• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.362-368
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• 2008

The purpose of this is providing employees who take charge of operation and maintenance at power plant with education contents that can be used for self-studying and on the job training through their computers. We developed the education contents for making actually application possible using this piping and instrument diagram(P&ID), operation and maintenance procedure, unit specification and material of 500MW thermal power plant those include unit equipment 3-dimension animation, character and narration performance considering making teaching plan, flexibility, extension, reuse, maintenance and focusing on user. Specially, we developed the flash type education contents about power plant operation based on the plant 3-dimension animation and the spot real picture concerned about new generation trend for power plant incoming employees actual knowledge. in addition, this contents apparently contributed to improve the level of employees technical power as distributed to employees.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.4
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• pp.25-34
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• 2001

As the topography of Korea consists of mountains at about seventy percent, there is necessarily an increasing demand for tunnel construction according to the expansion of the existing highway and construction of new highway. The concrete lining of tunnel portals has been designed with reinforced concrete to resist the cracking due to the difference in temperature in the inside and outside of tunnel. In the paper, the application of steel fiber reinforcement concrete was analyzed as the lining concrete at tunnel portals and through structure analysis and field model test the suitability of the steel fiber reinforcement concrete was assessed as the lining member of tunnel portal.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.499-505
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• 1994

Local stress concentrations often cause new micro-damaging induced by a healed pre-existing defects, and the macro-damage is developed by propagation and coalescence of the micro-damage. The micro-damage causes non-linear deformation in rock material. Considerable work has also been applied to describe mathematically the behavior of cracks under stress. Although these mathematical models can usually be made to agree quite well with the measured data, but it is questionable how well the models describe real rock including microcracks in pre-failure state, such as their micro-damage mechanisms. In the present study, micro-damage initiation and propagation in granitic rock under increasing stress were observed directly. Furthermore, a stress analysis considering the bisphere model was carried out using the homogenization theory to analyze the mechanics of the stress-induced micro-damage.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.423-426
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• 2009

POSTECH Graduate School of Wind Energy is trying to upgrade the PMSG used for Unison U50 to 900 kW class. Intensive optimization efforts are carried out the reduce the axial size and total weight of the generator while increasing the rated output to 900 kW. The generator features 3.32m stator inner radius, 671mm stator length, 84 pole, 25 rated rpm and 31.6kN/$m^2$ shear force density. To reduce the gross weight, the stronger magnetic material is applied with optimal magnet size resulting lowest cogging torque. Also, instead of stator skewing the stator, the magnet position along the circumference is optimized to further reduce the cogging torque. This scheme eliminates the stator skewing procedure and may enhance the productivity. This method also reduces the total harmonic distortion. In this report, upgrade method, no-load line to line voltage and phase voltage, cogging torque, loss calculations and thermal analysis are presented.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.177-186
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• 2006

In order to realize a three-dimensional shape on CAD, the machining process has been widely used because it offers practical advantages such as precision and versatility. However, the traditional machining process needs a large amount of time in cutting a product and the remained material causes trouble such as inconvenience due to cleaning process. Therefore, a new rapid manufacturing process, Rapid Heat Ablation process (RHA) using the hot tool, has been developed. In this paper, the hot tool for RHA process is designed to minimize radius of heat affected zone. TRIZ well-known as creative problem solving method is applied to overcome the contradictive requirements of the hot tool. For the detailed design of the hot tool, numerical model is established with several assumptions. In order to verify the numerical results, surface temperature of the hot tool is measured with K-type thermocouple at the predetermined location. Numerical and experimental results show that the devised hot tool fulfils its requirements. The practicality and effectiveness of the designed hot tool have been verified through experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.372-379
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• 2006

