• Applied Chemistry for Engineering
• /
• v.16 no.6
• /
• pp.809-814
• /
• 2005

In this work, the thermal properties of epoxy coating system on the liner plate in the containment structure of nuclear power plants had been examined by irradiation and design basis accident (DBA) conditions. The effect of immersion in hot water on adhesion strength of the coating system had been also studied. The glass transition temperature ($T_g$) and thermal stability of ET-5290/carbon steel A 32 epoxy coating systems were measured by DSC and TGA analyses, respectively. Contact angle measurements were used to determine the effect of immersion on the surface energetics of epoxy coating system, with a viewpoint of surface free energy. Adhesion tests were also executed to evaluate the adhesion strength at interfaces between carbon steel plate and epoxy resins. As a result, it was found that the irradiation led to an improvement of internal crosslinked structure in cured epoxy systems, resulting in significantly increasing the thermal stability, as well as the $T_g$. Also, the immersion in hot water made a role in the post-curing of epoxy resins and increased the mechanical interlocking of the network system, resulting in increasing the adhesion strength of the epoxy coating system.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.4
• /
• pp.915-923
• /
• 2017

The by-products of red ginseng marc showing the improvement of health has been strongly studied because of the expectation of possibility to be used as the functional foods. This research was to investigate the extraction, separation, isolation, and evaluation of crude acidic polysaccharides related to antioxidant activity, sequently chemical structure of those products was evaluated by FT-IR and NMR. Compared with other solvents such as ethanol, methanol, propanol, acetone, and butanol, ethanol was selected. The concentration of red ginseng solution for extraction was selected as 10%(w/v) related to extraction yield(11.95%) and amount(11.8 mg/ml). In the ion exchange chromatography, aidic polysaccharides showing the highest antioxidant activity was obtained when eluted by distilled water. As results of structural analysis by FT-IR and NMR, peaks corresponding to C-O, C-O-O-, C-H, anomeric C-6, and repeated C-1 and C-6 linkages was to be presumed to be ($1{\rightarrow}6$) glycosidic linkage with the typical acidic polysaccharide.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.4
• /
• pp.65-73
• /
• 2002

It has been recognized that the damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear time history analyses, monotonic static nonlinear analyses, or equivalent static analyses with simulated nonlinear influences. Some building codes propose the capacity spectrum method based on the nonlinear static analysis(pushover analysis) to determine the earthquake-induced demand given by the structure pushover curve. These procedures are conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) systems. The purpose of this paper is to investigate the accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters. The conclusions of this study are as follows; 1) NDSM is considered as practical method because the peak deformations of nonlinear system of MDF by NDSM are almost equal to the results of nonlinear time history analysis(NTHA) for various ground motions. 2) When the results of NDSM are compared with those of NTHA. mean of errors is the smallest in case of post-yielding stiffness factor 0.1, static force by MAD(modal adaptive distribution) and unloading stiffness degradation factor 0.2~0.3.

• FLOWER RESEARCH JOURNAL
• /
• v.19 no.1
• /
• pp.68-76
• /
• 2011

This study was conducted to investigate customer taste related to satisfaction of a baby's first birthday party and re-visit of venues. General characteristics of customers were similar in male and female or the married and the unmarried. Mainstream age of respondents was from in their 20's to 30's. Among them, the number of university graduates were the largest in education level. Theoretical model was composed with seven significant variables of design style and composition and design harmony and color sense for flower decoration, accessibility, facility, service and price, satisfaction, and intention of re-visit based on the result of analysis on these factors. Exploratory factor analysis was performed using SPSS 14.0K. Structural equation modeling(SEM) for simultaneous measure of path coefficient in all casualty of study model, measurement model of AMOS 7.0 for evaluation of validity, and reliability and factor analysis method using technical statistics, frequency analysis, and Cronbach's Alpha for data analysis were used. The result of hypothesis verification showed that design style and composition was the most significant item in satisfaction of parameter and it was followed by design harmony and color sense. While service and price had positive effect on satisfaction, accessibility and facility had no relation to it. It means that the most crucial variable was a flower decoration in planning and representation of the celebration of baby's first birthday. In conclusion, the finding of this study suggests that the effective utilization of these variables will contribute to the enhancement of satisfaction affecting improvement service and price or intention of re-visit.

