• Journal of Radiation Protection and Research
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• v.31 no.3
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• pp.149-153
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• 2006

An ionization chamber is still widely used in many fields by virtue of its' simple operational characteristics and the possibility of its' various shapes. A parallel type of an ionization chamber for a steel sheet thickness measurement was designed and fabricated. High pure xenon gas, which was pressurized up to 6 atm, was chosen as a filling gas to increase the current response and sensitivity for a radiation. A high pressure gas system was also constructed. The active volume and the incident window size of the fabricated ionization chamber were $30\;cm^3\;and\;12\;cm^2$, respectively. Preliminary tests with a 25 mCi $^{241}Am$ gamma-ray source and evaluation tests in a standard X-ray field were performed. The optimal operation voltage was set from the results of the collection efficiency calculation by using an experimental two-voltage method. Linearity for a variation of the steel sheet thickness, which is the most important factor for an application during a steel sheet thickness measurement, was 0.989 in this study.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.42-44
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• 2012

We have studied a means to control the composition of nickel-iron thin films. By changing current and voltage applied to a electroplating electrolyte we could manipulate the relative concentration of nickel and iron in the thin films, which caused variations of coercivity, squareness, and saturation magnetic field. As we increase the content of iron in the thin films by using potentiostatic and galvanostatic plating, the grain size was increased and the coercivity was reduced.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.566-575
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• 2008

We investigated the field emission characteristics from the planar field emitters made of double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapor deposition (CCVD) method. Transmission electron microscopy, Thermogravimetric and Raman analysis showed that the carbon materials have a low defect level in their atomic carbon structure, pointing to the synthesis of high-purity DWCNTs. For field emission properties of DWCNTs, the turn-on field of DWCNTs was $1.9\;V/{\mu}m$ and the current density was about $74\;mA/cm^2$ at $8.1\;V/{\mu}m$, which is sufficient for the applications of field emission displays and vacuum microelectronic devices. The DWCNT field emitters also exhibited a uniform field emission pattern and good field emission stability in a diode configuration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.105-109
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• 1992

ITO film, 1500${\AA}$ of thickness, onto glass and p-InP wafer was prepared by e-beam evaporator. The bet ITO film had the resistivity 5.3${\times}$10$\^$-3/ $\Omega$-cm, the concentration 6.5${\times}$10$\^$20/cm$\^$-3/, the transmittance above 80%, and the optical energy gap about 3.5eV. The higher pressure of injected oxygen, the less reverse bias saturation current and the more open circuit voltage. Under the optimum evaporation conditions, the efficiency was 7.19% and the series resistance, and the shunt resistance were respectively 8.5%, 3${\alpha}$, and 26K$\Omega$. The interdependence between activation energy and pre-exponential factor was found. We found he surface of the p-InP became n-type and consquently supposed that the buried homojunction formation, that is, n+-ITO/n-InP/p-InP was caused by Sn diffusion or loss of phosphorus in the interface layer.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.200-202
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• 1996

MgO film was deposited on the glass substrate by the hollow cathode discharge ion plating method and the characteristics of the MgO thin film such as deposition rate, crystalline orientation, surface morphology and secondary electron coefficient were investigated. The deposition rate of MgO thin films were $430^{\sim}1270{\AA}$/min at various temperatures and biases. The crystalline orientation of the MgO thin film changed from (200) to (220) upon increasing the HCD current from 100A to 200A. These results indicated that the crystallin orientation of the MgO thin film was determined by the super-saturation ratio. The (200) peak decreased and the (220) peak increased as the substrate bias increased, while both peaks increased as the substrate temperature increased. The grain size increased as the substrate bias increased and the secondary electron emission coefficient increased as the substrate bias increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.433-436
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• 2018

