• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1261-1262
• /
• 2008

Laser-based crystallization techniques are ideally-suited for forming high-quality crystalline Si films on active-matrix display backplanes, because the highly-localized energy deposition allows for transformation of the as-deposited a-Si without damaging high-temperature-intolerant glass and plastic substrates. However, certain significant and non-trivial attributes must be satisfied for a particular method and implementation to be considered manufacturing-worthy. The crystallization process step must yield a Si microstructure that permits fabrication of thin-film transistors with sufficient uniformity and performance for the intended application and, the realization and implementation of the method must meet specific requirements of viability, robustness and economy in order to be accepted in mass production environments. In recent years, Low Temperature Polycrystalline Silicon (LTPS) has demonstrated its advantages through successful implementation in the application spaces that include highly-integrated active-matrix liquid-crystal displays (AMLCDs), cost competitive AMLCDs, and most recently, active-matrix organic light-emitting diode displays (AMOLEDs). In the mobile display market segment, LTPS continues to gain market share, as consumers demand mobile devices with higher display performance, longer battery life and reduced form factor. LTPS-based mobile displays have clearly demonstrated significant advantages in this regard. While the benefits of LTPS for mobile phones are well recognized, other mobile electronic applications such as portable multimedia players, tablet computers, ultra-mobile personal computers and notebook computers also stand to benefit from the performance and potential cost advantages offered by LTPS. Recently, significant efforts have been made to enable robust and cost-effective LTPS backplane manufacturing for AMOLED displays. The majority of the technical focus has been placed on ensuring the formation of extremely uniform poly-Si films. Although current commercially available AMOLED displays are aimed primarily at mobile applications, it is expected that continued development of the technology will soon lead to larger display sizes. Since LTPS backplanes are essentially required for AMOLED displays, LTPS manufacturing technology must be ready to scale the high degree of uniformity beyond the small and medium displays sizes. It is imperative for the manufacturers of LTPS crystallization equipment to ensure that the widespread adoption of the technology is not hindered by limitations of performance, uniformity or display size. In our presentation, we plan to present the state of the art in light sources and beam delivery systems used in high-volume manufacturing laser crystallization equipment. We will show that excimer-laser-based crystallization technologies are currently meeting the stringent requirements of AMOLED display fabrication, and are well positioned to meet the future demands for manufacturing these displays as well.

• Korean Chemical Engineering Research
• /
• v.43 no.5
• /
• pp.609-615
• /
• 2005

$TiO_2$ particles, 30-300 nm in diameter, were prepared by thermal decomposition of titanium tetraisopropoxide (TTIP) using an aerosol microreactor, by which about $1{\mu}l$ of the liquid precursor is injected into an evaporator, 1 cc in volume, and vaporized precursor is then transported by nitrogen as a bolus to a tubular reactor 4 mm in diameter and 35 cm in length. Investigated were the effects of the reactor temperature and the concentration of TTIP vapor on the morphology, particle size distribution and crystalline structure of produced $TiO_2$ particles. With TTIP vapor concentration kept constant at 1 mol%, the reactor temperature was varied from 300 to 500 and $700^{\circ}C$. The primary particle size decreased with increasing the temperature, and the size distributions were mono-modal at 300 and $500^{\circ}C$, but bi-modal at $700^{\circ}C$. The TTIP vapor concentration was increased from 1 to 3.5 and 7 mol%, holding the reactor temperature at $700^{\circ}C$. The bi-modal distribution seen at the concentration of 1 mol% disappeared and the number of particles composing an agglomerate increased at the higher concentrations. These effects of the reactor temperature and the precursor concentration were discussed in comparison with experimental results reported earlier.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.842-848
• /
• 2013

