• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.386-393
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• 2011

In this study, we report an effective k-domain linearization method with a pre-calibrated indexed look-up table. The method minimizes k-domain nonlinear characteristics of a swept source optical coherence tomography (SS-OCT) system by using two arrays, a sample position shift index and an intensity compensation array. Two arrays are generated from an interference pattern acquired by connecting a Fabry-Perot interferometer (FPI) and an optical spectrum analyzer (OSA) to the system. At real time imaging, the sample position is modified by location movement and intensity compensation with two arrays for linearity of wavenumber. As a result of evaluating point spread functions (PSFs), the signal to noise ratio (SNR) is increased by 9.7 dB. When applied to infrared (IR) sensing card imaging, the SNR is increased by 1.29 dB and the contrast noise ratio (CNR) value is increased by 1.44. The time required for the linearization and intensity compensation is 30 ms for a multi thread method using a central processing unit (CPU) compared to 0.8 ms for compute unified device architecture (CUDA) processing using a graphics processing unit (GPU). We verified that our linearization method is appropriate for applying real time imaging of SS-OCT.

• 한국광학회지
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• 제13권6호
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• pp.521-529
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• 2002

본 연구에서는 삼차원 공간상에서 절대 좌표를 측정하기 위한 부피 간섭계의 오차원인을 분석하고 각 오차원인이 최종 결과에 미치는 영향을 계산했다. 계산결과 광검출기 배열의 비선형성, 압전소자의 비선형성, 광섬유 내부의 온도변화 둥이 오차의 주요 원인임을 알 수 있다. 제안된 간섭계의 성능을 실험적으로 검증하기 위해 분해능 측정 및 이차원 광학식 스케일과의 비교를 수행했다. 또한 간섭계의 성능을 좀 더 엄밀하게 검증하기 위해 자가보정법을 적용해서 공간상에서 간섭계가 갖는 계통오차를 추출했으며 60mm$\times$60mm$\times$20mm공간에서 최대오차 1 $\mu\textrm{m}$ 이하를 얻었다.

• 대한전자공학회논문지TC
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• 제37권7호
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• pp.18-23
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• 2000

능동 위상배열 안테나는 방사부 및 저잡음증폭기와 위상천이기를 포함하는 능동회로부가 결합된 다수의 채널들로 구성된다. 각각의 채널은 능동회로부의 초기위상 및 이득의 비균일성, 방사소자와 능동회로부의 인터페이스 및 빔성형회로의 편차 등으로 인하여 제각기 다른 양의 초기위상 및 이득값을 갖게 된다. 이는 능동 위상배열 안테나에 내재된 문제점으로서, 설계된 안테나 방사패턴 및 안테나 이득을 실제로 구현하기 위해서는 각각의 채널의 초기위상 및 이득 편차를 보정할 필요가 있다. 본 논문에서는 능동 위상배열 안테나에 대하여 초기위상 및 이득의 편차를 효율적으로 보정하여 안테나 성능을 최대로 향상시키는 새로운 보정 방법을 제시하였다. 실제 이 방법을 수행하여 12개의 상당히 비균일한 채널의 초기위상 천이 및 이득을 보정하여 안테나 이득을 2.0dB 이상 향상시켰다.

• 대한토목학회논문집
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• 제29권3C호
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• pp.127-136
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• 2009

본 연구의 목적은 포화지반의 전기적 특성파악을 위한 4전극 전기비저항 프로브(4-Electrode Resistivity Probe: 4ERP)의 개발과 검증이다. 4ERP는 웨너 배열을 적용하여 전극에서 분극작용 없이 전기비저항을 산정할 수 있도록 쐐기형과 평면형으로 제작되었다. 쐐기형은 지반속에 관입하기 위한 용도이며 평면형은 실내실험시 사용되는 셀등에 설치하기 위한 것이다. 크기가 다른 6종류의 글라스비드와 3종류의 모래를 사용하여 압밀시험을 수행한 결과, 간극률이 감소함에 따라 전기비저항이 증가하였으며, Arichie 공식에 사용되는 m값이 입자의 크기보다 형상에 영향을 받는 것으로 나타났다. 액상화 수조에서 수행된 실험결과 체적간극률과 유사한 전기비저항 간극률이 산정되었다. 대형 토조에서 수행된 관입실험으로부터 간극률 주상도를 얻을수 있었다. 본 논문에서 제시된 4ERP는 포화 지반의 간극률을 효과적으로 산정할 수 있는 장비가 될 수 있을것으로 판단된다.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1512-1512
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• 2001

