• Journal of Institute of Control, Robotics and Systems
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• v.21 no.1
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• pp.28-33
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• 2015

In this paper, we propose a near optimal controller design method for permanent magnet synchronous generators (PMSGs) of MW-class direct-driven wind turbine systems based on SDRE (State Dependent Riccati Equation) approach. Using the solution matrix of an SDRE, we parameterize the optimal controller gain. We present a simple algorithm to compute the near optimal controller gain. The proposed optimal controller can enable PMSGs to precisely track the reference speed determined by the MPPT algorithm. Finally, numerical simulation results are given to verify the effectiveness of the proposed optimal controller.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.591-601
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• 2006

In this paper, we present a new control methodology for perturbed crane systems. Nonlinear crane systems are transformed to linear models by feedback linearization. An inverse dynamic equation is applied to compute the system PD control force. The PD control parameters are selected based on a nominal model and are therefore suboptimal for a perturbed system. To achieve the desired performance despite model perturbations, we construct a neural network auxiliary controller to compensate for modeling errors and disturbances. The overall control input is the sum of the nominal PD control and the neural auxiliary control. The neural network is iteratively trained with a perturbed system until acceptable performance is attained. We apply the proposed control scheme to 2- and 3-degree-of-freedom (D.O.F.) crane systems, with known bounds on the payload mass. The effectiveness of the control approach is numerically demonstrated through computer simulation experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.663-668
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• 2011

Although multi-frame super resolution algorithm has many merits but it demands too much calculation time. Researches have shown that image processing time can be reduced using a CUDA(Compute unified device architecture) which is one of GPGPU(General purpose computing on graphics processing unit) models. In this paper, we show that the processing time of multi-frame super resolution algorithm can be reduced by employing the CUDA. It was applied not to the whole parts but to the largest time consuming parts of the program. The simulation result shows that using a CUDA can reduce an operation time dramatically. Therefore it can be possible that multi-frame super resolution algorithm is implemented in real time by using libraries of image processing algorithms which are made by a CUDA.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.10b
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• pp.89-100
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• 2000

Recently, marine traffic engineering has been developed until that possible to estimate a change in traffic flow caused from some transformations of the traffic condition and to assess whether changed traffic condition is can be accepted as a useful thing in navigation or not by compute simulation. This paper's main substance is assessment of the present marine traffic safety at these area adjacent to Pusan harbor. Also in this study, it was carried out in order to be convinced of validity of round about TSS to expect changing in traffic flows by the institution of round about TSS and to assess expected traffic flows by using Environmental Stress assessment model.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.138-144
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• 1998

The BGK equation, which is the kinetic model equation of Boltzmann equation, is solved using FDDO(finite difference with the discrete-ordinate method) to compute the rarefied flow of monatomic gas. Using reduced velocity distribution and discrete ordinate method, the scalar equation is transformed into a system of hyperbolic equations. High resolution ENO(Essentially Non-Oscillatory) scheme based on Harten-Yee's MFA(Modified Flux Approach) method with Strang-type explicit time integration is applied to solve the system equations. The calculated results are well compared with the experimental density field of NACA0012 airfoil, validating the developed computer code. Next. the computed results of circular cylinder flow for various Knudsen numbers are compared with the DSMC(Direct Simulation Monte Carlo) results by Vogenitz et al. The present scheme is found to be useful and efficient far the analysis of two-dimensional rarefied gas flows, especially in the transitional flow regime, when compared with the DSMC method.

• Journal of the military operations research society of Korea
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• v.34 no.2
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• pp.1-26
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• 2008

This study presents a new estimation of optimal amount of B/L for infantry rifles and artillery weapons which are currently using in Korean Army. To do that, we analyzed current concept of B/L and methodologies used to compute B/L before, and re-calculate optimal amount of B/L to solve some problems founded. We also applied ARENA simulation model to propose estimated values of optimal B/L. The proposed optimal B/L will certainly help to improve efficiency for wartime readiness in the future.

• Journal of Power Electronics
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• v.12 no.2
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• pp.294-304
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• 2012

This paper proposes a fuzzy speed tracking controller and a fuzzy rotor angular acceleration observer for a surface-mounted permanent magnet synchronous motor (SPMSM) based on the Takagi-Sugeno (T-S) fuzzy model. The proposed observer-based controller is robust to load torque variations since it utilizes rotor angular acceleration information instead of the load torque value. Linear matrix inequality (LMI) sufficient conditions are given to compute the gain matrices of the speed tracking controller and the observer. In addition, it is mathematically verified that the proposed observer-based control system is asymptotically stable. Simulation and experimental results are presented to confirm that the proposed control algorithm assures a better transient behavior and less sensitivity under model parameter variations than the conventional PI control method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.10
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• pp.500-506
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• 2005

With the advent of electric power systems moving to a deregulated retail electricity market environment, calculating distribution service tariffs has become a challenging theme for distribution industries and tariff regulators. As distribution business remains as a monopoly, it is necessary to be regulated. And as multiple distribution companies compete with each other, it would be efficient to adopt competition to the determination of distribution service tariffs. This paper proposes a method to calculate distribution service tariffs using yardstick regulation, which can lead to competition among multiple distribution companies. The proposed method takes into account not only recovering revenue requirements but also the advantages of the yardstick regulation based on long-term marginal costs of distribution network expansion algorithms. A computer simulation is carried out to illustrate effectiveness of the proposed method and it is estimated that the algorithm can be applied to compute the distribution service tariffs under retail electricity markets.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.513-516
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• 2002

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents two intelligent optimization algorithm techniques such as genetic algorithm and simulated annealing for the solution of the static EIT inverse problem. We summarize the simulation results for the three algorithm forms: modified Newton-Raphson, genetic algorithm, and simulated annealing.

• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.395-406
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• 2003

In this thesis, we propose a test statistic for testing exponentiality against NBU alternatives. Our test statistics is based on a linear function of the order statistics and is readily applied in the case of small sample as well as large sample. The exact and asymptotic distribution of the test statistics is derived and asymptotic efficiencies are studied. Our new test is easier to compute and performs better for several alternatives than test of Hollander and Proschan(1972).