José Javier Martínez | Universidad de Alcalá (original) (raw)
Papers by José Javier Martínez
19th IEEE International Conference on Tools with Artificial Intelligence(ICTAI 2007), 2007
Communications in Computer and Information Science, 2009
This project presents a new way of sightseeing, by adapting itself to new times and new technolog... more This project presents a new way of sightseeing, by adapting itself to new times and new technologies. It has been created a system able to guide the tourist at all times during a visit to a city by means of a PDA with GPS technology; it shows the most interesting points (both in text and multimedia contents), the most important routes, a street directory, a calendar events, etc. As additional support, the system has an internal web page that helps to manage in an easy way the touristic contents. Moreover, it is used a Wi-Fi wireless technology to update the PDA contents automatically. The system has a server that allows to use the web page and update the PDA, hiding the access to the database to other kind of services not allowed by the system. Therefore, the most noteworthy aspects of this project are the use of a Wi-Fi wireless technology and a GPS positioning technology.
ACM SIGCSE Bulletin, 2008
The process of creating e-learning courseware using reusable learning objects (LOs) can be broken... more The process of creating e-learning courseware using reusable learning objects (LOs) can be broken down in two sub-processes: LOs finding and LO sequencing. Sequencing is usually performed by instructors, who create courses targeting generic profiles rather than personalized materials. This paper proposes an evolutionary approach to automate this latter problem while, simultaneously, encourages reusability and interoperability by promoting standards employment.
Proceedings of the 10th annual conference on Genetic and evolutionary computation - GECCO '08, 2008
In e-learning initiatives content creators are usually required to arrange a set of learning reso... more In e-learning initiatives content creators are usually required to arrange a set of learning resources in order to present them in a comprehensive way to the learner. Course materials are usually divided into reusable chunks called Learning Objects (LOs) and the ordered set of LOs is called sequence, so the process is called LO sequencing. In this paper an intelligent agent that performs the LO sequencing process is presented. Metadata and competencies are used to define relations between LOs so that the sequencing problem can be characterized as a Constraint Satisfaction Problem (CSP) and artificial intelligent techniques can be used to solve it. A Particle Swarm Optimization (PSO) agent is proposed, built, tuned and tested. Results show that the agent succeeds in solving the problem and that it handles reasonably combinatorial explosion inherent to this kind of problems.
Proceedings of the fifteenth annual conference on Innovation and technology in computer science education - ITiCSE '10, 2010
This paper presents a new mobile application designed for auto-assessment that allows students to... more This paper presents a new mobile application designed for auto-assessment that allows students to test their knowledge and expertise in a specific topic using questionnaires designed by their teachers. Students' achievement was evaluated and results suggest that this kind of approaches can improve it.
2010 10th IEEE International Conference on Advanced Learning Technologies, 2010
This paper presents a web tool that uses Java Server Faces to design questions graphically, to te... more This paper presents a web tool that uses Java Server Faces to design questions graphically, to test the outcome in a learning environment and to export them using the QTI v2.1 specification in order to ensure interoperability between different learning systems.
2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, 2008
The process of creating e-learning contents using reusable learning objects (LOs) can be broken d... more The process of creating e-learning contents using reusable learning objects (LOs) can be broken down in two sub-processes: LOs finding and LO sequencing. Although semiautomatic tools that aid in the finding process exits, sequencing is usually performed by instructors, who create courses targeting generic profiles rather than personalized materials. This paper proposes an evolutionary approach to automate this latter problem while, simultaneously, encourages reusability and interoperability by promoting standards employment. A model that enables automated curriculum sequencing is proposed. By means of interoperable competency records and LO metadata, the sequencing problem is turn into a constraint satisfaction problem. Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) agents are designed, built and tested in real and simulated scenarios. Results show both approaches succeed in all test cases, and that they handle reasonably computational complexity inherent to this problem, but PSO approach outperforms GA.
ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C, 2011
A p-type Bi 0.4 Sb 1.6 Te 3 thermoelectric compound was fabricated via mechanical alloying of bis... more A p-type Bi 0.4 Sb 1.6 Te 3 thermoelectric compound was fabricated via mechanical alloying of bismuth, antimony and tellurium elemental powders as starting materials. The mechanically alloyed compositions were sintered through a spark-plasma sintering (SPS) process. The effect of the milling time was investigated. In order to characterize the powders obtained via mechanical alloying, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis were used. The morphological evolution was studied by scanning electron microscopy (SEM). Results showed that the p-type Bi 0.4 Sb 1.6 Te 3 compound was formed after 2 h of milling. Further, the variation of milling time showed that the synthesized phase was stable. All the powders exhibit the same morphology albeit with slight differences. Measurements of the electrical resistivity, Seebeck coefficient and thermal conductivity were performed in the temperature range 300-520 K for the SPS samples. The resulting thermoelectric figure of merit ZT reaches a maximum of 1.2 at 360 K for the p-type bulk material with a 5 h milling time. This study demonstrates the possibility of preparing thermoelectric materials of high performance and short processing time.
