• Proceedings of the KSRS Conference
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• 2009.03a
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• pp.147-150
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• 2009

본 논문에서는 해상 클러터를 고려하여 움직이는 물체의 SAR 원시 데이터를 생성하고, SAR 원시 데이터 중간 처리 결과인 range 압축 데이터의 azimuth 차분 신호로부터 물체의 속도를 측정하는 방법을 여러 가지 환경에 적용하여 그 정확도 및 적용 가능한 경우를 분석하였다. 움직이는 물체에 의한 도플러 중심 주파수의 변이가 azimuth 차분 신호에서 위상의 변화를 가져오므로, 이를 이용하여 움직이는 물체의 속도를 측정하는 알고리듬을 정리하였다. 이 알고리듬을 위에서 생성한 range 압축 데이터에 적용하여, 타깃이 되는 물체가 독립적으로 존재하는 경우, azimuth 상에 또 다른 속도를 가지는 산란체가 존재하는 경우, 그리고 높은 후방산란계수를 가지는 육지에 타깃이 되는 물체가 인접해 있는 경우를 가정하여 속도를 측정하였다. 그 결과, 타깃이 되는 물체가 SAR 영상에서 256 픽셀 범위 내에서 독립적으로 존재할 경우에는 높은 정확도로 물체의 속도를 측정할 수 있었으나, 128 픽셀 범위에 다른 움직이는 물체가 존재하거나, 높은 후방산란 계수를 갖는 육지와 인접해 있을 경우에는 최대 1m/s 의 오차를 나타냈다. 이는 주변 산란체의 영향에 의해 신호가 교란되어 목표물의 위치를 추정하는 과정에서 오차가 발생했기 때문이다.

• Journal of IKEEE
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• v.27 no.4
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• pp.486-493
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• 2023

In this paper, we propose an automatic hand gesture area extraction and recognition technique using FMCW radar-based point cloud and LSTM. The proposed technique has the following originality compared to existing methods. First, unlike methods that use 2D images as input vectors such as existing range-dopplers, point cloud input vectors in the form of time series are intuitive input data that can recognize movement over time that occurs in front of the radar in the form of a coordinate system. Second, because the size of the input vector is small, the deep learning model used for recognition can also be designed lightly. The implementation process of the proposed technique is as follows. Using the distance, speed, and angle information measured by the FMCW radar, a point cloud containing x, y, z coordinate format and Doppler velocity information is utilized. For the gesture area, the hand gesture area is automatically extracted by identifying the start and end points of the gesture using the Doppler point obtained through speed information. The point cloud in the form of a time series corresponding to the viewpoint of the extracted gesture area is ultimately used for learning and recognition of the LSTM deep learning model used in this paper. To evaluate the objective reliability of the proposed technique, an experiment calculating MAE with other deep learning models and an experiment calculating recognition rate with existing techniques were performed and compared. As a result of the experiment, the MAE value of the time series point cloud input vector + LSTM deep learning model was calculated to be 0.262 and the recognition rate was 97.5%. The lower the MAE and the higher the recognition rate, the better the results, proving the efficiency of the technique proposed in this paper.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.519-526
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• 2002

In this paper, a microstrip patch array antenna for a Doppler radar at 10.525GHz is desinged and fabricated. To be used for mobile radar system, the antenna is fabricated on a single layer laminate to resist a fire impact and is covered with the Teflon foam. To obtain the desired characteristics, the array antenna is designed 4$\times$8 array using a corporate 3-dB amplitude taper. Also, using square patch elements, the antenna can be converted to a circular polarized antenna later. The designed and fabricated array antenna has the reflection coefficient$({S_11})$ -53.498dB, the horizontal beam width of $10^{\circ}$, the vertical beam width of $18.8^{\circ}$, the gain of 21dBi, the bandwidth of 220MHz for VSWR<1.5 and a side lobe level of less than -17.5dB.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.99-106
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• 2005

Instantaneous Frequency(IF) of Doppler signals is used to get the information of relative velocity and miss distance between a missile and the corresponding target. Though Short-Time Fourier Transform(STFT) is mainly used to estimate IF, it has many errors in wide band signals where frequency changes sharply. Because it has a fixed window in time and frequency axes. This paper deals with IF estimation of Doppler signal using a Continuous Wavelet Transform(CWT) which has adaptive window in time and frequency axes. The proposed method is able to estimate IF regardless of frequency changes because it has a narrow window in high frequency band and a wide window in low frequency band. The experimental results demonstrate that the proposed method outperforms STFT in estimating IF.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1039-1049
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• 1994

