• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.121-131
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• 2003

Tunneling in difficult geological conditions is often inevitable especially in urban areas. Ground improvement and reinforcement techniques are often required to guarantee safe tunnel excavations and/or to prevent damage to adjacent structures. The steel pipe-reinforced multistep grouting method has been recently applied to tunnel sites in Korea as an auxiliary technique. In this study, the face stability with steel pipe-reinforced multistep grouting was evaluated emphasizing the effect of seepage forces. The study revealed that the influence of the steel pipe-reinforced multistep grouting on the support pressure in dry condition is not significant while there is relatively a large amount of reduction in seepage forces by adopting the technique in saturated condition. The effect of the anisotropy of permeability on the seepage force acting on the tunnel face was also estimated by conducting the coupled analysis. It was found that a higher horizontal permeability compared with the vertical one causes reduction in the seepage farce acting on the tunnel face.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.265-275
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• 2003

In this study, shaking table tests were conducted to estimate dynamic interface properties between geosynthetics such as geomembrane, geotextile and geosynthetic clay liner. Accelerations of both shaking table and upper box, and relative displacements between geosynthetics under dynamic loading were measured. Also, the influence of normal stress, frequency of excitation and dry/wet conditions were investigated through the analyses of test results. from the test results, it was found that there is a limited acceleration below which dynamic farce can be transmitted between geosynthetics without the loss of horizontal acceleration. Dynamic interface friction angle between geosynthetics could be calculated through the limited acceleration. Relative displacements induced along geosynthetic interfaces under dynamic loading were not consistent depending on the type of interface and test conditions. The maximum slip displacements between geosynthetics are normalized and normalized slip equations were developed for each interface. By using the normalized slip equation, maximum slip displacements for the geosynthetic interface could be predicted for the given base acceleration and frequency of excitation.

• Composites Research
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• v.14 no.2
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• pp.22-32
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• 2001

Damage induced by low-velocity impact on the curved composite laminates was experimentally evaluated for CFRP cylindrical shells with the radius of curvatures of 50, 150, 300, and 500 mm. The result was then compared with that of flat laminates and with the results by nonlinear finite-element analysis. The radius of curvatures and the effective shell stiffness appeared to considerably affect the dynamic impact response of curved shells. Under the same impact energy level, the maximum contact force increased with the decreasing radius of curvatures, with reaching 1.5 times that for plates at the radius of curvature of 50 mm. Since the maximum contact farce is directly related to the impact damage, curved laminates can be more susceptible to delamination and less resistant to the low-velocity impact damage. Delamination was distributed rather evenly at each interface along the thickness direction of curved laminates on the contrary to the case of flat laminates, where delamination is typically concentrated at the interfaces away from the impact point. This implies that the effect of curvatures has to be considered for the design of a curved composite laminate.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.136-145
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• 2007

When waves propagating over an underwater shoal break at the top of the shoal, wave heights are drastically decreased in the downstream breaking zone, but a secondary current shooting downstream with strong velocity can be induced by the breaking waves themselves. In the case that an offshore structure is placed in the breaking zone, the estimation of wave farce purely based on the visible wave height may cause an under-design of the structure. Thus, for the safe design of the structure, the breaking wave induced current should be necessarily considered in the comprehensive estimation of design load. In the present study, Boussinesq equation model to calculate the wave height distribution and breaking wave induced current was set up and applied to the scheme of a hydraulic model test previously undertaken. Based on the results of the Boussinesq model, fluid forces acting on the model structure were calculated and compared with the experimental results. The importance of the breaking wave induced current was quantitatively assessed by comparing fluid forces with or without current.

• Journal of Biomedical Engineering Research
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• v.23 no.2
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• pp.119-130
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• 2002

The nonlinear finite element program has been developed to analyze the design performance of an artificial hip prosthesis and long term behavior of a treated femur with stems made of composite material after cementless total hip arthroplasty(THA). The authors developed the three dimentional FEM models of femoral bone with designed composite stem which was taken with elliptic cross section of 816 brick elements under hip contact load and muscle farce in simulating single leg stand. Using the program, density changes, stress distributions and micromotions of the material femoral bone were evaluated by changing fiber orientation of stems for selected manufacturing method such as plate cut and bend mold. The results showed that the composite materials such as AS4/PEEK and T300/976 gave less bone resorption than the metallic material such as cobalt chrome alloy, titanium alloy and stainless steal. It was found that increasing the long term stability of the prosthesis in the femur could be obtained by selecting the appropriate ply orientation and stacking sequence of composite.

