• Clean Technology
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• v.12 no.4
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• pp.244-249
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• 2006

The photocatalytic degradation of trichloroethlylene (TCE), has been investigated over $TiO_2$ photocatalysts irradiated with solar light. The effect of operational parameters, i.e., initial TCE concentration, $TiO_2$ concentration, pH and additives ($H_2O_2$, persulphate($S_2O{_8}^-$)) on the degradation rate of aqueous solution of TCE has been examined. The results presented in this work demonstrated that degradation of the TCE with $TiO_2/solar$ light was enhanced by augumentation in $TiO_2$ loading, pH, and adding additives but was inhibited by increase in initial TCE concentration. Also individual use of $H_2O_2$ was far more effective than using persulphate in TCE removal efficiency. Furthermore, the relative toxicity with a $solar/TiO_2/H_2O_2$ system was about 15% lower than with a $solar/TiO_2/persulphate$ system and about 35% lower than with a $solar/TiO_2$ system within a reaction time of 150 min, respectively.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.393-402
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• 1995

The structural analysis of the reactor coolant system mainly consist of too fields. The one is the static analysis considering the impact of pressure and temperature built up during normal operation. The other is the dynamic analysis to estimate the impact of postulated events such as the seismic loads or postulated branch line pipe breaks event. Since the most important goal of the RCS structural analysis is to prove the safety of the RCS during normal operation or postulated events, a widely proven theory having enough conservatism is adopted. The load occurring on the RCS during normal operation is considered as the basic design loading condition throughout whole plant life time. The most typical characteristic of the RCS during normal operation is the thermal expansion of the RCS caused by reactor coolant with high temperature and pressure. Therefore, the exact estimation on the thermal movement of the RCS is needed to get more clear understanding on the thermal movement behavior of the RCS. In this study, the general structural analysis concept and modeling method to evaluate the thermal movement of the RCS under the normal plant operation condition are presented. To discuss the validation of the suggested analysis, analysis results are compared with the measured data which ore referred from the standardized 1000 MWe PWR plant under construction.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.520-526
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• 2015

Reinforcing bar splices are inevitable in reinforced concrete structure. In these days, there are three main types of splices used in reinforced concrete construction site - lapped splice, mechanical splice and welded splice. Low cost, practicality in construction site, less time consuming and high performance make gas pressure welding become a favorable splice method. However, reinforcing bar splice experiences thermal loading history during the welding procedure. This may lead to the presence of residual stress in the vicinity of the splice which affects the fatigue life of the reinforcing bar. Therefore, residual stress analysis and tensile test of the gas pressure welded splice are carried out in order to verify the load bearing capacity of the gas pressure welded splice. The reinforcing bar used in this work is SD400, which is manufactured in accordance with KS D 3504. The results show that the residual stresses in welded splice is relatively small, thus not affecting the performance of the reinforcing bar. Moreover, the strength of the gas pressure welded splice is high enough for the development of yielding in the bar. As such, the reinforcing bar with gas pressure welded splice has enough capacity to behave as continuous bar.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.4
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• pp.91-97
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• 2008

The objective of this research is to investigate the effect of the addition of granular activated carbon (GAC) and granular sludge on the performance of upflow anaerobic sludge blanket (UASB) reactors for treating leachate. For the control reactor, sludge obtained from an anaerobic digester was used as a seed material. On the other hand, GAC and granular sludge were incorporated with the seed sludge in the GAC reactor and the Granule reactor, respectively. The shortest acclimation period was observed in the Granule reactor. The GAC reactor also gave comparable performance to the Granule reactor at the beginning of operation. However, as the adsorptive capacity of GAC was exhausted, the effluent COD concentration increased gradually. Once the systems were stabilized, the GAC reactor showed slightly better results than the other two reactors in terms of chemical oxygen demand (COD) removal. COD removal in all reactors was more than 90% at hydraulic retention time of 1.0 day. Furthermore, GAC reactor showed little variation in COD removal rate and remained at 95% with organic loading rate (OLR) of 4.0 to $8.2kg\;COD/m^3.d$. Initial operating period was reduced by the addition of granular sludge, while the treatment efficiency was enhanced by the addition of GAC.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.619-627
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• 2000

