12,247 research outputs found
A clarification of the Goodwin model of the growth cycle
We show that there is a difficulty in the original Goodwin model which isalso found in some more recent applications. In it both the labour share and theproportion employed can exceed unity, properties which are untenable. However, weshow that the underlying dynamic structure of the model can be reformulated toensure that these variables cannot exceed unity. An illustrative example extends theoriginal model, and we argue it is both plausible and satisfies the necessary unit boxrestrictions. We show that there is a difficulty in the original Goodwin model which isalso found in some more recent applications. In it both the labour share and theproportion employed can exceed unity, properties which are untenable. However, weshow that the underlying dynamic structure of the model can be reformulated toensure that these variables cannot exceed unity. An illustrative example extends theoriginal model, and we argue it is both plausible and satisfies the necessary unit boxrestrictions
Microscale application of column theory for high resolution force and displacement sensing
We present the design, fabrication and experimental validation of a novel
device that exploits the amplification of displacement and attenuation of
structural stiffness in the post-buckling deformation of slender columns to
obtain pico-Newton force and nanometer displacement resolution even under an
optical microscope. The extremely small size, purely mechanical sensing scheme
and vacuum compatibility of the instrument makes it compatible with existing
visualization tools of nanotechnology. The instrument has a wide variety of
potential applications ranging from electro-mechanical characterization of one
dimensional solids to single biological cells
Solar Gamma Rays Powered by Secluded Dark Matter
Secluded dark matter models, in which WIMPs annihilate first into metastable
mediators, can present novel indirect detection signatures in the form of gamma
rays and fluxes of charged particles arriving from directions correlated with
the centers of large astrophysical bodies within the solar system, such as the
Sun and larger planets. This naturally occurs if the mean free path of the
mediator is in excess of the solar (or planetary) radius. We show that existing
constraints from water Cerenkov detectors already provide a novel probe of the
parameter space of these models, complementary to other sources, with
significant scope for future improvement from high angular resolution gamma-ray
telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator
decays are also capable of contributing a significant solar system component to
the spectrum of energetic electrons and positrons, a possibility which can be
tested with the directional and timing information of PAMELA and Fermi.Comment: 22 pages, 3 figure
Homotopy Analysis Approach of Boussinesq Equation for Infiltration Phenomenon in Unsaturated Porous Medium.
oai:ojs.pkp.sfu.ca:article/11Boussinesq’s equation is one-dimensional nonlinear partial differential equation which represents the infiltration phenomenon. This equation is frequently used to study the infiltration phenomenon in unsaturated porous medium. Infiltration is the process in which the groundwater of the water reservoir has entered in the unsaturated soil through vertical permeable wall. An approximate analytical solution of nonlinear partial differential equation is presented by homotopy analysis method. The convergence of homotopy analysis solution is discussed by choosing proper value of convergence control parameter. The solution represents the height of free surface of infiltrated water
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