• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.396.1-396.1
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• 2014

백색 유기발광소자는 빠른 응답속도, 높은 색재현율 및 높은 색안정성의 특성으로 차세대 친환경 백색 광원으로 많은 주목을 받고 있다. 유기발광소자와 양자점을 혼합하여 사용한 백색 유기발광소자는 양자점의 높은 색순도와 고효율의 장점을 가지고 있기 때문에 연구가 활발하게 진행되고 있다. 녹색 및 적색 양자점을 색변환층으로 이용한 백색 유기발광소자는 두 양자점의 혼합 비율에 따라 연색성 및 색안정성이 변화하기 때문에 이에 관련 된 연구가 필요하다. 본 연구에서는 높은 색안정성을 가지는 백색 유기발광소자를 제작하기 위해 청색 유기발광소자 위에 용액 공정으로 녹색 및 적색 빛을 방출하는 CdSe/ZnS 양자점을 포함하는 색변환층을 도포했다. 녹색 및 적색 양자점은 250 nm부터 500 nm의 넓은 광 흡수대역을 가지고 있기 때문에 465 nm의 청색 발광소자의 빛을 흡수하여 각각 적색과 녹색 발광을 할 수 있다. 녹색 및 적색 양자점의 혼합 비율에 따른 광발광 스펙트럼 측정 결과를 통해 녹색 및 적색 양자점의 최적 혼합 비율이 7:3임을 확인하였다. 최적의 혼합 비율을 사용하여 제작 된 백색 유기발광소자의 전기적 및 광학적 특성을 전류-전압 측정과 전계발광 측정으로 비교 분석하였다. 9 V에서 14 V로 전압이 변화하는 동안 백색 유기발광소자의 색좌표의 변화는 (0.35, 0.33)에서 (0.35, 0.32)로 높은 색안정성을 나타냈다. 본 연구 결과는 유기발광소자와 양자점을 혼합하여 사용한 백색 유기발광소자의 높은 색안정성에 대한 기초자료로 활용할 수 있다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.19-26
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• 2006

The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern for the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle area of the underground storage cavern. Based on the blast-induced nitration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the adjacent ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.479-484
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• 2005

The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle part of the underground storage cavern. Based on the blast-induced vibration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the nearest ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.181-191
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• 1997

Before cables are constructed, tower of suspension bridge is behaved as a cantilever type. Buffeting occured by unsteady loading of the tower due to velocity fluctuation in the oncoming flow has a wind velocity consistent with fundamental frequency of the tower and may give rise to large response by the tower resonance. To reduce the dynamic response by buffeting, the behavior of tower with TMD(Tuned Mass Damper) has studied using finite element method in time domain. The buffeting was obtained by transforming the velocity spectrum in frequency domain to random variable in certain time domain. The most probable maximum displacement which can be occured during the time interval was obtained using peak factor. The optimum location for TMD installation and TMD specification were decided by parametric study. Also, the effect of vibration control about various wind velocity was studied by the TMD which has optimum specification and location.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.23-32
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• 2004

The local geologic and dynamic site characteristics, which include soil profiles, shear wave velocity profiles and depths to the bed rock were gathered from 148 sites all over the Korean peninsula and those values are compared to those in the western USA. Site response analyses were performed based on equivalent linear scheme using design rock-outcrop acceleration of 0.154g which corresponds to the collapse level of earthquake for seismic category I structure. The results show that the amplification factor based on Korean seismic design guideline underestimates the motion in short-period range and overestimates the motion in mid-period range. It is suggested that the existing Korean seismic guideline based on UBC is required to be modified considering dynamic site characteristics in Korea for the reliable estimation of site amplification.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.67-77
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• 2007

Site coefficients in IBC and KBC codes have some limits to predict the rational seismic responses of a structure, because they take into account only the effect of the soil amplification without the effects of the structure-soil interaction. In this study, upper and lower limits of the site coefficients are estimated through the pseudo 3-D elastic seismic response analyses of structures built on the linear or nonlinear soil layers taking Into account the effects of the structure-soil interaction. Soil characteristics of site classes of A, B and C were assumed to be linear, and those of site classes of D and E were done to be nonlinear and the Ramberg-Osgood model was used to evaluate shear modulus and damping ratio of a soil layer depending on the shear wave velocity of the soil layer, Seismic analyses were performed with 12 weak or moderate earthquake records scaled the peak acceleration to 0.1g or 0.2g and deconvoluted as earthquake records at the bedrock located at 30m deep under the outcrop. With the study results of the elastic seismic response analyses of structures, new standard response spectrum and upper and lower limits of the site coefficients of $F_{a}\;and\;F_{v}$ at the short period range and the period of 1 second are suggested including the effects of the structure-soil interaction, and new site coefficients for the KBC code are also suggested.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.35-44
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• 2006

