• 전기학회논문지
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• 제67권12호
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• pp.1633-1640
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• 2018

Epoxy resin is a polar thermosetting polymer that is widely employed in different branches of industry and everyday life, due to their stable physical and chemical properties. Of all the polymer materials currently being used in the electrical insulation industry, epoxy resin is the most widely used kind, chosen as the base polymer material in the present study. Composites were prepared according to the mixing ratio (MS: MA, 1: 9, 3: 7, 5: 5, 7: 3, 9: 1)of mixture for Heterogeneous Minerals(Micro Silica:MS, Micro Alumina:MA) (MS+MA). We have investigated for AC electrical insulation breakdown characteristics and the dielectric properties (permittivity, dielectric loss, and conductivity) with frequency changes. The electrical AC insulation breakdown performance was improved with the increase of the mixing ratio of MS according to heterogeneous mineral material mixture(MS+MA). As Dielectric properties, the dielectric constant and dielectric loss increased with decreasing frequency and decreased with increasing MS content ratio of heterogeneous mineral mixture. Tensile strength and flexural strength according to the mixing ratio (MS + MA) of epoxy / heterogeneous mineral mixture were studied by mechanical properties. The performance of mechanical tensile and flexural strength was significantly improved as the fill contents ratio of MS increased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.143-150
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• 1994

To improve the qualities of high strength mortar and concrete with high range water reducing admixture, silica fume and gypsum is applied. The flow loss of mortar is reduced and the compressive strength of mortar and concrete is improved by silica fume. And the silica fume is effective for decreasing the temperature of high strength concrete. In addition to, the strength of high strength concrete is more improved by the gypsum.

• International Journal of Concrete Structures and Materials
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• 제7권4호
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• pp.287-293
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• 2013

Strength and some durability properties of concrete containing rice husk ash (RHA) predominantly composed of amorphous silica at a specific surface of 235 $m^2/kg$ produced using a charcoal incinerator were determined. The maximum ordinary Portland cement (OPC) replacement with the RHA increased with increase in water/binder (w/b) ratio of the concrete mixes. The results show that 15 % OPC could be substituted by the RHAwithout strength loss at w/b ratio of 0.50. The split tensile strength generally increased with increase in RHA content for the mixes.

• 한국결정성장학회지
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• 제27권5호
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• pp.249-255
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• 2017

화력발전소에서 발생되는 매립회의 지오폴리머 원료화를 위하여 자력선별 공정을 이용하여 자성체와 비자성체로 분리하였으며, 매립회의 입도 및 자석의 세기에 따른 미연탄소의 선별 특성을 관찰하였다. 3000 G 자석을 이용한 세립(0.15~0.84 mm)과 조립(0.84~2.4 mm) 매립회의 자력선별 결과, 매립회는 입도에 상관없이 비자성체의 무게분율과 강열감량이 자성체보다 높게 나타났으며, 세립 매립회의 경우 자석의 세기를 3000 G에서 10000 G로 증가시키면, 약한 자성을 띠는 물질들도 자성체로 분리됨에 따라 자성체의 무게 분율이 급격히 증가되면서 낮은 강열감량에도 불구하고 전체 강열감량의 32.6 wt%의 66.9 %(22.8 wt%)를 차지하였다. 자력 선별된 조립 매립회로 제조된 지오폴리머의 재령일별 압축강도 측정결과, 미연탄이 적게 포함된 자성체로 제조된 지오폴리머의 압축강도가 20 MPa를 나타내었다.

• 생명과학회지
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• 제12권6호
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• pp.780-785
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• 2002

본 연구는 고교 레슬링선수들의 단기간 체중감량에 따른 등속성 운동능력 중 다리의 peak torque, peak torque %BW, total work, total work %BW, endurance ratio에 대한 변화를 알아보기 위하여 자기 체중에서 체중감량이 없는 집단 7명, 5%이상 감량집단 7명을 대상으로 체중감량 전ㆍ후를 측정하여 얻은 결론은 다음과 같다. 1. Peak Torque의 변화. 굴근의 경우 5%이상 감량 집단의 $60^{\circ}C$sec, $90^{\circ}C$/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 $60^{\circ}C$/sec, $90^{\circ}C$/sec, $250^{\circ}C$/sec에서 모두 유의하게 감소하였다. 2. Peak Torque %BW의 변화. 굴근의 경우 5%이상 감량 집단의 60$^{\circ}$/sec, 90$^{\circ}$/sec, $150^{\circ}C$/sec에서 모두 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 $90^{\circ}C$/sec와 $250^{\circ}C$/sec에서 유의하게 감소하였다. 3. Total Work의 변화. 굴근의 경우 5%이상 감량 집단의 $60^{\circ}C$/sec,$90^{\circ}C$/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량집단의 $50^{\circ}C$/sec, $90^{\circ}C$/sec. $250^{\circ}C$/sec에서 모두 유의하게 감소하였다. 4. Total work %BW의 변화. 굴근의 경우 5%이상 감량 집단의 $60^{\circ}C$/sec, $90^{\circ}C$/sec, $250^{\circ}C$/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 $50^{\circ}C$/sec, $90^{\circ}C$/sec, $250^{\circ}C$/sec에서 모두 유의하게 감소하였다. 5. Endurance Ratio의 변화. 굴근과 신근의 경우 두 집단 모두 유의한 차이가 없었다. 단기간의 무리한 체중감량은 근력, 근지구력의 저하로 경기력을 저하시킬 뿐만 아니라 건강을 해칠 우려가 있기 때문에 단기간의 무리한 감량이 되지 않도록 과학적이고 체계적인 체중관리가 이루어져야 할 것으로 사료된다.

