• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.64-70
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• 2019

In this study, a compact series-fed center-fed open-stub (SFCFOS) linear array antenna for K-band applications is presented. The antenna is composed of a single-line 10-element linear array. A symmetrical Chebyshev amplitude distribution (CAD) is used to obtain a low sidelobe characteristic against a uniform amplitude distribution (UAD). The amplitude is controlled by varying the width of the microstrip patch elements, and open-ended stubs are arranged next to the last antenna element to use the energy of the radiating signal more effectively. We insert a series-fed stub between two patches and obtain a low mutual coupling for a 4.28-mm center-to-center spacing ($0.7{\lambda}$ at 21 GHz). A prototype of the antenna is fabricated and tested. The overall size of the uniform linear array is $7.04{\times}1.05{\times}0.0563{\lambda}_g^3$ and that of the Chebyshev linear array is $9.92{\times}1.48{\times}0.0793{\lambda}_g^3$. The UAD array yields a ${\mid}S_{11}{\mid}$ < -10 dB bandwidth of 1.33% (20.912-21.192 GHz) and 1.45% (20.89-21.196 GHz) for the CAD. The uniform array design gives a -23 dB return loss, and the Chebyshev array achieves a -30.68 dB return loss at the center frequency with gains of 15.3 dBi and 17 dBi, respectively. The simulated and measured results are in good agreement.

• Korean Journal of Human Ecology
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• v.21 no.4
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• pp.765-780
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• 2012

This study was investigated the clothing microclimate, subjective sensation for the improvement of traditional koran high school student uniform so called "Saenghwal Hanbok". For the purpose, casual hanbok school summer uniforms were made. They were made of 4 different textiles materials - P/R, P100, P/C, P/R/S for blouses, P/W, P100, P/R, P/W/F for skirts. Then their clothing microclimate, subjective sensation were tested at room temperature $25{\pm}1^{\circ}C$ and $50{\pm}10%$ R.H. Clothing Microclimates wearing on the blouses were good matched comfort temperature range. Subjective sensations wearing on the blouses were better than those of traditional koran clothes so called "Hanbok" and quite same for western style clothes. Thermal sensations were indicated some hot condition, and moisture sensations were indicated some wet condition but tactile sensations and comfortable sensations were agreeable. The temperatures of the forehead and the breast wearing on the skirts were indicated the same results with the cases of the blouses. Leg temperatures were some lower than the mean skin temperature, the other parts' temperatures were slightly higher than blouses but the mean skin temperatures were satisfied comfortable ranges. Subjective sensations wearing on the skirts were better than those of the other traditional clothes and even Western clothes. Thermal sensations and moisture sensations were resulted the same with the case of blouses. Currently, P/R material and P/W material seemed to be cool and respectively suitable for blouses and skirts in summer among the materials of modernized Korean traditional costumes and school uniforms, since those materials lowered skin temperature. But better, physiologically pleasant materials for summer clothes should be development in consideration of clothing microclimate and subjective sensation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.456-459
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• 2008

The purpose of this paper is to examine the aerodynamic characteristics of three hypersonic configurations including pure liftbody configuration, pure waverider configuration and liftbody integrated with waverider configuration. Hypersonic forbodies were designed based on these configurations. For the purpose to integrate with ramjet or scramjet, all the forebodies were designed integrated with hypersonic inlet. To better understand the forebody performance, three dimensional flow field calculation of these hypersonic forebodies integrated with hypersonic inlet were conducted in the design and off design conditions. The computational results show that waverider offer an aerodynamic performance advantage in the terms of higher lift-drag ratios over the other two configurations. Liftbody offer good aerodynamic performance in subsonic region. The aerodynamic performance of the liftbody integrated with waverider configuration is not comparable to that of pure waverider in the terms of lift-drag ratios and is not comparable to that of pure liftbody in subsonic. But the liftbody integrated with waverider configuration exhibit good lateral-directional and longitudinal-directional stability characteristics. Both pure waverider and liftbody integrated with waverider configuration can provide relatively uniform flow for the inlet and offer good aerodynamic characteristics in the terms of recovery coefficient of total pressure and uniformity coefficient.

• Journal of the Korean institute of surface engineering
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• v.44 no.6
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• pp.239-245
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• 2011

Magnesium alloys is the lightest by structural metals, but it is not good corrosion resistant because of pit, void. Particularly, AZ31B magnesium alloy sheets that have slag, scratch by rolling process indicate some defects. The objective of this research is to perform uniform plating on AZ31B by studying etching and zincate process. Especially, zincate treatment by zinc salt and pyrophosphate is the most important in the decoration plating. Dissolution of magnesium is reduced by the formation of uniform zinc conversion layer during strick and post process, which decreases defects for plating process.

