• 대한기계학회논문집B
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• 제33권5호
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• pp.311-317
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• 2009

Due to extremely small device size and velocity scale, mixing in microchannel take place very slowly by way of molecular diffusion transport. Mixing enhancement becomes a central issue in microfluidics for biomedical and chemical applications. In this work, The optimization results and validation through experiment and fabrication. In this efficient micromixer design, it is essential to evaluate mixing efficiency with good precision. Mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS). Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

• International Journal of Contents
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• 제8권1호
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• pp.82-87
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• 2012

Organizational improvisation, the convergence of planning and execution, has emerged as an alternative approach to the limitations in strategic planning. Organizational improvisation has a significant impact not only on organizational performance, but also on market orientation, which has emerged as a key issue in the field of technology commercialization. This study investigates both the effect of organizational improvisation on market orientation, as well as the effect of environmental turbulence and time pressure on organizational improvisation. Results show that organizational improvisation has a positive influence on market orientation, with a stronger effect on the diffusion of market information. This is greatly impacted by environmental turbulence and time pressure. As a result, promoting competencies in organizational improvisation at the corporate level is suggested as a significant means to enhance market-oriented organizational innovation.

• 미생물학회지
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• 제16권4호
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• pp.161-169
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• 1978

Escherichiae-like organisms were isolated from rectal specimens of 56 children who were either in preschool age or in elementary school. The isolated strains were subjected to tests to screen enteropathogens producing heat-labile enterotoxin and susceptibility test to various antibiotics by disc diffusion method on agar plates. Production of heat-labile enterotoxin by the strains was assyed in the sensitive and reproducible cultured adrenal tumor cell system. The assay was sterodogenesis of the cell in the presence of heat-labile enterotoxin. Among 56 strains, gave positive reaction in the test of toxin production. This meant that about 10% of the children population objected to the study harbored the toxigenic strain of enteropathogenes. Some of these toxigenic strains were resistant to the antibiotics employed in the test. This study suggested that considerable population in Korea may harbor entertoxigenic E. coli as a part of intestinal normal flora. The toxigenic strains which are resistant to antibiotics may bring issue of public health in the future.

• 한국가시화정보학회지
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• 제5권2호
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• pp.33-38
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• 2007

Water management in polymer electrolyte fuel cell (PEFC) has been receiving large attention as an important issue in practical applications. Proper water management is vital to achieve high performance and durability of PEFC. In this study, an X-ray imaging technique was employed to visualize the water distribution in a PEFC quantitatively. X-ray images of the PEFC components with and without water were distinguished clearly. From the visualized X-ray images, we could evaluate the water distribution in the region between separator and gas diffusion layer (GDL) quantitatively. In addition, the contact angle of water in the micro-channels was also clearly visualized.

• 전자공학회논문지A
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• 제30A권12호
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• pp.43-50
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• 1993

Three-dimensional simulator for the ion implantation process is developed. The simulator based on an analytical model which would be a choice with high computational efficiency and accuracy. This is an important issue for the simulation of a numerous number of processing steps required in the fabrication of ULSI or GSI. The model can explain scattering and bulk channeling mechanism (1D). It can also explain depth dependent lateral diffusion effect(2D) and mask effect(3D). The model is consist of one-dimensional JPD(Joined Pearson Distribution) function and two-dimensional modified Gaussian functions. Final implanted profiles under typical mask structures such as hole, line and island structure are obtained with varying ion species.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.66-71
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• 2004

Estimation of the CANDU pressure tube deflection is important since the deflection may cause significant structural failure due to hydrogen diffusion and blister. However, there is no appropriate engineering model to estimate it exactly. The purpose of this paper is to propose a new analysis method and program to resolve this issue. For development of proper analysis method, a series of finite element analyses has been carried under elastic-creep condition. In addition, for effective estimation of the creep deflection, an analysis program named PC-DAS was developed based on the proposed method. Comparison of simple case study results with corresponding reference ones showed good agreement. Therefore, the proposed method and program can be utilized as one of valuable toolkit for integrity assessment of CANDU pressure tube.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.5035-5048
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• 2016

Nano scale networks are futuristic networks deemed as enablers for the Internet of Nano Things, Body area nano networks, target tracking, anomaly/ abnormality detection at molecular level and neuronal therapy / drug delivery applications. Molecular communication is considered the most compatible communication technology for nano devices. However, connectivity in such networks is very low due to inter-symbol interference (ISI). Few research papers have addressed the issue of ISI mitigation in molecular communication. However, many of these methods are not adaptive to dynamic environmental conditions. This paper presents an enhancement over original Memory-1 ISI cancellation scheme using maximum likelihood estimation of a channel parameter (λ) to make it adaptable to variable channel conditions. Results of the Monte Carlo simulation show that, the connectivity (P_conn) improves by 28% for given simulation parameters and environmental conditions by using enhanced Memory-1 cancellation method. Moreover, this ISI mitigation method allows reduction in symbol time (Ts) up to 50 seconds i.e. an improvement of 75% is achieved.

