• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.202-210
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• 2005

In this study, the fly ash was employed as a possible alternative to the bentonite for its high sorption capacity against cationic heavy metal. To consider the constituents of barrier possibly used, the specimens were mixed with different material contents (fly ash : weathered soil : bentonite), then sorption test was performed. Also the specimens were molded on the wet side of optimum moisture contents like mixing ratio of sorption test and their hydraulic conductivities were measured in flexible-wall permeameters. And to confirm the effect of dissolved cations, the hydraulic conductivity tests were repeated by converting the permeant liquids from water to $Cd^{2+}$ solution. Finally, the Cd-concentration at the effluent was analyzed for 500hrs to compare the effectiveness of each specimen in contaminant retardation. Test results showed that the more the ratio of fly ash increase, the more Kd value increase, and the hydraulic conductivity of weathered soil/bentonite (95:5) mixture was the lowest $(2.9*10^{-8}cm/sec)$, and specimens made of fly ash and fly ash/weathered soil mixtures showed similar hydraulic conductivity. Although the permeant liquid was changed from water to $Cd^{2+}$ solution, the hydraulic conductivity of all specimens except for weathered soil maintained similarly like before. Consequently, the initial breakthrough point of Cd in weathered soil specimen was observed at about 5hrs after the test started while that of fly ash specimens was not observed during the whole test period of 500hrs. The results implied that fly ash had a sufficient retardation capacity against contaminant transport possibly by its high sorption capacity although it showed little effect on the reduction of hydraulic conductivity. Based on the test results, it could be concluded that the fly ash can be possibly used as a suitable barrier material in containment system to attenuate the contaminant transport for its high retardation capacity and for the low cost.

• Journal of Korean Society of Transportation
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• v.21 no.2
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• pp.95-105
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• 2003

Because the basic assumptions of deterministic user equilibrium assignment that all network users have perfect information of network condition and determine their routes without errors are known to be unrealistic, several stochastic assignment models have been proposed to relax this assumption. However. it is not easy to solve such stochastic assignment models due to the probability distribution they assume. Also. in order to avoid all path enumeration they restrict the number of feasible path set, thereby they can not preciously explain the travel behavior when the travel cost is varied in a network loading step. Another problem of the stochastic assignment models is stemmed from that they use heuristic approach in attaining optimal moving size, due to the difficulty for evaluation of their objective function. This paper presents a logit-based stochastic assignment model and its solution algorithm to cope with the problems above. We also provide a stochastic user equilibrium condition of the model. The model is based on path where all feasible paths are enumerated in advance. This kind of method needs a more computing demand for running the model compared to the link-based one. However, there are same advantages. It could describe the travel behavior more exactly, and too much computing time does not require than we expect, because we calculate the path set only one time in initial step Two numerical examples are also given in order to assess the model and to compare it with other methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.766-771
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• 2016

This study examined the long-term durability of PC boxes, which was manufactured by low-carbon eco-friendly concrete using an alternative binder to cement and alternative fine aggregate to sand and microwave heat curing system to reduce the construction cost of a near-surface transit system. Based on the test results, the initial compressive strength of microwave heat cured concrete was higher than that of the steam cured concrete, but those were similar in the long-term age. In addition, there was no significant difference between the two curing conditions in the chemical resistance and the freeze-thawing resistance, and the chloride ion penetration level of the concrete cured by two methods was very low. Therefore, low-carbon eco-friendly concrete and microwave heat curing technology are expected to contribute to the economic construction of a near-surface transit system, and reduce carbon dioxide emissions and environmental impact.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2945-2950
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• 2015

While perfluoroalkane (PFA), a liquid state nucleating agent for a rigid polyurethane foam (RPUF) to enhance the thermal insulation property, has the excellent nucleating characteristics, it is very expensive as well as environmentally harmful due to the fluoride compound. Many researches, therefore, have been performed to develop the alternative nucleating agents to replace PFA. In the present work, a multi-wall carbon nanotube (MWCNT) was used as a sloid state nucleating agent, and thereby the effects on the property changes of the RPUF were carried out. Average cell size decreased from 165.6 for base RPUF to $162.9{\mu}m$ and cell uniformity was also enhanced, showing the standard cell-size deviation of 45.6 and 35.2, respectively. While k-factor of base PUF was $0.01763kcal/m.hr.^{\circ}C$, that of the sample with 0.01 phr MWCNT showed 1.02% reduced value of $0.01745kcal/m.hr.^{\circ}C$. Though the compressive yield stress is nearly the same as $0.030{\times}105Pa$ for the both samples, initial modulus of the sample with 0.01 phr MWCNT was higher than that of base sample. it was considered as the results that small amount of MWCNT could play a sufficient role as the effective nucleating agent for RPUF, showing that an echo-friendly RPUF with reduced-cost could be fabricated, which has an enhanced thermal and mechanical properties.

