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Javed S. Ibrahim ,Rohit T. Mathew,M. J. N. V. Prasad,K. Narasimhan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10
Owing to high heat flux ability and good mechanical strength, copper has been used for micro-electro-mechanical systems(MEMS) components with dimensions in micrometers processed by electrochemical methods. In the present study, finegrained copper foils of different thicknesses and grain sizes produced by pulsed electrodeposition under different controlledcurrent densities were used to investigate the effect of total number of grains across thickness of foil on its tensile responseand formability. For a comparative study, commercially available rolled Cu foils were also used. Vacuum annealing wasemployed to obtain a wide range of fully recrystallized grain sizes within same thickness of the foils. Detailed microstructuralcharacterization was carried out using scanning electron microscope attached with electron backscattered diffraction detector. The foils were subjected to uniaxial tensile testing and formability testing using a miniaturized Nakazima test setup. Asanticipated, finer the grain size higher was the yield strength. However, the strength of copper reduced with decreasing thetotal number of grains across thickness of the foil. The electrodeposited Cu foil exhibited relatively higher strength levelsbut reduced tensile ductility along with decreased strain hardening ability compared to the fully recrystallized Cu foils havingsimilar grain sizes. Furthermore, the number of grains across thickness and the prior history of foils played significantrole on the shape and trend in variation of the forming limit curve of Cu. An α-fiber (< 110 >) texture evolved in Cu duringdeformation and its volume fraction strengthened under biaxial deformation conditions.
Antibacterial Principles from Myristica fragrans Seeds
Avinash S. Dhake,Balasubramanian Narasimhan 한국식품영양과학회 2006 Journal of medicinal food Vol.9 No.3
Nutmeg (Myristica fragrans) is used in food preparations for its aromatic flavor. The present investigation wasundertaken to evaluate the antibacterial activity of constituents of M. fragransseeds. Seeds of M. fragranswere powderedand extracted with chloroform to obtain trimyristin, which on saponification yielded myristic acid. The mother liquor re-maining after separation of trimyristin was concentrated and column-chromatographed with petroleum ether to separate myris-ticin. Antibacterial activity of these isolated constituents was evaluated by determination of minimum inhibitory concentra-tion against selected Gram-positive and Gram-negative organisms. All the constituents isolated from nutmeg exhibited goodantibacterial activity. This study shows the potential of natural compounds in replacement of synthetic preservatives.
Javed S. Ibrahim,M. J. N. V. Prasad,Partha Sarkar,K. Narasimhan 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.2
Ultra-low carbon (ULC) steels, containing a carbon content ~ 0.055 wt%, have been used in several applications in the formof thin foils. However, there are limited studies on the effects of foil thickness (t) to grain size (d) ratio and foil condition onthe tensile response and formability of thin ULC steel foils. In the present work, the tensile and forming behaviours of ULCsteel foils of thickness about 400 μm were evaluated in both annealed and prestrained (by cold reduction to 2–7%) conditionsas a function of t/d ratio and followed by detailed texture evolution analysis. Vacuum annealing was used to achievevarying t/d ratios in the specimens. Additionally, thin ULC steel foils of 100 μm thickness in annealed condition were alsoused for examining the thickness effect. Microstructural analysis was performed using the electron backscattered diffractiontechnique. Microformability was assessed by a miniaturised Nakazima test setup with specimen geometries designed toproduce three different strain paths. The annealed foils displayed a typical yield-point phenomenon, but the total yield-pointelongation decreased with decreasing thickness and grain size. The foils exhibited typical Hall–Petch strengthening, coldwork hardening, and forming limit curves; however, there were substantial reductions in both tensile strength and ductility,and consequently, the forming strains, with decreasing the t/d ratio. The tensile response and formability of the foils wereadversely affected by both thinning and prestraining. The texture studies revealed the formation of a γ-fibre i.e., < 111 >||normaldirection, and its intensity varied significantly with the t/d ratio and mode of strain path.
Direct Organogenesis in Geophila reniformis D. Don., an Important Medicinal Herb
Nisha, A.,Narasimhan, S.,Manjula, S.,Nair, G.M. The Korean Society of Plant Biotechnology 2004 Plant molecular biology and biotechnology research Vol.6 No.3
Adventitious multiple shoots were developed from leaf, petiole and internode explants of Geophila reniformis D. Don. on MS medium supplemented with various concentrations of $N^6$-benzylaminopurine (BAP) or Kinetin (KIN) alone or in combination with indole-3-acetic acid (IAA). Leaf showed maximum organogenetic potential, followed by petiole and internode. Murashige and Skoog (MS) medium supplemented with 22.22 $\mu{M}$ BAP and 4.57 $\mu{M}$ IAA induced maximum shoot buds from leaf explants. Internodal segments showed low potential of direct organogenesis. The regenerated shoots rooted the best in presence of 10.75 - 13.44 $\mu{M}$ $\alpha$-naphthalene acetic acid (NAA) along with 2.22 $\mu{M}$ BAP, and were successfully established in the field with a survival rate of 89.11%.
