• International Journal of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.128-133
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• 2023

Satellite based communication is networks in which users in a wide area can access without wired-based ground infrastructure. In particular, the need is emerging due to the recent Ukraine-Russia war. Satellite network systems acquire data that is difficult to observe on Earth as well as communication networks and are also used for research and development, which allows additional data to be produced. However, due to the nature of communication networks existing in outer space, certain vulnerabilities are revealed, and attacks based on them can be exposed. In this paper, we analyze vulnerabilities that may arise due to the nature of satellite communication networks and describes current research, countermeasures, and future research directions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.573-585
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• 2019

The objective of this study is to propose the drainage system that has been improved the workability, waterproofing and drainage performance to treat the leakage from the cement concrete structures in underground. It is improved that the pipe for conveying ground leak in the existing drainage system had the problem in workability and waterproof. The drainage systems with the improved pipe for conveying ground leak were constructed in conventional concrete lining tunnels to evaluate the workability, waterproofing and drainage. The waterproof and the drainage performance of the drainage system was evaluated by injecting 1,000 ml of red water in the back of the drainage system at 3 weeks, 6 weeks, 9 weeks, 11 weeks, 14 weeks, 17 weeks and 23 weeks. During 6 months of field performance test, the average daily temperature of the tunnel site was measured from $-12.4^{\circ}C$ to $19.7^{\circ}C$. The daily minimum temperature was $-17.2^{\circ}C$ and the daily maximum temperature was $26.7^{\circ}C$. There was no problem in waterproof and drainage performance on the pipe for conveying ground leak and the drainage system during 6 months for field performance test. It is concluded that the improved drainage system can be applied to various cement concrete underground structures where leakage occurs, and has little seasonal effect.

• Journal of the Korean Geotechnical Society
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• v.30 no.12
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• pp.63-72
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• 2014

To observe the behavior of lateral deformation of buried pipe and the preventing effect of embankment piles against the lateral deformation, a series of full-scale field tests were performed on a reclaimed coastal area. A buried pipe was installed in the west coast undergoing reclamation and embankment was performed by three steps. Then vertical settlement and lateral displacement were measured by the settlement plate and the inclinometer. Embankment pile system were applied to prevent the lateral displacement of buried pipe. Heave of the buried pipe slightly happens during embankment and following settlement. Finally the behavior steadily converged. The preventing effect of the embankment pile was approximately two times stronger than non-reinforcement. Both settlement and lateral displacement appear to be bigger at upper ground and smaller at lower ground.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.43-51
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• 2009

This paper holds three objects. The first is to analyze surveys of concerning zone and promotion department. The data were collected through an examination of construction excavated in coastal soft (marine) clay and measurements obtained during excavating construction. The second is to observe the appropriate selection and the application of support system on earth retaining wall in soft clay. Lateral deformation behavior during the excavating construction according to the differences in a soft ground pressuring degree was investigated. The third is to compare the results with those of numerical analysis. Therefore, the purpose of this study is to analyze the characteristics of lateral deformation when soft ground improvement for the expansion of infrastructure in object of study zone has been incompleted. Also, it is to identify the relationship between the degree of consolidation of soft ground and lateral deformation, in a method of displacement quantity in compliance with the numerical analysis and a quatitative analysis. In conclusion, displacement of excavated section after consolidation was fewer 60% averagely than section under consolidation.

• Earthquakes and Structures
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• v.13 no.4
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• pp.377-386
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• 2017

Earthquake-induced pounding damages to building structures were repeatedly observed in many previous major earthquakes. Extensive researches have been carried out in this field. Previous studies mainly focused on the regular shaped buildings and each building was normally simplified as a single-degree-of-freedom (SDOF) system or a multi-degree-of-freedom (MDOF) system by assuming the masses of the building lumped at the floor levels. The researches on the pounding responses between irregular asymmetric buildings are rare. For the asymmetric buildings subjected to earthquake loading, torsional vibration modes of the structures are excited, which in turn may significantly change the structural responses. Moreover, contact element was normally used to consider the pounding phenomenon in previous studies, which may result in inaccurate estimations of the structural responses since this method is based on the point-to-point pounding assumption with the predetermined pounding locations. In reality, poundings may take place between any locations. In other words, the pounding locations cannot be predefined. To more realistically consider the arbitrary poundings between asymmetric structures, detailed three-dimensional (3D) finite element models (FEM) and arbitrary pounding algorithm are necessary. This paper carries out numerical simulations on the pounding responses between a symmetric rectangular-shaped building and an asymmetric L-shaped building by using the explicit finite element code LS-DYNA. The detailed 3D FEMs are developed and arbitrary 3D pounding locations between these two buildings under bi-directional earthquake ground motions are investigated. Special attention is paid to the relative locations of two adjacent buildings. The influences of the left-and-right, fore-and-aft relative locations and separation gap between the two buildings on the pounding responses are systematically investigated.

