Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Dertli, Enes(24)
- Cuce, Erdem(18)
- İspirli, Hümeyra(14)
- Cuce, Pinar Mert(13)
- Alım, Bünyamin(12)
- Mercan, Emin(12)
- Sert, Durmuş(12)
- Şenay, Volkan(12)
- Tozlu, Alperen(11)
- Artar, Musa(10)
- Korkmaz, Şadan(10)
- Pat, Suat(10)
- Yilmaz, Mustafa Tahsin(10)
- Özen, Soner(10)
- Gökçe, H.S.(9)
- Sagdic, Osman(9)
- Şakar, Erdem(9)
- Bayram, Ozkan(8)
- Demirtas, M.(8)
- Purcek, G.(8)
- Ergün, Mustafa(7)
- Yanar, H.(7)
- Demir, Lütfü(6)
- Taylan, Osman(6)
- Abdioglu, M.(5)
- Abdioglu, Murat(5)
- Alim, Bünyamin(5)
- Carbas, Serdar(5)
- Guclu, Tamer(5)
- Gökçe, H. Süleyman(5)
- Sayyed, M.I.(5)
- Han, İbrahim(4)
- Ozturk, K.(4)
- Zhang, Z.F.(4)
- Zhang, Z.J.(4)
- Özahi, Emrah(4)
- Şahin, Engin(4)
- Abusoglu, Aysegul(3)
- Andiç-Çakır, Özge(3)
- Baltakesmez, Ali(3)
Yayınlar
- MakaleAçık Erişim2020Scopus SJRQ1An integrated neural-fuzzy methodology for characterisation and modelling of exopolysaccharide (EPS) production levels of Leuconostoc mesenteroides DL1
Kabli, Mohammad; Yilmaz, Mustafa Tahsin; Taylan, Osman; Kaya, Yasemin; İspirli, Hümeyra; Basahel, Abdulrahman; Sagdic, Osman; Dertli, Enes
Optimisation of exopolysaccharides (EPS) production in Lactic Acid Bacteria (LAB) is an important task as EPS production can be affected by different parameters. In this respect, this study aimed to characterise the structure of an EPS from Leuconstoc mesenteroides DL1 strain and to optimise the EPS production by determination of the effects of incubation time, sucrose concentration, incubation temperature and initial levan concentration (input parameters) using integrated ANNs (Artificial neural networks) and fuzzy modelling approaches. The characterisation of the EPS monomeric composition by HPLC analysis revealed that EPS DL1 was composed of glucose and fructose. The 1H and 13C NMR spectra of EPS DL1 also confirmed the glucan and fructan production. The effects of the input parameters on glucan and fructan production levels as output parameters by DL1 were optimised using neural network and fuzzy modelling tools. The fuzzy model was developed based on the recognition of basic elements of input-output parameters, and the power of ANNs used for system identification. A structural analysis was carried out to improve the flexibility of fuzzy model, and to design the unknown mappings of the input and output parameters more robustly. The parameters then were fine-tuned by qualitative reasoning to establish the relations of input output parameters using membership functions (MFs) and their intervals determination. A hybrid training algorithm was employed for parameter identification, MFs and their interval determination to obtain the fuzzy model. The model can predict the outcome parameters; glucan and fructan with high accuracy for the predetermined input parameters.
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İncele - MakaleAçık Erişim2020Scopus SJRQ2Evaluation the gamma, charged particle and fast neutron shielding performances of some important AISI-coded stainless steels: Part II
Alım, Bünyamin; Şakar, Erdem; Han, İbrahim; Sayyed, M.I.
