• Korean Journal of Microbiology
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• v.34 no.4
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• pp.212-218
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• 1998

An obligately methylotrophic bacterium which produces extracellular polysaccharide (EPS) was isolated through methanol-enrichment culture technique. The isolate was aerobic, nonmotile, and gram negative rod and exibited catalase, but no oxidase, activity. Plasmid, carotenoid, and poly-${\beta}$-hydroxybutyric acid were not found. The guanine plus cytosine content of DNA was 52-56%. The isolate was found to grow only on methanol and monomethylamine. Growth was optimal ($t_d=2.4h$) at $35^{\circ}C$ and pH 6.5 in a mineral medium containing 0.5% (v/v) methanol, 25 mM phosphate, and 0.212% ammonium sulfate. Methanol was assimilated through the ribulose monophosphate pathway. Maximun amount of EPS was produced in cells growing at the mid-stationary growth phase at $30^{\circ}C$ in a mineral medium (PH 6.5) containing 1.0% (v/v) methanol in the CIN ratio of 54.7. Thin-layer chromatographic and high performance liquid chromatographic analysis revealed that the EPS was composed of glucose and galactose. EPS which was not treated with ethanol (Pbe) exhibited stable viscosity under various concentrations of salts and temperatures hut showed high viscosity at low pH. EPS precipitated with ethanol (Pae) was found to be more stable in viscosity than the Pbe at various salt concentrations, temperatures, and pH. The Pae also exhibited higher viscosity than the Pbe and xanthan gum. Scanning electron microscopy revealed that the lyophilized Pbe and Pae have a multi-layered structure and a structure of thick fibers, respectively.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.81-88
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• 2024

The payload BioCabinet of CAS500-3 is designed for 3D stem cell differentiation, culture, and analysis utilizing bio 3D printing techniques in space. The 3D printing technique was initially developed for orbital use; however, it lacks separate validation for extreme launch vibration environments, necessitating a design that mitigates the launch load on the payload. This paper proposes a passive vibration isolator with a low-stiffness elastic support structure and high damping characteristics to reduce the launch loads affecting the BioCabinet. We explore the high-damping characteristics through the superelastic effects of SMA (Shape Memory Alloys) and a multi-layered structure incorporating viscoelastic tape. The effectiveness of the proposed vibration isolation system was confirmed via launch vibration tests on a qualification model.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.223-232
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• 2003

The co-precipitation method is applied to synthesize the cathode material Li[L $i_{x}$M $n_{1-x-y}$C $r_{y}$ ] $O_2$ for lithium rechargeable batteries at $650^{\circ}C$ (CR650) and 8$50^{\circ}C$ (CR850), respectively. Rietveld indices indicate that $R_{wp}$ with respect to $R_{exp}$ ( $R_{wp}$/ $R_{exp}$) are 9.2%/10.1% for CR650 and 15.9%/9.76% for CR850, respectively. $R_{B}$ and S (GofF) shows 10.9%, 8.54% and 1.9, 1.6, respectively. Rietveld structure refinement reveals that layer structure of LiMn $O_2$ (R3m) coexists with lower symmetry of Li[L $i_{1}$3/M $n_{2}$3/] $O_2$ (C2/c) due to superlattice ordering of Li and Mn in metal-transition containing layers. Unit-cell parameters are calculated as a=2.8520(2)$\AA$, c=14.248(2)$\AA$, V=100.40(l)$\AA^3$ for CR650, and a=2.8504(1)$\AA$, c=14.2371(7)$\AA$, V=100.179(8)$\AA^3$ for CR850. Final chemistry is obtained as Li[L $i_{0.35}$M $n_{0.56}$C $r_{0.09}$] $O_2$ (CR650) and Li[L $i_{0.27}$M $n_{0.61}$C $r_{0.13}$] $O_2$ (CR850), respectively.y...y..vely.y...y..

