• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.265-277
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• 2009

A long-term field demonstration experiment of selected stabilization method to reduce the heavy metal mobility in farmland soil contaminated by heavy metals around abandoned mine site was conducted. Field demonstration experiments were established on the contaminated farmland with the wooden plate(thickness=1cm) which dimension were width=200cm, Length=200cm, height=80cm and filled with treated soil, which was mixed with lime stone and steel refining slag except on control plot. Soil samples were collected and analyzed during the experiment period(2008. 2~2008. 8) after the installation of the plots. Field demonstration experiments results showed that the application ratio of lime stone 5% was effective for immobilizing heavy metal components in contaminated farmland soil.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.4
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• pp.155-160
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• 2003

In this study, an Alexandrite laser system for hair removal adopting a multi-discharge method in which three flash lamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp turn-on time. Specifically, this study demonstrates a technology that makes it possible to formulate various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC (program integrated circuit) one-chip microprocessor. With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and real-time control is possible with an external keyboard, enabling an assortment of pulse shapes. In addition, longer pulses can be more widely used for industrial processing as well as for numerous medical purposes.

• Journal of Ginseng Research
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• v.6 no.2
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• pp.168-203
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• 1982

Effects of soil moisture on growth of Panax ginseng, of various factors on soil moisture, and of moisture on nutrition, quality, physiological disorder, diseases and insect damage were reviewed. Optimum soil moisture was 32% of field capacity with sand during seed dehiscence, and 55-65% for plant growth in the fields. Optimum soil moisture content for growth was higher for aerial part than for root and higher for width than for length. Soil factors for high yield in ginseng fields appeared to be organic matter, silt, clay, agreggation, and porosity that contributed more to water holding capacity than rain fall did, and to drainage. Most practices for field preparation aimed to control soil moisture rather than nutrients and pathogens. Light intensity was a primary factor affecting soil moisture content through evaporation. Straw mulching was best for the increase of soil moisture especially in rear side of bed. Translocation to aerial part was inhibited by water stress in order of Mg, p, Ca, N an Mn while accelerated in order of Fe, Zn and K. Most physiological disorders(leaf yellowing, early leaf fall, papery leaf spot, root reddening, root scab, root cracking, root dormancy) and quality factors were mainly related to water stress. Most critical diseases were due to stress, excess and variation of soil water, and heavy rain fall. The role of water should be studied in multidiciplinary, especially in physiology and pathology.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.375-380
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• 2014

To enhance biocompatibility between the orthopedic implant stem and obsteoblast cells, bone-forming cells, micro-size holes are patterned in Ti plate surface. Initially, the house built laser power stabilization system is applied to the laser micro patterning machine to convince repeatable result. Various pulse widths are irradiated Ti plate and relationship between diameters of patterned holes and pulsed width is derived. Effect of multi pulse is observed and optimal pulse number is considered to avoid heat affected zone. After MG-63 osbeoblast cells are cultured, micro patterned Ti plates are compared with control plates. In SEM image, cells are well aligned and aggregation is observed in both 60, and $100{\mu}m$ patterned plates. Finally, free form surface stem model is prepared to test micro hole patterning.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.490-493
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• 2005

We have experimentally studied supercontinuum generation in a photonic crystal fiber as a function of pump wavelength and intensity with 100 fs pulsewidth. A supercontinuum over 750 nm spectral width with amplitude variation less than 10 dB has been achieved. It was generated by coupling femtosecond pulses from a mode-locked Ti:Sapphire laser into a 2 m long photonic crystal fiber. Adjusting the parameters of the pump source, it was also possible to control different spectral features of the supercontinuum radiation.

• Current Optics and Photonics
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• v.4 no.3
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• pp.238-246
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• 2020

The heat distribution in crystals in a 2-㎛ acousto-optic Q-switched Tm:LuAG laser pumped by pulsed-laser-diode (pulsed-LD) intermittent-pumping technology was analyzed using COMSOL software. The thermal lensing effect of the Tm:LuAG crystal can be mitigated by pulsed-LD intermittent-pumping techniques. An experimental setup using this kind of approach achieved maximum output energy of 8.31 mJ, minimum pulse width of 101.9 ns, and highest peak power of 81.55 kW, reached at a Q-switched repetition rate of 200 Hz. It offers significant improvement of performance of the output laser beam, compared to pulsed-LD double-ended pumping technology at the same repetition rate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.278-281
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• 2009

Selective laser sintering(SLS), a kind of rapid prototyping technology, can provide a process to form many types of coatings. Coated layers by selective laser melting are highly influenced by substrate, powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore an attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel has been performed by selective laser sintering. In this study, Fe-Ni-Cr coating was produced by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with Ar. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of coating layer was improved with fill spacing optimization or layer thickness decrease.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1247-1248
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• 2006

We fabricated YBCO film using a TFA-MOD method. In order to enhance the reaction kinetics and to control the formation of the second phases, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were used as precursors (the so called "211 process"). The films were calcined at $460^{\circ}C$ and then fired at $750^{\circ}C-800^{\circ}C$ in a 12.1% humidified $Ar-O_2$ atmosphere. We found that the microstructure varied significantly with the firing temperature. The textures of all of the films were similar and mainly biaxial. For the film fired at $775^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is 2.0 MA/$cm^2$).

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.4
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• pp.316-321
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• 2005

We designed and implemented fish robots for various purposes such as autonomous navigation, maneuverability control, posture balancing and improvement of quick turns in a tank of 120 X 120 X 180cm size. Typically, fish robots have 30-50 X 15-25 X 10-20cm dimensions; length, width and height, respectively. It is essential to have the ability of quick and smooth turning to avoid collision with obstacles or walls of the water pool at a close distance. Infrared distance sensors are used to detect obstacles, magneto-resistive sensors are used to read direction information, and a two-axis accelerometer is mounted to compensate output of direction sensors. Because of the swing action of its head due to the tail fin movement, the outputs of an infrared distance sensor contain a huge amount of noise around true distances. With the information from accelerometers and e-compass, much improved distance data can be obtained by fuzzy logic based estimation. Successful swimming and smooth turns without collision demonstrated the effectiveness of the distance estimation.

• ETRI Journal
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• v.32 no.1
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• pp.33-43
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• 2010

The increasing demand for non-sinusoidal currents affects the quality of distribution networks. Harmonic detection is a crucial step in the cancellation of those components by active power filters. In this paper, the discrete cosine transform (DCT) is compared with different implementations based on Fourier transforms, demonstrating their equivalences and the advantages provided by the former. We demonstrate that the phase error in the presence of grid frequency deviations and the transient length are reduced by half in comparison to the discrete Fourier transform. A novel algorithm is developed to provide frequency adaptation to the DCT, taking advantage of its good features. The window width is adjusted in real time according to the actual value of the grid fundamental frequency by means of a phase-locked loop. A technique based on dithering is employed to overcome the limitation caused by the truncation of the window number of samples, so the frequency resolution is enhanced. The theoretical approach is verified by simulated and experimental results.