• Journal of Biosystems Engineering
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• v.3 no.2
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• pp.114-125
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• 1978

The use of petroleum fuels in grain drying causes problems of high cost and management. To solve these problems, it is required to study on soLar energy as an alternative to petroleum fuels for grain drying. The purposes of this study were to find out the optimum received area and air flow rate of a flat-plate solar air collector for grain drying and to assess its effects on grain drying with a small grain bin. The results of this study are summarized as follows ; 1. The calculated optimum tilt angles of the collector in the summer and autumn drying seasons were 20 and 50 degress, respectively, in suwon area. 2. The outlet temperature of the collector was $36^\circ C$ on the daily average with the maximum of $36^\circ C$ at 12:00 o clock. Solar radiation on the collector surface was 1.04 ly( 1 langley = 1 cal/$cm^2$) per minute on the daily average and 1.30 ly per minute on the maximum at 11:00am. The thermal efficiency of the collector was 62.4 percent on the daily average, and the air flow-rate per unit receiving are was 1.03 $m^3$/min/$m^2$.4. The calculated optimum receiving area and the air flow-rate per unit cubic volume for paddy in autumn drying season was 2 $m^2$ and 2$m^3$/min , respectively. 5. not significantly difference in the collector efficiency was appeared between the rotating and fixed type of solar collector. 6. For drying of wheat with 0.6 meter of the depth in the bin, approximately 9 hours were required to reduce the moisture content from 21.6% to 13% with air follow rate of 5 $m^3$/min an initial moisture per cubic meter of wheat and with air temperature of $52^\circ C$. 7. In the drying test of rough rice with a turning operation in a grain bin approximately 21 hours were required to reduced the moisture from 21% to 14.5% with airflow rate of 2 $m^3$/min per cubic meter of rice and the air temperature of $43.5^\circ C$. 8. Over-drying at the bottom and less -drying at the top of the grain mass was resulted from the high -temperature of drying air which was obtained from the flat-plate solar collector in this test. An appropriate operation should be prepared for the uniform moisture of the grain in the bin.

• Korea Journal of Hospital Management
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• v.20 no.3
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• pp.45-55
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• 2015

While the influence of healthcare accreditation system to the quality improvement of hospitals has more increased, regarding the preparation costs for healthcare accreditation, it has never been empirically studied about the costs that are actually invested by hospitals. This study is going to determine the difficulties in the preparation process of accreditation and details of accreditation preparation costs for hospitals that participated in the healthcare accreditation system and acquired accreditation. The survey was performed in a self-reported form from February 28 to March 21 2014 for 189 acute hospitals accredited as a hospital from 2011 to February 2014. Of all questionaries of survey participants, 98 were recovered; the response rate was 51.9%. A total of 40 questionnaires were used except for 58 containing insincere answers. Main findings are followings: Firstly, findings showed that advanced general hospitals spent the most statistically significantly highest in terms of equipments and total costs among cost items for accreditation preparation. When accreditation preparation costs items were classified according to classification of hospitals, advanced general hospitals spent the most statistically significantly highest in the equipments and total costs. Also in terms of regional, Gyeonggi, Incheon regions were found to spend statistically significantly higher costs in the equipments costs. Secondly, as a result of the survey in the distribution of the total accreditation preparation costs, advanced general hospitals have disbursed the most out of all. However, the result in hospitals does not show significant difference to the expense of advanced general hospitals and that especially other regional hospitals spent higher costs. As such, all hospitals are under a heavy burden of higher costs on accreditation preparation, especially hospitals. The build-up of infrastructures by hospitals through an accreditation system consequently led to a higher initial investment; if the accreditation system is effective in improving the quality of health care and patient safety, appropriate responses are needed. In other words, financial support for investment costs needs to be given to allow hospitals to actively participate in the accreditation system.

