• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1094-1099
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• 2003

Nanometer-sized structures are being applied to many fields including micro/nano electronics, optoelectronics, quantum computing, biosensors, etc. Multi-scale analysis technology is required for designing the reliable nanometer-sized structures and predicting their mechanical, chemical and electronic behaviors. In this paper, some techniques for multi-scale analysis are reviewed and their applicability and limitation are discussed. Research activity of nano process analysis team in KIMM is outlined. Especially, we concentrate on OCTA of Nagoya University in Japan for the analysis of polymeric materials. Detailed structure of OCTA is described and some examples are presented.

• Journal of Microbiology and Biotechnology
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• v.20 no.7
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• pp.1061-1068
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• 2010

The biological synthesis of nanoparticles has gained considerable attention in view of their excellent biocompatibility and low toxicity. We isolated and purified rhamnolipids from Pseudomonas aeruginosa strain BS-161R, and these purified rhamnolipids were used to synthesize silver nanoparticles. The purified rhamnolipids were further characterized and the structure was elucidated based on one- and two-dimensional $^1H$ and $^{13}C$ NMR, FT-IR, and HR-MS spectral data. Purified rhamnolipids in a pseudoternary system of n-heptane and water system along with n-butanol as a cosurfactant were added to the aqueous solutions of silver nitrate and sodium borohydride to form reverse micelles. When these micelles were mixed, they resulted in the rapid formation of silver nanoparticles. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). The nanoparticles formed had a sharp adsorption peak at 410 nm, which is characteristic of surface plasmon resonance of the silver nanoparticles. The nanoparticles were monodispersed, with an average particle size of 15.1 nm (${\sigma}={\pm}5.82$ nm), and spherical in shape. The EDS analysis revealed the presence of elemental silver signal in the synthesized nanoparticles. The formed silver nanoparticles exhibited good antibiotic activity against both Grampositive and Gram-negative pathogens and Candida albicans, suggesting their broad-spectrum antimicrobial activity.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.465-473
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• 2019

Biocementation due to the microbially induced calcium carbonate precipitation (MICP) process is a potential technique that can be used for soil improvement. However, the effect of biocementation may be affected by many factors, including nutrient concentration, bacterial strains, injection strategy, temperature, pH, and soil type. This study investigates mainly the effect of chemical concentration on the formation of calcium carbonate (e.g., quantity, size, and crystalline structure) and unconfined compressive strength (UCS) using different treatment time and chemical concentration in the biotreatment. Two chemical concentrations (0.5 and 1.0 M) and three different treatment times (2, 4, and 8 cycles) were studied. The effect of chemical concentrations on the treatment was also examined by making the total amount of chemicals injected to be the same, but using different times of treatment and chemical concentrations (8 cycles for 0.50 M and 4 cycles for 1.00 M). The UCS and CCC were measured and scanning electron microscopy (SEM) analysis was carried out. The SEM images revealed that the sizes of calcium carbonate crystals increased with an increase in chemical concentrations. The UCS values resulting from the treatments using low concentration were slightly greater than those from the treatments using high concentration, given the CCC to be more or less the same. This trend can be attributed to the size of the precipitated crystals, in which the cementation efficiency increases as the crystal size decreases, for a given CCC. Furthermore, in the high concentration treatment, two mineral types of calcium carbonate were precipitated, namely, calcite and amorphous calcium carbonate (ACC). As the crystal shape and morphology of ACC differ from those of calcite, the bonding provided by ACC can be weaker than that provided by calcite. As a result, the conditions of calcium carbonate were affected by test key factors and eventually, contributed to the UCS values.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.166-174
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• 2014

This research investigated the aging properties of the $B-KNO_3$ system as the igniter. The $B-KNO_3$ system showed the degradation in ignition properties depending on the method and period of storage. It should be found out the cause of the degradation to predict the reliability of the igniters. The changes of the properties by the degradation after aging tests were analyzed by microstructure analysis, XRD analysis and thermal analysis using DSC. It was found out that the lattice parameters of the $KNO_3$ as the oxidizer in the ignition system was changed into the JCPDS values as the aging time increased. Conclusively, the changes of the crystal structure of oxidizer affected the activation energy increasing as aging time increased.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.303-308
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• 2005

A miniaturized time-of-flight mass spectrometer with an electron impact ionization source and sheet membrane introduction has been developed. The advantages and features of this mass spectrometer include high sensitivity, simple structure, low cost, compact volume with field portability, and ease of operation. A mass resolution of 400 at m/z 78 has been obtained with a 25 cm flight path length. Under optimized conditions, the detection limits for the volatile organic compounds (VOCs) studied were 0.2-10 ppm by volume with linear dynamic ranges greater than three orders of magnitude. The response times for various VOCs using a silicone membrane of 127 $\mu$m thickness were in the range 4.5-20 s, which provides a sample analysis time of less than 1 minute. These results indicate that the membrane introduction/time-of-flight mass spectrometer will be useful for a wide range of field applications, particularly for environmental monitoring.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.364-372
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• 2016

