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Your search keyword '"Dumitrache, Alexandru"' showing total 165 results
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165 results on '"Dumitrache, Alexandru"'

2. Design and analysis of an autonomous wind-photovoltaic hybrid system.

Author

Dumitrache, Alexandru, Popescu, Sergiu-Alexandru, Bogateanu, Radu, and Suatean, Bogdan

Subjects
*HYBRID systems, *WIND power, *ELECTRIC power consumption, *WIND turbines, *COMPUTER simulation, *WIND forecasting, *ENERGY industries
Abstract

This work is focused on the optimal sizing of hybrid stand-alone photovoltaic–wind power systems from real hourly wind and solar irradiation data and electricity demand from a specific location. For optimization method photovoltaic panels, wind turbine and batteries specifications have been used. Using all these data and parameters in computer model HOMER, the minimization of the net present cost (NPC) or cost of unit of energy (COE) is obtained by selecting an appropriate hybrid stand-alone system configuration. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Numerical simulations of some characteristics for electrohydrostatic actuators used in aviation.

Author

Buhaianu, Andra-Ramona, Dinca, Liviu, Dumitrache, Alexandru, and Benec-Mincu, Glencora-Maria

Subjects
COMPUTER simulation, HYDROSTATIC extrusion, ACTUATORS, MATHEMATICAL models
Abstract

This paper has numerically analyzed the problem of enhanced the dynamic response of an electrohydrostatic actuators used in aerospace systems. Based on physical and mathematical model using both Matlab / Simulink and AMESim Software Student Edition some characteristics of this type of servo actuator were obtained. The results proved that a good tracking of reference is achieved and that the servo actuator meets very well the design requirements imposed in the time domain. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Adjoint building design optimization coupled with a VAWT for wind energy harvesting through a sea coastal wind stream.

Author

Katona, Cosmin, Safta, Carmen Anca, and Dumitrache, Alexandru

Subjects
ENERGY harvesting, WIND power, LARGE eddy simulation models
Abstract

Nowadays, generation of renewal energies on-site are essentially to their optimum design configuration by achieving the extended final percentages of enhancement. This becomes a high necessity for accurate performance evaluation and incorporation of high-power computation in CFD strategies. The present work addresses to consolidate the Large Eddy Simulations in the integral design of buildings by aiming rigorous assessment of the flow field. Therefore, 3D steady RANS simulations are performed as an adaptation-based process of the building. The optimized geometry obtained thought the classical RANS approach is then used to demonstrate relevant design conditions and provide aerodynamics advantages to strengthen the local wind resource for forthcoming implementation of VAWT by means of LES. [ABSTRACT FROM AUTHOR]

Published
2024
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5. The Standard and Counter-Rotating VAWT Performances with LES

Author

Dumitrescu, Horia, Dumitrache, Alexandru, Malael, Ion, Bogateanu, Radu, Choi, Seung-Bok, Series Editor, Duan, Haibin, Series Editor, Fu, Yili, Series Editor, Guardiola, Carlos, Series Editor, Sun, Jian-Qiao, Series Editor, Kwon, Young W, Series Editor, Ferrer, Esteban, editor, and Montlaur, Adeline, editor

Published
2019
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6. Robotic 3D Surface Laser Scanning for Feature-Based Quality Control in Holonic Manufacturing

Author

Dumitrache, Alexandru, Borangiu, Theodor, Răileanu, Silviu, Kacprzyk, Janusz, Series editor, Pal, Nikhil R., Advisory editor, Bello Perez, Rafael, Advisory editor, Corchado, Emilio S., Advisory editor, Hagras, Hani, Advisory editor, Kóczy, László T., Advisory editor, Kreinovich, Vladik, Advisory editor, Lin, Chin-Teng, Advisory editor, Lu, Jie, Advisory editor, Melin, Patricia, Advisory editor, Nedjah, Nadia, Advisory editor, Nguyen, Ngoc Thanh, Advisory editor, Wang, Jun, Advisory editor, Rodić, Aleksandar, editor, and Borangiu, Theodor, editor

