Assessment of the SBAC atmospheric correction technique applied to Landsat 8-TIRS from ground LST measurements in the Barrax test site

La peculiar estructura y propiedades físico-químicas del silicio poroso nanoestructurado ha estimulado el uso de este material en una amplia variedad de aplicaciones. En el campo de la optoelectrónica, la posibilidad de producir estructuras multicapa en las que cada una de las capas tiene propiedades ópticas particulares, permite la fabricación de filtros ópticos interferenciales con un comportamiento predefinido. En este trabajo se han utilizado estructuras multicapa de silicio poroso para filtrar la luz incidente sobre un sustrato fotosensible de silicio con la intención de modular su respuesta espectral. El comportamiento óptico del filtro de silicio poroso fue simulado antes de su fabricación, y las medidas ópticas demostraron un buen acuerdo entre el comportamiento del filtro obtenido y las predicciones teóricas. Mediciones de fotocorriente han demostrado que los filtros de silicio poroso han reducido el rango espectral de fotosensibilidad del silicio, de los >750 nm originales a unos 150 nm. Filtros con distintos diseños han permitido no sólo estrechar la banda espectral de sensibilidad del detector pancromático de Si, sino también sintonizarla a lo lago de todo el rango visible. El silicio poroso nanoestructurado es compatible con las técnicas convencionales de fabricación microelectrónica, lo que hace posible incorporar estos filtros interferenciales sobre una amplia variedad de sensores y fotodiodos pancromáticos VIS, NIR o SWIR convencionales. Los resultados presentados en este trabajo demuestran que los filtros interferenciales de silicio poroso reestructurado resultan muy prometedores para el desarrollo de sensores multi- e hiperespectrales de bajo costeThe particular structure and physico-chemical properties of nanostructured porous silicon has stimulated the use of this material in many different applications. In the field of optoelectronics, the possibility of fabricating multilayer stacks where each individual layer has different optical properties allows the formation of optical interference filters with a predesigned behavior. In the present work, nanostructured porous silicon interference multilayer structures have been used to filter incident light reaching a Si photosensitive wafer in order to tailor its spectral response. The optical behavior of the porous silicon filters was simulated prior to their fabrication, and optical measurements showed good agreement between the simulated and experimental spectra. Photocurrent measurements have shown that the porous silicon filters narrowed the spectral responsitivity of silicon, from the original value of >750 nm down to around 150 nm. Different filter designs allowed to not only narrowen, but also tune the Si panchromatic sensitivity along the whole visible range. Porous silicon is compatible with standard microelectronic fabrication processes, making it possible to incorporate these interference filters onto a wide variety of conventional panchromatic VIS, NIR or SWIR broad band sensors. These results show that nanostructured silicon interference filters are a promising tool for developing cost-effective multi- and hyperspectral narrowband sensor

A new approach to dealing with missing values in data-driven fuzzy modeling

Real word data sets often contain many missing elements. Most algorithms that automatically develop a rule-based model are not well suited to deal with incomplete data. The usual technique is to disregard the missing values or substitute them by a best guess estimate, which can bias the results. In this paper we propose a new method for estimating the parameters of a Takagi-Sugeno fuzzy model in the presence of incomplete data. We also propose an inference mechanism that can deal with the incomplete data. The presented method has the added advantage that it does not require imputation or iterative guess-estimate of the missing values. This methodology is applied to fuzzy modeling of a classification and regression problem. The performance of the obtained models are comparable with the results obtained when using a complete data set

Large scale numerical investigation of excited states in poly(phenylene)

A density matrix renormalisation group scheme is developed, allowing for the first time essentially exact numerical solutions for the important excited states of a realistic semi-empirical model for oligo-phenylenes. By monitoring the evolution of the energies with chain length and comparing them to the experimental absorption peaks of oligomers and thin films, we assign the four characteristic absorption peaks of phenyl-based polymers. We also determine the position and nature of the nonlinear optical states in this model.Comment: RevTeX, 10 pages, 4 eps figures included using eps

