• Clean Technology
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• v.29 no.4
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• pp.297-304
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• 2023

The rapid advancement of the high-tech electronics industry has led to a significant increase in high-concentration ammonia wastewater. Various methods have been attempted to reliably treat wastewater containing high concentrations of ammonia, but no successful technology has yet been developed and applied. In this study, the removal efficiency and characteristics of ammonia nitrogen was evaluated according to changes in temperature, air loading rate, and liquid loading rate using a closed circulation countercurrent packed tower type demonstration facility for wastewater containing high concentrations of ammonia generated in the high-tech electronics industry. The temperature was varied while maintaining operating conditions of a wastewater flowrate of 20.8 m³ h^-1 and an air flow rate of 18,000 Nm³ h^-1. The results showed that at temperatures of 45,50,55, and 60℃, the removal efficiencies of ammonia nitrogen (NH₃-N) were 87.5%, 93.4%, 96.8%, and 98.7%, respectively. It was observed that temperature had the most significant impact on the removal efficiency of NH₃-N under these conditions. As the air loading rate increases, the removal rate also increases, but the increase in removal efficiency is not significant because droplets from the absorption tower flow into the stripping tower. Even if the liquid loading rate was changed by ±30%, the removal rate did not change significantly. This does not mean that the removal rate was unaffected, but was believed to be due to the relatively high air load rate. Through demonstration research, it was confirmed that ammonia stripping is a reliable technology that can stably treat high-concentration ammonia wastewater generated in the high-tech electronics industry.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.96-106
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• 2009

In this paper, correlation between the headphone's acoustical characteristics and the subjective preferences is analyzed, and a possibility of predicting the subjective preferences using the acoustical characteristics is investigated, The headphone's acoustical characteristics include the total harmonic distortions, the variation of the frequency response which were measured by separate channel and the inter-aural correlation coefficients, Those characteristics were measured in a noise-free anechoic chamber, using a head and torso simulator, The subjective preferences were scored in terms of loudness, clearness, spaciousness, fullness and overall impression, In the subjective listening test, 12 subjects were participated who have plentiful listening experiences, The programs include 5 kinds of musics; korean popular song, pop song, light music, male-voice and classic, The 8 models of the headphones were employed, including 4 closed-type circumaural headphones, 2 open-type supraaural headphones and 2 intra-concha headphones, A significant test was carred on the results from the subjective test, using a two-way ANOVA test, The correlation coefficients between the acoustical parameters and the subjective preferences were computed, Experimental results showed that the variation of the magnitude of frequency response measured from a right channel revealed higher correlation with the subjective preferences. Whereas the inter-aural correlation coefficients have very low correlation coefficients.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.27-35
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• 2024

Fuel gases such as methane and propane are used in explosion hazardous area of domestic plants and can form non-uniform mixtures with the influence of process conditions due to leakage. The fire-explosion risk assessment using literature data measured under uniform mixtures, damage prediction can be obtained the different results from actual explosion accidents by gas leaks. An explosion characteristics such as explosion pressure and flame velocity of non-uniform gas mixtures with concentration change similar to that of facility leak were examined. The experiments were conducted in a closed 0.82 m long stainless steel duct with observation recorded by color high speed camera and piezo pressure sensor. Also we proposed the quantification method of non-uniform mixtures from a regression analysis model on the change of concentration difference with time in explosion duct. For the non-uniform condition of this study, the area of flame surface enlarged with increasing the concentration non-uniform in the flame propagation of methane and was similar to the wrinkled flame structure existing in a turbulent flame. The time to peak pressure of methane decreased as the non-uniform increased and the explosion pressure increased with increasing the non-uniform. The ranges of K_G (Deflagration index) of methane with the concentration non-uniform were 1.30 to 1.58 [MPa·m/s] and the increase rate of K_G was 17.7% in methane with changing from uniform to non-uniform.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.285-291
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• 2009

