Effect of thermal annealing on the electrical and structural properties of Au/Y/p-type InP Schottky structure

Dasaradha Rao, L.,Shanthi Latha, K.,Rajagopal Reddy, V.,Choi, C.J. Pergamon Press [etc.] 2015 Vacuum Vol.119 No.-

The effects of rapid thermal annealing on the electrical and structural properties of a fabricated Au/Y/p-InP Schottky barrier diode (SBD) have been investigated. The estimated Schottky barrier heights (SBHs) of the as-deposited and 200 <SUP>o</SUP>C annealed Au/Y/p-InP SBDs are found to be 0.62 eV (I-V)/0.83 eV (C-V) and 0.63 eV (I-V)/0.92 eV (C-V) respectively. However, the SBH increases to 0.65 eV (I-V)/0.96 eV (C-V) upon annealing at 300 <SUP>o</SUP>C. Further, the SBH slightly decreases to 0.59 eV (I-V)/0.78 eV (C-V) for contact annealed at 400 <SUP>o</SUP>C. The SBH, ideality factor and series resistance of the Au/Y/p-InP SBD are estimated by Norde and Cheung's methods. Also, the discrepancy between SBHs estimated from I-V, C-V, Norde and Cheung's methods are described and discussed. It is noted that the interface state density of the Au/Y/p-InP SBD decreases upon annealing at 300 <SUP>o</SUP>C and then slightly increases after annealing at 400 <SUP>o</SUP>C. The AES and XRD measurements have revealed that the formation of Au-In, Au-P and Y-P interfacial phases at the interface may be the reason for the increase and decrease of SBHs upon annealing. The AFM results showed that the surface morphology of the Au/Y Schottky contact is fairly smooth at various annealing temperatures.

Fitted mesh method for singularly perturbed reaction-convection-diffusion problems with boundary and interior layers

V. Shanthi,N. Ramanujam,S. Natesan 한국전산응용수학회 2006 Journal of applied mathematics & informatics Vol.22 No.1-2

A robust numerical method for a singularly perturbed second– order ordinary differential equation having two parameters with a discontinuous source term is presented in this article. Theoretical bounds are derived for the derivatives of the solution and its smooth and singular components. An appropriate piecewise uniform mesh is constructed, and classical upwind finite difference schemes are used on this mesh to obtain the discrete system of equations. Parameter–uniform error bounds for the numerical approximations are established. Numerical results are provided to illustrate the convergence of the numerical approximations.

FITTED MESH METHOD FOR SINGULARLY PERTURBED REACTION-CONVECTION-DIFFUSION PROBLEMS WITH BOUNDARY AND INTERIOR LAYERS

Shanthi, V.,Ramanujam, N.,Natesan, S. 한국전산응용수학회 2006 Journal of applied mathematics & informatics Vol.22 No.1

A robust numerical method for a singularly perturbed second-order ordinary differential equation having two parameters with a discontinuous source term is presented in this article. Theoretical bounds are derived for the derivatives of the solution and its smooth and singular components. An appropriate piecewise uniform mesh is constructed, and classical upwind finite difference schemes are used on this mesh to obtain the discrete system of equations. Parameter-uniform error bounds for the numerical approximations are established. Numerical results are provided to illustrate the convergence of the numerical approximations.

A study on underwater optical wireless communication link capability in the Bay of Bengal

Sathyaram, V.,Prince, Shanthi,Vedachalam, N. Techno-Press 2018 Ocean systems engineering Vol.8 No.1

The paper presents a numerical underwater channel model developed in MATLAB for estimating the optical link budget between a light emitting diode (LED) based optical transmitter and a photo diode (PD) receiver when operated in the harbor, coastal and deep waters locations in the Bay of Bengal. The water samples are collected at different locations in the Bay of Bengal using a water sampler during an offshore research cruise. The optical attenuation, the main inherent parameter determining the range of the optical communication link is identified for the different waters using an underwater irradiance measurement system in the laboratory. The identified parameters are applied to the numerical model and found that a 10 W LED and a photo diode based system can provide the optical budget required for a horizontal underwater communication range of about 0.5, 14 and 35 m in the harbor, coastal and deep waters locations respectively. By increasing the transmitter power to 50 W, the operating range of the communication link could be increased up to 53 m in deep water locations in the Bay of Bengal.

A Schwarz method for fourth-order singularly perturbed reaction-diffusion problem with discontinuous source term

M. Chandru,V Shanthi 한국전산응용수학회 2016 Journal of applied mathematics & informatics Vol.34 No.5

A singularly perturbed reaction-diffusion fourth-order ordinary differential equation(ODE) with discontinuous source term is considered. Due to the discontinuity, interior layers also exist. The considered problem is converted into a system of weakly coupled system of two second-order ODEs, one without parameter and another with parameter $\varepsilon$ multiplying highest derivatives and suitable boundary conditions. In this paper a computational method for solving this system is presented. A zero-order asymptotic approximation expansion is applied in the second equation. Then, the resulting equation is solved by the numerical method which is constructed. This involves non-overlapping Schwarz method using Shishkin mesh. The computation shows quick convergence and results presented numerically support the theoretical results.

