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
- MakaleYalnız künye2022Scopus SJRQ1Characterisation and functional roles of a highly branched dextran produced by a bee pollen isolate Leuconostoc mesenteroides BI-20
Yilmaz, Mustafa Tahsin; İspirli, Hümeyra; Taylan, Osman; Taşdemir, Volkan; Sagdic, Osman; Dertli, Enes
Lactic Acid Bacteria (LAB) from different niches can be responsible for the production of distinct exopolysaccharides (EPS) that might possess important structural and technological features. In this respect, the aim of this study was to isolate an EPS producer LAB strain from bee pollen environment. Leuconostoc mesenteroides BI-20 with a slimy-mucoid colony morphology was identified from bee pollen and the structural, technological and functional characteristics of EPS produced by this strain were determined. EPS BI-20 was a highly branched dextran containing 20% (1 → 3)-linked α-D-glucose branches determined by 1H and 13C NMR analysis. The presence of (1 → 6)/(1 → 3)-linked α-D-glucose linkages in dextran BI-20 was also confirmed by FTIR analysis. Dextran BI-20, with a molecular weight of 1 × 108 Da, possessed strong thermal properties, amorphous nature and highly branched and fibrous microstructural characteristics determined by DSC, TGA, XRD and SEM analysis, respectively. In terms of functional roles, dextran BI-20 demonstrated strong antioxidant capacity detected by ABTS and CUPRAC tests. Finally, no digestion was observed in dextran BI-20 under simulated gastric conditions. Results of this study unveiled techno-functional characteristics of dextran BI-20 produced by a bee pollen isolate LAB strain.
AtıfScopus39WoS36OpenAlex39
İncele - MakaleYalnız künye2022Scopus SJRQ2Photocatalytic activity of cobalt aluminate nanoparticles synthesized by microwave-assisted combustion method
Karakaş, İbrahim Hakkı; Karcıoğlu Karakaş, Zeynep; Ertuğrul, Mehmet
Cobalt aluminate is one of the most widely-used spinel aluminate types. It is known that various structural, magnetic and morphological properties of spinel ceramics can vary depending on the synthesis technique and the starting chemicals used. In this study, initially, heat treatment was applied to cobalt aluminate nanoparticles synthesized by the microwave-assisted combustion method and the effects of the applied heat treatment on the structural properties were investigated. Characterization studies showed that cobalt aluminate spinel pigments were successfully synthesized. The optimum heat treatment temperature was determined as 700 °C. Then, the synthesized cobalt aluminate nanoparticles were used as photocatalysts for dye removal by photocatalytic oxidation from a synthetic wastewater containing Astrazon red textile dye and their photocatalytic activity was investigated at different catalyst dosages. Moreover, the same particles were also produced by conventional combustion technique. Then, their photocatalytic activities were studied and the data were compared with the results obtained from the experiments made with the samples produced with microwave assisted combustion method under the same experimental conditions. The results show that cobalt aluminate nanoparticles synthesized by microwave assisted combustion exhibit a better photocatalytic activity. In experiments performed with samples produced via microwave-assisted combustion method, all dyestuff content in the solution containing 50 mg/L dye was completely removed under UV irradiation for approximately 60 min. It was determined that the catalyst dosage had an effect on the reaction rate and the reaction was found to be compatible with the pseudo first order kinetic model.
AtıfScopus12WoS12OpenAlex13İncele - MakaleAçık Erişim2022Scopus SJRQ1Improvement of mechanical and transport properties of reactive powder concrete using graphene nanoplatelet and waste glass aggregate
Arslan, S.; Öksüzer, N.; Gökçe, H.S.
In this study, the use of graphene nanoplatelet (GNP) and waste glass aggregate (WGA) was investigated to improve the mechanical and transport properties of reactive powder concrete (RPC), which is an ultra-high strength concrete type. The co-addition of 0.14% GNP and 30% WGA resulted in a significant increase in the compressive strength of RPC from 192.9 to 258.9 MPa and flexural strength from 16.2 to 38.7 MPa. In the study, the most significant improvement (138.6%) was obtained for the flexural strength values of RPC. Considering the strength aspects, the relevant amounts of GNP and WGA enable production of RPC ensuring a conducted electrical charge of less than 100 Coulombs; that is, with negligible chloride ion permeability. Accordingly, the highest improvement (59.8%) after flexural strength was found for the resistance of the specimens against chloride ion penetrability. In conclusion, the findings of this study show that eco-efficient production of RPC with superior mechanical and durability characteristics can be achieved using GNP and WGA, with lower cement consumption per unit value of these studied characteristics, reaching 59%.
