• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.151-157
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• 2004

Ultrasonic testing is a kind of nondestructive test to detect a crack or discontinuity in materials or on material surfaces by sending ultrasound to it. This conventional ultrasonic technique has some limitations in reliably detecting crack or accurately assessing materials in the case of complex-shaped power plant components such as a turbine blade root. An alternative method for such a difficult inspection is highly needed. In this study, application of a phased array ultrasonic testing (UT) system to a turbine blade, one of the critical power plant components, has been considered, and the particular incident angle has been determined so that the greatest track detectability and the most accurate crack length evaluation nay be achieved. The response of ultrasonic phased array was also analyzed to establish a special method to determine the track )ength without moving the transducer. The result showed that the developed method for crack length assessment is a more accurate and effective method, compared with the conventional method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.237-245
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• 2017

In this paper, a monopulse sensor which determines a target location using amplitude-comparison monopulse technique is presented. This sensor can allow the missile to track the target when additional jamming signals are not presented. Then, we applied the spot noise jamming technique to the monopulse sensor. Based on the simulation results, we can effectively figure out the performances of the spot noise jamming technique for the monopulse sensor in various jamming scenarios.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.532-539
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• 2018

A position estimation technique is presented for a missile using high-resolution range profiles obtained by three wideband radars. Radar measures a target range using a reflected signal from the surface of a missile. However, it is difficult to obtain the range between the radar and the origin of the missile. For this reason, the interior angle between the moving missile and tracking radar is calculated, and a compensated range between surface of the missile and its origin is added to the tracking range of the radar. Therefore, position estimation of a missile can be achieved by using three total ranges from each radar to the origin of the missile. To verify the position estimation of the missile, electromagnetic numerical analysis software was used to prove the compensated range according to the flight position. Moreover, a wideband radar operating at 500-MHz bandwidth was applied, and its range profile was used for the position estimation of a missile.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2381-2387
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• 2013

This paper deals with an optimal angle error reduction method of magnetic hall sensor using hall effect elements with yoke. The magnetic position sensor is required to generate ideal sine and cosine waveforms from its hall effect elements according to rotation angle for precise angle information. However, the output signals are easy to include harmonics due to uneven magnetic field distribution from disturbance in the vicinity of hall effect elements. Thus, The paper studies a way which makes sine and cosine waveforms robust in disturbance and reduces harmonics by installing a yoke around Hall effect elements. The angle detection simulation for the magnetic hall sensor is performed by 3 dimensional finite element method and Taguchi method, one of the design of experiments. For the Taguchi method, three design parameters related to position of hall effect elements and shape of hall effect element yoke are selected.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.528-537
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• 2014

As the data traffic between ships and a land station continuously increase through the shipbuilding-IT convergence, several wireless communication technologies are being studied to process large amounts of data traffic. In particular, the multi-antenna system is one of the most expected technologies to provide high throughput. This paper proposes an algorithm for the base station to select the ship in consideration of channel characteristics and the transmission angle for a beam of the land station in spatial multiplexing marine communication systems. We increase the system capacity by maximizing the received signal strength of the ship using clustering characteristic of the radio channel. Also, we reduce the time to select the ship by excluding the ship with the large interference between the beams. On our computer simulation, the proposed scheme dramatically reduces the computational complexity with a little sacrifice of the throughput.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.585-592
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• 2014

In this study, a multibody simulator was developed to analyze the bio-mimetic motion of a lizard robot design. A RecurDyn multibody dynamics model of a lizard was created using a micro-computerized tomography scan and motion capture data. The bio-mimetic motion simulator consisted of a trajectory generator, an inverse kinematics module, and an inverse dynamics module, which were used for various walking motion analyses of the developed lizard model. The trajectory generation module produces spinal movements and gait trajectories based on the lizard's speed. Using the joint angle history from an inverse kinematic analysis, an inverse dynamic analysis can be carried out, and the required joint torques can be obtained for the lizard robot design. In order to investigate the effectiveness of the developed simulator, the required joint torques of the model were calculated using the simulator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.82-89
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• 2014

This paper discusses the methods for reducing the sampling time quantization errors of the body dither type ring laser gyroscope. A ring laser gyroscope has the angle quantization error which is generated by the frequency counting method of the laser beat signal and sampling time quantization error which is generated by the demodulation method for eliminating the body dithering in which the sampling periods are fitted to the dither periods. Generally, because the dither periods are longer than the calculation periods of the inertial navigation system, vehicle navigation errors are produced by long time attitude update missing during the vehicle move with a high dynamical motion. In this paper, the double demodulation method is proposed for reducing the sampling time quantization error and its effects under the dynamic situation are confirmed by simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.381-382
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• 2015

Small devices such as MLCC, sample inspection on the processing is not easy. If you can proceed with the sample inspection, the production process will be able to maximize the MLCC production efficiency. In this study, to minimize the interference of operator, and to maximize the operating efficiency of the equipment. Use image processing techniques for its extracts the position and angle of the MLCC. Implements an automatic inspection system with the high productivity.It is possible to inspect the final six MLCC devices. And once we Pick-Up to 200 Chip to check the accuracy of 98.4%. Based on the results of various studies are in progress to be expected to be applicable to the automatic inspection equipment side development of a variety of small devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.782-790
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• 2014

In this paper, we apply the 2-D Matrix Pencil Method(MPM) to the estimation of the direction of arrival(DOA) of multiple signals of interest(SOIs) in bistatic MIMO radar. The 2-D MPM shows remarkable performance under a low SNR environment and low computational complexity to estimate the DOA of multiple SOIs. Also, it is possible to estimate the direction of departure(DOD) which is an angle from transmitter to target. To verify the proposed algorithm, we applied the proposed algorithm to a uniformly spaced linear array(ULA) and compared the RMSE(Root Mean Square Error) of DOA and DOD under the various SNR with those of the 2-D Capon algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1039-1046
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• 2016

To study a habit and life patten of a wild animal, this paper do a research on the location tracing system of wild animal by yagi-antenna low pass filter, angle tracking technology. Commonly, VHF Radio Telemetry is used for the location tracing system of wild animal. Considering movement, Previous yagi-antenna has 4-element and has advantage of portability but the other advantages are small and preference is weak. To make the advantage of yagi-antenna higher than previous one, Supposed technology adapt to 6-element and make out Narrow space yagi-antenna technology. Also, It supposes that AOA (:Angle of arrival) technology is applied to detecting technology for a close direction from received signal. Based on this study suggest that position tracing technology is so as to figure out a life patten and habit of a wild animal which live in a certain area.