Estimation of flexible fuzzy GARCH models for conditional density estimation

In this work we introduce a new flexible fuzzy GARCH model for conditional density estimation. The model combines two different types of uncertainty, namely fuzziness or linguistic vagueness, and probabilistic uncertainty. The probabilistic uncertainty is modeled through a GARCH model while the fuzziness or linguistic vagueness is present in the antecedent and combination of the rule base system. The fuzzy GARCH model under study allows for a linguistic interpretation of the gradual changes in the output density, providing a simple understanding of the process. Such a system can capture different properties of data, such as fat tails, skewness and multimodality in one single model. This type of models can be useful in many fields such as macroeconomic analysis, quantitative finance and risk management. The relation to existing similar models is discussed, while the properties, interpretation and estimation of the proposed model are provided. The model performance is illustrated in simulated time series data exhibiting complex behavior and a real data application of volatility forecasting for the S&P 500 daily returns series

The critical Ising model via Kac-Ward matrices

The Kac-Ward formula allows to compute the Ising partition function on any finite graph G from the determinant of 2^{2g} matrices, where g is the genus of a surface in which G embeds. We show that in the case of isoradially embedded graphs with critical weights, these determinants have quite remarkable properties. First of all, they satisfy some generalized Kramers-Wannier duality: there is an explicit equality relating the determinants associated to a graph and to its dual graph. Also, they are proportional to the determinants of the discrete critical Laplacians on the graph G, exactly when the genus g is zero or one. Finally, they share several formal properties with the Ray-Singer \bar\partial-torsions of the Riemann surface in which G embeds.Comment: 30 pages, 10 figures; added section 4.4 in version

Sustainability metrics for coal power generation in Australia

The basis of this work was to investigate the relative environmental impacts of various power generators knowing that all plants are located in totally different environments and that different receptors will experience different impacts. Based on IChemE sustainability metrics paradigm, we calculated potential environmental indicators (P-EI) that represent the environmental burden of masses of potential pollutants discharged into different receiving media. However, a P-EI may not be of significance, as it may not be expressed at all in different conditions, so to try and include some receiver significance we developed a methodology to take into account some specific environmental indicators (S-EI) that refer to the environmental attributes of a specific site. In this context, we acquired site specific environmental data related to the airsheds and water catchment areas in different locations for a limited number of environmental indicators such as human health (carcinogenic) effects, atmospheric acidification, photochemical (ozone) smog and eutrophication. The S-EI results from this particular analysis show that atmospheric acidification has highest impact value while health risks due to fly ash emissions are considered not to be as significant. This is due to the fact that many coal power plants in Australia are located in low population density air sheds. The contribution of coal power plants to photochemical (ozone) smog and eutrophication were not significant. In this study, we have considered emission related data trends to reflect technology performance (e.g., P-EI indicators) while a real sustainability metric can be associated only with the specific environmental conditions of the relevant sites (e.g., S-EI indicators)

A mathematical analysis of the evolution of perturbations in a modified Chaplygin gas model

One approach in modern cosmology consists in supposing that dark matter and dark energy are different manifestations of a single `quartessential' fluid. Following such idea, this work presents a study of the evolution of perturbations of density in a flat cosmological model with a modified Chaplygin gas acting as a single component. Our goal is to obtain properties of the model which can be used to distinguish it from another cosmological models which have the same solutions for the general evolution of the scale factor of the universe, without the construction of the power spectrum. Our analytical results, which alone can be used to uniquely characterize the specific model studied in our work, show that the evolution of the density contrast can be seen, at least in one particular case, as composed by a spheroidal wave function. We also present a numerical analysis which clearly indicates as one interesting feature of the model the appearence of peaks in the evolution of the density constrast.Comment: 21 pages, accepted for publication in General Relativity and Gravitatio

Schottky barrier heights at polar metal/semiconductor interfaces

Using a first-principle pseudopotential approach, we have investigated the Schottky barrier heights of abrupt Al/Ge, Al/GaAs, Al/AlAs, and Al/ZnSe (100) junctions, and their dependence on the semiconductor chemical composition and surface termination. A model based on linear-response theory is developed, which provides a simple, yet accurate description of the barrier-height variations with the chemical composition of the semiconductor. The larger barrier values found for the anion- than for the cation-terminated surfaces are explained in terms of the screened charge of the polar semiconductor surface and its image charge at the metal surface. Atomic scale computations show how the classical image charge concept, valid for charges placed at large distances from the metal, extends to distances shorter than the decay length of the metal-induced-gap states.Comment: REVTeX 4, 11 pages, 6 EPS figure