Asymmetry Of Profiles Research Articles

Asymmetry of Line Profiles of Stellar Oscillations Measured by Kepler for Ensembles of Solar-like Oscillators: Impact on Mode Frequencies and Dependence on Effective Temperature

Abstract Oscillation properties are usually measured by fitting symmetric Lorentzian profiles to the power spectra of Sun-like stars. However, the line profiles of solar oscillations have been observed to be asymmetrical for the Sun. The physical origin of this line asymmetry is not fully understood; though, it should depend on the depth dependence of the source of wave excitation (convective turbulence) and details of the observable (velocity or intensity). For oscillations of the Sun, it has been shown that neglecting the asymmetry leads to systematic errors in the frequency determination. This could subsequently affect the results of seismic inferences of the solar internal structure. Using light curves from the Kepler spacecraft, we have measured mode asymmetries in 43 stars. We confirm that neglecting the asymmetry leads to systematic errors that can exceed the 1σ confidence intervals for seismic observations longer than one year. Therefore, the application of an asymmetric Lorentzian profile should be favored to improve the accuracy of the internal stellar structure and stellar fundamental parameters. We also show that the asymmetry changes sign between cool Sun-like stars and hotter stars. This provides the best constraints to date on the location of the excitation sources across the Hertzsprung–Russel diagram.

Parametric model fitting-based approach for retinal blood vessel caliber estimation in eye fundus images

BackgroundChanges in the retinal vessel caliber are associated with a variety of major diseases, namely diabetes, hypertension and atherosclerosis. The clinical assessment of these changes in fundus images is tiresome and prone to errors and thus automatic methods are desirable for objective and precise caliber measurement. However, the variability of blood vessel appearance, image quality and resolution make the development of these tools a non-trivial task.MetholodogyA method for the estimation of vessel caliber in eye fundus images via vessel cross-sectional intensity profile model fitting is herein proposed. First, the vessel centerlines are determined and individual segments are extracted and smoothed by spline approximation. Then, the corresponding cross-sectional intensity profiles are determined, post-processed and ultimately fitted by newly proposed parametric models. These models are based on Difference-of-Gaussians (DoG) curves modified through a multiplying line with varying inclination. With this, the proposed models can describe profile asymmetry, allowing a good adjustment to the most difficult profiles, namely those showing central light reflex. Finally, the parameters of the best-fit model are used to determine the vessel width using ensembles of bagged regression trees with random feature selection.Results and conclusionsThe performance of our approach is evaluated on the REVIEW public dataset by comparing the vessel cross-sectional profile fitting of the proposed modified DoG models with 7 and 8 parameters against a Hermite model with 6 parameters. Results on different goodness of fitness metrics indicate that our models are constantly better at fitting the vessel profiles. Furthermore, our width measurement algorithm achieves a precision close to the observers, outperforming state-of-the art methods, and retrieving the highest precision when evaluated using cross-validation. This high performance supports the robustness of the algorithm and validates its use in retinal vessel width measurement and possible integration in a system for retinal vasculature assessment.

Analysis of Poloidal Asymmetric Density Behaviors in SOL Induced by 4.6-GHz Lower Hybrid Launcher Power in EAST

On the experimental advanced superconducting tokamak (EAST), a series of striations, including a few strong emissivity striations and several low emissivity striations, were observed in front of the 4.6-GHz lower hybrid (LH) launcher with the visible video camera for the LH power discharge. These striations indicate that LH may create significant poloidal scrape-off layer (SOL) density profile asymmetries in front of the LH launcher. These poloidal asymmetric density behaviors are further confirmed with the edge density measured by two Langmuir probes installed at the top and bottom of the LH launcher. The measured density depends on LH power injection and magnetic field direction. A 2D diffusive convective model was used to study the mechanisms of the observed striations and poloidal asymmetric density. The simulation results qualitatively match with the measured density, indicating these poloidal asymmetric effects are ascribed to the LHW-induced ELH × B t drift.

Uma leitura de género sobre mobilidades e acessibilidades em meio rural

Nowadays there are still strong asymmetries in the relationship with territory (Carmo, 2014), and in Portugal the inner country has been for several decades the scene of depopulation and loss of services phenomena (Fermisson, 2000). At the same time, the relationship between gender and mobility has specific characteristics since women have different needs and uses of mobility and transportation and face specific obstacles (Hanson, 2013; Sales Oliveira, 2014). This article discusses both these questions and tries to address the issue of rural mobility and accessibility from a gender perspective in the Portuguese context. In order to develop an exploratory approach the methodological option was a case study, using the techniques of survey and mobility mapping, of a village in Beira Interior. We found a social composition with greater diversity than expected but still with a strong presence of elderly people and low qualifications. Ownership of a driving license and a private vehicle is an unequal resource and a central element for the asymmetry of mobility patterns and profiles. However, contrary to what could be expected, we cannot say that women experience less mobility than men, since although they are the ones who do not have a driving license or a private vehicle, they are also the ones who most often use other mobility resources in which their social networks represent an important factor.

