• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.33-43
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• 2010

Recently, users want to use real-time multimedia services, such as internet, VoIP, etc., using their IEEE 802.11 wireless lan mobile stations. In order to provide such services, a handoff among access points is essential to support the mobility of a node, in such an wide area. However, the legacy handoff methods of IEEE 802.11 technology are easy to lose connections. Also, the recognition of a disconnection and channel re-searching time make the major delay of the next AP to connect. In addition, because IEEE 802.11 decides the selection of an AP depending only on received signal strength, regardless of a node direction, position, etc., it cannot guarantee a stable bandwidth for communication. Therefore, in order to provide a real-time multimedia service, a node must reduce the disconnection time and needs an appropriate algorithm to support a sufficient communication bandwidth. In this paper, we suggest an algorithm which predicts a handoff point of a moving node by using GPS location information, and guarantees a high transmission bandwidth according to the signal strength and the distance. We implemented the suggested algorithm, and confirmed the superiority of our algorithm by reducing around 3.7ms of the layer-2 disconnection time, and guaranteed 24.8% of the communication bandwidth.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.507-515
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• 2020

The children's park, which was created uniformly during the industrialization period, is less utilized and is mainly used by the elderly during the day. In addition, sports facilities and rest facilities for the elderly are being installed, damaging the essence of children's parks. The main purpose of this study was to present the creation of a children's park that was appropriate to its essence and the utilization plan for the elderly. In this study, we conduct a survey to identify citizens' perception of children's parks and found that the opinions of children and the elderly were generally different. Children want to change and enjoy various games, while older people want to enjoy various programs while maintaining the status quo. As above, children do not dislike using the park with the elderly, but hope to create a separate park if possible. Meanwhile, the elderly want to renovate the current children's park and continue to use it. Therefore, in the future, some areas of children's parks will be created for the elderly or the entire area will be changed into small parks for the elderly, considering the location characteristics and population distribution of children's parks. In addition, the government should prepare measures for the introduction of programs for the elderly or maintenance using the elderly.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.683-690
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• 2021

The ventilation system of the engine room of a ship is generally installed to supply the combustion air necessary for the internal combustion engine and to remove the heat source generated in the engine room, and it must satisfy the international standard (ISO 8861) for the design conditions and calculation standards for the ventilation of the ship engine room. The response delay of the ventilation system including the fire detector is affected by the airflow formed inside the area and the location of the fire detector. In this study, to improve the initial fire detection response speed of a fire detector installed on a fishing vessel and to maintain the sensitivity of the installed detector, the smoke behavior was simulated using the air flow field inside the engine room, the amount of combustion air in the internal combustion engine, and the internal pressure of the engine room as variables. Analysis of the simulation results showed that reducing the flow rate in the air flow field and increasing the vortex by reducing the internal pressure of the engine room and installing a smoke curtain would accelerate the rise of the ceiling of the smoke component and improve the smoke detector response speed and ventilation system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.878-886
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• 2018

This study quantified the sounds of riffles and pools in natural rivers and conducted a comparative analysis of the frequency and sound pressure per flow velocity. The surveyed area was Namdaecheon basin in Yangyang-gun, Gangwon-do and the sounds of a total of 23 sites were analyzed. A hydro microphone was used to measure the sound and analyze the data using an acoustic analysis program. The location was also selected at places with minimal ambient noise and the measurement points were the depth of riffles and pools. The results revealed an average difference of 0.515 m/s for flow velocity at 8 riffles and 15 pools. The difference in sound pressure occurred due to the flow velocity. In the case of sound pressure, it was measured at an average of 176.8 dB for riffles and 168.2 dB for pools, demonstrating a difference of approximately 8.6 dB. Furthermore, in the case of maximum sound pressure, riffles showed a constant range between 200 Hz and 250 Hz, while the pools exhibited maximum sound pressure at various frequencies from 200 Hz to 1,000 Hz. This revealed the ecological stream reproduction, development of preferred sound sources for aquatic life, and design of structures.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.5
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• pp.79-88
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• 2018

