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OFDM 기반의 WLAN을 지원하는 디지털 IF단 설계
박찬훈,신동우,최연경,양훈기,양성현,박종철,Park, Chan-Hoon,Shin, Dong-Woo,Choi, Youn-Kyoung,Yang, Hoon-Gee,Yang, Sung-Hyun,Park, Jong-Chul 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.8
본 논문에서는 OFDM 기반의 WLAN을 지원하는 Digital IF 단을 설계하고 시뮬레이션을 통해서 시스템 성능을 조사한다. 이를 위해서 ADC 샘플률, NCO 주파수 및 데시메이션률 결정과정을 보이고 주워진 데시메이션률을 얻기 위한 CIC필터 및 MHBF 설계과정을 제시한다. 데시메이션 과정에서 발생되는 진폭왜곡 보상을 위해 시스템 복잡도를 최소화하면서 요구성능을 만족시키는 ISOP 필터 및 FIR 필터를 설계하는 과정을 제시한다. 최종적으로 설계된 DDC 블록에 대해서 BER 관점으로 성능을 조사한 후 이론적인 변복조 시스템과의 성능 차이를 보인다. In this paper, we propose the design procedure of a digital IF system for the OFDM based WLAN system and examine its performances. Along with the decision procedure of ADC sample rate, NCO frequency and the required decimation ratio, we show the decimation ratio is accomplished through the use of a CIC filter and a MHBF. We also show that the amplitude distortion occurred in the decimation filters can effectively be compensated by a ISOP filter and an additional FIR filter, which leads to the reduction of the overall hardware complexity. Finally, we examine the BER performance of the proposed system and compare it with a theoretical one that excludes filter non-linearities.
김두형(Doo-Hyeong Kim),박찬훈(Chan-Hoon Park),최태용(Tae-Yong Choi),김휘수(Hwi-Su Kim),김왕환(Yoang-Hwan Kim) 한국생산제조학회 2018 한국생산제조학회지 Vol.27 No.4
In the fields of air/gas compression, refrigeration, and chemical fluid transportation systems, single-screw compressors are widely used. A screw rotor and two gate rotors located at both sides are the main components of a single-screw compressor. Because of this simple construction, it has merits of low rotational speed of the rotor, efficient compression with low noise, low vibration, and long bearing life. However, it is difficult to design single-screw compressors. To accelerate the design and manufacturing of single-screw compressors, a design method for a gate rotor using coordinate transformation and numerical estimation by iteration of edge points is presented in this paper. The lines connecting the edge points can be used for CAD/CAM data for design and machining.
건설문화박물관의 웹사이트 구축을 위한 콘텐츠 서비스방안에 관한 연구
김미연(Kim Mi-Yun),박찬훈(Park Chan-Hoon),최진원(Choi Jin-Won) 대한건축학회 2008 대한건축학회논문집 Vol.24 No.1
With the widespread accessibility of Internet, there have emerged countless numbers of websites for various fields, along with their users. This expands the range of information accessible according to users' diverse purposes, personal characteristics, faced problems, environmental elements, and so on. In case of online museum, for example, it is possible to offer customized information that each user needs, with its capability of infinite exhibitions and variety of contents only accessible online, which cannot be found in offline museums. On the other hand, most online users feel frustrated when they find it hard to search and obtain necessary information, due to poor accessibility and of information that each site provides. This paper attempts to achieve the following purposes: first, it decides critical information related to construction culture by examining its specialty, value and efficiency; second, it organizes the specific information on the history of construction culture and details of essential buildings & related technology; finally, it makes it easy for users to access the information with visualization and the state-of-the-art web technology, not just showing texts and images. This paper examines previous website researches to study various info-visualization categories such as searching procedures, searching methods and development of new contents. and suggests a method to improve user accessibility to the virtual construction culture museum.
김준식(Joon-Shik Kim),박찬훈(Chan-Hoon Park),이은석(Eun-Seok Lee),장병탁(Byoung-Tak Zhang) 한국정보과학회 2008 정보과학회논문지 : 시스템 및 이론 Vol.35 No.3·4
We studied the variety and affinity between the successive words in the text document. A number of groups were defined by the frequency of a following word in the whole text (corpus). In the previous studies, the Zipf's power law was explained by Chinese restaurant process and hub node was searched after by examining the edge number profile in scale free network. We have observed both a power law and a hub profile at the same time by studying the conditional frequency and degeneracy of a group. A symmetry between the affinity and the variety between words were found during the data analysis. And this phenomenon can be explained within a viewpoint of "exploitation and exploration." We also remark on a small symmetry breaking phenomenon in TIPSTER data. 전체문서(corpus)에서의 두 단어 간 연결 상태를 파악하여 앞 단어 다음에 오는 단어의 빈도수를 기반으로 여러 형태의 그룹을 분류하여 단어 간 다양성과 긴밀성을 살펴보았다. 기존의 연구에서 Zipf’s Power Law는 Chinese Restaurant Process로 설명되었고 Scale Free Network에서는 edged의 수에 따른 노드의 profile을 조사하여 hub들을 찾는 연구가 수행되었다. 본 연구에서는 단어 간 연결의 유일성과 다양성을 조사하여 Zipf's Power Law와 hub profile을 동시에 살펴보았다. 데이타 분석 결과 단어 간 연결의 긴밀성과 다양성 사이에서 대칭성으로 함축되는 유의한 결과를 얻었으며 이는 소위 ‘exploitation’과 ‘exploration’의 관점에서 설명될 수 있다. 또한 분석 자료인 TIPSTER에서 관찰된 약간의 대칭성 깨짐(symmetry breaking)에 대해서도 논한다.