Nonlinear optical absorption and reflection of single wall carbon nanotube thin films by ZZ-scan technique

"Both the nonlinear optical transmission and reflection characteristics of HiPco-based single wall carbon nanotube (SWNT) thin films are studied by using the ZZ-scan method with femtosecond laser pulses at a wavelength of 1.46μm1.46μm. The nonlinear absorption coefficient and nonlinear refractive index are obtained as (5.4±2.0)×10−7cm/W(5.4±2.0)×10−7cm∕W and (1.1±0.5)×10−11cm2/W(1.1±0.5)×10−11cm2∕W, respectively, which are considerably greater than those of other optical materials. This large optical nonlinearity is ascribed to (a) homogeneously deposited thin nanotube film on optically transparent barium fluoride, (b) just-resonant excitation condition, and (c) intrinsic saturable absorption feature of SWNTs.

Google Cardboard Robotic Avatar

El objetivo principal de este Trabajo de Fin de Grado es desarrollar un sistema distribuido heterogéneo, combinando visión remota y realidad virtual, donde el usuario pueda ver a través de los ojos de un avatar robótico. El cliente consiste en unas gafas de realidad virtual, como lo son Google Cardboard. Es un artilugio de cartón con dos huecos para un par de lentes, que apuntan a una cavidad donde se ha de situar un smartphone. Una aplicación mostrará dos imágenes en la pantalla del dispositivo móvil que serán observadas a través de estas lentes por el usuario. En la parte del servidor habrá un par de videocámaras situadas en una estructura sobre un motor. Una parte del servidor envía los fotogramas capturados por las cámaras a través de un protocolo de multimedia en red hasta el cliente, donde cada transmisión se corresponde con un ojo del usuario. Por otra parte, el servidor también se encargará de hacer rotar la estructura con las cámaras, controlando el motor según los movimientos de la cabeza del usuario. La aplicación envía periódicamente la rotación del dispositivo, que se calcula utilizando el acelerómetro y la brújula del smartphone, a este servidor de control.The main goal of this Bachelor Thesis is to develop an heterogeneous distributed system, combining remote vision and virtual reality, where the user can look through the eyes of a robotic avatar. The client consists of a pair of virtual reality glasses, such as Google Cardboard. It is a cardboard made gadget with two holes for a pair of lens that look to a cavity where the smartphone must be placed. An application will show two images on the mobile device’s screen that will be observed through this lens by the user. There is a couple of videocameras on the server side, assembled in a structure on a motor. A part of the server sends the frames captured by the cameras using a multimedia networking protocol to the client, where each stream corresponds to an eye. On the other hand, the server is also responsible for rotating the structure with the cameras controlling the motor according to the movements of the user’s head. The application periodically sends the rotation of the device, which is calculated using the smartphone’s accelerometer and compass, to the control server

Implications of tree management on poplar and willow pasture-tree systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, Massey University, Palmerston North, New Zealand

