Simulating intergranular hydrogen enhanced decohesion in aluminium using density functional theory

Materials modelling at the atomistic scale provides a useful way of investigating the widely debated fundamental mechanisms of hydrogen embrittlement in materials like aluminium alloys. Density functional theory based tensile tests of grain boundaries (GBs) can be used to understand the hydrogen enhanced decohesion mechanism (HEDE). The cohesive zone model was employed to understand intergranular fracture from energies obtained in electronic structure calculations at small separation increments during ab initio tensile tests of an aluminium Σ11 GB supercell with variable coverages of H. The standard rigid grain shift test and a quasistatic sequential test, which aims to be faster and more realistic than the rigid grain shift method, were implemented. Both methods demonstrated the effects of H on the cohesive strength of the interface. The sequential method showed discrete structural changes during decohesion, along with significant deformation in general compared to the standard rigid approach. H was found to considerably weaken the GB, where increasing H content led to enhanced embrittlement such that, for the highest coverages of H, GB strength was reduced to approximately 20% of the strength of a pure Al GB - it is proposed that these results simulate HEDE. The possibility of finding H coverages required to induce this effect in real alloy systems is discussed in context by using calculations of the heat of segregation of H.

Joint Modeling of User Behaviors Based on Variable-Order Additive Markov Chain for POI Recommendation

The POI recommendation system has become an important means to help people discover attractive and interesting places. Based on our data analysis, we observe that users pay equal attention to conservatism and curiosity. In particular, adopting analysis corresponding to different time intervals, we find that users lean towards old POIs in the short term and look for new POIs with the increase of the time interval. However, existing approaches usually neglect users’ conservatism and curiosity preferences. Therefore, they are confronted with a bottleneck of depicting accurate user needs, making it difficult to improve the recommendation performance further. Besides, we further find that the number of user daily check-ins has uneven distribution, which is not conducive to capture the accurate transition patterns of user behaviors. In light of the above, we design a single POI sequential method. On this basis, we propose a recommendation method of the variable additive Markov chain. We consider the user sequential preferences, especially liking old and pursuing new features. In addition, our model exploits the geographical tendency of user behaviors. Finally, we conduct abundant experiments on four cities in the two real datasets, i.e., Foursquare and Jiepang. The experimental results show its superiority over other competitors.

Relatively-Integrated Ship Navigation by H¥ Fusion Filters

For the system with unknown statistical property noises, the property that the energies of the system noise and the observation noise are limited is utilized in this paper. On this basis, two novel fusion algorithms are proposed for ship integrated navigation with the relative navigation information, broadcasted by the Automatic Identification Systems (AISs) in the adjacent ships. Firstly, an H∞ fusion filtering algorithm is given to deal with the navigation observation messages, under the centralized fusion framework. The integrated navigation method based on this algorithm cannot deal with the asynchronous navigation messages in real time. Therefore, a sequential H∞ fusion filtering algorithm is also given to sequentially deal with the asynchronous navigation messages, secondly. Finally, a computer simulation is employed to illustrate the validity and feasibility of the sequential method.

Relatively Integrated Ship Navigation by H∞ Fusion Filters

For the system with unknown statistical property noises, the property that the energies of the system noise and the observation noise are limited is utilized in this paper. On this basis, two novel fusion algorithms are proposed for ship integrated navigation with the relative navigation information, broadcasted by the Automatic Identification Systems (AISs) in the adjacent ships. Firstly, an H∞ fusion filtering algorithm is given to deal with the navigation observation messages, under the centralized fusion framework. The integrated navigation method based on this algorithm cannot deal with the asynchronous navigation messages in real time. Therefore, a sequential H∞ fusion filtering algorithm is also given to sequentially deal with the asynchronous navigation messages, secondly. Finally, a computer simulation is employed to illustrate the validity and feasibility of the sequential method.

