The journal of physical chemistry letters, Jan 21, 2016
Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxi... more Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxide and oxide-metal interface in catalytic reactions. These systems can have special structural and catalytic properties due to strong oxide-metal interactions difficult to attain when depositing a metal on a regular oxide support. Oxide phases which are not seen or are metastable in a bulk oxide can become stable in an oxide/metal system opening the possibility for new chemical properties. Using these systems it has been possible to explore fundamental properties of the metal-oxide interface (composition, structure, electronic state) which determine catalytic performance in the oxidation of CO, the water-gas shift and the hydrogenation of CO2 to methanol. Recently, there has been a significant advance in the preparation of oxide/metal catalysts for technical or industrial applications. One goal is to identify methods able to control in a precise way the size of the deposited oxide partic...
Journal of the American Chemical Society, Jan 16, 2016
The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of glo... more The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of global warming. Thus, CO2 activation and conversion towards valuable added compounds is a major scientific challenge. A new set of Au/δ-MoC and Cu/δ-MoC catalysts exhibits high activity, selectivity, and stability for the reduction of CO2 to CO with some subsequent selective hydrogenation towards methanol. Sophisticated experiments under controlled conditions and calculations based on density functional theory have been used to study the unique behavior of these systems. A detailed comparison of the behavior of Au/-Mo2C and Au/δ-MoC catalysts provides clear evidence of the impact of the metal/carbon ratio in the carbide on the performance of the catalysts. The present results show that this ratio governs the chemical behavior of the carbide and the properties of the admetal. Overall, as a result of metal-support interactions and a synergy at the metal-carbide interface, Au/δ-MoC and Cu/δ-M...
Angewandte Chemie (International ed. in English), Jan 4, 2016
Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at rel... more Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal-support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2-x (111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way.
The study area is located west of San Juan city, on a marginal zone belonging to the Tulum Valley... more The study area is located west of San Juan city, on a marginal zone belonging to the Tulum Valley. There is a project there to set up a treatment plant for urban solid waste held by the Rivadavia community authority. This paper presents the geologic and geomorphic framework and the hydrogeologic units classified as aquifers and non-aquifers based on water
El diagnóstico de lesiones treponematósicas (sífilis; bejel o sífilis endémica; pian, frambesia, ... more El diagnóstico de lesiones treponematósicas (sífilis; bejel o sífilis endémica; pian, frambesia, yaws, épian, bubas; y la pinta, mal de pinto o carate) en restos óseos prehispánicos y en las fuentes escritas de los cronistas de los siglos XVI a XVII ha suscitado agudas discusiones en los medios históricos y paleopatológicos. Los cronistas, como se puede colegir de sus afirmaciones, señalaron la abundancia de bubas y épian en el territorio de Colombia y relacionaron sus orígenes con las condiciones climáticas de América, el comercio inmoderado con mujeres y por contagio con objetos usados por enfermos. Dada la carencia de conocimientos médicos de la época es muy difícil discernir si la sintomatología corresponde a yaws o a sífilis venérea; éstas se observarían tanto en clima templado (Bogotá, Tunja) como caliente (Caribe, istmo de Panamá, Tocaima). Lo cierto es, según las crónicas, que esta enfermedad no constituía un mal epidémico y se curaba fácilmente con infusiones de guayacán y otras hierbas, haciendo sudar copiosamente al enfermo y manteniéndole una estricta dieta altamente proteínica y control en sus relaciones s e x u a l e s . Así, para la región andina las Relaciones geográficas del Nuevo Reino de Granada de 1571 y la Relación de Tunja de 1610 mencionan que, además de cámaras de sangre, sarna y algunos dolores de costado había bubas en territorio muisca (PATIÑO, 1983: 105, 340, 344):
The activation process and performance of Fe2O3 and an industrial Cu, Cr-Fe2O3 catalyst for the w... more The activation process and performance of Fe2O3 and an industrial Cu, Cr-Fe2O3 catalyst for the water-gas shift reaction were analysed by in situ time-resolved X-ray diffraction. We show that the catalytic activity in the case of Fe2O3 is related to the Fe2O3-->Fe3O4 transformation. However, in the case of the industrial Cu, Cr-Fe2O3 catalyst, the presence of Cu has a major
Angewandte Chemie (International ed. in English), Jan 5, 2015
Propylene Epoxidation Catalysts. Cu(+) active sites on a Cu2 O surface are stabilized with TiOx .... more Propylene Epoxidation Catalysts. Cu(+) active sites on a Cu2 O surface are stabilized with TiOx . J. G. Chen et al. show in their Communication on page 11946 ff. that the resulting mixed oxide helps form an oxametallacycle intermediate with propylene giving higher selectivity for propylene epoxidation.
