• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.788-793
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• 2005

This paper presents harmonic evaluation of an IAT(Intra Airport Transit) system in Incheon International Airport. It will be used electric vehicles with 80 kW per car that are produced Mitsubishi Heavy Industries Ltd, and one car is constructed with SIV(Static Inverter), VVVF(Variable Voltage and Variable Frequency) and two induction motor. The operated vehicles in the IAT system are rapidly changing DC load, and at a feeding substation, 3-phase electric power is transferred to DC 750 V by rectifier. Since, vehicles are also changing continuously, the voltages for the DC load fluctuate in the IAT system, and moreover, the fluctuating voltages generate high-order harmonics. This means that there is the difficulty in maintaining power quality in KEPCO systems' side. Therefore, the power quality of the IAT system in Incheon International Airport is evaluated using PSCAD/EMTDC simulator in the paper. The THD(Total Harmonic Distortion) of voltages and TDD(Total Demand Distortion) of currents, indices are calculated for the IAT system using the results of PSCAD/EMTDC dynamic simulation.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1657-1668
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• 1998

In the analysis of a mushy solidification system with natural convection using a fixed grid method, the enthalpy method has been used to account for the release of latent heat. The variable viscosity, Darcy source, and hybrid methods have been employed for the velocity suppression in a mushy region. The choice of the values of solid viscosity and permeability constant in conjunction with the Darcy source term plays an important role in forming the location and shape of the phase boundaries. In this work the effects of these major parameters related to steady-state behavior in the system of mushy solidification are investigated through a simple test problem. The effective specific heat based on the spatial gradients of the enthalpy and temperature is adopted for the treatment of the release of latent heat. The effects of the Prandtl and Rayleigh numbers on the shape of mushy region are examined using the hybrid method.

• 한국통신학회논문지
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• 제12권4호
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• pp.386-398
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• 1987

本 論文은 PWM(Pulse Width Modulation)인버어터의 스위칭作用에 의해서 發生하는 高周波 影響을 最小化하기 위한 Suboptimal PAWM(Pulse Amplitude Width Modulation)을 提示하였다. 本 方式은 Suboptimal PWM에서 THD(Total Harmonic Distorition)가 最小가 되는 固定點(基本波 電壓 u1=1.2)에서 하나의 스위칭패턴을 決定하였다. 그리고 電壓은 DC Link에서 DC Chopper에 의해 制御하게 하고 인버어터에서는 단지 高周波만을 制御하도록 하였다. 本 方式은 3相 誘導電動機의 VSD(Variable Speed Drive)에 適用하여 電動機의 騷音, 인버어터의 線間電壓 및 電流, 電流高周波 스펙트럼을 測定하였으며, 他 方式과 比較해 보았다. 그 結果로부터 本 方式의 妥當性을 立證할 수 있었다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권3호
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• pp.81-89
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• 2002

The sensorless AC motor drive is a popular topic of study due to the cost and reliability of speed and position sensors. Most sensorless algorithms are based on the mathematical modeling of motors including electrical variables such as phase current and voltage. Therefore, the accuracy of such variables largely affects the performance of the sensorless AC motor drive. However, the output voltage of the SVPWM-VSI, which is widely used in sensorless AC motor drives, has considerable errors. In particular, the SVPWM-VSI is error-prone in the low speed range because the constant DC link voltage causes poor resolution in a low output voltage command and the output voltage is distorted due to dead time and voltage drop. This paper investigates a novel high-performance strategy for overcoming these problems in a sensorless ac motor drive. In this paper, a variation of the DC link voltage and a direct compensation for dead time and voltage drop are proposed. The variable DC link voltage leads to an improved resolution of the inverter output voltage, especially in the motor's low speed range. The direct compensation for dead time and voltage drop directly calculates the duration of the switching voltage vector without the modification of the reference voltage and needs no additional circuits. In addition, the proposed strategy reduces a current ripple, which deteriorates the accuracy of a monitored current and causes torque ripple and additional loss. Simulation and experimentation have been performed to verify the proposed strategy.

• 대한족부족관절학회지
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• 제15권4호
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• pp.187-194
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• 2011

Ankle injuries may involve the distal tibiofibular syndesmosis and can be associated with a variable degree of trauma to the soft tissue and osseous structures that play an important role in ankle joint stability. Ankle syndesmotic injury may occur solely as a soft tissue injury or in association with variable ankle fractures. Ankle syndesmotic injury does not necessarily lead to ankle instability; however, the coexistence of deltoid ligament injury critically destabilizes the ankle joint. The prevalence of these injuries may be higher than previously reported. The diagnosis of syndesmotic injury as not always easy because isolated ankle sprains may be missed in the absence of a frank diastasis and syndesmotic instability may be unnoticed in the presence of bimalleolar ankle fractures. Controversies arise at almost every phase of treatment includings : type of fixation(screw size, type of implant), number of cortices required for fixation and of need for hardware removal. Regardless of controversies, the most important goal should be restore and maintain the normal tibiofibular relationship to allow for healing of the ligamentous structures of the syndesmosis.

