Hybrid domain decomposition algorithms for compressible and almost incompressible elasticity

Overlapping Schwarz methods are considered for mixed finite element approximations of linear elasticity, with discontinuous pressure spaces, as well as for compressible elasticity approximated by standard conforming finite elements. The coarse components of the preconditioners are based on spaces, with a number of degrees of freedom per subdomain which are uniformly bounded, which are similar to those previously developed for scalar elliptic problems and domain decomposition methods of iterative substructuring type, i.e. methods based on nonoverlapping decompositions of the domain. The local components of the new preconditioners are based on solvers on a set of overlapping subdomains. In the current study, the dimension of the coarse spaces is smaller than in recently developed algorithms; in the compressible case all independent face degrees of freedom have been eliminated while in the almost incompressible case five out of six are not needed. In many cases, this will result in a reduction of the dimension of the coarse space by about one half compared with that of the algorithm previously considered. In addition, in spite of using overlapping subdomains to define the local components of the preconditioner, values of the residual and the approximate solution need only to be retained on the interface between the subdomains in the iteration of the new hybrid Schwarz algorithm. The use of discontinuous pressures makes it possible to work exclusively with symmetric, positive‐definite problems and the standard preconditioned conjugate gradient method. Bounds are established for the condition number of the preconditioned operators. The bound for the almost incompressible case grows in proportion to the square of the logarithm of the number of degrees of freedom of individual subdomains and the third power of the relative overlap between the overlapping subdomains, and it is independent of the Poisson ratio as well as jumps in the Lamé parameters across the interface between the subdomains. Numerical results illustrate the findings. Copyright © 2009 John Wiley & Sons, Ltd.     

Long-term impact of chronosequential land use change on soil carbon stocks on a Swedish farm

Agricultural practices and land use significantly influence soil carbon storage. The processes that are affected by land use and management are generally understood, but uncertainties in projections are high. In this paper, we investigate the long-term effects of chronosequential land use change from grassland to cropland and vice versa on soil carbon stock dynamics in four fields on a Swedish farm. Between 1850 and 1920, three of the fields were converted from grassland into cropland, and one was converted back to grassland in 1971. The fourth (control) field is a grassland that has never been ploughed. In 1937, the four fields were sampled at 111 points in a regular grid (25 or 50 m) and the dried soil samples were stored at our Department. In 1971 and 2002, the original grid points were revisited and re-sampled. Land use changes affected the soil C stock significantly. In 1937, carbon stocks were significantly smaller in the arable fields than in the grassland soil. In the field that was converted from arable back to grassland, soil C increased significantly at an average rate of about 0.4 Mg ha⁻¹ year⁻¹. A soil C balance model (ICBM) driven by standard meteorological data and soil carbon input estimated from yield records described soil carbon dynamics reasonably well, although the range of simulated relative changes in C stocks between 1937 and 2002 in the four fields (from −7.4 to +8.8%) was narrower than those measured (from −19.5 to +16.5%). There are only few long-term studies in Northern Europe available for quantifying the effect of land use change on soil carbon stocks and the results presented here are therefore useful for improving predictions of changes in soil carbon driven by land use change.     

Prehydrolysis in softwood pulping produces a valuable biorefinery fraction for material utilization

A scaled-up prehydrolysis process was elaborated to demonstrate an industrially feasible operation step in a pulping process that generates a valuable side product in addition to the cellulose pulp. The valuable side product is aqueous process liquor, a softwood hydrolysate (SWH) herein produced in 60 L batches, and its components were recovered and utilized as materials. The process parameters were shown to influence the yield, composition, and quality of the obtained hydrolysates. Furthermore, the process conditions were shown to influence the ability of SWHs to form free-standing, foldable films in blends with either microfibrillated cellulose (MFC) or carboxymethyl cellulose (CMC). Films with oxygen permeabilities (OP) as low as 0.35 cm(3) μm day(-1) m(-2) kPa(-1) at 50% relative humidity, were produced from aqueous solutions providing a viable and green alternative to petroleum-based packaging barriers. The OPs were very low regardless of SWH film composition and upgrading conditions, whereas the films' tensile performance was directly controlled by the ratio of SWH to cocomponent.     

Bioactive properties and clinical safety of a novel milk protein peptide

Background

Inadequate eating behavior and physical inactivity contribute to the current epidemic of childhood obesity. The aim of this study was to assess the association between eating behavior scores and childhood obesity in Chilean children.

Design and methods

We recruited 126 obese, 44 overweight and 124 normal-weight Chilean children (6-12 years-old; both genders) according to the International Obesity Task Force (IOTF) criteria. Eating behavior scores were calculated using the Child Eating Behavior Questionnaire (CEBQ). Factorial analysis in the culturally-adapted questionnaire for Chilean population was used to confirm the original eight-factor structure of CEBQ. The Cronbach's alpha statistic (>0.7 in most subscales) was used to assess internal consistency. Non-parametric methods were used to assess case-control associations.

Results

Eating behavior scores were strongly associated with childhood obesity in Chilean children. Childhood obesity was directly associated with high scores in the subscales "enjoyment of food" (P < 0.0001), "emotional overeating" (P < 0.001) and "food responsiveness" (P < 0.0001). Food-avoidant subscales "satiety responsiveness" and "slowness in eating" were inversely associated with childhood obesity (P < 0.001). There was a graded relation between the magnitude of these eating behavior scores across groups of normal-weight, overweight and obesity groups.

Conclusion

Our study shows a strong and graded association between specific eating behavior scores and childhood obesity in Chile.     

