61,984 research outputs found
Comments on the paper by D. G. Rea and B. T. O'Leary on the composition of the Venus clouds
Comments on ice particles as major scatterers of infrared radiation from Venus atmospher
Electric vehicle power train instrumentation: Some constraints and considerations
The application of pulse modulation control (choppers) to dc motors creates unique instrumentation problems. In particular, the high harmonic components contained in the current waveforms require frequency response accommodations not normally considered in dc instrumentation. In addition to current sensing, accurate power measurement requires not only adequate frequency response but must also address phase errors caused by the finite bandwidths and component characteristics involved. The implications of these problems are assessed
Screened electrostatic interactions between clay platelets
An effective pair potential for systems of uniformly charged lamellar
colloids in the presence of an electrolytic solution of microscopic co- and
counterions is derived. The charge distribution on the discs is expressed as a
collection of multipole moments, and the tensors which determine the
interactions between these multipoles are derived from a screened Coulomb
potential. Unlike previous studies of such systems, the interaction energy may
now be expressed for discs at arbitrary mutual orientation. The potential is
shown to be exactly equivalent to the use of linearized Poisson-Boltzmann
theory.Comment: 23 pages, 10 figures, created with Revtex. To appear in Molecular
Physic
Attraction between like-charged colloidal particles induced by a surface a density - functional analysis
We show that the first non-linear correction to the linearised
Poisson-Boltzman n (or DLVO) theory of effective pair interactions between
charge-stabilised, co lloidal particles near a charged wall leads to an
attractive component of entro pic origin. The position and depth of the
potential compare favourably with rec ent experimental measurementsComment: 12 pages including 2 figures. submitted to physical review letter
Non-linear Poisson-Boltzmann Theory for Swollen Clays
The non-linear Poisson-Boltzmann equation for a circular, uniformly charged
platelet, confined together with co- and counter-ions to a cylindrical cell, is
solved semi-analytically by transforming it into an integral equation and
solving the latter iteratively. This method proves efficient, robust, and can
be readily generalized to other problems based on cell models, treated within
non-linear Poisson-like theory. The solution to the PB equation is computed
over a wide range of physical conditions, and the resulting osmotic equation of
state is shown to be in fair agreement with recent experimental data for
Laponite clay suspensions, in the concentrated gel phase.Comment: 13 pages, 4 postscript figure
Wind tunnel measurements in the wake of a simple structure in a simulated atmospheric flow
Measurements of longitudinal mean velocity and turbulence intensity were made in the wake of a rectangular model building in a simulated atmospheric boundary-layer wind. The model building was a 1:50 scale model of a structure used in a wake measurement program at the George C. Marshall Space Flight Center 8-tower boundary-layer facility. The approach wind profile and measurement locations were chosen to match the field site conditions. The wakes of the building in winds from azimuths of 0 and 47 degrees referenced to the normal to the building long axis were examined. The effect of two lines of trees upwind of the building on the wake and the importance of the ratio of the building height to boundary-layer thickness on the extent of the wake were determined
Fundamental Gates for a Strongly Correlated Two-Electron Quantum Ring
We demonstrate that conditional as well as unconditional basic operations
which are prerequisite for universal quantum gates can be performed with almost
100% fidelity within a strongly interacting two-electron quantum ring. Both
sets of operations are based on a quantum control algorithm that optimizes a
driving electromagnetic pulse for a given quantum gate. The demonstrated
transitions occur on a time scale much shorter than typical decoherence times
of the system.Comment: 4 pages, 4 figures, copyright 2010 The American Physical Societ
Extensions of Lieb's concavity theorem
The operator function (A,B)\to\tr f(A,B)(K^*)K, defined on pairs of bounded
self-adjoint operators in the domain of a function f of two real variables, is
convex for every Hilbert Schmidt operator K, if and only if f is operator
convex. As a special case we obtain a new proof of Lieb's concavity theorem for
the function (A,B)\to\tr A^pK^*B^{q}K, where p and q are non-negative numbers
with sum p+q\le 1. In addition, we prove concavity of the operator function
(A,B)\to \tr(A(A+\mu_1)^{-1}K^* B(B+\mu_2)^{-1}K) on its natural domain
D_2(\mu_1,\mu_2), cf. Definition 4.1Comment: The format of one reference is changed such that CiteBase can
identify i
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