• 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.

• Solar Energy
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• v.12 no.3
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• pp.10-20
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• 1992

In this experiment, photochemical reaction has been applied to destroy TCE in water phase. The main target of this work is to investigate the technical feasibility of large scale of solar detoxification reactor for water treatment. The results have revealed that solar detoxification utilizing photon energy from the sun is the most attractive process to decompose organic toxins in water phase at room temperature. The detailed results from this work are as follows; (1) The highest conversion ratio of TCE was obtained by using $TiO_2$, annatase as a photocatalyst among $TiO_2$ anatase, $TiO_2$ rutile and $V_2O_5$ under the same experimental condition. The anatase crystal structure was confirmed with XRD analysis, and its surface area was 7.748 $m^2/g$ from the BET-$N_2$ measurement (2) 0.1 wt% of $TiO_2$ anatase has been adopted as optimal quantity for batch slurry reactor at this experimental conditions. (3) The effect of hydrogen peroxide on the conversion of TCE was investigated. Its optimal quantity was 0.06 vol. % under this experimental conditions. (4) The effect of oxygen on the conversion of TCE also was studied by controlling the head space in photoreactor. Results indicated that sufficient amount of oxygen should be supplied to accomplish the highest conversion rate of TCE in water phase.

• 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

• Korean Journal of Construction Engineering and Management
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• v.13 no.5
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• pp.84-93
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• 2012

Most of the studies on reduction of buildings' environmental burden in the construction industry have been focused on carbon dioxide emission, although there are various kinds of environmental issues such as global warming, acidification, and etc. which are considered by many researchers. Therefore, this study defined and suggested six impact categories and the principles to assess each impact for the assessment of comprehensive environmental impacts of buildings. The six impact categories are abiotic depletion, global warming, ozone layer depletion, acidification, eutrophication, and photochemical oxidation. A case study has been conducted through comparative analysis of two structural design alternatives to confirm the necessity of assessing the six impact categories. That is, the results of global warming potential and the six impacts proposed in this study were compared. By comparing the results of only global warming potential, the second design alternative using 24MPa concrete was chosen as a better alternative, while the first design alternative using 21MPa concrete was resulted as a better alternative when six impact categories were considered. The results mean that the assessment of various environmental impacts is an appropriate and reasonable approach and the comprehensive assessment offers more reliable results of environmental impacts in the building construction.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.2 s.51
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• pp.141-146
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• 2005

Unstable cosmetic active ingredients could rapidly break down in chemical and photochemical process. Therefore, it has become a very important issue to encapsulate active ingredient for the stabilization. 7-Dehydrocholesterol (7-DHC), a precursor of vitamin $D_3$, has been shown to increase levels of protein and mRNA for heat shock protein in normal human epidermal keratinocytes. However, topical dermal application of 7-DHC is restricted due to its poor solubility and chemical unstability. In this study, 7-DHC was incorporated into nano-emulsion (NE), solid lipid nano-particle (SLN), and chitosan coated solid lipid nano-particle (CASLN), respectively. In order to prepare NE and SLN dispersion, high-pressure homogenization at temperature above the melting point of lipid was used Hydrogenated lecithin and polysorbate 60 were used as stabilizer for NE and SLN. CASLN was prepared by high speed homogenizing after adding chitosan solution to the SLN dispersion and showed positively charged particle properties. Decomposition rate of 7-DHC in NE, SLN and CASLN was studied as a function of time at different temperature. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies were performed to characterize state of lipid modification. It appeared that CASLN is the most effective to stabilize 7-DHC and may be used for a useful topical dermal delivery system.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.4
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• pp.161-169
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• 2000

In the case of photocatalytic hydrogen production from water, the performance-property relationships of CdS-TiO2 film type composite catalysts were investigated. To control the physical properties of the primary particles, the mixture of CdS and TiO2 nano-sols prepared by the sol-gel method at room temperature was hydrothermally treated at 240oC for 12hr. The film electrodes were prepared by the casting method. The photocurrents measured by a photoelectrochemical method and the hydrogen production rates measured by a photochemical method were closely dependent on the physical properties such as crystalline form, primary particle size and CdS/TiO2 mole ratio, and these varied in the range of 1.2~2.6 mA/cm2 and $1.0{\sim}1.6{\times}10-3mol/hr$, respectively.

