• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.41-47
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• 2008

Line-of-sight communications cannot easily support korean armed forces because of mountainous terrain. ADD(Agency for Defense Development) introduced ANASIS(Army Navy Air-force Satellite Information System) to meet the Korean warfighter's operational needs. Currently, army's military satcom terminal is designed for either fixed site or on-the-pause operation. The US army is under development of multi-band integrated on-the-move satellite terminals to let the army's communication capability to keep pace with globally deployable Joint Task Force for network-centric application. In this paper we analyzed X-band and Ka-band link and subsystem requirement. Our focus here is to describe key technical issues. Especially, On the basis of 3dB beam width of 0.9m antenna, Tracking accuracy and disturbances compensation signal processing on-the-move of Antenna Tracking system is analyzed. Also, protocol is analyzed that minimize blockage on the move due to an obstacle. when the received signal blocked, it stop to transmit burst signal and retransmit when blockage removed through received synchronization signal monitoring. Analyzed specification will be used to make prototype terminal to analyze risk for mass production

• The Journal of the Korea Contents Association
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• v.20 no.10
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• pp.233-246
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• 2020

After the COVID-19 crisis, the world's terrain has changed completely to the extent that it has been divided before and after Corona. We are living in the era of new normals, things we never thought of before Corona19, such as wearing masks everywhere, maintaining social distance, sitting on one side in the cafeteria, and online face-to-face classes. Perhaps the most seriously affected by the COVID-19 incident is the church. How should the church respond to the various problems caused by COVID-19? This study intends to re-examine the five essential missions of the church in the post-Corona19 era. The five essences are the three essential functions of the intangible church: didake (teaching), kerygma (declaration), diakonia (service), and the two essential functions of the tangible church: koinonia (association) and leiturgia (worship). Of these, koinonia and leiturgia are the most seriously threatened by the restraint of face-to-face worship in the incident of COVID-19. In times of crisis, the church needs to strengthen its vertical koinonia with God in order to perform its didake function well and increase the efficiency of the horizontal koinonia among believers. However, in the situation where face-to-face worship is desired due to social distance, teaching and proclaiming the Bible is the most important part. For this, it is considered that a specialized ministry is needed to produce high quality contents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.144-152
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• 2018

Lunar exploration, which was led by the United States and the former Soviet Union, ceased in the 1970s. On the other hand, since massive lunar ice deposits and rare resources were found in 1990s, European Union, China, Japan, and India began to participate in lunar exploration to secure future lunar resource as well as to construct a lunar base. In the near future, it is expected that national space agencies and private industries will participate in the lunar exploration together. Their missions will include the exploration and sample return of lunar resources. Lunar resources have a close relationship with the lunar in-situ resource utilization (ISRU). To construct a lunar base, it is inevitable to bring huge amounts of resources from Earth. Water and oxygen, however, will need to be produced from local lunar resources and lunar terrain feature will need to be used to construct the lunar base. Therefore, in this paper, the global trends on lunar exploration and lunar construction technology are investigated and compared along with the ISRU technology to support human exploration and construct a lunar base on the Moon's surface.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.615-625
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• 2014

As many parts of Korea are mountainous, many tunnels have been constructed to be in step with rapid economic development since 1970's. However, the interest on maintenance of tunnels is far less than the awareness of need for tunnels. As the tunnel maintenance system is the responsive maintenance system which responds to the problems found during the inspection, it will be very difficult to respond to each problem with the limited budget and manpower of the government agencies when the number of aged tunnels rapidly increase in the future. As such, this study presents the need for the LCCA (Life Cycle Cost Analysis) based tunnel asset management system to transform the tunnel maintenance to a preventive management system in a strategic and long-term viewpoint and proposes the framework for development direction. It observed the asset management implementation cases of social infrastructure in other countries and analyzed the need for asset management technique to manage the tunnels in Korea. Moreover, it applied the LCCA model, which is the economic and engineering quantitative decision making technique, for tunnel asset management to present the concrete direction for development of an asset management model and designed the R&D framework to systemize it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6420-6426
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• 2013

The indoor areas for the commercial use of automatic monitoring systems of mobile robot localization improves the cognitive abilities and the needs of the environment with this emerging and existing mobile robot localization, and object recognition methods commonly around its great sensor are leveraged. On the other hand, there is a difficulty with a problem-solving self-location estimation in indoor mobile robots using only the sensors of the robot. Therefore, in this paper, a self-position estimation method for an enhanced and effective mobile robot is proposed using a marker and CCTV video that is already installed in the building. In particular, after recognizing a square mobile robot and the object from the input image, and the vertices were confirmed, the feature points of the marker were found, and marker recognition was then performed. First, a self-position estimation of the mobile robot was performed according to the relationship of the image marker and a coordinate transformation was performed. In particular, the estimation was converted to an absolute coordinate value based on CCTV information, such as robots and obstacles. The study results can be used to make a convenient self-position estimation of the robot in the indoor areas to verify the self-position estimation method of the mobile robot. In addition, experimental operation was performed based on the actual robot system.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.105-117
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• 2010

