• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권5호
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• pp.245-249
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• 2006

Corona characteristics of conductors are dependent on the electric field conditions in the immediate vicinity of the conductors. In case of DC transmission line, particularly, the space charge plays an important role in the electric field distribution. Therefore, DC corona cage simulation is necessary for long-term test in the same conditions. This paper presents the results of designing and constructing hardwares such as DC power supply, measurement system and DAS to carry out the simulation. The corona cage longitudinally is divided into five equal length sections and three inner sections of those are isolated from the ground of outer cage. The measurement items are radio noise, corona current, television noise, audible noise and meteorological conditions. In the next step, various simulations about the type and configuration of two or three candidate conductors will be conducted. And then finally an environmentally-friendly conductor for HVDC overhead transmission line will be decided.

• 대한전자공학회논문지
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• 제6권3호
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• pp.8-11
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• 1969

In the precision measurement of the voltage standing wave ratio (VSWR) or reflection coefficient by means of the slotted line technique, one of the important factors is the maximum error due to the discontinuities and multi-reflection in the slotted line. Particularly, this error becomes a critical factor when the VSWR or the reflection coefficient to be measured is very small. In this paper, the exact expression of this error is obtained by means of the Signal flow graph method.

• 한국분무공학회지
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• 제2권4호
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• pp.29-35
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• 1997

Liquid film thickness is measured by $moir\acute{e}$ topography which monitored liquid surface. $Moir\acute{e}$ fringe measurement techniques share the inherent simplicity found in optical interferometric techniques have the advantage of use over a greater range of displacement. $Moir\acute{e}$ fringe are the geometric interference patterns observed when two dense line grating are superposed. Light transmitted through a fixed line grating is deviated by the liquid film surface, producing a distored image of the grating. The $moir\acute{e}$ fringe produced by projection of this optically distored grating onto a second stationary grating permit visualization of the liquid surface and measurement of the liquid film thickness. This study measured the small amplitude of liquid film thickness to the $moir\acute{e}$ fringe pattern produced when spherical metal was dropped glycerin put)1 And the measurement of liquid film thickness flowing down an inclined plate are required to calculate the liquid slope in a position.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.575-580
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• 2007

As the volume of traffic in southern part of the republic of Korea grew, expansion of transportation was required. In that purpose, the railway between Samnangjin and Gwangyang is being extended to a double-track line. This construction includes Nakdong bridge located across Nakdong river. This truss bridge is constructed in incremental launching method (ILM) and composed of two sections, straight line and curved one. Bridge construction in the method goes with the shift of roller supports which results in the change of structural system. To accomplish safe construction, the measurement during the whole launching stages. The locations of member in severe condition and the corresponding response values were estimated through the preliminary construction stage analysis. Based on the analysis, the measurement during construction was planned. Several sensors and measurement devices were installed at appropriate locations. During the whole launching stages, the measurement was performed and the corresponding data were monitored and stored in real time. The comparison of the responses from the analysis and the measurement showed no indication of yielding of the structural members. Consequently, the construction of Nakdong bridge was concluded to be relevant.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1328-1334
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• 2015

A new system for evaluating the voltage management errors of distribution equipment is presented in this paper. The main concept of the new system is to use real distribution live-line voltage to evaluate and correct the voltage measurement data from distribution equipment. This new approach is suitable for a new Distribution Management System (DMS) which has been developed for a distribution power system due to the connection of distributed generation growth. The data from distribution equipment that is installed at distribution lines must be accurate for the performance of the DMS. The proposed system is expected to provide a solution for voltage measurement accuracy assessment for the reliable and efficient operation of the DMS. An experimental study on actual distribution equipment verifies that this voltage measurement accuracy assessment system can assess and calibrate the voltage measurement data from distribution equipment installed at the distribution line.

• 한국해양공학회지
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• 제19권5호
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• pp.71-77
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• 2005

This paper presents an integrated underwater navigational algorithm for unmanned underwater vehicles, using additional two-range transducers. This paper proposes a measurement model, using two range measurements, to improve the performance of an IMU-DVL (inertial measurement unit - Doppler velocity log) navigation system for long-time operation of underwater vehicles, excluding DVL measurement. Extended Kalman filter was adopted to propagate the error covariance, to update the measurement errors, and to correct the state equation when the external measurements are available. Simulation was conducted with the 6-d.o.f nonlinear numerical model of an AUV in lawn-mowing survey mode, at current flaw, where the velocity information is unavailable. Simulations illustrate the effectiveness of the integrated navigation system, assisted by the additional range measurements without DVL sensing.

