• Journal of the Korean Data and Information Science Society
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• 제26권1호
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• pp.271-280
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• 2015

In this paper, the maximum likelihood estimators for parameters are derived under three step-stress accelerated life tests for Type-I hybrid censored data. The exponential distribution and the cumulative exposure model are considered based on the assumption that a log quadratic relationship exits between stress and the mean lifetime ${\theta}$. The test plan to search optimal stress change times minimizing the asymptotic variance of maximum likelihood estimators are presented. A numerical example to illustrate the proposed inferential procedures and some simulation results to investigate the sensitivity of the optimal stress change times by the guessed parameters are given.

• 대한화학회지
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• 제19권4호
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• pp.269-279
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• 1975

合成한 pllyglyceryl phthalate, bisphenol A-epichlorohydrin 축중합물과 polyvinyl alcohol의 naphthoquinone-1,2-diazide-5-sulfonyl esters(PGND, BEND 및 PVAND)의 感光特性을 지배하는 諸因子를 이들에 대한 光照射前後의 溶解度 차이에 의하여 檢討하였다. 유리 또는 石英支持薄板上에 塗布한 各試料를 各種條件下에서 露光하고 알카리 水溶液에 침지시킨 다음 塗布된 필림의 殘膜收率(W/W0)을 計算하였다. 필름의 感光度와 직접적인 관계가 있는 殘膜收率은 母體樹脂의 重合度, 增感劑의 種類 및 添加濃度에 따라 영향이 있었다. 母體樹脂의 重合度가 크면 클수록 感光性이 더 우수하였으며, 增感劑의 添加濃度는 5%일때가 가장 좋은 效果를 나타내었다. PGND, BEND 및 PVAND에 대해 본실험에서 사용한 各種 增感制 중에서 가장 效果的인 것은 benzanthrone, 5-nitroacenaphthene, picramide이였다. 이들 樹脂와 增感劑를 添加한 경우의 固相에 있어서의 紫外線吸收스펙트럼과 感色性 寫眞을 각각 비교 검토하여 그 增感과 分光感度的 特性을 糾明하였다. PGND, BEND 및 PVAND는 使用한 增感制에 의하여 光學增感하였으며 增感效果가 현저한 것일수록 그 感光波長城이 長波長쪽으로 伸張하였다. 未增感, 增感試料에 있어서 分光吸收 極大 波長城과 分光感光極大波長城이 거의 一致하고 있는 점으로 보아 試料 樹脂들에 의해서 吸收된 波長城의 光은 그 分野에 有效하게 使用되고 있음을 확인하였다

• 한국지진공학회논문집
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• 제11권1호
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• pp.1-9
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• 2007

본 연구는 지진하중을 받는 콘크리트 표면차수벽형 석괴댐(CFRD)의 정상부 변위에 대한 사력재료 주요물성의 민감도를 정량적으로 분석하는데 그 목적이 있다. 이를 위해 현재 운영 중인 국내 CFRD 형식의 D댐에 대해 2가지 지진파, 각 지진파에 대해 2가지 설계진도, 사력재료에 대해 수행된 대형삼축압축시험 결과로부터 얻어진 물성값을 조합하여 만든 물성값이 다른 해석단면 27개를 작성, 총 108개 해석단면에 대한 동적 수치해석을 수행, 그 결과를 이용한 대역적 민감도분석을 수행하였다. 민감도분석 결과, 지진하중 작용 시 댐 정상부 침하량은 입력지진의 종류와 설계진도 크기에 상관없이 절대적으로 사력재료 전단탄성계수에만 영향을 받았으며 댐 정상부 횡변위의 경우에는, 사력재료 전단탄성계수의 영향이 크나 그 영향의 정도는 침하량에 미치는 정도에 비해 상대적으로 작으며, 침하량과는 달리 지진파의 종류와 크기에 따라 차이를 보였다. 본 연구결과에 한해 사력재료의 마찰각은 지진하중에 의한 CFRD 정상부 변위에는 전혀 영향을 주지 않는 것으로 나타났다.

