527 research outputs found
The optimality of public-private partnerships under financial and fiscal constraints
No full textThe government may delegate two sequential tasks (e.g., building and operating an infrastructure) to the same or different agents (i.e., partnership vs. sequential contracts). Agents are risk-neutral but face financial constraints, whereas the government's contractual capacity may be limited by the renegotiation-proofness and fiscal constraints. By relying on history-dependent incentives, the partnership contract corrects moral hazard more effectively than sequential contracts. Thus, it is socially preferred unless bundling different tasks deteriorates the agent's financial conditions. Our results shed new light on the role of firms' financial and government's fiscal conditions in driving the cost-benefit analysis of public-private partnerships
Conducted EMI issues in a Boost PFC design
No full textThe paper presents the results of an experimental activity concerned with the development of a 600 W Boost Power Factor Corrector (PFC) complying with the EMC standards for conducted EMI in the 150 kHz-30 MHz range. In order to accomplish this task, different circuit design and layout solutions are taken into account and their effect on the conducted EMI behavior of the converter is experimentally evaluated. Common-mode and differential-mode switching noise, together with input filters' design and topology and with the PCB layout (in terms of track length and spacing, ground and shielding planes etc.) are the key aspects which have been analyzed. In particular, the paper reports the conducted EMI measurements for different filter capacitor placements and values, for different power switch drive circuits together with several other provisions which have turned out to be decisive in the reduction of the generated EMI
A Line-Frequency Commutated Rectifier Complying with IEC 1000-3-2 Standard
No full textConsumer and household appliances require cheap AC/DC power supplies complying with EMC standards. The commonly employed passive solutions are bulky and do not provide output voltage stabilization. Active solutions, based on PFCs with high-frequency switching, provide compactness and regulation capability, but are generally expensive due to the need for fast-recovery diodes and complex EMI filters. This paper presents a high power factor rectifier, based on a modified conventional rectifier with passive L-C filter, which improves both the harmonic content of the input current and the power factor, by means of a low frequency commutated switch and a small line-frequency transformer, and allows compliance with IEC 1000-3-2 standard with reduced overall inductive components' volume
Line-frequency commutated rectifier complying with IEC 1000-3-2 standards
No full textConsumer and household appliances require cheap ac/dc power supplies complying with EMC standards. The commonly employed passive solutions are bulky and do not provide output voltage stabilization. Active solutions, based on PFC's with high-frequency switching, provide compactness and regulation capability, but are generally expensive due to the need for fast-recovery diodes and complex EMI filters. This paper presents a high power factor rectifier, based on a modified conventional rectifier with passive L-C filter, which improves both the harmonic content of the input current and the power factor, by means of a low frequency commutated switch and a small line-frequency transformer, and allows to comply with IEC 1000-3-2 standard with reduced overall inductive components' volume
Competition in smart distribution grids
No full textSmart grids are often considered a cornerstone of energy transition and market liberalization in electric industries. From a critical reading of the interdisciplinary academic and governmental literature, we draw a new definition of grid smartness that is based on the reduction of the volatility of market prices and flows. Then, relying on a simple industrial-organization model of the electric market, we analyze the impact of smart grids on competition among energy suppliers and on the incentives of distribution system operators to invest in it. We show that the risk-reduction effect of smart grids pushes firms to supply more energy. However, the latter can be compensated by an indirect competition effect of investments in smart grids which prevents the entry of firms into the market, though the aggregate effect on energy supply is always positive. We also find that distribution system operators under-invest in smart grids because they fail to internalize positive externalities on energy consumers and producers
Preliminary research on trace elements, ectomycorrhizal symbiosis and wood decline.
No full textLNL (Laboratori Nazionali Legnaro), Annual Report
Banco de DNA de plantas da Embrapa Recursos Genéticos e Biotecnologia: conservação de material genético e documentação.
No full textEdição especial com os Anais do V Congresso Brasileiro de Recursos Genéticos. Na publicação: Gláucia Buso, Vânia C. R. de Azevedo, Marília C. R. Pappas
Estudo das relações genéticas de Helicônias (Heliconiaceae) utilizando marcadores moleculares.
No full textAs Zingiberales incluem oito famílias: Musaceae, Strelitziaceae, Lowiaceae, Heliconiaceae, Zingiberaceae, Costaceae, Cannaceae e Marantaceae. A família Heliconiaceae compreende um único gênero, Heliconia L. com aproximadamente 200 a 250 espécies. São comumente utilizadas como plantas ornamentais, sendo crescente sua aceitação como flor de corte nos mercados nacionais e internacionais. A identificação dessas espécies é baseada em características morfológicas. Porém, variações naturais ocorrentes nessas espécies têm causado confusões em suas classificações, sendo os marcadores moleculares úteis para a caracterização e para o estudo da diversidade dessas plantas. O objetivo deste trabalho foi a investigação da relação entre algumas espécies de Heliconia e de representantes da ordem Zingiberales com base em marcadores RAPD. Foram analisados 63 acessos e até o momento, 65 marcadores RAPD, que possibilitaram a construção de um dendrograma composto por três grupos; um composto pelas Musáceas, Strelitzias e Helicônias; outro pelas Costáceas e Zingiberáceas e um terceiro grupo externo formado pelas Lamiáceas
Design of a Fuel Cell Based Backup System for Telecoms Applications
No full textThe aim of this project is to develop a modular 5.5 kW backup system for telecoms stations based on a Proton Exchange Membrane Fuel Cell. Here, we will focus on the sizing procedure both of the fuel cell and of the DC/DC converter, whose topology is determined by the choice of the fuel cell stack. In our case this is an interleaved boost converter always working in the discontinous conduction mode. We will present a Simulink dynamic
model we developed that integrates the fuel cell and the boost converter models, and their controller. The simulations show the system is capable of supplying the maximum power, and to regulate the output voltage with a good dynamic response in the whole 42–60 V range
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