• International Journal of Highway Engineering
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• v.9 no.4
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• pp.117-127
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• 2007

The exposed aggregate PCC(EAP) pavements have been successfully used in Europe and Japan as low-noise pavements. Coarse aggregate are exposed on the pavement surface texture of EAP by removing mortar of surface. The pavement surface texture should maintain not only low-noise characteristic but also adequate skid resistance level during the performance period. Skid resistance decreased with wearing and polishing of tire and pavement surface due to the repetition of tire-pavement contact. Since the tires mainly contact the exposed coarse aggregate, the shape and rock type of coarse aggregate significantly influence wearing and polishing of EAP pavements. The test for resistance to abrasion coarse aggregate by use of the Los Angeles machine(KS F 2508) and the method of test for resistance to abrasion coarse aggregate by use of the Accelerated Polishing Machine(ASTM D 3319-90) are generally used to evaluate polishing characteristics of aggregate. In this study, polishing of coarse aggregate of different five rock types were evaluated by KS F 2508(LA abrasion test) and ASTM D 3319-90(PSV method). The results of LA abrasion test and PSV method were contrary to each other. Since LA abrasion test is estimated the quantity of abrasion by the impact of aggregate, it may not be adequate to evaluate the polishing of aggregate by the repetition of tire. In the case of PSV method, the resistance of polishing is estimated the skid resistance variation of polished aggregate after repetition of tire. The PSV method is adequate for the evaluation on polishing of coarse aggregate. From the test results of PSV method, it was founded that rock type, specific gravity, coarse aggregate angularity, flat or elongated particles in coarse aggregate are significant to the resistance characteristic of coarse aggregate.

• Journal of radiological science and technology
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• v.28 no.3
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• pp.211-217
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• 2005

This study obtained the following conclusions by analyzing whether or not thyroid nodule, the number of nodules depending on age and gender, and the developed site of nodule, targeting 838 persons in their 30s-70s who were conducted the thyroid ultrasonography, without clinical symptoms, at the Health Promotion Center. 1. As for the general characteristics of 838 research subjects, men were 368 persons(44%), and women were 470 persons (56%), and the mean age was 51. 2. Among 838 whole subjects, a case, which was diagnosed to be normal, was 590 persons(70%), and persons with nodules findings were 248 persons (30%), thus it was indicated 30% on an average in having the thyroid nodules findings. 3. As for the frequency by age level in thyroid nodule, it was represented men with 10%-14% and women with $20{\sim}29%$ in their $30{\sim}40s$, and men with $27{\sim}33%$ and women with 37-52% in their 50-60s, and men with 46% and women with 50% in their 70s. 4. As a result of obtaining 248 persons, who have thyroid nodules findings, with the solitary nodule and the multiple nodule, it was indicated the solitary nodule of 50.5% with 125 persons and the multiple nodule of 49.5%, thereby representing the almost same ratio. 5. As for the size of thyroid nodule, the majority in all the age levels had the nodule in small size, and the size of $1{\sim}10\;mm$ was largest with 187 persons (75%) among 248 persons with abnormal findings, and it was 45 persons (18%) in $11{\sim}20\;mm$, 14 persons (5.6%) in $21{\sim}30\;mm$, and 2 persons in more than 31 mm. 6. As for the anatomically developed site in nodule, it was indicated the right lobe with 93 persons (38%), the left lobe with 67 persons (27%), both lobes with 75 persons (30%), and isthmus with 13 persons (5.3%), thereby representing the largest frequency in the right lobe, and it was discovered less in isthmus.

