• Journal of the Korean Vacuum Society
• /
• v.2 no.4
• /
• pp.433-438
• /
• 1993

전자의 파동성에 기인하는 여러 가지 양자간섭 현상을 연구하기 위하여, 금속의 미세고리구조을 제작하였다. 전자의 양자간섭과 가간섭 역충돌 효과에 의한 자기저항의 진동형상이 관측되었으며, 자기저항의 비주기 섭동 현상과 비국재현상도 관찰되어 중시적 전기 전도도의 일반식에 의하여 설명되었다. 또한 AlGaAs/GaAs 의 이차원 전자가스총을 이용한 고리구조도 제작되어, 양자 효과와 탄동적 수송의 영역에서 자기저항이 측정되었다.

• Bulletin of the Korean Mathematical Society
• /
• v.54 no.1
• /
• pp.145-158
• /
• 2017

We present a finite difference method for solving the Ohta-Kawasaki model, representing a model of mesoscopic phase separation for the block copolymer. The numerical methods for solving the Ohta-Kawasaki model need to inherit the mass conservation and energy dissipation properties. We prove these characteristic properties and solvability and unconditionally gradient stability of the scheme by using Hessian matrices of a discrete functional. We present numerical results that validate the mass conservation, and energy dissipation, and unconditional stability of the method.

• Journal of the Korean Vacuum Society
• /
• v.2 no.1
• /
• pp.23-27
• /
• 1993

NiSi2(111)을 Si(111) 표면 위에 증착하여 그 구조를 STM으로 연구하였다. 실리사이드는 그 표면이 (1$\times$1)의 구조를 띠고 여분의 trimer를 흡착 분자 구조로 가짐을 관찰하였다. 이 trimer로부터 실리사이드의 두 가지 구조 A, B를 구별할 수 있었다. 표면에 관착된 결함으로부터 표면구조는 내부와 같음을 보였다.

• Journal of Korean Society of Transportation
• /
• v.20 no.1
• /
• pp.19-38
• /
• 2002

To evaluate the effects of transportation system operation, usually measures of effectiveness(MOE) such as travel time, space mean speed, stop/delay ratio have been used. But, energy consumption as well as the existing MOE in transportation receives more attention as an alternative MOE in transportation operation. The purpose of this study is a development of procedure, which could measure the relative energy consumption for each alternative and compare the results. A mesoscopic simulator called INTEGRATION is used to evaluate the operation of high occupancy vehicle lane, signal optimization, lane expansion, and the application of ITS. Among those, the application of ITS shows the greatest effectiveness in energy reduction, and then lane expansion, signal optimization, and the operation of high occupancy vehicle lane in the order named. Because we don't consider the characteristics of vehicle class, Potential demand and the simulation time is just for an hour. it is recommended that a procedure for precise economic analysis and an improvement in methodology are needed in the future for the expanded application of this study.

• Geomechanics and Engineering
• /
• v.23 no.4
• /
• pp.327-338
• /
• 2020

The role of precise prediction of subsurface fluids and discrimination among them cannot be ignored in reservoir characterization and petroleum prospecting. A suitable rock physics model should be build for the extraction of valuable information form seismic data. The main intent of current work is to present a rock physics model to analyze the characteristics of seismic wave propagating through a cracked porous rock saturated by a three phase fluid. Furthermore, the influence on wave characteristics due to variation in saturation of water, oil and gas were also analyzed for oil and water as wet cases. With this approach the objective to explore wave attenuation and dispersion due to wave induce fluid flow (WIFF) at seismic and sub-seismic frequencies can be precisely achieved. We accomplished our proposed approach by using BISQ equations and by applying appropriate boundary conditions to incorporate heterogeneity due to saturation of three immiscible fluids forming a layered system. To authenticate the proposed methodology, we compared our results with White's mesoscopic theory and with the results obtained by using Biot's poroelastic relations. The outcomes reveals that, at low frequencies seismic wave characteristics are in good agreement with White's mesoscopic theory, however a slight increase in attenuation at seismic frequencies is because of the squirt flow. Moreover, our work crop up as a practical tool for the development of rock physical theories with the intention to identify and estimate properties of different fluids from seismic data.

