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排序方式: 共有476条查询结果,搜索用时 15 毫秒
81.
Gheorghe Juncu Aurelian Nicola Constantin Popa Elena Stroila 《Numerical Heat Transfer, Part A: Applications》2013,63(11):1268-1296
In a series of two papers, we analyze the numerical performances of the preconditioned conjugate gradient algorithms (BICGSTAB and GMRES) and multigrid method in solving two-dimensional multicomponent mass transfer equations. The present test problems are steady-state, linear and nonlinear diffusion-reaction equations. The nonlinear algorithm used in connection with the preconditioned conjugate gradient methods is the modified Picard iteration. Theoretical results about the preconditioning are presented. The multigrid algorithm used is the Full Approximation Storage algorithm. The finite difference method was used to discretize the mathematical model equations. The numerical results obtained show good numerical performances. 相似文献
82.
Krapal AM Popa OP Iorgu EI Costache M Popa LO 《International journal of molecular sciences》2012,13(2):2515-2520
The invasive softshell clam (Mya arenaria Linnaeus, 1758) is native to the northwestern region of the Atlantic Ocean. This species has been introduced in the northeast Pacific and along the European coasts, due to intense naval transports and aquaculture, and it is now present in all the European seas. In this paper we describe seven new microsatellite loci for Mya arenaria. The isolated loci are polymorphic with a number of alleles per locus between 6 and 14. The observed and expected heterozygosities ranged from 0.417 to 0.951, and from 0.643 to 0.895, with an average of 0.716 and 0.775, respectively. These microsatellite markers should be useful in analyzing this species' genetic diversity, which could explain various processes of its invasion history. 相似文献
83.
M. Ciopec C.M. Davidescu A. Negrea I. Grozav L. Lupa P. Negrea A. Popa 《Chemical Engineering Research and Design》2012
The present paper investigates the adsorption of Cr(III) ions using the SIR, prepared by impregnation of Amberlite XAD7 with di-(2-ethylhexyl)-phosphoric acid (DEHPA), which has been chosen as an extractant for the purpose of this study. The Amberlite XAD7–DEHPA resin was impregnated with DEHPA and ethylic alcohol as solvent trough dynamic column impregnation method. The influence of different physicochemical parameters (pH, resin dosage, initial concentration of Cr(III) ions, contact time and temperature) upon the adsorption capacity of XAD7–DEHPA, in the Cr(III) ions removal process from aqueous solution, has been investigated. The pH for Cr(III) ions adsorption was found as 3.0 for this material. The results showed that the adsorption equilibrium was reached after 45 min. The adsorption process is best described by the pseudo-second order kinetic model. Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. The maximum adsorption capacity is ∼3 mg Cr(III) ions/g SIR. The thermodynamic studies allowed us to determine the thermodynamic parameters ΔG°, ΔH° and ΔS°. In this paper the factorial design of experiments was used to study the performance of the adsorption process. 相似文献
84.
Anne M. Itsuno Jamie D. Phillips Silviu Velicu 《Journal of Electronic Materials》2012,41(10):2886-2892
A unipolar mercury cadmium telluride (HgCdTe) NBνN infrared (IR) device architecture is analyzed by physics-based numerical device simulations. The device structure is predicted to suppress Shockley–Read–Hall (SRH) and Auger generation–recombination (G–R) processes, while also providing a simplified fabrication process by eliminating p-type doping requirements. The performance characteristics of mid- and long-wavelength infrared (MWIR: λ c?=?5?μm; LWIR: λ c?=?12?μm) NBνN devices are calculated and compared with those of nBn and double-layer planar heterostructure (DLPH) devices. Theoretical dark current density (J dark) values of the MWIR and LWIR NBνN devices are lower by an order of magnitude or more for temperatures between 50?K and 225?K. Calculated peak detectivity (D *) values of 6.01?× 1014?cm?Hz0.5/W to 2.36?×?1010?cm?Hz0.5/W for temperatures from 95?K to 225?K, and 2.37?×?1014?cm?Hz0.5/W to 2.27?×?1011?cm?Hz0.5/W for temperatures from 50?K to 95?K are observed for MWIR and LWIR NBνN structures, respectively. A component of the NBνN structure, embodied in a unipolar MWIR nBn device, is also fabricated to experimentally demonstrate selective carrier extraction. 相似文献
85.
Monica Popa Jose Maria Calderon Moreno Cora Vasilescu Silviu Iulian Drob Elena Ionela Neacsu Andrej Coer Julija Hmeljak Gregor Zerjav Ingrid Milošev 《Metallurgical and Materials Transactions A》2014,45(7):3130-3143
This article analyses the microstructure, electrochemical behavior, and biocompatibility of a novel Ti-20Nb-10Zr-5Ta alloy with low Young’s modulus (59 GPa) much closer to that of bone, between 10 and 30 GPa, than Ti and other Ti alloys used as implant biomaterial. XRD and SEM measurements revealed a near β crystalline microstructure containing β phase matrix and secondary α phase, with a typical grain size of around 200 μm. The corrosion behavior in neutral Ringer solution evidenced: self-passivation behavior characterizing a very resistant passive film; an easy passivation as a result of favorable influence of the alloying elements Nb, Zr, and Ta that participate with their passive oxides to the formation of the alloy passive film; low corrosion and ion release rates corresponding with very low toxicity. In MEM solution, the novel alloy demonstrated very high corrosion resistance and no susceptibility to localized corrosion. Biocompatibility was evaluated on in vitro human osteoblast-like and human immortalized pulmonary fibroblast cell (Wi-38) lines and the new Ti-20Nb-10Zr-5Ta alloy exhibited no cytotoxicity. The new Ti-20Nb-10Zr5Ta alloy is a promising material for implants due to combined properties of low elastic modulus, very low corrosion rate, and good biocompatibility. 相似文献
86.
