구장입자의 현탁액에 관한 유동변형론

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.

단면형상이 변하는 박판보의 진동해석에 관한 연구

이기준,사진용,김준식 한국전산구조공학회 2017 한국전산구조공학회논문집 Vol.30 No.2

In this paper, a local deformation effect in thin-walled box beams is investigated via a finite element modal analysis. The analysis is carried out for single-cell and multi-cell box beam configurations. The single-cell box beam with and without a neck, which mimics a simple wind-turbine blade, is analyzed first. The results obtained by shell elements are compared to those of one-dimensional(1D) beam elements. It is observed that the wall thickness plays a crucial role in the natural frequencies of the beam. The 1D beam analysis deviates from the shell analysis when the wall thickness is either thin or thick. The shell modes(local deformations) are dominant as it becomes thin, whereas the shear deformation effects are significant as it does thick. The analysis is extended to the single-cell box beam with a neck, in which the shell modes are confined to near the neck. Finally the multi-cell box beam with a taper, which is quite similar to real wind-turbine blade configuration, is considered to investigate the local deformation effect. The results reveal that the 1D beam analysis cannot match with the shell analysis due to the local deformation, especially for the lagwise frequencies. There are approximately 5∼7% errors even if the number of segments is increased.

3.5미터급 소단면 TBM 및 수직구 시공 기술 개발을 위한 실대형 시험 기술 개발

이기준,강석준,조계춘,홍은수,김경열,권태혁,Lee, Gi-Jun,Gang, Seok-Jun,Jo, Gye-Chun,Hong, Eun-Su,Kim, Gyeong-Yeol,Gwon, Tae-Hyeok 한국터널지하공간학회 2019 자연, 터널 그리고 지하공간 Vol.21 No.3

특집 : 한국공학교육기술학회 설립 10주년 기념 말씀 ; 벌써 십년이....

이기준 한국공학교육학회 ( 구 한국공학기술학회 ) 2003 공학교육동향 Vol.10 No.1

한국공학교육인증원(ABEEK) 출범에 거는 기대

이기준 한국공학교육학회 1999 Ingenium(人材니움) Vol.6 No.3

공학교육 발전과 학부제 추진방향

이기준,김천욱 한국공학교육학회 1996 Ingenium(人材니움) Vol.2 No.4

CityGML과 IndoorGML의 비교 -실내공간정보 구축 사례 고찰-

이기준,김태훈,유형규,강혜경 대한공간정보학회 2015 Spatial Information Research Vol.23 No.4

Due to recent increase of indoor spatial information demands, several international standards have been published for indoor spatial information. OGC has also recently published two standards for indoor space; CityGML and IndoorGM. CityGML aims to provide a standard for 3D city modeling and the level of details (LoD) 4 covers the indoor space. IndoorGML focuses only on indoor space and provides several functions to complement the weakness of CityGML. It is therefore recommended to apply IndoorGML as a combination with CityGML. However since the weakness and strengths between these standards are not yet fully studied and understood, there is no well-defined guideline to apply them in a proper way. It means that we need to carry out a comparative study between them for their proper integration. For this reason, we discuss the pros and cons of these standards from two use-cases. The sites for the use-cases cover Lotte World Mall and Jongno-5 subway station, respectively. We studied these use-cases to compare CityGML and IndoorGML through the data construction of CityGML and IndoorGML for these sites. And based on several application scenarios, we also analyzed the weakness and strengths of each standard from different viewpoints. We expect that these comparative studies will be helpful to make a guideline on the application and integration between CityGML and CityGML 실내 공간정보의 중요성이 증대됨에 따라 여러 가지 실내 공간정보를 위한 국제표준이 최근에 만들어졌다. 그 대표적인 것이 OGC에서 표준으로 만든 CityGML과 IndoorGML이다. CityGML은 3차원 도시모델을 위한 표준으로 상세도 4가 실내공간을 대상으로 하고 있고, IndoorGML은 실내공간을 주 목적으로 만들어진 표준이다. 특히 IndoorGML은 CityGML의 약점을 보완하기 위하여 만들어진 것으로, CityGML과 통합되어 사용될 때, 그 효용가치가 높아진다. 그러나 이 두 가지 표준의 약점과 장점에 대한 이해가 정확하지 않아, 어떻게 통합하여 사용할 것인지에 대한 분명한 기준이 마련되어 있지 않다. 즉, 이 두 가지 표준을 효과적으로 결합하여 사용하려면 먼저 각각의 장단점에 대한 분석이 선행되어야 한다. 따라서 본 논문에서는 실제 적용사례를 분석하여 두 가지 표준의 차이점과 장단점을 분석한다. 실제 적용사례는 롯데월드몰과 종로5가 지하철역을 대상으로 하고 있으며, CityGML 및 IndoorGML 데이터를 구축하여 그 특징을 비교한다. 뿐만 아니라, 몇 가지 적용사례에 대한 시나리오를 정의하여 각각의 표준이 어떻게 이용될 수 있고, 그 장단점이 무엇인지를 분석한다. 이를 통하여 각 표준의 장단점을 분석하여 이 두 가지 표준을 어떻게 적절하게 사용할지 결정하는데, 본 연구의 결과를 활용할 수 있도록 한다.

