Evidence for compliance controlled oxygen vacancy and metal filament based resistive switching mechanisms in RRAM

We present electrical evidence on asymmetric metal-insulator-semiconductor (MIS) based test structures in support of the presence of two different independent switching mechanisms in a resistive random access memory (RRAM) device. The valid mechanism for switching depends on the compliance capping (I_gl) for forming/SET transition. Our results convincingly show that low compliance based switching only involves reversible oxygen ion drift to and from oxygen gettering gate electrodes, while high compliance switching involves formation and rupture of conductive metallic nanofilaments, as verified further by our physical analysis investigations. We have observed this unique dual mode switching mechanism only in NiSi-based gate electrodes, which have a moderate oxygen solubility as well as relatively low melting point.     

Interfacial Strain Gradients Control Nanoscale Domain Morphology in Epitaxial BiFeO3 Multiferroic Films

Domain switching pathways fundamentally control performance in ferroelectric thin film devices. In epitaxial bismuth ferrite (BiFeO₃) films, the domain morphology is known to influence the multiferroic orders. While both striped and mosaic domains have been observed, the origins of the latter have remained unclear. Here, it is shown that domain morphology is defined by the strain profile across the film–substrate interface. In samples with mosaic domains, X‐ray diffraction analysis reveals strong strain gradients, while geometric phase analysis using scanning transmission electron microscopy finds that within 5 nm of the film–substrate interface, the out‐of‐plane strain shows an anomalous dip while the in‐plane strain is constant. Conversely, if uniform strain is maintained across the interface with zero strain gradient, striped domains are formed. Critically, an ex situ thermal treatment, which eliminates the interfacial strain gradient, converts the domains from mosaic to striped. The antiferromagnetic state of the BiFeO₃ is also influenced by the domain structure, whereby the mosaic domains disrupt the long‐range spin cycloid. This work demonstrates that atomic scale tuning of interfacial strain gradients is a powerful route to manipulate the global multiferroic orders in epitaxial films.     

Design of high-speed data transfer turbo code for body channel communication transceivers

In this work, a digital differential transmitter based on low-power wireless compensation transceiver for body channel communication (BCC) is proposed. Further, the proposed transceiver is composed of Touch Status Detection Unit (TSDU), Wireless Status Compensation Unit (WSCU), and a reconfigurable preamplifier. Initially, the human body channel environment for wireless communication is investigated based on properties from 1 to 100 MHz. Further, the turbo code-based encoding scheme is used to encode the data before transferring the data on the transmitter side. Also, the proposed error-correcting parallel turbo decoder using a modified step-by-step algorithm is presented. The turbo code-based decoding scheme is used to recover the error-free transmitted data at the receiver side. Results demonstrate that the proposed BCC transceiver is designed using 90 nm CMOS technology and it is observed that the proposed BCC transceiver has utilized an area of 600mm². Also, the maximum data rate achieved by a proposed BCC transceiver was 100 Mbps, and the overall transceiver power consumption is 0.42 mW, and energy for communication is 0.02 nj/b.     

Network Lifetime Enhancement of Wireless Sensor Networks Using EFRP Protocol

This paper presents a novel transceiver architecture for in-band full duplex radio. A transceiver for full duplex radio requires a self-interference (SI) canceler to remove the SI occurring from the transmitter to the receiver, and a full duplex transceiver generally has two SI cancelers: one at the analog RF stage and the other at the baseband stage. The output from the SI canceler at the RF stage includes much residual SI, and it decreases the number of bits allocated to the analog baseband signal at the analog-to-digital converter. A 1-tap analog baseband SI canceler that uses a replica signal including only the direct path component of the residual SI has been presented for preventing degradation. However, the architecture cannot remove the SI well due to the high Ricial K-factor. To address the problem, the presented architecture has an SI canceler at the analog baseband stage, and this canceler employs a replica signal that is output from a digital-to-analog converter. Because the replica signal is generated in the digital domain, the architecture can generate a multipath replica signal, and improved performance can be expected. Numerical and theoretical analyses are shown to validate the effectiveness of the presented architecture.

     

Corrosion of Fe-10Al-Cr alloys by coal char

Corrosion of iron-base alloys at 982°C (1800°F) by coal char is observed and the phase morphologies are discussed. No sulfidation was observed at 50 hr exposure. After 100 hr internal aluminum-rich sulfides were observed along with thick outer scales of iron oxide. The species causing the hightemperature-induced corrosion are probably sulfides and sulfates, present in most coal chars. Possible mechanisms for the corrosion are also discussed.Department of Materials Science and Mineral Engineering.     