This is the second part of a two-part study on the investigation of radiation shielding performances of some important AISI-coded stainless steels (AISI-302, 304, 321 and 430). Part 1 addressed experimental evaluation by means of measured photon-material interaction parameters. In this second part, we focused on the calculation and discussion of other interaction parameters, which are a guide to choice optimum shielding materials in the nuclear processes for the present AISI-coded stainless steels. The present stainless steels have superior mechanical properties, high temperature and corrosion resistances and these properties can make them favorite materials for nuclear applications. For this reason, firstly, the incoherent scattering/total attenuation ratio (Rinc/total) and equivalent atomic number (Zeq) were calculated in the energy region of 0.015–15 MeV. Secondly, the exposure build-up factor (EBF) and energy absorption build-up factor (EABF) were determined to select steels by using Geometric Progression (G-P) fitting method, which have five parameters (a, b, c, d and XK coefficients), up to penetration depth of 40 MFP at energy 0.015–15 MeV. Thirdly, the mass stopping powers (MSPs; dE/ρdx; MeVcm2/g) and ranges (Re, Rp and Rα; μm) for electron, proton and alpha particle interactions were calculated at energy 10 keV-20 MeV. Finally, the fast neutron removal cross-sections (FNRCSs; ∑R; cm−1) were calculated. To be able to make comparison and a satisfying assessment about radiation shielding capabilities of present AISI-coded steels, all parameters were also computed for ordinary (OC), steel-scrap (SS) and steel-magnetite (SM) concretes (Fe-based steel concretes) that are most commonly used as a shielding material in many nuclear applications. The shielding capabilities of the present stainless steels against both gamma and the fast neutron and charged particle radiation were evaluated in the light of the calculated parameters. As a result of the mutual evaluation of the results obtained for the shielding concretes and the examined stainless steels, it was found that present stainless steels had excellent shielding properties compared to shielding concretes in terms of both photon radiation and particle radiation.
AtıfScopus38WoS35İncele - MakaleAçık Erişim2020Scopus SJRQ2Assessment of gamma-ray attenuation features for La+3 co-doped zinc borotellurite glasses
Rammah, Y.S.; Özpolat, Ö.F.; Alım, B.; Şakar, E.; El-Mallawany, R.; El-Agawany, F.I.
In this study, gamma ray and neutrons shielding features were evaluated for La+3 co-doped zinc borotellurite glasses with chemical formula {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1-x(La2O3)x: 0.01≤ x ≤ 0.05 mol%. Firstly, the mass and linear attenuation coefficients (MAC, LAC) for glasses were calculated via Photon Shielding and Dosimetry (PSD) software (Phy-X/PSD) in the energy range of 0.015–15 MeV. Depending on MAC and LAC, effective shielding parameters: Half value layer and mean free path (HVL, MFP), effective electron density, atomic number, and conductivity (Neff, Zeff, Ceff), exposure and energy absorption buildup factors (EBF, EABF) have been evaluated. In addition, effective fast neutron removal cross section (FNRCS) for the studied glasses have been calculated. The obtained data were compared with those of some commercial glasses and concrete. Results reveal that HVL for all samples can be arranged in the order TBZL1>TBZL2>TBZL3>TBZL4>TBZL5. The HVL, TVL and MFP values of TBZL5 glass are 2.988 cm, 9.927 cm, and 4.311 cm, respectively. TBZL5 glass has the highest Ceff values and TBZL1 glass has the lowest Ceff values. EBF values change range from 1 to 4 at 1 MFP and from 1-1010 at 40 MFP value. Therefore, it can be among the alternative materials that can be preferred in radiation application areas.
AtıfScopus48WoS47İncele - MakaleAçık Erişim2020Scopus SJRQ1Effects of churning with different concentrations of ozonated water on particle size, texture, oxidation, melting and microbiological characteristics of butter
Sert, Durmuş; Mercan, Emin
The effects of churning with different concentrations of ozonated water (OW) on fat particle size, texture, oxidation, melting and microbiological characteristics of butter from raw cream were investigated. For this purpose, butter samples were produced by churning with ozonated waters at concentrations of 0 (control), 0.15 (OW-15), 0.20 (OW-20), 0.25 (OW-25) and 0.30 (OW-30) mg L−1. Churning with OW increased the lightness and redness value of samples and decreased yellowness. Firmness value of samples ranged from 126.86 to 347.46 N, with an increase with ozone concentration. Mean fat particle size (D[4.3]) value of samples decreased with higher ozone concentration in churning water. OW reduced the oxidative stability of samples. Microbial reductions by churning with ozonated water ranged from 0.07 to 1.59 log. Microbiological analysis results showed that ozone treatment improved the microbial safety of butter samples produced from raw cream.
