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Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
International Journal of Heat and Mass Transfer | Year: 2012

Here we show that the main features of citations history (S-shaped curve, increasing h index, decreasing m quotient) are predictable with the constructal law of how an idea flows over a populated territory. It flows in two ways: fast and long, as "convection" along established channels of researchers interested in the idea, and slow and short, sideways from channels, by "diffusion" to new users. The first regime accounts for the rising portion of the S curve, and the second for the slow-down. Tree-shaped established channels spread the idea faster than single channels over the same area. The complexity of the design of fast channels increases in time due to the evolution of communications technologies. © 2011 Published by Elsevier Ltd. © 2011 Elsevier Ltd. All rights reserved. Source


Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
Physics of Life Reviews | Year: 2011

The constructal law accounts for the universal phenomenon of generation and evolution of design (configuration, shape, structure, pattern, rhythm). This phenomenon is observed across the board, in animate, inanimate and human systems. The constructal law states the time direction of the evolutionary design phenomenon. It defines the concept of design evolution in physics. Along with the first and second law, the constructal law elevates thermodynamics to a science of systems with configuration. In this article we review the more recent work of our group, with emphasis on the advances made with the constructal law in the natural sciences. Highlighted are the oneness of animate and inanimate designs, the origin of finite-size organs on animals and vehicles, the flow of stresses as the generator of design in solid structures (skeletons, vegetation), the universality and rigidity of hierarchy in all flow systems, and the global design of human flows. Noteworthy is the tapestry of distributed energy systems, which balances nodes of production with networks of distribution on the landscape, and serves as key to energy sustainability and empowerment. At the global level, the constructal law accounts for the geography and design of human movement, wealth and communications. © 2011 Elsevier B.V.. Source


Maillard P.,Center Technique Of Materiaux Naturels Of Construction Ctmnc | Aubert J.E.,CNRS Materials and Construction Durability Laboratory
Construction and Building Materials | Year: 2014

The study focuses on the thermal and hydric properties of extruded earth bricks. The thermal conductivity and water vapour permeability tests highlight anisotropic behaviour of the bricks depending on the extrusion direction during the production process. The results confirm that the extrusion process has a major influence on the orientation of clay layers and has an impact on the hygrothermal properties. © 2014 Elsevier Ltd. All rights reserved. Source


Bertron A.,CNRS Materials and Construction Durability Laboratory
Materials and Structures/Materiaux et Constructions | Year: 2014

Building materials can be exposed to microorganisms (mainly bacteria, fungi and algae) in almost every aqueous medium or damp environment, water being the indispensable condition for life development. The activity of microorganisms can be responsible for mineralogical, chemical and microstructural damage to the material (biodeterioration). Deleterious effects can also concern the aesthetics of a building (proliferation of colored biological stains on façades and roofs) or the quality of indoor air (presence of microorganisms in damp buildings). However, microorganisms can also have positive effects (healing of materials) and their action is explored through the development of bio-based protective systems intended for building materials. In all cases, understanding interactions between building materials and microorganisms is an indispensable step toward the development of more sustainable, better quality, safer structures in many environments. This paper presents two examples where the action of microorganisms has—or is likely to have—strong impact on the durability and safety of concrete structures. The first example concerns the biodeterioration of concrete in agricultural and agro-food environments. The second example is that of the abiotic and biotic reactivity of nitrates in repository of intermediate-level long-lived nuclear wastes. The paper presents the approaches used to explore and understand the phenomenology of bio-geo-chemical interactions in these complex environments. These studies notably comprise the development of test methods and experimental pilots to enable these explorations to be carried out. Current shortcomings in the scientific literature and in the standardization environment are also highlighted. © 2014, The Author(s). Source


Bejan A.,Duke University | Lorente S.,CNRS Materials and Construction Durability Laboratory
Journal of Applied Physics | Year: 2013

This is a review of the theoretical and applied progress made based on the Constructal law of design and evolution in nature, with emphasis on the last decade. The Constructal law is the law of physics that accounts for the natural tendency of all flow systems (animate and inanimate) to change into configurations that offer progressively greater flow access over time. The progress made with the Constructal law covers the broadest range of science, from heat and fluid flow and geophysics, to animal design, technology evolution, and social organization (economics, government). This review presents the state of this fast growing field, and draws attention to newly opened directions for original research. The Constructal law places the concepts of life, design, and evolution in physics. © 2013 American Institute of Physics. Source

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