396 research outputs found
A multilevel method for meshless solution of the poisson equation in heat transfer and fluid flow
No full textMeshless methods using radial basis functions (RBF) are an attractive alternative to grid based methods for solving partial differential equations in complex geometries. Gaussian, Multiquadratics and inverse Multiquadratics are some of the more popular RBF's, but the require a shape paramter for a stable and accurate solution and also face stagnation issues. Recently, Polyharmonic splines (PHS) with appended polynomials have overcome the aforementioned issues and offer spectral convergence of the discretization errors with the degree of appended polynomials. In this thesis, we present a non-nested multilevel algorithm using the PHS-RBF meshless method for the soluution of the Poisson equation, which commonly arises in numerous heat transfer and fluid flow applications. The PHS-RBF discretization of the Poisson equation leads to a sparse set of equations with unknown variables at each of the scattered point. The non-nested multilevel algorithm solves this set of equations by restricting and prolongating the values and corrections between multiple independently generated coarse set of points by making use of RBF interpolation. The performance of this algorithm is tested for the Poisson equation in three model geometries, using manufactured solutions. Rapid convergence of the residual is observed with Dirichlet boundary conditions using Successive Over-Relaxation(SOR) as the relaxation scheme . However, convergence is seen to be quite modest for the all-Neumann boundary condition, but this poor convergence is ameliorated by using the multilevel algorithm as a preconditioner to the GMRES, which is a Krylov Subspace Projection (KSP) method. This rapid convergence of the all-Neumann equation is then applied to the pressure Poisson equation arising in the fractional step method, with explicit convection and explicit diffusion. We demonstrate fast convergence, both with refinement of number of points and degree of appended polynomials, for various fluid flow problems in complex domains with high accuracy using the meshless fractional step algorithm.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2022-01-12 without embargo termsThe student, - Anand Radhakrishnan, accepted the attached license on 2021-06-18 at 20:07.The student, - Anand Radhakrishnan, submitted this Thesis for approval on 2021-06-18 at 20:13.This Thesis was approved for publication on 2021-06-23 at 13:08.DSpace SAF Submission Ingestion Package generated from Vireo submission #16698 on 2022-01-12 at 12:43:25Made available in DSpace on 2022-01-12T21:45:20Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Experimental and computational investigation of heat transfer in a microwave-assisted flow system
No full textMicrowave technology is gaining popularity as a tool for chemical process intensification and an alternative to conventional heating. However, in flow systems non-uniform temperature profiles are commonly encountered and hence methods to characterise and improve them are required. In this work, we studied the effects of various operational parameters-microwave power, inlet flow rate, tube orientation and pressure-on the electric field and temperature profiles of water flowing in a PTFE tube (2.4 mm internal diameter), placed in a commercial single-mode microwave applicator. A finite element model was developed to estimate the longitudinal temperature profiles and the absorbed microwave power, while in situ temperature monitoring was performed by a fibre optic probe placed at multiple locations inside the tube. The water temperature inside the tube increased by increasing the microwave power input and temperature profiles stabilised beyond 20 W, while the percentage absorbed microwave power showed the inverse trend. When changing the tube orientation or decreasing the inlet flow rate, microwave absorption decreased significantly. When the pressure was increased to 2.3 bara, water temperature increased by ~ 20 o C. Results from this study provide valuable insights on achievable temperature profiles and energy efficiency of microwave-assisted flow synthesis systems.
