• Corrosion Science and Technology
• /
• v.13 no.1
• /
• pp.20-27
• /
• 2014

The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of inner steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, multiple mortar test specimen(W/C:0.4) with six types having different cover thickness each other was prepared and was immerged in seawater solution for five years to evaluate the effect of cover thickness and immersion years to corrosion property of embedded steel bar. And the polarization characteristics of these embedded steel bars was investigated using electrochemical methods such as measuring corrosion potential, cathodic polarization curve, and cyclic voltammogram. At the beginning of immersion, the corrosion potentials exhibited increasingly nobler values with increasing cover thickness. However, after immersed for 5 years, the thicker cover of thickness, the corrosion potentials shifted in the negative direction, and the relationship between corrosion potential and cover thickness was not in good agreement with each other. Therefore, it is considered that the thinner cover of thickness, corrosive products deposited on the surface of the embedded steel bar plays the role as a resistance polarization which is resulted in decreasing the corrosion rate as well as shifting the corrosion potential in the positive direction. As a result, it seemed that the evaluation which corrosion possibility of the reinforced steel would be estimated by only measuring the corrosion potential may not be a completely desirable method. Therefore, it is suggested that we should take into account various parameters, including cover thickness, passed aged years as well as corrosion potential for more accurate assessment of corrosion possibility of reinforced steel which is exposed to partially or fully in marine environment for long years.

• Journal of the Korean Applied Science and Technology
• /
• v.40 no.3
• /
• pp.476-483
• /
• 2023

This study aimed to analyze the effects of athletic career and competition participation frequency on exercise commitment of women university taekwondo athletes. Study subjects were 20 women university taekwondo athletes. Athletic career and competition participation frequency was assessed by 4-points scale and the higher points indicate the higher level of each variables. Exercise commitment was assessed by Exercise Commitment Scale. The assessment consists of a total of 8 questions, 4 of which are action immersion and 4 of cognitive immersion, and is evaluated using a 5-point Likert scale. The higher the score, the higher the level of exercise commitment. As the results, positive relationship showed both correlation and casual relationship analysis between competition participation frequency and exercise commitment. Negative casual relationship (-) showed between athletic career and exercise commitment. These results indicated that the increase of competition participation frequency affects the exercise commitment and the longer of athletic career indicates the decrease the level of exercise commitment. Thus, to improve the exercise commitment of women university taekwondo athletes, the competition participation frequency and athletic career should be considered.

• Elastomers and Composites
• /
• v.40 no.3
• /
• pp.166-173
• /
• 2005

Effect of thermal aging on the weight loss and water absorption of epoxy adhesives was investigated in the presence of three types of different hardeners, such as D-230, G-5022, and HN-2200. Thermal and mechanical properties of the cured epoxy resins were also studied througth the glass transition temperature and shear adhesion strength measurements. Weight losses of DGEBA/D-230 and DGEBA/HN- 2200 systems were not varied. However, the weight of DGEBA/G-5022 system was significantly decreased with increasing the thermal aging time. The water absorption of the specimens was increased as the thermal aging time increased except that using G-5022. DEGBA/HN-2200 system showed higher $T_g$ value than those of other systems, due to the formation of the fine three-dimensional network structure containing aliphatic ring. Shear adhesion strength of all systems was increased with increasing the thermal aging tine, which is attributed to increased degree of cure and fine three-dimensional network structure formation. And $T_g$ values and shear adhesion strength of all specimens exposed to water was decreased as the immersion time increased.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.2
• /
• pp.180-185
• /
• 2004

Conventional ultrasonic examination to detect micro and small surface cracks is based on the pulse-echo technique using a normal immersion focused transducer with high frequency, or an angle-beam transducer generating surface waves. It is difficult to make an automatic ultrasonic system that can detect micro and small surface cracks and position in a large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of the transducer. In this study, a high-precision scanning acoustic microscope with a 10MHz large-aperture transducer has been used to assess the existence, position and depth of a surface crack from the real-time A, B, C scans obtained by exploiting the ultrasonic diffraction. The ultrasonic method with large aperture transducer has improved the accuracy of the crack depth assessment and also the scanning speed by ten times, compared with the conventional ultrasonic methods.

