• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.113-119
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• 2022

In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

• Journal of the Korea Institute of Building Construction
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• v.21 no.3
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• pp.181-188
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• 2021

In this study, the various performance of dry cement mortar for Korean floor heating system depending on water-to-dry mortar ratios (W/DM) applied in project site was evaluated. According to the experiment conducted, the importance of mixing water for dry cement mortar was revealed by resultant performance or quality of the dry cement mortar for floor finishing by changing W/DM controlled in project site by workers. As the general trend, the flow was increased, and the unit volume weight was decreased with increasing W/DM. Additionally, compressive strength and drying shrinkage were significantly influenced by W/DM. Hence, it can be stated that the adding water for dry cement mortar should be managed precisely since excessively increased W/DM for workability improvement can cause performance degradation of floor mortar with the failures such as excessive bleeding, and severe segregation during the fresh state. As a summary of the study, to achieve a desirable performance of dry cement mortar, approximately 20 % of W/DM can be suggested to be managed in project site.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.663-672
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• 2022

The purpose of this study is to evaluate the magnesium sulfate resistance of a geopolymer mixed with rice husk powder. General concrete, silica fume mixed concrete, and binary blended geopolymer were selected as comparison targets to confirm the magnesium sulfate resistance, and sulfate deterioration was calculated using the compressive strengths with ages. In addition, the weight change rate and the relative dynamic coefficient of the geopolymer were comparatively analyzed, and the degree of etteringite formation was confirmed using X-ray diffraction analysis. the experiment, the geopolymer mixed with 10% rice husk powder showed 10.8% higher compressive strength than concrete with silica fume when submerged for 56 days. Also, the geopolymer mixed with rice husk powder showed a small weight change rate of 0.9 to 1.45%. composition after immersion in magnesium sulfate through X-ray diffraction analysis, it was observed that a small amount of ettringite was dispersed in the geopolymer containing rice husk powder. Thus, there is a high correlation with the corrosion resistance of magnesium sulfate

• Science of Emotion and Sensibility
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• v.26 no.2
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• pp.103-116
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• 2023

This study aims to investigate the interaction between inward bias and canonical viewpoint, which are factors known to affect preference for meaningful objects. It also considered the familiarity of each entity in terms of their influence on the existence of a canonical viewpoint and demonstrated whether the relative strength of two preferences varies depending on familiarity. To confirm this, we conducted a behavior experiment using a two-alternative forced-choice task. The experimental stimuli were eight single objects for familiarity level (high/low), whereas the entity's inward bias and canonical viewpoint were observed or violated. Results showed that when inward bias was obeyed, the frequency of being chosen as a preferred option was higher, and the reaction time for preference judgment was shorter. However, the observation of a canonical viewpoint did not affect frequency and reaction time. Moreover, familiarity played an interference role in aesthetic judgment. These results indicate that inward bias is stronger than canonical viewpoint, ultimately implying that a single object's interaction with the visual context is superior to the entity's attribute as regards to preference judgment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.260-269
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• 1986

This experiment was conducted to investigate the effect of mulching materials on the emergence rate, root dry weight and grain weight of sesame using variety Poong Nyun Ggae and also their effects on physical properties of soil, evapotranspiration and weed growth on the respective plots were studied. The effect of soil water holding capacity at mulching with polyethylene film and straw increased 5.4%, 2.8% to non-mulched plot respectively. The maximum soil temperature was raised up to 4$^{\circ}C$ by applying clear film and was dropped down to 7$^{\circ}C$ by straw. The minimum soil temperature was raised up to 2$^{\circ}C$ by clear film and was dropped down to 3$^{\circ}C$ by straw. In the early stage, the soil physical properties of clear film mulching were better than those of non mulching, and so was in emergence rate. In the late stage, soil strength was high at non mulching, and soil porosity, soil aeration and water infiltration rate were high at film and straw mulchings. Total root dry weight was great at clear film mulching, and root dry weight was concentrated mainly in the upper 10 cm of soil profile. The amount of weeds collected was the least at black film mulching. There were of little difference in evapotranspiration among treatments. The grain yield of sesame was increased to 57% by polyethylene film and 25% by straw mulching.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.251-260
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• 2023

