Computer aided inspection procedures to support smart manufacturing of injection moulded components

This work presents Reverse Engineering and Computer Aided technologies to improve the inspection of injection moulded electro-mechanical parts. Through a strong integration and automation of these methods, tolerance analysis, acquisition tool-path optimization and data management are performed. The core of the procedure concerns the automation of the data measure originally developed through voxel-based segmentation. This paper discusses the overall framework and its integration made according to Smart Manufacturing requirements. The experimental set-up, now in operative conditions at ABB SACE, is composed of a laser scanner installed on a CMM machine able to measure components with lengths in the range of 5÷250 mm, (b) a tool path optimization procedure and (c) a data management both developed as CAD-based applications

Double solid twistor spaces: the case of arbitrary signature

In a recent paper (math.DG/0701278) we constructed a series of new Moishezon twistor spaces which is a kind of variant of the famous LeBrun twistor spaces. In this paper we explicitly give projective models of another series of Moishezon twistor spaces on nCP^2 for arbitrary n>2, which can be regarded as a generalization of the twistor spaces of a 'double solid type' on 3CP^2 studied by Kreussler, Kurke, Poon and the author. Similarly to the twistor spaces of 'double solid type' on 3CP^2, projective models of present twistor spaces have a natural structure of double covering of a CP^2-bundle over CP^1. We explicitly give a defining polynomial of the branch divisor of the double covering whose restriction to fibers are degree four. If n>3 these are new twistor spaces, to the best of the author's knowledge. We also compute the dimension of the moduli space of these twistor spaces. Differently from math.DG/0701278, the present investigation is based on analysis of pluri-(half-)anticanonical systems of the twistor spaces.Comment: 30 pages, 3 figures; v2: title changed (the original title was "Explicit construction of new Moishezon twistor spaces, II".

Leak-rate of seals: comparison of theory with experiment

Seals are extremely useful devices to prevent fluid leakage. We present experimental results for the leak-rate of rubber seals, and compare the results to a novel theory, which is based on percolation theory and a recently developed contact mechanics theory. We find good agreement between theory and experiment.Comment: 6 pages, 10 figure

The X-ray absorbing column density of a complete sample of bright Swift Gamma-Ray Bursts

A complete sample of bright Swift Gamma-ray Bursts (GRBs) has been recently selected by Salvaterra et al. (2011). The sample has a high level of completeness in redshift (91%). We derive here the intrinsic absorbing X-ray column densities of these GRBs making use of the Swift X-ray Telescope data. This distribution has a mean value of log(NH/cm-2)=21.7+-0.5. This value is consistent with the distribution of the column densities derived from the total sample of GRBs with redshift. We find a mild increase of the intrinsic column density with redshift. This can be interpreted as due to the contribution of intervening systems along the line of sight. Making use of the spectral index connecting optical and X-ray fluxes at 11 hr (beta_OX), we investigate the relation of the intrinsic column density and the GRB `darkness'. We find that there is a very tight correlation between dark GRBs and high X-ray column densities. This clearly indicates that the dark GRBs are formed in a metal-rich environment where dust must be present.Comment: MNRAS, 6 pages, 3 figures, 1 tabl

The Brera Multi-scale Wavelet (BMW) ROSAT HRI source catalog. II: application to the HRI and first results

The wavelet detection algorithm (WDA) described in the accompanying paper by Lazzati et al. is made suited for a fast and efficient analysis of images taken with the High Resolution Imager (HRI) instrument on board the ROSAT satellite. An extensive testing is carried out on the detection pipeline: HRI fields with different exposure times are simulated and analysed in the same fashion as the real data. Positions are recovered with few arcsecond errors, whereas fluxes are within a factor of two from their input values in more than 90% of the cases in the deepest images. At variance with the ``sliding-box'' detection algorithms, the WDA provides also a reliable description of the source extension, allowing for a complete search of e.g. supernova remnant or cluster of galaxies in the HRI fields. A completeness analysis on simulated fields shows that for the deepest exposures considered (~120 ks) a limiting flux of \~3x10^{-15} erg/cm2/s can be reached over the entire field of view. We test the algorithm on real HRI fields selected for their crowding and/or presence of extended or bright sources (e.g. cluster of galaxies and of stars, supernova remnants). We show that our algorithm compares favorably with other X-ray detection algorithms such as XIMAGE and EXSAS. A complete catalog will result from our analysis: it will consist of the Brera Multi-scale Wavelet Bright Source Catalog (BMW-BSC) with sources detected with a significance >4.5 sigma and of the Faint Source Catalog (BMW-FSC) with sources at >3.5 sigma. A conservative estimate based on the extragalactic log(N)-log(S) indicates that at least 16000 sources will be revealed in the complete analysis of the whole HRI dataset.Comment: 6 pages, 11 PostScript figures, 1 gif figure, ApJ in pres

