• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1163-1172
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• 2001

The two dimensional problem of a layered tribological system(TiN/Steel) containing a vertical surface breaking crack and subject to rolling contact is considered in this study. Using finite elements and stress extrapolation method, a series of preliminary models are developed. Preliminary results indicate that the extrapolation technique is valid to determine Modes I and II stress intensity factors for cracks. In the case of TiN/Steel medium, KI and KII were determined for variations in crack length, layer thickness, and load location. The results show that KII reaches maximum values when the contact is adjacent to the crack where Mode I stresses are compressive. KII values decrease with decreased crack length and significantly decrease for reduced layer thickness.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.742-743
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• 2006

Filling of the tool die directly influences dimensional tolerances and density variation. To minimize the variations in filling, both within different sections of the cavity and from part to part, are of great importance for produce high quality P/M parts. Filling of the tool die is also one of the limiting factors in the productivity in powder pressing. By using aeration filling in combination with bonded powder mixes, both weight scatter and productivity can be improved. In this presentation results are presented showing the benefit of using aeration filling for different types of powders

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.1
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• pp.87-92
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• 2002

We present a simple experimental method for determination of limiting intrinsic fixed-pattern non-uniformity (NU) due to fabrication process in two-dimensional CCD multiplexers (MUXs) that are used for hybrid focal plane arrays. Here, this is done by determining separately the two NUs viz. that are $V_T$ dependent and $V_T$ independent. From these measurements, process dependent NU can be extracted. It is argued that $V_T$ dependent NU can be eliminated by designing novel input circuits whereas $V_T$ independent NU, primarily, dependent on process control and material variations may be reduced but cannot be eliminated completely and hence limits the FPA performance eventually.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1169-1174
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• 2000

Since the cement-water reaction in exothermic by nature, the temperature rise within a large concrete mass. Significant tensile stresses may develop from the volume change associated with the increase and decrease of the temperature with the mass concrete. There thermal stresses will cause temperature-related cracking in mass concrete structure. These typical type of mass concrete include mat foundation, bridge piers, thick wall, box type walls, tunnel linings, etc. Crack control methods can be considered at such stages as designing, selecting the materials, and detailing the construction method. Temperature and analysis was performed by taking into consideration of the cement type and content, boundary and environment conditions including the variations of atmospheric temperature and wind velocity. This is paper, the effect of separate placement of thermal crack control footing was analysed by a three dimensional finite element method. As a result, using this method, thermal crack control can be easily performed for structures such as mat structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.62-69
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• 1996

In this study, an equivalent domain integral (EDI) method is presented to estimate the track-till integral parameter, J-value, for two dimensional cracked elastic bodies which may quantify the severity of the crack-tit) stress fields. The conventional J-integral method based on line integral has been converted to equivalent area or domain integrals by using the divergence theorem. It is noted that the EDI method is very attractive because all the quantities necessary for computation of the domain integrals are readily available in a finite element analysis. The details and its implementation are extened to both h-version finite element model with 8-node isoparametric element and p-version finite element model with high order hierarchic element using Legendre type shape fuctions. The variations with respect to the different path of domain integrals from the crack-tip front and the choice of 5-function have been tested by several examples.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.251-258
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• 2003

The early -age behavior of base restrained reinforced concrete (RC) walls is analyzed using a three-dimensional finite element method in this study. After calculating the temperature and internal relative humidity variations of an RC wall, determination of stresses due to thermal gradients, differential drying shrinkage, and average drying shrinkage is followed, and the relative contribution of these three stress components to the total stress is compared. The mechanical properties of early-age concrete, determined from many experimental studies, are taken into consideration, and a discrete reinforcing steel derived using the equivalent nodal force concept is also used to simulate the cracking behavior of RC walls. In advance, to Predict the crack spacing and maximum crack width in a base restrained RC wall, an analytical model which can simulate the post-cracking behavior of an RC tension member is introduced on the basis of the energy equilibrium before and after cracking of concrete.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.967-975
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• 2000

Transient characteristics of a boiler and turbine system for a steam power plant are simulated. One-dimensional unsteady models are introduced for each component. An interaction between boiler and turbine and a control of the water level in the drum are taken into account. Transient responses of the system to the variations of main system variables such as fuel and air flow rate, cooling water injection rate at the attemperator, gas recirculation rate at the furnace and opening of the turbine control valve are examined. Effect of fluid inertia and tube wall thermal inertia on predicted dynamic behavior is investigated.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.20-26
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• 2002

The fluid flow, mass transfer, heat transfer and film thickness variation during the spin coating process are numerically studied. The model is said to be 1-dimensional because radial variations in film thickness, concentration and temperature are ignored. The finite difference method is employed to solve the equations that are simplified using the similarity transformation. In early time film thinning is due to the radial convective outflow. However that slows during the first seconds of spinning so the film thinning due to evaporation of solvent becomes sole. The time various film thickness is analyzed according to the var ious solvent fraction in the coating liquid and in the bulk of the overlying gas and the temperature variation in the liquid film during the spin coating is estimated.

• Solar Energy
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• v.12 no.2
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• pp.51-61
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• 1992

A numerical study on the Trombe wall system, a kind of passive solar systems, has been peformed. The system is modelled as the 2-dimensional steady laminar flow with the natural convection. The PHOENICS code was employed to analyse the performance variation due to the change in the geometrical factor. The mass flow rate and the maximum temperature are changed by the variations in the width of the vents, the width between the window and the wall, and the location of the vents. And there exists the optimal condition to maximize the utilization factor. Further precise analysis has been performed to show the optimal geometry with regard to the above three factors.

• Water for future
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• v.23 no.1
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• pp.119-127
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• 1990

The concentration of cohesive suspended sediment is determined by the circulation of water and the material dispersion. The equations of the two-dimensional, depth-integrated dispersive transport are the Reynolds equation, continuity equation, and advection-dispersion equation based on the Fick's law. A finite difference method has been applied to two models of circulation and dispersion transport. The circulation model is solved by the explicit scheme and the dispersion transport model is solved by multi-operational scheme. It is investigated wheter advective terms are included when the equation of circulation is applied to the model. For advection-dispersion equation, it was also investigated about variations of suspended sediment concentration with respect to the critical shear stresses.