• Journal of Mechanical Science and Technology
• /
• v.14 no.1
• /
• pp.103-112
• /
• 2000

Numerical simulations of unsteady opposed-flow flames are performed using an adaptive time integration method designed for differential-algebraic systems. The compressibility effect is considered in deriving the system of equations, such that the numerical difficulties associated with a high-index system are alleviated. The numerical method is implemented for systems with detailed chemical mechanisms and transport properties by utilizing the Chemkin software. Two test simulations are performeds hydrogen/air diffusion flames with an oscillatory strain rate and transient ignition of methane against heated air. Both results show that the rapid transient behavior is successfully captured by the numerical method.

• Smart Structures and Systems
• /
• v.17 no.4
• /
• pp.611-629
• /
• 2016

This study presents a new approach of surrogate modeling for time-consuming finite element analysis. A surrogate model is widely used to reduce the computational cost under an iterative computational analysis. Although a variety of the methods have been widely investigated, there are still difficulties in surrogate modeling from a practical point of view: (1) How to derive optimal design of experiments (i.e., the number of training samples and their locations); and (2) diagnostics of the surrogate model. To overcome these difficulties, we propose a sequential surrogate modeling based on Gaussian process model (GPM) with self-adaptive sampling. The proposed approach not only enables further sampling to make GPM more accurate, but also evaluates the model adequacy within a sequential framework. The applicability of the proposed approach is first demonstrated by using mathematical test functions. Then, it is applied as a substitute of the iterative finite element analysis to Monte Carlo simulation for a response uncertainty analysis under correlated input uncertainties. In all numerical studies, it is successful to build GPM automatically with the minimal user intervention. The proposed approach can be customized for the various response surfaces and help a less experienced user save his/her efforts.

• 제어로봇시스템학회:학술대회논문집
• /
• 1987.10b
• /
• pp.658-663
• /
• 1987

The new controller developed here, which is the facility with only one measurement, is a new concept for the level controller of the existing nuclear steam generator. A MACS (Microcomputer-based Adaptive Control System of a Steam Generator) is quite practical and efficient, and has also simple structure and higher flexibility in the installment for actual plant. A key ingredient of this system is adaptive regulator which can calculate adaptive, optimal valve position in response to changes in the dynamics of the process and the disturbances. In spite of many difficulties in the steam generator water level control at low power, it can be concluded from the experimental and simulation results, that the MACS can provide optimal, robust steam generator level control from zero to full power. The amount of the control input effort can be reduced by adjusting the weighting factor. However, the steady state water level errors are generated. To avoid the steady errors, the different adaptive algorithm should be investigated in the future. The 3 second sampling time is acceptable for this system. However, action should be taken to shorten the sampling time for better digital control.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.1
• /
• pp.451-465
• /
• 2017

This paper presents a novel discriminative visual tracking algorithm with an adaptive incremental extreme learning machine. The parameters for an adaptive incremental extreme learning machine are initialized at the first frame with a target that is manually assigned. At each frame, the training samples are collected and random Haar-like features are extracted. The proposed tracker updates the overall output weights for each frame, and the updated tracker is used to estimate the new location of the target in the next frame. The adaptive learning rate for the update of the overall output weights is estimated by using the confidence of the predicted target location at the current frame. Our experimental results indicate that the proposed tracker can manage various difficulties and can achieve better performance than other state-of-the-art trackers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1995.03a
• /
• pp.211-223
• /
• 1995

The purpose of the present study is to examine shearing mechanism through rigidplastic finite element analysis. Difficulties arise in simulating shearing process due tothe narrow shear band formation andlackof proper fracture resolve these difficulties by using adaptive mesh generation crriterion. The simulation results are obtained for various punch clearances and these are compared with existing experimental results. It is shown that FEM simulation technique can be used to further understand the shearing mechanism.

• Journal of Korean Elementary Science Education
• /
• v.26 no.1
• /
• pp.97-107
• /
• 2007

The purpose of this study is to discover and develop any implications which may arise in relation to science teachers' professional growth and development by investigating the difficulties experienced by elementary school teachers in science classes. 196 elementary school teachers were requested to write an anecdotal report regarding their science lessons. 30 science teachers in middle school also answered the same questionnaire. By means of inductive categorical analyzing, the difficulties were grouped into several categories. The results were as follows: (1) The difficulties elementary teachers experience in their science lessons fall into three categories; 'professional science knowledge(9.8%)', 'science laboratory activities(78.3%)', 'teaching methodology(11.2%)'. (2) Science teachers in middle school experienced similar difficulties. However, distribution differed from that of elementary school teachers; 'professional science knowledge(39.0%)', 'science laboratory activities(35.6%)', 'teaching methodology(27.1%)'. (3) The causes of these difficulties were identified as follows; a lack of time to prepare for science classes, insufficient substantial pre-service teacher education, and a lack of adaptive support to elementary school teachers.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10a
• /
• pp.360-363
• /
• 1993

Fuzzy Logic Control immitating human decision making process is a novel control strategy based on expert's experience and knowledge and many process designers are developing its applications. But it is difficult to obtain a set of rules from human operator. And there is a limitation on adjusting to environmental changes. In this paper, we proposed adaptive fuzzy algorithm to overcome these difficulties using weights added to the rules. To verify the validity of this control strategy, we have implemented this algorithm for a DC servo motor with PD-type fuzzy controller.

• Journal of the Ergonomics Society of Korea
• /
• v.24 no.4
• /
• pp.73-78
• /
• 2005

As the number of functions in a menu increases, users have more difficulties in finding a desired function. Previous studies have shown that some functions are selected more frequently than others, and have suggested adaptive menus that support the selection of frequently used functions. Interestingly, studies on an adaptive toolbar are not easy to find as opposed to many studies on adaptive menus. This study suggested an adaptive toolbar (AT) that supported function selection, and conducted a usability test. Five or ten functions were presented in the AT according to the frequency of use or recency of use. A total of sixteen males in their twenties participated in the test. They freely selected functions from the menu or from the AT, and their pattern of selecting functions was analyzed. The results showed that the AT was more frequently used than the menu as time passed. The AT based on the recency of use showed more effective performance than that based on the frequency of use. In addition, keeping ten functions was better than five functions in terms of both performance and preference.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.5 no.3
• /
• pp.73-82
• /
• 1995

The paper demonstrates that an adaptive fuzzy controller can be used effectively for the control of the temperature and density of the Tokarnak fusion recator which is nonlinear and has dynamic uncertainties. The dynamic uncertainties are non-parametric but state dependent. Thus the conventional adaptive nonlinear control methods have difficulties to cope with the problem. The proposed adaptive fuzzy controller can be used as a solution and performs well in a predetermined local space. Simulation result verifies the effectiveness of the scheme.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.271-274
• /
• 2007

The finite element linear buckling analysis of folded plate structures using adaptive h-refinement methods is presented in this paper. The variable-node flat shell element used in this study possesses the drilling D.O.F. which, in addition to improvement of the element behavior, permits an easy connection to other elements with six degrees of freedom per node. The Box-typed structures can be analyzed using these developed flat shell elements. By introducing the variable node elements some difficulties associated with connecting the different layer patterns, which are common in the adaptive h-refinement on quadrilateral mesh, can be overcome. To obtain better stress field for the error estimation, the super-convergent patch recovery is used. The convergent buckling modes and the critical loads associated with these modes can be obtained.