A polynomial rule for the problem of sharing delay costs in PERT networks

In this paper we define the weighted serial cost sharing rule for the cost allocation problem. We apply this new rule to the problem of sharing delay costs in a PERT network. This rule belongs to the Core and is the Weighted Shapley Value for a particular game. Furthermore, we present a characterization of this rule and a polynomial algorithm for its calculation.     

A software engineering approach for the development of heterogeneous robotic applications

One of the most evident characteristics of robotic applications is heterogeneity: large robotic projects involve many different researchers with very different programming needs and areas of research, using a variety of hardware and software that must be integrated efficiently (i.e.: with a low development cost) to construct applications that satisfy not only classic robotic requirements (fault-tolerance, real-time specifications, intensive access to hardware, etc.) but also software engineering aspects (reusability, maintainability, etc.). Most existing solutions to this problem either do not deal with such heterogeneity or do not cover specific robotic needs. In this paper we propose a framework for the integration of heterogeneous robotic software through a software engineering approach: the BABEL development system, which is aimed to cover the main phases of the application lifecycle (design, implementation, testing, and maintainance) when unavoidable heterogeneity conditions are present. The capabilities of our system are shown by its support for designing and implementing diverse real robotic applications that use several programming languages (C, C++, JAVA), execution platforms (RT-operating systems, MS-Windows, no operating system at all), communication middleware (CORBA, TCP/IP, USB), and also a variety of hardware components (Personal Computers, microcontrollers, and a wide diversity of sensor and actuator devices in mobile robots and manipulator arms).     

A Class of OFT Controllers for Torque-Saturated Robot Manipulators: Lyapunov Stability and Experimental Evaluation

The trajectory tracking of robot manipulators is addressed in this paper. Two important practical situations are considered: the fact that robot actuators have limited power, and that only position measurements are carried out. Let us notice that a few solutions for the torque-bounded OFT (output feedback tracking) control has been proposed. In this paper we contribute to this subject by presenting a class of OFT controllers for torque-constrained robots. The theory of singularly perturbed systems is crucial in the analysis of the closed-loop system trajectories. As a second contribution of this paper, we present a detailed experimental study of six control schemes, which were tested in a two degrees-of-freedom direct-drive robot, confirming the advantages of the proposed methodology.     

From human regulations to regulated software agents’ behavior

In order to design and implement electronic institutions that incorporate norms governing the behavior of the participants of those institutions, some crucial steps should be taken. The first problem is that human norms are (on purpose) specified on an abstract level. This ensures applicability of the norms over long periods of time in many different circumstances. However, for an electronic institution to function according to those norms, they should be concrete enough to be able to check them run time. A second problem is that norms describe which behavior is desirable and permitted, but not how this is achieved in an institution. In the “real world" regulations often indicate procedures for implementing and enforcing the law. Likewise we should devise means to annotate the norms with practical aspects such as enforcement mechanisms, sanctions, etc. in order to get requirements for an institution that will enforce norms (by either constraining behavior within the norms or reacting to violation of the norms). The choice of which kind of mechanism is chosen is not a normative one, but usually based on criteria of efficiency and/or feasibility of the mechanism. In this paper we present our view on how to approach these problems and other related issues to be solved in order to develop e-institutions capable to operate in complex, highly regulated scenarios.

Conductimetric immunosensor for atrazine detection based on antibodies labelled with gold nanoparticles

A novel conductimetric immunosensor for atrazine detection has been designed and developed. This immunosensor is mainly based on antibodies labelled with gold nanoparticles. Additionally, the immunosensor consists of an array of two coplanar non-passivated interdigitated metallic μ-electrodes (IDμE) and immunoreagents specifically developed to detect this pesticide. The chemical recognition layer was covalent immobilized on the interdigital space. Immunochemical detection of the concentration of atrazine is achieved by a competitive reaction that occurs before the inclusion of the labelled antibodies. It is shown that the gold nanoparticles provide an amplification of the conductive signal and hence makes possible to detect atrazine by means of simple DC measurements.The conductimetric immunosensor and its biofunctionalization steps have been characterized by chemical affinity methods and impedance spectroscopy.This work describes the immunosensor structure, fabrication, physico-chemical and analytical characterization, and the immunosensor response using conductivity measurements. The immunosensor developed detects atrazine with limits of detection in the order of 0.1–1 μg L⁻¹, far below the maximum residue level (MRL) (100 μg L⁻¹) established by European Union (EU) for residues of this herbicide in the wine.Although in this paper the competitive reaction occurs in buffer, an initial study of the wine matrix effect is also described.     