• Journal of Korea Multimedia Society
• /
• v.17 no.1
• /
• pp.104-112
• /
• 2014

With recent development of virtual reality technology, coupled with the growth of the marine industry, virtual underwater simulation systems are under development in various studies, for educational purposes and to simulate virtual reality experiences. Current literature indicates many underwater simulation systems to date have focused on the quality of visual stimulus delivered through three-dimensional graphics user interface, limiting the reality of the experience. In order to improve the quality of the reality delivered by such virtual simulations, it is crucial to develop multi-sensory technology rather than focus on the conventional audio-visual interaction, which limits experiencer from the sense of underwater immersion and existence within the simulation. This work proposes the immersive multi-sensory effector system, delivering the users with a more realistic underwater experience. The sense of reality perceived was evaluated, as the main factor of the virtual reality system.

• Parasites, Hosts and Diseases
• /
• v.51 no.2
• /
• pp.155-163
• /
• 2013

This study aimed to evaluate the efficacy of fructose-1,6-bis phosphate aldolase (SMALDO) DNA vaccination against Schistosoma mansoni infection using different routes of injection. The SMALDO has been cloned into the eukaryotic expression vector pcDNA3.1/V5-His TOPO-TA and was used in injecting Swiss albino mice intramuscularly (IM), subcutaneously (SC), or intraperitoneally (IP) ($50{\mu}g/mouse$). Mice vaccinated with non-recombinant pcDNA3.1 served as controls. Each group was immunized 4 times at weeks 0, 2, 4, and 6. Two weeks after the last booster dose, all mice groups were infected with 80 S. mansoni cercariae via tail immersion. At week 8 post-infection, animals were sacrificed for assessment of parasitological and histopathological parameters. High anti-SMALDO IgG antibody titers were detected in sera of all vaccinated groups (P<0.01) compared to the control group. Both the IP and SC vaccination routes resulted in a significant reduction in worm burden (46.2% and 28.9%, respectively, P<0.01). This was accompanied by a significant reduction in hepatic and intestinal egg counts (41.7% and 40.2%, respectively, P<0.01) in the IP group only. The number of dead eggs was significantly increased in both IP and IM groups (P<0.01). IP vaccination recorded the highest significant reduction in granuloma number and diameter (54.7% and 29.2%, respectively, P<0.01) and significant increase in dead miracidia (P<0.01). In conclusion, changing the injection route of SMALDO DNA vaccination significantly influenced the efficacy of vaccination. SMALDO DNA vaccination via IP route could be a promising protective and antipathology vaccine candidate against S. mansoni infection.

• Corrosion Science and Technology
• /
• v.13 no.6
• /
• pp.214-223
• /
• 2014

Interest in the durability assessment and structural performance has increased according to an increase of concrete structures in salt damage environment recent years. Reliable way ensuring the most accelerated corrosion test is a method of performing the rebar corrosion monitoring as exposed directly to the marine test site exposure. However, long-term exposure test has a disadvantage because of a long period of time. Therefore, many studies on reinforced concrete in salt damage environments have been developed as alternatives to replace this. However, accelerated corrosion test is appropriate to evaluate the critical chlorine concentration in the short term, but only accelerated test method, is not easy to get correct answer. Accuracy of correlation acceleration test depends on the period of the degree of exposure environments. Therefore, in this study, depending on the concrete mix material, by the test was performed on the basis of the composite degradation of the salt damage, and investigate the difference of corrosion initiation time of the rebar, and indoor corrosion time of the structure, of the marine environment of the actual environments were inuestigated. The correlation coefficient was derived in the experiment. Long-term exposure test was actually conducted in consideration of the exposure conditions submerged zone, splash zone and tidal zone. The accelerated corrosion tests were carried out by immersion conditions, and by the combined deterioration due to the carbonation and accelerated corrosion due to wet and dry condition.

