• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.255-261
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• 2003

Tunnelling in poor and heterogeneous ground is a difficult task. Even with a good geological investigation, uncertainties with respect to the local rock mass structure will remain. Especially for such conditions, a reliable short-term prediction of the conditions ahead and outside the tunnel profile are of paramount importance for the choice of appropriate excavation and support methods. The information contained in the absolute displacement monitoring data allows a comprehensive evaluation of the displacements and the determination of the behaviour and influence of an anisotropic rock mass. Case histories and with numerical simulations show, that changes in the displacement vector orientation can indicate changing rock mass conditions ahead of the tunnel face (Schubert & Budil 1995, Steindorfer & Schubert 1997). Further research has been conducted to quantify the influence of weak zones on stresses and displacements (Grossauer 2001). Sellner (2000) developed software, which allows predicting displacements (GeoFit$\circledR$). The function parameters describe the time and advance dependent deformation of a tunnel. Routinely applying this method at each measuring section allows determining trends of those parameters. It shows, that the trends of parameter sets indicate changes in the stiffness of the rock mass outside the tunnel in a similar way, as the displacement vector orientation does. Three-dimensional Finite Element simulations of different weakness zone properties, thicknesses, and orientations relative to the tunnel axis were carried out and the function parameters evaluated from the results. The results are compared to monitoring results from alpine tunnels in heterogeneous rock. The good qualitative correlation between trends observed on site and numerical results gives hope that by a routine determination of the function parameters during excavation the prediction of rock mass conditions ahead of the tunnel face can be improved. Implementing the rules developed from experience and simulations into the monitoring data evaluation program allows to automatically issuing information on the expected rock mass quality ahead of the tunnel.

• 한국통신학회논문지
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• 제33권3C호
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• pp.219-233
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• 2008

스케줄링의 목적은 입력 작업(DAG)에 대한 스케줄 결과 길이를 최소화하는 것이다. 이런 스케줄링 문제는 잘 알려진 '정해진 시간 내에 해결하기 어려운 문제(NP-complete)'이며 최적의 스케줄링 결과 값을 얻기 위해서는 휴리스틱으로 해결해야 한다. 선후 관계의 제약을 갖는 노드들의 스케줄링을 효율적으로 수행하기 위해 부모 노드와 이질 프로세서에 대한 정보를 고려하는 TANH(the Task duplication based scheduling Algorithm for Network of Heterogeneous systems), GDL, BIL, TDS과 같은 많은 알고리즘이 제안되었다. 본 논문은 기존의 TANH 스케줄링에서 나타나는 여러 개의 부모 노드와 이질 프로세서에 대한 다양한 경우를 충분히 고려하지 못한 점을 보안하여 향상된 스케줄링을 수행할 수 있는 DTSC (Duplication based Task Scheduling with Communication Cost in Heterogeneous Systems)알고리즘을 제안하였다. 제안된 알고리즘의 성능은 기존 TANH, GDL 알고리즘과 비교하였으며, 스케줄링의 성능 향상을 보여 주었다.

• 자원환경지질
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• 제44권2호
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• pp.161-170
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• 2011

석유공학분야에서 보고된 분율 흐름 접근 방식을 이용하여 물리적 또는 화학적으로 불균질한 매질에서 완전한 삼상유체를 고려할 수 있는 다상 흐름 수치 모의 프로그램인 CHMPS가 개발되었다. 이 프로그램은 석희준과 G.T. Yeh (2008)에 의해 개발된 MPS을 확장하였는데, 친수성이 NAPL 거동에 미치는 영향을 모의하기 위하여 개발되었다. 대부분 존재하는 모델들은 물리적으로 불균질한 매질을 고려하고 이상흐름과 특정한 경계조건에 국한되어 있다. 게다가 대부분의 모델들은 주로 water-wet 매질에만 국한되어 있다. 그러나 실제 존재하는 시스템에서는 water-wet과 oil-wet 매질 사이의 친수성의 변화는 종종 일어난다 더군다나 기름에 의한 다공성 매질의 젖음은 균등하기 보다는 불균질 또는 부분적일 수 있다. 왜냐하면 친수성에 영향을 미치는 요소들과 지하 매질이 불균질하기 때문이다. 따라서, 이번 연구에서는 물리적으로 불균질한 매질 뿐만 아니라 친수성 변에서 화학적으로 불균질한 매질을 CHEMPS을 활용하여 수치모의 하였다. 그 외에도 개개의 상에 대해서 유량 경계조건 및 고정경계조건의 두 가지 형식의 결합으로 표현되는 일반경계조건이 고려되었다.

