ExPregel: a new computational model for large‐scale graph processing

These days, large‐scale graph processing becomes more and more important. Pregel, inspired by Bulk Synchronous Parallel, is one of the highly used systems to process large‐scale graph problems. In Pregel, each vertex executes a function and waits for a superstep to communicate its data to other vertices. Superstep is a very time‐consuming operation, used by Pregel, to synchronize distributed computations in a cluster of computers. However, it may become a bottleneck when the number of communications increases in a graph with million vertices. Superstep works like a barrier in Pregel that increases the side effect of skew problem in distributed computing environment. ExPregel is a Pregel‐like model that is designed to reduce the number of communication messages between two vertices resided on two different computational nodes. We have proven that ExPregel reduces the number of exchanged messages as well as the number of supersteps for all graph topologies. Enhancing parallelism in our new computational model is another important feature that manifolds the speed of graph analysis programs. More interestingly, ExPregel uses the same model of programming as Pregel. Our experiments on large‐scale real‐world graphs show that ExPregel can reduce network traffic as well as number of supersteps from 45% to 96%. Runtime speed up in the proposed model varies from 1.2× to 30×. Copyright © 2015 John Wiley & Sons, Ltd.     

Stability of nanoparticles during semibatch emulsion polymerization of butyl methacrylate,in the presence of methacrylic acid via RSM

The size and stability of latex particles in the semibatch emulsion polymerization of butyl methacrylate (BMA), in the presence of 0–10% methacrylic acid (MAA), were investigated. Response surface methodology (RSM), as a design of experiment, was used to obtain a more systematic understanding of the role of emulsifier and MAA in the stability of the particles. The amount of coagulum can be greatly reduced by increasing the concentration of sodium lauryl sulfate (SLS) in the monomer emulsion feed (MEF) and initial reactor charge (IRC). On the other hand, increasing the concentration of SLS in the IRC can result in a decrease of the particles size. According to the experimental data, the yield of reaction can be improved with incorporation of MAA into the emulsion polymers. The size and morphology of particles were obtained by scanning electron microscopy (SEM). FTIR and titration were used to determine the percentage of MAA in the copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Compatibilized Polypropylene/Ethylene–Propylene–Diene-Monomer/Polyamide6 ternary blends: Effect of twin screw extruder processing parameters

Polypropylene (PP)/Polyamide6 (PA6)/Ethylene–Propylene–Diene-Monomer (EPDM) (70/15/15) ternary polymer blends compatibilized with Maleic-anhydride grafted EPDM (EPDM-g-MA) were prepared by melt blending using a twin screw extruder (TSE). Effect of TSE processing parameters including barrel temperature, screw speed and blending sequence on the mechanical properties of ternary polymer blends was investigated by application of Taguchi experimental design methodology. Three different levels of barrel temperature (220 °C, 230 °C, 240 °C), screw speed (90 rpm, 120 rpm, 150 rpm) and blending sequence (nominated as: S1, S2 and S3) were selected. The response variables were tensile properties and impact strength of the prepared samples which are directly affected by the blend microstructure. Investigation of the statistical–mathematical analysis results performed by the software depicted that the optimum processing conditions for the ternary blends investigated here, to achieve balanced tensile and impact properties, are 220 °C, 150 rpm and S2 blending sequence.     

Estimation of Micellization Parameters of SDS in the Presence of Some Electrolytes for Emulsion Polymerization Systems

The critical micelle concentration and the effective degree of dissociation of micelles (α) of sodium dodecyl sulfate, which is the most extensively used surfactant in emulsion polymerization systems, were determined in the presence of various amounts of sodium carbonate and potassium persulfate, and some monomers, such as methyl methacrylate, butyl acrylate, and styrene by means of the conductometric procedure at 25 °C. In addition, the other micellization parameters, such as aggregation number and number of counter-ions per micelle, were computed directly from the obtained conductivity measurements data. The effect of the combination of sodium carbonate and potassium persulfate, on the critical micelle concentration of the sodium dodecyl sulfate solutions was studied at 60 °C (emulsion reaction temperature). The empirical formulations derived provide an easy way to estimate the critical micelle concentration and the effective degree of dissociation of micelles of a system at a given electrolyte and monomer concentration.     

