• 융합신호처리학회논문지
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• 제20권1호
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• pp.9-15
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• 2019

As the human population increases in the world, the ratio of health doctors is rapidly decreasing. Therefore, it is an urgent need to create new technologies to monitor the physical and mental health of people during their daily life. In particular, negative mental states like depression and anxiety are big problems in modern societies. Usually this happens due to stressful situations during everyday activities including work. This paper presents a machine learning approach to reliably estimating the level of human mental stress using wearable physiological sensors. And also, this paper presents an Android- and Arduino-based stress monitoring and relief system.

• 콘크리트학회논문집
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• 제14권3호
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• pp.341-348
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• 2002

유지관리 계측은 터널 구조물의 지속적인 안전성 확인과 최적의 유지관리가 되도록 객관적이고 연속적인 자료제공을 목적으로 한다. 최근 들어 각종 터널에 적용하는 사례가 급속하게 증가되고 있으나, 현재까지 터널에서 장기간 측정된 계측실적도 적고, 합리적인 분석방법 연구도 전무한 실정이다. 본 연구에서는 장기간 계측이 수행된 지하철 풍화대 통과 터널의 계측결과를 회귀분석하여 터널의 최종 지보재인 콘크리트 라이닝의 응력과 철근응력의 상관관계를 파악하였다. 또한, 터널 콘크리트 라이닝의 응력과 안전성의 분석을 통하여 유지관리 계측 빈도 및 관리 기준치의 현장 적용성을 검토하였다.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.465-482
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• 2013

Recently, a novel stress sensor, which utilizes the elasto-magnetic (EM) effect of ferromagnetic materials, has been developed to measure stress in steel cables and wires. In this study, the effectiveness of this EM based stress sensors for monitoring of the cable tension force of a real scale cable-stayed bridge was investigated. Two EM stress sensors were installed on two selected multi-strand cables in Hwa-Myung Bridge, Busan, South Korea. Conventional lift-off test was conducted to obtain reference cable tension forces of two test cables. The reference forces were used to calibrate and validate cable tension force measurements from the EM sensors. Tension force variations of two test cables during the second tensioning work on Hwa-Myung Bridge were monitored using the EM sensors. Numerical simulations were conducted to compare and verify the monitoring results. Based on the results, the effectiveness of EM sensors for accurate field monitoring of the cable tension force of cable-stayed bridge is discussed.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.49-52
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• 2007

Terrestrial Laser Scanning(TLS) was developed at the mid-to-late 1990s. This technique enables to perform reconnaissance surveying of regions or structures hard to access. Besides, TLS has been extended its application gradually such as preservation of historical remains, underground surveys, slopes, glaciers monitoring and so on. However, though the technique has a lot of advantages, an application for structural health and safety monitoring is a beginning stage and it need much research. Therefore in this study, as a groundwork, the estimation model on stress of structures using TLS and Finite Element Method(FEM) applied by the Digital Elevation Model(DEM) technique of geoinformatics is proposed. For the verification of this model, experiments were performed with a continuous steel beam subjected to point loads and outputs were compared with those of electrical strain sensors.

• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.33-37
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• 2009

Fiber Bragg grating (FBG) sensors already have been the focus for structural health monitoring (SHM) due to their distinguishing advantages. However, as bare optical fiber is very fragile, bare FBG strain sensor without encapsulation can not properly be applied in practical infrastructures. Therefore encapsulation techniques for making encapsulated FBG strain sensor show very important in pushing forward the application of FBG strain sensors in SHM. In this paper, a simplified approximate method to analyze the stress transferring rules for embedded FBG strain sensors in concrete monitoring is put forward according to mechanics of composite materials. Shear lag theory is applied to analyze the stress transferring rule of embedded FBG strain sensor in measured host material at the first time. The measured host objects (concrete) and the encapsulated FBG strain sensor are regarded as a composite, and then the stress transfer formula and stress transfer coefficient of encapsulated FBG strain sensor are obtained.

• 비파괴검사학회지
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• 제36권2호
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• pp.121-129
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• 2016

As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.91-92
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• 2015

This study was performed for application of Structural Health Monitoring system of Jamsil Lotte World Tower. Axial stresses of mega column and core wall are measured in the past 29 months for axial stress monitoring and evaluating predicted self weight. We use the midas gen program(FEM analysis program) with construction stage analysis mode to predict axial stress. 8 mega column axial stressmeters are installed at 21st floor and 4 core wall stressmeters are installed at 38th floor. Measurement data was obtained without creep and shrinkage effect.

• Smart Structures and Systems
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• 제2권2호
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• pp.155-169
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• 2006

In this paper, the application of magnetoelasticity in static tension monitoring for large steel cables is discussed. Magnetoelastic (EM) stress sensors make contact-free tension monitoring possible for hanger cables and post-tensioned cables on suspension and cable-stayed bridges. By quantifying the correlation of magnetic relative permeability with tension and temperature, the EM sensors inspect the load levels in the steel cables. Cable tension monitoring on Qiangjiang (QJ) 4th Bridge demonstrates the reliability of the EM sensors.

• Corrosion Science and Technology
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• 제7권3호
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• pp.173-178
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• 2008

Recently an electrochemical noise method (ENM) with three electrodes has gained attention as a corrosion monitoring system in chemical plants. So far a few studies have been carried out for localized corrosion and environmental cracking of chemical plant materials. In this paper the ENM system is briefly summarized. Then an application of ENM to general corrosion for chemical plant materials is described. The emphasis is focused upon the analysis of stress on the corrosion cracking process of austenitic stainless steel in 30% $MgCl_2$ aqueous solution and the corrosion fatigue crack initiation process of 12 Cr stainless steel in 3% NaCl aqueous solution by ENM. Finally future problems for ENM to monitor regarding corrosion and environmental cracking in chemical plants are discussed.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.195-197
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• 2003

Soil moisture is a crucial variable in research works of hydrology, meteorology and plant sciences. Adequate soil moisture is essential for plant growth; excesses and deficits of soil moisture must be considered in agricultural practices. There are already several remote sensing methods used for monitoring soil moisture, such as thermal inertia, vegetation water-supplying index, crop water stress index and multi-factor regression. In this paper, an improved method has been discussed which is based on the thermal inertia. We analyzed the problems of monitoring soil moisture using satellites at first, and then put forward an simplified method which directly uses land surface temperature differences to measure soil moisture. Also we have taken the influence of vegetation into account, and import NDVI into the model. The method was used in the study of soil moisture in Heilongjiang Province, China, and we draw the conclusion by the experiments that the model can evidently increase the precision of monitoring soil moisture.