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A NOTE ON CHAIN TRANSITIVITY OF LINEAR DYNAMICAL SYSTEMS
이현희,구남집 충청수학회 2023 충청수학회지 Vol.36 No.2
In this paper we study some topological modes of recurrent sets of linear homeomorphisms of a finite-dimensional topological vector space. More precisely, we show that there are no chain transitive linear homeomorphisms of a finite-dimensional Banach space having the shadowing property. Then, we give examples to illustrate our results.
이동통신 환경에서 핸드오프를 고려한 SIR 기반의 상향 링크 고정채널 알고리즘의 성능 측정
이현희,김동회 강원대학교 정보통신연구소 2008 정보통신논문지 Vol.12 No.-
The channel allocation in a cellular system is important form the performance analysis. Channel allocation usually deals with how a BS(Base Station) should assign traffic channels to the MS(Mobile Station)s. Also, handoff basically involves change of radio resources from one cell to another adjacent cell. From a handoff perspective, it is important that a free channel is available in a new cell whenever handoff generates, so that undisrupted service is available. This paper deals with a difference of performance in terms of new call blocking probability and forced termination probability between SIR-based FCA(Fixed Channel allocation) strategy without supporting handoff operation and SIR-based FCA strategy with supporting handoff operation in wireless communication network. From the simulation results, we find that SIR-based FCA strategy with supporting handoff operation has better performance than SIR-based FCA strategy without supporting handoff operation.
Synthesis and Characterization of Mesoporous Silica Molecular Sieve
이현희,박수진,서동학 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
Mesoporous silica molecular sieves have attacted much attention as catalyst supports, adsorbents, and hosts for large molecules, due to the large pore diameter compared with that of conventional microporous zeolites. In this work, the effect of pH adjustment for reaction mixtures on the synthesis of MCM-41 is investigated. MCM-41 is also made a study of morphological, physical, and textural properties. MCM-41 is obtained by hydrothermal synthesis using gel mixture of sodium silicate solution as silica source and hexadecyltrimethylammonium chloride (HTAC1) as the template. The X-ray diffraction (XRD), N2 BET, and scanning electron microscopy (SEM) are used for their characteristics. The results are found that the long-range structural order and textural uniformity of MCM-41 are improved due to a shift in the reaction equilibrium when acetic acid is repeatedly added during condensation reaction of silicateous anion to happen around micell of cationic surfactant. Adsorption behaviors are found to narrow mesopore size distribution and to increase adsorption ability by increasing the repeated times of pH adjustment.
이현희,정장표,장영환,이무강 慶星大學校 環境問題硏究所 2002 環境硏報 Vol.12 No.1
According to the conclusion of this study, air pollution concentration of Youngdo-gu belong to Seobu educational institution was in the lowest density.(SO_2 : 0.002 ppm, PM-10 : 32 ㎍/㎥, No_2 : 0.016 ppm) and Dongnae-gu belong to Dongnae educational institution was in the highest.(SO_2 : 0.002 ppm, PM-10 : 88㎍/㎥, No_2 : 0.047 ppm) Air pollution level by classification of each educational institution about elementary schools, middle schools, high schools in Busan appeared that the pollution level about all air pollutants appeared high in Dongnae, Dongbu, Bukbu, Haeundae, Nambu, Seobu in due order. Air pollution level by classification of each Gu about elementary schools, middle schools, high schools in Busan appeared that the pollution level of Geumjeong-gu was very high (SO_2 : 0.002 ppm, No_2 : 0.047 ppm, PM-10 : 89 ㎍/㎥) and level of pollution around high school in Busan was the highest. To improve air quality getting worse day by day, steady and systematic control of observing the air quality standards should be continued. The more effective and active method of air quality improvement should be considered.