995 resultados para rotational collective flow


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Hardware ventures are emerging entrepreneurial firms that create new market offerings based on development of digital devices. These ventures are important elements in the global economy but have not yet received much attention in the literature. Our interest in examining hardware ventures is specifically in the role that information system (IS) resources play in enabling them. We ask how the role of IS resources for hardware ventures can be conceptualized and develop a framework for assessment. Our framework builds on the distinction of operand and operant resources and distinguishes between two key lifecycle stages of hardware ventures: start-up and growth. We show how this framework can be used to discuss the role, nature, and use of IS for hardware ventures and outline empirical research strategies that flow from it. Our work contributes to broadening and enriching the IS field by drawing attention to its role in significant and novel phenomena.

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The rise of the mobile internet enables the creation of applications that provide new and easier ways for people to organise themselves, raise issues, take action and interact with their city. At the same time, society faces new problems that can only be solved when citizens work together. Nevertheless, a lack of motivation or knowledge often prevents many citizens from regularly contributing to the common good. In this position paper, we present DoGood – a mobile app – as a socio-technological system that aims at supporting the collective intelligence of citizens in their pursuit of civic engagement and civic collaboratories. Our study asks to what extent gamification can motivate users to “do good” deeds. The DoGood app uses gamified elements to encourage citizens to submit and promote their civic activities as well as to join the activities of others. Gamification is sometimes criticised for simply adding a limited number of game elements, such as leaderboards, on top of an existing experience with the hope of increasing motivation. However, in the case of the DoGood app, the process of game design was an integral part of the development, and the gamified elements target the user’s intrinsic motivations instead of providing them with an external reward. In this paper, we present design elements of the app and discuss their potential to support collective intelligence for the common good.

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Pharmacological MRI (phMRI) techniques can be used to monitor the neurophysiological effects of central nervous system (CNS) active drugs. In this study, we investigated whether dynamic susceptibility contrast (DSC) perfusion imaging employing the use of superparamagnetic iron oxide nanoparticles (Resovist) could be used to measure hemodynamic response to d-amphetamine challenge in human subjects at both 1.5 and 4 T. Significant changes in cerebral blood flow (CBF) were found in focal regions associated with the nigrostriatal circuit and mesolimbic and mesocortical dopaminergic pathways. More significant CBF responses were found at higher field strength, mainly within striatal structures. The results from this study indicate that DSC perfusion imaging using Resovist can be used to assess the efficacy of CNS-active drugs and may play a role in the development of novel psychiatric therapies at the preclinical level. © 2005 Wiley-Liss, Inc.

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This paper presents a novel vision-based underwater robotic system for the identification and control of Crown-Of-Thorns starfish (COTS) in coral reef environments. COTS have been identified as one of the most significant threats to Australia's Great Barrier Reef. These starfish literally eat coral, impacting large areas of reef and the marine ecosystem that depends on it. Evidence has suggested that land-based nutrient runoff has accelerated recent outbreaks of COTS requiring extensive use of divers to manually inject biological agents into the starfish in an attempt to control population numbers. Facilitating this control program using robotics is the goal of our research. In this paper we introduce a vision-based COTS detection and tracking system based on a Random Forest Classifier (RFC) trained on images from underwater footage. To track COTS with a moving camera, we embed the RFC in a particle filter detector and tracker where the predicted class probability of the RFC is used as an observation probability to weight the particles, and we use a sparse optical flow estimation for the prediction step of the filter. The system is experimentally evaluated in a realistic laboratory setup using a robotic arm that moves a camera at different speeds and heights over a range of real-size images of COTS in a reef environment.

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The Lagrangian particle tracking provides an effective method for simulating the deposition of nano- particles as well as micro-particles as it accounts for the particle inertia effect as well as the Brownian excitation. However, using the Lagrangian approach for simulating ultrafine particles has been limited due to computational cost and numerical difficulties. The aim of this paper is to study the deposition of nano-particles in cylindrical tubes under laminar condition using the Lagrangian particle tracking method. The commercial Fluent software is used to simulate the fluid flow in the pipes and to study the deposition and dispersion of nano-particles. Different particle diameters as well as different pipe lengths and flow rates are examined. The results show good agreement between the calculated deposition efficiency and different analytic correlations in the literature. Furthermore, for the nano-particles with higher diameters and when the effect of inertia has a higher importance, the calculated deposition efficiency by the Lagrangian method is less than the analytic correlations based on Eulerian method due to statistical error or the inertia effect.