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.277-285
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• 2008

For the soil nailing, recently, its application is expanded, but there is no officially approved method to design it yet. Furthermore, there are a great number of design valuables in soil nailing, it is also used without clear data under the situation that uncompleted detailed research on the sensibility between design variables. Especially, there has no deal with the installation angle of the nail - the major contents in this study. Therefore, this study based on the theoretical estimation analyzed safety rate about the angle of the nail, unit weight, adhesive force, internal friction angle and tensile farce worked on nail in the case of the rear of pond side is both horizontal and perpendicular. As a result, it could be verified that the safety rate increased on every cases in the situation of the nail installation angle was in upward direction than in downward direction.

• The Journal of Fisheries Business Administration
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• v.31 no.2
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• pp.67-91
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• 2000

Fisheries Agreements among Korea, China, and Japan, for the effective management of fisheries resources and protection of fisheries disputes, have been processed in a manner to conclude interim arrangements those are effective prior to the final demarcation of the maritime delimitation which often requires much time to settle among the relevant states, Based on this understanding, Korea, China, and Japan, had proceeded their mutual fisheries agreement ; and, two fisheries agreements, between Korea-Japan and China-Japan, have already entered into force on 22 January 1999 and on 1 June 2000, respectively. Lastly fisheries negotiation between Korea and China has been concluded in order to make it effective on 30 June 2001. As Korean fisheries have already experienced the impacts after the entry into force of Korea-Japan Fisheries Agreement, it is inevitable that the likewise will also be true for the Korea-china Fisheries Agreement. The results of fisheries negotiation should minimize the loss by ensuring Korean flagged vessels' fishing rights to the maximum level in the counterpart's waters, and to maximize our counterpart's loss by restricting its vessels' fishing rights to the minimum level in our waters. However, such goals are almost unreachable in an intergovernmental negotiation. On this ground, regardless of the results, the negotiation is highly criticized from all the interested realms of the society. First, this study reviews the negotiation process ana subject matters of the fisheries agreement, and then evaluates the disputed items issued by academic, political, and industry areas in an international law and fisheries perspective. After the entry into farce of fisheries agreement, various activities should be accommodated as future tasks, such as the adjustments of the domestic fisheries structure, the reorganization of the resource management based fisheries structure, the construction of EEz large surveillance system, and the construction of the multilateral fisheries cooperation system Through an earlier implementation of those tasks, the Korean fisheries will be better prepared in minimizing the predicted impacts once the Korea-China Fisheries Agreement becomes effective.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.84-88
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• 2006

The effects of tip voltage, deflection setpoint, and tip velocity on height of $SiO_2$ line drawn by local anodization on Si wafer using scanning probe microscope were investigated. No local anodization was detected at smaller than -3 V of tip voltage. The line height increased at rate of 0.47 nm/V when the tip voltage is stronger than -3 V at $1{\mu}m/s$ tip velocity. From deflection setpoint, mechanical force between tip and substrate could be calculated and the threshold farce was $12\sim18nN$. The height of anodized $SiO_2$ lines is independent of the magnitude of force above the threshold force. The line height decreased as increasing the tip velocity and limited to 0.7 nm at -5 V tip voltage.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.107-121
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• 2003

When the seismic stability of quay walls is analyzed, the magnitudes of force components acting on quay walls during earthquakes and the phase relations among these force components must be properly evaluated. In general, force components include inertia force of the quay wall, lateral earth force, and water force. The magnitude and the phase relation of each force component vary according to the magnitude of the excess pore pressures developed in backfill soils of the quay wall. The dynamic thrust mobilized at the contact surface between the backfill soil and the wall develops as a result of the interactions among these force components. We propose a simple model to evaluate the magnitude and phase variation of the dynamic thrust on the back of the wall in terms of the excess pore pressure. The proposed model can predict the dynamic thrust by summing the magnitudes of farce components calculated from design equations for seismic pressures on the wall. The proposed model was verified by comparing its results with the results from a series of shaking table tests.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.163-174
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• 2007

A New pre-loading system, through which a large pre-load could be charged was developed and applied to the braced wall in order to stabilize the adjacent tunnel. A pre-load larger than the designated axial force of bracing was imposed to prevent the horizontal displacement of the braced wall during the ground excavation. For this purpose, real scale model tests (1/10) were conducted, without and with pre-load on braced wall. And numerical analyses were performed for both the cases without and with pre-load, which were half (50%) and full (100%) respectively, and larger scale of the design axial farce of bracing. FEM program called PLAXIS was used for numerical analysis. As a result, it was found that the stability of the existing tunnel adjacent to the braced wall could be greatly enhanced when the horizontal displacement of braced wall was reduced by applying a pre-load, which was larger than the designated axial force of bracing.