• ETRI Journal
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• 제42권5호
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• pp.773-780
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• 2020

A 40 nm complementary metal oxide semiconductor carrier-aggregated drive amplifier with high linearity is presented for sub-GHz Internet of Things applications. The proposed drive amplifier consists of two high linear amplifiers, which are composed of five differential cascode cells. Carrier aggregation can be achieved by switching on both the driver amplifiers simultaneously and combining the two independent signals in the current mode. The common gate bias of the cascode cells is selected to maximize the output 1 dB compression point (P1dB) to support high-linear wideband applications, and is used for the local supply voltage of digital circuitry for gain control. The proposed circuit achieved an output P1dB of 10.7 dBm with over 22.8 dBm of output 3rd-order intercept point up to 0.9 GHz and demonstrated a 55 dBc adjacent channel leakage ratio (ACLR) for the 802.11af with -5 dBm channel power. To the best of our knowledge, this is the first demonstration of the wideband carrier-aggregated drive amplifier that achieves the highest ACLR performance.

• 한국강구조학회 논문집
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• 제26권6호
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• pp.581-594
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• 2014

HSB800과 HSB600 강재를 플랜지와 웨브에 적용하고 균일휨모멘트를 받는 하이브리드거더의 휨강도 평가를 위한 연구를 수행하였다. 비조밀 및 조밀플랜지와 세장, 비조밀 및 조밀 웨브를 갖는 이축 및 일축대칭 단면들을 대상으로 하였으며, 3차원 쉘요소 모델에 초기처짐과 잔류응력의 영향을 고려하여 '단면 휨강도' 및 '횡비틀림좌굴 강도'를 비선형해석으로부터 평가하였다. 수치해석 결과는 AASHTO LRFD 및 Eurocode 3 기준과 비교하였으며, 비조밀 및 조밀 웨브를 갖는 단면에 대해서는 AASHTO LRFD 부록 A6 기준의 적용성을 분석하였다.

• 한국항행학회논문지
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• 제26권6호
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• pp.516-521
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• 2022

본 논문에서는 변형된 전계-결합 유도-용량성(ELC; electric field-coupled inductive-capacitive) 공진기와 다중 슬롯 공진기를 이용한 소형 4-비트 chipless RFID(radio frequency identification) 태그를 제안하였다. 변형된 ELC 공진기는 기존의 ELC 공진기에서 인터디지털-커패시터 구조를 사용하여 레이다 단면적(RCS; radar cross section)의 공진 피크 주파수를 낮추었다. 다중 슬롯 공진기는 거꾸로 된 U-모양의 도체에 길이가 다른 3개의 슬롯을 에칭하여 설계하였다. 변형된 ELC 공진기의 RCS 공진 피크 주파수는 3.216 GHz로 설계하였고, 다중 슬롯 공진기는 각각 4.122 GHz, 4.64 GHz, 5.304 GHz로 설계하였다. 제안된 소형 4-비트 태그를 두께 0.8 mm의 50 mm×20 mm 크기의 RF-301 기판에 제작하였다. 실험 결과, 제작된 4-비트 chipless RFID 태그의 공진 피크 주파수는 3.285 GHz, 4.09 GHz, 4.63 GHz, 5.31 GHz로 0.78% ~ 2.16% 범위의 오차를 나타내며 시뮬레이션 결과와 유사하게 측정되었다.

• Transactions on Electrical and Electronic Materials
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• 제18권2호
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• pp.62-65
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• 2017

In this paper, three DC Block designs are presented which efficiently meet the need of modern-day compactsize wireless communication systems. As one of the important parts of a complete system design, the proposed microstrip-based DC block with coupled transmission lines efficiently attenuates unwanted frequencies that cause damage to the system. The compact-sized DC block structures are created by incorporating an extended coupled-line section with a radial stub, an enveloped coupled-line section, and using alternate up-down meandering techniques. The structures are analyzed for the L-Band using a high-resistive silicon substrate. At a resonating frequency of 1.575 GHz, the designed DC Block structures have a return loss better than -10 dB, an insertion loss of around -1 dB, and also possess wide pass-band characteristics.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1037-1049
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• 2001

Considerable interest has evolved in the flow of non-Newtonian fluids in channels of noncircular cross section in compact heat exchanges. Analytical solution was developed for prediction of the flow rate and maximum velocity in steady laminar flow of any incompressible, time-independent non-Newtonian fluids in straight closed and open channels of arbitrary, but axially unchanging cross section. The geometric parameters and function of shear describing the behavior of the fluid model were evaluated for fluid flow among a bundle of rods arranged in triangular and square array. Numerical values of dimensionless maximum velocities, mean velocities, pressure-drop-flow parameters and friction factors were evaluated as a function of porosity and pitch-to-radius ratio.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.148-154
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• 2008

