• Journal of electromagnetic engineering and science
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• 제11권3호
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• pp.152-155
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• 2011

This paper describes the role of mutual impedance and the transducer power gain which comes from key parameters to determine the amount of wireless power especially in a near-field environment. These two key parameters are applied to the two configurations; one is a dipole-dipole, and the other is a dipole-metal plate-loop configuration. Discussions are given on the achievable maximum power transfer between the sender and the receiver affected by the matching and the pass blockage.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (1)
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• pp.604-606
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• 2004

클라이언트/서버 시스템은 클라이언트가 수행할 수 없거나 곤란한 프로그램을 서버에서 수행하여 클라이언트의 부하를 줄여준다. 하지만 서버의 리소스를 요청하는 클라이언트의 수가 많아지면 이미 많은 리소스를 사용하고 있는 서버에게 리소스를 요청하거나, 리소스를 사용하지 않는 서비스에게는 요청하지 않는 경우가 발생하여 서버에게 너무 많은 부하를 주거나 전혀 부하가 생기지 않을 수 있다. 이에 본 논문에서는 Jini 기반의 Agent Manager를 이용하여 서버와 클라이언트의 정보를 수집한 다음 MAUT와 Maximum-Weight Matching을 이용하여 클라이언트와 서버 간 연결의 전체적인 만족도를 높이는 Jini 기반의 최적의 컴퓨팅 리소스 제안 시스템을 연구하였다.

• 대한전자공학회논문지
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• 제10권4호
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• pp.74-79
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• 1973

부성 저항을 갖는 다이오드를 사용한 마이크로파 발진기에서 최대의 출력을 내기 위한 임피이던스 정합조건이 공진기의 load 임피이던스가 다이오드 입피이던스의 1/2이라는 결과가 이론적으로 추출된다. 이 사실을 실험적으로 규명하기 위하여 임페트 다이오드의 임피이던스를 실험적으로 조사하고 마이크로와 공진기를 설계 제작하여 조사하였다.

• Journal of Electrical Engineering and information Science
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• 제3권2호
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• pp.211-221
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• 1998

It is becoming apparent that stereo matching algorithms need much information from high level cognitive processes. Otherwise, conventional algorithms based on bottom-up control alone are susceptible to local minima. We introduce a system that consists of two levels. A lower level, using a usual matching method, is based upon the local neighborhood and a second level, that can integrate the partial information, is aimed at contextual matching. Conceptually, the introduction of bottom-up and top-down feedback loop to the usual matching algorithm improves the overall performance. For this purpose, we model the image attributes using a Markov random field (MRF) and thereupon derive a maximum a posteriori (MAP) estimate. The energy equation, corresponding to the estimate, efficiently represents the natural constraints such as occlusion and the partial informations from the other levels. In addition to recognition, we derive a training method that can determine the system informations from the other levels. In addition to recognition, we derive a training method that can determine the system parameters automatically. As an experiment, we test the algorithms using random dot stereograms (RDS) as well as natural scenes. It is proven that the overall recognition error is drastically reduced by the introduction of contextual matching.

• Journal of Magnetics
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• 제18권4호
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• pp.428-431
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• 2013

We demonstrate that a partial loading of $Ni_{0.5}Zn_{0.5}Fe_2O_4$ (Ni-Zn ferrite) film remarkably improves impedance matching of electrically small $Ba_3Co_2Fe_{24}O_{41}$ ($Co_2Z$) hexaferrite antenna. A 3 ${\mu}m$ thick Ni-Zn ferrite film was deposited on a silicon wafer by the electrophoresis deposition process and post-annealed at $400^{\circ}C$. The fabricated Ni-Zn ferrite film has saturation magnetization of $268emu/cm^3$ and coercivity of 89 Oe. A partial loading of the Ni-Zn ferrite film on the $Co_2Z$ hexaferrite helical antenna increases antenna return loss to 24.7 dB from 9.0 dB of the $Co_2Z$ antenna. Experimental results show that impedance matching and maximum input power transmission to the antenna without additional matching elements can be realized, while keeping almost the same size as the $Co_2Z$ antenna size.

