• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.765-770
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• 2010

In this study, the behavior of underground pipeline subjected to pile driving is examined using the verified finite element model based on the field experiment. Young's modules of surface soil is varied and elastic modulus of the other soil layer is fixed. The pile driving force model proposed by Mounir E. Mabsout in 1999 was used and it was functions of time and of force. The forcing function applied on this study considers the kinetic energy of ram located at 1.2m height with 7 tonf. The 3-layered pipeline is composed of steel(inner) pipe, PUR(Polyurethane Resin, filler) and HDPE(outer) pipe, and the length/diameter of main steel pipe is 20m/0.8m(O.D). It is used for district heating pipes in Korea. The results are expressed in terms of Von Mises stress, displacement, and vibration velocity for each soil condition. From the results of the analyses, PUR which is originally intended as a thermal insulation of inner pipe shows performance as a structural member which distributes external pressure.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.49-52
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• 2008

The present study was to develop a dry PFB method similar to the existing gypsum board construction method in order to apply the existing wet PFB method that uses fire-resistant adhesive. It was found that the existing wet method can produce concrete compressive strength of 80MPa and fire resistance of 3 hours with 30mm PF boards. The goal of development in this study was fire resistance of 3 hours through dry construction of 15mm fire-resistant boards. 1. Improved PF board was prepared by adding inorganic fiber to existing board and using aggregate with grain size of 3mm or less. Molding was done at temperature higher than that for existing PF board molding. While wet curing is used for existing PF boards, this study used dry curing in order to enhance heat insulation performance. 2. According to the results of fire resistance test, when the dry PF method was applied, the temperature of the main reinforcing bar was 116℃ in 15mm, 103.8℃ in 20mm, and 94℃ in 25mm, and these results satisfied the current standards for fire resistance control presented by the Ministry of Land, Transport and Maritime Affairs. When a 3-hour fire resistance test was performed and the external properties of the specimen were examined, the outermost gypsum board hardly remained and internal PF board maintained its form without thermal strain.

• KIEE International Transactions on Power Engineering
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• 제3A권4호
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• pp.214-221
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• 2003

In view of the fact that gas insulated switchgear (GIS) is an important piece of equipment in a substation, it is highly desirable to continuously monitor the state of equipment by measuring the partial discharge (PD) activity in a GIS, as PD is a symptom of an insulation weakness/breakdown. However, since the PD signal is relatively weak and the external noise makes detection of the PD signal difficult, it therefore requires careful attention in its detection. In this paper, the algorithm for detection of PD in the GIS using the wavelet transform (WT) is proposed. The WT provides a direct quantitative measure of the spectral content and dynamic spectrum in the time-frequency domain. The most appropriate mother wavelet for this application is the Daubechies 4 (db4) wavelet. 'db4', the most commonly applied mother wavelet in the power quality analysis, is very well suited to detecting high frequency signals of very short duration, such as those associated with the PD phenomenon. The proposed algorithm is based on utilizing the absolute sum value of coefficients, which are a combination of D1 (Detail 1) and D2 (Detail 2) in multiresolution signal decomposition (MSD) based on WT after noise elimination and normalization.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.227-231
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• 2007

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication and ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

• 한국초전도ㆍ저온공학회논문지
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• 제14권3호
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• pp.53-59
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• 2012

Adiabatic demagnetization refrigerator (ADR) for hydrogen re-liquefaction operating between 24 K and 20 K has been designed. $Dy_{0.9}Gd_{0.1}Ni_2$, whose Curie temperature is 24 K, is selected as a magnetic refrigerant. The magnetic refrigerant powder is sintered with oxygen-free high purity copper (OFHC) powder to enhance its effective thermal conductivity as well as to achieve relatively high frequency. A perforated plate heat exchanger (PPHE) operated with forced convection is utilized as a heat switch. The forced convection heat switch is expected to have fast response relative to a conventional gas-gap heat switch. A conduction-cooled high Tc superconducting (HTS) magnet is employed to apply external magnetic field variation on a magnetic refrigerant. $2^{nd}$ generation GdBCO coated conductor HTS tape with Kapton$^{(R)}$ insulation (SUNAM Inc.) will be utilized for the HTS magnet. The magnetization and demagnetization processes are to be achieved by the AC operation of the HTS magnet. The designed magnetic field and target ramp rate of the HTS magnet are over 4 T with 180 A and 0.4 T/s, respectively. AC loss distribution on HTS magnet is theoretically estimated.

