• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.26-33
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• 2005

Smart UAV, which adopting tiltrotor aircraft concept, requires vertical take-off and landing, long endurance and high speed capability. These contradictable flight performances are hard to meet unless the operation of flap system which should reveal optimal performance for each flight mode. In order to design SUAV flaperon satisfying the three performance requirements, various configurations are generated and their aerodynamic performances are analyzed using numerical flow computations around flap systems. Considering aerodynamic performance and structural simplicity, a final flap configuration is selected and the performance is validated through the wind tunnel testing for 40% scale model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.790-797
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• 2010

Mode transition of the axi-symmetric screech tone in the low supersonic Mach number range from 1.0 to 1.20 is numerically analyzed. The axi-symmetric Navier-Stokes equations and the k-e turbulence model are solved in the cylindrical coordinate system. The dispersion-relation-preserving(DRP) scheme is applied for space discretization and the optimized four levels marching method are used for time integration. At low supersonic Mach numbers with an axi-symmetric A1 mode in the simulation, it is shown that acoustic propagation due to the nonlinear effects is seen in the lateral direction and the screech tone frequency is the same as the vortex passing frequency due to the generation of intense large-scale vortical motions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.395-405
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• 2020

Compartment fire tests were performed using kerosene and Jet A-1 as fire sources to evaluate the relationship between flame temperature and opening size. The tests were performed for a fire caused by the release of kerosene owing to vehicle impact, and for a fire caused by the release of Jet-A-1 owing to airplane collision. The compartment fire tests were performed using a 1/3-scale model of a metal storage cask when the flame temperature was deemed to be the highest. We found the combustion time of Jet-A-1 to be shorter than that of kerosene, and consequently, the flame temperature of Jet-A-1 was measured to be higher than that of kerosene. When the opening was installed on the compartment roof, even though the area of the opening was small, the ventilation factor was large, resulting in a high flame temperature and long combustion. Therefore, the position of the opening is a crucial factor that affects the flame temperature. When the metal storage cask was stored in the compartment, the flame temperature decreased proportionally with the energy that the metal storage cask received from the flame.

• Journal of Engineering Education Research
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• v.16 no.1
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• pp.54-63
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• 2013

This study aims to investigate relationships among self-directed learning readiness [SDLR], prerequisite mathematics test score and achievement level in college mathematics. For this purpose, the adjusted SDLRS (self-directed learning readiness scale) of Guglielmino's model, the score of mathematics diagnostic assesment and first semester college mathematics score among 424 freshmen students of engineering department of D university in 2011 were used and analyzed. Research results are as follows: Firstly, freshmen of engineering department had average level of SDLR, though they showed relative low level of self-direction, passion and time control ability. Secondly, considering SDLR with the mathematics diagnostic assesment score (3 groups: high, middle, low), there were no statistically significant differences. Thirdly, concerning SDLR according to the achievement level in college mathematics, a group which acquired good achievement showed higher level of SDLR compared with middle or lowachievement group. Differences among three groups were statistically significant. Lastly, there were affirmative relationships between SDLR, mathematics diagnostic assesment score and achievement in college mathematics. Furthermore, mathematics diagnostic assesment score and achievement level in college mathematics were found to be the most closely related. Based on the results, we suggest strategies to elevate SDLR of engineering department students and improve their achievement in college mathematics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.10
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• pp.4157-4175
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• 2020

Moving target defense, as a 'game-changing' security technique for network warfare, realizes proactive defense by increasing network dynamics, uncertainty and redundancy. How to select the best countermeasure from the candidate countermeasures to maximize defense payoff becomes one of the core issues. In order to improve the dynamic analysis for existing decision-making, a novel approach of selecting the optimal countermeasure using game theory is proposed. Based on the signal game theory, a multi-stage adversary model for dynamic defense is established. Afterwards, the payoffs of candidate attack-defense strategies are quantified from the viewpoint of attack surface transfer. Then the perfect Bayesian equilibrium is calculated. The inference of attacker type is presented through signal reception and recognition. Finally the countermeasure for selecting optimal defense strategy is designed on the tradeoff between defense cost and benefit for dynamic network. A case study of attack-defense confrontation in small-scale LAN shows that the proposed approach is correct and efficient.