The University of Cordoba conducts since 1991 a breeding program to obtain new olive cultivars from intraspecific crosses. The objective is to obtain new early bearing and high-quality cultivars. In plant breeding, many seedlings must be tested to increased the chance of getting desirable genotypes. Therefore, fast, cheap and accurate methods of analysis are necessary. The conventional laboratory techniques are costly and time-consuming. Near Infrared Spectroscopy (NIRS) can satisfy the characteristics requested by plant breeders and offers many advantages such as the simultaneous analysis of many traits and cheap cost. The objective of this work was to asses the performance of NIRS to estimate oil fruit components (fruit weight, flesh moisture, flesh/stone ratio and oil flesh content in dry weight basis) and fatty acid composition in olive fruit. Genotypes from reciprocal crosses between ‘Arbequina’, ‘Frantoio’ and ‘Picual’ cultivars have been used in this study. A total of 287 samples, each from a single plant, were scanned using a DA-7000 Diode Array VIS/NIR Analysis System (Perten Instruments), which covers the visible and NIR range from 400-1700 nm. All samples were analysed for fatty acid composition (gas chromatography) and 220 for oil fruit components (oil content by nuclear magnetic resonance), 70% and 30% of samples were randomly assign for the calibration and validation sets respectively. The preliminary results shows that calibration for palmitic, oleic and linoleic acids were highly accurate with calibration and validation values of $r^2$ from 0.85 to 0.95 and 0.76 to 0.91 respectively. Calibration for palmitoleic and estearic acids were less accurate, probably because of the narrow range of variability available for these fatty acids. For the oil fruit components, calibration were high accurate for flesh moisture and oil flesh content in dry weight basis ($r^2$ higher than 0.90 in both calibration and validation sets) and less accurate for the other characteristics evaluated. The first results obtained indicate that NIRS analysis could be an ideal technique to reduce the cost, time and chemical wasted necessary to evaluate a large number of genotypes and it is accurate enough to use for pre-selecting genotypes in a breeding program.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권4호
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• pp.246-252
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• 2002

Two kinds of PZT cantilevers integrated with a piezoresistor have been newly designed, fabricated, and characterized for high speed AFM. In first cantilever, a piezoresistor is used to sense atomic force acting on tip, while in second cantilever, a piezoresistor is integrated to calibrate hysteresis and creep phenomena of the PZT cantilever. The fabricated PZT cantilevers provide high tip displacement of $0.55\mu\textrm{m}/V$ and high resonant frequency of 73 KHz. A new cantilever structure has been designed to prevent electrical coupling between sensor and PZT actuator and the proposed cantilever shows 5 times lower coupling voltage than that of the previous cantilever. The fabricated PZT cantilever shows a crisp scanned image at 1mm/sec, while the conventional piezo-tube scanner shows blurred image even at $180\mu\textrm{m}/sec$. The non-linear properties of the PZT actuator are also well calibrated using the piezoresistive sensor for calibration.

• 약학회지
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• 제47권3호
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• pp.148-153
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• 2003

Skin moisture is an important factor in skin health. Measurement of moisture content can provide diagnostic information on the condition of skin. In this study, a portable near-infrared (NIR) system was newly integrated with a photo diode array detector that has no moving parts, and this system has been successfully applied for the evaluation of human skin moisture. Diffuse reflectance spectra were collected and transformed to absorbance using 1 nm step size over the wavelength range of 1100 nm to 2200 nm. Partial least squares regression (PLSR) was applied to develop a calibration model. For practical use for the evaluation of human skin moisture, the PLS model for human skin moisture was developed in vivo using the portable NIR system on the basis of the relative water content values of stratum corneum from the conventional capacitance method. The PLS model showed a good correlation. The calibration with the use of PLS model predicted human moisture with a standard error of prediction (SEP) of 3.5 at 1120∼1730 nm range. This study showed the possibility of skin moisture measurement using portable NIR system.

