• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.3
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• pp.15-23
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• 2014

There have been CFIT(Controlled Flight Into Terrain) accidents that can be prevented if the crew executed go-around. This study is to analyse the common factors of three typical CFIT accidents of Korea in TEM(threat and error management) frame, and the examples of go-around gate and the countermeasures of eight airlines through the survey facilitating go-around to prevent CFIT. The common factors found in three typical CFIT accidents occurred in Korea or by Korean carriers turned out to be in mountainous terrain, in bad weather while in non-precision approach or circling approach by captain as PF(Pilot Flying) when crew make monitoring errors and communication errors. It also turned out that the crew in all three typical tragic CFIT accidents did not execute go-around in unstabilized approaches. The captains did not respond immediately when first officers advised them to go-around until it is too late. Seven out of eight Airlines answered that they use stabilized approach height as 1,000 feet to be stabilized earlier to have more safety margin by enhancing go-around gate regardless of the weather to prevent CFIT in the survey.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.562-567
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• 2016

Morphing wing which has a configuration optimized to flight speed and condition is faced to a lot of barriers to be overcome such as actuator technique, structural mechanization technique, flexible skin material, control law, and so on. As the first step for developing a morphing wing with rapid response, we designed and fabricated the morphing airfoil using a SMA(shape memory alloy) wire actuator and torsional bias springs. The design concept of the morphing airfoil was verified through operation test. The measured results show that the flap deflects smoothly and fast.

• Atmosphere
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• v.28 no.3
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• pp.317-324
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• 2018

In this study, we review the ground-based whole-sky camera (WSC), which is developed to continuously capture day and night cloud images using the illumination data from a precision Lightmeter with a high temporal resolution. The WSC is combined with a precision Lightmeter developed in IYA (International Year of Astronomy) for analysis of an artificial light pollution at night and a DSLR camera equipped with a fish-eye lens widely applied in observational astronomy. The WSC is designed to adjust the shutter speed and ISO of the equipped camera according to illumination data in order to stably capture cloud images. And Raspberry Pi is applied to control automatically the related process of taking cloud and sky images every minute under various conditions depending on illumination data from Lightmeter for 24 hours. In addition, it is utilized to post-process and store the cloud images and to upload the data to web page in real time. Finally, we check the technical possibility of the method to observe the cloud distribution (cover, type, height) quantitatively and objectively by the optical system, through analysis of the captured cloud images from the developed device.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.109-116
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• 2004

In a satellite time management system, the GPS-based clock synchronization technique[1] has the merits of precision time management by knowing the time difference or the error between the OBT(On Board Time) of the internal processors and GPS time every second. It can be realized employing the DPLL(Digital Phase Loop Lock) and FEP(Front End Processor) circuitry for the clock synchronization[2]. In this paper, a refined DPLL & FEP scheme is proposed to provide the precision, stability and robustness of the operation, which is to compensate the errors and noise of the GPS signal, and also to cope with the case when the GPS signal is lost due to several reasons. The simulation and HIL (Hardware In the Loop) test results using the FM(Flight Model) in the course of KOMPSAT-2(Korea Multi Purpose Satellite-2) design and development are illustrated to demonstrate the salient features of this methodology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.581-588
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• 2015

In this paper, we researched that setting standard for RSC(Radar Cross Section) of naval surface ship could be determined and considered in various ways on ship's survivability, technical building feasibility, operation and so on. This study presented fundamental capacity on anti-ship missile, radar, flight and so no and the procedure to set of target/standards for RSC. The RCS standards is good at setting low as low as to improve survivability aspect, but because we should consider effect, technical limit, cost etc, this paper analyzed necessary elements to set standard than to suggest specific number and suggested procedure to set standars according to suggest the boundary of RCS.

