• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.140-144
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• 2007

As an electron scanning microscopes has traditionally required a considerably large room equipped with several service and pipe lines due to its inherent size. As an alternative, a small sized SEM, simply called a mini-SEM, is introduced even if the performance in terms of magnification and resolution is a little inferior to a classical thermal SEM. However, the size and fabrication cost is dramatically reduced, dedicating to opening a new market. The optical system in the mini-SEM is redesigned and specimen stage is quitely reduced and vertical axis is excluded. The design tools and calibration techniques to develope the mini-SEM are introduced and its performance is verified through numerical analysis experiments.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.314-318
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• 2002

We examine the adjustment of the semiconvergent angle and current for the miniaturized micro column working at low voltage but producing maximized current. Our study shows that the minimum electron beam sizes are 10 ㎚ for the cold field emitter (CFE) and 20 ㎚ for the thermal field emitter (TFE) at a given condition.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.365-373
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• 2005

Antioxidative activities of methanol extracts of 7 natural products which have been orientally used or studied as ophthalmic drugs were investigated. All of 7 extracts assayed - Rubus coreanus, Dendrobium monile, Eriocaulon sieboldianum, Ligustrum japonicum, Cassia tora, Cicadae Periostacum and Polygonatum odoratum var pluriflorum had some electron-donating ability to OPPH radicals, in which R. coreanus and D. monile showed strong activity as similar as ascorbic acid or BHT. At the concentration of $200{\mu}g/m{\ell}$, methanol extract of L. japonicum showed superoxide dismutase-like activity the same as 0.1 mM ascorbic acid and methanol extract of R. coreanus inhibited effectively the production of ABTS radical produced by $H_2O_2$. Furthermore, methanol extract of C. tora showed the highest nitrite scavenging ability. The inherent antioxidative activities of these natural products appear to be responsible for its ophthalmic effects.

• Laser Solutions
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• v.16 no.3
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• pp.27-31
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• 2013

To engrave high-density circuit-line patterns in IC substrates, we applied a projection ablation technique in which a dielectric ($ZrO_2/SiO_2$) mask, a DPSS UV laser instead of an excimer laser, a refractive beam shaping optics and a galvo scanner are used. The line/space dimension of line patterns of the dielectric mask is $10{\mu}m/10{\mu}m$. Using a ${\pi}$ -shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam; and a telecentric f-${\theta}$ lens focuses it to a $115{\mu}m{\times}105{\mu}m$ flat-top beam on the mask. The galvo scanner before the f-${\theta}$ lens moves the beam across the scan area of $40mm{\times}40mm$. An 1:1 projection lens was used. Experiments showed that the widths of the engraved patterns in a buildup film ranges from $8.1{\mu}m$ to $10.2{\mu}m$ and the depths from $8.8{\mu}m$ to $11.7{\mu}m$. Results indicates that it is required to increase the projection ratio to enhance profiles of the engraved patterns.

• Journal of Adhesion and Interface
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• v.11 no.4
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• pp.162-167
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• 2010

In the present work, the effect of electron beam irradiation on the chemical and thermal characteristics of cellulose-based jute fibers was explored by means of chemical analysis, electron spin resonance analysis, ATR-FTIR spectroscopy, thermogravimetric analysis and thermomechanical analysis. Jute fiber bundles were uniformly irradiated in the range of 2~100 kGy by a continuous method using a conveyor cartin an electron beam tunnel. Electron beam treatment, which is a physical approach to change the surfaces, more or less changed the chemical composition of jute fibers. It was also found that the radicals on the jute fibers can be increasingly formed with increasing electron beam intensity. However, the electron beam irradiation did not change significantly the chemical functional groups existing on the jute fiber surfaces. The electron beam irradiation influenced the thermal stability and thermal shrinkage/expansion behavior and the behavior depended on the electron beam intensity.

• Korean Journal of Materials Research
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• v.26 no.8
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• pp.412-416
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• 2016

The electrical properties of Au/n-type Ge Schottky contacts with different contact areas were investigated using current-voltage (I-V) measurements. Analyses of the reverse bias current characteristics showed that the Poole-Frenkel effect became strong with decreasing contact area. The contribution of the perimeter current density to the total current density was found to increase with increasing reverse bias voltage. Fitting of the forward bias I-V characteristics by considering various transport models revealed that the tunneling current is dominant in the low forward bias region. The contributions of both the thermionic emission (TE) and the generation-recombination (GR) currents to the total current were similar regardless of the contact area, indicating that these currents mainly flow through the bulk region. In contrast, the contribution of the tunneling current to the total current increased with decreasing contact area. The largest $E_{00}$ value (related to tunneling probability) for the smallest contact area was associated with higher tunneling effect.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.269-277
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• 1998

The TSDC(Thermally Stimulated Depolarization Current) measurement were carried out in the temperature range $30{\sim}500^{\circ}C$. We observed the anomalous two peaks that have a thousand times longer relaxation time than that of the space charge. It seems that the origin of the two peak are due to the electron trapping effect and to the adsorption of the vacancies at silver electrode.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.31-35
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• 2003

Several poly(6-dialkylamino-1,3,5-triazine-2,4-dithioxylene) derivatives were synthesized by the polycondensation of 6-dialkylamino-1,3,5-triazine-2.4-dithiol with m- and p-dibromide xylene in a cetyltrimethyl ammonium bromide at $70^{\circ}C$ for 24h. The synthesized derivatives had refractive Indexes of 1.580~1.697 and had molar absorptivity of 97~196.6. In these derivatives, we knew that they are a polymer having high refraction indexes without double refraction because they contain triazine rings and sulfur atoms with high electron density.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.2
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• pp.119-126
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• 2005

The purpose of this study was analyzed to compare on the physical characters of two companies of color contact lenses. Artificial tear solution was used for measuring the rate of protein deposits and wettability. The surface roughness of lenses was measured by SEM(scanning electron microscope, Japan) and AFM(atomic force microscope, MultimodeTM, USA). As a results, The color contact lenses was not different from general soft contact lenses in a respect of other properties. However, the colored contact lenses showed a severe crack on the surface under SEM observation. There was no irregularity on the surface of the colored contact lenses in AFM photograph. The dyes were deposited in inside of lenses by microscope observation.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.55-58
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• 2001

The rigid gas permeable(RGP) contact lens has nearly side effect on the cornea. So that, this lens has used the clinical reflective correction of the eye. This study have used several methods for research the fine internal structure on the RGP contact lens by scanning electron microscopy. The results have indicated that the postfixation of 1% $OsO_4$ and tannic acid is responsible for a fine structure in the internal plane of RGP contact lens. These internal surface of contact lens appeared the several shape of the hole of the stereo shape form with arrangement of round form. But, on the contact lens with non-postfixation, the stereo shape have not present and the boundary of the vesicle have not clear. Maybe, these results suggest that the fixation methods have effect on the morphological characters of materials on the RGP contact lens.