28,095 research outputs found
Charge storage in nanotubes: the case of a 2-1 electrolyte
We consider a 2-1 electrolyte in contact with a narrow nanotube, which only
allows one-dimensional storage along the axis. The asymmetry does not allow an
a priori definition of the potential of zero charge; instead, the natural
reference is the electrode potential at which both ions have the same
electrochemical potential; the value of the latter can serve as a measure of
ionophilicity. Near this potential, ionophobic tubes are filled with a dilute
gas, ionophilic tubes are filled with a one-dimensional solid containing about
the same number of the divalent ions and the monovalent counterions, a
structure that is stabilized by a strong screening of the Coulomb interaction
by an induced counter charge on the walls of the tube. The filling of the tube
by the application of an electrode potential exhibits a complicated pattern of
interactions between the two kinds of ions.Comment: 7 pages, 6 figure
Circularly polarized microwaves for magnetic resonance study in the GHz range: application to nitrogen-vacancy in diamonds
The ability to create time-dependent magnetic fields of controlled
polarization is essential for many experiments with magnetic resonance. We
describe a microstrip circuit that allows us to generate strong magnetic field
at microwave frequencies with arbitrary adjusted polarization. The circuit
performance is demonstrated by applying it to an optically detected magnetic
resonance and Rabi nutation experiments in nitrogen-vacancy color centers in
diamond. Thanks to high efficiency of the proposed microstrip circuit and
degree of circular polarization of 85% it is possible to address the specific
spin states of a diamond sample using a low power microwave generator.Comment: 4 pages, 7 figures, nitrogen-vacancy, microwave circular
polarization, spin-state addressin
Economic Impacts of Aquatic Vegetation to Angling in Two South Carolina Reservoirs
Angler creel surveys and economic impact models were
used to evaluate potential expansion of aquatic vegetation in
Lakes Murray and Moultrie, South Carolina. (PDF contains 4 pages.
Influence of anisotropic ion shape, asymmetric valency, and electrolyte concentration on structural and thermodynamic properties of an electric double layer
Grand canonical Monte Carlo simulation results are reported for an electric
double layer modelled by a planar charged hard wall, anisotropic shape cations,
and spherical anions at different electrolyte concentrations and asymmetric
valencies. The cations consist of two tangentially tethered hard spheres of the
same diameter, . One sphere is charged while the other is neutral. Spherical
anions are charged hard spheres of diameter . The ion valency asymmetry 1:2
and 2:1 is considered, with the ions being immersed in a solvent mimicked by a
continuum dielectric medium at standard temperature. The simulations are
carried out for the following electrolyte concentrations: 0.1, 1.0 and 2.0 M.
Profiles of the electrode-ion, electrode-neutral sphere singlet distributions,
the average orientation of dimers, and the mean electrostatic potential are
calculated for a given electrode surface charge, , while the contact
electrode potential and the differential capacitance are presented for varying
electrode charge. With an increasing electrolyte concentration, the shape of
differential capacitance curve changes from that with a minimum surrounded by
maxima into that of a distorted single maximum. For a 2:1 electrolyte, the
maximum is located at a small negative value while for 1:2, at a small
positive value.Comment: 10 pages, 6 figure
Double layer for hard spheres with an off-center charge
Simulations for the density and potential profiles of the ions in the planar
electrical double layer of a model electrolyte or an ionic liquid are reported.
The ions of a real electrolyte or an ionic liquid are usually not spheres; in
ionic liquids, the cations are molecular ions. In the past, this asymmetry has
been modelled by considering spheres that are asymmetric in size and/or valence
(viz., the primitive model) or by dimer cations that are formed by tangentially
touching spheres. In this paper we consider spherical ions that are asymmetric
in size and mimic the asymmetrical shape through an off-center charge that is
located away from the center of the cation spheres, while the anion charge is
at the center of anion spheres. The various singlet density and potential
profiles are compared to (i) the dimer situation, that is, the constituent
spheres of the dimer cation are tangentially tethered, and (ii) the standard
primitive model. The results reveal the double layer structure to be
substantially impacted especially when the cation is the counterion. As well as
being of intrinsic interest, this off-center charge model may be useful for
theories that consider spherical models and introduce the off-center charge as
a perturbation.Comment: 11 pages, 7 figure
The effect of operations on the ground noise footprints associated with a large multibladed, nonbanging helicopter
In order to expand the data base of helicopter external noise characteristics, a flyover noise measurement program was conducted utilizing the NASA Civil Helicopter Research Aircraft. The remotely operated multiple array acoustics range (ROMAAR) and a 2560-m linear microphone array were utilized for the purpose of documenting the noise characteristics of the test helicopter during flyby and landing operations. By utilizing both ROMAAR concept and the linear array, the data necessary to plot the ground noise footprints and noise radiation patterns were obtained. Examples of the measured noise signature of the test helicopter, the ground noise footprint or contours, and the directivity patterns measured during level flyby and landing operations of a large, multibladed, nonbanging helicopter, the CH-53, are presented
Modification of Coulomb's law in closed spaces
We obtain a modified version of Coulomb's law in two- and three-dimensional
closed spaces. We demonstrate that in a closed space the total electric charge
must be zero. We also discuss the relation between total charge neutrality of a
isotropic and homogenous universe to whether or not its spatial sector is
closed.Comment: 11 pages, 3 figure
A research program to reduce interior noise in general aviation airplanes. Design of an acoustic panel test facility
The design, construction, and costs of a test facility for determining the sound transmission loss characteristics of various panels and panel treatments are described. The pressurization system and electronic equipment used in experimental testing are discussed as well as the reliability of the facility and the data gathered. Tests results are compared to pertinent acoustical theories for panel behavior and minor anomalies in the data are examined. A method for predicting panel behavior in the stiffness region is also presented
Design evolution of the orbiter reaction control subsystem
The challenges of space shuttle orbiter reaction control subsystem development began with selection of the propellant for the subsystem. Various concepts were evaluated before the current Earth storable, bipropellant combination was selected. Once that task was accomplished, additional challenges of designing the system to satisfy the wide range of requirements dictated by operating environments, reusability, and long life were met. Verification of system adequacy was achieved by means of a combination of analysis and test. The studies, the design efforts, and the test and analysis techniques employed in meeting the challenges are described
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