• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1260-1268
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• 2009

Three methods(the stepped sine method, the statistical method(random excitation method) and the maximum-length sequence(MLS) method) for head-related transfer functions(HRTFs) are experimentally compared in view point of accuracy and efficiency. First, the stepped sine method has high signal-to-noise ratio, but low efficiency. Second, the statistical method is fast measurement speed, but weak to noise than the other methods. Finally, the MLS method shows both good efficiency and high signal-to-noise ratio, but it needs additional software or equipment such as MLS signal generator. For comparison of measurement accuracy, HRTFs of KEMAR dummy are measured for various azimuths and elevations. Error norms for magnitude and phase of HRTFs are defined and calculated for the measured HRTFs. The calculated error norms show that the methods give similar results in magnitude and phase except a little phase difference in the MLS method.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.146-151
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• 2012

This study was primarily focused on the experimental comparison of the particle emission characteristics for heavy duty engine. PM and particle number from various heavy duty engines and DPF type were analyzed with a golden particle measurement system recommended by the Particle Measurement Program. And the repeatability and reproducibility between test mode was analyzed. This study was conducted for the experimental comparison on particulate emission characteristics between the European and World-Harmonized test cycles for a heavy-duty diesel engine. To verify the particulate mass and particle number concentrations from various operating modes, ETC/ESC and WHTC/WHSC, both of which will be enacted in Euro VI emission legislation, were evaluated. Real-time particle formation of the transient cycles ETC and WHTC were strongly correlated with engine operating conditions and after-treatment device temperature. A higher particle number concentration during the ESC mode was ascribed to passive DPF regeneration and the thermal release of low volatile particles at high exhaust temperature conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.362-373
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• 2002

A stereoscopic PIV (SPIV) measurement system based on the translation configuration was developed and applied to the flow behind a forward-swept axial-fan. Measurement of three orthogonal velocity components is essential for flow analysis of three-dimensional flows such as flow around a fan or propeller. In this study, the translation configuration was adopted to calculate the out-of-plane velocity component from 2-D PIV data obtained from two CCD cameras. The error caused by the out-of-plane motion was estimated by direct comparison of the 2-D PIV and 3-D SPIV results that measured from the particle images captured simultaneously. The comparison shows that the error ratio is relatively high in the region of higher out-of-plane motion near the axial fan blade. The turbulence intensity measured by the 2-D PIV method is bigger by about 5.8% in maximum compared with that of the 3-D SPIV method. The phase-averaged velocity field results show that the wake behind an axial fan has a periodic flow structure with respect to the blade phase and the characteristic flow structure is shifted downstream in the next phase.

• Journal of Animal Science and Technology
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• v.61 no.1
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• pp.41-46
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• 2019

Different methodologies in hair cortisol extraction may alter the final output. Thus finding the standard methodology according to a laboratory facilities is pivotal. This study was carried out to validate the feasibility of two methods of grinding hair for cortisol extraction in Korean native (Hanwoo) cattle. Hair from nine cattle including mature cows, heifers, and calves were assigned to one of the following methods for grinding hair; 1) using bead beater (BB) and 2) using surgical scissors (SS). Hair samples (> 1 g) were harvested from forehead of each individual twice (first and second measurement) to validate the results. To improve the accuracy of the obtained data, each sample was duplicated into two wells during enzyme immunoassay (EIA) analysis. Overall comparison of hair cortisol concentration (HCC) showed that the data within the range (out of the range) of standards provided by the EIA kit were 88.9% (11.1%) and 66.7% (33.3%) for BB compared with SS, respectively. In the first measurement, application of BB was tended to show higher (p = 0.056) amount of HCC compared with SS. In the second measurement application of BB showed higher (p = 0.0028) amount of HCC compared with SS. Among the cattle, calves showed higher HCC using BB compared with SS (p < 0.05). Application of BB in hair grinding methodology for Hanwoo cattle may improve cortisol extraction in comparison to application of SS method, with more consistency. Thus, it would be the preferable method to use.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.606-608
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• 1999

