• Journal of the Korean Chemical Society
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• v.42 no.4
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• pp.369-377
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• 1998

The palladium(II) and platinum(II) complexes(where, $([M(L)_2X_2]$, M=Pd(II), Pt(II); L=isoxazole(isox), 3,5-dimethylisoxazole(3,5-diMeisox), 3-methyl, 5-phenylisoxazole(3-Me, 5-Ph-isox), and 4-amino-3,5-dimethylisoxazole (4-ADI); X=Cl, Br) with isoxazole and its derivatives were investigated on antitumor activity by MM2 and EHMO calculation. Because for all the complexes the ${\sigma}MO$ energy level $(E_{{\sigma}(M-X)})$ between $d_x^{2-}_y^2$ orbital of central metal and px orbital of halogen atom is less than ${\sigma}MO$ energy level $(E_{{\sigma}(M-N)})$ between $d_x^{2-}_y^2$ orbital of central metal and px orbital of N atom, without exception. And judging, from the lower $(E_{\'{o}(m-x)})$ value in trans, the bonding strength was found to be weaker in trans isomer than in cis. For the Pd(II) and Pt(II) complexes which have planar ligands, it was shown that for all the complexes dissociation of X-atom in the Pd(II) complexes is easier than that of X-atom in the Pt(II) complexes in both cis- and trans-complexes. Therefore it suggests that the easier dissociation of $X^-$ ion has some relations with antitumor activity, and a linear equation with correlation coefficient of 0.96 was found between ${\Delta}E_{{\sigma}(N-X)}(E_{{\sigma}(M-N)}-E_{{\sigma}(M-X)})$ and inhibitory activity coefficient, logIA.

• Membrane Journal
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• v.15 no.4
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• pp.310-319
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• 2005

This paper describes the preliminary study on the development of multi-stage membrane demonstration plant for removal of carbon dioxide from flue gas stream being emitted from LNG boiler in thermal power generation plant. The prerequisite requirement is to design and develop the membrane process producing a $99\%\;CO_2$ with $90\%$ recovery from LNG flue gas of 1,000 $Nm^3$/day. Asymmetric polyethersulfone hollow fiber membranes and membrane modules developed in this laboratory[1] were used in this study. Using the permeation data for the hollow fiber membranes, modelling on the membrane module and multi-stage membrane process was done to meet the requirement condition of the process design. The effects of the operating pressure of feed and permeate side and feed concentration on $CO_2$ purity and recovery were investigated experimentally with the developed hollow fiber modules. These experimental results matched well with theoretical modelling results.

• Journal of KIISE:Databases
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• v.31 no.6
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• pp.641-649
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• 2004

The relationship between chemical structures and biological activities is researched briskly in the area of 'Medicinal Chemistry' At the base of these structure-based drug design tries, medicinal chemists search the existing drugs of similar chemical structure to target drug for the development of a new drug. Therefore, it is such necessary that an automatic system selects drug files that have a set of chemical moieties matching a user-defined query moiety. Substructure searching is the process of identifying a set of chemical moieties that match a specific query moiety. Testing for substructure searching was developed in the late 1950s. In graph theoretical terms, this problem corresponds to determining which graphs in a set are subgraph isomorphic to a specified query moiety. Testing for subgraph isomorphism has been proved, in the general case, to be an NP- complete problem. For the purpose of overcoming this difficulty, there were computational approaches. On the 1990s, a US patent has been granted on an atom-centered indexing scheme, used by the RS3 system; this has the virtue that the indexes generated can be searched by direct text comparison. This system is commercially used(http://www.acelrys.com/rs3). We define the RS3 system's drawback and present a new indexing scheme. The RS3 system treats substructure searching with substring matching by means of expressing chemical structure aspredefined strings. However, it has insufficient 'rerall' and 'precision‘ because it is impossible to index structures uniquely for same atom and same bond. To resolve this problem, we make the minimum-cost- spanning tree for one centered atom and describe a structure with paths per levels. Expressing 2D chemical structure into 1D a string has limit. Therefore, we break 2D chemical structure into 1D structure fragments. We present in this paper a new index technique to improve recall and precision surprisingly.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.1-13
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• 2014

