• Title, Summary, Keyword: porous W

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Separation of Lithium Isotopes by Porous Sulfonated Styrene-Divinylbenzene Copolymer Ionexchanger (Porous Sulfonated Styrene-Divinylbenzene Copolymer Ionexchanger 에 의한 리튬 동위원소의 분리)

  • Dong Won Kim;Ki Suck Maeng;Hae Young Song;Hae Il Ryu
    • Journal of the Korean Chemical Society
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    • v.27 no.3
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    • pp.189-193
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    • 1983
  • The lithium isotopes separation experiments were carried out in hydrochloric acid with cation exchanger systerns. In these experiments were employed porous sulfonated styrene-divinylbenzene copolymer and Dowex 50w-x8 as cation exchanger. The contents of lithium of the fraction were determined with atomic absorption spectrophotometer. The relative mass of lithium isotopes of the fractions was analyzed on a mass spectrometer. The isotope separation factors of lithium were calculated from the isotope compositions of these eluted fractions. Separation factor for the system in hydrochloric acid and porous sulfonated styrene-divinylbenzene copolymer was found to be 1.0020, and for the case of system in hydrochloric acid and Dowex 50w-x8 was 1.0011${\om}$0.0002. From these results, we found that the separation factor for porous sulfonated styrene-divinylbenzene copolymer ionexchanger is larger than value of Dowex 50w-x8 ionexchanger.

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Sustained Release of Anthocyanin from Porous Poly(lactic-co-glycolide) Microsparticles Developed for the Treatment of Chronic Obstructive Pulmonary Disease

  • Yoo, Na-Young;Baik, Hye-Jung;Lee, Bo-Reum;Youn, Yu-Seok;Oh, Kyung-Taek;Lee, Eun-Seong
    • Journal of Pharmaceutical Investigation
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    • v.40 no.4
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    • pp.231-236
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    • 2010
  • This study was to fabricate the porous poly(lactide-co-glycolide) (PLGA) microparticles with anthocyanin (as a model antioxidant) for pulmonary drug delivery. The highly porous PLGA microparticles were prepared by the waterin-oil-in-water ($W_1/O/W_2$) multi-emulsion method, followed by the decomposition of ammonium bicarbonate (AB) in $W_1$ phase to the base of ammonia, carbon dioxide and water vapor at $50^{\circ}C$, making a porous structure in PLGA microparticles. Herein, hyaluronate (HA), a viscous polysaccharide, was incorporated in the porous microparticles for sustained anthocyanin release. In in vitro release studies, the anthocyanin release from the porous microparticles with HA continued up to 24 hours, while the porous microparticles without HA released 80 wt.% of encapsulated anthocyanin within 2 hours. In addition, these microparticle are expected to be effectively deposited at a lung epithelium due to its high porosity (low density) and avoid alveolar macrophage's uptake in the lung due to its large particle size. We believe that this system has a great pharmaceutical potential as a long acting antioxidant for relieving the oxidative stress in chronic obstructive pulmonary disease (COPD).

Theoretical Analysis of the Pressure Drop in Loop Heat Pipe by Sintered Porous Wick Structure (다공성소결윅구조에 따른 루프 히트파이프에서 압력손실의 이론적 분석)

  • Lee, K.W.;Lee, W.H.;Park, K.H.;Lee, K.J.;Chun, W.P.;Ihn, H.M.
    • Proceedings of the KSME Conference
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    • pp.1225-1230
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    • 2004
  • In this paper, the pressure drops were investigated according to the sintered porous wick structure in loop heat pipe(LHP) by theoretical analysis. LHP has the wick only in evaporator for the circulation of working fluid, so utilizes porous wick structure which pore diameter is very small for large capillary force. This paper investigates the effects of different parameters on the pressure drops of the LHP such as particle diameter of sintered porous wick, wick porosity, vapor line diameter, thickness of wick and heating capacity. Working fluid is water and the material of sintered porous wick is copper. According to the these different parameters, capillary pressure, pressure drop in wick were analized by theoretical design method of LHP.

