Vibration transmission between coupled plates using finite element methods and statistical energy analysis. Part 2: The effect of window apertures in masonry flanking walls

Part 1 of this paper demonstrated the validity of predictions of vibration transmission across junctions of masonry walls using Finite Element Methods (FEM). Part 2 uses numerical experiments with FEM to calculate the vibration transmission between masonry walls with window apertures at different positions in the flanking wall(s). Results from the numerical experiments are used to assess a simple “rule-of-thumb” estimate for calculating the change in the coupling parameters due to the introduction of an aperture into a flanking wall. Conclusions are drawn concerning use of the “rule-of-thumb” estimate for the coupling loss factor in Statistical Energy Analysis and the vibration reduction index in European standard EN 12354.     

A novel channel for vacuum decay

I show that cosmological bubble walls in the thin wall approximation are unstable to the creation of “barnacles” – loci of different wall tension adjacent to regions filled with a third vacuum. Barnacle formation appears to have the same observational consequences as the extensively studied bubble collision scenario, but occurs exponentially more often. The process is described by a saddle point of the thin wall action with two negative modes.     

Hysteresis loss subdivision

Assuming that different energy dissipation mechanisms are at work along hysteresis, a hysteresis loss subdivision procedure has been proposed, using the induction at maximum permeability (around 0.8 T, in electrical steels) as the boundary between the “low-induction” and the “high-induction” regions. This paper reviews the most important results obtained in 10 years of investigation of the effect of microstructure on these components of the hysteresis loss. As maximum induction increases, the “low-induction loss” increases linearly up to 1.2 T, while the “high-induction loss” is zero up to 0.7 T and then increases as a power law with n=5. Low-induction loss behavior is linearly related to H_c between 0.4 and 1.2 T. Grain size has a larger influence on low-induction losses than on high-induction losses. Texture has a much stronger influence on high loss than on low-induction loss, and it is related to the average magnetocrystalline energy. 6.5%Si steel shows smaller hysteresis loss at 1.5 T than 3.5%Si steel only because of its smaler high-induction component. The abrupt increase in hysteresis loss due to very small plastic deformation is strongly related to the high-induction loss component. These results are discussed in terms of energy dissipation mechanisms such as domain wall movement, irreversible rotation and domain wall energy dissipation at domain nucleation and annihilation.     

Relativistic analysis of the dielectric Einstein box: Abraham, Minkowski and total energy-momentum tensors

We analyse the “Einstein box” thought experiment and the definition of the momentum of light inside matter. We stress the importance of the total energy-momentum tensor of the closed system (electromagnetic field plus material medium) and derive in detail the relativistic expressions for the Abraham and Minkowski momenta, together with the corresponding balance equations for an isotropic and homogeneous medium. We identify some assumptions hidden in the Einstein box argument, which make it weaker than it is usually recognized. In particular, we show that the Abraham momentum is not uniquely selected as the momentum of light in this case.     

Erratum to “Model for domain wall avalanches in ferromagnetic thin films” [Physica A, 390 (2011) 4192–4197]

We detail typing corrections in the paper “Model for domain wall avalanches in ferromagnetic thin films”, R.C. Buceta, D. Muraca, Physica A, 390 (2011) 4192–4197.     

Emergent gravity in two dimensions

We explore models with emergent gravity and metric by means of numerical simulations. A particular type of two-dimensional non-linear sigma-model is regularized and discretized on a quadratic lattice. It is characterized by lattice diffeomorphism invariance which ensures in the continuum limit the symmetry of general coordinate transformations. We observe a collective order parameter with properties of a metric, showing Minkowski or Euclidean signature. The correlation functions of the metric reveal an interesting long-distance behavior with power-like decay. This universal critical behavior occurs without tuning of parameters and thus constitutes an example of “self-tuned criticality” for this type of sigma-models. We also find a non-vanishing expectation value of a “zweibein” related to the “internal” degrees of freedom of the scalar field, again with long-range correlations. The metric is well described as a composite of the zweibein. A scalar condensate breaks Euclidean rotation symmetry.     

Flanking transmission of metal stud walls with different junction details

Measurements of the normalised flanking sound level difference of different gypsum board flanking walls are reported. Results of a “standard” wall construction confirmed some results of the current draft standard of DIN 4109. Different constructions with various junction details and different wall constructions are described and measurement results are presented. By additional measurements on the walls, a prediction model for the weighted flanking level difference is suggested, based on the methodology of EN 12354. For the flanking transmission prediction of path Ff, three transmission paths are proposed. The model gives good agreement between calculated and measured weighted flanking level difference except for the case where the transmission along the inner lining of the flanking wall is dominant. In this case the prediction underestimates measurements by up to 7 dB.     

Saturation field direction dependence of domain structures in NiFe elements

The domain structures in NiFe elements were studied by magnetic force microscopy measurement and micromagnetic modeling. The remanent states in the elements were dependent on the direction of the saturation field. The “S” and “U” states were observed at remanence by applying the saturation field at different directions. The “S” and “U” states are metastable: magnetic force microscopy tip field-induced switching from the “S” and “U” states to the flux closure configuration was observed.     

