• Journal of the Korean earth science society
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• v.41 no.5
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• pp.478-489
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• 2020

This study presents an analysis of infrasonic signals from two accidental explosions in Gwangyang city, Jeonnam Province, Korea, on December 24, 2019, recorded at 12 infrasound stations located 151-435 km away. Infrasound propagation refracted at an altitude of ~40 km owing to higher stratospheric wind in the NNW direction, resulting in favorable detection at stations in that direction. However, tropospheric phases were observed at stations located in the NE and E directions from the explosion site because of the strong west wind jet formed at ~10 km. The transmission losses on the propagation path were calculated using the effective sound velocity structure and parabolic equation modeling. Based on the losses, the observed signal amplitudes were corrected, and overpressures were estimated at the reference distance. From the overpressures, the source energy was evaluated through the overpressure-explosive charge relationship. The two explosions were found to have energies equivalent to 14 and 65 kg TNT, respectively. At the first explosion, a flying fragment forced by an explosive shock wave was observed in the air. The energy causing the flying fragment was estimated to be equivalent to 49 kg or less of TNT, obtained from the relationship between the fragment motion and overpressure. Our infrasound propagation modeling is available to constrain the source energy for remote explosions. To enhance the confidence in energy estimations, further studies are required to reflect the uncertainty of the atmospheric structure models on the estimations and to verify the relationships by various ground truth explosions.

• Journal of the Korean Geophysical Society
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• v.3 no.3
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• pp.175-184
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• 2000

A nondestructive experimental feasibility study was conducted using magnetometer to find buried cultural objects at pottery and steel matters in low-relief mountaineous area of Doojeong-dong, Cheonan, Chungnam Province from May 23 to July 18, 1998. Magnetic survey was carried out with $20cm{\times}20cm$ grid in a site of $20m{\times}40m$ before excavation, and the distribution of magnetic anomalies was compared with the results of excavation. Magnetic sensor was located on the surface of ground during the magnetic survey on the basis of an experimental result. Positive magnetic anomalies of maximum 130 nT are found over a pair of potteries. Magnetic anomaly map reveals several anomalous points in the 1st and 4th quadrants of the survey site, from where potteries and their fragments were confirmed. Six points out of seven points cprrelated with magnetic anomaly are found contain earthwares, whereas a magnetically uncorrelated location produced earthware made of unbaked clay. Steel waste such as cans and wires hidden in soil and bushes also influenced magnetic anomalies. Therefore, it is better to remove such steel wastes prior to magnetic survey if possible. Some magnetically anomalous points produced no archaeological object on excavation. This may be explained by shallower level of excavation than burial depth.

• The Journal of Engineering Geology
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• v.30 no.1
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• pp.17-30
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• 2020

An optical televiewer is a geophysical logging device that produces continuous high-resolution full-azimuth images of a borehole wall using a light-emitting-diode and a complementary metal-oxide semiconductor image sensor to provide valuable information on subsurface discontinuities. Recently, borehole imaging logging has been applied in many fields, including ground subsidence monitoring, rock mass integrity evaluation, stress-induced fracture detection, and glacial annual-layer measurements in polar regions. Widely used commercial borehole imaging logging systems typically have limitations depending on equipment specifications, meaning that it is necessary to clearly verify the scope of applications while maintaining appropriate quality control for various borehole conditions. However, it is difficult to directly check the accuracy, implementation, and reliability for outcomes, as images derived from an optical televiewer constitute in situ data. In this study, we designed and constructed a modular fractured borehole model having similar conditions to a borehole environment to report unprecedented results regarding reliable data acquisition and processing. We investigate sonde magnetometer accuracy, color realization, and fracture resolution, and suggest data processing methods to obtain accurate aperture measurements. The experiment involving the fractured borehole model should enhance not only measurement quality but also interpretations of high-resolution and reliable optical imaging logs.

