According to the report, about 50% of helicopters in Korea are manufactured more than 30 years ago. For this reason, the large project on the development of the helicopter is proposed. In this research, relationship b...
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ISBN:
(纸本)9787561228999
According to the report, about 50% of helicopters in Korea are manufactured more than 30 years ago. For this reason, the large project on the development of the helicopter is proposed. In this research, relationship between the atomization properties and the characteristics of the reacting flow field in a small gas turbine engine are studied. In general, researches on the development of an injector need a lot of experiments. But those experiments always have the risks of explosion and an emission of toxic gases. Recently computational studies on a chemical reacting flow are widely used as the speed of CPU becomes faster. A spray structure can be expressed in terms of droplet size distribution, break-up length, spray angle, and penetration distance. Among those, the characteristics of the reacting flow field in the gas turbine engine according to various droplet sizes are investigated. Combustion chamber is modeled with 1. 3 million hybrid grid and n-pentane is used for the fuel. With those setting, spray droplet trajectory and temperature distribution are compared. For the cases with three different droplet's mean diameter, as the parcel size of the fuel decreases, reaction occurs faster in smaller area. But those small parcels cannot penetrate deeper, fuels is not equally distributed. Although heat transfer and diffusion occur, this inequality increases the pattern factor, important parameter on the combustor performance. Comparisons on the outlet temperature with two different sizes show that to get lower pattern factor, mean diameter of the spray parcels should be at least 80. This means that injection of smaller parcels than the specific value reduces overall performance of the engine. In this work, only the droplet size distribution and spray angle are considered. There are lots of variables to affect the injection properties, more researches are planed and we work on some of these.
We introduce an inverse problem for the local volatility model in option pricing. We solve the problem using the Levenberg-Marquardt algorithm and use the notion of the Fréchet derivative when calculating the Jac...
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We introduce an inverse problem for the local volatility model in option pricing. We solve the problem using the Levenberg-Marquardt algorithm and use the notion of the Frechet derivative when calculating the Jacobian...
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ISBN:
(纸本)9781424459421;9781424459438
We introduce an inverse problem for the local volatility model in option pricing. We solve the problem using the Levenberg-Marquardt algorithm and use the notion of the Frechet derivative when calculating the Jacobian matrix. We analyze the existence of the Frechet derivative and its numerical computation. To reduce the computational time of the inverse problem, a GP-GPU environment is considered for parallel computation. Numerical results confirm the validity and efficiency of the proposed method.
We present a microscopic model for the anisotropic exchange interactions in Sr2IrO4. A direct construction of Wannier functions from first-principles calculations proves the jeff=1/2 character of the spin-orbit integr...
We present a microscopic model for the anisotropic exchange interactions in Sr2IrO4. A direct construction of Wannier functions from first-principles calculations proves the jeff=1/2 character of the spin-orbit integrated states at the Fermi level. An effective jeff-spin Hamiltonian explains the observed weak ferromagnetism and anisotropy of antiferromagnetically ordered magnetic state, which arise naturally from the jeff=1/2 state with a rotation of IrO6 octahedra. It is suggested that Sr2IrO4 is a unique class of materials with effective exchange interactions in the spin-orbital Hilbert space.
In this paper, a simple spin-spin Ising interaction model for the surface ferromagnetism is combined with the bulk Au diamagnetic response to model the size dependence of the magnetization of a Au nanoparticle. Using ...
In this paper, a simple spin-spin Ising interaction model for the surface ferromagnetism is combined with the bulk Au diamagnetic response to model the size dependence of the magnetization of a Au nanoparticle. Using the maximum entropy formalism, we obtain the average temperature dependent magnetization within a mean field model. Our results qualitatively reproduce recent experimental observations of size-dependent magnetization of Au nanoparticles in which the ferromagnetic moment of thiol-capped nanoparticles is seen to increase for diameters larger than 0.7nm, peaking at approximately 3nm, and subsequently decreasing as the particle diameter increases further.
A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, cyclocopter rotor system is optimized for design variables su...
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A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, cyclocopter rotor system is optimized for design variables such as radius of rotor, rotating speed, maximum pitch angle, chord and span of blade, number of blades and airfoil. To apply response surface methodology, datum acquired by STAR-CD for aerodynamic design variables and MSC/NASTRAN for structural ones. Genetic algorithm is used to find the optimal values from the constructed response surface while objective functions are thrust, required power and stress of blade.
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