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User Grouping of Two-Stage MU-MIMO Precoding for Clustered User Geometry
Junyoung Nam,Young-Jo Ko,Jeongseok Ha IEEE 2015 IEEE communications letters Vol.19 No.8
<P>This letter investigates how user grouping, more specifically group partitioning, affects the sum-rate performance of a two-stage multiuser MIMO precoding scheme referred to as joint spatial division and multiplexing (JSDM). Taking a clustered user geometry model into account, we propose a new criterion for user grouping to noticeably improve the sum-rate performance of JSDM. Numerical results confirm that the user grouping based on the proposed criterion yields substantial performance enhancement.</P>
남준영(Junyoung Nam),이혜민(Christine Lee),Asif Ashraf Patankar,Hanxiang Wang,Yanfen Li,문현준(Hyeonjoon Moon) 한국방송·미디어공학회 2019 한국방송공학회 학술발표대회 논문집 Vol.2019 No.11
도시화 과정에서 도시의 생활폐기물 문제가 빠르게 증가되고 있고, 효과적이지 못한 생활폐기물 관리는 도시의 오염을 악화시키고 물리적인 환경오염과 경제적인 부분에서 극심한 문제들을 야기시킬 수 있다. 게다가 부피가 커서 관리하기 힘든 대형 생활폐기물들이 증가하여 도시 발전에도 방해가 된다. 생활폐기물을 처리하는데 있어 대형 생활폐기물 품목에 대해서는 요금을 청구하여 처리한다. 다양한 유형의 대형 생활폐기물을 수동으로 분류하는 것은 시간과 비용이 많이 든다. 그 결과 대형 생활폐기물을 자동으로 분류하는 시스템을 도입하는 것이 중요하다. 본 논문에서는 대형 생활폐기물 분류를 위한 시스템을 제안하며, 이 논문의 4 가지로 분류된다. 1) 높은 정확도와 강 분류(roust classification) 수행에 적합한 Convolution Neural Network(CNN) 모델 중 VGG-19, Inception-V3, ResNet50 의 정확도와 속도를 비교한다. 제안된 20 개의 클래스의 대형 생활폐기물의 데이터 셋(data set)에 대해 가장 높은 분류의 정확도는 86.19%이다. 2) 불균형 데이터 문제를 처리하기 Class Weight VGG-19(CW-VGG-19)와 Extreme Gradient Boosting VGG-19 두 가지 방법을 사용하였다. 3) 20 개의 클래스를 포함하는 데이터 셋을 수동으로 수집 및 검증하였으며 각 클래스의 컬러 이미지 수는 500 개 이상이다. 4) 딥 러닝(Deep Learning) 기반 모바일 애플리케이션을 개발하였다.
Manufacturing study of lower cryostat thermal shield cylinder component for ITER tokamak
Nam, Kwanwoo,Her, Namil,Hur, Junyoung,Park, Won Woo,Kang, Kyoung-O,Lim, Kisuk,Kim, Il Jin,Kang, Youngkil,Arzoumanian, Terenig,Panchal, Manoj,Pichel, German Perez,Noh, Chang Hyun,Kang, Dong Kwon Elsevier 2019 Fusion engineering and design Vol.146 No.1
<P><B>Abstract</B></P> <P>This paper describes the manufacturing study of ITER Lower Cryostat Thermal Shield (LCTS) cylinder components, which are to be delivered to ITER site. All LCTS cylinder 20 ° sectors will be assembled at the ITER site by the flange joints, which are welded to the shells. Reliability of cooling pipe welding was checked by two inspection methods: endoscopy and vacuum leak test. Pre-assembly of three 20 ° sectors is one of the important step to ensure dimensional tolerance and its process is described in details. Dimensions of the pre-assembled 60 ° sector was measured by a laser tracker. The qualification of silver coating facility was carried out using a simple well-defined plate mock-up. After the facility qualification, silver coating of LCTS cylinder 20 ° sectors had been conducted. Technical efforts to improve the coated surface quality are presented in this paper.</P>
Junyoung Park,Injoon Hong,Gyeonghoon Kim,Byeong-Gyu Nam,Hoi-Jun Yoo IEEE 2014 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 1 R Vol.61 No.2
<P>An intelligent Reinforcement Learning (RL) Network-on-Chip (NoC) is proposed as a communication architecture of a heterogeneous many-core processor for portable HD object recognition. The proposed RL NoC automatically learns bandwidth adjustment and resource allocation in the heterogeneous many-core processor without explicit modeling. By regulating the bandwidth and reallocating cores, the throughput performances of feature detection and description are increased by 20.4% and 11.5%, respectively. As a result, the overall execution time of the object recognition is reduced by 38%. The proposed processor with RL NoC is implemented in a 65 nm CMOS process, and it successfully demonstrates the real-time object recognition for a 720 p HD video stream while consuming 235 mW peak power at 200 MHz, 1.2 V.</P>
Cha, Junyoung,Jo, Young Suk,Jeong, Hyangsoo,Han, Jonghee,Nam, Suk Woo,Song, Kwang Ho,Yoon, Chang Won Elsevier 2018 APPLIED ENERGY Vol.224 No.-
