Dishwashing tools such as sponges, scourers, and dishcloths are known to harbor dense and diverse microbial communities, including pathogenic bacteria. In this study, the potential of corona discharge plasma jet (CDPJ) as a disinfectant was tested to improve the hygienic quality of dishwashing tools. For the simulation of microbial contamination, selective pathogenic bacteria (Escherichia coli O157:H7, Staphylococcus aureus, and Pseudomonas putida) were inoculated on selected dishwashing tools (dishcloth, sponge, and scourer) at concentrations of 6.55 to 8.77 log CFU/cm 2 . CDPJ generated at 20 kV voltage and 1.5A current was used for decontamination, whereas a sample-to-electrode distance of 25 mm was maintained during the treatment. Following CDPJ treatment for 5 min, the viable counts of E. coli O157:H7, S. aureus, and P. putida were reduced by 4.30-4.56, 3.71-4.78, and 3.50-3.83 log, respectively. The rates of inactivation were varied among the pathogens, decreasing in the order E. coli O157:H7 > S. aureus > P. putida. Among tested kinetic models, namely log-linear, log-linear with shoulder, and Weibull models, the log-linear with shoulder model was found to be the most suitable model to explain the CDPJ inactivation of the pathogens. In conclusion, CDPJ can be used as a potential sanitizing agent for dishwashing tools.

Since sewer rehabilitation program requires long construction period and enormous capital investment, determination of rehabilitation priorities is important with systematic planning considering appropriate evaluation parameters. In this research, we applied PROMETHEE(Preference Ranking Organization METHod for Evaluations) known as very objective and scientific multi-criteria decision-making analysis, using the weights determined by AHP(Analytic Hierarchy Process) for the selected sewer evaluation items to calculate the rehabilitation priorities for each sewer sub-catchment in basin Gusan 1 of Seoul. Preference functions and preference thresholds were estimated for each criterion of ratio of lack of hydraulic capacity of sewers, defect ratio, ratio of sewers with velocity less than its minimum criteria, and density of sewers in the sub-catchment. As a result, it was found that region d had the first priority among four sub-catchments. For each and every sewer located in region d, we could also rank sewers to be rehabilitated urgently.

Even though sewers have been conventionally designed to prevent from sediment deposition using a specified minimum velocity or shear stress at a particular depth of flow or with a particular frequency of occurrence, it was appreciated that these methods do not consider the characteristics and concentration of the sediment and the specific hydraulic conditions of the sewer with sediment. In this study, a densimetric Froude number formula was suggested considering particle diameter and volumetric concentration of the sediment as well as flow depth and flowrate, based on several domestic field inspections, which was compared with other formulas proposed by previous investigators. When the sediment concentration was not considered, the calibration coefficient of 0.125-1.5 to the densimetric Froude numbers of this study was needed to obtain the similar ones with previous investigators’. For the densimetric Froude number formula obtained with consideration of sediment concentration, the exponent value of term Cv was almost the same as that of previous results and that of d50/Rh was similar for Fr < 2.2.

Benzo[α]pyrene (BaP), a carcinogenic polycyclic aromatic hydrocarbon, is ubiquitous in nature. It is generally found in heat-treated foods like roasted sesame seeds. BaP degradation has attracted attention due to the recalcitrant nature of BaP. In this study, corona discharge plasma jet (CDPJ) was used to degrade BaP on glass slides and in food materials. The plasma discharges were generated using air as working gas under atmospheric pressure conditions and at different currents (1.00, 1.25, and 1.50 A). Optimal BaP degradation was observed upon using CDPJ generated at 1.50 A current and at 15 mm sample-to-electrode distance (STED). Under these conditions, initial BaP concentration on slides was reduced maximally by 87.09% in 30 min. The degradation kinetics were well-fitted by Weibull tail model compared with others. In food commodities (roasted sesame and perilla seeds), the average levels of BaP degradation ranged between 32.96-45.90% following CDPJ treatment for 30 min.

