• Computers and Concrete
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• 제19권6호
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• pp.711-716
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• 2017

This paper presents a method using artificial neural networks (ANNs) to predict the residual moment capacity of thermally insulated reinforced concrete (RC) beams exposed to fire. The use of heat resistant insulation material protects concrete beams against the harmful effects of fire. If it is desired to calculate the residual moment capacity of the beams in this state, the determination of the moment capacity of thermally insulated beams exposed to fire involves several consecutive calculations, which is significantly easier when ANNs are used. Beam width, beam effective depth, fire duration, concrete compressive and steel tensile strength, steel area, thermal conductivity of insulation material can influence behavior of RC beams exposed to high temperatures. In this study, a finite difference method was used to calculate the temperature distribution in a cross section of the beam, and temperature distribution, reduction mechanical properties of concrete and reinforcing steel and moment capacity were calculated using existing relations in literature. Data was generated for 336 beams with different beam width ($b_w$), beam account height (h), fire duration (t), mechanical properties of concrete ($f_{cd}$) and reinforcing steel ($f_{yd}$), steel area ($A_s$), insulation material thermal conductivity (kinsulation). Five input parameters ($b_w$, h, $f_{cd}$, $f_{yd}$, $A_s$ and $k_{insulation}$) were used in the ANN to estimate the moment capacity ($M_r$). The trained model allowed the investigation of the effects on the moment capacity of the insulation material and the results indicated that the use of insulation materials with the smallest value of the thermal conductivities used in calculations is effective in protecting the RC beam against fire.

• 한국가스학회지
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• 제22권4호
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• pp.1-6
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• 2018

IMO에서 규정하는 LNG 벙커링 선박용 연료 탱크 중 C형 가압탱크는 내외 2중 용기로 구성된 초저온 탱크에 $10^{-2}$ Torr 진공과 펄라이트 단열재가 충전되는 것이다. 그러나 이 단열방식은 LNG 기화량이 하루당 2.0 % 내외로 증발율이 커서 보다 단열효과가 좋은 탱크가 요구되어 진다. 본 연구에서는 내외탱크 사이에 고진공을 적용하고 외부탱크의 내벽체에 중간 단열로 펄라이트 진공단열을 적용하는 단열 방식을 새로이 고안하여 열해석을 수행하였다. 이의 장점으로는 진공 공간의 감소로 고진공 형성 시간을 크게 감소되고, 진공도 $10^{-4}$ Torr 이하에서 하루당 증발율이 0.16 %에 불과한 매우 효율이 높은 탱크 단열방식이 되었다. 만약 현재의 IMO C형 탱크의 진공펄라이트 단열에서 진공이 파괴되는 경우, C형 탱크는 하루당 4.9 %의 증발이 발생하고 새 고안 탱크는 5.23 %로 거의 동일하게 된다.

• 공업화학
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• 제33권6호
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• pp.588-593
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• 2022

MgO 입자 표면에 첨가된 P₂O₅의 가수분해, 발수성, 그리고 절연 거동에 미치는 영향을 조사하였다. MgO 표면에 첨가된 P₂O₅는 가수분해반응 억제와 발수성을 동시에 나타내기 때문에 독특한 절연거동을 나타내었다. 따라서 절연거동은 MgO의 표면수화반응에 의한 Mg(OH)₂와 OH^-전하 전달비와 친수성에 반비례하였다. 시효에 따른 MgO의 절연성은 표면수화반응, 첨가된 도펀트 종의 밴드갭, 그리고 도펀트의 친수성과 소수성에 강한 영향성과 의존성을 나타내었다. 마지막으로 친수성인 MgO의 표면수화반응을 억제하는 전기절연성을 발현하여 열전달매체 응용분야에서 큰 잠재력을 제공하는 것으로 나타났다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1235-1237
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• 2002

Insulation system(200 class} for stator coil is designed for traction motor with VVVF inverter. Sample coils for stator of the traction motor were tested by accelerative thermal degradation which composed of heat, vibration, moisture, and overvoltage apply. Reliability and expected life were evaluated on the insulation system for 200 class traction motor. After aging of 10 cycles, tan ${\delta}$ increased with voltage. This result is due to increase of internal defects and change of insulation structure.

• 한국초전도ㆍ저온공학회논문지
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• 제5권3호
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• pp.38-42
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• 2003

HTS transformer is promising one of HTS power applications to be commercialized in the near future. To realize the applications, insulation technology in the coolant, liquid nitrogen, should be established. So breakdown characteristics should be considered at insulation components; turn-to-turn, layer-to-layer, winding-to-winding, were investigated. Firstly breakdown strengths of Kapton films were compared with Kraft paper these are as turn insulator. And next the characteristics of surface flashover on FRP were measured and the influence on breakdown strength of bubble generated with joule heat was discussed with the shape of cooling channel between layers. Finally barrier effect at winding-to-winding was discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.891-893
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• 1992

Polymers have good electrical properties as an insulation material. Though they show more and less poor resistance to heat, radiation, and oxygen, the poor properties have been overcame by developing new resin with the saturated molecular structure and compounding resin with resistive fillers. Polymer insulators have many advantages; light weight, good mechanical properties, better contaimination performance, low cost by mass productivity, no destruction in many pieces, good flexibility in design, short manufacturing time. Usage of polymer insulators has increased rapidly with good credit on long term properties in advanced nations and will continue to grow.

• 전기학회논문지
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• 제60권10호
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• pp.1972-1977
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• 2011

The mechanical integrity of generator stator windings is one of the critical point because the electric power is generated and conducted to power system through these windings. To cool down the heat emitted from generator winding during its operation, a majority of generators use de-mineralized water characterized by high cooling efficiency. Contrary to such the excellent cooling efficiency, however, the damaged bar insulations attributed to the absorption of cooling water in the generator stator winding lead to highly time- and cost consuming efforts as well as to service deterioration due to unexpected forced outage of generator. It is described that the new design of water absorption sensor using cross capacitance for generator in power plant in order to increase the reliability of water absorption diagnostics for generator stator bar insulation.

• 한국군사과학기술학회지
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• 제21권4호
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• pp.464-470
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• 2018

A development of one-dimensional thermal analysis tool is performed to estimate the thickness of cork insulation for flight vehicle. In the calculation of cork temperature, the cork density model, heat of ablation and pyrolysis gas enthalpy model were applied. The calculation for the two-layer model of cork and metal was performed by the tool and compared with the experimental data. The results for the two aerodynamic heating conditions were 17 % and -12 % different from the experimental data, respectively. The effect of mechanical ablation not included in the calculation can be expected as the cause of the difference. The temperature-density curve of cork which adjusted by experimental data was also presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.151-154
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• 1988

Mica glass ceramics are known for their good electrical, mechanical, and thermal properties. These materials are produced by appropriate heat treatment of a suitable glass composition. In this paper electrical properties of mica glass ceramics with fluorcphlogopite crystalline phase have been investigated. At frequency range 1kHz-10MHz dielectric constants fall in the range fran 7.5 to 8.5 with law dissipation factors(0.002-0.008)at room temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1430-1432
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• 2001

In this paper, 200-class insulation system for form-wound stator coils is designed for form-wound stator coils is designed for AC traction driven with VVVF inverter. Model coils are made to embody all essential elements representing a winding insulation system and structure. Acceleration degradation for model coils is applied exposure to heat(235$^{\circ}C$). In order to investigate the condition of the coils and to determine their insulation reliability, high voltage test and the dielectric properties such as dielectric loss and capacitance are performed. Also, partial discharge measurement is investigated for internal defects.