• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1317-1325
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• 2000

A new efficient numerical method for computing three-dimensional, unsteady, incompressible flows is presented. To eliminate the restriction of CFL condition, a fully-implicit time advancement in which the Crank-Nicolson method is used for both the diffusion and convection terms, is adopted. Based on an approximate block LU decomposition method, the velocity -pressure decoupling is achieved. The additional decoupling of the intermediate velocity components in the convection term is made for the fully -implicit time advancement scheme. Since the iterative procedures for the momentum equations are not required, the velocity components decouplings bring forth the reduction of computational cost. The second-order accuracy in time of the present numerical algorithm is ascertained by computing decaying vortices. The present decoupling method is applied to minimal channel flow unit with DNS (Direct Numerical Simulation).

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.181-190
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• 2019

Active power decoupling circuits have emerged to eliminate the inherent second-order ripple power in a single-phase power conversion system. This study proposes a design method to determine the optimal capacitance for active power decoupling circuits to achieve high power density. Minimum capacitance is derived by analyzing ripple power in a passive power decoupling circuit, a buck-type circuit, and a capacitor-split-type circuit. Double-frequency ripple power decoupling capabilities are also analyzed in three decoupling circuits under a 3.3 kW load condition for a battery charger application. To verify the proposed design method, the performance of the three decoupling circuits with the derived minimum capacitance is compared and analyzed through the results of MATLAB -Simulink and hardware-in-the-loop simulations.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.326-342
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• 2022

Comparative analyses of a shield building subjected to a large commercial aircraft impact between decoupling method and coupling method are performed in this paper. The decoupling method is applying impact force time-history curves on impact area of the shield building to study impact damage effects on structure. The coupling method is using a model including aircraft and shield building to perform simulation of the entire impact process. Impact force time-history curves of the fuselage, wing and engine and their total impact force time-history curve are obtained by the entire aircraft normally impacting the rigid wall. Taking aircraft structure and impact progress into account some loading areas are determined to perform some comparative analyses between decoupling method and coupling method, the calculation results including displacement, plastic strain of concrete and stress of steel plate in impact area are given. If the loading area is determined unreasonably, it will be difficult to assess impact damage of impact area even though the accurate impact force of each part of aircraft obtained already. The coupling method presented at last in this paper can more reasonably evaluate the dynamic response of the shield building than the decoupling methods used in the current nuclear engineering design.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2645-2647
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• 2000

This paper presents an LMI(Linear Matrix Inequalities) method for designing the optimal decoupling controller. The proposed controller based on the Two-Degree-of-Freedom configuration considers both the performance of controller and decoupling properties. The decoupling controller parameters are obtained from LMI method for computational efficiency.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1617-1620
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• 2005

The current control for interior permanent magnet machines is more complicate than surface permanent magnet machine because of its torque characteristic depending on the reluctance. For high performance torque control, it requires state decoupling between the d-current and q-current dynamics. However the variation of the inductances, which couples the state dynamics of the currents, makes the state decoupling difficult. So some decoupling methods have developed to cope this variations and each current can be regulated independently. This paper presents a novel approach for fully decoupling the states cross-coupling using parameter adaptation. The adaptation method is based on the error between reference currents and the currents with state decoupling which have to follow the references. This method is more object-oriented than the other online parameter estimation methods in IPM machine and other electrical machines

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.486-487
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• 2012

In this paper, novel three-port active power decoupling (APD) method for applying 250[W] micro-inverter. This type using third port for active power decoupling stores the surplus energy and supplies sufficient energy to grid. Conventional decoupling circuit is applied in single phase grid connected micro-inverter especially single-stage configuration like flyback-type DC-AC inverter. In this passive power decoupling method, electrolytic capacitor with large capacitance is needed for decoupling from constant DC power and instantaneous AC power. However the decoupling capacitor is replaced with film capacitor by using APD, thus the overall system can achieve smaller size and long lifespan. Proposed three-port flyback inverter is verified by design and simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.61-72
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• 2005

This paper proposes a method which efficiently allocates decoupling capacitance to reduce power supply noise at the floorplan level. We observe problems of previous approach that the decoupling capacitance of each module was overestimated and the power supply noises of modules were changed by inserting additional area for decoupling capacitance, and then suggest a new approach. And, we also present a simple heuristic method which can effectively allocate white space modules for decoupling capacitance area within more faster time instead of LP technique. Experimental results show that our approach can reduce the area of decoupling capacitance to average 7.9 percent compared with Zhao's approach in [4]. Therefore both total area and wire length of nniflm result are decreased. Also, we confirm that our approach solves well the problem caused by inserting additional area. In execution time comparison, our approach shows average 11.6 percent improvement.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.633-636
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• 2000

The decoupling of the systems is to let the inputs and outputs correspond one to one, by performing the state feedback or the output feedback on the given systems. In this paper, we propose a method for decoupling the separable-denominator two-dimensional systems. And, we study about the realization dimension of the dynamical feedback and the dynamical feedforward performed for decoupling.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.129-134
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• 2000

An efficient numerical method to solve the unsteady incompressible Navier-Stokes equations is developed. A fully implicit time advancement is employed to avoid the CFL(Courant-Friedrichs-Lewy) restriction, where the Crank-Nicholson discretization is used for both the diffusion and convection terms. Based on a block LU decomposition, velocity-pressure decoupling is achieved in conjunction with the approximate factorization. Main emphasis is placed on the additional decoupling of the intermediate velocity components with only n th time step velocity The temporal second-order accuracy is Preserved with the approximate factorization without any modification of boundary conditions. Since the decoupled momentum equations are solved without iteration, the computational time is reduced significantly. The present decoupling method is validated by solving the turbulent minimal channel flow unit.

• Journal of Power Electronics
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• v.13 no.4
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• pp.558-568
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• 2013

In this paper, a new decoupling technique for a flyback inverter using an active power decoupling circuit with auxiliary winding and a novel switching pattern is proposed. The conventional passive power decoupling method is applied to control Maximum Power Point Tracking (MPPT) efficiently by attenuating double frequency power pulsation on the photovoltaic (PV) side. In this case, decoupling capacitor for a flyback inverter is essentially required large electrolytic capacitor of milli-farads. However using the electrolytic capacitor have problems of bulky size and short life-span. Because this electrolytic capacitor is strongly concerned with the life-span of an AC module system, an active power decoupling circuit to minimize input capacitance is needed. In the proposed topology, auxiliary winding defined as a Ripple port will partially cover difference between a PV power and an AC Power. Since input capacitor and auxiliary capacitor is reduced by Ripple port, it can be replaced by a film capacitor. To perform the operation of charging/discharging decoupling capacitor $C_x$, a novel switching sequence is also proposed. The proposed topology is verified by design analysis, simulation and experimental results.