排序方式: 共有219条查询结果,搜索用时 15 毫秒
81.
This paper presents a comprehensive experimental and theoretical investigation of the deformation behavior of high-purity, polycrystalline α-titanium under quasi-static conditions at room temperature. The initial material in this study was a cross-rolled plate with a strong basal texture. To quantify the plastic anisotropy and the tension–compression asymmetry of this material, monotonic tensile and compressive tests were conducted, on samples cut along different directions of the plate. A new anisotropic elastic/plastic model was developed to describe the quasi-static macroscopic response of the aggregate. Key in its formulation is the use of an anisotropic yield criterion that captures strength-differential effects and an anisotropic hardening rule that accounts for texture evolution associated to twinning. A very good agreement between FE simulations using the model developed and uniaxial data was obtained. 相似文献
82.
Vincent Monchiet Oana Cazacu Eric Charkaluk Djimedo Kondo 《International Journal of Plasticity》2008,24(7):1158-1189
The combined effects of void shape and matrix anisotropy on the macroscopic response of ductile porous solids is investigated. The Gologanu–Leblond–Devaux’s (GLD) analysis of an rigid-ideal plastic (von Mises) spheroidal volume containing a confocal spheroidal cavity loaded axisymmetrically is extended to the case when the matrix is anisotropic (obeying Hill’s [Hill, R., 1948. A theory of yielding and plastic flow of anisotropic solids. Proc. Roy. Soc. London A 193, 281–297] anisotropic yield criterion) and the representative volume element is subjected to arbitrary deformation. To derive the overall anisotropic yield criterion, a limit analysis approach is used. Conditions of homogeneous boundary strain rate are imposed on every ellipsoidal confocal with the cavity. A two-field trial velocity satisfying these boundary conditions are considered. It is shown that for cylindrical and spherical void geometries, the proposed criterion reduces to existing anisotropic Gurson-like yield criteria. Furthermore, it is shown that for the case when the matrix is considered isotropic, the new results provide a rigorous generalization to the GLD model. Finally, the accuracy of the proposed approximate yield criterion for plastic anisotropic media containing non-spherical voids is assessed through comparison with numerical results. 相似文献
83.
Marin Senila Emilia Neag Oana Cadar Maria-Alexandra Hoaghia Marius Roman Ana Moldovan Alexandru Hosu Angela Lupas Emoke Dalma Kovacs 《Molecules (Basel, Switzerland)》2022,27(11)
In the present work, the capability of the volcanic tuff from Macicasu (Romania) to remove ammonia (NH3) from air with different contamination levels during 24 h of adsorption experiments was investigated. The natural zeolitic volcanic tuff was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), the Brunauer–Emmett–Teller (BET) method, inductively coupled plasma optical emission spectrometry (ICP-OES), and thermogravimetric analysis (TGA). The adsorption capacities varied between 0.022 mg NH3 g−1 zeolite and 0.282 mg NH3 g−1 zeolite, depending on the NH3 concentrations in the air and at the contact time. The nonlinear forms of the Langmuir and Freundlich isotherm models were used to fit the experimental data. Additionally, the adsorption of NH3 was studied using nonlinear pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich kinetic model. Based on the total volume of pores of used volcanic tuff, the NH3 was removed from the air both due to the physical adsorption of NH3 gas and the ion exchange of NH4+ (resulted from a reaction between NH3 and H2O adsorbed by the zeolite). Depending on the initial NH3 concentration and the amount of volcanic tuff, the NH3 concentrations can be reduced below the threshold of this contaminant in the air. The adsorption capacity of NH3 per unit of zeolite (1 g) varied in the range of 0.022–0.282 mg NH3 g−1 depending on the NH3 concentration in the air. 相似文献
84.
Hosu Oana Barsan Madalina M. Cristea Cecilia Săndulescu Robert Brett Christopher M. A. 《Mikrochimica acta》2017,184(10):3919-3927
Microchimica Acta - The redox polymer poly(methylene blue) was synthesized by electropolymerization in ethaline deep eutectic solvent (PMBDES), and employed in a new nanostructured composite... 相似文献
85.
86.
Maria-Alexandra Hoaghia Oana Cadar Gheorghe-Gavrila Hognogi Erika Levei Corina Moisa Cecilia Roman 《Analytical letters》2019,52(8):1268-1281
The quality and potential health risk of drinking waters in Medias, a town near a former non-ferrous ore smelter in Romania, was assessed using the drinking water quality index (DWQI), hazard quotient (HQ) and total hazard quotient (THQ). A total of 29 water samples collected from 26 wells and 3 springs used as drinking water sources, located in near proximity to agricultural, industrial or household contamination sources, were characterized. The obtained results indicated high NO2?, NO3?, Cd and Mn levels that exceeded the corresponding maximum allowable concentrations. According to the DWQI values, only 10% of water sources have acceptable quality, while 21% are threatened, and 69% have poor- quality. The health risk assessment suggested a high risk for NO3? for more than 72% of the drinking waters HQNO3??>?1.0 but no risk for metals and NO2? (HQmetals< 1.0; HQNO2?< 1.0). 相似文献
87.
Pavel F. Vlad Alexandru G. Ciocarlan Calin Deleanu Oana Costan Yurii A. Simonov Janusz Lipkowski Aede de Groot 《Tetrahedron》2006,62(36):8489-8497
Valuable chiral drimanic dienic synthons have been prepared by a photolytic Norrish type II degradation of the corresponding 14,15-bisnorlabdene-13-ones. Minor by-products with unexpected bi- and tricyclic structures were formed and some of them were isolated and identified. 相似文献
88.
Oana Carp Luminita Patron G. Pascu Ioana Mindru N. Stanica 《Journal of Thermal Analysis and Calorimetry》2006,84(2):391-394
Nickel–zinc ferrites have been synthesized via thermal decomposition of polynuclear coordination compounds containing as ligand the anion of malic acid, namely (NH4)[Fe2NixZn1–x(C4H4O5)(OH)3]·nH2O (x =0.25, 0.5 and 0.75, n=3 and 5). A comparison between the thermal behaviour of the studied polynuclear coordination compounds is inferred. Fe2NixZn1–xO4 (n=0.25, 0.5 and 0.75) ferrites with mean particle sizes of 65–85 Å and free from other phases are formed after a heating treatment of only one hour at 500°C. 相似文献
89.
Lars Winther Christensen Oana Veliche 《Proceedings of the American Mathematical Society》2008,136(2):479-487
Let be a commutative noetherian ring with a dualizing complex. By recent work of Iyengar and Krause (2006), the difference between the category of acyclic complexes and its subcategory of totally acyclic complexes measures how far is from being Gorenstein. In particular, is Gorenstein if and only if every acyclic complex is totally acyclic.
In this note we exhibit a specific acyclic complex with the property that it is totally acyclic if and only if is Gorenstein.
90.
Alexandru C. Razus Liviu Birzan Oana Zaharia Cristian Enache 《Journal of heterocyclic chemistry》2008,45(4):1139-1147