Elliptical Profile Research Articles

Measurements for static shape control optimization of silicon mirror using nonlinear piezoceramic actuators

In this paper, experimental study for shape control of silicon mirror is done by nonlinear piezoceramic actuator. A piezoelectric unimorph-based silicon mirror (PUSiM) is fabricated using APC 850 piezoceramic for shape control analysis. The piezo response function of all the actuators and profile of PUSiM are measured by confocal sensor at various applied electric fields to verify the nonlinearity of piezoceramic actuator. For comparison, electromechanical coupled finite element model of PUSiM is developed. Recently proposed iterative piezo response function-based optimization is used to calculate the electric field of piezoceramic actuators to achieve the target elliptical profile of PUSiM. At optimum voltage the achieved profile of PUSiM is quite close to the target elliptical profile with 193 nm root-mean-square error. Knowing the nonlinearity inherent in the piezoceramic actuators at high voltages the proposed measurement technique is a way forward for the shape control of structures and deformable mirrors.

An elliptic velocity profile-based two-equation model in viscous film

An elliptic velocity profile-based depth-averaged two-equation model is derived for a viscous falling film in terms of the film thickness h(x, t) and the flow rate q(x, t), which is consistent up to first order in inertia terms and consistent up to second order in viscous diffusion terms. It is observed that the proposed depth-averaged two-equation model recovers the available analytical, numerical, and experimental findings of the literature very well as the free parameter involving eccentricity of the ellipse increases. In fact, the present depth-averaged two-equation model converges to the existing parabolic velocity profile-based depth-averaged two-equation model as the eccentricity approaches one because the elliptic velocity profile becomes a parabolic velocity profile. Furthermore, we see that [20, 100] is the suitable range of the free parameter for capturing the existing findings of the literature. In addition, the full second-order depth-averaged model, which is consistent up to second-order in inertia and viscous terms, is also developed in Appendix A.

Statistical inference for strong gravitational lensing observations in the presence of dark matter

AbstractWe study the properties of strong lenses generated by dark matter galaxy halos in the Universe and the statistical inference process to understand the density profile of the lens. For that, we used mock data of strong gravitational lenses using the publicly available software paltas, which is a pipeline based on the well‐known package lenstronomy and written in Python. The deflectors are modeled according to the so‐called elliptical power law lens profile, and the background cosmology is assumed to be that of the standard cosmological model ΛCDM. The generated lensing observations include the contribution of dark matter substructure in the form of either subhalos or halos along the line of sight. In both cases, the underlying profile is the Navarro‐Frenk‐White one, which corresponds to the cold dark matter model. Performing a statistical inference process on these mock observations, our final objective is to identify the influence of the substructure on the inferred parameters that describe the lens profile.

Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study

BackgroundRestoring or improving seated stability after spinal cord injury (SCI) can improve the ability to perform activities of daily living by providing a dynamic, yet stable, base for upper extremity motion. Seated stability can be obtained with activation of the otherwise paralyzed trunk and hip musculature with neural stimulation, which has been shown to extend upper limb reach and improve seated posture.MethodsWe implemented a proportional, integral, derivative (PID) controller to maintain upright seated posture by simultaneously modulating both forward flexion and lateral bending with functional neuromuscular stimulation. The controller was tested with a functional reaching task meant to require trunk movements and impart internal perturbations through rapid changes in inertia due to acquiring, moving, and replacing objects with one upper extremity. Five subjects with SCI at various injury levels who had received implanted stimulators targeting their trunk and hip muscles participated in the study. Each subject was asked to move a weighted jar radially from a center home station to one of three target stations. The task was performed with the controller active, inactive, or with a constant low level of neural stimulation. Trunk pitch (flexion) and roll (lateral bending) angles were measured with motion capture and plotted against each other to generate elliptical movement profiles for each task and condition. Postural sway was quantified by calculating the ellipse area. Additionally, the mean effective reach (distance between the shoulder and wrist) and the time required to return to an upright posture was determined during reaching movements.ResultsPostural sway was reduced by the controller in two of the subjects, and mean effective reach was increased in three subjects and decreased for one. Analysis of the major direction of motion showed return to upright movements were quickened by 0.17 to 0.32 s. A 15 to 25% improvement over low/no stimulation was observed for four subjects.ConclusionThese results suggest that feedback control of neural stimulation is a viable way to maintain upright seated posture by facilitating trunk movements necessary to complete reaching tasks in individuals with SCI. Replication of these findings on a larger number of subjects would be necessary for generalization to the various segments of the SCI population.