A SCHWARZ METHOD FOR FOURTH-ORDER SINGULARLY PERTURBED REACTION-DIFFUSION PROBLEM WITH DISCONTINUOUS SOURCE TERM

CHANDR, M.,SHANTHI, V. The Korean Society for Computational and Applied M 2016 Journal of applied mathematics & informatics Vol.34 No.5

A singularly perturbed reaction-diffusion fourth-order ordinary differential equation(ODE) with discontinuous source term is considered. Due to the discontinuity, interior layers also exist. The considered problem is converted into a system of weakly coupled system of two second-order ODEs, one without parameter and another with parameter ε multiplying highest derivatives and suitable boundary conditions. In this paper a computational method for solving this system is presented. A zero-order asymptotic approximation expansion is applied in the second equation. Then, the resulting equation is solved by the numerical method which is constructed. This involves non-overlapping Schwarz method using Shishkin mesh. The computation shows quick convergence and results presented numerically support the theoretical results.

A Hybrid Multi-Level Feature Selection Framework for prediction of Chronic Disease

G.S. Raghavendra,Shanthi Mahesh,M.V.P. Chandrasekhara Rao International Journal of Computer ScienceNetwork S 2023 International journal of computer science and netw Vol.23 No.12

Chronic illnesses are among the most common serious problems affecting human health. Early diagnosis of chronic diseases can assist to avoid or mitigate their consequences, potentially decreasing mortality rates. Using machine learning algorithms to identify risk factors is an exciting strategy. The issue with existing feature selection approaches is that each method provides a distinct set of properties that affect model correctness, and present methods cannot perform well on huge multidimensional datasets. We would like to introduce a novel model that contains a feature selection approach that selects optimal characteristics from big multidimensional data sets to provide reliable predictions of chronic illnesses without sacrificing data uniqueness.[1] To ensure the success of our proposed model, we employed balanced classes by employing hybrid balanced class sampling methods on the original dataset, as well as methods for data pre-processing and data transformation, to provide credible data for the training model. We ran and assessed our model on datasets with binary and multivalued classifications. We have used multiple datasets (Parkinson, arrythmia, breast cancer, kidney, diabetes). Suitable features are selected by using the Hybrid feature model consists of Lassocv, decision tree, random forest, gradient boosting,Adaboost, stochastic gradient descent and done voting of attributes which are common output from these methods.Accuracy of original dataset before applying framework is recorded and evaluated against reduced data set of attributes accuracy. The results are shown separately to provide comparisons. Based on the result analysis, we can conclude that our proposed model produced the highest accuracy on multi valued class datasets than on binary class attributes.[1]

Synthesis, characterization and application of polypyrrole-cellulose nanocomposite for efficient Ni(II) removal from aqueous solution: Box-Behnken design optimization

Rathika, R.,Byung-Taek, Oh,Vishnukumar, B.,Shanthi, K.,Kamala-Kannan, S.,Janaki, V. De Gruyter 2018 E-Polymers Vol.18 No.4

<P><B>Abstract</B></P><P>The role of polypyrrole-cellulose (PPy-Ce) nanocomposite for the removal of Ni(II) from aqueous solution was investigated by batch experiments. The PPy-Ce nanocomposite was prepared by chemical oxidate polymerization of pyrrole monomer with cellulose. Transmission electron micrography (TEM) showed the size of the particles varied from 80 to 95 nm. The characteristic C-O, O-H, C-N and C-C vibrations in the Fourier transform infrared (FTIR) spectra indicate that the cellulose successfully integrated with the pyrrole. Influence of experimental variables such as pH, contact time, adsorbent dose and initial Ni(II) concentration were optimized using the response surface methodology (RSM) based Box-Behnken design (BBD). The optimal conditions for maximum removal of Ni(II) were pH 8, time 65 min, adsorbent dose 0.3 mg/l and Ni(II) concentration 50 mg/l. The maximum removal efficiency under optimized conditions was >94%. The results indicate that BBD could be used to optimize experimental conditions for metal removal from aqueous solution.</P>

Vasculosyncytial membrane in relation to syncytial knots complicates the placenta in preeclampsia

K. Devi Sankar,P. Sharmila Bhanu,Sujatha Kiran,B. A. Ramakrishna,V. Shanthi 대한해부학회 2012 Anatomy & Cell Biology Vol.45 No.2

The vasculosyncytial membrane (VSM), primary site of fetomaternal exchange is formed when syncytiotrophoblast surrounds the terminal villi and make a close contact with capillaries. Some syncytiotrophoblast forms thin single layer of villous and some syncytial nuclei become piled up to form the syncytial knots (SKs). Undoubtedly there is a clear-cut inverse relation between villous VSM and fetal hypoxia. In preeclampsia (PE) the hypoxia injury disrupts the syncytial architecture which in turn initiates other complications of PE. Present study was designed to observe the morphological and histomorphometric features of 84 placentas from control and PE (42 each) collected from Department of Obstetrics and Gynecology. Neonatal weight and placental weight were reduced in PE than the controls but the feto-placental index did not differ. The SK density and VSM thickness was found to be increased and was statistically significant in PE cases. In relation to SKs, the VSM thickness was twofold increased than the controls and was statistically significant. The SKs in the present study were classified as type-1, 2a, 2b, and 3. Type 1 was found to be 62% in control and 47% in PE, type 2a and 2b were 38% in control and 37% in PE, and type 3 was in 8% of PE cases. All the parameters of present study reveal the adverse effects of PE influencing on both morphological and microscopical features of the placenta resulting in fetal hypoxia.