• 한국디지털건축인테리어학회논문집
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• 제12권3호
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• pp.59-66
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• 2012

Autoclaved Lightweight Concrete(ALC) features such as a high performance insulation, the fire resistance, the advantage of easy handing construction, and lightweight panels applied the curtain wall system. ALC materials are certified as non-toxic environmental and eco-friendly productions. But ALC external panels mixed with blast furnace slag pounder and silica fume have to be coated with a stucco compound or plaster because of resisting the ambient environment. This study is that mixing tests to evaluate a performance analysis of exterior paints to be make-up pigments(organic or inorganic) coated with panel surface. Testing compared by KS F 2476; flow test, KS F 2426; compression strength test, KS F 2762; bond strength test. In results, the case of the inorganic binder, ratio of alumina cement : anhydrite is 90:10 to 80:20 at the highest level of intensity. In the case of the organic binder, adhesive strength rating at surface of ALC, the pullout strength is below 0.5 $N/mm^2$ but the normal concrete is over 2.0$N/mm^2$. A contents ratio of EVA resin is more than 3% and then bond strength is effectively.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.61-66
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• 2014

The evaporative cooling technology used in Wind generator stator has unique advantages. Combined with the structure of motor stator and operating conditions, this report based on the research project for the evaporative cooling sleeve of the 3.6MW wind generator, introduces the material requirements and structural characteristics of the sleeve, simulates on the stress, displacement and stability by finite analysis method, and tests the products experimentally. The research results show that the epoxy resin-glass materials have a higher strength and better insulation properties, but the evaporative cooling of the wind generator stator sleeve, because of its thin-walled, and the external pressure, so it's the less rigid. Should make full use of the motor stator core structure, increase its stiffness and improve the stability of the epoxy resin-glass sleeve, which for thin-walled the epoxy resinglass sleeve on the successful application of wind turbines has played an important role.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1957-1959
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• 2000

The PD measurement method is very useful to detect insulation degradation. Recently, the HFPD(High Frequency Partial Discharge) measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires in-service diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In this study, simulated transformer is manufactured and HFPD occurred from simulated transformer is measured with broad band antenna and active-line RF measurement system in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages. Also the PD pattern which was measured with EMC analyzer and RF measurement system is compared.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.331-334
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• 1997

The electrical and physical charateristics of aluminum oxide and Pt thin films on it, deposited by reactive sputtering and DC magnetron sputtering, respectively, were analysed with increasing annealing temperature(400~80$0^{\circ}C$) by four point probe, SEM and XRD. Under $600^{\circ}C$ of annealing temperature, aluminum oxide had the properties of improving Pt adhesion to SiO$_2$and insulation without chemical reaction to Pt thin films and the resistivity of Pt thin finns was improved. But these properties of aluminum oxide and Pt thin finns on it were degraded over $700^{\circ}C$ of annealing temperature because aluminum oxide was changed into metal aluminum and then reacted to Pt thin films deposited on it. The thermal characteristics of Pt micro heater were analysed with Pt-RTD integrated on the same substrate. In the analysis of properties of Pt micro heater. active area was smaller size, Pt micro heater had better thermal characteristics. Temperature of Pt micro heater fabricated on membrane was up to 34$0^{\circ}C$ with 1.2watts of the heating power due to reduction of the external thermal loss.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.24-28
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• 2018

Insulators used in overhead transmission lines are continuously exposed to a number of mechanical and electrical stresses owing to external environmental factors, resulting in corrosion, reduction in durability, and deterioration. Widely used porcelain insulators are fabricated with cement and porcelain and are especially common in Korea. Changes in the hardness and chemical reactivity of the cement increase the leakage and fault currents and increase the possibility of flashover due to insulation breakdown. Therefore, it is important to evaluate the durability and defects of porcelain insulators. Studies on the reliability of various evaluation methods are needed to prevent accidents by accurately determining the replacement timing and potential defects in porcelain insulators. In this study, the hardness of the cement part of the porcelain insulator was measured using the Vickers hardness test and its composition was analyzed by energy dispersive spectroscopy and X-ray diffraction analysis. The performance of the insulators was compared in two different regions with varying climatic conditions. This study presents an evaluation method of the defects in porcelain insulators by measuring humidity, which can also be used to assess the reliability of the insulators.