Direction of arrival estimation using a cluster of beams in a cone-shaped digital array radar'

In this paper some potential system and processing advantages of conformal cone shaped digital array radar have been investigated, in particular in relation to potential alternative approaches for angle estimation with respect to the traditional monopulse. First of all potential benefit in terms of reduction of the number of radiating elements is shown when a conical array is considered with respect to a traditional system formed by four planar arrays, if a coverage of 360° must be assured. Secondly, having in mind an innovative digital array system where the received signals are analog to digital converted at element level and the corresponding data are possibly transferred to a central elaboration unit, an alternative approach is investigated for angular estimation. In this paper we derive the theoretical expression of the Cramer Rao Lower Bound for elevation angle estimation using a cluster of beams; we compare the limit performance of the traditional approach for angle estimation based on Sum and Difference beams with the approach based on a crowded cluster of RX beams properly spaced. The approaches show approximately equivalent performance, making the second particularly interesting for those situations where monopulse is known to experience performance degradation, as low elevation angle estimation; in this particular case an example of cluster design is shown, where the direct signal from a low altitude target must compete with a specular multipath

Hardware-In-the-Loop operations with an emulator rig for SOFC hybrid systems

This paper shows the Hardware-In-the-Loop (HIL) technique developed for the complete emulation of Solid Oxide Fuel Cell (SOFC) based hybrid systems. This approach is based on the coupling of an emulator test rig with a real-time software for components which are not included in the plant. The experimental facility is composed of a T100 microturbine (100 kW electrical power size) modified for the connection to an SOFC emulator device. This component is composed of both anodic and cathodic vessels including also the anodic recirculation system which is carried out with a single stage ejector, driven by an air flow in the primary duct. However, no real stack material was installed in the plant. For this reason, a real-time dynamic software was developed in the Matlab-Simulink environment including all the SOFC system components (the fuel cell stack with the calculation of the electrochemical aspects considering also the real losses, the reformer, and a cathodic recirculation based on a blower, etc.). This tool was coupled with the real system utilizing a User Datagram Protocol (UDP) data exchange approach (the model receives flow data from the plant at the inlet duct of the cathodic vessel, while it is able to operate on the turbine changing its set-point of electrical load or turbine outlet temperature). So, the software is operated to control plant properties to generate the effect of a real SOFC in the rig. In stand-alone mode the turbine load is changed with the objective of matching the measured Turbine Outlet Temperature (TOT) value with the calculated one by the model. In grid-connected mode the software/hardware matching is obtained through a direct manipulation of the TOT set-point. This approach was essential to analyze the matching issues between the SOFC and the micro gas turbine devoting several tests on critical operations, such as start-up, shutdown and load changes. Special attention was focused on tests carried out to solve the control system issues for the entire real hybrid plant emulated with this HIL approach. Hence, the innovative control strategies were developed and successfully tested considering both the Proportional Integral Derivative and advanced approaches. Thanks to the experimental tests carried out with this HIL system, a comparison between different control strategies was performed including a statistic analysis on the results The positive performance obtainable with a Model Predictive Control based technique was shown and discussed. So, the HIL system presented in this paper was essential to perform the experimental tests successfully (for real hybrid system development) without the risks of destroying the stack in case of failures. Mainly surge (especially during transient operations, such as load changes) and other critical conditions (e.g. carbon deposition, high pressure difference between the fuel cell sides, high thermal gradients in the stack, excessive thermal stress in the SOFC system components, etc.) have to be carefully avoided in complete plants

Hydrogen production system from photovoltaic panels: experimental characterization and size optimization

In this paper an approach for the determination of the optimal size and management of a plant for hydrogen production from renewable source (photovoltaic panels) is presented. Hydrogen is produced by a pressurized alkaline electrolyser (42 kW) installed at the University Campus of Savona (Italy) in 2014 and fed by electrical energy produced by photovoltaic panels. Experimental tests have been carried out in order to analyze the performance curve of the electrolyser in different operative conditions, investigating the influence of the different parameters on the efficiency. The results have been implemented in a software tool in order to describe the behavior of the systems in off-design conditions. Since the electrical energy produced by photovoltaic panels and used to feed the electrolyser is strongly variable because of the random nature of the solar irradiance, a time-dependent hierarchical thermoeconomic analysis is carried out to evaluate both the optimal size and the management approach related to the system, considering a fixed size of 1 MW for the photovoltaic panels. The thermo-economic analysis is performed with the software tool W-ECoMP, developed by the authors\u2019 research group: the Italian energy scenario is considered, investigating the impact of electricity cost on the results as well

