Tuning of Adaptive Weight Depth Map Generation Algorithms

In depth map generation algorithms, parameters settings to yield an accurate disparity map estimation are usually chosen empirically or based on unplanned experiments. Algorithms’ performance is measured based on the distance of the algorithm results vs. the Ground Truth by Middlebury’s standards. This work shows a systematic statistical approach including exploratory data analyses on over 14000 images and designs of experiments using 31 depth maps to measure the relative influence of the parameters and to fine-tune them based on the number of bad pixels. The implemented methodology improves the performance of adaptive weight based dense depth map algorithms. As a result, the algorithm improves from 16.78 to 14.48 % bad pixels using a classical exploratory data analysis of over 14000 existing images, while using designs of computer experiments with 31 runs yielded an even better performance by lowering bad pixels from 16.78 to 13 %.     

Brazil's 2001 energy crisis monitored from space

Data sensed by the US Air Force Defence Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) during the years 2000 and 2001 in Brazil were tested as a tool to monitor reduction of nocturnal lighting. This particular timing was examined as the Brazilian population and industry were forced to reduce electric power consumption by 20% during 2001, in relation to 2000, for a period of several months, starting officially on 1 June 2001. Large urban agglomerates were compelled to switch off city lights by at least the same amount. The Distrito Federal (DF), including the Brazilian capital, Brasilia, was one of the primary areas where the government actively sought electric power consumption reductions. Using the DF as a study case, we demonstrate that the mean grey levels derived from averaging DMSP-OLS data acquired over urban centres appear to be a useful index to monitor relative oscillations in energy consumption.     

A comparison of experimental energy balance components data and SEBAL model results in Dourados,Brazil

The understanding of surface energy flux is important as regards weather and climate models. Therefore, analysis of remotely sensed data, estimation of surface energy balance components (fluxes), validating experiments and results are discussed in this work. Data extracted from NOAA–AVHRR (National Oceanic and Atmospheric Administration–Advanced Very High Resolution Radiometer) satellite images were used to estimate the fluxes based on the SEBAL (Surface Energy Balance for Land) algorithm, as suggested by Bastiaanssen [Bastiaanssen, W.G.M., 1995, Regionalization of surface flux densites and moisture indicators in composite terrain. PhD thesis, Wageningen Agricultural University, The Netherlands.] To validate the results, one wide-ranging field experiment was organized near Dourados, municipality in the Brazilian state of Mato Grosso do Sul, during the summer of 1999. The experiment involved simultaneous taking of satellite images and in-situ measurements. SEBAL results are shown and discussed. The obtained average errors are less than 4%, 6% and 7% for net surface radiation, surface heat and latent flux estimations, respectively, as compared to the in-situ measurements.     

Merging WSR-88D stage III radar rainfall data with rain gauge measurements using wavelet analysis

Albeit weather surveillance radar (WSR)-88D stage III radar rainfall (RR) data can generally capture the spatial variability of precipitation fields, its rainfall depth for cold seasons dominated by stratiform storms tends to be underestimated. This study proposed merging WSR-88D stage III data with rain gauge data using the Haar wavelet scheme and compared its with that merged by the statistical objective analysis (SOA) scheme. The idea is to exploit the strength of radar that better captures the spatial variability of rainfall and that of rain gauges that measure the rainfall depth more accurately. A Haar wavelet was used because of its simplicity and the appealing physical interpretation of its coefficients as directional gradients of rainfall, whose spatial correlation structure was accounted for through a polynomial function. From analysing 89 storms over the Blue River Basin (BRB), Oklahoma, during 1994–2000, the results show that the underestimation problem of WSR-88D RR was generally more pronounced during the cold season dominated by stratiform storms than warm season dominated by convective storms. The wavelet scheme was better than SOA in reducing the radar's underestimation of rainfall depths while maintaining the spatial variability of the original radar data, as shown by its merged rainfall patterns and the more accurate streamflow hydrographs simulated by a semi-distributed, physics-based rainfall-runoff model – semi-distributed physics-based hydrologic model using remote sensing (DPHM-RS) – driven by the merged data.     