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Simvastatin loaded porous poly(lactide-co-glycolide)(PLGA) microspheres as delivery systems strategies for injuring tissue and invitro study

  • Bao, Trinh-Quang;Kim, Yang-Hee;Lee, Byong-Taek
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.38.2-38.2
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    • 2009
  • Regeration of natural tissuesor to create biological substitutes for defective or lost tissues and organs through the use of cells. In addition to cells and their porous, drugs are required to promote tissue regeneration. Therefore, the present studies were prepared using simvastatim loaded porous poly(lactide-co-glycolide) (PLGA) by double emulsion solvent evaporation water-in-oil-in-water technique (W/O/W) as drug delivery system strategies for injuring tissue. The resulting microspheres were evaluated for morphology, particle size, encapsulation efficiency, degradation of PLGA microspheres in vitro drug release and in vitro cell viability. Scanning electronic microscopic (SEM) showed that the porosities of the particles was changed by experimental conditions and cultured cells were attached well on porous microspheres surface. The X-ray diffraction (XRD) and differential scanning calometry (DSC) analysis indicate thatsimvastatim was highly dipersed in the microsphere at amorphousstate.

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Influence of Paste Fluidity and Vibration Time for Fundamental Properties of Porous Concrete (시멘트체이스트의 유동성 및 진동다짐시간이 포러스콘크리트의 기초물성에 미치는 영향)

  • 이성일;유범재;장종호;김재환;백용관;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.311-316
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    • 2001
  • This study analyzed the influence of paste fluidity and vibration time for fundamental properties of porous concrete. Results of this study were shown as follows; 1) Even if target void ratio is same, void ratio and compressive strength of porous concrete is different according to w/c, paste flow and vibration time. So, In case of target void ratio, we must consider the influence of w/c, paste flow, and vibration time. 2) Though w/c and vibration time are same, as paste flow increase, all void ratio, continuous void ratio, and compressive strength decrease and difference between upper and lower void ratio increase. 3) Though w/c and paste flow are same, as vibration time increase, all void ratio and continuous void ratio decrease and difference between upper and lower void ratio increase. Also, compressive strength increase by 10 seconds and decease after 10 seconds. 4) As types of superplasticizer is different, all void ratio, continuous void ratio, and compressive strength are different. So, we must give consideration to paste fluidity and vibration time in order that increase of strength of porous concrete and distribution of uniform void.

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Fabrication of Porous W-Ti by Freeze-Drying and Hydrogen Reduction of WO3-TiH2 Powder Mixtures (WO3-TiH2 혼합분말의 동결건조 및 수소환원에 의한 W-Ti 다공체 제조)

  • Kang, Hyunji;Park, Sung Hyun;Oh, Sung-Tag
    • Journal of Korean Powder Metallurgy Institute
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    • v.24 no.6
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    • pp.472-476
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    • 2017
  • Porous W-10 wt% Ti alloys are prepared by freeze-drying a $WO_3-TiH_2$/camphene slurry, using a sintering process. X-ray diffraction analysis of the heat-treated powder in an argon atmosphere shows the $WO_3$ peak of the starting powder and reaction-phase peaks such as $WO_{2.9}$, $WO_2$, and $TiO_2$ peaks. In contrast, a powder mixture heated in a hydrogen atmosphere is composed of the W and TiW phases. The formation of reaction phases that are dependent on the atmosphere is explained by a thermodynamic consideration of the reduction behavior of $WO_3$ and the dehydrogenation reaction of $TiH_2$. To fabricate a porous W-Ti alloy, the camphene slurry is frozen at $-30^{\circ}C$, and pores are generated in the frozen specimens by the sublimation of camphene while drying in air. The green body is hydrogen-reduced and sintered at $1000^{\circ}C$ for 1 h. The sintered sample prepared by freeze-drying the camphene slurry shows large and aligned parallel pores in the camphene growth direction, and small pores in the internal walls of the large pores. The strut between large pores consists of very fine particles with partial necking between them.

