1,138 research outputs found
Investigation of clouds spatial distribution using ground-based lidar
Certain investigations of spatial distribution of clouds by employing ground based lidar are presented. The great changeability is one of the main properties of the clouds in the boundary layer. As a result, their optical properties change rapidly which complicates the modeling of cloud evolution. Suitable equipped lidars are widely used for diagnostics of the clouds via a number of scattering and absorption processes. In particular, lidar can provide information on the distribution of meteorological parameters and of the other important cloud characteristics both in vertical and horizontal directions. Herein the time and spatial distribution of the aerosol backscattering coefficient of S sub t and S sub c type clouds are investigated by means of a correlation analysis of the lidar obtained data provided from several arbitrary directions and heights
Numerical Solutions for a Model of Tissue Invasion and Migration of Tumour Cells
The goal of this paper is to construct a new algorithm for the numerical simulations of the evolution of tumour invasion and metastasis. By means of mathematical model equations and their numerical solutions we investigate how cancer cells can produce and secrete matrix degradative enzymes, degrade extracellular matrix, and invade due to diffusion and haptotactic migration. For the numerical simulations of the interactions between the tumour cells and the surrounding tissue, we apply numerical approximations, which are spectrally accurate and based on small amounts of grid-points. Our numerical experiments illustrate the metastatic ability of tumour cells
Detection of SUSY Signals in Stau Neutralino Co-annihilation Region at the LHC
We study the prospects of detecting the signal in the stau neutralino
co-annihilation region at the LHC using tau leptons. The co-annihilation signal
is characterized by the stau and neutralino mass difference (dM) to be 5-15 GeV
to be consistent with the WMAP measurement of the cold dark matter relic
density as well as all other experimental bounds within the minimal
supergravity model. Focusing on tau's from neutralino_2 --> tau stau --> tau
tau neutralino_1 decays in gluino and squark production, we consider inclusive
MET+jet+3tau production, with two tau's above a high E_T threshold and a third
tau above a lower threshold. Two observables, the number of opposite-signed tau
pairs minus the number of like-signed tau pairs and the peak position of the
di-tau invariant mass distribution, allow for the simultaneous determination of
dM and M_gluino. For dM = 9 GeV and M_gluino = 850 GeV with 30 fb^-1 of data,
we can measure dM to 15% and M_gluino to 6%.Comment: 4 pages LaTex, 3 figures. To appear in Proceedings of SUSY06, the
14th International Conference on Supersymmetry and the Unification of
Fundamental Interactions, UC Irvine, California, 12-17 June 2006. A typo in a
reference is correcte
Topological Entropy of Braids on the Torus
A fast method is presented for computing the topological entropy of braids on
the torus. This work is motivated by the need to analyze large braids when
studying two-dimensional flows via the braiding of a large number of particle
trajectories. Our approach is a generalization of Moussafir's technique for
braids on the sphere. Previous methods for computing topological entropies
include the Bestvina--Handel train-track algorithm and matrix representations
of the braid group. However, the Bestvina--Handel algorithm quickly becomes
computationally intractable for large braid words, and matrix methods give only
lower bounds, which are often poor for large braids. Our method is
computationally fast and appears to give exponential convergence towards the
exact entropy. As an illustration we apply our approach to the braiding of both
periodic and aperiodic trajectories in the sine flow. The efficiency of the
method allows us to explore how much extra information about flow entropy is
encoded in the braid as the number of trajectories becomes large.Comment: 19 pages, 44 figures. SIAM journal styl
An intuitionistic fuzzy component based appoach for identifying web usage patterns
An intuitionistic fuzzy component based appoach fo
On geodesic exponential maps of the Virasoro group
We study the geodesic exponential maps corresponding to Sobolev type right-invariant (weak) Riemannian metricsÎŒ(k) (kâ„ 0) on the Virasoro group Vir and show that for kâ„ 2, but not for k=0,1, each of them defines a smooth FrĂ©chet chart of the unital element e âVir. In particular, the geodesic exponential map corresponding to the Korteweg-de Vries (KdV) equation (k=0) is not a local diffeomorphism near the origi
Not All Responses Are the Same: How CEO Cognitions Impact Strategy When Performance Falls Below Aspirations
This study integrates research on managerial discretion within the behavioral theory of the firm to examine how four CEO psychological traits serving as antecedents of managerial discretionâambiguity tolerance, cognitive complexity, locus of control, and commitment to the status quoâmoderate firm responses to poor performance. Using CEOsâ responses to questionnaires, CEO ambiguity tolerance is found to positively moderate the relationship between negative attainment discrepancy and strategic change when performance is slightly below aspirations, defined as average market return for the firmâs industry. Further, CEOs with greater cognitive complexity are found to engage in more strategic change when performance is farther below aspirations. Thus, this study begins to unpack the role of CEOsâ cognitive makeup on firm responses to performance shortfalls
Effects of post-anneal conditions on the dielectric properties of CaCu3Ti4O12 thin films prepared on Pt/Ti/SiO2/Si substrates
High-dielectric-constant CaCu3Ti4O12 (CCTO) thin films were prepared on
Pt/Ti/SiO2/Si(100) substrates by pulsed-laser deposition. The 480 nm thick
polycrystalline films have preferred orientation and show obvious
crystallization on the surface. The temperature-dependence of dielectric
constant and loss of the Pt/CCTO/Pt capacitors is comparable with that of
epitaxial CCTO films grown on oxides substrates. We found that the dielectric
properties are very sensitive to the post-annealing atmosphere and temperature.
Post-annealing in nitrogen atmosphere produces larger low-frequency dielectric
relaxation as the annealing temperature increases, while annealing in oxygen
atmosphere at high temperature suppresses the relaxation but lowers the
dielectric constant. Such results are attributed to the presence of insulating
grain boundary barrier layers.Comment: 10 pages, 3 figure
Ultrafast trapping times in ion implanted InP
Asâș and Pâșimplantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1Ă10Âčâ¶âcmâ»ÂČ and p-type InP was implanted with doses between 1Ă10ÂčÂČ and 1Ă10Âčâ¶âcmâ»ÂČ. Subsequently, rapid thermal annealing at temperatures between 400 and 700â°C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implantedp-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity
Positive Semidefiniteness and Positive Definiteness of a Linear Parametric Interval Matrix
We consider a symmetric matrix, the entries of which depend linearly on some
parameters. The domains of the parameters are compact real intervals. We
investigate the problem of checking whether for each (or some) setting of the
parameters, the matrix is positive definite (or positive semidefinite). We
state a characterization in the form of equivalent conditions, and also propose
some computationally cheap sufficient\,/\,necessary conditions. Our results
extend the classical results on positive (semi-)definiteness of interval
matrices. They may be useful for checking convexity or non-convexity in global
optimization methods based on branch and bound framework and using interval
techniques
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