A review of manufacturing flexibility: systematising the concept

The present work is an attempt to contribute to the conceptual systematisation of the manufacturing flexibility types by synthesising the vast literature available after a systematic review. We classified the papers in two perspectives (hierarchical and strategic), and engaged in a systematic process of standardisation of the definitions and names of various flexibility types leading to a better understanding of them. This process allowed us to clearly show: (a) the existence of a broader consensus in the field than expected; (b) that problems are limited to concrete aspects related to the level of analysis or the scope of certain flexibility types; (c) the possibility of a theoretical integration between the two perspectives which would permit a standardisation of the names and definitions for the flexibility types which make up the manufacturing flexibility construct.     

Hydroxyapatite growth on cotton fibers modified chemically

We have prepared carboxymethyl cellulose fibers (CMC) by chemically modifying cotton cellulose with monochloroacetic acid and calcium chloride solution. This modification favored the growth of hydroxyapatite (HAP) on the surface of the CMC fibers in contact with simulated body fluid solutions (SBF). After soaking in SBF for periods of 7, 14 and 21 days, formation of HAP was observed. Analysis by scanning electron microscopy and X-ray diffraction showed that crystallinity, crystallite size, and growth of HAP increased with the soaking time. The amount of HAP deposited on CMC fibers increased greatly after 21 days of immersion in the SBF, while the substrate surface was totally covered with hemispherical aggregates with the size of the order of 2 microns. Elemental analysis showed the presence of calcium and phosphate, with calcium/phosphate atomic ratio of 1.54. Fourier transform infrared spectroscopy bands confirmed the presence of HAP. The results suggest that cotton modified by calcium treatment has a nucleating ability and can accelerate the nucleation of HAP crystals.     

Design and optimization of electrochemical microreactors for continuous electrosynthesis

The study focuses on the design and construction, as well as the theoretical and experimental optimization of electrochemical filter press microreactors for the electrosynthesis of molecules with a high added value. The main characteristics of these devices are firstly a high-specific electrochemical area to increase conversion and selectivity, and secondly the shape and size of the microchannels designed for a uniform residence time distribution of the fluid. A heat exchanger is integrated into the microstructured electrode to rapidly remove (or supply) the heat required in exo- or endothermic reactions. The microreactors designed are used to perform-specific electrosynthesis reactions such as thermodynamically unfavorable reactions (continuous NADH regeneration), or reactions with high enthalpy changes.     

A dimensional reduction approach to modulate the core ruminal microbiome associated with methane emissions via selective breeding

The rumen is a complex microbial system of substantial importance in terms of greenhouse gas emissions and feed efficiency. This study proposes combining metagenomic and host genomic data for selective breeding of the cow hologenome toward reduced methane emissions. We analyzed nanopore long reads from the rumen metagenome of 437 Holstein cows from 14 commercial herds in 4 northern regions in Spain. After filtering, data were treated as compositional. The large complexity of the rumen microbiota was aggregated, through principal component analysis (PCA), into few principal components (PC) that were used as proxies of the core metagenome. The PCA allowed us to condense the huge and fuzzy taxonomical and functional information from the metagenome into a few PC. Bivariate animal models were applied using these PC and methane production as phenotypes. The variability condensed in these PC is controlled by the cow genome, with heritability estimates for the first PC of ~0.30 at all taxonomic levels, with a large probability (>83%) of the posterior distribution being >0.20 and with the 95% highest posterior density interval (95%HPD) not containing zero. Most genetic correlation estimates between PC1 and methane were large (≥0.70), with most of the posterior distribution (>82%) being >0.50 and with its 95%HPD not containing zero. Enteric methane production was positively associated with relative abundance of eukaryotes (protozoa and fungi) through the first component of the PCA at phylum, class, order, family, and genus. Nanopore long reads allowed the characterization of the core rumen metagenome using whole-metagenome sequencing, and the purposed aggregated variables could be used in animal breeding programs to reduce methane emissions in future generations.     

