• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.12
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• pp.1867-1872
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• 2010

Microbe and quality changes of vacuum-packaged ready-to-eat lettuce were analyzed. While the vacuumpackaged lettuce after chlorine sanitizer were stored at $5^{\circ}C$, $15^{\circ}C$, and $25^{\circ}C$ for 7 days, viable numbers of total aerobic bacteria (TAB), coliform, E. coli, food-borne pathogens and lactic acids bacteria (LAB) were counted with gas production and sensory evaluation. Before the storage, only TAB of 2 log CFU/g and coliform of 1 log CFU/g were detected and LAB was not detected. TAB, coliform and LAB increased by 1 log CFU/g at $5^{\circ}C$ for 7 days without any detection of the pathogens. Sensory evaluations for off-flavour and crispness dropped to half the best value at 5 day storage. TAB and coliform increased by 3 log CFU/g and 2 log CFU/g, respectively, but LAB grew very actively by 4 log CFU/g under anaerobic environment and only B. cereus were detected after enrichment of the lettuce at $15^{\circ}C$ for 3 days. The evaluations for off-flavour and crispness were half the best value for 3 days. However, TAB and coliform increased by 3 log CFU/g, 1 log CFU/g, and 4 log CFU/g, respectively only at 1 day storage under $25^{\circ}C$. Also B. cereus were detected after enrichment and the sensory evaluation were half the best value within 1 day storage. Therefore, preservation at the lowest temperature possible is required for growth inhibition of the bacteria contaminated in the lettuce. Interestingly, LAB among them grew most actively under the anaerobic condition and the adulteration of lettuce might be closely related with the growth of LAB.

• Journal of Bio-Environment Control
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• v.8 no.1
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• pp.56-66
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• 1999

Growth of Dendranthema grandiflorum R. ‘Bongwhang’plantlets, as affected by three levels of photosynthetic photon flux (PPF), 70, 150 and 220 $\mu$mol. $m^{-2}$ . $s^{-1}$ , three levels of C $O_{2}$ concentration, 400-500 (ambient), 1000 and 2000 $\mu$mol.mo $l^{-1}$ , and two levels of number of air exchanges per hour (NAEH), 0.1 $h^{-1}$ and 2.8 $h^{-l}$, was studied. Explants were obtained from photomixotrophically-micropropagated plantlets. Four explants were planted in each 3.7$\times$10$^{-4}$ $m^{3}$ polycarbonate box containing MS medium supplemented with 1.25 meq. $L^{-1}$ $H_{2}$P $O_{4}$$^{[-10]}$ and no added sugar. Explants were cultured under cool-white fluorescent lamps (16 h. $d^{-1}$ ), at 25$\pm$1$^{\circ}C$ temperature, and 70-80% relative humidity. In treatments of 2.8 $h^{-1}$ NAEH, a 10 mm round hole made on the vessel cap was sealed with a microporous filter For higher C $O_{2}$ concentrations in the culture room, C $O_{2}$ gas was provided from a tank of liquefied C $O_{2}$. Fresh and dry weights, height, length of the longest roots, number of leaves, and leaf area significantly increased with increasing PPF and especially, with increasing C $O_{2}$ concentration. Growth was enhanced with increased number of air exchanges per hour (2.8 $h^{-1}$ ). Overall, treatment of 220$\mu$mol. $m^{-2}$ . $s^{-1}$ PPF combined with 2000$\mu$mol.mo $l^{-1}$ C $O_{2}$ and 2.8 $h^{-1}$ NAEH gave the most vigorous growth of Dendranthema grandiflorum R. ‘Bongwhang’ plantlets in vitro.o.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.4
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• pp.181-190
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• 2008

To response climate change and Kyoto protocol and to reduce greenhouse gas emissions, marine geological storage of $CO_2$ is regarded as one of the most promising option. Marine geological storage of $CO_2$ is to capture $CO_2$ from major point sources(eg. power plant), to transport to the storage sites and to store $CO_2$ into the marine geological structure such as deep sea saline aquifer. To design a reliable $CO_2$ marine geological storage system, it is necessary to perform numerical process simulation using thermodynamic equation of state. The purpose of this paper is to compare and analyse the relevant equations of state including ideal, BWRS, PR, PRBM and SRK equation of state. To evaluate the predictive accuracy of the equation of the state, we compared numerical calculation results with reference experimental data. Ideal and SRK equation of state did not predict the density behavior above $29.85^{\circ}C$, 60 bar. Especially, they showed maximum 100% error in supercritical state. BWRS equation of state did not predict the density behavior between $60{\sim}80\;bar$ and near critical temperature. On the other hand, PR and PRBM equation of state showed good predictive capability in supercritical state. Since the thermodynamic conditions of $CO_2$ reservoir sites correspond to supercritical state(above $31.1^{\circ}C$ and 73.9 bar), we conclude that it is recommended to use PR and PRBM equation of state in designing of $CO_2$ marine geological storage process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.708-718
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• 2020

