• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.55-64
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• 2002

This paper presents a brief review of flexible retaining structure and the most significant methods developed to predict their behavior on underground excavations. Some observations are made about the future directions that the design of retaining systems may take , as there are still some problems where uncertainity exists, in soil-structure interaction and evaluation of strength parameters etc. And also reviewed papers presented in 2002 Fall National Conference of KGS.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.5
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• pp.23-29
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• 1991

Uncertainty is studied in the measurements of average packing density, thickness of packed spheres and transmittance in the experiments to study the effect of the bed height and the existence of the bed side walls on the transmittance of radiative energy through packed spheres. The packing density of the bed is obtained by counting the number of the spheres packed in three pipes with different heights. The bed height of the packed spheres is estimated from the number of spheres contained in the bed by using the relation between the bed height and the sphere number. The transmittance is obtained by dividing the intensity of the transmitted laser beam by the incoming-beam intensity. From the analysis, the uncertainity in the measurements of transmittance is shown to be less than 10.2%(95% coverage).

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.341-354
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• 2003

Radioactive iodine therapy using I-131 for hyperthyroidism has been used for more than 50 years, and generally considered safe and devoid of major side effects. Appropriate patient selection criteria and clinical judgement concerning patient preparation should be employed for its optimal use. It has not been possible to resolve the trade-off between efficient definite cure of hyperthyroidism and the high incidence of post-therapy hypothyroidism. The dose of the I-131 needed to maintain euthyroid state remains an area of uncertainity and debate. Early side effects are uncommon and readily managable. Other than the need for long-term monitoring and, in most cases, lifelong thyroid hormone treatment for late adverse consequences of this treatment remains only conjectural. We have reviewed general principles and recent advances in radioiodine treatment for Graves' hyperthyroidism, specially regarding to several controversies.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.560-564
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• 1996

A mixed H$^{2}$/$H^{\infty}$ controller design method for linear systems with time delay in all variables and parameter uncertainties in all system matrices is proposed. Robust $H^{\infty}$ performance and H$^{2}$ performance condition that accounts for model-matching of closed loop system and disturbance rejection is also derived. With expressing uncertain system with linear fractional transformation form, we transform the robust stability and performance problem to the H$^{2}$/$H^{\infty}$ optimization problem and design a mixed H$^{2}$/$H^{\infty}$ controller. Using the proposed method, mixed H$^{2}$/$H^{\infty}$ controller for underwater vehicle with time delay and parameter variations are designed. Simulations of a design example with hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.t performance.ance.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.1
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• pp.43-53
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• 1997

A robust stability condition for linear systems with time delay in all variables and parameter uncertainties in all system matrices is derived. Robust performance condition that accounts for robust model-matching of closed loop system and disturbance rejection is also derived. Using the robust performance condition, robust $H^{\infty}$ controller and .mu.(sgructured singular value) controller with two-degree-of-freedom(2DOF) are designed. The controller structure is considered for $H^{\infty}$ controller, while uncertainity structure is considered for .mu. controller. Using the proposed method, $H^{\infty}$ and .mu. controllers for underwater vehicle with time delay and parameter variations are designed. Simulations of a design example with hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.ce.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.05a
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• pp.195-198
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• 2000

We propose a new wavelet neural network structure, for which we apply new recurrent nodes to the network, in this paper for the dynamic system identification and control. We will construct the wavelet neural network by using wavelet frame function. The function does not have the best approximation property, but it may be possible to apply some modification to the structure of the network because the constriction of orthogonality is loosened a little. This wavelet neural network we propose can obtain previous state information by its structure of the network without any addition of input, though the conventional wavelet network needs additional previous state input for the improvement of the dynamic performance. In numerical experience, the performance of the new wavelet neural network we propose in the nonlinear system with uncertainity of parameter Is equal to that of the wavelet network which used the additional previous information input, superior to that of the conventional wavelet network.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.3 no.3
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• pp.13-22
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• 1980

Research and Development has a property that involves uncertainity and risk in itself. Therefore, in order to scheduling of R & D activity, it Is needed of a certain probabilistic network technique with due regard to feedback process used to occur in the R & D proceeding. It is GERT that was developed as the need arises . In this study, the network structure of GERT-I and GERT-II was combined and then simulation analysis was used to it. According to that analysis , an advanced GERT model which covers the following stochastic problems was examined. 1 Evaluating success feasibility under the complex condition (time and cost). 2 Selecting acceptance range for the worst. 3. Selecting optimum path on basis of time, cost and success. 4. Evaluating project utility among the project alternatives. It is for managing R&D projects more effectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.15-23
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• 2002

Uncertainty components and evaluation of the system of pressure measurement are presented in this paper. Since early in 1980s, measurement uncertainty is getting more important due to ISO/IEC 17025, which is established for international test and calibration laboratories. Up to now it is true that accuracy, precision, error and etc. have been commonly used in industry to define the amount of error to the products and equipment, but these terms ought to be united into uncertainity in the future. This paper describes how to indicate measurement uncertainty and types of measurement errors, and then shows the evaluation result of measurement system using piezoelectric pressure transducers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.109-116
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• 1988

The strength and load of structure are varied with the Passage of time, and become a process of probability. It is possible to estimate the reliability from the relation between strength and load. Considering the safety, It is reasonable to estimate allowable stress from the safety factor based on the reliability. In this study, the method to estimate probability of fracture, which is index of reliability for rail subjeict to long term fatigue load were examined. In estimation of reliablity it is meaningless to evaluate numerical value especially this difficult case estimating parameter of random variable. To overcome this problem, conventional design method estimating relative reliability were proposed. In this study the Cornell method were examined. The uncertainity of random variale, ie coefficient of variation which is the index of variation of strength and load were considered. The effect of uncertainity related to probability of fracture, and safety factor based on reliability were examined. The results of this study are followed. The reliability of weld metal were influenced by variation of strength more then load, and base metal were influenced by load. It is confirmed that the allowable stress range calculating with factor of safety based an reliability is conservative.

• Journal of Environmental Impact Assessment
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• v.4 no.3
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• pp.1-8
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• 1995

In generally speaking, the purpose of Environmental Impact Assessment(EIA) is to give the environment its due place in the decision-making process by clearly ealuating the environmental consequence of a proposed activity before action is taken. The introduction of conventional EIA is to be seen as an end product of a very long evolutionary process, starting with rudimentary but evolving pollution control measures for air, water, noise, land and chemicals, each governed by separate, and separately administered pieces of legislation. In EIA process, the measures of status, scoping, proposed mitigation and communication have not been very quantitative in their significancy. Of course, the determinations have uncertainity in the implications for significant impacts. To improve the determination of significant impacts, some more comprehensive methodologies of EIA has been proposed with the concepts of risk analysis in the proposed projects. The concepts of risk analysis has been introduced to the expression of human health impairment due to environmental pollutants since the early 1980's. The risk analysis being meant by the statistical significance of impact has a process quantitatively considering uncertainities and importances of ecological systems and human health as well. The process of risk analysis shows assessment, doseresponse in toxicity, exposure assessment and risk characterization. With the risk assessment, it could be suggested for the proper measurements against their anticipated risk in the EIA. This paper deals the priciples developing process and application of the risk-based analysis in EIA.