Detecting deforestation with multitemporal L‐band SAR imagery: a case study in western Brazilian Amazônia

Applications of L‐band SAR data to map deforestation are generally based on the assumption that undisturbed forests consistently exhibit higher radar backscatter than deforested areas. In this Letter we show that depending on the stage of the deforestation process (slashing, burning and terrain clearing), this assumption is not always valid, and deforested areas may display a stronger radar return backscatter than primary forest. The analysis of multitemporal SAR images, supported by several Landsat Thematic Mapper (TM) images and field knowledge, showed that wood materials left following the deforestation practices function as corner reflectors, causing an initial increase in the radar backscatter, which then subsequently decreases over time as the debris on these fields are removed.     

The direct Lyapunov method for the stabilisation of the Furuta pendulum

A nonlinear controller for the stabilisation of the Furuta pendulum is presented. The control strategy is based on a partial feedback linearisation. In a first stage only the actuated coordinate of the Furuta pendulum is linearised. Then, the stabilising feedback controller is obtained by applying the Lyapunov direct method. That is, using this method we prove local asymptotic stability and demonstrate that the closed-loop system has a large region of attraction. The stability analysis is carried out by means of LaSalle's invariance principle. To assess the controller effectiveness, the results of the corresponding numerical simulations are presented.     

Workspace analysis of positioning discontinuities due to clearances in parallel manipulators

Clearances at joints produce a loss of accuracy when positioning a mechanism. The end-effector pose error due to clearances depends on the mechanism configuration, the magnitude of the clearance itself and applied external wrenches. Sudden changes which occur in the actual posture of the mechanism owing to a change of contact mode at joints can be detected in the neighbourhood of some configuration. These sudden changes lead to positioning discontinuities on certain trajectories, or on the workspace. In this paper, a methodology for analysing the location of the discontinuities by means of a dynamic or kinetostatic analysis is presented. The advantages of choosing either the dynamic or the kinetostatic approach are analysed, making use of the 5R planar mechanism.     

Including different kinds of preferences in a multi-objective ant algorithm for time and space assembly line balancing on different Nissan scenarios

Most of the decision support systems for balancing industrial assembly lines are designed to report a huge number of possible line configurations, according to several criteria. In this contribution, we tackle a more realistic variant of the classical assembly line problem formulation, time and space assembly line balancing. Our goal is to study the influence of incorporating user preferences based on Nissan automotive domain knowledge to guide the multi-objective search process with two different aims. First, to reduce the number of equally preferred assembly line configurations (i.e., solutions in the decision space) according to Nissan plants requirements. Second, to only provide the plant managers with configurations of their contextual interest in the objective space (i.e., solutions within their preferred Pareto front region) based on real-world economical variables. We face the said problem with a multi-objective ant colony optimisation algorithm. Using the real data of the Nissan Pathfinder engine, a solid empirical study is carried out to obtain the most useful solutions for the decision makers in six different Nissan scenarios around the world.     

SocialVPN: Enabling wide-area collaboration with integrated social and overlay networks

Trusted collaborative systems require peers to be able to communicate over private, authenticated end-to-end channels. Network-layer approaches such as Virtual Private Networks (VPNs) exist, but require considerable setup and management which hinder the establishment of ad-hoc collaborative environments: trust needs to be established, cryptographic keys need to be exchanged, and private network tunnels need to be created and maintained among end users. In this paper, we propose a novel system architecture which leverages existing social infrastructures to enable ad-hoc VPNs which are self-configuring, self-managing, yet maintain security amongst trusted and untrusted third parties. The key principles of our approach are: (1) self-configuring virtual network overlays enable seamless bi-directional IP-layer connectivity to socially connected parties; (2) online social networking relationships facilitate the establishment of trust relationships among peers; and (3) both centralized and decentralized databases of social network relationships can be securely integrated into existing public-key cryptography (PKI) implementations to authenticate and encrypt end-to-end traffic flows. The main contribution of this paper is a new peer-to-peer overlay architecture that securely and autonomously creates VPN tunnels connecting social peers, where online identities and social networking relationships may be obtained from centralized infrastructures, or managed in a decentralized fashion by the peers themselves.This paper also reports on the design and performance of a prototype implementation that embodies the SocialVPN architecture. The SocialVPN router builds upon IP-over-P2P (IPOP) virtual networks and a PKI-based tunneling infrastructure, which integrates with both centralized and decentralized social networking systems including Facebook, the Drupal open-source content management system, and emailing systems with PGP support. We demonstrate our prototype’s ability to support existing, unmodified TCP/IP applications while transparently dealing with user connectivity behind Network Address Translators (NATs). We also present qualitative and quantitative analyses of functionality and performance based on wide-area network experiments using PlanetLab and Amazon EC2.