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Jeyakumar, V.,Kim, S.,Lee, G. M.,Li, G. Springer Science + Business Media 2016 Journal of global optimization Vol.65 No.2
<P>We propose a hierarchy of semidefinite programming (SDP) relaxations for polynomial optimization with sparse patterns over unbounded feasible sets. The convergence of the proposed SDP hierarchy is established for a class of polynomial optimization problems. This is done by employing known sums-of-squares sparsity techniques of Kojima and Muramatsu Comput Optim Appl 42(1):31-41, (2009) and Lasserre SIAM J Optim 17:822-843, (2006) together with a representation theorem for polynomials over unbounded sets obtained recently in Jeyakumar et al. J Optim Theory Appl 163(3):707-718, (2014). We demonstrate that the proposed sparse SDP hierarchy can solve some classes of large scale polynomial optimization problems with unbounded feasible sets using the polynomial optimization solver SparsePOP developed by Waki et al. ACM Trans Math Softw 35:15 (2008).</P>
Jeyakumar, Shanmugam M.,Sheril, Alex,Vajreswari, Ayyalasomayajula The Korean Society of Food Science and Nutrition 2017 Preventive Nutrition and Food Science Vol.22 No.3
Vitamin A and its metabolites modulate insulin resistance and regulate stearoyl-CoA desaturase 1 (SCD1), which are also known to affect insulin resistance. Here, we tested, whether vitamin A-mediated changes in insulin resistance markers are associated with SCD1 regulation or not. For this purpose, 30-week old male lean and glucose-intolerant obese rats of WNIN/GR-Ob strain were given either a stock or vitamin A-enriched diet, i.e. 2.6 mg or 129 mg vitamin A/kg diet, for 14 weeks. Compared to the stock diet, vitamin A-enriched diet feeding improved hyperglycemia and glucose-clearance rate in obese rats and no such changes were seen in lean rats receiving identical diets. These changes were corroborated with concomitant increase in circulatory insulin and glycogen levels of liver and muscle (whose insulin signaling pathway genes were up-regulated) in obese rats. Further, the observed increase in muscle glycogen content in these obese rats could be explained by increased levels of the active form of glycogen synthase, the key regulator of glycogen synthesis pathway, possibly inactivated through increased phosphorylation of its upstream inhibitor, glycogen synthase kinase. However, the unaltered hepatic SCD1 protein expression (despite decreased mRNA level) and increased muscle-SCD1 expression (both at gene and protein levels) suggest that vitamin A-mediated changes on glucose metabolism are not associated with SCD1 regulation. Chronic consumption of vitamin A-enriched diet improved hyperglycemia and glucose-intolerance, possibly, through the regulation of intracellular signaling and glycogen synthesis pathways of muscle and liver, but not associated with SCD1.
Sums of squares characterizations of containment of convex semialgebraic sets
Jeyakumar, V.,Lee, G. M.,Lee, J. H. YOKOHAMA PUBLISHERS 2016 Pacific journal of optimization Vol.12 No.1
<P>In this paper, we establish numerically checkable sums of squares characterizations of containment of a convex semialgebraic set in another reverse convex semialgebraic set, described by SOS-convex polynomials. The significance of these characterizations is that they hold without any qualifications. In particular, when the semialgebraic sets are described by convex quadratic functions, we obtain a simple linear matrix inequality characterization for the containment. We also present robust set containment characterizations for convex semialgebraic sets in the face of data uncertainty of the SOS-convex polynomials that define the convex semialgebraic sets.</P>
Jeyakumar, V.,Lee, G. M.,Linh, N. T. Springer Science + Business Media 2016 Journal of global optimization Vol.64 No.4
<P>Motivated by robust (non-convex) quadratic optimization over convex quadratic constraints, in this paper, we examine minimax difference of convex (dc) optimization over convex polynomial inequalities. By way of generalizing the celebrated Farkas' lemma to inequality systems involving the maximum of dc functions and convex polynomials, we show that there is no duality gap between a minimax DC polynomial program and its associated conjugate dual problem. We then obtain strong duality under a constraint qualification. Consequently, we present characterizations of robust solutions of uncertain general non-convex quadratic optimization problems with convex quadratic constraints, including uncertain trust-region problems.</P>
Terahertz Micro-Strip Patch Antenna Design and Modelling for 6G Mobile Communication
Jeyakumar P.,Anandpushparaj J.,Thanapal P.,Meenatchi S.,Dhamodaran M. 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3
The future mobile communication networks are emerging drastically and research is being pursued all around the world. To match with the increasing demand for high-speed data communication, wide bandwidth and a high gain antenna are required. Therefore, in this work, the frequency above 100 GHz is chosen as it provides high bandwidth and also suitable for short range communication. Initially, we have designed an antenna with carrier frequency of 300 GHz by comparing it with three different patch materials like Copper, Graphene and Gold and the antenna parameters are analysed. The obtained result shows that the graphene patch has a return loss of −27.70 dB, maximum bandwidth of 10.4 GHz and ideal radiation efficiency of 98.38%. Then the link budget evaluation for the target data rate is 100 Gbps at the bandwidth of 30 GHz on 10 m link distance is analyzed for mobile communication. By executing link budget evaluations in terms of code rate, target SNR, path loss and number of antenna elements required are validated. Finally, the proposed link budget is verified for various modulation schemes using MATLAB.
Trends in Bioremediation of Heavy Metal Contaminations
Parasakthi JEYAKUMAR,Chandrani DEBNATH,R Vijayaraghavan,Muthusivaramapandian MUTHURAJ 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.4
Heavy metal contamination of the ecosystem remains one of the severe global threats. Even in trace quantities, heavy metals and metalloids such as chromium, lead, mercury, cadmium, nickel, and cobalt are toxic and carcinogenic, posing a serious threat to human life. Certain microbes and plants have evolved detoxifying pathways to fight the harmful effects of these inorganic metals, paving the door for bioremediation. Because of its environmentally benign nature, economic viability, and low labor and effort requirements, bioremediation outperforms other approaches in eliminating heavy metals. This review highlights the potential of microbes on remediation of heavy metals in the context of environmental protection and also focuses on the critical tolerance mechanisms used by these microbes in combating heavy metal contaminations. Furthermore, the bioremediation potential of bacteria, fungus, algae, plants, biosurfactants, biofilms and genetically altered microorganisms for the removal of these heavy metals was reviewed in this study. Applying these techniques as a sustainable environmental technology in the near future has shown synergistic benefits with a many-fold increase in the removal of heavy metals.