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K. Arul jeyaraj,V. Rajasekaran,S. K. Nandha kumar,K. Chandrasekaran 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.2
This paper proposes a multi-objective optimal placement method of Phasor Measurement Units (PMUs) in large electric transmission systems. It is proposed for minimizing the number of PMUs for complete system observability and maximizing measurement redundancy of the buses, simultaneously. The measurement redundancy of the bus indicates that number of times a bus is able to monitor more than once by PMUs set. A high level of measurement redundancy can maximize the system observability and it is required for a reliable power system state estimation. Therefore, simultaneous optimizations of the two conflicting objectives are performed using a binary coded firefly algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is added to the main model. The practical measurement limitation of PMUs is also considered. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems and a real and large- scale Polish 2383 bus system. The valuable approach of firefly algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing its performance with earlier works.
H-coextension of the double four spiral semigroup Dsp4
K.Indhira,V.M.Chandrasekaran 장전수학회 2014 Advanced Studies in Contemporary Mathematics Vol.24 No.3
In 1978, Byleen, Meakin and Pastijn[2,3] introduced the four - spiral semigroup Sp4 and the double four-spiral semigroup DSp4 and studied their semigroup Sp4 and studied their properties in detail. These regular semigroups play an important role in the theory of idempotent generated bismple but not completely simple semigroups. The semigroup A(1, 2) was introduced as a tool to analyse the structure of DSp4 [3]. In 2003, Chandrasekaran and Loganathan[7] observed that A(1, 2) has an inverse transveral which is a bicyclic monoid and applied this fact to represent DSp4 as a regular Rees matrix semigroup over A(1,2). This result is analogous to the representation due to Byleen [1] of the fundamental four spiral semigroup analogous to Reilly`s description of the bisimple-w-semigroups[21]. So it is natural to ask the following question. Determine the H-coextension of the R-unipotent semigroup A(1, 2) and then we describe the H-coextension of the double four spiral semigroup DSp4.
Arul jeyaraj, K.,Rajasekaran, V.,Nandha kumar, S.K.,Chandrasekaran, K. The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.2
This paper proposes a multi-objective optimal placement method of Phasor Measurement Units (PMUs) in large electric transmission systems. It is proposed for minimizing the number of PMUs for complete system observability and maximizing measurement redundancy of the buses, simultaneously. The measurement redundancy of the bus indicates that number of times a bus is able to monitor more than once by PMUs set. A high level of measurement redundancy can maximize the system observability and it is required for a reliable power system state estimation. Therefore, simultaneous optimizations of the two conflicting objectives are performed using a binary coded firefly algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is added to the main model. The practical measurement limitation of PMUs is also considered. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems and a real and large- scale Polish 2383 bus system. The valuable approach of firefly algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing its performance with earlier works.
Chandrasekaran, S.,Kim, E.J.,Chung, J.S.,Yoo, I.K.,Senthilkumar, V.,Kim, Y.S.,Bowen, C.R.,Adamaki, V.,Hyun Hur, S. Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.309 No.-
This is the first demonstration of four distinct types of Lead Magnesium Titanate (PMT) perovskites including spheres, flakes, hierarchical flower and thin microbelt shapes that were finely tuned via facile solution method to develop cost effective and high performance photoanode materials for water splitting. The influence of solvent effects during structural tuning, purity, morphology, optical absorption, structural phase transition and stoichiometric formation of the prepared Lead Magnesium Titanate perovskites has been discussed in detail. A remarkable observation is that the thin microbelts structured PMT perovskite (PMTT) exhibited an excellent water splitting performance and it is more sensitive to the illuminated visible light. Owing to the unique structural features, the photoconversion efficiency value of PMTT perovskite is ~3.9, 3.54, 2.85 and 1.52 times higher than those of other prepared PMT perovskites including pristine PbTiO<SUB>3</SUB>. The excellent water splitting performance of PMTT (thin microbelts) may be ascribed to the remarkable structural features that include a large surface area, high optical absorbance, more active sites and high interface area of the microbelts, which provide large contact areas between the electrolyte and highly active materials for electrolyte diffusion and a rapid route for charge transfer with minimal diffusion resistance. In addition, each thin microbelt is directly in contact with the Ni foam substrate, which can also shorten the diffusion path for the electrons. The demonstrated approach paves the way for low-cost and high-throughput production of next generation, high performance and highly active water splitting perovskite photocatalysts.
