Tüm Yayınlar

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12597/2099

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1,2,3-Triazole substituted phthalocyanine metal complexes as potential inhibitors for anticholinesterase and antidiabetic enzymes with molecular docking studies.
(2022-07-01T00:00:00Z) Koçyiğit, Ümit M, Taslimi, Parham, Tüzün, Burak, Yakan, Hasan, Muğlu, Halit, Güzel, Emre; Kocyigit, UM, Taslimi, P, Tuzun, B, Yakan, H, Muglu, H, Guzel, E
In recent years, acetylcholinesterase (AChE) and α-glycosidase (α-gly) inhibition have emerged as a promising and important approach for pharmacological intervention in many diseases such as glaucoma, epilepsy, obesity, cancer, and Alzheimer's. In this manner, the preparation and enzyme inhibition activities of peripherally 1,2,3-triazole group substituted metallophthalocyanine derivatives with strong absorption in the visible region were presented. These novel metallophthalocyanine derivatives () effectively inhibited AChE, with values in the range of 40.11 ± 5.61 to 78.27 ± 15.42 µM. For α-glycosidase, the most effective values of compounds and were with values of 16.11 ± 3.13 and 18.31 ± 2.42 µM, respectively. Also, theoretical calculations were investigated to compare the chemical and biological activities of the ligand () and its metal complexes (-). Biological activities of and its complexes against acetylcholinesterase for ID 4M0E (AChE) and α-glycosidase for ID 1R47 (α-gly) are calculated. Theoretical calculations were compatible with the experimental results and these 1,2,3-triazole substituted phthalocyanine metal complexes were found to be efficient inhibitors for anticholinesterase and antidiabetic enzymes.Communicated by Ramaswamy H. Sarma.
2-(6-Oxo-3,4-diphenyl-1,6-dihydro-pyridazin-1-yl)acetic acid
(2007-11-09) Aydin A., Doǧruer D., Akkurt M., Büyükgüngör O.; Aydin, A, Dogruer, DS, Akkurt, M, Buyukgungor, O
In the title compound, C18H14N2O3, the pyridazine ring makes dihedral angles of 72.73 (11) and 49.97 (10)° with the two phenyl rings. The dihedral angle between the two phenyl rings is 52.42 (12)°. The crystal structure is stabilized by inter-molecular O - H⋯O and C - H⋯O hydrogen-bonding inter-actions. © International Union of Crystallography 2007.
21.2 mV/K High-Performance Ni(50 nm)-Au(100 nm)/Ga2O3/p-Si Vertical MOS Type Diode and the Temperature Sensing Characteristics with a Novel Drive Mode
(2022-12-15) Cicek O., Arslan E., Altindal S., Badali Y., Ozbay E.; Cicek, O, Arslan, E, Altindal, S, Badali, Y, Ozbay, E
Sensitivity (S) and drive mode are crucial issues for the vertical metal-oxide-semiconductor (MOS) type diode applied in temperature sensing. In this study, experimentally, we indicated that the {S} values of the Ni50nm - Au100nm /Ga2O3/ p -Si vertical MOS type diode, using the measured capacitance-voltage (Cm - V) outputs, are obtained with a novel drive mode. We applied the constant capacitance mode to drive the silicon thermo-diodes as well as constant current mode, and constant voltage mode, which are known as two different methods in the literature. Meanwhile, the S value is 21.2 mV/K at 1 nF. This value is the highest value proven in the literature excepting the cryogenic temperature region, and near room temperature. This study provided an original structure for the silicon thermo-diodes and a novel way to drive them.
3-[6-(2-Chlorobenzoyl)-2-oxo-2,3-dihydro-1,3-benzothiazol-3-yl] propanenitrile
(2006-12-01) Aydin A., Akkurt M., Önkol T., Büyükgüngör O.; Aydin, A, Akkurt, M, Onkol, T, Buyukgungor, O
The title compound, C17H11ClN2O 2S, crystallizes with two crystallographically independent molecules in the asymmetric unit. In the molecular structure, there are intramolecular weak C-H⋯O hydrogen bonds, which consolidate the molecular conformation. © 2006 International Union of Crystallography All rights reserved.
