Estudo do estado fundamental de aglomerados de silício via redes neurais

We introduce a global optimization method based on the cooperation between an Artificial Neural Net (ANN) and Genetic Algorithm (GA). We have used ANN to select the initial population for the GA. We have tested the new method to predict the ground-state geometry of silicon clusters. We have described the clusters as a piling of plane structures. We have trained three ANN architectures and compared their results with those of pure GA. ANN strongly reduces the total computational time. For Si10, it gained a factor of 5 in search speed. This method can be easily extended to other optimization problems.

Estudi i implementació pràctica d'una xarxa Wifi Mesh

En el projecte ens centrarem en el funcionament de les Xarxes mallades sense fils, es fa una breu explicació de les xarxes Ad-hoc, ja que aquestes formen un part important dintre d’una xarxa Mesh. S’explicaran diversos protocols d’enrutament com ara BATMAN, AODV, 802.11s i OLSR. Aquest últim és el que utilitzarem per a la configuració de la xarxa que realitzarem. S’explicarà el tipus de paquets que s’envien entre els nodes perquè el funcionament de la xarxa sigui òptim i tots els clients puguin tenir-hi accés i estiguin connectats entre ells. Al finalitzar l’estudi teòric d’aquest tipus de xarxa i veure les seves avantatges i desavantatges respecte altres tipus de xarxes sense fils, es muntaran dos petites xarxa. Per a muntar-les utilitzarem de Punts d’Accés els nodes Ubuquiti Nanoestation LocoM2. Una de les xarxes serà al poble Bellcaire d’Urgell, on és connectaran tres cases, on només una te accés a Internet i els nodes estaran connectats en línia, es a dir, del Node1 – Node2 – Node3. La segona serà a una casa de Barcelona on mitjançant els tres nodes obtindrem una connexió d’Internet a tota la casa, en aquest cas els tres nodes estaran connectats els tres formant un cercle, es a dir, Node1-Node2-Node3-Node1. Finalment, és mirarà una proposta de futur, on es parlaria amb l’Ajuntament del poble on s’ha fet la primera proba per realitzar una Xarxa mallada sense fils a tots els llocs públics del poble.

Parentesco, redes familiares y sociabilidad en el mundo hispanoamericano en los siglos XVII y XIX

Hasta hace algunos años, el interés por la historia de la familia, aunque no era escaso, estaba orientado a enfoques de tipo macrohistórico, ya que el énfasis estaba puesto en las estructuras de la sociedad. La dominación de los planteamientos cuantitativistas impuestos por los Annales, así como la fuerte influencia del marxismo, coadyuvaron en la consideración de la familia, no como objeto de investigación en sí misma, sino como expresión o ilustración de un funcionamiento económico social global. Los numerosos y excelentes trabajos sobre la élite colonial americana ejemplifican esta clase de acercamiento, fundamentado a partir de una reflexión acerca de los grupos sociales definidos en base a criterios socio-económicos. De la misma marreta, si la familia servia de base a los estudios de demografía histórica,lo que se pretendía a través de ella era la deconstrucción de modelos de comportamiento demográfico para un espacio definido. Fuera de estos planteos con sesgos estructuralistas y funcionalistas, la historia de la familia fue el refugio de la historiografia más tradicional y a veces rancia, fundada muchas veces en la aplicación de la reconstrucción genealógica como único método de estudio de los sectotes sociales más poderosos a nivel económico o político.

Desempenho físico-químico de metais e estruturas de concreto de redes de distribuição de energia: estudo de caso na região de Manaus

The influence of natural aging furthered by atmospheric corrosion of parts of electric transformers and materials, as well as of concrete poles and cross arms containing corrosion inhibitors was evaluated in Manaus. Results for painted materials, it could showed that loss of specular gloss was more intensive in aliphatic polyurethane points than in acrylic polyurethane ones. No corrosion was observed for metal and concrete samples until 400 days of natural aging. Corrosion in steel reinforcement was noticed in some poles, arising from manufacturing faults, such as low cement content, water/cement ratio, thin concrete cover thickness, etc. The performance of corrosion inhibitors was assessed by many techniques after natural and accelerated aging in a 3.5% saline aqueous solution. The results show the need for better chemical component selection and its concentration in the concrete mixture.

Convergencia de Servicios en redes de próxima generación

Descripción de la realidad que acompaña a la industria de las telecomunicaciones

Redes de acción : el caso de Birmania

El objetivo del presente ensayo es analizar el papel de las nuevas tecnologías en la formación de redes de acción. Para ello, comenzaré analizando brevemente ciertos puntos y características de las redes de acción y sus tipos, para a continuación, centrar el análisis en un caso real y de ardiente actualidad, como es el caso de Birmania.Una red de acción es un sistema que interconecta nodos. Estos nodos son autónomos y autoorganizados, de manera que cada uno de ellos aporta información y la red se encarga de intercambiar dicha información proveniente de los distintos nodos, así como proyectarla hacia espacios mayores de interacción. Por lo tanto, una red es un sistema exógeno, en la medida que trabaja en la búsqueda constante de interacciones e intercambios mas allá de sus propias fronteras. Las redes responden a la necesidad de conversar con otros para producir acuerdos, arreglos y consensos. Por lo que la red precisa de la polivalencia y la capacidad de adquirir nuevas competencias, por parte de los sujetos que la forman.

Parentesco, redes familiares y sociabilidad en el mundo hispanoamericano en los siglos XVIII y XIX

Hasta hace algunos años, el interés por la historia de la familia, aunque no era escaso, estaba orientado a enfoques de tipo macrohistórico, ya que el énfasis estaba puesto en las estructuras de la sociedad. La dominación de los planteamientos cuantitativistas impuestos por los Annales, así como la fuerte influencia del marxismo, coadyuvaron en la consideración de la familia, fio como objeto de investigación en sí misma, sino como expresión o ilustración de un funcionamiento económico social global.