K. M. Madhu,P. S. Beena,M. Chandrasekaran 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.4
A potential fungal strain producing extracellular β-glucosidase enzyme was isolated from sea water and identified as Aspergillus sydowii BTMFS 55 by a molecular approach based on 28S rDNA sequence homology which showed 93% identity with already reported sequences of Aspergillus sydowii in the GenBank. A sequential optimization strategy was used to enhance the production of β-glucosidase under solid state fermentation (SSF) with wheat bran (WB) as the growth medium. The two-level Plackett-Burman (PB) design was implemented to screen medium components that influence β-glucosidase production and among the 11 variables, moisture content, inoculums, and peptone were identified as the most significant factors for β-glucosidase production. The enzyme was purified by (NH4)2SO4 precipitation followed by ion exchange chromatography on DEAE sepharose. The enzyme was a monomeric protein with a molecular weight of ~95 kDa as determined by SDS-PAGE. It was optimally active at pH 5.0 and 50°C. It showed high affinity towards pNPG and enzyme has a Km and Vmax of 0.67 mM and 83.3 U/mL, respectively. The enzyme was tolerant to glucose inhibition with a Ki of 17 mM. Low concentration of alcohols (10%), especially ethanol, could activate the enzyme. A considerable level of ethanol could produce from wheat bran and rice straw after 48 and 24 h, respectively, with the help of Saccharomyces cerevisiae in presence of cellulase and the purified β-glucosidase of Aspergillus sydowii BTMFS 55.
Chandrasekaran, Sundaram,Kim, Eui Jung,Chung, Jin Suk,Bowen, Chris R.,Rajagopalan, Balasubramaniyan,Adamaki, Vaia,Misra, R. D. K.,Hur, Seung Hyun The Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.34
<P>The advances in cost effective, highly active and stable electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remain the major issues for the commercialization of metal air-batteries and alkaline fuel cells. In this aspect, a facile hydrothermal route was developed to prepare nonprecious metal electrocatalysts including pristine MoO3rods, nanospheres, and their hybrids with reduced graphene oxide (rGO). This is the first report of the use of rGO coupled with hexagonal MoO3nanocrystals that act as both ORR and OER catalysts. The rGO-MoO3sphere hybrid catalyst exhibited excellent catalytic activity toward both the ORR and OER compared to pristine MoO3rods, MoO3spheres and rGO-MoO3rods. In addition, the rGO-MoO3nanosphere hybrid exhibited excellent catalytic activity, long-term durability, and CO tolerance compared to a high quality commercial Pt/C catalyst. This makes the GMS hybrid composite a highly promising candidate for high-performance non-precious metal-based bi-functional electrocatalysts with low cost and high efficiency for electrochemical energy conversion. The enhanced activity of the rGO-MoO3nanosphere hybrid is due mainly to the enhanced structural openness in the tunnel structure of the hexagonal MoO3when it is coupled with rGO.</P>
Chandrasekaran, Sundaram,Bowen, Chris,Roscow, James,Zhang, Yan,Dang, Dinh Khoi,Kim, Eui Jung,Misra, R.D.K.,Deng, Libo,Chung, Jin Suk,Hur, Seung Hyun Elsevier 2019 Physics reports Vol.792 No.-
<P><B>Abstract</B></P> <P>This comprehensive review focuses on recent advances in energy harvesting of micro-scale and nano-scale generators based on piezoelectric and triboelectric effects. The development of flexible and hybrid devices for a variety of energy harvesting applications are systematically reviewed. A fundamental understanding of the important parameters that determine the performance of piezoelectric, triboelectric and hybrid devices are summarized. Current research directions being explored and the emerging factors to improve harvester functionality and advance progress in achieving high performance and durable energy conversion are provided. Investigations with regard to integrating flexible matrices and optimizing the composition of the piezoelectric and triboelectric materials are examined to enhance device performance and improve cost-effectiveness for the commercial arena. Finally, future research trends, emerging device structures and novel materials in view of imminent developments and harvesting applications are presented.</P>