• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.765-772
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• 2002

Many researchers have studied several vibration control devices such as TMD, TLD, and VED to reduce the acceleration level for tall buildings. Advantages of TLD (tuned liquid damper) include easy installation, low cost, and less maintenance. However, the dynamic characteristics of TLD must be verified by experiment and analysis due to the difficulties in evaluating the characteristics of water sloshing. In this study, free vibration and dynamic excitation experiments of structure with TLD were conducted to verify vibration control force of the proposed TLD for high-rise building. The parameters were mass ratio of water to structure, number of damping nets, and aspect ratio. From the test results, the responses of structure with water tank were observed to be smaller than those of structure alone. Furthermore, better damping effect could be achieved with larger mass ratio, more damping nets, and larger aspect ratio. However, in the case of water tank with no damping net, little damping effect was obtained.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.166-166
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• 2011

한국건설기술연구원내에 세계 최초로 UHPC(초고성능 콘크리트)를 활용한 보도사장교를 설계 및 시공하여 공용중이다. 초고성능 콘크리트(UHPC, Ultra High Performance Concrete)는 기존의 콘크리트의 단점을 극복하기 위하여 강섬유 및 혼화재료를 사용하여 고강도화와 더불어 인장강도, 휨강도, 균열에 대한 저항성, 전단강도 및 내충격성을 대폭 개선시켜서 구조부재의 연성 및 강도를 확보하기 위해 개발된 것으로서 한국건설기술연구원이 독자적 연구를 바탕으로 UHPC를 개발하였고, KICT-UHPC의 특성을 충분히 반영한 보도사장교를 한국건설기술원내에 실구조물로 시공하였다. 한국건설기술연구원내 본관 1, 2동 연결 보도사장교(SUPER BRIDGE 1)의 진동실험을 통해 UHPC 보도사장교의 동특성(고유진동수 및 모드형상)을 평가하였다. 대상교량에는 보도사장교의 캔틸레버 구조 특성에 의해 발생하는 진동을 제어하기 위한 질량 264kg의 난간형 수직진동제어장치(TMD) 4대가 설치되어 있으며, 부가질량의 운동을 기계적으로 구속하거나 구속을 해제하여 TMD의 작동을 켜거나 끌 수 있도록 되어있다. TMD의 가동 및 정지시 동특성을 비교하는 정밀한 검증 실험을 통하여 TMD 설치에 의한 동특성의 변화도 평가하였다. 가진망치에 의한 충격실험으로부터 획득한 가속도 시간이력 데이터와 가진망치의 가진력 시간이력 데이터를 사용하여 주파수응답함수(FRF, frequency response function)를 계산하고, 이로부터 Super Bridge I의 동적모드형상과 고유진동수를 추출하였다. 1차 모드의 고유진동수는 TMD 정지시 2.2949 Hz, TMD 작동시 2.0996 Hz로서 8%정도 감소하였다. 충격해머에 의한 가진 실험을 통해 세계 최초로 시공한 UHPC 보도사장교의 진동특성과 관련한 신뢰성 있는 자료를 확보할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.146.2-146.2
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• 2014

KIST 6MV 가속기는 이온빔 분석 그리고 가속기 질량 분석법(Accelerator mass spectrometry)으로 활용된다. 이온빔 분석으로는 RBS, TOF ERD, PIXE. ${\mu}$-Probe을 할 수 있으며 AMS(Accelerator mass spectrometry)는 액체섬광측정법(LSC)과 비교할때 민감도는 1,000배 정도로 3H, 14C, 26Al,41Ca 을 10-21 ~ 10-18 mole/mg 까지 검출 가능하여. 응용분야로는 BAMS(Biological AMS), 전통과학, 지구과학, 환경과학에 활용되고 있다. 이중 AMS의 생-의학분야(BAMS)의 응용은 최근 매우 중요하게 연구되고 있다. BAMS의 활용 연구에 사용하는 핵종으로는 주로 3H, 14C, 41Ca, 36Cl를 사용하며, 14C 화합물은 쉽게 구할 수 있고, 자연방사선 이하의 낮은 14C labeled drug 사용하기 때문에 1948년 이후 생물학 연구에 혁신적으로 활용되고 있다. 주 활용분야로는 (1) 신약개발은 임상실험 전(Phase 0) 이용되며, 14C로 표지된 bio-molecule을 자연수준의 방사선 농도에서 추적자로 사용하여 질량을 측정하는 방법을 활용. (2) 의과학분야는 인체 내에서의 추적자 연구수행 (3) 항암제 연구는 암조직 중 약물농도와 암효과의 상관성을 연구 (4) 바이오 기술 분야에서는 생약 유효물질의 체내 대사연구 등을 할 수 있어 전세계적으로 활발히 연구가 진행되고 있다. KIST에서는 6MV가속기를 BAMS 연구에 활용하기 위하여 전처리 단계의 Combustion, Gas transfer, Reduction 등을 자체 제작하여 테스트 중에 있으며, BAMS 샘플의 Gas는 호기중의 성분, 대기 성분이 있으며, Liquid는 혈액(혈장,혈청,적혈구), Solid는 DNA, 세포, 장기 뼈, 피부, 식물조직, 사료, Drug 및 그 대사 류가 있다. AMS 측정 결과는 14C/12C 비율로 나타나며 그 결과를 농도로 환산하여 분석하게 된다. 또한 분석 데이터 신뢰를 확보하기 위하여 표준시료 및 품질관리용 시료를 사용하여 BAMS분석법에 대한 검증을 실시하였다.

