• Spatial Information Research
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• v.18 no.5
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• pp.27-36
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• 2010

This study observed distribution of vegetation to confirm change of tundra-taiga boundary. Tundra-taiga boundary is used to observe the transfer of vegetation pattern because it is very sensitive to human activity, natural disturbances and climate change. The circumpolar tundra-taiga boundary could observe reaction about some change. Reaction and confirmation about climate change were definite than other place. This study used Leaf Area Index(LAI) 8-Day data in August from 2000 to 2009 that acquire from Terra satellite MODerate resolution Imaging Spectroradiometer(MODIS) sensor and used K$\"{o}$ppen Climate Map, Global Land Cover 2000 for reference data. This study conducted analysis of spatial distribution in low density vegetated areas and inter-annual / zonal analysis for using the long period data of LAI. Change of LAI was confirmed by analysis based on boundary value of LAI in study area. Development of vegetation could be confirmed by area of grown vegetation($730,325km^2$) than area of reduced vegetation ($22,372km^2$) in tundra climate. Also, area was increased with the latitude $64^{\circ}$ N~$66^{\circ}$ N as the center and around the latitude $62^{\circ}$ N through area analysis by latitude. Vegetation of tundra-taiga boundary was general increase from 2000 to 2009. While area of reduced vegetation was a little, area of vegetation growth and development was increased significantly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.135-146
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• 2020

To define an interface in a conventional level-set method, an analytical function must be revealed for an interfacial geometry. However, it is not always possible to define a functional form of level sets when interfaces become complex in a Cartesian coordinate system. To overcome this difficulty, we have developed a new level-set formalism that discriminates the interior from the exterior of a CAD modeled interface by parameterizing the stereolithography (STL) file format. The work outlined here confirms the accuracy and scalability of the hydrodynamic reactive solver that utilizes the new level set concept through a series of tests. In particular, the complex interaction between shock and geometrical confinements towards deflagration-to-detonation transition is numerically investigated. Also, a process of flame spreading and damages caused by point source detonation in a real-sized plant facility have been simulated to confirm the validity of the new method built for reactive hydrodynamic simulation in any complex three-dimensional geometries.

• Korea Petroleum Association Journal
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• s.300
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• pp.40-43
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• 2016

지난 3월, 서울에서 세기의 대결이 펼쳐졌다. 구글의 '알파고'와 이세돌 9단의 바둑 대결이 벌어진 것. 결과는 4대 1로 알파고의 승리였다. 인간이 기계에 졌다며 침통해 하는 반응이 쏟아지는 한편, 인공지능에 대한 국민의 관심이 최고조로 달아올랐다. '알파고 쇼크' 이후 인공지능으로 대표되는 최첨단 기술의 다음 단계는 무엇이며, 우리는 과연 어떤 미래를 맞이하게 될 것인지에 대해 갑론을박이 벌어졌다.

• Solar Energy
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• v.17 no.1
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• pp.67-77
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• 1997

To develop chemical heat pump of higher energy density and efficiency heat-release characteristics accompanied by exothermic hydration reaction in packed bed, $Ca(OH)_2/CaO$ reactor, are examined in a lab-scale unit. We have studied the enhancement effect of inserted fins in cylindical packed bed reactor. The results obtained by numerical analysis about profiles of temperature, completion time of reaction and exothermic heat amount released from the reactor read the insertion of fins in reactor can reduce the reaction completion time by half and the rate of thermochemical reaction depends on the temperature and concentration, and it is also governed by the boundary conditions and the rate of heat transfer in the particle packed bed.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.1015-1020
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• 2003

The Corrosion behavior of the matrix of the $\rho$-alumina bonded alumina vibrated castable was, on the basis of Jabsen's theory, elucidated by use of the Kingery's reaction mechanism. Corrosion of the matrix during induction period was controlled by the molecular diffusion. The temperature dependence of activation process is well established by the Arrhenius plots. The difference of Ca concentration between slag and interface is 23.2%, which causes a driving force of the materials transfer. The extent of the corrosion of the matrix is more deeper than that of the sintered mullite, but the corrosion mechanism can be well employed as the reaction mechanism proposed by the Kingery. The life time of the castable may be well estimated by the corrosion mechanism of Kingery.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.223-233
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• 1998

