• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.4
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• pp.317-322
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• 2003

This paper have calculated a relative heights of an each station using the data which were observed by GPS permanent stations(Chejudo, Homigoj, Jumunjin, Marado, Palmido, Ulengdo, Youndo) established in Korea. We performed spectrum analysis with a calculated relative heights by CLEAN algorithm. Through these process, we estimated vertical displacement of earth surface by semi-dinural ocean tidal loading components, and compared them with the results which were calculated by improving ocean tide model(NA099jb) for adjacent seas around Japan and Korea. As the result of this study, we determined the ocean tidal loading components with loading effects of $M_2$ and $N_2$, and we noted that the amplitude and the phase lags of ocean tidal loading components from observed GPS data were almost equal to values calculated from ocean tide models. However, the loading components about semi-diurnal tide $S_2$, $K_2$ couldn't estimate because of periods. Also, the diurnal ocean tide loading components were not considered, because the noise level have increased during the diurnal frequency.

• Journal of the Korean GEO-environmental Society
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• v.25 no.4
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• pp.29-35
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• 2024

This is an analytical study to confirm the passive resistance effect before post-tensioning of steel bar anchors. When using a steel bar as a permanent anchor, if displacement occurs within the slope even before the head load is applied, the displacement is suppressed by the passive resistance caused by the interaction between the steel bar, grout, and surrounding soil. Accordingly, the shape of the failure surface and changes in the safety factor were examined using limit equilibrium analysis and finite element analysis targeting sites where steel bar anchors were actually applied. It was found that the safety factor of the slope reinforced with steel bar anchors is 2.02 using finite element analysis, which is about 5.9% smaller than 2.14 using limit equilibrium analysis. Also, the location of the failure surface was found to be deeper compared to the unreinforced slope. Likewise, the factor of safety has a 153% and 163% increase using finite element method and limit equilibrium analysis, respectively. In addition, the maximum displacement occurs in the lower unreinforced section within the slope, and the displacement is found to be reduced by 42 to 83% at the location where the steel bar anchors are installed.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.79-93
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• 2009

This paper investigates the possibility of controlling the response of typical portal frame structures to blast loading using a combination of semi-active and passive control devices. A one storey reinforced concrete portal frame is modelled using non-linear finite elements with each column discretised into multiple elements to capture the higher frequency modes of column vibration response that are typical features of blast responses. The model structure is subjected to blast loads of varying duration, magnitude and shape, and the critical aspects of the response are investigated over a range of structural periods in the form of blast load response spectra. It is found that the shape or length of the blast load is not a factor in the response, as long as the period is less than 25% of the fundamental structural period. Thus, blast load response can be expressed strictly as a function of the momentum applied to the structure by a blast load. The optimal device arrangements are found to be those that reduce the first peak of the structural displacement and also reduce the subsequent free vibration of the structure. Semi-active devices that do not increase base shear demands on the foundations in combination with a passive yielding tendon are found to provide the most effective control, particularly if base shear demand is an important consideration, as with older structures. The overall results are summarised as response spectra for eventual potential use within standard structural design paradigms.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.973-981
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• 2008

This document presents the JES(Joint Element Structure) method that has been adopted for the firs time in our country for the construction of the structure crossing under the railroad without open excavation. Front Jacking Method, Tubular Roof Construction Method, New Tubular Roof Method and Joint Element Structure Method are commonly used for the construction of structures crossing under the railroad. JES Method, frequently used in Japan recently, is a new method to construct the structures crossing under the railroad in a safe manner and in a relatively short period of time by utilizing the steel elements with the joints through which the load in the vertical angle to the axial direction is transferred to the next element. The elements are tied to each other through the joints to form the permanent walls of a Rahmen structure under the road without open excavation and without limitation to the length in a convenient way. Through the case study in the project of a Subway Box Culvert Improvement for the Gyeonguiseon Railroad in front of Yonsei University using the JES Method, the cost and period of construction in various types of soil is investigated compared to the Front Jacking Method. Furthermore, by analyzing the results of instrumentation measurements carried out throughout the construction, comparison between the actual displacement in the ground and the predicted displacement in the design is made to provide the considerations to be counted for the design. In conclusion, comparison in the field of economic feasibility, constructability and safety between the JES Method and Front Jacking Method, which is most frequently adopted in our country at present, is made to present the JES Method as a new alternative for the non-open excavation construction method for the structures crossing under the railway.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.51.1-51.13
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• 2021

Objectives: This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year. Materials and Methods: Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy. Results: For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01). Conclusions: The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.600-612
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• 2001

The purpose of this study is concerned with an investigation of the actual condition of traumatic injuries of teeth and supporting structures in children to set up possible criteria for prevention and treatment of injured teeth. The materials consisted of the clinical records of 431 traumatically injured teeth of 212 children, accumulated during two years from the first of April in 1998 to the end of March in 2000, supplied from the Dept. of Pediatric Dentistry, Chonbuk National University Hospital. The incidence of injuries in boys was extremely high for permanent teeth, twice as high as in girls. Accidents to primary teeth were most common from 1 to 2 years of age and to permanent teeth were most from 8 to 9 years of age. The most common cause of trauma was a fall for both primary and permanent teeth, followed by collision. The anterior teeth in maxilla was most frequently affected by trauma in both the primary and permanent teeth. The most common type of trauma were loosening for the primary teeth, followed by luxation types which included the intrusion, displacement and extrusion and complete avulsion types. For the permanent teeth, the most common type of trauma were tooth fracture. The most common trauma of soft tissue was laceration of upper lip, lower lip and gingiva of maxilla Concerning treatment at the first visit, primary teeth with only loosening and concussion were not usually treated. Permanent teeth were often treated by crown restorations for crown fractures and by endodontic procedures for pulpal exposure. Though we could elucidate actual condition of traumatic injuries of teeth in children, we should make a follow-up survey to ensure the prognosis of injured teeth and establish the most desirable criteria for traumatized teeth in children.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.105-113
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• 2014

