레이저 스크라이빙 공정을 이용한 디자인된 그래핀의 패턴 합성

이동윤,남정태,김근수 한국물리학회 2019 새물리 Vol.69 No.6

In this study, a LASER scribing process in a vacuum chamber was used to reduce the process time and the energy consumption significantly and pattern synthesis of graphene into the desired shape was carried out. For this purpose, a LASER-assisted chemical vapor deposition (CVD) was used and a negative tone resist polymer film was coated onto various substrate, such as metal foil, quartz, and quartz coated with a thin metal film, to be used as a solid carbon source for graphene synthesis. On such a prepared substrate, patten synthesis of graphene by LASER ( = 1064 nm, pulse) local heating method was performed in a vacuum chamber, and each sample was evaluated by Raman spectroscopy to optimize the synthesis conditions. In the case of a metal substrate, the synthesis of patterns of graphene was difficult due to the good thermal conductivity of the metal. For the quartz substrates, the optimized conditions for graphene synthesis were a power of 1.4 W, a scan speed of 1mm/s, a frequency of 30 kHz, and five exposures. For the quartz substrate coated with a 300 nm Ni film. The optimized conditions were a power of 1.8 W, a scan speed of 2 mm/s, a frequency of 30 kHz and one exposure. 본 연구에서는 레이저 스크라이빙 공정과 진공 챔버를 결합하여 공정시간과 에너지 소모를 대폭적으로절감하여 그래핀을 원하는 위치에 원하는 모양으로 패턴 합성하는 연구를 수행하였다. 이를 위해서 LASER assisted CVD를 구축하고 금속호일, 퀄츠, 금속박막이 코팅된 퀄츠 등의 다양한 기판들에 Negative tone resist 폴리머 박막을 코팅하여 그래핀 합성의 고체 탄소원으로 사용하였다. 이와 같이 준비된 기판에서레이저( = 1064 nm, 펄스) 국소 가열법에 의한 그래핀의 패턴 합성을 진공 챔버에서 수행하였고, 각각의 시료는 라만분광법에 의해 특성을 평가하여 합성조건을 최적화하였다. 금속기판에서는 금속의 열전도성이좋아서 그래핀의 패턴 합성이 어려웠으나, 퀄츠 기판에서는 출력파워 1.4 W, 스캔속도 1 mm/s, 주파수30 kHz & 노출횟수 5회 , 금속박막(Ni 300 nm)이 증착된 퀄츠기판에서는 출력파워 1.8 W, 스캔속도 2 mm/s, 주파수 30 kHz로 최적화된 합성조건을 찾았다.

컨포멀 위상 배열 안테나의 패턴 합성에 대한 고찰

박동철(Dong-Chul Park),권오혁(Oh-Hyuk Kwon),류홍균(Hong-Kyun Ryu),이규송(Kyu-Song Lee) 한국전자파학회 2015 한국전자파학회논문지 Vol.26 No.12

본 논문에서는 Enhanced Adaptive Genetic Algorithm(EAGA)를 이용하여 두 가지 종류의 컨포멀 배열 안테나의 패턴합성 과정을 기술하였다. 한 종류는 2차 함수 형태의 실린더 도체 위에 배열된 1×16 배열 안테나이고, 다른 종류는 2차함수 곡선의 회전체 곡면 도체 위에 배열된 18개 소자 배열 안테나이다. 패턴 합성시 각 소자의 능동 소자 패턴을 이용하였고, 특히 회전체형 배열 안테나의 경우, 합성 시간을 크게 줄이기 위해 동심원형 평면 배열 안테나의 능동 소자 패턴을 구한 뒤 이를 변환하여 사용하였다. 제안한 합성 기법의 타당성을 검증하기 위해 MATLAB 내에서 합성된 배열 안테나의 패턴과 MWS(Microwave Studio) 내에서 구현된 배열 안테나의 패턴을 비교하였으며, 또한, 1×16 배열 안테나의 경우는 측정 패턴과 합성 패턴도 비교하였다. This paper describes the pattern synthesis method of two kinds of conformal array antenna using the Enhanced Adaptive Genetic Algorithm (EAGA). One is the 1×16 conformal array antenna on a curved cylindrical metallic surface with quadratic function, and the other is the 18-element conformal arrary antenna on a metallic surface obtained by the rotation of a quadratic function curve around the axis. The active element pattern is utilized in the pattern synthesis. Especially for the case of the rotated-type conformal array antenna the transformed active element pattern obtained from the Euler’s angle rotation of the active element pattern of the planar concentric array is utilized, which reduces the synthesis time a lot. To verify the validity of the proposed synthesis method the MATLAB results are compared with the MWS results. Furthermore, for the case of 1×16 conformal array antenna the measured results are compared with the MATLAB synthesized results.

