• Advances in materials Research
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• 제4권4호
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• pp.215-226
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• 2015

Experiment on roughness and micro pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The relation between roughness and glossiness with reduction in height, roll surface roughness, emulsion parameters was analyzed. The surface morphology of micro pit defects was observed by SEM, and the effects of micro pit defects on rolling reduction, roll surface roughness, emulsion parameters, lubrication oil in deformation zone and work roll diameter were discussed. With the increasing of reduction ratio strip surface roughness Ra(s), Rp(s) and Rv(s) were decreasing along rolling and width direction, the drop value in rolling direction was faster than that in width direction. The roughness and glossiness were obtained under emulsion concentration 3% and 6%, temperature $55^{\circ}C$ and $63^{\circ}C$, roll surface roughness $Ra(r)=0.5{\mu}m$, $Ra(r)=0.7{\mu}m$ and $Ra(r)=1.0{\mu}m$. The glossiness was declined rapidly when the micro defects ratio was above 23%. With the pass number increasing, the micro pit defects were reduced, uneven peak was decreased and gently along rolling direction. The micro pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. When work roll diameter was small, bite angle was increasing, lubrication oil in micro pit of deformation zone was decreased, micro defects were decreased, and glossiness value on the surface of strip was increased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.13-14
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• 2016

In the modern construction industry, since numerous skyscrapers have been built, there have been sought for developing various kinds of methods for shortening a construction period. Therefore, many kinds of studies on some kinds of cold-weather concrete have been conducted actively for the purpose of a year-round construction. Accordingly, this research team once developed a double-layered bubble sheet as a surface-coated curing material for winter. And there have been raised some worries that some initial damages to frozen concrete caused by low temperature of reinforcing bars which are exposed out of the wall areas of a wall-type apartment during winter. Therefore, in this study, it is intended to find out clearly whether it is possible for concrete to be damaged initially or not by analyzing the temperature characteristics of the exposed reinforcing bars of the wall areas under the temperature conditions during winter.

• KIEAE Journal
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• 제15권1호
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• pp.111-116
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• 2015

Heat loss from windows and condensation occuring on its surface due to its lower insulation value causes much discomfort to occupants. In this study, Heated glass was used to make a basic study on prevention of condensation on glass surface for its heating functionality through experimental measurement and simulation analysis of total heat flux on the interior and exterior surface of glass. Error between experimental results and three dimensional steady-state heat transfer analysis were caused firstly, beacuse in the experimental chambers, cold chamber and steady temperature and humidity chamber, air temperature setting was not constant but rather ON/OFF control, and secondly, due to error rate in heat flux meter due to heat flux direction even in stable conditions.

• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.94-100
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• 2004

We fabricated textured Ag substrates for YBCO coated conductor and evaluated the effects of annealing temperature on microstructural evolution, texture formation, and surface morphology. Ag ingot, as an initial specimen, was prepared by plasma arc melting(PAM). Subsequently, the ingot was cold rolled to 100 ${\mu}{\textrm}{m}$ thick tape and annealed at temperatures of 600-80$0^{\circ}C$. The texture and surface morphology of the substrate were characterized by pole-figure and atomic force microscopy(AFM) profile, respectively. It was observed that a strong ｛110｝<110> texture was formed after annealing and its symmetry improved as annealing temperature increased. The full-width at half-maximum(FWHM) of ｛110｝<110> pole was as sharp as 10$^{\circ}$ for the substrate annealed at 80$0^{\circ}C$. On the other hand, it was found that the thermal grooving and faceting became remarkable as annealing temperature increased : root-mean-square(RMS) roughness of the substrate annealed at 80$0^{\circ}C$ was 39.2 nm. The substrate of strong texture and smooth surface, fabricated in our study, is considered to be suitable for use as a substrate for the epitaxial deposition of superconductor film.

• 한국표면공학회지
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• 제34권5호
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• pp.448-454
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• 2001

Low field electron emission from novel carbon based cold cathodes is reported. The cathodes consisted of a layer of nanoseeded diamond and an over layer of nanocluster carbon films. The nanoseeded diamond was first coated on to thesubstrate. The nanocluster carbon films were then deposited on the nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. The heterostructured microcathodes were observed to exhibit electron emission currents of 1 $\mu$A/cm$^2$ at fields as low as 1.5 to 2V/$\mu$m. The effect of the nanoseeded diamond size and concentration and the properties of different nanocluster carbon films on emission characteristics is presented.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.164-169
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• 2001

There is a chilled ceiling panel which carries out the air conditioning by radiation and convection between the room and cold ceiling panel surface. In order to verify heat transfer characteristics between them in cooling system with radiant chilled ceiling panel, analytical and experimental studies were performed for various design and operating parameters such as tube space and diameter, inlet water temperature, mass flow rate, cooling load, and so on. In this study, we found that the tube space and inlet water temperature were more important elements than the tube diameter and water flow rate for the performance of radiant chilled ceiling panel. The cooling capacity of the radiant chilled ceiling panel had the maximum value of $65W/m^{2}$ because the highest cooling capacity was limited by the condensation on the panel surface. The results of comparison between numerical analysis and experiment showed a resonable agreement qualitatively, especially for low cooling capacity.

