8,814 research outputs found
Solar Energy Resource Potential in Alaska
Solar energy applications are receiving attention in Alaska as in
much of the rest of the country. Solar energy possibilities for Alaska
include domestic water heating, hot-water or hot-air collection for
space heating, and the use of passive solar heating in residential or
commercial buildings.
As a first analysis, this study concentrated on applying solar
energy to domestic hot-water heating needs (not space heating) in Alaska,
and an analysis of solar hot-water heating economics was performed using
the F-CHART solar energy simulation computer program. Results indicate
that solar energy cannot compete economically with oil-heated domestic
hot water at any of the five study locations in Alaska, but that it may
be economical in comparison with electrically heated hot water if solar
collector systems can be purchased and installed for 25 per
square foot.This work was made possible by a grant from the Solar Planning
Office, West, 3333 Quebec, Denver, Colorado. It was performed as the
Alaskan response to a western regional solar energy planning grant from
the U. S. Department of Energy.
The authors wish to acknowledge the support and cooperation of the
Alaska State Department of Commerce, Division of Energy and Power Development,
through whose efforts the grant was made available, especially
Clarissa Quinlan, Grant Peterson, and Don Markle
Can one identify non-equilibrium in a three-state system by analyzing two-state trajectories?
For a three-state Markov system in a stationary state, we discuss whether, on
the basis of data obtained from effective two-state (or on-off) trajectories,
it is possible to discriminate between an equilibrium state and a
non-equilibrium steady state. By calculating the full phase diagram we identify
a large region where such data will be consistent only with non-equilibrium
conditions. This regime is considerably larger than the region with oscillatory
relaxation, which has previously been identified as a sufficient criterion for
non-equilibrium.Comment: 4 pages, 2 figures, J. Chem. Phys. (2010) (in press
Nonequilibrium steady states in contact: Approximate thermodynamic structure and zero-th law for driven lattice gases
We explore driven lattice gases for the existence of an intensive
thermodynamic variable which could determine "equilibration" between two
nonequilibrium steady-state systems kept in weak contact. In simulations, we
find that these systems satisfy surprisingly simple thermodynamic laws, such as
the zero-th law and the fluctuation-response relation between the
particle-number fluctuation and the corresponding susceptibility remarkably
well. However at higher densities, small but observable deviations from these
laws occur due to nontrivial contact dynamics and the presence of long-range
spatial correlations.Comment: Revised, 4 pages, 5 figure
Profiling of fine and coarse particle mass : Case studies of Saharan dust and Eyjafjallajökull/Grimsvötn volcanic plumes
© Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 LicenseThe polarization lidar photometer networking (POLIPHON) method introduced to separate coarse-mode and fine-mode particle properties of Eyjafjallajokull volcanic aerosols in 2010 is extended to cover Saharan dust events as well. Furthermore, new volcanic dust observations performed after the Grimsvotn volcanic eruptions in 2011 are presented. The retrieval of particle mass concentrations requires mass-specific extinction coefficients. Therefore, a review of recently published mass-specific extinction coefficients for Saharan dust and volcanic dust is given. Case studies of four different scenarios corroborate the applicability of the profiling technique: (a) Saharan dust outbreak to central Europe, (b) Saharan dust plume mixed with biomass-burning smoke over Cape Verde, and volcanic aerosol layers originating from (c) the Eyjafjallajokull eruptions in 2010 and (d) the Grimsvotn eruptions in 2011. Strong differences in the vertical aerosol layering, aerosol mixing, and optical properties are observed for the different volcanic eventsPeer reviewe
Front Propagation in the Pearling Instability of Tubular Vesicles
Recently Bar-Ziv and Moses discovered a dynamical shape transformation
induced in cylindrical lipid bilayer vesicles by the action of laser tweezers.
We develop a hydrodynamic theory of fluid bilayers in interaction with the
surrounding water and argue that the effect of the laser is to induce a sudden
tension in the membrane. We refine our previous analysis to account for the
fact that the shape transformation is not uniform but propagates outward from
the laser trap. Applying the marginal stability criterion to this situation
gives us an improved prediction for the selected initial wavelength and a new
prediction for the propagation velocity, both in rough agreement with the
experimental values. For example, a tubule of initial radius 0.7\micron\ has a
predicted initial sinusoidal perturbation in its diameter with wavelength
5.5\micron, as observed. The perturbation propagates as a front with the
qualitatively correct front velocity a bit less than 100\micron/sec. In
particular we show why this velocity is initially constant, as observed, and so
much smaller than the natural scale set by the tension. We also predict that
the front velocity should increase linearly with laser power. Finally we
introduce an approximate hydrodynamic model applicable to the fully nonlinear
regime. This model exhibits propagating fronts as well as fully-developed
``pearled" vesicles similar to those seen in the experiments.Comment: 42 pages, 6 eps figures included with text in uuencoded file, ps file
available from ftp://dept.physics.upenn.edu/pub/Nelson/pearl_propagation.ps
submitted to Journal de Physiqu
Laser power stabilization for second-generation gravitational wave detectors
We present results on the power stabilization of a Nd:YAG laser in the frequency band from 1 Hz to 100 kHz. High-power, low-noise photodetectors are used in a dc-coupled control loop to achieve relative power fluctuations down to 5×10−9 Hz−1/2 at 10 Hz and 3.5×10−9 Hz−1/2 up to several kHz, which is very close to the shot-noise limit for 80 mA of detected photocurrent on each detector. We investigated and eliminated several noise sources such as ground loops and beam pointing. The achieved stability level is close to the requirements for the Advanced LIGO gravitational wave detector
Hydrodynamic lift on bound vesicles
Bound vesicles subject to lateral forces such as arising from shear flow are
investigated theoretically by combining a lubrication analysis of the bound
part with a scaling approach to the global motion. A minor inclination of the
bound part leads to significant lift due to the additive effects of lateral and
tank-treading motions. With increasing shear rate, the vesicle unbinds from the
substrate at a critical value. Estimates are in agreement with recent
experimental data.Comment: 9 pages, one figur
- …