• Journal of Welding and Joining
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• 제27권6호
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• pp.36-42
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• 2009

In the present day, new performances are demanded for automobile body steel sheet for example, light weight, durability, resistance corrosion and environmental protection. For an improvement of resistance corrosion, European automobile companies developed pre-sealed steel in 1990's. Pre-sealed steel have organic coated layer upper zinc coated layer. Evaluating a resistance spot weldability of pre-sealed steel plate is important because resistance spot welding is used mainly in automobile body joining process. In this study, evaluating a weldability of pre-sealed steel plate was carried out using lobe diagram, dynamic resistance and high-speed image. Usually, Pre-sealed steel has poor weldability than GA steel's. To improve a weldability of pre-sealed steel sheet, pre-current was applied to welding process. Pre-current is applied prior to base-current. In conclusion, the weldability of pre-sealed steel has been improved than GA steel's by applying pre-current.

• Journal of Power Electronics
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• 제12권5호
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• pp.689-698
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• 2012

This paper investigates the effects of applying different input current waveshapes on the performance of a continuous-conduction-mode (CCM) power-factor-correction (PFC) boost pre-regulator. It is found that the output voltage ripple of the pre-regulator can be reduced if the input current is modified to include controlled amount of higher order harmonics. This finding allows us to balance the performance of output regulation and the harmonic current emission when coming to the design of the pre-regulator. An experimental PFC boost pre-regulator prototype is constructed to verify the analysis and show the benefit of the pre-regulator operating with input current containing higher order harmonics.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.1193-1198
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• 2005

The pre-assembly takes a large portion of the fabrication cost of steel bridges. In order to save the fabrication cost through the improvement of the conventional pre-assembling process, this research investigates a numerical pre-assembly simulation as an alternative to current pre-assembling process. The 3D laser scanning was utilized in site and measuring data for steel box were analyzed. The productivity of pre-assembly simulation system is compared with the conventional pre-assembling system. This paper identifies feasibility on the alternative pre-assembling process and then proposes the scheme of the pre-assembly simulation system development satisfying the current pre-assembly inspection of standards.

• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1068-1075
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• 2018

We propose a method for driving loudspeakers from class D audio power amplifiers in current mode, instead of in conventional voltage mode, which was impossible with the feedback circuitry. Unlike analog audio amplifiers, Class D audio power amplifiers have signal delay between the input and output signals, which makes it difficult to apply the feedback circuitry for current-mode driving. The idea of the pre-distortion scheme used for the compensation of the non-linearity of RF power amplifiers is adapted to remedy the impedance variation effect of the loudspeakers for current driving. The method uses the speaker model for the pre-distorter to compensate for the speaker impedance variation with frequency. The simulation and test results confirms the validity of the proposed method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.104-107
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• 2005

Recently, according to the development of semiconductor industry, needed to high-integration and high-functionality. These changes are required for silicon wafer of large scale diameter and precision of TTV (Total Thickness variation). So, in this research, suggest that the method of monitoring system is using motor current. This method is needed for observation of silicon wafer grinding process. Motor current sensor is consisted of hall sensor. Hall sensor is known to catching of change of current. Received original signal is converted to the diginal, then, it is calculated RMS values, and then, it is analysed in computer. Generally, the change of force is relative to the change of current, So this reason, in this research tried to monitoring of motor current change, and then, it will be applied to analysis for silicon wafer grinding process. using motor current sensor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.12-14
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• 2003

This paper presents the small current interruption capability of $SF_6$ puffer circuit breaker considering pre-condition. Firstly, the change of dielectric strength of the 3 breakers was compared with testing breakers as clean contacts and eroded contacts after 3 shots of 760 according to new IEC 62271-100 standard. Also the dielectric strength curve of each model was calculated through flow and electric field simulations. From these results, we could modify the empirical equation, being used to predict the dielectric strength of small current interruption capability, considering the effects of pre-condition.

• 한국철도학회논문집
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• 제19권3호
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• pp.288-296
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• 2016

400km/h급 전차선로가 우리나라에 시범 부설되었다. 400km/h 심플 커티너리를 설계함에 있어서 사전이도를 어떻게 해야 하는가는 관심이 집중된 엔지니어링 항목이다. 사전이도는 일정 고속 대역에서 집전성능을 향상시키는 것으로 알려져 있다. 그러나 400km/h 속도에서 효과에 대해서는 아직 정립되어있지 않다. 400km/h 커티너리에서 적절한 사전이도량을 파악하기 위하여 사전이도 0과 1/3000 조건에서 전차선과 팬터그래프 사이 동적 성능 예측 시뮬레이션을 실시하였다. 이 예측에 근거하여 400km/h 전차선로 설계에서는 0 사전이도를 채택하였다. 그리고 400km/h 전차선로 시범구간(28km)을 건설하면서 일부구간에 1/3000 사전이도 구간(약 1km)을 조성하였다. HEMU-430X 열차를 투입하여 사전이도 조성 구간을 포함하여 시범구간에서 접촉력 측정을 실시하였다. 본 논문에서는 사전이도 조성 구간과 사전이도가 없는 구간의 동적 성능(접촉력)에 대하여 기술하며 그 둘을 비교한다. 결론적으로 400km/h 전차선로에서 사전이도를 주지 않은 구간이 1/3000 사전이도 구간보다 양호한 동적(집전) 성능을 나타냄을 해석적 및 실험적 검토를 통하여 확인하였다.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.18-23
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• 2010

We demonstrated that the solution processed organic light-emitting diodes (OLEDs) have the high efficiency with pre-treated indium-tin-oxide (ITO). ITO surface was pre-treated with four methods and compared each other. The pre-treatment of ITO surface improves the chemical and physical characteristics of ITO such as the surface roughness, adhesion property, and the hole injection ability. These properties were analyzed by the contact angle, atomic force microscope (AFM) image, and the current flow character in device. As a results, the device with ITO pre-treated by $O_2$ plasma shows the current efficiency of 5.93 cd/A, which is 1.5 times the device without pre-treatment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.353-355
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• 2007

A simple technique for PFC circuit is presented using UC3854. This technique is about current peak controlling by a reference current generator. Decreased peak currents of the boost pre-regulator reduce circuit current stress and so rated currents of circuit elements are minimized. Simulation and experimental results will verify the viability of the new scheme.

• 천문학논총
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• 제30권2호
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• pp.309-313
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• 2015

If the present universe is slightly open then pre-inflation curvature would appear as a cosmic dark-flow component of the CMB dipole moment. We summarize current cosmological constraints on this cosmic dark flow and analyze the possible constraints on parameters characterizing the pre-inflating universe in an inflation model with a present-day very slightly open ${\Lambda}CDM$ cosmology. We employ an analytic model to show that for a broad class of inflation-generating effective potentials, the simple requirement that the observed dipole moment represents the pre-inflation curvature as it enters the horizon allows one to set upper and lower limits on the magnitude and wavelength scale of pre-inflation fluctuations in the inflaton field and the curvature parameter of the pre-inflation universe, as a function of the fraction of the total initial energy density in the inflaton field. We estimate that if the current CMB dipole is a universal dark flow (or if it is near the upper limit set by the Planck Collaboration) then the present constraints on ${\Lambda}CDM$ cosmological parameters imply rather small curvature ${\Omega}_k{\sim}0.1$ for the pre-inflating universe for a broad range of the fraction of the total energy in the inflaton field at the onset of inflation. Such small pre-inflation curvature might be indicative of open-inflation models in which there are two epochs of inflation.