• Geomechanics and Engineering
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• v.33 no.4
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• pp.327-339
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• 2023

The expansion capacity and strength of expansive grout have a significant influence on the stress state of a supported rock mass and the strength of a grout-rock mass structure. The expansion and strength characteristics are vital in grouting preparation and application. To analyze the expansion performance and mechanical properties of expansive grout, uniaxial compressive strength (UCS) tests, expansion ratio tests, XRD, SEM, and microscopic scanning tests (MSTs) of expansive grout under different curing pressure conditions were conducted. The microevolution was analyzed by combining the failure characteristics, XRD patterns, SEM images, and surface morphologies of the specimens. The experimental results show that: (1) The final expansion ratio of the expansive grout was linear with increasing expansion agent content and nonlinear with increasing curing pressure. (2) The strength of the expansive grout was positively correlated with curing pressure and negatively correlated with expansion agent content. (3) The expansion of expansive grout was related mainly to the development of calcium hydroxide (Ca(OH)2) crystals. With an increase in expansion agent content, the final expansion ratio increased, but the expansion rate decreased. With an increase in the curing pressure, the grout expansion effect decreased significantly. (4) The proportion of the concave surfaces at the centre of the specimen cross-section reflected the specimen's porosity to a certain extent, which was linear with increasing expansion agent content and curing pressure.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.1-7
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• 2023

A set of foamed concrete specimens with different densities were prepared, and several microscopic techniques, such as scanning electron microscope (SEM) and X-ray micro-computed tomography (micro-CT) were used to characterize the foamed specimens. The pore and solid characteristics of the specimens at different ages were examined to investigate the effect of aging on the materials. The compressive strength and the thermal conductivity of the foamed specimens were also evaluated, and the relationship between the material characteristics and properties was integrated to identify the effect of density and aging on the material properties.

• Animal Systematics, Evolution and Diversity
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• v.40 no.3
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• pp.211-220
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• 2024

During the surveys of ciliates from hypoxic habitats, three marine anaerobic species were found: Metopus spiculatus, M. vestitus, and Muranothrix felix. These species have not been previously recorded in South Korea and belong to the taxonomic classes Armophorea and Muranotrichea. The morphology of these species was examined by both microscopic observations of live specimens, and stained cells using protargol impregnations. Metopus spiculatus has the following characteristics: body size 80-110×25-35 ㎛ in vivo, beak-like structure at the end of preoral dome, ectosymbiotic bacteria covering cell surface, intracytoplasmic needle-shaped structures and the conspicuous tail end. Metopus vestitus has the following distinguishing characteristics: body size 95-130×25-45 ㎛ in vivo, a cone-shaped body, a covering of ectosymbiotic bacteria on its cell surface, intracytoplasmic needleshaped structures, somatic kineties arranged in 26-28 longitudinal rows, and a posterior part tapered into a tail. Muranothrix felix has the following characteristics: body size 100-130×20-30 ㎛ in vivo, elongated body with twisted neck region, bristle-like cilia protruding perpendicular to the cell margin, ectosymbiotic bacteria covering the cell surface, about 10 macronuclear nodules, and a long, stiffened caudal cilium.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.94-103
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• 2015

This study analyzes the influence factors on elderly pedestrian accident. Elderly people are easy to be badly injured by car accidents compared to younger people. Therefore, various plans and measures are required to protect elderly pedestrian from accidents. However, pedestrian accidents studies only focused on microscopic factors such as attribute of driver, pedestrian, road design. In order to prevent pedestrian accident and reduce the severity of the accident, not only microscopic factors but macroscopic variables such as urban planning and facility should be considered. In this regard, this study develops an ordered probit model introduced the characteristics of urban facility which were not considered in the previous studies. The result shows that there is higher level of accident severity in such areas as large commercial area, well-developed area with transportation infrastructure service and non-pedestrian safety zone. Thus, various and appropriate countermeasures should be prepared in order that pedestrian accident can be prevented in the areas mentioned above. In addition to the aforementioned variables, it is revealed that other variables including vehicle speed, gender and age of pedestrian, weather condition, type of vehicle, etc. partly affect the severity of pedestrian accident.

• Applied Microscopy
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• v.20 no.1
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• pp.105-119
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• 1990

In order to know the morphological characteristics and changes according to the developmental stage, the comparative observations have been studied by light and electron microscope on the midgut(gastric caecum, stomach) of the grasshopper(Oxya sinuosa Mistshenko). The results obtained are summarized as follow : In light microscopic level, the cuboidal shaped cells of the gastric caecum in the 5th instar nymph are differentiated the columnar epithelium in the adult. A number of pigment granules are appeared in the gastric caecum of the 5th instar nymph, however the pigment granules were absent in the adult. Indistinct or undifferentiated folds of the epithelial layer were appeared in the 5th instar nymph, whereas the well-developed folds were appeared the gastric caecum in the adult. The well-developed muscular layers are seen in the 5th instar numph, however in the adult the muscular layers are appeared thin or a few layers. In electron microscopic level, in the midgut epithelium, a number of well-developed rER, a few lipid droplets, multi vesicular bodies, small vesicles and glycogen granules were found. Two types of the pigment granules in the gastric caecum of the 5th instar nymph were appeared, whereas the whorl-membrane, a few secretory granules and one type of the gastro-entero-endocrine cell were found in the adult midgut. The light and dark cells could be distinguished in the stomach epithelim of the 5th instar nymph.

