Nylon 6/Polyvinylalcohol 복합체의 비등온 결정화속도

박연흠,김연상 成均館大學校 科學技術硏究所 1988 論文集 Vol.39 No.1

The non-isothermal crystallization Kinetics of Nylon 6 from the blends of Nylon 6 and poiyvinylalcohol has been investigated by using differential scanning calorimetry. Avrami equation has been employed to analyze the non-isothermal crystallization behavior. By the addition of polyvinylalcohol the crystallization rate of Nylon 6 has been retarded and the crystallinity decreased. Rapid cooling or heating rates increase the crystallization rate due to the athermal nucleation. Avrami exponent n for non-isothermal crystallized samples was found to be in the range of 2.0∼2.3.

電導性 Polyvinylidene fluoride/Polyacrylonitrile/Polypyrrole 複合體 필름의 製造와 電氣的 性質

朴然欽,金連相,南成祐 成均館大學校 科學技術硏究所 1989 論文集 Vol.40 No.1

Electrically conducting PVDF/PAN/poly(pyrrole) composite r s have teen prepared by polymerizing pyrrole vapor in PVDF/PAN composite films impregnated with ferric chloride as an oxidant. As polymerization of pyrrole proceeds, poly(pyrrole) has been observed as uniform continuous phase in PVDF/PAN composites. The electrical conductivities of composite films reach in the range of 10^-3∼10^-2S/cm and the stability of conductivity to the ambient air exposure is excellent. The formation of poll (pyrrole) in PVDF/PAN composites has induced increasing disorder in host composite matrix and increased the tensile elongation.

Comparative Study on the Elastic Modulus of Polymer Concrete

Yeon, Kyu Seok,Kim, Kwan Kyu,Kim, Chul Young,Yeon, Jae Heum Trans Tech Publications, Ltd. 2015 Advanced materials research Vol.1129 No.-

<P>Polymer concrete is used for a wide range of precast structural applications and repair works for existing infrastructures. For these applications, one of the key mechanical propertiesthatneed to be consideredis the elastic modulus. In this study, the relationship between elastic modulus and compressive strength of polymer concrete made with three different types of resin (i.e., unsaturated polyester resin, acrylic resin, and epoxy resin) is comprehensively investigated using data sets available from previous studies in order to develop a prediction equation for elastic modulus that can be generally applied to polymer concrete. Results showed that the equation developed under this study can be reasonably adopted for the predictions of polymer concrete's elastic modulus as a function of compressive strength because the prediction equation has a high goodness of fit asrepresented by a R<SUP>2 </SUP>value of 0.77</P>

Continuous Preconcentration of Sn²⁺/Sn⁴⁺ by the On-line Sulfide Precipitation-Dissolution

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.

孔子之心論

( Yeon Jae-heum ) 성균관대학교 유교문화연구소 2005 儒敎文化硏究(中文版) Vol.5 No.-

The core of Confucius' philosophy system is "mercy". However, the basic order system of Confucius is no longer functioning as it should, and the world is in an increasingly confusing situation. Therefore, in this article, the author wanted to correct the situation by suggesting a compassionate value system. Confucius did not give specific explanations and definitions about the meaning of human mind. Confucius considers the system of mercy based on people's inner moral consciousness and moral feelings. From the point of view of “your own mercy,” we can see that we have the strength and the will to execute moral principles within ourselves. In terms of self-discipline, learning, and harmony, the accumulation of knowledge is based on the cognitive function of the mind. From this, it can be seen that in the Confucian philosophical system, "mind" performs two main functions: morality and cognition. It developed into a theoretical system based on the Confucian mind through Mencius and Shunxi's thoughts.

Preconcentration of Cd by Continuous Hydroxide Precipitation-Dissolution in Atomic Emission Spectrometry

Yeon,Pyung Heum,Pak,Yong-Nam,Huh,Girl 한국교원대학교 환경과학연구소 2000 환경연구논문집 Vol.- No.5

On-line preconcentration by direct precipitation with hydroxide has been developed and applied for the analysis of Cd in Inductively Coupled Plasma Atomic Emission Spectrometry. Cadmium is continuously precipitated with hydroxide and dissolved by nitric acid in on-line mode. Currently, the enrichment factor is more than 90 times for 20.0 mL of sample and could be further increased very easily. For large sample throughput, 1.0 mL of sample loop is used and the enrichment factor is 4.5 with the sampling speed of 15/hr. The method has been applied to the analysis of NIST reference sample and has yielded good results with the certified value

Potential applications of phase change materials to mitigate freeze-thaw deteriorations in concrete pavement

Yeon, Jung Heum,Kim, Kwan-Kyu Elsevier 2018 Construction and Building Materials Vol.177 No.-

<P><B>Abstract</B></P> <P>A study was performed to evaluate the feasibility of using phase change materials (PCMs) to mitigate freeze-thaw deteriorations in concrete pavements. The approach taken in this paper was to reduce the expected number of freeze-thaw cycles by harnessing the latent heat of fusion of a paraffin-based organic PCM with a phase transition temperature of 4.5 °C (N-Tetradecane). To ensure stable and proper functioning of PCM in mortar, the PCM was coated with tiny melamine-formaldehyde resin shells using a microencapsulation technique. A preliminary study verified successful thermal storage/release functions of the PCM microencapsulated with a melamine-formaldehyde resin. Thermal response tests showed that the low-transition temperature PCM has a promising potential to extend the service life of concrete pavements against freeze-thaw deteriorations even though its effect became minimal with prolonged exposure to ambient temperature far below the transition temperature. A microencapsulated PCM (mPCM) inclusion was found to negatively affect the compressive and flexural strengths or mortar, whereas the volume stability at early ages was rather enhanced in the presence of mPCM.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Potential applications of PCM to mitigate frost damage in concrete pavement were examined. </LI> <LI> Paraffin-based organic PCM microencapsulated with melamine-formaldehyde resin was used. </LI> <LI> The mPCM reduced the magnitude of temperature drop by releasing stored heat upon solidification. </LI> <LI> The mPCM inclusion negatively affected the mechanical properties of cement mortar. </LI> </UL> </P>

Coefficient of Thermal Expansion of Polymer Concrete with Different Polymeric Binders

Yeon, Kyu Seok,Kim, Kwan Kyu,Kim, Chul Young,Yeon, Jae Heum Trans Tech Publications, Ltd. 2015 Advanced materials research Vol.1129 No.-

<P>The coefficient of thermal expansion (CTE) is one of the material factors affecting the behavior of concrete structures. This study reports the typical range of CTE for polymer concrete with different types of polymeric binder based on extensive literature surveys. The results revealed the CTE of polymer concrete generally fell between 12.5 and 28.6 x 10<SUP>-6</SUP>/°C, which is about twice or three times higher than that of ordinary cement concrete, because the CTE of polymeric binder is much larger than that of cementitious binders. The findings of this study will provide useful information for the design and analysis of polymer concrete members and repair components.</P>

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>

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>