• 전자공학회논문지D
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• 제36D권7호
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• pp.1-8
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• 1999

3차원 분산 유한차분 시간영역 법을 이용하여 지하 침투 레이더에 대한 완전한 전자기적인 모의계산을 구현하였다. 제시된 모의계산 모델에는 공진기를 배후에 두고 있는 저항으로 중단된 bow-tie 안테나가 포함되어 있다. 그리고 수신안테나의 응답을 계산하기 위하여 안테나의 입력 임피던스와 급전선의 특성 임피던스로 구성된 등가회로를 사용하였다. 자체 제작한 bow-tie 안테나가 포함된 GPR 시스템을 사용한 실제 측정은 PVC 탱크에 담겨진 마른 모래 위에서 수행되었다. FDTD 모의계산 결과가 실제 측정자료와 거의 일치함을 확인할 수 있었다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.341-344
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• 2000

There are many researches to increase bandwidth of the microstrip patch antenna for wireless LAN. In spite of broad bandwidth, Bow-Tie microstrip patch antenna, broadband microstrip patch antenna, has disadvantages that are low gain and big size. In this paper, stacked Bow-Tie microstrip patch antenna for wireless LAN is designed in 5.725～5.825GHz band. This antenna has characteristics that are broadband bandwidth, high gain and small size compared with microstrip patch antenna. In simulated results, the return loss is -34.2dB at 5.78GHz and bandwidth is 11.345% for VSWR is 2:1 and 7.75% for VSWR is 1.5:1. In measured results, the return loss is -38-45dB at 5.78GHz and bandwidth is 13% for VSWR is 2:1 and 5.6% for VSWR is 1.5:1.

• 한국압력기기공학회 논문집
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• 제4권2호
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• pp.34-39
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• 2008

Steam Generator(SG) tubes are classified as one of the key components in nuclear power plants, and they should be periodically examined by the intensified management program for the assurance and diagnosis of their structural integrity. In this study, we use the optimum analysis technique to draw the detection and categorization of bowing(BOW) signals; abnormal tube-to-tube proximity in the SG upper bundle free span area. The locations in which BOW signals are detected likely have latent degradation of ODSCC(Outer Diameter Stress Corrosion Cracking). For the sake of timely and correct detection of BOW signals and diagnosis of ODSCC, we carried out the experimental demonstrations using a reduced mock-up. And we validated the MRPC(Motorized Rotating Pancake Coil) analysis technique is better than the bobbin. Hence, it comes to conclusion that the optimum analysis technique can be a good alternative for the reliable SG tube examination.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.31-37
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• 2005

An attempt to improve the speed performance through the minimizing in wave resistance has been done by an application of gooseneck and no bulb type to bulbous bow for the DSME 78,500 Class LPG Carrier on the basis of the CFD calculation and comparatives model tests. The hydrodynamic characteristics according to the variation of the shape of Cp-curve, design load water line, frame line and bulbous bow that have an important effect on the wave resistance has been evaluated/calculated by ship-flow code. A wide variety in hull variation have been tried to have a good hull form with three types of fore-body hull forms mainly classified by the shape of bulbous bow. The speed performances for the three final hull forms with different bulbous bows have been evaluated through the model tests.

• 대한조선학회논문집
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• 제44권3호
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• pp.279-284
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• 2007

As a container vessel becomes larger, the bow flare becomes larger. The large bow flare structures are often subjected to dynamic pressure loads due to bow flare slamming occurring in rough seas. The aim of this paper is to investigate the characteristics of bow flare slamming pressure measured in a real voyage through the North Pacific Ocean. The characteristics of impact pressure load caused by slamming is addressed in terms of the pressure pulse-time history which involves rising time, peak pressure, decaying time and type of pressure decay. The values were presented using non-dimensional parameters.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.302-312
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• 2013

While displacement type Deep-V mono hulls have superior seakeeping behaviour at speed, catamarans typically have modest behaviour in rough seas. It is therefore a logical progression to combine the superior seakeeping performance of a displacement type Deep-V mono-hull with the high-speed benefits of a catamaran to take the advantages of both hull forms. The displacement Deep-V catamaran concept was developed in Newcastle University and Newcastle University's own multi-purpose research vessel, which was launched in 2011, pushed the design envelope still further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. This paper presents the hullform development of this unique vessel to understand the contribution of the novel bow and stern features on the performance of the Deep-V catamaran. The study is also a further validation of the hull resistance by using advanced numerical analysis methods in conjunction with the model test. An assessment of the numerical predictions of the hull resistance is also made against physical model test results and shows a good agreement between them.

