• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.739-746
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• 2010

The purposes of this study are 1) to develop an advanced chamber system within ${\pm}10%$ of air velocity at the particulate matter (PM) collection area, 2) to research theoretical characteristics of PM10 and PM2.5 samplers, 3) to assess the performance characteristics of PM10 and PM2.5 samplers through chamber experiments. The total six one-hour experiments were conducted using the cornstarch with an mass median aerodynamic diameter (MMAD) of $20\;{\mu}m$ and an geometric standard deviation of 2.0 at the two different air velocity conditions of 0.67 m/s and 2.15 m/s in the chamber. The aerosol samplers used in the present study are one APM PM10 and one PM2.5 samplers accordance with the US federal reference methods and specially designed three mini-volume aerosol samplers (two for PM10 and one for PM2.5). The overall results indicate that PM10 and PM2.5 mini-volume samplers need correction factors of 0.25 and 0.39 respectively when APM PM samplers considered as reference samplers and there is significant difference between two mini-volume aerosol samplers when a two-way analysis of variance is tested using the measured PM10 mass concentrations. The PM10 and PM2.5 samplers with the cutpoints and slopes (PM10: $10{\pm}0.5\;{\mu}m$ and $1.5{\pm}0.1$, PM2.5: $2.5{\pm}0.2\;{\mu}m$ and $1.3{\pm}0.03$) theoretically collect the ranges of 86~114% and 64~152% considering the cornstarch characteristics used in this research. Furthermore, the calculated mass concentrations of PM samplers are higher than the ideal mass concentrations when the airborne MMADs for the cornstarch used are smaller than the cutpoints of PM samplers and the PM samplers collected less PM in another case. The chamber experiment also showed that PM10 and PM2.5 samplers had the bigger collection ranges of 37~158% and 55~149% than the theocratical calculated mass concentration ranges and the relatively similar mass concentration ranges were measured at the air velocity of 2.15 m/s comparing with the 0.67 m/s.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.18-29
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• 2010

Offshore subsurface storage of $CO_2$ is regarded as one of the most promising options to response severe climate change. Marine geological storage of $CO_2$ is to capture $CO_2$ from major point sources, to transport to the storage sites and to store $CO_2$ into the offshore subsurface geological structure such as the depleted gas reservoir and deep sea saline aquifer. Since 2005, we have developed relevant technologies for marine geological storage of $CO_2$. Those technologies include possible storage site surveys and basic designs for $CO_2$ transport and storage processes. To design a reliable $CO_2$ marine geological storage system, we devised a hypothetical scenario and used a numerical simulation tool to study its detailed processes. The process of transport $CO_2$ from the onshore capture sites to the offshore storage sites can be simulated with a thermodynamic equation of state. Before going to main calculation of process design, we compared and analyzed the relevant equation of states. To evaluate the predictive accuracies of the examined equation of states, we compare the results of numerical calculations with experimental reference data. Up to now, process design for this $CO_2$ marine geological storage has been carried out mainly on pure $CO_2$. Unfortunately the captured $CO_2$ mixture contains many impurities such as $N_2$, $O_2$, Ar, $H_{2}O$, $SO_{\chi}$, $H_{2}S$. A small amount of impurities can change the thermodynamic properties and then significantly affect the compression, purification and transport processes. This paper analyzes the major design parameters that are useful for constructing onshore and offshore $CO_2$ transport systems. On the basis of a parametric study of the hypothetical scenario, we suggest relevant variation ranges for the design parameters, particularly the flow rate, diameter, temperature, and pressure.

