Search results for " Opera"

An imprecise Fault Tree Analysis for the estimation of the Rate of OCcurrence Of Failure (ROCOF)

2013

Abstract The paper proposes an imprecise Fault Tree Analysis in order to characterize systems affected by the lack of reliability data. Differently from other research works, the paper introduces a classification of basic events into two categories, namely Initiators and Enablers . Actually, in real industrial systems some events refer to component failures or process parameter deviations from normal operating conditions ( Initiators ), whereas others refer to the functioning of safety barriers to be activated on demand ( Enablers ). As a consequence, the output parameter of interest is not the classical probability of occurrence of the top event, but its Rate of OCcurrence (ROCOF) over a s…

General information model for representing machining features in CAPP systems

2004

Today, the generality of computer-aided process planning (CAPP) systems and their standardization do not achieve satisfactory standards levels for industry. One of the major causes here is the difficulty of integration with computer-aided design applications, due mainly to the product model used. It is therefore necessary to identify models that are general with regard to the products, but at the same time suitable for CAPP. A product model suitable for CAPP must represent the product conceptually, enabling the development of process planning functions that operate with manufacturing concepts. It is therefore necessary to develop product information models using this philosophy. The present…

The New Nino Capability Index for Dynamic Process Capability Analysis

2013

The process capability analysis is a crucial activity to evaluate if the process outcome meets the design specifications. Classically, such analysis is performed by verifying the in-control condition of the process and evaluating suitable capability indices, by assuming the process in-control steady-state condition. However, the in-control period of the process characterizes only a part of the system functioning cycle, the one with the lower defective rate. In particular, the system functioning cycle is also characterized by the out-of-control period, during which a greater defective rate is produced, and such increasing is not considered by the widely adopted capability indices. As consequ…

Low-cost underwater navigation systems by multi-pressure measurements and AHRS data

2017

This paper deals with accurate navigation for underwater remotely operated vehicles. A feasibility study for a multi-pressure device to be mounted on an ROV is presented. The device can provide accurate estimates of a ROV orientation and angular speed. It is based on the well-known total pressure principle, also used in a Pitot tube, and allows reconstruction of static and dynamic pressures, which in turn provide good estimates of the ROV's orientation and rotational speed, respectively. An appealing feature of the proposed device is its ability to provide accurate estimates even for low-speed movements.

A model of goal dynamics in technology-based organizations

2011

The purpose of the present work is to build a suitable system dynamics model for goal dynamics in organizations, as proposed by Barlas and Yasarcan (2008). The proposed model does not bear any ambition of being exhaustive: the main objective of this paper is to propose a model of goal dynamics in which Goal Setting, Management by Objectives and Training are viewed as human resource practices able to enhance workers' goal commitment, and therefore, improve organizational performance. In the first part of this paper, an analysis of the Goal Setting Theory and the role of goal setting practices, in bettering worker's performance, are stressed. In the second part, a case-study, the causal loop …

2016

VISOCAR: an autonomous industrial transport vehicle guided by visual navigation

2003

The authors describe a vision system, called VISOCAR, for mobile robot guidance in industrial environments. VISOCAR is an optically navigating AGV (automatically guided vehicle) that, owing to its local intelligence, can travel automatically in its natural environment, does not need any dedicated floor installations, and does not impose any restrictions on the route network or factory environment. It can navigate accurately on its track and integrate multisensor information to enhance functional redundancy and system reliability. It is shown that the navigation task can be broken down into a hierarchy of goals, which can be attained by functionally independent modules. The system architectu…

Split-Delivery Capacitated Arc-Routing Problem: Lower Bound and Metaheuristic

2010

International audience; This paper proposes lower and upper bounds for the split-delivery capacitated arc-routing problem (SDCARP), a variant of the capacitated arc-routing problem in which an edge can be serviced by several vehicles. Recent papers on related problems in node routing have shown that this policy can bring significant savings. It is also more realistic in applications such as urban refuse collection, where a vehicle can become full in the middle of a street segment. This work presents the first lower bound for the SDCARP, computed with a cutting plane algorithm and an evolutionary local search reinforced by a multistart procedure and a variable neighborhood descent. Tests on …

Real-time weighting optimization in Chinese Postman Problem

2013

International audience; In this study, based on real-time constraint, an optimization method is proposed for solving the problem of the optimal tour. For that, we will construct a graph containing the real-time state of traffic. The collected data will be used to predict the future state traffic and to give an optimized cost of the tour. This optimization is tested in different sizes of the road networks. The results show that the proposed method is efficient and effective in solving the Chinese Postman Problem in real-time.

A polynomial algorithm solving a special class of hybrid optimal control problems

2006

Hybrid optimal control problems are, in general, difficult to solve. A current research goal is to isolate those problems that lead to tractable solutions [5]. In this paper, we identify a special class of hybrid optimal control problems which are easy to solve. We do this by using a paradigm borrowed from the Operations Research field. As main result, we present a solution algorithm that converges to the exact solution in polynomial time. Our approach consists in approximating the hybrid optimal control problem via an integer-linear programming reformulation. The integer-linear programming problem is a Set-covering one with a totally unimodular constraint matrix and therefore solving the S…