Unusual Amplitude Research Articles

Wind turbines as a metamaterial-like urban layer: an experimental investigation using a dense seismic array and complementary sensing technologies

The deflection and the control of the effects of the complex urban seismic wavefield on the built environment is a major challenge in earthquake engineering. The interactions between the soil and the structures and between the structures strongly modify the lateral variability of ground motion seen in connection to earthquake damage. Here we investigate the idea that flexural and compressional resonances of tall turbines in a wind farm strongly influence the propagation of the seismic wavefield. A large-scale geophysical experiment demonstrates that surface waves are strongly damped in several distinct frequency bands when interacting at the resonances of a set of wind turbines. The ground-anchored arrangement of these turbines produces unusual amplitude and phase patterns in the observed seismic wavefield, in the intensity ratio between stations inside and outside the wind farm and in surface wave polarization while there is no metamaterial-like complete extinction of the wavefield. This demonstration is done by setting up a dense grid of 400 geophones and another set of radial broadband stations outside the wind farm to study the properties of the seismic wavefield propagating through the wind farm. Additional geophysical equipment (e.g., an optical fiber, rotational and barometric sensors) was used to provide essential explanatory and complementary measurements. A numerical model of the turbine also confirms the mechanical resonances that are responsible for the strong coupling between the wind turbines and the seismic wavefield observed in certain frequency ranges of engineering interest.

General Formulation of Eliminating Unusual Amplitude Growth for Structure-Dependent Integration Algorithms

An unusual amplitude growth of the steady-state response for structures with high natural frequencies was found in explicit or semi-explicit structure-dependent integration algorithms with unconditional stability, second-order accuracy and no overshoot. This paper proposes a general formulation for eliminating such an unusual amplitude growth, by incorporating the load-dependent term into the displacement recursive formula without changing the numerical properties of the integration algorithm. Compared with the existing formulation using the local truncation error for eliminating the unusual amplitude growth, the proposed formulation has the advantages of less symbolic operations, while naturally including the existing formulation. In addition, it is observed that the coefficients of the load-dependent term are proportional to the limit values of the displacement coefficients in the displacement recursive formula as the natural frequency of the system tends to infinity. Then, the general formulation of the load-dependent term is tested for 15 structure-dependent integration algorithms to verify its correctness. Finally, numerical examples of linear and nonlinear multiple-degrees-of-freedom systems illustrate that the general formulation can remove effectively and conveniently the unusual amplitude growth for dynamic response analyses.

An unusual amplitude growth property and its remedy for structure-dependent integration methods

An unusual amplitude growth in the steady-state response of a high frequency mode for a structure-dependent integration method is numerically and analytically identified. This is a brand new type of amplitude growth and it has never been found in the conventional integration methods. The root cause of this unusual amplitude growth can be revealed by examining the local truncation error constructed from a forced vibration error, where the dominant error term for high frequency modes plays the key role for this unusual amplitude growth. An effective remedy is proposed by introducing a load-dependent term into the difference equation for displacement and/or velocity increment to remove the dominant error term. As a result, this adverse amplitude growth can be automatically removed. Consequently, the inclusion of the load-dependent term in the formulation of the difference equation for displacement increment and/or velocity increment is inevitable for a general structure-dependent integration method.

Long term variabilities and tendencies of mesospheric lunar semidiurnal tide over Tirunelveli (8.7°N, 77.8°E)

The medium frequency radar deployed at Tirunelveli (8.7°N, 77.8°E), which is located near the southmost tip of peninsular India, have been providing continuous data from the year 1993 to the year 2012 that helped to study the long term tendencies in the lunar tidal variabilities over this geographic location. In the present paper we present the results of seasonal, interannual and long-term variabilities of lunar semi-diurnal tides in the upper mesosphere over Tirunelveli. The present study also includes comparison with model values. The study shows that the tidal amplitudes are larger in the meridional components of the mesospheric winds than the zonal winds. The seasonal variations of the tides are similar in both the components. The tides show maximum amplitudes of about ∼5 m/s in February/March, secondary maximum amplitudes of about ∼3 m/s in September and minimum amplitudes during summer months (May–August). The observed seasonal variation of the lunar tides do not compare well with Vial and Forbes (1994) model values, though it is consistent with earlier observations. The lunar tidal phase in meridional winds leads that in zonal winds from January to June and from September to November, while the latter leads the former during July/August. The lunar tides show large interannual variability. There are unusual amplitude enhancements in the lunar tide in meridional winds during the winters of 2006 and 2009, when major sudden stratospheric warmings (SSW) occurred at high latitude northern hemisphere, whereas zonal lunar tide does not show any clear association with the SSW. Vertical wavelengths of lunar tides in zonal and meridional wind are in the range of 20–90 km. The vertical wavelengths of lunar tides in both zonal and meridional component are smaller in June and larger in November and December. The monthly mean zonal and meridional winds are subjected to regression analysis to study the tidal response to long-period oscillations, namely, quasi-biennial oscillation (QBO), solar cycle variation and El-nino southern oscillation (ENSO). It is found the lunar tide in both zonal and meridional winds show significant QBO response, whereas zonal tide only shows significant negative response to solar cycle and positive response to ENSO. Besides, zonal tide only shows significant long-term increasing trend.

