• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.272-277
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• 2001

A spin valve structure of Ta/NiFe/CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta which has a synthetic antiferromagnet (CoFe/Ru/CoFe), was fabricated by using a magnetron sputtering system. The thickness and composition of magnetic free and pinned layers affect the magnetic properties such as exchange interaction strength of each layer and so on. Even though Rutherford Backscattering Spectrometry (RBS) has advantages of quantitative and non-destructive analysis, it is almost impossible to determine the thickness and composition of magnetic thin films using lBS because of its poor mass resolution for a higher atom number (Z>20). In this study, quantitative analysis of the element composition and thickness for the spin valve sample was performed by combining both Proton Induced X-ray Emission Spectrometry (PIXE), which is one of element specific analysis techniques, and grazing-exit RBS with a highly improved depth resolution and absolute quantitative analysis. For the quantitative analysis, standardization of PIXE was carried out with NiFe, CoFe, and FeMn layers, which are one of constituent layers of spin valve films. Through PIXE standardization and the aid of PHE experimental results of the spin valve sample, ire overlapped signal in a grazing-exit RBS spectrum were successfully resolved and the thickness of the Ru layer was determined with a resolution of ∼1 .

• Journal of the Korean Chemical Society
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• v.34 no.5
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• pp.490-497
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• 1990

Two synthetic routes for the 1,4-diboracyclohexene-2 ring 8 have been developed. Method i) starts with 1,2-bis(dichloroaluminyl)ethane, in which the AlCl$_2$ group is replaced by BCl$_2$. Exchange of the chlorine with BI$_3$ in 1,2-bis-(dichloroboryl)ethane yields the corresponding iodo compound, which reacts with the alkynes to heterocycles 8a, b in good yield. In method ii) B$_2$Cl$_4$ is added to alkenes, replacement of chlorine with BI$_3$ yields the bis(diiodoboryl)ethane derivatives which undergo redox reactions with alkynes to give 8c, d. The diiodo derivative 8a forms the pyridine adduct 9a, and reacts with ether to give the ethoxy derivative 8f. 8a-d react with AlMe$_3$ to yield the corresponding dimethyl derivatives 8g-j, which give unstable radical anions when treated with potassium in THF. The ESR parameters are reported. In electrochemical experiments irreversible reductions of 8g-j are observed. 8g-j react with (C$_5$H$_5$)Co(C$_2$H$_4$)$_2$ to give the intermediate 16 VE complexes (C$_5$H$_5$)Co(8), in which C-H activation occurs with formation of the corresponding red 1,4-diboracyclohexadiene complexes 10. The X-ray structure analyses of 10h and 10j are reported.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.441-448
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• 2016

Heavy metal removal study is conducted from synthetic waste water by reduction and oxidation(redox) reaction of Cu-Zn metal alloy and adsorption reaction of aluminium silicate. Heavy metal whose ionization tendency is smaller than zinc are reducted in an aqueous solution, and the concentration of ionized zinc is reduced by adsorption reaction. The average diameter of metal alloy micro fiber is about $200{\mu}m$, and the surface area is wide enough to get equilibrium in a single cycle treatment. A single cycle treatment of redox reaction of Cu-Zn metal alloy, could remove 100.0 % of Cr(III), 98.0 % of Hg, 92.0 % of Sn and 91.4 % of Cu respectively. An ionization tendency of chromium is very close to zinc, but removal efficiency of chromium by redox reaction is significant. This result shows that trivalent chromium ion is expected to generate hydroxide precipitation with $OH^-$ ion generated by redox reaction. Zinc ion generated by redox reaction is readily removed by adsorption reaction of aluminium silicate in a single cycle treatment. Other heavy metal components which are not perfectly removed by redox reaction also showed very high removal efficiency of 98.0 % or more by adsorption reaction. Aluminium ion is not increased by adsorption reaction of aluminium silicate. That means heavy metal ion removal mechanism by adsorption reaction is turned out to be not an ion exchange reaction, but an adsorption reaction.

• Journal of the Korean Chemical Society
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• v.47 no.5
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• pp.472-478
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• 2003

In this work, the zeolite/diglycidylether of bisphenol A(DGEBA) systems were investigated in terms of the cure kinetics and mechanical interfacial properties of the composites. The 4, 4-diamino diphenyl methane(DDM) was used as a curing agent for epoxy. Two types of zeolite(PZ) were prepared with 15 and 35 wt% KOH treatments(15-BZ and 35-BZ, respectively) for 24 h, and their surface characteristics were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD). Cure kinetics of the composites were examined in the context of differential scanning calorimetry(DSC), and mechanical interfacial properties were investigated in critical stress intensity factor($K_{IC}$) and critical strain energy release rate($G_{IC}$). In the results of XPS and XRD, sodium ion(Na) of zeolite was exchanged for potassium ion(K), resulting from the treatment of KOH. Also, $Si_{2p}/Al{2p}$ composition ratios of the treated zeolite were increased, which could be attributed to the weakening of Al-O bond in framework. Cure activation energy($E_a$) of 15-BZ composites was decreased, whereas KIC and $G_{IC}$ were increased, compared with those of the pure zeolite/DGEBA composites. It was probably accounted that the acidity of zeolite was increased by surface treatments and the cure reaction between zeolite and epoxy was influenced on the increased acidity of zeolite.

