지진하중 및 임의의 하중을 받는 배관 시스템에 대한 응답을 추정하기 위한 데이터 기반 디지털 트윈

김동창,김건규,곽신영,임승현 한국지진공학회 2023 한국지진공학회논문집 Vol.27 No.6

The importance of Structural Health Monitoring (SHM) in the industry is increasing due to various loads, such as earthquakes and wind, having a significant impact on the performance of structures and equipment. Estimating responses is crucial for the effective health management of these assets. However, using numerous sensors in facilities and equipment for response estimation causes economic challenges. Additionally, it could require a response from locations where sensors cannot be attached. Digital twin technology has garnered significant attention in the industry to address these challenges. This paper constructs a digital twin system utilizing the Long Short-Term Memory (LSTM) model to estimate responses in a pipe system under simultaneous seismic load and arbitrary loads. The performance of the data-driven digital twin system was verified through a comparative analysis of experimental data, demonstrating that the constructed digital twin system successfully estimated the responses.

기저유출을 고려한 비점오염 유출특성 분석과 원단위 검증에 관한 연구

박재범,갈병석,이철구,홍선화,최무진 한국습지학회 2017 한국습지학회지 Vol.19 No.3

본 연구에서는 기저유출을 고려한 관측 자료 기반 오염부하량을 이용하여 비점오염 유출특성과 신규 원단위의 활용 가 능성을 검토하였다. 이를 위해 금강 수계 주원천 유역의 9개 강우사상을 대상으로 디지털 필터 기법을 이용하여 유출 성분을 분리하고 수치적분법을 적용하여 비점오염부하량을 산정하였다. 연구결과 비점오염 평균 기여율은 BOD 31.34%, T-N 58.94%, T-P 50.42%로 BOD의 경우 기저유출의 영향이 큰 것으로 분석되었다. 또한, 신 원단위를 적 용한 오염부하량이 구 원단위를 적용한 경우에 비해 관측부하량에 근접하는 것으로 분석되었다. 이러한 결과는 효율적 인 유역의 수질관리를 위해서는 직접유출에 따른 오염부하뿐만 아니라 기저유출에 따른 오염부하 관리도 필요함을 의미한다. In this study, the characteristics of non-point source pollution runoff and the possibility of using new unit load were investigated by using pollutant load based on monitoring data considering baseflow. For this purpose, the components of hydrograph were separated by using digital filter method and the numerical integration method was applied to calculate the non-point source pollutant load for nine rainfall events in Juwon river in the Geum River basin. As a result of this study, the mean contribution rate of non-point pollutant was 31.34% for BOD, 58.94% for T-N, and 50.42% for T-P and BOD was more influenced by baseflow pollutant. Also, it was analyzed the pollutant load using the new unit load is closer to the observation load than the old unit load. This result implies that it is necessary to manage not only pollutant load due to direct runoff but also pollutant load due to baseflow runoff for efficient water quality management of the watershed.

매체별 노트필기 방식에 따른 학습효과 연구

전수진,위지은,박인영 인제대학교 디자인연구소 2020 Journal of Integrated Design Research (JIDR) Vol.19 No.3

