• Journal of the Korean Chemical Society
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• v.45 no.2
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• pp.149-155
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• 2001

A new analytical method of cyanobacterial toxins, i, e, microcysins was deveeloped using supercritical fluid extraction(SFE). The microcystins mcluded in the study are sparsely soluble in neat supercritical fluid CO$_2$ However, the microcystins were successfully extracted with a temary mixture(90% CO$_2$,9.0% methanol 1.0% water) at 40$^{\circ}$C and 250 atm. The SFE method developed in this study has several advantages over solid-phase extraction(SPE) sample preparation for the analysis of microcystins. Sample handling steps are minimized thus reducing possible losses of analytes and saving analysis time. No clean-up steps are employed in this SFE method. Althouhgh many methods have been described for microcystim RR and LR, the method using solid-phase extraction with ODS cartridges is the most commonly used. However, the adsorbing power of ODS caridges for microcystins is weak, so we have attempted to use a more polar CN cartridge, to increase the adsorbing power for microcystins. Lyophilized cells(100mg) were wxtracted with 5% (v/v) acetic acid. The extract was centrifuged and then the supernatant was applied to a CN cartridge. The cartridge which contained microcystins was rinsed with 5 ml of water and 5 ml of 0.5 M acetic acid. followed by 5 ml of 5% acetonitrile in water , and were determined by HPLC. Better recoveries and chromatogram were observed than with ODS cartridge.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.123-132
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• 1987

Nucleophilic substitution reactions of methylthiocyanate(MTC) with anion nucleophiles,$SH^-,\;CN^-$ and $OH^-$, have been investigated using MNDO method. For the three reaction centers of MTC, gas-phase and solution-phase selectivities are discussed for each nucleophile by considering potential energy profiles calculated(intrinsic term) and magnitudes of negative charge on the nucleophile at the transition state(solvation term). It was found that both components of the selectivity for $SH^-$agreed with the experimental results obtained for 4-methylbenzylthiocyanate (4-MBTC), but the selectivity order for TEX>$CN^-$ was found to agree only with that of the intrinsic term and that of $OH^-$disagreed with any theoretical selectivity order. The MNDO optimized geometries for all species at the stationary points are reported.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.559-565
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• 2010

In Mobile IPv6 handover should be followed by RO(Route Optimization) to support direct communication between a MN(Mobile Node) and CN(Correspondent Node). For this RR MIPv6 must perform RR(Return Routability) procedure before BU(Binding Update) to CN. The Fast Handover for MIPv6(FMIPv6) also performs the RR test for MN to communicate with CN directly. However, Return Routability test has long latency resulting in handover delay in MIPv6. This paper proposes the method to reduce the handover deay by reducing RO latency in FastMobile IPv6.

• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1316-1322
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• 1998

The amount of VC and C/N ratio in Ti(CN) was varied to investigate the effect of VC addition on the mi-crostructural change in Ti(CN)-Ni system. As the amount of VC addition increases in Ti(C0.7N0.3)-20Ni sys-tem a complete solid solution was observed in Ti(C0.7N0.3)-20Ni-25VC system. It implies that the ratio of the dissolution rates of Ti(C0.7N0.3)to that of VC is nearly 2:1 at the sintering conditions used in this study. It was found from the experiments that the system composed of the Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. That is among Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. This is among Ti(C1-xNx) phases the dissolution rate of Ti(C0.3N0.7) is the lowest. Also fracture toughness(KIC) of the cermet was measured by indentation method. Attentions were paid to crack propagation path to look for a dominant fracture mode and to cor-relate it with fracture toughness values. The fracture toughness was relatively high with the addition of VC content. But the addition of a large VC content reduced the overall toughness of the cermet. This result is explained with the difference in fracture mode.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.294-300
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• 1995

The photoelectrochemical behavior of polypyrrole films on Pt, glassy-C and indium tin oxide(ITO) under illumination was studied in aqueous solution containing a redox couple such as I-/I2 or Fe(CN)64-/Fe(CN)63-. Polypyrrole(PPy) was coated on Pt, glassy-C and ITO electrodes using electrochemical polymerization of pyrrole by potentiostatic method. Illumination of the PPy film results in the increase of cathodic and anodic currents at redox potentials of the redox species. These enhanced currents are caused both by the semiconductor characteristics of PPy and by the photothermal acceleration of redox reaction at PPy-electrode surface, and are dependent on the pH of redox solutions and the dopants in PPy.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.9-18
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• 2011

