• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.226-241
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• 2000

Recently a new generation of crown and bridge veneering resins containing submicron glass fillers was introduced. These ultrasmall particle hybrid composite materials distinguish themselves, compared with conventional microfill crown and bridge resins, through improved mechanical properties. It is claimed that these composites are suitable for metal free crowns and even bridges using fiber reinforcement. The purpose of this study was to evaluate the effect of thermal cycling on the tensile strength of the following veneering composites: Artglass(Heraeus Kulzer Co., Wehrheim, Germany), Estonia(Kuraray Co.. Japan), Sculpture(Jeneric Pentron Co., Wallingford, U.S.A.), and Targis(Ivoclar Co., Schaan Liechenstein). According to manufacturer's instructions, rectangular tensile test specimens measuring $1.5{\times}2.0{\times}4.5mm$ were made using a teflon mold. Whole specimens were divided into two groups. One group was dried in a desiccator at $25^{\circ}C$ for 10 days, and another group was subjected to thermal cycling($10,000{\times}$) in water($5/55^{\circ}C$). All test specimens were placed in a universal testing machine and loaded until fracture with a crosshead speed of 0.5mm/min. Weibull analysis and Tukey's test were used to analyze the data. The fracture surfaces of specimens were observed in SEM and the aliphatic C=C absorbance peak of Estenia and Targis resin was analyzed using Fourier transform infrared(FTIR) spectroscopy. Within the limitations imposed in this study, the following conclusions can be drawn: 1. Both in drying condition and thermal cycling condition, the highest tensile strength was observed in Estenia testing group(p<0.05). 2. The strength data were at to single-mode Weibull distribution, and the Weibull modulus of all veneering composite resin specimens increased after thermal cycling treatment. 3. After thermal cycling test, the highest tensile strength was observed in the Estenia group, and the lowest value was observed in the Targis group. The tensile strength values showed the significant differences between each group(p<0.05) 4. The aliphatic C=C absorbance peak of Estonia and Targis resin was decreased after light curing, and there was no distinct change after thermal cycling.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.4
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• pp.679-700
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• 1996

Inferior alveolar nerve dysfunction may be the result of trauma, disease, or iatrogenic injury. Inferior alveolar nerve injury is inherent risk in endodontic therapy, orthognathic surgery of the mandible, and extraction of mandibular teeth, particularly the third molars. The sensory disturbances of inferior alveolar nerve associated with such injury have been well documented clinical problem that is commonly evaluated by several clinical sensory test including Tinels sign, Von Frey test(static light touch detection), directional discrimination, two-point discrimination, pin pressure nociceptive discrimination, and thermal test. These methods used to detect and assess inferior alveolar nerve injury have been subjective in nature, relying on the cooperation of the patients. In addition, many of these techniques are sensitive to differences in the examiners experience and skill with the particular technique. Data obtained at different times or by different examiners are therefore difficult to compare. Prior experimental studies have used electro diagnostic methods(sensory evoked potential) to objectively evaluate inferior alveolar nerve after nerve injury. This study was designed with inferior alveolar nerve of rabbit. Several types of injury including mind, moderate, severe compression and perforation with 19 gauze, 21 gauze needle and 6mm, 10mm traction were applied for taking the sesory evoked ppterntial. Latency and amplitude of injury rabbit inferior alveolar nerve were investigated with sensory evoked potential using unpaired t-test. The results were as follows : 1. Intensity of threshold (T1) was $128{\pm}16{\mu}A$ : latency, $0.87{\pm}0.07$ microsecond : amplitude, $0.4{\pm}0.1{\mu}V$ : conduction velocity, 23.3 m/s in sensory evoked potential of uninjured rabbit inferior alveolar nerve. 2. Rabbit inferior alveolar nerve consists of type II and III sensory nerve fiber. 3. Latency was increased and amplitude was decreased in compression injury. The more injured, the more changed in latency and amplitude. 4. Findings in perforation injury was similar to compression injury. Waveform for sensory evoked potential improved by increasing postinjured time. 5. Increasing latency was prominent in traction injury rabbit inferior alveolar nerve. 6. In microscopic histopathological findings, significant degeneration and disorganization of the internal architecture were seen in nerve facicle of severe compression and 10mm traction group. From the above findings, electrophysiological assessment(sensory evoked potential) of rabbit injured inferior alveolar nerve is reliable technique in diagnosis and prognosis of nerve injury.

