• 전기학회논문지P
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• 제60권1호
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• pp.19-26
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• 2011

In this paper, we designed Interpolation FIR(Finite Impulse Response) filter and 1-bit SDM(Sigma- Delta Modulator) for small digital audio speaker, which has low power consumption and high output characteristics. In order to achieve high linearity and low distortion performance of the systems, we adopt Type I Chevychev FIR filter which has equiripple characteristics in the pass band and proposed high efficient FIR filter structure. SDM is the most efficient modulation technique among the noise shaping techniques. In this paper, we implemented SDM using CIFB(Cascade of Intergrators, Feed-Back) which is generally used in DAC of small digital audio speakers. The proposed SDM structure can achieve high SNR, high-efficiency characteristics and low power consumption in mobile devices. Also considering manufacture of SoC(System on Chip), we performed simulation with Matlab and Verilog HDL to obtain optimal number of operational bits and verified a good experimental results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.147-150
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• 2003

In this paper, We fabricated a high temperature pressure sensor using SBD(silicon- direct-bonding) wafer of $Si/SiO_2$/Si-sub structure. This sensor was very sensitive because the piezoresistor is fabricated by single crystal silicon of the first layer of SDB wafer. Also, it was possible to operate the sensor at high temperature over $120^{\circ}C$ which is the temperature limitation of general silicon sensor because the piezoresistor was dielectric isolation from silicon substrate using silicon dioxide of the second layer. The sensitivity of this sensor is very high as the measured result of D2200 shows $183.6\;{\mu}V/V{\cdot}kPa$. Also, the output characteristic of linearity was very good. This sensor was available at high temperature as $300^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.1022-1025
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• 2001

This paper presents the characteristics of TaN thin-film as high-temperature strain gauges, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4∼20%)N$_2$). The electrical and mechanical characteristics of these films investigated with the thickness range 1650∼1870${\AA}$ and room temperature resistivities in the range 178.3 ${\mu}$$\Omega$cm to 3175.7 ${\mu}$$\Omega$cm. The TaN thin-film strain gauge deposited in Ar-(20%)N$_2$atmosphere is obtained a temperature coefficient of resistance(TCR), 0∼-1357 ppm/$^{\circ}C$ in the temperature range 25∼275$^{\circ}C$ and a high temporal stability with a longitudinal gauge factor, 2.92∼3.47. Because of their high resistivity, low TCR and linear gauge factor, these cermet thin-film may allow high-temperature strain gauges miniaturization.

• Fisheries and Aquatic Sciences
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• 제23권3호
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• pp.9.1-9.6
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• 2020

Background: Fucosterol is a compound commonly found in algae that has various biological activities. The purpose of this study was to develop a high-performance liquid chromatography (HPLC) validation method for fucosterol and to compare the fucosterol contents of 11 algal species from Ulleungdo, Korea. Method: In this study, we successfully isolated and identified fucosterol from a 70% EtOH extract of Sargassum miyabei, and subsequently conducted specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision analyses for development of an HPLC validation method. Fucosterol contents were compared using the established HPLC validation conditions. Results: We successfully isolated fucosterol from a 70% EtOH extract of S. miyabei and identified it based on spectroscopic analysis. On the basis of HPLC validation using the fucosterol isolated from S. miyabei, we confirmed specificity (8.5 min), linearity (R² = 0.9998), LOD (3.20 ㎍ mL^-1), LOQ (9.77 ㎍ mL^-1), accuracy (intra-day and inter-day variation, 90-110%), and precision (RSD, 1.07%). Fucosterol contents in the 11 assessed algal species ranged from 0.22 to 81.67 mg g^-1, with the highest content being recorded in a 70% EtOH extract of Desmarestia tabacoides (81.67 mg g^-1), followed by that of Agarum clathratum (78.70 mg g^-1). Conclusions: The results indicate that 70% EtOH extracts of D. tabacoides and A. clathratum containing fucosterol with various effects can be potential alternative sources of fucosterol.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3629-3634
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• 2013

In this study, an improved method for the quantitative analysis of ginkgolic acids (GAs) in Ginkgo biloba leaf extract was developed. The samples were extracted with a mixture of chloroform and 50 % ethanol, after which the chloroform extract was dried and reconstituted in methanol. GAs with 13:0, 15:1, and 17:1 in the extract were successfully separated within 40 min and determined with high throughput performance using an online column-switching HPLC method using an SP column C8 SG80 ($4.6{\times}150mm$, $5{\mu}m$) and a Cadenza 5CD C18 column ($4.6{\times}150mm$, $3{\mu}m$). The developed HPLC method was validated for Ginkgo biloba leaf extract. The validation parameters were specificity, linearity, precision, accuracy, and limits of detection and quantitation (LODs and LOQs, respectively). It was found that all of the calibration curves showed good linearity ($r^2$ > 0.9993) within the tested ranges. The LODs and LOQs were all lower than $0.04{\mu}g/mL$. The established method was found to be simple, rapid, and high throughput for the quantitative analysis of GAs in ten commercial Ginkgo biloba leaf extract and dietary supplements. The samples were also analyzed in LC-electrospray ionization (ESI) tandem mass spectrometry (MS/MS) - multiple-ion reaction monitoring (MRM) mode to confirm the identification results that were obtained by the column switching HPLC-DAD method. The developed method is considered to be suitable for the routine quality control and safety assurance of Ginkgo biloba leaf extract.

