- TEI of Larisa
Computer Science & Telecommunications
Larisa - 41110 - 2410684576
- TEI of Thessaly, Department of Computer Science and Engineering, Faculty Memberadd
- Instrumentation Engineering, Control Engineering, Digital Signal Processing, Cross Correlation, Sensors and Sensing, Robotics, and 13 moreBiomedical Engineering, Flowmetering, Electronic Engineering, Mechanical Engineering, Electrical Engineering, Image Processing, GAS TURBINE, Aerodynamics, Compressor, Turbomachinery, Software Engineering, Traffic Monitoring, and Human Reliability and Error in Transportation Systems IN ROADSedit
- Dr. VENTZAS Dimitrios (chartered Electrical & Mechanical Eng, SMISA) is professor at Informatics & Telecommunications... moreDr. VENTZAS Dimitrios (chartered Electrical & Mechanical Eng, SMISA) is professor at Informatics & Telecommunications Dpt at TEI of Larisa with a PhD in Control Eng and Specialization at DSP, Image and Video Processing, Sensors & Measurements and Biomedical Eng. He was Research assistant at University of Bradford, UK in multiphase flow, System and Instrument Eng at HARSA SA, Electronic Eng at Greek Railways and AMBER SA. He has taught at TEI Athens, Lamia and Larisa and at University of Thessaly Mech Eng and postgraduate courses of Mech Eng and Agricultural Eng at U.Th. He is the author of various lecture notes and 30 / 100 papers at international Journals / Conferences with over 100 citations.edit
Control Systems Illustrated (Theory & Technology)
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ABSTRACT Two post processing algorithms for the correction of linearity errors that occur at Analog/Digital Converter (ADC) outputs are presented in this paper. One of these algorithms corrects periodic DNL errors lower than 1LSB (Least... more
ABSTRACT Two post processing algorithms for the correction of linearity errors that occur at Analog/Digital Converter (ADC) outputs are presented in this paper. One of these algorithms corrects periodic DNL errors lower than 1LSB (Least Significant Bit) while the second one can be used in any case of severe DNL variation at successive ADC output codes. Simulations based on the output of a real ADC show that the combination of these two algorithms can improve the Signal to Noise and Distortion Ratio (SNDR) by up to 6dB in ...
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... Sze, SM, 'Semiconductor Sensors', John Wiley & Sons, New York, 1994. Ventzas, DE, Tsitsipis P, Kalovrektis K, Varzakas K, (1998) 'Microcontroller Control of... more
... Sze, SM, 'Semiconductor Sensors', John Wiley & Sons, New York, 1994. Ventzas, DE, Tsitsipis P, Kalovrektis K, Varzakas K, (1998) 'Microcontroller Control of anElectro-Pneumatic Manipulator', Euriscon 98, SIRES/IEEE/CSS, June, pp.98. ...
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Go to AGRIS search. Try it! MC68HC11 microcontroller control of a greenhouse environment as a time delay system. Ventzas, DE (Control and Instrumentation Eng., TEI Lamia- Lamia 35100 (Greece)). Publisher, Pergamon/Elsevier Science Ltd,... more
Go to AGRIS search. Try it! MC68HC11 microcontroller control of a greenhouse environment as a time delay system. Ventzas, DE (Control and Instrumentation Eng., TEI Lamia- Lamia 35100 (Greece)). Publisher, Pergamon/Elsevier Science Ltd, Oxford (United Kingdom). Date of publication, 1999. AGRIS Categories, ...
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In this paper a capnograph expert system that performs patient medical diagnosis and instrument fault detection is implemented, based on clinical capnography data and experience. This is achieved through a computerised capnograph.... more
In this paper a capnograph expert system that performs patient medical diagnosis and instrument fault detection is implemented, based on clinical capnography data and experience. This is achieved through a computerised capnograph. Capnography technology is summarised and a preliminary evaluation of the expert system is made.
