• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1081-1090
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• 2024

The liquid Lead-bismuth eutectic is used as the coolant for Gen-IV reactor concepts. However, due to its strong corrosive and high operating temperature, it is difficult to accurately measure the flow rate in long-term operating conditions. Venturi flowmeter is a simple structured flowmeter, which plays a very important role in the flow measurement of high-temperature liquid metals, especially since the existing flowmeters are difficult to be competent. It has the advantages of easy maintenance and stable operation. Therefore, it is necessary to study the operating conditions of the venturi flowmeter under high-temperature conditions. This work performs a series of simulations of the fluid-solid interaction between the flow liquid metal and venturi flowmeter with COMSOL software, including the dimensional sensitivity analysis of the venturi flowmeter to explore the most suitable structure and parameters for liquid heavy metal, the sensitivity analysis of the geometric parameters of the venturi tube on the varying conditions. It shows that when the contraction angle of the venturi flowmeter is 33°, the diffusion angle is 13°, the diameter of the throat is 8 mm, and the temperature of the lead-bismuth eutectic is 733.15 K, it is most suitable for the measurement in the lead-bismuth circuit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1753-1755
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• 1999

$LaCoO_3$ thick-film sensors were fabricated on alumina substrate by screen printing method. The sensitivity for gases was investigated by varying the heat treatment temperature of the films. X-Ray Diffractions and SEM photographs were used to examine their structural properties. The sensitivity of $LaCoO_3$ thick-film for CO gas was much better than for $C_4H_{10}$, $NH_3$ and NO gases. The best condition of heat treatment was $800^{\circ}C$ and the optimal operating temperature of $LaCoO_3$ thick-film for the highest sensitivity was $150^{\circ}C$. Sensitivities of the $LaCoO_3$ thick-film at 500ppm and l000ppm for CO gas were 72% and 95%, respectively.

• 한국강구조학회 논문집
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• 제17권5호통권78호
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• pp.519-526
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• 2005

혹서기에 레일의 높은 온도 상승(최대 $60^{\circ}C$)으로 인해 장대레일 궤도에는 매우 큰 압축력이 작용하게 된다. 이러한 압축력은 장대레일 궤도의 좌굴을 발생시키기도 한다. 본 연구에서는 장대레일 궤도의 좌굴에 영향을 미치는 많은 요소들 중에서 도상 횡저항력 그리고 도상 종저항력이 궤도 좌굴에 미치는 영향을 파악하기 위한 연구를 수행하였다. 또한 줄틀림과 궤간틀림의 민감도를 분석하였다.

• 설비공학논문집
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• 제17권11호
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• pp.998-1004
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• 2005

Recently natural ventilation rate is decreased due to the airtightness of apartment building. Therefore the use of heat recovery ventilator (HRV) has been greatly increased as an alternative method to supply fresh air and save energy in the building. In this research the experiment standard of HRV is compared between KS and JIS and the sensitivity analyses are experimented by both standards. Under cooling experiment condition indoor and outdoor wet-bulb temperature difference of JIS is 2 to 3 times higher than that of KS. It shows that the efficiency measurement of HRV by KS is expected to have greater sensitivity than by JIS and thus accurate measurement of web-bulb temperature is required. The experimental results provide that the efficiency of thermal exchange is resemblance to each others between KS and JIS. Under cooling experiment condition the efficiency of humidity exchange by KS presents higher than by JIS, however, under heating experiment condition the efficiency by KS shows lower than by JIS, reversely.

• 한국재료학회지
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• 제26권5호
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• pp.281-286
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• 2016

In the present study, the tensile properties and dynamic strain aging of an Fe-24.5Mn-4Cr-0.45C alloy were investigated in terms of strain rate. During tensile testing at room temperature, all the stress-strain curves exhibited serrated plastic flows related to dynamic strain aging, regardless of the strain rate. Serration appeared right after yield stress at lower strain rates, while it was hardly observed at high strain rates. On the other hand, strain-rate sensitivity, indicating a general relationship between flow stress and strain rate at constant strain and temperature, changed from positive to negative as the strain increased. The negative strain-rate sensitivity can be explained by the Portevin Le Chatelier effect, which is associated with dynamic strain aging and is dependent on the strain rate because it is very likely that the dynamic strain aging phenomenon in high-manganese steels is involved in the interaction between moving dislocations and point-defect complexes.

