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Showing papers by "Polytechnic University of Milan published in 2000"


Journal ArticleDOI
TL;DR: In this article, a new approach to the estimation of the atmospheric phase contributions, and the local displacement field is proposed based on simple statistical assumptions, is presented in order to cope with nonlinear motion of the targets.
Abstract: Discrete and temporarily stable natural reflectors or permanent scatterers (PS) can be identified from long temporal series of interferometric SAR images even with baselines larger than the so-called critical baseline. This subset of image pixels can be exploited successfully for high accuracy differential measurements. The authors discuss the use of PS in urban areas, like Pomona, CA, showing subsidence and absidence effects. A new approach to the estimation of the atmospheric phase contributions, and the local displacement field is proposed based on simple statistical assumptions. New solutions are presented in order to cope with nonlinear motion of the targets.

1,901 citations


Journal ArticleDOI
01 Jun 2000
TL;DR: The WebML language and its accompanying design method are fully implemented in a pre-competitive Web design tool suite, called ToriiSoft, supporting advanced features like multi-device access, personalization, and evolution management.
Abstract: Designing and maintaining Web applications is one of the major challenges for the software industry of the year 2000. In this paper we present Web Modeling Language (WebML), a notation for specifying complex Web sites at the conceptual level. WebML enables the high-level description of a Web site under distinct orthogonal dimensions: its data content (structural model), the pages that compose it (composition model), the topology of links between pages (navigation model), the layout and graphic requirements for page rendering (presentation model), and the customization features for one-to-one content delivery (personalization model). All the concepts of WebML are associated with a graphic notation and a textual XML syntax. WebML specifications are independent of both the client-side language used for delivering the application to users, and of the server-side platform used to bind data to pages, but they can be effectively used to produce a site implementation in a specific technological setting. WebML guarantees a model-driven approach to Web site development, which is a key factor for defining a novel generation of CASE tools for the construction of complex sites, supporting advanced features like multi-device access, personalization, and evolution management. The WebML language and its accompanying design method are fully implemented in a pre-competitive Web design tool suite, called ToriiSoft.

929 citations


Journal ArticleDOI
TL;DR: In this paper, a cointegration model with piecewise linear trend and known break points is proposed to test co-integration rank, restrictions on the cointegrating vector as well as the slopes of the broken linear trend.
Abstract: When analysing macroeconomic data it is often of relevance to allow for structural breaks in the statistical analysis. In particular, cointegration analysis in the presence of structural breaks could be of interest. We propose a cointegration model with piecewise linear trend and known break points. Within this model it is possible to test cointegration rank, restrictions on the cointegrating vector as well as restrictions on the slopes of the broken linear trend.

741 citations


Journal ArticleDOI
TL;DR: In this article, the dependence on initial conditions of the three-dimensional algebraic spatial instability of the Blasius boundary layer is examined by a recently developed method of receptivity analysis based on the upstream integration of adjoint equations.
Abstract: The dependence on initial conditions of the three-dimensional algebraic spatial instability of the Blasius boundary layer is examined by a recently developed method of receptivity analysis based on the upstream integration of adjoint equations. This method allows us to determine optimal perturbations, i.e. initial perturbations that maximize the energy growth, even in the wavenumber range where the problem is not amenable to a mode analysis, and thus to complement a previous paper in which the small-wavenumber regime was described.

517 citations


Proceedings ArticleDOI
01 Jun 2000
TL;DR: The tutorial provides a conceptual framework for code mobility by illustrating a taxonomy of related technologies, architectural paradigms, and applications and applies the concepts developed to a quantitative assessment of the benefits of mobile code technologies and architectures in the network management application domain.
Abstract: The tutorial provides a conceptual framework for code mobility by illustrating a taxonomy of related technologies, architectural paradigms, and applications. As a final case study, the concepts developed in the taxonomy are then applied to a quantitative assessment of the benefits of mobile code technologies and architectures in the network management application domain.

486 citations


Proceedings ArticleDOI
01 May 2000
TL;DR: The history and achievements of software process research, some critical evaluation of the results produced so far, and possible directions for future work are presented.
Abstract: Software process research deals with the methods and technologies used to assess, support, and improve software development activities. The field has grown up during the 80s to address the increasing complexity and criticality of software development activities. This paper aims to briefly present the history and achievements of software process research, some critical evaluation of the results produced so far, and possible directions for future work.

