• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.2
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• pp.153-170
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• 2022

Waterjet has been comprehensively used in urban areas owing to a suitable technique for cutting concrete and rock, and low noise and vibration. Recently, the abrasive waterjet technique has been adopted and applied by the Korea Atomic Energy Research Institute to demolish concrete plugging without disturbing and damaging In-situ Demonstration of Engineered Barrier System in the disposal research tunnel. In this study, the use of abrasive waterjet in the tunnel was evaluated for practical applicability and the existing cutting model was compared with the experimental results. As a variable for waterjet cutting, multi-cutting, water flow rate, abrasive flow rate, and standoff distance were selected for the diversity of analysis. As regarding the practical application, the waterjet facilitated path selection for cutting the concrete plugging and prevented additional disturbances in the periphery. The pump's noise at idling was 64.9 dB which is satisfied with the noise regulatory standard, but it exceeded the standard at ejection to air and target concrete because the experiment was performed in the tunnel space. The experimental result showed that the error between the predicted and measured cutting volume was 12~13% for the first cut and 16% for second cut. The standoff distance had a significant influence on the cutting depth and width, and the error tended to decrease with decrement of standoff distance.

• ALGAE
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• v.37 no.2
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• pp.149-161
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• 2022

Noctiluca scintillans is a heterotrophic dinoflagellate that causes red-colored oceans during the day (red tides) and glowing oceans at night (bioluminescence). This species feeds on diverse prey, including phytoplankton, heterotrophic protists, and eggs of metazoans. Thus, many scientists have conducted studies on the ecophysiology of this species. It is easy to cultivate N. scintillans at a scale of <1 L, but it is difficult to cultivate them at a scale of >100 L because N. scintillans cells usually stay near the surface, while prey cells stay below the surface in large water tanks. To obtain mass-cultured N. scintillans cells, we developed an automatic system for cultivating N. scintillans on a scale of 100 L. The system consisted of four tanks containing fresh nutrients, the chlorophyte Dunaliella salina as prey, N. scintillans for growth, and N. scintillans for storage, respectively. The light intensities supporting the high growth rates of D. salina and N. scintillans were 300 and 20 µmol photons m^-2 s^-1, respectively. Twenty liters of D. salina culture from the prey culture tank were transferred to the predator culture tank, and subsequently 20 L of nutrients from the nutrient tank were transferred to the prey culture tank every 2 d. When the volume of N. scintillans in the predator culture tank reached 90 L 6 d later, 70 L of the culture were transferred to the predator storage tank. To prevent N. scintillans cells from being separated from D. salina cells in the predator culture tank, the culture was mixed using an air pump, a sparger, and a stirrer. The highest abundance of N. scintillans in the predator culture tank was 45 cells mL^-1, which was more than twice the highest abundance when this dinoflagellate was cultivated manually. This automatic system supplies 100 L of N. scintillans pure culture with a high density every 10 d for diverse experiments on N. scintillans.

• Journal of Animal Environmental Science
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• v.18 no.3
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• pp.207-220
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• 2012

There are around 7,500 manure tanks to treat the manures from pigs in Korea. In the tank, there are too much sediments deposited on the base and wall, which causes low efficiency of stock capacity and manure fermentation. In order to minimize sediments and to ferment manure effectively, we developed a 2-fluid jet mixer for mixing sediments in liquid livestock manure tank. For developing the prototype, we tested a factorial experimental system with various nozzles, and simulated CFD models with two kinds of nozzle arrangement. From the results of factorial experiment and CFD simulation, we concluded the dia. ratio of primary : secondary nozzle should be 1:2 and the nozzles should be arranged at the same distances toward to the circumferential direction. With this results, we manufactured a 2-fluid jet mixer which is consists of four 2-phase nozzles, centrifugal slurry pump and root's type air blower. And, we carried out the performance test of the prototype in the round shaped liquid manure tank in the farm. The performance test results showed that the uniformity of TS (Total Solid) and VS (Volatile Solid) was raised from 21.3 g/L, 13.3 g/L In steady state to TS and VS to 23.0 g/L, 14.1 g/L in the mixing operation. Therefore, we could conclude that the prototype of 2-fluid mixer could make the solid material which could be sediments in the tank not to be deposited in the tank and to be contacted to air bubbles which could enhance the efficiency of the fermentation of livestock manure.