모노펄스 추적용 선형 배열 안테나 빔 패턴 및 여기 전류 가중치들의 최적 합성에 관한 연구

박의준(Eui Joon Park) 한국전자파학회 2008 한국전자파학회논문지 Vol.19 No.5

등간격 안테나 소자들로 구성된 모노펄스 추적용 선형 배열 안테나의 합 및 차 패턴 합성 문제에서 원하는 패턴을 만족시키도록 하는 개별 안테나 급전 여기 전류의 상대적인 가중치들을 도출하는 효율적인 수치적 방법을 제안한다. 이 방법은 패턴 배열 인자를 표현하는 Schelkunoff 다항식에 내재된 패턴 null 점들의 최적 섭동에 기본을 둔다. 따라서 여기 전류 가중치들을 직접 최적화하는 기존의 방식과는 달리, 이 방법은 null 점 제어에 의해 원하는 개별 sidelobe 레벨(SLL)들을 갖는 패턴과 해당 여기 전류 가중치들을 쉽게 합성할 수 있는 장점을 가진다. 또한, 최적화 과정에서 null 점 초기값에 따라 두 가지 형태의 차 패턴들을 합성할 수 있음을 보인다. 임의의 SLL들을 갖는 패턴들을 합성하고, 도출된 결과들을 배열 인자 식에 대입함으로써 제안한 방법의 타당성을 수치적으로 검증한다. In the sum and difference pattern synthesis problem of the equi-spaced monopulse tracking linear array antennas, an efficient numerical approach to deriving the relative excitation current weights of antenna elements is presented for the desired patterns. This method is based on the optimum perturbation of null points which are inherent to the Schelkunoff's polynomial representing the pattern array factor. Accordingly, opposite to the conventional method in which the excitation weights are directly optimized, this method is advantageous in that the patterns with the desired individual sidelobe levels(SLLs) and the corresponding excitation weights are easily synthesized by the control of null points. Furthermore, it is showed that two types of difference patterns can be synthesized as imposing the different initial values of null points in the optimization process. The proposed method is numerically validated by synthesizing the patterns with the arbitrary SLLs and substituting the extracted results into the array factor equation.

Design of a Compact Log Periodic Dipole Array Antenna for Broadband and High-Power Beam Synthesis Using Superposition

임창현,윤상운,임태흥,추호성 한국전자파학회 2024 Journal of Electromagnetic Engineering and Science Vol.24 No.3

This paper investigates various array beam shapes for high-power electronic warfare applications using an actual broadband array antenna. For use in a limited mounting space, a compact printed log periodic dipole array (LPDA) operating over a wide bandwidth is designed. The LPDA is then extended to an 8 × 1 array, with active element patterns (AEPs) obtained through simulation and measurement. Beam synthesis is performed by the superposition of several array patterns, which involves adjusting the weight of each AEP. To derive a synthe- sized array beam shape that is similar to the guided mask, the Taylor window weighting method is applied to each array pattern. Finally, beam synthesis for the flat-top beam, cosecant-squared beam, and iso-flux beam is performed using Taylor window-weighted AEPs, and the results are compared with those of beam shapes using ideal isotropic patterns. The results demonstrate that various beam shapes can be achieved for high-power electronic warfare applications using the AEPs of an actual array antenna.

Low-Temperature Metal-Oxide Thin-Film Transistors Formed by Directly Photopatternable and Combustible Solution Synthesis

Rim, You Seung,Lim, Hyun Soo,Kim, Hyun Jae American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.9