Software Engineering Research and Practice, 2010
International Conference on E-Business, Enterprise Information Systems, E-Government, and Outsourcing, 2010
Las competencias no técnicas o soft skills se consideran un factor esencial para el éxito profesi... more Las competencias no técnicas o soft skills se consideran un factor esencial para el éxito profesional de los egresados universitarios. En este trabajo se presentará una experiencia en la que se combinan dos objetivos: la concienciación sobre los beneficios del trabajo en equipo y la mejora de habilidades de comunicación escrita en un máster oficial de informática. El análisis de los resultados obtenidos durante el desarrollo de esta experiencia confirma su utilidad y revela algunos datos interesantes sobre el desarrollo de estas competencias.
The Journal of Physical Chemistry A, 2009
The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and ap... more The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and applied to the collision of O2(3Sigma(g)-) molecules using a new accurate ab initio potential energy surface (PES) for the quintet state of the composite system. The PES is based on calculations using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)] [Bartolomei; et al. J. Chem. Phys. 2008, 128, 214304.]. This PES is extended here for large intermolecular distances using the ab initio long-range coefficients of Hettema et al. [J. Chem. Phys. 1994, 100, 1297.]. Elastic and rotationally inelastic integral cross sections have been obtained by means of close coupling calculations in the subthermal energy range (center-of-mass velocities below 500 m/s). Results are compared with those obtained using a PES derived from molecular beam experiments [Aquilanti; et al. J. Am. Chem. Soc. 1999, 121, 10794.]. General agreement is found between both PESs, although the experimentally derived PES appears as somewhat more anisotropic at least for the studied energy range. There is, however, a significant difference in the absolute value of the elastic cross sections that is due to differences in the long-range dispersion interaction. The performance of the ab initio PES for higher velocities (relevant to experiments) is also explored by retaining just the isotropic component of the interaction. A satisfactory agreement is found for the shape of the glory pattern but shifted toward lower absolute values of the cross sections.
The Journal of Chemical Physics, 2011
The collision dynamics of 17 O 2 ( 3 Σ − g ) + 17 O 2 ( 3 Σ − g ) in the presence of a magnetic f... more The collision dynamics of 17 O 2 ( 3 Σ − g ) + 17 O 2 ( 3 Σ − g ) in the presence of a magnetic field is studied within the close-coupling formalism in the range between 10 nK and 50 mK. A recent global ab initio potential energy surface (PES) is employed and its effect on the dynamics is analyzed and compared with previous calculations where an experimentally derived PES was used [New J. Phys 11, 055021 ]. In contrast to the results using the older PES, magnetic field dependence of the low-field-seeking state in the ultracold regime is characterized by quite a large background scattering length, a bg , and, in addition, cross sections exhibit broad and pronounced Feshbach resonances. The marked resonance structure is somewhat surprising considering the influence of inelastic scattering, but it can be explained by resorting to the analytical van der Waals theory, where the short range amplitude of the entrance channel wave function is enhanced by the large a bg . This strong sensitivity to the short range of the ab initio PES persists up to relatively high energies (10 mK). After this study and despite quantitative predictions are very difficult, it can be concluded that the ratio between elastic and spin relaxation scattering is generally small, except for magnetic fields which are either low or close to an asymmetric Fano-type resonance. Some general trends found here, such as a large density of quasibound states and a propensity towards large scattering lengths, could be also characteristic of other anisotropic molecule-molecule systems.
The Journal of Chemical Physics, 2005
The importance of vibrational-to-electronic (V-E) energy transfer mediated by spin-orbit coupling... more The importance of vibrational-to-electronic (V-E) energy transfer mediated by spin-orbit coupling in the collisional removal of O2(X 3Sigmag-,upsilon>or=26) by O2 has been reported in a recent communication [F. Dayou, J. Campos-Martinez, M. I. Hernandez, and R. Hernandez-Lamoneda, J. Chem. Phys. 120, 10355 (2004)]. The present work provides details on the electronic properties of the dimer (O2)2 relevant to the self-relaxation of O2(X 3Sigmag-,upsilon>0) where V-E energy transfer involving the O2(a 1Deltag) and O2(b 1Sigmag+) states is incorporated. Two-dimensional electronic structure calculations based on highly correlated ab initio methods have been carried out for the potential-energy and spin-orbit coupling surfaces associated with the ground singlet and two low-lying excited triplet states of the dimer dissociating into O2(X 3Sigmag-)+O2(X 3Sigmag-), O2(a 1Deltag)+O2(X 3Sigmag-), and O2(b 1Sigmag+)+O2(X 3Sigmag-). The resulting interaction potentials for the two excited triplet states display very similar features along the intermolecular separation, whereas differences arise with the ground singlet state for which the spin-exchange interaction produces a shorter equilibrium distance and higher binding energy. The vibrational dependence is qualitatively similar for the three studied interaction potentials. The spin-orbit coupling between the ground and second excited states is already nonzero in the O2+O2 dissociation limit and keeps its asymptotic value up to relatively short intermolecular separations, where the coupling increases for intramolecular distances close to the equilibrium of the isolated diatom. On the other hand, state mixing between the two excited triplet states leads to a noticeable collision-induced spin-orbit coupling between the ground and first excited states. The results are discussed in terms of specific features of the dimer electronic structure (including a simple four-electron model) and compared with existing theoretical and experimental data. This work gives theoretical insight into the origin of electronic energy-transfer mechanisms in O2+O2 collisions.
