A hybrid MPI–OpenMP scheme for scalable parallel pseudospectral computations for fluid turbulence

A hybrid scheme that utilizes MPI for distributed memory parallelism and OpenMP for shared memory parallelism is presented. The work is motivated by the desire to achieve exceptionally high Reynolds numbers in pseudospectral computations of fluid turbulence on emerging petascale, high core-count, massively parallel processing systems. The hybrid implementation derives from and augments a well-tested scalable MPI-parallelized pseudospectral code. The hybrid paradigm leads to a new picture for the domain decomposition of the pseudospectral grids, which is helpful in understanding, among other things, the 3D transpose of the global data that is necessary for the parallel fast Fourier transforms that are the central component of the numerical discretizations. Details of the hybrid implementation are provided, and performance tests illustrate the utility of the method. It is shown that the hybrid scheme achieves good scalability up to ～20,000 compute cores with a maximum efficiency of 89%, and a mean of 79%. Data are presented that help guide the choice of the optimal number of MPI tasks and OpenMP threads in order to maximize code performance on two different platforms.     

Reconfiguration on nanocrossbar using material implication

Reconfigurable architectures (FPGA) with embedded memory elements face problems in retaining data for longer duration due to leakage current as it becomes dominant in nanometer devices in conventional technologies. Also, LUT-based designs consume more area, are slow in processing data and dissipate more power because of complex interconnection network. Memristor, a new nonvolatile memory element, can be used to overcome these limitations. In this paper, we propose an implication-NOR logic-gate-based FPGA architecture using memristors for implementation of logic functions and with embedded memory for storing data. The automation algorithm for the same is presented.     

Failure Analysis of Cracks Formed at Extrados of Bend Pipe of API 5L X65M Grade

A metallurgical and root cause analysis was performed on hot induction bent pipes that exhibited cracking at the extrados. The bent pipe of 1016 mm (40 in.) diameter by 18.5 mm wall thickness was API 5L X65 PSL2 line pipe containing a longitudinal submerged arc weld. A metallurgical cross section was removed at a crack on the bent pipe extrados to document the crack morphology using optical microscopy. In addition to the cracking, golden-yellow streaks were visible at the extrados of the bent pipe. The composition of the streaks was examined using scanning electron microscopy with energy dispersive spectroscopy.     

Platinum–Dendrimer Nanocomposite Films on Gold Surfaces for Electrocatalysis

In this communication, we report a strategy for the preparation of Pt nanoparticles encapsulated in Generation 4.5 (Polyamido amine) PAMAM dendrimer and subsequent chemical linking of the nanocomposite to the gold electrode through a self assembled cystamine monolayer. The modification resulted in the formation of a robust electrochemically active thin film with very high surface area, reflected by the enhanced hydrogen adsorption coverage. Interestingly, TEM images revealed self-assembly of Pt nanoparticles and the SAED (Selected Area Electron Diffraction) patterns showed the presence of Pt single crystals (111). The Pt-dendrimer nanocomposite film obtained using the novel modification procedure exhibited high electrocatalytic activity for the oxidation of organic fuels like methanol, ethanol and ethylene glycol. The film did not suffer from degradation even after repeated use in solution-phase voltammetry. It is however observed that the intermediate SAM layer and the bulky PAMAM dendrimer (generation 4.5) have slowed down the electron transfer kinetics which is reflected by a relatively high overpotential for methanol oxidation. Nevertheless this shortcoming is more than compensated by the existence of Pt(111) planes, which alleviate CO poisoning.     

Geometry‐driven Visualization of Microscopic Structures in Biology

At a microscopic resolution, biological structures are composed of cells, red blood corpuscles (RBCs), cytoplasm and other microstructural components. There is a natural pattern in terms of distribution, arrangement and packing density of these components in biological organization. In this work, we propose to use N‐point correlation functions to guide the analysis and exploration process in microscopic datasets. These functions provide useful feature spaces to aid segmentation and visualization tasks. We show 3D visualizations of mouse placenta tissue layers and mouse mammary ducts as well as 2D segmentation/tracking of clonal populations. Further confidence in our results stems from validation studies that were performed with manual ground‐truth for segmentation.     

