• Korean Journal of Weed Science
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• v.13 no.2
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• pp.104-113
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• 1993

The experiment was conducted in 1992 to find out the approach to the development of prediction model of weed population in paddy fields. The weed seeds of 88% over were separated from the soil by using $K_2CO_3$ 50% solution with specific gravity 1.34. The weed seeds which were floated on the solution due to the difference of specific gravity between soil particles and the seeds were effectively withdrawn by using a vaccum pump attached with an aspirator. The seeds withdrawn together with solution were taken by filtering with a nylon net of $0.31{\times}0.16mm$ mesh. The pressing method was more efficient and practical for the viability test of weed seeds separated from the soil compared with the germination test and the TTC test. For the prediction of weed population by the number of weed seedlings emerged at the sampled soil, the sampling method of 0-10cm deep at 5-6 sites per field was applicable. At the prediction method by the number of seedlings emerged, the smaller the seed sizes, the lower the prediction coefficients of weed species. It was considered that the prediction method by the number of seedlings emerged was more practical than the prediction method by the number of seeds separated from sampled soil, in relation to similarities to weed population, time and expenses required for examining, technical difficulties and applicability of weed species.

• Korean Journal of Environmental Biology
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• v.17 no.3
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• pp.293-303
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• 1999

Fish fauna of fishes collected from the Saemankum area in the west coast of Chollabuk-do was studied from October 1996 to April 1999. The specimens collected from the five sites in this area were identified into 107 species belonging to 83 genera and 52 families. Of them the largest group of fishes was order Perciformes, comprising 50 species and 21 families, and showed 46.7% in total numbers of species. Next larger groups were orders Scorpaeniformes and Pleuronectiformes containing 16 and 14 species respectively. In this area, the group comprising a lots of species was the family Gobiidae taking 13 species, and next groups were the families of Sciaenidae (6 species), Engraulidae (5 species) and Pleulonectidae (5 species). The dominant species was Engraulis japonicus which is 23.4 ％ in total indiyidual numbers, and subdominant species was Thryssa kummazensis which is 18.5%. The important species economically in the Saemankum area were Anguilla japonica, E. japonicus, T. kummalensis, Konosirus punctatus, Sardinella zunasi, Mugil cephalus, Argyrosomus argentatus, Pseudosciaena polyactis, Collichthys lucidus, Paralichthys olivuceus and Cynoglossus joyneri. The species of high frequency in this area from February to June every year were Anguilla japonica, E. japonicus, T. kammalensis, K. punctatus, S. zunasi, Coilia nasus, Syngnatuus schlegeli, P. polyactis, C. lucidus and Pholis fangi. Ophichthus rotundus, Repomucenus leucopoecitus and R. koreanus were Korean endemic species in the west coast of Chollabuk-do. On the other hand, Boleophthalmus pectinirostris was not found during this study, and Periophthalmus modertus, Tridentiger barbatus and Lophogobius ocellioauda sharply decreased in individual numbers in comparison to several years ago.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.136-141
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• 2010

In situ experiments of Nutrient Enrichment Bioassays (NEBs) were conducted in the field along with in the laboratory to determine which nutrient limited phytoplankton growth as a indicator of primary productivity. For the NEBs, the water was sampled using a polyethylene-lined container and dispensed into 6 L water tank in the laboratory. The control (C, no nutrient spike) and six treatments of phosphorus (P), 2-fold phosphorus (2P), 4-fold phosphorus (4P), nitrate nitrogen ($NO_3$-N), 2-fold nitrate nitrogen ($2NO_3$-N), and phosphorus and nitrate nitrogen (P+$NO_3$-N) were set up in the lacustrine zone near the dam site, Daechung Reservoir in September, 2009 and analyzed the diel changes of total nitrogen (TN), total phosphorus (TP), and chlorophyll-$\alpha$ (Chl-$\alpha$) in the cubitainers. The short-term NEBs showed that algal response in the treatments spiked phosphorus (P, 2P, and 4P) were significantly (p < 0.05) greater than the response in the control (C), and nitrogen-spike. Also, the response in 4P-treatment was greater than those in the P- and 2P-treatments. In contrast, there was no significant differences (p > 0.20) between the $NO_3$-N and $2NO_3$-N treatment. The outcomes of the NEBs suggest that phosphorus limited the phytoplankton growth and nitrogen was not limited in this system. Furthermore, in the N + P treatments, the response was minimum, compared to all other treatments and the control, indicating that even if the system is evidently P-limited system, when added the nitrogen, the response showed the inhibition. Also, > 95% of observed long-term TN:TP ratios in the ambient water showed > 17, which is the criteria of P-limitation, supporting the P-limitation in the system. Overall, these results suggest that phytoplankton biomass near the dam is a direct linear function of P-loading near the watershed, if the phosphorus pool is mainly dissolved fraction.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.393-398
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• 2012