Laser intensity mapping across a spatial light modulator to generate uniform and aberration-free focal spots

We present a novel and direct technique to map the incident laser intensity across the active area of a spatial light modulator (SLM) by using diffraction based setup in a holographic optical tweezers (HOTs) system to generate structured light. The incident laser beam profile on the SLM is used as input to the optical trap generating algorithms such as weighted Gerchberg Saxton algorithm, generalized adaptive additive algorithm etc. The input laser beam profile is generally assumed to be located at the center of SLM in these algorithms. However, it is not straight-forward to ensure that the center of the Gaussian laser beam coincides with the center of SLM. The importance of mapping the laser intensity across the SLM is demonstrated by a study of the effect of mismatch between the input laser beam center and the actual beam center on the trap properties such as uniformity of intensity, and sharpness of the focal spots. We also propose a method of centering the laser beam profile on the SLM which enables the use of known beam profile. This method allows the use of HOTs with any spatial transverse distribution of a laser beam, such as elliptical profile of diode lasers, Laguerre Gaussian beams or with any distorted beam shape deviating from Gaussian profile.

Joint lensing–dynamics constraint on the elliptical galaxy mass profile from the largest galaxy–galaxy lens sample

AbstractFrom various lensing and non-lensing observations, the total density profile in elliptical galaxies is well approximated by a power law mass distribution. However, as neither the dark matter nor the baryons individually follow the power law, this observational result has been referred to as the “bulge–halo conspiracy”. We investigate the consistency of this conspiracy with higher precision than previous studies with the largest ever sample of galaxy–galaxy lenses assembled from archival Hubble Space Telescope (HST) data. By performing lens modelling with power law profiles and combining them with stellar dynamics using the mass-sheet transformation, we can constrain the profile’s deviation from the power law model over a redshift range of 0.1 to 0.8. To uniformly model such a large sample of lens models, we use the automated modelling pipeline dolphin. We also investigate the evolutionary trend of the total mass density slope of the lensing galaxies.

A Fizeau interferometry stitching system to characterize X-ray mirrors with sub-nanometre errors

We present the development of a Fizeau interferometer stitching system to characterize the surface profile of state-of-the-art X-ray optics for synchrotron and free electron laser sources. Controls and acquisition software precisely translate and rotate the surface under test in synchrony with data capture by a Zygo Verifire HDX interferometer. Overlapping sub-aperture images are combined into a composite, high-spatial resolution topographical image of the entire optical surface using PyLOSt stitching software produced by the MooNpics collaboration. After minimization of random and systematic measurement errors, system performance was quantified by characterizing two challenging optics. These optics represent extreme cases for synchrotron X-ray mirrors: an aspheric elliptical profile with a slope error of ∼50 nrad rms, and a corresponding height error of 0.2 nm rms; and a chirped periodic structure superimposed upon a strong curvature (radius ∼ 9.33 m). Results are in very good agreement with the Diamond-NOM slope profilometer and Bruker GTX stitching micro-interferometer. Without a specialist transmission reference, both optics could not be measured by the interferometer without pitch and translation stitching. Any individual HDX scan, relative to the average of the ensemble, has an average slope error repeatability of < 15 nrad rms. After calibration of the transmission reference flat and zoom factor, a reproducibility of ∼ 27 nrad rms compared to the Diamond-NOM, was achieved for the elliptically curved mirror.

