• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.108-117
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• 2010

The main contents of this paper are the PQM system construction case and distribution system harmonic voltage analysis. The PQM system has constructed by KEPCO in order to investigate power quality of distribution power system for new power quality standard of KEPCO. In result, we have confirmed that voltage harmonic measurement value of the high voltage contract customer 8 households is suitable the KEPCO harmonic standard tentative plan. And the voltage harmonic value of distribution line end side is not always more high than source side by harmonic current offset effect. In the future, acquired data by season, region, load from the PQMS will be used on the resonable harmonic standard enactment in KEPCO.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.2
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• pp.244-249
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• 2000

Thermal gradient chemical vapor infiltration (TG-CVI) process, which is one of the CVI techniques to densify a porous fiber preform, requires for a heater to have uniform surface temperature distribution. Thus, it is essential to design the shape of the heater and to predict the temperature distribution when the heater has a profile which is not a simple cylinder. In this study, an analytical method has been used to design the inner profile of a conical heater showing uniform temperature distribution, if its outer shape is specified. Temperature distribution on the heater surface has been calculated with the finite difference method and compared with the experimental results. When a heater had a combined profile with a large cone and a small cylinder, temperature was higher in the cylindrical part. To reduce the temperature difference between these areas, a hole-machining method has been proposed including other possible ones. A shape design and optimization program has been made to improve the temperature uniformity of the TG-CVI heater better than that designed with the analytical method.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.262-270
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• 2013

A boundary protection method for power distribution line based on equivalent boundary effect is presented in this paper. In the proposed scheme, the equivalent resonance component with a certain central frequency is sleeve-mounted at the beginning of protected zone. The 'Line Boundary' is built by using boundary effect, which is created by introducing impedance in the primary-side of line. The 'Line Boundary' is significantly different from line wave impedance. Therefore, the boundary protection principle can be applied to power distribution line without line traps. To analyze the frequency characteristic corresponding to traveling-waves of introducing impedance in the primary-side of line, distributed parameters model of equivalent resonance component is established. The results of PSCAD/EMTDC simulation prove the obvious difference of voltage high frequency component between internal faults and external faults due to equivalent resonance component, and validate the scheme.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1403-1411
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• 2012

In this paper, we have evaluated theoretically the PEA method which is the most popular methods for the non-destructive measurement of space charge distribution in polymer dielectric materials and is recently one of big issues in DC high voltage cables. On the basis of theoretical evaluation, we have developed the space charge measurement system in polymer dielectrics under DC appled voltage and improved the accuracy of space charge distribution by applying the deconvolution process for distorted signals.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1563-1571
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• 2001

The effect of flow distribution on thermal and flow performance of a parallel flow heat exchanger has been numerically investigated. The flow distribution has been altered by varying the geometrica l parameters that included the locations of the separators, and the inlet/outlet of the heat exchanger. Flow nonuniformities along paths of the heat exchanger, which were believed to be dominantly influential to the thermal performance, have been observed to eventually optimize the design of the heat exchanger. The optimization has been accomplished by minimizing the flow nonuniformity that served as an object function when the Newton's searching method was applied. It was found that the heat transfer of the optimized model increased approximately 7.6%, and the pressure drop decreased 4.7%, compared to those of the base model of the heat exchanger.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.4
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• pp.130-136
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• 2008

The refrigerant R-134a flow distributions are experimentally studied for a round header/ten flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet orientations(parallel, normal, vertical) were investigated. Tests were conducted with downward flow for the mass flux from 70 to 130 $kg/m^2s$ and quality from 0.2 to 0.6. In the test section, tubes were flush-mounted with no protrusion into the header. It is shown that normal and vertical inlet yielded approximately similar flow distribution. At high mass fluxes or high qualities, however, slightly better results were obtained for normal inlet configuration. The flow distribution was worst for the parallel inlet configuration. Possible explanation is provided based on flow visualization results.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.69-76
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• 1991

A design method based on the surface vorticity distribution is developed to generate a two-dimensional blade section for prescribed velocity distribution in potential flow. The boundary condition used to determine the strength of vorticity distribution requires that the surface of blade section should be a streamline of the resulting flow. In order to obtain the required final geometry of a two-dimensional blade section, an iterative procedure is used. A computer program is developed and several numerical results are presented.

• Journal of Magnetics
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• v.6 no.3
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• pp.101-107
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• 2001

A model to describe the effect of stator slotting in the airgap region of a linear brushless permanent magnet motor (LBLPMM) is proposed for analytical prediction of magnetic field distribution. It is a two-dimensional model based on superposition of the effect of stator slotting and main field due to permanent magnet (PM) without stator slotting. The effect of stator slotting is expressed in form of a generalized equation, which is obtained by numerical analysis and is a function of motor geometric parameters, so the proposed model effectively accounts for the effect of stator slotting in the airgap field distribution according to change of motor geometry or relative motion of stator and armature. Results of prediction from the proposed model are compared with corresponding finite element analysis.

• Journal of Magnetics
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• v.15 no.4
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• pp.190-193
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• 2010

The design of joints in a transformer core significantly affects the transformer's efficiency. Air gaps cause variations in the flux distribution at the joints of the laminations, which depend on the geometry. Two similar samples consisting of electrical steel strips and amorphous ribbons were made. The spatial flux distributions were determined using an array of search coils for each sample. 2D models of these samples were created and examined by finite element analysis. The magnetic flux distribution for each lamination in the samples was computed. The results show that the flux density in amorphous ribbons above and below the air gap starts to approach saturation at lower flux density levels than for electrical steel. The flux density measured using the search coil under the air gap is increased in amorphous ribbons and decreased in the electrical steel with increasing frequency.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.225-234
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• 2011

In the fields of reliability application, the most commonly used test methods for reliability qualification are zero-failure acceptance tests since they require fewer test samples and less test time compared to other test methods that guarantee the same reliability with a given confidence level. Usually values of shape parameters are assumed to be known in designing reliability qualification tests for Weibull lifetime distribution. It is important to select correct values of shape parameters to guarantee the specified reliability with given confidence level exactly. The effect of using wrong values of shape parameters in designing reliability qualification test for products with Weibull lifetime distribution is examined and selecting proper values of shape parameters for conservative reliability qualification is discussed.