A. Dentsoras - Academia.edu (original) (raw)

Papers by A. Dentsoras

Research paper thumbnail of A Search Method In Knowledge-Based Systems Using Enclidean Space Norm - An Application To Design Of Robot Grippers

WIT Transactions on Information and Communication Technologies, 1970

Research paper thumbnail of Modelling the dynamic characteristics of a robot arm joint

Robotics and Computer-Integrated Manufacturing, 1991

ABSTRACT

Research paper thumbnail of Fatigue crack propagation in resonating machine members at elevated room temperatures

Research paper thumbnail of Redundancy Eliminations and Plausible Assumptions of Design Parameters for Evaluating Design Alternatives

Evaluation of design alternatives is an important task for engineering design and its results aff... more Evaluation of design alternatives is an important task for engineering design and its results affect strongly the outcome of decision-making processes and the quality of the artifact being designed. In the present paper, a method is proposed based on representation of alternatives through associative weighted digraphs of design parameters and use of performance variables defined according to evaluation criteria. The method relies on designer-guided eliminations of redundancies of common design parameters among different alternatives and plausible assumptions about value domains of design parameters that take part in the evaluation process. Eliminations of redundancies of common design parameters lead to unified digraphs for all alternatives and the introduction of Plausible Assumptions’ Matrix systematizes the process of assigning feasible value domains for all types of all design parameters. Linear approximate calculation formulas pertaining to the unified digraphs are also introdu...

Research paper thumbnail of Automatic configuration of chromosomes for genetic algorithm-based optimization in well-defined design problems

Research paper thumbnail of An index that correlates service performance and energy consumption of belt conveyors

FME Transaction

In the present paper, an index is proposed for belt conveyors that represents the evaluation of t... more In the present paper, an index is proposed for belt conveyors that represents the evaluation of the overall functional/design efficiency by considering both energy and service performance. To obtain index value, energy consumption data-that are extracted from a detailed energy analysis of the examined conveyor-are correlated to service performance data derived from the analysis of material handling capability of the conveyor within the context of the set operational requirements and functional conditions. The proposed index is exemplified through a case study of a simple inclined belt conveyor for which a detailed energy consumption model is developed. Different technical specifications and operational conditions are tested. The proposed approach proves that the index depicts adequately the effect of any design solution or operational decision to the overall efficiency of the conveyor.

Research paper thumbnail of Knowledge representation and reasoning in case-based design systems

Research paper thumbnail of A fuzzy system for AGV navigation and obstacle avoidance

Research paper thumbnail of Optimal initial positioning of excavators in digging processes

Research paper thumbnail of Determination of position of elevator systems in buildings based on expertise and heuristic problem space search

Research paper thumbnail of Artificial neural networks used for the performance prediction of a thermosiphon solar water heater

Renewable Energy, 1999

Arti_cial Neural Networks "ANN# are widely accepted as a technology o}ering an alternative way to... more Arti_cial Neural Networks "ANN# are widely accepted as a technology o}ering an alternative way to tackle complex and ill!de_ned problems[ They can learn from examples\ are fault tolerant\ are able to deal with non!linear problems\ and once trained can perform prediction at high speed[ ANNs have been used in diverse applications and they have shown to be particularly e}ective in system modelling as well as for system identi_cation[ The objective of this work is to train an arti_cial neural network "ANN# to learn to predict the performance of a thermosiphon solar domestic water heating system[ This performance is measured in terms of the useful energy extracted and of the stored water temperature rise[ An ANN has been trained using performance data for four types of systems\ all employing the same collector panel under varying weather conditions[ In this way the network was trained to accept and handle a number of unusual cases[ The data presented as input were\ the storage tank heat loss coe.cient "U!value#\ the type of system "open or closed#\ the storage volume\ and a total of _fty!four readings from real experiments of total daily solar radiation\ total daily di}use radiation\ ambient air temperature\ and the water temperature in storage tank at the beginning of the day[ The network output is the useful energy extracted from the system and the water temperature rise[ The statistical coe.cient of multiple determination "R 1 !value# obtained for the training data set was equal to 9[8803 and 9[8797 for the two output parameters respectively[ Both values are satisfactory because the closer R 1 !value is to unity the better is the mapping[ Unknown data for all four systems were subsequently used to investigate the accuracy of prediction[ These include performance data for the systems considered for the training of the network at di}erent weather conditions[ Predictions with maximum deviations of 0 MJ and 1[1>C were obtained respectively[ Random data were also used both with the performance Corresponding author[ Tel[] 99 246 1 295088^fax] 99 246 1 383842^e!mail] skalogirÝspidernet[com[cy