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This paper examines and compares the maintenance techniques met in refineries; it focus in the preventive maintenance methods and their statistics and technology. The comparison is extended to electronic/mechanical components - systems... more
This paper examines and compares the maintenance techniques met in refineries; it focus in the preventive maintenance methods and their statistics and technology. The comparison is extended to electronic/mechanical components - systems met in chemical and general production plants. Interaction of maintenance to other production phases is discussed. Maintenance has a strategic role inside a company due to safety, productivity and economic demands of their increasingly antagonistic environment. Cost analysis and efficient operation of the installed machinery is a must. The rapid recognition of developing problems and health monitoring during the operation should be a common practice of a modern factory.
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The requirements of the industry with regards to the safety from the instrumentation technology aspect, of electronics is discussed. Redundant codings protect against risks through defects in the hardware only, when the requirements of... more
The requirements of the industry with regards to the safety from the instrumentation technology aspect, of electronics is discussed. Redundant codings protect against risks through defects in the hardware only, when the requirements of instrumentation technology functioning are fulfilled.
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Temporal data warehouses (TDWs) have been developed for the management of time-varying data in dimensions. This paper presents a new approach for the logical modelling of TDWs. The novel design is based on the integration of two schemata,... more
Temporal data warehouses (TDWs) have been developed for the management of time-varying data in dimensions. This paper presents a new approach for the logical modelling of TDWs. The novel design is based on the integration of two schemata, the star schema and the snowflake schema, to the temporal starnest schema. Time in the temporal starnest schema is not treated as another dimension but as time attributes in every temporal dimension, i.e., dimension tables dependent on time. Time manipulation functions for the treatment of time attributes are provided in the query language. The temporal starnest schema proposed in this paper expresses naturally hierarchy levels by the clustering of data in nested tables, with resulting description of aggregation levels for a dimension in a natural way. The proposed extension is applied to a TDW for accident monitoring in crossroads where the expressive power of the model is exemplified with several temporal queries expressed in a suitable extension of SQL standard.
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Create New Account; Login. Search or Buy Articles; Browse Journals; Search Proceedings; Subscriptions; Submission Information; Submit your Paper; Journal Review; Recommend to Your Library. Browse Journals. Browse Proceedings. Peak... more
Create New Account; Login. Search or Buy Articles; Browse Journals; Search Proceedings; Subscriptions; Submission Information; Submit your Paper; Journal Review; Recommend to Your Library. Browse Journals. Browse Proceedings. Peak Searching Algorithms and Applications. Dimitrios Ventzas and Nikolaos Petrellis. Keywords. Peak, Maximum, Search, Algorithm, minimum, extreme. Abstract. The paper studies the peak searching algorithms and suggests future peak searching research tasks. ...
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ABSTRACT: The fluidized bed modeling and control is investigated, focusing in fluidized bed combustors. The two phase Davidson's flow model is limited, since it considers constant bubble size and rising velocity. Recent research work... more
ABSTRACT: The fluidized bed modeling and control is investigated, focusing in fluidized bed combustors. The two phase Davidson's flow model is limited, since it considers constant bubble size and rising velocity. Recent research work in two and three dimensional (atmospheric, circulating and pressurized) fluidized beds concluded that the intrinsic transient motion of gas bubbles in freely bubbling fluidized beds, contains multiple mechanisms for both fluidization, combustion and erosion processes, such as, bubble size ...
Abstract: A flow valve is an integral part of any process loop; it is usually accompanied by an accurate sensor (a flowmeter) giving an additional tool in treating valve with modern AI tools by integrating some intelligent features. The... more
Abstract: A flow valve is an integral part of any process loop; it is usually accompanied by an accurate sensor (a flowmeter) giving an additional tool in treating valve with modern AI tools by integrating some intelligent features. The control valve and its flow characteristic must fit the process, while the actuator must operate reliably. In conventional process flow loops this is an unquestioned matter after installation, but with AI this is continuously tested.