• Journal of The Korean Society of Grassland and Forage Science
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• v.41 no.4
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• pp.295-301
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• 2021

In this study we developed the ground-based multispectral camera system to determine proper period to build and apply the calibration equation for dry matter of winter forage corps monitoring by unmanned aerial vehicle (UAV). Normalized difference vegetation index (NDVI) of rye, whole barley and Italian ryegrass (IRG) were measured and the growth period was divide by NDVI increasing period and decreasing period. Day of the maximum NDVI value of rye, whole barley and IRG were 8th, 9th and 5th April 2020. Regression analysis showed that the correlation coefficients (R²) between dry matter and NDVI were 0.84, 0.84, 0.78 during NDVI increasing period and 0.00, 0.02, 0.27 during NDVI decreasing period. Therefore, detailed NDVI monitoring is required to determine the proper period to build and apply the calibration equation and the ground-based multispectral camera system was effective tool for detailed NDVI monitoring.

• Journal of the Korean Society of Systems Engineering
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• v.5 no.2
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• pp.49-56
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• 2009

KC-100(KAI Civil Aircraft, Small Series) aircraft is 4 seats general aviation aircraft with single piston engine which is developing under FAA part 23 category by Korea Aerospace Industries(KAI) and will be a shadow program for civil aircraft safety infrastructure improvement. This aircraft will be the first civil aircraft developed in Korea meeting the Korean regulatory KAS Part 23 requirements. Type certification for KC-100 aircraft was applied at the second half of this year. The type certificate is expected to be issued after 3 years of design, prototype manufacturing, ground and flight tests. In this paper the system engineering process for civil aircraft was first reviewed. Next, the differences and similarities in the system development between military and civil aircraft were systematically examined using experiences for KAI military aircraft development program.

• Smart Structures and Systems
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• v.5 no.6
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• pp.663-679
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• 2009

The use of Micro-Electro-Mechanical Systems (MEMS) accelerometers in geotechnical instrumentation is relatively new but on the rise. This paper describes a new MEMS-based system for in situ deformation and vibration monitoring. The system has been developed in an effort to combine recent advances in the miniaturization of sensors and electronics with an established wireless infrastructure for on-line geotechnical monitoring. The concept is based on triaxial MEMS accelerometer measurements of static acceleration (angles relative to gravity) and dynamic accelerations. The dynamic acceleration sensitivity range provides signals proportional to vibration during earthquakes or construction activities. This MEMS-based in-place inclinometer system utilizes the measurements to obtain three-dimensional (3D) ground acceleration and permanent deformation profiles up to a depth of one hundred meters. Each sensor array or group of arrays can be connected to a wireless earth station to enable real-time monitoring as well as remote sensor configuration. This paper provides a technical assessment of MEMS-based in-place inclinometer systems for geotechnical instrumentation applications by reviewing the sensor characteristics and providing small- and full-scale laboratory calibration tests. A description and validation of recorded field data from an instrumented unstable slope in California is also presented.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.1
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• pp.45-54
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• 2017

The youth unemployment problem has become a consistent issue with the number recently surpassing 1million. The marine and fisheries sector, being no exception, is having problems attracting outstanding individuals to the sector on the one hand, and in providing high quality jobs on the other, resulting in an imbalance in the supply and demand of the marine and fisheries sector workforce. In order to supply a workforce that meets the future and on the ground demands, addressing of the qualitative rather than the quantitative aspects of the imbalance issue is more important. Thus, the following strategies are recommended: 1) focus on developing a highly skilled workforce that corresponds to future and on the ground demands; 2) improve educational infrastructures such as training equipment, and enhance the professional capacity of school teachers; 3) establish an integrated system for the management of the education and re-education of human resources.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.263-267
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• 2013

This paper describes the progress and the plan of 'Wide Area Differential GPS (WA-DGPS) Development' project supported by Korean Ministry of Oceans and Fisheries. The project develops the main algorithms of the WA-DGPS which guarantees the improved accuracy, availability, and integrity all over the Korean peninsula. After the establishment of WA-DGPS ground infrastructure system, a real-time demonstration using pseudolite installed on the ground will be conducted in the final year. Also, the development of Korean Satellite-based Augmentation System (SBAS) is expected to be started from 2014, and the algorithms and the results in the WA-DGPS project will be used in the SBAS development.