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131.
The coherent Hall effect denotes the transient Hall response of impulsively excited coherent charge-carrier wave packets in a solid. We report the first experimental study of this phenomenon (i) using a semiconductor superlattice in crossed electric and magnetic fields as a model for three-dimensional materials and (ii) employing a contactless optoelectronic technique to probe the transient currents. Two field regimes with distinctly different oscillatory wave packet dynamics are found, separated from each other by a transition region where all oscillations are suppressed. 相似文献
132.
Yuriy Makhlin Gerd Schn Alexander Shnirman 《Physica C: Superconductivity and its Applications》2001,350(3-4):161-165
Various physical systems were proposed for quantum information processing. Among those nanoscale devices appear most promising for integration in electronic circuits and large-scale applications. We discuss Josephson junction circuits in two regimes where they can be used for quantum computing. These systems combine intrinsic coherence of the superconducting state with control possibilities of single-charge circuits. In the regime where the typical charging energy dominates over the Josephson coupling, the low-temperature dynamics is limited to two states differing by a Cooper-pair charge on a superconducting island. In the opposite regime of prevailing Josephson energy, the phase (or flux) degree of freedom can be used to store and process quantum information. Under suitable conditions the system reduces to two states with different flux configurations. Several qubits can be joined together into a register. The quantum state of a qubit register can be manipulated by voltage and magnetic field pulses. The qubits are inevitably coupled to the environment. However, estimates of the phase coherence time show that many elementary quantum logic operations can be performed before the phase coherence is lost. In addition to manipulations, the final state of the qubits has to be read out. This quantum measurement process can be accomplished using a single-electron transistor for charge Josephson qubits, and a d.c.-SQUID for flux qubits. Recent successful experiments with superconducting qubits demonstrate for the first time quantum coherence in macroscopic systems. 相似文献
133.
Based upon the direct integration method, the technique for analysis of residual stresses in a thin rectangular plate consisting of two butt-welded plates is presented. The material of plate is assumed to be elastic-plastic. The welded joint is modeled by a locally distributed field of longitudinal and transversal residual strains. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
Using the transient hot wire and pulsed field gradient nuclear magnetic resonance methods we determined the thermal conductivity
and the solvent self-diffusion coefficient (SDC) in aqueous suspensions of quasi-monodisperse spherical silica nanoparticles.
The thermal conductivity was found to increase at higher volume fraction of nanoparticles in accordance with the effective
medium theory albeit with a smaller slope. On the other hand, the SDC was found to decrease with nanoparticle volume fraction
faster than predicted by the effective medium theory. These deviations can be explained by the presence of an interfacial
heat-transfer resistance and water retention by the nanoparticles, respectively. We found no evidence for anomalous enhancement
in the transport properties of nanofluids reported earlier by other groups. 相似文献
135.
136.
Sergey V. ZhuravskyMykola T. Kartel Yuriy O. TarasenkoSilvia Villar-Rodil Gábor DobosAjna Tóth Juan M.D. TascónKrisztina László 《Applied Surface Science》2012,258(7):2410-2415
N-containing synthetic carbons with narrow porosity were prepared from a chlorinated styrene and divinylbenzene copolymer by a multistep method with a yield of 34 wt%. Surface chemical treatment and thermal carbonization of the starting copolymer was monitored by urea impregnation. Steam activation, oxidation and an additional heat treatment gave the final product. The synthesis route was designed in a cost-effective way. The porosity and the concentration of the introduced nitrogen atoms were determined at each step. The final product has a surface area of 1135 m2/g. More than 70% of the pore volume comes from micropores with an average width of 0.7 nm. The 2.3 at.% surface nitrogen atoms are distributed among five detectable species, of which about 44% is quaternary nitrogen. 相似文献
137.
Vasyl Sklyarchuk Yuriy Plevachuk Rada Novakovic Ivan Kaban 《Monatshefte für Chemie / Chemical Monthly》2012,45(8):1249-1254
Abstract
Surface tension and density measurements of liquid Ag–Bi–Sn alloys were carried out over a wide temperature range using the sessile drop method. The experimental data of surface tension were analyzed by the Butler thermodynamic model in the regular solution approximation. The Sn-rich Ag–Bi–Sn liquid alloys show better wetting behavior on the Cu substrates as compared to the Ni substrates. 相似文献138.
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