• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.15-18
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• 2006

The test result of mat concrete applying both hydration heat difference and insulation curing method on new construction of Cheongju university educational building are summarized as following. Both fresh concrete and compressive strength properties were satisfied In aimed value. Setting time of concrete incorporating 15% of fly ash(FA) retarded 1.2 hour than control concrete. Temperature history of mali concrete indicated that the highest temperature of center was exhibited at $126^{\circ}C$ after 51 hours while the highest temperature of upper section was $10.6^{\circ}C$ after 46 hours. Temperature Difference between center and surface was managed at less than $6^{\circ}C$ during whole curing period. In addition the temperature of upper section secured more than $3.3^{\circ}C$ while the temperature of outside was indicated at less than $-10^{\circ}C$. Maturity by parts of construction secured more than $30^{\circ}C$ DD higher than outside at 3 days. The more number of times, applying insulation curing method by double bubble sheets, increased, the higher economic effect was secured. Overall it was clear that applying both double bubble sheets and hydration heat difference method on this new construction can resist hydration heat crack, early frost demage and strength decrease. It also significantly contributed quality improvement of cold weather concreting

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.420-423
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• 2020

This study proposes an indirect constant voltage control algorithm for hybrid solid-state transformers (HSSTs) by using primary side information. Considering the structure of HSSTs, measuring voltage and current information on the primary side of a transformer is necessary to control the converter and inverter of the power converter. The secondary side output voltage is measured to apply the conventional secondary side constant voltage control algorithm, and thus, the digital control board requires the same rated insulation voltage as that of the transformer. To solve this problem, the secondary voltage of the transformer obtained from the tap voltage is used. Moreover, output voltage decreases as load increases because the proposed indirect constant voltage control scheme does not consider the cable impedance between the secondary output terminal and the load. This study also proposes a technique for compensating the secondary output voltage by using the primary current of the transformer and the resistance value of the cable. An experiment is conducted using a scale-down HSST prototype consisting of a 660 V/220 V tap transformer. The problem of the proposed indirect constant voltage control strategy and the improvement effect due to the application of the compensation method are compared using the derived experimental results.

• Transactions on Electrical and Electronic Materials
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• v.10 no.3
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• pp.97-101
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• 2009

The use of a filler material in epoxy composite materials is an essential condition for reducing the unit cost of production and reinforcing mechanical strength. However, the dielectric strength of insulators decreases rapidly due to interactions between the epoxy resin and filler particles. In contrast to existing composite materials, nano-composite materials have superior dielectric strength, mechanical strength, and enduring chemical properties due to an increase in the bond strength of the polymer and nano material, It is reported that nano-fillers provide new characteristics different from the properties of the polymer material. This study is to improve the insulation capability of epoxy resins used in the insulation of a power transformer apparatus and many electronic devices mold. To accomplish this, the additional amount of nano-$SiO_2$ to epoxy resin was changed and the epoxy/$SiO_2$ nano composite materials were made, and the fundamental electrical properties were investigated using a physical properties and an analysis breakdown test. Using allowable breakdown probability, the optimum breakdown strength for designing an electrical apparatus was determined. The results found that the electrical characteristics of the nano-$SiO_2$ content specimens were superior to the virgin specimens. The 0.4 wt% specimens showed the highest electrical properties among the specimens examined with an allowable breakdown probability of 20 %, which indicates stable breakdown strength in insulating machinery design.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.35-41
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• 2020

The thin coating material used in the outer insulation finishing method is a finishing material mainly based on acrylic emulsion. In this study, the properties of silane modified acrylic emulsion and silica dispersed acrylic emulsion were evaluated. Experimental results showed that the silane modified acrylic emulsion had no significant effect on improving tensile strength, but was effective in improving the performance of adhesion strength, water absorption coefficient, and hot and cold repeat resistance. Silica-dispersed acrylic emulsions were effective in improving tensile strength, and at 10% substitution rate, they were effective in improving the performance of adhesion strength, water absorption coefficient and hot / cold resistance. Through this, it was judged that a composite emulsion capable of improving the performance of the acrylic emulsion could be prepared.

• Fashion & Textile Research Journal
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• v.1 no.2
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• pp.160-165
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• 1999

The thermal properies of the pure linen fabrics available in the market and linen blended woven fabrics were measured at the moisture content of 0%, 20%, 40% and 60% using KES-F7 system (Thermo Iabo II type). The experimental properties were statistically analyzed by the rate of water absorbent. The main results were as follows; There is a positive correlation between the thermal insulation value (TIV) and thickness of pure linen fabrics and linen blended woven fabrics by water absorption. Whereas an negative correlation exists between the TIV and cover factor. There is a high positive correlation among the thermal conductivity (k), thickness and weight of pure linen fabrics and linen blended woven fabrics by water absorption. Wherase a high negative correlation exist between the k and air' permeability (Ap). There is a high positive correlation between the feeling of warmth/coldness and bulk density of pure linen and linen blended woven fabrics by water absorption. Wherase a high negative correlation exists between the feeling of warmth/coldness and porosity. There is a negative correlation between TIV and $q_{max}$ of pure linen fabrics and linen blended woven fabrics. The higher the rate of water absorbent, the lower the TIV. This means that TIV decreases by water absorption. As for the thermal property by rate of water absorbent $q_{max}$ and k increase by water absorption and reach max-value at 60% rate of water absorbent. The TIV decreases by water absorption and has +value at 0% rate of water absorbent, whereas it has -value with a feeling of coldness at 20%, 40%. and 60% rate of water absorbent.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.210-211
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• 2007

