• Journal of Korean Society of Water and Wastewater
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• v.27 no.5
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• pp.611-619
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• 2013

In this study, Back Tracing Calculation Method was developed to determine the leakage location and leakage amount. Previously developed determination method of monitoring location and newly developed Back Tracing Calculation Method were applied to the sample pipe network and real size pilot plant. After leakage was assumed in the pilot plant, leakage location and leakage amount could be traced by Back Tracing Calculation Method. From the results, it was found that Back Tracing Calculation Method can be applied for the leakage detection in water distribution system. Furthermore, this method can be applied for the pressure management or leakage detection as a pressure control method in water distribution system.

• Journal of Korea Water Resources Association
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• v.50 no.9
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• pp.609-616
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• 2017

In this study, algorithm for the selecting the optimum monitoring location and leakage detection algorithm based on back tracing calculation method were developed and verified by the experiments in pilot plant of water distribution system. First of all, optimum monitoring locations were selected and pressure changes were measured due to artificial leakage by pressure gauges in pilot plant. Simulations of leakage detection was performed for the verification of back tracing calculation method as a leakage detection method. From the results, it was found that leakage locations and leakage amount were exactly estimated. Various leakage amount from $0.0005m^3/s$ to $0.0018m^3/s$ were reproduced and leakage location was detected by back tracing calculation method. It was verified that back tracing calculation method as a leakage detection method is effective.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1883-1890
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• 2017

Transformers are one of the most precious elements of the electric power system. Stability and reliability of the electric power network mainly depend on the working of the transformer. Leakage reactance of the transformer is one of the important factors and accurate calculation of the leakage reactance is necessary for the transformer designers and electric distributors. Leakage reactance of the transformer depends on the geometry of the transformer. There are many different methods for the calculations of the leakage reactance however mostly are usable when the axial heights of the high voltage and low voltage windings are equal. When the axial heights of high voltage and low voltage windings are asymmetric most of the analytical methods are not reliable. In this study, a new analytical method is introduced for the calculation of the leakage reactance. Fourteen different transformers are investigated in this study and four of them are presented in this paper. The results of the new analytical method are compared with the experimental results. Other analytical and numerical methods are also compared with this new method. Results show that this method is more reliable and accurate as compared to the other analytical methods. The maximum relative error between short-circuit test and proposed method for these fourteen transformers was less than 2.8%.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.735-745
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• 2004

A linear cascade of NACA 65-1810 profiles are investigated for tip leakage flow characteristics. and calculation results are compared with experimental result. STAR-CD commercial code was used to solve the three dimensional incompressible Navier-Stokes equation that was adopted for steady flow and high Reynolds $\kappa$- $\varepsilon$turbulent model. Numerical calculation of a linear cascade is carried out to investigate effect of tip clearance on pitchwise variations of velocity Profiles. and static pressure distributions on the blade surface at spanwise positions. In case of evolution of tip vortex core location. tip vortex geometry and static pressure at the center of the tip vortex core compared with experimental results. Calculation results are agreed well with the experimental data, and validated. The static pressure losses by tip leakage flow at 2% tip clearance were more than those at 1% tip clearance.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.230-235
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• 2017

When the characteristics of a linear induction motor (LIM) are analyzed using finite element analysis (FEA), it is desirable to set the voltage source as an input. If the voltage source is set as an input in FEA, the leakage inductance and primary resistance of the equivalent circuit must be entered by direct calculation, and the magnetizing inductance and secondary reaction effects are directly considered in FEA. Exact calculation is necessary because the primary winding resistance and leakage inductance directly entered will have a significant effect on the LIM output. Therefore, in this study, we accurately calculated the primary leakage inductance and analyzed the resulting LIM characteristics. We calculated the leakage inductance using an analytical equation and FEA, and we confirmed the accuracy by comparing the results with the value experimentally calculated using a manufactured model. We also analyzed the instrument performance and thrust of the LIM as a function of the difference in the leakage inductance. Finally, we present the conclusions on the precise analysis based on the calculation of the leakage inductance.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.121-133
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• 2021

This study set up the estimates of leakage management efficiency evaluation and leakage management goal that could be used in local water distribution networks efficiency business and modernization business. The data were analyzed using data envelopment analysis and multiple regression analysis. To this end, with leakage management input indices concerning leakage reduction activities (e.g., aged pipe replacement, water meter replacement, leakage restoration, and leakage detection) and leakage management calculation indices (e.g., the increase of revenue water ratio and the reduction of leakage ratio), the data on 22 K-water consignment local water supply systems were analyzed for the years from 2004 through 2018. Using the results of efficiency analysis by data envelopment analysis, the other DMUs (Decision Making Unit) benchmarked the DMU with the highest efficiency to maximize the leakage management efficiency for all DMUs. Through this, leakage management goal estimates were drawn with the input indices of four leakage reduction activities and calculation indices of the increase of revenue water ratio and the reduction of leakage ratio by multiple regression analysis for each group based on the revenue water ratio and leakage ratio. The correlation coefficients of the leakage management goal estimate for the criteria for the revenue water ratio amounted to 0.553 and 0.771. The correlation coefficients of the leakage management goal estimate for the criteria for leakage ratio were 0.397 and 0.865. Accordingly, we estimated the quantity and priority of four leakage reduction activities for the target leakage ratio and revenue water ratio.

• Journal of Magnetics
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• v.19 no.1
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• pp.37-42
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• 2014

The equivalent model of a permanent magnet (PM) plays an important role in electromagnetic system calculation. A type of subsection model for a PM bar is established, to improve the accuracy of the traditional equivalent circuit method. The mathematical expression, and its end verification condition, are presented. Based on the analytical method and finite element method, the leakage permeance calculation of a PM bar in an open magnetic circuit is investigated. As an example, for a given certain type of PM bar, the magnetic flux of each section is validated by experiment, and by simulation. This model offers a foundation for building a high accuracy equivalent magnetic PM model in an electromagnetic system.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.18-20
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• 1995

In this paper we presented a calculation method of leakage inductance in electrical machines. For its accurate calculation the finite element method is applied to the analysis of magnetic field distribution. The self and mutual inductances are derived using the results of the magnetic field analysis and the leakage inductance is easily obtained from these inductances. As numerical examples, we tread a single phase transformer and a rotor slot model of induction motor. In the finite element analysis we used the 2D linear magnetostatic formulation with the first-order triangular element.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.232-238
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• 2001

Fast Fourier Transformation is employed to convert the head variation of a pipeline in the time domain to the amplitude of the frequency domain. Applying method of characteristics to a pipeline provides a significant frequency range for a surge introduced from the valve modulation. Inverse Fast Fourier Transformation and a Finite Impulse Response Filter can be used to remove any possible noise existing from the significant frequency range of an unsteady condition. A filtered signal shows higher potential for the inverse calculation of leakage detection than the noise-added signal does. The respective performances of Inverse Fast Fourier Transformation and a Finite Impulse Response Filter are compared in terms of leakage detection capability. Characteristics of the frequency range for multiple leakages were investigated to validate the effectiveness of the noise control method in the frequency domain.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.40-46
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• 1998

Leakage phenomena of flip-chip structures on common GaAs and alumina main substrates are characterized using the spectral domain approach to reduce the possible chip-to-chip crosstald and transmission resonance. We have found taht the longitudinal section magnetic mode is dominant for the coplanar waveguide leakage andthe leakage can be suppreassed by properly managing the gap height and the main substrate thickness in addition to the dielectric constant. These calculation results will be helpful for designing and flip-chip packagaing of high-frequency integrated circuits.