Undulating Behavior Research Articles

UNDULATING POTENTIALS OF RYDBERG Σ+-STATES OF ME-RG MOLECULES: NON-EMPIRICAL TREATMENT OF NA-HE EXCIPLEX

The multi-reference con guration interaction method based on single and double excitations (MR-CISD), l-independent core polarization potential (CPP) and diffuse function-saturated cc-pVQZ and aug-cc-pV5Z basis sets for Na and He atoms, respectively, have been used to perform non-relativistic calculations of potential energy curves and permanent dipole moment functions for the ground and excited electronic states of the exciplex Na-He molecule up to the Na(62S) state. The ab initio results obtained in a wide range of internuclear distances R [1.7, 20.0] (Å) have quantitatively claimed the undulating behavior of interatomic potentials, predicted within the framework of the inelastic scattering theory. It has been established that at large R the interatomic potentials and dipole moments of highly excited (3,6,10)2Σ+ states, converging to Na (n = 4, 5, 62S)+He(22S) atomic limits, are modulated by the nodal structure of the radial Rydberg wave function (n > 3) s-electron of Na atom during its scattering on the remote He atom.

Experimental electro-hydrodynamic investigation of flag-based energy harvesting in the wake of inverted C-shape cylinder

Series of water tunnel experiments are performed to study the improvement in energy harvesting by vortex-induced vibrations. Inverted C-shape cylinders with different cut angles are placed in the uniform fluid flow and electrical energy is harvested using the undulating behavior of the piezo-flag in the downstream vortices. Experimental results demonstrate different flapping modes like poorly and optimal coupling with the wake flow. It is also showed that the streamwise gap and flow speed have a significant impact on the amplitude and flapping frequency, which results in the variation of the energy output of piezo-flag. The results indicate that the highest gain in output power is 66% for an inverted C-shape cylinder with a 120° cut angle compared to a circular cylinder performance. For each cylinder and flow velocity, it is also observed that there exists a critical streamwise gap for which vortex shedding does not produce any energy using piezo-flag due to poor coupling with wake flow. The results show that there is no significant difference in the performance of circular and 60° inverted C-shape cylinders regarding energy harvesting. However, changing the shape and cut angle leads to a remarkable increase in the flapping amplitude and its growth rate along with the dominant frequency. Particle Image Velocimetry (PIV) experimentation also endorses the results as wake dynamics is in good agreement with the energy efficiency improvement. Therefore, a 120° cut angle configuration holds a vivid preeminence over a circular cylinder as the kinetic source of a fluid energy harvester. The present study contributes effectively to harvesting energy from impinging vortices by tuning the streamwise gap, flow velocity, and cut angle of the inverted C-shape cylinder.

Modeling Multifrequency Pol-InSAR Data From the Percolation Zone of the Greenland Ice Sheet

The analysis of data from an airborne synthetic aperture radar (SAR) campaign in the percolation zone of Greenland revealed an interferometric coherence undulation behavior with respect to vertical wavenumber, which cannot be explained with existing models. We propose a model extension that accounts for scattering from distinct layers below the surface. Simulations show that the periodicity of the coherence undulation is mainly driven by the vertical distance between dominant subsurface layers, while the amplitude of the undulation is determined by the ratio between scattering from distinct layers and scattering from the firn volume. We use the model to interpret quad-pol SAR data at X-, C-, S-, L-, and P-bands. The inferred layer depths match layer detections in ground-based radar data and in situ measurements. We conclude that in the percolation zone, scattering from subsurface layers has to be taken into account to correctly interpret SAR data and demonstrate the potential to retrieve geophysical information about the vertical subsurface structure.

Plane-wave scattering by an ellipsoid composed of an orthorhombic dielectric-magnetic material.

The extended boundary condition method can be used to study plane-wave scattering by an ellipsoid composed of an orthorhombic dielectric-magnetic material whose relative permittivity dyadic is a scalar multiple of its relative permeability dyadic. The scattered and internal field phasors can be expanded in terms of appropriate vector spherical wavefunctions with unknown expansion coefficients, whereas the incident-field phasors can be similarly expanded but with known expansion coefficients. The scattered-field coefficients are related to the incident-field coefficients through a matrix. The scattering, absorption, and extinction efficiencies were calculated thereby in relation to the propagation direction and the polarization state of the incident plane wave, the constitutive-anisotropy parameters, and the nonsphericity parameters of the ellipsoid, when the eigenvectors of the real permittivity dyadic are aligned along the three semi-axes of the ellipsoid. As the electrical size of the ellipsoid increases, multiple lobes appear in the scattering pattern. The total scattering efficiency can be smaller than the absorption efficiency for some configurations of the incident plane wave but not necessarily for others. The nonsphericity of the object has a stronger influence on the total scattering efficiency than on the absorption efficiency. The forward-scattering efficiency increases monotonically with the electrical size for all configurations of the incident plane wave, and so does the backscattering efficiency for some configurations. For other configurations, the backscattering efficiency has an undulating behavior with increase in electrical size and is highly affected by the shape and the constitutive anisotropy of the ellipsoid. Even though the ellipsoid is not necessarily a body of revolution, it is anisotropic, and it is not impedance matched to free space, the backscattering efficiency can be minuscule but the forward-scattering efficiency is not. This feature can be useful for harvesting electromagnetic energy.