PURPOSES: The objective of this paper is to select the confidential intervals by utilizing the second moment reliability index(Hasofer and Lind; 1974) related to the number of load applications to failure which explains the fatigue failure and rut depth that it indicates the permanent deformation. By using Finite Element Method (FEM) Program, we can easily confirm the rut depth and number of load repetitions without Pavement Design Procedures for generally designing pavement depths. METHODS : In this study, the predictive models for the rut depth and the number of load repetitions to fatigue failure were used for determining the second moment reliability index (${\beta}$). From the case study results using KICTPAVE, the results of the rut depth and the number of load repetitions to fatigue failure were deducted by calculating the empirical predictive equations. Also, the confidential intervals for rut depth and number of load repetitions were selected from the results of the predictive models. To determine the second moment reliability index, the spreadsheet method using Excel's Solver was used. RESULTS : From the case studies about pavement conditions, the results of stress, displacement and strain were different with depth conditions of layers and layer properties. In the clay soil conditions, the values of strain and stresses in the directly loaded sections are relatively greater than other conditions. It indicates that the second moment reliability index is small and confidential intervals for rut depth and the number of load applications are narrow when we apply the clay soil conditions comparing to the applications of other soil conditions. CONCLUSIONS : According to the results of the second moment reliability index and the confidential intervals, the minimum and maximum values of reliability index indicate approximately 1.79 at Case 9 and 2.19 at Case 22. The broadest widths of confidential intervals for rut depth and the number of load repetitions are respectively occurred in Case 9 and Case 7.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.87-94
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• 2002

Recently, there have been numerous attempts to expand the traditional temporary soil nailing system into a permanent wall. Two reasons for this include the soil nailed system's advantage of efficient and economic use of subgrade space and its ability to decrease the total construction cost. However, the systematic and logical design approach has not been proposed yet. The permanent soil nailing wall system, which utilizes precast concrete from soil nailing system, is already used in many countries, but the study of cast-in-place concrete lacing or rigid walls in bottom-up construction of traditional soil nailing walls is imperfect and insufficient. In this paper, various laboratory model tests have been carried out to investigate the influence of parameters, including stiffness of the rigid wall to the soil nailing structure with respect to failure mode, displacement patterns and tensile forces at the nail head in several levels of load. Then, the variation of earth pressure distribution on the soil nailing wall, built with a rigid front plate, is sought through different levels of surcharge load and tensile forces at the nail head.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.657-661
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• 2005

Various chemotherapeutic agents have been recommended for pulpotomy of primary teeth, and there are formocresol, ferric sulfate, and calcium hydroxide. Of those, formocresol has fixation effect of pulp tissue and high clinical success rate, so it is most commonly used agent. But formocresol has strong cytotoxic effects, thus many articles reported displacement and loss of permanent successor, amelogenesis imperfecta, mutation by general absorption, possibility of cancer induction. Recently, it has been reported that leakage by imperfect temporary sealing when FC-soaked cotton was inserted into the root canal caused necrosis of surrounding tissues. and that necrosis of alveolar bone related to the use of excessive formocresol. In this case, 2nd primary molar of upper left jaw was treated using formocresol in local clinic, but extracted because of lasting pain. Furthermore, symptoms didn't disappear so patient was refered to us. The patient was 8-year-old male, had foul odor from oral cavity and circular alveolar bone necrosis around the permanent successor' crown. Thus sequestrectomy was operated and observed through 19 months after operation, we found normal root development of permanent successor but no complete regeneration of alveolar bone defect and attached gingiva. Lesion of periodontal tissues by formocresol is irreversible, so we have to confirm the indication in using formocresol and pay attention to complete temporary sealing.

• Geomechanics and Engineering
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• v.13 no.4
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• pp.653-669
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• 2017

By increase in the population and consequently constructions, new structures may be built in vicinity of the soil slopes. Such structures can be regarded as an extra surcharge on the slopes. The intensity and location of the surcharge affects the displacements of the slopes. Few researchers have studied the effect of surcharge on displacements of soil slopes. In this research, using limit analysis method and upper bound theory with non-associated flow rule, displacements of soil slopes in vicinity of a surcharge has been estimated. The authors have improved the technique previously proposed by them and a new formulation is suggested for calculating the permanent displacements of the soil slope in presence of a surcharge for two failure modes, rotational and transitional. A comparison has also been made between the two mentioned modes for various conditions of surcharge and slope. The conditions resulting in the rotational mode to be more critical than the transitional mode have been investigated. Also, the effects of surcharge's intensity, location of surcharge as well as the soil properties have been investigated.