• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.309-309
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• 2000

The main objective of this study is to understand the regeneration step of the PTSA(Pressure and thermal swing adsorption) process below the atmospheric pressure by rigorous dynamic simulation. This target process is to recover toluene using activated carbon as an adsorbent. To do this, the dynamic simulations for the regeneration step are performed at 360, 490, 590mmHg and at high temperature after the simulation of the adsorption step at latm and 298K. A mathematical model was developed to simulate the column dynamics of the adsorption systems. This model is based on non-equilibrium, non-isothermal and non-adiabatic conditions, and axial dispersion and heat conduction are also considered. Heat transfer resistances are considered in gas-solid, gas-column wall and column wall-outside air. The LDF(Linear Driving Force) approximation model describes the mass transfer rate between the gas and solid phase. This study shows that the recovery of toluene by PTSA is more preferable than that by general TSA.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.53-59
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• 2011

We have developed a compact and high-power mode-locked fiber laser for multilayered optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The fiber laser we have developed is possible to use as a light source of multilayered optical memory. We also present a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. With these techniques we can present an all-fiber recording and readout system for multilayered memories.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.604-611
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• 2005

Polyethylene glycol (PEG) 6000-based solid dispersions (SDs), by incorporating various pharmaceutical excipients or microemulsion systems, were prepared using a fusion method, t o compare the dissolution rates and bioavailabilities in rats. The amorphous structure of the drug in SDs was also characterized by powder X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The ketoconazole (KT), as an antifungal agent, was selected as a model drug. The dissolution rate of KT increased when solubilizing excipients were incorporated into the PEG-based SDs. When hydrophilic and lipophilic excipients were combined and incorporated into PEG-based SDs, a remarkable enhancement of the dissolution rate was observed. The PEG-based SDs, incorporating a self microemulsifying drug delivery system (SMEDDS) or microemulsion (ME), were also useful at improving the dissolution rate by forming a microemulsion or dispersible particles within the aqueous medium. However, due to the limited solubilization capacity, these PEG-based SDs showed dissolution rates, below 50% in this study, under sink conditions. The PEG-based SD, with no pharmaceutical excipients incorporated, increased the maximum plasma concentration (C$_{max}$) and area under the plasma concentration curve (AUC$_{0-6h}$) two-fold compared to the drug only. The bioavailability was more pronounced in the cases of solubilizing and microemulsifying PEG-based SDs. The thermograms of the PEG-based SDs showed the characteristic peak of the carrier matrix around 60$^{\circ}C$, without a drug peak, indicating that the drug had changed into an amorphous structure. The diffraction pattern of the pure drug showed the drug to be highly crystalline in nature, as indicated by numerous distinctive peaks. The lack of the numerous distinctive peaks of the drug in the PEG-based SDs demonstrated that a high concentration of the drug molecules was dissolved in the solid-state carrier matrix of the amorphous structure. The utilization of oils, fatty acid and surfactant, or their mixtures, in PEG-based SD could be a useful tool to enhance the dissolution and bioavailability of poorly water-soluble drugs by forming solubilizing and microemulsifying systems when exposed to gastrointestinal fluid.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.705-712
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• 2000

In this study, the dispersion stability of CeO2 based complex oxide was studied, and density, porosity, and microstructure of green body were investigated using colloid surface chemistry to manufacture the Gd2O3 doped CeO2 solid electrolyte in an aqueous system. To prepare the stable slurry for slip casting, the dispersion stability was examined as a function of pH using ESA(electrokinetic sonic anplitude) analysis. The dynamic mobility of particles was enhanced with anionic and cationic dispersant were added the amount of 0.5wt% respectively, but pH value in slurries didn't move to below 6.0 because of the influence of dopants. This phenomenon also appeared in the CeO2-Y2O3 and CeO2-Sm2O3 systems, so it could be inferred that rare earth dopants such as Gd2O3, Sm2O3 and Y2O3 not only have the similar motion with changing pH in an aqueous system but also can be dissolved in the range of pH 6.0∼6.5. In CeO2-Gd2O3 system, when the anionic dispersant was added the amount of 0.5wt% and pH value in slurries was fixed at 9.5, the green body density was 4.07g/㎤, and the relative density of sintered body was 95.2%. It could be inferred from XRD analysis that Gd3+ substituted into Ce4+ site because there was no free Gd2O3 peak.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04a
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• pp.1-6
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• 1999

A study was made to determine the effect of plastic pigment on the coating structure and printability of coated paper. Three basic plastic pigments were investigated such as solid-bead type of plastic pigment, binder type of plastic pigment and hollow type of plastic pigment. In the systems investigated, it was observed that particle shape and structure of plastic pigment had influenced on the rheology of coating color, the state of packing, and the properties of coated paper. The materials investigated were restricted to plastic pigments commonly uesd in paper coating formualtion. Inorganic pigments used in this research were kaolin clay which is platelets and calcium carbonate which is rhombic. Three kinds of plastic pigments were blended in the color made up with two inorganic pigments, respectively. The combination of pigments were carried out (1) to determined the effect of paticle structure of plastic pigment on the state of dispersion of coating color, (2) to observe the effect of temperature of calender on the property of coated paper prepared with plastic pigment. The data indicated that binder and hollow type of plastic pigment had the best results on improving the properties of coated paper such as paper gloss, opacity and air permeability ect. and solid-bead type of plastic pigment in the next place.

