• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.249-255
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• 2010

Since the 1990's, a number of ULF geomagnetic disturbance associated with earthquake occurrences have actively been reported, and polarization analysis of geomagnetic fields becomes one of potential candidates to be capable of predicting short-term earthquake. This study develops the modified polarization analysis method based on the previous studies, and analyzes three-component geomagnetic fields obtained at Cheongyang geomagnetic observatory using the developed method. A daily polarization value (the ratio of spectral power of horizontal and vertical geomagnetic field) is calculated with a focus on the 0.01 Hz band, which is known to be the most sensitive to seismogenic ULF radiation. We analyze a total of 10 months of geomagnetic data obtained at Cheongyang observatory, and compare the polarization values with the Kp index and the earthquake occurred in the analysis period. The results show that there is little correlation between the temporal variations of polarization values and Kp index, but remarkable increases in polarization values are identified which are associated with two earthquakes. Comparison the polarization values obtained at Cheongyang and Kanoya observatory indicates that the increases of polarization values at Cheongyang might be due to not global geomagnetic induction but the locally occurred earthquakes. Furthermore, these features are clearly shown in normalized polarization values, which take account in the statistical characteristics of each geomagnetic field. On the basis of these results, polarization analysis can be used as promising tool for monitoring the earthquake-precursory phenomenon.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.782-783
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• 2011

본 연구에서는 자동차 부품 가공공정에서 적용하는 캐스케이드 디버링(cascade deburring) 후 잔존하는 스틸볼(steel ball)을 자동으로 감지하기위한 시스템을 구현하였다. 구현된 시스템은 자화부, 검출부, 제어부, PC 모니터링부로 구성되었다. 스틸볼 착자화 및 감지 정밀도의 향상, 외부노이즈 대응능력 등의 환경 변화에 영향을 받지 않는 신뢰성이 뛰어난 성능을 갖는 시스템을 구현하고자 하였으며 이를 위한 미세 스틸볼 감지시스템의 착자화부를 구현하고 성능평가를 수행하였다.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.40.1-40.1
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• 2010

한국천문연구원 우주과학연구본부 태양우주환경연구그룹은 일본 Tierra Tecnica사의 RFP-523C Overhauser Proton 자력계와 MISYS-09 삼축 MI 자력계를 2009년 11월에 보현산천문대 태양망원경동에 구축하였다. 한국천문연구원은 이미 2007년 11월에 RFP-523C Fluxgate 자력계를 보현산천문대 태양망원경동에 구축하여 K 지수 산출 등의 우주환경예 경보 연구에 활용하고 있다. Fluxgate 자력계는 지자기 3축 성분의 변화량을 측정하는 장비이고 이번에 설치한 Overhauser Proton 자력계는 지자기의 총 자기장을 측정하는 장비이다. 삼축 MI 자력계는 지자기장의wave를 측정하는 장비이다. 기존에 설치한 Fluxgate 자력계와 새로 설치한 Proton 자력계, 삼축 MI 자력계를 연계하여 운용할 경우 우주환경에 의한 지자기장 변화량의 측정 정밀도가 향상되고 지자기장을 효율적으로 관측할 수 있다. 보현산천문대에 구축한 각각의 자력계가 측정한 지자기 자료들은 S-FTP와 Socket 통신을 이용하여 대전에 있는 한국천문연구원 태양우주환경연구그룹의 데이터 서버로 실시간으로 전송되어 저장되고 있다. 데이터 서버로 전송된 지자기 측정 자료들은 한국천문연구원 우주환경감시실에서 모니터링하고 있다.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.232-240
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• 2015

Magnetotelluric (MT) survey investigates electrical structure of subsurface by measuring natural electromagnetic fields on the earth surface. For the accurate interpretation of MT data, the precise three-dimensional (3-D) modeling algorithm is prerequisite. Since MT responses are affected by electrical anisotropy of medium, the modeling algorithm has to incorporate the electrical anisotropy especially when analyzing time-lapse MT data sets, for monitoring engineered geothermal system (EGS) reservoir, because changes in different-vintage MT-data sets are small. This study developed a MT modeling algorithm for the simulation MT responses in the presence of electrical anisotropy by improving a pre-existing staggered-grid finite-difference MT modeling algorithm. After verifying the developed algorithm, we analyzed the effect of vertical transversely isotropic (VTI) anisotropy on MT responses. In addition, we are planning to extend the applicability of the developed algorithm which can simulate not only the horizontal transversely isotropic (HTI) anisotropy, but also the tiled transversely isotropic (TTI) anisotropy.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.2
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• pp.151-158
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• 2019

