2,767 research outputs found

    Geospatial analysis and living urban geometry

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    This essay outlines how to incorporate morphological rules within the exigencies of our technological age. We propose using the current evolution of GIS (Geographical Information Systems) technologies beyond their original representational domain, towards predictive and dynamic spatial models that help in constructing the new discipline of "urban seeding". We condemn the high-rise tower block as an unsuitable typology for a living city, and propose to re-establish human-scale urban fabric that resembles the traditional city. Pedestrian presence, density, and movement all reveal that open space between modernist buildings is not urban at all, but neither is the open space found in today's sprawling suburbs. True urban space contains and encourages pedestrian interactions, and has to be designed and built according to specific rules. The opposition between traditional self-organized versus modernist planned cities challenges the very core of the urban planning discipline. Planning has to be re-framed from being a tool creating a fixed future to become a visionary adaptive tool of dynamic states in evolution

    Do rural migrants 'float' in urban China? Neighbouring and neighbourhood sentiment in Beijing

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    Urban China reached 50% of the nationā€™s population by 2010, mainly as a result of massive ruralā€“urban migration. There is substantial evidence of their social marginality in terms of occupational and housing opportunities. Here we ask about their incorporation into the neighbourhoods where they live. Rural migrants are called the ā€˜floating populationā€™ in China, suggesting that their residence in the city is only temporary and that they are unlikely to develop strong local ties. This study contrasts the neighbourhood socialising of migrant tenants with that of urban homeowners who were born in the city. It draws on original survey research in Beijing that included questions on relations with neighbours and neighbourhood sentiment. It is found that migrants are more likely to engage in socialising and exchange of help with neighbours, and consequently their neighbouring helps strengthen their sentiment towards the neighbourhoods where they live. It is argued that contemporary social changes ā€“ including rising education and homeownership ā€“ may actually reduce neighbouring, while rural migrantsā€™ marginality makes them more dependent on their local social network

    Optimal Location of Sources in Transportation Networks

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    We consider the problem of optimizing the locations of source nodes in transportation networks. A reduction of the fraction of surplus nodes induces a glassy transition. In contrast to most constraint satisfaction problems involving discrete variables, our problem involves continuous variables which lead to cavity fields in the form of functions. The one-step replica symmetry breaking (1RSB) solution involves solving a stable distribution of functionals, which is in general infeasible. In this paper, we obtain small closed sets of functional cavity fields and demonstrate how functional recursions are converted to simple recursions of probabilities, which make the 1RSB solution feasible. The physical results in the replica symmetric (RS) and the 1RSB frameworks are thus derived and the stability of the RS and 1RSB solutions are examined.Comment: 38 pages, 18 figure

    Contractor tendering research: Going beyond bid/no-bid and markup models

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    Within a wider research programme into the effectiveness and efficiency of the tendering procedures of construction contractors (CCs), a content analysis of tender research published in 27 journals between 2010 and 2016 found that CC tendering procedure research remains a low-focus area. CC-related tender research commonly focuses on factors influencing ā€˜bid/no-bidā€™ and markup decisions, often combined with developed decision modelling. Comparing the content analysis results with semi-structured interviews with 20 Australian civil engineering CCs (including some of Australiaā€™s largest contractors, and with eight involved in international operations), it was found that the industry remains largely unaware and unsupportive of such developed tender decision tools. Instead, CCs suggest tender research should focus on efficient tendering procedures, encouraging clients to use standard rather than bespoke contracts, and improved quality and risk transfer in tender documents. The combined semi-structured interview findings and content analysis results provide researchers with contemporary tender research themes that civil engineering CCs, and potentially more general contractors, are more likely to embrace, thereby advancing the efficiency of construction tendering and contractorsā€™ work procurement management

    Dissociative recombination and electron-impact de-excitation in CH photon emission under ITER divertor-relevant plasma conditions

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    For understanding carbon erosion and redeposition in nuclear fusion devices, it is important to understand the transport and chemical break-up of hydrocarbon molecules in edge plasmas, often diagnosed by emission of the CH A^2\Delta - X^2\Pi Ger\"o band around 430 nm. The CH A-level can be excited either by electron-impact or by dissociative recombination (D.R.) of hydrocarbon ions. These processes were included in the 3D Monte Carlo impurity transport code ERO. A series of methane injection experiments was performed in the high-density, low-temperature linear plasma generator Pilot-PSI, and simulated emission intensity profiles were benchmarked against these experiments. It was confirmed that excitation by D.R. dominates at T_e < 1.5 eV. The results indicate that the fraction of D.R. events that lead to a CH radical in the A-level and consequent photon emission is at least 10%. Additionally, quenching of the excited CH radicals by electron impact de-excitation was included in the modeling. This quenching is shown to be significant: depending on the electron density, it reduces the effective CH emission by a factor of 1.4 at n_e=1.3*10^20 m^-3, to 2.8 at n_e=9.3*10^20 m^-3. Its inclusion significantly improved agreement between experiment and modeling
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