Wave Chaos in Elastodynamic Cavity Scattering

The exact elastodynamic scattering theory is constructed to describe the spectral properties of two- and more-cylindrical cavity systems, and compared to an elastodynamic generalization of the semi-classical Gutzwiller unstable periodic orbits formulas. In contrast to quantum mechanics, complex periodic orbits associated with the surface Rayleigh waves dominate the low-frequency spectrum, and already the two-cavity system displays chaotic features.Comment: 7 pages, 5 eps figures, latex (with epl.cls

Generalized nonlocal optical response in nanoplasmonics

Metallic nanostructures exhibit a multitude of optical resonances associated with localized surface plasmon excitations. Recent observations of plasmonic phenomena at the sub-nanometer to atomic scale have stimulated the development of various sophisticated theoretical approaches for their description. Here instead we present a comparatively simple semiclassical generalized nonlocal optical response (GNOR) theory that unifies quantum-pressure convection effects and induced-charge diffusion kinetics, with a concomitant complex-valued GNOR parameter. Our theory explains surprisingly well both the frequency shifts and size-dependent damping in individual metallic nanoparticles (MNPs) as well as the observed broadening of the cross-over regime from bonding-dipole plasmons to charge-transfer plasmons in MNP dimers, thus unraveling a classical broadening mechanism that even dominates the widely anticipated short-circuiting by quantum tunneling. We anticipate that the GNOR theory can be successfully applied in plasmonics to a wide class of conducting media, including doped semiconductors and low-dimensional materials such as graphene.Comment: 7 pages, including 3 figures. Supplementary information is available upon request to author

Gravity and Yang-Mills Amplitude Relations

Using only general features of the S-matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.Comment: 4 pages, REVTeX, minor typos corrected and references added. Published versio

Tracking vibrational energy on curved shell structures of variable thickness in the mid-to-high frequency - a ray tracing approach

Modelling the vibro-acoustic properties of mechanical built-up structures is a challenging task. Commonly employed techniques, such as finite element methods, are robust only in the low frequency regime. Recently, Discrete Flow Mapping has been forwarded as a cost efficient alternative method for mid- to high-frequency vibro-acoustic modelling. Discrete Flow Mapping employs local ray tracing approximations, providing a good model of the ray dynamics in homogeneous, isotropic flat plates or on curved shells in the geodesic high-frequency limit. However, in the mid-frequency case when the wavelength approaches the shell’s local radius of curvature, the resulting ray dynamics depend on the curvature in a non-trivial way. In this work, we consider ray-tracing approaches for modelling vibrational energy transport in curved shells of variable thickness at mid-to-high frequencies. In particular, we analyse mid-frequency effects on the dispersion curves for curved shells of variable thickness, and identify novel reflection/transmission behaviour

Extension of internationalisation models: drivers and processes for the globalisation of product development – a comparison of Danish and Chinese engineering firms

This paper develops an extension to established production- and supply chain management focused internationalisation models. It applies explorative case studies in Danish and Chinese engineering firms to discover how the globalisation process of product development differs from Danish and Chinese perspectives. The paper uses internationalisation and global product development theory to explain similarities and differences in the approaches. Grounded in case study results, a new model for internationalisation is proposed. The new model expands the internationalisation process model to include steps of product development and collaborative distributed development beyond sourcing, sales and production elements. The paper then provides propositions for how to further develop the suggested model, and how western companies can learn from the Chinese approaches, and globalise their product development activities from the front end of the value chain rather than from the back-end

Observation of Periodic Orbits on Curved Two - dimensional Geometries

We measure elastomechanical spectra for a family of thin shells. We show that these spectra can be described by a "semiclassical" trace formula comprising periodic orbits on geodesics, with the periods of these orbits consistent with those extracted from experiment. The influence of periodic orbits on spectra in the case of two-dimensional curved geometries is thereby demonstrated, where the parameter corresponding to Planck's constant in quantum systems involves the wave number and the curvature radius. We use these findings to explain the marked clustering of levels when the shell is hemispherical

Dynamical energy analysis on mesh grids: a new tool for describing the vibro-acoustic response of complex mechanical structures

We present a new approach for modelling noise and vibration in complex mechanical structures in the mid-to-high frequency regime. It is based on a dynamical energy analysis (DEA) formulation which extends standard techniques such as statistical energy analysis (SEA) towards non-diffusive wave fields. DEA takes into account the full directionality of the wave field and makes sub-structuring obsolete. It can thus be implemented on mesh grids commonly used, for example, in the finite element method (FEM). The resulting mesh based formulation of DEA can be implemented very efficiently using discrete flow mapping (DFM) as detailed in [1] and described here for applications in vibro-acoustics

Trace formula for noise corrections to trace formulas

We consider an evolution operator for a discrete Langevin equation with a strongly hyperbolic classical dynamics and Gaussian noise. Using an integral representation of the evolution operator we investigate the high order corrections to the trace of arbitary power of the operator. The asymptotic behaviour is found to be controlled by sub-dominant saddle points previously neglected in the perturbative expansion. We show that a trace formula can be derived to describe the high order noise corrections.Comment: 4 pages, 2 figure

Evolution of Harmonic Distortion in a Cablified Grid Island after Separation from the Meshed Transmission Grid - A Case Study from Denmark

Green transition in Denmark with more renewable energy production and electrification of consumption, transport, heating, energy conversion and storage accelerates expansion and reconstruction of the transmission grid. When electricity generation and consumption have common connection cables and substations in the transmission grid, such centres are called prosumers.The prosumers do not necessarily increase the net energy exchange with the transmission grid but their short-circuit current contribution may significantly increase due to utilization of inverter-based units. To keep the short-circuit current contribution below the required rating, the meshed 150 kV transmission grid will be separated into islands that are interconnected through the 400 kV meshed transmission system. At the same time, 150 kV overhead lines will be replaced with underground cables as part of the ongoing grid reconstruction in Denmark. This paper presents the simulation results of the 5th harmonic voltage distortion evolution from the present grid stage with the meshed 150 kV transmission grid and, mainly, with overhead lines, through a long-term grid development process with cabling and separation of the meshed grid into 150 kV grid islands. The paper explains foreseen changes of the 5th harmonic voltage distortion within a specific grid island using a measurement validated simulation model for harmonic assessment and benchmarking the simulation results to the harmonic voltage measurements in the present grid stage. The paper also demonstrates identification and usage of early warnings for not-yet-occurred critical increases of the harmonic voltage distortion and proposal of mitigation solutions.<br/

The Complete KLT-Map Between Gravity and Gauge Theories

We present the complete map of any pair of super Yang-Mills theories to supergravity theories as dictated by the KLT relations in four dimensions. Symmetries and the full set of associated vanishing identities are derived. A graphical method is introduced which simplifies counting of states, and helps in identifying the relevant set of symmetries.Comment: 41 pages, 16 figures, published version, typos corrected, references adde