• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.709-716
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• 2005

Patients with cleft tip and palate present severe maxillary hypoplasia due to scar of lip and palate, often accompanied by compromised mastication, speech abnormalities. Sometimes maxillary hypoplasia persist even though active orthodontic treatment was done. In theses cases, patients born with cleft lip and palate will be potential candidates for maxillary advancement with bone grafting after growth to correct the functional deformities and improve aesthetic facial proportions. But, maxillary advancement using standard surgical approaches has several limitations : increased relapse tendency after maxillary advancement, necessity of additional bone graft and mandibular setback surgery. Distraction osteogenesis is current treatment modality to overcome these limitations, thus has become popular for treatment of maxillary hypoplasia associated cleft lip and palate, craniosyntosis. Especially, rigid external distraction, contrary to internal device, has advantages : better vector control of osteotomized segment, effective traction of the bony segments, the ease of the application and removal the distraction device. This study showed that relatively successful result could be generated by using rigid external distraction osteogenesis(RED) in the case of cleft lip and palate with severe maxillary hypoplasia, 6 years 7 months old.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.224-235
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• 2013

A passively fitting prosthesis is an essential prerequisite to attain long-lasting success and maintenance of osseointegration. However, true "passive fit" can not be achieved with the present implant-supported prosthesis fabrication protocol. Many clinical situations are suitably treated with cantilevered implant-supported fixed restorations. The purpose of this study was to compare the stress distribution pattern and magnitude in supporting tissues around ITI implants with cantilevered, implant-supported, screw-retained fixed prosthesis according to the fitness of superstructures. Photoelastic model was made with PL-2 resin (Measurements, Raleigh, USA) and three ITI implants (${\phi}4.1{\times}10mm$) were placed in the mandibular posterior edentulous area distal to the canine. Anterior and posterior extended 4-unit cantilevered FPDs were made with different misfit in the superstructures. 4 types of prosthesis were made by placing a $100{\mu}m$ gap between the abutment and the crown on the second premolar and/or the first molar. Photoelastic stress analysis were carried out to measure the fringe order around the implant supporting structure under simulated loading conditions (30 lb).

• Journal of the Korean Wood Science and Technology
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• v.29 no.4
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• pp.1-8
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• 2001

This study was carried out to investigate the strength and stiffness of drift pinned and bolted joints with steel-plates by the tension-type lateral strength tests. Specimens were solid wood of Pinus densiflora. Bolt and drift pin were jointed with inserted steel plates. Tests were conducted with combinations of two loading directions (parallel to the grain : 0 degree, perpendicular to the grain : 90 degree) and three diameters of fasteners (d = 6 mm, 10 mm, 12 mm). The results obtained were as follow: 1. In the test of the parallel to the grain, maximum loads were increased with increasing of the diameter of bolt and drift pin in the same end distance. In the test of perpendicular to the grain with diameter 10 mm and 12 mm, specimens mostly were failed with horizontal splits in woods reaching the yield load of drift pinned and bolted joints. 2. The ratio of maximum load to the yield load determined by the so-called "5% offset method", was great in bolted joints in the parallel to the grain This trend become more remarkable as the slenderness ratio was increased. 3. The calculated yield strength was agreed well with the experimental results of drift pinned joint(0 degree).

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.116-124
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• 2015

The objective of this study is to evaluate the effects of the replacement levels of grinded fly-ash on the repaired mortar based on a polymer. The main parameters are the curing temperature and replacement levels of grinded fly-ash. The curing temperature and the replacement levels of grinded fly-ash are varied at $40^{\circ}C$, $20^{\circ}C$ and $5^{\circ}C$, and between 0% and 35% of the total binder by weight, respectively. The flow in fresh mortar and compressive strengths according to ages, the relationship of stress-strain, elastic modulus and modulus rupture in hardened mortar, as well as scanning the electron microscopy and the X-ray diffraction of mortar, were measured, respectively. The test results showed that the flow, elastic modulus and modulus rupture are great in mortar specimens with 20~30% of the replacement levels of grinded fly-ash. In addition, compressive strengths according to ages were affected by the replacement levels of grinded fly-ash and the curing temperature indicated that the strength development ratio of mortar with 20% of the replacement levels of grinded fly-ash was greater than others. In the prediction of the compressive strength specified by the ACI 209 code, the strength development at an early and late age can be generalized by the functions of the replacement levels of grinded fly-ash and the curing temperature. In the analysis of scanning the electron microscopy and the X-ray diffraction, the number and intensity of peaks increased and the form of CSH gels on the surface of the particle of grinded fly-ash was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.1
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• pp.61-68
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• 2010

Purpose: This article attempted to determine the factors affecting the preload and screw loosening. Methods: Available clinical studies from 1981 to 2008 from the PUBMED that presented screw loosening data and review articles regarding screw joint stability were evaluated. Eleven studies dealing the biomechanical principles of the screw mechanics were reviewed. Moreover, the results of our data were included. Results: The frequency of screw loosening was consequently reduced due to the advancement in torque tightening with torque wrench, screw material, coating technique for reducing the frictional force, and thread design, etc. If preload in the screw falls below a critical level, joint stability may be compromised, and the screw joint may fail clinically. The types of fatigue failure of screw were divided to adhesive wear, plastic deformation, and screw fracture. Conclusion: An optimum preload is essential to the success of the implant-abutment complex. To maintain optimum preload, using a torque wrench and re-tightening at recall time were needed.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.4
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• pp.492-498
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• 2018