Research paper thumbnail of Using Case-Based Reasoning and Soft Computing Techniques for the Initialization of Engineering Design Optimization

Volume 1: Advanced Energy Systems, Advanced Materials, Aerospace, Automation and Robotics, Noise Control and Acoustics, and Systems Engineering, 2006

ABSTRACT From a certain point of view, parametric engineering design may be considered as an opti... more ABSTRACT From a certain point of view, parametric engineering design may be considered as an optimization problem. The design problem may be represented through a set of design parameters. The optimal solution is located by using a set of competing design parameters and its evaluation is based upon specific criteria. A significant number of techniques and methodologies have been proposed in order to perform this difficult task. The selection of the appropriate one(s) depends strongly upon the nature and the specific characteristics of the design problem under consideration. The majority of these techniques and methodologies rely on the definition of some initial conditions. Wrong, misleading or incomplete initial conditions may result to solutions characterized by local optimality or may need excessive computational time in order to converge to either an optimal or a sub-optimal solution. In the context of the current work, two different approaches are used for initializing the optimization process: genetic algorithms and pattern search. Genetic algorithms need an initial population of individual solutions before the genetic operations could be deployed, while the pattern search techniques use a starting (initial) point for the optimization process. These two initial conditions (initial population and initial point) may be defined either randomly or deliberately. The present paper introduces a case-based design (CBD) module as pre-processor to the design optimization. This CBD module is based on an artificial competitive neural network, which is submitted to unsupervised learning by examples based on past design solutions. The new design is represented through fuzzy preferences and weighting factors, which are compiled by the neural network for retrieving similar past solutions. The retrieved solutions are used in order to determine the initial conditions of the optimization method (the initial population for the genetic algorithm (GA) or the starting point for the pattern search). The optimal solution is then searched using the criterion of the maximum aggregated overall preference. A system, namely Case-DeSC, has been developed in the purpose of evaluating the proposed framework in the application area of parametric design of oscillating conveyors. The results show that the proposed optimization methods converge faster to more efficient solutions if case-based reasoning (CBR) is utilized for defining the initial optimization conditions.

Research paper thumbnail of Resolving the Complexity of Functional Representation in Design: A Transition From Computational Relationships to Performance Hierarchical Trees

Volume 3, 2004

ABSTRACT In the present paper, a method is presented based on the exploitation of the computation... more ABSTRACT In the present paper, a method is presented based on the exploitation of the computational relationships among design entities in order to obtain valuable design knowledge concerning the performance and the function of the designed object (artifact, product, machine, etc.). The approach is applicable for most of the design problems and may be used in the design cases where the design problem under consideration can be formally decomposed and expressed in terms of design entities and associative relationships among them. The design knowledge is represented through different hierarchical tree types corresponding to the physical, computational and performance domains. The representation of the design knowledge in terms of computational relationships instead of terms of functional relationships is more convenient and flexible. Design modeling becomes simpler and more direct by assigning values to generic performance variables instead of defining and quantifying functional requirements, the design analysis resolution is adjustable and both the establishment and the categorization of computational operators into classes of sensitivity provide the ability of efficiently surveying and manipulating the relationships in case of value variations. The proposed method is applied to an example case of a conveyor’s design. Some remarks and a reference to future work conclude the paper.