3-Parameter Generalized Quaternions
(2022-09-01) Şentürk T.D., Ünal Z.; Senturk, TD, Unal, Z
In this article, we give a general form of the quaternions algebra depending on 3-parameters. We define 3-parameter generalized quaternions (3PGQs) and study various properties and applications. Firstly we present the definiton, the multiplication table and algebraic properties of 3PGQs. We give matrix representation and Hamilton operators for 3PGQs. We derive the polar represenation, De Moivre’s and Euler’s formulas with the matrix representations for 3PGQs. Additionally, we derive relations between the powers of the matrices associated with 3PGQs. Finally, Lie groups and Lie algebras are studied and their matrix representations are given. Also the Lie multiplication and the Killing bilinear form are given.
3D neutronic analysis in MHD calculations at ARIES-ST fusion reactors systems
(2014-01-01) Hançerliogulları A., Cini M.; Hancerliogullari, A, Cini, M
In this study, we developed new models for liquid wall (FW) state at ARIES-ST fusion reactor systems. ARIES-ST is a 1,000 MWe fusion reactor system based on a low aspect ratio ST plasma. In this article, we analyzed the characteristic properties of magnetohydrodynamics (MHD) and heat transfer conditions by using Monte-Carlo simulation methods (ARIES Team et al. in Fusion Eng Des 49-50:689-695, 2000; Tillack et al. in Fusion Eng Des 65:215-261, 2003). In fusion applications, liquid metals are traditionally considered to be the best working fluids. The working liquid must be a lithium-containing medium in order to provide adequate tritium that the plasma is self-sustained and that the fusion is a renewable energy source. As for Flibe free surface flows, the MHD effects caused by interaction with the mean flow is negligible, while a fairly uniform flow of thick can be maintained throughout the reactor based on 3-D MHD calculations. In this study, neutronic parameters, that is to say, energy multiplication factor radiation, heat flux and fissile fuel breeding were researched for fusion reactor with various thorium and uranium molten salts. Sufficient tritium amount is needed for the reactor to work itself. In the tritium breeding ratio (TBR) >1.05 ARIES-ST fusion model TBR is >1.1 so that tritium self-sufficiency is maintained for DT fusion systems (Starke et al. in Fusion Energ Des 84:1794-1798, 2009; Najmabadi et al. in Fusion Energ Des 80:3-23, 2006). © 2013 Springer Science+Business Media New York.
3D Printing of Gelatine/Alginate/β-Tricalcium Phosphate Composite Constructs for Bone Tissue Engineering
(2019-11-08) Kalkandelen C., Ulag S., Ozbek B., Eroglu G.O., Ozerkan D., Kuruca S.E., Oktar F.N., Sengor M., Gunduz O.; Kalkandelen, C, Ulag, S, Ozbek, B, Eroglu, GO, Ozerkan, D, Kuruca, SE, Oktar, FN, Sengor, M, Gunduz, O
Bone tissue engineering studies have brought three-dimensional scaffolds into focus that can provide tissue regeneration with designed porosity and strengthened structure. Current research has concentrated on the fabrication of natural and synthetic polymer-based complex structures that closely mimic biological tissues due to their superior biocompatibility and biodegradabilities. Gelatine/Sodium Alginate hydrogels reinforced with different concentrations of β-Tricalcium Phosphate (TCP) (10, 13, and 15 wt.%) were studied to form 3D bone tissue. Physical, mechanical, chemical, morphological properties and biodegradability of the constructs were investigated. Furthermore, in vitro biological assay with human osteosarcoma cell line (SAOS-2) was performed to determine the biocompatibility of the constructs. It is found that cell viability rates for all constructs were increased and maximum cell viability rate was attained for 20%Gelatine/2%Alginate/10%TCP (wt.). The present work demonstrates that 3D printed Gelatine/Alginate/TCP constructs with porous structures are potential candidates for bone tissue engineering applications.
