排序方式: 共有40条查询结果,搜索用时 15 毫秒
11.
Characterization of fractionated asphaltenes by UV-vis and NMR self-diffusion spectroscopy 总被引:1,自引:0,他引:1
Ostlund JA Wattana P Nydén M Fogler HS 《Journal of colloid and interface science》2004,271(2):372-380
Asphaltenes have been fractionated by liquid/liquid extraction, yielding four subfractions. The characteristics of fractionated asphaltenes were studied with respect to solubility, aromaticity, heteroatom content, and diffusion behavior. It was observed that asphaltenes from the four subfractions showed variations in their tendency to flocculate and also distinct differences in aromaticity. Furthermore, NMR self-diffusion studies showed that the average diffusion coefficients varied for asphaltenes from the different subfractions. The results suggest a variation in average size and stability between asphaltenes, depending on what subfraction they belong to. The subfraction that consisted of asphaltenes with the largest average size and the highest aromaticity was also found to contain the asphaltenes that had the strongest tendency to flocculate. 相似文献
12.
Kumar A Escoffier W Poumirol JM Faugeras C Arovas DP Fogler MM Guinea F Roche S Goiran M Raquet B 《Physical review letters》2011,107(12):126806
By using high-magnetic fields (up to 60 T), we observe compelling evidence of the integer quantum Hall effect in trilayer graphene. The magnetotransport fingerprints are similar to those of the graphene monolayer, except for the absence of a plateau at a filling factor of ν=2. At a very low filling factor, the Hall resistance vanishes due to the presence of mixed electron and hole carriers induced by disorder. The measured Hall resistivity plateaus are well reproduced theoretically, using a self-consistent Hartree calculations of the Landau levels and assuming an ABC stacking order of the three layers. 相似文献
13.
M. M. Fogler A. Yu. Dobin B. I. Shklovskii 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
The quantum localization is known to be responsible for the deep conductivity minima of the quantum Hall effect. In this paper we calculate the localization length
as a function of magnetic field
at such minima for several models of disorder (“white-noise”, short-range, and long-range random potentials). We find that
with the exponent
between one and
, depending on the model. In particular, for the “white-noise” random potential
roughly coincides with the classical cyclotron radius. Our results are in agreement with available experimental data. 相似文献
14.
Acoustic irradiation can result in increased inter-phase mass and heat transfer rates. The second-order acoustic effects of cavitation, interfacial instability, radiation pressure and acoustic streaming are responsible for the enhancement in these rate processes. The application of sonic and ultrasonic energy in industrial processing is reviewed. A number of units using acoustic energy to enhance rates of conventional unit processes, for example, drying, solid-liquid extraction, etc, are described. In addition, new applications in waste water treatment and oil-water emulsion fuels are described. The development of newer, more efficient generators should lead to a greater use of acoustic energy for large-scale industrial processing. 相似文献
15.
16.
We investigate theoretically the effect of a finite electric field on the resistivity of a disordered one-dimensional system in the variable-range hopping regime. We find that at low fields the transport is inhibited by rare fluctuations in the random distribution of localized states that create high-resistance breaks in the hopping network. As the field increases, the breaks become less resistive. In strong fields the breaks are overrun and the electron distribution function is driven far from equilibrium. The logarithm of the resistance initially shows a simple exponential drop with the field, followed by a logarithmic dependence, and finally, by an inverse square-root law. 相似文献
17.
H Machner M Betigeri J Bojowald A Budzanowski A Chatterjee J Ernst L Freindl D Frekers W Garske K Grewer A Hamacher J Ilieva L Jarczyk K Kilian S Kliczewski W Klimala D Kolev T Kutsarova J Lieb H Machner A Magiera H Nann L Pentchev HS Plendl D Protić B Razen P Von Rossen BJ Roy R Siudak J Smyrski RV Srikantiah A Strzałkowski R Tsenov K Zwoll 《Pramana》2001,57(2-3):399-416
Total and differential cross sections for the reactions p + d → 3He + m
0 with m=π, η and p + d → 3H+π+ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon
resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations.
The aspect of isospin symmetry breaking is studied.
Representing the GEM Collaboration 相似文献
18.
Edge nanoscrolls are shown to strongly influence transport properties of suspended graphene in the quantum Hall regime. The relatively long arclength of the scrolls in combination with their compact transverse size results in formation of many nonchiral transport channels in the scrolls. They short circuit the bulk current paths and inhibit the observation of the quantized two-terminal resistance. Unlike competing theoretical proposals, this mechanism of disrupting the Hall quantization in suspended graphene is not caused by ill-chosen placement of the contacts, singular elastic strains, or a small sample size. 相似文献
19.
A long one-dimensional wire with a finite density of strong random impurities is modeled as a chain of weakly coupled quantum dots. At low temperature T and applied voltage V its resistance is limited by breaks: randomly occurring clusters of quantum dots with a special length distribution pattern that inhibit the transport. Because of the interplay of interaction and disorder effects the resistance can exhibit T and V dependences that can be approximated by power laws. The corresponding two exponents differ greatly from each other and depend not only on the intrinsic electronic parameters but also on the impurity distribution statistics. 相似文献
20.
We study the charge density distribution, the electric field profile, and the resistance of an electrostatically created lateral p-n junction in graphene. We show that the electric field at the interface of the electron and hole regions is strongly enhanced due to limited screening capacity of Dirac quasiparticles. Accordingly, the junction resistance is lower than estimated in previous literature. 相似文献