Effects of different plasma target concentrations of remifentanil on the MACBAR of sevoflurane in children with laparoscopic surgery

Background To investigate the effects of different plasma target concentrations of remifentanil on the minimum alveolar concentration (MAC) for blocking adrenergic response (BAR) of sevoflurane in children with laparoscopic herniorrhaphy. Methods Seventy-five children with 3-7 years old scheduled for laparoscopic herniorrhaphy were randomly divided into group R0, group R1, and group R2 according to different remifentanil plasma target concentration (0, 1, and 2 ngml-1), respectively. The MACBAR of sevoflurane was determined by the up-and-down and sequential method in each group. The concentrations of epinephrine and noradrenaline were also determined at corresponding time points. Results A total of 52 child patients were used among the anticipated 75 patients. In groups R0, R1, and R2, the MACBAR of sevoflurane was (3.29 ± 0.17) %, (2.12 ± 0.10) % and (1.29 ± 0.11) %, respectively, and a significant difference was found among the three groups (P<0.05). The changes of epinephrine and noradrenaline concentrations in each group before and after insufflation of carbon dioxide pneumoperitoneum showed no significant differences. Conclusion Remifentanil by target-controlled infusion can effectively reduce the MACBAR of sevoflurane during laparoscopic surgery in children. At a similar effect of MACBAR, both the changes of epinephrine and noradrenaline concentrations are not affected by the infusion of different remifentanil target concentrations. Trial registration The trial was registered at http://www.chictr.org.cn(ChiCTR1800019393, 8, Nov, 2018).

Competency-based training in higher education

The change of contexts in university education refers to the academic and professional experiences that are combined during the academic course and that can complement the competency-based education provided by Higher Education Institutions, generating an important change from the pedagogical and didactic point of view that directly intervenes in the professional performance. From this work, the perception of the graduates of the University of Boyacá on the general competences applied in their professional performance is investigated. A descriptive-exploratory study was carried out, from an interpretative paradigm through a sequential method. For this purpose, 881 graduates of the 2017-10, 2016-10, 2014-10 and 2012-10 cohorts of the 21 undergraduate academic programs participated in the research. Among the results, satisfaction on the part of the graduates in the acquisition of general competencies applied to their professional performance in accordance with the institutional graduation profile stands out, with the most mastered competencies being leadership and change management and ethical-citizenship. In summary, these results point to possible lines of action to enhance the acquisition of general competencies within the academic programs, and consequently align the institutional graduate profile. El cambio de contextos en la formación universitaria alude a las experiencias académicas y profesionales que son combinadas durante el transcurrir académico y que pueden complementar la formación basada en competencias impartida por las Instituciones de Educación Superior, generando un cambio importante desde el punto de vista pedagógico y didáctico que interviene directamente en el desempeño profesional. Desde este trabajo se indaga la percepción de los egresados de la Universidad de Boyacá sobre las competencias generales aplicadas en su desempeño profesional. Se realizó un estudio descriptivo-exploratorio, desde un paradigma interpretativo a través de un método secuencial. Para ello, han participado en la investigación 881 egresados de las cohortes 2017-10, 2016-10, 2014-10 y 2012-10 de los 21 programas académicos de pregrado. Entre los resultados se destaca satisfacción por parte de los egresados en la adquisición de competencias generales aplicadas a su desempeño profesional acordes con el perfil de egreso institucional, siendo las competencias más dominadas liderazgo y manejo del cambio y ético-ciudadanas. En síntesis, estos resultados señalan las posibles líneas de actuación para potenciar la adquisición de competencias generales al interior de los programas académicos, y en consecuencia alinear el perfil de egreso institucional.

A Parallel Algorithm for Scheduling a Two-Machine Robotic Cell in Bicycle Frame Welding Process

Welding frames with differing geometries is one of the most crucial stages in the production of high-end bicycles. This paper proposes a parallel algorithm and a mixed integer linear programming formulation for scheduling a two-machine robotic welding station. The time complexity of the introduced parallel method is O(log2n) on an n3-processor Exclusive Read Exclusive Write Parallel Random-Access Machine (EREW PRAM), where n is the problem size. The algorithm is designed to take advantage of modern graphics cards to significantly accelerate the computations. To present the benefits of the parallelization, the algorithm is compared to the state of art sequential method and a solver-based approach. Experimental results show an impressive speedup for larger problem instances—up to 314 on a single Graphics Processing Unit (GPU), compared to a single-threaded CPU execution of the sequential algorithm.