• Journal of Korea Water Resources Association
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• v.56 no.8
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• pp.497-508
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• 2023

Agricultural reservoirs are crucial structures for water resources monitoring especially in Korea where the resources are seasonally unevenly distributed. Optical and Synthetic Aperture Radar (SAR) satellites, being utilized as tools for monitoring the reservoirs, have unique limitations in that optical sensors are sensitive to weather conditions and SAR sensors are sensitive to noises and multiple scattering over dense vegetations. In this study, we tried to improve water body detection accuracy through optical-SAR data fusion, and quantitatively analyze the complementary effects. We first detected water bodies at Edong, Cheontae reservoir using the Compact Advanced Satellite 500(CAS500), Kompsat-3/3A, and Sentinel-2 derived Normalized Difference Water Index (NDWI), and SAR backscattering coefficient from Sentinel-1 by K-means clustering technique. After that, the improvements in accuracies were analyzed by applying K-means clustering to the 2-D grid space consists of NDWI and SAR. Kompsat-3/3A was found to have the best accuracy (0.98 at both reservoirs), followed by Sentinel-2(0.83 at Edong, 0.97 at Cheontae), Sentinel-1(both 0.93), and CAS500(0.69, 0.78). By applying K-means clustering to the 2-D space at Cheontae reservoir, accuracy of CAS500 was improved around 22%(resulting accuracy: 0.95) with improve in precision (85%) and degradation in recall (14%). Precision of Kompsat-3A (Sentinel-2) was improved 3%(5%), and recall was degraded 4%(7%). More precise water resources monitoring is expected to be possible with developments of high-resolution SAR satellites including CAS500-5, developments of image fusion and water body detection techniques.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.4
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• pp.41-54
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• 2021

It is very essential to estimate the water body area using remote exploration for water resource management, analysis and prediction of water disaster damage. Hydrophysical detection using satellites has been mainly performed on large satellites equipped with optical and SAR sensors. However, due to the long repeat cycle, there is a limitation that timely utilization is impossible in the event of a disaster/disaster. With the recent active development of Micro satellites, it has served as an opportunity to overcome the limitations of time resolution centered on existing large satellites. The Micro satellites currently in active operation are ICEYE in Finland and Capella satellites in the United States, and are operated in the form of clusters for earth observation purposes. Due to clustering operation, it has a short revisit cycle and high resolution and has the advantage of being able to observe regardless of weather or day and night with the SAR sensor mounted. In this study, the operation status and characteristics of micro satellites were described, and the water area estimation technology optimized for micro SAR satellite images was applied to the Daecheong Dam basin on the Korean Peninsula. In addition, accuracy verification was performed based on the reference value of the water generated from the optical satellite Sentinel-2 satellite as a reference. In the case of the Capella satellite, the smallest difference in area was shown, and it was confirmed that all three images showed high correlation. Through the results of this study, it was confirmed that despite the low NESZ of Micro satellites, it is possible to estimate the water area, and it is believed that the limitations of water resource/water disaster monitoring using existing large SAR satellites can be overcome.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.946-953
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• 2018

Photo-plethysmography (PPG), which measures changes in the peripheral blood flow of a human body using difference in absorption rate of light, is a measurement method that is studied and used in clinical and various applications due to its simple circuit configuration and measurement convenience. Magneto-plethysmography (MPG), which is newly developed by our team, is a method of measuring changes in the conductivity of biological tissues by using a eddy current induced by a time-varying magnetic field, and is not subject to optical interference. In this study, we investigated the detection characteristics of MPG according to the change of the conductivity of the object and fluid to be measured by simultaneously measuring PPG and MPG. In order to control the speed of fluid known in advance, a blood flow simulator was implemented and used. The fluid used in the experiment was general mineral water and physiological saline (0.9% NaCl) solution. Experimental results show that the amplitude change of the measured PPG was 0.3% in normal water and saline solution, and that of MPG was 77.3%. Therefore, it is considered that the magneto-plethysmography (MPG) has a strong correlation with the conductivity of the fluid.

