根据Markusen and Venables(1999)的分析,在不完全竞争和规模收益递增的条件下,跨国公司和东道国企业之间除了"技术溢出效应"外,还可以通过"利润溢出效应"(Pecuniary Spillover)促进东道国企业发展。本文根据中国...根据Markusen and Venables(1999)的分析,在不完全竞争和规模收益递增的条件下,跨国公司和东道国企业之间除了"技术溢出效应"外,还可以通过"利润溢出效应"(Pecuniary Spillover)促进东道国企业发展。本文根据中国统计年鉴提供的36个行业的面板数据,考察了不同行业跨国公司对本地企业进入率的影响,结果表明:在大多数的行业中,跨国公司对本地企业都存在正向"利润溢出效应"。展开更多
The propulsive efficiency of a plunging NACA0012 airfoil is maximized by means of a simple numerical optimization method based on the response surface methodology （RSM）. The control parameters are the amplitude and ...The propulsive efficiency of a plunging NACA0012 airfoil is maximized by means of a simple numerical optimization method based on the response surface methodology （RSM）. The control parameters are the amplitude and the reduced frequency of the harmonic sinusoidal motion. The 2D unsteady laminar flow around the plunging airfoil is computed by solving the Navier-Stokes equations for three Reynolds number values （Re = 3.3× 10^3, 1.1×10^4, and 2.2 × 10^4）. The Nelder-Mead algorithm is used to find the best control parameters leading to the optimal propulsive efficiency over the constructed response surfaces. It is found that, for a given efficiency level and regardless of the considered Re value, it is possible either to obtain high thrust by selecting a high oscillation frequency or to reduce the input power by adopting a low plunging amplitude. Key words： Plunging airfoil, Propulsive efficiency, Optimization, Response surface methodology （RSM）展开更多
Penetration depth,spray dispersion angle,droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing engine.These processes will enhance air/fuel mixing ins...Penetration depth,spray dispersion angle,droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing engine.These processes will enhance air/fuel mixing inside the combustor.Experimental results from the pulsed air-assist liquid jet injected into a cross-flow are investigated.And experiments were conducted to a range of cross-flow velocities from 42～136 m/s.Air is injected with 0～300kPa,with air-assist pulsation frequency of 0～20Hz.Pulsation frequency was modulated by solenoid valve.Phase Doppler Particle Analyzer(PDPA) was utilized to quantitatively measuring droplet characteristics.High-speed CCD camera was used to obtain injected spray structure.Pulsed air-assist liquid jet will offer rapid mixing and good liquid jet penetration.Air-assist makes a very fine droplet which generated mist-like spray.Pulsed air-assist liquid jet will introduce additional supplementary turbulent mixing and control of penetration depth into a cross-flow field.The results show that pulsation frequency has an effect on penetration,transverse velocities and droplet sizes.The experimental data generated in these studies are used for a development of active control strategies to optimize the liquid jet penetration in subsonic cross-flow conditions and predict combustion low frequency instability.展开更多
文摘根据Markusen and Venables(1999)的分析,在不完全竞争和规模收益递增的条件下,跨国公司和东道国企业之间除了"技术溢出效应"外,还可以通过"利润溢出效应"(Pecuniary Spillover)促进东道国企业发展。本文根据中国统计年鉴提供的36个行业的面板数据,考察了不同行业跨国公司对本地企业进入率的影响,结果表明:在大多数的行业中,跨国公司对本地企业都存在正向"利润溢出效应"。
文摘The propulsive efficiency of a plunging NACA0012 airfoil is maximized by means of a simple numerical optimization method based on the response surface methodology （RSM）. The control parameters are the amplitude and the reduced frequency of the harmonic sinusoidal motion. The 2D unsteady laminar flow around the plunging airfoil is computed by solving the Navier-Stokes equations for three Reynolds number values （Re = 3.3× 10^3, 1.1×10^4, and 2.2 × 10^4）. The Nelder-Mead algorithm is used to find the best control parameters leading to the optimal propulsive efficiency over the constructed response surfaces. It is found that, for a given efficiency level and regardless of the considered Re value, it is possible either to obtain high thrust by selecting a high oscillation frequency or to reduce the input power by adopting a low plunging amplitude. Key words： Plunging airfoil, Propulsive efficiency, Optimization, Response surface methodology （RSM）
基金supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD,Basic Research Promotion Fund) (KRF-2007-D00084)
文摘Penetration depth,spray dispersion angle,droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing engine.These processes will enhance air/fuel mixing inside the combustor.Experimental results from the pulsed air-assist liquid jet injected into a cross-flow are investigated.And experiments were conducted to a range of cross-flow velocities from 42～136 m/s.Air is injected with 0～300kPa,with air-assist pulsation frequency of 0～20Hz.Pulsation frequency was modulated by solenoid valve.Phase Doppler Particle Analyzer(PDPA) was utilized to quantitatively measuring droplet characteristics.High-speed CCD camera was used to obtain injected spray structure.Pulsed air-assist liquid jet will offer rapid mixing and good liquid jet penetration.Air-assist makes a very fine droplet which generated mist-like spray.Pulsed air-assist liquid jet will introduce additional supplementary turbulent mixing and control of penetration depth into a cross-flow field.The results show that pulsation frequency has an effect on penetration,transverse velocities and droplet sizes.The experimental data generated in these studies are used for a development of active control strategies to optimize the liquid jet penetration in subsonic cross-flow conditions and predict combustion low frequency instability.