The atomic structure and electronic properties of Cun nanoclusters (n = 4, 6, 7, and 10) supporte... more The atomic structure and electronic properties of Cun nanoclusters (n = 4, 6, 7, and 10) supported on cubic nonpolar δ-MoC(001) and orthorhombic C- or Mo-terminated polar β-Mo2 C(001) surfaces have been investigated by means of periodic density functional theory based calculations. The electronic properties have been analyzed by means of the density of states, Bader charges, and electron localization function plots. The Cu nanoparticles supported on β-Mo2 C(001), either Mo- or C-terminated, tend to present a two-dimensional structure whereas a three-dimensional geometry is preferred when supported on δ-MoC(001), indicating that the Mo:C ratio and the surface polarity play a key role determining the structure of supported clusters. Nevertheless, calculations also reveal important differences between the C- and Mo-terminated β-Mo2 C(001) supports to the point that supported Cu particles exhibit different charge states, which opens a way to control the reactivity of these potential catalysts.
Angewandte Chemie (International ed. in English), Jan 17, 2015
Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for c... more Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate that by generating highly dispersed and stabilized Cu(+) active sites in a TiCuOx mixed oxide the epoxidation selectivity can be tuned. The TiCuOx surface anchors the key surface intermediate, an oxametallacycle, leading to higher selectivity for epoxidation of propylene.
Journal of the American Chemical Society, Jan 28, 2015
Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emi... more Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal-oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO2 substrate generates active centers for CO2 adsorption and its low pressure hydrogenation, leading to a higher selectivity towards methanol. This study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO2 hydrogenation.
Ion-scattering spectroscopy (ISS), synchrotron-based high-resolution photoemission spectroscopy (... more Ion-scattering spectroscopy (ISS), synchrotron-based high-resolution photoemission spectroscopy (PES) and firstprinciples density-functional (DF) calculations were used to study the adsorption of SO 2 on Cu/Au(1 1 1). ISS experiments for Cu/Au(1 1 1) clearly demonstrate that Cu intermixes with the Au(1 1 1) substrate at 300 K or higher temperature, but a substantial fraction of the Cu atoms stays on the Au(1 1 1) surface when the deposition is done at 100 K. When 1 ML of Cu was pre-deposited onto Au(1 1 1) at 300 K, the Cu/Au(1 1 1) surface exhibited a negligible reactivity towards SO 2 very similar to that of clean Au(1 1 1). However, when Cu was pre-deposited at 100 K, the Cu/Au(1 1 1) system bonded SO 2 well and the adsorbate remained on the surface up to temperatures above 300 K. DFT calculations for Cu/Au(1 1 1) show electronic perturbations in the Cu overlayer that should enhance their chemical reactivity, but the Cu atoms were more stable when penetrating into the substrate rather than sitting on the surface. Calculations for SO 2 adsorption on Cu/Au(1 1 1) surfaces with different h Cu showed that the value of h Cu determines the binding energy of SO 2 . In general, the more Cu atoms in the surface, the stronger the bonding energy towards SO 2 . Cu/Au(1 1 1) behaves differently from pure Cu. A temperature increase does not lead to S-O bond cleavage on the bimetallic system. Instead, the Cu atoms in the surface migrate into Au, accompanied by SO 2 desorption. Ensembles of the active sites necessary for the dissociation of SO 2 are not available. For Cu/Au(1 1 1), ensemble effects clearly overcome electronic effects. The Cu/ Au(1 1 1) interface illustrates how effective ensemble effects can be for the prevention of the corrosion of alloys by SO 2 .
