• Journal of Power System Engineering
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• v.18 no.1
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• pp.91-98
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• 2014

In this investigation, the effect of crack orientation on spatial randomness of fatigue crack growth rate (FCGR) in friction stir welded (FSWed) 7075-T651 aluminum alloy joints has been statistically analyzed by Weibull distribution. The fatigue crack growth tests are conducted under three different constant stress intensity factor range (SIFR) control at room temperature with R = 0.1 and frequency 10Hz on compact tension (CT) specimen machined at base metal (BM) and weld metal (WM). The experimental fatigue crack growth rate data were obtained for two types of specimens having LT and TL orientations. LT specimens both base metal and weld metal showed higher fatigue crack growth rate as compared to TL specimens. In the lower SIFR region, FCGR were found to be almost 3 times higher in higher SIFR region. The shape parameter of Weibull both LT and TL orientation for FCGR was increased with increasing SIFR, the scale parameter was also increased with increasing SIFR. The smallest value of the shape parameter was shown in weld metal specimens having LT orientation at lower SIFR region.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.50-58
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• 2003

We have developed a locally variable time-step scheme matching with discontinuous grids in the flute-difference method for the efficient simulation of seismic wave propagation. The first-order velocity-stress formulations are used to obtain the spatial derivatives using finite-difference operators on a staggered grid. A three-times coarser grid in the high-velocity region compared with the grid in the low-velocity region is used to avoid spatial oversampling. Temporal steps corresponding to the spatial sampling ratio between both regions are determined based on proper stability criteria. The wavefield in the margin of the region with smaller time-step are linearly interpolated in time using the values calculated in the region with larger one. The accuracy of the proposed scheme is tested through comparisons with analytic solutions and conventional finite-difference scheme with constant grid spacing and time step. The use of the locally variable time-step scheme with discontinuous grids results in remarkable saving of the computation time and memory requirement with dependency of the efficiency on the simulation model. This implies that ground motion for a realistic velocity structures including near-surface sediments can be modeled to high frequency (several Hz) without requiring severe computer memory

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1109-1116
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• 2013

This study aims to investigate the spatial randomness of fatigue crack growth rate for the friction stir welded (FSWed) 7075-T651 aluminum alloy joints. Our previous fatigue crack growth test data are adopted in this investigation. To clearly understand the spatial randomness of fatigue crack growth rate, fatigue crack growth tests were conducted under constant stress intensity factor range (SIFR) control testing. The experimental data were analyzed for two different materials-base metal (BM) and weld metal (WM)-to investigate the effects of spatial randomness of fatigue crack growth rate and material properties, the friction stir welded (FSWed) 7075-T651 aluminum alloy joints, namely weld metal (WM) and base metal (BM). The results showed that the variability, as evaluated by Weibull statistical analysis, of the WM is higher than that of the BM.

• Journal of The Korean Digital Architecture Interior Association
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• v.12 no.3
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• pp.49-58
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• 2012

In Regarding urban geo-spatial information visualization in this study, visualization of physical attribute information is mostly related to the representation of spatial domain and physical objects, and visualization of non-physical attribute information has to do with visualizing citizens and their activity information in the physical environment. In particular, a citizen, one of the non-physical information attributes, is characterized by a constant mobility in the physical environment, and thus visualization of his/her activity information is vital in conveying information because this information may not be depicted with any given, fixed figures. In consideration of this difficulty, this study integrates interrelationship among urban space, human needs, social relations, and lifestyles into a 'high-tech' service where experience in time and space is possible. To analyze the web-service and visualization cases, the study has selected visualization indicators consisting of information representation objective, information representation means, and information representation result. The results of the case analysis through specific indicators set a range in information representation objective, means, and result, thereby forming a user-friendly environment in which representational results are readily available to users, and ultimately expanding the users' selection range coming with a variety of options. This study also assumes that a wide range of service provision is needed to reflect users' needs in developing urban geo-spatial service model, and the display of its results should visualize users' satisfaction to construct the best information needed to users.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.3
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• pp.94-101
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• 1985

The flame temperature of LPG-air premixture flame was measured by extrapolation of limiting case corresponding to the infinitely thin diameter of Platinum-resistance-hot-wire. LPG-air premixture flame, initially under atmospheric pressure and room temperature, propagates downward from top of the model combustion chamber maintained at constant pressure through the whole combustion process. Analytical calculation technique was also applied to determine full temperature history or spatial temperature distribution from flame reaction zone to burnt gas region.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.89-90
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• 2009

To summarize, we observed a spatial distribution of damping tensor gives a different simulation result. When we use LLG equation, especially dealing with spatially-varying magnetization texture, it is expected that damping tensor should be considered instead of constant damping.

