Aeroelastic analysis of bridges using FEM and moving grids

Selvam, R. Panneer,Govindaswamy, S.,Bosch, Harold Techno-Press 2002 Wind and Structures, An International Journal (WAS Vol.5 No.2

In the recent years flow around bridges are investigated using computer modeling. Selvam (1998), Selvam and Bosch (1999), Frandsen and McRobie (1999) used finite element procedures. Larsen and Walther (1997) used discrete vorticity procedure. The aeroelastic instability is a major criterion to be checked for long span bridges. If the wind speed experienced by a bridge is greater than the critical wind speed for flutter, then the bridge fails due to aeroelastic instability. Larsen and Walther (1997) computed the critical velocity for flutter using discrete vortex method similar to wind tunnel procedures. In this work, the critical velocity for flutter will be calculated directly (free oscillation procedure) similar to the approaches reported by Selvam et al. (1998). It is expected that the computational time required to compute the critical velocity using this approach may be much shorter than the traditional approach. The computed critical flutter velocity of 69 m/s is in reasonable comparison with wind tunnel measurement. The no flutter and flutter conditions are illustrated using the bridge response in time.

A Copper(II) complex of a new hydrazone: A solid-state single source precursor for the preparation of both Cu and CuO nanoparticles

Selvam, Pitchai,Sathiyakumar, Subramani,Srinivasan, Krishnan,Premkumar, Thathan Elsevier 2019 Journal of molecular structure Vol.1177 No.-

<P><B>Abstract</B></P> <P>A novel hydrazone, ethyl 4-(pyridine-4yl-methylene) hydrazinecarboxylate (C<SUB>9</SUB>H<SUB>11</SUB>N<SUB>3</SUB>O<SUB>2</SUB>; 4-py), and Cu(II) complex [Cu(4-py)<SUB>2</SUB>(CH<SUB>3</SUB>COO)<SUB>2</SUB>(H<SUB>2</SUB>O)] (<B>1</B>) were synthesized and characterized via elemental analysis, FT-IR, <SUP>1</SUP>H NMR and <SUP>13</SUP>C NMR spectral techniques. The structure of <B>1</B> was determined through single crystal X-ray diffraction. The structure consists of monomers in which copper is penta-coordinated through a distorted square pyramidal geometry. The pyridine nitrogen atoms of two monodentate 4-py ligands and oxygen atoms from two monodentate acetate anions form the basal plane. The apical site is occupied by a water molecule. Nano sized copper metal (∼5 nm) and copper oxide (∼10 nm) were separately prepared via thermal decomposition of the as-prepared copper complex by varying the atmospheric conditions under which the complex was calcined at 400 °C for 1 h. Powder x-ray diffraction (PXRD) patterns confirmed that the prepared Cu and CuO nanoparticles were of high purity and crystallinity. Hence, this complex could be used as a single solid-state precursor to prepare both Cu and CuO nanoparticles via low temperature decomposition under different atmospheric conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We prepared a [Cu(4-py)<SUB>2</SUB>(CH<SUB>3</SUB>COO)<SUB>2</SUB>(H<SUB>2</SUB>O)] complex from a new hydrazine. </LI> <LI> Cu is penta-coordinated with a distorted square pyramidal geometry. </LI> <LI> Nano Cu and CuO can be synthesized by using this complex. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

MXene supported CoxAy (A = OH, P, Se) electrocatalysts for overall water splitting: unveiling the role of anions in intrinsic activity and stability

Selvam, N. Clament Sagaya,Lee, Jooyoung,Choi, Gwan H.,Oh, Min Jun,Xu, Shiyu,Lim, Byungkwon,Yoo, Pil J. The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.48