AtıfScopus31WoS26OpenAlex32İncele - MakaleAçık Erişim2022Scopus SJRQ1The impact of ozone treatment on whey concentrate on the flow behaviour, functional and microbiological characteristics of whey powder
Sert, Durmuş; Mercan, Emin
The impact of ozone treatment (OT) for 0 (control) 30, 60, 90 and 120 min to whey concentrate (WC) on powder flow, physicochemical, functional, and microbiological characteristics of whey powders (WPs) was examined. OT decreased the cohesiveness of WC, whereas the firmness, consistency and index of viscosity were not affected. OT caused higher L∗ and b∗ values in WP and improved the solubility and foaming capacity, but decreased foaming stability and bulk density. OT increased the mean particle size of WP samples depending on the treatment time. Higher treatment time of OT resulted in a lower cohesion index. OT decreased caking ability of WP samples and increased flow stability. Compaction coefficient and cohesion index depending on increasing test speed, were generally reduced with higher OT. Overall, powder flow analyses revealed that OT of WC resulted in improved flow behaviour of WP. The microbial load of WP was reduced using OT.
AtıfScopus14WoS10OpenAlex16İncele - MakaleYalnız künye2022Scopus SJRQ1Performance of fly ash-blended Portland cement concrete developed by using fine or coarse recycled concrete aggregate
Şimşek, O.; Pourghadri Sefidehkhan, H.; Gökçe, H.S.
The recycling of concrete and industrial wastes in the production of new concrete structures has increased its share due to the growing environmental concerns of the world. In this study, the use of recycled concrete aggregate at various replacement amounts (0–100 %) was investigated to be fine or coarse aggregate sources instead of crushed natural aggregate to understand better its effects on the dimensional stability and durability aspects of fly ash-blended Portland cement concrete. In the presence of recycled concrete aggregate, fly ash was very important for eliminating possible mechanical losses of concrete at 90 days. The use of coarse recycled concrete aggregate resulted in better compressive strength values of concrete exposed to with and without wetting–drying and freezing-thawing cycles when compared to fine ones. While the free drying shrinkage of concrete increased at significant amounts (68 and 79 %) for fine and coarse recycled concrete aggregate, the restrained drying shrinkage crack widths were reduced up to by 13.5 %. In conclusion, it should be noted that the amount and size of recycled concrete aggregate need to be designed by considering the residual quality and dimensional stability of concrete, which exposes weathering actions in place.
AtıfScopus57WoS50OpenAlex54İncele - MakaleYalnız künye2022Scopus SJRQ1Powder flow behaviour, functional characteristics and microstructure of whole milk powder produced from cow and buffalo milk mixtures
Sert, Durmuş; Mercan, Emin; Kılınç, Mehmet
The effects of cow and buffalo milk mixtures on powder flow behaviour, functional characteristics and microstructure of whole milk powder was investigated. Milk powder was produced from 100% cow milk (G1), 100% buffalo milk (G2), 75% cow/25% buffalo milk (G3), 50% cow/50% buffalo milk (G4) and 25% cow/75% buffalo milk (G5). A higher proportion of buffalo milk increased the hydroxymethylfurfural, thiobarbituric acid reactive substances and free fatty acid contents in powders, but decreased dispersibility and wettability. The lowest and highest mean particle size values were obtained in G3 and G2 samples. Milk powder containing a higher level of buffalo milk increased caking ability and compaction coefficients of milk powder. All samples had remarkably cohesive characteristics. A higher proportion of cow milk can improve the flow behaviour of milk powder containing cow and buffalo milk mixtures in terms of caking, cohesion, and powder speed flow dependency.
