Contact size-dependent switching instabilities in HfO2 RRAM

Journal of Materials Science: Materials in Electronics - A comprehensive understanding of the resistive switching mechanisms that activate REDOX-based random access memory devices is necessary to...     

Influence of thermal insulation and wind velocity on the SMA actuator for morphing applications

This paper presents the modeling and simulation of shape memory alloy (SMA) wire actuators for morphing micro air vehicles (MAVs) when exposed to high-velocity wind during flight. The specific operating conditions include thermal insulation, varying convective heat-transfer coefficients due to wind velocity, aerodynamic loads, and operation from MAV battery. Application-oriented modeling parameters were determined from a flyable morphing MAV. The simulation could dynamically generate the morphing angle as a function of the electrical input pulse duty cycle. The model showed that compared with 10 % duty cycle, a 25 % duty cycle achieves an energy saving of 33 % and an increase in actuation speed of 3.7 times. Further, increasing the duty cycle has a negligible improvement in energy saving, but the actuation rate is increased by 15.8 times. The SIMULINK® model, which was validated through the ground test, would help in the design of SMA actuators and controllers for aerospace vehicles and automobiles.

     

Purification,characterisation and kinetics of a trypsin inhibitor from black gram (Vigna mungo)

A black gram (Vigna mungo) trypsin inhibitor (BGTI) was purified to homogeneity by ammonium sulphate precipitation, DEAE-cellulose chromatography and affinity chromatography. The homogeneity of the inhibitor was identified by polyacrylamide gel electrophoresis (PAGE), SDS–PAGE, immunodiffusion and immunoelectrophoresis. The isoelectric point of BGTI was 8.32. The molecular weight of the BGTI was found to be about 12500 by both gel filtration and SDS–PAGE. One mole of the BGTI was found to contain 75 amino acid residues, and it was identified as a glycoprotein, comprising about 18.2% carbohydrate. The BGTI was an uncompetitive inhibitor, stable in the pH range 2–10 and in the temperature range 30–80°C for 30 min.     

Octadecyl grafted MCM-41 silica spheres using trifunctionalsilane precursors – preparation and characterization

MCM-41 silica spheres were prepared via the pseudomorphic route. Subsequent surface modification of the mesoporous silica spheres was achieved by two silylating agents, n-octadecyltrihydridosilane and n-octadecyltrimethoxysilane, which provided different surface coverages. The MCM-41 pore structure, surface properties and morphological features were examined by small angle X-ray scattering, nitrogen adsorption–desorption and scanning electron microscopy. The investigations revealed an influence of the silica source on the mesoporous structure, as reflected by a higher long-range order for the pores in MCM-41 spheres prepared from Kromasil silica. Surface modification is accompanied by a reduction of the surface area, pore diameter and pore volume of the MCM-41 materials, whereas the spherical morphology of the spheres is retained. The degree of grafting and cross-linking of the alkylsilanes was determined by ²⁹Si NMR spectroscopy. A higher degree of alkyl chain grafting was observed for the solvent extracted MCM-41 spheres and for samples prepared via surface polymerization.FTIR and ¹³C NMR spectroscopies were employed to study the conformational behaviour and mobility of the grafted octadecyl chains. The conformational order was found to strongly depend on the history of the MCM-41 supports (calcination, solvent extraction) and on the actual surface modification procedure. In general, a lower conformational order was observed for the present mesoporous alkyl modified silica spheres as compared to conventional C₁₈ modified silica gels which is mainly attributed to the lower surface coverage.     

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite based thin films for Schottky diode application

Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV–Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq⁻¹ and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes.     

Studies on black gram (Vigna mungo) trypsin inhibitor

The trypsin inhibitor fraction from black gram was isolated by ammonium sulphate fractionation (0-75%). It exerted maximum inhibition on trypsin and to a less extent on the endopeptidases, chymotrypsin, papain, pronase and pepsin in vitro, In-vitro digestibility of the raw black gram was found to be lower than autoclaved black gram and autoclaved black gram supplemented with native black gram trypsin inhibitor. Haemagglutinating activity was absent in the black gram extract as well as in the black gram trypsin inhibitor fractions. During the last 48 h of germination there was a steep decline in trypsin inhibitory activity and an increase was observed later. Trypsin inhibitory activity was greater in the leaves than the cotyledons during the fourth, fifth and sixth days of germination.     

Medical data transmission using the product of TLDPC and BCH error control coding systems with two interleavers

Medical data are very precious since it has the most sensitive data of patient which can save them. If it is handled wrongly or it is manipulated, then it could result in permanent problems or even it can result in fatal. So medical data widely used in a digital format with error detection and correction codes (EDC) in its transmission and storage process. EDC is a method of adding redundant bits to the static message bits to enhance the reliability of binary digital data broadcast while the medical data communication medium adds the errors in the course of transmission. In the proposed method, we use Bose–Chaudhuri–Hocquenghem codes (BCH) as an outline algorithm and trellis Low‐Density Parity Check code (TLDPC) as an inner algorithm along with two interleavers. Product of BCH code and TLDPC code with interleavers can control more errors as compared with its plain code and product of RS‐Hamming code. MATLAB used as a simulation tool. Plain BCH code is simulated first, and then plain LDPC code is simulated for the same information. Finally, the product of BCH and TLDPC with two interleavers is imposed on the same information. The result of our research work shows enhancement in bit error rate (BER) compared to other plain and product codes from 10^?2 to 10^?3. Also, frame error rate (FER) is improved in 0.5 scaling factors when compared with other trellis decoders. Hence, this proposed system can be utilized in an application where less error rate and high accuracy of information transmission between medical data processing systems are required.