• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1065-1070
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• 2004

Optimal collision avoidance algorithm for unmanned aerial vehicles based on proportional navigation guidance law is investigated this paper. Although proportional navigation guidance law is widely used in missile guidance problems, it can be used in collision avoidance problem by guiding the relative velocity vector to collision avoidance vector. The optimal navigation coefficient can be obtained if an obstacle if an obstacle moves at constant velocity vector. The stability of the proposed algorithm is also investigated. The stability can be obtained by choosing a proper navigation coefficient.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.737-749
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• 2003

This Paper analyzed simultaneous activities of the time use survey by Korea National Statistical Office to use data mining's association rule. The survey of National Statistical Office in 1999 considered general analysis for main activities like that personal care(eating), employment and study, leisure, travel by purpose. But if we use the association rule, we can found the ratio of simultaneous activities at the same time. And also we can found the probability that another activities practise if we act one particular activity. Using this association rule of data mining we can do more developed and analytical sociological study.

• Journal of applied mathematics & informatics
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• v.14 no.1_2
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• pp.69-80
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• 2004

We present a construction of the linear reduction of Hilbert type proof systems for propositional logic to if-then-else equational logic. This construction is an improvement over the same result found in [4] in the sense that the technique used in the construction can be extended to the linear reduction of first-order logic to if-then-else equational logic.

• Journal of the Korean Data and Information Science Society
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• v.28 no.6
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• pp.1547-1555
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• 2017

This paper studies Bayesian test of homogeneity in contingency tables made by discretizing a continuous variable. Sometimes when we are considering events of interest in small area setup, we can think of discretization approaches about the continuous variable. If we properly discretize the continuous variable, we can find invisible relationships between areas (groups) and a continuous variable of interest. The proper discretization of the continuous variable can support the alternative hypothesis of the homogeneity test in contingency tables even if the null hypothesis was not rejected through k-sample tests involving one-way ANOVA. In other words, the proportions of variables with a particular level can vary from group to group by the discretization. If we discretize the the continuous variable, it can be treated as an analysis of the contingency table. In this case, the chi-squared test is the most commonly employed method. However, further discretization gives rise to more cells in the table. As a result, the count in the cells becomes smaller and the accuracy of the test becomes lower. To prevent this, we can consider the Bayesian approach and apply it to the setup of the homogeneity test.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.1-8
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• 1997

In this paper, we propose a call admission control scheme which can be used in real environment for the traffic cibtrik if a base station if DS-CDNA cellular systems. The proposed scheme estimates the mean and variance of other cell interference by using the values used for the closed loop power control. The reerse link capacity of the base station can be calculated by using the estimated mean and variance of other cell interference. The base station admits a call only if the number of users is less than the calculated reverse link capacity. In addition, we propose a simple method to obtain the equivalent number of voice call users per one data call user in multi-rate traffic environment. The method can be applied to call admission control in multi-rate traffic environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.1
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• pp.141-148
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• 2001

Dynamic compaction is the ground improvement method by applying the impact energy. This impact energy can damage to adjacent structure in urban area. Therefore, if dynamic compaction method is applied, careful attention should be payed to surrounded structures. In this study, the method was performed in waste landfill and the frequency of vibrations were measured according to each distances, drop-heights, and vibrating directions. The measured data show that particle velocity bas low frequency and it is greatest in longitudinal direction. There was little differences between Maynes suggestion and measured data. Therefore, Maynes suggestion can be adopted if the range of vibration can be predicted. Also, It was found that minimum 45m distance is needed in order to satisfy the administrative code if dynamic compaction method is applied.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.1-5
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• 2019

The superconductor stability theories are consistently described by the integral formula. If the defined stability function is a simple decreasing function, it becomes a cryogenic stability condition. If the stability function has a maximum value and a minimum value, and the maximum value is less than 0, then it is a cold-end recovery condition. If the maximum value is more than 0, it can be shown that the unstable equilibrium temperature, that is, the MPZ (minimum propagation zone) temperature distribution can exist. The MPZ region is divided into two regions according to the current ratio. At the low current ratio, the maximum dimensionless temperature is greater than 1, and at the relatively high current ratio, the maximum dimensionless temperature is less than 1. In order to predict the minimum quench energy, the dimensionless energy was obtained for the MPZ temperature distribution. In particular, it was shown that the dimensionless energy can be obtained even when the MPZ maximum temperature is 1 or more.

• Bulletin of the Korean Mathematical Society
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• v.42 no.4
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• pp.807-815
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• 2005

Let R be a ring with identity, X the set of all nonzero, nonunits of Rand G the group of all units of R. We will consider two group actions on X by G, the regular action and the conjugate action. In this paper, by investigating two group actions we can have some results as follows: First, if G is a finitely generated abelian group, then the orbit O(x) under the regular action on X by G is finite for all nilpotents x $\in$ X. Secondly, if F is a field in which 2 is a unit and F $\backslash\;\{0\}$ is a finitley generated abelian group, then F is finite. Finally, if G in a unit-regular ring R is a torsion group and 2 is a unit in R, then the conjugate action on X by G is trivial if and only if G is abelian if and only if R is commutative.

• Wind and Structures
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• v.14 no.2
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• pp.113-131
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• 2011

Excessive wind-induced motion in tall buildings can cause discomfort, affect health, and disrupt the daily activities of the occupants of a building. Dynamic vibration absorbers such as the tuned mass dampers (TMDs) can be used to reduce the wind-induced motion below a specified tolerable serviceability limit state (SLS) criterion. This study investigates whether the same probability of not exceeding specified wind-induced motion levels can be achieved by torsionally sensitive structures without/with linear/nonlinear TMDs subjected to partially correlated wind forces, if they are designed to just meet the same SLS criterion. For the analyses, different structures and the uncertainty in the response, wind load and perception of motion is considered. Numerical results indicate that for structures that are designed or retrofitted without or with optimum linear TMDs and satisfying the same SLS criterion, their probability of exceeding the considered criterion is very consistent, if the inherent correlation between the wind forces is considered in design. However, this consistency deteriorates if nonlinear TMDs are employed. Furthermore, if the correlation is ignored in the design, in many cases a slightly unconservative design, as compared to the designed by considering correlation, is achieved.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.135-139
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• 2008

In this paper, tunable SC(switched capacitor) 2nd order bandpass $\Sigma-\Delta$(Sigma-Delta) modulator with novel architecture that can adjust the IF band center frequency by one coefficient value is proposed for data conversion in the IF(Intermediate Frequency) band. Its architecture can optionally adjust all the 2nd order noise transfer function in comparison with the conventional architecture. In order to adjust the center frequency, the conventional architecture needs the two variable coefficient values, basic clock and eight clocks. On the other hand, the proposed architecture can adjust the center frequency by one variable coefficient value and basic clock only.