Imaging ionospheric inhomogeneities using spaceborne synthetic aperture radar

We present a technique and results of 2-D imaging of Faraday rotation and total electron content using spaceborne L band polarimetric synthetic aperture radar (PolSAR). The results are obtained by processing PolSAR data collected using the Phased Array type L-band Synthetic Aperture Radar (PALSAR) on board the Advanced Land Observation Satellite. Distinguished ionospheric inhomogeneities are captured in 2-D images from space with relatively high resolutions of hundreds of meters to a couple of kilometers in auroral-, middle-, and low-latitude regions. The observed phenomena include aurora-associated ionospheric enhancement arcs, the middle-latitude trough, traveling ionospheric disturbances, and plasma bubbles, as well as ionospheric irregularities. These demonstrate a new capability of spaceborne synthetic aperture radar that will not only provide measurements to correction of ionospheric effects in Earth science imagery but also significantly benefit ionospheric studies

Vertically coupled double quantum rings at zero magnetic field

Within local-spin-density functional theory, we have investigated the `dissociation' of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble those of a single quantum ring in the few-electron limit. When the rings are quantum mechanically weakly coupled, the electronic states in the molecule are substantially localized in one ring or the other, although the rings can be electrostatically coupled. The effect of a slight mismatch introduced in the molecules from nominally identical quantum wells, or from changes in the inner radius of the constituent rings, induces localization by offsetting the energy levels in the quantum rings. This plays a crucial role in the appearance of the addition spectra as a function of coupling strength particularly in the weak coupling limit.Comment: 18 pages, 8 figures, submitted to Physical Review

An Evaluation Method for Context-Aware Systems in U-Health

Proceedings of: 3rd International Symposium on Ambient Intelligence (ISAmI 2012) Salamanca, March 28-30, 2012Evaluations for context-aware systems can not be conducted in the same manner evaluation is understood for other software systems where the concept of large corpus data, the establishment of ground truth and the metrics of precision and recall are used. Evaluation for changeable systems like context-aware and specially developed for AmI environments needs to be conducted to assess the impact and awareness of the users. E-Health represents a challenging domain where users(patients, patients' relatives and healthcare professionals) are very sensitive to systems' response. If system failure occurs it can conducts to a bad diagnosis or medication, or treatment. So a user-centred evaluation system is need to provide the system with users' feedback. In this paper, we present an evaluation method for context aware systems in AmI environments and specially to u-Heatlh domainFunded by projects CICYT TIN2008-06742-C02-02/TSI, CICYTTEC2008-06732 C02-02/TEC, SINPROB, CAM MADRINET S-0505/TIC/0255 and DPS2008-07029-C02-02.Publicad

Investigation of thermal resistance and power consumption in Ga-doped indium oxide (In2O3) nanowire phase change random access memory

The resistance stability and thermal resistance of phase change memory devices using similar to 40 nm diameter Ga-doped In2O3 nanowires (Ga:In2O3 NW) with different Ga-doping concentrations have been investigated. The estimated resistance stability (R(t)/R-0 ratio) improves with higher Ga concentration and is dependent on annealing temperature. The extracted thermal resistance (R-th) increases with higher Ga-concentration and thus the power consumption can be reduced by similar to 90% for the 11.5% Ga: In2O3 NW, compared to the 2.1% Ga: In2O3 NW. The excellent characteristics of Ga-doped In2O3 nanowire devices offer an avenue to develop low power and reliable phase change random access memory applications. (C) 2014 AIP Publishing LLC.X113sciescopu

Electric-field-induced phase transition of <001> oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were poled under different electric fields, i.e. Epoling=4 kV/cm and Epoling=13 kV/cm. In addition to the temperature-dependent dielectric constant measurement, X-ray diffraction was also used to identify the poling-induced phase transitions. Results showed that the phase transition significantly depends on the poling intensity. A weaker field (Epoling=4 kV/cm) can overcome the effect of random internal field to perform the phase transition from rhombohedral ferroelectric state with short range ordering (microdomain) FESRO to rhombohedral ferroelectric state with long range ordering (macrodomain) FElRO. But the rhombohedral ferroelectric to tetragonal ferroelectric phase transition originating from to polarization rotation can only be induced by a stronger field (Epoling=13 kV/cm). The sample poled at Epoling=4 kV/cm showed higher piezoelectric constant, d33>1500 pC/N, than the sample poled at Epoling=13 kV/cm.Comment: 7 pages, 2 figure

Bayesian optimization for materials design

We introduce Bayesian optimization, a technique developed for optimizing time-consuming engineering simulations and for fitting machine learning models on large datasets. Bayesian optimization guides the choice of experiments during materials design and discovery to find good material designs in as few experiments as possible. We focus on the case when materials designs are parameterized by a low-dimensional vector. Bayesian optimization is built on a statistical technique called Gaussian process regression, which allows predicting the performance of a new design based on previously tested designs. After providing a detailed introduction to Gaussian process regression, we introduce two Bayesian optimization methods: expected improvement, for design problems with noise-free evaluations; and the knowledge-gradient method, which generalizes expected improvement and may be used in design problems with noisy evaluations. Both methods are derived using a value-of-information analysis, and enjoy one-step Bayes-optimality

Ullemar's formula for the Jacobian of the complex moment mapping

The complex moment sequence m(P) is assigned to a univalent polynomial P by the Cauchy transform of the P(D), where D is the unit disk. We establish the representation of the Jacobian det dm(P) in terms of roots of the derivative P'. Combining this result with the special decomposition for the Hurwitz determinants, we prove a formula for the Jacobian which was previously conjectured by C. Ullemar. As a consequence, we show that the boundary of the class of all locally univalent polynomials in $U$ is contained in the union of three irreducible algebraic surfaces.Comment: 14 pages, submitted for "Complex Variables. Theory and Application

Funkcional za tvorbu vezanih stanja u QED

The manifestly Lorentz covariant formulation of quantum electrodynamics disregards Coulomb instantaneous interaction and its consequence - instantaneous bound states (IBS\u27s). In this article we consider the way of construction the IBS generating functional using the operator generalization of the initial data in the Dirac Hamiltonian approach to QED.Očito Lorentz-kovariantna formulacija kvantne elektrodinamike zanemaruje trenutno Coulombovo međudjelovanje i njegovu posljedicu – trenutna vezana stanja. U ovom se radu razmatra postavljanje tvorbenog funkcionala za trenutno vezana stanja primjenom operatora poopćenih početnih stanja u Dirac-Hamiltonovom pristupu QED

Game theoretic pricing models in hotel revenue management: an equilibrium choice-based conjoint analysis approach

This paper explores a game-theoretically founded approach to conjoint analysis that determines equilibrium room rates under differentiated price competition in an oligopolistic hotel market. Competition between hotels is specified in terms of market share functions that can be estimated using multinomial logit models of consumer choice. The approach is based on choice-based conjoint analysis that permits the estimation of attributes weights (“part-worths”) for an additive utility formulation of the utility function. From this, room rates that equilibrate the market, conditioned on the differences in services and facilities offered by competing hotels, can be determined. The approach is illustrated by an example