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Register a new userHigh Strength Over Density Ratio Invisible Cables
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Nicola M. Pugno
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Spiders suggest us that producing high strength over density ratio invisible cables could be of great importance. In this letter we show that such invisible cables could in principle be built, thanks to carbon nanotube bundles. Theoretical strength of about 10MPa, Young modulus of about 0.1GPa and density of 0.1Kg per cubic meter are estimated.
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In this paper the new concept of super-bridges, i.e. kilometre-long bridges suspended over carbon nanotube cables, is introduced. The analysis shows that the use of realistic (thus defective) carbon nanotube bundles as suspension cables can enlarge the current limit main span by a factor of 3.
Thanks to Victor Veselago for his hypothesis of negative index of refraction, metamaterials -- engineered composites -- can be designed to have properties difficult or impossible to find in nature: they can have both electrical permitivity ($epsilon$) and magnetic permeability ($mu$) simultaneously negative. The metamaterials -- henceforth negative-index materials (NIMs) -- owe their properties to subwavelength structure rather than to their chemical composition. The tailored electromagnetic response of the NIMs has had a dramatic impact on the classical optics: they are becoming known to have changed many basic notions related with the electromagnetism. The present article is focused on gathering and reviewing the fundamental characteristics of plasmon propagation in the coaxial cables fabricated of the right-handed medium (RHM) [with $epsilon>0$, $mu>0$] and the left-handed medium (LHM) [with $epsilon<0$, $mu<0$] in alternate shells starting from the innermost cable. Such structures as conceived here may pave the way to some interesting effects in relation to, e.g., the optical science exploiting the cylindrical symmetry of the coaxial waveguides that make it possible to perform all major functions of an optical fiber communication system in which the light is born, manipulated, and transmitted without ever leaving the fiber environment, with precise control over the polarization rotation and pulse broadening. The review also covers briefly the nomenclature, classification, potential applications, and the limitations (related, e.g., to the inherent losses) of the NIMs and their impact on the classical electrodynamics, in general, and in designing the cloaking devices, in particular. Recent surge in efforts on invisibility and the cloaking devices seems to have spoiled the researchers worldwide:
By using an elegant response function theory, which does not require matching of the messy boundary conditions, we investigate the surface plasmon excitations in the multicoaxial cylindrical cables made up of negative-index metamaterials. The multicoaxial cables with {em dispersive} metamaterial components exhibit rather richer (and complex) plasmon spectrum with each interface supporting two modes: one TM and the other TE for (the integer order of the Bessel function) $m e 0$. The cables with {em nondispersive} metamaterial components bear a different tale: they do not support simultaneously both TM and TE modes over the whole range of propagation vector. The computed local and total density of states enable us to substantiate spatial positions of the modes in the spectrum. Such quasi-one dimensional systems as studied here should prove to be the milestones of the emerging optoelectronics and telecommunications systems.
Diamond is used extensively as a component in high energy density experiments, but existing equation of state (EOS) models do not capture its observed response to dynamic loading. In particular, in contrast with first principles theoretical EOS models, no solid-solid phase changes have been detected, and no general-purpose EOS models match the measured ambient isotherm. We have performed density functional theory (DFT) calculations of the diamond phase to ~10TPa, well beyond its predicted range of thermodynamic stability, and used these results as the basis of a Mie-Greuneisen EOS. We also performed DFT calculations of the elastic moduli, and calibrated an algebraic elasticity model for use in simulations. We then estimated the flow stress of diamond by comparison with the stress-density relation measured experimentally in ramp-loading experiments. The resulting constitutive model allows us to place a constraint on the Taylor-Quinney factor (the fraction of plastic work converted to heat) from the observation that diamond does not melt on ramp compression.
We report on the theoretical investigation of the plasmonic wave propagation in the coaxial cylindrical cables fabricated of both right-handed medium (RHM) [with $epsilon >0$, $mu >0$] and left-handed medium (LHM) [with $epsilon(omega) <0$, $mu(omega) <0$], using a Green-function (or response function) theory in the absence of an applied magnetic field. The Green-function theory generalized to be applicable to such quasi-one dimensional systems enables us to derive explicit expressions for the corresponding response functions (associated with the EM fields), which can in turn be used to derive various physical properties of the system. The confined plasmonic wave excitations in such multi-interface structures are characterized by the electromagnetic fields that are localized at and decay exponentially away from the interfaces. A rigorous analytical diagnosis of the general results in diverse situations leads us to reproduce exactly the previously well-known results in other geometries, obtained within the different theoretical frameworks. As an application, we present several illustrative examples on the dispersion characteristics of the confined (and extended) plasmonic waves in single- and double-interface structures made up of dispersive metamaterials interlaced with conventional dielectrics. These dispersive modes are also substantiated through the computation of local as well as total density of states. It is observed that the dispersive components enable the system to support the simultaneous existence of s- and p-polarization modes in the system. Such effects as this one are solely attributed to the negative-index metamaterials and are otherwise impossible...
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