• Journal of the Korean Wood Science and Technology
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• 제30권3호
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• pp.75-84
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• 2002

In order to find out impact insulation properties, various types of current radiant floor heating systems and light-framed floors that are used in light-framed residential buildings were evaluated for two types of impact sources at the same time. Sound Pressure Level (SPL) was different from each impact sources for those spectrum patterns and peaks. In case of light-framed floor framework, the excitation position and the assumed effective vibrating area have effects on sound pressure level but it is not considerable, and Normalized SPL was reduced for each frequency by increasing the bending rigidity of joist. The mortar layer in the radiant heating system had relatively high density and high impedance, therefore, it distributed much of the impact power when it was excited, and reduced the Normalized SPL considerably. Nevertheless, Increasing a thickness of mortar layer had little influence on SPL. Ceiling components reduced the sound pressure level about 5~25 dB for each frequency. Namely, it had excellent sound insulation properties in a range from 200 to 4,000 Hz frequency for both heavy and lightweight impact sources. Also, there was a somewhat regular sound insulation pattern for each center frequency. The resilient channel reduced the SPL about 2~11 dB, irrelevant to impact source. Consequently, current radiant floor heating systems which were established in light-framed residential buildings have quite good impact sound insulation properties for both impact sources.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1552-1553
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• 2011

The HVDC transformer which is one of the main equipments for HVDC(High Voltage Direct Current) electric power transmission systems is exposed to not only AC voltage but also the inflowing DC voltage which comes from the DC-AC converter systems. Therefore, the HVDC transformer insulation system is required to withstand the electric field stress under AC, DC and DC polarity reversal conditions. However the electric field distributions under those conditions are different because the AC electric field and DC electric field are governed by permittivity and conductivity, respectively. In this study, the changes of electric potential and electric field of conventional AC transformer insulation system under DC polarity reversal test condition were analyzed by FEM(Finite Element Method). The DC electric field stress was concentrated in the solid insulators while the AC electric field stress was concentrated in the mineral oil. In addition, the electric stress under that condition which is affected by the surface charge accumulation at the interfaces between insulators was evaluated. The stress in some parts could be higher than that of AC and DC condition, during polarity reversal test. The result of this study would be helpful for the HVDC transformer insulation system design.

• International Journal of Ocean System Engineering
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• 제1권4호
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• pp.230-235
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• 2011

Reinforced polyurethane foam (RPUF) is one of the important materials of Mark III type insulation systems used in liquefied natural gas (LNG) cargo containment systems. However, RPUF is the most difficult material to use with regard to its safety assessment, because there is little public and reliable data on its mechanical properties, and even some public data show relatively large differences. In this study, to investigate the structural response of the system under compressive loads such as sloshing action, time-dependent characteristics of RPUF were examined. A series of compressive load tests of the insulation system including RPUF under various temperature conditions was carried out using specimens with rectangular section. As a result, the relationship between deformation of RPUF and time is linear and dependent on the loading rate, so the concept of strain rate could be applied to the analysis of the insulation system. Also, we found that the spring constant tends to converge to a value as the loading rate increases and that the convergence level is dependent on temperature.

• 한국전기전자재료학회논문지
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• 제15권12호
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• pp.1079-1084
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• 2002

Because complex insulation method is used in EHV(extra high voltage) insulation systems, macro Interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. Interface between toughened epoxy and silicone rubber was selected as a interface in EHV insulation systems and tested AC interfacial breakdown properties with variation of many conditions to influence on electrical Properties, such as interfacial pressure, roughness and oil. Specimen was designed to reduce the effect of charge transport from electrode in the process of breakdown and to have the tangential electrical potential with the direction of the interface between epoxy and silicone rubber by using FEM(finite elements method). It could control the interfacial pressure, roughness and viscosity of oil. From the result of this study, it was shown that the interfacial breakdown voltage is improved by increasing interfacial Pressure and oil. In particular, the dielectric strength saturates at certain interracial Pressure level. The decreasing ratio of the interfacial breakdown voltage in non-oiled specimen was increased by the temperature rising, while oiled specimen was not affected by temperature.

• 농촌계획
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• 제21권4호
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• pp.187-196
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• 2015

Among the factors of living environment, the one that is the most closely related with our living is the building. It is one of the biggest reasons for energy consumption as it forms 36% of the total energy consumption. Technologies equipped with excellent energy performance can hardly be applied to rural areas that are relatively poorer. Still, 89.8% rural residents are living in detached houses, and backward houses increase their financial burden and result in reduced insulation performance. Accordingly, this study is going to review the latest research written after 2000 dealing with rural houses and their insulation. The purpose of this study is to analyze the factors of insulation and how to improve insulation performance, conduct field research to find out how to apply low energy technologies applicable to houses with the subjects of experimental houses, the passive houses located in Jecheon City, Hongcheon Saldun zero energy houses, and energy independence villages, and find out how to perform follow-up research on insulation for rural houses. According to the findings, the latest research on insulation for rural houses is mostly focused on walls as well as windows and doors. Also, as ways to improve insulation performance, it suggests us to use high performance insulators, introduce new regeneration energy technology, and secure hermeticity. In addition, through field research, this author could find out low energy technologies applicable to houses such as solar energy facilities and heat recovery systems. Advanced research on insulation for rural houses has been focused on how to use materials or new regeneration energy, so follow-up research will have to consider the types of farming area or the residents' mode of living.

