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Stochastic optimization of linear sparse arrays for pulse-echo imaging systems
No full textWe apply the simulated annealing optimization algorithm
to linear arrays to be used in ultrasound imaging
systems under wide-band operation. We address
the optimization problem of both dense and sparse
wide-band arrays. In the first case, we compare the
optimized beam pattern with that obtained with a
classical shading function. In the latter case, we consider either the
optimization of the layout (element
positions and weights) or the optimization of only
element positions of sparse arrays which generate a
beam pattern with minimum side-lobe level. We show
that an about -7-dB further reduction of the side-lobe
level can be achieved with a wide-band sparse
array optimization, with respect to a narrow-band
optimization. The performances of the optimized arrays are
verified on some phantom images.5-
Prototipo di bollettino mensile di bilancio idrologico in atmosfera nella regione mediterranea: analisi degli output del LAM e sviluppo dei codici per il calcolo dei bilanci idrologici atmosferici nei due periodi prototipali
Get PDFLa presente relazione riassume l'attività svolta nell'ambito della seconda fase della convenzione CRS4-DSTNPC “prototipo del bollettino mensile di bilancio idrologico in atmosfera". In particolare, vengono analizzati gli output ottenuti con il BOLAM durante la prima fase del progetto dando particolare enfasi agli aspetti legati al bilancio idrologico. Si discutono poi le procedure per il calcolo del bilancio idrologico in atmosfera utilizzando i campi di umidità specifica, precipitazione, evapotraspirazione e vento prodotti dal BOLAM e le metodologie da utilizzare per stimare nel modo migliore tale bilancio. Infine vengono illustrati i risultati ottenuti relativamente ai due periodi prototipali oggetto del presente studio
Variable source areas, soil moisture and active microwave observations at Zwalmbeek and Coët-Dan
Get PDFThis chapter focuses on recent research to identify variable source areas from surface soil moisture dynamics observed at the catchment scale by means of active microwave images from satellites. It is hypothesized that variable source areas can be mapped if we can quantify the temporal variability of the surface soil moisture content. It is difficult to determine the soil moisture content from single synthetic aperture radar images because soil moisture, surface roughness, topography and vegetation all have a great effect on radar backscatter. However, seasonal soil moisture fluctuations can be studied by using multitemporal radar images. Two multitemporal image processing techniques are presented to map variable source areas. The first method computes the temporal standard deviation of radar backscatter. This leads to the definition of the so-called saturation potential index, which compares well with observed saturated areas. The second method makes use of a principal component analysis to separate the dominant effects, like topography, land use and soil moisture, on total radar backscatter. Again this leads to reliable mapping of the spatial patterns of variable source areas. Two humid catchments, the Zwalmbeek in Belgium and the Coët-Dan in France, are used in this study
Recenti sviluppi GIS-web
Get PDFQuesta breve relazione propone alcuni spunti legati a quelli che sono gli
sviluppi più recenti nel campo del web mapping e della distribuzione di dati e
servizi via web o location-based services
A beam window target design with independent cooling for the EADF
Get PDFThis report summarizes the study and the design of the window type target for the
Energy Amplifier Demonstration Facility (EADF) [1]. The behaviour of the system in
different condition has been analysed though extensive CFD simulations performed
with the Star-CD commercial code [2].
The target represents one of the main technological problems related not only to the
design of the EADF, but to all High Power Spallation Sources (HPSS) currently under
study or in construction world-wide [4],[5].
Different configurations of the spallation EADF target are possible. Advantages and
disadvantages of the different options are discussed elsewhere [6] and they are
studied and analysed separately.
The target device studied in this report is a window type target, cooled by diathermic
oil in an independent loop. This target configuration is completely independent from
the core operating conditions and gives advantages in terms of flexibility in the
operation.