A new method of measuring centre-of-mass velocities of radially pulsating stars from high-resolution spectroscopy

We present a radial velocity analysis of 20 solar neighborhood RR Lyrae and 3 Population II Cepheids variables. We obtained high-resolution, moderate-to-high signal-to-noise ratio spectra for most stars and obtained spectra were covering different pulsation phases for each star. To estimate the gamma (center-of-mass) velocities of the program stars, we use two independent methods. The first, `classic' method is based on RR Lyrae radial velocity curve templates. The second method is based on the analysis of absorption line profile asymmetry to determine both the pulsational and the gamma velocities. This second method is based on the Least Squares Deconvolution (LSD) technique applied to analyze the line asymmetry that occurs in the spectra. We obtain measurements of the pulsation component of the radial velocity with an accuracy of $\pm$ 3.5 km s$^{-1}$. The gamma velocity was determined with an accuracy $\pm$ 10 km s$^{-1}$, even for those stars having a small number of spectra. The main advantage of this method is the possibility to get the estimation of gamma velocity even from one spectroscopic observation with uncertain pulsation phase. A detailed investigation of the LSD profile asymmetry shows that the projection factor $p$ varies as a function of the pulsation phase -- this is a key parameter which converts observed spectral line radial velocity variations into photospheric pulsation velocities. As a byproduct of our study, we present 41 densely-spaced synthetic grids of LSD profile bisectors that are based on atmospheric models of RR Lyr covering all pulsation phases.

Poloidal asymmetries in the edge density profiles on ASDEX Upgrade

The evolution of the midplane edge electron density profiles and its link to divertor detachment is studied on ASDEX Upgrade, taking advantage of the high resolution high-field-side (HFS) / low-field-side (LFS) O-mode reflectometry measurements. Ohmic and L-mode discharges were studied where detachment was achieved through density ramps. We have shown that the region of high density on the HFS (HFSHD) expands to the midplane, leading to strong poloidal asymmetries in the main chamber SOL density, which are quantified by defining an asymmetry parameter based on reflectometry data. The evolution of the midplane edge density profile in the HFS was observed to respond to divertor oscillations, changing significantly for different divertor detachment states. The HFS/LFS density asymmetry was found to increase with input power and to decrease with seeding.

Formulation and optimization of involute spur gear in external gear pump

External gear pumps (EGPs) have gained popularity among applications in many fields like fluid power transmissions and systems, automotive, aerospace thanks to their advantage of simplicity, robustness and low cost. Several studies were performed to analyze and innovate the gear profiles of EGPs to achieve better performance, in terms of flow smoothness power to weight ratio. Asymmetric gears represent one of the possible choices. This paper is aimed at developing a methodology of designing asymmetric involute gear, and formulate analytical expression for the instantaneous flowrate and flow non-uniformity given by asymmetric, non-standard involute gear pumps. These analytical expressions are then used within a multi-objective numerical optimization algorithm aimed at minimizing both the flow non-uniformity and the pump size to achieve a specific displacement. The results illustrate the highly constrained nature of the optimization problem, and the relevant impact of certain parameters of the tooth profile. It is shown how gears obtained with the proposed procedure can have significantly higher performance of standard gears, and in particular how the parameters affecting tooth profile asymmetry can further improve the EGP flow irregularity and size.

Multi-scaled heterogeneous deformation behavior of pearlite steel studied by in situ neutron diffraction

Heterogeneous deformation of Fe-0.8mass%C pearlite steel was studied using in situ high-resolution neutron diffraction during tensile deformation, characterized by the superposition of multi-scaled stress partitioning behaviors between the ferrite and cementite phases (phase stress), 〈hkl〉-oriented grain families with respect to the tensile direction (intergranular stress), and colonies with different lamellar alignments (colony stress). The colony stress was evaluated by analyzing profile asymmetry. The influence of lamellar spacing on such stress partitioning was clarified, and large peak broadening of cementite was also determined in a deformed specimen.

Radial correlation length across magnetic islands: Simulations and experiments

The turbulence radial correlation length Lr of density fluctuations is studied across magnetic islands both numerically and experimentally. The numerical study has been carried out by a resistive MHD code (called FAR). It shows asymmetric Lr profiles when measured across magnetic islands. Subsequent simulations using a synthetic Doppler reflectometer suggest that this diagnostic has the capability to capture the effect observed in the results provided by FAR. Finally, experimental studies performed using the Doppler reflectometer installed at the TJ-II stellarator show asymmetries in the coherence profiles matching the radial position of magnetic islands. The similarities found between simulations and experiments indicate that radial correlation length measurements could be used to detect magnetic islands in fusion plasmas.

