• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.521-528
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• 2008

Purpose: Tunneling is a periodontal surgical procedure that creates access for patient cleansing and maintenance within the furcal area of a molar tooth with severe furcation involvement. Up to date, there are few studies about a long term clinical and radiographic stability of tunneling. The purpose of this retrospective study is to evaluate the long term prognosis after tunnel preparation of molars with through and through furcation. Material and Methods: 25 teeth of 23 patients aged 36 to 70 (mean age 51.7) were treated surgically with tunnel preparation. These cases were followed for 2 to 13 years (mean 6.5years) after surgery. Patients were recalled for an evaluation which was based on a questionnaire, a clinical examination, and radiographic analysis. Clinical assessment included plaque index, caries registration, probing pocket depth, bleeding on probing, tooth mobility. Baseline and over 2-year follow-up radiographs were collected and evaluated for this study. Result: 3 teeth(12%) had been extracted and 1 tooth(4%) hemisected. Root caries was detected in 3 teeth(12%). Thus 72% of the teeth were still caries tree and in function. Clinical parameters including PI, PD, BOP, mobility showed somewhat favourable results. Radiographic furcal bone loss showed no statistically significant difference compared to interproximal crestal bone loss ($3.59{\pm}1.69%$ vs $3.42{\pm}2.95%$) when root length was used as reference. There was no correlation between root trunk length and furcal bone loss. Conclusion: Over 2 years after tunneling procedure, teeth showed a clinically and radiographically stable condition, despite of slight root caries and alveolar bone loss within clinically acceptable range. The tunnel procedure may be considered as a viable periodontal treatment option for molar teeth with severe furcation involvement in individuals following a regular maintenance program.

• Journal of the Korean Society of Safety
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• v.34 no.3
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• pp.21-27
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• 2019

Many accidents have been occurring during welding and flame cutting work related to maintenance and repair as the domestic manufacturing facilities gradually become decrepit. However, it is not easy to find the accurate statistics and analysis data on accidents occurring during welding or flame cutting operations related to maintenance and repair of machinery and equipment. Therefore, in this study, the fatal accident cases of fire/explosion and asphyxiation that occurred during the welding and flame cutting work in the manufacturing industry were collected and their characteristics were analyzed. Then, we tried to find the connection of the accidents according to the machinery/equipment and the work content, and to provide the materials and measures that can be used to prevent the similar accidents. We collected 329 cases of the fatal accidents related to fire/explosion and leakage/contact of chemical substances in the domestic manufacturing industry during the last 10 years (2008 ~ 2017). Among them, 72 accidents occurred during welding or flame cutting were extracted and the related reports were investigated whether they occurred during usual work or unusual work. Also, the machinery/equipment and the work content related to the accidents were classified and analyzed based on the criteria. The analysis results showed that 31 cases of the fire/explosion accidents occurred during usual work and 32 cases during unusual work, and it was found that 9 cases of asphyxiation death occurred during usual work. Then, from the analysis results, the connections of the machinery/equipment and the work contents related to the accidents were schematized into a accident tree.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.175-182
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• 2008

In this paper, through the study and consideration of the recently prominent monitoring of cable stayed-bridge, practical but reasonable suggested for the evaluation of the probabilistic safety of the bridges using probable measured data from monitoring measurement system. It is shown in the paper that the live load effects can be evaluated using measured data of cable-stayed bridge and this the realistic probabilistic safety of the cable-stayed bridge could be assessed in term of element reliability and system reliability. As a practical method for the evalution of the system reliability of system cable-stayed bridges partial ETA method is uesd, which can find the critical failure path including combined failure modes of cable, deck and pylon. Compared with the conventional safety analysis method, the propsed approach may be considered as the practical method that shows the considerably actual and reasonable results the system redundancy of the structure.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.1
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• pp.98-107
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• 2013

