• Nuclear Engineering and Technology
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• 제36권3호
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• pp.237-247
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• 2004

To investigate the applicability of automated ball indentation (ABI) tests in the evaluation of the tensile properties of cast stainless steel (CSS), ABI tests were performed on four types of unaged CSS and on 316 stainless steel, all of which had a different microstructure and strength. The reliability of ABI test data was analyzed by evaluating the data scattering of the ABI test and by comparing tensile properties obtained from the ABI test and the tensile test. The results show that the degree of scattering of the ABI test data is reasonably acceptable in comparison with that of standard tensile data, when two points data that exhibit out-of-trend are excluded from five to seven points data tested on a specimen. In addition, the scattering decreases slightly as the content of ${\delta}-ferrite$ in CSS increases. Moreover, the ABI test can directly measure the flow parameters of CSS with error bounds of about ${\pm}10\%$ for the ultimate tensile stress and the strength coefficient, and about ${\pm}15\%$ for the yield stress and the strain hardening exponent. The accuracy of the ABI test data is independent of the amount of ${\delta}-ferrite$ in the CSS.

• 한국통신학회논문지
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• 제22권9호
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• pp.1998-2004
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• 1997

본 논문에서는 이전의 논문에서 제시된 칩확산 직교부호분할변조(OCDM) 시스템의 성능을 분석하고, 모의 실험을 통해 기존의 DS/CDMA 시스템과 성능을 비교한다. 성능분석 결과로서, 칩확산 OCDM 시스템의 비트 오류율의 상한선이 최대율 결합(MRC)을 사용하는 기존 DS/CDMA 시스템의 비트 오류율에 해당하며, 하한선은 그보다 훨씬 향상된 결과가 됨을 보인다. 모의 실험 결과, 실제로 OCDM 시스템의 비트 오류율 성능이 분석 결과로 얻어진 상한선과 하한선 사이에 위치하며, DS/CDMA 시스템보다 낮은 비트 오류율이 얻어짐을 확인한다.

• Journal of applied mathematics & informatics
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• 제28권5_6호
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• pp.1035-1054
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• 2010

We consider a mixed type singularly perturbed one dimensional elliptic problem with discontinuous source term. The domain under consideration is partitioned into two subdomains. A convection-diffusion and a reaction-diffusion type equations are posed on the first and second subdomains respectively. Two hybrid difference schemes on Shishkin mesh are constructed and we prove that the schemes are almost second order convergence in the maximum norm independent of the diffusion parameter. Error bounds for the numerical solution and its numerical derivative are established. Numerical results are presented which support the theoretical results.

• 전자공학회논문지S
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• 제34S권3호
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• pp.24-32
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• 1997

This paper is on a discrete controller order reduction with the closed-loop stability and performance guaranteed. to achieve this, after finding the solutionsof two lyapunov inequalities and balancing the full order controller system, we find the reudced order controlers using the balanced truncation (BT) and the balanced singular perturbation approximation (BSPA). When the solutions of the two lyapunov inequalities exist, it is shown that the resulting controllers guarantee the closed-loop stability, and .inf.-norm error bounds are derived for the closed-loop performance region for the BT and in low frequency region for the BSPA. Finally, a numerical example is given to illustrate the validity of the proposed method.

• East Asian mathematical journal
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• 제27권3호
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• pp.319-337
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• 2011

We approximate a locally unique solution of a nonlinear equation in a Banach space setting using an inexact two-step Newton-type method. It turn out that under our new idea of recurrent functions, our semilocal analysis provides tighter error bounds than before, and in many interesting cases, weaker sufficient convergence conditions. Applications including the solution of nonlinear Chandrasekhar-type integral equations appearing in radiative transfer and two point boundary value problems are also provided in this study.

• 한국항해학회지
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• 제12권3호
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• pp.1-21
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• 1988

A Satellite -aided search and rescue system is expected for its many advantage of global coverage, instantaneousness and low cost. In this paper, a calculation method is proposed , by which a position of distress can be determined with doppler frequency received through an orbital satellite. First, an algorithm and program is developed for calculating the position of distress with the received doppler frequency of EPIRB(Emergency Position Indicating Radio Beacon) with the least square method. Then, position error caused by the drift of the transmitting frequency is evaluated. The evaluation is made by the simulation using NNSS satellite orbital elements and varying position of EPIRB, numbers of Doppler data and magnitudes of various errors. As the result, the availability of this program for a satellite-aided search and rescue system is confirmed and the bounds of expected positioning accuracy is clarified.

• 전력전자학회논문지
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• 제1권1호
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• pp.7-11
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• 1996

From the cost-effective point of view, it is very important to design a current with the highest utilization factor of current capacity of power devices. This can be accomplished by a current controller without overshoot irrespective of the varying bounds of control voltage in PWM converters and the dead time due to the time delay. This paper suggests a novel decoupled controller with Smith-Predictor which has the fast control response without overshoot and steady stats error and also deal with the design method of the controller for PWM converters. The extensive digital simulations done by SIMULINK/MATLAB show that the suggested controller guarantees the full utilization of current capacity of power devices and the decoupled current control behavior.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.21-23
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• 1994

The degree of forecast accuracy with BP-algorithm largely depends upon the neuron number in hidden layer. In order to construct the optimal structure, first, we prescribe the error bounds of learning procedure, and then, we provid the method of incrementing the number of hidden neurons by using the derivative of errors with respect to an output neuron weights. For the case study, we apply the proposed method to forecast the component-wise residential load, and compare this results to that of time series forecasting.

• Geosystem Engineering
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• 제21권6호
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• pp.297-308
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• 2018

In this paper, we investigate the differences between LNG price of South Korea and Japan. Although S. Korean and Japanese LNG markets have similar structures, there are some differences in the price formation. From DCC-MGARCH, we confirm that Japan LNG price have less persistence of disturbance on time than S. Korean LNG price. The conditional correlation also shows linkage effects between LNG prices and impacts of S-curve and DS-curve. Moreover, ARDL estimation result shows that there is co-integration in all models and that impacts of Fukushima accident and LNG volumes are responsible for the increase in Japanese LNG price. Also, adjustment speed of error correction term shows that Japan's deviation from long-run equilibrium disappears faster than S. Korea does, indicating relatively strong Japanese linkage between LNG price and oil price.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.289-294
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• 1998

The distributed-parameter structures expressed with the partial differential equations are considered as the infinite-dimensional dynamic system. For implementation of a controller in multivariate systems, it is necessary to derive the state-space reduced order model. By the eigensystem realization algorithm, we can yield tile subspace system with the Markov parameters derived from the measured frequency response function by the inverse discrete Fourier transformation. We also review the necessary conditions for the convergence of the approximation system and the error bounds in terms of the singular values of Markov-parameter matrices. To determine the natural frequencies and modal damping ratios, the modal coordinate transformation is applied to the realization system. The vibration test for a smart structure is performed to provide the records of frequency response functions used in the subspace system realization.