127 research outputs found
Gli effetti dell'Interlocking Directorate sulla vita d'impresa
No full textIl nostro lavoro studia gli effetti dell'Interlocking Directorate (ID) sulla vita di impresa, concentrandosi sulla struttura del passivo e sulla performance d'impresa.
Abbiamo considerato due campioni molto estesi (1998-2007 e 2003-2010) che comprendono le società quotate alla Borsa valori di Milano.
Nella prima indagine, eseguita utilizzando il database '98-'07, abbiamo riscontrato un'assenza di relazione tra il fenomeno dell'ID bancario (quindi tra una banca e una società industriale) e il grado di indebitamento dell'impresa, diversamente da quanto rilevato da Byrd e Mizruchi (2005) per un campione di impresa USA. Di contro, esiste una relazione positiva effetto tra l'ID bancario e la percentuale di debito bancario sul totale del debito emesso.
Con il medesimo dataset, abbiamo analizzato gli effetti dell'ID sulla performance di impresa portando alla luce un effetto negativo e ritardato (1 ritardo) dell'ID.
Usando il campione 2003-2010 abbiamo poi analizzato le differenze di genere, mettendo in rilievo un effetto negativo dell'ID femminile sul risultato d'impresa. Questo è probabilmente dovuto al fatto che in Italia una percentuale rilevante delle donne che generano interlocking è espressione diretta della proprietà per rapporti di parentela.
Accanto a ciò, possiamo direi che in Italia il fenomeno dell'ID in generale presenta un trend decrescente, mentre quello dell'ID femminile acquista via via maggior rilevanza.Our research analyzes the phenomenon of Interlocking Directorate (ID) and its effects on firms' behavior, with focus on capital structure and firm's performance.
We consider two extensive and innovative datasets (1998-2007 and 2003-2010) which include all companies listed at the Milan Stock Exchange.
Our first analysis (with '98-'07 database), shows no relation between capital structure and "banking" ID (the link between a bank and an industrial firm). On the other hand, we found a positive relation between banking ID and the amount of bank debt with respect to the total amount of issued debt.
Using the same database, we analyze the relation between ID and firm's performance; what we discover is a negative and delayed effect (1 delay) of ID on firm's performance.
The last research was run with the second database (2003-2010) shows a negative effect of female ID on firm's performance. This result may be due to the fact that in Italy a relevant percentage of female IDs is about women that are expression of industrial families and therefore not strictly related to gender effect.
In addition, we show that in Italy the ID phenomenon is decreasing, while female ID is growing up (as well as female directorships)
Modeling NOx Storage and Reduction for a Diesel Automotive Catalyst Based on Synthetic Gas Bench Experiments
No full textTo comply with stringent NO
x
emission
regulations, automotive dies
el engines require advanced
aftertreatment catalytic systems, such as lean NO
x
traps
(LNTs). Considering that test bench and chassis dyno
experimental campaigns are costly and require a vast use of
resources for the generation of data; therefore, reliable and
computationally e
ffi
cient simulation models are essential in
order to identify the most promising technology mix to satisfy
emission regulations. In the literature, a large number of
simulation models for LNT kinetics can be found, realized for
laboratory-scale samples and validated over synthetic gas
bench (SGB) experimental tests, while full-size models validated over engine-dyno driving cycle data, crucial for industrial
applications, are missing. In the current work, a simulation model of an LNT device is built to predict NO
x
storage and
reduction, starting from SGB laboratory tests and
fi
nally validated over driving cycle data. The experiments including light-o
ff
,
NO
x
storage and reduction (NSR), and oxygen storage capacity (OSC) characterization, were performed on a laboratory-scale
sample extracted from a full-scale monolith. Light-o
ff
tests have been conducted under a temperature ramp cycle from 120
°
Cto
380
°
C, while OSC and NSR tests were performed under isothermal conditions at
fi
ve temperature levels, ranging from 150
°
C
to 400
°
C. OSC tests were performed to characterize oxygen storage capacity of ceria sites and water gas shift (WGS) reaction
over the precious metals by controlling inlet species concentrations with periodic lean/rich pulses. NSR experiments were then
performed by alternating a lean inlet composition to reproduce adsorption/desorption of NO
x
with a rich inlet composition
feed with three reductants (H
2
, CO, and C
3
H
6
) to replicate NO
x
reduction reactions. A global kinetic scheme was de
fi
ned by
means of a one-dimensional (1D) engine simulation
fl
uid-dynamic code, GT-SUITE, to model oxidation reactions (CO, HC,
NO), NO
x
adsorption/desorption, oxygen storage and NO
x
reduction reactions. The kinetic parameters were obtained using
Arrhenius plots with the aim to minimize the error between simulated and experimental NO
x
, reductants, N
2
O and NH
3
concentrations, reaching a satisfactory agreement with measurements
Digital Shaping and Optimization of Fuel Injection Pattern for a Common Rail Automotive Diesel Engine through Numerical Simulation