The kinetic and mechanism of the hydrothermal reaction between lime and quartz used solid state reaction equations have been investigated. Hydrothermal reaction on the starting materials was carried out in an autoclave that quartz mixed with calcium hydroxide in CaO/$SiO_2$ ratio of 0.8-1.0 for 0.5-8 hour at saturated steam pressure of $180-200^{\circ}C$. The rate of reaction was given from the ratio of uncombined lime and quartz content to the total lime and quartz content. The rate of reaction was obtained the results by the Jander's equation $[1-(1-\alpha)^{1/3}]^N=Kt$. The reaction of lime is controlled mainly by the dissolution such as N=1, and the reaction of quartz is controlled mostly by the diffusion such as $N\risingdotseq2$. The rate of hydrothermal reaction in the calcium silicate hydrates system is suggested to be determined generally by the mass transfer through the product laver formed around the reactant particles. The rate equation for whole hydrothermal reaction is shown that it is converted into the rate determining step by the diffusion from the boundary reaction such as approximately $N=1-2$.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.23-31
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• 2016

자유 라디칼을 이용한 RAFT 중합은 성장하는 고분자 반응을 제어할 수 있는 특성이 있어 주목 받고 있는 고분자 합성방법 중 하나이다. 이 반응의 기작은 agent라 불리는 분자를 주축으로 삼아 단량체들을 단계적으로 성장하는 가역적 방법으로 원하지 않는 종결반응으로부터 고분자 라디칼을 보호하는 역할을 수행한다. 보호의 근본적인 원인은 중간체 상태에서의 안정화 정도와 관련이 있으나 안정해진 만큼 반응속도가 느려지는 지연효과가 발생한다. 지연효과를 유도하는 원인은 많은 논란이 있었으며 그 중 하나로 agent에 존재하는 Z 치환기의 영향을 원인으로 지목하고 있다. 본 연구는 Z 치환기의 변화에 따른 안정화 정도를 파악하기 위하여 RAFT agent로 주로 이용하는 것 중 두 개의 황이 있는 dithioester와 xanthate를 WxMacMolplt 7.3.2를 이용하여 propagation 초기 단계를 구현한 후 GAMESS2 프로그램을 이용하여 양자화학적 계산을 수행하였다. 계산결과 안정화 에너지와 경계 궤도함수에서는 phenyl기가 있을 때 공명효과에 의하여 안정화가 이루어졌으며 또한 propyl benzyl에서도 늘어난 알킬 사슬의 donating effect로 인한 안정화 영향의 범위를 발견하였다. PES 기법을 통해 두 methyl 단량체를 움직이면서 반응하는 동안의 에너지 변화를 알아보았으며 그 결과 dithioester는 Z 치환기의 변화에 더 많이 의존한다는 것을 확인하였다. 본 연구를 종합해본 결과 phenyl을 제외한 aryl기가 있는 dithioester는 낮은 addition 퍼텐셜과 안정화 에너지를 가질 수 있을 것이고 지연효과를 줄일 수 있을 것으로 기대된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.625-630
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• 2013

The friction behavior of a 60-${\mu}m$-thick anodic aluminum oxide (AAO) film having cylindrical nanopores of 45-nm diameter was investigated as a function of impregnated oil viscosity ranging from 3.4 to 392.6 cSt. Reciprocating ball-on-flat sliding friction tests using a 1-mm-diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 to 1 N in an ambient environment. The friction coefficient significantly decreased with an increase in the oil viscosity. The boundary lubrication film remained effectively under all test conditions when high-viscosity oil was impregnated, whereas it was easily destroyed when low-viscosity oil was impregnated. Thin plastic deformed layer patches were formed on the worn surface with high-viscosity oil without evidence of tribochemical reaction and transfer of counterpart material.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.41-44
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• 2007

Steam reforming reaction of natural gas is an important process for fuelcell commercialization. In this paper, steam reforming reaction is studied by numerical method. Pseudo-homogeneous model is incorporated for chemical reactions and one medium approach is used to take into account thermally equilibrium phenomena between catalyst and bulk gas. The model is validated with our experimental results under the same operating conditions. Because performance of reformer has relation to heat flux from wall, heat flux profiles was investigated by using Nusselt number. Value of Nusselt number in steam reformer is larger than one in channel, which does not have chemical reaction because steam reforming reaction is an endothermic reaction. When the difference of Nusselt number at the front and the rear is larger, performance is improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1318-1324
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• 2003

There are two problems in the conventional ART1 algorithm. One is in similarity testing method of the conventional ART1 between input patterns and stored patterns. The other is that vigilance threshold of conventional ART1 influences the number of clusters and the rate of recognition. In this paper, new similarity testing method and dynamical vigilance threshold method are proposed to solve these problems. The former is similarity test method using the rate of norm of exclusive-NOR between input patterns and stored patterns and the rate of nodes have equivalence value, and the latter method dynamically controls vigilance threshold to similarity using fuzzy operations and the sum operation of Yager. To check the performance of new methods, we used 26 alphabet characters and nosed characters. In experiment results, the proposed methods are better than the conventional methods in ART1, because the proposed methods are less sensitive than the conventional methods for initial vigilance and the recognition rate of the proposed methods is higher than that of the conventional methods.