Viscoelastic flow in an obstructed microchannel at high Weissenberg number

Detailed measurements of the flow instability of dilute shear-thinning viscoelastic aqueous solutions, with relatively low zero-shear viscosities, in an obstructed microchannel flow are reported. We examine the flow behaviour resulting from a 100 μm post placed in the channel centreline over a range of Reynolds numbers (\(5<Re<300\)) and Weissenberg numbers (\(20<Wi<10^3\)). Micro-particle image velocimetry measurements show the onset of an upstream instability within a Reynolds number range and at a critical elasticity number corresponding to polymer concentrations above 25 ppm of long-chain polyacrylamide. The instability results in significant local fluctuations in the flow field approaching 30 % of the mean velocity. The magnitude of the local viscosity ratio in the region upstream of the post is proposed as a driving mechanism for the instability which resembles a buckling flow. Additionally, the classical instability owing to separation and vortex formation downstream of the post in Newtonian flow is suppressed and a very long stable wake is observed extending over 10 post-diameters downstream.     

CanarDeep: a hybrid deep neural model with mixed fusion for rumour detection in social data streams

Neural Computing and Applications - The unrelenting trend of doctored narratives, content spamming, fake news and rumour dissemination on social media can lead to grave consequences that range from...     

A simple calorimeter to measure specific heat of activated carbon prepared for pressure swing adsorption refrigeration system

A new calorimeter to measure specific heat of indigenously prepared granular activated carbon (AC) for application in a refrigeration system based on gas adsorption–desorption mechanism is presented. This calorimeter allows specific heat measurements in high (305.5–317.8 K) as well as low (254.6–264 K) temperature ranges. The specific heat of prepared AC on measurement using developed calorimeter has been found to be 1.062 J g^?1 K^?1. Preparation, instrumental analyses and influence of various physical properties of AC on its specific heat have also been discussed. Characterisation results of AC demonstrate that it can be efficiently used in such cold producing system down to refrigeration and cryogenic temperature. © 2012 Canadian Society for Chemical Engineering     

Investigations for the optimal combination of zinc oxide nanoparticle-diesel fuel with optimal compression ratio for improving performance and reducing the emission features of variable compression ratio diesel engine

Clean Technologies and Environmental Policy - The continual hike in environmental pollution from diesel engines has raised the concern of researchers to identify certain clean fuels. For this...     

Porous MgH2/C composite with fast hydrogen storage kinetics

A porous MgH₂/C composite can be synthesized through decomposition of an organo-magnesium precursor under hydrogen pressure. XRD patterns of the porous MgH₂/C composite exhibit a pure MgH₂ phase with a tetragonal structure. The morphology of the resulted samples is significantly dependent on the synthesis temperature and hydrogen pressure. The samples exhibit a rod-like structure and composed of nano-crystallites of MgH₂ with a size of less than 5 nm. TPD spectra of a sample synthesized at 220 °C for 4 h show a remarkable decrease of the onset hydrogen release temperature. Further, this sample also exhibits fast hydrogen adsorption kinetics adsorbing 6 wt % of hydrogen in 3 min at 250 °C. The same amount of hydrogen is adsorbed in 11 min at 200 °C and 40 min at 150 °C, respectively. N₂ physisorption measurements of this sample indicate meso-porosity with a BET surface area of 40.9 m² g⁻¹ and an average pore diameter of 20 nm.     

Combating I-O bottleneck using prefetching: model,algorithms, and ramifications

Multiple memory models have been proposed to capture the effects of memory hierarchy culminating in the I-O model of Aggarwal and Vitter (Commun. ACM 31(9):1116–1127, [1988]). More than a decade of architectural advancements have led to new features that are not captured in the I-O model—most notably the prefetching capability. We propose a relatively simple Prefetch model that incorporates data prefetching in the traditional I-O models and show how to design optimal algorithms that can attain close to peak memory bandwidth. Unlike (the inverse of) memory latency, the memory bandwidth is much closer to the processing speed, thereby, intelligent use of prefetching can considerably mitigate the I-O bottleneck. For some fundamental problems, our algorithms attain running times approaching that of the idealized random access machines under reasonable assumptions. Our work also explains more precisely the significantly superior performance of the I-O efficient algorithms in systems that support prefetching compared to ones that do not.