• 설비공학논문집
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• 제23권5호
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• pp.327-333
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• 2011

In the present work, a new freeze protection method has been proposed for a natural circulation system of solar water heater. Though electrothermal wire is popularly used for the purpose, there are freezing troubles by wire cut-off and shortage of excessive electric power consumption. In the experimental device, hot water in storage tank was used to heat the outlet pipe from the tank if the pipe surface temperature falls lower than a set point. The cold water pipe to the storage tank was installed to directly contact the hot water pipe surface temperature rose by transferred heat.

• 한국표면공학회지
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• 제37권1호
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• pp.64-70
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• 2004

Cryogenic characteristics of austenitic stainless steel based on 304 steel with nickel and nitrogen were investigated at room temperature and $-196^{\circ}C$. The alloys were fabricated by vacuum arc furnace and cold working after homogenization treatment. The addition of nickel and nitrogen decreased the stability of $\delta$-ferrite and induced the stability against the formation of martensite to result significantly in enhancing ductility at $-196^{\circ}C$. Nitrogen reduced Md temperature, which was beneficial to the tensile strength and elongation at $25^{\circ}C$ and -196$^{\circ}C$.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1412-1420
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• 2018

An experiment was performed using the large-scale test facility (LSTF), which simulated a 1% vessel upper head small-break loss-of-coolant accident with an accident management (AM) measure under an assumption of total-failure of high-pressure injection (HPI) system in a pressurized water reactor (PWR). In the LSTF test, liquid level in the upper head affected break flow rate. Coolant was manually injected from the HPI system into cold legs as the AM measure when the maximum core exit temperature reached 623 K. The cladding surface temperature largely increased due to late and slow response of the core exit thermocouples. The AM measure was confirmed to be effective for the core cooling. The RELAP5/MOD3.3 code indicated insufficient prediction of primary coolant distribution. The author conducted uncertainty analysis for the LSTF test employing created phenomena identification and ranking table for each component. The author clarified that peak cladding temperature was largely dependent on the combination of multiple uncertain parameters within the defined uncertain ranges.

• 한국식품위생안전성학회지
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• 제32권2호
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• pp.107-113
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• 2017

본 연구는 전북권내 냉장 냉동식품 유통차량을 대상으로 온도관리에 대한 현황을 파악하고자 중소기업 2곳과 대기업 5곳의 운송차량 총 8대를 대상으로 온도현황을 조사하였다. 냉장 냉동식품 유통차량의 실제공간상의 온도분포 조사결과, 참여 중소기업의 냉장차량과 냉동차량 평균 온도는 각각 $8.35{\pm}5.72^{\circ}C$, $-3.45{\pm}16.88^{\circ}C$이었고, 대기업의 냉장차량과 냉동차량 평균온도는 각각 $3.92{\pm}1.44^{\circ}C$, $-15.38{\pm}2.98^{\circ}C$로 중소기업 보다는 낮은 온도로 운영되는 것으로 나타났다. 냉장식품 적재함의 공간위치별 온도 차이는 평균적으로 $2.40^{\circ}C{\pm}1.45^{\circ}C$, 냉동식품 적재함은 $2.37^{\circ}C{\pm}2.52^{\circ}C$의 차이가 나타났지만 공간위치별 냉장, 냉동온도 모두 통계적으로 유의하지 않았다(p > 0.05). 냉장 냉동식품 하역에 따른 유통차량 문 개 폐 전 후의 식품 표면온도는 냉장식품의 경우 열린 직후 평균 $2.17{\pm}1.90^{\circ}C$에서 닫힌 직후 $2.72{\pm}2.36^{\circ}C$로 약 $0.55^{\circ}C$ 상승하였으며, 냉동 식품은 열린 직후 $-18.58{\pm}3.66^{\circ}C$에서 닫힌 직후 $-17.76{\pm}4.15^{\circ}C$로 약 $1.18^{\circ}C$의 온도 상승이 나타났다. 본 연구결과 냉장 냉동식품 유통차량의 공간위치별, 이동 시간별, 그리고 유통차량 문의 개 폐에 따라 다양한 온도변화가 나타날 수 있음이 확인되었다. 따라서 유통 및 이동과정 중 온도변화를 실시간으로 확인할 수 있는 온도이력(Time-Temperature History) 추적시스템 도입에 대한 현장 적용 연구가 수행되어야 할 것으로 생각된다.