• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.11
• /
• pp.1161-1169
• /
• 2008

The removals of TCE and PCE vapor with or without a supply of toluene as a primary substrate were compared in a biofiltration process, and the variations of microbial communities associated with the removal were also investigated. As a result of investigations on the removals of TCE/PCE in a biofilter B within which TCE/PCE-acclimated sludge was attached on the surface of media without a supply of primary substrate, and those in another biofilter A where toluene-acclimated sludge was attached with a supply of toluene as a primary substrate, followings were found: (i) parts of microbes responsible to the decomposition of toluene vapor participate in the removal of chlorinated VOCs such as TCE and PCE, and (ii) effective biological removals of TCE and PCE vapor do not necessarily need cometabolism. Sequencing of 16S rDNA obtained from the band profile of DGGE (Denaturating Gradient Gel Electrophoresis), it was confirmed that: (i) uncultured alpha proteobacterium, uncultured Desulfitobacterium, uncultured Rhodobacteraceae bacterium, Cupriavidus necator, and Pseudomonas putida were found to be toluene-decomposing microbes, (ii) alpha proteobacterium HTCC396 is a TCE-removing microbe, (iii) Desulfitobacterium sp. is a PCE-decomposing microbe, and (iv) particularly, uncultured Desulfitobacterium sp. is probably a microbe decomposable not only toluene but also various chlorinated VOC vapor including TCE and PCE.

• Journal of Convergence for Information Technology
• /
• v.12 no.5
• /
• pp.139-149
• /
• 2022

The purpose of this study is to develop and analyze the effects of an educational program that can cultivate artificial intelligence(AI) convergence education competency for future education and enhance students' understanding of pre-service teachers. For this end, an AI convergence education program using Machine Learning for Kids and Scratch 3 was developed for 15 weeks under the theme of classifying the state of matter. The developed program were treated by K University pre-service teachers who participated voluntarily. As a result, pre-service teachers were able to metaphorically understand the learning process of students through understanding of machine learning training process. In addition, the pre-post t-test result of AI teaching efficacy showed a statistically significant improvement with t=-7.137 (p<.000). Therefore, it is suggested that the AI convergence education program developed in this study can help to increase the understanding of the pre-service teacher's students in an indirect way other than practice teaching, and can contribute to foster AI education competency.

• Journal of the Institute of Convergence Signal Processing
• /
• v.23 no.4
• /
• pp.228-233
• /
• 2022

This study is an experimental study on how to use phase change materials(PCM) to generate electrical energy for long-term operation of underwater unmanned vehicles. The electrical energy generation method is a volume change and a pressure change that occur as a phase change material changes to a solid or liquid state according to temperature, and the change in pressure creates a flow of fluid to create electrical energy. Polyethylene glycol was used as a phase change material considering the temperature of the ocean. In addition, an electrical energy generating device that converts volume change into pressure at low temperature (1℃~2℃) in solid state and high temperature (21℃~25℃) in liquid state was fabricated. As a result of the experiment, the pressure change according to the phase change rapidly changed between 1 hour and 2 hours, and maintained a pressure of about 24MPa after 4 hours. Through this, it was confirmed that it can be used as a power source for underwater unmanned vehicles using phase change materials and temperature differences. In addition, it was found that a more improved design should be made in order to apply the phase change material to an underwater unmanned vehicle.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.1
• /
• pp.40-49
• /
• 1999

A laboratory flume experiment, using turbulence-generating acryl tank and natural sediments, was conducted to investigate the effects of salinity, concentration of suspended sediment, turbulence and clay minerals on the flocculation and settling of fine-grained suspended sediments. While experiments were run, a sequence of water samples were taken near the bottom of the tank to analyze the variations of size distribution and relative contents of clay minerals. The results of the salinity experiment indicate that median settling velocity ($W_{50}$) increases linearly with salinity. Different settling processes of suspended sediments under variable concentrations appear to be predictable, depending upon the range of the suspension concentration. At concentrations less than 200 mg/l, $W_{50}$ is rarely varied with concentration probably because of the individual--grain settling mode. In the range of 200 to 13,000 mg/l show $W_{50}$ and concentration a good relationship following an empirical formula: $W_{50}=0.45C^{0.44}$. This relationship, however, no longer holds in concentrations exceeding 13,000 mg/l; instead, a more or less reverse one is shown. This result suggests an effect of hindered settling. The turbulence effect is somewhat different from that of concentration. Turbulence accelerates the flocculation and settling susepended sediments at low concentration (200 mg/l), whereas at high concentration turbulence breaks floes down and impedes the settling. Size distribution of suspended sediments sampled near the bottom of the tank tend to be more negatively skewed and leptokurtic in turbulent conditions compared to those in static conditions. The clay mineral analysis from the sequential water samples shows that over time the content of smectite decreases most rapidly with illite remaining concentrated in suspension. This means that smectite, among other clay minerals, plays the most effective role in the flocculation of fine-grained sediment in saline water.