• Journal of Biosystems Engineering
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• 제29권4호
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• pp.323-328
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• 2004

A surface plasmon resonance (SPR) sensing system, which belonged to a family of thin film refractometry-based sensors, was fabricated to measure the alcohol contents in alcoholic beverages. In this study, a SPR owe was obtained by a photodiode array with 128 pixels and transformed into a refractive index which was calculated by means of the first moment of values below a baseline of 0.85. When the sensing system was applied to Soju, Cheonju, Igwaduju and Tacju highly linear relationships between the refractive index by SPR and the contents of alcohol were obtained. That is, the coefficients of determination in their linear models were 0.992, 0.933, 0.918 and 0.954, respectively. Meanwhile, the effect of sample preparations on the accuracy of measurement was analyzed. As for Soju and Tacju, the best calibration equations were obtained when no sample preparation was applied. The best calibration models for measurement of Cheonju and Igwaduju were obtained through the samples filtered by $C_{18}$ disks.

• 천문학회보
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• 제44권1호
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• pp.59.2-59.2
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• 2019

Event Horizon Telescope (EHT) aims to resolve the innermost region to the super massive black hole (SMBH) with its extremely high angular resolution (~20-25 uas) and enhanced sensitivity (down to 1-10 mJy) in concert with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm wavelength. This has a great importance as the first observational probe of the black hole shadow which has been theoretically predicted as a ring-like emission affected by the general relativistic effect under a strong gravitational field of SMBH. During the 2017 April 5-11, four nights of EHT observing campaign were carried out towards its primary targets, M87 and $SgrA{\ast}$. To robustly ensure the data processing, independent pipelines for various radio data calibration softwares (e.g., AIPS, HOPS, CASA) have been developed and cross-compared each other. The EHT has also been developing newer interferometric imaging techniques (e.g., eht-imaging-library, SMILI, dynamical imaging), as well as using an established method (CLEAN). With these, the EHT has designed various strategies which will be adopted for convincing imaging results. In this talk, I review how the robustness of EHT data processing and imaging will be validated so that the results can be ensured against well known uncertainties or biases in the interferometric data calibration and imaging.

• 한국가스학회지
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• 제24권2호
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• pp.44-49
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• 2020

본 논문에서는 산화주석 기반 반도체식 가스센서의 제조사양을 분석하여 측정회로를 설계하였다. 또한, 실제 가스안전관리 산업현장에서 가스센서를 사용하기 위하여 응답특성시험을 통한 최적 입출력 방정식을 도출하였다. 산화물 반도체 가스센서의 응답특성은 6종의 농도를 가진 표준가스를 제조하여 주입하며 출력전압을 측정을 통해 분석되었다. 각각 농도가 다른 가스의 주입에 대한 센서의 출력 전압의 관계를 룩업 테이블로 생성하였다. 생성된 룩업테이블의 데이터가 등간격이면 근사함수법으로 다항식을 도출할 수 있다. 그래서 5차의 다항식을 정의하고, 그 계수를 최소자승법으로 구하여 센서의 입출력 특성을 대표하는 5차 다항식을 완성하였다. 제안된 5차 다항식이 가스검지기 등에 실제로 적용되기 위해서는 다항식의 역변환이나 사이 값이 추가된 배열형태로 프로그래밍이 다시 생성되어져야 한다. 본 연구에서는 사이 값을 1/5로 세밀하게 구분 및 보간을 계산하여 배열형태로 구현되었다. 제안한 5차 캘리브레이션 교정식의성능은 표준가스를 주입 및 그 농도를 측정했을 때 일차방정식보다 오차가 감소됨을 확인되었다.