<P>We investigated the formation of ultraviolet (UV)-assisted directly patternable solution-processed oxide semiconductor films and successfully fabricated thin-film transistors (TFTs) based on these films. An InGaZnO (IGZO) solution that was modified chemically with benzoylacetone (BzAc), whose chelate rings decomposed via a π–π* transition as result of UV irradiation, was used for the direct patterning. A TFT was fabricated using the directly patterned IGZO film, and it had better electrical characteristics than those of conventional photoresist (PR)-patterned TFTs. In addition, the nitric acid (HNO<SUB>3</SUB>) and acetylacetone (AcAc) modified In<SUB>2</SUB>O<SUB>3</SUB> (NAc-In<SUB>2</SUB>O<SUB>3</SUB>) solution exhibited both strong UV absorption and high exothermic reaction. This method not only resulted in the formation of a low-energy path because of the combustion of the chemically modified metal-oxide solution but also allowed for photoreaction-induced direct patterning at low temperatures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-9/am302722h/production/images/medium/am-2012-02722h_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am302722h'>ACS Electronic Supporting Info</A></P>

개선된 2단 최소자승법을 이용한 선배열 소나의 조향 빔 형성

박경민(Kyung-Min Park),이석진(Seok-Jin Lee),정석문(Suk-Moon Chung) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.6

형태소 합성 기법을 이용한 형태소 패턴 사전의 반자동 구축

박인철(Park In-Chol) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.11

초고속 한국어 형태소 분석을 위한 하나의 방법은 사전에 형태소 결과를 미리 저장해 놓고 이를 이용하는 것이다. 이러한 형태소 패턴 사전을 수작업으로 구축하려면 많은 비용이 들 뿐만 아니라 적지 않은 오류가 포함될 수 있다. 본 논문은 한국어 형태소 합성을 이용하여 자동으로 형태소 패턴을 생성하는 방법을 제안한다. 실험을 통 해, 올바른 형태소 분석을 위해 사용한 형태소 패턴의 86%를 자동으로 생성함을 알 수 있었다. 형태소 패턴을 이용 한 형태소 분석기가 403MB의 한국어 코퍼스를 분석하는 데 걸린 시간은 2.8GHz 윈도우 시스템에서 52.68초였다. One approach for very high speed korean morphological analysis is to use pre-built morphological results in dictionary. It pays the high cost to build this morphological pattern dictionary manually, besides the dictionary may contain errors. This paper proposes a method to generate morphological patterns automatically using Korean morphological synthesis. The experiment shows that we automatically generate 86% morphological patterns for analyzing Korean sentences. It takes 52.68 seconds for the morphological system using the patterns to analyze 403MB Korean corpus on 2.8GHz Window system.

향상된 적응형 유전 알고리즘을 이용한 컨포멀 배열 안테나의 빔 합성 연구

성철민(Cheol-Min Seong),이재덕(Jae-Duk Lee),한인희(In-Hee Han),류홍균(Hong-Kyun Ryu),이규송(Kyu-Song Lee),박동철(Dong-Chul Park) 한국전자파학회 2014 한국전자파학회논문지 Vol.25 No.5

본 논문에서는 2차 함수 곡선의 회전체 곡면 위에 있는 배열 안테나의 빔 합성을 위한 Enhanced Adaptive Genetic Algorithm(EAGA)을 제안하였다. 제안된 알고리즘은 더 빠른 수렴 속도와 더 낮은 비용함수 값을 얻기 위해 Adaptive Genetic Algorithm(AGA)과 Invasive Weed Optimization(IWO)을 결합시켰다. 각 안테나 소자의 급전 크기와 위상의 최적화된 값은 EAGA를 통해 구하였으며, 이 결과를 통해 EAGA가 컨포멀 배열 안테나의 패턴 합성 알고리즘으로써 AGA보다 더 우수함을 보였다. This paper proposes an enhanced adaptive genetic algorithm(EAGA) dedicated to pattern synthesis of array antenna which conforms to a curved surface of rotation with quadratic function. EAGA combines adaptive genetic algorithm(AGA) with invasive weed optimization(IWO) for the faster convergence and the lower cost value of the cost function. The amplitude and phase of each excited weighting factor are optimized to meet the required goals using EAGA. The EAGA results indicate that the proposed algorithm is superior to AGA when applied to the problem of conformal array antenna pattern synthesis.

