• Computational Structural Engineering
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• v.2 no.4
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• pp.59-67
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• 1989

Effect of joints which pre-exist in the rock mass on the behavior of underground structures is studied. A finite element program is developed using a constitutive mode for rock masses exhibiting nonlinear anisotropic behavior. The initial loading scheme combined with reduced region of analysis is employed to minimize the problem size. A circular tunnel within rock mass is analyzed and the results are compared with those of elasto-plastic analysis to verify that the program is reasonable. The effect of joint direction is also analyzed in regard to stress relaxation, displacement, and deformation shape. It is concluded that the joint direction has significant influence on the nonlinear behavior of rock masses such that the vicinity of tunnel perpendicular to the direction of the joints is stressed to slide. It is also observed that the circular shape deforms to an elliptical shape with a major axis in the joint direction.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.218-231
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• 2006

Anisotropic/heterogeneous rock mass shows various deformation behavior types due to tunnelling because deformation behavior is largely controlled by the spacial characteristics of geological factors such as faults, joints and fractured zone in rock mass. In this paper 2-dimensional numerical analysis on the several influencing factors is performed considering fractured zone located near tunnel. This numerical analysis shows that deformation behavior of tunnel are very different according to the width and the location of fractured zone and supper method. However, 3-dimensional analysis is necessary to consider 3-dimensional geometrical characteristics sufficiently since discontinuity and fractured zone have 3-dimensional geometry. Also flexible design/construction guidelines for tunnelling are required to cope with uncertain ground condition and circumstance for technically safe and economic tunnel construction.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.31-46
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• 2009

An anisotropic damage mechanics approach is introduced which models the static and dynamic behavior of mass concrete in 3D space. The introduced numerical approach is able to model non-uniform cracking within the cracked element due to cracking in Gaussian points of elements. The validity of the proposed model is considered using available experimental and theoretical results under the static and dynamic loads. No instability and stress locking is observed in the conducted analyses. The Morrow Point dam is analyzed including dam-reservoir interaction effects to consider the nonlinear seismic behavior of the dam. It is found that the resulting crack profiles are in good agreement with those obtained from the smeared crack approach. It is concluded that the proposed model can be used in nonlinear static and dynamic analysis of concrete dams in 3D space and enables engineers to define the damage level of these infrastructures. The performance level of the considered system is used to assess the static and seismic safety using the defined performance based criteria.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.7
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• pp.60-74
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• 1993

Experiments of RIE of tungsten films using SF$_{6}$ plasma were conducted to investigate the effect of process parameters on etch rate, uniformity, anisotropy, and selectivity. As power increased, the etch rate increased. Maximum etch rate was obtained at 200mtorr As interelectrode spacing increased the etch rate increased for P < 200mtorr while it decreased for P> 200mtorr. Etch rate was maximum at 20 sccm gas flow rate. As substrate temperature increased, the etch rate increased and activation energy was 0.046 eV. In addition, maximum etch rate was acquired at 20% $O_{2}$ addition. The etch rate slightly increased when Ar was added up to 20% while it continuously decreased when N$_{2}$ was added. Uniformity got improved as pressure decreased and was less than 4% for P <100mtorr. Mass spectrometer was utilized to analyze gas composition and S and F peaks were observed from XPS analysis with increasing power. The anisotropy was better for smaller power and spacing, and lower pressure and temperature. It improved when CH$_{4}$ was added and anisotropic etch profile was obtained when about 10% $O_{2}$ was added. The selectjvity was better for smaller power larger pressure and spacing, and lower temperature. Especially. low temperature processing was proposed as a novel method to improve the anisotropy and selectivity.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.58.2-58.2
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• 2013

Both peculiar velocities and errors in the assumed redshift-distance relation ("Alcock-Paczynski effect") generate correlations between clustering amplitude and orientation with respect to the line-of-sight. In this talk we propose a novel technique to extract the Alcock-Paczynski, geometric, distortion information from the anisotropic clustering of galaxies in 3-dimensional redshift space while minimizing non-linear clustering and peculiar velocity effects. We capitalize on the recent, large dataset from the Sloan Digital Sky Survey III (SDSS-III), which provides a large comoving sample of the universe out to high redshift. We focus our analysis on the Baryon Oscillation Spectroscopic Survey (BOSS) constant mass (CMASS) sample of 549,005 bright galaxies in the redshift range 0.43

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1021-1029
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• 1992

A rational and straightforward method is introduced for developing continuum models of large platelike periodic lattice structures based on energy equivalence. The procedure for developing continuum plate models involves the use of existing well-defined finite element matrices for the easy calculation of strain and kinetic energies of a repeating cell, from which the reduced stiffness and mass matrices are obtained in terms of continuum degrees- of-freedom defined in this paper. The equivalent continuum plate properties are obtained from the direct comparison of the reduced matrices for continuum plate with those for lattice plate. The advantages of the present continuum method are that it may be applied to arbitrary lattice configurations and may give most diverse equivalent continuum plate properties including all kinds of coupling, while other methods may give only limited structural properties. To evaluate the continuum method developed in this paper, free vibration analyses for both of continuum and lattice plates are conducted. Numerical results show that the present continuum method gives very reliable structural and dynamic properties compared to other well-recognized methods.

