• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.24-33
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• 2000

This paper investigates the relationship between J-integral and crack tip opening displacement, ${\delta}_t$ using Gordens results of numerical analysis. Estimation were carried out for several strength levels such as ultimate, flow, yield, ultimate-flow, flow-yield stress to determine the influence of strain hardening and the ratio of crack length to width on the $J-{\delta}_t$ relationship. It was found that for SE(B) specimens, the $J-{\delta}_t$ relationship can be applied to relate J to ${\delta}_t$ as follows $J=m_j{\times}{\sigma}_i{\times}{\delta}_t$ where $m_j=1.27773+0.8307({\alpha}/W)$, ${\sigma}_i:{\sigma}_U$, ${\sigma}_{U-F}={\frac{1}{2}} ({\sigma}_U+{\sigma}_F$), ${\sigma}_F$, ${\sigma}_F}$ $Y=({\sigma}_F+{\sigma}_Y)$, ${\sigma}_Y$

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.59-67
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• 2002

The comparison of $J_{Rice}$-resistance considering a few strength ratio in Rice J-integral formula and $J_{\delta}$-resistance curves converted from experimental CTOD using appropriate strength chosen according to strain hardening level, n=10.6 (A533B steel) and n=8.1 (BS4360 steel) is carried out. The optimal dimensionless strength ratio like the factor of revision, (see full text)reflecting strain hardening level in Rice\`s experimental formula is found out and the reliability of appropriate reference strength chosen according to strain hardening level in different materials is investigated through doing that CTOD is transformed from $J_{\delta}$-integral using relationship between J-integral and CTOD. The results are as follows; 1) The optimal factor of revision is when m equals to 3 in (see full text) for Rice's and the above optimal factor of revision multiplies by coefficient, η in Rice's experimental formula instead of n=2, 2) and the pertinent reference strength for high strain hardening material like BS4360 steel is ultimate strength, $\sigma_{u}$ and for material like A533B steel is ultimate-flow strength, $\sigma_{u-f}$. The incompatible of the behavior of both experimental J-resistance curves using Rice's formula and CTOD-resistance curves for A533B and BS4360 steel by Gordon, et al., could be corrected using the optimal factor of revision in Rice\`s and the pertinent reference strength in J=$m_{j}$${\times}$$\sigma_{i}$${\times}$CTOD.

• Geotechnical Engineering
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• v.11 no.3
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• pp.123-138
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• 1995

To study the grout flow in jointed rock, various nurser characteristics of grout in a single joint plane and two-dperorbed. The joint plane is described as a channel nets properties of grout are considered. To deal with various prob generator and i oint network generator are used. A loss of head due to friction in laminal flow is adopted to between the grout and joint wall. The grout flow is stopped, setting time. To consider this phenomenon, the idea of maxim From the results of numerical simulation on the single jai etration of grout is confirmed. The basic principles for the ation and the selection of the grout are presented. Correlation ant and grouting pressure is defined by analyzing the effects grout flow. Finally, the grout flow around a tunnel is simulate ins grouting operation for jointed rock mass.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.344-350
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• 2013

The purpose of this study is to examine the structural stability of a low speed 200 W class gyromill type vertical axis wind turbine system. For the analysis, a commercial code is adopted. The pressure distribution on the rotor blade surface is examined in detail. In order to perform unidirectional FSI(Fluid-Structure Interaction) analysis, the pressure resulted from CFD analysis has been mapped on the surface of wind turbine as load condition. The rotational speed and gravitational force of wind turbine are also considered. The results of FSI analysis show that the wind turbine reveals an enough structural margin. The maximum structural displacement occurs at trailing edge of blade and the maximum stress occurs at the strut.

• Composites Research
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• v.24 no.5
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• pp.29-33
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• 2011

The application of high performance materials for the deck can represent a fair alternative to reduce the weight of the deck and improve the econimic efficiency of the bridge even if high performance materials are costly. In UHPC(Ultra High Performance Concrete) bridges, it is necessary to verify that exiting headed stud can be used to transfer longitudinal shear forces across the steel-concrete interface. In this paper, the push-out tests are performed to analisys the composite behavior between UHPC bridge deck and steel girder. The ultimate strength of test specimens is proportional to the diameter of headed studs in push-out test for static loading. Test results show that the shear strength of headed stud is improved for the case of normal concrete bridge decks.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1031-1038
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• 2017

In order to improve the performance of the air breathing engines, it is important to maximize the total pressure recovery through air intake. In this study, we investigated whether the Oswatitsch method, which guarantees the maximum pressure recovery for supersonic intake, is effective at hypersonic speed by compressing the intake air with the same intensity at each ramp. The non-linearity of the shock wave normal Mach number at each ramp stage was analyzed by comparing the compression ramp angle and the number of ramp to the inflow Mach number in terms of compressible thermodynamics and the operation limits of the inlet. Based on this analysis, the Oswaitisch technique yields valid conditions not only in supersonic but also hypersonic flight regime.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.307-313
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• 2016

When liquefied natural gas (LNG) is stored in a tank, it is necessary to maintain low temperature. It is very important that insulation techniques are applied to the LNG cargo because of this extreme environment. Hence, laminated wood, especially plywood, is widely used as the structural member and insulation material in LNG cargo containment systems (CCS). However, fracture of plywood has been reported recently, owing to sloshing effect. Therefore, it is necessary to increase the strength of the structural member for solving the problem. In this study, compressed wood, which is used as a support in LNG independent type B tanks, was considered as a substitute for plywood. Compression and bending tests were performed on compressed wood under ambient and cryogenic temperatures to estimate the mechanical behaviors and fracture characteristics. In addition, the direction normal to the laminates surface was considered as an experimental variable. Finally, the feasibility of using compressed wood for an LNG CCS was evaluated from the test results.

