Dynamic characteristics evaluation and structural health monitoring for offshore structures

Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure’s natural frequencies fluctuate with a constant cycle—i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass(3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.(2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structuremoreover, the structural system became nonlinear when the damage was severeChapter 1. INTRODUCTION 1.1 Research Background 1 1.2 Literature Survey 3 1.3 Research Objectives and Scope 4 Chapter 2. THEORETICAL BACKGROUND 2.1 Added mass 6 2.2 Displacement Estimation Using Data Fusion 8 2.2.1 Example of Displacement Estimation Algorithm 10 2.3 Damage index(β) 15 Chapter 3. EXPERIMENTAL STUDY 3.1 General Information on the Lab-scale Experiments 18 3.2 Information on the Lab-scale Test Structure 20 3.3 Outline of the Lab-scale Experiment 25 3.4 Analysis of Experimental Results 27 3.4.1 Added Mass Effect 27 3.4.2 Boundary Damage Effect from Current Velocity Change 31 3.4.3 Damage Index (β) 33 3.4.4 Displacement Estimation 35 Chapter 4. VERIFICATION OF THE EXPERIMENT 4.1 Outline of the Numerical Modeling 41 4.2 Added Mass Effect 43 Chapter 5. CONCLUSION 5.1 Conclusion 45 5.2 Future Study 47 References 5

A smart handover decision algorithm using location prediction for hierarchical macro/femto-cell networks

학위논문(석사) - 한국과학기술원 : 전산학과, 2012.2, [ iv, 27 p. ]한국과학기술원 : 전산학과

APPARATUS AND METHOD FOR EVALUATING FATIQUE LIFE IN A SUPPORTING STRUCTURE OF A WIND TURBINE

본 발명은 계측이 용이한 지지구조물의 임의의 계측지점에서 정적응답과 동적응답을 계측하여 이를 이용하 여 계측하고자 하는 목표 지점 즉, 응력 집중부에서의 응력 및 피로수명을 평가하는 풍력터빈 기초의 피로 수명 평가 장치 및 그 방법에 관한 것이다. 본 발명에 의한 풍력터빈의 지지구조물에서의 피로수명을 평가 하는 장치는 지지구조물에 장착되어 가속도를 계측하도록 구성된 가속도계 지지구조물에 장착되어 변형률 을 측정하도록 구성된 변형률계 지지구조물에 장착되어 경사도를 측정하도록 구성된 경사계 풍력터빈의 설계도면을 이용하여 수치 해석 모델을 구성하고, 가속도계, 변형률계 및 경사계로부터 계측된 결과를 이 용하여 수치해석 모델을 개선하며, 개선된 수치 해석 모델을 이용하여 계측 지점에서의 응답값과 목표지점 에서의 변형률 사이의 관계식을 구성하며, 목표지점에서의 변형률을 이용하여 응력값을 획득하며, 이 획득 된 응력값을 이용하여 잔존 피로 수명을 평가하도록 구성된 제어수단 및 제어수단으로부터 출력되는 표 시 제어 신호를 입력받아 디스플레이하도록 구성된 표시부를 포함한다

Quasi real-time and continuous non-stationary strain estimation in bottom-fixed offshore structures by multimetric data fusion

Offshore structures are generally exposed to harsh environments such as strong tidal currents and wind loadings. Monitoring the structural soundness and integrity of offshore structures is crucial to prevent catastrophic collapses and to prolong their lifetime however, it is intrinsically challenging because of the difficulties in accessing the critical structural members that are located under water for installing and repairing sensors and data acquisition systems. Virtualsensing technologies have the potential to alleviate such difficulties by estimating the unmeasured structural responses at the desired locations using other measured responses. Despite the usefulness of virtual sensing, its performance and applicability to the structural health monitoring of offshore structures have not been fully studied to date. This study investigates the use of virtual sensing of offshore structures. A Kalman filter based virtual sensing algorithm is developed to estimate responses at the location of interest. Further, this algorithm performs a multi-sensor data fusion to improve the estimation accuracy under non-stationary tidal loading. Numerical analysis and laboratory experiments are conducted to verify the performance of the virtual sensing strategy using a bottom-fixed offshore structural model. Numerical and experimental results show that the unmeasured responses can be reasonably recovered from the measured responses1

Deep Point Cloud Reconstruction

1

Stepwise approximation for linear wave scattering

한국해양과학기술

Development of construction technology for offshore wind turbine support structures

한국해양과학기술

Performance evaluation of interlocking Caisson-Type breakwaters against abnormal high waves

한국해양과학기술

유지관리 고효율화를 위한 재래식 부잔교(함선) 개선방안 수립 보고서

해양수산

Development of primer design program for multiplex PCR

funder : 국무조정실agency : 한국과학기술정보연구원agency : Korea Institute of Science and Technology Information다중 PCR법은 진단 및 유전자의 특정 지역에 대한 invitro cloning등에 이용되어지는 강력한 기술이 다. 이러한 다중 PCR에 의해 생성되는 false-positive 산물을 최소화하기 위해 우리는 연구자들이 최적의 primer 쌍을 선택 할 수 있는 응용 프로그램을 개발하였다. Primer 디자인에는 융해온도, GC 조성, primer-이 합체 형성, primer -고리 모양 형성, primer 길이 등이 최적의 pr imer 쌍을 구하는데 매개변수로 이용되어졌다. 본 프로그램은 다중 PCR primer 쌍을 선별하기 위한 알고리즘으로 새로운 점수법을 도입하여 구현했으며, 자바가지 원하는 모든 플랫폼에서 실행 가능하다.The main contents and scop of the study is the following: o Development of pr imer desi gn modul e - Melting temperature and GC Contents - Selection algorithm for multiple primer - Dimer and hairpin formation - Selection method of the optimal primer pairs for each gene o Development of sear chi ng funct ion on whol e genome - I ndexi ng method and sear ching funct ion f or genome sequenc