• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.128-134
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• 2003

Numerical study on interactions of waves and currents has considerable practical interests in coastal and ocean engineering. And wave-current interactions strongly influence wave characteristics, current profiles, and forces on offshore structures. Presence of currents affects wave properties such as wave height and wave profiles. Furthermore, in case of the irregular waves, it is more complicated problem. The propose of present study, using the one-dimensional wave-current numerical model is based on the extended Boussinesq equation(Madsen, 1991) and an alternative form of wave-current dispersion relation(Mohiuddin, 1999, 2000) including wave action concept, is to simulate wave propagation in a current field including the irregular waves and discuss applicability of the model in a wave-current field.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.62.1-62.1
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• 2011

Warp phenomenon seems to be ubiquitous among spiral galaxies, and a a number of mechanisms have been suggested as the origin including cosmic infall and tidal interactions. In this work, we compare warp characteristics of cluster spirals and the ones in the field in order to investigate the influence of environment on warping, in particular of gas disks. We make use of a tilted-ring modeling (TRM) method to VLA HI (21cm) data cubes of carefully selected 20 spiral galaxies in the Virgo cluster. The TRM allows us to probe kinematics, e.g., inclination, position angle, and velocity dispersion of HI disks. We compare the properties of each tilted-ring component to mean properties based on optical images. In this contribution, we present preliminary yet important findings on the warp characteristics of spiral galaxies in dense environment, and discuss possible origins of those kinematical structures.

• Korean Institute of Interior Design Journal
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• v.24 no.5
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• pp.128-135
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• 2015

The purpose of this study is to propose a planning method for increasing visitors' usage attraction by understanding user circulation in the large scale commercial complex. Focusing on the impact of anchor tenant on the pedestrian traffic arousing visitors' usage attraction flow, this study analyzed pedestrian circulation and traffic volume of Lotte World Mall, a large scale commercial complex. In this study, the change of pedestrian traffic in the commercial complex was investigated and the circulation flow of anchor tenant visitors such as movie theater in the commercial complex was simulated by computer. By analyzing both characteristics of pedestrian circulation and traffic volume in large scale commercial complex and movie theater users' pedestrian traffic with network-based computer simulation, positive relationship between pedestrian traffic to movie theater and pedestrian traffic dispersion of the whole commercial complex users was emerged. In addition, It is necessary to plan of distributing pedestrian traffic of vertical moving line in central space appropriately for using attraction function of anchor tenant.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.118-122
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• 2013

For safe evacuation in the fire disaster, the evacuees must find the exit and evacuate quickly. Especially, if the evacuees don't know the location of the exit, they have to depend on the evacuation guidance system. Because the more smoke spread, the less visibility is decreasing, it is difficult to find the way to the exit by the naked eye. For theses reasons, the evacuation guidance system is highly important. However, the evacuation guidance system without change of direction has the risk that introduce to the dangerous area. In the evacuation safety assessment scenario by the evacuation simulation has the same problem. Because the evacuee in the simulation evacuate by the shortest route to the exit, the simulation result is same like the evacuation without the evacuation guidance system. In this study, it was used with MAS (Multi Agent System)-based simulation program including the evacuation guidance system to implement the change of evacuation by fire. Using this method, confidence of evacuation safety assessment can be increase.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.1
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• pp.34-41
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• 2003

Connectivity is a quantitative indicator of landscape structure, and connectivity of urban green areas is an indicator of ecological integrity in urban landscapes. The purposes of this study are to assess the connectivity of urban green areas in Seoul, and to develop a method of siting new green areas for better connectivity. Diverse methods for connectivity assessment and indices of connectivity are reviewed and applied to the connectivity assesment of green areas in Seoul. The indices of connectivity of green areas in Seoul turned out to be higher than expected, maybe because many of them are rather evenly distributed, serving as stepping stones, and because there are many riparian corridors, including the Han River. Analysis also shows the optimum location of new green space patches or corridors will be those spots that would link the mainland, or large green areas outside the city, and existing green areas in the city. Restoration of urban streams as ecological corridors will significantly enhance connectivity. Three different scenarios with increasing numbers of new green areas in the city were then prepared. The changes of connectivity were measured and the possible success rates of animal dispersal were simulated. The results revealed that restoration of streams will increase the connectivity and success rates of animal dispersal.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.3
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• pp.13-24
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• 2000

