Showing papers by "National Technical University of Athens published in 2001"

Emotion recognition in human-computer interaction

Abstract: Two channels have been distinguished in human interaction: one transmits explicit messages, which may be about anything or nothing; the other transmits implicit messages about the speakers themselves. Both linguistics and technology have invested enormous efforts in understanding the first, explicit channel, but the second is not as well understood. Understanding the other party's emotions is one of the key tasks associated with the second, implicit channel. To tackle that task, signal processing and analysis techniques have to be developed, while, at the same time, consolidating psychological and linguistic analyses of emotion. This article examines basic issues in those areas. It is motivated by the PKYSTA project, in which we aim to develop a hybrid system capable of using information from faces and voices to recognize people's emotions.

Modern Control Engineering

Abstract: Introduction to automatic control systems mathematical background mathematical models of systems classical time-domain analysis of control systems state-space analysis of control systems stability the root locus method frequency domain analysis classical control design methods state-space design methods optimal control digital control system identification adaptive control robust control fuzzy control. Appendices: Laplace transform tables the Z-transform transform tables.

Java-based graphical user interface for the MRUI quantitation package

Abstract: This article describes the Java-based version of the magnetic resonance user interface (MRUI) quantitation package. This package allows MR spectroscopists to easily perform time-domain analysis of in vivo MR spectroscopy data. We show that the Java programming language is very well suited for developing highly interactive graphical software applications such as the MRUI software. We have also established that MR quantitation algorithms, programmed in other languages, can easily be embedded into the Java-based MRUI by using the Java native interface (JNI). This new graphical user interface (GUI) has been conceived for the processing of large data sets and uses prior knowledge data-bases to make interactive quantitation algorithms more userfriendly.

Estimating the geotechnical properties of heterogeneous rock masses such as flysch

Abstract: The design of tunnels and slopes in heterogeneous rock masses such as flysch presents a major challenge to geologists and engineers. The complex structure of these materials, resulting from their depositional and tectonic history, means that they cannot easily be classified in terms of widely used rock mass classification systems. A methodology for estimating the Geological Strength Index and the rock mass properties for these geological formations is presented in this paper.

Inducing Passive Nonlinear Energy Sinks in Vibrating Systems

Abstract: We study the inducement of passive nonlinear sinks in linear vibrating systems. These are substructures that absorb vibrational energy in a one-way, irreversible fashion. The systems considered are composed of strongly coupled, grounded damped linear oscillators with a strongly nonlinear attachment at the end. Applying a complex averaging technique we derive a set of modulation equations that is directly amenable to physical interpretation, and provides insight into the energy pumping phenomenon. For the case of a two DOF system we show that nonlinear energy pumping occurs when a certain frequency of envelope modulation crosses through zero; then the dynamics of the envelope modulation of the motion resemble the dynamics of a forced rigid body. For the case of an impulsively loaded multi-DOF chain with a nonlinear attachment at the end, we show that after some initial transients the response of the nonlinear attachment sets to a motion dominated by a fast frequency identical to the lower bound of the propagation zone of the linear chain. This feature reduces the study of energy pumping in the chain to a two DOF equivalent problem. The applications of the energy pumping phenomenon to practical engineering problems are discussed.

Aessessment of biomass potential for power production: a GIS based method

Abstract: A method is presented, which estimates the potential for power production from agriculture residues. A GIS decision support system (DSS) has been developed, which implements the method and provides the tools to identify the geographic distribution of the economically exploited biomass potential. The procedure introduces a four level analysis to determine the theoretical, available, technological and economically exploitable potential. The DSS handles all possible restrictions and candidate power plants are identified using an iterative procedure that locates bioenergy units and establishes the needed cultivated area for biomass collection. Electricity production cost is used as a criterion in the identification of the sites of economically exploited biomass potential. The island of Crete is used as an example of the decision-making analysis. A significant biomass potential exists that could be economically and competitively harvested. The main parameters that affect the location and number of bioenergy conversion facilities are plant capacity and spatial distribution of the available biomass potential.

The effect of the method of drying on the colour of dehydrated products.

Abstract: Summary We tested the hypothesis that an optimum method of drying fruit could be designed. The effect of the method used for drying on colour of apple, banana, potato and carrot was investigated for five different methods of drying: conventional, vacuum, microwave, freeze and osmotic drying. Colour characteristics were studied by measuring lightness (L), redness (a) and yellowness (b) using a Hunter Lab chromatometer. The method used to dry the material was found to significantly affect the three colour parameters. The changes in redness (a) and yellowness (b) were found to follow a first order kinetic model. Air-, vacuum- and microwave-dried materials caused extensive browning in the fruits and vegetables, this was manifested by a significant drop of the L parameter and an increase of the a and b parameters. Osmotically pretreated samples did not brown as much as the untreated samples and the value for lightness (L) decreased only slightly while a and b increased slightly. Freeze drying seems to prevent colour changes, resulting in products with improved colour characteristics.

