1,722 research outputs found
Pengaruh Variasi Ukuran Partikel Marmer Statuari Terhadap Sifat Mekanik Komposit Partikel Marmer Statuari
Manufacture a composite material with a matrix resin epoxy and marble statuary powder as filler is one industry-utilization of waste. Mechanical properties of the composite material is influenced by the particle size of the particles. variations in particle size would form different mechanical properties. This research was conducted to investigate the effect variations in particle size on the mechanical properties of the composite particles. In this research variation in particle size marble statuary used is 60 mesh, 100 mesh, 140 mesh and 200 mesh. Resin used is epoxy resin, and composition of the volume ratio between the matrix and the particles used in research was 80%: 20%. The method is used in the manufacture of composite hand lay-up method. Tests performed in this research is XRD testing on solid marble, bending strength, hardness, and SEM. XRD results obtained from the testing phase identified in the marble statuary are Ca2O5Si , CaCO3, CaO, SiO2 , MgO , MgCO3 , and SiC. Hardness value of composite particles of marble is 22.3 to 48.33 HB, and flexural strength values of composite particles of marble statuary is from 13.89 to 38.89 N/mm . Particle size is good for filler in the composite is 140 mesh particles. Marble composite particles 140 mesh particle size has a flexural strength and hardness highest, because SEM photograph composite of 140 mesh particle distribution in the matrix evenly, and there is a good bond between the matrix and particles of marble statuary
An Observational Determination of the Proton to Electron Mass Ratio in the Early Universe
In an effort to resolve the discrepancy between two measurements of the
fundamental constant mu, the proton to electron mass ratio, at early times in
the universe we reanalyze the same data used in the earlier studies. Our
analysis of the molecular hydrogen absorption lines in archival VLT/UVES
spectra of the damped Lyman alpha systems in the QSOs Q0347-383 and Q0405-443
yields a combined measurement of a (Delta mu)/mu value of (-7 +/- 8) x 10^{-6},
consistent with no change in the value of mu over a time span of 11.5
gigayears. Here we define (Delta mu) as (mu_z - mu_0) where mu_z is the value
of mu at a redshift of z and mu_0 is the present day value. Our null result is
consistent with the recent measurements of King et al. 2009, (Delta mu)/u =
(2.6 +/- 3.0) x 10^{-6}, and inconsistent with the positive detection of a
change in mu by Reinhold et al. 2006. Both of the previous studies and this
study are based on the same data but with differing analysis methods.
Improvements in the wavelength calibration over the UVES pipeline calibration
is a key element in both of the null results. This leads to the conclusion that
the fundamental constant mu is unchanged to an accuracy of 10^{-5} over the
last 80% of the age of the universe, well into the matter dominated epoch. This
limit provides constraints on models of dark energy that invoke rolling scalar
fields and also limits the parameter space of Super Symmetric or string theory
models of physics. New instruments, both planned and under construction, will
provide opportunities to greatly improve the accuracy of these measurements.Comment: Accepted for publication in the Astrophysical Journa
Experimental investigation of elastic mode control on a model of a transport aircraft
A 4.5 percent DC-10 derivative flexible model with active controls is fabricated, developed, and tested to investigate the ability to suppress flutter and reduce gust loads with active controlled surfaces. The model is analyzed and tested in both semispan and complete model configuration. Analytical methods are refined and control laws are developed and successfully tested on both versions of the model. A 15 to 25 percent increase in flutter speed due to the active system is demonstrated. The capability of an active control system to significantly reduce wing bending moments due to turbulence is demonstrated. Good correlation is obtained between test and analytical prediction
Magnetic field symmetry of pump currents of adiabatically driven mesoscopic structures
We examine the scattering properties of a slowly and periodically driven
mesoscopic sample using the Floquet function approach. One might expect that at
sufficiently low driving frequencies it is only the frozen scattering matrix
which is important. The frozen scattering matrix reflects the properties of the
sample at a given instant of time. Indeed many aspects of adiabatic scattering
can be described in terms of the frozen scattering matrix. However, we
demonstrate that the Floquet scattering matrix, to first order in the driving
frequency, is determined by an additional matrix which reflects the fact that
the scatterer is time-dependent. This low frequency irreducible part of the
Floquet matrix has symmetry properties with respect to time and/or a magnetic
field direction reversal opposite to that of the frozen scattering matrix. We
