• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.3
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• pp.117-126
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• 2012

This study configuration Vector Control System which is stable and has outstanding Dynamic Characteristics in Very Low Speed Region and Low Speed Region, and proposes Instantaneous Speed Observer and Very Low Speed Control method using Reduced-Dimensional State Observer. The Observer proposed in this system, by appling Reduced-Dimensional State Observer to Load-Torque estimation and using for speed estimation, implements system composition simply and is capable of accurate Instantaneous Speed estimation in Very Low Speed Region. Also, this study reduces influence by System Noise and suggests an induction motor speed control system which is effective in Load Disturbance, modeling error, estimation noise and so on without changing pole of an Observer.

• Journal of Energy Engineering
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• v.4 no.3
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• pp.402-406
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• 1995

다리우스 풍력터빈의 속도설정을 터빈이 만드는 토크와 발전기가 요구하는 토크의 \평형을 통해 찾아 낼 수 있음을 검토하였다. 풍속에 따른 속도-토크곡선에서 일정충력곡선이 만나는 점이 터빈의 동작점으로 되며 이는 안정 및 불안정이 될 수도 있다. 풍속과 출력이 각각 변할 때 이 동작점이 어떻게 이동되는가 하는 점을 제시하였다. 또한 터빈의 속도에 관한 제어 블록선도를 제시하여 그 출력변화에 따른 속도변화의 전달함수를 알아내고 이의 형태는 1차 시지연 함수로 유도된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.150-156
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• 2001

This paper proposed a speed estimator using MRAC(Model Reference Adaptive Control) for sensorless vector control. It is robust for parameter variation or disturbance and the estimated speed is used as feedback in a vector control system. Experiment is presented to confirm the theoretical analysis.

• Journal of the korean Society of Automotive Engineers
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• v.2 no.2
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• pp.25-30
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• 1980

자동차용 추진축의 위험회전속도를 원심력에 의한 탄성변형의 관계로부터 유도하여 보았다. 회전체의 unbalance량은 보통 회전속도에 관계없이 거의 일정하나 자동차용 추진축과 같이 외 경에 비하여 전장이 길고 고속회전하는 경우에는 축의 탄성변형에 의하여 unbalance량이 커진다. 회전속도에 따른 unbalance 변화량을 역시 원심력-탄성변형관계로부터 구하고 balancing을 위한 최적회전속도, tube의 편심도 기타 balancing 작업을 어렵게 하는 요소들에 대하여 정리하여 보았다.

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.174-182
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• 1997

결정성 고분자수지는 가공조건에 의해 결정되는 미세구조의 변화에 따라 최종물성 이 현저히 달라지므로 최종 성형품의 물성을 극대화하기 위해서는 성형가공 중에 필연적으 로 부가되는 열이력 뿐만 아니라 전단이력이 결정화 거동에 미치는 영향을 규명하고 가공조 건의 최적화를 통하여 미세구조를 적절히 제어하는 것이 요구된다. 따라서 본 연구에서 in-situ 상태로 전단유도 결정화거동을 조사할수 있는 rheo-kinetic 실험 방법을 개발하고 결정화 거동에 미치는 열이력과 전단이력의 영향을 규명하고자 하였다. 이를 위해 비교적 결정화 속도가 빠른 폴리 부틸렌 테레프탈레이트 수지를 대상으로 냉각조건, 전단부가시간, 전단속도등을 다양하게 변화시키면서 plate-plate 레오미터로 시간에 따른 전단응력의 변화 를 조사하는 rheo-kinetic 연구를 수행하였다. 아울러 실험 중에 액체 질소로 급냉하여 얻은 시료를 대상으로 등온 및 비등온의 열분석 실험을 수행하고 JMA식과 Hoffman-Lauritzentlr 을 사용하여 분석한 다음, 그 결과를 rheo-kinetic 해석결과와 비교함으로써 결정화 거동에 미치는 전단응력의 영향을 규명하였다. 일정전단속동하에서 수행한 rheo-kinetic 실험결과, 시간에 따른 저난응력의 증가와 용융열이 증가하는 경향이 매우 유사한 거동을 보이므로 전 단응력의 증가는 결정화가 일어남에 기인한 결과임을 확인할수 있었으며 고분자수지가 전단 이력을 받게 되면 분자배향의 결과로 결정화 유도시간이 짧아지고 결정화속도가 증가할 뿐 만 아니라 보다 더 높은 온도에서 결정화가 일어나게 됨을 알수 있었다. 또 결정화 반가기 시간과 Hoffman-Lauritzen 식의 매개변수들이 전단속도, 전단부가시간, 결정화 온도 등의 이력에 무관하게 전단응력에 따라 선형적으로 변하고 있으므로 전단유도 결정화거동은 수지 에 부가되는 전단응력에 직접적인 영향을 받음을 알수 있었다. 이상과같은 전단유도 결정화 거동에 관한 결과를 가공공정상의 열전달 현상과 결합하여 해서하면 성형품 내부의모폴로지 의 예측이 가능하므로 성형품 물성의 극대화 방안의 수립에 이용될수 있을것으로 사료된다.