Lines-based rotating beam profiling algorithm using pixel ionization chamber with dead pixels

In a pencil beam scanning proton therapy system, critical beam parameters, including the spot size, spot center position, and tilt angle, are monitored for security by beam profile detectors such as two-dimensional (2D) pixel-segmented ionization chambers. A method, named lines-based beam profiling (LBBP), is proposed to identify the five geometric parameters μx,μy,σx,σy,θ of rotating elliptical beam profiles using several lines (rows and columns) in the 2D detector data. The method provides solid results even in the presence of dead pixels, which can be located using a wavelet analysis. Simulation experiments were used to define the number of lines used by the LBBP method and to characterize its performance as a function of the signal-to-noise (SNR). For SNR greater than 30, the root mean square errors (RMSEs) of the beam spot size, spot center position, and rotation angle obtained with the LBBP method are less than 0.16 mm, 0.05 mm, and 0.78 degrees, respectively. The LBBP method was applied to the data collected by a pixel chamber illuminated by an X-ray source, demonstrating the capability of identifying dead pixels and providing more accurate measurements of the beam spot size and center position than the standard Gaussian fitting.

Morphology Driven Evolution of Barred Galaxies in OMEGAWINGS Clusters

We present a study of barred galaxies in the cluster environment, exploiting a sample of galaxies drawn from the extended WIde-field Nearby Galaxy-cluster Survey (OmegaWINGS) that covers up to the outer regions of 32 local X-ray selected clusters. Barred galaxies are identified through a semiautomatic analysis of ellipticity and position angle profiles. We find, in agreement with previous studies, a strong codependence of the bar fraction with the galaxy stellar mass and morphological type, being maximum for massive late-type galaxies. The fraction of barred galaxies decreases with increasing cluster mass and with decreasing clustercentric distance, a dependence that vanishes once we control for morphological type, which indicates that the likelihood of a galaxy hosting a bar in the cluster environment is determined by its morphological transformation. At large clustercentric distances, we detect a dependence on the distance to the nearest neighbor galaxy, suggesting that tidal forces with close companions are able to suppress the formation of bars or even destroy them. Barred galaxies in our sample are either early-type, star-forming galaxies located within the virial radii of the clusters or late-type quenched galaxies found beyond the virial radii of the clusters. We propose a scenario in which already quenched barred galaxies that fall into the clusters are centrally rejuvenated by the interplay of the perturbed gas by ram pressure and the bar, in galaxies that are undergoing a morphological transformation.

Numerical investigation of erosion characteristics of coupling separators with different conical profiles

Solid particles exist widely in liquid–liquid systems. Although a separator coupled centrifugal and electric fields can achieve liquid–liquid separation efficiently, the solid particles are usually not considered, and the erosion characteristics are unclear. Thus, in this study, a numerical model was established to investigate the erosion characteristics of coupling devices. Two conical profiles, namely bi-cone and elliptical, were examined. The effect of structural parameters on erosion was investigated, and the relationships between the erosion rate and the inlet velocity, initial drop size and solid loading were explored. The results showed that maximum erosion occurred in the interaction regions of the two cones for the bi-cone, and that the cone with an elliptical profile had a lower erosion rate. The maximum erosion rate depended on the centrifugal force acting on the solid particles and the inertial effect of particles in the mixture. Furthermore, the precessing vortex core was the dominant factor influencing the position, including maximum erosion rate, which depended on the centrifugal force and the vortex core radial deviation. Moreover, the potential reason for the effect of geometric parameters on wall erosion is different. From the perspective of erosion resistance, the optimal values of straight and underflow pipe section diameters and conical structure length for the device with an elliptical profile cone were 35, 400, and 430 mm. Additionally, increasing inlet velocity, initial drop size and solid loading can increase average erosion rate on the walls, and strengthen of breakage effect can indirectly reflect that the increase in erosion rate.

Eliptik Dişli Tasarımı, İmalatı, Analizi ve Eliptik Dişlilerin Endüstriyel Uygulamaları

