• 기계와재료
• /
• v.21 no.4
• /
• pp.30-37
• /
• 2010

최근 산업의 고도화에 따른 부품 소재의 고성능화에 따라 기존의 고온 세라믹의 한계를 극복하기 위한 노력으로 초고온 세라믹 재료에 대한 활발한 연구가 진행되고 있다. 초고온 세라믹은 대부분 붕화물이나 탄화물인 비산화물 세라믹으로 3000도 이상의 녹는점을 갖으며 2000도 부근에서는 사용을 목표로 하고 있다. 이 재료는 다른 세라믹들과 마찬가지로 취성파괴 거동을 나타내며, 이를 보완하기 위한 섬유강화 복합재료화도 활발히 진행되고 있다. 본고에서는 고온용 세라믹 장섬유와 세라믹 복합재료, 그리고 초고온 세라믹의 개발 현황과 산업화 전망을 정리하였다. 또한 초고온 세라믹의 발전 방향을 전망하였으며, 재료연구소에서 수행중인 초고온 세라믹의 연구 활동에 대해 간략히 언급하였다.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.5
• /
• pp.345-350
• /
• 2012

To investigate the exposure and health risk assessment for the residents near the D-asbestos mine in Chungbuk, Korea. We analyzed asbestos in the 20 ambient air and 23 activity based samples near the mine. The airborne sample results are showed that 8 of 20 samples ranged between 0.0025 to 0.0029 f/cc (fiber per cubic centimeter) and the others were below the detection limit by phase contrast microscopy (PCM). In addition, asbestos fibers were under the detection limit or not being by transmission electron microscopy (TEM). Based on interview and survey targeting the local residents, we made the activity based sampling (ABS) scenarios fit to the conditions of field. At the same time, we calculated the excess lifetime cancer risk (ELCR) of these ABS scenarios according to the ELCR average value and 95% upper confidence limit (UCL). At the case of weed whacking, soil digging and sweeping yard scenario, 95% UCL of ELCR exceeded the $1{\times}10^{-4}$, acceptable risk range for exposure. Based on our study results, it is necessary safety measures such as risk communication, abatement or management of naturally occurring asbestos (NOA).

• Particle and aerosol research
• /
• v.14 no.2
• /
• pp.25-33
• /
• 2018

In this study, the concentration of fine indoor dust and the size distribution of fine indoor dust were analyzed by measuring the dust generated during the cleaning process of an indoor office. We measured $PM_{10}$, $PM_{2.5}$, and $PM_{1.0}$ and analyzed the size distributions of dust larger than $0.3{\mu}m$ in diameter during cleaning. The results showed that the concentration of $PM_{10}$ increased rapidly during cleaning, however $PM_{1.0}$ did not increase. Before cleaning with a broom, the fine dust concentration was about $50{\mu}g/m^3$, but increased to about $400{\mu}g/m^3$ as cleaning progressed. In the case of indoor cleaning with a vacuum cleaner, the concentration of $PM_{10}$ increased during the cleaning process and the increase of $PM_{2.5}$ was relatively small. $PM_{1.0}$ did not increase as in the case of cleaning the broom.

• Fire Science and Engineering
• /
• v.24 no.5
• /
• pp.68-78
• /
• 2010

The purpose of this study, fire officials during the field activities find causes fugitive dust of containing asbestos is the seriousness of the phenomenon is a threat case and through questionnaires, during on-site activities to prevent exposure to asbestos is effectively. Analysis of the relationship to field activities of fire officials and about the dangers of asbestos dust, asbestos cancer caused by asbestos, and to protect fire officials from the same disease like malignant mesothelioma, by varying the conditions of irrational, fire officials at the scene activities in advance of a deadly hazard is aimed to eliminate through optimization of organizational management and a safe and pleasant working conditions for fire officials through the deadly hazards at the scene of action is aimed to obviate. Also according to asbestos exposure by wearing protective equipment as well as thoroughly strengthen firefighting, firefighting awards to recognize the seriousness of the hazard factors, disease and provide compensation to the legal system, for diseases not yet recognized officially recognized by disaster supplemented by institutional, fire officials to improve morale and working conditions, etc. versus expectations is to improve public services.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.1
• /
• pp.9-18
• /
• 2017