AtıfScopus11WoS7OpenAlex8İncele - MakaleAçık Erişim2022Scopus SJRQ1Optimum sizing design of steel frame structures through maximum energy dissipation of friction dampers under seismic excitations
Artar, Musa; Carbas, Serdar
This paper focuses on optimum sizing design of steel frame structures equipped with friction dampers (FDs) in order to prevent the vulnerable effect of an earthquake. The fundamental concept is to maximize the energy dissipation of implemented FDs under different seismic excitations. The FDs utilized as passive energy dissipation devices in a steel structure increase the energy dissipation capacity of the structure by decreasing the seismic demand during an earthquake. In this context, the Pall friction dampers (PFDs) are implemented as diagonal damped brace members in investigated structures. Three different earthquake records (Kobe, Kocaeli-Duzce, Erzincan) are utilized to acquire nonlinear dynamic responses of the steel frame structures through time-history analyses. The open application programming interface (OAPI) functions are used to integrate a finite element modelling based structural analysis program, SAP2000, with a design optimization algorithm encoded in MATLAB for achieving the exact structural behaviours by synchronously data transferring. As an optimizer, one of the recent nature-inspired metaheuristic techniques, so-called Grey Wolf (GW) algorithm is used. Initially, under effect of seismic excitations, the steel frame structures are optimally sized for attaining minimum design weights without implementing the PFD elements by subjecting only strength, displacement, drift, and geometric structural design constraints taken from AISC-LRFD practice code provisions. Afterward, in order for optimally modelling the PFD elements, the frames are equipped with PFDs to calculate optimum yield strengths that is defined as slip load of a PFD. To do so, the GW algorithm ensures the maximizing of the dissipated energy and controls the yield strengths between the stories since the shear force due to the earthquake increases towards the base of the structure. Eventually, the provisions-based sizing design optimizations of the steel frame structures equipped with optimally modelled PFD elements are conducted under seismic excitations for conclusive evaluations.
AtıfScopus21WoS18OpenAlex20İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ2Evaluation of photon interaction parameters of Anti-HIV drugs
Akbaba, Uğur; Şakar, Erdem; Abu Al-Sayyed, Mohammed Ibrahim; Alim, Bünyamin; Özpolat, Özgür Fırat
Medical treatment inevitably exposes individuals to radiation, including those taking drugs used to treat and prevent human immunodeficiency virus (HIV). Motivated by this, we investigated the radiation interaction properties of several HIV drugs to determine the interaction parameters, mass attenuation coefficient (MAC), atomic cross section (ACS), electronic cross section (ECS), effective atomic numbers (Zeff), and effective electron density (Neff). We calculated the values using the Phy-X/PSD software in the range of 0.015–15 MeV. Additionally, we calculated the exposure build-up factor (EBF), and energy absorption build-up factor (EABF) values of the drugs up to 40 mean free path (MFP) using the geometric progression (G-P) method. From our findings, we determined that Combivir, with its relatively high heavy element content, had the highest radiation attenuation capacity, whereas the probability of Lopinavir interacting with photons was the lowest compared with the other drugs. The results of the EBF and EABF parameters, including the scattering effects, ordered the drugs opposite to the primary interaction parameters such as MAC, ACS, ECS, and Zeff. These findings can guide the treatment process of HIV-positive patients and inform HIV prevention practices conducted alongside radiotherapy, as the interaction between radiation and a drug may cause deterioration in the drug's structure.
AtıfScopus9WoS8OpenAlex12İncele - MakaleYalnız künye2022Scopus SJRQ1Comparison of the probiotic characteristics of Lactic Acid Bacteria (LAB) isolated from sourdough and infant feces
Kaya, Yasemin; Erten, Tayyibe; Vurmaz, Melike; İspirli, Hümeyra; Şimşek, Ömer; Dertli, Enes
Probiotics are beneficial microorganisms with certain characteristics such as survival under gastrointestinal conditions, adhesion to intestinal surface and different functions which result in several health benefits to host. With this regards, this study aimed to isolate Lactic Acid Bacteria (LAB) from sourdough and human feces as two different environments and to test their potential probiotic functions. In total nine distinct isolates were assessed with several probiotic functions such as in vitro adhesion to human colon cells, antimicrobial activities and survival under harsh gastrointestinal conditions. In general, distinct strains showed strong antimicrobial activity against the pathogenic and fungal strains tested in this study. Importantly, the adhesion levels to HT29 cells were determined between 0.29 % and 9.54% and Lactobacillus paracasei F7B showed the highest adhesion. All isolates tolerated the bile salt after 24 h and the infant feces isolates showed good survival characteristics at pH 4.
