Amplification Phenomenon Research Articles

An auto-parametrically excited vibration energy harvester

Parametric resonance, as a resonant amplification phenomenon, is a superior mechanical amplifier than direct resonance and has already been demonstrated to possess the potential to offer over an order of magnitude higher power output for vibration energy harvesting than the conventional direct excitation. However, unlike directly excited systems, parametric resonance has a minimum threshold amplitude that must be attained prior to its activation. The authors have previously presented the addition of initial spring designs to minimise this threshold, through non-resonant direct amplification of the base excitation that is subsequently fed into the parametric resonator. This paper explores the integration of auto-parametric resonance, as a form of resonant amplification of the base excitation, to further minimise this activation criterion and realise the profitable regions of parametric resonance at even lower input acceleration levels. Numerical and experimental results have demonstrated in excess of an order of magnitude reduction in the initiation threshold amplitude for an auto-parametric resonator (∼0.6 ms−2) as well as several folds lower for a parametric resonator with a non-resonant base amplifier (∼4.0 ms−2), as oppose to a sole parametric resonator without any threshold reduction mechanisms (10's ms−2). Therefore, the superior power performance of parametric resonance over direct resonance has been activated and demonstrated at much lower input levels.

Nonlinear geometric optics for contact discontinuities in three dimensional compressible isentropic steady flows

In this paper, the stability of supersonic contact discontinuities in the three-dimensional compressible isentropic steady Euler flows is investigated by using the nonlinear geometric optics. We construct the asymptotic expansions of highly oscillatory contact discontinuities when a planar contact discontinuity is perturbed by a small amplitude high frequency oscillatory incident wave, and deduce there exists a large amplification of amplitudes in the reflected and refracted oscillatory waves when the high frequency oscillatory wave strikes the contact discontinuity front at three critical angles. Moreover, we obtain that the leading profiles of highly oscillatory waves are described by an initial boundary value problem of Burgers-transport equations, and the leading profile of contact discontinuity front satisfies an initial value problem of a Hamilton-Jacobi equation, respectively. The amplification phenomenon shows that this supersonic contact discontinuity is only weakly stable in the sense of Wang and Yu [“Stability of contact discontinuities in three-dimensional compressible steady flows,” J. Differ. Equ. 255, 1278–1356 (2013)].

Polarization effects of dielectric nanoparticles in aqueous charge-asymmetric electrolytes.

Small nanoparticles, globular proteins, viral capsids, and other nanoscopic biomolecules usually display dielectric properties that are different from those of the medium in which they are dispersed. These dielectric heterogeneities can significantly influence the surrounding ion distribution, which determines the self-assembly and colloidal stability of these nanoparticles in solution. Here, we study the impact of a dielectric discontinuity in the structural and thermodynamic properties of a spherical nanoparticle made of different dielectric materials when it is immersed in a charge-asymmetric 1:z supporting electrolyte. The mean electrostatic potential, integrated charge, and ionic profiles are analyzed as a function of both the salt concentration and the nanoparticle's valence via Monte Carlo simulations and the nonlinear Poisson-Boltzmann theory. We observe that the electrostatic screening and charge neutralization near the surface of a nanoparticle increase when the nanoparticle's dielectric permittivity increases in all instances. For 1:1 salts, this effect is small and the nonlinear Poisson-Boltzmann theory displays a good agreement with simulation results. Nevertheless, significant deviations are displayed by the mean field scheme regarding simulation results in the presence of multivalent ions. In particular, for trivalent counterions we observe that increasing the dielectric permittivity or the valence of the nanoparticle decreases the critical salt concentration at which occurs a sign inversion of the mean electrostatic potential at the Helmholtz plane, which is closely related to the behavior of the ζ potential and the electrophoretic mobility. Moreover, we observe that the phenomenon of surface charge amplification, or the augmenting of the net charge of a nanoparticle by the adsorption of like-charged ions on its surface, can be promoted by polarization effects in weakly charged spherical nanoparticles with low dielectric permittivity.

