• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.433-442
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• 2013

This paper presents experimental research work for the evaluation of one-dimensional and two-dimensional acoustic source locations with 50m length of a precast prestressed concrete box girder. Acoustic events are generated by the impacts of Schmidt Hammer and the impact signals are detected by acoustic emission sensors mounted on the concrete web surface of PSC box girder with the average spacing of 9.34m. Based on the amplitude of detected acoustic signals, considering the noises developed in PSC box girder bridges, the arrival times of acoustic signals are estimated by the first arrival times of 0Volt, 0.5Volt, and 1.0Volt amplitude in each signal. Using Least Square Method, the velocities and the source locations of acoustic signals are evaluated. Based on the test results, the spacing of AE sensors and the AE sensor networks are discussed to reduce the source location errors.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.577-587
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• 2021

Drought is generally considered to be a natural disaster caused by accumulated water shortages over a long period of time, taking months or years and slowly occurring. However, climate change has led to rapid changes in weather and environmental factors that directly affect agriculture, and extreme weather conditions have led to an increase in the frequency of rapidly developing droughts within weeks to months. This phenomenon is defined as 'Flash Drought', which is caused by an increase in surface temperature over a relatively short period of time and abnormally low and rapidly decreasing soil moisture. The detection and analysis of flash drought is essential because it has a significant impact on agriculture and natural ecosystems, and its impacts are associated with agricultural drought impacts. In South Korea, there is no clear definition of flash drought, so the purpose of this study is to identify and analyze its characteristics. In this study, flash drought detection condition was presented based on the satellite-derived drought index Evaporative Stress Index (ESI) from 2014 to 2018. ESI is used as an early warning indicator for rapidly-occurring flash drought a short period of time due to its similar relationship with reduced soil moisture content, lack of precipitation, increased evaporative demand due to low humidity, high temperature, and strong winds. The flash droughts were analyzed using hydrometeorological characteristics by comparing Standardized Precipitation Index (SPI), soil moisture, maximum temperature, relative humidity, wind speed, and precipitation. The correlation was analyzed based on the 8 weeks prior to the occurrence of the flash drought, and in most cases, a high correlation of 0.8(-0.8) or higher(lower) was expressed for ESI and SPI, soil moisture, and maximum temperature.

• Journal of Korea Water Resources Association
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• v.54 no.9
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• pp.681-692
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• 2021

Vegetation processes have a significant impact on rainfall runoff processes through evapotranspiration control, but are rarely considered in the conceptual lumped hydrological model. This study evaluated the model performance of the Hapcheon Dam watershed by integrating the ecological module expressing the leaf area index data sensed remotely from the satellite into the hydrological partition module. The proposed eco-hydrological model has three main features to better represent the eco-hydrological process in humid regions. 1) The growth rate of vegetation is constrained by water shortage stress in the watershed. 2) The maximum growth of vegetation is limited by the energy of the watershed climate. 3) The interaction of vegetation and aquifers is reflected. The proposed model simultaneously simulates hydrologic components and vegetation dynamics of watershed scale. The following findings were found from the validation results using the model parameters estimated by the SCEM algorithm. 1) Estimating the parameters of the eco-hydrological model using the leaf area index and streamflow data can predict the streamflow with similar accuracy and robustness to the hydrological model without the ecological module. 2) Using the remotely sensed leaf area index without filtering as input data is not helpful in estimating streamflow. 3) The integrated eco-hydrological model can provide an excellent estimate of the seasonal variability of the leaf area index.

• Journal of IKEEE
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• v.13 no.3
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• pp.1-6
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• 2009

In this paper, the external matching circuits were designed in order to compensate the efficiency which decreases by human body effect in the internal antenna phone. Comparing the two types of matching circuit, we selected the structure to minimize the switch stress. RF MEMS switch using low voltage was compared with FET switch and measured the performance in the handset. Here, the detection circuit which can couple th reflection power from antenna was added in the handset and we set up the demonstration system that can compensate the loss of hand effect automatically. In this system, when hand effect occurred, the radiation power increased 2.5dB by operation the matching circuit.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.92-95
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• 2003

본 논문에서는 철도차량 견인전동기에 대한 상태진단 및 상시감시 기술에 관하여 소개하였다. 권선의 절연상태 진단을 위한 비파괴 시험법에서는 부분방전량 Q에 대한 평균열화도 $\Delta$로 표현되는 D-Map에 의해 잔여 절연내력(residual dielectric strength)을 예측하고, 기기의 운전이력측면에서 기동-정지 횟수와 열적, 전기적 및 열싸이클 스트레스 등에 의해 각 열화 인자를 고려한 운전시간에 기반한 N-Y 수명예측을 수행한다. 그리고 견인전동기의 전류에 대한 온라인 상태감시를 통해 베어링 고장, 고정자 및 전기자 고장, 고장 또는 전동기축 손상에 기인하는 비정상 운전상태 의 감지를 수행한다.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1647-1648
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• 2006

