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8th AGILE International Conference on Geographic Information Science, AGILE 2005

作者： Kamarianakis, Yiannis Prastacos, Poulicos Department of Economics University of Crete Rethymnon Greece Regional Analysis Division Institute of Applied and Computational Mathematics Foundation for Research and Technology-Hellas Vasilika Vouton P.O. Box 1527 GR-711 10 Heraklion-Crete Greece

This paper discusses three modelling techniques, which apply to multiple time series data that correspond to different spatial locations (spatial time series). The first two methods, namely the Space-Time ARIMA (STARIMA) and the Bayesian Vector Autoregressive (BVAR) model with spatial priors apply when interest lies on the spatio-temporal evolution of a single variable. The former is better suited for applications of large spatial and temporal dimension whereas the latter can be realistically performed when the number of locations of the study is rather small. Next, we consider models that aim to describe relationships between variables with a spatio-temporal reference and discuss the general class of dynamic space-time models in the framework presented by Elhorst (2001). Each model class is introduced through a motivating application.

关键词： Time series

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Treatment of an elastic bottom in the parabolic approximation

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The Journal of the Acoustical Society of America 2005年第S1期86卷 S65-S65页

作者： John S. Papadakis Michael I. Taroudakis Betty Mayfield Foundation for Research and Technology—Hellas Institute of Applied and Computational Mathematics P.O. Box 1527 711 10 Iraklion Crete Greece Hood College Frederick MD 21701

The use of impedance boundary conditions in the solution of the parabolic equation in underwater acoustics enables the treatment of bottoms of various types provided that appropriate boundary conditions can be expressed. The conditions are incorporated in an implicit finite difference (IFD) scheme for the parabolic equation. The integrals appearing in the computing scheme are evaluated either analytically, if possible, or numerically. For a sea bottom considered as an elastic homogeneous half‐space, an impedance boundary condition can be evaluated relating the acoustic field in the sea at the water‐bottom interface with that of the elastic bottom. The condition is inserted in the IFD scheme and the pertinent integrals are evaluated numerically by means of a fast Fourier transform algorithm. Results demonstrating the satisfactory behavior of the scheme are presented for range‐independent environments. However, the method is also directly applicable to range‐dependent environments.

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GIS web services and satellite imaging as a framework for environmental monitoring: The design and implementation of a vegetation indices calculation test case 20

GIS web services and satellite imaging as a framework for en...

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20th ISPRS Congress on Technical Commission VII

作者： Kotzinos, D. Chrysoulakis, N. Computer Science Department University of Crete P.O. Box 2208 Heraklio71110 Greece Institute of Applied and Computational Mathematics Foundation for Research and Technology - Hellas P.O. Box 1527 Heraklio71110 Greece

GIS web services bring to the Geographic information arena the promise to deliver algorithmic implementations and data services to the broader community, following a simple yet powerful paradigm. Under this paradigm, a solution to a problem is sought by providing individual services that can be used either in combination or standalone, as part of a greater application to solve the bigger problem. The main advantage is that the service can be used remotely without the user’s actual knowledge and intervention and by multiple users at the same time, eliminating the need for constant updates to locally installed software. Moreover it minimizes the network traffic, since data do not need to be transferred to the client in every step of the operation. This overall framework is currently being developed and tested and the one major test application presented is the development as a web service of an algorithm that calculates vegetation indices using low spatial resolution satellite images. To achieve the overall result two separate web services are developed: a) One handling the acquisition and manipulation of the satellite images being used. A low-resolution satellite ground receiving station is used to provide real time satellite data. b) A second one implementing a vegetation index calculation algorithm, using results form the first web service. It’s worth noting here that the system has the potential to be expanded by more algorithms (e.g. for surface temperature estimation, for aerosol spatial distribution monitoring, for perceptible water calculation) that will still use one or both of the already developed web services, leading to a services-chaining effect. Web services can by nature be used by both web-based and desktop applications alike so, as part of this work, two small client applications are developed – one web-based and one desktop, in order to showcase the applicability and availability of the framework. End users will use the two already mentioned clients

关键词： Geographic information systems

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Students' level of satisfaction with an on-line seminar based on a social-constructivist pedagogic design

Students' level of satisfaction with an on-line seminar base...

