• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.20-24
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• 2006

Wind tunnel tests were conducted to compare gliding and turning performance of normal cruciform parachutes with newly modified cruciform parachutes. Modified cruciform parachute has better gliding performance than original cruciform parachutes but, modified cruciform parachute has worse turning performance than original cruciform parachute.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.628-633
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• 2008

Cruciform parachute has advantage in manufacture and expanse compare with circular parachute. But it has disadvantage in stability. Wind tunnel test were conducted to investigate the effects of reefing-line on the cruciform parachutes with the purpose of finding aerodynamics characteristics of the parachute such as drag coefficient, normal force coefficient. Aerodynamics characteristics are measured accurately with 6-components pyramidal balance and load cells which were installed in the fixed-body. Four different models were tested and the test results were compared with each other. The aerodynamics characteristics were changed with reefing-line length. Separation edge was developed due to reefing-line also it made increasing of the stability. The cruciform parachute which improve stability is supposed to be used in variety purpose.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.1-7
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• 1997

This paper presents an analysis of the wave propagation in cross-type tunnels using the finite volume time domain (FVTD) method. Because the FVTD method is based on the volume intergrations of themaxwell's equations with respected to arbitrary shaped small polyhedron cells and the fields at every center point of the cells ar eassigned in a average fashion, the method can handle arbitrary boundary problems with inhomogeneous media. In this paper, the wave propagation in cross-type tunnels has been analyzed using the fVTD method with the PML (perfectly matched layer) absorbing bundary conditons, and the numerical results are verified with a set of experimental data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.508-512
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• 2007

In this paper, a novel wideband crossed planar monopole antenna with the double resonance characteristics is proposed. The proposed monopole antenna consists of a wideband crossed planar monopole antenna and L-shaped slits. In order to generate double resonance characteristics on the proposed monopole antenna, the length of L-shaped slit on the antenna surface is obtained from the quarter-wavelength of the second resonance frequency The double resonance characteristics of the proposed antenna can be easily designed by the control of length of L shaped slit at an interesting frequency. The proposed antenna having an omnidirectional radiation pattern and a high gain over the double resonance frequency bands, respectively, is suitable for mobile multiband antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.2
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• pp.364-372
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• 1994

Theoretical method for analyzing the radiation pattern of cross-type 5-patch rectangular microstrip antenna is presented. The equivalent circuit of the array antenna is represented by the conventional transmission line model and the radiation admittance derived from the equivalent circuit of the slitted parallel-plate waveguide filled with a dielectric. The calculated results for the radiation pattern are compared with the measured values.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.215-218
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• 1999

본 논문에서는 직사각형 마이크로스트립 슬롯 안테나에서 폭이 넓은 슬롯에는 적합하지 않은 기존의 급전 구조대 신 T자형 급전 방식과 십자형 급전 방식으로 안테나를 설계하였다. 여기서 제시한 T자형 급전 방식을 이용하여 슬롯 폭이 20㎜일 때 41%의 대역폭 특성을 얻었고. 십자형 급전 방식으로는 슬롯 폭이 32 ㎜일 때 96%의 대역폭을 얻었다. 또한 기존의 원형 링 슬롯 안테나의 구조를 바꾸어 슬롯의 원주(circumference)가 163 ㎜일 때 1.35 octave의 광대역 특성을 얻었고, 원형 슬롯 안테나와 이에 적합한 급전 방식을 제시하여 슬롯의 원주가 같을 때 3.25 octave의 광대역 특성을 얻었다.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.43-50
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• 2000

In this paper, the consolidation efficiency and the equivalent diameter of the cross shaped drain are examined by using the laboratory test and the numerical model, and the results are compared with those of the band shaped drain. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The efficiency of the cross shaped drain is evaluated by using the 3-D flow program which was validated by the settlement-time test fill data. The results of laboratory test show that the equivalent diameter of the band shaped drain was close to the Rixner's formula and that of the cross shaped drain was fit to the following formula: $d_w\;=\; \\tarc{3}{4}.(b+t)$The results of the numerical analysis show that the cross shaped drain can reduce the consolidation time by 9-10% from that for the band shaped drain. The equivalent diameter obtained from the numerical flow model by using the field data is 3.5 times smaller than that obtained from the laboratory consolidation test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.233-240
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• 2007

In this paper, the broadband cross monopole antenna is presented and the radiation characteristics are investigated. The presented broadband cross monopole antenna is composed of the cross monopole element and the folded short stub, which has a excellent band characteristics more than the existing cross monopole antenna. To conform the broadband characteristics of the presented antenna, the experimental antenna is designed, fabricated, and its radiation characteristics are measured in $1.75\sim2.655\;GHz$. It is shown that the designed antenna has the nondirectional pattern in the horizontal plane, the directional pattern in the vertical plane, VSWR less than 1.5, and gain in $2.17\sim4.87\;dBi$. From these results, the presented antenna is conformed as a broadband indoor antenna which can be used for PCS, WCDMA, Wibro, and satellite DMB band.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.13-18
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• 2015

This study presents the structure design of antenna to have the dual band characteristics in a desired frequency band through the structural modification of an antenna structure. For the experiment, a wideband crossed planar monopole antenna was used. The target frequency band was set to ISM 2.45GHz/5.8GHz. To give the properties, an additional antenna element was added to the crossed planar monopole antenna, which is a main body of the antenna. And then structural adjustment parameter was set to change the length(shape) of the antenna. Various simulations were conducted to find the dual band characteristics in the desired frequency band. The simulations brought forth the antenna bandwidth above the normal values for ISM 2.45GHz/5.8GHz. The structural adjustment parameter introduced in this study for structural modification of an antenna can be useful in developing an antenna featured with dual band(multiband) characteristics.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.703-710
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• 2011

As the spacer in the membrane module provide the channel space to flow the feed solution smoothly and induce the flow turbulence, it could help to reduce both the concentration polarization and to take the long-term operation of membrane modules with high permeate flux by mixing the accumulated contaminants on the membrane surface into the bulk solution. In this study, the concentration distribution in membrane module with respect to the spacers which have the cross-sectional shapes of circle, cross, diamond and hexagon, the angles of spacer configuration, solute rejection and permeate flux were interpreted and optimized numerically using the "COMSOL Multiphysics" software. The concentration on the membrane surface was kept the lowest level for the cross-shape among the above four types of spacers. Also the 30 degree spacer configuration was showed as the most efficient case. The concentrations on the membrane surface at the module outlet for without spacer and the cross shape with the 30 degree spacer configuration were 2.09 and 1.29 times higher than those at inlet, respectively. The reduction effect of concentration polarization increased rapidly as the permeate flux increased.