473 citations




Journal ArticleDOI
TL;DR: In this paper, an alternative decision model is presented to evaluate the relative performance of suppliers that have multiple outputs and inputs, based on a multivariate statistical method, principal component analysis, that uses information obtained from eigenvalues to combine different ratio measures defined by every input and every output.
Abstract: SUMMARY Purchasing managers need to periodically evaluate supplier performance in order to retain those suppliers which meet their requirements in terms of several performance criteria. The evaluation element typically consists of identifying the attributes, criteria, or factors relevant to the decision and then measuring or rating each vendor by considering each of the relevant factors. A critical part of the overall supplier selection process is the determination of the relative importance of each of the factors. This article presents an alternative decision model to evaluate the relative performance of suppliers that have multiple outputs and inputs. This approach is based on a multivariate statistical method, principal component analysis, that uses information obtained from eigenvalues to combine different ratio measures defined by every input and every output. The method has been employed to aggregate multiple performance measures for a real-world data set of suppliers of a medium-sized firm operating in the bottling machinery industry.

275 citations


Journal ArticleDOI
TL;DR: In recent years, network behaviour has been analysed extensively as the emerging model for economic growth as mentioned in this paper. But it is not a metaphor for co-operative behaviour among individuals, corporate...
Abstract: In recent years, network behaviour has been analysed extensively as the emerging model for economic growth. By network behaviour, a metaphor for co-operative behaviour among individuals, corporate ...

264 citations


Journal ArticleDOI
TL;DR: In this paper, a finite element projection method for the computation of incompressible viscous flows of nonuniform density was proposed, which consists in factorizing the density variable partly outside and partly inside the time evolution operator in the momentum equation to prevent spatial discretization errors in the mass conservation to affect the kinetic energy balance of the fluid.

Book ChapterDOI
27 Mar 2000
TL;DR: This work presents an access control model to protect information distributed on the Web that, by exploiting XML's own capabilities, allows the definition and enforcement of access restrictions directly on the structure and content of XML documents.
Abstract: Web-based applications greatly increase information availability and ease of access, which is optimal for public information. The distribution and sharing by theWeb of information that must be accessed in a selective way requires the definition and enforcement of security controls, ensuring that information will be accessible only to authorized entities. Approaches proposed to this end level, independently from the semantics of the data to be protected and for this reason result limited. The eXtensible Markup Language (XML), a markup language promoted by the World Wide Web Consortium (W3C), represents an important opportunity to solve this problem. We present an access control model to protect information distributed on the Web that, by exploiting XML's own capabilities, allows the definition and enforcement of access restrictions directly on the structure and content of XML documents. We also present a language for the specification of access restrictions that uses standard notations and concepts and briefly describe a system architecture for access control enforcement based on existing technology.

Journal ArticleDOI
TL;DR: In this paper, a survey of 46 small high-tech Italian firms was conducted to explore the problems experienced by small businesses in gaining access to debt and equity finance, and the results highlight that traditional financial sources are inadequate to finance innovative projects.
Abstract: Financial constraints to the development of innovation are often considered one of the main impediments to high-technology firms seeking to expand and grow. In particular this is the case of small and medium size high-tech firms. In the U.S. and the U.K. a variety of sources of finance are available to the start-ups of innovative firms; in the other European countries, and particularly in Italy, these means are still uncommon so that the development of technology is often prevented. This paper, based on an empirical analysis on a survey of 46 small high-tech Italian firms, aims at exploring the problems experienced by small businesses in gaining access to debt and equity finance. The results highlight that traditional financial sources are inadequate to finance innovative projects. The questioned firms rely mainly on personal finance, and secondly on short term bank debt; they are truly involved in maintaining control over the firm activities and are willing to issue outside equity only if the new investors also provide non financial competencies. Among the 46 interviewed firms, only 10 are willing to be listed in the future on small firms' stock markets.

Journal ArticleDOI
TL;DR: In this paper, the authors propose four different vendor selection systems (VSSs) depending on the time frame (short-term versus long-term) and on the content (logistic versus strategic) of the co-operative customer/supplier relationships.
Abstract: Literature on supply chain management has been recently stressing the need for co‐operation and integration between suppliers and customers, highlighting the critical role played by the supplier in contributing to the overall performance of the purchaser. Consequently supplier selection is one of the purchasing manager’s most critical tasks, as demonstrated by the number of articles that have dealt with vendor selection criteria and techniques in the light of the requirements of the new environment. The paper proposes four different vendor selection systems (VSSs) depending on the time frame (short‐term versus long‐term) and on the content (logistic versus strategic) of the co‐operative customer/supplier relationships. More precisely, the suggested VSSs consider, in an analytic hierarchy process framework, different sets of measures, deriving from a non‐conventional model of the supplier based on the dynamic system and on the resource‐based approach.

Journal ArticleDOI
TL;DR: In this article, the authors present a critical view of theoretical works on city size, starting with the consideration that, during the 1960s and 1970s, the question of optimal city size tended to b...
Abstract: The aim of the paper is to present a critical view of theoretical works on city size. We begin with the consideration that, during the 1960s and 1970s, the question of optimal city size tended to b...


