• Fibers and Polymers
• /
• v.6 no.1
• /
• pp.6-12
• /
• 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
• /
• v.12 no.3
• /
• pp.541-560
• /
• 2017

In this research, experimental and numerical simulations were adopted to investigate the effects of ligament angle on compressive strength and failure mode of rock-like material specimens containing two non-coplanar filled fissures under uniaxial compression. The experimental results show that with the increase of ligament angle, the compressive strength decreases to a nadir at the ligament angle of $60^{\circ}$, before increasing to the maximum at the ligament angle of $120^{\circ}$, while the elastic modulus is not obviously related to the ligament angle. The shear coalescence type easily occurred when ${\alpha}$ < ${\beta}$, although having the same degree difference between the angle of ligament and fissure. Numerical simulations using $PFC^{2D}$ were performed for flawed specimens under uniaxial compression, and the results are in good consistency with the experimental results. By analyzing the crack evolution process and parallel bond force field of rock-like material specimen containing two non-coplanar filled fissures, we can conclude that the coalescence and propagation of crack are mainly derived from parallel bond force, and the crack initiation and propagation also affect the distribution of parallel bond force. Finally, the displacement vectors in ligament region were used to identify the type of coalescence, and the results coincided with that obtained by analyzing parallel bond force field. These experimental and numerical results are expected to improve the understanding of the mechanism of flawed rock engineering structures.

• Geomechanics and Engineering
• /
• v.36 no.2
• /
• pp.121-130
• /
• 2024

Many foundation projects are built on red-bed soft rocks, and the damage evolution of this kind of rocks affects the safety of these projects. At present, there is insufficient research on the damage evolution of red-bed soft rocks, especially the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation. Therefore, based on the dual-porosity characteristics of pores and fissures in soft rock, we adopted a cellular automata model to simulate the propagation of these voids in soft rocks under an external load. Further, we established a macro-mesoscopic damage model of red-bed soft rocks, and its reliability was verified by tests. The results indicate that the relationship between the number and voids size conformed to a quartic polynomial, whereas the relationship between the damage variable and damage porosity conformed to a logistic curve. The damage porosity was affected by dual-porosity parameters such as the fractal dimension of pores and fissures. We verified the reliability of the model by comparing the test results with an established damage model. Our research results described the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation and provided a theoretical basis for the damage evolution of these rocks.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1993.06b
• /
• pp.99-118
• /
• 1993

• Archives of Craniofacial Surgery
• /
• v.18 no.2
• /
• pp.89-91
• /
• 2017

Background: The superior orbital fissure is a small area that connects the middle cranial fossa and the orbit. Many studies have measured the size of the superior orbital fissure. However, there is no standard value for the size of the superior orbital fissure. Therefore, we conducted this study to provide the average size of the superior orbital fissure in Korean adults. Methods: We measured the widths of the superior orbital fissures of 142 patients using computed tomography scans. Because the width of the superior orbital fissure varies at different locations, we measured the superior orbital fissure width at the level of the optic canal. Results: In the males, the width of the superior orbital fissure on both sides was $3.79{\pm}0.93mm$, and these values were $3.79{\pm}0.96mm$ for the left side and $3.783{\pm}0.92mm$ for the right side. In the females, the widths of the superior orbital fissures were $3.62{\pm}1.35mm$ on the left side, $3.69{\pm}1.18mm$ on the right side, and $3.65{\pm}1.26mm$ across both sides. Conclusion: There were no significant differences between the males and females or between the left and right sides. The present study suggests that we may accept the hypothesis that a congenitally narrow superior orbital fissure may be a risk factor for the superior orbital fissure syndrome. Surgeons should take precaution with patients who have narrow superior orbital fissures during the perioperative period.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 1995.03a
• /
• pp.121-134
• /
• 1995

대수층의 수리상수를 산출하기 위한 양수시험 분석에 이용되는 가장 기본적인 이론은 Theis 이론이다. Theis 이론에서는 지하수의 흐름은 2차원의 방사상 흐름이다. 그러나, 1차 공극으로 이루어진 충적층 대수층이나 사암과 같은 다공질 대수층과는 달리 기반암내에 발달되어 있는 균열 대수층은 균열(fractures), 열극(fissures) 또는 단층과 같은 2차 공극으로 이루어져 있다. (중략)

• Journal of KIISE:Software and Applications
• /
• v.31 no.3
• /
• pp.276-292
• /
• 2004

In this paper. we present methods that extract lung regions from chest EBT(electron beam tomography) images then segment the extracted lung region into lung lobes. We use histogram based thresholding and mathematical morphology for extracting lung regions. For detecting pulmonary fissures, we use edge detector and knowledge-based search method. We suggest this edge detector, which uses adaptive filter scale, to work very well for real edge and insensitive for edge by noise. Our experiments showed about 95% accuracy or higher in extracting lung regions and about 5 pixel distance error in detecting pulmonary fissures.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.28 no.3
• /
• pp.504-511
• /
• 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 Korean Ophthalmic Optics Society
• /
• v.2 no.1
• /
• pp.25-30
• /
• 1997

The palpebral fissures of 1529 healthy Koreans ranging in age from one month to 92 years were examined. The length and width of palpebral fissure, distance of folded upper lid(FUL), inter outer canthal distance(IOCD) and appearance of double upper lid (DUL) were studied. The most commonly occuring length of the normal palpebral fissure was 30 mm(13.7%) followed by 28 mm(9.8%) and 27 mm(8.8%), and almost four fifths(79.1%) of the palpebral fissures measured less than 30mm in length. Of the ages 11~60 examined over 70 % averaged palpebral fissures measuring bet ween 27 mm and 32 mm. The commonest width of 1443 normal palpebral fissure was 8 mm(28.2%) followed by 9mm(16.3%) and 7mm(15.0%), and average widths according to 5 major age groups were 5~8mm, 6~10mm, 7~11mm, 7~11mm and 5~9mm, and there is some tendency to a decrease with age. The average of FUL without frontalis action was 8~11 mm. The distances between exocanthions, IOCD, according to age groups were estimated to be 77~82mm for one to 10, 94~101mm for 11 to 60 and 89~95mm for over-60 age group, respectively. The DUL was appeared in 44 % of sample, and DUL in female was more than in male.

• Journal of the Mineralogical Society of Korea
• /
• v.17 no.3
• /
• pp.189-199
• /
• 2004

Cretaceous sedimentary rocks bearing dinosaur tracks in the Goseong interchange area were studied for their conservation and public display in the aspect of applied mineralogy. Black clay layers alternate with silt layers in the sedimentary rocks. The verical and horizontal fissures are commonly filled with calcite veinlets, supergenetic iron and manganese oxides. The rocks are composed of quartz, albite, K-feldspar, calcite, chlorite, illite, muscovite, and biotite, with minor apatite and rutile. Silt layers are relatively rich in calcite and albite, whereas clay layers are abundant in quartz, illite, and chlorite. Al, Fe, Mg, K, Ti, and P are enriched in the clay layers, while Ca, Na, and Mn in silt. Most of trace elements including V, Cr, Co, Ni, Cs, Zr, REE, Th, and U are enriched in clay layers. Inorganic carbon are present in silt layers as calcite, while organic carbon in black clay layers. The black clay layers were partly altered to yellow clay layers along the fissures, simultaneously with the decrease of organic carbon. Selective exfoliation of clay-rich black and yellow clay layers, calcite matrix of silt layers and calcite infillings of fissures are estimated as the major weakness potentially promoting chemical and physical degradation of the track-bearing rock specimens.