• Structural Engineering and Mechanics
• /
• v.50 no.5
• /
• pp.589-603
• /
• 2014

Expressions for determining the value of the impact force as reported in the literature and incorporated into code provisions are essentially quasi-static forces for emulating deflection. Quasi-static forces are not to be confused with contact force which is generated in the vicinity of the point of contact between the impactor and target, and contact force is responsible for damage featuring perforation and denting. The distinction between the two types of forces in the context of impact actions is not widely understood and few guidelines have been developed for their estimation. The value of the contact force can be many times higher than that of the quasi-static force and lasts for a matter of a few milli-seconds whereas the deflection of the target can evolve over a much longer time span. The stiffer the impactor the shorter the period of time to deliver the impulsive action onto the target and consequently the higher the peak value of the contact force. This phenomenon is not taken into account by any contemporary codified method of modelling impact actions which are mostly based on the considerations of momentum and energy principles. Computer software such as LS-DYNA has the capability of predicting contact force but the dynamic stiffness parameters of the impactor material which is required for input into the program has not been documented for debris materials. The alternative, direct, approach for an accurate evaluation of the damage potential of an impact scenario is by physical experimentation. However, it can be difficult to extrapolate observations from laboratory testings to behaviour in real scenarios when the underlying principles have not been established. Contact force is also difficult to measure. Thus, the amount of useful information that can be retrieved from isolated impact experiments to guide design and to quantify risk is very limited. In this paper, practical methods for estimating the amount of contact force that can be generated by the impact of a fallen debris object are introduced along with the governing principles. An experimental-calibration procedure forming part of the assessment procedure has also been verified.

• Geophysics and Geophysical Exploration
• /
• v.13 no.2
• /
• pp.137-143
• /
• 2010

An earthquake with local magnitude $(M_L)$ 3.7 on December 9, 2000 occurred offshore Yeongdeok area, South Korea. In case of applying Chang and Baag (2006) crustal velocity model, the epicenter is $36.4462^{\circ}N\;and\;129.9789^{\circ}E$, which belongs to the inside of the Korean Peninsula Continental Shelf. Although we use the modified model reducing crustal thickness of Chang and Baag (2006) model by 5 km considering the transition from continental crust to oceanic crust in the East Sea, the epicenter was little changed. We carried out the waveform inversion analysis to estimate focal depth and focal mechanism of this event. The focal depth is estimated to be 11 ~ 12 km. The seismic moment is estimated to be $1.0{\times}10^{15}N{\cdot}m$, and this value corresponds to the moment magnitude $(M_W)$ 3.9. The offshore Yeongdeok event including May 29, 2004 offshore Uljin one show typical thrust faulting, and the direction of P-axis is ESE-WNW. The moment magnitude estimated by the spectral analysis is 4.0, which is similar to that by the waveform inversion analysis. Average stress drop is estimated to be 3.4 MPa.

• Journal of Korean Elementary Science Education
• /
• v.40 no.3
• /
• pp.366-389
• /
• 2021

The purpose of this study is to extract the factors that compose the image of science teacher desired by elementary school students in inquiry-based instruction and analyze the structural associations between them. Factors that compose the image of science teacher desired by elementary school students in inquiry-based instruction were extracted through exploratory factor analysis (EFA). Based on the findings of EFA, the questionnaire has been further analyzed using confirmatory factor analysis (CFA). In addition, based on the factor structure identified through factor analysis, we comprehensively analyzed the image of science teacher desired by elementary school students in inquiry-based instruction. As a result of EFA, five factors were identified which compose the image of science teacher desired by elementary school students in inquiry-based instruction: namely, teaching strategy, assessment strategy, prior guidance, understanding students, learning development. The CFA results showed a relatively strong correlation between teaching strategy and learning development, teaching strategy and understanding students. As a result of a comprehensive review of students' perception of the image of science teachers in inquiry-based instruction based on the extracted factor structure, students perceived that it is important for science teachers to run inquiry-based instruction by reflecting their understanding of students. Students also perceived importantly that science teachers run inquiry-based instruction using effective teaching strategies and proper evaluation strategies.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.4
• /
• pp.169-177
• /
• 2018