5-HT7 receptors as a new target for prostate cancer physiopathology and treatment: an experimental study on PC-3 cells and FFPE tissues.
(2021-06-01T00:00:00Z) Cinar, Irfan, Sirin, Busra, Halici, Zekai, Palabiyik-Yucelik, Saziye Sezin, Akpinar, Erol, Cadirci, Elif; Cinar, I, Sirin, B, Halici, Z, Palabiyik-Yucelik, SS, Akpinar, E, Cadirci, E
Prostate cancer (PCa) is one of the most common types of cancer seen among men worldwide. Previous studies have demonstrated that serotonin regulates cell proliferation, migration, and invasion in vitro; the presence of 5-HT receptors in cancer cells; and the role of serotonin in tumor development. The most recently discovered of these receptors is 5-HT7 but also least characterized receptors of serotonin. The aim of this study is to investigate the existence and possible role of 5-HT7 receptors in healthy and cancerous prostate tissues and also investigate effects of receptor agonists and antagonists on PC-3 cells to evaluate potential therapeutic effects. PC-3 cells were cultured and effects of 5-HT7 receptor agonist (LP-44) and antagonist (SB-269970) were evaluated on these cells. After proliferation analyses, relative expression of apoptotic markers and 5-HT7 receptor mRNA expression levels were determined through real-time PCR. Annexin V-FITC/PI double staining and Hoechst 33258 staining assay methods were applied to determine apoptosis. Additional PCR studies were performed on healthy and cancerous prostate tissue to see existence of receptors in human samples. The viability of PC-3 cells was decreased by SB-269970 after 48 and 72 h of incubation. However, LP-44 increased PC-3 cell proliferation at all time points. In 10 M SB-269970 treated PC-3 cells, there was significant increase in the expression of CAS-3 (4-fold), CAS-9 (2.5-fold), BAX (1.9-fold), and Tp-53 (4.8-fold) gene mRNA levels when compared to non-treated control group. Conversely, there was a significant decrease in NF-κB (2.9-fold) and 5-HT7 receptor (3.6-fold) mRNA expression in cells treated with SB-269970 when compared to control. SB-269970 that antagonized 5-HT7 receptors also induced apoptosis in Annexin V-FITC/PI double staining assay and Hoechst 33258 staining assays when compared with other groups. In human samples, 5-HT7 receptor mRNA expression was approximately 200-fold higher than that of heathy ones. In this study, for the first time, the 5-HT7 receptor antagonist SB-269970 has been shown to inhibit proliferation in PC-3 cells and to be associated with an apoptosis-inducing effect. These results suggest blocking 5-HT7 receptors can be a novel therapeutic target for the treatment of prostate cancer.
A 2-year aeropalynological survey of allergenic pollen in the atmosphere of Kastamonu, Turkey
(2012-09-01) Çeter T., Pinar N.M., Güney K., Yildiz A., Aşci B., Smith M.; Ceter, T, Pinar, NM, Guney, K, Yildiz, A, Asci, B, Smith, M
Knowledge of airborne pollen concentrations and the weather conditions influencing them is important for air quality forecasters, allergists and allergy sufferers. For this reason, a 7-day recording volumetric spore trap of the Hirst design was used for pollen monitoring between January 2006 and December 2007 in Kastamonu, Turkey. A total of 293,427 pollen grains belonging to 51 taxa were recorded during the study period. In the 2 years of study, the period March-August was identified as the main pollination season for Kastamonu. The highest monthly pollen counts were observed in May in both years. Six taxa made up 86.5% of the total amount of pollen recorded in the atmosphere of Kastamonu. These were as follows: Pinaceae (42.9%), Cupressaceae (20.6%), Poaceae (9.7%), Quercus (5.5%) Betula (5.3%) and Carpinus (2.6%). Four of these are considered to be highly allergenic (Betula, Carpinus, Cupressaceae and Poaceae). There were also a greater percentage of highly allergenic taxa found within the city, including Betula pendula that is not part of the local flora. This shows that through urban planting, the public and municipalities can unconsciously create a high risk for allergy sufferers. Daily average pollen counts from the six most frequently recorded pollen types were entered into Spearman's correlation analysis with meteorological data. Mean daily temperature, relative humidity, daily rainfall and wind speed were found to significantly (p < 0.05) affect atmospheric pollen concentrations, but the relationships between pollen concentrations and meteorological variables can vary and so there is a need for more local studies of this nature. © 2011 Springer Science+Business Media B.V.
