摘要 :
Theoretical studies of the conductance of ferromagnetic and paramagnetic nanowires are performed within the framework of a three-dimensional s-d model. The attention is focused on spin-dependent conductance quantization, which man...
展开
Theoretical studies of the conductance of ferromagnetic and paramagnetic nanowires are performed within the framework of a three-dimensional s-d model. The attention is focused on spin-dependent conductance quantization, which manifests itself in a spectacular way when a circuit becomes open and the conduction goes down in discrete steps. A new approach is developed by assuming that in the last stages of the breaking of the nanocontact, there are fewer and fewer conduction paths, distributed at random and stretching across the contact region. Conductances are calculated within the quasiballistic regime, using the Kubo formula and a recursion Green's function technique. The results for weak ferromagnets (both majority and minority d bands intersect the Fermi surface) are qualitatively different from those for strong ferromagnets (only the minority d bands do), which may explain why experimental cumulative histograms of the conductance reveal more pronounced peaks in the case of Fe than for Ni, and consequently the latter are more sensitive to surface contaminations (oxidization). [References: 13]
收起
摘要 :
Conductance steps for atomic point contacts of An, Ni, and Pt have been measured. Jump-to-contact and jump-to-tunnel processes have been identified and their conductances measured. Differences between conductance steps for noble a...
展开
Conductance steps for atomic point contacts of An, Ni, and Pt have been measured. Jump-to-contact and jump-to-tunnel processes have been identified and their conductances measured. Differences between conductance steps for noble and transition metals are interpreted as being due to the d orbitals that, in transition metals, provide new channels to the electron conductance. This interpretation is supported by a theoretical analysis, which shows good agreement with the experimental data. [References: 25]
收起
摘要 :
We present measurements on conductance quantization in atomic scale metallic constrictions at room temperature. Conductance measurements as a function of constriction size reveal pronounced horizontal plateaus separated by sharp d...
展开
We present measurements on conductance quantization in atomic scale metallic constrictions at room temperature. Conductance measurements as a function of constriction size reveal pronounced horizontal plateaus separated by sharp discrete steps. Most individual conductance plateaus are close to integer multiples of the fundamental conductance unit but definite deviations are also present. After averaging over many contact configurations, conductance quantization is seen clearly and more prominently than in similar recent low temperature measurements on the same metals. [References: 16]
收起
摘要 :
Handling tire models like Pacejka (Tire and Vehicle Dynamics, 3rd edn., Elsevier, Amsterdam, 2012) or TMeasy (Rill in Proc. of the XV Int. Symp. on Dynamic Problems of Mechanics, Buzios, RJ, Brazil, 2013) consider the contact patc...
展开
Handling tire models like Pacejka (Tire and Vehicle Dynamics, 3rd edn., Elsevier, Amsterdam, 2012) or TMeasy (Rill in Proc. of the XV Int. Symp. on Dynamic Problems of Mechanics, Buzios, RJ, Brazil, 2013) consider the contact patch as one coherent plane. As a consequence, the irregularities of a rough road profile must be approximated by an appropriate local road plane that serves as an effective road plane in order to calculate the geometric contact point and the corresponding contact velocities. The Pacejka/SWIFT tire model employs a road enveloping model that generates the effective height and slope by elliptical cams. TMeasy just uses four representative road points for that purpose. In addition, TMeasy replaces the geometric contact point by the static contact point and shifts it finally to the dynamic contact point that represents the point where the contact forces are applied. In doing so, a rather sophisticated but still simple contact calculation is possible. Simulations obtained with a virtual tire test rig and fully nonlinear three-dimensional multibody system models of a motor-scooter and a passenger car demonstrate the potential of this contact approach.
收起
摘要 :
A model of the dynamics of a mechanical system that includes bodies whose contact is accompanied by the appearance of small relative displacement and brittle failure of their surfaces with the resultant appearance of an interlayer...
展开
A model of the dynamics of a mechanical system that includes bodies whose contact is accompanied by the appearance of small relative displacement and brittle failure of their surfaces with the resultant appearance of an interlayer of chipped off elements between the bodies is constructed. The variation of the potential energy of the system upon displacement of the bodies through interlayer elements is investigated. Cases in which the limit model obtained when the rate of the relative displacement of the bodies reaches a zero value differs from the classical non-holonomic model of the dynamics of the system are identified. Sufficient conditions, which enable evaluation of the error and the boundaries of the applicability of the limit model, are formulated. (C) 2017 (C) 2018 Elsevier Ltd. All rights reserved.
