• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.74-83
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• 2020

A number of so-called 'Type IV' cracking was reported to occur at the welded joints of the P91 steel or P92 steel reheat steam piping systems in Korean supercritical thermal power plants. The reheat steam piping systems are subjected to severe thermal and pressure loading conditions of coolant higher than 570℃ and 4MPa, respectively. In this study, piping analyses and design evaluations were conducted for the piping system of a specific thermal plant in Korea and suggestions were made how structural integrity could be improved so that type IV cracks at the welded joints could be prevented. Integrity evaluations were conducted as per ASME B31.1 code with implicit consideration of creep effects which was used in original design of the piping system and as per nuclear-grade RCC-MRx code with explicit consideration of creep effects. Comparisons were made between the evaluation results from the two design rules. Another approach with modification or reduction of the redundant supports in the piping systems was investigated as a tool to mitigate thermal stresses which should essentially contribute to prevention of Type IV cracking without major modification of the existing piping systems. In addition, a post weld heat treatment method and repair weld method which could improve integrity of the welded joint of P91 steel were investigated.

• Journal of the Korean association of regional geographers
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• v.19 no.2
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• pp.340-351
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• 2013

International society has been making a lively discussion about natural disaster by climate change to mitigate natural hazard centering around intra-government association. This study dealt with a strategic mitigation and technical adaptation to support a habitual natural disaster region such as Bangladesh in terms of international cooperation for assistance to protect against the natural hazard. The land-cover on scale of one third of Bangladesh is situated lower than sea level that causes habitual flooding accident which gets increasing in the strengthen every single year. Most of people lives around exterior sea coast being faced with disaster of abnormal storm forming every three year cycle. Especially, the socio-economic status of the people in the coast is usually very low, and it need to get help from international cooperation aid. Therefor, the case study for the vulnerability of natural disaster in Bangladesh on geographical analysis is meaningful to join the international cooperation taking a part of role on technical support and education for adaptation of the natural disaster.

• Microbiology and Biotechnology Letters
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• v.46 no.2
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• pp.154-161
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• 2018

Currently, urban greening projects and research are attracting attention as a way to mitigate urban heat island phenomenon. In this study, nitrogen fixative bacteria were isolated and their effects on plant growth were confirmed. First, enrichment was performed in a nitrogen-free medium to isolate the nitrogen-fixing bacteria, and the colony showing high growth in a medium with limited nitrogen source was isolated and purified. Separated bacterial isolates were reduced by more than 90% acetylene by ARA and indirectly confirmed the activity of nitrogenase by ethylene production. Cedecea sp. MK7 and Enterobacter sp. Y8 with confirmed reproducibility were selected as nitrogen fixative bacteria. Nitrogen fixing bacteria were applied to the growth of perennial rye grass, and it was found that the dry weight increased to 34.80 mg (186.60%) compared with the control with 18.65 mg dry weight. After plant growth, microbial community analysis of soil applied by bacteria showed similarity to the control group. Therefore, in this study, it is expected that the efficiency will be increased if plant growth is promoted by using nitrogen fixing bacteria in urban greenery system.

• Ocean and Polar Research
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• v.26 no.2
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• pp.155-163
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• 2004

The Protocol on Environmental Protection to the Antarctic Treaty was ratified in 1991. With the aim to ensure comprehensive protection of the Antarctic environment, it contains provisions on environmental protection and conservation of the Antarctic area, including provisions for Environmental Impact Assessment. Environmental Impact Assessment is a method used to predict environmental impacts at an early stage in project planning and design, and find ways to mitigate or prevent adverse impacts in order to maintain balance between development activities and environmental conservation. Internationally, the Environmental Impact Assessment (EIA) in the Antarctic is classified into three types - preliminary, Initial, and Comprehensive - based on the environmental impacts of the proposed activities. In case of the Preliminary Environmental Review (PER), proposed activity may proceed in accordance to the national procedures and drafting of an outline. However, Initial (IEE) and Comprehensive Environmental Evaluation (CEE) assess and verify the impacts of the proposed activity, and require methods or alternatives for mitigating or eliminating negative impacts on the environment. Although Korea's Act of 'Activities and Environmental Protection in Antarctica' also includes provisions on EIA for activities in Antarctica, there are obvious contrasts with the EIAs currently being conducted in Korea, in regards to deciding the level of EIA through screening and identifying key issues for assessment through scoping. In order to implement the proper EIA, more improved methods for drafting and reviewing the EIA to Antarctica in Korea are necessary.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.8-16
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• 2015