A B3LYP/DFT Study on the Structure Activity Relationship for Benzimidazole Derivatives in Water Solution
(2022-08-01) Al-Sawaff Z.H., Basaran M.A., Kandemirli F.; Al-Sawaff, ZH, Basaran, MA, Kandemirli, F
Abstract: In this article, a theoretical chemical study on 41 benzimidazole derivatives compounds used to treat osteoporosis was performed in water phase using density functional theory (DFT) based on the 6-311 basis set and B3LYP method as the level of theory to calculate energetic behavior and quantitative chemical descriptors such as energy gap between HOMO and LUMO, the total energy of different orbital transitions, chemical hardness, softness, electrophilicity index, and electronegativity. The results showed a noticeable difference between the compounds concerning chemical parameters due to substituting the active chemical molecules at the compounds’ R1, R2, R3, and R4 sites. The results showed that compound no. 3 could be considered the most exciting compound due to its unique values obtained. On the other hand, it was found an appropriate relationship between the quantitative arithmetic variables and the IC50 values for each compound. Statistical analysis between the compounds under test and a quantitative descriptor of the ten traits were included to produce two different prediction models based on artificial neural networks due to negative and positive IC50 values after data pre-processing.
A Bayesian network model for prediction and analysis of possible forest fire causes
(2020-02-01) Sevinc V., Kucuk O., Goltas M.; Sevinc, V, Kucuk, O, Goltas, M
Possible causes of a forest fire ignition could be human-caused (arson, smoking, hunting, picnic fire, shepherd fire, stubble burning) or natural-caused (lightning strikes, power lines). Temperature, relative humidity, tree species, distance from road, wind speed, distance from agricultural land, amount of burnt area, month and distance from settlement are the risk factors that may affect the occurrence of forest fires. This study introduces the use of Bayesian network model to predict the possible forest fire causes, as well as to perform an analysis of the multilateral interactive relations among them. The study was conducted in Mugla Regional Directorate of Forestry area located in the southwest of Turkey. The fire data, which were recorded between 2008 and 2018 in the area, were provided by General Directorate of Forestry. In this study, after applying some different structural learning algorithms, a Bayesian network, which is built on the nodes relative humidity, temperature, wind speed, month, distance from settlement, amount of burnt area, distance from agricultural land, distance from road and tree species, was estimated. The model showed that month is the first and temperature is the second most effective factor on the forest fire ignitions. The Bayesian network model approach adopted in this study could also be used with data obtained from different areas having different sizes.
A change in the amount of CO2 at the center of the examination halls: Case study of Turkey
(2016-04-01) Cetin M.; Cetin, M
The performances of candidates during the exam period depend on several factors, such as the temperature in exam halls. The indoor amount of CO2 is over 1000 ppm, which in turn, could directly affect the performances of the candidates directly via headache, dizziness, fatigue, and a loss of concentration. In this study, changes in the indoor amount of CO2 in some central exam were examined, and certain evaluations were made. The findings of the present study indicate that the threshold value is usually exceeded within 10 minutes, following the start of exams, and when indoor CO2 amounts are higher than 1500 ppm, which is considered in most exams as the limit of harm to health, and circulating air in the hallways and keeping the doors of exam halls open throughout the exam period are not adequate for keeping the indoor CO2 amounts below 1000 ppm. Air circulation is a must in exam halls to ensure healthy exam environments.