University-Industry Cooperation in the Context of the European Framework Programmes

Abstract: This paper investigates the characteristics of university-industry collaboration in a large set of research joint ventures (RJVs) established in the context of the European Framework Programmes over a period of fourteen years. The share of university-industry RJVs is found to have gradually increased. Such RJVs have tended to be relatively larger in terms of participant numbers. Universities from peripheral European regions have been rather active in the examined RJVs. Firms cooperate with Universities to exploit research synergies leading to cost savings or improvements in R&D productivity, keeping up with major technological developments, and sharing R&D cost. Firms reported that the most important benefit from such collaboration has been the positive impact on their knowledge base.

Kinematic pile bending during earthquakes: analysis and field measurements

Abstract: The passage of seismic waves through the soil surrounding a pile imposes lateral displacements and curvatures on the pile, thereby generating ‘kinematic’ bending moments even in the absence of a su...

Prediction of Permeation Properties of CO2 and N2 through Silicalite via Molecular Simulations

Abstract: The sorption isotherms and self-diffusivities of CO2 and N2 in silicalite have been calculated via grand canonical Monte Carlo and equilibrium molecular dynamics simulations over a wide range of occupancies, using various force fields proposed in the literature. Predictions for the sorption thermodynamics are in very favorable agreement with the experiment, especially when detailed point-charge models are used to represent the interaction of the quadrupole moments of the sorbate molecules with the lattice field and with each other. They indicate that the zeolite cannot be in its para (P212121) form under the conditions of the measurements. Permeabilities corresponding to a perfectly crystalline membrane have been estimated for CO2 and N2, as well as for methane, examined in past simulation work, from the predicted sorption isotherms and low-occupancy self-diffusivities by invoking the Darken equation. The ratios of pure component permeabilities obtained in this way agree very well with actual macroscopic ...

Volumetric sand production model and experiment

Abstract: A sand production model was developed for volumetric sand production predictions that take into account the effects of the external stresses and fluid flow rate. The model couples the poro-mechanical behaviour of the solid–fluid system with the erosion behaviour of the solids due to fluid flow. It predicts reasonably experimental volumetric sand production data from a hollow cylinder test on a weak sandstone. The test results show that in weak and compactive sandstones, sand production is associated with decohesioning and plasticification of a zone around the inner hole which can then be mobilized by the hydrodynamic forces of the fluid flow. The sand production rate increases both with external applied stress and fluid flow rate but it is constant with time under constant external stress and fluid flow rate. In both cases a critical lower limit has to be exceeded for sand production initiation. Copyright © 2001 John Wiley & Sons, Ltd.

Introduction to Riemannian Manifolds

Abstract: Let M (resp. N) be a connected. smooth (= C x ) n-dimensional manifold without boundary. We denote by C x (M) the ring of smooth real valued functions on M and by x(M) the Lie-algebra of all smooth vector fields on M. Recall that X ∈ x(M) is a smooth map $$X:M \to TM = \mathop U\limits_{x \in M} {T_x}M$$ such that X (x) = X x , ∈ T x M (= the tangent space of Mat x) for each x ∈ M. T x M may be characterized as the space of all derivations of the algebra of smooth real valued functions defined on neighborhoods of x. Note that a vector field X and a function f ∈ C x (M) give rise to a new function X (f) ∈ C x (M) defined by $$X(f)(x) = {X_x}(f).x \in M$$ .

Optimal Feeder Routing in Distribution System Planning Using Dynamic Programming Technique and GIS Facilities

Abstract: Optimal feeder routing is an important part of the general optimal distribution network planning. This paper proposes a new algorithm for the optimal feeder routing problem using the dynamic programming technique and geographical information systems (GIS) facilities. All practical issues, such as cost parameters (investments, line losses, reliability) and technical constraints (voltage drop and thermal limits), as well as physical routing constraints (obstacles, high-cost passages, existing line sections) are taken into consideration. The algorithm developed is validated comparing its results for a simplified study case, with those obtained by an established solver. The effectiveness of the algorithm is further illustrated for a "real-world" study case.