Need for a national epilepsy control program
No full textThis article briefly outlines the proposed national epilepsy control program. The content of the article is based on four meetings held by invitation of the Ministry of Health. Invitees by ministry - Drs. D. C. Jain, M. Gourie Devi, V. Saxena, S. Jain, P. Satish. Chandra, M. Gupta, K. Bala, V. Puri, K. S. Anand, S. Gulati, S. Johri, P. S. Chandra, M. Behari, K. Radhakrishnan, D. Bachani. Presentations were made by Dr. M. Tripathi.The program will involve all neurologists across the country in teaching and training at state levels and a central monitoring committee
Impacts of Ta Buffer Layer and Cu-Ge-Te Composition on the Reliability of GeSe-Based CBRAM
No full textsponsorship: This work was supported by imec's Core Partner Industrial Affiliation Program on Emerging Memories. The review of this article was arranged by Editor P. Du. (Corresponding author: Janaki Radhakrishnan.) (imec's Core Partner Industrial Affiliation Program on Emerging Memories)status: Publishe
Efficacy of sugarcane bagasse to produce bacterial biofilm in water for fish culture
No full textThe present study has been conducted to understand the efficacy of sugarcane bagasse to produce bacterial biofilm in water. The study period was 90 days. Total Plate count (TPC) in water and substrate was estimated on nutrient agar at room temperature by spread plate method. The TPC in water was the highest (2.10 x 104 ml–1) after 45 days. The average TPC of bacteria on bagasse varied from 140.0 (15d) to 30.25 (90d) x104·g–1. The present study demonstrates that the sugarcane bagasse can produce more bacteria in water thereby the fish can effectively utilize biofilm grown on sugarcane bagasse and provision of a substrate reduces the need for artificial feed.---------------------------------------------------------------------------------------------------------Efficacy of sugarcane bagasse to produce bacterial biofilm in water for fish culture M.V. Radhakrishnan and E.SugumaranDepartment of Zoology, Annamalai University, Annamalainagar – 608 002, Tamilnadu, India *Corresponding Author, Email: [email protected] Cite This Article As: M.V. Radhakrishnan, E. Sugumaran. 2010. Efficacy of sugarcane bagasse to produce bacterial biofilm in water for fish culture. J. Ecobiotechnol. 2(2):41-44
Baclofen-induced neurotoxicity in a patient with end-stage renal disease
No full textBaclofen, predominantly excreted by the kidneys is accumulated in patients with renal insufficiency leading to the central nervous system toxicity. Here the author reports a patient with end-stage renal disease on maintenance hemodialysis (HD) who developed drowsiness and became unresponsive within a day after taking single 10 mg dose of baclofen. Patient improved completely after two sessions of HD
A monolithically integrated power JFET and Junction Barrier Schottky diode in 4H silicon carbide
No full textEfficiency of power management circuits depends significantly on their constituent switches and rectifiers. The demands of technology are increasingly running up against the intrinsic properties of Si based power devices. 4H-Silicon Carbide (SiC) has superior properties that make it attractive for high power applications. SiC rectifiers are already a competitive choice and SiC switches have also been commercialized recently. Junction Barrier Schottky (JBS) diodes, which combine the advantages of PN and Schottky, have higher Figure of Merit (FOM) as rectifiers. Among switches, a robust and mature process has been developed for Silicon Carbide Vertical Junction Field Effect Transistors (VJFETs), which currently gives it the highest unipolar FOM. Switches are frequently combined with anti-parallel diodes in power circuits. This thesis describes the development of a SiC-based monolithically integrated power switch and diode. Monolithic integration increases reliability and efficiency, and reduces cost. Because of their superior properties and similarities in fabrication, we chose the SiC VJFET and JBS diode as the switch and rectifier. Detailed design, fabrication and characterization of the integrated switch to block above 800 V and conduct current beyond 100 A/cm2 is explained. In this process, the first physics-based 2-D compact model is developed for reverse leakage in a JBS diode as a function of design parameters. Since the gate-channel junctions of SiC VJFETs cannot be assumed to be abrupt, an existing analytical model for Si VJFETs is extended to account for graded gate-channel junctions. Using these analytical models, design rules are developed for the VJFET and JBS diode. Finite element simulations are used to find the best anode layout of the JBS diode and optimize electric field termination in the integrated device to ensure their capability to operate at high voltage. Finally, a spin-on glass based process is developed for filling the gate trenches of the VJFET to improve long-term robustness in extreme environments. The integrated power switch developed in this thesis points to the attractions of monolithic integration in SiC power circuits. Analytical compact design equations derived here will facilitate faster and easier design of switches and rectifiers for desired circuit operation.Ph. D.Includes bibliographical referencesIncludes vitaby Rahul Radhakrishna
Clinical characteristics of a South Indian cohort of juvenile myoclonic epilepsy probands
No full textDespite the distinctive clinical and electroencephalographic features known for five decades, even today, juvenile myoclonic epilepsy (JME) is frequently unrecognised and misdiagnosed in both developed and developing countries. Utilising 183 JME probands belonging to the South Indian state of Kerala, assembled through a tertiary referral centre for molecular genetic studies, we explored the phenotypic peculiarities, clinical genetics, and problems and pitfalls in the diagnosis of JME. At referral, only six (3.3%) patients carried the diagnostic label of JME, default in diagnosis resulted from failure to elicit the history of myoclonic jerks by the referring physicians. During the mean delay of 8.6 +/- 7.0 years in diagnosing JME, seizure control in the majority was poor due to inappropriate antiepileptic drug (AED) therapy. A history of epileptic seizures was obtained in 6.2% of the first-degree and 2.2% of the second-degree relatives of the probands; 37.7 and 11.1% of them, respectively, were diagnosed as JME. Although most of the clinical features of our cohort were in accordance with the literature, two notable differences we observed were the relatively increased occurrence of absence seizures and low frequency of photoparoxysmal responses. Although the variability in the clinical characteristics of JME may be apparent due to differences in the ascertainment of the data, they may well be an expression of a true clinical heterogeneity, and are in accordance with the complex and variable mode of inheritance and conflicting linkage studies reported for this syndrome from different ethnic groups. (C) 2003 BEA Trading Ltd. Published by Elsevier Science Ltd. All rights reserved
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