AtıfScopus14WoS10OpenAlex15İncele - MakaleAçık Erişim2019Scopus SJRQ1High temperature resistance of boron active belite cement mortars containing fly ash
Gökçe, H.Süleyman
Boron allowing stability of reactive belite phase in clinker production enhances neutron shielding capability of cement. In the study, neutron attenuation factor of boron active belite cements at various fly ash introduction was theoretically revealed by comparing with an alternative low heat cement (portland composite cement). High temperature resistance of the cements with and without fly ash introduction was determined on standard mortar prisms at elevated temperatures up to 900 °C with regard to compressive strength and flexural strength. Neutron shielding performance of boron active belite cement was found almost 25 times higher than Portland composite cement. Fly ash introduction significantly reduced the neutron attenuation factor of boron active belite cement. High temperature resistance of boron active belite cement mortar was found lower than that of Portland composite cement mortar at 700 °C at later curing time. 10% fly ash introduction improved the high temperature performance of boron active belite cement mortar exposed to 900 °C. Residual compressive strength values of the mortars containing fly ash were between 16% and 28% after exposing 900 °C.
AtıfScopus39WoS36OpenAlex39İncele - MakaleAçık Erişim2019Scopus SJRQ2Physicochemical characterisation of an α-glucan from Lactobacillus reuteri E81 as a potential exopolysaccharide suitable for food applications
İspirli, Hümeyra; Sagdic, Osman; Yılmaz, Mustafa Tahsin; Dertli, Enes
Lactobacillus reuteri strain (E81) is an alpha glucan producer from traditional sourdough and the physicochemical characteristics of this glucan was determined in this study. The HPLC analysis confirmed the presence of glucose as the only sugar monomer in the repeating structure of this exopolysaccharide (EPS). The functional groups within the glucan structure was detected by FTIR analysis. The scanning electron microscopy (SEM) analysis demonstrated the web-like branched structure of the glucan. Morphological characterisation of the glucan E81 by atomic force microscopy (AFM) analysis showed clear roundness lumps and chains. Importantly, thermal characteristics of glucan E81 determined by thermogram analysis (TGA) and differential scanning calorimeter (DSC) analysis revealed that glucan E81 has a melting point of 290 °C making it promising to be used in thermal processed foods including sourdough bread.
AtıfScopus77WoS71OpenAlex77İncele - MakaleAçık Erişim2019Scopus SJRQ2Characterization of an interesting selenium-dependent glutathione peroxidase (Se-GPx) protecting cells against environmental stress: The Camelus dromedarius erythrocytes Se-GPx
Chafik, Abdelbasset; Essamadi, Abdelkhalid; Çelik, Safinur Yildirim; Solak, Kübra; Mavi, Ahmet
Camel lives most of its life under high environmental stress in the desert. Glutathione peroxidase plays a key role in protecting cells against oxidative stress. For the first time, selenium-dependent glutathione peroxidase (Se-GPx) was purified from camel erythrocytes, biochemically characterized, and some of its properties were studied. The enzyme was purified using ethanol-chloroform treatment, acetone precipitation and ion exchange chromatography. A purification fold of 33.72 with 0.19% yield were obtained. The native molecular weight of the enzyme was estimated to be about 69 kDa. On SDS-PAGE, the enzyme was composed of two different subunits with a molecular weight of approximately 53 and 21 kDa. An optimum temperature of 47 °C and an optimum pH of 7.2 were found. The activation energy was 41.71 kJ/mol. This enzyme was inhibited by thiol reagents, D,L-Dithiothreitol and β-Mercaptoethanol, and was sensitive to bivalent cations. The enzyme had a general specificity toward hydroperoxides, and high specificity for reduced glutathione. The purified enzyme contained 3.06 mol of selenium per mol of protein. The Km and Vmax values for hydrogen peroxide and reduced glutathione were 0.72 and 1.58 mM, and 25.33 and 31.03 U/mg, respectively. The biochemical properties of camel Se-GPx were different comparing to those of mammalian species. Lower molecular weight, heterodimeric structure, higher optimum temperature, relatively lower optimum pH, lower content of selenium and higher affinity for hydrogen peroxide at low reduced glutathione concentration, these could be explained by the fact that camel is able to live in the intense environmental stress in the desert.
