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31.
Awadesh Kumar Mallik Nurcan Calis Acikbas Ferhat Kara Hasan Mandal Debabrata Basu 《Ceramics International》2012,38(7):5757-5767
Two different varieties of Si3N4 powders were used to prepare SiAlON ceramics. 100% β-Si3N4 was used from refractory grade powders (B1) and another purer 98% α-Si3N4 (50A) powder was used to prepare the SiAlON samples. Since SiC + SiAlON composites reportedly perform better, batches were prepared with 15% SiC addition to the refractory powders (B1) and 17.5% SiC was added to the other SiAlON composition (50A). The samples were gas pressure sintered at 1840 °C and at 22 bar with 1 h dwelling time. Thereby, we could achieve 97–98% theoretical density. The hardness was recorded 14–17 GPa while fracture toughness varied from 4.3 to 5 MPa m1/2. Fretting experiments showed initial running-in period of 300 cycles for all the tribo-couples. After which, the steady state coefficient of frictions (COF) were achieved. Steel ball of 10 mm diameter, fretting against 50A composition, showed 0.6 average steady state COF while the same composition while fretting against alumina ball of the same diameter, showed 0.57 average steady state COF. Results have been compared with SiAlON composition derived from refractory powder (B1) and found that the 50A composition performs better under identical test conditions. Moreover, cytocompatibility study also suggests that the investigated 50A composition can be used as substrate to support cell adhesion and proliferation of L929 mouse fibroblast cell lines whereas B1 composition derived from refractory powders are toxic in nature. 相似文献
32.
Abdullah Goktas Ferhat Aslan ?brahim Halil Mutlu 《Journal of Materials Science: Materials in Electronics》2012,23(2):605-611
The effect of annealing temperature on selected characteristics of polycrystalline La0.67Sr0.33MnO3 films, which have been produced on quartz substrates, was investigated. X-Ray powder diffraction patterns showed that the phase formation started at 873 K and all the films had perovskite structure. By increasing the annealing temperature, the lattice parameters were decreased. Scanning electron microscope indicated that the film thicknesses were approximately 3 μm and the average grain size of the samples varied between 30–100, 50–110, 70–120, and 100–150 nm for films annealed at 873, 973, 1,073, and 1,173 K, respectively. All the films showed a paramagnetic–ferromagnetic (TC) and metal–insulator (TIM) phase transition. The TC indicated a small variation [from 131 K (S4) to 124 K (S1)] as a function of annealing temperature, whereas the TIM went down from 212 K (S4) to 110 K (S1), a strong decrease of 102 K. A colossal magneto resistance with magneto resistance ratios of 130, 139, 156, and 163% were observed near TC and at 6 T magnetic field. 相似文献
33.
Nihan Kaya Ferhat Arslan Zeynep Yildiz Uzun 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(10):769-780
AbstractIn this study, hazelnut shell and walnut shell which are the agricultural wastes existent abundantly in many countries were pyrolyzed at different temperatures in the temperature range of 400–700?°C in order to optimize the physicochemical properties of biochars. The biochars with large surface area were used to removal of lead (Pb2+) ions, one of the most important heavy metal pollutant, from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, BET, SEM, partial and elemental analysis techniques. In order to determine the adsorption characteristics of both biochars, batch adsorption experiments were carried out under different experimental conditions. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of Pb2+ ions from aqueous solution. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion model, and the model constants were investigated. 相似文献
34.
Lipid Emulsions Containing Medium Chain Triacylglycerols Blunt Bradykinin-Induced Endothelium-Dependent Relaxation in Porcine Coronary Artery Rings 下载免费PDF全文
Said Amissi Julie Boisramé-Helms Mélanie Burban Sherzad K. Rashid Antonio J. León-González Cyril Auger Florence Toti Ferhat Meziani Valérie B. Schini-Kerth 《Lipids》2017,52(3):235-243
Lipid emulsions for parenteral nutrition are used to provide calories and essential fatty acids for patients. They have been associated with hypertriglyceridemia, hypercholesterolemia, and metabolic stress, which may promote the development of endothelial dysfunction in patients. The aim of the present study was to determine whether five different industrial lipid emulsions may affect the endothelial function of coronary arteries. Porcine coronary artery rings were incubated with lipid emulsions 0.5, 1, or 2% (v/v) for 30 min before the determination of vascular reactivity in organ chambers and the level of oxidative stress using electron paramagnetic resonance. Incubation of coronary artery rings with either Lipidem®, Medialipid® containing long- and medium-chain triacylglycerols (LCT/MCT), or SMOFlipid® containing LCT, MCT, omega-9, and -3, significantly reduced the bradykinin-induced endothelium-dependent relaxation, affecting both the nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) components, whereas, Intralipid® containing LCT (soybean oil) and ClinOleic® containing LCT (soybean and olive oil) did not have such an effect. The endothelial dysfunction induced by Lipidem® was significantly improved by indomethacin, a cyclooxygenase (COX) inhibitor, inhibitors of oxidative stress (N-acetylcysteine, superoxide dismutase, catalase) and transition metal chelating agents (neocuproine, tetrathiomolybdate, deferoxamine and l-histidine). Lipidem® significantly increased the arterial level of oxidative stress. The present findings indicate that lipid emulsions containing LCT/MCT induce endothelial dysfunction in coronary artery rings by blunting both NO- and EDH-mediated relaxations. The Lipidem®-induced endothelial dysfunction is associated with increased vascular oxidative stress and the formation of COX-derived vasoconstrictor prostanoids. 相似文献
35.
