• IEIE Transactions on Smart Processing and Computing
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• 제5권6호
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• pp.440-444
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• 2016

In this paper, an equivalent circuit model for near-field noise emission is proposed to implement a multimedia operation-monitoring system for mobile devices. The proposed model includes a magnetic field probe that captures noise emissions from multimedia components, and a transfer function for near-field noise coupling from a transmission line source to a magnetic field probe. The proposed model was empirically verified with transfer function measurements of near-field noise emissions from 10 kHz to 500 MHz. With the proposed model, a magnetic field probe was optimally designed for noise measurement on a camera module and an audio codec in a mobile device. It was demonstrated that the probe successfully captured the near-field noise emissions, depending on the operating conditions of the multimedia components, with enhanced sensitivity from a conventional reference probe.

• 전기학회논문지
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• 제65권4호
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• pp.652-658
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• 2016

In practical control systems differences between nominal and real systems arise from internal uncertainties and/or external disturbances. This paper presents a model-based low-order disturbance observer for a sinusoidal disturbance with unknown constant offset. By using the disturbance model of a biased harmonic signal, the proposed method can successfully estimate the biased sinusoidal disturbance with unknown amplitude and phase but known frequency. At the first stage of the observer design, a model-based disturbance observer is designed when all the system states are measurable. Next, a sufficient condition is presented for the proposed observer to estimate the sinusoidal disturbance with a minimal-order additional dynamics using only output measurement. Comparative computer simulations are performed to test the performance of the proposed method. The simulation results show the enhanced performance of the proposed disturbance observer.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2749-2761
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing. Finite element results by using the proposed model also well predicted experimental data in the literature for densification behavior of nanocrystalline zirconia powder during pressureless sintering and sinter forging.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.148-157
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• 1996

Availability of input trajectories corresponding to desired output trajectories is often important in designing control systems for batch and other transient processes. In this paper, we propose a predictive control-type model-based iterative learning algorithm which is applicable to finding the nominal input trajectories of a linear time-invariant batch process. Unlike the other existing learning control algorithms, the proposed algorithm can be applied to nonsquare systems and has an ability to adjust noise sensitivity as well as convergence rate. A simple model identification technique with which performance of the proposed learning algorithm can be significantly enhanced is also proposed. Performance of the proposed learning algorithm is demonstrated through numerical simulations.

• 대한기계학회논문집
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• 제17권7호
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• pp.1668-1677
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• 1993

The objective of this paper is to develop a computational model for predicting the fatigue propagation of collinear multiple surface cracks under constant amplitude and variable amplitude loadings. After examining fatigue crack growth behavior for CT specimens and single surface crack specimens, empirical equations of(11) and(12) are proposed for the prediction of fatigue life in a multiple surface crack geometry. The accuracy of the proposed model is verified using a life prediction computer program. Several case studies were performed to check the accuracy of the proposed model and to verify the usefulness of the developed program. Good agreement is observed between the numerical results based on the proposed model and the published experimental data.

• The Journal of the Acoustical Society of Korea
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• 제15권3E호
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• pp.37-44
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• 1996

A new method for efficient modeling of the Head-Related Transfer Functions(HRTF's) without loss of any directional information is proposed. In this paper, the HRTF's were empirically measured in a real room and modeled as the ARMA models with common AR coefficients and different MA coefficients. To assess the validity of the proposed ARMA model, psychophysical tests show that the proposed ARMA model, in comparison with the conventional MA model, requires a small number of parameters to represent empirical HRTF's and improves the back-to-front confusions in sound-field localization. Thus, significant simplifications in the implementations of sound-field synthesis systems could be obtained by using the proposed ARMA model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.563-565
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• 1998

In this paper, we are proposed optimization method of fuzzy model in order to complex and nonlinear system. In the fuzzy modeling, a premise identification is very important to describe the charateristics of a given unknown system. Then, the proposed fuzzy model implements system structure and parameter identification, using the fuzzy inference method and genetic algorithms. Inference method for fuzzy model presented in our paper include the simplified inference and linear inference. Time series data for gas furance and sewage treatment process are used to evaluate the performance of the proposed model. Also, the performance index with weighted value is proposed to achieve a balance between the results of performance for the training and testing data.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제14권3호
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• pp.171-180
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• 2014

In this paper, a multiple sliding surface (MSS) controller for a twin rotor multi-input-multioutput system (TRMS) with mismatched model uncertainties is proposed. The nonlinear terms in the model are regarded as model uncertainties, which do not satisfy the standard matching condition, and an MSS control technique is adopted to overcome them. In order to control the position of the TRMS, the system dynamics are pseudo-decomposed into horizontal and vertical subsystems, and two MSSs are separately designed for each subsystem. The stability of the TRMS with the proposed controller is guaranteed by the Lyapunov stability theory. Some simulation results are given to verify the proposed scheme, and the real time performances of the TRMS with the MSS controller show the effectiveness of the proposed controller.

• Geomechanics and Engineering
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• 제7권4호
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• pp.335-353
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• 2014

The softening hyperelastic model based on the strain energy limitation is of clear concepts and simple forms to describe the failure of materials. In this study, a linear and a nonlinear softening hyperelastic model are proposed to characterize the deformation and the failure in granular materials by introducing a softening function into the shear part of the strain energy. A method to determine material parameters introduced in the models is suggested. Based on the proposed models the numerical examples focus on bearing capacity and strain localization of granular materials. Compared with Volokh softening hyperelasticity and classical Mohr-Coulomb plasticity, our proposed models are able to capture the typical characters of granular materials such as the strain softening and the critical state. In addition, the issue of mesh dependency of the proposed models is investigated.

• 통합자연과학논문집
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• 제14권2호
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• pp.35-40
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• 2021

In this paper, we proposed a multi-subject-level sentiment analysis model for user reviews using the Latent Dirichlet Allocation (LDA) method targeting user-generated content (UGC). Data were collected from users' online reviews of hotels in major tourist cities in the world, and 30 hotel-related topics were extracted using the entire user reviews through the LDA technique. Six major hotel-related themes (Cleanliness, Location, Rooms, Service, Sleep Quality, and Value) were selected from the extracted themes, and emotions were evaluated for sentences corresponding to six themes in each user review in the proposed sentiment analysis model. Sentiment was analyzed using a dictionary. In addition, the performance of the proposed sentiment analysis model was evaluated by comparing the emotional values for each subject in the user reviews and the detailed scores evaluated by the user directly for each hotel attribute. As a result of analyzing the values of accuracy and recall of the proposed sentiment analysis model, it was analyzed that the efficiency was high.