• Journal of the Korean Chemical Society
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• v.32 no.2
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• pp.135-143
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• 1988

The correlations between chromatographic parameters of monosubstituted benzenes and several physical parameters in reversed phase liquid chromatography were studied. The relationships between retention data and polarity index were investigated by plotting $log(log k'_S/k'_B)$ vs. $P'_S/P'_B$ which were relative retention and relative polarity index of monosubstituted benzenes with respect to benzene, respectively. The linear relationship between relative retention and polarity index was observed for the monosubstituted benzenes having polar group, while in case of those having nonpolar group, the good linearity was observed by combination with relative molecular weight i.e. $(P'_S/P'_B)/(MW_S/MW_B)$. Multivariant regression analysis, $a(P'_S/P'_B)+b(MW_S/MW_B)$+c did not give significantly better correlations compared to single variant analysis, $a[(P'_S/P'_B)/(MW_S/MW_B)]$+c, but multiple stepwise regression analysis was recommended when several physical parameters simultaneously were chosen. The best correlation between retention data for monosubstituted benzenes taken from the literature and substituent constant(${\pi}$), derived from hydrophobic parameter and the first order molecular connectivity index$(^1{\chi}^{\nu})$, was established for methanol/water mobile phase system. The larger the surface coverage of the stationary phase, the higher was the correlation coefficient between these two parameters and retention data.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.879-888
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• 1992

Separation of the optical isomers of free amino acids by a reversed phase high performance liquid chromatography has been studied by adding a copper(II) complex of L-proline or L-proline derivatives (hydroxy-L-proline, N-benzyl-L-proline, p-xylenyl-L-proline, p-xylenyl-hydroxy-L-proline) in the mobile phase. An OPA postcolumn detection system was used for the detection of amino acids. The chromatographic properties for the free amino acids were discussed in terms of the pH, the kinds and concentration of chelate or organic modifier. The retention behaviors of the free amino acids were considerably different from, those of DNS-amino acids or DABS-amino acids. The enantioselectivity of the free amino acids was better than that of derivatized amino acids. The enantioselectivity between the optical isomers observed by use of the Cu(II)-p-xylenyl-L-proline chiral cheleate was the best among the several copper(II) chelate. A separation mechanism could be illustrated not only by the hydrophobic interaction of the diastereomer with stationary phase but also by the steric effect of the ligand exchange reaction between the free-amino acids and copper chelate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.316-325
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• 1986

Characteristics of fatigue crack propagation in martensite-ferrite duel phase steels have been investigated. In low .DELTA.K region, fatigue crack propagation resistance increases with increasing volume fraction of martensite, but the difference of crack propagation resistance resulted from the volume fraction decreases with increasing .DELTA.K. Also, threshold stress intensity factor range .DELTA.K$_{th}$ increases with increasing volume fraction of martensite, But fatigue crack propagation rates of dual-phase steels in terms of .DELTA.K$_{eff}$ are independent to volume fraction of martensite. These phenomena can be explained by the roughness induced crack closure due to crack deflection.n.n.

• YAKHAK HOEJI
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• v.50 no.1
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• pp.21-25
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• 2006

Reiterated normal-phase column chromatography lead to the isolation and purification of six known compounds but for the first time from the whole plant of Sasa borealis (Hack.) Makino (Gramineae): tricin 4'-O-(erythro-${\beta}$-guaia-cylglyceryl) ether (1), tricin 4'-O-(threo-${\beta}$-guaiacylglyceryl) ether (2), tricin 4'-O-[erythro-${\beta}$-guaiacyl-(9'-O-acetyl)-glyceryl] ether (3), tricin 4'-O-[threo-${\beta}$-guaiacyl-(9'-O-acetyl)-glyceryl] ether (4), (-)-pinoresinol (5), and vanillin (6). The structures of the compounds (1-6) were established based on interpretation of high resolution NMR (COSY, HSQC, HMBC, and NOESY) spectral data. In particular, compounds 1 and 3 were diastereomers of compounds 2 and 4, respectively. These two sets of diastereomers were able to be simultaneously identified and quantified by a gradient reversed-phase HPLC method with UV photodiode array, This sensitive HPLC method is noteworthy as a simultaneous separation and identification method to test the extract of the family Gramineae which contains these compounds.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.779-786
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• 1998