Amid booming PV(photovoltaic) industry, BIPV(Building Integrated PV) is one of the best fascinating PV application technologies. To apply PV in building, variable factors should be reflected such as installation position, shading, temperature effect and so on. Especially a temperature should be considered, for it affects both electrical efficiency of PV module and heating and cooling load in building. Transparent PV modules were designed as finished material for spandrels are presented in this paper. The temperature variation of the modules with and without air gap and insulation were compared and analyzed. The results showed that the module with air gap and insulation has a much larger temperature variation than another transparent module. The temperature of the module reached by 55degree C under vertical irradiance of lower 500$W/m^2$. And the temperature difference between these modules was about 15degree C. To analyze the output performance of module according to temperature variation, separate module was manufactured and measured by sun-simulator. The results showed that 1 degree temperature rise reduced about 0.45% of output power.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.61-69
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• 2021

This paper presents the analysis and experiment results on the electrical and thermal characteristics of metal insulation (MI) REBCO racetrack coil, which was wound with stainless steel (SS) tape between turn-to-turn layers, under rotating magnetic field and conduction cooling system. Although the field windings of superconducting rotating machine are designed to operate on a direct current, they may be subjected to external magnetic field due to the unsynchronized armature windings during electrical or mechanical load fluctuations. The field windings show the voltage and magnetic field fluctuations and the critical current reduction when they are exposed to an external magnetic field. Moreover, the cryogenic cooling conditions are also identified as the factors that affect the electrical and thermal characteristics of the HTS coil because the characteristic resistance changes according to the cryogenic cooling conditions. Therefore, it is necessary to investigate the effect of external magnetic field on the electrical and thermal characteristics of MI-SS racetrack coil for further development reliable HTS field windings of superconducting rotating machine. First, the major components of the experiment test (i.e., HTS racetrack coil construction, armature winding of 75 kW class induction motor, and conduction cooling system) were fabricated and assembled. Then, the MI racetrack coil was performed under liquid nitrogen bath and conduction cooling conditions to estimate the key parameters (i.e., critical current, time constant, and characteristic resistance) for the test coil in the steady state operation. Further, the test coil was charged to the target value under conduction cooling of 35 K then exposed to the rotating magnetic field, which was generated by three phrase armature windings of 75 kW class induction motor, to investigate the electrical and thermal characteristics during the transient state.

• Journal of Bio-Environment Control
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• v.22 no.3
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• pp.270-278
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• 2013

The objective of the present study is to provide data needed to decide covering method to be able to increase the thermal insulation and light transmittance efficiency of commercial greenhouse. The thermal insulation effect, PPF transmittance and quantity of condensation water were estimated in experimental tomato greenhouses covered with three types of coverings of single layer, air inflated and conventional double layers covering. The overall heat flow of air inflated double layers greenhouse was similar to that of conventional double layers greenhouse, but the temperature between covering material and thermal screen in air inflated double layers greenhouse was lower than that in conventional double layers greenhouse at the same outside temperature condition due to air leakage through the gap of roof vent. The overall heat transfer coefficients acquired by experiment that was performed in single layer and conventional double layers greenhouses were close to those obtained from model experiment. Even though the PPF transmittance of air inflated double layers greenhouse was lower than that of single layer greenhouse, which was greater than that of conventional double layers greenhouse. The quantity of condensation water on covering surface of single layer greenhouse was greater than that of air inflated double layers greenhouse due to lower covering surface temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.4
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• pp.345-352
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• 2017

In this study, the effect of cryogenic liquefied natural gas leakage and loading on liquefied natural gas cargo hold is investigated to observe the performance of the polymer foam material that comprises the cryogenic insulation of the cargo hold. The primary barriers of liquefied natural gas carrier that are in contact with the liquefied natural gas will leak if damage is accumulated, owing to fluid impact loads or liquefied natural gas loading / unloading over a long period. The leakage of the cryogenic fluid affects the interior of the polymer foam, which is a porous closed cell structure, and causes a change in behavior with respect to the working load. In this study, mechanical properties of polyisocyanurate foam specimen, which is a polymer material used as insulation, are evaluated. The performance of the specimens, owing to the cold brittleness and the impregnation effects of the cryogenic fluids, are quantitatively compared and analyzed.

• Journal of Navigation and Port Research
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• v.39 no.4
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• pp.285-291
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• 2015

Exposure to cold sea water can be life-threatening to the drowned individual. Although appropriate life jacket can be usually be provided for the buoyance at the drowning accident, heat loss can make the drowned individual experience the hypothermia. Inflatable life jackets filled with inflatable air pocket can increase the thermal protection as well as the buoyancy force. Because it is important to know how the human body behaves unde the different life jacket, present study compares the thermal insulation capacity of solid type life jacket with that of inflatable life jacket. In order to represent the insulation capacity of life jacket, thermal resistance is estimated based on the assumption of steady-state. Also, a transient three-dimensional thermal distribution of the thigh is analyzed by using finite element method implementing the Pennes bioheat equation. The finite element model is a segmental, multi-layered representation of the body section which considers the heat conduction within tissue, bone, fat and local blood flow rate.