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최각규,Jintu Francis Kurisingal,CHUNG YONGCHUL GREGO,박대원 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.6
A two-dimensional Zn-based metal-organic framework has been synthesized by using Zn(II) ions and H2SDC (4,4'-stilbenedicarboxylic acid) under solvothermal conditions. The framework having a trinuclear Zn3-(RCO2)6 SBUs connected by the 4,4'-stilbenedicarboxylic acid to form a hexagonal network, shows a two-dimensional structure and displays high thermal stability up to approximately 330 oC. The role of Zn2+ (from Zn-SDC) for epoxide activation and Br- ion (from TBABr) for ring opening of epoxide was studied for the cycloaddition reaction of CO2 and propylene oxide (PO) under ambient conditions. Zn-SDC was found catalytically efficient towards CO2-epoxide coupling under ambient reaction conditions with high selectivity towards the desired cyclic carbonates under solvent-free conditions. The effects of various reaction parameters such as catalyst loading, temperature, CO2 pressure, and time were evaluated. Zn-SDC was easily separable and reusable at least five times without any considerable loss in the initial activity. A plausible reaction mechanism for the cycloaddition reaction was also proposed based on literature and experimental inferences.
밀리미터파 탐색기에서 ESPRIT 기법을 이용한 탄도 미사일 탄두 식별 신호처리 기법 개발
최각규(Gak-Gyu Choi),한승구(Seung-Ku Han),조희진(Hee-Jin Jo),김효태(Hyo-Tae Kim),김경태(Kyung-Tae Kim),송성찬(Sung-Chan Song),나영진(Young-Jin Na) 한국전자파학회 2012 한국전자파학회논문지 Vol.23 No.2
본 논문은 탄도 미사일의 탄두를 식별하는 신호 처리 기법의 개발에 관하여 소개한다. 요격 미사일이 적 미사일을 파괴하기 위해서 적 미사일 탄두 위치의 정보가 필요하다. 적 미사일을 탐지하고 위치를 찾기 위해 요격 미사일의 밀리미터파 탐색기(millimeter-wave seeker)는 chirp 파형을 사용하여 HRRPs(High Resolution Range Profiles)을 발생시킨다. 표적의 산란점(scattering center)을 찾아내기 위해 대표적인 스펙트럼 추정 방법(spectral estimation technique)인 ESPRIT(Estimation of Signal Parameters by Rotational Invariance Technique) 기법을 HRRPs에 적용하였다. 1차원 산란점의 정보를 이용하고 미사일의 길이를 추정함으로써 탄두의 위치를 식별하였다. 시뮬레이션 결과는 이러한 신호 처리 기법이 탄도 미사일의 탄두 식별에 적용하기에 효율적임을 보여준다. This paper introduces a signal processing technique for discrimination of ballistic missile"s warhead. An interceptor missile to destroy the enemy"s ballistic missile requires an information on the location of missile"s warhead. In order to detect and locate the missile"s warhead, a seeker radar in the interceptor missile makes use of chirp waveform to generate high resolution range profiles(HRRPs). We applied one of the well known spectral estimation technique called ESPRIT (Estimation of Signal Parameters by Rotational Invariance Technique) to these HRRPs to estimate scattering centers on the target. Using the information on the one-dimensional(1-D) scattering centers, we can find the location of the warhead by estimating the length of the missile, Simulation results show that the proposed signal processing technique is efficient in discriminating the warhead of an ballistic missile.
