• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.86-95
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• 2010

Ground movements during tunnelling have the potential for major impact on nearby buildings, utilities and streets. The impacts on buildings are assessed by linking the magnitude of ground loss at the source of ground loss around tunnel to the lateral and vertical displacements on the ground surface, and then to the lateral strain and angular distortion, and resulting damage in the building. To prevent or mitigate the impacts on nearby buildings, it is important to understand the whole mechanism from tunnelling to building damage. This paper discusses tunneling-induced ground movements and their impacts on nearby buildings, including the importance of the soil-structure interactions. In addition, a building damage criterion, which is based on the state of strain, is presented and discussed in detail and the overall damage assessment procedure is provided for the estimation of tunnelling-induced building damage considering the effect of soil-structure interaction.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.442-453
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• 2013

A large-scale high-temperature thermal energy storage(TES) was numerically modeled and the heat loss through storage tank walls was analyzed using a commercial code, FLAC3D. The operations of rock cavern type and above-ground type thermal energy storages with identical operating condition were simulated for a period of five consecutive years, in which it was assumed that the dominant heat transfer mechanism would be conduction in massive rock for the former and convection in the atmosphere for the latter. The variation of storage temperature resulting from periodic charging and discharging of thermal energy was considered in each simulation, and the effect of insulation thickness on the characteristics of heat loss was also examined. A comparison of the simulation results of different storage models presented that the heat loss rate of above-ground type TES was maintained constant over the operation period, while that of rock cavern type TES decreased rapidly in the early operation stage and tended to converge towards a certain value. The decrease in heat loss rate of rock cavern type TES can be attributed to the reduction in heat flux through storage tank walls followed by increase in surrounding rock mass temperature. The amount of cumulative heat loss from rock cavern type TES over a period of five-year operation was 72.7% of that from above-ground type TES. The heat loss rate of rock cavern type obtained in long-period operation showed less sensitive variations to insulation thickness than that of above-ground type TES.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.675-682
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• 2011

This paper presents two ground plane effects due to the size of two rectangular apertures for two-wire transmission line with equal line length crossing the changeable rectangular apertures in infinite ground planes. The CST MWS is used to determine the characteristics of the insertion loss of the transmission line from the load section in accordance with the ground plane aperture size. The results show that the insertion gain and the insertion loss are periodically observed for the multiple frequency of the half wavelength resonance by the wire length when the transmission line is nearby to horizontal side or vertical side of the aperture. The measurements of the insertion loss are performed to verify the theoretical analysis.

• Geomechanics and Engineering
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• v.34 no.4
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• pp.397-408
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• 2023

Pipe pile walls are commonly used as retaining structures for excavation projects, particularly in densely populated coastal cities such as Hong Kong. Pipe pile walls are preferred in reclaimed land due to their cost-effectiveness and convenience for installation. However, the pre-bored piling techniques used to install pipe piles can cause significant ground disturbance, posing risks to nearby sensitive structures. This study reports a well-documented case history in a reclamation site, and it was found that pipe piling could induce ground settlement of up to 100 mm. Statutory design submissions in Hong Kong typically specify a ground settlement alarm level of 10 mm, which is significantly lower than the actual settlement observed in this study. In addition, lateral soil movement of approximately 70 mm was detected in the marine deposit. The lateral soil displacement in the marine deposit was found to be up to 3.4 and 3.1 times that of sand fill and CDG, respectively, mainly due to the relatively low stiffness of the marine deposit. Based on the monitoring data and site-investigation data, a 3D numerical analysis was established to back-analyze soil movements due to the installation of the pipe pile wall. The comparison between measured and computed results indicates that the equivalent ground loss ratio is 20%, 40%, and 20% for the fill, marine deposit and CDG, respectively. The maximum ground settlement increases with an increase in the ground loss ratio of the marine deposit, whereas the associated influence radius remains stationary at 1.2 times the pipe pile wall depth (H). The maximum ground settlement increases rapidly when the thickness of marine deposit is less than 0.32H, particularly for the ground loss ratio of larger than 40%. This study provides new insights into the pipe piling construction in reclamation sites.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.36.2-36.2
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• 2008

This paper presents the impact of Japanese radio source on the S-Band communication between KOMPSAT-2 satellite and TT&C ground system. Major specifications such as transmitting EIRP (Effective Isotropic Radiated Power) and location of Japanese terrestrial station were informed from Radio Research Laboratory in Korea Communication Commission. To estimate path loss in S-Band, the distance between Japanese station and TT&C ground system was obtained by using COTS (Commercial Off-The-Shelf) software. After that the signal strength of Japanese radio source placed at the TT&C ground system was calculated from link parameters such as transmitting EIRP, path loss, and receiving antenna gain. Consequently, this paper shows that the degradation caused by Japanese radio source is acceptable to TT&C ground system for satellite operation.

