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FCUP - Artigo em Acta de Conferência Internacional
Probabilistic surface change detection and measurement from digital aerial stereo images
We propose a new method to measure changes in terrain topography from two optical stereo image pairs acquired at different
dates. The main novelty is in the ability of computing the spatial distribution of uncertainty, thanks to stochastic modeling and
probabilistic inference. Thus, scientists will have access to quantitative error estimates of local surface variation, so they can
check the statistical significance of elevation changes, and make, where changes have occurred, consistent measurements of
volume or shape evolution. The main application area is geomorphology, as the method can help study phenomena such as
coastal cliff erosion, sand dune displacement and various transport mechanisms through the...
The use of similarity images on multi-sensor automatic image registration
Automatic image registration (AIR) is still a present challenge regarding remote sensing applications. Although several methods
have been proposed in the last few years, geometric correction is often a time and effort consuming manual task. The only AIR
method which is commonly used is the correlation-based template matching method. It usually consists on considering a window
from one image and passing it throughout the other, looking for a maximum of correlation, which may be associated to the
displacement between the two images. This approach leads sometimes (for example with multi-sensor image registration) to low
correlation coefficient values, which do not give sufficient confidence to associate...
MONITORING OF BEACHES AND SAND DUNES USING DIGITAL AERIAL
PHOTOGRAPHY WITH DIRECT GEOREFERENCING
Beaches in the Portuguese western coast suffer sudden changes due to the action of the sea during winter. Frequent
acquisition of digital surface models (DSM) is needed in order to assess volumetric changes. This paper presents a
monitoring program carried in an area of 15 km near the city of Porto. Digital aerial photography is acquired twice
a year, using a Zeiss-Intergraph DMC camera, with a spatial resolution of 10 cm, by a local company. Images are
provided with exterior orientation provided by direct georeferencing equipment. An assessment of the exterior
orientation parameters provided was done using field survey points. It could be concluded that...
Deployment and evaluation of a usage based collaborative filtering recommendation system with blacklists
Social web sites, like Palco Principal (PP), have considerably sized
databases with the most varied types of information from user subscription
information to user interactions. All that information is susceptible of being
processed using data mining algorithms in order to extract knowledge relevant
for the business. This document describes the implementation and evaluation of
a system that uses data mining techniques, and that has been developed with the
specific intent of generating recommendations, namely music
recommendations, to users of the PP web site. The implemented system uses
collaborative filtering techniques to recommend music additions to a user’s
playlist. The impact of the deployed system has been evaluated online.
Kostia Beidar's contribution to module and ring theory
At the beginning of his mathematical career Kostia Beidar was working on rings with polynomial identities and primeness conditions for rings. By Posner’s theorem the two-sided quotient ring of a prime PI-ring is a finite matrix ring over some field. This result was extended by Martindale to rings with generalised polynomial identities by the construction of the central closure of a prime ring. Kostia was working extensively in this setting and made crucial contributions to the understanding of the theory.
While his contribution to general PI theory will be outlined
elsewhere we want to sketch here his work on prime rings and...
Comparability, distributivity and non-commutative φ-rings.
The purpose of this paper is to develop the theory of non-commutative φ-rings using concepts from distributive rings and rings with comparability. We recover the main statements for commutative φ-rings as obtained by Anderson and Badawi.
The splitting of the dual Goldie torsion theory
The splitting of the Goldie (or singular) torsion theory has been extensively studied. Here we determine an appropriate dual Goldie torsion theory, discuss its splitting and answer in the negative a question proposed by Ozcan and Harmanci as to whether the splitting of the dual Goldie torsion theory implies the ring to be quasi-Frobenius.