http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
PGA(Phase Gradient Autofocus)기반 ISAR영상 자동초점기법 성능개선
김관성,양은정,김찬홍,박성철,Kim, Kwan Sung,Yang, Eun Jung,Kim, Chan Hong,Park, Sung Chul 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.5
PGA(phase gradient autofocus) has been widely used to remove motion induced phase errors in the ISAR(inverse synthetic aperture radar) imaging. The critical process for the processing time and image quality is windowing stage in PGA. In this paper, the new method to determine window size based on polynomial least square approximation is proposed. Moreover, dominant range bins are selected for efficient phase error estimation, which improve image quality and speed up convergence. The simulation results show that the proposed algorithm provides high quality ISAR images while computational efficiency of inherent PGA is retained.
김관성,Kim, Kwan-Sung 한국군사과학기술학회 2007 한국군사과학기술학회지 Vol.10 No.4
The dynamic range of the radar which uses digital signal processors is limited by ADC(Analog-to-Digital Converter). That parameter and ADC loss depend on the noise level of radar receiver. In order to stabilize the performance of radar systems, it is necessary to maintain the noise level constantly. This paper presents the noise AGC(Automatic Gain Control) concept that can keep the noise level constantly and proves that the concept is acceptable through the hardware test and evaluation.
실시간으로 적응빔형성 및 신호처리를 수행하는 평면능동위상배열 레이더 시스템 개발
김관성,이민준,정창식,염동진,Kim, Kwan Sung,Lee, Min Joon,Jung, Chang Sik,Yeom, Dong Jin 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.6
Interference and jamming are becoming increasing concern to a radar system nowdays. AESA(Active Electronically Steered Array) antennas and adaptive beamforming(ABF), in which antenna beam patterns can be modified to reject the interference, offer a potential solution to overcome the problems encountered. In this paper, we've developed a planar active phased array radar system, in which ABF, target detection and tracking algorithm operate in real-time. For the high output power and the low noise figure of the antenna, we've designed the S-band TRMs based on GaN HEMT. For real-time processing, we've used wavelenth division multiplexing technique on fiber optic communication which enables rapid data communication between the antenna and the signal processor. Also, we've implemented the HW and SW architecture of Real-time Signal Processor(RSP) for adaptive beamforming that uses SMI(Sample Matrix Inversion) technique based on MVDR(Minimum Variance Distortionless Response). The performance of this radar system has been verified by near-field and far-field tests.
다중경로 환경에서 다중빔 탐색레이더에 적용 가능한 표적 고각오차 혼성 보정 기법
김관성,정명수,정창식,Kim, Kwan Sung,Chung, Myung Soo,Jung, Chang Sik 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.3
The multibeam surveillance radar is a state-of-art of 3D radar technology. It applies the stacked beams realized by a digital beamformer. In this paper, a hybrid compensation technique on elevation angle errors for low elevation angle targets over the sea in multipath radar environments is proposed. The proposed method can be applied to stacked beam radars. Double null algorithm based on maximum likelihood method in 3-D beamspace domain works well unless the phase difference between the two rays(direct and specular path) is close to $0^{\circ}$ and the magnitude of reflection coefficient is close to 0. To overcome these problems, we propose a hybrid compensation technique which uses the selective double null algorithm and the beam-ratio compensation technique for low-elevation errors on a log scale. Results of computer simulation show that the proposed method outperform conventional monopulse method and double null algorithm only under various multipath environments.
환원법에 의한 직접 메탄올 연료전지(DMFC)용 Pt-Bi/Carbon 전극제조
김관성 ( Kwan Sung Kim ),김민경 ( Min Kyung Kim ),노동균 ( Dong Kyun Noh ),탁용석 ( Yong Sug Tak ),백성현 ( Sung Hyeon Baeck ) 한국공업화학회 2011 공업화학 Vol.22 No.5
다양한 비율의 Pt와 Bi를 carbon black (Vulcan XC-72R)에 담지시킨 Pt-Bi/C 촉매를 환원법을 이용하여 합성하였다. Pt와 Bi의 전구체로는 염화백금산(H2PtCl6 ·xH2O)과 비스무스트리질산(Bi(NO3)3 ·5H2O) 수용액을 각각 사용하였으며, 금속을 carbon에 담지하기 전, 금속물질의 분산도를 높여주기 위해 열처리와 산처리를 수행한 carbon black을 사용하였다. XRD (X-ray Diffraction) 분석과 XPS (X-ray Photoelectron Spectroscopy) 분석을 통하여 Pt-Bi/C 촉매 내에 Pt와 Bi가 소성 시키기 전에는 BiPt 혹은 Bi2Pt로 존재하지만 500 ℃에서 소성을 한 후에는 Pt 격자구조 안으로 Bi가 침투하여 alloy을 형성하는 것을 확인하였다. 합성한 전극의 메탄올 산화반응은 전기화학분석장치(Potentiostat; Princeton applied research, VSP)를 사용하여 0.5 M CH3OH와 0.5 M H2SO4의 혼합수용액에서 순환전압법(cyclic voltammetry, CV)을 이용해 측정하였다. 메탄올 산화에 대한 전기화학적 촉매 활성을 평가한 결과 적절한 양의 Bi를 첨가한 경우, 메탄올 산화반응에 대한 높은 촉매활성을 나타냄을 확인하였다. 메탄올 산화에 대한 활성은 전극과 전해질 사이의 안정성과 밀접한 관련이 있다. 정전압법(Chronoamperometry, CA)을 이용하여 전극의 안정성을 평가한 결과 메탄올 산화반응에 높은 활성을 나타내는 촉매일수록 전극의 안정성도 높은 것을 확인하였다. Pt-Bi/C catalysts supported on carbon black with various Pt/Bi ratios were synthesized by a reduction method. Chloroplatinic acid hydrate (H2PtCl6 ·xH2O) and bismuth (III) nitrate pentahydrate (Bi(NO3)3 ·5H2O) were used as precursors for Pt and Bi, respectively. Before loading metal on carbon, heat treatment and pretreatment of carbon black in an acidic solution was conducted to enhance the degree of dispersion. The physical property of the synthesized catalysts was investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The XRD pattern of untreated Pt-Bi/C catalyst showed BiPt and Bi2Pt peaks in addition to Pt peaks. These results imply that Bi atoms were incorporated into the Pt crystal lattice by Pt-Bi alloy formation. The catalytic activity for methanol oxidation was measured using cyclic voltammetry in a mixture of 0.5 M H2SO4 and 0.5 M CH3OH aqueous solution. The addition of proper amount of Bi was found to significantly improve catalytic activity for methanol oxidation. The catalytic activity for methanol oxidation was closely related to the stability between electrode and electrolyte. In order to investigate the stability of catalysts, chronoamperometry analysis was carried out in the same solution at 0.6 V.