We investigated the changes in chemical properties of paddy field soils at 300 different sampling sites containing 4 topography in Jeonbuk province, Korea. The soil samples were collected 43.0% from local valley and fans, 39.3% from fluvio-marine deposits, 15.0% from alluvial plains, and 2.7% from diluvium sites. The optimal values of soil properties in the total soil samples were as follows: 65.3% of total samples in soil pH value, 48.3% of total samples in cation exchange capacity (CEC) value, and 22.3% of total samples in available phosphorus content, whereas the deficient values of soil properties were 63.3% of total samples in soil organic matter (SOM) content, 75.7% of total samples in available silicate content, and 61.3%, 51.0%, and 59.3% of total samples in exchangeable $K^+$, $Ca^{2+}$, and $Mg^{2+}$ concentrations, respectively. There were different soil types in the paddy fields: that is, 34.4% immature paddy and 33.6% sandy paddy in the local valley and fans, 57.8% sandy paddy in the alluvial plains, 47.4% normal paddy in the fluvio-marine deposits, and 75.7% immature paddy in the diluvium. Soil textures were also different: 53.5% loam in the local valley and fans, 37.8% sandy loam in the alluvial plains, and 55.1% silty loam in the fluvio-marine deposits. Soil pH and SOM contents were not different among the different topographical sampling sites. However, the mean value of available phosphorus content, 224 mg $kg^{-1}$, was exceeded optimal values in the diluvium. The contents of exchangeable cations were optimal in all the sites, except exchangeable $Ca^{2+}$ contents in the local valley and fans. The contents of available silicate ranged between 112 and 127 mg $kg^{-1}$ in all the sites, which were lower than optimal value. In addition, soil pH values were proportionally correlated to the order of available silicate, exchangeable $Ca^{2+}$, $Mg^{2+}$, $Na^+$, CEC, and exchangeable $K^+$. The contents of SOM were proportionally correlated to the order of CEC, available $P_2O_5$, exchangeable $Ca^{2+}$, and available silicate. The contents of heavy metals, Cd, Cr, Cu, Ni, Pb, and Zn, were only 10% of the threshold levels of the metals, and As content was about 20 to 30% of the threshold level.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.551-563
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• 2016

According to the 4th and 5th assessment of the Intergovernmental Panel on Climate Change (IPCC), global climate has been rapidly changing because of the human activities since Industrial Revolution. The perceived changes were appeared strongly in temperature and concentration of carbon dioxide ($CO_2$). Global average temperature has increased about $0.74^{\circ}C$ over last 100 years (IPCC, 2007) and concentration of $CO_2$ is unprecedented in at least the last 800,000 years (IPCC, 2014). These phenomena influence precipitation, evapotranspiration and soil moisture which have an important role in hydrology, and that is the reason why there is a necessity to study climate change. In this study, Asia region was selected to simulate primary energy index from 1951 to 2100. To predict future climate change effect, Common Land Model (CLM) which is used for various fields across the world was employed. The forcing data was Representative Concentration Pathway (RCP) data which is the newest greenhouse gas emission scenario published in IPCC 5th assessment. Validation of net radiation ($R_n$), sensible heat flux (H), latent heat flux (LE) for historical period was performed with 5 flux tower site-data in the region of AsiaFlux and the monthly trends of simulation results were almost equaled to observation data. The simulation results for 2006-2100 showed almost stable net radiation, slightly decreasing sensible heat flux and quite increasing latent heat flux. Especially the uptrend for RCP 8.5 has been about doubled compared to RCP 4.5 and since late 2060s, variations of net radiation and sensible heat flux would be significantly risen becoming an extreme climate condition. In a follow-up study, a simulation for energy index and hydrological index under the detailed condition will be conducted with various scenario established from this study.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.297-303
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• 2014