A comparative assessment of different methods for Landsat 7/ETM+ pansharpening

This article compares a set of relevant methods, based on different mathematical approaches, for Landsat 7 Enhanced Thematic Mapper Plus (ETM+) pansharpening. These are classical procedures such as principal component analysis and fast intensity hue saturation; methods based on wavelet transforms, such as wavelet à trous, additive wavelet luminance proportional and multidirectional–multiresolution methods; a method of a geostatistical nature, called downscaling cokriging (DCK); and finally, a Bayesian method (1cor). The comparison of the fused images is based on the qualitative and quantitative evaluation of their spatial and spectral characteristics by calculating statistical indices and parameters that measure the quality and coherence of the images. Moreover, the quality of the spectral information is studied indirectly by means of the Iterative Self-Organizing Data Analysis Technique (ISODATA) classification of the products of fusion. The results show that DCK and 1cor methods yielded better results than the wavelet-based methods. Particularly, DCK does not introduce artefacts in the estimation of the digital numbers corresponding with the source multispectral image and, therefore, it can be considered as the most coherent method.     

Interactive virtual probing of 4D MRI blood-flow

Better understanding of hemodynamics conceivably leads to improved diagnosis and prognosis of cardiovascular diseases. Therefore, an elaborate analysis of the blood-flow in heart and thoracic arteries is essential. Contemporary MRI techniques enable acquisition of quantitative time-resolved flow information, resulting in 4D velocity fields that capture the blood-flow behavior. Visual exploration of these fields provides comprehensive insight into the unsteady blood-flow behavior, and precedes a quantitative analysis of additional blood-flow parameters. The complete inspection requires accurate segmentation of anatomical structures, encompassing a time-consuming and hard-to-automate process, especially for malformed morphologies. We present a way to avoid the laborious segmentation process in case of qualitative inspection, by introducing an interactive virtual probe. This probe is positioned semi-automatically within the blood-flow field, and serves as a navigational object for visual exploration. The difficult task of determining position and orientation along the view-direction is automated by a fitting approach, aligning the probe with the orientations of the velocity field. The aligned probe provides an interactive seeding basis for various flow visualization approaches. We demonstrate illustration-inspired particles, integral lines and integral surfaces, conveying distinct characteristics of the unsteady blood-flow. Lastly, we present the results of an evaluation with domain experts, valuing the practical use of our probe and flow visualization techniques.     

Incorporating ionic size in the transport equations for charged nanopores

Nanopores with fixed charges show ionic selectivity because of the high surface potential and the small pore radius. In this limit, the size of the ions could no longer be ignored because they occupy a significant fraction of the pore and, in addition, they would reach unrealistic concentrations at the surface if treated as point charges. However, most models of selectivity assume point ions and ignore this fact. Although this approach shows the essential qualitative trends of the problem, it is not strictly valid for high surface potentials and low nanopore radii, which is just the case where a high ionic selectivity should be expected. We consider the effect of ion size on the electrical double layer within a charged cylindrical nanopore using an extended Poisson–Boltzmann equation, paying special attention to (non-equilibrium) transport properties such as the streaming potential, the counter-ion transport number, and the electrical conductance. The first two quantities are related to the nanopore selectivity while the third one characterizes the conductive properties. We discuss the nanopore characteristics in terms of the ratio between the electrolyte and fixed charge concentrations and the ratio between the ionic and nanopore radii showing the experimental range where the point ion model can still be useful. Even for relatively small inorganic ions at intermediate concentrations, ion size effects could be significant for a quantitative estimation of the nanopore selectivity in the case of high surface charge densities.