K. M. Begam

New Lithiated NASICON-Type Li2Ni2 ( MoO4 ) 3 for Rechargeable Lithium Batteries Synthesis, Structural, and Electrochemical Properties

We report on the first synthesis of a new NASICON framework Li 2 Ni 2 (MoO 4 ) 3 and on the investigation of its electrochemical behavior upon Li extraction coupled with structural analysis. Li 2 Ni 2 (MoO 4 ) 3 was synthesizedby a novel soft-combustion approach involving glycine as a combustion agent and the product was found to crystallize in an orthorhombic structure (space group Pmcn) with lattice parameters a = 10.424(4) A, b = 17.525(1) A, and c = 5.074(3) A. Reversible extraction and insertion of lithium from and into the framework structure delivered a reversible capacity of ∼115 mAh/g (4.9-1.5 V window) after the first charge/discharge cycle.

Synthesis of a Polyanion Cathode Material, Li2Co2 ( MoO4 ) 3 , and Its Electrochemical Properties for Lithium Batteries

High voltage redox properties of a polyanion material, Li2Co2(MoO4)(3), as positive electrode was demonstrated against lithium for the first time. The orthorhombic structure showed reversible extraction and insertion cycles of lithium at a potential of ca. 4.9 V vs. Li+/Li as well as 1.5 V. The former potential was attributed to Co2+/Co3+ and the latter to Mo6+/Mo5+. The reason for the change in charge/discharge curves after the first charge is clearly demonstrated by the structural changes (monoclinic, P2/m) caused by electrochemical extraction and insertion of lithium as deduced from the ex situ X-ray diffraction analysis on the cycled electrode pellet

Despeckling of ultrasound images of bone fracture using multiple filtering algorithms

Abstract Ultrasound images are popularly known to contain speckle noise that degrades the quality of the images for good and fast interpretation in many areas of medicine, especially for bone fracture detection. This necessitates the need for robust despeckling techniques for clinical practice. Therefore, a study was carried out to reduce speckle using filtering algorithms such as Wiener, Average, Median, Anisotropic Diffusion and Wavelets. This paper discusses the level of improvement obtained through these filtering algorithms using the peak signal-to-noise ratio (PSNR) as a measurement tool. The results of our work presented in this paper suggest that the combination of Daubechies–Wiener which we call as a hybrid technique with Anisotropic Diffusion, gave the best performance, which is a new contribution in this field. This despeckling algorithm can be further developed and evaluated at a larger scale.

The Role of Al2O3 Buffer Layer in the Growth of Aligned CNTs

Carbon nanotube (CNT) can be thought of as a hexagonal network of carbon atoms that has been rolled up to make a seamless cylinder. If they are consisting of one layer, they are termed singled-walled CNTs (SWNTs) while if there are multiple walls, they are called multi-walled CNTs (MWNTs). For most functional devices application, an aligned arrangement of CNTs is desired. Aligned multiwalled carbon nanotubes (MWNTs) have been successfully grown by the inclusion of a buffer layer of oxidized Al. An Al2O3 layer has been proven to be an important contributing factor towards obtaining good quality aligned CNTs. In this work, Al is deposited onto the Si wafer using electron beam evaporation and later oxidized by heating in air. A thin layer of iron catalyst is then deposited on top of the oxidized Al layer and annealed at 400oC. The result shows an improvement in the intensity of the graphitization peak (G-band) in the Raman spectra and aligned MWNTs is observed in these samples compared to the ones that have undergone the same process parameter except the Al2O3 layer.

Simulation of an inductive coupled high frequency resonant gate driver circuit

The implementation of an independent-duty-cycled high frequency resonant gate driver (RGD) circuit utilizing an inductive coupled linear transformer is proposed and simulated using PSpice circuit simulator. The totem-poled configuration of driving MOSFETs that makes the resonant LC network is used in the proposed RGD circuit. The free-wheeling diodes are used to recover full energy where most of the charged and discharged operating current flow in the resonant inductor is returned back to the input source during switching cycle transition. The work has been carried out using 1 MHz switching frequency with fixed input and load conditions. With each pair of driving MOSFETs providing D and 1-D of switching ratios, the turn-on and turn-off speed has been improved by 12% and 23 respectively while the total RGD losses reduced to 4%.

