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81.
We study how to build optimal light-field or plenoptic models. We quantify geometric errors in light-field representations and show how geometric error bounds directly affect rendering artifacts. Artifacts depend on how the light-field is parameterized, stored, reconstructed and rendered. We present the rendering artifacts and relate them to the presence of geometric errors in the four most common light-field implementations.We show how to optimize a light-field model. We take an arbitrary bounded object and construct the best possible representation using each of the four parameterizations. The best representation has the least geometric error bounds. We use two geometric errors, a positional and a directional error. We also quantify pixelation artifacts. Our analysis is useful to decide how to build a light-field model. It helps select a parameterization, build an optimal representation, and choose the samplings of the parameter spaces so that geometric errors and rendering artifacts are minimized. 相似文献
82.
Carina A. Emilio Raquel Gettar Marta I. Litter 《Journal of Applied Electrochemistry》2005,35(7-8):733-740
TiO2-heterogeneous photocatalysis of nitrilotriacetic acid (NTA) at pH 2.5 was studied to establish the kinetic regime and the
reaction mechanism. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed
over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a
change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates
and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in
different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA
was not accompanied by a corresponding total organic carbon (TOC) reduction, but 84% of TOC decrease was obtained on P25 after
24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction,
suggested to be the same over the three catalysts here tested. 相似文献
83.
Coupled reliability model of biodeterioration, chloride ingress and cracking for reinforced concrete structures 总被引:1,自引:0,他引:1
Emilio Bastidas-Arteaga Mauricio Snchez-Silva Alaa Chateauneuf Moema Ribas Silva 《Structural Safety》2008,30(2):110-129
Maintaining and operating civil infrastructure systems has been recognized as a critical issue worldwide. Among all possible causes of safety reduction during the structural lifetime, deterioration is particularly important. Structural deterioration is usually a slow time-dependent process controlled by safety and operation threshold specifications. This paper presents a model of RC deterioration by coupling biodeterioration (i.e., chemical, physical and mechanical action of live organisms), steel corrosion, and concrete cracking. The final purpose of the model is to compute the reduction of the concrete section and the area of steel reinforcement in order to assess the change of structural capacity with time. Given the uncertainties in both the parameters and the model, the probabilistic nature of loads, the material properties and the diffusion process are taken into account to evaluate structural reliability. The model is illustrated with an example where the inelastic behavior of a pile subject to random loading is considered. The results of the analysis have shown that the effect of biodeterioration on the structural performance is significant and can cause an important reduction of its lifetime. On the whole, the paper states that modeling the effects of biodeterioration in RC structures should be included as part of infrastructure planning and design, especially, when they are located in aggressive environments. 相似文献
84.
Alexander D’ Avignon Flávia Azevedo Carloni Emilio Lèbre La Rovere Carolina Burle Schmidt Dubeux 《Energy Policy》2010
Global concern with climate change has led to the development of a variety of solutions to monitor and reduce emissions on both local and global scales. Under the United Nations Framework Convention on Climate Change (UNFCCC), both developed and emerging countries have assumed responsibility for developing and updating national inventories of greenhouse gas emissions from anthropic sources. This creates opportunities and incentives for cities to carry out their own local inventories and, thereby, develop air quality management plans including both essential key players and stakeholders at the local level. The aim of this paper is to discuss the role of local inventories as an urban public policy instrument and how this type of local instrument may bring advantages countrywide in enhancing the global position of a country. Local inventories have been carried out in many cities of the world and the main advantage of this is that it allows an overview of emissions produced by different municipal activities, thereby, helps decision makers in the elaboration of efficient air quality management plans. In that way, measures aimed at the reduction of fossil fuel consumption to lower local atmospheric pollution levels can also, in some ways, reduce GHG emissions. 相似文献
85.
René Flükiger Roman E. Gladyshevskii Emilio Bellingeri 《Journal of Superconductivity》1998,11(1):23-26
Different methods to prepare superconducting mono- and multifilamentary T1(I223) tapes were developed. High-purity ceramics could be produced by ex-situ or in-situ reaction under a high isostatic gas pressure. Tapes prepared by the PIT method and an in-situ reaction carried out close to the melting point of the oxide were relatively dense and textured. Interesting results were obtained for samples where part of the oxygen atoms in Tl(1223) had been substituted by fluorine. Critical current densities up to 20'000 A/cm2 (77 K, 0 T) were reached for tapes produced by the PIT method. Well textured samples were obtained by electrophoretic deposition, the deposited Tl(1223) grains being produced by a synthesis involving substantial melting. 相似文献
86.
Gengler RY Toma LM Pardo E Lloret F Ke X Van Tendeloo G Gournis D Rudolf P 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(16):2532-2540
Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir-Blodgett technique, where the PBA is synthesized from precursors in a self-limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low-dimensional arrangements, and the influence of the "on surface" synthesis on the final properties and dimensionality of the system. 相似文献
87.
Journal of Low Temperature Physics - We have investigated disorder phenomena in solid 4He near megting in presence of vacancies by means of Quantum Monte Carlo (MC) simulations using the Shadow... 相似文献
88.
Riccioli C Pérez-Marín D Guerrero-Ginel JE Saeys W Garrido-Varo A 《Applied spectroscopy》2011,65(7):771-781
This paper proposes a method based on near-infrared hyperspectral imaging for discriminating between terrestrial and fish species in animal protein by-products used in livestock feed. Four algorithms (Mahalanobis distance, Kennard-Stone, spatial interpolation, and binning) were compared in order to select an appropriate subset of pixels for further partial least squares discriminant analysis (PLS-DA). The method was applied to a set of 50 terrestrial and 40 fish meals analyzed in the 1000-1700 nm range. Models were then tested using an external validation set comprising 45 samples (25 fish and 20 terrestrial). The PLS-DA models obtained using the four subset-selection algorithms yielded a classification accuracy of 99.80%, 99.79%, 99.85%, and 99.61%, respectively. The results represent a first step for the analysis of mixtures of species and suggest that NIR-CI, providing valuable information on the origin of animal components in processed animal proteins, is a promising method that could be used as part of the EU feed control program aimed at eradicating and preventing bovine spongiform encephalopathy (BSE) and related diseases. 相似文献
89.
90.
We analyze the classical asset pricing model assuming non fully rationalagents.Agents forecast future prices cum dividend through an adaptive learning rule.This assumption provides an explanation of some anomalies encounteredin the empirical analysis of asset prices under full rationality:returns are serially correlated(positively over a short horizon and negatively over a longer horizon)and the dividend yield predicts future returns (positive correlation).Considering the continuous time limit process,the same regularities are established analytically for price increments. 相似文献