• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.344-347
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• 2005

The purpose of the study for the development of the technologies of water quality monitoring and contamination protection at water resource aquifer is to secure the groundwater as potable water resources. The results of water analysis as a basis of potable water criteria showed that 30 groundwater samples among 138 samples of small water supply system (21.7%) were exceeded the water criteria. The concentrations of Cl, $NO_3$ and Na for granite area are higher than those of gneiss and metasedimentary rocks of Ogcheon belt area and they are caused by the high vulnerability of groundwater at granite region where the residential area and cultivated land are concentrated. The spatial distribution of components indicated the close relationships between water quality and geology, land use, and topography. The multivariate statistical results showed that the water samples are divided into three groups by geology.

• 생태와환경
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• 제41권spc호
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• pp.1-10
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• 2008

We patterned water quality of agricultural reservoirs according to the differences of six physico-chemical environmental factors (TN, TP, DO, BOD, COD, and SS) using four different ordination methods: Principal Components Analysis (PCA), Detrended Correspondence Analysis (DCA), Nonmetric Multidimensional Scaling (NMS), and Isometric Feature Mapping (Isomap). The data set was obtained from the water quality monitoring networks operated by the Ministry of Agriculture and Forestry and the Ministry of Environments. Chlorophyll-${\alpha}$ displayed the highest correlation with COD, followed by TP, BOD, SS, and TN (p<0.01), while negatively correlated with altitude and bank height of the reservoirs (p<0.01). Although four different ordination methods similarly patterned the reservoirs according to the gradient of nutrient concentration, PCA and NMS appeared to be the most efficient methods to pattern water quality of reservoirs based on the explanation power. Considering variable scores in the ordination map, the concentration of nutrients was positively correlated with Chl-${\alpha}$, while negatively correlated with altitude and bank height. These ordination methods may help to pattern agricultural reservoirs according to their water quality characteristics.

• Journal of the Korean Data and Information Science Society
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• 제28권2호
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• pp.451-459
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• 2017

There are many researches showing that when a process change has occurred, variable sampling intervals (VSI) control chart is better than the fixed sampling interval (FSI) control chart in terms of reducing the required time to signal. When the process engineers use VSI control procedure, frequent switching between different sampling intervals can be a complicating factor. However, average number of samples to signal (ANSS), which is the amount of required samples to signal, and average time to signal (ATS) do not provide any control statistics about switching performances of VSI charts. In this study, we evaluate numerical switching performances of multivariate VSI EWMA chart including average number of switches to signal (ANSW) and average switching rate (ASWR). In addition, numerical study has been carried out to examine how to improve the performance of considered chart with accumulate-combine approach under several different smoothing constant and sample size. In conclusion, process engineers, who want to manage the correlation coefficients of related quality variables, are recommended to make sample size as large and smoothing constant as small as possible under permission of process conditions.

• 약학회지
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• 제47권6호
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• pp.461-468
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• 2003

A method is described for measuring clinically relevant levels of glucose in a pH 7.4 phosphate buffer by nearinfrared (NIR) absorption spectroscopy. Three types of NIR spectrometer, dispersive type, photo-diode array (PDA) type, and fourier transform (FT) type spectrometer were used and the performance was compared. Spectra were collected with a cuvette cell or quartz liquid fiber of 1 mm or 2 mm optical pathlength as transmittance method. Glucose absorption band appeared at second overtone, first overtone, and combination region for all systems. By use of the multivariate technigue of partial least squares (PLS) regression, glucose concentrations can be determined with a 16, 44, and 9.1 mg/d l standard error of prediction for dispersive type, photo-diode array type, and fourier transform type system, respectively. Sensitivity of spectrometer was evaluated by absorbance for the difference of 10 mg/d l glucose. Three absorption bands, second overtone, first overtone, and combination region were suited to three types systems, dispersive type, photo-diode array type, and fourier transform type systems, respectively. This investigation showed that three types NIR spectrometer were proper method for identification and quantitative analysis of glucose and possible for noninvasive blood glucose monitoring.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3000-3005
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• 2015

신뢰할 수 있는 공정 감시와 진단은 생산 공정의 안전과 최종제품의 품질을 보장이라는 관점에서 중요하다. 공정진단의 목적은 특정한 공정 이상의 원인을 밝혀내는 것이다. 본 연구에서는 분류기법에 기반한 공정진단 체계를 제시한다. 여기서는 공정데이터를 비선형 데이터 표현기법을 통해 변환함으로써 데이터의 크기를 줄이며 효율적인 데이터 표현이 가능하다. 추가적인 단계로서 공정 데이터의 전처리 과정을 통해 진단에 무관한 공정 패턴을 제거하고 진단 성능을 높이고자 한다. 진단 성능을 평가하기 위해 회분식 공정에 대한 사례연구를 수행한 결과 기존 선형 진단 방법론 및 전처리 과정이 없는 방법론에 비해 향상된 진단 결과를 얻을 수 있었다.

• Journal of Information Processing Systems
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• 제14권3호
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• pp.590-599
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• 2018

Multivariate finite mixture model is becoming more and more popular in image processing. Performing image denoising from image patches to the whole image has been widely studied and applied. However, there remains a problem that the structure information is always ignored when transforming the patch into the vector form. In this paper, we study the operator which extracts patches from image and then transforms them to the vector form. Then, we find that some pixels which should be continuous in the image patches are discontinuous in the vector. Due to the poor anti-noise and the loss of structure information, we propose a new operator which may keep more information when extracting image patches. We compare the new operator with the old one by performing image denoising in Expected Patch Log Likelihood (EPLL) method, and we obtain better results in both visual effect and the value of PSNR.