Published
2017
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20. Influences of some parameters on the performance of a small vertical axis wind turbine

Author

Dumitrache Alexandru, Frunzulica Florin, Dumitrescu Horia, and Suatean Bogdan

Subjects
Energy conservation, TJ163.26-163.5, Renewable energy sources, TJ807-830
Abstract

The effects of various parameters on the performance of a straight bladed vertical axis wind turbine, using the vortex model, have been numerically investigated. A vortex model has been used to evaluate the performance of a vertical axis wind turbine, by means of aerodynamic characteristics of different airfoils for Reynolds numbers between 105 and 106. Parameters such as the thickness and the camber of the blade airfoil, the solidity, the type of blade profile, the number of blades and the pitch angle, which influence the power coefficient, CP, and the start-up regime. This study can be used in the designing an optimal vertical axis wind turbine in a specific location, when the prevailed wind regime is known.

Published
2016
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21. Thrust and jet directional control using the Coanda effect

Author

Frunzulica Florin, Dumitrache Alexandru, Preotu Octavian, and Ionescu Tudor

Subjects
Physics, Jet (fluid), thrust vectoring, lcsh:Motor vehicles. Aeronautics. Astronautics, Aerospace Engineering, Thrust, Mechanics, Coandă effect, symbols.namesake, Control and Systems Engineering, symbols, lcsh:TL1-4050, CFD
Abstract

The application of the Coandă effect to the directional control of a jet or thrust is presented. Deviation of the thrust force by direct flow can be achieved by using the Coandă effect to change the angle of the primary jet engine exhaust nozzle. Major interest in the study of this phenomenon is caused by the possibility of using this effect for aircrafts with short take-off and landing, for thrust vectoring. The numerical investigations are performed using a RANS solver with an adequate turbulence model, showing a change of the jet direction. Thus, the conditions and the limits within which one can benefit from the advantages of Coandă-type flows are determined.

Published
2018

22. Silencing Folylpolyglutamate Synthetase1 (FPGS1) in Switchgrass (Panicum virgatum L.) Improves Lignocellulosic Biofuel Production

Author

Mazarei, Mitra, primary, Baxter, Holly L., additional, Srivastava, Avinash, additional, Li, Guifen, additional, Xie, Hongli, additional, Dumitrache, Alexandru, additional, Rodriguez, Miguel, additional, Natzke, Jace M., additional, Zhang, Ji-Yi, additional, Turner, Geoffrey B., additional, Sykes, Robert W., additional, Davis, Mark F., additional, Udvardi, Michael K., additional, Wang, Zeng-Yu, additional, Davison, Brian H., additional, Blancaflor, Elison B., additional, Tang, Yuhong, additional, and Stewart, Charles Neal, additional

Published
2020
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27. Numerical Simulation of the Flow around a Mobile Winglet.

Author

Anghel, Şerban, Blănariu, Andrei-Petru, Frunzulică, Florin, Crunţeanu, Daniel, and Dumitrache, Alexandru

Subjects
FLOW simulations, COMPUTER simulation, AIRPLANE wings, AIRPLANE piloting, TURBULENT flow, VORTEX generators
Abstract

The purpose of this paper was to determine the improvements that could be achieved by retrofitting a mobile winglet to a small airplane wing, taking into account only the aerodynamic effects (not considering the structural aspect). The CFD analysis is a crucial step in any conceptual design phase, as it provides reasonably accurate data before the experiments take place. Therefore, we performed numerical simulations for 9 winglet configurations and a test wing at 7 different angles of attack, considering a fully developed turbulent flow (Re ∼ 106) to see if and how substantial are the aerodynamic advantages. A NACA2412 airfoil was used as it is quite common for small airplanes used in pilot schools and for recreational flights. We chose the RANS model, combined with Realizable k-ε and SIMPLE algorithm as they have an acceptable computational cost and reasonable accuracy [ABSTRACT FROM AUTHOR]

Published
2020
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32. Patterns of digital behaviour on instant messaging platforms. WhatsApp uses among young people from Romania.