• Explosives and Blasting
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• v.23 no.2
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• pp.23-35
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• 2005

Excavation of an opening in a saturated porous rock may lead to the development of pore pressure around the opening due to the redistribution of initial rock stresses. The built-up of pore pressure, in turn, may affect the mechanical behavior of rock mass and give the different pattern of stress distribution around the opening from that of the case where the coupling is neglected. In this study, the short time response of an opening excavated in saturated ground under anisotropic initial stress conditions was investigated numerically. Not on the wall of opening but at a short distance from the wall, the tangential stresses were peak during the short period after excavation when the hydro-mechanical coupling is considered.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.148-151
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• 2005

Field-scale DNAPL dissolution is controlled by the topology of DNAPL distributions with respect to the velocity field. A high resolution percolation model was developed and employed to simulate the distribution of DNAPL within source zones. Statistically anisotropic permeability values and capillary parameters were generated for 10${\times}$10${\times}$10 m domains at a resolution of 0.05 to 0.1 m for various statistical properties. TCE leakage was simulated at various rates and the distribution of residual DNAPL in 'fingers' and 'lenses' was computed. Variations in finger and lens geometries, frequencies, average DNAPL saturations, and overall source topology were predicted to be strongly influenced by statistical properties of the medium as well as by injection rate and fluid properties. Model results were found to be consistent with observations from controlled DNAPL release experiments reported in the literature. The computed distributions of aquifer properties and DNAPL were utilized to perform high-resolution numerical simulations of groundwater flow and dissolved transport. Simulations were performed to assess the effect of grout or foam injection in bore holes within the source zone and of shallow point-releases of fluids with various properties on dissolution in DNAPL dissolution rate, even for widely spaced injection points. The results indicate that measures that induced partial flow reductions through DNAPL source zones can significantly decrease dissolution rates from residual DNAPL. The benefit from induced partial flow reductions is two-fold: 1) local flow reduction in DNAPL contaminated zones reduces mass transfer rates, and 2) contaminant flux reductions occur due to the decrease in groundwater velocity

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.132-139
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• 2000

This paper reports a novel micromachining process based on UV-LIGA process and (110) silicon anisotropic etching for fabrication of a high-aspect-ratio comb actuator. The comb electrodes are fabricated by (110) SILICON comb structure considering the etch-rate-ratio between (110) and (111) planes and lateral etch rate of a beam-type structure. The fabricated structure was$ 400\mum \; thick\; and\; 18\mum$ wide comb electrodes separated by $7\mim$ so that the height-gap ratio was about 57. Also considering resonant frequency of the comb actuator and the frequency-matching between sensing and driving mode for gyroscope application, we designed the number, width, height and length of the spring structures. Electroplated gold springs on both sides of the seismic mass were $15\mum\; wide,\; 14\mum\; thick\; and \; 500\mum$ long. The fabricated comb actuator had resonant frequency ay 1430Hz, which was calculated to be 1441Hz. The proposed fabrication process can be applicable to the fabrication of a high-aspect-ratio comb actuator for a large displacement actuator and precision sensors. Moreover, this combined process enables to fabricate a more complex structure which cannot be fabricate only by surface or bulk micromachining.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.95-95
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• 2013

The NdFeB magnet can be classified into the sintered magnet and bonded magnet. The former has superior magnet characteristics but the degree of freedom in shape is highly restricted, whereas the latter has a high degree of freedom, but its magnet characteristics are inferior to the former. When a NdFeB magnet is used at the elevated temperature, part of Nd must be replaced with a high priced Dy to increase its coercive force. For these reasons, a Dy free and high performance NdFeB bonded magnet is desired strongly. The author successfully developed a Dy free NdFeB anisotropic bonded magnet based on discovery of new phenomena called as d-HDDR reaction and its mass production process such as a thermally balanced hydrogen reaction furnace, micro capsuled powder, compression molding / injection molding under magnetic field, magnetic die and so on. Applied to DC brush seat motor for automotive use, the motor has become 50% small in size and weight. The commercialization of a half sized motor for automotive use has been realized up to the market share of 30%. At present, its commercialization is extending to various types of motors such as power tool, ABS motor, wiper motor, window motor, electric bike power motor, and compressor motor. It is expected that the applications will be increasingly enlarged to EV motor, wind generator, EPS motor, washing machine, and glass cutting machine. This innovative technology has realized Dy free high performance magnet and mudt make big contribution to not only rare element strategies but also energy conservation.