The Effect of Nickel Electroplating on Corrosion Behavior of Metal Matrix Composites

Nickel electroplating was applied to A356.2 aluminum alloy and its composites for improving its corrosion resistance. The corrosion resistance of the A356.2 and composites reinforced with rice husk ash particulates was evaluated by potentio-dynamic polarization tests in aerated 3.5% NaCl solution. Composites were fabricated by using the liquid state processing technique. Scanning electron microscopy, energy dispersive spectroscopy, techniques were used for surface analysis of the coatings before the corrosion tests and optical microscope was used to study the surface morphology of the uncoated and coated specimens after polarization tests. Results demonstrated that the nickel coated specimens exhibited higher corrosion resistance than the uncoated specimens. However, it was noticed that there was no significant change in the corrosion resistance for the nickel plated composites.     

Visible Light Communications (VLC) for Ambient Assisted Living

With the advent of high efficacy light emitting diode directional lamps as a key component in focal lighting, new possibilities emerge for re-designing the smart home scenario. A smart home scenario is characterized by enabled intelligent interworking of various wireless and wired technologies to provide inhabitants with ease of use of appliances, while creating a personalized and safe ambience space. More and more high and low data rate circulates within the indoor ambient space (e.g., home, hospitals, offices). Although, unlicensed technologies, such as wireless local area networks can take upon part of the indoor traffic, the ever increasing demand for such data, and users, calls for either use of licensed or novel unlicensed wireless communication technologies as part of the smart home enablers. This paper focuses on the potentials of visible light communications (VLCs), jointly with radio and fiber communications, to support very dense low and high data rate connectivity, while enabling deployment of secure-sensitive indoor applications, including indoor tracking and localization. The paper proposes a scenario for integrating VLC into the smart home scenario and a conceptual supporting architecture for its deployment. Further, the technical challenges and possible roadmap for the actual deployment are analyzed for the particular case of an eHealth scenario where the utilization of VLC technology is the enabler of the cost-efficient rollout of the required infrastructure and thus the game-changer in a multi-billion eHealth niche that is seeking for cost affordable solutions.     

An ultra-low power high-performance CMOS temperature sensor with an inaccuracy of − 0.3 °C/ + 0.1 °C for aerospace applications

Microsystem Technologies - In the current paper, a new temperature sensor with improved temperature inaccuracy and with very low power consumption has been designed for avionic industry. The...     

Detecting localized homogeneous anomalies over spatio-temporal data

The last decade has witnessed an unprecedented growth in availability of data having spatio-temporal characteristics. Given the scale and richness of such data, finding spatio-temporal patterns that demonstrate significantly different behavior from their neighbors could be of interest for various application scenarios such as—weather modeling, analyzing spread of disease outbreaks, monitoring traffic congestions, and so on. In this paper, we propose an automated approach of exploring and discovering such anomalous patterns irrespective of the underlying domain from which the data is recovered. Our approach differs significantly from traditional methods of spatial outlier detection, and employs two phases—(i) discovering homogeneous regions, and (ii) evaluating these regions as anomalies based on their statistical difference from a generalized neighborhood. We evaluate the quality of our approach and distinguish it from existing techniques via an extensive experimental evaluation.     

Efficient Host-Guest Complexation of a Bisporphyrin Host with Electron Deficient Guests: Synthesis,Structure, and Photoinduced Electron Transfer

The encapsulation of 1,8-naphthalic anhydride (NAN), 9-dicyanomethylenefluorene (9-DCF), acenaphthenequinone (ANQ), and 4-chloro-7-nitrobenzofurazan (NBD-Cl) by diethylpyrrole-bridged bisporphyrin (H₄DEP) and its dizinc(II) analogue (Zn₂DEP) are employed to investigate the structural and spectroscopic changes within the bisporphyrin cavity upon substrate binding. Synthesis and X-ray structures of all four encapsulated host-guest complexes (H₄DEP⋅NAN, H₄DEP⋅9-DCF, Zn₂DEP⋅ANQ, and Zn₂DEP⋅NBD-Cl) are reported here. The binding constant calculations show strong 1 : 1 binding between the hosts (H₄DEP and Zn₂DEP) and the guests (NAN/9-DCF/ANQ/NBD-Cl). ¹H-NMR spectra also support the retention of the host-guest assemblies in solution. Negative and positive shifts of the reduction and oxidation potentials, respectively, indicate that it is difficult to reduce/oxidize the encapsulated complexes. The emission intensities of the bisporphyrins (H₄DEP and Zn₂DEP) are substantially quenched in all the complexes, owing to photoinduced electron transfer from the excited state of the bisporphyrins to guest molecules. All the experimental evidence is further substantiated by DFT calculations. Such an efficient electron transfer is only possible when the donor and the acceptor moieties are in close propinquity to each other, which eventually lowers the reorganization energy.     