• Journal of Periodontal and Implant Science
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• v.24 no.3
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• pp.671-689
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• 1994

The purpose of this study was to compare effects of various bone grafts on periodontal regeneration of alveolar bone defects in dogs. Seven adult dogs aged 12 to 18 months were used in this study. Experimental alveolar bone defects were created surgically with a #1/2 round bur at the furcation area of the buccal surface of the mandibular 3rd, 4th premolars and 1st molar. Each experimental alveolar bone defects were grafted with dense hydroxyapatite, natural coral, and decalcified freeze-dried bone, and respectively divided into DHA, NC, DFDB group. An area without bone graft was divided into control group. At 1,2,4,6, and 12 weeks, dogs were serially sacrificed and specimens were prepared with Hematoxylin-Eosin stain and Mallory stain for light microscopic evaluation. The results of this study were as follows : 1. In control group, the matrix change of granulation tissue was observed at 1 week. And in experimental groups, the appearance of connective tissue around graft materials was loosely formed at 1 week, but densely formed at 2 weeks. 2. In every group, the slight formation of new trabecular bone was seen from remaining bone at 1 week. 3. The DHA and NC particles were gradually encapsulated by new trabecular bone from remaining bone, and the osteoid tissue was directly induced from DFDB particles. 4. The presence of osteoblasts was first observed at 1 week in control group and at 2 weeks in NC group, but at 6 weeks in DHA group. 5. In DHA group, the resorption of particles was not observed until 12 weeks. But in NC and DFDB group, the particles were resorbed at 6 weeks and replaced by new bone. And the amount and size of particles were reduced, and their border represented irregular form. In summary, in three experimental groups the inflammatory or foreign body reaction were slight, but the regeneration of new osteoid tissue and the matrix change of dense connective tissue fiber were observed. Especially, NC and DFDB materials were considered as the biocompatible graft materials which were effective in the regenertion of new bone.

• Korean Journal of Optics and Photonics
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• v.29 no.5
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• pp.204-214
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• 2018

Since LIDAR is advantageous for accurate information acquisition and realization of a high-resolution 3D image based on characteristics that can be precisely measured, it is essential to autonomous navigation systems that require acquisition and judgment of accurate peripheral information without user intervention. Recently, as an autonomous navigation system applying LIDAR has been utilized in human living space, it is necessary to solve the eye-safety problem, and to make reliable judgment through accurate obstacle recognition in various environments. In this paper, we construct a single-shot LIDAR system (SSLs) using a 1550-nm eye-safe light source, and report the analysis method and results of LIDAR signals for various measurement environments, reflective materials, and material angles. We analyze the signals of materials with different reflectance in each measurement environment by using a 5% Al reflector and a building wall located at a distance of 25 m, under indoor, daytime, and nighttime conditions. In addition, signal analysis of the angle change of the material is carried out, considering actual obstacles at various angles. This signal analysis has the merit of possibly confirming the correlation between measurement environment, reflection conditions, and LIDAR signal, by using the SNR to determine the reliability of the received information, and the timing jitter, which is an index of the accuracy of the distance information.

• Development and Reproduction
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• v.10 no.2
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• pp.93-96
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• 2006

The total length, head length, head height, eye diameter, retina thickness, and lens diameter of the dotted gizzard shad, Konosirus punctatus, showed positive allometric relationships between hatching and 30 days post-hatching (dph). The increase in total length relative to head length and head height, head length growth relative to eye and lens diameter, head height growth relative to eye diameter and lens diameter, and thickness of the retina relative to eye diameter, lens diameter, head length, and head height were showed allometric relationships. The eyes were formed completely at 9 dph. At this age, the eye has a lens, an optic nerve fiber layer, a ganglion cell layer, an inner plexiform layer, an inner nuclear layer, an outer plexiform layer, an outer nuclear layer, an outer limiting membrane, a rod and cone layer, and an epithelial layer. The essential demands that must be met by the retina in this species pertain to light sensitivity and spatial resolution.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.6
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• pp.847-854
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• 2015

