• Journal of Korean Society of Environmental Engineers
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• v.34 no.9
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• pp.637-643
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• 2012

This study was carried out to investigate how reversible and irreversible fouling were distributed in the filtration using ceramic membrane of 300 kDa pore size for secondary effluent of wastewater. It was performed by calculating fouling as numerical method for diverse TMPs and measured F-EEM and SEC for raw water, treated water and backwashed water. Water quality was also checked to know whether treated water quality was stable or not. The results showed that reversible fouling formation was increased when lower TMP was applied and it is caused by protein like organic matters having higher molecular weights. The secondary wastewater effluent had diverse molecular weight materials, especially contaminants lower than 0.5 kDa and bigger than 12 kDa. Decreasing TMP induced contaminants above 12 kDa and below 1 kDa to become reversible fouling.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.834-846
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• 2011

The objective of this study is to development of IDFIS system, that are consisted of hydrocyclone, rapid flocculation and inclined settler with chitosan coagulant. As the results of Jar test, a chitosan optimum dosage of 40 mg/L for river sediment, and 5 mg/L for tunnelling wastewater sediment, which these conditions leaves of residual turbidity of less than 5 NTU. Because of the effectiveness of chitosan in removing turbidity was independent on pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, river sediment, river suspended sediment, and tunnelling wastewater sediment. Results indicate that the mean overall removal efficiency of turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. Chitosan is very efficient in removing turbidity in the entire turbidity range examined. IDFIS system would have possibility with compact design, because of the increase of floc size favours the floc settling speed and reduces the settling time.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.35-41
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• 2002

본 연구는 기존 벼 펠렛종자 제조장치의 제조성능 및 제조 벼 펠렛종자 품질향상을 위하여 펠렛재료 공급부, 성형부, 펠렛종자 배출부를 개선 설계 제작하여 그 성능과 제조 벼 펠렛종자 특성을 구명함으로써 직파용 벼 펠렛종자 대량생산을 위한 제조장치 개발의 기초 자료를 얻고자 수행하였으며 그 주요 결과를 요약하면 다음과 같다. 펠렛재료의 일정한 공급과 펠렛재료가 성형 홈으로부터의 이탈하는 것을 줄이고, 펠렛종자의 완전한 배출이 가능하도록 한 벼 펠렛종자 제조장치를 설계·제작하였으며, 벼 펠렛종자 제조장치를 상토 종자혼합비, 성형롤의 회전속도에 따라 실험한 결과 벼 펠렛종자 제조 능력은 성능 개선 전의 펠렛종자 제조장치에 비하언 약 1.7배 향상된 제조능력을 보였으며, 성형률은 최대 약 89 %로 나타나 개선 전의 71%에 비해 18 %정도 성형률이 향상되었다. 그러나, 벼 종자손실률은 약 24% ∼ 49%로 거의 비슷한 수준인 것으로 나타났다. 제조된 벼 펠렛종자의 특성을 분석한 결과 펠렛종자의 구형률은 99.1%로 거의 구형으로 제조됨을 알 수 있었으며, 무게는 제조 직후에는 약 1.70 g, 완전 건조 후에는 1.31 g으로 나타났고, 직경은 약 12.03 mm에서 건조 후 11.53 mm로 축소되었다. 개선 전에 비해 직경과 무게가 약간씩 증가한 것으로 나타났다. 이러한 결과는 재선된 제조장치에서 펠렛재료가 성형롤의 성형 홈에 압축 공급되고, 펠렛재료의 손실도 적었기 때문으로 판단된다. 제조된 한 개의 벼 펠렛종자 내에 포함된 완전 벼 종자의 개수는 상토 종자혼합비가 커질수록 성형롤의 회전속도가 낮을수록 많아지는 것으로 분석되었으며, 모두 펠렛종자 당 평균 약 3 개 이상의 완전 벼 종자를 포함하고 있는 것으로 나타났다. 개선 전에 비하여 펠렛종자 내에 포함된 평균 완전 종자수도 증가하였으며, 3개 이상 완전 종자를 포함한 펠렛종자의 비율도 증가하여 유압에 의한 펠렛재료 공급과 성형롤의 개선효과가 있었던 것으로 보인다. 음지 건조 후 벼 펠렛종자의 압축강도는 약 132 N ∼ 152 N으로 조사되었으며, 개선전에 비하면, 약 30 %가 증가한 것으로 나타났다. 출아율 실험 결과 상토 종자혼합비 6 : 1, 성형롤 회전속도 7 rpm에서 건답직파는 100%, 답수직파는 97 %의 출아율을 보여 만족할 만한 결과를 얻었으나, 그 외의 경우는 거의 90 % 이하의 출아율을 보여 출아율을 높이기 위한 방안이 필요한 것으로 보인다. 본 연구의 벼 펠렛종자 제조장치의 적정운전 조건은 제조된 벼 펠렛종자의 특성과 출아율을 고려해 볼 때 상토 종자혼합비 6 : 1, 성형롤 회전속도 약 7 rpm으로 판단되며, 이 때 제조능력은 시간당 약 65 Kg(펠렛종자 약 39,000 개), 성형률 약 87 %, 종자손실률은 약 30 %, 펠렛종자 내 평균 종자수는 약 5.5 개, 완전 벼 종자 3개 이상 포함 펠렛종자 비율은 약 100 %가 될 것으로 보인다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1524-1532
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• 2015

