6,785 research outputs found
The thermodynamic properties of the wustite phase are studied
Study of the precise location of the wustite phase boundaries and the dependence of the partial pressure of oxygen on the temperature and composition of the solid phase was made. From the pressure of oxygen, the temperature and the composition thermodynamic quantities can be determined
Multiangle observations of Arctic clouds from FIRE ACE: June 3, 1998, case study
In May and June 1998 the Airborne Multiangle Imaging Spectroradiometer (AirMISR) participated in the FIRE Arctic Cloud Experiment (ACE). AirMISR is an airborne instrument for obtaining multiangle imagery similar to that of the satellite-borne MISR instrument. This paper presents a detailed analysis of the data collected on June 3, 1998. In particular, AirMISR radiance measurements are compared with measurements made by two other instruments, the Cloud Absorption Radiometer (CAR) and the MODIS airborne simulator (MAS), as well as to plane-parallel radiative transfer simulations. It is found that the AirMISR radiance measurements and albedo estimates compare favorably both with the other instruments and with the radiative transfer simulations. In addition to radiance and albedo, the multiangle AirMISR data can be used to obtain estimates of cloud top height using stereoimaging techniques. Comparison of AirMISR retrieved cloud top height (using the complete MISR-based stereoimaging approach) shows excellent agreement with the measurements from the airborne Cloud Lidar System (CLS) and ground-based millimeterwave cloud radar
Design approaches and materials processes for ultrahigh efficiency lattice mismatched multi-junction solar cells
In this study, we report synthesis of large area
(>2cm^2), crack-free GaAs and GaInP double
heterostructures grown in a multi-junction solar cell-like
structure by MOCVD. Initial solar cell data are also
reported for GaInP top cells. These samples were grown
on Ge/Si templates fabricated using wafer bonding and ion
implantation induced layer transfer techniques. The double
heterostructures exhibit radiative emission with uniform
intensity and wavelength in regions not containing
interfacial bubble defects. The minority carrier lifetime of
~1ns was estimated from photoluminescence decay
measurements in both double heterostructures.
We also report on the structural characteristics of
heterostructures, determined via atomic force microscopy
and transmission electron microscopy, and correlate these
characteristics to the spatial variation of the minority
carrier lifetime
Comparisons of downwelling radiation to model predictions based on groundbased measurements during FIRE 1991
Surface radiation measurements and simultaneous ground-based measurements of the atmosphere during the FIRE'91 cirrus field experiment provided an opportunity to identify crucial measurements and parameterization deficiencies in current cloud-radiation models. Comparisons between measured and calculated broadband surface fluxes with only a small data subset already reveal these needs: accurate humidity and aerosol vertical profiles for clear cases, accurate vertical extinction profiles and dimensions for clouds, and understanding of the (solar) scattering properties of cirrus
Dark Matter and Dark Radiation
We explore the feasibility and astrophysical consequences of a new long-range
U(1) gauge field ("dark electromagnetism") that couples only to dark matter,
not to the Standard Model. The dark matter consists of an equal number of
positive and negative charges under the new force, but annihilations are
suppressed if the dark matter mass is sufficiently high and the dark
fine-structure constant is sufficiently small. The correct relic
abundance can be obtained if the dark matter also couples to the conventional
weak interactions, and we verify that this is consistent with particle-physics
constraints. The primary limit on comes from the demand that the
dark matter be effectively collisionless in galactic dynamics, which implies
for TeV-scale dark matter. These values are
easily compatible with constraints from structure formation and primordial
nucleosynthesis. We raise the prospect of interesting new plasma effects in
dark matter dynamics, which remain to be explored.Comment: 14 pages, 6 figures Updated equations and figure
Beyond Outerplanarity
We study straight-line drawings of graphs where the vertices are placed in
convex position in the plane, i.e., convex drawings. We consider two families
of graph classes with nice convex drawings: outer -planar graphs, where each
edge is crossed by at most other edges; and, outer -quasi-planar graphs
where no edges can mutually cross. We show that the outer -planar graphs
are -degenerate, and consequently that every
outer -planar graph can be -colored, and this
bound is tight. We further show that every outer -planar graph has a
balanced separator of size . This implies that every outer -planar
graph has treewidth . For fixed , these small balanced separators
allow us to obtain a simple quasi-polynomial time algorithm to test whether a
given graph is outer -planar, i.e., none of these recognition problems are
NP-complete unless ETH fails. For the outer -quasi-planar graphs we prove
that, unlike other beyond-planar graph classes, every edge-maximal -vertex
outer -quasi planar graph has the same number of edges, namely . We also construct planar 3-trees that are not outer
-quasi-planar. Finally, we restrict outer -planar and outer
-quasi-planar drawings to \emph{closed} drawings, where the vertex sequence
on the boundary is a cycle in the graph. For each , we express closed outer
-planarity and \emph{closed outer -quasi-planarity} in extended monadic
second-order logic. Thus, closed outer -planarity is linear-time testable by
Courcelle's Theorem.Comment: Appears in the Proceedings of the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Edge Partitions of Optimal -plane and -plane Graphs
A topological graph is a graph drawn in the plane. A topological graph is
-plane, , if each edge is crossed at most times. We study the
problem of partitioning the edges of a -plane graph such that each partite
set forms a graph with a simpler structure. While this problem has been studied
for , we focus on optimal -plane and -plane graphs, which are
-plane and -plane graphs with maximum density. We prove the following
results. (i) It is not possible to partition the edges of a simple optimal
-plane graph into a -plane graph and a forest, while (ii) an edge
partition formed by a -plane graph and two plane forests always exists and
can be computed in linear time. (iii) We describe efficient algorithms to
partition the edges of a simple optimal -plane graph into a -plane graph
and a plane graph with maximum vertex degree , or with maximum vertex
degree if the optimal -plane graph is such that its crossing-free edges
form a graph with no separating triangles. (iv) We exhibit an infinite family
of simple optimal -plane graphs such that in any edge partition composed of
a -plane graph and a plane graph, the plane graph has maximum vertex degree
at least and the -plane graph has maximum vertex degree at least .
(v) We show that every optimal -plane graph whose crossing-free edges form a
biconnected graph can be decomposed, in linear time, into a -plane graph and
two plane forests
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