5,244 research outputs found
The role of water in slip casting
Slips and casting are considered in terms of physical and colloidal chemistry. Casting slips are polydisperse suspensions of lyophobic particles in water, whose degree of coagulation is controlled by interaction of flocculating and deflocculating agents. Slip casting rate and viscosity are functions of temperature. Slip rheology and response to deflocculating agents varies significantly as the kinds and amounts of colloid modifiers change. Water is considered as a raw material. Various concepts of water/clay interactions and structures are discussed. Casting is a de-watering operation in which water moves from slip to cast to mold in response to a potential energy termed moisture stress. Drying is an evaporative process from a free water surface
Laser phase noise effects on the dynamics of optomechanical resonators
We investigate theoretically the influence of laser phase noise on the
cooling and heating of a generic cavity optomechanical system. We derive the
back-action damping and heating rates and the mechanical frequency shift of the
radiation pressure-driven oscillating mirror, and derive the minimum phonon
occupation number for small laser linewidths. We find that in practice laser
phase noise does not pose serious limitations to ground state cooling. We then
consider the effects of laser phase noise in a parametric cavity driving scheme
that minimizes the back-action heating of one of the quadratures of the
mechanical oscillator motion. Laser linewidths narrow compared to the decay
rate of the cavity field will not pose any problems in an experimental setting,
but broader linewidths limit the practicality of this back-action evasion
method.Comment: 9 pages, 7 figure
Tunable Transient Decay Times in Nonlinear Systems: Application to Magnetic Precession
The dynamical motion of the magnetization plays a key role in the properties
of magnetic materials. If the magnetization is initially away from the
equilibrium direction in a magnetic nanoparticle, it will precess at a natural
frequency and, with some damping present, will decay to the equilibrium
position in a short lifetime. Here we investigate a simple but important
situation where a magnetic nanoparticle is driven non-resonantly by an
oscillating magnetic field, not at the natural frequency. We find a surprising
result that the lifetime of the transient motion is strongly tunable, by
factors of over 10,000, by varying the amplitude of the driving field.Comment: EPL Preprin
Laser gas-discharge absorption measurements of the ratio of two transition rates in argon
The ratio of two line strengths at 922.7 nm and 978.7 nm of argon is measured
in an argon pulsed discharge with the use of a single-mode Ti:Sapphire laser.
The result 3.29(0.13) is in agreement with our theoretical prediction 3.23 and
with a less accurate ratio 2.89(0.43) from the NIST database.Comment: 5 pages, 2 figures, 1 tabl
States on pseudo effect algebras and integrals
We show that every state on an interval pseudo effect algebra satisfying
some kind of the Riesz Decomposition Properties (RDP) is an integral through a
regular Borel probability measure defined on the Borel -algebra of a
Choquet simplex . In particular, if satisfies the strongest type of
(RDP), the representing Borel probability measure can be uniquely chosen to
have its support in the set of the extreme points of $K.
Growth-Quality Evaluation of Black Walnut Wood. Part II-Color Analyses of Veneer Produced on Different Sites
Heartwood color is an important wood quality parameter in the grading of black walnut veneer. One of the primary factors that causes a reduction in veneer grade is variability in heartwood color. This variability may be in the form of streaked heartwood or in coloration not of a uniform light chocolate brown nature. Black walnut trees from four distinctly different sites were selected to describe wood color of commercially prepared veneer sheets, using standard color measurement techniques, so that within-tree, between-tree, and between-site variations could be determined. Selected logs were sliced into veneer by a commercial process and the veneer was graded according to industrial standards. Reflectance data were obtained from selected veneer samples and these data were transformed into standard color parameters. Wide ranges in luminance and purity parameters were obtained. However, only the differences in luminance were detectable upon visual examination. This suggests that variability in luminance (i.e., darkness or lightness) is the primary cause of heartwood color variability. These analyses revealed statistically significant within-site differences in heartwood luminance, but within-tree differences were also observed. Between-site differences were considered less important than within-site differences
Walks of molecular motors in two and three dimensions
Molecular motors interacting with cytoskeletal filaments undergo peculiar
random walks consisting of alternating sequences of directed movements along
the filaments and diffusive motion in the surrounding solution. An ensemble of
motors is studied which interacts with a single filament in two and three
dimensions. The time evolution of the probability distribution for the bound
and unbound motors is determined analytically. The diffusion of the motors is
strongly enhanced parallel to the filament. The analytical expressions are in
excellent agreement with the results of Monte Carlo simulations.Comment: 7 pages, 2 figures, to be published in Europhys. Let
Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H
A model of the collisional kinetics of energetic hydrogen atoms, molecules,
and ions in pure H discharges is used to predict H emission
profiles and spatial distributions of emission from the cathode regions of
low-pressure, weakly-ionized discharges for comparison with a wide variety of
experiments. Positive and negative ion energy distributions are also predicted.
The model developed for spatially uniform electric fields and current densities
less than A/m is extended to non-uniform electric fields, current
densities of A/m, and electric field to gas density ratios MTd at 0.002 to 5 Torr pressure. (1 Td = V m and 1 Torr =
133 Pa) The observed far-wing Doppler broadening and spatial distribution of
the H emission is consistent with reactions among H, H,
H, and H ions, fast H atoms, and fast H molecules, and with
reflection, excitation, and attachment to fast H atoms at surfaces. The
H excitation and H formation occur principally by collisions of
fast H, fast H, and H with H. Simplifications include using a
one-dimensional geometry, a multi-beam transport model, and the average
cathode-fall electric field. The H emission is linear with current
density over eight orders of magnitude. The calculated ion energy distributions
agree satisfactorily with experiment for H and H, but are only in
qualitative agreement for H and H. The experiments successfully modeled
range from short-gap, parallel-plane glow discharges to beam-like,
electrostatic-confinement discharges.Comment: Submitted to Plasmas Sources Science and Technology 8/18/201
The Lattice and Simplex Structure of States on Pseudo Effect Algebras
We study states, measures, and signed measures on pseudo effect algebras with
some kind of the Riesz Decomposition Property, (RDP). We show that the set of
all Jordan signed measures is always an Abelian Dedekind complete -group.
Therefore, the state space of the pseudo effect algebra with (RDP) is either
empty or a nonempty Choquet simplex or even a Bauer simplex. This will allow
represent states on pseudo effect algebras by standard integrals
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