The construction of free-form structures with intricate curved exteriors necessitates the use of bespoke molds. To fulfill this requirement, a blend of Phase Change Material(PCM) and Ultra-High Performance Concrete(UHPC) is utilized. PCM endows the solution with recyclability, while UHPC facilitates the effortless execution of curvature in the mold fabrication process. However, it's worth mentioning that the melting point of PCM hovers around 58-64℃, and the heat emanating from UHPC's hydration process can potentially jeopardize the integrity of the PCM mold. Hence, experimental validation of the mold shape is a prerequisite. In the conducted experiment, UHPC was poured into two distinct mold types: one that incorporated a 3mm silicone sheet mounted on the fabricated PCM mold(Panel A), and the other devoid of the silicone sheet(Panel B). The experimental outcomes revealed that Panel A possessed a thickness of 3.793mm, while Panel B exhibited a thickness of 5.72mm. This suggests that the mold lacking the silicone sheet(Panel B) was more susceptible to the thermal effects of hydration. These investigations furnish invaluable fundamental data for the manufacturing of ultra-high strength irregular panels and PCM molds. They contribute substantially to the enrichment of comprehension and application of these materials within the realm of construction.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.17-30
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• 2009

Underground construction such as tunneling can induce damages on the surrounding rock mass, due to the stress concentration of in situ stresses and excessive energy input during construction sequence, such as blasting. The developed damage on the rock mass can have substantial influence on the mechanical and hydraulic behaviors of the rock masses around a tunnel. In this study, investigation on the generation of damage around an opening in a jointed rock model under biaxial compression condition was conducted. The joint dip angles employed are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made using early strength cement and water. From the biaxial compression test, initiation and propagation of tensile cracks at norm to the joint angle were found. The propagated tensile cracks eventually developed rock blocks, which were dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The development of the tensile crack can be explained under the hypothesis that the rock segment encompassed by the joint set is subjected to the developing moment, which can be induced by the geometric irregularity around the opening in the rock model. The experiment results were simulated by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

• The Korean Journal of Franchise Management
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• v.8 no.4
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• pp.7-19
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• 2017

Purpose - The purpose of this study is to investigate the effect of model attractiveness on brand attitude and purchase intention, and examine whether product-model match-up plays a moderating role in the relationship between model attractiveness and brand attitude and purchase intention. The model attractiveness is consist of psychological and physical attractiveness of the model. The authors investigate how product-model match-up influence the strength of the relationship between model attractiveness - brand attitude and purchase intention. The purpose of this is to test whether product-model match-up influence the form and effectiveness of a model attractiveness on brand attitude and purchase intention and suggest the effective and efficient methods in the model selection strategies to increase advertising effectiveness based on the results of this study. Research design, data, and methodology - The experimental design for this study was the between subject design based on 2 group of the psychological attractiveness(high vs. low) × product-model match-up(high vs low) and 2 group of the physical attractiveness(high vs. low) × product-model match-up(high vs low). And a preliminary investigation was conducted to develop experimental stimuli through manipulation check to enhance the external validity of experimental research. The attractiveness of the model and product-model match-up are independent variables and manipulative variables in presentation of experimental stimuli. The self-administered methode experiment was conducted on 300 subjects in four groups constructed according to the independent variables. Result - The findings provide partial support for a moderator for product-model match-up on the model attractiveness - brand attitude and purchase intention. First, the influence of psychological attractiveness and physical attractiveness on brand attitude and purchase intention was shown significant. Also, it was found that the average value of brand attitude and purchase intention according to psychological attractiveness was significantly higher than the average value of brand attitude and purchase intention according to physical attractiveness in additional analysis. Second, the average value of brand attitude and purchase intention were higher when product - model match-up was high in both high and low psychological attractiveness and physical attractiveness of the model. However, in the case of psychological attractiveness, the correlation effect with product - model match-up was significant, but in the case of physical attractiveness, it was not significant. Conclusions - The results of this study suggest that the attractiveness factor should be considered in selecting the ad model by verifying the effect of the attractiveness of the model on the advertising effect. In particular, this study has great significance both academically and practically in terms of suggesting such implications that the advertising effect of psychological attractiveness and physical attractiveness may be different depending on the product type by additional analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.25-32
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• 2023

In this study, a double wall system is introduced, which was invented to simplify the complicated manufacturing process of the existing precast concrete (PC) double wall systems and to remove defects such as laitance that may occur during the production of concrete panels. An experimental study was conducted to investigate the tensile resisting capacity of the steel tube which is embedded in the precast concrete panel to keep the spacing between PC panels and to prevent damage of the PC panels during transportation and casting concrete onsite. The experiment was planned to determine the detail of effective steel tube connection considering the steel plate treatment method according to the formation of the opening, the presence of embedded concrete, and the reinforcement welding for additional dowel action as key variables. As a result, the ultimate tensile strength increased by 20-30% compared to the control specimen (ST) except for the steel tube specimen (ST_CP) which has steel plates bent inward at the end part of the steel tube. Since the specimen (ST_CON) filled with concrete inside the control specimen has no additional process and cost for the steel tube connections compared to the control specimen during the production of the developed double wall system, it is determined to be the appropriate detail of steel tube connection.