• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.113-118
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• 2014

So many nationwide drinking water treatment plants are under much difficulties by new reinforced discharged effluent standards. Generally, the sludge at thickener should be retended for a long time during usual days. Sometime, the soluble manganese and chloroform may be formed under the anaerobic condition in the sludge thickener when the sludge retention time is longer with low turbidity. This phenomenon results in difficulties to keep regulatory level of the discharged effluent. It was necessary to improve the operation conditions and process itself in order to meet water quality standard recently reinforced. For an effort to overcome the problems, a sludge aeration was successfully implemented into the thickening process. Sludge aeration prevent particle oxidated Manganese eluting soluble de-oxidated Manganese, excrete formated Chloroform from effluent to air, and improve sludge settling through homogenized sludge particle. We aerated sludge at the conventional water treatment plant, measured Manganese and Chloroform of clarified water at upper sludge, and solid-fluid interface height of sludge in mass cylinder. As a result, contaminant's concentrations of the final effluent was much decreased : 41% of manganese, approximately 62% of chloroform and 35% of sludge volume, compared with non-aeration sludge.

• Analytical Science and Technology
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• v.23 no.5
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• pp.465-476
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• 2010

In this study, a number of volatile organic compounds (VOCs) including benzene, toluene, p-xylene, styrene, and methyl ethyl ketone were analyzed from samples collected in ambient air and under the field conditions. These samples were analyzed independently by two different set-ups for VOC analyses, i.e., between [1] gas chromatography/flame ionization detector with tube sampling - (F-T system) and [2] gas chromatography/mass spectrometer with bag sampling (M-B system). The analytical results derived by both systems showed fairly similar patterns in relative sense but with moderately large differences in absolute sense. The results of M-B system were high relative to F-T system with the F-T/M-B ratio below 1. If the relative biases of the two measurement techniques are derived in terms of percent difference (PD) in concentration values, the results were generally above 35% on average. A student t-test was applied to investigate the statistical significance of those differences between the systems. The results of both analytical systems were different at 95% confidence level for toluene, p-xylene, styrene, and methyl ethyl ketone (P < 0.043). However, F-T and M-B systems showed strong correlations for toluene and p-xylene. The observed bias is explained in large part by such factors as the differences in standard phases used for each system and the chemical loss inside the bag sampler.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.5
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• pp.449-460
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• 2014

Since the emergence of domestically produced automobiles in 1964, the number of automobiles in circulation in South Korea has increased constantly. With this rapidly increasing number of automobiles, automobile-induced environmental pollution has become an issue of great concern, especially with regard to air pollution. Of the carbon composites contained in automobile exhaust gas, PAHs are known to be carcinogenic and highly deleterious to humans and thus need to be urgently mitigated. To address this issue of PAHs, this study was conducted to estimate qualitative of particulate PAHs contained in carbon composites in automobile exhaust gas, by capturing all particulate matter discharged from the latter. To allow for differentiated analyses, the automobiles investigated were divided into 4 groups: gasoline vehicle, motocycle, diesel vehicle, and LPG vehicle. Samples were analyzed using two methods. First, in-depth analysis was performed on organic carbon (OC) and elemental carbon (EC) composites with analysis parameters, using the Thermal Optical Transmittance Method (NIOSH 5040). Second, for the examination of particulate PAHs, GC/MSD was used to analyze the 16 PAH species specified by the Environmental Protection Agency (EPA). The analyses yielded the findings that diesel vehicles had the highest mass concentration ($2,007{\mu}g/m^3$), followed by motocycle ($1,066{\mu}g/m^3$), LPG vehicle ($392{\mu}g/m^3$), and gasoline vehicles ($270{\mu}g/m^3$). The highest carbon concentrations in total particulate matter by vehicle weight were produced from LPG vehicle (79.8%), followed by gasoline vehicle (77.4%), motocycle (69.8%), and diesel vehicle (59.1%).

