• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.359-364
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• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of regenerative combustion system through the recovery of sensible heat of exhaust gases. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of regenerator with spherical particles, were numerically analyzed to evaluate the heat transfer and pressure losses and to suggest the parameter for designing heat regenerator. It is confirmed that the computational results, such as air preheat temperature, exhausted gases outlet temperature, and pressure losses, agreed well with the experimental data conducted from Chugairo. The thermal flow in heat regenerator varies with porosity, configuration of regenerator and diameter of regenerative particle. Assuming a given exhaust gases temperature at the regenerator outlet, the regenerator length need to be linearly increased with inlet Reynolds number of exhaust gases. It is considered that inlet Reynolds number of exhaust gases should be introduced as a regenerator design parameter.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.1
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• pp.61-68
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• 1994

Neglecting distant zones in the computation of geoidal heights using Stokes'formula give rise to some truncation errors. The GRS80 Korean Gravimetric geoid Model 1993(KGM93) of the South Korea region was implemented, in this paper, using a combination of satellite-derived GEM-T2 gravity and terrestrial gravity data. A spherical cap size of 30 degree is used on the integration and the truncation error is compensated to the free-air geoid. The results of this study show that the accuracy of the KGM93-C has one meter level.

• Geomechanics and Engineering
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• v.20 no.2
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• pp.147-154
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• 2020

A novel approach for predicting lateral displacement caused by pile installation in anisotropic clay is presented, on the basis of the cylindrical and spherical cavities expansion theory. The K₀-based modified Cam-clay (K₀-MCC) model is adopted for the K₀-consolidated clay and the process of pile installation is taken as the cavity expansion problem in undrained condition. The radial displacement of plastic region is obtained by combining the cavity wall boundary and the elastic-plastic (EP) boundary conditions. The predicted equations of lateral displacement during single pile and multi-pile installation are proposed, and the hydraulic fracture problem in the vicinity of the pile tip is investigated. The comparison between the lateral displacement obtained from the presented approach and the measured data from Chai et al. (2005) is carried out and shows a good agreement. It is suggested that the presented approach is a useful tool for the design of soft subsoil improvement resulting from the pile installation.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.158-160
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• 2005

Zener coefficient on cubic shaped particle was proposed. Most previous researches about Zener coefficient were developed on the assumption that the shape of particle is spherical. But, some particle has other shape, and modification of Zener coefficient needs with shape of particle. In this research, TiN particle that has a cubic shape was considered. A Zener coefficient of a cubic shape TiN was theoretically calculated with appropriate assumptions. And, using a semi-empirical method, Zener coefficient was also measured. Finally, the proposed Zener coefficient was proved by comparing with experimentally measured data.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1254-1255
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• 2006

For precise property control of sintered products, it is important to understand accurately the packing density of the powder. We developed a packing simulation program that could make a packed bed of spherical particles having particle size distribution. In addition, the influence of the particle shape of the actual powder on the packing density was quantitatively analyzed. The predicted packing densities corresponded well to the actual data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.84-90
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• 1993

Iterative solution procedure (Conjugate Gradient Method, Panchang et al., 1991) is implemented for solving the complete mild slope equation for the spherical shoal and the coast with detached breakwater. The numerical results agreed well with the experimental data. The disadvantage that mild slope eguation could be solved only for small domains is now overcome by using this solution procedure. Moreover it can be easily applied to the coastal regions with complex geometry and structures, and needs not so much computer time as the conventional models.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.32.1-32.1
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• 2014

Astronomical observations strongly suggest that the expansion rate of our universe is currently under acceleration. The nature of the so-called dark energy causing the acceleration is unknown, and it is one of the fundamental mysteries in the present day theoretical cosmology. Here we briefly review the current state of cosmic dark energy research in both theoretical and observational sides. Constraints on dynamical dark energy models (e.g., w-fluid, quintessence, and modified gravity) with recent observational data from type Ia supernovae, cosmic microwave background radiation, and large-scale structures in the universe indicate a preferred direction toward the simplest ${\Lambda}$CDM world model. We also discuss some issues regarding the early dark energy model and the spherical collapse of matter in the presence of dark energy.

• Geotechnical Engineering
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• v.14 no.1
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• pp.29-36
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• 1998

The application of a multiple rock classification method, which is a generalization of a binary rock classification, is studied in this paper. In particular, this paper shows how to incorporate qualitative data through a case study. The method suggested in this paper can be effectively used for a systematic multiple rock classification such as RMR system developed by Bieniawski. It will be very useful for rock classifications. In addition, it is known that the expected cost of errors can be atopted to indicate how well a investigation plan is made.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.167-170
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• 2007

In this study, clinical data for emmetopia in young Koreans was taken in order to design the finite schematic eye, which had optical properties of real eyes including spherical aberration, astigmatism, field curvature and distortion. Furthermore, the crystalline lens with GRIN medium was optically analyzed, and the finite schematic eye with the GRIN crystalline lens was designed.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.165-168
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• 2015

To measure laminar burning velocity in methane/air/ethylene mixture flame, propagating centrally ignited spherical premixed flame to radial direction was measured by high-speed schlieren images with elevated pressure. In this study, The experimentally measured unstretched laminar burning velocities of methane was compared with GRI mech 3.0 to validate experimental data and choose the radius range, respectively. numerical prediction using the PREMIX code with GRI mech 3.0, USC mech II,, and Wang mech were evaluated through comparison with experimental burning velocity with consideration of extrapolation on linear/nonlinear model.