919 research outputs found
On the Effect of Functionally Graded Materials on Resonances of Rotating Beams
Radially rotating beams attached to a rigid stem occur in several important engineering applications. Some examples include helicopter blades, turbine blades and certain aerospace applications. In most studies the beams have been treated as homogeneous. Here, with a goal of system improvement, non-homogeneous beams made of functionally graded materials are explored. The effects on the natural frequencies of the system are investigated. Euler-Bernoulli theory, including an axial stiffening effect and variations of both Young\u27s modulus and density, is employed. An assumed mode approach is utilized, with the modes taken to be beam characteristic orthogonal polynomials. Results are obtained via Rayleigh-Ritz method and are compared for both the homogeneous and non-homogeneous cases. It was found, for example, that allowing Young\u27s modulus and density to vary by approximately 2.15 and 1.15 times, respectively, leads to an increase of 23% in the lowest bending rotating natural frequency of the bea
On the Effect of Functionally Graded Materials on Resonances of Rotating Beams
Radially rotating beams attached to a rigid stem occur in several important engineering applications. Some examples include helicopter blades, turbine blades and certain aerospace applications. In most studies the beams have been treated as homogeneous. Here, with a goal of system improvement, non-homogeneous beams made of functionally graded materials are explored. The effects on the natural frequencies of the system are investigated. Euler-Bernoulli theory, including an axial stiffening effect and variations of both Young's modulus and density, is employed. An assumed mode approach is utilized, with the modes taken to be beam characteristic orthogonal polynomials. Results are obtained via Rayleigh-Ritz method and are compared for both the homogeneous and non-homogeneous cases. It was found, for example, that allowing Young's modulus and density to vary by approximately 2.15 and 1.15 times, respectively, leads to an increase of 23% in the lowest bending rotating natural frequency of the beam
Big Data and Strategy: Theoretical Foundations and New Opportunities
The digitization of products, processes, and business models—and the corresponding explosion of big data—has led to an evolution within business organizations. Reaching far beyond information technology’s traditional role in business strategy, the implications of this big data phenomenon are considered through an exploration into what big data is, how it is currently being used by existing firms, and how it factors into strategic thinking. As different organizational approaches have developed toward big data, we use resource-based theory and organizational learning as anchoring perspectives to link this phenomenon with traditional strategic management. We also identify four avenues for future scholarship as the nature of business moves increasingly digital
Applicability of a drift-flux model of aerosol deposition in a test tunnel and an indoor heritage environment
Near-wall turbulence associated with air flows parallel to walls can promote aerosol deposition. In indoor environments, where this kind of flow is frequently present, this results in local deposition gradients near ventilation inlets and outlets. This phenomenon is of special interest to the heritage field, which is often concerned about the spatial distribution of deposition and its links to environmental management. In this paper we investigate the capability of a drift-flux model of particulate matter deposition to describe this mechanism. This model has often been validated using decay rates of particulate matter concentration; however, in several indoor applications the interest is not in concentration but in the spatial distribution of the deposition flux. To test the model, we use untreated atmospheric aerosols in two different cases: an experimental tunnel designed to induce near-wall velocity gradients and an actual indoor room with various ventilation regimes. Both systems exhibit significantly inhomogeneous deposition distributions. While the first system is operated under controlled laboratory conditions, the second yields data collected in-situ during a six-month monitoring campaign. In either case the model reproduces the experimental values with enough accuracy to allow understanding how the environment behaves. This work confirms the usability of the drift-flux approach as an analysis tool for particle deposition in complex environments in a wide range of geometries
Gas-Rich Dwarf Galaxies from the PSS-II --- II. Optical Properties
We describe the optical properties of a sample of 101 gas-rich field dwarf
galaxies found on PSS-II (Second Palomar Sky Survey) plates, most newly
discovered as part of a survey to investigate the clustering properties of
dwarf galaxies relative to giants. These galaxies have low surface brightnesses
and are relatively distant, with recession velocities ranging up to 10,000
km/s. They have bluer V-I colors (median value of 0.75) than either actively
star-forming giant galaxies or low metallicity globular clusters, implying that
these dwarfs have both low metallicities and little past star formation. These
galaxies are also extremely gas rich, with a median HI mass to V luminosity
ratio of approximately 2 in solar units. We divide the sample into two groups:
true dwarfs with diameters (at 25 I mag arcsec^-2) less than 7.5 kpc and
Magellanic dwarfs with diameters greater than that value. The true dwarfs have
greater HI mass to V luminosity ratios and slightly bluer V-I colors than the
Magellanic dwarfs. Overall, the optical properties of our sample of dwarf
galaxies point towards their being quiescent objects that have undergone little
star formation over the age of the universe. They are not faded objects, but
instead may be going through one of their first periods of weak star formation.Comment: 27 pages, to appear in 20 May 1997 ApJ, paper also available at
http://www.astro.nwu.edu/astro/pildis/dwarfphot.html and
http://zebu.uoregon.edu/~js/dwarf.htm
Teaching and Doing Strategy as an Intentional Strategic Innovation Mindset
There are many important keys in learning, teaching, and doing strategy today. We propose rethinking the learning strategies employed at the MBA level to make the degree more relevant. Recent calls from academia and practice indicate the need to stress adaptability using soft knowledge and skills to make MBA courses more aligned with the realities of strategic decision-making in today’s business environments. We emphasize that while traditional strategic framework models and diagrams have their place, today’s professionals must be prepared to make decisions in unstructured and highly ambiguous situations that traditional models do not address
Forest resilience depends on stand variations: forest dynamics of an Amazonian forest 30 years after logging.
Edição dos abstracts do 24º IUFRO World Congress, 2014, Salt Lake City. Sustaining forests, sustaining people: the role of research
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