• 한국결정성장학회지
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• 제25권1호
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• pp.6-12
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• 2015

율속제어소결은 소결 공정 중 실시간으로 측정되는 시편의 팽창/수축거동을 이용해 일정한 수축거동을 하도록 로의 파워를 조정하는 소결방법으로, 온도를 조절하기 위해 로의 파워를 제어하는 일반적인 소결에 비해 시편의 소결 과정을 세밀히 제어할 수 있으며, 특히 소결공정의 최적화를 이룰 수 있는 장점이 있다. 본 연구에서는 탄화붕소의 소결에 율속 제어소결을 적용해 각 공정변수의 조절에 따른 소결온도 및 입자성장의 변화를 조사하여 그 상관관계를 규명하고 이를 기존의 이론에 맞추어 해석함으로써 율속제어소결을 어떻게 소결공정 최적화에 이용할 수 있는지 그 가능성을 알아보았으며 이를 통해 향후 미지 소재의 소결공정에 율속제어공정을 어떻게 적용할 수 있는지 고찰해 보았다.

• Journal of Pharmaceutical Investigation
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• 제23권3호spc1호
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• pp.9-18
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• 1993

Sugar spheres loaded with melatonin (MT) were coated with $Aquacoat^{\circledR}$ to control the release rate of MT over 8 hours. A zero-order release pattern over 8 hours was obtained with 20% coating on 8-10 mesh beads in USP basket dissolution studies. MT in 20% coated beads was quite stable at room temperature with less than 5% MT degraded during 6 months' storage. Dissolution profiles were also unchanged after 6 months. An oral preparation containing MT-loaded uncoated beads for immediate release and 20% coated beads with $Aquacoat^{\circledR}$ for controlled release over 8 hours was evaluated in six human subjects. When total 0.5 mg MT as low dose (immediate release portion of MT, 0.1 mg) was administered to four subjects, average peak plasma MT concentration was reached at about 600 pg/ml and maintained at about 10 pg/ml over 8 hours. Plasma MT concentration-time profiles were similar in shape to computer-simulated profiles. However, maximal plasma MT concentrations were three times greater compared to computer simulated curve. These results suggest that MT dose, ratio of immediate and controlled release MT, and pharmacokinetic parameters selected are adjusted to mimic endogenous MT concentration-time curve. In another study, 0.2 mg MT having 10% of immediate release portion and 80% controlled release portion produced plasma MT concentration-time curve which is more similar to endogenous profiles. A low bioavailability (<20%) may result from extensive first pass metabolism and remaining amounts of MT from controlled beads. A good correlation between plasma MT concentration and urinary excretion rate of 6-sulphatoxymelatonin (6-STMT), a major metabolite of MT was observed. As plasma MT concentration increased, urinary excretion rate of 6-STMT increased concomitantly. The linear relation between plasma MT and urinary excretion rate of 6-STMT was statistically significant. This result suggests that urinary 6-STMT may be used as an index of circadian rhythms of MT in humans.

• 한국산학기술학회논문지
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• 제15권3호
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• pp.1685-1690
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• 2014

본 논문에서는 유도전동기 벡터제어 인버터에서 상전류를 검출할 때 발생하는 측정 오차를 실시간으로 보상하는 방법을 제안한다. 전류측정에 오프셋 오차와 변환이득 오차가 포함될 경우의 3상 유도전동기 토크 방정식을 유도하여 이러한 측정 오차들이 전동기의 토크 리플을 유발하는 것을 보였으며, 이러한 토크 리플을 제거할 수 있는 방법을 제시하였다. 특히, 본 논문에서는 전동기의 운전 상태에서 실시간으로 변환이득 오차에 의한 토크 리플을 제거하는 방법을 제안하였다. 이를 200[W]급 3상 유도전동기의 벡터제어 인버터에 적용하여 컴퓨터 시뮬레이션 및 실험을 수행함으로써 제안된 방법의 유효성을 검증하였으며, 그 결과 전류측정에서 변환이득 오차가 있더라도 전동기의 토크가 상당히 제거되는 것을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.113-117
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• 2003

The digital systems include the noise in power supply, ground and packaging due to a simultaneous switching of signal, signal reflections and distortions on single and multiple transmission lines. The requirement for the controlled impedance on a PCB can be both a critical success factor and a design challenge. So, the invented tool simulates the tracks controlled impedance with the test coupon. It can saves the design time and supports the economical PCB design.

• KSBB Journal
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• 제5권4호
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• pp.377-382
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• 1990

The characteristics controlled drug release have been studied for biodegradable polymer matrix. Polymer matrix was prepared from glycerine, prednisolone and dextran. Mathematical analysis of the data showed that the release behavior actually conformed to the Higuchi's diffusion controlled model. The release time was increased as drug loading doses increased, whereas decreased as glycerine concentration increased. The release rate did not change by varying molecular weight of dextran.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1540-1542
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• 2005

In SMPS, digital control techniques are adopted widely. But Digital controlled SMPS has poor performance of regulation and transient response than analog controlled SMPS. Delay time of control computing and low frequency of updating duty ratio make digital controlled SMPS poor performance. This paper proposed the optimized control computation to increase not only frequency of updating duty ratio but also switching frequency of SMPS.

• Journal of Power Electronics
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• 제9권3호
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• pp.438-446
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• 2009

The performance of direct torque controlled (DTC) interior permanent magnet (IPM) machines is poor at low speeds due to a few reasons, namely limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. Due to factors such as forward voltage drop across switching devices in the three phase inverter and dead-time of the devices, the voltage across the machine terminals differ from the reference voltage vector used to estimate stator flux and electromagnetic torque. This can lead to instability of the IPM drive during low speed operation. Compensation schemes for forward voltage drops and dead-time are proposed and implemented in real-time control, resulting in improved performance of the space vector modulated DTC IPM drive, especially at low speeds. No additional hardware is required for these compensators.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.179-185
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• 2005

This paper presents a novel circuit topology of a high efficiency single-phase power conditioner. This power conditioner is composed of time-sharing sinewave absolute pulse width modulated boost chopper with a bypass diode in the first power processing stage and time-sharing sinewave pulse width modulated full-bridge inverter in the second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the two power processing stage with time-sharing dual mode sinewave modulation scheme is described with a design example. This paper proposes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle of this novel power conditioner related to new energy utilization system is presented and discussed through the experimental results.

• 전자공학회논문지A
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• 제32A권5호
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• pp.42-53
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• 1995

Token bus protocols have been sidely accepted for Medium Access Control (MAC) in real-time networks such as those used in factory automation, distributed process control, nuclear power plant, aircraft and spacecraft. Token bus protocols provide timer-controlled priority mechanism, which offers multiple level of privilege of medium access to different type of traffic. This paper presents and approximate analytical model for the evaluation of variance of waiting time in the time-controlled proiority scheme of token bus protocols. Token bus system is assumed to be operated with singe-service discipline which is the practical case of real-time networks such as those used in distributed process control and factory automations. The approximate analytical model is validated by comparison with the simulation resuls.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1039-1041
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• 2000

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.