Generating cluster submodels from a multistage stochastic mixed integer optimization model using break stage

We present a scheme to generate clusters submodels with stage ordering from a (symmetric or a nonsymmetric one) multistage stochastic mixed integer optimization model using break stage. We consider a stochastic model in compact representation and MPS format with a known scenario tree. The cluster submodels are built by storing first the 0-1 the variables, stage by stage, and then the continuous ones, also stage by stage. A C++ experimental code has been implemented for reordering the stochastic model as well as the cluster decomposition after the relaxation of the non-anticipativiy constraints until the so-called breakstage. The computational experience shows better performance of the stage ordering in terms of elapsed time in a randomly generated testbed of multistage stochastic mixed integer problems.

Cluster analisiaren aplikazio bat ekonomian Donostiako auzoen ikerketa

Lan honekin Donostiako bizitza kalitatea ikertu nahi dute, hau da etxebizitzetako bizilagunen eta etxebizitzen egitura eta erabileraren arteko erlazio posiblea. Biztanle mota, etxebizitza mota eta Donostiako eremu homogeneoen arteko lotura bilatzen saiatuko dira, Aldagai Anitzeko Analisia, batez ere Osagai Nagusizko Analisia, erabiliz aldagai kopurua murrizteko eta faktore edo osagai gutxitan aldagaien informazio gehiena jasotzeko. Jarraian, Cluster aplikatuko dute auzo homogeneoen taldeak osatzeko.

Estrategias de Marketing para la gestión público-privada del comercio de Guipúzcoa. Un modelo basado en el análisis cluster.

Este artículo trata sobre el desarrollo de áreas comerciales en los alrededores de las ciudades y de cómo el centro urbano ha ido perdiendo atractivo comercial. Esta situación, común en la mayor parte de los países de nuestro entorno, plantea importantes problemas para el comercio tradicional de centro ciudad, que ve como gran parte de sus clientes optan por la oferta de la periferia, con la siguiente fuga de ingresos.

Grouping materials and processes for the designer: an application for cluster analysis.

In this paper, an analytical tool - cluster analysis - that is commonly used in biology, archaeology, linguistics and psychology is applied to materials and design. Here we use it to cluster materials and the processes that shape them, using their attributes as indicators of relationship. The attributes that are chosen are important to design and designers. The resulting clusters, and the classifications that can be developed from them, depend on the selected attributes and - to some extent - on the method of clustering. Alternative classifications for design that is focused on the technical or aesthetic attributes of materials and the materials and shapes allowed by processes are explored.

Development of catalytic methane reforming systems integrating hydrogen selective PdCu membrane modules

En la presente tesis doctoral se ha estudiado la integración del proceso de producción de hidrógeno con su purificación mediante el empleo de membranas selectivas de hidrógeno. La producción de hidrógeno se realiza empleando catalizadores no convencionales de níquel soportado sobre magnesia y alúmina en un reactor catalítico. Se analiza la actividad de los catalizadores y la producción de hidrógeno mediante distintos procesos con metano como son la oxidación parcial catalítica (OPC), OPC húmeda y reformadoLa purificación de hidrógeno se realiza en un módulo provisto de una membrana selectiva de hidrógeno de PdCu depositado en un soporte poroso cerámico. Una vez optimizada su preparación mediante deposición no electrolítica se caracterizan. Para ello se determina su permeabilidad a distintas temperaturas y realizando ciclos térmicos en atmósferas inerte y de hidrógeno, que puede fragilizar el metal. Una vez preparados los catalizadores y las membranas se integran los dos sistemas y se determinan los parámetros de operación óptimos como la presión de la línea de alimentación y el caudal de gas de arrastre en el módulo de membrana. Ambos parámetros se optimizan para lograr la máxima recuperación de hidrógeno en el módulo de membrana. Por últimos se realizan ensayos completos de producción y purificación, que permiten observar el rendimiento del sistema y también el efecto que los compuestos de la mezcla compleja alimentada a las membranas tienen en su comportamiento. Para concluir la integración de procesos se realizan ensayos añadiendo azufre de forma que el sistema sea más similar al proceso real. Esto permite también analizar el efecto del azufre tanto en los catalizadores como en las membranas.

Laminar Burning Velocities and Markstein Lengths of Premixed Methane/Air Flames near the Lean Flammability Limit in Microgravity

Effects of flame stretch on the laminar burning velocities of near-limit fuel-lean methane/air flames have been studied experimentally using a microgravity environment to minimize the complications of buoyancy. Outwardly propagating spherical flames were employed to assess the sensitivities of the laminar burning velocity to flame stretch, represented by Markstein lengths, and the fundamental laminar burning velocities of unstretched flames. Resulting data were reported for methane/air mixtures at ambient temperature and pressure, over the specific range of equivalence ratio that extended from 0.512 (the microgravity flammability limit found in the combustion chamber) to 0.601. Present measurements of unstretched laminar burning velocities were in good agreement with the unique existing microgravity data set at all measured equivalence ratios. Most of previous 1-g experiments using a variety of experimental techniques, however, appeared to give significantly higher burning velocities than the microgravity results. Furthermore, the burning velocities predicted by three chemical reaction mechanisms, which have been tuned primarily under off-limit conditions, were also considerably higher than the present experimental data. Additional results of the present investigation were derived for the overall activation energy and corresponding Zeldovich numbers, and the variation of the global flame Lewis numbers with equivalence ratio. The implications of these results were discussed. 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Sulfur-Cycling in Methane-Rich Ecosystems: Uncovering Microbial Processes and Novel Niches