AtıfScopus18WoS15OpenAlex18İncele - MakaleAçık Erişim2022Scopus SJRQ1Thermoeconomic analysis of a low-temperature waste-energy assisted power and hydrogen plant at off-NG grid region
Tozlu, Alperen; Kayabasi, Erhan; Ozcan, Hasan
In this study, thermoeconomic analysis of a CO2 power cycle and PEM hydrogen system using ultra-low temperature waste heat from a milk production facility is conducted. In the transcritical CO2 cycle, low-temperature LNG evaporation is used for cooling the condenser to increase the temperature difference enabling low temperature waste heat use. In addition, a PEM electrolyzer produces hydrogen to reduce the LNG requirement at the plant. A CO2-water exchanger has been designed to recover the pasteurized water's excess heat and evaporate the CO2 using Simcenter-Flomaster software. The inlet mass flow rates and outlet temperatures of the heat exchanger were optimized by performing thermoecomic analysis, and the thermal and economic performance of the facility was examined. The power cycle has 14% higher efficiency when LNG is used as the heat sink compared to ambient temperature condensation with an electricity production cost range at 0.05–0.11 $/kWh, and the hydrogen generation cost is between $2.6–5.20 kg−1. It is found that the plant could only be economically feasible when less than 50% of the power produced is used for hydrogen generation. Consequently, the proposed system can co-generate power and on-demand hydrogen in off-NG grid regions with reasonable investment and product costs.
AtıfScopus6WoS6OpenAlex8İncele - MakaleYalnız künye2022Scopus SJRQ1Bioactive compounds of deep eutectic solvents extracts of Hypericum perforatum L.: Polyphenolic- organic acid profile by LC-MS/MS and pharmaceutical activity
Bayram, Sinan; Kutlu, Naciye; Gerçek, Yusuf Can; Çelik, Saffet; Ecem Bayram, Nesrin
Deep eutectic solvents (DESs) are known as environmentally-friendly solvents that have emerged as an alternative to conventional organic solvents in recent years. In this study, the effects of ten different DESs on the extraction of bioactive components from the Hypericum perforatum were investigated. Total phenolic content, total flavonoid content, phenolic profile (32 phenolics), organic acid profile (52 organic acids), as well as antioxidant and antimicrobial activities of H. perforatum extracts prepared using DESs and ultrasonic-assisted extraction method were determined. Total phenolic, total flavonoid content, and antioxidant activities of extracts were determined between 3.10 ± 0.86–16.64 ± 2.09 mg GA/g, 0.02 ± 0.00–12.29 ± 0.30 mg QE/g, and 8.40 ± 0.50–44.78 ± 2.66 mg TE/g, respectively. DES2 (choline chloride:ethylene glycol) and DES7 (choline chloride:lactic acid) demonstrated higher extraction success than other DESs for extracting phenolics and organic acids, respectively. DESs prepared using organic acid as hydrogen bond donor were found to have an antibacterial effect against all bacterial samples. However, the inhibitory effect against yeast-like fungi was observed in a narrower spectrum. Moreover, the results from principal component analysis also confirmed that the type of solvent used for extraction has a significant influence on the phenolics, organic acid, and other parameters. As a result, it was seen that DES components directly affect the extraction efficiency of target compounds from H. perforatum. This is a first and original report about use of DESs in extracting different bioactive components from H. perforatum.
