• Structural Engineering and Mechanics
• /
• v.25 no.3
• /
• pp.311-330
• /
• 2007

Model-based predictions of structural behavior are negatively affected by uncertainties of various type and in various stages of the structural analysis. The present paper focusses on dynamic analysis and addresses the effects of uncertainties concerning material and geometric parameters, mainly in the context of modal analysis of large-scale structures. Given the large number of uncertain parameters arising in this case, highly scalable simulation-based methods are adopted, which can deal with possibly thousands of uncertain parameters. In order to solve the reliability problem, i.e., the estimation of very small exceedance probabilities, an advanced simulation method called Line Sampling is used. In combination with an efficient algorithm for the estimation of the most important uncertain parameters, the method provides good estimates of the failure probability and enables one to quantify the error in the estimate. Another aspect here considered is the uncertainty quantification for closely-spaced eigenfrequencies. The solution here adopted represents each eigenfrequency as a weighted superposition of the full set of eigenfrequencies. In a case study performed with the FE model of a satellite it is shown that the effects of uncertain parameters can be very different in magnitude, depending on the considered response quantity. In particular, the uncertainty in the quantities of interest (eigenfrequencies) turns out to be mainly caused by very few of the uncertain parameters, which results in sharp estimates of the failure probabilities at low computational cost.

• Journal of the Korean Magnetic Resonance Society
• /
• v.24 no.2
• /
• pp.53-58
• /
• 2020

Free radicals including reactive oxygen species (ROS) are important chemicals in the research area of biology, pharmaceutical, medical, and environmental science as well as human health risk assessment as they are highly involved in diverse metabolism and toxicity mechanisms through chemical reactions with various components of living bodies. Electron spin resonance (ESR) spectroscopy is a powerful tool for detecting and quantifying those radicals in biological environments. In this work we observed the ESR signal of 2,2,6,6-Tetra-methyl piperidine 1-oxyl (TEMPO) in aqueous solution at various concentrations to estimate the uncertainty factors arising from the experimental conditions and signal treatment methods. As the sample position highly influences the signal intensity, dual ESR tube geometry (consists of a detachable sample tube and a position fixed external tube) was adopted. This type of measurement geometry allowed to get the relative uncertainty of signal intensity lower than 1% when triple measurements are averaged. Linear dependence of signal intensity on the TEMPO concentration, which is required for the quantification of unknown sample, could be obtained over a concentration range of ~10³ by optimizing the signal treatment method depending on the concentration range.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.765-769
• /
• 2014

An analytical methodology was developed for qualitative and quantitative impurity profiling of the coloring agent Sudan III by high-performance liquid chromatography (HPLC)-diode array detection (DAD). The impurities in commercial Sudan III were characterized by comparison of their retention times and UV spectra with those of authentic standards. Four impurities regulated by International Committees in Sudan III were quantified by HPLC-selective UV detection. The impurities in Sudan dye were successfully separated on a reversed phase C18-column within 25 min and sensitively detected by UV spectrometry at two selective wavelengths. Method validation was conducted to determine linearity, precision, accuracy, and limit of quantification (LOQ). The linear dynamic range extended from 0.002 to 4.0%, with a correlation coefficient (R2) greater than 0.995. The LOQs of the impurities ranged from 8.04 to $54.29{\mu}g/mg$. Based on the established method, the levels of regulated impurities in five commercial Sudan III dyes were determined.

• Smart Structures and Systems
• /
• v.22 no.2
• /
• pp.239-247
• /
• 2018

A magnetic flux leakage (MFL) method was applied to detect and quantify defects in a steel bar. A multi-channel MFL sensor head was fabricated using Hall sensors and magnetization yokes with permanent magnets. The MFL sensor head scanned a damaged specimen with five levels of defects to measure the magnetic flux density. A series of signal processing procedures, including an enveloping process based on the Hilbert transform, was performed to clarify the flux leakage signal. The objective damage detection of the enveloped signals was then analyzed by comparing them to a threshold value. To quantitatively analyze the MFL signal according to the damage level, five kinds of damage indices based on the relationship between the enveloped MFL signal and the threshold value were applied. Using the proposed damage indices and the general damage index for the MFL method, the detected MFL signals were quantified and analyzed relative to the magnitude of the damage increase.

• Nuclear Engineering and Technology
• /
• v.52 no.2
• /
• pp.287-295
• /
• 2020

Group method of data handling (GMDH) is considered one of the earliest deep learning methods. Deep learning gained additional interest in today's applications due to its capability to handle complex and high dimensional problems. In this study, multi-layer GMDH networks are used to perform uncertainty quantification (UQ) and sensitivity analysis (SA) of nuclear reactor simulations. GMDH is utilized as a surrogate/metamodel to replace high fidelity computer models with cheap-to-evaluate surrogate models, which facilitate UQ and SA tasks (e.g. variance decomposition, uncertainty propagation, etc.). GMDH performance is validated through two UQ applications in reactor simulations: (1) low dimensional input space (two-phase flow in a reactor channel), and (2) high dimensional space (8-group homogenized cross-sections). In both applications, GMDH networks show very good performance with small mean absolute and squared errors as well as high accuracy in capturing the target variance. GMDH is utilized afterward to perform UQ tasks such as variance decomposition through Sobol indices, and GMDH-based uncertainty propagation with large number of samples. GMDH performance is also compared to other surrogates including Gaussian processes and polynomial chaos expansions. The comparison shows that GMDH has competitive performance with the other methods for the low dimensional problem, and reliable performance for the high dimensional problem.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.5
• /
• pp.350-356
• /
• 2013

