Search results for "NBA"
showing 10 items of 476 documents
Particle distribution in dilute solid liquid unbaffled tanks via a novel laser sheet and image analysis based technique
2013
The availability of experimental information on particle distribution inside stirred tanks is a topic of great importance for many industrial applications such as catalysis and polymerization. The measurement of solid particle distribution is not simple and the development of suitable measuring techniques is still an open problem in chemical engineering research. In this work, a non-intrusive optical technique for measuring particle concentration fields in solid–liquid systems is discussed. The “Laser Sheet Image Analysis” (LSIA) technique described here makes use of a laser sheet, a digital camera for image acquisition and a suitable procedure for post-processing. It is able to provide sol…
Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis
2013
There is a growing interest in using unbaffled stirred tanks for addressing a number of processing needs such as low shear damage (sensitive biocultures), low attrition (solid–liquid applications), deep-cleaning/sterilization (pharmaceutical applications). The main feature of uncovered, unbaffled stirred tanks is highly swirling motion of the fluid that results in a deformation of the free liquid surface. At sufficiently high agitation speeds the resulting whirlpool reaches the impeller and gives rise to a gas–liquid dispersion, so leading to the formation of a dispersion without the use of gas-sparger; the so-called self-inducing operation of the vessel. In this work, digital image analysi…
Diagnosis of mechanical unbalance for double cage induction motor load in time-varying conditions based on motor vibration signature analysis
2013
This paper investigates the detectability of mechanical unbalance in double cage induction motor load using motor vibration signature analysis technique. Rotor imbalances induce specific harmonic components in electrical, electromagnetical, and mechanical quantities. Harmonic components characteristic of this category of rotor faults, issued from vibration signals analysis, are closely related to rotating speed of the rotor, which complicates its detection under non-stationary operating conditions of the motor. Firstly, experimental results were performed first under healthy and mechanical load unbalance cases, for different load levels under steady-state operating conditions to evaluate th…
Large-Eddy Simulation of Turbulent Flow in an Unbaffled Stirred Tank Driven by a Rushton Turbine
2005
The turbulent flow fieldgeneratedin an unbaffledstirredtank by a Rushton turbine was computedby large-eddy simulation (LES). The Smagorinsky model was used to model the unresolved, or sub-grid, scales. A general purpose CFD code was appropriately modified in order to allow the computation of the sub-gridviscosity andto perform statistics on the computedresults. The numerical predictions were comparedwith the literature results for comparable configurations andwith experimental data obtainedusing particle image velocimetry. A very goodagreement was foundas regards both time-averagedresolv edfield s andturb ulence quantities. 2004 Elsevier Ltd. All rights reserved.
Kanban Systems in the Context of the Enterprise Systems
2021
Companies are under increasing pressure from customers, competitors, limited resources, etc. These conditions oblige companies to permanently improve their organizational structure and the activities of all system’s flows. The paper analyses the types of Kanban systems, in the broader context of the enterprise systems. The most important reference architectures were analysed (with the emphasis on the modules dedicated to flow description) and the standards that allow the activity modelling of a manufacturing enterprises. Starting from this context, the paper describes three models of Kanban systems that are specific to companies with different information systems development. Models are: Pu…
Psychometric Properties Of A Questionnaire Measuring The Antecedents Of Entrepreneurship Education Intention
2017
A limit of the questionnaires measuring Entrepreneurial Intention (EI) is the lack of a multidimensional vision of its antecedents. The definition of a multidimensional model of the main drivers affecting the intentions of aspiring entrepreneurs in building a start-up seems a fundamental milestone to overcome this pitfall. This paper aims to explore the internal consistency reliability of a new multidimensional questionnaire measuring the antecedents of EI and Entrepreneurial Education Intention (EEI). The tool consists in a self-administered online questionnaire that has been built in accordance with the Theory of Planned Behavior in entrepreneurship research. It includes 54 items adapted …
A dempster-shafer theory-based approach to compute the birnbaum importance measure under epistemic uncertainty
2016
Importance Measures (IMs) aim at quantifying the contribution of components to the system performance. In Process Risk Assessment (PRA), they are commonly used by risk managers to derive information about the risk/safety significance of events. However, IMs are typically calculated without taking into account the uncertainty that inevitably occurs whenever the input reliability data are poor. In literature, uncertainty arising from the lack of knowledge on the system/process parameters is defined as epistemic or subjective uncertainty. The present work aims at investigating on its influence on the Birnbaum IM and on how such an uncertainty could be accounted for in the components ranking. I…
Avoiding strange attractors in efficient parametric families of iterative methods for solving nonlinear problems
2019
[EN] Searching zeros of nonlinear functions often employs iterative procedures. In this paper, we construct several families of iterative methods with memory from one without memory, that is, we have increased the order of convergence without adding new functional evaluations. The main aim of this manuscript yields in the advantage that the use of real multidimensional dynamics gives us to decide among the different classes designed and, afterwards, to select its most stable members. Moreover, we have found some elements of the family whose behavior includes strange attractors of different kinds that must be avoided in practice. In this sense, Feigenbaum diagrams have resulted an extremely …
Caries and dental fluorosis in a western Saharan population of refugee children
2008
The aim of this study was to investigate the relationship between dental fluorosis and dental caries among western Saharan refugee children. The western Saharan child population is characterized by adverse living conditions, an unbalanced diet, poor oral hygiene habits, and a concentration of fluoride in the drinking water of around 2 p.p.m. (2 mg l(-1)). A sample consisting of 360 children, 6-7 yr of age, and 212 children, 11-13 yr of age, was obtained from four refugee camps (Smara, Awsard, El-Aaiun, and 27-February) situated in the vicinity of Tindouf (southern Algeria). The children were examined using the World Health Organization criteria for caries diagnosis and Dean's index for fluo…
Scale-up and viscosity effects on gas–liquid mass transfer rates in unbaffled stirred tanks
2018
Abstract The interest in the process industry on unbaffled stirred tanks has greatly expanded in the last years because they may bring about significant advantages in a number of applications, including biochemical, food and pharmaceutical processes where the presence of baffles is undesirable for several reasons. Despite their application potential, unbaffled vessels still lack fundamental information, due to the fact that only recently their capabilities have started being dug out. The lack of information on scale up effects is possibly the main reason hindering practical applications. In this work the influence of vessel size and liquid viscosity on the mass transfer performance in unbaf…