Dimitrios Kalles
Hellenic Open University, School of Science and Technology, Faculty Member
Distance learning universities usually afford their students the flexibility to advance their studies at their own pace. This can lead to a considerable fluctuation of student populations within a program's courses, possibly affecting... more
Distance learning universities usually afford their students the flexibility to advance their studies at their own pace. This can lead to a considerable fluctuation of student populations within a program's courses, possibly affecting the academic viability of a program as well as the related required resources. Providing a method that estimates this population could be of substantial help to university
Research Interests:
Conventional predictive maintenance involves continuous processing of real-time data from plant sensors of critical variables that are indicators of the health of the equipment. Some intelligent monitoring systems using rules elicited... more
Conventional predictive maintenance involves continuous processing of real-time data from plant sensors of critical variables that are indicators of the health of the equipment. Some intelligent monitoring systems using rules elicited from maintenance personnel have being developed to infer the causes of impending faults. In this paper we propose a novel approach to intelligent predictive maintenance based on reinforcement learning.
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This work deals with stability in incremental induction of decision trees. Stability problems arise when an induction algorithm must revise a decision tree very often and oscillations between similar concepts decrease learning speed. We... more
This work deals with stability in incremental induction of decision trees. Stability problems arise when an induction algorithm must revise a decision tree very often and oscillations between similar concepts decrease learning speed. We introduce a heuristic and an algorithm with theoretical and experimental backing to tackle this problem.
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There is currently a high activity in the transportation tunnelling industry in the countries of the Union with the highest seismicity. In this work, and in order to assure the safety of vulnerable tunnel cross-sections or cross-sections... more
There is currently a high activity in the transportation tunnelling industry in the countries of the Union with the highest seismicity. In this work, and in order to assure the safety of vulnerable tunnel cross-sections or cross-sections where very high standards of safety are required, an integrated package is being developed that includes a deformation monitoring system that can provide
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We examine sorting on the assumption we do not know in advance which way to sort. We use simple local comparison and swap operators and demonstrate that their repeated application ends up in sorted sequences. These are the basic elements... more
We examine sorting on the assumption we do not know in advance which way to sort. We use simple local comparison and swap operators and demonstrate that their repeated application ends up in sorted sequences. These are the basic elements of Emerge-Sort, an approach to self-organizing sorting, which we experimentally validate and observe a run-time behavior of O (n 2).
Abstract This work deals with stability in incremental induction of decision trees. Stability problems arise when an induction algorithm must revise a decision tree very often and oscillations between similar concepts decrease learning... more
Abstract This work deals with stability in incremental induction of decision trees. Stability problems arise when an induction algorithm must revise a decision tree very often and oscillations between similar concepts decrease learning speed. We introduce a heuristic and an algorithm with theoretical and experimental backing to tackle this problem
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ABSTRACT This paper is about designing, developing and training a neural network for short-term forecasting of buy-sell trends in foreign exchange markets. We use a set of established financial technical indicators as inputs to the neural... more
ABSTRACT This paper is about designing, developing and training a neural network for short-term forecasting of buy-sell trends in foreign exchange markets. We use a set of established financial technical indicators as inputs to the neural network and we develop the architecture to predict a trend and then train the network based on the accuracy of the prediction. We perform extensive real time testing with the closing prices (one per minute) of the USD/EUR exchange rates for a one-year period. The overall approach delivers a system that predicts trends substantially better than individual technical indicators.
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Abstract All undergraduate and postgraduate students of the Hellenic Open University (HOU) attend courses at a distance. The lack of a live academic community is reported by many as a drawback in their studies. Systematic exploitation of... more
Abstract All undergraduate and postgraduate students of the Hellenic Open University (HOU) attend courses at a distance. The lack of a live academic community is reported by many as a drawback in their studies. Systematic exploitation of new communication and collaboration technologies is desirable in HOU but cannot be imposed universally as the average student's IT competence level is relatively low. In this work, we present a key aspect of the development of an integrated communication environment in which collaboration ...
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UtilNets is a decision-support system (DSS) for rehabilitation planning and optimisation of the maintenance of underground pipe networks of water utilities. The DSS performs reliability based life predictions of the pipes and determines... more
UtilNets is a decision-support system (DSS) for rehabilitation planning and optimisation of the maintenance of underground pipe networks of water utilities. The DSS performs reliability based life predictions of the pipes and determines the consequences of maintenance and neglect over time in order to optimise rehabilitation policy.
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Research Interests: Peer Review and Computer
The paper examines the development of e-commerce in the context of the burgeoning of the WorldWide Web. The key web service technologies that have supported this development are reviewed and certain limitations of these technologies are... more
The paper examines the development of e-commerce in the context of the burgeoning of the WorldWide Web. The key web service technologies that have supported this development are reviewed and certain limitations of these technologies are discussed. The paper argues that, if e-commerce services are to continue their rapid expansion, the underlying technologies will need to change to provide greater flexibility, scalability and integration with enterprise systems. The paper describes some recent developments in ...
