• 한국컴퓨터정보학회논문지
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• 제26권2호
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• pp.53-60
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• 2021

본 논문에서는 전기 전자부품 및 기구의 절연재료로 널리 적용되고 있는 에폭시 복합재료의 절연 특성 및 신뢰도를 파악하고자 한다. 이를 위해 경제적, 기계적 요인에 의해 필수적으로 첨가되어야 하는 충진재의 분포에 따른 전계 변화를 예측하기 위하여 전계해석 시뮬레이터를 이용하여 그 결과를 확인하였다. 또한 직류 전압 인가 조건하에서 주변 온도 변화 및 충진재 분포에 따른 절연파괴시험을 수행하였고 그 변화를 관찰하였다. 시편은 에폭시 수지에 충진재를 0, 50, 100[phr] 첨가하여 3종류가 제작되었으며 모든 시편의 경우에서 온도가 증가함에 따라 절연파괴강도가 저하됨을 확인하였다. 시뮬레이션 결과 및 실제 절연강도시험 결과를 비교 고찰하여 전기 기구의 절연설계에 필요한 기술적 적용 가능성을 확인하였다.

• 대한통합의학회지
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• 제8권4호
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• pp.213-221
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• 2020

Purpose : This study aimed to evaluate the changes in visual perception and daily life activities after simultaneously applying the visual perception training program and transcranial DC stimulation. Particularly, this study tried to understand what changes in abilities among daily life activities influenced cognition. Methods : This study selected 50 dementia patients to achieve the objective. This study applied transcranial DC stimulation and a visual perception training program to a treatment group (n=25) and a visual perception training program to a control group (n=25). The intervention was applied five times per week and 30 minutes per session (total of 30 intervention sessions). This study measured visual perception functions and daily life activities using MVPT and FIM before and after applying the intervention. Results : The visual perception, mobility of daily life activities, cognition, and total score of the treatment group (n=25), which received the visual perception training program and transcranial DC at the same time, were significantly (p<.05) different between before and after the intervention. Moreover, when the visual perception and daily life activities of the treatment group and those of the control group after implementing the intervention were compared, they were significantly (p<.05) different between the two groups. Conclusion : The results of this study showed that the simultaneous application of the visual perception training program and transcranial DC stimulation was an effective means to enhance the visual perception and daily life activities of dementia patients. The results implied that transcranial DC stimulation, as well as the application of visual perception training program, as well as a visual perception training program, was effective for improving the visual perception functions and daily life activities dementia patients and simultaneous application of the two interventions would increase the effect even further.

• 한국전자통신학회논문지
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• 제16권6호
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• pp.1339-1348
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• 2021

재생에너지 출력제한은 송전용량과 전력계통 안정성 부족을 포함하여 다양한 원인이 있다. 제주도 지역에서는 태양광 및 풍력 발전설비의 증가로 이미 전력수요에 비해 공급이 많아지는 사례가 자주 발생하고 있으며, 이에 따라 풍력발전의 출력제한 횟수가 증가하고 있다. 본 연구에서는 제주도 전력공급의 핵심 역할을 담당하고 있는 HVDC(고전압 직류)와 BESS(배터리 에너지 저장장치) 설비를 활용하여 재생에너지의 효과적인 수용과 전력계통의 안정적 운영 방향을 찾는 것이다. 그리고 이 논문에서는 각 설비들의 실질적인 운전방안을 제시하고 향후 태양광 및 풍력 발전설비의 확대에 따른 육지 전력계통의 운영 방향을 제안한다.

• 한국수자원학회논문집
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• 제55권10호
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• pp.801-810
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• 2022

본 연구에서는 홍수터 식생에 의한 하안의 안정성을 고려하여 하도에서 사주의 거동과 하도의 지형변화 적응과정을 실내실험을 수행하여 분석하였다. 초기 직류하도에서 하안침식이 발생하고 하폭이 증가한다. 하폭 대 수심의 비가 증가한 후에, 교호사주가 발달하고, 하류로 이동한다. 시간이 증가함에 따라, 사주의 이동속도는 감소하고 사주의 파장은 증가한다. 홍수터에서 식생 밀도가 증가함에 따라, 하안침식율은 감소한다. 그러나 사주의 이동속도는 증가한다. 이는 하안의 안정성 변화가 사주의 이동속도에 영향을 주기 때문이다. 하폭이 증가하고 수심이 감소하면서 무차원 소류력인 Shield Number는 증가하며, 사주의 이동속도도 증가한다. 이는 또한 이동하는 교호사주와 선택적 침식에 의해 발생한 불규칙한 하안 사이에 작용하는 강제효과 때문에 하안의 안정성이 작은 하도에서 사주의 이동속도는 감소한다. 시간이 증가함에 따라 사주의 파장은 증가한다. 사주의 파장이 증가하면서 사주의 이동속도는 감소한다.

• 한국결정성장학회지
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• 제32권5호
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• pp.199-204
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• 2022

유연한 구조의 p-XBP4 리간드를 활용하여 새로운 3차원 구조의 Gd-MOF를 합성하고 단결정 회절 분석기를 활용하여 정확한 구조를 분석하였다. 중심 금속인 Gd는 6개의 p-XBP4와 1개의 물 분자에 의해 총 7배위 되어 있으며, W(CN)₈는 배위되지 않고 전하 균형을 맞추기 위해 구조체 내에 위치하고 있다. 중심 금속인 Gd는 배위된 p-XBP4에 의해 이웃한 Gd와 연결되어 3차원의 입체구조를 형성한다. 란탄 금속의 특성을 고려하여 직류 자화율 측정을 활용하여 자성 특성에 대한 연구를 진행하였다.

