• Bulletin of the Korean Chemical Society
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• 제21권3호
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• pp.310-316
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• 2000

Molecular dynamics simulation studies for thermotropic liquid crystalline systems conposed of rodlike molecules with 6 Lennard-Jones interaction sites wre performed in NPT ensemble. Within the range of temperature studied, the system exhibited isotropic and smectic phase. For the characterization of the smectic phase, we examined the structure of the liquid crystalline phase via the radial distribution function, its longitudinal and transverse components to the director, and other orientational correlation function, its longitudinal and transverse components to the director, and other orientational correlation functions. In the smectic A phase, our results showed a large anisotropy in translational motion (i.e.,$D_⊥ >> D_∥$), and the decay of the collective orientational correlation function of rank two became slower than that of the single particle orientational correlation function of rank one. Comments on the spontaneous growth of orientational order directly from the isotropic phase are given.

• 생태와환경
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• 제37권3호통권108호
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• pp.304-312
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• 2004

수 생태계 내에서 흔히 볼 수 있는 3영양단계 먹이사슬 구조를 이루는 종들이 밀도비 의존 모델로써 구현 될 때 외부 환경에 대해서 어떻게 반응하는지를 연구하였다. 환경 요인은 주기적 요인과 일반적 노이즈 두 부분으로 나누었다. 주기적 요인이 온도로써 대표되었을 때 온도변이를 바이어스와 주기로 나누었고, 기타 복합적인 노이즈는 가우스 분포로 나타내었다. 온도변이 바이어스 ${\varepsilon}$, 온도주기 ${\Omega}$, 및 가우스 노이즈 크기 ${\'{O}}$가 서로 결합하여 3영양단계 먹이사슬에서 개체군 멸절을 포함한 다양한 개체군 동태를 보여 주었다. 변수의 적절한 값에 따라 '안정된 제한 사이클'이나 '이상한 끌개'를 보여 주었으며, 전체적으로 개체군 동태는 환경 변수에 따라 민감하게 반응하였고, 포식자 및 최상위포식자 개체군의 멸절시간이 조절되었다.

• Journal of Microbiology and Biotechnology
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• 제17권3호
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• pp.496-510
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• 2007

This paper describes the use of a discrete mathematical model to represent the basic mechanisms of regulation of the bacteria E. coli in batch fermentation. The specific phenomena studied were the changes in metabolism and genetic regulation when the bacteria use three different carbon substrates (glucose, glycerol, and acetate). The model correctly predicts the behavior of E. coli vis-a-vis substrate mixtures. In a mixture of glucose, glycerol, and acetate, it prefers glucose, then glycerol, and finally acetate. The model included 67 nodes; 28 were genes, 20 enzymes, and 19 regulators/biochemical compounds. The model represents both the genetic regulation and metabolic networks in an integrated form, which is how they function biologically. This is one of the first attempts to include both of these networks in one model. Previously, discrete mathematical models were used only to describe genetic regulation networks. The study of the network dynamics generated 8 $(2^3)$ fixed points, one for each nutrient configuration (substrate mixture) in the medium. The fixed points of the discrete model reflect the phenotypes described. Gene expression and the patterns of the metabolic fluxes generated are described accurately. The activation of the gene regulation network depends basically on the presence of glucose and glycerol. The model predicts the behavior when mixed carbon sources are utilized as well as when there is no carbon source present. Fictitious jokers (Joker1, Joker2, and Repressor SdhC) had to be created to control 12 genes whose regulation mechanism is unknown, since glycerol and glucose do not act directly on the genes. The approach presented in this paper is particularly useful to investigate potential unknown gene regulation mechanisms; such a novel approach can also be used to describe other gene regulation situations such as the comparison between non-recombinant and recombinant yeast strain, producing recombinant proteins, presently under investigation in our group.

• 한국습지학회지
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• 제20권3호
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• pp.256-262
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• 2018

생태계 내에서 개체군 변동을 이해하는데 다양한 시간 스케일에서의 분석이 유용한 방법이 될 수 있다. 최근까지 다양한 시간 스케일에서의 개체군 변동에 대한 연구는 거의 드물다. 본 연구는 2014년부터 2017년까지 4년간 충남 당진시 석문면 논에 도래하는 백로류 개체군을 대상으로 시간 스케일에 따른 이들 개체군 변동에 영향을 미치는 요인을 확인하기 위해 수행되었다. 백로류는 황로, 왜가리, 중대백로, 중백로, 쇠백로만을 대상으로 하였으며, 고정된 지점에 설치된 무인모니터링 시스템을 활용하여 백로류의 개체군 변동을 다른 시간 단위의 스케일인 월 단위와 일 단위 변동으로 나누어 확인하였다. 그 결과, 월별 개체군 변동에 영향을 미치는 요인은 시기, 평균 온도, 평균 강수량으로 나타났고, 일별 개체군 변동에 영향을 미치는 요인은 평균 온도와 서식지 유형이 중요한 것으로 확인되었다. 시기의 통계적 유의성이 일 단위에서는 나타나지 않고 월 단위에서 확인된 이유는 백로류의 논 이용 패턴이 일 단위보다는 월 단위 스케일에서 명확히 구별되기 때문으로 판단된다. 이를 통해 시간 스케일에 따라 백로류에 영향을 미치는 요인에 차이가 있다는 것을 확인할 수 있었다.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.293-310
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• 2006

In seismic prone areas it is possible to meet very different objects (equipment components, on shelf artefacts, simple architectural elements) that can be modelled as a rigid body rocking on a rigid foundation. The interest in their behaviour can have different reasons: seismological, in order to estimate the ground motion intensity, or more strictly mechanical, in order to limit the response severity and to avoid overturning. The behaviour of many rigid bodies subjected to twenty wide ranging acceleration recordings is studied here. The response of the blocks is described using kinematic and energy parameters. A condition under which a so called scale effect is tangible is highlighted. The capacity of the signals to produce overturning is compared to different ground motion parameters, and a good correlation with the Peak Ground Velocity is unveiled.