Diverging channel from gas burner exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B) of 300 kW HRSG system, two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of boiler(Case C) and uniformity has been improved considerably. Secondly, the diverging channel length can be further reduced for compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 한국전산유체공학회지
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• 제14권3호
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• pp.1-8
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• 2009

Diverging channel from gas engine exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B), two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of the boiler(Case C) and uniformity in velocity and temperature distribution has been improved considerably. Secondly, the diverging channel length can be further reduced to compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 한국항행학회논문지
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• 제21권4호
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• pp.413-421
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• 2017

본 논문에서는 전술 및 조작 상황, 목표 위치 정보 확인이 가능한 Link-K (한국 합동 전술 데이터 링크 시스템)를 활용하여 목표물 재설정을 위한 소형 UHF(ultra high frequency) 수신 모듈을 설계 및 제작하였고, 시뮬레이션을 통해 목표물 재설정에 대한 효과를 분석하였다. 설계된 모듈은 UHF 수신반, 제어반 및 전원분배반으로 구성된다. UHF 수신반은 주파수 하향 변환, 필터링 및 자동이득 제어 등을 수행한다. 제어반은 주파수 하향 변환 된 신호를 복조하고, 정보를 추출하고, 외부 연동을 수행한다. 전원분배반은 외부 전원을 공급하고 각 구성품에 필요한 전원을 생성 및 공급한다. 제작 된 모듈의 크기는 $105{\times}105{\times}80mm$이고 무게는 1.10 kg이며, 수신 가능 거리는 50km 이상이다.

• 대한수학회보
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• 제26권2호
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• pp.139-149
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• 1989

pp.Hartman and G. Stampacchia [6] proved the following theorem in 1966: If f:X.rarw. $R^{n}$ is a continuous map on a compact convex subset X of $R^{n}$ , then there exists $x_{0}$ ..mem.X such that $x_{0}$ , $x_{0}$ -x>.geq.0 for all x.mem.X. This remarkable result has been investigated and generalized by F.E. Browder [1], [2], W. Takahashi [9], S. Park [8] and others. For example, Browder extended this theorem to a map f defined on a compact convex subser X of a topological vector space E into the dual space $E^{*}$; see [2, Theorem 2]. And Takahashi extended Browder's theorem to closed convex sets in topological vector space; see [9, Theorem 3]. In Section 2, we obtain some variational inequalities, especially, generalizations of Browder's and Takahashi's theorems. The generalization of Browder's is an earlier result of the first author [8]. In Section 3, using Theorem 1, we improve and extend some known fixed pint theorems. Theorems 4 and 8 improve Takahashi's results [9, Theorems 5 and 9], respectively. Theorem 4 extends the first author's fixed point theorem [8, Theorem 8] (Theorem 5 in this paper) which is a generalization of Browder [1, Theroem 1]. Theorem 8 extends Theorem 9 which is a generalization of Browder [2, Theorem 3]. Finally, in Section 4, we obtain variational inequalities for multivalued maps by using Theorem 1. We improve Takahashi's results [9, Theorems 21 and 22] which are generalization of Browder [2, Theorem 6] and the Kakutani fixed point theorem [7], respectively.ani fixed point theorem [7], respectively.

• 한국강구조학회 논문집
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• 제28권3호
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• pp.185-194
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• 2016

본 연구에서는 탄소섬유쉬트로 보강된 각형강관 기둥의 유한요소 해석결과를 소개하고 있다. 실험체 개수는 총 6개이며, 각형강관에 대해서는 비조밀 단면 단주, 세장판 단면 단주, 비조밀 단면 장주로 구성되어 있다. 실험변수는 탄소섬유쉬트 보강겹수이다. AFRP 스트립과 강재사이의 부착거동과 부착응력-슬립관계를 규명하였다. 총 6개의 실험체에 대하여 ANSYS V.14.0을 사용하여 유한요소해석을 수행하였으며, 파괴모드, 하중-변위곡선, 최대내력, 초기강성에 대해 실험결과와 비교하였다. 끝으로, AISC cold-formed steel structures 기준에 근거하여 세장비에 따른 좌굴응력값을 산정하였으며, 각 단면타입에 대한 좌굴응력값 및 보강효과를 비교하였다.