Derivation of rainfall IDF relations by third-order polynomial normal transform

Establishing the rainfall intensity–duration–frequency (IDF) relations by the conventional method, the use of parametric distribution models has the advantage of automatic compliance of monotonicity condition of rainfall intensity and frequency. However, fitting rainfall data to a distribution separately by individual duration may possibly produce undulation and crossover of IDF curves which does not comply physical reality. This frequently occurs when rainfall record length is relatively short which often is the case. To tackle this problem this study presents a methodological framework that integrates the third-order polynomial normal transform (TPNT) with the least squares (LS) method to establish rainfall IDF relations by simultaneously considering multi-duration rainfall data. The constraints to preserve the monotonicity and non-crossover in the IDF relations can be incorporated easily in the LS-based TPNT framework. Hourly rainfall data at Zhongli rain gauge station in Taiwan with 27-year record are used to establish rainfall IDF relations and to illustrate the proposed methodology. Numerical investigation indicates that the undulation and crossover behavior of IDF curves can be effectively circumvented by the proposed approach to establish reasonable IDF relations.

Nonstationary Flood Frequency Analysis Using Univariate and Bivariate Time-Varying Models Based on GAMLSS

With the changing environment, a number of researches have revealed that the assumption of stationarity of flood sequences is questionable. In this paper, we established univariate and bivariate models to investigate nonstationary flood frequency with distribution parameters changing over time. Flood peak Q and one-day flood volume W1 of the Wangkuai Reservoir catchment were used as basic data. In the univariate model, the log-normal distribution performed best and tended to describe the nonstationarity in both flood peak and volume sequences reasonably well. In the bivariate model, the optimal log-normal distributions were taken as marginal distributions, and copula functions were addressed to construct the dependence structure of Q and W1. The results showed that the Gumbel-Hougaard copula offered the best joint distribution. The most likely events had an undulating behavior similar to the univariate models, and the combination values of flood peak and volume under the same OR-joint and AND-joint exceedance probability both displayed a decreasing trend. Before 1970, the most likely combination values considering the variation of distribution parameters over time were larger than fixed parameters (stationary), while it became the opposite after 1980. The results highlight the necessity of nonstationary flood frequency analysis.

Impact of Postsynthetic Surface Modification on Photoluminescence Intermittency in Formamidinium Lead Bromide Perovskite Nanocrystals.

We study the origin of photoluminescence (PL) intermittency in formamidinium lead bromide (FAPbBr3, FA = HC(NH2)2) nanocrystals and the impact of postsynthetic surface treatments on the PL intermittency. Single-dot spectroscopy revealed the existence of different individual nanocrystals exhibiting either a blinking (binary on-off switching) or flickering (gradual undulation) behavior of the PL intermittency. Although the PL lifetimes of blinking nanocrystals clearly correlate with the individual absorption cross sections, those of flickering nanocrystals show no correlation with the absorption cross sections. This indicates that flickering has an extrinsic origin, which is in contrast to blinking. We demonstrate that the postsynthetic surface treatment with sodium thiocyanate improves the PL quantum yields and completely suppresses the flickering, while it has no significant effect on the blinking behavior. We conclude that the blinking is caused by Auger recombination of charged excitons, and the flickering is due to a temporal drift of the exciton recombination rate induced by surface-trapped electrons.

TiN films fabricated by reactive gas pulse sputtering: A hybrid design of multilayered and compositionally graded structures

Reactive gas pulse (RGP) sputtering approach was used to prepare TiN thin films through periodically changing the N2/Ar gas flow ratio. The obtained RGPTiN film possessed a hybrid architecture containing compositionally graded and multilayered structures, composed of hcp Ti-phase and fcc TiN-phase sublayers. Meanwhile, the RGP-TiN film exhibited a composition-oscillation along the film thickness direction, where the Ti-phase sublayer had a compositional gradient and the TiN-phase retained a constant stoichiometric ratio of Ti:N≈1. The film modulation ratio λ (the thicknesses ratio of the Ti and TiN-phase sublayer) can be effectively tuned by controlling the undulation behavior of the N2 partial flow rate. Detailed analysis showed that this hybrid structure originated from a periodic transition of the film growth mode during the reactive sputtering process.

