• 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.

• Korean Journal of Organic Agriculture
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• v.21 no.4
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• pp.487-500
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• 2013

The purpose of this study is to estimate efficiency of environmental-friendly agricultural product by using Data Envelopment Analysis. A proposed method employs a bootstrapping approach to generating efficiency estimates through Monte Carlo simulation resampling process. The technical efficiency, pure technical efficiency, and scale efficiency measure of strawberry by pesticide-free certification is 0.967, 0.995, 0.968 respectively. However those of bias-corrected estimates are 0.918, 0.983, 0.934. We know that the DEA estimator is an upward biased estimator. In technical efficiency, average lower and upper confidence bounds of 0.807 and 0.960. According to these results, the DEA bootstrapping model used here provides bias-corrected and confidence intervals for the point estimates, it is more preferable.

• Journal of applied mathematics & informatics
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• v.32 no.1_2
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• pp.227-245
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• 2014

Suppose G is a simple graph. The ${\ell}$-eigenvalues ${\delta}_1$, ${\delta}_2$,..., ${\delta}_n$ of G are the eigenvalues of its normalized Laplacian ${\ell}$. The normalized Laplacian Estrada index of the graph G is dened as ${\ell}EE$ = ${\ell}EE$(G) = ${\sum}^n_{i=1}e^{{\delta}_i}$. In this paper the basic properties of ${\ell}EE$ are investigated. Moreover, some lower and upper bounds for the normalized Laplacian Estrada index in terms of the number of vertices, edges and the Randic index are obtained. In addition, some relations between ${\ell}EE$ and graph energy $E_{\ell}$(G) are presented.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1196-1201
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• 2004

H₂ controller is proposed for networked control systems with time-varying delay. The time-varying network delay is assumed to be unknown, but its lower and upper bounds are assumed to be known. The time-varying delay is treated like a parameter variation and robust control technique is used to deal with the time-varying delay. The proposed controller can be computed by solving linear matrix inequalities. Through numerical simulations, the proposed controller is verified.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1249-1253
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• 2003

License plate recognition is very important in an automobile society. This is because, since plate detection accuracy has large influence on subsequent number recognition, it is very important. However, it is very difficult to do it, because a background and a body color of cars are similar to that of the license plate. In this paper, we propose a new thresholds determination method in the various background by using the real-coded genetic algorithm (RGA). By using RGA, the most likely plate colors are decided under various lighting conditions. First, the average brightness Y values of images are calculated. Next, relationship between the Y value and the most likely plate color thresholds (upper and lower bounds)are obtained by RGA. The relationship between thresholds decided from RGA and brightness average is aproximate by using the recursive least squares (RLS) algorithm. In the case of plate detection, thresholds are decided from these functions.

• Korean Journal of Mathematics
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• v.27 no.4
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• pp.831-841
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• 2019

A Radiocoloring (RC) of a graph G is a function f from the vertex set V (G) to the set of all non-negative integers (labels) such that |f(u) - f(v)| ≥ 2 if d(u, v) = 1 and |f(u) - f(v)| ≥ 1 if d(u, v) = 2. The number of discrete labels and the range of labels used are called order and span, respectively. In this paper, we concentrate on the minimum order span Radiocoloring Problem (RCP) of trees. The optimization version of the minimum order span RCP that tries to find, from all minimum order assignments, one that uses the minimum span. We provide attainable lower and upper bounds for trees. Moreover, a complete characterization of caterpillars (as a subclass of trees) with the minimum order span is given.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.830-842
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• 2015

Trust and trustworthiness of web services and organizations is calculated as scalar values. But there is still a certain level of risk for the overall reliability of this value. In this article, we focus on calculating trust values as intervals between upper and lower bounds based on predefined confidence values through an additional confidence probability. This will give us a more realistic approach to the trust assessments between individuals and organizations. We also developed a web-based software tool, TAST (Trust Assessment Software Tool) that collects the web services' evaluation of different customer groups for similar organizations through the user interface and calculates the trust intervals for predefined and previously selected confidence values. Our model uses a weighted calculation of mean and variances of customer groups in specific periods and analyses the total and incremental trust of different customer groups.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1805-1810
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• 1991

This paper derives the upper and the lower bound of the mean cycle time and the mean service time of the class 6 and the class 4, within which the minimum utilization constrain of the class 4 is guaranteed. Also, derived are conditions under which the token bus network is stable or unstable. These bounds and stable conditions are represented in terms of the high priority token hold time, the token rotation time and the arrival rate and the total station number etc. This paper suggest a parameter tuning algorithm in a partially symmetric token bus network with two classes, which maximizes the token rotation time for a suitable high priority token hold time and at the same time meets the stability condition of the network, the real time constraint and the minimum utilization constraint of the class 4.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1496-1506
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• 2003

The SIMP (solid isotropic material with penalization) approach is perhaps the most popular density variable relaxation method in topology optimization. This method has been very successful in many applications, but the optimization solution convergence can be improved when new variables, not the direct density variables, are used as the design variables. In this work, we newly propose S-shape functions mapping the original density variables nonlinearly to new design variables. The main role of S-shape function is to push intermediate densities to either lower or upper bounds. In particular, this method works well with nonlinear mathematical programming methods. A method of feasible directions is chosen as a nonlinear mathematical programming method in order to show the effects of the S-shape scaling function on the solution convergence.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.6
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• pp.433-440
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• 2000

To flexibly evaluate performance and reliability of a real-time system which is intrinsically characterized by stringent timing constraints to generate correct responses, we propose fuzzyrandom variables and build a discrete event model embedded with fuzzy-random variables. Also, we adapt fuzzy-variables to a path-space approach, which derives the upper and lower bounds of reliability by using a semi-Markov model that explicitly contains the deadline information. Consequently, we propose certain formulas of state automata properly transformed by fuzzy-random variables, and present numerical examples applying the formulas to RTP(Rapid Thermal Process) to show that a complex system can be properly evaluated based on this model by computer simulation.