This study was conducted to investigate the characteristics of subculture times in the early, middle, and late passages by measuring the time under subculture until it was judged that the supernumerary tooth-derived pulp stem cells (sDPSCS) were no longer proliferating. Three supernumerary teeth from two healthy six-years old boys were extracted and stem cells were obtained from the pulp tissue. This was called SNT1 (supernumerary tooth 1), SNT2, and the supernumerary tooth from another child was named SNT3. SNT1 and 2 were subcultured at the same time and SNT3 was subcultured a little faster. The mean time of complete subculture was $3.6{\pm}1.1$ days. Total passages were cultured up to $23.3{\pm}0.6$ and took 83 days. These were divided into three groups based on the passage. The increase rate of time taken in subculture between group I and group II was 11.9%, but the rate between group II and group III was 28.6%, which was 2.4 times increased. The time taken between passages during long-term subculture up to 22 passages shows a regressive pattern y = 0.1169x + 2.25 and y = 0.1169x + 2.0. In conclusion, the passage time of SPSCs increased in late passages, and it shows a similar pattern.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.93-98
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• 2011

Saline corrosion is one of the major degradation mechanisms for stainless steel type 304 (SS304) dry storage cask during the spent fuel interim storage period. Slow strain rate test (SSRT) and neutral salt spray test (NSS) were performed at $85^{\circ}C$ and $200^{\circ}C$ with 0.5 wt% sodium chloride mist sprayed on the cold-rolled SS304 specimens of different degrees of reduction in this study. The weight changes of the NSS specimens tested at $85^{\circ}C$ for 2000 hours differed greatly from those at $200^{\circ}C$. The weight loss of NSS specimens was not significant at $85^{\circ}C$ but the weight gain decreased gradually with increasing the cold-rolled reduction. The yield strength (YS) and ultimate tensile stress (UTS) values obtained from the SSRT tests for lightly cold-rolled specimens in the salt spray environment at $85^{\circ}C$ and $200^{\circ}C$ are slightly lower than in air. But for those with 20% reductions, the specimen strengths were no longer changed by the saline corrosion. The preliminary results demonstrated that the quality and performance of cold-rolled SS304 is acceptable for fabrication of dry storage casks. However, more work on the corrosion behavior of cold-rolled stainless steel in the saline atmosphere is needed to better understand its long-term performance.

• Tunnel and Underground Space
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• v.30 no.1
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• pp.39-62
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• 2020

In this study, Barcelona Basic Model (BBM) was implemented into TOUGH2-MP/FLAC3D for the numerical analysis of coupled thermo-hydro-mechanical (THM) behavior of unsaturated soils and the prediction of long-term behaviors. Similar to the methodology described in a previous study for the implementation of BBM into TOUGH-FLAC, the User Defined Model (UDM) of FLAC based on the Modified Cam Clay Model (MCCM) and the FISH function of FLAC3D were used to extend the existing MCCM module in FLAC3D for the implementation of BBM into TOUGH2-MP/FLAC3D. In the developed BBM module in TOUGH2-MP/FLAC3D, the plastic strains due to change in suction increase (SI) in addition to mean effective stress are calculated. In addition to loading-collapse (LC) yield surface, suction increase (SI) yield surface is changed by hardening rules in the developed BBM module. Several numerical simulations were conducted to verify and validate the implementation of BBM: using an example presented in the FLAC3D manual for the standard MCCM, simulation results using COMSOL, and experimental data presented in SKB Reports. In addition, the developed BBM analysis module was validated by simultaneously performing a series of modeling tests that were performed for the validation of the Quick tools developed for the purpose of effectively deriving BBM parameters, and by comparing the Quick tools and Code_Bright results reported in a previous study.

• Journal of Chest Surgery
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• v.29 no.11
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• pp.1212-1217
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• 1996

From Dec. 1993 to May 1995, 9 male and 5 female patients ranging in age from 25 to 65 years, were operated on for ascending aorta and/or aortic arch diseases. Six patients had acute aortic dissection, type A(ruptured in 4 cases); four had ruptured ascending aortic aneurysm; three had annuloaortic ectasia(ruptured in 1 cases); one had aortic arch aneurysm. The diagnostic procedures were echo cardiography and dynamic CT scan in all patients having acute dissection or rupture. The aortic angiography was performed in two cases. Indications for operations were rupture in five cases, acute aortic dissection in five cases, severe congestive heart failure in two cases, progressive aortic insufficiency in one case and impending rupture in one case. The emergent repair was performed in ten cases(71%). The surgical treatment consisted of 6 Cabrol operations, a Cabrol operation combined with arch replacement, a modified Bentall operation, 4 replacement of ascending aorta, a replacement of aortic arch, and a replacement of ascending aorta and aortic arch. Complications were a hypoxic encephalopathy, two atrial fibrillations, a sternal deheiscence, and a mediastinitis. Two early mortality(14%) were due to intractable bleeding and multiple organ failure, and one late mortality(7%) was due to ventricular arrhythmia. In eleven survivors, follow-up period was from 2 months to 12 months and the course was uneventful.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.