Lithium ion batteries (LIBs) are the state-of-the-art technology among electrochemical energy storage and conversion cells, and are still considered the most attractive class of battery in the future due to their high specific energy density, high efficiency, and long cycle life. Rapid development of power-hungry commercial electronics and large-scale energy storage applications (e.g. off-peak electrical energy storage), however, requires novel anode materials that have higher energy densities to replace conventional graphite electrodes. Germanium (Ge) and silicon (Si) are thought to be ideal prospect candidates for next generation LIB anodes due to their extremely high theoretical energy capacities. For instance, Ge offers relatively lower volume change during cycling, better Li insertion/extraction kinetics, and higher electronic conductivity than Si. In this focused review, we briefly describe the basic concepts of LIBs and then look at the characteristics of ideal anode materials that can provide greatly improved electrochemical performance, including high capacity, better cycling behavior, and rate capability. We then discuss how, in the future, Ge anode materials (Ge and Ge oxides, Ge-carbon composites, and other Ge-based composites) could increase the capacity of today's Li batteries. In recent years, considerable efforts have been made to fulfill the requirements of excellent anode materials, especially using these materials at the nanoscale. This article shall serve as a handy reference, as well as starting point, for future research related to high capacity LIB anodes, especially based on semiconductor Ge and Si.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.530-535
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• 2019

In this study, an optimization for the emulsification process with coconut oil and sugar ester was performed in conjunction with the central composite design (CCD) model of response surface methodology (RSM). Response values for the CCD model were the viscosity of the emulsion, mean droplet size, and emulsion stability index (ESI) after 7days from the reaction. On the other hand, the emulsification time, emulsification rate, and amount of emulsifier were selected as quantitative factors. According to the result of CCD, optimum conditions for the emulsification were as follows; the emulsification time of 22.63 min, emulsification speed of 6,627.41 rpm, and amount of emulsifier of 2.29 wt.%. Under these conditions, the viscosity, mean droplet size, and emulsion stability index (ESI) after 7 days from reaction were estimated as 1,707.56 cP, 1877.05 nm, and 93.23%, respectively. The comprehensive satisfaction of the CCD was indicated as 0.8848 with an average error of $1.2{\pm}0.1%$ from the experiment compared to that of the theoretical one. Overall, a very low error rate could be obtained when the central composite model was applied to the optimized coconut oil to water emulsification.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.639-645
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• 2020

Among the components of redox flow battery (RFB), the electrode serves as a diffusion layer of an electrolyte and a path for electrons and also is a major component that directly affects the RFB performance. In this paper, chloric/sulfuric mixed acidwas used as a supporting electrolyte in RFB system with Fe2+/Fe3+ and V2+/V3+ as redox couple. The optimum electrode and activation temperature were suggested by comparing the capacity, coulombic efficiency and energy efficiency according to the electrode type and activation temperature. In the RFB single cell evaluation using 5 types of carbon electrodes used in the experiments, all of them showed close to the theoretical capacity to retain the reliability of the evaluation results. GFD4EA showed relatively excellent energy efficiency and charge/discharge capacity. In order to investigate the electrochemical performance according to the activation temperature, GFD4EA electrode was activated by heat treatment at different temperatures of 400, 450, 500, 600 and 700 ℃ under an air atmosphere. Changes in physical properties before and after the activation were observed using electrode mass retention, scanning electron microscope (SEM), XPS analysis, and electrochemical performance was compared by conducting RFB single evaluation using electrodes activated at each temperature given above.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.58-63
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• 2022