The Journal of Chemical Physics, 2005
A time-dependent wave packet method has been used to study different competing products of H(2)+H... more A time-dependent wave packet method has been used to study different competing products of H(2)+H(2) collisions: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. A three-degree-of-freedom reduced dimensionality model has been used for five different geometries of the colliding complex (parallel H, crossed X, collinear L, and two T-shaped geometries T(I) and T(II)), with reactants in selected vibrational states with one diatom vibrationally "hot" and the other one vibrationally "cold." Product probabilities have been calculated using two potential energy surfaces [J. Chem. Phys. 101, 4004 (1994); J. Chem. Phys. 116, 666 (2002)] in order to compare their performance in the dynamics. The regions of the potential energy surfaces responsible of the threshold behavior of the probabilities have been identified. Overall, we have found that the most recent potential energy surface is less anisotropic, provides a smaller propensity for insertion-type processes, and gives lower energy thresholds.
+O[sub 2] collisions. II. Quantum scattering calculations on dimer states involving the X [sup 3]Σ[sub g][sup −], a [sup 1]Δ[sub g], and b [sup 1]Σ[sub g][sup +] states of O[sub 2]](https://attachments.academia-assets.com/41178718/thumbnails/1.jpg)
](The Journal of Chemical Physics, 2007
The dynamics of collisional deactivation of O 2 ͑X 3 ⌺ g − , v =20-32͒ by O 2 ͑X 3 ⌺ g − , vЈ =0͒... more The dynamics of collisional deactivation of O 2 ͑X 3 ⌺ g − , v =20-32͒ by O 2 ͑X 3 ⌺ g − , vЈ =0͒ is investigated in detail by means of quantum-mechanical calculations. The theoretical approach involves ab initio potential energy surfaces correlating to the X 3 ⌺ g − , a 1 ⌬ g , and b 1 ⌺ g + states of O 2 and their corresponding spin-orbit couplings ͓F. Dayou, M. I. Hernández, J. Campos-Martínez, and R. Hernández-Lamoneda, J. Chem. Phys. 123, 074311 ͑2005͔͒. Accurate Rydberg-Klein-Rees potentials are included in order to improve the description of the vibrational structure of the fragments. The calculated Boltzmann-averaged depletion probabilities display a dependence with v in good agreement with experimental measurements. The onset of the vibrational-to-electronic ͑V-E͒ depletion mechanism is noticeable for v ജ 26, and it is due to energy transfer to both a 1 ⌬ g and b 1 ⌺ g + states of the diatom. For O 2 ͑X 3 ⌺ g − , v =28͒, a further and sharp increase in the removal probabilities is caused by a near degeneracy with the O 2 ͑b 1 ⌺ g + , v =19͒ vibrational state. Analysis of the temperature dependence of the Boltzmann-averaged probabilities indicates a transition from the vibrational-to-translational to the V-E energy transfer regime, which can be traced back to the behavior of the inelastic probabilities as functions of kinetic energy. Furthermore, branching ratios for outcomes through the three different electronic states show a strong propensity towards populating a unique vibrational level within each electronic state. These results provide supported evidence that spin-orbit couplings account for a large portion of the "dark channel" reported in total depletion measurements. New insight for further experimental and theoretical investigations is also given.
The Journal of Chemical Physics, 2007
Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) c... more Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) collisions within a three degrees of freedom model where five different geometries of the colliding complex were considered. Within this approach, probabilities for different competitive processes are studied: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. The purpose is to compare in detail with equivalent quantum-mechanical wave packet calculations [Bartolomei et al., J. Chem. Phys 122, 064305 (2005)], especially the behavior of the probabilities near reaction thresholds. Quasiclassical calculations compare quite well with the quantum-mechanical ones for collision induced dissociation as well as for the four center reaction, although quantum effects become very important near thresholds, particularly for lower v(1)'s and for the four center process. Less quantitative agreement is found for reactive dissociation and three-body complex formation. It is found that most quantum effects are due to differences between quantum and classical vibrational distributions of H(2)(v(1)=high). Zero point energy violation has been found in the classical reactive-dissociative probabilities. Extension of these findings to full-dimensional treatments is examined.