A reversed-phase high-performance liquid chromatogrphy (RP-HPLC) has been developed to analyze the metabolites of arachidonic acid based on the specificities of ultraviolet absorption of these various metabolites and is sensitive to the nanogram level. This procedure makes it possible to extract complex mixtures of eicosanoids efficiently with a single step and to analyze them simultaneously by RP-HPLC from biological samples using octadesylsilyl silica extraction column and $PGB_2$ as an internal standard. The cyclooxygenase products {prostaglandin $(PG)D_2,\;PGE_1,\;PGE_2,\;PGF_{1{\alpha}},\;PGF{2{\alpha}},\;6-keto-PGF_{1{\alpha}},$ and thromboxane $B_2(TXB_2)}$ and lipid peroxidation product, isoprostanes, of arachidonic acid were monitored by one isocratic HPLC system at 195 nm wavelength. The lipoxygenase products ${leukotriene(LT)B_4,\;LTC_4,\;LTD_4,$ and 5-hydroxyeicosatetraenoic acid (5-HETE), 12-HETE, 15-HETE} were measured by another isocratic HPLC system at 280 nm for LTs and 235 nm for HETEs. This method provides a simple and reliable way to extract and assess quantitatively the final arachidonic acid metabolites.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.30.3-30.3
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• 2008

In this study, we investigate the magnetic latitude of phase reversal on the sudden commencement (SC)-associated preliminary impulse with 267 SC events using the ground magnetometer data of the IMAGE from 1997 to 2005. During SC event, geomagnetic fields are affected by various currents flowing in the magnetosphere and/or ionosphere. In particular, high-latitude geomagnetic field variations are significantly dominated by the change of SC-associated field aligned current (FAC). Until now, however, there are few studies to examine where the location of the FAC in the ionosphere is and what determines the location of the FAC. The location of the SC-associated FAC can be examined by using magnetometer data obtained from high-latitude stations distributed along the same magnetic meridian. The phase reversal locations are concentrated two regions, ~62 deg (L~4.5) and ~70 deg (L~8.5) in magnetic latitude. If FAC is a result of a mode conversion from fast mode to Alfven mode, then the FAC location could be determine by the duration time of the input energy. When we use the rise time, dT, as the input energy, there is no relationship between dT and the location where the first pulse of SC is reversed. We consider other factors such as local time and solar wind condition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.72-77
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• 2015

When connecting 6 lead wires from stator windings to the terminals of 3 phase induction motors for Y or ${\triangle}$ connection, it is feared that the polarities of windings could be reversed each other if the wire tags are lost or erased, resulting in inadmissibly high current to motors in case of starting. To protect motors against such situations, some test procedures are necessary during wire connection which need to be easy ways to electricians without particular tools except a general multi-tester and with less time-consuming in the field. This study focuses on a test measure to satisfy these requirements which is able to provide them a convenient procedure for winding polarity discrimination considering the field condition. Here, the proposed measure utilizes the residual magnetism of the rotor and checks the indication of voltage or current at windings which are induced by the residual flux of rotor when rotating it by hands with 3 stator windings connected in the form of I connection. Principle characteristics and experiment results for this method are analyzed in the view of the effectiveness and applicability for the winding polarity discrimination.

• Archives of Pharmacal Research
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• v.24 no.5
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• pp.407-411
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• 2001

Reversed-phase high performance liquid chromatographic method was applied for the determination of eleutheroside B and E in the various Acanthopanax species collected In Korea. The stationary phase used was Zorbax 300 SB $C_{18}$ and a mobile phase program was used, which started at 6% acetonitrile for 2 min, and then a linear gradient was operated for the next 18 min to 17% acetonitrile at a flow rate of 1.0 ml/min. The column effluent was monitored at UV 210 nm. Identification was carried out by comparing the retention time and the LC/MS spectrum of each peak corresponding to eleutheroside B and E from sample with those of standards. In general, the contents of eleutheroside B and 1 in stems were higher than those In roots. Acanthopanax species could be classified into two groups based upon the contents of eleutheroside B and E: one group contains no or very little eleutheroside B and another contains both eleutheroside B and E.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.4
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• pp.200-205
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• 2015

Effects of austenite on the uniform corrosion in the solution of $1\;N\;H_2SO_4$ were investigated through the electrochemical polarization test. Two phases structures of martensite and austenite were obtained by annealing treatment at the range of $500^{\circ}C{\sim}700^{\circ}C$ for 10min. in 70% cold-rolled 202 stainless steel. Volume fraction of reversed austenite increased rapidly with an increase of annealing temperature. Uniform Corrosion was occur mainly on martensite phase in 202 austenitic stainless steel with two phase of austenite and martensite. Corrosion current density increased with an increase of volume fraction of austenite, therefore uniform corrosion was affected by volume fraction of austenite

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.397-404
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• 1991

Nonchromophore compounds such as aliphatic acids, alcohols and tetraalkylammonium salts could be detected by indirect photometric detection on the revered-phase liquid chromatography. Benzyltriethylammonium bromide(BTEAB) was used as a detection reagent. Also, the retention mechanism and response of samples were investigated to the several factors such as pH, temperature, and concentration of MeOH as well as concentration of detection reagents in mobile phase. And some mixture of samples were able to be separated under optimum condition.