• Korean Journal of Remote Sensing
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• v.36 no.5_2
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• pp.881-891
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• 2020

Recently, the Ministry of Land, Infrastructure and Transport and the Ministry of Science and ICT are developing the Land Observation Satellite (CAS-500) to meet increased demand for high-resolution satellite images. Expected image products of CAS-500 includes precision orthoimage, Digital Surface Model (DSM), change detection map, etc. The quality of these products is determined based on the geometric accuracy of satellite images. Therefore, it is important to make precision geometric corrections of CAS-500 images to produce high-quality products. Geometric correction requires the Ground Control Point (GCP), which is usually extracted manually using orthoimages and digital map. This requires a lot of time to acquire GCPs. Therefore, it is necessary to automatically extract GCPs and reduce the time required for GCP extraction and orthoimage generation. To this end, the Precision Image Processing (PIP) System was developed for CAS-500 images to minimize user intervention in GCP extraction. This paper explains the products, processing steps and the function modules and Database of the PIP System. The performance of the System in terms of processing speed, is also presented. It is expected that through the developed System, precise orthoimages can be generated from all CAS-500 images over the Korean peninsula promptly. As future studies, we need to extend the System to handle automated orthoimage generation for overseas regions.

• Journal of Radiation Protection and Research
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• v.20 no.4
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• pp.275-283
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• 1995

PERALS(Photon Electron Rejecting Alpha Liquid Scintillation) spectrometry coupled with solvent extraction method has been set up for the analysis of $^{222}Rn\;and\;^{226}Ra$ in the groundwater. This analytical method offers low background, better energy resolution and lower quenching problem than the other techniques. By the analysis of NIST SRM 4966 $^{226}Ra$ standard, the analytical accuracy and precision were found to be 3% and 1%, respectively, and the relative standard deviation of the recovery of Rn extraction between pH2 and pH10 was 7%. Detection limits of $^{222}Rn$ and $^{226}Ra$ for 10 hours counting were counted to be $0.42 pCi/{\iota}\;and\;0.016 pCi/{\iota}$, respectively. For the test analysis of $^{222}Rn\;and\;^{226}Ra$ in the graundwater, hot spring water samples of 17 regions were analyzed. The concentration of $^{222}Rn$ were in the range of $90{\sim}5200pCi/{\iota}$ and average value was $1470pCi/{\iota}\;^{226}Ra$ concentration showed a peak value of $97.9pCi/{\iota}$ in a Kangwon region, but the average value was $1.14pCi/{\iota}$ except that region.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.437-445
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• 2020

Smoke grenades are the primary means of protection used by tanks to disrupt enemy detection systems. Such smoke grenades are a critical factor that determines the survival of tanks in the engagement of ground weapon systems, but it can only be used once. Owing to its destructive property, the performance and safety of the smoke grenade cannot be confirmed prior to use. Therefore, the reliability of smoke grenades can be evaluated through various tests during the storage period. This paper presents the results of estimating the reliability and shelf life of IR screening smoke grenade launchers based on the result of the Ammunition Stockpile Reliability Program conducted in 2019. Among the smoke grenade launcher lots currently stored, 16 lots and samples were selected for each year of manufacture and tested. The reliability and shelf life were estimated by examining the number of defects and the change in quality characteristics of each test item. The results of this study can be used to assess the reliability of the smoke grenade launchers and to improve the quality of manufacturing sites.

• Journal of the Society of Disaster Information
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• v.16 no.1
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• pp.60-69
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• 2020

Purpose: Cavity growth process monitoring is to periodically monitor changes in common size and topography for general and observational grades to predict the rate of common growth. The purpose of this study is to establish a systematic cavity management plan by evaluating the general and observational class community in a non-destructive method. Method: Using GPR exploration equipment, the acquired surface image and the surrounding status image are analyzed in the GPR probe radargram in depth, profile, and cross section of the location. The exact location is selected using the distance and surrounding markings shown on the road surface of the initial detection cavity, and the test cavity is analyzed by calling the radar at the corresponding location. Result: As a result of monitoring tests conducted at a cavity 30 sites of general and observation grade, nine sites have been recovered. Changes in scale were seen in 21 cavity locations, and changes in size and grade occurred in 13 locations. Conclusion: The under road cavity is caused by various causes such as damage to the burial site, poor construction, soil leakage caused by groundwater leakage, waste and ground vibration. Among them, indirect factors could infer the effects of groundwater and localized rainfall.

