2,779 research outputs found
Phase Transitions in a Dusty Plasma with Two Distinct Particle Sizes
In semiconductor manufacturing, contamination due to particulates
significantly decreases the yield and quality of device fabrication, therefore
increasing the cost of production. Dust particle clouds can be found in almost
all plasma processing environments including both plasma etching devices and in
plasma deposition processes. Dust particles suspended within such plasmas will
acquire an electric charge from collisions with free electrons in the plasma.
If the ratio of inter-particle potential energy to the average kinetic energy
is sufficient, the particles will form either a liquid structure with short
range ordering or a crystalline structure with long range ordering. Otherwise,
the dust particle system will remain in a gaseous state. Many experiments have
been conducted over the past decade on such colloidal plasmas to discover the
character of the systems formed, but more work is needed to fully understand
these structures. The preponderance of previous experiments used monodisperse
spheres to form complex plasma systems
Tensor correlations in the Unitary Correlation Operator Method
We present a unitary correlation operator that explicitly induces into shell
model type many-body states short ranged two-body correlations caused by the
strong repulsive core and the pronounced tensor part of the nucleon-nucleon
interaction. Alternatively an effective Hamiltonian can be defined by applying
this unitary correlator to the realistic nucleon-nucleon interaction.
The momentum space representation shows that realistic interactions which
differ in their short range behaviour are mapped on the same correlated
Hamiltonian, indicating a successful provision for the correlations at high
momenta. Calculations for He4 using the one- and two-body part of the
correlated Hamiltonian compare favorably with exact many-body methods. For
heavier nuclei like O16 and Ca40 where exact many-body calculations are not
possible we compare our results with other approximations. The correlated
single-particle momentum distributions describe the occupation of states above
the Fermi momentum. The Unitary Correlation Operator Method (UCOM) can be used
in mean-field and shell model configuration spaces that are not able to
describe these repulsive and tensor correlations explicitly.Comment: 73 pages, 65 figure
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To own or not to own: How ownership impacts user innovation-An empirical study
User innovation studies have mainly concentrated on markets in which users purchase products and,
thus, both own and control the acquired good. However, users also use products that they do not own, in
which case ownership and control are separated. Property rights theory predicts that the separation of
ownership and control is a user innovation barrier. When innovating, users need to accommodate an
additional actor: the owner. Separation of ownership and control thus induces uncertainty and
complexity in the user innovation process, increasing users' costs to innovate.
The results of hierarchical regression analyses of data from 743 German rowers show that separation
of ownership and control negatively impacts user innovativeness. Use experience positively moderates
this relationship with regard to idea generation, but negatively with regard to idea realization. To
remedy the negative impact, we propose approaches to manufacturers that employ co-creation-based
innovation strategies (e.g. grant back clauses in use contracts).This is the accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0166497214001588
Benchmarks of the full configuration interaction, Monte Carlo shell model, and no-core full configuration methods
We report no-core solutions for properties of light nuclei with three
different approaches in order to assess the accuracy and convergence rates of
each method. Full configuration interaction (FCI), Monte Carlo shell model
(MCSM) and no core full configuration (NCFC) approaches are solved separately
for the ground state energy and other properties of seven light nuclei using
the realistic JISP16 nucleon-nucleon interaction. The results are consistent
among the different approaches. The methods differ significantly in how the
required computational resources scale with increasing particle number for a
given accuracy.Comment: 19 pages, 14 figures, 6 table
Dusty Plasma Correlation Function Experiment
Dust particles immersed within a plasma environment, such as those in
protostellar clouds, planetary rings or cometary environments, will acquire an
electric charge. If the ratio of the inter-particle potential energy to the
average kinetic energy is high enough the particles will form either a "liquid"
structure with short-range ordering or a crystalline structure with long range
ordering. Many experiments have been conducted over the past several years on
such colloidal plasmas to discover the nature of the crystals formed, but more
work is needed to fully understand these complex colloidal systems. Most
previous experiments have employed monodisperse spheres to form Coulomb
crystals. However, in nature (as well as in most plasma processing
environments) the distribution of particle sizes is more randomized and
disperse. This paper reports experiments which were carried out in a GEC rf
reference cell modified for use as a dusty plasma system, using varying sizes
of particles to determine the manner in which the correlation function depends
upon the overall dust grain size distribution. (The correlation function
determines the overall crystalline structure of the lattice.) Two dimensional
plasma crystals were formed of assorted glass spheres with specific size
distributions in an argon plasma. Using various optical techniques, the pair
correlation function was determined and compared to those calculated
numerically.Comment: 6 pages, Presented at COSPAR '0
Microscopic shell-model description of the exotic nucleus ^{16}C
The structure of the neutron-rich carbon nucleus ^{16}C is described by
introducing a new microscopic shell model of no-core type. The model space is
composed of the 0s, 0p, 1s0d, and 1p0f shells. The effective interaction is
microscopically derived from the CD-Bonn potential and the Coulomb force
through a unitary transformation theory. Calculated low-lying energy levels of
^{16}C agree well with the experiment. The B(E2;2_{1}^{+} \to 0_{1}^{+}) value
is calculated with the bare charges. The anomalously hindered B(E2) value for
^{16}C, measured recently, is well reproduced.Comment: 14 pages, 4 figures, considerable results and discussion are added,
but the main conclusion is unchanged, accepted for publication in Phys. Lett.
Nuclear Structure based on Correlated Realistic Nucleon-Nucleon Potentials
We present a novel scheme for nuclear structure calculations based on
realistic nucleon-nucleon potentials. The essential ingredient is the explicit
treatment of the dominant interaction-induced correlations by means of the
Unitary Correlation Operator Method (UCOM). Short-range central and tensor
correlations are imprinted into simple, uncorrelated many-body states through a
state-independent unitary transformation. Applying the unitary transformation
to the realistic Hamiltonian leads to a correlated, low-momentum interaction,
well suited for all kinds of many-body models, e.g., Hartree-Fock or
shell-model. We employ the correlated interaction, supplemented by a
phenomenological correction to account for genuine three-body forces, in the
framework of variational calculations with antisymmetrised Gaussian trial
states (Fermionic Molecular Dynamics). Ground state properties of nuclei up to
mass numbers A<~60 are discussed. Binding energies, charge radii, and charge
distributions are in good agreement with experimental data. We perform angular
momentum projections of the intrinsically deformed variational states to
extract rotational spectra.Comment: 32 pages, 15 figure
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