Cycling reliability of RF-MEMS switches with Gold–Platinum multilayers as contact material

Microsystem Technologies - Contact resistance is the main parameter used for assessing the high cycling reliability of RF microelectromechanical (RF-MEMS) switches. In this paper the use of a...     

Polylactide latex/nanofibrillated cellulose bionanocomposites of high nanofibrillated cellulose content and nanopaper network structure prepared by a papermaking route

Previous attempts to use polylactide (PLA) latex particles and nanofibrillated cellulose (NFC) in papermaking processing have been limited to low NFC content. In the present study, a bionanocomposite material was successfully produced using a PLA latex and NFC. The components were mixed using a wet mixing method and bionanocomposite films were made by filtration followed by hot pressing. In composite materials, the dispersion of the reinforcing component in the matrix is critical for the material properties. Biopolymers such as PLA are non-polar and soluble only in organic solvents; NFC is, however, highly hydrophilic. By utilizing latex, i.e., an aqueous dispersion of biopolymer micro-particles, wet mixing is possible and the problem of aggregation of the hydrophilic nanocellulose in organic solvent is avoided. The properties of the resulting NFC/PLA latex bionanocomposite films were analyzed. Thorough blending resulted in good dispersion of the reinforcing component within the matrix. Adding increasing amounts of NFC improved the Young's modulus, tensile strength, and strain at break of the bionanocomposite material. The increase in the tensile properties was linear with increasing NFC content as a result of the good dispersion. The NFC also improved the thermal stability of the bionanocomposite material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Controlled-NOT gate sequences for mixed spin qubit architectures in a noisy environment

Explicit controlled-NOT gate sequences between two qubits of different types are presented in view of applications for large-scale quantum computation. Here, the building blocks for such composite systems are qubits based on the electrostatically confined electronic spin in semiconductor quantum dots. For each system the effective Hamiltonian models expressed by only exchange interactions between pair of electrons are exploited in two different geometrical configurations. A numerical genetic algorithm that takes into account the realistic physical parameters involved is adopted. Gate operations are addressed by modulating the tunneling barriers and the energy offsets between different couple of quantum dots. Gate infidelities are calculated considering limitations due to unideal control of gate sequence pulses, hyperfine interaction and charge noise.     

Effects of hydrogen addition on the high temperature deformation behavior of TC21 titanium alloy

The true stress-strain curves of TC21 titanium alloy charged with up to 0.7 wt.% hydrogen were obtained by the isothermal hot compression tests which were carried out on an Instron 5500 machine at 1023 to 1223 K and 0.001 to 0.1 s⁻¹. The dependence of the steady state flow stress on hydrogen content was determined. The results showed that with the increase of hydrogen content flow stress decreased at lower hydrogen content and then increased at higher hydrogen content. Suitable hydrogen addition can significantly decrease the flow stress and improve the hot workability of TC21 titanium alloy. The flow stress behaviors and the dependence of hydrogen content on flow stress were clarified by microstructural observation. The optimum hydrogen content at different deformation temperature was determined.     

Recent developments in membrane-based technologies for CO2 capture

Developing new methods and technologies that compete with conventional industrial processes for CO₂ capture and recovery is a hot topic in the current research. Conventional processes do not fit with the current approach of process intensification but take advantage due to their maturity and large-scale implementation. Acting in a precombusion scenario or post-combustion scenario involves the separation of CO₂/H₂ or CO₂/N₂, respectively.     

Inverse modelling of an aneurysm’s stiffness using surrogate-based optimization and fluid-structure interaction simulations

Characterization of the mechanical properties of arterial tissues is highly relevant. In this work, we apply an inverse modelling approach to a model accounting for an aneurysm and the distal part of the circulation which can be modified using two independent stiffness parameters. For given values of these parameters, the position of the arterial wall as a function of time is calculated using a forward simulation which takes the fluid-structure interaction (FSI) into account. Using this forward simulation, the correct values of the stiffness parameters are obtained by minimizing a cost function, which is defined as the difference between the forward simulation and a measurement. The minimization is performed by means of surrogate-based optimization using a Kriging model combined with the expected improvement infill criterion. The results show that the stiffness parameters converge to the correct values, both for a zero-dimensional and for a three-dimensional model of the aneurysm.     

Improving the results of spectral unmixing of Landsat Thematic Mapper imagery by enhancing the orthogonality of end-members

Spectral unmixing is a technique that has been developed to derive fractions of spectrally pure materials that contribute to observed spectral reflectance characteristics of a mixture through a inverse least-squares deconvolution using end-member spectra. This technique has been shown to be very successful when applied to high spectral resolution imaging or non-imaging data where subtle diagnostic absorption features largely determine the spectral characteristics of the data. A large and vastly growing number of papers where spectral unmixing is applied to analyse low resolution image data (e.g. Landsat Thematic Mapper (TM), NOAA AVHRR, etc.) often to derive abundances of different materials as input parameters for models (i.e. land degradation models, crop growth models, hydrologic models, etc.) has evolved throughout recent years. This justifies efforts put into the quality assessment of these abundance estimates. In this paper we evaluate the effect of end-member redundancy on the deconvolution of spectral mixtures in unconstrained unmixing using simulated, one-dimensional spectral mixtures of three end-members that we unmix with two out of three of these components. Our analysis shows a relationship between the unmixing error and the difference between the true and estimated abundance with an index which combines (1) the weighted correlation of end-members in the mixture, (2) the correlation between the end-members used in unmixing this mixture, and (3) the amount of 'information' mapped in the end-members. Given this result we investigate the reduction of correlation in the spectral unmixing process and present an application of unmixing to decorrelated Landsat TM data using the minimum noise fraction transformation. The statistical evaluation of this experiment shows that over-and undershooting rather than the error in the unmixed spectrum can be significantly improved when decorrelating the data.