• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.759-768
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• 2015

The ground motions of large dimensional structures such as long span bridges at different stations during an earthquake, are inevitably different, which is known as the ground motion spatial variation effect. There are many causes that may result in the spatial variability in seismic ground motion, e.g., the wave passage effect due to the different arrival times of waves at different locations; the loss of coherency due to seismic waves scattering in the heterogeneous medium of the ground; the site amplification effect owing to different local soil properties. In previous researches, the site amplification effects have not been considered or considered by a single-layered soil model only. In this study, however, the ground motion amplification and filtering effects are evaluated by multi-layered soil model. Spatially varying ground motion at the sites with different number of layers, depths, and soil characteristics are generated and the variation characteristics of ground motion time histories according to the correlation of coherency loss function and soil conditions are evaluated. For the bridge system composed of two unit bridges, seismic behavior characteristics are analyzed using the generated seismic waves as input ground motion. Especially, relative displacement due to coherency loss and site effect which can cause the unseating and pounding between girders are evaluated. As a result, considering the soil conditions of each site are always important and should not be neglected for an accurate structural response analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.37-46
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• 2009

In this study, the seismic performance of the Buckling Restrained Knee Bracing (BRKB) system was evaluated through a pin-connected 1-bay 1-story frame. The BRKB system using a bolted channel section developed was composed of a steel plate as a load-resisting core member and two channel sections as a restrainment of the local and global buckling of the core plate. The main purpose of the BRKB system is to be used as an effective tool to re-strengthen/rehabilitate old low- and mid-rise RC frame buildings, which do not have enough seismic resistance to earthquake loadings. The main variables for the test specimens were the size of the core plates, stiffeners and the use of guide plates. The test results showed that the size of the core plate, which was the main element for the load-resisting member, was the most important parameter to achieve ductile behavior under tension as well as compression, until the maximum displacement exceed twice the design drift limit given by the AISC Seismic Provisions.

• Journal of Energy Engineering
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• v.26 no.2
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• pp.1-11
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• 2017

While they are becoming more viable, synthetic natural gas (SNG) plants, with their high temperatures and pressures, are still heavily dependent on advancements in the state-of-the-art technologies. However, most of the current work in the literature is focused on optimizing chemical processes and process variables, with little work being done on relevant mechanical damage and maintenance engineering. In this study, a combination of pipe system stress analysis and detailed local stress analysis was implemented to prioritize the inspection locations for main pipes of SNG plant in accordance to ASME B31.3. A pipe system stress analysis was conducted for pre-selecting critical locations by considering design condition and actual operating conditions such as heat-up and cool-down. Identified critical locations were further analyzed using a finite element method to locate specific high-stress points. Resultant stress values met ASME B31.3 code standards for the gasification reactor and lower transition piece (bend Y in Fig.1); however, it is recommended that the vertical displacement of bend Y be restricted more. The results presented here provide valuable information for future risk based maintenance inspection and further safe operation considerations.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.322-331
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• 2009

This paper proposes an efficient data representation of stereo images using edge-based mesh optimization. Mash-based two dimensional warping for stereo images mainly depends on the performance of a node selection and a disparity estimation of selected nodes. Therefore, the proposed method first of all constructs the feature map which consists of both strong edges and boundary lines of objects for node selection and then generates a grid-based mesh structure using initial nodes. The displacement of each nodal position is iteratively estimated by minimizing the predicted errors between target image and predicted image after two dimensional warping for local area. Generally, iterative two dimensional warping for optimized nodal position required a high time complexity. To overcome this problem, we assume that input stereo images are only horizontal disparity and that optimal nodal position is located on the edge include object boundary lines. Therefore, proposed iterative warping method performs searching process to find optimal nodal position only on edge lines along the horizontal lines. In the experiments, we compare our proposed method with the other mesh-based methods with respect to the quality by using Peak Signal to Noise Ratio (PSNR) according to the number of nodes. Furthermore, computational complexity for an optimal mesh generation is also estimated. Therefore, we have the results that our proposed method provides an efficient stereo image representation not only fast optimal mesh generation but also decreasing of quality deterioration in spite of a small number of nodes through our experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.604-609
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• 2016

This study evaluated the long-term performance of RSR (Reinforced Subgrade for Railways) technology which increases the railway line capacity without the need for additional land. Its characteristics include the use of a short reinforcement with rigid wall, which make it possible to apply it in confined spaces. The 7m high and 40m long testbed employed to evaluate the long-term performance was designed and constructed near Jupo station on the Chang-hang line. This line, located close to a local bus route, had collapsed at the subgrade following heavy rainfall. The performance of the new type of subgrade was verified with long term measurements over a 2 year period including the surface and ground settlement, horizontal displacement of the wall, tensile strain of the reinforcement, and settlement of the rail top on the side track. Based on the results of the measurements made until now, we concluded that it had sufficient safety and serviceability for use as a railway subgrade. It is expected that RSR technology could be frequently used at sites which lack the necessary construction materials for an embankment and are located close to functional railway lines and boundaries, in order to settle civil complaints.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.429-436
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• 2014