Structural,mechanical and electrical-contact properties of nanocrystalline-NbC/amorphous-C coatings deposited by magnetron sputtering

Niobium-carbide nanocomposite coatings with a carbon content varying from 43 to 64 at.% were deposited by dual DC magnetron sputtering. X-ray diffraction, x-ray photoelectron spectroscopy and electron microscopy showed that all coatings consisted of nanometer sized NbC grains embedded in a matrix of amorphous carbon. Mechanical properties and electrical resistivity showed a strong dependency on the amount of amorphous carbon (a-C) and NbC grain size in the coating. The highest hardness (23 GPa), elastic modulus (295 GPa) and the lowest resistivity (260 μΩ cm) were measured for the coating with about 15% of a-C phase. Contact resistance measurements using a crossed cylinder set-up showed lowest contact resistance for the coating containing 33% a-C (140 μΩ at a contact force of 100 N), which is comparable to a Ag reference (45 μΩ at a contact force of 100 N). Comparison with TiC-based nanocomposites studied under similar conditions showed that the NbC system has less tendency to form a-C and that lowest contact resistance is obtained at comparable amounts of a-C phase in both material systems (33% for NbC compared to 35% for TiC). With these good electrical contact properties, the NbC nanocomposites can be considered as a potential material for electrical contact applications.     

Quinones As Additives During Soda Cooking

Anthraquinone-1-acetic acid is a less effective delignification catalyst than anthraquinone but it gives an enhanced carbohydrate stabilization by converting reducing sugar end groups more effectively to aldonic acid end groups. This reaction produces the hydroquinone form of the additive which is then easily oxidized by oxygen at 80°C. Oxygen treatment favors the end group stabilization. Depolymerization of the cellulose is suppressed by the presence of magnesium hydroxide but cannot be avoided completely.     

Structure,thermal, and mechanical properties of DDM‐hardened epoxy/benzoxazine hybrids: Effects of epoxy resin functionality and ETBN toughening

Bifunctional, trifunctional, and tetrafunctional epoxy (EP) resins were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was constant, viz. 50/50 wt %. For the bifunctional EP, the EP/BOX range covered the ratios 75/25 and 25/75 wt %, as well. Epoxy‐terminated liquid nitrile rubber (ETBN) was incorporated in 10 wt % in the systems with trifunctional and tetrafunctional EP, and in 10, 15, and 20 wt % in the EP/BOX with bifunctional EP to improve their toughness. Information on the structure and morphology of the hybrid systems was received from differential scanning calorimetric, dynamic‐mechanical thermal analysis, atomic force microscopic, and scanning electron microscopic studies. The flexural, fracture mechanical properties, thermal degradation, and fire resistance of the EP/BOX and EP/BOX/ETBN hybrids were determined. It was found that some homopolymerized BOX was built in the EP/BOX conetwork in form of nanoscale inclusions, whereas ETBN formed micron scaled droplets of sea‐island structure. Incorporation of BOX improved the charring and fire resistance, enhanced the flexural modulus and strength, reduced the glass transition (T_g), the fracture toughness, and energy. Additional modification with ETBN decreased the charring, fire resistance, flexural modulus and strength, as well as T_g, however, improved the fracture toughness and especially the fracture energy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Behavior Of Calcium,Magnesium and Manganese Compounds During Oxygen Bleaching of Kraft Pulps

During oxygen bleaching of kraft pulps manganese compounds can, depending on their amounts, the charges of sodium hydroxide and of magnesium protector, and on the presence of trace amounts of catalytically active transition metals retard or promote the depolymerization of the cellulose. The present report deals with pulps pretreated with 2 % nitrogen dioxide. As shown in forthcoming papers similar results were obtained with pulps without pretreatment with nitrogen compounds.

Pretreatment with nitrogen dioxide at 80°C followed by washing with water removed about 95 % of the magnesium and manganese from kraft pulps. Subsequent oxygen bleaching for 180 min removed 40–90 % of the calcium remaining in the pretreated pulps. Produced hydroxycarboxylate ions gave rise to low molecular complexes of calcium and of magnesium, added as protector. Competition for complexing ligands contributed to a decreased dissolution of calcium with increasing addition of magnesium. When magnesium was applied large amounts of colloids of polynuclear magnesium species were produced. These contained lignin fragments and less abundant metal compounds such as manganese and calcium.

Wet oxidation of both low molecular complexing agents and of organic fragments of larger size contributed to a decreased or unchanged concentration of low molecular metal complexes and metal compounds linked to the colloids with hydrated magnesium oxide as the main constituent. The conditions which favored the wet oxidation were similar to those which led to an increased attack on the lignin and carbohydrates in the fibers and thus promoted the dissolution of low molecular metal complexes and the formation of metal ions containing colloids. Under certain conditions precipitation of sparingly soluble manganese compounds of oxidation states higher than +2 had a predominant influence on the concentration of manganese in the liquor.     

Regional Innovation Measured by Patent Data—Does Quality Matter?

This paper devises a new way of measuring the geographical scope of innovation based on patent data and compares its geographical distribution with that of patents granted and production. Indicators of patent quality are used to form an index of regional innovation, which is argued to be an improvement over patent counts, which are seen as indicators of inventions. Innovations are more concentrated than inventions, which in turn are more concentrated than production, gauged by employment levels. Innovations are, moreover, concentrated to regions with already high production and invention levels. This indicates that the concentration of innovation is understated, as raw patent counts are used to proxy for innovation rather than quality patents. The results further point to the need for revaluing effect of R&D on local innovative activity.