• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.23-29
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• 1990

The effect of a rapid freeze pretreatment of organic ion exchange resins on their grinding properties was studied. It was found that the structure of ion exchange resins was defected by freezing pressure formed in the process of rapid freezing. The defected resins didn't recover their own structure after thawing and those could be easy to be broken at room temperature by small force. Therefore, organic ion exchange resins could be ground readily at room temperature after rapid-freezing the fully swelled resins using by solid carbon dioxide, or liquid nitrogen. The rapid freeze pretreatment of cation exchange resins was very effective on grinding in particular. However, the effect of the pretreatment of anion exchange resins on grinding was less than that of cation exchange resins. In case of anion exchange resins, the ionic form of affected the grindability remarkably.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.959-967
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• 2003

The polyphenol compounds of Korean pears were extracted with 60% acetone for 4 days at room temperature and purified using Sephadex LH-20 column chromatography, MCI gel column chromatography, Bondapak $C_{18}$ column chromatography, TLC, and HPLC. As a result, three compounds were isolated. The chemical structures of each compound were determined and identified using NMR, FAM-mass, and FT-IR. The compounds were confirmed as (+)-catechin (compound A), (+)-gallocatechin (compound B), (-)-epigallocatechin (compound C), and procyanidin B-3-3-o-gallate (compound D).

• Journal of the Korean housing association
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• v.28 no.2
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• pp.57-65
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• 2017

This study intended to change the environment of a classroom in the existing child care center by applying the home environmental characteristics. The progress of environmental improvement for this study was conducted throughout the three stages. First, analyze the problems of existing child care center, which reflect the environmental characteristics and user opinions of the environment. Second, based on the analysis of the problems of the existing classroom, the classroom is improved by applying the environmental characteristics of the home. Third, compare the effect of improving the environmental characteristics of the home. The results of the study are as follows. First, the classroom was surveyed with a long rectangular space structure and was examined as a wide area when compared with the legal standards of $4.32m^2$ per child. Second, the emphasis is to complement the defects of the spatial structure and seek changes to the comfort environment, such as the proper stimuli and alterations to the atmosphere. Third, the effectiveness of the environmental improvement was assessed by comparing the results before and after the improvement of the environment. In terms of child environmental demands, movement and movement have increased. integrated configurations of the activity areas showed increased functionality, and overall, it was evaluated as a whole in terms of the atmosphere and the placeness.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.247-256
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• 1999

The leaky wave emanated from the dielectric-coated parallel-plate waveguide with finite periodic thick slot in its upper plate is investigated theoretically for H-polarization case. For this structure, fields in slot regions are expressed as a summation of the parallel-plate waveguide TM modes, and in other regions are expressed in the spectral domain by use of the inverse Fourier transform. Boundary conditions at the interfaces are enforced, and the simultaneous linear equations are derived. The influences of the slot width, slot thickness, thickness of a dielectric coating, and finite slot number on the radiation characteristics (phase constant, leakage constant, radiation pattern) are examined. The results of the finite periodic slot are compared with those of the infinite extent structure and good agreement has been found.

• Journal of Wetlands Research
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• v.5 no.2
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• pp.43-55
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• 2003

Vegetation structure was investigated in the Hyeonchang wetland and its watershed around the Nakdong-gang, Changryeong-county, Gyeongsangnamdo, Korea. from May to August, 2001. The vegetation type of the Hyeonchang wetland was classified into 12 communities based on the actual vegetation map: Phragmites communis community, Zizania latifolia community, Phragmites communis - Persicaria perfoliata community, Salix koreensis community, Persicaria perfoliata - Phragmites communis community, Spirodela polyrhiza community, Persicaria perfoliata community, Cyperus amuricus community, Cyperus amuricus-EchinochJoa crus-galli var. frumentacea community, Phragmites communis-Zizania latifolia community, EchinochJoa crus-galli var. frumentacea community, and Persicaria maackiana community. Among them, Phragmites communis community was the largest (4.3 ha, 24%). The dominant vegetation type were Phragmites communis community, Echinochloa crus-galli var. frumentacea-Persicaria maackiana community, and Cyperus amuricus subcommunity based on the phytosociological method. The vegetation type of the Hyeonchang wetland watershed was classified into five communities based on the actual vegetation map: Pinus densilflora community, Pinus rigida community, Pinus densiflora-Quercus acutissima community, Pinus densiflora-Larix gmelini var. principis-ruprechtii community, and Populus tomentiglandulosa community. Among them, Distribution area of Pinus densiflora community was largest (399.3 ha, 61.8%). And the degree of green naturality of the Pinus densiflora community was 7 and 8 degree.

• Journal of the Korean Chemical Society
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• v.47 no.2
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• pp.104-108
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• 2003

The reaction of $[Cu(L)]Cl_2{\cdot}H_2O(L=3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^{1.18},0^{7.12}]docosane)$ with 2,5-pyridinedicarboxylate(pdc) led to the formation of $[Cu(L)(H_2O)](pdc){\cdot}6H_2O(1)$. The structure was characterized by X-ray crystallography and spectroscopic method. The coordination geometry around the copper atom is a distorted square-pyramid with four secondary amines of the macrocycle occupying the basal sites and a water molecule at the axial position. Intermolecular hydrogen bonds in 1 form a three-dimensional molecular network.

• Corrosion Science and Technology
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• v.19 no.1
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• pp.16-22
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• 2020

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.990-997
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• 2015

The condition factor (CF) were calculated by the morphometric data, and gonadal maturation and reproductive potential associated with fecundities of indoor cultured Hapalogenys nitens were investigated by microscopic and morphometric analysis from August 2011 to October 2012. Monthly changes in the GSI and CF were closely related to gonadal maturation and spawning. The ovary consisted of a pair of saccular structure with many ovarian lobules, the testis is a pair of lobular structure with many testicular lobules. The relationship between total fecundity (F) and total length (TL) of fish was expressed as $F=0.0449TL^{2.7926}$($r^2=0.0653$), and body weight (BW) was expressed as $F=1.4492BW^{0.8964}$($r^2=0.0863$). In this study, some exceptional special cases and phenomena were observed: absolute and relative fecundities were not increased with the increases of total length and body weight, respectively. Absolute and relative fecundities were no concerned with the increases of age classes of total length (cm) and of body weight (g).

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.213-220
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• 2013

Korean Lunar Explorer is planned to be launched in the 2020s according to national space development strategy. The Lunar Explorer will be developed as two unmanned light weight models: a lunar orbiter and a lunar lander. The Lunar Explorer's structure should be designed to have light weight due to constraints from launcher as well as to provide structural safety against launch load, in-orbit condition and landing condition and to serve accommodation space for mission equipment. Core technology related to structural development of lunar explorer should be developed in advance. Especially, for lunar lander, technology for developing landing gear which enables lander to land safely on lunar surface is required essentially. This paper deals with structural development of lunar lander ground test model including design, manufacturing and test.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.838-842
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• 2017

The thruster valve, which is one of the key components applied to the mono-propellant system for the satellite, has a circular plate spring structure. It can be designed as a structure that does not have positional deformation and particles by friction and repetitive motion. In this study, finite element analysis and verification were performed by setting the width of the circular plate spring as a design parameter with the material, thickness and radius of the circular plate spring as fixed variables. The linearity of the spring constant is shown by the graph that is spring force with displacement. It is confirmed that the optimization design of the circular plate spring is possible by the spring force tendency according to the total area of circular plate spring.