• 한국전자파학회논문지
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• 제18권2호
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• pp.151-157
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• 2007

본 논문에서는 모바일 장치의 T-DMB 안테나로 사용될 수 있는 급전 반대편에 open stub를 가지는 소형 two-wire helical 안테나를 제안하였다. Open stub의 길이를 조절하거나 open stub에 유전 물질을 발라 T-DMB 대역인 200 MHz에서 높이가 8 cm(200 MHz에서 0.053 $\lambda$임)인 안테나의 입력 임피던스를 쉽게 매칭시킬 수 있다. 이 안테나의 unbalanced 모드와 balanced 모드의 등가 회로를 이용하여 이 안테나의 등가 회로를 나타내고, 동작 원리를 설명하였다. 등가 회로의 해석을 토대로 open stub의 영향을 검증했다. 몇 가지 다른 파라미터 값을 가지는 안테나를 제작하였으며, 이 안테나의 $S_{11}$ 및 $S_{21}$을 측정하였다. 제작된 안테나의 임력 임피던스 대역폭($S_{11}{\leq}-10dB$)은 $196{\sim}204$ MHz(8 MHz)로 T-DMB의 한 채널(6 MHz)을 만족한다. 이 안테나의 측정된 $S_{21}$은 -38.6 dB로 동일한 높이의 모노폴 안테나와 open stub를 가지지 않은 two-wire helical 안테나의 $S_{21}$보다 약 17 dB 높다.

• 한국통신학회논문지
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• 제39B권5호
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• pp.309-316
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• 2014

안드로이드 앱(Android app, APK)을 역공학하여 디컴파일된 소스 코드를 획득하는 것이 용이하다. 공격자는 디컴파일된 소스코드를 불법적으로 사용하여 경제적 이득을 얻거나 악성코드를 삽입하여 앱을 변조하기도 한다. 이러한 문제를 해결하기 위해, 본 논문에서는 역공학 방지 방법을 사용하여 안드로이드 앱에 대한 불법 변조를 방지하는 APK 덮어쓰기 기법을 제안한다. 연구 대상은 임의 프로그래머에 의해 작성된 앱들이다. '대상 앱'(원본 앱)에 대해, 서버 시스템은 (1) 대상 앱의 복사본 생성, (2) 그 대상 앱을 암호화, (3) 복사본의 DEX (Dalvik Executable) 부분을 스텁(stub) DEX로 교체하여 스텁 앱 생성, (4) 암호화된 대상 앱 및 스텁 앱을 배포한다. 스마트폰 사용자는 암호화된 대상 앱 및 스텁 앱을 다운받는다. 스텁 앱이 스마트폰에서 실행될 때마다, 스텁 앱은 런처(launcher) 앱과 협력하여 암호화된 대상 앱을 복호화한 후 자신을 덮어쓰게 하여 원본 대상 앱이 실행되게 한다. 실행이 끝나면 복호화된 앱은 삭제된다. 제안 기법의 가능성을 검증하기 위해 여러 대중적인 앱들로 실험하여 보았다. 실험 결과, 제안 기법이 안드로이드 앱에 대해 역공학 및 변조 공격을 방지하는데 효과적임을 알 수 있다.

• ETRI Journal
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• 제36권4호
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• pp.690-693
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• 2014

Compact multi-band bandpass filters using quad-mode stub-loaded resonators are proposed in this letter. Firstly, a novel approach about the mode-splitting characteristics of the quadruple-mode resonator is investigated, which can provide dual-band behavior. Secondly, a quad-band filter is proposed and designed by cascading two quadruple-mode resonators; the upper one operates at 1.8/2.4 GHz (GSM- and WiMax-band) and the lower one at 1.57/2.1 GHz (GPS- and WCDMA-band). Finally, the proposed filters have been fabricated. Respectable agreement between simulation and measurement verifies the validity of this design methodology.

• Steel and Composite Structures
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• 제5권1호
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• pp.17-34
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• 2005

This paper presents an experimental study and its findings of the behavior of circular and square stub columns filled with high strength concrete ($f_c^{\prime}$=49MPa) and polymer cement concrete (PCC) under concentric compressive load. Twenty-four specimens were tested to investigate the effects of variations in the tube shape (circular, square), wall thickness, and concrete type on the axial strength of stub columns. The characteristics of CFT stub columns filled with two types of concrete were investigated in order to collect the basic design data for using the PCC for the CFT columns. The experimental investigations included consideration of the effects of the concrete fill on the failure mode, ultimate strength, initial stiffness and deformation capacity. One of the key findings of this study was that circular section members filled with PCC retain their structural resistance without reduction far beyond the ultimate capacity. The results presented in this paper will provide experimental data to aid in the development of design procedures for the use of advanced concretes in CFT columns. Additionally, these results give structural designers invaluable insight into the realistic behavior of CFT columns.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3930-3943
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• 2021

