2,174 research outputs found
Complex scale-free networks with tunable power-law exponent and clustering
No full textThis article is made available through the Brunel Open Access Publishing Fund. It is distributed under a Creative Commons License (http://creativecommons.org/licenses/by/3.0/). Copyright @ 2013 Elsevier B.V.We introduce a network evolution process motivated by the network of citations in the scientific literature. In each iteration of the process a node is born and directed links are created from the new node to a set of target nodes already in the network. This set includes mm “ambassador” nodes and ll of each ambassador’s descendants where mm and ll are random variables selected from any choice of distributions plpl and qmqm. The process mimics the tendency of authors to cite varying numbers of papers included in the bibliographies of the other papers they cite. We show that the degree distributions of the networks generated after a large number of iterations are scale-free and derive an expression for the power-law exponent. In a particular case of the model where the number of ambassadors is always the constant mm and the number of selected descendants from each ambassador is the constant ll, the power-law exponent is (2l+1)/l(2l+1)/l. For this example we derive expressions for the degree distribution and clustering coefficient in terms of ll and mm. We conclude that the proposed model can be tuned to have the same power law exponent and clustering coefficient of a broad range of the scale-free distributions that have been studied empirically.EPSR
Crossover to self-organized criticality in an inertial sandpile model
No full textWe introduce a one-dimensional sandpile model which incorporates particle inertia. The inertial dynamics are governed by a new parameter which, as it passes through a threshold value, alters the toppling dynamics in such a way that the system no longer evolves to a self-organized critical state. A range of mean-field theories based on a kinetic equation approach is presented which confirm the numerical findings. We conclude by considering the physical applications of this model, particularly with reference to recent experimental results
Stable distribution in fragmentation processes
No full textWe introduce three models of fragmentation in which the largest fragment in the system can be broken at each time step with a fixed probability, p. We solve these models exactly in the long time limit to reveal stable time invariant (scaling) solutions which depend on p and the precise details of the fragmentation process. Various features of these models are compared with those of conventional fragmentation models.
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Design of a new Faculty of Architecture - Investigation and design of Media Facades
No full textGraduation Project [G.J. Smit] for both Architecture & Building Technology. [architecture] : design of a new Faculty of Architecture [building technology] : investigation and design of Media FacadesStrategic Architectural Design DevelopmentArchitecture & Building TechnologyArchitectur
Watertovenaars: Delftse ideeën voor nog 200 jaar Rijkswaterstaat
No full textEen bundel artikelen met inspiratie voor Rijkswaterstaat voor de ontwikkeling in de volgende 200 jaar. Watertovenaar of tovenaarsleerling? (K. d'Angremond, P. Huisman en G.I. Schiereek) De oudste deltawerken: dammen en duikers uit het begin van de jaartelling (T. de Ridder) Een erfenis uit de Bataafse periode (W.M. de Jong) Wat eerst: wonen, water, wegen of welvaart? (T.M. de Jong) Een nieuwe rol voor de waterstaatsingenieur (F.M. Sanders) De terugkeer van de stedenbouwkundige discipline (V.J. Meyer Water (P. Huisman, K. d'Angremond en G.J. Schiereek) Dynamische buffers in autosnelwegen (D. Westland en P.H.L. Bovy) Op de automatische piloot door de Randstad? (R. van der Heijden, V. Marchau, E. Molin en K. van Wees) Niet bruggen bouwen, maar zelf brug zijn (B. Enserink, M.P.M. van der Ploeg, WAH. Thissen en G.J. de Vreede) Nederland als vervoersemplacement? (M.P.C. Weijnen, W.A.H. Thissen en E.F. ten Heuvelhof) Immobilisatie van gevaarlijk afval (Ch.F.Hendriks) Dubbel verduurzamen van wegconstructies (A.A.A. Molenaar) Innovatie van de geometrische infrastructuur (P.J.G.Teunissen) Radarhoogtemetingen en de (voorname) rol van Delft (M. Naeije) Een hoog(water)standje (T. Rientjes, C. van den Akker en P. van der Veer) Naar één beslismodel voor de veiligheid (J.K. Vrijling en J. Stoop) De betrouwbaarheid van dijken (A. Verruijt) Windgolven, een fascinerend fenomeen (L.H. Holthuijsen en J.A. Battjes) Mijn droom: het railvaartuig (B. Boon) Een waterfilm in plaats van wielen (A. van Beek) Uren worden minuten (E.A.H. Vollebregt, H. Jansen en M.R.T. Roest) Een kwestie van schuiven (R.Brouwer, A.Hof en J. Schuurmans) Energie door vergisting van slib (M.S.M. letten en M.C.M. van Loosdrecht) Nóg een poldermodel: hoge-sterkte beton (J.C. Walraven) Atollen voor de Noordzeekust (J. Kristinsson) Van maker naar regisseur (H.A.J. de Ridder
Sustainable Chemical Processes and Products. New Design Methodology and Design Tools
