Electromechanical impedance-based long-term SHM for jacket-type tidal current power plant structure

Min, Jiyoung,Yi, Jin-Hak,Yun, Chung-Bang Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.2

Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for an offshore structure, there are few cases to apply a structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure in Korea under changes in temperature and transverse loadings. Principal component analysis (PCA)-based approach was applied with a conventional damage index to eliminate environmental changes by removing principal components sensitive to them. Experimental results showed that the proposed approach is an effective tool for long-term SHM under significant environmental changes.

Response to Neoadjuvant Therapy and Prognosis in Patients with Resectable Pancreatic Cancer: A Propensity Score Matching Analysis

( Min Sung Yoon ),( Hee Seung Lee ),( Chang Moo Kang ),( Woo Jung Lee ),( Jiyoung Keum ),( Min Je Sung ),( Seungseob Kim ),( Mi-suk Park ),( Jung Hyun Jo ),( Moon Jae Chung ),( Jeong Youp Park ),( Seu 대한소화기학회 2022 Gut and Liver Vol.16 No.1

Background/Aims: Controversy regarding the effectiveness of neoadjuvant therapy for resectable pancreatic ductal adenocarcinoma (PDAC) still exists. Here, we aimed to identify the potential benefits of neoadjuvant therapy followed by surgery for resectable PDAC. Methods: We reviewed radiologically resectable PDAC patients who received resection with curative intent at a tertiary hospital in South Korea between January 2012 and August 2019. A total of 202 patients underwent curative resection for resectable PDAC: 167 underwent surgical resection first during this period, and 35 received neoadjuvant chemotherapy/chemoradiation therapy followed by surgery. Resectable PDAC patients were subdivided, and 1:3 propensity score matching (PSM) was performed to reduce selection bias. Results: Compared with the group that received surgery first, the group that received neoadjuvant treatment followed by surgery had significantly smaller tumors (22.0 mm vs 27.0 mm, p=0.004), a smaller proportion of patients with postoperative pathologic T stage (p=0.026), a smaller proportion of patients with lymphovascular invasion (20.0% vs 40.7%, p=0.022), and a larger proportion of patients with negative resection margins (74.3% vs 51.5%, p=0.049). After PSM, the group that received neoadjuvant therapy had a significantly longer progression-free survival than those in the group that underwent surgery first (29.6 months vs 15.1 months, p=0.002). Overall survival was not significantly different between the two groups after PSM analysis. Conclusions: We observed significantly better surgical outcomes and progression-free survival with the addition of neoadjuvant therapy to the management of resectable PDAC. However, despite PSM, there was still selection bias due to the use of different regimens between the groups receiving surgery first and neoadjuvant therapy. Large homogeneous samples are needed in the future prospective studies. (Gut Liver 2022;16:118-128)

Toward Korea-Belarus Cooperation in the ICT Sector

Jiyoung Min 대외경제정책연구원 2014 World Economy Brief Vol.2014 No.01

Impedance-based structural health monitoring using neural networks for autonomous frequency range selection

Min, Jiyoung,Park, Seunghee,Yun, Chung-Bang Institute of Physics Publishing 2010 Smart materials & structures Vol.19 No.12

<P>The impedance-based structural health monitoring (SHM) method has come to the forefront in the SHM community due to its practical potential for real applications. In the impedance-based SHM method, the selection of optimal frequency ranges plays an important role in improving the sensitivity of damage detection, since an improper frequency range can lead to erroneous damage detection results and provide false positive damage alarms. To tackle this issue, this paper proposes an innovative technique for autonomous selection of damage-sensitive frequency ranges using artificial neural networks (ANNs). First, the impedance signals are obtained in a wide frequency band, and the signals are split into multiple sub-ranges of this wide band. Then, the predefined damage index is evaluated for each sub-range by comparing impedance signals between the intact and the concurrent cases. Here, the cross correlation coefficients (CCs) are used as the predefined damage index. The ANN is constructed and trained using all CC values at multiple frequency ranges as multi-inputs and the real damage severity as the single output for various preselected damage scenarios, so that subsequent damage estimations may be carried out by selecting the governing frequency ranges autonomously. The performance of the proposed approach has been examined via a series of experimental studies to detect loose bolts and cracks induced on real steel bridge and building structures. It is found that the proposed approach autonomously determines the damage-sensitive frequency ranges and can be used for effective evaluation of damage severity in a wide variety of damage cases in real structures.</P>