The Journal of Chemical Physics, 1991
The dynamics of multidimensional wave packet motion on nonadiabatically coupled electronic potent... more The dynamics of multidimensional wave packet motion on nonadiabatically coupled electronic potential surfaces is explored by numerically exact time‐dependent quantum mechanics and by the time‐dependent Hartree grid (TDHG) approximation. Excellent ...
+O[sub 2]([sup 3]Σ[sub g][sup −]) interaction](https://attachments.academia-assets.com/41178611/thumbnails/1.jpg)
](The Journal of Chemical Physics, 2010
Completely ab initio global potential energy surfaces ͑PESs͒ for the singlet and triplet spin mul... more Completely ab initio global potential energy surfaces ͑PESs͒ for the singlet and triplet spin multiplicities of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g − ͒ are reported for the first time. They have been obtained by combining an accurate restricted coupled cluster theory with singles, doubles, and perturbative triple excitations ͓RCCSD͑T͔͒ quintet potential ͓Bartolomei et al.,J. Chem. Phys. 128, 214304 ͑2008͔͒ with complete active space second order perturbation theory ͑CASPT2͒ or, alternatively, multireference configuration interaction ͑MRCI͒ calculations of the singlet-quintet and triplet-quintet splittings. Spherical harmonic expansions, containing a large number of terms due to the high anisotropy of the interaction, have been built from the ab initio data. The radial coefficients of these expansions are matched at long range distances with analytical functions based on recent ab initio calculations of the electric properties of the monomers ͓M. Bartolomei, E. Carmona-Novillo, M. I. Hernández, J. Campos-Martínez, and R. Hernández-Lamoneda, J. Comput. Chem. ͑2010͒͑ in press͔͒. The singlet and triplet PESs obtained from either RCCSD͑T͒-CASPT2 or RCCSD͑T͒-MRCI calculations are quite similar, although quantitative differences appear in specific terms of the expansion. CASPT2 calculations are the ones giving rise to larger splittings and more attractive interactions, particularly in the region of the absolute minima ͑in the rectangular D 2h geometry͒. The new singlet, triplet, and quintet PESs are tested against second virial coefficient B͑T͒ data and, their spherically averaged components, against integral cross sections measured with rotationally hot effusive beams. Both types of multiconfigurational approaches provide quite similar results, which, in turn, are in good agreement with the measurements. It is found that discrepancies with the experiments could be removed if the PESs were slightly more attractive. In this regard, the most attractive RCCSD͑T͒-CASPT2 PESs perform slightly better than the RCCSD͑T͒-MRCI counterpart.
The Journal of Chemical Physics, 2012
Rovibrational bound states of the O(2)((3)Σ(g)(-), v = 0)-O(2)((3)Σ(g)(-), v = 0) dimer in its si... more Rovibrational bound states of the O(2)((3)Σ(g)(-), v = 0)-O(2)((3)Σ(g)(-), v = 0) dimer in its singlet electronic state have been obtained by solving the time-independent Schrödinger equation for the nuclear degrees of freedom. We have employed two different ab initio potential energy surfaces, based on high level multiconfigurational methods, which are expected to give upper and lower bounds for the real values of the interaction. Results are compared with spectroscopy experiments as well as with calculations using other semi ab initio and empirical interaction potentials. For the two ab initio potentials studied here, the ground vibrational state has a rectangular geometry and behaves as a semi-rigid molecule. The associated rotational constant is found in very good agreement with high resolution spectra. However, the computed dissociation energy and the frequency of the torsion mode are larger than previous experimental determinations, and possible reasons for these discrepancies are discussed. On the other hand, we have computed the splitting between the rovibrational states of the singlet and triplet electronic states and have found a fair agreement with measurements of the dimer spectra in a solid rare gas host.
–O[sub 2]([sup 3]Σ[sub g][sup −]) dimer](https://attachments.academia-assets.com/41192045/thumbnails/1.jpg)
](The Journal of Chemical Physics, 2008
A new potential energy surface ͑PES͒ for the quintet state of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g ... more A new potential energy surface ͑PES͒ for the quintet state of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g − ͒ has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations ͓RCCSD͑T͔͒. A large number of relative orientations of the monomers ͑65͒ and intermolecular distances ͑17͒ have been considered. A spherical harmonic expansion of the interaction potential has been built from the ab initio data. It involves 29 terms, as a consequence of the large anisotropy of the interaction. The spherically averaged term agrees quite well with the one obtained from analysis of total integral cross sections. The absolute minimum of the PES corresponds to the crossed ͑D 2d ͒ structure ͑X shape͒ with an intermolecular distance of 6.224 bohrs and a well depth of 16.27 meV. Interestingly, the PES presents another ͑local͒ minimum close in energy ͑15.66 meV͒ at 6.50 bohrs and within a planar skewed geometry ͑S shape͒. We find that the origin of this second structure is due to the orientational dependence of the spin-exchange interactions which break the spin degeneracy and leads to three distinct intermolecular PESs with singlet, triplet, and quintet multiplicities. The lowest vibrational bound states of the O 2 -O 2 dimer have been obtained and it is found that they reflect the above mentioned topological features of the PES: The first allowed bound state for the 16 O isotope has an X structure but the next state is just 0.12 meV higher in energy and exhibits an S shape.