• Food Science of Animal Resources
• /
• v.31 no.3
• /
• pp.428-435
• /
• 2011

This study was conducted to investigate the effect of immersion treatment using lactic acid (LA) and sodium benzoate (SB) on the physicochemical quality and freshness of spent hen breast meats. A total of 135 spent hen breast meats were subjected to 9 different treatments using various concentrations of LA and/or SB in sterile DW. The 9 treatment groups were as follows: Control, sterile DW without LA or SB; T1, 1% LA; T2, 2% LA; T3, 4% LA; T4, 1% LA and 0.1% SB; T5, 2% LA and 0.1% SB; T6 2% LA and 0.2% SB; T7, 2% LA and 0.4% SB; T8, 4% LA and 0.2% SB, respectively. All groups were kept at 4oC for 15 d. The microbial counts in the control group gradually increased during storage, but those for the treated groups were significantly lower than the control or were not detected. The pH values of the control were significantly higher than those of the treated groups (p<0.05). In the color measurements, the lightness ($L^*$) and yellowness ($b^*$) values increased during storage and the redness ($a^*$) values decreased (p<0.05). The K-value and volatile basic nitrogen of the treated groups were significantly lower than those of the control group (p<0.05). Overall, the combined results of this study indicate that LA and SB could be used as favorable preservatives for spent hen breast meats to extend their shelf-life during refrigerated storage.

• Journal of Broadcast Engineering
• /
• v.25 no.5
• /
• pp.685-697
• /
• 2020

Immersive media videos, such as panorama and 360-degree videos, must provide a sense of realism as if the user visited the space in the video, so they should be able to represent the reality of the real world. However, in panorama and 360-degree videos, objects appear to overlap or disappear due to parallax between cameras, and such parallax distortion may interfere with immersion of the user's content. Accordingly, although many video stitching algorithms have been proposed to overcome parallax distortion, parallax distortion still occurs due to the low performance of the Object detection module and limitations of the Seam generation method. Therefore, this paper analyzes the limitations of the existing video stitching technology and proposes a method for detecting and correcting parallax distortion of video stitching using the LDPM (Local Differential Pixel Mean) image evaluation method that overcomes the limitations of the video stitching technique.

• Journal of dental hygiene science
• /
• v.23 no.4
• /
• pp.271-281
• /
• 2023

Background: This study aims to improve dental hygiene education by investigating the relationship between metacognition, learning flow, and problem-solving abilities in dental hygiene majors. Methods: A survey was conducted on 2nd to 4th-year students from dental hygiene programs, with 132 responses analyzed. Data analysis involved t-tests and ANOVA to examine the differences in metacognition, learning flow, and problem-solving abilities based on the general characteristics. Multiple regression analysis was employed to investigate the factors influencing the dependent variable, which is problem-solving abilities. The collected data were analyzed using SPSS. Results: First, when comparing metacognition, learning flow, and problem-solving abilities based on the general characteristics of the study participants, statistically significant differences were observed in common factors such as major satisfaction, subjective academic performance, GPA (grade point average), and reason for major choice (p<0.05). Second, it was found that there is a significant positive correlation between metacognition, learning flow, and problem-solving abilities in dental hygiene students (r≥0.79, p<0.05). In other words, higher levels of metacognition and learning flow were associated with better problem-solving abilities. Third, factors influencing problem-solving abilities were identified, with both metacognition and learning flow having a statistically significant positive impact. It was also noted that metacognition had a greater influence on problem-solving abilities compared to learning flow (adjusted R²=0.815, p<0.05). Conclusion: To enhance the core competency of problem-solving abilities, it is essential to improve metacognition and learning flow. To enhance metacognition and promote learning flow, strategies such as goal setting, utilizing effective learning methods, boosting self-efficacy, managing the learning environment, choosing activities that foster immersion, stress management, self-assessment and feedback integration, improving focus, and utilization a variety of learning experiences will be necessary.