• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.48-58
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• 2015

The bandwidth enhancement of an aperture coupled microstrip patch antenna(ACMPA) with a high permittivity feed substrate suitable for the integration with MMIC is investigated using variation of an aperture width. As an aperture width increases, the 10 dB return loss bandwidth increases due to the increase of the mutual resonance region between a patch resonance and an aperture resonance. The bandwidth of an ACMPA with extended aperture width is increased up to 35.3 % from 20.8 % of the ACMPA with an aperture of a typical aspect ratio 10:1. The degradation of the radiation characteristics of an ACMPA due to the increase of an aperture width is very small.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.399-409
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• 2017

This study numerically investigates the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy acting as the main external forces of the salient formed behind the permeable submerged breakwaters. Shoreline response is also predicted by the longshore-induced flux. In this paper, a three-dimensional numerical wave tank based on the OLAFOAM, CFD open source code, is utilized to simulate the velocity field around permeable submerged breakwaters under the formation condition of salient. The characteristics of the velocity field around permeable submerged breakwaters with respect to the gap width between breakwaters and the installing position away from the shoreline under a range of regular waves for different wave height are evaluated. The numerical results revealed that as the gap width between breakwaters increases, the longshore currents become stronger. Furthermore, as the gap width becomes narrower, the point where flow converges moves from the center of the breakwater to the head part. As a result, it is possible to understand the formation of the salient formed behind the submerged breakwaters. In addition, it was found that the longshore currents caused by the gap width between breakwaters and the installation position away from the shoreline are closely related to the turbulent kinetic energy.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.40-47
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• 2022

The present study aimed to examine the effectiveness of different techniques for controlling the diagonal cracks at the corners of openings on the strength, deformation, and crack propagation in reinforced concrete walls. The crack control strip proposed in this study, the conventional diagonal steel reinforcing bars, and stress-dispersion curved plates were investigated for controlling the diagonal cracks at the opening corners. An additional crack self-healing function was also considered for the crack control strip. To evaluate the volume change ratio and crack width propagation around the opening, downsized wall specimens with a opening were tested under the diagonal shear force at the opening corner. Test result showed that the proposed crack control strip was more effective in reducing the volume change and controlling the crack width around the opening when compared to the conventional previous methods. The crack control strip with crack healing feature displayed the superior performance in improving the strength of the wall and reducing the crack width while healing cracks occurred in the previous tests.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.703-711
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• 2015

In large-scale factories, there are usually openings in the building to increase the efficiency of workers. However, if the factory is heated during winter, openings significantly increase the heating load. Therefore, there is a need for air curtains to be installed at the top of openings in factories to reduce the heating load due to the cold air entering from outside. The main design variables of these air curtains are the discharge angle, speed, and temperature, etc. While there have already been many studies focusing on these design variables, the distance from the opening and the width of the discharge have not been studied even though they also affect the sealing performance. As a result, when the distance from the opening decreases and the width of the discharge increases, we realize an optimum air curtain performance. However, if the distance from the opening is about 1.5 m, by adjusting the discharge angle and the distance from the opening, the sealing performance of the air curtain is improved by 13.7％.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.12-15
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• 2001

본 논문에서는 무한 도체판에 존재하는 폭이 좁은 슬롯에 단락도체를 설치하였을 때 슬롯을 통하여 침투하는 침투전자파의 크기를 검토하고 있다. 이론해석으로서는 슬롯 개구면의 전계분포에 관한 적분방정식을 유도하고, 개구면 전계분포를 등가 반경의 개념을 적용한 선자류로 가정하여 구분정현함수를 사용한 Galerkin의 모멘트법으로 침투전자파의 크기를 계산하였다. 슬롯에 평면파가 입사할 때 슬롯 개구에 설치된 단락도체에 의해 개구면 전계분포가 제어되고 침투전자파의 크기가 감소된다는 것을 확인하고 있다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.6
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• pp.408-415
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• 2016

Small fishing ports and coastal structures installed in a relatively low sea water depth disturb the wave induced current and cause the collapse of equilibrium state of sediment transport. These structures creates diffracted waves and matter the concentration of waves to cause the beach erosion. In order to mitigate these eroding problems on the beach, many counter measurements were proposed such as detached breakwater, groin or headland; however, these methods interrupt the aesthetic view of sandy beach due to the exposed structures above the sea level and have difficulty of applying to those beaches with the good scenery. Furthermore, some of these methods create secondary environmental problems after the installations. To eliminate these problems, one of the countermeasures, artificial reefs have been selected and used worldwide to minimize the disturbance of the scenery and secondary effects on the environment. Meanwhile, it is important to set the design elements for installing the artificial reefs such as that of length, opening width, clearing distances from the shoreline and more. Nevertheless, there are no construction manuals or standards for designing the artificial reefs with these important design elements yet. In this study, different conditions of artificial reefs were used with various cases throughout hydraulic model test to precisely analyze the changes of waves and currents to propose the standards of design elements to install the artificial reefs.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.697-704
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• 2003

