Molecular design and synthesis of ruthenium(<small>II</small>) sensitizers for highly efficient dye-sensitized solar cells

Anthonysamy, A.,Lee, Y.,Karunagaran, B.,Ganapathy, V.,Rhee, S.-W.,Karthikeyan, S.,Kim, K. S.,Ko, M. J.,Park, N.-G.,Ju, M.-J.,Kim, J. K. Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.33

<P>We synthesized hydrophobic ruthenium(<SMALL>II</SMALL>) sensitizers (SY-04 and SY-05) with high molar extinction coefficient by extending the π-conjugation of 3,4- or 3-alkylthiophene-substituted bipyridine ligands. Both dyes displayed a remarkably high molar extinction coefficient of 21.7 × 10<SUP>3</SUP> M<SUP>−1</SUP> cm<SUP>−1</SUP> arising from red-shift of their metal-to-ligand charge transfer band when compared to a commonly used N3 sensitizer. The solar-to-electrical energy conversion efficiency (<I>η</I>) of the SY-04 based dye-sensitized solar cell (DSC) was 7.70%, which is 27% higher than that (6.05%) of the N3-based DSC under the same cell fabrication conditions. The increased <I>η</I> was attributed to the increase in life time and recombination half-life measured by electrochemical impedance and transition absorption spectroscopy, respectively. Density functional theory and time-dependent density functional theory calculations of two dyes in both gas phase and solution were performed. The calculated values of the highest occupied and the lowest unoccupied molecular orbitals and absorption spectra are in good agreement with the experimental results.</P> <P>Graphic Abstract</P><P>DSCs based on hydrophobic ruthenium(<SMALL>II</SMALL>) sensitizers with thiophene-substituted bipyridine ligands showed the solar-to-electrical energy conversion of 7.70%, which is 27% higher than that of N3-based DSC at the same fabrication condition. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm11760b'> </P>

Optimization of active area of proton exchange membrane fuel cell with better water management

M. Karthikeyan,M. Muthukumar,P. Karthikeyan,C. Mathan 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5

Water flooding is one of the major issues which is influencing the performance of PEMFC, while scaling up the active area. Water accumulation in between the GDL and cathode flow field landing in PEMFC can be removed by fixing porous inserts along the landing area of the cathode flow field. In this paper, the optimum active area of the PEMFC is found from the experimental investigations of three active area sizes of 25 cm2, 36 cm2 and 70 cm2 with better water management by fixing porous inserts along the landing surface. All three active areas of PEMFCs with three different flow fields viz. Serpentine; Uniform and Stagger patterned pin types having porous inserts on cathode side have been investigated experimentally. The PEMFCs with active area of 25 cm2, 36 cm2 and 70 cm2 with stagger patterned pin types having porous inserts have obtained maximum power densities as 0.270 W/cm2, 0.338 W/cm2and 0.170 W/cm2 respectively. The PEMFC with active area of 36 cm2 yields higher power density compared to 25 cm2 and 70 cm2 PEMFCs. So it is found that the active area of 36 cm2 is the optimum active area of single cell PEMFC for maximum performance.

Effect of modes of transportation on commuters' exposure to fine particulate matter (PM<SUB>2.5</SUB>) and nitrogen dioxide (NO₂) in Chennai, India

M. Gokul Raj,S. Karthikeyan 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.6

Daily commuting increases level of contaminants inhaled by urban community and it is influenced by mode and time of commuting. In this study, the commuters’ exposure to ambient particulate matter (PM2.5) and nitrogen dioxide (NO₂) was assessed during three modes of travel in six different road stretches of Chennai. The mean distance of road stretches was 25 km and the exposure to pollutants was assessed during peak hours and off-peak hours. The average travel duration was in the range of 39 to 91 min in motorbike, 83 to 140 min in car and 110 to 161 min in bus. Though there was variation on exposure to concentration in modes of transportation, the maximum exposure concentration of PM2.5 was observed as 709 μg/m³ in bus and the minimum exposure concentration was 29 μg/m³ in closed car. Similarly, the maximum exposure concentration of NO₂ was observed to be 312 μg/m³ in bus and the minimum exposure concentration was 21 μg/m³ in car. The concentration of elements in PM2.5 was in the order of Si > Na > Ca > Al ≥ K > S ≥ Cd, with Si and Cd concentration as 60% and < 1% of the PM2.5 concentration.

