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Design Optimization, Modeling, and Control of Unmanned Aerial Vehicle Lifted By Coandă Effect
Lee, Hyunyong,Han, Seonhye,Lee, Hyoju,Jeon, Jaehyeok,Lee, Choonghan,Kim, Yong Bum,Song, Seung Hwan,Choi, Hyouk Ryeol IEEE 2017 IEEE/ASME transactions on mechatronics Vol.22 No.3
<P>The Coanda effect is a natural phenomenon, which is that flowing fluid on a certain surface is pulled to the surface due to the viscosity of the fluid. This phenomenon can be utilized to produce the lift force of a flying object. This paper presents a new type of unmanned aerial vehicle (UAV) lifted by the Coanda effect, called SCoanda. We introduce the empirical study of its design and implementations. The principle of the Coanda effect is briefly explained in the first section. The design optimization and control of the UAV, and implementation issues are explained. The structural design of SCoanda is devised to use the maximum lift force produced by the Coanda effect. Since there are a plenty of cases about the shape of SCoanda, it has been limited to oval. It is investigated through computational fluid dynamics. As the result, an optimized design is determined among several candidates and appropriate structural materials are selected via tests. Also, dynamic modeling is suggested under several conditions of SCoanda before simulations are conducted to build up a controller and determine gains according to the dynamic modeling. Finally, the UAV is manufactured and its performances are successfully demonstrated in the indoor and the outdoor environments.</P>
이현용 ( Hyunyong Lee ),김낙우 ( Nac-woo Kim ),이준기 ( Jun-gi Lee ),이병탁 ( Byung-tak Lee ) 한국정보처리학회 2020 한국정보처리학회 학술대회논문집 Vol.27 No.1
이상 진단은 주어진 데이터의 정상 유무를 진단하는 방법으로써 다양한 분야에 걸쳐 요구되는 기능이다. 이상 진단은 대상 환경에서 데이터의 특성 등에 따라 다양한 방법으로 구현이 될 수 있는데, 본 연구에서는 정상 데이터가 다수의 클래스로 구분될 수 있는 상황에서의 이상 진단을 효과적으로 할 수 있는 방법에 대해서 다루고자 한다. 특히, 실험을 통해 정상 데이터를 유사한 데이터들끼리 구분하여 구분하여 처리하는 경우와 그렇지 않은 경우의 비교를 통해서, 정상 데이터를 유사한 데이터들끼리 구분하여 이상 진단을 진행하는 방법의 타당성을 검증한다.
Approaches for Improving Bloom Filter-Based Set Membership Query
Lee, HyunYong,Lee, Byung-Tak Korea Information Processing Society 2019 Journal of information processing systems Vol.15 No.3
We propose approaches for improving Bloom filter in terms of false positive probability and membership query speed. To reduce the false positive probability, we propose special type of additional Bloom filters that are used to handle false positives caused by the original Bloom filter. Implementing the proposed approach for a routing table lookup, we show that our approach reduces the routing table lookup time by up to 28% compared to the original Bloom filter by handling most false positives within the fast memory. We also introduce an approach for improving the membership query speed. Taking the hash table-like approach while storing only values, the proposed approach shows much faster membership query speed than the original Bloom filter (e.g., 34 times faster with 10 subsets). Even compared to a hash table, our approach reduces the routing table lookup time by up to 58%.
Approaches for Improving Bloom Filter-Based Set Membership Query
( Hyunyong Lee ),( Byung-tak Lee ) 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.3
We propose approaches for improving Bloom filter in terms of false positive probability and membership query speed. To reduce the false positive probability, we propose special type of additional Bloom filters that are used to handle false positives caused by the original Bloom filter. Implementing the proposed approach for a routing table lookup, we show that our approach reduces the routing table lookup time by up to 28% compared to the original Bloom filter by handling most false positives within the fast memory. We also introduce an approach for improving the membership query speed. Taking the hash table-like approach while storing only values, the proposed approach shows much faster membership query speed than the original Bloom filter (e.g., 34 times faster with 10 subsets). Even compared to a hash table, our approach reduces the routing table lookup time by up to 58%.
Improving Routing Table Lookup in Software Routers
HyunYong Lee,Nakao, Akihiro IEEE 2015 IEEE Communications Letters Vol.19 No.6
<P>For the speed-up in the routing table lookup in software routers, we introduce a new data structure called, sTable that achieves space efficiency while causing low processing overhead without hardware parallelism. Using a hash table-like approach, sTable stores only next hop information to handle most packets within the on-chip fast memory while causing some accesses to the off-chip slow memory to handle lookup errors. Routing table lookup experiments using Click show that, causing less processing overhead and a smaller number of lookup errors than Bloom filter, sTable reduces the average table lookup time by 44% (i.e., from 119 ns to 67 ns) compared to Bloom filter.</P>
Resonating valence bond states with trimer motifs
Lee, Hyunyong,Oh, Yun-tak,Han, Jung Hoon,Katsura, Hosho American Physical Society 2017 Physical Review B Vol.95 No.6
<P>A trimer resonating valence bond (tRVB) state consisting of an equal-weight superposition of trimer coverings on a square lattice is proposed. A model Hamiltonian of the Rokhsar-Kivelson type for which the tRVB becomes the exact ground state is written. The state is shown to have 9(g) topological degeneracy on a genus g surface and support Z(3) vortex excitations. Correlation functions show exponential behavior with a very short correlation length consistent with the gapped spectrum. The classical problem of the degeneracy of trimer configurations is investigated by the transfer matrix method.</P>