High-pressure release and dispersion of hydrogen in a partially enclosed compartment: Effect of natural and forced ventilation

The study of compressed hydrogen releases from high-pressure storage systems has practical application for hydrogen and fuel cell technologies. Such releases may occur either due to accidental damage to a storage tank, connecting piping, or due to failure of a pressure release device (PRD). Understanding hydrogen behavior during and after the unintended release from a high-pressure storage device is important for development of appropriate hydrogen safety codes and standards and for the evaluation of risk mitigation requirements and technologies. In this paper, the natural and forced mixing and dispersion of hydrogen released from a high-pressure tank into a partially enclosed compartment is investigated using analytical models. Simple models are developed to estimate the volumetric flow rate through a choked nozzle of a high-pressure tank. The hydrogen released in the compartment is vented through buoyancy induced flow or through forced ventilation. The model is useful in understanding the important physical processes involved during the release and dispersion of hydrogen from a high-pressure tank into a compartment with vents at multiple levels. Parametric studies are presented to identify the relative importance of various parameters such as diameter of the release port and air changes per hour (ACH) characteristic of the enclosure. Compartment overpressure as a function of the size of the release port is predicted. Conditions that can lead to major damage of the compartment due to overpressure are identified. Results of the analytical model indicate that the fastest way to reduce flammable levels of hydrogen concentration in a compartment is by blowing through the vents. Model predictions for forced ventilation are presented which show that it is feasible to effectively and rapidly reduce the flammable concentration of hydrogen in the compartment following the release of hydrogen from a high-pressure tank.     

Thermal analysis of randomly oriented carbon nanotube reinforced functionally graded timoshenko beam

The unique thermal properties of carbon nanotubes (CNT) are utilized to increase the use of functionally graded material (FGM) at higher temperatures which resulted in introduction of a new type of material called as functionally graded carbon nanotube-reinforced composites (FG-CNTRCs). To use the FG-CNTRCs at elevated temperatures, their thermal analysis is very important. In this context, this article presents the thermal analysis of a CNT based FG Timoshenko beam. Material properties distribution is assumed to vary along the thickness direction according to power law distribution and linear distributions. Finite difference method is implemented to find out the temperature distribution. Using first order shear deformation theory (FSDT), expressions for strains and stresses are obtained. The results are compared with temperature distribution according to power law. The effect of CNT distribution on strains and stresses is also observed. Based on these results important conclusions have been drawn.     

Study on Alloying Behaviour of Uranium Zirconium Alloy

Uranium–zirconium alloy is the potential candidate material as metallic fuels for nuclear reactor applications. Fabrication of uranium zirconium alloy can be made either by powder metallurgy or by melting method. Both the method has its own advantages and selection of the fabrication route depends on its application as fuel. In this work investigations were carried out on fabrication of uranium–zirconium alloys (i.e. U–40 wt% Zr, U–50 wt% Zr, U–60 wt% Zr and U–70 wt% Zr) using both powder metallurgy and melting method. It is heat treated at different conditions. Apart from other characterization, X-ray diffraction analysis was carried out to evaluate phase content of the alloy and reported here.     

Macro- and microscale variables regulate stent haemodynamics,fibrin deposition and thrombomodulin expression

Drug eluting stents are associated with late stent thrombosis (LST), delayed healing and prolonged exposure of stent struts to blood flow. Using macroscale disturbed and undisturbed fluid flow waveforms, we numerically and experimentally determined the effects of microscale model strut geometries upon the generation of prothrombotic conditions that are mediated by flow perturbations. Rectangular cross-sectional stent strut geometries of varying heights and corresponding streamlined versions were studied in the presence of disturbed and undisturbed bulk fluid flow. Numerical simulations and particle flow visualization experiments demonstrated that the interaction of bulk fluid flow and stent struts regulated the generation, size and dynamics of the peristrut flow recirculation zones. In the absence of endothelial cells, deposition of thrombin-generated fibrin occurred primarily in the recirculation zones. When endothelium was present, peristrut expression of anticoagulant thrombomodulin (TM) was dependent on strut height and geometry. Thinner and streamlined strut geometries reduced peristrut flow recirculation zones decreasing prothrombotic fibrin deposition and increasing endothelial anticoagulant TM expression. The studies define physical and functional consequences of macro- and microscale variables that relate to thrombogenicity associated with the most current stent designs, and particularly to LST.