• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.109-111
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• 2001

Modern power grids are becoming more and more stressed with the load demands increasing continually. Therefore large stressed power systems exhibit complicated dynamic behavior when subjected to small disturbance. Especially, it is needed to analyze special conditions which make small signal stability structure varied according to operating conditions. This paper shows that the relation between small signal stability and operating conditions can be predicted well using node-focus point and 1:1 resonance point. Also, the weak point which limits operating range can be identified by the analysis of resonance condition. The proposed method is applied to test systems, and the results illustrate its capabilities.

• 한국안전학회지
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• 제34권5호
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• pp.95-102
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• 2019

Non-destructive methods such as rebound hardness method and ultrasonic method are widely studied for evaluating the physical properties, condition and damage of concrete, but are not suitable for detecting delamination and cracks near the surface due to various constraints of the site as well as the accuracy. Therefore, in this study, the impact resonance method was applied to detect the separation cracks occurring near the surface of the concrete slab and bridge deck. As a next step, the principal component analysis were performed by extracting various features using the FFT data. As a result of principal component analysis, it was analyzed that the reliability was high in distinguishing defects in concrete. This feature extraction and application of principal component analysis can be used as basic data for future use of machine learning technique for the better accuracy.

• 한국자기공명학회논문지
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• 제27권1호
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• pp.1-4
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• 2023

Transthyretin (TTR) is an indispensable transporter protein of thyroxine and a retinol molecule in humans. TTR has a stable homo-tetrameric structure in its native state, while upon dissociation into monomers, it becomes aggregation-prone and can form an amyloid fibril. Although the amyloidogenic propensity of TTR has been known and investigated since the late 1990s, the structural information regarding TTR's amyloidogenic species is still elusive. Here, we employed high-pressure nuclear magnetic resonance (HP-NMR) approaches on the monomeric variant of TTR (TTR[F87M/L110M]; M-TTR) and observed that it experiences a two-step transition in response to the pressurized condition. Our study demonstrated that M-TTR in an ambient condition has heterogeneous structural features, which is likely related to the amyloidogenic propensity of TTR.

• 항공우주기술
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• 제7권1호
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• pp.151-160
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• 2008

본 논문에서는 발사체에 적용하는 전기-유압식 추력벡터제어 구동장치시스템의 합성공진 현상에 대한 해석 연구결과를 기술한다. 합성공진 현상은 위치서보 구동장치시스템을 유연한 발사체 기체구조체 지지부에 장착하였을 때 발생한다. 이는 관성부하를 갖는 전기-유압식 위치서보 시스템의 유압공진 현상과 유연한 기체구조체 지지부의 구조공진 현상의 합성에 의하여 발생한다. 합성공진 현상은 발사체 제어시스템에 의하여 되먹임 및 증폭되어 안정성을 악화시킬 수 있다. 이와 같은 현상을 정확하게 예측 및 분석할 수 있는 비선형 모델을 개발하였으며 이에 기반을 둔 합성공진 억제 특성이 우수한 동적 압력 되먹임(dynamic pressure feedback) 제어기법을 개발하였다.

• 센서학회지
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• 제29권1호
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• pp.45-50
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• 2020

Magnetoelectric (ME) composites were designed using the PMN-PZT single crystal and Ni foils; the properties and magnetic-field sensitivities of ME composites with different piezoelectric vibration modes (i.e., 31, 32, and 36 modes that depend on the crystal orientation of the single crystal) were compared. In the off-resonance condition, the ME coupling properties of the ME composites with the 32 and 36 piezoelectric vibration modes were better than those of the ME composites with the 31 piezoelectric vibration mode. However, in the resonance condition, the ME coupling properties of the ME composites were almost similar, irrespective of the piezoelectric vibration mode. Additionally, in the off-resonance condition (at 1 kHz), the magnetic-field sensitivity of the ME composites with the 36 piezoelectric vibration mode was up to 2 nT and those of the ME composites with the 31 and 32 piezoelectric vibration modes were up to 5 nT. These magnetic-field sensitivities are similar to those offered by conventional high-sensitivity magnetic-field sensors; the potential of the proposed sensor to replace costly and bulky high-sensitivity magnetic field sensors is significant.

