Integration of solar thermal energy in a conventionaf power plant: The Colon solar project

This paper reports on the first phase of the Colón Solar Project, originally conceived as the hybrid repowering of an existing thermal power plant, with the addition of a gas turbine in a topping configuration integrating thermal energy (steam) produced by a solar system. However, the project developed in a changing economic environment, in which a new legal structure, still incomplete, as of January, 1998 has liberalized the electricity generation market. This forced the original configuration to be modified, resulting in an all-new combined cycle with solar energy integrated into a Heat Recovery Boiler. Basic plant engineering placed special emphasis on the most important solar components (heliostat and receiver), and an economic analysis showed that the plant is profitable under the assumptions of the analysis. Nevertheless, the relatively low IRR, as well as the uncertainty of realization of some of those assumptions, made the utility postpone its decision to build the plant

Weed seed dormancy as a survival mechanism: brief review

Um dos principais mecanismos de sobrevivência das plantas daninhas em ambientes constantemente perturbados é a alta produção de sementes. Essas possuem geralmente algum mecanismo de dormência, o qual contribui para a perpetuação de espécies interferentes nos cultivos agrícolas. A dormência pode ser caracterizada pela ausência temporária da germinação, mesmo quando em condições adequadas de sua ocorrência. Isso permite que inúmeras espécies vegetais sobrevivam às adversidades, sobretudo aquelas que dificultam ou impeçam o seu crescimento vegetativo e reprodutivo. As causas da dormência são provenientes de dois mecanismos básicos, sendo o primeiro relacionado a eventos internos das sementes (embrião) e o segundo, às características externas (tegumento, endosperma ou as barreiras impostas pelo fruto). Conceitualmente, a dormência pode ser distinguida em dois tipos: dormência primária (quando os mecanismos de dormência ocorrem ainda na planta-mãe) e secundária (quando os mecanismos de estabelecimento da dormência ocorrem após a dispersão das sementes). A ocorrência desses dois tipos de dormência é comum em plantas daninhas. A sua alternância ou ciclagem garante o fluxo de germinação destas espécies, o qual depende das características iniciais durante a formação das sementes (dormência primária) e, posteriormente, das condições ambientais (dormência secundária). Todavia, muitos são os mecanismos que coordenam a dormência, sendo a distinção destes ainda controversos. Nesse sentido, este estudo tem por objetivo abordar alguns dos principais conceitos e mecanismos de dormência em plantas daninhas, com intuito de contribuir e estimular as pesquisas, ainda escassas, nessa área.The high production of seeds in constantly disturbed environments is one of the main mechanisms of weeds survival. These seeds have usually some dormancy mechanism which constitutes weed species perpetuation in the crops. Seed dormancy can be characterized by temporally absence of the germination capacity, even though the seeds have satisfactorily conditions to germinate, thus allowing species survival under adversities, mainly those that make it difficult or hinder vegetative and reproductive growth. The causes of dormancy stem from two basic mechanisms: the first is related to inner seed events (embryo) and the second to outer characteristics in the seeds (tegument, endosperm or fruit barriers). Conceptually, dormancy can be classified as primary dormancy (when the mechanisms occur in plants-mother) and secondary dormancy (when the mechanisms causing dormancy occur after seed dispersion). These types of dormancy occur normally in weeds. Their alternation or cycling ensures germination flow these species, which depends on the characteristics occurring at the initial stages of seed formation (primary dormancy), and later, on the environmental conditions (secondary dormancy). However, many mechanisms coordinate dormancy, with the differences among them being still controversial. Thus, this study aimed to approach some of the main concepts and mechanisms in weed dormancy, in order to contribute and stimulate research which is still scarce in this area

Primary pleural myxoid liposarcoma: case report and literature review

Myxoid liposarcoma is a histological subtype of malignant tumors within the group of sarcomas. It is more common in men between the ages of 40 and 50 years. Diagnosis is difficult because they are usually asymptomatic lesions, computed tomography (CT) scan and magnetic resonance are the studies of choice. The gold of treatment is surgical resection with free margins. Chemotherapy and radiotherapy have shown a good response. A 46-year-old male was detected incidental mediastinal lesion by radiography, CT scan showed a hypodense lesion in the right hemithorax that extended to the left hemithorax, infiltrating the diaphragm and large vessels. The patient underwent an exploratory thoracotomy, finding a multilobulated tumor and mucous content approximately 600 ml, adjacent structures were infiltrated, so complete resection was not possible. Subsequently, adjuvant chemotherapy given. The histopathological diagnosis was myxoid liposarcoma. Myxoid liposarcoma is a malignant lesion. The primary pleural origin is rare. Surgical resection with free margins has a good prognosis. Due to advanced disease, a complete resection in this case was not possible, that compromised the patient prognosis

Weibel instability and associated strong fields in a fully 3D simulation of a relativistic shock

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context.Comment: 4 pages, 3 figures, ApJ Letters, in pres

Superfield covariant analysis of the divergence structure of noncommutative supersymmetric QED4_4