Shearing rate effect on residual strength of landslide soils in the slow rate range

In the present study, we investigate the influence of shearing rate on the residual strength parameters, ϕ r, in landslide soils using ring-shear tests at two shearing rates (0.01 and 0.5 mm/min) under selected effective normal stresses. The landslide soil samples used for this study cover a wide range of soil types and properties. Relationships between the ϕ r and soil properties, such as liquid limit, plasticity index, and the clay fraction show that the ϕ r decreases with increasing soil LL, I p and CF. The differences in the ϕ r at two shearing rates, ϕ r (0.5) − ϕ r (0.01), under different effective normal stresses are either negative or positive values of which the maximum magnitude is generally about 1.0°. The relationships between the ϕ r (0.5) − ϕ r (0.01) and the soil properties (LL, I p, and CF) are not exhibited in a regular pattern. On the other hand, the ϕ r (0.5) and ϕ r (0.01) determined at each effective normal stress suggest that the tendency for increased negative effect of the ϕ r with decreasing effective normal stress is more noticeable in the slow shearing rate range. The absolute value of ϕ r (0.5) − ϕ r (0.01) at lower effective normal stress is found to be greater than 1.0°, with the maximum of about 4.0°. The negative shearing rate effect on ϕ r at low effective normal stress is affected by the undulating shear behavior due to poor or no slickenside development.

Anisotropic TGO morphology and stress distribution in EB-PVD Y2O3-ZrO2 thermal barrier coating after in-phase thermo-mechanical test

An in-phase stress controlled thermo-mechanical fatigue test (IP-TMF) on an electron beam physical-vapor-deposition (EB-PVD) 7-wt.% Y2O3-ZrO2-coated CoNiCrAlY bond coat, called an IN-738LC thermal barrier coating (TBC) system, was carried out. The temperature gradient in the through-thickness direction was achieved. Examination of the system's deformation behavior showed clear creep and superimposed ratcheting behaviors similar to those of the substrate superalloy tested by the same IP-TMF test. The EB-PVD TBC also follows the creep deformation behavior of the substrate. Anisotropic undulation of the thermally grown oxide (TGO) layer was observed in polished section observations. The undulation behavior appeared only perpendicular to the loading direction and was not observed parallel to the loading direction. The average compressive stress distribution of the TGO layer depends on the undulation behavior. The compressive stress parallel to the loading direction is nearly constant and the value agrees with the estimated thermal stress, while the stress in the undulating section is distributed unevenly such that the compressive stress is enhanced at the bottom of concave region.

The three-dimensional flow organization past a micro-ramp in a supersonic boundary layer

The three-dimensional instantaneous flow organization in the near wake of a micro-ramp interacting with a Mach 2.0 supersonic turbulent boundary layer is studied using tomographic particle image velocimetry. The mean flow reveals a wake with approximately circular cross section dominated by a pair of counter-rotating streamwise vortices generating a focused upwash motion at the symmetry plane. In the instantaneous flow organization a flow instability of Kelvin-Helmholtz (K-H) type is observed in the shear layer between the wake and outer flow. Intermittent arc-shaped vortices are visualized that locally accelerate the outer fluid and further decelerate the inner region. The streamwise vortex pair displays an undulating behavior. Their interaction with the K-H vortices considerably increases the overall complexity of the wake. It appears that the streamwise vortex filaments under the K-H vortex train approach each other due to the focused ejection activity resulting from the K-H vortex. The statistical properties of turbulent fluctuations yield maximum activity at the core of the streamwise vortex and within the upwash region, and the Reynolds stresses peak within the shear layer. The topological organization of the wake vortices is formulated through a conditional average over the vorticity field.