Author

Corbu, Nicoleta, Boțan, Mădălina, Buturoiu, Raluca, and Dumitrache, Alexandru

Subjects
INSTANT messaging, DEPENDENCY (Psychology), LONELINESS, ELECTRONIC paper, BEHAVIOR, MOTIVATION (Psychology)
Abstract

This paper examines the digital behaviour on one widely used instant messaging (IM) platform, namely WhatsApp, of young people in Romania, with a focus on the reasons for sharing information on the platform and dependency of using it. Within the broad framework of the digital single market, little is known about the motivations and behavioural patterns of young Europeans while using the increasingly popular IM platforms, nor is it clear whether country characteristics are relevant or not when evaluating the impact of such technological platforms on the life of young audiences. Rooted in the uses and gratifications perspective, this study uses media diaries (N = 229), filled in by young people in an ordinary day of the week and self-administered questionnaires in order to assess what might be the main gratifications that lead young and educated people to share information on WhatsApp and what makes them spend more time and be dependent on the platform on a daily basis. Main results show that the most frequent reasons why young Romanians use WhatsApp are social, professional, and instrumental. Moreover, the tendency to share content on the platform is higher for people who use it for instrumental and informative purposes. Dependency on the platform is significantly higher for young people who use it to fulfil affective needs (i.e., to express or receive affection or emotional support and avoid loneliness). [ABSTRACT FROM AUTHOR]

Published
2020

35. Sugar release and growth of biofuel crops are improved by downregulation of pectin biosynthesis

Author

Biswal, Ajaya K, primary, Atmodjo, Melani A, additional, Li, Mi, additional, Baxter, Holly L, additional, Yoo, Chang Geun, additional, Pu, Yunqiao, additional, Lee, Yi-Ching, additional, Mazarei, Mitra, additional, Black, Ian M, additional, Zhang, Ji-Yi, additional, Ramanna, Hema, additional, Bray, Adam L, additional, King, Zachary R, additional, LaFayette, Peter R, additional, Pattathil, Sivakumar, additional, Donohoe, Bryon S, additional, Mohanty, Sushree S, additional, Ryno, David, additional, Yee, Kelsey, additional, Thompson, Olivia A, additional, Rodriguez, Miguel, additional, Dumitrache, Alexandru, additional, Natzke, Jace, additional, Winkeler, Kim, additional, Collins, Cassandra, additional, Yang, Xiaohan, additional, Tan, Li, additional, Sykes, Robert W, additional, Gjersing, Erica L, additional, Ziebell, Angela, additional, Turner, Geoffrey B, additional, Decker, Stephen R, additional, Hahn, Michael G, additional, Davison, Brian H, additional, Udvardi, Michael K, additional, Mielenz, Jonathan R, additional, Davis, Mark F, additional, Nelson, Richard S, additional, Parrott, Wayne A, additional, Ragauskas, Arthur J, additional, Neal Stewart, C, additional, and Mohnen, Debra, additional

Published
2018
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40. FLOW CONTROL INVESTIGATION USING THE COANDA EFFECT ON AIRFOILS.

Author

DUMITRACHE, Alexandru, FRUNZULICA, Florin, DUMITRESCU, Horia, and IONESCU, Tudor

Subjects
*AEROFOILS, *JETS (Fluid dynamics), *FLOW separation
Abstract

Numerical investigations on the flow control around airfoils, in conjunction with Coandă effect, based on RANS equations are done. The circulation control uses the tangential blowing jet on the upper surface of the airfoil near the trailing edge with the rounded or modified flatback surface. Flow field spectra around such a configurations, involving the delayed of flow separation are obtained and analyzed by CFD methods. Thus can be identified the optimum domain of the geometric and jet flow parameters in which this flow control method should be used. [ABSTRACT FROM AUTHOR]

Published
2019
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41. Airfoil optimization based on low fidelity flow models.

