L0 and L1 Guidance and Path-Following Control for Airborne Wind Energy Systems

For an efficient and reliable operation of an Airborne Wind Energy System, it is widely accepted that the kite should follow a pre-defined optimized path. In this article, we address the problem of designing a trajectory controller so that such path is closely followed. The path-following controllers investigated are based on a well-known nonlinear guidance logic termed L1 and on a proposed modification of it, which we termed L0. We have developed and implemented both L0 and L1 controllers for an AWES. The two controllers have an easy implementation with an explicit expression for the control law based on the cross-track error, on the heading angle relative to the path, and on a single parameter L (L0 or L1, depending on each controller) that we are able to tune. The L0 controller has an even easier implementation since the explicit control law can be used without the need to switch controllers. Since the switching of controllers might jeopardize stability, the L0 controller has an important theoretical advantage in being able to guarantee stability on a larger domain of attraction.The simulation study shows that both nonlinear guidance logic controllers exhibit appropriate performance when the L parameter is adequately tuned, with the L0 controller showing a better performance when measured in terms of the average cross-track error. (c) 2022 by the authors. Licensee MDPI, Basel, Switzerland

Cascade Control of the Ground Station Module of an Airborne Wind Energy System

An airborne wind energy system (AWES) can harvest stronger wind streams at higher altitudes which are not accessible to conventional wind turbines. The operation of AWES requires a controller for the tethered aircraft/kite module (KM), as well as a controller for the ground station module (GSM). The literature regarding the control of AWES mostly focuses on the trajectory tracking of the KM. However, an advanced control of the GSM is also key to the successful operation of an AWES. In this paper we propose a cascaded control strategy for the GSM of an AWES during the traction or power generation phase. The GSM comprises a winch and a three-phase induction machine (IM), which acts as a generator. In the outer control-loop, an integral sliding mode control (SMC) algorithm is designed to keep the winch velocity at the prescribed level. A detailed stability analysis is also presented for the existence of the SMC for the perturbed winch system. The rotor flux-based field oriented control (RFOC) of the IM constitutes the inner control-loop. Due to the sophisticated RFOC, the decoupled and instantaneous control of torque and rotor flux is made possible using decentralized proportional integral (PI) controllers. The unknown states required to design RFOC are estimated using a discrete time Kalman filter (DKF), which is based on the quasi-linear model of the IM. The designed GSM controller is integrated with an already developed KM, and the AWES is simulated using MATLAB and Simulink. The simulation study shows that the GSM control system exhibits appropriate performance even in the presence of the wind gusts, which account for the external disturbance

School climate evaluation : designing and validating measurement instruments

O objetivo deste estudo consiste na apresentação do processo de construção, testagem e validação de instrumentos de medida para mensurar o clima escolar, na perspectiva de alunos a partir do 7º ano do ensino fundamental, seus professores e gestores. Realizou-se uma revisão da literatura nacional e internacional sobre a temática, constituiu-se o conceito, a matriz de referência composta de oito dimensões inter-relacionadas e os instrumentos de medida. Com base numa amostra de 11.516 respondentes, procedeu-se às análises estatísticas e qualitativas concernentes ao processo de validação: evidências de validade de conteúdo e de constructo. As dimensões e seus respectivos itens indicaram boa carga componencial e bons índices de fidedignidade, de modo a validar os instrumentos de medida49172312334FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão temThis study aims to present the process of designing, testing and validating measurement instruments to measure the school climate from the perspective of students from the 7th grade of primary education onwards, as well as their teachers and managers. We reviewed the national and international literature on the subject, built the concept, the reference framework formed by eight interrelated dimensions and the measurement instruments. Based on a sample of 11,516 respondents, we carried out the statistical and qualitative analyzes concerning the validation process: Evidence content and construct validity. The dimensions and their respective items indicated good componential load and good reliability indices, which validates the measurement instrument

Coffee industrial waste as a natural source of bioactive compounds with antibacterial and antifungal activities

Coffee is one of the most popular and consumed beverages in the world, which leads to a high contents of solid residue known as spent coffee grounds (SCG). As is known, coffee beans contain several classes of health related chemicals, including phenolic compounds, melanoidins, diterpenes, xanthines and carotenoids which are associated with therapeutic and pharmaceutical effects, due to antimicrobial, antioxidant, anti-infectious and antitumour activities. Considering that this coffee industrial waste has no commercial value and are currently disposed as a solid waste or employed as fertilizers, we intend to highlight the use of SCG as a raw material with potential interest to the food and pharmaceutical industries. Moreover, this work seems to be valuable to promote the use of SCG as natural and an inexpensive food supplements or pharmaceutical additive. The phytochemical compounds content among the crude aqueous extracts of SCG followed this order: phenolics > flavonoids > carotenoids (mg/ g dry waste), respectively. Caffeine content found in SCG was ~ 0.82 g/100 g dry waste, 70 % lower than coffee roasting beans. Coffee ground extracts showed inhibition to S. aureus and E. coli growth for concentrations of 1.0 mg/ mL and a stronger inhibition was also observed against C. albicans, C. krusei and C. parapsilosis growth using lower concentration (0.5 mg/ mL).info:eu-repo/semantics/publishedVersio