• Elastomers and Composites
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• v.38 no.1
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• pp.57-64
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• 2003

Metal oxide(MgO) was added to FKM rubber in order to develop automotive fuel hose which ran show elastic characteristics under extreme condition. Cure characteristics, physical properties, thermal resistance and fuel resistance of FKM compounded rubber with MgO were investigated. MgO was mixed to FKM rubber materials within the range of $0{\sim}20phr$. From the test results of rheological properties and Mooney viscosity, the $t_{s2}$, $T_{c90}$ values increased as the MgO contents increased in FKM rubber compounding. Hardness and 100% modulus of FKM compounded rubber slightly increased, but tensile strength and elongations at break slightly decreased. From the test results of thermal resistance of rubber specimens at 130, 150, and $170^{\circ}C$ for 70 hrs, the changing rate of physical properties was found to be relatively small. Fuel resistance tests were carried out for fuel A, B, C and D at $40^{\circ}C$ for 70hrs, and the results showed that the changing rate in physical properties was found to increase from Fuel A to D, Furthermore thermal properties of FKM compounded rubber containing MgO were also investigated by using TGA/DSC. The optimum mixing ratio of additive to FKM rubber to get the maximum effect on thermal resistance and fuel resistance, within the range of desirable specification for rubber material, was determined to be 6 phr for MgO.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.1
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• pp.1-12
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• 2004

Sedimentary facies and high-resolution echo facies were analyzed to elucidate sedimentation pattern of the late Quaternary glacial-marine deposits in the northern continental margin of the South Shetland Islands. Six sedimentary facies are classified, based on grain texture and sedimentary structures in gravity cores. The high-resolution (3.5 ㎑) echo characters are classified into 6 echo facies on the basis of clarity, continuity, and shape of bottom and subbottom echoes together with seafloor topography. Distribution of the echo and sedimentary facies suggest that there was a significant change in sedimentation pattern between the Last Glacial Maximum (LGM) and subsequent glacier-retreating period. When the grounded glaciers extended to the present shelfbreak during LGM, coarse-grained subglacial tills were widespread in the shelf area, and deep troughs in the shelf were carved beneath the fast-flowing ice steam. As the glacial margin retreated landward after LGM, dense meltwater plumes released from the retreating ice-front were funneled along the glacier-carved troughs, and accumulated channel- or cannyon-fill deposits in the shelf and the upper to mid slope. At that time, slope sediments seem to have been reworked by slope failures and unsteady contour currents, and further transported by fine-grained turbidity currents along the South Shetland Trench. After the glacial retreat, sediments in the shelf and slope areas have been mainly introduced by persistent (hemi) pelagic settling, and fine-grained turbidity currents frequently occur along the axis of the South Shetland Trench.

• Korean Journal of Remote Sensing
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• v.31 no.6
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• pp.501-512
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• 2015

Landfast sea ice (LFI) in Terra Nova Bay, East Antarctica where the Jangbogo Antarctic Research Station is located, has significant influences on marine ecosystem and the sailing of an icebreaker. Therefore, it is essential to analyze the spatio-temporal variation of the LFI in Terra Nova Bay. In this study, we chose interferometric pairs with the temporal baseline from 1 to 9 days out of a total of 62 COSMO-SkyMed synthetic aperture radar (SAR) images over Terra Nova Bay obtained from December 2010 to January 2012, and then constructed the coherence image of each pair. The LFI showed coherence values higher than 0.3 even in the interferometric SAR (InSAR) pairs of up to 9-days of temporal baseline. This was because the LFI was fixed at coastline and thus showed low temporal phase decorrelation. Based on the characteristics of the coherence on LFI, We defined the areas of LFI that show spatially homogeneous coherence values higher than 0.5. Pack ice (PI) and open water showed low coherence values due to large temporal phase decorreation caused by current and wind. Distinguishing PI from open water in the coherence images was difficult due to their similarly low coherence values. PI was identified in SAR amplitude images by investigating cracks on the ice. The extents of the LFI and PI were estimated from the coherence and SAR amplitude images and their temporal variations were analyzed. The extent of the LFI increased from March to July (maximum extent of $170.7km^2$) and decreased from October. The extent of the PI increased from February to May and decreased from May to July when the LFI increases dramatically. The extent of the LFI and air temperature showed an inverse correlation with a time lag of about 2 months, i.e., the extent of the LFI decreases after 2 months of the increase in the air temperature. Meanwhile the correlation between wind speed and the extent of the LFI was very low. This represents that the extent of LFI in Terra Nova Bay are influenced more by the air temperature than wind speed.