• 한국광학회지
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• 제33권4호
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• pp.177-186
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• 2022

표면 플라즈몬 공명 센서에서 센서의 성능은 민감도(nm/RIU)와 분해능인 공명 픽의 형태에 의해서 결정된다. 이러한 특성은 센서에 활용되는 구조체의 물질과 구조적 특성에 따라 달라진다. 본 연구에서는 insulator-metal-insulator (IMI) 다중 층 구조를 기반으로 한 표면 플라즈몬 공명 센서 구조의 최적화 과정을 통해 센싱 레이어의 굴절률 변화에 대한 높은 민감도 달성과 동시에 좁은 full width at half maximum (FWHM)과 픽의 깊이 이 두 가지의 요소를 기반으로 한 분해능이 큰 공명 픽을 형성하도록 하는 구조를 찾았다. 이 구조를 통해 센싱 레이어의 굴절률이 1.45-1.46 범위에서 변화할 때 FWHM = 11.92 nm, 픽 깊이 93.1%의 공명 픽이 형성되었고 최대 8,390 nm/RIU의 민감도 성능을 확인했다. 특히 금 박막을 활용한 파장 기반의 표면 플라즈몬 센서는 공명 픽의 너비 확장이 발생하나 금 박막을 사용하고도 좁은 FWHM을 달성함에 의의가 있다. 본 연구에서 제안하는 다중 층 설계를 기반으로 한 센서는 미세한 굴절률 변화 값에 대한 높은 민감도와 더불어 높은 분해능을 가지는 파장 기반 표면 플라즈몬 센서로 활용 가능하다.

• Structural Engineering and Mechanics
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• 제59권3호
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• pp.559-577
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• 2016

There are many theoretical analyses and experimental studies of the hydrodynamics for the tension leg platform (TLP) of a floating wind turbine. However, there has been little research on the arrangement of the TLP's internal structure. In this study, a TLP model and a 5-MW wind turbine model as proposed by the Minstitute of Technology and the National Renewable Energy Laboratory have been adopted, respectively, to comprehensively analyze wind effects and wave and current combinations. The external additional coupling loads on the TLP and the effects of the loads on variables of the internal structure have been calculated. The study investigates preliminary layout parameters-namely, the thickness of the tension leg body, the contact mode of the top tower on the tension leg, the internal stiffening arrangement, and the formation of the spoke structure-and conducts sensitivity analyses of the TLP internal structure. Stress is found to be at a maximum at the top of the tension leg structure and the maximum stress has low sensitivity to the load application point. Different methods of reducing maximum stress have been researched and analyzed, and the effectiveness of these methods is analyzed. Filling of the spoke structure with concrete is discussed. Since the TLP structure for offshore wind power is still under early exploration, arrangements and the configuration of the internal structure, exploration and improvements are ongoing. With regard to its research and analysis process, this paper aims to guide future applications of tension leg structures for floating wind turbine.

• Advances in environmental research
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• 제3권4호
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• pp.307-319
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• 2014