Protective Immunity against Listeria monocytogenes in Rats,Provided by HCl- and NaOH-Induced Listeria monocytogenes Bacterial Ghosts (LMGs) as Vaccine Candidates

Listeria monocytogenes (Lm) bacterial ghosts (LMGs) were produced by the minimum inhibitory concentration (MIC) of HCl, H₂SO₄, and NaOH. Acid and alkali effects on the LMGs were compared by in vitro and in vivo analyses. Scanning electron microscope showed that all chemicals form lysis pores on the Lm cell envelopes. Real-time qPCR revealed a complete absence of genomic DNA in HCl- and H₂SO₄-induced LMGs but not in NaOH-induced LMGs. HCl-, H₂SO₄- and NaOH-induced LMGs showed weaker or missing protein bands on SDS-PAGE gel when compared to wild-type Lm. Murine macrophages exposed to the HCl-induced LMGs showed higher cell viability than those exposed to NaOH-induced LMGs or wild-type Lm. The maximum level of cytokine expression (TNF-α, iNOS, IFN-γ, and IL-10 mRNA) was observed in the macrophages exposed to NaOH-induced LMGs, while that of IL-1β mRNA was observed in the macrophages exposed to HCl-induced LMGs. To investigate LMGs as a vaccine candidate, mice were divided into PBS buffer-injected, HCl- and NaOH-induced LMGs immunized groups. Mice vaccinated with HCl- and NOH-induced LMGs, respectively, significantly increased in specific IgG antibodies, bactericidal activities of serum, and CD4⁺ and CD8⁺ T-cell population. Antigenic Lm proteins reacted with antisera against HCl- and NOH-induced LMGs, respectively. Bacterial loads in HCl- and NaOH-induced LMGs immunized mice were significantly lower than PBS-injected mice after virulent Lm challenges. It suggested that vaccination with LMGs induces both humoral and cell-mediated immune responses and protects against virulent challenges.     

Effect of ultrasound on bubble breakup within the mixing chamber of an effervescent atomizer

Gas bubbles introduced into a liquid in the mixing chamber help to break up the liquid into fine droplets on being expanded to the ambient pressure. The passage of gas bubbles through the orifice of the nozzle requires that the size of the bubbles be much smaller than the diameter of the orifice. In the present work, the effectiveness of 20 kHz ultrasound to increase number density of fine bubbles within the mixing chamber of an effervescent atomizer by breaking up bubbles introduced in it by an aerator was investigated. Bubbles of initial size in the range of 5-10 mm were shown to get disintegrated into clusters of micron and sub-micron sized bubbles. A fine spray was produced in the presence of ultrasound at a gas-to-liquid mass flowrate ratio (GLR) of 0.063%. The half-cone angle of spray was in the range of 6-10°, which compares favorably with conventional atomizers. The experimental findings of bubble breakup were theoretically modeled by the Rayleigh-Plesset equation. The results of the model indicate that bubbles having initial radius less than 3 mm undergo growth and subsequent disintegration at 20 kHz for the given acoustic pressure of 0.3 MPa.     

Anodic dissolution of U, Zr and U–Zr alloy and convolution voltammetry of Zr|Zr couple in molten LiCl–KCl eutectic

The anodic dissolution of U and Zr metal was studied in LiCl–KCl–UCl₃ and LiCl–KCl–ZrCl₄, respectively, at 773 K by cyclic voltammetry and compared with their respective dissolution behaviour in blank LiCl–KCl eutectic. The anodic dissolution of U–Zr alloy in LiCl–KCl–UCl₃ was also studied at 773 K to compare with the dissolution of U and Zr. The transfer coefficients evaluated by Tafel analysis and the method of Allen–Hickling for U and Zr dissolution were found to be in fair agreement with each other. U dissolution in LiCl–KCl–UCl₃ and Zr dissolution LiCl–KCl–ZrCl₄ were also studied by chronoamperometry and the diffusion coefficient value of U³⁺ was calculated to be in the range of 2.9 × 10⁻⁵ to 3.3 × 10⁻⁵ cm² s⁻¹ which is in agreement with those reported in literature. Convolution voltammetric analysis of Zr⁴⁺/Zr²⁺ redox couple in LiCl–KCl–ZrCl₄ was carried out for the first time to have a comprehensive understanding of the electrode kinetics.     

MgNb2O6:Dy3+ nanophosphor: A facile preparation,down conversion photoluminescence and UV driven photocatalytic properties

Series of (1–9 mol %) dysprosium (Dy³⁺) ions doped MgNb₂O₆ (MNO) nanophosphors were synthesized by chemical combustion process and their photo luminescent and photocatalytic behaviours were examined. Powder X-ray diffraction (PXRD) reveals the columbite structure and crystal structure parameters were calculated. The average crystallite size was found to be in the range of 20–30 nm as calculated by Scherrer's method. The photoluminescence (PL) of MgNb₂O₆:Dy³⁺ (λ_exc-393 nm) reflects white emission for the prepared samples as confirmed by CIE and CCT. The photocatalytic activities of these nanophosphors were probed for the decolorization of acid red 88 (AR-88) under UV light irradiation. The photocatalyst with MgNb₂O₆:Dy³⁺ (5 mol %) showed enhanced activity of 97%, attributed to effective separation of charge carriers. All the above experimental results confirm that, the optimized phosphor is quite useful for WLEDs, solid-state lighting applications and as a photocatalyst.