• Fibers and Polymers
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• v.6 no.1
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• pp.6-12
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• 2005

Fiber surface morphologies and associated internal structures are closely related to its properties. Unlike other fibers including cotton, bast fibers possess transverse nodes and fissures in cross-sectional and longitudinal directions. Their morphologies and associated internal structures were anatomically examined under the scanning electron microscope. The results showed that the morphologies of the nodes and the fissures of bast fibers varied depending on the construction of the inner fibril cellular layers. The transverse nodes and fissures were formed by the folding and spiralling of the cellular layers during plant growth. The dimensions of nodes and fissures were determined by the dislocations of the cellular layers. There were also many longitudinal fissures in bast fibers. Some deep longitudinal fissures even opened the fiber lumen for a short way along the fiber. In addition, the lumen channel of the bast fibers could be disturbed or disrupted by the nodes and the spi­rals of the internal cellular layers. The existence of the transverse nodes and fissures in the bast fibers could degrade the fiber mechanical properties, whereas the longitudinal fissures may contribute to the very rapid moisture absorption and desorption.

• Geomechanics and Engineering
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• v.42 no.5
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• pp.333-345
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• 2025

With the continuous expansion of urban construction land and the development and utilization of underground space, the conflict between ground fissures, which are widely developed in urban areas, and urban construction has become increasingly prominent. It has become a particularly prominent geological problem in urban construction, seriously affecting the planned construction of urban buildings and the safe service of the entire life cycle of existing infrastructure. Based on the principle of limit equilibrium, the calculation formulas of soil pressure, internal force and lateral displacement of the isolation wall are derived, and the variation laws of soil pressure and lateral displacement of the isolation wall under different wall parameters and soil parameters are analyzed, and the applicability of the theoretical formula was verified through numerical simulation. On this basis, taking the ground fissures site of Beijing Capital International Airport as an example, and a disaster mitigation method for Beijing Capital International Airport ground fissure settlement deformation based on rigid isolation walls was proposed. Research shows that the soil pressure of the isolation wall above the intersection point of the ground fissure and the isolation wall is distributed in a triangular pattern, and below the intersection point, it is distributed in a trapezoidal pattern, the analytical solution and the numerical solution have the same changing trend, the soil pressure at any depth obtained by the analytical solution is always greater than that of the numerical solution, which is approximately 1.11 times. With the increase of the thickness of isolation wall, the soil pressure of isolation wall gradually increases and the lateral displacement gradually decreases. When the wall thickness increases from 0.5m to 1.5m, the maximum soil pressure value increases by 5.62% and the lateral displacement at the top decreases by 8.62%, at the bottom increases by 22.7%. When the wall thickness increased from 1.5 m to 2.5 m, the maximum soil pressure decreased by 1.16%, the lateral displacement at the top increased by 4.3%, and the lateral displacement at the bottom decreased by 15%. The soil pressure and lateral displacement of the isolation wall gradually decrease with the increase of the elastic modulus and Poisson's ratio of the soil, when the elastic modulus of the soil increases by 1.2 times, the soil pressure exerted on the retaining wall decreases by 42.02%, when the Poisson's ratio of the soil increases 0.05, the soil pressure exerted on the retaining wall decreases by 29.3%. The soil pressure and lateral displacement of the isolation wall are minimally affected by the elastic modulus of the wall, only about 1%. The disaster mitigation method based on the uneven settlement deformation of ground fissures caused by isolation wall can alleviate the ground fissures disaster at Beijing International Airport, with the increase in the active dislocation amount of ground fissures, the soil pressure, lateral displacement and bending moment of the isolation wall increase. The research results will deepen the understanding of the disaster reduction mechanism of ground fissures and provide theoretical support for the design of ground fissures disaster reduction and prevention.

• Journal of the Korean Society of Safety
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• v.39 no.4
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• pp.8-14
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• 2024

This work presents a failure analysis for a boiler water-wall tube. The causes of failure were investigated using various methods, such as visual inspection, chemical analysis, optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The fractured tubes exhibited little wall thinning on the outside and the fire-facing sides when the thicknesses of the tube walls were taken. Upon visual inspection, lamination lines were observed in the middle of the fracture surface. The line was located at the center between the brittle fracture region of the inner part and the ductile fracture region of the outer part. All material-specification-related requirements were satisfied, given the chemical composition of the tube material. Micro-fissures were observed along the grain boundary in the inner part of the tube near the fracture and crack. Although the micro-fissures were far from the fracture crack, they were still visible in the decarburized layer of the inner surface of the tube. Therefore, it can be concluded that hydrogen damage was the cause of the fracture in the water-wall tube.