STUDY ON BEHAVIOR OF LIQUID NITROGEN IN POROUS MEDIA (다공성 매질에서 액화질소의 거동에 대한 연구)

  • Choi, S.W.;Lee, W.I.
    • Journal of computational fluids engineering
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    • v.18 no.2
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    • pp.17-25
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    • 2013
  • The process of flow through porous media is of interest a wide range of engineering fields and areas, and the importance of fluid flow with a change in phase arises from the fact that many industrial processes rely on these phenomena for materials process, energy transfer. Especially, the flow phenomena of cryogenic liquid subjected to evaporation is of interest to investigate how the cryogenic liquid behaves in the porous structure. In this study, thermo physical properties, morphological properties of the glass wool with different bulk densities in terms of its temperature-dependence and permeability behaviors under different applying pressure are discussed. Using the experimentally determined properties, characteristics of two main experimental results are investigated. In addition, simulation results are used to realize the cryogenic liquid's flow in porous media, and are compared with experimental results. By using the experimentally determined properties, more reasonable results can be suggested in dealing with porous media flow.

Fabrication of Porous W by Heat Treatment of Pore Forming Agent of PMMA and WO3 Powder Compacts (기공형성제 PMMA와 WO3 분말 성형체의 열처리를 이용한 W 다공체 제조)

  • Jeon, Ki Cheol;Kim, Young Do;Suk, Myung-Jin;Oh, Sung-Tag
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.2
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    • pp.129-133
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    • 2015
  • Porous W with controlled pore structure was fabricated by thermal decomposition and hydrogen reduction process of PMMA beads and $WO_3$ powder compacts. The PMMA sizes of 8 and $50{\mu}m$ were used as pore forming agent for fabricating the porous W. The $WO_3$ powder compacts with 20 and 70 vol% PMMA were prepared by uniaxial pressing and sintered for 2 h at $1200^{\circ}C$ in hydrogen atmosphere. TGA analysis revealed that the PMMA was decomposed at about $400^{\circ}C$ and $WO_3$ was reduced to metallic W at $800^{\circ}C$. Large pores in the sintered specimens were formed by thermal decomposition of spherical PMMA, and their size was increased with increase in PMMA size and the amount of PMMA addition. Also the pore shape was changed from spherical to irregular form with increasing PMMA contents due to the agglomeration of PMMA in the powder mixing process.

Characteristics of Porous YAG Powders Fabricated by PVA Polymer Solution Technique

  • Lee, S.J.;Shin, P.W.;Kim, J.W.;Chun, S.Y.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.438-439
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    • 2006
  • Pure and stable YAG $(Y_3Al_5O_{12})$ powders were synthesized by a PVA (polyvinyl alcohol) polymer solution technique. PVA was used as an organic carrier for the precursor ceramic gel. The precursor gels were crystallized to YAG at relatively a low temperature of $900\;^{\circ}C$. The synthesized powders, which have nano-sized primary particles, were soft and porous, and the porous powders were ground to sub-micron size by a simple ball milling process. The ball-milled powders were densified to 94% relative density at $1500\;^{\circ}C$ for 1h. In this study, the characteristics of the synthesized YAG powders were examined.

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Preparation of Porous SiC by Freeze Drying of Polycarbosilane Emulsion (폴리카보실란 에멀젼의 동결건조를 이용한 다공체 SiC 제조)

  • Hwang, Yeon
    • Korean Journal of Materials Research
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    • v.26 no.6
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    • pp.320-324
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    • 2016
  • Porous SiC beads were prepared by freeze-drying a polycarbosilane (PCS) emulsion. The water-in-oil (w/o) emulsion, which was composed of water, PCS dissolved p-xylene, and sodium xylenesulfonate (SXS) as an emulsifier, was frozen by dropping it onto a liquid $N_2$ bath; this process resulted in 1~2 mm sized beads. Beads were cured at $200^{\circ}C$ for 1 h in air and heat-treated at $800^{\circ}C$ and $1400^{\circ}C$ for 1 h in an Ar gas flow. Two types of pores, lamella-shaped and spherical pores, were observed. Lamellar-shaped pores were found to develop during the freezing of the xylene solvent. Water droplets in the w/o emulsion were changed into spherical pores under freeze-drying. At $1400^{\circ}C$ of heat-treatment, porous SiC was synthesized with a low level of impurities.