a note on torsion of nonlocal composite nanobeams

The ERINGENelastic constitutive relation is used in this paper in order to assess small-scale effects in nanobeams. Structural behavior is studied for functionally graded materials in the cross-sectional plane and torsional loading conditions. The governing boundary value problem has been formulated in a mixed framework. Torsional rotations and equilibrated moments are evaluated by solving a first-order differential equation of elastic equilibrium with boundary conditions of kinematic-type. Benchmarks examples are briefly discussed, enlightening thus effectiveness of the proposed methodology

On Bending of Bernoulli-Euler Nanobeams for Nonlocal Composite Materials

Evaluation of size effects in functionally graded elastic nanobeams is carried out by making recourse to the nonlocal continuum mechanics. The Bernoulli-Euler kinematic assumption and the Eringen nonlocal constitutive law are assumed in the formulation of the elastic equilibrium problem. An innovative methodology, characterized by a lowering in the order of governing differential equation, is adopted in the present manuscript in order to solve the boundary value problem of a nanobeam under flexure. Unlike standard treatments, a second-order differential equation of nonlocal equilibrium elastic is integrated in terms of transverse displacements and equilibrated bending moments. Benchmark examples are developed, thus providing the nonlocality effect in nanocantilever and clampled-simply supported nanobeams for selected values of the Eringen scale parameter

On the photon Green functions in curved space-time

Quantization of electrodynamics in curved space-time in the Lorenz gauge and with arbitrary gauge parameter makes it necessary to study Green functions of non-minimal operators with variable coefficients. Starting from the integral representation of photon Green functions, we link them to the evaluation of integrals involving Gamma functions. Eventually, the full asymptotic expansion of the Feynman photon Green function at small values of the world function, as well as its explicit dependence on the gauge parameter, are obtained without adding by hand a mass term to the Faddeev--Popov Lagrangian. Coincidence limits of second covariant derivatives of the associated Hadamard function are also evaluated, as a first step towards the energy-momentum tensor in the non-minimal case.Comment: 22 pages, plain Tex. All sections and appendices have been improve

Liquid actuated gravity experiments

We describe a new actuation technique for gravity experiments based on a liquid field mass. The Characterizing idea is to modulate the gravity force acting on a test mass by controlling the level of a liquid in a suitable container. This allows to obtain a periodical gravity force without moving parts (except the liquid level) close to the TM. We describe in detail the most relevant aspects of the liquid actuator and discuss how it can be used in gravity experiments. In particular we analyse an application to test the inverse square law in the mm to cm distance region

A NOVEL METHODOLOGY TO DESIGN SECURITY PROTOCOLS BASED ON A NEW SET OF DESIGN PRINCIPLES

This paper presents a novel design methodology based on a new set of design principles to develop step-by-step security protocols for up to three participants, guiding the designer on each step. It accompanies the designer through a succession of six abstraction levels proposed in this work: protocol objectives, protocol constraints, security mechanisms, message flow, protocol conformation and authentication tests. The methodology proposed is based on a new set of design principles extracted from different sources and combined using the systemic approach, which considers the designer and client’s security and functional needs. The resulting model separates highlevel tasks from implementation details, allowing the designer to specify the security requirements and functionality desired for each abstraction level. Consequently, the protocol design is linked with the best-fitting design principle. To corroborate the results of the methodology, the resulting protocol in the Alice and Bob notation in the fifth level is tested using the “Strand Spaces” Model. The Needham-Schroeder protocol with symmetric keys was successfully used as a test. The security goals achieved were: authentication, confidentiality, integrity, and non-repudiation

Static versus dynamic longevity­ risk hedging

This paper provides the static, swap-based hedge for an annuity, and compares it with the dynamic, delta-based hedge, achieved using longevity bonds. We assume that the longevity intensity is distributed according to a CIR-type process and provide closed-form derivatives prices and hedges, also in presence of an analogous CIR process for interest rate risk. Our calibration to 65-year old UK males shows that – once interest rate risk is perfectly hedged – the average hedging error of the dynamic hedge is moderate, and both its variance and the thickness of the tails of its distribution are decreasing with the rebalancing frequency. The spread over the basic "swap rate" which makes 99.5% quantile of the distribution of the dynamic hedging error equal to the cost of the static hedge lies between 0.01 and 0.04%

Towards weighing the condensation energy to ascertain the Archimedes force of vacuum

The force exerted by the gravitational field on a Casimir cavity in terms of Archimedes force of vacuum is discussed, the force that can be tested against observation is identified, and it is shown that the present technology makes it possible to perform the first experimental tests. The use of suitable high-Tc superconductors as modulators of Archimedes force is motivated. The possibility is analyzed of using gravitational wave interferometers as detectors of the force, transported through an optical spring from the Archimedes vacuum force apparatus to the gravitational interferometer test masses to maintain the two systems well separated. The use of balances to actuate and detect the force is also analyzed, the different solutions are compared, and the most important experimental issues are discussed.Comment: Revtex, 33 pages, 8 figures. In the final version, the title has been changed, and all sections have been improved, while 2 appendices have been adde

Nano-beams under torsion: a stress-driven nonlocal approach

Purpose This study aims to model scale effects in nano-beams under torsion. Design/methodology/approach The elastostatic problem of a nano-beam is formulated by a novel stress-driven nonlocal approach. Findings Unlike the standard strain-driven nonlocal methodology, the proposed stress-driven nonlocal model is mathematically and mechanically consistent. The contributed results are useful for the design of modern devices at nanoscale. Originality/value The innovative stress-driven integral nonlocal model, recently proposed in literature for inflected nano-beams, is formulated in the present submission to study size-dependent torsional behavior of nano-beams