929 resultados para shape and surface modeling


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En este proyecto miraremos como los campos de Diseño Participativo de las tecnologías de la información (DP, Participatory IT Design) y el diseño empresarial de modelos de negocio interactúan entre sí. Exploraremos el hueco que existe en los asuntos que aborda un proyecto de DP señalado por Kyng (2010). DP es una forma de enfocar el diseño para diseñar sistemas informáticos que tiene su propia ideología, haciendo mucho hincapié en la participación de los usuarios en el proceso. Esta ideología propia de DP da paso a un conjunto de métodos y herramientas para diseñar. DP tiene sus orígenes en Escandinavia en la década de los setenta cuando cambios de progreso social de la sociedad se introdujeron en el lugar de trabajo. Ya hay algunos investigadores del campo de DP que empiezan a estudiar este hueco señalado por Kyng. Un modelo de negocios es la forma en que un negocio crea, entrega y captura valor. En las últimas décadas las empresas informáticas han cambiado su modelo de negocios, transformándose en una oferta de servicios informáticos mayoritariamente. El mundo empresarial ya conoce los beneficios de las metodologías de diseño orientadas al usuario, sin embargo no acaban de ser adoptadas por las empresas informáticas. En el proyecto buscamos responder a las preguntas que surgen al juntar estas dos áreas de estudio. ¿Cómo interpreta la comunidad de DP el mundo empresarial? ¿La teoría empresarial como trata la metodología de diseño orientado al usuario? ¿Cómo afecta en una compañía real su política de usuario a su modelo de negocio y que técnicas utilizan para involucrar al usuario? ¿Qué intereses comunes y opuestos existen entre DP y el mundo empresarial? ¿Cuál es el futuro de DP en el mundo empresarial? En cuanto a la metodología del proyecto realice un estudio de la literatura de los campos de DP y el mundo empresarial usando fuentes recomendadas por expertos de cada área así como trabajos encontrados por mi propia cuenta que eran relevantes al tema tratado. Además realice un estudio de compañías desarrolladoras de software locales a Copenhague. Mediante una serie de visitas y entrevistas con esas compañías obtuve información del modelo de negocio y proceso de desarrollo de software de las mismas. También dialogamos en cuanto a su visión de DP y metodologías de diseño orientado al usuario y como se podrían beneficiar de ellas. Durante el desarrollo del proyecto he encontrado que DP y el mundo empresarial tienen dos visiones muy diferentes. Mientras uno busca obtener el máximo beneficio el otro busca apoderar a los usuarios en su área de trabajo. Aunque al igual que DP las empresas necesitan obtener información acerca de los usuario como sus necesidades, gustos, etc. Está claro que el software producido para el mundo empresarial tiene mucho espacio para mejorar ya que suele venir con manuales de instrucciones extensos y es necesario un entrenamiento previo para su utilización. Un problema importante de la introducción de DP en las empresas es la falta de predisposición de los usuarios en colaborar en el proceso de desarrollo ya que no hay demasiada tendencia a usuarios a dar feedback. El trabajo de investigacion de Timpka y Vimarlund (1998) Participatory Design In Economic Terms: A Theoretical Discussion llega a la conclusión de que DP es económicamente favorable para los desarrolladores. Pero omite muchos factores críticos de la economía de una empresa. En cuanto al futuro de DP en el mundo empresarial, DP tiene que adaptarse a las compañías desarrolladoras de software. A sus necesidades y teniendo en cuenta sus límites de recursos. Pero hay ciertos aspectos que deben ser abordados. El primer aspecto es el uso de recursos en las técnicas de DP, ya que utilizan demasiados. Otro aspecto que debería abordar es el uso de las nuevas tecnologías de comunicación y redes sociales, ya que apenas se han utilizado en DP. Mientras que otras áreas de estudio han hecho uso de estas nuevas tecnologías y se han revolucionado DP no ha sido capaz de integrarlas en sus técnicas. Por último en el proyecto realizo una comparativa del actual modelo de negocios y proceso de desarrollo de software de la compañía Forecast.it. En esta comparativa miro como cambiaria el negocio en el caso de que se produjeran cambios en ella al introducir la ideología de DP. Donde más se notan los cambios seria en su esquema de desarrollo de software ya que habría que hacer hueco para nuevos factores y pasos.

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The theoretical study of forced bubble oscillations is motivated by the importance of cavitation bubbles and oscillating encapsulated microbubbles (i.e. contrast agents) in medical sciences. In more details,theoretical studies on bubble dynamics addressing the sound-bubble interaction phenomenon provide the basis for understanding the dynamics of contrast agent microbubbles used in medical diagnosis and of non-linearly oscillating cavitation bubbles in the case of high-intensity ultrasound therapy. Moreover, the inclusion of viscoelasticity is of vital importance for an accurate theoretical analysis since most biological tissues and fluids exhibit non-Newtonian behavior.