Facies development and sequence stratigraphy of the Ludfordian (Upper Silurian) deposits in the Zbruch River Valley, Podolia, western Ukraine: local facies overprint on the δ13Ccarb record of a global stable carbon isotope excursion

The Ludfordian (Upper Silurian) succession in Podolia, western Ukraine, represents a Silurian carbonate platform developed in an epicontinental sea on the shelf of the paleocontinent of Baltica. Coeval deposits throughout this basin record a positive stable carbon isotope excursion known as the Lau excursion. The record of this excursion in Podolia exhibits an unusual amplitude from highly positive (+6.9 ‰) to highly negative (−5.0 ‰) δ13Ccarb values. In order to link δ13Ccarb development with facies, five sections in the Zbruch River Valley were examined, providing microfacies characterization and revised definitions of the Isakivtsy, Prygorodok, and Varnytsya Formations. The Isakivtsy Fm. is developed as dolosparite replacing originally bioclastic limestone. The Prygorodok Fm., recording strongly depleted (down to −10.53 ‰) to near zero (0.12 ‰) δ13Ccarb values is developed as laminated, organic-rich dolomicrite with metabentonite and quartz siltstone beds. The Varnytsya Fm. is characterized by peritidal deposition with consistent, slightly negative δ13Ccarb values (−0.57 to −3.20 ‰). It is proposed that dolomitization of the Isakivtsy Fm. is associated with a sequence boundary and erosional surface. The overlying Prygorodok Fm. represents the proximal part of a TST deposited in restricted and laterally extremely variable environments dominated by microbial carbonate production. The transition to the overlying Varnytsya Fm. facies is marked by a maximum flooding surface. The SB and MFS are potentially correlative within the basin and support a global rapid sea-level fall previously proposed for this interval. The interpretation of the Prygorodok Fm. as coastal lake deposits may explain the unusual δ13Ccarb values and constitute one of the few records of this type of environment identified in the early Paleozoic.

Economic Crisis, a Paradoxical Efficiency Dynamic

The common characteristic of recent evolutions for powerful economies and small ones, as well, reveals a background of quasi-general slowing down of the growth index, under the zero level, into negative areas. In 2009, the world economic decline had an average of 1.1%, huge economies like USA, Germany, Japan, declined with more than 3%, Euro-zone pole had a decline of 4.6% (IMF Outlook). Because of the unusual high amplitude of the phenomena connected to the goods and services production shrinking, the interventionist policy became a priority, and authorities are expected to take action in a co-coordinated way at central, regional and local levels, in order to prevent and limit the climbing over normal situation of the socio-economic unbalances. Consequently to their spreading negative effects, the economic cycles have been closely observed in order to find the mechanism which would make possible a dedicated curing political instrument. The economics grounded theoreticians emphasize the mechanism where microeconomic cost policy balances the macroeconomic structural changes, while the management-tools adepts, considering the economy as the space of decision makers, promote a doctrinaire line based on the policy mix of externalization and internalization activities, with their correspondent fiscal legislation. In fact, the explanation of the economic policy relies in the optimum area of solutions which save, or more efficiently use, the given resources in the direction of buying from out-borders, meanwhile developing an inner, convenient alternative. Agriculture and rural development are closely connected to global evolutions.

Anomalous reflection amplitudes from fractured reservoirs—Failure of AVOA?

