• Polymer(Korea)
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• v.24 no.2
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• pp.201-210
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• 2000

To determine the effect of chain length of linear amine curing agents on the thermal and mechanical properties, standard epoxy resin, diglycidyl ether of bisphenol A (DGEBA) was cured with diethylenetriamine (DETA), triethylenetetraamine (TETA) and tetraethylenepentaamine (TEPA) in a stoichiometrically equivalent ratio. From this work, the effect of linear amine curing agents on the thermal and mechanical properties was significantly influenced by chain length of curing agents. In contrast, the results showed that the DGEBA/DETA system had higher values than the DGEBA/TETA and DGEBA/TEPA system in the density, shrinkage (%), thermal expansion coefficient, tensile modulus, and flexural strength. Whereas the DGEBA/DETA cure system had lower values than the DGEBA/TETA and DGEBA/TEPA cure system in the maximum exothermic temperature, conversion (%), and T$_{g}$. These findings imply that the differences in the maximum conversion about the chain length of curing agents affect the thermal and mechanical properties.s.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.100-105
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• 2005

$Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by DTA/TGA, XRD, SEM, and $M\ddot{o}ssbauer$ spectroscopy, VSM. $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ has spinel structure and behaved superparamagnetically. The estimated size of superparammagnetic Ni-Zn ferrite nanoparticle is around 10 nm. The hyperfine fields at 13 K for the A and B patterns were found to be 533 and 507 kOe, respectively. The blocking temperature ($T_B$) of superparammagnetic $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle is about 250 K. The magnetic anisotropy constant and relaxation time constant of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle were calculated to be $1.6\times10^6\;ergs/cm^3$ and ${\tau}_0=5.0{\times}10^{-13}$ s, respectively. Also, Temperature increased up to $43^{\circ}C$ within 10 minutes under AC magnetic field of 7 MHz. It is considered that $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ is available for biomedicine application such as hyperthermia, drug delivery system and contrast agents in MRI.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.3-6
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• 2008

Heat release characteristics of live fire load are an important parameter for performance oriented fire safety design of a building. While investigations have been carried out on the fire load and its burning behavior in office, residential and commercial buildings and so on, little effort has been paid for the rational treatment of fire load in bookstore. In this report, burning behavior of typical combustible objects in bookstore are studied by measuring heat release rates of bookshelf with book.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.193-194
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• 2016

일반적으로 자기장을 이용하는 무선전력 전송 방식은 노이즈, 금속 영향성, 발열, 위치에 따른 에너지 효율이 달라지는 문제점을 가지고 있다. 본 연구에서는 전기장을 이용하여 자동차 전, 후면에 있는 유리를 통해 전기자동차를 무선으로 충전하는 컨버터를 제안한다. 송, 수신부 회로는 유리를 유전체로 만들어진 작은 커패시터와 Quality-factor (Q-factor)를 보상하기 위해 두 개의 변압기를 이용한 임피던스 변환과 스위칭 손실을 최소화하기 위한 LLC직렬공진 동작을 사용하였다. 그 결과 제안하는 컨버터는 대용량 전력전송과 소프트 스위칭을 통한 높은 효율을 얻을 수 있었다. 제안하는 회로의 동작과 특성을 검증하기 위하여 유리를 이용한 커패시터를 구성하고 1.2KW 송, 수신 회로를 설계 및 제작하여 검증 하였다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.181-182
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• 2011

수중에서는 대기와는 달리 매질의 차이로 인하여 통신의 제약이 따르므로 초음파를 이용하여 정보를 송 수신한다. 수중통신을 하기 위해서는 신호를 증폭시키는 전력증폭기와 초음파를 발생시키는 트랜스듀서가 필요하다. 전력증폭기는 수중에서의 발열과 연료문제로 인하여 높은 효율로 동작하여야한다. 하지만 전력증폭기에 인가되는 고정전압과 출력전압의 차이로 인해 손실이 발생하여 효율이 저하된다. 그러므로 본 논문에서는 전력증폭기의 효율 향상을 위해 출력전압에 따라 인가전압을 가변하는 ET(Envelope Tracking) 기술을 적용하기 위한 4[kW]급, 20[kHz]의 대역폭을 갖는 가변 DC-DC 컨버터를 설계하고 시뮬레이션을 통해 특성을 확인하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.364-367
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• 2005