Adhesion of Different Concrete Repair Systems Exposed to Different Environments

This article presents the results of experiments conducted to assess the effects of aging under dry laboratory conditions, underwater storage, cyclic freeze-thaw, and temperature changes on the adhesion between the repair and the substrate concrete. The repair systems considered for these studies included ordinary sand/cement (S/C) mortar, with and without bonding agents, two polymer modified cementitious mortars, and two resinous mortars. The specimens were concrete slabs of 600 × 300 × 100 mm dimensions with saw cut face 600 × 300 mm on which a repair layer of 20 mm had been applied. In order to eliminate the effects of surface texture and surface strength of the concrete on the adhesion of repair systems, repair applied surfaces were all saw cut surfaces of concrete with 28-day design compressive strength of 65 MPa. Tensile bond strengths of these specimens were measured using a direct tensile test (pull-off) method. The results indicated that the tensile bond strengths of different repair systems under dry laboratory conditions, and stored underwater, ranged from 1.51 to 5.27 Mpa. Exposure to 300 cycles of freeze-thaw and to 200 cycles of temperature changes resulted in 6 to 100 percent reduction in their tensile bond strengths.     

Energy and Quality Attributes of Combined Hot-Air/Infrared Drying of Paddy

The kinetics of combined hot-air/infrared thin-layer drying of paddy was studied. The mechanical quality aspects of paddy kernels dried at different drying conditions were evaluated in terms of percentage of cracked kernels and also required failure force obtained from bending tests. The well-known Artificial Neural Network (ANN) modeling technique was applied to predict the drying time, variations in paddy moisture content, the percentages of cracked kernels, and the values of required failure force of paddy at different drying conditions. The best ANN topologies, transfer functions, and training algorithms were determined for prediction of the mentioned parameters. In addition to the product quality aspects, the specific energy consumption (SEC) was estimated for all drying conditions. The results indicated that application of a low-intensity IR radiation (2000 W/m²), together with lower values of inlet air temperature (30°C) and moderate values of inlet air velocity (0.15 m/s), can effectively improve the final quality of paddy (as a heat-sensitive product) with a reasonable SEC.     

CMOS high‐precision loser‐take‐all circuit

This paper presents a new current‐mode CMOS loser‐take‐all circuit. The proposed circuit consists of a basic cell that allows implementation of a multi‐input configuration by repeating the cell for each additional input. A high‐speed feedback structure is employed to determine the minimum current among the applied inputs. The significant feature of the circuit is its high accuracy and high‐speed operation. Additionally, the input dynamic range of the circuit can be efficiently controlled via the biasing current. HSPICE simulation results are presented to verify the performance of the circuit, where under a supply voltage of 2.5 V, bias current of 100 µA, and frequency of 10 MHz, the input dynamic range increases within 0–100 µA and the corresponding error remains as low as 0.4%. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Thermomechanical advantages of functionally graded dental posts: A finite element analysis

This study aimed to fabricate dental posts with functionally graded structures comprised of zirconia, titanium, and hydroxyapatite and compare their thermomechanical behavior with homogeneous zirconia and titanium posts in simulated models of upper central incisor. The results indicated the gradual behavior of functionally graded dental posts in terms of physical and mechanical properties. The finite element analysis revealed a more efficient equilibration to the oral environment after removing the thermal stress in functionally graded dental post compared to the homogeneous counterparts. Therefore, the functionally graded structures could reduce the stress/strain concentrations and interfacial stresses in root canal and minimize the likelihood of root fracture.     

Extended Isogeometric Analysis (XIGA) of Fatigue Life in Attachment Lug

In the present paper, extended isogeometric analysis (XIGA) is used to compute the stress intensity factor (SIF) in straight lugs of Aluminum 7075-T6. XIGA uses the non-uniform rational B-spline (NURBS) functions and enrichment functions through the partition of unity. The Heaviside function is enriched to capture jump at the crack faces, while the analytical asymptotic solutions are incorporate with NURBS to perform the crack tip singularity. The XIGA-based SIF of edge-cracked plate and straight attachment lug are compared with analytical solution and extended finite element method capability available in ABAQUS. Also, crack growth and fatigue life of single crack in attachment lug are estimated and then compared with the available experimental data for two different load ratios equal to 0.1 and 0.5. The SIF calculated from XIGA are in reasonable agreement with the available data.