| 1 | Optimal deployment schedule of an active twist rotor for performance enhancement and vibration reduction in high-speed flights显示文摘The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input. An advanced Particle Swarm assisted Genetic Algorithm(PSGA) is employed for the optimizer. A rotorcraft Computational Structural Dynamics(CSD) code CAMRAD II is used to perform the rotor aeromechanics analysis. A Computation Fluid Dynamics(CFD) code is coupled with CSD for verification and some physical insights. The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation. The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases. A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration. The mechanism of reduction to the performance gains is identified illustrating the section airloads, angle-of-attack distribution, and elastic twist deformation predicted by the present approaches. | Young H.YOU Sung N.JUNG Chang J.KIM | 2017 | Chinese Journal of Aeronautics2017，30，4： | 2 |
| 4 | Change of Electrical and Transport Properties of Nickel Oxide by Carrier Concentration and Temperature through First‑Principle Calculations显示文摘Nickel is typically used as one of the main components in electrical contact devices or connectors.Nickel oxide(NiO)is usually formed on the surfaces of electrodes and can negatively impact system performance by introducing electrical contact resistance.The thermal,electrical,and transport properties of NiO,as a Mott insulator or a p-type semiconductor,can be altered by operating and environmental conditions such as temperature and stress/strain by contact.In this study,we inves-tigate the fundamental material properties of NiO through the first-principle calculations.First,we obtain and compare the lattice parameter,magnetic moment,and electronic structure for NiO via the WIEN2K simulations with four different poten-tials(i.e.,GGA,GGA+U,LSDA,and LSDA+U).Then,using the WIEN2K simulation results with LSDA+U potential that produces a highly accurate bandgap for NiO,we calculate the electrical conductivity and electrical part of the thermal conductivity of nickel and NiO as a function of temperature and carrier concentration through the BoltzTraP simulations.Systematic simulation results revealed that the electrical conductivity relative to the relaxation time for NiO increases with the carrier concentration,while it shows a slightly decreasing trend with temperature under a fixed carrier concentration.By contrast,the electrical part of the thermal conductivity shows an increasing trend considering carrier concentration and temperature. | Nayem Md.Reza Shah Chang‑Dong Yeo Minyeong Choi Yang‑Ki Hong Jeong H.You | 2023 | Nanomanufacturing and Metrology2023，6，4： | 0 |
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