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Joong-Yeon Cho,김규태,Sungwook Kim,이헌 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.4
The hydrophobicity of a dragonfly’s wing originates from the naturally occurring nano-structure on its surface. The nano-structure on a dragonfly’s wing consists of an array of nano-sized pillars, 100 nm in diameter. We re-create this hydrophobicity on various substrates, such as Si, glass, curved acrylic polymer, and flexible PET film, by replicating the nano-structure using UV curable nano-imprint lithography (NIL) and PDMS molding. The success of the nano-structure duplication was confirmed using scanning electron microscopy (SEM). The hydrophobicity was measured by water-based contact angle measurements. The water contact angle of the replica made of UV cured polymer was 135° ± 2°, which was slightly lower than that of the original dragonfly’s wing (145° ± 2°), but much higher than that of the UV cured polymer surface without any nano-sized pillars (80°). The hydrophobicity was further improved by applying a coating of Teflon-like material.
Exploring the Performance Impact of Emerging Many-Core Architectures on MPI Communication
Joong-Yeon Cho,Hyun-Wook Jin,Dukyun Nam 한국정보과학회 2018 Journal of Computing Science and Engineering Vol.12 No.4
As major architectural changes emerge to resolve the scalability issues in many-core processors, it is critical to understand their impact on the performance of parallel programming models and run-time supports. For example, the Intel Xeon Phi KNL processor is equipped with a high-bandwidth memory and deploys a mesh-based processor interconnect. In this paper, we comprehensively analyze the impact of high-bandwidth memory and processor interconnects on the message passing interface (MPI) communication bandwidth. The results show that the bandwidth of MPI intra-node communication can be improved up to 372% by exploiting the high-bandwidth memory. In addition, we show that the bandwidth of MPI inter-node communication can be improved up to 143% with optimal core affinity. Our comprehensive study provides insight into optimization of the performance of MPI communication in emerging manycore architectures.
슈퍼컴퓨팅 시스템 기술 : 통신 프로세스의 프로세서 친화도 결정을 위한 최적화 도구
조중연 ( Joong Yeon Cho ),진현욱 ( Hyun Wook Jin ) 한국정보처리학회 2013 정보처리학회논문지. 소프트웨어 및 데이터 공학 Vol.2 No.2
Multi-core processors can improve parallelism of application processes and thus can enhance the system throughput. Researchers have recently revealed that the processor affinity is an important factor to determine network I/O performance due to architectural characteristics of multi-core processors; thus, many researchers are trying to suggest a scheme to decide an optimal processor affinity. Existing schemes to dynamically decide the processor affinity are able to transparently adapt for system changes, such as modifications of application and upgrades of hardware, but these have limited access to characteristics of application behavior and run-time information that can be collected heuristically. Thus, these can provide only sub-optimal processor affinity. In this paper, we define meaningful system variables for determining optimal processor affinity and suggest a tool to gather such information. We show that the implemented tool can overcome limitations of existing schemes and can improve network bandwidth.