Willow and poplar trees planted at wide spacing have proved their effectiveness as a biological method to control soil erosion in pastoral hill country. Due to lack of management, many trees aged 30+ years have grown very large (>60 cm diameter at breast height), resulting in excessive shading of understorey pasture. The large trees are also prone to breakage of branches and toppling during strong winds, potentially damaging farm infrastructure or injuring livestock. Management of tree size can coincide with providing edible poplar and willow foliage as a source of supplementary fodder in summer droughts. Trees can be pollarded, involving total canopy removal, but the effects of pollarding on tree root dynamics are poorly understood. This thesis evaluated the effect of the tree canopy removal on the root dynamics and root non-structural carbohydrate dynamics of pollarded mature willow and poplar trees and decapitated young willow and poplar trees grown from cuttings. Impacts of tree canopy removal when trees were at different phenological stages were also studied in pollarded mature willow trees and decapitated young willow and poplar trees. Finally, herbage accumulation under pollarded trees was contrasted with herbage accumulated under unpollarded (UP) trees and in open pasture sites (OP) away from direct tree influence. Pollarding did not impose a unique impact on the root structure of mature willow and poplar trees. However some similarities were found in both species. For instance, pollarding had its main impact in the roots closest to the trunk and above 300 mm soil depth. In these root sections disrupted by pollarding, fine root length and mass of pollarded (P) trees were, one year after above-ground removal, from 2× to 4× less than equivalent unpollarded (UP) trees. However, one year after pollarding, pollarded trees recovered or maintained the initial fine root densities recorded in the same trees prior to pollarding. The study conducted with young willow and poplar trees grown from cuttings showed that willow trees had a greater ability to recover from damage in the root structure after decapitation. Nine months after decapitation in early autumn, root mass of young willow decapitated trees was 57% greater than prior to decapitation and 64% less than non-decapitated (ND) trees. In contrast, within the same time frame, root mass of young poplar trees decapitated in early autumn was 80% less than ND trees and 52% less than the initial root mass recorded prior to decapitation. Greater resprouting ability of willow trees than poplar trees after decapitation was proposed as the cause for the greater resilience to decapitation observed in willow trees than in poplar ones. Further evidence for a greater resilience to pollarding of willow trees was found in the root starch dynamics evaluated after tree canopy removal. Pollarded or decapitated willow trees (mature or grown from cuttings) were able to replenish their root starch concentrations similarly to UP or ND trees in the growing season following tree canopy removal. In contrast, both pollarded and decapitated poplar trees (mature or grown from cuttings) had lesser root starch concentrations than intact trees one year after tree canopy removal. Pollarding (P) or decapitation (D) at dormancy (DP or DD trees) showed no clear advantages in terms of the tree root structure maintenance or recovery after above-ground removal, over pollarding or decapitating the trees towards the end of the growing season in early autumn (AP or AD trees), when trees still had leaves. With mature willow trees, annual average fine root density (fRD) recovery of DP trees relative to pre-pollarding density was greater than annual average fRD recovery of AP trees. However, this difference was attributed to record moisture restrictions that disrupted the root growth of both AP and UP trees during the growing season following early autumn pollarding. Similarly, young DD and AD willow and poplar trees showed that four and a half months after decapitation, both treatment trees were able to recover or maintain initial root mass recorded prior to decapitation. The study on herbage accumulation beneath pollarded trees, suggests that 4 years after being pollarded, P willow trees shaded pasture in a similar way to UP trees, as annual net herbage accumulation (NHA) attained in these two environments was statistically not different. Annual NHA under P and UP environments, were, respectively, 30 and 43% less than annual net herbage accumulation recorded in open pasture sites (4.9 t DM ha-1 yr -1). Ability of willow trees to recover, within the first year after pollarding or decapitation, initial root densities recorded prior to canopy removal, and to replenish root starch concentration similar to intact trees, suggests these trees could have pollarding cycles of 2 to 3 years. Short pollarding cycles could lessen herbage accumulation reductions on a pasture-tree stand level as more trees or more frequent repollarding is practised. However, results derived in this thesis from willow trees, need to be confirmed in at least two year lasting studies before recommending shorter pollarding cycles than currently advised of 3 or 4 years. In contrast, poplar trees require longer pollarding cycles or higher tree stand densities if a pollarding program is instituted, as these trees were not able to recover within the first year after canopy removal, the root values recorded prior to pollarding and/or to replenish the root starch reserves

Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides

"Although bulk hexagonal phases of layered semiconducting transition metal dichalcogenides (STMD) such as MoS2, WS2, WSe2 and MoSe2 exhibit indirect band gaps, a mono-layer of STMD possesses a direct band gap which could be used in the construction of novel optoelectronic devices, catalysts, sensors and valleytronic components. Unfortunately, the direct band gap only occurs for mono-layered STMD. We have found, using first principles calculations, that by alternating individual layers of different STMD (MoS2, WS2, WSe2 and MoSe2) with particular stackings, it is possible to generate direct band gap bi-layers ranging from 0.79 eV to 1.157 eV. Interestingly, in this direct band gap, electrons and holes are physically separated and localized in different layers. We foresee that the alternation of different STMD would result in the fabrication of materials with unprecedented optical and physico-chemical properties that would need further experimental and theoretical investigations.

An anticorrosive magnesium/carbon nanotube composite

"Here, we report a drastically improved anticorrosive characteristic of magnesium alloy composites with the introduction of multiwalled carbon nanotubes. Highly depressed corrosion of nanotube-filled magnesium composite in salt water is due to the formation of stable oxide films along the grain boundaries of magnesium. Our results indicate that carbon nanotube acted as effective multifunctional filler to improve both mechanical and anticorrosive performances of magnesium alloy.