Las redes de innovación docente de la Universitat de Girona : la perspectiva de los coordinadores

In 2009 the University of Girona (Spain) created four interest groups on teaching innovation. The objective of the project is that lecturers with an interest in teaching innovation can exchange their points of view and learn from one another, so University teaching is improved as a result. There are four such groups: “Problem based learning (ABP)”, “Cooperative learning”, “Evaluation”, and “Information and Communication Technologies (ICTs) and Teaching”. The coordinators of the groups or networks, as they are also called, are chosen on a free basis by its members. This paper presents their point of view as regards the current activity of encouragement of interest in higher education and they elaborate on the main difficulties involved. The implications of the interdisciplinary work are explored, as well as the challenges of an initiative of this kind. The evolution of the ongoing work is reviewed, taking into account the context of a changing University, the lack of previous experience regarding projects of this kind, the asynchronous communication among the participants, and the necessity of a flexible approach in organizational matters

A tabela periódica dos elementos químicos prevista por redes neurais artificiais de Kohonen

Although several chemical elements were not known by end of the 18th century, Mendeleyev came up with an astonishing achievement: the periodic table of elements. He was not only able to predict the existence of (then) new elements but also to provide accurate estimates of their chemical and physical properties. This is certainly a relevant example of the human intelligence. Here, we intend to shed some light on the following question: Can an artificial intelligence system yield a classification of the elements that resembles, in some sense, the periodic table? To achieve our goal, we have fed a self-organized map (SOM) with information available at Mendeleyev's time. Our results show that similar elements tend to form individual clusters. Thus, SOM generates clusters of halogens, alkaline metals and transition metals that show a similarity with the periodic table of elements.

Aplicação de redes neurais artificiais na identificação de gasolinas adulteradas comercializadas na região de Londrina - Paraná

The multilayer perceptron network was used to classify the gasoline. The main parameters used in the classification were established by the Ordinance nº 309 of the Agência Nacional do Petróleo, but without informing the network the legal limits of these parameters. The network used had 10 neurons in a single hidden layer, learning rate of 0.04 and 250 training epochs. The application of artificial neural network served classify 100% of the commercialized gas in the region of Londrina-PR and to identify the tampered gasoline even those suspected of tampering.

Determinação de constituintes químicos em madeira de eucalipto por Pi-CG/EM e calibração multivariada: comparação entre redes neurais artificiais e máquinas de vetor suporte

Multivariate models were developed using Artificial Neural Network (ANN) and Least Square - Support Vector Machines (LS-SVM) for estimating lignin siringyl/guaiacyl ratio and the contents of cellulose, hemicelluloses and lignin in eucalyptus wood by pyrolysis associated to gaseous chromatography and mass spectrometry (Py-GC/MS). The results obtained by two calibration methods were in agreement with those of reference methods. However a comparison indicated that the LS-SVM model presented better predictive capacity for the cellulose and lignin contents, while the ANN model presented was more adequate for estimating the hemicelluloses content and lignin siringyl/guaiacyl ratio.

Uso de redes neurais recorrentes na determinação das constantes de acidez para a 7-epiclusianona em misturas etanol-água

This work propose a recursive neural network to solve inverse equilibrium problem. The acidity constants of 7-epiclusianone in ethanol-water binary mixtures were determined from multiwavelength spectrophotmetric data. A linear relationship between acidity constants and the %w/v of ethanol in the solvent mixture was observed. The proposed method efficiency is compared with the Simplex method, commonly used in nonlinear optimization techniques. The neural network method is simple, numerically stable and has a broad range of applicability.

Redes de colaboração científica na área de química no Brasil: um estudo baseado nas coautorias dos artigos da revista Química Nova

In this paper we built three co-authorship networks displaying the acquaintances between countries, universities and authors that have published papers in Quimica Nova from 1995 to 2008. Our research was conducted applying a bibliometric approach to 1782 papers and over 4200 authors. Centrality measures were used and the most significant actors of each network were pointed out. The results using the centrality metrics and the network structures indicated that Quimica Nova resembles a typical scientific community.

Triagem de suportes orgânicos e protocolos de ativação na imobilização e estabilização de lipase de Thermomyces lanuginosus

Lipase from Thermomyces lanuginosus was covalently immobilized on activated poly-hydroxybutyrate, sugarcane bagasse and the chemically modified hybrid hydrogel chitosan-alginate prepared by different strategies. Among the tested supports, chitosan-alginate chemically modified with 2,4,6-trinitrobenzenesulfonic acid rendered derivatives with the highest hydrolytic activity and thermal-stability, 45-fold more stable than soluble lipase and was then selected for further studies. The pH of maximum activity was similar for both immobilized and free lipase (pH 8.0) while optimum temperature was 5 - 10 ºC higher for the immobilized lipase. Higher yields in the butyl butyrate synthesis were found for the derivatives prepared by activation with glycidol and epichlorohydrin.

Redes metalorgânicas e suas aplicações em catálise

Metal-organic frameworks (MOFs) form a new class of materials with well-defined yet tunable properties. These are crystalline, highly porous and exhibit strong metal-ligand interactions. Importantly, their physical and chemical properties, including pore size, pore structure, acidity, and magnetic and optical characteristics, can be tailored by choosing the appropriate ligands and metal precursors. Here we review the key aspects of synthesis and characterization of MOFs, focusing on lanthanide-based and vanadium-based materials. We also outline some of their applications in catalysis and materials science.