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다경로 환경에서 WLAN 시스템을 위한 스마트 안테나의 성능 분석에 관한 연구
김현웅,장병건,Kim Hyun-Woong,Chang Byong-Kun 한국전자파학회 2005 한국전자파학회논문지 Vol.16 No.2
본 논문에서는 IEEE 802.11b WLAN시스템에서 간섭 억제에 관한 효과적인 기술을 제시하였다 선형 제약형 적응 어레이 처리기는 동일 채널 간섭 신호와 다중 경로 효과를 효과적으로 감소시켜 WLAN 장치의 수신 성능 향상을 위하여 제안되었다. 공간 유화 방법은 다중경로 환경에서 원하는 신호의 왜곡을 방지하는데 사용되며, integral null 지정 방법은 실내 환경에서 어레이 성능을 향상시키기 위해 제안하였다. 공간 유화 방법이 선형 제약형 방법보다 성능이 보다 우수하였으며, integral null지정 방법을 적용한 어레이 시스템이 가장 좋은 성능을 나타내었다. 본 논문에서 제안된 방법은 동일 채널 신호, 다중 경로 신호, 그리고 긴WPAN 간섭을 효과적으로 제거함으로써 WLAN의 성능이 향상될 것으로 기대된다. This paper presents an efficient technique for interference suppression in IEEE 802.11b WLAN systems. A linearly constrained adaptive array processor which may improve reception performance of WLAN device by reducing co-channel interference signal and multipath effects effectively was proposed. A spatial smoothing method is used to prevent cancellation of a desired signal in a coherent environment and also integral nulling method is employed to improve the array performance in indoor environment. It was shown that the integral nulling approach performed best while the spatial smoothing method performed better than linearly constrained array processing. The performance of the WLAN system may be improved by the proposed methods which reduce co-channel, coherent, and WPAN interferences effectively.
김현웅(Kim Hyun-Woong),문대섭(Moon Dae-Seop) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
The ability of freight users to identify and to utilize options to move is limited. Saving in time and in fare to freight users could be significant if whole transport sequences could be planned and implemented with high level of service. In oder to improve the attractiveness of rail freight, it is essential that the industrial railway tracks between railway network and large scale logistics facilities are completely equipped. This article present the direction of the master plan of Korean industrial railway tracks.
김현웅(Hyun-Woong Kim) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.10
The purpose of this paper is to provide basic information on how to make better policies that improves efficiencies of urban railways and to derive policy directions using DEA (data envelopment analysis) model. Through this paper, I can identify whether or not the urban railway service has an excellent performance, if there are any structural problems. I analyzed the efficiency by means of measuring the technical efficiencies of Korean urban railways, these were estimated with data envelopment analysis. The inputs considered are the length of urban railway lines, the number of staff, the operating cost, the number of cars, the number of stations, and the outputs are the cars movement, the traffic of passenger, and the revenue.
김현웅(Kim Hyun-Woong),문대섭(Moon Dae-Seop),박춘수(Park Chun-Soo) 한국철도학회 2003 한국철도학회 학술발표대회논문집 Vol.- No.-
This paper is aiming to analyse the prefeasibility study of introduction of high speed rail freight system to transport some parcels for train operation efficiencies. As it does, this system can be meant a kind of multimodal system considering the passenger and freight in the same trainset, simultaneously. First, we implemented the parcel service market survey for customers preference, predicted demand forecast for high speed rail freight, and analysed B/C, NPV, etc.. As the result, this new system is feasible of applying the passenger-freight operation system economically, find the needs such as some revision of motor car for parcel freight transportation at the initial stage.
김현웅(Hyun-Woong Kim) 한국철도학회 2010 한국철도학회 학술발표대회논문집 Vol.2010 No.7
This paper investigates the productivity growth in Korean railway lines. The productivity growth is calculated by a process of measuring of pure efficiency change index(PECI), scale efficiency change index(SECI), and technical change index(TCI), using Data envelopment analysis (DEA) method. The data cover the period 1990~2007 1990~2003 are the pre-structural reform years and the post-structural reform years are 2005~2007. The framework for the analysis is Malmquist Productivity Index (MPI) of the to investigate the impacts of structural reform on productivity growth, respectively. The inputs considered are the length of operating line, the number of staff, the number of coach and wagon, and the outputs are the trains movement of passenger and freight, and the traffic of passenger and freight.