Big and old trees in the scenic spots with the attributes of remote villas are vulnerable to man-made damages and very sensitive to the external environment such as soil conditions, so the corresponding management plans are required. Thus this study has been conducted to survey the big and old trees in the scenic remote villas and suggest the ideal management plans. The results can be summarized as follows. First, regarding the tree heath above the ground, transformation of tree, death of branches, and death of barks are closely related to tree vigor. Particularly, the areas receiving many visitors require prompt countermeasures against the dried and dead tress above the ground and the areas in which dried and dead tress occurred and also the safety measures for the visitors and facilities. Second, regarding the soil environment, visitor traffic is closely related to the tree vigor. In 15 remote villa gardens, 64% of trees are exposed to heavy traffic and the tree vigor has declined due to an increase of visitor. Thus, there is a need to give positive consideration the installation of the complementary facilities and the plantation of herbal plants in the congested areas to form the ground surface that can tolerate the heavy visitor traffic. Third, remote gardens are in general located adjacent to ponds and mountain streams and thus the trees in the waterfront areas require the prompt countermeasures against the decline of growth due to the excess-moisture in the soil. Further the blockage of the sewage system due to the heavy rains dampens the surrounding soil, which results in lethal damages to the trees. Thus, there is a need of the maintenance of the waterfront areas and sewage system before and after the rainy season. In addition, there is a need to establish medium-long term management polices through the recognition of the importance of the main trees of remote villa gardens in scenic spots and prepare the tree management manual depending on the attributes of the corresponding areas. I strongly suggest making manuals for the systematic management as well as the extensive PR activities and education for the preservation of tress on a long-term basis; and furthermore securing the budget and manpower for the research and development of a systematic management system.

• Land and Housing Review
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• v.6 no.4
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• pp.221-229
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• 2015

Large trees in the apartment complex are playing an important role to decide the quality of external environment. They are planted with the object of utilizing themselves as a landmark of the complex and enhancing space symbolism. Since planting large trees would require high maintenance costs and generate defect, it would cause decline in quality of external environment. This study researches on large trees in artificial ground of the apartment complex. This study analyzes actual condition of planting and tries to provide improvement direction of planting. In order to conduct this research, three target areas (over R30) and 265 trees are selected. Based on the drawings and specifications this study researches on the plan of landscape design, changes of field design, actual condition of completion, present condition of planting, minimum soil depth of growth and development and types of extra action for soil depth. The result shows that 85% of drawings and specifications for large trees in the apartment complex are deep-rooted tree species. On average large trees with R 35 are planted in artificial ground and there is lack of on average 65cm minimum soil depth of growth and development. Reviewing changes of field design is conducted in such limited size as mainly R30 and R40 and there is no extra plan for lack of soil depth. The plan for securing additional soil depth is done by 85% of mounding. However, since there is only 10% of satisfaction, the inappropriateness in securing additional soil is pointed out. This research also points out that the size of large trees, root characteristics and location-allocation for planting are pivotal factors for securing minimum soil depth of growth and development. This research also provides improvement direction in case of planning planting.

• Journal of the Korean Institute of Landscape Architecture
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• v.24 no.2
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• pp.86-98
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• 1996

This study is intended to revaluate old tree, five of the shot of the Natural Monument and 66 shot trees under protection in the city at present. The study covers distribution, management of usage, investigation and research into various matters relating to the situation of old trees in Pusan. Because 60% of the old trees selected for protection is on private land, citizens have difficulty gaining access to them. Also space for growth is impinged on by various urban facilities. Some trees have problems of growth because the land is covered with cement and asphalt. As regards space for old trees, many places have been destroyed due to the lack of protection fences and the failure to establish a guidance board. Only 40% of the space has been set aside for rest. In these places the establishment of rest areas, benches and handy chairs is needed. And there are 20 holy places where people observe religious ceremonies. As for space security necessary for old trees according to trunk width, the minimum trunk width and availale area needed are more than 1:1.5, but less than 30% have the necessary space. The growth of many old trees is threatended because of the small apace for growth. The prescription of the boundary space is divided between inside and outside. This indicates the domain nature and space rank of the old tree. It can be classified into five forms for research purposes. The elements for prescription of critical space outside are connected with the security of space, and the elements relating to inside space portray the conditions for sensitive growth according to the institution and the ground conditions. The open and closed nature of old tree space has some connection with the relationship between usage and the intimacy of the user. Most of the spaces for old trees can't be used or are difficult to gain access to, so it is necessary to secure enough space for them. The 18 places, despite having easy access, are near farmland, hills or forest. So the intimacy factor is low, and the security of space of the old trees is not generally sufficient. Henceforth, it will be necessary to have security of area for old trees as well as maintenance control to protect them. Also the space should be used as a communal and recreation are in the city. It is the time to construct a landscaped area which people can easily approach, a place with a secure entrance where they can play, rest and converse.

