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Papers by Andrei Ungureanu

Research paper thumbnail of ABOUT AXIAL CLAMPING FORCE MONITORING AT POWER TRANSFORMER WINDINGS DURING THEIR ACTIVE LIFETIME

The variation of the axial clamping forces of the windings cannot be monitored over the active li... more The variation of the axial clamping forces of the windings cannot be monitored over the active lifetime of the transformers. The insurance of a preset level of the forces has a determinant role in maintaining the safety in operation at short-circuit stresses. The paper describes the generation modes of the axial forces in transformers as well as the evaluation of the mechanical condition of the power transformers. Axial force calculation and the theoretical aspects referring to the mechanical structure for the fastening of the corewinding assembly shows the importance of these constructive part design in maintaining the mechanical stability under the action of the short-circuit forces. There are presented critical situations related to the behaviour of the multi-layer windings from the Continuously Transposed Cables (CTC).

Research paper thumbnail of Implementation of Fuzzy Logic in Power Engineering using Virtual Instrumentation

Abstract—Curricula for power engineering programs have undergone substantial change in the past y... more Abstract—Curricula for power engineering programs have undergone substantial change in the past years as modern techniques for analysis and design of power systems find their way,into these courses. The paper presents a laboratory controller, implemented as a virtual instrument that mimics a real fuzzy logic controller for a boiler system in a thermal power plant. The instrument is dedicated to

Research paper thumbnail of Distributed Intelligent System for Personalized Therapy of Speech Disorders

The aim of this paper is to describe an intelligent system designed for assisting the personalize... more The aim of this paper is to describe an intelligent system designed for assisting the personalized therapy of dyslalia for the Romanian prescholars children. This system is developed in the frame of TERAPERS project that can be included in a very important research area: informational technologies in response to society challenges -for health: early diagnosis, personalized therapy. Taking into consideration the fact that Romanian language is a phonetic one that has its own special linguistic particularities, there is a real need for the development and use of audio-video systems, which can be used in the therapy of different speech problems. The system has a high degree of originality because his objective is to treat the pronunciation disorders in Romanian language. Also the complexity of the project results from the high number of different research areas involved: artificial intelligence, virtual reality, digital signal processing, digital electronic and psychology.

Research paper thumbnail of Patient Monitoring: Wearable Device for Patient Monitoring

The increasing request of patients, suffering of chronic diseases, who wish to stay at home rathe... more The increasing request of patients, suffering of chronic diseases, who wish to stay at home rather then in a hospital and also the increasing need of homecare monitoring for elderly people, have lead to a high demand of wearable medical devices. Also, extended patient monitoring during normal activity has become a very important target. Low power consumption is essential in continuously monitoring of vital-signs and can be achieved combining very high storage capacity, wireless communication, and ultra-low power circuits together with firmware management of power consumption. This approach allows the patient to move unconstraint around an area, city or country. In this paper the design of ultra low power wearable monitoring devices based on ultra low power circuits, high storage memory flash, bluetooth communication and the firmware for the management of the monitoring device are presented.

Research paper thumbnail of Using a zero-magnetization ferromagnet as the pinning layer in exchange-bias systems

Physical Review B, 2010

Exchange bias properties have been investigated in a (Sm1-xGdxAl2/SmAl2) bilayer (for x=0.028 ) w... more Exchange bias properties have been investigated in a (Sm1-xGdxAl2/SmAl2) bilayer (for x=0.028 ) with perpendicular magnetization, an original exchange-coupled system based on the zero magnetization ferromagnet (Sm1-xGdxAl2) as the pinning layer. This unusual magnet exhibits a magnetic compensation temperature where it presents both a zero magnetization and a long-range spin ferromagnetic order. In the (Sm1-0.028Gd0.028Al2/SmAl2) bilayer, a large positive exchange bias has been observed for the SmAl2 magnetization reversal, attesting for the exchange coupling between both compounds, even at the Sm1-0.028Gd0.028Al2 magnetic compensation temperature; the magnetization of the Sm1-0.028Gd0.028Al2 part of the bilayer appears to be pinned but the pinned component is obviously smaller than the one observed in a single uncovered Sm1-0.028Gd0.028Al2 . X-ray Magnetic Circular Dichroïsm experiments have been undertaken to investigate the magnetization reversal in both layers independently and more particularly to probe the Sm1-0.028Gd0.028Al2 behavior in its zero-magnetization state. They reveal that approximately 20% of the Sm1-0.028Gd0.028Al2 layer is driven to reverse by exchange coupling to SmAl2 . The presence of lateral domains in the Sm1-0.028Gd0.028Al2 layer likely accounts for the relatively large proportion of rotatable moments and for the observed temperature dependence of exchange-bias field.

Research paper thumbnail of The modification of phenyl - pyridine compounds under UV irradiation: FTIR investigation

Phenyl-pyridine compounds present a high interest for Photodynamic Therapy due to their important... more Phenyl-pyridine compounds present a high interest for Photodynamic Therapy due to their important anti-inflammatory and anti-tumor properties. In this study, two phenyl-pyridine compounds were investigated BG204 (3-amino, 9-thio [2-N-Ndiethylaminoethyl] acridine) and BG 1120 (4,5 bis [thio(2-N-N-diethylaminoethyl)], 9methyl 1,8-diazantracene), because they present modification during UV irradiation. In order to elucidate these modifications FTIR spectroscopy was used. BG204 and BG1120 were UV irradiated using a Xe lamp, with a power density of 11mW/cm 2 , for 1 hour, and 3 hours, respectively. The FTIR spectra, in the range of 4000 cm -1 -400 cm -1 , were performed by a Nicolet Magna IR 550 spectrometer. The results of the analyzed samples showed that these molecules are photo-reactive, and their therapeutic effects can be improved by UV irradiation.

