• Polymer(Korea)
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• v.37 no.5
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• pp.592-599
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• 2013

In this study, polyacrylonitrile (PAN)-based porous carbon nanofibers were prepared from PAN polymer solution by electrospinning and KOH activation with various concentrations, and the characterization of pore structures and carbon dioxide adsorption was investigated. Manufactured PAN-based activated carbon nanofibers tend to decrease diameter and increase surface oxygen functional groups depending on the increasing concentration of KOH solution. In addition, according to the results of nitrogen adsorption for pore properties analysis, it indicated increase of the specific surface area in conformity with increasing concentration of KOH solution. Micropore volume of treated activated carbon nanofibers (ANCF) by 4 M KOH was the largest compared with other samples and mesopore volume of treated ANCF by 8 M KOH was the largest volume, respectively. The concentration of KOH effects textural and surface properties, as represented by BET and XPS, which enhance carbon dioxide adsorption capacity at 0 and $25^{\circ}C$.

• Journal of the Korean Geotechnical Society
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• v.30 no.11
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• pp.39-49
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• 2014

Volcanic rocks in Jeju island show vesicular structure caused by various environmental factors, and indicate the differences in geological and mechanical characteristics from region to region. Previous studies on the volcanic rocks in Jeju island have been actively conducted on geological and chemical properties in terms of geophysics and geology and on physical and mechanical properties in terms of engineering. But comprehensive comparative analysis on physical and mechanical properties of volcanic rocks in Jeju island is not conducted. In this study, the physical and mechanical properties of volcanic rocks in Jeju island were compared and analyzed comprehensively through the existing research papers and reports about volcanic rocks in Jeju island. As a result, it was found that the relationship between absorption (porosity) and apparent specific gravity is commonly linear and could be represented as two different linear approximations. In addition, it was found that the relationship between P-wave velocity and S-wave velocity and the relationship between absorption (porosity) and uniaxial compressive strength could be classified more clearly, considering two different linear relationships in absorption (porosity) and apparent specific gravity.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.846-850
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• 2011

Nanocomposite anodes for rechargeable lithium battery are prepared by mixing tin and nickel nanoparticles via wet method and their electrochemical properties are examined. The Sn-Ni nanocomposite anode shows a maximum discharge capacity of 700 mAh $g^{-1}$ at the first cycle but very poor cycle performance. This means that the electrode porosity and the Ni component formed by the simple mixing of nanoparticles no longer play the role of buffering the volume expansion/contraction of Sn component during charge-discharge. To solve the cycle performance problem, a novel nanostructured Sn-Ni anode should be designed and tested.

• Composites Research
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• v.33 no.2
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• pp.76-80
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• 2020

In this study, vacuum bag hot-press (V-HP) process can be used as an out-of-autoclave (OOA) process by improving the inefficient process of the autoclave forming method with excellent physical properties and surface quality. A carbon fiber composite was molded via V-HP process and analyzed the physical properties and microstructures between composites manufactured by autoclave (AC) process and hot-press process (HP). The tensile strength of the composite materials using the V-HP process was 320.6 MPa and the AC process samples found to be substantially close to the tensile strength of 335.3 MPa. As a result of confirming the surface quality of the composite material using SEM, it was confirmed that in the V-HP process, the removal state of pores due to volatile solvent in the resin was slightly lower than that of the AC process, but it had a considerably superior surface compared to the HP process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.235-240
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• 2010

Transpiration cooling is the most effective cooling technique for liquid rocket and air-breathing engines operating in aggressive environments with higher pressures and temperatures. Combustor liners and turbine vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. However, its practical implementation has been hampered by the limitations of available porous materials. The search for more practical methods of increasing the internal heat transfer within the walls has led to the development of multi-laminate porous structures, such as Lamilloy$^{(R)}$ and Transply$^{(R)}$. This paper reviews recent research activities of transpiration cooling for the propulsions of liquid rocket, gas turbine, and scramjet.

