• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1673-1675
• /
• 2001

In this paper, Partial Discharge(PD) patterns are compared by means of Low Frequency PD(LFPD, based on the IEC 270) and recently proposed High Frequency PD(HFPD). For this purpose, three different types of artificial defects are provided such as corona in air, void in epoxy insulator and needle defect in XLPE cable insulation. PD were generated from each defect and then detected respectively by two different methods such as LFPD and HFPD. As a result, remarkable resemblance in PD pattern for differ detecting method have been observed from each defect. Accordingly, it could be deduced that the pattern recognition by LFPD could be regarded as the reference for the investigations by HFPD.

• Journal of Industrial Technology
• /
• v.7
• /
• pp.9-14
• /
• 1987

The maximum specific gravity of asphaltic concrete can be calculated based on the effective specific gravity of aggregates and the specific gravity of asphalt cement. The maximum specific gravity is sometimes obtained based on the apparent specific gravity of aggregates and specific gravity of asphalt concrete. However, the apparent specific gravity is in general greater than the effective specific gravity for most aggregates. This study showed, by comparing the results obtained based on two specific gravities, that application of the apparent specific gravity instead of the effective specific gravity resulted in discrepancies in the calculated values of effective asphalt content, air void and maximum density.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.6
• /
• pp.1128-1146
• /
• 1989

본 논문에서는 2상 횡유동의 진동 메카니즘을 규명하기 위한 실험계획의 일환으로 실시된 실험으로 부터 튜브집합체의 추가질량(hydrodynamic mass)과 감쇠 (damping)에 대해 고찰하였다. 실험은 튜브배열과 피치 대 직경비(pitch-over-di- ameter:.rho./ｄ)가 상이한 튜브집합체에 대해 2상 유체를 모의한 공기-물(air-water) 혼합물에서 수행하였다. 액체상태로부터 99%의 보이드율까지 변화된 2상 유체의 유량은 튜브가 유체탄성 불안정성 (fluidelastic instability)에 도달할 때까지 점진적으로 증가하였다.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.711-714
• /
• 2003

Factors causing deterioration of concrete structures under marine environment are various, especially penetration and diffusion of chloride ion, carbon dioxide, and water through pore effects on the durability of concrete as well as mechanical properties of concrete. Pore of porous materials like concrete can be classified as micro-, meso-, and macro-pore. And pore of cement matrix is classified as pore which occupied by water, air void, and ITZ between cement paste and aggregates. In this study, to verify the relationship between pore of cement matrix and the property of chloride ion diffusivity, the regression analysis is producted. From the result of regression analysis, the average pore diameter more than total pore volume effects on the diffusivity of chloride ion.

• Journal of Industrial Technology
• /
• v.33 no.A
• /
• pp.101-107
• /
• 2013

The purpose of this study was to investigate bond strength between substrate and HES-LMS mortar, durability of HES-LMS mortar with latex content(0%, 5%, 10%). To measure the bond strength, the direct tensile test based on uniaxial tensile test was used, which was proposed by Kuhlman(1990). Also, Resistance for water permeability, water absorption and image analysis for air void system were conducted to estimating durability of HES-LMS mortar.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.4
• /
• pp.183-188
• /
• 2006

Abstract - In order to investigate the possibility of separating PD(partial discharge) and noises through the pulse analysis by use of a HFCT, pulse shapes measured by a resistive sensor and a HFCT were analyzed and adequate PA(pulse analysis) algorithms were studied. For the purpose, the HFPD detection and PA system has been developed. Also void discharges and air corona were adopted as the artificial defect and noises, respectively. As a result, it is possible to separate partial discharges and noises through the PA method using the $100kHz{\sim}20MHz$ frequency range HFCT. It is expected to apply the developed system to on-site PD measurements for the electric equipments.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.176-186
• /
• 1996

The phenomena of drag reduction using small quantities of a liner macromolecules has attracted the attention of many experimental investigations. On the other hand drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. But the research on dragreduction in two phase flow is not sufficient. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity and turbulent intensity whether polymer additives a horizontal single and two phase system or not. Flow pattern of air-water two phase flow was classified by electrical conductivity probe signal. Velocities and turbulent intensities of signal were measured simultaneously with a Hot-film anemometer.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.4
• /
• pp.107-114
• /
• 2003

This study was performed to develop the plantable concrete block using rice straw ash and apply for inclined plane. For the planting, plantable concrete block needs infiltration of water and air through void of block. The materials used for plantable concrete block are cement, rice straw ash, and coarse aggregate (5-10, 10-20 mm). Plantable block size is $23\times23\times4$ cm, and species of planting are Tall fescue, Lespedeza cyrtobotrya and Lespedeza cuneata. At the 6 months after seeding, germination ratio and grown-up length of Tall fescue, Lespedeza cyrtobotrya and Lespedeza cuneata are shown in 90%, 60%, 50%, and 40~50 cm, 90~120 cm, 60~75 cm, respectively.

• Geotechnical Engineering
• /
• v.10 no.2
• /
• pp.97-108
• /
• 1994

A new RI calibration curve acquired from the laboratory tests on typical embankment materials is found to be adequate for testing subgrade materials in Korea but may not be suitable for testing materials containing gravels. Therefore this study aims for the modification of RI values that enables the usage of RI to all kinds of roadbed materials. Also other factors available for the criteria of compaction control such as air void ratio and degree of saturation were reviewed for their applicability.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2002.11a
• /
• pp.52-52
• /
• 2002

Recently, nanoporous low-k materials using porogen (pore generating material) template method have gained much attraction due to the feasible advantage of dielectric constant decrease with the increase of porogen content, which is burning out and making air void by thermal curing. In nanoporous thin films, further, control of pore size and its distribution is very important to retain suitable thermal, mechanical and electrical properties. In this study, nanoporous low-k films were prepared with MTMS-BTMSE copolymer and porogen. The effect of interaction of copolymer matrix and porogen on pore size and distribution was comparatively to investigate with molecular structure and end functional group. The characterization of nanoporous thin film prepared was also performed using various techniques including NMR, GPC, Ellipsometer, FE-SEM, TGA, and FT-IR.