• 한국항공우주학회지
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• 제42권7호
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• pp.576-585
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• 2014

본 논문에서는 소형무인항공기용 이동표적 표시기법(MTI, Moving Target Indication)에 대한 기술 동향분석을 하였다. MTI는 크게 이미지 정렬과 차영상 오류보정 단계로 구성되는데 이중 이미지 정렬 기법에는 매개변수방식과 비매개변수방식이 있으며 본 논문에서는 매개변수방식을 사용한 이용한 MTI에 초점을 맞췄다. 소형무인항공기의 경우, 저고도 운용에 의한 시차문제가 발생하는데 이를 보정하기 위해서 등극기하학이 사용된다. MTI의 성능을 향상시키기 위한 관련기법들도 살펴보았으며 향후 발전방향을 제시하였다.

• 한국항공우주학회지
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• 제30권8호
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• pp.87-93
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• 2002

일반적으로 궤도재배치는 주어진 시간동안 현재 경도에서 목표 경도로 옮기는 작업이며, 궤도재배치 기동은 표류제도 기동과 목표제도 기동으로 나누어진다. 정지궤도 위성은 지구비대칭에 의한 중력장 때문에 동서방향의 표류에 끊임없이 영향을 받는다. 따라서 기동을 계획할 때, 이러한 영향을 고려하지 않는다면 위성은 성공적으로 궤도재배치 되지 않을 수 있다. 본 연구에서는 기동시각과 delta-V를 구하기 위해서 선형화된 궤도전이 방정식을 사용하여 구하였으며, 궤도재배치를 수행할 경우 위성들간의 접근여부를 확인하기 위하여 비선형 시뮬레이션을 수행하였다.

• 대한전자공학회논문지TC
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• 제48권4호
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• pp.47-52
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• 2011

CFAR(constant false alarm rate)는 능동 소나 시스템에서 사용되는 자동 탐지 신호처리 알고리듬이다. CFAR 알고리듬 중에서도 OS(ordered statistics) CFAR는 CA(cell averaging), SO(smallest of), GO(greatest of)에 비해 비균일 환경에서 탐지 성능이 우수하다. 그러나 OS CFAR는 다중 표적 상황에서 일정 개수 이상의 표적이 나타나면 탐지 성능이 나빠지는 단점을 갖고 있다. 이에 본 논문에서는 다중 표적 환경에서 OS CFAR보다 좀 더 강인한 OSR(ordered statistics ratio) CFAR 알고리듬을 제안하고 컴퓨터 모의실험을 통하여 간섭 표적 개수에 따른 성능을 기존의 CFAR 기법과 비교 분석하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.552-554
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• 1998

In target tracking problems the fixed gain Kalman filter is primarily used to predict a target state vector. This filter, however, has a poor precision for maneuvering targets while it has a good performance for non-maneuvering targets. To overcome the problem this paper proposes the system which estimates the acceleration with neural networks using the input estimation technique. The ability to efficiently fuse information of different forms is one of the major capabilities of trained multi-layer neural networks. The primary motivation for employing neural networks in these applications comes from the efficiency with which more features can be utilized as inputs for estimating target maneuvers. The parallel processing capability of a properly trained neural network can permit fast processing of features to yield correct acceleration estimates. The features used as inputs can be extracted from the combinations of innovation data and heading changes, and for this we set the two dimensional model. The properly trained neural network system outputs the acceleration estimates and compensates for the primary Kalman filter. Finally the proposed system shows the optimum performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.2094-2112
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• 2019

Focusing on the issue that the conventional Kernel Correlation Filter (KCF) algorithm has poor performance in handling scale change and obscured objects, this paper proposes an anti-occlusion and scale adaptive tracking algorithm in the basis of KCF. The average Peak-to Correlation Energy and the peak value of correlation filtering response are used as the confidence indexes to determine whether the target is obscured. In the case of non-occlusion, we modify the searching scheme of the KCF. Instead of searching for a target with a fixed sample size, we search for the target area with multiple scales and then resize it into the sample size to compare with the learnt model. The scale factor with the maximum filter response is the best target scaling and is updated as the optimal scale for the following tracking. Once occlusion is detected, the model updating and scale updating are stopped. Experiments have been conducted on the OTB benchmark video sequences for compassion with other state-of-the-art tracking methods. The results demonstrate the proposed method can effectively improve the tracking success rate and the accuracy in the cases of scale change and occlusion, and meanwhile ensure a real-time performance.

• Current Optics and Photonics
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• 제2권6호
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• pp.532-539
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• 2018

Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.

