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Search Results: 1 - 10 of 223809 matches for " R. Udhayakumar "
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Covers and Envelopes of $\mathcal{X}$-injective and $\mathcal{U}_\mathcal{X}$-projective modules
C. Selvaraj,A. Umamaheswaran,R. Udhayakumar
Mathematics , 2015,
Abstract: In this paper, we investigate the notions of $\mathcal{U}_\mathcal{X}$-projective, $\mathcal{X}$-injective and $\mathcal{X}$-flat modules and give their characterizations, where $\mathcal{X}$ is the class of left $R$-modules. We prove the class of all $\mathcal{U}_\mathcal{X}$-projective modules is Kaplansky and show the existence of $\widetilde{\mathcal{U}_\mathcal{X}}$-covers and $\mathcal{U}_\mathcal{X}$-envelopes over a $\mathcal{U}_\mathcal{X}$-hereditary ring $R.$ Moreover, we prove that decomposition of a $\mathcal{U}_\mathcal{X}$-projective module into a projective and a coreduced $\mathcal{U}_\mathcal{X}$-projective module over a self $\mathcal{X}$-injective and $\mathcal{U}_\mathcal{X}$-hereditary ring. Finally, we prove that every module has an $\mathcal{X}$-injective cover over a Noetherian ring $R,$ where $\mathcal{X}$ is the class of all pure projective modules.
Prediction of Better Flow Control Parameters in MHD Flows Using a High Accuracy Finite Difference Scheme  [PDF]
A. D. Abin Rejeesh, S. Udhayakumar, T. V. S. Sekhar, R. Sivakumar
American Journal of Computational Mathematics (AJCM) , 2017, DOI: 10.4236/ajcm.2017.73021
Abstract: We have successfully attempted to solve the equations of full-MHD model within the framework of Ψ - ω formulation with an objective to evaluate the performance of a new higher order scheme to predict better values of control parameters of the flow. In particular for MHD flows, magnetic field and electrical conductivity are the control parameters. In this work, the results from our efficient high order accurate scheme are compared with the results of second order method and significant discrepancies are noted in separation length, drag coefficient and mean Nusselt number. The governing Navier-Stokes equation is fully nonlinear due to its coupling with Maxwell’s equations. The momentum equation has several highly nonlinear body-force terms due to full-MHD model in cylindrical polar system. Our high accuracy results predict that a relatively lower magnetic field is sufficient to achieve full suppression of boundary layer and this is a favorable result for practical applications. The present computational scheme predicts that a drag-coefficient minimum can be achieved when β=0.4 which is much lower when compared to the value β=1 as given by second order method. For a special value of β=0.65, it is found that the heat transfer rate is independent of electrical conductivity of the fluid. From the numerical values of physical quantities, we establish that the order of accuracy of the computed numerical results is fourth order accurate by using the method of divided differences.
Design and Implementation of ANFIS Controller Based Grid Connected Voltage Source Inverters in RTOS Environment  [PDF]
D. Thalapathi Udhayakumar, P. S. Manoharan
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.79212
Abstract: In this manuscript it is proposed and demonstrated that how an ANFIS (Adaptive Neuro Fuzzy Inference System) can be used in the control of a Voltage Source Inverter (VSI) connected to the grid. Volatile changes in the gird parameters rising by its variable demands and other related issues may humiliate the efficiency with which power can be injected into the grid. The system becomes a higher order one with the filters used at the terminal of the Voltage Source Inverter (VSI) along with the parameters of the grid which change from time to time. Single time tuned mathematical controllers like the PID variants are not suitable for such applications. Considering the increased order of the system and the associated non-linearity we have to look out for intelligent controllers. An ANFIS based control is found to be promising; the development and implementation of one such are demonstrated in this paper using the MATLAB SIMULINK platform and through experimental verification using the Reduced Instruction Set Computer (RISC) Microcontroller Advanced RISC Machine (ARM) processor as the central controller for the VSI.
Defenses against Large Scale Online Password Guessing by Using Persuasive Cued Click Points
International Journal of Computer Science and Mobile Computing , 2013,
Abstract: This paper presents a detailed evaluation of the Persuasive Cued Click Points password schemewhich provides high level of security. An important goal of the authentication system is to provide support tousers in selecting better passwords thus increasing security by expanding password space. The use of click -based pass words leads to the selection of passwords which can be easily hacked. We use persuasivetechnique to influence the user in selecting the password in random manner rather than using a particularsequence. Our method significantly reduces the drawbacks of the current authentication method that is beingused.
