• Journal of Pharmaceutical Investigation
• /
• v.37 no.6
• /
• pp.349-354
• /
• 2007

For decades, the various virtues of ${\alpha}-lipoic$ acid (ALA), a natural material synthesized in most cells, have been intensively studied and proved. Recently it was reported that ALA caused significant bodyweight reduction via appetite suppression. Unfortunately, the efficacy requires an administration over 50 mg/kg. The low bioavailability and the short plasma half life of ALA lead us to explore novel pharmaceutical dosage forms using nanoparticles. In this study, the effect of polymeric stabilizers on the bioavailability improvement of ALA nanoparticles was investigated. The reduction of particle size via nano-comminution technology was successful resulting in volume average particle sizes of 320 - 340 nm. The in vitro release rate of ALA did not reflect the decrease of particle size, possibly because of the self polymerization of ALA during nano-comminution. The type of polymeric stabilizers could not affect the release rate either. However, the in vivo food intake results of ALA showed that nano-suspensions were more effective than microparticles or a salt form. The nano-suspension containing polyvinyl pyrrolidone as the primary stabilizer and polyacrylic acid as the secondary stabilizer showed more improved efficacy for 2 hours.

• Resources Recycling
• /
• v.7 no.4
• /
• pp.64-75
• /
• 1998

The purpose of this study is to produce high putity composite powder composed of Fe-oxide, Mn-oxide and Mn-ferrite having superior homogencity in composition and particle size distribution by co-roasting process. Binary component metal (Fe, Mn) chloride solutions were produced by dissolving mill scale and ferro-mangancse alloy in hydrochloric acid. These chloride solutions contained the impurities such as SiO$_{2}$, P, Al, Ca and Na, which were originated from the Fe/Mn source materials. The neutralization and polymeric coagulant method were adoped to refine the hydrochloric liquor. When pH is far below the isoelectric point (pH 2-3), the SiO$_{2}$ was the most effectively reduced element, while other impurities remained unchanged. By increasing pH above 3, most of the impurities could be reduced effectively due to the coprecipitation reaction. The polymeric coagulants such as poly vinyl alcohol, resin amine and ammonium molybdate were found to have no effect on the spray roaster designed by the authors. The produced oxide powders were confirmed to be mixtures of Fe-oxide, Mn-oxide and mn-ferrite. the powders were homogeneously mixed and the particle size increased sleeply with increasing co-roasting temperature.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.309-314
• /
• 2004

This study focused on the introduction of damage repair for polymeric composite carbody. called selfing tech-healinique. using microcapsules loaded with the healing agent The manufacturing process for microcapsules with the healing agent was introduced and tile characteristics of microcapsules manufactured by varying with various manufacturing process variables were evaluated. The DCPD was used for the healing agent and microcapsules were made of urea-formaldehyde resin. The magnitude and the size distribution of microcapsules were measured by a particle size analyzer using laser diffraction technique. Thermal stability was investigated by using a TGA under continuous and isothermal heating conditions for the healing agent. microcapsules without the healing agent. microcapsules with the healing agent.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2002.05a
• /
• pp.224-233
• /
• 2002

A common YBCO powder has been made from a mixture of Y123 and Y211 that heated at different temperatures, respectively. The synthesis temperature of Y211 is lower than Y123. If Y211 has been heated as a synthesis temperature of Y123, a particle size of it may be very coarse. It exist as one of main defects for superconductor. But We simultaneously synthesize a YBCO(its composition is (Y123+0.4Y211)+$lwt%CeO_2$) using polymeric complex method. In the YBCO, the Y123 is synthesized lower temperature than other methodes, and its crystal structure is orthorombic. For measurement of these superconducting properties, we fabricated a YBCO single crystal. The manufactured YBCO single crystal is measured a magnetic distribution device using 0.5Tesla magnet and trapped magnet fields in it are 0.2Tesla.

• Journal of Industrial Technology
• /
• v.43 no.1
• /
• pp.43-48
• /
• 2023

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) has been considered as one of most promising cathode material, because of its low-cost and competitive energy density. However, 4.7V vs. Li/Li⁺ of high operating potential facilitates electrolyte degradation on cathode-electrolyte interface during charge-discharge process. In particular, commercial polyvinylidene fluoride (PVDF) is not sutaible for LNMO cathode binder because its weak van der waals force induces thick and non-uniform coverage on the cathode surface. In this review, we study high performance binders for LNMO cathode, which forms uniform coating layer to prevent direct contact between electrolyte and LNMO particle as well as modifying high quality cathode electrolyte interphase, improved cell performace.