The topographical depressions in urban areas, the lack in drainage capability, sewage backward flow, road drainage, etc. cause internal inundation, and the increase in rainfall resulting from recent climate change, the rapid urbanization accompanied by economic development and population growth, and the increase in an impervious area in urban areas deteriorate the risk of internal inundation in the urban areas. In this study, the vulnerability of internal inundation in urban areas is analyzed and SWMM model is applied into Oncheoncheon watershed, which represents urban river of Busan, as a target basin. Based on the results, the representative storm sewers in individual sub-catchments is selected and the risk of vulnerability to internal inundation due to rainfall in urban streams is analyzed. In order to analyze the risk and vulnerability of internal inundation, capacity is applied as an index indicating the volume of a storm sewer in the SWMM model, and the risk of internal inundation is into 4 steps. For the analysis on the risk of internal inundation, simulation results by using a SMMM model are compared with the actual inundation areas resulting from localized heavy rain on July 7, 2009 at Busan and comparison results are analyzed to prove the validity of the designed model. Accordingly, probabilistic rainfall at Busan was input to the model for each frequency (10, 20, 50, 100 years) and duration (6, 12, 18, 24hr) at Busan. In this study, it suggests that the findings can be used to preliminarily alarm the possibility of internal inundation and selecting the vulnerable zones in urban areas.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.91-100
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• 2008

Numerical implementation with a Cartesian cut-cell method is conducted in this study. A Cartesian cut-cell method is an easy and efficient mesh generation methodology for complex geometries. In this method, a background Cartesian grid is employed for most of computational domain and a cut-cell grid is applied for the peculiar grids where the flow characteristics are changed such as solid boundary to enhance the accuracy, applicability and efficiency. Accurate representation of complex geometries can be obtained by using the cut-cell method. The cut-cell grids are constructed with irregular meshes which have various shape and size. Therefore, the finite volume method is applied to numerical discretization on a irregular domain. The HLLC approximate Riemann solver, a Godunov-type finite volume method, is employed to discretize the advection terms in the governing equations. The weighted average flux method applied on the Cartesian cut cell grid for stabilization of the numerical results. To validate the numerical model using the Cartesian cut-cell grids, the model is applied to the rectangular tank problem of which the exact solutions exist. As a comparison of numerical results with the analytical solutions, the numerical scheme well represents flow characteristics such as free surface elevation and velocities in x-and y-directions in a rectangular tank with the Cartesian and cut-cell grids.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.285-293
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• 2016

In the paper, we propose a data transmission repeating system that allows data transmission for the effective supervision of cows grazing in the pasture. It is normal practice to divide the pasture into different areas for the purpose of distributing the grazing. However, this makes it difficult to supply electrical power and transmit data, because some of the pastures are far away from the office used for collecting data. To solve this problem, we developed a repeating system that can allow data transmission in the pasture using a solar charging system that consists of a 60W solar panel, 12V/100A battery and 6A solar controller for the power supply and a data transmission algorithm which extends the range of data transmission when using the proposed repeating system. We verified the performance of the repeating system by checking whether the data transmission is successful or not when transmitting from various test points when there is an obstacle between the receiver and repeating system. We also verified the solar charging system by measuring the battery voltage when the system is operated continuously for 31 days and whether the system can supply sufficient power when the weather is cloudy or rainy for a few days. Finally, we verified the performance of the repeating system and data transmission algorithm by conducting experiments in a pasture.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.761-776
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• 2003

Numerical models were employed to investigate the hydrodynamics of water flow in the lake behind a dam and the spillway where supercritical flows and negative pressures are likely to occur. In this study, 2-D model, RMA2 was employed to examine the upstream flow pattern and 3-D CFD model, FLUENT was used to evaluate the three-dimensional flow in the approaching region and flow distributions in the spillways and discharge culverts. The bathymetry and the details of structures were carefully taken into consideration in building the models. The results from applying the 2-D model for the planned Hantan River Dam show that large eddies, the velocity of which reaches up to 1 m/s are occurring in several places upstream of the dam. That means that the 2-D numerical model could be utilized to investigate the two-dimensional flow patterns after the construction of a dam. Three-dimensional numerical results show that the approach flow varies depending on stages and discharge conditions, and velocities at spillways, discharge culverts, and sediment flushing tunnels are differently distributed. The velocity distributions obtained from the numerical model and a hydraulic model at the centerline of spillways 100 m upstream of the dam show reasonably similar results. It is expected that 2-D and 3-D numerical models ate useful tools to help optimize the dam design through investigating the flow patterns in the spillway and at the upstream of the dam, which is not always feasible in hydraulic modeling.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.667-679
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• 2010

The distributed hydrologic model has been considerably improved due to rapid development of computer hardware technology as well as the increased accessibility and the applicability of hydro-geologic information using GIS. It has been acknowledged that physically-based distributed hydrologic model require significant amounts of data for their calibration, so its application at ungauged catchments is very limited. In this regard, this study was intended to develop a distributed hydrologic model (S-RAT) that is mainly based on conceptually grid-based water balance model. The proposed model shows advantages as a new distributed rainfall-runoff model in terms of their simplicity and model performance. Another advantage of the proposed model is to effectively assess spatio-temporal variation for the entire runoff process. In addition, S-RAT does not rely on any commercial GIS pre-processing tools because a built-in GIS pre-processing module was developed and included in the model. Through the application to the two pilot basins, it was found that S-RAT model has temporal and spatial transferability of parameters and also S-RAT model can be effectively used as a radar data-driven rainfall-runoff model.