• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.63-74
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• 1999

A sliding mode fuzzy control (SMFC) algorithm is presented for vibration of large structures. Rule-base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the nonlinear control algorithms. Fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation. Non-linearity of the control rule makes the controller more effective than linear controllers. Design procedure based on the present fuzzy control is more convenient than those of the conventional algorithms based on complex mathematical analysis, such as linear quadratic regulator and sliding mode control(SMC). Robustness of presented controller is illustrated by examining the loop transfer function. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator-structure interaction, modeling error, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as $H_{mixed 2/{\infty}}$ optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is an efficient and attractive control method, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.45-54
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• 2007

Time/frequency analysis has been extensively used in biomedical signal processing. By extracting some essential features from the electro-physiological signals, these methods are able to determine the clinical pathology mechanisms of some diseases. However, this method assumes that the signal should be stationary, which limits its application in non-stationary system. In this paper, we develop a new signal processing method using Hilbert-Huang Transform to perform analysis of the nonlinear and non-stationary ventricular fibrillation(VF). Hilbert-Huang Transform combines two major analytical theories: Empirical Mode Decomposition(EMD) and the Hilbert Transform. Hilbert-Huang Transform can be used to decompose natural data into independent Intrinsic Mode Functions using the theories of EMD. Furthermore, Hilbert-Huang Transform employs Hilbert Transform to determine instantaneous frequency and amplitude, and therefore can be used to accurately describe the local behavior of signals. This paper studied for Return Of Spontaneous Circulation(ROSC) and non-ROSC prediction performance by Support Vector Machine and three parameters(EMD-IF, EMD-FFT) extracted from ventricular fibrillation ECG waveform using Hilbert-Huang transform. On the average results of sensitivity and specificity were 87.35% and 76.88% respectively. Hilbert-Huang Transform shows that it enables us to predict the ROSC of VF more precisely.

• Geotechnical Engineering
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• v.13 no.5
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• pp.59-74
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• 1997

This paper shows the results of a series of model bests on the behavior of single steel pipe pile which is subjected to lateral load in Nak-dong river sand. The purpose of the present paper is to estimate the effect of Non -homogeneous soil, constraint condition of pile head, lateral load velocity, relative density of soil, embedded pile length, and flexural stiffness of pile on the behavior of single pile which is embedded in Nak-dong river strand. These effects can be quantined only by the results of model tests. The nonlinear responses of lateral loadieflection relationships are fitted to 2nd polynomial equations by model tests results. Also, the lateral load of a deflection, yield and ultimate lateral load max. bending moment, and yield bending moment can be expressed as exponential function in terms of relative density and deflection ratio. By comparing Brom's results with model results on the lateral ultimate load, it is found that short and long pile show the contrary results with each other. The contrary results are due to the smaller assumed soil reaction than the soil reaction of the Nakiong river sand at deep point. By comparing lateral behavior on the homogeneous soil with non-homogeneous soil, it is shown that lateral loadieflection relationship is very dependent on the upper relative density. This phenomenon is shown remarkably as the difference between upper and lower relative density increases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.325-333
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• 2020

Current methods of measuring the sediment concentration of natural streams can be affected by weather conditions and have lower reliability in bed-load sections due to mechanical limits. Theoretical methods have to be used to solve this problem, but they have low reliability compared to the measured values and diverse results for the bed-load sediment concentration. This study proposes a new way to reliably determine the bed-load sediment concentration from the relation with theoretical depth-integrated concentration based on the informational entropy concept. Sediment distribution shows a uniform probability distribution under maximized entropy conditions under some constraints, so a function can be calculated for the sediment distribution and depth-integrated concentration. The parameters of a stream were estimated by a nonlinear regression method using the concentration data from a past experiment. Equilibrium N (EN) was estimated using the relation between two different formulas proposed in this study, which can ease the estimation of both the total sediment distribution and depth-integrated sediment concentration with high reliable results with an average R2 of 0.924.

• Journal of Korean Society of Forest Science
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• v.86 no.3
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• pp.365-377
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• 1997

Much of the Cumberland Plateau of Tennessee, USA is in mixed hardwoods for which there are no applicable growth and yield predictors. Use of site index as a variable in growth and yield prediction models is limited in most stands because their history is not known and many may not be even-aged. Landtypes may offer an alternative to site index for these mixed stands because they were designed to include land of about equal productivity. To determine vegetation by landtype, dependency between landtype and detailed forest type was tested with Chi-square. Differences in productivity among landtypes were tested by employing regression analyses and analysis of variance(ANOVA). Basal area growth was fitted to the nonlinear models developed by Moser and Hall(1969). Basal area growth and volume growth were also predicted as a function of initial total basal area and initial volume with linear regression by landtype and by landtype class. Differences in basal area growth and volume growth by landtype were tested with ANOVA. Dependency between site class and landtype was tested with Chi-square. Vegetation types seem to be related to landtypes in the study area although the validity of the test is questionable because of a high proportion of sparsely occupied cells. No statistically significant differences in productivity among landtypes were found in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.4
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• pp.343-350
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• 2000

