• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.275-279
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• 1991

Ultra-fine alumina, ${\alpha}-Al_2O_3$, with ${\phi}$ = 0.1∼0.5 ${\mu}$m was obtained from pure ammonium aluminum sulfate(alum) as the thermal decomposition product. Pure alum(> 99.7%) could be prepared by the precepitation and the successive recrystallization in an acidic aqueous solution at pH = 1.5∼2.5, which was theoretically predicted by only considering the concentrations of hydroxide and carbonate for aluminum and sodium in the solution, and also experimentally confirmed as the optimum precepitation condition for alum without forming any impurities like aluminum hydroxide or sodium one.

• Journal of Magnetics
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• v.20 no.1
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• pp.79-85
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• 2015

This paper presents a comparative study of a Tubular Linear Machine (TLM) with an Axially Magnetized Single-sided Permanent Magnet (AMSPM) and an Axially Magnetized Double-sided Permanent Magnet (AMDPM) based on analytical field calculations. Using a two-dimensional (2-D) polar coordinate system and a magnetic vector potential, analytical solutions for the flux density produced by the stator windings are derived. This technique is significant for the design and control implementation of electromagnetic machines. The field solution is obtained by solving Maxwell's equations in the simplified boundary value problem consisting of the air gap and coil. These analytical solutions are then used to estimate the self and mutual inductances. Two different types of machine are used to verify the validity of these model simplifications, and the analytical results are compared to results obtained using the finite element method (FEM) and experimental measurement.

• Korean journal of food and cookery science
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• v.13 no.2
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• pp.173-178
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• 1997

The contents of ergocalcife.of (vit D$_2$) and cholecalciferol (vit D$_3$) in mushrooms (Lentinus edodes, Agaricus bisporus, Pleurotus ostreatus, Flammulina velutipes, Auricularia auricular, Gyropora esculenta, Romaria botftis, Coriorus versicolar, Ganoderma lucidum) were determined by high-performance liquid chromatography (HPLC), using external standard method. The methods included saponification, extraction, drying, filtering and quantification with analytical HPLC (waters Inc.). The contents of vit D$_2$ and D$_3$ found in different mushroom species. A. auricular, and L. edodes contained high amounts of vit D, 167.8, 72.6 $\mu\textrm{g}$/100 g of edible portion, respectively. On the other hand A. bisporus showed the lowest contents of vit D among analyzed mushrooms.

• Archives of Pharmacal Research
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• v.4 no.1
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• pp.1-8
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• 1981

Our need for a convenient method of analytical estimation of the precise optical purity of d-2 aminobutanol (d-2AB) and d-ethambutol has prompted us to examine in detail the preparation and G. L. C. separation of the N-TFA-L-prolyl derivatives of their optical isomers (d-and l-2AB, d-, meso-and l-ethambutol). Silicon OV-1 columns were used for the G. L. C. separation.

• Analytical Science and Technology
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• v.17 no.3
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• pp.240-250
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• 2004

A gas chromatography-mass spectrometric (GC-MS) assay method was developed for the rapid and sensitive determination of volatile- and semivolatile organic compounds in water. Two hundreds mL of water sample was extracted in a 250 mL separatory funnel with 1 ml of pentane at pH 6.5. Fluorobenzene and 1,2-dichlorobenzene-d4 as internal standards were added to water sample and the solution was mechanically shaken for 5 min and analyzed by GC-MS (selected ion monitoring) without more any concentration or purification steps. The peaks had good chromatographic properties and the extraction of these compounds from water also gave relatively high recoveries with small variations. The range of detection limits of the assay was 0.5-10 ng/L. Turnaround time for up to about 40 samples was one day. This method is simple, convenient, and can be learned easily by relatively inexperienced personnel. This method was used to analyze 15 volatile- and semivolatile organic compounds in water of a Lake, and raw and treated water from three Water Treatment Plants in Korea. As the analytical results, benzene, toluene, xylene, isopropylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, naphthalene and 2,4,6-trichlorophenol were detected at concentrations of up to 0.4, 1.9, 1.3, 0.2, 1.8, 13.0, 1.7 and $1.1{\mu}g/L$, respectively. But chlorobenzene, trichloroethylene, tetrachloroethylene, ethylbenzene, n-butylbenzene and dibromochloropropane levels during that period were not significant. The removal effect of the compounds in three Water Treatment Plants was calculated. The compounds studied were generally removed during conventional water treatment, especially during the active carbon filtration.

• Journal of electromagnetic engineering and science
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• v.3 no.1
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• pp.39-44
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• 2003

An unconditionally stable compact 2D Alternating-Direction Implicit (ADI) FDTD method for calculating dispersion characteristics of waveguide structures is proposed. The numerical stability and numerical dispersion relation of the proposed method are also presented and discussed. Numerical wavelengths for the dominant and higher order modes in a hollow waveguide are obtained from numerical simulations and compared with those from the analytical dispersion relation. The numerical results show that the proposed scheme has the potential to successfully analyze a class of waveguides having locally fine geometry with reduced numerical costs.

• Structural Engineering and Mechanics
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• v.43 no.1
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• pp.71-87
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• 2012

This paper extends a single equation, semi-analytical approach for three-span bridges to multi-span ones for the rapid and precise determination of natural frequencies and natural mode shapes of an orthotropic, multi-span plate. This method can be used to study the dynamic interaction between bridges and vehicles. It is based on the modal superposition method taking into account intermodal coupling to determine natural frequencies and mode shapes of a bridge deck. In this paper, a four- and a five-span orthotropic roadway bridge deck are compared in the first 10 modes with a finite element method analysis using ANSYS software. This simplified implementation matches numerical modeling within 2% in all cases. This paper verifies that applicability of a single formula approach as a simpler alternative to finite element modeling.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1204-1206
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• 2005

This paper deals with magnetic field analysis and computation of cogging torque in IPM motor with an analytical method, which is based on the Conformal Mapping technique. The magnetic field is analyzed by solving space harmonic field analysis due to inserted PM magnetizing distribution. Conformal Mapping method is then used for considering the slot opening effect and rotor saliency effect on the air-gap field magnetic distribution. Then, by integrating the field over the stator surface, cogging torque is calculated. The validity of the proposed analytical method is confirmed by comparing the results with 2-D FEA results.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.775-789
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• 2013

The current paper proposes a boundary element formulation, applicable to 2-D and 3-D elastostatics problems using a unified approach for transformations of the domain integrals into boundary integrals. The method is applicable to linear problems encompassing both finite and infinite multi-region domains allowing non-vanishing body forces. Numerical results agree quite well with the analytical solutions; while the present method offers easy formulation with less numerical efforts in comparison to FEM or some BEM which need interior points to treat arbitrary body forces. It is demonstrated that the method has the potential to have profound impact on engineering design, notably in dam-foundation interaction.

• Analytical Science and Technology
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• v.20 no.2
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• pp.109-114
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• 2007

In this study, soxhlet extraction and dissolution-precipitation method are used for separating analyte from polymer materials. In soxhlet extraction efficiency test, it has been found that the DCM, Toluene, THF, and mixtures Acetone/Hexane (1:4, v/v) gave good extraction efficiency, while the use of the ethyl ether, acetone/ethyl ether (1:4, v/v), acetone/hexane (1:1, v/v), DCM/hexane (1:1, v/v) resulted in significantly lower values. In case of dissolution-precipitation method, there is no considerable difference with used different dissolving solvent. The elution amount of multi layer silica and Florisil column were determined with hexane 250 mL and 70 mL of hexane, respectively. Range of PBDE in real waste plastics was N.D.~1,028 ppm.