Mutual Recognition Agreement(MRA) between national metrology institutes is started on October 1999 and International Key Comparison is essentially to be used as technical basis for the agreement. High resistance is one of the Key Comparison and high resistance measurement system is established in KRISS for the purpose of the Key Comparison. Total combined uncertainty of the system is about 4ppm in $10M{\Omega}$ and 8ppm in $1G{\Omega}$. With the system, the difference of comparison results for $10M{\Omega}$ and $1G{\Omega}$ among KRISS, VNIIM in Russia and NIM in China is agreed about 6ppm within total combined uncertainty of three institutes.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1368-1370
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• 1995

Lightning impulse voltage is essential to evaluate the insulation performance of electric power apparatus. Recently international standard(IEC-60) on high voltage measurement techniques are being revised. In the draft of this standard, a new calibration method is introduced and the accuracy of most industrial measuring systems is maintained by means of comparison test against the reference measuring systems. Intercomparison tests of dividers for lightning impulse measurement were carried out by KERI. The shielded resisitive divider with 700kV rating developed by KERI were done comparison test with PTB divider with 300kV rating which have the similar charateristics as that were circulated among the laboratories. This paper reports on the comparison test results with full lightning impulse voltages from 126kV to 240kV. It is demonstrated that KERI are capable of realizing the idea in the revision of the IEC standand, that is, to establish traceability.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.1
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• pp.25-31
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• 2015

In this paper, we described the timing-offset comparison results between various daily jump compensation methods for GPS carrier phase (CP) measurement data. For the performance comparison, we used about 70 days GPS measurement data obtained from two GPS geodetic receivers which share the reference 1 PPS and RF signals and closely located in each other within a few meters. From the experiment results, the followings were observed. First, daily jumps existed in CP measurements depend on not only the environment but also the receiver which will make a full compensation be very hard or impossible. Second, clock bias can be occurred in the case of using a simple compensation with accumulation of daily jumps but it could be used in a short-period frequency comparison campaign (less than about 7 days) despite of its drawback.

• Journal of Digital Convergence
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• v.9 no.5
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• pp.253-263
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• 2011

In this study of the domestic high school and middle school students to use the online education-website to measure the quality of service between SERVPERF model and the KS-SQI model fits which were analyzed further. Analysis using AMOS 7, SERVPERF for measuring quality of service reliability, responsiveness, assurance, empathy and tangibility, was a measurement model. KS-SQI for primary needs fulfillment, unexpected benefit were performance dimensions, reliability, individual empathy, positive assistance, accessibility and media tangibility, consist of process dimension was measured. In comparison of two models, the KS-SQI model on a path analysis showed better in terms of model fit indexes.

• Journal of Radiation Protection and Research
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• v.10 no.2
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• pp.130-136
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• 1985

The activity measurement of a solution of $^{133}Ba$ which is an electron capture nuclide was carried out by the ${\beta}-{\gamma}$ coincidence method. The counting rates at the ${\beta}-,\;{\gamma}-$, and coincidence-channels were measured using a $4{\pi}$ proportional counter and two NaI(Tl) scintillation detectors. The specific activity of the solution calculated by the efficiency extrapolation was $(1151.01{\pm}2.99)kBqg^{-1}$ at the reference time(00h UT, 03-15-84). According to an international comparison of activity measurements organized by the Bureau International des Poids et Mesures, this result showed the difference of 0.94% to the mean value derived from the comparison.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.3
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• pp.205-211
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• 2011

On board comparison of pH and total alkalinity measurement in seawater was carried out during the JES expedition on R/V Roger Revelle in the East Sea using 550 real seawater samples from the surface to the bottom. Spectrophotometry and potentiometry without liquid junction were compared for pH measurement. The pH values of two methods are generally in a good agreement. Spectrophotometry with a pipette provides higher value compare with the potentiometry in the deep layer, where pH values are lower. However, spectrophotometry without a pipette shows same values with potentiometry within their precision range. The pipetting procedure may remove of $CO_2$ in the sample, which causes increase of pH. Potentiometric titration methods using a closed-cell and an open-cell were compared for the total alkalinity measurement. Values from open cell method are smaller by about 5~10 ${\mu}mol\;kg^{-1}$ than those from closed cell method. This may be caused by the bubble formed in the closed cell during the experiment. Although any analytical method compared in this study for the pH or TA measurement can be applied, special attentions should be paid for satisfactory results.