Науково-дослідна робота з антистресової підготовки авіаспеціалістів за чверть віку

Виконано аналітичний огляд навчання людини-оператора протидії одночасному впливу негативних факторів.Основну увагу приділено навчанню операторів зняттю негативних ефектів у польоті, які пов’язані з явищемпідсилення динамічного стереотипу у авіаспеціалістів

Semilinear geometric optics with boundary amplification

We study weakly stable semilinear hyperbolic boundary value problems with highly oscillatory data. Here weak stability means that exponentially growing modes are absent, but the so-called uniform Lopatinskii condition fails at some boundary frequency $\beta$ in the hyperbolic region. As a consequence of this degeneracy there is an amplification phenomenon: outgoing waves of amplitude $O(\eps^2)$ and wavelength $\eps$ give rise to reflected waves of amplitude $O(\eps)$, so the overall solution has amplitude $O(\eps)$. Moreover, the reflecting waves emanate from a radiating wave that propagates in the boundary along a characteristic of the Lopatinskii determinant. An approximate solution that displays the qualitative behavior just described is constructed by solving suitable profile equations that exhibit a loss of derivatives, so we solve the profile equations by a Nash-Moser iteration. The exact solution is constructed by solving an associated singular problem involving singular derivatives of the form $\partial_{x'}+\beta\frac{\partial_{\theta_0}}{\eps}$, $x'$ being the tangential variables with respect to the boundary. Tame estimates for the linearization of that problem are proved using a first-order calculus of singular pseudodifferential operators constructed in the companion article \cite{CGW2}. These estimates exhibit a loss of one singular derivative and force us to construct the exact solution by a separate Nash-Moser iteration. The same estimates are used in the error analysis, which shows that the exact and approximate solutions are close in $L^\infty$ on a fixed time interval independent of the (small) wavelength $\eps$. The approach using singular systems allows us to avoid constructing high order expansions and making small divisor assumptions.

Geometric optics expansions for linear hyperbolic boundary value problems and optimality of energy estimates for surface waves

In this article we are interested in energy estimates for hyperbolic initial boundary value problem when surface waves occur. More precisely, we construct rigorous geometric optics expansions for so-called elliptic and mixed frequencies and we show, using those expansions, that the amplification phenomenon is greater in the case of mixed frequencies. As a consequence, this result allow us to give a partial classification of weakly well-posed hyperbolic initial boundary value problems according to the region where the uniform Kreiss Lopatinskii condition degenerates.

Reasons and laws of ground vibration amplification induced by vertical dynamic load

The phenomenon of ground vibration amplification caused by railway traffic was found and proved. In order to study the reasons which cause the amplification, a drop-weight test was performed. Then, the model for both homogeneous and layered soil subjected to a harmonic vertical load was built. With the help of this model, displacement Green’s function was calculated and the propagation laws of ground vibration responses were discussed. Results show that: 1) When applying a harmonic load on the half-space surface, the amplitude of ground vibrations attenuate with fluctuation, which is caused by the superposition of bulk and Rayleigh waves. 2) Vibration amplification can be enlarged under the conditions of embedded source and the soil layers. 3) In practice, the fluctuant attenuation should be paid attention to especially for the vibration receivers who are sensitive to single low frequencies (<10 Hz). Moreover, for the case of embedded loads, it should also be paid attention to that the receivers are located at the place where the horizontal distance is similar to embedded depth, usually 10 to 30 m for metro lines.

The seismic microzonation of level 3 of Sant’Agata Fossili (northern Italy) based on a multidisciplinary approach

&lt;p&gt;In this paper the results of a detailed seismic microzonation, performed at Sant’Agata Fossili (Piemonte region, northern Italy) are presented. We study the local seismic response of this small village using a level 3, that is the most accurate level following the Italian code of seismic microzonation. The activity steps consist in a gradual widening of knowledge of the different aspects of the amplification phenomena. A multidisciplinary approach has been performed to obtain the local seismic response: including a study of local geology, geophysical and geotechnical characterization of the lithologies, and numerical and experimental analyses. We finally compare the obtained elastic response spectra to the prescribed spectra of the Italian Building Code (in Italian: Norme Tecniche per le Costruzioni). Our results show the geologic and geophysical differences of the subsoil, that produce different local seismic response in terms of amplification factors and acceleration response spectra.&lt;/p&gt;

