Accelerating Distributed Graphical Fluid Simulations with Micro-partitioning

Graphical fluid simulations are CPU-bound. Parallelizing simulations on hundreds of cores in the computing cloud would make them faster, but requires evenly balancing load across nodes. Good load balancing depends on manual decisions from experts, which are time-consuming and error prone, or dynamic approaches that estimate and react to future load, which are non-deterministic and hard to debug. This paper proposes Birdshot scheduling, an automatic and purely static load balancing algorithm whose performance is close to expert decisions and reactive algorithms without their difficulty or complexity. Birdshot scheduling's key insight is to leverage the high-latency, high-throughput, full bisection bandwidth of cloud computing nodes. Birdshot scheduling splits the simulation domain into many micro-partitions and statically assigns them to nodes randomly. Analytical results show that randomly assigned micro-partitions balance load with high probability. The high-throughput network easily handles the increased data transfers from micro-partitions, and full bisection bandwidth allows random placement with no performance penalty. Overlapping the communications and computations of different micro-partitions masks latency. Experiments with particle-level set, SPH, FLIP and explicit Eulerian methods show that Birdshot scheduling speeds up simulations by a factor of 2-3, and can out-perform reactive scheduling algorithms. Birdshot scheduling performs within 21% of state-of-the-art dynamic methods that require running a second, parallel simulation. Unlike speculative algorithms, Birdshot scheduling is purely static: it requires no controller, runtime data collection, partition migration or support for these operations from the programmer.     

A new systematic design approach for low-power analog integrated circuits

In this paper, a new design approach for systematic design and optimization of low-power analog integrated circuits is presented based on the proper combination of a simulation-equation based optimization algorithm using geometric programming as an optimization approach and HSPICE as a simulation and verification tool by a knowledge-based transistor sizing tool which uses physical-based gm/I_D characteristic in all regions of transistor operation to increase the accuracy in a reasonable simulation time. The proposed design methodology is successfully used for automated design and optimization of an operational amplifier with hybrid-cascode compensation using 0.18 μm CMOS technology parameters with the main purpose of minimizing the power consumption of the circuit.     

Mixed matrix membranes of aminosilanes grafted FAU/EMT zeolite and cross-linked polyimide for CO2/CH4 separation

Intergrowth Faujasite and EMC-2 zeolites (FAU/EMT) were grafted with 3-aminopropyltriethoxysilane (APTES), 3-aminopropylmethyldiethoxysilane (APMDES), and 3-aminopropyldimethylethoxysilane (APDMES) containing respectively trihydrolyzable ethoxy groups (3E), di-hydrolyzable ethoxy groups (2E), and monohydrolyzable ethoxy group (1E) in different polarities solvent of isopropanol (IPA), isopropanol/water mixture, 95/5 V/V (IPAW) and toluene (TOL) to prepare mixed matrix membranes with 6FDA-ODA polyimide cross-linked by APTMDS (Bis(3-aminopropyl)-tetramethyldisiloxane) as the organic phase. Membrane comprising amine-grafted zeolite with a commercial polyimide (Matrimid 5218 US) was also fabricated for comparison. The gas transport properties of these mixed matrix membranes (MMM) for pure gas and blends of CO₂ and CH₄ were investigated at 35 °C and 150 psi. The results showed that the performance of MMM with 6FDA-ODA at 25 wt.% zeolite is excellent for CO₂/CH₄ separation. A detailed study of the relation between MMM properties and their morphology as affected by their interactions with the amine-grafted inorganic phase and the cross-linking agent is reported.     

Synthesis and characterization of different morphologies CuGaS<Subscript>2</Subscript>/CuS nanostructures with a simple sonochemical method

In this experimental work, different morphologies of CuGaS₂/CuS nanostructures were synthesized via a simple ultrasonic method. The effect of different parameters was investigated on the product size and morphology, such as copper source, sulfur source, ultrasonic power and time, solvent and the reaction vessel. It was found the mentioned parameters have significant effects on the product size and morphology. The obtained products were characterized by X-ray diffraction pattern to study the product structure and scanning electron microscopy was used to study the products morphologies.     

