• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.592-600
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• 2005

Ship have cutout inner bottom and girder and floor etc. Ship's structure is used much, and structure strength must be situated, but establish new concept when high stress interacts sometimes fatally the area. There is no big problem usually by aim of weight reduction, a person and change of freight, piping etc.. Because cutout's existence grow up in this place, and elastic buckling strength by load causes large effect in ultimate strength. Therefore, stiffened perforated plate considering buckling strength and ultimate strength is one of important design criteria which must examine when decide structural concept at initial design. Therefore, md, reasonable buckling strength about stiffened perforated plate need to ultimate strength limited design . Calculated ultimate strength varied several web height and cutout's dimension, and thickness in this investigated data. Used program(ANSYS) applied F.E.A code based on finite element method

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.412-416
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• 2005

In this paper we propose low-impedance and miniaturized a wilkinson power divider on MMIC passive component which was fabricated by a novel microstrip line structure employing periodically perforated ground metal (PPGM). The novel microstrip line structure showed much lower impedance and shorter guided-wavelength than conventional one. Using the novel microstrip line with periodically perforated ground metal, a miniaturized 17 ${\Omega}$ power divider was fabricated. The line width of the power divider was 20 ${\mu}m$, and the size of it was 0.110 $mm^2$, which is 21 % of conventional one. The power divider exhibited good RF performances from 10 to 20 GHz.

• KIEAE Journal
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• v.1 no.2
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• pp.47-54
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• 2001

Single sound absorbers such as porous materials, panels, and Helmholts resonators have limited performance with some extents of frequency region. For example, porous materials do not attenuate low frequency sounds, while panels do not absorb high frequency sounds. Composite absorption structure with coverings, porous materials, and air gaps are an alternative for wide band sound absorption. Slits, panels, perforated panels are those materials for coverings, glass wool, mineral wool, polyester, and polyurethane are frequently used porous materials. Air gap between the porous material and background surface is one of major factors which governs the absorption characteristics of composite absorption structures, especially in the low frequency area. Calculations and measurements show that the absorption coefficients of composite absorption structure, in mid and low frequency bands, are getting higher with increased air gaps. Perforated panels rather than slits and panels are good coverings with higher number as far as absorption coefficient is concerned. Perforated panels with porous materials and 37 cm of air gaps in background have high absorption coefficients for all frequency bands, above 0.7 to 1.0. All measurements are performed in reverberation chamber, Mokpo National University, according to ISO 354 and ISO 3382.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.727-733
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• 2003

In order to realize miniaturized and low-impedance MMIC passive component, a novel microstripline structure employing periodically perforated ground metal was proposed. The novel microstripline structure showed much lower impedance, and shorter guided-wavelength than conventional one. Using the novel microstripline with periodically perforated ground metal, a miniaturized 15 $\Omega$ ratrace was fabricated. The line width of the ratrace was 20 $\mu\textrm{m}$, and the size of it was 0.375 mm$^2$, which is 9.3 % of conventional one. The ratrace exhibited good RF performances from 20 to 30 GHz.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1323-1338
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• 2006

An analytical method to estimate the coupled frequencies of the circular plate submerged in fluid is developed using the finite Fourier-Bessel series expansion and Rayleigh-Ritz method. To verify the validity of the analytical method developed, finite element method is used and the frequency comparisons between them are found to be in good agreement. For the perforated plate submerged in fluid, it is almost impossible to develop a finite element model due to the necessity of the fine meshing of the plate and the fluid at the same time. This necessitates the use of solid plate with equivalent material properties. Unfortunately the effective elastic constants suggested by the ASME code are found to be not valid for the modal analysis. Therefore in this study the equivalent material properties of perforated plate are suggested by performing several finite element analyses with respect to the ligament efficiencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.345.1-345
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• 2002

This paper dealt with an experimental study on the hydroelastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energies and compared with the experimental results. (omitted)

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.25-27
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• 2012

In this paper, combustion process in the perforated silicon carbide(SiC) tube using a two dimensional approaches with GRI Mechanism 1.2 was investigated. The computational mesh structure which is divided into $60{\times}15$ and boundary conditions are set to constant mass flow rate at the inlet and constant pressure condition at the outlet respectively. Its result shows that the temperature on this peak was roughly 100K higher than the adiabatic flame temperature of 2223K for a free laminar flame at these conditions.

• Steel and Composite Structures
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• v.2 no.1
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• pp.51-66
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• 2002

Perforated shear connectors currently used in composite steel and concrete structures are described and evaluated. Modifications of the perforated connector suitable for common use injavascript:confirm_mark('abe', '1'); civil and bridge engineering are proposed. The connectors were tested in laboratories of CTU Prague for shear load capacity. Push tests of connectors with 32 mm openings and with 60 mm openings, both in normal and lightweight concrete of different strength characteristics and with different transverse reinforcement, were carried out. The experimental study also dealt with the connector height and parallel arrangement of two connectors and their influence on shear resistance. While extensive tests with static loading were carried out, fatigue tests under repeated loading are still in progress. After statistical evaluation of the experimental results and comparisons with other available data the authors developed reasonable shear resistance formulas for all proposed arrangements.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3150-3155
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• 2007

This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.210-224
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• 2010

The aim of the present study is to investigate the buckling strength of plates and stiffened panels with opening under transverse thrust and shear actions. It is observed that the existing design formulation for critical-buckling strength of plates are not valid for perforated plates, because the current design formulation trends can significantly overestimate or underestimate the load-carrying capacity of plates when plates have large opening and/or are thick. A series of eigen value and elastic.plastic large deflection finite element analyses are carried out with varying the aspect ratio of plate, the opening size and location on plate until and after the ultimate strength is reached. Based on the results obtained from the present study, closed-form design formulations for the elastic buckling strength of plates and stiffened panels with opening are derived. The derived design formulations are considered plasticity correction of the material and verified by experimental tests and results of nonlinear finite element computations.