Notes on nonlocal projective measurements in relativistic systems

In quantum mechanical bipartite systems, naive extensions of von Neumann’s projective measurement to nonlocal variables can produce superluminal signals and thus violate causality. We analyze the projective quantum nondemolition state-verification in a two-spin system and see how the projection introduces nonlocality without entanglement. For the ideal measurements of “R-nonlocal” variables, we argue that causality violation can be resolved by introducing further restrictions on the post-measurement states, which makes the measurement “Q-nonlocal”. After we generalize these ideas to quantum mechanical harmonic oscillators, we look into the projective measurements of the particle number of a single mode or a wave-packet of a relativistic quantum field in Minkowski space. It turns out that the causality-violating terms in the expectation values of the local operators, generated either by the ideal measurement of the “R-nonlocal” variable or the quantum nondemolition verification of a Fock state, are all suppressed by the IR and UV cutoffs of the theory. Thus relativistic quantum field theories with such projective measurements are effectively causal.     

Electromagnetic momentum conservation in media

That static electric and magnetic fields can store momentum may be perplexing, but is necessary to ensure total conservation of momentum. Simple situations in which such field momentum is transferred to nearby bodies and point charges have often been considered for pedagogical purposes, normally assuming vacuum surroundings. If dielectric media are involved, however, the analysis becomes more delicate, not least since one encounters the electromagnetic energy–momentum problem in matter, the ‘Abraham–Minkowski enigma’, of what the momentum is of a photon in matter. We analyze the momentum balance in three nontrivial examples obeying azimuthal symmetry, showing how the momentum conservation is satisfied as the magnetic field decays and momentum is transferred to bodies present. In the last of the examples, that of point charge outside a dielectric sphere in an infinite magnetic field, we find that not all of the field momentum is transferred to the nearby bodies; a part of the momentum appears to vanish as momentum flux towards infinity. We discuss this and other surprising observations which can be attributed to the assumption of magnetic fields of infinite extent. We emphasize how formal arguments of conserved quantities cannot determine which energy–momentum tensor is more “correct”, and each of our conservation checks may be performed equally well in the Minkowski or Abraham framework.     

Formation mechanism of “memory” phenomenon of microchannel plate image intensifier

A discrete resistance capacitance dynodes chain of channel multiplication model worked in a continuous variable dynode number described here is an attempt to explain the formation mechanism of “memory” phenomenon of microchannel plate image intensifier, wherein it was concluded conclusion that “memory” phenomenon of image intensifiers were the results of a silicon-rich layer, which existed between emission layer and conduction layer of channel inner wall of microchannel plate, having much higher resistance as compared with the conduction layer, and there are two distinct appearance ways of “negative memory” and “positive memory” only due to a difference in illumination and duration of the image intensifier suffered, and a strictly controlled MCP manufacture process would make considerable reduction of “memory” phenomenon occurrence ratio.     

A note on a Casimir effect in a uniformly accelerated reference frame

Maxwell's equations are established for the free electromagnetic field in two-dimensional space-times. In Minkowski space they are solved under the boundary conditions set by a pair of uniformly accelerated plates. With the help of these solutions we determine the regularized energy-momentum tensor of the canonically quantized electromagnetic field at the position of one of the plates. Thereby (as a new result) we arrive at a Casimir effect in an accelerated reference frame.University of New Mexico Albuquerque New Mexico 87131This paper is dedicated to Professor Peter Mittelstaedt, University of Cologne, in honour of his sixtieth birthday.On leave of absence from the NBC Defense Research and Development Institute, D-3042 Munster, P.O.B. 1320, Federal Republic of Germany.     

A planar electromagnetic “black hole” based on graphene

Graphene can be used as a platform for transformation-optics devices due to its tunability of conductivity. Besides conductivity, we show that the loss of graphene can also be controlled. Using this priority and taking the advantage of transformation optics, we realize the concept of electromagnetic “black hole” by using of a single-layer graphene. Numerical simulations demonstrate that the surface plasmon polariton waves incident to the “black hole” are bent towards the central area and absorbed by the inner core. The advantages of graphene-based “black hole” are its planar, isotropic, and nonmagnetic characteristics.     

Theory of magnetic inhomogeneities in ferrite-garnets with mixed anisotropy

Inhomogeneous states of ferrite-garnet crystals with mixed anisotropy have been studied. A mechanism for the occurrence in these crystals of new types of magnetic inhomogeneities, frozen solitons or 0° domain walls, is presented. Their stability, static properties, and connection with homogeneous metastable states are investigated. The influence of the metastable states on the structure of domain walls of a normal type is also shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 51–56, August, 1988.     

On Non-Riemannian Domain Walls

Two classes of non-Riemannian domain walls are obtained as distributional planar sources for the linearized Einstein-Cartan (EC) field equations of gravity. The first class represents spin polarized particles distributed on the non-Minkowskian side of the wall and an analogy with the ferromagnetic domains is displayed since the spin distributions are different on both sides of the walls. The other class represents a gravitational analog of Type I superconductor where Cartan torsion plays the role of the magnetic field. The interior solution is obtained by using matching conditions in EC-gravity and is matched to a torsionless vacuum in the last case.     

