10,192 research outputs found

    Managing knowledge in the context of sustainable construction

    Get PDF
    The 21st century has been a growing awareness of the importance of the sustainability agenda. Moreover for construction, it has become increasingly important as clients are pushing for a more sustainable product to complement their organisations’ own strategic plans. Sustainable development can be defined as development that meets the needs of the present without compromising the ability of future generations to meet their needs. Sustainable construction is therefore seen as the application of sustainable practices to the activities of the construction sector. One of the key factors in making construction projects more sustainable is overcoming the obstacles of capturing and managing the knowledge required by project teams to effect such change. Managing this knowledge is key to the construction industry because of the unique characteristics of its projects, i.e. multi-disciplinary teams, dynamic participation of team members, heavy reliance on previous experiences/heuristics, the one-off nature of the projects, tight schedules, limited budget, etc. Initiatives within the industry and academic research are developing mechanisms and tools for managing knowledge in construction firms and projects. Such work has so far addressed the issues of capturing, storing, and transferring knowledge

    The Aggregation Kinetics of a Simulated Telechelic Polymer

    Full text link
    We investigate the aggregation kinetics of a simulated telechelic polymer gel. In the hybrid Molecular Dynamics (MD) / Monte Carlo (MC) algorithm, aggregates of associating end groups form and break according to MC rules, while the position of the polymers in space is dictated by MD. As a result, the aggregate sizes change every time step. In order to describe this aggregation process, we employ master equations. They define changes in the number of aggregates of a certain size in terms of reaction rates. These reaction rates indicate the likelihood that two aggregates combine to form a large one, or that a large aggregate splits into two smaller parts. The reaction rates are obtained from the simulations for a range of temperatures. Our results indicate that the rates are not only temperature dependent, but also a function of the sizes of the aggregates involved in the reaction. Using the measured rates, solutions to the master equations are shown to be stable and in agreement with the aggregate size distribution, as obtained directly from simulation data. Furthermore, we show how temperature induced variations in these rates give rise to the observed changes in the aggregate distribution that characterizes the sol-gel transition.Comment: 9 pages, 10 figure

    Fractal Scales in a Schwarzschild Atmosphere

    Get PDF
    Recently, Glass and Krisch have extended the Vaidya radiating metric to include both a radiation fluid and a string fluid [1999 Class. Quantum Grav. vol 16, 1175]. Mass diffusion in the extended Schwarzschild atmosphere was studied. The continuous solutions of classical diffusive transport are believed to describe the envelope of underlying fractal behavior. In this work we examine the classical picture at scales on which fractal behavior might be evident.Comment: to appear in Class. Quantum Gra

    Converting genetic network oscillations into somite spatial pattern

    Full text link
    In most vertebrate species, the body axis is generated by the formation of repeated transient structures called somites. This spatial periodicity in somitogenesis has been related to the temporally sustained oscillations in certain mRNAs and their associated gene products in the cells forming the presomatic mesoderm. The mechanism underlying these oscillations have been identified as due to the delays involved in the synthesis of mRNA and translation into protein molecules [J. Lewis, Current Biol. {\bf 13}, 1398 (2003)]. In addition, in the zebrafish embryo intercellular Notch signalling couples these oscillators and a longitudinal positional information signal in the form of an Fgf8 gradient exists that could be used to transform these coupled temporal oscillations into the observed spatial periodicity of somites. Here we consider a simple model based on this known biology and study its consequences for somitogenesis. Comparison is made with the known properties of somite formation in the zebrafish embryo . We also study the effects of localized Fgf8 perturbations on somite patterning.Comment: 7 pages, 7 figure

    ISOGAL Survey of Baade's Windows in the Mid-infrared

    Get PDF
    The ISOGAL mid-infrared survey of areas close to the Galactic Plane aims to determine their stellar content and its possible bearing on the history of the Galaxy. The NGC6522 and Sgr I Baade's Windows of low obscuration towards the inner parts of the Bulge represent ideal places in which to calibrate and understand the ISOGAL colour-magnitude diagrams. The survey observations were made with the ISOCAM instrument of the ISO satellite. The filter bands chosen were LW2(~7 microns) and LW3(~15 microns). The results presented here show that most of the detected objects are late M-type giants on the AGB, with a cut-off for those earlier than M3-M4. The most luminous members of these two Bulge fields at 7 microns are the Mira variables. However, it is evident that they represent the end of a sequence of increasing 15 micron dust emission which commences with M giants of earlier sub-type. In observations of late-type giants the ISOCAM 15 micron band is mainly sensitive to the cool silicate or aluminate dust shells which overwhelm the photospheric emission. However, in ordinary M-giant stars, the 7 micron band is not strongly affected by dust emission and may be influenced instead by absorption. The nu2 band of water at 6.25 microns and the SiO fundamental at 7.9 microns are likely contribitors to this effect. A group of late M stars has been found which vary little or not at all but have infrared colours typical of well-developed dust shells. Their luminosities are similar to those of 200-300 day Miras but they have slightly redder [7]-[15] colours which form an extension of the ordinary M giant sequence. The Mira dust shells show a mid-infrared [7]-[15] colour-period relation. ca 700 days.Comment: 13 pages 15 figure

    The spike train statistics for consonant and dissonant musical accords

    Full text link
    The simple system composed of three neural-like noisy elements is considered. Two of them (sensory neurons or sensors) are stimulated by noise and periodic signals with different ratio of frequencies, and the third one (interneuron) receives the output of these two sensors and noise. We propose the analytical approach to analysis of Interspike Intervals (ISI) statistics of the spike train generated by the interneuron. The ISI distributions of the sensory neurons are considered to be known. The frequencies of the input sinusoidal signals are in ratios, which are usual for music. We show that in the case of small integer ratios (musical consonance) the input pair of sinusoids results in the ISI distribution appropriate for more regular output spike train than in a case of large integer ratios (musical dissonance) of input frequencies. These effects are explained from the viewpoint of the proposed theory.Comment: 22 pages, 6 figure

    FU Orionis resolved by infrared long baseline interferometry at a 2-AU scale

    Full text link
    We present the first infrared interferometric observations of a young stellar object with a spatial projected resolution better than 2 AU. The observations were obtained with the Palomar Testbed Interferometer. FU Ori exhibits a visibility of V^2 =0.72 +/- 0.07 for a 103 +/- 5 m projected baseline at lambda = 2.2 microns. The data are consistent on the spatial scale probed by PTI both with a binary system scenario (maximum magnitude difference of 2.7 +/- 0.5 mag and smallest separation of 0.35 +/- 0.05 AU) and a standard luminous accretion disk model (approx. accretion rate of 6e-5 Mo/yr) where the thermal emission dominates the stellar scattering, and inconsistent with a single stellar photosphere.Comment: 13 pages, 4 figures, accepted for publication in ApJ
    corecore