Eliptik dişliler üzerine yapılan çalışmaların diş profillerinin tasarımı üzerine yoğunlaştığı ve prototip imalatlarına yönelik araştırmaların arttığı görülmektedir. Eliptik dişlilerin diş profillerinin silindirik dişliler gibi özdeş olmayacağından hareketle geliştirilen eliptik dişlinin diş profili; kramayer veya silindirik düz dişli formlu kesicinin bölüm elipsi üzerinde yuvarlanma yöntemine uygun olarak evolvent eğriye sahip diş yanaklarının şekillendirilmesiyle elde edilmektedir. Eliptik dişlilerin imalatında CNC tel erozyon tezgahlarından faydalanmanın yaygınlaştığı, bununla birlikte azdırma tezgâhları için elektronik dişli kutuları geliştirilerek eliptik dişlilerin standart modülde imalatının da mümkün olduğu tespit edilmiştir. Eliptik dişli çiftleri farklı makine ve teçhizatta kullanılmakta, özellikle eliptik dişli çiftine sahip debimetre ve pompaların yaygınlaştığı görülmektedir. Enerji verimliliğinin son derece önem kazandığı günümüzde, yüksek akışkan miktarlarının doğru ve hassas ölçülmesi ve işletmelerin akışkan transferindeki kayıplarının giderilmesi de gerekmektedir. Bu genel değerlendirme çalışmasında eliptik dişlilerin tasarımı, geleneksel ve geleneksel olmayan imal usulleri ile imalatı, dayanım ve titreşim analizleri ve literatürde yer alan muhtelif endüstriyel uygulamaları gözen geçirilmiş ve çalışmanın ortak bulguları elde edilmiştir. Eliptik dişlilerin yakın gelecekte bünyesinde mekanik kısım barındıran birçok akıllı ürünün vazgeçilmez bir organı olacağı öngörülmektedir.

Strong lensing in UNIONS: Toward a pipeline from discovery to modeling

We present a search for galaxy-scale strong gravitational lenses in the initial 2500 square degrees of the Canada-France Imaging Survey (CFIS). We designed a convolutional neural network (CNN) committee that we applied to a selection of 2 344 002 exquisite-seeingr-band images of color-selected luminous red galaxies. Our classification uses a realistic training set where the lensing galaxies and the lensed sources are both taken from real data, namely the CFISr-band images themselves and theHubbleSpace Telescope (HST). A total of 9460 candidates obtain a score above 0.5 with the CNN committee. After a visual inspection of the candidates, we find a total of 133 lens candidates, of which 104 are completely new. The set of false positives mainly contains ring, spiral, and merger galaxies, and to a lesser extent galaxies with nearby companions. We classify 32 of the lens candidates as secure lenses and 101 as maybe lenses. For the 32 highest quality lenses, we also fit a singular isothermal ellipsoid mass profile with external shear along with an elliptical Sersic profile for the lens and source light. This automated modeling step provides distributions of properties for both sources and lenses that have Einstein radii in the range 0.5″ &lt; θE &lt; 2.5″. Finally, we introduce a new lens and/or source single-band deblending algorithm based on auto-encoder representation of our candidates. This is the first time an end-to-end lens-finding and modeling pipeline is assembled together, in view of future lens searches in a single band, as will be possible withEuclid.

A lensed radio jet at milliarcsecond resolution I: Bayesian comparison of parametric lens models

ABSTRACT We investigate the mass structure of a strong gravitational lens galaxy at z = 0.350, taking advantage of the milliarcsecond (mas) angular resolution of very long baseline interferometric (VLBI) observations. In the first analysis of its kind at this resolution, we jointly infer the lens model parameters and pixellated radio source surface brightness. We consider several lens models of increasing complexity, starting from an elliptical power-law density profile. We extend this model to include angular multipole structures, a separate stellar mass component, additional nearby field galaxies, and/or a generic external potential. We compare these models using their relative Bayesian log-evidence (Bayes factor). We find strong evidence for angular structure in the lens; our best model is comprised of a power-law profile plus multipole perturbations and external potential, with a Bayes factor of +14984 relative to the elliptical power-law model. It is noteworthy that the elliptical power-law mass distribution is a remarkably good fit on its own, with additional model complexity correcting the deflection angles only at the ∼5 mas level. We also consider the effects of added complexity in the lens model on time-delay cosmography and flux-ratio analyses. We find that an overly simplistic power-law ellipsoid lens model can bias the measurement of H0 by ∼3 per cent and mimic flux ratio anomalies of ∼8 per cent. Our results demonstrate the power of high-resolution VLBI observations to provide strong constraints on the inner density profiles of lens galaxies.

