11,362 research outputs found
Electromagnetic and physical properties of sea ice formed in the presence of wave action
Estimating the magnitude of brine flux to the upper ocean requires an ability to assess the dynamics of the formation of sea ice in a region. Brine storage and rate of expulsion is determined by the environmental conditions under which the sea ice forms. In this paper, the physical and electromagnetic properties of sea ice, formed under wave-agitated conditions, are studied and compared with results obtained from ice formed under quiescent conditions. Wave agitation is known to have a profound effect on the air-ice interface and internal ice structure. A variety of sensors, both active and passive, optical and microwave, were used to perform this characterization. Measured electromagnetic parameters included radar backscatter, microwave emission, and spectral albedo in the visible and infrared. Measured physical properties included ice structure, brine and temperature distribution, profiles of the vertical height of the air-ice interface, and ice formation processes. Results showed that emission, backscatter, and albedo all take different signature paths during the transformation from saline water to young sea ice and that the paths depend on sea surface state during ice formation
Technical background, chapter 3, part B
A description is given of the physics of electromagnetic scattering from the sea and a guideline is presented to relate an observable (such as the radar cross section) to the hydrodynamics or physical properties of the sea. As specific examples of the interdisciplinary science of electromagnetics and geophysical oceanography, the physics is discussed in connection with data provided by three instruments: namely, the scatterometer, the altimeter, and the imaging radar. The data provided by each instrument are discussed in context with specular point and Bragg scattering theories. Finally, the degrading effect of extraneous sources of noise is discussed as a limiting mechanism of the accuracy of the ocean surface measurement
NASA Thesaurus supplement: A four part cumulative supplement to the 1988 edition of the NASA Thesaurus (supplement 3)
The four-part cumulative supplement to the 1988 edition of the NASA Thesaurus includes the Hierarchical Listing (Part 1), Access Vocabulary (Part 2), Definitions (Part 3), and Changes (Part 4). The semiannual supplement gives complete hierarchies and accepted upper/lowercase forms for new terms
Broad spectral, interdisciplinary investigation of the electromagnetic properties of sea ice
Journal ArticleThis paper highlights the interrelationship of research completed by a team of investigators and presented in the several individual papers comprising this Special Section on the Office of Naval Research (ONR), Arlington, VA, Sponsored Sea Ice Electromagnetics Accelerated Research Initiative (ARI)
Half-filled Landau level, topological insulator surfaces, and three dimensional quantum spin liquids
We synthesize and partly review recent developments relating the physics of
the half-filled Landau level in two dimensions to correlated surface states of
topological insulators in three dimensions. The latter are in turn related to
the physics of certain three dimensional quantum spin liquid states. The
resulting insights provide an interesting answer to the old question of how
particle-hole symmetry is realized in composite fermion liquids. Specifically
the metallic state at filling - described originally in
pioneering work by Halperin , Lee, and Read as a liquid of composite fermions -
was proposed recently by Son to be described by a particle-hole symmetric
effective field theory distinct from that in the prior literature. We show how
the relation to topological insulator surface states leads to a physical
understanding of the correctness of this proposal. We develop a simple picture
of the particle-hole symmetric composite fermion through a modification of
older pictures as electrically neutral "dipolar" particles. We revisit the
phenomenology of composite fermi liquids (with or without particle-hole
symmetry), and show that their heat/electrical transport dramatically violates
the conventional Wiedemann-Franz law but satisfies a modified one. We also
discuss the implications of these insights for finding physical realizations of
correlated topological insulator surfaces.Comment: 22 pages, 7 figures; (v2) Added some clarifications and corrected
typo
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