• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.1003-1009
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• 2005

In this paper, small-size high-power single pole double throw(SPDT) switch with defected pound structure(DGS) is presented for wireless broadband internet application. To reduce the circuit size using slow-wave characteristic, the DGS is applied to ${\lambda}/4$ transmission line of the switch and the measured results are compared with them of conventional switch. To secure high degree of isolation, the switch with the DGS is composed of shunt-connected PIN diodes and shows insertion loss of 0.8 dB and isolation more than 50 dB at 2.3 GHz. The size of the switch is reduced about $50\%$ only with the DGS patterns while it has very similar performance to the conventional shunt-type switch.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.90-95
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• 2006

For single engine application like T-50, advanced supersonic jet trainer, airstart capability is very important. This paper presents the results of airstart tests performed to verify T-50 airstart capability for various flight condition. The tests include spooldown, APU assisted and auto-relight airstart tests. Except for the auto-relight tests T-50 engine was successfully restarted for all airstart tests. After modifying FADEC flameout detection schedule, auto-relight tests also were successfully demonstrated. Through T-50 engine airstart tests excellent T-50 airstart capability was validated.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.91-97
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• 2013

In this paper, a current steering 10-bit CMOS D/A converter to drive a NTSC/PAL analog TV is proposed. The proposed D/A converter has a 50MS/s operating speed with a 6+4 segmented type. Further, in order to minimize the device mismatch, a self-calibration bias technique with a fully integrated termination resistance is discussed. The chip has been fabricated with a 3.3V 0.11um 1-poly 6-metal CMOS technology. The effective chip area is $0.35mm^2$ and power consumption is about 88mW. The experimental result of SFDR is 63.1dB, when the input frequency is 1MHz at the 50MHz of sampling frequency.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.1
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• pp.161-167
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• 2001

The purpose of this study is to find out the difference of Zoysia matrella's evaporation in between 100 percent soil and mixed soil with 50 percent of perlite to create green spaces on the artificial ground. It is believed that the weight against the artificial ground will be reduced, provided the vegetation is possible in the circumstance of the mixed sol with 50 percent of perlite. The study employed a modified Makkink's model by Iwasa who had developed the model for estimating Zoysia matrella's evaporation in the natural ground using the Makkink's formula in 1997 at Chiba University, Japan. The parameter of Makkink's formula is the solar radiation. For that reason, the Makkink's formula is simple and easy to measure the parameter and has a high utility. If the outcomes from mixed soil are close to modified Makkinks formula, the modified Makkink's formula will be applied to estimate in the artificial ground with mixed soil with 50 percent of perlite. Weather observation and actual amount of evaporation of Zoysia matrella have been measured, and the relation between weather condition and actual amount of evaporation had been also investigated. In line with this, we found out that there is a relevant relationship between daily average temperature, the modified Makkink's model by Iwasa, and the actual amount of evaporation. As the results of the experiment, the outcomes from mixed soil with 50 percent of perlite have very high relation to 100 percent soil. In addition, mixed soil has more adhesion with water than natural soil. However, it needs to be adequately maintained in terms of fertilization and damage from disease and harmful insects until the gras fastens its roots into the soil. By using mixed soil with 50 percent of perlite, the load from soil on the artificial ground can be reduced. The study on the growth of the grass throughout the plant vegetation and the actual amount of evaporation in the mixed soil with 50 percent of perlite should be performed in the future.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.25-34
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• 2005

The governing design point of shallow foundation is not its bearing capacity but its settlemen and N-value by the SPT is one of the key parameters for settlement estimation. However, if the N-value is more than 50/30, such as 50/10 or 50/20, the N-vlaues are not blow count of 30cm depth penetration. In these cases, the estimated settlements have big difference with the measured values because the applied maximum N value for the settlement estimation is 50. Therefore, in this study, the modified method for N-value estimation is suggested. The settlements by four methods, which are based on Elastic Theory with application of modified N-value, are compared with the Origina Plate Load Test data. The same comparision was carried out with another seven Empirical Methods. The result of this study showed that the error range of settlement is decreased from 260.4~2136.5% to 20.3~272.7%. Among four methods which are based on Elastic Theory, the original method by Elastic Theory is the most accurate with the application of modified N-value. Among Empirical Methods, Terzaghi-Peck's(1948, 1967) modified method 1 is the most accurate with the application of modified N-value. The differences between the original method by Elastic Theory and Terzaghi-Peck's(1948, 1967) modified method 1 are neglectable.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.799-802
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• 2002