The purpose of this study is to analyze the plan type of excavation remains during the Mid to Late Joseon period around Jong-ro area in Seoul. 523 building remains were selected in accordance with plan type could identified through the excavation investigation report. Among these, 276 building remains were verified to the $15-16^{th}$, 145 and 102 building were verified to the 17-18th and the $19^{th}$ century. By classifying excavation remains, four dominant plan type of the each century came out. First, -shape was the most common plan type took nearly 50 percent. In a considerable proportion of cases, this plan type seems an annex of main building. However, -shape plan type also seemed to be used for main building in some cases. ㄱ and ㄷshape plan type took the second and the third. In most cases, these types seemed typical plan used for a main housing building. For the last, ㅁshape plan type identified the most unusual. This plan type merely took under five percent but, these cases are meaningful because it shows the plan alteration from ㄷshape to ㅁshape plan type. Existence proportion between each plan types of the $15-16^{th}$ century were continued to the $18-19^{th}$century without small changes between -and ㄱ types in $17-18^h$ century. By examining selected excavation remains, installing front Toi space on ㄱ, ㄷ and ㅁshape plan type stand out clearly compared with -shape plan type. From this tendency, it could be considered that plan type became a significant factor influenced installing Toi space. Similar to periodical tendency of plan type was not changed dramatically, the rate of installing Toi space in the $15-16^{th}$ century was not changed much until the $18-19^{th}$ century. It also shows the close relation between plan type and installing Toi space. In some excavation remains, floor type in the $15-16^{th}$ century also verified. There are some points of similarities on installing typical location of On-dol, Ma-ru and Bu-eok in these excavation remains with later period housing type such as Ut-Bang-Gguk-Oem-Jib and Ddeul-Jib.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.245-256
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• 2023

When restoring with a dental digital system for implant-supported prosthesis, a double digital scanning technique is required: an intraoral scan of the three-dimensional implant location and intraoral scan after placement of temporary denture or provisional prosthesis. During the intraoral scan, the use of scan body as a stable landmark can improve the accuracy of digital impression and simplify laboratory process. In this case, a full-digital system was used to plan and fabricate a custom abutment, provisional prosthesis, and definitive prosthesis. After implant placement, the scan area of the intraoral scan body connected with implant and the intraoral scan body marked on the inside of temporary denture were superimposed. Out of the superimposed files, a custom abutment and provisional prosthesis were fabricated which match the vertical dimension of temporary denture, and definitive prosthesis was fabricated based on provisional prosthesis. We report this case because result has been functionally and esthetically satisfactory by using vertical dimension and central relation set during the fabrication of temporary denture to the definitive prosthesis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.77-84
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• 2024

In the fourth industrial-revolution era, the construction industry is transitioning from traditional methods to digital processes. This shift has been challenging owing to the industry's employment of diverse processes and extensive human resources, leading to a gradual adoption of digital technologies through trial and error. One critical area of focus is the safety management at construction sites, which is undergoing significant research and efforts towards digitization and automation. Despite these initiatives, recent statistics indicate a persistent occurrence of accidents and fatalities in construction sites. To address this issue, this study utilizes large-scale language-model artificial intelligence to analyze big data from a construction safety-management information network. The findings are integrated into on-site models, which incorporate real-time updates from detailed design models and are enriched with location information and spatial characteristics, for enhanced safety management. This research aims to develop a big-data-driven safety-management platform to bolster facility and worker safety by digitizing construction-site safety data. This platform can help prevent construction accidents and provide effective education for safety practices.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.249-262
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• 2024