AtıfScopus33WoS31OpenAlex32İncele - MakaleYalnız künye2022Scopus SJRQ1High-speed treatment of low strength domestic wastewater for irrigation water production in pilot-scale classical, moving bed and fixed bed hybrid MBRs
Tuluk, Banu; Yildiz, Ergun; Nuhoglu, Alper; Tataroglu, Numan Suadi; Gulluce, Ekrem; Cengiz, Ibrahim; Degermenci, Nejdet; Angin, Ilker
To evaluate the treatability of domestic wastewater under conditions of low hydraulic retention time and high organic loadings, 3 pilot-scale automatically controlled membrane bioreactors (MBRs) as classical (C-MBR), moving bed (MB-MBR), and fixed bed (FB-MBR) were established and operated for a total of 268 days. Established pilot plants were compared in terms of treatment performance, membrane fouling, irrigation water criteria, and power consumption values. Results obtained have shown that all three systems were able to achieve more than 93% removal of chemical oxygen demand (COD) in an average hydraulic retention time (HRT) of 1 hour, and MB-MBR and FB-MBR were superior in terms of total nitrogen (TN) and total phosphorus (TP) removals. It has been determined that MB-MBR and FB-MBR are also advantageous in terms of power consumption. Especially it has been found that FB-MBR can produce better quality irrigation water with 40% lower power consumption than C-MBR under the same conditions. It was concluded that biofilm-supported hybrid systems could be a practical application in the fight against increasing water scarcity and global warming, both in obtaining clean water with less power consumption and in protecting human and environmental health.
AtıfScopus16WoS11OpenAlex17İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ1Time-dependent fresh properties characterization of 3D printing engineered cementitious composites (3DP-ECC): On the evaluation of buildability
Zhou, Wen; McGee, Wes; Zhu, He; Gökçe, H. Süleyman; Li, Victor C.
Failure of the structure due to poor buildability is a major concern in 3D printing of cementitious materials. Evaluation of buildability based on fresh material properties and print parameters is of significance. In this paper, the buildability of printable engineered cementitious composites was investigated and quantified at the material and the structural scale. Fresh ECC material showed excellent load capacity and deformation resistance at the material scale, therefore preventing material failure of the bottom layers, as confirmed by constant shear rate tests and incremental loading tests. To predict vertical deformation of a 3DP structure, a time-dependent strain-stress model of printable ECC was proposed and validated based on the green strength evolution of the material and the buildup rate of the designed structure. At the structural scale, the approach of predicting critical height at self-buckling failure based on stiffness evolution was validated by printing a straight wall and a cylinder structure.
AtıfScopus56WoS46OpenAlex52İncele - MakaleAçık Erişim2022Scopus SJRQ1Identification of Lactic Acid Bacteria (LAB) from pre-fermented liquids of selected cereals and legumes and characterization of their exopolysaccharides (EPS)
Yalmanci, Dilara; İspirli, Hümeyra; Dertli, Enes
Recently, isolation of Lactic Acid Bacteria (LAB) strains with important technological functions from plant-based products has gained special interests related with the increment of consumer preferences to the plant-based fermented products. In this context, various cereals and legumes that were underwent to germination or not were selected for the isolation of exopolysaccharide (EPS) producer LAB strains in this study. Following genotypic discrimination, 17 distinct strains belonging to Weissella confusa, Weissella cibaria, Lactococcus lactis subsp. hordniae, Leuconostoc lactis, Lactiplantibacillus plantarum and Leuconostoc mesenteroides were identified from pre-ferment liquids. Two strains Weissella confusa W-16 and Leuconostoc lactis GW-6 were the highest EPS producers, and their EPSs were further characterized. The 1H and 13C NMR results revealed that both strains were dextran producers containing (1 → 3)-linked α-D-glucose units as branches with 9.2% and 6.9% levels for Weissella confusa W-16 and Leuconostoc lactis GW-6, respectively. FTIR analysis also supported the dextran structure and demonstrated the functional groups within the dextrans. A high level of thermal stability was observed in both dextrans detected by TGA and DSC analysis. Both dextrans were in amorphous characteristics determined by XRD analysis. These findings demonstrate that pre-fermented liquids of different cereals and legumes can be source of technologically important LAB strains with EPS production characteristics.
AtıfScopus41WoS41OpenAlex42İncele - MakaleYalnız künye2022Scopus SJRQ1Effect of using hybrid nanofluids as a coolant on the thermal performance of portable thermoelectric refrigerators
Mert Cuce, Pinar; Cuce, Erdem; Guclu, Tamer; Shaik, Saboor; Alshahrani, Saad; Ahamed Saleel, C.