Developments of Solid-State Gyroscopy during last decades are impressive and were based on thin-walled shell resonators like HRG or CRG made from fused quartz or leuko-sapphire. However, a number of design choices for inertial-grade gyroscopes, which can be used for high-g applications and for mass- or middle-scale production, is still very limited. So, considerations of fundamental physical effects in solids that can be used for development of a miniature, completely solid-state, and lower-cost sensor look urgent. There is a variety of different types of bulk acoustic (elastic) waves (BAW) in anisotropic solids. Shear waves with different variants of their polarization have to be studied especially carefully, because shear sounds in glasses and crystals are sensitive to a turn of the solid as a whole, and, so, they can be used for development of gyroscopic sensors. For an isotropic medium (for a glass or a fine polycrystalline body), classic Lame's theorem (so-called, a general solution of Elasticity Theory or Green-Lame's representation) has been modified for enough general case: an elastic medium rotated about an arbitrary set of axes. Travelling, standing, and mixed shear waves propagating in an infinite isotopic medium (or between a pair of parallel reflecting surfaces) have been considered too. An analogy with classic Foucault's pendulum has been underlined for the effect of a turn of a polarizational plane (i.e., an integration effect for an input angular rate) due to a medium's turn about the axis of the wave propagation. These cases demonstrate a whole-angle regime of gyroscopic operation. Single-crystals are anisotropic media, and, therefore, to reflect influence of the crystal's rotation, classic Christoffel-Green's tensors have been modified. Cases of acoustic axes corresponding to equal velocities for a pair of the pure-transverse (shear) waves have of an evident applied interest. For such a special direction in a crystal, different polarizations of waves are possible, and the gyroscopic effect of "polarizational precession" can be observed like for a glass. Naturally, formation of a wave pattern in a massive elastic body is much more complex due to reflections from its boundaries. Some of these complexities can be eliminated. However, a non-homogeneity has a fundamental nature for any amorphous medium due to its thermodynamically-unstable micro-structure, having fluctuations of the rapidly-frozen liquid. For single-crystalline structures, blockness (walls of dislocations) plays a similar role. Physical nature and kinematic particularities of several typical "drifts" in polarizational BAW gyros (P-BAW) have been considered briefly too. They include irregular precessions ("polarizational beats") due to: non-homogeneity of mass density and elastic moduli, dissymmetry of intrinsic losses, and an angular mismatch between propagation and acoustic axes.

• Applied Biological Chemistry
• /
• v.42 no.2
• /
• pp.99-104
• /
• 1999

Soil actinomycetes of 703 strains were isolated from 25 sampling points in Cheju Island using 4 different media. Arginine glycerol salts agar containing soil extract was found to be the best medium for the isolation of soil actinomycetes. Soil samples from pasture land showed higher population and diversity of the actinomycetes than those from citrus field, forest, island, hill or valley. When the antibacterial activity of the 526 isolates was tested against three bacterial strains, Escherichia coli, Staphylococcus aureus and Pseudomonas solanacearum the frequency of the isolates with antibacterial activity varied much depending upon the media used for isolation and cultivation. BL106Ba, one of the 10 isolates that showed antibacterial activity against all the above 3 test strains, was chosen based upon the pH and heat stability of its antibacterial metabolites, and was identified as Streptomyces sp. based upon its cultural, morphological and physiological characteristics. The partially purified white crystalline substance obtained from the culture supematant of BL1063a through cation exchange chromatography(AG MP-50) and three times consecutive gel filtration(Sephadex G-10) showed high antimicrobial activity against gram positive and negative bacteria, but low activity against yeasts. The partially purified substance was found to contain at least four different compounds with antibacterial activity by both thin layer chromatography and high performance liquid chromatography.

