• Applied Chemistry for Engineering
• /
• v.9 no.6
• /
• pp.829-834
• /
• 1998

Concerned with environmental issue, a new decomposition method for CFCs that caused the destruction of ozone layer was proposed. Using thermal plasma process, CFC113 decomposed completely. In order to quantify the tendency in decomposition and recombination of CFC113, thermodynamic equilibrium calculations were performed. The calculation was conducted with CFC113, $H_2$, $O_2$ at 1 atm and 300 K~5000 K. In the experiment, products which are generated after decomposition in the plasma were examined by varying reacting gases($H_2$, $O_2$) flow rates and the changes of inside diameters of quenching tubes. Decomposition products were analyzed using Gas Chromatograph. The results are very promising with a decomposition efficiency greater than 99.99%. As to CFC113/$H_2$=1/3, conversion to CO decreased with increasing $O_2$ ratio. When CFC113/$O_2$=1/1, 1/1.5 and 1/2, conversion to CO increases above $H_2$ ratio of 3. The change of CO conversion is not sensitive to power changes. As total flow rate increased, CO conversion was slightly decreased. When the inside diameter of the quenching tube was changed from 8mm into 4mm, CO conversion was increased due to enhanced quenching rate.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.37 no.4
• /
• pp.429-437
• /
• 2010

The aim of this study was to evaluate the fluoride release and microhardness of Beautifil II as giomer(Group I), F2000 Compomer as compomer(Group II), GC Fuji II LC Capsule as resin-modified glass ionomer(Group III) and $Filtek^{TM}$ Z350 as composite resin(Group IV) according to time. Forty discs(5 mm diameter and 2 mm height) were prepared for each material. Each disc was immersed in 3 ml of de-ionized water within polyethylene tube and stored at $37^{\circ}C$. Evaluations were performed by pH/ISE meter for analysis of fluoride release and hardness testing machine for analysis of microhardness over 31 days. The results can be summarized as follows : 1. For all groups except group IV, the greatest fluoride release was observed after the first day of the study period and then dramatically diminished over time. On the 7th day of the study period, fluoride release level was stabilized. 2. Group III showed the highest fluoride release among test groups and then group II, group I were followed. Significant difference in cumulative fluoride release over 31 days was found between each groups. Group IV showed no fluoride release during study period. 3. Group IV showed the highest microhardness among test groups and then group I, group II, group III were followed. Significant difference in microhardness was found between each group, except between group I and group II. 4. After 31 days, microhardness was slightly diminished in every group. However, no significant difference was found.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.1
• /
• pp.73-85
• /
• 2014

The CFT (Concrete Filled steel Tubes) column-footing connection is cast-in-place embedded type which provides simple construction procedure, low cost, and superior structural performance. In this study, CFT column-footing connection of modular pier is proposed and structural performance is evaluated by experimental tests. To evaluate structural performance of the CFT column-footing connection, a series of experimental tests were performed for the 4 specimens with different embedded depth. As a result of the quasi-static test, the specimen with 0.6D (0.6 times the outside diameter of steel tube) embedded depth showed relatively low ductility than other specimens with larger embedded depth due to cone failure of base concrete occurred during the lower loading step. On the contrary, cone failure of the base concrete was not observed in the specimens with larger embedded depth than 0.9D, but typical flexural failure in lower part of CFT column was observed. With the analyses of force-displacement curve, displacement ductility, and energy dissipation capacity, it is concluded that the rational range of embedded depth of the CFT column-footing connection is from 0.9D to 1.2D in view of good seismic performance.