The result of this report is a set of design data and constraints to take into account
while engineering the spallation target
TOM: totally ordered mesh. A multiresolution data structure for time-critical graphics applications
Get PDFTridimensional interactive applications are confronted to situations where very large databases have to be animated, transmitted and displayed in very short bounded times. As it is generally impossible to handle the complete graphics description while meeting timing constraint, techniques enabling the extraction and manipulation of a significant part of the geometric database have been the focus of many research works in the field of computer graphics. Multiresolution representations of 3D models provide access to 3D objects at arbitrary resolutions while minimizing appearance degradation. Several kinds of data structures have been recently proposed for dealing with polygonal or parametric representations, but where not generally optimized for time-critical applications. We describe the TOM (Totally Ordered Mesh), a multiresolution triangle mesh structure tailored to the support of time-critical adaptive rendering. The structure grants high speed access to the continuous levels of detail of a mesh and allows very fast traversal of the list of triangles at arbitrary resolution so that bottlenecks in the graphic pipeline are avoided. Moreover, and without specific compression, the memory footprint of the TOM is small (about 108% of the single resolution object in face-vertex form) so that large scenes can be effectively handled. The TOM structure also supports storage of per vertex (or per corner of triangle) attributes such as colors, normals, texture coordinates or dynamic properties. Implementation details are presented along with the results of tests for memory needs, approximation quality, timing and efficacy
The SITAI project for the industrial areas of Sardinia: from a GIS database to a web-based site selection tool
Get PDFSITAI, Sistema Informativo Territoriale delle Aree Industriali della Sardegna (Geographic Information System for the Industrial Areas of Sardinia) is a product which is being developed in Sardinia by Osservatorio Industriale della Sardegna with the support of CRS4. The system has been conceived with three main aims. The first is to conduct economic studies related to site and resource optimization, through analysis of the firms,
facilities and infrastructure available in the Sardinian region and within each industrial area. The second is to promote Sardinia's industrial parks and to offer a site selection tool to potential investors, providing an integrated and harmonized view of the various industrial sites by means of a web-based interface to the data.
Finally, the system is being proposed as a common starting point for the implementation of facility management applications within the industrial parks. The core of the SITAI database is represented by a set of geographic layers for each of the 23 currently active parks, linked to detailed information on the available infrastructure, the existing utilities, the characteristics of the firms located in the area, and on the costs for siting a new activity. This information is complemented by a regional-level view of the transportation networks and administrative boundaries, allowing to perform complex analyses on the available information. The project is now in its fourth year of life. After a prototype phase conducted in 1996-1997 on a single industrial park, the complete "desktop" version of the system has been implemented in 1998, and is currently being used by Osservatorio Industriale to provide, jointly with its other databases concerning the regional economy, a support to local policy makers, private companies, and consultants. During the past year, in addition to the development of the web-based interface to the database (released in May 2000) and the update of the database, one of the key issues faced has concerned the technology transfer towards the various actors involved in the project, either as data providers (i.e. the managers and the technicians of the parks), or as users (i.e.
Osservatorio Industriale in their role as socio-economic analysts), in terms both of awareness raising on the potential of GIS-enabled applications and of training on the use of the system. The presentation will describe the features of the system, discuss some of the issues which have emerged as critical during the project, and present
its possible further developments. In particular, we will focus on the site selection functionality offered by the web-based interface
Self-propagating high-temperature reactions: remarks and recent results
Get PDFSolid-solid and gas-solid self-propagating high temperature reactions are exploited for interesting and relatively new technological applications based on the so called Self-propagating High-temperature Synthesis (SHS) technique
This paper reviews the recent results obtained, also in the framework of national and international
collaborations, by Cao and coworkers in the field of self-propagating high-temperature reactions with particular emphasis on SHS fundamentals and applications. In particular, the research activity conducted so far can be divided into three main topics: Macrokinetics studies on SHS using structural statics as well as dynamics approaches; Modeling studies on SHS, with the aim of developing analytical expressions of combustion front velocity and simulating experimental techniques applied for macrokinetics investigations; Technological applications related to the synthesis of centrifugal coatings and environmental protection.
The activities outlined above will be described in this review paper in separate sections as discussed
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Use of propellants different from hydrogen for the space propulsion
No full textThe possibility of hydrogen heating by the fission fragments has been widely
discussed in the work “Fission fragment heating for space propulsion” [1], in
which an innovative method, developed by C. Rubbia, is presented. In that
work the criterions in the choice of the propellant for a spacecraft have been
well discussed; for instance, a high enthalpy at an acceptable temperature is an
important requirement in order to obtain a high exhaust speed, as shown in
the St. Vennant and Wenzel formula