• Journal of applied mathematics & informatics
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• 제7권3호
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• pp.773-785
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• 2000

In this paper an algorithm is presented based on the additive Schwarz method for steady groundwater flow in a porous medium. The subproblems in the algorithm correspond to the problem on a coarse grid and some overlapping subdomains. It will be shown that the rate of convergence is independent of the mesh parameters and discontinuities of the coefficients, and depends on the overlap ratio.

• 한국인쇄학회지
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• 제20권2호
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• pp.45-56
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• 2002

In these day, our life has been developed with the computer. Printing Industry was introduced the information industry as computer, internet, etc. These are now in daily use and covers the entire work flow - from the planing of the product and the production at domestic printing industry. Then, I suggest the correspondence of changing printing work flow, understanding of digital printing technique, rearing of a special line of business, adjustment in the environment changing of printing technique etc. for the purpose of development of domestic printing industry.

• 한국전산유체공학회지
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• 제15권1호
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• pp.56-63
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• 2010

Since emission regulations for vehicles have become more stringent, SCR technology has drawn a strong attention in order to reduce NOx emissions. Optimal design of a reductant injection nozzle and a multi-hole plate located between the cone and catalyst is critical in that the uniform distribution of reductant is necessary to maximize the NOx conversion efficiency and minimize the slip of reductant in SCR. In this work, an LPG fuel(C3H8 in vapor state) was used as a reductant for LPG vehicles. A Realizable k-$\varepsilon$ model is used for turbulence, and SCR body is defined as porous media with inertia and viscous resistances measured in this work. Effect of the number of nozzle holes on the flow mixing index was analyzed, which revealed that a four hole nozzle shows the best performance in terms of uniformity of flow. An installment of a multi-hole plate at the entrance of catalyst was evaluated with flow mixing index, uniformity of flow, and pressure drop. A multi-hole plate with gradual hole diameter change in three steps showed the best uniformity of flow within the conditions suggested in this work.

• 한국분무공학회지
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• 제22권1호
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• pp.13-21
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• 2017

The fog screen is a device projecting the media to the aerosol flow field. As major parameters to generate dense and steady fog screen, shear stress, optical blockage ratio and SMD were obtained result through experiment. The micro droplet was generated by the piezo oscillation element, and the aerosol flow mixed with an air flow was sprayed into the vertical direction from the top of the fog screen through the 280 mm slot. For produce a dense, uniform fog screen, the shear effect, optical blockage ratio and SMD between aerosol and air curtain were measured. The minimum and maximum shear stress conditions were selected and it was confirmed that the optical transmission deviation of the aerosol flow field was small when the aerosol and air curtain flow rates were changed. When the aerosol and air curtain flow power were 18 V (1.51 m/s) and 24 V (2.55 m/s), respectively, under the condition of the minimum shear stress and laminar flow, the optical blockage ratios with the spray length were small, and it produced a most stable and high density uniform fog screen by injecting a constant of $10{\mu}m$ or less.

• 정보화연구
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• 제11권4호
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• pp.471-483
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• 2014

본 연구에서는 사회네트워크 분석을 활용하여 소셜 미디어를 통해 이루어지는 관광목적지의 관광정보에 대한 공유 및 흐름에 대하여 살펴보고자 하였다. 이를 위해 트위터의 서울과 부산 관광에 대한 네트워크 그룹의 사용자 간에 이루어지는 정보공유와 교환 및 확산 관계를 비교하였다. 전체적(Global) 관점에서 트위터 네트워크의 정보 쏠림현상, 정보의 확산력 등을 도출하였다. 미시적(Node) 관점에서 트위터 내의 정보에 대한 영향력 있는 유저를 파악하여 정보의 흐름과 정보공유에 대한 특성을 파악하였다. 본 연구 결과를 통해 소셜 미디어 사용자들의 정보 탐색행동과 정보공유 및 확산 패턴을 이해할 수 있는 학문적 근거를 제시하였으며, 소셜 미디어를 단순한 제품 및 서비스의 홍보 수단이 아닌 궁극적으로 정보 수용자가 원하는 정보를 제공해 줄 수 있는 마케팅 도구로써의 활용 방안 제시하였다.

• 유기물자원화
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• 제16권1호
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• pp.46-52
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• 2008

자연계로 유출된 유류 및 유기용매 등 비수용성액체는 토양공극사이에 존재하며 서서히 용해되면서 지속적인 수질오염원으로 작용한다. 본 연구는 유리로 제작된 다공성매체 실험장치를 이용하여 토양 공극사이에 위치한 비수용성액체의 용해현상을 시각화하였고, 이미지 분석기술을 이용하여 용해속도를 정량화하였다. 다공성매체 공극사이 TCE는 물의 유량을 빠르게 할수록 용해속도가 증가하는 것으로 나타났다. 이는 TCE로 오염된 지역의 강우량이 많거나, 지하수 유속이 빠른 지역일 경우 토양내 TCE 제거는 용이하게 일어날 수 있지만, 용해된 TCE의 지하수 유입으로 증가한다는 점을 시사한다. 다공성매체 공극사이 TCE의 현미경 이미지 관측결과, 물의 유량이 빠른 경우 역시 TCE blob 수가 급격히 감소함을 확인하였다. 물의 흐름이 용이한 우선흐름경로에 존재하고 있는 TCE는 물과의 용이한 접촉으로 용해가 빠르게 진행되었다. 반면 정체구역에 존재하는 TCE의 용해속도는 매우 느리게 나타났다. 현장 토양에서도 동일한 현상이 일어날 것이므로 지하수 조사결과 TCE의 검출이 계속된다면, 토양 공극사이에 여전히 TCE가 존재하고 있음을 암시하므로 이에 대한 대책이 강구되어야 한다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제29권1호
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• pp.72-83
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• 2024