• 한국입자에어로졸학회지
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• 제18권4호
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• pp.109-127
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• 2022

Recently, low-cost particulate matter (PM) sensors have been widely used in monitoring mass concentration. Maintaining the accuracy of the sensors is important and requires rigorous performance evaluation and calibration. In this study, two commercial low-cost PM sensors(LCS), Plantower PMS3003 and Plantower PMS7003, were evaluated in the laboratory and field with a reference-grade PM monitor (GRIMM 11-D). Laboratory evaluation was conducted with single/mixed particles of PSL (Poly Styrene Latex) in an acrylic chamber at 20℃ and relative humidity of 20%. Field evaluation was conducted inside a building of Yonsei University (Shinchon) from February 12 to March 31, 2022. In both evaluations, LCS measured values became different from reference measured values when the relative humidity was high or the outdoor air PM10/PM2.5 ratio was high. Based on the field evaluation, the LCS measured values were corrected through four different regression analysis models. As a result, the multivariate polynomial regression analysis model showed highest matching with the reference PM monitor (PM2.5 >0.9, PM10 >0.85). In this model, the PM10/PM2.5 ratio and relative humidity were chosen as independent variables.

• 한국해양학회지:바다
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• 제11권2호
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• pp.92-96
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• 2006

비선형 주성분 분석은 기존에 널리 알려져 있는 주성분 분석기법과 유사한 다변수 데이터 분석을 위한 새로운 접근 방법이다. 비선형 주성분 분석은 AANN(Auto Associative Neural Network)으로 PCA와 마찬가지로 변수들 간에 존재하는 상관관계를 제거함으로써 고차의 다변수 데이터를 정보의 손실을 최소화하면서 최소 차원의 데이터로 변환하는 기법이다. AANN기반 센서 고장 검출 기법을 실제 방재시스템에 적용하여 봄으로써 센서 드리프트 등과 같은 센서 고장의 검출 및 유효한 센서 보정 성능을 확인하였다.

• Structural Monitoring and Maintenance
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• 제11권1호
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• pp.41-55
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• 2024

This study aims to determine the characteristics of concrete as identified by Rebound Hammer and Ultrasonic Pulse Velocity (UPV) tests, focusing particularly on their efficacy in estimating compressive strength of concrete material. The study involved three concrete samples designed to achieve a target strength of 29 MPa, comprising normal concrete, instant concrete, and concrete with additives. These were cast into cube specimens measuring 150×150×150 mm. Compressive strength values were determined through both destructive and non-destructive testing on the cubic specimens. As a result, the non-destructive methods yielded varying outcomes for each correlation approach, influenced by the differing constituent materials in the tested concretes. However, normal concrete consistently showed the most reliable correlation, followed by concrete with additives, and lastly, instant concrete. The study found that combining Rebound Hammer and UPV tests enhances the prediction accuracy of compressive strength of concrete. This synergy was quantified through multivariate regression, considering UPV, rebound number, and actual compressive strength. The findings also suggest a more significant influence of the Rebound Hammer measurements on predicting compressive strength for BN and BA, whereas UPV and RN had a similar impact on predicting BI compressive strength.

• Korean Chemical Engineering Research
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• 제50권6호
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• pp.980-987
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• 2012

비점오염원은 세정에 의해 하수관 내로 유입되어 수계까지 흘러 수계의 오염부하를 가중시킬 뿐만 아니라, 관의 상태에 따라 누수 및 월류를 야기하여 오염을 일으킨다. 이에 따라 하수관거의 유지관리 및 환경오염 방지를 위한 관거내 하수의 유량, 수질, 불명수 및 월류 등을 효율적으로 관리하기 위한 모니터링의 필요성이 증가하고 있다. 그러나 하수관거의 경우, 지하에 설계되며 그 구조 및 연결이 복잡한 특성으로 인해 실제 하수관거에 대한 모니터링은 쉽지 않다. 본 연구에서는 시스템해석이론에 기초한 하수관망 오염제거 해석과 관망 모니터링 및 이상진단방법을 제시하였다. 먼저 하수관망 공정모사 프로그램인 Stormwater & Wastewater Management Model for expert (XP-SWMM)을 이용하여 관망 내의 오염물질의 거동패턴을 해석하였다. 둘째, 다변량 통계 모니터링을 이용하여 하수관망 내의 수질 모니터링 및 하수관망 유출을 탐지하는 관망 이상 진단을 수행하였다. 정적/동적 상태 시스템에 기초한 하수관망 오염 매카니즘 해석결과, 강우시 총질소와 총인 부하량이 비강우시보다 급격하게 증가함을 확인하였으며, 이는 수계의 오염부하를 가중시킬 것으로 판단되다. 이에 따라 하수관망 내 유출은 강우로 생긴 유량 및 유입오염물질의 농도 증가로 인한 관망이상으로 사료된다. 제안된 하수관망 모니터링 및 이상진단 기법은 도시 유역에서의 비점오염원 관리와 지속적인 모니터링에 있어 효과적으로 사용될 수 있을 것으로 예상된다.