5,096 research outputs found
Use of a 2.3-GHz traveling-wave maser on the Usuda 64-meter antenna
A 2.3 GHz traveling-wave maser/closed-cycle refrigeration system was installed on the 64 m antenna at Usuda, Japan. This was done to evaluate the beam-waveguide antenna noise performance, and to support the International Cometary Explorer's (ICE's) comet flyby mission. System noise temperature at 2270 MHz was measured to be 15 K, including the maser noise contribution of 2.5 K. Maser installation and noise performance are described. The Usuda 64 m antenna is of high quality with a system operating noise temperature better than the DSN 64 m antennas
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Boundary interactions: Resolving interdisciplinary collaboration challenges using digitized embodied performances
Little is known about the collaborative learning processes of interdisciplinary teams designing technology-enabled immersive learning systems. In this conceptual paper, we reflect on the role of digitally captured embodied performances as boundary objects within our heterogeneous two-team collective of learning scientists and computer scientists as we design an embodied, animated virtual tutor embedded in a physically immersive mathematics learning system. Beyond just a communicative resource, we demonstrate how these digitized, embodied performances constitute a powerful mode for both inter- and intra-team learning and innovation. Our work illustrates the utility of mobilizing the material conditions of learning
Nucleon-nucleon potentials in phase-space representation
A phase-space representation of nuclear interactions, which depends on the
distance and relative momentum of the nucleons, is
presented. A method is developed that permits to extract the interaction
from antisymmetrized matrix elements given in a spherical
basis with angular momentum quantum numbers, either in momentum or coordinate
space representation. This representation visualizes in an intuitive way the
non-local behavior introduced by cutoffs in momentum space or renormalization
procedures that are used to adapt the interaction to low momentum many-body
Hilbert spaces, as done in the unitary correlation operator method or with the
similarity renormalization group. It allows to develop intuition about the
various interactions and illustrates how the softened interactions reduce the
short-range repulsion in favor of non-locality or momentum dependence while
keeping the scattering phase shifts invariant. It also reveals that these
effective interactions can have undesired complicated momentum dependencies at
momenta around and above the Fermi momentum. Properties, similarities and
differences of the phase-space representations of the Argonne and the N3LO
chiral potential, and their UCOM and SRG derivatives are discussed
From nucleon-nucleon interaction matrix elements in momentum space to an operator representation
Starting from the matrix elements of the nucleon-nucleon interaction in
momentum space we present a method to derive an operator representation with a
minimal set of operators that is required to provide an optimal description of
the partial waves with low angular momentum. As a first application we use this
method to obtain an operator representation for the Argonne potential
transformed by means of the unitary correlation operator method and discuss the
necessity of including momentum dependent operators. The resulting operator
representation leads to the same results as the original momentum space matrix
elements when applied to the two-nucleon system and various light nuclei. For
applications in fermionic and antisymmetrized molecular dynamics, where an
operator representation of a soft but realistic effective interaction is
indispensable, a simplified version using a reduced set of operators is given
Band gaps in the relaxed linear micromorphic continuum
In this note we show that the relaxed linear micromorphic model recently
proposed by the authors can be suitably used to describe the presence of
band-gaps in metamaterials with microstructures in which strong contrasts of
the mechanical properties are present (e.g. phononic crystals and lattice
structures). This relaxed micromorphic model only has 6 constitutive parameters
instead of 18 parameters needed in Mindlin- and Eringen-type classical
micromorphic models. We show that the onset of band-gaps is related to a unique
constitutive parameter, the Cosserat couple modulus which starts to
account for band-gaps when reaching a suitable threshold value. The limited
number of parameters of our model, as well as the specific effect of some of
them on wave propagation can be seen as an important step towards indirect
measurement campaigns
Research and development program on magnetic electrical conductor, electrical insulation, and bore seal materials - Electrical conductor and electrical insulation materials topical report
Electrical, mechanical, and thermo-physical properties of conductor and insulation materials for application to advanced space electric power system
Supply assurance in the nuclear fuel cycle
Errata sheet inserted.The economic, technical and political issues which bear on the
security of nuclear fuel supply internationally are addressed. The
structure of international markets for nuclear fuel is delineated; this
includes an analysis of the political constraints on fuel availability,
especially the connection to supplier nonproliferation policies. The
historical development of nuclear fuel assurance problems is explored and
an assessment is made of future trends in supply and demand and in the
political context in which fuel trade will take place in the future.
Finally, key events and policies which will affect future assurance are
identified.U.S. Dept. of Energy Contract no. 426365-S
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