튜브형 이산화질소 passive sampler의 태양광 영향에 관한 분석

이범진,김학민,인치경,김선태 대전대학교 산업기술연구소 2000 산업기술연구소 論文集 Vol.11 No.2

The purpose of this study is to estimate the effect of sunlight on the measurement results of the tube type of NO2 passive sampler. Total 252 samples; seven duplicates, two sites with different concentration level, and nine days concerning to both exposure to sunlight and screened passive samplers with aluminium foil, were measured and analyzed. Relative standard deviation(%) of measurement data in this study was calculated as less than 10%, and it meant that even the simplest passive sampler showed comparatively high precision. The average concentration values of the screened passive samplers were turned out to be 22.4%∼25.5% higher than that of the passive samplers which were exposed to sunlight. Consequently, the sunlight was found to be the most important meteorological factor to affect the measurement for the tube type of passive samplers.

암모니아 공간분포 조사를 위한 Passive Sampler 개발에 관한 연구

김학민,이범진,김선태 대전대학교 환경문제연구소 2001 환경문제연구소 논문집 Vol.5 No.-

Passive and active samplers are widely deployed for measuring gaseous pollutants such as nitrogen dioxide, sulfur dioxide and ozone in urban and rural air, however odorous compounds like ammonia, hydrogen sulfide are rarely deployed, because they are easily changed by circumstance conditions and perceived that they need a large number of measuring sites to assess mean concentration over the area. So, it is considered that the odor related phenomena could not be easily defined by cost-effective and convenient method. In this study, we developed the new sampling tool for ammonia evaluation in ambient air and the results of evaluation for evaluate the suitability of developed passive sampler for the measurement of daily averaged ammonia concentrations and spatial distribution survey are presented. Three types of absorbing solutions, filters and caps were tested at laboratory condition and the conversion factor, precision and suitability of the samplers were derived from triplicated measurement at paper mill. It is defined that for absoubing ammonia, 2% of phosphoric acid and glycerine mix(1:1) solution and chromatography filter are suitable and rubber cap is unsuitable to use during sampling and storage period. The conversion factor was derived 7.0μA at ordinary ambient air by comparison with reference method(indo-phenol method) at three different conditions. The calculated results of standard deviation among the samplers were lower than 2ppb at 86% sampling sites of total 40 sites and we could recognize the ammonia sources and variation with change of wastewater treatment plant process. Therefore the developed passive samplers are appropriate to survey ammonia spatial distrivution.

Structural performance evaluation of a steel-plate girder bridge using ambient acceleration measurements

Yi, Jin-Hak,Cho, Soojin,Koo, Ki-Young,Yun, Chung-Bang,Kim, Jeong-Tae,Lee, Chang-Geun,Lee, Won-Tae Techno-Press 2007 Smart Structures and Systems, An International Jou Vol.3 No.3

The load carrying capacity of a bridge needs to be properly assessed to operate the bridge safely and maintain it efficiently. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized. In these tests, the deflection (or strain) of the structural members loaded by the controlled vehicles are measured and analyzed. Using the measured data, deflection (or strain) correction factor and impact correction factor are calculated. These correction factors are used in the enhancement of the load carrying capacity of a bridge, reflecting the real state of a bridge. However, full or partial control of the traffic during the tests and difficulties during the installment of displacement transducers or strain gauges may cause not only inconvenience to the traffic but also the increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using an excited response part of full measured ambient acceleration data by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of a bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection of a bridge akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection, which is obtained by double-integration of the acceleration data with removal of the linear components on the acceleration data. For validation, a series of tests were carried out on a steel plategirder bridge of an expressway in Korea in four different seasons, and the evaluated load carrying capacities of the bridge by the proposed method are compared with the result obtained by the conventional load test method.

Numerical investigation on effects of rotor control strategy and wind data on optimal wind turbine blade shape

Yi, Jin-Hak,Yoon, Gil-Lim,Li, Ye Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.18 No.2

Recently, the horizontal axis rotor performance optimizer (HARP_Opt) tool was developed in the National Renewable Energy Laboratory, USA. This innovative tool is becoming more popular in the wind turbine industry and in the field of academic research. HARP_Optwas developed on the basis of two fundamental modules, namely, WT_Perf, a performance evaluator computer code using the blade element momentum theory; and a genetic algorithm module, which is used as an optimizer. A pattern search algorithm was more recently incorporated to enhance the optimization capability, especially the calculation time and consistency of the solutions. The blade optimization is an aspect that is highly dependent on experience and requires significant consideration on rotor control strategies, wind data, and generator type. In this study, the effects of rotor control strategies including fixed speed and fixed pitch, variable speed and fixed pitch, fixed speed and variable pitch, and variable speed and variable pitch algorithms on optimal blade shapes and rotor performance are investigated using optimized blade designs. The effects of environmental wind data and the objective functions used for optimization are also quantitatively evaluated using the HARP_Opt tool. Performance indices such as annual energy production, thrust, torque, and roof-flap moment forces are compared.

