• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.2
• /
• pp.495-508
• /
• 1995

The self-excited vibrations of airfoil is related to the classical flutter problems, and it has been studied as a system with linear stiffness and small damping. However, since the actual aircraft wing and the many mechanical elements of airfoil type have various design variables and parameters, some of these could have strong nonlinearities, and the nonlinearities could be unexpectedly strong as the parameters vary. This abrupt chaotic behavior undergoes ordered routes, and the behaviors after these routes are uncontrollable and unexpectable since it is extremely sensitive to initial conditions. In order to study the chaotic behavior of the system, three parameters are considered, i.e., free-stream velocity, elastic distance and zero-lift angle. If the chaotic parameter region can be identified from the mathematically modeled nonlinear differential equation system, the designs which avoid chaotic regions could be suggested. In this study, by using recently developed dynamically system methods, and chaotic regions on the parameter plane will be found and the safe design variables will be suggested.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.2
• /
• pp.357-364
• /
• 2022

A pseudo-random number generator (PRNG) is a program used when a large amount of random numbers is needed. It is used to generate symmetric keys in symmetric key cryptography systems, generate public key pairs in public key cryptography or digital signatures, and generate columns used for padding with disposable pads. Cellular Automata (CA), which is useful for specific representing nonlinear dynamics in various scientific fields, is a discrete and abstract computational system that can be implemented in hardware and is applied as a PRNG that generates keys in cryptographic systems. In this paper, I propose an algorithm for synthesizing a programmable 5-neighbor CA based PRNG that can effectively generate a nonlinear sequence using 5-neighbor CA with the radius of the neighboring cell increased by 2.

• Journal of Korea Multimedia Society
• /
• v.8 no.5
• /
• pp.670-678
• /
• 2005

A Cellular Automaton(CA) is a dynamical system in which space and time are discrete, the state of each cell is unite and is updated by local interaction. Since the characteristics of CA is diffusion and local interaction, CA is used by crypto-systems and VLSI structure. In this study, we proposed a hash function based on the concept of 2-dimensional cellular automata and analyzed the proposed hash function.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.5
• /
• pp.483-488
• /
• 2016

Plug-In Digital Framework is a system response analysis tool that is employed when system components are composed of black-box modules. Generally, the dynamic characteristics of joints between the system components significantly affect system responses, and they lead to displacement- and frequency-dependent stiffness and loss factor. Thus, the sensitivity of each joint parameters should be estimated from a global perspective. In this study, we introduce a global sensitivity analysis procedure under the Plug-In Digital Framework. To efficiently calculate the system responses, we introduce the frequency response function (FRF)-based substructuring method. Using the random balance designs (RBD), we generate the system responses and estimate the global first-order sensitivities for each joint stiffness. We apply the proposed global sensitivity analysis method to an interior noise problem of a passenger car, and we evaluate the efficiency of the global sensitivity analysis method.

• Journal of the Korean Data and Information Science Society
• /
• v.28 no.2
• /
• pp.371-381
• /
• 2017

There has never been research on Chaos analysis using real estate auction sale price rate in Korea. In this study, three Chaos analysis methodologies - Hurst exponent, correlation dimension, and maximum Lyapunov exponent - in order to capture the nonlinear deterministic dynamic system characteristics. High level of Hurst exponent and the extremely low maximum Lyapunov exponent provide the tendency and the persistence of the data. The empirical results give two meaningful facts. First, monthly time lags of the correlation dimension are coincident with the time period from the approval auction start day to the sale price fixing day. Second, its weekly time lags correspond to the time period from the last day of request for sale price allocation to the sale price fixing day. Then, this study potentially examines the predictability of the real estate auction price rate time series.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.3 s.234
• /
• pp.369-386
• /
• 2005

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes