• Journal of the Korean Society for Heat Treatment
• /
• v.7 no.1
• /
• pp.61-71
• /
• 1994

This study is to investigate the stress distributions, crystal orientations and magnetic properties during die-upsetting according to working temperature of Nd-Fe-B-Cu alloys. The stress distributions in the specimens during compressing process were calculated by a finite element method program(SPID). The calculated stresses were effective stress (${\sigma}_{eff}$), compression stress(${\sigma}_z$), radial direction stress(${\sigma}_r$) rotational direction stress(${\sigma}_e$) and shear stress(${\tau}_{rz}$). The stress distributions of ${\sigma}_z$, obtained by a computer simulation showed that the stress components causing the magnetic alignment during die-upsetting of the cast magnets were very high at the center-part of a specimen, and decreased toward the periphery-part of a specimen. In view of the above results the magnetic properties should be better at the center-part of a specimen than any other parts. But the measured magnetic properties were better at the mid-part. These results should be due to the fact that the specimens were casted. Normally the magnetic properties are affected by the casting process as well as by the stress levels. ${\sigma}_r$, ${\sigma}_e$ are thought to affect the liquid phase flowing and domain patterns, respectively. The influence of ${\tau}_{rz}$ was trivial, ${\sigma}_{eff}$ distributed similar throughout the specimen. The Nd-rich phase appeared at the peripheral of the specimen where the stress level of ${\sigma}_r$, ${\sigma}_z$, was low or the stress level of ${\sigma}_e$ was high. The Nd-rich phase was squeezed out during die-upsetting. This phase had an effect on the crystal orientation and grain growth. The stress distributions of alloy were irregular at the parts of the specimen where the die contacted with specimen.

• Journal of Sericultural and Entomological Science
• /
• v.38 no.2
• /
• pp.160-167
• /
• 1996

The middle silk gland, that is a liquid silk thread gland consisting of silk protein, was taken out and a silk monofilament was made by drawing rapidly to approximately 3 times. In order to deteriorate the inter molecular hydrogen bonding force and to stretch in, the drawn silk filament was swoolen in boiling water. The results obtained are as follows ; The silk gland sample that just dried silk gland was occupied in crystalline region of silk-I type and random amorphous region. According to the examination of X-ray diffraction and thermal analysis, silk-II type crystal begins to appear partially in monofilament sample and spread to almost complet silk-II type crystal in 65.2% drawn sample. And, orientation of silk fibroin mlecule increased suddenly in early stage with a rise of drawing ratiofrom birefringence and density, and it was found that orientation of fibroin molecule was completed. As drawing ratio increases relation with time of hydrolysis, birefringence appeared almost fixed a tendency. Crystallization collapse by hydrolysis was not found in X-ray diffraction and thermal analysis. But, amorphous region began to flow by treated hydrolysis, that orientation of crystallization part was disturbed was supposed.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.25 no.3
• /
• pp.260-265
• /
• 2015

This paper proposes a alignment system using edge feature. An alignment system obtains the position and orientation of printed circuit board(PCB) or liquid crystal display(LCD) panel through the fiducial marks. Thus, it is the indicator of the system performance how accurate we detect the positions of the fiducial marks in the target image. Edges have the geometrical characteristics such as positions, lengths, and shapes. These features are suitable for finding the marks and have the advantages of lighting variations, model occlusion, as well as variations in scale and angle. The performance of the proposed system is validated through the alignment experiment using an display panel alignment system included X, Y axis, and rotatable stage.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.6 no.5
• /
• pp.27-37
• /
• 1992

We studied the dielectric and dynamic mechanical losses according to the quenching condition in low density polyethylene being used to power cables. According to severe quenching condition, characteristics of the temperature in internal friction los peak have decreased the magnitude of loss peak as amorphous region lengthen. From now on, the frequency dependent characteristics of dielectric loss have investigated at room temperature, and the dielectric loss peak due to interface polarization, between crystal and amorphous region, occurs about 30[Hz], and that, the peak due to orientation polarization in correspondence to the loss peak in internal friction has observed at about 3 [MHz]. As quenching velocity increased, the effect on quenching condition about the dielectric loss has decreased the magnitude of the loss peak. Thus, estimation has been carried out on the activation energies nd the degree of crystallinity by means of X-ray diffraction are obtained as follows: room quenching : 26.4 [kal/mole] and 54.73 [%], ice quenching : 25.6 [kcal/mole] and 48.47 [%], liquid nitrogen quenching specimens : 22.56 [kcal/mole] and 40.95 [%].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.788-791
• /
• 2002