In urban area, urban forests work as an ecological center that mitigates the environmental pollution of the area. In order to maintain the ecological function of a forest, the management method should be established based on ht through investigation of the vegetation structure of the forest. In this study, the vegetation structure of Namsan in Kyungju area was investigated in order to study the ecological value of Namsan and to suggest a desirable management alternative. 21 plots were selected as survey areas. Using the TWINSPAN technique, the forest of Namsan was classified into four communities: Quercus serrata community(I), Castanea crenata-Q. serrata-Q. mongolica community(II), Pinus densiflora community(III) and P. densiflora-P. rigida-Robinia pseudoacacia community(IV). The survey results were summarized by five: 1) the distribution of vegetation showed 2) P. densiflora was the absolutely dominant species in Namsan, 3) number of the average species was 12.6$^{\circ}$$\pm$3.1, 4) number of individual was 131.1$^{\circ}$$\pm$47.8 per a plot(100$m^2$), 5) the results of annual ring analysis revealed that the age of P. densiflora in Namsan was about 3 0$^{\circ}$~60$^{\circ}$years old. From the above results, it was found out that the forest has two problems. One thing is maintenance of P.densiflora against succession, another is artificial forest dispersion. The problems of Namsan forest management will be solved with further studies related.

• Journal of Sensor Science and Technology
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• v.22 no.5
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• pp.315-320
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• 2013

In this paper, the properties of strain sensors made of spin-capable multi-walled carbon nanotubes (MWCNTs) were characterized and their sensing mechanisms analyzed. The key contribution of this paper is a new fabrication technique that introduces a simpler transfer method compared to spin-coating or dispersion CNT. Resistance of the MWCNT sheet strain sensor increased linearly with higher strain. To investigate the effect of CNT concentration on sensitivity, two strain sensors with different layer numbers of MWCNT sheets (one and three layers) were fabricated. According to the results, the sensor with a three-layer sheet showed higher sensitivity than that with one layer. In addition, experiments were conducted to examine the effects of environmental factors, temperature, and gas on sensor sensitivity. An increase in temperature resulted in a reduction in sensor sensitivity. It was also observed that ambient gas influenced the properties of the MWCNT sheet due to charge transfer. Experimental results showed that there was a linear change in resistance in response to strain, and the resistance of the sensor fully recovered to its unstressed state and exhibited stable electromechanical properties.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.400-403
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• 2013

The piezoelectric composite film of ferroelectric PZT ceramic ($PbZr_xTi_{1-x}O_3$) and polymer (PDMS, Polydimethylsiloxane) was prepared to improve the flexibility of piezoelectric material. The bar coating method was applied to fabricate flexible nanocomposite film with large surface area by low cost process. In the case of using metal electrode on the composite film, although there is no problem by bending process, the electrode is usually broken away from the film by stretching process. However, the well-attached, flexible CNT electrode on PZT/PDMS film improved flexibility, especially stretchability. PZT particles was usually settled down into polymer matrix due to gravity of the weighty particle, so to improve the dispersion of PZT powder in polymer matrix, small amount of additives (CNT powder, Carbon nanotube powder) was physically mixed with the matrix. By stretching the film, an output voltage of PZT(70 wt%)/PDMS with CNT (0.5 wt%) was measured.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.6
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• pp.508-519
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• 2006

In solar power system, the height and azimuth of the sun are important parameters which control generated power magnitude. The tracking method that controls the daily generation magnitude according to latitude and longitude using the two axles is often used in the existing sunlight tracking system today. In this two-axle PV track control system, the self-load is concentrated on one FRAME. It is influenced of the regular load, snow load and the wind load, etc. It is difficult to set up the system in the conventional building. This research is a development about the small-scale economy track device of independent load-dispersing solar generation system. The position tracking algorithm is through the new coordinates transformation calculating the height and azimuth of the sun.

• Microbiology and Biotechnology Letters
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• v.18 no.1
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• pp.66-70
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• 1990

A study on 11 $\alpha$-hydroxylation of progesterone by using Rhizopus nigricans was carried out to produce efficiently 11 $\alpha$-hydroxyprogesterone which is an essential intermediate of corticosteroids synthesis. Firstly, medium was optimized in view of bioconversion yield and cell growth. Glucose and casamino acid were selected as carbon and nitrogen source and the ratio of carbon to nitrogen which maximize bioconversion yield was determined to be 2:1. Secondly, the addition time of progesterone and dispersion method were studied. When progesterone dispersed with 0.01% (v/v) Tween 80 was added at 12-14 hr of cultivation, higher bioconversion yield was obtained. When 20g/$\ell$ of progesterone was added, the yield reached 70% under optimized conditions.