467 research outputs found
Presas del Ecuador
No full textThis work presents preliminary information on the problems of planning, design, construction and behavior of dams built in Ecuador during this century. This work corresponds to some chapters, as a synthesis of a book that the author is preparing called DAMS OF ECUADOR in the process of preparation.En este trabajo se presentan la in- formación preliminar sobre los problemas de la planificación, diseño, construcción y comporta miento de las presas construídas en el Ecuador durante el presente siglo. Este trabajo corresponde a algunos capítulos, a manera de síntesis de un libro que está pre- parando el autor denominado PRESAS DE ECUADOR en proceso de elaboración.
Audiência de custódia: instrumento para um possível controle da banalização das prisões provisórias
No full textTCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Jurídicas. Direito.O sistema de justiça criminal brasileiro convive com uma série de problemas, dentre eles o excessivo número de encarcerados provisórios, o déficit de vagas do sistema prisional e o desrespeito aos princípios e garantias fundamentais dos indivíduos investigados. O presente trabalho tem como objetivo apresentar a audiência de custódia, uma prática que poderá auxiliar no controle da banalização das prisões provisórias e garantir efetividade aos tratados internacionais de direitos humanos que o Brasil é signatário. Para o desenvolvimento do mesmo foi empregado dados obtidos por meio de pesquisas realizadas por órgãos oficiais do governo, referente às prisões no Brasil, além de pesquisa bibliográfica referente à audiência de custódia
On the numerical prediction of added damping and added mass of vibrating disc-like structures in heavy fluids
No full textDisk-like structures are common in hydraulic turbomachinery. These structures are prone to near-resonant vibrations. Accurately determining their modal parameters, however, is not a trivial task. Due to the submersion in a heavy, viscous fluid, the inertia and damping of the structure are significantly influenced by the fluid added mass and damping. As a step towards accurate vibration prediction, the added damping and mass of a vibrating, water-submerged disc with a variable axial distance from a rigid wall is numerically investigated. First, a computation approach of the added mass and added damping is derived based on the vibration-induced fluid reaction force. Using this approach, requirements on numerical flow simulation for accurate added damping prediction and related uncertainties are identified by validation against experimental results. Next, the numerical flow field is analyzed, exposing the vibration-induced fluid phenomena. Additionally, we propose a methodology to study the mechanisms of the added mass and added damping effects and their transfer from fluid to structure. As a result, a numerical configuration that accurately predicts the added mass and added damping in both trend and magnitude for a set of vibration modes, vibration amplitudes, and axial gap sizes is presented for the disc system. Moreover, the cause of the nonlinear behavior of the added damping force is revealed. We demonstrate that the phase lead of the fluid reaction force with respect to the structural oscillations increases with rising vibration amplitude, implying that both the added mass and added damping depend on the vibration level of the system.The author Karim Khalfaoui would like to acknowledge the Global Glimpse program of the University of Stuttgart, Germany for their financial support for the valuable research stay at CDIF at the Polytechnical University of Catalonia. Alexandre Presas acknowledges the Serra Hunter Programme from Generalitat de Catalunya. Alexandre Presas and Greco Moraga would like to acknowledge the PID2022–139479OB-C21 project founded by the AEI of SPAIN.Peer ReviewedPostprint (published version
Research on the influence mechanism of operating characteristics of an 11-stage pump as turbine under turbine mode
No full textUnder the background of sustainable development of renewable energy, it is more and more important to recover the energy of high-pressure medium produced in the petrochemical process. In the field of petrochemicals, the multi-stage pump as turbine (PAT) has a strong economy. PAT can not only generate the high-pressure medium required in the petrochemical process but also recover the high-pressure medium energy that has been completed. When the multi-stage PAT is operated under the turbine condition, the internal flow state is more complicated than that under the pump condition. The hydraulic performance often has problems such as a narrow high-efficiency zone, low efficiency, and flow instability. The hydraulic performance will decrease, but the reason for