• 대한방사선기술학회지:방사선기술과학
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• 제40권2호
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• pp.245-251
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• 2017

복부-골반 CT검사 시 피폭선량을 측정해 보고, 영상 판독에 영향을 미치지 않는 범위에서 복부와 골반의 피폭선량 최적화를 위한 프로토콜을 제시하고자 하였다. 기존 임상의 스캔 방식인 120 kVp, AEC(auto exposure control) 기법을 이용한 복부-골반을 1 phase로 스캔을 하였고, 새로 제시한 2 phase 스캔 방식은 1 phase 복부검사와 2 phase 골반검사로 각각 나누어 복부검사는 관전압 120 kVp, AEC, 골반검사는 120 kVp, 100, 150, 200, 250, 300, 350, 400 mA로 고정 관전류 기법을 이용하여 실시하였다. 스캔 시 측정된 $CTDI_{VOL}$, DLP 값을 이용해 선량값을 비교하였고, 각 스캔 영상에서 CT 감약계수와 노이즈, SNR의 평균값을 구해 영상을 평가하였다. 연구결과는 2 phase 스캔 시 1 phase 스캔 시보다 $CTDI_{VOL}$ 값은 복부에서 26%, 골반 100~250 mA에서 1.8~59.5% 감소, 300~400 mA에서 12.7~30% 증가로 유의한 차이를 보였다. 또한, DLP값은 2 phase 스캔 시 1 phase 스캔 시보다 복부에서 약 53%, 골반에서 약 41~81% 감소를 보였으나 통계적으로 유의하지 않았다. SNR은 심장주변에서 2 phase 스캔 시, 골반주변에서는 1 phase 스캔 시, 상복부와 하복부에서 1 phase 스캔 시보다 2 phase 200~250 mA 스캔 시 높게 나타났다. 또한, CT Number와 노이즈는 전반적으로 비슷한 양상을 보였지만, 골반 주변에서 노이즈가 높게 나타났다. 그러나 2 phase의 골반주변 250 mA 스캔 시 1 phase와 비슷한 노이즈값을 나타냈고 통계적으로 유의한 차이를 보이지 않았기에 통상적인 1 phase 400 mA보다 골반을 분리시켜 250 mA 스캔 시 화질에 차이 없이 피폭선량 감소효과를 볼 수 있을 것으로 본다. 그러므로 잦은 복부-골반 CT를 시행하는 환자 혹은 가임기여성, 소아의 골반은 피폭을 줄이면서 화질차이 없이 검사를 위한 2 phase 검사를 제안한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.216-218
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• 2017

The imbalance at the 3-phase side at the railway power supply substation has been a well-known issue. Due to the difference in status of loads at each phase at any given moment, it is difficult to maintain the balance in the 2-phase side of the transformer. Consequently, the 3-phase side also presents a certain level of imbalance as well. A co-phase power supply was proposed as a solution. The real application of such system is gradually expanding, proving the effectiveness of the system. In this paper, the application of the single phase D-Q rotating frame theory was applied to the control of the co-phase power supply system. In addition, the power stack of the system was composed of MMC valves, which offers superior operational characteristics. The effectiveness of the system was verified with a real-time simulation, and the results are presented.

• 한국콘텐츠학회논문지
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• 제15권9호
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• pp.395-402
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• 2015

