• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.295-302
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• 2006

In this study, computational structural dynamic analyses of a gyrocopter have been conducted considering unsteady dynamic hub-loads due to rotating blades. 3D CATIA models with detailed mechanical parts we constructed and virtually assembled into the complete aircraft configuration. The dynamic loading generated by rotating blades in the forward flight condition are calculated by a commercial computational fluid dynamics (CFD) code such as FLUENT. Modal based transient and frequency response analyses are used to efficiently investigate vibration characteristics of the gyrocopter. Free vibration analysis results for different fuel and pilot conditions, frequency responses and transient responses for critical flight conditions are also presented in detail.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.105-114
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• 2003

It is conducted to analyze vibration loads on the 1st stage of KSR-III(KSR : Korea Sounding Rocket) during their ground transportation and various handling process. These loads may be different from the real flight environment. Inadequate assessment of these loads can cause not only local damages on the rocket system but also the critical problem like flight mission failure. Therefore, transportation and handling loads must be considered during design and attenuated to ensure that the rocket structural damage does not occur. This work is concerned with the generation of criteria and prediction of transportation and handling loads for KSR-III. The results show that the shipping container is well designed to satisfy the design requirements. The maximum vibration level recorded during whole transportation and handling for KSR-III is less than 2g, the criteria of KSR-III movement condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.41-49
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• 2005

This paper discusses the test procedure, instrumentation, verification methodology and the results of the ground vibration test(GVT) performed on the KF-16D aircraft to estimate experimentally dynamic characteristics of the aircraft. The modal tests for 7 external store configurations were conducted to estimate effects of external stores on the aircraft vibration modes. To emulate free-free boundary conditions the test aircraft was mounted on its landing gear structure with deflated tires during the GVT. The airframe modal tests were done by burst random excitations with 6 to 8 shakers and about 200 accelerometers. Frequency response functions(FRFs) were measured for each test, and the FRFs were reduced and analyzed to identify the dynamic parameters interested. The analyses were carried out in two steps. To extract modal parameters such as, frequencies and damping ratios, the poly-reference least square complex exponential method was used in the time domain. The mode shape coefficients were estimated with the least squares frequency domain method to identify the vibration modes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.516-523
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• 2013

The tip clearance effect on counter-rotating ducted fan of VTOL UAV in hovering condition, was investigate using computational analysis. The $k-{\omega}$ SST turbulence model is employed in this study. The numerical results of baseline model are validated by wind tunnel test in hovering and forward conditions. It is observed that if tip clearance of one rotor in the counter-rotating ducted fan increase then the thrust coefficient of another rotor increases. In Addition to this, when the tip clearance of the rear rotor increases, the thrust of the ducted fan is improved due to increasing of average total pressure at exit plane.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.929-937
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• 2008

A GPS receiver system utilized on satellite launch vehicles should operate normally under harsh environments as well as high-dynamic conditions. The GPS receiver system to use for range safety of KSLV(Korea Space Launch Vehicle)-I that is the first satellite launch vehicle developed by KARI(Korea Aerospace Research Institute) has been confirmed to survive under the environment of the launcher through extensive terrestrial tests including humidity, high and low temperatures, vacuum, sinusoidal and random vibrations, shocks, acceleration, EMI/EMC(Electromagnetic Interference/ Electromagnetic Compatibility), etc. Several performance tests have been also carried out in order to evaluate tracking capability and accuracy of the GPS receiver under high-dynamic conditions using a GPS signal simulator. Some lessons-learned during development of the GPS receiver system and its special characteristics compared with COTS(Commercial-Off-The-Shelf) GPS receiver systems are described in this paper.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.103-120
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• 2010

A development history of the thrusters used for space-vehicle orbit maneuver/attitude control is reviewed with their performance characteristics. Especially, a scrutiny is made for the current and practical application of TVC/Gimbal/Thrusters to the roll/pitch/yaw-axis control of each stage of launch vehicles. It is well perceived that a precise 3-axis attitude control system (ACS) must be equipped on the final stage of space launch vehicles (SLV) for an attainment of orbit-insertion accuracy. Under the superior reliability as well as moderate performance features, the monopropellant hydrazine thrusters occupy most of the SLV's 3-axis ACS currently operated. Domestic development status of the medium-thrust-level thruster is shortly introduced, finally.

• Journal of Advanced Navigation Technology
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• v.19 no.5
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• pp.363-369
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• 2015

This paper describes deployment of a sea based sensor platform for the detection of a submarine launched ballistic missile (SLBM). Recently, North Korea successfully conducted the underwater launching test of the SLBM, which will seriously threaten the global security. To defend these threats successfully, a sensor platform of the ballistic missile defense (BMD) should be deployed in the area of high detection probability of the missile. The maximum detection range characteristics of the typical radar sensor system, however, depend on the radar cross section (RCS) and flight trajectories of the target. In this point of view, this work analyzed the flight trajectories based on the tactics and calculated the RCS of the SLBM. In addition, sea based sensor platform position is proposed from the analysis of the detection time.

• Journal of Convergence for Information Technology
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• v.10 no.10
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• pp.135-142
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• 2020

In the recent farming industry, there is a growing diffusion of drones, which are recognized as a crucial technology of the 4 th industrial revolution to cope with aging. Especially, filming and pest control using drones are representative fields that have different age groups for obtaining a national license of multicopter that is a ultra-light flying device, and can create profits after getting a license. However, pest control technology using drones has different spray effects depending on levels of operational proficiency, since this highly relies on an operator's operating skills. It is anticipated that if this issue is supplemented, the use of drones for pest control in the farming industry will diversify. For analysis of spraying characteristics of agricultural pest control drones, this study aims to formulate effective spraying hours and effective spraying intervals and suggest an algorithm, which facilitates an accurate calculation of pest control area depending on the kinds of pest control drones. This algorithm can be used in the field of pest control by improving scatterling issues caused by drone flight methods of drone pest controllers and building an optimum pest control manual in future.

• Convergence Security Journal
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• v.15 no.6_2
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• pp.37-44
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• 2015

There appears a variety forms of crime type and age in accordance with the change of social structure. In this paper it is described for combining the Anomie theory of Emile Durkheim. Anomie refers to the absence of dual standards or norms. In other words, while weakening the existing norms prevailing when the new rules has not been established. That situation would cause social chaos. Rules on the dissemination and utilization of SNS due to the development of information and communication technology undermine the social norms while online regulations are being a weak state not established. In the confusion of these norms it has been shown to increase in juvenile delinquency. Social media has characteristics such as openness, accessibility, relationships, and content diversity. The social media itself is not subject to the general mechanisms of consumption and production due to growing as a kind of organism. It has characteristic to make the most content by utilizing the users to voluntarily share information. Social media using as communication, contact and information in the youth, thus the possibility of crime is high. Social media is also direct and indirect influence on youth crime but no apparent systemic regulation of this situation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.311-314
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• 2007

Aerodynamic characteristics of an insect-type flapping wings were carried out to obtain the design parameters of Micro Hovering Air Vehicle. A pair of wing model was scaled up about 200 times and applied two pairs of 4-bar linkage mechanism to mimic the wing motion of a fruit fly(Drosophila). To verify the Weis-Fogh mechanism, a pair of wings revolved on the 'Delayed Rotation'. Lift and drag were measured in conditions of the Reynolds number based on wing tip velocity of about 1,200 and the maximum angle of attack of 40$40^{\circ}$. Inertia forces of a wing model were also measured by using a 99.98% vacuum chamber and subtracted on measured data in air. In the present study, high lift effect of Weis-Fogh mechanism was appeared in the middle of upstroke motion.