• KSBB Journal
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• v.14 no.1
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• pp.9-16
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• 1999

Transforming growth factor $\beta$1(TGF-$\beta$1) has potentials to be used as a new therapeutic agent. However, studies with TGF-$\beta$ were hindered by its high cost. In this study, we developed an improved method to purify TGF-$\beta$1 from human platelets, for which four purification steps were used: platelet extraction, gel filtration, cation exchange chromatography, and reverse phase high performance liquid chromatography. After a final step of purification, a pure protein with a molecular weight of 25,000 corresponding to the commercially available TGF-$\beta$1 was obtained, which were confirmed by silver staining and Western blotting after SDS-polyacrylamide gel electrophoresis (SDS-PAGE). It was confirmed by the inhibitory effects of TGF-$\beta$1 on a mink lung epithelial cell line that the purified TGF-$\beta$1 had its biological activity, whose activity is slightly higher than that of the commercially available TGF-$\beta$1. About 3.7$\mug of the purified TGF-$\beta$1 was obtained from 10 units of concentrated human platelets, the final yield of which is about 21%.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.160-169
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• 1996

Parametric studies are conducted for optimizing the integration design between gas turbine compressor and air separation unit (ASU) of integrated gasification combined cycle power plant. The present study adopts the ASU of double-distillation column process, from which integration conditions with compressor such as the heat exchanger condition between air and nitrogen, the amount and the pressure of extracted air are defined and mathematically formulated. The performance variations of the compressor integrated with ASU are analyzed by combining streamline curvature method and pressure loss models, and the predicted results are compared with the performance test results of actual compressors to verify the prediction accuracy. Using the present performance prediction method, the effects of pinch-point temperature difference (PTD) in the heat exchanger, the amount and the pressure of extracted air on compressor performances are quantitatively examined. As the extraction air amount or the PTD is increased, the pressure ratio and the power consumption of compressor are increased. The compressor efficiency deteriorates as the increase of the flow rate of air extracted at higher pressure level while improving at lower pressure air extraction. Furthermore, through the characteristic curve between generalized inlet condition and efficiency of compressor, optimal integration condition is presented to maximize the compressor efficiency.

• Communications of Mathematical Education
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• v.25 no.2
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• pp.473-495
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• 2011

Across the secondary school, students deal with the algebraic conditions like as identity, inverse, commutative law, associative law and distributive law. The algebraic structures, group, ring and field, are determined by these algebraic conditions. But the conditioning of these algebraic structures are not mentioned at all, as well as the meaning of the algebraic structures. Thus, students is likely to be considered the algebraic conditions as productions from the number sets. In this study, we systematize didactically the meanings of algebraic conditions and algebraic structures, considering connections between the number systems and the solutions of the equation. Didactically systematizing is to construct the model for student's natural mental activity, that is, to construct the stream of experience through which students are considered mathematical concepts as productions from necessities and high probability. For this purpose, we develop the program for the gifted, which its objective is to teach the meanings of the number system and to grasp the algebraic structure conceptually that is guaranteed to solve equations. And we verify the effectiveness of this developed program using didactical experiment. Moreover, the program can be used in ordinary students by replacement the term 'algebraic structure' with the term such as identity, inverse, commutative law, associative law and distributive law, to teach their meaning.

• Analytical Science and Technology
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• v.9 no.3
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• pp.270-278
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• 1996

Response mechanism for the chloride-selective membrane doped with 5, 10, 15, 20-tetraphenyl(porphyrinato)manganase(III) chloride(Mn(TPP)Cl) in PVC/DOS matrix is proposed by examining the visible spectra of the corresponding optode membrane. The visible spectra of Mn(TPP)Cl-doped membrane placed in aqueous solution show that the chloride ligand is easily replaced with water molecule. When other halogen ions, such as $F^-$, $Br^-$ and $I^-$, are added to the sample solution, they replace the water ligand, exhibiting distinctive change in the Soret band of Mn(TPP). On the other hand, bulky anions, such as SCN and salicylate, do not form a bond with the central metal. These results suggests that the potentiometric response of Mn(TPP)-based membrane results either from the ligand exchange (water with halides) at the central metal or from the counter ion exchange (chlorides with bulky lipophilic anions) around the positively charged porphyrin molecule in membrane phase. It was also noted that both hydration enthalpies of anions and their binding constants to Mn(TPP) play critical role in determining the potentiometric selectivity pattern of the membrane.

• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• The Korean Journal of Mycology
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• v.27 no.2 s.89
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• pp.170-174
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• 1999

Water-soluble polysaccharides from the fruiting bodies of Agaricus blazei Murill were extracted with 0.9% sodium chloride and hot water, successively. The purified polysaccharides showed a potent immunostimulating activity. Eight major polysaccharides, which were named from AG-l to AG-8, were fractionated and purified by ethanol precipitation, ion exchange chromatography on DEAE-cellulose and gel filtration on Toyopearl HW 65F. These polysaccharides were identified to be homogeneous by analysis of HPLC. Three major active polysaccharides (AG-2, -3, and -6) showed relatively strong immunostimulating activity. AG-2 and -3 were composed of glucose, galactose and mannose in the molar ratios of 74.0:15.3:10.7 and 63.6:17.6:12.7, respectively. AG-6 was composed of glucose and ribose in the molar ratios of 81.4:12.6.