Stand - Alone Wind Energy Supply System Using Permanent Magnet Synchronous Generator
Udhayakumar P,,Saravanan C,,M. Lydia
International Journal of Innovative Technology and Exploring Engineering , 2013,
Abstract: Energy demand across the world is increasing and the resources are becoming scarce. The major source of power is from the conventional sources only. Some of the conventional sources of energies like thermal energy is produced from the fossil fuel coal which are depleting and is only limited to 2030. Renewable sources of energies are Solar, Wind, Biomass, etc hold bright prospect for the future. Wind industry has made rapid strides in the recent years. Wind power penetration has increased significantly in many interconnected power systems. Wind farms in remote places can also serve as stand – alone wind energy supply system. In this paper simulation of stand – alone wind energy supply system using permanent magnet synchronous generator is done.
Hybrid posicast controller for a DC-DC buck converter
Kaithamalai Udhayakumar,Ponnusamy Lakshmi,Kandasamy Boobal
Serbian Journal of Electrical Engineering , 2008, DOI: 10.2298/sjee0801121k
Abstract: A new Posicast compensated hybrid controller for the DC-DC Buck converter is investigated. Posicast is a feed forward compensator, which eliminates the overshoot in the step response of a lightly damped system. However, the traditional method is sensitive to variations in natural frequency. The new method described here reduces this undesirable sensitivity by using Posicast within the feedback loop. Design of the Posicast function is independent of computational delay. The new controller results in a lower noise in the control signal, when compared to a conventional PID controller.
Electronic Properties of Boron and Silicon Doped (10, 0) Zigzag Single-Walled Carbon Nanotube upon Gas Molecular Adsorption: A DFT Comparative Study
P. A. Gowri sankar,K. Udhayakumar
Journal of Nanomaterials , 2013, DOI: 10.1155/2013/293936
Abstract: We have performed a comparative study of nine predominant gas molecules (H2, H2O, O2, CO, CO2, NO, NO2, NH3, and CH3OH) adsorption property on the top surface of the (10, 0) zigzag single-walled pristine Carbon nanotube (C-CNT), Boron doped carbon nanotube (B-CNT), and Silicon doped carbon nanotube (Si-CNT) are investigated by using density functional theory (DFT) computations to exploit their potential applications as gas sensors. For the first time, we calculated the optimal equilibrium position, absorption energy ( ), and density of states (DOS) of the considered gas molecules adsorbed on the open end of zigzag single-walled (10, 0) B-CNT and Si-CNT. Our first principle calculations demonstrate that the B-CNT and Si-CNT adsorbent materials are able to adsorb the considered gas molecules with variety of adsorption energy and their electronic structure dramatic changes in the density of states near the Fermi level. The obtained comparative DFT studies results are useful for designing a high-fidelity gas sensor materials and selective adsorbents for a selective gas sensor. 1. Introduction Gas molecular adsorption in nanostructures is an important issue for both fundamental research and technical application. In recent years, carbon nanotubes have been intensively studied due to their importance as building blocks in nanotechnology. The special geometry and unique properties of carbon nanotubes offer great potential applications, such as nanoelectronic devices, fuel cell, energy storage, chemical probes and biosensors, field emission display, and gas sensor [1–4]. Carbon nanotubes (CNTs) have the potential to be developed as a new gas sensing material due to their inherent properties such as their small size, great strength, high electrical and thermal conductivity, high surface-to-volume ratio, and hollow structure of nanomaterials. As a result, it is possible to create a miniaturized sensor, which can lead to low power consumption, lighter, and low cost. Therefore, CNTs-based gas sensors and their mechanisms have been widely studied recently. Different kinds of nanotubes have been investigated for gas molecules adsorption, such as carbon nanotubes (CNTs) [5–15], boron nitride nanotubes (BNNTs) [16–22], boron doped nanotubes [23–27], silicon carbide nanotubes [28–46], zinc oxide nanotube, TiO2 nanotube, tungsten carbide nanotube, and MgO nanotube [47]. Meanwhile, the efficiency of gas adsorption on pristine carbon nanotubes can be enhanced by doping process [16–46]. Doping (heteroatom substitution) is also a promising approach to enable single-walled
Stock Market Trend Analysis Using Hidden Markov Models
G. Kavitha,A. Udhayakumar,D. Nagarajan
Quantitative Finance , 2013,
Abstract: Price movements of stock market are not totally random. In fact, what drives the financial market and what pattern financial time series follows have long been the interest that attracts economists, mathematicians and most recently computer scientists [17]. This paper gives an idea about the trend analysis of stock market behaviour using Hidden Markov Model (HMM). The trend once followed over a particular period will sure repeat in future. The one day difference in close value of stocks for a certain period is found and its corresponding steady state probability distribution values are determined. The pattern of the stock market behaviour is then decided based on these probability values for a particular time. The goal is to figure out the hidden state sequence given the observation sequence so that the trend can be analyzed using the steady state probability distribution( ) values. Six optimal hidden state sequences are generated and compared. The one day difference in close value when considered is found to give the best optimum state sequence.