AtıfScopus11WoS10OpenAlex10İncele - MakaleAçık Erişim2019Scopus SJRQ1Electrospraying method for fabrication of essential oil loaded-chitosan nanoparticle delivery systems characterized by molecular, thermal, morphological and antifungal properties
Yilmaz, Mustafa Tahsin; Yilmaz, Azime; Akman, Perihan Kubra; Bozkurt, Fatih; Dertli, Enes; Basahel, Abdulrahman; Al-Sasi, Basil; Taylan, Osman; Sagdic, Osman
Fabrication of essential oil loaded-chitosan nanoparticles using electrospraying technique appears to be a novel strategy to develop thermally stable nanoparticles possessing higher encapsulation efficiency and particle stability. This study aims to fabricate chitosan nanoparticles (CNPs) loaded with Origanum vulgare essential oil (OEO, Origanum vulgare L.) at different proportions (OEO/CH proportions of 0:1, 0.0625:1, 0.125:1, 0.25:1 and 0.5:1 mL/g) using electrospraying technique. The CNPs were characterized in term of their particle size and stability (dynamic light scattering), encapsulation efficiency (spectrophotometry), and molecular (Fourier transform infrared spectroscopy), thermal (differential scanning calorimetry/thermogravimetric analysis), morphological (scanning electron microscopy) and antifungal (agar dilution method) and fungistatic activity properties. The average particle sizes of the CNPs ranged between 290 and 483 nm with a spherical morphology. Positively charged surface characteristics were observed to increase with the increment of OEO concentration in CNPs. The encapsulation efficiency values were determined in the range of 70.1 and 79.6%. The molecular and thermal analyses exposed very decent encapsulation of OEO into thermally stable chitosan nanoparticles. Morphological analysis verified the spherical shapes of these nanoparticles. Above all, the antifungal effectiveness of OEO against the Alternaria alternata AY1 could be significantly (p < 0.05) increased by its encapsulation into chitosan nanoparticles fabricated by the electrospraying technique. Consequently, it can be stated that the electrospraying technique developed is able to fabricate thermally stable nanoparticles owning higher encapsulation efficiency and particle stability. The results and findings suggest that the electrospraying technique would be a promising method to fabricate chitosan-based nanoparticles as an antimicrobial agent to control their release in a prolonged preservative effect in cosmetic, pharmaceutical and food applications for adjustable dosage forms. Industrial relevance: The fungal agents such as Alternaria alternata cause great damages on post-harvest fresh fruits and vegetables, thus leading to a great economical lose. Therefore, a great variety of methods in struggling with disease have been previously proposed. Nowadays, the most effective leading methods to struggle against plant diseases are those applied with synthetic fungicides to minimize such lose in post-harvest fruit and vegetables. However, intensive and unconscious use of the fungicides leads the pathogens to develop resistance against these agents as well as to accumulation of chemical residues in soil, water and air and finally to formation of carcinogenic effects on human health. Nowadays, a great effort is being exerted to develop novel biodegradable and natural antimicrobial agents for struggling fungal spoilage in postharvest products. Essential oils are among the most widely used natural struggling methods. Essential oils obtained from plants have been extensively used since they are natural antimicrobial agents. However, they cannot be effectively used in spite of their extensive applications. Recently, some researches in the field of nanotechnology have demonstrated that the effectiveness of active substances could be increased by using some techniques. In this respect, we aimed at developing essential-oil-loaded-chitosan-nanoparticle delivery systems using an electrospraying deposition system to prevent fungal colonization on food and plant materials. By increasing antifungal effectiveness of essential oils by their encapsulation into nanoparticles, it will be possible to decrease the levels of regularly applied dose and reflect the obtained outcomes to the food and agriculture industry. This study is the first example of production of essential oil loaded nanoparticles using the electrospraying-hydrodynamic process and showed that encapsulation of oregano essential oil into chitosan based nanoparticles (CNPs) by using the electrospraying deposition technique considerably increased the antifungal effectiveness of the Origanum vulgare essential oil. Our results highlight the potential use of the chitosan nanoparticles (CNPs) loaded with different amounts of Origanum vulgare in food and agriculture industry as an effective fungicidal material against Alternaria alternata, suggesting that the CNPs can be promising tools to compete with synthetic fungicide counterparts and limit use of synthetic ones for struggling of food and plant pathogens. Therefore, the results of this study should be of great importance to industrial applications in terms of development of natural, but effective preservatives as alternative to synthetic ones. In this respect, the CNPs would find a great industrial application area in the food and agriculture industry which seek natural preservatives due to the recent health concerns.
