• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.801-805
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• 2008

A fibrous material (p-phenylene-2,5-benzobisoxazole, PBO) was used as an adsorbent for solid phase extraction in order to simplify the extraction procedure. The extraction performance for di-(2-ethylhexyl) phthalate (DEHP) was examined with two types of PBO fibers (HM (High modulus) and AS (Regular type) types) by batch type sorption/desorption experiments. When 100 mg of the HM fibers were applied to 20 mL of the aqueous DEHP solution (less than $50{\mu}g/L$), more than 95% of DEHP was adsorbed on the fibers, however, the AS type fibers adsorbed alkyl phthalate up to 80%. In the case of $50{\mu}g/L$ of the initial concentration of DEHP, the adsorbed DEHP was extracted effectively with methanol and the maximum overall recovery ratio was 92.3%. The results indicated that the PBO fibers could be used as an adsorbent for alkyl phthalate analysis, and that the extraction procedure was not affected by suspended solids in a water sample.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.585-590
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• 1998

Fibrous $Na_xTi_nO_{2n+1}$ whisker was prepared by $H^+/Na^+$ ion-exchange on layered hydrous titanium dioxide ($H_2Ti_4O_9{\cdot}nH_2O$). The ion-exchange reaction was proceeded at 0.5~2.0 M NaOH solution. In the ion-exchange at 2.0 M NaOH solution, 73% of sodium was exchanged and the prepared $Na_xTi_nO_{2n+1}$ whisker was a fibrous crystal of about $10{\sim}20{\mu}m$ of length and about $0.7{\mu}m$ of diameter. The phase transition of the ion-exchange phases identified by the thermal analysis. The result showed that the $Na_xTi_nO_{2n+1}$ whisker was decomposed into $Na_2Ti_6O_{13}$ and $TiO_2$ in the temperature of $200{\sim}600^{\circ}C$.

• Proceedings of the Korean Society of Veterinary Pathology Conference
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• 2002.11a
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• pp.9-9
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• 2002

Grossly, the liver exhibits marked cirrhotic changes characteristics of the pre-transformation phase of WHV. Microscopically, focal hepatocyte necrosis and inflammatory cells were observed in midzonal and periportal areas. Bridging portal fibrosis produced pseudolobulation due to entrapment of hyperplastic hepatocytes. Biliary hyperplasia, ductal cell proliferation, and increased amounts of fibrous connective tissue expanded portal areas and extended into periportal areas. Myofibroblasts stained positive for -SMA were detected in proliferating fibrotic tissue and sinusoids.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.343-349
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• 2000

Fabrication of various carbide fibers from carbon fibers and elementary powders of Ti, Zr, Nb, Zi, W, B, and Mo by self-propagating high temperature synthesis was attempted. It was found the almost pure phase of TiC, ZrC, NbC, SiC, $B_4$C, and $Mo_2$C carbides were successfully produced. The three types of morphologies were ob-served, TiC, ZrC, NbC, and $B_4$C had a hollow-type fibrous shape. SiC had fiber shape consisting of smaller particles and fine whiskers. WC and $Mo_2$C had non-fibrous shapes. The reason for the different morphologies was explained. The formation mechanism of hollow fibers was suggested.

• Journal of Powder Materials
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• v.26 no.5
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• pp.395-404
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• 2019

Aluminum nitride (AlN) has excellent electrical insulation property, high thermal conductivity, and a low thermal expansion coefficient; therefore, it is widely used as a heat sink, heat-conductive filler, and heat dissipation substrate. However, it is well known that the AlN-based materials have disadvantages such as low sinterability and poor mechanical properties. In this study, the effects of addition of various amounts (1-6 wt.%) of sintering additives $Y_2O_3$ and $Sm_2O_3$ on the thermal and mechanical properties of AlN samples pressureless sintered at $1850^{\circ}C$ in an $N_2$ atmosphere for a holding time of 2 h are examined. All AlN samples exhibit relative densities of more than 97%. It showed that the higher thermal conductivity as the $Y_2O_3$ content increased than the $Sm_2O_3$ additive, whereas all AlN samples exhibited higher mechanical properties as $Sm_2O_3$ content increased. The formation of secondary phases by reaction of $Y_2O_3$, $Sm_2O_3$ with oxygen from AlN lattice influenced the thermal and mechanical properties of AlN samples due to the reaction of the oxygen contents in AlN lattice.

