• Tunnel and Underground Space
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• v.32 no.2
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• pp.131-143
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• 2022

The lunar exploration autonomous vehicle operates based on the lunar topography information obtained from real-time image characterization. For highly accurate topography characterization, a large number of training images with various background conditions are required. Since the real lunar topography images are difficult to obtain, it should be helpful to be able to generate mimic lunar image data artificially on the basis of the planetary analogs site images and real lunar images available. In this study, we aim to artificially create lunar topography images by using the location information-based style transfer algorithm known as Wavelet Correct Transform (WCT2). We conducted comparative experiments using lunar analog site images and real lunar topography images taken during China's and America's lunar-exploring projects (i.e., Chang'e and Apollo) to assess the efficacy of our suggested approach. The results show that the proposed techniques can create realistic images, which preserve the topography information of the analog site image while still showing the same condition as an image taken on lunar surface. The proposed algorithm also outperforms a conventional algorithm, Deep Photo Style Transfer (DPST) in terms of temporal and visual aspects. For future work, we intend to use the generated styled image data in combination with real image data for training lunar topography objects to be applied for topographic detection and segmentation. It is expected that this approach can significantly improve the performance of detection and segmentation models on real lunar topography images.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.44-52
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• 2011

In this article, we present a QoS-guaranteed IP mobility management scheme of Internet service for fast moving vehicles with multiple wireless network interfaces. The idea of the proposed mechanism consists of two things. One is that new wireless connections are established to available wireless channels whenever the measured data rate at the vehicle equipped with mobile gateway drops below to the required data rate of the user requirement. The other is that parallel distribution packet tunnels between an access router and the mobile gateway are dynamically constructed using multiple wireless network interfaces in order to guarantee the required data rate during the mobile gateway's movement. By doing these methods, the required data rate of the mobile gateway can be preserved while eliminating the possible delay and packet loss during handover operation, thus resulting in the guaranteed QoS. The architecture of the IETF standard HMIPv6 has been extended to realize the proposed scheme, and detailed algorithms for the extension of HMIPv6 has been designed. Finally, simulation has been done for performance evaluation, and the simulation results show that the proposed mechanism demonstrates guaranteed QoS during the handover with regard to the handover delay, packet loss and throughput.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.97-107
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• 2007

Accurate evaluation of the slope stability by assuming failure block as the entire slope is considered to be apposite for the small scale slope, whereas it is not the case for the large scale slope. Hence, appropriate estimation of a failure block size is required since the safety factor and the joint strength parameters are the function of the failure block size. In this paper, the size of failure block was investigated by generating 3-dimensional rock joint system based on statistical data of joints obtained from research slope, such as joint orientation, spacing and 3-dimensional joint intensity. The result indicates that 33 potential failure blocks exist in research slope, as large as 1.4 meters at least and 38.7 meters at most, and average block height is 15.2 meters. In addition, the data obtained from 3 dimensional joint system were directly applicable to the probability analysis and 2 and 3 dimensional discontinuity analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.1
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• pp.51-61
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• 2014

It is necessary to perform a dynamic analysis to numerically evaluate the effect of blasting on nearby facilities. The blast load time history, which cannot be directly measured, is most often determined from empirical equation. The load has to be adjusted to account for various factors influencing the load and the frequency, but there is not a clear guideline on how to adjust the load. In this study, a series of 2D dynamic numerical analyses that simulates a closely monitored test blasting is performed, from which the blast load that matches the measured vibrations are derived. In the analyses, it is assumed that the hole generated by the blasting is in the form of a circle, and the load was applied normally to the wall of the opening. Special attention was given in selecting the damping ratio for the ground, since it has important influence on the wave propagation and attenuation characteristics of the blast induce waves. The damping ratio was selected such that it matches favorably with the attenuation curve of the measurement. The analyses demonstrate that the empirical blast load widely used in practice highly overstimates the vibration since it does not account for the energy loss due to rock fragmentation. If the empirical load is used without proper adjustment, the numerical analysis may seriously overstimate the predicted vibration, and thus has to be reduced in the analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.6
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• pp.669-680
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• 2020