• Journal of Convergence for Information Technology
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• v.11 no.3
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• pp.132-139
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• 2021

The response characteristics of the forced vibration generated when the high-damped vehicle pass the bumped barrier was studied, and in particular, the response behavior of displacement, velocity and acceleration was analyzed for the forced vibration model. In addition, in order to obtain responses such as displacement, velocity, and acceleration, a numerical analysis technique of the Runge-Kutta-Gill method was performed in time domain. The response was successfully obtained in detail under several high damping conditions. As a numerical analysis result, the response of the vehicle was obtained by considering the vehicle body to which the impulse impact was applied. Also, the analysis result was compared with the experimental result in order to verify the validity of vehicle model. The amplitude and natural frequency of the vehicle were considered and analyzed. The Nyquist diagram of the vehicle model was also obtained and the relationship could be analyzed. And the vibration response was analyzed on different mass, damping and stiffness.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.47-55
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• 2009

The purpose of this study is to verify the transfer function of input acceleration and output control force by linearizing a velocity-dependent damping term of Liquid Column Vibration Absorber (LCVA). Analytical and experimental research is conducted to identify natural frequency, damping ratio and participated mass ratio of LCVA with various section ratios of vertical and horizontal areas. Findings obtained experimentally by the shaking table test are compared with analytical findings using optimization technique with constraints. The results indicate that the level of liquid and section ratio of LCVA affect the characteristics of damping ratio and mass ratio. Damping and mass ratio increase as the section of vertical column of LCVA decreases, due to turbulence in the elbow of LCVA.

• Analytical Science and Technology
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• v.18 no.6
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• pp.483-490
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• 2005

Mass resolution of the time of flight aerosol mass spectrometer for an aerosol component analysis depends on the initial direction and the initial energy of the ions. We have found that the shape of the optimum post focusing electric field is not linear. The maximum electric potential should be applied to the ions whose initial direction is 90 degree. To check on the post focusing effects, we have installed a laser ablation mass spectrometer. By using this LA-MS, we have found that the average energy distribution of the laser ablated ions is 8 eV. To establish the optimum mass resolution, a time delay and a high voltage are needed, and the results of the study show that 1500 nsec, and 3.7 kV are the optimum parameters for our system respectively. The isotope mass signals of copper show a good resolution.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.3
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• pp.91-98
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• 2021

The installation and performance test of the ISOL (Isotope Separation On Line) system for the generation and separation of Rare Isotopes (RI) beams is in progress at the Rare Isotope Science Project (RISP), Institute for Basic Science (IBS). The various RI beams generated by the ISOL target/ion source go through the beam lines and separators, and only the RI beam desired by the user is selected and transmitted to the superconducting linear accelerator at the downstream of the ISOL. In the ISOL system, two separators are installed to separate a specific RI beam, and control is performed by the Experimental Physics and Industrial Control System (EPICS). In this study, an EPICS IOC (Input-Output Control) was developed to measure the magnetic field of a dipole magnet for mass separation of a multivalent (n+) RI beam in the A/Q separator, which is one of the ISOL RI beam separators. The operational stability of the A/Q separator was tested through a magnetic field measurement using a Hall probe.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1381-1384
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• 2005

In these days, the piezoresistive material has been applied to various sensors in order to measure the change of physical quantities. But the relationship between the sensitivity of a sensor and the position and size of piezoresistor has rarely been studied. Therefore, this paper was focused on the distribution of the resistance change ratio on the diaphragm and bridge surface where piezoresistor would be formed, and proposed the proper size and position of piezoresistor with which the sensitivity of sensor was increased. As the width of mass and boss was increased, the distance between piezoresistors was closed and the maximum value of resistance change ratio was decreased by the increase of the structure stiffness. And according to the increment of seismic mass size, the value of resistance change ratio is decreased by increase of the structure stiffness. Y directional piezoresistor is formed in the position of $100\mu{m}\;apart\;from\;cantilever\;edge\;and\;length\;of\;that\;is\;800\mu{m}$.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.177-185
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• 2009

The failure analysis of scales deposited on automotive thermostat housing has been carried out. Observations using energy dispersive spectroscopy and electron probe micro analyzer indicate that the main components of scales are some of additives of coolant used. For a detailed investigation of organic matters pyrolysis-GC/MS is employed. The result shows that the main organic component is benzoic acid and furthermore, a small amount of acetophenone, benzene and phenyl group is detected. Based on the results of failure analysis performed, the scales on automotive thermostat housing appear due to the deposition of coolant components, followed by crevice corrosion, into gap between housing and rubber horse. New accelerated test methodology, which could mimic the scale formation and the crevice corrosion on thermostat housing, is developed considering the above results. In order to reproduce the real operating conditions, the accelerating factors, i.e. temperature and humidity, are changed and programmed. The reproducibility of the accelerated test proposed is confirmed after analyzing the scales obtained from the accelerated test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.303-310
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• 2020

In this study, a method for selection of the location and number of monitoring sensors in a building structure using artificial neural networks is proposed. The acceleration-history values obtained from the installed accelerometers are defined as the input values, and the mass and stiffness values of each story in a building structure are defined as the output values. To select the installation location and number of accelerometers, several installation scenarios are assumed, artificial neural networks are obtained, and the prediction performance is compared. The installation location and number of sensors are selected based on the prediction accuracy obtained in this study. The proposed method is verified by applying it to 6- and 10-story structure examples.