Microbial sulfur cycling communities were investigated in two methane-rich ecosystems, terrestrial mud volcanoes (TMVs) and marine methane seeps, in order to investigate niches and processes that would likely be central to the functioning of these crucial ecosystems. Terrestrial mud volcanoes represent geochemically diverse habitats with varying sulfur sources and yet sulfur-cycling in these environments remains largely unexplored. Here we characterized the sulfur-metabolizing microorganisms and activity in 4 TMVs in Azerbaijan, supporting the presence of active sulfur-oxidizing and sulfate-reducing guilds in all 4 TMVs across a range of physiochemical conditions, with diversity of these guilds being unique to each TMV. We also found evidence for the anaerobic oxidation of methane coupled to sulfate reduction, a process which we explored further in the more tractable marine methane seeps. Diverse associations between methanotrophic archaea (ANME) and sulfate-reducing bacterial groups (SRB) often co-occur in marine methane seeps, however the ecophysiology of these different symbiotic associations has not been examined. Using a combination of molecular, geochemical and fluorescence in situ hybridization coupled to nano-scale secondary ion mass spectrometry (FISH-NanoSIMS) analyses of in situ seep sediments and methane-amended sediment incubations from diverse locations, we show that the unexplained diversity in SRB associated with ANME cells can be at least partially explained by preferential nitrate utilization by one particular partner, the seepDBB. This discovery reveals that nitrate is likely an important factor in community structuring and diversity in marine methane seep ecosystems. The thesis concludes with a study of the dynamics between ANME and their associated SRB partners. We inhibited sulfate reduction and followed the metabolic processes of the community as well as the effect of ANME/SRB aggregate composition and growth on a cellular level by tracking 15N substrate incorporation into biomass using FISH-NanoSIMS. We revealed that while sulfate-reducing bacteria gradually disappeared over time in incubations with an SRB inhibitor, the ANME archaea persisted in the form of ANME-only aggregates, which are capable of little to no growth when sulfate reduction is inhibited. These data suggest ANME are not able to synthesize new proteins when sulfate reduction is inhibited.

A plasma channel scheme for the interaction of an intense femtosecond laser pulse with a deuterium cluster jet

We propose a plasma channel scheme to obtain an improved table-top laser driven fusion neutron yield as a result of explosions of large deuterium clusters irradiated by an intense laser pulse. A cylindrical plasma channel is created by two moderate intensity laser prepulses at the edge of a deuterium cluster jet along which an intense main laser pulse propagates several nanoseconds later. With the aid of this plasma channel, the main laser pulse will be allowed to deposit its energy into the central region of the deuterium gas jet where the cluster sizes are larger and the atomic density is higher. The plasma channel formation and its impact on the deuterium ion energy spectrum and the consequent fusion neutron yield have been investigated. The calculated results show that a remarkable increase of the table-top laser driven fusion neutron yield would be expected.

Effect of laser spot size on fusion neutron yield in laser-deuterium cluster interactions

The effect of the laser spot size on the neutron yield of table-top nuclear fusion from explosions of a femtosecond intense laser pulse heated deuterium clusters is investigated by using a simplified model, in which the cluster size distribution and the energy attenuation of the laser as it propagates through the cluster jet are taken into account. It has been found that there exists a proper laser spot size for the maximum fusion neutron yield for a given laser pulse and a specific deuterium gas cluster jet. The proper spot size, which is dependent on the laser parameters and the cluster jet parameters, has been calculated and compared with the available experimental data. A reasonable agreement between the calculated results and the published experimental results is found.

Selective hydroxylation of small alkanes by the particulate methane monooxygenase

The particulate methane monooxygenase (pMMO) catalyzes the oxidation of methane to methanol under ambient temperatures and pressures. Other small alkanes and alkenes are also substrates of this enzyme. We measured and compared the initial rate constants of oxidation of small alkanes (C1 to C5) catalyzed by pMMO. Both primary and secondary alcohols were formed from oxidation of n-butane and n-pentane. The alcohols produced from alkane oxidation can be further oxidized, probably by pMMO, to aldehydes and ketones. The apparent regioselectivity for n-butane and n-pentane is 100% 2-alcohols because the formation of primary alcohols is slower than further oxidation of these alcohols. The hydroxylation at the secondary carbons is highly stereoselective: (R)-alcohols are preferentially formed. The enantiomeric excess increases slightly with decreasing reaction temperature. The steric course of hydroxylation on primary carbons was also studied by using isotopically substituted ethane: (S)- or (R)-CH_3-CHDT, and (S)- or (R)-CD_3- CHDT and the reactions were found to proceed with 100% retention of configuration. A primary isotopic effect of k_H/k_D=5.0 was observed in these experiments.