• Journal of the Korean Vacuum Society
• /
• v.16 no.3
• /
• pp.172-180
• /
• 2007

A new diagnostics of plasma electron temperature and plasma density is introduced with the observation of the light emission along the tube of external electrode fluorescent lamps. With two different methods operating an external electrode fluorescent lamp of outer diameter 4.0 mm and length 860 mm for the back-light source of 37-inch LCD-TVs, the lighting modes and the plasma properties are investigated. In the center balance operation, the light-emission propagates simultaneously from both sides of the high voltage electrodes to the center of the lamp, while in conventional operation the light-emission propagates from the one end of a high voltage to the other ground electrode. In the operation value of luminance $10,000{\sim}15,000cd/m^2$, the electron plasma thermal energy $(kT_e)$ is about $1.3{\sim}2.7eV$ with the electron density $(n_e)$ is about $(1.6{\sim}3.6){\times}10^{16}m^{-3}$.

• Progress in Medical Physics
• /
• v.23 no.3
• /
• pp.127-137
• /
• 2012

A conversing beam is firstly designed for radiosurgery by a neurosugern Lars Leksell in 1949 with orthogonal x-rays tube moving through horizontal moving arc to focusing the beam at target center. After 2 decades he composits 201 source of the Co-60 for gamma knife which beams focused at locus. Sveral linac-based stereotactic radiosurgery using the circular collimated beam which size range for 0.4~4.0 cm in a diameter by non-coplanar multiarc have been developed over the decades. The irregular lesions can be treated by superimposing with several spherical shots of radiation over the tumour volume. Linac based techniques include the use of between 4 and 11 non-co-planar arcs and a dynamic rotation technique and use photon beam energies in the range of 6~10 MV. Reviews of the characteristics of several treatment techniques can be found in the literature (Podgorsak 1989, Schell 1991). More in recent, static conformal beams defined by custom shaped collimators or a mini- or micro-multileaf collimator (mMLC) have been used in SRS. Finally, in the last few years, intensity-modulated mMLC SRS has also been introduced. Today, many commercial and in-house SRS programs have also introduced non-invasive immobilization systems include the cyberknife and tomotherapy and proton beam. This document will be compared the characteristics of dose distribution of radiosurgery as introduced gamma knife, BrainLab include photon knife in-house SRS program and cyberknife in currently wide used for a cranial SRS.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.4
• /
• pp.878-885
• /
• 2008

The FPDs(Flat Panel Displays) such as LCD(Liquid Crystal Display) and PDP(Plasma Display Panel) and OLED(Organic Light Emitting Diode), recently, have been substituted for CRT(Cathode Ray Tube) displays because they have a convex surface, small volume, light weight and lower electric power consumption. The productivity of FPDs is greatly dependent on the area of thin glass panel with 0.6 - 0.8mm thickness because FPDs are manufactured by cutting a large-scaled thin glass panel with patterns to the required product dimensions. So FPD's industries are trying to increase the area of thin glass panel. For example, the thin glass panel size of the 8th generation is 2,200mm in width, 2,600mm in length and 0.7mm in thickness. The air flows both in the thin glass panel and in the porous PE-plate surface were modeled and analyzed, from which a working condition was estimated. The thin glass panel on the porous PE-plate surface with self-lubricating characteristics was investigated and compared with that on the square duct floating bar surface with many holes of 1mm diameter when the thin glass panel contacts the floating bar surface due to malfunction of electric power supply.

• Resources Recycling
• /
• v.22 no.2
• /
• pp.22-28
• /
• 2013

In the present study, the possibility of recovering and recycling the silicon carbide(SiC) from a silicon sludge by removing Fe and Si impurities was investigated. Si and SiC were separated from the silicon sludge using centrifugation. The separated SiC concentrate consisted of Fe, Si and SiC, in which Fe and Si were removed to recover the pure SiC. Leaching with acid/alkali solution was compared with the vapor-phase chlorination. The Fe concentration removed in the SiC was 49 ppm, and it was separated by leaching with 1 M HCl solution at $80^{\circ}C$ for 1 h. The Si concentration removed in the SiC was 860 ppm, and it was separated by leaching with 1M NaOH solution at $50^{\circ}C$ for 1 h. The SiC concentrate was chlorinated in a tubular reactor, 2.4 cm in diameter and 32 cm in length. The boat filled with SiC concentrate was located at the midpoint of the alumina tube, then, the chlorine and nitrogen gas mixture was introduced. The Fe and Si concentration removed in the SiC were 48 ppm and 405 ppm, respectively, at $500^{\circ}C$ reactor temperature, 4 h reaction time, 300 cc/min gas flow rate, and 10% $Cl_2$ gas mole fraction.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.5
• /
• pp.698-713
• /
• 1999