A combined electrochemical and theoretical study into the effect of 2-((thiazole-2-ylimino)methyl)phenol as a corrosion inhibitor for mild steel in a highly acidic environment
(2016-10-01) Yilmaz N., Fitoz A., Ergun Ü., Emregül K.; Yilmaz, N, Fitoz, A, Ergun, U, Emregul, KC
2-((Thiazole-2-ylimino)methyl)phenol (THYMP) was studied as a corrosion inhibitor for the protection of mild steel in 2 M HCl solution by means of weight loss, polarization, electrochemical impedance spectroscopy and scanning electron microscopy. The potential of zero charge (Epzc), was also determined for evaluation of the adsorption mechanism. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (μ) etc. were calculated using density functional theory (DFT) at B3LYP/6-31G(d,p) level. Theoretical and experimental results were in fairly good agreement.
A combined experimental and computational study of electrochemical and photophysical properties of new benzophenone derivatives functionalized with N-substituted-phenyl-1,3,4-thiadiazole-2-amine
(2020-03-05) Şener İ., Şahin Ç., Demir S., Şener N., Gür M.; Sener, I, Sahin,C, Demir, S, Sener, N, Gur, M
New benzophenone derivatives with N-substituted-1,3,4-thiadiazole including different substituents were synthesized and characterized by using FTIR, NMR, UV/Visible, and fluorescence spectroscopies and cyclic voltammetry. The effect of –F, -Cl, –OCH3 and –NO2 substitutions at ortho-, meta-, para-positions on the photoluminescence properties of the molecules have been investigated. The results indicate that the electron-donating and electron-withdrawing moieties at the ortho-, meta-, and para-positions have an important effect on the photoluminescence properties of the molecules. The calculated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels are in the range of (−5.55) to (−5.65) eV and (−2.83) to (−3.02), respectively. The lower LUMO energy levels were observed for the molecules with –OCH3 substituents due to the donor strength of the substituent. Excited states and electrochemical properties of the molecules were also comprehensively and quantitatively studied by Density Functional Theory and Time-Dependent Density Functional Theory calculations. Experimental trends were successfully revealed by calculated data.
A combined experimental and DFT investigation of disazo dye having pyrazole skeleton
(2017-02-05) Şener N., Bayrakdar A., Kart H., Şener İ.; Sener, N, Bayrakdar, A, Kart, HH, Sener, I
Disazo dye containing pyrazole skeleton has been synthesized. The structure of the dye has been confirmed by using FT-IR, 1H NMR, 13C NMR, HRMS spectral technique and elemental analysis. The molecular geometry and infrared spectrum are also calculated by the Density Functional Theory (DFT) employing B3LYP level with 6-311G (d,p) basis set. The chemical shifts calculation for 1H NMR of the title molecule is done by using by Gauge-Invariant Atomic Orbital (GIAO) method by utilizing the same basis sets. The total density of state, the partial density of state and the overlap population density of state diagram analysis are done via Gauss Sum 3.0 program. Frontier molecular orbitals such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and molecular electrostatic potential surface on the title molecule are predicted for various intramolecular interactions that are responsible for the stabilization of the molecule. The experimental results and theoretical values have been compared.
A comparative DFT study on Al- and Si- doped single-wall carbon nanotubes (SWCNTs) for Ribavirin drug sensing and detection
(2023-05-01) Dalgic S.S., Al-Sawaff Z.H., Dalgic S., Kandemirli F.