Environmental economic analysis of speed reduction measure onboard container ships

: The International Maritime Organization (IMO) has concerned significant care to the reduction of ship emissions and improvement of energy efficiency through operational measures. One of those measures is ship speed reduction, which is classified as a short-term measure; in which the speed is reduced below its designed value. The present paper aims at evaluating the potential energy efficiency, and environmental and economic benefits because of applying speed reduction measures. The research methodology depends on establishing a simple mathematical model for technical, environmental, and economical aspects because of this concept. As a case study, container ships from different categories in a range of 2500-15,000 twenty-foot equivalent units (TEU) are investigated. The results show that a 2500 TEU ship can comply with the energy efficiency existing ship index (EEXI) by reducing the service speed to 19 knots. While for the bigger ships, the service speed must be 21.5 knots or below. Furthermore, the operational carbon intensity indicator (CII) has been evaluated for the case studies and found that the CII rating will keep its score between A and C levels if the service speed is equal to or below 19.5 knots. Moreover, the annual profit margin of the ship will be calculated based on applying speed reduction measures. Based on the economical results, the annual profit margin value, and its corresponding optimum speed change with the size of the vessel and the applicable status of carbon taxes

Los Mapuches del siglo XVIII. Dinámica interétnica y estrategias de resistencia

José Manuel Zavala.Santiago de Chile, Universidad Bolivariana, 2008

Análise político-jurídica da repartição das competências em matéria de saneamento básico no Brasil

Orientador : Prof. Dr. Edson Luiz PetersCoorientador: Profª. M.Sc. Sandra Mara Pereira de QueirozDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Mestrado Profissional em Meio Ambiente Urbano e Industrial, em parceria com o Serviço Nacional de Aprendizagem Industrial e a Universität Stuttgart. Defesa: Curitiba, 27/02/2015Inclui referências : f. 134-140Resumo: A Lei 11.445/2007, chamada de Lei de Saneamento, estabeleceu no Brasil as diretrizes nacionais para o saneamento básico e instituiu a política federal de saneamento básico. Em decorrência da evolução histórica do conceito, os serviços públicos de saneamento básico passaram a ser definidos pela lei como sendo (i) captação, tratamento e distribuição de água; (ii) coleta, afastamento, tratamento e disposição final adequada de esgotos sanitários domésticos; (iii) drenagem urbana; e (iv) limpeza urbana e manejo dos resíduos sólidos. Referidos serviços são de interesse local, cujas atividades de organizar e prestar diretamente ou sob regime de concessão ou mediante cooperação federativa são atribuídas pela Constituição aos Municípios. Paralelamente a Constituição estabeleceu a competência comum da União, dos Estados, do Distrito Federal e dos Municípios promover programas visando a melhoria das condições de saneamento básico. A realidade demonstra que as companhias estaduais de saneamento básico operam a maioria dos sistemas de água e esgoto no País, bem como, que a União é o principal agente financiador do setor. Este quadro implica na necessária distribuição de atribuições e competências legislativas e administrativas entre os entes federados. Passados dois séculos das primeiras iniciativas de implantação de sistemas de saneamento básico no Brasil, constata-se que percentual significativo da população ainda não tem acesso a serviços de água e esgoto. A identificação adequada das atribuições de cada ente federado se mostra essencial para o atingimento da universalização com eficiência e modicidade de tarifa, sem descuidar do retorno ao capital investido. O presente trabalho se destina a identificar as atribuições dos entes federados no desempenho das atividades de saneamento básico de acordo com a Constituição e a Lei 11.445/2007, apontar as formas jurídicas possíveis para sua prestação e analisar a proposta de gestão associada trazida pela Lei 11.107/2005. Saneamento básico. Política federal. Diretrizes nacionais. Atribuições dos entes federados. Gestão associada. Competências.Abstract: Law 11.445/2007 nominated as Law of the Sanitation, set to Brazil the national guidelines for the basic sanitation and grounded the federal police for basic sanitation. As a consequence of the historic evolution of the concept, the public services of basic sanitation started to defined by law as being (i) abstraction of water, treatment and distribution of drinkable water; (ii) the adequate collection, removal, treatment and final disposition of domestic sewage; (iii) urban drainage; (iv) urban cleaning and urban solid waste management. Such services are all defined as being of local interest and the services related to them, their organization, direct or through concession or federative cooperation are all devolved upon the Municipalities according to the Federal Constitution. Necessary to that the Federal Constitution also set that there is common competence shared by Union, States, Federal District and Municipalities to promote programmers to ward the betterment of the basic sanitation conditions. The reality has shown that the state basic sanitation companies operate the great majority of the water and sewerage systems In the country and that the Union is the main financial agent of the sector. This scenario implies the need for distribution of attributions and legislative as well as administrative competence among the federal units. After two centuries from the first initiatives of implantation of basic sanitation systems In Brazil, one can see that a meaningful percentage of the population does not have the water and sewerage service rendered. The proper identification of the attributions to each federated unit In the performance of the activities is seen as material to the fulfillment of the universalization with efficiency and adequate tariff, avoiding being regardless to the return of invested capital. The present work seeks to identify the attributions to the federated units In the performance of the sanitation basic activities In accordance with Constitution and Law 11.445/2007; point the suitable lawful ways to the rendering of services; analyze the proposal of associated management as Law 11.107/2005 intends. Basic sanitation. Federal policy. National directives. Attributions of federated units. Associated management competences