한국공학한림원 공식출범

이기준 한국공학교육학회 1996 Ingenium(人材니움) Vol.3 No.2

고속 플래시 AD 변환기를 위한 Successive Selection Encoder의 Logical Effort에 의한 설계

이기준,김병수,Lee Kijun,Choi Kyusun,Kim Byung-soo 대한전자공학회 2005 電子工學會論文誌-SD (Semiconductor and devices) Vol.42 No.4

고속 flash ADC를 위하여, Successive Selection Encoder (SSE)라고 명명된 새로운 형태의 TC-to-BC encoder를 제안한다. 기존의 fat tree encoder가 OR 논리에 의하여 동작되는데 반하여, 제안된 SSE는 MUX 논리에 의하여 입력 TC 신호 들 중에서 직접 출력 BC 신호를 선택한다. 제안한 SSE의 구현을 위하여, Logical Effort 방법과 Hynix 0.25um 제조 공정에 의한 실험을 바탕으로 효율적인 SSE의 구현 구조를 정하였다. 이론적 모델과 실험 결과를 보면, SSE가 fat tree encoder에 비하여 (1) one-out-of-n 신호를 발생할 필요가 없고, (2) 사용되는 게이트 수는 약 1/3로 감소하며, (3) 동작속도는 2배 이상 빨라진다. 제안된 SSE는 고속 ADC에 적합한 TC-to-BC encoder로 사용될 수 있다. In this paper, a new type of the TC-to-BC encoder for high speed flash ADC's, called the Successive Selection Encoder (SSE), is proposed. In contrast to the conventional fat tree encoder based on OR operations, the W- outputs, in the new design, are obtained directly from TC inputs through simple MUX operations. The detailed structure of the SSE has been determined systematically by the method of the logical effort and the simulation oil Hynix 0.25um process. The theoretical and experimental results show that (1) it is not required to generate one-out-of-n signals, (2) the number of gates is reduced by the factor of 1/3, and (3) the speed is improved more than 2-times, compared to the fat tree encoder. It is speculated that the SSE proposed in this study is an effective solution for bottleneck problems in high speed ADCs.

수평동심원 환장공간에서의 자연대유현상에 관한 수치모사연구

이기준,서문호,이형만 한국화학공학회 1981 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.19 No.4

同心의 두 水平圓筒으로 이루어진 環狀空間에서의 自然對流에 의한 流體의 流動 및 傳熱現象을 해석하기 위하여 運動方程式과 에너지式을 有限差分化하여 數値模寫實驗을 행하였다. 內壁의 표면을 가열하는 경우, 空洞 내부의 空氣는 密度差에 의하여 自然對流 熱傳達이 일어나는데 이 現象을 Boussinesq의 가정을 도입하여, 運動方程式과 에너지式으로 表示하고 stream function과 vorticity를 이용하여 有限差分化한 후 시간 變化에 따라 溫度分布화 streamline을 계산하였다. 또, 壁 外部의 溫度가 垂直成層勾配(vertical temperature gradient)로 유지되고 內壁에서는 斷熱 또는 等溫條件으로 되는 경우에 대하여 축대칭성 2차원 空間에서의 溫度分布와 streamline의 變化를 時間變化에 따라 模寫하였다. Transient natural convection phenomena in an annulus between horizontal concentric cylinders were studied numerically for the axisymmetric cases using the finite difference, schemes. Boussinesq approximation was applied to the equations of motion describing the buoyant circulation of air, and the vorticity-stream function approach was adopted for the solution of the problems. The simulations of temperature distribution, streamline and vorticity variations were performed under the prescribed conditions such that the outside cylinder was maintained at a variable temperature of Vertical stratification condition and the inner cylinder was either thermally insulated to be adiabatic or its surface temperature was kept constant.