The Experts below are selected from a list of 9 Experts worldwide ranked by ideXlab platform

David Wood - One of the best experts on this subject based on the ideXlab platform.

  • A cascade model of blade element interaction for wind turbines with unequal blades
    International Journal of Sustainable Energy, 2014
    Co-Authors: David Wood
    Abstract:

    Horizontal-axis wind turbines often operate with unequally performing blades. A simple extension of blade element analysis for unequal blades is developed using the two-dimensional cascade analogue of wind turbines. The vortex strengths of the blade elements can vary with blade number. For three-bladed rotors, the unequal strengths induce an extra velocity at each blade, but for two blades there is no additional velocity. For both blade numbers, there is a modification to the rotational Inflow Factor. To determine the significance of blade differences, test calculations are presented for two- and three-bladed turbines with different blade pitch angles. The modifications proposed here do not substantially alter the calculations of turbine power and thrust near the point of maximum performance. However, some substantial differences were found at higher thrust. Furthermore, the new method predicts much larger variations in the blade element torque between the blades in the hub region for most operating condi...

Efthymios Nikolopoulos - One of the best experts on this subject based on the ideXlab platform.

  • European Monetary Union and Foreign Direct Investment Inflows
    SPOUDAI Journal of Economics and Business, 2020
    Co-Authors: Pantelis Pantelidis, Dimitrios Kyrkilis, Efthymios Nikolopoulos
    Abstract:

    The aim of this paper is to construct and test a model explaining the inward Foreign Direct Investment (FDI) position of various members of European Monetary Union (EMU), on the basis of their location advantages during 1980-2010 period. The model focuses on the impact of EMU on FDI Inflows and indicates that the monetary union has differentiated impact on FDI Inflows across individual member countries. Euro zone membership is statistically significant but a negative determinant in the cases of Greece, Portugal, France, Belgium and Spain. Furthermore, for both Germany and Ireland the Euro area membership is a negative but statistically insignificant FDI Inflow Factor, while in the cases of Netherlands and Finland it is positive but also statistically insignificant. The results imply that countries with low competitiveness have not gained from the entrance in European Monetary Union, in terms of Foreign Direct Investment Inflows.

Fredric - One of the best experts on this subject based on the ideXlab platform.

  • Longitudinal-Plane Simultaneous Non-Interfering Approach Trajectory Design for Noise Minimization
    2003
    Co-Authors: Gopalan, Schmitz, Fredric
    Abstract:

    Runway-independent aircraft (RIA) operating under simultaneous non-interfering (SNI) traffic procedures have been proposed to alleviate airspace congestion at crowded urban airports. This paper introduces a methodology for designing minimum-noise longitudinal SNI approach trajectories for rotorcraft. An analytical model for ground noise annoyance associated with out of plane Blade-Vortex Interaction (BVI) noise is introduced and its application as the cost function for SNI trajectory optimization is described. The noise model relies on a physicsbased semi-empirical expression developed to approximate the average annoyance levels associated with BVI noise on a representative ground plane. To guarantee strictly SNI trajectories, fixed-wing traffic corridors are treated as impenetrable obstacles modeled by their cross-sections in the longitudinal approach plane. Two optimization procedures are employed: a heuristic strategy that specifies trajectories using a small approach waypoint set and a globally-optimal cell-based algorithm. The feasibility and practicality of example minimumBVI noise solutions are discussed. Nomenclature Ao = Ground plane total area ∆A = Elemental area on the ground plane a = Acceleration parallel to flight path CT = Thrust coefficient d = Miss-distance at a blade-vortex interaction location Deff = Effective drag force acting on the helicopter F(X) = Objective function fλ = Inflow Factor g = Acceleration due to gravity (32.2 ft/sec) g(X) = Non-linear constraint function I = Indices used for curve-fits K = Indices used for curve-fits MHT = Hover-tip Mach number, ΩR/ao SPL = Sound pressure level SEL = Sound exposure level T = Main rotor revolution period ∆t = Elemental time-step V = Flight velocity V& = Acceleration parallel to flight path W = Helicopter weight x,z = Spatial coordinates z = Height of the helicopter above the ground αTPP = Main rotor tip-path-plane angle (positive nose up) χ = Wake skew angle μ = Advance ratio, V/ΩR γ = Flight path angle (negative in descent) λ = Average rotor Inflow ratio (positive for downwash) λi = Induced Inflow ratio (positive) λi,o = Induced Inflow ratio corresponding to zero tip-path plane angle (positive) ψv = Vortex azimuth angle corresponding to a blade vortex intersection location ∆ψv = Wake age corresponding to a blade vortex intersection location Subscripts av = spatial averaging dB = expressed in decibel n = spatial index over the ground plane i = temporal index or time-step associated with the trajectory o = peak level or reference value

Pantelis Pantelidis - One of the best experts on this subject based on the ideXlab platform.

