• Proceedings of the KSME Conference
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• 2008.11a
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• pp.418-423
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• 2008

Among various sensitivity evaluation techniques, semi-analytical method is quite popular since this method is more advantageous than analytical method and global finite difference method. However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, the adjoint variable method combined with complex variable is proposed to obtain the shape and size sensitivity for structural optimization. The complex variable can present accurate results regardless of the perturbation size as well as easy to be implemented. Through a few numerical examples of the static problem for the structural sensitivity, the efficiency and reliability of the adjoint variable method combined with complex variable is demonstrated.

• YAKHAK HOEJI
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• v.58 no.3
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• pp.190-199
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• 2014

The Korean Pharmaceutical Codex (KPC) analytical method of ambroxol hydrochloride and clenbuterol hydrochloride formulation is complicated and needed to carry out multiple processes during the test. To improve the low efficiency of analytical procedure that makes pharmaceutical laboratory consume much time and high cost to conduct the test of this formulation, this study was performed for simplifying the pretreatment process and optimizing conditions of the HPLC assay. The analytical procedure using HPLC was developed to establish analytical specification for ambroxol hydrochloride and clenbuterol hydrochloride formulations. The newly developed analytical method has good linearity ($R^2$ >0.999), specificity, precision (RSD<1.0%) and the recovery ranges of 98.50~101.84% for ambroxol, 98.29~101.35% for clenbuterol syrup and 98.66~101.71% for clenbuterol tablets. The LOQs were 0.204 ${\mu}g/ml$ for ambroxol, 0.021 ${\mu}g/ml$ for clenbuterol syrup and 0.073 ${\mu}g/ml$ for clenbuterol tablets. The new method was performed with commercially available samples to confirm analytical conditions and validated to be suitable for saving time and cost to control the quality of routine manufactured products. This analytical method will be used for revising the monograph of ambroxol hydrochloride and clenbuterol hydrochloride formulation in next supplement of KPC.

• Analytical Science and Technology
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• v.26 no.1
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• pp.80-85
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• 2013

The sixty nine accident preparedness substances (APS) having high probability of chemical accident are controlled under the Toxic Chemicals Control Act (TCCA). Around the world, there has been a growing interest in the analysis of chemical warfare agent (CWAs). When a chemical accident occurs, it is generally required to detect and identify APS. However, the quantitative analytical data remain limited in Korea. In this study, an analytical method using GC/MS for volatile organic chemicals was established and a quantitative analysis method was studied. The calibration curve for 25 chemicals were obtained and 21 chemicals showed higher coefficient of determination ($r^2$ >0.998).

• Advances in Computational Design
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• v.4 no.1
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• pp.15-32
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• 2019

One of the efficient and useful tools to achieve the optimal design of structures is employing the sensitivity analysis in the finite element model. In the numerical optimization process, often the semi-analytical method is used for estimation of derivatives of the objective function with respect to design variables. Numerical methods for calculation of sensitivities are susceptible to the step size in design parameters perturbation and this is one of the great disadvantages of these methods. This article uses complex variables method to calculate the sensitivity analysis and combine it with discrete sensitivity analysis. Finally, it provides a new method to obtain the sensitivity analysis for linear structures. The use of complex variables method for sensitivity analysis has several advantages compared to other numerical methods. Implementing the finite element to calculate first derivatives of sensitivity using this method has no complexity and only requires the change in finite element meshing in the imaginary axis. This means that the real value of coordinates does not change. Second, this method has the lower dependency on the step size. In this research, the process of sensitivity analysis calculation using a finite element model based on complex variables is explained for linear problems, and some examples that have known analytical solution are solved. Results obtained by using the presented method in comparison with exact solution and also finite difference method indicate the excellent efficiency of the proposed method, and it can predict the sustainable and accurate results with the several different step sizes, despite low dependence on step size.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2293-2298
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• 2007

In this study, a dithizone extraction technique involving purge & trap GC-MS was developed for the determination of methylmercury in biological samples, especially blood and fish. After alkaline digestion, methylmercury in biological samples was extracted into dithizone and back-extracted into aqueous sulfide solution. The extracted methylmercury was converted to the volatile ethyl derivative, purged and trapped onto a solid-phase collection medium, and then introduced into the GC-MS system. The determined MDLs of the established method were 0.9 ng·g?1 for biological samples and its accuracy and precision were found to be 93% and 3.8%, respectively. The method was validated by analysis of CRMs such as SRM 966, BCR 463 and IAEA 407 and all analytical results were within certified ranges with average RSDs of less than 6%. The analytical results of field-sampled fish also showed that the method can be successfully used as an alternative for commonly used distillation method followed by GC-CVAFS detection.

