• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.76-86
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• 2012

Macrozoobenthos were collected from 24 sites using small grab ($0.05m^2$) in order to see the spatial distribution of them at Sueocheon stream at the northern part of Gwangyang Bay during summer season when the maximum ecological processes are occurring. A total of 44 species of macrozoobenthos occurred, and their mean density was $789individuals/m^2$. Mollusks was the dominant faunal group accounted for 43.1% and 86.8% of the whole community density and biomass, respectively. Top five dominant species were a molluscan, Corbicula japonica (40.7%), two polychaete worms, Neanthes japonica (19.3%) and Heteromastus filiformis( 8.1%), and two crustaceans, Paranthura japonica (6.9%) and Jaeropsis sp. (6.9%). Species diversity index was very low with mean value of 1.12 and maximum value was recorded at the river mouth. At the upper stream, a brackish water species such as Corbicula japonica showed their maximum population density. The overall distribution of stream macrobenthos showed a rather simple pattern along with salinity and grain size gradients with few brackish water species occurring at coarse sediments in the stream but more diverse faunas inhabiting fine sediments in the river mouth.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.389-390
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• 2013

본 논문에서는 블록 놀이의 질적 향상을 위한다. 일반 블록 완구의 해결하지 못한 문제점인 조립과 완성으로 즐거움이 끝나고 분리시의 지루함을 해결하기위한 블록 자동분리 시스템에 관한 것으로, 좀 더 구체적으로는 블록을 이용하여 물체를 완성시키는 것에서 더 나아가 자동분리 블록의 외부에 부착된 마커를 스마트 폰을 이용하여 인식하고, 인식된 마커에 해당하는 영상을 스마트 폰을 통해 보며 미션을 수행하여 흥미를 유발시키고, 미션 완료 후 블록을 자동 분리 시키기 위한 블록 자동분리 시스템에 관한 것이다. 특히, 블록에 분리장치를 구성함으로써 스마트 폰과의 통신에 의해 분리장치가 동작하여 블록을 자동으로 분리 가능하도록 하여 물체를 완성 후 분리 시에 느끼는 지루함을 최소화하고, 흥미를 극대화시킬 수 있도록 한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.346-353
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• 2005

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.330-333
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• 2003

본 논문에서는 조립/제작, 시험과정을 통하여 개발된 통신방송위성용 Ka 대역 통신위성 중계기의 구조 및 성능에 대하여 기술한다. 개발된 중계기는 전체 400MHz 대역 내에 100 MHz 대역폭을 갖는 3 개의 통신채널을 수용하여 광대역 멀티미디어 서비스를 지원할 수 있도록 설계되었으며 국내 기술로 제작되어 우주인증을 거친 IFA, RxDC, IMUX, CH-AMP 등의 부품으로 구성되어 있다. 중계기에 대한 성능시험은 EGSE를 이용해 자동으로 수행되었으며, 성능시험결과 대부분의 성능 항목이 요구사항과 부합됨을 확인하였다. 제작된 Ka 대역 중계기에 적용된 위성 중계기 및 부품의 제작 및 시험 기술은 향후 통신해양기상위성에 탑재될 중계기의 개발에 직접 응용이 가능하다.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.3-6
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• 2006

초고속 광대역서비스 제공을 위한 FTTH-PON 광선로의 특성을 시험하기 위해 선로구축 단계, 개통단계, 고장처리 단계로 나누어 측정할 수 있는 방법에 대해 고찰해 보았다. 시스템의 허용손실 기준에 따라 구축된 광선로는 대표적으로 광손실, 광반사손실을 측정하여 접속품질을 확인할 수 있는데 OTDR 및 광파워메터를 활용한 구간별 측정방법을 다루었다. 또한 광옥외선의 단말에 현장조립형광커넥터를 사용하는 경우 접속 후 불량여부를 판단하기 위한 실험 결과를 소개하였다.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.189-197
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• 1999

