• 한국음향학회지
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• 제10권1호
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• pp.20-29
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• 1991

기존의 선형 예측법에 의한 음성 분석의 기본적인 가정은 전극점 성도 필터의 입력은 백색 신호라는 것이다. 그러나, 주기성 입력 신호의 경우 피치 바이오스 오차가 기존 선형 예측 계수에 개입된다. 만일 여기 신호의 추정값을 이용할 수 있다면 멀티 펄스에 의한 선형 예측 분석으로 이러한 바이어스를 제거할 수 있다. 기존의 선형 예측 분석에서의 예측 오차는 멀티 펄스 여기 신호열과 불규칙 잡음 신호열의합으로 나타내어질 수 있으므로 선형 예측 오차로부터 멀티 펄스 신호열을 찾아내는 것은 고전적인 검출 및 추정의 문제로 생각될 수 있다. 본 논문에서는 먼저 LRT 를 이용하여 예측오차로부터 멀티 펄스 신호의 위치와 크기를 찾아낸 다음 이 신호열로부터 피치 바이어스가 제거된 선형 예측 계수를 구하는 알고리즘을 제안한다. 매번 적응된 임계값을 적용하여 반복 수행을 함으로써 성능향상을 입증하였다.

• 한국산업보건학회지
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• 제26권1호
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• pp.48-57
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• 2016

Objectives: This study was conducted to evaluate the accuracy and precision of airborne metal analysis using polyvinyl chloride(PVC) membrane filter by pretreatment methods. Methods: A total of 75 spiked PVC samples for Cr, Fe and Mn ranged from 6 ug/sample to 40 ug/sample were used to evaluate recovery rates for three pretreatment methods: acid extraction, hot plate ashing and microwave digestion. For Mn, an additional 75 spiked mixed cellulose ester(MCE) membrane filters were analysed to compare the recovery rates of PVC samples. All samples were analysed with an inductively coupled plasma optical emission spectrometer(ICP-OES) and manganese samples were additionally analyzed by atomic absorption spectrometer(AAS). Results: The overall mean recovery rates of PVC samples for Cr, Fe and Mn were 90% or higher regardless of pretreatment methods, but there were statistically significant differences in recovery rates for Cr(p<0.05) and Mn(p<0.01) samples by pretreatment methods. The biases and the coefficient variations of PVC samples for three metals pretreated with three kinds of pretreatment methods ranged from 1.7% to 4.7% and from 1.6% to 6.5%, respectively. The manganese PVC samples pretreated by microwave digestion and analyzed with ICP-OES had the lowest bias at 1.9% and also showed lower bias than the bias for MCE samples, 2.7%. Conclusions: In order to accurately analyze the metals sampled with PVC membrane filters, microwave digestion and ICP-OES can be recommended.

• Animal Bioscience
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• 제34권10호
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• pp.1623-1631
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• 2021

Objective: This study aimed to validate and evaluate the dry matter (DM) intake prediction model of the Korean feeding standards for dairy cattle (KFSD). Methods: The KFSD DM intake (DMI) model was developed using a database containing the data from the Journal of Dairy Science from 2006 to 2011 (1,065 observations 287 studies). The development (458 observations from 103 studies) and evaluation databases (168 observations from 74 studies) were constructed from the database. The body weight (kg; BW), metabolic BW (BW^0.75, MBW), 4% fat-corrected milk (FCM), forage as a percentage of dietary DM, and the dietary content of nutrients (% DM) were chosen as possible explanatory variables. A random coefficient model with the study as a random variable and a linear model without the random effect was used to select model variables and estimate parameters, respectively, during the model development. The best-fit equation was compared to published equations, and sensitivity analysis of the prediction equation was conducted. The KFSD model was also evaluated using in vivo feeding trial data. Results: The KFSD DMI equation is 4.103 (±2.994)+0.112 (±0.022)×MBW+0.284 (±0.020)×FCM-0.119 (±0.028)×neutral detergent fiber (NDF), explaining 47% of the variation in the evaluation dataset with no mean nor slope bias (p>0.05). The root mean square prediction error was 2.70 kg/d, best among the tested equations. The sensitivity analysis showed that the model is the most sensitive to FCM, followed by MBW and NDF. With the in vivo data, the KFSD equation showed slightly higher precision (R² = 0.39) than the NRC equation (R² = 0.37), with a mean bias of 1.19 kg and no slope bias (p>0.05). Conclusion: The KFSD DMI model is suitable for predicting the DMI of lactating dairy cows in practical situations in Korea.