Proceedings of the 9th annual conference on Genetic and evolutionary computation - GECCO '07, 2007
An Estimation of Distribution Algorithm (EDA) is proposed to approach the Hybrid Flow Shop with S... more An Estimation of Distribution Algorithm (EDA) is proposed to approach the Hybrid Flow Shop with Sequence Dependent Setup Times and Uniform Machines in parallel (HFS-SDST-UM) problem. The latter motivated by the needs of a real world company. The proposed EDA implements a fairly new mechanism to improve the search of more traditional EDAs. This is the Guided Mutation (GM). EDA-GM generates new solutions by using the information from a probability model, as all EDAs, and the local information from a good known solution. The approach is tested on several instances of HFS-SDST-UM and compared with adaptations of meta-heuristics designed for very similar problems. Encouraging results are reported.
En la última década se han incrementado los reportes de descripciones de heridas producidas por p... more En la última década se han incrementado los reportes de descripciones de heridas producidas por puntas de proyectil elaboradas en sílex (flechas), clavadas en material óseo arqueológico, tanto en el Viejo Mundo (PERROT, 1988; ETXEBERRÍA, VEGAS, 1992) como en el Nuevo Mundo, particularmente en Argentina. Aunque las representaciones de personajes flechando a animales y a otros hombres parecen confirmar la importancia del empleo de las flechas como arma de caza y de ataque en los conflictos intra-intergrupales de las poblaciones humanas, la interpretación de varios contextos arqueológicos, no obstante, deja serias dudas sobre la confirmación de las heridas por puntas de proyectil, por cuanto las mismas fueron también utilizadas en forma de ajuar funerario. Por otro lado, la utilización de material diferente al sílex, como la madera o el hueso, no favorece su localización por ser perecedero. Mientras no se encuentren incrustadas en el tejido óseo y asociadas a lesiones, difícilmente se pueden interpretar como prueba fehaciente. En Colombia, hasta el momento no se han reportado casos paleopatológicos similares, aunque se han realizado estudios sobre materiales tanto precerámicos como del periodo agroalfarero (RODRÍGUEZ, ETXEBERRÍA, MORALES, 1999). El presente informe describe el primer hallazgo sobre territorio de este país y quizá de primera lesión por punta en espina de pescado.
Page 1. A Robust Meta-Hyper-Heuristic Approach José Antonio Vázquez Rodrıguez and Abdellah Salhi ... more Page 1. A Robust Meta-Hyper-Heuristic Approach José Antonio Vázquez Rodrıguez and Abdellah Salhi Mathematical Sciences Department, University of Essex, Wivenhoe Park, Colchester, UK {[email protected], [email protected]} Summary. ...
For tiny crystals, their diffraction intensities at and between the Bragg peaks become measurable... more For tiny crystals, their diffraction intensities at and between the Bragg peaks become measurable due to the limited number of the unit cells, which can in principle be used to directly phase the crystal structures.
Conference on Lasers and Electro-Optics 2010, 2010
We demonstrate that high numerical aperture coherent diffractive imaging enables three-dimensiona... more We demonstrate that high numerical aperture coherent diffractive imaging enables three-dimensional imaging from a single exposure angle under certain conditions. We demonstrate this technique, called ankylography, with simulations and experiment from a tabletop soft-x-ray laser.
