Structural, electrochromic and FT-IR studies on electrodeposited tungsten trioxide films

R.Vijayalakshmi,M.Jayachandran,C.Sanjeeviraja 한국물리학회 2003 Current Applied Physics Vol.3 No.2, 3

Tungsten trioxide (WO3conductor and hence it has recently attracted much interest in the field of solid state ionics. When the intercalation of the film is taken in the cyclic voltammograms for various concentrations (0.1, 0.5 and 1.0 N) of H2SO4, the voltage is recorded for the peakcurrent. The powder X-ray diraction pattern is taken and the peaks are compared with the JCPDS values. It is found to be thetriclinic structure. The FT-IR spectra are taken for the WO3 lms electrodeposited at dierent deposition current densities (0.25,0.50, 0.65 and 0.75 mA/cm2temperature of the bath constant. The lm exhibits a broad peak from 3780 to 3500 cm. 1 which indicated the OHH stretchingvibration. The peak at 3543 cm. 1 depends upon the coloration increase in the electrodeposited tungsten trioxide lm. A littleamount of molecular water may exist in the electrodeposited WO3 lm, which corresponds to a broad peak at 2500 cm. 1. A smallpeak at 820 cm. 1 exhibits WO stretching. After ion intercalation the peak positions are slightly changed.

Hybrid Key Management Scheme for Wireless Sensor Networks

R.Sharmila,V.Vijayalakshmi 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.11

Many key management schemes have been proposed in systematically deployed Wireless Sensor Networks (WSNs).The sensor nodes are equipped with inadequate battery power, low memory, limited computation and communication range. Energy efficient secure routing is major issue in wireless sensor networks. In this paper, the hybrid key management scheme is proposed by combining public key cryptography scheme with symmetric scheme. The symmetric keys are generated by using genetic algorithm. Initial input for the genetic algorithm is the seed key generated by Hyperelliptic Curve Cryptography (HECC).The proposed scheme addresses the energy efficiency, resilience against node capture attack, key refreshment between the cluster head and member nodes in the cluster. The simulation results show that the hybrid scheme is more robustness, efficient energy with reduced key size.

Analysis of Multimodal Biometric Fusion Based Authentication Techniques for Network Security

R.Divya,V.Vijayalakshmi 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.4

Multibiometrics is the usage of more than one physiological or behavioral characteristic to identify an individual. Multibiometrics is advantageous over unibiometrics as it is resilience to spoofing and has low False Acceptance Rate (FAR). However Multibiometrics requires storage of multiple biometric templates for each user, which results in increased risk to user privacy and system security. This paper will discuss the concept off biometrics and biometric system, multimodal biometric fusion techniques, crypto-biometrics and an algorithm for session key generation for secure communication of data.

A Novel Double Frequency SEPIC Converter with Improved Transient Characteristics and Efficiency

Vijayalakshmi S.,Marimuthu M.,Jayakumar N.,Vighneshwari B. Devi,Paranthagan B.,Rani Nisha C.,Shenbagalakshmi R. 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

A novel double frequency SEPIC converter is discussed in this paper. Effi ciency, static and dynamic characteristics of the dc to dc power converters are the concerned factors in power electronics. In order to improve the above factors, switching frequency play a vital role in converters. Hence, include High switching frequency in the converter can improve the dynamic characteristics, but it reduces the effi ciency. In other words, put in low switching frequency in the converter may result in better effi ciency but produces poor dynamic characteristic. In this concern double-frequency SEPIC converter is proposed. This SEPIC dc-dc converter consists of two SEPIC cells: one functions at high switching frequency, and other functions at low switching frequency. The proposed SEPIC converter reveals enhanced steady state and transient characteristic than the other single frequency SEPIC converter and produces high effi ciency also. The results of simulation and hardware prove that the anticipated converter extremely progresses the effi ciency and displays more or less equal the same dynamics as the traditional high frequency SEPIC converter.

Investigations on Z-Source Based Cascaded Five Level Inverter

K. Vijayalakshmi,C. R. Balamurugan 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.12

The Z source inverter is a novel power conversion topology that can buck and boost the given input voltage. Voltage source inverter (VSI) and current source inverter (CSI) have some common problems. The proposed work eliminates the limitations of both voltage source inverter and current source inverter by replacing multilevel inverter. This paper presents the new inverter topology based on combination of Z Source Inverter (ZSI) and Multi Level Inverter (MLI). The Z source inverter employs a unique impedance network to couple the main circuit to the power source. The basic structure includes one DC voltage source, Z network and multilevel inverter. Thus providing unique features that cannot be provided in both traditional voltage source and current source inverter. The cascaded MLI composed of eight switches to generating five voltage levels. The presence of multilevel inverters provide high output voltages with low harmonics without the use of transformers. The Z source concept can be applied to ac-dc, dc-ac, ac-ac and dc-dc power conversions. This work observes the rms (Root Mean Square) output voltage and presence of THD (Total Harmonic Distortion) in the output waveform by simulating the Z source based multilevel inverter using MATLAB/simulink.

