• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.67-76
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• 1996

This study was performed to estimate total dust concentrations and particle size distribution of wood dust in the furniture and sawmill industries. To compare total wood dust concentrations, two samplers recommended by the American Conference of Governmental Industrial Hygienists and by the National Institute for Occupational Safety and Health were used. Concentration data were analyzed by paired-t tests using the SAS program and two parameters of the particle size distributions were determined by histogram. The results were as follows: 1. Particle size distributions showed a unimodal pattern in cutting and a bimodal in sanding operations. Mass median aerodynamic diameters(MMAD) were $17.35{\mu}m$ in cutting, and $1.39{\mu}m$ for small mode and $18.89{\mu}m$ for large mode in sanding operations. The proportions of particle size larger than $9.8{\mu}m$ estimated by the impactor were 61.16 % in cutting and 62.33 % in sanding operations, respectively. 2. The average personal total dust concentrations measured by IPM sampler were $17.12mg/m^3$ (GSD=1.45) from indoor samples, $2.97mg/m^3$(GSD=1.90) from outdoor samples in cutting, and $8.01mg/m^3$(GSD=1.58) from sanding operation. And those of by 37 mm closed-face cassette were $9.12mg/m^3$(GSD=1.46), $1.06mg/m^3$(GSD=1.99) from cutting, and $3.32mg/m^3$(GSD=2.16) from sanding operations. 3. The average area total dust concentrations measured by IPM sampler were $1.88mg/m^3$(GSD=2.04) from indoor cutting, $4.76mg/m^3$(GSD=2.83) from indoor sanding operations. And those of by 37mm closed-face cassette were $0.49mg/m^3$(GSD=2.34) from cutting, and $1.32mg/m^3$(GSD=3.03) from sanding operations. 4. The ratio of personal total dust concentrations measured by 37 mm closed-face cassette to those by IPM sampler were 35.7 %, 53.3 % from cutting, and 41.4 % from sanding operations. 5. The ratio of area total dust concentrations measured by 37 mm closed-face cassette to those by IPM sampler were 26.1 % from cutting, and 27.7 % from sanding operations. 6. A statistically significant difference of total dust concentrations between the 37 mm closed-face cassette and the IPM sampler was found.

• Journal of Soil and Groundwater Environment
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• v.22 no.3
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• pp.27-41
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• 2017

This study dealt with the characteristics and the interrelations of hydrogeological parameters such as hydraulic conductivity, dispersivity and effective porosity of unconsolidated sediments for providing the basic data necessary for the planning of the management and preservation of groundwater quality in the Nakdong River Delta of Busan City, Korea. Groundwater quality in this area has been deteriorated due to seawater intrusion, agricultural fertilizer and pesticide, industrial wastewater, and contaminated river water. The physical properties (grain size distribution, sediment type, sorting) and aquifer parameters (hydraulic conductivity, effective porosity, longitudinal dispersivity) were determined from grain size analysis, laboratory permeability test and column tracer test. Among 36 samples, there were 18 Sand (S), 7 Gravelly Sand (gS), 5 Silty Sand (zS), 5 Muddy Sand (mS), and 1 Sandy Silt (sZ). Hydraulic conductivity was determined through a falling head test, and ranged from $9.2{\times}10^{-5}$ to $2.9{\times}10^{-2}cm/sec$ (0.08 to 25.6 m/day). From breakthrough curves, dispersivity was calculated to be 0.35~3.92 cm. Also, effective porosity and average linear velocity were obtained through the column tracer test, and their values were 0.04~0.46 and 1.06E-04~6.49E-02 cm/sec, respectively. Statistical methods were used to understand the interrelations among aquifer parameters of hydraulic conductivity, effective porosity and dispersivity. The relation between dispersivity and hydraulic conductivity or effective porosity considered the sample length, because dispersivity was affected by experimental scale. The relations between dispersivity and hydraulic conductivity or effective porosity were all in inverse proportion for all long and short samples. The reason was because dispersivity was in inverse proportion to the groundwater velocity in case of steady hydrodynamic dispersion coefficient, and groundwater velocity was in proportion to the hydraulic conductivity or effective porosity. This study also elucidated that longitudinal dispersivity was dependent on the scale of column tracer test, and all hydrogeological parameters were low to high values due to the sand quantity of sediments. It is expected that the hydrogeological parameter data of sediments will be very useful for the planning of groundwater management and preservation in the Nakdong River Delta of Busan City, Korea.