The reaction of the amino acid dl-proline is studied over stoichiometric and Ar-ions sputtered (r... more The reaction of the amino acid dl-proline is studied over stoichiometric and Ar-ions sputtered (reduced) TiO2(110) single crystal surfaces by synchrotron High Resolution X-ray Photoelectron Spectroscopy (HRXPS). On the stoichiometric surface proline gives two different species at 300K: dissociated and zwitterionic. Upon heating the zwitterionic structure is removed first from the surface followed by the dissociated form. The C1s signal for the COO function is found close to 288.5eV for both forms while the N1s for the dissociated form is found at 400.0eV and that of the zwitterionic from close to 401.8eV. From the attenuation of the Ti2p signal the surface coverage was estimated less than ½ (about 0.35). This smaller coverage than dissociatively adsorbed carboxylic acids on this surface (usually close to ½), is attributed to lateral repulsion caused by the ring of adjacent proline molecules adsorbed on five-fold coordinated Ti cations along the [001] direction. On the reduced surface the amount of zwitterion structure is found two times higher than that on the stoichiometric surface, at 300K, most likely due to the considerable decrease of the amount of surface oxygen available. The stability of the zwitterionic structure on this surface is however found similar to that found on the stoichiometric surface. In addition, evidence of oxidation of reduced Ti cations upon adsorption at 300K is noticed and explained as breaking of the carbon–oxygen bond of a fraction of adsorbed proline. Variable temperature HRXPS has been collected and results indicated that proline is more stable on the reduced surface compared to the stoichiometric surface.
Abstract Predictive direct torque control for a three-level neutral point clamped inverter is pro... more Abstract Predictive direct torque control for a three-level neutral point clamped inverter is proposed. The main differences between standard direct torque control and the proposed approach are the flexibility and simple algorithm implementation, which does not require complex predefined switching tables nor logic to select among them, as standard direct torque control requires. The dynamic performance is similar between them although torque ripple is smaller using the proposed controller. Predictive torque control is sensitive to ...
The journal of physical chemistry letters, Jan 21, 2016
Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxi... more Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxide and oxide-metal interface in catalytic reactions. These systems can have special structural and catalytic properties due to strong oxide-metal interactions difficult to attain when depositing a metal on a regular oxide support. Oxide phases which are not seen or are metastable in a bulk oxide can become stable in an oxide/metal system opening the possibility for new chemical properties. Using these systems it has been possible to explore fundamental properties of the metal-oxide interface (composition, structure, electronic state) which determine catalytic performance in the oxidation of CO, the water-gas shift and the hydrogenation of CO2 to methanol. Recently, there has been a significant advance in the preparation of oxide/metal catalysts for technical or industrial applications. One goal is to identify methods able to control in a precise way the size of the deposited oxide partic...
Journal of the American Chemical Society, Jan 16, 2016
The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of glo... more The ever growing increase of CO2 concentration in the atmosphere is one of the main causes of global warming. Thus, CO2 activation and conversion towards valuable added compounds is a major scientific challenge. A new set of Au/δ-MoC and Cu/δ-MoC catalysts exhibits high activity, selectivity, and stability for the reduction of CO2 to CO with some subsequent selective hydrogenation towards methanol. Sophisticated experiments under controlled conditions and calculations based on density functional theory have been used to study the unique behavior of these systems. A detailed comparison of the behavior of Au/-Mo2C and Au/δ-MoC catalysts provides clear evidence of the impact of the metal/carbon ratio in the carbide on the performance of the catalysts. The present results show that this ratio governs the chemical behavior of the carbide and the properties of the admetal. Overall, as a result of metal-support interactions and a synergy at the metal-carbide interface, Au/δ-MoC and Cu/δ-M...
Angewandte Chemie (International ed. in English), Jan 4, 2016
Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at rel... more Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal-support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2-x (111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way.
