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A reverse engineering approach to measure the deformations of a sailing yacht
2016
In this work, a multidisciplinary experience, aimed to study the permanent deformations of the hull of a regatta sailing yacht is described. In particular, a procedure to compare two different surfaces of the hull of a small sailing yacht, designed and manufactured at the University of Palermo, has been developed. The first one represents the original CAD model while the second one has been obtained by means of a reverse engineering approach. The reverse engineering process was performed through an automatic close-range photogrammetry survey, that has allowed to obtain very accurate measures of the hull, and a 3D modelling step by the well-known 3D computer graphics software Rhinoceros. The…
Capturing gypsum rillenkarren morphometry by a 3D-photo reconstruction (3D-PR) technique
2020
Abstract Rillenkarren are small scale, straight, narrow solution channels that head at the crest of a bare rock slope and are extinguished downslope. In this paper the applicability of 3D-photo reconstruction technique of the rock surface is proposed for capturing the rillenkarren morphometry on gypsum. At first, the measurements are used to assess a relationship between the width/depth ratio and the depth of the rillenkarren. The exponent of this power relationship resulted different from the theoretical value - 0.5, confirming that the cross-section profiles of a rillenkarren can have a shape different from parabolic. The analysis developed for the cross-section area, the perimeter and th…
Computer vision-based approach for rite decryption in old societies
2015
International audience; This paper presents an approach to determine the spatial arrangement of bones of horses in an excavation site and perform the 3D reconstruction of the scene. The relative 3D positioning of the bones was computed exploiting the information in images acquired at different levels, and used to relocate provided 3D models of the bones. A novel semi-supervised approach was proposed to generate dense point clouds of the bones from sparse features. The point clouds were later matched with the given models using Iterative Closest Point (ICP).
Internal spring distribution for quasi brittle fracture via Symmetric Boundary Element Method
2009
Abstract In this paper the symmetric boundary element formulation is applied to the fracture mechanics problems for quasi brittle materials . The basic aim of the present work is the development and implementation of two discrete cohesive zone models using Symmetric Galerkin multi-zone Boundary Elements Method . The non-linearity at the process zone of the crack will be simulated through a discrete distribution of nodal springs whose generalized (or weighted) stiffnesses are obtainable by the cohesive forces and relative displacements modelling. This goal is reached coherently with the constitutive relation σ − Δ u that describes the interaction between mechanical and kinematical quantities…
Registration of arbitrary multi-view 3D acquisitions
2013
International audience; To register 3D meshes representing smooth surfaces we track the 3D digitization system using photogrammetric techniques and calibrations. We present an example by digitizing a 800 mm x 600 mm portion of a car door. To increase the tracking accuracy the 3D scanner is placed in a cubic frame of side 0.5 m covered with 78 targets. The target frame moves in a volume that is approximately 1100 mm x 850 mm x 900 mm, to digitize the area of interest. Using four cameras this target frame is tracked with of an accuracy of 0.03 mm spatially and 0.180 mrad angularly. A registration accuracy between 0.1 mm and 2 mm is reached. This method can be used for the registration of mesh…
A closed-form solution for natural frequencies of thin-walled cylinders with clamped edges
2016
Abstract This paper presents an approximate closed-form solution for the free-vibration problem of thin-walled clamped–clamped cylinders. The used indefinite equations of motion are classic. They derive from Reissner׳s version of Love׳s theory, properly modified with Donnell׳s assumptions, but an innovative approach has been used to find the equations of natural frequencies, based on a solving technique similar to Rayleigh׳s method, on the Hamilton׳s principle and on a proper constructions of the eigenfuctions. Thanks to the used approach, given the geometric and mechanical characteristics of the cylinder, the model provides the natural frequencies via a sequence of explicit algebraic equat…
Prevention of Violence against Children and Psychosocial Models of Intervention: Network Analysis of an Inter-Institutional Service
2014
This study describes an Italian service, the Inter-institutional Groups Operating against child Abuse and Maltreatment (GOIAM), which specializes in the treatment of child abuse. The GOIAM service is composed of 53 professionals divided into four different categories: social workers, psychologists, child neuropsychiatrists, and psychopedagogists. With the aim of detecting strengths and weaknesses of the operative model adopted by GOIAM, the whole service was analyzed through the application of social network analysis (SNA). The analysis revealed a low-density network, while the study of centrality yielded different distributions of power indicators (degree, closeness, and betweenness): pres…
Female-released sex pheromones mediating courtship behavior in Lysiphlebus testaceipes males
2013
Ethological aspects and chemical communication at close-range between the sexes of Lysiphlebus testaceipes Cresson (Hymenoptera: Braconidae) have been investigated through behavioral bioassays and chemical analysis. The attractiveness toward males of whole-body extracts of females and males in hexane and acetone was evaluated, adopting male fanning behavior as a key behavioral component. Also, the activity of polar and nonpolar fraction of female-body extract in hexane obtained using solid-phase extraction technique was investigated. In order to identify cuticular compounds, male and female whole-body extracts with hexane and acetone were analyzed by gas chromatography-mass spectrometry. Th…
Sub-Optimal Control Law for Active Magnetic Bearings Suspension
2012
This paper deals with the comparison of three types of sub-optimal control law for the stable levitation of a turbojet shaft, sustained by two radial active magnetic bearings (AMBs). Shaft is considered rigid for the procedure simplification. The utilized approach leads to development of different sub-optimal control laws to use in speed-varying simulations in the angular speed of the shaft. The first control matrix is obtained by explicit relationships of the parameters of the control law vs. speed, obtained using a curve-fitting procedure neglecting the speed-varying elements out of the main diagonal of each single block constituting the entire control matrix. The second control law is ob…
A novel Reverse Electrodialysis application to generate power from low-grade heat
2015
A novel idea for the conversion of low-temperature heat into electricity is based on the generation of electricity from salinity gradients using a Reverse Electrodialysis (RED) device in a closed-loop system. In this concept a limited amount of artificial saline solutions can be used as the working fluids in a closed-loop. The solutions exiting from the RED unit are then regenerated, in order to restore the original salinity gradient, by means of a separation step, which uses low-temperature heat (40-100°C) as its energy source. A theoretical analysis of potentials of this technology is illustrated in the present work.