6,785 research outputs found

    The thermodynamic properties of the wustite phase are studied

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    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

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    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

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    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

    Open Government Data in Russia

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    Comparisons of downwelling radiation to model predictions based on groundbased measurements during FIRE 1991

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    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

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    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 α^\hat\alpha 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 α^\hat\alpha comes from the demand that the dark matter be effectively collisionless in galactic dynamics, which implies α^104\hat\alpha \lesssim 10^{-4} 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

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    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 kk-planar graphs, where each edge is crossed by at most kk other edges; and, outer kk-quasi-planar graphs where no kk edges can mutually cross. We show that the outer kk-planar graphs are (4k+1+1)(\lfloor\sqrt{4k+1}\rfloor+1)-degenerate, and consequently that every outer kk-planar graph can be (4k+1+2)(\lfloor\sqrt{4k+1}\rfloor+2)-colored, and this bound is tight. We further show that every outer kk-planar graph has a balanced separator of size O(k)O(k). This implies that every outer kk-planar graph has treewidth O(k)O(k). For fixed kk, these small balanced separators allow us to obtain a simple quasi-polynomial time algorithm to test whether a given graph is outer kk-planar, i.e., none of these recognition problems are NP-complete unless ETH fails. For the outer kk-quasi-planar graphs we prove that, unlike other beyond-planar graph classes, every edge-maximal nn-vertex outer kk-quasi planar graph has the same number of edges, namely 2(k1)n(2k12)2(k-1)n - \binom{2k-1}{2}. We also construct planar 3-trees that are not outer 33-quasi-planar. Finally, we restrict outer kk-planar and outer kk-quasi-planar drawings to \emph{closed} drawings, where the vertex sequence on the boundary is a cycle in the graph. For each kk, we express closed outer kk-planarity and \emph{closed outer kk-quasi-planarity} in extended monadic second-order logic. Thus, closed outer kk-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 22-plane and 33-plane Graphs

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    A topological graph is a graph drawn in the plane. A topological graph is kk-plane, k>0k>0, if each edge is crossed at most kk times. We study the problem of partitioning the edges of a kk-plane graph such that each partite set forms a graph with a simpler structure. While this problem has been studied for k=1k=1, we focus on optimal 22-plane and 33-plane graphs, which are 22-plane and 33-plane graphs with maximum density. We prove the following results. (i) It is not possible to partition the edges of a simple optimal 22-plane graph into a 11-plane graph and a forest, while (ii) an edge partition formed by a 11-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 22-plane graph into a 11-plane graph and a plane graph with maximum vertex degree 1212, or with maximum vertex degree 88 if the optimal 22-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 22-plane graphs such that in any edge partition composed of a 11-plane graph and a plane graph, the plane graph has maximum vertex degree at least 66 and the 11-plane graph has maximum vertex degree at least 1212. (v) We show that every optimal 33-plane graph whose crossing-free edges form a biconnected graph can be decomposed, in linear time, into a 22-plane graph and two plane forests
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