• Nuclear Engineering and Technology
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• 제22권1호
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• pp.20-28
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• 1990

처분 안전성 평가를 위해서는 지하매질을 통한 방사성핵종의 이동특성 규명과 신뢰성 있는 지하 핵종이동 모델의 확보가 무엇보다 중요하다. 본 연구에서는 지하핵종이동 모델 개발을 위한 기초연구로서 충전층 실험을 수행하고, 실험결과를 제안된 핵종이동모델과 비교ㆍ검토하였다. 실험에서는 분쇄응회암으로 충전된 칼럼에서의 핵종이동 현상을 규명하고, 모델 시뮬레이션을 통해서는 세공확산을 모델에 고려하여 핵종이동에서 세공확산의 역할을 검토하였다. 충전층 실험에서 수력학적 분산계수는 비흡착성의 iodine을 사용하여 측정하였으며, 이 때 측정한 분산계수는 공극율 $\varepsilon$=0.483, 평균유속 (equation omitted)=0.915$\times$$10^{-2}$ cm/min에서 D$_{L}$=0.11$\times$$10^{-2}$ $\textrm{cm}^2$/min이었다. 그리고 중ㆍ저준위 방사성폐기물의 대표 핵종으로 사용한 Cs-137은 응회암에 대해 높은 지연특성을 보였으며, 파과곡선은 비대칭 형태로서 단말현상이 길게 나타났다. 모델 시뮬레이션 결과, 매질 세공내 확산과정은 다공성의 지하매질을 통한 핵종이동에서 중요한 율속단계 역할을 하였다.다.

• 대한수학회보
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• 제50권2호
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• pp.353-373
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• 2013

In this paper, a class of delayed predator-prey models of prey migration and predator switching is considered. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulations for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given.

• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.269-278
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• 2014

When concrete is being transported through a pipe, the lubrication layer is formed at the interface between concrete and the pipe wall and is the major factor facilitating concrete pumping. A possible mechanism that illustrates to the formation of the layer is the shear-induced particle migration and determining the rheological parameters is a paramount factor to simulate the concrete flow in pipe. In this study, numerical simulations considering various rheological models in the shear-induced particle migration were conducted and compared with 170 m full-scale pumping tests. It was found that the multimodal viscosity model representing concrete as a three-phase suspension consisting of cement paste, sand and gravel can accurately simulate the lubrication layer. Moreover, considering the particle shape effects of concrete constituents with increased intrinsic viscosity can more exactly predict the pipe flow of pumped concrete.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1638-1642
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• 2008

Cell migration is one of the essential mechanisms responsible for complex biological processes. Intensive researches have begun to elucidate the mechanisms and search intriguing conditions for efficient control of cell migration. One general mechanism which is widely applicable for cells including neutrophil, Escherichia coli and endothelial cell is chemotaxis. Especially, understanding the chemotactic mechanics of cell crawling has important implications for various medical and biological applications. The single cell study for chemotaxis has an advantage over studies with the population of cells in providing a clearer observation of cell migration, which leads to more accurate assessments of chemotaxis. In this paper, we propose a three-dimensional model considering a single crawling cell to study its chemotaxis. The semi-implicit Fourier spectral method is applied for high efficiency and numerical stability. The simulation results reveal rich dynamics of cell.

• 물과 미래
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• 제25권2호
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• pp.79-87
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• 1992

본 연구는 굴곡도(sinuosity)가 작은 정현파형(SWR)하천에서 사행 이행의 크기와 방향 및 제방부근의 하상세굴 위치와 크기를 예측할 수 있는 이행특성 모형을 운동량 방정식, 질량보존법칙, 하상 안정식을 적용하여 개발하였다. 본연구에서 황방향 하상계수 B'와 질량 이송계수 a 는 SWR 하천에서 중요한 역할을 하는 변수임이 확인되었으며, 그 값은 각각 B'는 4.0, a는 0.40이 합리적인 값으로 나타났다. 본 모형은 SWR 하천 유역의 개발계획 및 설계시 유용한 정보를 제공해 줄 것이다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권15호
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• pp.6349-6352
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• 2014

The present study was undertaken to determine the roles of insulin in the growth of transplanted breast cancer in nude mice, and the proliferation and migration of MCF-7 human breast cancer cells and assess its influence on downstream signaling pathways. In a xenograft mouse model with injection of MCF-7 human breast cancer cells, tumor size was measured every other day. The insulin level and insulin receptor (IR) were increased in the breast cancer patient tissues. Insulin injected subcutaneously around the tumor site in mice caused increase in the size and weight of tumor masses, and promoted proliferation and migration of MCF-7 cells. The effects of insulin on the increase in the proliferation and migration of MCF-7 human breast cancer cells were abolished by pretreatment with the extracellular regulated kinase (ERK) inhibitor PD98059. Insulin increased the phosphorylation of ERK in the MCF-7 cells. These results indicate that insulin promotes the growth of breast cancer in nude mice, and increases the proliferation and migration of MCF-7 human breast cancer cells via the ERK pathway.

