Real-time visualization of the Forum of Pompei

This paper describes the process to create a single realistic 3D digital model of a wide archeological site, to be used for virtual reality application. The incoming data are texturized models coming from an accurate 3D survey of the entire area: the ground, buildings and finds were acquired with active and passive sensors and converted into polygonal models. Afterwards, the models were assembled in a single virtual scene that reproduces the Forum as it would actually appear to a tourist. The scene can be visualized by means of stereoscopic devices to increase the feeling of immersion. During the data conversion process we had to face three main kind of problems: the database optimization, the correction of digital objects position into the scene and the realism of the displayed model. The real time rendered model of the Forum was displayed on a large screen with stereoscopic technology, as a support for archeological studies

PRODUCT DESIGN SOFTWARE DRIVEN VS IDEAS DRIVEN: HOW CAID LEARNING METHOD CAN CHANGE THE DESIGN APPROACH?

Nowadays Product Design is strictly linked to Computer Aided Industrial Design (CAID) learning and the approaches and the methods used inside University can heavily influence the Design results. Starting from the contributions of Shön, Oxman and Cunliffe that outline the boundaries of design knowledge, the paper will underline the need to redefine the educational tasks of designer instruction, through the shift from an artefact production orientation to a cognitive-constructive approach. Considering the case study of the Faculty of Design at the Politecnico di Milano, where Computer Graphics studios are an important step of the curriculum, we'll try to show how an ideas driven approach can help students to enhance their creativity through a 3D software. The second part of the paper, defining the two possible approach to digital modelling education, will discuss the different ways in which technologies support Industrial Design learning. The result of the overlapping of this two levels of analysis will represent a new model which attempt to support the community actions in design education though a metacognitive approach. The original contribution relies in the identification of a learning model consonant with the idea of a flexible environment as Industrial Design learning requires. The metacognitive approach may open new ways for CAID education, centered on the learner and allowing an active, creative construction of his knowledge through a tool independent method

Research intelligence : bulletin of the British Educational Research Association

Thin detectors have been proposed to investigate the possibility to limit the full depletion voltage and the leakage current of heavily irradiated silicon devices. In this work we compare typical silicon detectors (p–n junctions over a $300 \mu \rm{m }$ thick substrate) with thinned devices ($50–100 \mu \rm{m}$ of thickness). In order to investigate the performances of these structures, simulations have been carried out using the ISE-TCAD DESSIS device simulator. The so called three-level model has been used to investigate the effects of the radiation fluence on charge collection efficiency of thin and thick silicon structures. For each thickness, we simulate the hit of a minimum ionizing particle and then we calculate the current at the diode's electrode. We consider a $7 \times 10^{11} \rm{cm}^{−3}$ n-doped substrate (a high resistivity substrate); all the structures are composed of a $40 \mu \rm{m}$ diode contact and a $15 \mu \rm{m}$ distant guard ring. The simulated collected charge of the $300 \mu \rm{m}$ diode is in agreement with the experimental results; the simulation of thinner structures ($50–100 \mu \rm{m}$) shows a saturation of the number of e–h pairs collected at the diode's electrodes. These results suggest that thin detectors may have a better performance at higher fluences than thick ones. They are maximizing the collected charge at lower depletion voltage

A very high spatial resolution small animal PET scanner based on high granularity silicon photomultipliers

Small animal Positron Emission Tomography (PET) studies require high-resolution detectors. Traditionally, inorganic scintillators coupled to Position Sensitive PMTs are used. Such PSPMTs are somewhat costly, operate at high voltage and have a relatively low packing fraction. However, the advantage, compared to standard solid state photodetectors, is their high signal-to-noise ratio. The Silicon Photomultiplier (SiPM) is a novel silicon diode detector that shows great promise as a photodetector for scintillators and hence for application in Nuclear Medicine imaging. The SiPM is a densely packed matrix of small, Geiger-mode avalanche photodiode (GAPD) cells (typically ~ 40 micron x 40 micron), with individual quenching resistors. The SiPMs developed within this project will have of the order of 1000 microcells and a quantum efficiency (QE) maximized in the wavelength range 420 - 470 nm. The Geiger-mode operation of each cell produces a large gain (of the order of 10^6) at low bias voltage (about 50 V). All the cell outputs are then connected in parallel to have the summed signal. This microcell MRS (Metal-Resistor-Semiconductor) structure of the SiPM gives an output proportional to the number of incident photons for moderate photon flux. The characterization of individual SiPMs showed their suitability for radiation detection, but their small dimensions are not adequate for the development of big active area detector. Hence, the goal of this project is to realize a large area 2D array of SiPMS on the same silicon substrate. As a first step, up to 1.2x1.2 cm^2 matrices of 8 x 8 SiPMs will be developed with read-out pads on the front side located at the edge of the die. The matrices will be composed of 1x1 mm2 active area SiPM pixels, on a 1.5 mm pitch. Then, 2 x 4 matrices will be arranged to form a 2.5 x 5.0 cm^2 total surface with minimum dead area. A dedicated readout system consisting of an integrated CMOS front-end electronics and a data acquisition system based on Field Programmable Gate Array (FPGA), will be also designed and developed. Such a compact silicon detector, with a performance similar to a PMT, is obviously well disposed to being developed into a close-packed array in order to have a position-sensitive detection surface. Current systems tend to rely on finely pixilated matrices of scintillators (1.5x1.5 - 2x2 mm^2 pixels) to maximize the spatial resolution. In order to achieve sub-millimeter resolution, the pixels should be made increasingly small, whilst retaining a reasonable length to maintain efficiency. This cross-section reduction has two important consequences: the light yield is decreased and the cost of the matrix production is greatly increased. Therefore, a method that eliminates the use of pixels and returns to a continuous crystal would be desirable. Moreover, the continuous crystal approach would make viable the use in PET of advanced scintillators like LuI3, that can not be made in form of pixels. With these considerations in mind, we propose a novel, miniature, high-resolution camera for a small-animal PET imaging system that is based on a combination of SiPM with a continuous scintillation crystal. The design is based upon the classic Anger camera principle; a detector module consists of a continuous slab of scintillator crystal (i.e. LYSO), viewed by 8 matrices of SiPM. The interaction position is measured by calculating the center of mass of the measured signals. Two of such SiPM gamma cameras will be mounted on a rotating gantry, being the opposite heads in time coincidence to implement the PET concept. The system as a whole is expected to provide a potentially sub-millimeter spatial resolution after image reconstruction. The spatial resolution achievable with the proposed system will be close to the intrinsic limit of the PET technique and it will represent a significant step forward with respect to the state of art of the present small animal PET scanners. The SiPM base..

Numerical simulation of radiation damage effects in p-type and n-type FZ silicon detectors

In the framework of the CERN-RD50 Collaboration, the adoption of p-type substrates has been proposed as a suitable mean to improve the radiation hardness of silicon detectors up to fluencies of $1 \times 10^{16} \rm{n}/cm^2$. In this work two numerical simulation models will be presented for p-type and n-type silicon detectors, respectively. A comprehensive analysis of the variation of the effective doping concentration ($N_{\rm{eff}}$), the leakage current density and the charge collection efficiency as a function of the fluence has been performed using the Synopsys T-CAD device simulator. The simulated electrical characteristics of irradiated detectors have been compared with experimental measurements extracted from the literature, showing a very good agreement. The predicted behaviour of p-type silicon detectors after irradiation up to $10^{16} \rm{n}/cm^2$ shows better results in terms of charge collection efficiency and full depletion voltage, with respect to n-type material, while comparable behaviour has been observed in terms of leakage current density