Research paper thumbnail of Optimalno pozicioniranje liftovskog okna u zgradama na osnovu uprošćenog modela cirkulacije

Research paper thumbnail of Evaluation of standardization level of mechanical systems in engineering design

Research paper thumbnail of Formulation and use of criteria for the evaluation of aesthetic attributes of products in engineering design

Research paper thumbnail of Applying expert systems to belt conveyor design

Research paper thumbnail of Integration of computational intelligence applications in engineering design

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2008

Several techniques have been proposed recently as a result of the intensive research done in the ... more Several techniques have been proposed recently as a result of the intensive research done in the field of computational intelligence. These techniques seem to act beneficially in a variety of scientific domains by performing better than the conventional methodologies. The current paper focuses on the domain of engineering design, whose demanding nature motivates the research for domain-independent and efficient tools

Research paper thumbnail of Fuzzy representation and synthesis of concepts in engineering design

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2008

In the present paper a new mathematical fuzzy-logic-based formulation of the design objects and t... more In the present paper a new mathematical fuzzy-logic-based formulation of the design objects and the rules that govern a design problem during the conceptual design phase is presented.. A procedure for the automatic generation of degrees of satisfaction of the design specifications for each feasible solutionsubjected to design constraints -is introduced. A table containing the satisfaction degrees is used for the derivation of the set of all possible synthesized solutions. The determination of this set, which is a subset of the set of the synthesised solutions, is based on a suitable partition of the Euclidean space. An illustrative example of a knowledge based system for the conceptual design of grippers for handling fabrics is presented. The advantages of this model are revealed via a comparison with previous implementations of the conceptual design phase based on crisp production rules or certainty factors.

Research paper thumbnail of Floor circulation index and optimal positioning of elevator hoistways

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2010

ABSTRACT In modern buildings, the position(s) of elevator system(s) affects strongly the efficien... more ABSTRACT In modern buildings, the position(s) of elevator system(s) affects strongly the efficiency of people circulation especially during periods of peak demand. The present study introduces a simple model that correlates circulation data (building type, population size and density, space use, etc.) with structural/architectural data (net usable space, circulation space, structural intrusions, facilities etc) of a typical floor of a building. A circulation index is defined as function of these data and its value is calculated for every cell of the grid that partitions all usable spaces. Euclidean norms are used for calculating weighted mean distance values and for locating the point on floor’s surface that corresponds to minimal mean walking distance to/from the floor’s usable spaces. A heuristic search algorithm combines calculations of distance values, constraints and empirical knowledge for fine tuning hoistway position around this point. A case study of a typical building floor served by a single-elevator system exemplifies the proposed approach.

Research paper thumbnail of A Search Method In Knowledge-Based Systems Using Enclidean Space Norm - An Application To Design Of Robot Grippers

WIT Transactions on Information and Communication Technologies, 1970

Research paper thumbnail of Modelling the dynamic characteristics of a robot arm joint

Robotics and Computer-Integrated Manufacturing, 1991

ABSTRACT

Research paper thumbnail of Fatigue crack propagation in resonating machine members at elevated room temperatures

Research paper thumbnail of Redundancy Eliminations and Plausible Assumptions of Design Parameters for Evaluating Design Alternatives

Evaluation of design alternatives is an important task for engineering design and its results aff... more Evaluation of design alternatives is an important task for engineering design and its results affect strongly the outcome of decision-making processes and the quality of the artifact being designed. In the present paper, a method is proposed based on representation of alternatives through associative weighted digraphs of design parameters and use of performance variables defined according to evaluation criteria. The method relies on designer-guided eliminations of redundancies of common design parameters among different alternatives and plausible assumptions about value domains of design parameters that take part in the evaluation process. Eliminations of redundancies of common design parameters lead to unified digraphs for all alternatives and the introduction of Plausible Assumptions’ Matrix systematizes the process of assigning feasible value domains for all types of all design parameters. Linear approximate calculation formulas pertaining to the unified digraphs are also introdu...

Research paper thumbnail of Automatic configuration of chromosomes for genetic algorithm-based optimization in well-defined design problems

Research paper thumbnail of An index that correlates service performance and energy consumption of belt conveyors

FME Transaction

In the present paper, an index is proposed for belt conveyors that represents the evaluation of t... more In the present paper, an index is proposed for belt conveyors that represents the evaluation of the overall functional/design efficiency by considering both energy and service performance. To obtain index value, energy consumption data-that are extracted from a detailed energy analysis of the examined conveyor-are correlated to service performance data derived from the analysis of material handling capability of the conveyor within the context of the set operational requirements and functional conditions. The proposed index is exemplified through a case study of a simple inclined belt conveyor for which a detailed energy consumption model is developed. Different technical specifications and operational conditions are tested. The proposed approach proves that the index depicts adequately the effect of any design solution or operational decision to the overall efficiency of the conveyor.