In this paper, we propose the Multi-FPNN(Fuzzy Polynomial Neural Networks) model based on FNN and PNN(Polyomial Neural Networks) for optimal system identifacation. Here FNN structure is designed using fuzzy input space divided by each separated input variable, and urilized both in order to get better output performace. Each node of PNN structure based on GMDH(Group Method of Data handing) method uses two types of high-order polynomials such as linearane and quadratic, and the input of that node uses three kinds of multi-variable inputs such as linear and quadratic, and the input of that node and Genetic Algorithms(GAs) to identify both the structure and the prepocessing of parameters of a Multi-FPNN model. Here, HCM clustering method, which is carried out for data preproessing of process system, is utilized to determine the structure method, which is carried out for data preprocessing of process system, is utilized to determance index with a weighting factor is used to according to the divisions of input-output space. A aggregate performance inddex with a wegihting factor is used to achieve a sound balance between approximation and generalization abilities of the model. According to the selection and adjustment of a weighting factor of this aggregate abjective function which it is acailable and effective to design to design and optimal Multi-FPNN model. The study is illustrated with the aid of two representative numerical examples and the aggregate performance index related to the approximation and generalization abilities of the model is evaluated and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.717-722
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• 2011

The purpose of this study is to predict the residual stress in Al6061 during T6 heat treatment. In this study, the variable residual stress in case of the solid solution($530^{\circ}C$, 2h) and artificial ageing($175^{\circ}C$, 9h) of Al6061 subjected to T6 heat treatment is determined at different ageing times. A heat treatment experiment is conducted to determine the heat transfer coefficient, on the basis of which the residual stress during the T6 heat treatment is predicted. In order to take into account the relaxation of residual stress during artificial ageing, a Zener-Wert-Avrami function is used and elasto-plastic nonlinear analysis is conducted through FE-simulation. Further, the residual stress is measured by using the X-ray diffraction(XRD) method, and the result is compared with the result from the FE-simulation. It is found that the residual stress predicted form the FE-simulation is in good agreement with the residual stress measured by using the XRD method.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.46-51
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• 2014

The most important process of engineering system optimal design is to identify the relationship between the design variables and system response. In case of the system optimization, Response Surface Method (RSM) is widely used. The optimization process of RSM generates the design space using the typical alternative candidates and finds the optimal design point in the generated design space. By changing the optimal point depending on the configuration of the design space, it is important to generate the design space. Therefor in this study, the design space is generated by using the relationship between design variables and system response based on Neuro-Response Surface Method (NRSM). And I try to construct the framework for optimal shape design based on NRSM that the optimum shape can be predicted using the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) within the generated design space. In order to verify the usefulness of the constructed framework, we applied the nonlinear mathematical function problem. In this study, we can solve the constraints of time in the optimization process for the engineering problem and effective to determine the optimal design was possible. by using the generated framework for optimal shape design based on NRSM. In the future research, we try to apply the optimization problem for Naval Architectural & Ocean Engineering based on the results of this study.

• Korean journal of applied entomology
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• v.35 no.2
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• pp.119-125
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• 1996

Temperature-dependent development study for overwintered eggs of Pseudococcus comstocki (Kuwana) wasconducted to develop a forecasting model for egg hatch date. Hatch times of overwintered eggs were comparedat five constant temperatures (10, 15, 20, 25, 27$^{\circ}$C) and different collection dates. A nonlinear, four-parameterdevelopmental model with high temperature inhibition accurately described (R2=0.9948) mean developmentalrates of all temperatures. Variation in developmental times was modeled(~~=0.972w9)it h a cumulative Weibullfunction. Least-squares linear regression (rate=O.O06358[Temp.]-0.07566)d escribed development in the linearregion (15-25$^{\circ}$C) of the development curve. The low development threshold temperature was estimated 11.9"Cand 154.14 degree-days were required for complete development. The linear degree-day model (thermal summation)and rate summation model (Wagner et al. 1985) were validated using field phenology data. In degreedaymodels, mean-minus-base method, sine wave method, and rectangle method were used in estimation of dailythermal units. Mean-minus-base method was 18 to 28d late, sine wave method was 11 to 14d late, rectanglemethod was 3 to 5d late, and rate summation model was 2 to 3d late in predicting 50% hatch of overwinteredeggs. hatch of overwintered eggs.