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In adhesion, the wetting process depends on three fundamental factors: the surface topography of the adherend, the viscosity of the adhesive, and the surface energy of both. The aim of this paper is to study the influence of viscosity and surface roughness on the wetting and their effect on the bond strength. For this purpose, an acrylic adhesive with different viscosities was synthesized and some properties, such as viscosity and surface tension, were studied before adhesive curing took place. Furthermore, the contact angle and the lap-shear strength were analyzed using aluminum adherends with two different roughnesses. Scanning electron microscopy was used to determine the effect of the viscosity and the roughness on the joint interface. The results showed that the adhesive exhibits an optimal value of viscosity. Below this value, at low viscosities, the low neoprene content produces poor bond strength due to the reduced toughness of the adhesive. Additionally, it also produces a high shrinkage during curing, which leads to the apparition of residual stresses that weakens the interfacial strength. However, once the optimum value, an increase in the viscosity produces a negative effect on the joint strength as a result of an important decrease in the wettability.

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Epidemics of soil-borne plant disease are characterized by patchiness because of restricted dispersal of inoculum. The density of inoculum within disease patches depends on a sequence comprising local amplification during the parasitic phase followed by dispersal of inoculum by cultivation during the intercrop period. The mechanisms that control size, shape, and persistence have received very little rigorous attention in epidemiological theory. Here we derive a model for dispersal of inoculum in soil by cultivation that takes account into the discrete stochastic nature of the system in time and space. Two parameters, probability of movement and mean dispersal distance, characterize lateral dispersal of inoculum by cultivation. The dispersal parameters are used in combination with the characteristic area and dimensions of host plants to identify criteria that control the shape and size of disease patches. We derive a critical value for the probability of movement for the formation of cross-shaped patches and show that this is independent of the amount of inoculum. We examine the interaction between local amplification of inoculum by parasitic activity and subsequent dilution by dispersal and identify criteria whereby asymptomatic patches may persist as inoculum falls below a threshold necessary for symptoms to appear in the subsequent crop. The model is motivated by the spread of rhizomania, an economically important soil-borne disease of sugar beet. However, the results have broad applicability to a very wide range of diseases that survive as discrete units of inoculum. The application of the model to patch dynamics of weed seeds and local introductions of genetically modified seeds is also discussed.

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Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface and cut segments were conditioned to develop competence for H2O2 elicitation. Alkaline hydrolysates of cutin from cucumber, tomato, and apple elicited H2O2 in such conditioned segments. The most active constituent of cucumber cutin was identified as dodecan-1-ol, a novel cutin monomer capable of forming hydrophobic terminal chains. Additionally, the cutin hydrolysates enhanced the activity of a fungal H2O2 elicitor, similar to cucumber surface wax, which contained newly identified alkan-1,3-diols. The specificity of elicitor and enhancement activity was further elaborated using some pure model compounds. Certain saturated hydroxy fatty acids were potent H2O2 elicitors as well as enhancers. Some unsaturated epoxy and hydroxy fatty acids were also excellent H2O2 elicitors but inhibited the fungal elicitor activity. Short-chain alkanols exhibited good elicitor and enhancer activity, whereas longer-chain alkan-1-ols were barely active. The enhancement effect was also observed for H2O2 elicitation by ergosterol and chitosan. The physiological significance of these observations might be that once the cuticle is degraded by fungal cutinase, the cutin monomers may act as H2O2 elicitors. Corrosion of cutin may also bring surface wax constituents in contact with protoplasts and enhance elicitation.

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We show, through some examples, that chemical activation by alkaline hydroxides permits the preparation of activated carbons with tailored pore volume, pore size distribution, pore structure and surface chemistry, which are useful for their application as electrodes in supercapacitors. Examples are presented discussing the importance of each of these properties on the double layer capacitance, on the kinetics of the electric double-layer charge-discharge process and on the pseudo-capacitative contribution from the surface functional groups or the addition of a conducting polymer.

