1,721,448 research outputs found
Aerodynamic shape optimization of rotary wing aircraft components using advanced multiobjective evolutionary algorithms
Full text linkThe aim of this Doctoral Thesis, sponsored by AgustaWestland, is the design and development of a multi-objective optimization procedure that involves the application of the GeDEA-II, a powerful and time-saving evolutionary algorithm recently developed by the author at the University of Padova, able to perform multi-objective optimization analyses with the general approach of the Pareto frontier search. When compared to other state-of-the-art multi-objective evolutionary algorithms, it features novel crossover and mutation operators, and demonstrated superior performance.
This optimizer supervises an automatic optimization loop involving the CFD commercial and free, open source solvers, respectively Fluent® and OpenFOAM®.
Altair Hyperworks package is chosen as the free-form-deformation parameterization engine.
The test cases chosen to demonstrate the strength of the procedure implemented concern the aerodynamic optimization of the AgustaWestland ERICA nose region, and the optimization of the intake 1 of the AW101 helicopter, that is really challenging problems from both the engineering and the industrial point of view.
Starting from the the geometry elaboration and proceeding to the results discussion, each step of the optimization procedure is described in details, with particular focus on the automatic optimization loop, directly programmed by the author in both UNIX/Linux and Windows environments.
The results obtained surely demonstrate the effectiveness of the multiobjective approach chosen to carry out this work.
Furthermore, some suggestions for future improvements and developments are provided, with the purpose to increase the strength of the discussed multi-objective optimization tool.Lo scopo di questa tesi di Dottorato in Energetica, finanziata da AgustaWestland, consiste nella progettazione e sviluppo di una procedura di ottimizzazione multi-obiettivo, che comprende l’applicazione del GeDEA-II, un algoritmo genetico/evolutivo recentemente sviluppato dall’autore presso l’Università di Padova.
Tale algoritmo permette di effettuare analisi di ottimizzazione multiobiettivo, sfruttando l’approccio del tutto generale che va sotto il nome di “Ricerca del Fronte di Pareto”. Rispetto ad altri algoritmi evolutivi multi-obiettivo “state-of-the-art”, esso presenta operatori di crossover e mutazione innovativi, che ne migliorano in maniera significativa le performance.
Questo ottimizzatore è accoppiato con i codici CFD commerciali e gratuiti, rispettivamente Fluent® and OpenFOAM®. Il pacchetto Altair Hyperworks, codice ufficiale presso AgustaWestland per il pre-processing di fusoliere di elicottero, è scelto quale software per la parametrizzazione free-form. I casi test scelti per dimostrare l’efficacia di tale procedura consistono nell’ottimizzazione aerodinamica della regione frontale del tilt rotor dimostrativo ERICA, e della presa d’aria 1 dell’elicottero AW101. Tali casi costituiscono problemi stimolanti sia da un punto di vista puramente ingegneristico, sia da un punto di vista industriale. A partire dall’elaborazione della geometria, e procedendo con la discussione dei risultati ottenuti, ogni passo della procedura di ottimizzazione è descritto in dettaglio, con particolare enfasi dedicata al ciclo di ottimizzazione, sviluppato dall’autore sia in ambiente UNIX, sia in ambiente Windows. I risultati ottenuti dimostrano l’efficacia dell’approccio di ottimizzazione basato sull’algoritmo GeDEAII, scelto per sviluppare questo lavoro. Inoltre, vengono forniti alcuni consigli inerenti lo sviluppo futuro di questa procedura di ottimizzazione, con l’obiettivo di migliorare ulteriormente le capacità e la robustezza del ciclo di ottimizzazione
Expanded Hemodialysis: A New Therapy for a New Class of Membranes
No full textA wide spectrum of molecules is retained in end-stage kidney disease, normally defined as uremic toxins. These solutes have different molecular weights and radii. Current dialysis membranes and techniques only remove solutes in the range of 50-15,000 Da, with limited or no capability to remove solutes in the middle to high molecular weight range (up to 50,000 Da). Improved removal has been obtained with high cut-off (HCO) membranes, with albumin loss representing a limitation to their practical application. Hemodiafiltration (HDF) at high volumes (>23 L/session) has produced some results on middle molecules and clinical outcomes, although complex hardware and high blood flows are required. A new class of membrane has been recently developed with a cut off (MWCO) close to the molecular weight of albumin. While presenting negligible albumin loss, these membranes have a very high retention onset (MWRO), allowing high clearances of solutes in a wide spectrum of molecular weights. These membranes originally defined (medium cut off) are probably better classified as high retention onset. The introduction of such membranes in the clinical routine has allowed the development of a new concept therapy called "expanded hemodialysis" (HDx). The new therapy is based on a special hollow fiber and dialyzer design. Its simple set-up and application offer the possibility to use it even in patients with suboptimal vascular access or even with an indwelling catheter. The system does not require a particular hardware or unusual nursing skill. The quality of dialysis fluid is, however, mandatory to ensure a safe conduction of the dialysis session. This new therapy is likely to modify the outcome of end-stage kidney disease patients, thanks to the enhanced removal of molecules traditionally retained by current dialysis techniques
Soluble FcγRIA expressed on monocytes (sCD64): A new serum biomarker of acute kidney injury in patients with suspected infection at emergency department admission
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Kidney disease in heart failure: the importance of novel biomarkers for type 1 cardio-renal syndrome detection
No full textChronic kidney disease (CKD) in heart failure (HF) has been recognized as an independent risk factor for adverse outcome, although the most important clinical trials tend to exclude patients with moderate and severe renal insufficiency. Despite this common association, the precise pathophysiological connection and liaison between heart and kidney is partially understood. Moreover, is it not enough considering how much cardio-renal syndrome type 1 is attributable to previous CKD, and how much to new-onset acute kidney injury (AKI). Neither development of AKI, its progression and time nor duration is related to an adverse outcome. An AKI definition is not universally recognized, and many confounding terms have been used in literature: “worsening renal function”, “renal impairment”, “renal dysfunction”, etc., are all names that contribute to misunderstanding, and do not facilitate an universal classification. Therefore, AKI development should be the consequence of the basal clinical characteristics of patients, different primitive kidney disease and hemodynamic status. AKI could also be the mirror of several underlying associated diseases poorly controlled. Finally, it is not clear which is the optimal laboratory tool for identifying patients with an increased risk of AKI. In the current report, we review the different kidney diseases’ impact in HF, and we analyze the modalities for AKI recognition during HF focusing our attention about some new biomarkers with potential application in the current setting
Acute Kidney Injury in the Geriatric Population
No full textThe aging kidney is more susceptible to injury. Thus, it is not surprising that acute kidney injury (AKI) is a disorder with a relative high incidence in the elderly population, especially those with critical illness. Given the comorbid conditions common in the geriatric population as well as the increase in exposure to various nephrotoxic insults, it is likely that the incidence of AKI will grow in the coming decades. Thus, it is critical to gain an understanding of the cellular and molecular pathways operative in increasing the susceptibility to AKI with an aim to design therapies that will mitigate the risk of AKI. In the meanwhile, meticulous attention to preventative strategic is critical. When AKI does occur and renal replacement therapy is needed, individual decision making is required and should not be based on age alone
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