• Journal of Korean Society of Transportation
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• v.34 no.5
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• pp.421-436
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• 2016

Public-Private-Partnerships tend to be committed high project development cost and recover the cost through future revenue during the operation period. In general, long-term concession can bring on more revenue to private investors, but short-term concession less revenue due to the short recovering opportunities. The concession period is usually determined by government in advance or by the private sectors's proposal although it is a very crucial factor for the PPPs. Accurate traffic forecasting should be most important in planing and evaluating the operation period in that the forecasted traffic determines the project revenue with user fees in PPPs. In this regards, governments and the private investors are required to consider the traffic forecast risk when determining concession period. This study proposed a model for the optimal concession period in the PPPs transportation projects. Monte Carlo simulation was performed to find out the optimal concession period while traffic forecast uncertainty is considered as a project risk under the expected return of the private sector. The simulation results showed that the optimal concession periods are 17 years and 21 years at 5.5% and 7% discount level, respectively. This study result can be applied for the private investors and/or any other concerned decision makers for PPPs projects to set up a more resonable concession period.

• Journal of the Korean Society of Radiology
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• v.12 no.4
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• pp.443-450
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• 2018

The Geant 4 simulated the linear accelerator (VARIAN CLINAC) based on the previously implemented BEAMnrC data, using the head structure of the linear accelerator. In the 10 MV photon flux, Geant4 was compared with the measured value of the percentage of the deep dose and the lateral dose of the water phantom. In order to apply the dose calculation to the body part, the actual patient's lung area was scanned at 5 mm intervals. Geant4 dose distributions were obtained by irradiating 10 MV photons at the irradiation field ($5{\times}5cm^2$) and SAD 100 cm of the water phantom. This result is difficult to measure the dose absorbed in the actual lung of the patient so the doses by the treatment planning system were compared. The deep dose curve measured by water phantom and the deep dose curve calculated by Geant4 were well within ${\pm}3%$ of most depths except the build-up area. However, at the 5 cm and 20 cm sites, 2.95% and 2.87% were somewhat higher in the calculation of the dose using Geant4. These two points were confirmed by the geometry file of Genat4, and it was found that the dose was increased because thoracic spine and sternum were located. In cone beam CT, the dose distribution error of the lungs was similar within 3%. Therefore, if the contour map of the dose can be directly expressed in the DICOM file when calculating the dose using Geant4, the clinical application of Geant4 will be used variously.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.16-24
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• 2014

Long-term measured wind data are absolutely necessary to estimate extreme offshore wind speed. However, it is almost impossible to collect offshore wind measured data. Therefore, typhoon simulation is widely used to analyze offshore wind conditions. In this paper, 74 typhoons which affected the western sea of Korea during 1978-2012(35 years) were simulated using Holland(1980) model. The results showed that 49.02 m/s maximum wind speed affected by BOLAVEN(1215) at 100 m heights of HeMOSU-1 (Herald of Meteorological and Oceanographic Special Unit - 1) was the biggest wind speed for 35 years. Meanwhile, estimated wind speeds were compared with observed data for MUIFA, BOLAVEN, SANBA at HeMOSU-1. And to estimate extreme wind speed having return periods, extreme analysis was conducted by assuming 35 annual maximum wind speed at four site(HeMOSU-1, Gunsan, Mokpo and Jeju) in western sea of the Korean Peninsular to be Gumbel distribution. As a results, extreme wind speed having 50-year return period was 50 m/s, that of 100-year was 54.92 m/s at 100 m heights, respectively. The maximum wind speed by BOLAVEN could be considered as a extreme winds having 50-year return period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.266-273
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• 2015