• Fashion & Textile Research Journal
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• v.8 no.1
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• pp.25-33
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• 2006

As the cultures of the world are getting diverse and plural, many trials to find their own unique culture of their own national and racial characteristics are made where fashion and traditional culture is used as good materials; in Korea, this trend is also studied by many authors. To achieve this goal, this study recognized the importance of tourism industry by inviting hosting of international event like '2005 APEC Summit Conference and Economical Ministers' Conference', and invented a uniform design that can make identification in the world market including Korea 'Gust' and 'Emotion' in developing uniforms for employees of regular traditional restaurant or hotels that contribute to tourism industry. As a material of this study from this perspective, Soo Bok pattern among many other Korean traditional patterns were chosen, and used them to design uniforms by applying diverse expressions methods through modernization task. This study tried to suggest ideas in creating new designs with a modeling sense of our people, by emphasizing on tradition motive through analysis of conditions and problem regarding the current uniforms worn in traditional restaurants. The development of uniform that modernly reinterprets traditional patterns and design that uses tradition on modern design shows endless possibility of development of our uniform, and even shows the possibility of mixture between tradition and modernity. By applying traditional beauty not only in traditional restaurants but also in many places and businesses that foreigners frequently visit can allow to spread the excellency our culture; and the Korean uniform can be successful in the international market as Korean will have pride in our tradition by wearing this new uniform.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.42-47
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• 2019

This paper introduces a modified Wilkinson power divider that uses uniform transmission lines for various terminated impedances and an arbitrary power ratio. For the designed power ratio, the proposed divider changes only the electrical lengths of the transmission lines between the input and output ports, and those between the output ports and the isolation resistor. In this case, even when various termination impedances of the ports exist, the divider characteristics are satisfied. To verify the feasibility of the proposed divider, two circuits were designed to operate at a frequency of 2 GHz with 2:1 and 4:1 power splitting ratios and various terminated impedances of 40, 70, and $60{\Omega}$ for one circuit, and 50, 70, and $60{\Omega}$ for the other. The measurement and simulation results were in good agreement.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1068-1071
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• 2004

We report the techniques to obtain the high uniformity of the phosphor film thickness in the cold cathode fluorescent lamps, which are widely used as a back-light for the liquid crystal display. The thickness variation of the phosphor layer was sensitive to blowing conditions. The optimum conditions were obtained at flow rate of 15 sccm for 30 min at 40 $^{\circ}C$. The optimum and uniform thickness of a phosphor layer gives good luminous output.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.579-584
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• 2005

Unsteady state free natural gas jets injected from several types of injectors were numerically simulated. Simulations showed good agreements with the schlieren experimental results. Moreover, injections of natural gas in intake manifolds of a single-valve engine and a double-valve engine were predicted as well. Predictions revealed that large volumetric injections of natural gas in intake manifolds led to strong impingement of natural gas with the intake valves, which as a result, gave rise to pronounced backward reflection of natural gas towards the inlets of intake manifolds, together with significant increase in pressure in intake manifold. Based on our simulations, we speculated that for engines with short intake manifolds, reflections of the mixture of natural gas and air were likely to approach the inlets of intake manifolds and subsequently be inbreathed into other cylinders, resulting in non-uniform mixture distributions between the cylinders. For engines with long intake manifolds, inasmuch as the degrees of intake interferences between the cylinders were not identical in light of the ignition sequences, non-uniform intake charge distributions between the cylinders would occur.

• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.199-207
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• 1997

$Al_2O_3$/SiC particulate composites were fabircated by pressureless sintering. The dispersed phase was SiC of which the content was varied from 1.0 to 10 vol%. Three SiC powders having different median diameters from 0.28 $\mu\textrm{m}$ to 1.9 $\mu\textrm{m}$ were used. The microstructure became finer and more uniform as the SiC content increased except the 10 vol% specimens, which were sintered at a higher temperature. Under the same sintering condition, densification as well as grain growth was retarded more severly when the SiC content was higher or the SiC particle size was smaller. The highest flexural strength obtained at 5.0 vol% SiC regardless of the SiC particle size seemed to be owing to the finer and more uniform microstructures of the specimens. Annealing of the specimens at $1300^{\circ}C$ improved the strength in general and this annealing effect was good for the specimens containing as low as 1.0 vol% of SiC. Fracture toughness did not change appreciably with the SiC content but, for the composites containing 10 vol% SiC, a significantly higher toughness was obtained with the specimen containing 1.9$\mu\textrm{m}$ SiC particles.

• Journal of Information Display
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• v.9 no.4
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• pp.6-10
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• 2008

In this study, the selective-wettability-inscription (SWI) technique for the wet-etchingless fabrication of surface microstructures applicable to wide-viewing liquid crystal displays (LCDs) on plastic substrates was demonstrated. On the basis of the selective wetting of the photopolymer, the bi-level microstructures were spontaneously formed to serve as spacers for maintaining uniform cell gap and protrusions for the generation of multi-domains. The LC cell that has bi-level microstructures shows good extinction in the field-off state and a wide-viewing property in the field-on state. The SWI technique would be useful for the fabrication of flexible displays on plastic substrates.