Antitumor Effects of Combined Polyphenols with Radiotherapy in Head and Neck Squamous Cell Carcinoma

Jiyoung Yeo,Kyung-min Kim,Eun-Ji Park,Min-Sik Kim 한국식품영양과학회 2012 한국식품영양과학회 학술대회발표집 Vol.2012 No.10

Development of a low-cost multifunctional wireless impedance sensor node

Min, Jiyoung,Park, Seunghee,Yun, Chung-Bang,Song, Byunghun Techno-Press 2010 Smart Structures and Systems, An International Jou Vol.6 No.5

In this paper, a low cost, low power but multifunctional wireless sensor node is presented for the impedance-based SHM using piezoelectric sensors. Firstly, a miniaturized impedance measuring chip device is utilized for low cost and low power structural excitation/sensing. Then, structural damage detection/sensor self-diagnosis algorithms are embedded on the on-board microcontroller. This sensor node uses the power harvested from the solar energy to measure and analyze the impedance data. Simultaneously it monitors temperature on the structure near the piezoelectric sensor and battery power consumption. The wireless sensor node is based on the TinyOS platform for operation, and users can take MATLAB$^{(R)}$ interface for the control of the sensor node through serial communication. In order to validate the performance of this multifunctional wireless impedance sensor node, a series of experimental studies have been carried out for detecting loose bolts and crack damages on lab-scale steel structural members as well as on real steel bridge and building structures. It has been found that the proposed sensor nodes can be effectively used for local wireless health monitoring of structural components and for constructing a low-cost and multifunctional SHM system as "place and forget" wireless sensors.

An electromechanical impedance-based method for tensile force estimation and damage diagnosis of post-tensioning systems

Jiyoung Min,Hyojin Shim,Chung-Bang Yun,홍정욱 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.1

We propose an effective methodology using electromechanical impedance characteristics for estimating the remaining tensile force of tendons and simultaneously detecting damages of the anchorage blocks. Once one piezoelectric patch is attached on the anchor head and the other is bonded on the bearing plate, impedance responses are measured through these two patches under varying tensile force conditions. Then statistical indices are calculated from the impedances, and two types of relationship curves between the tensile force and the statistical index (TE Curve) and between statistical indices of two patches (SR Curve) are established. Those are considered as database for monitoring both the tendon and the anchorage system. If damage exists on the bearing plate, the statistical index of patch on the bearing plate would be out of bounds of the SR curve and damage can be detected. A change in the statistical index by damage is calibrated with the SR curve, and the tensile force can be estimated with the corrected index and the TE Curve. For validation of the developed methodology, experimental studies are performed on the scaled model of an anchorage system that is simplified only with 3 solid wedges, a 3-hole anchor head, and a bearing plate. Then, the methodology is applied to a real scale anchorage system that has 19 strands, wedges, an anchor head, a bearing plate, and a steel duct. It is observed that the proposed scheme gives quite accurate estimation of the remaining tensile forces. Therefore, this methodology has great potential for practical use to evaluate the remaining tensile forces and damage status in the post-tensioned structural members.

국도 상 도로시설물 대상 열화환경 조건 별 콘크리트 염화물 침투 특성 분석

민지영 ( Jiyoung Min ),이종석 ( Jong-suk Lee ),이탁곤 ( Tack-gon Lee ),차기혁 ( Ki-hyuk Cha ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 논문집 Vol.25 No.5