investigate the quantum rectification properties of a pump which additionally
is subject to an external dc voltage. We split the dc current flowing through
the pump into several parts with well defined properties with respect to a
magnetic field and/or an applied voltage inversion.Comment: 13 pages, 4 figure
Time independent description of rapidly oscillating potentials
The classical and quantum dynamics in a high frequency field are found to be
described by an effective time independent Hamiltonian. It is calculated in a
systematic expansion in the inverse of the frequency () to order
. The work is an extension of the classical result for the Kapitza
pendulum, which was calculated in the past to order . The analysis
makes use of an implementation of the method of separation of time scales and
of a quantum gauge transformation in the framework of Floquet theory. The
effective time independent Hamiltonian enables one to explore the dynamics in
presence of rapidly oscillating fields, in the framework of theories that were
developed for systems with time independent Hamiltonians. The results are
relevant, in particular, for exploration of the dynamics of cold atoms.Comment: 4 pages, 1 figure. Revised versio
Lifetime of d-holes at Cu surfaces: Theory and experiment
We have investigated the hole dynamics at copper surfaces by high-resolution
angle-resolved photoemission experiments and many-body quasiparticle GW
calculations. Large deviations from a free-electron-like picture are observed
both in the magnitude and the energy dependence of the lifetimes, with a clear
indication that holes exhibit longer lifetimes than electrons with the same
excitation energy. Our calculations show that the small overlap of d- and
sp-states below the Fermi level is responsible for the observed enhancement.
Although there is qualitative good agreement of our theoretical predictions and
the measured lifetimes, there still exist some discrepancies pointing to the
need of a better description of the actual band structure of the solid.Comment: 15 pages, 7 figures, 1 table, to appear in Phys. Rev.
Phase diffusion as a model for coherent suppression of tunneling in the presence of noise
We study the stabilization of coherent suppression of tunneling in a driven
double-well system subject to random periodic function ``kicks''. We
model dissipation due to this stochastic process as a phase diffusion process
for an effective two-level system and derive a corresponding set of Bloch
equations with phase damping terms that agree with the periodically kicked
system at discrete times. We demonstrate that the ability of noise to localize
the system on either side of the double-well potenital arises from overdamping
of the phase of oscillation and not from any cooperative effect between the
noise and the driving field. The model is investigated with a square wave
drive, which has qualitatively similar features to the widely studied
cosinusoidal drive, but has the additional advantage of allowing one to derive
exact analytic expressions.Comment: 17 pages, 4 figures, submitted to Phys. Rev.
Time evolution of the Rabi Hamiltonian from the unexcited vacuum
The Rabi Hamiltonian describes a single mode of electromagnetic radiation
interacting with a two-level atom. Using the coupled cluster method, we
investigate the time evolution of this system from an initially empty field
mode and an unexcited atom. We give results for the atomic inversion and field
occupation, and find that the virtual processes cause the field to be squeezed.
No anti-bunching occurs.Comment: 25 pages, 8 figures, RevTe
Energetic and spatial bonding properties from angular distributions of ultraviolet photoelectrons: application to the GaAs(110) surface
Angle-resolved ultraviolet photoemission spectra are interpreted by combining
the energetics and spatial properties of the contributing states. One-step
calculations are in excellent agreement with new azimuthal experimental data
for GaAs(110). Strong variations caused by the dispersion of the surface bands
permit an accurate mapping of the electronic structure. The delocalization of
the valence states is discussed analogous to photoelectron diffraction. The
spatial origin of the electrons is determined, and found to be strongly energy
dependent, with uv excitation probing the bonding region.Comment: 5 pages, 3 figures, submitted for publicatio
Quasienergy Spectroscopy of Excitons
We theoretically study nonlinear optics of excitons under intense THz
irradiation. In particular, the linear near infrared absorption and resonantly
enhanced nonlinear sideband generation are described. We predict a rich
structure in the spectra which can be interpreted in terms of the quasienergy
spectrum of the exciton, via a remarkably transparent expression for the
susceptibility, and show that the effects of strongly avoided quasienergy
crossings manifest themselves directly, both in the absorption and transmitted
sidebands.Comment: 4 pages RevTex, 3 eps figs included, as publishe
- …