• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.5
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• pp.57-63
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• 2009

A modeling and simulation program for an environmental control system (ECS) of a pod installed under wings of an aircraft was developed in order to estimate the system‘s performance during a flight. First, through the system configuration analysis in the main operational condition of the aircraft system, an ECS configuration adopting an air cycle machine (ACM) was selected. Therefore the modeling program was developed to simulate the ECS with an ACM. Second, the sensitivity analyses on performance variation of main components were conducted to complete the conceptual design of the ECS. A design point for the system and its components was obtained through the analysis with the modeling and simulation program. The design point for the system and components was obtained through the analysis with the modeling and simulation program. Third, in order to study the feasibility of the ECS configuration, off-design performances of the ECS on various flight conditions, such as take off, maneuver, cruise and landing etc were estimated. Dynamic characteristics were analyzed by transient performance evaluations.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.491-504
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• 2008

CSSA (Coarse Sun Sensor Assembly) is the essential sensor for satellite attitude control. CSSA measures the direction of the sun's rays and determines whether the satellite is in the ellipse. The paper shows the development process and test results of Path-finder & Qualified Model CSSA as the preceding development in order to develop the CSSA for low earth orbit satellite. We needs the definite and precision procedure and lots of experience. This paper shows that we can improve those through the development of Path-finder and Qualified Model CSSA. Therefore, we can obtain the results to meet the functional requirement.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.1
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• pp.121-131
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• 1999

Automatic Rudder Trim System(ARTS) is a device to reduce the pilot's work load for rudder trimming greatly required in varying abruptly aircraft's engine power. This paper represents a technical analysis and a design of control law of the ARTS. The control law of the ARTS is designed based on the analysis of aircraft's characteristics, system's requirements, and limitations. The control law is comprised of open loop control using the rudder trim map for a specific aircraft and closed loop control to compensate the error of the open loop control system. flight test results show that the ARTS can reduce pilot's work load for rudder trimming dramatically and can compensate the aircraft's transient yaw motion.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.73-84
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• 2020

To overcome ground congestions due to growing number of cars, a lot of companies have proposed personal aerial vehicle (PAV). Among PAV, electric vertical take-off and landing (eVTOL) aircrafts capable of vertical take-off and landing with electric power are drawing attention, and their configurations vary from multicopters to tilt ducted fans. This study tries to analyze the characteristics of each eVTOL design configurations. Parasite drag was calculated using component build up method for Vahana, Aurora, Volocopter representing each eVTOL PAV type of tilt-wing, compound, and multicopter. Wetted area and induced drag was calculated using OpenVSP and XFLR5 that are aircraft design and aerodynamic analysis software. The batteries used in the eVTOL PAV was assumed as Tesla 2170 batteries and flight ranges were calculated. Also, energy consumption and maximum flight time for the given mission profile including take-off and landing, cruising segments were compared for each eVTOL.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.59-66
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• 2014

In the case of a propeller-driven aircraft, power-on effect generated by the propeller has a strong influence on the performance and the stability of an aircraft directly and indirectly. A numerical study on the power-on effect has been performed using the CFD based on the multiple reference frame and sliding mesh model. The power-on effect increases the overall lift and the maximum lift of the aircraft. In addition to lift increment, power-on effect delays the stall of the aircraft. On the other hand, the power-on effect increases the drag significantly and consequently decreases the lift-to-drag ratio of the aircraft. Furthermore, the power-on effect decreases the nose-down pitching moment and consequently decreases the longitudinal static stability of the aircraft. It is expected that the analysis results presented and discussed in this report will be used as an important material for analyzing the aircraft performance and stability and will contribute the development of the propeller-driven aircraft with the pusher propeller.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.937-946
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• 2014

This paper presents system identification of a single tilt wing UAV. A Modified Equation Error Method(MEEM) and Extended Kalman Filter(EKF) are used for the identification of a single tilt wing UAV system in frequency-domain and time-domain, respectively. Simulated flight data is obtained from CNUX-3's vertical mode linear simulation with realistic sensor noise. System identification performance is analyzed with respect to a variety of design parameters of the MEEM. Also, High accuracy Fourier Transform(HFT) is applied to enhance the performance of MEEM. The results of the MEEM is compared with those of the EKF. Design parameters of the MEEM and initial conditions of the EKF are decided from optimization.