Graphite has been used as an anode material for lithium-ion batteries for the past 30 years due to its low de-/lithiation voltage, high theoretical capacity of 372 mAh/g, low price, and long life properties. Recently, all-solid-state lithium-ion batteries (ASSLB), which are composed of inorganic solid materials with high stability, have received great attention as electric vehicles and next-generation energy storage devices, but research works on graphite that works well for ASSLB systems are insufficient. Therefore, we induced the performance improvement of ASSLB anode electrode graphite material by removing the amorphous carbon present in the carbon material surface, acting as a resistive layer from the graphite. As a result of X-ray diffraction (XRD) analysis using heat treated graphite in air at 400, 500, and 600 ℃, the full width at half maximum (FWHM) at (002) peak was reduced compared to that of bare graphite, indicating that the crystallinity of graphite was improved after heat treatment. In addition, the discharge capacity, initial coulombic efficiency (ICE) and cycle stability increased as the crystallinity of graphite increased after heat treatment. In the case of graphite annealed in air at 500 ℃, the high capacity retention rate of 331.1 mAh/g and ICE of 86.2% and capacity retention of 92.7% after 10-cycle measurement were shown.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.309-315
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• 2024

Silicon and carbon composite (SiC) is considered one of the most promising anode materials for the commercialization of Si-based anodes, as it could simultaneously satisfy the high theoretical capacity of Si and the high electronic conductivity of carbon. However, SiC active material undergoes repeated volumetric changes during charge/discharge processes, leading to continuous electrolyte decomposition and capacity fading, which is still considered an issue that needs to be addressed. To solve this issue, we suggest a 4,4'-Methylenebis(cyclohexyl isocyanate) (H₁₂MDI)-based waterborne polyurethane binder (HPUD), which forms a 3D network structure through thermal cross-linking reaction. The cross-linked HPUD (denoted as CHPU) was prepared using an epoxy ring-opening reaction of the cross-linker, triglycidyl isocyanurate (TGIC), via simple thermal treatment during the SiC anode drying process. The SiC anode with the CHPU binder, which exhibited superior mechanical and adhesion properties, not only demonstrated excellent rate and cycling performance but also alleviated the volume expansion of the SiC anode. This work implies that eco-friendly binders with cross-linked structures could be utilized for various Si-based anodes.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.222-229
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• 2024

The use of low-toxic, hypoallergenic, and environmentally friendly natural pigments has increased. With growing interest in health, research on natural extracts containing beneficial substances for the human body is actively underway. In this study, natural pigments were extracted from sprout barley using a solvent extraction method and CCD-RSM was used to optimize the extraction process. The experiment's independent variables included extraction temperature, alcohol/ultra-pure volume ratio, and extraction time. The response variables were set to achieve a target chromaticity (L = 45, a = -35, b = 45), and to maximize DPPH radical scavenging activity evaluating the antioxidant capacity. The statistical significance of the main effect, interaction effect, and effect on the response value was evaluated and analyzed through the F and P values for the regression equation variables calculated using RSM optimization. Additionally, the reliability of the experiment was also confirmed through the P values of the probability plot graph. The extraction conditions for optimizing the four reaction values are 76.1 vol.% alcohol/ultra pure water volume ratio, an extraction temperature of 52.9 ℃ , and an extraction time of 49.6 min. Under these conditions, the theoretical values of the reaction values are L = 45.4, a = -36.8, and b = 45.0 DPPH radical scavenging activity = 30.9%. When the actual experiment was conducted under these optimal extraction conditions and analyzed, the measured values were L = 46.2, a = -36.1, and b = 48.2, and antioxidant capacity = 31.1% with an average error rate of 2.9%.

• The Korean Journal of Pesticide Science
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• v.17 no.1
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• pp.13-19
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• 2013

Isopyrazam, a new pyrazolecarboxamide fungicide developed by Syngenta, was highly active against foliar powdery mildew pathogens on cucumber, oriental melon and various vegetables. Following foliar applications on cucumber and oriental melon, crop residues were determined using high performance liquid chromatography. For all studies, limit of quantification was 0.02 mg/kg and minimum detection level was 2.0 ng and recoveries were 83.0-88.0% on cucumber, 92.4-104.5% on oriental melon. Isopyrazam was detected 0.07-0.72 mg/kg on cucumber and < 0.02-0.68 mg/kg on oriental melon, respectively. The TMDI (Theoretical Maximum Dailly Intake) of isopyrazam on cucumber and oriental melon was estimated to less than 1.765% of ADI.