• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.37-48
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• 2003

A study for the structural strength evaluation of doubler plates subjected to the in-plane combined load and lateral pressure load has been performed through a systematic evaluation process. In order to properly estimate the static strength of doubler plate, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on the analysis results. Also, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of fiat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested In order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent plate thickness formula and the developed buckling strength formulas for intact plates by author et al. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.4
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• pp.242-253
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• 2011

Skin frictional drag reduction efficiency of "stiff" compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties) during half a year was documented as well. A design procedure proposed by Kulik et al. (2008) was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4~5% drag reduction within a velocity range 30~40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.113-120
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• 2008

Potential application of the scroll type machine to air compressor for fuel cell has been studied. Among the seven configuration factors which determine scroll wrap profile, the wrap thickness and the orbiting radius were chosen as two independent variables to generate various scroll wrap profiles. A conceptual design practice was conducted for scroll air compressor for SOFC with power output of 2 kW. With larger wrap thickness and orbiting radius, base plate area of the orbiting scroll becomes smaller, so is the axial gas force acting on the base plate, resulting in reduced thrust loss in spite of larger friction velocity. Performance analysis on the designed model showed that its total efficiency was 64.4% with the mass flow rate per unit compressor input of 0.00905 kg/(s kW) for the wrap thickness of 3.5 mm and the orbiting radius of 3.0 mm.

• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.7-13
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• 2011

In Korea, the car mobile phone service had started in 1961 and with this Korea Mobile Telecommunications Services was established in 1984. Its service was mainly focused on the mobile phone service for the car which led the popularity of the full-scale mobile phone service. There are many kinds of materials, colors and patterns which are the elements of surface coating techniques. In light of that, we are focused on the UV coating that is ranked as an important part of the techniques in this study. In the first, the use of various materials for the cellular phone and surface processing techniques for the cellular phone were searched. On the basis of the results, the experiments of actual consumer experience with the exfoliation of the surface were done and through that we proposed the best way of processing the surface for the cellular phone and the materials. The result of the Wear Test showed that thick coating was detached more slowly and each company differed in their results with UV paints despite the same thickness of UV coating. The seal (UV) exfoliation of cellular phone is deeply related with the film thickness and the film formation when the users use the cellular phones and the exfoliation of the cellular phone surface will be decreased if the manufacturers meet the best conditions for the cellular phone.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.245-256
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• 1995

Rugate filters of inhomogeneous refractive index were designed using the Fourier transform and the effect of reflectance, stop bandwidth, optical thickness, and Q function on the rugate filter was investigated. An iterative correction process using a merit function was employed to fit an initial design to the target spectrum. Three Q functions derived by Sossi, Bovard, and Fabricius, respectively, were compared in terms of the number of iteration, merit function, and optimum optical thickness. The result shows that after a number of iterations the Q functions by Bovard and Fabricius produce high rejection rugate filters closer to the target spectrum than the Sossi's Q function and the optimal optical thickness is determined by the stop-band width of the rugate filter. ilter.

• Steel and Composite Structures
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• v.8 no.5
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• pp.389-402
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• 2008

In December 2005, one(A) of the two pre-engineered warehouse buildings in the port of K City of Korea was completely destroyed and the other(B) was seriously damaged to be demolished. Over-loaded snow and unexpected blast of wind were the causes of the accident and destructive behavior was brittle fracture caused by web local buckling and lateral torsional buckling at the flange below rafter. However, the architectural design technology of today based on material non-linear method does not consider the tolerances to solve the problem of such brittle fracture. So, geometric non-linear evaluation which includes initial deformation, width-thickness ratio, web stiffener and unbraced length is required. This study evaluates the structural safety of 4 models in terms of width-thickness ratio and unbraced length using ANSYS 9.0 with parameters such as width-thickness ratio of web, existence/non-existence of stiffener and unbraced length. The purpose of this study is to analyze destructive mechanism of the above-mentioned two warehouse buildings and to provide ways to promote the safety of pre-engineered buildings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.43-50
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• 1999

Electromagnetic wave absorbers for anechoic chamber are needed to broaden the useful frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer. Therefore, an air layer is formed absorber between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 450 MHz in frequency band, far narrower than the aimed bandwidth. The purpose of this paper is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for prevention of TV ghost, etc. Accordingly, in this paper, a broadened electromagnetic wave absorber is designed, which has the reflection characteristics less than -20 dB from 30 MHz to 5,430 or 8,000 MHz in the bandwidth. Then we will design a super broadband electromagnetic wave absorber by inserting square Ferrite Cylinders Type with the thickness less than 23.5 m in three-layed type and with the frequency band from 30 MHz to 5,430-8,000 MHz under the above tolerance limits.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.39-45
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• 2022

In this study, we investigated whether the interference occurring in forming roll surfaces could be eliminated by increasing the radius of the variable section forming rolls. The surfaces of the rolls capable of forming products with different flange heights and bend angles with the bend line tilted at an angle of 1° from the longitudinal axis were created using the general CAD software CATIA. Roll interferences were determined for the change in the forming roll radius. The minimum gaps between the upper and lower roll surfaces were measured for the change in the forming roll radius, and the roll interferences were calculated from the difference between the measured value and the thickness of the product. It was observed that the thickness of the product had a slight effect on the roll interference when the thickness was between 0.8 and 1.2 mm. It was also observed that the roll interference could be eliminated by increasing the roll radius.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.529-533
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• 2000

This paper present a new sort of multilayer piezoelectric ceramic transformer for AC-adapt. This piezoelectric transformer operates n the second thickness extensional vibration mode. The output voltage of the multilayer piezoelectric transformer was simulated using ANSYS. As results, the maximum stress appeared at the two points where one is the middle of input and the other is middle of output side in Second thickness extensional vibration mode. And output voltage was inversely decreased by increasing number of output layers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.293-298
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• 1995

A digital preview controller is designed for tandem cold mills to achieve a better improvement of the thickness accuracy. And simultaneously a blocked noniteracting controller is synthesized for rejecting the interactive effects among adjacent stands and for controlling independently each roll stand of landem cold mills. The performance effects and characteristics of the suggested roll control system are discussed in the practical view points. The simulation results show that the thickness accuracy of tandem cold mills can be largely improved by the blocked noninteracting and digital preview contoller.