기구의 운동에 있어서 공차는 필연적으로 운동 오차를 발생시키게 된다. 이상적인 기구의 운동을 위하여 공차를 작게 설정하는 것은 가공 또는 조립 비용을 증가시키는 반면에 제작 비용의 절감을 위하여 공차를 크게 설정하는 것은 기구의 운동 오차를 크게 증가시키게 된다. 따라서 기구의 운동오차를 고려한 효율적인 공차의 설정 및 배분이 중요하다. 이 논문은 민감도 해석을 이용하여 기구의 운동에 영향을 미치는 설계변수들에 어떻게 공차를 효율적으로 지정하고 분배하는 가를 연구하였다. 민감도 해석에서는 각 설계변수의 민감도 계수를 유도하였으며 설계변수에 공차를 지정하였을 때 발생할 수 있는 기구 운동의 최대 응답오차를 수식화 하였으며 역으로 기구 운동에 있어서 허용 응답오차를 설정하였을 때 각 설계 변수의 공차를 분배하는 과정을 유도하였다. 실제로 공차 분배 과정을 공업용 본봉 재봉기의 이송조절기구에 적용하여 허용 응답오차를 고려한 공차 설정을 합리적으로 수행할 수 있었다. 본 논문에서 제시한 공차 분배 과정은 재봉기 또는 로봇과 같이 기구운동과 밀접한 관련이 있는 기계의 설계에 유용할 것이다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.435-440
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• 2004

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.543-552
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• 2015

This study examines the processes of rock weathering and tafoni formation targeting tafoni at Mt. Cheonsaeng, Gumi-si, Gyeongsangbuk-do. In the study area, a frequency of tafoni is high in conglomerate and conglomeratic sandstone among regional sedimentary rocks, which means that an initial stage of the formation begins a breakaway of gravel from bedrock and also exfoliation from rock surface. Geomorphologically tafoni have intensively been developed at the southfacing slope with exposed rocks, which means that its formation was favorably controlled by environmental conditions including strong influences of mechanical weathering in winter and chemical weathering in summer times. The results of measuring water content at a tafoni-bearing rock surface using GIS interpolation analysis indicate that moisture rate in/around tafoni is higher than the periphery. Thus, it is considered that moisture distribution at a rock surface plays a role in its formation. Analysis of percipitation and secondary minerals induced by chemical weathering is in progress.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.180-185
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• 2001

In the life assessment for plant structural component, the research on deterioration of toughness and material properties occurred in weldments has been considered as very important problems. In general, the microstructures composed in weldments are hugely classified with weld metal(W.M), fusion line(F.L), heat affected zone(HAZ), and base metal(B.M). It has been reported that the creep characteristics on weldments having variable microstructures could be unpredictably changed. Furthermore, it is also known that HAZ adjacent to F.L exhibits the decreased creep strength compared to those in base or weld metals, and promotes the occurrence of Type III and Type IV cracking due to the growth of grains and the coarsening carbides precipitated in ferritic matrix by welding and PWHT processes. However, the lots of works reported up to date on creep damage in power plant components have been mostly conducted on B.M and the creep properties on a localized microstructures in weldments have not as yet been throughly investigated. In this paper, for various microstructures such as coarse grain HAZ(CGHAZ), W.M and B.M in X20CrMoV121 steel weldment, the small punch-creep(SP-Creep) test using miniaturized specimen(t=0.5mm, 0.25mm) is performed to investigate a possibility for creep characteristics evaluation.

• Journal of Welding and Joining
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• v.3 no.1
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• pp.22-31
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• 1985

Hot straining embrittlement is one of the most important factors which cause the brittle fracture initiation even in the service temperature in the case of mild steel and high tensile steel. Therefore it is necessary to analyze thoroughly the hot straining embrittlement occurred in weld HAZ of the structural steels. The behaviors of plastic deformation and fracture toughness at the notch tip of the hot strained weld HAZ in structural steels (SB 41 KS, SA 588-Grade A ASTM) have been studied by the recrystallization technique and crack opening displacement (COD) test method. The obtained results are summarized as follows; 1. The plastic zone is formed at the notch tip of weld HAZ owing to nomotonic and cyclic hot stran, and the maximum plastic strain increases with the accumulated hot straining amounts. 2. The distribution of the effective strain at the plastic deformed zone in HAZ can be determined as follows; (.epsilon. over bar $_{p}$ )$_{\chi}$=.epsilon. over bar $_{cr}$ ( $R_{/chi}$/.chi.)$^{m}$ where, .epsilon. over bar $_{cr}$ : (SB 41; .epsilon. over bar $_{cr}$ = 0.2, SA 588; .epsilon. over bar $_{cr}$ = 0.1) 3. The embrittlement of weld HAZ in SB 41 and SA 588 is influenced by hot strain, and the degree of embrittlement becomes deeper with hot straining amounts. 4. The embrittlement of weld HAZ of SB 41 is not influenced by the hot straining amounts until .epsilon. over bar $_{max}$ = 0.36, $R_{\chi}$ = 0.065mm, however the embrittlement of structure in SA 588 is considerably influenced even by a small quantity of the hot straining amounts.s.