• Spatial Information Research
• /
• v.11 no.1
• /
• pp.13-22
• /
• 2003

The study of geomorphology of tidal flat using remote sensing image has been considered useful because of it's ability to acquire data periodically. Especially, the Near Infrared band of satellite image has been used to divide between land and sea area. This study extracted a borderline of the tidal flat using Landsat-5 images and generated DEM(Digital elevation model) using tide level data as elevation value. DEM is a useful tool for three-dimensional survey of geomorphology and can be used for survey of tidal flat. This study divided 8 images of 1990's into two parts - before 1994 and after 1994 - and generated DEM respectively. In this work, the areas of tidal flats are calculated and it was revealed the area of tidal flat was decreased after 1994.

• Clean Technology
• /
• v.6 no.1
• /
• pp.39-49
• /
• 2000

Ultra Rapid Coagulation (URC) can dramatically remove pollutants loaded in wastewater by adding weighted coagulation additives (WCA) and recycling sludge into the coagulation basin to increase settling velocity and surface adsorption ability of floc. Also settling chamber together with lamella plates offers the high rate settling velocity, which can economically treat a considerable amount of pollutants like as combined sewage overflow (CSO) during the heavy rainfall and reduce the pollutants load into the receiving water for securing water source. It was estimated optimal configuration of settling chamber by using fluent model and the possibilities of reusing the sludge generated in this system.

• Clean Technology
• /
• v.6 no.1
• /
• pp.27-38
• /
• 2000

A physicochemical process called Ultra Rapid Coagulation(URC) can dramatically remove organics, metals, and phosphates in wastewater by adding weighted coagulation additive(WCA) and recycling sludge into the coagulation basin to increase the growth rate and adsorption ability of floc. Also this process can improve floc settling rate than conventional coagulation process and reduce the pollutants loaded into the receiving water for securing water source. It was evaluated that WCA and sludge added have effects on the removal efficiency and estimated the possibilities of reusing the effluent from this process.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.381.2-381.2
• /
• 2016

It was known conceptually that ferrofluid or air driven flows induced by waste heat energy could generate electric power in surrounding windings by changing the magnetic flux with time through the colis. In the last decade, a ferrohydrodynamics energy harvesting system based on magnetorheology has been investigated experimentally and numerically. However, it was focused on the movement of air droplets or nanoparticles in the ferrofluid, therefore the electric power generated in the device was not enough to use practically. In this study, we developed the electrical generation concept based on magnetic particle flows for harvesting large amount of electric power and conducted measurements and computations for verifying the concept of electrical generation. In order to obtain a significant amount of electrical energy by using magnetic particle flows, it was critical to control the magnetization direction of magnetic nanoparticles in the fluid by a permanent magnet and to change the magnetic flux with time by air bubbles when the fluid flows in a millimeter-sized channel passed through surrounding windings.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.337.1-337.1
• /
• 2016

단일벽 탄소나노튜브(Single-walled carbon nanotubes, SWNTs)는 나노 스케일의 크기와 우수한 물성을 갖고 있어, 전자, 에너지, 바이오 등 다양한 분야로의 응용이 기대되고 있다. 이러한 응용의 실현을 위해서는 경제적, 산업적인 면에서 보다 손쉬운 합성법이 요구된다. SWNTs의 합성에는 대면적의 균일한 CNTs를 합성할 수 있다는 장점이 있는 열화학기상증착법(Thermal chemical vapor deposition, TCVD)이 가장 일반적으로 사용되고 있다. 하지만 탄화수소가스를 효율적으로 분해하기 위하여 $900^{\circ}C$ 이상의 고온공정이 요구되며, 이는 경제적, 산업적인 면에서 사용이 제한적이다. 따라서 저결함, 고수율의 SWNTs를 저온합성 할 수 있는 공정의 개발이 지속적으로 필요하다. 본 연구에서는, TCVD법을 이용하여 에틸렌 원료가스로 SWNTs의 저온합성 가능성을 확인하였다. 합성을 위한 기판과 촉매로는 실리콘 산화막 기판(SiO2/Si wafer)에 철 나노입자를 지닌 ferritin을 스핀코팅 후 산화하여 이용하였다. 저온합성 공정의 변수로는 합성온도와 원료가스인 에틸렌의 분율을 설정하여, 변수가 SWNTs의 결정성과 수율에 미치는 영향을 고찰하였다. 합성된 SWNTs의 분석의 용이함과 손지기(Chirality)의 제어 가능성을 확인하기 위하여 나노 다공성 물질인 제올라이트(Zeolite)를 보조 기판으로 사용하였다. 실험결과 에틸렌 원료가스로 합성한 SWNTs는 메탄을 원료가스로 사용한 경우보다 낮은 $700^{\circ}C$ 부근에서도 합성이 가능함을 확인하였다. 또한 에틸렌의 분율과 합성 시간의 정밀한 제어를 통해 SWNTs의 합성온도를 더욱 감소시키는 것도 가능할 것으로 예상된다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.239.1-239.1
• /
• 2015