AtıfScopus119WoS101OpenAlex118İncele - MakaleAçık Erişim2019Scopus SJRQ1Characterization of chemical, molecular, thermal and rheological properties of medlar pectin extracted at optimum conditions as determined by Box-Behnken and ANFIS models
Al-Amoudi, Rami H.; Taylan, Osman; Kutlu, Gozde; Can, Asli Muslu; Sagdic, Osman; Dertli, Enes; Yilmaz, Mustafa Tahsin
In this work, response surface methodology and adaptive neuro-fuzzy inference system approaches were used to predict and model effect of extraction conditions of pectin from medlar fruit (Mespilus germanica L.). The pectin extracted at optimized conditions (89 °C, 4.83 h and 4.2 pH) could be classified as high methoxyl pectin. Sugar composition analysis showed that pectin was mainly composed of D-galacturonic acid, L-arabinose, L-rhamnose, D-galactose and D-glucose. Fourier Transform Infrared Spectroscopy, RAMAN and nuclear magnetic resonance spectra confirmed molecular structure, revealing presence of D-galacturonic acid backbone. X-ray diffraction patterns revealed an amorphous structure. Differential scanning calorimetry showed endothermic (123 °C) and exothermic peaks (192 °C). Thermogravimetric analysis revealed three decomposition regions, 50–225 °C, 225–400 °C and 400–600 °C. Steady and dynamic shear analyses revealed that pectin had a pseudo-plastic behavior with storage (G′) and loss (G″) modulus increasing with increment in frequency, indicating viscoelastic structure more predominantly elastic than viscous.
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İncele - MakaleYalnız künye2019Scopus SJRQ1Vertically oriented graphene nano-sheets grown by plasma enhanced chemical vapor deposition technique at low temperature
Bayram, Ozkan; Simsek, Onder
In this study, it was aimed to obtain vertically-oriented graphene nano-sheets (VGNs) on copper foils using CH 4 gas as the precursor material by means of plasma enhanced chemical vapor deposition (PECVD) technique. VGNs were obtained at 50 W, 75 W and 100 W Radio Frequency (RF) powers by this technique and the effect of RF power on the morphological structure of graphene layers was investigated. VGNs were also analyzed by Raman spectroscopy, scanning electron microscopy (SEM) and water contact angle (WCA) measurements. The SEM images showed that the VGNs became more tightly packed with the increase of RF power and thus these coating parameters had a significant effect on the morphological structure. WCA analyzes for VGNs were also performed and it was found that VGNs obtained at 100 W RF power had higher contact angle value than the other RF powers. These VGNs, which have both large surface area and optically transparent, are thought to be materials that have the potential to be used in supercapacitors and solar cells.
AtıfScopus19WoS17OpenAlex19İncele - MakaleYalnız künye2019Scopus SJRQ2Leaded brass alloys for gamma-ray shielding applications
Şakar, Erdem; Büyükyıldız, Mehmet; Alım, Bünyamin; Şakar, Betül Ceviz; Kurudirek, Murat
The leaded brasses show high machinability and atmospheric corrosion resistance. Hence, they are being used in different applications such as machine parts, valves, fittings etc. Besides, they can serve as radiation shields as they contain lead and their radiation shielding properties were not investigated so far. Thus, the aim of this study is to determine the radiation shielding properties of leaded brasses. Standard (CuZn) and leaded (CuZnPb) brasses were prepared and their mass attenuation coefficients (μ/ρ), half-value layers (HVL), tenth-value layers (TVL), mean free paths (MFP) and effective atomic numbers (Z eff ) were determined. Linear attenuation coefficients (μ) of the alloys were measured first at 53, 276, 302, 356 and 383 keV using a HPGe detector and a 133 Ba radioactive source. These values were then used to obtain other parameters. A good agreement was observed between experimental and theoretical results for HVL, TVL and MFP (Dif. ≤ 9%). Photon buildup through the present materials was studied in terms of exposure buildup factor (EBF). Results were presented and discussed regarding the photon energy and penetration depths. Fast neutron removal cross sections were also calculated for the given alloys. Some alloys were also evaluated morphologically by using EDX mapping. The leaded brasses were compared with standard shielding concretes and superior shielding properties against gammas and fast neutrons were obtained when compared with concretes.