Rheological properties of fluid fruit and vegetable puree products: compilation of literature data

Abstract: Recently published values of rheological properties of fluid fruit and vegetable puree products were retrieved from the literature and analyzed. The results of more than 10 materials are presented, concerning the reported ranges of variation of Consistency Coefficient and Flow Behavior Index, together with the corresponding ranges of variation of concentration and temperature. The related literature sources are presented for each material. Empirical models, relating both Consistency Coefficient and Flow Behavior Index to concentration and temperature, are proposed and fitted to all retrieved data for each material. The data were screened carefully, using residual analysis techniques.

Enzymatic synthesis of hydrophilic and hydrophobic derivatives of natural phenolic acids in organic media

Abstract: The enzymatic esterification of natural phenolic antioxidants such as cinnamic acid and benzoic acid derivatives, with aliphatic alcohols, monosaccharides as well as alkylglucosides, using various lipases and esterases in non-aqueous media, was investigated. Reaction rate and esterification yield seems to be linked to the structural characteristics of the substrates (aromatic acids and alcohols or sugars) used.

Structural properties of dehydrated products during rehydration

Abstract: The following structural properties of dehydrated apple, banana, carrot and potato were examined during rehydration: true density, apparent density, porosity and specific volume. Samples were dehydrated using five different drying methods: conventional, vacuum, freeze, microwave and osmotic; after which they were rehydrated in an air dryer at 50 °C and 80% air humidity. Structural properties were examined during rehydration to various moisture contents, ranging from 0.01 to 3.5 kg kg -1 (dry basis). The dehydrated products did not recover their structural properties after rehydration as a result of structural damage that occurred during drying and the hysteresis phenomenon which took place during rehydration. Porosity of the rehydrated products was higher during rehydration than during dehydration. A generalized structural model was used to describe the structural properties, and of the four parameters that were incorporated, only the shrinkage coefficient, which represents volume expansion, changed on rehydration. Les proprietes structurales (densite, porosite, volume specifique) des pommes, bananes, carottes, pommes de terre deshydratees selon 5 procedes (conventionnel, sous vide, lyophilisation, microonde, et osmotique) ont ete etudiees lors de leur rehydratation dans un secheur a 50° et 80% d'humidite. Les produits deshydrates ne recuperent pas toutes leurs proprietes apres rehydratation a cause des dommages occasionnes par la deshydratation.

Knowledge networking: a holistic solution for leveraging corporate knowledge

Abstract: Two main approaches to knowledge management (KM) have been followed by early adopters of the principle: the process‐centred approach, that mainly treats KM as a social communication process; and the product‐centred approach, that focuses on knowledge artefacts, their creation, storage and reuse in computer‐based corporate memories. This distinction is evident not only in KM implementations in companies, but also in supporting methodologies and tools. This paper presents the Know‐Net solution that aims to innovatively fuse the process‐centred approach with the product‐centred approach by developing a knowledge asset‐centric design. The Know‐Net solution includes a theoretical framework, a corporate transformation and measurement method and a software tool.

A finite element displacement formulation for gradient elastoplasticity

Abstract: We present a second gradient elastoplastic model for strain-softening materials based entirely on a finite element displacement formulation. The stress increment is related to both the strain increment and its Laplacian. The displacement field is the only field needed to be discretized using a C-1 continuity element. The required higher-order boundary conditions arise naturally from the displacement field. The model is developed to regularize the ill-posedness caused by strain-softening material behaviour. The gradient terms in the constitutive equations introduce an extra material parameter with dimensions of length allowing robust modelling of the post-peak material behaviour leading to localization of deformation. Mesh insensitivity is demonstrated by modelling localization of deformation in biaxial tests. It is shown that both the thickness and inclination of the shear-band zone are insensitive to the mesh directionality and refinement and agree with the expected theoretical and experimental values.

Machine Learning in Medical Applications

Abstract: Machine Learning (ML) provides methods, techniques, and tools that can help solving diagnostic and prognostic problems in a variety of medical domains. ML is being used for the analysis of the importance of clinical parameters and their combinations for prognosis, e.g. prediction of disease progression, extraction of medical knowledge for outcome research, therapy planning and support, and for the overall patient management. ML is also being used for data analysis, such as detection of regularities in the data by appropriately dealing with imperfect data, interpretation of continuous data used in the Intensive Care Unit, and intelligent alarming resulting in effective and efficient monitoring. It is argued that the successful implementation of ML methods can help the integration of computer-based systems in the healthcare environment providing opportunities to facilitate and enhance the work of medical experts and ultimately to improve the efficiency and quality of medical care. Below, we summarize some major ML applications in medicine.