4,271 research outputs found

    Reactive dynamics on fractal sets: anomalous fluctuations and memory effects

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    We study the effect of fractal initial conditions in closed reactive systems in the cases of both mobile and immobile reactants. For the reaction A+AAA+A\to A, in the absence of diffusion, the mean number of particles AA is shown to decay exponentially to a steady state which depends on the details of the initial conditions. The nature of this dependence is demonstrated both analytically and numerically. In contrast, when diffusion is incorporated, it is shown that the mean number of particles decays asymptotically as tdf/2t^{-d_f/2}, the memory of the initial conditions being now carried by the dynamical power law exponent. The latter is fully determined by the fractal dimension dfd_f of the initial conditions.Comment: 7 pages, 2 figures, uses epl.cl

    A study on the concepts and themes of color and light in the exquisite islamic architecture

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    Today, diverse ideologies, thoughts, and beliefs exist in the world all of which try to transfer concepts and ideas to others using the indirect language of semantics. In this regard, architecture, especially the valuable architecture of Iran with wide application and permanent presence in human life has gained considerable attention. Iranian art has always been in coordination with the spirit of Islam and an indicator of its truth. Architecture is where meaning is represented in the formal, structural, and spatial aspects. Light and color are two important visual elements of formation and cognition of architectural works. Color does not manifest by itself unless it is seen through a design, when becomes the origin of work and intervenes in its sense of space.It should be considered that how the existence of light and color in the patterns has been effective in the environmental psychology and how the space is defined in terms of these two elements? And whether the sole use of light and color in the historical architecture was to represent meaning?The present study adopts a descriptive-analytical approach to review and explain the semantic elements of light and color, their application and conceptual features in the historical architecture and hence examines these two distinct elements in the art and architecture of the past and tries to find their semantic features to the extent that have influenced the face and essence of modern architecture in the hope of providing useful insights for the modern architecture.Keywords: Islamic architecture, light, color, concepts, exquisite architectur

    Cyber-physical system based on image recognition to improve traffic flow: A case study

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    Vehicular traffic in metropolitan areas turns congested along either paths or periods. As a case study, we have considered a mass transport system with a bus fleet that rides over exclusive lanes across streets and avenues in an urban area that does not allow the circulation of lightweight vehicles, cargo, and motorcycles. This traffic flow becomes congested due to the absence of restriction policies based on criteria. Moreover, the exclusive lanes are at ground level, decreasing lanes for other vehicles. The main objective of this proposal consists of controlling the access to the exclusive lanes by a cyber-physical system following authorization conditions, verifying the permission status of a vehicle by the accurate recognition of license plates to reduce traffic congestion. Therefore, in the case of invading an exclusive lane without permission, the vehicle owner gets a notification of the fine with the respective evidence

    Integrable su(3) spin chain combining different representations

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    The general expression for the local matrix t(θ)t(\theta) of a quantum chain with the site space in any representation of su(3) is obtained. This is made by generalizing t(θ)t(\theta) from the fundamental representation and imposing the fulfillment of the Yang-Baxter equation. Then, a non-homogeneous spin chain combining different representations of su(3) is solved by developing a method inspired in the nested Bethe ansatz. The solution for the eigenvalues of the trace of the monodromy matrix is given as two coupled Bethe equations. A conjecture about the solution of a chain with the site states in different representations of su(n) is presented. The thermodynamic limit of the ground state is calculated.Comment: PlainTex harvmac, 30 pages, 7 figures, to appear in Journal of Physics

    The Effects of Retrogression and Reaging on Aluminum Alloy 2099 (C458)

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    The objective of this study was to investigate the feasibility of performing retrogression and reaging (RRA) heat treatments on 2099 aluminum-lithium alloy. The retrogression temperatures were 200-250 A degrees C and retrogression times were 5-60 min. Half of the samples were exposed to a salt fog environment. Interestingly, the samples exposed to salt spray had consistently higher mechanical tensile properties than those which were not exposed

    The Effects of Retrogression and Reaging on Aluminum Alloy 2195

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    A retrogression and reaging (RRA) treatment was performed on 2195 Al-Li Alloy. The exposure times were from 5 to 60 min, and the temperatures were from 200 to 250 A degrees C. Samples that were exposed to a salt spray test had overall similar mechanical properties as compared to those that were not exposed. The percent elongation, however, was significantly deteriorated due to the salt spray exposure. The mechanical properties of the 2195 samples were compared to those of 2099 samples exposed to similar treatments in an earlier study
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