The Analysis of Parameter Limitation in Diode-Clamped Resonant Gate Drive Circuit

 Abstract—Switching loss has to be reduced in order to improve converters performance and efficiency. In high switching frequency, the effect of the loss is much greater. The duty ratio, dead time and inductor value are the limiting parameters which bring implications on the switching loss and hence total gate drive loss. Using PSpice circuit simulator, the optimization of these parameters have been carried out and it is found that the duty ratio, dead time and resonant inductor value are 20 %, 15 ns and 9 nH respectively. The details for choosing these values are presented in this paper.

Performance analysis of Fixed Duty Ratio and Adaptive Gate Drive in high frequency gate driver design

The performance analysis of the Fixed Duty Ratio (FDR) and Adaptive Gate Drive (AGD) in high frequency gate driver design is analyzed in this paper. FDR is well known for its simplicity. The limitation of this control scheme requires a longer delay time before the next switching can be executed. As for AGD, the delay adjustment can be controlled for different MOSFET. However, it is hard to detect whether the MOSFET channel is fully turned off before the adaptive delay can be applied. Simulation using the Pspice circuit simulator is carried out to analyze the performances of both control methods on the proposed synchronous buck rectifier converter (SRBC) circuit. The findings show the analysis in converter performance, advantages and limitations of the methods. It is found that even though AGD is known to be better in reducing dead time, using accurate settings of FDR scheme may also introduce significant positive advantage to the converter.

Load effects analysis of Synchronous Rectifier Buck Converter using fixed PWM Technique

The analysis of loading effects on Synchronous Rectifier Buck Converter (SRBC) performance using fixed Pulse Width Modulation (PWM) technique is presented in this paper. The main objective of this paper is to analyze the effects of load variations on switching loss, conduction loss and body-diode conduction loss in SRBC circuit. There are three load conditions: critical load, light load and heavy load where PWM is commonly preferred from mid to heavy loads. The simulation analysis is carried out to determine the optimized load value for the best performance of the converter. It is found that towards heavy loads the switching loss decreases thus eventually improves the switching power loss savings.

Design and Simulation of an Improved Soft-Switched Synchronous Buck Converter

This paper proposes an improved soft switched synchronous buck converter in a fixed load condition. The switching energy can be fully recovered during current commutation phase in the gate driver while the diode conduction losses in the low and high side switches can be substantially reduced by employing additional L and C resonant in the circuit. Using PSpice simulation, the optimization technique has been studied. From the predetermined pulse width of the generated signals, the optimized resonant inductor current is observed to generate less oscillation and hence lower the switching loss. In addition, an optimized dead time interval is inserted between high side and low side of the transistors in the synchronous buck converter to minimize their body diode conduction losses. The detailed operations of both circuits are analyzed.

NASICON Open Framework Structured Transition Metal Oxides for Lithium Batteries

Since the dawn of civilization, world has become increasingly addicted to electricity due to its utmost necessity for human life. The demand for electrically operated devices led to a variety of different energy storage systems which are chosen depending on the field of application. Among the available stationary power sources, rechargeable lithium-ion batteries substantially impact the areas of energy storage, energy efficiency and advanced vehicles. These batteries are the most advanced and true portable power sources combined with advantages of small size, reduced weight, longer operating time and easy operation. Such batteries can be recharged anytime (no memory effect) regardless of the charge current/voltage and they are reliable and safe. These unique features render their application in a variety of consumer electronic gadgets such as mobile phones, digital cameras, personal digital assistants (PDAs), portable CD players and palmtop computers. The high-end applications of this smart power source are projected for Hybrid Electric Vehicles (HEVs) as potential source of propulsion. The evolution of rechargeable lithium batteries since their inception by Sony Corporation (Reimers & Dahn, 1992) has led to the development of new electrode materials (Kobayashi et al., 2000; Gaubicher, et al., 2000; Zhang et al., 2009; Zhu et al., 2008) for their effective operation in the real ICT environment. Among the new materials search for Li-ion batteries, polyanion compounds are growing into incredible dimensions owing to their intriguing properties (Manthiram & Goodenough, 1989; Huang et al., 2001; Yang et al., 2002; Chung et al., 2002). In this chapter, we present a systematic study of a group of new polyanion materials, namely, lithium-rich [Li2M2(MoO4)3] and lithium-free [LixM2(MoO4)3] (M= Ni, Co) phases of transition metal oxides having NASICON open framework structure. A simple and efficient approach to prepare the materials and a combination of characterization techniques to reveal the physical and electrochemical properties of these materials are covered at length. A separate section is devoted to a nano-composite approach wherein conductivity enhancement of all the four materials is enlightened. We begin this chapter with a brief 5