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황지우(Jiwoo Hwang),한민규(Mingyu Han),김민지(Minji Kim),김아욱(Auk Kim) 한국HCI학회 2022 한국HCI학회 학술대회 Vol.2022 No.2
조건부 자율주행 자동차가 대중화되고 있다. 자율주행 기술이 발전할수록 운전자는 운전이 아닌 2차 과업에 더 많은 시간을 소비할 수 있게 되며, 이에 따라 운전자의 편의를 위한 차량용 서비스가 더 다양해질 것이다. 그러나 역설적으로, 운전자의 편의를 위한 서비스가 조건부 자율주행 자동차의 사고 위험성을 높일 수 있다. 자율주행 중 운전자는 시스템이 제어할 수 없는 상황발생 시 곧바로 제어권을 전환(수동운전)하여야 하는데 2차 과업에 의한 주의분산은 반응 속도를 늦추기 때문이다. 이로 인해 운전자의 안전을 보장하기 어려워진다. 따라서 이러한 서비스가 운전자에게 미치는 부정적인 영향을 분석하는 연구가 선행되어야 한다. 관련 연구의 활성화를 위해 본 논문에서는 저렴하게 자율주행 자동차를 시뮬레이션 할 수 있는 시뮬레이터를 개발하였고, 실제 연구에 활용할 수 있는지를 판단하기 위해 타당성과 사용성 테스트를 진행하였다.
OFDM/CDMA 통신용 부분 병렬 FWHT 프로세서 설계
황지우(Jiwoo Hwang),황용택(Yongtaek Hwang),김민수(Minsu Kim),유호영(Hoyoung Yoo) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6
In this paper, we propose an efficient FWHT architecture for OFDM and CDMA communications, aiming to achieve low hardware complexity and intuitive structure compared to previous designs. Since FWHT is based on Cooley-Tukey algorithm, it has a similar data flow to FFT. Previous research has explored applying FFT structures to FWHT architectures but encountered the trade-off issues between hardware complexity and process ing throughput in limited hardware resources. The proposed Partially parallel FWHT architecture utilizes an efficient data reordering process to provide improved performance in terms of hardware complexity and efficiency compared to previous architecture.
Optimized Implementation of Interpolation Filters for HEVC Encoder
Taejin Hwang,Yongjo Ahn,Jiwoo Ryu,Donggyu Sim 대한전자공학회 2013 전자공학회논문지 Vol.50 No.10
In this paper, a fast algorithm of discrete cosine transform-based interpolation filter (DCT-IF) for HEVC (high efficiency video coding) encoder is proposed. DCT-IF filter accounts for around 30% of encoder complexity, according to the computational complexity analysis with the HEVC reference software. In this work, the proposed DCT-IF is optimized by applying frame-level interpolation, SIMD optimization, and task-level parallelization via OpenMP on a developed C-based HEVC encoder. Performance analysis is conducted by measuring speed-up factor of the proposed optimization technique on the developed encoder. The results show that speed-up factors by frame-level interpolation, SIMD, and OpenMP are approximately 38-46, 3.6-4.4, and 3.0-3.7, respectively. In the end, we achieved the speed-up factor of 498.4 with the proposed fast algorithm.
불완전 구속된 케이블 구동 병렬로봇의 잔류 진동을 억제하기 위한 슬라이딩 모드 제어기 설계
이지우(Jiwoo Lee),황성욱(Sung Wook Hwang),박종현(Jong Hyeon Park) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Under-constrained cable-driven parallel robots (U-CDPRs) have many advantages in comparison with the conventional serial manipulator such as low inertia and large workspace, etc. However, problem about the unwanted oscillations of the end-effector caused by under-constraints condition is occurred and it can adversely affect tracking performance. In this paper, a control method based on sliding mode control (SMC) is proposed to suppress more residual oscillation. To suppress residual oscillation, both position and orientation have to be considered simultaneously. However, in the case that the number of degree of freedom to control is not same as the number of control input like UCDPR, the system is hard to apply classical sliding surface. In order to address the problem and control both position and orientation of the U-CDPR simultaneously, coupled sliding surface is proposed. To prove effectiveness of proposed controller, computer simulation was carried out.
Statistical Analysis of Pc1 Pulsations Observed by a BOH Magnetometer
Kim, Jiwoo,Hwang, Junga,Kim, Hyangpyo,Yi, Yu The Korean Space Science Society 2020 Journal of Astronomy and Space Sciences Vol.37 No.1
Pc1 pulsations are important to consider for the interpretation of wave-particle interactions in the Earth's magnetosphere. In fact, the wave properties of these pulsations change dynamically when they propagate from the source region in the space to the ground. A detailed study of the wave features can help understanding their time evolution mechanisms. In this study, we statistically analyzed Pc1 pulsations observed by a Bohyunsan (BOH) magneto-impedance (MI) sensor located in Korea (L = 1.3) for ~one solar cycle (November 2009-August 2018). In particular, we investigated the temporal occurrence ratio of Pc1 pulsations (considering seasonal, diurnal, and annual variations in the solar cycle), their wave properties (e.g., duration, peak frequency, and bandwidth), and their relationship with geomagnetic activities by considering the Kp and Dst indices in correspondence of the Pc1 pulsation events. We found that the Pc1 waves frequently occurred in March in the dawn (1-3 magnetic local time (MLT)) sector, during the declining phase of the solar cycle. They generally continued for 2-5 minutes, reaching a peak frequency of ~0.9 Hz. Finally, most of the pulsations have strong dependence on the geomagnetic storm and observed during the early recovery phase of the geomagnetic storm.