• Journal of the Korean Statistical Society
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• 제32권3호
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• pp.289-298
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• 2003

We consider the estimation problem for the scale parameter of the Rayleigh distribution using weighted balanced loss function (WBLF) which reflects both goodness of fit and precision. Under WBLF, we obtain the optimal estimator which creates a kind of balance between Bayesian and non-Bayesian estimation. We also deal with the estimation of R ＝ P(Y < X) when Y and X are two independent but not identically distributed Rayleigh distribution under squared error loss function.

• 한국염색가공학회지
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• 제10권5호
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• pp.39-47
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• 1998

The purpose of this study was to investigate the effect of alkali treatment on EG solution of polyester/silk union cloth(P/S cloth) . Tensile strength, moisture regain, crease resistance, and reduction ratio of the treated P/S cloth were measured. The results of this study were as follows ： 1) The weight loss of P/S cloth treated with EG solution was three times higher than those of P/S cloth treated with $H_2O$. The weight loss of P/S cloth was increased greatly with increasing concentration of NaOH, temperature, and time. Favorable weight reduction of treating condition could be obtained when lower concentration of NaOH was used with longer time. 2) If it was added $H_2O$ on EG solution, weight loss of polyester increased, while those of silk decreased. In addition, decreasing ratio of tensile strength warp direction (polyester) was lower, while those of weft direction(silk) was higher. 3) Moisture regain of P/S cloth treated with EG solution increased with weight loss up to 10% . Crease resistance of P/S cloth was the highest at weight loss of 10~15%.

• Journal of the Korean Wood Science and Technology
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• 제36권5호
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• pp.24-32
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• 2008

Artificial brown-rot decay was induced to two wood species, Pinus densiflora and Pinus radiata. A modified direct inoculation method was used and the decay indicators of mass loss and two compressive mechanical properties, maximum compressive strength (MCS) and compressive stiffness, were estimated over the period of 8 weeks of fungal exposure. Measurable mass loss occurred 2 weeks after the fungal attack, with 15% to 22% of the loss occurring 8 weeks after fungal exposure with Fornitopsis palustris and Gloeophyllurn trabeurn. Mechanical properties proved to be far more sensitive than mass loss detection: approximately five to six times by quantity. Of the two mechanical properties, MCS was more sensitive to and consistent with progressive brown-rot decay. An ultrasonic test was performed to determine the feasibility and accuracy of this method for nondestructive detection of brown-rot decay. The ultrasonic test is highly sensitive at qualitative detection of the early stages of brown-rot decay.

• 한국의류학회지
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• 제23권7호
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• pp.998-1006
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• 1999

This study has investigated the relation between the sewing speed and seam breaking strength applied perpendicular to the seam direction. Breaking strength efficiency breaking mode of seams were examined under various sewing conditions using three kinds of sewing threads and four kinds of fabrics. The results obtained are as follows : 1. According to the increase in sewing speed seam strength was remarkably decreased. Seam strength and its loss difference were shown variously as threads and fabrics were mixed. 2. In case of fabrics with higher strength seam strength showed higher. And the seam strength was determined by the loop strength. 3. In case of fabrics with lower strength seam strength and its difference for every sample showed lower. So the strength of fabrics dominated the seam strength than those of threads. 4. In the experiment using various fabrics and sewing threads there was a type of thread appropriate to each fabric. Fabrics and threads with have similar physical properties were shown proper seam efficiency. 5. The breaking mode was different for every sample seam that was tested.

• 한국세라믹학회지
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• 제52권1호
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• pp.28-32
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• 2015

In this article, the influence of a hydrolyzed wheat protein retarder on the hydration process, ion concentration in liquid phase, degree of supersaturation, and crystal morphology of plaster was investigated. Furthermore, the retarding mechanism and the strength loss of gypsum were also studied by scanning electron microscopy (SEM). The results indicate that the use of the hydrolyzed wheat protein retarder for plaster achieved a better retarding effect and lower strength loss. The combination of gypsum plaster with the retarder not only decreased the plaster's early hydration rate and prolonged its setting time efficiently, but also militated against the crystal morphology of dihydrate gypsum. For example, the crystal dimensions changed little, but the proportion of needle-shaped crystals decreased. Combination with calcium ions on the surface of dihydrate gypsum crystal nuclei may form a chemisorbed layer, reduce the surface energy of the crystal nuclei, and inhibit the growth of the crystal nuclei of dihydrate gypsum. Consequently, the hydration process of building gypsum becomes greatly extended and is slowed down significantly.