PET의 절연파괴와 공간전하효과

金永煜,신추연,김인수,윤성도 군산대학교 1993 群山水産專門大學 硏究報告 Vol.28 No.1

This paper examined the existance behavior of charged particles by measuring polarity inversion current Thermally Stimulate Current (TSC) and analyed appearance mechanism of polarity inversion current peak and also investigated relation between ionic space charge formation and dielectric breakdown by measuring D.C breakdown impulse breakdown D.C-impulse superposition as a sample of PET. As a result, we found that dielectric breakdown is likely to happen due to ionic space charge at the transient state when applied polarity inversion voltage and that charged partion of TSC peak at the high temperature was the same as that of polarity inversion current. Also there was no effect on ionic space charge about the dielectric breakdown in stationary state when applied D.C voltage.

Effect of Loading Frequency on Small-Strain Shear Modulus of Soils

Yun Wook Choo,Dong Soo Kim 한국지반공학회 2010 international journal of geo-engineering Vol.2 No.3

The effects of loading frequency on small-strain shear modulus of various types of soils were investigated by using resonant column (RC) and torsional shear (TS) tests. Both RC and TS tests were performed with a same piece of equipment, eliminating variability due to preparing "identical" samples. Tested soils include washed mortar sand, ten compacted subgrade soils, and 37 undisturbed natural soils. Frequency effect was investigated at small strain where the effect of the number of loading cycles is negligible. Loading frequency has almost no effect on the stiffness of the washed mortar sand. The stiffness of undisturbed natural soils and compacted subgrade soils increase linearly as a function of the logarithm of loading frequency, and the effect of loading frequency was quantified. The frequency effect on undisturbed natural soils varies from 0.15% to 9.15% per log cycle of loading frequency and that of compacted subgrade soils ranges from 4.5% to 8.4%. The frequency effect on the natural sandy soils is not negligible but the value is less than 3.5%. The frequency effect of undisturbed natural soils was well correlated with index properties such as the plasticity index, void ratio, and water content, and it increases as each index property increases. The frequency effect on natural sandy soils was difficult to correlate with soil index properties and is affected by the characteristics of fine particles included in the soils.

Numerical Studies on Piled Gravity Base Foundation for Offshore Wind Turbine

Choo, Yun Wook,Seo, Ji-hoon,Kim, Young-Nam,Goo, Jeong-min,Kim, Young-ho Taylor Francis 2016 Marine georesources & geotechnology Vol.34 No.8

<P>This study aims to investigate a hybrid gravity base foundation to support offshore wind tower. A new hybrid gravity base foundation considered in this study has five component piles, referred to as 'piled gravity base foundation'. The three-dimensional finite element analyses were carried out for the piled gravity base foundation subjected to a combined load with a lateral load and overturning moment. The parametric analyses were undertaken varying the loading height and direction, the rigidity of the piled gravity base foundation, the field soil layers, and the clay strength. Overall, the response of the piled gravity base foundation was significantly influenced by the interaction between the cone base piles and the surrounding soil. The increased strength of the soil led to a significant reduction of the pile and gravity base foundation responses, in terms of the bending moments, axial forces, lateral displacements, and rotations.</P>

Experimental Development of the p-y Relationship for Large-Diameter Offshore Monopiles in Sands: Centrifuge Tests

Choo, Yun Wook,Kim, Dongwook American Society of Civil Engineers 2016 Journal of geotechnical and geoenvironmental engin Vol.142 No.1

<P>The validity of using the existing numerical p-y methods [American Petroleum Institute (API) and Reese methods] for the design of offshore wind turbines' large-diameter monopiles in sands is questionable, as many researchers have raised concerns related to the diameter effects in p-y models. This study presents the development of experimental p-y relationships for large-diameter monopiles in dense sands based on results from centrifuge tests exhibiting a softer monopile behavior than those proposed by the API and Reese methods. The effect of socketing the tip of a pile in rock bearing layers was also investigated. The initial gradients of the p-y relationships in dense sand layers were shown to become significantly stiffer as the depth reaches the much stiffer and stronger rock-bearing layer. The lateral load-displacement curves obtained based on the developed experimental p-y relationships were found to be well matched with the measured lateral load-displacement curves; therefore, it was concluded that the developed experimental p-y relationships reasonably predict the lateral responses of large-diameter monopiles.</P>

Development of a New Asymmetric Anchor Plate for Prefabricated Vertical Drain Installation via Centrifuge Model Tests

Choo, Yun Wook,Kim, Jae-Hyun,Park, Hyun-Il,Kim, Dong-Soo American Society of Civil Engineers 2013 Journal of geotechnical and geoenvironmental engin Vol.139 No.6

배수 조건에 따른 사질토 지반의 동적 변형특성

추연욱(Yun Wook Choo),김동수(Dong Soo Kim) 한국지반공학회 2005 한국지반공학회논문집 Vol.21 No.3

원심모형시험을 이용한 필댐 취약부 모니터링

추연욱(Choo Yun Wook),조성은(Cho Sung Eun),신동훈(Shin Dong Hoon) 대한토목학회 2012 대한토목학회논문집 C Vol.32 No.2