A fractured reservoir embedded in an isotropic background is equivalent to an anisotropic medium whose symmetry depends on fracture orientation. For this configuration, a variation of PP-reflection amplitude as a function of azimuth, φ at a given incidence angle is often observed. Here we report on an observation of unusual amplitude behavior for reflections from the top Cadotte and Falher formations in the Lynx Field, Western Canadian Sedimentary Basin, Alberta, Canada. Formation microscanner (FMS) images suggest considerable fracturing in the shallower Cadotte interval and resistivity measurements show fracturing in the Falher zone. Interestingly, reflection amplitudes from the Cadotte do not show the expected azimuthal variation consistent with a vertically fractured medium. Reflections from the deeper Falher interval, however, do exhibit large, unexpected azimuthal variation.

Multiplet patterns due to co-existing intermolecular dipolar and intramolecular scalar couplings in liquid nuclear magnetic resonance

When both intermolecular dipolar couplings (D couplings) and intramolecular scalar couplings (J couplings) exist in a highly polarized multiple-spin liquid, some forbidden nuclear magnetic resonance signals originating from intermolecular multiple-quantum coherences may become observable. Moreover, their multiplet patterns are quite different from what are observed in a multiple-spin system with J couplings only. In this paper, these forbidden resonance peaks and unique multiplet patterns are studied theoretically and experimentally. For comparison and verification, an I2S3+X spin system is chosen as an example to present five types of signal patterns from the interactions of D and J couplings with either selective or non-selective radio-frequency pulse sequences for double-quantum coherences. The multiplet pattern rules for a more general IpSq+Xk (p,q,k = 1,2,3,...) spin system are derived as well. It is demonstrated that some unusual multiplet amplitude patterns such as (1:0:–1) may ``magnify'' J splittings, allowing more accurate measurement of J coupling in the case of small J coupling constants and/or in inhomogeneous fields. It is shown that the theoretical predictions, computer simulations and experimental observations are all in agreement with one another very well.

Importance of multiple-scattering phenomena in XAS structural determinations of [Ni(CN)4]2- in condensed phases.

A quantitative analysis of the XAS spectra of the tetracyanonickelate complex [Ni(CN)4]2- has been carried out. The simultaneous study of the EXAFS and XANES regions yielded complementary information regarding the geometric and electronic structures of the complex. XANES spectra were modeled by applying recently developed self-consistent, full multiple-scattering algorithms in the FEFF8 code (version 8 x 34). XANES spectra for clusters of different sizes (from 9 to 125 atoms) were computed and compared with experimental spectra. This region of the spectra was proportional to a broadened Ni p-density of states diagram above the Fermi level. Although the main features of the XANES spectra were reasonably reproduced by computations, the weak dependence of the theoretical spectra on cluster size contrasts with the close similarity between the experimental spectra of the solid and solution systems. Because of the special geometry of the complex, calculations with polarized light parallel and perpendicular to the molecular plane were carried out, yielding a reasonable reproduction of the experimental data from another report for cluster sizes equal to or higher than 45 atoms. The highly symmetric square planar structure of the complex was found to be responsible for the unusual amplitude of the multiple-scattering (MS) contributions to the EXAFS spectra. Spectra in this region were fitted using the FEFFIT EXAFS analysis program, taking into account only the MS paths that simultaneously have both a high amplitude, as calculated with the ab initio code FEFF, and a small Debye-Waller factor, as estimated by the independent-vibration approximation model. Fitting results yielded very similar structures for the Ni2+ complex in the solid state and in solution, though the larger Debye-Waller factors found for the solid suggest higher static disorder in this state.

Amplitude and frequency dissociation spectra of ion-protein complexes rotating in magnetic fields

A mechanism is presented that predicts new biological effects of static and sinusoidal weak magnetic fields. The model is based on an earlier proposed interference mechanism of quantum states of ions within protein cavities. The quantum dynamics of an ion is studied for the case of ion-protein complexes that rotate in magnetic fields. Both the individual molecular rotation and rotation together with a biological sample are taken into account. A formula is derived for the magnetic field-dependent part of the dissociation probability of an ion-protein in these conditions. The formula explains the unusual amplitude dependence of the known biological effect in PC-12 cells exposed to AC-DC magnetic field. The dependence had the functional motif J(2)(1)(2H(AC)/H(DC)), where J(1) is the first order Bessel function of the first kind. A good fit was obtained assuming individual rotation of the Li-protein complex in MF. The macroscopic rotation of a biological system, even at low speed 1.5-2 Hz, is predicted to reduce the biological effects of a "magnetic vacuum" and to shift the spectral peaks in the field and frequency dependencies of some magnetobiological effects.

