• Journal of Bio-Environment Control
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• v.17 no.3
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• pp.188-196
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• 2008

Single span pipe greenhouses (pipe houses) are widely used in Korea because these simple structures are suitable for construction by farmers thus reducing labor cost. However, these pipe houses are very weak and frequently damaged by heavy snow and strong wind. Pipe house is constructed by pipe fabricator, which is anchored to the ground by inserting each pipe end into ground to $30\sim40cm$, so the ground support condition of pipe end is not clear for theoretical analysis on greenhouse structure. This study was carried out to find out the suitable ground support condition needed f3r structural analysis when pipe house was designed. The snow and wind loading tests on the actual size pipe house were conducted to measure the collapsing shape, displacement and strain. The experimental results were compared with the structural analysis results for 4 different ground support conditions of pipe ends(fixed at ground surface, hinged at ground surface, fixed under ground and hinged under ground). The pipe house under snow load was collapsed at the eaves as predicted, and the actual strain at the windward eave and ground support under wind load was larger than that under snow load. The displacement was the largest at the hinged support under ground, followed by the hinged at ground surface, the fixed under ground and then the fixed at ground surface independent of displacement direction and experimental loading condition. The experimental results agreed most closely with the results of theoretical analysis at the fixed condition under ground among 4 different ground support conditions. As the results, it was recommended that the pipe end support condition of single span pipe greenhouse was the fixed under ground for structural analysis.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.60-67
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• 2001

Multicast Protocol for multimedia service on the Internet can be classified into two types, e.g., source based tree and shared tree according to difference of tree construction method. Shared tree based multicast is known to show outstanding results in the aspect of scalability than source based tree. Generally, There have been lots of researches on the method to satisfy QoS constraints through proper Rendezvous Point (RP) in the shared tree. In addition, as the multicast group members join and leave dynamically in the service time, RP of the shared tree should b be reselected for guranteeing Qos to new member, But, RP reselection method has not been considered generally as the solution to satisfy QoS C constraints. In this paper, new initial RP selection and RP reselection method are proposed, which utilize RTCP (Real Time Control Protocol) report packet fields. Proposed initial RP selection and RP reselection method use RTCP protocol which underlying multimedia application service So, the proposed method does not need any special process for collecting network information to calculate RP. New initial RP selection method s shows better performance than random and topology based one by 40-50% in simulation. Also, RP reselection method improves delay p performance by 50% after initial RP selection according to the member’s dynamicity.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.251-267
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• 2008

In this paper, we present a distributed topology control algorithm for constructing an optimized topology having a minimal search-time in unstructured peer-to-peer network. According to the proposed algorithm, each node selects the best nodes having higher hit-ratio than other nodes as many as the number being exponentially proportional to the hit-ratio of the node itself, and then it connects to them. The ensemble behavior of the proposed algorithm is very similar to the recrystrallizing phenomenon that is observed in nature. There is a partial order relationship among the hit-ratios of most nodes of constructed topology. Therefore once query message visits a node, it has a higher hit-ratio than the node that was visited last by the message. The query message even sent from freeloader can escape to the node having high hit-ratio by one hop forwarding, and it never revisits any freeloader again. Thus the search can be completed within a limited search time. We also propose the Chain-reactive search scheme using the constructed topology. Such a controlled multicasting reduces the query messages by 43 percent compared to that of the naive Gnutella using broadcasting, while it saves the search time by 94 percent. The search success rate of the proposed scheme is 99 percent.