Offensive odor is recognized as a social environmental problem due to its olfactory effects. Ammonia(NH₃), hydrogen sulfide(H₂S) and benzene(C₆H₆) are produced from various petrochemical plants, public sewage treatment plants, public livestock wastes, and food waste disposal facilities in large quantities. Therefore efficient decomposition of offensive odor is needed. In this study, the removal efficiency of atmospheric-pressure plasma operating at an ambient condition was investigated by evaluating the concentrations at upflow and downflow between the plasma reactor. The decomposition of offensive odor using plasma is based on the mechanism of photochemical oxidation of offensive odor using free radical and ozone(O₃) generated when discharging plasma, which enables the decomposition of offensive odor at ordinary temperature and has the advantage of no secondary pollutants. As a result, all three odor substances were completely decontaminated within 1 minute as soon as discharging the plasma up to 500 W. This result confirms that high concentration odors or mixed odor materials can be reduced using atmospheric-pressure plasma.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.970-977
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• 2005

The commercial $V_2O_5-WO_3/TiO_2$ catalysts which had been exposed to the off gas from incinerator for a long time were remanufactured by washing with distilled water and arid solution and reimpregnation with catalytic active components($V_2O_5-WO_3$). The catalytic properties and NOx conversion reactivity of those catalysts were examined by analysis equipment and NOx conversion experiment. Under the experimental condition used in this study, the remanufactured catalysts activated by distilled water ultra sonic cleaning, the catalytic activity was recovered in the range of $66{\sim}93%$ of that of the fresh and the maximum activity was showed when the ultra sonic cleaning time was more than 3 minutes. The remanufactured catalysts by acid solution ultra sonic cleaning, the catalytic activity was recovered in the range of $81{\sim}97%$ of that of the fresh catalyst and the maximum catalytic activity was shooed when the pH of the acid solution was 5. The remanufactured catalysts by reimpregnation with $V_2O_5$ and $WO_3$, the catalytic activity was recovered in the range of $87{\sim}100%$ of that of the fresh catalyst. Maximum catalytic activity was showed when the $V_2O_5$ was reimpregnated more than 1.0 wt %. In this case, the catalytic activity was recovered 97% of that of the fresh catalyst especially at the $150^{\circ}C$ of the experimental temperature.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.223-231
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• 2012

The purpose of this study is to investigate basically the mechanism of heat transfer by the resolution of complex fluid flow inside a sophisticated designed screw dryer for the treatment of sewage sludge by using numerical analysis and experimental study. By doing this, the result was quite helpful to obtain the design criteria for enhancing drying efficiency, thereby achieving the optimal design of a multiple screw type dryer for treating inorganic and organic sludge wastes. One notable design feature of the dryer was to bypass a certain of fraction of the hot combustion gases into the bottom of the screw cylinder, by the fluid flow induction, across the delicately designed holes on the screw surface to agitate internally the sticky sludges. This offers many benefits not only in the enhancement of thermal efficiency even for the high viscosity material but also greater flexibility in the application of system design and operation. However, one careful precaution was made in operation in that when distributing the hot flue gas over the lump of sludge for internal agitation not to make any pore blocking and to avoid too much pressure drop caused by inertial resistance across the lump of sludge. The optimal retention time for rotating the screw at 1 rpm in order to treat 200 kg/hr of sewage sludge was determined empirically about 100 minutes. The corresponding optimal heat source was found to be 150,000 kcal/hr. A series of numerical calculation is performed to resolve flow characteristics in order to assist in the system design as function of important system and operational variables. The numerical calculation is successfully evaluated against experimental temperature profile and flow field characteristics. In general, the calculation results are physically reasonable and consistent in parametric study. In further studies, more quantitative data analyses such as pressure drop across the type and loading of drying sludge will be made for the system evaluation in experiment and calculation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.1-7
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• 2009

This study has been focused on determining the chemical composition of $^{14}C$ - in terms of both organic and inorganic $^{14}C$ contents - in reactor coolant from 3 different PWR's reactor type. The purpose was to evaluate the characteristic of $^{14}C$ that can serve as a basis for reliable estimation of the environmental release at domestic PWR sites. $^{14}C$ is the most important nuclide in the inventory, since it contributes one of the main dose contributors in future release scenarios. The reason for this is its high mobility in the environment, biological availability and long half-life(5730yr). More recent studies - where a more detailed investigation of organic $^{14}C$ species believed to be formed in the coolant under reducing conditions have been made - show that the organic compounds not only are limited to hydrocarbons and CO. Possible organic compounds formed including formaldehyde, formic acid and acetic acid, etc. Under oxidizing conditions shows the oxidized carbon forms, possibly mainly carbon dioxide and bicarbonate forms. Measurements of organic and inorganic $^{14}C$ in various water systems were also performed. The $^{14}C$ inventory in the reactor water was found to be 3.1 GBq/kg in PWR of which less than 10% was in inorganic form. Generally, the $^{14}C$ activity in the water was divided equally between the gas- and water- phase. Even though organic $^{14}C$ compound shows that dominant species during the reactor operation, But during the releasing of $^{14}C$ from the plant stack, chemical forms of $^{14}C$ shows the different composition due to the operation conditions such as temperature, pH, volume control tank venting and shut down chemistry.

