• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.461-467
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• 2006

The seasonal change in attached algae and microbial community structure at sedimentation basin of water treatment plant was investigated by using quinone profiles and denaturing gel gradient electrophoresis (DGGE). The photosynthetic bacteria and algae contains PQ-9 and VK-1 as major quinone are major component of the total quinone fraction in attached algae and microorganisms on sedimentation basin trough. The microorganisms containing menaquinones appear to be sensitivity to the change in temperature than those containing ubiquinones. The plot of the mole fraction of dominant quinone species ($f_d$) to the DQ values showed higher sensitivity to the seasonal change in the microbial community structure. The results indicated that quinone and DGGE are useful tool for the evaluation of the changes in the microbial community structure.

• International Journal of Control, Automation, and Systems
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• v.4 no.1
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• pp.1-9
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• 2006

This paper presents the modeling and multivariable feedback control of a novel high-precision multi-dimensional positioning stage. This integrated 6-degree-of-freedom. (DOF) motion stage is levitated by three aerostatic bearings and actuated by 3 three-phase synchronous permanent-magnet planar motors (SPMPMs). It can generate all 6-DOF motions with only a single moving part. With the DQ decomposition theory, this positioning stage is modeled as a multi-input multi-output (MIMO) electromechanical system with six inputs (currents) and six outputs (displacements). To achieve high-precision positioning capability, discrete-time integrator-augmented linear-quadratic-regulator (LQR) and reduced-order linearquadratic-Gaussian (LQG) control methodologies are applied. Digital multivariable controllers are designed and implemented on the positioning system, and experimental results are also presented in this paper to demonstrate the stage's dynamic performance.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.53-57
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• 2012

The mathematical model of a three-phase voltage source pulse-width modulation (PWM) DC/AC inverter is non-linear, and in view of the traditional linear control strategy it can not meet the requirements of designing a high-performance inverter. What's more, when the loads are not pure resistive loads, the inverter further requires that the controller possess high-performance. This paper proposes a nonlinear control strategy for the inverter called Passivity-based Control. We can alter the inverter model in three-phase abc coordinate to two-phase synchronous rotating dq coordinate for establishing the port-control Hamiltonian (PCH) model for this system. We can control the distribution of energy in the system to achieve the control aim. Simulation results show that the passivity-based control method can make this system possess a level of high-performance that is both robust and dynamic.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.245-249
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• 1989

From the careful analysis of the transformed dq system equations of a PWM Voltage Source Converter ( PWM - VSC ), a novel voltage control is proposed which is based on the derivative of in-phase current component of line currents and the relation between dc-link voltage and in-phase current component. A simple logical algorithm to implement the proposed scheme is also presented at transient state. The sinusoidal PWM is adopted at steady state. The simulation results show good transient characteristics.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1282-1286
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• 1999

This paper presents the DQ transfomation and space vector modulation method to develop a control algorithm of distribution STATCON(STATic CONdenser) for line voltage regulation, dc link voltage regulation and harmonics compensation. The Performance analysis of a PI with ramp comparision and synchronous reference frame current controller is carried out. Based on these analysis, the control performances are desirable to compensate the harmonics and to regulate de link and line voltage of Distribution line.

• Steel and Composite Structures
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• v.16 no.1
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• pp.77-96
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• 2014

In this paper, magneto-thermo-elastic problem of a thick truncated conical shell immersed in a uniform magnetic field and subjected to internal pressure is investigated. Material properties of the shell including the elastic modulus, magnetic permeability, coefficients of thermal expansion and conduction are assumed to be isotropic and graded through the thickness obeying the simple power law distribution, while the poison's ratio is assumed to be constant. The temperature distribution is assumed to be a function of the thickness direction. Governing equations of the truncated conical shell are derived in terms of components of displacement and thermal fields and discretised with the help of differential quadrature (DQ) method. Results are obtained for different values of power law index of material properties and effects of thermal load on displacement, stress, temperature and magnetic fields are studied. Results of the present method are compared with those of the finite element method.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.27-31
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• 2004

Through time-series CCD photometry using a 155mm refractor, we found a new $\delta$ Scuti type variable star, HD 235428, near a known bright $\delta$ Scuti type star, DQ Cep. We performed follow-up observations using a 61cm telescope at Sobaeksan Optical Astronomy Observatory. Four frequencies have been derived by multiple-frequency analysis, which are 15.804, 5.498, 15.351 and 24.516cycle $day^{-1}$, respectively. V-amplitude of HD 235428 is ${\Delta} V$ = 0.026.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.42-45
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• 1997

A synchronous solid-state var compensator(SSVC) system which employs a three-phase neutral-point-darned (NPC) inverter is presented and analyzed for high voltage and high power applications. The proposed SSVC system can compensate for leading and lagging displacement factor. An optimal pulse-width-modulation (PWM) is used as a means of reducing the size of reactive components. A equivalent model is obtained using DQ-transform, and the characteristic of open-loop system are archived from DC and AC analyzes. A $\alpha$ phase-shift control is suggested using a self-controlled dc bus.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.749-753
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• 2003

This paper presents an output voltage regulation system using PWM Buck-Boost AC-AC converter for power qualify improvement of custom power. This paper proposes dynamic modeling of the system for control object and in addition, a controller design example. Therefore, system state equation is derived whereby the transfer function could be obtained. The paper shows a regulation controller for tracking the output voltage to the reference under specific operating point. Finally, this paper shows validity and practical applicability of the proposed modelling and system design by experimental results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.10
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• pp.1029-1036
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• 1990

This paper presents a systematic study for control loops in the induction motor drive system employing a load commutated current source inverter (LCCSI) which has appeared since the early 1980's, and their effects on the dynamic stability of the system. A set of dq equations which amalgamate the overall system is developed, and from the equations it is revealed that the steady state characteristics of the LCCSI-induction motor system are between VSI and ASCI. When the speed control loop is constructed without a speed sensor, the evaluation of the pole/zero locations and the assessment of the stability for the added loops are investigated. We also show that the V/F loop is essential in this type of drive without the speed sensor.