AtıfScopus114WoS108OpenAlex128İncele - MakaleAçık Erişim2019Scopus SJRQ2Preparation of gentiobiose-derived oligosaccharides by glucansucrase E81 and determination of prebiotic and immune-modulatory functions
İspirli, Hümeyra; Colquhoun, Ian J.; Şahin, Engin; Sagdic, Osman; Dertli, Enes
Gentiobiose-derived oligosaccharides were synthesized by the acceptor reaction of glucansucrase E81 obtained from Lactobacillus reuteri E81 with sucrose and gentiobiose as donor-acceptor sugars, respectively. The reaction products were monitored by TLC analysis and gentiobiose-derived oligosaccharides up to DP 8 were formed during the acceptor reaction as determined by ESI-MS/MS analysis. The glycosylation of the gentiobiose with α-(1 → 6) linkages and α-(1 → 3) linkages was shown by 1H and 13C NMR analysis confirming the structure of these gentiobiose-derived oligosaccharides. The in vitro prebiotic function of the oligosaccharides was determined in which probiotic strains were stimulated whereas no growth was observed in pathogen strains. Gentiobiose-derived oligosaccharides showed immune-modulatory functions in vitro and triggered the production of IL-4, IL12 and TNF-α cytokines in HT29 cells in a dose dependent manner. This study showed the production and functional characterisation of gentiobiose-derived oligosaccharides establishing a promising avenue for future applications.
AtıfScopus26WoS21OpenAlex22İncele - MakaleYalnız künye2019Scopus SJRQ1Hydrogen generation via the catalytic hydrolysis of morpholine-borane: A new, efficient and cost-effective hydrogen storage medium
Can, Hasan; Metin, Önder
Herein, for the first time, we introduce the morpholine-borane complex (MB) as a new, efficient, cost-effective and commercially available chemical hydrogen storage material for mobile applications. In this regard, hydrogen production from the hydrolysis of MB catalyzed by in situ generated water-soluble polymer stabilized Ag(0) and Pd(0) nanoparticles (NPs) is reported for the first time. In situ generated PSMA-stabilized Ag(0) and Pd(0) NPs showed remarkable activity in hydrogen production from the hydrolysis of MB at room temperature, providing initial TOFs of 16.1 min−1 and 37.3 min−1, respectively. A set of kinetic studies on the catalytic hydrolysis of MB were conducted by changing the catalyst/substrate amount and temperature, and the rate law expression and activation parameters were produced by collecting the kinetic data. The apparent activation energies for the in situ generated Ag(0) and Pd(0) NPs catalyzed MB hydrolysis were calculated to be 71.4 and 32.5 kJ mol−1, respectively.
AtıfScopus20WoS20OpenAlex22İncele - MakaleAçık Erişim2019Scopus SJRQ1Production of skim milk powder by spray-drying from transglutaminase treated milk concentrates: Effects on physicochemical, powder flow, thermal and microstructural characteristics
Er, Betül; Sert, Durmuş; Mercan, Emin
The effects of transglutaminase (TGase) treatment of skim milk concentrates on physicochemical, powder flow, thermal, microstructural characteristics and protein profiles of skim milk powders (SMP) were investigated. Spray-dried SMP samples produced from milk concentrates were TGase-treated at enzyme concentrations of 0 (control), 0.020% (TG-20), 0.030% (TG-30) and 0.035% (TG-35). Lower particle size values were observed in TGase-treated samples. TGase treatment slightly decreased zeta potential and increased the a* value (redness) of SMPs. Up to a concentration of 0.030%, TGase treatment decreased caking characteristics and increased glass transition temperatures of samples. The TGase treatment above 0.035% significantly decreased cohesion index and compaction coefficient at different speeds. TG-35 showed free flowing flow behaviour depending on the cohesion index, whereas control, TG-20, and TG-30 showed easy flowing behaviour. SDS-PAGE analysis revealed that high molecular mass bands indicated cross-linking in TGase-treated milk powders.