• Geomechanics and Engineering
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• v.43 no.5
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• pp.405-417
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• 2025

Rock fracture is a process of energy accumulation and subsequent release, in which rock mass strength significantly influences this process. This study investigates the energy release and evolution of failure mechanisms in models with different compressive strengths through uniaxial compression tests, acoustic emission techniques, and digital image correlation. The experimental results indicate that during the yielding stage, there is a notable increase in the number of small-scale failures in the models. The failure of the models, initially dominated by shear failure, progressively involves more tensile cracks. Before global instability occurs, significant horizontal relative displacement and localized surface deformation are observed at the pre-existing fissures. As the strength decreases, the models tend to exhibit a larger number of small-scale failures, and the failure mechanism shifts toward a composite shear-tensile mode.

• Journal of the Korean Academy of Pediatric Dentistry
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• v.34 no.1
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• pp.106-121
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• 2007

The purpose of this study was to examine the effects of suggested etching method on the performance of pits and fissures sealant. In the first part, seventy extracted sound human permanent third molars and premolars were used. The teeth were randomly divided and performed in three different groups as follows : conventional etching, enameloplasty, and testing group. Non-pumicing, dye-guidance vigorous brushing-start etching technique was applied on the occlusal of testing group. Then the pit and fissure sealant was applied on all of the specimens. After the thermocycling and immersing in 1% methylene blue, the resin embedded sections were made. The microleakage data on the section were then recorded under the stereoscope and statistic analysis was done. Additional experiments were also performed : direct fissure surface etched pattern experiment, replica study, and micro-shear bond strength testing observation. The second part included two groups. A paired study was designed to evaluate the influence the environment has on the performance of the sealant. After etching, half of each occlusal surface received one of the two following treatments in succession: sealing in laboratory and intraoral condition (group 1), sealing in intraoral condition with and without a single-bonding agent (group 2). The results of present study can be summarized as follows: - The microleakage of testing group was significant different with conventional method (P<.05) and was not different with the enameloplasty group (P>.05). - The quality and quantity of etched enamel were improved. - Microshear bond strength of testing group was higher than control group (p<.05). - The environmental condition was influenced on the performance of the sealant. The testing etching method modified the capacity of the etching agent to penetrate into the pits and fissures, and simultaneous enhance their efficiency in vitro condition.

• Journal of the Korean Academy of Pediatric Dentistry
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• v.28 no.3
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• pp.504-511
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• 2001

Preventive resin restoration, extended concept of occlusal pit and fissure sealing, is procedure composed of as follows. Cavity preparation is limited to areas of initial caries The cavity is then restored with composite resin, while other sound pits and fissures are sealed with pit and fissure sealant. If pit and assure sealant with which microrestoration is possible is used, it may be of great benefit to both patient and operator in case of difficult-to-control children s treatment. However study on preventive resin restoration using this kind of materials have been scarce. The purpose of this study was to compare the microleakage of four different modes of preventive resin restoration. Restoration using only composite resin was compared together Fifty-five bicuspids were prepared with small class I cavity preparation on the occlusal surface, divided into the following groups and restored accordingly. Group 1 : Cavity was restored with Z-100 composite resin Group 2 : Cavity was restored with Z-100 composite resin. Pits and fissures were then sealed with Teethmate F-1 Group 3 : Cavity was restored with Z-100 composite resin Pits and fissures were then sealed with Ultraseal XT-plus Group 4 : Cavity and pits and fissures were restored with Ultraseal XT-plus altogrether Group 5 : Cavity was restored with Ultraseal XT-plus. Pits and fissures were then sealed with the same material. After restoration, the samples were thermocycled 500 times between $5^{\circ}C$ and $55^{\circ}C$ with a dwell time of 30 seconds. After thermocycling, the samples were dipped into 1% methylene blue solution for 24 hours, then rinsed with tap water. The teeth were then embedded in resin and cut buccolingually along the tooth axis and observed with a stereomicroscope to determine the degree of microleakage. The results were as follows : 1. Group 4 showed the greatest microleakage, while group 3, showed the least. The mean microleakage decreased in the following order:4>1>5>2>3. 2. There was no stastically significant difference between group 1 and group 5(p>0.05). However, group 1 showed significantly greater microleakage compared to group 2 and 3(p<0.05) Group 1 showed significantly less microleakage compared to group 4(p<0.05). 3. Group 2 showed no statistically significant difference compared to group 3(p>0.05). However group 2 showed significantly less microleakage compared to group 4 and 5(p<0.05) 4. Group 3 showed significantly less microleakage compared to group 4 and 5(p<0.05). 5. Group 5 showed significantly less microleakage than group 4(p<0.05).

