A Study on Multi-Layer Electromagnetic Wave Absorber Using Natural Lacquer as a Binder

With the progress of electronics industry and radio communication technology, human being might enjoy its abundant life. On the other hand, serious social problems such as electromagnetic interference (EMI), have been arisen due to the increased use of electromagnetic (EM) waves. Therefore, International organizations such as CISPR, FCC, ANSI, have provided the standards for the EM wave environments and for countermeasure of the electromagnetic compatibility (EMC). Generally, a silicone rubber and a chlorinated polyethylene(CPE) have been used as a binder for high-performance composite EM wave absorbers. In this dissertation, the EM wave absorption performance of natural lacquer which is newly proposed as a binder was investigated. MnZn ferrite EM wave absorbers mixed with natural lacquer were prepared and their absorption ability was also investigated. The EM wave absorbers are fabricated in different proportions of MnZn, or NiZn ferrite and natural lacquer, and their reflection coefficients are measured. The permittivity and permeability are calculated by using the measured reflection coefficients. The EM wave absorption abilities are calculated according to different thicknesses of the EM wave absorbers, and then multi-layer type EM wave absorbers with broad bandwidth are calculated and fabricated in accordance with different layer-sequence. The measured results are analyzed by comparing with the calculated ones. As a result, the prepared MnZn ferrite EM wave absorbers which are mixed with natural lacquer showed excellent EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers which are mixed with the conventional binders, such as a silicone rubber and a chlorinated polyethylene(CPE). The measured results of the single-layered type EM wave absorbers are a function of thickness agree well with the simulated ones. In addition, the measured results of the two-layered EM wave absorbers composed of MnZn Ferrite and NiZn Ferrite and fabricated with natural lacquer binders are similar with the simulated ones. Thus, it was shown that the multi-layered EM wave absorbers have more broadband characteristics than the single-layered ones.제 1 장 서론 = 1 1.1 연구 배경 = 1 1.2 연구 목적 = 3 1.3 연구 방법 = 4 제 2 장 전파흡수체의 기본이론 = 5 2.1 전파흡수체의 의의 = 5 2.2 전파흡수체의 원리 = 6 2.2.1 평면파와 흡수원리 = 6 2.2.2 에너지의 흡수 = 9 2.3 전파흡수체의 분류 = 12 2.3.1 전파흡수 재료에 의한 분류 = 12 2.3.2 층수에 의한 분류 = 13 2.3.4 용도에 의한 분류 = 14 2.3.5 주파수 특성에 의한 분류 = 18 2.4 정합조건 = 19 2.4.1 단층형 전파흡수체 = 19 2.4.2 다층형 전파흡수체 = 22 2.4.3 광대역형 전파흡수체 = 25 제 3 장 전파흡수체 설계 이론 및 측정법 = 28 3.1 전파흡수체의 분포정수회로화 = 28 3.1.1 파동방정식(Helmholtz Equation) = 28 3.1.2 분포정수회로화 = 33 3.2 전파흡수체 재료와 측정 = 38 3.2.1 손실재료 = 38 3.2.2 재료의 측정법 = 47 제 4 장 전파흡수체 제작 및 재료정수 측정 = 54 4.1 옻에 대한 특성분석 = 54 4.1.1 옻의 특징 = 54 4.1.2 옻의 약리작용 = 55 4.1.3 옻의 구성성분 = 56 4.2 샘플의 제작환경 및 조성비 = 57 4.2.1 샘플의 제작환경 = 57 4.2.2 시료의 조성비 = 58 4.3 옻의 흡수능 = 59 4.4 재료정수 측정 = 63 4.4.1 사용된 Sample 및 Sample Holder = 63 4.4.2 재료정수 계산방법 = 65 4.4.3 샘플의 조성비에 따른 재료정수 = 67 제 5 장 시뮬레이션 및 측정 결과 = 79 5.1 단층일 경우 = 80 5.1.1 시뮬레이션 결과 = 80 5.1.2 실측정 결과 = 85 5.1.3 시뮬레이션 값과 실측치 비교 = 89 5.2 다층일 경우 = 94 5.2.1 시뮬레이션 결과 = 95 5.2.2 실측정 결과 = 98 5.2.3 시뮬레이션 값과 실측치 비교 = 99 제 6 장 결론 = 102 참 고 문 헌 = 10

연안해양 박테리아 생태연구 및 해양생태계 교란 조사에의 응용

Thesis (doctoral)--서울대학교 대학원 :지구환경과학부,2003.Docto

Picocyanobacterial Diversity and Distribution During Summer in the Northern East China Sea

In order to understand the spatial distribution of picocyanobacterial diversity during the summer in the northern East China Sea (ECS), their abundance and genetic diversity were investigated using flow cytometry and barcoded amplicon pyrosequencing of 16S-23S internal transcribed spacer sequences. Synechococcus abundance was high, with a range of 0.2 × 105 to 1.8 × 105 cells ml−1. However, Prochlorococcus were found only in the eastern part of the studied area, showing a marked variation among stations [range of n.d. (not detected) to 3.3 × 104 cells ml−1]. Eleven Synechococcus clades and five Prochlorococcus ecotypes were found to have a proportion higher than 1% among picocyanobacterial sequences, indicating high picocyanobacterial diversity in the ECS. The picocyanobacterial compositions were markedly different among stations, as well as among depths. Inflow of the Tsushima Warm Current and Changjiang diluted water was of primary importance in determining picocyanobacterial lineage diversity in the studied area. In addition, light intensity and nutrient conditions also appeared to be important in the vertical and horizontal distribution of picocyanobacterial diversity.11scopuskc

