• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.1021-1026
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• 1995

The seismic responses of a base isolated Pressurized Water Reactor (PWR) are investigated using a mathematical model which expresses the superstructure as lumped mass-spring model and the seismic isolator as an equivalent spring-damper. Time history analyses are performed for the 1940 E1 Centre earthquakes in both horizontal and vertical directions. In the analysis, structural damping of 5% is used for the superstructure. The isolator damping ratios of 12% for horizontal and 5% for vertical directions are used. The acceleration responses in base isolated PWR superstructure with high damping rubber bearings are much smaller than those in fixed base structure in horizontal direction. However, the vertical acceleration responses at the superstructure in the base isolation system are amplified to some extent. It is suggested that the vertical seismic responses at the superstructure should be reduced by introducing a soft vertical isolation device.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.360-366
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• 2001

This paper show the designing, manufacturing and performance test procedure of a high speed, fixed ratio planetary roller type traction drive as a speed reducer. The arrangement and size design for sun roller, planetary rollers and ring roller are carried out and a proper pre-load mechanism are adopted. To improve transmitting power capacity and endurance limit, nitro-carburized bearing steel and a synthetic traction oil are used. The manufactured and assembled traction drive operated successfully under unloaded conditions. Further tests for various load and speed conditions are executing now to improve the performance of the traction drive.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.714-715
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• 2015

Drill and blast method has been most widely used in tunnel excavation, after NATM (New Austrian Tunneling Method) was introduced in 1983. The NATM method utilized mass of shotcrete to secure the bearing capacity of tunnels. Overbreak defined how much larger the actual excavation was than the planned. When it became larger, more shotcrete was required to fill in it Here, payline fixed allowable overbreak, referring to payable amounts of shotcrete. Since owner was not responsible for shotcrete exceeding payline, it was important to properly establish the standards for payline. Although the standards were provided in 'Poom-sam'(standardized quantity per unit), they did not properly reflect the actual conditions for excavation. Thus, this study reviewed existing domestic and foreign standards for overbreak, and estimated overbreak for each type of support using survey data, and finally provided the improvements on the current standards.

• Journal of Trauma and Injury
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• v.36 no.3
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• pp.265-268
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• 2023

Ankle fractures with syndesmotic injuries often require fixation, where metal screw fixation is a popular method. However, as the patient begins weight-bearing, most syndesmotic screws tend to loosen or break, and removal of such screws has been challenging for the surgeons, as the available techniques require predrilling or trephination and are associated with risks of bone damage. This study presents a case with technical tip for the removal of broken tricortical-fixed non-cannulated syndesmotic screws. It implements the generation of a small cortical window in the medial distal tibia and the use of pliers to engage the screw tip and remove through the medial side. The technique presented in the current study overcomes these limitations and facilitates minimal bone damage and reduced exposure to radiation.

• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.62-70
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• 2012

Dynamic behaviors of line type bearings, spherical bearings and disk bearings which are being used for railway steel bridges are investigated, and that of the bridges is also analyzed. For the purpose, the vertical displacements of the three bearings including fixed and expansion type are measured and analyzed. Also, the deformation of the PTFE plate placed inside of spherical and disk bearings of expansion type is measured and its effect on the dynamic behavior of the bridges is discussed. The up-lift phenomenon at the bearings installed for the steel bridges is estimated. The vertical displacements at mid-span of the bridges are compared according to the bearing types. Finally, the 1st mode natural frequencies are estimated and the relationship to the vertical displacement is discussed.

• The Journal of Advanced Prosthodontics
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• v.6 no.5
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• pp.346-350
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• 2014

PURPOSE. Impact forces in implant supported FDP (fixed dental prosthesis) are higher than that of tooth supported FDPs and the compositions used in frameworks also has a paramount role for biomechanical reasons. The aim of this study was to evaluate the flexural strength of two different zirconia frameworks. MATERIALS AND METHODS. Two implant abutments with 3.8 mm and 4.5 mm platform were used as premolar and molar. They were mounted vertically in an acrylic resin block. A model with steel retainers and removable abutments was fabricated by milling machine; and 10 FDP frameworks were fabricated for each Biodenta and Cercon systems. All samples were thermo-cycled for 2000 times in $5-55^{\circ}C$ temperature and embedded in $37^{\circ}C$ artificial saliva for one week. The flexural test was done by a rod with 2 mm ending diameter which was applied to the multi-electromechanical machine. The force was inserted until observing fracture. The collected data were analyzed with SPSS software ver.15, using Weibull modulus and independent t-test with the level of significance at ${\alpha}=.05$. RESULTS. The mean load bearing capacity values were higher in Biodenta but with no significant differences (P>.05). The Biodenta frameworks showed higher load bearing capacity ($F_0=1700$) than Cercon frameworks ($F_0=1520$) but the reliability (m) was higher in Cercon (m=7.5). CONCLUSION. There was no significant difference between flexural strengths of both zirconia based framework systems; and both Biodenta and Cercon systems are capable to withstand biting force (even parafunctions) in posterior implant-supported bridges with no significant differences.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.93-99
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• 2006

