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- 저자 : 이기준 (검색결과 554 건)
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이기준,Sather,N F 한국화학공학회 1971 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.9 No.4
This paper presents a statistical mechanical description of the random motion of particles in suspension and some results derived there-from for the viscosity of concentrated suspensions of solid spherical particles. In statistical mechanics the information about the probability of dynamical states of the particles of a fluid (i. e., their positions, translational velocities and rotational velocities) is embedded in a particle distribution function, and all of the macroscopic properties of the fluid are specified as integral moments of the distribution function. In particular, the local stress in a suspension is defined as the integral over all particle states of the distribution weighted with the stress at a point for a given instantaneous total particle state. Thus, the calculation of the rheological properties of the suspension comes down to a determination of the distribution function and this local stress function. If the overall shear rate in the suspension is steady and not too large and the particles are neutrally buoyant solid spheres, the net forces and torques on the particles are zero and the local fluid motion is governed by the Stokes equations. It is shown that under these conditions 1) the particle distribution function is independent of the linear and angular velocities of the particles and so is uniquely determined by the particle positions, 2) the viscosity of the suspension must be independent of the shear rate for all concentrations, and 3) the viscosity can be written in a power series in the concentration of particles in which the term of the nth power is the incremental contribution to the viscosity from interactions involving particles. In order to calculate the coefficients of these terms the fluid velocity near the surface of a sphere moving with its neighbors in a, shear field is required. Since an exact determination of the flow field is impractical to obtain for groups of more than two particles, an approximate solution of the Stokes equations obtained by the method of weighted residuals is used in the calculations of the suspension viscosity reported here. The particle configuration is assumed to be simple cubic, and the distribution of interparticle distances is obtained from an approximate statistical model. The viscosity-concentration relationship calculated under these assumptions is found to agree closely with the compilations of experimental data reported by Rutgers and Thomas.
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이기준,윤세중,이현구 한국화학공학회 1986 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.24 No.1
구형 무연탄 입자에 대하여 수축핵모델을 적용하여 비등온 연소현상을 연구하였다. 설정된 모델의 해가 존재하는 가능성영역(feasibility region)을 추적하여 연소현상의 예측에 이용하였으며 이 영역의 경계곡선은 단일회분층모델과 이중회분층모델로 표현되는 3종류의 한계상황을 해석하여 결정될 수 있음을 보였다. 이로부터 여러가지 입자표면온도에 대응하는 미반응탄 표면온도의 상한과 하한을 추정하였으며, 또한 입자표면에서의 반응물 및 생성물의 속(束)들과 에너지속(束)의 상한과 하한을 식으로 표현하고 반응의 진행에 따라 가능성영역이 변화하는 추이를 관찰하였다. 무연탄입자 연소의 경우 해의 다중성이 나타날 가능성은 적으며 입자표면온도가 높을 때 회분층에서 CO의 재연소반응은 무시될 수 있는 것으로 추론된다. A nonisothermal combustion model for a spherical anthracite briquette is developed and studied on the basis of the unreacted shrinking core model. The feasibility region, in which the solution must lie, is constructed and used for the prediction of the combustion characteristics. It turns out that the bounding curves of the feasibility region may be determined by analyzing the three limiting cases known as the single ash layer model and the double ash layer model. This treatment enables us to find the upper and lower bounds of the unreacted core surface temperature corresponding to various particle surface temperature. The solutions of the limiting cases provide expressions for the upper and lower bounds of the mo'1ar fluxes of the reactants and products as well as those of the energy flux at the particle surface. Also examined is the way how the feasibility region changes as the combustion proceeds. In the case of anthracite briquitte combustion it is unlikely that multiple solutions may exist and it is deduced that the oxidation reaction of carbon monoxide in the ash layer may be neglected when the particle surface temperature is sufficiently high.
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이기준,이지영 대한공간정보학회 2013 Spatial Information Research Vol.21 No.3
Indoor space is a new horizon of spatial information services. With recent progress of indoor positioning technologies and mobile devices such as smart phones, indoor spatial information services become available and an emerging market. Accordingly, exchanging and sharing indoor spatial information between independent services become an important issue. For this reason, a standardization working group, called IndoorGML has been launched last year in OGC with the aim of publishing IndoorGML standard by September, 2013. Its primary goal is to provide a framework for representing network topology in indoor space, which is a fundamental element of indoor LBS. In this paper, we will explain the basic concepts of indoorGML and discuss the modeling issues. And several application use-cases of IndoorGML will be also presented in this paper. 실내공간은 공간정보 서비스의 새로운 대상이다. 최근 실내공간 측위 기술의 발달과 스마트폰 등 이동기기의 보편화로 실내공간도 위치기반 서비스와 같은 서비스가 가능하여지고 있다. 따라서 실내공간 정보의 교환 및 공유를 위한 표준화도 중요한 요구사항으로 떠오르고 있다. 이러한 배경에서 국제공간정보 표준화기구인 OGC에서는 실내공간정보 표준인 IndoorGML 표준화 작업반을 2012년에 조직하고 2013년 9월 표준화를 목적으로 현재 작업 중이다. IndoorGML은 특히 실내공간의 위치기반 서비스를 제공하기 위하여 가장 기초가 되는 네트워크 위상을 표현하는 것을 목적으로 한다. 본 논문에서는 첫 번째로 현재 표준화되고 있는 IndoorGML의 기본 개념을 설명한다. 두 번째로 IndoorGML의 모델의 구체적 사항을 살펴보고, 세 번째 간단한 응용 사례를 제시한다.
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