61,015 research outputs found
Geometric adjustment of the South American satellite densification (PC-1000) network
Reduced normal equations were computed from observation data and combined with reduced normal equations of other satellite networks to provide station coordinates from a single least square adjustment. Terrestrial data, which include base-lines, heights, and survey coordinates, provide the necessary relative position constraints between collocated stations of two satellite networks. Survey information regarding the observation stations is summarized, and constraints used in the solution are given. Geoidal undulations are computed by using the formula and constants shown
The OSU 275 system of satellite tracking station coordinates
A brief review of the methods and data used in the OSU 275 geodetic system is given along with the summary of the results. Survey information regarding the tracking stations in the system is given in tabular form along with the geodetic and geophysical parameters, origin and orientation, Cartisian coordinates, and systematic differences with global and nonglobal geodetic systems
Jamming of directed traffic on a square lattice
Phase transition from a free-flow phase to a jammed phase is an important
feature of traffic networks. We study this transition in the case of a simple
square lattice network for different values of data posting rate by
introducing a parameter which selects a neighbour for onward data transfer
depending on queued traffic. For every there is a critical value of
above which the system become jammed. The phase diagram shows some
interesting features. We also show that the average load diverges
logarithmically as approaches and the queue length distribution
exhibits exponential and algebraic nature in different regions of the phase
diagram.Comment: 12 pages, 9 figure
Magnetic fluxes and moduli stabilization
Stabilization of closed string moduli in toroidal orientifold
compactifications of type IIB string theory are studied using constant internal
magnetic fields on D-branes and 3-form fluxes that preserve N=1 supersymmetry
in four dimensions. Our analysis corrects and extends previous work by us, and
indicates that charged scalar VEV's need to be turned on, in addition to the
fluxes, in order to construct a consistent supersymmetric model. As an explicit
example, we first show the stabilization of all Kahler class and complex
structure moduli by turning on magnetic fluxes on different sets of D9-branes
that wrap the internal space T^6 in a compactified type I string theory, when a
charged scalar on one of these branes acquires a non-zero VEV. The latter can
also be determined by adding extra magnetized branes, as we demonstrate in a
subsequent example. In a different model with magnetized D7-branes, in a IIB
orientifold on T^6/Z_2, we show the stabilization of all the closed string
moduli, including the axion-dilaton at weak string coupling g_s, by turning on
appropriate closed string 3-form fluxes.Comment: v2: minor changes, added discussio
Moduli stabilization with open and closed string fluxes
We study the stabilization of all closed string moduli in the T^6/Z_2
orientifold, using constant internal magnetic fields and 3-form fluxes that
preserve N=1 supersymmetry in four dimensions. We first analyze the
stabilization of Kahler class and complex structure moduli by turning on
magnetic fluxes on different sets of D9 branes that wrap the internal space
T^6/Z_2. We present explicit consistent string constructions, satisfying in
particular tadpole cancellation, where the radii can take arbitrarily large
values by tuning the winding numbers appropriately. We then show that the
dilaton-axion modulus can also be fixed by turning on closed string constant
3-form fluxes, consistently with the supersymmetry preserved by the magnetic
fields, providing at the same time perturbative values for the string coupling.
Finally, several models are presented combining open string magnetic fields
that fix part of Kahler class and complex structure moduli, with closed string
3-form fluxes that stabilize the remaining ones together with the dilaton.Comment: 49 pages, a new model added, as well as improvements and reference
Identified Hadron Production from the RHIC Beam Energy Scan
A current focus at RHIC is the Beam Energy Scan to study the QCD phase
diagram -- temperature () vs. baryon chemical potential (). The
STAR experiment has collected data for Au+Au collisions at 7.7
GeV, 11.5 GeV, and 39 GeV in the year 2010. We present midrapidity results on
rapidity density, average transverse mass, and particle ratios for identified
hadrons from the STAR experiment. Collision dynamics are studied in the
framework of chemical and kinetic freeze-out conditions.Comment: 4 pages, 3 figures, to appear as proceedings of QM2011 conference at
Annecy, Franc
Free geometric adjustment of the SECOR Equatorial Network (Solution SECOR-27)
The basic purpose of this experiment is to compute reduced normal equations from the observational data of the SECOR Equatorial Network obtained from DMA/Topographic Center, D/Geodesy, Geosciences Div. Washington, D.C. These reduced normal equations are to be combined with reduced normal equations of other satellite networks of the National Geodetic Satellite Program to provide station coordinates from a single least square adjustment. An individual SECOR solution was also obtained and is presented in this report, using direction constraints computed from BC-4 optical data from stations collocated with SECOR stations. Due to the critical configuration present in the range observations, weighted height constraints were also applied in order to break the near coplanarity of the observing stations
Line asymmetry of solar p-modes: Reversal of asymmetry in intensity power spectra
The sense of line asymmetry of solar p-modes in the intensity power spectra
is observed to be opposite of that seen in the velocity power spectra.
Theoretical calculations provide a good understanding and fit to the observed
velocity power spectra whereas the reverse sense of asymmetry in the intensity
power spectrum has been poorly understood. We show that when turbulent eddies
arrive at the top of the convection zone they give rise to an observable
intensity fluctuation which is correlated with the oscillation they generate,
thereby affecting the shape of the line in the p-mode power spectra and
reversing the sense of asymmetry (this point was recognized by Nigam et al. and
Roxburgh & Vorontsov). The addition of the correlated noise displaces the
frequencies of peaks in the power spectrum. Depending on the amplitude of the
noise source the shift in the position of the peak can be substantially larger
than the frequency shift in the velocity power spectra. In neither case are the
peak frequencies precisely equal to the eigenfrequencies of p-modes. We suggest
two observations which can provide a test of the model discussed here.Comment: Revised version. To appear in Ap
Chip-integrated plasmonic cavity-enhanced single nitrogen-vacancy center emission
High temporal stability and spin dynamics of individual nitrogen-vacancy (NV)
centers in diamond crystals make them one of the most promising quantum
emitters operating at room temperature. We demonstrate a chip-integrated
cavity-coupled emission into propagating surface plasmon polariton (SPP) modes
narrowing NV center's broad emission bandwidth with enhanced coupling
efficiency. The cavity resonator consists of two distributed Bragg mirrors that
are built at opposite sides of the coupled NV emitter and are integrated with a
dielectric-loaded SPP waveguide (DLSPPW), using electron-beam lithography of
hydrogen silsesquioxane resist deposited on silver-coated silicon substrates. A
quality factor of ~ 70 for the cavity (full width at half maximum ~ 10 nm) with
full tunability of the resonance wavelength is demonstrated. An up to 42-fold
decay rate enhancement of the spontaneous emission at the cavity resonance is
achieved, indicating high DLSPPW mode confinement
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