• Journal of the Chungcheong Mathematical Society
• /
• v.30 no.4
• /
• pp.397-409
• /
• 2017

In this paper, we investigated the extinction, positivity, and decay estimates of the solutions to the initial-boundary value problem of the semilinear parabolic equation with nonlinear gradient source and interior absorption terms by using the integral norm estimate method. We found that the decay estimates depend on the choices of initial data, coefficients and domain, and the first eigenvalue of the Laplacean operator with homogeneous Dirichlet boundary condition plays an important role in the proofs of main results.

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.11
• /
• pp.86-89
• /
• 1996

This paper describes compensation method to evaluate arousal level in different initial arousal state. Arousal level was measured by the relationship between IRI and Nz. The value of Nz is affected by BI which is variable with initial drowsiness. we introduced a correction factor to compensate these differences.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.176-178
• /
• 1998

Recently, Control method of induction Motor is applied in full circuit model, as circular diagram. In Elevetor moderization problem, there is no circuit information. Nothing but, Motor terminal voltage and HP of motor. So, in this study, using KS induction Motor table, try to solve initial valve problem and make some implementations of manual tuning for use of automatic tuning of induction motor parameter.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4A
• /
• pp.465-474
• /
• 2008

Generally design of frame structures composed of beam-column member is accomplished by stability evaluation of each member considering the effective buckling length. This study selects a member of the smallest non-dimension slenderness ratio using the buckling eigenvalue calculated by the elastic buckling eigen-value analysis and axial force of the each member, and decides the initial deflection quantity reflected geometric and material nonlinearities from a suggested equation on the base of standard strength curve of Korea Bridge Design Code. Second-order elastic analysis applying the initial deflection is executed and the stability of each member is evaluated and decides ultimate strength. Through examples of eight-stories and four-stories plane frame structures, the evaluation of the stability is compared with the existing method and ultimate strength of the suggested method is compared with ultimate strength by the nonlinear inelastic analysis. Through these procedures, the increasing of effective buckling length by elastic buckling eigenvalue analysis is prevented from a new design method that considers initial imperfections. And the validity of this method is proved.

• 제어로봇시스템학회:학술대회논문집
• /
• 1998.10a
• /
• pp.85-88
• /
• 1998

We have developed an eigenvalue method for impedance computed tomography to improve the ill-conditioning problem. We have compared the performance of this method and the balancing method by computer simulations. As a result, it was proved that this method is better than the balancing method very much. It was found that the initial value condition is not so severe to obtain good images.

• Structural Engineering and Mechanics
• /
• v.66 no.6
• /
• pp.677-691
• /
• 2018

Reliability assessment of complex structures using simulation methods is time-consuming. Thus, surrogate models are usually employed to reduce computational cost. AK-MCS is a surrogate-based Active learning method combining Kriging and Monte-Carlo Simulation for structural reliability analysis. This paper proposes three modifications of the AK-MCS method to reduce the number of calls to the performance function. The first modification is related to the definition of an initial Design of Experiments (DoE). In the original AK-MCS method, an initial DoE is created by a random selection of samples among the Monte Carlo population. Therefore, samples in the failure region have fewer chances to be selected, because a small number of samples are usually located in the failure region compared to the safe region. The proposed method in this paper is based on a uniform selection of samples in the predefined domain, so more samples may be selected from the failure region. Another important parameter in the AK-MCS method is the size of the initial DoE. The algorithm may not predict the exact limit state surface with an insufficient number of initial samples. Thus, the second modification of the AK-MCS method is proposed to overcome this problem. The third modification is relevant to the type of regression trend in the AK-MCS method. The original AK-MCS method uses an ordinary Kriging model, so the regression part of Kriging model is an unknown constant value. In this paper, the effect of regression trend in the AK-MCS method is investigated for a benchmark problem, and it is shown that the appropriate choice of regression type could reduce the number of calls to the performance function. A stepwise approach is also presented to select a suitable trend of the Kriging model. The numerical results show the effectiveness of the proposed modifications.

