• 한국수산과학회지
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• 제54권6호
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• pp.1036-1044
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• 2021

A linear array acoustic transducer with 12 tonpilz elements mounted independently on a gradual wedge-shaped tail mass was fabricated, tested and analyzed. The compensated transducer, which is modified by including a series inductance of 137 µH in the developed linear array transducer, attained improved figure of merit (FOM) performance characteristics compared with the uncompensated transducer. The four resonant frequency bands were identified from the measured FOM curve. The FOM response patterns over the frequency ranges of 31 to 40 kHz and 50 to 60 kHz were relatively uniform, whereas sharp resonance peaks were observed at around 73 kHz and 84 kHz. These results indicate that the developed linear array transducer can be used as an enhanced broadband transducer of echo sounder, and the operating frequency can be selected for more effective echo surveys in the fishing ground.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.729-731
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• 2013

축적된 분산(dispersion)과 비선형 효과에 의한 광 신호의 왜곡을 보상하기 위해 사용되는 분산 계수가 -125 ps/nm/km인 분산 보상 광섬유의 성능 지수 (figure of merit)에 따른 40 Gbps의 광 펄스의 보상 특성을 살펴보았다. 보상 특성이 광전송 링크를 구성하는 중계 구간 (fiber span)의 수가 많고 광 펄스의 입사 전력이 클수록 DCF의 성능 지수의 영향을 많이 받는 것을 확인할 수 있었다. 또한 광 펄스의 파장이 광섬유의 영 분산 파장으로부터 많이 벗어날수록 DCF의 성능 지수의 영향을 많이 받는 것을 확인하였다. 그러나 광전송 링크의 비선형 효과가 클수록 효과적인 보상을 위한 DCF의 성능 지수는 낮아져야 한다는 것을 동시에 확인하였다.

• 전기전자학회논문지
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• 제27권4호
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• pp.567-572
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• 2023

본 논문에서는 Partial isolation lateral double diffused metal oxide semiconductor(Pi-LDMOS)의 항복전압에 대해 시뮬레이션을 통해 분석하였다. 항복전압 변화는 Partial buried oxide(P-BOX)의 다양한 파라미터(길이, 두께, 위치)에 따라 조사되었고, 그 메커니즘에 대해 명기하였다. 또한 항복전압과 trade-off 관계에 있는 온저항의 변화를 P-BOX 파라미터 변화에 따라 분석하였고 Figure of merit(FOM)을 계산하여 비교하였다. 제안된 구조에서 L_box=5㎛, t_box=2㎛, L_bc=2㎛일 경우 138V의 가장 높은 항복전압을 나타내었고, L_box=5㎛, t_box=1.6㎛, L_bc=2㎛일 경우 가장 높은 FOM을 나타내었다. 이는 conventional LDMOS 대비 항복전압은 123%, FOM은 3.89배 향상된 수치이다. 따라서 Pi-LDMOS는 높은 항복전압과 FOM을 가져 Power IC의 안정적인 동작범위 향상에 기여할 수 있다.

• 설비공학논문집
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• 제9권3호
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• pp.284-291
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• 1997

A hydrogen liquefaction equipment by direct cooling has been designed and built at KIST. Cool-down characteristics and liquefaction performance of the equipment have been investigated. The hydrogen liquefaction equipment consists of a GM refrigerator, a liquefaction velssel, a radiation shield and a cryostat. It is found that the hydrogen starts to be liquefied in the liquefaction vessel after 40~50 minutes of cool-down from the gas state of 270K. The effect of natural convection phenomena of charged gas in liquefaction vessel on the cool-down characteristics is evaluated by comparing with those in vacuum of liquefaction vessel. It is seen that the cool-down time of a liquefaction vessel is substantially increased in vacuum environment of liquefaction vessel. The experiments have been performed for 1~5 atm of hydrogen pressure to investigate the influence of hydrogen pressure on the liquefaction rate and figure of merit(FOM). It is found that both liquefaction rate and FOM are increased as the charged hydrogen pressure is increased.

• Current Optics and Photonics
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• 제4권2호
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• pp.134-140
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• 2020

A significant enhancement of the magneto-optical Faraday rotation and extraordinary optical transmission (EOT) in the cascaded double-fishnet (CDF) structure with periodic rectangular apertures is theoretically predicted by using the extended finite difference time domain (FDTD) method. The results demonstrate that the transmittance spectrum of the CDF structure has two EOT resonant peaks in a broad spectrum spanning visible to near-infrared wavebands, one of them coinciding with the enhanced Faraday rotation and large figure of merit (FOM) at the same wavelength. It is most important that the resonant position and intensity of the transmittance, Faraday rotation and FOM can be simply tailored by adjusting the incident wavelength, the thickness of the magnetic layer, and the offset between two metallic rectangular apertures, etc. Furthermore, the intrinsic physical mechanism of the resonance characteristics of the transmittance and Faraday rotation is thoroughly studied by investigating the electromagnetic field distributions at the location of resonance. It is shown that the transmittance resonance is mainly determined by different hybrid modes of surface plasmons (SPs) and plasmonic electromagnetically induced transparency (EIT) behavior, and the enhancement of Faraday rotation is mostly governed by the plasmonic electromagnetically induced absorption (EIA) behavior and the conversion of the transverse magnetic (TM) mode and transverse electric (TE) mode in the magnetic dielectric layer.