• The Korean Journal of Pesticide Science
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• v.17 no.2
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• pp.94-106
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• 2013

The proficiency testing for the residue laboratories of pesticide registration was conducted in order to improve the reliability and the ability for pesticide residue analysis. On October 2011 the testing was carried out using the soil collected and kept as the moistened state for five years, which is expected to very low residue levels of pesticides. The soil was fortified with chlorpyrifos, metolachlor and procymidone in a manner similar to prepare soil sample for indoor soil degradation test, and then sub-samples were prepared for the distribution to participants. Some of them were randomly selected for confirm of homogeneity and to ensure the stability of samples at room temperature. Samples were consisted of two soil treated as different levels, one of which was used to the assesment and another used to confirm. In addition, provide three standard solutions, respectively concentration of 10 mg/L, and untreated soil. Forty seven institutions submitted results. The medians of results were used as the assigned values for pesticide residues. Fitness for purpose standard deviation of proficiency test was calculated by applying 20% RSD as the coefficient of variation allowed in the soil residue test. Z-score was applied for evaluation of individual pesticides, and the average of the absolute value of the Z-score for the overall assessment of pesticides. Laboratories evaluated the absolute value of the Z-score less than 2 to fit the case of chlorpyrifos and procymidone were 44, metolachlor 40.

• Korean Journal of Remote Sensing
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• v.33 no.2
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• pp.135-147
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• 2017

We, for the first time, estimated daily and monthly surface nitrogen dioxide ($NO_2$) volume mixing ratio (VMR) using three regression models with $NO_2$ tropospheric vertical column density (OMIT-rop $NO_2$ VCD) data obtained from Ozone Monitoring Instrument (OMI) in Seoul in South Korea at OMI overpass time (13:45 local time). First linear regression model (M1) is a linear regression equation between OMI-Trop $NO_2$ VCD and in situ $NO_2$ VMR, whereas second linear regression model (M2) incorporates boundary layer height (BLH), temperature, and pressure obtained from Atmospheric Infrared Sounder (AIRS) and OMI-Trop $NO_2$ VCD. Last models (M3M & M3D) are a multiple linear regression equations which include OMI-Trop $NO_2$ VCD, BLH and various meteorological data. In this study, we determined three types of regression models for the training period between 2009 and 2011, and the performance of those regression models was evaluated via comparison with the surface $NO_2$ VMR data obtained from in situ measurements (in situ $NO_2$ VMR) in 2012. The monthly mean surface $NO_2$ VMRs estimated by M3M showed good agreements with those of in situ measurements(avg. R = 0.77). In terms of the daily (13:45LT) $NO_2$ estimation, the highest correlations were found between the daily surface $NO_2$ VMRs estimated by M3D and in-situ $NO_2$ VMRs (avg. R = 0.55). The estimated surface $NO_2$ VMRs by three modelstend to be underestimated. We also discussed the performance of these empirical modelsfor surface $NO_2$ VMR estimation with respect to otherstatistical data such asroot mean square error (RMSE), mean bias, mean absolute error (MAE), and percent difference. This present study shows a possibility of estimating surface $NO_2$ VMR using the satellite measurement.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.360-365
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• 2010

The effects of precooling treatments on the storability of chicon were investigated during modified atmosphere (MA) storage. The forced air cooling showed faster precooling rate that reduced the internal temperature of chicon to $2{\pm}1^{\circ}C$, and the precooling time of forced air cooling was 1/6 of room cooling. The half cooling time was 3 hr 21 min in room cooling and 1 hr 17 min in forced air cooling. Weight loss was less than 0.5% in all treatments both $5^{\circ}C$ and $10^{\circ}C$ MA storage and maintained higher in forced air cooling treatment. The concentration of carbon dioxide, oxygen, and ethylene of $50{\mu}m$ ceramic film packages were observed higher at $10^{\circ}C$ than $5^{\circ}C$. The precooling effect on respiration reduction was not shown at $5^{\circ}C$, but appeared that the gas concentration of precooling treatments showed less carbon dioxide and higher oxygen than non precooling treatment by 9 days after $10^{\circ}C$ storage. Ethylene concentration of precooling treatments showed lower than non precooling treatment until 3 days both $5^{\circ}C$ and $10^{\circ}C$ MA storage. Precooling showed the effect on maintaining visual quality of chicon both $5^{\circ}C$ and $10^{\circ}C$ MA storage. However, the forced air cooling that showed faster precooling rate did not appeared more precooling effect on the visual quality than room cooling because the fast air flow (6.0 m/sec) of forced air cooling hit directly on chicon outer leaves and might cause physical damage to chicon. Although the forced air cooling showed the effect on maintaining quality of chicon, but additional studies should be needed that investigated proper air flow rate and cooling box structure can prevent physical damage by air flow.