27,988 research outputs found
Propagation of ultrahigh-energy neutrinos through the Earth
The dispersion relation in matter of ultrahigh-energy neutrinos above the
pole of the resonance (E_{\nu} \gsim {\rm 10}^{7} {\rm GeV} ), is
studied. We perform our calculation using the real-time formulation of Thermal
Field Theory in which the massless limit for the boson is taken. The range
of active-to-sterile neutrino oscillation parameters for which there is
significant mixing enhancement during propagation through the interior of the
Earth, and therefore significant attenuation of neutrino beams in the Earth at
high energies, is estimated. Finally, this range is considered in view of the
cosmological and astrophysical constraints.Comment: 8 pages, some comments and references added, to appear in Phys. Lett.
A user guide for the EMTAC-MZ CFD code
The computer code (EMTAC-MZ) was applied to investigate the flow field over a variety of very complex three-dimensional (3-D) configurations across the Mach number range (subsonic, transonic, supersonic, and hypersonic flow). In the code, a finite volume, multizone implementation of high accuracy, total variation diminishing (TVD) formulation (based on Roe's scheme) is used to solve the unsteady Euler equations. In the supersonic regions of the flow, an infinitely large time step and a space-marching scheme is employed. A finite time step and a relaxation or 3-D approximate factorization method is used in subsonic flow regions. The multizone technique allows very complicated configurations to be modeled without geometry modifications, and can easily handle combined internal and external flow problems. An elliptic grid generation package is built into the EMTAC-MZ code. To generate the computational grid, only the surface geometry data are required. Results obtained for a variety of configurations, such as fighter-like configurations (F-14, AVSTOL), flow through inlet, multi-bodies (shuttle with external tank and SRBs), are reported and shown to be in good agreement with available experimental data
Cryogenic combustion laboratory
The objective is to establish a major experimental laboratory for studying fundamental processes such as mixing and combustion under liquid rocket engine conditions. The capability of this laboratory will include operation using a variety of fuel and oxidizer systems including liquid oxygen and liquid hydrocarbons. In addition to providing the proper facilities for supplying and controlling these fuels and oxidizers, a specific effort is being made to provide a state-of-the-art diagnostic capability for combustion measurements. In particular, optical and laser-based techniques are being emphasized for measurements of species, velocities, and spray characteristics
Monthly mean forecast experiments with the GISS model
The GISS general circulation model was used to compute global monthly mean forecasts for January 1973, 1974, and 1975 from initial conditions on the first day of each month and constant sea surface temperatures. Forecasts were evaluated in terms of global and hemispheric energetics, zonally averaged meridional and vertical profiles, forecast error statistics, and monthly mean synoptic fields. Although it generated a realistic mean meridional structure, the model did not adequately reproduce the observed interannual variations in the large scale monthly mean energetics and zonally averaged circulation. The monthly mean sea level pressure field was not predicted satisfactorily, but annual changes in the Icelandic low were simulated. The impact of temporal sea surface temperature variations on the forecasts was investigated by comparing two parallel forecasts for January 1974, one using climatological ocean temperatures and the other observed daily ocean temperatures. The use of daily updated sea surface temperatures produced no discernible beneficial effect
Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues
Using the triangular matrix techniques of Kuo et al and Chiu et al for the
four and five texture zero cases, with vanishing (11) elements for U and D
matrices, it is shown, from the general eigenvalue equations and hierarchy
conditions, that the quark mass matrices, and the CKM matrix can be expressed
(except for the phases) entirely in terms of quark masses. The matrix
structures are then quite simple and transparent. We confirm their results for
the five texture zero case but find, upon closer examination of all the CKM
elements which our results provide, that six of their nine patterns for the
four texture zero case are not compatible with experiments. In total, only one
five-texture zero and three four-texture zero patterns are allowed.Comment: 15 pages, 3 table
Low-momentum interactions with Brown-Rho-Ericson scalings and the density dependence of the nuclear symmetry energy
We have calculated the nuclear symmetry energy up to
densities of with the effects from the Brown-Rho (BR) and
Ericson scalings for the in-medium mesons included. Using the
low-momentum interaction with and without such scalings, the equations of state
(EOS) of symmetric and asymmetric nuclear matter have been calculated using a
ring-diagarm formalism where the particle-particle-hole-hole ring diagrams are
included to all orders. The EOS for symmetric nuclear matter and neutron matter
obtained with linear BR scaling are both overly stiff compared with the
empirical constraints of Danielewicz {\it et al.} \cite{daniel02}. In contrast,
satisfactory results are obtained by either using the nonlinear Ericson scaling
or by adding a Skyrme-type three-nucleon force (TNF) to the unscaled
interaction.
Our results for obtained with the nonlinear Ericson scaling
are in good agreement with the empirical values of Tsang {\it et al.}
\cite{tsang09} and Li {\it et al.} \cite{li05}, while those with TNF are
slightly below these values. For densities below the nuclear saturation density
, the results of the above calculations are nearly equivalent to each
other and all in satisfactory agreement with the empirical values.Comment: 7 pages, 6 figure
Laboratory requirements for in-situ and remote sensing of suspended material
Recommendations for laboratory and in-situ measurements required for remote sensing of suspended material are presented. This study investigates the properties of the suspended materials, factors influencing the upwelling radiance, and the various types of remote sensing techniques. Calibration and correlation procedures are given to obtain the accuracy necessary to quantify the suspended materials by remote sensing. In addition, the report presents a survey of the national need for sediment data, the agencies that deal with and require the data of suspended sediment, and a summary of some recent findings of sediment measurements
Laboratory requirements for in-situ and remote sensing of suspended material
Recommendations for laboratory and in-situ measurements required for remote sensing of suspended material are presented. This study investigates the properties of the suspended materials, factors influencing the upwelling radiance, and the various types of remote sensing techniques. Calibration and correlation procedures are given to obtain the accuracy necessary to quantify the suspended materials by remote sensing. In addition, the report presents a survey of the national need for sediment data, the agencies that deal with and require the data of suspended sediment, and a summary of some recent findings of sediment measurements
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