• Journal of Institute of Control, Robotics and Systems
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• v.13 no.6
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• pp.581-588
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• 2007

In this paper, we propose a delayed feedback guaranteed cost controller design method for linear time-delay systems with norm-bounded parameter uncertainties and nonlinear perturbations. A quadratic cost function is considered as the performance measure for the given system. Based on the Lyapunov method, an LMI optimization problem is formulated to design a controller such that the closed-loop cost function value is not more than a specified upper bound for all admissible system uncertainties and nonlinear perturbations. Numerical example show the effectiveness of the proposed method.

• Journal of KIISE:Software and Applications
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• v.37 no.1
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• pp.60-73
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• 2010

This paper aims to describe KorLexClas 1.5 which provides us with a very large list of Korean numeral classifiers, and with the co-occurring noun categories that select each numeral classifier. Differently from KorLex of other POS, of which the structure depends largely on their reference model (Princeton WordNet), KorLexClas 1.0 and its extended version 1.5 adopt a direct building method. They demand a considerable time and expert knowledge to establish the hierarchies of numeral classifiers and the relationships between lexical items. For the efficiency of construction as well as the reliability of KorLexClas 1.5, we use following processes: (1) to use various language resources while their cross-checking for the selection of classifier candidates; (2) to extend the list of numeral classifiers by using a shallow parsing techniques; (3) to set up the hierarchies of the numeral classifiers based on the previous linguistic studies; and (4) to determine LUB(Least Upper Bound) of the numeral classifiers in KorLexNoun 1.5. The last process provides the open list of the co-occurring nouns for KorLexClas 1.5 with the extensibility. KorLexClas 1.5 is expected to be used in a variety of NLP applications, including MT.

• Membrane Journal
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• v.22 no.1
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• pp.72-76
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• 2012

$SF_6$ has an extremely high global worming potential (GWP). Therefore, there has been an effort to reduce the use of $SF_6$ and its emission into atmosphere. One possible solution for minimizing the use of $SF_6$ in electrical equipments is utilization of gas mixtures such as $SF_6/N_2$. The $SF_6$ concentration in the gas mixture varies from 10 to 60%. However, when the apparatus is repaired or dismantled, we have to recover $SF_6$ from the gas mixture. Since the boiling point of $SF_6$is low (${\sim}-60^{\circ}C$), the liquefaction method is difficult to apply. One possible alternative is the membrane separation technology. In this study, we investigated the $SF_6$ and $N_2$ permeation properties of 5 polymeric membranes. For example, permeability of $N_2$ in BOPP membrane at $25^{\circ}C$was 0.19 barrer, whereas that of $SF_6$ was only 0.0012 barrer, resulting in the selectivity of 158. An upper bound for $SF_6/N_2$ gas pair was suggested for the first time with n = -1.33 and k = 160 (barrer).

• Geomechanics and Engineering
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• v.32 no.6
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• pp.639-652
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• 2023

Stepped earth slopes incorporated with anti-slide piles are widely utilized in landslide disaster preventions. Explicit consideration of the three-dimensional (3D) effect in the slope design warrants producing more realistic solutions. A 3D limit analysis of the stability of pile stabilized stepped slopes is performed in light of the kinematic limit analysis theorem. The influences of seismic excitation and surcharge load are both considered from a kinematic perspective. The upper bound solution to the factor of safety is optimized and compared with published solutions, demonstrating the capability and applicability of the proposed method. Comparative studies are performed with respect to the roles of 3D effect, pile location, pile spacing, seismic and surcharge loads in the safety assessments of stepped slopes. The results demonstrate that the stability of pile reinforced stepped slopes differ with that of single stage slopes dramatically. The optimum pile location lies in the upper portion of the slope around L_x/L = 0.9, but may also lies in the shoulder of the bench. The pile reinforcement reaches 10% universally for a looser pile spacing D_c/d_p = 5.0, and approaches 70% when the pile spacing reaches D_c/d_p = 2.0.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.183-189
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• 2013

This paper presents a stabilization method for NCS (Networked Control Systems) with two additive time-varying delays. Each time delay component between the plant and the controller has different characteristics depending on communication network, and has the upper and lower bounds. The time delay occurring from the controller to the plant has an effect on the time delay occurring from the plant to the controller, and the relationship between two delays is taken into account on the stability analysis. Based on the two additive delay components and the bound conditions, the appropriate Lyapunov-Krasovskii functional and the LMI (Linear Matrix Inequality) method derive the stability condition and the $H_{\infty}$ norm constraint for time-varying delayed NCS. Simulation results are finally given to demonstrate the effectiveness of the proposed method.