Coffee industrial waste as a natural source of bioactive compounds with antibacterial and antifungal activities

Coffee is one of the most popular and consumed beverages in the world, which leads to a high contents of solid residue known as spent coffee grounds (SCG). As is known, coffee beans contain several classes of health related chemicals, including phenolic compounds, melanoidins, diterpenes, xanthines and carotenoids which are associated with therapeutic and pharmaceutical effects, due to antimicrobial, antioxidant, anti-infectious and antitumour activities. Considering that this coffee industrial waste has no commercial value and are currently disposed as a solid waste or employed as fertilizers, we intend to highlight the use of SCG as a raw material with potential interest to the food and pharmaceutical industries. Moreover, this work seems to be valuable to promote the use of SCG as natural and an inexpensive food supplements or pharmaceutical additive. The phytochemical compounds content among the crude aqueous extracts of SCG followed this order: phenolics > flavonoids > carotenoids (mg/ g dry waste), respectively. Caffeine content found in SCG was ~ 0.82 g/100 g dry waste, 70 % lower than coffee roasting beans. Coffee ground extracts showed inhibition to S. aureus and E. coli growth for concentrations of 1.0 mg/ mL and a stronger inhibition was also observed against C. albicans, C. krusei and C. parapsilosis growth using lower concentration (0.5 mg/ mL).info:eu-repo/semantics/publishedVersio

Paradigmas da Geografia Agrária brasileira - Temas, tendências e perspectivas: Diálogo com Janaina Francisca de Souza Campos Vinha

Recentemente foi lançado no Brasil o livro “Paradigmas da Geografia Agrária Brasileira. Temas, tendências e perspectivas” (2022). Resultado do trabalho e pesquisa coletiva, nos traz um mapa das principais temáticas que ocupam os estudos da geografia agrária brasileira nas duas últimas décadas. Mas para conhecer um livro por dentro e nas entrelinhas é sempre um requisito conhecer a quem escreve. Este diálogo com a geógrafa Janaina Francisca de Souza Campos Vinha, que tem dedicado grande parte de sua trajetória ao estudo das lutas dos povos do campo, das águas e das florestas, assim como à compreensão da epistemologia do pensamento geográfico no Brasil, nos permite ter uma visão mais íntima de sua caminhada e do processo de construção desta obra, que com certeza será uma referência para o ensino e pesquisas na geografia. Por meio da troca, Janaina nos permite conectar à autora com a obra, para desmistificar a ideia ‘do pensador moderno’- intocado, estranho- e estabelecer conexões com o pensamento em corpo de mulher. Uma conversa cuidadosa entre companheiras, construída de forma remota, no marco deste dossiê “A produção feminista do conhecimento sobre o campo na Geografia, através do qual também pretendemos reivindicar a relevância do trabalho das mulheres nos estudos da geografia agrária no Brasil

Cymbopogon citratus EO antimicrobial activity against multi-drug resistant Gram-positive strains and non-albicans-Candida species

We studied the antibacterial and antifungal activity of Cymbopogon citratus. These properties were studied on hospital isolated multidrug resistant strains Staphylococcus aureus, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumonia and their respective ATCC control strains. Pathogenic Candida albicans, Candida parapsilosis, and Candida tropicalis were also tested. Results of the present investigation provide evidence that the EO of Cymbopogon citratus could have a potential application in the treatment and prevention of diseases caused by Staphylococcus aureus methicillin-resistant strains and by vancomicin-resistant Staphylococcus epidermidis. Cymbopogon citratus EO is also effective against Candida albicans as well as the emerging Candida parapsilosis and Candida tropicalis pointing to its usefulness as an antifungal agent.info:eu-repo/semantics/publishedVersio

Nutritional, chemical and antioxidant/pro-oxidant profiles of silverskin, a coffee roasting by-product

Coffee silverskin (a coffee roasting by-product) contains high amounts of dietary fibre (49% insoluble and 7% soluble) and protein (19%). Potassium (∼5 g/100 g), magnesium (2 g/100 g) and calcium (0.6 g/100 g) are the major macrominerals. The vitamin E profile of silverskin comprises α-tocopherol, β-tocopherol, ɣ-tocopherol, δ-tocopherol, β-tocotrienol, ɣ-tocotrienol, and δ-tocotrienol. The fatty acid profile is mainly saturated (C16:0 and C22:0), but the total amount of fat is low (2.4%). Caffeine (1.25 g/100 g), chlorogenic acid (246 mg/100 g), and 5-hydroxymethylfurfural (5.68 mg/100 g) are also present in silverskin. Total phenolics and flavonoids are partially responsible for the in vitro antioxidant activity. Silverskin extracts protected erythrocytes from oxidative AAPH- and H2O2-induced hemolysis, but at high concentrations a pro-oxidant effect on erythrocyte morphology was observed.info:eu-repo/semantics/publishedVersio