• BMB Reports
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• 제56권11호
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• pp.606-611
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• 2023

The main protease (Mpro) of SARS-CoV-2 cleaves 11 sites of viral polypeptide chains and generates essential non-structural proteins for viral replication. Mpro is an important drug target against COVID-19. In this study, we developed a real-time fluorometric turn-on assay system to evaluate Mpro proteolytic activity for a substrate peptide between NSP4 and NSP5. It produced reproducible and reliable results suitable for HTS inhibitor assays. Thus far, most inhibitors against Mpro target the active site for substrate binding. Mpro exists as a dimer, which is essential for its activity. We investigated the potential of the Mpro dimer interface to act as a drug target. The dimer interface is formed of domain II and domain III of each protomer, in which N-terminal ten amino acids of the domain I are bound in the middle as a sandwich. The N-terminal part provides approximately 39% of the dimer interface between two protomers. In the real-time fluorometric turn-on assay system, peptides of the N-terminal ten amino acids, N10, can inhibit the Mpro activity. The dimer interface could be a prospective drug target against Mpro. The N-terminal sequence can help develop a potential inhibitor.

• 한국음향학회지
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• 제28권4호
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• pp.336-342
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• 2009

일정한 주파수의 음향신호를 발생시키는 표적이 기동할 때 한 개의 고정된 센서에서 관측된 신호의 주파수는 시간에 따라 도플러 변이가 발생한다. 이러한 도플러 변이 현상을 이용한 기존의 CPA (Closest Point of Approach) 분석으로 센서 수신기에 표적이 최단거리로 근접했을 때의 시간, 거리, 속력 그리고 실제 신호의 중심주파수를 추정할 수 있다. 본 논문에서는 고정된 단일 센서 대신에 일정한 속도로 기동하는 배열센서 수신기에서 주파수뿐만 아니라 표적의 방위각을 관측하여 이로부터 표적의 실제 기동속도를 추정하는 기법을 제안한다. 그리고 제안한 기법의 성능검증을 위해 오차 분석 및 모의 실험을 수행하였다.

• Journal of the Optical Society of Korea
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• 제17권2호
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• pp.213-218
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• 2013

Although infrared focal plane array (IRFPA) detectors have been commonly used, non-uniformity correction (NUC) remains an important problem in the infrared imaging realm. Non-uniformity severely degrades image quality and affects radiometric accuracy in infrared imaging applications. Residual non-uniformity (RNU) significantly affects the detection range of infrared surveillance and reconnaissance systems. More effort should be exerted to improve IRFPA uniformity. A novel NUC method that considers the surrounding temperature variation compensation is proposed based on the binary nonlinear non-uniformity theory model. The implementing procedure is described in detail. This approach simultaneously corrects response nonlinearity and compensates for the influence of surrounding temperature shift. Both qualitative evaluation and quantitative test comparison are performed among several correction technologies. The experimental result shows that the residual non-uniformity, which is corrected by the proposed method, is steady at approximately 0.02 percentage points within the target temperature range of 283 K to 373 K. Real-time imaging shows that the proposed method improves image quality better than traditional techniques.

• Biomolecules & Therapeutics
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• 제26권2호
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• pp.101-108
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• 2018

G protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane receptors and have vital signaling functions in various organs. Because of their critical roles in physiology and pathology, GPCRs are the most commonly used therapeutic target. It has been suggested that GPCRs undergo massive genetic variations such as genetic polymorphisms and DNA insertions or deletions. Among these genetic variations, non-synonymous natural variations change the amino acid sequence and could thus alter GPCR functions such as expression, localization, signaling, and ligand binding, which may be involved in disease development and altered responses to GPCR-targeting drugs. Despite the clinical importance of GPCRs, studies on the genotype-phenotype relationship of GPCR natural variants have been limited to a few GPCRs such as b-adrenergic receptors and opioid receptors. Comprehensive understanding of non-synonymous natural variations within GPCRs would help to predict the unknown genotype-phenotype relationship and yet-to-be-discovered natural variants. Here, we analyzed the non-synonymous natural variants of all non-olfactory GPCRs available from a public database, UniProt. The results suggest that non-synonymous natural variations occur extensively within the GPCR superfamily especially in the N-terminus and transmembrane domains. Within the transmembrane domains, natural variations observed more frequently in the conserved residues, which leads to disruption of the receptor function. Our analysis also suggests that only few non-synonymous natural variations have been studied in efforts to link the variations with functional consequences.