• Smart Structures and Systems
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• v.20 no.3
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• pp.329-342
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• 2017

In this paper, the dispersion characteristics of elastic waves propagation in sandwich nano-beams with functionally graded (FG) face-sheets reinforced with carbon nanotubes (CNTs) is investigated based on various high order shear deformation beam theories (HOSDBTs) as well as nonlocal strain gradient theory (NSGT). In order to align CNTs as symmetric and asymmetric in top and bottom face-sheets with respect to neutral geometric axis of the sandwich nano-beam, various patterns are employed in this analysis. The sandwich nano-beam resting on Pasternak foundation is subjected to thermal, magnetic and electrical fields. In order to involve small scale parameter in governing equations, the NSGT is employed for this analysis. The governing equations of motion are derived using Hamilton's principle based on various HSDBTs. Then the governing equations are solved using analytical method. A detailed parametric study is conducted to study the effects of length scale parameter, different HSDBTs, the nonlocal parameter, various aligning of CNTs in thickness direction of face-sheets, different volume fraction of CNTs, foundation stiffness, applied voltage, magnetic intensity field and temperature change on the wave propagation characteristics of sandwich nano-beam. Also cut-off frequency and phase velocity are investigated in detail. According to results obtained, UU and VA patterns have the same cut-off frequency value but AV pattern has the lower value with respect to them.

• Journal of Pharmaceutical Investigation
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• v.36 no.4
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• pp.271-276
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• 2006

Felodipine, a calcium-antagonist of dihydropyridine type, is a poorly water soluble drug and has very low bioavailability. As preceding studies, use of solid dispersion systems and surfactants(solubilizers) has been suggested to increase dissolution and to improve bioavailability of felodipine. But in case of solid dispersion systems, large amount of toxic organic solvents should be used and manufacturing process time become longer than conventional process. In case of using surfactants, as time elapsed, decreasing of dissolution rate of felodipine due to crystallization has been reported. In this study, Copovidon as a hydrophilic polymer and $Transcutol^{\circledR}$ as a surfactant were combined to formulations if order to increase dissolution of felodipine and conventional wet granulation process were applied to manufacturing of formulations. The effect of Copovidon and $Transcutol^{\circledR}$ on the dissolution oi felodipine was investigated in-vitro. When Copovidon and $Transcutol^{\circledR}$ used simultaneously, the dissolution rate of felodipine was prominently increased compared with when used separately and the maximum increase in the dissolution of felodipine was 5.8 fold compared to control. This is most probably due to synergy effect by combination of Copovidon and $Transcutol^{\circledR}$. Felodipine sustained release tablets were successfully formulated using several grades of HPMC as a release retarding agent. The stability of felodipine sustained release tablet was evaluated after storage at accelerated condition($40^{\circ}C/75%\;RH$) for 6months in HDPE(High density polyethylene) bottle. Neither significant degradation nor change of dissolution rate for felodipine was observed after 6months. In conclusion, felodipine sustained release tablet was successfully formulated and dissolution of felodipine, poorly water soluble drug, was prominently increased and also stability was guaranteed by using combination system of hydrophilic polymer and surfactant.

• Journal of Pharmaceutical Investigation
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• v.39 no.2
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• pp.97-106
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• 2009

Although lovastatin (LS) is widely used in the treatment of hypercholesterolemia, its bioavailability is known to be around 5%. This study was aimed to increase the solubility and dissolution-permeation rates of LS using solid dispersions (SDs) with bile salts. The solubilities of LS in water, aqueous bile salt solutions and non-aqueous vehicles were determined, and effects of bile salts on the cellulose or duodenal permeation of LS from SDs were evaluated using a horizontal permeation system. SDs were prepared at various ratios of LS to carriers, such as sodium deoxycholate (SDC), sodium glycocholate (SGC) and/or 2-hydroxypropyl-$\beta$-cyclodextrin (HPCD). The addition of bile salts (25 mM) in water increased markedly the solubility of LS by the micellar solubilization. Some non-aqueous vehicles were effective in solubilizing LS. From differential scanning calorimetric studies, it was found that the crystallinity of LS in SDs disappeared, indicating a formation of amorphous state. The SDs showed markedly enhanced dissolution compared with those of their physical mixtures (PMs) and drug alone. In the dissolution-permeation studies using a cellulose membrane, the donor and receptor solutions were maintained as a sink condition using pH 7.0 phosphate buffer containing 0.05% sodium lauryl sulfate (SLS). The flux of LS alone was nearly same as that of LS-SDC-HPCD (1:3:6) PM. However, the flux of LS-SDC-HPCD (1:3:6) SD slightly increased compared with drug alone and PM, suggesting that entrapment of LS in micelles does not significantly hinder the permeation across cellulose membrane. In the dissolution-duodenal permeation studies using a LS-HPCD-SDC (1:3:6) SD, the addition of various bile salts in donor solutions (25 mM) enhanced the permeation of LS markedly, and the fluxes were found to be $0.69{\pm}0.41$, $0.87{\pm}0.51$, $0.84{\pm}0.46$, $0.47{\pm}0.17$ and $0.68{\pm}0.32{\mu}g/cm^2/hr$ for sodium cholate (SC), SDC, SGC, sodium taurodeoxycholate (STDC) and sodium taurocholate (STC), respectively. The stepwise increase of donor SGC concentration increased the flux dose-dependently. From the relationship of donor SGC concentration and flux, the concentration of SGC initiating the permeation across the duodenal mucosa was calculated to be 11.1 mM, which is nearly same as the critical micelle concentration (CMC, 11.6 mM) of SGC. However, with no addition of bile salts and below CMC, the permeation was very limited and irratic, indicating that LS itself is very poor permeable. Higher protions of bile salt in SD such as LS-SDC or LS-SGC (1 : 49 and 1 : 69) showed highly promoted fluxes. In conclusion, SD systems with bile salts, which may form their micelles in intestinal fluids, might be a promising means for providing enhanced dissolution and intestinal permeation of practically insoluble and non-absorbable LS.