oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 211 )

2019 ( 917 )

2018 ( 1002 )

2017 ( 1047 )

Custom range...

Search Results: 1 - 10 of 653111 matches for " P. R. M.;Willmersdorf "
All listed articles are free for downloading (OA Articles)
Page 1 /653111
Display every page Item
A methodology and computational system for the simulation of fluid-structure interaction problem
Antunes, A. R. E.;Lyra, P. R. M.;Willmersdorf, R. B.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2005, DOI: 10.1590/S1678-58782005000300007
Abstract: in this paper a flexible finite element computational tool developed to investigate fluid-structure interaction applications in two dimensions is described. we consider problems which can be modelled as a viscous incompressible fluid flow and a rigid body-spring system interacting nonlinearly with each other. the coupling is dealt with the use of an interface approach, in which each physics involved is solved with different schemes and the required information is transferred through the interface of both systems. this approach is, at least in principle, very flexible and computationally efficient as the best available scheme can be adopted to solve each physics. here, a stabilized fem considering the "ale" (arbitrary lagrangian-eulerian) formulation with crank-nicholson time-integration is employed for the fluid-dynamics analysis, and the newmark method is used for the structural dynamics. several important tools were incorporated into our system including different possibilities for the mesh movement algorithm, the computational domain decomposition into regions with and without mesh deformation, and the remeshing strategy (either global or local) to keep the necessary mesh quality. as application we present a study of the forced lock-in phenomena and a preliminary investigation on the suppression (or at least the reduction) of the vortex induced vibrations (viv) on a solid circular cylinder using an idealization of a periodic acoustic excitation.
A methodology and computational system for the simulation of fluid-structure interaction problem
Antunes A. R. E.,Lyra P. R. M.,Willmersdorf R. B.
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2005,
Abstract: In this paper a flexible finite element computational tool developed to investigate fluid-structure interaction applications in two dimensions is described. We consider problems which can be modelled as a viscous incompressible fluid flow and a rigid body-spring system interacting nonlinearly with each other. The coupling is dealt with the use of an interface approach, in which each physics involved is solved with different schemes and the required information is transferred through the interface of both systems. This approach is, at least in principle, very flexible and computationally efficient as the best available scheme can be adopted to solve each physics. Here, a stabilized FEM considering the "ALE" (Arbitrary Lagrangian-Eulerian) formulation with Crank-Nicholson time-integration is employed for the fluid-dynamics analysis, and the Newmark Method is used for the structural dynamics. Several important tools were incorporated into our system including different possibilities for the mesh movement algorithm, the computational domain decomposition into regions with and without mesh deformation, and the remeshing strategy (either global or local) to keep the necessary mesh quality. As application we present a study of the forced lock-in phenomena and a preliminary investigation on the suppression (or at least the reduction) of the vortex induced vibrations (VIV) on a solid circular cylinder using an idealization of a periodic acoustic excitation.
An edge-based unstructured mesh formulation for high speed tridimensional compressible flow simulation
Ventura, D. M.;Lyra, P. R. M.;Willmersdorf, R. B.;Silva, R. S.;Antunes, A. R. E.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2012, DOI: 10.1590/S1678-58782012000100013
Abstract: numerical simulation of realistic compressible flows is very important and requires accurate and flexible tridimensional formulations, which should furthermore be robust and efficient. in this work we describe the development of a computational tool for numerical simulation of inviscid compressible 3-d fluid flow problems. this tool uses as the main building block an edge-based galerkin fem (finite element method) together with a muscl (monotonic upstream-centered schemes for conservations laws) approach to get a higher-order scheme with led (local extremum diminishing) property. the code is particularly developed for the simulation of supersonic and hypersonic flow regimes and several important (sometimes unavoidable) numerical procedures incorporated to increase its robustness are described. some aspects related to the adoption of an edge-based data structure and other implementation issues are also described. finally, some numerical model problems are analyzed and compared with results found in the literature demonstrating the effectiveness of the developed tool.
FPGA Based Speed Control of SRM with Optimized Switching Angles by Self Tuning  [PDF]
P. Saravanan, R. Arumugam, M. Senthil Kumaran
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.78134
Abstract:

