• ETRI Journal
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• v.45 no.4
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• pp.581-593
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• 2023

This paper proposes four-ring slot resonator-based MIMO antennas of 75×150 mm² without and with CSRR structures in the sub-6-GHz range. These orthogonal-fed antennas have shown diverse characteristics with dual polarization. L-shaped parasitic structures have increased the isolation (i.e., >40 dB) in the single-element antenna over the band of 3.4 GHz-3.8 GHz. A set of three CSRR structures in the MIMO antenna reduced the coupling between antenna ports placed in an inline arrangement and enhanced the isolation from 12 dB to 20 dB and the diversity characteristics. The S-parameters of both MIMO antennas are measured and used to evaluate MIMO parameters like ECC, TARC, MEG, and channel capacity loss. The simulation results show the variations in the gain and directivity on exciting linear and dual polarizations. The diversity performance of the reported MIMO antennas is suitable for 5G applications.

• Bulletin of the Korean Mathematical Society
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• v.61 no.1
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• pp.247-262
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• 2024

In this paper we introduce and study the notions of topological sensitivity and its stronger forms on semiflows and on product semiflows. We give a relationship between multi-topological sensitivity and thick topological sensitivity on semiflows. We prove that for a Urysohn space X, a syndetically transitive semiflow (T, X, 𝜋) having a point of proper compact orbit is syndetic topologically sensitive. Moreover, it is proved that for a T₃ space X, a transitive, nonminimal semiflow (T, X, 𝜋) having a dense set of almost periodic points is syndetic topologically sensitive. Also, wherever necessary examples/counterexamples are given.

• Management Science and Financial Engineering
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• v.14 no.2
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• pp.25-44
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• 2008

This paper concentrates on reduction of a Quadratic Fractional Integer Programming Problem (QFIP) to a 0-1 Mixed Linear Programming Problem (0-1 MLP). The solution technique is based on converting the integer variables to binary variables and then the resulting Quadratic Fractional 0-1 Programming Problem is linearized to a 0-1 Mixed Linear Programming problem. It is illustrated with the help of a numerical example and is solved using the LINDO software.

• Journal of the Korean Statistical Society
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• v.28 no.3
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• pp.279-296
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• 1999

In this paper we establish some recurrence relations for both single and product moments of order statistics from a doubly truncated linear- exponential distribution with increasing hazard rate. These recurrence relations would enable one to compute all the higher order moments of order statistics for all sample sizes from those of the lower order in a simple recursive way. In addition, percentage points of order statistics are also discussed. These generalize the corresponding results for the linear- exponential distribution with increasing hazard rate derived by Balakrishnan and Malik(1986)

• Bulletin of the Korean Mathematical Society
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• v.50 no.2
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• pp.697-704
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• 2013

The function $g{\mapsto}{\zeta}^k_G(g)$ which counts the number of solutions of $x^k=g$ in a finite group G, is not necessarily a character of G. We study this function for the case of dihedral groups and generalized quaternion groups.

• Management Science and Financial Engineering
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• v.7 no.2
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• pp.13-30
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• 2001

This paper discusses a paradox in an Indefinite Quadratic transportation Problem. Here, the objective function is the product of two linear functions. A paradox arises when the transportation problem admits of a total cost which is lower than the optimum cost, by transporting larger quantities of goods over the same route. A sufficient condition for the existence of a paradox is established. Paradoxical Range of flow is obtained for any given flow in which the corresponding objective function value is less than the optimum value of the given transportation problem. It is illustrated with the help of a numerical example.

• Communications of the Korean Mathematical Society
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• v.35 no.1
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• pp.151-159
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• 2020

We introduce the notion of (m, n)-paranormal operators and (m, n)^⁎-paranormal operators on Hilbert space and study their properties. We also characterize these operators. Examples of operators are given which are (m, n)-paranormal but not (m, n)^⁎-paranormal, and vice-versa.

• Communications of the Korean Mathematical Society
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• v.35 no.1
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• pp.229-241
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• 2020

For a second order linear differential equation f" + A(z)f' + B(z)f = 0, with A(z) and B(z) being transcendental entire functions under some restrictions, we have established that all non-trivial solutions are of infinite order. In addition, we have proved that these solutions, with a condition, have exponent of convergence of zeros equal to infinity. Also, we have extended these results to higher order linear differential equations.

• Communications of the Korean Mathematical Society
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• v.35 no.1
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• pp.287-300
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• 2020

We introduce and study notions of expansivity, topological stability and persistence for Borel measures with respect to time varying bi-measurable maps on metric spaces. We prove that on Mandelkern locally compact metric spaces expansive persistent measures are topologically stable in the class of all time varying homeomorphisms.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.3
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• pp.227-236
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• 1996

In this paper an algorithm based on cutting plane approach is developed which constructs all the efficient p-tuples of multiobjective integer linear fractional programming problem. The integer solution is constrained to satisfy and h out of n additional constraint sets. A numerical illustration in support of the proposed algorithm is developed.