• Korean Journal of Food Science and Technology
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• v.13 no.2
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• pp.153-159
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• 1981

A study was carried out to determine the optimal sterilization conditions of cooked rice packed in retort pouch and processed in a steam-air system retort. The cooked rice packed in retort pouch in various thickness (15, 20 and 25 mm) was processed at various heating temperature (110, 115 and $120^{\circ}C$) with $F_0$-value 6.0. In order to evaluate quality change during the thermal prosessing, C-values, based on z-value $33^{\circ}C$ and $F_0$ value 6.0, were also calculated at surface, center and mass average temperatures. Subsequent storage study revealed that the cooked rice packed in 15 mm thickness and processed at $120^{\circ}C$ with$F_0$-value 6.0 could be held without any spoilage and color change, when stored for 6 months at $38{\pm}1^{\circ}C$ under saturation humidity.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.71-79
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• 2010

The influence of fines of the frost susceptibility of subgrade soils were established by laboratory freezing system test simulating closely the thermal conditions in the field. During the winter season, the climate is heavily influenced by the cold and dry continental high pressure. Because of siberian air mass, the temperature of January is $-6{\sim}-7^{\circ}C$ on average. This chilly weather generate the frost heaving by freezing the moisture of soil and damage potential of the road structure. In the freezing soil, the ice lenses increase the freeze portion of soil by absorbing the ground water with capillary action. However, the capillary characteristics differ from the sort of soil on the state of freezing condition. In the current design codes for anti-freezing layer, the thickness of anti freezing layer is calculated by freezing depth against the temperature condition. Therefore, they have a tendency of over-design and uniform thickness without the considerations of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential for studying the appropriateness and bearing capacity besides the seasonal and mechanical properties of pavement materials to take a appropriate and reasonable design of the road structure. In this Paper, the evaluation of frost susceptibility was conducted by means of the mechanical property test and laboratory freezing system apparatus. The temperature, heaving amount, heaving pressure and unfrozen water contents of soil samples, the subgrade soils of highway construction site, were measured to determine the frost susceptibility.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.100-105
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• 2016

The use of 3D scanners has increased gradually according to increasing 3D printer applications. The precision inspection of car parts or electronic components is an important issue not only in the field of mass production, but also in small-scale production. Recently, 3D scanner equipment efficiency and recognition technology has been improved continuously. On the other hand, the spraying time to prepare 3D scanning is time-consuming and has environmental problems. Therefore, an automatic spray system has been in demand by the manufacturing industry. Automatic spray equipment was newly developed for the preparation of a 3D scanner. In this research, the automatic spray system guarantees uniform spray operation. To determine the optimal spray parameters, various spraying methods, solutions and conditions were tested and compared with the experiments. The preparation time for 3D scanning was reduced to 1/10 compared to the manual spraying time, and indicates the optimal spraying conditions through a comparison of various spray coating conditions.

• Korean Journal of Environmental Agriculture
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• v.20 no.3
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• pp.135-142
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• 2001

Compostable household wastes(mainly food wastes), after waste papers and cardboard being removed, were daily fed into small bins and mixed thoroughly while the air was supplied into the bin. Three small bins were employed: in case I, only recycled compost was composted, after being once fed at the beginning of composting, in case II, compostable household wastes(less than 50 mm) torn roughly by the hands with recycled compost, and in case III, compostable household wastes(less than 2 mm) ground by a kitchen mixer for vegetables with recycled compost. The straight-line was maintained between the wet or the dry residual mass of composting mixture versus composting time date(the coefficient of determination $R^2{\geq}0.98$ for the wet and $R^2{\geq}0.90$ for the dry). The decomposition rate of each composted material was estimated during composting. The total weight reduction rate after 30 days was 67.86% and 66.14% for case II and III, respectively. For case II, the daily weight reduction 6.82% and the daily decomposition rate 8.81% with the composting mixture, but the daily weight reduction rate was 56.43% and the daily decomposition rate 19.26% with only compostable household wastes. For case III, the daily reduction rate was 6.93% and the daily decomposition rate 7.70% with the composting mixture, but the daily weight reduction rate was 53.30% and the daily decomposition rate 22.95% with only compostable household wastes. The physicochemical characteristics of composting mixture did not show much difference between case II and III as was expected.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.4 s.59
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• pp.227-231
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• 2006

Wrinkle formation is mainly attributed to the environmental factors such as UV rays, air pollution, smoking and stress etc. Especially, UV rays induce premature skin aging which is characterized by deep wrinkle, leathery dryness etc. Recently, researches on the wrinkle formation and its prevention have been the main theme in cosmetics fields. We have studied the various plant extracts having anti-wrinkle effects and finally showed that Noni (Morinda citrifolia) extracts have the efficacy of promoting the type I collagen synthesis in normal human fibroblast, using PICP assay. We purified one active compound from Noni extracts and identified its structure. It was identified as 6,7-Dimethoxy-2H-1-Benzopyran-2-one; scopoletin by $^1H-NMR,\;^{13}C-NMR,$ IR, Mass analysis. Scopoletin increased collagen synthesis in a dose dependent manner (89.5% at $0.2{\mu}g/mL$). In order to verify the anti-aging effectiveness of the cream containing 3% noni extracsts, we performed the in vivo test with some female volunteers for 12 weeks. It reduced the signs of aging, especially face wrinkles. From these results, we conclude that the noni extracts could be used as an useful anti-wrinkle agent.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1998.10a
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• pp.83-92
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• 1998

