• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.569-576
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• 2018

In modern society, a huge number of the buildings have been constructed with RC structure. RC structures have many structural instabilities due to earthquake, typhoon, construction fault, design phase errors. Therefore, many reinforcement methods are being implemented to solve this problem. In the reinforcement method, the organic epoxy adhesive used in the FRP reinforcing method is abruptly damaged when exposed to high temperature, which is directly connected to the fall of the reinforcing material. Therefore, the present study was conducted to develop inorganic refractory mortar with a certain level of adhesion ability to reduce the heat transferred to FRP reinforcement when exposed to high temperatures. As a result of the test, it showed high adhesion strength at room temperature condition with the inclusion of EVA resin, and showed no performance deterioration up to about $300^{\circ}C$ even under heating conditions. Also, it was confirmed that the backside temperature was lower as the thickness increased, and converged to a constant temperature of about $780^{\circ}C$ after 2 hours of heating.

• The Korean Journal of Franchise Management
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• v.10 no.4
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• pp.7-18
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• 2019

Purpose: This study identifies the relative importance of the sub - factors of initial services and continuous services using AHP (Analytic Hierarchy Process) method, and calculates the competitive index for the detailed factors. The purpose of this paper is to propose the establishment of long - term and short - term management strategy for expansion of business of food service franchise, franchisors, long - term and win - win relationship with franchisees, and rationalization of operating system. Research design, data, and methodology: The population for the survey is 92 franchisees in 46 foreign brands and 46 domestic brands in the Seoul metropolitan area (Seoul / Gyeonggi / Incheon). The survey was conducted from July 1 to August 31, 2018 through the survey agency with a telephone interview and a surveyor's direct visit. A total of 100 questionnaires were collected, but a total of 92 parts were used for analysis except 8 parts that were considered to contain false information. Using the AHP method, relative importance and competitiveness index were calculated for the details of initial services and continuous services. Results: The results shows continuous services were significantly higher for both foreign brand franchises, domestic brand franchises, and overall than initial services, This suggests that the continuous services of the affiliated franchisors has a higher relative importance than the initial services. Among the continuous services, brand reinforcement and promotion were significantly higher for both foreign brand merchants and domestic brand franchises. This can be regarded as the most important factor in brand reinforcement and promotion when selecting a food service franchisors. Conclusions: In the Standard Terms and Conditions governed by the Fair Trade Commission, the franchisors should increase the fairness by creating manuals for supporting services, especially after opening, and regularly checking whether the supporting services have been carried out like manuals since the establishment of franchisees. In addition, the Brand Strengthening and Public Relations Committee (tentative name) jointly participated by the franchisors and franchisees for the purpose of strengthening and promoting the brand, suggesting a system for transparent and efficient execution of the brand reinforcement and promotion budget and monitoring afterwards.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.4244-4274
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• 2021

The utilization of UAVs in various fields has led to the development of flying ad hoc network (FANET) technology. In a network environment with highly dynamic topology and frequent link changes, the traditional routing technology of FANET cannot satisfy the new communication demands. Traditional routing algorithm, based on geographic location, can "fall" into a routing hole. In view of this problem, we propose a geolocation routing protocol based on multi-agent reinforcement learning, which decreases the packet loss rate and routing cost of the routing protocol. The protocol views each node as an intelligent agent and evaluates the value of its neighbor nodes through the local information. In the value function, nodes consider information such as link quality, residual energy and queue length, which reduces the possibility of a routing hole. The protocol uses global rewards to enable individual nodes to collaborate in transmitting data. The performance of the protocol is experimentally analyzed for UAVs under extreme conditions such as topology changes and energy constraints. Simulation results show that our proposed QLGR-S protocol has advantages in performance parameters such as throughput, end-to-end delay, and energy consumption compared with the traditional GPSR protocol. QLGR-S provides more reliable connectivity for UAV networking technology, safeguards the communication requirements between UAVs, and further promotes the development of UAV technology.

• Textile Coloration and Finishing
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• v.34 no.3
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• pp.185-196
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• 2022

In this study, carbon fiber and coated glass fiber are applied to warp and weft fiber in order to reduce the amount of carbon fiber used in carbon fiber fabrics, which are often used for reinforcement of building structures. A low-cost thermoplastic resin was coated on glass fibers to prepare a shape-stabilizing glass fiber. A unidirectional carbon fiber sheet was manufactured using the prepared coated glass fiber and carbon fiber. In order to identify whether it can be used for reinforcing architectural and civil structures, it was attached to a concrete specimen and its mechanical properties were analyzed. The optimum manufacturing conditions for the coated glass fiber were 0.3 mm in diameter of the coating nozzle, the coating temperature was 190 ℃, and the coating speed was 0.3 m/s. 14 mm was optimal for the weft spacing of the coated glass fiber. The flexural strength of the concrete reinforced with the manufactured unidirectional carbon fiber sheet was slightly lower than that of the concrete reinforced with carbon fiber fabric, but it was confirmed that the reinforcement effect was better when the amount of carbon fiber was considered.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.25-37
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• 2023

Cellular Foundation Mattress made of new materials such as high density polyethylene, are not currently use for the foundation of small and medium-sized buildings in Korea. Therefore, they need to be developed and verified based on domestic ground and field conditions. This study presents the basic design and construction method of Cellular Foundation Mattress. Since the foundation reinforcement effect of Cellular Foundation Mattress should be evaluated and verified for soft ground, a performance comparison evaluation was conducted using the Soilbag method, which is commonly used for the foundation of small and medium-sized buildings in Korea. After the mattress reinforcement, the settlement amount decreased by 38.4% compared to the original ground and the bearing capacity increased by 159%, confirming the same ground reinforcement effect and ground stability as the Soilbag method.

• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.5-13
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• 2006

Effective stresses may decrease due to generation of excessive pore pressure at the interface between soil and reinforcement in undrained condition such as rapid drawdownof groundwater level, resulting in the decrease in pullout capacity of the reinforcement. In this research, a series of laboratory pullout tests have been performed on different materials (clean sand, 5, 10, 15 and 35% silty sand), different overburden pressures (30, 100 and 200 kPa), and different drainage conditions (drained and undrained) in order to compare drained pullout capacity with undrained pullout capacity. The test results show that both drained and undrained pullout capacity are influenced by silt contents and increase with the increase of friction angle of the soil. The pullout capacity and the pullout displacement required to reach the peak value also increase as the overburden pressure increases. In undrained condition, the effective stresses acting on the reinforcement decrease as excessive pore pressures are generated, resulting in the decrease in pullout capacity and pullout displacement.

• Wind and Structures
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• v.39 no.4
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• pp.271-285
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• 2024

The multiple-fan wind tunnel is an important facility for reproducing target wind field. Existing control methods for the multiple-fan wind tunnel can generate wind speeds that satisfy the target statistical characteristics of a wind field (e.g., power spectrum). However, the frequency-domain features cannot well represent the nonstationary winds of extreme storms (e.g., downburst). Therefore, this study proposes a multiple-fan wind tunnel control scheme based on Deep Reinforcement Learning (DRL), which will completely transform into a data-driven closed-loop control problem, to reproduce the target wind field in the time domain. Specifically, the control scheme adopts the Deep Deterministic Policy Gradient (DDPG) paradigm in which the strong fitting ability of Deep Neural Networks (DNN) is utilized. It can establish the complex relationship between the target wind speed time series and the current control strategy in the DRL-agent. To address the fluid memory effect of the wind field, this study innovatively designs the system state and control reward to improve the reproduction performance based on historical data. To validate the performance of the model, we established a simplified flow field based on Navier Stokes equations to simulate a two-dimensional numerical multiple-fan wind tunnel environment. Using the strategy of DRL decision maker, we generated a wind speed time series with minor error from the target under low Reynolds number conditions. This is the first time that the AI methods have been used to generate target wind speed time series in a multiple-fan wind tunnel environment. The hyperparameters in the DDPG paradigm are analyzed to identify a set of optimal parameters. With these efforts, the trained DRL-agent can simultaneously reproduce the wind speed time series in multiple positions.

• Advances in concrete construction
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• v.9 no.3
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• pp.235-248
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• 2020

Progressive collapse in a structure occurs when load bearing members are failed and the adjoining structural elements cannot resist the redistributed forces and fails subsequently, that leads to complete collapse of structure. Recently, construction using precast concrete technology is adopted increasingly because it offers many advantages like faster construction, less requirement of skilled labours at site, reduced formwork and scaffolding, massive production with reduced amount of construction waste, better quality and better surface finishing as compared to conventional reinforced concrete construction. Connections are the critical elements for any precast structure, because in past, major collapse of precast structure took place because of connection failure. In this study, behavior of four different precast wet connections with U shaped reinforcement bars provided at different locations is evaluated. Reduced 1/3^rd scale precast beam column assemblies having two span beam and three columns with removed middle column are constructed and examined by performing experiments. The response of precast connections is compared with monolithic connection, under column removal scenario. The connection region of test specimens are filled by cast-in-place micro concrete with and without polypropylene fibers. Performance of specimen is evaluated on the basis of ultimate load carrying capacity, maximum deflection at the location of removed middle column, crack formation and failure propagation. Further, Finite element (FE) analysis is carried out for validation of experimental studies and understanding the performance of structural components. Monolithic and precast beam column assemblies are modeled using non-linear Finite Element (FE) analysis based software ABAQUS. Actual experimental conditions are simulated using appropriate boundary and loading conditions. Finite Element simulation results in terms of load versus deflection are compared with that of experimental study. The nonlinear FE analysis results shows good agreement with experimental results.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.117-127
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• 2015

Recently, there has been a string of negligent accidents for the retaining wall and slope. In order to measure the ground deformation for the MSE wall, the authors carried out the model test to assess behavioral characteristics of geogrid MSE walls in active failure state with different conditions of geogrid reinforcement. The models are built in the soil container box having dimension, 100 cm long, 90 cm height, and 10 cm wide. The reinforcement used in the model test is geogrid (polyvinyl chloride, PVC). Three geogrids are sized by $30cm{\times}60cm$, $30cm{\times}70cm$, $30cm{\times}80cm$ (width ${\times}$ length) respectively. In this study, the laboratory model tests represented for several conditions of the MSE wall, and then its results were compared to 2D FE analysis.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.58-64
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• 2010

GLI model was verified to consider the interaction between a ground and a tunnel lining and to rationally reduce the ground load acting on the secondary lining(concrete lining) of a tunnel. In this study, the economy and the construction condition of tunnel concrete linings designed by a conventional frame model at Lot O of OO line were highly enhanced through a field design change using GLI model. For a few safe considerations, not only about 50% saving of reinforcing steel could reduce the material cost but also the wide space between bars could make it easy to pour concrete mix without voids. There was large saving effect of reinforcing steel for poor ground conditions because Terzaghi's load used in the conventional frame model produces too much high loads for those conditions.