The study area is located west of San Juan city, on a marginal zone belonging to the Tulum Valley... more The study area is located west of San Juan city, on a marginal zone belonging to the Tulum Valley. There is a project there to set up a treatment plant for urban solid waste held by the Rivadavia community authority. This paper presents the geologic and geomorphic framework and the hydrogeologic units classified as aquifers and non-aquifers based on water
El diagnóstico de lesiones treponematósicas (sífilis; bejel o sífilis endémica; pian, frambesia, ... more El diagnóstico de lesiones treponematósicas (sífilis; bejel o sífilis endémica; pian, frambesia, yaws, épian, bubas; y la pinta, mal de pinto o carate) en restos óseos prehispánicos y en las fuentes escritas de los cronistas de los siglos XVI a XVII ha suscitado agudas discusiones en los medios históricos y paleopatológicos. Los cronistas, como se puede colegir de sus afirmaciones, señalaron la abundancia de bubas y épian en el territorio de Colombia y relacionaron sus orígenes con las condiciones climáticas de América, el comercio inmoderado con mujeres y por contagio con objetos usados por enfermos. Dada la carencia de conocimientos médicos de la época es muy difícil discernir si la sintomatología corresponde a yaws o a sífilis venérea; éstas se observarían tanto en clima templado (Bogotá, Tunja) como caliente (Caribe, istmo de Panamá, Tocaima). Lo cierto es, según las crónicas, que esta enfermedad no constituía un mal epidémico y se curaba fácilmente con infusiones de guayacán y otras hierbas, haciendo sudar copiosamente al enfermo y manteniéndole una estricta dieta altamente proteínica y control en sus relaciones s e x u a l e s . Así, para la región andina las Relaciones geográficas del Nuevo Reino de Granada de 1571 y la Relación de Tunja de 1610 mencionan que, además de cámaras de sangre, sarna y algunos dolores de costado había bubas en territorio muisca (PATIÑO, 1983: 105, 340, 344):
The activation process and performance of Fe2O3 and an industrial Cu, Cr-Fe2O3 catalyst for the w... more The activation process and performance of Fe2O3 and an industrial Cu, Cr-Fe2O3 catalyst for the water-gas shift reaction were analysed by in situ time-resolved X-ray diffraction. We show that the catalytic activity in the case of Fe2O3 is related to the Fe2O3-->Fe3O4 transformation. However, in the case of the industrial Cu, Cr-Fe2O3 catalyst, the presence of Cu has a major
Angewandte Chemie (International ed. in English), Jan 5, 2015
Propylene Epoxidation Catalysts. Cu(+) active sites on a Cu2 O surface are stabilized with TiOx .... more Propylene Epoxidation Catalysts. Cu(+) active sites on a Cu2 O surface are stabilized with TiOx . J. G. Chen et al. show in their Communication on page 11946 ff. that the resulting mixed oxide helps form an oxametallacycle intermediate with propylene giving higher selectivity for propylene epoxidation.
The atomic structure and electronic properties of Cun nanoclusters (n = 4, 6, 7, and 10) supporte... more The atomic structure and electronic properties of Cun nanoclusters (n = 4, 6, 7, and 10) supported on cubic nonpolar δ-MoC(001) and orthorhombic C- or Mo-terminated polar β-Mo2 C(001) surfaces have been investigated by means of periodic density functional theory based calculations. The electronic properties have been analyzed by means of the density of states, Bader charges, and electron localization function plots. The Cu nanoparticles supported on β-Mo2 C(001), either Mo- or C-terminated, tend to present a two-dimensional structure whereas a three-dimensional geometry is preferred when supported on δ-MoC(001), indicating that the Mo:C ratio and the surface polarity play a key role determining the structure of supported clusters. Nevertheless, calculations also reveal important differences between the C- and Mo-terminated β-Mo2 C(001) supports to the point that supported Cu particles exhibit different charge states, which opens a way to control the reactivity of these potential catalysts.
