Wear Resistance Enhancement in Cryotreated En 52 and 21-4N Valve Steels

Maria Arockia Jaswin,Gobi Subbarathinam Shankar,Dhasan Mohan Lal 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.1

This experimental study investigates the wear resistance improvement in En 52 and 21-4N valve steels through shallow and deep cryogenic treatment using a reciprocatory friction and wear monitor as per the ASTM standard G-133. It has been observed that the wear resistance of En 52 and 21-4N has improved by 81.15% & 13.49%respectively, due to shallow cryogenic treatment, 86.54% & 22.08% respectively, due to deep cryogenic treatment,when compared to the conventional heat treatment. The microstructural study suggests that the improvement in wear resistance and hardness is attributed to the conversion of retained austenite into martensite, along with precipitation and distribution of the carbides brought in by the cryogenic treatment.

Enhancement of biogas production from microalgal biomass through cellulolytic bacterial pretreatment

Kavitha, S.,Subbulakshmi, P.,Rajesh Banu, J.,Gobi, Muthukaruppan,Tae Yeom, Ick Elsevier 2017 Bioresource technology Vol.233 No.-

<P><B>Abstract</B></P> <P>Generation of bioenergy from microalgal biomass has been a focus of interest in recent years. The recalcitrant nature of microalgal biomass owing to its high cellulose content limits methane generation. Thus, the present study investigates the effect of bacterial-based biological pretreatment on liquefaction of the microalga <I>Chlorella vulgaris</I> prior to anaerobic biodegradation to gain insights into energy efficient biomethanation. Liquefaction of microalgae resulted in a higher biomass stress index of about 18% in the experimental (pretreated with cellulose-secreting bacteria) vs. 11.8% in the control (non-pretreated) group. Mathematical modelling of the biomethanation studies implied that bacterial pretreatment had a greater influence on sustainable methane recovery, with a methane yield of about 0.08 (g Chemical Oxygen Demand/g Chemical Oxygen Demand), than did control pretreatment, with a yield of 0.04 (g Chemical Oxygen Demand/g Chemical Oxygen Demand). Energetic analysis of the proposed method of pretreatment showed a positive energy ratio of 1.04.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microalgal biomass pretreatment by bacteria enhances liquefaction of about 18%. </LI> <LI> Bacterial pretreatment increases the macromolecular release considerably. </LI> <LI> Experimental microalgae improves the methane to 0.08gCOD/gCOD comparing to control. </LI> <LI> Methane production rate increased with hydrolysis constant of about 0.24day<SUP>−1</SUP>. </LI> <LI> A positive energy ratio of about 1.04 was achieved in experimental microalgae. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigating biological impact of HAp from goat femur reinforced with Zr–Ag for bone tissue engineering application

Alagarsamy Karthik,Vishwakarma Vinita,Kaliaraj Gobi Saravanan,Kanagasabai Viswanathan,Ramasamy Sathiskumar 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.4

In this study, the diff erent weight percentages of ZrO 2 –Ag-reinforced HAp were prepared by the planetary mill and cal- cinated at 800 °C for 5 h. Synthesized nano-composites evolved the hexagonal phase of HAp in addition to ZrO 2 and Ag peaks. Raman spectroscopy confi rmed the high-intensity band of PO 4 −3 group and major bands of Zr and Ag. Staphylococ- cus epidermidis and Pseudomonas aeruginosa bacterial growth were arrested in HA20Zr10Ag nano-composites evaluated by in vitro antibacterial activity. Hemocompatible behavior of the reinforced HAp revealed that the nanocomposites was non-hemolytic with distinct RBC morphology and this eff ect was more pronounced while increasing ZrO 2 concentration. Biocompatibility studies, such as protein adsorption, cell viability, fl uorescence staining, mineralization, and quantifi cation of BMP-2, were analyzed with MG-63. The nanocomposites have adsorbed a high amount of proteins (~ 300 to 700 μg) from the serum. MTT assay revealed the percentage of the viability of the cells was ~ 70% to 80%. In vitro cytotoxic behavior of MG-63 cells illustrated that HA20Zr10Ag nanocomposites expressed polygonal structure with elongated morphology by Alexa Fluor 488 phalloidin and DAPI staining. Similarly, nano-composites powder proved its mineralization capability through intracellular calcium uptake up to the 5th day of MG-63 incubation. While, BMP-2 expression was slightly higher in HA20Zr10Ag nano-composite at 5th day of incubation. From the results, it is illustrated that HAp with 20 wt% of ZrO 2 and 10 wt% Ag nanocomposites has an important role in osteoblastic bone formation.

Evolutionary Algorithm-based Space Diversity for Imperfect Channel Estimation

( Zienab Pouladmast Ghadiri ),( Ayman A. El-saleh ),( Gobi Vetharatnam ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.5

In space diversity combining, conventional methods such as maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) are commonly used to improve the output signal-to-noise ratio (SNR) provided that the channel is perfectly estimated at the receiver. However, in practice, channel estimation is often imperfect and this indeed deteriorates the system performance. In this paper, diversity combining techniques based on two evolutionary algorithms, namely genetic algorithm (GA) and particle swarm optimization (PSO) are proposed and compared. Numerical results indicate that the proposed methods outperform the conventional MRC, EGC and SC methods when the channel estimation is imperfect while it shows similar performance as that of MRC when the channel is perfectly estimated.