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Currently, one of the most attractive and desirable ways to solve the energy challenge is harvesting energy directly from the sunlight through the so-called artificial photosynthesis. Among the ternary oxides based on earth–abundant metals, bismuth vanadate has recently emerged as a promising photoanode. Herein, BiVO4 thin film photoanodes have been successfully synthesized by a modified metal-organic precursor decomposition method, followed by an annealing treatment. In an attempt to improve the photocatalytic properties of this semiconductor material for photoelectrochemical water oxidation, the electrodes have been modified (i) by doping with La and Ce (by modifying the composition of the BiVO4 precursor solution with the desired concentration of the doping element), and (ii) by surface modification with Au nanoparticles potentiostatically electrodeposited. La and Ce doping at concentrations of 1 and 2 at% in the BiVO4 precursor solution, respectively, enhances significantly the photoelectrocatalytic performance of BiVO4 without introducing important changes in either the material structure or the electrode morphology, according to XRD and SEM characterization. In addition, surface modification of the electrodes with Au nanoparticles further enhances the photocurrent as such metallic nanoparticles act as co-catalysts, promoting charge transfer at the semiconductor/solution interface. The combination of these two complementary ways of modifying the electrodes has resulted in a significant increase in the photoresponse, facilitating their potential application in artificial photosynthesis devices.

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Il presente elaborato è incentrato sulla modellizzazione del plasma di bordo nei dispositivi per la produzione di energia da fusione nucleare noti come tokamak. La tecnologia che nel corso di tutta la seconda metà del XX secolo fino ad oggi è stata sviluppata a questo fine deve necessariamente scontrarsi con alcuni limiti. Nei tokamak il confinamento del plasma è di tipo magnetico e vincola le particelle a muoversi di moto elicoidale all'interno del vessel, tuttavia il confinamento non risulta perfetto e parte dell'energia si scarica sulle pareti della camera, rischiando pertanto di fondere i materiali. Alcune strategie possono essere messe in atto per limitare questo problema, per esempio agendo sulla geometria del tokamak, oppure sulla fisica, inducendo nel plasma una data concentrazione di impurezze che ionizzino irraggiando parte dell'energia di plasma. Proprio tale meccanismo di perdita è stato simulato in un modello monodimensionale di plasma monofluido di bordo. I risultati del codice numerico relativo al modello dimostrano che per concentrazioni di impurezze crescenti è possibile diminuire in modo significativo flusso di calore e temperatura al divertore. Per di più risulta possibile controllare la posizione del fronte di irraggiamento per mezzo di parametri di controllo del plasma quali la pressione. Si osserva inoltre l'insorgere del cosiddetto fenomeno di biforcazione alle basse temperature di divertore, fenomeno in cui il plasma si comporta in modo instabile a causa di fenomeni fisici tipici delle basse energie ("detachment") e a seguito del quale può improvvisamente spegnersi (disruzione). Infine lo stesso modello è stato migliorato inserendo l'ipotesi di plasma bifluido. Anche per gli ioni viene osservato il fenomeno di biforcazione. I risultati numerici evidenziano le dinamiche dello scambio energetico fra le specie gettando le basi di una progettazione efficiente della chimica del plasma finalizzata al raffreddamento del divertore.

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The shapes and surface textures of sand-sized quartz grains from the sediments cored at Site 645 in southern Baffin Bay during ODP Leg 105 were studied to characterize the terrigenous materials and the settling processes involved in the deposition of these sediments. Here, we show a homogeneous sand fraction that results from mixing grains from various provenances. The characteristics inherited from terrestrial processes (varying degrees of wear; fluviatile, aeolian, and diagenetic features) dominate the characteristics that result from evolution in a high-energy marine environment. Thus, the influence of the last stage of sedimentation in a deep-marine environment was difficult to distinguish. However, fluctuations in the relative proportions of particular features reveal that the terrigenous material derived from sedimentary formations of Baffin Island and East Greenland or from direct abrasion of the crystalline shield, which changed through time as the dominant settling processes evolved. In particular, this study confirms the onset of major ice rafting as old as late Miocene.

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Perceptual accuracy is known to be influenced by stimuli location within the visual field. In particular, it seems to be enhanced in the lower visual hemifield (VH) for motion and space processing, and in the upper VH for object and face processing. The origins of such asymmetries are attributed to attentional biases across the visual field, and in the functional organization of the visual system. In this article, we tested content-dependent perceptual asymmetries in different regions of the visual field. Twenty-five healthy volunteers participated in this study. They performed three visual tests involving perception of shapes, orientation and motion, in the four quadrants of the visual field. The results of the visual tests showed that perceptual accuracy was better in the lower than in the upper visual field for motion perception, and better in the upper than in the lower visual field for shape perception. Orientation perception did not show any vertical bias. No difference was found when comparing right and left VHs. The functional organization of the visual system seems to indicate that the dorsal and the ventral visual streams, responsible for motion and shape perception, respectively, show a bias for the lower and upper VHs, respectively. Such a bias depends on the content of the visual information.

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Mode of access: Internet.

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"February 1979."

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Federal Highway Administration, Washington, D.C.