Reconfiguration of Photovoltaic Arrays under Partial Shading Conditions Using LSG Method for Maximum Power Extraction

Karthikeyan M.,Manimegalai D. 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

The foremost goal of this paper is to analyse output power, power Mismatch Loss (ML), Fill-Factor (FF), and efficiency metrics for different configurations. The aim of this research work is to investigate and quantify the performance of various configurations under different shading patterns. Partial shading is a significant impediment to photovoltaic (PV) array performance. This problem has the solution of reconfiguring the panels in the case of partial shadowing to give better outcomes. MATLAB/SIMULINK model was used to discuss, analyse, and compare various pv arrangements such as Series-Parallel (SP), Total-Cross-Tied (TCT), SuDoKu, and Logic-based Square Grid (LSG). The implementation and evaluation of all configurations are described using a simulation approach. The LSG method has the maximum power output of 9624 W, the highest efficiency of 11.6%, the Fill Factor of 0.61, and the lowest Mismatch Loss of 6056 W in Long-Wide (LW) shading pattern compare to all the configurations. Also, maximum power enhancement by LSG method is verified by experimentally using 7 × 7 PV array. The results shows that maximum power is enhanced by LSG method are 5.29, 8.44, 6.34, 4.26 and 8.24% when compared with TCT configuration under SN, SW, LN, LW and Diagonal shading patterns respectively.

Synthesis, characterization, and transport properties of single-layer pure and molybdenum-doped vanadium oxide thin films on metallic conductive substrates

Karthikeyan, M.,Um, S. Elsevier Sequoia 2016 THIN SOLID FILMS - Vol.606 No.-

Single-layer undoped and 10mol% molybdenum (Mo)-doped vanadium oxide (V<SUB>2</SUB>O<SUB>3</SUB>) thin films with thicknesses of approximately 342nm are fabricated by an aqueous sol-gel method and then deposited onto 316L stainless steel conductive substrates. The influence of various annealing temperatures (in a nitrogen atmosphere) on the structural and electrical properties of undoped and Mo-doped vanadium oxide thin films is investigated. Through a controlled annealing process, the electrical resistances of the single-layer thin films are optimized to attain the required amount of Joule heating for cold-start fuel cell applications within an ambient temperature range (273.15 to 253.15K). The films show a negative temperature coefficient (NTC) behavior and a transition from a metal to an insulator at sub-zero temperatures. The highest electrical resistivities are measured to be 0.032@?.cm and 0.071@?.cm for undoped and Mo-doped vanadium oxide films, respectively, after annealing under 20sccm N<SUB>2</SUB> at 673.15K. Consequently, the equilibrium surface temperature of the single-layer Mo-doped vanadium oxide thin film increases from 253.15K to 299.46K upon induced Joule heating at a current density of 0.1A.cm<SUP>-2</SUP>. Thus, it is concluded that single-layer NTC Mo-doped vanadium oxides can be effectively used for cold-start fuel cell applications.

ACC deaminase containing diazotrophic endophytic bacteria ameliorate salt stress in Catharanthus roseus through reduced ethylene levels and induction of antioxidative defense systems

Karthikeyan, B.,Joe, M. M.,Islam, M. R.,Sa, T. INTERNATIONAL SCIENCE SERVICES ZEIST 2012 Symbiosis Vol.56 No.2

Efficient Sign Language Recognition and Classification Using African Buffalo Optimization Using Support Vector Machine System

Karthikeyan M. P.,Vu Cao Lam,Dac-Nhuong Le International Journal of Computer ScienceNetwork S 2024 International journal of computer science and netw Vol.24 No.6

Communication with the deaf has always been crucial. Deaf and hard-of-hearing persons can now express their thoughts and opinions to teachers through sign language, which has become a universal language and a very effective tool. This helps to improve their education. This facilitates and simplifies the referral procedure between them and the teachers. There are various bodily movements used in sign language, including those of arms, legs, and face. Pure expressiveness, proximity, and shared interests are examples of nonverbal physical communication that is distinct from gestures that convey a particular message. The meanings of gestures vary depending on your social or cultural background and are quite unique. Sign language prediction recognition is a highly popular and Research is ongoing in this area, and the SVM has shown value. Research in a number of fields where SVMs struggle has encouraged the development of numerous applications, such as SVM for enormous data sets, SVM for multi-classification, and SVM for unbalanced data sets.Without a precise diagnosis of the signs, right control measures cannot be applied when they are needed. One of the methods that is frequently utilized for the identification and categorization of sign languages is image processing. African Buffalo Optimization using Support Vector Machine (ABO+SVM) classification technology is used in this work to help identify and categorize peoples' sign languages. Segmentation by K-means clustering is used to first identify the sign region, after which color and texture features are extracted. The accuracy, sensitivity, Precision, specificity, and F1-score of the proposed system African Buffalo Optimization using Support Vector Machine (ABOSVM) are validated against the existing classifiers SVM, CNN, and PSO+ANN.