Tin doped indium oxide(ITO) films are highly conductive and transparent in the visible region whose property leads to the applications in solar cell, liquid crystal display, thermal heater, and other sensors. This paper investigated ITO films as a transparent conducting films for application of PDP. ITO films were grown on glass substrate by RF magnetron sputtering method. To achieve high transmittance and low resistivity, we examined the various film deposition such as substrate temperature, gas pressure, annealing temperature, and deposition time. We recommend the substrate temperature of $500^{\circ}C$ and post annealing of $200^{\circ}C$ in $O_2$ atmosphere for good conductivity and transmittance. From XRD examination, ITO films showed a preferred(222) orientation. As substrate temperature increased from RT to $500^{\circ}C$, the intensity of the (222) peak increased. The highest peak intensity was observed at a substrate temperature of $500^{\circ}C$. with the optimum growth conditions, ITO films showed resistivity of $1.04{\times}10^{-4}{\Omega}-cm$ and transmittance of 81.2% for a film 300nm thick in the wavelength range of the visible spectrum.

• Macromolecular Research
• /
• v.14 no.1
• /
• pp.1-33
• /
• 2006

Polyimides (PIs) exhibit excellent thermal stability, mechanical, dielectric, and chemical resistance properties due to their heterocyclic imide rings and aromatic rings on the backbone. Due to these advantageous properties, PIs have found diverse applications in industry. Most PIs are insoluble because of the nature of the high chemical resistance. Thus, they are generally used as a soluble precursor polymer, which forms complexes with solvent molecules, and then finally converts to the corresponding polyimides via imidization reaction. This complexation with solvent has caused severe difficulty in the characterization of the precursor polymers. However, significant progress has recently been made on the detailed characterization of PI precursors and their imidization reaction. On the other hand, much research effort has been exerted to reduce the dielectric constant of PIs, as demanded in the microelectronics industry, through chemical modifications, as well as to develop high performance, light-emitting PIs and liquid crystal (LC) alignment layer PIs with both rubbing and rubbing-free processibility, which are desired in the flat-panel display industry. This article reviews this recent research progresses in characterizing PIs and their precursors and in developing low dielectric constant, light-emitting, and LC alignment layer PIs.

• Journal of Satellite, Information and Communications
• /
• v.10 no.3
• /
• pp.89-93
• /
• 2015

Ion-beam irradiation(IB) on $HfO_2$ surface induced high-performance liquidcrystal(LC) driving at a 1-V threshold with vertical alignment of liquid crystals(LC). The high-k materials Atomic layer deposition was used to obtain LC orientation on ultrathin and high-quality films of $HfO_2$ layers. To analyze surface morphological transition of $HfO_2$ which can act as physical alignment effect of LC, atomic force microscopy images are employed with various IB intensities. The contact angle was measured to elucidate the mechanism of vertical alignment of LC on $HfO_2$ with IB irradiation. Contact angle measurement show the surface energy changes via IB intensity increasing.

• Korean Journal of Materials Research
• /
• v.30 no.7
• /
• pp.343-349
• /
• 2020

NKN [(Na,K)NbO₃] is a candidate lead-free piezoelectric material to replace PZT [Pb(Zr,Ti)O₃]. A single crystal has excellent piezoelectric-properties and its properties are dependent of the crystal orientation direction. However, it is hard to fabricate a single crystal with stoichiometrically stable composition due to volatilization of sodium during the growth process. To solve this problem, a solid solution composition is designed (Na,K)NbO₃-Ba(Cu,Nb)O₃ and solid state grain growth is studied for a sizable single crystal. Ceramic powders of (Na,K)NbO₃-M(Cu,Nb)O₃ (M = Ca, Sr, Ba) are synthesized and grain growth behavior is investigated for different temperatures and times. Average normal grain sizes of individual specimens, which are heat-treated at 1,125 ℃ for 10 h, are 6.9, 2.8, and 1.6 ㎛ for M = Ca, Sr, and Ba, respectively. Depending on M, the distortion of NKN structure can be altered. XRD results show that (NKN-CaCuN: shrunken orthorhombic; NKN-SrCuN: orthorhombic; NKN-BaCuN: cubic). For the sample heat-treated at 1,125 ℃ for 10 h, the maximum grain sizes of individual specimens are measured as 40, 5, and 4,000 ㎛ for M = Ca, Sr, and Ba, respectively. This abnormal grain size is related to the partial melting temperature (NKN-CaCuN: 960 ℃; NKN-SrCuN: 971 ℃; NKN-BaCuN: 945 ℃).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.04a
• /
• pp.41-41
• /
• 2008

