• Progress in Superconductivity
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• 제4권1호
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• pp.80-85
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• 2002

In order to disseminate the IEC international standard of RRR measurement of Cu／Nb／-Ti composite superconductors, a measuring system was developed at KRISS. The system consisted of helium reservoir, base plate, thermometer, voltmeter and current source. The helium reservoir and base plate provided a stable temperature of a range from 4.2 K to 300 K and the voltmeter measured several order of $mutextrm{V}$ on specimen for obtaining RRR of the Cu／Nb-Ti composite superconductor. Three specimens of the Cu／Nb-Ti composite superconductors were measured using this system for characterizing their RRR. The resistance-temperature curves ortho specimens showed 10／sup -6／ to 10／sup -5／ Ohms near transition temperature and 10／sup -4／ to 10／sup -3／ Ohms at 293 K. The RRR values of the specimens were 145, 71 and 140, respectively.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1404-1411
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• 2016

Pipe wall thinning in the secondary piping system of a nuclear power plant is currently a major problem that typically affects the safety and reliability of the nuclear power plant directly. Regular in-service inspections are carried out to manage the piping system only during the overhaul. Online thickness monitoring is necessary to avoid abrupt breakage due to wall thinning. To this end, a transducer that can withstand a high-temperature environment and should be installed under the insulation layer. We propose a thin plate type of embedded ultrasonic transducer based on magnetostriction. The transducer was designed and fabricated to measure the thickness of a pipe under a high-temperature condition. A number of experimental results confirmed the validity of the present transducer.

• Journal of Korean Vacuum Science & Technology
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• 제4권3호
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• pp.63-67
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• 2000

We have studied the photoluminescence properties of undoped epitaxial layers of GaN on sapphire substrate grown by horizontal low pressure metal organic chemical vapor deposition method in the temperature range of 9-300 K. At 9 K the spectra are dominated by the well resolved interband free excitons A and B as well as bound excitons. Temperature dependence of free exciton transitions was studied and Varshni's coefficients for the temperature variation of bandgap were determined.

• Mass Spectrometry Letters
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• 제8권2호
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• pp.44-47
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• 2017

Isothiazolinone derivatives are widely used in consumer products as disinfectants or preservatives, but there are growing concerns about their impact on human health. Therefore, rapid screening of these biocides is very important for proper control and regulation of potentially hazardous substances. To this end, low-temperature plasma (LTP) ionization mass spectrometry (MS) was investigated to demonstrate its potential for direct and selective analysis of isothiazolinones from sprayed aerosol samples. Benzisothiazolinone (BIT) was clearly identified from a commercial fabric deodorant using LTP ionization MS and MS/MS. LTP allowed selective ionization of BIT directly from the simply sprayed aerosol sample and illustrated its potential for fast screening without sample pre-treatments. Selective nature of LTP ionization, on the other hands, implicates use of LTP ionization MS as a general screening method for specific groups of hazardous chemicals in commercial products.

• 대한영양사협회학술지
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• 제13권4호
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• pp.389-406
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• 2007

This study was conducted to estimate the safety level of non-cooking and cooking processed foods to propose the sanitary management of foods donated to foodbanks. The time and temperature were measured and the microbial levels of aerobic plate counts (APC), coliforms, E. coli, Salmonella spp., S. aureus, B. cereus, and E. coli O157:H7 were analyzed on ten food items donated to seven foodbanks. The amount of cooked foods donated to each foodbank was about 10 to 40 servings. All foodbanks hired a supervisor and had at least one refrigerator/freezer and one temperature-controlled vehicle, but only four foodbanks had the separate offices to manage the foodbank operation. The flow of donated foods was gone through the steps; production, meal service and holding at donator, collection by foodbank, transport (or holding after transport) and distribution to recipients. After production, the levels of APC of both non-cooking and cooking processed foods were complied with the standards by Ministry of Education & Human Resources Development, and were not increased till distribution. Only the level of coliforms in dried squid & cucumber salad (1.5×$10^3$ CFU/g) was not met the standards. E. coli and other pathogens were not detected in all tested samples. The microbial levels of delivery vessels and work tables were satisfactory, but the APC levels of two of four tested serving tables (6.9×$10^3$ and 5.3×$10^3$ CFU/100$cm^2$) and the coliforms level of one (1.1×$10^3$ CFU/100$cm^2$) were over the standards. The air-borne microflora level in serving room was estimated as satisfactory. It took about 3.0 to 6.5 hours from after-production to distribution and the temperatures of donated foods were exposed mostly to temperature danger zone, which had a high potential of microbial growth. These results imply that a checklist to monitor time and temperature in each step should be provided and the employees involving foodbank operation should be properly educated to ensure the safety of donated foods.

