196,761 research outputs found
New Hybrid (Oren-Al-Bayati) Self-Scaling Algorithm With Armijo Line Search
No full textABSTRACT In this paper the development, and numerical testing of a class of self-scaling Quasi-Newton update with adaptive step -size are presented . In our work a new combined (Oren-Al-Bayati) self-scaling algorithm is presented with a modified Armijo line search procedure. This algorithm has implemented both theoretically and numerically and tested on some well-known test cases. Numerical experiments indicate that this new algorithm is effective and superior to the standard, with respect to the number of functions evaluations (NOF) and number of iterations (NOI)
Wind Tunnel Wake Measurements of Floating Offshore Wind Turbines
No full textThis paper reports the results of a wake measurement campaign carried out at Politecnico di Milano wind tunnel to support current studies of the authors about unsteady aerodynamics of floating offshore wind turbines (FOWT) as well as evaluating experimental evidence for wind farm applications of FOWT. The wind turbine scale model adopted for these tests is the 1/75 DTU 10 MW wind turbine developed for the LIFES50+ project. In this study, imposed surge motions, at different frequencies and amplitudes, were provided at the base of the turbine's tower, to investigate the influence of motion on the wake. Results reported show good agreement with the state-of-the-art of wind turbines wake aerodynamics in steady conditions; concerning the unsteady conditions (imposed motion) interesting data are reported and collected with respect to a "wake reduced frequency" parameter which is, according to the authors, a straightforward value to estimate the "level" of unsteadiness connected to a specific dynamic condition due to floating motion. Interesting and consistent phenomena are observed and commented, although opening to the need of further experimental and numerical investigations
Study of the Effect of Water Depth on Potential Flow Solution of the OC4 Semisubmersible Floating Offshore Wind Turbine
No full textAbstractThis work aims at assessing the influence of water depth on the potential flow solution for a semisubersible floating offshore wind turbine. More specifically, the system developed for the Offshore Code Comparison Collaboration Continuation (OC4) of the Inter- national Energy Agency IEA was considered for this paper. This work has been inspired by previous studies concerning the effect of shallow water on Liquified Natural Gas Carriers (LNGC). The influence of water depth on the hydrodynamics of such systems is evident from measurements as well as from simulations, specifically when secondary effects in the wave and flow modelling are addressed. This scenario has motivated the comparative study for the Floating Wind Turbine herein reported, also taking into account second order hydrodynamics (Quadratic Transfer Functions, QTF) as well as low frequency contribution in the incoming wave, due to shallow water (Setdown effect). The simulations were conducted relying on the codes DIFFRAC and aNySIM, de- veloped at Maritime Research Institute of Netherlands (MARIN) and the results are presented for a range of water depth between the nominal value of 200 m and the extreme shallow water of 30 m
Multibody/FEM numerical tool for HIL scaled offshorewind turbine
No full textNowadays the study of the renewable sources of energy is one of the most important lines of research. For this reason the wind tunnel researchers of Politecnico di Milano want to apply new hardware in the loop approach to study floating offshore wind turbines scale models by reproducing at the same time both the aerodynamic and hydrodynamic phenomena involved. These experiments allow to have a better understanding of the operating conditions of these structures and to properly set the control algorithm for the blades pitch in order to have a better exploitation of the wind stream. In addition the results of the experimental phase could be used to validate the numerical codes. While it is possible to physically reproduce the wind profile with a good approximation, the sea waves effect has to be simulated by means of a 6-DoF parallel kinematic machine. The result is a coupled system in which two flexible structures, the turbine and the robot, cannot be regarded as two separate entities. The aim of this paper is to provide a multibody model to perform dynamic analysis of this coupled system and to study how the pose of the manipulator and the wind profile affect the results
A device for pressure measurements on yacht sails
No full textThe present invention relates to the field of ship building, in particular ships propelled by sails, more in particular to sail design.
