• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.42-49
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• 2016

Aerodynamic analysis of a low-voltage electric motor has been performed with various inlet vent shapes. Effects of inlet vent shape on aerodynamic performance of a motor cooling fan have been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The k-${\varepsilon}$ turbulence model was used for the analysis of turbulence. The finite volume method and unstructured tetrahedral grids were used in the numerical analysis. Optimal grid system in the computational domain was selected through a grid-dependency test. From the results of the flow analysis, considerable energy loss by flow separation was observed in the flow passage. It was found that mass flow rate through the cooling fan in the low-voltage motor can be increased by modifying the inlet vent shape. And, some inlet vent shapes were suggested to improve the aerodynamic performance of the motor cooling fan.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2139-2144
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• 2008

There are eight kinds of railroad vehicles such as KTX, PP(Push-Pull), NEL(New Electric Locomotive), EL(Electric Locomotive), DL(Diesel Locomotive), CDC(Commuter's Diesel Car), VVVF(Variable Voltage Variable Frequency) and Resistance Control Car that Korail corporation presently runs, and a variety of vehicles just like EMU(Electric Multiple Unit) and DMU(Diesel Multiple Unit) currently developed and accepted are running in the near future. However, There is still no design standard of the control stand of cockpit and the same compatibility of forms and control unit arrangements for locomotive engineers because no one has tried to approach in an ergonomic way. It can cause Locomotive engineers to make errors using the machinery. when the new vehicles are adopted, The efficiency of operation will quite fall down due to the separate training of the engineers. Therefore, We'd like to improve the accuracy of manipulating the machinery used by the engineers at all times according to the design standard of ergonomic technology and safety engineering and increase the operational efficiency and the safety of railroad vehicles in order to handle the problems as quickly as we can in an emergent situation.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.3
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• pp.174-183
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• 1997

Turbine rotor disc consists of disc, bore, keyway, hub, and rim in which the typical defects are located. And these part of disc has very complicated geometry, therefore proper transducer selection, wedge design, fabrication, classification and evaluation of the signal identification are required. In this research, test block with the artificial flaws at keyway and boresurface parts have been used in order to establish the ultrasonic inspection technique for flaw detectability on disc. The analysis of the signals from the test blocks was performed. The wedges were designed according to the curvature from the discs. All the ultrasonic signals were collected and identified for evaluation. The ultrasonic inspection technique for the flaw-detection was established from this research. And it is proved that the result of this research can be applicable in the field inspection.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.17-17
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• 2017

In electric agricultural machine the gearhead is needed to convert the high speed low torque rotation motion generated by DC motor to lower speed high torque motion used by the vehicle. The gearhead consist of several spur gears works as reduction gears. Spur gear have straight tooth and are parallel to the axis of the wheel. Spur gears are the most easily visualized gears that transmit motion between two parallel shafts and easy to produce. The modeling and simulation of spur gears in DC motor gearhead is important to predict the actual motion behavior. A pair of spur gear tooth in action is generally subjected to two types of cyclic stress: contact stress and bending stress including bending fatigue. The stress may not attain their maximum values at the same point of contact fatigue. These types of failure can be minimized by analysis of the problem during the design stage and creating proper tooth surface profile with proper manufacturing methods. To improve its life expectation in this study modal and stress analysis of gearhead is simulated using ansys work bench software based on finite element method (FEM). The modal analysis was done to understand gearhead deformation behaviour when vibration occurs. FEM static stress analysis is also simulated on gearhead to simulate the gear teeth bending stress and contact stress behavior. This methodology serves as an approach for gearhead design evaluation, and the study of gear stress behavior in DC motor gearhead which is needed in the small workshop scale industries.

• 연구논문집
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• s.30
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• pp.93-99
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• 2000

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. The electrical and rheological properties of zeolite based the ER fluids were reported. The electric field dependent yield stress are obtained from experimental investigation on the Bingham property of the ER fluid. Using ER fluids, it is possible to directly interface between electric drop and flow rate of the ER fluid was hydraulic control valve measured under application of an electric field. The purpose of the present study is pressure drop measurement of an ER valve by using strain gage. The performance characteristics of the valve system are evalusted in terms of pressrue fixed with respect to the intensity of employed electric fields and flow rates. As a result, it is esperimentally confirmed that pressure control valve using ER fluids applicable to use in hydraulic power systems.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.3-8
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• 1998