Journal ArticleDOI
TL;DR: A methodology for the development of WWW applications and a tool environment specifically tailored for the methodology, based upon models and techniques already used in the hypermedia, information systems, and software engineering fields, adapted and blended in an original mix.
Abstract: This paper describes a methodology for the development of WWW applications and a tool environment specifically tailored for the methodology. The methodology and the development environment are based upon models and techniques already used in the hypermedia, information systems, and software engineering fields, adapted and blended in an original mix. The foundation of the proposal is the conceptual design of WWW applications, using HDM-lite, a notation for the specification of structure, navigation, and presentation semantics. The conceptual schema is then translated into a “traditional” database schema, which describes both the organization of the content and the desired navigation and presentation features. The WWW pages can therefore be dynamically generated from the database content, following the navigation requests of the user. A CASE environment, called Autoweb System, offers a set of software tools, which assist the design and the execution of a WWW application, in all its different aspects, Real-life experiences of the use of the methodology and of the AutoWeb System in both the industrial and academic context are reported.

Journal ArticleDOI
TL;DR: The MOESP class of identification algorithms are made recursive on the basis of various updating schemes for subspace tracking.

Journal ArticleDOI
01 Mar 2000
TL;DR: In this paper, a comparison of five representative query languages for XML, highlighting their common features and differences, is presented, with a focus on XML query languages. But no standard for XML query language has yet been decided, but discussion is ongoing within the World Wide Web Consortium and within many academic institutions and Internet-related major companies.
Abstract: XML is becoming the most relevant new standard for data representation and exchange on the WWW. Novel languages for extracting and restructuring the XML content have been proposed, some in the tradition of database query languages (i.e. SQL, OQL), others more closely inspired by XML. No standard for XML query language has yet been decided, but the discussion is ongoing within the World Wide Web Consortium and within many academic institutions and Internet-related major companies. We present a comparison of five, representative query languages for XML, highlighting their common features and differences.

Journal ArticleDOI
TL;DR: In this paper it is shown that a wise parametrization of the extended Kalman frequency tracker is characterized by just one parameter: the /spl epsi/ must be set to zero to achieve the basic property of unbiasedness in a noise-free setting.
Abstract: The problem of estimating the frequency of a harmonic signal embedded in broad-band noise is considered. The paper focuses on the extended Kalman filter frequency tracker, which is the application of the extended Kalman filter (EKF) framework to the frequency estimation problem. The EKF frequency tracker recently proposed in the literature is characterized by a vector of three design parameters {q,r,/spl epsi/}, whose role and tuning is still a controversial and unclear issue. In this paper it is shown that a wise parametrization of the extended Kalman frequency tracker is characterized by just one parameter: the /spl epsi/ must be set to zero to achieve the basic property of unbiasedness in a noise-free setting; the performances of the tracker are not influenced independently by q and r; and what really matters is the ratio /spl lambda/=r/q only. The proposed simplification of the extended Kalman filter frequency tracker allows an easier and more transparent tuning of its tracking behavior.

Journal ArticleDOI
TL;DR: TiN-coated titanium alloy femoral heads are inadequate in the task of resisting third body wear mechanisms in vivo according to the results of the study performed on four titanium nitride (TiN) coated prosthetic femoral Heads collected at revision surgery together with patient data.

Journal ArticleDOI
01 Jun 2000
TL;DR: An Access Control System for XML is described allowing for definition and enforcement of access restrictions directly on the structure and content of XML documents, thus providing a simple and effective way for users to protect information at the same granularity level provided by the language itself.
Abstract: More and more information is distributed in XML format, both on corporate Intranets and on the global Net. In this paper an Access Control System for XML is described allowing for definition and enforcement of access restrictions directly on the structure and content of XML documents, thus providing a simple and effective way for users to protect information at the same granularity level provided by the language itself.

Journal ArticleDOI
TL;DR: In this article, the results of quantum chemical calculations (DFT and MP2) on the intermolecular interactions involving ammonia and halofluoromethanes are described.
Abstract: We describe the results of quantum chemical calculations (DFT and MP2) on the intermolecular interactions involving ammonia and halofluoromethanes. The equilibrium C−X···N geometries are linear and the X···N distances are shorter than the sum of the van der Waals radii. The binding energies of CF3X···NH3 increase from 2 to 6 kcal/mol on following the sequence X = Cl, Br, I. Also, progressive introduction of F atoms in methyliodides raises the interaction energy from 2 kcal/mol for CH3I to 6 kcal/mol for CF3I. Therefore, halogen bonding involving perfluorinated alkylhalides and appropriate donors can be comparable in strength to strong hydrogen bonding. This agrees with recent experimental observations, that also the former can drive the construction of supramolecular edifices overcoming the low affinity between perfluorocarbons and hydrocarbons. Calculation of the atomic charges by the Atoms in Molecules method indicates that the charge-transfer contribution to the interaction energy is much less importan...

