• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3587-3595
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• 2015

Low-carbon eco-friendly precast concrete (PC) box structure has been recently was developed as an low-cost infrastructure of near-surface transit system. The concrete of PC box was manufactured by industrial byproducts such as ground granulated blast furnace (GGBF) slag, flyash and rapid-cooling electric arc furnace (EAF) oxidizing slag, its mechanical property and durability were estimated in this study. Based on the mechanical and durability tests, it is found that low-carbon eco-friendly concrete shows high initial compressive strength, more than 90% of design strength (35MPa), and high resistance to salt-attack, chemical- attack and freeze-thaw. Therefore, low-carbon eco-friendly PC box concrete technology is expected to contribute to the railway with low environmental impact.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.56-62
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• 2021

The purpose of this study was to address a Remote Airborne Control Simulator that could simulate manned-unmanned teaming (MUM-T mission) for fixed wing UAV. With rapid technological development of unmanned aerial vehicle (UAV), the mission capability of UAV has tremendously grown. The role of UAV extends from simple reconnaissance to highly automated wingman. Accordingly, the requirement of UAV ground simulator should be modified as well to meet function requirements for simulating a MUM-T mission. A developed remote airborne control simulator was developed for conducting fixed wing UAV MUM-T operation simulations on the ground. The newest MUM-T examples, usage, and application of the developed remote airborne control simulator for MUM-T simulation are also presented in this study.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.207-218
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• 2022

In submerged floating tunnels (SFTs), a next-generation maritime transportation infrastructure, the tunnel module floats in water due to buoyancy. For the effective and economical use of SFTs, connection with the ground is inevitable, but the stability of the shore connection is weak due to stress concentration caused by the displacement difference between the subsea bored tunnel and the SFT. The use of an elastic joint has been proposed as a solution to solve the stability problem, but it changes the dynamic characteristics of the SFT, such as natural frequency and mode shape. In this study, the finite element method (FEM) was used to simulate the elastic joints in shore connections, assuming that the ground is a hard rock without displacement. In addition, a small-scale model test was performed for FEM model validation. A parametric study was conducted on the resonance behavior such as the natural frequency change and velocity, stress, and reaction force distribution change of the SFT system by varying the joint stiffness under loading conditions of various frequencies and directions. The results indicated that the natural frequency of the SFT system increased as the stiffness of the elastic joint increased, and the risk of resonance was the highest in the low-frequency environment. Moreover, stress concentration was observed in both the SFT and the shore connection when resonance occurred in the vertical mode. The results of this study are expected to be utilized in the process of quantitative research such as designing elastic joints to prevent resonance in the future.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.4
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• pp.9-20
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• 2011

Future warfare paradigm is changing to network-centric warfare and effects-based operations. In order to find first and strike the enemy in the battlefield, friendly unit requires real-time target acquisition, intelligence collection, accurate situation assessment, and timely decision. The rapid development in advanced sensor technology and wireless networks requires a significant change in operational concepts of the battlefield surveillance. In particular, the introduction of a battlefield surveillance sensor network system is a big challenge to the ground forces which have lack of automated information collection assets. Therefore this paper proposes an ontology-based context-aware framework for the battlefield surveillance sensor network system which is needed for early finding the enemy and visualizing the battlefield in the ground force operations. Compared with the performance of existing systems, the one of the proposed framework has shown highly positive results by applying the context systems evaluation method. The framework has also proven to be satisfactory by the structured evaluation method using device collaboration. Since the proposed ontology-based context-aware framework has a lot of advantages in terms of scalability and reusability, the ground force's reconnaissance and surveillance system can be widely applied to expand in the future. And, ontology-based model has some weak points such as ontology data size, processing time, and limitation of network bandwidth. However, these problems can be resolved by customizing properly to fit the mission and characteristics of the unit. Moreover, development of the next-generation communication infrastructure can expedite the intelligent surveillance and reconnaissance service and may be expected to contribute greatly to expanding the information capacity.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.6_1
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• pp.565-574
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• 2007

Because of most current cadastral systems maintain 2D geometric descriptions of parcels linked to administrative records, the system may not reflect current tendency to use space above and under the surface. The land has been used in multi-levels, e.g. constructions of multi-used complex buildings, subways and infrastructure above/under the ground. This cadastre situation of multilevel use of lands cannot be defined as cadastre objects (2D parcel-based) in the cadastre systems. This trend has requested a new system in which right to land is clearly and indisputably recorded because a right of ownership on a parcel relates to a space in 3D, not any more relates to 2D surface area. Therefore, this article proposes a 3D spatial data model to represent geometrical and topological data of 3D (property) situation on multilevel uses of lands in 3D cadastre systems, and a conceptual 3D cadastral model in Korea to design a conceptual schema for a 3D cadastre. Lastly, this paper presents the results of an experimental implementation of the 3D Cadastre to perform topological analyses based on 3D Network Data Model to identify spatial neighbors.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.826-841
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• 2018