In this study the optimal volume for non-point source control retention is estimated considering spatio-temporal variation of land surface. The 3-parameter mixed exponential probability density function is used to represent the statistical properties of rainfall events, and NRCS-CN method is applied as rainfall-runoff transformation. The catchment drainage area is divided into individual $30m{\times}30m$ cells, and runoff curve number is estimated at each cell. Using the derived probability density function theory, the stormwater probability density function at each cell is derived from the rainfall probability density function and NRCS-CN rainfall-runoff transformation. Considering the antecedent soil moisture condition at each cell and the spatial variation of CN value at the whole catchment drainage area, the ensemble stormwater capture curve is established to estimate the optimal volume for an non-point source control retention. The comparison between spatio-temporally varied land surface and constant land surface is presented as a case study for a urban drainage area.

• Journal of the Korean Chemical Society
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• v.68 no.2
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• pp.82-86
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• 2024

This paper presents the solid-state synthesis of insoluble Prussian blue (Fe₄[Fe(CN)₆]₃·xH₂O, PB) in a ball mill, utilizing the fundamental components of PB. Solid-state synthesis offers several advantages, such as being solvent-free, quantitative, and easily scalable for industrial production. Traditionally, the solid-state synthesis of PB has been limited to the reaction between iron(II/III) ions and hexacyanoferrate(II/III) complex ions, essentially an extension of the solution-based coprecipitation method to solid-state reaction. Taking a bottom-up approach, a reaction is designed where the reactants consist of the basic building blocks of PB: Fe²⁺ ions and CN^- ions. The reaction, with a molar ratio of Fe²⁺ and CN^- corresponding to 1:2.8, yields PB, while a ratio of 1:6.6 results in a mixture of potassium hexacyanoferrate(II) (K₄Fe(CN)₆), potassium chloride (KCl), and potassium cyanide (KCN). This synthetic approach holds promise for environmentally friendly methods to synthesize multimetallic PB with maximum entropy in nearly quantitative yield.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3323-3326
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• 2011

Various aldoximes and ketoximes were efficiently reduced to their corresponding amines with $NaBH_3CN$ in the presence of $MoCl_5/NaHSO_4{\cdot}H_2O$ system. Reduction reactions were carried out in refluxing EtOH or DMF within 0.3-3.8 h to afford the amines in high to excellent yields.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1794-1798
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• 2010

침투형 우수유출저감시설 중 침투트렌치에 대한 치수효과를 다양한 유입유량을 적용하여 실험하였고 침투량, 유출량, 유출 시작시간, 종기침투능 및 종기침투능에 도달하는 시간 등을 계측하여 정량적으로 분석하고 적용방안을 도출하고자 하였다. 수리실험에 사용된 침투트렌치의 규모는 배수구역을 $130m^2$($6.5m{\times}20m$)로 가정하여 CN을 산정하였으며 그 결과 AMC-I 조건하에서 5개의 침투트렌치수심에 대하여 CN은 트렌치경사 2%일 때 84, 경사 5%일 때 83으로 산정되었고, AMC-III 조건하에서 CN은 트렌치 경사 2%, 5% 모두 84로 산정되었다.

• Korean Journal of Remote Sensing
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• v.20 no.3
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• pp.215-225
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• 2004

A multistage hierarchical clustering technique, which is an unsupervised technique, was suggested in this paper for classifying large remotely-sensed imagery. The multistage algorithm consists of two stages. The 'local' segmentor of the first stage performs region-growing segmentation by employing the hierarchical clustering procedure of CN-chain with the restriction that pixels in a cluster must be spatially contiguous. The 'global' segmentor of the second stage, which has not spatial constraints for merging, clusters the segments resulting from the previous stage, using the conventional agglomerative approach. Using simulation data, the proposed method was compared with another hierarchical clustering technique based on 'mutual closest neighbor.' The experimental results show that the new approach proposed in this study considerably increases in computational efficiency for larger images with a low number of bands. The technique was then applied to classify the land-cover types using the remotely-sensed data acquired from the Korean peninsula.