• Applied Microscopy
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• v.14 no.2
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• pp.81-93
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• 1984

Structural differences in various divisions of the rabbit colon were investigated using light and scanning electron microscopy. For light microscopic study, various Portions of the colon from seven rabbits (2.5 kg body weight) were fixed in 10% neutral buffered formalin, and paraffin sections were stained with hematoxylin-eosin. Tissues for scanning electron microscopy were fixed in 1% glutaraldehyde-1.5% paraformaldehyde and postfixed in 1% $OsO_4$, dehydrated to 100% alcohol, transfered to isoamilacetate and dried by the critical point method. Subsequently, specimens were coated with gold and viewed with a JSM-35C scanning electron microscope. The colon displays a morphological diversity along its proximo-distal axis. Five regions can be discerned based on the macroscopic and microscopic characteristics. 1) The first segment immediately distal to the cecocolical junction possessing three teniae is approximately 5 cm ($4{\sim}6cm$) in length, and displays irregular folds of the mucosa oriented transversely similar to those of the cecum. 2) The second segment possessing three teniae is about 7 cm ($5{\sim}8cm$) in length, and is characterized by the papilla-like protrusions on the mucosal surface. 3) The third segment, possessing a single tenia is about 16 cm ($12{\sim}20cm$) in length, and also displays the papilla-like protrusions similar to the aforegoing segment. 4) Fusus coli, approximately 4 cm ($3{\sim}5cm$) in length, is free of teniae and exhibits longitudinal folds on the mucosal surface. These four portions together constitute the proximal colon. 5) The distal colon reaches a length of about 58 cm ($53{\sim}55cm$) and shows a pattern of surface irregularities with minor ridges on the mucosal folds.

• Archives of Plastic Surgery
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• v.34 no.6
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• pp.796-798
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• 2007

Purpose: Giant cell tumor is the second most common benign neoplasm in upper extremity. Unlike usual chief complaint of painless mass, an atypical case with giant cell tumor presented a distinguishing characteristics of which accompany pain and tenderness and is histologically giant-cell free. Methods: A 31-year-old male patient complained of a rapid growing painful mass on the proximal phalanx of the left ring finger. Under microscopic operation, a $1.6{\times}1.3cm$ sized mass was found to be surrounded by areolar tissue and attached to a tendon sheath, encircling the digital nerve and artery. Diagnostic confirmation was assisted by positive finding in histologic immunohistochemical stain-CD68. Characteristic pathologic finding is an atypical distribution of spindle cells & histiocytes without giant cells in fascicular pattern. Results: Giant cell tumor was carefully removed under microscopic approach, while preserving digital nerve & artery. In postoperative 13th month, the patient presented with a 6mm of static two-point discrimination test, similar to that of the adjacent fingers. Conclusion: We report an atypical case with painful mass on tendon sheath, surrounding the digital nerve and artery that was diagnosed of giant cell tumor, but without giant cells on pathology. This case provides broader understanding of the giant cell tumor that should not only rely its typical findings of the painless mass and positive sign on H&E stain.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.7-18
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• 2007

There are few studies on air pollution due to vehicle emissions in spite of the importance of this field. Therefore, this study describes trends and suggests implications through analysis relating to existing emissions research. This study has been divided into three areas. The first part is about estimating vehicle emissions. In this part, the authors analyze limits in ways of calculating emissions in the existing macroscopic view and then suggest the development of a model for calculating emissions considering velocity and acceleration. These variables are a function of traffic and individual driving behavior in the microscopic view. The second part is about management techniques for reducing vehicle emissions. The traffic management techniques for reducing vehicle emissions should conform to regional characteristics. The final part is about traffic operation for reducing vehicle emissions. The authors suggest the development of a micro-simulator and then the development of strategies for traffic operation. It is necessary to design better models estimating emissions and then, using real time data, to make a monitoring system simulating emission rates. This study serves as a literature review to make a foundation for further research about emissions research for transportation engineering.

• Journal of Korean Neurosurgical Society
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• v.37 no.3
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• pp.217-222
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• 2005

Objective: To achieve optimal fit of implant, it is necessary to bend the implant during spine surgery. Bending procedure may decrease stiffness of plate especially made of titanium and stainless steel. Typically titanium suffers adverse effects including early crack propagation when it is bent. We investigate whether 6 degree bending of titanium plates would decrease the stiffness after full cyclic loading by comparing with non-bending titanium plates group. Methods: Authors experimented 40 titanium alloy plates of 57mm in length, manufactured by 5 different companies. Total 40 plates were divided into two groups (20 bent plates for experimental group and 20 non-bent plates for control group). Twenty plates of experimental group were bent to 6 degree with 3-point bending technique and verified with image analyzer. Using the electron microscope, we sought for a initial crack before and after 3-point bending. Mechanical testing by means of 6000 cyclic axial-compression loading of 35N in compression with moment arm of 35mm-1.1 Nm was conducted on each plate and followed by the electron microscopic examination to detect crack or fissure on plates. Results: The stiffness was decreased after 6000 cyclic loading, but there was no statistically significant difference in stiffness between experimental and control group. There was no evidence of change in grain structure on the electron microscopic magnification. Conclusion: The titanium cervical plates can be bent to 6 degree without any crack or weakness of plate. We also assume that minimal bending may increase the resistance to fatigue fracture in cervical flexion-extension movement.