The impact of ICT on intermodal transportation systems: A modelling approach by Petri nets

The paper addresses the issues of modelling and managing Intermodal Transportation Systems (ITS) at the operational level, considering the impact of the new Information and Communication Technologies (ICT). ITS are regarded as discrete event systems and are modelled in a timed Petri net framework. In order to show the efficiency of the ITS modelling and controlling technique, the case study of the ferry terminal of Trieste (Italy) is considered. The results show that the approach can be employed to verify the potential of ICT for efficient real time management of ITS, and their impact on the ITS infrastructures.     

Determination of biogenic amines in fresh and processed meat by ion chromatography and integrated pulsed amperometric detection on Au electrode

A selective cation exchange chromatographic method, coupled to integrated pulsed amperometric detection, has been developed to quantify biogenic amines in fresh and processed meat. The method is based on gradient elution of aqueous methanesulfonic acid with post column addition of a strong base to obtain suitable conditions for amperometric detection. A potential wave-form able to keep long time performance of the Au electrode was set up. The analysis time is about 68 min. Amounts of tyramine, putrescine, cadaverine, histamine, agmatine, spermidine and spermine were measured, after extraction with perchloric acid. The method was used to determine analytes in fresh and processed meat. Analyte quantification was made with external calibration method after demonstration that matrix effects were not present. All analytes were identified in real samples except phenethylamine which is eluted in a zone of the chromatogram rich of interfering peaks. Repeatabilities, computed on their amounts in real samples, were better than 9% for all of them. Detection limits were computed according to the Hubaux–Vos method. The obtained values ranged between 0.70 and 2.12 mg/l corresponding to 7–21 mg/kg, low enough to determine all analytes in real matrices.     

Prematurity and maternal folate deficiency: anemia during pregnancy study group results in Valencia, Venezuela

The purpose of this study was to determine the association and its magnitude between prematurity and folate deficiency in women in their third trimester of pregnancy, and at labor. An incident case-control study was conducted using 2 controls per case. Data was obtained in a tertiary hospital in Valencia, Venezuela. A total of 543 women who delivered between May and December 1996 entered into the study. Women having a preterm delivery (< 37 weeks of gestation at delivery) were defined as cases (n = 181). Anemia was defined according to WHO as Hb less than 11 g/dL, when a pregnant woman had a folate serum level < 3 microg/ml was considered a folate deficiency. Logistic regression was used to analyze the data and likelihood ratio test was done for model comparison. Folate deficiency was found to be significantly associated with prematurity (Odds Ratio: 1.97; 95%CI = 1.06 to 3.68 P = .032), after adjusting for prior preterm labor, prenatal care visits, prior abortion, prior fetal death, placental abruption, and premature rupture oval membranes. In conclusion, maternal folate deficiency at the end of the third trimester of pregnancy, at labor, was associated with an increased risk of prematurity.     

Frequency-related effects in the optimization of coils for the magnetic stimulation of the nervous system

Magnetic stimulation of the nervous system is a non-invasive technique with a large number of applications in neurological diagnosis, brain research, and, recently, therapy. New applications require engineering modifications in order to decrease power consumption and coil heating. This can be accomplished by optimized coils with minimized resistance. In this study the influence of some frequency-related effects (skin and proximity effect) on the coil resistance will be discussed, together with the role played by wire shape, wire section, and twisting effect. The results show that the coil resistance increases with frequency. As an example, for a 20-mm2 circular wire section, the skin effect in the typical frequency range of magnetic stimulator devices (2-4 kHz) increases the coil resistance up to about 45% with respect to its dc value. Moreover, the influence of the frequency is lower for flat wire sections and reasonably small helix twist angle of the coil.     

Propagation of cylindrically symmetric fields in uniaxial crystals

We investigate the paraxial propagation along the optical axis of a uniaxially anisotropic crystal of a general paraxial beam whose boundary Cartesian components possess cylindrical symmetry. This property allows us to obtain expressions whose dependence on the azimuth angle phi (in cylindrical coordinates) is fully described and very simple. We also find that the beam loses its boundary cylindrical symmetry during propagation, as a consequence of medium anisotropy. Further, these expressions elucidate the way in which the anisotropy changes the state of polarization. As an example, we discuss the case of a Gaussian beam focused into the crystal by a thin spherical lens.     

3-D Reconstruction of Urban Scenes from Image Sequences

In this paper, we address the problem of the recovery of a realistic textured model of a scene from a sequence of images, without any prior knowledge either about the parameters of the cameras or about their motion. We do not require any knowledge of the absolute coordinates of some control points in the scene to achieve this goal. First, using various computer vision tools, we establish correspondences between the images and recover the epipolar geometry, from which we show how to compute the complete set of perspective projection matrices for all camera positions. Then, we proceed to reconstruct the geometry of the scene. We show how to rely on information of the scene such as parallel lines or known angles in order to reconstruct the geometry of the scene up to, respectively, an unknown affine transformation or an unknown similitude. Alternatively, if this information is not available, we can still recover the Euclidean structure of the scene through the techniques of self-calibration. The scene geometry is modeled as a set of polyhedra. Textures to be mapped on the scene polygons are extracted automatically from the images. We show how several images can be combined through mosaicing in order to automatically remove visual artifacts such as pedestrians or trees from the textures.This vision system has been implemented as a vision server, which provides to a CAD-CAM modeler geometry or texture information extracted from the set of images. The whole system allows efficient and fast production of scene models of high quality for such applications as simulation, virtual, or augmented reality.     

Dependability issues in visual–haptic interfaces

Dependability of a system is commonly referred to its reliability, its availability and its maintenability (RAM), but when this concept is applied to user interfaces there is no common agreement on what aspects of user–system interaction are related to a satisfactory RAM level for the whole system. In particular, when dealing with haptic systems, interface dependability may become a crucial issue in medical and in military domains when life-critical systems are to be manipulated or where costly remote control operations are to be performed, like in industrial processes control or in aerospace/automotive engineering and manufacturing. This paper discusses the role of dependability in haptic user interfaces, aiming to the definition of a framework for the assessment of the usability and dependability properties of haptic systems and their possible correlations. The research is based on the analysis of a visual–haptic-based simulator targeted to maintenance activity training for aerospace industry which is taken as a case study. As a result, we propose a novel framework able to collect and then process relevant interaction data during the execution of haptic tasks, enabling to analyze dependability vs. usability correlations.     

A branch-and-cut algorithm for a production scheduling problem with sequence-dependent and time-dependent setup times

This paper introduces and compares three different formulations of a production scheduling problem with sequence-dependent and time-dependent setup times on a single machine. The setup is divided into two parts: one that can be performed at any time and another one that is restricted to be performed outside of a given time interval. As a result, the setup time between two jobs is a function of the completion time of the first job. The problem can be formulated as a time-dependent traveling salesman problem, where the travel time between two nodes is a function of the departure time from the first node. We show that the resulting formulation can be strengthened to provide better linear programming relaxation lower bounds. We also introduce several families of valid inequalities which are used within a branch-and-cut algorithm. Computational experiments show that this algorithm can solve some instances with up to 50 jobs within reasonable computing times.