• Nuclear Engineering and Technology
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• 제35권3호
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• pp.226-233
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• 2003

The discharge characteristics of a prototype ion source was investigated, which was developed and upgraded for the NBI (Neutral Beam Injection) heating system of KSTAR (Korea Superconducting Tokamak Advanced Research). The ion source was designed for the arc discharge of magnetic bucket chamber with multi-pole cusp fields. The ion source was discharged by the emission-limited mode with the control of filament heating voltage. The maximum ion density was 4 times larger than the previous discharge controlled by a space-charge-limited mode with fully heated filament. The plasma (ion) density and arc current were proportional to the filament voltage, but the discharge efficiency was inversely proportional to the operating pressure of hydrogen gas. The maximum ion density and arc current were obtained with constant arc voltage ($80{\sim}100V$), as $8{\times}10^{11}cm^{-3}$ and 1200 A, respectively. The estimated maximum beam current was about 35 A, extracted by the accelerating voltage of 80kV.

• Journal of Periodontal and Implant Science
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• 제46권3호
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• pp.152-165
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• 2016

Purpose: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results: The maximum extent of micromotion was approximately $100{\mu}m$ in the low-density cancellous bone models, whereas it was under $30{\mu}m$ in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.529-534
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• 1998

To find out an adequate failure criterion in two-dimensional linear elastic crack problems, finite element programs, SED, which determine stress intensity factors $K_I, K_{II}$, crack angle and peak load by the minimum strain energy density failure criterion were developed. In this program, the conventional quadratic isoparametric elements were used in all regions except the crack tip zone where triangular singular elements with 6 nodes were used. The results of SED were compared with the results of those which followed by the maximum circumferential tensile stress criteria and those by the maximum energy release rate criteria and those by Jenq and Shah`s experiments of the same geometry and material properties. The maximum energy release rate criteria were better close to those of the Jenq and Shah`s experiments than the maximum circumferential tensile stress criteria and the minimum strain energy density criteria.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.102-109
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• 2002

The fatigue crack growth under mixed mode condition has been discussed within the scope of linear fracture mechanics such as maximum tangential stress, maximum tangential principal stress and minimum strain energy density. The purpose of this study is to investigate the characteristics of fatigue test crack growth in 304 stainless steel under mixed node. The fatigue test results carried out by using inclined pre-crack specimens was compared to both of the theoretical predictions of the criteria, maximum tangential stress and stain energy density. As difference from theoretical analysis, the transition region from mixed mode to mode I appeared in the fatigue test. There is deep relationship between the angle of slanted pre-crack and transition. Therefore, as applying the different stress intensity factor to each node I+II and mode I, the directions and rates of fatigue crack growth are evaluated more accurately under mixed mode.

• 한국농공학회지
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• 제18권3호
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• pp.4171-4183
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• 1976

This study is to investigate the effect of some physical properties of soil on the compaction. The compaction effect depends upon various factors such as soil type, moisture content, gradation and compaction energy. In this study, with steady compaction energy, the relationships between maximum dry density and moisture content, gradation and consistency were analyzed by soil types. Some results obtained in this study are summarized as follows 1. Generally, the coarser the grain size, the bigger is the maximum dry density and the smaller is the optimum moisture content and its moisture-dry denisty curve is relatively steep. The finner the grain size, the smaller is the max. dry density and the bigger is the opt. moisture content and its moisture-dry density curve is less steep. 2. The relationship between max. dry density (${\gamma}$dmax) and opt. moisture content, void ratio, clay content, percent passing of No. 200 sieve, liquid limit and plastic limit can be represented by the equation ${\gamma}$dmax =ao+a1X(a0>0, a1<0) 3. The relationship between opt. moisture content (Wopt) and clay content, percent passing of No. 200 sieve, liquid limit and plastic limit can be represented by the equation Wopt=a0+a1X(a0>0, al>0). 4. The fact that maximum dry density of the compacted soil is decreased with the increase of the optimum moisture content in any types of soil tested, and the fact that optimum moisture content can be positively correlated with clay content, percent passing of No. 200 sieve, liquid limit and plastic limit of the soil, lead to the conclusion that clay content, percent passing of No. 200 sieve, liquid limit and plastic limit of the soil are direct factors in reduction of the maximum dry density of engineering soil.

• Journal of the Korean Data and Information Science Society
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• 제25권1호
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• pp.219-226
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• 2014

In this paper, we derived estimators of reliability P(Y < X) and the distribution of ratio in the bivariate exponential density. We also considered the means and variances of M = max{X,Y} and m = min{X,Y}. We finally presented how E(M), E(m), Var(M) and Var(m) are varied with respect to the ones in the bivariate exponential density.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.305-310
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• 2001

Within some degree of journal misalignment, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined under the condition of variable density and specific heat. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the effects of variable density and specific heat on shaft misalignment are significant in determining the load capacity of a journal bearing operating at high speed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.287-292
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• 2001

Under the condition of variable density and specific heat, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the condition of variable density and specific heat play important roles in determining friction and load of journal bearing at high speed operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1055-1056
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• 2011

This paper deals with optimum design criteria for maximum torque density & minimum current density of a single phase line-start permanent-magnet motor (LSPMM) using RSM (Response Surface Methodology) & FEM (Finite Element Method). The focus of this paper is to find a design solution through the comparison of torque density and minimum current density resulting from rotor shape variations. And then, a central composite design (CCD) mixed resolution is introduced, and analysis of variance (ANOVA) is conducted to determine the significance of the fitted regression model.

• Journal of the Korean Data and Information Science Society
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• 제23권1호
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• pp.219-225
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• 2012

We derive approximate maximum likelihood estimators of two parameters in a weighted exponential distribution, and derive the density function for the ratio Y=(X+Y) of two independent weighted exponential random variables X and Y, and then observe the skewness of the ratio density.