This study analyzed traffic accident characteristics in Chungcheong Region through the factor analysis, cluster analysis and questionnaire survey using traffic accident analysis data for Chungcheong Region in order to improve Korea's traffic safety level. Based on the analysis results, this study suggests traffic safety technologies suitable for the situation of Chungcheong Region. According to the results of the questionnaire survey carried out for transporters in Chungcheong Region, 'the passage of pedestrians and aged people' and 'a problem of lacking visibility' were the biggest threatening factors of major traffic accidents in Chungcheong Region. The facilities required the most were 'lighting equipment in driving at night', and the expected effect by the equipment installation was high. As a result of the factor analysis and cluster analysis using the traffic accident analysis data, traffic accident risk by city type in Chungcheong Region was higher in rural areas, compared to urban areas. Especially, this study confirmed the risks of pedestrian and agricultural machine traffic accidents were high. Therefore, this study suggests three technologies to improve traffic safety level in Chungcheong Region, based on the analysis results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.795-801
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• 2010

As the fabrication technology of LCDs (Liquid Crystal Displays) advances, the size of mother glass substrates is getting larger, and the fabrication process is becoming finer. Accordingly, the importance of cleaning processes grows in the fabrication process of LCDs. In this study, we have compared and evaluated the particle removal efficiency for three different methods of physical cleaning, which are brush, bubble jet, and aqua/air cleaning. Using the seventh generation glass substrate, the particle removal efficiency has been investigated by changing operation conditions such as a flow rate of deionized water, pressure, contact depth between a brush bristle and a glass substrate, and so forth. In the case of brush cleaning, the cleaning efficiency barely changes after a critical point when the contact depth is varied. While the cleaning efficiency of bubble jet cleaning is almost independent of pressure, that of aqua/air cleaning is affected by pressure up to a critical point, but is not changed after it. We note the brush cleaning is the most effective among the three cleaning methods under our experimental conditions.

• Journal of the Korean Institute of Gas
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• v.17 no.5
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• pp.1-7
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• 2013

In this study, simulation work of HCNG refueling system was performed. The hydrogen was produced from steam reforming process by natural gas. The conversion of natural gas is increased as SCR is increased. but it was no significant difference more than 3 of SCR and fuel throughput is increased as GHSV is increased. Both conversion and fuel throughput levels was optimized when the $1700h^{-1}$ of GHSV. CNG was compressed from low pressure natural gas. For the mixing of $H_2$ and CNG is mixed with the high pressure conditions such as 400bar of $H_2$ and 250bar of natural gas. Single-stage compression was required more power than multi stage. So, multi stage compression was suggested for high pressure compression. We calculated the intermediate pressure to minimize total required power of compressors. The intermediate pressure for $H_2$ and natural gas were derived at 61 and 65 bar, respectively.