Wave transformation and hydrodynamic characteristics of wave-breaking models coupled with Boussinesq equations

ABSTRACTThis paper investigates the different wave transformation and hydrodynamic characteristics of three different wave-breaking models – friction-type, eddy viscosity-type and surface roller-type models – coupled with the weakly nonlinear Boussinesq equations with improved linear dispersion characteristics based on comparisons between predicted and measured wave-breaking phenomena. The experimental cases consider not only different breaker types but also different bathymetry conditions, i.e. uniform slopes and a uniform slope with a submerged breakwater. Although all of the properly calibrated wave-breaking models yield equally good predictions of wave heights, mean water levels and trough levels of breaking and broken waves, the models show clear differences in their predictions of the undertow velocity, near-bottom wave orbital velocity profile, wave skewness, and wave asymmetry. The importance of such differences in the predictive capabilities of these widely used wave-breaking models should be highlighted, particularly when extending the model to the prediction of coastal morphodynamics around the surf zone.

Tunability of Multipolar Plasmon Resonances and Fano Resonances in Bimetallic Nanoshells

We study the multipolar surface plasmon modes and its link to Fano resonances in bimetallic nanoparticles. General expressions for the multipolar surface plasmon frequencies and damping rates are analytically derived by long-wave approximation. The results are in agreement with that from plasmon hybridization model for nanoshell system. Numerical results show that the surface plasmon resonances and damping rates for Au/Ag and Ag/Au nanoshells exhibit quite different behavior with the increase of shell thickness. In addition, both the near-field diagram and the far-field quantity are theoretically investigated. Fano resonances of scattering efficiency by Ag/Au core-shell nanoparticles occur due to the dipole-dipole coupling. The asymmetry of Fano profiles can be tuned by adjusting the size ratio of the core and the shell. Our results may found some potential applications in optical devices and biomedicine.

Severe open bite with mandibular asymmetry treated using micro-implant anchorage

Abstract Background This case report describes the orthodontic treatment of a 20 year-old female who presented with a severe anterior open bite, increased lower facial height and mandibular asymmetry. The patient was diagnosed with a Class I skeletal pattern but a Class III dental relationship, an anterior and unilateral posterior open bite, a canted posterior occlusal plane, a clockwise rotation and vertical growth pattern of the mandible incorporating a chin deviation to the right. Aim The aim of treatment was to correct identified adverse oral habits, improve the facial profile and mandibular asymmetry, provide a satisfactory occlusion and restore TMJ health, which could not be guaranteed. Methods An occlusal splint was used in the first stage of treatment to intrude the posterior teeth, eliminate the occlusal disturbance and control the adverse oral habits. Two micro-implant anchorage devices were placed on the buccal and lingual sides of the left buccal segment to further intrude the left posterior teeth. MEAW technology was used after aligning and levelling the teeth. Results Satisfactory overbite, overjet and molar relationships were obtained and the facial profile greatly improved after orthodontic treatment, the outcome of which was stable at 24 months’ review.

Fe/FeO/Fe/FeV Multilayers Characterized by Magnetometry and Polarized Neutron Reflectometry

We use argon ion-bombardment during Fe layer deposition as a way to tailor the structural and magnetic properties of bilayer and multilayer systems containing Fe/FeV components. We present structural and magnetic results on Fe/FeV bilayer and Fe/Fe-oxide/Fe/FeV multilayer systems. Magnetization measurements were taken over a range of temperatures and show the expected ferromagnetic behavior for the Fe/FeV bilayer. The Fe/Fe-oxide/Fe/FeV multilayer demonstrates an enhanced coercivity and exchange bias at low temperatures, both due to the presence of the antiferromagnetic Fe-oxide layer. Polarized neutron reflectometry results (scattering length density depth profile and neutron spin asymmetry) were used to identify mixed interfacial layers resulting from ion-bombardment. These demonstrated a lower magnetic moment than bulk Fe layers and may undergo a reversal process that differs from non-mixed layers within the sample.

Stability of thermoviscous fluid flow under high temperature gradients

In present study the influence of temperature-dependent viscosity, i.e. thermoviscosity on the pressure-driven flow in inhomogeneous temperature field has been recalled. Such viscous stratification impacts on the velocity profile asymmetry, significantly increases the entry length, and causes the velocity inflection point to appear. In certain cases, particularly under high temperature differences of channel walls, the thermoviscosity generates instability that in a view of high local Reynolds numbers can create turbulent zones.

