41,445 research outputs found

    Cities as emergent models: the morphological logic of Manhattan and Barcelona

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    This paper is set to unveil several particulars about the logic embedded in the diachronic model of city growth and the rules which govern the emergence of urban spaces. The paper outlines an attempt to detect and define the generative rules of a growing urban structure by means of evaluation techniques. The initial approach in this regards will be to study the evolution of existing urban regions or cities which in our case are Manhattan and Barcelona and investigate the rules and causes of their emergence and growth. The paper will concentrate on the spatial aspect of the generative rules and investigate their behaviour and dimensionality. Several Space Syntax evaluation methods will be implemented to capture the change of spatial configurations within the growing urban structures. In addition, certain spatial elements will be isolated and tested aiming to illustrate their influence on the main spatial structures. Both urban regions were found to be emergent products of a bottom up organic growth mostly distinguished in the vicinities of the first settlements. Despite the imposition of a uniform grid on both cities in later stages of their development these cities managed to deform the regularity in the preplanned grid in an emergent manner to end up with an efficient model embodied in their current spatial arrangement. The paper reveals several consistencies in the spatial morphology of both urban regions and provides explanation of these regularities in an approach to extract the underlying rules which contributed to the growth optimization process

    Abelian homotopy Dijkgraaf-Witten theory

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    We construct a version of Dijkgraaf-Witten theory based on a compact abelian Lie group within the formalism of Turaev's homotopy quantum field theory. As an application we show that the 2+1-dimensional theory based on U(1) classifies lens spaces up to homotopy type.Comment: 23 pages, 1 figur

    The topological glass in ring polymers

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    We study the dynamics of concentrated, long, semi-flexible, unknotted and unlinked ring polymers embedded in a gel by Monte Carlo simulation of a coarse-grained model. This involves the ansatz that the rings compactify into a duplex structure where they can be modelled as linear polymers. The classical polymer glass transition involves a rapid loss of microscopic freedom within the polymer molecule as the temperature is reduced toward Tg. Here we are interested in temperatures well above Tg where the polymers retain high microscopic mobility. We analyse the slowing of stress relaxation originating from inter-ring penetrations (threadings). For long polymers an extended network of quasi-topological penetrations forms. The longest relaxation time appears to depend exponentially on the ring polymer contour length, reminiscent of the usual exponential slowing (e.g., with temperature) in classical glasses. Finally, we discuss how this represents a universality class for glassy dynamics

    Preliminary basic performance analysis of the Cedar multiprocessor memory system

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    Some preliminary basic results on the performance of the Cedar multiprocessor memory system are presented. Empirical results are presented and used to calibrate a memory system simulator which is then used to discuss the scalability of the system

    Living with Hearing Loss in a Connected Home: White Paper

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    This paper provides insights into the requirements and expectations of people with hearing loss in engagement with connected devices at home, derived from a questionnaire and a stakeholder workshop, and supported by relevant literature. The paper details challenges facing people with hearing loss in engagement with connected technologies and identifies priority areas for technology intervention and development. The workshop was organised by the PETRAS National Centre of Excellence for IoT Systems Cybersecurity. It was attended by representatives from technology companies and various UK groups for people with hearing loss (both profoundly deaf and hard-of-hearing, as well as cochlear implant users), some individual end-users with various types of hearing loss, and researchers. Whether they like it or not, people with hearing loss may depend on a hearing person or technologies (e.g. hearing aid and voice recognition to text) to communicate and interact with the hearing world. While technology intervention can reduce needs for help from hearing people, it inevitably increases dependency on technologies. This can lead to people with hearing loss feeling out of control, especially when communication technologies do not function as expected, often without any back-up, failsafe or contingency plans. Without reliable technologies – mainstream and/or specialist – to bridge the gap between visual- and voice-based (oral) communications, people with hearing loss are at risk of isolation and exclusion

    Indirect Self-Modulation Instability Measurement Concept for the AWAKE Proton Beam

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    AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment, is a proof-of-principle R&D experiment at CERN using a 400 GeV/c proton beam from the CERN SPS (longitudinal beam size sigma_z = 12 cm) which will be sent into a 10 m long plasma section with a nominal density of approx. 7x10^14 atoms/cm3 (plasma wavelength lambda_p = 1.2mm). In this paper we show that by measuring the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma, information about the occurrence of the self-modulation instability (SMI) can be inferred. In particular we show that measuring defocused protons with an angle of 1 mrad corresponds to having electric fields in the order of GV/m and fully developed self-modulation of the proton bunch. Additionally, by measuring the defocused beam edge of the self-modulated bunch, information about the growth rate of the instability can be extracted. If hosing instability occurs, it could be detected by measuring a non-uniform defocused beam shape with changing radius. Using a 1 mm thick Chromox scintillation screen for imaging of the self-modulated proton bunch, an edge resolution of 0.6 mm and hence a SMI saturation point resolution of 1.2 m can be achieved.Comment: 4 pages, 4 figures, EAAC conference proceeding
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