Correlation-based method for comparing and reconstructing nearly identical two-dimensional structures

A method for comparing and reconstructing two nearly identical planar objects that are composed of the same number of identical apertures is presented. These structures differ only in the location of one of the apertures. The method is based on a subtraction algorithm, which involves the cross-correlation and autocorrelation functions of the compared structures. Simulated results illustrate the feasibility of the method.     

A comprehensive skeletal mechanism for the oxidation of n-heptane generated by chemistry-guided reduction

Applied to the primary reference fuel n-heptane, we present the chemistry-guided reduction (CGR) formalism for generating kinetic hydrocarbon oxidation models. The approach is based on chemical lumping and species removal with the necessity analysis method, a combined reaction flow and sensitivity analysis. Independent of the fuel size, the CGR formalism generates very compact submodels for the alkane low-temperature oxidation and provides a general concept for the development of compact oxidation models for large model fuel components such as n-decane and n-tetradecane. A defined sequence of simplification steps, consisting of the compilation of a compact detailed chemical model, the application of linear chemical lumping, and finally species removal based on species necessity values, allows a significantly increased degree of reduction compared to the simple application of the necessity analysis, previously published species, or reaction removal methods. The skeletal model derived by this procedure consists of 110 species and 1170 forward and backward reactions and is validated against the full range of combustion conditions including low and high temperatures, fuel-lean and fuel-rich mixtures, pressures between 1 and 40 bar, and local (species concentration profiles in flames, plug flow and jet-stirred reactors, and reaction sensitivity coefficients) and global parameters (ignition delay times in shock tube experiments, ignition timing in a HCCI engine, and flame speeds). The species removal is based on calculations using a minimum number of parameter configurations, but complemented by a very broad parameter variation in the process of compiling the kinetic input data. We further demonstrate that the inclusion of sensitivity coefficients in the validation process allows efficient control of the reduction process. Additionally, a compact high-temperature n-heptane oxidation model of 47 species and 468 reactions was generated by the application of necessity analysis to the skeletal mechanism.     

The fluidized-bed catalytic cracking unit building its future environment

Fluidized-bed catalytic cracking (FCC) has been considered as one of the largest catalytic process in the world. FCC is the name for a complex process unit that cracks long molecules from gas oils and residua into added value shorter fuel compounds; additionally, this process can be used to produce important petrochemical precursors, such as propylenes. Although historically FCC has been used to optimise production of light cycle oils, gasoline and olefins, nowadays is convenient to revisit its mission. In order to integrate FCC process inside current development and environment respect, it is necessary to see it as a very flexible process. This flexibility will require deeper knowledge about environmental impact of process operation and production objectives, transport phenomena and catalytic reactions taking place inside the riser, the main reactor of the FCC converter, and energy balance integrating energy recovered/generated in the regenerator. This work is devoted to briefly review some propositions about the use of FCC converters and how these aspects demand knowledge of riser reactors, change in the methodology to estimate effective reaction rates (consequence of variation of kinetic and transport phenomena, at catalyst scale and along the riser) and catalyst activity, as well as control actions and its effect on the energy balance of the converter; operation and environmental concerns surrounding this process are addressed. Finally, it tries to draw attention on some facts that need to be analysed in order to ensure the sustainable development of this important process in the short future.     

Nominal energy optimisation method of constrained battery packs through the iteration of the series‐parallel topology

