Universitatea valahia din targoviste

Bucharest, Romania

Universitatea valahia din targoviste

Bucharest, Romania
SEARCH FILTERS
Time filter
Source Type

The paper presents the main aspects of the concept of modelling in microelectronics, as a tool used to describe the electric behaviour of devices and integrated circuits, before their manufacture, or technological processes required for manufacturing, by simulation. They highlight the main stages of technological design, in terms of simulation of a flow sheet: technological process simulation, devices simulation that make up the circuit and circuit simulation. From this point of view, there are three types of models: models of the processes that make up a flow sheet, models describing the electric behaviour of semiconductor devices and integrated circuits. There are exposed, briefly, methods of solving differential equations, with examples of analytical solution (one-dimensional Poisson equation, in the case of ideal MOS structure) and numerical solution (grid generation, discretization of differential equations), exemplifying numerical solving of Poisson equation for electrostatic potential simulation in two-dimensional structure of the MOS transistor. 1D diffusion model is considered for modelling the diffusion of low and high impurities concentration, with an example of solving one-dimensional diffusion equation by finite difference method. It also gives the Newton-Raphson iteration method for linearization of nonlinear algebraic equations, using as an example the semiconductor diode I-V characteristic. © 2017, ICPE Electra Publishing House. All rights reserved.


Radulescu C.,Universitatea Valahia din Targoviste | Radulescu C.,University Valahia of Targoviste | Ionita I.,Universitatea Valahia din Targoviste | Ionita I.,University Valahia of Targoviste | And 4 more authors.
Industria Textila | Year: 2010

In this paper, a photo-stabilization alternative is presented for the cationic dyes applied to the poly-acrylic fibres, Melana type. In order to increase the dyes light fastness and to photo-stabilize the un-dyed and dyed fibres, the UV absorber 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole was used. The cationic dyes derived by the compact condensed systems with thiazolic ring and UV absorber uptake, and the light and sublimation fastness of the dyed poly-acrylic fibres were determined and compared with thoso obtained for the corresponding fibres dyed in the absence of an UV absorber. The UV absorber was applied to the fibre by using different procedures: directly in the dye-bath anc after the treatment of the fibres dyed. The tinctorial efficiency of the cationic dyes applied to poly-acrylic fibres was analyzed as well. The research shows that the 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole absorber introduction in the cationic dyes leads to the increment of dyes absorption capacity, after exposure to UV radiations. In the UV area, the absorption intensity for the UV absorber is higher than the dyes absorption intensity; therefore, the UV radiations are absorbed by the 2-(2′-hydroxy- 5′-methylphenyl)-benzotriazole, the presence of the UV absorber moving the absorption maximum of dyes from the visible to the highest wavelength (bathochromic shift).


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


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.


Vasile N.,Universitatea valahia din targoviste | Vasile F.,Universitatea valahia din targoviste
Electrotehnica, Electronica, Automatica | Year: 2012

The electric car cumulates technical, economic and service innovation. The technical innovation refers at a lot of patents on electric energy power supply, traction electric motors and new structures of the mass distribution. Economic innovation refers at avoidance of the indisponibile or perishable fuel and raw materials. Services innovation, consisting in new methods of chipper exploitation, could represent a support for project. The paper propose a way to combine that three innovation solution to the common fezability.


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.


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.


Ungureanu D.N.,Universitatea Valahia din Targoviste | Angelescu N.,Universitatea Valahia din Targoviste | Tsakiris V.,Institutul National Of Cercetare Dezvoltare Pentru Inginerie Electrica Icpe Ca | Marinescu V.,Institutul National Of Cercetare Dezvoltare Pentru Inginerie Electrica Icpe Ca
Revista Romana de Materiale/ Romanian Journal of Materials | Year: 2012

In this paper is presented a synthesis method of calcium phosphate bioceramics such as hydroxiapatite, the mineral component of bones and hard tissue in mammals. Hydroxyapatite powders have been obtained by chemical coprecipitation, by using calcium hydroxide and ortophosphoric acid as a source of calcium and phosphorus. The synthesized powders were characterized by X - ray diffraction, dynamic light scattering technique (DLS) and scanning electron microscopy (SEM). The proposed method lead to obtain a hydroxyapatite with a degree of crystallinity, greater than 80%, in case of all samples thermal treated at 800°C.


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.

Loading Universitatea valahia din targoviste collaborators
Loading Universitatea valahia din targoviste collaborators