Sand tubules, made up of sand grains cemented by microbe-induced calcium carbonate precipitation, have been found in China's Ningxia Province. Sand tubules grow like a tree's roots about 40-60 cm below the surface. The properties of sand tubules and their bacterial community were examined. X-Ray diffraction analysis revealed that the sand tubules were associated with crystalline calcite. Scanning electron microscopy showed that the crystalline solid had a lamellar structure and lacked the presence of cells, suggesting that no bacteria acted as nucleation sites, nor that the crystalline solid was formed by the aggregation of bacteria. Denaturing gradient gel electrophoresis analysis showed 11 of the 12 detectable bands were uncultured bacteria by BLAST analysis in the GenBank database, and the rest were closely related to Paenibacillus sp. (100% identity). By cultivation techniques, the only strain isolated from the sand tubule was suggested to be related to Paenibacillus sp.; no archaea were found. Furthermore, Paenibacillus sp. was demonstrated to induce calcium carbonate precipitation in vitro.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1665-1668
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• 2010

The spin exchange interactions of $(VO)_2(H_2O){O_3P-(CH_2)_3-PO_3}{\cdot}2H_2O$ were examined by spin dimer analysis based on extended Huckel tight binding method. The strongest spin exchange interaction occurs through the super-superexchange path $J_2$ and the second strongest spin exchange interaction occurs through the superexchange interaction path $J_1$. There are two strongly interacting spin exchange paths in $(VO)_2(H_2O){O_3P-(CH_2)_3-PO_3}{\cdot}2H_2O$. Therefore, magnetic susceptibility curve of $(VO)_2(H_2O){O_3P-(CH_2)_3-PO_3}{\cdot}2H_2O$ can be well reproduced by an alternating onedimensional antiferromagnetic chain model rather than an isolated spin dimer model.

• The Korean Journal of Mycology
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• v.49 no.1
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• pp.109-118
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• 2021

In this study, we analyzed the diversity of ectomycorrhizal (ECM) fungal communities of Quercus spp. roots in the limestone area. We identified 45 generd of ECM using next generation sequencing (NGS) analysis. Soil chemical composition analysis confirmed soil pH, substitution calcium concentration, total nitrogen content, organic phosphate, and organic matter content. Shannon's Index was calculated according to the changes in soil chemical composition. The results of cluster analysis showed that Sebacina, Tomentella, Tuber, Densospora, Inocybe, Suillus, and Piloderma were the main genera of symbiotic ECM fungi that thrived in soil with high pH and calcium content.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.31-42
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• 2007

To investigate the pyrolytic and anatomical characteristics of Korean softwood, Pinus densi-flora, Pinus rigida and Larix leptolepis, and hardwood, Acer palntatum, Fraxinus rhynchophylla and Quercus variabilis, chemical components analysis, TG-DTA (Thermogravimetric Analysis & Differential Thermal Analysis), MBA (Methylene Blue Adsorption) test and SEM observation were carried out. For TG-DTA, samples were carbonized up to $800^{\circ}C$ at the heating rate of $10^{\circ}C$/min under $N_2$ flows 1 l/min using thermogravimetric analyzer. Chemical component analysis of all samples resulted in typical contents of major wood component. In TG-DTA results, softwood showed higher char yield than hardwood, and lignin displayed the highest char yield among the major wood components. All samples showed typical TGA, DTG and DTA curves for wood pyrolysis except a few differences between softwood and hardwood. Content of lignin influenced its pyrolysis characteristics, while molecular structure of lignin affected not only the weight loss but also the yield of char. In MBA test results, MBA of softwoods was higher than that of hardwoods. Char of Pinus densiflora showed the highest MBA, but its degree was lower than activated carbon or fine charcoal about 23 and 4 times, respectively. SEM observation showed carbonization process preserves wood structure and retain the micro-structure of wood fibers.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.990-995
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• 1999

To determine the effect of chemical structure of linear amine curing agents on thermal and mechanical properties, standard epoxy resin DGEBA was cured with ethylene diamine(EDA) and hexamethylene diamine(HMDA) in a stoichiometrically equivalent ratio. From this work, the effect of linear amine curing agents on the thermal and mechanical properties is significantly influenced by the chemical structure or chain length of curing agents. In contrast, the results show that the DGEBA/EDA system having the two carbons had higher values in the thermal stability, maximum conversion of epoxide, density, glass transition temperature, tensile modulus, flexural strength, and flexural modulus than the DGEBA/HMDA system having the six carbons, whereas the DGEBA/EDA cure system had relatively low values in the shrinkage(%), thermal expansion coefficient, tensile strength, and had similar values in the maximum exothermic temperature, and conversion of epoxide compared to the DGEBA/HMDA cure system. This findings indicate that packing ability in the HMDA structure affects the thermal and mechanical properties.