The design of a battery pack commonly deals with high performance goals and challenging constraints in terms of cost, volume or weight. One of the most crucial variables to maximise is the nominal energy, which depends on the number of discrete battery cells that can be allocated and their individual technical specifications. This work proposes a systematic method to optimise the nominal energy of a constrained battery pack from the perspective of the series‐parallel topology. A mathematical and graphical characterisation is presented on how the main battery's variables are related to a topology bounded to discretisation procedures. It was theoretically found that the effects of rounding the values of the topology may lead to a considerable loss of potential nominal energy, a risk that increases linearly with the number of series. The behaviour of the battery is assessed under nominal conditions and under the event of a cell failure. The theoretical analysis suggests that the detrimental effects due to an open‐circuit increase as the number of series increases, while it is the opposite in the case of a shorted cell. The method is satisfactorily implemented in the development of two different battery packs for solar competition cars with limiting regulations. The candidate topologies outperformed the nominal energy of topologies defined without the method in up to 5%. It was also found that selecting an energy‐maximising topology is not always the most convenient choice, because other variables may be of interest and are dependent on the topology as well. The method is of great use to guide the topology definition process in early theoretical stages, which is usually a compromise between allocating as much cells as possible within constraints, and approaching other performance goals such as a given nominal voltage or capacity. Copyright © 2017 John Wiley & Sons, Ltd.     

Natural carbonation of aged alkali-activated slag concretes

Alkali-activated slag concretes stored for 7 years under atmospheric conditions are assessed, and the structural characteristics of naturally carbonated regions are determined. Concretes formulated with a 400 kg/m³ and water/binder (w/b) ratio between 0.42 and 0.48 present similar natural carbonation depths, although these concretes report different permeabilities after 28 days of curing. The inclusion of increased contents of binder leads to a substantial reduction of the CO₂ penetration in these concretes, so that negligible carbonation depth values (2 mm) are identified in concretes formulated with 500 kg/m³ of binder. Calcite, vaterite, and natron are identified as the main carbonation products formed in these concretes. These observations differ from the trends which would be expected in comparable ordinary Portland cement-based concretes, which is attributable to the physical (permeability) and chemical properties of alkali-activated slag concretes promoting high long-term stability and acceptably slow carbonation progress under natural atmospheric conditions.     

Hard-to-cook phenomenon in beans: Changes in antinutrient factors and nitrogenous compounds during storage

Five different bean varieties (Phaseolus vulgaris) from Kenya, which were either freshly collected or stored for 5 years in tropical conditions (30–40°C; >75% humidity), were compared for their cooking characteristics. The beans under storage develop an irreversible phenomenon classified as ‘hard-to-cook’ (HTC) which results in undesirable characteristics limiting their acceptability. Our aims were to determine the effects of the HTC phenomenon on the proteins and antinutrient factors in these beans. Both fresh and HTC beans contained nutritionally significant amounts of lectins, trypsin and α-amylase inhibitors. HTC samples had higher lectin and lower α-amylase inhibitor contents, while the amounts of trypsin and chymotrypsin inhibitors were the same. Storage appeared to reduce water-extractable nitrogen. Fractionation with sodium dodecyl sulphate also showed that less protein may be available in HTC than fresh beans. We established that the undesirable changes in beans, such as increased cooking time, which often accompany the storage of harvested seeds under tropical conditions produce an overall decrease in soluble-N fractions, particularly proteins. The results can provide guidelines on how to utilise these seed(s) and their products. Furthermore, appropriate processing is needed to reduce their antinutrients for human nutrition.     

Effects of lead-arsenic combined exposure on central monoaminergic systems

Lead acetate (116 mg/kg/day), arsenic (11 or 13.8 mg/kg/day as sodium arsenite), a lead-arsenic mixture or vehicle were administered to adult mice through gastric intubation during 14 days. Then, the regional content of norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4 dihydroxyphenyl-acetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA), arsenic, and lead were quantified. Compared with the accumulation after single element exposures, the mixture elicited a higher accumulation of lead and a lower arsenic accumulation in the brain. Compared to controls, lead induced only an augmentation of DOPAC (200%) in the hypothalamus. By contrast, the mixture provoked increases of DOPAC in the hypothalamus (250%), DA and 5-HIAA in the striatum (67 and 187%, respectively) and NE decreased in the hypothalamus (45%). Although these alterations were similar to those produced by arsenic alone, the mixture provoked a 38% decrease of NE in the hippocampus and increases of 5-HT in midbrain and frontal cortex (100 and 90%, respectively) over control values, alterations that were not elicited by either metal alone. These results demonstrate an interaction arsenic/lead on the central monoaminergic systems of the adult mouse.