• Journal of Biosystems Engineering
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• 제25권3호
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• pp.233-240
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• 2000

A commercially available Doppler radar was modified and evaluated for on-board monitoring of ground speed. The radar output was corrected for pitch angle of aircraft based on the output of an electrolytic tilt sensor. The effects of aircraft speed, height and mounting angle on error in the ground speed were evaluated. The speed error decreased with an increase of the mounting angle since the radar contact angle with respect to the ground approached to the mounting angle. The error increased with an increase of the nominal aircraft speed. The altitude insignificantly affected the speed error. The Doppler radar provided acceptable percent errors within 5% in most measurements. The error can be reduced within ${\pm}$1.5% by increasing the mounting angle ($43^{\circ}$). The error of -3.8% at the mounting angle of $29^{\circ}$could be reduced by adjusting the mounting angle with respect to the radar contact angle.

• 한국유체기계학회 논문집
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• 제4권2호
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• pp.22-28
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• 2001

This study was performed to evaluate the dynamic behavior of turbo pump unit. The acceptable separate margin of $1^{st}$ critical speed was obtained by the use of elastic-ring inserted ball bearing, while the poor separate margin of $1^{\st}$ critical speed was appeared in the case without the elastic-ring. In addition, the results show that the stiffness and damping of plain seals give more separate margin of $2^{nd}$ critical speed. However the wear or the failure of seals could reduce the $2^{nd}$ critical speed near the operating speed.

• 한국도로학회논문집
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• 제14권2호
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• pp.165-174
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• 2012

본 연구에서는 차량검지기의 속도측정 성능평가방법을 개발하였다. 개발된 성능평가방법에서는 오차요인들을 기준속도에 반영하며 측정불확도의 개념을 적용하였다. 기존연구, 통계적 처리기법, 기존교통단속장비 및 차량검지시스템의 속도측정 성능평가방법 등에 대한 고찰을 통해 기존평가방법의 문제점을 도출하고 개선된 성능평가방법을 개발하였다, 실제 현장에 설치된 차량검지기에 대해서 기존평가방법과 개발방법을 적용해본 결과 기존평가방법은 평가기준에 적합하나 개발방법은 평가기준을 만족시키지 못하고 있다. 이러한 결과는 기존성능평가방법이 측정 시의 오차요인들을 충분히 고려하지 못해서 평가대상장비의 성능을 고평가할 가능성이 있음을 의미하며, 반면에 개발모형은 측정 시의 변동요인인 오차를 고려하므로 기존평가방법 보다 정확함을 나타낸다.

• Tribology and Lubricants
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• 제22권1호
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• pp.33-39
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• 2006

During the high speed train operation in the conventional line, it was found to have extremely severe flange wear, due to the curvy routes. This paper looks at the actions that have been taken to bring the wear to an acceptable level. In particular, it have been presented for flange wear variation depending on curve radius, cant, transition curve length by using numerical method. And the impacts on the flange wear by the application of stick type solid lubricant are also presented.

• International Journal of Korean Welding Society
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• 제1권1호
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• pp.13-16
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• 2001

High speed seam weldability of tin coated steels was investigated. Welding was performed by the laboratory wire seam welder that was equipped with process monitoring system Test results showed that increase in applied current and pressure reduced the total resistance across the welding electrodes. Lower and upper limits of welding current increased as the sheet thickness increased, while the acceptable welding condition range decreased. However, extremely low electrode pressure produced unstable welding condition range. The results also demonstrated that slower welding speeds widened the optimum welding heat input range.

• 자동차안전학회지
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• 제7권3호
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• pp.30-34
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• 2015

This study examined the Korean drivers' acceptance of SAS(Speed Assistance systems) and traffic sign conditions in Korea roads for SLIF(Speed Limit Information Function) that is a part of SAS. Exceeding the speed limit is a factor in the severity of many road accidents and SAS would help the driver to observe a speed limit by warning and/or effectively limiting the speed of the vehicle. SAS are in the initial phase in Korea, Korean drivers could not be familiar with automatical speed limiting during driving, SAS interface design would be considered to be more readily acceptable to the public. And advanced SAS have been introduced onto the market which are able to inform the driver of the current speed limit based on camera and/or digital maps based SLIF. These systems are based on external data using sensors, so environmental conditions are an important factor which could cause malfunction of SLIF functions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.635-638
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• 2002

Blowfish is a symmetric block cipher that can be used as a drop-in replacement fur DES or IDEA. It takes a variable-length key, from 32bit to 448bit, making it ideal for both domestic and exportable use. This paper is somewhere middle-of-the-line, where this paper made significant tradeoffs between speed, size and ease of implementation. The main focus was to make an implementation that was usable, moderately compact, and would still run at an acceptable clock speed. For the real time process of blowfish, it is required that high-speed operation and small size hardware. So, A structure of new adders constructed in this study has all advantages abstracted from other adders. As for this new adder, area cost increases by 1.06 times and operation speed increases by 1.42 times.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.735-743
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• 2001

This study was performed to evaluate the dynamic behavior of turbo pump unit. The acceptable separate margin of 1st critical speed was obtained by the use of elastic-ring inserted ball bearing, while the poor separate margin of 1$\^$st/ critical speed was appeared in the case without the elastic-ring. In addition, the results show that the stiffness and damping of plain seals gain more separate margin of 2nd critical speed. However the wear or the failure of seals could reduce the 2$\^$nd/ critical speeds near the operating speed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.150-151
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• 2017

This paper deals with the suppression of subharmonic current oscillation of V/F controlled high speed induction motor drive in turbo blower applications. High speed induction motor has a relatively low stator impedance for high speed operation and therefore the dc link voltage ripple may result in subharmonic current oscillation at the steady state in high speed operation. This paper shows that the subharmonic oscillation is caused by the dc link voltage ripple and also proposes the suppression method, which generates the compensation voltage through the proportional current controller to reduce the subharmonic current oscillation. The simulation and experimental results show that the proposed suppression method reduces the subharmonic current oscillation to the acceptable low level in turbo blower applications.

• Journal of Welding and Joining
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• 제15권6호
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• pp.49-56
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• 1997

Effect of process parameters on the quality of condenser discharge weld for coated sheet steels was discussed. The welding specimens were coated with pure Zn of 20/20 g/m2 in the production line. Direct measurements of welding parameters such as the discharge current, the pressures and the voltage drop across the electrodes were carried out with welding process monitoring system. High speed camera was also utilized to analyze the weld formation process. Test results indicated that the relation between weld strength and applied energy was stabilized at the acceptable welding heat input range. It was thought that the acceptable welding heat input should be redefined based on the monitored data because the calculated value of the welding heat input could hardly be utilized if the discharge condition was changed. Mechanical test results and high speed photographs showed that expulsion deteriorated the weld quality and the strength at the same time especially when the size of the spatter was large enough to carry the molten metal, which should form the nugget, out of the welding spot. Results also demonstrated that the discharge current should be applied at the appropriate time during the process because sufficient nugget was not produced if the time was deviated from the optimum range.