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International Conference on Information technology Based Higher Education and Training, ITHET

作者： A. Kollias K. Kikis Education and Training Group. Institute of Applied and.Computational Mathematics Foundation for Research and Technology Hellas Heraklion Greece

The research reported in This work is part of a 2-years evaluation activity of an on-line seminar based on a social-constructivist pedagogic design. Its purpose is to investigate the level of students' satisfaction with five different dimensions of the seminar, namely the organization and clarity, the pedagogic approach, the interaction within learning groups, the delivery platform, and their learning experiences. The relationships between the students' level of satisfaction with these dimensions and their gender, age, professional category, and prior experience in online courses are further explored.

关键词： Seminars Law Collaborative work Legal factors mathematics Educational technology Gears Computer science Environmental economics Protection

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Technical note: Using NOAA and FY imagery to track plumes caused by the 2003 bombing of Baghdad

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International Journal of Remote Sensing 2004年第23期25卷 5247-5254页

作者： Chrysoulakis, N. zedd2@jiacm.forth.gr Opie, C. Foundation for Research and Technology - Hellas (FORTH) Institute of Applied and Computational Mathematics Regional Analysis Division Vassilika Vouton PO Box 1527 GR-71110 Heraklion Crete Greece Dartcom Powdermills Postbridge Yelverton Devon PL20 6SP UK

In this study, the usability of a 1.1 km satellite receiving station in Greece as an operational tool for monitoring wide scale man-made disasters is demonstrated. The plumes caused by major fires in Baghdad during the 2003 bombing campaign were detected and monitored using the real-time acquisition of National Oceanic and Atmospheric Administration (NOAA) and Feng Yun satellite imagery at the foundation for research and technology - hellas (FORTH) satellite receiving station. A set of false colour composites of Advanced Very High Resolution Radiometer (AVHRR) and Multichannel Visible and Infrared Scan Radiometer (MVISR) images was used to investigate the dispersion of the plumes, which may contain toxic substances, over the wider Baghdad area, as well as to estimate plume spatial characteristics. In some cases, the area covered by these plumes was estimated to be more than 6000 km 2 . [ABSTRACT FROM AUTHOR]

关键词： DISASTERS ENVIRONMENTAL monitoring REMOTE-sensing images ARTIFICIAL satellites in remote sensing

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A GIS interfaced numerical model for the simulation of sound propagation in the atmosphere over irregular terrain

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Systems Analysis Modelling Simulation 2003年第9期43卷 1199-1212页

作者： Kampanis, Nikolaos A. Flouri, Evangelia T. Institute of Applied and Computational Mathematics Foundation for Research and Technology - Hellas 71110 Heraklion Crete Greece

The effort to control environmental noise levels calls for the study of sound propagation in the atmosphere, rather over irregular terrain. We interface a numerical model for low-frequency aeroacoustics, capable of treating complex terrain, with a GIS for retrieving the ground surface topography. The model at hand uses the 'standard' parabolic equation to simulate the far-field, low-frequency sound propagation in a refracting atmosphere. The discretization is based on a finite element technique coupled with a nonlocal artificial boundary condition to cope with a homogeneous atmosphere above the artificial boundary. The proposed model is accurate and efficient for the prediction of atmospheric noise levels.