Author

Pricop, Mihai Victor, Boșcoianu, Mircea, Cojocaru, Marius Gabriel, and Dumitrache, Alexandru

Subjects
AEROFOILS, AERODYNAMICS, INCOMPRESSIBLE flow, SEPARATION (Technology), THICKNESS measurement
Abstract

Direct airfoil optimization with single or multiple objectives is always required in preliminary aircraft design. Low fidelity aerodynamic methods like incompressible potential and incompressible boundary layer are still attractive when used under a genetic algorithm that although is relatively slow, it enables the identification of the global solution while handling generic constraints in a simple way. The work is focused on small angles of attack, for flows without large separations, where the current low fidelity models provide a good level of certainty. Geometric parametrisation of airfoils considers NACA 4, generic polynomial and a combination of Class Shape for thickness and Bernstein polynomials for camber line. Few objective functions are tested and it is shown with numerical results that constraint optimization is fully consistent at high Reynolds, achieving solution uniqueness according to engineering requirements, while for low Reynolds there is a need for special treatment. [ABSTRACT FROM AUTHOR]

Published
2018
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42. Significance of Lignin S/G Ratio in Biomass Recalcitrance of Populus trichocarpa Variants for Bioethanol Production

Author

Yoo, Chang Geun, primary, Dumitrache, Alexandru, additional, Muchero, Wellington, additional, Natzke, Jace, additional, Akinosho, Hannah, additional, Li, Mi, additional, Sykes, Robert W., additional, Brown, Steven D., additional, Davison, Brian, additional, Tuskan, Gerald A., additional, Pu, Yunqiao, additional, and Ragauskas, Arthur J., additional

Published
2017
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44. MOESM1 of Consolidated bioprocessing of Populus using Clostridium (Ruminiclostridium) thermocellum: a case study on the impact of lignin composition and structure

Author

Dumitrache, Alexandru, Akinosho, Hannah, Rodriguez, Miguel, Xianzhi Meng, Yoo, Chang, Natzke, Jace, Engle, Nancy, Sykes, Robert, Tschaplinski, Timothy, Wellington Muchero, Ragauskas, Arthur, Davison, Brian, and Brown, Steven

Subjects
fungi, food and beverages
Abstract

Additional file 1: Figure A.1. Carbohydrate composition of initially screened Populus biomass. Figure A.2. Fermentation products of Avicel-control CBP cultures. Figure A.3. Carbohydrate content in Populus before and after repeat autoclave sterilization. Figure A.4. Lignin content in Populus before and after repeat autoclave sterilization.

Published
2016
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48. Transgenic miR156 switchgrass in the field: growth, recalcitrance and rust susceptibility

Author

Baxter, Holly L., primary, Mazarei, Mitra, additional, Dumitrache, Alexandru, additional, Natzke, Jace M., additional, Rodriguez, Miguel, additional, Gou, Jiqing, additional, Fu, Chunxiang, additional, Sykes, Robert W., additional, Turner, Geoffrey B., additional, Davis, Mark F., additional, Brown, Steven D., additional, Davison, Brian H., additional, Wang, Zeng‐Yu, additional, and Stewart, C. Neal, additional

Published
2017
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50. Transgenic switchgrass (Panicum virgatum L.) targeted for reduced recalcitrance to bioconversion: a 2‐year comparative analysis of field‐grown lines modified for target gene or genetic element expression

Author

Dumitrache, Alexandru, primary, Natzke, Jace, additional, Rodriguez, Miguel, additional, Yee, Kelsey L., additional, Thompson, Olivia A., additional, Poovaiah, Charleson R., additional, Shen, Hui, additional, Mazarei, Mitra, additional, Baxter, Holly L., additional, Fu, Chunxiang, additional, Wang, Zeng‐Yu, additional, Biswal, Ajaya K., additional, Li, Guifen, additional, Srivastava, Avinash C., additional, Tang, Yuhong, additional, Stewart, Charles Neal, additional, Dixon, Richard A., additional, Nelson, Richard S., additional, Mohnen, Debra, additional, Mielenz, Jonathan, additional, Brown, Steven D., additional, and Davison, Brian H., additional

Published
2017
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