• Applied Chemistry for Engineering
• /
• v.18 no.5
• /
• pp.475-482
• /
• 2007

The thermal and optical properties of glucose penta(cholesteryloxycarbonyl)alkanoates (CAGLn, n = 2~8, 10, the number of methylene units in the spacer) were investigated. All the CAGLn formed monotropic cholesteric phases with left-handed helical structures. CAGLn with n = 2 or 10, in contrast with CAGLn with $3{\leq}n{\leq}8$, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer joining the cholesteryl group to the glucose chain. The isotropic-cholesteric transition point ($T_{ic}$) decreased with increasing n and showed no odd-even effect. The plot of transition entropy at $T_{ic}$ against n had a sharp negative inflection at n = 7. The optical pitches (${{\lambda}_m}^{\prime}$ s) of CAGLn with $3{\leq}n{\leq}8$ decreased with increasing temperature. However, the temperature dependence of the ${\lambda}_m$ of the derivatives exhibited pronounced dependence on n. The transitional properties and the temperature dependence of the ${\lambda}_m$ observed for CAGLn were discussed in terms of the differences in arrangement of the cholesteryl groups and the conformation of the molecules.

• Applied Chemistry for Engineering
• /
• v.21 no.3
• /
• pp.284-290
• /
• 2010

In this study, as one of the carbon dioxide ($CO_2$) adsorbents the aqueous potassium carbonate ($K_2CO_3$)/promoter mixtures were investigated. Equilibrium partial pressure ($P_{CO_2}^*$) and pressure change were measured by using VLE (Vapor-liquid equilibrium) equipment in the mixture solution at 60 and $80^{\circ}C$, respectively. Absorption capacity was estimated in the semi-batch absorption apparatus at 40, 60 and $80^{\circ}C$. We proposed to use homopiperazine (homoPZ), cyclic diamine compound as a promoter of $K_2CO_3$ solution, to prevent crystalline formation and increase absorption capacity of aqueous $K_2CO_3$ solution. The absorption capacity of $K_2CO_3$/homoPZ was compared with MEA, $K_2CO_3$ and $K_2CO_3$/piperazine (PZ). Based on the results, we found that the mixture solution containing homoPZ had lower equilibrium partial pressure than that of $K_2CO_3$ solution and the absorption rate was approximately 0.375-times faster at $60^{\circ}C$, 0.343-times faster at $80^{\circ}C$ than that of aqueous $K_2CO_3$ solution without homoPZ. $K_2CO_3$/homoPZ solution showed excellent CO2 loading capacity compared with MEA solution at $60^{\circ}C$.

• Microbiology and Biotechnology Letters
• /
• v.38 no.1
• /
• pp.105-111
• /
• 2010

Caesalpinia sappan L. has long been commonly used in oriental folk medicines to treat diseases. To investigate the antibacterial effects from C. sappan L. heart wood, the MeOH soluble extract was successively fractionated by using hexane, $CHC1_3$, EtOAc, BuOH, MeOH, and $H_2O$. Among of these extracts, the EtOAc fraction which partitioned to 3.94% of the highest yields was to be the most active against all human pathogenic bacteria in this experiment. In addition, the antibacterial activities of the EtOAc fraction were more effective against Gram (+) bacteria compared to those against Gram (-) bacteria, which showed difference of the antibacterial activities against Gram (-) bacteria. To confirm the identity of the active substances, the EtOAc fraction was further separated by silica gel adsorption column, high performance liquid chromatography, and 98.48% purity of brazilin (1.67 mg)/EtOAc (10 mg) fraction was obtained from 300 g of C. sappan L. heart wood. The isolated active substance was a single compound of yellow crystalline, and was identified as brazilin ($C_{16}H_{14}O_5$) by MS, and $^lH$-NMR and $^{13}C$-NMR. These results suggest that the brazilin in the EtOAc fraction from MeOH extract of C. sappan L. has a potential as a natural therapeutic agent against human pathogenic Gram (+) bacteria such as Staphylococcus aureus.