Adherence of Candida albicans(C. albicans) to the surface of a denture is believed to be an initial and essential step in the formation of denture-induced stematitis. Previous studies have provided enormous infomation on the relationship between composition of palatine gland/parotid saliva and upper denture stomatitis. Relatively little information is available on the correlation between lower denture stomatitis and sublingual-submandibular ( SLSM ) saliva. The plaque samples were collected from the two sites($100mm^2$) on the inner surface of lower partial denture corresponding to the stematitis and healthy region of the lower partial dentures of 12 denture stomatitis patients and 6 nor-mal persons who wore lower partial dentures. The samples were plated to isolate C. albicans on a selective Saboraud's dextrose agar plate and the isolates were identified by germ tube test and gram staining. The subjects were divided into group I (stomatitis with C. albican), group II (lesion without C. albicans), group III (no lesion but C. albicans), and group IV (normal and healthy denture wearer). Individual SLSM saliva($20{\mu}g$ of protein) was analyzed by SDS-PAGE (SDS -poly-acrylamide gel electrophoresis) with Coomassie brilliant blue and PAS(Periodic Acid Schinff) stain-ing. The salivary proteins separated in the polyacryamide gels were subjected to immunoblot anaysis using anti-lactoferrin, anti-sIgA, and anti-secretory component of sIgA. In this study using custom made acrylic denture resin beads(5mm in diameter) coated with stimulated individual SLSM saliva, the binding ability of individual C. albicans strains to the beads was observed. Levels of C, albicans adhered to the acrylic resin beads were determined by measuring the optical density of the bound C. albicans to the beads at 580nm. The results showed that a higher number of C. albicans was observed in the lesion site than healthy site. The saliva of group I contained more high molecular weight glycoprotein(mucin, MGI) as compared to group II, III and IV. And lactoferrin and sIgA affected to the binding ability of C. albicans to acylic resin beads. Binding ability of individual C. albicans to the acrylic resin coated with respective individual saliva was found to be greater in group I than the other 3 groups. And when bound cells of C. albicans isolated from individual subject #2 to the saliva coated beads were used binding ability of subject #2 saliva coated beads was founed to be greater than the other sutjects. These results suggested that denture induced stomatitis is related to individual patient's salivary protein composition, especially MG-1. Future studies will be directed toward saliva exam-ination of patients who have general disease and analysis of pellicles formed on prosthesis with respect to oral disease.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.6
• /
• pp.5-16
• /
• 2011

Post-grouting for the drilled shaft is known to remarkably increase the end bearing capacity of pile by consolidating and reinforcing the disturbed ground containing slime around the pile tip. However, the general design guideline for post-grouting has not been established yet in Korea. Especially in the domestic application, the post-grouting is employed just for repairing the pile with unacceptable resistance rather than for increasing the design resistance of pile. Therefore, little is reported about the effect of post-grouting on the pile resistance itself. In this study, the effect of post-grouting on the resistance of drilled shafts installed in the weathered rock in Korea was estimated by performing the bi-directional load tests on the piles with and without the post-grouting. The test results presented that the initial slope of end bearing-base displacement curve in the pile with post-grouting was 4 times higher than that without post-grouting. At the acceptable settlement (1% of pile diameter), the end bearing capacities of piles with and without the post-grouting were estimated to be 12.0 MPa and 7.0 MPa, respectively, which indicate that the post-grouting could increase the end bearing resistance of pile in weathered rock more than 70%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.264-264
• /
• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.