• Korean Journal of Environment and Ecology
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• v.10 no.2
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• pp.191-204
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• 1997

Eight major trails of Soraksan National Park were selected to investigate the use impacts on environmental edterioration of trail according to the different amount of use. The entire width, bare width, maximum depth and slope of trail as the trail condition surveyed at the total of 188 points were significantly greater on the more heavily-used trail. Major deterioration types of trail were root-exposure, widening, rock-exposure, divergence in order of frequency. And trail conditions of edteriorated points were significantly different from those of non-deteriorated points. The damaged area more severe than Class 4 on trail reached about 10,864m$^{2}$ in total, and especially about 4,560m$^{2}$ in the section between Huiunkak Shelter-Munomigogae trail. The dominant trees of trail edge vegetation were be Quercus mongolica in upper layer, but in lower lauer Carpinus laxiflora, Lespedeza maximowiczii for valley and Carpinus laxiflora, Ghododendron mucronulatum var. cilatum, Tripterygium regelii for ridge.. Especially coverage and number of individuals was highest on Munomighgae-Taech'ongbong trail of the largest use of amount, and each trail was dissimilar in species composition of lower layer of edge vegetation.

• Journal of IKEEE
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• v.18 no.2
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• pp.214-219
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• 2014

In this paper, the usage of tilt-implanted trench Schottky diode(TITSD) based on silicon carbide is proposed. A tilt-implanted trench termination technique modified for SiC is proposed as a method to keep all the potentials confined in the trench insulator when reverse blocking mode is operated. With the side wall doping concentration of $1{\times}10^{19}cm^{-3}$ nitrogen, the termination area of the TITSD is reduced without any sacrifice in breakdown voltage while potential is confined within insulator. When the trench depth is set to 11um and the width is optimized, a breakdown voltage of 2750V is obtained and termination area is 38.7% smaller than that of other devices which use guard rings for the same breakdown voltage. A Sentaurus device simulator is used to analyze the characteristics of the TITSD. The performance of the TITSD is compared to the conventional trench Schottky diode.

• Steel and Composite Structures
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• v.42 no.4
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• pp.427-446
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• 2022

Cutouts in the beams or plates are often unavoidable due to inspection, maintenance, ventilation, structural aesthetics purpose, and sometimes to lighten the structures. Therefore, there will be a substantial reduction in the strength of the structure due to the introduction of the cutouts. However, these cutouts can be reinforced with the different patterns of ribs (stiffener) to enhance the strength of the structure. The present study highlights the influence of the elliptical cutout reinforced with a different pattern of ribs on the stability performance of such stiffened composite panels subjected to non-uniform edge loads by employing the Finite element (FE) technique. In the present formulation, a 9-noded heterosis element is used to model the skin, and a 3-noded isoparametric beam element is used to simulate the rib that is attached around a cutout in different patterns. The displacement compatibility condition is employed between the plate and stiffener, and arbitrary orientations are taken care by introducing respective transformation matrices. The effect of shear deformation and rotary inertia are incorporated in the formulation. A new mesh configuration is developed to house the attached ribs around an elliptical cutout with different patterns. Initially, a study is performed on the panels with different stiffener schemes for various ply orientations and for different stiffener depth to width ratios (d_s/b_s) to determine an optimal stiffener configuration. Further, various parametric studies are conducted on an obtained optimal stiffened panel to understand the effect of cutout size, cutout orientation, panel aspect ratio, and boundary conditions. Finally, from the analysis, it can be observed that the arrangement of the stiffener attached to a panel has a major impact on the buckling capacity of the stiffened panel. The stiffener's depth to width ratio also significantly influences the buckling characteristic.

• Progress in Superconductivity
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• v.11 no.2
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• pp.152-157
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• 2010

We have fabricated the low noise liquid helium(LHe) dewar with a different shape of thermal shield to apply the 64-channel SQUID(Superconducting Quantum Interference Device) gradiometer. The first shape of thermal shield was made of an aluminum plate with a wide width of 100 mm slit and the other shape was modified with a narrow width of 20 mm slit. The two types of dewars were estimated by comparing the thermal noise and the signal-to-noise ratio(SNR) of magnetocardiography(MCG) using the $1^{st}$ order SQUID gradiometer system cooled each dewar. The white noise was different as a point of the dewar. The noise was increased as close as the edge of dewar, and also increased at the thermal shield with the more wide width slit. The white noise of the dewar with thermal shield of 100 mm slit was 6.5 fT/$Hz^{1/2}$ at the center of dewar and 25 fT/$Hz^{1/2}$ at the edge, and the white noise of the other one was 3.5 - 7 fT/$Hz^{1/2}$. We measured the MCG using 64-channel SQUID gradiometer cooled at each LHe dewar and compared the SNR of MCG signal. The SNR was improved of 10 times at the LHe dewar with a modified thermal shield.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.7-14
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• 2002