the decrease in hydraulic performance is still unclear. In this paper, the mechanism of PAT internal flow loss and evolution of pressure pulsation is studied. The hydraulic performance and internal flow characteristics of the multi-stage PAT are studied by comparing the experimental and numerical simulation results. The influence of inflow conditions on the internal loss and internal flow characteristics of the PAT stage is found, and the relationship between inflow low-frequency signals 0.2fBPF and internal loss and the cumulative effect of inflow pressure pulsation is revealed.This study was supported by Joint Funds of the National Natural Science Foundation of China (U20A20292); Natural Science Foundation of Jiangsu Province (BK20210771); National Natural Science Foundation of China (51906085); China Postdoctoral Science Foundation Funded Project (2021M701847). Alexandre Presas would like to acknowledge the Serra Hunter Programme. Alexandre Presas and Yonggang Lu would like to acknowledge the PID2022-139479OB-C21 project founded by the AEI of SPAIN.Peer ReviewedPostprint (author's final draft
Hybridization of a RoR HPP with a BESS—The XFLEX HYDRO Vogelgrun Demonstrator
No full textIn the XFLEX HYDRO Vogelgrun demonstrator, a run-of-river hydropower plant, the hybridization of one turbine-generator unit with a battery energy storage system is being investigated. This paper describes the integration methodology of the hybrid control algorithm without replacing the existing speed governor of the unit. Furthermore, the comparison of the performances of a non-hybrid and hybrid unit is discussed, and first experiences gained during the operation and monitoring of the hybrid operating mode are presented.This work has been realized with the participation of INES.2S. David Valentín and Alexandre Presas acknowledge the Serra Húnter program. The corresponding author would like to express his gratitude to Nicolas Ruchonnet for his contributions during the revision.Postprint (published version
O papel de presas contaminadas no comportamento e fisiologia das planárias na investigação de microplásticos
No full textMicroplastics (1 μm to 1 mm) have become a concerning topic in the scientific community when associated with poor plastic waste management. Although the presence and abundance of these particles in freshwater environments have been previously reported, there is still an insufficient number of studies providing information about the potential trophic transfer and its consequences on freshwater benthic organisms. This work aimed to evaluate the behavioural and physiological responses of planarian Girardia tigrina after consuming contaminated prey - Chironomus riparius 4th instar larvae previously exposed to microplastics of Polyurethane (PU-MPs).
For this purpose, two investigations were carried out. In the first investigation, it was assessed the effects of PU-MPs (concentrations up to 750 mg/Kg) on C. riparius life history traits (larval size, emergence); and, when exposed to a no-observed-effect-concentration (NOEC), larvae behaviour (locomotion) and biochemical responses (oxidative damage, aerobic energy production, and energy reserves). Exposure to PU-MPs did not affect larval size nor imagoes emergence. Notwithstanding, contaminated larvae revealed higher aerobic metabolism underlined by a higher locomotion activity (curling/uncurling) but without compromising energy reserves.
In the second experiment, it was assessed the effects of the consumption of contaminated alive prey (exposed to PU-MP NOEC) in a 3h feeding assay on planarians' behaviour (nr of consumed prey, locomotion), regeneration, and physiology (energy reserves, aerobic metabolism, oxidative damage). After the feeding test, planarians consumed 20% more contaminated prey with no changes in their locomotion. The consumption of contaminated prey delayed auricles' regeneration by one day, without resulting in oxidative damage, altered aerobic metabolism or energy reserves.
These investigations bring new intel on the role of contaminated prey on planarians' behaviour and physiology in microplastic research.Os microplásticos (1 μm a 1 mm) tornaram-se um tópico preocupante na comunidade científica quando associados a uma má gestão de resíduos plásticos. Embora a presença e abundância destas partículas em ambientes de água doce tenha sido previamente reportada, ainda há um número insuficiente de estudos que fornecem informações sobre a potencial transferência trófica e as suas consequências nos organismos bentónicos de água doce. Este trabalho visou avaliar as respostas comportamentais e fisiológicas da planaria Girardia tigrina após o consumo de presas contaminadas - Chironomus riparius 4th instar larvae previamente expostas a microplásticos de Poliuretano (PU-MPs).