• Journal of the Korean Chemical Society
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• v.40 no.2
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• pp.128-134
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• 1996

The kinetics of the hydrolysis of dihydro-1, 4-oxathiin derivatives were investigated by ultraviolet spectrophotometry in H2O at $25^{\circ}C.$ A rate equation which can be applied over a wide pH range was obtained. The substituent effects on the hydrolysis of dihydro-1, 4-oxathiin derivatives were studied and the rate of hydrolysis was shown to be accelerated by electron accepting groups. Final product of the hydrolysis was 2-(2-hydroxyethylthio)acetoacet-anilide enol form. On the basis of rate equations derived and judging from hydrolysis products obtained and from general base effect and substituent effects, plausible mechanism of the hydrolysis in various pH range have been proposed. Below pH 3.5, the hydrolysis was initiated by the protonation and followed by the addition of water to 2-carbon. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxide to 2-carbon. In the range of pH 4.0∼10.0, the addition of water to dihydro-1,4-oxathiin is rate controlling step.

• Clinical and Experimental Reproductive Medicine
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• v.37 no.3
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• pp.253-259
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• 2010

Objective: To evaluate if there is any correlation between the growth rate of dominant follicles and clinical characteristics or outcome variables in women undergoing controlled ovarian hyperstimulation (COH). Methods: This study was performed in 313 in vitro fertilization (IVF) cycles. Follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2) were measured on day 3 of menstrual cycle, and serial ultrasonographic measurement of the diameter of growing follicles was performed. The growth rates of dominant follicles calculated by diameter difference divided by days were correlated with clinical characteristics and outcome variables. Results: There was no significant difference in the growth rate of the dominant follicles between gonadotropin releasing hormone (GnRH) agonist and antagonist cycles. No significant correlation was found between the growth rates and evaluated factors such as age, body mass index, LH, FSH, $E_2$, retrieved oocytes and fertilization rate. Conclusion: The Growth rate of dominant follicles seems to show an independent feature of basal characteristics and ovarian response.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.65-74
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• 1993

A miniature size electrostatic induction motor has been fabricated and studied with emphasis on the role of the surface resistivity, the relative dielectric constant and the charge relaxation time constant of the rotor surface materials and the rotor liner materials, which, however, control the surface charge induction and relaxation on the rotor material surface and the field intensity between the rotor and the stator of the motor. It is found that the surface resistivity and/or the relative dielectric constant, and the charge relaxation time constant of the rotor surface material enfluenced significantly to motor speed controlled by the surface charge induction and relaxation on the rotor surface depending on the applied voltage and/or frequency changing. The resistivity of the rotor liner material is also found to be effected to the motor speed greatly by control of the field intensity between the rotor and the stator and of the surface charge distribution of the induced charge on the rotor. As a result, a maximum no load rotor speed of the motor tested was about 5500 rpm at the applied voltage of 4.5 kV and the frequency of 220 Hz for the case of the rotor surface material of $BaTiO_{3}$ 80% in the resin binder layered on the copper-foil rotor liner material.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.8-16
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• 2002

The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.1
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• pp.29-34
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• 2005

The wound induction motor can provide high starting torque and reduced starting current simultaneously by inserting large resistor externally when starting. And this technique is one of the well known methods among the induction motor starting methods and generally used for heavy load starting such as crane and cement factories. The conventional PI controller has been widely used in industrial application due to the simple control algorithm and is generally used for control of current torque, position, and speed for the wound induction motor drive system. However, the conventional control system for wound induction motor may result in poor performance because sensors have to be used but are often limited by the environmental condition. Recently, to overcome these problems, many sensorless vector control methods for the wound induction motor have been studied. This paper presents a MRAS method for sensorless vector control of the wound induction motor drive. In the conventional MRAS method, in low frequency, the stator resistance variation may result in poor performance. Therefore, this paper presents a MRAS method with stator and rotor resistance tuning for sensorless vector control of the wound induction motor to overcome several shortages of the conventional MRAS caused by parameter variation and to enhance the robustness of the sensorless vector control. The validity and effectiveness of the proposed method is verified through digital simulation.