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Pulse width modulation (PWM) converter based variable-frequency drives to control AC machines have been widely used in motor drive system. However, it also leads to early bearing degradation in inverter driven machine due to the transient shaft voltage and high frequency bearing currents resulted from the PWM switching. To reduce the machine bearing current and extend the bearing lifetime, one possible...
Controlled hovering of motor driven flapping wing micro aerial vehicles (FWMAVs) is challenging due to its limited control authority, large inertia, vibration produced by wing strokes, and limited components accuracy due to fabrication methods. In this work, we present a hummingbird inspired FWMAV with 12 grams of weight and 20 grams of maximum lift. We present its full non-linear dynamic model including...
Flying animals with flapping wings may best exemplify the astonishing ability of natural selection on design optimization by excelling both stability and maneuverability at insect/hummingbird scale. Flapping Wing Micro Air Vehicle (FWMAV) holds great promise in bridging the performance gap between engineering system and their natural counterparts. Designing and constructing such a system is a challenging...
In recent years, carpooling service provided by corporations like Uber (UberPool), Didi (DidiPool) and Lyft (Lift Link) have become more and more popular. It helps alleviating the urban traffic congestion, by decreasing the empty seats rate. To balance the supply and demand of the taxi service, a dynamic pricing method is needed. More specifically, passengers taking a same vehicle may be charged differently,...
With the rapid development of cloud computing, large scale of cloud services are provided to users. Recommender systems have been proven to be valuable tools to deal with information overload and be able to provide appropriate recommendations to users. The cloud environment is dynamic and uncertain, which makes the quality of cloud services time-sensitive. However, most existing recommender systems...
A design principle for selecting the stiffness of a wing rotational flexure hinge on bio-inspired flapping wing robots is presented. In this work, a systematic approach of selecting rotational stiffness values such that the primary mode of resonance occurs at harmonics of the wing stroke frequency is proposed. Using the quasi-steady aerodynamic model as a basis, simulations were performed to assess...
In the present work, the tidal stream energy resource in Langyatai (LYT) strait was calculated based on tidal current velocity. To obtain the tidal current velocity, a tidal current numerical model was setup and validated by measurements of tidal current in 2 points around LYT strait with observing period of 25 hours in spring tide. The calculated tidal current velocities agree well with the measured...
The components and yield of the oil obtained by co-pyrolysis of a mixture of tobacco stem and waste rubber tire powder were investigated. The results shows that 450°C is an optimal temperature in terms of liquid product yield when the reactants are mixtures of tobacco stem and waste rubber tire powder with a mass ratio of 1∶1. It is found that the liquid product from co-pyrolysis contains less water...
Glycerol is a model whose ingredients are dominant in bio-oil, that is the reason why this thesis chooses glycerol as the model to pyrolyze biomass into oil. The thesis adopts coprecipitation method to produce a series of Ni-based catalysts, researches the rules and principles of restructuring glycerol into hydrogen in gasification reactor and explores the reaction conditions and reaction principles...
Pyrolysis of the macroseaweed Ulva rigida was conducted using microwave as eating source which is 2450Hz in frequency and 1kW in power. The gaseous, liquid and solid product was obtained and the gaseous product consists of CO2,CO,H2 and CH4, among which the first appears the earliest and the third appears at the later stage of pyrolysis with the irradiation time. The second component is absent or...
The fractional Fourier transform (FRFT) can transform the linear frequency modulation (LFM) signal into delta function for a proper orders, since the kernel of FRFT has a property of LFM. Using this property, the paper proposes the filter for LFM signal with noise, which avoids cross-term of quadratic distribution due to the linearity of FRFT. The method can reduce noise by optimizing the parameter...
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