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Parametric studies on split S-shaped composite meta atom for X-band communication

Hasan M. M., Faruque M. R. I., Islam M. T.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 4

533--539

EN

The aim of this paper is to describe a split S-shaped composite meta atom which shows double negative characteristics at resonance frequency. The proposed meta-atom structure exhibits an almost 3.70 GHz bandwidth when the operating frequency from 8 to 14 GHz (X-band). In this study, the ring width, split width, size of substrate material, and the substrate material itself are varying to investigate their effect on the resonance frequencies. Metal strips of the outer resonator are the splits and the inner ring resonator is designed in a way that it forms a split S-shaped structure on the epoxy resin fibre (FR-4) substrate material. The CST Microwave Studio electromagnetic simulator software was used for the design and simulation purposes, and an Agilent N5227A vector network analyser was used for practical measurements.

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Computing a Longest Common Palindromic Subsequence

Chowdhury S. R., Hasan M. M., Iqbal S., Rahman M. S.

Fundamenta Informaticae

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2014

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Vol. 129, nr 4

329--340

EN

The longest common subsequence (LCS) problem is a classic and well-studied problem in computer science. Palindrome is a word which reads the same forward as it does backward. The longest common palindromic subsequence (LCPS) problem is a variant of the classic LCS problem which finds a longest common subsequence between two given strings such that the computed subsequence is also a palindrome. In this paper, we study the LCPS problem and give two novel algorithms to solve it. To the best of our knowledge, this is the first attempt to study and solve this problem.

3

Conduction in nanostructured La1=x Sr x FeO3 (0 <= x <= 1)

Zafar A., Imran Z., Rafiq M. A., Shah S. H., Hasan M. M.

Materials Science Poland

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2012

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Vol. 30, No. 3

240--247

EN

We investigated electrical properties of nanostructured La1?x Sr x FeO3 (0 <= x <= 1) from 300 K-400 K. The nanostructured La1-x Sr x FeO3 (0 <= x <= 1) was synthesized by citrate gel method requiring no pH control. X-ray diffraction pattern showed that single phase LaFeO3 with an orthorhombic structure was formed. The structure changed into rhombohedral for x = 0.5 and it became cubic for x = 1.0. For x <= 0.5, our material showed non-linear current-voltage characteristics and for x > 0.5 it showed linear current-voltage characteristics. Poole Frenkel type conduction mechanism was found to be operative in LaFeO3 from 300 K-400 K. The experimental values of field-lowering coefficient were by 2.56-6.41 times higher than the predicted value and were attributed to the presence of localized fields. The increase in conductance with Sr content was due to formation of Fe4+ ions in addition to Fe3+ with the increase in Sr content. Impedance spectroscopy and ac conductivity analysis of La1-x Sr x FeO3 (0 <= x <= 1) was also carried out in the temperature range from 300 K-400 K and frequency was varied from 20 Hz - 2 MHz. The ac conduction followed the correlated barrier hopping model in La0.9Sr0.1FeO3.