learning disabilities. The data were collected through semistructured and task-based interviews, and analysed via content analysis method. The findings suggest that width, length, and height conceptions of students with learning disabilities are influenced by their conceptions of length and visual-spatial abilities.
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