• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.50 no.3
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• pp.166-169
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• 2024

Ankylosis of the temporomandibular joint (TMJ) is a condition in which the mandibular condyle fuses with the mandibular fossa through fibrous or bone tissue. It is a debilitating pathology that interferes with chewing, speaking, and oral hygiene. Currently, alloplastic reconstruction is considered the gold standard for treating severely compromised TMJs, such as in ankylosis. The article describes a patient with a history of facial trauma, with bilateral ankylosis of the TMJs, inability to open his mouth, and poor dental condition. Due to a long period of immobilization of approximately 40 years, the initial treatment plan was to remove the ankylosis bilaterally and install customized PMMA (polymethylmethacrylate) spacers. The patient gained mouth opening and improved chewing quality with one year of customized spacer use prior to definitive alloplastic replacement with stock-type TMJ prostheses. Customized joint spacers are a provisional treatment option when definitive alloplastic reconstruction is not indicated. Spacers provide the patient with progressive jaw function and mobility gains.

• Journal of Intelligence and Information Systems
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• v.27 no.1
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• pp.65-82
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• 2021

Stock market investors are generally split into foreign investors, institutional investors, and individual investors. Compared to individual investor groups, professional investor groups such as foreign investors have an advantage in information and financial power and, as a result, foreign investors are known to show good investment performance among market participants. The purpose of this study is to propose an investment strategy that combines investor-specific transaction information and machine learning, and to analyze the portfolio investment performance of the proposed model using actual stock price and investor-specific transaction data. The Korea Exchange offers daily information on the volume of purchase and sale of each investor to securities firms. We developed a data collection program in C# programming language using an API provided by Daishin Securities Cybosplus, and collected 151 out of 200 KOSPI stocks with daily opening price, closing price and investor-specific net purchase data from January 2, 2007 to July 31, 2017. The self-organizing map model is an artificial neural network that performs clustering by unsupervised learning and has been introduced by Teuvo Kohonen since 1984. We implement competition among intra-surface artificial neurons, and all connections are non-recursive artificial neural networks that go from bottom to top. It can also be expanded to multiple layers, although many fault layers are commonly used. Linear functions are used by active functions of artificial nerve cells, and learning rules use Instar rules as well as general competitive learning. The core of the backpropagation model is the model that performs classification by supervised learning as an artificial neural network. We grouped and transformed investor-specific transaction volume data to learn backpropagation models through the self-organizing map model of artificial neural networks. As a result of the estimation of verification data through training, the portfolios were rebalanced monthly. For performance analysis, a passive portfolio was designated and the KOSPI 200 and KOSPI index returns for proxies on market returns were also obtained. Performance analysis was conducted using the equally-weighted portfolio return, compound interest rate, annual return, Maximum Draw Down, standard deviation, and Sharpe Ratio. Buy and hold returns of the top 10 market capitalization stocks are designated as a benchmark. Buy and hold strategy is the best strategy under the efficient market hypothesis. The prediction rate of learning data using backpropagation model was significantly high at 96.61%, while the prediction rate of verification data was also relatively high in the results of the 57.1% verification data. The performance evaluation of self-organizing map grouping can be determined as a result of a backpropagation model. This is because if the grouping results of the self-organizing map model had been poor, the learning results of the backpropagation model would have been poor. In this way, the performance assessment of machine learning is judged to be better learned than previous studies. Our portfolio doubled the return on the benchmark and performed better than the market returns on the KOSPI and KOSPI 200 indexes. In contrast to the benchmark, the MDD and standard deviation for portfolio risk indicators also showed better results. The Sharpe Ratio performed higher than benchmarks and stock market indexes. Through this, we presented the direction of portfolio composition program using machine learning and investor-specific transaction information and showed that it can be used to develop programs for real stock investment. The return is the result of monthly portfolio composition and asset rebalancing to the same proportion. Better outcomes are predicted when forming a monthly portfolio if the system is enforced by rebalancing the suggested stocks continuously without selling and re-buying it. Therefore, real transactions appear to be relevant.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.378-382
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• 2005

The opening of high speed railway upgraded our land transportation speed limit, causing lots of changes including living and culture and also paving the way for stepping up the railway technology. However, it is also true that we had a limit to adopt the existing railway system structured for 150km/h to the new structure requiring a higher speed of approximate 300km/h due to technological, based on the time and experience. More importantly, heading toward a step of operating such a high speed railway system, it has been practically and quickly proposed that the railway needs high speed railway engineering, maintenance technology of parts of the vehicles to have a stable maintenance foundation and localization of major parts. Therefore, this study was intended to research the actual displacement characteristics in runningg on an actual track for the purpose of developing the protective and maintenance technology of springs and dampers, which are core parts among suspension elements of a high speed railway vehicle. For this, it was researched the actual vehicle test and its interpretation centered on primary spring, which is used for the suspension system of a bogie, body-body dampers and body-bogie yaw damper. Also, to analyze the displacement characteristics of suspension system in the actual conditions of high speed railway vehicles, a vehicle‘s dynamic characteristics was analyzed and interpreted. At the same time, a tester for measuring the actual displacement of such suspension elements was designed and attached to actual vehicles, to measure the displacements that occur in running it on the Seoul-Busan line, one of major lines serviced by KTX. The displacement data gained from the test with actual vehicles was analyzed for its displacement distribution depending on the service sections and frequency, with which the valuable data necessary for any potential breakdown or maintenance in the future could be obtained.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.322-326
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• 2003

