• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.348-352
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• 2004

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and ow loss, but it needs some cooling method because heat radiation between each winding is difficult. The life of transformer is significantly dependent on the thermal behavior in windings. Many transformer designers have calculated temperature distribution and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, The thermal analysis of pole mount mold transformer with one body molding by duct condition is investigated and the test result of temperature rise is compared with simulation data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1154-1159
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• 2006

The mold transformers have been widely used in underground substations of large building and have some advantages when compared with oil-transformer. Those advantages are low fire risk, environmental compatibility, compact size and high reliability. The mold transformer is generally known to have cooling duct between low voltage and high voltage coil. To achieve better compact structure and low loss, mold transformers made by one body molding method has been developed. Nevertheless, such kinds of transformer need better cooling method because heat radiation between each winding is still of problem. The life of transformer is significantly dependent on the thermal behavior in windings. Many designers have calculated temperature distribution in transformers and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, the temperature distribution analysis of 100 kVA pole mold transformer for power distribution were investigated by FEM program and the thermal analysis results were compared with temperature rise test.

• Advanced Composite Materials
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• v.18 no.2
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• pp.153-166
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• 2009

A matrix method for evaluating effective electro-magneto-thermo-elastic properties of a generally anisotropic multilayered composite is presented. Physical variables are categorized into two groups: one that satisfies the continuity across the interface between layers and another that satisfies an average inter-layer compatibility (which is also exact). The coupled electro-magneto-thermo-elastic constitutive equation is accordingly reassembled into submatrices, which leads to the derivation of concise and exact matrix expressions for effective properties of a multilayered composite having the coupled physical effects. Comparing the results for a purely elastic multiplayer with those from other theoretical approaches validates the developed method. Examples are given for a PZT-graphite/epoxy composite and a $BaTiO_3-CoFe_2O_4$ multiplayer which exhibit piezo-thermoelastic and magnetoelectric properties, respectively. The result shows how a strong magnetoelectric effect can be achieved by combining piezoelectric and piezomagnetic materials in a multilayered structure. The magnetoelectric coefficient of the $BaTiO_3-CoFe_2O_4$ multiplayer is compared with those for fibrous and particulate composites fabricated with the same constituents.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.392-397
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• 2014

Recently, there is an increase in the need for precision linear stages with vacuum compatibility in such areas as lithography equipment for wafer or mask manufacturing, mask mastering equipment for optical data storage and electron beam equipment. A simple design, high stiffness and low cost can be achieved by using ball bearings. However, a ball bearing have friction and wear problems just as in ambient air. In order to decrease the friction, a special finish, a diamond-like carbon (DLC) film coating, is applied to the surface of a guide rail by sputtering deposition. This paper presents the result of an experimental investigation on the control performance of a ball bearing-guided linear motion stage under two environmental conditions: in air and vacuum. A comparison between the results with and without the DLC coating was also considered in the experimental investigation.

• Structural Engineering and Mechanics
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• v.16 no.2
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• pp.127-139
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• 2003

Reinforced concrete buildings with shearwalls are very efficient to resist earthquake disturbances. In general, reinforced concrete frames are governed by flexure and shearwalls are governed by shear. If a structure included both frames and shearwalls, it is generally governed by shearwalls. However, the ductility of ordinary reinforced concrete is very limited. To improve the ductility, a series of tests on framed shearwalls made of corrugated steel was performed previously and the experimental results were compared with ordinary reinforced concrete frames and shearwalls. It was found that ductility of framed shearwalls could be greatly improved if the thickness of the corrugated steel wall is appropriate to the surrounding reinforced concrete frame. In this paper, an analytical model is developed to predict the horizontal load-displacement relationship of hybrid reinforced concrete frame-steel wall systems according to the analogy of truss models. This analytical model is based on equilibrium and compatibility conditions as well as constitutive laws of corrugated steel. The analytical predictions are compared with the results of tests reported in the previous paper. It is found that proposed analytical model can predict the test results with acceptable accuracy.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.152-158
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• 2003

Stromata of the white root rot fungus, Rosellinia necatrix, were produced on diseased roots although they were reported to develop rarely in nature. Forty-two (42) out of 47 samples produced synnemata while 23 developed stromata. Forty-seven (47) isolates obtained from diseased root samples were divided into 24 mycelium compatibility groups (MCGs). Sixteen (16) out of 24 MCGs produced stromata. Single ascospore isolates from 10 stroma samples produced dsRNA-containing isolates from diseased tissue beneath stromata. The frequency of synnema production on axenic culture varied among isolates with different origin. The dsRNA was not transmitted vertically to the ascospore offspring despite the infection of various dsRNA in the parental isolates. The dsRNA was absent in 35 ascospore isolates in two stroma samples that originated from the isolates, in which dsRNA was not eliminated by hyphal tip isolation. Consequently, sexual reproduction in the white root rot fungus was suggested to produce propagules as a new infection source and to have the function to eliminate infectious factors such as mycoviruses.

• Structural Engineering and Mechanics
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• v.30 no.2
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• pp.165-176
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• 2008

In this paper, a new iterative method for solving vehicle-bridge interaction problems is proposed. Iterative methods have advantages over the non-iterative methods in that it is not necessary to update the system matrix for a given wheel location, and the method can be applied for a new type of car or bridge with few or no modifications. In the proposed method, the necessity of system matrices update is eliminated using the equivalent interaction force acting on the bridge, which is obtained iteratively. Ballast stiffness is included in the interaction forces and the geometric compatibility at the contact points are used as convergence criteria. The bridge is considered as an elastic Bernoulli-Euler beam with surface irregularity and ballast stiffness. The moving vehicle is modeled as a multi-axle mass-spring-damper system having many degrees of freedom depending on the number of axles. The pitching effect, which is the interaction effect between the rear and front wheels when a vehicle begins to enter or leave the bridge, is also considered in the formulation including extended ground boundaries having surface irregularity and ballast stiffness. The applicability of the proposed method is illustrated in the numerical studies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.132-137
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.116-123
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• 2002

This paper describes the development of gimbals engine actuation system for KSR(Korean Sounding Rocket)-III which performs the attitude control of pitch and yaw axes by thrust vector control of liquid propellant gimbals engine. The development requirements of configuration, performance and environment are introduced, and the principles and details of components and system development are discussed. The developed system successfully fulfilled its own performance and environmental evaluation. It will be planned to perform verification of interface and integration compatibility with other related systems, and then mounted on KSR-III as a flight hardware system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.484-487
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. In this paper, the proto type mold transformer of 50kVA class is investigated by routine, type, special test. The outdoor energized aging test is investigated by back-to-back method to verify the long time performance of pole mold transformer. The aging process of transformer is analyzed by various diagnosis method such as DC voltage-current test, $tan{\delta}$, Meggar measurement, winding temperature and etc.