Performance of SOR methods on modern vector and scalar processors

The building-cube method (BCM) is a new generation algorithm for CFD simulations. The basic idea of BCM is to simplify the algorithm in all stages of flow computation to achieve large-scale simulations. Calculation of a pressure field using the Successive Over Relaxation (SOR) method consumes most of the total execution time required for BCM. In this paper, effective implementations on modern vector and scalar processors are investigated. NEC SX-9 and Intel Nehalem-EX are the latest vector and scalar processors. Those processors have much higher peak performances than their previous-generation processors. However, their memory bandwidth improvement cannot catch up with the performance improvement of processors. This is the so-called memory wall problem. In our paper, we discuss optimization techniques for implementation of the SOR method based on architectural characteristics of these modern processors, and evaluate their effects on the sustained performances of these processors for BCM.     

Transport of single cells using an actin bundle-myosin bionanomotor transport system

The potential of using actin bundles for the transport of liposomes and single cells across myosin-coated surfaces is investigated. Compared to that observed with filamentous actin, the liposome transport using actin bundles was more linear in nature and able to occur over longer distances. Bundles, but not filamentous actin, were capable of moving single cells. Cargo unloading from bundles was achieved by incubation with Triton X-100. These data suggest that actin bundling may improve the ability of the myosin motor system for nanotransport applications.     

Mechanochemically synthesized ZIF-8 nanoparticles blended into 6FDA-TrMPD membranes for C3H6/C3H8 separation

The mixed matrix membranes (MMMs) consisting zeolitic-imidazolate framework-8 (ZIF-8) nanoparticles in a polymer have been of considerable interest in separation applications. The fillers used are mostly synthesized using the solvothermal method. In this study, the ZIF-8 nanoparticles were synthesized using a solvent-less and salt-free mechanochemical method and were added to 6FDA-TrMPD polyimide to prepare MMMs. The single gas permeation of C₃H₆ and C₃H₈ through the MMMs was investigated. The C₃H₆ permeability and C₃H₆/C₃H₈ ideal selectivity of a 20 wt% mechano-synthesized ZIF-8/6FDA-TrMPD MMM were 70% and 32% higher than those of the neat polymer membrane at 0.1 MPa and 308 K, respectively. The C₃H₆/C₃H₈ separation performance of the mechano-synthesized ZIF-8 MMM was similar to that of the conventional solvothermal-synthesized ZIF-8 MMM. This separation performance was in good agreement with the Maxwell model. Temperature and pressure dependence analyses confirmed that the mechano-synthesized ZIF-8 nanoparticles acted as molecular sieves in the MMMs for the C₃H₆ and C₃H₈ permeation.     

Velocity and absorption coefficient of ultrasonic waves in molten and glassy silicates and borates

The velocity and absorption coefficient of longitudinal ultrasonic waves with 5 and 10 MHz in molten and glassy silicates and borates have been measured by means of the pulse-echo method in 300 to 1600 K. The silicate and borate were Na₂O−SiO₂, K₂O−SiO₂, PbO−SiO₂, Na₂O−B₂O₃, and PbO−B₂O₃. The velocity of sound decreased with increasing temperature and decreased rapidly near the transition temperature of glasses. The product of the one-third power of velocity of sound and the molar volume of the oxide melt was constant and independent of temperature. The absorption coefficient of ultrasonic waves in the oxide melts increased with an increase in viscosity. The absorption mechanisms of ultrasonic waves and the mean free path of phonons in the oxide melts were discussed.     

