• Journal of the Korean Magnetics Society
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• v.11 no.4
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• pp.157-162
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• 2001

Rheological characteristics of Sm-Co type plastic magnet compound for powder injection molding process were investigated with the variation of the magnetic powder size, their relative contents and volume fraction using the mixture of fine and coarse powder. Shear viscosity of Sm-Co type compound was decreased with increasing the size of coarse powder due to the increase of powder packing density. However, the smaller the average size of fine powder resulted in the higher viscosity of compound due to the increase of agglomeration force. In case of mechanically milled Sm-Co type powder, the viscosity of compound with the mixture of coarse powder of 125∼75 ㎛ and fine powder of average size of 4.9 ㎛ greatly depends on their relative contents and shows a minimum value at the 60 % coarse powder fraction. This means that the compound shows a maximum packing density at the 60% coarse powder fraction. Compound viscosities satisfied well the rheological model with the volume fraction of magnetic powder, and maximum volume fraction of magnetic powder in Sm-Co type compound for powder injection molding was about 66%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1051-1057
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• 2008

In this paper, we analyzed the characteristics of the EM wave absorber which was fabricated by using flake sendust (soft metal magnetic powder). The flake sendust was made of 3 different granularity by attrition mill. First, we have fabricated 3 kind of EM wave absorbers using the flake sendust and CPE(Chlorinated Polyethylene) and measured the S-parameters of the EM wave absorber. The complex relative permittivity and permeability were calculated from the measured data and the variations according to a change of granularity were researched. As a result, it was confirmed that the EM wave absorber using flake sendust with the $140{\mu}m$ average granularity has outstanding absorption ability in high frequency range(C band) for the reduction of eddy current loss(increase of permeability) and the increase of space charge polarization(increase of permittivity).

• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.49-58
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• 2003

The suction of unsaturated soil is one of the important variables to influence on volume change behavior. This research was performed to analyze the soil-water characteristic of decomposed granite soils in Chung Cheong area, and showed relationship with grain-size distribution. Empirical parameters a, n, m are main variables that can be used in the empirical equations in order to predict unsaturated soil. Decomposed granite soils is taken at 12 field, and redistributed due to a, n, m parameters. The result of Extractor test is showed that matric suction is effected by the grain-size distribution curve's left-right location, degree of an angle and fine contents of a soil.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.24-27
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• 2006

16개 기상관측소에서 채취한 토양 시료에 대한 토양 물성 및 열특성를 측정하였으며 이를 통하여 공극률, 함수비, 충적밀도, 입도 분포, 유기물 함량, 토양구성광물의 종류 및 함량이 열전도도에 미치는 영향을 파악하였다. 상관성 분석결과 입도분포, 유기물함량 및 토양 구성광물의 종류 및 함량은 낮은 상관성을 보였으며 용적밀도 $(R^2=0.60)$, 함수비$(R^2=0.54)$와 공극률$(R^2=0.56)$은 높은 상관성을 보였다. 또한 함수비(2%)와 토양의 종류에 따른 다중회귀 분석을 통하여 토양의 열전도도를 추정할 수 있는 회귀식을 제시하였다.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.141-151
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• 2004

The physical properties of gold investment materials are depending on it's thermal expansion coefficients, compressive strength, and particles size distributions. Normally the gold investment materials are consisted of cristobalite, quartz and plaster. Since the thermal expansion coefficient of cristobalite and quartz are $2.6\times10^{-6}/^\circC$, $2.32\times10^{-6}/^\circC$, respectively, the composition ratio of each components influence the thermal and clinical properties of gold investment materials. Recently are imported from overseas and the commercial market is expected to expand. Thus it is necessary to develop the optimum strength and compressive strength of gold investment materials which the an homogeneous size distribution and thermal expansion coefficients. Therefore two different experiments has been done. Firstly the homogeneous cristobalite and quartz are made by pulverizing milling. Secondly the compressive strength and thermal expansion coefficients are analysed by the composition ratio of cristobalite and quartz. As a results of experiments, homogeneous distribution of cristobalite and quartz are observed by pulverizing and milling. The optimum compressive strength was obtained at the ratio of 45:25 cristobalite, quartz respectively.