Centrifuge model experiments were performed to investigate the confining effects of the sheet piles, installed to the sides of soft clay ground treated with sand compaction piles, on the bearing capacity and concentration ratio of composite ground. For the given g-level in the centrifuge model tests, replacement ratio of SCP and the width of surcharge loads on the surface of ground with SCP, the confining effects of installing the sheet piles on the edges of SCP ground on the bearing capacity, change of stress concentration ratio and failure mechanism were investigated. Kaolin, one of typical clay mineral, and Jumunjin standard sand were used as a soft clay ground and sand compaction pile irrespectively. As results of experiments, lateral confining effect by inserting the model sheet piles fixed to the loading plate was observed. For the strip surcharge loading condition, the yielding stress intensity in the form of the strip surcharge loads tends to increase with increasing the embedded depth of sheet piles. The stress concentration ratio was found not to be influenced consistently with the embedded depth of sheet piles whereas the effect of stress intensity on stress concentration ratio shows the general trend that values of stress concentration ratio are relatively high at the initial stage of loading and tend to decrease and converge to the certain values. For the failure mechanism in the case of reinforced with sheet piles, displacement behavior related to the punching failure, settlement right beneath the loading plate occurred since the soil was confined with sheet piles, was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.1-16
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• 1991

In order to see the possible effect of the functional load-bearing after osseointegration of the titanium root form implant in dog a histologic study was conducted. One side of lower jaw was surgically prepared edentulousness and titanium implants were inserted. Some implants were functionally loaded through fixed detachable prosthesis and some are isolated and unloaded. The dog was sacrificed four months later and bone sections with implants were processed for histologic evaluation and the results were as follows ; (1) The bone to implant interface after four months of load bearing presented no mobility and no marginal bone loss radiographically and histologically. (2) The interface zone between compact bone and implant revealed a direct bone to implant contact and in some areas marrow tissue contacts were examined at the light microscopic level. (3) At the ultrastructural level the interface of surrounding compact bone matrix and implant, three types of superficial layers were found ; one with moderate electron dense amorphous granular substance layer, other with high electron dense fine granular substance layer, and another type of amorphous granular substance covered with high electron dense line of minute granules. (4) The osteoblasts in the marrow tissue neighboring implants and osteocytes in compact bone showed typical normal characteristics and in the marrow tissues some of lymphocytes and mast cells were observed. (5) The abscence of abnormal tissue reactions at a cellular level indicates a high degree of biocompatibility for the experimental titanium implant and basically no difference was found between functionally loaded and unloaded implants.

• Journal of Veterinary Clinics
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• v.25 no.5
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• pp.408-410
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• 2008

A four months old, 3.6 kg intact female Miniature Dachshund dog was referred for non-weight bearing lameness at right hind limb due to car accident. On physical examination, the patient was non-weight bearing on the right hind leg and had moderate swelling in the proximal to middle tibia region. There was palpable crepitus. Radiographs revealed a slightly displaced, spiral, oblique fracture involving the proximal diaphyseal region of the right tibia. Fibular fracture was also noted. Internal fixation was performed to repair the fracture. Due to bowed shape of fractured tibia, it was not possible to apply K-wire, containing appropriate diameter ($60{\sim}80%$ of bone marrow diameter) for intramedullary fixation. We fixed the bowed tibia fracture using a smaller diameter (30% of bone marrow diameter) K-wire with cross pins and cerclage wires. Four weeks after the operation, radiographs demonstrated healing of the tibia fracture as well as the fibular fracture.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.118-124
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• 2006

SThe rigidities of bridge substructures are the important data in the rail-bridge interaction analysis in Korean High -Speed Railway. This experimental study is being performed because of followings. 1) More correct longitudinal stiffness of the structure including substructure should be considered in the calculation of stresses in rails. 2) There are many uncertainties in the design and construction of the piers and foundations. 3) Actual guideline for the rigidities of piers and foundations in the design is necessary. 4) Measurement on the rigidity of pier according to the types of piers, foundations and soil-conditions is needed. Curve for estimating the total rigidity of substructure will be obtained through this and further experimental studies. It may be used in the analysis of Korean High-Speed Railway bridge and then, longitudinal stresses in the rails can be estimated more accurately. One pair of piers, which consist of pot-bearing for fixed support and pad-bearing for movable support, are loaded by steel frame devices with steel wire ropes and hydraulic jack. The responses which are measured at each loading stages in those field tests are displacements and tilted angles on the top and bottom of piers. This study is being performed testing and analysis about several piers in the construction field.