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Cano-Crespo A.,Potsdam Institute for Climate Impact Research | Cano-Crespo A.,Humboldt University of Berlin | Oliveira P.J.C.,Potsdam Institute for Climate Impact Research | Boit A.,Potsdam Institute for Climate Impact Research | And 2 more authors.
Journal of Geophysical Research G: Biogeosciences | Year: 2015

Understanding to what extent different land uses influence fire occurrence in the Amazonian forest is particularly relevant for its conservation. We evaluate the relationship between forest fires and different anthropogenic activities linked to a variety of land uses in the Brazilian states of Mato Grosso, Pará, and Rondônia. We combine the new high-resolution (30 m) TerraClass land use database with Moderate Resolution Imaging Spectroradiometer burned area data for 2008 and the extreme dry year of 2010. Excluding the non-forest class, most of the burned area was found in pastures, primary and secondary forests, and agricultural lands across all three states, while only around 1% of the total was located in deforested areas. The trend in burned area did not follow the declining deforestation rates from 2001 to 2010, and the spatial overlap between deforested and burned areas was only 8% on average. This supports the claim of deforestation being disconnected from burning since 2005. Forest degradation showed an even lower correlation with burned area. We found that fires used in managing pastoral and agricultural lands that escape into the neighboring forests largely contribute to forest fires. Such escaping fires are responsible for up to 52% of the burned forest edges adjacent to burned pastures and up to 22% of the burned forest edges adjacent to burned agricultural fields, respectively. Our findings call for the development of control and monitoring plans to prevent fires from escaping from managed lands into forests to support effective land use and ecosystem management. ©2015. American Geophysical Union. All Rights Reserved.


Schroeder W.,University of Maryland University College | Oliva P.,University of Maryland University College | Giglio L.,University of Maryland University College | Quayle B.,U.S. Department of Agriculture | And 2 more authors.
Remote Sensing of Environment | Year: 2015

The gradual increase in Landsat-class data availability creates new opportunities for fire science and management applications that require higher-fidelity information about biomass burning, improving upon existing coarser spatial resolution (≥. 1. km) satellite active fire data sets. Targeting those enhanced capabilities we describe an active fire detection algorithm for use with Landsat-8 Operational Land Imager (OLI) daytime and nighttime data. The approach builds on the fire-sensitive short-wave infrared channel 7 complemented by visible and near-infrared channel 1-6 data (daytime only), while also expanding on the use of multi-temporal analysis to improve pixel classification results. Despite frequent saturation of OLI's fire-affected pixels, which includes radiometric artifacts resulting from folding of digital numbers, our initial assessment based on visual image analysis indicated high algorithm fidelity across a wide range of biomass burning scenarios, gas flares and active volcanoes. Additional field data verification confirmed the sensor's and algorithm's ability to resolve fires of significantly small areas compared to current operational satellite fire products. Commission errors were greatly reduced with the addition of multi-temporal analysis tests applied to co-located pixels, averaging less than 0.2% globally. Because of its overall quality, Landsat-8/OLI active fire data could become part of a network of emerging earth observation systems providing enhanced spatial and temporal coverage of biomass burning at global scales. © 2015.


De Vasconcelos L.G.,Brazilian Institute for Space Research | Dos Santos R.D.C.,Brazilian Institute for Space Research | Baldochi L.A.,Federal University of Itajubá
Proceedings of the 13th International Conference WWW/Internet 2014, ICWI 2014 | Year: 2014

With the increasing use of the Internet, the Web has become the predominant means by which people obtain information. However, due to the fast growth of the amount and (sometimes competing) sources of resources available on the Web, users want to find information quickly and efficiently. Currently, web personalization has been explored in order to encourage user's feedback, improve usability and provide interesting content. In the literature, the most common approach is to analyze server logs, which contain information about what pages the user accesses during browsing. However, client logs contain more information about the user navigation. The amount of data of the client logs is significantly greater than the amount of server logs, and this is one factor that discourages analysis of client logs. In this paper, an approach is presented to classify the level of user's experience in real time, using indices of efficiency and effectiveness. The proposed approach, called RUX (Real-time User eXperience), contains an efficient algorithm for analyzing the user's behavior of web applications in real time using client logs. RUX focuses on the paths that a user goes through during the interaction, comparing them to previously defined tasks. RUX approach can be used by application developer to consume the classification of user's experience in real time, previously programming actions that can be taken. Experimental results show that the approach is efficient for aspects of data collection, latency and scalability.


