• Progress in Superconductivity
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• v.12 no.1
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• pp.57-61
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• 2010

We have developed a whole-head MEG system for basic brain research and clinical application. The sensor system consists of a 152 SQUID gradiometer array oriented and located in a suitable way to cover a whole head of the human. The system measures magnetic fields generated by neuronal currents in the brain to get information on the brain activities. For this purpose, the field sensitivity determined by the position, orientation and geometry of the pickup coil as well as amplification factor of the electronic circuits should be known precisely. However, the position and orientation of the pickup coil might be changed from the designed specifications during cool down of the dewar and it is necessary to characterize the field sensitivity. In this study, we made calibration systems to determine the actual position and orientation of the 152 pickup coils and compared the localization results of the N100m source in the auditory cortex.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.991-993
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• 1999

The method of measurement for contactless eddy-current conductivity using magnetic dipole field theory was suggested by M.C Chen[1], which calculate the eddy-current caused by exciting coil with Faraday's induction law. In this work, we have developed the apparatus for contactless measurement of conductivity or resistivity with the dipole field theory. The resistivity can be measured from several to a dozen $m{\Omega}{\cdot}cm$ range within maximum 30% error. At the high resistivity range above $100{\Omega}{\cdot}cm$, the standard deviation of measurement was very large as the induced voltage of sensing coil is small so it was difficult to measure the value precisely.

• Journal of Astronomy and Space Sciences
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• v.9 no.2
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• pp.193-202
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• 1992

The fist sounding rocket in Korea, KSR-420S has been under the development at Korea Aerospace Research Institute (KARI), and is expected to be launched in 1993 to measure the vertical ozone profile over the Korean Peninsula. The KSR-420S is expected to provide the fist in situ measurement of ozone concentrations over the Korean Peninsula. An optical ozone detector has been developed at Korea Research Institute of Standards and Science (KRISS), and its calibration has been completed recently. In this paper, measurement principles of the ozone detector in KSR-420S, its calibration data, ozone measurement procedure and data reduction algorithm are presented with sample calculations.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.313-321
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• 2011

The Korea Research Institute of Standards and Science (KRISS) has three major vacuum systems: an ultrasonic interferometer manometer (UIM), a static volume expansion system (SVES), and an orifice-type dynamic expansion system (ODES). For each system explict measurement model equations with multiple variables are respectively given. According to ISO standards, all these system variables errors were used to calculate the expanded uncertainty (U).

• Journal of Korean Society for Quality Management
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• v.34 no.1
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• pp.54-72
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• 2006

In recent years, the widespread application of quality management and measurement reliability has put increasing emphasis on procedures for periodic instrument calibration. By optimizing calibration intervals, unnecessary calibrations can be minimized, thereby reducing costs. Moreover, optimizing intervals will improve compliance with regulatory directives while ensuring maximal compliance with reliability targets. In this paper, we present Calibration Interval Analysis Program developed using several establishment methodologies of calibration interval for measurement quality and reliability improvement. Also, we perform calibration interval analysis for some measurement instruments and analyse its results.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.739-743
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• 2009

Japan is leading standards for the hydrogen fuel quality on the PEMFC(Proton Exchange Membrane Fuel Cell) vehicle at ISO/TC197/WG12. However, it has many problems to solve the standard of measurement and the test method. because the standard of measurement which was proposed in Japan is too high to reach the technique for many countries. it might not control standards for the hydrogen fuel quality on the PEMFC vehicle in Korea. So we need to develop the study of standards and the technique of measurement continuously for the International Standards Meeting.

• Progress in Superconductivity
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• v.13 no.1
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• pp.1-6
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• 2011