• Economic and Environmental Geology
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• v.44 no.3
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• pp.217-228
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• 2011

The feasibility study for the stabilization process using 5 amendments was performed to quantify As-immobilization efficiency in farmland soils around Samkwang abandoned mine, Korea. For the batch experiments, with 2% and 3% of granular lime(2-5 mm in diameter), leaching concentration of As from the soil decreased by 86% and 95% respectively, compared to that without the amendment. When 5% and 10% of granular limestone was added in the soil, As concentration decreased by 82% and 95%, showing that lime and limestone has a great capability to immobilize As in the soil. From the results of batch experiments, continuous column(15 cm in dimeter and 100 cm in length) tests using granular lime and limestone as amendments was performed. Without the amendment, As concentration from the effluent of the column ranged from 167 ${\mu}g$/L to 845 ${\mu}g$/L, which were higher than Korea Drinking Water Limit(50 ${\mu}g$/L). However, only with 1% and 2% of lime, As concentration from the column dramatically decreased by 97% for 9 years rainfall and maintained below 50 ${\mu}g$/L. With 5% of limestone and the mixed amendment(1% of lime + 2% of limestone), more than 95% diminution of As leaching from the column occurred within I year rainfall and maintained below 20 ${\mu}g$/L, suggesting that the capability of limestone to immobilize As in the farmland soil was outstanding and similar to that of lime. Results of experiments suggested that As stabilization process using limestone could be more available to immobilize As from the soil than using lime because of low pH increase and thus less harmful side effect.

• Economic and Environmental Geology
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• v.43 no.6
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• pp.555-564
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• 2010

Remediation process by using the bio-carrier (beads) with dead Bacillus sp. B1 and polysulfone was investigated for heavy metal contaminated groundwater. Sorption batch experiments using the bio-carrier were performed to quantify the heavy metal removal efficiencies from the contaminated solution. The analyses using SEM/EDS and TEM for the structure and the characteristic of precipitates on/inside the beads were also conducted to understand the sorption mechanism by the bio-carrier. Various amounts of freeze-dried dead Bacillus sp. B1 were mixed with polysulfone + DMF(N,N-dimethylformamide) solution to produce the bio-carrier (beads; less than 2mm in diameter) and 5% of Bacillus sp. B1 in the bio-carrier was optimal for Pb removal in the solution. The removal efficiency ratings of the bio-carrier for Pb, Cu and Cd were greater than 80% after adding 2g of bio-carrier in 50ml of aqueous solution (<10mg/L of each heavy metal concentration). Reaction time of the bio-carrier was very fast and most of the sorption reaction for heavy metals were completed within few hours. Batch experiments were duplicated at various pH conditions of aqueous solutions and Cu and Pb removal efficiencies highly maintained at wide pH ranges (pH 2-12), suggesting that the bio-carrier can be useful to clean up the acidic waste water such as AMD. From SEM/EDS and TEM analyses, it was observed that the bio-carrier was spherical shape and was overlapped by many porous layers. During the sorption experiment, Pb was crystallized on the surface of porous layers and also was mainly concentrated at the boundary of Bacillus sp. B1 stroma and polysulfone substrate, showing that the main mechanism of the bio-carrier to remove heavy metals is the sorption on/inside of the bio-carriers and the bio-carriers are excellent biosorbents for the removal of heavy metal ions from groundwater.

• Korean Journal of Environmental Agriculture
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• v.23 no.4
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• pp.211-219
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• 2004

Three sludge types from pharmaceutical byproducts and one sludge type from cosmetic waste-water sludge as raw materials of compost were used in a field based concrete pot ($4\;m^2$, $2\;m{\times}2\;m$) for investigating damage of red pepper cultivation. These sludges and pig manure (1 Mg/10a, dry basis) were incorporated into the upper of clay loam soil prior to transplanting with red pepper. Changes in concentration and properties of heavy metal for both of soil and plant were investigated 4 times during of red pepper growth. Plant height and stem diameter of red pepper in sludge treatments except to Pharmaceutical sludge 3 were poor than those of NPK treatment. This result were regarded as an effect of incompleted decomposition sludge which has a lot of organic matter concentration. Amount of total As was increased rapidly Jul. 8. in soil, total Zn Cu Pb Cd were in harvest time, and 1 N-HCl extractable Zn Cu Pb Cd As were in harvest at middle stage and then decreased. Amounts of nitrogen in plant (leaf and stem) were high in Phamaceutical Sludge 1 and fig Manure treatment in early and middle stage because of organic matter and nitrogen concentrations and characteristics. Amounts of Zn, Pb, and Ni in leaf and amount of Zn and Pb in stem were increased in harvest time so that we need to have a concern in detail. Total yield of red pepper was Pig Manure > Phamaceutical Sludge 3 > Phamaceutical Sludge 1 > NPK > Phamaceutical Sludge 2 and Cosmetic Sludge treatment was decreased considerably to compare to others. Amounts of Zn and Cu in green and red pepper in harvest time were higher than the other heavy metals. Finally these results can use to utilize that finding damage on crop for authorization and suitability estimation of raw material of compost.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.130-136
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• 2009