• Tribology and Lubricants
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• 제38권6호
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• pp.255-260
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• 2022

This research presents tetrahedral amorphous (ta-C) coating on the artificial tooth for improving the durability and functionality (esthtics, foreign body of tooth) by filtered cathodic vacuum arc (FCVA). A differentiated coating method is required for a ta-C coating on polymer owing to the low melting point of the polymer, inter-facial adhesion, low friction, and non-conductivity. Herein, ta-C coating is applied below 50℃, and the potential difference of the carbon plasma drawn to the substrate was controlled by applying a positive duct bias voltage without using a substrate bias voltage. Consequently, the ta-C coating with a thickness of 70nm using the duct bias condition of 20V with the highest plasma intensity satisfies the esthetics of the artificial tooth and had a 5B level of inter-facial adhesion. In addition, the composite hardness of ta-C/polymer is 380 MPa, and correlations with esthetics, sp³ bonding, and mechanical properties. The friction coefficient (CoF) of the ta-C coating in a water-lubricated environment is 0.07, showing a six-fold reduction in CoF compared with that of a polymer.

• 대기
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• 제33권4호
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• pp.423-440
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• 2023

The updated version of Global Ocean Data Assimilation and Prediction System (GODAPS) in the NIMS/KMA (National Institute of Meteorological Sciences/Korea Meteorological Administration), which has been in operation since December 2021, is being introduced. This technical note on GODAPS2 describes main progress and updates to the previous version of GODAPS, a software tool for the operating system, and its improvements. GODAPS2 is based on Forecasting Ocean Assimilation Model (FOAM) vn14.1, instead of previous version, FOAM vn13. The southern limit of the model domain has been extended from 77°S to 85°S, allowing the modelling of the circulation under ice shelves in Antarctica. The adoption of non-linear free surface and variable volume layers, the update of vertical mixing parameterization, and the adjustment of isopycnal diffusion coefficient for the ocean model decrease the model biases. For the sea-ice model, four vertical ice layers and an additional snow layer on top of the ice layers are being used instead of previous single ice and snow layers. The changes for data assimilation include the updated treatment for background error covariance, a newly added bias scheme combined with observation bias, the application of a new bias correction for sea level anomaly, an extension of the assimilation window from 1 day to 2 days, and separate assimilations for ocean and sea-ice. For comparison, we present the difference between GODAPS and GODAPS2. The verification results show that GODAPS2 yields an overall improved simulation compared to GODAPS.

• 한국항해항만학회지
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• 제28권3호
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• pp.213-219
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• 2004

본 논문에서는 1,452∼l,492 MHz L-Band 대역의 위성 DAB 수신기를 위한 저잡음증폭기를 입ㆍ출력 반사계수와 전압정재파비를 개선하기 위하여 평형증폭기 형태로 설계 및 제작하였다. 저 잡음증폭기는 GaAs FET소자인 ATF-10136을 사용한 저 잡음증폭단과 MMIC 소자인 VNA-25을 사용한 이득증폭단을 하이브리드 방식으로 구성하였으며, 최적의 바이어스를 인가하기 위하여 능동 바이어스 회로를 사용하였다. 적용된 능동 바이어스 회로는 소자의 펀치오프전압($V_P$)과 포화드래인 전류($I_{DSS}$)의 변화에 따라 주어진 바이어스 조건을 만족시키기 위해 소스 저항과 드래인 저항의 조절이 필요없다. 즉, 능동 바이어스 회로는 요구된 드래인 전류와 전압을 공급하기 위해 게이트-소스 전압($V_{gs}$)을 자동적으로 조절한다. 저잡음증폭기는 바이어스 회로와 RF 회로를 FR-4기판 위에 제작하였고, 알류미늄 기구물에 장착하였다. 제작된 저잡음증폭기는 이득 32 dB, 이득평탄도 0.2 dB, 0,95 dB 이하의 잡음지수, 입ㆍ출력 전압정재파비는 각각 1.28, 1.43이고, $P_{1dB}$ 는 13 dBm으로 측정되었다.

• 한국지구과학회지
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• 제36권4호
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• pp.330-340
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• 2015

본 연구에서는 CCD 카메라가 장착된 Skyviewer로부터 촬영된 하늘 영상 자료를 이용하여 전운량을 산출하는 알고리즘을 개발하였다. 전운량 산출은 RGB 영상 내의 차폐 영역을 제거하고 GBR 빈도분포에 따른 영상을 분류하며, RBR 경계값을 결정하여 구름 화소를 분류한다. 분류된 구름 화소에서 태양광 영역을 제거한 후 유효성 검사를 통해 전운량을 산출하게 된다. 전운량 산출 알고리즘의 정확성을 검증하기 위하여 관측소와 가장 가까운 강원지방기상청의 목측 전운량 자료와 편이(Bias), 평균제곱근오차(RMSE), 상관계수를 분석하였다. 선정된 사례는 계절별 일 사례로 8시부터 17시까지의 정시 자료를 사용하였다. 분석 결과 Skyviewer로부터 산출된 전운량의 편이는 평균적으로 -0.8할의 차이를 보였으며, 평균제곱근오차는 1.6할로 전운량의 차이가 2할 내에서 나타나고 있었다. 또한, 두 관측소는 떨어진 거리의 차이가 있음(약 4 km)에도 불구하고 상관계수가 모든 사례에서 평균 0.91 이상으로 매우 높았다.

