86,763 research outputs found
Stillbirth and mortality during the lst year of life in various Italian regions : analysis of temporal trends, 1955-1979
No full textPreliminary design of a mechanism for flapping flight - Durability analysis and vibration modes
No full textThe object of the paper is the kinematic and structural design of a flapping wing UAV, in order to develop an Unmanned Aerial Vehicle, a drone capable of executing reconnaissance and videosurveillance missions. To define the characteristic dimensions of the vehicle a biological study was initially carried out, analyzing, for example, the weight-wingspan ratio for the correct kinematics of the flight. On the other hand, several mechanisms apt to reproduce flapping flight were analyzed, searching for the best solution in terms of wings' articulation. Then, an optimization of the length of the different parts of the mechanism was needed to reproduce the kinematic law, provided by CFD (computational fluid dynamics) simulations. The results of the optimization were the starting point for the design of the mechanism parts and for the diagnostic aspects. The stress resistance of the mechanical parts and fatigue life were verified in a FEM environment developing several simulations of the working conditions of the wing mechanism
Preliminary design of a Small-Sized Flapping UAV. I. Kinematic and Structural Aspects
No full textThe aim of the article is the kinematic and geometric design of a flapping wing UAV, in order to develop an Unmanned Aerial Vehicle, capable of executing reconnaissance and video-surveillance missions. To define the characteristic dimensions of the vehicle a biological study was initially carried out, analyzing, for example, the weight-wingspan ratio for the correct kinematics of the flight. On the other hand, several mechanisms capable to reproduce flapping flight were analyzed, searching for the best solution in terms of wings’ articulation. Then, an optimization of the length of the different parts of the mechanism was needed to reproduce the kinematic law, provided by CFD (computational fluid dynamics) simulations. The results of the optimization were the basis on which the design of the mechanism parts will be produced. In the related article the flight stability and the effects of flapping wing on the dynamics of flight are studied
Designing with Nature Climate-Resilient Cities: A Lesson from Copenhagen
No full textClimate change is accelerating more than expected, and many cities are still unprepared for this transition.
The need to revise the approach to the design of public space points the attention toward the enhancement
of design figures that can convey different knowledge for adaptation to climate change. It emerges how the
landscape architect through nature-based solutions can be the figure able to regenerate the urban fabric of
the city. The case study of this research is the city of Copenhagen, which has become the stage of the most
innovative experiments to create climate-resilient urban spaces. It emerges how a multidisciplinary and
site-specific approach can be the ingredients of a transition that occurs only with innovative project
management in which municipalities, private stakeholders, and citizens work together. The NBS, therefore
the ecosystem approach to the project, proves to be able to respond to environmental, social, and economic
challenges
Toward the improvement of 3D-printed vessels’ anatomical models for robotic surgery training
No full textMulti-Detector Computed Tomography is nowadays the gold standard for the pre-operative imaging for several surgical interventions, thanks to its excellent morphological definition. As for vascular structures, only the blood flowing inside vessels can be highlighted, while vessels’ wall remains mostly invisible. Image segmentation and three-dimensional-printing technology can be used to create physical replica of patient-specific anatomy, to be used for the training of novice surgeons in robotic surgery. To this aim, it is fundamental that the model correctly resembles the morphological properties of the structure of interest, especially concerning vessels on which crucial operations are performed during the intervention. To reach the goal, vessels’ actual size must be restored, including information on their wall. Starting from the correlation between vessels’ lumen diameter and their wall thickness, we developed a semi-automatic approach to compute the local vessels’ wall, bringing the vascular structures as close as possible to their actual size. The optimized virtual models are suitable for manufacturing by means of three-dimensional-printing technology to build patient-specific phantoms for the surgical simulation of robotic abdominal interventions. The proposed approach can effectively lead to the generation of vascular models of optimized thickness wall. The feasibility of the approach is also tested on a selection of clinical cases in abdominal surgery, on which the robotic surgery is performed on the three-dimensional-printed replica before the actual intervention
Spin wave dispersion in bilayer hybrid systems composed of artificial spin ice and thin film: Brillouin light scattering measurements and simulations
No full textWe performed a joint experimental and theoretical study of the spin-wave dispersion in
hybrid magnonic structures made of a NiFe artificial spin ice (ASI) layer deposited on top of a
continuous (unpatterned) NiFe thin film. The ASI lattice consists of 20 nm thick ellipses with
lateral dimensions of 260x90 nm2 either in contact with the 20 nm thick NiFe film, or separated
from the NiFe film by a 10 nm thick nonmagnetic spacer. The ASI is defined using electron
beam lithography, electron beam deposition, and lift off [1]. We performed Brillouin light
scattering measurements as a function of the light incidence angle (symbols in fig. 1 right
panel), i.e., by varying the probed spin-wave wavevector, and hence the experimental
dispersions omega(kappa) are obtained. Depending on the separation between the underlayer and the ASI nanostructure, we observe a rich mode spectrum that exhibits characteristics both spin waves in the extended film (Damon-Eshbach mode) and higher-order ASI modes. Among the latter, we experimentally reveal a weakly dispersive magnon mode. By means of mumax3
simulations [2], and by performing the space-resolved time Fourier transform, we calculated
the spin-wave dispersions omega(kappa) (which we compared to the measured ones), the spatial profile of the spin mode cell functions, and the power spectra (k=0). We found a dynamic interplay between ASI and the film underneath. In particular, the ASI is forcing a nonuniform
magnetization in the film layer [3], impressing its periodicity, and the film is found to increase
the intensities of the ASI resonances and to alter the mode bandwidth. We finally draw
important considerations of having a tuneable system which possesses different spin-wave
modes that are either propagating or are stationary, as well as localized or extended
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Preliminary design of a small-sized flapping UAV: II. Kinematic and structural aspects
No full textThe design of the actuating mechanism of a flapping wing unmanned aerial-vehicle is addressed. Several configurations able to reproduce the desired flapping wing kinematics are analyzed and an optimization study is conducted to select the best configuration. The optimization results are used as the starting point for the design of the different structural components of the flapping mechanism. During the mechanism design stage, the linkages are optimized to match the desired wing’s motion during a flapping cycle. A structural and durability analysis is then conducted to verify that the mechanism and its components are able to withstand the aerodynamic and inertial loads
Dynamic coupling and spin-wave dispersions in a magnetic hybrid system made of an artificial spin-ice structure and an extended NiFe underlayer
No full textWe present a combined experimental and numerical study of the spin-wave dispersion in a NiFe artificial spin-ice (ASI) system consisting of an array of stadium-shaped nanoislands deposited on the top of a continuous NiFe film with non-magnetic spacer layers of varying thickness. The spin-wave dispersion, measured by wavevector resolved Brillouin light scattering spectroscopy in the Damon–Eshbach configuration, consists of a rich number of modes, with either stationary or propagating character. We find that the lowest frequency mode displays a bandwidth of ∼0.5 GHz, which is independent of the presence of the film underneath. On the contrary, the Brillouin light scattering intensity of some of the detected modes strongly depends on the presence of the extended thin-film underlayer. Micromagnetic simulations unveil the details of the dynamic coupling between the ASI lattice and film underlayer. Interestingly, the ASI lattice facilitates dynamics of the film either specific wavelengths or intensity modulation peculiar to the modes of the ASI elements imprinted in the film. Our results demonstrate that propagating spin waves can be modulated at the nanometer length scale by harnessing the dynamic mode coupling in the vertical, i.e., the out-of-plane direction of suitably designed magnonic structures
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