• Structural Engineering and Mechanics
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• v.42 no.2
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• pp.247-267
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• 2012

Calculating the displacements of retaining walls under seismic loads is a crucial part in optimum design of these structures and unfortunately the techniques based on active seismic pressure are not sufficient alone for an appropriate design of the wall. Using limit analysis concepts, the seismic displacements of retaining walls are studied in present research. In this regard, applying limit analysis method and upper bound theorem, a new procedure is proposed for calculating the yield acceleration, critical angle of failure wedge, and permanent displacements of retaining walls in seismic conditions for two failure mechanisms, namely sliding and sliding-rotational modes. Also, the effect of internal friction angle of soil, the friction angle between wall and soil, maximum acceleration of the earthquake and height of the wall all in the magnitude of seismic displacements has been investigated by the suggested method. Two sets of ground acceleration records related to near-field and far-field domains are employed in analyses and eventually the results obtained from the suggested method are compared with those from other techniques.

• Journal of Korean Society for Quality Management
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• v.35 no.2
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• pp.99-105
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• 2007

Most of systems used in real fields are considered as multistate systems with multistate components. As one of methods for performance evaluation of the system, reliability analysis has been popularly used. In this paper, we propose an improved reliability analysis method which is based on state space decomposition method of Aven (1985). In deriving upper bounds, our method uses sets of unspecified states whereas Aven (1985) excludes sets of unacceptance states. Also, closer lower bounds to an exact reliability are obtained by considering of importance of min-path vectors.

• Management Science and Financial Engineering
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• v.10 no.1
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• pp.97-106
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• 2004

In this paper, we propose an effective cut generation method based on the Chvatal-Gomory procedure for a variable-capacity (0,l)-Knapsack problem with two general integer variables. We first derive a class of valid inequalities for the problem using Chvatal-Gomory procedure, then analyze the associated separation problem. Based on the results, we show that there exists a pseudo-polynomial time algorithm to solve the separation problem. By analyzing the theoretical strength of the inequalities which can be generated by the proposed cut generation method, we show that generated inequalties define facets under mild conditions. We also extend the result to the case in which a nontrivial upper bound is imposed on a general integer variable.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.350-353
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• 1994

This paper presents a method to calculate the characteristic root areas and loci band of control systems with uncertainties. First, equations of boundary curves of root areas in the case of additive and multiplicative perturbation are derived. Then, an algorithm for the calculation of the array of closed curves is presented. When the upper bound of the absolute values of frequency responses for the uncertain part, is also frequency-dependent, the frequency-dependent, terms are included in the characteristic equation of the nominal system. This lead to the boundary equations of the root, areas for control systems with frequency-dependent uncertainty. Numerical examples of the control systems with multiplicative perturbations including frequency-dependent terms are presented to verify this calculation method. Finally, its applications to the design of robust control systems, e.g., passive adaptive control systems are also discussed.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.11
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• pp.503-509
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• 2002

In this paper, the robust non-fragile guaranteed cost control problem is studied for a class of linear large-scale systems with uncertainties and a given quadratic cost functions. The uncertainty in the system is assumed to be norm-bounded and time-varying. Also, the state-feedback gains for subsystems of the large-scale system are assumed to have norm-bounded controller gain variations. The problem is to design a state feedback control laws such that the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound for all admissible uncertainties and controller gain variations. Sufficient conditions for the existence of such controllers are derived based on the linear matrix inequality (LMI) approach combined with the Lyapunov method. A parameterized characterization of the robust non-fragile guaranteed cost controllers is given in terms of the feasible solutions to a certain LMI. A numerical example is given to illustrate the proposed method.