The purpose of this experimental study is to investigate the relationship of the shear behavior and the variety of width, depth and location of an opening in reinforced concrete deep beams with rectangular web openings, and to present an improved shear strength equation of those members. The main parameters considered were concrete strength(fck), shear span-to-overall depth ratio(a/h), and the size and vortical position of the web openings. Twenty five deep beams were tested under two symmetric loading-points. Test results showed that the shear behavior of deep beams with web openings was influenced by a/h and the size of opening. In addition, the KCI shear design provision is a tendency to be more unconservative according to the increase in a/h and the area-ratio of opening to shear span(Ao/Ash). Based on the concrete strut action of top and bottom member of an opening and the tie action of longitudinal reinforcement, a proper design equation which closely predicts the capacity of deep beams with rectangular openings is developed.

• Journal of Oral Medicine and Pain
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• v.25 no.3
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• pp.293-303
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• 2000

앵글씨 분류에 따른 최대개구시 하악의 수직 변위에 대한 차이를 확인하고, 수직 하악운동에 영향을 주는 골격요소를 확인하기 위하여, 측두하악관절 및 저작계 이상에 대한 증상 및 병력이 없으며 발치 및 교정치료의 경험이 없는 광주지역 대학에 재학중인 학생들을 대상으로, 앵글씨 구치부 관계에 근거하여 1급군(남:30명, 여:49명), 2급군(남:18명, 여:24명)과 3급군(남:18명, 여:33명)으로 분류하여 총 172명(연령 범주:20-30세)의 학생을 선택하였다. 전남대학교 병원 구강내과에서 사용하는 계측용자를 이용하여 최대 개구시 상하악 중절치 절단면간의 거리를 측정하였다. 대상자들의 진단모형을 만들어 상하악궁 길이와 폭경를 측정하였다. 대상자들에 대한 두부 규격방사선 사진을 촬영, 작도하고 방사선학적 지표를 계측, 비교분석하였다. 앵글씨 분류 1급군, 2급군 그리고 3급군 절치간 최대개구량은 3급군이 가장 컸으며 모든 군에서 남자가 여자보다 컸다. 구치간 최대개구량은 앵글씨 분류 1급군, 2급군 그리고 3급군에서 각 군간의 유의한 차이는 없었으나, 모든 군에서 남자가 더 컸다. 앵글씨 분류 1급군과 2급군의 하악운동에서 총 하악골 길이, 하악지 길이, 하악 하연부 길이 그리고 상악궁 폭경이 변수로 나타났으며, 상하악궁 길이와는 역상관관계를 나타내었다. 앵글씨 분류 3급군의 하악운동에서 상하악궁 길이와 안면 부길이가 1급군과 2급군과는 다른 중요한 변수로 나타났으며, 상악궁의 폭경과는 역상관관계를 나타내었다. 이상의 결과로 보아 앵글씨 분류 각 군에서 하악개구운동은 안면 골격구조의 영향을 받으며, 각 군간에 영향을 주는 안면 골격 요소들은 차이가 있었다. 따라서 이러한 골격적 요소들은 개구량 개선을 위한 진단과 치료시 고려되어야 할 것으로 사료된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1647-1652
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• 2011

This paper presents the shielding effectiveness for the IEC 61000-2-9 standard when HEMP source penetrates through an aperture in a planar conducting plane of infinite extent. An integral equation is derived and solved by applying Galerkin's method of moments for calculating the electric shielding effectiveness. The electric shielding effectiveness is examined based on changing the aperture length and width. It is shown that the electric shielding effectiveness is suddenly decreases as the aperture width of 0.4 ~ 0.45${\lambda}$. It is also found that the penetrated electric field for the IEC 61000-2-9 incident field is different from the Bell Laboratory incident field, but the frequency characteristic of the electric shielding effectiveness becomes the same shape.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.153-165
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• 2018

In this study, the performance of irregular wave field generation of olaFlow is first verified by comparing the frequency spectrum of the generated waves by the wave-source using olaFlow and the target wave. Based on the wave performance of irregular waves of olaFlow, the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy around the three-dimensional permeable submerged breakwaters, which act as the main external forces of the salient formation, are numerically investigated. The numerical results show that as the gap width between breakwaters decreases, the wave height in the center of the gap increases and as the gap width between breakwaters increases, the longshore currents become stronger. As a result, it is possible to understand the formation of the salient formed behind the submerged breakwaters.