No full textDevelopment trends in modern Common Rail Fuel Injection System (FIS) show dramatically increasing capabilities in terms of optimization of the fuel injection pattern through a constantly increasing number of injection events per engine cycle along with a modulation and shaping of the injection rate. In order to fully exploit the potential of the abovementioned fuel injection pattern optimization, numerical simulation can play a fundamental role by allowing the creation of a kind of a virtual injection rate generator for the assessment of the corresponding engine outputs in terms of combustion characteristics such as burn rate, emission formation and combustion noise (CN). This paper is focused on the analysis of the effects of digitalization of pilot events in the injection pattern on Brake Specific Fuel Consumption (BSFC), CN and emissions for a EURO 6 passenger car 4-cylinder diesel engine. The numerical evaluation was performed considering steady-state conditions for 3 key points representative of typical operating conditions in the low-medium load range. The optimization process was carried out through numerical simulation, by means of a suitable target function aiming to minimize BSFC and CN while not exceeding the target NOx emissions level. By means of a previously developed fuel injection system model, possible different injection patterns with high number of pilot injections were evaluated thus obtaining a kind of virtual injection rate generator, the outcomes of which were then used as input for a DIPulse combustion model in order to predict BSFC, combustion noise and emissions. Through numerical optimization of pilot injection pattern digitalization, potential for achieving significant reductions in BSFC and CN for low load engine points while not exceeding the target NOx emissions level, was demonstrated
Multi-Objective optimization of fuel injection pattern for a Light Duty Diesel engine through numerical simulation
No full textDevelopment trends in modern common rail fuel injection systems (FIS) show dramatically increasing capabilities in terms of optimization of the fuel injection strategy through a constantly increasing number of injection events per engine cycle as well as through the modulation and shaping of the injection rate. In order to fully exploit the potential of the abovementioned fuel injection strategy optimization, numerical simulation can play a fundamental role by allowing the creation of a kind of a virtual test rig, where the input is the fuel injection rate and the optimization targets are the combustion outputs, such as the burn rate, the pollutant emissions, and the combustion noise (CN). Starting from a previously developed 1D-CFD (Computational Fluid Dynamics) virtual test rig, obtained coupling a 1.6L, 4-cylinder turbocharged diesel engine model with a 1D-CFD injector model, this article presents a methodology for optimizing the fuel injection strategy aiming to minimize brake-specific fuel consumption (BSFC) and CN without exceeding the brake-specific NOx (BSNOx) baseline value. The Non-dominated Sorting Genetic Algorithm (NSGA-III) was used in GT-SUITE environment for Pareto optimization in the BSFC-CN space, for three different engine operating conditions in the low-medium speed and low-medium load range. The proposed approach highlighted that significant improvements in terms of BSFC and CN can be achieved by adopting digitalized close pilot events with respect to the Design of Experiments (DoE) analysis previously presented in [1], also highlighting relevant computational time savings for the optimization process
Real Time Energy Management Control Strategies for an Electrically Supercharged Gasoline Hybrid Vehicle
No full textThe high level of electric power available on a Hybrid Electric Vehicle (HEV) enables the introduction of electrical auxiliaries in addition or in substitution to the ones currently available on a conventional powertrain. Among these auxiliaries, electric Superchargers (eSC) for the improvement of the vehicle performance or electrically heated catalysts for the reduction of the light-off time of the after-treatment may dramatically affect the Energy Management System (EMS) of an HEV. Moreover, since these devices are only fluid-dynamically, but not mechanically, linked to the powertrain, they are traditionally neglected in the optimization of the powersplit between internal combustion engine and electric machines by the EMS. The aim of the current work is the development of an EMS that is able to consider in real time the overall electric energy consumption of the entire powertrain. More in detail, this activity focuses on the refinement of the Equivalent Consumption Minimization Strategy (ECMS) including the power required by an eSC installed on a turbocharged gasoline engine. This innovative EMS is tested by means of numerical simulation on a small SUV (Sport Utility Vehicle) featuring a 48 V electric network over Type Approval and Real Driving Emissions (RDE) driving cycles. The novel EMS shows promising results in terms of eSC energy management and vehicle fuel consumption compared with the baseline
Numerical Investigation on the Effects of Different Thermal Insulation Strategies for a Passenger Car Diesel Engine
No full textAbstractOne of the key technologies for the improvement of the diesel engine thermal efficiency is the reduction of the engine heat transfer through the thermal insulation of the combustion chamber. This paper presents a numerical investigation on the effects of the combustion chamber insulation on the heat transfer, thermal efficiency and exhaust temperatures of a 1.6 l passenger car, turbo-charged diesel engine. First, the complete insulation of the engine components, like pistons, liner, firedeck and valves, has been simulated. This analysis has showed that the piston is the component with the greatest potential for the in-cylinder heat transfer reduction and for Brake Specific Fuel Consumption (BSFC) reduction, followed by firedeck, liner and valves. Afterwards, the study has been focused on the impact of different piston Thermal Barrier Coatings (TBCs) on heat transfer, performance and wall temperatures. This analysis has been performed using a 1-D engine simulation code coupled with a lumped mass thermal model, representing the engine structure. A time-periodic wall conduction model has been used to calculate the wall temperature swings along the combustion chamber surface and within the engine cycle. Two different TBC materials, Yttria-Partially Stabilized Zirconia (Y-PSZ) and anodized aluminum, and different layer thicknesses have been simulated
Numerical investigation of 48 V electrification potential in terms of fuel economy and vehicle performance for a lambda-1 gasoline passenger car
