114,285 research outputs found
Pulse Profiles, Spectra and Polarization Characteristics of Non-Thermal Emissions from the Crab-Like Pulsars
We discuss non-thermal emission mechanism of the Crab-like pulsars with both
a two-dimensional electrodynamical study and a three-dimensional model. We
investigate the emission process in the outer gap accelerator. In the
two-dimensional electrodynamical study, we solve the Poisson equation of the
accelerating electric field in the outer gap and the equation of motion of the
primary particles with the synchrotron and the curvature radiation process and
the pair-creation process. We show a solved gap structure which produces a
consistent gamma-ray spectrum with EGRET observation. Based on the
two-dimensional model, we conduct a three-dimensional emission model to
calculate the synchrotron and the inverse-Compton processes of the secondary
pairs produced outside the outer gap. We calculate the pulse profiles, the
phase-resolved spectra and the polarization characteristics in optical to
-ray bands to compare the observation of the Crab pulsar and PSR
B0540-69. For the Crab pulsar, we find that the outer gap geometry extending
from near the stellar surface to near the light cylinder produces a complex
morphology change of the pulse profiles as a function of the photon energy.
This predicted morphology change is quite similar with that of the
observations. The calculated phase-resolved spectra are consistent with the
data through optical to the -ray bands. We demonstrate that the
1020 % of the polarization degree in the optical emissions from the Crab
pulsar and the Vela pulsar are explained by the synchrotron emissions with the
particle gyration motion.Comment: 39 pages, 11 figures, Accepted for publication in Ap
A Study of the LEP and SLD Measurements of
A systematic study is made of the data dependence of the parameter
, that, since 1995, has shown a deviation from the Standard Model
prediction of between 2.4 and 3.1 standard deviations. Issues addressed
include: the effect of particular measurements, values found by individual
experiments, LEP/SLD comparison, and the treatment of systematic errors. The
effect, currently at the 2.4 level, is found to vary in the range from
1.7 to 2.9 by excluding marginal or particularly sensitive
data. Since essentially the full LEP and SLD Z decay data sets are now analysed
the meaning of the deviation, (new physics, or marginal statistical
fluctuation) is unlikely to be given by the present generation of colliders.Comment: 15 pages 7 figures 7 table
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The Approach of Complex Insert Packaging Fabrication in Stereolithography
The approach of complex insert packaging fabrication in stereolithography is studied in the
paper. There are many difficulties being overcome, such as the dispensing shadowing problem
caused by the geometric shape of insert, the polymer feeding problem caused by greater insert
height than the layer thickness, and the positioning problem of insert that leads to instability of
packaging. These drawbacks led to unsatisfactory results of the insert packaging in
stereolithography. In order to solve the problems, a new method of complex inserts
packaging fabrication in stereolithography is proposed in this paper. Based on the geometric
information, function and assembly direction of the inserts, the packaging approach is developed.
The approach proposed in this paper has been verified by experiments. It brings considerable
contributions to the application of insert packaging in stereolithography. It is also favorable to
the improvement of insert packaging efficiency and assembly fabricationMechanical Engineerin
Systolic VLSI for Kalman filters
A novel two-dimensional parallel computing method for real-time Kalman filtering is presented. The mathematical formulation of a Kalman filter algorithm is rearranged to be the type of Faddeev algorithm for generalizing signal processing. The data flow mapping from the Faddeev algorithm to a two-dimensional concurrent computing structure is developed. The architecture of the resulting processor cells is regular, simple, expandable, and therefore naturally suitable for VLSI chip implementation. The computing methodology and the two-dimensional systolic arrays are useful for Kalman filter applications as well as other matrix/vector based algebraic computations
Fitting Precision Electroweak Data with Exotic Heavy Quarks
The 1999 precision electroweak data from LEP and SLC persist in showing some
slight discrepancies from the assumed standard model, mostly regarding and
quarks. We show how their mixing with exotic heavy quarks could result in a
more consistent fit of all the data, including two unconventional
interpretations of the top quark.Comment: 7 pages, no figure, 2 typos corrected, 1 reference update
Estimating Form Factors of and their Applications to Semi-leptonic and Non-leptonic Decays
and weak transition
form factors are estimated for the whole physical region with a method based on
an instantaneous approximated Mandelstam formulation of transition matrix
elements and the instantaneous Bethe-Salpeter equation. We apply the estimated
form factors to branching ratios, CP asymmetries and polarization fractions of
non-leptonic decays within the factorization approximation. And we study the
non-factorizable effects and annihilation contributions with the perturbative
QCD approach. The branching ratios of semi-leptonic decays are also evaluated. We show that the calculated
decay rates agree well with the available experimental data. The longitudinal
polarization fraction of decays are when
denotes a light meson, and are when denotes a
() meson.Comment: Final version published in J Phys. G 39 (2012) 045002 (Title also
changed
Scheduling algorithm for mission planning and logistics evaluation users' guide
The scheduling algorithm for mission planning and logistics evaluation (SAMPLE) program is a mission planning tool composed of three subsystems; the mission payloads subsystem (MPLS), which generates a list of feasible combinations from a payload model for a given calendar year; GREEDY, which is a heuristic model used to find the best traffic model; and the operations simulation and resources scheduling subsystem (OSARS), which determines traffic model feasibility for available resources. The SAMPLE provides the user with options to allow the execution of MPLS, GREEDY, GREEDY-OSARS, or MPLS-GREEDY-OSARS
Scaling studies of solar pumped lasers
A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow
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