收起
摘要 :
A 'spreading resistance' contact between electrode and specimen can increase or even dominate the apparent bulk resistance of an electroceramic specimen. For true point contacts, a single arc will appear in impedance spectra, whos...
展开
A 'spreading resistance' contact between electrode and specimen can increase or even dominate the apparent bulk resistance of an electroceramic specimen. For true point contacts, a single arc will appear in impedance spectra, whose diameter is essentially the spreading resistance due to the contact and whose time constant is identical to that of the bulk, but with a correspondingly smaller capacitance. When a planar electrode with multiple point contacts is involved, a separate electrode arc occurs whose diameter is due to spreading resistance, but whose capacitance tends to be dominated by the 'air gap' capacitance between the electrode and the rough surface of the ceramic. In this study impedance spectroscopy was employed to study the effects of temperature, oxygen partial pressure, and mechanical loading on the contact impedance of gold electrodes on nanophase cerium dioxide. Results were confirmed by pixel-based computer simulations.
收起
摘要 :
Research methods based on recording parameters of electrical conductivity are considered for future application in nanotribology. Design relationships of conductivity are presented for idealized models of interface under condition...
展开
Research methods based on recording parameters of electrical conductivity are considered for future application in nanotribology. Design relationships of conductivity are presented for idealized models of interface under conditions of boundary lubrication; contributions of various conductivity types in the total contact conductivity are estimated. An application methodology is. described for the methods to study the properties of boundary lubricating layers. Some of the results obtained from the study of strength and frictional properties of boundary lubricating nanometre layers under normal load and sliding conditions are discussed.
收起
摘要 :
MS — Bruce, could tell us about mentors who were important to you.BG - I have had a number of mentors who were quite important. I would say the heroic figure in my field was definitely Bertram Brockhouse, and I had the pleasure o...
展开
MS — Bruce, could tell us about mentors who were important to you.BG - I have had a number of mentors who were quite important. I would say the heroic figure in my field was definitely Bertram Brockhouse, and I had the pleasure of knowing him just before he retired. I started as a grad student in 1981 and he retired in 1984. I really only had one significant point of contact with him, which was actually not long before he won the Nobel Prize. So it would have been in the early 1990's when I co-authored a review chapter for the Encyclopedia of Physics with him and that was a great experience. That presented me with an opportunity to work with him off and on for the better part of six months to write this relatively short article. It gave me some insight into the way he thought about things, and he definitely thought about things differently than is typical for an experimentalist in my field. So that was a great experience.
收起
摘要 :
Point contacts (PC) Andreev reflection dV/dI spectra for the antiferromagnetic (T-N similar or equal to 6K) superconductor (T-c similar or equal to 11 K) ErNi2B2C have been measured for the two main crystallographic directions. Th...
展开
Point contacts (PC) Andreev reflection dV/dI spectra for the antiferromagnetic (T-N similar or equal to 6K) superconductor (T-c similar or equal to 11 K) ErNi2B2C have been measured for the two main crystallographic directions. The observed retention of the Andreev reflection minima in dV/dI up to T-c directly points to an unusual superconducting order parameter (OP) vanishing at T-c. The temperature dependence of the OP was obtained from dV/dI using the recent theory of Andreev reflection including the pair-breaking effect. For the first time the existence of two superconducting OPs in ErNi2B2C is shown. A distinct decrease of both OPs as temperature is lowered below T-N is observed. Copyright (C) EPLA, 2008.
收起
摘要 :
We report on the Study of the modification of crystalline electric field (CEF) energy scheme of van Vleck paramagnet PrNi5 when Cc-ions are substituting Pr-ions, using point-contact (PC) spectroscopy. The intensity of the main CEF...
展开
We report on the Study of the modification of crystalline electric field (CEF) energy scheme of van Vleck paramagnet PrNi5 when Cc-ions are substituting Pr-ions, using point-contact (PC) spectroscopy. The intensity of the main CEF peak at 4 meV in PrNi5 is decreasing, its position is shifted to higher energy with increasing Ce content, and it disappears only for x = 1 while the peak at similar to 2.5 meV connected with spin fluctuations disappears for I = 0.8, (C) 2000 Elsevier Science B.V. All rights reserved. [References: 4]
收起
原文获取