• Journal of applied mathematics & informatics
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• v.8 no.2
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• pp.361-370
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• 2001

Testing equality of covariance matrix of k populations has long been an interesting issue in statistical inference. To overcome the sparseness of data points in a high-dimensional space and deal with the general cases, we suggest several projection pursuit type statistics. Some results on the limiting distributions of the statistics are obtained. some properties of Bootstrap approximation are investigated. Furthermore, for computational reasons an approximation which is based on Number theoretic method for the statistics is adopted. Several simulation experiments are performed.

• Bulletin of the Korean Mathematical Society
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• v.51 no.1
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• pp.1-11
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• 2014

In this paper, we show that general nonlinear switched systems are asymptotically controllable if and only if there exist control-Lyapunov functions for their relaxation systems. If the switching signal is dependent on the time, then the control-Lyapunov functions are continuous. And if the switching signal is dependent on the state, then the control-Lyapunov functions are $C^1$-smooth. We obtain the results from the viewpoint of control system theory. Our approach is based on the relaxation theorems of differential inclusions and the classic Lyapunov characterization.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1300-1303
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• 1996

In this paper a typical problem is examined that a light, general aviation airplane, such as Cessna or Navion, in gliding turn flight shows helical-dive phenomenon when pilots try to stop the descent by using elevator only. It is known from pilot's experience that in a certain flight trim it is impossible to recover from helical-dive by using elevator only. From this study it is shown that helical-dive phenomenon is involved with longitudinal/lateral dynamics coupling to airplane's aerodynamics. Also this phenomenon consists of three parts of flight dynamics; first of all, fast longitudinal motion occurs, then is followed by a little slow lateral motion, and finally logitudinal/lateral coupled motion is fully developed.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.15-20
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• 2016

The optimal estimation of a general continuous-discrete system can be achieved through the solution of the Fokker-Planck equation and the Bayesian update. Due the high nonlinearity of the equation of motion of the system and the measurement model, it is necessary to linearize the both equation. To avoid linearization, the filter based on Fokker-Planck equation is designed. with the unscented transformation update mechanism, in which the associated Fokker-Planck equation was solved efficiently and accurately via discrete quadrature and the measurement update was done through the unscented transformation update mechanism. This filter based on the Direct Quadrature Moment of Method(DQMOM) and the unscented transformation update is applied to the bearing only target tracking problem. The proposed filter can still provide more accurate estimation of the state than those of the extended Kalman filter especially when measurements are sparse. Simulation results indicate that the advantages of the proposed filter based on the DQMOM and the unscented transformation update make it a promising alternative to the extended Kalman filter.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.1
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• pp.41-47
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• 2010

The carbon fiber reinforced plastics, one of unidirectional fiber-reinforced composite materials, are widely used in various field including space and aviation industries, sports and leisure industries and general structural members and parts as have high strength in comparison with the weight, elasticity coefficient, high fatigue strength and lower thermal transformation. This paper present analytical behavior of CFRP pipe reinforced rib under the external force. From the results, the maximum compressive stress occurs at the upper flange of CFRP pipe and tensile stress occurs middle flange of the CFRP pipe. The stress of rib CFRP pipe by increasing effective cross-sectional area was reduced by approximately 35%.

• Journal of the Korean Data and Information Science Society
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• v.11 no.2
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• pp.235-245
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• 2000

In this paper, we consider the Regression Quantiles Estimators in nonlinear regression models. This paper provides the sufficient conditions for strong consistency and asymptotic normality of proposed estimation and drives asymptotic relative efficiency of proposed estimatiors with least square estimation. We give some examples and results of Monte Carlo simulation to compare least square and regression quantile estimators.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.10 no.2
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• pp.49-60
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• 1985

This study has suggested more rational and effective improvement of tariff system, analysing the present condition and problems of telephone tariff system, taking into account CCITT general tariff principles and comparing the rate structure in major countries.

• Journal of Aerospace System Engineering
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• v.8 no.3
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• pp.47-54
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• 2014

This is a research on the method of how to improve stall characteristics for the small general aviation airplanes to meet the FAR part 23 requirements. This research is based on the experience of certification flight tests of KC-100 airplane for Korea type certification. KAS/FAR Part 23.201/203 are the stall characteristics requirements. 23.201 requires to show the stable stalling tendency of the wings level stall and 23.203 requires to show the stable stalling tendency of stall characteristics during turning flight. In this paper, the stall characteristics requirements, improvement methods and flight test experience of KC-100 airplane for type certification.

• Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.7-12
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• 2011

The goal of fire prevention research is to eliminate fires as a cause of fatal accidents and there are two main areas of research. One is to prevent flame propagation during in-flight and it addresses fire hazards. The other is to minimize the possibility of flame penetration or fuselage burn-through and it aims toward post-crash survival include crash protection, emergency evacuation and post-evacuation survival. Civil aviation authorities world-wide are trying to identify threats and measure performance for fire prevention. The results of research are standardized and given as general directions of test methods. This paper has prepared to study and present the means of compliance to the fire prevention requirements and applicable test methods.

• Journal of Applied Reliability
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• v.8 no.4
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• pp.167-179
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• 2008

System risk is the totality of all safety risks to customers, employees, suppliers, and other third parties that arise due to system operations. To assess the risk of major hazards with the potential to cause fatality to the customers and other members of the public, quantitative risk assessment methodologies are used. This paper presents the general principles of risk based management approach to improve the safety of high risk systems such as aviation, railway, and nuclear power plants. For the suitable risk control arrangement, case studies of acceptable risk level, risk rating matrix, and safety management philosophy are presented.