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INTRODUCTION: Combustion in fluidized bed combustors includes mixing, reaction kinetics and bed particle motions, ie it is highly nonlinear dynamic process. The paper statistically correlates flow, acoustic, ultrasonic, pressure data... more
INTRODUCTION: Combustion in fluidized bed combustors includes mixing, reaction kinetics and bed particle motions, ie it is highly nonlinear dynamic process. The paper statistically correlates flow, acoustic, ultrasonic, pressure data series, ie these parameters with bed fluid dynamics. The data are used for statistical analysis (stationarity), state classification and combustor diagnostics. Nostationary processes behave as transport phenomena, ie present similar statistical properties, but in space, not in time.
A method to implement the optimal distributed Lainiotis filter is proposed. The method is based on the a-priori determination of the optimal distribution of the measurements in parallel processors, in the sense of minimizing the... more
A method to implement the optimal distributed Lainiotis filter is proposed. The method is based on the a-priori determination of the optimal distribution of the measurements in parallel processors, in the sense of minimizing the computation time. The resulting optimal Lainiotis filter presents high parallelism speedup. This is very important due to the fact that, in most real-time applications, it is essential to obtain the estimate in the shortest possible time.
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A powder feeder consisting of a fluidized bed rig and transfer nozzle was modeled. A multiphase mass flowmeter was designed and calibrated. The system is transfer function and the MIMO closed loop control response comprised the... more
A powder feeder consisting of a fluidized bed rig and transfer nozzle was modeled. A multiphase mass flowmeter was designed and calibrated. The system is transfer function and the MIMO closed loop control response comprised the multivariable controller model. Theoretical modeling was simulated by a computer and experimental rig results were obtained to describe the partial and the overall fluidized bed response.
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This paper is dealing with the modelling of the mechanism of coastal oil spill and the recruiting coastal clean-up operations. No two spill operations are alike. There are however. common features in each oil spill which can be of use in... more
This paper is dealing with the modelling of the mechanism of coastal oil spill and the recruiting coastal clean-up operations. No two spill operations are alike. There are however. common features in each oil spill which can be of use in pre-planning activities.
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" Severe Pipeline Analog/Digital Converter (ADC) linearity errors often occur at specific codes that represent the maximum and minimum... more
" Severe Pipeline Analog/Digital Converter (ADC) linearity errors often occur at specific codes that represent the maximum and minimum values of a pipeline stage. If a 2-stage pipeline 8-bit ADC consisting of a 4-bit coarse and a 4-bit fine ADC stage is considered, then the highest linearity error is observed at output codes of the binary form: xxxx0000 or xxxx1111. This is caused by the slightly different component behavior at different input signal ranges as well as the component mismatches and process variations. The post-processing scheme proposed by the authors is a low complexity digital Output Mapper that assigns the actual ADC output codes to a representation with a 1-bit higher resolution. The original codes that have an excessively long duration are assigned to a sequence of successive codes with 1-bit higher resolution (through interpolation) taking into consideration the input signal frequency, while the rest of the codes are simply shifted properly. Behavioral simulations of the proposed architecture show that the Signal to Noise and Distortion Ratio (SNDR) of an 8-bit ADC can be increased by up to 6dB. The proof of concept is evaluated by a spreadsheet application while the behavior of the Output Mapper is simulated in Matlab. "
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A method for the short term prediction and correction of an A/D Converter output behaviour is described in this paper. It actually smooths the A/D Converter output curve by removing severe linearity and non-monotonic errors. The iterative... more
A method for the short term prediction and correction of an A/D Converter output behaviour is described in this paper. It actually smooths the A/D Converter output curve by removing severe linearity and non-monotonic errors. The iterative use of this method can enhance the Signal to Noise and Distortion Ratio of an A/D Converter by more than 10dB or 35% in some cases. A digital implementation with low complexity for this short term predictor is proposed.
