• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.52-60
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• 2009

High reliability is essential for power transformers, and their fault causes are reportedly more related to mechanical causes than electrical ones. The transformer soundness judgment currently depends only on the electrical insulation characteristic and the chemical test of the insulation oil, so that there are few fundamental measures against the frequent mechanical damages and failures in transformers. The mechanical soundness judgment techniques are conducted through processes that include structural analysis and vibration resistance treatment during the manufacturing process of each manufacturer, but the vibration is not tested during the design, manufacturing, and operating processes since there are no detailed technical standards and procedures on the vibration problem, which are important in terms of maintenance. Therefore, in this study, vibration phenomena were measured from the 32 power transformers in operation in the substations under the Daejeon Power Transmission District Office of the Korean Electric Power Corporation (KEPCO). The vibration was measured at 24 sections ($6{\times}4$) on one side, and only the maximum values were selected from the measured vibration values. This was because the maximum vibration values more significantly affect the soundness of the transformer than the average vibration values. The vibration classes were given considering the maximum vibration based on ISO 10016-1 (2001).

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.99-105
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• 2007

Currently, BLDC fuel pump was applied on LPi vehicle using 3rd fuel supply system as liquified phase LPG injection method had already shown better performance than others. Its cost, however, is rather expensive because of drawbacks such as complicated structure, a fault of localization of system. In this work, demonstration system for a developed turbine type fuel pump to replace BLDC system was setup and investigated. This study results that fuel mass flow rate of turbine type pump and injection performance of injector were better compared to BLDC type. Comparing flow rate of summer LPG with that of winter LPG, the flow rate decreased about 25% using winter LPG. Performance applying turbine type LPi fuel pump to engine is confirmed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.262-263
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• 2005

For mechanical and electrical stability and environment protection, Cu and stainless steel stabilizer is laminated to Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. this architecture allows the wire to meet operational requirements including stresses at cryogenic temperature, winding tensions, mechanical bending requirements thermal and electrical stability under fault conditions. we have experimentally studied mechanical properties of laminated stainless steel stabilizer on YBCO coated conductors. we have laminated YBCO coated conductors by continuous dipping soldering process. we have investigated lamination interface between solder and stabilizer, YBCO coated conductor. we evaluated bonding properties tensile / shear bonding strength, peeling strength laminated YBCO coated conductors.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.14-22
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• 2021

A plan for the development of reliability-based ROK amphibious assault vehicles is proposed. By analyzing the development case of the U.S. EFV, considerations for the successful development of the next-generation Korea Forces amphibious assault vehicle are presented. If the vehicle reliability can be improved to the level of the fourth highest priority electric unit for power units, suspensions, decelerators, and body groups, which have the highest priority among fault frequency items, a system level MTBF of 36.4%↑ can be achieved, and the operational availability can be increased by 3.5%↑. The next-generation amphibious assault vehicles must fulfill certain operating and performance requirements, the underlying systems must be built, and sequencing of the hybrid engine and the modular concept should be considered. Along with big-data- and machine-learning-based failure prediction, machine maintenance based on augmented reality/virtual reality and remote maintenance should be used to improve the ability to maintain combat readiness and reduce lifecycle costs.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.23-26
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• 2006

For mechanical and electrical stability and environment protection. Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature. winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties. tensile / shear bonding strength. and peeling strength laminated YBCO coated conductors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.169-177
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• 2017

In this paper, classification of spall and crack faults of gear teeth is studied by applying the ensemble empirical mode decomposition(EEMD) for the gear transmission error(TE). Finite element models of the gears with the two faults are built, and TE is obtained by simulation of the gears under loaded contact. EEMD is applied to the residuals of the TE which are the difference between the normal and faulty signal. From the result, the difference of spall and crack faults are clearly identified by the intrinsic mode functions(IMF). A simple test bed is installed to illustrate the approach, which consists of motor, brake and a pair of spur gears. Two gears are employed to obtain the TE for the normal, spalled, and cracked gears, and the type of the faults are separated by the same EEMD application process. In order to quantify the results, crest factors are applied to each IMF. Characteristics of spall and crack are well represented by the crest factors of the first and the third IMF, which are used as the feature signals. The classification is carried out using the Bayes decision theory using the feature signals acquired through the experiments.