• Current Optics and Photonics
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• 제5권4호
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• pp.458-465
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• 2021

Borate nonlinear optical crystals have been used as frequency conversion devices in many fields due to their unique transparency and nonlinearity from ultraviolet to visible spectral range. In this study, we theoretically and numerically investigate the properties of broadband second harmonic generation (SHG) in the recently reported Pna2₁-Ba₃Mg₃(BO₃)₃F₃ (BMBF) crystal. The technique is based on the simultaneous achievement of birefringence phase matching and group velocity matching between interacting waves. We discussed all factors required for broadband SHG in the BMBF in terms of two types of phase matching and group velocity matching conditions, the beam propagation direction and the corresponding effective nonlinearity and spatial walk-off, and the spectral responses. The results show that bandwidths calculated in the broadband SHG scheme are 220.90 nm (for Type I) and 165.85 nm (for Type II) in full-width-half-maximum (FWHM). The central wavelength in each case is 2047.76 nm for Type I and 1828.66 nm for Type II at room temperature. The results were compared with the non-broadband scheme at the telecom C-band.

• Journal of Information Display
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• 제11권4호
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• pp.173-181
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• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.

• 한국인터넷방송통신학회논문지
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• 제14권3호
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• pp.111-117
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• 2014

본 논문은 안정된 결혼문제의 최적 해를 쉽고 빠르게 찾는 알고리즘을 제안하였다. 첫 번째로, 남성의 여성선호도와 여성의 남성 선호도 합 $p_{ij}$의 $n{\times}n$ 정방행렬 할당문제로 변환시킨다. 두 번째로, 행렬에서 최대 선호도 합(최소 값)인 $_{min}p_{ij}$를 선택하고 i행과 j열을 삭제한다. 이 과정을 $i=0{\cap}j=0$일 때까지 수행한다. 세 번째로, 가능한 최초 또는 마지막 선택 $_{min}p_{ij}$에 대해 다른 값으로 변경시 선호도를 증가시킬 수 있으면 상호 교환하는 검증 절차를 수행한다. 제안된 알고리즘을 7개의 안정된 결혼문제에 적용한 결과 기존 알고리즘의 해를 개선하는 효과를 얻었다.

• ETRI Journal
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• 제38권5호
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• pp.962-971
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• 2016

A wireless power transfer (WPT) system is generally designed with the optimum source and load impedance in order to achieve the maximum power transfer efficiency (PTE) at a specific coupling coefficient. Empirically or intuitively, however, it is well known that a high PTE can be attained by adjusting either the source or load impedance. In this paper, we estimate the maximum achievable PTE of WPT systems with the given load impedance, and propose the condition of source impedance for the maximum PTE. This condition can be reciprocally applied to the load impedance of a WPT system with the given source impedance. First, we review the transducer power gain of a two-port network as the PTE of the WPT system. Next, we derive two candidate conditions, the critical coupling and the optimum conditions, from the transducer power gain. Finally, we compare the two conditions carefully, and the results therefore indicate that the optimum condition is more suitable for a highly efficient WPT system with a given load impedance.

• 대한전자공학회논문지TC
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• 제46권2호
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• pp.141-146
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• 2009

본 논문에서는 새로운 고조파 조절 회로를 이용한 Si LDMOSFET 고효율 전력증폭기를 구현하였다. 본 고조파 조절 회로는 2차, 3차 고조파 성분에 대하여 단락 임피던스를 갖으며, 입출력 정합 회로를 설계하기 위하여 사용된다. 제안된 고조파 조절 회로의 효율 개선 효과가 class-F 혹은 inverse class-F 고조파 조절 회로 보다 우수하다는 것을 증명하였다. 또한, 고조파 조절 회로가 출력 정합 회로뿐만 아니라, 입력 정합 회로에도 사용될 경우, 제안된 전력증폭기의 효율은 더욱 더 개선된다. 제안된 전력증폭기의 최대 전력 효율 (PAE)의 측정값은 1.71 GHz의 주파수 대역에서 82.68%이다. Class-F와 inverse class-F 전력증폭기와 비교할 때, 제안된 전력증폭기의 최대 PAE 측정값은 $5.08\;{\sim}\;9.91\;%$ 향상된다.