• Journal of environmental and Sanitary engineering
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• v.18 no.3 s.49
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• pp.100-109
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• 2003

Recently, Indoor air quality(IAQ) in workplace, residential environments and schools has been concern of people, scientists and related the public. And so in Seoul has recognized the healthy effect related to IAQ in schools. Therefore, the objective of this study reported in this article were to measure and compare the perception of IAQ of selected air pollutants at three different schools in Seoul. We performed a questionnaire survey of 400 students about their awareness for the importance of IAQ in our school. And we measured the IAQ of 3 schools considering as site region, construction year and studying level. The indoor air pollutants and parameters such as temperature, relative humidity, respirable particulate matter(PM10), formaldehyde(HCHO), total bacteria counts(TBC), carbon dioxide(CO$_2$), and noise were monitored in indoors. In results, all most response of occupant has recognized the awareness of IAQ at schools. The PMIO, TBC and Noise level of all schools were higher than the standard of the public 150 ${mu}$g/m$^3$ and 500CFU/m$^3$, the level formaldehyde(HCHO) was below 0.1 ppm of the healthy guideline of Korea And the concentration of CO$_2$ were investigated below 1,000 ppm of the standard implying ventilation in 2 schools except for 1 school(c school). Finally, the control of most important pollutants of IAQ in school were PM10, TBC and Noise. Therefore, it can be concluded that the indoor air quality of selected 3 schools studied was perceived as acceptable, it is recommended that the government related IAQ was suggested the guideline and control of IAQ problems in schools, and all member relating school need to be effort to reduce the exposure of sources to undesirable indoor pollutants such as Particlate and Noise.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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• pp.278-285
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• 2016

The key features of maritime accidents are the change of their attributes by new risks from time to time. To prevent maritime accidents in Korea, the impacts by new risks on domestic safety environments should be identified or predicted. The purpose of this paper is to find the hazard factors by new risks on maritime safety in Korea. The meaning of new risks is the elements of accident hazard which is compiled from new or rare or unprecedented events in the worldwide maritime transportations. The problems of new risks are the lacks of optimum countermeasures to mitigate accident risks. Using the questionnaires with 152 event scenarios classified by 20 accident causes, the hazard identification and risk analysis of new risks was performed based on the Formal Safety Assessment (FSA) by IMO. A total of 22 Influence Diagrams, which is to depict the transit flows between accident causes to consequences, is used in the construction of 152 event scenarios. A total of 20 accidents causes is the same contents as the causation factors represented in Statistical Year Book for Maritime Accidents of Korean Maritime Safety Tribunals. After defining the evaluation equations to the response results of questionnaires by 46 experts, the work for risk analysis is carried out. As results from the analysis of 152 scenarios, it is known that the root cause to affect on maritime safety in Korea is the pressure of business competition and it led to the lacks of well experienced crews, the overload of vessel operations and crew's fatigue. In addition, as results from the analysis of 20 accident causes, the three accident causes are to be candidate as main issues in Korea such as the inadequate preparedness of departure, the neglecting of watch keeping in bridge and the inadequate management of ship operations. All of the results are thought to be as basic hazard factors to safety impediments. It is thus found that the optimum Risk Control Options to remove the hazard factors and to mitigate consequences required are the following two factors: business competition and crewing problems.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.354-364
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• 2017

The importance of marine pollution prevention is increasing day by day both at home and overseas. Against this context, this study proposes policy directions to forge an improved system of coastal control for local governments. I have analyzed the coastal pollution response capacity of local governments to find out how the central government can better support these efforts to reinforce capacity. For the purposes of this research, I carried out a number of case studies on large-scale marine pollution accidents that occurred at home and abroad. According to the results, I identified the implications of the coastal pollution response capacity of local governments and suggested several alternatives such as construction of step by step response system, strengthening education and training, part of human network activation, establishment of grounds for securing response resources, and establishment of dedicated department to prepare for potential future marine pollution accidents. However, as little research has been done on the coastal pollution response capacity of local governments, this work may be regarded as an experimental study to help facilitate follow-up research in the future.