A total internal reflection (TIR) linear lens of size $190(W){\times}5(D){\times}2.1(H)mm^3$ has a directivity of $25^{\circ}$ and was made of a polydimethysiloxane (PDMS) silicone resin with a refractive index of 1.4 and a transmittance of 93% at 365 nm UV wavelength. A light source with a size of $190{\times}25.5mm^2$ was fabricated by installing a TIR linear lens on a chip on board (COB) type LED module mounted with a $1.1{\times}1.1mm^2$ size UV LED. The optical characteristics of the light source showed a maximum irradiation density of $3,840mW/cm^2$ at a working distance of 5 mm and a high uniformity of 91.6% over a $150{\times}25mm^2$ irradiation area. The thermal characteristics of the light source were measured at a supply current of 500 mA. The saturation temperature was reached after 30 min of operation, and measured to be $95^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.963-968
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• 2000

Magnetic properties and microstructures of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were investigated as a function of addition of element Ag, (X$\_$Ag/=0 to 6 at.%) and annealing temperature, T$\_$a/=300$\^{C}$ to 600$\^{C}$. In the case of adding Ag, magnetic properties of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were improved than those of Ag-free Fe$\_$93/Zr$_3$B$_4$thin films. The prominent soft magnetic properties with coercivity of 1.1 Oe, saturation magnetization of 2.2 T and permeability of 5400 at 50㎒ were obtained from Fe$\_$88/Zr$_3$B$_4$Ag$\_$5/ thin film annealed was lower than that of Fe-base or Co-base thin films reported previously. Such enhanced magnetic properties are presumably attributed to the format in ultra fine grains. Also, the reduced eddy current loss in the annealed sample is due to refined micro magnetic domains with increasing the amount of Ag in Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films.

• Korean Institute of Interior Design Journal
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• v.18 no.6
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• pp.229-238
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• 2009

Currently, subway is becoming a major part of transportation and living environment in large cities such as Seoul or Hong Kong. As the numbers of subway lines and stations increase, visual cues indicating places are needed for users with various destinations, and environmental colors as well as line colors can be expected as effective informations for easy wayfinding. The purpose of this study is to understand the current color applications in terms of creating regional differentiation and informing subway lines in the transfer stations of Seoul and Hong Kong, by field investigation. The investigation has been proceed on 24 transfer stations from February to April, 2009 by taking photos and measuring environmental colors using Minolta spectrophotometer CM-2600d. As a result, regional differentiation in color application appeared generally low in both Seoul and Hong Kong but various 'hues' differing each station are used in Hong Kong, compared to limited use of 'hues' in Seoul, In terms of 'value', the rate of Seoul appeared lightly higher than that of Hong Kong, and the use of medium high rate of 'saturation' of main and secondary colors are shown as a remarkable character of Hong Kong.

• Journal of Power Electronics
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• v.15 no.2
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• pp.469-478
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• 2015

In order to promote the application of switched reluctance machines (SRM) in electric vehicles (EVs), the braking torque closed-loop control of a SRM is proposed. A hysteresis current regulator with the soft chopping mode is employed to reduce the switching frequency and switching loss. A torque estimator is designed to estimate the braking torque online and to achieve braking torque feedback. A feed-forward plus saturation compensation torque regulator is designed to decrease the dynamic response time and to improve the steady-state accuracy of the braking torque. The turn-on and turn-off angles are optimized by a genetic algorithm (GA) to reduce the braking torque ripple and to improve the braking energy feedback efficiency. Finally, a simulation model and an experimental platform are built. The simulation and experimental results demonstrate the correctness of the proposed control strategy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.61-62
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• 2006

In this paper, it was demonstrated that organic thin- film transistors (OTFTs) were fabricated with the organic adhesion layer between an organic semiconductor and a gate insulator by vapor deposition polymerization (VDP) processing. In order to form polymeric film as an adhesion layer, VDP process was also introduced instead of spin-coating process, where polymeric film was co-deposited by high-vacuum thermal evaporation from 6FDA and ODA followed by curing. The saturated slop in the saturation region and the subthreshold nonlinearity in the triode region were c1early observed in the electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure. Field effect mobility, threshold voltage, and on-off current ratio in 15-nm-thick organic adhesion layer were about $0.5\;cm^2/Vs$, -1 V, and $10^6$, respectively. We also demonstrated that threshold voltage depends strongly on the delay time when a gate voltage has been applied to bias stress.