• Structural Engineering and Mechanics
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• 제84권6호
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• pp.831-849
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• 2022

One of the most prevalent causes of reinforced concrete (RC) structural deterioration is chloride-induced corrosion. This paper aims to provide a comprehensive insight into the environmental effect of RC's chloride ingress process. The first step is to investigate how relative humidity, temperature, and wind influence chloride ingress into concrete. The probability of initiation time of chloride-induced corrosion is predicted using a probabilistic model that considers these aspects. Parametric analysis is conducted on several factors impacting the corrosion process, including the depth of concrete cover, surface chloride concentration, relative humidity, and temperature to expose environmental features. According to the findings, environmental factors such as surface chloride concentration, relative humidity and temperature substantially impact on the time to corrosion initiation. The long- and short-distance impacts are also examined. The meteorological data from the National Meteorological Center of China are collected and used to analyze the environmental characteristics of the chloride ingress issue for structures along China's coastline. Finally, various recommendations are made for improving durability design against chloride attacks.

• Steel and Composite Structures
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• 제47권4호
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• pp.539-550
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• 2023

Owing to the obstruction of section steel on the moisture diffusion in concrete, the existing shrinkage prediction models overestimate the time-dependent deformation of steel reinforced concrete (SRC) columns, particularly for the SRC columns with enclosed section steels. To solve this issue, this study deals with analytical and experimental studies on the drying shrinkage for this type of column. First, an effective method for predicting the drying shrinkage of concrete based on finite element model is introduced and two crucial parameters for simulation of humidity field are determined. Then, the drying shrinkage of SRC columns with enclosed section steels is investigated and two modified parameters, which depend on the ambient relative humidity and the ratio of section steel size to column size, are introduced to the B3 model. Finally, an experiment on the shrinkage deformation of SRC columns with enclosed section steels is conducted. Comparing the predicted results with the experimental ones, it demonstrates that the modified B3 model is quite reasonable.

• 기술혁신연구
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• 제23권4호
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• pp.33-61
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• 2015

국가가 새로운 경제체제로 들어서게 되면서 겪는 어려움과 피해는 생각보다 크다. 지금까지 경제 패러다임이 바뀌면서 국가들이 겪었던 과정을 거치며 경제의 성장과 수렴을 일으킨 여러 가지 요인이 있었다. 특히 혁신과 제도는 그간의 경제성장에 있어서 중요한 요소임에도 횡단면 분석이나 경제적 모형측면에서만 다루어졌던 한계성이 있다. 본 연구에서는 국가혁신역량의 다양성과 제도의 질이 국가의 경제성장에 미치는 요인을 살펴보려고 한다. 또한 최근 경제성장의 주요요인으로 다루어지고 있는 인적자본역량과 해외직접투자와의 관계도 살펴보며, 경제성장 모형에 대한 심층적 고찰을 한다. 경제수준에 따라서 총 4개의 국가그룹으로 64개 국가를 대상으로 분석하였으며, 1995년부터 2011년까지의 데이터를 기반으로 패널모형을 사용해 연구문제에 대해 구조적인 측면의 시사점을 살펴보았다. 연구결과, 국가의 경제수준에 따라서 연구개발 비중과 혁신역량의 다양성은 경제성장에 의미있는 변화를 주었으며, 해외직접투자는 모든 소득그룹에서 경제성장에 긍정적인 효과를 보였다. 국가혁신역량에 있어서는 확산성과 개방성이 경제성장에 가장 의미있는 변수였으며, 이는 경제수준이 높은 국가들의 혁신역량이 경제성장에 미치는 영향이 크기 때문이라고 보인다. 반대로, 경제수준이 낮을수록 혁신역량 및 제도의 수준이 경제성장에 부정적인 영향을 미친다. 개별 국가의 제도의 질 및 경제수준에 따라서 차별적이기에 모호한 측면이 있다고 판단된다. 본 연구를 통해서 국가의 경제수준에 따른 혁신 요소 및 제도적 요인의 적절한 투입과 정책수립에 중요하다는 시사점을 줄 수 있다고 보인다.