The electromagnetic torque and speed in Switched Reluctance Motor (SRM) greatly depend on the excitation parametersi.e.?turn-on angle, turn-off angle, dwell angle and magnitude of the phase currents of its phases. At lower speeds, a change in the current contributes the torque requirement which can be achieved either by voltage control (pulse width modulation) or instantaneous current control techniques. At high speeds, due to high back EMF, the regulation of current is crucial and achieved with the control of switching angles of phases. This type of control is referred as average torque control, where the torque is averaged over one stroke (2π/Nr). With constant dwell angle, advancing the phase angle influences the current into the phase winding at minimum inductance position. It has more time to get the current out of the phase winding before the rotor reaches the negative inductance slope. To maintain the speed of the motor at different load conditions, the turn-on and turn-off angles are adaptively varied. The change in dwell angle may be required where the turn-on and turn-off angle may not be sufficient to reach the required speed. In this paper, a new algorithm is proposed for self tuning of switching parameters of SRM. The proposed algorithm is simulated in MATLAB-Simulink and experimentally validated with Field Programmable Gated Array (FPGA) using MATLAB- system generator environment.

Spacetime as an Emergent Phenomenon: A Possible Way to Explain Entanglement and the Tunnel Effect  [PDF]
P. Castro, M. Gatta, J. R. Croca, R. Moreira
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.610177
Abstract: Entanglement and the tunnel effect phenomena have been repeatedly observed and are generically accepted under orthodox quantum mechanics formalism. However, they remain rather inexplicable in the context of spacetime usual conceptualization. In the present work, we suggest an alternative quantum mechanics formalism, refining the pilot-wave theory initially proposed by de Broglie. We suggest that spacetime is an emergent phenomenon from a prior subquantum medium and that entanglement and the tunnel effect can be explained in terms of a nonlinear relation between space and time that is imposed by subquantum waves.
Compact Wideband Rectangular Monopole Antenna for Wireless Applications  [PDF]
S. M. Naveen, R. M. Vani, P. V. Hunagund
Wireless Engineering and Technology (WET) , 2012, DOI: 10.4236/wet.2012.34034
Abstract: This article presents a compact wideband microstrip-fed planar monopole antenna composed of a rectangular patch and slotted ground structure. By placing pair of symmetrical square stubs, making slots in the stubs, putting stubs on the sides of the radiating patch, gives wide-band characteristics. The antenna only one of its kinds in structure, small in size and simple design due to less number of design parameters, compared with the existing UWB antennas in the literature. The bandwidth, radiation pattern and other antenna parameters are at acceptable level. IE3D method of moments based simulation software is used for design and analysis. The simulated results are confirmed by conducting experiments with the help of Rohde and Schwarz, German make ZVK model No.8651 Vector Network Analyzer and discussed.
Integration of Health Promotion into Nursing Practice: A Case Study in Pakistan  [PDF]
M. A. Vastani, R. Karmalani, P. M. Petrucka
Open Journal of Nursing (OJN) , 2016, DOI: 10.4236/ojn.2016.61004
Abstract: The purpose of this study was to understand the concept of health promotion and perceptions related to the integration of health promotion in nursing practice in Pakistan. The study utilized the qualitative single case study approach to explore and describe the concept of health promotion, its significance and ways to integrate health promotion strategies in nursing practice. The data were collected from three different sources; focus group discussion among final year Post-RN BScN students, key informant interviews of practicing nurses, faculty, and MScN students, as well as a document review of the Post-RN BScN curriculum. Data analysis included a content and thematic analysis, yielding four major themes—”Health Promotion as Diverse”, “Health Promotion as Necessary”, “Health Promotion as Nursing Role”, and “Health Promotion as a Strategic Imperative”. Further, the findings highlighted the competencies, support mechanisms, and barriers which select nurses faced while integrating the health promotion strategies in practice.
First Flight from Europe to the South Atlantic  [PDF]
André R. R. Silva, Jorge M. M. Barata, Candido M. P. Morgado, Fernando M. S. P. Neves
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.610064