• Archives of Craniofacial Surgery
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• v.24 no.2
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• pp.59-65
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• 2023

Background: Fibrous dysplasia (FD) is a localized bone disorder in which fibro-osseous tissue replaces the normal bone structure. Patients with craniofacial FD often present with gradual swelling, deformity, and compromised vision or hearing. We previously introduced "the core extirpation method," a novel surgical technique that is minimally invasive like traditional bone shaving but has longer-lasting effects. This study presents the long-term outcomes of our core extirpation method. Methods: We conducted a retrospective analysis of patients who underwent core extirpation for FD of the zygomaticomaxillary region from 2012 through 2021. Computed tomography (CT) scans were performed 6 to 12 months before the operation, immediately before and after the operation, and during follow-up visits. We performed all operations using the upper gingivobuccal approach, and we extirpated the core of the lesion while preserving the cortical structures of the zygoma and the maxilla to maintain symmetrical facial contour. Results: In 12 patients with lesions in the growth phase, anteroposterior/mediolateral (AP/ML) length discrepancies and the volume increased between preoperative and immediate postoperative CT scans. All patients' immediate postoperative AP/ML discrepancies were stable up to 12-17 months postoperatively. Postoperative volume showed continuous lesion growth; the median volume growth rate was 0.61 cc per month. Conclusion: In this article, we present our experiences managing FD using the minimally invasive core extirpation technique, which entails small expected blood loss and can be performed as day surgery. It provides similar cosmetic outcomes as traditional bone shaving but with longer-lasting results. Although there are some limitations with the study's retrospective nature and small sample size, our 4-year follow-up results show promising results of the core extirpation method in well-indicated patients.

• Journal of Korea Foundry Society
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• v.38 no.1
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• pp.1-8
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• 2018

In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and ${\alpha}-Al$ phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1819-1824
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• 2006

The general objective of the present study was to investigate the potential application of the UV spectroscopic method for determination of the polymeric additives present in papermaking fibrous stock solutions. The study also intended to establish the surface-chemical retention model associated with the adsorption kinetics of additives on fiber surfaces. Polyamide epichlorohydrin (PAE) wet strength resin and imidazolinium quaternary (IZQ) softening agents were selected to evaluate the analytical method. Concentrations of PAE and IZQ in solution were proportional to the UV absorption at 314 and 400 nm, respectively. The time-dependent behavior of polymeric additives obeyed a mono-molecular layer adsorption as characterized in Langmuir-type expression. The kinetic modeling for polymeric adsorption on fiber surfaces was based on a concept that polymeric adsorption on fiber surfaces has two distinguishable stages including initial dynamic adsorption phase and the final near-equilibrium state. The simulation model predicted not only the real-time additive adsorption behavior for polymeric additives at high accuracy once the kinetic parameters were determined, but showed a good agreement with the experimental data. The spectroscopic method examined on the PAE and IZQ adsorption study could potentially be considered as an effective tool for the wet-end retention control as applied to the paper industry.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.160-175
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• 1994

Fibrous potassium hexatitanate whisker with the size of $ID=0.5{\sim}1{\mu}m$ and length=$100{\sim}1000{\mu}m$ (aspect ratio=100~1000) was produced through the reaction between titanium dioxide and potassium carbonate using the slow-cooling calcination followed by water leaching treatment. The optimum condition for the production of fibrous potassium titanate was calcination temperature of $1100^{\circ}C$ for 5hrs, $TiO_2$ mole ratlo to $K_2CO_3$ of 4.5 and slow-cooling rate of $0.5^{\circ}C/min$ to $860^{\circ}C$. Fibrous crystal are grown by the association between the solid potassium titanate and liquid phase during the slow-cooling process. The Proper water leaching condition for removing of K component was leaching time of 10hrs in boiling water. Pressurizing of the mixture of $K_2CO_3$ and $TiO_2$ to be calcinated became effective on the growth of fibrous crystal.