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Craciunescu A.,Polytechnic University of Bucharest | Albu M.,Polytechnic University of Bucharest | Ciumbulea G.S.,Polytechnic University of Bucharest | Necula Dumitrica C.,Universitatea valahia din targoviste
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2014

Voltage unbalance is a common phenomenon in AC power network. This disturbance can bring to the three-phase induction motors connected to the power supply system important drawbacks such as overheating, drop of efficiency and reduction in output torque. Therefore, operation of an induction motor with voltage unbalance above 5% is not recommended and therefore continuous monitoring of voltage unbalance o the supply system is need. In this paper a new method of evaluating the voltage unbalanc index in power distribution networks is proposed. This new approach uses voltage space phasor geometrical locus in polar coordinates based on a modified 'a-b-c' to 'd-q' coordinate transformation which gives the possibility to localize the unbalanced phases and to estimate the severity of the voltage unbalance. © 2014 IEEE. Source


Margarit M.,Universitatea valahia din targoviste | Radu V.,Muzeul National de Istorie A Romaniei | Popovici D.N.,Muzeul National de Istorie A Romaniei
Environmental Archaeology | Year: 2015

Significant amounts of opercular bones from Cyprinus carpio, used to manufacture circular pearls for adornments, were found from the Romanian Eneolithic, associated with the Gumelnita culture. The origins of this raw material are local: the carp was an important food resource for the communities located close to the River Danube. An experimental program was undertaken to obtain replicas of pearls of C. carpio, to compare with the archaeological pieces, in order to identify an a chain of manufacture resulting in the finished pieces. The study of the adornments represents an inexhaustible source of reflection because, through them we can identify aspects of the human groups' symbolical behaviour, and socio-economical aspects of these communities' evolution. In this case they suggest that the aquatic world, with its resources, had an important position in the spiritual life of these communities. © Association for Environmental Archaeology 2016 Source


Lakatos E.S.,Universitatea valahia din targoviste
Electrotehnica, Electronica, Automatica | Year: 2014

The purpose of this paper is to present the basic contributions of Physics in the development of Microelectronics, a science field found at the edge between Physics and Electronics. We will show the road followed by the 20th century science and technique, beginning with 1900, from the rise of quantum theory, elaborated by Max Plank, continuing with the invention of bipolar transistor, up to the manufacturing of the first microprocessor and of the first integrated memory, this way opening the way to the construction of the first personal computer. In this paper we will present a short review of the main Physics chapters which contributed to the development of the Microelectronics field, of the main theoretical concepts and of physical models which led to the development of the semiconductor devices manufacturing technologies industry. We will present, from the point of view physical phenomena and of modeling, the basic processes in integrated-circuit fabrication: oxidation, epitaxial growth, ion implantation and solid-state diffusion. We will describe the physical models of these processes, models which led to the design of the process flows from Microelectronics industry. These physical models are also used in simulation software of technological processes. For two of the basic processes, oxidation and solid-state diffusion, we will shortly describe the characterization methods, emphasizing once more the role of Physics in Microelectronics field. We will also refer, using examples, to the main process flows used in integrated circuits structures manufacturing that led to the development of Microelectronics. Source


Lakatos E.S.,Universitatea valahia din targoviste
Electrotehnica, Electronica, Automatica | Year: 2014

The purpose of this paper is to present the basic contributions of Physics in the development of Microelectronics, a science field found at the edge between Physics and Electronics. We will show the road followed by the 20th century science and technique, beginning with 1900, from the rise of quantum theory, elaborated by Max Plank, continuing with the invention of bipolar transistor, up to the manufacturing of the first microprocessor and of the first integrated memory, this way opening the way to the construction of the first personal computer. In this paper we will present a short review of the main Physics chapters which contributed to the development of the Microelectronics field, of the main theoretical concepts and of physical models which led to the development of the semiconductor devices manufacturing technologies industry. We will present, from the point of view physical phenomena and of modelling, the basic processes in integrated-circuit fabrication: oxidation, epitaxial growth, ion implantation and solid-state diffusion. We will describe the physical models of these processes, models which led to the design of the process flows from Microelectronics industry. These physical models are also used in simulation software of technological processes. For two of the basic processes, oxidation and solid-state diffusion, we will shortly describe the characterization methods, emphasizing once more the role of Physics in Microelectronics field. We will also refer, using examples, to the main process flows used in integrated circuits structures manufacturing that led to the development of Microelectronics. Source


Craciunescu A.,Polytechnic University of Bucharest | Ciumbulea G.S.,Polytechnic University of Bucharest | Dumitrica C.N.,Universitatea valahia din targoviste
2013 - 8th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2013 | Year: 2013

Voltage unbalance is a common phenomenon in AC power network. This disturbance can cause on the three-phase induction motors connected to the power supply system serious ill effects such as overheating, drop of efficiency and reduction in output torque. Therefore, operation of an induction motor for any length of time above 5% of voltage-unbalance condition is not recommended and on-line voltage unbalance monitoring is required from economical reasons. In this paper a new method of evaluating the degree of unbalanced voltage in power network is proposed. This new approach uses voltage space phasor geometrical locus in polar coordinates based on a modified 'a-b-c' to 'd-q' coordinate transformation which gives the possibility to localize the unbalanced phases and to appreciate the severity of the voltage unbalance. © 2013 IEEE. Source

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