Research paper thumbnail of ABOUT AXIAL CLAMPING FORCE MONITORING AT POWER TRANSFORMER WINDINGS DURING THEIR ACTIVE LIFETIME

The variation of the axial clamping forces of the windings cannot be monitored over the active li... more The variation of the axial clamping forces of the windings cannot be monitored over the active lifetime of the transformers. The insurance of a preset level of the forces has a determinant role in maintaining the safety in operation at short-circuit stresses. The paper describes the generation modes of the axial forces in transformers as well as the evaluation of the mechanical condition of the power transformers. Axial force calculation and the theoretical aspects referring to the mechanical structure for the fastening of the corewinding assembly shows the importance of these constructive part design in maintaining the mechanical stability under the action of the short-circuit forces. There are presented critical situations related to the behaviour of the multi-layer windings from the Continuously Transposed Cables (CTC).

Research paper thumbnail of Implementation of Fuzzy Logic in Power Engineering using Virtual Instrumentation

Abstract—Curricula for power engineering programs have undergone substantial change in the past y... more Abstract—Curricula for power engineering programs have undergone substantial change in the past years as modern techniques for analysis and design of power systems find their way,into these courses. The paper presents a laboratory controller, implemented as a virtual instrument that mimics a real fuzzy logic controller for a boiler system in a thermal power plant. The instrument is dedicated to

Research paper thumbnail of Distributed Intelligent System for Personalized Therapy of Speech Disorders

The aim of this paper is to describe an intelligent system designed for assisting the personalize... more The aim of this paper is to describe an intelligent system designed for assisting the personalized therapy of dyslalia for the Romanian prescholars children. This system is developed in the frame of TERAPERS project that can be included in a very important research area: informational technologies in response to society challenges -for health: early diagnosis, personalized therapy. Taking into consideration the fact that Romanian language is a phonetic one that has its own special linguistic particularities, there is a real need for the development and use of audio-video systems, which can be used in the therapy of different speech problems. The system has a high degree of originality because his objective is to treat the pronunciation disorders in Romanian language. Also the complexity of the project results from the high number of different research areas involved: artificial intelligence, virtual reality, digital signal processing, digital electronic and psychology.

Research paper thumbnail of Patient Monitoring: Wearable Device for Patient Monitoring

The increasing request of patients, suffering of chronic diseases, who wish to stay at home rathe... more The increasing request of patients, suffering of chronic diseases, who wish to stay at home rather then in a hospital and also the increasing need of homecare monitoring for elderly people, have lead to a high demand of wearable medical devices. Also, extended patient monitoring during normal activity has become a very important target. Low power consumption is essential in continuously monitoring of vital-signs and can be achieved combining very high storage capacity, wireless communication, and ultra-low power circuits together with firmware management of power consumption. This approach allows the patient to move unconstraint around an area, city or country. In this paper the design of ultra low power wearable monitoring devices based on ultra low power circuits, high storage memory flash, bluetooth communication and the firmware for the management of the monitoring device are presented.

Research paper thumbnail of Using a zero-magnetization ferromagnet as the pinning layer in exchange-bias systems

Physical Review B, 2010

Exchange bias properties have been investigated in a (Sm1-xGdxAl2/SmAl2) bilayer (for x=0.028 ) w... more Exchange bias properties have been investigated in a (Sm1-xGdxAl2/SmAl2) bilayer (for x=0.028 ) with perpendicular magnetization, an original exchange-coupled system based on the zero magnetization ferromagnet (Sm1-xGdxAl2) as the pinning layer. This unusual magnet exhibits a magnetic compensation temperature where it presents both a zero magnetization and a long-range spin ferromagnetic order. In the (Sm1-0.028Gd0.028Al2/SmAl2) bilayer, a large positive exchange bias has been observed for the SmAl2 magnetization reversal, attesting for the exchange coupling between both compounds, even at the Sm1-0.028Gd0.028Al2 magnetic compensation temperature; the magnetization of the Sm1-0.028Gd0.028Al2 part of the bilayer appears to be pinned but the pinned component is obviously smaller than the one observed in a single uncovered Sm1-0.028Gd0.028Al2 . X-ray Magnetic Circular Dichroïsm experiments have been undertaken to investigate the magnetization reversal in both layers independently and more particularly to probe the Sm1-0.028Gd0.028Al2 behavior in its zero-magnetization state. They reveal that approximately 20% of the Sm1-0.028Gd0.028Al2 layer is driven to reverse by exchange coupling to SmAl2 . The presence of lateral domains in the Sm1-0.028Gd0.028Al2 layer likely accounts for the relatively large proportion of rotatable moments and for the observed temperature dependence of exchange-bias field.

Research paper thumbnail of The modification of phenyl - pyridine compounds under UV irradiation: FTIR investigation

Phenyl-pyridine compounds present a high interest for Photodynamic Therapy due to their important... more Phenyl-pyridine compounds present a high interest for Photodynamic Therapy due to their important anti-inflammatory and anti-tumor properties. In this study, two phenyl-pyridine compounds were investigated BG204 (3-amino, 9-thio [2-N-Ndiethylaminoethyl] acridine) and BG 1120 (4,5 bis [thio(2-N-N-diethylaminoethyl)], 9methyl 1,8-diazantracene), because they present modification during UV irradiation. In order to elucidate these modifications FTIR spectroscopy was used. BG204 and BG1120 were UV irradiated using a Xe lamp, with a power density of 11mW/cm 2 , for 1 hour, and 3 hours, respectively. The FTIR spectra, in the range of 4000 cm -1 -400 cm -1 , were performed by a Nicolet Magna IR 550 spectrometer. The results of the analyzed samples showed that these molecules are photo-reactive, and their therapeutic effects can be improved by UV irradiation.