Distance learning universities usually afford their students the flexibility to advance their studies at their own pace. This can lead to a considerable fluctuation of student populations within a programme's courses. The evolution... more
Distance learning universities usually afford their students the flexibility to advance their studies at their own pace. This can lead to a considerable fluctuation of student populations within a programme's courses. The evolution of the student population may be an important factor in determining the academic viability of a programme as well as the resources that have to be budgeted and administered. Providing a method that estimates this population could be of substantial help to university management and academic ...
Abstract. We use decision trees and genetic algorithms to analyze the academic performance of students and the homogeneity of tutoring teams in the undergraduate program on Informatics at the Hellenic Open University (HOU). Based on the... more
Abstract. We use decision trees and genetic algorithms to analyze the academic performance of students and the homogeneity of tutoring teams in the undergraduate program on Informatics at the Hellenic Open University (HOU). Based on the accuracy of the generated rules, we examine the applicability of the techniques at large and reflect on how one can deploy such techniques in academic performance alert systems.
Research Interests:
Abstract: In this paper we examine sorting on the assumption that we do not know in advance which way to sort a sequence of numbers and we set at work simple local comparison and swap operators whose repeating application ends up in... more
Abstract: In this paper we examine sorting on the assumption that we do not know in advance which way to sort a sequence of numbers and we set at work simple local comparison and swap operators whose repeating application ends up in sorted sequences. These are the basic elements of Emerge-Sort, our approach to self-organizing sorting, which we then validate experimentally across a range of samples. Observing an O (n2) run-time behaviour, we note that the n/logn delay coefficient that differentiates Emerge-Sort from ...
We describe a web intelligent system that demonstrates many of the challenges and implications arising from building such systems on the web. The particular system is an on-line fun portal that adopts several key ideas spanning from site... more
We describe a web intelligent system that demonstrates many of the challenges and implications arising from building such systems on the web. The particular system is an on-line fun portal that adopts several key ideas spanning from site design to user walk-through and user-input analysis, in order to “intelligently” adapt to user interests and, consequently, improve user experience. We build on concepts from machine learning and statistics (naïve Bayes analysis and user models), agent theory (dynamic responses by ...
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Abstract: We investigate systematically the impact of human intervention in the training of computer players in a strategy board game. In that game, computer players utilise reinforcement learning with neural networks for evolving their... more
Abstract: We investigate systematically the impact of human intervention in the training of computer players in a strategy board game. In that game, computer players utilise reinforcement learning with neural networks for evolving their playing strategies and demonstrate a slow learning speed. Human intervention can significantly enhance learning performance, but carry-ing it out systematically seems to be more of a problem of an integrated game development environment as opposed to automatic evolutionary learning.
Conventional predictive maintenance involves continuous processing of real-time data from plant sensors of critical variables that are indicators of the health of the equipment. Some intelligent monitoring systems using rules elicited... more
Conventional predictive maintenance involves continuous processing of real-time data from plant sensors of critical variables that are indicators of the health of the equipment. Some intelligent monitoring systems using rules elicited from maintenance personnel have being developed to infer the causes of impending faults. In this paper we propose a novel approach to intelligent predictive maintenance based on reinforcement learning. Following an outline of reinforcement learning, we explore the possibility of ...
Research Interests:
Conventional algorithms for decision tree induction use an attribute-value representation scheme for instances. This paper explores the empirical consequences of using set-valued attributes. This simple representational extension, when... more
Conventional algorithms for decision tree induction use an attribute-value representation scheme for instances. This paper explores the empirical consequences of using set-valued attributes. This simple representational extension, when used as a pre-processor for numeric data, is shown to yield significant gains in accuracy combined with attractive build times. It is also shown to improve the accuracy for the second best classification option, which has valuable ramifications for post-processing. To do so an intuitive and practical ...
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Abstract. We review an experiment in co-evolutionary learning of game playing where we show experimental evidence that the straightforward composition of individually learned models more often than not results in diluting what was earlier... more
Abstract. We review an experiment in co-evolutionary learning of game playing where we show experimental evidence that the straightforward composition of individually learned models more often than not results in diluting what was earlier learned and that self-playing can result in reaching plateaus of uninteresting playing behavior. These observations suggest that learning cannot be easily distributed when one hopes to harness multiple experts to develop a quality computer player and reinforce the need to develop tools that ...
Research Interests:
The Hellenic Open University (HOU) has embarked on a large-scale effort to enhance its textbookbased material with content that is conducive to mature students’ learning needs and supports the basic tenets of distance learning. It has... more
The Hellenic Open University (HOU) has embarked on a large-scale effort to enhance its textbookbased
material with content that is conducive to mature students’ learning needs and supports the
basic tenets of distance learning. It has selected the development and deployment of streaming
media based content as one of its key priorities and now faces the challenge of setting up a
framework that allows for the production-level creation, distribution and consumption of content,
as well as the issue of evaluating its effort in terms of technological, educational and organisational
knowledge gained. To assist in the effort, our approach has also delivered a custom tool for the
development of such content
material with content that is conducive to mature students’ learning needs and supports the
basic tenets of distance learning. It has selected the development and deployment of streaming
media based content as one of its key priorities and now faces the challenge of setting up a
framework that allows for the production-level creation, distribution and consumption of content,
as well as the issue of evaluating its effort in terms of technological, educational and organisational
knowledge gained. To assist in the effort, our approach has also delivered a custom tool for the
development of such content