• Journal of Information Processing Systems
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• 제16권2호
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• pp.394-405
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• 2020

The parameters of transmission lines have an influence on the electromagnetic environment surrounding the line. This paper proposes a method based on phasor measurement unit (PMU) and supervisory control and data acquisition (SCADA) to achieve online estimation of transmission line full parameters, such as resistance, reactance and susceptance. The proposed full parameter estimation method is compared with the traditional method of estimating resistance independently based on SCADA system. Then, the electromagnetic environment is analyzed based on the different parameter estimation methods. The example results illustrate that online estimation of transmission line full parameters is more accurate in the analysis of electromagnetic environment, which further confirms its necessity and significance in engineering application.

• Corrosion Science and Technology
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• 제11권4호
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• pp.135-140
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• 2012

The linear polarization resistance method is one of the widely used techniques for the corrosion rate monitoring in the water circulating systems of plants. The measurement is simple and rapid, so that a continuous on-line monitoring is possible without any shutdown of plants. A 2-electrode polarization corrosion rate measurement system was installed in a laboratory using a data acquisition board and PC. The signal processing parameters were optimized for the accurate corrosion rate measurement, and the polarization resistance was compensated with the solution resistance measured by the high frequency sine wave signal of an output channel. The precision of corrosion rate data was greatly improved by removing the initial noise signals on measuring the polarization resistance.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제22권4호
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• pp.261-282
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• 2019

The research related to testing pupils' achievement in the field of Measurement and Measure in initial teaching of geometry points to an insufficient adoption of the basic components of the length measurement concept among pupils. In order to discover the cause, we looked at the basic components on which the procedure of measuring length using a ruler is based, highlighted the possibilities of introducing the procedure in measuring length, and determined pupils' achievement during the procedure of measuring length using a ruler. The research sample consisted of 145 pupils, out of which 72 were the 2^nd grade pupils and 73 were the 4^th grade pupils. A descriptive method was applied in the research. The technique we used was testing, and for the statistical data processing we used a χ² test. The results of the research show that, when drawing a straight line of a given length using a ruler, there is no statistical difference in achievement between the 2^nd and 4^th grade pupils, nor in the pupils' knowledge regarding drawing a ruler independently, while drawing a straight line of a given length using a "broken" ruler 4^th grade pupils are statistically better. The results of the research indicate that pupils' achievement is better in doing standard tasks than in non-standard ones, given that the latter require conceptual knowledge. The components of the concept of length measurement using ruler have not been sufficiently developed yet, and these include: zero-point, partitioning a measured object in a series of consecutive measurement units and their iteration. We shed more light on the critical stage in the procedure of length measurement - the transition from non-standard to standard units and the formation of the length measurement scale. For further research, we propose to look at the formation of the concept of length measurement using the ruler through all its components and their inclusion in the mathematics curriculum, as well as examining the correlation of pupils' achievement in the procedure of measuring length with their achievement in measuring area (and volume).

• 한국유체기계학회 논문집
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• 제6권1호
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• pp.57-65
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• 2003

The measurement uncertainties of an ultrasonic flowmeter were analyzed to evaluate its applicability to the measurement of the steam generator feedwater flow-rate in a nuclear power plant. The analyses of measurement uncertainties of a reactor power were also performed with the analyses of feedwater flow measurement uncertainties. Two ultrasonic flowmeters based on a cross-correlation technique and a transit time method were used in this study. The ultrasonic flowmeters were installed on a feedwater pipe line of a typical 1000 MWe Korea-standardized nuclear power plant to take the necessary data. The results have shown that the measurement uncertainties of the ultrasonic flowmeters are adequately smaller than those or a venturi meter. The research has also indicated that the measurement uncertainties of the reactor power based on the ultrasonic flowmeter uncertainties are sufficiently bounded by the uncertainty range usually assumed in nuclear safety analyses.