• 한국전산유체공학회지
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• 제15권4호
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• pp.25-31
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• 2010

Interface tracking of two phase is significant to analyze multi-phase phenomena. The VOF(Volume of Fluid) and level set are well known interface tracking method. However, they have limitations to solve compressible flow and incompressible flow at the same time. CIP(Cubic Interpolate Propagation) method is appropriate for considering compressible and incompressible flow at once by solving the governing equation which is divided up into advection and non-advection term. In this article, we analyze the droplet impingement according to various We number using improved CIP method which treats nonlinear term once more comparison with original CIP method. Furthermore, we compare spread radius after droplet impingement on the wall with the experimental data and original CIP method. The result using improved CIP method shows the better result of the experiments, comparison with result of original CIP method, and it reduces the mass conservation error which is generated in the numerical analysis comparison with original CIP method.

• Journal of Positioning, Navigation, and Timing
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• 제4권1호
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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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권6호
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• pp.313-316
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• 2006

A method for evaluation of the linearity of both the ratio error and phase angle error in the current transformer(CT) comparison measurement equipment has been developed by employing the standard resistors with negligible AC-DC resistance difference less than $10^{-5}$. The non-reactive standard resistors for the linearity check of the system are used as the external burden connected with the secondary of CT under test. These burdens consist of nine standard resistors, with the nominal resistance of $0.01{\Omega},\;0.1{\Omega},\;0.2{\Omega},\;0.4{\Omega},\;0.6{\Omega},\;1{\Omega},\;2{\Omega},\;4{\Omega}$, and $10{\Omega}$. For linearity check, the developed method has been applied in the CT comparison measurement equipment belonging to the industry.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1243-1249
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• 2004

This study is focused on the comparison between the internal saturation temperature of the working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves. Distilled water, methanol and ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The results show that the numbers of grooves and the type of working fluids are very important factors for the operation of thermosyphons. A good agreement between the internal saturation temperature of working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves is obtained.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.109-114
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• 2010

Interface tracking of two phase is significant to analyze multi-phase phenomena. The VOF(Volume of Fluid) and level set are well known interface tracking method. However, they have limitations to solve compressible flow and incompressible flow at the same time. CIP(Cubic Interpolate Propagation) method is appropriate for considering compressible and incompressible flow at once by solving the governing equation which is divided up into advection and non-advection term. In this article, we analyze the droplet impingement according to various We number using improved CIP method which treats nonlinear term once more comparison with original CIP method. Furthermore, we compare spread radius after droplet impingement on the wall with the experimental data and original CIP original CIP method, and it reduces the mass conservation error which is generated in the numerical analysis comparison with original CIP method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1104-1107
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• 2005

This paper presents a comparison of core losses for the four cases of Switched Reluctance Motors (SRM) with different winding method and switching sequence. With concentrated winding SRM, two kinds of switching sequence are considered for one-phase exciting and two-phase simultaneously exciting driving. With both distributed winding and toroidal winding, two-phase exciting driving is considered. The ratio of calculated core losses to input power is able to be used a guide or reference for deciding the winding method and switching sequence of in the initial design stage of SRM.

• Journal of Positioning, Navigation, and Timing
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• 제12권3호
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• pp.245-255
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• 2023

Time comparison techniques are necessary for generating and keeping Coordinated Universal Time (UTC) and distributing standard time clocks. Global Navigation Satellite System (GNSS) Common View, GNSS All-in-View, Two-Way Satellite Time and Frequency Transfer (TWSTFT), Very Long Baseline Interferometry (VLBI), optical fiber, and Network Time Protocol (NTP) based methods have been used for time comparison. In these methods, GNSS based time comparison techniques are widely used for time synchronization in critical national infrastructures and in common areas of application such as finance, military, and wireless communication. However, GNSS-based time comparison techniques are vulnerable to jamming or interference environments and it is difficult to respond to GNSS signal disconnection according to the international situation. In response, in this paper, Code-Division Multiple Access (CDMA) based All-to-All TWSTFT operation method is proposed. A software-based simulation platform also was designed for performance analysis in multi-TWSTFT signal environments. Furthermore, code and carrier measurement jitters were calculated in multi-signal environments using the designed simulation platform. By using the technique proposed in this paper, it is anticipated that the TWSTFT-based time comparison method will be used in various fields and satisfy high-performance requirements such as those of a GNSS master station and power plant network reference station.

• 조명전기설비학회논문지
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• 제24권4호
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• pp.156-165
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• 2010

본 논문에서는 토로이달 타입 SRM(switched reluctance motor)과 일반적인 SRM의 특성에 대해 비교 연구하였다. TSRM(toroidal SRM)은 CSRM(conventional SRM)과는 다르게 권선이 고정자의 돌극이 아닌 요크에 감겨있는 형태로 되어 있다. 따라서 TSRM은 구조뿐만 아니라 구동회로, 구동방법, 전류, 유기전압, 쇄교자속 등이 CSRM과는 다른 특성을 갖는다. 본 논문에서는 TSRM과 CSRM을 이론적으로 비교하고 시뮬레이션을 통하여 각각의 구동 특성을 분석하여 비교하였다.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.761-768
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• 2019

Understanding the phenomena of formation of single drops is necessary to understand the hydrodynamics in solvent extraction equipment which are used for separation of nuclear materials. In this work, the phenomena of aqueous phase and organic phase drop formation at submerged nozzles are compared by conducting experiments with 30%TBP (v/v) in dodecane as the organic phase and nitric acid as the aqueous phase. Two different nozzles and three different nitric acid concentrations are used. For each nozzle and nitric acid concentration, velocity of the dispersed phase is varied. Drops of aqueous phase formed at downward oriented nozzles submerged in organic phase are observed to be smaller than the drops of organic phase formed at upward oriented nozzles submerged in aqueous phase. Correlations to estimate drop diameter are proposed.