Upstream monotonic interpolation for scalar transport with application to complex turbulent flows

A new monotonic scheme for the approximation of steady scalar transport is formulated and implemented within a collocated finite-volume/pressure-correction algorithm for general turbulent flows in complex geometries. The scheme is essentially a monotonic implementation of the quadratic QUICK interpolation and uses a continuous and compact limiter to secure monotonicity. The principal purpose is to allow an accurate and fully bounded, hence stable, approximation of turbulence convection in the context of two-equation eddy viscosity and Reynolds stress transport modelling of two- and three-dimensional flows, both subsonic and transonic. Among other benefits, this capability permits an assessment to be made of the adequacy of approximating turbulence convection with first-order upwind schemes in conjunction with higher-order formulations for mean-flow properties—a widespread practice. The performance characteristics of the bounded scheme are illustrated by reference to computations for scalar transport, for a transonic flow in a Laval nozzle, for one separated laminar flow and for two separated turbulent flows computed with a non-linear RNG model and full Reynolds stress closure.     

Radionuclide mobility and bioavailability in Norwegian and Soviet soils.

A sequential extraction procedure has been applied to study the speciation of Chernobyl-derived radionuclides (137Cs and 90Sr) in soils from Norway, and from Byelorussia and the Chernobyl region in the USSR. Most 137Cs (greater than 80%) was strongly associated with soil components, whereas 90Sr was more mobile, up to 70% being found in the easily extractable fractions. The 90Sr: 137Cs ratio decreased with the distance from the reactor, reflecting the higher proportion of hot particles deposited in the regions close to the reactor, and the easily extractable fraction of 90Sr was significantly lower in the soils collected from the Chernobyl area. The distribution of stable Cs and stable Sr in the extraction fractions was similar for the various sites. Therefore, the location-specific differences in the distribution of 90Sr and, to a lesser extent, 137Cs arise because of fallout speciation rather than because of local environmental factors.     

Towards a Unified Turbulence Simulation Approach for Wall-Bounded Flows

A hybrid Reynolds-averaged Navier–Stokes/Large-Eddy Simulation (RANS/LES) methodology has received considerable attention in recent years, especially in its application to wall-bounded flows at high-Reynolds numbers. In the conventional zonal hybrid approach, eddy-viscosity-type RANS and subgrid scale models are applied in the RANS and LES zones, respectively. In contrast, the non-zonal hybrid approach uses only a generalized turbulence model, which provides a unified simulation approach that spans the continuous spectrum of modeling/simulation schemes from RANS to LES. A particular realization of the non-zonal approach, known as partially resolved numerical simulation (PRNS), uses a generalized turbulence model obtained from a rescaling of a conventional RANS model through the introduction of a resolution control function F _R , where F _R is used to characterize the degree of modeling required to represent the unresolved scales of turbulent motion. A new generalized functional form for F _R in PRNS is proposed in this study, and its performance is compared with unsteady RANS (URANS) and LES computations for attached and separated wall-bounded turbulent flows. It is demonstrated that PRNS behaves similarly to LES, but outperforms URANS in general.     

An efficient and green synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines using highly active and stable poly acrylic acid-supported layered double hydroxides

A facile and efficient method for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines has been achieved via highly active and reusable heterogeneous poly acrylic acid-supported layered double hydroxides (PAA-g-LDHs) catalyst promoted one-pot reaction of 1H-benzo[d]imidazol-2-amine, with α,β-unsaturated carbonyl compounds under solvent-free conditions. PAA-g-LDHs catalyst was successfully synthesized via reversible addition-fragmentation chain-transfer polymerization using grafting reaction and was characterized by different analytical techniques. The significant features of this reaction include expedient one-pot process, short reaction time, excellent yields, wide substrate scope and operational simplicity. Also, the catalyst could be reused for several consecutive runs without any apparent loss in its catalytic activity.     

Mechanochromic and vapochromic fluorescence of a bulky π-system: Alkyl chain-length effects,triplex emission,and differential sensing of aniline vapors

The interplay of mechanical grinding and aniline vapor fuming on the fluorescence of the pentiptycene-anthracene-pentiptycene π-conjugated molecules PAP-Cn, where n is 4, 8, 12, or 16 and refers to the number of carbon atom in the terminal alkyl chains, in solid films are reported. The differences and similarities among the four homologs have led to a conclusion of the formation of an emissive triplex state for the ground and fumed films. Thermogravimetric analysis reveals the guest-host molar ratio and the retention ability of the aniline on the various types of films. A stepwise protocol of fuming-grinding-annealing is developed for fluorimetric differential sensing of eight substituted aniline vapors with a single probe of PAP-C8. The role of the bulky pentiptycene groups in the observed fluorescence properties is also discussed.     

