A new class of copulas with tail dependence and a generalized tail dependence estimator

We present a new family of copulas (generalized mean copulas) which is positive comprehensive and allows for upper tail dependence. It includes the Spearman copula and a specific Fréchet copula as special cases. Some properties and a generalized tail dependence estimator are derived. Finally, a small simulation study is conducted. --Geometric mean,arithmetic mean,copula,tail dependence

Flexible Stereo: Constrained, Non-rigid, Wide-baseline Stereo Vision for Fixed-wing Aerial Platforms

This paper proposes a computationally efficient method to estimate the time-varying relative pose between two visual-inertial sensor rigs mounted on the flexible wings of a fixed-wing unmanned aerial vehicle (UAV). The estimated relative poses are used to generate highly accurate depth maps in real-time and can be employed for obstacle avoidance in low-altitude flights or landing maneuvers. The approach is structured as follows: Initially, a wing model is identified by fitting a probability density function to measured deviations from the nominal relative baseline transformation. At run-time, the prior knowledge about the wing model is fused in an Extended Kalman filter~(EKF) together with relative pose measurements obtained from solving a relative perspective N-point problem (PNP), and the linear accelerations and angular velocities measured by the two inertial measurement units (IMU) which are rigidly attached to the cameras. Results obtained from extensive synthetic experiments demonstrate that our proposed framework is able to estimate highly accurate baseline transformations and depth maps.Comment: Accepted for publication in IEEE International Conference on Robotics and Automation (ICRA), 2018, Brisban

The role of geographical proximity for project performance: Evidence from the German "Leading-Edge Cluster Competition"

The role of geographical proximity in fostering connections and knowledge flows between innovative actors ranks among the most controversial themes in the research of innovation systems, regional networks and new economic geography. While there is ample empirical evidence on the constituent force of co-location for the formation of research alliances, little attention has been paid to the actual consequences of geographical concentration of alliance partners for the subsequent performance of these linkages. In this paper we address this underexplored issue and aim to complement the rare examples of studies on the relevance of geographical proximity for research outputs. We utilize original and unique survey data from collaborative R&D projects that were funded within the "Leading-Edge Cluster Competition" - the main national cluster funding program in Germany in recent years. We find that the perception of the necessity of spatial proximity for project success is rather heterogeneous among the respondents of the funded projects. Moreover, the relationship between geographical distance and project success is by no means univocal and is mediated by various technological, organizational and institutional aspects. Our findings strongly support the assumption that the nature of knowledge involved determines the degree to which collaborators are reliant on being closely located to each other. The relevance of spatial proximity increases in exploration contexts when knowledge is novel and the innovation endeavor is more radical while this effect is less pronounced for projects with a stronger focus on basic research. Moreover, geographical proximity and project satisfaction foster cross- fertilization effects of LECC projects

Automated Reconstruction of Particle Cascades in High Energy Physics Experiments

We present a procedure for reconstructing particle cascades from event data measured in a high energy physics experiment. For evaluating the hypothesis of a specific physics process causing the observed data, all possible reconstruction versions of the scattering process are constructed from the final state objects. We describe the procedure as well as examples of physics processes of different complexity studied at hadron-hadron colliders. We estimate the performance by 20 microseconds per reconstructed decay vertex, and 0.6 kByte per reconstructed particle in the decay trees.Comment: 8 pages, 2 figures. Submitted to Computational Science & Discover

Phytoplankton survey of “Barrinha”lagoon (Mira – Portugal)

This work reports a one year survey (October 2008 to October 2009) where limnology and plankton data from Barrinha lagoon (Mira-Portugal - 40° 27′ 22″ N, 8° 48′ 7″ W) were analyzed. This lagoon shows peculiar geochemical features being one of the few places in Portugal where the freshwater bivalve Anodonta cygnea can be found. This study consisted on monthly collections of water samples, with identification and quantification of the planktonic communities found in the water. Physical-chemical parameters of the water were also analyzed (temperature, dissolved oxygen, conductivity, pH, nitrites, nitrates, ammonia) as well as organic and inorganic particles and bacteria in the water. The importance of plankton and of phytoplankton in particular is unquestionable; it is the base of the food chain, source of oxygen and can also be used as bio-indicator of water quality. A total of 75 taxa of plankton were identified in the water samples, being 71 of phytoplankton and 4 of zooplankton. The most abundant taxon was Chlorophyceae with 30 taxa (abundances vary from 25% to 75%), then by Bacillariophyceae with 20 taxa (abundances vary from 10% to 75%), followed by the Cryptophyceae represented dominantly by only one genus the Crypotmonas (abundances vary from 10% to 35%) and Cyanophyceae 10 taxa (which reach up a maximum of 7.5% of total abundances of phytoplankton). Among the zooplankton, that was always very scarce, the Protozoa were the main group found. In term of physical-chemical parameters of the water the data were quite uniform except in the end of summer, in this period the lagoon begins to show some signs of eutrophication: decay of nutrients concentration, organic and inorganic particles, followed by oxygen depletion, which favours a simple algae to growth (Cryptomonas) in detriment of all other species of plankton, that in this period reach its minimums. Escherischia coli, Enterococci and total aerobic mesophilic (TAM) microorganisms were indentified and quantified in the water, their abundances change throughout the year, their occurrence are human correlated and they give a good scenario about the water quality in the habitat

A new class of copulas with tail dependence and a generalized tail dependence estimator

We present a new family of copulas (generalized mean copulas) which is positive comprehensive and allows for upper tail dependence. It includes the Spearman copula and a specific Fréchet copula as special cases. Some properties and a generalized tail dependence estimator are derived. Finally, a small simulation study is conducted

Estudos preliminares de populações de náiades nos sectores terminais dos rios Tua e Sabor (bacia do Douro): análise do habitat e da qualidade da água e sedimentos

O exíguo conhecimento das condições ecológicas presentes nos rios Tua e Sabor, que permitem a existência de populações viáveis das náiades Unio delphinus (anteriormente designado por Unio cf. pictorum), Anodonta anatina e Potomida littoralis, é condição básica para a monitorização destes ecossistemas. Neste sentido, no Verão de 2009 foram feitos estudos preliminares de caracterização do habitat e microhabitat usado pelas espécies de náiades bem como análises à qualidade da água e sedimentos. No que concerne ao habitat, foi aplicada a metodologia RHS (River Habitat Survey) complementada com uma análise do microhabitat baseada em transeptos por cada troço de rio seleccionado. Foram, por isso, determinadas as variáveis profundidade, substrato dominante e sub-dominante, velocidade da corrente medida na coluna de água e no leito, e cobertura em cada área amostrada (0,25 m2). As náiades apresentaram uma distribuição espacial característica, concentrando-se principalmente em zonas ensombradas e de substrato fino. Relativamente à qualidade da água detectaram-se valores de condutividade >100 µS.cm-1, nutrientes, Amónia 0,18 +/- 0,02 mg/L, Nitritos e Nitratos 4cm) 7,0 x 103 ufc/ml e biofilme 5,0 x 104 ufc/ml e especialmente de E.coli (água 115 ufc/ml, sedimento superior (4cm) 12 ufc/ml e biofilme 400 ufc/ml) indicadoras de perturbação de origem antrópica. Como medida de conservação das diferentes espécies encontradas e destes ecossistemas aquáticos (rios Tua e Sabor), considera-se essencial a monitorização que vise a manutenção/melhoria da qualidade da água e do habitat, controlo das espécies exóticas e minimização dos efeitos da regularização e sobrepesca com o intuito de evitar a regressão assinalada noutros rios de Portugal