• 한국음향학회지
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• 제19권2호
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• pp.8-12
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• 2000

본 논문은 주위 환경인 수압 및 수온변화에 따른 맨드릴형 광-음향센서의 감도특성을 분석한 것에 관한 것이다. 음향감지부의 구조로는 실린더형, 중공 층상복합체형 및 air cavity가 삽입된 중공 층상복합체를 선정하고, 주위 수압과 수온변화에 따른 광-음향센서의 감도특성을 분석하였다. 맨드릴형 광-음향센서는 주위 정수압의 변화에 대해 0.15dB 미만의 음향감도 변화를 나타내고, 수압변화에 대해 안정적인 특성을 보유하고 있다. 주위 수온변화에 대한 음향감도의 상대적인 안정성은 air cavity가 삽입된 중공 나일론 층상복합체를 이용한 맨드릴형 광-음향센서가 가장 우수한 것으로 나타났다.

• 한국세라믹학회지
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• 제41권2호
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• pp.97-101
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• 2004

W $O_{x}$-based semiconductor type thin film gas sensor was fabricated for the detection of N $O_{x}$ by reactive d.c. sputtering method. The relative oxidation state of the deposited W $O_{x}$ films was approximately compared by the calculation of the difference of the binding energy between Ols to W4 $f_{7}$2/ core level XPS spectra in the standard W $O_3$ powder of known composition. As the annealing temperature increased from 500 to 80$0^{\circ}C$, relative oxygen contents and grain size of the sputtered films were gradually increased. As the results of sensitivity ( $R_{gas}$/ $R_{air}$) measurements for the 5 ppm N $O_2$ gas, the sensitivity was 110 and the sensor showed recovery time as fast as 200 s. The other sensor properties were examined in terms of surface microstructure, annealing temperature, and relative oxygen contents. These results indicated that the W $O_3$ thin film with well controlled structure is a good candidate for monitoring and controlling of automobile exhaust.haust.t.t.t.

• Asian-Australasian Journal of Animal Sciences
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• 제21권1호
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• pp.124-130
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• 2008

Streptococcus (Strep.) agalactiae is one of the major pathogens of bovine mastitis and is the main cause of subclinical infection. This study attempted to develop a rapid PCR diagnosis procedure using milk samples collected on filter paper disks. Chromatographic filter paper was employed as the preservation media and kept at room temperature for one to four weeks. The revival rate of Strep. agalactiae kept on dried filter paper disks was affected by the pretreatment preservation time. The revival test suggested that not all the bacteria in artificially contaminated milk samples on the filter paper disks could be recovered. After that, a PCR based on the 16-23S intergenic spacer region of Strep agalactiae was performed. The results distinguished the strep. agalactiae from major pathogens of bovine mastitis at a $2{\times}10^2$ colony forming units (CFU)/ml level, which showed similar sensitivity to the results from liquid milk samples. The results also showed that milk samples collected on filter paper disks could be kept at room temperature for one to four weeks with little negative effect on sensitivity and specificity. The field test showed that the diagnostic sensitivity and specificity was 96.15% and 98.60%, respectively. In conclusion, the protocol will provide a rapid and economic procedure for the detection of bovine mastitis.

• Water Engineering Research
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• 제1권4호
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• pp.267-277
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• 2000

This study reports an examination of the sensitivity of water resources in the Keum River basin to climate change. Assuming a doubling in $CO_2$ concentrations, a cooperative study provided four climate change scenarios for this study, which have been translated into temperature and precipitation scenarios on a basin scale. The study utilized these temperature and precipitation data for each climate change scenario as inputs to the NWS-PC model to generate the corresponding streamflow scenario over the Keum River basin. A reservoir simulation model for the Dae-Chung Dam in the Keum River basin has been developed with an object-oriented simulation environment, STELLA. For each streamflow scenario, the performance of the reservoir was assessed in terms of reliability, resiliency, and vulnerability. Although the simulation results are heavily dependent on the choice of the climate change scenarios, the following conclusions can be clearly concluded: (1) the future streamflow over the Dae-Chung Dam tends to decease during the dry period, which seriously increases competitive water use issues and (2) flood control issues predominate under the $2CO_2$-High case.

• Journal of Magnetics
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• 제18권2호
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• pp.173-177
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• 2013

Cantilever-detected high-frequency electron spin resonance (ESR) is a powerful method of sub-terahertz and terahertz ESR spectroscopy for a tiny magnetic sample at low temperature. In this technique, a small magnetization change associated with ESR transition is detected as deflection of a sample-mounted cantilever. So far, we have succeeded in ESR detection at 370 GHz using a commercial piezoresistive microcantilever. The spin sensitivity was estimated to ${\sim}10^{12}$ spins/gauss. In order to further increase the sensitivity, we adopt a fiber-optic-based detection system using a Fabry-Perot interferometer in place of piezoresistive system. Fabry-Perot cavity is formed between an optical-fiber end and microcantilever surface, and a change in the interference signal, corresponding to the cantilever deflection, is sensitively detected. This system is suitable for low-temperature and high-magnetic-field experiments because of its compact setup and less heat dissipation. In this study, performance of Fabry-Perot interferometer is evaluated, and its application to cantilever-detected ESR measurement is described.