• Journal of the Korean Applied Science and Technology
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• v.37 no.3
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• pp.484-495
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• 2020

This study is a mixed surfactant (MimicLipid-MSM1000) that forms the same structure as that of the stratum corneum, sucrose distearate, polyglyceryl-2 dioleate, fermented squalane, ergosterol, 10-hydroxystearic acid, mixture consisting of was synthesized. When using 2~5 wt% of this mixed surfactant, it was possible to make an artificial skin mimetic that forms a multi-layer lamellar structure of 5~30 layers. An emulsion was prepared using this mixed surfactant, and a multi-layered lamellar phase was formed and analyzed mechanically. The appearance of this surfactant was a light brown hard wax, the hydrophilic lipophilic balance (HLB) was 12.53, the critical parameter value was 0.987, and the acid value was 0.13. Stability according to pH change was also stable in acidic (3.8), neutral (7.2) and alkaline (10.8). The particle size of the liquid crystal was found to be the most stable maltese cross lamellar crystalline droplet at 5~25mm. The size of the emulsified particles according to the change in the speed of the homo agitator is 2500 rpm (17.9mm±2.6mm), 3500rpm (12.5mm±2.1mm), 4500rpm (6.2mm±1.8mm) particles were formed. Liquid crystal forming particles were observed through a polarization microscope, and the formation structure of the liquid crystal was precisely analyzed with a scanning electron microscope (cryo-SEM). As an application field, it is expected that it will be widely applicable to the development of various prescriptions, such as various skin care cosmetics, makeup care cosmetics, and scalp protection cosmetics, by using a skin-mimicking surfactant.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.2
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• pp.111-123
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• 2022

Carbonate green rust (CGR) and sulfate green rust (SGR) commonly occur in nature. In this study, CGR and SGR were synthesized through co-precipitation, and their formation mechanisms and physicochemical properties were investigated. X-ray diffraction (XRD) and Rietveld refinement showed both CGR and SGR with layered double hydroxide structure were successfully synthesized without any secondary phases under each synthetic condition. Refined structural parameters (unit cell) for two green rusts were a (=b) = 3.17 Å and c = 22.52 Å for CGR and a (=b) = 5.50 Å and c = 10.97 Å for SGR with the crystallite size 57.8 nm in diameter from (003) reflection and 40.1 nm from (001) reflections, respectively. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) results showed that both CGR and SGR had typical hexagonal plate-like crystal morphologies but their chemical composition is different in the content of C and S. In addition, Fourier transform infrared (FT-IR) spectroscopy analysis revealed that carbonate (CO₃^2-) and sulfate (SO₄^2-) molecules were occupied as interlayer anions of CGR and SGR, respectively. These SEM/EDS and FT-IR results were in good agreement with XRD results. Changes in the solution chemistry (i.e., pH, Eh and residual iron concentrations (Fe(II):Fe(III)) of the mixed solution) were observed as a function of the injection time of hydroxyl ion (OH^-) into the iron solution. Three different stages were observed in the formation of both CGR and SGR; precursor, intermediator, and green rust in the formation of both CGR and SGR. This study provides co-precipitation methods for CGR and SGR in a way of the stable synthesis. In addition, our findings for the formation mechanisms of the two green rusts and their physicochemical properties will provide crucial information with researches and industrials in utilizing green rust.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.89-97
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• 2007