• Journal of Environmental Health Sciences
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• v.44 no.1
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• pp.1-14
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• 2018

Objectives: The purpose of this study is to investigate the main cause of visibility impairment by analyzing the contributions of the light extinction coefficient of major air pollution components and the change of the light extinction coefficient by relative humidity. Methods: The characteristics of the light extinction coefficient calculated by the photochemical method using fine particle component data measured in 2015 in the Gwangju area were examined. Results: The extinction efficiency per unit mass of $PM_{2.5}$ particles was $4.5m^2/g$ and that of $PM_{10-2.5}$ particles was $0.6m^2/g$. This difference indicates that most of the visibility impairment in Gwangju was caused by $PM_{2.5}$ particles. When visibility was poor, the contribution of ammonium sulphate and ammonium nitrate was significantly increased. Relative humidity was also a major cause of visibility decay. The influx of air currents in Gwangju was mostly caused by the long distance movement of pollutants emitted from the eastern part of China. Ammonium sulphate and ammonium nitrate, which are hygroscopic secondary contaminants, were the main causative agents of visibility impairment. Conclusions: Ammonium sulphate and ammonium nitrate were the main causative agents of visibility impairment in Gwangju. The influx of air currents in Gwangju was mostly caused by the long distance movement of pollutants emitted from the eastern part of China.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.898-905
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• 2019

As the positive feedback between the absorption of chromophoric dissolved organic matter (CDOM) and acceleration of ice melt can impact the aquatic biota and dynamic heat budget, long-term monitoring of the CDOM variation in the polar ocean is necessary. However, the monitoring of CDOM is not easy because of harsh weather and difficult access, especially in the Antarctic Ocean. Therefore, the purpose of this study was to find a suitable long-term monitoring site for CDOM variation; we selected Maxwell Bay and Marian Cove at Sejong Base and horizontal and vertical distributions of CDOM were measured. After a 72 hr time-series measurement test of the CDOM variation at Sejong Dock and Sejong Cape in Maxwell Bay, Sejong Dock was selected, as it does not haveland discharge effects. The seasonal variation of CDOM was evident and the average CDOM concentration of Maxwell Bay was comparable with the adjacent sea. The CDOM at Sejong Dock from February to November 2010 was the highest in the fall and winter and the lowest during spring and summer. Thus, based on our one-year CDOM data, we suggest that Sejong Dock in Maxwell Bay is suitable for long-term monitoring of CDOM as an indicator of photochemical and biological environmental change and an important factor in determining the heating budget in the Antarctic Ocean.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.91-101
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• 2000

The emission sources of volatile organic compounds (VOCs) are wastewater treatment plants. sanitary landfills, automobile industries, and so on. The VOCs are harmful to human beings because of their toxicity and carcinogenicity, and cause the serious air pollution problem producing ozone ($O_3$) as a result of photochemical reaction. To investigate the emission of VOCs from wastewater treatment plant, aeration basins at the City of Los Angeles' Hyperion Treatment Plant were selected and measured flux was compared with calculated flux. For compounds commonly associated with wastewater (DCM, TCM, PCE, UM, DCB, UND) and not expected in vehicle exhaust or ambient air coming off the ocean, concentrations immediately downwind of the aeration basins were a factor of ten or higher than those measured in the upwind air. The airborne flux of less degradable or non-biodegradable compounds, e.g., DCE, DCM, TCA, DCA, TCM, PCE, DCB, through an imaginary plane at the downwind side of the aeration basins was in agreement with the estimated flux from measured liquid phase concentrations. Henry's constant. aeration rate, and an assumption of bubble saturation. For several compounds (PCE, DCE, TCA), the ratio (measured flux/calculated flux) is almost unity.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.143-150
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• 2009

Deicing salt is used to melt snow and ice on the road for traffic safety during the winter season, which accumulates in the roadside vegetation and induces visible injuries. The damage may accelerate particularly when it coincides with early spring leaf out. In order to better understand the response mechanisms, C. kousa (3-year-old) was irrigated twice prior to leaf bud in a rhizosphere with solutions of 0.5, 1.0, and 3.0% calcium chloride ($CaCl_2$) concentration, that were made by using an industrial $CaCl_2$ reagent practical deicing material in Seoul. Physiological traits of the mature leaves were progressively reduced by $CaCl_2$ treatment, resulting in reductions of total chlorophyll contents, chlorophyll a:b, photosynthetic rate, quantum yield, stomatal conductance, $F_V/F_M$, and NPQ. On the contrary, light compensation point and dark respiration were increased at high $CaCl_2$ concentration. A decrease in intercellular $CO_2$ concentration by stomatal closure first resulted in a reduced photosynthetic rate and then was accompanied by low substance metabolic rates and photochemical damage. Based on the reduction of physiological activities at all treatments ($CaCl_2$ 0.5%, 1.0%, and 3.0%), C. kousa was determined as one of the sensitive species to $CaCl_2$.