In Korea, fireproof performance is evaluated through a series of fire-resistance tests for important structures, and the performance standard follows the guidelines suggested by ITA. The fireproof duct slab manufactured by combining the slab and the fireproof material with a precast method is effective in that it can eliminate the construction time of the fireproof material. In this study, a series of fire resistance tests was performed on the fire test specimens under the RWS fire scenario in order to secure the fire resistance performance of the precast fireproof duct slab. As a result of the test, it was found that the fireproof performance was secured when the thickness of the fireproof material was 30 mm or more. In both fireproof materials and concrete, the rate of temperature change initially increased, then decreased, and then increased again, and the temperature at the inflection point was measured as 110℃ for all fireproof materials and concrete. It is judged that this occurs when the C-S-H (CaO-SiO₂-H₂O) generated by the hydration reaction in both the fireproof material and concrete is dehydrated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.485-500
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• 2020

Due to various advantages such as small facilities, ease of construction and so on, the grouting technology which is widely used in construction field has developed remarkably compared with the past. However, the efforts to improve the homogeneity of quality, long-term durability and environmental problems have been continued. In recent years, new grouting method has been developed in order to solve problems such as low strength, durability and leaching phenomenon of liquid glass (sodium silicate) grouting material in Korea. A newly developed method integrates the injection material with the ground by the self-healing material of crystallization growth type. For this reason, it is known that improvement of the durability and water quality of the ground, prevention of leaching, and environment friendliness can be expected. The present study applied a newly developed method to test sites and verified its effect such as injection range, improvement effect, waterproofing performance and so on. Standard penetration test, field permeability test, borehole shear test, pressuremeter test and pH test were conducted, and the results were compared between before and after developed method application. As results of tests, the field applicability and improvement effect of developed method were proved to be excellent.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.127-136
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• 2019

Tunnel construction by TBMs should be supported by the performance of a screw conveyor in order to obtain the optimum penetration rate, so studies related to the screw conveyor performance have been being conducted. Compared to the study on the performance of the screw conveyor for the soil, however, the research on the performance of the screw conveyor for the rock is insufficient. Considering the domestic tunnel sites with more rock layers than soil layers, simulation of discharge of 6 types of rock chips by the screw conveyor was conducted using DEM. Regardless of the shape and volume of the rock chips, the discharge rates of the rock chips by the parallel placed screw conveyor at a speed of 10 RPM in the same rock mass were about 20% (standard deviation: 1.3%) of the maximum volume of discharge rate by the screw conveyor. It is expected that this study can be used as a reference material for screw conveyor design and operation in TBM excavations in rock masses.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.45-58
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• 2000

Cyclic shear test system, which is capable of measuring flow rate inside rock joint, was established to investigate the hydraulic behavior of rough rock joints under various loading conditions. Laboratory hydraulic tests during compression and shear were conducted for artificial rough rock joints. Prior to tests, aperture characteristics of specimens were examined by measuring surface topography. Permeability changes under compression were well approximated with several hydraulic model. Hydraulic behavior conformed to dilation characteristics in the first stage, and permeability increased with increase of dilation. As the shear displacement progressed, flow rate became somewhat constant due to gouge production and offset of apertures. Hydraulic behavior under cyclic shear loading was also influenced by the degradation of asperities and gouge production. In addition. the relation between hydraulic aperture and mechanical aperture under compression and shear loading was investigated and compared.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.196-204
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• 2012

Quantification of roughness plays an important role in modeling strength deformability and fluid flow behaviors of rock joints. A procedure was suggested to simulate joint roughness, and characteristics of the roughness was investigated in this study. Stationary fractional Brownian profiles with known input values of the fractal parameter and other profile properties were generated based on random midpoint displacement method. Also, a procedure to simulate three dimensional roughness surface was suggested using the random midpoint displacement method. Selected statistical roughness parameters were calculated for the generated self-affine profiles to investigate the attribute of roughness. Obtained results show that statistical parameters applied in this study were able to consider correlation structure and amplitude of the profiles. However, effect of data density should be tackled to use statistical parameters for roughness quantification.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.327-337
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• 2016

In this study, laboratory hydraulic fracturing tests are carried out to evaluate the effects of the cleavage anisotropy of Pocheon granite. Breakdown pressure is smaller when cracks are generated to the direction of rift plane in constant pressurization rate condition because of higher microcracks density. Besides not only injection rate changes but also the amount of injection pressure for fracture initiation and crack expansion is detected while testing due to internal deformation. Pressurization rate is higher while hydraulic fracture testing with constant injection rate condition in case of the specimen which has rift plane perpendicular to borehole because there are much flow paths to penetrate compared to the specimen which has hardway plane perpendicular to borehole. Observation by X-ray CT scanning shows that almost all of cracks due to hydraulic fracturing are generated to the direction of plane which has higher microcrack density that is rift plane or grain plane.