Prestressed concrete (PSC) is a method in which prestressed tendon is placed inside and/or outside the reinforced concrete member and the compressive force applied to the concrete in advance to enhance the engineering properties of concrete member which is weak under tension. In this paper we suggested the precast PSC girder assembled with segments of portable size and weight at the factory. The segments of precast PSC girder will be delivered and assembled as a unit of PSC girder at the site. Consequently, we suggested new-type of precast segmented PSC girder with different shapes of segment cross-section (i.e., I-shape, Box-shape). To mitigate the problems associated with the field splice between the segments of precast PSC girder anchor system is attached near the neutral axis of the girder and relatively uniform compression throughout the girder cross-section is applied. Prior to the experimental investigation, analytical investigation on the structural behavior of precast PSC girder was performed and the serviceability (deflection) and safety (strength) of the girder were confirmed. In addition, 4-point bending test on the girder was conducted to investigate the structural performance under bending. From the experimental investigation, it was found that the precast PSC girder spliced with 3 and 5 segments has sufficient in serviceability and safety conditions and it was also observed that the point where the segments spliced has no defects and the girder behaves as a unit.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.2
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• pp.86-99
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• 2007

Packet filtering is to filter out potentially malicious network packets. In order to test a packet filtering function we should verify whether security policies are performed correctly as intended. However there are few existing tools to test the function. Besides, they need user participation when generating test cases or deciding test results. Many security administrators have a burden to test systematically new security policies when they establish new policies or modify the existing ones. To mitigate the burdens we suggest a new test method with minimal user articipation. Our tool automates generation steps of the test cases and the test oracles, respectively. By using the test oracles generated automatically, deciding test results is possible without user intervention. Our method realizes an automatic testing in three phases; test preparation phase, test execution, and test evaluation. As a result it may enhance confidence of test activities more highly. This paper describes the design and implementation of our test method and tool.

• Journal of Korea Multimedia Society
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• v.13 no.9
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• pp.1357-1364
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• 2010

With the emergence of digital TV broadcasting, various TV channels are provided to a TV audience. But it is getting hard for the audience to find his or her preferred TV programs due to the huge number of TV channels. In order to mitigate the difficulty, channel navigation schemes have been proposed. The schemes predict preferred TV channel from viewer's previous watching histories, and provide the predicted channels when the viewer wants to change TV channel. As channel navigation schemes, there are Most Recently Selected (MRS) scheme providing the most recently watched channel, and Most Frequently Selected (MFS) scheme providing the most frequently selected channel. However, MFS and MRS scheme could be inappropriate to current TV system broadcasting various TV programs in a channel because they are based on the viewer's patterns of watching TV channels. Therefore, this paper proposes an efficient channel navigation scheme, Program Most Frequently Selected (PMFS), based on patterns of watching TV programs instead of TV channels. Simulation results show that the proposed scheme PMFS reduces the seek distance compared to the previous channel navigation schemes, MFS and MRS.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.580-587
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• 2016

In the purpose of suggesting the necessity and proper method of providing the standard reference material for acquiring the aircraft pilot license, this study provides the FAA and ROKAF case study, and positively analyzes the materials of 178 pilots and student pilots who acquired the aircraft pilot license. The result of case study shows that compared to the case of Korea which the restriction on the standard reference material providing exists, the FAA(Federal Aviation Administration) and ROKAF are currently providing the standard reference material. Additionally, the result of positive analysis indicates the fact that the necessity of standard reference material providing is well recognized and its importance also found to be remarkably high. These results represent that the standard reference material providing is necessary for training competent aircraft pilots. Also, this will mitigate the current shortage of aircraft pilots due to the rapid growth of air transportation industry, and this will play an important role in preventing diverse aircraft-related accidents.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.469-481
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• 2004

Previous works for the AF(Assured Forwarding) service in the Diffserv network have no sufficient consideration on the fairness of bandwidth share based on RTTs, the target rates, and the impact of UDP against TCP. In this paper, in order to solve these problems, we propose a FDSA(Fair Differentiated Service Architecture) composed of TRA3CM(Target rate and RTT Aware 3 Color Marking) and TRBD(Target Rate Based Dropping) mechanisms. The TRA3CM and TRBD mechanisms provide three color marking and fair transmission rates among aggregate flows by considering RTT, target rate, and UDP flows simultaneously. In the results of comparing the performance among existing mechanisms and the TRA3CM-TRBD, the TRA3CM-TRBD mechanism was able to mitigate the RTT and UDP effect better than the former. The TRA3CM-TRBD is shown to provide good performance for transmission rates proportional to various target rates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1844-1852
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• 2015

The purpose of this study was to identity the mediating effect of emotional intelligence on the relationships between creative home environment and creative personality of young children. The subjects of the study were 225 young children from daycare center in Busan. The results of the study are as follow; first, creative home environment were significantly positively correlated to emotional or creative personality of young children. And emotional intelligence were significantly positively correlated to creative personality of young children. Second, emotional intelligence worked as a part mediation variable between creative home environment and creative personality of young children. According to, this study suggests that the creative home environment during early childhood predict their creative personality. Their emotional intelligence, especially is the impact factor that can mitigate effects of the creative home environment.