Journal ArticleDOI
TL;DR: In this article, the authors used a pulsed picosecond diode laser and detected the scattered signal from a non-cooperative target surface using a semiconductor single-photon detector.
Abstract: In this paper, we report results obtained with a time-of-flight ranging/scanning system based on time-correlated single-photon counting. This system uses a pulsed picosecond diode laser and detects the scattered signal from a non-cooperative target surface using a semiconductor single-photon detector. A demonstration system has been constructed and used to examine the depth resolution obtainable as a function of the integrated number of photon returns. The depth resolution has been examined for integrated photon returns varying by five orders of magnitude, both by obtaining experimental measurements and by computer simulation. Depth resolutions of approximately 3 mm were obtained for only ten returned photons. The effect of the background signal, originating either from temporally uncorrelated light signals or from detector noise, has also been examined.

Journal ArticleDOI
TL;DR: Alpha(XXAR) is comparable to or significantly smaller than the baroreflex gains derived from sequence, power spectrum, and cross-spectrum analyses and from less complex causal parametric models, thus demonstrating that simpler estimates may be biased by the contemporaneous presence of regulatory mechanisms other than barore Flex mechanisms.
Abstract: A double exogenous autoregressive (XXAR) causal parametric model was used to estimate the baroreflex gain (αXXAR) from spontaneous R-R interval and systolic arterial pressure (SAP) variabilities in...

Journal ArticleDOI
TL;DR: This survey paper is to present a complete and clear picture on time-invariant representations for discrete-time periodic systems around the concept of periodic transfer function.

Proceedings ArticleDOI
01 May 2000
TL;DR: This work seeks to sort out this chaotic form of computing by focusing its attention on the formulation of a simple framework for viewing mobility, on precise definition of terms, and on research issues mobility poses for the software engineering community.
Abstract: The term distributed computing conjures the image of a fixed network structure whose nodes support the execution of processes that communicate with each other via messages traveling along links. Peer-to-peer communication is feasible but client-server relationships dominate. More recently, servers have been augmented with brokerage capabilities to facilitate discovery of available services. Stability is the ideal mode of operation; changes are relatively slow; even in the case of failure, nodes and links are expected eventually to come back up. By contrast, mobility represents a total meltdown of all the stability assumptions (explicit or implicit) associated with distributed computing. The network structure is no longer fixed, nodes may come and go, processes may move among nodes, and even programs (the code executed by processes) may evolve and change structure. The challenges and opportunities associated with this computational melee form the main subject of this paper. We seek to sort out this chaotic form of computing by focusing our attention on the formulation of a simple framework for viewing mobility, on precise definition of terms, and on research issues mobility poses for the software engineering community.

Journal ArticleDOI
TL;DR: It is concluded that optoelectronic plethysmography is a feasible technique able to provide unique data on the distribution of chest wall volume changes in intensive care patients.
Abstract: We used optoelectronic plethysmography to study 11 normal subjects during quiet and deep breathing, six sedated and paralyzed patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) receiving continuous positive pressure ventilation (CPPV) (positive end-expiratory pressure [PEEP] = 10 cm H2O, tidal volume [Vt] = 300, 600, 900 ml), and seven ALI/ARDS patients receiving pressure support ventilation (PSV) (PEEP 10 cm H2O, pressure support = 5, 10, 15, 25 cm H2O). The volumes measured using optoelectronic plethysmography were compared with measurements taken using spirometry and pneumotachography. The three methods were highly correlated. The discrepancies found were 1.7 ± 5.9%, − 1.6 ± 5.4%, and 4.9 ± 6.4% when comparing optoelectronic plethysmography with spirometry, optoelectronic plethysmography with pneumotachography, and spirometry with pneumotachography, respectively. Accuracy of the compartmentalization procedure (upper thorax, lower thorax, and abdomen) was assessed by calc...

Journal ArticleDOI
TL;DR: A general approach for the numerical approximation of incompressible Navier-Stokes equations based on splitting the original problem into successive subproblems which are cheaper to solve and the so called Yosida method, which can be investigated in the framework of quasi-compressibility schemes.

Journal ArticleDOI
TL;DR: In this article, a numerical model to calculate the high-order harmonics spectrum of a macroscopic gas target irradiated by a few-optical-cycle laser pulse is presented.
Abstract: A numerical model to calculate the high-order harmonics spectrum of a macroscopic gas target irradiated by a few-optical-cycle laser pulse is presented. The single-atom response, calculated within the nonadiabatic strong-field approximation, is the source term of a three-dimensional propagation code. The simulation results show remarkably good agreement with experiments performed in neon using laser pulses with durations of 30 and 7 fs. Both simulations and experiments show discrete and well-resolved harmonics even for the shortest driving pulses.