Validated ejector model for hybrid system applications

The aim of this work is the presentation of a new model for ejector performance calculation using a commercial tool. Due to the critical issues in recirculation performance, special attention is devoted to applications in hybrid systems based on high temperature fuel cells. The theoretical activity is supported by an experimental rig able to operate tests on ejectors at different operative conditions, with a layout similar to the fuel cell anodic recirculation. The model validation, operated considering experimental data obtained with this rig, is essential to evaluate the tool performance for design and off-design calculations. This aspect is particularly critical due to important limitations in the recirculation ratio (especially for the anodic side), to avoid unacceptable operative conditions in the fuel cells. The results presented in this work were obtained with this validated model for an ejector applied on the anodic side of a Solid Oxide Fuel Cell (SOFC). A parametric analysis was carried out to show the effects of several parameters on the recirculation performance. The fully independent analysis of the influence of different properties (carried out with a specifically validated model) is an important innovative result for the application of such ejectors on high temperature fuel cells

“Todo esto fue un fracaso, un terremoto tremendo que remeció todo, desde dentro”. Una conversación con Guillermo Núñez

“Todo esto fue un fracaso, un terremoto tremendo que remeció todo, desde dentro”. Una conversación con Guillermo Núñez (agosto de 2021 – mayo de 2023)   por Elisa Massardo &nbsp

Surge prevention for gas turbines connected with large volume size: Experimental demonstration with a microturbine

The aim of this work is the demonstration of a surge prevention technique for advanced gas turbine cycles. There is significant surge risk in dynamic operation for turbines connected with large volume size additional components, such as a fuel cell stack, a saturator, a solar receiver or a heat exchanger for external combustion. In comparison with standard gas turbines, the volume size generates different behaviour during dynamic operations (with significant surge risk), especially considering that such additional components are including important dynamic constraints. In order to prevent the surge events, a vibration analysis was carried out to develop precursors which are able to highlight the approach of this unstable operative zone. Since the sub-synchronous content of the measured vibrations is significantly increasing approaching the surge line, special attention was devoted to this parameter. The demonstration of a surge prevention system based on the sub-synchronous vibration content was carried out at the Innovative Energy Systems Laboratory of the University of Genoa. In this laboratory, a recuperated microturbine connected with a large size vessel was used. Starting from the stable operation, closing a valve in the main air line or increasing the compressor inlet temperature produced operative conditions with significant surge risk. The increase in sub-synchronous vibration content detected by the control system was used to perform an active operation (bleed valve opening) to avoid the approaching surge event