• Korean Journal of Environmental Agriculture
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• v.35 no.4
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• pp.286-293
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• 2016

BACKGROUND: 18% of difenoconazole+iminoctadin triacetate microemulsion (3%+15%) formulation were mixed and sprayed as closely as possible to normal practice on the ten of farms located in the Youngju of South Korea. Patches, cotton gloves, socks, masks and XAD-2 resin were used to measure the potential exposure for applicators wearing standardized whole-body outer and inner dosimeter (WBD). This study has been carried out to determine the dermal and inhalation exposure to difenoconazole during preparation of spray suspension and application with a power sprayer on a grape orchard. METHODS AND RESULTS: A personal air monitor equipped with an air pump IOM sampler and cassette and glass fiber filter were used for inhalation exposure. The field studies were carried out in a grape orchard. The temperature and relative humidity were monitored with a thermometer and a hygrometer. Wind speed was measured using a pocket weather meter. All mean field fortification recoveries were between 97.3% and 119.6% in the level of 100 LOQ (limit of quantification) while the LOQ for difenoconazole was $0.025{\mu}g/mL$ using HPLC-UVD. The arms exposure to difenoconazole for the mixer/loader (0.0794 mg) was higher than other body parts (head, hands, upper body, legs). The exposure to difenoconazole in the legs for applicator (3.78 mg) was highest in the parts of body. The dermal exposure for mixer/loader and applicator were 0.02 and 2.28 mg on a grape orchard, respectively. The inhalation exposure during application was estimated as 0.02 mg. The ratio of inhalation exposure to dermal exposure was equivalent to 0.9% of the dermal exposure. CONCLUSION: The inhalation exposure for applicator indicated $18.8{\times}10^{-3}mg$, which was level of 0.9% of the dermal exposure (2.28 mg). Operator exposure (0.004 mg/kg bw/day) to difenoconazole during treatment for grape is calculated as 2.5% of the established AOEL (0.16 mg/kg bw/day).

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.263-270
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• 2010

This is a research on development of water purification equipment called artificial floating island (=AFI) for the stagnant water area which can secure exuberant landscape and water-friendility. The equipment devised in this study is designed to make up the weakness of conventional AFIs and improves the removal efficiency of pollutants using the mixture of media and plants. The air compressor positioned at the inlet releases air with inflow continuously, the water pump at the outlet sprays as a form of fountain with causing a disturbance on stable water column, then, both of them contribute improvement of water quality over a large area. We applied Bio-stone as a media in this system and performed an experiment of pre-efficiency test, and we concluded that the higher pollutants concentration of inflow, the higher removal efficiency we obtained. At the result of lab-scale experiment, in the case of high-concentration inflow, in the removal efficiency of SS is 62.2%, BOD is 50.2%, COD is 55.1%, T-N is 31.6%, T-P is 38.4%. In addition, to evaluate the field application, we set up the facilities in Sin-gal lake located in Yongin-Si Gyeonggi-Do, and researched on the removal efficiency of outflow relative to the inflow. As a result, SS is 53.5%, BOD is 32.8%, COD is 36.9%, T-N is 22.6%, T-N is 33.2%.

• Journal of the Korean Society of Safety
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• v.7 no.2
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• pp.63-70
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• 1992

The aim of this research is to obtain a basic quantitative understanding of the effect of a noncondensable gas on the absorption of water vapor by a $H_2O$ / LiBr combination with n-octanol as the surfactant. Nonflowing aqueous solutions of LiBr (40,45,50 mass％) were exposed to saturated water vapor following the addition of an n-octanol sufactant (0.01 and 0.6 mass％). A small amount of a noncondensable gas (air) was allowed into the absorber (0.03 volume％) and its effect was analyzed by measuring the amount of water vapor absorbed. This study will aid to predict the performance of heat pump and safety operating condition when the noncondensable gas is not allowed in the absorber The results indicate that, in the presence of small amounts of a noncondensable gas, vapor absorption enhancement ratios are less than half o( those obtained under the same experimental conditions when a noncondensable gas is not present (1). The presence of a noncondensable gas causes the partial vapor pressure of air to increase at the vapor / liquid interface, which results in an instability of vapor absorption rate nd. hence, in an inhibition of interfacial disturbance.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.302-311
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• 2018

BACKGROUND: Dithianon (75%) formulation were mixed and sprayed as closely as possible by normal practice on the ten farms located in the Mungeong of South Korea. Patches, cotton gloves, socks, masks, and XAD-2 resin were used for measurement of the potential exposure of dithianon on the applicators wearing standardized whole-body outer and inner dosimeter (WBD). This study has been carried out to determine the dermal and inhalation exposure to dithianon during preparation of spray suspension and application with a power sprayer on a apple orchard. METHODS AND RESULTS: A personal air monitor equipped with an air pump, IOM sampler and cassette, and glass fiber filter was used for inhalation exposure. The field studies were carried out in a apple orchard. The temperature and relative humidity were monitored with a thermometer and a hygrometer. Wind speed was measured using a pocket weather meter. All mean field fortification recoveries were between 85.1% and 99.1% in the level of 100 LOQ (limit of quantification), while the LOQ for dithianon was $0.05{\mu}g/mL$ using HPLC-DAD. The exposure to dithianon on arms of the mixer/loader (0.0794 mg) was higher than other body parts (head, hands, upper body, or legs). The exposure to dithianon on the applicator's legs (3.78 mg) was highest in the body parts. The dermal exposures for mixer/loader and applicator were 10 and 8.10 mg, respectively, from a grape orchard. The inhalation exposure during application was estimated as 0.151 mg, and the ratio of inhalation exposure was 11.2% of the dermal exposure (inner clothes). CONCLUSION: The dermal and inhalation exposure on the applicator appeared to be 4.203 mg - 25.064 mg and $0.529{\mu}g-116.241{\mu}g$, respectively. The total exposures on the agricultural applicators were at the level of 2.596 mg - 25.069 mg to dithianon during treatment for apple orchard. The TER showed 3.421 (>1) when AOEL of dithianon was used as a reference dose for the purpose of risk assessment of the mixing/loading and application.