• KSBB Journal
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• v.16 no.2
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• pp.133-139
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• 2001

To treat piggery wastewaters containing refractory compounds including nitrogen, biological treatments were investigated. In biological treatment, the removal efficiencies of organics and nitrogen by the activated sludge process and bioreactor using a BACC (Biological Activated Carbon Cartridge) media filled with granular activated carbon were examined. The results were as follows; in the biological process, when the approximate influent BOD concentration of 620 mg/L, through dilution, was treated by the activated sludge process, the process should be operated at a HRT of over 8 days to maintain an effluent BOD concentration of lower than 100 mg/L. In the treatment of piggery wastewater using a BACC bioreactor, when the HRT was 200 hours, the BOD, COD(sub)cr, and TKN removal efficiency of the effluent were 94, 75 and 64.3%, respectively. Comparing the BACC bioreactor with the activated sludge process, when the volumetric loading rate was 0.3 g BOD/L.day, the specific substrate removal rate of BOD was 0.14 g BOD removed/L.day in the activated sludge process which compared with 0.27 g BOD removed/L$.$day in the BACC bioreactor. The BACC bioreactor showed on average a 2-fold higher removal rate and was superior to the activated sludge process in wastewater treatment in terms of variations of loading time and high loading time. Therefore, the BACC process can effectively treat piggery wastewater containing high concentrations of nitrogen and organic compounds.

• Membrane Journal
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• v.8 no.2
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• pp.77-85
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• 1998

To treat effectively EDIR (electrodeposition ion removal) wastewater in terms of CO$_{Mn}$ 1,500~2,000 ppm generated from aluminum painting process, a RO (reverse osmosis) process was designed and installed to recover and reuse the concentrated solvent sent back to the electrocodeposition tank while the permeate reused as rinse water. A RO system in which three polyamide-spiral wound modules ($102\Phi \times 1,016L$ mm) connnected in series had been running to treat 20 m$^3$ in waste volume in 3 days batch operation at the condition of system recovery of 30 %, applied pressure 11.5 $kg_f/cm^2$ and room temperature. During 42 hours continuous operation leading to 5-fold decrease in waste volume, nearly constant permeation flux of 390 l/m$^2$-hr was maintained and the permeate with average CO$_{Mn}$, 300 ppm was obtained which could be used for washing the remaining paint solution in ion-exchange tower instead of demineralized water. Also COD$_{Mn}$ rejection as a function of running time was observed to be in the range of 78~87 % and the observed solvent rejections for ethyl cellusolve, buthyl cellusolve and n-butanol were 79 %, 87 % and 70 %, respectively.

• Membrane Journal
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• v.22 no.1
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• pp.46-53
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• 2012

Low-temperature carbon dioxide stripping by a vacuum membrane stripping technology was studied as a substitute for the stripping process in a conventional aqueous amine process. Composite membranes with $5{\mu}m$ thickness of PDMS (polydimethylsiloxane) dense layer on a PE (polyethylene) support layer were prepared by a casting method and used as a membrane contactor for $CO_2$ stripping. Aqueous amine solutions of 30 wt% MEA (monoethanolamine) were used as absorbents. $CO_2$ flux was examined under various operating conditions by varying the vacuum pressure (60~360 mmHg (abs.)), stripping temperature ($25{\sim}80^{\circ}C$), $CO_2$ loading (0.5~0.7). $CO_2$ stripping flux increased with increasing temperature and $CO_2$ loading as well as decreasing vacuum pressure. PDMS-PE composite membrane has stability for vacuum stripping process compared with PTFE porous membrane.

• Journal of Korean Society of Transportation
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• v.31 no.1
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• pp.3-13
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• 2013

This paper reviews the characteristics of dilemma zone by analysing the influence exerted by actual location of intersection traffic signal on behaviour of drivers approaching signalized intersection in urban area. The analysis of approach speed was based upon a 'before and after' comparison, measured at three sites where the locations of traffic signals were changed. The study demonstrated that, when traffic signal changed to yellow, the scales of dilemma zone were narrowed in case of stopping cars by moving up the starting point of the dilemma zone due to lowered spot speed. On the other hand, in case of passing cars, the end points of dilemma zone were moved further out to the rear due to increased spot speed. Therefore, changing traffic signal locations could make an impact to increase intersection safety through reducing the scales of dilemma zone. This study also found that, in cases involving vehicles with similar approach speeds, spot speeds could be differentiated following the change of signal locations due to the fact that there can be greater differences in both braking point and deceleration rate. Thus, when considering the appropriate measuring of dilemma zone, 'spot speed' rather than 'approach speed' appeared to be more appropriate criterion.