• Title/Summary/Keyword: melting time

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Microwave hybrid sintering of NTC themistor (마이크로파 하이브리드 소결법에 의한 NTC 서미스터의 제조)

  • 최영락;안진용;안주삼;백동규;최승철
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.3
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    • pp.508-512
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    • 1998
  • The NTC thermistors were sintered by using microwave hybrid heating method at 1100C~1300C and those electrical properties were investigated. The obtained B25C/85C values from temperature dependence of electrical resisitivity were around 3100~3200 K which were almost the same values as conventionally sintered ones. Compared with conventional sintering process, this process could complete whole sintering process within 20 minutes. This the processing time and energy consumption could be reduced through this rapid heating by using microwave hybrid heating.t there were showed only two peaks, glycolide melting peak and lower molecular weight melting peak without lauryl alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.ssional energy and bending hysteresis increased. \circled3 Surface characteristics such as friction coefficient and thickness variation of highly shrinkage fabrics became relatively roughened state. \circled4 Since stiffened and roughened characteristics of highly shrinkage fabrics, drapabilities of them were significantly lowered. Additionally thermal insulation property of high shrinkage fabric was higher than that of low shrinkage fabric due to bulky and thickened feature. From the results, it is considered that the silk fabrics with high filling shrinkage have the good bulkiness and heat keeping properties and thus they have the suitable characteristics for high quality men's and women's formal garments.

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A Study on Field Applicability of Underground Electric Heating Mesh (매설용 전기 발열 매시의 융설 효과에 대한 현장 적용성 연구)

  • Suh, Young-Chan;Seo, Byung-Seok;Song, Jung-Kon;Cho, Nam-Hyun
    • International Journal of Highway Engineering
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    • v.15 no.2
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    • pp.19-27
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    • 2013
  • PURPOSES : This study aims to investigate the snow-melt effects of an underground electric heater's snow-melt system via a field performance test, for evaluating the suitability of the system for use on a concrete pavement. The study also investigates the effectiveness of dynamic measures for clearing snow after snowfall events. METHODS : In order to check the field applicability, in November 2010, specimens were prepared from materials used for constructing concrete pavements, and underground electric heating meshes (HOT-mesh) were buried at depths of 50 mm and 100 mm at the site of the Incheon International Airport Construction Research Institute. Further, an automatic heating control system, including a motion sensor and pavement-temperature-controlled sensor, were installed at the site; the former sensor was intended for determining snow-melt effects of the heating control system for different snowfall intensities. Pavement snow-melt effects on snowy days from December 2010 to January 2011 were examined by managing the electric heating meshes and the heating control system. In addition, data on pavement temperature changes resulting from the use of the heating meshes and heating control system and on the dependence of the correlation between the outdoor air temperature and the time taken for the required temperature rise on the depth of the heating meshes were collected and analyzed. RESULTS : The effects of the heating control system's preheat temperature and the hot meshes buried at depths of 50 mm and 100 mm on the melting of snow for snowfalls of different intensities have been verified. From the study of the time taken for the specimen's surface temperature to increase from the preheat temperature (0C) to the reference temperature (58C) for different snowfall intensities, the correlation between the burial depth and outdoor air temperature has been determined to be as follows: Time=15.10+1.141Depth-6.465Temp CONCLUSIONS : The following measures are suggested. For the effective use of the electric heating mesh, it should be located under a slab it may be put to practical use by positioning it under a slab. From the management aspect, the heating control system should be adjusted according to weather conditions, that is, the snowfall intensity.

Operating characteristics of high Tc superconducting current limiting fuse at various voltages (고온 초전도 한류퓨즈의 전압별 동작특성)

  • Choi, Hyo-Sang;Hyun, Ok-Bae;Kim, Hye-Rim;Hwang, Si-Dole;Park, Kwon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.05c
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    • pp.161-163
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    • 2001
  • We present the basic properties of a superconducting current limiting fuse (SCLF) based on YBCO/Au films. The SCLFs consists of YBCO stripes covered with Au layers for current shunt. Under the source voltage of 100 Vrms, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 Vrms. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.

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Real-Time PCB Inspection System using the Line Scan Camera (Line Scan Camera를 이용한 실시간 PCB 검사 시스템)

  • 하종수;이영아;이영동;최강선;고성제
    • Proceedings of the IEEK Conference
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    • 2002.06d
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    • pp.81-84
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    • 2002
  • This paper presents the real-time PCB(Printed circuit board) inspection system that can detect thin open/short error using the line scan camera. After a overall introduction of our system, the outline of our inspection methods are described. The goal of our inspection system is the real time and detailed inspection using the line scan camera. To perform inspection processing in real-time, we utilize double buffering structure. In order to solve the problem of unexpectable pixels of PCB, we propose melting process which eliminates unexpectable pixels of PCB. The design and development of our prototype of PCB ins- pection system is discussed and test results are presented to show the effectiveness of the developed inspection algorithm.

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Characteristics of a superconductive fuse according to applied voltages (초전도 퓨즈의 전압별 특성)

  • Choi, Hyo-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.05b
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    • pp.169-172
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    • 2004
  • We present the basic properties of a superconducting current limiting fuse (SCLF) based on YBCO/Au films. The SCLFs consists of YBCO stripes covered with Au layers for current shunt. Under the source voltage of 100 Vrms, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 Vrms. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.

