• Journal of the korean Society of Automotive Engineers
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• v.15 no.3
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• pp.47-54
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• 1993

This paper describes briefly the effect of ultrasonic fuel supply device on the performance of four stroke cycle gasoline engine. Experiments were carried out to clarify the effect of ultrasonic fuel supply device on the engine output, traveling fuel consumption ratio, exhaust emissions. The results were obtained as follows: 1.Engine output was increased 9-14% in comparison with that of the conventional injector. 2.Travelling fuel consumption ratio was improved 17-29% in comparison with that of the conventional injector. 3. CO, HC exhaust emissions was decreased compared to the value of the conventional injector. 4.Fuel consumption ratio in highway driving test was improved about 10% in comparison with that of the conventional injector.

• Journal of Digital Contents Society
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• v.10 no.3
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• pp.389-393
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• 2009

In this paper, the single patch microstrip antenna and gap coupled broadband microstrip patch antenna using FDTD(Finite Difference Time Domain method) are analyzed. Mur's 2nd absorbing boundary condition to minimize reflected wave is applied. Return loss, voltage standing wave ratio, and input impedance by the length and width of driving patch, the length and width of parasitic patch, and the distance between driving patch and parasitic patch have been analyzed. Design parameters and radiation patterns of broadband antenna have been also shown.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.2
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• pp.105-112
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• 2018

This paper manufactured an active GPS antenna for ground vehicles and presented a method to verify the performances of the antenna and component technology of the low noise amplifier (LNA) board manufacturing. The manufactured GPS antenna is an active antenna where microstrip patch and LNA board were combined. The main performances were standing wave ratio, antenna gain, and axial ratio, and all satisfied the target specifications. The proposed component technology can be utilized as a basis data in which the performance of LNA board can be compensated in the mass production process inspection, and employed as a method to verify whether antennas are properly working in environmental tests.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.902-905
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• 2006

This paper presents a new RF testing scheme based on a design-for-testability (DFT) method for measuring functional specifications of RF integrated circuits (IC). The proposed method provides input impedance. gain, noise figure. input voltage standing wave ratio (VSWR) and output signal-to-noise ratio (SNR) of a low noise amplifier (LNA). The RF test scheme is based on theoretical expressions that produce the actual RF device specifications by output DC voltages from the DR chip.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.668-677
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• 1998

This paper is to verify the availability of the finite difference time domain (FDTD) method for the analysis of millimeter wave microstrip patch antenna. Using this method, the size of the microstrip patch antenna resonating at 32.153 GHz is optimized and the input impedance, the voltage standing wave ratio and the radiation pattern are calculated. The resonance frequencies of the microstrip patch antenna are calculated by MOM and FDTD method and then compared with the measured results, showing the difference of 12.27% and 1.27% respectively. Also, the bandwidth of this Ka-band patch antenna is about 8% which is similar to the case of X-band.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.324-338
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• 2015

Analytical solutions for interaction between seabed and waves such as progressive wave or partial standing wave with arbitrary reflection ratio or standing wave have been developed by many researchers including Lee et al.(2014; 2015a; 2015b; 2015c; 2015d) and Yamamoto et al.(1978). They handled the pore-water pressure as oscillating pore-water pressure and residual pore-water pressure separately and discussed the seabed response on each pore-water pressure. However, based on field observations and laboratory experiments, the oscillating and residual pore-water pressures in the seabed do occur not separately but together at the same time. Therefore, the pore-water pressure should be investigated from a total pore-water pressure point of view. Thus, in this paper, the wave-induced seabed response including liquefaction depth was discussed among oscillating, residual, and total pore-water pressures' point of view according to the variation of wave, seabed, and flow conditions. From the results, in the field of flow with the same direction of progressive wave, the following seabed response has been identified; with increase of flow velocity, the dimensionless oscillating pore-water pressure increases, but the dimensionless residual pore-water pressure decreases, and consequently the dimensionless total pore-water pressure and the dimensionless liquefaction depth decrease.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1484-1486
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• 1998

Recently, extending the local broadcasting and increasing lots of informations, the low-loss communication cable is required in proportion as frequency. The reason of transportation loss causes to using the high frequencies like hundreds of MHz or decades of GHz. For the low transportation loss, it is required the developing-technology of foaming and the high foamed insulator with the dielectric ratio of the nearest to 1. Therefore, there is the purpose of developing the insulating materials for the low dielectric ratio. Also it is important to measure the attenuation, which is one of the important parameters, as the evaluation of transportation characteristic with frequency in the communication cable. In this paper, the result showed that the dielectric ratio(1.4) of the nearest to 1 and low attenuation with high frequency were very related to the transportation and reflection characteristics such as propagation velocity(82.27%), delay time and voltage standing wave ratio(VSWR).