The effects of water temperature on oxygen consumption (OC) of starry flounder Platichthys stellatus reared in seawater (SW) and freshwater (FW) was performed in closed water-recirculating system containing respiratory chamber. Fish acclimated in separate indoor tanks with SW (nine of fish used, $263.0{\pm}40.4$ g) or FW (nine of fish used, $265.8{\pm}34.8$ g) were sampled. The OC of starry flounder at $15^{\circ}C,\;20^{\circ}C$ and $25^{\circ}C$ were $74.4{\pm}17.0,\;85.9{\pm}15.8,\;98.3{\pm}11.4\;mg\;O_2\;kg^{-1}hr^{-1}$ in SW and $46.7{\pm}12.0,\;63.3{\pm}7.5,\;82.6{\pm}5.3\;mg\;O_2\;kg^{-1}hr^{-1}$ in FW, respectively, showing a linear increase in OC with water temperature. The OC of fish reared in both SW and FW clear diel rhythm, with lower values at daytime and higher values in the night, in accordance with light (09:00~21:00 hr) and dark (21:00~09:00 hr) phases of the diel cycle (12L : 12D) in water temperature at $15^{\circ}C$ and $20^{\circ}C$. However OC of fish reared in both SW and FW showed unclear diel rhythm with light and dark phases of the diel cycle in water temperature at $25^{\circ}C$. Starry flounder reared in FW had higher ventilation rates than those in SW, but SW had higher OC per breath than those in FW.

• The Korean Journal of Food And Nutrition
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• v.24 no.4
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• pp.551-558
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• 2011

This present study was performed to analyze the efficiency and volatility of a porous film containing $Chamaecyparis$ $obtusa$ extract as a method to effectively package food compounds. Phytoncide was contacted the state of gas and showed effective antimicrobial properties. Limonene can be distilled without decomposition as a relatively stable terpene and was one of the extract components. $Chamaecyparis$ $obtusa$ essential oil. The optimal solvent composition was a ratio 5:20:0.3 of T-500:ethanol:hardener to effectively manufacture film containing phytoncide essential oil and the minimum antibacterial concentration was 2%. The films were made under different conditions(A-50LF1, A-25SF2, B-50SF1, C-50LF1, C-25SF2 and D-50SF1) containing phytoncide and the amounts of limonene inside the 1-L reaction chamber depending on storage were measured by gas chromatography-mass selective detention. The results showed that the 25SF2(width, 25 mm; length, 20 cm) revealed more amount of limonene compared with 50LF1(width 50 mm, length 20 cm). We confirmed that the gas emission amount showed a better layer on the film side than on the internal film. An effect of film thickness on phytoncide emissions was observed in that the amounts was less than the expectation for a thicker film at the beginning time, but the emitting amounts increased with increasing storage periods. In the storage testing of various films at $35^{\circ}C$ and 70% humidity for 14 days, 25SF2 showed longer preservation compared with that of 50LF in the case of bread. $C.$ $obtusa$ essential oil is a useful fresh ingredients, hence, analysis of limonene emission kinetics from various film was helpful to develop films with an optimal antimicrobial effect, and will allow application of such films in food packaging systems.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.297-302
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• 2017

Recently, building materials and air purification filters with eco-friendly charcoal are actively studying to reduce the concentration of radon gas in indoor air. In this study, radon reduction performance was assessed by designing and producing new panel-type activated carbon filter that can be handled more efficiently than conventional charcoal filters, which can reduce radon gas. For the fabrication of our panel-type activated carbon filter, first the pressed molding product after mixing activated carbon powder and polyurethane. Then, through diamond cutting, the activated carbon filter of 2 mm, 4 mm and 6 mm thickness were fabricated. To investigate the physical characteristics of the fabricated activated carbon filter, a surface area and flexural strength measurement was performed. In addition, to evaluate the reduction performance of radon gas in indoor, the radon concentration of before and after the filter passes from a constant amount of air flow using three acrylic chambers was measured, respectively. As a result, the surface area of the fabricated activated carbon was approximately $1,008m^2/g$ showing similar value to conventional products. Also, the flexural load was found to have three times higher value than the gypsum board with 435 N. Finally, the radon reduction efficiency from indoor gas improved as the thickness of the activated carbon increases, resulting in an excellent radon removal rate of more than 90 % in the 6 mm thick filter. From the experimental results, the panel-type activated carbon is considered to be available as an eco-friendly building material to reduce radon gas in an enclosed indoor environment.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.459-467
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• 2016