오존 경보제와 예보제의 실시가 오존 오염에 관한 일반인의 관심을 증폭시키는 중요한 계기가 되었음에도 우리 연구계와 정책 당국의 대응은 이에 훨씬 못미치고 있다. 1990년 이래 학회지 관련 논문 편수는 연간 1∼3편에 그치고 있고, 다른 이차오염 현상과 달리 정책 당국은 여전히 지원을 고려하지 않고 있다. 오존 연구가 뿌리를 내리지 못한 가운데 강행된 경보제와 예보제의 와중에 책임을 떠맡은 지방자치단체는 조급하게 노련한 예보 모델을 찾고 있고 충분한 검토도 없이 외국의 사례에서 대책을 구하고 있다. 논란이 되고 있는 오존 예보의 부정확성은 모델 선택의 문제가 아니라 모델 이용이 잘못된 때문이다. 현재 오존 대책의 일환으로 검토되고 있는 차량 부제 실시와 같은 단기 대책은 역효과를 낼 수 있다는 연구결과도 있다. 선진국의 오존 연구는 도시 규모에서 지역 규모로 확대되고 있고, 구츰 등 액상반응의 효과 규명과 1 kin 이하 미세 변화 모델링이 시도되고 있고, 지구 단위 대류권 실험의 일환으로 태평양 상공의 오존과 오존 전구물질의 대기화학이 조사되고 있다. 우리는 우선 우리의 오존 문제를 정확히 이해하도록 노력하여야 한다 합리적 계획 아래 체계적으로 접근하여 갈 때 당장은 아니지만 우리의 오존에 대한 이해가 깊어갈수록 예보의 정확성은 향상될 수 있다. 많은 비용과 노력이 필요한 오존 대책의 시행은 충분히 신중하여야 한다. 서울과 같은 대도시라면 적합한 수치모델을 구비하여 효과를 점검할 수 있어야 한다. 일부에서는 예보의 정확성을 높일 수 있는 방안의 하나로 수치모델 이용을 거론하고 있으나 수치모델은 매일의 예보와 같이 일상적 목적을 위하여 사용될 수 있는 모델이 아니며, 현재와 같이 기초가 갖추어져 있지 않은 상황에서는 더욱 그러하다. 정상적 모델 이용이 가능할 수 있도록 배출원 자료 체계를 갖추어야 하고, 서을 등 특징적 지역에 대하여서는 집중적 현장 조사를 실시하여야 한다.3)와 NAS(National Academy of Sciences, 1983), 미국에서 발행되는 정부 지침서 (Federal Register)에 고시된 내용 등을 토대로 하였다. 연구는 당면현실로 다가온 정보화 및 세계화의 기업환경에서 예견되는 몰입(committment)의 약화에 대한 치유방안으로서, 정보화된 경영모의게임의 기업 교육훈련 시스템(Business Training System)으로의 발전 가능성을 제시한다 하겠다.암시하며, 따라서 우리 교육문화에 맞는 재택수업 형태의 개발이 시급함을 제시한다고 하겠다.column density of HCaN is (1-3):n1014cm-2. Column density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.업순서들의 상관관계를 고려하여 보다 개선된 해를 구하기 위한 연구가 요구된다. 또한, 준비작업비용을 발생시키는 작업장의 작업순서결정에 대해서도 연구를 행하여, 보완작업비용과 준비비용을 고려한 GMMAL 작업순서문제를 해결하기 위한 연구가 수행되어야 할 것이다.로 이루어 져야 할 것이다.태를 보다 효율적으로 증진시킬 수 있는 대안이 마련되어져야 한다고 사료된다.$\ulcorner$순응$\lrcorner$의 범위를 벗어나지 않는다. 그렇기 때문에도 $\ulcorner$순응$\lrcorner$과 $\ulcorner$표현$\lrcorner$의 성격과 형태를 외형상으로 더욱이 공간