Sketching space

In this paper, we present a sketch modelling system which we call Stilton. The program resembles a desktop VRML browser, allowing a user to navigate a three-dimensional model in a perspective projection, or panoramic photographs, which the program maps onto the scene as a `floor' and `walls'. We place an imaginary two-dimensional drawing plane in front of the user, and any geometric information that user sketches onto this plane may be reconstructed to form solid objects through an optimization process. We show how the system can be used to reconstruct geometry from panoramic images, or to add new objects to an existing model. While panoramic imaging can greatly assist with some aspects of site familiarization and qualitative assessment of a site, without the addition of some foreground geometry they offer only limited utility in a design context. Therefore, we suggest that the system may be of use in `just-in-time' CAD recovery of complex environments, such as shop floors, or construction sites, by recovering objects through sketched overlays, where other methods such as automatic line-retrieval may be impossible. The result of using the system in this manner is the `sketching of space' - sketching out a volume around the user - and once the geometry has been recovered, the designer is free to quickly sketch design ideas into the newly constructed context, or analyze the space around them. Although end-user trials have not, as yet, been undertaken we believe that this implementation may afford a user-interface that is both accessible and robust, and that the rapid growth of pen-computing devices will further stimulate activity in this area

The COMPASS Experiment at CERN

The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given.Comment: 84 papes, 74 figure

The High-Acceptance Dielectron Spectrometer HADES

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18 to 85 degree, a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system

On Computer Stereo Vision with Wire Frame Models

Coordinated Science Laboratory changed its name from Control Systems LaboratoryShould have been numbered UILU-ENG 77-2252, and that number may have been distributed on some copies.Joint Services Electronics Program / DAAB-07-72-C-0259Ope

Imaging applications from a laser wakefield accelerator

Laser-plasma wakefield acceleration (LWFA) is a promising technology that is attracting the attention of the scientific community. It is a new acceleration concept where electrons can be accelerated to very high energy (~150 MeV) in a very short distance (mm scale). Electrons "surf" plasma waves excited by the passage of a high power laser (~1018 Wcm-2) through plasma. Electrons in the LWFA can undergo transverse oscillation and emit synchrotron-like X-ray radiation, commonly known as betatron radiation, in a narrow cone along the laser propagation axis. The properties of both the electrons and the X-rays produced by the LWFA make them excellent candidates for a wide range of applications. In this thesis, both betatron X-ray and bremsstrahlung sources from the ALPHA-X laboratory are used to carry out both conventional imaging and X-ray phase-contrast imaging experiments to explore the feasibility of real-world applications. The characterisation of the betatron X-ray radiation produced by the LWFA in the ALPHA-X laboratory is presented. In the last Chapter, a brief discussion of the potential of LWFA technology for clinical applications is presented.Laser-plasma wakefield acceleration (LWFA) is a promising technology that is attracting the attention of the scientific community. It is a new acceleration concept where electrons can be accelerated to very high energy (~150 MeV) in a very short distance (mm scale). Electrons "surf" plasma waves excited by the passage of a high power laser (~1018 Wcm-2) through plasma. Electrons in the LWFA can undergo transverse oscillation and emit synchrotron-like X-ray radiation, commonly known as betatron radiation, in a narrow cone along the laser propagation axis. The properties of both the electrons and the X-rays produced by the LWFA make them excellent candidates for a wide range of applications. In this thesis, both betatron X-ray and bremsstrahlung sources from the ALPHA-X laboratory are used to carry out both conventional imaging and X-ray phase-contrast imaging experiments to explore the feasibility of real-world applications. The characterisation of the betatron X-ray radiation produced by the LWFA in the ALPHA-X laboratory is presented. In the last Chapter, a brief discussion of the potential of LWFA technology for clinical applications is presented

Application of X-ray Grating Interferometry to Polymer/Flame Retardant Blends in Additive Manufacturing

X-ray grating interferometry is a nondestructive tool for visualizing the internal structures of samples. Image contrast can be generated from the absorption of X-rays, the change in phase of the beam and small-angle X-ray scattering (dark-field). The attenuation and differential phase data obtained complement each other to give the internal composition of a material and large-scale structural information. The dark-field signal reveals sub-pixel structural detail usually invisible to the attenuation and phase probe, with the potential to highlight size distribution detail in a fashion faster than conventional small-angle scattering techniques. This work applies X-ray grating interferometry to the study of additively manufactured polymeric objects. Additively manufactured bunnies made from single material—acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA)—were studied by grating-based X-ray interferometric two-dimensional imaging and tomography. The dark-field images detected poor adhesion in the plane perpendicular to the build plate. Curvature analysis of the sample perimeter revealed a slightly higher propensity to errors in regions of higher curvature. Incorporation of flame-retardant molecules to near-surface regions of otherwise flammable objects through the fused deposition modeling additive manufacturing technique was also explored. The anticipated advantage was efficient use of the flame retardants while keeping them away from the surface for safety. To determine heat propagation effects, two-dimensional grating-based interferometry imaging at LSU CAMD was used to study heated samples. The focus was on the dark-field signals to highlight voids and gaps arising from layer delamination or gasification of chemical components. The resulting differential phase and dark-field x images were tainted by fringes attributed to inaccuracies in the grating-step position. Attempts to correct this will be presented. Interferometric tomography was also carried out on the heated samples using the W. M. Keck interferometric system at LSU. Grating-based interferometry was also used to probe scattering structure sizes of heated samples. Comparison of the data with the conventional small-angle x-ray scattering technique, SAXS, is being pursued. The results obtained so far from the above-mentioned experimental works are presented in this document