2,256 research outputs found
Presentazione libro “Con-tatto con il mondo costruito. Rieducare il corpo allo spazio nell’era post-pandemica” a cura di Francesca Casalino e Lucia Nicolai
No full textPresentazione del libro "Con-tatto con il mondo costruito. Rieducare il corpo allo spazio nell’era post-pandemica” a cura di Francesca Casalino e Lucia Nicolai, presso il Lavatoio Contumaciale sito in Piazza Perin del Vaga 4 (Roma), il 18 novembre 2022
Toward inclusion of atmospheric effects in the aircraft community noise predictions
No full textThis paper presents an atmospheric propagation model, based on ray acoustics, that accounts for realistic weather conditions in the evaluation of the noise footprint of an aircraft. Noise sources, obtained using the Ffowcs Williams and Hawkings acoustic analogy applied to scale-resolved flow simulation data, are stored on a hemisphere surrounding the vehicle. These noise sources are propagated using a propagation model that takes into account the vertical variability of air temperature and wind velocity. The electric vertical takeoff and landing aircraft, presented by Casalino, van der Velden, and Romani [(2019). in Proceedings of the AIAA Scitech 2019 Forum, January 7-11, San Diego, CA, pp. 1834-1851], is used as a case study; noise footprints, obtained considering various vertically varying temperature and wind velocity distributions, are compared. It is shown that weather conditions in the acoustic wave propagation can contribute to mismatch up to 4 dBA in the illuminated zone and a significant drop in the refractive shadow zone caused by the vertical air temperature and wind velocity gradients. This work constitutes the first accomplishment in including realistic atmospheric effects in aircraft community noise prediction based on scale-resolved flow simulations.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind Energ
A Dehydrogenase Dual Hydrogen Abstraction Mechanism Promotes Estrogen Biosynthesis: Can We Expand the Functional Annotation of the Aromatase Enzyme?
No full textCytochrome P450 (CYP450) enzymes are involved in the metabolism of exogenous compounds and in the synthesis of signaling molecules. Among the latter, human aromatase (HA) promotes estrogen biosynthesis, which is a key pharmacological target against breast cancers. After decades of debate, interest in gaining a comprehensive picture of HA catalysis has been renewed by the recent discovery that compound I (Cpd I) is the reactive species of the peculiar aromatization step. Herein, for the first time, a complete atomic-level picture of all controversial steps of estrogen biosynthesis is presented. By performing cumulative quantum-classical molecular dynamics and metadynamics simulations of about 180 ps, it is revealed that the most likely enzymatic path relies on three factors: 1) androstenedione enolization and compound 0 (Cpd 0) formation through a proton network mediated by Asp309; 2) subsequent formation of Cpd I, upon rearrangement of the Asp309 side chain and the establishment of a proton network involving Asp309 and Thr310; and 3) after two hydroxylation reactions, 19,19-gem-diol is converted into estrone by Cpd I, through an uncommon dehydrogenase-like dual hydrogen abstraction mechanism. As a result, HA performs estrogen biosynthesis by merging hydroxylase with dehydrogenase activity, which suggests that the need to perform complex chemical transformations led nature to engineer HA, and possibly other steroidogenic CYP450s, by expanding its range of functions to achieve an optimal catalytic efficiency
Space Trajectory Planning with a General Reinforcement-Learning Algorithm
No full textSpace trajectory planning is a complex combinatorial problem that requires selecting discrete sequences of celestial bodies while simultaneously optimizing continuous transfer parameters. Traditional optimization methods struggle with the increasing computational complexity as the number of possible targets grows. This paper presents a novel reinforcement-learning algorithm, inspired by AlphaZero, designed to handle hybrid discrete–continuous action spaces without relying on discretization. The proposed framework integrates Monte Carlo Tree Search with a neural network to efficiently explore and optimize space trajectories. While developed for space trajectory planning, the algorithm is broadly applicable to any problem involving hybrid action spaces. Applied to the Global Trajectory Optimization Competition XI problem, the method achieves competitive performance, surpassing state-of-the-art results despite limited computational resources. These results highlight the potential of reinforcement learning for autonomous space mission planning, offering a scalable and cost-effective alternative to traditional trajectory optimization techniques. Notably, all experiments were conducted on a single workstation, demonstrating the feasibility of reinforcement learning for practical mission planning. Moreover, the self-play approach used in training suggests that even stronger solutions could be achieved with increased computational resources
A rod-linear cascade model for emulating rotor-stator interaction noise in turbofans: A numerical study
No full textThis manuscript presents a rod-linear cascade model for emulating rotor-stator interaction noise. The model is intended as a test platform for studying noise mitigation techniques for a turbofan fan stage, while it also extends the classical rod-airfoil configuration by considering a row of blades based on realistic geometrical details. The rod-linear cascade model consists of a rod positioned upstream of a 7-blade linear cascade, such that the rod wake impinges onto the central blade. The rod is scaled to obtain a fundamental shedding frequency equal to the first blade passing frequency of the NASA-Glenn Source Diagnostics Test (SDT)fan stage at approach condition. The cascade blade profile is also based on the OGV of the SDT sampled at 90% of the radial span. Subsequently, numerical simulations are performed using lattice-Boltzmann Method on a computational setup comprised of a contraction and a test section enclosing the rod-linear cascade model. The integral length scales of the rod wake and the mean loading of the central blade have been found to be in good agreement with the trends observed in the SDT fan stage. The primary noise sources are localized at the central blade leading edge, although noise propagation to the far-field is influenced by additional diffraction by the other blades. Furthermore, the acoustic-blade row interaction causes intense pressure fluctuation within the inter-blade channels, including in those that are not directly affected by the rod wake.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind Energ