• Steel and Composite Structures
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• v.33 no.2
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• pp.163-180
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• 2019

A semi analytical method is employed to analyze free vibration characteristics of uniform and stepped functionally graded circular cylindrical shells under complex boundary conditions. The analytical model is established based on multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are handled by unified Jacobi polynomials and Fourier series. In order to obtain continuous conditions and satisfy complex boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behavior of functionally graded circular cylindrical shells were obtained by approach of Rayleigh-Ritz. To confirm the dependability and validity of present approach, numerical verifications and convergence studies are conducted on functionally graded cylindrical shells under various influencing factors such as boundaries, spring parameters et al. The present method apparently has rapid convergence ability and excellent stability, and the results of the paper are closely agreed with those obtained by FEM and published literatures.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.58-63
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• 1998

B.Widrow established fundamental relations between the least-mean-square (LMS) algorithm and the digital Fourier transform［1］. By extending these relations, we proposed the short time spectra analysis system using the LMS algorithm［2]. In that paper, we used the normal LMS algorithm on the thought of dealing with only real analytical signal. This algorithm minimizes the real mean-square by recursively altering the complex weight vector at each sampling instant. But, the short time spectra analysis sometimes deals with the complex signal that is outputted from complex analog filter. So, in order to optimize and develop this methods, furthermore it is necessary to derive an algorithm for the complex analytical signal. In this paper, we first discuss the new adaptive system for the spectra analysis using the complex LMS algorithm and then derive convergence condition, time constant of coefficient adjustment and frequency resolution by extending the discussion. Finally, the effectiveness of the proposed method is experimentally demonstrated by applying it to the measurement of transfer performance on complex analog filter.

• Analytical Science and Technology
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• v.36 no.1
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• pp.44-52
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• 2023

This protocol clarifies a simple and precise method for measuring the activity of xanthine oxidase (XO) enzyme inhibitor. XO enzyme, which accelerates oxidative stress-related disorders through its capacity to generate hydrogen peroxide and superoxide anion radicals (O₂^•-), has been found to be inhibited by several plant extracts. Enzyme samples were incubated with a suitable buffer containing adequate amounts of xanthine as a substrate to determine XO activity. The method depends on direct measurements of uric acid and hydrogen peroxide production to test XO with and without interference. The CUPRAC reagent (Cu(Nc)₂²⁺) was used to inhibit enzyme reaction after incubation was complete. The generated urate and peroxide reduced the Cu(II)-neocuproine complex (Cu(Nc)₂²⁺) to a brightly colored Cu(I)-neocuproine complex (Cu(Nc)₂⁺), which was assessed with a spectrophotometer at 450 nm. XO activity was found to be directly related to the increased absorbance of the colored Cu(I)-neocuproine complex (Cu(Nc)₂⁺). To eliminate catalase enzyme interference, the proposed method used sodium azide and was validated against XO activity using the UV method in matched samples with t-test analysis. The proposed assay can determine XO activity with high precision, as indicated by the correlation coefficient (R² = 0.9935) from comparison with the reference protocol.

• Archives of Pharmacal Research
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• v.17 no.6
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• pp.415-419
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• 1994

A simple nad rapid colorimetric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug base with bromophenol blue to give a ion-pair complex. The spectra of the complex shows a maxima at 415-420 nm with high apparent molar absorptivities. Beer's law was obeyed in the concentration range 1-8, 2-10 and $2-12{\;}{\mu}{\cdot}ml^{-1}$ for amodiaquine hydrochloride, primaquine phosphate and chloroquine phosphate respectively. The proposed method was applied to the determination of these drugs in certain formulations and the results were favourably comparable to the official methods.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.245-259
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• 2021

In this research, the influence of the laminate stacking sequence on thermal stress distribution in symmetric composite plates with a quasi-square cutout subjected to uniform heat flux is examined analytically using the complex variable technique. The analytical solution is obtained based on the thermo-elastic theory and the Lekhnitskii's method. Furthermore, by employing a suitable mapping function, the solution of symmetric laminates containing a circular cutout is extended to the quasi-square cutout. The effect of important parameters including the stacking sequence of laminates, the angular position, the bluntness, the aspect ratio of cutout, the flux angle and the composite material are examined on the thermal stress distribution. It is found out that the circular shape for cutout may not necessarily be the optimum geometry for all stacking sequences. The finite element analysis results are used to validate the analytical solution.