Research paper thumbnail of Knowledge representation and reasoning in case-based design systems

Research paper thumbnail of A fuzzy system for AGV navigation and obstacle avoidance

Research paper thumbnail of Optimal initial positioning of excavators in digging processes

Research paper thumbnail of Determination of position of elevator systems in buildings based on expertise and heuristic problem space search

Research paper thumbnail of Artificial neural networks used for the performance prediction of a thermosiphon solar water heater

Renewable Energy, 1999

Arti_cial Neural Networks "ANN# are widely accepted as a technology o}ering an alternative way to... more Arti_cial Neural Networks "ANN# are widely accepted as a technology o}ering an alternative way to tackle complex and ill!de_ned problems[ They can learn from examples\ are fault tolerant\ are able to deal with non!linear problems\ and once trained can perform prediction at high speed[ ANNs have been used in diverse applications and they have shown to be particularly e}ective in system modelling as well as for system identi_cation[ The objective of this work is to train an arti_cial neural network "ANN# to learn to predict the performance of a thermosiphon solar domestic water heating system[ This performance is measured in terms of the useful energy extracted and of the stored water temperature rise[ An ANN has been trained using performance data for four types of systems\ all employing the same collector panel under varying weather conditions[ In this way the network was trained to accept and handle a number of unusual cases[ The data presented as input were\ the storage tank heat loss coe.cient "U!value#\ the type of system "open or closed#\ the storage volume\ and a total of _fty!four readings from real experiments of total daily solar radiation\ total daily di}use radiation\ ambient air temperature\ and the water temperature in storage tank at the beginning of the day[ The network output is the useful energy extracted from the system and the water temperature rise[ The statistical coe.cient of multiple determination "R 1 !value# obtained for the training data set was equal to 9[8803 and 9[8797 for the two output parameters respectively[ Both values are satisfactory because the closer R 1 !value is to unity the better is the mapping[ Unknown data for all four systems were subsequently used to investigate the accuracy of prediction[ These include performance data for the systems considered for the training of the network at di}erent weather conditions[ Predictions with maximum deviations of 0 MJ and 1[1>C were obtained respectively[ Random data were also used both with the performance Corresponding author[ Tel[] 99 246 1 295088^fax] 99 246 1 383842^e!mail] skalogirÝspidernet[com[cy

Research paper thumbnail of Using Case-Based Reasoning and Soft Computing Techniques for the Initialization of Engineering Design Optimization

Volume 1: Advanced Energy Systems, Advanced Materials, Aerospace, Automation and Robotics, Noise Control and Acoustics, and Systems Engineering, 2006

ABSTRACT From a certain point of view, parametric engineering design may be considered as an opti... more ABSTRACT From a certain point of view, parametric engineering design may be considered as an optimization problem. The design problem may be represented through a set of design parameters. The optimal solution is located by using a set of competing design parameters and its evaluation is based upon specific criteria. A significant number of techniques and methodologies have been proposed in order to perform this difficult task. The selection of the appropriate one(s) depends strongly upon the nature and the specific characteristics of the design problem under consideration. The majority of these techniques and methodologies rely on the definition of some initial conditions. Wrong, misleading or incomplete initial conditions may result to solutions characterized by local optimality or may need excessive computational time in order to converge to either an optimal or a sub-optimal solution. In the context of the current work, two different approaches are used for initializing the optimization process: genetic algorithms and pattern search. Genetic algorithms need an initial population of individual solutions before the genetic operations could be deployed, while the pattern search techniques use a starting (initial) point for the optimization process. These two initial conditions (initial population and initial point) may be defined either randomly or deliberately. The present paper introduces a case-based design (CBD) module as pre-processor to the design optimization. This CBD module is based on an artificial competitive neural network, which is submitted to unsupervised learning by examples based on past design solutions. The new design is represented through fuzzy preferences and weighting factors, which are compiled by the neural network for retrieving similar past solutions. The retrieved solutions are used in order to determine the initial conditions of the optimization method (the initial population for the genetic algorithm (GA) or the starting point for the pattern search). The optimal solution is then searched using the criterion of the maximum aggregated overall preference. A system, namely Case-DeSC, has been developed in the purpose of evaluating the proposed framework in the application area of parametric design of oscillating conveyors. The results show that the proposed optimization methods converge faster to more efficient solutions if case-based reasoning (CBR) is utilized for defining the initial optimization conditions.