• 대한조선학회논문집
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• 제50권5호
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• pp.273-281
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• 2013

In this paper, the effects of bow deck shape on the green water are studied by numerical and experimental method. Varying the deck shapes to triangular, elliptic and circular, the thickness and advancing velocity of green water leading edge are compared using numerical method. Also the motion, the pressure on the vertical wall and the height on the deck of green water are compared among the three bow deck shapes in the heave and pitch motion free condition by experimental method. To remove the effects of the difference of motions among the deck shapes, numerical simulations are performed varying the deck shape with the same motion. In the same motion condition, smallest impulsive pressure occurred in the condition of elliptic deck shape.

• ETRI Journal
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• 제40권5호
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• pp.561-569
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• 2018

Modern communication systems employ wideband antennas with circular polarization (CP) radiation. In this work, asymmetric modified bow-tie (ABT) and symmetric modified bow-tie (SBT) slotted circularly polarized single-point probe-fed circular patch antennas with dimensions of $40mm{\times}40mm$ for wideband applications are proposed. A 10 dB RL bandwidth of 350 MHz with CP, 3 dB axial ratio (AR) bandwidth of 100 MHz, peak gain of 4.9 dBic, and 10 dB RL bandwidth of 530 MHz with CP, 3 dB AR bandwidth of 140 MHz, peak gain of 5 dBic are obtained for ABT and SBT slotted circular patch antennas, respectively. The proposed SBT slotted patch is scaled up and down to $50mm{\times}50mm$ and $30mm{\times}30mm$, respectively. The proposed scaled-up version offers 10 dB RL and 3 dB AR bandwidths of 340 MHz and 80 MHz, with a peak gain of 5 dBic. The scaled-down version offers 10 dB RL and 3 dB AR bandwidths of 710 MHz and 180 MHz, with a peak gain of 5.25 dBic. These prototypes are suitable to work in IEEE 802.11a WLAN, ISM, and IEEE 802.11ac applications. The measured and simulated results are then discussed and compared.

• 대한조선학회논문집
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• 제50권1호
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• pp.49-58
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• 2013

Recently, the design of commercial ships with less green-house gas is one of great interests in naval architecture fields. Ship designers are asked to find optimum hull forms with minimum resistance in ocean waves. The accurate computation of added resistance, therefore, is getting more important for the prediction of power increase in random ocean waves. This study focuses on the numerical computation of added resistance on ships with Ax-bow shapes which are designed to reduce added resistance. To this end, the time-domain Rankine panel methods based on weakly-nonlinear and weak-scatterer approaches are applied, which can reflect the influence of above-still-water bow shape. As computational models, KCS and KVLCC2 hull forms are considered. Each ship is combined with the three types of Ax-bow shape, and computational results are compared each other.

• 대한조선학회논문집
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• 제45권2호
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• pp.124-131
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• 2008

This paper presents the analysis of resistance performance and bow waves for the resistance-minimized hull form of small fishing boat by using numerical simulations and model tests. The resistance-minimized hull form is developed from an original hull form which is selected from existing small fisher boats in our country. In order to estimate the resistance performance for the original and the developed hull form, several numerical simulations and model tests are carried out. Marker and Cell(MAC) method and Marker-Density method are adopted to simulate the free-surface bow waves around advancing hull surface. The results of numerical simulations are compared with the model tests in towing tank. The results show that the resistance performance of the resistance-minimized hull form is improved than that of the original hull form. The results of this study will be a good guide to the hull form development of small fishing boats in future.