• Journal of Conservation Science
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• v.31 no.4
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• pp.387-393
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• 2015

Damages of wooden cultural heritages caused by various bio-species have been a trend that is increasing on climate change. The decay and bio-damage caused by microbial organisms or insect species are also known to factors of the shape changes and structural problems of wooden cultural heritages. There are so many phenomenons of damage and weathering in wooden cultural heritage for many years and particularly termite can threaten seriously wooden cultural heritage. We investigated with respect to internal and external environment and termite inhabitation around the wooden cultural heritage in Jeollanam-do, Jeollabuk-do, and Jeju-do. As this investigation results, we confirmed that there were the difference in between resident and non-resident about temperature, humidity, moisture contents of wooden building. Resident building is high temperature but humidity and moisture contents is low and these factors are sources of inhabitation condition change about insects as termites. Now we suggest to carry out in parallel to the target wooden cultural heritage and the surrounding habitat for wooden cultural heritage termite damage investigation. Also with the chemical control methods, we must consider necessary to present eco-friendly control management such as construction of heating facilities, residential status, periodic management.

• Journal of KIISE:Information Networking
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• v.34 no.3
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• pp.226-238
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• 2007

In this paper, we present a novel fully distributed topology control protocol that can construct the multiple-ring topology of Minimal Connected Dominating Set (MCDS) as the transport backbone for mobile ad hoc networks. It makes a topology from the minimal nodes that are chosen from all the nodes, and the constructed topology is comprised of the minimal physical links while preserving connectivity. This topology reduces the interference. The all nodes work as the nodes of the distributed parallel Boltzmann machine, of which the objective function is consisted of two Boltzmann factors: the link degree and the connection domination degree. To define these Boltzmann factors, we extend the Connected Dominating Set into a fuzzy set, and also define the fuzzy set of nodes by which the multiple-ring topology can be constructed. To construct the transport backbone of the mobile ad hoc network, the proposed protocol chooses the nodes that are the strong members of these two fuzzy sets as the clusterheads. We also ran simulations to provide the quantitative comparison against the related works in terms of the packet loss rate and the energy consumption rate. As a result, we show that the network that is constructed by the proposed protocol has far better than the other ones with respect to the packet loss rate and the energy consumption rate.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.167-174
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• 2010

Recently the distributed topology control algorithm for constructing the Recrystallization Topology in the unstructured peer-to-peer network was proposed. In this paper, we prove that such a hierarchical topology is a scale-free power-law network. We present a model of a construction process of the distributed protocol, and analyze it based on a mean-field approximation and the continuum theory, so that we show that the constructed Recrystallization Topology is a scale-free network. In the proposed model, all nodes are born with some initial attractiveness and the system incorporates the rewiring of some links at every time step. Some old links are removed with the anti-preferential probability, and some new links are added with preferential probability. In other words, according to the distributed algorithm, each node makes connections to the more-preferential nodes having higher hit-ratio than other nodes, while it disconnects the anti-preferential nodes having lesser hit-ratio. This gives a realistic description of the local processes forming the recrystallization topology in unstructured peer-to-peer network. We calculate analytically the degree distribution. The analytic result indicates that the constructed network is a scale-free network, of which the scaling exponent is 3.

• Journal of Korea Water Resources Association
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• v.43 no.10
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• pp.883-891
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• 2010

More recently, there have been significant changes in the forms of channels due to runoff characteristics driven by climate changes and other alterations in basin/channel environments. Particularly, increasing local deposition in major channels is being observed nationwide. Of such phenomena, it is noteworthy that flood-plains show unidirectional growth and lowering of channels within compound channels in the form of a high-flow plain. These changes are supposed to affect management of the river ecology as well as flood control. In this study, the research on channels in Korea confirmed that the phenomenon of local deposition in those channels is actually taking place, rendering a problem to be urgently addressed. Previous studies on bed changes have been focused on low channels based on bed materials distributed over the channels. However, this research has proved that surface-layer deposition of a high-flow plain is closely related with changes in the conditions of ground surfaces and, ultimately, affects the bed of the entire channel as well. According to the intensive research on the condition of the high-flow plain of the mouth of the Han River, the silt deposited in the high-flow plain was the main cause of settlement/growth of vegetation. And this leads to landforming along with woods-forming, disturbing flood control as well as the normal river ecology.