Biodegradation of the C. I. Reactive Blue 114 was investigated in an upflow anaerobic sludge blanket (UASB) reactor. Important parameters studied include dye concentration, the kind and concentration of carbon source, hydraulic retention time (HRT), and influent pH. Glucose was found to be a better co-substrate than the mixture of volatile fatty acids (VFAs), although its concentration did not affect dye removal efficiency in the range of $1000{\sim}3000mg/{\ell}$. When HRT increased from 6 hr to 24 hr, dye removal efficiency increased up to 12 hr and remained almost constant thereafter at about 40%. When influent pH was varied in the range of 6.0~8.0, the effluent pH was varied in the range of 6.8~7.5 with maximum efficiency at pH 7.0. The highest dye removal rate obtained was $52mg/{\ell}{\cdot}day$, while the maximum dye load to meet the discharge limit of color intensity was estimated to be $46mg/{\ell}{\cdot}day$ at HRT of 12 hr and an influent glucose concentration of $2200mg/{\ell}$.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.373-381
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• 2012

An automatic flow and water quality monitoring system was applied to estimate pollutant loads to an urban stream during storm events in DTV (Daeduk Techno Valley), Daejeon, Korea. The monitoring system consists of rainfall gage, ultrasonic water level meter, water quality sensors for DO, temperature, pH, conductivity, turbidity and automatic water sampler for further laboratory analysis. All data are transmitted through on-line system and the monitoring system is designed to be controlled manually in the field and remotely from laboratory computer. Flow rates were verified with field measurements during storm events and showed good agreements. Automatic sampler was used to collect real time samples and analyzed for BOD, COD, TN, TP, SS and other pollutant concentrations in the laboratory. SWMM (Storm Water Management Model) urban watershed model was applied and calibrated using the observed flow and water quality data for the study area. While flow modeling results showed good agreement for all events, water quality modeling results showed variable levels of agreement. These results indicate that current options in the SWMM model to predict pollutant build up and wash-off effects are not sufficient to satisfy modeling of all the rainfall events under study and thus need further modification. This study showed the automatic monitoring system can be used to provide data to assist further refinement of modeling accuracy. This automatic stormwater monitoring and modeling system can be used to develop basin scale water quality management strategies of urban streams in storm events.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.10
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• pp.583-589
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• 2015

This study was performed to evaluate the feasibility of anaerobic pretreatment for the leachate solubilized from thermal hydrolysis of sewage sludge cake. Overall process for the treatment of sludge cake consists of thermal hydrolysis, crystallization of magnesium, ammonium, and phosphate (MAP) for the leachate and anaerobic digestion of supernatant from MAP crystallization. The experimental evidence showed that the optimum ratio of Mg : P for the struvite crystallization of leachate solubilized from thermal hydrolysis of sludge cake was 1.5 to 1.0 as weight basis at the pH of 9.5. With this operational condition, the removal efficiencies of ammonia nitrogen and phosphorous achieved 50% and 97%, respectively. The mesophilic batch test showed that the ultimate biodegradability of the supernatant from MAP crystallization reached 63% at S/I ratio of 0.5. The readily biodegradable fraction of 90% ($S_1$) of the MAP supernatant BVS (Biodegradable Volatile Solids, $S_0$) degraded with $k_1$ of $0.207day^{-1}$ for the initial 17 days where as the rest slowly biodegradable fraction ($S_2$) of 10% of BVS degraded with $k_2$ of $0.02day^{-1}$ for the rest of the operational period. Semi-Continuously Fed and Mixed Reactor (SCFMR) was chosen as one of the best candidates to treat the MAP supernatant because of its total solids content over 6%. Maximum average biogas production rates reached 0.45 v/v-d and TVS removal efficiency of 37~41% was achieved at an hydraulic retention time (HRT) of 20 days and its corresponding organic loading rate (OLR) of 1.43 g VS/L-d.