No full textReal Driving Emissions (RDE) regulations require the adoption of stoichiometric operation across the entire engine map for downsized turbocharged gasoline engines, which have been so far generally exploiting spark timing retard and mixture enrichment for knock mitigation. However, stoichiometric operation has a detrimental effect on engine and vehicle performances if no countermeasures are taken, such as alternative approaches for knock mitigation, as the exploitation of Miller cycle and/or powertrain electrification to improve vehicle acceleration performance. This research activity aims, therefore, to assess the potential of 48 V electrification and of the adoption of Miller cycle for a downsized and stoichiometric turbocharged gasoline engine. An integrated vehicle and powertrain model was developed for a reference passenger car, equipped with a EU5 gasoline turbocharged engine. Afterwards, two different 48 V electrified powertrain concepts, one featuring a Belt Starter Generator (BSG) mild-hybrid architecture, the other featuring, in addition to the BSG, a Miller cycle engine combined with an e-supercharger were developed and investigated. Vehicle performances were evaluated both in terms of elasticity maneuvers and of CO2 emissions for type approval and RDE driving cycles. Numerical simulations highlighted potential improvements up to 16% CO2 reduction on RDE driving cycle of a 48 V electrified vehicle featuring a high efficiency powertrain with respect to a EU5 engine and more than 10% of transient performance improvement
Development and validation of a predictive combustion model for hydrogen-fuelled internal combustion engines
No full textInternal combustion engines (ICEs) fuelled with hydrogen can play a major role in the short-term future transportation sector since they abate all criteria pollutants at engine-out reducing tailpipe CO2 emissions to near-zero levels. However, optimizing hydrogen ICEs is a challenging task that can be addressed through the development of a robust simulation tool capable to predict the H2 combustion process. In this study, a previously
developed two-zone combustion model has been updated considering different laminar flame speed computations, both based on a detailed chemistry scheme: a polynomial correlation function and a tabulated approach.
The predictive capabilities of the combustion model have been validated against experimental data coming from
a 0.5L PFI single-cylinder engine under several operating conditions. The tabulated approach for laminar flame
speed definition proved to be the best solution, leading to a combustion duration average error lower than 3 deg
over a dataset containing more than 45 different operating conditions
Pre-chamber ignition systems for high-speed large-bore gas engine: technology investigation through 3D-CFD analysis
No full textNowadays large bore gas engines are gaining popularity in the market for power generation and marine applications. Methane is preferred over conventional diesel because of its favourable H/C ratio and lower soot emissions. Furthermore, the global transition to renewable energy sees eMethane as one of the most promising options for clean energy storage. Consequently, the enhancement of the efficiency of large bore gas engines through innovative combustion strategies, such as pre-chamber ignition, is of growing importance. This technology increases ignition energy, shortens combustion duration, and achieves higher thermal efficiency compared with conventional ignition systems due to extended lean operation. However, it remains unclear which factors fundamentally limit the achievable lean operation of passive and active pre-chamber ignition systems, thereby influencing their combustion behaviour and pollutant emission.
In this context, this paper presents a 3D-CFD numerical investigation of a large bore gas engine (∼4 L/cyl.) equipped with both passive and active pre-chamber systems, operating under lean air/methane mixtures at high load. The study aims to evaluate the influence of calibration and geometric parameters, define and optimize the lean limit of each system, and assess the resulting impact on engine thermal efficiency and pollutant emissions.
A comprehensive comparison between the two systems is provided. Finally, the results of the optimization process demonstrate that both passive and active pre-chamber systems can be effectively tailored through geometry and calibration to address the dual challenge of high efficiency and low NOx emissions in large bore methane engines
Drawing on the walls from architecture to street art. Interview with “MILLO” the street artist architect
No full textFrancesco Camillo Giorgino in art MILLO was born in Mesagne in the province of Brindisi, in 2007 he graduated in architecture in Pescara, the city where he lives and which he considers foster. Street artist of international fame, he has created murals scattered in suburbs of Italian and continental cities, his works are distinguished by the constant presence of an anonymous and infinitely replicable urban context. The colorless habitat in which he inserts the pure and giant characters represent a satire of the contemporary way of life, the lack of urban planning choices that have failed to solve the problems related to public spaces, services, sociality, present in all the cities of the world. With the architect’s critical eye he observes the spaces defined by the blind walls on which to intervene in order to launch messages, to stimulate attention and promote urban redevelopment initiatives. The interview concluded in the emergency moment of the pandemic. It was conducted in telematic way and offered the cue to interface and talk about possible alternative ways for street art, which the artist immediately implemented to create a charity work for the hospital of Pescara by drawing live on social networks. The answers of Millo, artist of great sensitivity, help us to understand his artistic and social choices, his drawn messages that, as he likes to emphasize, leave ample space for the free interpretation of the viewers.DOI: https://doi.org/10.20365/disegnarecon.24.2020.i5</p
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