Purpose : The purpose of this study is reproducibility evaluation of deep inspiration breath-hold(DIBH) technique by respiration data and heart position analysis in radiation therapy for Left Breast cancer patients. Materials and Methods : Free breathing(FB) Computed Tomography(CT) images and DIBH CT images of three left breast cancer patients were used to evaluate the heart volume and dose during treatment planing system( Eclipse version 10.0, Varian, USA ). The signal of RPM (Real-time Position Management) Respiratory Gating System (version 1.7.5, Varian, USA) was used to evaluate respiration stability of DIBH during breast radiation therapy. The images for measurement of heart position were acquired by the Electronic portal imaging device(EPID) cine acquisition mode. The distance of heart at the three measuring points(A, B, C) on each image was measured by Offline Review (ARIA 10, Varian, USA). Results : Significant differences were found between the FB and DIBH plans for mean heart dose (6.82 vs. 1.91 Gy), heart $V_{30}$ (68.57 vs. $8.26cm^3$), $V_{20}$ (76.43 vs. $11.34cm^3$). The standard deviation of DIBH signal of each patient was ${\pm}0.07cm$, ${\pm}0.04cm$, ${\pm}0.13cm$, respectively. The Maximum and Minimum heart distance on EPID images were measured as 0.32 cm and 0.00 cm. Conclusion : Consequently, using the DIBH technique with radiation therapy for left breast cancer patients is very useful to establish the treatment plan and to reduce the heart dose. In addition, it is beneficial to using the Cine acquisition mode of EPID for the reproducibility evaluation of DIBH.

• Journal of Environmental Science International
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• v.12 no.6
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• pp.665-676
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• 2003

To investigate the chemical characteristics of PM$\_$2.5/ in Seoul, Korea, atmospheric particulate matters were collected using a PM$\_$10/ dichotomous sampler including PM$\_$10/ and PM$\_$2.5/ inlet during the period of October 2000 to September 2001. The Inductively Coupled Plasma-Mass Spectromety (ICP-MS), ion Chromatography (IC) methods were used to determine the concentration of both metal and ionic species. A statistical analysis was performed for the heavy metals data set using a principal component analysis (PCA) to derived important factors inherent in the interactions among the variables. The mean concentrations of ambient PM$\_$2.5/ and PM/sub10/ were 24.47 and 45.27 $\mu\textrm{g}$/㎥, respectively. PM$\_$2.5/ masses also showed temporal variations both yearly and seasonally. The ratios of PM$\_$2.5/PM$\_$10/ was 0.54, which similar to the value of 0.60 in North America. Soil-related chemical components (such as Al, Ca, Fe, Si, and Mn) were abundant in PM$\_$10/, while anthropogenic components (such as As, Cd, Cr, V, Zn and Pb) were abundant in PM2s. Total water soluble ions constituted 30∼50 % of PM$\_$2.5/ mass, and sulfate, nitrate and ammonium were main components in water soluble ions. Reactive farms of NH$_4$$\^$+/were considered as NH$_4$NO$_3$ and (NH$_4$)$_2$SO$_4$ during the sampling periods. In the results of PCA for PM$\_$2.5/, we identified three principal components. Major contribution to PM$\_$2.5/ seemed to be soil, oil combustion, unidentified source. Further study, the detailed interpretation of these data will need efforts in order to identify emission sources.