• Solar Energy
• /
• v.8 no.1
• /
• pp.82-94
• /
• 1988

The hydrodynamic stability equations for natural convection flows adjacent to a vertical isothermal surface in cold or warm water (Boussinesq or non-Boussinesq situation for density relation), constitute a two-point-boundary-value (eigenvalue) problem, which was solved numerically using the simple shooting and the orthogonal collocation method. This is the first instance in which these stability equations have been solved using a computer code COLSYS, that is based on the orthogonal collocation method, designed to solve accurately two-point-boundary-value problem. Use of the orthogonal collocation method significantly reduces the error propagation which occurs in solving the initial value problem and avoids the inaccuracy of superposition of asymptotic solutions using the conventional technique of simple shooting.

• Nuclear Engineering and Technology
• /
• v.30 no.3
• /
• pp.202-211
• /
• 1998

Interfacial stresses at two-material interfaces and initial displacement field over the entire domain are obtained by modifying the potential energy functional with a penalty function, which enforces continuity of the stresses at the interface of two materials. Based on the initial displacement field and interfacial stresses, a new methodology to generate a continuous stress field over the entire domain has been proposed by combining the modified projection method of stress-smoothing and Loubignac's iterative method of improving the displacement field. Stress analysis is carried out on two examples made of dissimilar materials : one is a two-material cantilever composed of highly dissimilar materials and the other is a zirconium-lined cladding tube made of slightly dissimilar materials. Results of the analysis show that the proposed method provides an improved continuous stress field over the entire domain, and accurately predicts the nodal stresses at the interface, while the conventional displacement-based finite element method produces significant stress discontinuities at the interface. In addition, the total strain energy evaluated from the improved continuous stress field converges to the exact value in a few iterations.

• Proceedings of the KIEE Conference
• /
• 2000.07d
• /
• pp.3019-3021
• /
• 2000

In this paper. a new fuzzy modeling algorithm is proposed : it can express a given unknown system with a small number of fuzzy rules and be easily implemented. This method uses an independent array instead of a lattice form for a premise membership function. For the purpose of getting the initial value of fuzzy rules. the method uses the fuzzy c-means clustering method. To optimally tune the initial fuzzy rule. the DNA coding method is also utilized at same time. Box and Jenkins's gas furnace data is used to illustrate the validity of the proposed algorithm.

• Journal of The Korean Society of Clinical Toxicology
• /
• v.2 no.2
• /
• pp.72-76
• /
• 2004

Purpose: Dealing patients with organophosphate poisoning, cholinesterase level has been used as a diagnostic and prognostic value. But there are some controversies that the cholinesterase level is significantly related to the severity or prognosis of acute organophosphate poisoning. We evaluated the correlation between initial serum level of cholinesterase and APACHE II score as an index for severity, and we assessed cholinesterase levels for predicting value of weaning from mechanical ventilation. Method: From August 1996 to March 2003, 23 patients with organophosphate poisoning who needed ventilatory care were enrolled. Retrospective review was done for the serum level of cholinesterase, APACHE II score, and the duration of ventilatory care. The percentage of measured serum cholinesterase to median normal value was used to standardize cholinesterase levels from different laboratories. Result: There were tendencies that the lower initial serum of cholinesterase, the higher the APACHE II score (r=0.297) and the longer the duration of mechanical ventilation (r=-0.204), but they were not significant (p=0.264 and p=0.351 respectively). In 9 patients whose serum cholinesterase level were checked at the time of weaning, mean of measured cholinesterase level was $10.3\pm7.60\%$ of normal value. Conclusion: There was no significant relationship between initial level of serum cholinesterase and severity or duration of mechanical ventilation. General health status of patient, amount of ingestion, toxicity of agent should be considered as important factors for severity of poisoning. And the decision of weaning should be based not solely on the cholinesterase level but on the consideration of general and respiratory state of individual patients.