• Journal of the Korean Academy of Pediatric Dentistry
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• v.32 no.3
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• pp.472-480
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• 2005

The purpose of this study was to investigate the effective penetration methods of acid etching agents in the pit and fissures on the occlusal surface. Extracted maxillary first and second premolars were divided into 4 groups : to Group I only acid etching agent was applied, to Group II ultrasonic scaler as well as acid etching agent were applied, to Group III after fissurotomy acid etching agent was applied, and to Group IV after fissurotomy the same process performed with Group II. The comparison between the 4 groups by the use of scanning electron microscope showed the results as follows : 1. Comparing each groups with regard to the penetration rate(%) of acid etching agents, Group III and Group IV showed improved penetration rate(%) compared with Group I. Group II made no significant different results from Group I, but had somewhat better penetration rate(%). 2. Comparing each groups with regard to the penetration rate(%) of acid etching agents according to regions within fissures, Group III and Group IV showed more improved penetration rate than Group I in the mesial pit and distal pit. However, no significant difference between each groups was showed in the middle fissure.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.307-319
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• 2023

Ground fissures have a huge effect on the integrity of surface structures. In high-intensity ground fissure regions, however, land resource would be wasted and city building and economic development would be limited if the area avoiding principle was used. In view of this challenge, to reveal the seismic response and seismic failure characteristics of ground fissure sites, a shaking table test on model soil based on a 1:15 scale experiment was carried out. In the test, the spatial distribution characteristics of acceleration response and Arias intensity were obtained for a site exposed to earthquakes with different characteristics. Furthermore, the failure characteristics and damage evolution of the model soil were analyzed. The test results indicated that, with the increase in the earthquake acceleration magnitude, the crack width of the ground fissure enlarged from 0 to 5 mm. The soil of the hanging wall was characterized by earlier cracking and a higher abundance of secondary fissures at 45°. Under strong earthquakes, the model soil, especially the soil near the ground fissure, was severely damaged and exhibited reduced stiffness. As a result, its natural frequency also decreased from 11.41 Hz to 8.05 Hz, whereas the damping ratio increased from 4.8% to 9.1%. Due to the existence of ground fissure, the acceleration was amplified to nearly 0.476 m/s², as high as 2.38 times of the input acceleration magnitude. The maximum of acceleration and Arias intensity appeared at the fissure zone, which decreased from the main fissure toward both sides, showing hanging wall effects. The seismic intensity, duration and frequency spectrum all had certain effects on the seismic response of the ground fissure site, but their influence degrees were different. The seismic response of the site induced by the seismic wave that had richer low-frequency components and longer duration was larger. The discrepancies of seismic response between the hanging wall and the footwall declined obviously when the magnitude of the earthquake acceleration increased. The research results will be propitious to enhancing the utilizing ratio of the limited landing resource, alleviation of property damages and casualties, and provide a good engineering application foreground.

• Journal of the Korean Academy of Pediatric Dentistry
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• v.27 no.1
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• pp.40-44
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• 2000

The purpose of study was to measure the interrater reliability of the newly developed caries diagnostic instrument, Diagnodent(KaVo, Germany), using a new laser fluorescence techinique. One hundred and three extracted human premolars and molars were examined by Diagnodent, three times for fissures and five times for smooth surfaces. There was no significant difference among the three fissure means, but two combinations showed significant differences among the five smooth surface means. Correlation coefficients of Pearson and Spearman were all above 0.9(P<0.01). The $\alpha$ values from reliability analysis were 0.9980 or 0.9981 for fissures and 0.9992 for smooth surfaces.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.25 no.4
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• pp.70-79
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• 2012

Background and Objective : Bowen's disease is a type of an in situ squamous cell carcinoma. Typical type of Bowen's disease present as a gradually growing well-dermarcated erythematous plaque with an irregular border and surface crusting or scaling. This case demonstrates that Bowen's disease which had a relapse during applying the topical imiquimod can be treated by herbal medicine. Methods : A 72-year-old man patient presented with a erythematous plaque on his right medial malleolar area. The diagnosis of Bowen's disease was based on the clinical features. The chief complaints were scales, fissures, crusts and dryness of skin, erythema plaque, hyperpigmentation, bleeding, tenderness on the lesion. He was treated with Mahaengeuigam-Tang for 77 days. The severity of Bowen's disease was evaluated by visible assessment to determine the end-point of clearance. Results : After the treatment, fissures, crusts and dryness of skin and bleeding, tenderness on the lesion were vanished. Scales and erythema plaque, hyperpigmentation of the lesion little remained. Conclusions : Mahaengeuigam-Tang can be used on the treatment of skin disease which has characteristics plaques and crusts of skin.