Coupling between meteorological factors and ambient aerosol load

The coarser (CPM) and respirable (RPM) fractions of aerosol loads collected in a time sequence, during the onset of winter season in Delhi region, were subjected to Principal Component Analysis (15 elemental variables, 39 samples); the absolute mass contributed by each identified source to the CPM and RPM was quantified by using Absolute Principal Component Score (APCS) and Positive Matrix Factorization (PMF) method. Interestingly, the mass contributed by the local crustal source (material) to both fractions manifested undulating periodic behavior, a dominating harmonic corresponding to 24-h period was detected by using Discrete Fourier Transform (DFT). The corresponding harmonics, of varying strengths, were also detected in the recorded meteorological factors: Planetary Boundary Layer (PBL), Surface Level Temperature (T), Surface Level Relative Humidity (RH) and Wind Speed (WS). The analysis of the respective harmonic strength within the CPM, RPM, and meteorological factors suggested that the undulation observed in both size fractions of aerosol load from the local crust was affected by the meteorological factors. The large proportion of undulating loads (CPM and RPM), explained by the dominating harmonic, was fully accounted for by the empirical relation involving the discrete coupling parameters, and the recorded meteorological factors: PBL, T, RH and WS. The analysis suggests that the magnitude and the direction (‘positive’ load increase and ‘negative’ the reverse) of coupled meteorological factors'(s) effect on ambient CPM, RPM load is determined by the phase difference between the harmonic explaining the aerosol fraction's load and the corresponding harmonic present in the respective meteorological factor. The absolute mass contributions arising from the identified sources (APCS and PMF) allowed us to calculate the baseline ambient concentrations of undulating CPM and RPM loads, in the region of this study, affected by meteorological factors only.

The role of particle surface texture on case material selection and silk lining in caddis flies

Many organisms construct external structures to increase their fitness. However, there is a considerable energetic cost for construction that often involves a trade-off with other physical or behavioral traits or construction processes. Cylindrical casebearing caddis fly larvae need a smooth interior case wall, presumably to undulate their abdomen for respiration. We studied 5 species of caddis fly that build cases with sand grains. Experiments were conducted to force these species to reconstruct or repair their cases using 20 paired combinations from 11 types of artificial materials with different surface textures. Surface roughness was determined by confocal laser scanning microscopy. Among the 4 species that display voluntary undulation behavior for respiration, 2 species (Goera japonica and Apatania sp.) that make their case wall smooth by secreting silk showed only moderate preference for smooth particles. The other 2 species (Psilotreta kisoensis and Perissoneura paradoxa; Odontoceridae), which do not line their cases with silk, showed a strong preference for smoother particles. The results suggest that these 2 types of case bearers employ antithetical strategies that being a trade-off between costs for secreting silk and selecting smoother particles to make a smooth case wall. The fifth species (Glossosoma ussuricum), which does not display voluntary undulation behavior or interior silk lining, was nonselective for surface roughness of the case-building particles. It is indicated that these differences are related to both the conformation of cases and respiration behavior. Key words: caddis fly, confocal laser scanning microscopy, construction behavior, surface roughness, trade-off, Trichoptera. [Behav Ecol]

An Experiment Study of Erosion Characteristics of Sediment Bed at the Yellow River Delta

The modern Yellow River Delta is formed by fine-grained sediments through fast transportation and accumulation. Its coast is characterized by partially consolidated bed structure, high water content and weak erosion resistance. Despite recent advances in numerical morphodynamic modeling techniques, the current ability to predict long-term coastal changes at the Yellow River Delta is hampered by the lack of reliable data on the erosion resistance of the sediments deep in the bed. This paper describes a laboratory-based erosion study using a 30 m sediment core collected from the tidal flat on the northern coast of the Yellow River Delta in April 2004. The influence of various sediment properties such as bed stratification, grain composition, wet bulk density and water content on the measured erosion resistance has been analyzed in detail. The results reveal that there exist a definite negative relationship between the critical erosion shear stress and water content or median diameter, and also a clear positive relationship between the critical erosion shear stress and clay content. For the sediments of the same type, there was a positive relationship between the critical erosion shear stress and wet bulk density. It was also found that the erosion resistance changes considerably through depth with the lowest being near the surface and the highest at a depth of 9.1-13.5 m. The relationship between erosion rate and shear stress for erosion was shown to be dependent in a complex way on the grain distribution, sedimentation structure, wet bulk density and water content of the sediments. A number of distinct erosion behavior have been identified and although in most cases the erosion rate (ε) can be related linearly to the net bed shear stress (τ – τc), further study is needed to establish the erosion-stress relationship for the case were the erosion seems to show undulating behavior.