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Alkaline Weight Reduction and Physical Properties of 0.01d Polyester Ultramicro Fiber (0.01d 폴리에스테르 초극세 섬유의 알칼리 감량과 물성)

  • Park, Jae-Min;Jeong, Dong-Seok;Rho, Hwan-Kown;Lee, Mun-Cheul
    • Textile Coloration and Finishing
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    • v.18 no.4
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    • pp.37-42
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    • 2006
  • Two kinds of sea-island type polyester ultramicro fibers (fiber fineness : 0.01 and 0.05 denier) were treated with NaOH varying time and concentration. Surface morphology of the treated fibers with alkaline weight loss was observed by SEM. The treated effects were investigated by measuring density, melting temperature, and X-ray diffraction patterns. The surface morphology of the polyester ultramicro fiber was changed by NaOH concentration. Weight loss of 0.01d fiber was much larger than that of 0.05d fiber. Density and crystallinity were increased with weight loss of fiber. After the weight loss had finished, the density and crystallinity were decreased because of attack of island partition of the fiber. A melting temperature(Tm) is 250circ at untreated fiber on the whole and in 0.05d fiber the (Tm) is 252circ at untreated. In 0.01d fiber the (Tm) was increased with weight loss of fiber.

A Study on the Change of Conservation Materials Properties Using Artificial Weathering Test (인공풍화 실험을 이용한 보존처리제의 물성 변화 연구)

  • Do, Min-Hwan;Han, Min-Su;Lee, Jang-Jon;Jun, Byung-Kyu;Song, Chi-Young
    • 보존과학연구
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    • s.29
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    • pp.149-162
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    • 2008
  • Because stone cultural heritages in Korea are mostly situated outdoors without any notable protection, there are severe damages from physical, chemical and biological weathering. And this in turn causes deformation and structural damage. To counteract this problem and increase durability, various kinds of conservation materials are used in the conservation and restoration treatment. However, there are not many practical and technological experiments on this subject. Accordingly this research is for analysis of effect for treatment to make use a resin of the ethyl silicate for the granite in Mt. Nam of Gyeongju. It takes a long time to confirm the test result regarding durability and side effects of the conservatives after treatment. So we built up an artificial environment through freezing and melting test, and evaluated the conservation materials. As a result of this experiment, porosity and absorptivity was increased in accordance with processing of freezing and melting test. But other things such as elastic wave speed, elastic modulus, uniaxial compressive strength and tensile strength was decreased. It will make a plan to form a method of research systematically for mechanism and element of weathering and to elicit a correlation among experiment of artificial weathering and practical natural weathering from next research.

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Assessment of Fire-induced Damage to Tunnel Structural Members at Different Fire Scenarios (화재이력에 따른 터널구조물 시공재료의 화재손상 평가)

  • Choi, Soon-Wook;Chang, Soo-Ho;Kwon, Jong-Wook;Bae, Gyu-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.960-969
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    • 2006
  • In this study, a series of fire tests was carried out to evaluate fire-induced damage to structural members in tunnels. From the tests, the loss amount of concrete materials by the RWS fire scenario was slightly bigger than by the RABT fire scenario. Especially under the RWS fire scenario where the maximum temperature is over 1,200, the loss of concrete materials was mainly induced by melting. Generally, the loss of materials in reinforced concrete was slightly smaller than that in unreinforced concrete. Depending upon an applied fire scenario, fire-induced damage to shotcrete was quite different. From the real-time investigation of a specimen surface by a digital camcorder, it was proved that the material loss under the RABT fire scenario was mainly induced by spalling. However, it was also revealed that although fire-induced damage in the initial heating stage under the RWS was so close to that under the RABT, the material loss under the RWS at the later stage after 50 minutes elapsed since fire initiation was induced not by spalling but by melting.

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Thermal Properties of Semiconductive Materials(Shield) by Sonic Impurities in Carbon Black (카본블랙내 이온성 불순물들에 따른 반도전 재료(층)의 열적특성)

  • Lee Yong-Sung;Choi Yong-Sung;Park Dae-Hee;Lee Kyoung-Yong
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.54 no.4
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    • pp.149-153
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    • 2005
  • We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Heat capacity (ΔH), glass transition temperature (Tg) and melting temperature (Tm) were measured by DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from -100(C) to 100(C), and heating rate was 4(C/min). And then thermal diffusivity was measured by LFA 447. The dimension of measurement temperature was 25[C]. Glass transition temperature of specimens was showed near -25[C] and the heat capacity and the melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

Temperature Calibration of a Specimen-heating Holder for Transmission Electron Microscopy

  • Kim, Tae-Hoon;Bae, Jee-Hwan;Lee, Jae-Wook;Shin, Keesam;Lee, Joon-Hwan;Kim, Mi-Yang;Yang, Cheol-Woong
    • Applied Microscopy
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    • v.45 no.2
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    • pp.95-100
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    • 2015
  • The in-situ heating transmission electron microscopy experiment allows us to observe the time- and temperature-dependent dynamic processes in nanoscale materials by examining the same specimen. The temperature, which is a major experimental parameter, must be measured accurately during in-situ heating experiments. Therefore, calibrating the thermocouple readout of the heating holder prior to the experiment is essential. The calibration can be performed using reference materials whose phase-transformation (melting, oxidation, reduction, etc.) temperatures are well-established. In this study, the calibration experiment was performed with four reference materials, i.e., pure Sn, Al-95 wt%Zn eutectic alloy, NiO/carbon nanotube composite, and pure Al, and the calibration curve and formula were obtained. The thermocouple readout of the holder used in this study provided a reliable temperature value with a relative error of <4%.