• Progress in Medical Physics
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• v.18 no.3
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• pp.118-125
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• 2007

In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of $315^{\circ}$) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.191-205
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• 1997

Measurements on subsurface movement of the Songsanri tomb site including the Muryong royal tomb was conducted using a tiltmeter system for the period of 15 months form July 7, 1996 to September 30, 1997. Two coordinate tilt monitoring data shows the biggest movement rate of 2.3mm/m/yr toward south in the frontal wall(N-S tilt) of the Muryong royal tomb. Southward tilting of bricks above the southern fire place in the western wall of the Muryong royal tomb is a proof of southward tilting of the royal tomb since its excavation in 1971. The eastern wall of the Muryong royal tomb is also tilting toward inside the tomb with the rate of 1.523mm/m/yr. Furthermore, tilting rate of wall increases twice in rainy season. It is interpreted tbat infiltration of water into the tomb and nearby ground in rainy season results in dangerous status for the safety of tomb structure. On the whole, normal component tilting of the walls of the 5th tomb is large than its shear component. It shows a small displacement toward one direction without no abrupt change in its direction and amount of tilting. The tilting rate of walls of the 6th tomb is about 8.8mm/m/yr in the dry season which is much bigger than those of other tombs in rainy season. Deformation events of walls of the tombs are closely related to amount of precipitation and variation of temperature. In comparison with different weather conditions, tilting is much bigger during the period of rainy weather than sunny weather. It is interpreted that rainwater flew into the turm through faults and nearby ground. High water content in nearby ground resulted strength of ground. The tilting event of walls shows a hysterisis phenomenon in analysis of temperature effect on tilting event. The walls tilt rapidly with steep rising of temperature, but the tilted walls do not come back to original position with temperature falling. Therefore, a factor of steep increase of the temperature must be removed. It means the tomb have to be kept with constant temperature. The observation of groundwater level using three boreholes located in construction site and original ground represented that groundwater level in construction site is higher than that of original ground during the rainy season from the end of June to August. It means that the drainage system of the Muryong royal tomb is worse than original ground, and it is interpreted that the poor drainage system is related to safety of tomb structure. As above mentioned, it is interpreted that artificial changes of the tomb environment since the excavation, infiltration of rainwater and groundwater into the tomb site and poor drainage system had resulted in dangerous situation for the tomb structure. According to the result of the long period observation for the tomb site, it is interpreted that protection of the tomb site from high water content should be carried out at first, and the rise of temperature by means of the dehumidifier inside the tomb must be removed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.320-334
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• 2000

Deep-sea surface sediment were analyzed for their geotechnical properties, and the sediment samples were collected with a multiple-corer from 31 stations along the track line (131$^{\circ}$30'W, 5-12$^{\circ}$N) in the northeast equatorial Paciflc. Most of the sediments from the northern part (8-12$^{\circ}$N) showed typical properties of siliceous sediments, whereas the southern part (5-6$^{\circ}$N) showed calcareous characteristics due to high biogenic carbonate productivity in the surface waters, where its water depth was shallower than the carbonate compensation depth (CCD: 4,400 m). Geotechnical properties changed sharply at the boundary of 7$^{\circ}$N. Calcareous sediments from the southern part had low water contents, low porosity, low shear strength, high bulk density and high specific grain density, whereas siliceous sediments from the northern part attained high water content, high porosity, high shear strength, low bulk density and low specific grain density. Higher sediment activities were observed in the northern sediment samples than the southern sediment samples. The core samples of the northern sediments were divided into a semi-liquid upper layer and a consolidated lower layer with a boundary at 5-8 cm. These sediment samples showed a rapid increasing pattern along the downcore in original shear strength when an opposite trend was observed in the southern samples. The results showed that sediment variabilities in geotechnical properties between the northern and southern parts such as productivities of surface water, grain solubility due to water depth variation, sedimentation rate, erosion and redistribution of sediment, and combined sedimentary processes were distinctly different along the latitude.