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Design and Analysis of a Frequency Reconfigurable Penta-Band Antenna for WLAN and 5G Applications
Rekha Shanmugam 한국전자파학회JEES 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.3
This paper presents a discussion on a low-profile, frequency-reconfigurable penta-band antenna. This antenna consists of two asymmetric L-shaped rectangular patches electrically connected by a single PIN diode. The proposed antenna operates at five frequency bands depending upon the switching states of the PIN diode. It operates at 2.4 ㎓ (WLAN) and 5.3 ㎓ (5G) during forward bias of the diode, 3.3 ㎓ (5G) and 5.9 ㎓ (WLAN) during reverse bias of the diode and 4 ㎓ during zero bias condition providing a wide bandwidth (3.6–4.8 ㎓) at this state. The antenna has voltage standing wave ratio (VSWR) ranges from 1 to 2, gain value ranges from 2.6 to 5.0 ㏈i, and a maximum radiation efficiency of 85%. This antenna can be integrated with modern devices such as smart phones, laptops, and other handheld devices due to its simplistic geometry. A prototype of the model is fabricated, and the results are validated.
Compression and Enhancement of Medical Images using Opposition Based Harmony Search Algorithm
Rekha Haridoss,Samundiswary Punniyakodi 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.2
The growth of telemedicine-based wireless communication for images—magnetic resonance imaging (MRI)and computed tomography (CT)—leads to the necessity of learning the concept of image compression. Overthe years, the transform based and spatial based compression techniques have attracted many types ofresearches and achieve better results at the cost of high computational complexity. In order to overcome this,the optimization techniques are considered with the existing image compression techniques. However, it failsto preserve the original content of the diagnostic information and cause artifacts at high compression ratio. In this paper, the concept of histogram based multilevel thresholding (HMT) using entropy is appended withthe optimization algorithm to compress the medical images effectively. However, the method becomes timeconsuming during the measurement of the randomness from the image pixel group and not suitable formedical applications. Hence, an attempt has been made in this paper to develop an HMT based imagecompression by utilizing the opposition based improved harmony search algorithm (OIHSA) as anoptimization technique along with the entropy. Further, the enhancement of the significant informationpresent in the medical images are improved by the proper selection of entropy and the number of thresholdschosen to reconstruct the compressed image.
Study on NOx reduction capacity of catalytic coated cordierite monolith
Rekha Durairaj,Neelakrishnan Subramanyan,Divakar Duraiswamy 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.6
Legislation world-wide imposes stringent emission norms, particularly EURO V and beyond. In this regard, extensive research is being conducted for improving the existing filter design, material properties and developing alternative design, materials, testing procedures for more sensitive to reduce NOX values. Cordierite ceramics are having good chemical and electrical properties like high thermal resistance, low dielectric constant, low thermal expansion coefficient, and high chemical and mechanical stability, which makes it for many industrial applications like manufacturing of the thermal insulation materials, optoelectronic devices, plasma display panels, solar panels, catalytic convertors etc. In this work, a pair of cordierite monolith with catalyst coating to NOx storage and reduction was developed. The effectiveness of the catalysis was verified with engine exhaust gas analyser. The testing was carried out with diesel as fuel in a Kirloskar engine with Non-filter, NSR, and combined NSR-SCR system. The investigation was done for five trials with different emission parameters and analysed.
Rekha, V. P. B.,Ghosh, Mrinmoy,Adapa, Vijayanand,Oh, Sung-Jong,Pulicherla, K. K.,Sambasiva Rao, K. R. S. Hindawi Publishing Corporation 2013 BioMed research international Vol.2013 No.-
<P>The present study deals with the production of cold active polygalacturonase (PGase) by submerged fermentation using <I>Thalassospira frigidphilosprofundus</I>, a novel species isolated from deep waters of Bay of Bengal. Nonlinear models were applied to optimize the medium components for enhanced production of PGase. Taguchi orthogonal array design was adopted to evaluate the factors influencing the yield of PGase, followed by the central composite design (CCD) of response surface methodology (RSM) to identify the optimum concentrations of the key factors responsible for PGase production. Data obtained from the above mentioned statistical experimental design was used for final optimization study by linking the artificial neural network and genetic algorithm (ANN-GA). Using ANN-GA hybrid model, the maximum PGase activity (32.54 U/mL) was achieved at the optimized concentrations of medium components. In a comparison between the optimal output of RSM and ANN-GA hybrid, the latter favored the production of PGase. In addition, the study also focused on the determination of factors responsible for pectin hydrolysis by crude pectinase extracted from <I>T. frigidphilosprofundus</I> through the central composite design. Results indicated 80% degradation of pectin in banana fiber at 20°C in 120 min, suggesting the scope of cold active PGase usage in the treatment of raw banana fibers.</P>
Rekha Panda,Om Shankar Dinkar,Archana Kumari,Rajesh Gupta,Manis Kumar Jha,Devendra Deo Pathak 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.93 No.-
Present research reports a novel and feasible process to recover Ag and generate concentrate of preciousmetals (Au, Pd and Pt) from waste ICs present in PCBs of computers. Initially, depopulated ICs werepulverized and beneficiated to obtain metallic concentrate, which contained (per ton) 7 Kg Ag, 5 Kg Au,110 g Pd and 4 g Pt along with Cu, Pb, Fe and Ni. Leaching was carried out and found that at optimizedcondition i.e. 3 M HNO3, temperature 80 C, pulp density 50 g/L and mixing time 1 h, >90% of Ag, Cu, Pband Ni were leached leaving Au, Pt and Pd in the residue. From the leach liquor, Ag was precipitated using1 M KCl in 30 min and other metals were recovered by precipitation, solvent extraction and cementationmethods. All wastes (solid/ liquid) generated during process development could be treated usingstandard environmental procedure.
Performance of fly ash stabilized clay reinforced with human hair fiber
Rekha, L. Abi,Keerthana, B.,Ameerlal, H. Techno-Press 2016 Geomechanics & engineering Vol.10 No.5
Industrialization and urbanization are the two phenomena that are going relentless all over the world. The consequence of this economic success has been a massive increase in waste on one hand and increasing demand for suitable sites for construction on the other. Owing to the surplus raw materials and energy requirement needed for manufacturing synthetic fibers, applications of waste fibers for reinforcing soils evidenced to offer economic and environmental benefits. The main objective of the proposed work is to explore the possibilities of improving the strength of soil using fly ash waste as an admixture and Human Hair Fiber (HHF) as reinforcement such that they can be used for construction of embankments and land reclamation projects. The effect of fiber content on soil - fly ash mixture was observed through a series of laboratory tests such as compaction tests, CBR and unconfined compression tests. From the stress - strain curves, it was observed that the UCC strength for the optimised soil - flyash mixture reinforced with 0.75% human hair fibers is nearly 2.85 times higher than that of the untreated soil. Further, it has been noticed that there is about 7.73 times increase in CBR for the reinforced soil compared to untreated soil. This drastic increase in strength may be due to the fact that HHF offer more pull-out resistance which makes the fibers act like a bridge to prevent further cracking and thereby it improves the toughness which in turn prevent the brittle failure of soil-flyash specimen. Hence, the test results reveal that the inclusion of randomly distributed HHF in soil significantly improves the engineering properties of soil and can be effectively utilized in pavements. SEM analysis explained the change of microstructures and the formation of hydration products that offered increase in strength and it was found to be in accordance with strength tests.