Least squares dip and coherency attributes

Seismic images exhibit considerable local continuity. With the exception of unusual amplitude anomalies and faults, most seismic events can be characterized as exhibiting smoothly varying local dip. Bahorich and Farmer and Gersztenkorn and Marfurt (see “Suggestions for further reading”) show that deviations from local planar behavior can be crucial in unraveling complex fault patterns, improving interpretations, and delineating reservoir extent.

Geochemical Data on Marine Sediments of the Permian-Triassic Boundary Interval: A Review

Described as the turning point in the Pangean environmental history, the Permian-Triassic boundary interval (PTBI) records major global events as biotic crisis, variations of sea level and a large volcanic activity. The increasing number of geochemical studies across the PTBI have outlined variations of unusual amplitudes. A survey of 13 tethyan sections across the PTBI (Baud et al., 1989) confirmed that the variations of ~13C values of carbonates described previously had a global character. The most detailed geochemical study across a Permian-Triassic boundary section has been carried out on the Gartnerkofel core, Southern Alps (papers in Holser and Sch6nlaub, 1991) with three main objectives: the calibration of the 813Ccarb and ~13Corg curves, the research of rare earth and Ir anomalies and the analysis of anoxia. Among the reviews on the Permian-Triassic boundary that consider geochemical data, the most recent one has been published by Hallam and Wignall (1997). The goal of the present note is to review the most recent literature and to discuss the use of geochemistry in problems related to the PTBI.

Curious Consequences of Strong Coupling in NMR Experiments Involving Selective Pulses

This study is concerned with the effects of applying selective pulses to systems with strong second-order scalar couplings in isotropic phase, where different transitions (rs) are associated with different transition matrix elements F+(rs). Two unusual features can be distinguished: the nutation angle ("flip angle") depends on the matrix element of the irradiated transition (rs), and, in contrast to the behavior of an isolated spin-(1/2) system, the norm of the three single-transition operators [I(rs)x, I(rs)y, I(rs)z] associated with the fictitious spin-(1/2) space of the irradiated transition (rs) is generally not conserved. It is necessary to consider the single-transition operators [I(rp)x, I(rp)y, I(rp)z] and [I(sq)x, I(sq)y, I(sq)z] associated with all connected transitions (rp) and (sq) that share a common energy level r or s with the irradiated transition (rs). If the pulse applied to the (rs) transition is sufficiently selective, the transverse components I(rp)x, I(rp)y, I(sq)x, and I(sq)y, can be neglected, since their expectation values remain equal to zero after application of a selective pulse to the (rs) transition, but the longitudinal components I(rp)z and I(sq)z acquire nonvanishing expectation values. When the selective pulse affects several transitions simultaneously, the response varies from one transition to another, depending on the matrix elements and the connectivities. These effects manifest themselves in unusual amplitudes and phases of signals excited by selective pulses, in particular in selective two-dimensional correlation spectra.

Effects of the modulation of magnetic exchange interactions on the electron paramagnetic resonance spectra of some carboxylate-bridged oxovanadium(IV) dimers

The fluid solution EPR spectra of [VO(L)(µ- L1)VO(L)(dmpz)]· 2C6H5Me (I), [{VO(L)(dmpz)}2(µ- L2)]· 2MeCN · 2H2O (II) and [{VO(L)(dmpz)}2(µ- L3)]· 1.2C6H5Me (III)[L = hydrotris(3,5- dimethylpyrazolyl)borato, H2L1= malonic acid, H2L2= acetylenedicarboxylic acid, H2L3= benzene- 1,4-dicarboxylic acid, dmpz = 3,5- dimethylpyrazole] in CH2Cl2, CH2Cl2–toluene, CH2Cl2–MeCN and CH2Cl2–MeOH mixtures, at X-band frequency, and over the temperature range 300–240 K are reported. The spectra are consistent with the dimeric formulations wherein there is an exchange interaction with |J|/|A > 1. In addition, the spectra exhibit unusual amplitude variations of the lines which are attributed to fluctuations in the exchange interactions.

