A network of integrate and fire neurons for visual selection

Biological systems have facility to capture salient object(s) in a given scene, but it is still a difficult task to be accomplished by artificial vision systems. In this paper a visual selection mechanism based on the integrate and fire neural network is proposed. The model not only can discriminate objects in a given visual scene, but also can deliver focus of attention to the salient object. Moreover, it processes a combination of relevant features of an input scene, such as intensity, color, orientation, and the contrast of them. In comparison to other visual selection approaches, this model presents several interesting features. It is able to capture attention of objects in complex forms, including those linearly nonseparable. Moreover, computer simulations show that the model produces results similar to those observed in natural vision systems.

Aerosol properties, in-canopy gradients, turbulent fluxes and VOC concentrations at a pristine forest site in Amazonia

Aerosol physical and chemical properties were measured in a forest site in central Amazonia (Cuieiras reservation, 2.61S; 60.21W) during the dry season of 2004 (Aug-Oct). Aerosol light scattering and absorption, mass concentration, elemental composition and size distributions were measured at three tower levels (Ground: 2 m; Canopy: 28 m, and Top: 40 m). For the first time, simultaneous eddy covariance fluxes of fine mode particles and volatile organic compounds (VOC) were measured above the Amazonian forest canopy. Aerosol fluxes were measured by eddy covariance using a Condensation Particle Counter (CPC) and a sonic anemometer. VOC fluxes were measured by disjunct eddy covariance using a Proton Transfer Reaction Mass Spectrometer (PTR-MS). At nighttime, a strong vertical gradient of phosphorus and potassium in the aerosol coarse mode was observed, with higher concentrations at Ground level. This suggests a source of primary biogenic particles below the canopy. Equivalent black carbon measurements indicate the presence of light-absorbing aerosols from biogenic origin. Aerosol number size distributions typically consisted of superimposed Aitken (76 nm) and accumulation modes (144 nm), without clear events of new particle formation. Isoprene and monoterpene fluxes reached respectively 7.4 and 0.82 mg m(-2) s(-1) around noon. An average fine particle flux of 0.05 +/- 0.10 10(6) m(-2) s(-1) was calculated, denoting an equilibrium between emission and deposition fluxes of fine mode particles at daytime. No significant correlations were found between VOC and fine mode aerosol concentrations or fluxes. (C) 2009 Elsevier Ltd. All rights reserved.

Electric field gradients in (111)In-doped (Hf/Zr)(3)Al(2) and (Hf/Zr)(4)Al(3) mixed compounds: ab initio calculations, perturbed angular correlation measurements and site preference

The quadrupolar hyperfine interactions of in-diffused (111)In -> (111)Cd probes in polycrystalline isostructural Zr(4)Al(3) and Hf(4)Al(3) samples containing small admixtures of the phases (Zr/Hf)(3)Al(2) were investigated. A strong preference of (111)In solutes for the contaminant (Zr/Hf)(3)Al(2) minority phases was observed. Detailed calculations of the electric field gradient (EFG) at the Cd nucleus using the full-potential augmented plane wave + local orbital formalism allowed us to assign the observed EFG fractions to the various lattice sites in the (Zr/Hf)(3)Al(2) compounds and to understand the preferential site occupation of the minority phases by the (111)In atoms. The effects of the size of the supercell and relaxation around the oversized In and Cd probe atoms were investigated in detail.

U-curve: A branch-and-bound optimization algorithm for U-shaped cost functions on Boolean lattices applied to the feature selection problem

This paper presents the formulation of a combinatorial optimization problem with the following characteristics: (i) the search space is the power set of a finite set structured as a Boolean lattice; (ii) the cost function forms a U-shaped curve when applied to any lattice chain. This formulation applies for feature selection in the context of pattern recognition. The known approaches for this problem are branch-and-bound algorithms and heuristics that explore partially the search space. Branch-and-bound algorithms are equivalent to the full search, while heuristics are not. This paper presents a branch-and-bound algorithm that differs from the others known by exploring the lattice structure and the U-shaped chain curves of the search space. The main contribution of this paper is the architecture of this algorithm that is based on the representation and exploration of the search space by new lattice properties proven here. Several experiments, with well known public data, indicate the superiority of the proposed method to the sequential floating forward selection (SFFS), which is a popular heuristic that gives good results in very short computational time. In all experiments, the proposed method got better or equal results in similar or even smaller computational time. (C) 2009 Elsevier Ltd. All rights reserved.

