Showing papers by "Polytechnic University of Milan published in 1985"

Elite: A Digital Dedicated Hardware System for Movement Analysis Via Real-Time TV Signal Processing

Abstract: The system illustrated in this paper has been designed and developed particularly for automatic and reliable analysis of body movement in various conditions and environments. It is based on real-time processing of the TV images to recognize multiple passive markers and compute their coordinates. This performance is achieved by using a special algorithm allowing the recognition of markers only if their shape matches a predetermined "mask." The main feature of the system is a two-level processing architecture, the first of which includes a dedicated peripheral fast processor for shape recognition (FPSR), designed and implemented by using fast VLSI chips. The second level consists of a general purpose computer and provides the overall system with high flexibility. The main characteristics are: no restriction on the number of markers, resolution of one part in 2500, and a 50 Hz sampling rate independent of the number of markers detected. The prototype has been fully developed, and preliminary results obtained from the analysis of several movements are illustrated.

On the estimation of asymptotic stability regions: State of the art and new proposals

Abstract: This paper deals with the problem of the estimation of regions of asymptotic stability for continuous, autonomous, nonlinear systems. The first part of the work provides a comprehensive survey of the existing methods and of their applications in engineering fields. In the second part certain topological considerations are first developed and the "trajectory reversing method" is then presented together with a theorem on which it is based. In the final part, several examples of application are reported, showing the efficiency of the proposed technique for low-order (second and third) systems.

Geometric modeling of solid objects by using a face adjacency graph representation

Abstract: A relational graph structure based on a boundary representation of solid objects is described. In this structure, called face adjacency graph, nodes represent object faces, whereas edges and vertices are encoded into arcs and hyperarcs. Based on the face adjacency graph, we define a set of primitive face-oriented Euler operators, and a set of macrooperators for face manipulation, which allow a compact definition and an efficient updating of solid objects. We briefly describe a hierarchical graph structure based on the face adjacency graph, which provides a representation of an object at different levels of detail. Thus it is consistent with the stepwise refinement process through which the object description is produced.

Semiconductor drift chambers for position and energy measurements

Abstract: Semiconductor drift chambers have been recently suggested and feasibility tests performed. This paper presents the first operative silicon drift detectors for position and energy measurements. Design criteria and experimental results in the laboratory and on an accelerator beam are reported.

Translating SQL Into Relational Algebra: Optimization, Semantics, and Equivalence of SQL Queries

Abstract: In this paper, we present a translator from a relevant subset of SQL into relational algebra The translation is syntax-directed, with translation rules associated with grammar productions; each production corresponds to a particular type of SQL subquery

Reduction techniques for infinite-dimensional Hamiltonian systems: some ideas and applications

Abstract: In the language of tensor analysis on differentiable manifolds, we present a reduction method of integrability structures, and apply it to recover some well-known hierarchies of integrable nonlinear evolution equations.

Discrete-time linear periodic systems: gramian and modal criteria for reachability and controllability†

Abstract: This paper deals with the reachability and controllability of periodic discrete-time systems. First, we supply two necessary and sufficient complete reachability conditions, which apply to reversible and non-reversible systems, respectively. Then, a necessary and sufficient complete controllability condition is provided. This condition, as well as the complete reachability criteria, is given in terms of the reachability gramian matrix. Equivalent modal criteria for reachability and controllability are established in the second part of the paper.

Carrier diffusion effects in the time-response of a fast photodiode

Abstract: A single-photon avalanche diode (SPAD), in which single carrier events can be measured, is used as a probe for accurate measurements of time-dependent carrier diffusion effects in silicon. Basic criteria are discussed for a Monte Carlo simulation program for computing such diffusion effects in various device geometries. A simple program, suitable also for small minicomputers ( e.g. PDP 11 23 ) has been developed. Its accuracy has been checked by comparison with the experimental data obtained from the available SPAD devices, with pulsed illumination at various wavelengths from laser sources. Results are discussed showing that the simulation program can be reliably employed as a tool for analysis and design of new devices.

Silicon strip detectors with capacitive charge division

Abstract: Measurements of the behaviour of various high-resolution silicon strip detectors with capacitive charge division have been made in a high-energy particle beam. The results are compared with an electrostatic model which calculates the charges deposited on the strips after the passage of a minimum ionizing particle. Good agreement is found and the model is used to propose a method of improving the charge-division properties of such detectors.