A three-dimensional (3D) magnetotelluric (MT) survey has been carried out to delineate subsurface structures and possible fractures, for development of low-temperature geothermal resources in Pohang, Korea. Quite good quality MT data could be obtained throughout the survey region by locating the remote reference in Kyushu, Japan, which is ${\sim}480\;km$ from the centre of the field site. 3D modelling and inversion are performed taking into account the sea effect in MT measurements near the seashore. The nearby sea in the Pohang area affects MT data at frequencies below $1\;Hz{\sim}0.2\;Hz$, depending on the distance from the seashore. The most severe sea effects were observed in the south-east parts of the survey area, closer to Youngil Bay. 3D inversion with and without the seawater constraint showed very similar results at shallow depths, roughly down to 2 km. At greater depths, however, a strong sea effect seems to form a fictitious conductive structure in ordinary 3D inversion, especially in the south-eastern part of the survey region. Comparison between drilling results and the resistivity profiles from inversions showed that five layered structures can be distinguished the subsurface beneath the target area. They are: (a) semi-consolidated mudstones with resistivity less than $10\;{\Omega}m$, which are ${\sim}300\;m$ thick in the northern part and ${\sim}600\;m$ thick in the southern part of the survey area; (b) occasional occurrence of trachybasalt and lapilli tuff within the mudstone layer has resistivity of a few tens of${\Omega}m$, (c) intrusive rhyolite ${\sim}400\;m$ thick has resistivity of several hundreds of ${\Omega}m$, (d) alternating sandstone and mudstone down to 1.5 km depth shows resistivity of ${\sim}100\;{\Omega}m$, (e) a conductive structure was found at a depth of ${\sim}3\;km$, but more geological and geophysical study should be carried out to identify this structure.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.242-246
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• 2017

The application of composite cathode materials including $LiFePO_4$ (lithium iron phosphate) of olivine crystal structure, which has high thermal stability, were investigated as alternatives for hybrid battery-capacitors with a $LiMn_2O_4$ (spinel crystal structure) cathode, which exhibits decreased performance at high temperatures due to Mn-dissolution. However, these composite cathode materials have been shown to have a reduction in capacity by conducting life cycle experiments in which a $LiFePO_4$/activated carbon cell was charged and discharged between 1.0 V and 2.3 V at two temperatures, $25^{\circ}C$ and $60^{\circ}C$, which caused a degradation of the anode due to the lowered voltage in the anode. To avoid the degradation of the anode, composite cathodes of $LiFePO_4/LiMn_2O_4$ (50:50 wt%), $LiFePO_4$/activated carbon (50:50 wt%) and $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (50:50 wt%) were prepared and the life cycle experiments were conducted on these cells. The composite cathode including $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ of layered crystal structure showed stable voltage behavior. The discharge capacity retention ratio of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ was about twice as high as that of a $LiFePO_4/LiMn_2O_4$ cell at thermal stability experiment for a duration of 1,000 hours charged at 2.3 V and a temperature of $80^{\circ}C$.

• Korean Journal of Environment and Ecology
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• v.27 no.4
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• pp.487-497
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• 2013

This study was conducted to suggest vegetation management plan for Gugok landscape maintenance and improvement by deducing the vegetation landscape factors inherent in Yongha Gugok and understanding vegetation structure through the investigate of existing vegetation and plant community structure of Yongha valley in Woraksan National Park. There were broad and flat rocks, natural layered stones, clear water, light stones, stream, valleys, waterfalls, Pinus densiflora and Acer pseudosieboldianum as a result of deducing natural factors on poetry. There were P. densiflora and A. pseudosieboldianum appeared as one of main vegetation landscape elements. The actual vegetation analysis results were as followed. The natural vegetation occupied 67.5% and it was classified as P. densiflora community, Quercus variabilis community, Q. variabilis-P. densiflora community, Q. variabilis-Q. serrata community, Q. serrata community, Q. mongolica community, Q. mongolica-P. densiflora community, Deciduous broad-leaved tree community. The artificial vegetation(18.7%) was classified as Q. serrata community-Larix kaempferi community, Q. mongolica- Castanea crenata community, L. kaempferi community, L. kaempferi-C. crenata community, fruticeta, L. kaempferi-Q. mongolica community. The grassland area(2.0%) was classified as Miscanthus sinensis community, Phragmites communis community, and other areas were classified as landscape tree planting area, farm, orchard, residential area. The representative vegetation were P. densiflora community, Q. variabilis-Q. serrata community, L. kaempferi community, Deciduous broad-leaved tree community in Yongha Gugok. The species diversity index of Shannon was 0.6274~0.9908 on the whole. Yongha Gugok, as a symbol of succession on confucianism and reverence for nature, should be preserved natural valley landscape being clean and wijungchuksa at the end of Joseon Dynasty and Japanese Colonial era. In this historical and cultural Gugok, vegetation landscape management plan is needed to landscape maintenance with P. densiflora community, density control with L. kaempferi community. And it is considered when natural disasters and artificial damages happened, P. densiflora-oriented vegetation restoration plan should be applied in order to restore.

