50,380 research outputs found
Debris Disk Radiative Transfer Simulation Tool (DDS)
A WWW interface for the simulation of spectral energy distributions of
optically thin dust configurations with an embedded radiative source is
presented. The density distribution, radiative source, and dust parameters can
be selected either from an internal database or defined by the user. This tool
is optimized for studying circumstellar debris disks where large grains are
expected to determine the far-infrared through millimeter dust reemission
spectral energy distribution. The tool is available at
http://aida28.mpia-hd.mpg.de/~swolf/ddsComment: Comp. Phys. Comm, 2005, in pres
Justifications in Constraint Handling Rules for Logical Retraction in Dynamic Algorithms
We present a straightforward source-to-source transformation that introduces
justifications for user-defined constraints into the CHR programming language.
Then a scheme of two rules suffices to allow for logical retraction (deletion,
removal) of constraints during computation. Without the need to recompute from
scratch, these rules remove not only the constraint but also undo all
consequences of the rule applications that involved the constraint. We prove a
confluence result concerning the rule scheme and show its correctness. When
algorithms are written in CHR, constraints represent both data and operations.
CHR is already incremental by nature, i.e. constraints can be added at runtime.
Logical retraction adds decrementality. Hence any algorithm written in CHR with
justifications will become fully dynamic. Operations can be undone and data can
be removed at any point in the computation without compromising the correctness
of the result. We present two classical examples of dynamic algorithms, written
in our prototype implementation of CHR with justifications that is available
online: maintaining the minimum of a changing set of numbers and shortest paths
in a graph whose edges change.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
Bose-Einstein Correlations in e+e- -> W+W- at a Linear Collider
We show that the most popular method to simulate Bose-Einstein (BE)
interference effects predicts negligible correlations between identical pions
originating from the hadronic decay of different W's produced in e+e- -> W+W-
-> 4 jets at typical linear collider energies.Comment: 5 pages, 2 eps figures, Proccedings of the Workshop "Physics Studies
for a Future Linear Collider", QCD Working Group, 2000, DESY 123
Correlation of normal and superconducting properties and unified approach to the description of high Tc oxides
We present a unified approach based on the Fermi liquid picture which allows us to describe the normal as well as the superconducting properties of the doped cuprates. The theory that is presented is for the doped compounds which are metallic. One can distinguish two interrelated, but nevertheless, different directions in the physics of high T(sub c): one involving the problem of carrier doping and the transition to the metallic state, and the second being the description of the metallic state. It is important that this metallic phase undergoes the transition into the superconducting state; as a result, our analysis is directly related to the origin of high T(sub c). We are using a quasi-2D Fermi liquid model to estimate the fundamental parameters of these very interesting materials. We find that this description is able to describe these materials and also that phonons and plasmons play a major role in the mechanism of high T(sub c)
Magnetic shielding and vacuum test for passive hydrogen masers
Vibration tests on high permeability magnetic shields used in the SAO-NRL Advanced Development Model (ADM) hydrogen maser were made. Magnetic shielding factors were measured before and after vibration. Preliminary results indicate considerable (25%) degradation. Test results on the NRL designed vacuum pumping station for the ADM hydrogen maser are also discussed. This system employs sintered zirconium carbon getter pumps to pump hydrogen plus small ion pumps to pump the inert gases. In situ activation tests and pumping characteristics indicate that the system can meet design specifications
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