In this work, we have presented a comparative study on Ribavirin (RBV) drug sensing and detection on the pristine and functionalized single-wall carbon nanotubes (f-SWCNTs) by Density Functional Theory (DFT) method. The pristine and metal-doped zigzag (4,0) and (6,0) SWCNTs were first considered for the RBV adsorption. All the probable positions of RBV adsorption were investigated to find which one is energetically favourable. The topology analysis of the Quantum theory of atoms in a molecule (QTAIM) with non-covalent interactions (NCI-RDG), Frontier molecular orbitals (FMO), Density of states (DOS), and non-linear optical (NLO) analysis were carried out to understand the molecular structure, electrical, electronic and optical properties of complexes. The charge analysis indicates that charge transfer is from the adsorbed RBV to the pristine and metal-doped (4,0) and (6,0) SWCNTs. The highest values of adsorption energies for Al-, Si-doped and pristine (4,0) SWCNTs were determined as −34.688, −87.999 and −10.382 kcal/mol, respectively, whereas corresponding values for metal-doped and pristine (6,0) SWCNTs are about −43.592, −20.661 and −12.414 kcal/mol, respectively. The results suggest that those bare and metal-doped (4,0) SWCNTs and (6,0) Si-SWCNTs can serve as promising sensors in practical applications to detect, recognize and carrier RBV drug for its medicinal drug delivery applications. Based on the NLO properties of (6,0) Si-SWCNTs and pristine (6,0) SWCNT (with an acceptable recovery time of 279s and first hyper polarizability value of β = 229.25 × 10−30 cm5 esu−1), those nanotubes may be possible candidates to be used as the optoelectronic sensor for RBV drug. The appropriate short length of nanotubes was obtained.
A comparative evaluation of hematological and biochemical parameters between the italian mullet mugil cephalus (Linnaeus 1758) and the turkish mullet chelon auratus (risso 1810)
(2020-01-01) Fazio F., Saoca C., Acar Ü., Tezel R., Çelik M., Yilmaz S., Kesbiç O., Yalgin F., Yiğit M.; Murat YİĞİT, Rifat TEZEL, Ferhat YALGIN, Osman Sabri KESBİÇ, Murat ÇELİK, Francesco FAZIO, Ümit ACAR, Sevdan YILMAZ, Concetta SAOCA; Fazio, F, Saoca, C, Acar, U, Tezel, R, Celik, M, Yilmaz, S, Kesbic, OS, Yalgin, F, Yigit, M
This study aimed to carry out a comparative evaluation of the hematological profile (erythrocyte count, hemoglobin concentration, hematocrit, and Wintrobe index parameters such as mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration), in addition to certain biochemical parameters (aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, serum total protein, albumin, glucose, total cholesterol, and triglycerides), in the Italian mullet Mugil cephalus (Linnaeus 1758) and the Turkish mullet Chelon auratus (Risso 1810). Accordingly, two groups of fish were used in this study: 30 flathead grey mullets, M. cephalus, caught in Lake Faro, Italy, and 30 golden grey mullets, C. auratus, caught in the estuarine channel system of Köyceğiz–Dalyan, Turkey. Statistical evaluations (unpaired t-test) revealed that there were no significant differences in weight or total length values between the two mullet groups. However, the differences between all the evaluated blood parameters (except alanine aminotransferase) between the Italian and the Turkish mullet were significant (P < 0.0001). The present study demonstrated that there were significant hematological and biochemical differences between the Italian (M. cephalus) and the Turkish (C. auratus) mullet. Our findings also contribute to expanding the knowledge on the hematology and biochemistry of two different species of mullet originating from two different habitats. Since the evaluation of blood parameters represents an essential tool in examining the effects of environmental conditions on fish physiology and, consequently, on fish health status, further research in this field is encouraged and would be very useful.