Korea Aerospace Research Institute has been developing a 50-meter class airship to demonstrate the technology to be used in the development of a stratospheric airship, and importance of accurate prediction of the dynamic behavior of an airship before flight test is widely conceived. The added mass has large impact on the dynamic characteristics of an airship unlike for an airplane and the added mass of the airship with empennage is predicted in this paper. At first, the usability of the strip theory is examined which integrates the analytic two dimensional results in the cross section along the longitudinal axis. A panel method with the surface distribution of sources is developed and its validity is also examined. Finally, the panel method with both source and doublet distributions is implemented, and it is validated and applied for the calculation of the added mass of a 50-meter class airship. Using the methods developed, the influence of empennage and control surface deflection on the added mass property of the airship is studied.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.786-791
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• 2013

A high voltage pulse generator based on the Blumlein pulse forming line (PFL) was fabricated to produce a voltage pulse whose peak value is ~300 kV and pulse duration is ~50 ns. Three cylindrical electrodes, such as inner, middle, and outer electrodes, are concentrically placed to make a compact PFL. To increase the pulse duration of the output pulse without any change of the size of the generator, the middle electrode is replaced by a helical strip electrode. To determine the radius of the helical electrode, the impedance of the helical Blumlein PFL is calculated using an approximate formula where the dispersive property of the helical Blumlein PFL is not considered. The dependence of the impedance on the frequency is computed by a commercial program. The number of turns in the helical electrode is decided to provide a demanded pulse duration. The experimental result shows that the helical Blumlein PFL is capable of making a high voltage pulse of ~50 ns pulse duration.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.909-912
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• 2001

This paper presents the validities of the removal time of side forms considering the relationship between rebound number of P type schmidt hammer and compressive strength. According to test results, compressive strength of 40% of W/C at 12 hours shows 16kgf/$cm^{2}$ and 50% of W/C at 15 hours, 13kgf/$cm^{2}$. Rebound number at 9 hours after casting shows 13 and 9 (W/C 40% and W/C 50%). According to the regression analysis, rebound number of P type schmidt hammer to gain 50kgf/$cm^{2}$ of is estimated 20.1. It is thought that desirable rebound number of P type schmidt hammer to gain 50kgf/$cm^{2}$ is determined 25 considering safety factor.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.131-135
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• 2006

The aerodynamic characteristics of a T-50 aircraft configuration are investigated by a subsonic panel method. Panel methods are best applicable to the lifting surfaces such as wings and airfoils. Source and doublets are used in the present code as a basic singularities of the panel technique. The panel method is first assessed by applying it to several benchmark problems for which other solutions and experimental data are available, such as a swept wing and wing body configuration. The prediction results are compared with experimental data and show good agreement in all cases considered. Finally, the method is applied to a T-50 aircraft configuration and excellent agreement with flight test data in lift coefficients is found.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1378-1381
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• 2003

Recently, high-performance composite materials have been used for various industrial fields because of their superior high strength, high stiffness and lower weight. In this study, manufactured fiber reinforced metal laminate materials are composed of two parts. One is hard-anodized A15083-O alloy as a face material and the other is high strength aramid fiber (Twaron CT709) and polyethylene fiber(Dyneema HB25) laminates as a back-up material. Resistance to penetration is determined by protection ballistic limit(V$\sub$50/, a static velocity with 50% probability for complete penetration) test method. V$\sub$50/ tests with 0$^{\circ}$ obliquity at room temperature were conducted with 5.56mm ball projectiles that were able to achieve near or complete penetration during high velocity impact tests.