This paper presents the seismic performance of a geometrically unsymmetrical reinforced concrete building considering torsional effect and material nonlinearity of concrete and steel. The reinforced concrete building is a structure for seismic performance evaluation in the SMART-2013 international benchmark program. Nonlinear constitutive models for concrete and steel were constructed, and their numerical performance was demonstrated by various local tests. Modal analysis showed that the first three natural frequencies and mode shapes were close to the experimental results from the SMART-2013 program. In the time history analysis for low-intensity seismic loadings, displacement and acceleration responses at sampling points were similar to the experimental results. In the end, nonlinear time history analysis was conducted for Northridge earthquake to predict the behavior of the reinforced concrete structure under high-intensity seismic loadings.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.1
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• pp.46-53
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• 2001

The prevalence of supernumerary teeth is between $1{\sim}3%$. Of these, $90{\sim}98%$ occur in the maxilla with particular predilection for the premaxilla, preceded by mandibular third premolars, mandibular forth molars and maxillary paramolars. The most common ones occur in the maxillary anterior region, they may occur singly between the central incisors(mesiodens), or they may be double(mesiodentes). Maxillary anterior supernumeraries may erupt into the oral cavity or remain unerupted. It is found that approximately 25% are erupted, while the rest are unerupted. They are usually a small tooth with a cone-shaped crown and a short root. They may cause delayed eruption, median diastema, bodily displacement or rotation of the adjacent permanent teeth. Occasionally they may lead to the developement of dentigerous cyst or primordial cyst, or eruption into nasal cavity. In this study, 109 supernumeraries surgically extracted from premaxilla in 84 patients are analysed. The results are as follows : 1. Sex distribution of male and female is 2.2 : 1. 2. Almost cases are in pediatric age from 5 to 12 years old (87%). 3. Problems with supernumeraries are tooth malpositon, diastema, delayed eruption, eruption to nasal cavity and cyst formation. 4. Of 109 supernumeraries, 16(15%) are erupted into oral cavity, 92(84%) are impacted, and 1(1%) is erupted into nasal cavity. 5. Of 84 patients, 59(70%) have one supernumeray while 25(30%) have two supernumeraries. 6. Of 109 supernumeraries, 96(88%) are found within the region of the central incisors. 7. Of 109 supernumeraries, 94(86%) are vertically impacted, 11(10%) are horizontally impacted, 3(3%) are labiopalatally impacted and 1(1%) is impacted in nasal cavity. 8. Of 84 patients, we used palatal flap in 67(80%), labial flap in 6(7%), both flaps in 4(5%) and no flap in 7(8%). And incisive nerve was cut in 33(49%) of 67 palatal flaps. 9. Extration with ostectomy was done in 72 supernumeraries(66%), without ostectomy in 37 teeth(34%). 10. Extraction with tooth sectioning was done in 21 supernumeraries(19%), without tooth sectioning was done in 88 teeth(81%). 11. We used local anesthesia in 70 patients(83%) and general anesthesia in 14 ones(17%).

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.481-488
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• 2009

Buckley's formocresol was first introduced as a pulp medicament in 1904, and since 1930, it has been the treatment of choice for primary molar pulpotomies. Formocresol has fixation effect of pulp tissue and high clinical success rate. But side effect such as displacement and loss of permanent successor, amelogenesis imperfecta, cyst formation, mutation by general absorption, possibility of cancer induction have been reported. Of those, dentigerous cyst can form in the periradicular region after formocresol pulpotomy caused by an alteration of the reduced enamel epithelium, which result in fluid accumulation between the epithelium and the tooth crown. The present case describes a 6-year-old girl who had accidentally discovered in the panoramic radiograph a single, well-defined, radioluscent area enclosing the second unerupted mandibular premolar. The second left primary molar had been pulpotomizied 3 year before. Surgical treatment was carried out, the primary molar was extracted and cystectomy was performed under local anesthesia. In the extracted second primary molar, formocresol cotton pellet was left in the pulp chamber. Histologic study confirmed the suspected diagnosis of dentigerous cyst. This report present a case of dentigerous cyst associated with inadequate formocresol pulpotomized deciduous molar.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.1
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• pp.49-55
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• 2007

To improved the multi-resolution fast hierarchical motion estimation by using de-interlacing algorithm that is effective in term of both performance and VLSI implementation, is proposed so as to cover large search area field-based as well as frame based image processing in SoC design. In this paper, we have simulated a various picture mode M=2 or M=3. As a results, the proposed algorithm achieved the motion estimation performance PSNR compare with the full search block matching algorithm, the average performance degradation reached to -0.7dB, which did not affect on the subjective quality of reconstructed images at all. And acquiring the more desirable to adopt design SoC for the fast hierarchical motion estimation, we exploit foreground and background search algorithm (FBSA) base on the dual arithmetic processor element(DAPE). It is possible to estimate the large search area motion displacement using a half of number PE in general operation methods. And the proposed architecture of MHME improve the VLSI design hardware through the proposed FBSA structure with DAPE to remove the local memory. The proposed FBSA which use bit array processing in search area can improve structure as like multiple processor array unit(MPAU).

• 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.