• 한국운동역학회지
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• 제16권2호
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• pp.37-44
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• 2006

The purposes of this study were to analyze and compare EMG activities of the pectoralis major, biceps brachii, triceps brachii, and brachioradialis muscles during biceps curls using a VRT device and an elastic tubing. Fifteen male college students were recruited as subjects and they performed 10-RM and 20-RM biceps curls. For each load and device condition, the mean and peak normalized EMG levels during different phases of a biceps curl were computed. For each load and phase, paired t-test (p.05) was used to find the significant difference between two devices. ANOVA with repeated measures was also used to find the significant difference among phases in terms of EMG values for each muscle. For each load and device condition, the peak and mean EMG levels during different phases of a biceps curl were computed The significant differences between devices were found in biceps brachii for EA, MD, LD phases, and triceps brachii muscles for all phases, respectively. However, no differences were found among phases for any muscle. This indicated that elastic band could have a similar characteristics of VRT. High antagonistic muscle activity as a function of injury prevention which found particularly in VRT device may suggest that elastic tubing can be a safer training device than VRT. This also imply that elastic tubing could be very effective as a home exercise tool for rehabilitation patients and elderly people.

• 천문학회보
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• 제41권1호
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• pp.43.1-43.1
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• 2016

With the Korean VLBI Network (KVN), both single dish and VLBI monitoring observations of H2O and SiO masers were performed toward the semi-regular variable star R Crateris. In the case of 11 VLBI monitoring observations from Jan. 5, 2014 to Jan. 7, 2016, successful superposed maps of H2O and SiO masers were obtained at 7 epochs by adopting the Source Frequency Phase Referencing (SFPR) method. These results enable us to investigate the development of outflow and asymmetric motions from SiO maser to H2O maser regions according to stellar pulsation which are closely related with a mass-loss process. Single dish monitoring observations of H2O and SiO masers were also carried out from 2009 June to 2016 Feb. Intensity variations between H2O and SiO masers were investigated according to stellar optical phases together with peak velocity variations with respect to the stellar velocity. We will compare the VLBI results among different maser transitions with those of single dish.

• 한국지능시스템학회논문지
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• 제26권4호
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• pp.273-278
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• 2016

본 논문에서는 로렌츠 카오스 회로를 곱셈기, 커패시터, 연산증폭기, 제어저항 등을 이용하여 설계하였다. 제안하는 회로는 SPICE 프로그램을 통하여 시간파형, 주파수 특성, 위상특성 등을 해석하였고, 로렌츠 하드웨어를 구현하여서 시간파형, 주파수 특성, 위상특성, 분기도 특성을 측정하였다. 측정결과, $500k{\Omega}$ 가변 제어 저항의 조건에 따라, 로렌츠 회로는 제어저항의 특정 영역 ($10{\sim}100k{\Omega}$)에서 카오스 신호가 생성됨을 확인하였다. SPICE 모의실험 결과와 일치함을 보였고, 하드웨어의 가변저항을 변화주면서 분기도 특성을 측정하여서 저항 변화에 따라 카오스와 주기적인 분기도 형태를 나타내는 것을 확인하였다.

• 청정기술
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• 제14권3호
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• pp.153-159
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• 2008

여드름 치료제인 트리클로산의 초임계이산화탄소에 대한 용해도를 가변부피셀(Variable volume cell)을 이용하여 온도 313.15, 323.15와 333.15 K에 대해서 10 - 40 MPa 압력범위에서 측정되었다. QLF (Quasi-chemical nonrandom lattice fluid) 상태방정식을 이용하여 측정된 용해도를 잘 계산할 수 있었고, 이 자료를 미세입자공정에 활용하였고. 입자크기에 미치는 온도와 압력의 효과를 해석하였다.

• 한국전자파학회논문지
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• 제12권1호
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• pp.99-106
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• 2001

본 논문에서는 선형화 특성이 우수하고, 대역폭이 넓은 feedforward 선형화 기법을 이용하여 IMT-2000용 1-Watt 급 증폭기를 설계 제작하였다. Feedforward는 외부환경(온도, 입력 전력 레벨, 시간 등)의 변화에 민감하므로 마이크로컨트롤러를 이용하여 이를 제어하였다. 35dB 의 이득과 40dBm의 최고전력을 갖는 주증폭기를 설계하였고, 각 루프의 신호를 상쇄하기 위해서 반사형 가변감쇄기와 위상변화기를 사용하였다. 2.11 2.17GHz 대역에서 측정 결과 신호루프에서 주신호를 35dB이상 상쇄하였으며, 오차루프에서 30dB 이상 오차신호를 상쇄하여 60dBc 이상의 선형화 특성을 얻을 수 있었다.