In general, polyimides (PIs) are used in alignment layers in liquid crystal displays (LCDs). The rubbing alignment technique has been widely used to align the LC molecules on the PI layer. Although this method is suitable for mass production of LCDs because of its simple process and high productivity, it has certain limitations. A rubbed PI surface includes debris left by the cloth, and the generation of electrostatic charges during the rubbing induces local defects, streaks, and a grating-like wavy surface due to nonuniform microgrooves that degrade the display resolution of computer displays and digital television. Additional washing and drying to remove the debris, and overwriting for multi-domain formation to improve the electro-optical characteristics such as the wide viewing angle, reduce the cost-effectiveness of the process. Therefore, an alternative to non-rubbing techniques without changing the LC alignment layer (i.e, PI) is proposed. The surface of LC alignment layers as a function of the ion beam (IE) energy was modified. Various pretilt angles were created on the IB-irradiated PI surfaces. After IB irradiation, the Ar ions did not change the morphology of the PI surface, indicating that the pretilt angle was not due to microgrooves. To verify the compositional behavior for the LC alignment, the chemical bonding states of the ill-irradiated PI surfaces were analyzed in detail by XPS. The chemical structure analysis showed that ability of LCs to align was due to the preferential orientation of the carbon network, which was caused by the breaking of C=O double bonds in the imide ring, parallel to the incident 18 direction. The potential of non-rubbing technology for fabricating display devices was further conformed by achieving the superior electro-optical characteristics, compared to rubbed PI.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.489-492
• /
• 2005

We report new polymer stabilized ferroelectric liquid crystal (PSFLC) cells with mechanical stability which is achievable by introducing photospacers in the cells. It was found that the mechanical st ability of the PSFLC cell was effected by introduction of photo spacers. We analyzed the dependence of mechanical stability and memory property on the density of photospacers in the PSFLC cell. The stability and memory properties of PSFLC Cells depending on photospacer density are discussed. 1. Introduction Recently, flexible displays have attracted much attention because they have remarkable advantages: thinner, lighter, non-breakable and conformable features. Flexible displays have various potential applications such as e-book and e-paper displays utilizing the distinct features. E-book and E-paper displays demand very low power consumption, so that bistable memory liquid crystal modes are required in case of flexible plastic LCDs for those application. Three kinds of memory LC modes have been developed; bistable nematic, bistable cholesteric and bistable FLC. Among them SSFLC as one of bistable FLC has big advantages such as low driving voltage, wide view angle and fast response time, SSFLC cells are, however, very weak against mechanical shock. Polymer stabilized FLC (PSFLC) has been developed to overcome the poor mechanical stability of SSFLC. PSFLC was known to have network structure that FLCs are oriented with smectic layer ordering in polymer network. The polymer network stabilizes the FLC orientation, which leads to improvement of mechanical stability of PSFLCD. A lot of studies have been done for the application of PSFLC to flexible $LCDs.^{[1{\sim}12]}$ However, it should be noted that PSFLC does not have sufficient mechanical stability for the particular applications such as smart card LCD, where LCD is highly bendable.Bead spacer was mainly used to maintain cell gap of conventional PSFLCDs. But the spacer density of it is not locally uniform in the cell, so that it is generally difficult that the PSFLCDs with bead spacers show sufficient mechanical stability. In order to more improve the mechanical stability of PSFLCDs, we introduced photospacers into PSFLCDs. In this paper, we describe the improvement of mechanical stability by introducing photospacers into PSFLCDs.