The aim of this study was to develop a method for measuring the slumping resistance of flowable resin composites and to evaluate the efficacy using rheological methodology. Five commercial flowable composites (Aelitefil flow:AF, Filtek flow:FF, DenFil flow:DF, Tetric flow:TF and Revolution:RV) were used. Same volume of composites in a syringe was extruded on a glass slide using a custom-made loading device. The resin composites were allowed to slump for 10 seconds at $25^{\circ}C$ and light cured. The aspect ratio (height/diameter) of cone or dome shaped specimen was measured for estimating the slumping tendency of composites. The complex viscosity of each composite was measured by a dynamic oscillatory shear test as a function of angular frequency using a rheometer. To compare the slumping tendency of composites, one way-ANOVA and Turkey's post hoc test was performed for the aspect ratio at 95% confidence level. Regression analysis was performed to investigate the relationship between the complex viscosity and the aspect ratio. The results were as follows. 1. Slumping tendency based on the aspect ratio varied among the five materials (AF

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.145-153
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• 2009

The purpose of this study was to evaluate the effect of instrument compliance on the polymerization shrinkage stress measurements of dental composites. The contraction strain and stress of composites during light curing were measured by a custom made stress-strain analyzer, which consisted of a displacement sensor, a cantilever load cell and a negative feedback mechanism. The instrument can measure the polymerization stress by two modes: with compliance mode in which the instrument compliance is allowed, or without compliance mode in which the instrument compliance is not allowed. A flowable (Filtek Flow: FF) and two universal hybrid (Z100: Z1 and Z250: Z2) composites were studied. A silane treated metal rod with a diameter of 3.0 mm was fixed at free end of the load cell, and other metal rod was fixed on the base plate. Composite of 1.0 mm thickness was placed between the two rods and light cured. The axial shrinkage strain and stress of the composite were recorded for 10 minutes during polymerization. and the tensile modulus of the materials was also determined with the instrument. The statistical analysis was conducted by ANOVA. paired t-test and Tukey's test (${\alpha}<0.05$). There were significant differences between the two measurement modes and among materials. With compliance mode, the contraction stress of FF was the highest: 3.11 (0.13). followed by Z1: 2.91 (0.10) and Z2: 1.94 (0.09) MPa. When the instrument compliance is not allowed, the contraction stress of Z1 was the highest: 17.08 (0.89), followed by FF: 10.11 (0.29) and Z2: 9.46 (1.63) MPa. The tensile modulus for Z1, Z2 and FF was 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa, respectively. With compliance mode. the measured stress correlated with the axial shrinkage strain of composite: while without compliance the elastic modulus of materials played a significant role in the stress measurement.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.183-189
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• 2000