• Smart Structures and Systems
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• v.5 no.4
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• pp.317-328
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• 2009

Current maintenance operations and integrity checks on a wide array of structures require personnel entry into normally-inaccessible or hazardous areas to perform necessary nondestructive inspections. To gain access for these inspections, structure must be disassembled and removed or personnel must be transported to remote locations. The use of in-situ sensors, coupled with remote interrogation, can be employed to overcome a myriad of inspection impediments stemming from accessibility limitations, complex geometries, the location and depth of hidden damage, and the isolated location of the structure. Furthermore, prevention of unexpected flaw growth and structural failure could be improved if on-board health monitoring systems were used to more regularly assess structural integrity. A research program has been completed to develop and validate Comparative Vacuum Monitoring (CVM) Sensors for surface crack detection. Statistical methods using one-sided tolerance intervals were employed to derive Probability of Detection (POD) levels for a wide array of application scenarios. Multi-year field tests were also conducted to study the deployment and long-term operation of CVM sensors on aircraft. This paper presents the quantitative crack detection capabilities of the CVM sensor, its performance in actual flight environments, and the prospects for structural health monitoring applications on aircraft and other civil structures.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.580-586
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• 2015

A brushless DC (BLDC) motor control system for four-axis driving fins to control the flight attitude of a guided artillery munition is developed in this study. This system adopts a simple sensorless control scheme without a Hall sensor. A 12-step driving sensorless BLDC motor scheme is used to improve the output torque. This system has many restrictive problems that hinder the verification of a real system. For example, this has cost and environmental limitations. Therefore, this study develops HILS to verify a four-axis driving fin control system and verifies the position control system hardware by HILS operation.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.88-98
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• 2014

A supercavitation is modern technology that can be used to reduce the frictional resistance of the underwater vehicle. In the process of reaching the supercavity condition which cavity envelops whole vehicle body, a vehicle passes through transition phase from fully-wetted to supercaviting operation. During this phase of flight, unsteady hydrodynamic forces and moments are created by partial cavity. In this paper, analytical and numerical investigations into the dynamics of supercavitating vehicle in transition phase are presented. The ventilated cavity model is used to lead rapid supercavity condition, when the cavitation number is relatively high. Immersion depth of fins and body, which is decided by the cavity profile, is calculated to determine hydrodynamical effects on the body. Additionally, the frictional drag reduction associated by the downstream flow is considered. Numerical simulation for depth tracking control is performed to verify modeling quality using PID controller. Depth command is transformed to attitude control using double loop control structure.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.11 no.2
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• pp.59-77
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• 2003

Air Traffic Control Tower is one of the most important units in Airport operation. It provides services related to safe and efficient traffic flows that control aircraft on the ground maneuvering area and terminal airspace. Also It is responsible for managing of ground operators. The major objective of this study is to evaluates relative efficiency of ATC towers in Domestic airports using data envelopment analysis so that it helps the ATC authority to improve the tower efficiency, to decide the level of benchmarking target and to establish the best alternative. The results of this study are the following; First, as a result of analysis for the potential improvement, it has analysed that the common problems of each ATC tower are to increase its number of flight and to reduce its number of runway followed by airside area, the number of air traffic controller and the number of stand. Second, it has shown that the each tower in RKPC(8), RKPT(5), RKPK(l) and RKSS(l) are used as the reference set. Especially, the tower in RKPC analyzed as a relatively efficient unit is the most main target for the towers in RKTU, RKTH, RKPS and RKTY to do bench marking and to set up the strategy for improving relative efficiency of the tower. Third, tower is actually not able to control the input and output data in this study except the number of controller, so that ATC authority is recommended to improve inefficiency of the towers through handling the number of controller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.807-813
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• 2009

A Satellite transponder is the Communication system to process signal with up-link signal recovery, and transmit to ground station through down-link. The orbit flight in the deep space causes high doppler shift in the received signals from the ground station so that the Carrier recovery and fast synchronization system are essential for the transponder system. The conventional analog transponder is employing the system's carrier recovery along with the PLL (Phase Locked Loop) designed for satellite's operation. This paper presents a digital carrier recovery scheme which can provide more reliable and software reconfigurable implementation technique for satellite transponder system without verifying scheme along with transponder designed for short distance or deep space satellite.