A series of computational simulations have been carried out for non-reacting and reacting flows in channel-type and divergent scramjet combustor configurations with and without a cavity. Transverse injection of hydrogen is considered with the injection pressure varying from 0.5 to 1.5 MPa. The detailed resolution of the oscillatory flow and flame dynamics are captured at sufficient scale to identify the underlying physical mechanisms, and the role of combustor configuration, cavity and amount of heat addition could be understood.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.156-161
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• 2008

The present article reports a numerical study on the fire characteristic change by water-mist in under-ventilated compartments. The natural gas and heptane pool fires are used as fire sources, which are located in the bottom center of the 2/5 reduced-scaled model of the ISO 9705 standard room. The fire modeling using the FDS (Fire Dynamics Simulator) is validated by comparison with previously published experimental results. For temperature and combustion gas concentrations at two positions located in the upper layer of compartment, the predicted results with and without water-mist are compared each other. The results show that under the water-mist operation, the predicted temperature and carbon monoxide concentration reduce as $300{\sim}400^{\circ}C$ and about 20%, respectively, compared to those without water-mist.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.315-318
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• 1999

This paper deals with the relationships between the exotherm temperature and working life of lightweight polyester mortar. Polyester mortars using types of lightweight aggregate compositions are prepared, and tested for exotherm temperature during hardening and working life. It is concluded from the test results that the behavior of exotherm temperature of lightweight polyester mortars is considerably affected by the lightweight aggregate composition. The lightweight polyester mortars using a lightweight aggregate compositeion ES gradually develop an exotherm temperature from 2$0^{\circ}C$, and give a working life. Then the exotherm temperature rises sharply up to a maximum exotherm temperature. The working life of the lightweight polyester mortars shortens with increasing catalyst and accelerator contents. The maximum exotherm temperature of the lightweight polyester mortars rises with increasing catalyst and accelerator contents.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.238-242
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• 1994

Recently, construction of mass concrete structures except Dam are increased very often. Generation heat due to the hydrating reaction of mass concrete is generally larger than the heat released to the air, foundations and the exist structures. Therefore, internal temperature of mass concrete is remarkably risen and temperature gap between center and surface is extended by various effect. It this gap get large, the crack may be occurred. This crack must be controlled as little as possible to ensure the soundness and durability of structure. Firstly, Temperature rising history of Mass concrete is expected correctly to constrain the crack of mass concrete. So, objectives of this research is to quantify the effects of hydration temperature for the purpose of evaluating accurately the temperature history of mass concrete.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.07a
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• pp.313-319
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• 1999

간접열식 LPG온풍난방기는 LP(Liquefied Petroleum)가스를 열원으로 한 온풍난방기를 말한다. LP가스는 프로판(Propane, $C_3$H$_{8}$)과 부탄(Butane, $C_4$H$_{10}$)을 주성분으로 하는 혼합물로 에탄, 프로필렌, 부틸렌 등이 약간 포함되어 있는 기체로 액화 및 기화가 쉬우며 기체상태에서는 비중이 공기보다 무겁고 액체상태에서는 물보다 가볍다. 또한, 기화할 때는 다량의 열과 연소시 많은 공기를 필요로 하고 온도에 따라 액체의 부피가 변하는 특성을 가지고 있으며 무색, 무취, 무독하다. LP가스의 발열량은 12,000kcal/kg으로 경유나 보일러등유 보다 약 30% 정도 높아 난방연료로서의 사용 및 취급성이 우수하다. (중략)