<P>The development of efficient and stable bifunctional catalysts that outperform noble metal catalysts is a crucial task and an ongoing challenge for sustainable water electrolysis. In this work, large-size-exfoliated MXene sheets render a flat and flexible platform for the decoration of Co(OH)F, CoP and Co7Se8, allowing them to exhibit high electrocatalytic performances; thanks to the maximized surface area and conductivity. CoP/MXene shows enhanced oxygen evolution reaction (OER) activity, with substantially lower overpotential (<I>η</I> = 230 mV) at 10 mA cm<SUP>−2</SUP> compared to those of IrO2 (300 mV). Furthermore, a hybrid bifunctional electrode (CoP/MXene//CoP/MXene) exhibits highly stable and efficient overall water splitting performance (1.56 V@10 mA cm<SUP>−2</SUP>) as compared to the benchmark electrode couple IrO2/C//Pt/C (1.62 V@10 mA cm<SUP>−2</SUP>) in alkaline solution. Furthermore, we elucidate the oxidation process of the anion components (P and Se) of the hybrid catalysts under OER conditions and verify their significant influence on the activity and stability. Notably, the surface oxidation of CoP/MXene results in a POx-enriched Co-OOH/CoP/MXene hybrid, which enables retention of consistent activity and stability. On the other hand, SeOx deposition on the Co-OOH/Co7Se8/MXene surface significantly deteriorates the activity and stability of the catalyst. These results not only highlight the insight on the correlation between oxidized anion species and the intrinsic activity of hybridized electrocatalysts but also impart the systematic synthetic design of MXene-supported catalysts with high water-splitting efficiency.</P>

Machine Learning Perspective Gene Optimization for Efficient Induction Machine Design

Selvam, Ponmurugan Panneer,Narayanan, Rengarajan The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

In this paper, induction machine operation efficiency and torque is improved using Machine Learning based Gene Optimization (ML-GO) Technique is introduced. Optimized Genetic Algorithm (OGA) is used to select the optimal induction machine data. In OGA, selection, crossover and mutation process is carried out to find the optimal electrical machine data for induction machine design. Initially, many number of induction machine data are given as input for OGA. Then, fitness value is calculated for all induction machine data to find whether the criterion is satisfied or not through fitness function (i.e., objective function such as starting to full load torque ratio, rotor current, power factor and maximum flux density of stator and rotor teeth). When the criterion is not satisfied, annealed selection approach in OGA is used to move the selection criteria from exploration to exploitation to attain the optimal solution (i.e., efficient machine data). After the selection process, two point crossovers is carried out to select two crossover points within a chromosomes (i.e., design variables) and then swaps two parent's chromosomes for producing two new offspring. Finally, Adaptive Levy Mutation is used in OGA to select any value in random manner and gets mutated to obtain the optimal value. This process gets iterated till finding the optimal value for induction machine design. Experimental evaluation of ML-GO technique is carried out with performance metrics such as torque, rotor current, induction machine operation efficiency and rotor power factor compared to the state-of-the-art works.

Enhanced L‑Dopa production from elicited cell suspension culture of Hybanthus enneaspermus (L.) F. Muell

Selvam Sathish,Venkatachalam Vasudevan,Sivabalan Karthik,Gadamchetty Pavan,Markandan Manickavasagam 한국식물생명공학회 2019 Plant biotechnology reports Vol.13 No.6

Hybanthus enneaspermus is an important source for L-Dopa production. This study reports elicited L-Dopa production in cell suspension cultures of Hybanthus enneaspermus. Cell suspension culture was established using green friable calli from leaf explants cultured on MS medium containing 2.0 mg/l 2,4-D. Effects of different elicitors such as SA, YE, MeJA and AgNO3 on biomass accumulation and L-Dopa content were studied. Among the elicitor tested SA treated culture produced highest biomass and L-Dopa according to their exposure time and concentration. Maximum biomass of 15.5 ± 0.16 g FW, 4.05 ± 0.18 g DW and L-Dopa production of 8.88 mg/g DW were observed at 150 μM concentration of SA. This was 9.25-fold higher compared to that of the unelicited control culture. The results obtained in this study clearly show that the elicita-tion strategy is a promising method for biosynthesis of L-Dopa production by cell suspension cultures of H. enneaspermus.