Evaluation of enzyme-assisted extraction on quality of garlic volatile oil

Application of enzymes to garlic prior to steam distillation/hydrodistillation resulted in a two fold increase in the yield of oil. The oil yield in case of cellulase, pectinase, protease and viscozyme pretreatment was in the range of 0.39–0.51%, as against 0.28% in a control sample by steam distillation, and in the range of 0.45–0.57% by hydrodistillation as against 0.31% in a control sample. Profiling of the garlic oil thus obtained was carried out by GC–MS. Di-2-propenyl trisulfide (52%) along with the corresponding di- and tetra-sulphides (11% and 5%) constituted the major portion of the oil. The other major flavour compounds identified were methyl 2-propenyl trisulfide (11.8%), vinyl dithiins (9.9%) and dithianes (4.1%). The studies demonstrate that enzymes facilitate the extraction of garlic oil, resulting in an increase in the yield of oil, with little change either in flavour profile or physicochemical properties of the oil.     

An investigation on room temperature synthesis of vertically oriented arrays of iron oxide nanotubes by anodization of iron

Formation of iron oxide nanotubes on to pure iron substrate by an electrochemical anodization method was investigated in fluoride containing electrolytes. Anodization of iron foil in fluoride containing borate solution resulted in stacked nano-ring type oxide morphology. Nanoporous oxide layer was observed at low pH and a granular oxide layer was formed at higher pH of phosphate + fluoride solutions. Formation of either nanoporous or nanotubular oxide layer was observed in ethylene glycol (EG) solution containing 0.05-0.1 M fluoride + 1.5-3.0 vol.% water. Transition from nanoporous structure to nanotubular structure was critically controlled by anodization potential, water addition and fluoride concentration of the EG solution. The potential required for this transition decreased with increase in the water content up to 7 vol.% beyond which enhanced dissolution occurred. Annealing of the nanotubes at 500 °C resulted in predominantly α-Fe₂O₃ crystal structure. The annealed Fe₂O₃ samples consisting of a single layer of nanotubular structure showed a photo current density of 0.4 mA/cm² at 0.5 V Ag/AgCl in 1 M KOH solution under simulated solar light illumination.     

Physicochemical characterization of poly(ethylene glycol) plasticized poly(methyl vinyl ether‐co‐maleic acid) films

The influence of the poly(ethylene glycol) (PEG) plasticizer content and molecular weight on the physicochemical properties of films cast from aqueous blends of poly(methyl vinyl ether‐co‐maleic acid) (PMVE/MA) was investigated with tensile mechanical testing, thermal analysis, and attenuated total reflectance/Fourier transform infrared spectroscopy. Unplasticized films and those containing high copolymer contents were very difficult to handle and proved difficult to test. PEG with a molecular weight of 200 Da was the most efficient plasticizer. However, films cast from aqueous blends containing 10% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 4 : 3 and those cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 2 : 1 possessed mechanical properties most closely mimicking those of a formulation we have used clinically in photodynamic therapy. Importantly, we found previously that films cast from aqueous blends containing 10% (w/w) PMVE/MA performed rather poorly in the clinical setting, where uptake of moisture from patients' skin led to reversion of the formulation to a thick gel. Consequently, we are now investigating films cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000, where the copolymer/plasticizer ratio is 2 : 1, as possible Food and Drug Administration approved replacements for our current formulation, which must currently be used only on a named patient basis as its plasticizer, tripropylene glycol methyl ether, is not currently available in pharmaceutical grade. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A Survey of Tables of Probability Distributions

This article is a survey of the tables of probability distributions published about or after the publication in 1964 of the Handbook of Mathematical Functions, edited by Abramowitz and Stegun     

Evaluation of fatigue damage in materials using indentation testing and infrared thermography

Damage identification due to fatigue has been studied on 304-Stainless Steel and Al-Cu-Mg alloys 2014-T651 and 7175-T7351, using two different experimental methods: a) cyclic indentation, and b) infrared thermography. Indentation response during load controlled cyclic loading is used to characterize fatigue response of materials. The load vs. depth of penetration data obtained continuously during fatigue testing is used to obtain information on cyclic stress-strain behavior and onset of failure. Infrared thermography is used to study the heat generation during fatigue loading on specimens. The variables that affect the process are: frequency of loading, magnitude of strain (elastic-plastic), thermal properties. The temperature curve can be considered to be having three regions, initial region of rapid increase in temperature, followed by stable temperature rise and final rapid heat generation prior to failure. The slopes in the initial region and stable region are independent of prior damage history in materials in case of specimens subjected to pure elastic load reversals. In case of elastic-plastic loadings, the rate at which the temperature rises in initial region changes as a function of fatigue damage and can thus be used to estimate prior damage in materials.