36,119 research outputs found

    Development of a high-performance W-band duplexer for plasma diagnosis using a single band with dual circular polarization

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    Discrepancia entre la información que aparece en el artículo que indica que el copyright es de Elsevier, y la información que aparece en la página de la revista y en el Copyright Clearance Center que indican © 2019 The Authors. Published by Elsevier B.V., así como que el artículo está publicado en Open Access under a Creative Commons licenceThis work presents the design and experimental validation of a high performance, compact, waveguide duplexer operating from 91.5 to 96.5 GHz for its integration in diverse W-band microwave equipment as in plasma diagnosis applications. It uses a single frequency band, with two signals discriminated by different orthogonal circular polarization, which is generated by means of a septum orthomode transducer (OMT) polarizer. Moreover, this component is optimized loaded with the horn antenna for improving the overall system performance. It is explained how these two components are integrated into a very compact duplexer, designed using efficient numerical algorithms. The manufacturing process by mean of high precision milling, and including electrical discharge machining (EDM) has led to excellent performances. The measured return loss level and isolation are higher than 30 dB, and the insertion loss level is below 0.3 dB. Finally, the key parameter in this device, which reflects the symmetry in the manufacturing process, i.e., the axial ratio, is lower than 0.6 dB for both polarizations, an excellent result showing the potential of the presented designThis work was supported by the Spanish government under grants (ADDMATE) TEC2016-76070-C3-1/2-R (Agencia Estatal de Investigación, Spain, Fondo Europeo de Desarrollo Regional: AEI/FEDER/UE) and the program of Comunidad de Madrid, Spain S2013/ICE-3000 (SPADERADARCM

    Internationalization and business model decisions: A business case in mobile telecommunication industry

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    In a world characterized by hyper-competition (Gunther and D'Aveni 1994) and globalization (Knight 2000), the business model concept is becoming more and more popular. From the literature review arises a lack of a generally accepted definition of what it is, despite the growing importance of this concept. The paper is structured in five main sections. In the first one we present a review of the business model literature. The literature on business models is not exhaustive and moreover many authors often mixed up the business model with other concepts such as strategy and finance. Two main streams of literature are identifiable: the first one emerged in the mid Nineties and generally focused on e-business contexts; the second one emerged at the beginning of this decade and is not exclusively ascribable to high-tech companies. In the second paragraph we underline how relevant the decisions are about location; since in the literature on international entrepreneurship does not emerge a business model perspective of the matter the analysis is a lacking. In the third paragraph we focus our attention on Onetti and Zucchella’s business model (2008). The authors proposed a business model framework characterized by two main aspects: the clear separation among the business model, strategy and finance, and the emphasis on the relevance of location decisions. The outputs of the business model are the focus, locus and modus of companies activities. In the fourth section we try to apply this business model to Fi.Mo.Tec.’s business case, trying to explain the company’s past and to devise a way to manage the future. The conclusions complete the paper.Business model - International Entrepreneurship

    Beyond representations: towards an action-centric perspective on tangible interaction

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    In the light of theoretical as well as concrete technical development, we discuss a conceptual shift from an information-centric to an action-centric perspective on tangible interactive technology. We explicitly emphasise the qualities of shareable use, and the importance of designing tangibles that allow for meaningful manipulation and control of the digital material. This involves a broadened focus from studying properties of the interface, to instead aim for qualities of the activity of using a system, a general tendency towards designing for social and sharable use settings and an increased openness towards multiple and subjective interpretations. An effect of this is that tangibles are not designed as representations of data, but as resources for action. We discuss four ways that tangible artefacts work as resources for action: (1) for physical manipulation; (2) for referential, social and contextually oriented action; (3) for perception and sensory experience; (4) for digitally mediated action

    Walkabout : an asynchronous messaging architecture for mobile devices

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    Modern mobile devices are prolific producers and consumers of digital data, and wireless networking capabilities enable them to transfer their data over the Internet while moving. Applications running on these devices may perform transfers to upload data for backup or distribution, or to download new content on demand. Unfortunately, the limited connectivity that mobile devices experience can make these transfers slow and impractical as the amount of data increases. This thesis argues that asynchronous messaging supported by local proxies can improve the transfer capabilities of mobile devices, making it practical for them to participate in large Internet transfers. The design of the Walkabout architecture follows this approach: proxies form store-and-forward overlay networks to deliver messages asynchronously across the Internet on behalf of devices. A mobile device uploads a message to a local proxy at rapid speed, and the overlay delivers it to one or more destination devices, caching the message until each one is able to retrieve it from a local proxy. A device is able to partially upload or download a message whenever it has network connectivity, and can resume this transfer at any proxy if interrupted through disconnection. Simulation results show that Walkabout provides better throughput for mobile devices than is possible under existing methods, for a range of movement patterns. Upload and end-to-end to transfer speeds are always high when the device sending the message is mobile. In the basic Walkabout model, a message sent to a mobile device that is repeatedly moving between a small selection of connection points experiences high download and end-to-end transfer speeds, but these speeds fall as the number of connection points grows. Pre-emptive message delivery extensions improve this situation, making fast end-to-end transfers and device downloads possible under any pattern of movement. This thesis describes the design and evaluation of Walkabout, with both practical implementation and extensive simulation under real-world scenarios
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