• The Journal of Asian Finance, Economics and Business
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• 제9권1호
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• pp.63-71
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• 2022

To investigate the short-run effects of social capital on migration decisions of individuals in the rural areas of Vietnam, we conducted dataset mining and performed regression model analysis in the form of panel data. As control variables, we employed the variable of social capital, which is measured by an individual's network, as well as demographic characteristics of individuals and households. We discovered that when a household is in financial distress, social networks such as linkages or asking for aid from others often enhance individual capacity. Individuals with a large social network outside of their immediate area are more inclined to relocate to the location where their connectors live. Individual participation and degree of participation in the organizational community, on the other hand, have little bearing on the likelihood of migration. In addition, this research examines theories and empirical research on the relationship between social capital and migration. Based on our research findings, we have recommended some measures to boost the efficiency of social capital and migration in rural areas of Vietnam through local government solutions.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.203-207
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• 2008

Prestack depth migration is used to image for complex geological structure such as faults, folds, and subsalt. In this case, it is widely used the surface reflection data as a input data. However, the surface reflection data have intrinsic problems to image the subsalt and the salt flank due to the complex wavefields and multiples which come from overburden. For overcoming the structural defect of the surface reflection data in the imaging, I used the virtual sources in terms of seismic interferometry to image the subsurface and suppress the multiples using the velocity model of the lower part of the virtual sources. The results of the prestack depth migration using virtual source gathers and velocity model below receivers are similar geological interfaces to the results from shot gathers of the conventional ocean bottom seismic survey. And especially artificial interfaces by multiples were suppressed without applying any other data processing to eliminate multiples. This study results by numerical modeling can make a valuable imaging tool when it is applied to satisfied field data for specific condition.

• KDI Journal of Economic Policy
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• 제12권3호
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• pp.27-45
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• 1990

이촌향도형(離村向都型) 인구이동(人口移動) 농촌지역경제(農村地域經濟)에 미치는 영향(影響)에 관해 두가지 상반(相反)된 견해(見解)가 있다. 신고전학파적(新古典學派的) 낙관론(樂觀論) 따르면 이농현상(離農現象)은 농촌지역(農村地域)의 소득(所得)이나 후생수준(厚生水準)을 저해(沮害)하지 않는다고 보는 반면 Lipton (1980)은 그 반대의 견해(見解)를 취하고 있다. 본고(本稿)에서는 비교역재(非交易財)(nontraded goods)에 대한 국제무역이론(國濟貿易理論)과 화란병(和蘭病)(Dutch Disease)의 이론(理論)을 원용하여 농촌(農村)에서 도시(都市)로의 인구이동모형을 개발했다. 이 모형은 이농인구이동(離農人口移動)이 농촌지역(農村地域)의 소득(所得)과 후생수준(厚生水準)을 저해(沮害)한다는 점에서는 Lipton의 견해(見解)와 일치하나 소득(所得)을 감소(減少)시키는 요인들은 Lipton의 모형(模型)에서 지적(指摘)된 것들과는 다르다. 본고(本稿)는 이농현상(離農現象)이 농촌소득(農村所得)을 감소(減少)시키는 이유가 농업생산성(農業生産性)의 하락(下落) 때문이 아니라 농촌노동 및 소비인구의 격감으로 인한 농업부문(農業部門)의 이윤감소(利潤減少)와 농촌(農村) 서비스부문(部門)와 쇠퇴(衰退)때문이라고 주장한다. 1966, 1970, 1975, 1980 및 1985년의 한국인구(韓國人口)센서스 통계자료(統計資料)를 이용하여 주요가설(主要假說)들에 대해 실증분석(實證分析)을 한 결과 신고전학파(新古典學派)의 주장(主張)이나 Lipton의 견해(見解)보다 본(本) 연구모형(硏究模型)의 설명력(說明力)이 더 높은 것으로 밝혀졌다.

• 한국식품영양과학회지
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• 제33권2호
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• pp.447-450
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• 2004

목재에 코팅재로 사용되는 에폭시 수지로부터의 총괄이행량에 대한 모델을 정립하고, 이를 이용하여 안전성확보에 필요한 두께의 정도를 계산하였다. 에폭시 수지를 통한 총괄이행은 위생적 관심영역에서 확산모델에 의하여 해석이 가능하였고, 투과성 겉보기 투과성 지표에 미치는 온도의 영향은 Arrhenius 방정식으로 설명이 가능하였다. 그리고 일반적인 식품공전의 6$0^{\circ}C$, 30분의 용출조건에서 위생적 한도를 만족시키기 위한 최소의 코팅두께는 0.004 mm였다.