Most of the slags generated from steel-making industry in Korea are recycled into media-contact aggregates such as fill and cover materials. For their use as media-contact aggregates, the slags must meet not only the waste quality criteria, but also the Daphnia magna acute toxicity test criteria. In this study, Korean Leaching Test ES 06150.e (Korea), Japanese Leaching Test JIS K 0058-1(Japan), Detuch Leaching Test DIN 19529 (Germany), Toxicity Characteristic Leaching Procedure (USA) were conducted for batch leaching test of slags from 6 Korean steel-making companies. In addition, Korean Standard up-flow percolation test (ES 06151.1) mimicking field conditions was conducted to assess the impact of the slag leachate on the surrounding environment indirectly. Heavy metals such as Cr⁶⁺ and Zn²⁺ were detected from both extractant and leachate samples, but all of them did not exceed waste quality criteria of each country. However, Daphnia magna acute toxicity tests using the leachate samples from up-flow percolation test with slag alone and slag/natural soil conditions exceeded ecotoxicity standard (TU=2) due to their high pH (11.3-12.5). After neutralizing the pH of the slag leachate to 6.5~8.5, the Daphnia magna mortality and immobilization were reduced to satisfy ecotoxicity standard. As the reducing pH of slag leachate would be extremely difficult, appropriate recycling management considering the physicochemical characteristics of he slags should be stuided further.

• 디지털융복합연구
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• 제9권1호
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• pp.177-187
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• 2011

개방, 참여, 공유로 대표되는 웹2.0 인터넷 흐름 속에 새롭게 세간의 화두가 되면서 급성장하고 있는 소셜 미디어, 모바일 미디어 환경 속에서 경제, 사회, 문화는 물론, 정치 분야에도 전반적이고 다양한 변화를 꾀하여야 한다. 한국은 과거의 IT기술력을 바탕으로 새로 다가오고 있는 소셜미디어 환경 속에서도 세계 시장에서 선도적인 역할을 해나가는 위치를 찾아 가고 있다. 우리 국민은 과거 IT 분야에서 새로운 제품에 대한 Early Adopter역할을 해내어 국제 사회에 관심을 끌은바 있다. 급속히 변하해가는 소셜미디어 환경 속에서 정치 분야에서도 이에 맞는 방식으로 친 국민 의사소통 방식이 이루어 질수 있도록 노력해야 한다. 스마트 시민 정당 조직으로서의 비전을 정비하고 소셜미디어 전략을 마련하고 실행하는 등 변화의 노력을 시도하여야 한다. 본 연구에서는 이러한 소셜미디어 환경 속에서 어떠한 방법론으로 변해야 보다 더 친밀하게 국민에게 다가가고 국민과 하나가 되는 성공을 거둘 수 있는가에 대해 연구하고 방향을 제시 해 보고자 한다. 이 연구가 기존 정부 운영이나 정당 운영 방식에 대해 되돌아보게 하고 소셜미디어 환경에 맞는 효율적인 운영 전략을 되새겨 보게 하는 데 일조하게 될 것이다.

• 센서학회지
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• 제30권2호
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• pp.109-113
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• 2021

In this study, an automated culture media replacement system was developed to analyze changes in the contraction characteristics of cardiomyocytes according to the state of the culture media. For the long-term storage of culture media, a Peltier refrigerator with a temperature of 5 to 8℃ was provided and a pH of 7.4 was maintained. The cell culture media of the cardiomyocytes was continuously replaced using interlocking pumps at a flow rate of 0.83 μl/h. The cardiomyocytes in which the culture media was replaced automatically demonstrated lower heartbeats per minute compared to samples in which there was no replacement. However, these cardiomyocytes moved more uniformly and produced greater displacement in one heartbeat cycle. It was observed that the sarcomere length of the cardiomyocytes increased due to the automated culture media replacement system. These cardiomyocytes were found to demonstrate better maturation compared to the control group. The maturation of cardiomyocytes was verified through staining images. The proposed automated culture media replacement system generates a uniform heart rate and improvements in contraction force. Based on the study, patient-specific drug toxicity assessments can be conducted using differentiated cardiomyocytes in induced pluripotent stem cells.

• Environmental Engineering Research
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• 제16권4호
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• pp.231-236
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• 2011

Biological nitrogen removal, using a continuous flow packed-bed reactor (CPBR) in a consecutive nitrification and denitrification process, was evaluated. An apparent decline in the nitrification efficiency coincided with the steady increase in $NH_4{^+}$-N load. Sustained nitrification efficiency was found to be higher at longer empty bed contact times (EBCTs). The relationship between the rate of alkalinity consumption and $NH_4{^+}$-N utilization ratio followed zero-order reaction kinetics. The heterotrophic denitrification rate at a carbon-tonitrogen (C/N) ratio of >4 was found to be >74%. This rate was higher by a factor of 8.5 or 8.9 for $NO_3{^-}$-N/volatile solids (VS)/day or $NO_3{^-}-N/m^3$ ceramic media/day, respectively, relative to the rates measured at a C/N ratio of 1.1. Autotrophic denitrification efficiencies were 80-90%. It corresponds to an average denitrification rate of 0.96 kg $NO_3{^-}-N/m^3$ ceramic media/day and a relevant average denitrification rate of 0.28 g $NO_3{^-}$-N/g VS/day, were also obtained. Results presented here also constitute the usability of an innovative porous sulfur ceramic media. This enhanced the dissolution rate of elemental sulfur via a higher contact surface area.