A Novel Non-isolated Single Switch Multilevel Cascaded DC–DC Boost Converter for Multilevel Inverter Application

M. Marimuthu,S. Vijayalakshmi,R. Shenbagalakshmi 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.5

This paper presents a high gain non isolated Multilevel Cascaded Boost Converter (MCBC) for Electric vehicle applications. The proposed converter associates the basic cascaded Boost converter along with multilevel boost converter for boosting the voltages generated from diff erent sources like solar energy, fuel cell and Battery. The multilevel boost converter is intended to be utilized as a dc link in which the high gain boosted voltage is provided to the multilevel inverter. By expending a single driven semiconductor switch and an inductor, the proposed converter is capable of producing high voltage gain with continuous input current and much higher step up conversion ratio. It not only allow to operate at much higher frequencies but aids in operating with a minimum duty cycle without a transformer. The proposed converter with fi ve cascaded levels are simulated and is verifi ed experimentally. The results thus illustrated go in concurrence with each other.

Dazzling red emission from TiO2 nanoparticles impregnated co-doped Gd3++Eu3+: PVA polymer nanocomposites for photonic applications

K. Naveen Kumar,R. Padma,L. Vijayalakshmi,강미숙 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

Red emission was obtained from rare earth doped polymer nanocomposites, namely, composites ofpolyvinyl-alcohol (PVA) co-doped with Gd3+ and Eu3+ and embedded with TiO2 nanoparticles (TiO2NP),under ultraviolet (UV) excitation. We successfully synthesized Eu3+: PVA, Gd3+: PVA, (Gd3+ + Eu3+): PVA,and (Gd3+ + Eu3+ + TiO2NP): PVAfilms by solution casting method. From X-ray diffraction patterns andFourier-transform infrared spectral profiles, the structural details of thefilms and the ion–polymerinteraction mechanism responsible for their formation were systematically analyzed. The thermalstability and decomposition dynamics of the prepared samples were evaluated by thermogravimetry anddifferential thermal analysis. Pertinent optical absorption bands related to Eu3+ and Gd3+ ions in thepolymer composites were observed and assigned to the corresponding electronic transitions. The PVAfilm containing different concentrations of the Eu3+ dopant displayed red emission at 618 nm (5D0!7F2)under UV excitation at 396 nm (7F0!5L6). Upon co-doping with Gd3+ to form the (Gd3+ + Eu3+): PVAfilm,it exhibited red emission that was stronger than that from the singly doped Eu3+: PVAfilm under 270 nmexcitation because of the energy transfer from Gd3+ to Eu3+ ions. After the TiO2 nanoparticles were evenlydispersed in the co-doped (Gd3+ + Eu3+): PVAfilms, the photoluminescence properties were remarkablyenhanced and prominent red emission was observed under 274 nm excitation. The red emission of Eu3+was significantly enhanced through an efficient energy-transfer process from the Gd3+ ions to Eu3+ ionsand from the TiO2 nanoparticles to Eu3+ ions. A possible energy-transfer mechanism was clearlydemonstrated by severalfluorescent methods and lifetime decay dynamics. Based on the above results,these polymer compositefilms are promising candidates for red luminescent photonic devices.

Investigations on the structural, optical and electronic properties of Nd doped ZnO thin films

Subramanian, M,Thakur, P,Gautam, S,Chae, K H,Tanemura, M,Hihara, T,Vijayalakshmi, S,Soga, T,Kim, S S,Asokan, K,Jayavel, R Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.10

<P>We report the synthesis and characterization of Nd doped ZnO thin films grown on Si (1 0 0) substrates by the spray pyrolysis method. The surface morphology of these thin films was investigated by scanning electron microscopy and shows the presence of randomly distributed structures of nanorods. Grazing angle x-ray diffraction studies confirm that the doped Nd ions occupied Zn sites and these samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The micro-photoluminescence measurement shows a decrease in the near band edge position with Nd doping in the ZnO matrix due to the impurity levels. The near-edge x-ray absorption fine structure (NEXAFS) measurements at the O K edge clearly exhibit a pre-edge spectral feature which evolves with Nd doping, suggesting incorporation of more charge carriers in the ZnO system and the presence of strong hybridization between O 2p–Nd 5d orbitals. The Nd M<SUB>5</SUB> edge NEXAFS spectra reveal that the Nd ions are in the trivalent state.</P>