• The Korean Journal of Pesticide Science
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• v.16 no.4
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• pp.322-327
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• 2012

Fate of fenitrothion aerially sprayed to control pine wood nematode (Bursaphelenchus xylophilus) was studied in a forest of Haman area. And the monitoring of fenitrothion was conducted in a stream flowed from forest area of Gijang sprayed fenitrothion. Fenitrothion 50% EC was diluted 100 times and applied two or three times using helicopter in Haman and Gijang, respectively. Average fenitrothion deposits on forest floor ranged from 6% of standard aerial application rate. Following to the second application, fenitrothion deposits in the pine needle ranged from 0.6 to 0.9 mg/kg and then rapidly decreased to 0.01 mg/kg after 109 days. Deposits on the plant washed off by rainfall and reached to soil surface was 1.3% of the application rate. All of fenitrothion on the ground resided in the forest floor covering the soil surface, where fenitrothion residues were decreased to a tenth at 109 days after the second application, but they were not detected in sol beneath it. And the only low level of fenitrothion residues, 0.0009 mg/L, was detected in runnel of the experimental forest just after aerial application. The concentration of fenitrothion in effluent from Gijang area was less than detection limit (0.0001 mg/L) during the entire period.

• Journal of Sensor Science and Technology
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• v.11 no.4
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• pp.209-217
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• 2002

The developing of buried fiber optic sensor with high sensitivity and broad-area detecting intruders is carried out using fiber optic ROTDR(Rayleigh Optical Time Domain Reflectometry). The sensing part was designed to be able to broad-area detect intrusion effect per optical fiber length under ground. The bending light losses in optical fibers are investigated by commercial mini ROTDR with wavelength $1.55{\mu}m$, distance range 5km, pulse width 20ns, SNR=5.7. The sensing fibers are selected as the common telecommunication fibers are the 1.5mm, 3.5 mm outer diameter, 4km each length fiber products. Experiments were investigate the characteristics of signal sensitivity according to applied intrusion weight. The relation between the applied weight and the bending loss was almost linear, and broad-area detect intrusion effects are the 2m resolution and $1.3m^2$ per optical fiber length respectively. The light loss by the applied weight on fiber was 0.17 dB/kg. that the sensitivity of the optical fiber sensor was sufficient to detect intruders passing over the buried optical fiber.

• The Korean Journal of Nuclear Medicine
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• v.26 no.2
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• pp.318-326
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• 1992

Ga-67 citrate scan has been requested for detection or follow-up of inflammatory or neoplastic disease. Visualization of Ga-67 citrate in the kidneys at 48 and 72 hr post injection is usually interpreted as evidence of renal pathology. But precise mechanisms of abnormal Ga-67 uptake in kidneys were unknown. We undertook a study to determine the clinical value of Ga-67 citrate imaging of the kidneys in 68 patients with primary or secondary nephropathy confirmed by renal biopsy and 66 control patients without renal disease. Renal uptake in 48 to 72 hr images was graded as follows: Grade 0=back-ground activity:1=faint uptake greater than background;2=definite uptake, but less than lumbar vertebrae; 3=same uptake as lumbar vertebrae, but less than liver; 4=same or higher uptake than liver. The results were as follows. 1) 42 of 65 (62%) patients with noninfectious nephritis showed grade 2 or higher Ga-67 renal uptake but only 10 percent of control patients showed similar uptake. 2) In 14 patients with systemic lupus erythematosus, 8 of 9 (89%) patients with lupus nephritis exhibited marked renal uptake 3) 36 of 41 patients (88%) with combined nephrotic syndrome showed Grade 2 or higher renal uptake. 4) Renal Ga-67 uptake was correlated with clinical severity of nephrotic syndrome determined by serum albumin level, 24 hr urine protein excretion and serum lipid levels. 5) After complete remission of nephrotic syndrome, renal uptake in all 8 patients who were initially Grade 3 or 4, decreased to Grade 1 or 0. In conclusion, we think that the mechanism of renal Ga-67 uptake in nephrotic syndrome might be related to the pathogenesis of nephrotic syndrome. In systemic lupus erythematosus, Ga-67 citrate scan is useful in predicting renal involvement.