19th IEEE International Conference on Tools with Artificial Intelligence(ICTAI 2007), 2007
Communications in Computer and Information Science, 2009
This project presents a new way of sightseeing, by adapting itself to new times and new technolog... more This project presents a new way of sightseeing, by adapting itself to new times and new technologies. It has been created a system able to guide the tourist at all times during a visit to a city by means of a PDA with GPS technology; it shows the most interesting points (both in text and multimedia contents), the most important routes, a street directory, a calendar events, etc. As additional support, the system has an internal web page that helps to manage in an easy way the touristic contents. Moreover, it is used a Wi-Fi wireless technology to update the PDA contents automatically. The system has a server that allows to use the web page and update the PDA, hiding the access to the database to other kind of services not allowed by the system. Therefore, the most noteworthy aspects of this project are the use of a Wi-Fi wireless technology and a GPS positioning technology.
ACM SIGCSE Bulletin, 2008
The process of creating e-learning courseware using reusable learning objects (LOs) can be broken... more The process of creating e-learning courseware using reusable learning objects (LOs) can be broken down in two sub-processes: LOs finding and LO sequencing. Sequencing is usually performed by instructors, who create courses targeting generic profiles rather than personalized materials. This paper proposes an evolutionary approach to automate this latter problem while, simultaneously, encourages reusability and interoperability by promoting standards employment.
Proceedings of the 10th annual conference on Genetic and evolutionary computation - GECCO '08, 2008
In e-learning initiatives content creators are usually required to arrange a set of learning reso... more In e-learning initiatives content creators are usually required to arrange a set of learning resources in order to present them in a comprehensive way to the learner. Course materials are usually divided into reusable chunks called Learning Objects (LOs) and the ordered set of LOs is called sequence, so the process is called LO sequencing. In this paper an intelligent agent that performs the LO sequencing process is presented. Metadata and competencies are used to define relations between LOs so that the sequencing problem can be characterized as a Constraint Satisfaction Problem (CSP) and artificial intelligent techniques can be used to solve it. A Particle Swarm Optimization (PSO) agent is proposed, built, tuned and tested. Results show that the agent succeeds in solving the problem and that it handles reasonably combinatorial explosion inherent to this kind of problems.
Proceedings of the fifteenth annual conference on Innovation and technology in computer science education - ITiCSE '10, 2010
This paper presents a new mobile application designed for auto-assessment that allows students to... more This paper presents a new mobile application designed for auto-assessment that allows students to test their knowledge and expertise in a specific topic using questionnaires designed by their teachers. Students' achievement was evaluated and results suggest that this kind of approaches can improve it.
2010 10th IEEE International Conference on Advanced Learning Technologies, 2010
This paper presents a web tool that uses Java Server Faces to design questions graphically, to te... more This paper presents a web tool that uses Java Server Faces to design questions graphically, to test the outcome in a learning environment and to export them using the QTI v2.1 specification in order to ensure interoperability between different learning systems.
2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, 2008
The process of creating e-learning contents using reusable learning objects (LOs) can be broken d... more The process of creating e-learning contents using reusable learning objects (LOs) can be broken down in two sub-processes: LOs finding and LO sequencing. Although semiautomatic tools that aid in the finding process exits, sequencing is usually performed by instructors, who create courses targeting generic profiles rather than personalized materials. This paper proposes an evolutionary approach to automate this latter problem while, simultaneously, encourages reusability and interoperability by promoting standards employment. A model that enables automated curriculum sequencing is proposed. By means of interoperable competency records and LO metadata, the sequencing problem is turn into a constraint satisfaction problem. Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) agents are designed, built and tested in real and simulated scenarios. Results show both approaches succeed in all test cases, and that they handle reasonably computational complexity inherent to this problem, but PSO approach outperforms GA.
ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C, 2011
A p-type Bi 0.4 Sb 1.6 Te 3 thermoelectric compound was fabricated via mechanical alloying of bis... more A p-type Bi 0.4 Sb 1.6 Te 3 thermoelectric compound was fabricated via mechanical alloying of bismuth, antimony and tellurium elemental powders as starting materials. The mechanically alloyed compositions were sintered through a spark-plasma sintering (SPS) process. The effect of the milling time was investigated. In order to characterize the powders obtained via mechanical alloying, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis were used. The morphological evolution was studied by scanning electron microscopy (SEM). Results showed that the p-type Bi 0.4 Sb 1.6 Te 3 compound was formed after 2 h of milling. Further, the variation of milling time showed that the synthesized phase was stable. All the powders exhibit the same morphology albeit with slight differences. Measurements of the electrical resistivity, Seebeck coefficient and thermal conductivity were performed in the temperature range 300-520 K for the SPS samples. The resulting thermoelectric figure of merit ZT reaches a maximum of 1.2 at 360 K for the p-type bulk material with a 5 h milling time. This study demonstrates the possibility of preparing thermoelectric materials of high performance and short processing time.