This study investigated the effect of using hybrid nanofluids as a refrigerant in portable thermoelectric refrigerator applications on thermal performance. For this purpose, a cooling cabinet with an internal volume of 36 L was designed and produced. Then, the Peltier assembly, with a water-cooled block attached to its hot surface, was placed in this cooling cabinet from the middle of its front cover. With the help of a refrigerant, the heat was removed from the Peltier's hot surface and transferred to the atmosphere via a water-to-air heat exchanger. Hybrid nanofluids prepared with Al2O3-TiO2-SiO2 and nanoparticles and water were used as the refrigerant in the system. To evaluate the thermal performances of these hybrid nanofluids, the tests were repeated using water without added nanoparticles as the reference case. According to the results obtained from the experimental study, it was observed that in all cases, tests using nanofluids gave better results than the reference cases. In addition, it was determined that the efficiency obtained from the system increased as the nanoparticle ratio in the mixture increased in all cases. Despite significant improvements in cooling cabinet and cooled product temperatures in hybrid nanofluids, the COP values of the systems are slightly lower than in the reference case due to the Peltier effect. Considering the difference between the first and last temperatures of the cooled cabinet, the greatest improvement compared to the reference situation was determined as 30.3 % in the case of loaded state conditions and in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. For the unloaded conditions, this value was obtained as 25.1 % in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. On the other hand, for the unloaded condition, the lowest COP value was calculated as 0.47 and 0.45 when Al2O3-TiO2-SiO2-Water nanofluid was used in 1 % and 2 % mass fraction, respectively. For the loaded condition, this value was found as 0.48 in the case where 1 % Al2O3-TiO2-SiO2-Water and 0.47 in the case where 2 % Al2O3-TiO2-SiO2-Water nanofluid was used.
AtıfScopus27WoS21İncele - MakaleAçık Erişim2021Scopus SJRQ1Investigation of time-history response of a historical masonry minaret under seismic loads
Yurdakul, Muhammet; Yılmaz, Fatih; Artar, Musa; Can, Ömer; Öner, Erdal; Daloğlu, Ayşe T.
This study presents an investigation of the seismic performance of a historical masonry minaret which was built in the 12th century in Bayburt. The minaret was built as masonry with regional stones and handmade bricks. The most important feature of the minaret is its longitudinally conical geometry. An experimental investigation was made to obtain the mechanical properties of the regional stone used in the historical minaret. A three-dimensional Finite Element Model of the historical minaret was created in SAP2000. Three earthquake ground motions such as Erzincan, Kocaeli-Duzce, and Van-Ercis were used to investigate the seismic performance of the historical minaret. The results show that Erzincan, Kocaeli-Duzce and Van-Ercis earthquakes may cause some damages in the same zone of the minaret body since the tensile stresses occurred due to the earthquakes exceed the limit tensile stress of the masonry brick. The use of the data obtained from the experimental investigation of the Bayburt yellow stone in the analysis is important for the reliability of the results.
AtıfScopus44WoS43OpenAlex44İncele - MakaleAçık Erişim2021Scopus SJRQ1Investigation of mechanical properties of high-performance hybrid fiber concretes adding nanomaterials using with coarse aggregate
Öksüzer, Nurullah; Anil, Özgür; Aldemir, Alper; Şahmaran, Mustafa
High-performance hybrid fiber cement composites have more ductility and higher strength than traditional concrete. This is because crack development is limited due to multiple small cracks are formed instead of a single large crack as the fibers enter the matrix. It is customary to produce these concrete composites with fine aggregates. In this study, concrete composites with coarse aggregates were strived to be produced to gain some feasibility. To this end, different mixtures composed of different aggregate/binder ratios and different fly ash/binder ratios were designed. In order to compare the effectiveness of the combination of different fibers were utilized in these mixtures. The volumetric ratios of fibers (excluding reference samples) were kept constant at a value of 2%. For each mixture, four-point bending and compressive tests were performed. The increase in the aggregate ratio was observed to cause a more ductile flexural behavior in mixtures composed of PVA and steel fibers. In contrast, the ductility was reduced in mixtures with Nylon-mono and steel fibers. In addition, the ductility values were enhanced with the increase in FA/PC ratio. In addition, the possibility to use the cheaper Nylon-mono fibers in hybrid fiber mixtures was proved with optimization of aggregate-binder (A/B) and FA/PC ratios, enabling more feasible high-performance concrete mixtures.