Mediation effect of cord blood cortisol levels between maternal prepregnancy body mass index and birth weight: a hospital-based cross-sectional study

Selvam Nisanth,K Jayashree,Mithra Prasanna 대한소아청소년과학회 2022 Clinical and Experimental Pediatrics (CEP) Vol.65 No.10

Background: Changes in maternal weight affect the maternal and fetal hypothalamic-pituitary-adrenal axis, influencing birth weight and contributing to the fetal origin of adult diseases (Barker’s hypothesis). This study primarily focused on cord blood cortisol levels and identified the association between maternal prepregnancy body mass index (pre-BMI) and birth weight. It also assessed cord blood lipid profile changes related to maternal pre-BMI, birth weight, and cord blood cortisol levels.Purpose: To study the mediation effect of cord blood cortisol level between maternal pre-BMI and birth weight and its correlation with cord blood lipid profile.Methods: A total of 169 maternal-neonatal pairs were included at 2 tertiary care centers. Mediation analysis was used to estimate the extent of the association between maternal weight changes and birth weight.Results: For each unit increase in maternal pre-BMI, birth weight increased by 90.5 g; for every kilogram increase in gestational weight, birth weight increased by 128.44 g. No considerable mediation effect of cortisol was found between pre-BMI and gestational weight gain or between rate of weight gain and birth weight. Pre-BMI and birth weight had a significant negative correlation with high-density lipoprotein cholesterol (HDL-C) levels, i.e., HDL-C was decreased by 1.1 mg/dL for every unit increase in BMI (P=0.017) and for every 100-g increase in birth weight, HDL-C decreased by 0.6 mg/dL (P=0.046). A significant positive correlation was found between cord blood lipid profile and cortisol levels, especially HDL-C (P=0.041).Conclusion: Cord blood cortisol levels did not mediate the association between maternal weight change and birth weight. A positive correlation was noted between cord blood cortisol levels and HDL-C level. Cord blood HDL-C level was negatively correlated with maternal pre-BMI and birth weight.

Simultaneous electrochemical deposition of an e-rGO/β-CD/MnO₂ ternary composite for a self-powered supercapacitor based caffeine sensor

Selvam, S.,Balamuralitharan, B.,Karthick, S. N.,Hemalatha, K. V.,Prabakar, K.,Kim, Hee-Je The Royal Society of Chemistry 2016 Analytical methods Vol.8 No.44

<▼1><▼1><P>A self-powered supercapacitor based on a caffeine sensor electrode has been developed using an electrochemically deposited rGO/β-CD/MnO2 ternary composite with ionic liquid assistance.</P></▼1><▼2><P>A self-powered supercapacitor based on a caffeine sensor electrode has been developed using an electrochemically deposited rGO/β-CD/MnO2 ternary composite with ionic liquid assistance. This typical composite electrode was prepared from electrochemically reduced e-rGO followed by the addition of β-cyclodextrin and MnO2 from Mn(CH3COOH)2·4H2O on FTO surfaces. The composite material is indexed to the corresponding crystalline phase of MnO2 in the XRD investigation and Mn 3p, Mn 2p, C 1s, and O 1s signals were identified from XPS analysis. The cyclic voltammetry study reveals that the potential of the caffeine samples and the square wave voltammetry peak currents indicate an increasing trend for caffeine oxidation. The sensor expressed a sensitivity of 0.187 μA cm<SUP>2</SUP> μM<SUP>−1</SUP> with a linear range of 10–550 μM (<I>n</I> = 3.12). The corresponding supercapacitor also exhibited a specific capacitance of 352 F g<SUP>−1</SUP> and it showed a very good life time from a long term cyclic test. The proposed ternary composite electrodes may be suitable electrodes for self-powered sensor devices.</P></▼2></▼1>

Functional analyses of the novel salt-inducible genes from Korean halophytes

Selvam Ayarpadikannan,Eunsook Chung,Hyun-A So,Kyoung-Mee Kim,Kenneth Ryan Schraufnagle,Ji Hae Park,Se Hyun Park,Jai-Heon Lee 한국육종학회 2013 한국육종학회 심포지엄 Vol.2013 No.07