Sol–gel synthesis and structural and luminescent characteristics of a Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 polycomponent solid solution

Palatnikov Mikhail N.,Shcherbina Olga B.,Masloboeva Sofja M.,Smirnov Maxim V.,Sidorova Olga V.,Kadetova Alexandra V.,Zelenina Elena V.,Efremov Vadim V.,Fedorinova Yulia P. 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.4

In the work, a fine powder of GdNb0.9Ta0.1O4-mixed gadolinium tantalum niobate activated with rare earth (REE) cations (Sm3+, Eu3+, Tb3+ and Er3+) was obtained by sol–gel synthesis. The evolution of the powder from amorphous to crystalline form was also studied in the work. The evolution was studied by synchronous thermal and X-ray analysis. The phase composition and structure of the resulting Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 powders were analyzed in detail. Ceramic samples of the Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 polycomponent solid solution were prepared from the sol–gel synthesized powder using traditional ceramic technology. The phase composition and characteristics of the structure of individual phases of the Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 ceramic solid solution was determined by full-profile analysis of XRD patterns of polycrystals. We established that incorporation of REE (Tb, Er, Eu, Sm) into the gadolinium site in GdNb0.9Ta0.1O4 solid solution leads to various distortions of the corresponding polyhedra. Note that the distortion degree in this case is much greater than the distortion of the initial GdNbO4 structure. The photoluminescent (PL) properties of the Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 solid solution were studied in the visible wavelength range. Analysis of literature and our own data revealed: electronic relaxation pathways in Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 ceramics can be different depending on the energy of the exciting radiation. Excitation by the 376 nm line leads to internal energy conversion over 4fn–4fn levels of REE cations (Sm3+, Eu3+, Tb3+ and Er3+). The energy transfer between the Nb4+–O−–Ta4+–O− groups and REE is maximal in this case, while the radiation of the matrix from Nb4+–O−–Ta4+–O− emission centers is minimal. Upon excitation in the near-UV range (376 nm), Gd3+ cations do not participate in the energy transfer between the matrix and 4fn–4fn levels of REE dopants. The maximum PL of Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 ceramics is observed in the green–red region of the spectrum from 5D0–7F2 and 4G5/2–6H7/2 transitions of Eu3+ and Sm3+. The emission is maximal at ~ 612 nm; it corresponds to the 5D0–7F2 electric dipole transition of the Eu3+ cation. We established that the efficiency of energy transfer between the matrix and doping REE cations for Gd0.96Eu0.01Sm0.01Tb0.01Er0.01Nb0.9Ta0.1O4 ceramics strongly depends on the energy of the exciting radiation.

능동위상배열안테나의 적응형 패턴 널 형성에 관한 연구

정진우(Jin-Woo Jung),박성일(Sung-Il Park) 한국전자통신학회 2021 한국전자통신학회 논문지 Vol.16 No.3

능동위상배열안테나는 적절한 급전신호 가중치 선택에 따라 대국을 향해 주 빔을 조향할 수 있을 뿐만 아니라 간섭원 방향으로 패턴 널을 형성할 수 있다. 주 빔의 조향을 위한 급전신호 가중치는 방사소자의 위치를 기반으로 쉽게 산출할 수 있다. 그리고 패턴 널 형성을 위한 급전신호 가중치 또한 적절한 요구 방사패턴 설정과 WLSM(Weighted Least Squares Method)을 이용하면 산출할 수 있다. 그러나 일반적인 무선 통신망 환경에서 간섭원의 위치는 미인지 상황에 있다. 따라서 적응형 패턴 널 형성 기법이 필요하다. 본 논문에서는 요구 방사특성 설정에 따른 패턴 널 형성이 가능함을 확인하고, 이를 기반으로 관측 영역 기준 이진탐색 알고리즘을 이용하여 간섭원 적응형 패턴 널 형성 기법에 관하여 연구하였다. 제시된 기법을 기반으로 모의실험을 수행한 결과, 효율적으로 간섭 적응형 패턴 널 형성이 가능함을 확인하였다. An active phased array antennas can not only electrically steer the beam by controlling the weighting of the excitation signal, but can also form a pattern null in the direction of the interference source. The weight of the excitation signal to steer the main beam can be easily calculated based on the position of the radiating element. In addition, the weight of the excited signal for pattern null formation can also be calculated by setting the required radiation pattern and using WLSM(Weighted Least Squares Method). However, in a general wireless communication network environment, the location of the interference source is unknown. Therefore, an adaptive pattern null synthesis is needed. In this paper, it was confirmed that pattern null synthesis according to the required radiation characteristic was possible. And based on this, adaptive pattern null synthesis into the direction of an interference source was studied using a binary search algorithm based on observation area. As a result of conducting a simulation based on the presented technique, it was confirmed that adaptive pattern null forming into the direction of an interference is possible in efficient way.