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51.
Tiberiu Roman Ramona-Laura Asavei Nikolaos E. Karkalos Claudiu Roman Constantin Virlan Nicanor Cimpoesu Bogdan Istrate Marius Zaharia Angelos P. Markopoulos Konstantinos Kordatos Sergiu Stanciu Aurel Pui 《International Journal of Applied Ceramic Technology》2019,16(2):693-705
Nanocrystalline ferrites are known to be used in different applications, including industrial wastewater management. For environmental water issues, one of the most widely applied techniques is the adsorption of pollutants. The adsorption capacity of Congo red (CR) dye on different MFe2O4 (M = Co2+, Mg2+, Mn2+, Ni2+, and Zn2+) ferrites, synthesized by coprecipitation method, was determined. Specific isotherms and kinetic models were used to characterize the adsorption process. Interesting results were obtained for MgFe2O4 with adsorption capacity ranging from 39% up to 70% dependent on the initial dye concentration. Furthermore, an artificial intelligence model based on neural network was developed in order to model the adsorption rates followed by the generation of 3D adsorption rate models for each type of synthesized ferrite. These models were obtained in order to provide information about the particle-dye system`s kinetics at various initial CR concentration. Specific techniques were used to characterize the functionalized magnetic particles. 相似文献
52.
53.
A study of the carboxymethylation of wood pulp cellulose and cotton linters cellulose in different organic media, namely, ethanol, acetone, and ethanol-acetone mixtures, is performed. Previously, the ethanol-acetone 1 : 1 (w/w) mixture used as reaction medium was found to give a higher degree of substitution (DS) than the pure solvents separately. In the present work, the kinetic investigation of cellulose carboxymethylation was carried out in ethanol-acetone 3 : 7 (w/w) mixture, as well as in acetone as reaction media, and the same synergistic effect of the solvents mixture was observed. The data suggested a pseudo-first-order kinetic behavior satisfactorily described by the following equation: ln(1.11 − DS) = −kt. The two reaction steps observed are related to the transformations of less ordered regions with higher reaction rate and more ordered regions with smaller reaction rates, respectively. A possible explanation for this behaviour is given, taking into account the different structural changes of cellulose crystallinity and accessibility produced by ethanol-acetone 3 : 7 (w/w) mixture, ethanol, and acetone, as revealed by X-ray diffraction and calorimetry determinations. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 481–486, 1998 相似文献
54.
Dorin Dadarlat Dane Bicanic Jurgen Gibkes Vasile Surducan Aurel Pasca 《Journal of the science of food and agriculture》1998,78(2):182-186
Photopyroelectric (PPE) study of some saturated (C5 : 0, and C23 : 0) and unsaturated (C18 : 2 and C18 : 3) free fatty acids was performed in a temperature range that included their melting points. The standard PPE configuration was used consistently during the experiment; the special PPE case requests thermally thick sample and sensor and optically opaque sample. For those fatty acids for which literature data on volume-specific heat were available (C18 : 2, C18 : 3), the behaviour around the melting point of all static and dynamic thermal parameters (specific heat, thermal conductivity, diffusivity and effusivity) was obtained. Since no data for volume-specific heat of C5 : 0 and C23 : 0 were found in the literature, only the temperature behaviour of the thermal diffusivity was obtained for these specimens. © 1998 Society of Chemical Industry 相似文献
55.
Aurel Qinami Anna Pandolfi Michael Kaliske 《International journal for numerical methods in engineering》2020,121(7):1388-1409
In the context of eigenfracture scheme, the work at hand introduces a variational eigenerosion approach for inelastic materials. The theory seizes situations where the material accumulates large amounts of plastic deformations. For these cases, the surface energy entering the energy balance equation is rescaled to favor fracture, thus energy minimization delivers automatically the crack-tracking solution also for inelastic cases. The minimization approach is sound and preserves the mathematical properties necessary for the Γ-limit proof, thus the existence of (local) minimizers is guaranteed by the Γ-convergence theory. Although it is not possible to demonstrate that the obtained minimizers are global, satisfactory results are obtained with the local minimizers provided by the method. Furthermore, with the goal of addressing the constitutive behavior of concrete, a Drucker-Prager viscoplastic consistency model is introduced in the microplane setting. The model delivers a rate-dependent three-surface smooth yield function that requires hardening and hardening-rate parameters. The independent evolution of viscoplasticity in different microplanes induces anisotropy in the mechanical response. The sound performance of the model is illustrated via numerical examples for both rate-independent and rate-dependent plasticity. 相似文献
56.
