• Journal of Korean Society of Transportation
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• v.16 no.3
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• pp.101-111
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• 1998

현재 고속도로 교통관리시스템(FTMS)에 사용되고 있는 차량 검지기는 주로 루프 식 검지기가 이용되고 있으나, 유지관리에 많은 어려움이 있다. 본 연구에서는 이러한 문제 점을 갖고 있는 루프 검지기를 대체하기 위한 대체 검지기를 개발하는데 그 목적이 있다. 자기 검지기 신뢰도 평가는 현장 실험으로 이루어지며 비디오 촬영 및 루프 검지기, test car를 이용하여 교통량·속도·점유율의 기준자료를 마련하고 자기 검지기 자료와 비교·분석 및 통계적 검정을 실시하였다. 1차 실험과 2차 실험의 결과, 교통량과 속도는 실측자료와 유사했으나 점유율은 실측치와 다소 차이가 발생함을 보였다. 향후 점유율에 대한 보정이 이루어진다면 현재 사용중인 루프 검지기를 대체할 수 있을 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.8
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• pp.662-670
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• 2018

The altitude compensation nozzle is a nozzle designed for optimum performance at all altitudes. A method of improving the specific impulse of the space launch vehicle is a method of improving the characteristic exhaust velocity which is a characteristic of the combustion chamber and a method of improving the thrust coefficient which is a characteristic of the nozzle. The altitude compensation nozzle enables improvement of the performance of the space launch vehicle by improving the nozzle performance for the same combustor. Research on altitude compensation nozzles has been actively carried out in the DLR in Germany and is being carried out in advanced countries such as the US, Russia, UK, Australia and Japan. In this paper, the technology trends and patent trends of altitude compensation nozzles are investigated and summarized. Based on this, the technical trends of altitude compensation nozzles is grasped and utilized as basic data for the study on the performance improvement of a launch vehicle.

• Journal of radiological science and technology
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• v.39 no.3
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• pp.377-384
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• 2016

This is a study on the optimized dispensing of the auto dispenser used for the purpose of reducing the exposure dose and accurate radiation dose of radioisotope with regard to the PET/CT practitioners. The research method was to find the optimized dispensing method through evaluating the results according to the syringe type, dispensing rate, and vial pressure and through the application of corrected values. As a result of this study, 9.38 mCi has been dispensed on average in the case of 5 ml syringe, and the reproducibility close to 10 mCi was shown at the dispense of 9.55 mCi in the case of 3 ml syringe. In the evaluation according to the dispensing rate, the quantity of radioisotope close to 10 mCi was dispensed at the rate of 5 mm/min when the measurement was carried out by increasing the rate by 5 mm/min units in the order of 5, 10, 15 and 20 mm/min. In the evaluation result according to the vial pressure before/after the use of Needle filter, it was measured to be 9.53 mCi before use and 9.84 mCi after use confirming that the dispensing after using Needle filter showed the optimal value. In addition, in the evaluation of radioactivity before/after the application of corrected values according to the increase in dispense frequency, it was measured 9.53 mCi before correction and 10.07 mCi after correction confirming that the value with correction applied was closer to the quantitative value. Thus, a good optimized method was confirmed to use a 3 ml syringe with dispensing rate of 5 mm/min, to use a Needle filter at dispensing, and to set the corrected value of [$y=0.097{\times}x$] according to the dispensing frequency of equipment.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.36-43
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• 2010

A GEO satellite launched by Arian 5 ECA launcher will be located in a transfer orbit where it requires several Apogee burn maneuvers to reach the target orbit. To obtain the required performance of Apogee burn maneuvers, a calibration of gyro drift error needs to be performed before each maneuver. In this paper, a unique gyro calibration scheme which is applied to COMS is described and the calibration error budget analysis is performed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.27-33
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• 2004