?brahim Çanak Ferhat Hasekiler Duygu Kebapc? 《Computers & Mathematics with Applications》2011,62(12):4486-4491
In this paper, we establish some Tauberian theorems for the Abel summability method in terms of regularly generated sequences which generalizes some results obtained in Çanak and Totur [?. Çanak, Ü. Totur, A note on Tauberian theorems for regularly generated sequences, Tamkang J. Math. 39 (2) (2008) 187-191]. 相似文献
36.
We report first-principles calculations of the structural, lattice-dynamical and dielectric properties for zinc-blend beryllium chalcogenides: BeS, BeSe, and BeTe. The ground state properties, such as the lattice structure and bulk modulus, are calculated using a plane wave pseudopotential method within the density functional theory. A linear response approach is employed in order to derive the high-frequency dielectric constants, Born effective charges and phonon frequencies. Furthermore, the pressure dependence of phonon modes is also detailed. 相似文献
37.
38.
Hong Peng Sofiène Tahar Ferhat Khendek 《International Journal on Software Tools for Technology Transfer (STTT)》2003,4(2):234-245
In this paper, we compare and contrast SPIN and VIS, two widely used formal verification tools. In particular, we devote special
attention to the efficiency of these tools for the verification of communications protocols that can be implemented either
in software or hardware. As a basis of our comparison, we formally describe and verify the Asynchronous Transfer Mode Ring
(ATMR) medium access protocol using SPIN and its hardware model using VIS. We believe that this study is of particular interest
as more and more protocols, like ATM protocols, are implemented in hardware to match high-speed requirements.
Published online: 1 March 2002 相似文献
39.
Preparation and characterization of membranes obtained from blends of acrylonitrile copolymers with poly(vinyl alcohol) 下载免费PDF全文
Teodor Sandu Andrei Sârbu Celina Maria Damian Adela Marin Silviu Vulpe Temenuzhka Budinova Boyko Tsyntsarski M. Ferhat Yardim Ahmet Sirkecioglu 《应用聚合物科学杂志》2014,131(21)
New microfiltration and ultrafiltration membranes were obtained using acrylonitrile‐vinyl acetate copolymers in mixture with poly(vinyl alcohol) (PVA). Thus, a blend polymer solution was prepared in dimethylsulfoxide (DMSO) and used to obtain bicomponent polymer membranes by phase inversion. The rheological behavior of the DMSO polymer solutions was, mostly, dilatant at low shear gradients and pseudo plastic with quasi Newtonian tendency at higher gradients. Membranes were characterized by Fourier transform infrared spectrometry (FTIR), optical microscopy, atomic force microscopy, thermal gravimetric analysis‐differential thermal gravimetry, and pure water flux (PWF). FTIR spectra displayed the characteristic bands for acrylonitrile, vinyl acetate, and PVA. The morphology and the porosity can be tailored by the preparation conditions. PVA allows controlling the size of the pores and enables, in principle, to use the resulted membranes as supports for enzyme immobilization. PVA content influences the thermal stability. PWF values depend on the copolymer, on the content in PVA, but also on the coagulation bath composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41013. 相似文献
40.
Ayse Kalemtas Gulsum Topates Hüseyin Özcoban Hasan Mandal Ferhat Kara Rolf Janssen 《Journal of the European Ceramic Society》2013,33(9):1507-1515
In this study, porous β-Si3N4 ceramics containing limited amount of Sm2O3 and CaO as sintering aids were produced by addition of potato starch (10 and 20 vol.%) and partial sintering. Two different Si3N4 powders, α- and β-, were used as starting materials. Scanning electron microscopy investigations revealed that development of elongated β-Si3N4 grains were much more pronounced when α-Si3N4 starting powder was used. Even though porosity values of the compositions prepared by using α-Si3N4 (~57.0–58.4%) is significantly higher than the samples produced by β-Si3N4 (42.6%), no significant change was observed for the bending strength, fracture toughness and Weibull modulus. This indicates that microstructural features have a significant contribution to the mechanical properties of the porous materials in terms of bending strength and fracture toughness. 相似文献