• Corrosion Science and Technology
• /
• v.11 no.1
• /
• pp.1-8
• /
• 2012

The development of martensitic grades which can be processed in continuous galvanizing lines requires the reduction of the oxides formed on the steel during the hot dip process. This reduction mechanism was investigated in detail by means of High Resolution Transmission Electron Microscopy (HR-TEM) of cross-sectional samples. Annealing of a martensitic steel in a 10% $H_2+N_2$ atmosphere with the dew point of $-35^{\circ}C$ resulted in the formation of a thin $_{C-X}MnO.SiO_{2}$ (x>1) oxide film and amorphous $_{a-X}MnO.SiO_{2}$ oxide particles on the surface. During the hot dip galvanizing in Zn-0.13%Al, the thin $_{C-X}MnO.SiO_{2}$ (x>1) oxide film was reduced by the Al. The $_{a-X}MnO.SiO_{2}$ (x<0.9) and $a-SiO_{2}$ oxides however remained embedded in the Zn coating close to the steel/coating interface. No $Fe_{2}Al_{5-X}Zn_{X}$ inhibition layer formation was observed. During hot dip galvanizing in Zn-0.20%Al, the $_{C-X}MnO.SiO_{2}$ (x>1) oxide film was also reduced and the amorphous $_{a-X}MnO.SiO_{2}$ and $a-SiO_{2}$ particles were embedded in the $Fe_{2}Al_{5-X}Zn_{X}$ inhibition layer formed at the steel/coating interface during hot dipping. The results clearly show that Al in the liquid Zn bath can reduce the crystalline $_{C-X}MnO.SiO_{2}$ (x>1) oxides but not the amorphous $_{a-X}MnO.SiO_{2}$ (x<0.9) and $a-SiO_{2}$ oxides. These oxides remain embedded in the Zn layer or in the inhibition layer, making it possible to apply a Zn or Zn-alloy coating on martensitic steel by hot dipping. The hot dipping process was also found to deteriorate the mechanical properties, independently of the Zn bath composition.

• Polymer(Korea)
• /
• v.33 no.3
• /
• pp.254-262
• /
• 2009

Nine kinds of hydroxypropyl celluloses (HPCs) with degree of substitution (DS) and molar substitution (MS) ranging from 2.10 to 2.71 and 2.3 to 6.7, respectively and seven kinds of fully butanoated HPCs (BPCs) based on the HPCs with $2.3\;{\le}\;MS\;{\le}\;6.7$ were synthesized, and the molecular characteristics of HPCs and the thermotropic liquid crystalline properties of the derivatives were investigated. MS was nearly equal to DS for small value of DS, but it became exceedly larger than DS for $DS{\gtrsim}1$, showing that in the later stages of reaction, propylene oxide preferentially adds to the side chains rather than the main chain. All the derivatives formed enantiotropic cholesteric phases with right-handed helical structures. The glass and clearing transition temperatures of both HPCs and BPCs were decreased with increasing MS. The optical pitches (${\lambda}_m'S$) of BPCs, as well as HPCs themselves, increased with increasing temperature. However, the ${\lambda}_m'S$ of both HPCs and BPCs at the same temperature increased with increasing MS. Moreover, the temperature dependence of ${\lambda}_m$ of HPCs was weaker than that of BPCs, suggesting that the helical twisting power of the cellulose chain highly depends on the length and chemical structure of the side chain introduced in cellulose chain.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.30 no.4
• /
• pp.646-650
• /
• 2001

In this study, we investigated the thermotropic behavior of Daucus carota L. (DCS) extracts in phosphatidylcholine(PC) liposomes using high-sensitivity differential scanning calorimetry (nano-DSC). We used dipalmitoylphosphatidylcholine (DPPC) bilayers which made most stable liposomes among the other phosphatidylcholine. The sample DCS was extracted and fractionated to four different types, hexane(DCSMH), ethylacetate (DCSMEA), butanol (DCSMB) and aqueous(DCSMA) fractions. Compared to the other fractions of Daucus carota L., the DCSMH and DCSMEA fractions markedly affected the thermotropic properties of DPPC liposomes, broadened and shifted the thermograms of transition to lower temperatures. The incorporation of DCSMH and DCSMEA in DPPC liposomes were preferentially located in the hydrophobic core of DPPC bilayers, where it reduced the lipid packing orderness (cooperative unit) in the gel state compared to it in the liquid-crystalline state. These results suggest that the activities of the Daucus carota L. extracts to enhance the fluidity of the liposomal membrane have implication in their biological activities.