Cutpoint selection for discretizing a continuous covariate for generalized estimating equations

We consider consider the problem of dichotomizing a continuous covariate when performing a regression analysis based on a generalized estimation approach. The problem involves estimation of the cutpoint for the covariate and testing the hypothesis that the binary covariate constructed from the continuous covariate has a significant impact on the outcome. Due to the multiple testing used to find the optimal cutpoint, we need to make an adjustment to the usual significance test to preserve the type-I error rates. We illustrate the techniques on one data set of patients given unrelated hematopoietic stem cell transplantation. Here the question is whether the CD34 cell dose given to patient affects the outcome of the transplant and what is the smallest cell dose which is needed for good outcomes. (C) 2010 Elsevier BM. All rights reserved.

A non-normal topology generated by a two-point selection

We construct a two-point selection f : [P](2) -> P, where P is the set of the irrational numbers, such that the space (P, tau(f)) is not normal and it is not collectionwise Hausdorff either. Here, tau(f) denotes the topology generated by the two-point selection f. This example answers a question posed by V. Gutev and T. Nogura. We also show that if f :[X](2) -> X is a two-point selection such that the topology tau(f) has countable pseudocharacter, then tau(f) is a Tychonoff topology. (C) 2008 Elsevier B.V. All rights reserved.

International conference site selection criteria : And a case study of Stockholm as an international conference city

The purpose of this thesis is to identify the destination site selection criteria for internationalconferences from the perspectives of the three main players of the conference industry,conference buyers (organizers and delegates) and suppliers. Additionally, the researchidentifies the strengths and weaknesses of the congress cities of Stockholm and Vienna.Through a comparison with Vienna, the top city for hosting international conferences, a roadmap for Stockholm has been designed, to strengthen its congress tourism opportunities, thus,obtaining a higher status as an international congress city. This qualitative research hascombined both primary and secondary data methods, through semi-standardized expertinterviews and secondary studies respectively, to fulfil the study’s aim. The data have beenanalysed by applying the techniques of qualitative content analysis; the secondary dataadopting an inductive approach according to Mayring (2003) while the expert interviewsusing a deductive approach according to Meuser & Nagel (2009). The conclusions of thesecondary data have been further compared and contrasted with the outcomes of the primarydata, to propose fresh discoveries, clarifications, and concepts related to the site selectioncriteria for international conferences, and for the congress tourism industry of Stockholm. Theresearch discusses the discoveries of the site selection criteria, the implications of thestrengths and weaknesses of Stockholm in comparison to Vienna, recommendations forStockholm via a road map, and future research areas in detail. The findings andrecommendation, not only provide specific steps and inceptions that Stockholm as aninternational conference city can apply, but also propose findings, which can aid conferencebuyers and suppliers to cooperate, to strengthen their marketing strategies and developsuccessful international conferences and destinations to help achieve a greater competitiveadvantage.

Likelihood estimate of treatment effects under selection bias

We consider methods for estimating causal effects of treatment in the situation where the individuals in the treatment and the control group are self selected, i.e., the selection mechanism is not randomized. In this case, simple comparison of treated and control outcomes will not generally yield valid estimates of casual effects. The propensity score method is frequently used for the evaluation of treatment effect. However, this method is based onsome strong assumptions, which are not directly testable. In this paper, we present an alternative modeling approachto draw causal inference by using share random-effect model and the computational algorithm to draw likelihood based inference with such a model. With small numerical studies and a real data analysis, we show that our approach gives not only more efficient estimates but it is also less sensitive to model misspecifications, which we consider, than the existing methods.

Towards a Methodology for Coordination Mechanism Selection in Open Systems

Agent-oriented software engineering (AOSE) is a promising approach to developing applications for dynamic open systems. If well developed, these applications can be opportunistic, taking advantage of services implemented by other developers at appropriate times. However, methodologies are needed to aid the development of systems that are both flexible enough to be opportunistic and tightly defined by the application requirements. In this paper, we investigate how developers can choose the coordination mechanisms of agents so that the agents will best fulfil application requirements in an open system.