Solar-wind controlled pulsations at low latitudes

Past observations and present models of the solar-wind controlled dayside Pc 3-Pc 4 pulsations are reviewed. A year-long comparison between solar-wind parameters obtained from IMP-8 and micropulsation measurements made at L'Aquila is presented. This study shows that at low latitudes the relationship between the two phenomena is more clear than at high latitudes. In particular, in agreement with the upstream-wave source mechanism, different frequency regimes of pulsations can be related to different regions of the high-velocity streams. Some examples of spectacular wave trains, with unusual amplitude and period, occurred during the strong geomagnetic storm of March 13, 1989 are also presented.

The evolution of the layered lower crust and the Moho through geological time in Western Europe: contribution of deep seismic reflection profiles

ABSTRACTDeep seismic reflection images from a set of profiles shot in Western Europe have been reviewed and compared, and tentative conclusions have been proposed concerning the evolution of the layered lower crust and the Moho. The disappearance of Variscan mountain roots is related to the set‐up of a new Moho at a typical 30‐km depth and the creation of seismic layering in the lower crust. Deep seismic profiles suggest that these processes resulted, at least in part, from magmatic intrusion, partial crustal melting and metamorphism of deep crustal rocks into eclogite. On the other hand, the layered lower crust is greatly attenuated beneath Cretaceous basins and Tertiary rifts in relation to prominent Moho upwellings. The unusual amplitude of the Moho reflection and the presence of anomalously high seismic velocities in the lowermost crust beneath the Tertiary rifts suggest that the Moho and part of the layering are comparatively young features related to interactions between crust and mantle. Beneath Triassic‐Jurassic basins, the layered lower crust was not affected by the subsidence of the basement, with the whole crustal thinning being entirely concentrated in the upper crust. This indicates that the layered lower crust and the Moho were formed or restored during or after the main rifting phase. Seismic data reveal constraints on the processes that affect the crust‐mantle transition and seem to restore the Moho to its typical depth after any mechanical deformation of the lithosphere.

Prediction and observation of pocket vibrational modes in crystals.

A perturbed-shell-model calculation for the impurity system KI:${\mathrm{Ag}}^{+}$ predicts three nearly-degenerate localized gap modes of different symmetry and unusual amplitude patterns: The displacements of the defect's fourth-nearest neighbors are more than an order of magnitude larger than those of the impurity or its nearest neighbors. Far-infrared isotope-effect measurements directly confirm the existence of these localized pocket modes.

Recent stratospheric warmings at mid-latitudes and planetary-scale wave activity

Recent stratospheric warmings are herewith examined in association with the influence of long-period planetary waves. Investigations on height and time variations of geopotential and wind data obtained in the winters of 1980–87 at different tropo-stratospheric levels from messages of the radiosondes situated in the Central Europe take necessarily into account the propagation of quasi-stationary and free planetary waves which in proper conditions mutually interfere with each other. The definition and evolution of the different types of warming are connected with the structure of these waves and enable one to interpret more completely coupling phenomena among different regions of the neutal atmosphere during the most disturbed winters. Distinct spectral analysis methods permit to extract from geopotential data series prominent wave periods within 1÷3 weeks. Westerly winds in the stratosphere reach unusual amplitudes before a sudden stratospheric warming, and this amplification is seen to be in connection with transient normal modes which are able to interact even with the mean circulation of the mesosphere and lower thermosphere.

Fourth sound shock waves in 3HeB

Abstract The relative density of the superfluid component of 3He is expected to be significantly depressed by flow. For this reason the distortion of a finite amplitude fourth sound wave exhibits an unusual amplitude dependence. For waves of sufficiently large initial amplitude, a fully developed shock wave will contain two discontinuities per wavelength. Waves of amplitude twenty times greater than the threshold for this unusual behavior have been reported in the literature.

Nonlinear distortion of 4th sound in superfluid 3He-B

The relative density of the superfluid component of 3He is expected to be significantly depressed by flow. For this reason the distortion of a finite amplitude fourth sound wave exhibits an unusual amplitude dependence. For waves of sufficiently large initial amplitude, a fully developed shock wave will contain two discontinuities per wavelength. Calculations which determine the threshold amplitude are presented and comparisons with thermodynamic data suggest that waves of sufficient amplitude should be experimentally accessible. A tabulation of the most recent thermodynamic data for 3He is included.