AtıfScopus30WoS24OpenAlex31İncele - 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 - MakaleAçık Erişim2019Scopus SJRQ1Effect of fly ash and silica fume on hardened properties of foam concrete
Gökçe, H. Süleyman; Hatungimana, Daniel; Ramyar, Kambiz
In this study, the effects of foam content as well as fly ash and silica fume inclusion on some physical and mechanical properties of foam concrete, subjected to various curing regimes, were researched. Totally, forty-five series of foam concrete mixtures were prepared at three replacement levels of fly ash and silica fume (0, 10 and 20%, by weight of cement), at three foam contents (0, 31 and 47%, by volume) and at three curing regimes (7- and 28-day standard water curing and autoclave curing). Density, water absorption, compressive strength and thermal conductivity values of the mixtures were determined on prismatic specimens with dimensions of 40 × 40 × 160 mm. The density (oven dry), water absorption, compressive strength and thermal conductivity results of the foam concrete were found to be between 873–1998 kg/m3, 3.5–35.9%, 1.5–88.1 MPa and, 0.239–0.942 W/m.K, respectively. A balanced benefit with regard to both compressive strength and water absorption of foam concrete was found in the mix with density of 1320 kg/m3. Particularly in the mixtures having high foam content, silica fume introduction resulted in superior compressive strength values and greater compressive strength/thermal conductivity ratios than fly ash introduction.
AtıfScopus271WoS237OpenAlex276İncele - MakaleYalnız künye2019Scopus SJRQ1Bleeding characteristics of high consistency heavyweight concrete mixtures
Gökçe, H. Süleyman; Andiç-Çakır, Özge
Bleeding, a type of static segregation derives from density difference of concrete ingredients in fresh state. Due to having this difference higher than normal weight counterparts, heavyweight concrete is more susceptible to bleeding, thus, this type of concrete is commonly produced in low slump values. In order to give a response to advances and demands in concrete technology, heavyweight concrete mixtures with high slump values were designed at various mixture characteristics, and their bleeding characteristics were researched in the study. For this purpose, totally, thirty-five concrete mixtures with ≥150 mm slump values were produced by using common cement replacement materials (silica fume and fly ash), viscosity modifier, and various water/binder ratios at two binder dosages. The mixtures showed excessive bleeding capacities ranged from 0 to 11.7% and bleeding rates ranged from 0 to 5.1 kg/m2/h. Silica fume was found as the most effective admixture for reducing or elimination of the bleeding. Bleeding time generally shorten at high binder content and at high water/binder ratio. It was observed that the bleeding adversely affects the hardened characteristics of heavyweight concrete mixtures.
AtıfScopus62WoS54OpenAlex59İncele - MakaleAçık Erişim2019Scopus SJRQ1An analysis on the relation between the seed distance and vertical levitation force for the multi−seeded YBCO using the modified advanced frozen image (MAFI) and experimental methods
Ozturk, K.; Guner, S.B.; Abdioglu, M.; Demirci, M.; Celik, S.; Cansiz, A.