Sander de Carvalho L.A.,Brazilian Institute for Space Research | Faria Barbosa C.C.,Brazilian Institute for Space Research | Leao de Moraes Novo E.M.,Brazilian Institute for Space Research | de Moraes Rudorff C.,Brazilian Institute for Space Research
Remote Sensing of Environment | Year: 2015

Amazon floodplain lakes range widely in concentrations of optically active constituents (OAC) driven by seasonality in hydrological and biogeochemical processes, but in general they are characterized by high turbidity (NTU from 90 to 1645) compared to coastal waters. In this work, instruments for measuring inherent optical properties (IOPs) of water bodies were evaluated for the first time in floodplain lakes in the lower Amazon River during the falling limb of the hydrograph. Water column profiles of total attenuation and absorption were measured using the Spectral Absorption and Attenuation Meter (AC-S-WETLabs), and of backscattering using Hydroscat. These measurements, however, are subject to uncertainties and require corrections for turbid waters. In this paper, we assessed the implications of scattering correction methods for the absorption tube, proposed by the AC-S manufacturer, in the simulation of the Remote Sensing Reflectance (Rrs). The closure experiment comparing Hydrolight (Mobley & Sundman, 2001) simulated Rrs and in situ Rrs demonstrated that neither of the corrections was able to thoroughly account for the scattering errors which were propagated to the absorption measurements with AC-S and backscattering with Hydroscat. The three scattering correction methods (Flat, Proportional and "Kirk") either under or overestimated the absorption coefficient that resulted in either under or overestimation of the simulated Rrs. Flat and Proportional Methods resulted in an underestimation of Rrs from 400 to 550nm and overestimation from 600 to 700nm, indicating that the assumption of zero (0) absorption in the near infrared does not apply to inland turbid water. The Rrs errors varied also according to water OAC composition. Overall, "Kirk" correction method provided the best results regarding the spectral shape of the Rrs, however, failed to account for magnitude. Based on the tuning tests, the errors in spectra magnitude seem to be sensitive to the constant fraction of scattering (CFS) used in the Kirk method. Tests carried out with CFS values varying from 0.18 to 0.38 indicated that magnitude error can be partially overcomed by tuning CFS according to water composition. Improvements in the scattering correction methods are required in order to obtain reliable IOPs in turbid inland Amazon lakes. © 2014 Elsevier Inc.


Alcantara E.H.,Brazilian Institute for Space Research | Stech J.L.,Brazilian Institute for Space Research | Lorenzzetti J.A.,Brazilian Institute for Space Research | Bonnet M.P.,CIRAD - Agricultural Research for Development | And 3 more authors.
Remote Sensing of Environment | Year: 2010

Water temperature plays an important role in ecological functioning and in controlling the biogeochemical processes of a water body. Conventional water quality monitoring is expensive and time consuming. It is particularly problematic if the water bodies to be examined are large. Conventional techniques also bring about a high probability of undersampling. Conversely, remote sensing is a powerful tool to assess aquatic systems. The objective of this study was to map the surface water temperature and improve understanding of spatiotemporal variations in a hydroelectric reservoir. In this work, MODIS land-surface temperature (LST) level 2, 1-km nominal resolution data (MOD11L2, version 5) were used. All available clear-sky MODIS/Terra images from 2003 to 2008 were used, resulting in a total of 786 daytime and 473 nighttime images. Descriptive statistics (mean, maximum and minimum) were computed for the historical images to build a time series of daytime and nighttime monthly mean temperatures. The thermal amplitude and anomaly were also computed. In-situ meteorological variables were used from 2003 to 2008 to help understand the spatiotemporal variability of the surface water temperature. The surface energy budget and the depth at which the wind can distribute the heat input of a given surface were also measured. A correlation between daytime and nighttime surface water temperatures and the computed heat fluxes were made. These relationships and the causes of the water surface temperature variability are discussed. © 2010 Elsevier Inc.