Angewandte Chemie (International ed. in English), Jan 17, 2015
Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for c... more Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate that by generating highly dispersed and stabilized Cu(+) active sites in a TiCuOx mixed oxide the epoxidation selectivity can be tuned. The TiCuOx surface anchors the key surface intermediate, an oxametallacycle, leading to higher selectivity for epoxidation of propylene.
Journal of the American Chemical Society, Jan 28, 2015
Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emi... more Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal-oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO2 substrate generates active centers for CO2 adsorption and its low pressure hydrogenation, leading to a higher selectivity towards methanol. This study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO2 hydrogenation.
Ion-scattering spectroscopy (ISS), synchrotron-based high-resolution photoemission spectroscopy (... more Ion-scattering spectroscopy (ISS), synchrotron-based high-resolution photoemission spectroscopy (PES) and firstprinciples density-functional (DF) calculations were used to study the adsorption of SO 2 on Cu/Au(1 1 1). ISS experiments for Cu/Au(1 1 1) clearly demonstrate that Cu intermixes with the Au(1 1 1) substrate at 300 K or higher temperature, but a substantial fraction of the Cu atoms stays on the Au(1 1 1) surface when the deposition is done at 100 K. When 1 ML of Cu was pre-deposited onto Au(1 1 1) at 300 K, the Cu/Au(1 1 1) surface exhibited a negligible reactivity towards SO 2 very similar to that of clean Au(1 1 1). However, when Cu was pre-deposited at 100 K, the Cu/Au(1 1 1) system bonded SO 2 well and the adsorbate remained on the surface up to temperatures above 300 K. DFT calculations for Cu/Au(1 1 1) show electronic perturbations in the Cu overlayer that should enhance their chemical reactivity, but the Cu atoms were more stable when penetrating into the substrate rather than sitting on the surface. Calculations for SO 2 adsorption on Cu/Au(1 1 1) surfaces with different h Cu showed that the value of h Cu determines the binding energy of SO 2 . In general, the more Cu atoms in the surface, the stronger the bonding energy towards SO 2 . Cu/Au(1 1 1) behaves differently from pure Cu. A temperature increase does not lead to S-O bond cleavage on the bimetallic system. Instead, the Cu atoms in the surface migrate into Au, accompanied by SO 2 desorption. Ensembles of the active sites necessary for the dissociation of SO 2 are not available. For Cu/Au(1 1 1), ensemble effects clearly overcome electronic effects. The Cu/ Au(1 1 1) interface illustrates how effective ensemble effects can be for the prevention of the corrosion of alloys by SO 2 .
Proceedings of the 9th annual conference on Genetic and evolutionary computation - GECCO '07, 2007
An Estimation of Distribution Algorithm (EDA) is proposed to approach the Hybrid Flow Shop with S... more An Estimation of Distribution Algorithm (EDA) is proposed to approach the Hybrid Flow Shop with Sequence Dependent Setup Times and Uniform Machines in parallel (HFS-SDST-UM) problem. The latter motivated by the needs of a real world company. The proposed EDA implements a fairly new mechanism to improve the search of more traditional EDAs. This is the Guided Mutation (GM). EDA-GM generates new solutions by using the information from a probability model, as all EDAs, and the local information from a good known solution. The approach is tested on several instances of HFS-SDST-UM and compared with adaptations of meta-heuristics designed for very similar problems. Encouraging results are reported.