1차원 탄소나노재료이며 한 겹의 흑연을 말아 놓은 형태인 단일벽 탄소나노튜브(Single-walled carbon nanotubes, SWNTs)는 감긴 형태에 따라 반도체성, 금속성 성질을 나타내는 특이성과 우수한 기계적 성질을 지니고 있어 광범위한 분야로 응용이 기대되어왔다. 이러한 SWNTs의 응용가능성을 실현시키기 위해서는 보다 경제적, 산업적인 면에서 손쉬운 합성방법의 개발이 필요한 실정이다. SWNTs의 합성 방법들로는 아크방전법과 레이저 증발법, 그리고 열화학기상증착법(Thermal chemical vapor deposition, TCVD) 등이 이용되었다. 이 중 TCVD법은 대면적의 균일한 CNTs를 합성할 수 있다는 장점이 있다. 그러나 탄화수소가스를 효율적으로 분해하기 위하여 $800^{\circ}C$ 이상의 고온 공정이 요구되며, 이는 경제적, 산업적인 면에서 사용이 제한적이다. 따라서 저결함, 고수율의 SWNTs를 저온합성 할 수 있는 공정의 개발이 지속적으로 필요하다. 본 연구에서는, TCVD법을 이용하여 에틸렌 원료가스로 SWNTs의 저온합성 가능성을 확인하였다. 합성을 위한 기판과 촉매로는 실리콘 산화막 기판(SiO2/Si wafer)에 철 나노입자를 지닌 ferritin을 스핀코팅 후 산화하여 이용하였다. 저온합성 공정의 변수로는 합성온도와 원료가스인 에틸렌의 분율을 설정하여, 변수가 SWNTs의 결정성과 수율에 미치는 영향을 고찰하였다. 합성된 SWNTs의 분석의 용이함과 손지기(Chirality)의 제어를 위하여 나노 다공성 물질인 제올라이트(Zeolite)를 보조 기판으로 사용하였다. 실험결과 에틸렌 원료가스로 합성한 SWNTs는 $700^{\circ}C$ 부근의 저온에서도 합성이 가능함을 확인하였다. 또한 에틸렌 원료가스의 분율과 합성시간의 정밀한 제어를 통해 SWNTs의 합성온도를 더욱 감소시키는 것도 가능할 것으로 예상된다.

• Journal of the Korean Electrochemical Society
• /
• v.18 no.2
• /
• pp.81-85
• /
• 2015

A method for degradation of the perchlorate anion ($ClO{_4}^-$) has been studied using electrochemically generated zero-valent iron (ZVI) deposited on a porous carbon electrode. The first strategy of this study is to produce the ZVI via the electrochemical reduction of iron (II) on a porous carbon electrode coated with a conducting polymer, instead of employing expensive $NaBH_4$. The present method produced well distributed ZVI on conducting polymer (polypyrrole thin film) and increased surface area. ZVI surface can be regenerated easily for successive reduction. The second strategy is to apply a mild reducing condition (-0.3 V) to enhance the efficiency of the degradation of perchlorate with ZVI without the evolution of hydrogen. The electrochemically generated ZVI nanoparticles may offer an alternative means for the complete destruction perchlorate without evolution of hydrogen in water with high efficiency and at low cost.

• Journal of Environmental Health Sciences
• /
• v.24 no.3
• /
• pp.114-123
• /
• 1998

Particulate matters(less than 10 $\mu$m, PM10) at Kanghwa and Yangyang, which are located in the western and the eastern coastal regions in Korea, were measured in using low volume air sampler from December 1995 to November 1996, and their characteristics were investigated from the view point of background level.(and in order to characterize the particulate matters.) The particulate matters were analyzed for major water soluble ionic components(SO$_{4}^{2-}$, NO$_{3}^{-}$, Cl$^{-}$, Na$^{+}$, NH$_{4}^{+}$, K$^{+}$, Mg$^{2+}$ and Ca$^{2+}$) by ion chromatography. Mass concentrations of particulate matters were $48.77 \pm 22.45 \mug/m^{3}$ at Kanghwa and $54.04 \pm 32.98 \mug/m^{3}$ at Yangyang and SO$_{4}^{2-}$, NO$_{3}^{-}$ and NH$_{4}^{+}$ contributed largely to water soluble ionic components. nss(non sea salt)-SO$_{4}^{2-}$, contributed more than 95 percentage to SO$_{4}^{2-}$ and nss-K$^{+}$ and nss-Ca$^{2+}$ also contributed high percentages to K$^{+}$ and Ca$^{2+}$. It was supposed that most SO$_{4}^{2-}$, was originated from anthropogenic sources, and K$^{+}$ and Ca$^{+}$ were mainty originated from soil. The results of factor analysis suggested possibility of interpreting the correlation between air pollutants and regional characteristics.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.4
• /
• pp.21-26
• /
• 2008

In this paper, a novel 622Mbps burst-mode clock and data recovery (CDR) circuit is proposed for passive optical network (PON) applications. The CDR circuits are implemented with 0.35um CMOS process technology. Locking dynamics is accomplished with instantaneous feature and data are sampled at an optimal timing. This is realized by seven different delay configurations, which are generated from precisely-controlled delay buffers. The experimental results show that the proposed CDR circuits are operating as expected, recovering an incoming 622Mbps burst-mode input data without errors.

• Journal of computational fluids engineering
• /
• v.15 no.1
• /
• pp.71-80
• /
• 2010

The violent free-surface motions and the corresponding impact loads are numerically simulated by using the Moving Particle Semi-implicit (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flows. In the original MPS method, there were several shortcoming including non-optimal source term, gradient and collision models, and search of free-surface particles, which led to less-accurate fluid motions and non-physical pressure fluctuations. In the present study, how those defects can be remedied is illustrated by step-by-step improvements in respective processes of the revised MPS method. The improvement of each step is explained and numerically demonstrated. The numerical results are also compared with the experimental results of Martin and Moyce (1952) for dam-breaking problem. The current numerical results for violent free-surface motions and impact pressures are in good agreement with their experimental data.