• 대한치매학회지
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• 제16권2호
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• pp.48-53
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• 2017

Background and Purpose Torrance Tests of Creative Thinking (TTCT) is a well-known and commonly used measure of creativity. However, the TTCT-induced creative hemodynamic brain activity is rarely revealed. The purpose of this study is to elucidate the neural correlates of creative thinking in the setting of a modified version of the figural TTCT adapted for an functional magnetic resonance imaging (fMRI) experiment. Methods We designed a blocked fMRI experiment. Twenty-five participants (11 males, 14 females, mean age $19.9{\pm}1.8$) were asked to complete the partially presented line drawing of the figural TTCT (creative drawing imagery; creative). As a control condition, subjects were asked to keep tracking the line on the screen (line tracking; control). Results Compared to the control condition, creative condition revealed greater activation in the distributed and bilateral brain regions including the left anterior cingulate, bilateral frontal, parietal, temporal and occipital regions as shown in the previous creativity studies. Conclusions The present revealed the neural basis underlying the figural TTCT using fMRI, providing an evidence of brain areas encompassing the figural TTCT. Considering the significance of a creativity test for dementia patients, the neural correlates of TTCT elucidated by this study may be valuable to evaluate the brain function of patients in the clinical field.

• Ocean and Polar Research
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• 제25권spc3호
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• pp.423-426
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• 2003

The seawater exchange breakwater equipped with an oscillating water channel and water transmitting pipes has a very spectacular function that seawater supply can be greatly increased due to the upsurge of the water surface inside the channel at resonance condition which can be reached when the incident wave period becomes close to the natural period of the channel. The variations of the water level and period inside the channel are very important factors in enhancing the efficiency of sea water exchange, especially when designing the breakwater cross-section in shallow water zone which requires longer resonance period with the elongated horizontal projection of the channel. In the present study, a hydraulic experiment was performed varying the length of the oscillating channel, and the resonance periods and water surface variations are analyzed in terms of water transmission through the pipes.

• Investigative Magnetic Resonance Imaging
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• 제21권3호
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• pp.195-198
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• 2017

Idiopathic brain herniation is a rare condition. We believe that this is the first reported case of idiopathic herniation of the lingual gyrus. The case involves a 57-year-old woman presenting with frontal headache without overt visual symptoms. Magnetic resonance imaging (MRI) revealed an idiopathic herniation of the lingual gyrus of the occipital lobe extending into the quadrigeminal cistern. No other adjacent intracranial abnormalities were observed. Although some conditions may be considered in the differential diagnosis, accurate diagnosis of idiopathic brain herniation in medical practice can prevent unnecessary additional imaging procedures and invasive open biopsy in patients with typical imaging findings.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.103-112
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• 2002

The photoproduced cation radical of N-methylphenothiazine $(PC_1)$ doped into phenyltriehtoxysilane (PhiTEOS), vinyltriethoxysilane (VTEOS) and methyltriethoxysilane (METOS) was studied with electron spin resonance (ESR) and electron nuclear double resonance (ENDOR). The photoinduced charge separation efficiency was determined by integration of ESR spectra which correspond to the amount of photoproduced cation radical in the matrices. This was correlatively studied with the polarity and pore size of the gel matrices. The relative polarity of the matrices was determined by measuring ${\lambda}_{max}$ values of $PC_1$ in the different matrices. The relative pore size among the matrices was determined by measuring relative proton matrix ENDOR line widths of the photoproduced cation of $PC_1$. The decay kinetic constants of the cation radical of $PC_1$ in the different matrices with relatively studied with fitting the biexponential decay curves after exposure at the ambient condition. This is correlatively interpreted with the polarity and pore size of the matrices.

• 전기학회논문지P
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• 제57권4호
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• pp.370-376
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• 2008

Power capacitors is widely used for power factor correction and component of passive filter in the user power systems. Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current. There are series resonance and parallel resonance when capacitors are applied in the user electrical application. If this harmonic component matches resonance, voltage and current is magnified and has severely an influences on capacitor. This paper purposes a new method for the magnitude of voltage and current by the frequency scan analysis without equivalent circuit for the actual circuit at the resonance condition.