The higher magnetic levitation force and related stiffness values are very important for Maglev and magnetic bearing applications. Also, larger superconducting surface area is needed for continuous and larger magnetic mediums with different geometries and dimensions in real scale industrial applications of superconducting systems. In this study, the cylindrical YBCO superconductors were fabricated by top−seeded melt growth (TSMG) method in single and two−seeded forms with different seed distances and then the magnetic force and stiffness measurements were carried out by three axes magnetic force measurement system in different cooling heights (CH) of 20 mm and 75 mm. Additionally, a new analytical method, based on the magnetic dipole approximation, is proposed to calculate the levitation force in this study, named as Modified Advanced Frozen Image Method (MAFI), since although the Advanced Frozen Image Method in literature can calculate the levitation force with hysteresis, this method does not include the size effect of the superconductor. In the experimental studies, it is seen that the maximum levitation force values obtained by PMG with three PMs (named PMG−1) are more than two times higher than that of obtained with single PM for all samples with different distance of seeds, because of the higher magnetic flux distribution of related PMG arrangement than the single PM. In addition, the maximum magnetic levitation force value firstly increased and then decreased due to current coupling effect weakness by increasing distance of seeds. The calculated analytical levitation force results are not compatible with the experimental results without current coupling effect, but a well agreement is observed when the current coupling effect is taken into account in calculations. Also the MAFI method was tested with different dimensions of superconductors and the obtained results indicated the success of the proposed method. The maximum levitation force values obtained with MAFI method increased with increasing dimensions of HTS and PMs. Thus, one can say that the MAFI method is useful for the levitation force calculations between multi−seeded superconductors and PMGs with different dimensions and for different CHs. As a result, the analytical levitation force values obtained with the MAFI method are agree with the experimental levitation force sufficiently and this method can give fast calculation results without any divergence problem. This method can be thought as an alternative to the numerical calculation methods, having serious divergence problems for much amount and bigger size superconducting samples, therefore it will be useful to clarify bulk superconducting properties as supporter to the experimental studies.
AtıfScopus19WoS18OpenAlex22İncele - MakaleYalnız künye2019Scopus SJRQ2The relationship between the external magnetic field and K X-ray intensity ratios of immiscible MoxAg1-x alloys
Uğurlu, Mine; Alım, Bünyamin; Demir, Lütfü
Kβ/Kα intensity ratios were obtained for Molybdenum-Silver alloys produced in different concentration range in different magnetic fields. It was seen that these values without magnetic field were found slight different from each other for pure Mo, pure Ag, alloyed Mo and alloyed Ag. It was determined that Kβ/Kα intensity ratios change slightly by depending on alloying element composition and it was seen that Kβ/Kα intensity ratios of Mo and Ag are in the range of the literature valuesFurthermore, that these values have same direction with the changing of the magnetic field for all alloying composition may take us conclusion which alloys in different concentration may have same magnetic properties.
AtıfScopus3WoS2OpenAlex4İncele - MakaleYalnız künye2019Scopus SJRQ1Dynamic analyses of experimentally-updated FE model of historical masonry clock towers using site-specific seismic characteristics and scaling parameters according to the 2018 Turkey building earthquake code
Genç, Ali Fuat; Ergün, Mustafa; Günaydin, M.; Altunişik, Ahmet Can; Ateş, Şevket; Okur, Fatih Yesevi; Mosallam, Ayman S.
This paper presents a dynamic analysis considering site-specific seismic characteristics for a masonry clock tower located at the city of Çorum, Turkey according to the new Turkish earthquake code. Finite element model of the tower was modeled using ANSYS software in order to determine numerical dynamic characteristics of the structure such as natural frequencies and mode shapes. Non-destructive experimental measurements were performed to extract the experimental dynamic characteristics. Experimental results were used as a reference parameter for finite element model updating to reflect the current structural behavior of clock tower. Model updating procedure was carried out by changing of initial material properties of structural stone elements, and maximum differences were reduced from 23.44% to 4.90%. Numerical results indicated that displacements have an increasing trend with the height of the clock tower. Furthermore, the maximum displacements occurred at the top point between the values of 18.88 mm to 42.5 mm. Numerical results also showed that both the maximum and minimum principal stresses occurred at the upper body (clock zone) walls and transition segment between the values of 1.08 MPa/2.86 MPa and − 0.87 MPa/−3.00 MPa, respectively. The maximum and minimum principal strains occurred at the upper body (clock zone) walls between the values of 0.65E-3/1.56E-3 and − 0.78E-3/−1.50E-3, respectively. It is also concluded that non-destructive experimental measurement is very useful method to evaluate in-situ structural identification, validate and update the initial finite element model for further analyses.
AtıfScopus46WoS43OpenAlex51İncele