Software Engineering Research and Practice, 2010
International Conference on E-Business, Enterprise Information Systems, E-Government, and Outsourcing, 2010
Las competencias no técnicas o soft skills se consideran un factor esencial para el éxito profesi... more Las competencias no técnicas o soft skills se consideran un factor esencial para el éxito profesional de los egresados universitarios. En este trabajo se presentará una experiencia en la que se combinan dos objetivos: la concienciación sobre los beneficios del trabajo en equipo y la mejora de habilidades de comunicación escrita en un máster oficial de informática. El análisis de los resultados obtenidos durante el desarrollo de esta experiencia confirma su utilidad y revela algunos datos interesantes sobre el desarrollo de estas competencias.
The Journal of Physical Chemistry A, 2009
The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and ap... more The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and applied to the collision of O2(3Sigma(g)-) molecules using a new accurate ab initio potential energy surface (PES) for the quintet state of the composite system. The PES is based on calculations using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)] [Bartolomei; et al. J. Chem. Phys. 2008, 128, 214304.]. This PES is extended here for large intermolecular distances using the ab initio long-range coefficients of Hettema et al. [J. Chem. Phys. 1994, 100, 1297.]. Elastic and rotationally inelastic integral cross sections have been obtained by means of close coupling calculations in the subthermal energy range (center-of-mass velocities below 500 m/s). Results are compared with those obtained using a PES derived from molecular beam experiments [Aquilanti; et al. J. Am. Chem. Soc. 1999, 121, 10794.]. General agreement is found between both PESs, although the experimentally derived PES appears as somewhat more anisotropic at least for the studied energy range. There is, however, a significant difference in the absolute value of the elastic cross sections that is due to differences in the long-range dispersion interaction. The performance of the ab initio PES for higher velocities (relevant to experiments) is also explored by retaining just the isotropic component of the interaction. A satisfactory agreement is found for the shape of the glory pattern but shifted toward lower absolute values of the cross sections.
The Journal of Chemical Physics, 2011
The collision dynamics of 17 O 2 ( 3 Σ − g ) + 17 O 2 ( 3 Σ − g ) in the presence of a magnetic f... more The collision dynamics of 17 O 2 ( 3 Σ − g ) + 17 O 2 ( 3 Σ − g ) in the presence of a magnetic field is studied within the close-coupling formalism in the range between 10 nK and 50 mK. A recent global ab initio potential energy surface (PES) is employed and its effect on the dynamics is analyzed and compared with previous calculations where an experimentally derived PES was used [New J. Phys 11, 055021 ]. In contrast to the results using the older PES, magnetic field dependence of the low-field-seeking state in the ultracold regime is characterized by quite a large background scattering length, a bg , and, in addition, cross sections exhibit broad and pronounced Feshbach resonances. The marked resonance structure is somewhat surprising considering the influence of inelastic scattering, but it can be explained by resorting to the analytical van der Waals theory, where the short range amplitude of the entrance channel wave function is enhanced by the large a bg . This strong sensitivity to the short range of the ab initio PES persists up to relatively high energies (10 mK). After this study and despite quantitative predictions are very difficult, it can be concluded that the ratio between elastic and spin relaxation scattering is generally small, except for magnetic fields which are either low or close to an asymmetric Fano-type resonance. Some general trends found here, such as a large density of quasibound states and a propensity towards large scattering lengths, could be also characteristic of other anisotropic molecule-molecule systems.
The Journal of Chemical Physics, 2005
The importance of vibrational-to-electronic (V-E) energy transfer mediated by spin-orbit coupling... more The importance of vibrational-to-electronic (V-E) energy transfer mediated by spin-orbit coupling in the collisional removal of O2(X 3Sigmag-,upsilon>or=26) by O2 has been reported in a recent communication [F. Dayou, J. Campos-Martinez, M. I. Hernandez, and R. Hernandez-Lamoneda, J. Chem. Phys. 120, 10355 (2004)]. The present work provides details on the electronic properties of the dimer (O2)2 relevant to the self-relaxation of O2(X 3Sigmag-,upsilon>0) where V-E energy transfer involving the O2(a 1Deltag) and O2(b 1Sigmag+) states is incorporated. Two-dimensional electronic structure calculations based on highly correlated ab initio methods have been carried out for the potential-energy and spin-orbit coupling surfaces associated with the ground singlet and two low-lying excited triplet states of the dimer dissociating into O2(X 3Sigmag-)+O2(X 3Sigmag-), O2(a 1Deltag)+O2(X 3Sigmag-), and O2(b 1Sigmag+)+O2(X 3Sigmag-). The resulting interaction potentials for the two excited triplet states display very similar features along the intermolecular separation, whereas differences arise with the ground singlet state for which the spin-exchange interaction produces a shorter equilibrium distance and higher binding energy. The vibrational dependence is qualitatively similar for the three studied interaction potentials. The spin-orbit coupling between the ground and second excited states is already nonzero in the O2+O2 dissociation limit and keeps its asymptotic value up to relatively short intermolecular separations, where the coupling increases for intramolecular distances close to the equilibrium of the isolated diatom. On the other hand, state mixing between the two excited triplet states leads to a noticeable collision-induced spin-orbit coupling between the ground and first excited states. The results are discussed in terms of specific features of the dimer electronic structure (including a simple four-electron model) and compared with existing theoretical and experimental data. This work gives theoretical insight into the origin of electronic energy-transfer mechanisms in O2+O2 collisions.