지능형 차량을 위한 후방 감시용 레이더 신호 처리 기법에 관한 연구
최각규(Gak-Gyu Choi),한승구(Seung-Ku Han),김효태(Hyo-Tae Kim),김경태(Kyung-Tae Kim) 한국전자파학회 2011 한국전자파학회논문지 Vol.22 No.11
본 논문은 도로상의 차량용 지능형 후방 감시를 위한 레이더의 신호 처리 기법에 관하여 소개한다. 주파수 변조 연속 파형(Frequency Modulation Continuous Wave: FMCW) 신호에 주파수 편이(Frequency Shift Keying: FSK) 변조 방식을 결합한 선형 주파수 변조-주파수 편이(Linear Frequency Modulation-Frequency Shift Keying, LFM-FSK) 신호를 차량의 차로 변경 보조 장치에 적용하여 도로 상의 차량의 거리 및 각도와 속도를 추정할 수 있다. 또한 이 신호는 후방 차량 감시에 용이하게 사용할 수 있다. FMCW 신호는 높은 거리 분해능을 가지는 장점이 있지만, 다중 표적 상황에서 고스트 표적이 발생하는 문제점이 있다. 또한 FSK 신호는 높은 속도 분해능을 가지며 고스트 현상을 피할 수 있지만, 레이더의 가시선 방향에 다중 표적이 존재할 때 구분하지 못하는 문제점이 있다. LFM-FSK 신호를 이용하면 다중 표적 상황에서 높은 거리 분해능과 속도 분해능을 가지면서 고스트 발생의 문제를 완벽히 해결할 수 있다. 시뮬레이션 결과는 위의 LFM-FSK 신호가 차량의 차선 변경 보조장치 적용에 적합함을 보여준다. This paper introduces a radar signal processing technique for intelligent rear view monitoring of an automobile. The linear frequency modulation-frequency shift keying(LFM-FSK) waveform, which is the combination of frequency modulation continuous wave(FMCW) and frequency shift keying(FSK) waveform, is employed to simultaneously estimate the range, relative aspect angle, and velocity of an automobile. Hence, it can be applied to monitor the rear view of an automobile. FMCW waveform has high range resolution capability, but it produces ghost targets under a multiple target environment. In contrast, FSK waveform can provide high velocity resolution and avoids the problem of ghost targets. However, it fails to identify multiple targets along the radar"s line of sight. With LFM-FSK waveform, we can estimate the ranges and velocities of multiple targets with very high resolution, which avoids the ghost target problem of an FMCW waveform. Simulation result shows that LFM-FSK wavefrom is suitable for use in the lane change assistance system for an automobile.
표적 개수 추정 및 근접 채프 탐지를 위한 고해상도 거리 프로파일을 이용한 움직임 미분 기반 엔트로피 특징 추출 기법
이정원,최각규,나경일 한국군사과학기술학회 2019 한국군사과학기술학회지 Vol.22 No.2
This paper proposes a new feature extraction method for automatically estimating the number of target and detecting the chaff using high range resolution profile(HRRP). Feature of one-dimensional range profile is expected to be limited or missing due to lack of information according to the time. The proposed method considers the dynamic movements of targets depending on the radial velocity. The observed HRRP sequence is used to construct a time-range distribution matrix, then assuming diverse radial velocities reflect the number of target and seduction chaff launch, the proposed method utilizes the characteristic of the gradient distribution on the time-range distribution matrix image, which is validated by electromagnetic computation data and dynamic simulation.
( Robin Babu ),박대원,김현준,최각규 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
A novel energy-efficient bimetallic heterogeneous catalyst system consisting of Zn and Co as active centers was synthesized at room temperature using low-boiling solvents. The newly synthesized material possesses RHO topology, similar to that of the parent monometallic zeolitic imidazolate frameworks (ZIFs), and the similar ionic radii of Zn<sup>2+</sup> and Co<sup>2+</sup> allow uniform distribution throughout the framework, as was confirmed through various physicochemical analytical techniques. The structural peculiarities of the newly synthesized bimetallic ZIF (denoted as ZnCo-ZIF) were exploited for CO<sub>2</sub>-epoxide cycloaddition reactions at room temperature and atmospheric pressure. The synergistic effects of multiple metal centers that cooperatively activate the epoxides led to superior catalytic activity compared to those of the corresponding monometallic ZIFs. In addition, a mechanism for the solvent-free CO<sub>2</sub>-epoxide cycloaddition reaction catalyzed by the bimetallic ZIF was proposed.