• Nuclear Engineering and Technology
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• v.23 no.2
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• pp.174-182
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• 1991

Effects of human error relevant to the periodic test are incorporated in the evaluations of the unavailability and optimal test interval of a safety system. Two types of possible human error with respect to the test and maintenance are considered. One is the possibility that a good safety system is inadvertently left in a bad state after test（Type A human error) and the other is the possibility that a bad safety system is undetected upon the test（Type B human error). An event tree model is developed for the steady-state unavailability of a safety system in order to determine the effects of human errors on the system unavailability and the optimal test interval. A reliability analysis of the Safety Injection System (SIS) was peformed to evaluate the effects of human error on the SIS unavailability. Results of various sensitivity analyses show that ; (1) the steady-state unavailability of the safety system increases as the probabilities of both types of human error increase and it is far more sensitive to Type A human error, (2) the optimal test interval increases slightly as the probability of Type A human error increases but it decreases as the probability of Type B human error increases, and (3) provided that the test interval of the safety injction pump is kept unchanged, the unavailability of SIS increases significantly as the probability of Type A human error increases but slightly as the probability of Type B human error increases. Therefore, to obtain the realistic result of reliability analysis, one should take shorter test interval (not optimal test interval) so that the unavailability of SIS can be maintained at the same level irrespective of human error. Since Type A human error during test & maintenance influeces greatly on the system unavailability, special efforts to reduce the possibility of Type A human error are essential in the course of test & maintenance.

• Journal of Environmental Science International
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• v.21 no.7
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• pp.883-890
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• 2012

Emission characteristics of gaseous odor compounds emitted from the charcoal manufacturing process were investigated, and evaluated the odor removal efficiency of odor control devices. It was found that the measured odor dilution ratio of emission gases ranged from 10,000 to 44,814, which exceed largely the emission standard in the stack. Methylmercaptan, trimethylamine, hydrogen sulfide, acetaldehyde were turned out as major odor compounds of the charcoal manufacturing process. It was revealed that the odor removal ratio of odor control devices were very low due to the its improper maintenance and wrong design.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.1911-1930
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• 2017

Overlay routing has emerged as a promising approach to improve reliability and efficiency of the Internet. The key to overlay routing is the placement and maintenance of the overlay infrastructure, especially, the selection and placement of key relay nodes. Spurred by the observation that a few relay nodes with high betweenness centrality can provide more optimal routes for a large number of node pairs, we propose a resilient routing overlay network construction method by introducing Super-Relay nodes. In detail, we present the K-Minimum Spanning Tree with Super-Relay nodes algorithm (SR-KMST), in which we focus on the selection and connection of Super-Relay nodes to optimize the routing quality in a resilient and scalable manner. For the simultaneous path failures between the default physical path and the overlay backup path, we also address the selection of recovery path. The objective is to select a proper one-hop recovery path with minimum cost in path probing and measurement. Simulations based on a real ISP network and a synthetic Internet topology show that our approach can provide high-quality overlay routing service, while achieving good robustness.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.269-274
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• 2013

In this paper, we propose the design and implementation method of picking system using zigbee wireless communication in order to solve problems of the conventional picking system which has expensive labors and maintenance costs. We use multi router based star-tree topology as a default routing topology to provide the reliable data transmission and define the method of ID configuration and data transmission. We confirm that successful data transmission ratio of multi router based picking system is maximum 20% higher than that of single router based picking system.