1,721,002 research outputs found
CONDITION ASSESSMENT OF RC BRIDGES. INTEGRATING MACHINE LEARNING, PHOTOGRAMMETRY AND BIM
Full text linkThe survey of building pathologies is focused on reading the state of conservation of the building, composed by the survey of constructive and decorative details, the masonry layering, the crack pattern, the degradation and the color recognition. The drawing of these representations is a time-consuming task, accomplished by manual work by skilled operators who often rely on in-situ analysis and on pictures. In this project three-dimensional an automated method for the condition survey of reinforced concrete spalling has been developed. To realize the automated image-based survey it has been exploited the Mask R-CNN neural network. The training phase has been executed over the original model, providing new examples of images with concrete cover detachments. At the same time, a photogrammetry process involved the images, in order to obtain a point cloud which acts as a reference to a Scan to BIM process. The BIM environment serves as a collector of information, as it owns the ontology to recreate entities and relationships. The information as extracted by neural network and photogrammetry serve to create the pictures which depict the concrete spalling in the BIM environment. A process of projecting information from the images to the BIM recreates the shapes of the pathology on the objects of the model, which becomes a decision support system for the built environment. A case study of a concrete beam bridge in northern Italy demonstrates the validity of the process
Form follows function in a hyperboloidical cooling Tower
No full textThe paper proposes a computational method to study and test the relationship between shape and performance for the built environment, sustaining the use of smart geometry to support design operation. A comprehensive study of the geometry and working principles of a hyperboloidical cooling tower is presented. A case study in Marghera (Venice), built in 1938 is explored. Thanks to knowledge in descriptive geometry and mathematics, scripting procedures, digital survey, Building Information Modeling (BIM) and Computational Fluid Dynamics (CFD) analysis, the paper demonstrates how hyperboloidical cooling towers represent a reference in shape optimization. Varying the fundamental parameter of the shape, reducing the throat diameter, the simulation shows the enhanced efficiency of the tower in terms of velocity and temperature. Consequently, the proposed method may be applied to other surfaces and structures
Asymmetries in the dust flux at Mercury
No full textThe planet Mercury has an extended and tenuous exosphere made up of atoms that are ejected from the surface by energetic processes, including hypervelocity micrometeoritic impacts, photon-stimulated desorption by UV radiation, and ion sputtering. Meteoroid impacts of particles smaller than 1 cm, which are important for replenishing the exosphere daily, are not well-studied. We present a systematic investigation of spatial asymmetries in the impactor rate of micrometeoroids over Mercury's surface as a function of planetary true anomaly (TAA). Since the orbit of Mercury is quite eccentric a seasonal variation of the impact rate is to be expected. We find that the source peaks near the planetary equator for most TAA. Contrary to previous assumptions, we find the source to be non-uniform in local time. Only certain regions of Mercury are exposed to dust as a result of the orbital elements of Mercury and of the Main Belt particles (inclination less than 20°). Our results offer important constraints on transport models used for interpreting measurements of this exosphere, but also inform studies of space weathering of Mercury's surface. <P /
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Estimate of the neutral atoms' contribution to the Mercury exosphere caused by a new flux of micrometeoroids
No full textContext. The planet Mercury has an extended and tenuous exosphere made up of atoms that are ejected from the surface by energetic processes, including hypervelocity micrometeoritic impacts, photon-stimulated desorption by UV radiation, and ion sputtering. The well known constituents of the Hermean exosphere are H, He, O, Na, K, and Ca but, from the new MESSENGER data from flybys, many others elements are expected, as for instance Mg.
Aims: Meteoroid impacts are an important source of neutral atoms in the exosphere of Mercury. We estimate the vapor and neutral atom production rates on Mercury caused by impacts of micrometeoroids of sizes between 5-100 μ m. The micrometeoritic flux is derived from a new statistical approach based on direct numerical integrations of dust particle trajectories under the action of the Poynting-Robertson drag and the gravitational attraction of all planets.
Methods: We included two different calibration sources for the meteoroid flux in our calculations of the vapor and neutral atoms and also considered both asteroidal and cometary sources for the dust. Three different surface compositions, which might be found on the planet, have been adopted, each with a different mass fraction of atoms in the regolith of the planet.
Results: We derive different values of neutral atom vapor production rates assuming different calibration sources for the meteoroid flux. The three simple mineralogical surface compositions show significant differences in the related production rates, and they are all greater than those reported in the previous papers assuming other dominant source mechanisms. Our neutral atom production rates are about one order of magnitude higher than the previous estimates. This implies that the impact vaporization has a much higher contribution than previously assumed
Variations on the Author
Full text link“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
Statistical analysis of micrometeoroids flux on Mercury
No full textContext: Meteoroid impacts are an important source of neutral atoms in the exosphere of Mercury. Impacting particles of size smaller than 1 cm have been proposed to be the major contribution to exospheric gases. However, our knowledge of the fluxes and impact velocities of different sizes is based on old extrapolations of similar quantities on Earth.
Aims: We compute by means of N-body numerical integrations the orbital evolution of a large number of dust particles supposedly produced in the Main Belt. They migrate inward under the effect of drag forces until they encounter a terrestrial planet or eventually fall into the Sun. From our numerical simulations, we compute the flux of particles hitting Mercury's surface and the corresponding distribution of impact velocities.
Methods: The orbital evolution of dust particles of different sizes is computed with a numerical code based on a physical model developed previously by Marzari & Vanzani (1994, A&A, 283, 275). It includes the effects of Poynting-Robertson drag, solar wind drag, and planetary perturbations. A precise calibration of the particle flux on Mercury has been performed by comparing our model predictions for dust infall on to Earth with observational data.
Results: We provide predictions of the flux to different size particles impacting Mercury and their collisional velocity distribution. We compare our results with previous estimates and we find that these collisional velocities are lower but that the fluxes are significantly higher
- …