Background: Using digital devices such as laptops and tablet PCs in note-taking is becoming more common with the rise of information technology. The majority of note-taking studies have reported that digital devices degrade learning abilities by increasing cognitive loads. Yet, more recent studies suggest that note-taking with digital devices could rather augment the amount of recall and comprehension of contents. More importantly, previous studies generally focused on the different levels of information processing caused by different media. Only a small number of studies defined functional differences between media and suggested ideas to advance the media interface. Methods: We analyzed how the contents and structural characteristics of written notes differ in media: a paper, laptop, and tablet PC with a stylus. Then we also examined the effect of these characteristics on learning. Result: The difference in contents(i.e. the amount of entire written notes and written keywords within notes), according to the note-taking methods did not affect learning. In terms of perceived media utilities and cognitive loads, papers have the highest, followed by laptops and tablet PCs in order. Based on the post-experiment questionnaire, we found that both the familiarity to the media and media skills do not have significant effects on learning. Conclusion: This study examined whether differences in functional characteristics of note-taking between media affect learning. This study presents somewhat different findings from previous studies. It could be due to the fact that current research focuses on a digital-friendly generation. Further, unlike prior research, we looked into distinct characteristics of each medium. Physical and functional characteristics of the media should not be overlooked and such properties should be incorporated in designing media interfaces. 연구배경: 정보기술의 발전으로 노트필기에도 노트북 컴퓨터, 태블릿 PC 등의 디지털 디바이스를 사용하는 사례가 증가하고 있다. 전통적인 노트필기 연구에서는 디지털 디바이스가 인지 부하(cognitive load)를 가중시켜 학습능력을 저하시킨다고 보고하였으나, 최근에는 디지털 디바이스를 사용할 때 오히려 기억과 이해에 긍정적인 영향을 미친다는 결과도 보고되었다. 그러나 이들 선행연구는 모두 매체의 차이에 따른 학습자들의 정보 처리 과정에 초점을 맞추어 진행되었으며, 각 매체들의 특성을 사용자들의 매체친숙도와 숙련도와 관련지어 매체별 학습효과 차이를 살펴본 연구는 아직 부족한 실정이다. 연구방법 : 본 연구에서는 필기한 노트의 내용과 구조적 특성이 종이 노트, 노트북 컴퓨터, 펜 기반 태블릿 PC에서 어떻게 다르게 나타나는지를 분석하고 이러한 특성이 학습에 미치는 영향을 회상(recall) 기법을 이용하여 살펴보았다. 연구결과 : 본 연구는 매체별 노트필기 방식에 따른 노트내용의 차이(필기 전체 분량 핵심어 필기 비율)가 학습에 영향을 주지 않았음을 확인하였다. 지각된 매체효용성과 인지부하의 경우 종이 노트, 노트북 컴퓨터, 태블릿 PC의 순으로 조사되었다. 사후 설문으로 진행된 매체친숙도와 숙련도 역시 실제 학습효과와는 유의미한 상관관계가 드러나지 않았다. 결론 : 본 연구는 평소에 필기를 많이 하는 집단인 20대 대학생을 대상으로 매체 간 노트필기 특성의 차이가 강의 내용을 회상하는 데 영향을 미치는지를 살펴보았다. 그러나 선행연구와는 달리 본 연구의 결과가 보여주듯이 매체 간 명확한 차이가 나타나지 않았다. 이는 디지털 디바이스에 익숙한 20대 대학원생의 특징으로도 볼 수 있지만, 그간의 연구가 매체별 특성을 고려하지 않은 채 정보처리라는 인지적 과정에만 초점을 맞추어 진행되었기 때문으로 판단된다. 따라서 각 매체가 가지고 있는 기능적 특성을 고려한 인터페이스 디자인 연구가 필요하며 이에 따른 학습효과 연구가 수행되어야 할 것이다.

고조파 정합 기법을 이용한 고효율 GaN HEMT 전력 증폭기

진태훈(Tae-Hoon Jin),권태엽(Tae-Yeop Kwon),정진호(Jinho Jeong) 한국전자파학회 2014 한국전자파학회논문지 Vol.25 No.1

본 논문에서는 고조파 정합 기법을 이용하여 고효율 GaN HEMT 전력 증폭기를 설계 및 제작하고, 그 특성을 측정하였다. 고효율 특성을 얻기 위해 고조파 로드풀 시뮬레이션을 활용하였다. 즉, 기본 주파수뿐만 아니라 2차, 3차 등의 고조파에서 최적의 부하 임피던스를 찾아내었다. 이러한 고조파 로드풀 시뮬레이션 결과를 바탕으로 출력 정합 회로를 설계하였다. 제작한 전력 증폭기는 중심 주파수 1.85 ㎓에서 선형 전력 이득 20 ㏈ 및 33.7 ㏈m의 P1㏈(1 ㏈ gain compression point) 특성을 보였다. 그리고, 출력 전력 38.6 ㏈m에서 80.9 %의 최대 전력 부가 효율(Power Added Efficiency: PAE)을 나타냈으며, 이는 기존에 설계된 고효율 전력 증폭기와 비교했을 때 아주 우수한 효율 특성이다. 또한, W-CDMA 신호입력에 대한 측정 결과, 28.4 ㏈m의 평균 출력 전력에서 27.8 %의 PAE와 5 MHz offset 주파수에서 ?38.8 ㏈c의 ACLR(Adjacent Channel Leakage Ratio)을 보였다. 그리고, 다항식 맞춤 방식의 디지털 전치 왜곡(Digital Predistorion: DPD) 선형화 알고리듬을 구현하여 제작된 전력 증폭기의 ACLR을 6.2 ㏈ 정도 향상시킬 수 있었다. In this paper, we present the design, fabrication and measurement of high efficiency GaN HEMT power amplifier using harmonic matching technique. In order to achieve high efficiency, harmonic load-pull simulation is performed, that is, the optimum load impedances are determined at 2nd and 3rd harmonic frequencies as well as at the fundamental. Then, the output matching circuit is designed based on harmonic load-pull simulation. The measurement of the fabricated power amplifier shows the linear gain of 20 ㏈ and P1㏈(1 ㏈ gain compression point) of 33.7 ㏈m at 1.85 ㎓. The maximum power added efficiency(PAE) of 80.9 % is achieved at the output power of 38.6 ㏈m, which belongs to best efficiency performance among the reported high efficiency power amplifiers. For W-CDMA input signal, the power amplifier shows a PAE of 27.8 % at the average output power of 28.4 ㏈m, where an ACLR (Adjacent Channel Leakage Ratio) is measured to be ?38.8 ㏈c. Digital predistortion using polynomial fitting was implemented to linearize the power amplifiers, which allowed about 6.2 ㏈ improvement of an ACLR performance.

