• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.65-74
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• 1994

Various substructure synthesis methods, such as component mode synthesis, building block analysis and reduced impedance method, are studied for the determination of vibration characteristics of plate problems. Comparisons are made for each methods in terms of accuracy and computational efficiency. Following conclusions are made from the results of computer simulations and experiments. i) The computation time of component mode synthesis is much shorter than that of whole structure analysis. The natural frequencies of lower modes obtained from component mode synthesis are almost same as those obtained from whole structure analysis, but in higher modes the differences between those two methods are increases. ii) The transfer function obtained from building block analysis is same as that obtained from the finite element method. iii) Same transfer functions can be obtained by the reduced impedance method. The computation time of reduced impedance mathod is shorter that that of general finite element method, but for the solutions in broad frequency band it requires long calculation time.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.217-225
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• 2005

Because of the limitation of controllable operation variables for the wastewater treatment process with variable hydrodynamic flow patterns, it may preclude the use of this type of nutrient removal activated sludge process. As the operation variables, only temperature and dissolved oxygen (DO) have been used to operate the process. This study made an effort to improve treatment efficiency and operability of the process by the following methodologies: 1) process and operation data analysis using process simulation, 2) determination of optimal control logic or algorithm using a pilot-scaled experimental apparatus and its operations, and 3) application of experimental and simulation results to find the optimal process operation modes. In this study, it was found that the optimal operation mode named 'save mode' in the basis of process variables, such as the ammonia-nitrogen concentration of inlet flow, temperature and flow rate, can reduce the operation cost comparing with the present normal operation mode. And the stable conditions in nitrification were also shown by the proportional control of DO with the inlet air flow rate of blower and the mixing rate of mechanical aeration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.347-353
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• 2021

In this study, we presented a novel size optimization framework to control the linear buckling temperature and several buckling modes of plates, by optimizing thickness values of composite structures for practical engineering applications. Predicting the buckling temperature and mode shape of structures is a vital research topic in engineering to achieve structural stability. However, optimizing designs of engineering structures through engineering intuition is challenging. To address this limitation, we proposed a method that combines finite element simulation and size optimization. Based on the idea that the structural buckling temperature and mode shape of a plate are affected by the thickness of the structure, the thickness values of the nodes of the target structure were set as the design variables in this optimization method; and the buckling temperature values, and buckling mode shapes were set as the objective functions. This size optimization method enabled the determination of optimal thickness distributions, to induce the desired buckling temperature values and mode shapes. The validity of the proposed method was verified in terms of their buckling temperature values and buckling mode shapes, using several numerical examples of rectangular composite structures.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.304-309
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• 2006

Near infrared reflectance spectroscopy (NIRS) was used to develop a rapid and nondestructive method for the determination of fatty acid composition in sesame (Sesamum indicum L.) seed oil. A total of ninety-three samples of intact seeds were scanned in the reflectance mode of a scanning monochromator, and reference values for fatty acid composition were measured by gas-liquid chromatography. Calibration equations were developed using modified partial least square regression with internal cross validation (n=63). The equations obtained had low standard errors of cross-validation and moderate $R^2$ (coefficient of determination in calibration). Prediction of an external validation set (n=30) showed significant correlation between reference values and NIRS estimated values based on the SEP (standard error of prediction), $r^2$ (coefficient of determination in prediction) and the ratio of standard deviation (SD) of reference data to SEP. The models developed in this study had relatively higher values (more than 2.0) of SD/SEP(C) for oleic and linoleic acid, having good correlation between reference and NIRS estimate. The results indicated that NIRS, a nondestructive screening method could be used to rapidly determine fatty acid composition in sesame seeds in the breeding programs for high quality sesame oil.

• Journal of Photoscience
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• v.12 no.3
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• pp.137-141
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• 2005

The chemiluminescence reaction of lophine with $H_2O_2$ in alkaline solution has been investigated for use in determination of $Cu^{2+}$ ions. The observed chemiluminescence intensity is found to be a function of the concentration of $Cu^{2+}$. Under the optimum reagent concentrations such as $4{\times}10^{-4}M$ lophine, 0.8 M KOH, 0.2M $H_2O_2,{\lambda}_{em}$, 533nm, the linear range and the detection limit were found to be 0.048ug/ml-48.32ug/ml (R=0.99897) and 0.005ulg/ml respectively. Relative standard deviation for five determinations of 24.16ug/ml $Cu^{2+}$ is 2.35%. The interference from other species was investigated. The proposed method was applied to the determination of $Cu^{2+}$ in different water samples.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.197-203
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• 2014