Imaging filopodia dynamics in the mouse blastocyst

During mammalian development, the first cell lineage diversification event occurs in the blastocyst, when the trophectoderm (TE) and the inner cell mass (ICM) become established. Part of the TE (polar) remains in contact with the ICM and differs from the mural TE (mTE) which is separated from the ICM by a cavity known as the blastocoele. The presence of filopodia connecting ICM cells with the distant mural TE cells through the blastocoelic fluid was investigated in this work. We describe two types of actin-based cell projections found in freshly dissected and in vitro cultured expanding blastocysts: abundant short filopodia projecting into the blastocoelic cavity that present a continuous undulating behavior; and long, thin traversing filopodia connecting the mural TE with the ICM. Videomicroscopy analyses revealed the presence of vesicle-like structures moving along traversing filopodia and dynamic cytoskeletal rearrangements. These observations, together with immunolocalization of the FGFR2 and the ErbB3 receptors to these cell extensions, suggest that they display signal transduction activity. We propose that traversing filopodia are employed by mitotic mTE cells to receive the required signals for cell division after they become distant to the ICM.

Rayleigh Wave Dispersion And Three‐Dimensional Velocity Structure in the Continent And Its Margin of Southeastern China

AbstractWith the matched‐filter of using frequency‐time analysis (FTAN) technology, we process the Rayleigh wave data recorded by China seismic stations, and then obtain the dispersion of Rayleigh wave of crossing southeastern China continent and margin belt. We obtain pure path dispersion data of 40 × 40 grid for the southeastern China continent and margin belt by using a stochastic method. Based on the gridding inversion, we obtain the three‐dimensional velocity structure for shear wave velocities by using the surface wave inversion program of Harkrider. The result indicates that: 1. The Moho depth of Southern China continent is 30–40 km and becomes thinner from west to east. At the margin and shallow sea region the Moho depth is 25–28 km and shows a clear zonal pattern. 2. The buried depth of low‐velocity layer in upper mantle lies between 60 to 150 km and exhibits strong lateral variation related to the distribution of deep faults and deep internal dynamic processes. The undulatory variation of the interface in the NS direction is flatter than that in theWE direction. 3. The margin of the southeastern continent is the sea‐continent transition belt of the East Asia continent. The depth of the Moho interface is shallow and the average velocity in the crust is low. The undulation behavior of the deep mantle interface indicates the heterogeneity of the structure and the coupling affect of deep and shallow medium.

Fluctuations and light scattering in thin smectic films.

An analysis of the layer-displacement fluctuations in thin smectic-A liquid-crystal films is presented. Explicit formulas for the displacement-displacement correlation function, taking into account the surface tension and the anchoring strength, are derived. It is shown that the boundary conditions essentially affect the fluctuations not only on the surface but in the interior of the film as well. The light scattering on the displacement-associated director fluctuations is considered. This consideration is carried out on the basis of the Green's function of the electromagnetic field for an optically anisotropic film. The calculations include multiple-reflection effects for incident and scattered light beams. It is shown that the scattered light intensity differs essentially from the intensity for the same volume in an infinite smectic medium. There is no forward scattering in the case of normal incidence and an undulation behavior of the intensity as a function of scattering angle takes place. There are maxima in the angular distribution. The magnitudes of the maxima are sensitive to the surface-tension coefficient. The possibility of measuring the surface-tension coefficient by means of an optical experiment is discussed.

Complex degree of spatial coherence in an optical fiber: theory and experiment

The modulus and the phase of the complex degree of spatial coherence at the exit face of a coherently excited optical fiber have been analyzed, taking into account interference between modes. The pointwise correlation between two axially symmetrical points across the fiber core exhibits an undulating behavior, varying with longitudinal coordinate as cos(βl − βk)z. It was found that the mean values for the modulus and the phase can be obtained by averaging over the undulating period. This theory has been confirmed by an experiment that measures the spatial coherence using a computer-aided wave-front-reversing interferometer.

Problems in bandwith measurement and a suggested solution

A recent series of bandwidth measurements by several Bell Labs and Western Electric locations on the same set of fibers (a bandwidth measurement round robin) has addressed and clarified some of the problems that cause disagreement between test sets. Three measurements out of twelve had a large standard deviation (based on the results of all participants), which raised the overall ratio of the standard deviation to the mean ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sigma/\mu</tex> ) to 12 percent. These three fibers had double-peaked outputs; the resulting transfer functions had either a plateau or an undulating behavior around the 3-dB level: changes in the launch conditions or source spectral width could shift the plateau or undulations from above the 3-dB level to below it, producing large changes in measured 3-dB bandwidth. Reducing measurement variations for such fibers will require closer control over the launch conditions and, for short wavelength measurements, the source spectral width. In addition, using the 3-dB bandwidth from a Gaussian fit to the transfer function instead of the transfer function itself greatly reduces measurement variations and in some cases provides a better prediction of the bandwidth of fiber concatenations.