• Transactions on Electrical and Electronic Materials
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• v.18 no.6
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• pp.359-363
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• 2017

A slotted implantable patch antenna with microstrip feeding is proposed for industrial, scientific, and medical band applications. The result is verified by implanting the antenna in animal tissue. Further, by varying the ground width and introducing a defect into the ground structure, the antenna becomes applicable for worldwide interoperability for microwave access operations. A simulation is performed using Empire XCcel software. An Agilent vector network analyzer is used for analyzing the return loss performance. Simulated and measured results are compared. Antennas with and without defected ground structure both have key advantages including low profile, desirable return loss, good impedance matching and required bandwidth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.55-63
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• 2018

In this paper, we measured the propagation path loss by a ground to air flight communication test at UHF band and analyzed the results. The ground receiving terminal was located at 1,100m above sea level in Cheju Island and the airborne transmit terminal flew at an altitude of 3.5km from 150 to 220km from the ground terminal. In this case, the ground terminal and the airborne terminal are on the Line of Sight. Therefore loss in this communications environment can be predicted based on Free Space Loss. However, in this test, the sea level exists between two terminals, and due to the very small angle of incidence on the reflecting surface due to the long-range communication environment, it is not possible to accurately predict the loss of free space only. Therefore, considering that there are no surrounding obstacles and that a line of sight is secured between the end of two terminals, we applied a plane earth reflection model and a spherical earth reflection model to estimate the propagation path loss and compared with the actual test results. As a result of the comparison, the predicted propagation path loss by a spherical earth reflection model were quite similar to the actual test values.

• Journal of Astronomy and Space Sciences
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• v.38 no.1
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• pp.65-82
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• 2021

For the vast majority of geostationary satellites currently in orbit, station keeping activities including orbit determination and maneuver planning and execution are ground-directed and dependent on the availability of ground-based satellite control personnel and facilities. However, a requirement linked to satellite autonomy and survivability in cases of interrupted ground support is often one of the stipulated provisions on the satellite platform design. It is especially important for a geostationary military-purposed satellite to remain within its designated orbital window, in order to provide reliable uninterrupted telecommunications services, in the absence of ground-based resources due to warfare or other disasters. In this paper we investigate factors affecting the robustness of a geostationary satellite's orbit in terms of the maximum duration the satellite's station keeping window can be maintained without ground intervention. By comparing simulations of orbit evolution, given different initial conditions and operations strategies, a variation of parameters study has been performed and we have analyzed which factors the duration is most sensitive to. This also provides valuable insights into which factors may be worth controlling by a military or civilian geostationary satellite operator. Our simulations show that the most beneficial factor for maximizing the time a satellite will remain in the station keeping window is the operational practice of pre-emptively loading East-West station keeping maneuvers for automatic execution on board the satellite should ground control capability be lost. The second most beneficial factor is using short station keeping maneuver cycle durations.

• Journal of the Korea Institute of Building Construction
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• v.5 no.4 s.18
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• pp.139-144
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• 2005

A ground anchor system is used as a load carrying element in soil work. The conventional systems with ground anthers bring about the anchorage loss of wedges when anchors are installed for the support of soil structures. Hence we developed the new type of anchor system using both the spacing apparatus and spring (length 60mm, diameter 6mm). In this system, we tan directly check the condition of wedges and PS strands and modify the problems with the slip and anchorage of wedges under construction. For demonstrating the superiority of this system, we carried out a series of the laboratory test. Consequently, we can obtain satisfactory result (18.99$\%$ reduction to the loss of conventional systems). Moreover, the replacement of wedges is easy and simple when retensioning of strands.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.3
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• pp.71-77
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• 1996

This paper is described on the eddy current for a peripheral magnetic objects of under ground power cable. The materials of cable rack is used FRP and SUS in the place of iron. Each specimen were measureed for eddy current loss and Hysteresis loss by Epstein's method. The results is compared each other. Hysteresis loss is inversely proportional to $\textrm{f}^{0.6}$ of frequence as supply voltage is constant. Also, iron loss is increased to 0.86 times for varinace of frequency from 60[Hz] to 50[Hz] as a maxium flux density is constant. In the case of Fe, Hysteresis loss is above 70[% ] of total iron loss. In the other hand, SUS is decreased to go[%] of Fe. by the simulation results using Loss Program Package. The iron loss of materials SUS, FRP is near zeor by Epstein's method.