• The KIPS Transactions:PartD
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• v.16D no.4
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• pp.561-570
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• 2009

In order to manage repair and maintenance efficiently in the mobile environment, the system structure to manage service as a policy and the policy description language are needed. This research defined the structure of PEP, which is the executioner of policy in the IETF policy framework, and proposed the policy description language which can be carried out under the PEP structure. The proposed policy description language derived demand matters based on documentary data and the characteristics of mobile and the policy information model was designed with the three stage approaches and was defined as policy description language. The three stage approaches are made up of the policy domain that decides the scope to which the policy applies, the policy rules which distinguish the kinds of policy application and control, and policy grammar which contextualizes the policy structure. In order to verify the efficiency of the policy description language, scenarios are defined with the policy description language and verified it by using policy tool and proved the expansive nature by comparing and analyzing other policy description language.

• Korean Journal of Construction Engineering and Management
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• v.9 no.3
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• pp.85-94
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• 2008

The process of construction industry basically consists of many complicated phase, such as planning, design, construction, MO&R(Maintenance, Operation, and Repair), and deconstruction. And various participants communicate each other during every phase of process. Since construction components have become more complex and diverse recently, many researches on how to exchange and standardization of building. However, in Korea research on IFC(Industry Foundation Classes) which is a standard for international data exchange have been conducted with only study limited Issues, such as studies on the development of 2D extension model for IFC, researches on 3D or 4D based IFC extension, and etc. This stuff covers tests of the compatibility among commercial 3D CAD programs using IFC file format. Several problems of the current IFC model are retrieved as a result.

• Journal of Soil and Groundwater Environment
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• v.22 no.4
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• pp.60-70
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• 2017

As water sources become more vulnerable to the effects of climate change such as drought and contamination, the diversification of water sources is important for securing water supply. This study examines the properties of five water sources for public supply, including river and river-bed water, dams, reservoirs, and groundwater, while ensuring that the quantities available from such sources are stable and the water itself is safe for use. This study also analyzes the power, chemical, repair and maintenance, and labor costs associated with each water source. The results demonstrate that groundwater has high potential as a water source because it is readily available (about $12.89billion\;m^3/yr$), but only a small portion of it is currently used. Analyses indicated that groundwater is the most efficient source of water to meet water demand below $1,000,000m^3/yr$, which covers 62.5% of water supply facilicities. With the implementation of groundwater dams, groundwater can become cost-efficient even for larger water demand. Additionally, the water source protection areas are the smallest for groundwater among the five water sources. In conclusion, the use of groundwater as an alternative water source is feasible becasue it is readily available, safe, cost-efficient, and requires the lowest amount of environmental regulations for the diversification of water supply sources.

• Tribology and Lubricants
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• v.37 no.2
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• pp.48-53
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• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• Advances in materials Research
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• v.8 no.2
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• pp.117-135
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• 2019

The lifetime of a gas turbine combustor is typically limited by the durability of its liner, the structure that encloses the high-temperature combustion products. The primary objective of the combustor thermal design process is to ensure that the liner temperatures do not exceed a maximum value set by material limits. Liner temperatures exceeding these limits hasten the onset of cracking which increase the frequency of unscheduled engine removals and cause the maintenance and repair costs of the engine to increase. Hot gas temperature prediction can be considered a preliminary step for combustor liner temperature prediction which can make a suitable view of combustion chamber conditions. In this study, the temperature distribution of ceramic panels for a V94.2 gas turbine combustor subjected to realistic operation conditions is presented using three-dimensional finite difference method. A simplified model of alumina ceramic is used to obtain the temperature distribution. The external thermal loads consist of convection and radiation heat transfers are considered that these loads are applied to flat segmented panel on hot side and forced convection cooling on the other side. First the temperatures of hot and cold sides of ceramic are calculated. Then, the thermal boundary conditions of all other ceramic sides are estimated by the field observations. Finally, the temperature distributions of ceramic panels for a V94.2 gas turbine combustor are computed by MATLAB software. The results show that the gas emissivity for diffusion mode is more than premix therefore the radiation heat flux and temperature will be more. The results of this work are validated by ANSYS and ABAQUS softwares. It is showed that there is a good agreement between all results.

• International journal of steel structures
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• v.18 no.4
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• pp.1336-1349
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• 2018

Generally, a precast prestressed concrete (PSC) beam is used as girders for short-to-medium span (less than 30 m) bridges due to the advantages of simple design and construction, reduction of construction budget, maintenance convenience. In order to increase the span length beyond 50 m of precast PSC girder, PSC hollow box girder with unbonded prestressed H-type steel beam placed at the compressive region is proposed. The unbonded compressive prestressing in the H-type steel beams in the girder is made to recover plastic deflection of PSC girder when the pre-stressing is released. Also, the H-steel beams allow minimization of depth-to-length ratio of the girder by reducing the compressive region of the cross-section, thereby reducing the weight of the girder. A quasi-static 3-point bending test with 4 different loading steps is performed to verify safety and plastic deflection recovery of the girder. The experimental results showed that the maximum applied load exceeded the maximum design load and most of the plastic deflection was recovered when the compressive prestressing of H-type steel beams is released. Also using prestressed H-type steel as compression reinforcements in the upper part of cross section, repair and restoration difficulty and cost of PSC girders should be significantly reduced. The study result and analysis are discussed in detail in the paper.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1159-1168
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• 2020

