• Journal of Advanced Marine Engineering and Technology
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• 제32권3호
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• pp.437-445
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• 2008

This paper deals with the experimental assessment of the vibration suppression of the smart structures. First. we have presented a new high-speed active control system using the DSP320C6713 microprocessor. A peripheral system developed is composed of a data acquisition system, N/D and D/A converters, piezoelectric (PZT) actuator/sensors, and drivers for fast data processing. Next, we have tested the processing time of the peripheral devices, and provided the corresponding test results. Since fast data processing is very important in the active vibration control of the structures, we have focused on achieving the fast loop times of the control system. Finally, numerous experiments were carried out on the aluminum plate to validate the superior performance of the vibration control system at different control loop times.

• Smart Structures and Systems
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• 제11권6호
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• pp.623-635
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• 2013

This paper investigates application of a control algorithm called model predictive sliding mode control (MPSMC) to active vibration suppression of a cantilevered aluminum beam. MPSMC is a relatively new control algorithm where model predictive control is employed to enhance sliding mode control by enforcing the system to reach the sliding surface in an optimal manner. In previous studies, it was shown that MPSMC can be applied to reduce hysteretic effects of piezoelectric actuators in dynamic displacement tracking applications. In the current study, a cantilevered beam with unknown mass distribution is selected as an experimental test bed in order to verify the robustness of MPSMC in active vibration control applications. Experimental results show that MPSMC can reduce vibration of an aluminum cantilevered beam at least by 29% regardless of modified mass distribution.

• 한국해양공학회지
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• 제1권2호
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• pp.113-122
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• 1987

Ships and offshore strrctures are exposed to the corrosive surroundings, and the extablishment of the design criteria and the elucidation on the influence by this environment are requested to maintain the safety and to demonstrate the function of the structure. In this paper, the fatigue-crack-growth behavior on the compact tension specimens of quenched, tempered HT80 grade steels and RA36 high tensile steels having a single edge fatigue cracked notch respectively, were investigated under the repeated tensile stress with constant stroke in sea water for the welded parts by shielded metal arc welding. Main results obtained are summerized as follows; 1. The fatigue-crack-growth rates da/dN in sea water appeared to be greater behavior than those in air environment at the same stress intensisy factor range $\DeltaK$. 2. The correlation data of da/dN$\DeltaK$ of the two kinds of high tensile steels in sea water showed no great difference, however, the correlation data of da/dN$\DeltaK/\sigma_y$($\sigma_y$ stands for yield strength of the material) showed that the fatigue-crack-growth behavior of RA36 plate is affected by active path corrosion(APC) mechanism, while that of HT80 grade plate is mainly affected by hydrogen embrittlement mechanism.

• 약학회지
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• 제33권2호
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• pp.129-139
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• 1989

New diamide chiral stationary phases of four systematically substituted optically active N-(N-benzoyl-L-amino acid)-anilide synthesized from L-valine, L-leucine, L-isoleucine, and L-phenylalanine were described. The behaviors of these diamides as optically active stationary phases for the separation of N-trifluoroacetyl-D,L-amino acids were examined with respect to separation factors(${\alpha}$) and thermodynamic properties of interaction. The separation of twelve N-trifluoroacetyl-D,L-amino acid isopropyl esters were improved by the order of N-(N-benzoyl-L-leucyl)-anilide>N-(N-benzoyl-L-isoleucyl)-anilide>N-(N-benzoyl-L-valyl)-anilide>N-(N-benzoyl-L-phenylalanyl)-anilide. Eight amino acid derivatives with non-polar R-group and threonine, serine, aspartic acid, and glutamic acid enantiomers were separated on N-(N-benzoyl-L-leucyl)-anilide as chiral stationary phase with good separation factor between 1.07-1.25. The separation factors decreased with respect to increasing column temperature. Possible working temperature of diamide phase was between $130-190^{\circ}C$ for N-(N-benzoyl-L-phenylalanyl)-anilide and $130-180^{\circ}C$ for other three diamide phases. The differential Gibb's free energy (${\Delta}{\Delta}G$) of enantiomers was in the range of -100--180 cal/mol for ten amino acids and -40--60 cal/mol for alanine and aspartic acid.

• 전자공학회논문지
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• 제51권7호
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• pp.26-36
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• 2014