• The Journal of the Petrological Society of Korea
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• v.28 no.3
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• pp.157-169
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• 2019

Pseudotachylytes, produced by frictional heating during seismic slip, provide information that is critical to understanding the physics of earthquakes. We report the results of occurrence, structural characteristics, scanning electron microscopic observation and geochemical analysis of pseudotachylytes, which is presumed to have formed after the Late Cretaceous in outcrops of the Paleoproterozoic granitic gneiss on the Bulil waterfall of the Jirisan area, Yeongnam massif, Korea. Fault rocks, which are the products of brittle deformation under the same shear stress regime in the study area, are classified as pseudotachylyte and foliated cataclasite. The occurrences of pseudotachylyte identified on the basis of thickness and morphology are fault vein-type and injection vein-type pseudotachylyte. A number of fault vein-type pseudotachylytes occur as thin (as thick as 2 cm) layers generated on the fault plane, and are cutting general foliation and sheared foliation developed in granitic gneiss. Smaller injection vein-type pseudotachylytes are found along the fault vein-type pseudotachylytes, and appear in a variety of shapes based on field occurrence and vein geometry. At a first glance fault vein-type seudotachylyte looks like a mafic vein, but it has a chemical composition almost identical to the wall rock of granitic gneiss. Also, it has many subrounded clasts which consist predominantly of quartz, feldspar, biotite and secondary minerals including clay minerals, calcite and glassy materials. Embayed clasts, phenocryst with reaction rim, oxide droplets, amygdules, and flow structures are also observed. All of these evidences indicate the pseudotachylyte formed due to frictional melting of the wall rock minerals during fault slip related to strong seismic faulting events in the shallow depth of low temperature-low pressure. Further studies will be conducted to determine the age and mechanical aspect of the pseudotachylyte formation.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.68-74
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• 2001

A lane detection based on a road model or feature all needs correct acquirement of information on the lane in an image. It is inefficient to implement a lane detection algorithm through the full range of an image when it is applied to a real road in real time because of the calculating time. This paper defines two (other proper terms including"modes") for detecting lanes on a road. First is searching mode that is searching the lane without any prior information of a road. Second is recognition mode, which is able to reduce the size and change the position of a searching range by predicting the position of a lane through the acquired information in a previous frame. It allows to extract accurately and efficiently the edge candidate points of a lane without any unnecessary searching. By means of inverse perspective transform which removes the perspective effect on the edge candidate points, we transform the edge candidate information in the Image Coordinate System(ICS) into the plan-view image in the World Coordinate System(WCS). We define a linear approximation filter and remove faulty edge candidate points by using it. This paper aims at approximating more correctly the lane of an actual road by applying the least-mean square method with the fault-removed edge information for curve fitting.e fitting.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.166-180
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• 2016

The present study numerically simulated the CO2 injection into the saline aquifer of CO2CRC Otway pilot project and the resulting hydrological-mechanical coupled process in the storage site by TOUGH-FLAC simulator. A three-dimensional numerical model was generated using the stochastic geological model which was established based on well log and core data. It was estimated that the CO2 injection of 30,000t over a period of 200 days increased the pressure near the injection point by 0.5 MPa at the most. The pressure increased rapidly and tended to approach a certain value at an early stage of the injection. The hydrological and mechanical behavior observed from the CO2 flow, effective stress change and stress-strength ratio revealed that the CO2 injection into the saline aquifer under the given condition would not have significant effects on the mechanical safety of the storage site and the hydrological state around the adjacent fault.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2011-2018
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• 2011

The paper demonstrates how to deal with the Near-field Acoustic Holography method (NAH) for reducing noise source which is generated in air-conditioning compressor. Sound radiation was measured for both normal compressor and fault compressor. The acoustic noise holograms are predicted by measuring at discrete multiple points around the two compressors and are thereafter reconstructed on the surface of the compressors. 1344 measuring points are used by two microphones in which one is scanning microphone and the other is reference microphone. NAH is a good tool for the visualization of Sound so we can show the source of sound graphically. In this paper, the NAH method found the exact noise source position on the surface of the compressor and the noise-related sub part in the compressor. We found the NAH and is very useful as a noise reduction tool for home-appliance device.