• The Korean Journal of Pesticide Science
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• v.20 no.3
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• pp.271-279
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• 2016

To evaluate exposure characteristics of the insecticide imidacloprid to apple orchard workers during treatment on orchard fields and evaluate its potential risk using a whole body dosimetry (WBD) method, 1,000-time diluted acephate+imidacloprid 25(20+5)% solutions were sprayed on 10 apple orchard fields in Cheongju with a speed sprayer at a rate of 3,000 L/ha/person, after put on clothes such as inner/outer clothes, personal air pump with a IOM sampler, nitrile glove and mask. Exposure test included mixing, loading and application steps. The test pesticide imidacloprid residues in the collected samples were analyzed with a HPLC-DAD. Recoveries ranged from 81.5 to 108.6% for analytical method validation and from 73.8 to 86.7% for field recovery. Total exposed amounts to mixer/loader and applicator were found to be 0.0014-0.0279% of total applied active ingredient of imidacloprid. Glove exposure of both mixer/loader and applicator was higher than the other parts. Margins of safety of mixer/loader and applicator were calculated to be 97-355 and 46-196, respectively, indicating that exposure risk of imidacloprid to apple orchard workers by spraying with a speed sprayer was very low.

• Journal of Applied Biological Chemistry
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• v.57 no.1
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• pp.73-81
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• 2014

The present study was carried out to assess exposure and risk to thiophanate-methyl wettable powder for agricultural worker during mixing/loading and application with power sprayer in green pepper, cucumber and apple fields. Dermal exposure was measured with patches, gloves, socks and masks, while inhalation exposure was evaluated with personal air pump and solid sorbent. Those methods were full validated before experiment. During mixing/loading, dermal exposure amount in green pepper, cucumber and apple fields was $24.0{\pm}6.7$, $4.5{\pm}1.5$ and $18.5{\pm}0.6mg$, corresponding to mean 0.007, 0.001 and 0.005% of prepared active ingredient, respectively. The major exposed part for mixer/loader was hands (78-92%). Dermal exposure amount for applicator in green pepper, cucumber and apple fields was $84.9{\pm}14.0$, $34.0{\pm}20.8$ and $30.7{\pm}9.1mg$, corresponding to mean 0.024, 0.016 and 0.013% of applied active ingredient, respectively. The main body parts of exposure in apple field were hands, while thighs and shins in other fields. Inhalation exposure amount in green pepper, cucumber and apple fields was $1.5{\pm}2.2$, $52.7{\pm}48.9$ and $4.0{\pm}4.9{\mu}g$ during mixing/loading and $0.2{\pm}0.1$, $23.2{\pm}12.4$ and $0.4{\pm}0.6{\mu}g$ for applicator, respectively. These results were suggested that main factors affecting dermal exposure were contact frequency to the plants, foliage density, hygienic behavior, work type, and working environment, while inhalation exposure was affected mainly by working environment, especially wind. In risk assessment, margin of safety for thiophanate-methyl in all cases was over 1. However, during application in green pepper field, margin of safety was close to 1.

• Journal of Animal Environmental Science
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• v.17 no.2
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• pp.71-80
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• 2011

Trickling filter has been extensively studied for the domestic wastewater treatment especially for the small scale plants in rural area. The purpose of this research is to survey the physical and microbial characteristics of wood chip media and the removal efficiency of animal wastewater using wood chip trickling filter system. The trickling filtration system comprises a filtration bed packed with wood chip media having a particle dia. of 5~7cm. The method comprises natural air from the bottom of the bed. The system also comprises a control mechanism including a time a constant discharge pump for controlling supply of the wastewater into the bed. The following conclusions were obtained from the results of this research. 1. The specific surface area of wood chip was 0.4123 $m^2$/g, pore volume was 0.0947 $cm^3$/g, density was 0.49 g/$cm^3$. It has forms of parallelogram and oblong which have numerous small pore space. This wood chip has been good condition for microorganism's habitat, having very larger specific surface area by complex the three dimension structure of cellulose at wood's major ingredients. 2. The total counts of in attached aerobic microbes were ranged from $10^6$ to $10^8$ CFU/g, and anaerobes microbial numbers were from $10^4$ to $10^7$. The aerobic microbial numbers appeared to be much more than those of anaerobic microbial numbers. 3. The average efficiency of $BOD_5$ and CODcr were 74.5% and 51.5%, respectively. The removal efficiency of T-N and T-P were 61.4%, 56.2%, respectively. But SS removal levels remain 19.3%.