복부 및 흉부의 방사선 치료 시 호흡에 의한 종양의 움직임을 평가하고, 그 데이터를 활용하여 종양과 정상조직을 구분함으로써 정상조직에 대한 손상을 최소화하고 종양 치료 효과를 극대화 하고자 하였다. 폐암과 간암 환자를 각 20명씩 대상으로 4D-CT simulation과 GE사의 Light speed-16 검사장비로 50% top phase를 기준으로 30~70 % gating phase 구간과 0~90 % full phase 구간에서 움직임을 측정하였다. 폐와 간에서 종양의 full phase가 0~90 % 와 gating phase가 30~70 % 일 경우 GTV의 움직임과 크기를 비교하였다. I(inferior)에서 가장 큰 차이가 있었으며, full phase가 0~90%일 때 종양 움직임의 정도는 상대적으로 컸으며, gating phase를 30~70 % 하였을 때 종양 움직임이 평균 7.1mm 감소된 다는 것을 확인하였다. 동일한 방법으로 4D-CT simulation에서 full phase가 0~90 %일 때 움직임 값과 gating phase가 30~70 % 일 때 움직임 값을 비교해보면 full phase가 0~90% 보다 gating phase가 30~70% 일 때 2배 이상 움직임이 감소한다는 것을 확인하였다. 따라서 4D-CT simulation에서 얻을 결과를 이용하여 환자치료에 적용한다면 정상조직에 대한 피폭을 현저히 경감시킬 수 있을 것이며, 치료 후 방사선 장해와 환자의 고통 감소 등 효과적인 치료 결과를 얻을 수 있을 것으로 사료된다.

• 한국산학기술학회논문지
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• 제21권5호
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• pp.672-678
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• 2020

교류전기철도 급전시스템에 병렬급전방식을 적용할 경우, 전동차 부하로 인한 전압강하 및 최대순시부하를 감소시켜 급전구간을 연장하고 급전용량을 향상시킬 수 있다는 장점이 있다. 그러나 변전소 간에 위상차가 있을 경우 순환전력이 발생하기 때문에 적용이 제한되며, 전동차 운행에 따른 부하 분포에 따라 변전소 부하 불균형이 커져서 급전용량이 저하되는 문제점이 있다. 본 논문에서는 변전소 위상차 및 전동차 부하분포에 따라 변동하는 순환전력을 실시간 제어하고 변전소 부하 불균형을 해소하기 위하여 사이리스터 제어 위상조정장치 (TCPAR: Thyristor Controlled Phase Angle Regulator, 이하 TCPAR)를 적용하는 방식을 제안하고, 이를 구현하기 위한 검토를 수행하였다. 전기철도 급전 시스템에 TCPAR을 적용하기 위한 제어 기법으로서, 변전소 공급전력을 입력으로 이용하여 변전소 위상차 및 전동차 부하 분포에 따라 변동하는 순환전력과 변전소 부하 불균형을 효과적으로 억제하는 제어모델을 제시하였다. PSCAD/EMTDC를 이용한 시뮬레이션 결과, 전기철도 병렬급전에 제안한 TCPAR을 적용함으로써 변전소 위상차 및 전동차 부하분포에 따라 변동하는 순환전력 및 변전소 부하 불균형을 효과적으로 억제시킬 수 있다는 것을 확인하였다. 제안 기법을 전기철도 병렬급전에 적용할 경우, 병렬급전 적용 범위를 확대하고 급전용량을 증가시킬 수 있을 것으로 기대된다.

• 한국운동역학회지
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• 제16권2호
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• pp.45-53
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• 2006

The purpose of this study was to analyze exercise related mechanical variables according to performance levels and Kumi-kata types in elite judo players (G1) and non-elite judo players, namely university players (G2). To achieve this purpose, three players in G1 whose main special skill was Morote-Seoinage and three university judo players(G2) was selected as comparative group. Then they were examined for distinguishing A and B types of Kumi-kata. Analyzed variables were the time required to show skills, knee degree, elbow degree. After analysing this study, conclusions were derived as follows. 1. In total necessary time of showing skills according to group of Kumi-kata type, G2 was longer than G1 in both A type (20.9%) and B type (23.7%). In necessary time of phase, in only 3P, G1 was shorter than G2 in A type (50%) and B type (75%). There was no difference in time required of 1P and 2P according to Kumi-kata type of group and in only 3P, B type was shorter than A type in both B type (75%) of G1 and B type (50%) of G2 2 There was no difference in elbow degree of offensive arm according to group of Kumi-kata type, however in A and B types, G1 could use skills by extending in kake phase, but G2 could use skills by bending. Elbow degree of offensive arm according to Kumi-kata type of group showed difference in E1. and F2 of G1. A and B types of G1 extended elbow degree in Kake phase, but G2 bent elbow degree so exercise program which could movable range extensively in Kake phase is needed.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1246-1250
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• 2005

