Optimizing the periodic pick-up of raw materials for a manufacturer of auto parts

We describe a solution procedure for a special case of the periodic vehicle routing problem (PVRP). Operation managers at an auto parts manufacturer in the north of Spain described the optimization problem to the authors. The manufacturer must pick up parts (raw material) from geographically dispersed locations. The parts are picked up periodically at scheduled times. The problem consists of assigning a pickup schedule to each of its supplier’s locations and also establishing daily routes in order to minimize total transportation costs. The time horizon under consideration may be as long as 90 days. The resulting PVRP is such that the critical decision is the assignment of locations to schedules, because once this is done, the daily routing of vehicles is relatively straightforward. Through extensive computational experiments, we show that the metaheuristic procedure described in this paper is capable of finding high-quality solutions within a reasonable amount of computer time. Our main contribution is the development of a procedure that is more effective at handling PVRP instances with long planning horizons when compared to those proposed in the literature.     

On the Hahn-Banach Theorem in Certain Linear Quasi-uniform Structures

A Hahn-Banach type theorem in the frame of quasi-normed spaces (a class of linear spaces with a quasi-uniform structure that contains all linear lattices) is given. The classical result for positive functionals follows as a particular case.     

Effect of 1-octanethiol as an electrolyte additive on the performance of the iron-air battery electrodes

It has recently been established that 1-octanethiol in the electrolyte can allow iron electrodes to be discharged at higher rates. However, the effect of thiol additives on the air electrode has not yet been studied. The effect of solvated thiols on the surface positive electrode reaction is of prime importance if these are to be used in an iron-air battery. This work shows that the air-electrode catalyst is poisoned by the presence of octanethiol, with the oxygen reduction overpotential at the air electrode increasing with time of exposure to the solution and increased 1-octanethiol concentration in the range 0–0.1 mol dm⁻³. Post-mortem XPS analyses were performed over the used air electrodes suggesting the adsorption of sulphur species over the catalyst surface, reducing its performance. Therefore, although sulphur-based additives may be suitable for nickel-iron batteries, they are not recommended for iron-air batteries except in concentrations well below 10 × 10⁻³ mol dm⁻³.

Graphical abstract

     

Surface effects on the diagnostic of carbon/nitrogen low‐pressure plasmas studied by differentially pumped mass spectrometry

In this work, the characterization of the species produced in reactive plasmas by differentially pumped mass spectrometry is addressed. A H₂/CH₄/N₂ mixture (90 : 5 : 5) was fed into a direct current glow discharge and analysed by conventional and cryo‐trap assisted mass spectrometry. The gaseous mixture was chosen because of its particular relevance in the inhibition of tritium‐rich carbon film deposition in fusion plasmas (scavenger technique) and in the deposition of amorphous hydrogenated carbon films by plasma‐assisted chemical vapour deposition. Important changes in the composition of the detected species upon surface modification of the reactor walls (stainless steel or covered by an amorphous hydrogenated carbon layer) or in the way they are sampled (length and spatial configuration of the stainless steel duct) were detected. They are analysed in terms of radical formation and recombination on the reactor walls or into the sampling duct, thus providing some insight into the underlying chemistry. In general, when the reactor walls are covered by an amorphous hydrogenated carbon layer, more hydrocarbons are produced, but the radical production is lower and seem to be less reactive than in stainless steel. Also, two sources of oxygen contamination in the plasma have been identified, from the native oxide layer in stainless steel and from unintended water contamination in the chamber, which modify considerably the detected species. Copyright © 2014 John Wiley & Sons, Ltd.     

The first contribution of capillary electrophoresis to the study of abiotic origins of homochirality: investigation of the enantioselective adsorption of 3-carboxy adipic acid on minerals

CE with UV detection was used for the first time to determine the enantioselective adsorption of the short-chain tricarboxylic acid, 3-carboxy adipic acid, on minerals as a mean of investigating plausible mechanisms for the origin of biochemical homochirality on Earth. The use of vancomycine as chiral selector in the separation buffer using the partial filling technique enabled the separation of the two enantiomers of this organic acid in about 12 min. Taking into account that this compound has a low absorption of the UV light, and in order to achieve the sensitivity needed to determine the enantiomeric excess of samples of 3-carboxy adipic acid adsorbed on minerals, we applied a strategy consisting of a field-amplified sample stacking together with the use of a bubble capillary and detection at low wavelength (192 nm). This combination enabled an LOD of about 10(-7) M and the determination of the enantiomeric excess of 3-carboxy adipic acid adsorbed on calcite and feldspar mineral samples at subnanomol levels of this acid. Results showed that an enantioselective adsorption of the enantiomers of 3-carboxy adipic acid on minerals took place.     

The game of futsal as an adaptive process

Some researchers have described team sports as complex, open, and hierarchical systems. This study aimed to investigate and describe how the game of futsal could be characterized as a dynamic adaptive process. One game, which included participation by two amateur teams, was analyzed by examining players' individual (space occupied, skills with and without ball) and collective actions (attacks and defenses). Data were collected through time-continuum notation, and were analyzed through frequencies and clustering, using trend analysis and multiple comparisons, and Ward's minimum variance method with Euclidean distance, respectively. Results revealed four attack patterns for each team, with four defense patterns for one (Blue), and seven for the other (Red), and they showed within-pattern variability. All were performed in an unpredictable manner, with no absolute correspondence between attacks and defenses. The futsal game as an adaptive process was characterized by changing intra- and inter-patterns.     

Major and trace element assessment of Tietê river sediments, São Paulo, Brazil

The objective of this study was to quantify major and trace elements present in sediments collected from the one of Brazil’s most important rivers, Tietê River. Sediments from 5 different sampling points (P₀–P₄), in 3 campaigns (2008/2009), from the headwaters to Suzano County upstream from São Paulo city were collected. X-ray fluorescence was applied for measuring total concentration of major elements and instrumental neutron activation analysis (INAA) for trace elements. The elements Cd, Hg and Pb were determined by atomic absorption spectrometry after digestion using the US EPA 3,051 procedure. These metal concentrations were compared to the PEL and TEL oriented values from CCME. The sampling sites P₃ and P₄, near industrialized areas, showed the highest concentrations for potentially bioavailable metals, mainly Pb and Hg. The results obtained by INAA were compared to upper continental crust values. A strong enrichment was found for the elements As, Br, Sb, Th, U and Zn. These results evidenced contamination by industrial effluents and sewage even relatively close to the Tietê River headwaters. The worst biological effects (acute toxicity) on benthonic organism Hyalella azteca were also observed at P₃ and P₄.     

Analysis of the Influence of the Thickness and the Hole Radius on the Calibration Coefficients in the Hole-Drilling Method for the Determination of Non-uniform Residual Stresses

Experimental Mechanics - The Hole-Drilling method is a semi-destructive technique useful for obtaining residual stress distributions by drilling and measuring relieved strains. The standard for...     

Correction to: Analysis of the Influence of the Thickness and the Hole Radius on the Calibration Coefficients in the Hole-Drilling Method for the Determination of Non-uniform Residual Stresses

Experimental Mechanics - Due to an error introduced during the production process, Fig. 11 appeared incorrectly in the original publication of this article. It appears correctly here.     

On a class of real normed lattices

We say that a real normed lattice is quasi-Baire if the intersection of each sequence of monotonic open dense sets is dense. An example of a Baire-convex space, due to M. Valdivia, which is not quasi-Baire is given. We obtain that E is a quasi-Baire space iff is a pairwise Baire bitopological space, where , is a quasi-uniformity that determines, in L. Nachbin's sense, the topological ordered space E.