박테리아 생산력 측정을 위한 [³H]thymidine 고정법: 전환 상수의 고찰

학위논문(석사)--서울대학교 대학원 :해양학과,1997.Maste

Diversity of Synechococcus Strain Isolated from the East Sea and the East China Sea

In order to investigate diversity of marine synechococcus strians isolated from seawater within euphotic depth of the East China Sea and the East Sea, phylogenetic analyses based on sequences of 16SrRNA gene and 16S-23S rRNA internal transcribed spacer region(ITS) and the ratio of PUB:PEB(phycorobilin:phycoerythrobilin) were investigazted for 33 culture isolates. The phylogeny of 16S rRNS gene showed that the islates were clustered into 10 clades including 2 novel and 8 previously described clades. Congruent result was obtained from a phylogenetic analysis of ITS sequences. The islated strains could be categorized into 4 types by pigment compositions - clade VIII without PUB & PEB, clade V with only PEB, clades II, IV, IX, X & XVIII with low PUB:PEB ratio, and clades III & XVIII with high PUB: PEB ratio. Interestingly, the pigment compositions of isolateds belonging to clades V and VI differe from those reported fro other oceanic regions. The presence of novel lineages and the different pigment patterns in the ECS and ES suggest the possibility that some Synechococcus lineage are distributed only in geographically resticted areas and have evolved to fit in these regions.1

Synechococcus abundance and diversity in the East China Sea and the East Sea

Synechococcus, phycoerytherin containing cyanobacteria, are ubiquitously distributed in huge numbers and are dominant contributors to primary production and biomass in vast area of world's oceans. Although many investigations on distribution of Synechoccous and their diversity were conducted in various oceanic regions, there was few data in the wetsern Pacific ocean, especiallly for diversity of Synechococcus. We have investigated Synechococcus abundance in the East china Sea(ECS) and the East Sea (ES) since 2001 and maintained Synechococcus cultrues isolated from the surveys. Synechococcus abudances were counted by flow cytometry. Molecular phylogenetic relationships of 34 Synechoccous culture strains were studied using 16S rRNA gene sequences an 16S-23S rRNA ITS (internal transcribed spacer) sequences. IN addition, pigment chracteristics of the culture strains was also examined. The presence of novel lineages and the different pigment patterns in some cldes suggests a possibility that some Synechococcus lineages distribute only at geographically restricted areas and have evolved in there. Therefore, eludication of physiological, ecological and genetical characteritstics of the diverse Synechococcus strains is needed to understand their spatial and geographical distribution.2

Cyanobacterial diversity in the North-West Pacific Ocean

Cyanobacteria are well known as an important primary producer in aquatic environments. In marine environments, two genera, Synechococcus and Prochlorococcus are exclusively dominant cyanobacteria. Synechococcus are ubiquitously distributed throughout the world’s oceans and especially dominant in coastal waters. Contrary to Synechococcus, Prochlorococcus are dominant in oligotrophic tropical open oceans, account for over 50% of total chlorophyll and photosynthetic biomass [1]. Synechococcus and Prochlorococcus abundance and diversity have been studied across various oceans [2]. Prochlorococcus can be broadly divided in to two ecotypes, high-light (HL)-adpated and low-light (LL)-adapted and HL and LL groups can be further divided into at least 6 clades [3]. Since a description of distinct 10 clades belonging to Synechococcus 5.1 sub-cluster based on 16 S rRNA gene analysis [4], at least eight lineages have been designated [5]. Although much knowledge on their ecology and diversity has been gained in various oceanic regions, studies on distribution and diversity of these cyanobacteria are rare in the north-western Pacific Oceans. In this study, latitudinal investigations of Synechococcus and Prochlorococcus distribution were conducted 4 times from 10oN to 35oN, including various water masses of the north-west Pacific Ocean [North Equatorial current (NEC), Kurhshio current (KC), East China Sea (ECS)]. Synechococcus and Prochlorococcus showed obviously contrasting distribution patterns in the NW Pacific Ocean. Prochlorococcus showed high abundances (avg. 10.0x104 cells ml-1) in NEC and Kuroshio (avg. 7.4x104 cells ml-1) waters. However, the abundances were remarkably low in the ECS (avg. 2.5x104 cells ml-1) or not detected in northern part of the ECS. Contrary to Prochlorococcus, Synechococcus were most abundant (max. 26x104 cells ml-1) in the ECS whereas the abundances were very low (max. 0.04 x104 cells ml-1) in NEC waters. Thus, Prochlorococcus and Synechococcu1

Diversity of Synechococcus Strain Isolated from the East Sea and the East China Sea

In order to investigate diversity of marine synechococcus strians isolated from seawater within euphotic depth of the East China Sea and the East Sea, phylogenetic analyses based on sequences of 16SrRNA gene and 16S-23S rRNA internal transcribed spacer region(ITS) and the ratio of PUB:PEB(phycorobilin:phycoerythrobilin) were investigazted for 33 culture isolates. The phylogeny of 16S rRNS gene showed that the islates were clustered into 10 clades including 2 novel and 8 previously described clades. Congruent result was obtained from a phylogenetic analysis of ITS sequences. The islated strains could be categorized into 4 types by pigment compositions - clade VIII without PUB & PEB, clade V with only PEB, clades II, IV, IX, X & XVIII with low PUB:PEB ratio, and clades III & XVIII with high PUB: PEB ratio. Interestingly, the pigment compositions of isolateds belonging to clades V and VI differe from those reported fro other oceanic regions. The presence of novel lineages and the different pigment patterns in the ECS and ES suggest the possibility that some Synechococcus lineage are distributed only in geographically resticted areas and have evolved to fit in these regions.1