• Korean Journal of Environment and Ecology
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• v.26 no.4
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• pp.604-619
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• 2012

According to the concept of woodland aesthetic in Germany and forest design in United Kingdom, artificial forest should be restore ecologically step by step in National Park, Korea. This study was carried out to provide the density criterion of thinning for the inducement of the ecological succession by analysing of vegetational structure in Artificial Forest, National Parks. Eleven plots(size is $20m{\times}20m$) were set up in the artificial forest such as Pinus koraiensis forest, Abies holophylla forest, Chamaecyparis obtusa forest, Populus tomentiglandulosa forest, and Larix kaempferi forest and in the natural forest such as Pinus densiflora community, Pinus densiflora-Quercus serrata community, and Quercus serrata community in Chiaksan, Songnisan, Deogyusan, and Naejangsan National Parks, Korea. We classified the artificial forest into undeveloped type of succession, type of alien young trees developing, and early phase type of succession based on the vegetational structure. According to the index of Shnnon's diversity(unit: $400m^2$), undeveloped type of succession was ranged from 0.9681 to 1.1323, type of alien young trees developing was ranged from 1.0192 to 1.1870, early phase type of succession was ranged from 1.3071 to 1.3892, and natural vegetation was ranged from 1.2202 to 1.3428, therefore early phase type of succession forest and natural vegetation are more higher than simple-layered artificial forest with one needle leaf tree species. The limit for the step-by-step thinning was in the range of 30~60%. In case of undeveloped type of succession, we should thin out from large trees throughout three phases, because alien species dominated high value 88~90% in canopy layer. In case of type of alien young trees developing, we should thin out from alien young trees such as Populus tomentiglandulosa throughout one or two phases, because alien species dominated high value 60~97% and young trees with saplings growing up in understory and shrub layer. In case of early phase type of succession, we should thin out from alien trees that compete with native species throughout one or two phases, because alien species dominated less than value 30%.

• Clean Technology
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• v.20 no.2
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• pp.189-201
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• 2014

Partial oxidation, $CO_2$ reforming and the oxidative $CO_2$ reforming of $CH_4$ to produce synthesis gas over supported Ni hydrotalcite-type ($Ni_{0.5}Ca_{2.5}Al$ catalyst) catalysts were carried out and the effects of metal supports (i.e.; Mg and Ca) on the formation of a stable double-layer structure on the catalysts were evaluated. The $CH_4$ reforming stability was determined to be affected by the differences in the interaction strength between the active Ni ions and support metal ions. Only a Ni-Mg-Al composition produced a highly stable hydrotalcite-type double-layered structure; while the Ni-Ca-Al-type composition did not. Such structure provides excellent stability for the catalyst (-80% efficiency) as confirmed by the long-term $CO_2$ reforming test (-100 h), while the Ni-Ca-Al catalyst exhibited deactivation phases starting at the beginning of the reaction. The interaction strength between the active metal (Ni) and the supporting components (Mg and Al) was determined by temperature-programed reduction (TPR) analyses. The affinity was also confirmed by the TPR temperature because the Ni-Mg-Al catalyst required a higher temperature to reduce the Ni relative to the Ni-Ca-Al catalyst. The highest initial activity for synthesis gas production was observed for the $Ni_{0.5}Ca_{2.5}Al$ catalyst; however, this activity decreased quickly due to coke formation. The $Ni_{0.5}Ca_{2.5}Al$ catalyst exhibited a high reactivity and was more stable than the other catalysts because it had a higher resistance to coke formation.