• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.305-306
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• 2006

자동차의 난방 열원은 HVAC(Heating, Ventilating & Air Conditioning)에 내장되어 있는 히터코어 (Heater Core) 에서 공급하게 되며, 이 히터코어는 엔진에서 가열된 냉각수 열원을 이용하게 된다. 그러나 최근 디젤 엔진의 경우 연소효율의 개선과 CEGR(Cooled Exhaust Gas Recirculation) 시스템의 적용으로 냉각부하가 증가하여 냉각수가 가지는 가용 열원이 기종보다 약 30~40% 정도 저하되고 있다. 따라서 디젤 자동차 및 하이브리드용 자동차의 난방 보조 히터의 국산화 개발이 시급해진 상황이며 초정밀, 고효율 보조 히터의 개발이 요구되고 있다. 현재 적용되고 있는 보조 히터 중에서 PTC 히터는 PTC 소자의 발열을 이용하여 공기를 직접 가열하기 때문에 추가적인 연료소비가 없고 소형 및 저가라는 장점이 있다. PTC 세라믹 소자는 $BaTiO_3$를 모체로 하며, 이의 특성 항상 및 제어를 위해서는 적절한 dopant를 선택하여 균일하게 doping 해야 한다. 지금까지 dopant에 따른 구성 요소 및 역할은 비교적 잘 알려져 있다. 하지만, 자동차용으로 사용되기 위해서는 12V의 저전압에서 동작해야 하며, 또한 소자의 두께가 얇아지게 됨에 따라서 발생하는 전기적 short와 같은 문제점들을 해결하여야 한다. 따라서 본 연구에서는 PTC 세라믹 소자에서 도펀트 종류와 양 조절을 통한 저저항을 확보하고, PTC 세라믹 소자의 박막화를 달성하고자 하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.379-385
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• 2020

This paper presents a design for preventing coolant leaks in the core part of a heater mounted in a combat vehicle. The heater is a device that makes heated coolant flow through the heater core in the crew room. A problem with coolant leaks in the heater core area during the operation of a combat vehicle was identified. This problem is caused mainly by high pressure at the junction of the tank and tube due to the vulnerability of this area. To solve this problem, an improved core was made by improving the welding method and changing the end region of the heater core to a structure that can withstand high pressure. When pressure was applied sequentially to the existing core and improved core, a leak occurred at 7.0 kgf/㎠ in the existing core while the improved core maintained its structure up to 17.0 kgf/㎠, highlighting the improvement. Finally, performance tests and environment tests were conducted to demonstrate the suitability of the improved structure. The improved heater will be applied to combat vehicles. This paper is expected to serve as a reference for improving defense capabilities by securing reliability as well as the design and analysis of failures of similar equipment.nse capabilities through securing reliability as well as the design and analysis of failures of similar equipment.

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.254-260
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• 2005

By incorporating large core polymer waveguides, which have been developed for increased alignment tolerance in passive fiber attachment, highly efficient variable optical attenuators are proposed. In order to find optimum device structures, 3-dimensional beam propagation method (BPM) simulations are performed. Heat distribution over the polymer film is calculated to find the 3-dimensional index profile data for the BPM simulation. Due to the small index contrast between the core and cladding materials in the large core waveguide, heat-induced radiation occurs for small heating power. While the ordinary VOA needs the temperature to change over $150^{\circ}C$ for 20 dB attenuation, the large core VOA requires only $70^{\circ}C$. In addition to the merit of passive fiber attachment, the proposed VOA has enhanced attenuation efficiency for the lower temperature change.

• Tunnel and Underground Space
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• v.23 no.4
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• pp.297-307
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• 2013

In this study, the thermal analysis is carried out for a result of borehole heater test using ABAQUS ver 6.10 based on finite element analysis code. Thermal-mechanical rock properties as determined by laboratory tests before the in situ test and characteristics of the atmosphere at the test section are used as the initial condition. When comparing the results of the in situ test and thermal analysis, the temperature of C3 observation hole that is 0.9 m away from the heater showed very similar patterns and figures (about $1.3^{\circ}C$ difference). But the results of the A and B observation hole showed a significant difference around $15^{\circ}C{\sim}20^{\circ}C$. To find the reason for these results, the over-coring is carried out for the A1 and B1 observation holes. As a result of checking the excavated rock core with the naked eye, there is no problem on the number and position of the sensor as the test plan. However the state of cement injection in the observation hole is poor.

• Korean Journal of Optics and Photonics
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• v.3 no.4
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• pp.244-251
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• 1992

Buried Bragg filters of single mode $Si_{3}N_{4}$ rib waveguide with a cover layer of $SiO_{2}$ and grating at the interface of $Si_{3}N_{4}$ and $SiO_{2}$ are designed and fabricated. Etching of the grating on $Si_{3}N_{4}$ waveguide core by buffered HF showed uniform etching with good control up to 1 nm. This buried type of Bragg filters are immune to contamination of the surface of device. The mode index and bandwidth of filters are determined by measurements of the transmission spectrum of Bragg filters and compared with that of calculation. Waveguide Bragg filters loaded with the micro-heater of Cr film and the cladding of silicone rubber are made to control the Brag wavelength of the filter. As a result the filter wavelength of the device moved by 0.41 nm for 10 mA current to the shorter side of wavelength proportional to the square of the current.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.186-193
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• 2009

In this paper, we adopted E-MOLD patent technology in order to fabricate Prismless LGP(Light Guide Panel) fur cellular phone and estimate the transcription of injection-molded parts. Then, we manufactured the Ni stamper fur Prismless LGP using MEMS process. And the stamper was installed in the movable heated core which is the key part of a patented mold. Using this mold, we manufactured injection-molded plastic LGP parts with different mold temperatures so that we investigate effect of the temperature on the transcription of the parts. The CAE analysis was also conducted in order to compare with the experimental results. The transcription of LGP parts with various mold temperature displayed $100^{\circ}C$(25.0nm), $140^{\circ}C$(48.4nm), $180^{\circ}C$(52.1nm) and when compared with stamper(521Inm), transcription was superior at $180^{\circ}C$. According to the CAE results, moldability was improved as mold temperature ($50^{\circ}C{\sim}180^{\circ}C$) increased, but when filling time($1{\sim}2sec$) increases, it decreased at $160^{\circ}C$. And transcription and moldability were improved markedly at glass transition temperature($140^{\circ}C$).