Measurement of magnetic signals generated from electric activity of myocardium provides useful information for the functional diagnosis of heart diseases. Key technical component of the magnetocardiography (MCG) technology is SQUID. To measure MCG signals with high signal-to-noise ratio, sensitive SQUID magnetic field sensors are needed. Present magnetic field sensors based on Nb SQUIDs have field sensitivity good enough to measure most of MCG signals. However, for accurate measurement of fine signal pattern or detection of local atrial fibrillation signals, we may need higher field sensitivity. In addition to field sensitivity, economic aspect of the SQUID system is also important. To simplify the SQUID readout electronics, the output voltage or flux-to-voltage transfer of SQUID should be large enough so that direct measurement of SQUID output can be done using room-temperature preamplifiers. Double relaxation oscillation SQUID (DROS), having about 10 times larger flux-to-voltage transfers than those of DC-SQUIDs, was shown to be a good choice to make the electronics compact. For effective cancellation of external noise inside a thin economic shielded room, first-order axial gradiometer with high balance, simple structure and long-baseline is needed. We developed a technology to make the axial gradiometer compact using direct bonding of superconductive wires between pickup coil and input coil. Conventional insert has mechanical support to hold the gradiometer array, and the dewar neck has equal diameter with the dewar bottom. Boiling of the liquid He can generate mechanical vibrations in the gradiometer array due to mechanical connection structure. Elimination of the mechanical support, and direct mounting of the gradiometer array into the dewar bottom can reduce the dewar neck diameter, resulting in the reduction of liquid He consumption.

• Journal of Sensor Science and Technology
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• v.14 no.5
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• pp.350-356
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• 2005

We have developed a dual-channel type automatic measurement system to evaluate AC-DC current transfer difference of the thermal current converter(TCC) which is primary standard of AC current. The output drift effect of the TCC is minimized by measuring simultaneously the output voltages of two TCCs using voltmeter. Furthermore, the offset voltage of the voltmeter is cancelled nearly out by taking the average values of two outputs of TCCs measured with the forward-reverse directions using dual channel scanner. The uncertainties of the automatic system were 7 to $86{\mu}A/A$ for 3 mA to 10 A at 40 Hz to 20 kHz, which were evaluated by the comparisons between adjacent range of TCCs and inter-comparison with national measurement institute of Germany(PTB). The capability for ac-dc transfer difference measurement was improved by one order compared with that for the manual ac-dc measurement system.

• Journal of Korean Elementary Science Education
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• v.26 no.1
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• pp.87-96
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• 2007

The purpose of this study was to examine the features of the standards of observation and measurement in foreign national science curriculums. For the purpose of this study, we analyzed the science standards of the USA (National Science Education Standards, the Science Standards of the State of California, Massachusetts, Colorado, Nebraska, Virginia and Florida), the United Kingdom (England), Singapore, Canada (the State of Alberta), Australia (the State of Victoria) and New Zealand. The results of the study indicated that foreign national science curriculums put an emphasis on accurate and systematical observation, usage of the five senses, usage of observation tools, and an understanding of observation. Regarding the 'measurement' factors, foreign national science curriculums emphasized systematic and accurate measurement. Measurement targets and tools were presented for each grade. The usage of appropriate units was also included in the foreign national curriculums which we examined.

• Mass Spectrometry Letters
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• v.4 no.4
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• pp.75-78
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• 2013

A gas chromatography/mass spectrometric (GC/MS) method was developed as a candidate reference method for the accurate determination of essential fatty acids (linoleic acid, ${\alpha}$- and ${\gamma}$-linolenic acids) in food supplemental oil products. Samples were spiked with three internal standards (stearic acid-$d_{35}$, $^{13}C_{18}$-linoleic acid, and $^{13}C_{18}$-${\alpha}$-linolenic acid). Samples were then subject to saponification, derivatization for methylation, and extraction by organic solvent. For GC/MS measurement, an Agilent HP-88 column, designed for the separation of fatty acid methyl esters, was selected after comparing with other columns as it provided better separation for target analytes. Target analytes and internal standards were detected by selected ion monitoring of molecular ions of their methyl ester forms. The GC/MS method was applied for the measurement of three botanical oils in NIST SRM 3274 (borage oil, evening primrose oil, and flax oil), and measurement results agreed with the certified values. Measurement results for target analytes which have corresponding isotope-labeled analogues as internal standard were calculated based on isotope dilution mass spectrometry (IDMS) approach, and compared with results calculated by using the other two internal standards. Results from the IDMS approach and the typical internal standard approach were in good agreement within their measurement uncertainties. It proves that the developed GC/MS method can provide similar metrological quality with IDMS methods for the measurement of fatty acids in natural oil samples if a proper fatty acid is used as an internal standard.