• 전기의세계
• /
• v.16 no.3
• /
• pp.42-51
• /
• 1967

현재는 각종물질중의 전자 energy 상태를 자유를 제어하고, 그 energy차에 의한 energy의 흐름을 이용하는 기술이 발전되어 있다고 볼 수 있으며, 양자론적입장에 입각한 electronics라고 할 수 있다. 이러한 electronics에 있어서의 부품및 재료에 대해서 새로운 경향 오늘날의 움직임을 살피고, 아울러 모든 전자재료를 물성론적으로 고찰해보기로 한다.

• Proceedings of the Korean Nutrition Society Conference
• /
• 2003.05a
• /
• pp.144.2-144.2
• /
• 2003

• Proceedings of the Korea Water Resources Association Conference
• /
• 1997.05a
• /
• pp.45-50
• /
• 1997

• Journal of the Korean Chemical Society
• /
• v.48 no.1
• /
• pp.53-65
• /
• 2004

This study aimed to analyze the historical evolution of general ideas concerning the particles that represent matter properties and matter changes divided into physical change and chemical change. In the science historical viewpoint, the general ideas of the base that represent matter properties has been variously revised the 5types. The definition of the matter change have also changed the 3 types. From the analysis of the definitions in secondary school science textbooks and general chemistry textbooks, we found that a lot of confusion of eras in the contents that define the concepts. Sometimes, the definition presented in one textbook was contradictory to the definitions in other textbooks. This tendency has been sustained in the textbooks from the 4th to 7th science curriculum.

• Korean Chemical Engineering Research
• /
• v.53 no.4
• /
• pp.489-495
• /
• 2015

A fundamental mathematical model for mass transfer processes has been used to understand the air pollution control process in biotrickling filtration and to evaluate the mass transfer coefficients of gas/liquid (trickling liquid), gas/solid (biomass) and liquid/solid based upon experimental results and mathematical model calculations for selected operating conditions. The mass transfer models for the utilization of the steady-state mass balance for gas/liquid, and dynamic mass balance model for gas/solid & liquid/solid in biotrickling filters were established and discussed. The mass transfer model considered the reactor to comprise finite sections, for each of which dynamic mass balances for gas/solid and liquid/solid system were solved by numerical analysis code (numerical iteration). To determine the mass transfer coefficients ($K_La$) of gas/liquid, gas/solid & liquid/solid in a biotrickling filter, the calculation results based upon mass balance equation was optimized to coincide with the experimental results for the selected operating conditions. Finally, this study contributed the development of experimental methods and discussed the mathematical model to determine the mass transfer coefficients in a biotrickling filtration for air pollution control.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1078-1082
• /
• 2006

본 연구에서는 현재 날로 심각해지는 흥부지역 농업용수의 수질을 개선하기 위한 기본계획을 수립하는데 있어, 기초데이터의 확충 및 현황 파악을 위하여 흥부지구 강우시 저수지내의 퇴적물 상태를 조사 하고자 하였다. 또한 조사된 자료를 바탕으로 저수지 퇴적물에 의한 내부오염 발생여부 및 저수지의 수질에 미치는 영향을 예측하고, 퇴적물에 의한 오염 방지 및 필요수량을 안정적으로 유지하기 위하여 준설여부를 검토함으로 써 흥부지역 농업용수의 수질개선방안을 제시하는 것이 목적이다. 본 조사연구는 1) 저수지 내 퇴적물 추정량, 2) 퇴적물의 입도분포 및 유기물질 무기물질 분석으로 이루어졌다. 본 조사연구 결과는 퇴적물의 준설을 결정하는데 있어서 중요한 인자로 인식되는 저수지의 퇴적속도, 저수지 내 퇴적물의 용적량, 잠재적 오염물질의 함유량에 대한 연구 자료로서, 앞으로 흥부저수지를 효율적으로 관리함에 있어 중요한 근거자료가 될 수 있을 것으로 판단되며, 수질개선 사업의 수행 시 설계 인자로 반영 하고자 한다.