• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.1-7
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• 2021

Detect and avoid (DAA) system, which is essential for the operation of UAS, detects intruding aircraft and offers the ranges of turn and climb/descent maneuver that are required to avoid the intruder. This paper uses detect and avoid alerting logic for unmanned systems (DAIDALUS) developed at NASA as a DAA algorithm. Since DAIDALUS offers ranges of avoidance maneuvers, the actual avoidance maneuver must be decided by the UAS pilot as well as the timing and method of returning to the original route. It can be readily used in real-time human-in-the-loop (HiTL) simulations where a human pilot is making the decision, but a pilot decision model is required in fast-time simulations that proceed without human pilot intervention. This paper proposes a pilot decision model that maneuvers the aircraft based on the DAIDALUS avoidance maneuver range. A series of tests were conducted using test vectors from radio technical commission for aeronautics (RTCA) minimum operational performance standards (MOPS). The alert levels differed by the types of encounters, but loss of well clear (LoWC) was avoided. This model will be useful in fast-time simulation of high-volume traffic involving UAS.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.49-57
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• 2020

The KC-100 has completed civil type certification with the Ministry of Land, Infrastructure, and Transport, and is currently under development as an unmanned aerial vehicle as part of the Ministry of Land, Infrastructure, and Transport. The Certification Technology of small Unmanned Airplane system (CTsUA system), which is an unmanned KC-100, is being developed to enable the installation of heavy-duty mission equipment and long-time flight missions. This study investigated the process and results of analyzing various parameters such as aircraft weight, airspeed, flight altitude, required horsepower, and fuel consumption at each stage to construct a mission profile based on the operational concept of the CTsUA system. To maintain a maximum take-off weight of 3,600 lbs (1,633 kg), the analysis determined that the weight of the application equipment for the unmanned system should be kept below 80 lbs (36 kg).

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.5
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• pp.369-376
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• 2014

This paper presents a method that integrates passive and active-sensing techniques for the structural health monitoring of plate-like structures. Three piezoelectric transducers are deployed in a L-shape to detect and locate an impact event by measuring and processing the acoustic emission data. The same sensor arrays are used to estimate the subsequent structural damage using guided waves. Because this method does not require a prior knowledge of the structural parameters, such as the wave velocity profile in various directions, accurate results could be achieved even on anisotropic or curved plates. A series of experiments was performed on plates, including a spar-wing structure, to demonstrate the capability of the proposed method. The performance was also compared to that of traditional approaches and the superior capability of the proposed method was experimentally demonstrated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.23-33
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• 2004

MDO framework, which provides multidisciplinary system design and optimization environment, requires integration of the analyses codes developed at various computer languages and operating systems, integration of CAD and DBMS, and development of complex GUI. Emphases must be given to the software modification and upgrades in conjunction with the analysis code addition and MDO method implementation. In this study, techniques about system integration and analysis code interface have been studied extensively, and the database design and communication methods which can handle the MDO methods like MDF and CO have been studied. Using the dedicated MDO framework developed for the air vehicle design, the multidisciplinary fighter aircraft wing design has been performed to demonstrate the efficiency and usefulness of the software. Optimum wing configuration is derived using the gradient-based optimization methods within thirty design iterations.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.233-239
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• 2004

Smart material is used in various applications such as for glass frame, for medical instruments and for a part of sensors. Smart composite materials ran be applied to a part of aircraft and to the on-line monitoring system for industrial structures, using the shape memory effect. However, it is very difficult to simulate and analyze the shape memory effect in smart composites. In this paper, a two dimensional axisymmetric model was proposed to analyze the smart composite of one fiber and matrix using the finite element method(FEM). The finite element analysis was carried out in two renditions of the room temperature(293K) and a higher temperature (363K). The results we.e compared with the experimental results to confirm the validity of the analysis. In addition, the acoustic emission(AE) technique was used to study the microscopic damage behavior and the effect of pre-strains on TiNi/A16061 shape memory alloy composite.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.379-384
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• 2014

The most critical rotating parts of a gas turbine engine are turbine blades and disc, given that they must operate under severe conditions such as high turbine inlet temperature, high speeds, and high compression ratios. Owing to theses operating conditions and high rotational speed energy, some failures caused by turbine disks and blades are categorized into catastrophic and critical, respectively. To maximize the margin of structural integrity, we aim to optimize the vulnerable area of disc-blade interface region. Then, to check the robustness of the obtained optimized solution, we evaluated structural reliability under uncertainties such as dimensional tolerance and fatigue life variant. The results highlighted the necessity for and limitations of optimization which is one of deterministic methods, and pointed out the requirement for introducing reliability-based design optimization which is one of stochastic methods. Thermal-structural coupled-filed analysis and contact analysis are performed for them.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.513-520
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• 2014

An unmanned aerial vehicle (UAV) should be designed to be as small and lightweight as possible to optimize the efficiency of changing the blade shape to enhance the aerodynamic performance, such as the thrust and power. In this study, a computational fluid dynamics (CFD) simulation of an unmanned multi-rotor aerial vehicle in hover mode was performed to explore the thrust performance in terms of the blade rotational speed and blade shape parameters (i.e., taper ratio and twist angle). The commercial ADINA-CFD program was used to generate the CFD data, and the results were compared with those obtained from blade element theory (BET). The results showed that changes in the blade shape clearly affect the aerodynamic thrust of a UAV rotor blade.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.255-266
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• 2009

In this study, a robust aerospace system design process for the aerospace system is developed by considering the uncertainties of user requirements, manufacturing errors, and operational environment variation. User requirements are analyzed and quantified by decision making models and system engineering methods to select alternative concepts which satisfies the various requirements. Robust design and optimization method is applied to derive the robust solution of the selected system. First, a variance of objective function is calculated, and a mean value and a variance of target value are determined by the deterministic design optimization results of the system. A robust optimum design formulation is then needed to derive the robust solution that minimizes the variance of the response and moves the mean values to the target value. It is applied to Very Light Jet (VLJ) aircraft to which much attention is paid recently in civil aerospace market.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.40-51
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• 2021

In this paper, the design requirements was produced by analyzing domestic and foreign regulations of the vertical takeoff and landing site required to operate the urban air mobility (UAM) system in Korea and the size of the take-off and landing pads were defined, and the configuration of vertiport was proposed. First, for the metropolitan area with high population density, pilot locations of the vertical take-off and landing site were selected based on the demonstration routes suggested by the Ministry of Land, Infrastructure and Transport and analyzed the characteristics of each location and determined the number of possible installations of vertiport by measuring each site. After that, variables necessary for the operation of the vertical takeoff and landing area were set, and the hourly, daily, monthly aircraft operating cycle, the number of acceptable people, and efficiency were calculated according to the number of simultaneous operation and the number of stand. Finally, using CATIA, the configurations of the virtual vertiport was created by applying the design requirements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.109-117
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• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.