• Food Science and Preservation
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• v.22 no.4
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• pp.559-566
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• 2015

The aim of this study was to develop an analytical method for determination of T-2 toxin and HT-2 toxin level in cereals and to survey their levels using LC-MS/MS. The T-2 and HT-2 toxins were simultaneously analyzed by electrospray ionization with a positive ion mode and multiple reaction monitoring (MRM) after filteration and immuno-affinity column clean-up. A matrix-matched standard calibration used for quantification and recoveries of T-2 and HT-3 toxins were in the range of $100.6{\pm}7.2%$ and $96.8{\pm}9.4%$, respectively. Limits of detection and quantification of T-2 and HT-2 toxins were estimated to be 0.5 and $1.5{\mu}g/kg$, respectively. Each repeatability (RSRr) of T-2 and HT-2 toxins was determined to be 0.9~6.0%, and 4.9~6.1%, respectively. Total 115 samples cereals were collected from 9 types of cereals for analysis. The positive percentages of T-2 and HT-2 toxins obtained from collected samples were found to be 72% and 80%, respectively. The contamination level of T-2 toxin and HT-2 toxin in cereals were $37.1{\mu}g/kg$, and $5.4{\mu}g/kg$, respectively. Therefore, this study suggests that the developed method could be an useful analytical method to determine the T-2 and HT-2 toxin level in cereals and the present data could be used as a reference to estimate the risk assessment.

• Composites Research
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• v.28 no.3
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• pp.81-88
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• 2015

In this paper, we evaluate structural integrity of the wearable robot by using finite element analysis, which is made of CFRP(Carbon Fiber Reinforced Plastic) composite materials to be lightened. On the basis of the ASTM(American Standard Test Method), mechanical tests of the material are carried out in tensile, compressive and shear test for analytical evaluation. With the tested composite material, the main frame and two femoral frames of the robot is redesigned to satisfy the lightening design requirements. It is verified with the structural analysis that the redesigned frames are good for the part of the wearable robot.

• Geomechanics and Engineering
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• v.22 no.4
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• pp.361-374
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• 2020

This paper is concerned with the thermoelastic bending of FG beams resting on two-layer elastic foundations. One of these layers is Winkler springs with a variable modulus while the other is considered as a shear layer with a constant modulus. The beams are considered simply supported and subjected to thermo-mechanical loading. Temperature-dependent material properties are considered for the FG beams, which are assumed to be graded continuously across the panel thickness. The used theories contain undetermined integral terms which lead to a reduction of unknowns functions. Several micromechanical models are used to estimate the effective two-phase FG material properties as a function of the particles' volume fraction considering thermal effects. Analytical solutions for the thermo-mechanical bending analysis are obtained based on Navier's method that satisfies the boundary conditions. Finally, the numerical results are provided to reveal the effect of explicit micromechanical models, geometric parameters, temperature distribution and elastic foundation parameters on the thermoelastic response of FG beams.

• Geomechanics and Engineering
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• v.23 no.5
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• pp.455-466
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• 2020

This paper presents analysis of the interaction between tunnel and Qanat with a particular interest for the optimization of Qanat shape using the discrete element code, PFC2D, and the results will be compared with the FEM results of PLAXIS2D. For these concerns, using software PFC2D based on Discrete Element Method (DEM), a model with dimension of 100m ^⁎ 100 m was prepared. A circular tunnel with dimension of 9 m was situated 20 m below the ground surface. Also one Qanat was situated perpendicularly above the tunnel roof. Distance between Qanat center and ground surface was 8 m. Five different shapes for Qanat were selected i.e., square, semi-circular, vertical ellipse, circular and horizontal ellipse. Confining pressure of 5 MPa was applied to the model. The vertical displacement of balls situated in ground surface was picked up to measure the ground subsidence. Also two measuring circles were situated at the tunnel roof and at the Qanat roof to check the vertical displacements. The properties of the alluvial soil of Tehran city are: γ_dry=19 (KN/㎥), E= 750 (kg/㎠), ν=0.35, c=0.3(kg/㎠), φ=34°. In order to validate the DEM results, a comparison between the numerical results (obtained in this study) and analytical and field monitoring have been done. The PFC2D results are compared with the FEM results. The results shows that when Qanat has rectangular shape, the tensile stress concentration at the Qanat corners has maximum value while it has minimum value for vertical ellipse shape. The ground subsidence for Qanat rectangular shape has maximum value while it has minimum value for ellipse shape of Qanat. The vertical displacements at the tunnel roof for Qanat rectangular shape has maximum value while it has minimum value for ellipse shape of Qanat. Historical shape of Qante approved the finding of this research.