Reflective semiconductor optical amplifiers(R-SOAs) were designed with high gain, wide optical bandwidth, high thermal reliability and wide modulation bandwidth in TO-can package for the transmitter of wavelength division multiplexed-passive optical network(WDM-PON) application. Double trench structure and current block layer were introduced in designing the active layer of R-SOA to enable high speed modulation. The injection power requirement and the viable temperature range of WDM-PON system are experimentally analysed in based on Amplified Spontaneous Emission(ASE)-injected R-SOAs. The effect of the different injection spectrum in the gain-saturated R-SOA was experimentally characterized based on the measurements of excessive intensity noise, Q factor, and BER. The proposed spectral pre-composition method reduces the bandwidth of injection source below the AWG bandwidth and thereby avoids spectrum distortion impeding the intensity noise reduction originated from the amplitude squeezing.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.135-145
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• 2019

The slope collapse can be classified into internal and external factors. Internal factors are engineering factors inherent in the formation of slopes such as soil depth, slope angle, shear strength of soil, and external factors are external loading such as earthquakes. The external factor for earthquake can be expressed by various values such as peak ground acceleration (PGA), peak ground velocity (PGV), Arias coefficient (I), natural period (T_p), and spectral acceleration (S_aT=1.0). Specially, PGA is the most typical value that defines the magnitude of the ground motion of an earthquake. However, it is not enough to consider the displacement in the slope which depends on the duration of the earthquake even if the vibration has the same peak ground acceleration. In this study, numerical analysis of two-dimensional plane strain conditions was performed on engineered block, and slope responses due to seismic motion of scaling PGA to 0.2 g various event scenarios was analyzed. As a result, the response of slope is different depending on the presence or absence of sliding block; it is shown that slope response depend on the seismic wave triggering sliding block than the input motion factors.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.203-218
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• 2010

The site categorization and corresponding site amplification factors in the current Korean seismic design guideline are based on provisions for the western United States (US), although the site effects resulting in the amplification of earthquake ground motions are directly dependent on the regional and local site characteristic conditions. In these seismic codes, two amplification factors called site coefficients, $F_a$ and $F_v$, for the short-period band and midperiod band, respectively, are listed according to a criterion, mean shear wave velocity ($V_S$) to a depth of 30 m, into five classes composed of A to E. To suggest a site classification system reflecting Korean site conditions, in this study, systematic site characterization was carried out at four regional areas, Gyeongju, Hongsung, Haemi and Sacheon, to obtain the $V_S$ profiles from surface to bedrock in field and the non-linear soil properties in laboratory. The soil deposits in Korea, which were shallower and stiffer than those in the western US, were examined, and thus the site period in Korea was distributed in the low and narrow band comparing with those in western US. Based on the geotechnical characteristic properties obtained in the field and laboratory, various site-specific seismic response analyses were conducted for total 75 sites by adopting both equivalent-linear and non-linear methods. The analysis results showed that the site coefficients specified in the current Korean provision underestimate the ground motion in the short-period range and overestimate in the mid-period range. These differences can be explained by the differences in the local site characteristics including the depth to bedrock between Korea and western US. Based on the analysis results in this study and the prior research results for the Korean peninsula, new site classification system was developed by introducing the site period as representative criterion and the mean $V_S$ to a depth of shallower than 30 m as additional criterion, to reliably determine the ground motions and the corresponding design spectra taking into account the regional site characteristics in Korea.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.65-71
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• 2001

The nuclear power plant(NPP) should be shut down for inspection and tests prior to a return to power if the earthquake exceeds the operating basis earthquake(OBE). The OBE at the plant is considered to have been exceeded if the computed cumulative absolute velocity(CAV) from the earthquake record is greater than 0.16g-sec. However, the CAV criterion should be determined considering the seismic and structural characteristics of the plant. An experimental study using shaking table is conducted in this study to evaluate intensity of CAV criterion. Appropriate level of CAV is evaluated based on the test results using the developed seismic damage indicator(SDI) model. The model consists of stacked acrylic cylinders and is developed to behave consistently for each directional seismic load. The result of the experimental study in dicates that the CAV criterion of 0.16g-sec is conservative enough to be applied to Korean NPPs since the CAV value of the seismic input motion of the Korean standard NPPs ranges from 0.3 to 0.5 g-sec. The developed SDI is expected to be useful not only in easily determining OBE exceedance but also in evaluating earthquake damage quantitatively to provide guidelines for better post-shutdown inspection and test.