Para este efeito, foram efetuadas duas investigações. Na primeira investigação, foram avaliados os efeitos dos PU-MPs (concentrações até 750 mg/Kg) sobre os parâmetros da história de vida de C. riparius (tamanho larvar, emergência); e, quando expostos a uma concentração sem efeitos observados (NOEC), comportamento larvar (locomoção) e respostas bioquímicas (danos oxidativos, produção de energia aeróbica, e reservas energéticas). A exposição a PU-MPs não afetou o tamanho das larvas nem a emergência dos adultos. Não obstante, as larvas contaminadas revelaram um metabolismo aeróbio mais elevado sublinhado por uma maior atividade de locomoção (N.º de contrações corporais) mas sem comprometer as reservas energéticas.
Na segunda experiência, foram avaliados os efeitos do consumo de presas vivas contaminadas (expostas a PU-MP NOEC) num ensaio de alimentação de 3h sobre o comportamento das planárias (nº de presas consumidas, locomoção), regeneração, e fisiologia (reservas energéticas, metabolismo aeróbio, danos oxidativos). Após o ensaio de alimentação, as planárias consumiram mais 20% de presas contaminadas, sem alterações na sua locomoção. O consumo de presas contaminadas atrasou a regeneração das aurículas num dia, sem resultar em danos oxidativos, alteração do metabolismo aeróbico ou das reservas energéticas.
Estas investigações trazem novas informações sobre o papel das presas contaminadas no comportamento e fisiologia das planárias na investigação de microplásticos.Mestrado em Eco-toxicologia e Análise de Risc
Experimental study on the detection of vibrations of an operating turbine runner with sensors on the casing
No full textHydraulic turbine runners experience strong vibrations in operation, especially when resonances between runner natural frequencies and hydraulic excitations occur. Precise determination of prototype runner frequencies in operation is essential, but direct measurements are costly and technically challenging. This study presents an experimental investigation on a reduced-scale Francis model to evaluate the use of non-intrusive stationary sensors to measure runner vibrations. The runner was instrumented with accelerometers and piezoelectric patches, and an accelerometer was installed on the casing. The natural frequencies of the operating runner were excited with the patches and the vibration was measured simultaneously in the rotating and stationary structures. Results prove the feasibility of monitoring runner vibrations externally and demonstrate the correlation between rotating and stationary frames. Runner natural frequencies change and split due to confined rotation. The stationary sensor measures them with a frequency shift depending on rotating speed and nodal diameters of the excited mode shape.Mònica Egusquiza wishes to acknowledge the financial aid provided by the European Union-NextGenerationEU, Ministry of Universities and Recovery, Transformation and Resilience Plan, which through the call of Universitat Politècnica de Catalunya (Grant Ref. 2021UPC-MS-66165) provided the funds to perform the research presented in this paper. Alexandre Presas and David Valentin would like to acknowledge the Serra Hunter programme of Generalitat de Catalunya.Peer ReviewedPreprin
A composite robust adaptive control for double-fed variable-speed pumped storage units considering stochastic uncertainty
No full textAs an advanced technology in pumped storage, the doubly-fed variable-speed pumped storage unit (DFIM-VSU) enhances flexibility, overcomes conventional constraints, and emerges as a transformative solution for power systems. However, its implementation faces challenges, including dynamic uncertainties, complex couplings, and control limitations. To address these issues, this paper proposes an adaptive control strategy to mitigate stochastic uncertainties and suppress composite disturbances, enhancing the safety of DFIM-VSU regulation. First, a coupled VSU governor-excitation model with parameter perturbations is developed. Leveraging probability density theory, a framework for dynamic response quantification is established, highlighting the regional probability distribution of key states. Building on this, a novel and efficient nonlinear disturbance observer and model reference adaptive composite controller (NDOB-MRAC) is proposed. Through state matrix reconstruction and real-time disturbance feedforward compensation, the controller can effectively optimize overshoot, maximum deviation, and regulation time in unit speed. Experimental results demonstrated that NDOB-MRAC expanded the stable domain and significantly enhanced multi-condition adaptability and dynamic performance. Notably, under low-head, high-load conditions, the proposed method reduced regulation time by 39.8 % compared to PI control while eliminating speed overshoot. These findings clarify operational uncertainties of VSUs and provide a reliable foundation for robust control in pumped storage systems.The authors acknowledge financial support from the Smart Gird- National Science and Technology Major Project (2024ZD0801800), the National Natural Science Foundation of China (No. 52279085), the Hubei Provincial Natural Science Foundation of China (2023AFD186), the National Natural Science Foundation of China (No. U23B20143) for the research, authorship, and publication of this article. Alexandre Presas acknowledge the Serra Hunter Programme of Generalitat de Catalunya.Peer ReviewedPostprint (author's final draft