The intermitternt and transient fuel spray have been investigated from the simultaneous measurement of droplet sizes and velocities by using Phase/Doppler Particle Analyzer(PDPA). Measurement have been done on the spray axis and at the edge of the spray near nozzle at various gas-to-liquid density ratios(.rho./sub g//.rho./sub l/) that ranges from those found in free atmospheric jets to conditions typical of diesel engines. Probability density distributions of the droplet size and velocity were obtained from raw data and mathematical probability density functions which can fit the experimental distribations were extracted using the principle of maximum likelihood. In the near nozzle region on the spray axis, droplet sizes ranged from the lower limit of the measurement system to the order of nozzle diameter for all (.rho./sub g/ /.rho./sub l/) and droplet sizes tended to be small on the spray edge. At the edge of spray, average droplet velocity peaked during needle opening and needle closing. The rms intensity is greatly incresed as the radial distance from the nozzle is increased. The probability density function which can best fit the physical breakage process such as breakup of fuel drops is exponecially decreasing log-hypebolic function with 4 parameters.

• Journal of IKEEE
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• v.22 no.3
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• pp.599-604
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• 2018

A Stepped Frequency Radar(SFR) is a method that realizes high resolution range estimation by increasing the frequency of transmission pulses at regular intervals to generate a wide synthetic bandwidth. However, in the case of a moving target, accurate range estimation becomes difficult due to the range-Doppler coupling. In this paper, the process of high resolution range estimation by compensation of the range-Doppler coupling with estimated velocity of the moving target using the SFR waveform with Coherent Pulse Train(CPT) is analyzed and it was verified through simulation.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1353-1359
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• 2004

There are many massive components added on the railway overhead-line. These components cause larger fluctuations of contact forces, which are due to wave reflections and Doppler effects when a high-speed train passes those. In this paper, mathematical formula are derived for the relation between the added mass and contact force fluctuations. Using the derived formula, we calculate a added mass on the overhead-line which cause amplification factor to become 2.5. German design practice requires that amplification factor due to the wave reflection should be less than 2.5 to obtain good current collection performance. To show the validity of the formula, simulation results are compared with the calculation results. Simulation results showed that contact force fluctuations grow rapidly when an added mass is larger than the calculation result. Therefore, the simple form of formula can be used for estimating maximum added mass not to cause large fluctuations of contact forces in early design phase.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.3
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• pp.300-307
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• 2017

This study is to investigate particle size and velocity profile of gasoline port injector using Phase Doppler Particle Analyzer (PDPA). In this experiment, a GV 250 Delphi port injector used for motorcycles was used for liquid injection. The injector consists of four holes and has a static flow rate of 2.13 g/s. The fuel used in the injection was N-heptane, which is similar to gasoline, as an alternative fuel. The test fuel was injected at an atmospheric temperature of $20^{\circ}C$ and an open atmosphere of 1 atm. The injection time was 10 ms and the injection pressure was 3.5 bar in PDPA experiment. The experimental target position was fiexd at 30, 50 and 75 mm from the nozzle tip and data were collected for a total of 10,000 samples. The experimental results show that the length diameter (D10), the Sauter mean diameter ($D_{32}$), and the mean droplet velocity (MDV) are $45-54{\mu}m$, $99-115{\mu}m$ and 15-21 m/s, respectively.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.77-81
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• 2014

This paper propose a method to detect moving object and locating in real time from video sequence. first the proposed method extract moving object by differencing two consecutive frames from the video sequence. If the interval between captured two frames is long, it cause to generate fake moving object as tail of the real moving object. secondly this paper proposed method to overcome this problem by using doppler effects and HSV color model. finally the object segmentation and locating is done by combining the result that obtained from steps above. The proposed method has 99.2% of detection rate in practical and also this method is comparatively speed than other similar methods those proposed in past. Since the complexity of the algorithm is directly affects to the speed of the system, the proposed method can be used as low complexity algorithm for real time moving object detection.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.5
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• pp.455-460
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• 2012

In this paper, an experimental and numerical investigation of transition characteristics in a square-sectional curved duct flow under Centrifugal force is presented. The experimental study is carried out to measure axial velocity profiles by using Laser Doppler Velocimeter (LDV) system. Computational fluid dynamic (CFD) simulation was performed using the commercial CFD code FLUENT to investigate the transition characteristics. The flow development is found to depend upon Dean number and curvature ratio. The velocity profiles in center of the duct have lower value than those of the inner and outer walls because of the centrifugal forces.