• 한국세라믹학회지
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• 제54권6호
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• pp.530-534
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• 2017

The figures of merit in the on-resonance and off-resonance conditions ($FOM_{on}$ and $FOM_{off}$) for the piezoelectric energy harvester (PEH) were measured and compared in $[(K_{0.485}Na_{0.515})_{1-X}Li_X](Nb_{0.99}Ta_{0.01})O_3$ (x = 0.04 ~ 0.09) (KNLNT) ceramics with various Li contents. The crystal structure of CuO-doped KNLNT ceramics changes from orthorhombic to tetragonal around the Li fraction of 0.065. The stable temperature range for the tetragonal phase widens to both higher and lower temperatures as Li is substituted. The piezoelectric charge constant ($d_{33}$), electromechanical coupling factor ($k_p$) and mechanical quality factor ($Q_m$) have maximum values at the Li fraction between 0.055 and 0.065 where the phase boundary lies between the orthorhombic and tetragonal phases. Both $FOM_{on}$ and $FOM_{off}$ have peak values around the phase boundary but the peak compositions are not exactly coincided. The optimal Li fraction in the KNLNT ceramic for a PEH application was found to be between 0.055 and 0.065.

• Journal of Power Electronics
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• 제19권6호
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• pp.1440-1448
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• 2019

In wireless power transfer systems, it is important to design resonant energy links in order to increase the power transfer efficiency and to obtain desired system performances. This paper proposes a method for designing and analyzing the resonant energy links in a series-series configured IPT (inductive power transfer) system using the FOM-rd plane. The proposed FOM-rd graphical design plane can analyze and design the voltage gain and the power efficiency of the energy links while considering changes in the misalignment between the coils and the termination load condition. In addition, the region of the bifurcation phenomena, where voltage gain peaks are split over the frequency, can also be distinctly identified on the graphical plane. An example of the design and analysis of a 100 W inductive power transfer system with the proposed method is illustrated. The proposed method is verified by measuring the voltage gain and power efficiency of implemented hardware.

• 한국전기전자재료학회논문지
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• 제30권2호
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• pp.81-85
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• 2017

$SnO_2/Ag/Nb_2O_5/SiO_2/SnO_2$ multilayer films were prepared on glass substrate by sequential using RF/DC magnetron sputtering at room temperature. The influence of top $SnO_2$ layer thickness on optical and electrical properties of the multilayer films was investigated. Experimentally measured results exhibit transmittances over 84.3 ~ 85.8% at 550 nm wavelength. As the top $SnO_2$ layer thickness increased from 40 to 55 nm, the sheet resistance (Rs) increased from 5.81 to $6.94{\Omega}/sq$. The Haacke's figure of merit (FOM) calculated for the samples with various $SnO_2$ layer thicknesses was a maximum at 45 nm ($35.3{\times}10^{-3}{\Omega}^{-1}$).

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.464-466
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• 2003

In this paper an advanced algorithm for selecting a seam line automatically, which used to be selected by human operator for mosaicked images is presented. In addition to four factors proposed by automation theory, the FOM(Figure Of Merit) of tie point were taken into account to suggest the method to select a seam line applicatively and the algorithm was applied to mosaic test images.

• 설비공학논문집
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• 제12권2호
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• pp.131-139
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• 2000

A direct hydrogen liquefaction equipment has been developed and tested, which consists of a GM refrigerator, a liquefaction vessel, a radiation shield, a cryostat, and an ortho-para converter with catalyst. The effect of ortho-para hydrogen conversion on the performance of hydrogen liquefaction has been investigated. The time needed for the hydrogen liquefaction process with hydrogen pressure charge of 4 atm was delayed to around 75 minutes, and the liquefied mass flow rate of the hydrogen was about 0.0150∼ 0.0205 g/s when the hydrogen was liquefied with the direct hydrogen liquefaction system considering ortho-para conversion. With ortho-para conversion, the liquefied mass flow rate decreased up to 20%. Considering ortho-para conversion, there were up to 30% increase in the work input per unit liquefied mass flow rate. When the ortho-para conversion was considered, FOM decreased to be about 0.031∼0.045.