Costin Pribeanu Paul Fogarassy-Neszly Aurel Pătru 《Universal Access in the Information Society》2014,13(3):339-349
Despite the existing regulations and standards at national and international level, web content is still difficult to use, if not completely unusable, for visually impaired people. This paper presents the evaluation results for three municipal web sites. A combined method, based on conformance review and expert review, was employed. Overall, the results reveal a low conformance to WCAG2 and many accessibility and usability problems. The content is not properly structured, and this reduces usability even for sighted user. The analysis of the evaluation data suggests that many accessibility barriers could be avoided by adopting a user-centered approach during web design. 相似文献
57.
Cathode ray tubes (CRTs) glass waste with a high lead concentration can be used as supplementary cementitious material in mortars based on portland cement and slag cement, as well as for the partial replacement of the solid component in alkali activated slag/fly ash binders. The values of cumulative lead released at 64 days, assessed by monolith leaching test NEN 7345, were below the emission limit stipulated in current legislation and consequently the mortars can be used without environmental restriction. The substitution of the active binding component (cement, slag or fly ash) with CRT glass waste decreases the rate of hardening processes, but due to its high fineness, the CRT glass waste powder exerts also a filler effect which can compensate the compressive strength reduction. Compressive strengths of mortar specimens cured in different conditions (air or water with different pH values) were assessed in order to evaluate their possible use as building materials. 相似文献
58.
Aurel Prstić Zagorka Aćimović‐Pavlović Anja Terzić Ljubica Pavlović Snežana Grujić 《International Journal of Applied Ceramic Technology》2014,11(2):321-331
In this study, new refractory coatings based on synthesized cordierite for the casting applications were developed. The investigation included starting raw materials characterization, synthesis of the cordierite, design of the refractory coating as final product, and its application testing. The obtained results pointed out that coating suspension sediment stability was crucial quality parameter. Design and optimization of the coatings composition, with controlled rheological properties included, were achieved by application of different coating components, namely different suspension agents and by alteration of the coating production procedure. Cordierite, used as filler, was obtained by means of synthesis in the solid‐state reaction on the basis of talc, kaolin, and alumina. The investigation showed that the application of these particular types of water/alcohol‐based coatings has positive influence on surface quality and structural and mechanical properties of the castings of aluminum alloys obtained by casting into sand molds by means of evaporable models method, that is, evaporate pattern casting process. 相似文献
59.
Gabriela Toader Edina Rusen Mircea Teodorescu Aurel Diacon Paul O. Stanescu Traian Rotariu Adrian Rotariu 《应用聚合物科学杂志》2016,133(38)
The present work describes the preparation of a set of new polyurea polymers suitable for ballistic protection applications by employing different aromatic diamines derivatives with different flexibility degrees. This modification would allow the synthesis of polymers with both enhanced and controllable mechanical properties through the combination of aliphatic and aromatic molecules. Besides the classical methylene diphenyl diisocyanate and polypropylene glycol bis(2‐aminopropyl ether) (PPG), benzidine, 4,4′‐diaminodiphenylmethane and 3,6‐diamino carbazole were chosen as the third monomer and used in different ratios toward PPG, in order to optimize the polymer properties. The proportions between the polyurea components were selected as such to achieve the total consumption of the monomers. The different types of polyurea obtained have been characterized by Fourier transform infrared spectroscopy, thermal measurements (differential scanning calorimetry and thermogravimetric analysis), tensile tests, and scanning electron microscope. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43967. 相似文献
60.
Marco Deluca Catalina A. Vasilescu Adelina C. Ianculescu Daniela C. Berger Cristina E. Ciomaga Lavinia P. Curecheriu Laurentiu Stoleriu Andreja Gajovic Liliana Mitoseriu Carmen Galassi 《Journal of the European Ceramic Society》2012,32(13):3551-3566
Single phase and dense BaTi1?xZrxO3 (BTZ) ceramics (x = 0.10, 0.15 and 0.20) were obtained from nanopowders synthesised by the modified Pechini method. The evolution of both Raman spectra and low-field dielectric properties against temperature indicated the occurrence of diffuse ferroelectric–paraelectric phase transitions for all the BTZ compositions under investigation. The evolution of first-order reversal curves (FORC) diagrams emphasised the crossover from the ferroelectric towards the relaxor state as the Zr content increased. Lower values of the Curie temperatures than those usually reported earlier in the literature were obtained for all the BTZ samples analysed here. The high-field tunability data completed the low-field and Raman results, showing that by increasing Zr addition, multiple polarisation components with various weights are responsible for the dielectric and ferroelectric properties. 相似文献