A Simple Modularity Measure for Search Spaces based on Information Theory

Within the context of Artificial Life the question about the role of modularity has turned out to be crucial, especially with regard to the problem of evolvability. In order to be able to observe the development of modular structure, appropriate modularity measures are important. We introduce a continuous measure based on information theory which can characterize the coupling among subsystems in a search problem. In order to illustrate the concepts developed, they are applied to a very simple and intuitive set of combinatorial problems similar to scenarios used in the seminal work by Simon (1969). It is shown that this measure is closely related to the classification of search problems in terms of Separability, Non-Decomposability and Modular Interdependency as introduced in (Watson and Pollack, 2005)

Influence de la teneur en ciment sur les propriétés thermomécaniques des blocs d’argile comprimée et stabilisée

Ce travail vise à déterminer la résistance à la compression et la conductivité thermique des blocs à base d’argile comprimée et stabilisée au ciment d’une part et à étudier la variation de ces propriétés en fonction de la teneur en ciment d’autre part. Les mesures réalisées indiquent que la résistance des blocs sans ciment est de 3,7 MPa par « voie sèche » pour une conductivité thermique de 0,91 Wm-1K-1 (déterminée à l’aide d’un fluxmètre). L’incorporation de ciment entraine une variation de ces deux propriétés. Ainsi on note d’abord une baisse de la résistance suivie d’une augmentation au delà de 4% de ciment. Toutefois la conductivité thermique des blocs ayant les teneurs en ciment les plus importantes reste proche de celle des blocs sans ciment.Mots-clés: bloc d’argile, ciment portland, stabilisation, résistance en compression, conductivité thermique. Influence of cement content on the thermomechanical properties of compressed and stabilized clay blocks This work aims to determine the compressive strength and the thermal conductivity of clay compressed blocks and stabilized with cement and to study the influence of the cement ratio on these characteristics of the blocks. The resistance of blocks without cement is (determined at dry state) is 3.7 MPa and measurements made with a fluxmeter show that the thermal conductivity of these blocks is 0,91 Wm-1 K-1. The results show also that the thermal conductivity and the compressive strength of the blocks vary according to the cement ratio. However the thermal conductivity of the blocks with high cement ratio is close to that of the blocks without cement.Keywords: clay blocks, Portland cement, stabilization, compressive strength, thermal conductivity

Prediction of Anisotropic Single-Dirac-Cones in Bi1−x{}_{1-x}Sbx{}_{x} Thin Films

The electronic band structures of Bi${}_{1-x}$Sb${}_{x}$ thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi${}_{1-x}$Sb${}_{x}$ thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band-gap, which can be used in a general two-dimensional system that has a non-parabolic dispersion relation as in a Bi${}_{1-x}$Sb${}_{x}$ thin film system

Growth of a textured quasicrystalline phase in Ti-Ni-Zr films prepared by pulsed laser deposition

International audienceThe preparation in thin film form of the known icosahedral phase in Ti-Ni-Zr bulk alloys has been investigated as a function of substrate temperature. Films were deposited by Pulsed Laser Deposition on sapphire substrates at temperatures ranging from room temperature to 350°C. Morphological and structural modifications have been followed by grazing incidence and θ-2θ X-ray diffraction, transmission electron diffraction and imaging. Chemical composition has been analysed by Electron Probe Micro-Analysis. The in-depth variation of composition has been studied by Secondary Neutral Mass Spectroscopy. We show that Pulsed Laser Deposition at 275°C makes the formation of a 1 m thick film of Ti-Ni-Zr quasicrystalline textured nanocrystallites possible

Experimental setup for the measurement of the electrical resistivity and thermopower of thin films and bulk materials

An experimental setup was developed for the simultaneous measurements of the electrical resistivity and the thermopower in the temperature range going from 77 up to 330 K. The system combines accuracy, rapidity, few efforts for the sample mounting, and is fully automated. Pressure contacts are used for contacting the thermocouples to the sample and the sample to the heat sink, making possible the measurement of both thin films and bulk materials with a great flexibility on their geometrical dimensions. Tests of the system have been made on a 99.98% pure Ni bulk sample and on PbTe/BaF2 thin films for illustration