CFD study of non-premixed swirling burners: Effect of turbulence models

This research investigates a numerical simulation of swirling turbulent non-premixed combustion. The effects on the combustion characteristics are examined with three turbulence models: namely as the Reynolds stress model, spectral turbulence analysis and Re-Normalization Group. In addition, the P-1 and discrete ordinate (DO) models are used to simulate the radiative heat transfer in this model. The governing equations associated with the required boundary conditions are solved using the numerical model. The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities. Among different models proposed in this research, the Reynolds stress model with the Probability Density Function (PDF) approach is more accurate (nearly up to 50%) than other turbulent models for a swirling flow field. Regarding the effect of radiative heat transfer model, it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior. This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion.     

Experimental Investigations on Microstructure,Properties and Workability Behavior of Zinc Oxide Reinforced Al–Si–Mg Matrix Composites

Silicon - Al-Si based alloy matrix composites are now broadly utilized by the industrial sectors like automobile, structural, aerospace and more practical industrial applications due to its...     

Comparative examination of adhesive and cohesive properties of fluorinated coatings on stone/tile surfaces

A NanoScratch methodology was used to evaluate the relative adhesive and cohesive strength of fluorinated poly(methyl methacrylate-co-methacrylic acid) and fluorinated phosphate coatings on stone and tile surfaces. In general, all coatings showed ability to bind to the stone and tile surfaces, and polymer-based coatings expressed stronger adhesion compared to a small-molecule fluorinated phosphate coating. Also, anionic fluorinated polymers containing methacrylic acid (MAA) residues in the ammonium carboxylate form adhered more strongly compared to corresponding acidic polymer counterparts. In addition, anionic fluorinated polymers, shown to adhere more strongly to granite than marble, possibly due to strong Lewis acid-base interaction between carboxylate and aluminosilicates. Conversely, the fluorinated polymers, bearing the MAA side-chains in their free-acid form, bound more strongly to marble via possible Brønsted acid-base interactions between carboxylic acid and calcium carbonate. Lastly, in most cases, comparable fracture thresholds were observed for the same coating material on different substrates. This was expected since fracture threshold is a measure of the mechanical strength of the coating material, independent of the substrate difference.     

A multiscale approach to network event identification using geolocated twitter data

The large volume of data associated with social networks hinders the unaided user from interpreting network content in real time. This problem is compounded by the fact that there are limited tools available for enabling robust visual social network exploration. We present a network activity visualization using a novel aggregation glyph called the clyph. The clyph intuitively combines spatial, temporal, and quantity data about multiple network events. We also present several case studies where major network events were easily identified using clyphs, establishing them as a powerful aid for network users and owners.     

Design of a cost-effective on-grid hybrid wind–hydrogen based CHP system using a modified heuristic approach

An economic model and optimization procedure is developed in this paper for grid-connected hybrid wind–hydrogen combined heat and power systems for residential applications in northeastern Iran. The model considers various significant factors: energy production cost, electrical trade with local grid, electrical power generation from the wind/hydrogen energy system, thermal recovery from the fuel cell, and maintenance. Also, various tariffs for purchasing and selling electrical energy from the local grid are considered for the hybrid system operation. The optimization objective is to minimize the system total cost subject to relevant constraints for residential applications. To achieve this aim, an efficient optimization method is proposed based on particle swarm optimization. The proposed algorithm performance is compared with that for the imperialist competition algorithm. The results show that the hybrid system is the most cost-effective for the residential load, and the results of the proposed algorithm are more promising than those for the alternative algorithm.     

A method for reverse engineering of material microstructure for heterogeneous CAD

Integration of material composition, microstructure, and mechanical properties with geometry information enables design and analysis of materials and products in a computer-aided design (CAD) environment. In this paper, we propose a method for the construction of material models from microstructure images, that can be integrated into a heterogeneous CAD representation. The method utilizes Radon and wavelet transforms to compute a surfacelet representation. A novel feature recognition method was developed to identify microstructure features, including embedded fibers and grain boundaries, from the surfacelet representation. The models and methods were demonstrated with examples of synthetic and engineered polymer nanocomposites, a metal alloy, and a medical dataset of human feet.     

Techno-economic assessment of a solar-geothermal multigeneration system for buildings

A techno-economic assessment is conducted for a multigeneration system comprised of two renewable energy subsystems—geothermal and solar—to supply electrical power, cooling, heating, hydrogen and hot water for buildings. The proposed system is evaluated in terms of energy and exergy efficiencies. The simulation results show that the electrolyzer produces 2.7 kg/h hydrogen. A parametric study is carried out to assess the effect of various parameters on the system energy and exergy efficiencies. The economic assessment, performed using the Hybrid Optimization of Multiple Energy Resources (HOMER) software, shows that the net present cost of the optimized electrical power system is $476,000 and the levelized cost of electricity is $0.089/kWh.     

Double dissociation in the anatomy of socioemotional disinhibition and executive functioning in dementia.

Objective: To determine whether socioemotional disinhibition and executive dysfunction are related to dissociable patterns of brain atrophy in neurodegenerative disease. Previous studies have indicated that behavioral and cognitive dysfunction in neurodegenerative disease are linked to atrophy in different parts of the frontal lobes, but these prior studies did not establish that these relationships were specific, which would best be demonstrated by a double dissociation. Method: Subjects included 157 patients with neurodegenerative disease. A semiautomated parcellation program (Freesurfer) was used to generate regional cortical volumes from structural MRI scans. Regions of interest (ROIs) included anterior cingulate cortex (ACC), orbitofrontal cortex (OFC), middle frontal gyrus (MFG), and inferior frontal gyrus (IFG). Socioemotional disinhibition was measured using the Neuropsychiatric Inventory. Principal component analysis including 3 tasks of executive function (EF; verbal fluency, Stroop Interference, modified Trails) was used to generate a single-factor score to represent EF. Results: Partial correlations between ROIs, disinhibition, and EF were computed after controlling for total intracranial volume, Mini-Mental State Examination, diagnosis, age, and education. Brain regions significantly correlated with disinhibition (ACC, OFC, IFG, and temporal lobes) and EF (MFG) were entered into separate hierarchical regressions to determine which brain regions predicted disinhibition and EF. OFC was the only brain region to significantly predict disinhibition, and MFG significantly predicted EF performance. A multivariate general linear model demonstrated a significant interaction between ROIs and cognitive–behavioral functions. Conclusions: These results support a specific association between orbitofrontal areas and behavioral management as compared with dorsolateral areas and EF. (PsycINFO Database Record (c) 2011 APA, all rights reserved)