• Fire Science and Engineering
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• v.9 no.1
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• pp.20-29
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• 1995

The sprinkler head is a component of the sprinkler system intended to discharge water for automatic detection and extinguishment of fires. On this study, thermal characteristic values affecting the sensitivity of the fusible alloy type sprinkler head were obtained and analyzed under heated air stream condition which had constant temperature and velocity. The experiment was carried out under the forced convection condition with both the conductive heat loss considered and neglected. The thermal characteristic values of the sprinkler head were obtained in accordance with the material and shape of the heat responsive element and the conditions of the main body.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.382-383
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• 2008

In this paper we presented experimental results of a gas sensor utilizing multi-walled carbon nanotube (MWNT)composites for the alcohol detection which is useful to checking drinking and driving, for example. The MWNT-composites were deposited using spray method on PES substrates suitable for use in low-cost and flexible sensors. We observed the variation of conductance from the sensors exposed to alcohol vapors evaporated at 37C equal to the human body temperature to match real condition. As the result, the conductance was decreased with the increase of ethanol vol% diluted in water. The sensors showed good sensitivity and linearity.

• Environmental Analysis Health and Toxicology
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• v.20 no.3 s.50
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• pp.223-228
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• 2005

Rockfish Sebastes schlegeli was exposed to fluoranthene, a ubiquitous polycyclic aromatic hydrocarbon, at 1 and 10 $\mu$g/L for 4 weeks followed by depuration period of 8 weeks. Although the fluoranthene in the p]asma reached only 1.8$\~$1.9 times seawater concentration, it was 6.5 $\~$ 15.7 times higher in the liver, spleen and bile indicating efficient accumulation in the lipid -containing body tissues. When the exposed fish were then maintained in clean water, rapid fluoranthene decline occurred in the initial 2 weeks followed by a rather slow phase. This result suggests that fluoranthene accumulates efficiently provided the existence in the culture medium, but the contaminant disappears rapidly once the chemical source is removed. The fluoranthne residue in fish tissues my be a good indifator for relent PAHs exposure.

• Parasites, Hosts and Diseases
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• v.21 no.2
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• pp.187-192
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• 1983

In order to clarify infestation Pattern for the encysted larvae of digenetic trematodes from fresh-water fishes, this survey was carried out from March to September, 1983. A total of 380 fishes of 32 species wore collected with netting at the three reaches, upper, middle and lower in Mangyeong riverside area. After the fishes were dissected into small scraps, they were pressed under cover glass and examined-for the presence of those of digenetic trematodes with a microscope. The resillts obtailled were as follows; Out of a total of 380 knishes inspected, 320 fishes(84%) from 31 species were found positive with, digenetic trematode metacercariae; more than 10 species of the metacercariae Ivere detected in Pseuderasbora parva; .Gnnthepegen mtajimae, Microphysogokio yaluensis, Cultriculus eigenmanni and Gnnthopogon coreanus (more than 8 species) ; Aphyocypris chinensis (8 species) and etc. respectively. Clonorchis sinensis metacercariae were found positive from 93 fishes (25%) from 12 species and detection rates in other species of digenetic trematode metacercariae from various fishes were; Exorchis oviformis, 261 fisles (57%) from 28 species; Cyathocotyle criensalis, 47 fishcs (12%) from 12 species; Metorchis orientalis, 21 fishes (6%) from 12 species; Metagonimus yokogawai, 164 fishes (43%) from 26 species; Pseudesorchis major, 71 fishes (19%) from 18 species; Metacercaria haiegawai, 77 fishes (20%) from 25 species; Centrocestus armatus, 24 fishes (6%) from 7 species; Echinochasmus japonicus, 2 fishes (0.5%) from 2 species, and unidentified species, 34 fishes (9%) from 15 species respectively. The sums of average number of the encysted larvae of all species found in fish body/gram showed 83 in P.parva, Cobitis taenia (74.2), A. chinensis (28.5), Pseudoperilampus uyekii (26.6), G. majimae (19.6) and etc. respectively and the average peak number of each metacercaria in fish body/gram showed 21.7 C. sinensis, 245. ovifcrmis, 15, 3 M, crientalis and 6.1 5. japonicus in P. parva. 42.7 C. orientalis and 25.1 M. yohogawai in C. taenia; 8.3 C. armatus and 8.3 M. hasegawai in P. uyekii. 6.3 P. major in Carassius carassius, and 2.9 unidentified species in G, niajimae respectively.