Survival of Azospirillum brasilense flocculated cells in alginate and its inoculation effect on growth and yield of maize under water deficit conditions

Joe, M.M.,Karthikeyan, B.,Chauhan, P.S.,Shagol, C.,Islam, Md.R.,Deiveekasundaram, M.,Sa, T. Gauthier-Villars ; Elsevier Science Ltd 2012 European journal of soil biology Vol.50 No.-

The objective of this study was to compare the efficiency of Azospirillum brasilense MTCC125 flocculated cells with standard grown cells under in vitro conditions and in association with maize (Zea mays L.) under field conditions. The results revealed that A. brasilense flocculated cells had higher survivability in alginate bead (37 x 10<SUP>6</SUP> CFU g<SUP>-1</SUP> dry wt.) and disinfected soil (11 x 10<SUP>6</SUP> CFU g<SUP>-1</SUP> dry wt.) after 12 months of storage in room temperature. A. brasilense flocculated cells offered a higher degree of resistance to dehydration in terms of reduction in water availability (a<SUB>w</SUB>) and their survivability was 12% higher in soil and 27% higher in alginate compared to standard grown cells. The adhesion efficiency of A. brasilense flocculated cells was 54% higher to hydrophobic polystyrene and 101% higher to maize roots when compared to standard grown A. brasilense cells. Furthermore, flocculated cells had better spermoplane survivability (48%) and spermosphere colonization (73%) along with a concomitant enhancement on the germination percentage (11%) and vigor index (23%) of maize. Field studies with A. brasilense flocculated cells conducted under normal irrigated conditions and by withholding irrigation at 25, 50, and 75% available water-holding capacity (AWHC) showed a significant increase in plant height (19%), plant dry weight (16%), grain yield (31%), stover yield (17%) and nitrogen uptake (18%) compared with standard grown cell treatment.

Feasibility and performance study of turpentine fueled DI diesel engine operated under HCCI combustion mode

M. Kannan,R. Karthikeyan,B. Deepanraj,R. Baskaran 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

In the present investigation a volatile fraction of Pinus resin called Turpentine has been experimented in a direct injection diesel engineunder HCCI combustion mode. The engine chosen to experiment is a single cylinder DI diesel engine and modified in such a way toignite Turpentine in a diesel engine under HCCI mode. As the Turpentine has a higher self ignition temperature the ignition of Turpentinein regular diesel engines with auto-ignition is not possible. Hence, suitable modification is made in the engine to ignite Turpentine ina diesel engine like diesel fuel. The modified engine has ECM controlled fuel spray and an air preheater in the suction side of the engine. The combined effort of adiabatic compression and supply of preheated air ignites turpentine by auto-ignition and its timing of ignition isprecisely controlled by changing intake air temperature. This investigation revealed that the engine operated with turpentine performedwell with little loss of brake thermal efficiency. And, emitted comparatively lower emissions such as NOx and smoke and proved that theturpentine is a best suited fuel for HCCI operation.

A highly efficient 2D siloxene coated Ni foam catalyst for methane dry reforming and an effective approach to recycle the spent catalyst for energy storage applications

Krishnamoorthy, Karthikeyan,M. S. P., Sudhakaran,Pazhamalai, Parthiban,Mariappan, Vimal Kumar,Mok, Young Sun,Kim, Sang-Jae The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.32

<P>The dry reforming of methane (DRM) using CO2 for the production of syngas (H2 and CO) has received increasing attention for reducing global CO2 emissions. The main drawback of DRM reactions is the limited reusability of the spent catalyst due to carbon deposition on its surface. Thus, designing an appropriate catalytic system is adequate to achieve increased syngas production with low carbon deposition, and developing smart strategies to reuse the carbon deposited spent catalyst is highly desirable. In this work, two dimensional siloxene sheet (silicon analog of graphene oxide) coated nickel foam is examined as a novel catalyst for the DRM reaction. The siloxene/Ni foam catalyst demonstrated superior catalytic performance in terms of conversion efficiencies (for CH4 and CO2) and syngas production (H2 and CO) with a high H2/CO ratio of 1.5. Further, the carbon deposited siloxene/Ni spent catalyst recovered after the DRM reaction was effectively re-utilized as electrodes for a symmetric supercapacitor (SSC) using an organic electrolyte. The fabricated SSC (using the spent catalyst as electrodes) delivered a high device capacitance (24.65 F g<SUP>−1</SUP>), high energy density (30.81 Wh kg<SUP>−1</SUP>), and high-power density (15 625 W kg<SUP>−1</SUP>) with a long cycle life. Considering that the estimated carbon cost for developing a supercapacitor electrode is about $15 per kilogram, our strategy to effectively reutilize the recovered carbon deposited spent catalyst for energy storage applications might be a promising and economical approach for utilization of the spent catalyst.</P>