• 한국초지조사료학회지
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• 제17권3호
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• pp.223-230
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• 1997

The experiments were undertaken to investigate the dynamics of $NO_3\;^-$ uptake at low temperature with forage rape(Bmssica napus), barle(Hordeum vulgare) and winter rye (Scale cereale). A net $NO_3\;^-$uptake and the contents of nitrogenous compound in tissues at low temperature ($5^{\circ}C$) were compared with normal temperature ($25^{\circ}C$).The net uptake of $NO_3\;^-$ by Brass ica nqus was the highest among three species at both temperature applied. During 9 hours after temperature treatment, $NO_3\;^-$ uptake of Brassica napus, Hordeum vulgm and Scale c e d e grown at $5^{\circ}C$ decreased to about 31, 50 and 27% compared with those grown at $25^{\circ}C$. $NO_3\;^-$ contents in roots were much sensitively affected by low temperature than those of leaves. Comparing with the plants grown at $25^{\circ}C$, $NO_3\;^-$ contents in roots of increased to 48.3, 38.7 and 53.5% repectively, for Brassica napus, Hordeum vulgare and Scale cereale during 9 days. A relatively less changes in the content of $NH_4\;^+$-N were observed according to the temperature treatment. The ontents of amino acids-N in leaves at $5^{\circ}C$ slightly decreased while that of roods remarkably increased compared with $25^{\circ}C$. Protein-N was the largest pool of nitrogen and its contents in leaves and roots showed a similar response on the temperature treatment. These results suggested that $NO_3\;^-$uptake was inhibited at low temperature. The dynamics of $NO_3\;^-$ uptake could be closely related to the increased concentration of $NO_3\;^-$ and amino acids in roots.

• Asia pacific journal of information systems
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• 제13권3호
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• pp.23-39
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• 2003

Recently, many organizations in various industries have introduced e-business for the purpose of adding value to their business. But, the e-business model has not existed before and so, it is difficult to analyze clear effectiveness. It frequently does not live up to an organization's expectations. It is due to an absence of environmental changes analysis in the new model, not by a new model itself. System Dynamics(SD) may provide effective results as a tool of analysis for the new model. This research shows the analysis of the effects of a simulated e channel model, which was expanded from existing channel modeling with actual data in basic materials industries. The results show average prices increasing by auction process on the e-market and an increase in sales. So, by increasing the speed of sale revolution stock expenses are reduced. Additionally, we applied a possible scenario to the developed simulation model and investigated strategic issues to draw desirable strategies with market changes.

• Smart Structures and Systems
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• 제22권1호
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• pp.13-25
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• 2018

Pedro $G{\acute{o}}mez$ Bosque footbridge is a slender and lightweight structure that creates a pedestrian link over the Pisuerga River, Valladolid, Spain. This footbridge is a singular stress ribbon structure with one span of 85 m consisting on a steel plate and precast concrete slabs laying on it. Rubber pavement and a railing made of stainless steel and glass complete the footbridge. Because of its lively dynamics, prone to oscillate, a simple and affordable structural health monitoring system was installed in order to continuously evaluate its structural serviceability and to estimate its modal parameters. Once certain problems (conditioning and 3D orientation of the triaxial accelerometers) are overcome, the monitoring system is validated by comparison with a general purpose laboratory portable analyzer. Representative data is presented, including acceleration magnitudes and modal estimates. The evolution of these parameters has been analysed over one-year time.

• 한국정밀공학회지
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• 제27권3호
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• pp.95-103
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• 2010

Roll to Roll (R2R) is one of the most promising production technologies in the printed electronics such as OLEDs, e-paper, backplanes, RFID because this technology can save production cost and increase production speed. Printed electronics includes various processes such as printing, drying, winding, unwinding, and so on. In printed electronics R2R system, air-flotation oven is employed for drying process. Therefore, it is essential to introduce efficient and fast drying process when printing is finished. This paper considers the analysis of drying process in R2R that involves hot air flow. Air-flotation oven consists of non-contact supports and drying of coated web materials such as plastic films and paper. In this paper, experimental results and numerical analysis of pressure-pad air bar are investigated. The aerodynamic characteristics of pressure-pad air bar are numerically calculated using computational fluid dynamics (CFD) approach. Then the measured values of the aerodynamic forces for air bars are compared with those of CFD analysis.

• Bulletin of the Korean Chemical Society
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• 제23권1호
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• pp.48-52
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• 2002

Using several molecular modeling programs we have performed computer simulations to investigate the complexation behaviors of an ester derivative of p-tert-butylcalix[5]arene (1e) toward a variety of butylammonium ions. Semi-empirical AM1 method was used for calculating the binding energies and the formation enthalpies. MM and CVFF forcefields for molecular mechanics calculations were adapted to express the complexation energies of the host. Molecular dynamics were performed to the calculated complex systems to simulate the ionophoric behavior of the host-guest complexes. The absolute Gibbs free energies of the host (1e) complexed with four kinds of butylammonium ions have been calculated using the Finite Difference Thermodynamic Integration (FDTI) method in Discover. Calculation results show that the trend in complex formation is n-$BuNH_3^+$ > iso-$BuNH_3^+$ >> sec-$BuNH_3^+$ > tert-$BuNH_3^+$, which is in good agreement with the experimental results.