• 센서학회지
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• 제4권1호
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• pp.43-50
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• 1995

고온에서 교정용 표준기로 사용되는 S형 열전대를 사용하여, 국내의 9개 고온분야 교정검사기관의 고온측정 능력을 순회교정을 통하여 평가하여 고온의 소급성 오차를 측정하였다. 참여기관 중 3개교정검사기관만이 열전대의 교정불확도인 ${\pm}0.5^{\circ}C$이내에서 한국표준과학연구원의 측정값과 일치하였으며, 나머지 6개 기관의 측정값은 규정된 불확도를 벗어났다. 각 측정값의 차이는 온도가 높아질수록 증가하여 비교측정점 중 가장 높은 온도인 금점에서 가장 큰 차이가 $2^{\circ}C$로 교정 불확도를 크게 벗어났다. 이 연구에서 측정된 국내 고온분야 교정검사기관의 소급성 오차는 $2.0^{\circ}C$ 이내였다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.27-32
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• 1999

We developed a 40-channel superconducting quantum interference device (SQUID) system for neuromagnetic measurements. The main features of the system are use of double relaxation oscillation SQUID (DROS), and planar gradiometer for measuring tangential field components. The DROSS with high flux-to-voltage transfers enabled direct readout of the SQUID output by room-temperature electronics and simple flux-locked loop circuits could be used for SQUID operation. The pickup coil is an integrated first-order planar gradiometer with a baseline of 40 mm. The average noise of the 40 channels is around 1.2 fT/cm/${\sqrt{Hz}}$ at 100 Hz, corresponding to the field noise of 5 fT/${\sqrt{Hz}}$ at 100 Hz, operated inside a magnetically shielded room. The 40-Channel system was applied to measure auditory-evoked neuromagnetic fields.

• 대한기계학회논문집A
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• 제37권3호
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• pp.353-358
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• 2013

본 논문은 등온열처리 온도 및 시간에 따른 2.25Cr-1Mo강의 초음파 특성 변화를 조사하였다. Charpy 충격시험과 경도시험이 3종류의 열처리조건을 가지는 각 시편들에 대하여 실시되었다. 종파를 이용한 펄스-에코법이 초음파의 감쇠와 속도 측정에 사용되었다. 연취성천이온도(FATT)는 등온열처리 시간이 길어짐에 따라 증가하였는데, 이는 인성이 감소되고 있음을 의미한다. 등온열처리 시간과 온도의 증가와 함께 종파의 속도 및 초음파의 감쇠계수는 증가하였다.

• Mass Spectrometry Letters
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• 제6권3호
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• pp.71-74
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• 2015

Low temperature plasma (LTP) ionization mass spectrometry (MS) is one of the widely used ambient analysis methods which allows soft-ionization and rapid analysis of samples in ambient condition with minimal or no sample preparation. One of the major advantages of LTP MS is selective analysis of low-molecular weight, volatile and low- to medium-polarity analytes in a sample. On the contrary, the selectivity for particular class of compound also implies its limitation in general analysis. One of the critical factors limiting LTP ionization efficiency is poor desorption of analytes with low volatility. In this study, a home-built LTP ionization source with Peltier heating sample stage was constructed to enhance desorption and ionization efficiencies of analytes in a sample and its performance was evaluated using standard mixture containing fatty acid ethyl esters (FAEEs). It was also used to reproduce the previous bacterial identification experiment using pattern-recognition for FAEEs. Our result indicates, however, that the bacterial differentiation from FAEE pattern recognition using LTP ionization MS still has many limitations.

• 대한화학회지
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• 제36권6호
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• pp.857-863
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• 1992

기전력의 단위인 volt를 유지하기 위하여 사용되는 Weston 산성 포화전지를 만들어, 온도가 일정하도록 특별히 고안하여 제작한 enclosure에 넣어 성능을 평가하였다. 전지 제조에 사용되는 황산카드뮴은 진공 상태에서 재결정하였으며, 수은이 분산된 황산수은(I) 침전은 전기분해에 의해 제조하였으며, 카드뮴 아말감도 전기분해에 의하여 정확한 조성으로 제조할 수 있었다. 표준전지 항온함은 순환식 항온조를 이용하여 제작하였으며, 실내 온도가 심하게 변하는 경우에도 ${\pm}$5 mK 이내로 표준전지의 온도를 안정시킬 수 있었다. 표준전지의 기전력을 5${\sim} 30^{\circ}C$의 온도 범위에서 측정하였으며 전지간의 기전력 표준편차는 약 1ppm이었다.