Arsenic (As) has been considered as the most toxic one among various hazardous materials and As contamination can be caused naturally and anthropogenically. Major forms of arsenic in groundwater are arsenite [(As(III)] and/or arsenate [(As(V)], depending on redox condition: arsenite and arsenate are predominant in reduced and oxidized environments, respectively. Because arsenite is much more toxic and mobile than arsenate, there have been a number of studies on the reduction of its toxicity through oxidation of As(III) to As(V). This study was initiated to develop photocatalytic oxidation process for treatment of groundwater contaminated with arsenite. The performance of two types of light sources (UV lamp and UV LED) was compared and the feasibility of goethite as a photocatalyst was evaluated. The highest removal efficiency of the process was achieved at a goethite dose of 0.05 g/L. Based on the comparison of oxidation efficiencies of arsenite between two light sources, the apparent performance of UV LED was inferior to that of UV lamp. However, when the results were appraised on the basis of their emitting UV irradiation, the higher performance was achieved by UV LED than by UV lamp. This study demonstrates that environmentally friendly process of goethite-catalytic photo-oxidation without any addition of foreign catalyst is feasible for the reduction of arsenite in groundwater containing naturally-occurring goethite. In addition, this study confirms that UV LED can be used in the photo-oxidation of arsenite as an alternative light source of UV lamp to remedy the drawbacks of UV lamp, such as long stabilization time, high electrical power consumption, short lifespan, and high heat output requiring large cooling facilities.

• Korean Journal of Remote Sensing
• /
• v.36 no.6_3
• /
• pp.1691-1710
• /
• 2020

We measured PM2.5 and PM10 (particulate matter less than 2.5 ㎛ and 10 ㎛ in diameter, respectively) simultaneously at 16 locations around an elementary school and classrooms in Busan and Pyeongtaek, South Korea. In this study, we compared the results of this field intensive with those in the literature (144 cases of 30 studies), focusing on I/O (Indoor/Outdoor) ratios. We also reviewed the results of previous studies, categorizing them into related sub-categories for indoor-activities, seasons, building-uses, and the surrounding environment. We conclude that indoor PM10 is affected more by indoor-sources (e.g., physical activities) than PM2.5 in the absence of combustion sources like smoking and cooking. Additionally, PM10 and PM2.5 likely have different indoor-outdoor infiltration efficiencies. Conclusively, PM10 in classrooms can be more sensitively affected by both indoor activities and ambient concentrations, and mechanical ventilation can be more efficient in reducing PM concentrations than natural ventilation.

• Journal of Korean Society of Forest Science
• /
• v.101 no.3
• /
• pp.365-373
• /
• 2012

This study purposed to extract and assess the accuracy of assessment for deforestation area in Wonju city using medium resolution satellite image. The total size of deforestation area during the last nine years (2000-2008) was about 467 ha, and it was occurred annually about 52 ha. The most frequent form of deforestation was settlements (72%). Ninety percent of the size of deforestation was less than 2 ha in size. In addition, 79 percent of deforestation area was found within 500 m from the road network and within 100 m of the Forest/Non-forest boundary. This study compared the deforestation based on the administrative information (GIS deforestationI) with the deforestation (RS deforestation) extracted from the satellite imagery by vegetation indices (NDVI, NBR, NDWI). Extraction accuracy, mean-standard deviation${\times}1.5$ applied 3 by 3 filtering, showed reliable accuracy 35.47% k-value 0.20. However, error could be occurred because of the difference of land-use change and land-cover change. The actual rate of land-cover change deforestation area was 32% on administrative information. The 7.52% of forest management activities area was misjudged as deforestation by RS deforestation. Finally, the comparison of land-cover change deforestation (GIS deforestationII) with the RS deforestation accuracy, as a result NDVI mean-standard deviation${\times}2$ applied 3 by 3 filtering, showed improved accuracy 61.23%, k-value 0.23.