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The paper presents the systematic steps to design an Image Processing software system for greenhouse agricultural environment management. By monitoring general and specific environment scenes we can parameterize the agricultural... more
The paper presents the systematic steps to design an Image Processing software system for greenhouse agricultural environment management. By monitoring general and specific environment scenes we can parameterize the agricultural environment in a greenhouse. Decision making reliability is enhanced by expert system knowledge acquisition and comparison in automatic and manual video monitoring systems. The system is intended to be integrated into an automatic Unattended Autonomous Surveillance (UAS), by using an Intelligent Greenhouse Monitoring System (IGMS) based on email, SMS (short message service) and streaming video or MMS technology.
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A knowledge intensive "shallow" Expert System designed for Process Control normally requiring human operator... more
A knowledge intensive "shallow" Expert System designed for Process Control normally requiring human operator expertise is described. The inference engine of the system, that part of the Expert System that selects data and rules to immitate the human expert's decision making process is supported by forward chaining reasoning methods.
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"In the present work, a scheme for industrial active control of a circulating biomass fluidized bed combustor - heater system is proposed, modeled and simulated. Different control... more
"In the present work, a scheme for industrial active control of a circulating biomass fluidized bed combustor - heater system is proposed, modeled and simulated. Different control architectures are considered, based on overall fluidization and combustion control dynamics rather than control theory alone. Classical multivariable control based on modern instrumentation is applied on the fluidized bed combustion reactor, in close conformity with fluidization and combustion dynamics, if an optimal result must be achieved. "
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The paper presents a counter current flow rotary dryer model for heat transfer and for humidity control; dryer state variables functions and relations are given. Control algorithms such as single or multiple control variables and... more
The paper presents a counter current flow rotary dryer model for heat transfer and for humidity control; dryer state variables functions and relations are given. Control algorithms such as single or multiple control variables and conventional or model-based and intelligent control schemes are investigated. Simulation results are given.
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Distributed Control Systems tend to dominate in modern process industries due to safety, reliability, availability and redndancy reasons. DCS have to perform complicated control functions. This paper describes the use of microprogrammed... more
Distributed Control Systems tend to dominate in modern process industries due to safety, reliability, availability and redndancy reasons. DCS have to perform complicated control functions. This paper describes the use of microprogrammed structures in LSI architectures and bit-slice computers for process control.
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The paper describes the design philosophy taken into consideration for a refinery's distributed process control system. It ensures reliability, availability and maintenability. The entire DPCS incudes... more
The paper describes the design philosophy taken into consideration for a refinery's distributed process control system. It ensures reliability, availability and maintenability. The entire DPCS incudes 9 control centers. The architecture of the field control station is discussed. The memory copy and data transfer ensures smooth transfer to the back-up controller. Redundancy is enhanced by customer additional requirements, such as communication bus redundancy, operational grouping and duplication of displays. The signals interface to the DPCS and the man-machine interface are presented. Industrial environment realistic problems are incuded.
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Obstacles detection techniques complement vision in many applications including robotics minimizing the danger to damage the device itself. The mechanism presented here is a simple mechanical one. It uses a high speed dc motor which... more
Obstacles detection techniques complement vision in many applications including robotics minimizing the danger to damage the device itself. The mechanism presented here is a simple mechanical one. It uses a high speed dc motor which energizes through a system of gears a moving wheel; the friction of this wheel to the floor is used to rotate the gyroscopic mechanism of its support to the robot/vehicle and change the direction of its motion. The rotation is achieved by the eccetricity of the moving wheel to teh vertical axis of robot's freedom of movement. The paper presents the model of such a mechanism and its stability margins, related to its main design and operation parameters. A combiantion of such a mechanism in robots can give bidirectional rotation.
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This paper gives the design features / paremeters of a prototype software correlator suitable for flowmeters based on the cross-correlation principle. The algorithm used is a... more
This paper gives the design features / paremeters of a prototype software correlator suitable for flowmeters based on the cross-correlation principle. The algorithm used is a "skip" one (Lumley, 1978); it minimizes the processing load while it achieves adequate repeatability in correlogram representation and therefore increases the BW of the processed signals.