Identification of Critical Flood Prone Areas in Data-Scarce and Ungauged Regions: A Comparison of Three Data Mining Models

Flood is one of the most devastating natural disasters with socio-economic consequences. Thus, preparation of the flood prone areas (FPA) map is essential for flood disaster management, and for planning further development activities. The main goal of this study is to investigate new applications of the evidential belief function (EBF), random forest (RF), and boosted regression trees (BRT) models for identifying the FPA in the Galikesh region, Iran. This research was conducted in three main stages such as data preparation, flood susceptibility mapping using EBF, RF, and BRT models and validation of constructed models using receiver operating characteristic (ROC) curve. At first, a flood inventory map was prepared using documentary sources of Iranian Water Resources Department (IWRD) and extensive field surveys. In total, 63 flood locations were identified in the study area. Of these, 47 (75%) floods were randomly selected as training/model building and the remaining 16 (25%) cases were used for the validation purposes. The flood conditioning factors considered in the study area are altitude, slope aspect, slope angle, topographic wetness index, plan curvature, geology, landuse, distance from rivers, drainage density, and soil texture. Subsequently, the FPA maps were prepared using EBF, RF, and BRT models in a GIS environment. Finally, the results were validated using ROC curve and area under the curve (AUC) analysis. From the analysis, it was seen that the EBF (AUC?=?78.67%) and BRT models (AUC?=?78.22%) performed better than RF model (AUC?=?73.33%). Therefore, the resultant FPA maps can be useful for researchers and planner in flood mitigation strategies.     

Effect of non-uniform parallel channel on performance of passive direct methanol fuel cell

In this paper, the effects of current collector on passive direct methanol fuel cell's (passive DMFC) performance and removing CO₂ gas is studied. For this purpose, a single cell with two arrangements of current collector in anode and cathode side is considered. In first arrangement, non-uniform parallel channels with 53.76% open ratio is used in the anode side and a perforated flow field with 34.5% open ratio is applied in the cathode side. In second arrangement, uniform parallel channels with 42.28% open ratio has been used in both anode and cathode sides. At the first arrangement, a maximum power of 20 mW cm⁻² in 4 M methanol concentrations and in the second arrangement a maximum power of 17.7 mW cm⁻² in 5 M methanol concentrations has been obtained. Furthermore, it is shown that using the current collector with non-uniform parallel channels is more effective in removing CO₂ gas than other parallel channels.     

Novel fabrication route for porous silicon carbide ceramics through the combination of in situ polymerization and reaction bonding techniques

For the first time, an in situ polymerization technique was applied to produce mullite‐bonded porous SiC ceramics via a reaction bonding technique. In this study, SiC microsized particles and alumina nanopowders were successfully coated by polyethylene (PE), which was synthesized from the particle surface in a slurry phase reactor with a Ziegler–Natta catalyst system. The thermal studies of the resulting samples were performed with differential scanning calorimetry and thermogravimetric analysis. The morphology analysis obtained by transmission electron microscopy and scanning electron microscopy (SEM) confirmed that PE was successfully grafted onto the particle surface. Furthermore, the obtained porous ceramics were characterized in terms of their morphologies, phase composition, open porosity, pore size distribution, and mechanical strength. SEM observations and mercury porosimtery analysis revealed that the quality of the dispersion of nanosized alumina powder into the microsized SiC particles was strongly enhanced when the particles were coated by polymers with in situ polymerization. This resulted in a higher strength and porosity of the formed ceramic porous materials with respect to the traditional process. In addition, the X‐ray diffraction results reveal that the amount of mullite as the binder increased significantly for the samples fabricated by this novel method. The effects of the sintering temperature, forming pressure, and polymer content on the physical and mechanical properties of the final porous ceramic were also evaluated in this study. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40425.