Nonlinear seismic response for the 2011 Tohoku earthquake: borehole records versus one-directional three-component propagation models

The seismic response of surficial multilayered soils to strong earthquakes is analysed through a non-linear one-directional three-component (1D-3C) wave propagation model. The three components (3C-polarization) of the incident wave are simultaneously propagated into a horizontal multilayered soil. A 3-D non-linear constitutive relation for dry soils under cyclic loading is implemented in a quadratic line finite element model. The soil rheology is modelled by mean of a multisurface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan type. Its major advantage is that the rheology is characterized by few non-linear parameters commonly available. Previous studies showed that, when comparing one to 3C unidirectional wave propagation simulations, the soil shear modulus decreases and the dissipation increases, for a given maximum strain amplitude. The 3-D loading path due to the 3C-polarization leads to multiaxial stress interaction that reduces soil strength and increases non-linear effects. Non-linearity and coupling effects between components are more obvious with decreasing seismic velocity ratio in the soil and increasing vertical to horizontal component ratio for the incident wave. This research aims at comparing computed ground motions at the surface of soil profiles in the Tohoku area (Japan) with 3C seismic signals recorded during the 2011 Tohoku earthquake. The 3C recorded downhole motion is imposed as boundary condition at the base of soil layer stack. Notable amplification phenomena are shown, comparing seismograms at the bottom and at the surface. The 1D-3C approach evidences the influence of the 3-D loading path and input wavefield polarization. 3C motion and 3-D stress and strain evolution are evaluated all over the soil profile. The triaxial mechanical coupling is pointed out by observing the variation of the propagating wave polarization all along the duration of seismograms. The variation of the maximum horizontal component of motion with time, as well as the influence of the vertical component, confirm the interest of taking into account the 3C non-linear coupling in 1D wave propagation models for such a large event.

Experimental Evaluation of Vibration Effects Induced by Planed Railway Line on Surrounding Historic Tower

Using field experiments, the vibration effects of historic tower induced by planed railway line are estimated. The vibrations include the construction vibration and the traffic-induced vibration. The results show that the blasting construction leads to the significant increase in vertical velocity and acceleration. There is no difference between the background vibration of field and foundation of tower. Different types of the sites soil around the tower cause little change. Each measurement time showed an upward trend of vibration level with the increase of frequency. The closer the tower is to the vibration source, the larger the structural vibrations would be. The dominant frequency range for highway-induced vibration is 10-20Hz. For train-induced vibration, the dominant frequency range is more than 40Hz. Surface waves will result in amplification phenomenon of vibration velocity of ancient structures within a certain range.

SPONTANEOUS AMPLIFICATION OF THERMAL NOISE BY A SLACK JOINT

Recently the phenomenon of enforced thermal noise amplification in a conductor exposed to an electrostatic field has been discovered in a lab- oratory experiment and qualitatively explained by computations concerning a simplified quantum model. The dispersion of the velocity operator of an elec- tron at thermal equilibrium has turned out to be an appropriate indicator of the thermal noise level inherent in a metal. In the present contribution the behavior of this indicator is studied for an electron confined within a lattice which is interpreted as a quantum position space in the sense of a tight binding model. It turns out that the dispersion of the velocity operator increases when a narrow gap is arranged between two pieces of a metal. An empirical pendant of this computational result is also reported.

The origin of galactic cosmic rays

One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data. I will mostly focus on supernova remnants as the most plausible sources of Galactic cosmic rays, and I will review the main aspects of the modern theory of diffusive particle acceleration at supernova remnant shocks, with special attention for the dynamical reaction of accelerated particles on the shock and the phenomenon of magnetic field amplification at the shock. Cosmic ray escape from the sources is discussed as a necessary step to determine the spectrum of cosmic rays at the Earth. In the end of this review I will also discuss the phenomenon of cosmic ray acceleration at shocks propagating in partially ionized media and the implications of this phenomenon in terms of width of the Balmer line emission.