본 연구에서는 필댐을 위한 모니터링 기술에 적용할 수 있는 물리량으로 간극수압, 온도와 전기저항을 선정하였고, 이를 원심모형시험 상에서 계측할 수 있는 시스템을 구축하였다. 또한 코아형 필댑 모형 단면을 설계하고, 코아죤에 취약부가 없는 정상적인 경우, 코아죤 하부에 부분적인 위약부가 발생한 경우, 코아죤 하부에 취약부가 커져서 상하류 사력죤이 연결되는 경우를 포함하여, 총 세가지 모형을 제작하고, 원심모형시험을 수행하였다. 원심력장이 작용하는 조건에서, 담수시에 나타나는 침추 흐름의 변화에 따라 간극수압, 온도 및 전기저항의 변화를 모니터링하였다. 원심모형시험을 통하여, 간극수압, 온도 및 전기저항의 변화가 취앾ㄱ부 존재에 따라 다르게 나타나는 것을 확인 할 수 있었고, 간극수압, 온도와 전기 저항이 필댐의 내부 취약부를 탐지하기 위한 모니터링 기술 개발에 적용될 수 있음을 확인하였다. In this study, three centrifuge tests were performed to evaluate the feasibility of three physical quantities for detecting internal defect of earth core fill dam: pore water pressure, temperature, and electrical resistance. For this purpose, the measurement system for pore water pressure, temperature and electrical resistance on centrifuge model dams was established. Three centrifuge tests included a fill dam without internal defect and two other dams with artificial internal defect in the core. The effectiveness of seepage monitoring was examined during the centrifuge test. Test results showed the applicability of monitoring techniques to detect internal defect by monitoring pore water pressure, temperature, and electrical resistance.

조밀한 모래지반에 설치된 해상풍력 석션기초의 스커트길이에 따른 지진하중시 거동특성

추연욱(Yun Wook Choo),Leonardo Olalo,배경태(Kyung-Tae Bae) 한국해안해양공학회 2016 한국해안해양공학회 논문집 Vol.28 No.4

본 연구는 해상풍력지지구조물로 적용되는 석션기초의 지진하중에 대한 동적거동 분석을 목적으로 하였다. 이를 위하여 동적원심모형실험을 수행하였다. 석션기초의 스커트길이는 외력에 대한 지지거동에 중요한 역할을 한다. 스커트길이/석션기초외경 비가 0.5, 0.75, 1의 3가지 석션기초 모형이 조밀한 모래지반에 설치된 경우에 대하여 동적원심모형실험 결과를 제시하였다. 실험결과로 스커트길이에 따른 석션기초에서의 가속도증폭특성, 잔류침하량, 잔류회전각을 비교하였다. This study aims to analyze seismic responses of suction foundations for offshore wind turbine. For this purpose, dynamic centrifuge model tests were carried out. The skirt length of the suction foundation is a critical element for bearing mechanism against environmental loads. Thus, dynamic centrifuge model tests were performed and analyzed for three suction foundation models with the ratios of skirt length to suction foundation diameter of 0.5, 0.75, and 1 installed in dense sand. As results, the acceleration amplification at the suction foundation, residual settlement, and residual tilting angle were compared.

The Growth Performance, Carcass Characteristics, and Meat Quality of Egg-Type Male Growing Chicken and White-Mini Broiler in Comparison with Commercial Broiler (Ross 308)

Yun Kyung Choo,Sung Taek Oh,Kyung Woo Lee,Chang Won Kang,Hyun Wook Kim,Cheon Jei Kim,Eun Jib Kim,Hee Sung Kim,Byoung Ki An 한국축산식품학회 2014 한국축산식품학회지 Vol.34 No.5

The present study was conducted to compare the growth performance, carcass characteristics, and meat quality of the eggtype male growing chicken (EM), white-mini broiler (WB), and commercial broiler (Ross 308, CB). A total of 360 1-d-old chicks were reared together using a completely randomized design with 4 replicates for each group under the identical feeding and rearing conditions. The ADG and gain:feed were the highest in CB, intermediate in WB, and the lowest in EM (p< 0.05), and the live and carcass weights of CB and EM were significantly higher than those of WB (p<0.05). The pH of breast meat from WB and CB was significantly higher (p<0.05) than that from EM with a similar body weight. The EM had the lowest moisture (p<0.05) and the highest protein content (p<0.05), whereas the fat and ash contents were not different among groups. The mystiric acid (C14:0), palmitoleic acid (C16:1 ω7), and oleic acid (C18:1 ω9) levels were significantly higher in breast meat from CB (p<0.05). The monounsaturated fatty acid (MUFA) content showed the highest (p<0.05) levels in CB. In contrast, the polyunsaturated fatty acid (PUFA) contents of breast meat, including linoleic acid (C18:2 ω6) and arachidonic acid (C20:4 ω6), were higher (p<0.05) in EM and WB than in CB. In conclusion, the EM and WB had less growth performances in comparison with CB, but they each had some unique features (taste, flavor, and physiological characteristics) when raised under the identical rearing and feeding conditions.

Natural radon reduction rate of the community groundwater system in South Korea

Yun, Uk,Seong Kim, Tae,Kim, Hyun Koo,Kim, Moon Su,Cho, Soo Young,Choo, Chang Oh,Cho, Byong Wook Elsevier 2017 Applied radiation and isotopes Vol.126 No.-

<P><B>Abstract</B></P> <P>Tank waters from 13 Community Groundwater Systems (CGS) showed average radon reduction rate of 26.5% (varying from −17.9% to 63.3%). When applying the reduction rate of 26.5% to the nationwide CGS, the percentage of CGS having radon level above 100Bq/L decreases from 28.8% to 22.0%. The natural radon reduction method would be applied to the CGS having radon level slightly exceeding guideline of WHO, as an alternative for aeration or GAC.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We measured radon contents of groundwater and tank water from 13 villages in Korea. </LI> <LI> The natural reduction rates of radon range from -17.9% to 63.3% (average of 26.5%). </LI> <LI> When applying the average natural reduction rate of 26.5% to the nationwide CGS. </LI> <LI> Percentage of CGS having radon level above 100 Bq/L decreases from 28.8% to 22.0%. </LI> </UL> </P>