Mean pressure prediction for the case of 3D unsteady turbulent flow past isolated prismatic cylinder
V. Ramesh,S. Vengadesan,J.L. Narasimhan 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.5
Unsteady 3D Reynolds Averaged Navier-Stokes (URANS) solver is used to simulate the turbulent flow past an isolated prismatic cylinder at Re = 37,400. The aspect ratio of height to base width of the body is 5. The turbulence closure is achieved through a non-linear k - e model. The applicability of this model to predict unsteady forces associated with this flow is examined. The study shows that the present URANS solver with standard wall functions predicts all the major unsteady phenomena showing closer agreement with experiment. This investigation concludes that URANS simulations with the non-linear k - e model as a turbulence closure provides a promising alternative to LES with view to study flows having complex features.
Kim Kyongsong,Siddharth Narasimhan Aiyer,Vignesh Gunasekaran,Latha Mani,Sri Vijay Anand K. S.,Shanmuganathan Rajasekaran,Ajoy Prasad Shetty 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.3
Study Design: Prospective case series. Purpose: This study aimed to investigate the impact of education, financial income, occupation, and patient counseling on the timing of enrolment in a spinal cord injury (SCI) rehabilitation program. Overview of Literature: A rehabilitation program following SCI is essential to improve functional outcomes. Socioeconomic factors can affect the timing of enrolment to a rehabilitation program. Literature on the effects of socioeconomic factors among patients with SCI in the Indian scenario is limited. Methods: A prospective, consecutive analysis of patients with SCI was performed with 1-year follow-up. Assessment of the timing of enrolment to a rehabilitation program was performed using the modified Kuppuswamy socioeconomic scores (MKSS). Patients admitted to the SCI unit (group A), underwent intensive individual, group, and family counseling sessions to encourage early enrolment into a rehabilitation program. Patients presenting directly for rehabilitation (group B) were analyzed for comparison. Results: A total of 153 patients were recruited. Group A was composed of 122 patients who started the rehabilitation program after a mean of 28 days, compared with a mean of 149 days for 31 patients in group B. In group A, 104 patients (85%; mean MKSS, 14.02) and 18 patients (15%; mean MKSS, 15.61) enrolled for rehabilitation <6 weeks and ≥6 weeks, respectively. In group B, 12 patients (39%; mean MKSS, 13.69) and 19 patients (61%; mean MKSS, 12.10) enrolled for rehabilitation <6 weeks and ≥6 weeks, respectively. The total MKSS and scores for education, income, and occupation did not show a significant difference between the two both groups (p>0.05). Conclusions: Early patient counseling in the acute care unit helps in the early enrolment of patients with poor socioeconomic demographic profile to a rehabilitation program.
Mean pressure prediction for the case of 3D unsteady turbulent flow past isolated prismatic cylinder
Ramesh, V.,Vengadesan, S.,Narasimhan, J.L. Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.5
Unsteady 3D Reynolds Averaged Navier-Stokes (URANS) solver is used to simulate the turbulent flow past an isolated prismatic cylinder at Re=37,400. The aspect ratio of height to base width of the body is 5. The turbulence closure is achieved through a non-linear $k-{\varepsilon}$ model. The applicability of this model to predict unsteady forces associated with this flow is examined. The study shows that the present URANS solver with standard wall functions predicts all the major unsteady phenomena showing closer agreement with experiment. This investigation concludes that URANS simulations with the non-linear $k-{\varepsilon}$ model as a turbulence closure provides a promising alternative to LES with view to study flows having complex features.
Development of High Performance Stainless Steel Powders
Schade Christopher,Schaberl John,Narasimhan Kalathur S. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance-processing route has allowed the more consistent production of existing products, and has allowed enhanced properties, such as improved green strength and green density. This paper will review these processing changes along with the potential new products that are being developed utilizing this technology. These include high strength stainless steels such as duplex and dual phase as well as stainless steel powders used in high temperature applications such as diesel filters and fuel cells.