• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.7
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• pp.506-511
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• 2009

Insect flight is adapted to cope with each circumstance by controlling a variety of the parameters of wing motion in nature. Many researchers have struggled to solve the fundamental concept of insect flight, but it has not been solved yet clearly. In this study, to find the most effective flapping wing dynamics, we conducted to analyze CFD data on fixing some of the optimal parameters of wing motion such as stoke amplitude, flip duration and wing rotation type and then controlled the deviation angle by fabricating wing tip motion. Although all patterns have the similar value of lift coefficient and drag coefficient, pattern A(pear-shape type) indicates the highest lift coefficient and pattern H(pear-shape type) has the lowest lift coefficient among four wing tip motions and three deviation angles. This result suggest that the lift and drag coefficient depends on the angle of attack and the deviation angle combined, and it could be explained by delayed stall and wake capture effect.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.2
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• pp.82-99
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• 2024

The aim of this study is to propose strategies for in-flight OTT services by examining differences in binge-watching patterns through online video streaming services based on age. Additionally, it investigates how the moderating effects of need for cognition and critical media literacy influence the relationship between age and binge-watching. Data from the 2020 Korean Media Panel Survey conducted by the Korea Information Society Development Institute were utilized, with moderating effects analyzed using Process Macro Model 1. Results indicate that as age increases, the frequency of binge-watching content rises while the duration decreases. Moreover, moderating effects of need for cognition and critical media literacy in the age-binge-watching relationship were confirmed. This study analyzed binge-watching behaviors among online video streaming service users, confirming the influence of age, binge-watching habits, need for cognition, and critical media literacy. Theoretical and practical implications include insights for in-flight service providers, content marketers, and online video streaming service operators.

• International Journal of Computer Science & Network Security
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• v.22 no.2
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• pp.357-361
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• 2022

Employing the available technologies and utilizing the advanced means to improve the level of health care provided to citizens in their various locations. Citizens have the right to get a proper health care services despite the location of their residency or the distance from the health care delivery centers, a goal that can be achieved by utilizing air ambulance systems. In such systems, aircrafts and their life spans are the essential component, the flight duration of the aircraft during its life span is determined by the maintenance schedule. This research, enhances the air ambulance systems by presenting a proposal that maximizes the aircraft flight duration during its life span. The enhancement will be reached by developing a set of algorithms that handles the aircraft maintenance problem. The objective of these algorithms is to minimize the maximum completion time of all maintenance tasks, thus increasing the aircraft operation time. Practical experiments performed to these algorithms showed the ability of these algorithms to achieve the desired goal. The developed algorithms will manage the maintenance scheduling problem to maximize the uptime of the air ambulance which can be achieved by maximizing the minimum life of spare parts. The developed algorithms showed good performance measures during experimental tests. The 3LSL algorithm showed a higher performance compared to other algorithms during all performed experiments.

• Journal of Environmental Science International
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• v.26 no.6
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• pp.779-788
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• 2017

In this study, we analyzed the changes in the echolocation and prey-capture behavior of the horseshoe bat Rhinolophus ferrumequinum from search phase to capture time. The experiment was conducted in an indoor free-flight room fitted with an ultra-high-speed camera. We found that the bats searched for food while hanging from a structure, and capturing was carried out using the flight membrane. In addition, it was confirmed that the mouth and uropatagium were continuously used in tandem during the capturing process. Furthermore, using Constant Frequency (CF), we confirmed that the prey catching method reflected the wing morphology and echolocation pattern of R. ferrumequinum. The echolocation analysis revealed that the pulse duration, pulse interval, peak frequency, start-FM-bandwidth, and CF duration decreased as the search phase approached the terminal phase. Detailed analysis of echolocation pulse showed that the end-FM bandwidth, which increases as it gets nearer to the capture time of prey, was closely related to the accurate grasp of the location of an insect. At the final moment of prey capture, the passive listening that stopped the divergence of the echolocation was identified; this was determined to be the process of minimizing the interruption from the echo of the echolocation call emitted from the bat itself and sound waves emitted from the prey.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.3
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• pp.1-7
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• 2015

In the present study, we conducted the research on the high efficiency propulsion system for the development of long-endurance UAV with an electric propulsion system. For the long endurance UAV, fair aerodynamic characteristics with the high efficiency of the propulsion system is required because the flight power and the duration time of the long-endurance UAV vary greatly depending on the efficiency of the propulsion system. Therefore, in this study, the tracking program which records the performance of motor, propeller was developed because of their wide variation in the efficiency depending on the using condition, and records from the existing flight test program were utilized to check the accuracy of the program we had developed. For the development of future long-endurance solar UAV, we confirmed the applied voltage of motor, the optimal rotation of propeller and the gear ratio of reduction gear in order to get the highest efficiency on the propulsion system at the optimal flying condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.343-344
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• 2007

Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350 nm was illuminated on the surface of a-Se with thickness of $400\;{\mu}m$. The measured transit times of hole and electron were about $8.73\;{\mu}s\;and\;229.17\;{\mu}s$, respectively. The experimental results showed that the hole and electron drifting mobility were $0.04584\;cm^2V^{-1}S^{-1}\;and\;0.00174\;cm^2V^{-1}s^{-1}\;at\;10\;V/{\mu}m$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.115-118
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• 2009

Life time and number of use of liquid propellant rocket engine (LRE) should be carefully defined since those are crucial parameters affecting development costs and period. The present study surveyed the development and qualification records of LRE for space launch vehicles, especially concerning about test numbers and duration. It was shown that a single engine for expendable launch vehicle is tested with tens of ignition and several times duration of flight at least.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.238-243
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• 1995

A pulsed molecular beam source having short pulse duration (typically 70 ${\mu}s)$ and narrow velocity distribution (${\Delta}$v/v=8% for helium) has been costructed utilizing a commercial fuel injector. Beam characteristics of helium and ammonia seeded in helium expansions are accomplished by the use of an electron impact time-or-flight mass spectrometer. The comparisons between experimental data and theoretical calculations show that the proper beam speed is important to predict the evolution of stream temperature and valve shutter function. The decreasing tendency of pulse duration with increasing cluster size leads to the conclusion that the cluster beam property is described as a function of cluster mass and disinct cluster temperature.

• Journal of the military operations research society of Korea
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• v.6 no.1
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• pp.103-117
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• 1980

Stochastic duels have been studied by Ancker, William, Bhashyam, Gafarian, Jaiswal, Singh, and others, Stochastic duels are classified in terms of factors such as kill probability, ammunition, time duration, surprise, mobility, time of flight, etc. The purpose of this paper is to summarize and analyze the models of stochastic duels that have been studied so far, and to study the effect of the factors to the win probability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.227-230
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• 2005

This paper describes the problems in measuring and evaluating the aviation noises and the differences on the noise characteristics between fighter and civil aircraft. From a standpoint of the duration time for aviation noise and the dynamic characteristics related with the sampling time, the measured values for landing and taking-off noises from the fighter are presented and explained in comparison with those from the civil aircraft. And also the aviation noises by the fighter and civil aircraft are evaluated by equivalent sound level and WECPNL, respectively. From the obtained results, it is recommended that the duration time and dynamic characteristics be deeply considered in evaluating and measuring the aviation noises, since they have a great influence on the final assessment results. As the number of flight is not sufficient and the noise source is strong impulse type, moreover, the aviation noise should be assessed by WECPNL.