• Clean Technology
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• v.7 no.1
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• pp.81-88
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• 2001

Limestone has been used as absorbent in the FGD(Flue Gas Desulfurization) system, the DeSOx system of thermal power plant. This study investigated the desulfurization characteristics of the two different limestones, 325mesh and 200mesh particle size. Experimental analysis showed that the dissolving rate of limestone became much slower as the particle size increased. But the desulfurization efficiency depended on the L/G(liquid/gas) ratio and slurry pH regardless of the limestone particle size. The quality of gypsum produced in the FGD process increased as the limestone particle size or the slurry pH decreased. To reduce the cost of absorbent, the mixed limestone which were composed of 200 and 325mesh limestone with 5 different ratios were tested.

• 한국해양학회지
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• v.28 no.2
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• pp.114-120
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• 1993

Numerical method of nonlinear regression was introduced to characterize grain-size distribution more effectively than using the traditional textural parameters. This technique proved critical particularly to multimodal size distributions, as exemplified by samples from Cheju strait continental shelf. Grain-size analysis of samples collected from the Cheju Strait continental shelf reveals that 86% of the grain-size distributions are multimodal. As multimodal grain-size distribution deviates from the statistical (log) normal distribution, the grain-size parameters traditionally used in sediment studies do not describe the distribution efficiently. Therefore, the use of grain-size curves into elementary normal component curves was used. Means and standard deviations of 387 decomposed normal components were decided by a decomposition method (nonlinear least square regression) from 167 size curves of the Cheju Strait sediments. The mean values of decomposed normal components show peaks at 1-3 phi and 8-9 phi size classes. The plot of mean values of the coarse fraction normal components on the map shows a characteristic and complex areal distribution. On the basis of the areal distribution of the mean values of the components and that of isopach of total Plenipotence sediment, the areal distribution of layers composing a transgressive sand of Late Plenipotence age were revealed.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.372-381
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• 1995

본 논문에서는 분체 특성 평가 연구의 국제 동향과 입자형태, 입도분포, 비표면적, 분체밀도, 기공도, 화학분석 평가분야의 기본원리, 특히 측정시 변수들의 영향과 이러한 특성변화에 따른 전기적성질 변화에 대하여 간단히 언급을 하였다. 분체 특성평가분야의 연구는 선진국에 비해 낙후되어 있고 관심도 또한 낮은 형편이다. 이 분야의 학문적, 산업적인 중요점을 고려할 때, 분체 특성 평가에 대한 기초 및 응용연구가 활성화되었으면 한다.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03a
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• pp.146-157
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• 2004

다짐에너지는 D-2 수정다짐과 5층 35회, 45회 및 65회로 변화시켜 다짐시험을 행하였고 이때 각 시료는 자연입도에 근접하게 동일입도로 조정 사용하였으며, 건조법 및 비반복법으로 흐트러진 시료를 사용하여 시험하였다. 다짐에너지를 변화시키면서 다짐 시험한 결과는 그림 1, 2와 같다. 이들 그림에 대하여 최소자승법으로 다음과 같은 관계식을 얻었다. $r_{dmax}$=0.9834＋0.0312 ln(E) $W_{opt}$=54.25-0.3778E $r_{dmax}$=1.8494-0.0158 $W_{opt}$ e=-0.07576 ln(E) ＋ 1.5443(중략)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.304-312
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• 2011

Grain size analysis was conducted for a total of 402 surface sediments collected from 67 sites along three (upper, middle, and lower) transects corresponding to the high-, mid-, and low-intertidal zone of beach on the Sinjado, Nakdong River estuary in Nov. 2005 and May 2006. Sinja-do beach sediments showed uni-modal grain size distributions, in which the mode of $3.0{\phi}$ was dominant in 2005 whereas the mode of $2.5{\phi}$ in 2006. This coarsening trend was more remarkable in the western side of beach as well as in the mid- and low-intertidal zone. In this study, we focused on investigating characteristics of sediment size changes on the basis of transect data that differ in tidal elevation. For this purpose, a statistical test was applied for transect by transect comparison of grain size parameters such as mean, sorting, and skewness. Mean values between middle and lower transect, sorting values between upper and lower transect, and skewness values over the beach reflected statistically significant temporal changes. Also, mean and skewness parameters showed an inverse relationship which was more stronger in 2006 than in 2005. Temporal changes in Sinja-do beach sediments resulted in decrease of mean and sorting values but increase of skewness values, intensifying the inverse relationship between mean and skewness parameters.