• Journal of Environmental Impact Assessment
• /
• v.29 no.4
• /
• pp.252-271
• /
• 2020

In this study, we investigated physical and chemical properties such as grain size, heavy metal pollution, magnetic properties, and their environmental impacts of road dusts (RD) collected from 14 sampling points in Daebul industrial Complex. Heavy metal concentrations in RD were in the order of Fe>Zn>Cu>Pb>Cr>Ni>As>Cd>Hg, and this pollution pattern was related to major industries and traffic activities in this area. The results of the correlation analysis between heavy metal elements and particle size in RD showed that Fe and all of analyzed heavy metals had a significant correlation with each other and metal concentrations had a significantly negative correlation (p<0.05). However, due to the input of large metal particles some heavy metal concentrations in the particle fraction of >1000 ㎛ were highest. Pollution load per unit area of this fraction was the highest among the grain size fractions. Cr, Ni, Cu, Zn, Cd, Pb levels in RD decreased and the levels of Cr, Ni, Cu, Zn, Cd, and Pb were reduced to 85 (As) -22 (Ni)% of the whole after removal of MFs fraction from RD. The mean heavy metal levels in the study area did not exceed the soil contamination guide value of Korea, indicating that heavy metal levels in RD were not a concern. However, at some sampling points, Zn concentrations were exceeded the soil contamination guide value for the 3rd areas of Korea and this result indicated that further studies of the impact of RD on the surrounding environment through re-suspension or non-point pollution, and of effective management methods are required.

• Journal of Convergence for Information Technology
• /
• v.10 no.10
• /
• pp.135-142
• /
• 2020

In the recent farming industry, there is a growing diffusion of drones, which are recognized as a crucial technology of the 4 th industrial revolution to cope with aging. Especially, filming and pest control using drones are representative fields that have different age groups for obtaining a national license of multicopter that is a ultra-light flying device, and can create profits after getting a license. However, pest control technology using drones has different spray effects depending on levels of operational proficiency, since this highly relies on an operator's operating skills. It is anticipated that if this issue is supplemented, the use of drones for pest control in the farming industry will diversify. For analysis of spraying characteristics of agricultural pest control drones, this study aims to formulate effective spraying hours and effective spraying intervals and suggest an algorithm, which facilitates an accurate calculation of pest control area depending on the kinds of pest control drones. This algorithm can be used in the field of pest control by improving scatterling issues caused by drone flight methods of drone pest controllers and building an optimum pest control manual in future.

• Journal of the Korean Chemical Society
• /
• v.37 no.6
• /
• pp.562-569
• /
• 1993

The pseudophase separation model is used to describe the effects of pH and n-propanol on the mixed micellar formation of protonated and unprotonated dimethyldodecylamine oxides. Dimethyl-dodecylamine oxide surfactant molecules may exist in aqueous solution in either nonionic (unprotonated) or cationic (protonated) form, and they can be modeled thermodynamically as a binary mixture of cationic and nonionic surfactants. The composition of the binary mixture is varied by adjusting the solution pH. And activities, micellar compositions, and monomeric compositions of two surfactant species can be calculated directly from the experimental titration data by applying pseudophase separation model to the micellar system of DDAO in water/n-propanol. The critical micellar concentrations and the p$K_a$ values of the binary mixture systems are dependent on the micellar composition of the protonated cationic surfactant (X); especially they show the minimum phenomena when they are plotted against the micellar composition of the protonated cationic surfactant (X). The critical micellar concentration of the binary mixed DDAO system is generally decreased when n-propanol is added to the binary mixture system, and the degree of decrease is dependent on the concentration of n-propanol.