A Symmetrical Diester as the Sex Attractant Pheromone of the North American Click Beetle Parallelostethus attenuatus (Say) (Coleoptera: Elateridae)

Hexanoic acid, 1-octanol, 1,8-octanediol, octyl hexanoate, 1,8-octanediol monohexanoate, and 1,8-octanediol dihexanoate were identified in headspace volatiles collected from the crushed abdomen of a female click beetle of the species Parallelostethus attenuatus (Say) (Elaterinae, tribe Elaterini). In field trials carried out in Illinois, South Carolina, North Carolina, and Virginia, adult male beetles were strongly attracted to 1,8-octanediol dihexanoate alone. Blends of the dihexanoate with one or more of the other compounds proved to be less attractive than the dihexanoate alone, suggesting that the pheromone of this species may consist of a single compound. The symmetrical diester structure of the pheromone is a novel natural product and appears to be structurally unique among insect pheromones.

     

Numerical modeling and design of supercritical CO2 pre-cooler for fusion nuclear reactors

One of the key issues of fusion technology is the efficient recovery of the fusion power extracted by heat transfer fluids in the breeding blanket. The Spanish National Program TECNO_FUS is exploring a dual-coolant breeding blanket design concept and its plant auxiliary systems for a future power reactor (DEMO), with liquid lead–lithium as main primary nuclear power recovering fluid. Supercritical CO₂ is chosen for the secondary circuit, since its high efficiency at significantly lower required temperatures than for the Brayton helium cycle, due to low compression work near the critical point and also because its additional major benefits in terms of tritium control. Use of printed circuit heat exchangers (PCHE) is suggested in literature due to its highly compact design and robustness for the high pressures found. This work deals with the heat exchanger devoted to release the thermal energy of the power cycle to the thermal sink. The aim of this work is analyzing how the nearness of the CO₂ to its critical point affects the performance of the heat exchanger. Computer Fluid Dynamics (CFD) simulations that include the complex thermal behavior of CO₂ properties at supercritical conditions are used in order to achieve an accurate approach to the design of this heat exchanger. These results are compared with others obtained through correlations found in the open literature. The behavior of CO₂ close to its critical point results in an inefficient use of the exchange area, giving a temperature profile in CO₂ which remembers a condensation process and an overall heat transfer coefficient 1.4 times higher than the one achieved with literature correlations design.     

Enhanced photocatalytic hydrogen production by improving the Pt dispersion over mesostructured TiO2

Among other potential applications, mesoporous titania with high surface area and crystalline framework is attractive in photocatalytic hydrogen production. The mesoporous structure with pore walls formed by nanocrystals of anatase would provide a shorter distance of the electron–hole pairs to reach the photocatalyst surface and a higher surface area to deposit modifiers of its photocatalytic activity. In this work, we have successfully applied a hard-templating pathway to obtain ordered mesoporous titania (m-TiO₂) with high surface area and anatase as main crystalline phase. Subsequently, various amounts of metallic Pt have been deposited using different impregnation methods. All reactions performed exhibit, at short times, a rapid increase in the hydrogen production rate until a point in which a nearly constant value is achieved. The material prepared by the “citrate method”, based on reduction and encapsulation with sodium citrate of Pt nanoparticles before the photocatalytic reaction, leads to the highest hydrogen production rates with the shortest time to reach the change on the trend of the activity curve. The reason of this result is that citrate method provides very good dispersion and, specially, because the Pt nanoparticles are deposited and reduced preferentially within the pores of m-TiO₂, leading to stronger interactions than the other two explored dispersion routes (wetness impregnation and photodeposition). Thus, despite introducing less than half of the theoretical amount of Pt, citrate method produces close to twice the amount of hydrogen obtained by the other dispersion routes. This production capacity is even higher when the amount of Pt loaded is increased, with the optimal concentration being determined as 2% (w/w).