Spatial and Temporal Quantification of Community Resilience: Gotham City under Attack

Mitigating the impact of disasters on communities requires not only a deep understanding of the essential features of infrastructure, social, and economical components that make a community resilient; but also the development of mathematical models that can seamlessly integrate these features. This article lays the foundation for an integrative model that captures interaction between these components. The underlying fundamentals of the proposed model hinges on the principle of a damped harmonic oscillator by assuming the behavior of a community in response to a hazard is equivalent to the response of a vibrating mass of finite stiffness and damping. We implemented the dynamic model by developing a novel finite element formulation capable of quantifying resilience both temporally and spatially. We then used the developed model to devise a suitable hazard‐agnostic definition of community resilience. This was realized through a set of demonstration and logical verification tests conducted on Gotham City, the fictional city of the infamous character, Batman. It was observed that the model can be used to identify sensitive and vulnerable areas in a community, provide a spatial and temporal quantification of community resilience, and accommodate various types of hazards such as physical disruptions, economic downtimes, and even social disorders.     

N‐Doped CsTaWO6 as a New Photocatalyst for Hydrogen Production from Water Splitting Under Solar Irradiation

Photocatalysts for efficient solar hydrogen production are highly sought after. Here a new type of nitrogen‐doped tantalum tungstenate (CsTaWO₆) material, which demonstrates excellent visible light absorption and improved photocatalytic activity, is demonstrated. X‐ray diffraction (XRD) patterns reveal that the defect pyrochlore‐type structure of CsTaWO₆ remained intact upon nitrogen doping. UV‐vis spectra indicate that nitrogen doping in the compound results in a red‐shift of the absorption edge from 358 nm to 580 nm, thus offering significantly increased visible light absorption. X‐ray photoelectron spectroscopy (XPS) further indicates that [Ta/W]–N bonds were formed by inducing nitrogen to replace a small amount of oxygen in the material, resulting in a compound of CsTaWO_6‐xN_x. The explanation of the experimental results is supported by density functional theory calculations. The density of states (DOS) and the projected DOS after substitutional doping of nitrogen in CsTaWO₆ indicated that N‐doping reduces the bandgap significantly from 3.8 to 2.3 eV due to N 2p and O 2p orbital mixing. The role of the new N 2p states is also investigated by studying the production of the ?OH radicals in the visible light region (>420 nm). In CsTaWO_6‐xN_x, the N 2p orbitals are the main contributors to the top of the valence band, causing bandgap narrowing while the bottom of conduction band, due to Ta 4d orbitals, remains almost unchanged. Compared with its undoped counterpart, nitrogen‐doped CsTaWO_6‐xN_x exhibits a nearly 100% increase in solar hydrogen production efficiency.     

General store placement for response time minimization in parallel disks

We investigate the placement of N enterprise data-stores (e.g., database tables, application data) across an array of disks with the aim of minimizing the response time averaged over all served requests, while balancing the load evenly across all the disks in the parallel disk array. Incorporating the non-FCFS serving discipline and non-work-conserving nature of disk drives in formulation of the placement problem is difficult and current placement strategies do not take them into account.We present a novel formulation of the placement problem to incorporate these crucial features and identify the runlength of requests accessing a store as the most important criterion for placing the stores. We use these insights to design a fast (running time of NlogN) placement algorithm that is optimal under the assumption that transfer times are small. Further, we develop polynomial-time extensions of the algorithm that minimize response time even if transfer times are large, while balancing the loads across the disks. Comprehensive experimental studies establish the efficacy of the proposed algorithm under a wide variety of workloads with the proposed algorithm reducing the response time for real storage traces by more than a factor of 2 under heterogeneous workload scenarios.