화학적, 생물학적 분석, 즉 특정 물질의 존재 유무를 측정하기 위해 마이크로캔틸레버라는 구조체를 제작하여 이를 바이오센서로 응용하였다. 마이크로캔틸레버의 장점은 분석하고자 하는 시료의 양이 적더라도 감지가 가능하고 이를 통하여 분석시간을 단축할 수 있다는 장점을 가지고 있다. 마이크로캔틸레버 구조물 제작을 위해 보편적으로 많이 이용되는 bulk 미세 가공 기술을 대신하여 표면 미세 가공기술을 이용하였다. 이러한 표면 미세 가공기술은 bulk 미세 가공기술에 비해 공정이 간단하고 값이 싸다는 장점이 있다. 또 액상 실험을 위하여 polydimethylsiloxane (PDMS)와 fused silica glass를 사용한 유체 제어 시스템을 제작하였다. 본 연구에서는 자기조림 이라는 특성을 이용하여 생물분자를 유체 제어 시스템 내의 마이크로캔틸레버 상단에 immobilization 시킨 후 마이크로캔틸레버 상, 하단의 표면 스트레스 차이에 따른 마이크로캔틸레버 자체의 휘어지는 정도를 측정하였다. 이러한 휘어지는 현상을 관찰함으로서 마이크로캔틸레버의 바이오센서로 응용 가능성을 확인한 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.928-931
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• 2018

고립된 해상 작업 환경에서의 작업자의 건강상태 관리와 혹시 모를 추락탐지는 작업자의 안전을 위해 매우 중요하다. 본 논문에서는 이러한 고립공간 작업자의 안전을 모니터링하기 위한 헬멧에 부착할 수 있는 IoT 시스템을 위한 알고리즘을 제안한다. 이는 장치가 작업 중에 긴급 상황인지 신속하게 판단할 수 있다. 스마트폰은 누구나 들고 다니기 때문에 사용자 환경은 스마트폰을 이용하여 적용되었다. 작업자들이 착용할 용도이기 때문에 PPG 센서는 불편하지 않도록 귀에 부착한다. PPG 센서를 단독으로 사용하여 스트레스 정도를 파악한다. 3축 가속도 센서는 헬멧에 부착되고 추락을 감지하는데 사용된다. 우리는 여러 센서와 블루투스 통신을 이용하여 발전된 센서 시스템을 만든다. 또한, 우리는 3축 가속도 샘플을 분석하고 정규화하는 알고리즘을 JAVA에서 구현하였다. 스마트 폰을 사용하는 이점은 신호 처리를 위해 별도의 마이크로프로세서(mcu)가 필요하지 않으며 내부 통신 시스템을 통해 제어 센터에 정보를 전송할 수 있다는 것이다.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.667-677
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• 2020

Crop water stress can be detected based on soil moisture content, crop physiological characteristics and remote-sensing technology. The detection of crop water stress is an important issue for the accurate assessment of yield decline. The crop water stress index (CWSI) has been introduced based on the difference between leaf and air temperature. In this paper, drone-based thermal infrared image was used to map of crop water stress in water control plot (WCP) and water deficit plot (WDP) over spring chinese cabbage fields. The spatial distribution map of CWSI was in strong agreement with the abnormal growth response factors (plant height, plant diameter, and measured value by chlorophyll meter). From these results, CWSI can be used as a good method for evaluation of crop abnormal growth monitoring.

• Korean Journal of Microbiology
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• v.47 no.4
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• pp.295-301
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• 2011

Aquaporin is a water channel protein, which is classified as Major Intrinsic Protein (MIP), found in almost all organisms from bacteria to human. To date, more than 200 members of this family were identified. There are two major categories of MIP channels, orthodox aquaporins and aquaglyceroporins, which facilitate the diffusion across biological membranes of water or glycerol and other uncharged compounds, respectively. The full genome sequencing of various fungal species revealed 3 to 5 aquaporins in their genome. Although some functions of aquaporins found in yeast were characterized, however, no functional characteristics were studied so far in filamentous fungi, including Aspergillus sp. In this study, one orthodox aquaporin homolog gene, aqpA, and four aquaglyceroporin homologs, aqpB-E, in a model filamentous fungus Aspergillus nidulans were identified and the function of the aqpA gene was characterized. Knock-out of the aqpA gene didn't show any obvious phenotypic change under the osmotic stress, indicating that the function of the gene does not involved in the osmotic stress response or the function could be redundant. However, the mutant showed antifungal susceptibility resistance phenotype, suggesting that the function of the aqpA gene could be involved in sensing the antifungal substances rather than the osmotic stress response.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.69 no.2
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• pp.78-87
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• 2024

The risk of global warming is increasing due to rapid climate change and increased greenhouse gas (GHG) emissions. Among the greenhouse gases, methane has a strong warming effect; in particular, 51.2% of the agricultural sector's methane emissions are from flooded rice fields. According to the current standard rice cultivation method, rice is grown during the maximum tillering stage with an intermittent drainage period of approximately 2 weeks. During the flooding period, methane-producing bacteria are active, but the activity of methane-producing bacteria and the amount of methane gas produced are reduced when the soil becomes oxidized through watering. Accordingly, this study used multiple-sensing technology to analyze the growth response according to the intermittent drainage period and to identify the extended intermittent drainage period with less impact on rice production. The equipment used for growth observations included NDVI, PRI, and IR sensors. The results confirmed that growth indices related to stress, such as NDVI and PRI, were not significantly different from those of the control when treated within 3 weeks of drainage, but drastically decreased when the drainage period was extended beyond 4 weeks. These results appear to result from the fact that soil water content (volumetric water content) also dropped to below 20% 4 weeks after irrigation, creating actual drought stress conditions. The 22^nd day after treatment, when the soil moisture content reached 20%, was considered the point in time when drought stress conditions were formed. The point at which the SPAD value decreased to 0.6% of normal was estimated to be 23.5 days after treatment by using the regression equation between NDVI and SPAD.