1,721,772 research outputs found
Particle size effects on the particle deposition from non-isothermal stagnation point flows
No full textThe deposition (transport) of particles onto cold smooth walls (about 1159-1345 K) from high temperature combustion suspensions (about 1565 K) undergoing a two-dimensional stagnation point flow was investigated experimentally for a wide range of particle sizes (having diameter from 0.1 to 30 μm) by SEM (Scanning Electron Microscopy) techniques. Using an LDA (Laser-Doppler Anemometry) system, the velocities of the two-phase and the particle size were measured simultaneously. Particle sizes were measured using the maximum pedestal amplitude of Doppler signal and the visibility. Also, particle motion that considered the effects of thermophoresis and inertial impaction was computed by numerically solving Eulerian partial differential equations of momentum, energy and mass for the gas and particle phases (two-fluid model). The experimental data were compared to the numerical results for variation of Stokes numbers. Good agreements between experimental and numerical results were obtained for velocity, temperature and particle deposition rates. Also, the importance of combined thermophoresis and inertial impaction was examined. © 1991
Reactive Power Ancillary Service of Synchronous DGs in Coordination with Voltage Control Devices
No full textThis paper presents an optimal way to control steady-state voltage in distribution feeders using reactive power ancillary service that is provided by synchronous distributed generators (DGs). Based on load forecasts provided one day in advance, DG reactive power is dispatched on the hour in coordination with the switching operations of an on-load tap changer (OLTC) and shunt capacitors (SCs). This aims to reduce not only distribution line power losses but also the number of switching operations of the OLTC and the SCs, which affect the feeder voltage quality and switching device lifetime. For the reactive power dispatch, a mixed-integer nonlinear optimization problem is formulated using a multiobjective function and solved using a particle swarm optimization (PSO) algorithm. Modules using evolutionary and dynamic programming are incorporated into the PSO algorithm to be less susceptible to becoming trapped in local optima and have a better chance of reaching global optimum. Simulation case studies using small- and large-scale distribution networks were performed using MATLAB to demonstrate that the coordinated reactive power support of the DGs, OLTC, and SCs can achieve the objective effectively, resulting in improved voltage quality.118sciescopu
Prosody Control Based on Syntactic Information in Korean Text-to-Speech Conversion System
No full textDelamination Cracks Origination from Transverse Cracking in Cross-Ply Lmintes under Plane Strain Bending and Anti-plane shearing
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Mode decomposition of three-dimensional mixed-mode cracks via two-state integrals
No full textA numerical scheme is proposed to obtain the individual stress intensity factors in an axisymmetric crack and in a three-dimensional mixed-mode crack. The procedures presented here are based on the path independence of J and M integrals and mutual or two-state conservation integrals, which involve two elastic fields. A useful method to decompose the stress intensity factors along curved three-dimensional cracks under mixed mode is derived by using appropriate auxiliary fields for the plane problems. The choice of the auxiliary fields available is critical to success of the present scheme, and in this study it is made of not only the asymptotic plane-strain solution, which requires some remedy in application of the two-state integral due to the lack of equilibrium and compatibility, but a numerical solution with a given stress intensity as well. Some numerical examples of penny-shaped cracks are presented to investigate the applicability and effectiveness of the method for problems of axisymmetric and three-dimensional cracks. (C) 2001 Elsevier Science Ltd. All rights reserved.The authors gratefully acknowledge the financial support by the Korea Research Foundation (grant no. 1998-018-E00049) in the course of this study
Transition Cycle Behavior of the Pan-Shape Transuranic Burner Core with Low Sodium Void Reactivity
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