64,156 research outputs found
Spin Effects in High Energy Fragmentation Processes
Recent measurements, in particular those on polarization and spin
alignment of vector mesons in annihilation at LEP, and those on the
azimuthal asymmetry at HERA, have attracted much attention on the spin effects
in high energy fragmentation processes. In this talk, we make a brief
introduction to the different topics studied in this connection and a short
summary of the available data. After that, we present a short summary of the
main theoretical results that we obtained in studying these different topics.
The talk was mainly based on the publications [5-9] which have been finished in
collaboration with C.Boros, Liu Chun-xiu and Xu Qing-hua.Comment: Plenary talk given at the 3rd Circum-Pan-Pacifc Symposium on High
Energy Spin Physics, October 2001, 8 pages, 4 figure
Liquid rocket combustor computer code development
The Advanced Rocket Injector/Combustor Code (ARICC) that has been developed to model the complete chemical/fluid/thermal processes occurring inside rocket combustion chambers are highlighted. The code, derived from the CONCHAS-SPRAY code originally developed at Los Alamos National Laboratory incorporates powerful features such as the ability to model complex injector combustion chamber geometries, Lagrangian tracking of droplets, full chemical equilibrium and kinetic reactions for multiple species, a fractional volume of fluid (VOF) description of liquid jet injection in addition to the gaseous phase fluid dynamics, and turbulent mass, energy, and momentum transport. Atomization and droplet dynamic models from earlier generation codes are transplated into the present code. Currently, ARICC is specialized for liquid oxygen/hydrogen propellants, although other fuel/oxidizer pairs can be easily substituted
Emission model of gamma-ray bursts
The emission mechanisms of cosmic gamma-ray bursts are reviewed. In particular, the thermal synchrotron model is discussed as the most viable mechanism for the majority of the continuum emission. Within this framework various information about the source region can be extracted. The picture that emerges is that of a hot (kT = .2 - 1.0 sq mc), thin sheet of dense pair-dominated plasma emitting via cyclo-synchrotron radiation in a strong magnetic field (B approximately one-hundred billion to one trillion gauss). Speculations on the origin and structure of this sheet are attempted. The problem of high-energy photons above pair production threshold escaping from the source is also considered
Soft gamma rays from black holes versus neutron stars
The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard x ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The soft gamma ray spectral data is reviewed of black holes and neutron stars, radiation, and particle energization mechanisms and potentially distinguishing gamma ray signatures. These may include soft x ray excesses versus deficiencies, thermal versus nonthermal processes, transient gamma ray bumps versus power law tails, lines, and periodicities. Some of the highest priority future observations are outlines which will shed much light on such systems
Controllable Persistent Atom Current of Bose-Einstein Condensates in an Optical Lattice Ring
In this paper the macroscopic quantum states of Bose-Einstein condensates in
optical lattices is studied by solving the periodic Gross-Pitaevskii equation
in one-dimensional geometry. It is shown that an exact solution seen to be a
travelling wave of excited macroscopic quantum states resultes in a persistent
atom current which can be controlled by adjusting of the barrier height of the
optical periodic potential. A critical condition to generate the travelling
wave is demonstrated and we moreover propose a practical experiment to realize
the persistent atom current in a toroidal atom waveguide.Comment: 9 pages, 1 figure
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Building multi-layer social knowledge maps with google maps API
Google Maps is an intuitive online-map service which changes people's way of navigation on Geo-maps. People can explore the maps in a multi-layer fashion in order to avoid information overloading. This paper reports an innovative approach to extend the "power" of Google Maps to adaptive learning. We have designed and implemented a navigator for multi-layer social knowledge maps, namely ProgressiveZoom, with Google Maps API. In our demonstration, the knowledge maps are built from the Interactive System Design (ISD) course at the School of Information Science, University of Pittsburgh. Students can read the textbooks and reflect their individual and social learning progress in a context of pedagogical hierarchical structure
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