변전소 모선전압 관리개선을 통한 배전 규정전압 유지에 관한 연구

김세호,이중현 제주대학교 공과대학 첨단기술연구소 2001 尖端技術硏究所論文集 Vol.12 No.2

This paper proposes the method maintaining the distribution voltage within specified limits by the management improvement of substation bus voltage. It is common to install OLTC(On Load Tap changer) equipped with AVR(Automatic Voltage Regulator) and DVM(Digital Volt Meter) at the distribution substation to regulate load voltage against the variation of load demand. The present method of voltage regulation has the possibility to lead to overvoltage or under-voltage because of not considering heavy or light condition of load. In proposed voltage regulation method, load patterns are classified into three categories(peak, normal and light load) and three DVMs are paralleled. The results shows that the voltage profile is improved.

비선형 부하에서 커패시터 전류 궤환을 통한 고성능 UPS 설계

이우철(Woo-Cheol Lee),이택기(Taeck-Kie Lee) 한국조명·전기설비학회 2012 조명·전기설비학회논문지 Vol.26 No.5

This paper presents a digital control solution to process capacitor current feedback of high performance single-phase UPS for non-linear loads. In all UPS the goal is to maintain the desired output voltage waveform and RMS value over all unknown load conditions and transient response. The proposed UPS uses instantaneous load voltage and filter capacitor current feedback, which is based on the double regulation loop such as the outer voltage control loop and inner current control loop. The proposed DSP-based digital-controlled PWM inverter system has fast dynamic response and low total harmonic distortion (THD) for nonlinear load. The control system was implemented on a 32-bit Floating-point DSP controller TMS320C32 and tested on a 5[KVA] IGBT based inverter switching at 11[Khz]. The validity of the proposed scheme is investigated through simulation and experimental results.

Experimental Study of Evolution of Fracture Process Zone in Dam Concrete under Cyclic Loading Using Digital Image Correlation

Xudong Chen,Shengtao Li,Xiyuan Cheng 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2

In this paper, three-point bending tests were carried out o investigate the post-peak cyclic loading behavior of dam concrete under two loading rates. The fracture parameters, residual load capacity, cyclic modulus, dissipated energy, and deformation recovery were presented and analyzed. The analysis was made to understand the evolution of fracture process zone (FPZ) under post-peak cyclic loading for dam concrete by utilizing digital image correlation (DIC) technique. The results showed while the dam concrete under a higher loading rate showed an increase in maximum load, it is not necessarily the same for post-peak bearing capacity. The specimens with higher post-peak bearing capacity had higher residual stiffness, higher dissipation energy, and higher Crack Mouth Opening Displacement (CMOD) reversibility under cyclic loading. The FPZ development was investigated quantitatively, and the extension and retraction of its tip were observed. Moreover, it was found that the FPZ in specimens with higher residual stiffness developed more slowly, and FPZ had a more significant retraction rate during unloading for the specimens with higher residual bearing capacity.

Comparative Study on 220V AC Feed System and 300V DC Feed System for Internet Data Centers

Kim, Hyo-Sung The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.

Comparative Study on 220V AC Feed System and 300V DC Feed System for Internet Data Centers

Hyosung Kim 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.

Comparative Study on 220V AC Feed System and 300V DC Feed System for Internet Data Centers

김효성 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.