Salinity stress severely affects plant growth and development causing crop loss worldwide. Suaeda asparagoides is a salt-marsh euhalophyte widely distributed in southwestern foreshore of Korea. To isolate salt tolerance genes from S. asparagoides, we constructed a cDNA library from leaf tissues of S. asparagoides that was treated with 200 mM NaCl. A total of 1,056 clones were randomly selected for EST sequencing, and 932 of them produced readable sequence. By sequence analysis, we identified 538 unigenes and registered each in National Center for Biotechnology Information. The 80 salt stress related genes were selected to study their differential expression. Reverse Transcriptase-PCR and Northern blot analysis revealed that 23 genes were differentially expressed under the high salinity stress conditions in S. asparagoides. They are functionally diverse including transport, signal transduction, transcription factor, metabolism and stress associated protein, and unknown function. Among them dehydrin (SaDhn) and RNA binding protein (SaRBP1) were examined for their abiotic stress tolerance in yeast (Saccharomyces cerevisiae). Yeast overexpressing SaDhn and SaRBP1 showed enhanced tolerance to osmotic, freezing and heat shock stresses. This study provides the evidence that SaRBP1 and SaDhn from S.asparagoides exert abiotic stress tolerance in yeast. Information of salt stress related genes from S. asparagoides will contribute for the accumulating genetic resources to improve osmotic tolerance in plants.

Adaptive p-finite element method for wind engineering

Selvam, R. Panneer,Qu, Zu-Qing Techno-Press 2002 Wind and Structures, An International Journal (WAS Vol.5 No.2

An important goal of computational wind engineering is to impact the design process with simulations of flow around buildings and bridges. One challenging aspect of this goal is to solve the Navier-Stokes (NS) equations accurately. For the unsteady computations, an adaptive finite element technique may reduce the computer time and storage. The preliminary application of a p-version as well as an h-version adaptive technique to computational wind engineering has been reported in previous paper. The details on the implementation of p-adaptive technique will be discussed in this paper. In this technique, two posteriori error estimations, which are based on the velocity and vorticity, are first presented. Then, the polynomial order of the interpolation function is increased continuously element by element until the estimated error is less than the accepted. The second through sixth orders of hierarchical functions are used as the interpolation polynomials. Unequal order interpolations are used for velocity and pressure. Using the flow around a circular cylinder with Reynolds number of 1000 the two error estimators are compared. The result show that the estimated error based on the velocity is lower than that based on the vorticity.

Functional analyses of the novel salt-inducible genes from Korean halophytes

Selvam Ayarpadikannan,Eunsook Chung,Hyun-A So,Kyoung-Mee Kim,Kenneth Ryan Schraufnagle,Kim Hyo Young,Jae-Sung Kwak,Hai Yang Yu,Soon-Ok Kim,Joo-Min Jeon,Myoung-HaeKwak,Jai-Heon Lee 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07

Salinity stress severely affects plant growth and development causing crop loss worldwide. Suaeda asparagoides is a salt-marsh euhalophyte widely distributed in southwestern foreshore of Korea. To isolate salt tolerance genes from S. asparagoides, we constructed a cDNA library from leaf tissues of S. asparagoides that was treated with 200 mM NaCl. A total of 1,056 clones were randomly selected for EST sequencing, and 932 of them produced readable sequence. By sequence analysis, we identified 538 unigenes and registered each in National Center for Biotechnology Information. The 80 salt stress related genes were selected to study their differential expression. Reverse Transcriptase-PCR and Northern blot analysis revealed that 23 genes were differentially expressed under the high salinity stress conditions in S. asparagoides. They are functionally diverse including transport, signal transduction, transcription factor, metabolism and stress associated protein, and unknown function. Among them dehydrin (SaDhn) and RNA binding protein (SaRBP1) were examined for their abiotic stress tolerance in yeast (Saccharomyces cerevisiae). Yeast overexpressing SaDhn and SaRBP1 showed enhanced tolerance to osmotic, freezing and heat shock stresses. This study provides the evidence that SaRBP1 and SaDhn from S.asparagoides exert abiotic stress tolerance in yeast. Information of salt stress related genes from S. asparagoides will contribute for the accumulating genetic resources to improve osmotic tolerance in plants.