• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.4
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• pp.336-346
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• 2017

Applications of Sigma-Delta STAP, and a method of GMTI processing are presented for GMTI(Ground Moving Target Indication) mode of airborne radar with sigma, delta, and guard channels. We showed results of performance analyses of presented methods by clutter simulation with ICM(Internal Clutter Motion), signal processing simulation and MDV(Minimum Detectable Velocity). Presented methods for Sigma-Delta STAP and GMTI processing are easy to apply practically in GMTI mode of airborne radar without restriction by specific airborne radar system.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.4
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• pp.390-399
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• 2011

Generally the life-cycle cost of complex systems composed of several sub systems or equipments such as train, aircraft weapon systems is spent much more during operation and maintenance phase than development phase. The maintenance cost for maintaining the availability and extending the life span of systems comprise a large proportion of systems operation cost. The cycle of preventive maintenance affects operation and maintenance cost a lot. In this study we introduce a way minimizing life-cycle cost of systems by calculating more reliable preventive maintenance period than the results of previous study using systems reliability data considered the reliability and failure effect ratio of sub-systems or components. We can solve the preventive maintenance period problem known as NP-Hard as quick as possible by using modified genetic algorithm than using other models introduced in previous study.

• International Journal of Advanced Culture Technology
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• v.7 no.4
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• pp.236-241
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• 2019

This paper will read about a multichannel frequency-modulated continuous wave (FMCW) radar sensor with switching transmit (TX) antennas is developed at W-band. To achieve a high angular resolution, a uniform linear array consisting of 5 switching-TX and 12 receive (RX) antennas is employed with the digital beamforming technique. The overall radar front-end module comprises a W-band transceiver and TX/RX antennas. A multichannel transceiver module consists of 5 up-conversion and 12 down-conversion channels, where one of the TX channels is sequentially switched ON. For developing transmitter, we developed an HPA (high power amplified) MMIC chip for W-band radar system and fabricated a transmitter module using this chip. In order to develop the W-band transmitter, we analyzed the important antenna transition structure from HPA MMIC line to W/G (Waveguide)antenna via M/S(microstrip) and fabricated it with 5 transmission channels. As a result, the output power of the transmitter was within 1 dB of the error range after analysis and measurement under normal temperature and environmental conditions.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.386-391
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• 2019

This paper presents analysis results for the effect of the directional group delay of the antenna to implement a precision radio navigation system. The analysis was conducted through antenna simulation and test, and the test was performed in an anechoic chamber. The directional group delay of the antenna was calculated in phase-based analysis method. The results showed that a variation of up to 7.7ns in group delay occurred per antenna direction. The group delay variation from the analysis is 2.31 meters when converted into distance. It was tested using a real radio navigation system based on the time of arrival (TOA). The test verified the distance variation of 2.1 meters, and this value is similar to those obtained from the simulation and chamber test analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.283-289
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• 2018

Launch Acceptability Region(LAR) means an area for successfully hitting the target. And LAR should be calculated in real time on aircraft so that LAR can be seen by pilot. LAR can be changed by the launch condition of the bomb, the impact condition of the target, and the atmospheric condition at the time of flight of the bomb. In this paper, we propose the calculation method of LAR using Artificial Neural Network(ANN). The learning data was generated by changing each condition from existing LAR model, and LAR model was derived through ANN learning. We confirmed the accuracy of the new LAR model by comparing the difference between the result data of existing LAR model and the new LAR model. And we confirmed the possibility of real time calculation of the LAR model on the aircraft by comparing the calculation time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.6
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• pp.445-451
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• 2018

This paper describes on introduction of CASE 4(Delta Wing) for EFD-CFD comparison workshop which is in charged of aerodynamic subcommittee of The Korean Society for Aeronautical and Space Science. The wind tunnel test will be performed later, angle of attack is set -5~20deg and mach number is set 0.7, 0.85, 1.2 to solve the transonic flow. The simulation test of grid dependency is conducted to determine the proper grid size of delta wing analysis. The tendency of lift and drag coefficient is determined according to the change of angle of attack based on the selected grid size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.982-992
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• 2017

In this paper, we introduce a method of selection for the optimal transmission polarization of a W-band seeker through the extraction of the one-dimensional scattering center of a ground tank target. We calculated the surface scattering and edge scattering using the shooting and bouncing ray tracing method of the CST A-solver. Based on 4-channel RCS data, using the one-dimensional RELAX algorithm, which is a kind of spectral estimation technique, scattering centers of ground targets were extracted. According to the changes in the polarization state and look angle, we compared and analyzed the scattering center results. Through simulation, we verified that the scattering center results can be applied when feature vectors are used for target recognition.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.243-252
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• 2016

Conventionally, the static angle of attack and static elevator tests are carried out separately to estimate hydrodynamic stability derivatives of underwater vehicles. However, it is difficult to verify the interaction between the angle of attack and elevator angle in such cases. In this study, we perform a static elevator with angle of attack test where both the angle of attack and elevator angle are varied simultaneously. The experimental results show that the angle of attack has an influence on the elevator control force and that this tendency is dependent on the sense in which the angle of attack and elevator angle are varied. We predict level flight performance using hydrodynamic derivatives estimated through this experiment. The predictions considering the effect of angle of attack show good agreement with trials conducted in the open sea.

• Journal of Advanced Navigation Technology
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• v.25 no.5
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• pp.336-343
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• 2021

Avionics corresponds to the brain, nerves and five senses of an aircraft, and consists of aircraft mounted electronic equipment of communication, identification, navigation, weapon, and display systems to perform flight and missions. It occupies about 50% of the aircraft system, and its importance is increasing as the technology based on the 4th industrial revolution is developed. As the development period of the aircraft is getting shorter, it is definitely necessary to develop a stable avionics SIL in a timely manner for the integration and verification of the avionics system. In this paper, we propose a method to replace the legacy SIL with the avionics simulation model framework based one and evaluate the framework based on the result of alternative application.