Chandra observations of the millisecond X-ray pulsar IGR J00291+5934 in quiescence

In this Paper we report on our analysis of three Chandra observations of the accretion-powered millisecond X-ray pulsar IGR J00291+5934 obtained during the late stages of the 2004 outburst. We also report the serendipitous detection of the source in quiescence by ROSAT during MJD 48830-48839. The detected 0.3-10 keV source count rates varied significantly between the Chandra observations from (7.2+-1.2)x10^-3, (6.8+-0.9)x10^-3, and (1.4+-0.1)x10^-2 counts per second for the 1st, 2nd, and 3rd Chandra observation, on MJD 53371.88, 53383.99, and 53407.57, respectively. The count rate for the 3rd observation is 2.0+-0.4 times as high as that of the average of the first two observations. The unabsorbed 0.5-10 keV source flux for the best-fit power-law model to the source spectrum was (7.9+-2.5)x10^-14, (7.3+-2.0)x10^-14, and (1.17+-0.22)x10^-13 erg cm^-2 s^-1 for the 1st, 2nd, and 3rd Chandra observation, respectively. We find that this source flux is consistent with that found by ROSAT [~(5.4+-2.4)x10^-14 erg cm^-2 s^-1]. Under the assumption that the interstellar extinction, N_H, does not vary between the observations, we find that the blackbody temperature during the 2nd Chandra observation is significantly higher than that during the 1st and 3rd observation. Furthermore, the effective temperature of the neutron star derived from fitting an absorbed blackbody or neutron star atmosphere model to the data is rather high in comparison with many other neutron star soft X-ray transients in quiescence, even during the 1st and 3rd observation. If we assume that the source quiescent luminosity is similar to that measured for two other accretion powered millisecond pulsars in quiescence, the distance to IGR J00291+5934 is 2.6-3.6 kpc.Comment: 7 pages, 3 Figures, accepted for publication in MNRA

Optimisation of build orientation to achieve minimum environmental impact in Stereo-lithography

Abstract Additive Manufacturing includes a number of techniques that combine a specific equipment with certain materials but some common principles concerning the product design and aspects related to manufacturing optimisations can be identified. Amongst these principles, some process parameters are included that contribute to determining the environmental sustainability of engineering products and, in particular, that affect their Life Cycle Impact Assessment. This paper aims to provide a method to find out build orientation for the additive stereo-lithography process by minimising the environmental impact. More precisely, environmental indicators related to product design, materials and machines are included and combined in order to estimate the process time and the volume of needed supports. Besides, Genetic Algorithms have been used to find out the product orientation that optimises the manufacturing process in terms of quantity and volume of used material, thus minimizing its environmental impact. The proposed method has been implemented by a new software application that is presented in a nutshell

A 1 mm Scintillating Fibre Tracker Readout by a Multi-anode Photomultiplier

This note describes a prototype particle tracking detector constructed with 1 mm plastic scintillating fibres with a 64 channel Hamamatsu H8500 flat-panel multi-anode photomultiplier readout. Cosmic ray tracks from an array of 11 gas-filled drift tubes were matched to signals in the scintillating fibres in order to measure the resolution and efficiency of tracks reconstructed in the fibre-based tracker. A GEANT4 detector simulation was also developed to compare cosmic ray data with MC results and is discussed in the note. Using the parameters measured in this experimental setup, modified fibre tracker designs are suggested to improve resolution and efficiency in future prototypes to meet modern detector specifications.Comment: Laboratori Nazionali Di Frascati SIDS-Pubblicazioni LNF - 10 / 21(P) October 26, 201

Interfacial separation between elastic solids with randomly rough surfaces: comparison of experiment with theory

We study the average separation between an elastic solid and a hard solid with a nominal flat but randomly rough surface, as a function of the squeezing pressure. We present experimental results for a silicon rubber (PDMS) block with a flat surface squeezed against an asphalt road surface. The theory shows that an effective repulse pressure act between the surfaces of the form p proportional to exp(-u/u0), where u is the average separation between the surfaces and u0 a constant of order the root-mean-square roughness, in good agreement with the experimental results.Comment: 6 pages, 10 figure

There is a short gamma-ray burst prompt phase at the beginning of each long one

We compare the prompt intrinsic spectral properties of a sample of short Gamma--ray Burst (GRB) with the first 0.3 seconds (rest frame) of long GRBs observed by Fermi/GBM. We find that short GRBs and the first part of long GRBs lie on the same E_p--E_iso correlation, that is parallel to the relation for the time averaged spectra of long GRBs. Moreover, they are indistinguishable in the E_p--L_iso plane. This suggests that the emission mechanism is the same for short and for the beginning of long events, and both short and long GRBs are very similar phenomena, occurring on different timescales. If the central engine of a long GRB would stop after ~0.3 * (1+z) seconds the resulting event would be spectrally indistinguishable from a short GRB.Comment: 14 pages, 6 figures, MNRAS accepte