Mesoporous Nickel Electrode for the Detection of Alcohol

Mesoporous nickel electrodes have been shown to be excellent amperometric sensors for alcohol detection over a wide‐range of concentrations. At a higher electrolyte concentrations (NaOH, 4 M), the electrodes exhibited a remarkably higher sensitivity (1072.7 μA mM^?1 cm^?2) than conventional nickel based electrodes, within an alcohol concentration range 0.5–3 M. Additionally, electrodeposited Ni electrodes formed with Brij 56 as a template, have significantly higher roughness than similar electrodes made without template. Higher roughness factors correlated with higher sensitivities for alcohol sensing, but needed longer times to remove the template from the Ni film.     

Pure white‐light‐emitting diodes from phosphorescent single polymer systems

New white polymeric light‐emitting diodes from phosphorescent single polymer systems have been developed using a blue‐light‐emitting fluorene monomer copolymerized with a red‐light‐emitting phosphorescent dye, and end‐capped with a green‐light‐emission dye. All of the copolymers have good thermal stability with 5% weight loss temperatures at 380–413 °C and glass transition temperatures at 75–137 °C. We obtained white‐light‐emission devices by adjusting the molar ratio of the comonomers with a structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid)/polyvinylcarbazole (PVK)/emission layer/Ca/Ag. The highest brightness in such a device configuration is 300 cd/m² at a current density of 2900 A/m² with high white color quality (Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.34)). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 464–472, 2008     

Tracking error decision rules and accumulated wealth

There is compelling evidence that typical decision‐makers, including individual investors and even professional money managers, care about the difference between their portfolio returns and a reference point, or benchmark return. In the context of financial markets, likely benchmarks against which investors compare their own returns include easy‐to‐focus‐on numbers such as one's own past payoffs, historical average payoffs, and the payoffs of competitors. Referring to the gap between one's current portfolio return and the benchmark return as ‘tracking error’, this paper develops a simple model to study the consequences and possible origins of investors who use expected tracking error to guide their portfolio decisions, referred to as ‘tracking error types’. In particular, this paper analyses the level of risk‐taking and accumulated wealth of tracking error types using standard mean‐variance investors as a comparison group. The behaviour of these two types are studied first in isolation, and then in an equilibrium model. Simple analytic results together with statistics summarizing simulated wealth accumulations point to the conclusion that tracking error—whether it is interpreted as reflecting inertia, habituation, or a propensity to make social comparisons in evaluating one's own performance—leads to greater risk‐taking and greater shares of accumulated wealth. This result holds even though the two types are calibrated to be identically risk‐averse when expected tracking error equals zero. In the equilibrium model, increased aggregate levels of risk‐taking reduce the returns on risk. Therefore, the net social effect of tracking‐error‐induced risk‐taking is potentially ambiguous. This paper shows, however, that tracking error promotes a pattern of specialization that helps the economy move towards the path of maximum accumulated wealth.     

Total weight choosability of graphs

A graph G = (V, E) is called (k, k′)‐total weight choosable if the following holds: For any total list assignment L which assigns to each vertex x a set L(x) of k real numbers, and assigns to each edge e a set L(e) of k′ real numbers, there is a mapping f: V∪E→? such that f(y)∈L(y) for any y∈V∪Eand for any two adjacent vertices x, x′, . We conjecture that every graph is (2, 2)‐total weight choosable and every graph without isolated edges is (1, 3)‐total weight choosable. It follows from results in [7] that complete graphs, complete bipartite graphs, trees other than K₂ are (1, 3)‐total weight choosable. Also a graph G obtained from an arbitrary graph H by subdividing each edge with at least three vertices is (1, 3)‐total weight choosable. This article proves that complete graphs, trees, generalized theta graphs are (2, 2)‐total weight choosable. We also prove that for any graph H, a graph G obtained from H by subdividing each edge with at least two vertices is (2, 2)‐total weight choosable as well as (1, 3)‐total weight choosable. © 2010 Wiley Periodicals, Inc. J Graph Theory 66:198‐212, 2011