We have evaluated the hydroxyl group-solvent specific interactions by using a Lichrosorb RP18 stationary phase and by measuring the retention data of carefully selected solutes in 50/50, 60/40, 70/30, 80/20, and 90/10(v/v%) methanol/water eluents at 25, 30, 35, 40, 45, and 50 ${^{\circ}C}$. The selected solutes are 3 positional isomers of phenylpropanol, that is, 1-phenyl-1-propanol, 1-phenyl-2-propanol, and 3-phenyl-1-propanol. There exist clear discrepancies in ${\Delta}H^o$ (solute transfer enthalpy from the mobile to the stationary phase) and $T{\Delta}S^o$ (solute transfer entropy) among positional isomers. The difference in ${\Delta}H^o$ and $T{\Delta}S^o$ between secondary alcohols (1-phenyl-1-propanol and 1-phenyl-2-propanol)is negligible compared to the difference between the primary alcohol (1-phenyl-3-propanol) and secondary alcohols. The $T{\Delta}S^o$ values of 3-phenyl-1-propanol are close to those of butylbenzene while the $T{\Delta}S^o$ values of secondary alcohols are close to those of propylbenzene. The difference in ${\Delta}{\Delta}H^o$ (specific solute-mobile phase interaction enthalpy) between the primary alcohol and the secondary alcohol decreases with increase of methanol content in the mobile phase. A unique observation is an extremum for 1-phenyl-3-propanol in the plot of $T{\Delta}{\Delta}S^o$ vs. methanol volume %. The positive sign of $T{\Delta}{\Delta}S^o$ of 3-phenyl-1-propanol implies that the entropy of 3-phenyl-1-propanol is greater than that of the hypothetical alkylbenzene (the same size and shape as phenylpropanol) in the mobile phase.

• 전기학회논문지
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• 제64권1호
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• pp.182-187
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• 2015

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.

• 전기학회논문지
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• 제66권3호
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• pp.587-592
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• 2017

In the three-phase four-wire low-voltage power distribution equipment, single-phase and three-phase load have been used mainly mixed. Also linear and nonlinear loads have been used together in the same conditions. In a three-phase four-wire distribution line, the current distribution of three-phase linear load is almost constant in each phase during driving or stopping, but the single-phase load is different from each other for each phase in accordance with the operation and stop. So that the voltage unbalance is caused by the current difference of each phase. In the three-phase four-wire distribution system, non-linear load is used with linear load. The presence of single-phase nonlinear loads can produce an increase in harmonic currents in three-phase and neutral line. It can also cause voltage unbalance. In the present study, we analyzed for the voltage unbalance fluctuations by the operation pattern of the single and three-phase linear and non-linear load in three-phase four-wire low voltage distribution system.

• 대한전기학회논문지:전력기술부문A
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• 제51권9호
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• pp.460-466
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• 2002

A reliable fault phase selection algorithm plays a very important role in transmission line protection, Particularly in Extra High Voltage (EHV) networks. The conventional fault phase selection algorithm used the phase difference between positive and negative sequence current excluding load current. But, it is difficult to pick out only fault current since we can not know when a fault occurs and select the fault phase in weak-infeed conditions that dominate zero-sequence current in phase current. The proposed algorithm can select the accurately fault phase using the sum of unit vectors which are calculated by positive-sequence voltage and negative-sequence voltage.

• 대한전기학회논문지
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• 제33권4호
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• pp.127-133
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• 1984

In this paper the performance of a variable-phase thyristor motor combined with a phase splitter and a single-phase tapped induction motor is investigated. The phase splitter consists of a bridge type thyristor switching circuit. The regulating power flow of the phase splitter is obtained from the switching phase difference of thyristor switching sequences. The proper switching performance improves the torque-speed-characteristics of the motor and its operation efficiency. We simplify the motor system th using the tapped windng reactances of the motor as the complementary element of the thyristor phase splitter. We discussed the practicality of this motor system through the analysis of simulation result and the voltage and the current wave forms obtained froms obtained from the experiment.