The industrial revolution in England was based on the manufacturing systems by the power of water mill and rapidly progressed by the innovation of steam engine. It is no exaggeration to say that today's civilization is realized by the development of various types of power machinery, namely fluid machinery and heat engine. The electric energy is converted mainly from thermal energy (mainly steam) of mineral oil, coal and nuclear fuel through generator connected with steam turbine which is a kind of power machinery. There are various types of power machinery as shown in Tables 1a and 1b. They are classified into two types by use. One is absorption type of fluid and/or thermal energy, for examples, windmill and heat engine. The other is provision type of the energies for examples, pump, compressor and propulsion. By flow type, they are also classified by two types, turbo type and positive-displacement type. The turbo type began from water mill and windmill and evolve to steam turbine and finally to gas turbine. The positive-displacement type started from reciprocating water pump and developed into steam engine and changed to reciprocating combustion engine. The pumps and motors used in oil hydraulic system for power control are also positive-displacement type.

• Journal of Drive and Control
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• v.19 no.3
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• pp.32-38
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• 2022

The in-wheel drive gearbox for military special vehicles converts the high-speed & low-torque output generated by the electric servomotor, into low-speed & high-torque mechanical power. As the vehicle is remotely maneuvered in mountainous terrain, wet fields, rough terrain, etc., the gearbox must generate a maximum input speed exceeding 5,000 rpm, a maximum torque of 245 Nm, and MTBF of 9,600 km. The purpose of this study was to analyze the failure mode of the gearbox, to ensure the durability of the in-wheel drive gearbox. Also, the field load test data of the vehicle was analyzed, the acceleration durability test standards were established, the acceleration durability test was conducted, and the durability test results were analyzed as well.

• Journal of Biosystems Engineering
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• v.26 no.2
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• pp.177-188
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• 2001

This research was carried out to examine the optimum design conditions of a vertical small-scale milling machine where the rough rice is processed directly into the white rice in one pass. Effects of the main spindle speed, feed screw pitch and ceramic coating length of the roller on various milling characteristics such as white rice processing capacity, electric energy consumption, rice temperature increase, broken rice ratio, moisture reduction, outlet force and crack ratio increase were studied. The results are as follows. 1. The maximum white rice processing capacity and the lowest crack ratio increase, were obtained from a machine with specification: main spindle speed of 970rpm having a feed screw pitch of 19㎜. 2. The minimum electric energy consumption was obtained with the main spindle speeds of 900 and 970rpm respectively having a feed screw pitch of 19㎜. 3. The rice temperature was increased as the feed screw pitch decreased and the main spindle speed increased. 4. Broken rice ratio was relatively low with the range of 0.8∼1.3%. 5. Moisture content loss was with the range of 0.05∼0.4%. 6. The highest outlet force was 0.72kg$\_$f/ with 900rpm of the main spindle speed and 19㎜ of the feed screw pitch and the lowest outlet force was 0.18∼0.34kg$\_$f/ with 970rpm of the main spindle speed and 16㎜ of the feed screw pitch. 7. The optimum design conditions for the vertical small-scale milling machine were obtained at 970rpm of the main spindle speed, 19㎜ of the feed screw pitch and 20㎜ of the ceramics coating length.

• Elastomers and Composites
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• v.44 no.2
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• pp.98-105
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• 2009

The cochlea of the inner ear has two core components, basilar membrane and hair cells. The basilar membrane disperses incoming sound waves by their frequencies. The hair cells are on the basilar membrane, and they are the sensory receptors generating bioelectric signals. In this paper, a biomimetic technology using ZnO piezoelectric nano-pillar was studied as the part of developing process for artificial cochlea and novel artificial mechanosensory system mimicking human auditory senses. In particular, ZnO piezoelectric nano-pillar was fabricated by both low and high temperature growth methods. ZnO piezoelectric nano-pillars were grown on solid (high temperature growth) and flexible (low temperature growth) substrates. The substrates were patterned prior to ZnO nano-pillar growth so that we can selectively grow ZnO nano-pillar on the substrates. A multi-physical simulation was also conducted to understand the behavior of ZnO nano-pillar. The simulation results show electric potential, von Mises stress, and deformation in the ZnO nano-pillar. Both the experimental and computational works help characterize and optimize ZnO nano-pillar.