• 한국정보통신학회논문지
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• 제24권8호
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• pp.1058-1063
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• 2020

본 논문에서는 IT 접지 시스템의 감전 및 화재사고 방지를 위한 새로운 절연 저항 계산 기법을 소개한다. 최근 신재생 에너지와 에너지 저장 장치의 확대 보급으로 태양광 발전 시장이 급속하게 성장하고 있으나 절연이 파괴되어 화재사고가 빈번히 발생함에 따라 IT 접지 방식에도 절연 저항 상태를 감시하는 장치가 필수적으로 요구되고 있다. 제안하는 절연 저항 계산 기법은 기존의 고정된 시정수곱 계수기반의 알고리즘에 비해 절연 임피던스의 조건에 따라 동적시정수곱계수를 적용함으로써 넓은 절연 저항 범위에서 빠른 응답 시간과 높은 정확도를 갖는다. 제안하는 동적 시정수 기반 절연 저항 계산 기법은 기존의 방법에 비해 최대 응답 시간은 39.29초, 오차율은 20.11%를 개선시키는 효과를 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1000-1002
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• 1999

In this study, we were developed to provide a method for evaluating insulation systems for mold transformers with high-voltage ratings greater than 600V, in order to establish a uniform method for determining the temperature classification of mold transformer insulation system by testing rather than by chemical composition. Since these procedures are considered to be new, and have been tested exhaustively, further testing may prove the need for future revisions.

• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.27-30
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• 2011

A sub-cooled liquid nitrogen cooling system is known as a most promising method to develop large scale superconducting apparatuses such as superconducting fault current limiters and superconducting cables [1]. Gaseous helium (GHe), gaseous nitrogen ($GN_2$) and sulfur hexafluoride ($SF_6$) are commonly used for designing an high voltage applied superconducting device as an injection gaseous medium [2, 3]. In this paper, the analysis on the dielectric characteristics of GHe, $GN_2$ and $SF_6$ are conducted by designing and manufacturing sphere-to-plane electrode systems. The AC withstand voltage experiments on the various gaseous insulation media are carried out and the results are analyzed by using finite element method (FEM) considering field utilization factors (${\xi}$). It is found that the electric field intensity at sparkover ($E_{MAX}$) of insulation media exponentially decreases according to ${\xi}$ increases. Also, the empirical expressions of the functional relations between $E_{MAX}$ and ${\xi}$ of insulation media are deduced by dielectric experiments and computational analyses. It is expected that the electrical insulation design of applied superconducting devices could be performed by using the deduced empirical formulae without dielectric experiments.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1152-1155
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• 2007

Lately concerns about structure have been increased by advantages of floor impact noise, poilitical induction and changeability. Hence, Flat Plate Structure has been constructed increasingly. This study shows the comparison of the performance of sound insulation of Flat Plate Structure System and the existing Wall Structure. For this study, taking the same level organization of Daelim Architectural Environmental Research Center, I found the performance of sound insulation between the upper and lower floors about Wall Structure and Flat Plate Structure. Consequently, the performance of sound insulation between upper and lower floors of Flat Plate Structure was 3-5dB higher was approximately 3-5dB higher than one of Wall Structure. Especially, the performance of sound insulation on the upper floor was 1-3dB higher than on the lower floor. In addition, as the result of comparing radiation sound which radiates from the wall of lower floors with each structure system, Flat Plate Structure was about 4dB higher with Rw than Wall Structure. As we see totally, the performance of sound insulation of Flat Plate Structure is highter than one of the Wall Structure. It is 3-5dB higher and the main reason for this result depends on the existence of the wall which can radiate sound and nonexistence.

• Journal of Power Electronics
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• 제14권1호
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• pp.143-155
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• 2014

The stability issues of a multi-module distributed DC power system without current-sharing loop are analyzed in this study. The physical understanding of the terminal characteristics of each sub-module is focused on. All the modules are divided into two groups based on the different terminal property types, namely, impedance (Z) and admittance (Y) types. The equivalent circuits of each group are established to analyze the stability issues, and the mathematical equations of the equivalent circuits are derived. A generalized criterion for multi-module distributed systems is proposed based on the stability criterion in a cascade system. The proposed criterion is independent of the power flow direction.