• Journal of Chest Surgery
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• v.30 no.11
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• pp.1092-1096
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• 1997

Thromboelastography(TEG) enables a global assessment of hemostatic function to be made from a single blood sample, documenting the interaction of platelets with protein coagulation cascade from the time of the initial platelet-fibrin interaction, through platelet aggregation, clot strengthening and fibrin cross linking to eventual clot Iysis. Thirty-five patients(mean age 34$\pm$ 12) undergoing open heart surgery from April 1st, 1996 to August 31th, 1996 were investigated at preoperatively and immediate, one hour, and 24 hours after cessation of cardiopulmonary bypass using TEG. Comparisons were made between classic hematological indices and TEG data. There were statistically significant correlation between maximal amplitude(MA) and platelet count before CPB, activating clotting time(ACT) and TEG date(R time, K time and a angle) at 24-hour after CPB. The data on the predictive accuracy for postoperative bleeding at 24-hour after CPB, the TEG was significantly better than ACT(57%) or the coagulation profiles(43%) as a predictor of postoperative bleeding, with an accuracy rate of 100% (P=0.0043). In conclusion, TEG seems to be easy to use, clinically accurate, cost effective and provides data which can effectively manage a patient's hemostasis.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.3
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• pp.77-87
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• 2001

Composting is a cost-effective and environmentally-sound technology to treat soils contaminated with hazardous organic pollutants. Pollutants to be treated are as follows: explosives, phenolic compounds, PAHs, petroleum hydrocarbons, pesticides, and etc. Composting systems are windrow, static pile, and in-vessel. Design and operational parameters of composting are aeration modes, temperature, moisture content, nutrient supplement, amendment added, and etc. Appropriate oxygen concentration of composting for contaminated soils are 5~15%, while some compounds are degraded well at the low $O_2$ concentration of 2~5%. The most diverse microorganisms live in the temperature of $25{\sim}40^{\circ}$. 50~90% of the soil field capacity is the moisture content not to make a problem in composting. Assuming a bacterial chemical equation is $C_{60}H_{87}O_{23}N_{12}P$, theoretical C : N : P from bacterial chemical portion is approximately 20 : 5 : 1. It should be noted that the ratio does not apply to the total organic carbon measured in a waste because not all carbon metabolized by bacteria is synthesized to new cellular material. Initial C/N ratio of 25~40 is optimum. It is more economical to recycle soils or composts than to add commercial microbes.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.240-248
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• 2006

In this study, a retrofitting BNR process that was modified for the economical applicability was proposed and evaluated in the pilot plant($50m^3/d$). At the same time the bacterial community structure was investigated in the pilot plant by using FISH(fluorescent in situ hybridization) method. Economically 16% of the initial construction cost for the proposed process(introduction of a biological nutrient removal process of $60,000m^3/d$ scale basis) was reduced due to the absence of a bioreactor. Water treatment efficiencies and maintenance facilities of the modified process were satisfied with the strengthened discharge permits in Korea throughout a long term pilot plant operating including a winter season. Bacterial populations in the pilot plant and in the control plant(A2/O process, B SIP(Sewage Treatment Plant)) were remained uniformly during the test period, but bacterial structure in the bioreactor was changed drastically. Proportions of ${\beta}$-proteobacteria group including soil bacteria which play a important role in wastewater treatment increased $25{\sim}607%$ in population.

• Journal of the Korea Society for Simulation
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• v.24 no.1
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• pp.35-43
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• 2015

This research proposed a new method to evaluate the objective validity to launch smart transportation services that various stakeholders are complicatedly inter-connected. First of all, we have designed the fundamental business model to form the smart transportation services and defined the stakeholders taking part in the services. Also, the criteria to evaluate the economical validity has been proposed based on the relationship among stakeholders. Especially, in the case EV drivers and charging service providers, the economical validity depends on the scale of spreading. Therefore, we have compared the two extreme scenarios, the poor and stable level of EV spreading. According to the result, it may be said that EV drivers and charging service providers cannot be guaranteed the economical validity due to the burden of initial investment. On the contrary to this, suppliers of EV and charging gears may secure more than a certain level of profit. In addition, the government may have great profit due to reducing the CO2 emission and cost for importing energy sources. Therefore, it is needed to enhance the level of supporting EV drivers and charging service providers at the first stage. Also, the impact of the ratio of EV and charging service stations on the economical validity of smart transportation should be further investigated.