En la última década se han incrementado los reportes de descripciones de heridas producidas por p... more En la última década se han incrementado los reportes de descripciones de heridas producidas por puntas de proyectil elaboradas en sílex (flechas), clavadas en material óseo arqueológico, tanto en el Viejo Mundo (PERROT, 1988; ETXEBERRÍA, VEGAS, 1992) como en el Nuevo Mundo, particularmente en Argentina. Aunque las representaciones de personajes flechando a animales y a otros hombres parecen confirmar la importancia del empleo de las flechas como arma de caza y de ataque en los conflictos intra-intergrupales de las poblaciones humanas, la interpretación de varios contextos arqueológicos, no obstante, deja serias dudas sobre la confirmación de las heridas por puntas de proyectil, por cuanto las mismas fueron también utilizadas en forma de ajuar funerario. Por otro lado, la utilización de material diferente al sílex, como la madera o el hueso, no favorece su localización por ser perecedero. Mientras no se encuentren incrustadas en el tejido óseo y asociadas a lesiones, difícilmente se pueden interpretar como prueba fehaciente. En Colombia, hasta el momento no se han reportado casos paleopatológicos similares, aunque se han realizado estudios sobre materiales tanto precerámicos como del periodo agroalfarero (RODRÍGUEZ, ETXEBERRÍA, MORALES, 1999). El presente informe describe el primer hallazgo sobre territorio de este país y quizá de primera lesión por punta en espina de pescado.
Page 1. A Robust Meta-Hyper-Heuristic Approach José Antonio Vázquez Rodrıguez and Abdellah Salhi ... more Page 1. A Robust Meta-Hyper-Heuristic Approach José Antonio Vázquez Rodrıguez and Abdellah Salhi Mathematical Sciences Department, University of Essex, Wivenhoe Park, Colchester, UK {[email protected], [email protected]} Summary. ...
For tiny crystals, their diffraction intensities at and between the Bragg peaks become measurable... more For tiny crystals, their diffraction intensities at and between the Bragg peaks become measurable due to the limited number of the unit cells, which can in principle be used to directly phase the crystal structures.
Conference on Lasers and Electro-Optics 2010, 2010
We demonstrate that high numerical aperture coherent diffractive imaging enables three-dimensiona... more We demonstrate that high numerical aperture coherent diffractive imaging enables three-dimensional imaging from a single exposure angle under certain conditions. We demonstrate this technique, called ankylography, with simulations and experiment from a tabletop soft-x-ray laser.
The reaction of the amino acid dl-proline is studied over stoichiometric and Ar-ions sputtered (r... more The reaction of the amino acid dl-proline is studied over stoichiometric and Ar-ions sputtered (reduced) TiO2(110) single crystal surfaces by synchrotron High Resolution X-ray Photoelectron Spectroscopy (HRXPS). On the stoichiometric surface proline gives two different species at 300K: dissociated and zwitterionic. Upon heating the zwitterionic structure is removed first from the surface followed by the dissociated form. The C1s signal for the COO function is found close to 288.5eV for both forms while the N1s for the dissociated form is found at 400.0eV and that of the zwitterionic from close to 401.8eV. From the attenuation of the Ti2p signal the surface coverage was estimated less than ½ (about 0.35). This smaller coverage than dissociatively adsorbed carboxylic acids on this surface (usually close to ½), is attributed to lateral repulsion caused by the ring of adjacent proline molecules adsorbed on five-fold coordinated Ti cations along the [001] direction. On the reduced surface the amount of zwitterion structure is found two times higher than that on the stoichiometric surface, at 300K, most likely due to the considerable decrease of the amount of surface oxygen available. The stability of the zwitterionic structure on this surface is however found similar to that found on the stoichiometric surface. In addition, evidence of oxidation of reduced Ti cations upon adsorption at 300K is noticed and explained as breaking of the carbon–oxygen bond of a fraction of adsorbed proline. Variable temperature HRXPS has been collected and results indicated that proline is more stable on the reduced surface compared to the stoichiometric surface.
Abstract Predictive direct torque control for a three-level neutral point clamped inverter is pro... more Abstract Predictive direct torque control for a three-level neutral point clamped inverter is proposed. The main differences between standard direct torque control and the proposed approach are the flexibility and simple algorithm implementation, which does not require complex predefined switching tables nor logic to select among them, as standard direct torque control requires. The dynamic performance is similar between them although torque ripple is smaller using the proposed controller. Predictive torque control is sensitive to ...
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