• Journal of radiological science and technology
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• v.35 no.2
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• pp.119-124
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• 2012

Recently, Glass Dosimeter (GD) with thermoluminescent Dosimeter (TLD) are comprehensively used to measure absorbed dose from diagnostic field to therapy field that means from low energy field to high energy field. However, such studies about dose characteristics of GD, such as reproducibility and energy dependency, are mostly results in high energy field. Because characteristic study for measurement devices of radiation dose and radiation detector is performed using 137Cs and 60Co which emit high energy radiations. Thus, this study was evaluated the linearity according to Piranha dose which measured by changing tube voltage (50kV, 80kV and 100kV which are low energy radiations), reproducibility and reproducibility according to delay time using GD. Measurement of radiation dose is performed using internal detector of Piranha 657 which is multi-function QA device (RTI Electronic, Sweden). Condition of measurement was 25mA, 0.02sec, 2.5mAs, SSD of 100 cm and exposure area with $10{\times}10cm^2$. As above method, GD was exposed to radiation. Sixty GDs were divided into three groups (50kV, 80kV, 100kV), then measured. In this study, GD was indicated the linearity in low energy field as high energy existing reported results. The reproducibility and reproducibility according to delay time were acceptable. In this study, we could know that GD can be used to not only measure the high energy field but also low energy field.

• Journal of radiological science and technology
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• v.36 no.2
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• pp.165-173
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• 2013

This study was the estimation of the dose distribution for proton, prompt gamma rays and proton induced neutron particles, in case of exposing the proton beam to polymer gel dosimeter and water phantom. The polymer gel dosimeter was compositeness material of Gelatin, Methacrylic acid, Hydroquinone, Tetrakis and Distilled water. The density of gel dosimeter was $1.04g/cm^3$ which was similar to water. The 72, 116 and 140 MeV proton beams were used in the simulation. Proton beam interacted with the nuclei of the phantom and the nuclei in excited states emitted prompt gamma rays and proton induced neutron particles during the process of de-excitation. The proton particles, prompt gamma rays, proton induced neutron particles were detected by polymer gel dosimeter and water phantom, respectively. The gap of the axis for gel was 2 mm. The Bragg-peak for proton particles in gel dosimeter was similar to water phantom. The dose distribution for proton and prompt gamma rays in gel dosimeter and water phantom was approximately identical in case of 72, 116 and 140 MeV for proton beam. However, in case of proton induced neutron particles for 72, 116 and 140 MeV proton beam, particles were not detected in gel dosimeter, while the Water phantom absorbed neutron particles. Considering the resulting data, gel dosimeter which was developed in the normoxic state attentively detected the dose distribution for proton beam exposure except proton induced neutron particles.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.647-655
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• 2017

This study was conducted to review the mediating effects of retirement preparation in how the degree of requirements for retirement education and the degree of preparation for retirement education affects quality of life, and how the degree of participation in retirement education which is a moderating variable is moderated. The study findings show that first, in terms of the difference in quality of life across different general characteristics, those who live in a city rather than a Gun, those who had received education of graduate school or higher rather than those with an education of undergraduate university programs or lower, those who were public officers or employees of corporations rather than those who were self-employed had a higher quality of life. The group satisfied with their economic status and health status were found to be more satisfied with their quality of life. Second, a correlation analysis showed that there was a positive correlation between retirement preparation, quality of life, and degree of requirements for retirement preparation. Moreover, there was also a positive correlation between quality of life, retirement education and the degree of requirements for retirement education. There was a positive correlation between retirement education and the degree of requirements for retirement preparation. Third, participation in retirement education moderated the indirect effect that the degree of preparation for retirement education affected quality of life through the degree of retirement preparation. In other words, the degree of requirements for retirement education affects retirement preparation and affects quality of life through the indirect effects of retirement education. As such, the moderated mediating effects of retirement education on retirement preparation was found to be greater. This indicates that quality of life may also vary in accordance with the requirements for retirement education.

