• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.141-148
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• 1996

Use of stone column for deep ground treatment in soft clay soils is an effective method. The stone column significantly increases load carrying capacity of the soft clay soil. A analysis method for bearing capacity of stone column in soft clay soil is developed. The capacity made by developed method are compared wity observed values from field load test and a reasonable correlation is noted.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.29-36
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• 2008

In this paper, mechanical reliability issues of copper through-wafer interconnections are investigated numerically and experimentally. A hermetic wafer level packaging for MEMS devices is developed. Au-Sn eutectic bonding technology is used to achieve hermetic sealing, and the vertical through-hole via filled with electroplated copper for the electrical connection is also used. The MEMS package has the size of $1mm{\times}1mm{\times}700{\mu}m$. The robustness of the package is confirmed by several reliability tests. Several factors which could induce via hole cracking failure are investigated such as thermal expansion mismatch, via etch profile, and copper diffusion phenomenon. Alternative electroplating process is suggested for preventing Cu diffusion and increasing the adhesion performance of the electroplating process. After implementing several improvements, reliability tests were performed, and via hole cracking as well as significant changes in the shear strength were not observed. Helium leak testing indicated that the leak rate of the package meets the requirements of MIL-STD-883F specification.

• Journal of Korean Society of Forest Science
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• v.77 no.2
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• pp.252-257
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• 1988

This study was carried out to investigate the physical and mechanical properties of sawdust boards combined with sycamore and polypropylene-net flakes. Both the sycamore and polypropylene-net flakes were adjusted to the sizes of $1.0{\times}1.0$, $1.0{\times}2.0$, and $1.5{\times}1.5cm^2$ and these flakes were mixed at 1, 2, 3, and 4% levels based on ovendry weights of sawdusts, respectively. The results obtained in this study were summarized as follows : 1. Thickness swellings of sawdust boards combined with sycamore flakes decreased with the increase of mixture levels and similar effects were also recognized in combination with polypropylene-net flakes. 2. Moduli of rupture both in sawdust boards combined with sycamore and polypropylene-net flakes increased with the increase of their mixture levels, and sawdust boards combined with sycamore flakes of $1.0{\times}2.0cm^2$ size and polypropylene-net flakes of $1.5{\times}1.5cm^2$ size showed higher moduli of rupture than control boards. 3. Moduli of elasticity both in sawdust hoards combined with sycamore and polypropylene-net flakes increased with the increase of their mixture levels as in moduli of rupture. 4. The physical and mechanical properties of sawdust boards combined with sycamore and polypropylene-net flakes were mainly dependent on aspect ratio of sycamore flakes and size of polypropylene-net flakes respectively, and these properties were improved with the respective increase of aspect ratio and size.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.231-240
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• 2017

Recently, there have been frequent occurrences of ground sink in the urban area, which have resulted in human and material damage and are accompanied by economic losses. This is caused by artificial factors such as soil loss, poor compaction, horizontal excavation due to the breakage of the aged sewage pipe, and lack of water proof at vertical excavation. The ground sink can be prevented by preliminary restoration and reinforcement through exploration, but it can be considered that it is not suitable for urgent restoration by the existing method. In this study, a model experiment was carried out to simulate the in-ground cavities caused by groundwater flow for developing non-excavation urgent restoration in underground cavity and the range of the relaxation zone was estimated by detecting the around the cavity using a relaxation zone detector. In addition, disturbance region and relaxation region were separated by injecting gypsum into cavity formed in simulated ground. The shape of the underground cavity due to the groundwater flow was similar to that of the failure mode III formed in the dense relative density ground due to water pipe breakage in the previous study. It was confirmed that the relaxed region detected using the relaxation zone detector is formed in an arch shape in the cavity top. The length ratio of the relaxation region to the disturbance region in the upper part of the cavity center is 2: 1, and it can be distinguished by the difference in the decrease of the shear resistance against the external force. In other words, it was confirmed that the secondary damage should not occur in consideration of the expandability of the material used as the injecting material in the pre-repair and reinforcement, and various ground deformation states will be additionally performed through additional experiments.