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排序方式: 共有554条查询结果,搜索用时 718 毫秒
31.
Adina L. Ghirişan Simion Drǎgan Alexandru Pop Marinela Simihǎian Vasile Miclǎuş 《加拿大化工杂志》2007,85(6):900-905
The influence of the apatite on the efficiency of neutralization and on heavy metal removal of acid mine waste water has been studied. The analysis of the treated waste water samples with apatite has shown an advanced purification, the concentration of the heavy metals after the treatment of the waste water with apatite being 25 to 1000 times less than the Maximum Concentration Limits admitted by European Norms (NTPA 001/2005). In order to establish the macro‐kinetic mechanism in the neutralization process, the activation energy, Ea, and the kinetic parameters, rate coefficient of reaction, kr, and kt were determined from the experimental results obtained in “ceramic ball‐mill” reactor. The obtained values of the activation energy Ea >> 42 kJ mol?1 (e.g. Ea = 115.50 ± 7.50 kJ mol?1 for a conversion of sulphuric acid ηH2SO4 = 0.05, Ea = 60.90 ± 9.50 kJ mol?1 for η H2SO4 = 0.10 and Ea = 55.75 ± 10.45 kJ mol‐1 for η H2SO4 = 0.15) suggest that up to a conversion of H2SO4 equal 0.15 the global process is controlled by the transformation process, adsorption followed by reaction, which means surface‐controlled reactions. At a conversion of sulphuric acid η H2SO4 > 0.15, the obtained values of activation energy Ea < 42 kJ mol‐1 (e.g. Ea = 37.55 ± 4.05 kJ mol‐1 for η H2SO4 = 0.2, Ea = 37.54 ± 2.54 kJ mol‐1 for η H2SO4 = 0.3 and Ea = 37.44 ± 2.90 kJ mol‐1 for η H2SO4 = 0.4) indicate diffusion‐controlled processes. This means a combined process model, which involves the transfer in the liquid phase followed by the chemical reaction at the surface of the solid. Kinetic parameters as rate coefficient of reaction, kr with values ranging from (5.02 ± 1.62) 10‐4 to (8.00 ± 1.55) 10‐4 (s‐1) and transfer coefficient, kt, ranging from (8.40 ± 0.50) 10‐5 to (10.42 ± 0.65) 10‐5 (m s‐1) were determined. 相似文献
32.
Gabriela Huminic Alexandru Vrdaru Angel Huminic Claudiu Fleac Florian Dumitrache Ion Morjan 《International journal of molecular sciences》2022,23(6)
In the current paper, a new hybrid nanofluid based on graphene oxide sheets and silicon nanoparticles is proposed for thermal applications. GO sheets and Si nanoparticles with different mixture ratios are dispersed in distilled water. Dynamic viscosity is measured at temperatures within the range 20–50 °C and the values are compared to the results available in the literature. The results indicated that the viscosity increases with increasing the mixture ratio of graphene oxide. A new correlation for the dynamic viscosity based on the experimental findings is proposed. Finally, the criteria for the performance of new hybrid nanofluid for thermal applications are analyzed. 相似文献
33.
Corneliu Hamciuc Elena Hamciuc Diana Serbezeanu Tachita Vlad‐Bubulac Maria Cazacu 《Polymer International》2011,60(2):312-321
New phosphorus‐containing poly(ester‐imide)‐polydimethylsiloxane copolymers were prepared by solution polycondensation of 1,4‐[2‐(6‐oxido‐6H‐dibenz < c,e > < 1, 2 > oxaphosphorin‐6‐yl)]naphthalene‐bis(trimellitate) dianhydride with a mixture of an aromatic diamine (1,3‐bis(4‐aminophenoxy)benzene) and α,ω‐bis(3‐aminopropyl)oligodimethylsiloxane of controlled molecular weight, in various ratios. Poly(amic acid) intermediates were converted quantitatively to the corresponding polyimide structures using a solution imidization procedure. The polymers are easily soluble in polar organic solvents, such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylformamide, as well as in less polar solvents such as tetrahydrofuran. They show good thermal stability, the decomposition temperature being above 370 °C. The glass transition temperatures are in the range 165–216 °C. Solutions of the polymers in N‐methyl‐2‐pyrrolidone exhibit photoluminescence in the blue region. Copyright © 2010 Society of Chemical Industry 相似文献
34.
Nanofiltration membranes have been developed by interfacial polymerization using base PES ultrafiltration membranes. By varying the concentration of the reactive monomers present as well as the reaction conditions, the structure of the polymerized barrier layer has been modified. Here, the ability to concentrate low molecular weight sugars while allowing dissolved ionic liquids in aqueous solution to be recovered in the permeate has been investigated for application in biomass hydrolysis. The results obtained here indicate that the selectivity for 1-butyl-3-methylimidazoliumchloride (BmimCl) over glucose can be as high as 36.6. The membrane permeance was 2.31 L m?2 h?1 bar?1. 相似文献
35.
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37.
Glutamate receptors play a major role in neural cell plasticity, growth, and maturation. The degree to which ionotropic glutamate
receptors (iGluR) conduct current is dependent on binding of extracellular ligands, of which glutamate is the native agonist.
Although the glutamate binding site of the GluR2 class of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) iGluR
has been structurally characterized, the allosteric sites attributed to neurosteroid binding have yet to be localized. Here,
using intrinsic tryptophan fluorescence spectroscopy, we show that the extracellular glutamate binding core of the GluR2 class
of AMPA receptors also binds to two neurosteroids, pregnenolone sulfate (PS) and 3α-hydroxy-5β-pregnan-20-one sulfate, both
of which negatively modulate its activity. Interest in these sulfated neurosteroids stems from their differential modulation
of other members of the iGluR family and their potential use as endogeneous agents for stroke therapy. In particular, whereas
PS inhibits AMPA and other non-N-methyl-d-aspartate (NMDA) family members, it activates the NMDA receptor. In addition to providing evidence for binding of these neurosteroids
to the glutamate binding core of the GluR2 class of AMPA receptors, our data suggests that both neurosteroids bind in a similar
manner, consistent with their modulation of activity of this class of iGluR. Interestingly, the conformational change induced
upon binding of these neurosteroids is distinct from that induced upon glutamate binding. 相似文献
38.
39.
The paper presents the properties of WO3 films considering the possibility to build a photoelectrochemical cell (PECC) for hydrogen production. The photocurrent response of the PECC containing WO3/TCO as photoanode and Pt as cathode was analysed. The morphology, crystalline structure and electrical aspects were investigated. Tungsten trioxide (WO3) thin film with porous morphology and high crystallinity was obtained using the spray pyrolysis deposition technique. 相似文献
40.
Alexandru Agapie Mircea Agapie Gheorghita Zbaganu 《International journal of systems science》2013,44(3):502-512
From a global viewpoint, evolutionary algorithms (EAs) working on continuous search-spaces can be regarded as homogeneous Markov chains (MCs) with discrete time and continuous state. We analyse from this viewpoint the (1?+?1)EA on the inclined plane fitness landscape, and derive a closed-form expression for the probability of occupancy of an arbitrary target zone, at an arbitrary iteration of the EA. For the hitting-time of an arbitrary target zone, we provide lower and upper bounds, as well as an asymptotic limit. Discretization leads to an MC with discrete time, whose simple structure is exploited to carry out efficient numerical investigations of the theoretical results obtained. The numerical results thoroughly confirm the theoretical ones, and also suggest various conjectures which go beyond the theory. 相似文献