Mixed Convection and Heat Transfer Studies in Non-Uniformly Heated Buoyancy Driven Cavity Flow  [PDF]
A. D. Abin Rejeesh, Selvarasu Udhayakumar, T. V. S. Sekhar, Rajagopalan Sivakumar
Open Journal of Fluid Dynamics (OJFD) , 2017, DOI: 10.4236/ojfd.2017.72016
Abstract: We analyse the mixed convection flow in a cavity flow which is driven by buoyancy generated due to a non-uniformly heated top wall which is moving uniformly. A fourth order accurate finite difference scheme is used in this study and our code is first validated against available data in the literature. The results are obtained for different sets of Reynolds number Re, Prandtl number Pr and Grashof number Gr which are in the ranges 100 - 3000, 0.0152 - 10 and 102 - 106 respectively. Here Gr is related to the Richardson number according to Ri=Gr/Re2. While increasing the Richardson number, the growth of upstream secondary eddy (USE) is observed together with a degradation of downstream secondary eddy (DSE). When mixed convection is dominant, the upstream secondary eddy and the downstream secondary eddy merge to form a large recirculation region. When the effect of Pr is studied in the forced convection regime, Ri<<1, the temperature in the central region of the cavity remains nearly a constant. However, in the mixed convection regime, the temperature in cavity undergoes non-monotonic changes. Finally, using the method of divided differences, it is shown that numerical accuracy of the derived numerical scheme used in this work is four.
Evaluation of three PCR-based diagnostic assays for detecting mixed Plasmodium infection
Tonya Mixson-Hayden, Naomi W Lucchi, Venkatachalam Udhayakumar
BMC Research Notes , 2010, DOI: 10.1186/1756-0500-3-88
Abstract: Here we evaluated three PCR assays (nested, semi-nested multiplex, and one-tube multiplex) for the simultaneous detection of human malaria parasites using experimentally mixed cocktails of known quantities of laboratory derived DNA. All three assays detected individual species with high sensitivity and specificity when DNA was from any one single species; however, experimentally mixed DNA cocktails with all four species present were correctly identified most consistently with the nested method. The other two methods failed to consistently identify all four species correctly, especially at lower concentrations of DNA -subclinical levels of malaria (DNA equivalent to or less than 10 parasites per microliter).The nested PCR method remains the method of choice for the detection of mixed malaria infections and especially of sub-clinical infections. Further optimization and/or new molecular gene targets may improve the success rate of detecting multiple parasite species simultaneously using traditional PCR assays.Approximately 2 billion people are exposed to malaria with an estimated 250 million clinical cases and about 800,000 deaths annually [1,2]. Four Plasmodium species are known to cause malaria in humans: P. falciparum, P. vivax, P. malariae and P. ovale. Many malaria endemic regions report mixed infections of these species and the prevalence of mixed infections varies depending on the geographic region. For example, within India, Hamer et al. [3] reported 9.3% of malaria cases as mixed P. falciparum/P. vivax infection and Rasheed et al. [4] reported 18% of cases were P. falciparum/P. vivax mixed infection. The clinical presentation of malaria is often nonspecific; consequently many febrile illnesses with unknown etiology are attributed to malaria (resulting in presumptive diagnosis and treatment). Therefore, appropriate laboratory tools are critical for the prompt diagnosis and treatment of malaria. This is especially true for mixed infections which are often not r
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