• Korean Journal of Environment and Ecology
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• v.24 no.3
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• pp.334-342
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• 2010

The purpose of this study is conducted to examine the change of flora and fauna in the extensive rooftop green area from 2005 to 2009. The experimental site is on the rooftop green area of Seoul Women's University which was constructed in 2005. This research was consisted of four parts: soil, potted plants, invading plants and small animals especially insects. The plants were surveyed by enumeration, while animals were surveyed by two methods which are 'Netting and Searching' and 'Pit fall trap'. The initial group of plants planted in 2005 was 100 species of 26 families whereas in 2009 there were 62 species of 23 families including 22 invading species of 11 families. In case of insects in 2009, 21 species of 7 families (9 orders) were detected; 19 species of 15 families (8 orders) were discovered by 'Netting and Searching' and 5 species of 5 families (5 orders) by 'Pit fall trap'.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.2
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• pp.171-179
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• 2017

In this paper, microstrip antenna using multi-layer and folded structure for GPS application is presented for aircraft loading. Existing microstrip patch antenna used dielectric of high specific inductive capacity to miniaturize that cause smaller bandwidth and decline of efficiency due to dielectric loss. To compensate the existing flaws, Rogers TMM 10i(dielectric constant=9.8, loss tangent=0.002) is used for multi-layer dielectric miniaturization, and we construct folded radiating element on the surface of the dielectric applying perturbation effect. The antenna is designed in the bandwidth of GPS $L_1$ band, and the size of the antenna's radiating element is $20.3mm{\times}19.93mm$, and it gets 94.2% miniaturized characteristic of basic ${\lambda}/2$ microstrip patch antenna. Also the measured -10 dB bandwidth is 32.3 MHz(2.05%), 3 dB axial ratio bandwidth is 6.7 MHz(0.43%). Measured radiation patterns was maximum gain of 0.56 dBi at x axis polarization, 1.23 dBi at y axis polarization.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.3
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• pp.218-225
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• 2016

It is important to select the personnel with ideal pilot aptitude considering dramatically advancing aircraft performance and complexity of military operations as a consequence to the highly developed science and technology. The opportunity cost lost from dropouts and human error being the first cause of aviation accidents are the realistic reasons for the significance of personnel selection based on their aptitude. This study analyses the ROKAF pilot aptitude test that was improved in 2004, using various classification models. This study discusses the significance of the selected variables along with the direction of ROKAF pilot aptitude test for its development in the future. The accuracy of the classification models was improved by taking into account differing personnel characteristics of individuals on the test.

• Korean Journal of Child Studies
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• v.38 no.2
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• pp.165-176
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• 2017

Objective: Delinquent peers are important predictors of adolescent delinquent behavior. Few studies have classified individuals into groups based on patterns of delinquent behavior among youth and their peers. This study identified latent groups based on adolescent-peer delinquency and examined psychosocial characteristics of each latent group. Methods: First, the study employed latent class analysis based on a nationally representative data of South Korean middle school students (N = 2,277). Both adolescent and peer delinquent behaviors comprised 13 items in the questionnaire that was self-reported by adolescents. Second, the study used multivariate regression models to analyze psychosocial symptoms of latent groups and conducted Wald tests to compare differences among latent groups. Results: Patterns of adolescent-peer delinquency were classified into six latent groups. "Mutual total delinquent group (1.2%)" showed high rates in most delinquent experiences. "Mutual status delinquent group (5.7%)" mainly experienced status delinquency, "Mutual violence delinquent group (5.3%)" showed high rates of violent delinquency. "Peer-only total high delinquent group (3.8%)" reported friends to have engaged in all types of delinquency and "Peer-only total medium delinquent group (11.8%)" reported peer involvement in multiple status and few violent delinquency. Finally, "low risk group (72.2%)" reported low rates of delinquency for themselves and their friends. Regression analysis showed that every "mutual" delinquent group presented significantly worse psychosocial problems than the "low risk group." Conclusion: Using person centered latent class analysis, this study classified six latent classes while considering both delinquent agents and various types of delinquency and investigated specific groups with greater risk of psychosocial problems.