The military satellite communication of ROK military, ANASIS is designed for analog data such as voice and streaming data. ANASIS cannot fully support ALL-IP communications due to its long propagation delay. The next generation satellite communication system is being designed to overcome the limitation. Next generation satellite communications system considers both high-speed and low-speed networks to support various operating environment. The low-speed satellite supports both broadband and narrow-band communication. This network works as the infrastructure for of wide-area internetworking over multiple AS's in the terrestrial network. It requires minimum satellite frequency and minimum power and works without PEP and router. In this paper, we propose a network operation structure to enable the inter-operation between high and low-speed satellite networks. In addition, we propose a data link protocol for low speed satellite networks.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.45-52
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• 2019

Accident analysis models were developed to improve the construction site safety and case studies was conducted. In 2016, 86% of fatality accidents occurred due to simple unsafe acts. Structure related accidents are less frequent than the non structure related causes, but the number of casualties per accident is two times higher than non structure one. In the view of risk perception, efforts should be given to reduce accidents caused by low frequency - high consequence structure related causes. In case of structure related accident, structural safety inspection and management (including quality), ground condition management / inspection technology, and provision of risk information delivery system in case of non structure related accident were proposed as a solution. In analysis of relationship between safety related stakeholder, the main problem were the lack of knowledge of controller and player, loss of control due to duplicated controls, lack of communication system of risk information, and relative position error of controller and player.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.1
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• pp.47-59
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• 2023

Due to climate change and urbanization, abnormally high temperatures and heat waves are expected to increase in urban and deteriorate thermal comfort. Planting of street trees and changing the albedo of urban surfaces are the strategies for mitigating the thermal environment of urban, and both of these strategies affect the exposure and blocking of radiative fluxes to pedestrians. After measuring the shortwave and longwave radiation according to the ground surface with different albedo and the presence of street trees using the CNR4 net radiometer, this study analyzed the relationship between this two strategies in terms of thermal environment mitigation by calculating the MRT(Mean Radiant Temperature) of each environment. As a result of comparing the difference between the downward shortwave radiation measured under the right tree and at the control, the shortwave radiation blocking effect of the tree increased as the downward shortwave radiation increased. During daytime hours (from 11 am to 3 pm), the MRT difference caused by the albedo difference(The albedo of the surfaces are 0.479 and 0.131, respectively.) on surfaces with no tree is approximately 3.58℃. When tree is present, the MRT difference caused by the albedo difference is approximately 0.49℃. In addition, in the case of the light-colored ground surface with high albedo, the surface temperature was low and the range of temperature change was lower than the surrounding surface with low albedo. This result shows that the urban thermal environment can be midigate through the planting of street trees, and that the ground surface with high albedo can be considered for short pedestrians. These results can be utilized in planning street and open space in urban by choosing surfaces with high albedo along with the shading effect of vegetation, considering the use by various users.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.9-16
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• 2016

During the 2004 Niigata-ken Chuetsu, Japan, earthquake, more than 1,450 underground structures, known as sewer manhole, were uplifted up to 1.5m in Nagaoka and Ojiya city. The uplift damage can be a serious matter because they not only hinder the flow of wastewater systems, as a part of lifeline systems, but also disturb traffic flows. For restoration works, an open-cut investigation of damaged wastewater system was conducted by the Nagaoka city government. The results from the investigation compiled valuable data sets for buried pipeline damage due to earthquakes. In the present study, the factors affecting the uplift amount of the underground structure is investigated by using the data sets which include locations of damaged sections and inclination of pipeline before and after the earthquake and the SPT borehole logs in the affected area. Correlation analysis between the underground structure uplift and the geological settings in the affected area revealed that ground water depth and original subsoil, including thickness of clay layer, SPT N-value and fill thickness are the key parameters for the uplift phenomenon.

• Earthquakes and Structures
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• v.18 no.2
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• pp.147-162
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• 2020

This paper presents a novel precast energy dissipation shear wall (PEDSW) structure system that using mild steel dampers as dry connectors at the vertical joints to connect adjacent wall panels. Analytical studies are systematically conducted to investigate the seismic performance of the proposed PEDSW under sequence-type ground motions. During earthquake events, earthquake sequences have the potential to cause severe damage to structures and threaten life safety. To date, the damage probability of engineering structures under earthquake sequence has not been included in structural design codes. In this study, numerical simulations on single-story PEDSW are carried out to validate the feasibility and reliability of using mild steel dampers to connect the precast shear walls. The seismic responses of the PEDSW and cast-in-place shear wall (CIPSW) are comparatively studied based on nonlinear time-history analyses, and the effectiveness of the proposed high-rise PEDSW is demonstrated. Next, the foreshock-mainshock-aftershock type earthquake sequences are constructed, and the seismic response and fragility curves of the PEDSW under single mainshock and earthquake sequences are analyzed and compared. Finally, the fragility analysis of PEDSW structure under earthquake sequences is performed. The influences of scaling factor of the aftershocks (foreshocks) to the mainshocks on the fragility of the PEDSW structure under different damage states are investigated. The numerical results reveal that neglecting the effect of earthquake sequence can lead to underestimated seismic responses and fragilities, which may result in unsafe design schemes of PEDSW structures.