Tensile behavior of polypropylene blended with bimodal distribution of styrene‐ethylene‐butadiene‐styrene particle size

The objective is to characterize the effects of the bimodal distribution of rubber particles and its blend ratio on the mechanical properties of the thermoplastic polypropylene blended with two different styrene‐ethylene‐butadiene‐styrene triblock copolymer at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 3 × 10^?1 to 10² (1/s). Phase morphology is investigated to estimate the bimodal rubber particle size distribution. In addition, the in situ observation is conducted during uniaxially stretching within transmission electron microscopy step by step to investigate the deformation events depending on the elongation of samples. The elastic modulus increased gradually as the blend ratio of large rubber particle increased. An increase in the rupture strain and the strain energy up to failure was found for the bimodal rubber particle distributed blend system where the blend ratios of small rubber particle and large rubber particle were same. This is because the smaller particles dominant blend systems show the bandlike craze deformation while the localized plastic deformation is taken place in the larger particles dominated blend systems. The synergistic effect of these rubber particles gives rise to a strong increase in the ductility of these bimodal rubber particle distributed polypropylene systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Evaluation of mixing profiles for a new micromixer design strategy

The relationship between mixing history and reaction performance in microreactors using computational fluid dynamics (CFD) simulations is identified. In the idealized, simplified mixing model, mixing proceeds linearly and only the mixing time determined the reaction performance. However, in the case of realistic models where mixing proceeds unequally, the partial rapid progression of mixing, more than the mixing time, significantly impacts the reaction. The use of the fluid segment size distribution to capture this effect is proposed. The effective Damköhler number derived from the fluid segment size distribution predicted the reaction yield well. To demonstrate the utility of the mixing profile design strategy, we fabricated a novel micromixer with multiple partial rapid mixing zones. This micromixer achieved excellent results both in a CFD simulation and an experiment. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1154–1161, 2016     

Multi-objective topology optimization of multi-component continuum structures via a Kriging-interpolated level set approach

This paper explores a framework for topology optimization of multi-component sheet metal structures, such as those often used in the automotive industry. The primary reason for having multiple components in a structure is to reduce the manufacturing cost, which can become prohibitively expensive otherwise. Having a multi-component structure necessitates re-joining, which often comes at sacrifices in the assembly cost, weight and structural performance. The problem of designing a multi-component structure is thus posed in a multi-objective framework. Approaches to solve the problem may be classified into single and two stage approaches. Two-stage approaches start by focusing solely on structural performance in order to obtain optimal monolithic (single piece) designs, and then the decomposition into multiple components is considered without changing the base topology (identical to the monolithic design). Single-stage approaches simultaneously attempt to optimize both the base topology and its decomposition. Decomposition is an inherently discrete problem, and as such, non-gradient methods are needed for single-stage and second stage of two-stage approaches. This paper adopts an implicit formulation (level-sets) of the design variables, which significantly reduces the number of design variables needed in either single or two stage approaches. The number of design variables in the formulation is independent from the meshing size, which enables application of non-gradient methods to realistic designs. Test results of a short cantilever and an L-shaped bracket studies show reasonable success of both single and two stage approaches, with each approach having different merits.     

Multi-walled carbon nanotube-reinforced copper nanocomposite coating fabricated by low-pressure cold spray process

Multi-walled carbon nanotube (MWCNT)-reinforced copper (Cu) nanocomposite coatings were successfully deposited on aluminum (Al) substrate by a cold spraying process at a low pressure. The microstructure and the Raman spectrum of the low-pressure-cold-sprayed MWCNT–Cu nanocomposite coating showed that the MWCNTs maintained their tube structure in the Cu matrix, even though structural damage to the MWCNTs increased slightly. MWCNT–Cu nanocomposite-coated Al exhibits higher thermal diffusivity than pure-Cu-coated Al with a comparable hardness. The higher thermal diffusivity of the MWCNT–Cu coating could be explained by the dispersion of MWCNTs within the clean and closed CNT/Cu interfaces, which were achieved with the aid of compressive stress during the cold spraying.     

The Effect of Small Additions of Fe and Heavy Deformation on the Precipitation in an Al–1.1Mg–0.5Cu–0.3Si At. Pct Alloy

Metallurgical and Materials Transactions A - The effect of 0.03 and 0.08 at. pct Fe additions on the formation of secondary phases in an Al–1.1Mg–0.5Cu–0.3Si at. pct alloy was...