• Journal of the Institute of Convergence Signal Processing
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• v.13 no.4
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• pp.233-237
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• 2012

In this paper, We propose a control system which compensate a output of a main Neual Network using a RTDNN(Recurrent Time Delayed Neural Network) with a FLC(Fuzzy Logic Controller)After a learn of main neural network, it can occur a Over shoot or Under shoot from a disturbance or a load variations. In order to adjust above case, we used the fuzzy compensator to get an expected results. And the weight of main neural network can be changed with the result of learning a inverse model neural network of plant, so a expected dynamic characteristics of plant can be got. We can confirm good response characteristics of proposed neural network controller by the results of simulation.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.42-48
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• 2005

The present study investigates the effect of balcony on external smoke movement of high rise building through the fire tests of the 1/10 reduced model scale using Froude scaling. A hexane pool fire is used to examine the smoke movement for various opening sizes of balcony and temperature distributions are measured by T-type thermocouples. Also, hydrogen bubble technique is applied to visualize the smoke movement near the balcony. Measured temperatures of the closed balcony is 2.5 times higher than those of the open balcony because the external smoke in case of the closed balcony rise along the vertical wall. The maximum vertical temperature of partially closed balcony is similar with fully closed balcony and mean temperature inside of balcony increases as opening size of balcony decreases. The experimental results show that the balcony space plays an important roles in preventing fire propagation and cooling of smoke layer. In order to ensure the fire safety in high rise building design, a series of systematic researches are required to examine the various type of balconies.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.151-158
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• 2000

Since Pusan metropolitanarea where is composed complex terrain is connected to sea the sea-land breeze circulation and the mountain-valley circulation are apt to form A regional scale circulation system is formed at a region which has complex terrain because of curves of its and affect to the dispersion and advection of air pollutants. LCM Local Circulation Model which a propriety was verified described that sea breeze and valley wind at the daytime and land breeze and mountain wind at the nighttime were well devellped over the Pusan metropolital area. Next for the investigation of accuracy of simulated results an observed value at Kae-Kum and Su-Young on the pusan metropolitan area were compared with it at those points. From the comparison of the temperature and horizontal velocity between the results of LCM and an observed values they have a similar trend of a diurnal variation. For the prediction of dispersion and transportation of air pollutants the wind field should be calculated with high accuracy. A numerical simulation using LCM can provide more accuracy results around Pusan metropolitan area.

• Journal of Korean society of Dental Hygiene
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• v.16 no.5
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• pp.759-766
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• 2016

Objectives: The purpose of the study was to investigate the impact of dental fear on the oral health related quality of life in teenagers. Methods: A self-reported questionnaire by Likert 5 point scale was completed by 900 high school students in J area from March 10 to April 20, 2014. The questionnaire consisted of general characteristics of the subjects, dental fear survey, and oral health related quality of life. Data were analyzed by t-test and One-way ANOVA using SPSS 12.0 program. Results: Oral symptoms had no significant differences in mother's education and family economic status. Emotional well-being factors had no significant difference in age, religion, school performance, and family economic strength. Dental fear was closely related to emotional well-being, Oral symptoms, social stabilities, functional limit and mental stabilities. Explanation power of the model was 29.1%. Conclusions: It is very important to explain the dental fear procedure to teenagrers before dental surgery and this will enhance the oral health related quality of life in teenagers.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.2
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• pp.77-90
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• 2011

In these days, almost all existing contents have been digitalized because of development of IT(Information Technology) and the emergence of various distribution channels. Those digitalized Contents has increased so rapidly, particularly Video contents, and brought new market and open new business. Now it became a lucrative industry. Therefore it's necessary to study Digital contents. This study is to find out the factors which have an influence on Intention to Use and Use charged the digital contents. To carry out this study, TAM(Technology Acceptance Model), IDT(Innovation Diffusion Theory) and Use& Gratifications Theory were applied. An empirical method has been adopted, using Likert-style 7 point measurement scale, data were collected by e-mail and direct survey in Daejeon, Korea. On the collected data, after the validity test and reliability test has been taken by factor analysis and using Cronbach's alpha respectively, following 5 variables were extracted such as Perceived Usefulness, Perceived Easy Of Use, Compatibility, Intention to Use and Use.