86,791 research outputs found
(Introduction to) The Literary Genres in the Flavian Age. Canons, Transformations, Reception
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Reduction of the design space to optimize blade fir-tree attachments
No full textThe blade attachment, both dovetail or fir-tree, transfers the centrifugal load from the blade to the disc, generating high mean and peak stresses in notches as well as on contact surfaces. Hence, the strength of the attachment is one of the main concern of the designers for improving the performance of the engine and several optimization procedure have been put forward to minimize the state of stress in the attachment for a given centrifugal load. The optimization process is generally driven by a parametric model. The selection of the proper parameters and their variation ranges represent one of the main issues for the process to converge in a reasonable amount of time. Simulation methods and optimization algorithms have been improved a lot in the past years. Nevertheless, the computational effort of the finite element analysis involved in the optimization procedure of complex geometries remains a critical task. Moreover, an accurate evaluation of the local contact stresses is highly dependent on the mesh refinement, increasing the computing time of the whole optimization process. Moreover, a multi-objective optimization, in addition to robustness design approach, is the designer tool to improve the attachment performance.
The searching domain reduction of the optimization process improves the computational performance reducing the convergence time of the solution. To achieve this goal, a preliminary selection of the design space has been performed by means of an analytical approach.
This paper describes a new design criterion based on one dimensional approach. The criterion has been implemented in an in-house tool that takes faster decisions, if compared with a two or a three dimensional model, about the number of possible feasible solutions. During the geometrical optimization phase of the blade fir-tree attachment, in which a parametric model is used, the authors try to handle the geometrical non-feasibility with a combination of Latin Hypercube Sampling (LHS) and an adaptive penalty method. The optimization is done via the genetic algorithm and the computational time of the reduced domain is compared with the original one
Prototyping of Lunar surface geological sampling tools for Moon spacewalk simulations by ESA
No full textApollo Lunar missions returned to scientists on Earth the first collection of geological extra-terrestrial planetary
samples, other than meteorites. Scientists around the world are still studying rocks and soil samples that were
collected, by the Apollo 11 through 17 missions, using modern equipment, methods and technologies. The return of samples has allowed the field of planetary science to advance in ways unthinkable with the restrictions of in-situ analysis and remote observations.
As for every other aspect of the Apollo programme, the design and manufacturing of the tools utilized by
astronauts for sample collection had to meet rigorous planetary protection requirements, whilst respecting stringent environmental and operability constraints. Many of those tools went through various redesign efforts, based on feedback from the very skillful and resourceful astronauts using them. In future planetary exploration missions, geological and geo-microbiological sampling will be a key to further development of our understanding of the evolution of the solar system, and to develop successful technologies for in-situ resource utilization and 3D printing. Designing and manufacturing technologies and ergonomics have developed since the 1960s, and so have chemical and biological hazard containment protocols, and analytical tools. Whilst it is important to solidly build on the lessons learned in the Apollo era, there is a serious opportunity for innovative design solutions. The European Space Agency (ESA) Neutral Buoyancy Facility (NBF) based in the European Astronaut Centre (EAC) in Cologne has a large experience in performing 0g simulations for ISS (International Space Station) Extra Vehicular Activities (EVA), and has recently engaged in simulations of Lunar surface operations, replicating reduced gravity and mobility constraints, in order to prepare future human and robotics surface operations. One of the main objectives within this area is prototyping and testing new geological sampling tools which could be used in future human surface Lunar missions. The tools are being developed in cooperation with the team of planetary geologists of the PANGAEA project (Planetary ANalogue Geological and Astrobiological Exercise for Astronauts), and field tested during the PANGAEA Space Analogue test campaigns.
This paper discusses the requirements and objectives to be met while developing such tools, the challenges
related to EVA suits and Lunar environment which impact the astronauts’ mobility and tools performance. It presents the status of development achieved during NBF and PANGAEA analogue field testing. The examples include a variety of sample collectors, containers, markers and the outcome of test performed in various mission scenarios
Il monaulos: strumenti musicali, flautiste e pointe oscena in Marziale, Apophoreta 63
No full textL'epigramma, apparentemente anodino, ha come oggetto le tibiae, il doppio flauto: ma la menzione del monaulos potrebbe nascondere una pointe oscena fino ad oggi non riconosciuta, con l'allusione alle pratiche, non interamente musicali, tradizionalmente attribuite dalle fonti antiche alle flautiste durante i banchetti.The epigram, apparently anodyne, has as its object the tibiae, the double flute: but the mention of the monaulos could hide an obscene pointe up to now unrecognized, with the allusion to the practices, not entirely musical, traditionally attributed by ancient sources to flutists during banquets
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