The Journal of Chemical Physics, 2005
A time-dependent wave packet method has been used to study different competing products of H(2)+H... more A time-dependent wave packet method has been used to study different competing products of H(2)+H(2) collisions: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. A three-degree-of-freedom reduced dimensionality model has been used for five different geometries of the colliding complex (parallel H, crossed X, collinear L, and two T-shaped geometries T(I) and T(II)), with reactants in selected vibrational states with one diatom vibrationally "hot" and the other one vibrationally "cold." Product probabilities have been calculated using two potential energy surfaces [J. Chem. Phys. 101, 4004 (1994); J. Chem. Phys. 116, 666 (2002)] in order to compare their performance in the dynamics. The regions of the potential energy surfaces responsible of the threshold behavior of the probabilities have been identified. Overall, we have found that the most recent potential energy surface is less anisotropic, provides a smaller propensity for insertion-type processes, and gives lower energy thresholds.
The Journal of Chemical Physics, 2007
The dynamics of collisional deactivation of O 2 ͑X 3 ⌺ g − , v =20-32͒ by O 2 ͑X 3 ⌺ g − , vЈ =0͒... more The dynamics of collisional deactivation of O 2 ͑X 3 ⌺ g − , v =20-32͒ by O 2 ͑X 3 ⌺ g − , vЈ =0͒ is investigated in detail by means of quantum-mechanical calculations. The theoretical approach involves ab initio potential energy surfaces correlating to the X 3 ⌺ g − , a 1 ⌬ g , and b 1 ⌺ g + states of O 2 and their corresponding spin-orbit couplings ͓F. Dayou, M. I. Hernández, J. Campos-Martínez, and R. Hernández-Lamoneda, J. Chem. Phys. 123, 074311 ͑2005͔͒. Accurate Rydberg-Klein-Rees potentials are included in order to improve the description of the vibrational structure of the fragments. The calculated Boltzmann-averaged depletion probabilities display a dependence with v in good agreement with experimental measurements. The onset of the vibrational-to-electronic ͑V-E͒ depletion mechanism is noticeable for v ജ 26, and it is due to energy transfer to both a 1 ⌬ g and b 1 ⌺ g + states of the diatom. For O 2 ͑X 3 ⌺ g − , v =28͒, a further and sharp increase in the removal probabilities is caused by a near degeneracy with the O 2 ͑b 1 ⌺ g + , v =19͒ vibrational state. Analysis of the temperature dependence of the Boltzmann-averaged probabilities indicates a transition from the vibrational-to-translational to the V-E energy transfer regime, which can be traced back to the behavior of the inelastic probabilities as functions of kinetic energy. Furthermore, branching ratios for outcomes through the three different electronic states show a strong propensity towards populating a unique vibrational level within each electronic state. These results provide supported evidence that spin-orbit couplings account for a large portion of the "dark channel" reported in total depletion measurements. New insight for further experimental and theoretical investigations is also given.
The Journal of Chemical Physics, 2007
Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) c... more Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) collisions within a three degrees of freedom model where five different geometries of the colliding complex were considered. Within this approach, probabilities for different competitive processes are studied: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. The purpose is to compare in detail with equivalent quantum-mechanical wave packet calculations [Bartolomei et al., J. Chem. Phys 122, 064305 (2005)], especially the behavior of the probabilities near reaction thresholds. Quasiclassical calculations compare quite well with the quantum-mechanical ones for collision induced dissociation as well as for the four center reaction, although quantum effects become very important near thresholds, particularly for lower v(1)'s and for the four center process. Less quantitative agreement is found for reactive dissociation and three-body complex formation. It is found that most quantum effects are due to differences between quantum and classical vibrational distributions of H(2)(v(1)=high). Zero point energy violation has been found in the classical reactive-dissociative probabilities. Extension of these findings to full-dimensional treatments is examined.