This study was carried out to analyze ecophysiological responses for seedling of Quercus serrata, Quercus mongolica and Quercus variabilis that are the typical species of deciduous broadleaved forests in Korea. And executed experiments in the climatic control room to provide necessary information to ecological forest management and methods of natural regeneration through the analysis of seedling responses. The details of experimental analysis were growth processes of 4 months after seeding that vary with the condition of three light intensity[relative light intensity(RLI) 8%, 20%, 52%] and three soil moisture[water suction(WS) Ψ=100 hPa, Ψ=280 hPa, Ψ=330 hPa] gradient, growth factors after harvesting and the nutrition condition of leaves. The results of this study are followings: 1) Early growth was prosperous after germination for the species which have more weight of acorn. 2) The formation of lammas shoot was favourable with Q. variabilis and Q. mongolica. And the rate of the occurrence was the highest in the RLI 20%, and it was remarkably reduced in the RLI 8%. 3) As the height growth of seedling of all 3 species were greater in the RLI 20% and 8% than that of the RLI 52%, they showed strong shade tolerance. 4) The increase of light intensity promoted the diameter at root collar growth, and development of main and lateral roots with all 3 species. 5) It showed that the increase of light intensity in the experimental radiation condition raised special leaf area weight(mg/cm$^2$) and leaf area productivity(mg/cm$^2$). Consequently, these resulted in the increase of leaf thickness and total dry biomass per the unit area of leaf. 6) As the increase of light intensity, the minerals contents of leaves such as N, P and K were lowered, and the increase of soil moisture resulted in the increase of P, K, Ca and Mg.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.280-292
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• 2017

Hail is not a frequently occurring weather event, and there are even fewer reports of hail damages to forest stands. Since the 2000s, an increase in hail incidence has been documented in Europe and the United States. In Korea, severe hails occurred in Jeollanam-do province on May 31 and in Gyeongsangbuk-do province on June 1, 2017. Hail size was ranged from 0.5 to 5.0 cm in diameter in Jeollanam-do, and from 1.5 to 3.0 cm in Gyeongsangbuk-do. This study was aimed to analyze the hail damages to forests by species and topography based on damage-categorized maps created by using drones and aerial photographs, and to analyze relationships of the damages with meteorological factors. The total damaged forest area was 1,163.1ha in Jeollanam-do, and 2,942.3ha in Gyeongsangbuk-do. Among the 'severe' damaged area 326.7ha, 91% was distributed in Jeollanam-do, and concentrated in the city of Hwasun which covers 57.2% of the total 'severe' damaged area. The most heavily damaged species was Korean red pine(Pinus densiflora S. & Z.) followed by P. rigida. Most broad-leaved trees species including oaks were recovered without any dead trees found. Liliodendron tulipifera was the most severely damaged in terms of the rate of 'severe' degree individuals which are needed to be checked whether they will die or be recovered. Cause of the death of pines was considered as the combination of physical damage caused by the hail and long-lasting drought with high air temperature that occurred before and after the hail event. No pathogens and insects were found which might have affected to tree deaths. We suggested a dieback mechanism of the pine trees damaged by hail and drought.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.702-708
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• 2002

Although Umboniunm thomasi is one of marine mollusc (Archaeogastropoda: Trochidae) inhabiting the sands in the intertidal zone of the west coast of Korea, aspects of its reproductive biology are still not too well known. Reproductive cycle, gametogenesis, and first sexual maturity of U. thomasi collected at the west coast of Buan-gun, Jeollabuk-do, Korea were investigated monthly from January to December 1999. U. thomasi was dioecious, and an oviparous. The gonad was placed in the rear of the flesh part in the spiral shell. The external colors of the ripe ovary and testis appeared to be green and milk-white or yellowish white, respectively. Meat weigh rate peaked in July ($37.5\%$). And then the value sharply decreased in September ($28.3\%$), thereafter, gradually increased in November ($31.7\%$). Fully ripe oocytes were approximately 100$\~$110 $/mu$m in diameter, and their cytoplasm contained a great number of yolk Branules. Based on the monthly changes of the Bonadal development, gametogenesis, and meat weight rate, the reproductive cycle of U. thomasi could be devided into five successive stages: early active (November to April), late active (February to May), ripe (April to August), spawning (July to October), and recovery (September to February). Gonadal development and spawning were closely related to the seawater temperature, the main spawning occurred in September when the temperature reached above 24.2$^{\circ}C$. Individuals of 4.4 mm and less in shell height could not take part in reproduction in both sexes. Percentages of first sexual maturity of female and male shells ranging from 5.5 to 6.4 mm were $55.0\%$ and $61.9\%$, respectively, and $100\%$ of those over 7.5 mm in shell heights in both sexes participated in the reproduction.