• Korean Journal of Remote Sensing
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• v.31 no.6
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• pp.501-512
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• 2015

Landfast sea ice (LFI) in Terra Nova Bay, East Antarctica where the Jangbogo Antarctic Research Station is located, has significant influences on marine ecosystem and the sailing of an icebreaker. Therefore, it is essential to analyze the spatio-temporal variation of the LFI in Terra Nova Bay. In this study, we chose interferometric pairs with the temporal baseline from 1 to 9 days out of a total of 62 COSMO-SkyMed synthetic aperture radar (SAR) images over Terra Nova Bay obtained from December 2010 to January 2012, and then constructed the coherence image of each pair. The LFI showed coherence values higher than 0.3 even in the interferometric SAR (InSAR) pairs of up to 9-days of temporal baseline. This was because the LFI was fixed at coastline and thus showed low temporal phase decorrelation. Based on the characteristics of the coherence on LFI, We defined the areas of LFI that show spatially homogeneous coherence values higher than 0.5. Pack ice (PI) and open water showed low coherence values due to large temporal phase decorreation caused by current and wind. Distinguishing PI from open water in the coherence images was difficult due to their similarly low coherence values. PI was identified in SAR amplitude images by investigating cracks on the ice. The extents of the LFI and PI were estimated from the coherence and SAR amplitude images and their temporal variations were analyzed. The extent of the LFI increased from March to July (maximum extent of $170.7km^2$) and decreased from October. The extent of the PI increased from February to May and decreased from May to July when the LFI increases dramatically. The extent of the LFI and air temperature showed an inverse correlation with a time lag of about 2 months, i.e., the extent of the LFI decreases after 2 months of the increase in the air temperature. Meanwhile the correlation between wind speed and the extent of the LFI was very low. This represents that the extent of LFI in Terra Nova Bay are influenced more by the air temperature than wind speed.

• Korean Journal of Remote Sensing
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• v.30 no.5
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• pp.597-605
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• 2014

The continuous observations for atmospheric aerosols were conducted during 3 years (2009 to 2011) by using Gwangju Institute of Science and Technology (GIST) multi-wavelength Raman lidar at Gwangju, Korea ($35.10^{\circ}N$, $126.53^{\circ}E$). The aerosol depolarization ratios calculated from lidar data were used to identify the Asian dust layer. The optical properties of Asian dust layer were different according to its vertical distribution. In order to investigate the difference between the optical properties of each individual dust layers, the transport pathway and the transport altitude of Asian dust were analyzed by Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. We consider that the variation of optical properties were influenced not only their transport pathway but also their transport height when it passed over anthropogenic pollution source regions in China. The lower particle depolarization ratio values of $0.12{\pm}0.01$, higher lidar ratio of $67{\pm}9sr$ and $68{\pm}9sr$ at 355 nm and 532 nm, respectively, and higher ${\AA}ngstr\ddot{o}m$ exponent of $1.05{\pm}0.57$ which are considered as the optical properties of pollution were found. In contrast with this, the higher particle depolarization ratio values of $0.21{\pm}0.09$, lower lidar ratio of $48{\pm}5sr$ and $46{\pm}4sr$ at 355 nm and 532 nm, respectively, and lower ${\AA}ngstr\ddot{o}m$ exponent of $0.57{\pm}0.24$ which are considered as the optical properties of dust were found. We found that the degree of mixing of anthropogenic pollutant aerosols in mixed Asian dust govern the variation of optical properties of Asian dust and it depends on their altitude when it passed over the polluted regions over China.

• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.31-42
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• 2006

Drought indices, such as PDSI (palmer Drought Severity Index), SWSI (Surface Water Supply Index) and SPI (Standardized Precipitation Index), have been developed to assess and forecast an intensity of drought. To find the applicability of groundwater level data to a drought assessment, a correlation analysis between SPI and groundwater levels was conducted for each time series at a drought season in 2001. The comparative results between SPI and groundwater levels of shallow wells of three national groundwater monitoring stations, Chungju Gageum, Yangpyung Gaegun, and Yeongju Munjeong, show that these two factors are highly correlated. In case of SPI with a duration of 1 month, cross-correlation coefficients between two factors are 0.843 at Chungju Gageum, 0.825 at Yangpyung Gaegun, and 0.737 at Yeongju Munjeong. The time lag between peak values of two factors is nearly zero in case of SPI with a duration of 1 month, which means that groundwater level fluctuation is similar to SPI values. Moreover, in case of SPI with a duration of 3 month, it is found that groundwater level can be a leading indicator to predict the SPI values I week later. Some of the national groundwater monitoring stations can be designated as DIW (Drought Index Well) based on the detailed survey of site characteristics and also new DIWs need to be drilled to assess and forecast the drought in this country.

• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.33-44
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• 2005

On the basis of a stepwise and careful integration of various field and laboratory methods the analysis of groundwater flow characterization was performed with five boreholes (BH-1, -2, -3, -4, -5) on a pilot site of Natural Forest Park in Guemsan-gun, Chungcheongbook-do, Korea. The regional lineaments of NW-SE are primarily developed on the area, which results in the development of many fractures of NW-SE direction around boreholes made in the test site for the study. A series of surface geological survey, core logging, geophysical logging, tomography, tracer tests, and heat-pulse flowmeter logging were carried out to determine fracture characteristics and fracture connectivity between the boreholes. In the result of fracture connectivity analysis BH-1 the injection well has a poor connectivity with BH-2 and BH-3, whereas a good with BH-4 and BH-5. In order to analyse the hydraulic connectivity between BH-1 and BH-5, in particular, a conspicuous groundwater outflux in the depth of 12 m and influx in the depth of 65 m and 70 m, but partly in/outflux occurred in other depths in BH-5 were observed as pumping from BH-1. On the other hand, when pumping from BH-5 the strong outflux in the depths of 17 m and 70 m was occurred. The spatial connectivity between the boreholes was examined in the depth of 15 m, 67 m, and 71 m in BH-1 as well as in the depth of 15 m, 17 m, 22 m, 72 m, and 83 m in BH-5.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.3
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• pp.140-151
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• 1999

Groundwater samples from the southern area composed of andesitic rocks and the northwestern area composed of granite in Pusan city, have been collected and analyzed. According to the Piper diagram. groundwater in the southern area belongs to Ca$\^$2＋/－HCO$_3$$\^$－/ and Ca$\^$2＋/－(Cl$\^$－/＋SO$_4$$\^$2－/) types, and that in the northwestern area mostly belongs to Ca$\^$2＋/－HCO$_3$$\^$－/ type and partly Na$\^$＋/－HCO$_3$$\^$－/ type. Two factors (factor 1 and factor 2) were obtained from the result of the factor analysis in the southern area. Factor 1, consisting of Mg$\^$2＋/, Ca$\^$2＋/, Cl$\^$－/, SO$_4$$\^$2－/, NH$_4$$\^$＋/, EC and NO$_3$$\^$－/ is represented by the dissolution of Ca-plagioclase and calcite, and the influence of anthropogenic sources. Factor 2, consisting of K$\^$＋/, Na$\^$＋/. SiO$_2$, SO$_4$$\^$2－/, and HCO$_3$$\^$－/ is mainly represented by the dissolution of feldspar. Three factors were obtained from the result of the factor analysis in the northwestern area Factor 1, consisting of Na$\^$＋/, K$\^$＋/, NH$_4$$\^$＋/, Cl$\^$－/, SO$_4$$\^$2－/ and NO$_3$$\^$－/ explains dissolution of plagioclase and mica, the influence of anthropogenic sources and salt water. Factor 2, consisting of Ca$\^$2＋/ and HCO$_3$$\^$－/ explains the dissolution of Ca-plagioclase. Factor 3, consisting of Mg$\^$2＋/ and SiO$_2$, explains the dissolution of silicate minces. and contaminants. Based on the phase stability diagrams, groundwater both in the southern and in the northwestern area is mostly in equilibrium with kaolinite. Cl$\^$－/ with respect to Na$\^$＋/, Ca$\^$2＋/, Mg$\^$2＋/, K$\^$＋/, SO$_4$$\^$2－/ and HCO$_3$$\^$－/ indicates that both the northwestern area and the southern area are influenced by the salt water.