Quantum discord amplification of fermionic systems in an accelerated frame

Quantum discord of fermionic systems in the relativistic regime, that is, beyond the single-mode approximation (SMA) is investigated. It is shown that quantum discord is amplified for the fermionic system in non-inertial frames irrespective of the choice of state, region and level of mixedness. This ensures that the phenomenon of amplification can actually happen in the relativistic regime. It is seen that quantum discord converges at infinite acceleration limit, which means that it becomes independent of $$q_{R}$$qR (Unruh modes) beyond SMA. This implies that most of the tensor product structures already used in the literature to compute quantum field correlations in relativistic quantum information cannot give rise to physical results. The dynamics of quantum discord is investigated under amplitude damping, depolarizing and flipping channels. The vanishing behavior of quantum discord is seen for higher level of decoherence in the infinite acceleration limit. The depolarizing channel dominantly affects the fermionic quantum discord as compared to the amplitude damping channel. It means that the depolarizing channel has most destructive influence on the discord of the fermionic systems. Moreover, the effect of environment on the discord is much stronger than that of the acceleration of non-inertial frames.

Quantification of EGFR autoantibodies in the amplification phenomenon of HER2 in breast cancer

Gene amplification or overexpression of human epidermal growth factor receptor HER2/ErB2 is seen in 25-30% of patients with breast cancer and is related to an aggressive disease. The mechanism behind the HER2 gene amplification is unknown, but it may be caused by continuous stimulation and activation. We hypothesised that autoantibodies against EGFR might have a stimulatory effect. To investigate this we developed a quantitative method to measure autoantibodies against EGFR in serum (S-EGFRAb). Serum samples from primary breast cancer patients were selected based on the degree of HER2 protein and gene amplification in the cancer tissue. Fifty patients had low levels of HER2 (≤ 16 ng/mg total protein) and no HER2 gene amplification; 43 patients had high levels of HER2 (≥ 200 ng/mg total protein) and HER2 gene amplification. Serum was also collected from controls consisting of 50 healthy age-matched women. An ELISA was developed to measure S-EGFRAb quantitatively. No significant differences in S-EGFRAb concentrations were seen between patients with high and low levels of HER2 or between the patients and the controls. Furthermore, no significant correlations were observed between S-EGFRAb and stage, differentiation state, age or prognosis. A negative correlation (p=0.0022) was found between S-EGFRAb and disease free survival in the group of patients with relapse or death. S-EGFRAb can be measured accurately using the ELISA we developed. We conclude that autoantibodies against EGFR do not seem to be associated with the HER2 gene amplification phenomenon.

Trampoline metamaterial: Local resonance enhancement by springboards

We investigate the dispersion characteristics of locally resonant elastic metamaterials formed by the erection of pillars on the solid regions in a plate patterned by a periodic array of holes. We show that these solid regions effectively act as springboards leading to an enhanced resonance behavior by the pillars when compared to the nominal case of pillars with no holes. This local resonance amplification phenomenon, which we define as the "trampoline effect", is shown to cause subwavelength band gaps to increase in size by up to a factor of 4. This outcome facilitates the utilization of subwavelength metamaterial properties over exceedingly broad frequency ranges.

Central antarctic climate response to the solar cycle

Antarctic “Vostok” station works most closely to the center of the ice cap among permanent year-around stations. Climate conditions are exclusively stable: low precipitation level, cloudiness and wind velocity. These conditions can be considered as an ideal model laboratory to study the surface temperature response on solar irradiance variability during 11-year cycle of solar activity. Here we solve an inverse heat conductivity problem: calculate the boundary heat flux density (HFD) from known evolution of temperature. Using meteorological temperature record during (1958–2011) we calculated the HFD variation about 0.2–0.3 W/m2 in phase with solar activity cycle. This HFD variation is derived from 0.5 to 1 °C temperature variation and shows relatively high climate sensitivity per 0.1 % of solar radiation change. This effect can be due to the polar amplification phenomenon, which predicts a similar response 0.3–0.8 °C/0.1 % (Gal-Chen and Schneider in Tellus 28:108–121, 1975). The solar forcing (TSI) is disturbed by volcanic forcing (VF), so that their linear combination TSI + 0.5VF empirically provides higher correlation with HFD (r = 0.63 ± 0.22) than TSI (r = 0.50 ± 0.24) and VF (r = 0.41 ± 0.25) separately. TSI shows higher wavelet coherence and phase agreement with HFD than VF.