The present invention discloses a sail pressure measurement system based on MEMS sensors and pressure strips and pads technology. The system is capable to give differential measurement between the leeward and windward side of the sails
La poesía de Abd Al-Wahhab al-Bayati entre la tradición árabe y la española
No full textEl objetivo de nuestra investigación es analizar la evolución de la obra y de la poética de Abd Al-Wahhab al-Bayati, un exponente fundamental de la literatura árabe por su papel como portavoz y líder de la Escuela del verso libre, y, más en particular, la influencia de la literatura hispánica en el poeta, siguiendo, tal como él mismo dijo, la raya de luz y sangre que une a ambas culturas. En nuestro trabajo se aportan datos e informaciones novedosas al respecto, no tratadas en los estudios anteriores dedicados al poeta iraquí, y se ofrecen nuevas claves de interpretación de una obra poco conocida para el lector occidental. Para analizar las vertientes más relevantes del autor, nuestra tesis se estructura en cinco capítulos. En ellos se consideran sus versos y se profundiza tanto en su estructura formal como en la dimensión más significativa de los poemas y la repercusión que estos lograron desde un punto de vista más pragmático. El primer capítulo propone una introducción al mundo personal de al-Bayati. Se hace en él un recorrido por los hitos principales de su biografía (la infancia, los años de su formación como poeta, las primeras influencias literarias y políticas, el exilio, etc.) y se repasan los libros que configuran la totalidad de su obra literaria. El segundo capítulo presenta a al-Bayati como innovador de la poesía árabe contemporánea debido a su relevancia dentro de la Escuela del verso libre. Así, se examinan las escuelas poéticas anteriores y las características del verso libre, atendiendo al contexto social y político y a su lugar en el patrimonio literario árabe. El tercer capítulo se centra en el influjo que la cultura árabe tuvo en la poesía del autor iraquí; se revisan conceptos capitales como la ciudad, la naturaleza y la experiencia del exilio, que le condujeron a un tipo de poesía nostálgica, y también se aborda su poesía más rebelde, la relacionada con los ámbitos político, social y filosófico. El cuarto capítulo atiende a las fuentes españolas que alimentaron la poesía de al-Bayati, a las ciudades que le marcaron (Madrid, Granada y Córdoba) y a las figuras artísticas y literarias que resultaron más decisivas para la construcción de su mundo creativo, como Federico García Lorca, Pablo Picasso, Salvador Dalí o Rafael Alberti, con los que tomó contacto durante sus estancias en España, donde trabajó como consejero cultural de la Embajada de Iraq. Se añade finalmente un apéndice con dos partes: una antología en la que se recoge la totalidad de los poemas analizados y citados parcialmente a lo largo del trabajo, de los que se aporta una traducción personal que corrige algunos errores de las versiones anteriores; y una breve selección de la obra de tres poetas árabes pertenecientes a la misma escuela innovadora de al-Bayati, igualmente en traducción propia que permitirá al lector español conocer algunas de las voces más representativas de la poesía árabe contemporánea. Enfrentarse a una obra como la de al-Bayati, de gran complejidad, obliga a una investigación dilatada en el tiempo. Sus poemarios incluyen temáticas variadas, y las imágenes que emplea para la transmisión de sus ideas y emociones requieren una lectura en paralelo. La originalidad en el tratamiento de los temas fundamentales de su poesía (los vínculos culturales, el olvido, el dolor y el exilio) justifica la tentativa. Nuestro trabajo aspira a llamar la atención y a conseguir un mejor conocimiento de un autor fundamental para la poesía contemporánea, que, pese a ello, ha sido injustamente olvidado
Belief propagation for weighted b-matchings on arbitrary graphs and its relation to linear programs with integer solutions
No full textExperimental investigation of the unsteady aerodynamics of FOWT through PIV and hot-wire wake measurements
No full textThis work presents a selected set of results from an extensive experimental campaign aimed at characterizing the wake aerodynamics of a floating offshore wind turbines (FOWT) in dynamic conditions. The campaign was carried out in the Politecnico di Milano 14m x 4m atmospheric boundary layer test section, under UNAFLOW project (UNsteady Aerodynamics of FLoating Wind turbines). Wake measurements were carried out either through hot-wire anemometers with a traversing system as well as through Particle Image Velocimetry (PIV) technique. A 1/75 scale model of the DTU 10 MW reference wind turbine was adopted, which was mounted on a hydraulically actuated mechanism imposing sinusoidal surge motion at different frequencies and amplitudes, and for different tip speed ratios λ. Selected results are reported with the aim of giving a first interpretation of the novel set of measurements, also completing previous measurements conducted by the authors, to put the basis of a more comprehensive understanding of unsteady aerodynamics of FOWT for control and wind farm purposes
Deep learning methods and evaluation of the extensive carbon emission predictive solution for Danish grid
No full textThe increase in industrialization and the rise of large commercial cities have significantly contributed to the escalation of carbon emissions over the last few centuries. Accurate forecasting of carbon emissions is critical for governing bodies to implement effective policies aimed at promoting sustainable development. This study investigates both deterministic and probabilistic forecasting models, assessing their prediction accuracy and reliability. The deterministic models applied four deep learning algorithms—Convolutional Neural Networks (CNN), Deep Feedforward Neural Networks (DFNN), Long Short-Term Memory (LSTM), and Multi-Headed Attention LSTM (MHA-LSTM). Probabilistic forecasting models were further enhanced using Monte Carlo simulations (MCS). The performance of these algorithms was evaluated across multiple metrics. MHA-LSTM demonstrated superior performance in both deterministic and probabilistic forecasting. In deterministic predictions, it achieved the lowest Mean Absolute Error (MAE) at 0.014 during training and 0.017 during testing, outperforming CNN, DFNN, and LSTM. It also recorded minimal Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE). In probabilistic forecasting, Attention LSTM excelled with the lowest Absolute Calibration Error (ACE%) at -0.150 and Interval Score (IS) of −2.892×105, significantly outperforming other models. Its strong performance across metrics and confidence levels, particularly in Pinball metrics for prediction bounds, highlights its robustness and accuracy, making it ideal for carbon emission forecasting and policy planning
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