• Proceedings of the KWS Conference
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• 2002.10a
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• pp.101-106
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• 2002

Requirements to fabrication processes for arc welding of highly loaded thick-walled joint and problems of research and development in term s of the tendency for the modern aircraft structure development are outlined. A justified, choice of the development line of the new promising welding processes for solution of these problems is presented. A complex of new welding processes and technologies for making highly reliable joints with different thickness (up to 120 mm and more) and length of weld (up to 0.1 m; 0.1-0.5 m and more than 0.5 m) has bee developed. It is shown that the possibility to control the heat flow distribution over the groove surface of the welded joints provides for improved reliability. The new welding processes are equipment are effectively used in serial production of the Mykoyan md Sukhoi supersonic aircrafts as well as in AN-124 Ruslan and AN-225 Mriya wide body aircrafts.

• Journal of Information Display
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• v.7 no.1
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• pp.19-24
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• 2006

We propose optical configurations of a double-cellgap liquid crystal cell for transflective displays with wide viewing angle and high contrast ratio. The reflective part is designed in the wide-band quarter wave structure to achieve good dark state. For the transmissive part, the compensation method is applied to achieve the super-achromatic dark state, and three switching methods are used : which are vertical switching, horizontal switching to $30^{\circ}$and horizontal switching to $120^{\circ}$, to achieve the bright state.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.511-518
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• 2000

Characteristics of joint orientation, length, spacing and their distribution are very important factors for slope stability, Especially, the effect of joint spacing is an essential factor of slope stability. This study is to analyze the effect of joint spacing in cases of sliding and toppling, which is a typical failure mode. Joint spacing can divided into vertical spacing(spacing) and horizontal spacing(gap). And then, the spacing/length ratio of joint directly affect rock slope failure. When the ratio is below 0.05, the possibility of failure is rapidly increased. In case of toppling, the possibility of failure depends on the ratio of spacing to height of slope ratio slope. As the ratio decreases, the possibility of toppling failure increased. The critical ratio of spacing to height of slope is determined by the dip angle of the slope and the orientation of joint sets.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.985-990
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• 2002

The electrical breakdown characteristics of liquid nitrogen(LN$\sub$2/) were studied under simulated quenching conditions for application of HTS apparatus. The experimental results for various quenching condition revealed that the breakdown voltage of LN$\sub$2/ with bubble flow velocity and gap spacing. In the case, breakdown voltage decreases gradually with the bubble velocity. When it is bubble velocity from 0 to 1 $\ell$ /min, breakdown voltage rapidly decreases but decreases from 2 $\ell$/min to 10 $\ell$/min slowly. The breakdown voltage for vertical electrode arrangement is higher than that for horizontal electrode arrangement. Also, it did a electric field and potential distribution interpreting at the liquid nitrogen when the bubble existed. The plots of equipotential lines for three cases are also shown.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.148-153
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• 1998

In order to control thermal deformation of machine origin of machine tools due to internal and external heat sources, the real-time compensation system has been developed. First, GMDH models were constructed to estimate thermal deformation of machine origin for a vertical machining center through the measurement of deformation data and temperature data of specific points on the machine tool. Thermocouples and gap sensors are used respectively for measurement. These models are nonlinear equations with high-order polynomials and implemented in a multilayered perceptron type network structure. Secondly, work origin shift method were developed by implementing digital I/O interface board between CNC controller and IBM-PC. The work origin shift method is to shift the work origin by the compensation amounts which is calculated by pre-established GMDH model. From the experimental result, thermal deformation of machine origin was reduced to below $\pm$5${\mu}{\textrm}{m}$.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.224-229
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• 1996

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced- circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m. inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, chum-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.844-853
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• 1998

Natural and forced convection experiments were carried out in order to investigate the effects of channel spacing gap between protrusions and number of rows of protrusion, In natural convection the optimum channel spacing was found to be approximately 20mm regardless of the protrusion gaps. For optimum channel spacing the heat transfer coefficients were converged to an asymptotic value after the fourth row. The heat transfer coefficient for each row approaches to constant values for protrusion gaps larger than 10 mm. An experimental correlation has been suggested by using a modified Rayleigh number based on the dimensionless characteristic length(G/L). In forced convec-tion the heat transfer coefficients were not merged to an asymptote until the fifty row and increases as the channel spacing at the constant Reynolds number decreases.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.424-427
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• 2006

Soil contamination with petroleum oil around a military army was investigated. It showed that soils of a riverside highland, an entrance of the military army, and nearby roads were contaminated with total petroleum hydrocarbons (TPH) released from the military army to the depth of approximately 2 m. The measured concentrations were as high as 15,277 mg/kg. A wide range of soil in the riverside highland was contaminated by the movement of oil to the surface soil, which occurred with the vertical movement of groundwater table caused by the change of river water level and groundwater level. Spilled petroleum oil components were released into Wonju Stream by the increase of hydraulic conductivity and the groundwater flow.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.156-163
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• 2005

A monoleaflet polymer artificial heart valve showed the remarkable improvement in pressure drop compared with other types of artificial valve. So, in this study we designed a monoleaflet polymer artificial valve with two supporting members to minimize the deformation and bending stress of the valve with respect to the variation of the gap between two supporting members using nonlinear contact analysis. The marginal valve thickness was also predicted in accordance with the relationship between the thickness and horizontal displacement in order to prevent the dislocation of the valve tip from the frame wall.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.559-559
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• 2012

We developed a new scheme for the highly sensitive near-field scanning optical microscope (NSOM) by using a dithering sample stage rather than a dithering probe. In the proposed scheme, the sample is directly loaded on one prong surface of a dithering bare tuning fork. Gap control between probe and sample is performed by detecting the shear force between an immobile fiber probe and the dithering sample. In a conventional NSOM, the Q factor drastically decreases from 7783 to 1000 or even to 100 by attaching a probe to the tuning fork. In our proposed NSOM, on the contrary, the Q factor does not change significantly, 7783 to 7480, when the sample is loaded directly to the tuning fork instead of attaching a probe. Consequently, the graphene sheets that cannot be observed by a conventional NSOM were clearly observed by the proposed method with sub-nanometer vertical resolution due to the extremely high Q factor.