A comprehensive comparison study of traditional classifiers and deep neural networks for forest fire detection
(2023-01-01) Akyol K.; Akyol, K
Forest fires cause great harm to people, environment, and nature. Fire detection using forest landscape images can play a critical role in the design of expert systems required to solve the forest fire problem. The main aim of this study is to evaluate the classification accuracy of different classifier models for efficiently detecting forest fires and to present an effective and successful model. At this point, classification performances of traditional and deep neural networks (DNN) based classifiers were compared on landscape images dataset taken from the Mendeley repository within the frame of well-known metrics such as accuracy, sensitivity, specificity, precision and false negative rate. The DNN-3 classifier performed very well on the ResNet50 deep features extracted from images with 97.11% accuracy, 96.84% sensitivity, 3.16% false negative rate, 97.37% specificity, and 97.35% precision. This model (ResNet50+DNN-3) offered the most area under the curve with 0.971. In this context, it is thought that the proposed model could play an active role in the design of expert systems that will support the forest protection and monitoring units by easily integrating with real-time internet of things and embedded system applications.
A Comprehensive Numerical Study on Thermohydraulic Performance of Fluid Flow in Triangular Ducts with Delta-Winglet Vortex Generators
(2018-01-20) Akcayoglu A., Nazli C.; Akcayoglu, A, Nazli, C
Triangular ducts fitted with various kinds of delta-winglet type vortex generators (VGs) are commonly used to achieve compactness and heat transfer enhancement in many industries. Successive locations of VGs on the inner surfaces of the ducts can be arranged in Common Flow Up (CFU) and Common Flow Down (CFD) orientations. In the present numerical study simultaneous effects of orientation and streamwise distance between VGs on triangular fin performance is carried out considering both global and local flow and heat transfer fields. With the configurations considered in this study, a CFD–CFU orientation and a nondimensional streamwise distance of 0.5 is determined as the best configuration. “RNG k-ϵ” turbulence model with “Enhanced wall treatment” option is determined as the best turbulence model to predict the flow fields inside the triangular duct with built-in VGs, for Reynolds number of 5000.
A comprehensive study on mechanical properties of Bi1.8Pb 0.4Sr2MnxCa2.2Cu3.0O y superconductors
(2013-08-01) Dogruer M., Karaboga F., Yildirim G., Terzioglu C., Ozturk O.; Dogruer, M, Karaboga, F, Yildirim, G, Terzioglu, C, Ozturk, O
This study manifests the crucial change in the mechanical performances of Bi1.8Pb0.4Sr2MnxCa 2.2Cu3.0Oy superconductor samples (x = 0, 0.03, 0.06, 0.15, 0.3 and 0.6) prepared by conventional solid-state reaction method by use of Vickers microhardness (Hv) measurements carried out at different applied loads, (0.245 N ≤ F ≤ 2.940 N). Load dependent microhardness, load independent microhardness, Young's (elastic) modulus and yield strength values being account for the potential technological and industrial applications are evaluated from the hardness curves and compared with each other. It is found that the Hv, elastic modulus and yield strength obtained decrease (increase) with the enhancement of the applied load for the undoped (doped) samples. Surprisingly, the results of the Hv values illustrate that the samples doped with x = 0.03, 0.06, 0.15, 0.3 and 0.6 exhibit reverse indentation size effect (RISE) feature whereas the pure sample obeys indentation size effect (ISE) behavior. Furthermore, the experimental results are examined with the aid of the available methods such as Meyer's law, proportional sample resistance model (PSR), elastic/plastic deformation (EPD), Hays-Kendall (HK) approach and indentation-induced cracking (IIC) model. The results inferred show that the hardness values calculated by PSR and EPD models are far from the values of the plateau region, meaning that these models are not adequate approaches to determine the real microhardness value of the Mn doped Bi-2223 materials. On the other hand, the HK approach is completely successful for the explanation of the ISE nature for the pure sample while the IIC model is obtained to be the best model to describe the hardness values of the doped materials exhibiting the RISE behavior. Additionally, the bulk porosity analysis for the samples reveals that the porosity increases monotonously with the increment in the Mn inclusions inserted in the Bi-2223 system, presenting the degradation of the grain connectivity. © 2013 Springer Science+Business Media New York.

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