No full textThe current chemical industry is not sustainable, which leads to the fact that innovation of chemical processes and products is too often hazardous for society in general and the environment in particular. It really is a challenge to implement sustainability considerations in the design activities of chemical engineers. Therefore, the main question of this thesis is: how can a trained chemical engineer develop a conceptual design of a chemical process or a chemical product in such a way that the final result clearly contributes to sustainable development? This question is answered after a profound discussion about the current chemical engineering practice and its relation to the sustainability debate. This dissertation claims that sustainable development of chemical engineering practices requires a general design methodology accompanied by a set of design tools. Such a combination of methodology and tools does not exist in the chemical engineering field. The author developed a new design methodology and seven new design tools that enable the incorporation of sustainability issues into the design practice of the chemical engineering field. The application and validity of the methodology and its tools are shown in seven, mainly industrial, case studies.Applied Science
Image and Reputational Impact on Managers' Assessment of Auditing Activities
No full textThe efficient use of knowledge assets allows organizations to compete more effectively in the marketplace. Some of these knowledge assets are embedded in an organization socialization and internalization processes. Image and reputation may better leverage knowledge by strengthening its core capabilities of knowledge assets. Image and reputation is viewed as a collective 'perception' pertaining to a person, group, or organization's attributes. We suggest that by combining the use of reputational data and structural equation modeling of narrative analysis, we can build a better process theory along with better explanations in general. Throughput modeling techniques are used in this research to capitalize on how line managers' narratives are captured in framing their international environment, the information used, as well as deciding whether audits are assisting them in promoting increase profits or decrease expenses. This model is useful in highlighting the elements that support a view of managers being proactive. This analysis captures forward looking throughput modeling techniques whereby in-house managerial procedures can help aid and assist line managers performing their primary functions. Findings indicated that managers' perception of image/reputation influence what they viewed as important knowledge assets relating to productivity and profitability. --
Preferential Behaviour and Scaling in Diffusive Dynamics on Networks
No full textWe study the fluctuation properties and return-time statistics on inhomogeneous scale-free networks using packets moving with two different dynamical rules; random diffusion and locally navigated diffusive motion with preferred edges. Scaling in the fluctuations occurs when the dispersion of a quantity at each node or edge increases like the its mean to the power . We show that the occurrence of scaling in the fluctuations of both the number of packets passing nodes and the number flowing along edges is related to preferential behaviour in either the topology (in the case of nodes) or in the dynamics (in case the of edges). Within our model the absence of any preference leads to the absence of scaling, and when scaling occurs it is non-universal; for random diffusion the number of packets passing a node scales with an exponent which increases continuously with increased acquisition time window from at small windows, to at long time windows; In the preferentially navigated diffusive motion, busy nodes and edges have exponent , in contrast to less busy parts of the network, where an exponent is found. Broad distributions of the return times at nodes and edges illustrate that the basis of the observed scaling is the cooperative behaviour between groups of nodes or edges. These conclusions are relevant for a large class of diffusive dynamics on networks, including packet transport with local navigation rules
Author response
No full textMost motile bacteria sense and respond to their environment through a transmembrane chemoreceptor array whose structure and function have been well-studied, but many species also contain an additional cluster of chemoreceptors in their cytoplasm. Although the cytoplasmic cluster is essential for normal chemotaxis in some organisms, its structure and function remain unknown. Here we use electron cryotomography to image the cytoplasmic chemoreceptor
cluster in Rhodobacter sphaeroides and Vibrio cholerae. We show that just like transmembrane arrays, cytoplasmic clusters contain trimers-of-receptor-dimers organized in 12-nm hexagonal arrays. In contrast to transmembrane arrays, however, cytoplasmic clusters comprise two CheA/
CheW baseplates sandwiching two opposed receptor arrays. We further show that cytoplasmic fragments of normally transmembrane E. coli chemoreceptors form similar sandwiched structures in the presence of molecular crowding agents. Together these results suggest that the 12-nm
hexagonal architecture is fundamentally important and that sandwiching and crowding can replace the stabilizing effect of the membrane
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