Abstract: The History of the transatlantic flights goes back to 1919 and began with a flight performed from Newfoundland to Lisbon; two weeks later another flight was performed between Newfoundland and Ireland. On 1922, the Portuguese airmen Gago Coutinho and Sacadura Cabral crossed the South Atlantic Ocean by air in a flight performed exclusively with internal means of navigation: a new instrument that consisted in a type of sextant improved with two spirit levels to provide an artificial horizon and also with the help of a “path corrector”. Despite this journey had lasted 79 days to cross South Atlantic Ocean, their flight time was only 62:26 minutes, and they’ve flown 8,383 nautical miles, using 3 different hydroplanes christened: Lusitania, Pátria and Santa Cruz. Despite this journey had lasted 79 days, their flight time was only 62 h 26 m; they’ve flown 8,383 nautical miles using 3 different hydroplanes christened: Lusitania, Pátria and Santa Cruz. The new artificial horizon sextant had proven itself while flying over the ocean, without external references.
Sacadura Cabral and the Dawn of Portuguese Aviation  [PDF]
Fernando M. S. P. Neves, Jorge M. M. Barata, André R. R. Silva
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.61003
Abstract: Sacadura Cabral was one of the two Portuguese navigators that crossed by air the South Atlantic in the beginning of the 20th century. From 1901 to 1915 Sacadura was at Mozambique and Angola where he developed geodetic and geographical missions of the greatest importance for Portuguese interest at Africa. With the Great World War requirements as a Navy Officer with 34 years old he decided to serve Portugal at the Aviation. In 1915 he went to France and obtained its pilot license. In 1916 Sacadura returned to Portugal and begun its instructor pilot career. He developed the “path corrector” which he created to compensate the drift caused by wind. In 1922 Sacadura made the First Air cross from Europe to South Atlantic. In 1923 he proposes himself to make an attempt to the First Air Circumnavigation Journey. He developed all its possible efforts to initiate this journey in March of 1924; however some delays had forced him to postpone the journey. Sacadura received important official medals and prizes, including the PhD Honoris Causa from the Universities of Lisbon and Oporto. In 1924 he died before he could carry out its Circumnavigation Air Journey.
The First Aerial Journey from Portugal to Macau  [PDF]
Fernando M. S. P. Neves, Jorge M. M. Barata, André R. R. Silva
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.610066
Abstract: On 1920, Brito Pais and Sarmento Beires tried an unsuccessful flight attempt from Amadora, Lisbon to Madeira Island onboard an airplane Breguet XIV A2, named “Cavaleiro Negro”. Despite the scarce means of navigation both navigators managed to reach Madeira, which failed to land due to dense fog. On their way back after 8 hours of flight time, they alight at the Atlantic Ocean for lack of fuel and were rescued at about 500 km from Lisbon. On 1922, Gago Coutinho and Sacadura Cabral conducted the First Aerial Cross of the South Atlantic, flying from Lisbon to Rio de Janeiro. The Portuguese Aeronautics rejoiced auspicious days that time, with its aviation pioneers trying consecutively to reach more distant places along intercontinental flights. On 1923, Gago Coutinho and Sacadura Cabral were contemplating to perform an Around the World Flight. However, Sacadura died in 1924, while piloting an airplane acquired for the circumnavigation voyage. Later on 1924 the pilots Brito Pais and Sarmento Beires idealized the conducting of an aerial flight from Lisbon to Macau as an aspiration for a future Portuguese Around the World Flight attempt: on 7 April 1924, those pilots departed from Vila Nova de Milfontes in a Breguet XIV Bn2 airplane, starting their Journey to Macau. During a flight stage on 7 May an engine failure forced them to crash the airplane at India; on 30 May, both pilots managed to continue the Voyage in a De Havilland DH9 aircraft before being forced to end their attempt in 20 June in flying over Macau. A typhoon hindered their efforts to land and the airplane was crash landed in Chinese Territory about 800 meters from the Hong Kong Border. On 25 June 1924, they were shuttled back to Macau by boat. Brito Pais, Sarmento Beires and Manuel Gouveia returned to Portugal, via North America, visiting several Portugueses nuclei at China, Japan, United States and England. They went to Portugal on 9 September, after having flown a total of 16,760 km in 117:41 h facing often extremely adverse atmospheric conditions, sandstorms and inaccurate navigation maps.
Page 1 /653111
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.