关键词： Acoustic wave propagation

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Energy in the urban environment: Use of terra/aster imagery as a tool in urban planning

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Journal of the Indian Society of Remote Sensing 2002年第4期30卷 245-254页

作者： Chrysoulakis, N. Foundation for Research and Technology - Hellas Institute of Applied and Computational Mathematics Regional Analysis Division FORTH - IACM GR-71110 Heraklion Crete Vassilika Vouton P.O. Box 1527 Greece

In the present paper, Terra/ASTER imagery has been analysed together with in-situ spatial data to examine the potential of multi-spectral remote sensing to support urban planning. The potential of ASTER imagery to support energy budget estimation has been also examined by defining and mapping some microclimatic parameters for the centre of the city of Athens. Images in visible, near infrared and thermal infrared areas of the electromagnetic spectrum have been processed to define the urban land cover and topographic characteristics as well as to estimate the spatial distributions of vegetation, visible reflected radiation and brightness temperature. It has been found that ASTER multi-spectral imagery enables a better understanding of energy'aspects, their causes and effects, providing an important addition to conventional methods of monitoring the urban environment.

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Inverse boundary value problem for ocean acoustics

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Mathematical Methods in the applied Sciences 2000年第1期24卷

作者： M. Ikehata G. N. Makrakis G. Nakamura Faculty of Engineering Gunma University Kiryu Gunma 376-8515 Japan Foundation for Research and Technology-Hellas Institute of Applied and Computational Mathematics P.O. Box 1527 711 10 Heraklion Crete Greece

For an ocean with constant depth and rigid bottom which contains compactly supported inhomogeneity of the water sound velocity, we prove uniqueness for the identification of the inhomogeneity from the Dirichlet-to-Neumann (DtN) map on the surface of a bounded region containing the inhomogeneity. The DtN map is the map which maps the pressure applied on the boundary of this region to the corresponding flux (displacement). In an analogous geometric configuration and with similar boundary conditions, the uniqueness for the inverse electroconductivity problem from the DtN map (i.e. voltage-to-current map) can be proved in the same framework. Copyright © 2001 John Wiley & Sons, Ltd.

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Sur la stabilité des approximations implicites des lois de conservation scalaires non homogènes

Comptes Rendus de l'Académie des Sciences - Series I - Math...

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Comptes Rendus de l'Académie des Sciences - Series I - mathematics 1999年第1期329卷 79-84页

作者： Laurent Gosse Foundation for Research and Technology Hellas Institute of applied and Computational Mathematics P.O. Box 1527 71110 Heraklion Crete Greece

Dans cette Note, on s'intéresse aux propriétés de stabilité des méthodes de quadrature numériques implicites dans le contexte des lois de conservation scalaires avec terme source. In ...

Dans cette Note, on s'intéresse aux propriétés de stabilité des méthodes de quadrature numériques implicites dans le contexte des lois de conservation scalaires avec terme source. In this Note, we are interested in the stability properties of implicit numerical integration methods in the context of scalar conservation laws with source terms.

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Ocean botton recognition from acoustic reflection data

Ocean botton recognition from acoustic reflection data

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International Conference on Acoustic Sensing and Imaging, 1993.

作者： P.J. Papadakis J.S. Papadakis M.I. Taroudakis M. Tsachnopoulou University of Crete Greece National and Technical University of Athens Greece Institute of Applied and Computational Mathematics Foundation for Research and Technology Hellas Crete Greece

In this paper we present an algorithm for the density and sound speed reconstruction of a two-layered bottom consisting of a fluid sediment layer over a fluid substrate of semi-infinite extend. The thickness of the sediment as well as the attenuation coefficients in the botton layer are also recovered. Measurements of the reflection coefficients of plane waves for eight source frequencies incident normally upon the water bottom interface are needed. The minimum number of frequencies needed for the algorithm is eight as it will be seen in the following sections, however if the reflection coefficient is known for more than eight frequencies the method makes use of the excess frequencies, improving the final solution in a postprocessing way. We first introduce our model, explain the method of solution and present the major steps of the algorithm. Then we will show results using synthetic data, for four cases which were tested, as well as results from a tank experiment.< >

关键词： Acoustic reflection Acoustic velocity Sea measurements Sea Underwater acoustics

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