To improve the capability of the SAS4A code, which simulates the initiating phase of core disruptive accidents for MOX-fueled Sodium-cooled Fast Reactors (SFRs), the authors have investigated in detail the physical phenomena under unprotected loss-of-flow (ULOF) conditions in a previous paper (Kawada and Suzuki, 2020) [1]. As the conclusion of the last article, fuel stub motion, in which the residual fuel pellets would move toward the core central region after fuel pin disruption, was identified as one of the key phenomena to be appropriately simulated for the initiating phase of ULOF. In the present paper, based on the analysis of the experimental data, the behaviors related to the stub motion were evaluated and quantified by the author from scratch. A simple model describing fuel stub motion, which was not modeled in the previous SAS4A code, was newly proposed. The applicability of the proposed model was validated through a series of analyses for the CABRI experiments, by which the stub motion would be represented with reasonable conservativeness for the reactivity evaluation of disrupted core.

• 한국전자파학회논문지
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• 제23권5호
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• pp.559-569
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• 2012

본 논문에서는 단일 급전부를 갖는 레이다 디턱테용 X 밴드(10.525 GHz) $1{\times}2$ 배열 안테나와 K 밴드(24.15 GHz) $3{\times}6$ 배열 안테나를 제안한다. 제안된 배열 안테나의 왼편에는 X 밴드 배열 안테나가 있고 오른편에는 K 밴드 배열 안테나가 있다. 두 개의 배열 안테나는 하나의 전송 선로를 통해 급전이 되고, stub가 각 배열 안테나의 앞부분에 있다. 서로 다른 동작 주파수를 갖는 배열 안테나를 일반적인 T-junction을 이용하여 하나의 전송선로로 급전할 경우, 서로 영향을 주어 배열 안테나의 특성이 크게 바뀌게 된다. 이러한 영향을 차단하기 위해 open, short 특성을 이용하여 stub를 설계하였다. 먼저 각 배열 안테나에 stub가 연결되어도 안테나 특성이 바뀌지 않는 것을 확인하였고, 최종적으로 두 개의 배열 안테나를 연결하여 하나의 전송 선로로 급전을 하여도 성능이 바뀌지 않는 것을 확인하였다. 측정한 이득은 X 밴드에서 6.47 dBi, K 밴드에서 13.07 dBi로 시뮬레이션 결과와 잘 일치하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.175-178
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• 2006

We present a ring hybrid balun with additional two ${\lambda}/4$ short stubs that offers excellent amplitude and phase balance performance. The phase difference which is essentially occurred in $180^{\circ}$ ring hybrid is compensated by a ${\lambda}/4$ short stub in one output port. To compensate the amplitude imbalance inherent in the ring hybrid, the series resistance will be added to the second stub which is connected to another output port. The measured balun shows that phase imbalance is less than $2.5^{\circ}$ and magnitude imbalance is less than 0.2dB over a 1.75-2.25 GHz.

• Journal of electromagnetic engineering and science
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• 제14권4호
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• pp.387-392
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• 2014

In this paper, a size-reduced Wilkinson balun with wide harmonic-suppressed band is presented. An accurate analysis of the parallel coupled line with an open stub (PCL-OS) is carried out. The PCL-OS structure shows excellent low pass filter and harmonic-suppression characteristics, which is useful for designing a low pass filter unit cell (LUC) with a reduced size. The designed Wilkinson balun at a 2.45 GHz center frequency not only shows an excellent harmonic suppression including the 5th harmonics up to 14 GHz over 15 dB, but it also has an area reduced to 48% of the conventional one.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2309-2311
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• 2005

A broadband microstrip balun is proposed and designed using a ${\lambda}/4$short-stub in order to compensate phase imbalance. For the demonstration, two baluns are proposed and designed using a ${\lambda}/4$ shorted stub. One is a modified form of the conventional Wilkinson balun, and the other is a modified ring hybrid. Baluns are implemented on TLX-9 substrate of which the dielectric constant is 2.54 and the thickness is 0.5mm. The measurements show a bandwidth of 500MHz at the center frequency of 2GHz.

• Steel and Composite Structures
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• 제21권6호
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• pp.1251-1264
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• 2016

After observing relatively poor performance of bolted web-welded flange beam-to-column connections during 1994 Northridge earthquake, various types of connections based on two concepts of: (i) strengthening the connection; and (ii) weakening the beam ends were proposed. Among these modified or newly proposed connections, bolted T-stub connection follows the concept of strengthening. One of the connections with the idea of weakening the beam ends is reduced beam section (RBS). In this paper, finite element simulation is used to study the cyclic behavior of a new proposed connection developed by using a combination of both mentioned concepts. Investigated connections are exterior beam-to-column connections designed to comply with AISC provisions. The results show that moment capacity and dissipated energy of the new proposed connection is almost the same as those computed for a T-stub connection and higher than corresponding values for an RBS connection.