Local site effect microzonation of Lorca town (SE Spain)

Local site effect assessment based on subsurface ground conditions is often the key to evaluate urban seismic hazard. The site effect evaluation in Lorca town (south-eastern Spain) started with a classification of urban geology through the geological mapping at scale 1:10,000 and the use of geotechnical data and geophysical surveys. The 17 geological formations identified were classified into 5 geological/seismic formations according to their seismic amplification capacity obtained from ambient vibration measurements as well as from simultaneous strong motion records. The shear-wave velocity structure of each geological/seismic formation was evaluated by means of inversion of Rayleigh wave dispersion data obtained from vertical-component array records of ambient noise. Nakamura’s method was applied to determine a predominant period distribution map. The spectral amplification factors were fourfold the values recorded in a reference hard-rock site. Finally, the capability of this study for explaining the damage distribution caused by the May 11th, 2011 Lorca destructive earthquake (Mw \(=\) 5.2) was examined. The methods used in this work are of assistance to evaluate ground amplification phenomena in urban areas of complex geology as Lorca town due to future earthquakes with applicability on urban seismic risk management.

Chiral Amplification during Asymmetric‐Induced Copolymerization of Phenylacetylenes with Tight Cis‐Cisoidal Main Chains

A novel phenylacetylene (1) having two hydroxyl groups and a chiral pinanyl group together with the other three related phenylacetylenes has been synthesized and (co)polymerized by using an achiral catalytic system. Among the four monomers, only 1 is suitable to the asymmetric-induced polymerization (AIP). Chiral amplification phenomenon is only observed in the copolymerization of 1 with an achiral phenylacetylene having two hydroxyl groups (3). The tight helical cis-cisoidal main chain formed by making intramolecular hydrogen bonds between the hydroxyl groups in the copoly(1/3) enhances the efficiency of chiral induction and as a result chiral amplification phenomenon is observed during the copolymerization.

Racemic synthetic polymers and chirality

This review is mainly devoted to the chiral-optical behavior in the solid state of racemic synthetic polymers, which are able to form co-crystalline phases with low molecular mass guest molecules and whose chirality is induced by non-racemic (also temporary) guest molecules. The article starts with the description of chiral features relevant for the synthesis of stereoregular polymers. Subsequently, the chirality of chain helicity and the related phenomena of macromolecular amplification of chirality, both in solution and in the solid state, are discussed. The final part of the article describes the recent achievement of robust chiral-optical films being constituted by a racemic commercial host polymer and achiral guest chromophores.

Synergistic analgesic effects between neuronostatin and morphine at the supraspinal level

Neuronostatin, a 13-amino acid peptide, is encoded in the somatostatin pro-hormone. I.c.v. administration of neuronostatin produces a significant antinociceptive effect in the mouse tail-flick test, which is mediated by endogenous opioid receptor. However, the direct functional interaction between morphine and neuronostatin has not been characterized. In the present study, effect of neuronostatin on morphine analgesia was investigated in the tail-flick test. Our findings showed that i.c.v. administration of neuronostatin (0.3nmol/mouse i.c.v.) significantly enhanced the antinociceptive effect of morphine (2.5, 5 or 10μg/kg) at the supraspinal level. Results of antagonism experiments suggested that the synergistic analgesia induced by morphine and neuronostatin was mediated by μ- and к-opioid receptors not δ-opioid receptor. In conclusion, there may be a cascade amplification phenomenon when morphine and neuronostatin were co-administered in acute pain model. The above results provide evidence for the potential use of neuronostatin in combination with morphine to control pain and addiction.