「시설물의 안전 및 유지관리 실시 세부지침(성능평가편)」의 내구성능 평가에서 열화환경 평가항목으로 제시된 제설제 및 비래염분에 의한 염해환경, 동해환경이 국내 국도 상 콘크리트 도로시설물의 염화물 침투특성에 미치는 영향을 살펴보았다. 강원 고성, 서울, 경기 고양, 부산에 위치한 교량 총 4개소, 강원권 방호울타리 4개소, 부산권 방호울타리 3개소 및 옹벽 1개소를 대상 시설물로 선정하였으며, 제설제에 의한 직접·간접적인 염해환경, 해안거리 및 교각 높이별 비래염분에 의한 염해환경에서 염화물 침투특성을 분석하였다. 분석 결과, (1) 제설제 살포일수(강설일수)에 따른 지역별 특성이 명확하게 구분되었고, (2) 바닥판 관통 누수 혹은 신축이음부를 통한 누수 등이 발생한 경우 침투 염화물량이 유의미한 수준까지 증가하였으며, (3) 부산 해안가에 위치한 교량의 경우 높이 20m까지 비래염분의 영향권에 해당함을 확인하였다. 이로부터, 동일한 시설물이라도 노출된 열화환경, 부재의 위치 및 높이, 열화진전상태에 따라 염화물 침투특성이 달라지기 때문에 시설물 점검 시 점검대상 부재 및 위치의 선정이 매우 중요함을 확인하였으며, 국내 지역별 및 부재별 열화환경에서의 염화물 침투특성에 관한 데이터 베이스를 구축한다면 콘크리트 시설물에 대한 선제적인 내구성능 관리가 가능할 것으로 기대된다. The deterioration environments caused by de-icing salt and airborne chlorides in the seashore, evaluated in the “Detailed guideline for safety and management practice of facilities (performance evaluation)”, were reviewed in terms of penetrated chlorides into concrete on various road facilities. Target concrete structures, in this study, were 4 concrete barriers in Gangwon area, 3 concrete barriers and 1 retaining wall in Busan area, and 4 bridges in Gangwon-do, Seoul, Gyeonggi-do, and Busan. The deterioration environments were classified into three categories: direct and indirect de-icing salt attack, and airborne salt attack depending on the distance to seashore and the height of pier, and the penetrated chlorides in to concrete were analyzed. The results showed that (1) the regional deterioration environments were clearly classified by de-icing salt sprayed days (snowfall days), (2) the penetrated chlorides increased significantly when leakage occurred through slabs or expansion joints, and (3) the airborne chlorides affected to a height of 20 m concrete in the seashore, Busan. From these, it could be confirmed that the chloride ion penetration properties depend on the exposed aging environment, member location and height, and deterioration status, even on the same structure, so the selection of target members and location is very important in the inspection and maintenance. If the database of penetrated chlorides properties in various deterioration environments is constructed, it is expected that the proactive durability management on concrete structures will be possible in the field.

압전 임피던스 기반 텐던 긴장력 추정 기술

민지영 ( Min Jiyoung ) 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.20 No.1

XHTML 기반의 무선 인터넷 문서 편집기의 설계 및 구현

민지영(Jiyoung Min),이낙규(Nakgyu Lee),심정민(Jungmin Sim),서동민(Dongmin Seo),민영수(Youngsu Min),유재수(Jaesoo Yoo) 한국정보과학회 2002 한국정보과학회 학술발표논문집 Vol.29 No.2Ⅰ

최근 무선 인터넷 시장이 급속히 성장함에 따라 다양한 무선 인터넷 컨텐츠에 대한 개발 수요가 급증하고 있다. 또한 다양한 인터넷 단말기와 플랫폼을 유연하게 지원할 수 있는 확장성이 추가된 XHTML이 세계적인 표준 마크업 언어로 자리잡고 있다. 이러한 XHTML은 HTML에 XML을 적용시켜 재정의 함으로써, 기존의 유무선 인터넷 컨텐츠 통합과 상호 운용성(interoperability)의 증진을 위한 핵심 기술로 인식되고 있다. 이에 본 논문에서는 XHTML을 기반으로 한 무선 인터넷 언어인 XHTML Basic 1.0과 WML 2.0 문서를 WYSIWYG 방식으로 쉽고 빠르게 작성할 수 있는 무선 인터넷 문서 편집기를 설계하고 구현한다. 설계한 XHTML 기반의 문서 편집기는 문서를 원하는 형태로 표현 가능하도록 CSS와 WCSS를 지원한다.