Research paper thumbnail of Resolving the Complexity of Functional Representation in Design: A Transition From Computational Relationships to Performance Hierarchical Trees

Volume 3, 2004

ABSTRACT In the present paper, a method is presented based on the exploitation of the computation... more ABSTRACT In the present paper, a method is presented based on the exploitation of the computational relationships among design entities in order to obtain valuable design knowledge concerning the performance and the function of the designed object (artifact, product, machine, etc.). The approach is applicable for most of the design problems and may be used in the design cases where the design problem under consideration can be formally decomposed and expressed in terms of design entities and associative relationships among them. The design knowledge is represented through different hierarchical tree types corresponding to the physical, computational and performance domains. The representation of the design knowledge in terms of computational relationships instead of terms of functional relationships is more convenient and flexible. Design modeling becomes simpler and more direct by assigning values to generic performance variables instead of defining and quantifying functional requirements, the design analysis resolution is adjustable and both the establishment and the categorization of computational operators into classes of sensitivity provide the ability of efficiently surveying and manipulating the relationships in case of value variations. The proposed method is applied to an example case of a conveyor’s design. Some remarks and a reference to future work conclude the paper.

Research paper thumbnail of Optimalno pozicioniranje liftovskog okna u zgradama na osnovu uprošćenog modela cirkulacije

Research paper thumbnail of Evaluation of standardization level of mechanical systems in engineering design

Research paper thumbnail of Formulation and use of criteria for the evaluation of aesthetic attributes of products in engineering design

Research paper thumbnail of Applying expert systems to belt conveyor design

Research paper thumbnail of Integration of computational intelligence applications in engineering design

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2008

Several techniques have been proposed recently as a result of the intensive research done in the ... more Several techniques have been proposed recently as a result of the intensive research done in the field of computational intelligence. These techniques seem to act beneficially in a variety of scientific domains by performing better than the conventional methodologies. The current paper focuses on the domain of engineering design, whose demanding nature motivates the research for domain-independent and efficient tools

Research paper thumbnail of Fuzzy representation and synthesis of concepts in engineering design

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2008

In the present paper a new mathematical fuzzy-logic-based formulation of the design objects and t... more In the present paper a new mathematical fuzzy-logic-based formulation of the design objects and the rules that govern a design problem during the conceptual design phase is presented.. A procedure for the automatic generation of degrees of satisfaction of the design specifications for each feasible solutionsubjected to design constraints -is introduced. A table containing the satisfaction degrees is used for the derivation of the set of all possible synthesized solutions. The determination of this set, which is a subset of the set of the synthesised solutions, is based on a suitable partition of the Euclidean space. An illustrative example of a knowledge based system for the conceptual design of grippers for handling fabrics is presented. The advantages of this model are revealed via a comparison with previous implementations of the conceptual design phase based on crisp production rules or certainty factors.

Research paper thumbnail of Floor circulation index and optimal positioning of elevator hoistways

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2010

ABSTRACT In modern buildings, the position(s) of elevator system(s) affects strongly the efficien... more ABSTRACT In modern buildings, the position(s) of elevator system(s) affects strongly the efficiency of people circulation especially during periods of peak demand. The present study introduces a simple model that correlates circulation data (building type, population size and density, space use, etc.) with structural/architectural data (net usable space, circulation space, structural intrusions, facilities etc) of a typical floor of a building. A circulation index is defined as function of these data and its value is calculated for every cell of the grid that partitions all usable spaces. Euclidean norms are used for calculating weighted mean distance values and for locating the point on floor’s surface that corresponds to minimal mean walking distance to/from the floor’s usable spaces. A heuristic search algorithm combines calculations of distance values, constraints and empirical knowledge for fine tuning hoistway position around this point. A case study of a typical building floor served by a single-elevator system exemplifies the proposed approach.