• Geomechanics and Engineering
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• v.15 no.3
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• pp.823-831
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• 2018

The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.2
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• pp.101-108
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• 2013

GPS is the most widely-used Positioning, Navigation, and Timing (PNT) system. Since GPS is an important PNT infrastructure, the vulnerability of GPS to signal jamming has received significant attention. Especially, South Korea has experienced intentional high-power jamming from North Korea for the past three years, and thus realized the necessity of a complementary PNT system. South Korea recently decided to deploy a high-power terrestrial navigation system, eLoran, as a complementary PNT system. According to the plan, the initial operational capability of the Korean eLoran system is expected by 2016, and the full operational capability is expected by 2018. As a necessary research tool to support the Korean eLoran program, an eLoran performance simulation tool for Korea is under development. In this paper, the received signal strength, which is necessary to simulate eLoran performance, from the suggested Korean eLoran transmitters is simulated with the consideration of effective ground conductivities over Korea. Then, eLoran signal-to-noise ratios are also simulated based on atmospheric noise data over Korea. This basic simulation tool will be expanded to estimate the navigation performance (e.g., accuracy, integrity, continuity, and availability) of the Korean eLoran system.

• Tunnel and Underground Space
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• v.25 no.5
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• pp.417-422
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• 2015

This paper introduces the design and operational considerations for TBM tunneling in boulder bed which poses significant problems in terms of advance rate and machine wear. Managing these problems is difficult since normal soil investigation techniques do not accurately predict the presence and frequency of boulders. This has leads to considerable extra costs and delays during construction. In this paper, EPBM design and operational parameters, cutter wear characteristics and soil conditioning method in soft ground condition were studied and key successes were highlighted for future projects in similar ground condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.441-450
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• 2007

In this paper, it is proposed the link performance analysis results using SNRAT(Satellite Network Resource Allocation & Analysis Tool) and verified the anticipated results by satellite communication network simulator. A communication satellite cannot be corrected or fixed for the error in orbit operation after launching unlike the ground operation equipment and has a restricted operation life. So, it is important to make possible to use satellite communications in the proper time. It is expected the link BER(Bit Error Rate), throughput and AJ(Anti-Jamming) performance using SNRAT tool before launching. And it is verified the performance of the repeaters and ground equipment specification using the satellite network simulator and is extracted the optimum operational scenarios through the tests of various network operational plans.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.4
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• pp.115-125
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• 2014

Ground-Based Augmentation System (GBAS) is providing precision approach and landing service with aircraft around airport. FAA granted System Design Approval (SDA) of SLS-4000 to Honeywell as the first GBAS category I system on September 2009. Since then, according to their own kind of approval process including System Design Approval, Facility Approval and Operational Approval, USA, Germany, Spain and Australia have approved GBAS category I system which are installed in some airports in order to provide commercial GBAS service. Recently, KARI has also installed GBAS category I system into Gimpo international airport to establish operational technology of GBAS domestically and to validate effectiveness of GBAS system in Korea. This paper introduces overseas trends and activities regarding approval process of GBAS system and presents approval process and criteria appropriate for future commercial operation of GBAS in Korea.

• Tunnel and Underground Space
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• v.29 no.6
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• pp.394-406
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• 2019

Difficult ground conditions (e.g., fault zone and mixed grounds) are highly probable to appear in subsea and urban tunnels because of the shallow working depth and alluvial characteristics. TBM usually experienced decrease of penetration rate and increase of downtime when it meets these difficult ground conditions. The problems are usually caused by the adverse geological conditions, and it is preferable to determine the optimal operational parameters of TBM based on the previous operational data obtained while excavating a preceding tunnel. This study carried out for efficient TBM excavation in fault zone and mixed grounds. TBM excavation data from the tunnel site in Singapore and the characteristics of the TBM excavation data was analyzed. The key operational parameters (i.e., thrust, torque, and RPM), penetration rate, and downtime were highly influenced by the presence of fault zones and mixed grounds, and the features was discussed. It is expected that the results and main discussions will be useful information for future tunneling projects in similar geological conditions.

• Journal of the Economic Geographical Society of Korea
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• v.14 no.4
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• pp.583-602
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• 2011

Based on the survey, this paper examines entrepreneurs' attitude toward corporate lending in Pusan region. The results show that the relationships of manufacturing firmswith banks are different from those of non-manufacturing firms. These are mainly due to the differences in the operational grounds between them. The non-manufacturing firms have their operational ground in Pusan, thus they have local banks as their mainbanks and depend heavily on mainbanks' credits. However the business network of the local banks is not broad enough to satisfy the manufacturing firms financial service needs. Therefore, the manufacturing firms maintain close relationship with not only regional local banks but also other banks. The results of the study demand the local banks to produce information of the regional firms and to monitor them more widely and tightly. One of the important contributions of this paper is that it has succeeded in making clear the importance of relationship banking of the local banks.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.137-145
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• 2007

The flight test of ADS-B is to demonstrate operational benefits to air traffic controllers and pilots when other aircraft data including the aiming altitude is displayed on CDTI. Additionally, This ADS-B study is to provide first operational experience of ADS-B in ATCS environment of South Korea and provide practical information to ATCS before deployment of ADS-B in South Korea is considered. Participation in the flight test has been limited to 2 Aircraft of H University which are installed ADS-B equipment and the ground station has installed in Tae-An airport. This test have been experimented according to the pre-arranged flight procedures of Tae-An airport. As a result of the test, it has shown that the number of radio transmitting and the time of radio occupied between controller and pilot are remarkably reduced. Besides, as both pilot and air traffic controller are able to see the traffic information in the vicinity of the aircraft, the test has demonstrated that it is possible for ADS-B not only to decline the controller's workload, but also to enhance pilot situational awareness in the near future.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.3
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• pp.61-67
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• 2017

The Nose Landing Gear(NLG) of Rotary Wing Aircraft is an essential equipment in Landing System for pilot to perform a flight mission. It supports the fuselage at ground and absorbs the impact from the ground when landing, thereby, these functions sustain operational capability for pilot and crew. However, the A aircraft caused stick-slip behavior when it was stationed on the ground. Therefore, this paper summarizes pilot comment in operation which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1709-1714
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• 2004

Pressurization system of a 50m unmanned airship was manufactured according to the detailed design. In this paper. the whole procedures including system design. simulation and fabrication were described. The fabricated part were ground tested to check compliances with design requirements. Ground tests include operational tests, leakage tests, endurace tests and low temperature environmental tests. Results shows pressurization system of a 50m unmanned airship meets design requirements. Currently. pressurization system is installed to the KARI airship, Via 50m and performance verification through the flight tests are being conducted.