In this paper, annual wind data in 2014 at six locations(Seosudo, Gadaeam, Sibidongpa, Galmaeyeo, Haesuseo, Jigwido) are collected and analyzed in order to review optimal candidate site for offshore wind farm in the Western Seas of Korea. Observed wind data is fitted to Rayleigh and Weibull distribution and annual energy production is estimated according to wind frequency. GWE-3kH(3 kW-class) and GWE-10KU (10 kW-class) turbine are selected as wind turbine. Also, power curve are used to calculate wind energy potential. As a result, annual mean wind speed at six locations(Seosudo, Gadaeam, Sibidongpa, Galmaeyeo, Haesuseo, Jigwido) were calculated about 4.60, 4.5, 5.00, 5.13, 5.51, 5.90 m/s, respectively. In addition, annual energy production were estimated at 10,622.752, 11,313.05, 13,509.41, 14,899.55, 17,106.13, 19,660.85 kWh. Generally, annual mean energy density were between poor and marginal class and capacity factor at Jigwido was calculated at 22.44%. Its value is higher than the others.

• Journal of Korean society of Dental Hygiene
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• v.3 no.1
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• pp.25-43
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• 2003

In Korea, changes in children's diet patterns accelerate their physical growth and development: frequent snacking has been presumed to be a major cause of increasing dental caries. The present study attempts to clarify the relationship between the physical development of growing children and their tooth decay. For this purpose, 632 six-grade children in 4 elementary school located in Urban(Seoul) and Rural(Po-gok, Yang-In) were classified into three groups based on the Weight Length Index(WLI), known to reflect the nutritional conditions of school-age children, and the relationship was analyzed between each group and the variables considered to be related with dental caries. The result is as follows: The average weight and height of the male is $44.88{\pm}10.89$ kg, $148.49{\pm}7.33$ cm and female is $43.35{\pm}9.60$ kg, $149.23{\pm}6.73$ cm, respectively, which are in the similar level with the Korean Physical Standard. The classification of the children by the WLI reveals a relatively high distribution of over-weighted child ren - 212 persons, 335% of the entire population. The DMFT Index was a little high in the rural area(3.15 teeth in urban and 3.31, in rural). Among the groups of children classified by the WLI, the over-weight group have the highest DMFT index(3.69 teeth). The relationship between the frequency of taking in basic nutrients and the DMFT index is also found: the relationship is not evident in case of the foods containing rich calcium, protein, as well as fruits and vegetables. But, in the protein-rich food, higher frequency of its intake means significantly lower DMFT index in the normal-weight group of the urban children. In case of carbohydrate, higher frequency of its intake means significantly higher DMFT index in all the groups of the rural children. The DMFT index has some correlations with the relevant variables: the index has a positive correlation with the frequency of snacking, and a negative correlation with the economic status. That is, the higher the frequency of snacking is, and the lower the economic status is, the higher the DMFT index may be. In the logistic multiple regression analysis conducted with the presence of DMFT as a dependent variable, only the frequency of tooth brushing is turned to be a variable affecting the presence of either decayed, missing, or filled teeth. Based on the above result, the variables affecting the DMFT index are a time spent on eating, frequency of intake of protein and carbohydrate for a week, frequency of snacking, regular dental check-ups, preventive behaviors for oral health(fluoride gargling, tooth brusing after each meal, proper tooth brushing method). These variables have a relationship with the DMFT index, but the degree is somewhat different between the groups classified either by the region or by the WLI. Therefore, appropriate nutrition management should be conducted according to the individual's nutritional conditions when the services like nutritional education are provided based on the closely-examined characteristics of each target group. And, at the same time, oral health education should be strengthened, and its importance should also be emphasized so that people can pay attention to their own oral health.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.159-170
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• 2017