Alcantara E.,Brazilian Institute for Space Research | Novo E.,Brazilian Institute for Space Research | Stech J.,Brazilian Institute for Space Research | Assireu A.,Brazilian Institute for Space Research | And 3 more authors.
Journal of Hydrology | Year: 2010

This paper proposes a fast and inexpensive method for estimating the bathymetry of hydroelectric reservoirs. Brazil has more than 30 large hydroelectric reservoirs with a combined volume exceeding one billion cubic meters. The hydroelectric sector is responsible for 97% of the energy production in Brazil and is the largest hydroelectric park in the world. Among the variables affecting the environmental impacts of reservoirs, depth plays a major role because it influences the aquatic system hydrodynamics. Reservoir depth distribution (i.e., the bathymetry) is also a fundamental factor controlling the physical-chemical and biological properties of the system. However, the acquisition of bathymetric information for the large reservoirs in Brazil is not a simple task because: (1) most of the topographic maps available in the area of the lake have a very small scale (1:100,000 and smaller), (2) larger charts are the property of the hydropower companies and are classified, and (3) the size of the reservoirs prevent the use of bathymetric surveys. The proposed method of integrating historical and Shuttle Radar Topography Mission (SRTM) topographic data allowed for the estimation of the bathymetry of the Itumbiara reservoir with R2=0.98 (n=100, ρ=0.00) and RMSE=3.78m. For researchers who need a rapid and simple method to develop bathymetric maps of hydroelectric reservoirs, the proposed method can provide a simple and fast alternative to more data intensive methods. © 2010 Elsevier B.V.


Ricci M.C.,Brazilian Institute for Space Research
World Academy of Science, Engineering and Technology | Year: 2010

An alternative iterative computational procedure is proposed for internal normal ball loads calculation in statically loaded single-row, angular-contact ball bearings, subjected to a known thrust load, which is applied in the inner ring at the geometric bearing center line. An accurate method for curvature radii at contacts with inner and outer raceways in the direction of the motion is used. Numerical aspects of the iterative procedure are discussed. Numerical examples results for a 218 angular-contact ball bearing have been compared with those from the literature. Twenty figures are presented showing the geometrical features, the behavior of the convergence variables and the following parameters as functions of the thrust load: normal ball loads, contact angle, distance between curvature centers, and normal ball and axial deflections.


Ricci M.C.,Brazilian Institute for Space Research
World Academy of Science, Engineering and Technology | Year: 2010

A known iterative computational procedure is used for internal normal ball loads calculation in statically loaded single-row, angular-contact ball bearings, subjected to a known thrust load, which is applied in the inner ring at the geometric bearing center line. Numerical aspects of the iterative procedure are discussed. Numerical examples results for a 218 angular-contact ball bearing have been compared with those from the literature. Twenty figures are presented showing the geometrical features, the behavior of the convergence variables and the following parameters as functions of the thrust load: normal ball loads, contact angle, distance between curvature centers, and normal ball and axial deflections between the raceways.


Gomes V.,Brazilian Institute for Space Research | Velho H.C.,Brazilian Institute for Space Research | Charao A.,Federal University of Santa Maria
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

This paper presents the design and implementation of a fast Poisson solver on a reconfigurable hybrid system. Our hybrid solver integrates a FPGA-based FFT coprocessor to collaborate in the solution of a numerical meteorological model involving one-dimensional shallow water equations. The Poisson equation is solved using a singular value decomposition associated with the Moore-Penrose inverse. The hybrid fast Poisson solver is evaluated under different amount of data entry and shows performance gains compared to the reference application. © 2013 Springer-Verlag.


Alcantara E.,Brazilian Institute for Space Research | Novo E.,Brazilian Institute for Space Research | Stech J.,Brazilian Institute for Space Research | Lorenzzetti J.,Brazilian Institute for Space Research | And 3 more authors.
Hydrology and Earth System Sciences | Year: 2010

Observations of turbidity provide quantitative information about water quality. However, the number of available in situ measurements for water quality determination is usually limited in time and space. Here, we present an analysis of the temporal and spatial variability of the turbidity of an Amazon floodplain lake using two approaches: (1) wavelet analysis of a turbidity time series measured by an automatic monitoring system, which should be improved/simplified, and (2) turbidity samples measured in different locations and then interpolated using an ordinary Kriging algorithm. The spatial and temporal variability of turbidity are clearly related to the Amazon River flood pulses in the floodplain. When the water level in the floodplain is rising or receding, the exchange between the Amazon River and the floodplain is the major driving force in turbidity variability. At high-water levels, turbidity variability is controlled by Lake Bathymetry. When the water level is low, wind action and Lake Morphometry are the main causes of turbidity variability. The combined use of temporal and spatial data shows a good potential for better understanding of the turbidity behaviour in a complex aquatic system such as the Amazon floodplain.

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