• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.397-404
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• 2008

Excessive amount of groundwater flowed into tunnel, while constructing Incheon international airport railway. Tunnel passes under subway line no. 2 with only 1.76 m below. To protect the existing structure, TRcM excavation method was applied. As station and construction shaft are already constructed, which are located back and forth of TRcM section, 86.4 ton per day of groundwater inflow is against expectation. To identify mechanism of excessive water inflow, hydraulic back analyses were performed. Then, hydro-mechanical coupled analysis were also performed with the hydrogeologic parameters identified, whose results are investigated for checking the stability of adjacent structures to the tunnel under construction. And a number of mechanical analyses were also performed to check the hydro-mechanical coupling effect. The result from the mechanical analysis shows that subsidence and tunnel ceiling displacement will be 0.85 mm and 1.32 mm. The result of hydro-mechanical couple analysis shows that subsidence and maximum tunnel ceiling displacement will be 1.2 mm and 1.72 mm. Additional displacements caused by groundwater draw down were identified, however, displacement is minute.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.9
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• pp.465-471
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• 2006

In this paper, a synchronous permanent magnet planar motor (SPMPM) with Halbach array is proposed. First, we give the equations of the magnetic scalar potential and a series of boundary conditions. The magnetization and flux density distribution of Halbach array are obtained by analytical method; then, the characteristics of this SPMPM such as inductance, back-EMF, and thrust are evaluated. At last, the experiment results are used to verify the analysis property of this SPMPM. By comparison, it can be concluded that the analysis of SPMPM with Halbach magnet array is credible and feasible.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.6-8
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• 2004

Recently, it is increasing to use more Brushless DC Motor with high energy density permanent magnet and semiconductor control unit for complementing the mechanical defect of Brushed DC Motors. For designing of BLDC Motors are required complex parameters like as rated characteristic, Geometries, B-H curve of magnet and steel materials, winding factor, etc. Moreover, design and manufacturing are difficult because of additional control circuits. Generally, Design parameters are gotten by analysis of Motor which is used. And the design parameters are used to design a new motor. But getting the design parameters through the eyes and experience is limited and it takes a long time. In this paper a method is proposed to efficiently analyze motor design parameters through the No load and Load Test, Back EMF Test, Simulation Analysis and Patent Analysis Method for existing BLDC Motor for a cooling Fan in Vehicle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.44-49
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• 2008

The characteristic of magnesium alloy is the most light in utility metal, the effect of electromagnetic wave interception, excellent specific strength and absorptiveness of vibration. Although magnesium alloy with above characteristic is a subject matter which is suitable in world-wide tendency of electrical component frame, sheet magnesium alloy is difficult to process. Therefore, forming analysis of sheet magnesium alloy and applying warm-working to process are indispensable. Among Finite element method, the static implicit finite element method is applied effectively to analyze sheet magnesium alloy stamping process, which include the forming stage. In this study, it was focused on the crack, wrinkling and spring back on sheet magnesium alloy stamping by the static implicit analysis. According to this study, the result of simulation will give engineers good information to access the forming technique on sheet magnesium alloy. And its application is being increased especially in the production of electrical component frame for the cost reduction, saving of defective ratio, and improvement of Productivity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1396-1404
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• 2012

A composite pile consisted of a concrete lower part with a steel tubular pile at upper part was installed by pre-drilling method. Seven pairs of strain gauges and inclinometer were attached on the pile in order to measure stresses and displacement along the pile during the lateral loading test. The results of instrumentation were analyzed using various theoretical approaches. The back analysis showed that the measured stresses were smaller than those of the calculated. The maximum stress is measured at the steel upper part and decreased rapidly with depth of the pile. The calculated lateral displacement along the pile provide very good agreement with the measured values if the coefficient of subgrade reaction is selected properly. The design concept of a composite pile is verified by the measured stresses and displacement which is within the tolerable limits of the pile.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.12
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• pp.718-724
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• 2004

This study investigates the design factors of Interior Permanent Magnet Synchronous Motor(IPMSM) which is applied to Hybrid electric vehicle as a driving power. Recently, there are many studies of IPMSM for application to Hybrid Electric Vehicle, because IPMSM has characteristics of high torque, high power density and high efficiency which come from reluctance torque due to difference of inductance as well as magnet torque. This study analyzes the inductance and design characteristics of IPMSM by using finite element method and focuses on design and analysis of IPMSM which can operates with high efficiency at low speed range. For this embodiment, magnet shape is changed from conventional block type to arc type without any change of outline dimension of motor and this change of magnet shape makes it possible to increase back EMF and sinusoidal waveform. Analysis results are verified by test of improved and embodied motor. As a test result , increased back EMF and sharply decrease of harmonics are secured and through this contribution of reduced fuel consumption of Hybrid electric vehicle is expected.

• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.18-23
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• 2011

A CFD analysis method is developed and applied for investigating the gas flow and the byproduct particle trajectory in Roots type vacuum pump. The internal fluid flow and thermal fields between the rotors and the housing of vacuum pump are analyzed by using the dynamic mesh, the numerical methods for unsteady 2-D Navier-Stokes equation and the standard k-$\varepsilon$ turbulence model of the Fluent code. Coupled with the flow simulation results, the particle trajectory of the byproduct flowing into the pump with gas stream is analyzed by using discrete phase modeling technique. The CFD analysis results show the pressure, the velocity and the temperature distributions in pump change abruptly due to the rotation of rotors, and back flows are produced due to the strong reverse pressure gradients at rotor/rotor and rotor/housing clearances. The predicted byproduct particle trajectory results also show the particles impinge on the clearance surfaces between the housing and the rotor of pump and then may form the deposit layer causing the failure of pump.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.9
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• pp.434-441
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• 2003

This paper deals with the temperature characteristics according to the cooling medium and the duct size in model transformers. For the analysis and the temperature-rise tests, two 400kVA model transformers have been manufactured. One has been filled with the alpha oil as the cooling medium and constructed the duct sizes of $3\textrm{mm}$ and $5\textrm{mm}$ in the low-voltage and high-voltage windings respectively. The other has been filled the beta oil and the duct sizes were $4\textrm{mm}$ and $6\textrm{mm}$. The temperature-rise tests have been performed by the back-to-back method and the load factor has been controlled the range of 90%∼130%. The temperature values have been measured by the thermocouple and from the sixteen points in each transformer. A commercial CFD program "FLUENT" has been used for the analysis of temperature distribution. The geometry of transformer has been modeled to 3-dimensional by using the hybrid calculation mesh including the radiator. And also, the natural convection velocity has been measured at the oil top position, and compared with the calculated results.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.26-31
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• 2014

In this paper, we present performance analysis of video smoke detection based on BPN-Network that is using multi-smoke feature, and Neural Network. Conventional smoke detection method consist of simple or mixed functions using color, temporal, spatial characteristics. However, most of all, they don't consider the early fire conditions. In this paper, we analysis the smoke color and motion characteristics, and revised distinguish the candidate smoke region. Smoke diffusion, transparency and shape features are used for detection stage. Then it apply the BPN-Network (Back-Propagation Neural Network). The simulation results showed 91.31% accuracy and 2.62% of false detection rate.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.601-613
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• 2007

It is reported that factors affecting the behavior of reinforced earth retaining walls built on soft ground are not only basic physical properties but also the increase of load by the reinforced earth retaining walls, consolidation period, pore water pressure, etc. This study analyzed the behavior of reinforced earth retaining walls and soft ground using SAGE CRISP, a ground analysis program. First, we examined the effect of the replacement method, which was to prevent the excessive displacement of reinforced earth retaining walls, in improving the behavior of the walls. Second, we compared and analyzed how the behavior of ground is affected by the vertical interval of stiffeners on the back of reinforced earth retaining walls after the application of the replacement method. Lastly, we proposed the optimal replacement width and depth in the application of the replacement method. The results of this study proved that the replacement method is considerably effective in improving the behavior of reinforced earth retaining walls. In addition, the vertical interval of stiffeners on the back of reinforced earth retaining walls appeared effective in improving the horizontal displacement of the top of retaining walls but not much effective in improving the vertical displacement of the back of retaining walls. In addition, improvement in horizontal-vertical displacement resulting from the increase in replacement width was not significant and this suggests that the increase of replacement width is not necessary. With regard to an adequate replacement depth, we proposed the ratio of replacement depth to the height of retaining walls(D/H) according to the ratio of the thickness of the soft layer to the height of retaining walls(H/T).