The temporal and spatial temperature distribution of the heat storage mortar made of porous feldspar was measured and the thermal properties and electricity consumption were analyzed. For the experiment, two real size chambers (control model and test model) with hot water pipes were constructed. Two large scale models with hot water pipes were constructed. The surface temperature change of the heat storage layer was remotely monitored during the heating and cooling process using infrared thermal imaging camera and temperature sensor. The temperature increased from $20^{\circ}C$ to $30^{\circ}C$ under the heating condition. The temperature of the heat storage layer of the test model was $2.0-3.5^{\circ}C$ higher than the control model and the time to reach the target temperature was shortened. As the distance from the hot water pipe increased, the temperature gap increased from $4.0^{\circ}C$ to $4.8^{\circ}C$. The power consumed until the surface temperature of the heat storage layer reached $30^{\circ}C$ was 2.2 times that of the control model. From the heating experiment, the stepwise temperature and electricity consumption were calculated, and the electricity consumption of the heat storage layer of the test model was reduced by 66%. In the cooling experiment, the surface temperature of the heat storage layer of the test model was maintained $2^{\circ}C$ higher than that of the control model. The heat storage effect of the porous feldspar mortar was confirmed by the temperature experiment. With considering that the time to reheat the heat storage layer is extended, the energy efficiency will be increased.

• Journal of the Korean association of regional geographers
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• v.14 no.6
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• pp.709-717
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• 2008

This study is to analyze environmental problems which have caused by changes of the population and agriculture in North Korea. Main results of the research are following. First, Population of the North Korea shows lower increase ratio less than 2% growth from 1970's to middle of 1990's. This is interpreted by food shortages. Second, population distribution by provinces represented that northern and eastern part of the North Korea were comparatively lower and other western areas were higher. Third, Food situation of the North Korea was relatively better in 1970's, but, 1990's was the worst in the way. Fourth, on the agricultural productivity according to each province, western areas possessing more plains were more higher than mountainous areas of the northern and eastern parts of North Korea. Fifth, Growth ratio of food production and population have grown very steadily until 1990's, but the increase ratio of population exceeded food productivity after 1990's. Sixth, Cropland reclamation for improving these situation have caused deforestation and environmental problems and especially eastern and northern areas became more serious. For the solving these problems of North Korea, it is necessary to get the help of South Korea and international societies with efforts by itself.

• Applied Biological Chemistry
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• v.35 no.6
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• pp.449-456
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• 1992

Expermient were conducted to determine the effect of phosphorus stress on bacteroid content and energy status of soybean (Glycine max [L.] Merr.) nodules. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed (0.05 mM-P) and control (1 mM-P) treatment in the greenhouse. Phosphorus stress decreased nodule mass per plant and nodule mass to whole plant mass ratio. Phosphorus concentration in leaf, stem and root tissues were reduced by 75% but in nodule tissue was reduced only by 40% under phosphorus stress during 3 week experimental period. The bacteroid content per unit nodule mass and the distribution of total nitrogen and total phosphorus among the bacteroid and plant cell fractions of nodule were not affected significantly by phosphorus stress. Regardless of phosphorus treatment, 22% of the nitrogen and 27% of the phosphorus in whole nodules were associated with the bacteroid fraction. The ATP and total adenylate concentrations in and energy charge of whole nodule were decreased 77%, 46% and 37%, respectively, by phosphorus stress. The ATP concentration in and energy charge of the host plant cell fraction of nodules were decreased 86% and 59%, respectively, but these parametres in bacteroid in nodules were not affected by phosphorus stress. These results indicated that nodule is a strong phosphorus sink and that nodule growth and development are regulated to maintain a high phosphorus and energy content in bacteroid even when the host plant is subjected to phosphorus deficiency.