  • European Monetary Union and Foreign Direct Investment Inflows
    SPOUDAI Journal of Economics and Business, 2020
    Co-Authors: Pantelis Pantelidis, Dimitrios Kyrkilis, Efthymios Nikolopoulos
    Abstract:

    The aim of this paper is to construct and test a model explaining the inward Foreign Direct Investment (FDI) position of various members of European Monetary Union (EMU), on the basis of their location advantages during 1980-2010 period. The model focuses on the impact of EMU on FDI Inflows and indicates that the monetary union has differentiated impact on FDI Inflows across individual member countries. Euro zone membership is statistically significant but a negative determinant in the cases of Greece, Portugal, France, Belgium and Spain. Furthermore, for both Germany and Ireland the Euro area membership is a negative but statistically insignificant FDI Inflow Factor, while in the cases of Netherlands and Finland it is positive but also statistically insignificant. The results imply that countries with low competitiveness have not gained from the entrance in European Monetary Union, in terms of Foreign Direct Investment Inflows.

Gopalan - One of the best experts on this subject based on the ideXlab platform.

  • Longitudinal-Plane Simultaneous Non-Interfering Approach Trajectory Design for Noise Minimization
    2003
    Co-Authors: Gopalan, Schmitz, Fredric
    Abstract:

    Runway-independent aircraft (RIA) operating under simultaneous non-interfering (SNI) traffic procedures have been proposed to alleviate airspace congestion at crowded urban airports. This paper introduces a methodology for designing minimum-noise longitudinal SNI approach trajectories for rotorcraft. An analytical model for ground noise annoyance associated with out of plane Blade-Vortex Interaction (BVI) noise is introduced and its application as the cost function for SNI trajectory optimization is described. The noise model relies on a physicsbased semi-empirical expression developed to approximate the average annoyance levels associated with BVI noise on a representative ground plane. To guarantee strictly SNI trajectories, fixed-wing traffic corridors are treated as impenetrable obstacles modeled by their cross-sections in the longitudinal approach plane. Two optimization procedures are employed: a heuristic strategy that specifies trajectories using a small approach waypoint set and a globally-optimal cell-based algorithm. The feasibility and practicality of example minimumBVI noise solutions are discussed. Nomenclature Ao = Ground plane total area ∆A = Elemental area on the ground plane a = Acceleration parallel to flight path CT = Thrust coefficient d = Miss-distance at a blade-vortex interaction location Deff = Effective drag force acting on the helicopter F(X) = Objective function fλ = Inflow Factor g = Acceleration due to gravity (32.2 ft/sec) g(X) = Non-linear constraint function I = Indices used for curve-fits K = Indices used for curve-fits MHT = Hover-tip Mach number, ΩR/ao SPL = Sound pressure level SEL = Sound exposure level T = Main rotor revolution period ∆t = Elemental time-step V = Flight velocity V& = Acceleration parallel to flight path W = Helicopter weight x,z = Spatial coordinates z = Height of the helicopter above the ground αTPP = Main rotor tip-path-plane angle (positive nose up) χ = Wake skew angle μ = Advance ratio, V/ΩR γ = Flight path angle (negative in descent) λ = Average rotor Inflow ratio (positive for downwash) λi = Induced Inflow ratio (positive) λi,o = Induced Inflow ratio corresponding to zero tip-path plane angle (positive) ψv = Vortex azimuth angle corresponding to a blade vortex intersection location ∆ψv = Wake age corresponding to a blade vortex intersection location Subscripts av = spatial averaging dB = expressed in decibel n = spatial index over the ground plane i = temporal index or time-step associated with the trajectory o = peak level or reference value