A rapid, accurate and precise method for the determination of 22 amino acids in Isatidis Radix by Hydrophilic Interaction Ultra-High-Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (HILIC-UPLC-MS/MS) was established. Chromatographic separation was carried out on a Acquity UPLC BEH Amide column ($2.1mm{\times}100mm$, $1.7{\mu}m$) with gradient elution of acetonitrile (containing 0.05% formic acid and 2 mM ammonium formate) and water (containing 0.15% formic acid and 10 mM ammonium formate) at a flow rate of 0.4 mL/min; Waters Xevo$^{TM}$ TQ worked in multiple reaction monitoring mode. All components were separated in 17 min. All calibration curves were linear ($R^2$ > 0.991) over the tested ranges. The limits of detection (LOD) and limits of quantitation (LOQ) for these compounds were 0.21-79.55 and 0.72-294.23 ng/mL, respectively. The average recoveries were in the range of 93.75-104.16% with RSD value less than 6.56%. Therefore, this method could be an alternative assay for the determination of 22 amino acids in Isatidis Radix due to its rapidness, sensitivity, less sample and solvent consumption.

• Analytical Science and Technology
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• v.16 no.1
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• pp.82-89
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• 2003

Isotope dilution mass spectrometry (IDMS) was applied to the determination of Ni, Cr, Mo in low alloy steel reference materials. The Mo isotope ratio measurement was performed by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP/MS) using ammonia as a reaction cell gas. In the case of Ni and Cr measurement, all data were obtained at medium resolution mode (m/${\Delta}m=3000$) of double focusing sector field high resolution inductively coupled plasma mass spectrometry (HR-ICP/MS). For the method validation of the technique was assessed using the certified reference materials such as NIST SRM 361, NIST SRM 362, NIST SRM 363, NIST SRM 364, NIST SRM 36b. This method was applied to the determination of Ni, Cr and Mo in low alloy steel sample (CCQM-P25) provided by NMIJ for international comparison study.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.230-235
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• 2014

The failure modes of pneumatic directional control valves include leakage, wear of the spool seal, and sticking of the spool. Among them, the main failure mode of the valve is leakage. The leakage is caused by the wear of the spool seal. However, due to the characteristics of the seal material, the leakage rate is fluctuated a lot rather than constantly increased over time. If life analysis is performed using the first time data of leakage failure, predicted life cycles can be different from the real life cycles. This paper predicts life cycles of the pilot pneumatic directional control valve based on the three point moving average which considers the average of the fluctuating leakage rate.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.161-166
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• 2011

This paper proposes an algorithm for determining critical generator lists using accelerating power and synchronizing power coefficient (SPC), and critical generator group (CGG) from CGG candidates, which is a combination of critical generators. The accurate determination of CGG provides a more accurate energy margin while providing system operator with information of possible unstable generator group. Classical transient energy function (TEF) method selects the critical generators with big corrected kinetic energy of each generator at the moment of fault removal. However, the generator with small acceleration after fault, that is, the generator with small corrected kinetic energy, is also likely to belong to CGG if the generator has small synchronizing power. The proposed algorithm has been verified to be effective compared with the classical TEF method. We utilized the power system of Korean Electric Power Corporation(KEPCO) as a test system.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.05a
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• pp.145-145
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• 2003

A method for the determination of alkylphenols, chlorophenols and bisphenol A in paper materials using GC/MS-SIM has been developed. Eleven endocrine disrupting chemicals (EDCs) of phenols in paper samples were extracted with acetonitrile. Also, solid-phase extraction (SPE) with XAD-4 and subsequent conversion to isobutoxycarbonyl derivatives or tert.-butyldimethylsilyl derivatives for sensitive analysis with the selected ion-monitoring (SIM) mode. The recoveries were 82.4∼108.8 % by area ratio of pheranthrene-d$\sub$10/ vs bisphenol A d$\sub$l6/. (isoBOC derivatization and TBDMS derivatization) The SIM responses were linear with the correlation coefficient varying 0.9717∼0.9995 (isoBOC derivatization), and 0.9842∼0.9980 (TBDMS derivatization). The range of concentrations was respectively, 0.95∼l.44 ng/g in 2,4-dichlorophenol, 1.01∼1.17 ng/g in t-butylphenol, 2.17∼5.84 ng/g in pentachlorophenol, 12.68∼14.88 ng/g in nonylphenol and 30.84∼153.72 ng/g in bisphenol A.