해상 클러터 환경에서 성능 개선을 위한 환경적응형 CFAR에 관한 연구
홍성원(Sungwon Hong),김관성(Kwan-Sung Kim),조병래(Byung-Lae Cho),김찬홍(Chan-Hong Kim) 한국정보기술학회 2021 한국정보기술학회논문지 Vol.19 No.7
This study proposes the constant false alarm rate (CFAR) method which improves the detection probability and decreases the false alarm rate under sea clutter environments. Under sea clutter environments, target signals may not be detected or a false alarm may occur due to clutter signals. Using the conventional CFAR method, the detection probability is lowered or the false alarm rate is increased depending on the surrounding environment of the target signal. To improve it, we propose a method to select the optimal CFAR method according to the environment of the target signal. The environment is estimated by calculating mean power around the test cell. Then the proposed method is confirmed by the data from the real experiment.
환원법에 의한 직접 메탄올 연료전지(DMFC)용 Pt-Sn/Carbon 전극제조
정소미 ( So Mi Jung ),신주경 ( Ju Kyung Shin ),김관성 ( Kwan Sung Kim ),백성현 ( Sung Hyeon Baeck ),탁용석 ( Yong Sug Tak ) 한국공업화학회 2010 공업화학 Vol.21 No.5
금속물질의 분산도를 높여주기 위해 열처리와 산처리를 수행한 carbon black에 다양한 비율의 Pt와 Sn을 담지 시킨 촉매를 환원법을 이용하여 합성하였다. Pt/Sn의 비율은 전구체 용액 내에서 상대적인 농도를 변화시켜 조절하였으며, Pt/Sn 비율에 따른 반응 특성을 조사하였다. XRD (X-ray Diffraction) 분석을 통해 합성된 촉매의 결정도를 확인하였고, XPS (X-ray Photoelectron Spectroscopy) 분석으로 Pt와 Sn의 산화가를 확인하였다. 합성된 촉매의 조성과 구조를 분석하기 위해 SEM (Scanning Electron Microscopy)-EDS (Energy Dispersive Spectroscopy) 분석과 TEM (Transmission Electron Microscopy) 분석을 수행하였다. 산소 환원 반응 특성은 0.5 M H2SO4 수용액에서 RDE (Rotating Disk Electrode)를 이용하여 조사하였으며, 산소환원 촉매활성은 Pt/Sn의 비율에 크게 의존함을 확인하였다. 합성한 전극의 메탄올 산화반응은 전기화학분석장치(Potentiostat; Princeton applied research, VSP)를 이용하여 0.5 M CH3OH와 0.5 M H2SO4의 혼합수용액에서 수행하였다. 메탄올 산화에 대한 전기화학적 촉매활성과 안정성을 평가한 결과 적절한 양의 Sn을 첨가한 촉매가 높은 촉매활성과 안정성을 나타냄을 확인하였다. Pt-Sn with various ratios was supported on carbon black after pretreatment in an acidic solution by a reduction method. The Pt/Sn ratio was controlled by varying the concentration of each component in the solution, and the influence of the composition on the electrocatalytic activities was investigated. The crystallinity of the synthesized materials was investigated by XRD (X-ray Diffraction), and the oxidation states of both the platinum and tin were determined by XPS (X-ray Photoelectron Spectroscopy). SEM (Scanning Electron Microscopy)-EDS (Energy Dispersive Spectroscopy) was utilized to examine the morphology and composition of the synthesized electrode, and the particle size of the Pt-Sn was analyzed by TEM (Transmission Electron Microscopy). The electrocatalytic activity for oxygen reduction was evaluated in a 0.5 M H2SO4 solution using a rotating disk electrode system. The activity and stability were found to be strongly dependent on the electrode composition (Pt/Sn ratio). The catalytic activity and stability for methanol oxidation were also measured using cyclic voltammetry (CV) in a mixture of 0.5 M H2SO4 and 0.5 M CH3OH aqueous solution. The addition of proper amount of Sn was found to significantly improve both catalytic activity and stability for methanol oxidation.