• Korean Journal of Oriental Medicine
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• v.16 no.1
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• pp.157-171
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• 2010

This study aimed to investigate the effect of four common types of Qigong position (standing, sitting, supine, and horse-riding position) on the autonomic nervous system. Thirty healthy subjects participated in this study once a week for four weeks. Electroencephalogram (EEG) was measured three times (before, during, and after the position) while the subject maintained one of four positions for ten minutes. There were significant changes in HRV components compared with EEG power spectra in the standing position. Especially, the ratio of low-to-high frequency (LF/HF) which represents a state of balance of autonomic nervous system was increased. In the sitting position, $\beta$ wave which reflects a state of alert consciousness was increased and both the sympathetic and parasympathetic nerves were activated. On the other hand, in the spine position, $\theta$ wave which signifies a state of relaxation was increased and heart rate (HR) was decreased. Activation of sympathetic and parasympathetic nerves was also observed in this position. Significant increases of indices related to awakening and concentration were observed accompanied by increase of HR and a sympathetic nerve was activated in the riding-horse position. In the present study, it was shown that each Qigong position caused various and significant changes in autonomic nervous system. It would be expected that these results can be applied in the choice of appropriate Qigong position according to objective of Qigong therapy although it is remained to further evaluate the effects of long-term maintenance of Qigong positions and repeated Qigong training.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.134.2-134.2
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• 2017

최근 고성능, 저 전력 반도체 소자를 위한 미세 공정 기술이 발전함에 따라, gate oxide의 두께 및 선폭이 감소하고, aspect ratio가 증가하고 있는 추세이다. 따라서 얇아진 gate oxide를 통한 채널 물질로의 boron 확산을 막기 위한 고농도 질화 막 증착의 필요성이 높아지고 있으며, high aspect ratio의 gate oxide에 적용 가능한 우수한 step coverage의 질화막 또한 요구되고 있다. 이러한 요구조건을 만족시키기 위해 일반적인 13.56MHz의 플라즈마 소스를 이용한 질화연구들이 선행되어져 왔으나, 높은 binding energy(~24 eV)를 가지고 있는 N2 molecule gas를 효과적으로 dissociation 하지 못해 충분한 질화공정이 수행되어질 수 없었을 뿐만 아니라 높은 공정온도($>200^{\circ}C$에서 진행되어 반도체소자에 손상을 줄 수 있다. 본 연구에서는 이러한 문제들을 해결하기 위해 VHF (162MHz)를 이용한 플라즈마를 통해 고밀도에서 낮은 전자온도와 높은 진동온도의 플라즈마를 구현하여 20%이상의 높은 질화율을 얻을 수 있었고, multi-tile push-pull 플라즈마 소스를 통해 VHF 사용 시 나타나는 standing wave effect를 제어하여 high aspect ratio의 gate sidewall spacer에 우수한 step coverage의 질화막을 형성시킬 수 있었다.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.518-520
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• 2005

Effects of the $O_2/Ar$ flow ratio in the sputtering process on the crystallinity, surface roughness, carrier concentration, carrier mobility, and optical properties of Al-doped ZnO thin films deposited on sapphire (001) substrates by RF magnetron sputtering were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM of the (002) XRD intensity peak for the $O_2/Ar$ flow ratio of 0.5. The (101)peak also appeared and the degree of preferred orientation decreased as the $O_2/Ar$ flow ratio increased from 0.5 to 1.0. AFM analysis results showed that the surface roughness was lowest at the $O_2/Ar$ flow ratio of 0.5 and tended to increase owing to the increase of the grain size as the $O_2/Ar$ flow ratio increased further. According to the Hall measurement results the carrier concentration and carrier mobility of the fan decreased and thus the resistivity increased as the $O_2/Ar$ flow ratio increased. The transmittance of the ZnO:Al film deposited on the glass substrate was characteristic of a standing wave. The transmittance increased as the $O_2/Ar$ flow ratio in-RF magnetron sputtering increased up to 0.5. Considering the effects of the $O_2/Ar$ flow ratio on the surface roughness, electrical resistivity and transmittance properties of the ZnO:Al film the optimum $O_2/Ar$ flow ratio was 0.5 in the RF magnetron sputter deposition of the ZnO:Al film.