The conduits of agricultural reservoirs undergo deterioration over a considerable period of time and this is highly likely to cause structural problems such as cracks. It is therefore important to consider the effects of structural defects on the body from the viewpoint of stability and maintenance of the embankment. In this study, basic data on the effects of the crack location on the stability of the embankment is obtained by identifying, comparing, and analyzing the erosion characteristics and pore water pressure behavior through a large-scale model experiment that involves classifying the location of the conduit cracks. From the results of the experiment, it was confirmed that when a crack occurred, the amount of leakage increased as the location of the crack portion was closer to the water level, and the internal erosion phenomenon accelerated, thereby increasing the possibility of piping. It was also found that an upstream conduit crack affects the erosion and water pressure change of the central and downstream conduit of the embankment, and the conduit crack has a very large effect on the pore water pressure despite the low upstream water level. Therefore, the seepage behavior of the embankment for each conduit crack identified in this study is considered to be useful basic data for preparing a repair and reinforcement plan according to the crack location in the future.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.2 no.1
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• pp.42-52
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• 2021

In order to secure basic data on biodiversity for wetland conservation and management used the data from Wetland Protected Area surveys conducted in South Korea (2015-2019) to analyze the distribution of fish from a total of 15 orders, 45 families, 134 species, and 12,972 individuals. The predominant species identified were Zacco platypus (Temminck and Schlegel) (19.47%) and Zacco koreanus (Kim, Oh and Hosoya) (8.16%). Of all emergent species, 52.9% (n=71 species) were freshwater species, 26.9% (n=36) were brackish species, 3.0% (n=4) were migratory species, 27% (n=36) were marine species, and 9.0% (n=12) were riffle benthic species. Overall, 5.2% (n=7 species) were endangered species, 3.0% (n=4) were exotic species, and 23.1% (n=31) were Korean endemic species. The eight identified Wetland Protected Areas (WPA) were classified based on their habitat characteristics and on the analysis of their emergent fish communities, as estuarine (n=2), coastal dune (n=1), marsh (n=2), stream (n=2), and stream-marsh (n=1) types. The environmental factors revealed to have the greatest influence on the species diversity of emergent fish were maintenance and repair, installation of reservoirs, and construction of artificial wetlands around them. The present study offers basic information on the diversity of fish species in different Wetland Protected Area types that can be used to inform conservation and management decisions for WPA.

• International Journal of Computer Science & Network Security
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• v.22 no.2
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• pp.107-114
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• 2022

The main purpose of this study is to substantiate the theoretical and methodological foundations of the organizational and economic mechanism of development of the agro-industrial complex in modern conditions. Organizational and economic mechanism is presented as a complex organizational structure of the system type, which is aimed at performing specific functions, the characteristic feature of which is the constant support of process changes without which the organizational and economic mechanism can not exist. There are four components of the agro-industrial complex, represented by agriculture and the national economy, which ensure its operation, including industry, processing of agricultural products, its storage and transportation, sale and repair and maintenance of agricultural machinery and more. It is proved that the organizational and economic mechanism of development of agro-industrial complex in modern conditions it is expedient to consider: from the point of view of system and process approaches; as a set of economic levers and organizational measures to influence the agro-industrial complex; constituent components of organizational influence on the development of the complex; a set of components, elements that are integrated into the system of economic relations of the subjects of the agro-industrial complex; a set of purposeful stimulators of agro-industrial complex development. The functions of the organizational component of the mechanism of agro-industrial complex include: redistributive, planning, interaction, control, integration and regulatory functions, the functions of the economic component include consumer, investment and innovation, social, incentive, monitoring functions of the mechanism. The symbiosis of the functions of organizational and economic components ensure the effectiveness of the organizational and economic mechanism of the organizational and economic mechanism through its functionalities as a whole.

• Journal of Korea Port Economic Association
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• v.37 no.3
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• pp.105-116
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• 2021

Harbor floating pier is a structure in which one or several floating vessels are connected to have a port function so that ships can be bordered regardless of tide level in places where differences between tidal rocks are severe. There are 233 harbor floating piers in Korea, and 27.5% of harbor floating pier are over 30 years old. Harbor floating piers older than 30 years are potentially at high risk of accidents. However, there is no clear standard for disposal or sale of aging harbor floating pier, and the management regulations on the timing of maintenance inspection and repair are ambiguous. In this study, the AHP model was designed by classifying the problems and improvement factors of harbor floating pier facility operation through interviews with port managers and existing literature studies. The AHP analysis showed that the relative importance of the evaluation factors of the higher class was in the order of improvement of the legal system, improvement of operational management and technical improvement. This study can be used as basic data for improving the operation of Korea harbor floating pier facilities.