• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.173-174
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• 2006

High power amplifier (HPA), which is used in transmitter of wireless communication systems, usually works in near saturation point in order to achieve maximum efficiency. In this region, HPA can introduce undesirable nonlinear effects. In this paper, we present a polynomial modeling method for efficient techniques to compensate for nonlinear distortion introduced by nonlinear HPA. Proposed polynomial predistorter inverses actual amplifier. Namely, we derive polynomials of amplifiers from analytical method and the electrical parameters in the data sheet of an actual amplifier and then can derive polynomial predistorter by inversing them. It is an effective and a simple method to compensate nonlinear distortion. SSPA(Solid-state power amplifier) is considered. We also analyze the effects of predistortion on the SER performance of communication system with 16-QAM modulation format. The results have shown the efficiency of this model.

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.181-191
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• 2006

As an alternative to traditional life testing, degradation tests can be effective in assessing product reliability when measurements of degradation leading to failure can be observed. This article proposes a new model to describe the nonlinear degradation paths caused by nano-contamination for plasma display panels (PDPs) : a bi-exponential model with random coefficients. A sequential likelihood ratio test was executed to select random effects in the nonlinear model. Analysis results indicate that the reliability estimation can be improved substantially by using the nonlinear random-coefficients model to incorporate both inherent degradation characteristics and contamination effects of impurities for PDP degradation paths.

• Steel and Composite Structures
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• v.32 no.3
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• pp.293-304
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• 2019

In the present paper, the element free Galerkin (EFG) method is developed for geometrically nonlinear analysis of deep beams considering small scale effect. To interpret the behavior of structure at the nano scale, the higher-order gradient elasticity nonlocal theory is taken into account. The radial point interpolation method with high order of continuity is used to construct the shape functions. The nonlinear equation of motion is derived using the principle of the minimization of total potential energy based on total Lagrangian approach. The Newmark method with the small time steps is used to solve the time dependent equations. At each time step, the iterative Newton-Raphson technique is applied to minimize the residential forces caused by the nonlinearity of the equations. The effects of nonlocal parameter and aspect ratio on stiffness and dynamic parameters are discussed by numerical examples. This paper furnishes a ground to develop the EFG method for large deformation analysis of structures considering small scale effects.

• Structural Engineering and Mechanics
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• v.82 no.2
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• pp.205-224
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• 2022

This paper presents a refined finite element formulation for nonlinear static and dynamic analysis of sliding cable structures, overcoming the limitation of the existing approaches that neglect or approximate the friction, pulley dimension, temperature and geometric nonlinearity. A new family of elements with the same framework is proposed, consisting of the cable-pulley (CP) elements considering sliding friction, and the non-sliding cable-pulley (NSCP) elements considering static friction. Thereafter, the complete procedure of static and dynamic analysis using the proposed elements is developed, with the capability of accurately dealing with the friction at each pulley. Several examples are utilized to verify the validity and accuracy of the proposed elements and analysis strategy, and investigate the frictional, thermal and pulley-dimension effects as well. The numerical examples show that the results obtained in this work are in good accordance with the existing works when using the same approximations of friction, pulley dimension and temperature. By avoiding the approximations, the proposed formulation can be effectively adopted in predicting the more precise nonlinear responses of sliding cable structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.6
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• pp.237-244
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• 2023

This study analyzes the seismic response of traffic light poles, considering soil-foundation effects through nonlinear static and time history analyses. Two poles are investigated, uni-directional and bi-directional, each with 9 m mast arms. Finite element models incorporate the poles, soil, and concrete foundations for analysis. Results show that the initial stiffness of the traffic light poles decreases by approximately 38% due to soil effects, and the drift ratio at which their nonlinear behavior occurs is 77% of scenarios without considering soil effects. The maximum acceleration response increases by about 82% for uni-directional poles and 73% for bi-directional poles, while displacement response increases by approximately 10% for uni-directional and 16% for bi-directional poles when considering soil-foundation effects. Additionally, increasing ground motion intensity reduces soil restraints, making significant rotational displacement the dominant response mechanism over flexural displacement for the traffic light poles. These findings underscore the importance of considering soil-foundation interactions in analyzing the seismic behavior of traffic light poles and provide valuable insights to enhance their seismic resilience and safety.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.454-457
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• 1997

As in most industrial processes, the dynamic characteristics of an electric power system are subject to changes. Amongst those effects which cause the system to be uncertain, faults on transmission lines are considered. For the stabilization of the power system, we present an indirect adaptive control method, which is capable of tracking a sudden change in the effective reactance of a transmission line. As the plant dynamics are nonlinear, an input-output feedback linearization method equipped with nonlinear damping terms is combined with an identification algorithm which estimates the effect of a fault. The stability of the resulting adaptive nonlinear system is investigated.

• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.913-917
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• 2009

The measures of leverage in linear regression has been extended to nonlinear regression models. We consider several curvature measures of nonlinearity in an estimation situation. The relationship between measures of leverage and statistical curvature are explored in nonlinear regression models. The circumstances under which the Jacobian leverage reduces to a tangent plane leverage are discussed in connection with the effective residual curvature of the nonlinear model.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.182-187
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• 2014

We propose nonlinear GMM-based transformation functions in an attempt to deal with the over-smoothing effects of linear transformation for voice processing. The proposed methods adopt RBF networks as a local transformation function to overcome the drawbacks of global nonlinear transformation functions. In order to obtain high-quality modifications of speech signals, our voice conversion is implemented using the Harmonic plus Noise Model analysis/synthesis framework. Experimental results are reported on the English corpus, MOCHA-TIMIT.

• International Journal of Aeronautical and Space Sciences
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• v.3 no.2
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• pp.24-30
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• 2002

This paper demonstrates a comparison of linear and nonlinear analyses for thermo-optic effects of optical temperature sensor based on the etched silica-based planar waveguide Bragg grating. Topics include theoretical analyses and experiment of the etched planar waveguide Bragg grating optical temperature sensor. Theoretical models with nonlinear than linear temperature effect for the grating response based on waveguide and plate deformation theories agree with experiments to within acceptable tolerance.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.768-770
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• 2001

The topology optimizations of electromagnetic systems with the nonlinear and the eddy current effects are studied using the finite element method. The topology design sensitivity formulations of nonlinear magnetostatics and eddy current systems are derived using the adjoint variable method. A computer program is developed using object orient programming and applied to the topology optimization of a C-core actuator. A numerical study shows the effects of saturation and eddy current by comparing results of topology optimizations.