Glass fiber reinforced polyester (GFRP) composites are widely used as structural materials in harsh environment such as underground pipes, tanks and boat hulls, which requires long-term water resistance. Especially, these materials might be damaged due to delamination between gelcoat and composites through an osmotic process when they are immersed in water. In this study, GFRP laminates were prepared by surface treatment of UPE (unsaturated polyester) gelcoat by vacuum infusion process to improve the durability of composite materials used in underground pipes. The composite surface coated with gelcoat was examined for surface defects, cracking, and hardness change characteristics in water-immersion environments (different temperatures of $60^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$). The penetration depth of cracks was investigated by micro CT imaging according to water immersion temperature. It was confirmed that cracks developed into the composites material at $75^{\circ}C$ and $85^{\circ}C$ causing loss of durability of the materials. The point at which the initial crack initiated was defined as the failure time and the life expectancy at $23^{\circ}C$ was measured using the Arrhenius equation. The results from this study is expected to be applied to reliability evaluation of various industrial fields where gelcoat is applied such as civil engineering, construction, and marine industry.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.8
• /
• pp.133-138
• /
• 2019

This study evaluated the tensile properties of SAPH440, a hot-rolled steel for automotive structural applications, based on GMAW lap welding, the welding current, the welding voltage, and the feed rate. Tensile tests were performed according to the joint parameters of the GMAW process, for which specimens were fabricated according to KS B ISO 9018 by lap welding. The bead appearance was observed in each condition, and the weldability was evaluated by the tensile test. Higher the welding current resulted in a deeper weld, but the tensile strength was not significantly different from when the parameter was fixed due to the fracture of the base material. When the current was higher than the voltage, as in the case of a welding current of 200 A and welding voltage of 17 V, a large amount of spatter is generated, the welding is unstable, and the welded part breaks. Higher the voltage resulted in the bead not causing defects in general, and it also affected the weldability. If the current and voltage were too low, the welding was not performed normally, and the tensile strength could not be measured. However, as the current increased, the increase of the voltage and the feed rate did not affect the tensile strength.

• Journal of Korea Technology Innovation Society
• /
• v.21 no.3
• /
• pp.1101-1126
• /
• 2018

As incipient organizations progress from formation to become larger entities, the procedures and rules that provided managerial and structural advantages in having established the organizations and promoting the growth impede the innovation and creativity vital to maintain the competitive advantage. Adopting Corporate Entrepreneurship (CE), large corporations have tried to overcome the dilemma and to sustain the innovation and creativity in order to effectively cope with harsh competitive realities. Recently, some advanced corporations are trying to enhance CE by setting up an internal venture program as a seed organization for CE. By making an in-depth analysis of the internal venture program, 'C-Lab' of Samsung that is promoting CE-related characteristics for enhancing CE, we attempt to shed light on (1) what kinds of environments should be built around the seed organization for CE (2) what are the major characteristics that should be promoted through the seed organization in relation to CE (3) What kinds of achievements can be made from the promoted characteristics (4) How the characteristics are spread over the entire organization. Based on the analysis, we suggest a generalized process in which CE can be enhanced. Since different approaches should be taken for managing the seed organization and spreading the characteristics depending on the strengths and weaknesses of a corporation, there must be the step, 'evaluation of corporate internal capabilities' in the process. We believe that each corporation can enhance CE by taking advantage of the process with reference to the C-Lab case study.