• Advances in Computational Design
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• 제9권1호
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• pp.39-52
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• 2024

If the governing differential equation arising from engineering problems is treated as an analytic, continuous and derivable function, it can be expanded by one point as a series of finite numbers. For the function to be zero for each value of its domain, the coefficients of each term of the same power must be zero. This results in a recursive relationship which, after applying the natural conditions or the boundary conditions, makes it possible to obtain the values of the derivatives of the function with acceptable accuracy. The elastoplastic analysis of an inhomogeneous thick sphere of metallic materials with linear variation of the modulus of elasticity, yield stress and Poisson's ratio as a function of radius subjected to internal pressure is presented. The Beltrami-Michell equation is established by combining equilibrium, compatibility and constitutive equations. Assuming axisymmetric conditions, the spherical coordinate parameters can be used as principal stress axes. Since there is no analytical solution, the natural boundary conditions are applied and the governing equations are solved using a proposed new method. The maximum effective stress of the von Mises yield criterion occurs at the inner surface; therefore, the negative sign of the linear yield stress gradation parameter should be considered to calculate the optimal yield pressure. The numerical examples are performed and the plots of the numerical results are presented. The validation of the numerical results is observed by modeling the elastoplastic heterogeneous thick sphere as a pressurized multilayer composite reservoir in Abaqus software. The subroutine USDFLD was additionally written to model the continuous gradation of the material.

• Mass Spectrometry Letters
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• 제3권4호
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• pp.108-111
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• 2012

An experimental study on the nascent product of the OH heterogeneous reaction with NaCl was performed under dry and wet conditions using a bead-filled flow tube system coupled to a high-pressure chemical ionization mass spectrometer. The ozone concentration in the flow tube for the atomic hydrogen removal was varied in order to control the conversion reaction of molecular chlorine into HCl for the identification of the nascent product. The mass spectrometric observation was that the $O_3$ introduction reduced the concentration HCl, while it increased the concentration of $Cl_2$ and ClO. Based on the experimental results, we suggest that the nascent product of the titled reaction is gaseous $Cl_2$, which is followed by fast conversion into HCl in presence of H. No significant difference in the concentration profile between under dry and wet (RH = 2%) conditions was observed.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2367-2374
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• 2013

Lysine (Lys) immobilized on zeolite 4A was prepared by a simple adsorption method. The physical and chemical properties of Lys/zeolite 4A were investigated by X-ray diffraction (XRD), FT-IR, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis. The obtained organic-inorganic composite was effectively employed as a heterogeneous basic catalyst for synthesis of ${\alpha},{\beta}$-unsaturated carbonyl compounds. No by-product formation, high yields, short reaction times, mild reaction conditions, operational simplicity with reusability of the catalyst are the salient features of the present catalyst.

• 한국미생물·생명공학회지
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• 제23권4호
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• pp.425-431
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• 1995

A kinetic model of the cyclodextrin formation in a heterogeneous enzyme reaction system using swollen extrusion starch as substrate was derived emphasing the structural features of extrusion starch. The degree of gelatinization, the ratio of accessible and inaccessible portion of extrusion starch, adsorption of CGTase on swollen starch, the structural transformation during reaction, and product inhibition caused by produced CDs were considered in deriving kinetic model. Various kinetic constants were also evaluated. The derived kinetic equation was numerically simulated, which result showed that the derived kinetic equations can be used to predict the experimental data reasonably well under the various experimental conditions. Kinetic model can be utilized for the optimization of enzyme reactor and the process development for CD production from swollen extrusion starch.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.152-161
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• 2000

The catalytically stabilized combustion of $CH_4$-air mixture on platinum catalyst was investigated numerically using a 2-D boundary layer model with detailed heterogeneous and homogeneous chemistries. The actual surface site density of monolith coated with platinum was decided by the comparison with experimental data. The comparisons were made between results for cases where only heterogeneous chemistry was allowed and both heterogeneous and homogeneous chemistries were allowed. It was found that the homogeneous reaction in the monolith had little effect on the change of temperature profile, methane conversion rate and light off location. The contributions of each reactions related with CO formation were discussed on the surface. The effects of operation conditions such as equivalence ratio, temperature, velocity and pressure at the entrance were studied. In thermal combustor, CO and NOx was produced less than 1 ppm at the exit and the production of $N_{2}O$ was more dominant than that of NO.

• Journal of Multimedia Information System
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• 제2권1호
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• pp.153-162
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• 2015

In today's pervasive computing environments, multimedia content should be adapted to meet various conditions of network connections, terminals, and user characteristics. Scalable Video Coding (SVC) is a key solution for video communication over heterogeneous networks, where user terminals have different capabilities. This paper presents a standard-compliant approach that adapts an SVC bitstream to support multiple users. The adaptation problem is formulated as an optimization problem, focusing on the tradeoff between qualities of different spatial layers of an SVC video. Then the adaptation process is represented by standard metadata of MPEG-21, which can be solved by universal processing to enable interoperable and automatic operation. Our approach provides the users with optimal quality, a wide flexibility, and seamless adaptation. To the best of our knowledge, this is the first study that shows the adaptation tradeoff between spatial layers of a conforming SVC bitstream.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2419-2421
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• 2009

A simple and efficient method has been developed for Knoevenagel condensation between aldehydes or ketones and active methylene group by stirring in methylene chloride at 60 ${^{\circ}C}$ under heterogeneous conditions using silica supported ammonium acetate. The products are obtained in excellent yields and are in a state of high purity. The structures of the products were confirmed by IR, $^1H$ NMR and mass spectral data and comparison with authentic samples available commercially.