• Journal of Welding and Joining
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• v.17 no.2
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• pp.61-65
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• 1999

Because of the need for packages which accommodate high pin count, high density and high speed device, PBGA(plastic ball grid array) package gets more spotlight. But the substrate material which is used for PBGA package is in nature susceptible to moisture penetration. The objective of the study is to find out the path of delamination in the stacked structure of substrate. To increase the adhesion between the cooper laminate and PSR(photo solder resist) which is the weakest part, experiments were performed by changing parameters of printing pre-treatment and post-treatment process. As a result of experiments, the factor effects on the adhesion between the cooper laminate and PSR is caused by all of the pre-treatment and post-treatment condition. A considerable change was observed depending on the amount of UV irradiation after thermal cure which is typical of printing post-treatment condition rather than pre-treatment condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.517-525
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• 2015

A grid connected inverter must be operated as the main electricity source under an isolated condition caused by the grid problem. Conventionally, the dual loop controller is used for the grid inverter, and the controller is used for control under the stand-alone mode. Generally, the PI(Proportional - Integral) controller is highly efficient under a synchronous reference frame, and stable control can be available. However, in this synchronous frame-based control, high-quality DSP is required because many sinusoidal calculations are necessary. When the PI control is conducted under a stationary frame, the controller constructions are made simple so that they work even with a low-price micro controller. However, given the characteristics of the PI controller, it should be designed with the phase of reference voltage considered. Otherwise, the phase delay of the output voltage can occur. Although the current controller also has a higher bandwidth than the voltage controller, distortion of the voltage is difficult to avoid only by the rapid response of the PI controller, as a sudden load change can occur in the nonlinear load. In this study, a new control method that solves the voltage controller bandwidth problem and rapidly copes with it even in the nonlinear load situation is proposed. The validity of the proposed method is proved by simulation and experimental results.

• The Journal of the Korea Contents Association
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• v.15 no.7
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• pp.289-299
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• 2015

The purpose of this study is to evaluate and compare the quality of digital X-ray imaging system. The image quality evaluation was conducted By using Modulation transfer function indicating the quantitative resolution of the image and the noise power spectrum showing the noise characteristics. Using a IEC61267 radiation quality was applied to the geometry to be used in clinical and geometry presented in IEC62220-1 and Additional filter, grid, the clinical dose and the MTF value of edge phantom was measured. Result of the MTF corresponding to each item(Grid, Filter, SID, kVp, mAs), the clinical condition 100cm, 180cm, measurements of the spatial frequency of the MTF IEC62220-1Geometry 150cm became similarly apparent, rather spatial frequency was also the case high in clinical conditions 100cm. NPS results, as the dose(mAs) is increased, NPS showed that reduced. The image quality evaluation using IEC61267 the Radiation quality, Image quality of the video using the clinical conditions Geometry than image quality evaluation using IEC62220-1Geometry was better. It shows that MTF and NPC in IEC and clinical condition were not significantly different. In order to apply the evaluation method of image quality applied with clinical conditions rather than the future method, to be presented evaluation of IEC standard, based on the results of the image characterization studies in this paper, the methods that shows good quality of spatial resolution and decrease NPS value as the least dose, used suitable parameters for whether or not using added filter, grid, change SID and clinical quality(kVp), dose(mAs) etc should be found. then It is believed to be able to properly maintain the actual quality of the image of the digital radiographic imaging system in clinical.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.87-89
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• 2009

In the present paper, transition turbulence model is applied to the NACA64(3)618 and detailed flow features are studied. The turbulence model is sensitive to the boundary layer grid quality and y+ of the grid was limited to 1. The prediction of the transition region is dependent on the local flow condition. The pressure coefficient distribution of the transition turbulence model is compared with that of the fully turbulent mode and the drag distribution of the transition turbulence model was compared with that of the wind tunnel test.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.101-102
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• 2017

This paper presents analysis of losses of switching device for full bridge inverter connected to grid. The losses are a dominant factor that judges efficiency of the system. The losses of switching device are divided to switching loss and conduction loss. They are can be estimated by analyzing periodic switching waveforms. The switching loss is generated at the point that turn-on and off. And the conduction loss is generated while the switch is on condition. The estimated losses of switch are compared to simulation result in this paper.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.293-299
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• 2001

Since the previous cut-and-try design algorithm require much cost and time, it has recently been concerned the automatic design technique using the CFD and optimum design algorithm. In this study, the Navier-Stokes equations is solved to consider the more detail viscous flow informations of cascade interaction and O-H multiblock grid system is generated to impose an accurate boundary condition. The cubic-spline interpolation is applied to handle a relative motion of a rotor to the stator. To validate present procedure, the time averaged aerodynamic loads are compared with experiment and good agreement obtained. Once the N-S equations have been solved, the computed aerodynamic loads may be used to computed the sensitivities of the aerodynamic objective function. The Modified Method of feasible Direction(MMFD) is usef to compute the

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.588-594
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• 2013

Under the condition of Baader aging, the chemical composition variation and the influence of transformer oil aging on electrical properties such as dielectric loss factor and physic-chemical properties such as interfacial tension were studied in the aging precess. Moreover, the correlation between hydrogenated transformer oil electrical and physic-chemical properties and its chemical composition variation were also investigated. The results show that these parameters of physic-chemical and electrical properties of hydrogenated transformer oil relate to each other and have closed correlation with chemical composition.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.969-972
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• 2003

This paper deal with a necessary factors for design grid connected photovoltaic system with stand-alone operation, and show simulation results of individual functions and multi- operation according to utility condition. Generally, photovoltaic system have only one operation of either stand-alone or line interactive, and have a isolation transformer for electrical isolation from utility therefore it is bulky, weighty, and a high price system as compared with usefulness. In this paper, A topology and algorithm adequate for lightweight, high efficiency, low price, multi function is selected and inquired into the validity using simulation of variable conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.261-264
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• 2006

In this paper, doubly-fed induction-type wind power generation system simulation model for grid connection is developed. The simulation model is based on PSCAD/EMTDC and consists of rotor-blade, blade controller, generator power converter and generator controller Blade controller controls the blade pitch angle for starting, peak power limiting and emergency condition. Generator controller controls the generator output power to maximize the system efficiency. Simulation results are shown for the variable wind speed conditions. The simulation model can be utilized for study of actual interaction between wind turbine and grid for reliable operation and protection of power system.

• Progress in Medical Physics
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• v.28 no.3
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• pp.83-91
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• 2017

In this work, we investigated the recently proposed phase-contrast x-ray imaging (PCXI) technique, the so-called single grid-based PCXI, which has great simplicity and minimal requirements on the setup alignment. It allows for imaging of smaller features and variations in the examined sample than conventional attenuation-based x-ray imaging with lower x-ray dose. We performed a systematic simulation using a simulation platform developed by us to investigate the image characteristics. We also performed a preliminary PCXI experiment using an established a table-top setup to demonstrate the performance of the simulation platform. The system consists of an x-ray tube ($50kV_p$, 5 mAs), a focused-linear grid (200-lines/inch), and a flat-panel detector ($48-{\mu}m$ pixel size). According to our results, the simulated contrast of phase images was much enhanced, compared to that of the absorption images. The scattering length scale estimated for a given simulation condition was about 117 nm. It was very similar, at least qualitatively, to the experimental contrast, which demonstrates the performance of the simulation platform. We also found that the level of the phase gradient of oriented structures strongly depended on the orientation of the structure relative to that of linear grids.