Sodium dodecylbenzen sulfonate (DBS) and linear alkylbenzene sulfonate (LAS) are widely used in dishwashing products. Residual levels of these surfactants are commonly found on the surfaces of dishware following dishwashing. Residual surfactants and detergents can act as potential toxicants and may pose health risks. This study explored the applicability of dielectric barrier discharge plasma (DBDP) for the degradation of residual surfactants in order to minimize their harmful effects. The plasma was generated using 10 kV pulsed DC power supply at different input currents (2.0-3.0 A) and at various inter-electrode gaps (2.0-3.0 mm). Under simulatory treatment conditions, diluted surfactants (DBS and LAS) and DBS-containing dishwashing detergents dispersed on slide glasses were exposed to DBDP for predetermined periods of time. Results indicated that, under optimal treatment conditions of 3.0 A current and 2.0 mm inter-electrode gap, tested surfactants and surfactants in detergents were degraded in the range of 60- 70% following the plasma treatment for 120 min. Modeling of degradation kinetics indicated that Weibull distribution was the best-fit model, and decimal degradation times (δ) were calculated. Pure surfactants were degraded at relatively higher level than surfactants in detergents. Among these anionic surfactants, DBS was more rapidly degraded than LAS by plasma treatment.

If sewage flows for an extended time at low velocities, solids may be deposited in the sewer. Sufficient velocity or tractive force should be developed regularly to flush out any solids that may have been deposited during low flow periods. This study aims to evaluate the periods (T) during which sewage flow greater than the minimum tractive force maintains on a spot in sewer pipe system with lower tractive force or lower velocity than expected in the design step, when a storage tank installed in a place upsteam pours water into the sewer. The effect to T of design factors of storage tank and sewer pipes was evaluated assuming the uniform flow in sewers. When the area of orifice in the storage tank is 0.062 ㎡(or 0.28 m diameter), the maximum T of 31sec was maintained using the usually used preset range of values of several design factors. As the horizontal cross section of storage tank and water depth of storage tank and roughness in sewers increase, T linearly increases. Also, T linearly decreases as the diameter of a sewer pipe increases. Although T gradually decreases as the sewer pipe slope decreases to around 0.005, T decreases sharply when the slope is less than 0.003.

자동차 부품기업들은 플랫폼 기반 대량맞춤형 제품개발과 생산을 통해 비용 절감과 아시아 신흥시장 수주 확대를 목표로 하고 있다. 그러나 신흥시장은 수주량이 적고, 변동성이 높아 목표 달성이 어렵다. 본 연구는 부품기업 관점에서 신흥시장의 수주량 변동성 위험을 적정 수준으로 관리하면서, 영업이익을 극대화할 수 있는 제품 포트폴리오 최적화 방법을 제안한다. 기존 제품 포트폴리오 최적화 접근법과의 차별점은 세가지다. 첫째, 플랫폼 기반 대량맞춤형 생산에 의한 비용 절감효과를 반영한다. 둘째, 수주량 변동성을 고려한다. 셋째, 최소 영업이익률 유지라는 강건성 조건을 반영한다. 실무적으로는 신흥시장 개척의 재무 위험을 최소한도로 유지하면서, 점진적으로 시장점유율을 높여가는 동적 제품개발 전략 수립의 토대를 제공한다. 북미, 유럽, 아시아 18개 업체에 납품하는 다국적 부품제조기업의 파워리프트게이트 제품을 대상으로 실증연구를 수행했다.

Stream of afterglow of an atmospheric pressure plasma can conveniently be used for large scale decontamination operations. In the present study, an afterglow dielectric-barrier discharge air plasma (ADDAP) was used to inactivate Escherichia coli O157:H7 as a model microorganism for studying the plasma inactivation effect. The plasma was generated at current levels in the range of 0.4 - 0.8 A. The power consumption of ADDAP generation system ranged 169.5 - 221.9 W with respect to the current intensity range. At this current level, the temperature observed in the treatment chamber remained less than 30℃. Regarding chemical composition of ADDAP in the treatment chamber, NOx species were predominantly generated. The levels of NOx species increased as the current intensity increases and the maximum NO and NO2, concentrations noted were 6 and 4 ppm, respectively, but that of CO was less than 1 ppm level at 0.8 A. Upon treating with the ADDAP generated at 0.4 - 0.8 A for 180 min, E. coli O157:H7 showed 1.24 – 2.71 log reductions. The inactivation patterns exhibited better fit to Weibull-tail model. The comparison of delta values indicated that superior inactivation effects were observed as the current intensity increased.