• 대한전자공학회논문지SD
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• 제41권11호
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• pp.29-34
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• 2004

본 논문에서는 molecular beam epitaxy (MBE)로 성장한 AlGaN/InGaN/GaN high electron-mobility transistors (HEMTs)의 선형성과 RF dispersion 특성을 조사하였다. 전극 길이가 0.5 ㎛인 AlGaN/InGaN HEMT는 최대 전류 밀도가 730mA/mm, 최대 전달정수가 156 mS/mm인 비교적 우수한 DC 특성과 함께, 기존의 AlGaN/GaN HEMT와는 달리 높은 게이트 전압에도 완만한 전류 전달 특성을 보여 선형성이 우수함을 나타내었다. 또한 여러 다른 온도에서 측정한 펄스 전류 특성에서 소자 표면에 존재하는 트랩에 의한 전류 와해 (current collapse) 현상이 발생되지 않음을 확인하였다. 이 연구 결과는 InGaN를 채널층으로 하는 GaN HEMT의 경우 선형성이 우수하고, 고전압 RF 동작조건에서 출력저하가 발생하지 않는 고출력 소자를 제작할 수 있음을 보여준다.

• 대한수의학회지
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• 제57권4호
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• pp.223-226
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• 2017

This study was undertaken to develop new analytical methods for assessment of anticoccidials. High-performance liquid chromatography (HPLC) was found to be a fast, reliable, and practical method. The anticoccidials used in this experiment were toltrazuril and diclazuril, and the analysis factors were specificity, linearity, accuracy, repeatability, and intermediate precision. The linearity of each anticoccidial was better than 0.99, and the accuracies were 99.5% and 99.1% with relative SD of 0.5 and 0.4, respectively. To assess whether the developed HPLC method could be effectively applied, toltrazuril and diclazuril post-market veterinary products (five products) that are currently sold were tested. The results revealed no non-compliant items and the method was applied successfully. Therefore, the newly developed HPLC method for anticoccidial assessment described in this study may be useful as a reference method in the Korean Standards of Veterinary Pharmaceuticals for the analysis of toltrazuril and diclazuril.

• 한국전자파학회논문지
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• 제25권6호
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• pp.671-678
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• 2014

본 논문에서는 전압 제어 발진기의 비선형 영향에 의한 문제점을 개선한 FMCW 신호 생성 구조를 제안한다. 단순히 전압 제어 발진기(voltage controlled oscillator)의 튜닝 전압(tunning voltage)을 스위프(sweep)하여 FMCW(Frequency Modulated Continuous Wave) 신호를 생성하는 방식의 경우에는 전압 제어 발진기 자체의 비선형 영향으로 인해 센서에서 검출하고자 하는 비트 주파수(beat frequency)에 변동(drift)이 발생하게 되어 그로부터 추출된 정보의 정확도가 저하되거나, 잘못 해석될 수 있는 오류를 갖게 된다. 이러한 비선형 영향을 배제하기 위해 본 연구에서는 직접 주파수 합성기(direct digital synthesizer)와 위상 동기 루프(phase locked loop)를 포함한 하이브리드 방식의 신호 생성 방안을 적용하여 고선형성을 갖는 FMCW 신호를 생성하였고, 제작 후 시험을 통해 FMCW 센서에서 검출한 비트 주파수가 매우 정확함을 검증하였다.

• 센서학회지
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• 제12권5호
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• pp.199-204
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• 2003

본 논문에서는 Ta-N 스트레인게이지를 이용한 극한 환경용 세라믹 박막형 압력센서의 제작 및 특성에 관하여 연구하였다. 압력감지부로 Ta-N 스트레인게이지를 사용하였으며, SDB(Si-wafer Direct Bonding)와 전기화학적 식각정지법을 이용하여 매몰 cavity를 가지는 저가격 고수율의 Si 박막 다이어프램을 제작하였다. 또한, 실리콘 박막 다이어프램상에 박막형 스트레인게이지를 형성하여 세라믹 박막형 압력센서를 제작하였다. 제작된 세라믹 박막형 압력 센서는 기존의 스트레인 게이지를 이용한 로드셀에 비해서 온도특성이 우수하고 재현성, 소형화, 집적화 및 저가격화가 가능하기 때문에 고온, 고압 등의 각한 환경에서도 사용이 가능할 것으로 기대된다.

• Journal of Advanced Research in Ocean Engineering
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• 제4권1호
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• pp.7-15
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• 2018

The submarine is an underwater weapon system which covertly attacks the enemy. Pressure hull of a submarine is a main system which has to have a capacity which can improve the survivability (e.g., protection of crews) from the high pressure and air pollution by a leakage of water, a fire caused by outside shock, explosion, and/or operational errors. In addition, pressure hull should keep the functional performance under the harsh environment. In this study, optimal design of submarine pressure hull is dealt with 7 case studies done by analytic method and then each result's adequacy is verified by numerical method such as Finite Element Analysis (FEA). For the structural analysis by FEM, material non-linearity and geometric non-linearity are considered. After FEA, the results by analytic method and numerical method are compared. Weight optimized pressure hull initial scantling methods are suggested such as a ratio with shell thickness, flange width, web height and/or relations with radius, yield strength and design pressure (DP). The suggested initial scantling formulae can reduce the pressure hull weight from 6% and 19%.