144 research outputs found
A New Simple Friction Model for S. I. Engine
No full textInternal combustion engine modeling is nowadays a widely employed tool for modern engine development. Zero and mono dimensional models of the intake and exhaust systems, combined with multi-zone combustion models, proved to be reliable enough for the accurate evaluation of in-cylinder pressure, which in turn allow the estimation of the engine performance in terms of indicated mean effective pressure (IMEP). In order to evaluate the net engine output, both the torque dissipation due to friction and the energy drawn by accessories must be taken into consideration, hence a model for the friction mean effective pressure (FMEP) evaluation is needed. One of the most used models accounts for engine speed dependent friction by means of a quadratic law, while the effect of engine load (i.e. the thrust that the gas exercises on the piston surface) is considered by means of a linear dependence from the maximum in-cylinder pressure: hence the model requires the calibration of four constants by means of experimental data. The author, on the basis of data acquired during an extensive experimental campaign carried out on the engine test bed, found this model to give an unsatisfying prediction, above all for retarded pressure cycles (i.e. with peak pressure positions higher than 20 crank angle degrees after top dead centre): hence, by means of analysis performed using these experimental data, the author arrived at a new formulation of the friction model, which substantially take into account the effect of engine load by means of the Location of Pressure Peak (LPP). The new model, once calibrated, proved to be effectively more accurate in the prediction of the FMEP than the Chen-Flynn model
Building an ANFIS-based Decision Support System for Regional Growth: The Case of European Regions
No full textThis paper proposes a Decision Support System that can provide European policy makers with systematic guidance in allocating and prioritizing scant public resources. We do so by taking the stance of the Smart Specialisation Strategies which aim at consolidating the regional strengths and make effective and efficient use of public investment in R&D. By applying the ANFIS method we were able to understand how – and to what extent – the competitiveness drivers promoted technological development and how the latter contributes to the economic growth of European regions. We used socio-economic, spatial, and patent-based data to train, test and validate the models. What emerges is that an increase of R&D investments enhances the regional employment rate and the number of patents per capita; in turn, by taking into account the several combinations of specialization and diversification indicators, this leads to an increase of the regional GDP
Internal migration and technical efficiency: the case of Italy
No full textThe aim of the paper is to contribute to the study of the determinants of the internal mobility of people. To study the determinants of internal migration, we introduce a new explanatory variable, i.e. technical efficiency of Local Labour Market Areas. This variable is particularly relevant, as it allows us to summarize the entrepreneurial capacity connected to the cultural and social context of an area. Our results, for the case of Italy, suggest that technical efficiency contributes greatly to explaining internal migratory flows and the various patterns of migration among different groups of individuals. By looking more specifically at different groups of individuals, we also uncover important differences between natives and foreigners and among different age-groups
A COMPARISON BETWEEN COMBUSTION PHASE INDICATORS FOR OPTIMAL SPARK TIMING
No full textThe closed-loop control of internal combustion engine spark timing may be accomplished by means of a combustion phase indicator i.e., a parameter derived from in-cylinder pressure analysis, whose variation is mainly referable to combustion phase shift and assumes a fixed reference value under optimal spark timing operation. The aim of the present work is a comparison between different combustion phase indicators, focusing on the performance attainable by a feedback spark timing control, which uses the indicator as pilot variable. An extensive experimental investigation has been carried out, verifying the relationship between indicators' optimal values and the main engine running parameters: engine speed, load, and mixture strength. Moreover assessment on the effect of the most common pressure measurement problems (which are mainly related to pressure referencing, sampling resolution, top dead center determination, and cycle-by-cycle variations) on the indicators' values and on the performance attainable by the spark timing control is included. The results of the comparison point out two indicators as the most suitable: the location of pressure peak and the location of maximum heat release rate. The latter, not available in literature, has been introduced by the author as an alternative to the 50% of mass fraction burned
Analisi economica delle politiche di gestione della pesca nel Golfo di Castellammare
No full textThis paper describes the effects of the trawl ban in the Gulf of Castellammare (NW Sicily) on the economics of the local trawl fishery, focusing on the effectiveness of monetary fines and on the failures of regulation enforcement.THE FULL VERSION OF THIS ARTICLE SHOULD BE REQUESTED TO THE AUTHOR (CARLO PIPITONE: [email protected]) WITH PROPER JUSTIFICATION
Spark ignition feedback control by means of combustion phase indicators on steady and transient operation