The Journal of Chemical Physics, 1991
The dynamics of multidimensional wave packet motion on nonadiabatically coupled electronic potent... more The dynamics of multidimensional wave packet motion on nonadiabatically coupled electronic potential surfaces is explored by numerically exact time‐dependent quantum mechanics and by the time‐dependent Hartree grid (TDHG) approximation. Excellent ...
The Journal of Chemical Physics, 2010
Completely ab initio global potential energy surfaces ͑PESs͒ for the singlet and triplet spin mul... more Completely ab initio global potential energy surfaces ͑PESs͒ for the singlet and triplet spin multiplicities of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g − ͒ are reported for the first time. They have been obtained by combining an accurate restricted coupled cluster theory with singles, doubles, and perturbative triple excitations ͓RCCSD͑T͔͒ quintet potential ͓Bartolomei et al.,J. Chem. Phys. 128, 214304 ͑2008͔͒ with complete active space second order perturbation theory ͑CASPT2͒ or, alternatively, multireference configuration interaction ͑MRCI͒ calculations of the singlet-quintet and triplet-quintet splittings. Spherical harmonic expansions, containing a large number of terms due to the high anisotropy of the interaction, have been built from the ab initio data. The radial coefficients of these expansions are matched at long range distances with analytical functions based on recent ab initio calculations of the electric properties of the monomers ͓M. Bartolomei, E. Carmona-Novillo, M. I. Hernández, J. Campos-Martínez, and R. Hernández-Lamoneda, J. Comput. Chem. ͑2010͒͑ in press͔͒. The singlet and triplet PESs obtained from either RCCSD͑T͒-CASPT2 or RCCSD͑T͒-MRCI calculations are quite similar, although quantitative differences appear in specific terms of the expansion. CASPT2 calculations are the ones giving rise to larger splittings and more attractive interactions, particularly in the region of the absolute minima ͑in the rectangular D 2h geometry͒. The new singlet, triplet, and quintet PESs are tested against second virial coefficient B͑T͒ data and, their spherically averaged components, against integral cross sections measured with rotationally hot effusive beams. Both types of multiconfigurational approaches provide quite similar results, which, in turn, are in good agreement with the measurements. It is found that discrepancies with the experiments could be removed if the PESs were slightly more attractive. In this regard, the most attractive RCCSD͑T͒-CASPT2 PESs perform slightly better than the RCCSD͑T͒-MRCI counterpart.
The Journal of Chemical Physics, 2012
Rovibrational bound states of the O(2)((3)Σ(g)(-), v = 0)-O(2)((3)Σ(g)(-), v = 0) dimer in its si... more Rovibrational bound states of the O(2)((3)Σ(g)(-), v = 0)-O(2)((3)Σ(g)(-), v = 0) dimer in its singlet electronic state have been obtained by solving the time-independent Schrödinger equation for the nuclear degrees of freedom. We have employed two different ab initio potential energy surfaces, based on high level multiconfigurational methods, which are expected to give upper and lower bounds for the real values of the interaction. Results are compared with spectroscopy experiments as well as with calculations using other semi ab initio and empirical interaction potentials. For the two ab initio potentials studied here, the ground vibrational state has a rectangular geometry and behaves as a semi-rigid molecule. The associated rotational constant is found in very good agreement with high resolution spectra. However, the computed dissociation energy and the frequency of the torsion mode are larger than previous experimental determinations, and possible reasons for these discrepancies are discussed. On the other hand, we have computed the splitting between the rovibrational states of the singlet and triplet electronic states and have found a fair agreement with measurements of the dimer spectra in a solid rare gas host.
The Journal of Chemical Physics, 2008
A new potential energy surface ͑PES͒ for the quintet state of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g ... more A new potential energy surface ͑PES͒ for the quintet state of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g − ͒ has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations ͓RCCSD͑T͔͒. A large number of relative orientations of the monomers ͑65͒ and intermolecular distances ͑17͒ have been considered. A spherical harmonic expansion of the interaction potential has been built from the ab initio data. It involves 29 terms, as a consequence of the large anisotropy of the interaction. The spherically averaged term agrees quite well with the one obtained from analysis of total integral cross sections. The absolute minimum of the PES corresponds to the crossed ͑D 2d ͒ structure ͑X shape͒ with an intermolecular distance of 6.224 bohrs and a well depth of 16.27 meV. Interestingly, the PES presents another ͑local͒ minimum close in energy ͑15.66 meV͒ at 6.50 bohrs and within a planar skewed geometry ͑S shape͒. We find that the origin of this second structure is due to the orientational dependence of the spin-exchange interactions which break the spin degeneracy and leads to three distinct intermolecular PESs with singlet, triplet, and quintet multiplicities. The lowest vibrational bound states of the O 2 -O 2 dimer have been obtained and it is found that they reflect the above mentioned topological features of the PES: The first allowed bound state for the 16 O isotope has an X structure but the next state is just 0.12 meV higher in energy and exhibits an S shape.