PAPIA: Pyramidal architecture for parallel image analysis

Abstract: In 1981 a national research program for the design, simulation and construction of a multiprocessor image processing system was started. After a first phase devoted to the comparison of suggested and existing systems and to the definition of a set of benchmarks and to the evaluation of the performances of the major classes of machines, a new system has been defined. The structure of the new system is based on a pyramid of processors and many applications in which this machine may be exploited are highlighted. The multiprocessor architecture has been fully designed and the chip will be built by an Italian silicon. foundry, the SGS company, within the framework of the multichip national project.

Nonlinear phenomena in click- and tone-burst-evoked otoacoustic emissions from human ears.

Abstract: Otoacoustic emissions have been recorded from normally hearing subjects in response to clicks and 1-kHz tone bursts. Input-output relationships for response magnitudes and wave delays are presented. For the response magnitudes, two main effects are seen: (i) nonlinearities are maximal at moderate to high intensity levels (saturation), while deviations from linearity are minimal at the lowest levels (around the psychoacoustic threshold); (ii) the nonlinear behaviour is different at different time intervals (after stimulation): deviations from linearity are maximal for the latest parts of the response. Level- and time-dependent phenomena are also observed in the delay of identifiable response waves.Phenomenes non lineaires dans les emissions otoacoustiques evoquees par clic et bouffee tonale dans des oreilles humainesDes emissions otoacoustiques ont ete enregistrees chez des sujets normo-entendants en reponse a des clics et des bouffees tonales a 1 kHz. Les relations entree-sortie pour l'amplitude des repon...

Multiple-Valued Logic Trees: Meaning and Prime Implicants

Abstract: Multiple-valued logic (MVL) allows assessment of the reliability of systems where the inherent complexity leads to consider a discrete number of non-ordered classes of equivalent behaviors (CEBs). The concept of equivalent behavior is introduced to provide a comprehensive description of states and state transitions in the system and its components. MVL tree links all CEBs of interest in the engineered system by means of a combination of the CEBs of elementary components. Logic operators in the tree are defined by truth tables. The analysis of the MVL tree is aimed at eliciting the prime implicants for any one of the CEBs of the system or their groups. Prime implicants correspond to the largest set of CEBs in the smallest number of elementary components, thus extending the concept of minimal cut set which is found in binary fault-tree analysis. In reliability assessment, partitions among equivalent behaviors are often the result of subjective judgment. The methods presented in the paper for finding prime implicants are based upon criteria that recover unnecessary partitions among different CEBs. The methods indeed entail no theoretical constraint with regard to the number of CEBs that can be dealt with or their ordering. Our focus is on the tabular method, the Nelson algorithm, and generalized consensus. The tabular method has tutorial interest only. The Nelson algorithm appears easier to implement in a computer code, although the algorithm asks for the computation of the complete base of prime implicants as an unavoidable step.

Spatial diffusion of pervasive process innovation

Abstract: Only a few years ago it was reasonable to maintain that the theory of spatial innovation diffusion was situated in a “spacious cul-de-sac” (Blaikie 1978). On the one hand, the very limited and dispersed empirical research carried out was not an adequate basis for generalisations of any real substance, or far the proposal of new conjectures or credible research assumptions. On the other hand, the only line of theoretical or empirical analysis of a purely spatial origin to focus on the channels of communication and the diffusion of information (Hagerstrand 1967) appeared to apply uncritically to the social sciences and was derived from models in other sciences such as epidemiology.

Time modeling in office information systems

Abstract: __-Time management 1s d feature essential to offlce informnat1on systems. I? the OI\ environnent, in dddltlon to a static deflnltlon of time attrlbutes attached to data, a more complete definition 1s needed, to handle both static and transltlon times and representation of temporal relatlonshlps The TSOS model, an extension of the SOS model for office descrtptlon, contains a time model suitable for both of these requirements. In addition, the TSOS time model allows the representation of calendar times at different levels of abstractIon and contains a prectse deEinitlon of temporal and logical functions on time. Another main goal of the TSOS time model is to allow a f lexlble representation of temporal conditions for triegering and cant rol rules In the office environment, so that dn Intelligent rule invocatlon is possible. 1. IUTRODUCTLON Offlce Informatlon Systems (015) are a class of Informatlon C,ystems where some features are novel or more crltlcal than In tradItIona Information systems. Among these aspects, In thli paper we address the prohlrrl of time modeling and management. Several models for time handling have been proposed in the literature, In dlEferent computer science research areas [Bol 82) As It wrll be Illustrated in Section 2., each of these models takes into account sonew'lat different aspects in ttme manaqement. The purpose of this paper 1s to define the TSOS (Temporal Semantic Office System) time model to specify rule lnvocatlon condlt ions of control rule5, and to present d Formal deEinltLon of temporal functions in the presence of time abstrdctlons. PermissIon to copy wlthout fee all or part of this material IS granted provided that the copies are not made or dlstrlbuted for direct commercial advantage, the ACM copyrlght notlce and the title of the pubhcatlon and its date appear, and notlce 1s given that copying 15 by permlsslon of the Assoclatlon for Computmg Machmery To copy otherwIse, or lo repubhsh, reqmres a fee and/or specdic permlsslon T\OS 1s an extension of the Semantic OffLce System (SOS) for office systems descrlptlon [Bra 841 In TSOS It is possible to handle temporal attributes-____-of data and to verify static and dyndmlc con$tral?tS on them. Functions ?re provided for handling relationships-_-between e, as It is necessary, for Instance, in-planning systems, where causality relatlonships between times are more lmportdnt that the corresponding precise times. For instance, the time of response to a letter may not be relevant as a precise time, while it …

