Search results for "Computer Science::Databases"
showing 10 items of 183 documents
Graph-theoretical derivation of brain structural connectivity
2020
Brain connectivity at the single neuron level can provide fundamental insights into how information is integrated and propagated within and between brain regions. However, it is almost impossible to adequately study this problem experimentally and, despite intense efforts in the field, no mathematical description has been obtained so far. Here, we present a mathematical framework based on a graph-theoretical approach that, starting from experimental data obtained from a few small subsets of neurons, can quantitatively explain and predict the corresponding full network properties. This model also changes the paradigm with which large-scale model networks can be built, from using probabilisti…
High spin polarization in Co2CrAl–Cr superlattice
2009
The electronic structure, magnetic properties and interface effects in Co2CrAl?Cr superstructures have been investigated by the use of first principle calculations. The results show that at the interface, a large magnetic moment and a high spin polarization can be induced by a strong ferromagnetic exchange interaction at the Cr?Co interface. However, at the CrAl?Cr interface, both the magnetic moment and the spin polarization of the Cr atoms are decreased due to a Cr?Cr antiferromagnetic interaction. It can also be found that the interface effect is only a short range effect. So, high spin polarization in Co2CrAl?Cr superlattice can be obtained. Based on this theoretical analysis, a large g…
<title>Fibers supporting super-Gaussian beams: cladding effects</title>
1996
We define a matching function that describes the amplitude variations produced over supergaussian beams, by cladding optical fibers that, if uncladded, can sustain this type of beams as Eigenmodes.
Non-linear oscillators under parametric and external poisson pulses
1994
The extended Ito calculus for non-normal excitations is applied in order to study the response behaviour of some non-linear oscillators subjected to Poisson pulses. The results obtained show that the non-normality of the input can strongly affect the response, so that, in general, it can not be neglected.
Recent Advances in Bayesian Inference in Cosmology and Astroparticle Physics Thanks to the MultiNest Algorithm
2012
We present a new algorithm, called MultiNest, which is a highly efficient alternative to traditional Markov Chain Monte Carlo (MCMC) sampling of posterior distributions. MultiNest is more efficient than MCMC, can deal with highly multi-modal likelihoods and returns the Bayesian evidence (or model likelihood, the prime quantity for Bayesian model comparison) together with posterior samples. It can thus be used as an all-around Bayesian inference engine. When appropriately tuned, it also provides an exploration of the profile likelihood that is competitive with what can be obtained with dedicated algorithms.
Optical security and encryption with totally incoherent light
2001
We present a method for securing and encrypting information optically by use of totally incoherent illumination. Encryption is performed with a multichannel optical processor working under natural (both temporal and spatially incoherent) light. In this way, the information that is to be secured can be codified by use of color signals and self-luminous displays. The encryption key is a phase-only mask, providing high security from counterfeiting. Output encrypted information is recorded as an intensity image that can be easily stored and transmitted optically or electrically. Decryption or authentication can also be performed optically or digitally. Experimental results are presented.
A distance metric on binary trees using lattice-theoretic measures
1990
A so called height function which is a strictly antitone supervaluation is defined on binary trees. Via lattice-theoretic results and using the height function, we can define a distance metric on binary trees of size n which can be computed in expected time O(n 3/2 )
Surface-plasmon hopping along coupled coplanar cavities
2007
International audience; We report on surface-plasmon propagation along coupled coplanar cavities periodically distributed in an otherwise unperturbed plasmonic crystal. We show that the dispersion of particular Bloch modes can exhibit multiple energy gaps that can be adjusted by choosing the cavity size. For resonant sizes, the composite crystals composed of juxtaposed cavities can support plasmon modes at frequencies within the gap of the unperturbed grating. In this case, we demonstrate that the surface-plasmon propagation relies on a hopping mechanism.
Complex Ground-State and Excitation Energies in Coupled-Cluster Theory
2021
Since in coupled-cluster (CC) theory ground-state and excitation energies are eigenvalues of a non-Hermitian matrix, these energies can in principle take on complex values. In this paper we discuss the appearance of complex energy values in CC calculations from a mathematical perspective. We analyze the behaviour of the eigenvalues of Hermitian matrices that are perturbed (in a non-Hermitian manner) by a real parameter. Based on these results we show that for CC calculations with real-valued Hamiltonian matrices the ground-state energy generally takes a real value. Furthermore, we show that in the case of real-valued Hamiltonian matrices complex excitation energies only occur in the context…
The arithmetic decomposition of central Cantor sets
2018
Abstract Every central Cantor set of positive Lebesgue measure is the arithmetic sum of two central Cantor sets of Lebesgue measure zero. Under some mild condition this result can be strengthened by stating that the summands can be chosen to be C s regular if the initial set is of this class.