The dense α-√3 × √3Pb/Si(1 1 1) phase: A comprehensive STM and SPA-LEED study of ordering, phase transitions and interactions

The T-θ phase diagram for the system Pb/Si(1 1 1) was determined in the coverage range 6/5 ML < θ < 4/3 ML from complementary STM and SPA-LEED experiments. This coverage is within the range where a “Devil’s Staircase” (DS) has been realized. The numerous DS phases answer conflicting information in the Pb/Si(1 1 1) literature and update the previously published phase diagram. The measurements reveal the thermal stability of the different linear DS phases with the transition temperature found to be a function of phase period. Because of additional complexity in the experimental system (i.e. two-dimensionality and 3-fold symmetry) the linear DS phases transform at higher temperature into commensurate phases of 3-fold symmetry HIC (historically named “hexagonal incommensurate phase”). Different types of HIC phases have been discovered differing in the size of the supercell built out of √3 × √3 domains separated by domain walls of the √7 × √3 phase. The detailed structures of these HIC phases (coverage, binding site, twist angle, etc.) have been deduced from the comparison of STM images and diffraction patterns. After heating the system to even higher temperature the HIC phase transforms into the disordered phase. For sufficiently high coverage a SIC (“striped incommensurate phase” which is also built from √3 × √3 domains but meandering √7 × √3 domain walls) is observed which also disorders at high temperatures.     

Combined effect of demagnetizing field and induced magnetic anisotropy on the magnetic properties of manganese-zinc ferrite composites

This work is devoted to the analysis of factors responsible for the high-frequency shift of the complex permeability (μ^?) dispersion region in polymer composites of manganese-zinc (MnZn) ferrite, as well as to the increase in their thermomagnetic stability. The magnetic spectra of the ferrite and its composites with polyurethane (MnZn-PU) and polyaniline (MnZn-PANI) are measured in the frequency range from 1 MHz to 3 GHz in a longitudinal magnetization field of up to 700 Ое and in the temperature interval from −20 °С to +150 °С. The approximation of the magnetic spectra by a model, which takes into account the role of domain wall motion and magnetization rotation, allows one to determine the specific contribution of resonance processes associated with domain wall motion and the natural ferromagnetic resonance to the μ^?. It is established that, at high frequencies, the μ^? of the MnZn ferrite is determined solely by magnetization rotation, which occurs in the region of natural ferromagnetic resonance when the ferrite is in the “single domain” state. In the polymer composites of the MnZn ferrite, the high-frequency permeability is also determined mainly by the magnetization rotation; however, up to high values of magnetizing fields, there is a contribution of domain wall motion, thus the “single domain” state in ferrite is not reached. The frequency and temperature dependence of μ^? in polymer composites are governed by demagnetizing field and the induced magnetic anisotropy. The contribution of the induced magnetic anisotropy is crucial for MnZn-PANI. It is attributed to the elastic stresses that arise due to the domain wall pinning by a polyaniline film adsorbed on the surface of the ferrite during in-situ polymerization.     

Magnetization reversal in [Ni/Pt]6/Pt(x)/[Co/Pt]6 multilayers

The magnetization reversal is studied in magnetron sputtered artificial superstructures of the form [Ni/Pt]₆/Pt(x)/[Co/Pt]₆ with perpendicular anisotropy, in which the [Co/Pt]₆ stacks have higher coercivity than the [Ni/Pt]₆. For x≥2 nm the two stacks reverse separately and exhibit characteristic stepped loops with a “plateau” in the region between the two switching fields. First-Order Reversal Curves (FORCs) reveal that the maximum coupling is obtained for x=1.5 nm. While each of the Ni/Pt and Co/Pt stacks by itself is thin enough to reverse in large domains when they are coupled, formation of maze like domains is observed. In this case some reversibility of the demagnetization curves associated with interfacial domain wall pinning appears while in the rest of the cases the reversal mechanism is based on lateral domain wall pinning with low reversibility. In the loops monitored by Extraordinary Hall Effect (EHE) measurements this “plateau” appears as a hump due to the different sign of the EHE coefficient between the [Ni/Pt]₆ and [Co/Pt]₆.     

In situ Video-STM study of the potential-induced (1 × 1) → “hex” transition on Au(1 0 0) electrode surfaces in Cl containing solution

The potential-induced (1 × 1) → “hex” transition on Au(1 0 0) electrodes in 0.01 M Na₂SO₄ + 1 mM HCl was studied by in situ scanning tunneling microscopy at high time resolution (Video-STM). According to these observations the elementary units of the “hex” surface reconstruction, hexagonally-ordered strings in the Au surface layer, are highly dynamic nanoscale objects. Isolated “hex” strings exhibit dynamic fluctuations in structure and position on the millisecond timescale. These fluctuations exceed the mobility of multistring “hex” domains by several orders of magnitude and can be explained by collective dynamic processes within the strings. Furthermore, the observations reveal a novel 1D mass transport mechanism along the strings, details on the nucleation and growth of “hex” strings and complex string restructuring processes, facilitating “hex” domain ripening.