IMT-Advanced 시스템을 효율적으로 서비스하고 시스템 효율을 증대시키기 위해서는 능동위상 배열구조의 안테나 시스템이 요구된다. 능동위상 배열 구조는 다수의 송수신 모듈과 다수의 복사소자로 구성되어 시스템의 효율을 증대시킬 수 있으며, 시스템을 구현하기 위해서는 초소형 고효율 송수신 모듈이 핵심이다. 최종 출력과 밀접한 관련이 있는 송신모듈의 전력증폭기는 기지국 시스템의 효율을 결정하는 핵심요소이다. 본 논문에서는 IMT-Advanced 능동위상배열 시스템에 적합한 초소형 고효율 송수신 모듈을 설계하고 구현하고자 하였다. 송수신 모듈은 온도보상 회로를 구현하여 이득 오차를 줄였으며, 선형화기는 소형화를 위하여 아날로그 방식으로 구현하였다. 초소형 고효율 전력증폭기를 구현하기 위해서 GaN MMIC Doherty 구조로 구현하였다. 구현된 송수신모듈은 $40mm{\times}90mm{\times}50mm$ 크기로 구현되었으며, LTE band 7에서 47.65 dBm의 출력을 가졌다. 실제 운용전력인 37 dBm에서 40.7%의 효율과 12 dB이상의 선형성 개선도를 보였다. 수신부의 잡음지수는 1.28 dB이하로 설계규격을 만족하였으며, 송수신 모듈의 이득과 위상은 6 bit로 제어로 최대 오차는 각각 0.38 dB와 2.77 degree를 보였다.

• 전력전자학회논문지
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• 제24권4호
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• pp.259-267
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• 2019

An active clamp flyback (ACF) converter applies a clamp circuit and circulates the energy of leakage inductance to the input side, thereby achieving a zero-voltage switching (ZVS) operation and greatly reducing switching losses. The switching losses are further reduced by applying a gallium nitride field effect transistor (GaN-FET) with excellent switching characteristics, and ZVS operation can be accomplished under light load with boundary conduction mode (BCM) operation. Optimal design is performed on the basis of loss analysis by selecting magnetization inductance based on BCM operation and a clamp capacitor for loss reduction. Therefore, the size of the reactive element can be reduced through high-frequency operation, and a high-efficiency and high-power-density converter can be achieved. This study proposes an optimal design for a high-efficiency and high-power-density BCM ACF converter based on GaN-FETs and verifies it through experimental results of a 65 W-rated prototype.

• 한국통신학회논문지
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• 제7권3호
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• pp.120-124
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• 1982

本論文에서는 스트라입 構造型 DH LD의 lateral waveguiding mechanism에 대한 理論的解析이 시도되었다. 解析過程에서 실제에 아주 근사한 활성충의 利得 및 屈折率變化에 대한 數學的모델을 이용하여 섭동이론에 의한 DH LD의 2차원적 waveguiding을 해석하고 미소굴절률변화(n), 활성층두께(d), cavity length(L)에 대한 빔폭 의존성을 해석하였다.

• 한국인터넷방송통신학회논문지
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• 제15권2호
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• pp.175-180
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• 2015

본 논문에서는 GPS/GLONASS 수신용 소형 액티브 안테나를 제안하였다. GPS(1.575.42MHz)와 GLONASS(1.602MHz) 듀얼 대역을 지원하는 마이크로스트립 패치 안테나를 최적화하였고, 안테나의 크기는 $13{\times}13{\times}3.6mm$이다. 제안한 안테나 특성 확인을 위하여 지그 크기 변화를 주었고, 패치안테나의 급전 간격을 조정하였고, LNA 쉴드 케이스 유무에 따른 변화로 확인하였다. 안테나 지그의 크기는 $65.6{\times}13{\times}0.8mm$이다. GPS 대역의 최대 이득은 3.78dBi이고, GLONASS 대역의 최대 이득은 4dBi이다. 위성 수신레벨을 증폭하기 위한 저잡음 증폭기는 1단 LNA를 설계하였다. LNA 칩은 BGA715N7를 이용하였고, LNA 이득은 19.9dB이다. 시뮬레이션과 측정 데이터를 비교 분석한 결과 GPS/GLONASS 수신용 소형 액티브 안테나의 실용화 가능성을 확인할 수 있었다.

• 전자공학회논문지D
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• 제34D권8호
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• pp.52-61
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• 1997

In this paper it is proposed a new architecture for N*N optical packet switching system. It consists of active-splitter type pf packet router, travelling type of optical buffer memory for packet contention resoltuion and an electronic controller. the BER performance of the proposed switching system is analyzed with respect to channel crosstalks and amplified spontaneous emissio noise form switching elements and optical amplifiers respectively. Operational validity of the proposed switching system is also experimentally proved by realizing 2*2 optical packet switching system.

• 공업화학
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• 제17권3호
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• pp.286-290
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• 2006

새로운 4급 염화 암모늄염, {alkyldimethyl-[5-(2-phenylthiazol-4-yl]-1,3,4-oxadiazol-2-ylmethyl]quaternary ammonium chlorides (ADOQACs): 6}을 화합물 5와 몇 가지 N,N-dimethylalkyl amine을 반응시켜 합성하였다. 합성한 화합물들의 구조와 물리적 특성을 조사하였고 계면활성을 측정하였다. 화합물 6의 표면장력($\gamma_{cmc}$)과 최소저해농도(MIC)는 알킬기의 영향을 받은 것으로 나타났으며, 특히 화합물 6c와 6d가 좋은 항균력과 계면활성을 보였다.