No full textIn order to reduce fuel cost and CO2 emissions, modern spark ignition (SI) engines need to lower as much as possible fuel consumption. A crucial factor for efficiency improvement is represented by the combustion phase, which in an SI engine is controlled acting on the spark advance. This fundamental engine parameter is currently controlled in an open-loop by means of maps stored in the electronic control unit (ECU) memory: such kind of control, however, does not allow running the engine always at its best performance, since optimal combustion phase depends on many variables, like ambient conditions, fuel quality, engine aging, and wear, etc. A better choice would be represented by a closed-loop spark timing control, which may be pursued by means of combustion phase indicators, i.e., parameters mostly derived from in-cylinder pressure analysis that assume fixed reference values when the combustion phase is optimal. As documented in literature, the use of combustion phase indicators allows the determination of the best spark advance, apart from any variable or boundary condition. The implementation of a feedback spark timing control, based on the use of these combustion phase indicators, would ensure the minimum fuel consumption in every possible condition. Despite the presence of many literature references on the use combustion phase indicators, there is no evidence of any experimental comparison on the performance obtainable, in terms of both control accuracy and transient response, by the use of such indicators in a spark timing feedback control. The author, hence, carried out a proper experimental campaign comparing the performances of a proportional-integral spark timing control based on the use of five different in-cylinder pressure derived indicators. The experiments were carried out on a bench test, equipped with a series production four cylinder spark ignition engine and an eddy current dynamometer, using two data acquisition (DAQ) systems for data acquisition and spark timing control. Pressure sampling was performed by means of a flush mounted piezoelectric pressure transducer with the resolution of one crank angle degree. The feedback control was compared to the conventional map based control in terms of response time, control stability, and control accuracy in three different kinds of tests: steady-state, step response, and transient operation. All the combustion phase indicators proved to be suitable for proportionalintegral feedback spark advance control, allowing fast and reliable control even in transient operations. [DOI: 10.1115/1.4026966
Analisi economica delle politiche di gestione della pesca nel Golfo di Castellammare. Economic analysis of fisheries management policies (i.e., trawl ban) in the Gulf of Castellammare.
No full textThis paper describes the effects of the trawl ban in the Gulf of Castellammare (NW Sicily) on the economics of the local trawl fishery, focusing on the effectiveness of monetary fines and on the failures of regulation enforcement.THE FULL VERSION OF THIS ARTICLE SHOULD BE REQUESTED TO THE AUTHOR (CARLO PIPITONE: [email protected]) WITH PROPER JUSTIFICATION
Analisi economica delle politiche di gestione della pesca nel Golfo di Castellammare. Economic analysis of fisheries management policies (i.e., trawl ban) in the Gulf of Castellammare.
No full textThis paper describes the effects of the trawl ban in the Gulf of Castellammare (NW Sicily) on the economics of the local trawl fishery, focusing on the effectiveness of monetary fines and on the failures of regulation enforcement.THE FULL VERSION OF THIS ARTICLE SHOULD BE REQUESTED TO THE AUTHOR (CARLO PIPITONE: [email protected]) WITH PROPER JUSTIFICATION
Howerd: a Hidden Markov Model for Automatic OWL-ERD Alignment
No full textThe HOWERD model for estimating the most likely alignment between an OWL ontology and an Entity Relation Diagram (ERD) is presented. Automatic alignment between relational schema and ontology represents a big challenge in Semantic Web research due to the different expressiveness of these representations. A relational schema is less expressive than the ontology; this is a non trivial problem when accessing data via an ontology and for ontology storing by means of a relational schema. Existent alignment methodologies fail in loosing some contents of the involved representations because the ontology captures more semantic information, and several elements are left unaligned.
HOWERD relies on a Hidden Markov Model (HMM) to estimate the most likely sequence of ERD symbols in a relational schema that correspond to the constructs of an OWL axiom in the ontology to be aligned. Such constructs are the observable states in the HMM, while hidden states are modeled as the symbols of a context free grammar defined purposely for describing the input ERD lexically. The theoretical background, the model and the implemented system are described in detail. Finally, HOWERD is compared to the most widespread tools in the reference literature
An Innovative Statistical Tool for Automatic OWL-ERD Alignment
No full textAligning two representations of the same domain with different expressiveness is a crucial topic in nowadays semantic web and big data research. OWL ontologies and Entity Relation Diagrams are the most widespread representations whose alignment allows for semantic data access via ontology interface, and ontology storing techniques. The term ""alignment" encompasses three different processes: OWL-to-ERD and ERD-to-OWL transformation, and OWL-ERD mapping. In this paper an innovative statistical tool is presented to accomplish all the three aspects of the alignment. The main idea relies on the use of a HMM to estimate the most likely ERD sentence that is stated in a suitable grammar, and corresponds to the observed OWL axiom. The system and its theoretical background are presented, and some experiments are reported
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