Proposta de um mecanismo de acompanhamento econômico-financeiro do devedor de uma instituição financeira para previnir sua inadimplência
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.O objetivo do presente estudo consistiu em desenvolver um mecanismo de acompanhamento econômico-financeiro do devedor de uma instituição financeira, por meio da análise das demonstrações contábeis, visando prevenir a inadimplência. A metodologia da pesquisa adotada compreendeu uma abordagem qualitativa, com análise descritiva de um estudo de caso na área de operações de crédito em uma instituição financeira. Assim, na primeira etapa da pesquisa fez-se uma incursão teórica sobre o Sistema Financeiro Brasileiro, análise de risco na concessão do crédito, os principais instrumentos e formas de análise econômico-financeira das empresas. No que diz respeito ao estudo de caso, foram levantados os procedimentos, hoje adotados para a prevenção da inadimplência junto à instituição financeira. Verificou-se que eles estão fortemente focados na fase que antecede a concessão do crédito. O acompanhamento do cliente após a liberação dos recursos, normalmente ocorre quando são identificados problemas no recebimento ou por iniciativa dos administradores das carteiras. A partir dessas observações, elaborou-se uma proposta de acompanhamento econômico-financeiro do devedor que, por meio da análise das demonstrações contábeis, visa prevenir a inadimplência na instituição financeira. Acredita-se que o conhecimento e a experiência desses profissionais, consolidadas num sistema de informação, aliados às metodologias de avaliação de risco e acompanhamento dos clientes, poderá se transformar numa importante aplicação para o controle do crédito. Os indicadores que contribuiram nos modelos preditivos, com alto grau de precisão, foram sugeridos para serem analisados como forma de acompanhamento da situação econômico-financeira, com a finalidade de identificar os sinais de alerta ao longo do processo, e assim, reduzir a inadimplência. Concluiu-se que a eficácia do controle depende do acompanhamento constante junto aos clientes, da revisão dos indicadores utilizados, do uso de recursos tecnológicos, treinamento de pessoal e, principalmente, do envolvimento e comprometimento do Banco para com o cliente e vice-versa, conforme recomendados no presente trabalho
From world of life to narrative identity: Mario Presas in Revista Latinoamericana de Filosofía (1975-2000)
No full textEn el presente artículo analizaremos los artículos publicados por Mario Presas en la Revista Latinoamericana de Filosofía, en el período que va de 1975 a 2000. El propósito es esbozar una aproximación de conjunto a este corpus, distinguiendo básicamente dos períodos de su desenvolvimiento intelectual. El primero se centra en aspectos fenomenológicos y existenciales de la temporalidad y la corporalidad en el contexto de investigación del mundo de la vida. El segundo se aboca al análisis de problemas estéticos y hermenéuticos de la recepción textual y artística, con particular énfasis en las operaciones constitutivas de la actividad lectora. En conformidad con el autor, puede resumirse esa evolución como una reflexión que lleva del ser a la palabra. En el trabajo sostenemos que el trayecto filosófico de Mario Presas, mediante un despliegue coherente de la temática que conecta el mundo de la vida con la identidad narrativa pasando por el acto de leer, permite comprender que la experiencia estética es una dimensión esencial del existente humano.In this article we will analyze the articles published by Mario Presas in the Revista Latinoamericana de Filosofía, in the period from 1975 to 2000. The purpose is to outline an overall approach to this corpus, basically distinguishing two periods of its intellectual development. The first focuses on phenomenological and existential aspects of temporality and corporality in the context of lifeworld research. The second deals with the analysis of aesthetic and hermeneutical problems of textual and artistic reception, with particular emphasis on the constitutive operations of the reading activity. According to the author, this evolution can be summarized as a reflection that leads from being to words. In the work we maintain that the philosophical journey of Mario Presas, through a coherent deployment of the theme that connects the world of life with the narrative identity through the act of reading, allows us to understand that the aesthetic experience is an essential dimension of the human existent.Fil: Oviedo, Gerardo. Universidad de Buenos Aires / Universidad Nacional de Lanús / CONICET, Argentina
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