• Analytical Science and Technology
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• v.13 no.4
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• pp.403-411
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• 2000

This study described a method of thermoluminescence dating of pottery shards using subtraction method. TL measurement was achieved using two different types of samples prepared by quartz inclusion method and fine-grain technique. Fine grains (size range: $5-10{\mu}m$) were separated by suspending grounded pottery samples into acetone solution and sedimentation quantitatively. In quartz inclusion method quartz grains in the size range of 90 to $125{\mu}m$ diameter were obtained by extracting the quartz crystals embed in the pottery shards and etching them with 1.0 M HF solutions. The archaeological dose of both the quartz and fine grains was determined from the dose calibration curves obtained from sequential irradiation of $^{137}Cs$ gamma and $^{241}Am$ alpha source to the samples and TL measurement of natural samples, in which the alpha dose of 4.60 Gy for the Packjae pottery was obtained using subtraction method. Annual alpha dose rates ($3.05{\pm}0.11$ mGy/yr.) were determined by the analysis of U, Th contents in the pottery shards and evaluation of the values with Bell's equation. Dividing the alpha dose accumulated in the pottery shards by the annual alpha dose rate, we found age of approximately $1508{\pm}80$ years B.P. (AD. ca. 492 yr.) for the Packjae pottery. It matches well with the archeological age estimate (middle of 5th century) within 10 percent uncertainty and thereby conforms the age of the pottery sample.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.107-110
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• 2003

High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.3-12
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• 2010

Vertical drains have been commonly used to increase the rate of the consolidation of dredged material. The installation of vertical drains additionally provides a radial flow path in the dredged foundation. The objective of this study develops a numerical model for 2-D axisymmetric non-linear finite strain consolidation considering self-weight consolidation to predict the effect of vertical drain in dredged foundation which is in process of self-weight consolidation. The non-linear relationship between the void ratio and effective stress and permeability during consolidation are taken into account in the numerical model. The results of the numerical analysis are compared with that of the self-weight consolidation test in which an artificial vertical drain is installed. In addition, the numerical model developed in this paper is the simplified analytical method proposed by Ahn et, al (2010). The comparisons show that the developed numerical model can properly simulate the consolidation of the dredged material with the vertical drains installed.

• Archives of Pharmacal Research
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• v.26 no.9
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• pp.763-767
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• 2003

The differences in pharmacokinetic behavior and tissue distribution of verapamil and its enantiomers were investigated in rats. In high-performance liquid chromatographic method, an achiral ODS column (150 mm $\times$ 4.6 mm i.d.) with the mobile phase consisting of methanol-water (73:30, v/v) was used for the determination of the concentration for racemic verapamil, and a Chiralcel OJ column (250 mm$\times$4.6 mm i.d.) with the mixture of n-haxane-ethanol-triethylamine (85:15:0.2, v/v/v) as mobile phase was used to determine the concentrations of verapamil enantiomers. A fluorescence detector in the analytical system was set at excitation and emission wavelengths of 275 nm and 315 nm. The differences between enantiomers were apparent in the pharmacokinetics in rats. The area under the concentration-time curve (AUC) of S-(-) verapamil was higher than that of R-(+) verapamil. The half-distribution time ($T_{1/2(\alpha)}$) of S-(-) verapamil which distributing to tissue from blood was shorter than that of R-(+) verapamil, but the elimination half-time ($T_{1/2(\beta)}$) was longer in rat following oral administration of racemic verapamil. At 1.3 h after oral administration of racemic verapamil, however, there were no significant differences between enantiomers for the distributions in major tissues such as heart, cerebrum, cerebellum, liver, spleen and kidney.

• Steel and Composite Structures
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• v.52 no.1
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• pp.45-56
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• 2024

This paper proposes an analytical solution for the free vibration, bending and buckling a functionally graded (FG) beam resting on viscoelastic foundation. The materials characteristics of the FG beam are considered to be varying across the thickness according several power law functions. The governing equations are found analytically using a quasi-3D model that contains undetermined integral forms and involves few unknowns to derive. Navier's method for simply supported beam is employed to solve the problem. Numerical examples are presented and studied to demonstrate the accuracy and effectiveness of the proposed model. Then, a detailed parametric study is presented in the form of tables and graphs to study and analyze the effects of the different parameters on the response of FG beams with different material compositions resting on a viscoelastic foundation.

• Journal of Food Hygiene and Safety
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• v.20 no.4
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• pp.258-266
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• 2005

Licorice Extract and Erythritol, food additives used in korea, are widely used in foods as sweetener. Its application for use in food is regulated by the standard and specification for food additives but official analytical method far determination of these sweetener in food has not been established. Accordingly, we has been carried out to set up analytical method of the glycyrrhizic acid in several foods by the way of thin layer chromatography and high performance liquid chromatography glycyrrhizic acid is qualitative anaylsis technique consists of clean-up with a sep-pak $C_{18}$ cartridge, separation of the sweeteners by Silica gel 60 F254 TLC plate using 1-butanol:4Nammonia solution:ethanol (50:20:10) as mobile solvent. Also, the quantitative analysis for glycyrrhizic acid, was performed using Capcell prk $C_{18}$ column at wavelength 254nm and DW:Acetonitrile (62:38 (pH2.5)) as mobile phase. and we has been carried out to set up analytical method of the erythritol in several foods by the way of high performance liquid chromatography. erythritol is qualitative anaylsis technique consists of clean-up with a DW and hexane. The quantitative analysis for erythritol, was performed using Asahipak NH2P-50 column, Rl and DW:Acetonitrile (25:75) as mobile phase. The glycyrrhizic acid results determined as glycyrrhizic acid in 105 items were as follows; N.D$\∼$48.7ppm for 18 items in soy sauce, N.D$\∼$5.3ppm for 12 items in sauce, N.D$\∼$988.93ppm for 15 items in health food, N.D$\∼$180.7ppm for 26 items in beverages, N.D$\∼$2.6ppm for 8 items in alcoholic beverages repectively and ND for 63 items in the ethers. The erythritol results determined as erythritol in 52 items were as follows; N.D$\∼$155.6ppm for 13 items in gm, N.D$\∼$398.1ppm for 12 items in health foods repectively and ND for 45 items in the others.