• 대한통합의학회지
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• 제9권3호
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• pp.155-164
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• 2021

Purpose : The purpose of this study is to investigate the effects of transcranial direct current stimulation and virtual reality program application on cognition and depression of patients with mild cognitive impairment, and to find an intervention method that can enhance active participation of patients with mild cognitive impairment. Methods : In this study, 50 mild cognitive impairment patients were divided into a treatment group (25 patients) and a control group (25 patients). The treatment group was applied with a transcranial direct current stimulation and a virtual reality program, while the control group received a placebo transcranial direct current stimulation and a virtual reality program. Both groups received five 50-minute sessions per week (one session per day) for six weeks (total of 30 sessions). NCSE was used to evaluate the cognitive functions of the patients before and after treatment intervention. Moreover, K-BDI was conducted to examine the depression of the patients. Results : As a result of the transcranial direct current stimulation and a virtual reality program intervention, the cognitive function of both treatment and control group significantly (p<.05) improved, and the depression of both treatment and control group significantly (p<.05) decreased. Moreover, the changes in cognitive functions and depression were significant between the two groups¸ treatment and control group (p<.05). Conclusion : The results of the study showed that the application of the transcranial direct current stimulation and virtual reality program significantly improved the cognitive function of mild cognitive impairment patients and decreased the depression of them. Therefore, it could be concluded that the transcranial direct current stimulation and virtual reality program was an intervention method which positively affects the cognitive function and depression of mild cognitive impairment patients.

• 대한통합의학회지
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• 제10권2호
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• pp.105-113
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• 2022

Purpose: The purpose of this study is to investigate the effect of non-invasive transcranial direct current stimulation (tDCS) on muscle activity, including 10 m WT, TUG, and BBS, in hemiplegic stroke patients. Methods: This study was conducted on 42 inpatients diagnosed with hemiplegia due to stroke at hospital B in Daejeon for more than 6 months. Walking training was conducted for six weeks, five times a week for 30 minutes, with a general walking group (14 people), tDCS walking group (14 people), and tDCS (sham) walking group (14 people). Results: As a result of the study, the change in the muscle activity before and after tDCS intervention was significantly increased in the tibialis anterior muscle in the CG group. In the EG group, the erector spine (lumbar), rectus femoris, and tibialis anterior muscles significantly increased. In the SEG group, significant increases were observed in the rectus femoris and tibialis anterior muscles. Significant differences were found in the rectus femoris and tibialis anterior muscles in the comparison between groups after intervention according to tDCS application. Also, 10 m WT, TUG, and BBS were significantly increased in the CG, EG, and SEG groups after intervention, and there were significant differences in 10 m WT, TUG, and BBS in comparison between groups after intervention according to tDCS application. Conclusion: As a result, tDCS is an effective in improving the walking ability of stroke patients, and in particular, it effectively increases the muscle activity of the rectus femoris and tibialis anterior muscles, which act directly on walking, and also improves the speed and stability of walking. It is considered being an effective method to increase the gait of stroke patients by combining it with the existing gait training.

• 대한정형도수물리치료학회지
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• 제28권3호
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• pp.79-87
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• 2022

Background: The purpose of this study was to examine the effect of transcranial direct current stimulation (tDCS) on the pain and balance of patients who receive total knee arthroplasty (TKA). Methods: This study subjects were 24 patients in Hospital T, located in Daegu, South Korea who received TKA after being diagnosed with degenerative arthritis. The subjects were randomly divided into and experimental group and a control group, with each group including 12 patients. Both group received superfical thermal therapy, interferential current therapy (ICT), and continue passive motion (CPM), which are conventional knee therapy on the knee joint. The experimental group received the tDCS treatment three times a week for three weeks, from October 1st to October 20th. The visual analogue scale and Wii Balance Board system were used to measure the pain and balancing ability, respectively, of both groups. In the statistical result analysis, to compare about pre and post test difference in each groups was accomplished. Statistical analysis of independent t-test and paired t-test were conducted using SPSS version 23.0. Results: After three weeks of intervation, there were significantly difference in balance ability in pre and post test in the tDCS group. VAS decreased significantly in both groups(p<.05), There was a significantly difference in pain, balance ability in the tDCS group compared to the sham group. Conclusion: These results indicate that applying tDCS together with conventional knee joint therapy for TKA patients is effective in promoting the patients' recovery.

• 전기전자학회논문지
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• 제26권4호
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• pp.584-589
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• 2022

고전압 태양광 패널에서 단상 계통으로의 직류-교류 전력 변환을 위해 벅부스트 컨버터에 풀브리지 인버터를 종속적으로 연결하는 두 단계의 무변압기 인버터가 주로 사용된다. 태양광 패널의 큰 기생 커패시턴스에 기인하는 과도한 누설 전류를 피하기 위해 풀브리지 인버터는 단극성 PWM에 비해 훨씬 더 많은 전력 손실을 초래하는 양극성 PWM으로만 스위칭할 수 있다. 그런 낮은 효율을 개선하기 위해 본 논문은 벅부스트 컨버터에 회로 절연을 위한 IGBT와 다이오드를 하나씩 추가한 새로운 토폴로지를 제안한다. 제안된 회로 절연 방식은 누설 전류를 증가시키지 않으면서 풀브리지 인버터에서 단극성 PWM을 가능케 함으로써 전체 효율을 개선한다. 제안된 방법의 타당성은 컴퓨터 시뮬레이션과 전력 손실 계산을 통해 검증한다.

• 한국안전학회지
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• 제37권1호
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• pp.12-19
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• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.