Little attention has been paid to static-strain-dependence of dynamic complex modulus of viscolelastic materials in computational analysisso far. Current commercial Finite Element Method (FEM) codes do not take such characteristics into consideration in constitutive equations of viscoelastic materials. Recent experimental observations that static-strain-dependence of dynamic complex modulus of viscolelastic materials, especially filled rubbers, are significant, however, require that solutions somehow are necessary. In this study, a simple technique of using a commercial FEM code, ABAQUS, is introduced, which seems to be far more cost/time saving than development of a new software with such capabilities. A static-strain-dependent correction factor is used to reflect the influence of static-strains in Merman model, which is currently the base of the ABAQUS. The proposed technique is applied to viscoelastic components of rather complicated shape to predict the dynamic stiffness under static-strain and the predictions are compared with experimental results.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.463-469
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• 2003

PWR-GALE Code is a computerized mathematical model for calculating the releases of radioactive material in gaseous and liquid effluents from PWRs. In PWR-GALE Code, Auxiliary building iodine removal efficiency, one of the code input data, did not reflect adequately the new design of KSNP which has two auxiliary buildings(PAB and SAB). In this study, we developed a revised method how to correct iodine removal efficiency in KSNP. And newly proposed methodology through case study using Ul-Jin 5, 6 design data was verified.

• Electrical & Electronic Materials
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• v.10 no.4
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• pp.349-354
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• 1997

This paper aims at studying the improvement of test method for t-weight sensitive fault (t-wsf) detect. The development of RAM fabrication technology results in not only the increase at device density on chips but also the decrease in line widths in VLSI. But, the chip size that was large and complex is shortened and simplified while the cost of chips remains at the present level, in many cases, even lowering. First of all, The testing patterns for RAM fault detect, which is apt to be complicated , need to be simplified. This new testing method made use of Local Lower Bound (L.L.B) which has the memory with the beginning pattern of 0(l) and the finishing pattern of 0(1). The proposed testing patterns can detect all of RAM faults which contain stuck-at faults, coupling faults. The number of operation is 6N at 1-weight sensitive fault, 9,5N at 2-weight sensitive fault, 7N at 3-weight sensitive fault, and 3N at 4-weight sensitive fault. This test techniques can reduce the number of test pattern in memory cells, saving much more time in test, This testing patterns can detect all static weight sensitive faults and pattern sensitive faults in RAM.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.43-50
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• 1998

The current design equations for ultimate strength of tubular joints are based on a limited number of experimental results performed on simple joints with simple loading conditions and depend on value of the branch to the chord diameter- ratio $\beta$ too much. Therefore, the purpose of this study is to estimate the ultimate strength of CHS tilbular joints considering the effects of branch inclination angles $\theta$, chord length to diametel ratio $\alpha$ and chord end conditions by finite element analysis. The analyses are performed using finite element software ADINA that is capable of modeling elasto-plastic material behavior as well as geometric nonlinearities. The results show that the current use of sin $\theta$ in normalized design equations for inclined branches is reasonable, but somewhat conservative. When compared with the previous experimental database, the close numerical results are obtained from the parametric studies on the static strength of T-, Y-, DT- and X-joints. Also, a new design equation for ultimate stregth of CHS tubular joints is derived using a modified version of the ring model which can include the effects of $\alpha$ and chord end condtion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2089-2104
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• 1995

A novel and efficient cutter path planning method for machining intricately shaped curved surfaces, called the steepest directed tree method, is presented. The curved surface is defined by triangular facets, the density and structure of which are determined by the intricacy and form accuracy of the surface. Geometrical form definition and recognition of the topological features are used to connect the nodes of the triangulated surface meshes for the successive and interconnected steepest pathways, which makes good use of end milling characteristics. The planetary cutter centers are determined to locate along smoothly changing paths and then the height values of the cutter are adjusted to avoid surface interference. Several machined examples of intersecting and intricate surfaces are presented to illustrate the benefits of the new approach. It is shown that due to more consistent geometry matching between cutter and surface(in comparison with the current CC Cartesian method) surface finish can be typically improved. Moreover, the material in concave fillets which is difficult to be removed by ball mills can be removed efficiently. The built-in positioning of cutter to avoid interference runs minutely in the sharp and discontinuous regions. The steepest upward movement of the cutter gives a stable dynamic cutting state and allows increase in the feedrate and spindle speed while remaining the stable cutting state.