Impingement of a propeller-slipstream on a leading edge with a flow-permeable insert: A computational aeroacoustic study
No full textThis manuscript describes an aeroacoustic computational study on the impingement of a tractor-propeller slipstream on the leading edge of a pylon. Both the flow and acoustic fields are studied for two pylon leading edges: a solid and a flow-permeable one. The computational set-up replicates experiments performed at Delft University of Technology. Computational results are validated against measurements. It is found that the installation of the flow-permeable leading-edge insert generates a thicker boundary layer on the retreating blade side of the pylon. This is caused by an aerodynamic asymmetry induced by the helicoidal motion of the propeller wake, which promotes a flow motion through the cavity from the advancing to the retreating blade side of the pylon. The flow-permeable leading-edge insert mitigates the amplitude of the surface pressure fluctuations only on the pylon-retreating blade side towards the trailing edge, thus reducing structure-borne noise. Furthermore, it causes a reduction of the near-field noise only for receiver angles oriented in the upstream direction at the pylon-retreating blade side. In this range of receiver angles, it is found that the flow-permeable leading-edge insert reduces the amplitude of the tonal peaks for the third and fourth blade passage frequency, but strongly increases the broadband noise for frequencies higher that the seventh blade passage frequency.Wind Energ
Laminar Separation Bubble Noise on a Propeller Operating at Low Reynolds Numbers
No full textThis paper explains the presence and relevance of noise caused by a laminar separation bubble (LSB) on a propeller operating at a low Reynolds number. Microphone measurements of a propeller with both clean and forced boundary-layer transition blades are carried out in an anechoic wind tunnel by varying the propeller advance ratio J from 0 to 0.6, corresponding to a tip Reynolds number ranging from 4.3⋅104 to 105. The flow behavior on the blade surface and around the propeller is investigated with oil-flow visualizations and particle image velocimetry. At J=0.4 and 0.6, vortex shedding from the LSB causes high-frequency noise that appears as a hump in the far-field noise spectra. Forcing the location of the boundary-layer transition suppresses the LSB and, consequently, the hump, reducing the noise emission of about 5 and 10 dB at J=0.4 and 0.6, respectively. The fact that the hump is caused by LSB vortex shedding noise is further assessed by using a semi-empirical noise model; it shows that the hump is constituted by tones of different amplitudes and frequencies, emitted at different spanwise sections along the blade.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind Energ
Etno-Graphs. The (textural, graphical, photographical) transcription of field observation as a specific pratice of architectural ethnography
No full textAllestimento mostra “Etno-Graphs. The (textural, graphical, photographical) transcription of field observation as a specific pratice of architectural ethnography” (22-26 maggio 2023) a cura di G. Postiglione, P. Briata, V. Saitto con N. Ambrosino, P. Buccaro, F. Casalino, L. Esposito, M. Masi, C. Priore, M. Russo presso l’ambulacro di Palazzo Gravina – Facoltà di Architettura, via Monteoliveto 3, Napoli
Multivariate process incapability index for non-normal data: a case study
No full textWhen several quality characteristics have to be considered in process capability analysis, conventional indices are difficultly applicable. Above all when different processes have to be compared in terms of capability, they rarely univocally express which process can be considered the best one. Moreover, conventional process capability indices (PCIs) separately consider quality characteristics regardless of eventual mutual dependencies existing between them. In order to offset these weaknesses, useful tools are the multivariate capability indices. In this study, based on the non-normal Cpp formulation, the multivariate process incapability index for non-normal data, MCpp(q), is proposed. The non-normal Cpp has been constructed using Clements’ method; however, Burr XII distribution has been used in place of the Pearson distributions family for assessing non-normal percentiles. The bootstrap methodology has been used to draw an interval estimate of the index proposed. A case study on the comparison between two different cold extrusion processes has been presented to demonstrate how the proposed index can be applied to real data
Structural, dynamical and catalytic interplay between Mg2+ ions and RNA. Vices and virtues of atomistic simulations
No full textMg2+ ions are essential for RNA biology as they allow RNA filaments to assume their natively folded structure and promote their function in a variety of biological processes. The Mg2+ positive charge screens the negative one of the phosphate backbone, permitting RNAs to assume compact tertiary structures. Moreover, key biological processes, such as formation of mature messenger RNA or transfer RNA, are promoted by catalytic Mg2+-dependent RNA enzymes. Mg2+ ions regulate this very broad range of functions by interacting non-specifically and/or specifically (either directly or via water-mediated contacts) with RNA in several possible binding architectures.
Despite being Mg2+ an alkaline earth ion and binding to RNA without forming coordination bonds, its unique interplay with RNA is ascribable to the large charge transfer and polarization effects exerted on the polynucleotide chain. This key feature makes difficult a correct description of we interactions with simple empirical force field models, requiring the use of ab initio or multiscale methods.
In this review we provide a survey of strengths and limitations of different atomistic simulation techniques, ranging from force field-based molecular dynamics to oh initio and hybrid quantum-classical (QM/MM) methods, in the structural and functional description of Mg2+-RNA binding, showing how in silico studies have contributed to reveal important aspects of RNA biology. Computational perspectives in this field are finally given
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