Enhanced thermal conductivity of carbon fiber/phenolic resin composites by the introduction of carbon nanotubes

"The authors report a significant enhancement in the thermal conductivity of a conventional carbon fiber/phenolic resin composite system when adding highly crystalline multiwalled carbon nanotubes. They demonstrate that 7wt%7wt% of carbon nanotubes dispersed homogeneously in a phenolic resin acted as an effective thermal bridge between adjacent carbon fibers and resulted in an enhancement of the thermal conductivity (e.g., from 250to393W∕mK250to393W∕mK). These results indicate that highly crystalline carbon nanotubes can be used as a multifunctional filler to enhance simultaneously the mechanical and thermal properties of the carbon fiber/phenolic resin composites.

4,4'-Dimethyl-2,2'-{[2,3,3a,4,5,6,7,7a-octa-hydro-1H-benzimidazole-1,3-di-yl]bis-(methyl-ene)}diphenol

The asymmetric unit of the title compound, C23H30N2O2, contains one half-mol-ecule, with a twofold axis splitting the mol-ecule in two identical halves. The structure of the racemic mixture has been reported previously [Rivera et al. (2009>) J. Chem. Crystallogr. 39, 827-830] but the enanti-omer reported here crystallized in the ortho-rhom-bic space group P21212 (Z = 2), whereas the racemate occurs in the triclinic space group P-1 (Z = 2). The observed mol-ecular conformation is stabilized by two intra-molecular O-H⋯N hydrogen bonds, which generate rings with graph-set motif S(6). In the crystal, mol-ecules are linked via non-classical C-H⋯O inter-actions, which stack the mol-ecules along the b axis

Low-technology industries and regional innovation systems: the salmon industry in Chile

Results show that the worldwide competitiveness of the low-tech Salmon Industry in the Los Lagos region has not developed the principal factors permitting the consolidation of a Regional Innovation System (RIS). On the contrary we identify important gaps in terms of the regional conditions such as "networking", "knowledge creation and diffusion", among others, capable to stimulate the innovation behavior of salmon firms

Some reasons to implement reverse logistics in companies

This article aims to present a reflexion on some of the main reasons for companies to implement reverse logistics processes. Companies have difficulties in implementing reverse logistics as part of their business processes due to high cost of implementation and due to difficulties in measuring material returns. However, companies that have succeeded in implementing it have increased their competitiveness and improved their corporate image. This paper proposes six critical success factors for the implementation of reverse logistics: good income control, standardised and mapped processes, reduced time cycle, information systems, planned logistic grid and collaborative relations between customers and suppliers. Well-structured and implemented reverse logistics process brings up benefits and advantages to companies, beyond environmental ones

Catching up in knowledge intensive business services: the case of the software and IT services from Argentina and Brazil

América Latina está experimentando, en los últimos años, un incremento de actividades en los sectores vinculados a los Servicios Intensivos en Conocimiento. Dicha participación trae aparejadas nuevas perspectivas de desarrollo para la región. El objetivo de este artículo es comparar las características estructurales y el desempeño innovativo del sector de Software y Servicios Informáticos en dos economías latinoamericanas: Argentina y Brasil. Ello se realizará desde el enfoque de los Sistemas Sectoriales de Innovación, intentando ofrecer elementos para comprender los patrones de comportamiento innovativo de ambos sectores en términos de sus similitudes y diferencias, poniendo especial énfasis en las políticas sectoriales implementadas en ambos países. A partir de un estudio de carácter exploratorio y descriptivo, que ofrece amplias posibilidades de extensión y profundización, el artículo muestra la existencia de un desempeño innovador diferencial entre ambos países y destaca la concurrencia de una serie de diferencias cualitativas entre sus sistemas sectoriales, particularmente referidas a la cobertura efectiva de sus instrumentos de política y al perfil del destino de producción en cada caso.In recent years, Latin America has undergone an increase of activities in the sectors related to knowledge intensive business services. Such increase brings with it new development prospects for the region. The aim of this paper is to compare the structural characteristics and innovative performance of the software and IT services sector in two of the largest Latin American economies: Argentina and Brazil. The authors of this study have adopted a sectoral systems of innovation perspective, trying to offer insights into the innovative behavior patterns of both sectors in terms of their similarities and differences, and emphasizing specially on sectoral policies implemented in both countries. From an exploratory and descriptive point of view that offers wide possibilities for a deeper analysis, this paper shows a differential innovative performance between these two economies in this sector. It also highlights some qualitative differences between its sectoral systems, particularly related to the effective coverage of the policy promoting instruments and the production profile of each case.Fil: Uriona Maldonado, Mauricio. Universidade Federal Da Santa Catarina; BrasilFil: Morero, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones y Estudio Sobre Cultura y Sociedad; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Borrastero, Carina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martin. Instituto de Altos Estudios Sociales; Argentin