• International Journal of Advanced Culture Technology
• /
• v.3 no.1
• /
• pp.21-30
• /
• 2015

Ceramic foams are prepared as positive images corresponding to a plastic foam structure which exhibits high porosities (85-90%). This structure makes the ceramic foams attractive as a catalyst in a dry reforming process, because it could reduce a high pressure drop problem. This problem causes low mass and heat transfers in the process. Furthermore, the reactants would shortly contact to catalyst surface, thus low conversion could occur. Therefore, this research addressed the preparation of dry reforming catalysts using a sol-gel catalyst preparation via a polymeric sponge method. The specific objectives of this work are to investigate the effects of polymer foam structure (such as porosity, pore sizes, and cell characteristics) on a catalyst performance and to observe the influences of catalyst preparation parameters to yield a replica of the original structure of polymeric foam. To accomplish these objectives industrial waste foams, polyurethane (PU) and polyvinyl alcohol (PVA) foams, were used as a polymeric template. Results indicated that the porosity of the polyurethane and polyvinyl alcohol foams were about 99% and 97%. Their average cell sizes were approximate 200 and 50 micrometres, respectively. The cell characteristics of polymer foams exhibited the character of a high permeability material that can be able to dip with ceramic slurry, which was synthesized with various viscosities, during a catalyst preparation step. Next, morphology of ceramic foams was explored using scanning electron microscopy (SEM), and catalyst properties, such as; temperature profile of catalyst reduction, metal dispersion, and surface area, were also characterized by $H_2-TPR$ and $H_2-TPD$ techniques, and BET, respectively. From the results, it was found that metal-particle dispersion was relatively high about 5.89%, whereas the surface area of ceramic foam catalysts was $64.52m^2/g$. Finally, the catalytic behaviour toward hydrogen production through the dry reforming of methane using a fixed-bed reactor was evaluated under certain operating conditions. The approaches from this research provide a direction for further improvement of marketable environmental friendly catalyst production.

• Polymer(Korea)
• /
• v.30 no.6
• /
• pp.512-518
• /
• 2006

A biodegradable polymer poly((R) -3-hydroxybutyric acid) (PHB) was conjugated with a hydrophilic polymer poly(ethylene glycol) (PEG) by the ttansesterification reaction to form the amphiphilic block copolymer. PHB with low molecular weight ($3000{\sim}30000$) was appropriated for the drug delivery materials. High molecular weight PHB was hydrolyzed by an acid-catalyst to produce the low molecular weight one. Amphiphilic block copolymer was formed the self-assembled polymeric micelle system in the aqueous solution that the hydrophillic PEG was wraped the hydrophobic PHB. Generally, polymeric micelle forms the small particle between $10{\sim}200nm$. These polymeric micelle systems have been widely used for the drug delivery systems because they were biodegradable, biocompatible, non-toxic and patient compliant. The hydroxyl group of PEG was substituted with carboxyl group which has the reactivity to the ester group of PHB. Amphiphilic block copolymer was conjugated between PHB, and modified PEG at $176^{\circ}C$ which was higher than the melting point of PHB. Transesterification reaction was verified with DSC, FTIR, $^1H-NMR$. In the aqueous solution, critical micelle concentration (CMC) of the mPEG-co-PHB copolymer measured by the fluororescence scanning spectrometer was $5{\times}10^{-5}g/L$. The shape and size of the nanoparticle was taken by dynamic light scattering and atomic force microscopy. The size of the nanoparticle was about 130 nm and the shape was spherical. Our polymeric micelle system can be used as the passive targeting drug delivery system.

• Journal of the Korean Ceramic Society
• /
• v.32 no.1
• /
• pp.17-24
• /
• 1995

The TEA complex polymeric sol was prepared by the alkoxide sol-gel method. The purpsoe of this experiment was to vefity the particle shape in the sol from the investigation of the rheological properties. TEA retarded hydrolysis rate by the reaction with alkoxide enough to make a stable transparent sol in the wide range of composition. From the results of the viscosity change with time, the optimum mole ratio for spinning was selected as 0.5 mole of TEA, 3 mole of H2O and the optimum viscosity was 104 cPs. The rheological behavior of the sol showed that the particle shape in the sol was linear, which was adequate for fiber drawing.

• YAKHAK HOEJI
• /
• v.27 no.3
• /
• pp.229-234
• /
• 1983

In the manufacture of precipitated sulfur calcium pentasulfide ($CaS_{5}$, train product) and calcium thiosulfate ($CaS_{2}O_{3}$, by-product) are decomposed simultaneously by hydrochloricacid into coarse (not being uniform) particle-size products. To improve this drawback, calcium thiosulfate was prepared directly without making calcium pentasulfide and obtained $S_{6}$ by the acid-decomposition. In the conversion of hexatomic sulfur to octatomic sulfur, the polymerization and the depolymerization were observed by using purification method. The conversion of $S_{6}$ to $S_{8}$ is proceeded by two steps. The first step reaction is affected by impurities (especially $SO_{2}$ and $H_{2}S$), Hexatomic sulfur is inert to triethylamine for the time being by purification, and thereafter a slow conversion to polymeric and then to octatomic sulfur occurs. Instead of calcium pentasulfide, the acid decomposition of calcium thiosulfate has several advantages; uniformity of particle-size of product, increase of yield, and simplicity of procedure.

• Membrane Journal
• /
• v.27 no.2
• /
• pp.121-128
• /
• 2017

Mesoscale simulation is a type of molecular simulation techniques where groups of atoms are defined as a single bead for calculations, and accordingly, is possible to simulate longer time ($ns{\sim}{\mu}s$) and bigger size ($nm{\sim}{\mu}m$). There are two types of mesoscale simulations : (1) particle-based mesoscale which simulates the system by calculating the movement of the particles themselves and (2) field theory which simulates the system by calculating changes in the chemical potential filed or density field. Mesoscale simulations are powerful tools to study the macroscopic properties of polymers for various applications of energy and environment. In this review, we report the trends and useful information in mesoscale simulation and provide an opportunity for membrane researchers working in the energy-environment field to understand mesoscale simulation techniques.