Role of the Input Profile Asymmetry and the Chirp on the Propagation in Highly Dispersive and Nonlinear Fibers

We report the role played by the pulse shape asymmetry and the initial chirp on the propagation in highly dispersive single mode fibers and on the drastic spectral broadening well known as the supercontinuum generation (SCG) in highly nonlinear waveguides. We deal with finite energy Airy pulse (FEAP) for the asymmetric pulse and with the sech-type pulse for a compared study. We find that chirping an Airy pulse allows us to obtain asymmetric spectral outputs and the time domain inversion mechanism in optical systems. For the SCG analysis, the weakly truncated chirped FEAPs are more suitable than the common symmetric profiles to generate coherent and ultrabroadband spectra.

Femtosecond laser inscription waveguides in Nd:GdVO4crystal

Channel waveguides in Nd:GdVO4 crystals were fabricated by using low-repetition-rate (1 kHz) femtosecond laser inscription. The influences of pulse energy and scanning velocity were investigated. Guiding occurs in the surroundings of the focal spot. Single-line, double-line, and double-layer waveguides were realized. The near-field mode images, refractive-index profile reconstruction, and mode analysis of waveguides are presented. The double-line waveguides show strong guidance at 632.8 nm with a loss of about 0.5 dB/mm and an index increase of 3×10−4. The mode profile asymmetry of single-line waveguide has been improved by using multipass scanning.

Pockmark asymmetry and seafloor currents in the Santos Basin offshore Brazil

Pockmarks form by gas/fluid expulsion into the ocean and are preserved under conditions of negligible sedimentation. Ideally, they are circular at the seafloor and symmetrical in profile. Elliptical pockmarks are more enigmatic. They are associated with seafloor currents while asymmetry is connected to sedimentation patterns. This study examines these associations through morphological analysis of new multibeam data collected across the Santos continental slope offshore Brazil in 2011 (353–865 mbsl). Of 984 pockmarks, 78% are both elliptical and asymmetric. Geometric criteria divide the pockmarks into three depth ranges that correlate with a transition between two currents: the Brazil Current transfers Tropical Water and South Atlantic Central Water southwestwards while the Intermediate Western Boundary Current transfers Antarctic Intermediate Water northeastwards. It is suggested that the velocity of seafloor currents and their persistence dictate pockmark ellipticity, orientation and profile asymmetry. Fast currents (>20 cm/s) are capable of maintaining pockmark flank steepness close to the angle of repose. These morphological expressions present direct evidence for an edge effect of the South Atlantic Subtropical Gyre and, in general, provide a correlation between pockmark geometry and seafloor currents that can be applied at other locations worldwide.

Comparison of Conventional Sprocket Drum and Sprocket Drum with Modified Design

Abstract Seats in conventional sprocket drums are symmetrical. Due to the set general direction of sprocket drum revolutions resulting from the direction of rock transport, the wear of the seat bottoms and teeth flanks may be reduced by introducing the asymmetry of the profile of the sprocket drum seats. The proposed modification of sprocket drum seats’ profile consists of inclining the seat bottom towards the expected direction of the basic drum revolutions. The work compares the loads on the seats and teeth of a conventional drum with its profile conforming to the standard to a modified drum with an asymmetric profile of seats. For the general direction of sprocket drum revolutions, the maximum values of all forces are higher for a standard drum than for a modified drum. The profile asymmetry substantially shortens the friction path of the horizontal link front torus on the seat bottom and relative total friction work on the seat bottom and lessens the occurrence probability of the slide of the horizontal link rear torus on the tooth flank. The modification of the profile causes also the asymmetric wear of link joints. The total relative friction work is considerably reduced in the front joint as compared to a conventional drum, and the total relative friction work in the rear joint is increasing at the same time.

Computational Analysis of Swirling Pipe Flow

Swirling pipe flow was investigated using advanced scale-adaptive turbulence model (?? - ?? SST SAS). The analysis of turbulent swirling fluid motion in pipe focuses mainly on the model prediction capabilities. Forvalidation purposes were used experimental data from (Pashtrapanska et al., 2006). Global instability was produces by a contraction ring placed downstream of swirl generator. Predicted data were sampled at several distances from the swirl generator to compare them with experiment. Repeated simulations were performed on several computational grids involving unstructured and structured meshes. Grid tests revealed strong influence of computational grid on fluid flow behaviour predicted by the model. Most distinguishing feature of the predictions is asymmetry of mean velocity profiles, which is contrary to results obtained from experiment.

Dawn–dusk asymmetry and adiabatic dynamic of the radiation belt electrons during magnetic storm

The changes of the latitudinal profiles of outer belt energetic electrons during magnetic storms are mostly explained by the precipitation into the loss cone caused by VLF and EMIC waves or by the scattering into the magnetopause. In present work, energetic electron dynamics during magnetic storm of August 29–30, 2004 we attributed at most to the adiabatic transformation of the magnetic drift trajectories and Dst effect. This conclusion was based on the analysis of dawn–dusk asymmetry of the electron latitudinal profiles measured by low altitude polar orbiter SERVIS-1 and on the coincidence of pre-storm and after-storm profiles of radiation belt electrons and protons.