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Management of sodic soils under irrigation often requires application of chemical ameliorants to improve permeability combined with leaching of excess salts. Modeling irrigation, soil treatments, and leaching in these sodic soils requires a model that can adequately represent the physical and chemical changes in the soil associated with the amelioration process. While there are a number of models that simulate reactive solute transport, UNSATCHEM and HYDRUS-1D are currently the only models that also include an ability to simulate the impacts of soil chemistry on hydraulic conductivity. Previous researchers have successfully applied these models to simulate amelioration experiments on a sodic loam soil. To further gauge their applicability, we extended the previous work by comparing HYDRUS simulations of sodic soil amelioration with the results from recently published laboratory experiments on a more reactive, repacked sodic clay soil. The general trends observed in the laboratory experiments were able to be simulated using HYDRUS. Differences between measured and simulated results were attributed to the limited flexibility of the function that represents chemistry-dependent hydraulic conductivity in HYDRUS. While improvements in the function could be made, the present work indicates that HYDRUS-UNSATCHEM captures the key changes in soil hydraulic properties that occur during sodic clay soil amelioration and thus extends the findings of previous researchers studying sodic loams.

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This paper presents a visual SLAM method for temporary satellite dropout navigation, here applied on fixed- wing aircraft. It is designed for flight altitudes beyond typical stereo ranges, but within the range of distance measurement sensors. The proposed visual SLAM method consists of a common localization step with monocular camera resectioning, and a mapping step which incorporates radar altimeter data for absolute scale estimation. With that, there will be no scale drift of the map and the estimated flight path. The method does not require simplifications like known landmarks and it is thus suitable for unknown and nearly arbitrary terrain. The method is tested with sensor datasets from a manned Cessna 172 aircraft. With 5% absolute scale error from radar measurements causing approximately 2-6% accumulation error over the flown distance, stable positioning is achieved over several minutes of flight time. The main limitations are flight altitudes above the radar range of 750 m where the monocular method will suffer from scale drift, and, depending on the flight speed, flights below 50 m where image processing gets difficult with a downwards-looking camera due to the high optical flow rates and the low image overlap.

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This research describes some of the salient features of Indigenous ways of working with multimodal literacies in digital contexts of use that emerged within an Indigenous school community with the oversight of Aboriginal Elders. This is significant because the use of multimodal literacy practices among a growing number of Indigenous school community groups has not been an emphasis of multimodal literacy research to date. Furthermore, authentic examples of Indigenous multimodal texts are often difficult to locate within Euro-centric educational systems of postcolonial countries. The research was conducted over a full year with students from middle and upper primary (aged 8.5–12.5 years) in an Indigenous Independent school in South-East Queensland, Australia. The project applied participatory research methods in which the research agenda was negotiated with the cultural community. Indigenous ways of multimodal literacy practices emerged as transgenerational, multimodal, placed, and collective. The findings have implications for teachers and researchers to re-envisage Indigenous ways of multimodal literacy practices in the digital age.

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This chapter considers the legal ramifications of Wikipedia, and other online media, such as the Encyclopedia of Life. Nathaniel Tkacz (2007) has observed: 'Wikipedia is an ideal entry-point from which to approach the shifting character of knowledge in contemporary society.' He observes: 'Scholarship on Wikipedia from computer science, history, philosophy, pedagogy and media studies has moved beyond speculation regarding its considerable potential, to the task of interpreting - and potentially intervening in - the significance of Wikipedia's impact' (Tkacz 2007). After an introduction, Part II considers the evolution and development of Wikipedia, and the legal troubles that have attended it. It also considers the establishment of rival online encyclopedia - such as Citizendium set up by Larry Sanger, the co-founder of Wikipedia; and Knol, the mysterious new project of Google. Part III explores the use of mass, collaborative authorship in the field of science. In particular, it looks at the development of the Encyclopedia of Life, which seeks to document the world's biodiversity. This chapter expresses concern that Wiki-based software had to develop in a largely hostile and inimical legal environment. It contends that copyright law and related fields of intellectual property need to be reformed in order better to accommodate users of copyright material (Rimmer 2007). This chapter makes a number of recommendations. First, there is a need to acknowledge and recognize forms of mass, collaborative production and consumption - not just individual authorship. Second, the view of a copyright 'work' and other subject matter as a complete and closed piece of cultural production also should be reconceptualised. Third, the defense of fair use should be expanded to accommodate a wide range of amateur, peer-to-peer production activities - not only in the United States, but in other jurisdictions as well. Fourth, the safe harbor protections accorded to Internet intermediaries, such as Wikipedia, should be strengthened. Fifth, there should be a defense in respect of the use of 'orphan works' - especially in cases of large-scale digitization. Sixth, the innovations of open source licensing should be expressly incorporated and entrenched within the formal framework of copyright laws. Finally, courts should craft judicial remedies to take into account concerns about political censorship and freedom of speech.