• The KIPS Transactions:PartA
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• v.16A no.4
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• pp.255-262
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• 2009

We present an autonomous entertainment dolphin robot system based on ubiquitous sensor networks(USN). Generally, It is impossible to apply to USN and GPS in underwater bio-mimetic robots. But An Entertainment dolphin robot which presented in this paper operates on the water not underwater. Navigation of the underwater robot in a given area is based on GPS data and the acquired position information from deployed USN motes with emphasis on user interaction. Body structures, sensors and actuators, governing microcontroller boards, and swimming and interaction features are described for a typical entertainment dolphin robot. Actions of mouth-opening, tail splash or water blow through a spout hole are typical responses of interaction when touch sensors on the body detect users' demand. Dolphin robots should turn towards people who demand to interact with them, while swimming autonomously. The functions that are relevant to human-robot interaction as well as robot movement such as path control, obstacle detection and avoidance are managed by microcontrollers on the robot for autonomy. Distance errors are calibrated periodically by the known position data of the deployed USN motes.

• Korean Journal of Remote Sensing
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• v.21 no.5
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• pp.405-415
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• 2005

It is difficult to classify tidal flat surface that is composed of a mixture of mud, sand, water and microphytobenthos. We used a Linear Spectral Unmixing (LSU) method for effectively classifying the tidal flat surface characteristics within a pixel. This study aims at 1) detecting algal mat using LSU in the Saemangeum tidal flats, 2) determining a suitable end-member selection method in tidal flats, and 3) find out a habitual characteristics of algal mat. Two types of end-member were built; one is a reference end-member derived from field spectrometer measurements and the other image end-member. A field spectrometer was used to measure spectral reflectance, and a spectral library was accomplished by shape difference of spectra, r.m.s. difference of spectra, continuum removal and Mann-Whitney U-test. Reference end-members were extracted from the spectral library. Image end-members were obtained by applying Principle Component Analysis (PCA) to an image. The LSU method was effective to detect microphytobenthos, and successfully classified the intertidal zone into algal mat, sediment, and water body components. The reference end-member was slightly more effective than the image end-member for the classification. Fine grained upper tidal flat is generally considered as a rich habitat for algal mat. We also identified unusual microphytobenthos that inhabited coarse grained lower tidal flats.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.59-73
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• 2021

There frequently exists inadequacy regarding the number of boreholes installed along tunnel alignment. While geophysical imaging techniques are available for pre-tunnelling geological characterization, they aim to detect specific object (e.g., water body and karst cave). There remains great motivation for the industry to develop a real-time identification technology relating complex geological conditions with the existing tunnelling parameters. This study explores the potential for the use of machine learning-based data driven approaches to identify the change in geology during tunnel excavation. Further, the feasibility for machine learning-based anomaly detection approaches to detect the development of clayey clogging is also assessed. The results of an application of the machine learning-based approaches to Xi'an Metro line 4 are presented in this paper where two tunnels buried in the water-rich sandy soils at depths of 12-14 m are excavated using a 6.288 m diameter EPB shield machine. A reasonable agreement with the measurements verifies their applicability towards widening the application horizon of machine learning-based approaches.