Four chickpea cultivars viz. kabuli (Pusa 1088 and Pusa 1053) and desi (Pusa 1103 and Pusa 547) differing in sensitivity to high temperature conditions were analyzed in earthern pot (30 cm) at different stages of growth and development in the year of 2010 and 2011. Pusa-1053 (kabuli type) showed maximum photosynthetic rate and least by Pusa-547 (desi type), whereas maximum cell membrane thermostability were recorded in Pusa-1103 and minimum in Pusa-1088. Among the treatments, the plants grown under elevated temperature conditions had produced 13.01% more significant data in comparison to plants grown under continuous natural conditions. Stomatal conductance were reduced 44.25% under elevated temperature conditions than natural conditions, whereas 35.56%, when plants grown under initially natural conditions upto 30DAS, then 30-60DAS elevated temperature and finally shifted to natural conditions till harvest. In case of Pusa-1103, stomatal conductance was maximum as compared to rest of 2.7% from Pusa-1053, 8.9% from Pusa-1088, and 10.3% in Pusa-547 throughout the study. Plants grown under continuous elevated temperature conditions had produced 15.30% and 15.32% more significant membrane thermostability index in comparison to continuous natural conditions at vegetative stage and 19.40% and 18.44% at flowering stage, while the better response was recorded at pod formation stage. Pusa-1053 had given 2.8% more membrane thermostability index than Pusa-1088 and Pusa-1103 had given 1.6% more membrane thermostability index than Pusa-547 in the present study. The membrane disruption caused by high temperature may alter water ion and inorganic solutes movement, photosynthesis and respiration. Thus, thermostability of the cell membrane depends on the degree of the electrolyte leakage.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3017-3029
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• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• 한국안광학회지
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• 제5권1호
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• pp.43-48
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• 2000

Polarizer와 Analyzer의 Rotation 각에 의해 광의 luminance를 조절할 수 있다. Contrast Sensitivity에 대응한 luminance 값 $L_{max}$, $L_{min}$은 평균 luminance($L_m$)의 회전각 ${\theta}_m$ 최대 진폭과 최소 진폭에 대응하는 회전각 (${\theta}_{max}$, ${\theta}_{min}$)로 부터 구할 수 있다. $$L_{max}=I(0)e^{-2at}{\cdot}cos^2{\theta}_m(1+C_s^{-1})$$ $$L_{min}=I(0)e^{-2at}{\cdot}cos^2{\theta}_m(1-C_s^{-1})$$ 평균 luminance($L_m$)의 회전각 ${\theta}_m$과 측정할 Contrast Sensitivity($C_s$)로부터 polarizer와 analyzer의 회전각(${\theta}_{max}$, ${\theta}_{min}$)을 얻었다. $${\theta}_{max}=cos^{-1}[cos{\theta}_m{\cdot}(1+C_s^{-1})^{1/2}]$$ $${\theta}_{min}=cos^{-1}[cos{\theta}_m{\cdot}(1-C_s^{-1})^{1/2}]$$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.846-853
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam with this input parameter. The rockfill material properties for parametric study were obtained from the results of large scale triaxial tests on 34 rockfill materials in the 22 different sites. From the statistical analysis on these data, some statistical characteristics of rockfill material properties such as property range, distribution characteristics, and correlation between the properties were investigated. based on these characteristics, 27 property combinations were constituted by Latin Hypercube sampling method. Dam crest displacements after construction, impounding, and earthquake loading were evaluated by static and dynamic numerical analysis on each combination. From the sensitivity analysis, it was found that the crest displacement of CFR type dam was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the settlement and horizontal displacement of dam crest logarithmically decreased as the shear modulus increased and the difference between the maximum value and the minimum vale amounted to about 9.5 times in case of settlement and about 10 times in case of horizontal displacement.

• 방송공학회논문지
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• 제21권4호
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• pp.506-514
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• 2016

본 연구에서는 HEVC로 인코딩된 스트림을 6MHz 대역폭 DVB-T2 시스템을 통해서 전송하는 우리나라 지상파 4K-UHD 실험방송 환경에서, 상용 수신기 3종에 대해서 양시청 최소 신호 대 잡음비(ToV C/N)와 양시청 수신기 최소 입력 전계 레벨(Sensitivity)을 실험실 테스트를 통해서 측정하였다. 26.37Mbps 전송률을 기준으로, ToV 평균 C/N=18.8dB 정도로 측정되었고, 수신기 Sensitivity는 최소 -84.2dBm에서 최대 -80.0dBm으로 측정되었다. 이로부터, 수신기 노이즈 바닥(Floor)은 평균 -100dBm 가량으로 계산되었다.