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Collective cell spreading is frequently observed in development, tissue repair and disease progression. Mathematical modelling used in conjunction with experimental investigation can provide key insights into the mechanisms driving the spread of cell populations. In this study, we investigated how experimental and modelling frameworks can be used to identify several key features underlying collective cell spreading. In particular, we were able to independently quantify the roles of cell motility and cell proliferation in a spreading cell population, and investigate how these roles are influenced by factors such as the initial cell density, type of cell population and the assay geometry.

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With the level of urbanization in China now exceeding 50%, its collective rural land system is under increasing pressure, creating conditions in which there is increasing conflict between the efficient use of land for agricultural purposes and its retention as security for the rural population. This paper first examines the fundamental nature of China's collective land system by analyzing the collectivization history of China, then provides a comprehensive appraisal of the strengths and weaknesses of the collective land system's role in history and the challenges it faces in modern times. The main changes needed for the current collective system are identified as (1) the establishment of a new transfer mechanism for potential collective construction land, (2) the completion of land rights verification and consolidation work, and (3) the endowment of villagers with more rights to enjoy the distribution of land incremental value. The paper's main contribution is to question the relevance of collective rural land system in contemporary China, where a shift is now taking place from one of pure economic development to one involving more social concerns, and propose potential viable amendments to integrate the need for both perspectives.

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This study is an evaluation of design students’ perceptions of the benefits of collective learning in a real-world collaborative design studio. Third year students worked in inter-disciplinary teams representing architecture, interior design, landscape architecture, and industrial design. Responding to a real-world brief and in consultation with an industry partner client and early childhood education pre-service teachers, the teams were required to collectively propose a design response for a community-based child and family centre, on an iconic koala sanctuary site. Data were collected using several methods including a participatory action research method, through the form of a large analogue, collaborative jigsaw puzzle. Using a grounded theory methodology, qualitative data were thematically analysed to reveal six distinct aspects of collaboration, which positively impacted the students’ learning experience. The results of this study include recommendations for improving real world collaboration in the design studio in preparation for students’ transition into professional practice.

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The transition from a steady to an unsteady flow induced by an adiabatic fin on the sidewall of a differentially heated air-filled cavity is numerically investigated. Numerical simulations have been performed over the range of Rayleigh numbers from Ra = 105–109. The temporal development and spatial structures of natural convection flows in the cavity with a fin are described. It has been demonstrated that the fin may induce the transition to an unsteady flow and the critical Rayleigh number for the occurrence of the transition is between 3.72 × 106 and 3.73 × 106. Furthermore, the peak frequencies of the oscillations triggered by different mechanisms are obtained through spectral analysis. It has been found that the flow rate through the cavity with a fin is larger than that without a fin under the unsteady flow, indicating that the fin may improve the unsteady flow in the cavity.

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Double diffusive Marangoni convection flow of viscous incompressible electrically conducting fluid in a square cavity is studied in this paper by taking into consideration of the effect of applied magnetic field in arbitrary direction and the chemical reaction. The governing equations are solved numerically by using alternate direct implicit (ADI) method together with the successive over relaxation (SOR) technique. The flow pattern with the effect of governing parameters, namely the buoyancy ratio W, diffusocapillary ratio w, and the Hartmann number Ha, is investigated. It is revealed from the numerical simulations that the average Nusselt number decreases; whereas the average Sherwood number increases as the orientation of magnetic field is shifted from horizontal to vertical. Moreover, the effect of buoyancy due to species concentration on the flow is stronger than the one due to thermal buoyancy. The increase in diffusocapillary parameter, w caus

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The Warburton Basin of central Australia has experienced a complex tectonic and fluid-flow history, resulting in the formation of various authigenic minerals. Geochemical and geochronological analyses were undertaken on vein carbonates from core samples of clastic sediments. Results were then integrated with zircon U–Pb dating and uraninite U–Th–total Pb dating from the underlying granite. Stable and radiogenic isotopes (δ18O, Sr and εNd), as well as trace element data of carbonate veins indicate that >200 °C basinal fluids of evolved meteoric origin circulated through the Warburton Basin. Almost coincidental ages of these carbonates (Sm–Nd; 432 ± 12 Ma) with primary zircon (421 ± 3.8 Ma) and uraninite (407 ± 16 Ma) ages from the granitic intrusion point towards a substantial period of active tectonism and an elevated thermal regime during the mid Silurian. We hypothesise that such a thermal regime may have resulted from extensional tectonism and concomitant magmatic activity following regional orogenesis. This study shows that the combined application of geochemical and geochronological analyses of both primary and secondary species may constrain the timing of tectonomagmatic events and associated fluid flow in intraplate sedimentary basins. Furthermore, this work suggests that the Sm–Nd-isotopic system is surprisingly robust and can record geologically meaningful age data from hydrothermal mineral species.