• Speech Sciences
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• v.6
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• pp.25-32
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• 1999

Not only Korean scholars but also many scholars in the field of phonetic science were interested in Korean forced sounds from the viewpoint of general phonetics as a way to clarify the process of production and the physical characteristics of speech sounds. The author also tried to elucidate the characteristics of Korean forced sounds using the sound spectrograph (Umeda & Umeda 1965). Over the past 30 years since this study, many scholars have analyzed these sounds from various standpoints resulting in copious amounts of literature. In this paper, the author critically examined the results of previous studies on this subject dealing with VOT, spectral characteristics, fundamental frequency, states of glottis obtained from fiber-optic investigations, and patterns of tongue-palate contact acquired from observation by use of dynamic palatograph. These points were discussed in relation to the author's field of investigation.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.425-430
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• 1991

For satellite orbit determination, a satellite (K-3H) which is affected by the earth's gravitational field and the earth's atmospheric drag, the sun, and the moon is chosen as a dynamic model. The state vector include orbit parameters, uncertain parameters associated with perturbations and tracking stations. These perturbations include gravitational constant, atmospheric drag, and jonal harmonics due to the earth nonsphericity. Early orbit was obtained with given the predicted orbital parameter of the satellite. And orbit determination, which is applied to Extended Kalman Filter(EKF) for real time implementation , use the observation data which is given by satellite tracking radar system and then orbit estimation is accomplished. As a result, extended sequential estimation algorithm has a fast convergence and also indicate effectiveness for real time operation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.475-478
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• 2002

Maximum drag reduction (MDR) in turbulent channel flow by polymer additives is studied by direct numerical simulation. An Oldroyd-B model is adopted to express the polymer stress because it is believed that MDR is closely related to the elasticity of the polymeric liquids. The Reynolds number based on the bulk velocity and the channel height is 40000. MDR in the present study is $44{\%}$ and this is in a good agreement with the Virk's asymptote. Turbulence statistics are also in good agreements with the experimental observation. In the 'large drag reduction', the decrease of turbulent kinetic energy is compensated by the increase of energy transfer from the polymer to the flow. Therefore, MDR is a dynamic equilibrium state of the energy transfer between the polymer and the flow.

• Journal of KSNVE
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• v.6 no.4
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• pp.439-446
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• 1996

This paper introduces a newly designed pendulum system that enables the more accurate boservation of dynamic behaviour arising from both horizontal and vertical(i.e. two dimension) excitation. First, experiments were carried out to examine the frequency responses of the devised pendulum system. Interestingly, experimental results for the three excitation angles of 22, 32 and 48 degree show 'new' jump phenomena. For the further understanding of these phenomena, experimental investigationhas been made to identify the equation of motion of the pendulum system from experimental data. This attempt has revealed that the viscous, coulomb and aerodynamic damping factors are involved in the equation of motion. By applying the Ritz averaging method to the equation, it becomes apparent that the jumping phenomena of the pendulum system in this work is more theoretically understood.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1216-1221
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• 1990

An algorithm for multiple fault diagnosis of linear dynamic systems is proposed. The algorithm is constructed by using of the geometric approach based on observation that, when the number of faulty units of the system is known, the set of faulty units can be differentiated from other sets by checking linear varieties in the measurement data space. It is further shown that the system with t number of faults can be diagnosed within (t+1) sample-time units if the input-output measurements are rich and that the algorithm can be used for diagnosis even when the number of faults is not known in advance.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.101-107
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• 2007

A coaxial rotor flying robot is developed for surveying and reconnoitering various circumstances under calamity environment. The robot has two contrarotating rotors on a common axis, an embedded microcontroller, an IMU(Inertial Measurement Unit), an IR sensor for height control, a micro camera for surveillance, ultrasonic position sensors and wireless communication devices. A bell-bar mounted on the top of the upper rotor hub increases stability and improves flight performance. In this paper, we present a dynamic model of a coaxial rotor flying robot and design an embedded controller far the robot, and implement them to control the developed flying robot. Experimental results show that the proposed controller is valid for autonomous hovering and position control.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.10
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• pp.149-157
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• 1994

A method of applying a recurrent backpropagation network to identifying or modelling a dynamic system is proposed. After the recurrent backpropagation network having both the characteristicsof interpolative network and associative network is applied to XOR problem, a new model of recurrent backpropagation network is proposed and compared with the original recurrent backpropagation network by applying them to XOR problem. based on the observation thata function can be approximated with polynomials to arbitrary accuracy, the new model is developed so that it may generate higher-order terms in the internal states Moreover, it is shown that the new network is succesfully applied to recognizing noisy patterns of numbers.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.72-78
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• 1991

An improved procedure for earthquake resistant design of multistory building structures is proposed in this study. The effect of gravity load on seismic response of structures is evaluated through nonlinear dynamic analyses of a single story example structure. The presence of gravity load tends to initiate plastic hinge formation in earlier stage of a strong earthquake. However, the effect of gravity load seems to disapper as ground motion is getting stronger. And one of shortcomings in current earthquake resistant codes is overestimation of gravity load effects when earthquake load is applied at the same time so that it may leads to less inelastic deformation or structural damage in upper stories, and inelastic deformation is increased in lower stories. Based on these observation, an improved procedure for earthquake resistant design is derived by reducing the factor for gravity load and inceasing that for seismic load. Structures designed by the proposed design procedure turned out to have increased safety and stability against strong earthquakes.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.498-503
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• 2011

The strain rate sensitivity index, m, plays an important role in plastic deformation at elevated temperatures. It is affected by strain rate, temperature, and the microstructure of the material. The strain rate sensitivity index has been used as a constant in numerical analysis of plastic forming at a specified strain rate and temperature. However, the value of m varies as deformation proceeds at an elevated temperature and a certain strain rate. Thus, in this present study, the value of m has been characterized as a function of strain by multiple tensile jump tests for AZ31 magnesium alloy sheet, and the variation of m has been discussed in conjunction with the microstructural observations before and after deformation. The experimental results show that the variation of m is dependent on the temperature and strain rate. Grain growth with dynamic recrystallization also affects the variation of m.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.156-158
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• 2004

The microstructural evolution in a 304 stainless steel weld during FSW was examined. The SZ and TMAZ showed typical dynamically recrystallized and recovered microstructures, respectively, The microstructural observation revealed that sigma phase was formed at the advancing side of the stir zone. A possibility was suggested that the rapid formation of the sigma phase is related to the transformation of austenite to delta-ferrite in the stir zone, from introduction of high strain and dynamic recrystallization during FSW.