• Journal of Ginseng Research
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• v.41 no.4
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• pp.487-495
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• 2017

Background: Although flowers of Panax ginseng Meyer (FPG), Panax quinquefolius L. (FPQ), and Panax notoginseng Burk. (FPN) have been historically used as both medicine and food, each is used differently in practice. Methods: To investigate the connection between components and enhancing immunity activity of FPG, FPQ, and FPN, a method based on a rapid LC coupled with quadrupole time-of-flight MS and immunomodulatory activity study evaluated by a carbon clearance test were combined. Results: According to quantitative results, the ratio of the total content of protopanaxatiol-type ginsenosides to protopanaxadiol-type ginsenosides in FPN was 0, but ranged from 1.10 to 1.32 and from 0.23 to 0.35 in FPG and FPQ, respectively. The ratio of the total content of neutral ginsenosides to the corresponding malonyl-ginsenosides in FPN ($5.52{\pm}1.33%$) was higher than FPG ($3.2{\pm}0.64%$) and FPQ ($2.39{\pm}0.57%$). The colorimetric analysis showed the content of total ginsenosides in FPQ, FPG, and FPN to be $13.75{\pm}0.60%$, $17.45{\pm}0.42%$, and $12.45{\pm}1.77%$, respectively. The carbon clearance assay indicated that the phagocytic activity of FPG and FPQ was higher than that of FPN. A clear discrimination among FPG, FPQ, and FPN was observed in the principal component analysis score plots. Seven compounds were confirmed to contribute strongly by loading plots, which may be the cause of differences in efficacy. Conclusion: This study provides basic information about the chemical and bioactive comparison of FPG, FPQ, and FPN, indicating that protopanaxtriol-type ginsenosides and malonyl-ginsenosides may play a key role in their enhancing immunity properties.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.321-330
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• 2011

Recently, the effects of high temperature and fiber content on the residual mechnical properties of high-strength concrete were experimentally investigated. In this paper, residual mechanical properties of concrete with water to cement (w/c) ratios of 0.55, 0.42 and 0.35 exposed to high temperature are compared with those obtained in fiber reinforced concrete with similar characteristics ranging from 0.05% to 0.20% polypropylene (PP) fiber volume percentage. Also, factors including pre-load levels of 20% and 40% of the maximum load at room temperature are considered. Outbreak time, thermal strain, length change, and mass loss were tested to determine compressive strength, modulus of elasticity, and energy absorption capacity. From the results, in order to prevent the explosive spalling of 50 MPa grade concretes exposed to high temperature, more than 0.05 vol. % of PP fibers is needed. Also, the cross-sectional area of PP fiber can influence the residual mechanical properties and spalling tendency of fiber reinforced concrete exposed to high temperature. Especially, the external loading increases not only the residual mechanical properties of concrete but also the risk of spalling and brittle failure tendency.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.245-252
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• 2004

Two biofilter tests were conducted under different operating conditions. Test # 1 was performed to treat VOCs generated from a paint booth. The second test was performed to treat VOCs generated from chemical manufacturing processes. The volume of biofilter media was 4.3 $m^3$. For the test # 1, the biofilter was operated for 30 days with 99.9% reduction ratio. Range of temperature of each stage of the biofilter media was measured between $34^{\circ}C$ and $73^{\circ}C$. All the temperatures of stages reduced gradually after the initial dramatic increase. For the test # 2, the biofilter experiment was conducted for 14 days. In this case, the biofilter was installed outdoor and the experiment was performed during wintertime. Therefore, temperature management for the biofilter was needed. Seven-centimeter thick fiberglass insulation and $150^{\circ}C$ steam heating were used to overcome the outside freezing cold weather during test # 2. Temperature of stage # 5 was measured the highest and that of stage # 1 was the lowest. More acclimation time and test period was needed to determine the maximum loading rate.