In this paper, we present a carrier recovery circuit using the polarity-decision algorithm that recovers a phase and a frequency error simultaneously. The proposed algorithm catches a frequency error based on a differential of an angular velocity of the signal constellations. Using the differential of a phase error may compensate the frequency error. The symbol prediction method in the proposed algorithm accumulates the symbols, which makes easy to calculate a phase differential. The hardware size of the algerian is small since we use Q data or I only to get phase information. As a result, the algerian shows a pull-in range of normalized frequency error 0.5 under AWGN 15dB.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.291-295
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• 2008

In this paper, we propose an input image reduction method to solve the problems of Radon transform which is a line structure analysis tool to correct a rotated object through a vision system. First we extract an object image removed background from the input image. Then we also select a reduced object image as a final input mage of Radon transform from the object image by considering slope. Finally we extract a rotated angle by using Radon transform with the final input image and correct the rotated object with the angle. In experimental results, we could improve the process time of about 64%, reduce the memory space of about 18% and make progress the line detection rate of about 18%.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.237-249
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• 2003

Wind effects on a rain gauge can cause a significant underestimation of rainfall depths and contribute to the inconsistency in rainfall data. To revise the rainfall data requires the study about calculation of deficiency percentages of rain catch. There are few studies which reflect the variation of wind speed. in this study, the raindrop terminal velocity is quantified according to the particle size of rainfall. The model for calculating deficiency percentages of rain catch according to the particle size of rainfall is examined by experimentation. Experimentation shows that deficiency percentages of rain catch have no relationship with rainfall intensity and affected by raindrop diameter. In conclusion, the estimated deficiency percentages of rain catch coincided with the experimental results and can be used as recommended adjustment factors.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.4
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• pp.245-251
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• 2019

Sonar bearing accuracy is the correspondence between the target orientation predicted by sonar and actual target orientation, and is obtained from measurements. However, when measuring sonar bearing accuracy, many errors are included in the results because they are made at sea, where complex and diverse environmental factors are applied. In particular, parallax error caused by the difference between the position of the GPS receiver and the sonar sensor, and the time delay error generated between the speed of underwater sound waves and the speed of electromagnetic waves in the air have a great influence on the accuracy. Correcting these parallax errors and time delay errors without an automated tool is a laborious task. Therefore, in this study, we propose a sonar bearing accuracy measurement equipment with parallax error and time delay error correction. The tests were carried out through simulation data and real data. As a result of the test it was confirmed that the parallax error and time delay error were systematically corrected so that 51.7% for simulation data and more than 18.5% for real data. The proposed method is expected to improve the efficiency and accuracy of sonar system detection performance verification in the future.

• Geophysics and Geophysical Exploration
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• v.16 no.2
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• pp.71-78
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• 2013

The one-way wave equation migration is much more computationally efficient comparing with reverse time migration and it can provide better image than the migration algorithm based on the ray theory. We have developed the prestack depth migration module adopting (GS) propagator designed for vertical transverse isotropic media. Since GS propagator considers the higher-order term by expanding the Taylor series of the vertical slowness in the thin slab of the phase-screen propagator, the GS migration can offer more correct image for the complex subsurface with large lateral velocity variation or steep dip. To verify the validity of the developed GS migration module, we analyzed the accuracy with the order of the GS propagator for VTI media (GSVTI propagator) and confirmed that the accuracy of the wavefield propagation with the wide angles increases as the order of the GS propagator increases. Using the synthetic seismic data, we compared the migration results obtained from the isotropic GS migration module with the anisotropic GS migration module. The results show that the anisotropic GS migration provides better images and the improvement is more evident on steeply dipping structures and in a strongly anisotropic medium.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.886-890
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• 2011

Induction motors are relatively cheap and rugged machines. For the vector control of induction motors, a position or speed sensor is needed. But a speed sensor increases motor cost and reduces reliability in harsh environment. Recently, many studies have been performed for sensorless speed control. This paper investigates an improved flux observer with the parameter error compensation for a sensorless induction motor. The proposed algorithm is verified through simulation and experiment.