Fast multipliers for two's-complement numbers in serial form

Abstract: Schemes for designing multipliers of binary-two's-complement numbers in serial form are considered with the condition of the least possible delay between inputs and output. Such schemes are composed by two parts: the first, the array generator, produces the terms of the multiplier array; the second, the summer, is fed by the array generator and produces the product. Two classes of multipliers are illustrated: the first generating the multiplier array by diagonals and rows, the second by columns. The array generators are composed by shift and/or stack registers and linear arrays of logic gates; the summer is shown to be conveniently built using parallel counters.

Comparative study of the optical pumping efficiency in solid-state lasers

Abstract: The optical pump efficiency of a solid-state laser has been calculated, in an unified manner, for the active materials ruby, Nd:YAG, Nd:glass, alexandrite, and Nd:Cr:GSGG under typical operating conditions. This unified presentation allows for a critical comparison and points toward possible future improvements.

Representing procedural knowledge in expert systems: an application to process control

Abstract: The paper presents a novel expert system architecture which supports explicit representation and effective use of both declarative and procedural knowledge These two types of expert knowledge are represented by means of production rules and event-graphs respectively, and they are processed by a unified inference engine Communication between the rule level and the event-graph level is based on a full visibility of each level on the internal state of the other, and it is structured in such a way as to allow each level to expert control on the other This structure offers several advantages over more traditional architectures Knowledge representation is more natural and transparent; knowledge acquisition turns out to be easier as pieces of knowledge can be immediately represented without the need of complex transformation and restructuring; inference is more effective due to reduced non-determinism resulting from explicit representation of fragments of procedural knowledge in event-graphs; finally, explanations are more natural and understandable The proposed architecture has been adopted for the design of PROP, an expert system for on-line monitoring of the cycle water pollution in a thermal power plant PROP is running on a SUN-2 workstation and has been tested on a sample of real cases

An edge-face relational scheme for boundary representations

Abstract: We propose a relational scheme for representing and modelling regular objects, which is based on the adjacency relations between faces and edges. In this structure, called edge-face graph, the nodes represent the faces and the arcs the edges of the corresponding object. Other topological entities, such as vertices, loops of edges, and shells, can be obtained from this relational scheme. We give a formal description of the edge-face graph, and the relationships between its properties and the topological entities of the object are analyzed in detail. Furthermore, a set of basic Euler operators based on the edge-face adjacency relation is denned, which allow the incremental manipulation of boundary representations of solid objects.

Orbital and site diversity systems in rain environment: Radar-derived results

Abstract: During the summers of 1981 and 1982, an experiment was carried out in the Po River Valley with the scope of evaluating the statistical performance of diversity systems for earth to satellite links experiencing rain attenuation. The data were collected by an S -band meteorological radar scanning a 32\deg inclined plane having the SIRIO path as its highest radial. Attenuation values directly measured through the satellite beacon at 11.6 GHz were used to "calibrate" the radar on event basis, in order to properly convert reflectivity into specific attenuation. In a previous paper the performance of site diversity (SD) systems was presented for earth terminals spaced from 1 to 20 km. In this paper, the same set of data is processed to simulate orbital diversity (OD) systems, which employ two satellites angularly spaced and one earth terminal. Aperture angles \theta up to 95\deg have been considered. The results show that this diversity scheme already has a significant gain with \theta = 30\deg where at 10 dB single link attentuation the gain (as defined by Hodge) is 2.5 dB and it increases steadily as \theta increases. The comparison between orbital diversity and site diversity performances shows that the site separation is linearly related to the orbital diversity aperture angle for any single link attenuation of the site diversity configuration.