AtıfScopus12WoS9OpenAlex13İncele - MakaleAçık Erişim2021Scopus SJRQ2Magnetic levitation force performance of benzil added bulk MgTi0,06B2 superconductors
Abdioglu, Murat
MgB2 superconductors can be proposed as a good candidate for Maglev systems due to their superior structural and superconducting properties. Besides, magnetic levitation and guidance force properties of these superconductors should be increased for commercial applications of Maglev systems. Therefore, the critical current density and magnetic levitation and guidance force properties of MgTi0.06B2 superconducting samples were investigated in this study, at measurement temperatures of 20 K and 25 K, depending on benzil (C14H10O2) addition in different adding amounts of 0, 1.5, 3, 4.5, 6 and 9 wt%. In addition to benzil, nanometer-sized silver particles were added to the samples in a constant ratio of 2 wt% to enhance the structural properties. The maximum critical current density values increased from 67 kA/cm2 for pure sample to 92 kA/cm2 with benzil adding amount of 3 wt% at T = 20 K, indicating an increment of 37%. In addition, the levitation force in ZFC (zero field cooling) regime and the guidance force in FC (field cooling) regime at 20 K increased at an amount of 46% and 57%, respectively, with 3% benzil addition. It can be said that the suitable amount of benzil addition as a carbon source produces additional pinning centres inside the MgTi0.06B2 and thus structural properties, critical current density and therefore, magnetic levitation properties of the samples are increased.
AtıfScopus3WoS3OpenAlex3İncele - MakaleYalnız künye2021Scopus SJRQ1An investigation of the fatigue performance of adhesively bonded step-lap joints: An experimental and numerical analysis
Gavgali, Esma; Sahin, Resul; Akpinar, Salih
Adhesively bonded joints are used in many engineering applications and are manufactured by joining various materials together. Static and dynamic analysis of adhesively bonded joints is very important in both scientific and sector studies on these joints. In this study, the static and fatigue strengths of single-lap joints (SLJs) and three-step-lap joints (TSLJs) that were subjected to tensile and four-point bending tests were examined experimentally and numerically. Adhesively bonded joints were produced using DP460 toughened type adhesive and AA2024-T3 aluminum alloy was used as the adherent. Fatigue tests were performed at a loading ratio (R) of 0.1 and a frequency of 10 Hz. As a result, applying a step-lap to the overlap area of adhesively bonded joints considerably increased the tensile static and fatigue strength of the joint. For the single-lap joint, both the static tensile and the tensile fatigue lifetime limit value of the three-step-lap joint increased approximately 100%. One of the reasons for that increase was that the moment effect formed in single lap joints due to the eccentric loading is minimized and the other is that a step-lap applied to the overlap area retards the formation of damage. However, static bending and fatigue strength values of TSLJs significantly decreased compared to those of SLJs. In addition, the results of the experimental and numerical analyses were found to be highly compatible with each other.
AtıfScopus29WoS28OpenAlex35İncele - MakaleYalnız künye2021Scopus SJRQ1An embedded mixed method study on teaching algebraic expressions using metacognition-based training
Öztürk, Mesut
That the students are aware of the learning process and know how they learn is important in terms of both controlling their previous learning and building their new learning on the previous ones. This thinking process, which generally requires metacognitive skills, may facilitate the difficulties experienced by the students while passing on from arithmetic to algebraic thinking. This study had two purposes:(1) to examine the effect of the IMPROVE method, a metacognitive training method, on the academic achievement of middle school students regarding algebraic expressions and (2) to examine the teaching process of algebraic expressions with IMPROVE. This study was conducted as an embedded mixed design. Forty-nine sixth grade students participated in the quantitative part of the study, while only six students from the experimental group participated in the qualitative part. The quantitative results of the study showed that there was a significant difference between the students’ total achievement scores regarding algebraic expressions and the achievement scores in the questions requiring high-level thinking skills in favor of the experimental group. It has been found in the comparisons made based on cognitive field levels that there is a statistically significant difference in favor of the group that received metacognition-based education in synthesis level questions. The qualitative results indicated that this teaching method increased students’ interest, contributed to their conceptual learning and improved their various affective characteristics. Also, it has been determined that the students who receive metacognition-based education do enjoy learning with this teaching method and that they think this method should be sustainable for the upcoming lessons.
AtıfScopus15WoS10OpenAlex22İncele