Carbon nanotube ensembled hybrid nanocomposite electrode for direct electrochemical detection of epinephrine in pharmaceutical tablets and urine

Koteshwara Reddy, K.,Satyanarayana, M.,Yugender Goud, K.,Vengatajalabathy Gobi, K.,Kim, Hern Elsevier 2017 Materials Science and Engineering C Vol.79 No.-

<P><B>Abstract</B></P> <P>An efficient electrochemical sensor for selective detection of the neurotransmitter, epinephrine (Epn), has been fabricated with the aid of a functionalized multiwall carbon nanotube–chitosan biopolymer nanocomposite (<I>Chit</I>-<I>fCNT</I>) electrode. Multiwall carbon nanotubes (CNT) were successfully functionalized with the aid of nitric acid and confirmed by the Raman spectral data. Functionalized carbon nanotubes (<I>fCNT</I>) were dispersed in chitosan solution and the resulting bio-nanocomposite was used for the fabrication of sensor surface by drop and cast method. Electrochemical characteristics of the fabricated sensor were understood using cyclic, differential pulse voltammetry (CV, DPV) and electrochemical impedance analysis for the detection of Epn in phosphate buffer (pH7.4). CV and impedance analysis revealed that the <I>Chit</I>-<I>fCNT</I> modified electrode enhances the electrodic reaction of Epn and facilitated the electron transfer more readily compared to that of bare electrode. Applying DPV for the detection of Epn, achieved 30nM as the lowest detection limit in the determination range of 0.05–10μM and the analytical time as low as 10s. Selective determination of Epn against the coexistence of a number of biological electroactive interferents and reproducible results for the determination of Epn were demonstrated. The present biosensor has been found efficient for successful direct determination of Epn from pharmaceutical adrenaline formulations and urine samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Chitosan</I>-<I>fCNT</I> facilitated a stable and uniform nanocomposite film on the electrode surface. </LI> <LI> Raman spectral data substantiated the functionalization of CNT. </LI> <LI> Best selectivity towards epinephrine in the presence of potential biological interferents </LI> <LI> Very good reproducibility of results with significant low-detection limit of epinephrine </LI> <LI> Applicable to the direct detection of epinephrine from urine and pharmaceutical samples </LI> </UL> </P>

Effect of Transition Metal and Different Rare-Earth Inhibitors-Based Sol–gel Coatings on Corrosion Protection of Mild Steel

Aarti Gautam,K. R. C. Soma Raju,K. V. Gobi,R. Subasri 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

Autonomous healing coatings based on encapsulation of corrosion inhibitors into nanocontainers is gaining a lot of attention. In the present work, coating formulations based on hybrid organic–inorganic sol–gel coatings impregnated with chrome-free corrosion inhibitors such as Zr4+ (Z) and various rare-earth elements (RE: Ce3+, La3+, Gd3+, Er3+) were investigated on mild steel substrates. Effects for both the direct addition of corrosion inhibitor (Z/RE) into the matrix sol and the addition of halloysite nanoclay encapsulated corrosion inhibitor (Z/RE-H) were evaluated. To evaluate the coating performance and self-healing action of different corrosion inhibitors, various characterization techniques such as potentiodynamic polarization studies, electrochemical impedance spectroscopy, micro-Raman spectroscopy, salt spray test and scanning electron microscopy-elemental analysis were used. Electrochemical studies and salt spray tests clearly confirm that coatings derived from a direct addition of corrosion inhibitors to the matrix sol result in an excellent performance. The current densities of coatings based on direct addition of Zr4+ and Ce3+ were very low, in the order of 10–10 and 10–9 A/cm2, respectively, when compared to other RE and all Z/RE-H coatings, which exhibited a current density of 10–6 A/cm2. Micro-Raman analysis confirmed the self-healing action of zirconium and cerium-based coatings.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review

Goud, K. Yugender,Kailasa, Suresh Kumar,Kumar, Vanish,Tsang, Yiu Fai,Lee, S.E.,Gobi, K. Vengatajalabathy,Kim, Ki-Hyun Elsevier 2018 Biosensors & bioelectronics Vol.121 No.-

<P><B>Abstract</B></P> <P>Nanomaterial-embedded sensors have been developed and applied to monitor various targets. Mycotoxins are fungal secondary metabolites that can exert carcinogenic, mutagenic, teratogenic, immunotoxic, and estrogenic effects on humans and animals. Consequently, the need for the proper regulation on foodstuff and feed materials has been recognized from times long past. This review provides an overview of recent developments in electrochemical sensors and biosensors employed for the detection of mycotoxins. Basic aspects of the toxicity of mycotoxins and the implications of their detection are comprehensively discussed. Furthermore, the development of different molecular recognition elements and nanomaterials required for the detection of mycotoxins (such as portable biosensing systems for point-of-care analysis) is described. The current capabilities, limitations, and future challenges in mycotoxin detection and analysis are also addressed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mycotoxins are fungal secondary metabolites that exert toxic effects on humans and animals. </LI> <LI> Exploration of mycotoxins is an interdisciplinary research area that has progressed intensively. </LI> <LI> Different nanomaterials (NMs) were used for the detection of small molecules, including mycotoxins. </LI> <LI> Here the recent developments of NM-based EC biosensors are described for mycotoxin detection. </LI> <LI> The role of EC sensors is assessed for combined applications with diverse recognition elements. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>