In this study, a stress analysis is made fur an ankle foot orthosis (AFO) in the view point of structural stability. The investigated AFO is a solid and standard type. To analyze the stress distribution on the neck of AFO, the maximum AFO angular translation data is obtained by gait analysis. The material test of polypropylene is made to obtain the mechanical properties of AFO. The maximum dorsiflexion appears at the midstance in the gait analysis. The experimental angular translation at the top of AFO is about 10.3$^{\circ}$ at mid stance. Three models of AFO with different width of neck are made and analyzed with ABAQUS 6.1. The stress levels and distributions of 3 different width(W$_1$, W$_2$=0.85W$_1$, W$_3$=0.60W$_1$) AFO are investigated. As a result, the standard type(W$_1$) appears to the maximum stresses at the medial edge of cutout area surrounding ankle joint. The maximum stresses of the narrower type(W$_2$) are occured on medial edge and center of ankle. The narrowest type(W$_3$) appears to the maximum stresses at center of ankle. The maximum stresses become smaller as ankle width of AFO is narrower.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.

• Journal of Bio-Environment Control
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• v.1 no.2
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• pp.142-147
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• 1992

The wind pressure distributions were analyzed to provide fundamental criteria for the structural design on the two-span arched house according to the wind directions through the wind tunnel experiment. In order to investigate the wind force distributions, the variation of the wind force coefficients, the mean wind force coefficients, the drag force coefficients and the lift force coefficients were estimated using the experimental data. The results obtained are as follows : 1. The variation of the wind force with wind directions on the side walls was the greatest at the upwind edge of the walls. 2. The maximum negative wind force along the length of the roof appeared at the upwind edge at the wind direction of 60$^{\circ}$. 3. The maximum negative wind force along the width of the roof appeared at the width ratio and wind direction of 0$^{\circ}$ and 0.4 in the first house and 0.6 and 30$^{\circ}$ in the second house, respectively. 4. The mean negative wind force on the side walls of the first house at the wind direction of 0$^{\circ}$ was far greater than that of the second house, and the maximum negative wind force on the roof occurred at the wind direction of 30$^{\circ}$. 5. The maximum lift force appeared on the second house at the wind direction of 30$^{\circ}$, but the lift force on the first house was far greater than that on the second house at the wind direction of 0$^{\circ}$. 6. The parts to be considered for the local wind forces were the edges of the walls, and the edges of the x-direction and the width ratio, 0.4 of the y-direction in the roofs.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1121-1126
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• 1998

For vacuum seated panel, stresses and displacements in the glass plate were calculated. The geometric variables for our experiment were the thickness of glass plate, the size of panel and the width of sealing line. The fracture behaviors and displacements of its under the vacuum were measured. From the measurement of strains and fracture, it was considered that the maximum stress acted at the middle of the sides of the panel. The stresses and displacement distribution of manufactured panels were greatly dependent on the width of the sealing line in the panel. The measured values are more similar to the values which were calculated from the condition of built-in edge as the width of the sealing line is larger. The measured displacement of the panel, made of 3mm thick glass plate, with size of $80\Times120\textrm{mm}^2$ and 20mm sealing line was $57\mu\textrm{m}$. This value is similar to calculated value, $54\mu\textrm{m}$, from built- in edge condition in the finite element method.

• Geomechanics and Engineering
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• v.34 no.1
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• pp.103-113
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• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.763-769
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• 2012

We investigated the width (N) dependence on the magnetization of N-ZSiC NR with electron and hole doping on the basis of systematic DFT calculations. The critical values of the upper and down critical concentration to give the maximum and zero magnetic moment at edge Si/C atoms by electron/hole doping ($x_{up,e}$, $x_{down,e}$, $x_{up,h}$, and $x_{down,h}$) depend on the width of N-ZSiC NR. Moreover, due to $x_{up,e}\;{\neq}\;x_{up,h}$ and $x_{down,e}\;{\neq}\;x_{down,h}$, the electron and hole doping effect are asymmetry, i.e, the critical electron doping value ($x_{down,e}$) is smaller than the critical hole doping value ($x_{down,h}$) and is almost independent of the width of NZSiC NR though the other critical values of the electron and hole doping that influence the magnetization of N-ZSiC NR depend on the width. It was also found that at $x_{down,e}$ or $x_{down,h}$ doping, the N-ZSiC NR turns into unusual non-magnetic metallic state. The magnetic behavior was discussed based on the band structures and projected density of states (PDOS) under the effect of electron/hole doping.