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Flexural fatigue life analysis of unsaturated polyester-methyl methacrylate polymer concrete
Yeon, Kyu-Seok,Choi, Yoon-Sang,Kim, Kwan-Kyu,Yeon, Jung Heum Elsevier 2017 Construction and Building Materials Vol.140 No.-
<P><B>Abstract</B></P> <P>Laboratory and statistical evaluations were performed to examine the flexural fatigue performance of unsaturated polyester-methyl methacrylate (UP-MMA) polymer concrete. Target stress levels were 0.9, 0.8, 0.7, and 0.6 with a fixed stress ratio of 0.1. A 5Hz sinusoidal load with a constant-amplitude frequency was applied to a prismatic specimen (100×100×400mm) using a 250-kN universal testing machine (UTM). MMA contents considered were 0, 10, 20, and 30wt.%. In addition, the two-parameter Weibull distribution was employed to analyze the fatigue life probability distributions of UP-MMA polymer concrete. Three different analysis methods—the graphical method, method of moment, and method of maximum likelihood estimation—were applied to estimate the distribution parameters of the two-parameter Weibull distribution. The results have shown that the two-parameter Weibull distribution describes the fatigue life probability distributions of UP-MMA polymer concrete with quite high statistical correlation coefficients. Also, the goodness-of-the-fit of the fatigue life data obtained was verified by means of the Kolmogorov-Smirnov test, which were all accepted at a 5% significance level. Finally, a single-log fatigue equation was derived to predict the fatigue life of UP-MMA polymer concrete.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Laboratory evaluations were performed to examine the flexural fatigue behavior of UP-MMA polymer concrete. </LI> <LI> A two-parameter Weibull distribution was used to analyze the fatigue life probability distributions. </LI> <LI> The goodness-of-the-fit of the fatigue life data was verified by means of the Kolmogorov-Smirnov test. </LI> <LI> A single-log fatigue equation was derived to predict the fatigue life of UP-MMA polymer concrete. </LI> </UL> </P>
Effect of In Vivo Embryo Production and Embryo Transfer Following Superovulation in Hanwoo
Sang-Rae Cho,Sun-Ho Choi,ChangYong Choe,Jun-Kyu Son,Soo-Ho Choi,Young-joo Kim,Poongyeon Lee,Yeoung-Gyu Ko,Sung-Heum Yeon,Jin-Woo Jung,Sung-Jae Kim,Yeon-Sub Jung,Nan-Hee Bok,Hyun-Jong Kim,Dong-Soo Son 한국동물생명공학회(구 한국동물번식학회) 2010 발생공학 국제심포지엄 및 학술대회 Vol.2010 No.1
Sang-Rae Cho,Kuldeep Kumar,Seong-Heum Yeon,Sung-Hwan Lee,Ui-Hyung Kim,Ki-Yong Chung,Hyeon-Shup Kim,Myeung Sik Lee,Chang-Seok Park,Byoung-Chul Yang 한국수정란이식학회 2014 한국동물생명공학회지 Vol.29 No.4
The present study was performed on farm animals to test the effectiveness of progesterone-releasing intravaginal device (Cue-Mate® 1.56 g) and injection of prostaglandin F2α (PGF2α) for synchronization estrus in Hanwoo cattle. The cattle were at random stage of the estrus cycle. The cows were artificially inseminated at day 7 after Cue-Mate withdrawal, using commercial semen from Korean native bulls. There was a season effect on the estrus synchronization rate. It was higher in spring (94.3%) followed by winter (93.3%), autumn (90.4%) and summer (67.2%). In summary, The results of this study revealed that season has influences on estrus behavior of cattle with no significant effect on pregnancy rate. In summary, we suggest summer reproductive management to alleviate the effects of heat stress. It should be based on intensive cooling combined with hormonal treatment. Given that different subgroups of cows benefit differently from the treatments, selective hormonal administration should be considered.
Yeon, Pyung-Heum,Yoon, Young-Suk,Oh, Se-Woung,Nam, Sang-Ho,Par, Yong-Nam Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.8
The technique of an on-line preconcentration by the direct sulfide precipitation has been developed. Sn was homogeneously precipitated by sulfide, which was generated in situ from the hydrolysis of thioaceteamide. Precipitate was collected on a filter in the line and dissolved out instantaneously by KOH to be sent to an ICP. The enrichment factor was 4 with the sampling speed of 15/hr for 1.0 mL of sample. It was increased to more than 40 times when the sampling volume was increased to 10 mL with the sampling speed of 5/hr. $Sn^{2+}/Sn^{4+}$ could be separately determined with the on-line precipitation technique. The method was applied to the analysis of NIST SRM 1566 Oyster sample and yielded good agreement with the certified value.
Remodeling of Deteriorated Irrigation Aqueducts Using Precast Polymer Concrete Flume
Yeon, Kyu Seok,Kawakami, Makoto,Choi, Yoon Sang,Hwang, Jin Yong,Min, Seung Ho,Yeon, Jung Heum Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.687 No.-
<P>This study is designed to review the causes and modes of deterioration in irrigation aqueducts constructed with reinforced concrete, and introduce existing rehabilitation and new remodeling methods. As a result, because of the typical nature of irrigation aqueducts that are exposed to severe natural environment, the causes and modes of deterioration were more complex and diverse than other concrete structures. Also, due to the thinner cross sectional thickness of the structure, conducting a rehabilitation work was turned out to be difficult. As an active method for settling this problem, this study developed a method to remove the entire flume, upper structure of aqueduct, and replace with a precast flume constructed with polymer concrete. A loading test was performed using full-scale specimens, and then the suggested remodeling method was implemented in the actual field structures. The investigation showed that the suggested remodeling method was appropriate to secure the sustainability.</P>
Hyun, Sang-Hoon,Yeon, Jung Heum Elsevier 2012 Construction and Building Materials Vol.37 No.-
<P><B>Abstract</B></P> <P>In this study, the effects of curing temperature, age, and unsaturated polyester (UP)-methyl methacrylate (MMA) ratio on the strength development characteristics of UP-MMA based polymer concrete are investigated. This study distinguishes itself from previous research in that MMA monomer was used to adjust the viscosity of UP resin, instead of styrene monomer. The result showed that as the curing temperature decreased from 20 to −20°C, the strengths were reduced by 32.8% on average. Also, research revealed that the UP-MMA based polymer concrete significantly develops its strengths within the first 6h, and the average strength at 72h was 86.6% of the strength at 168h. As the MMA content increases, the strengths of UP-MMA based polymer concrete tended to decrease. However, the effect of MMA on the strength reduction was less significant than that of curing temperature. Also, this study proposes a strength predictive model based on the maturity concept. The result of regression analysis between the measured strengths and computed maturity yielded high coefficients of determination of 0.91–0.97, validating the applicability of the maturity model suggested by Ohama. The findings of this study could be utilized as important data for field applications as well as manufacturing of precast products.</P> <P><B>Highlights</B></P> <P>► Effects of curing temperature, age, and unsaturated polyester (UP)-methyl methacrylate (MMA) ratio on strengths were examined. ► The strengths were reduced by 32.8% on average as the curing temperature decreased from 20 to −20°C. ► The strengths significantly developed within the first 6h. ► The strengths tended to decrease as the MMA content increases. ► This study proposed strength predictive models based on maturity concept.</P>