Due to the limited areal space for installation, borehole heat exchangers (BHEs) at depths deeper than 300 m are considered for geothermal heating and cooling in the urban area. The deep vertical closed-loop BHEs are unconventional due to the depth and the range of the typical installation depth is between 100 and 200 m in Korea. The BHE in the study consists of 50A (outer diameter 50 mm, SDR 11) PE U-tube pipe in a 150 mm diameter borehole with the depth of 300 m. In order to compensate the buoyancy caused by the low density of PE pipe ($0.94{\sim}0.96g/cm^3$) in the borehole filled with ground water, 10 weight band sets (4.6 kg/set) were attached to the bottom of U-tube. A thermal response test (TRT) and fundamental basic surveys on the thermophysical characteristics of the ground were conducted. Ground temperature measures around $15^{\circ}C$ from the surface to 100 m, and the geothermal gradient represents $1.9^{\circ}C/100m$ below 100 m. The TRT was conducted for 48 hours with 17.5 kW heat injection, 28.65 l/min at a circulation fluid flow rate indicates an average temperature difference $8.9^{\circ}C$ between inlet and outlet circulation fluid. The estimated thermophysical parameters are 3.0 W/mk of ground thermal conductivity and 0.104 mk/W of borehole thermal resistance. In the stepwise evaluation of TRT, the ground thermal conductivity was calculated at the standard deviation of 0.16 after the initial 13 hours. The sensitivity analysis on the borehole thermal resistance was also conducted with respect to the PE pipe diameter and the thermal conductivity of backfill material. The borehole thermal resistivity slightly decreased with the increase of the two parameters.

• Analytical Science and Technology
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• v.28 no.6
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• pp.398-408
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• 2015

Carbon monoxide (CO) intoxication, arising from CO from an ignited charcoal briquette (ICB), is a popular means of committing suicide in Korea. Most CO intoxications are related to suicide attempts; however, the possibility of a homicide disguised as a suicide cannot be ruled out. Therefore, forensic investigation of the deceased and the crime scene is crucial to confirm that the deceased committed suicide. Detection of the components of an ICB on the objects suspected of being contacted by the deceased, such as the hands, nostrils, and doorknobs, is essential for linking the crime scene to the victim in the case of suicides by ignited ICBs. The traces from an ICB were analyzed by investigating the morphological characteristics and obtaining elemental compositions. The ICBs were completely different from blackened wood, as detected by discriminant analysis with the elements of carbon and oxygen. We analyzed one case of CO intoxication to demonstrate an excellent procedure for verifying whether a suicide occurred with an ICB. We employed SEM-EDX for the analysis of an ICB, microscope-FT/IR and pyrolysis-GC/MS for a partly burnt resin-type substance, GC/MS for diphenhydramine (a sleeping drug), and GC/TCD for the CO-Hb level. We detected traces of an ICB on the hands, nostrils, and doorknobs, which were all discriminated into an ICB group. Detection of ICB traces from the nostrils could indicate that the deceased started the fire themselves to commit suicide. The partially burnt black material was analyzed as an acrylronitrilestyrene polymer, which is normally used to make bags for carrying or wrapping and could be assumed to have been used to transport the ICB. Diphenhydramine, a sleeping drug, was detected at a level of 2.3 mg/L in the blood, which was lower than that in fatal cases (8-31 mg/L; mean 16 mg/L). A CO-Hb level of 79% was found in the blood, which means that the cause of death was CO intoxication. The steps shown here could represent an ideal method for reaching a verdict of suicide by CO intoxication produced by burning an ICB in a sealed room or a car.

• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.55-66
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• 2000

A U.S EPA Synthetic soil matrix was used for reference neat soil and pyrene contaminated soil. For the contaminated soil, 4.79 wt.% pyrene was dissolved completely into the djchlorornethane, and the soil was evenly soaked with the pyrene solution. The contaminated soil samples(50$\pm$0.5mg) were heated in a modified electrical screen heater reactor which consisted of a thin stainless foil (3.5cm$\times$13cm$\times$0.00254cm, 302 stainless steel shim), two electrodes, and a 20cm dia. $\times$30cm tall cylindrical Pyrex chamber sealed at both ends by aluminum flanges. The heating rate and time conditions were selected as $455^{\circ}C$ @ $1137^{\circ}C$ /s, $760^{\circ}C$ @ $950^{\circ}C$ /s and $977^{\circ}C$ @ $977^{\circ}C$/s. Tar samples after heating the soils were collected on the aluminum foil funnel and a glass filter paper (25mm dia. filter paper) The tar sample and remnant soil on the reactor were extracted with dichloromethane covering the filters, foils and soil by sonicating each in the waterbath for 10 minutes. The extractions were run on a HPLC. At the low peak temperature(about $455^{\circ}C$ @ $1137^{\circ}C$/s) the color of tar was "white", at the middle peak temperature (about 76$0^{\circ}C$ @ 95$0^{\circ}C$/s) the color of tar was "pink brown", at the high peak temperature (about 977$^{\circ}C$ @ 977$^{\circ}C$/s) the color of tar was "dark brown". Cyclopeta(cd)pyrene (CPEP) , which is an interesting species due to mutagenic effect on human cells, was detected in tar samples only above the middle peak temperature. This species was not detected at the low peak temperature. Six isomers of bipyrene were detected. Phenanthrene(C$_{14}$ $H_{10}$) and cyclopenta(def)phenanthrene(C$_{15}$ $H_{10}$) were also detected, but their content was very small relative to the other listed compounds.to the other listed compounds.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.3
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• pp.172-178
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• 2004

When soybean sprouts aye grown in the closed condition (where the ratio of $\textrm{O}_2$ and $\textrm{CO}_2$ is 7 ： 3), amount of $\textrm{CO}_2$ is increased and $\textrm{O}_2$ is decreased with the passage of time. At the same time, the amount of ethylene is automatically increased. By increasing the concentration of ethylene gas up to 0.5-1.0 ppm in the growth room, the length of sprouts was restricted to 6-7 cm and the thickness of sprouts was increased to 2.70$\pm$0.30 mm. The production of good quality sprouts which were fat and short was possible without application of any growth regulators such as indole-3-acetic acid known to have accumulation problem in humane body. To maintain the freshness during the transportation and prevent sprouts from rotting and bad smell at market, cold storage at 2-$5^{\circ}$ and airtightness which will restrict photosynthesis and respiration (higher than $10^{\circ}$) are needed. The freshness of sprouts is depended on the increase of $\textrm{CO}_2$ and the depletion of $\textrm{O}_2$ in the package. When the sprouts were stored below 1$0^{\circ}C$ (preferably below 8$^{\circ}C$), the concentration of $\textrm{CO}_2$ in the package remained below 30% for more than 60 hours, which was possible to keep sprouts in freshness without any offensive odor, But sprouts were maintained at $13^{\circ}$ for more than 25 hours, the concentration of $\textrm{CO}_2$ increased over 30% and produced an offensive odor. The little amount of $\textrm{O}_2$ gas was existing for 30 hours at $5^{\circ}$ but it was disappeared completely within 7 hours over $10^{\circ}$ and the sprouts became rot and produced severe offensive odor.