Retaining walls are widely used in the construction of underground structures. This study reviews the stability of the high-strength joint buried pile method at a site in Korea. [Consider giving details of the location.] The method is assessed by considering the amount of ground settlement, as calculated by finite element analysis and measured at the site. Comparison of the measured and numerical results confirmed the method's stability and field applicability. Settlement of 13.42~13.65 mm was calculated for seven cross-sections [The Abstract should be comprehensible without reference to the main text. The labels A-A' to G-G' should not be introduced here without explanation.] using numerical analysis, and the measured settlement reached a maximum of 2.00 mm. The observed differences and variations [Please state what differed/varied.] did not exceed the design expectations in any section. Instruments installed at the back of the excavation area were used to assess the conditions. An underground gradient meter recorded a cumulative horizontal displacement of between -0.40 and 0.60 mm, and an underground water meter recorded slight displacements of between -0.21 and 0.28 m compared with the initial measurements. A surface settlement meter observed very little movement, with a maximum of -2.00 mm compared with the initial measurement, thereby confirming the establishment of a stable state within the management criteria.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.6
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• pp.36-45
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• 2011

Public open space(Gong-Gae-Gong-Ji) is an important part of the open-space system in an urban environment. Though part of the private sector, it has a significant public function as there are as always open to the free use of every citizen for rest and amenities. A field survey of the public open space of 71 major buildings was carried out to investigate the actual state of public open spaces in the city of Daegu. As a result of this investigation, several point of issues were discussed. In distribution by 'Gu', newly-emerging sub-centers of Daegu-City, such as Bug-Gu and Dalseo-Gu as well as downtown area have many public open spaces. By the use type of buildings, retail buildings such as shopping centers and SSM account for36.6%, business buildings21.1%, and residential and commercial complexes 15.5%, respectively. Location wise, the front areas accounted for the greatest amount(42.9%) with 1 in side area(20%), and 2 in the front/side area(20%), respectively. Degree of division was 1 spot type(45.7%), 2 division type(35.7%). The misuse of public open space for private use, such as shopping and parking lots, was26.6%. On the basis and analysis of the actual status, 6 improvement devices for public open spaces were suggested: 1) The improvement of the legal regulative system, 2) the establishment of design guidelines and strengthening of deliberation, 3) administrative and financial support, 4) periodic supervision and guidance, 5) installment of signs that shows the space is open for use to every citizen, and 6) the participation of citizens in management of public open space.

• Journal of Environmental Impact Assessment
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• v.24 no.6
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• pp.607-618
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• 2015

Five years have passed since the first set of environmental samples was taken in 2011 to represent various ecosystems which would help future generations lead back to the past environment. Those samples have been preserved cryogenically in the National Environmental Specimen Bank(NESB) at the National Institute of Environmental Research. Even though there is a strict regulation (SOP, standard operating procedure) that rules over the whole sampling procedure to ensure each sample to represent the sampling area, it has not been put to the test for the validation. The question needs to be answered to clear any doubts on the representativeness and the quality of the samples. In order to address the question and ensure the sampling practice set in the SOP, many steps to the measurement of the sample, that is, from sampling in the field and the chemical analysis in the lab are broken down to evaluate the uncertainty at each level. Of the 8 species currently taken for the cryogenic preservation in the NESB, pine tree samples from two different sites were selected for this study. Duplicate samples were taken from each site according to the sampling protocol followed by the duplicate analyses which were carried out for each discrete sample. The uncertainties were evaluated by Robust ANOVA; two levels of uncertainty, one is the uncertainty from the sampling practice, and the other from the analytical process, were then compiled to give the measurement uncertainty on a measured concentration of the measurand. As a result, it was confirmed that it is the sampling practice not the analytical process that accounts for the most of the measurement uncertainty. Based on the top-down approach for the measurement uncertainty, the efficient way to ensure the representativeness of the sample was to increase the quantity of each discrete sample for the making of a composite sample, than to increase the number of the discrete samples across the site. Furthermore, the cost-effective approach to enhance the confidence level on the measurement can be expected from the efforts to lower the sampling uncertainty, not the analytical uncertainty. To test the representativeness of a composite sample of a sampling area, the variance within the site should be less than the difference from duplicate sampling. For that, a criterion, ${i.e.s^2}_{geochem}$(across the site variance) <${s^2}_{samp}$(variance at the sampling location) was proposed. In light of the criterion, the two representative samples for the two study areas passed the requirement. In contrast, whenever the variance of among the sampling locations (i.e. across the site) is larger than the sampling variance, more sampling increments need to be added within the sampling area until the requirement for the representativeness is achieved.