• Journal of ILASS-Korea
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• v.9 no.4
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• pp.1-8
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0MPa. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity, It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• Journal of the Korea Safety Management & Science
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• v.13 no.1
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• pp.69-73
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• 2011

Questionnaire survey has been made for the above study. First, 65 question sheets have been distributed to railway operators and 55 sheets of them have been collected from them. SPSS 12.0 program package has been used to analyze those sheets concerning age, experience, school, background as a frequency analysis and t-test has been made to find out recognition level difference of a cheer response, depending on the operator's experience. T-verification has been made for two groups such as less than 10 years, and 10 years or more experience. Result from correlation analysis showed that there was no difference due to operators' experience.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.173-179
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0㎫. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity. It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• KCI Concrete Journal
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• v.12 no.1
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• pp.113-120
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• 2000

This paper presents the behavior and strengthening effect of reinforced concrete rectangular beams strengthened using CFRP sheets with different strengthening level. In general, normally strengthened beams are failed by interfacial shear failure (delamination) within concrete, instead of by tensile failure of the CFRP sheets. The delamination occurred suddenly and the concrete cover cracked vertically by flexure was spalled off due to the release energy. The strengthened beams were stiffer than the control beam before and after reinforcement yielding. The ultimate load considerably increased with an increase of strengthening level, while the ultimate deflection significantly decreased. The tensile force of CFRP sheets and average shear stress of concrete at delamination failure were curvilinearly proportional to the strengthening level. Therefore, the increment of ultimate load obtained by strengthening was curvilinearly proportional to the strengthening level. The averaged horizontal shear stress of concrete at the interface ranges between (equation omitted) and (equation omitted) (in kg/$\textrm{cm}^2$) depending on strengthening level.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.107-110
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• 2005

This paper presents the reduction methods of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the resistive sheets loading on the slot. The magnitude of the penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by the resistive sheets on the slot aperture.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.89-96
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• 1997

The paper presents the results of experimental studies on two strengthening methods for reinforced concrete (RC) slabs. Bending tests on RC slabs have been carried out to investigate the influence of the increased thickness and externally bonded carbon fiber sheets. The interfaces of new and old concrete of increased thickness specimens have been chipped and treated with bonding agent. The conclusions have been reached as followings. (1) The behavior of specimens with chipped interface is good enough to calculate flexural strength of RC slabs for increased depth. (2) The flexural stiffness of increased depth specimen is severely increased and the deformation of RC slabs is controled. (3) The specimens with externally bonded carbon fiber sheets can be assumed to behave monolithically.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.4
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• pp.476-489
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• 1999

This paper is concerned with the deployment of core technologies for automotive steel sheets, based on the structural change of global market. The main tasks of automotive industry are to ensure the energy consumption, environmental regulations, and driving safety. With social and legal requirements, this study analyzes the market creation processes with technological innovations for hot rolled, cold rolled and galvanized steel sheets during the 20th century. It has been proven that the leading country in the steel industry was also that in the automotive. The purchaser-supplier relations of sheet materials are then patternized in the regional markets of the United States and Japan, who share nearly 50% of market in the world. According to the paradigm shift of globalization, the balance of power in Porter's 5 forces has been moved to the buyers', and both industries pursue Win-Win strategies such as the PNGV(Partnership for a New Generation of Vehicles ) and design-in system with the competition.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.281-283
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• 2006

This paper presents the reduction methods of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the resistive sheets loading on the slot. The magnitude of the penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by the resistive sheets on the slot aperture.

• Journal of information and communication convergence engineering
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• v.2 no.2
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• pp.97-101
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• 2004

This paper is about the use of existing evaluation methods, which evaluate learning determined by the score of an exam, which is either a multiple-choice type or single choice type question. These scores don't show the objective evaluations that cause some negative opinions about the scores. In this paper, we propose that the evaluation of the methods of self-directed learning use the triangle-type function of the fuzzy theory so that the learner can objectively evaluate their own learning ability. The proposed method classifies the result of learning into three fuzzy grades to calculate membership, and evaluate the result of an exam according to the final fuzzy grade degree as applied to the fuzzy grade sheets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06a
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• pp.121-130
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• 1998

In order to analyze the forming characteristics of laser welded tailored blanks, laser welded blanks of different thickness and strength combinations were prepared and tensile, stretching, stretch flanging and deep drawing tests were done. The tensile elongation perpendicular to the weld line, stretching and stretch flanging formability decreased with increasing the deformation restraining force (strength ${\times}$ thickness) ratio between two welded sheets. The tensile elongation along weld line reached a value above 90% of the single sheet's elongation. Stretch flanging formability was reduced to approximately 10% of the single sheet value when the deformation restraining force ratio between two welded sheets was increased to two. Weld line movement of deep drawing test specimens was also affected by the strength ratio of the combined sheets, the weld line location and forming conditions. In all forming modes of tailored blanks, excessive weld line movement resulted from strain concentrations at the weaker sheet and resulted in fracture of the weaker side.