• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.105-114
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• 1998

Flow field and near-field noise of a centrifugal fan has been studied with an efrcient compressible method and STAR-CD. The flow field of the centrifugal fan is assumed two-dimensional. Most of the compressible studies has been done by inviscid solver because viscous simulation shows little difference. The near field noise is estimated in term s of sound pressure level in frequency domain transformed from the computed pressure fluctuations using FFT. The simulation has been done on various design elements such as impeller blade shapes, the number of blades and cut-off clearance. The comparison shows that the number of blades has a significant effect on near-field noise without losing aerodynamic performance.

• 한국정밀공학회지
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• 제20권11호
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• pp.142-149
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• 2003

Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.35-35
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• 2010

This paper illustrates the use of electric field computation to optimize the design of high voltage composite bushing. In the bushing, a high electric stress occurred between field shaper and central conductor by the closely space. Also coaxial cylindrical shield has a great height along the axis to control an electric field. Consequently, all the potentials are raised axially along the field shaper and electric stress is concentrated on a part of the surface of the FRP tube near the upper end of the field shaper. Maxwell 2D simulator based on the boundary element method was also introduced in order to verify the reliability of the polymer bushing. The optimized design uses internal elements for electric stress grading at critical parts of the bushing.

• 한국안전학회지
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• 제21권5호
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• pp.34-39
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• 2006

In this paper, we investigated the electric field distribution according to the roughness in aramid insulating paper for electric machine. Aramid insulating paper has been used to electric insulating of the traction motor and generators for large capacity. We studied the electric field distribution using boundary element method for Aramid insulating paper. As a result of simulation, the electric field increased according to the surface roughness existence. Electric field decreased due to radius of surface roughness reduction, and Electric field concentration appeared at electrode boundary and rough surface.

• 소성∙가공
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• 제8권2호
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• pp.127-134
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• 1999

This study suggests the practical method which can reduce the lead time of the field trial and design of the dies. The virtual manufacturing, with which the die design is evaluated by computer analysis, reveals the impropriety of a design before die makings. Three methods for reducing the die making process occupying over 60% of the automotive development are like follows: First, the crack and wrinkle occurrence can be prevented by virtually adjusting the blank holding force and drawbead force with a computer simulation. Second, the parts which can not remove the forming defects in spite of the adjustment of forming parameters need to modify the part geometry or punch temporary shape. Third, the simulation before field trial, and field trial simulation can be effectively used in die design.

• 한국대기환경학회지
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• 제12권3호
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• pp.243-254
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• 1996

The main purpose of this study is to investigate the collection efficiency characteristics of a cylindrical ESP. To do that, it is necessary to analyze the electric field, gas flow field, and mechanism of particle movement by numerical simulation based on EHD model. For a gas flow field, Navier-Stokes equation involving the electric source term was solved by SIMPLE algorithm. In case of the electric field, the current continuity and electric field equations were solved by S.O.R. method. The analysis of particle movement was performed on the basis of PSI-CELL model from the Lagrangian viewpoint. The results showed that the influence on the gas flow field by the electric field is almost negligible in a cylindrical ESP. The particle drift velocity $V_P$ toward the collection surface is increased continuously by the electrostatic force due to the rise of particle charge as the particle is moving to the flow direction and the particle size becomes larger. The collection efficiency is to quitely higher with the increase of applied voltage for the same particle size, while becomes smaller as the inlet velocity is increased.

• 한국유체기계학회 논문집
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• 제2권1호
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• pp.43-49
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• 1999

Flow field and near-field noise of a centrifugal fan has been studied with an efficient compressible method and STAR-CD. The flow field of the centrifugal fan is assumed to be two-dimensional. Most of the compressible studies have been done by inviscid solver because viscous simulation shows little difference. The near field noise is estimated in terms of sound pressure level in frequency domain transformed from the computed pressure fluctuations using FFT. The simulation has been done on various design elements such as impeller blade shapes, the number of blades and cut-off clearance. The comparison shows that the number of blades has a significant effect on near-field noise without losing aerodynamic performance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.478-479
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• 2008

this paper describes the electric field distribution interpretation along a shield form inner vacuum interrupter(VI). The equipotential line and electric field and field vector in a VI are analysed by a finite element method at various shield form. in result, The equipotential line and electric field distribution was affected to VI shield form. The reason is as it gets distortion of equipotential line done. shield of cup type is how to electric field distribution, finally, this paper recognized whether or not affected, and proposed gap with the most suitable shield length and an external insulation.

• 한국전기전자재료학회논문지
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• 제30권4호
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• pp.253-257
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• 2017

Nowadays, it is increasingly important to detect whether cables are live for the operator's safety if there is a sudden power failure. It is especially hard to detect the electrical field of an underground line because of shielding. This paper on detection of live-line states in cables studied the detection characteristics of the change in the magnetic field and axis as the frequency, voltage, and distance at the same load are changed using 3 axes. A search coil type was used as a magnetic field sensor with non-contact. We found that magnetic fields decrease proportionally to the square of the distance and the decrease of rated voltage with load effected to magnetic field. The magnetic field was detected by 3-axis sensors given correct proximity, but appeared as noise components beyond a distance of 2 cm.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권8호
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• pp.382-389
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• 2002

We present experimental results on the multiplexed and stack-wise recording of near-field holograms. Experiments on angular multiplexing show that the angular selectivity of near-field hologram is better than that of the conventional hologram. Experiments on stack-wise recording prove that near-fields originated from sub-diffraction-limit-size objects could be stored in a photorefractive crystal at 2mm apart from the crystal surface. In addition, to improve the data access and transfer time, a silicon nano-aperture array was introduced and applied to the recording of near-field holograms.