• Journal of Plant Biology
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• v.30 no.2
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• pp.79-94
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• 1987

This study was carried out to investigate the epidermal structure, the stomatal types, the ontogeny of stomara in various parts of each organ of K. blossfeldiana, K. kewensis, and K. tometosa belonging to Kalanchoe. The epidermal cells were polygonal or isodiametric ones in the leaves, and mostly rectangular, tetragonal, and elongated ones in the leaves, and mostly rectangular, tetragonal, and elongated ones in the other organs. The candelabrum-like, triradiate stellete trichomes in the aerial parts of all organs of K. tomentosa were found. The cuticular striations and square crystals of calcium oxalate in the epidermal cells of petals of K. blossfeldiana were observed. The great majority of the mature stomata in various parts of all the organs were commonly helicocytic types. This type was subdivided into three subtypes such as parahelicocytic, anomohelicocytic, and dianisocytic stomata on the basis of the division angle of the guard mother cells. Somethies, the anisocytic type was found in most organs. This type was subdivided into three subtyes such as paranisocytic, nomoanisocytic, and dianisocytic stomata in the same way as the helicocytic type. A new stomataltype with anisocytic stoma within a girdle of four subsidiary cells of tetracytic type in the leaf of K. kewensis was firstly observed in the vascular plants. This type was termed the coaniso-tetracytic type. The anomomeristic pattern in the mesogenous category of stomatal types was found in various organs of all the material plants. Developmental mode of stomata was constant in all the parts of each organ within the same plant. The stomata was observed to be a few similar stomatal types in various parts of each organ within the same plant. The ontogeny of all the types is eumesogenous or mesogenous type. The ontogenetic type of stomata was mostly helico-eumesogenous type in all the organs of all the material plants. The mature stoma varied from organ to in regard of the number and arrangement of subsidiary cells.

• Korean journal of applied entomology
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• v.5_6
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• pp.9-18
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• 1968

Morphological studios on the mouth parts of some aphids belonging to 5 sub-families and on the penetration of stylets into their host plants were carried out in order to find out possible relationship between mouth parts and capability of virus transmission. 1. There were no differences between the aphid species in general morphology of mouth parts. 2. Mouth parts could be observed in detail especially in Toxoptera citricidus and Chaitophorus chinensis. 3. Accessory salivary gland was larger than principal salivary gland in Toxoptera citricidus. 4. In 4 species, e. g. Chaitophorus chinensis, Myzus persicae, Aphis craccivora, Toxoptem citricidus, the stylets were usually inserted in plant tissues intercellularly and reached phloem, however, in Lachnus tropicalis only intracellularly and in Eriosoma clemalis more frequently intracellularly. 5. The stylets tracks of Eriosoma clemalis, Lachnus tropicalis and Myzus persicae were clearly visible but not in Toxoptera citricidus, Chaitophorus chinensis and Aphis craccivora. The tracks were stained with yellowish brown or red brown. 6. Saliva was seceted between the cell walls in most species and some substances in saliva seem to cause loosend cell walls. 7. The penetration of the stylets might cause physiological disturbance to host plants and could make the host plants susceptible to the plant diseases.

• The Journal of Natural Sciences
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• v.6 no.1
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• pp.103-108
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• 1993

Zeolites were discovered as a natural mineral more than two hundred ago. In the beginning, the mineral was used as ion-exchange material and adsorbent. After the end of World War II , however, a variety of zeolites have become available in large amounts because of the establishment of low temperature synthesis and the discobery of natural zeolite deposits of sedimentary origin. Various uses of xeolite were developed utilizing the unique crystal strucrure and function of these minerals. In connection with this development remakable progress has also been made in basic stuides on the related geology and mineralogy, crystallization from sols and gels, structure, ion exchange, adsorption and cataiysis. As a result, zeolites, which had been known only as mineral specimens displayed in museums. established a firm position among the high-technology masterials with excellent functional capabilities.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.140-146
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• 2010

This paper addresses recent status and trends of carbon dioxide capture technologies using dry sorbents in the flue gas. The advantages of dry sorbent $CO_2$ capture technology are broader operating temperature range, less energy loss, less waste water, less corrosion problem, and natural properties of solid wastes. Recently, U.S.A. and Korea have been developing processes capturing $CO_2$ from real coal flue gas as well as sorbents improving sorption capacity to decrease total $CO_2$ capture cost. New class of dry sorbents have been developed such as chemisorbents with alkali metals of which material cost is low, amines physically adsorbed on silica supports, amines covalently tethered to the silica support, carbon-supported amines, polymer-supported amines, amine-containing solid organic resins and metal-organic framework. The breakthrough is needed in the materials on dry sorbents to decrease capture cost.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.412-419
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• 2006

We design and fabricate an autostigmatic null lens system assembled in a fixed tube mount in order to evaluate the shape of an aluminum hyperbolic mirror with the diameter of 300 mm and the f-number of 1.98, which is fabricated by a high precision aspherical DTM (diamond turning machine). Also, we evaluate the degree of shape of the aspherical mirror by this autostigmatic null lens testing method. The autostigmatic null lens system assembling in a fixed tube mount has several advantages of light weight, good mechanical stability, etc. The permissible fabricating limits of null lenses and a mount are determined by considering various tolerances to assure the measurement reliability.