The objective of this study was to determine the effects of graded inclusions of wheat bran (0%, 9.65%, 48.25% wheat bran) and two growth stages (from 32.5 to 47.2 kg and 59.4 to 78.7 kg, respectively) on the apparent ileal digestibility (AID), apparent total tract digestibility (ATTD) and hindgut fermentation of nutrients and energy in growing pigs. Six light pigs (initial body weight [BW] $32.5{\pm}2.1kg$) and six heavy pigs (initial BW $59.4{\pm}3.2kg$) were surgically prepared with a T-cannula in the distal ileum. A difference method was used to calculate the nutrient and energy digestibility of wheat bran by means of comparison with a basal diet consisting of corn-soybean meal (0% wheat bran). Two additional diets were formulated by replacing 9.65% and 48.25% wheat bran by the basal diet, respectively. Each group of pigs was allotted to a $6{\times}3$ Youden square design, and pigs were fed to three experimental diets during three 11-d periods. Hindgut fermentation values were calculated as the differences between ATTD and AID values. For the wheat bran diets, the AID and ATTD of dry matter (DM), ash, organic matter (OM), carbohydrates (CHO), gross energy (GE), and digestible energy (DE) decreased with increasing inclusion levels of wheat bran (p<0.05). While only AID of CHO and ATTD of DM, ash, OM, CHO, GE, and DE content differed (p<0.05) when considering the BW effect. For the wheat bran ingredient, there was a wider variation effect (p<0.01) on the nutrient and energy digestibility of wheat bran in 9.65% inclusion level due to the coefficient of variation (CV) of the nutrient and energy digestibility being higher at 9.65% compared to 48.25% inclusion level of wheat bran. Digestible energy content of wheat bran at 48.25% inclusion level (4.8 and 6.7 MJ/kg of DM, respectively) fermented by hindgut was significantly higher (p<0.05) than that in 9.65% wheat bran inclusion level (2.56 and 2.12 MJ/kg of DM, respectively), which was also affected (p<0.05) by two growth stages. This increase in hindgut fermentation caused the difference in ileal DE (p<0.05) to disappear at total tract level. All in all, increasing wheat bran levels in diets negatively influences the digestibility of some nutrients in pigs, while it positively affects the DE fermentation in the hindgut.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.283-292
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• 2013

A calcareous rock slope failed during excavation of the slope for construction of a tunnel entrance. The slope is located at the construction site for widening highway in Yeongwol, Korea. Field surveys, laboratory tests, and numerical analyses were performed to determine the reason for the slope failure. The numerical analysis revealed that the safety factor of the slope before construction of the entrance was less than 1, and that this decreased after construction. After construction of the entrance, the sliding zone of the slope increased and slope stability decreased because the shear strain and plastic zone in the slope over the tunnel entrance showed an increase relative to the lower part of the slope. To enhance the stability of the slope for construction of the tunnel entrance, countermeasures such as rock bolts, rock anchors, and FRP (Fiber glass Reinforced Plastic) grouting were adopted in light of the field conditions. Serial field monitoring performed to confirm the reinforcing effects of the adopted countermeasures revealed a small amount of horizontal deformation of the slope soils, most of the elastic deformation that can regain its former value. In addition, the axial forces of the rock bolt and anchor were more strongly affected by slope excavation during construction of the tunnel entrance than by tunnel excavation or the rainy season, and the axial forces tended to converge after excavation of the tunnel. Therefore, we can confirm that the slope is currently safe.

• Applied Microscopy
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• v.41 no.2
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• pp.99-107
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• 2011

Light microscope, and scanning and transmission electron microscopy were used to investigate the fine structure of sperm of the Korea squirrel, Tamias sibiricus. The sperm head of T. sibiricus was paddle in shape. The total length of T. sibiricus sperm was 67.8 ${\mu}m$. The length of sperm head was 7.8 ${\mu}m$, and the tail (60.0 ${\mu}m$) was consisted of four major segments: the neck (1.0 ${\mu}m$), middle (8.0 ${\mu}m$), principal (48.5 ${\mu}m$) and end piece (2.5 ${\mu}m$), respectively. Especially, the length of the middle piece is short, and end piece was very shorter than those of other rodents. The post-nuclear cap was occupied about a fifth of nucleus. The equatorial segment is located between the post-nuclear cap segment and acrosomal cap on the nuclear surface. Nine segmented columns were surrounded by the mitochondria, and numbers of gyres of mitochondria were 26. One segmented column was consisted ten to twelve knobs, and each of segmented column in the neck region connected with the nine outer dense fiber in the middle piece. Numerous satellite-like fibers were scattered around the segmented columns. Nos. 1, 5 and 6 of the outer dense fibers in the middle piece were larger than the others. A fibrous sheath and longitudinal column of the principal piece were in evidence, but the fibrous sheath and longitudinal column was not seen at the end piece. In conclusion, the structural features of sperm head and tail may be useful information to patterns of sperm evolution and classification of species.

