• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.72-77
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• 2014

We have demonstrated a terahertz (THz) time-domain spectroscopy and imaging system using compact fiber-coupled THz modules. Using this THz spectroscopy system we have measured the absorption spectrum of water vapor in free space over 3 THz, as well as the refractive indices of various substrates such as Si, $Al_2O_3$, and GaAs using the transfer-function method. Through the THz imaging system we have observed a high-quality THz image of a medical knife and metal clip sample, with a resolution of $192{\times}89$ pixels using a step size of 250 ${\mu}m$.

• Applied Microscopy
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• v.31 no.1
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• pp.37-47
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• 2001

In order to investigate a pathogenesis of liver damage induced by skin burn, thermal injury was induced by scald burn on entirely dorsal surface in rats (total burn surface area $20\sim25\%$) except for inhalated injury. At 5 and 24 h after scald burn, biochemical assay and morphological changes in serum and liver tissue were examined. Skin burn increased liver weight (% of body weight, p<0.05) and the activity of serum aniline amino-transferase (ALT, p<0.05), in addition, the activity of xanthine oxidase (XO), an enzyme of oxygen free radical generating system, was elevated (p<0.01) in serum, but not in skin and in liver. Postburn treatment of allopurinol intraperitoneally decreased liver weight, serum ALT activity and serum XO activity. Scald burn induced ultrastructurally swelling of endoplasmic reticulum, ribosome detachment, accumulation of lipid, dilatation of bile canaliculi and intercellular space, neutrophil infiltration, activation of Kupffer's cells and degeneration of hepatocytic microvilli. Futhermore , thermal injury decreased not only the protein concentration in plasma but also the number of intravascular leukocytes, that indicates induction of edema formation with protein exudation and inflammation by neutrophil infiltration into the internal organs. However allopurinol injection after burn inhibited post burn ultrastructural changes. These data suggest that acute dermal scald burn injury leads to liver damage, that is related to elevation of xanthine oxidase activity in serum. Xanthine oxidase may be a key role in the pathogenesis of liver damage induced by skin burn.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.150-156
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• 2024

One of the key factors in research regarding long-distance laser beam propagation, as in free-space optical communication or laser power transmission, is the transmission efficiency of the laser beam. As a way to improve efficiency, we perform extensive numerical simulations of the effect of modifying the laser beam's profile, especially replacing the fundamental Gaussian beam with a super-Gaussian beam. Numerical simulations of the transmitted power in the ideal diffraction-limited beam diameter determined by the optical system of the transmitter, after about 1-km propagation, reveal that the second-order super-Gaussian beam can yield superior performance to that of the fundamental Gaussian beam, in both single-channel and coherently combined multi-channel laser transmitters. The improvement of the transmission efficiency for a 1-km propagation distance when using a second-order super-Gaussian beam, in comparison with a fundamental Gaussian beam, is estimated at over 1.2% in the singlechannel laser transmitter, and over 4.2% and over 4.6% in coherently combined 3- and 7-channel laser transmitters, respectively. For a range of the propagation distance varying from 750 to 1,250 m, the improvement in transmission efficiency by use of the second-order super-Gaussian beam is estimated at over 1.2% in the single-channel laser transmitter, and over 4.1% and over 4.0% in the coherently combined 3- and 7-channel laser transmitters, respectively. These simulation results will pave the way for future advances in the generation of higher-order super-Gaussian beams and the development of long-distance optical energy-transfer technology.