• Advances in concrete construction
• /
• v.16 no.6
• /
• pp.277-290
• /
• 2023

In order to study the mechanical properties of basalt fiber reinforced ultra-fine fly ash concrete (BFUFARC), the effects of ultra-fine fly ash (UFA) content, basalt fiber content, basalt fiber length and water reducing agent content on the compressive strength, splitting tensile strength and flexural strength of the composite material were studied through experimental and theoretical analysis. Also, a scanning electron microscope (SEM) was employed to analyze the mesoscopic structure in the fracture surface of composite material specimens at magnifications of 500 and 3500. Besides, the energy release rate (G_c) and surface free energy (γ_s) of crack tip cracking on BFUFARC in different basalt fiber content were studied from the perspective of fracture mechanics. Further, the cracking resistance, reinforcement, and toughening mechanisms of basalt fibers on concrete substrate were revealed by surface free energy of BFUFARC. The experimental results indicated that basalt fiber content is the main influence factor on the splitting tensile strength of BFUFARC. In case that fiber content increased from 0 to 0.3%, the concrete surface free energy at the tip of single-sided crack showed a trend of increased at first and then decreased. The surface free energy reached at maximum, about 3.59 × 10^-5 MN/m. During the process of increasing fiber content from 0 to 0.1%, G_C-2_γS showed a gradually decreasing trend. As a result, an appropriate amount of basalt fiber can play a preventing cracking role by increasing the concrete surface free energy, further effectively improve the concrete splitting tensile performance.

• Tribology and Lubricants
• /
• v.20 no.5
• /
• pp.252-258
• /
• 2004

In this study, using high cycle fatigue (HCF) criteria, the simulation of rolling contact fatigue is conducted under elliptical contact. The HCF criteria fall into three categories: the critical plane approach, the stress invariant approach and the approach based on the mesoscopic scale. The accurate calculation of contact stresses and subsurface stresses is essential to the prediction of crack initiation life. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface stress field is obtained using rectangular patch solutions. The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when the friction coefficient exceeds a specific value for all of three fatigue criteria.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.115-115
• /
• 2003

Silica nanostructures have been attached considerable attention because of theirs potential application in mesoscopic research and the potential use of large surface area structure of catalysts. SiO2 nannowire and nanorods was synthesized various methods including thermal evaporation, chemical vapor deposition (CVD), and laser ablation methods. In this experiments, SiO2 nanowire were grown using thermal evaporation method followed by VS (Vapor-Solid) growth mechanisms. Grown SiO2 nanowires were amorphous phases because of its low growth temperatures. Grown nanowires diameters were about 20-40nm at all growth conditions, but its microstructres were different by that used substrate because of it's oxygen contents.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.5
• /
• pp.133-138
• /
• 2007

Surface pitting is a major failure mode for gears. The contact fatigue life analysis of transmission gear considering running-in process is presented in this paper. Surface roughness change of rolling test is used in a life analysis. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. The life analysis considering running-in is in good agreement with the experimental results.

• Structural Engineering and Mechanics
• /
• v.30 no.1
• /
• pp.99-117
• /
• 2008

This paper presents a comprehensive approach to the evaluation of macroscopic material parameters for natural stone and quarry masonry. To that end, a reliable non-linear material model on a meso-scale is developed to cover the random arrangement of stone blocks and quasi-brittle behaviour of both basic components, as well as the impaired cohesion and tensile strength on the interface between the blocks and mortar joints. The paper thus interrelates the following three problems: (i) definition of a suitable periodic unit cell (PUC) representing a particular masonry structure; (ii) derivation of material parameters of individual constituents either experimentally or running a mixed numerical-experimental problem; (iii) assessment of the macroscopic material parameters including the tensile and compressive strengths and fracture energy.