• Journal of Periodontal and Implant Science
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• v.26 no.2
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• pp.511-521
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• 1996

Periodontal pocket is one of the most frequently developed clinical feature on the teeth with periodontal disease. In order to determine the gingival curettage effect of intrapocket irradiation of a pulsed Nd : YAG laser on periodontally involved teeth, bilateral 60 teeth with $4{\sim}6mm$ in probing pocket depth 1 week after supragingival scaling were selected. On half of them the intrapocket irradiation($300{\mu}m$ fiber optic, 1.5W power, for 2min.) of a pulsed-Nd : YAG laser(EL.EN.EN06O, Italy) was applied as the lased group. On the contralateral 30 teeth the subgingival curettage was accomplished by Gracey curettes as the curattage group. The periodontal pocket tissues were surgically excised by the modified Widman flap technique immediately after the intrapocket irradiation or subgingival curettage, subsequently fixed with 10% neutral formalin, sectioned in $4{\sim}6{\mu}m$ thickness, and stained with hematoxylin-eosin. Surface characteristics and incomplete removal of the pocket epithelium were evaluated under light microscope. And the difference between the lased group and the curettage group was statistically analyzed by Chi-square test in Microstat program. The results were as follows ; 1. The plane surface was observed more frequently in the curettage group(73.3%) than in the lased group(23.3%), and the rough surface was observed more frequently in the lased grOoup(63.3%) than in the curettage group(6.7%)(p<0.05). 2. The rate of incomplete removal of the pocket epithelium was relatively high in both the lased group(76.6%) and the curettage group(86.6%), and there was no significant difference between the lased group and the curettage group(p>0.l). The results suggest that the further studies including various power control of laser should be succeeded in order to obtain more favorable results by the intrapocket irradiation of a pulsed Nd:YAG laser than the subgingival curettage with Gracey curettes.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.133-144
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• 2009

Incheon Bridge, 18.4 km long sea-crossing bridge, will be opened to the traffic in October 2009 and this will be the new landmark of the gearing up north-east Asia as well as the largest & longest bridge of Korea. Incheon Bridge is the integrated set of several special featured bridges including a magnificent cable-stayed girder bridge which has a main span of 800 m width to cross the navigation channel in and out of the Port of Incheon. Incheon Bridge is making an epoch of long-span bridge designs thanks to the fully application of the AASHTO LRFD (load & resistance factor design) to both the superstructures and the substructures. A state-of-the-art of the geotechnologies which were applied to the Incheon Bridge construction project is introduced. The most Large-diameter drilled shafts were penetrated into the bedrock to support the colossal superstructures. The bearing capacity and deformational characteristics of the foundations were verified through the world's largest static pile load test. 8 full-scale pilot piles were tested in both offshore site and onshore area prior to the commencement of constructions. Compressible load beyond 30,000 tonf pressed a single 3 m diameter foundation pile by means of bi-directional loading method including the Osterberg cell techniques. Detailed site investigation to characterize the subsurface properties had been carried out. Geotextile tubes, tied sheet pile walls, and trestles were utilized to overcome the very large tidal difference between ebb and flow at the foreshore site. 44 circular-cell type dolphins surround the piers near the navigation channel to protect the bridge against the collision with aberrant vessels. Each dolphin structure consists of the flat sheet piled wall and infilled aggregates to absorb the collision impact. Geo-centrifugal tests were performed to evaluate the behavior of the dolphin in the seabed and to verify the numerical model for the design. Rip-rap embankments on the seabed are expected to prevent the scouring of the foundation. Prefabricated vertical drains, sand compaction piles, deep cement mixings, horizontal natural-fiber drains, and other subsidiary methods were used to improve the soft ground for the site of abutments, toll plazas, and access roads. Light-weight backfill using EPS blocks helps to reduce the earth pressure behind the abutment on the soft ground. Some kinds of reinforced earth like as MSE using geosynthetics were utilized for the ring wall of the abutment. Soil steel bridges made of corrugated steel plates and engineered backfills were constructed for the open-cut tunnel and the culvert. Diverse experiences of advanced designs and constructions from the Incheon Bridge project have been propagated by relevant engineers and it is strongly expected that significant achievements in geotechnical engineering through this project will contribute to the national development of the longspan bridge technologies remarkably.