• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.57-66
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• 2015

Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calculated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the generally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of $${\sim_\sim}$$ 1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of $r{\leq}0.5$ kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of $1{\leq}r{\leq}2kpc$. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.62-65
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• 2001

The effects of the initial torture of workpiece as well as the process conditions such as punch speed and lubrication on the formablity of sheet stretching are investigated by experiments. Two types of the initial textures of aluminum sheet plane strain compression torture and recrystallization texture are chosen since those are the most common in practice. Punch loads vs depth and thickness strain distributions along radial directions having the slope of $0^{\circ},\;45^{\circ},\;90^{\circ}$ with rolling directions are reported for hemishperical punch stretchings under a variety of process conditions.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.661-666
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• 2004

The purpose of this study is to measure the rotational vibration, radial vibration, and axial vibration for the helical gear with the wide face width relative to the whole depth. For this purpose, the experimental apparatus is designed and manufactured. The gear vibration of each direction is measured by the accelerometers attached at the gear body. As a result, meshing frequency and second harmonic component are greatly contributed to the gear vibration. As the rotational speed is increased, meshing frequency component has the more significant peak than the second harmonic one. However, the doubled torque decreases the vibration magnitude on the contrary and changes order of the vibration magnitude in each direction.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.1-9
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• 2018

We propose a borehole test technique to estimate permeability of rocks in borehole. The borehole tests are hydraulic injection tests such as leak-off test and hydraulic fracturing tests, which are originally conducted for stress or casing integrity assessment and not for permeability measurement. We use one-dimensional radial diffusion equation to interpret fluid injection test results in terms of permeability. We apply this technique to a leak-off test conducted at a depth of 700 m in a wellbore, where rock formation is mudstone. The estimated permeability is at an order of $10^{-16}m^2$, which is somewhat high but within the range reported for mudstones previously. Quantitative rick assessment suggests that an accurate measurement of open hole section length is important to improve reliability of results. More data may be needed to ensure the reliability of this technique. If validated, however, this technique can provide cost-effective estimation of in situ permeability without conducting independent permeability tests in borehole.

• Journal of the Korea Furniture Society
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• v.19 no.2
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• pp.151-155
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• 2008

An experiment was conducted to observe the 5% CCFZ solution penetration depth through ray parenchyma and ray tracheid of Larix kapempferi. Moisture content was adjusted 28% for both sapwood and heartwood. Even though the moisture content was same, heartwood was 1.3 times less permeable than sapwood and the difference was found statistically significant. Due to anatomical differences between ray parenchyma and ray tracheid, ray parenchyma was about 1.3 times more permeable than ray tracheid. Penetration speed was high initially and it decreased rapidly in course of time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.778-781
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• 2004

As the technique of high-speed end-milling is widely adopted to in machining field. The investigation for microscopic precision of workpiece is necessary for machinability evolution. In this study, cutting force, cutting temperature and microhardness were investigated to evaluate damaged layer in conventional machining and high-speed machining. Damaged layer was measured using optical microscope. The thickness of damaged layer depends on cutting process parameters, specially feed per tooth and radial depth. It is obtained that the characteristics of damaged layer is high-speed machining better than conventional machining.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1049-1050
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• 2008

It is difficult to measure the pulse wave in a short time because radial artery position and located depth are different depending on the person. In this paper, the pulse wave measurement system was developed using 3 channel piezoresistive sensor array to detect the most significant pulse wave. Augmentation Index(AI) and Heart Rate(HR) analysis are also available for predicting cardiovascular risks. The developed system is small and easy to use. And it is promising to be used as home healthcare device.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.112-115
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• 2004

An analytical study is conducted using the Galerkin technique to determine the behaviour of thin fibre-reinforced composite pipes under soil pressure. Geometric nonlinearity and material linearity are assumed. It is assumed that the vertical and lateral soil pressures are proportional to the depth and the lateral displacement of the pipe respectively. It is also assumed that the radial shear stress is negligible because the ratio of the thickness to the radius of the pipe is very small. The calculation results are compared with the finite element analysis result.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.399-407
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• 2001

The Surface, generated by end milling operation, is deteriorated by tool runout, vibration, friction, tool deflection, etc. Especially in cornering cut, surface accuracy is usually determined by varying cutting forces, which causes tool deflections. Cutting conditions like feed rate is usually kept constant during machining a part, which causes dimensional error in severe cutting. Cornering cut is a typical example of deterioration of surface accuracy when constant feed rate is applied. Therefore it becomes important to develop NC post processor module to determine optimal cutting conditions in various cutting situations. In this paper, cutting force is predicted in cornering cut with flat end mill and feed rate is determined by constraining constantly resultant force. Also some control characteristics of CNC machining center are evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.37-45
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• 2007

End-milling is intermittent cutting process performed by a tool with a number of teeth. Its cutting forces are commonly measured by the tool dynamometer which has rectangular coordinates. In this case, the pattern of cutting forces is different according to cutting conditions. At a certain cutting condition, the sign of cutting force changes from positive to negative during a revolution of one tooth. The change of force direction excites a cutting tool and severe vibration arises when radial depth of cut increases. In this study, cutting experiments and simulations were carried out in order to explain the cause of the change of the cutting force direction. In addition, the effect of the cutting force change was discussed in terms of chatter vibration in end milling.