• Journal of the Korean housing association
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• v.6 no.2
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• pp.51-55
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• 1995

This study presents a real neutral floor surface temperature in floor panel heating system(Ondol). The Ondol heating system can keep the constant temperature. However, the actual temperature when a person sits on a floor can be different from the surface temparature of a floor it self. The contents of this study are as follows : 1) measuring the spatial distributions of thermal conditions 2) the thermal sensation vote of residents is taken in order to investigate the relation between thermal condition and human thermal sensation in sedentary condition 3) estimating the neutral floor surface temperatures by measuring floor surface temperatures.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.230-237
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• 2004

In this study, equation of finite element is formulated to analyze relations of large deformation-small deformation considering geometrical nonlinear for membrane structure. Total Lagrangian Formulation(TLF) is introduced to formulate theory and equation of motion considering Triangular Constant Strain(TCS) element in finite, element analysis is formulated. Finite element program is made by equation of motion considering TLF. This study analyzed a variety of examples, so compared with the past results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.345-350
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• 2017

Downsizing is widely applied to diesel engines in order to improve fuel efficiency and reduce exhaust emissions. Engine sizes are becoming smaller but pressure and temperature inside combustion chambers are increasing. Therefore, research for fuel spray under high pressure and temperature conditions is important. A constant volume chamber which simulates high temperature and pressure likely to be found in diesel engines was developed in this study. Pressure and temperature were increased abruptly because of ignition of the pre-mixture in the constant volume chamber. Then pressure and temperature were gradually decreased due to the heat loss through the chamber wall. Fuel spray occurred when temperature and pressure were reached at the target condition. In this experiment, the temperature condition should be exactly defined to understand the relation between fuel evaporation and ambient temperature. A fast response thermocouple was developed and used to measure the temporal and spatial temperature distribution during the combustion process inside the combustion chamber. In the results, the core temperature was slightly higher than the bulk temperature calculated by the gas equation. Ed-note: do you want to say 'ideal gas equation'? This was attributed to the heat transfer loss through the chamber wall. The vertical temperature deviation was higher than the horizontal temperature deviation by 5% which resulted from the buoyancy effect.

• Geophysics and Geophysical Exploration
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• v.21 no.2
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• pp.103-111
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• 2018

The recent research aim of seismic trace interpolation is to effectively interpolate the data with spatial aliasing. Among various interpolation methods, the Matching Pursuit interpolation, that finds the proper combination of basis functions which can best recover traces, has been developed. However, this method cannot interpolate aliased data. Thus, the multi-component Matching Pursuit interpolation and moveout correction method have been proposed for interpolation of spatially aliased data. It is difficult to apply the multi-component Matching Pursuit interpolation to interpolating the OBC (Ocean Bottom Cable) data which is the multi-component data obtained at the ocean bottom because the isolation of P wave component is required in advance. Thus, in this study, we dealt with an effective single-component matching Pursuit interpolation method in OBC data where P-wave and S-wave are mixed and spatial aliasing is present. To do this, we proposed the Ricker wavelet based single-component Matching Pursuit interpolation workflow with moveoutcorrection and systematically investigated its effectiveness. In this workflow, the spatial aliasing problem is solved by applying constant value moveout correction to the data before the interpolation is performed. After finishing the interpolation, the inverse moveout correction is applied to the interpolated data using the same constant velocity. Through the application of our workflow to the synthetic OBC seismic data, we verified the effectiveness of the proposed workflow. In addition, we showed that the interpolation of field OBC data with severe spatial aliasing was successfully performed using our workflow.