• ETRI Journal
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• 제42권3호
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• pp.411-419
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• 2020

In real-world intelligent transportation systems, accuracy in vehicle license plate detection and recognition is considered quite critical. Many algorithms have been proposed for still images, but their accuracy on actual videos is not satisfactory. This stems from several problematic conditions in videos, such as vehicle motion blur, variety in viewpoints, outliers, and the lack of publicly available video datasets. In this study, we focus on these challenges and propose a license plate detection and recognition scheme for videos based on a temporal matching prior network. Specifically, to improve the robustness of detection and recognition accuracy in the presence of motion blur and outliers, forward and bidirectional matching priors between consecutive frames are properly combined with layer structures specifically designed for plate detection. We also built our own video dataset for the deep training of the proposed network. During network training, we perform data augmentation based on image rotation to increase robustness regarding the various viewpoints in videos.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.4087-4102
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• 2014

Two-way relaying is an effective way of improving system spectral efficiency by making use of physical layer network coding. However, energy efficiency in OFDM-based bidirectional relaying with asymmetric traffic requirement has not been investigated. In this study, we focused on subcarrier transmission mode selection, bit loading, and power allocation in a multicarrier single amplified-and-forward relay system. In this scheme, each subcarrier can operate in two transmission modes: one-way relaying and two-way relaying. The problem is formulated as a mixed integer programming problem. We adopt a structural approximation optimization method that first decouples the original problem into two suboptimal problems with fixed subcarrier subsets and then finds the optimal subcarrier assignment subsets. Although the suboptimal problems are nonconvex, the results obtained for a single-tone system are used to transform them to convex problems. To find the optimal subcarrier assignment subsets, an iterative algorithm based on subcarrier ranking and matching is developed. Simulation results show that the proposed method can improve system performance compared with conventional methods. Some interesting insights are also obtained via simulation.

• 한국전자파학회논문지
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• 제22권11호
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• pp.1111-1116
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• 2011

본 논문에서는 기존 CMOS 수동 스위치를 사용한 switched - line 타입 위상변화기의 수동 스위치를 공통게이트 증폭기(양방향 증폭기)로 대체한 60 GHz CMOS 양방향 능동 위상변화기를 제안한다. 양방향 능동 위상변화기는 양방향 증폭기 블록과 수동 delay line 네트워크 블록으로 구성된다. 양방향 증폭기 블록은 순방향과 역방향의 특성이 같도록 설계하기 위해 공통 게이트 증폭기(CGA) 구조가 적합하며, 입력단과 출력단의 매칭은 대칭으로 이루어진다. 또한, 통합 바이어스 회로를 이용하여 1개의 바이어스 전압($V_{DS}$)만으로도 증폭의 방향(순방향, 역방향)과 크기를 조절할 수 있도록 구성하였다. 수동 delay line 네트워크 블록은 마이크로스트립 라인으로 구성하였다. 동부 하이텍 1P8M 130-nm CMOS 공정을 이용하여 90도, 180도 1-bit 양방향 능동 위상변화기를 각각 설계하였고, 시뮬레이션 결과 60 GHz에서 평균 -3 dB의 삽입 손실을 얻었으며, 각각 90도 180도의 위상차를 얻었다.

• Journal of Information Processing Systems
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• 제18권4호
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• pp.549-561
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• 2022

In the Khmer writing system, the Khmer script is the official letter of Cambodia, written from left to right without a space separator; it is complicated and requires more analysis studies. Without clear standard guidelines, a space separator in the Khmer language is used inconsistently and informally to separate words in sentences. Therefore, a segmented method should be discussed with the combination of the future Khmer natural language processing (NLP) to define the appropriate rule for Khmer sentences. The critical process in NLP with the capability of extensive data language analysis necessitates applying in this scenario. One of the essential components in Khmer language processing is how to split the word into a series of sentences and count the words used in the sentences. Currently, Microsoft Word cannot count Khmer words correctly. So, this study presents a systematic library to segment Khmer phrases using the bi-directional maximal matching (BiMM) method to address these problematic constraints. In the BiMM algorithm, the paper focuses on the Bidirectional implementation of forward maximal matching (FMM) and backward maximal matching (BMM) to improve word segmentation accuracy. A digital or prefix tree of data structure algorithm, also known as a trie, enhances the segmentation accuracy procedure by finding the children of each word parent node. The accuracy of BiMM is higher than using FMM or BMM independently; moreover, the proposed approach improves dictionary structures and reduces the number of errors. The result of this study can reduce the error by 8.57% compared to FMM and BFF algorithms with 94,807 Khmer words.