Commutative supersymmetric Yang-Mills is known to be renormalizable for ${\cal N} = 1, 2$, while finite for ${\cal N} = 4$. However, in the noncommutative version of the model (NCSQED$_4$) the UV/IR mechanism gives rise to infrared divergences which may spoil the perturbative expansion. In this work we pursue the study of the consistency of NCSQED$_4$ by working systematically within the covariant superfield formulation. In the Landau gauge, it has already been shown for ${\cal N} = 1$ that the gauge field two-point function is free of harmful UV/IR infrared singularities, in the one-loop approximation. Here we show that this result holds without restrictions on the number of allowed supersymmetries and for any arbitrary covariant gauge. We also investigate the divergence structure of the gauge field three-point function in the one-loop approximation. It is first proved that the cancellation of the leading UV/IR infrared divergences is a gauge invariant statement. Surprisingly, we have also found that there exist subleading harmful UV/IR infrared singularities whose cancellation only takes place in a particular covariant gauge. Thus, we conclude that these last mentioned singularities are in the gauge sector and, therefore, do not jeopardize the perturbative expansion and/or the renormalization of the theory.Comment: 36 pages, 11 figures. Minor correction

Combinations of adaptive filters

Adaptive filters are at the core of many signal processing applications, ranging from acoustic noise supression to echo cancelation [1], array beamforming [2], channel equalization [3], to more recent sensor network applications in surveillance, target localization, and tracking. A trending approach in this direction is to recur to in-network distributed processing in which individual nodes implement adaptation rules and diffuse their estimation to the network [4], [5].The work of Jerónimo Arenas-García and Luis Azpicueta-Ruiz was partially supported by the Spanish Ministry of Economy and Competitiveness (under projects TEC2011-22480 and PRI-PIBIN-2011-1266. The work of Magno M.T. Silva was partially supported by CNPq under Grant 304275/2014-0 and by FAPESP under Grant 2012/24835-1. The work of Vítor H. Nascimento was partially supported by CNPq under grant 306268/2014-0 and FAPESP under grant 2014/04256-2. The work of Ali Sayed was supported in part by NSF grants CCF-1011918 and ECCS-1407712. We are grateful to the colleagues with whom we have shared discussions and coauthorship of papers along this research line, especially Prof. Aníbal R. Figueiras-Vidal

Climatic elements variability affecting maize yield in Northern Minas Gerais, Brazil.

Conference

Identificação e quantificação do efeito de fatores ambientais na produtividade da cultura do milho na região de Janaúba, MG.

Na região do semiárido do Estado de Minas Gerais, Brasil, há um grande déficit na oferta de milho, mesmo para subsistência familiar. O entendimento dos fatores que afetam a produtividade desta cultura é crucial para o desenvolvimento de estratégias de manejo adequadas. Neste contexto, o objetivo deste trabalho foi identificar os fatores climáticos que podem influenciar a produtividade da cultura do milho na região de Janaúba, MG, e quantificar o grau de influência desses fatores, a partir da análise de dados de produtividade da cultura simulados com o modelo CSM-CERES-Maize. O modelo foi utilizado para simular o rendimento de grãos de milho semeado semanalmente ao longo do ano, em condições de sequeiro e irrigado no período de 1977 a 2008. A análise estatística indicou que os fatores data da semeadura, ano e irrigação (sequeiro e irrigado) e suas interações duplas foram significativos ao nível de significância de 5%. A disponibilidade hídrica foi responsável pela maior proporção da variação total na produtividade de milho na região de estudo (61,9%), seguida pela data de semeadura e suas interações duplas com os outros fatores (26,2%). Em condições ótimas de disponibilidade hídrica (cultivo irrigado), os fatores, que mais influenciam o rendimento da cultura do milho são, basicamente, a variações de temperatura do ar e a radiação solar incidente. Fato evidenciado pelos baixos valores de produtividade simulada encontrados em anos nos quais a radiação solar incidente ficou abaixo da média geral observada

Reliability analysis of Solar-Gas Hybrid Receivers for central tower plants

A novel Solar-Gas Hybrid Receiver (SGHR) that combines the function of a solar receiver and a gas boiler in a single device is presented. This concept requires less equipment and maintenance compared to the Solar Gas Hybrid (SGH) concept, in which the boiler and the solar receiver (SR) are independent devices. The economic benefit is attributed to the increased sharing of infrastructures. Additionally, it has less thermal stress, cycles and shocks, which reduce the failure risk. However, the additional benefit in the reliability of these receivers has not been analyzed so far. In this work, a mathematical model of SGHR is presented. It determines the stress in steady state which is used to estimate the allowable transient stress in order to achieve the required 30 years life design. The results show that the SGHR is exposed to lower thermal stress due to much better temperature distribution. Moreover the higher absorber heat flux of SGHR is translated in a higher mechanical stress with could jeopardizes the durability. However the reduced number of cycles and the lower thermal stress of a SGHR allows higher transient stresses than the conventional tube type solar receiver, which lead to more reliable and efficient designs