<P><B>Abstract</B></P> <P>A CO<SUB>X</SUB>-free 1 kW-class hydrogen power pack fueled by liquid ammonia is presented. For applications in a practical-scale hydrogen production system in conjunction with a polymer electrolyte membrane fuel cell, Ru catalysts supported on La-doped alumina (Ru/La(x)-Al<SUB>2</SUB>O<SUB>3</SUB>) were pelletized by varying the lanthanum doping content (x mol%) to control catalytic activities. An optimized Ru(1.06 wt%)/La(20)-Al<SUB>2</SUB>O<SUB>3</SUB> pellet catalyst presents a >99.7% conversion efficiency at 500 °C under a gas hourly space velocity of 5000 mL g<SUB>cat</SUB> <SUP>−1</SUP> h<SUP>−1</SUP>. Various materials were screened to remove residual ammonia from the product stream, and the X zeolite was chosen as a highly capable adsorbent. Based on the synthesized catalyst and screened adsorbent, a power pack consisting of a dehydrogenation reactor, an adsorbent tower, and a 1 kW-class polymer electrolyte membrane fuel cell was designed and manufactured. The as-integrated system can convert 9 L min<SUP>−1</SUP> of ammonia into 13.4 L min<SUP>−1</SUP> of hydrogen, powering a 1 kW-class fuel-cell continuously for >2 h without any performance degradation. To achieve autothermal and CO<SUB>X</SUB>-free operations, heat required for ammonia dehydrogenation was provided by unutilized hydrogen from the fuel cell, drastically increasing the overall efficiency of the system to >49% while removing the external heat source, isobutane. Finally, a drone tethered to the system was operated, demonstrating the feasibility of an elongated flight time of >4 h, much longer than 14 min with Li-polymer battery loaded on the drone. The system is expected to meet the United States Department of Energy’s 2020 gravimetric and volumetric hydrogen storage targets of 4.5 wt% and 30 gH<SUB>2</SUB> L<SUP>−1</SUP> at system weights of 43 kg and 50 kg, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pelletized Ru/La-Al<SUB>2</SUB>O<SUB>3</SUB> catalysts have superior NH<SUB>3</SUB> dehydrogenation activity. </LI> <LI> The CO<SUB>x</SUB>-free H<SUB>2</SUB> generator is integrated to produce hydrogen on demand from NH<SUB>3</SUB>. </LI> <LI> The H<SUB>2</SUB> generator powers a 1 kW-class fuel cell without performance degradation. </LI> <LI> Reformer efficiency of >84% is achieved by recirculating H<SUB>2</SUB> from a fuel cell. </LI> <LI> A potential H<SUB>2</SUB> storage density of the system is ca. 7.0 wt% (system based). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Junyoung,Xing, Jingchao,Nam, Hyeong Soo,Song, Joon Woo,Kim, Jin Won,Yoo, Hongki Optical Society of America 2017 Optics letters Vol.42 No.3
<P>Micro-optical coherence tomography (mu OCT) is an advanced imaging technique that acquires a three-dimensional microstructure of biological samples with a high spatial resolution, up to 1 mu m, by using a broadband light source and a high numerical aperture (NA) lens. As high NA produces a short depth of focus (DOF), extending the DOF is necessary to obtain a reasonable imaging depth. However, due to the complexity of optics and the limited space, it has been challenging to fabricate endoscopic mu OCT, which is essential for clinical translation. Here, we report an endoscopic mu OCT probe with an extended DOF by using a binary phase spatial filter. The imaging results from latex beads demonstrated that the mu OCT probe achieved an axial resolution of 2.49 mu m and a lateral resolution of 2.59 mu m with a DOF extended by a factor of 2. The feasibility of clinical use was demonstrated by ex vivo imaging of the rabbit iliac artery. (C) 2017 Optical Society of America.</P>
Jinsu Nam,Jaehee Lyu,Junyoung Park 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.7
There are computation time constraints caused by the number and size of particles in the powder packing simulation using DEM. In this paper, newly suggested packing model transforms a general packing sequence –particle generation, stack, and compressioninto particle generation and packing by growing particles. To verify the new packing model, it was compared using three contact models widely used in DEM, in terms of radial distribution function, porosity, and coordination number. As a result, contact between particles showed a similar trend, and the pore distribution was also similar. Using the new packing model can reduce simulation time by 400 % compared to the normal packing model without any other coarse graining methods. This model has only been applied to particle packing simulations in this paper, but it can be expanded to other simulations with complex domain based on DEM.