Sorin Iorga Mihai Cojocaru Adriana Chivu Sorin Ciuca Mihail Burdusel Petre Badica Cédric Leuvrey Guy Schmerber Corinne Ulhaq-Bouillet Silviu Colis 《Metallurgical and Materials Transactions A》2014,45(7):3088-3096
We report on the changes on the microstructural, hardness, and corrosion properties induced by carbo-chromization of 316L stainless steel prepared by Spark Plasma Sintering technique. The thermo-chemical treatments have been performed using pack cementation. The carburizing and chromization were carried out between 1153 K (880 °C)/4 h to 1253 K (980 °C)/12 h and 1223 K (950 °C)/6 h to 1273 K (1000 °C)/12 h in a solid powder mixture of charcoal/BaCO3 and ferrochromium/alumina/NH4Cl, respectively. The obtained layers were investigated using X-ray and electron diffraction, optical and scanning electron microscopies, Vickers micro-hardness, and potentiodynamic measurements. The thickness of the carbo-chromized layer ranges between 300 and 500 μm. Besides the host γ-phase, the layers are mainly constituted of carbides (Fe7C3, Cr23C6, Cr7C3, and Fe3C) and traces of α′-martensite. The average hardness values decrease smoothly from 650 HV at the sample surface down to 200 HV at the center of the sample. The potentiodynamic tests revealed that the carbo-chromized samples have smaller corrosion resistance with respect to the untreated material. For strong chromization regimes, the corrosion rate is increased by a factor of four with respect to that of the untreated material, while the micro-hardness of the layer is three times larger. Such materials are suited to be used in environments where good corrosion resistance and wear properties are required. 相似文献
87.
Marcel Popa Nicu Bajan Marcel Ionel Popa Aura Angelica Popa 《Polymer-Plastics Technology and Engineering》2013,52(1):23-28
This paper presents a diffusional system consisting of tolazoline hydrochloride included into a carboxymethylcellulose based hydrogel, showing a high swelling capacity in water. The process kinetics of the drug inclusion into hydrogel as well as of the drug releasing have been studied. The tolazoline hydrochloride release was performed by elution with a simulated biological fluid within the digestive tract, at the small intestine level (pH = 8.2) where the drug is mostly absorbed. The results make evident a zero-order kinetics over the 30–400 min range, which would place the system among those with ‘sustained’ release, with obvious advantages compared with the classical drug administration. 相似文献
88.
Cong Tam Nguyen Nicolas Galanis Guillaume Polidori Stéphane Fohanno Catalin V. Popa Arnaud Le Bechec 《International Journal of Thermal Sciences》2009,48(2):401-411
An experimental investigation was performed to study the heat transfer performance of a 36 nm-Al2O3-particle–water nanofluid in a confined and submerged impinging jet on a flat, horizontal and circular heated surface. The tests were realized for the following ranges of the governing parameters: the nozzle diameter is 3 mm and the distance nozzle-to-heated-surface was set to 2, 5 and 10 mm; the flow Reynolds number varies from 3800 to 88 000, the Prandtl number from 5 to 10, and the particle volume fraction is ranging from 0 to 6%. Experimental data, obtained for both laminar and turbulent flow regimes, have clearly shown that, depending upon the combination of nozzle-to-heated surface distance and particle volume fraction, the use of a nanofluid can provide a heat transfer enhancement in some cases; conversely, for other combinations, an adverse effect on the convective heat transfer coefficient may occur. Within the experimental parameters used, it has been observed that highest surface heat transfer coefficients can be achieved using an intermediate nozzle-to-surface distance of 5 mm and a 2.8% particle volume fraction nanofluid. Nanofluids with high particle volume fractions, say 6% or higher, have been found not appropriate for the heat transfer enhancement purpose under the confined impinging jet configuration. On the other hand, for a very small and a large distance of nozzle-to-heated-surface, it has been observed that the nanofluid use does not provide a perceptible heat transfer enhancement and has, for some particular cases, produced a clear decrease of the convective heat transfer coefficient while compared to that obtained using distilled water. 相似文献
89.
Teodora Zecheru Traian Rotariu Edina Rusen Bogdan Mărculescu Florin Miculescu Laura Alexandrescu Iulian Antoniac Izabela-Cristina Stancu 《Journal of materials science. Materials in medicine》2010,21(10):2793-2804
In the present study polymeric microbeads of poly(2-hydroxyethyl methacrylate-co-dodecyl methacrylate-co-acrylic acid) or
p(HEMA-co-dDMA-co-AA) were synthesised and characterized through FT-IR and scanning electron microscopy (SEM); their swelling
behavior against saline solution was explored and their in vitro cytotoxicity was evaluated. Further, in order to elucidate
kinetic aspects regarding the ternary system p(HEMA-co-dDMA-co-AA), a mathematical model of the reactivity ratios of the comonomers
in the terpolymer has been conceived and analyzed. An intensified tendency of AA units accumulation in the copolymer has been
noticed, in spite of HEMA units, while dDMA conserves in the copolymer the fraction from the feed. Three compositions have
been selected for nafcillin-loading and their in vitro release capacity was evaluated. The compositions of 80:10:10 and 75:10:15 M
ratios appear suitable for further in vivo testing, in order to be used as drug delivery systems in the treatment of different
osseous diseases. 相似文献
90.