Dae-gu subway accident raise whole points in connection with safety facilities and operating of national urban transit system like rolling stocks, facilities, management of human. Rolling stock is made every effort for improvement of performance, guarantee of comfortableness, insurance of economical efficiency. But Security like safety of fire is not thoroughgoing enough. Especially, interior material has used although it is not prove its degree of safety. it is a main cause of Dae-gu subway accident. Safety regulation of urban transit vehicle that legislate for security in March 2000 does not applied manufacturing vehicles before in 2000. It has be prescribed in the regulations that incombustibles must be used. But detailed test standard related with incombustibles is not prescribe. Thus that regulation be required reinforcement of detailed test standard. Main cause of Dae-Gu subway accident is a fire in vehicle. However, many defects are found in infrastructure and operating vehicle of urban transit, such as inexperienced disposal of driver and CCC in early stage of the fire accident, unskilled opening and closing doors, insufficient escape facilities and safety facilities of a station house and tunnel, and incomplete communication system between vehicle and CTC, extraordinary step. Thus the aims of this study are prevention of urban transit accident, improvement plan of safety driving, and proposal of quick action plan through analysis of total faculty of vehicle.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.47 no.4
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• pp.239-248
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• 2021

The paper reviews various classifications and surgical techniques for the treatment of temporomandibular joint ankylosis. PubMed, EBSCO, Web of Science, and Google Scholar were searched using a combination of keywords. Articles related to classification, resection-reconstruction of the temporomandibular joint, and management of airway obstruction were considered and categorized based on the objectives. Seventy-nine articles were selected, which included randomized clinical trials, non-randomized controlled cohort studies, and case series. Though several classifications exist, most classifications are centered on the radiographic extent of the ankylotic mass and do not include the clinical and functional parameters. Hence there is a need for a comprehensive staging system that takes into consideration the age of the patient, severity of the disease, clinical, functional, and radiographic findings. Staging the disease will help the clinician to adopt a holistic approach in treating these patients. Interpositional arthroplasty (IA) results in better maximal incisal opening compared with gap arthroplasty, with no significant difference in recurrent rates. Distraction osteogenesis (DO) is emerging as a popular technique for the restoration of symmetry and function as well as for relieving airway obstruction. IA, with a costochondral graft, is recommended in growing patients and may be combined with or preceded by DO in cases of severe airway obstruction. Alloplastic total joint replacement combined with fat grafts and simultaneous osteotomy procedures are gaining popularity. A custom-made total joint prosthesis using CAD/CAM can efficiently overcome the shortcomings of stock prostheses.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.8
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• pp.851-860
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• 2015

Transport Social Overhead Capital refers to public utilities necessary for a nation's basic economic activities, and is divided into roads, railway, subway, ports and so on. It is important to be able to provide these SOC in the right place at the right time to enhance productivity and competitiveness of a nation. In this study, correlation and factor analysis on countries' socioeconomic and transport indicators were performed in order to understand the need for expansion of SOCs including railway, and to identify the impact they have on national competitiveness(productivity). As a result, GDP showed high correlativity(0.59~0.99) with factors such as population, land area, extension of available railroad, and road extension. Specifically, through the analysis of Russia's urban transport system and comparison between socioeconomic indices and SOCs of OECD countries, it was examined that how increasing transport infrastructure investments could enhance national competitiveness. In conclusion, opening new Light Rail greatly affects the growth of GDP followed by the increasing extension of available railroad. Furthermore, if available railroad extension is increased by 10 % from 2014, assuming high speed tram is opened, GDP will likely increase by 21.6%.

• International Area Studies Review
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• v.15 no.1
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• pp.341-365
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• 2011

This study used a non-parametric linear program, Data Envelopment Analysis to compare the efficiency of South Korean and Chinese banks from 2000 to 2008, which is said to be the reformation period of their financial structure. The sample banks were 10 commercial banks and 6 regional banks in Korea, and 4 state-owned commercial banks and 11 stock commercial banks in China. The main objective of our research is to compare their efficiency, as well as the changes in efficiency periodically according to the types of the banks. According to the periodical analysis, both of the countries showed steady increase in efficiency. This shows that finance restructure and merging were positive factors for bank's efficiency during the revolution of finance structure. The study showed that between Korea and China, the bank of Korea has higher efficiency than that of China. Although the reconstruction period happened around the same time, due to the earlier acceleration period to opening Korea's financial market, made the difference in efficiency.