Structural performance evaluation of a steel-plate girder bridge using ambient acceleration measurements

Jin-Hak Yi,조수진,구기영,윤정방,김정태,Chang-Geun Lee,Won-Tae Lee 국제구조공학회 2007 Smart Structures and Systems, An International Jou Vol.3 No.3

The load carrying capacity of a bridge needs to be properly assessed to operate the bridge safely and maintain it efficiently. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized. In these tests, the deflection (or strain) of the structural members loaded by the controlled vehicles are measured and analyzed. Using the measured data, deflection (or strain) correction factor and impact correction factor are calculated. These correction factors are used in the enhancement of the load carrying capacity of a bridge, reflecting the real state of a bridge. However, full or partial control of the traffic during the tests and difficulties during the installment of displacement transducers or strain gauges may cause not only inconvenience to the traffic but also the increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using an excited response part of full measured ambient acceleration data by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of a bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection of a bridge akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection, which is obtained by double-integration of the acceleration data with removal of the linear components on the acceleration data. For validation, a series of tests were carried out on a steel plate-girder bridge of an expressway in Korea in four different seasons, and the evaluated load carrying capacities of the bridge by the proposed method are compared with the result obtained by the conventional load test method.

Comparative study on modal identification methods using output-only information

Jin-Hak Yi,윤정방 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3-4

In this paper, several modal identification techniques for output-only structural systems areextensively investigated. The methods considered are the power spectral method, the frequency domaindecomposition method, the Ibrahim time domain method, the eigensystem realization algorithm, and thestochastic subspace identification method. Generally, the power spectral method is most widely used inpractical area, however, the other methods may give better estimates particularly for the cases with closedmodes and/or with large measurement noise. Example analyses were carried out on typical structuralsystems under three different loading cases, and the identification performances were examined throughtthe comparisons between the estimates by various methods.

Comparative study on modal identification methods using output-only information

Yi, Jin-Hak,Yun, Chung-Bang Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3

In this paper, several modal identification techniques for output-only structural systems are extensively investigated. The methods considered are the power spectral method, the frequency domain decomposition method, the Ibrahim time domain method, the eigensystem realization algorithm, and the stochastic subspace identification method. Generally, the power spectral method is most widely used in practical area, however, the other methods may give better estimates particularly for the cases with closed modes and/or with large measurement noise. Example analyses were carried out on typical structural systems under three different loading cases, and the identification performances were examined throught the comparisons between the estimates by various methods.

Analysis of Structural Dynamic Responses of a 10 kW Vertical Axis Wind Turbine

Jin-Hak Yi(이진학),Wonsul Kim(김원술),Taek Hee Han(한택희),Seungryul Im(임승률) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.10

Periodic seismic performance evaluation of highway bridges using structural health monitoring system

Yi, Jin-Hak,Kim, Dookie,Feng, Maria Q. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.5

In this study, the periodic seismic performance evaluation scheme is proposed using a structural health monitoring system in terms of seismic fragility. An instrumented highway bridge is used to demonstrate the evaluation procedure involving (1) measuring ambient vibration of a bridge under general vehicle loadings, (2) identifying modal parameters from the measured acceleration data by applying output-only modal identification method, (3) updating a preliminary finite element model (obtained from structural design drawings) with the identified modal parameters using real-coded genetic algorithm, (4) analyzing nonlinear response time histories of the structure under earthquake excitations, and finally (5) developing fragility curves represented by a log-normal distribution function using maximum likelihood estimation. It is found that the seismic fragility of a highway bridge can be updated using extracted modal parameters and can also be monitored further by utilizing the instrumented structural health monitoring system.

Evaluation of Vibration Characteristics of an Existing Harbor Caisson Structure Using Tugboat Impact Tests and Modal Analysis

Yi, Jin-Hak,Park, Woo-Sun,Lee, So-Young,Huynh, Thanh-Canh,Kim, Jeong-Tae,Seo, Chun-Kyo SAGE Publications 2013 International journal of distributed sensor networ Vol.2013 No.-