Objectives of this study were to identify the hotspot for displacement of the on-line water quality sensors, in order to detect illicit discharge of untreated wastewater. A total of twenty-six water quality parameters were measured in sewer networks of the industrial complex located in Daejeon city as a test-bed site of this study. For the water qualities measured on a daily basis by 2-hour interval, the self-organizing maps(SOMs), one of the artificial neural networks(ANNs), were applied to classify the catchments to the clusters in accordance with patterns of water qualities discharged, and to determine the hotspot for priority sensor allocation in the study. The results revealed that the catchments were classified into four clusters in terms of extent of water qualities, in which the grouping were validated by the Euclidean distance and Davies-Bouldin index. Of the on-line sensors, total organic carbon(TOC) sensor, selected to be suitable for organic pollutants monitoring, would be effective to be allocated in D and a part of E catchments. Pb sensor, of heavy metals, would be suitable to be displaced in A and a part of B catchments.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.33-39
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• 2016

With recent advances in sensor technology, CMOS-based semiconductor devices and networking protocol, the areas for application of wireless sensor networks greatly expanded and diversified. Such diversification of uses for wireless sensor networks creates a multitude of beneficial possibilities for several industries. In the application of wireless sensor networks for monitoring systems' data transmission process from the sensor node to the sink node, transmission through multi-hop paths have been used. Also mobile sink techniques have been applied. However, high energy costs, unbalanced energy consumption of nodes and time gaps between the measured data values and the actual value have created a need for advancement. Therefore, this thesis proposes a new model which alleviates these problems. To reduce the communication costs due to frequent data exchange, a State Prediction Model has been developed to predict the situation of the peripheral node using a geographic autocorrelation of sensor nodes constituting the wireless sensor networks. Also, a Risk Analysis Model has developed to quickly alert the monitoring system of any fatal abnormalities when they occur. Simulation results have shown, in the case of applying the State Prediction Model, errors were smaller than otherwise. When the Risk Analysis Model is applied, the data transfer latency was reduced. The results of this study are expected to be utilized in any efficient communication method for wireless sensor network monitoring systems where all nodes are able to identify their geographic location.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.304-309
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• 2011

A monitoring system for magnetic abrasive polishing process is necessary to ensure the polishing products the high quality and integrity. Acoustic emission (AE) signal is known to reflect the material removal phenomena in other machining processes. In a case of the magnetic abrasive polishing of non-magnetic materials, application of AE method is very difficult because of lower machining force on the surface of workpiece and the level of AE signal is extremely lower. In this study, AE sensor-based monitoring system is applied to the magnetic abrasive polishing. The relation between the level of the AE RMS and the surface roughness during the magnetic abrasive polishing of magnesium alloy steel is investigated.

• Journal of the Korean Society of Radiology
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• v.85 no.3
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• pp.549-565
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• 2024

MRI is a crucial tool for diagnosing adenomyosis and identifying its related pathologies. To accurately diagnose adenomyosis, it is necessary to recognize both the typical MRI findings and atypical features of the condition. Recently, a standardized classification system has been developed to facilitate precise presurgical diagnosis of adenomyosis and to determine the appropriate treatment method. Differentiating between various subtypes based on MRI-based classification and identifying different MRI phenotypes can aid in categorizing patients with adenomyosis into specific treatment groups and monitoring their response to therapy.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.335-342
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• 2022

In this study, self-healing hybrid capsules were prepared by mixing self-healing solid capsules and self-healing microcapsules using inorganic materials as core materials. Self-healing hybrid capsules were mixed with 3 % according to the composition ratio of 3:7, 5:5, and 7:3 based on the mass of the cement to prepare a self-healing cement composite material. The healing properties of crack self-healing hybrid capsules were evaluated through hydrostatic water permeability test and surface crack monitoring. It was found that the self-healing hybrid capsules prepared by mixing the composition ratio of the self-healing solid capsules and the self-healing microcapsules at 7:3 has a great effect on improving the crack self-healing performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2975-2981
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• 2014

Micro-magnetic detection system is used to detect small particles in an automatic transmission valve body, which signal noise and time-delay may occurs in process of signal transmitting and filtering. In this paper, we present the design and implement of a micro-magnetic detection system based on wireless sensor networks in conveyer belt. Micro-magnetic detection system consists of five modules which are magnetic sensor detector, signal processing unit, wireless sensor networks, system control unit and system monitoring unit. Our experimental results show that the proposed wireless micro-magnetic detection system improves both accuracy and time delay compared to the wired system; therefore, it may apply for wireless micro-magnetic detection system by analysis of packet reception rate.