A control oriented model for manual-pick warehouses

Nowadays the low cost of wireless communications allows the real time monitoring of the state of manual-pick warehouse systems making possible the real time control of these systems. At this aim, an approach based on a two-level model is presented in this paper. At the lower level, Petri nets are used to build online a model representing the active missions state and to detect conflicts among resources. At the upper level, logical expressions are used to add constraints for a single mission or item. The model is proved to be effective for online monitoring, scheduling and rescheduling of warehouse activities.     

A hybrid model for real time simulation of urban traffic

In this paper a hybrid model is presented to predict the behavior of traffic in urban area. Intersections and on/off-ramps are modeled by Colored Timed Petri Nets while road links are modeled by a stochastic discrete time model. It is assumed that vehicle routings at each intersection are stochastic. A Particle Filter algorithm based on the hybrid model is developed to estimate the system state. The validation of the model by using real data is discussed. The limited computational effort required makes the model suitable to be used in simulation-based control schemes for urban traffic.     

Finite element shakedown analysis of two‐dimensional structures

In the present paper, the formulation proposed by Casciaro and Garcea (Comput. Meth. Appl. Mech. Eng., 2002; 191 :5761–5792) and applied to the shakedown analysis of plane frames, is extended to the analysis of two‐dimensional flat structures in both the cases of plane‐stress and plane‐strain. The discrete formulation is obtained using a mixed finite element in which both stress and displacement fields are interpolated. The material is assumed to be elasto‐plastic and a linearization of the elastic domain is performed. The result is a versatile iterative scheme well suited to implementation in general purpose FEM codes. An extensive series of numerical tests is presented showing the reliability of the proposed formulation. Copyright © 2005 John Wiley & Sons, Ltd.     

A Traffic Generator for Testing Communication Systems: Presentation,Implementation and Performance

This paper presents a multi-application traffic generator (MTG), aimed at the generation of packets over a LAN. The generated traffic simulates the one produced by a number of both isochronous and anisochronous applications, thus allowing the measurement of a number of parameters relevant to the communication network. From a test point of view, data generated by the MTG system is equivalent to data generated by real applications spread over a LAN. The MTG system is presented, its implementation is described, some figures relevant to the MTG performance are shown, and the statistical analysis which can be performed on the recorded data is briefly introduced. The user manual of the MTG system is referenced in (Celandroni, Ferro, and Potorti 1995).     

Integration of XML Schemas at various “severity” levels

This paper presents a novel approach for the integration of a set of eXtensible Markup Language (XML) Schemas. The proposed approach is specialized for XML, almost automatic, semantic and “light”. Further, an original peculiarity is that it is parametric w.r.t. a “severity” level against which the integration task is performed. The paper describes the approach in all details, illustrates various theoretical results, presents the experiments we have performed for testing it and, finally, compares it with various related approaches already proposed in the literature.     

Effects of secondary electron emission from a floating surface on the plasma sheath

The paper describes the region between a Maxwellian plasma source and a floating surface by a 1D-3 V fully kinetic, electrostatic particle simulation. The electric field is self-consistently computed from the Poisson equation. The secondary electron emission is modelled by considering an expression for the secondary emission coefficient dependent on the primary electron energy and surface materials and a realistic secondary electron distribution function is introduced at the collector surface. The model is able to simulate the space-charge-limited conditions as well as the positively charged wall cases.     

Psychological and Social Predictors of Changes in Fruit and Vegetable Consumption Over 12 Months Following Behavioral and Nutrition Education Counseling.

This study assessed psychological and social factors predicting 12-month changes in fruit and vegetable consumption achieved by 271 men and women from a low-income population randomized to brief behavioral and nutrition education counseling. Greater increases in fruit and vegetable intake were achieved in the behavioral than in the nutrition education condition (1.49 vs. 0.87 portions per day, p=.021). Increases were predicted by baseline social support for dietary change but not by baseline psychological measures. However, short-term (8-week) changes in dietary self-efficacy, encouragement, anticipated regret, perceived benefits, and knowledge of recommended intake predicted 12-month changes in fruit and vegetable consumption independently of gender, age, ethnicity, income, and baseline intake. These factors accounted for 51% of the superiority of behavioral counseling over nutrition education. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental and Numerical Analysis of Soil–Pipe Interaction

Cases of pipeline damage caused by landslides are common in coastal or mountainous regions, where a continuous monitoring/repair activity is planned in order to maintain their serviceability. The analysis of the soil–structure interaction phenomenon can be invoked to improve the planning and design of buried pipelines, to guide monitoring, and to reduce the risk of damage or failure. Two different approaches are considered in this paper: small scale laboratory tests and numerical simulations using the distinct element method (DEM). The experimental setup consists of a box filled with sand and water. Several experiments were performed, in which the diameter and the depth of the tube varied. The numerical simulations are divided in two separate series: in the first, the numerical model is calibrated and its reliability in reproducing the experimental tests is checked; in the second series, the direction of the relative displacement between the tube and the surrounding “numerical soil” varies over the range ±90° with respect to the horizontal. In the latter, both vertical and horizontal components of the drag force are measured and the corresponding interaction diagrams are constructed. The DEM simulations provide useful information about the shape of the failure mechanisms and the force transfer within the soil.     

Languages generated by P systems with active membranes

We propose an alternative approach to generate languages by means of P systems: building up an appropriate representation for a string by means of a corresponding membrane structure and then generating the string by visiting the membrane structure according to a well-specified strategy. To this aim, we consider P systems with active membranes, allowing membrane creation or division or duplication and dissolution, where the output of a computation may be obtained either by visiting the tree associated with the membrane structure, or by following the traces of a specific object, called traveller, or sending out the objects. For each of these approaches, we provide characterizations of recursively enumerable languages based on P systems that use different sets of operations for modifying the membrane structure. Francesco Bernardini: He started his Ph.D. at the University of Sheffield in December 2002 after having previously got a master degree in Computer Science from the University of Pisa in Italy. His research is dedicated to the study of theoretical aspects of membrane computing (P systems) and discrete models of biological systems based on P systems. Marian Gheorghe, Ph.D.: His main research interests are in computational models and their applications to software modelling and testing, formal specifications of agent based systems, software engineering. He was investigating computational power of various generative devices (regular, context-free, fully initial; grammar systems; L-systems and variants). He is currently interested in natural computing (membrane calculus) and biological modelling.     

Checking secure information flow in Java bytecode by code transformation and standard bytecode verification

A method is presented for checking secure information flow in Java bytecode, assuming a multilevel security policy that assigns security levels to the objects. The method exploits the type‐level abstract interpretation of standard bytecode verification to detect illegal information flows. We define an algorithm transforming the original code into another code in such a way that a typing error detected by the Verifier on the transformed code corresponds to a possible illicit information flow in the original code. We present a prototype tool that implements the method and we show an example of application. Copyright © 2004 John Wiley & Sons, Ltd.