Photogrammetry has been widely used for measuring the important physical quantities in aerospace areas because it is a remote and non-contact measurement method. In this study, we analyzed photogrammetric error which can be occur in six degrees of freedom(6DOF) analysis among coordinates systems with single camera. Error analysis program were developed, and validated using geometric problem converted from imaging process. We analogized that the statistic from estimated camera pose which is need to 6DOF analysis is normally distributed, and quantified the photogrammetric error using estimated population standard deviation.

• Korean Journal of Pharmacognosy
• /
• v.49 no.1
• /
• pp.70-75
• /
• 2018

Acer tegmentosum Maxim (ATM) has been used to treat hepatic disorders in traditional oriental medicine. However, there is little information about phytochemical constituents for quality control of ATM. In this study, we developed and established a simultaneous analytical method of the 10 marker compounds (three coumarins, 3 flavonoids, 1 lignan, 3 phenolics) in ATM using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Chromatographic separation of ten target analytes was achieved with a Waters Acquity UPLC BEH $C_{18}$ analytical column ($2.1{\times}100mm$, $1.7{\mu}m$), using a mobile phase of 0.1% (v/v) formic acid in water and acetonitrile with gradient elution. Identifications and quantitation of all analytes were performed using a Q-Exactive UPLC-MS/MS system. Correlation coefficients of the calibration curve for all analytes were ${\geq}0.9986$. The values of limits of detection and quantification of all analytes were 0.5-10.0 and 5.0-50.0 ng/mL, respectively. The established UPLC-MS/MS method successfully identified all target analytes in ATM, and the phytochemicals were 0.01-67.98 mg/g in its lyophilized water extract.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.6
• /
• pp.127-139
• /
• 2000

In the study, an expert system was developed to predict the safety of tunnel and select proper tunnel reinforcement system using fuzzy quantification theory and fuzzy inference rule based on tunnel information database, For this development, many tunnelling sites were investigated and the applied countermeasures were studied after building tunnel database. There will be benefit for the deciding tunnel reinforcement method in the case of poor ground condition. The expert system developed in the study has two main parts, pre-module and post-module. Pre-module is used to decide input items of tunnel information based on the tunnel face mapping information which can be easily obtained in in-situ site. Then, using fuzzy quantification theory II, fuzzy membership function is composed and tunnel safety level is inferred through this membership function. Post-module is used to infer the applicability of each reinforcement methods according to the face level. The result of the predicted reinforcement system level was similar to measured ones. In-situ data were obtained in three tunnel sites including subway tunnel under Han River. Therefore, this system will be helpful to make the mose of in-situ data available and suggest proper applicability of tunnel reinforcement system to development more resonable tunnel support method without dependance of some experienced experts opinions.

• Journal of Biomedical Engineering Research
• /
• v.32 no.2
• /
• pp.85-92
• /
• 2011

Bioluminescence imaging (BLI) is the most sensitive animal imaging technique for molecular imaging research. Generally, highly sensitive CCD is used to detect an optical probe introduced in a living mouse. However, in many cases, the light signal emitted from a probe is too small to detect because it is scattered and attenuated by the tissue prior to being detected. The problem is that scattering and attenuation not only inhibit accurate measurement but also make image quality down. Thus we introduced a new method to reduce noise by using property of CCD and method to improve image quality of bioluminescence image by using two steps Gaussian blurring.

• Korean Journal of Pharmacognosy
• /
• v.50 no.1
• /
• pp.59-64
• /
• 2019

Cudrania tricuspidata Bureau (Moraceae) has been used for physical weakness, impotence and insomnia in traditional Korean medicine. In this study, cudratricusxanthone A and cudraxanthone D were isolated from roots of C. tricuspidata and quantification were achieved by using high performance liquid chromatography (HPLC) method with diode array detector. The isolated compound was identified by NMR analysis and HPLC method was validated by linearity, precision and specificity test. The results showed that calibration curves of two compounds indicated great linearity with a correlation coefficient ($R^2$) of 0.9976 and 0.9995. The limits of detection (LOD) for cudratricusxanthone A and cudraxanthone D were 1.15, $0.11{\mu}g/ml$. Intra-day precision of cudratricusxanthone A and cudraxanthone D were 0.32~1.99%, 0.09~3.32% and inter-day precision were 0.59~2.40%, 0.28~1.55% RSD (%) values, respectively. The specificity was confirmed by chromatograph and quantitative contents of cudratricusxanthone A and cudraxanthone D were $0.46{\pm}0.02%$ and $1.53{\pm}0.06%$. Therefore, this study can be used as a basic research data for the quantitative analysis of derived compounds from roots of C. tricuspidata.