• 대한원격탐사학회지
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• 제29권6호
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• pp.601-610
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• 2013

As a standard water clarity variable, the vertical underwater visibility, called Secchi depth, is estimated with ocean color satellite data. In the present study, Moderate Resolvtion Imaging Spectradiometer (MODIS) data are used to measure the Secchi depth which is a useful indicator of ocean transparency for estimating the water quality and productivity. To estimate the Secchi depth $Z_v$, the empirical regression model is developed based on the satellite optical data and in-situ data. In the previous study, a semi-analytical algorithm for estimating $Z_v$ was developed and validated for Case 1 and 2 waters in both coastal and oceanic waters using extensive sets of satellite and in-situ data. The algorithm uses the vertical diffuse attenuation coefficient, $K_d$($m^{-1}$) and the beam attenuation coefficient, c($m^{-1}$) obtained from satellite ocean color data to estimate $Z_v$. In this study, the semi-analytical algorithm is validated using temporal MODIS data and in-situ data over the Yellow, Southern and East Seas including Case 1 and 2 waters. Using total 156 matching data, MODIS $Z_v$ data showed about 3.6m RMSE value and 1.7m bias value. The $Z_v$ values of the East Sea and Southern Sea showed higher RMSE than the Yellow Sea. Although the semi-analytical algorithm used the fixed coupling constant (= 6.0) transformed from Inherent Optical Properties (IOP) and Apparent Optical Properties (AOP) to Secchi depth, various coupling constants are needed for different sea types and water depth for the optimum estimation of $Z_v$.

• 대한원격탐사학회지
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• 제37권1호
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• pp.169-176
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• 2021

The Global Space-based Inter-Calibration System (GSICS) is an international partnership sponsored by World Meteorological Organization (WMO) to continue and improve climate monitoring and to ensure consistent accuracy between observation data from meteorological satellites operating around the world. The objective for GSICS is to inter-calibration from pairs of satellites observations, which includes direct comparison of collocated Geostationary Earth Orbit (GEO)-Low Earth Orbit (LEO) observations. One of the GSICS inter-calibration methods, the Ray-matching technique, is a surrogate approach that uses matched, co-angled and co-located pixels to transfer the calibration from a well calibrated satellite sensor to another sensor. In Korea, the first GEO satellite, Communication Ocean and Meteorological Satellite (COMS), is used to participate in the GSICS program. The National Meteorological Satellite Center (NMSC), which operated COMS/MI, calculated the Radiative Transfer Model (RTM)-based GSICS coefficient coefficients. The L1P reproduced through GSICS correction coefficient showed lower RMSE and Bias than L1B without GSICS correction coefficient applied. The calculation cycles of the GSICS correction coefficients for COMS/MI visible channel are provided annual and diurnal (2, 5, 10, 14-day), but long-term evaluation according to these cycles was not performed. The purpose of this paper is to perform evaluation depending on the annual/diurnal cycles of COMS/MI GSICS correction coefficients based on the ray-matching technique using Suomi-NPP/Visible Infrared Imaging Radiometer Suite (VIIRS) data as reference data. As a result of evaluation, the diurnal cycle had a higher coincidence rate with the reference data than the annual cycle, and the 14-day diurnal cycle was the most suitable for use as the GSICS correction coefficient.

• 대한원격탐사학회지
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• 제35권6_4호
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• pp.1373-1389
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• 2019

KOMPSAT-5는 우리나라 최초의 X 밴드 Synthetic Aperture Radar (SAR) 탑재 인공위성으로, 2013년 8월부터 운영되고 있다. KOMPSAT-5는 운영 목적에 따라 지구환경 감시에 적극적으로 활용되고 있으며, 연안 환경 감시를 위한 고해상도 해상풍의 필요성이 강조되면서 KOMPSAT-5의 활용도도 부각되고 있다. 하지만, 기존의 해상풍 정확도 검증 연구에서는 다른 SAR 탑재 인공위성 기반 해상풍에 비해 정확도가 낮은 것으로 나타났다. 따라서 본 연구에서는 KOMPSAT-5 기반 해상풍의 정확도 개선을 위한 후방산란계수 보정식을 산출하였고, 보정식의 개선 효과를 해양 부이 자료를 활용하여 검증하였다. 18장의 미국 서부와 하와이 연안을 관측한 KOMPSAT-5 자료와 해양 부이 자료를 활용하여 후방산란계수 보정식을 산출하였고, 산출한 후방산란계수 보정식은 18장의 한반도 연안을 관측한 KOMPSAT-5 자료에 적용하여 해상풍을 산출하였다. 이론적으로 산출된 후방산란계수와 KOMPSAT-5에서 관측된 후방산란계수는 입사각에 따른 1차 함수 관계식을 따르는 것으로 나타났다. 보정식을 적용하기 전에는 2.89 m s^-1의 상대적으로 큰 평균 제곱근 오차와 -0.55 m s^-1의 편차를 보였다. 보정식을 적용한 후에는 각각 1.60 m s^-1, -0.38 m s^-1로 개선되었다. 입사각의 범위에 따라 후방산란계수 보정식의 개선 효과는 다르게 나타났다.