Four-dimensional emittance measurement at the Spallation Neutron Source

A coasting hadron beam with an elliptical transverse profile, uniform charge density, and small transverse four-dimensional (4D) emittance could improve accelerator performance in several contexts. A phase space painting method to generate such a distribution is being tested in the Spallation Neutron Source (SNS) accumulator ring. A critical component of these efforts is to measure the 4D emittance of the beam during accumulation. The 4D emittance can be reconstructed from measured beam profiles in two ways: in the multi-optics method, the optics between a reconstruction and measurement location are varied; in the fixed-optics method, multiple measurement locations are used without modifying the optics. The fixed-optics method is faster but can lead to large uncertainty in the reconstructed 4D emittance. In this paper, we implement a variant of the multi-optics method using the four available wire-scanners near the SNS target. We also modify the wire-scanner region to reduce the uncertainty of the fixed-optics method. We then demonstrate the usefulness of the fixed-optics method by reconstructing the 4D emittance evolution during accumulation in the SNS ring.

Efficiency improvement of Roots vacuum pump working process

SummaryIn this paper influence of rotor profile type of Roots vacuum pumps on backward leakage through channels of rotor mechanism and pumping speed is considered.Elliptical, involute, and circular profiles are widely used. Backward leakage through channels of rotor mechanism with different rotor profiles is determined from conductance which was calculated by angular coefficients method for free molecular flow regime at different rotors rotating angles. It is shown that backward leakage is maximal at rotors rotating angles 25–45° due to maximal inter‐rotor channel opening for gas flow and is minimal at 0°. Elliptical rotor profile provides minimal backward leakage over one revolution.Numerical modeling of Roots pump working process was carried out on the basis of CFD ANSYS‐CFX complex by dynamic meshing method. SST turbulence model was used for calculations. It is confirmed that maximal pumping speed is provided by Roots pump with elliptical rotor profile.

Quantitative mapping of depth profile of fatigue cracks using eddy current pulsed thermography assisted by PCA and 2D wavelet transformation

Fatigue cracks are widely generated in numerous engineering components under alternating loads, whose sudden brittle fracture would seriously shorten the service life and cause significant hazards. A large number of nondestructive testing (NDT) techniques have been utilized to quantitatively evaluate the fatigue cracks, however, most of these methods are difficult to be used for a full characterization of the cracks’ depth profile. The eddy current pulsed thermography (ECPT) as a promising NDT technique shows great potential for fatigue crack evaluation due to its high detection efficiency, large inspection area, and high spatial resolution. In this article, a ferrite yoke was utilized to generate a homogeneous eddy current field, and as such to enhance the detection sensitivity and to provide a wide open-view area for the camera. The hybrid processing strategy combining principal component analysis (PCA) and 2D wavelet transformation was proposed to extract spatial features of the thermographic image sequences. Firstly, numerical results demonstrate that the profiles of slot cracks can be identified directly from the thermographic images in the early heating stage. Afterward, the ECPT experiments on slot cracks with different depth profiles demonstrate the feasibility of the hybrid processing strategy. Then, three fatigue cracks were manufactured through the three-point bending method and detected by ECPT. The results of the hybrid processing method indicate that these three fatigue cracks have elliptical profiles. Finally, the authentic depth profile of a fatigue crack with an elliptical shape is extracted through a destructive experiment. The comparison results between the real depth profile and the profile characterized through the proposed strategy show great consistency and validate the superiority of the proposed strategy.

Calibration Method for Line-Structured Light Three-Dimensional Measurement Based on a Simple Target

Line-structured light three-dimensional (3D) measurement is apt for measuring the 3D profile of objects in complex industrial environments. The light-plane calibration, which is a crucial link, greatly affects the accuracy of measurement results. This paper proposes a novel calibration method for line-structured light 3D measurement based on a simple target, i.e., a single cylindrical target (SCT). First, the line-structured light intersects with the target to generate a light stripe. Meanwhile, the camera captures the calibration images, extracts the refined subpixel center points of the light stripe (RSCP) and detects the elliptic profiles of the two ends of the cylindrical target (EPCT). Second, two elliptical cones defined by the EPCT and the camera optical center are determined. Combining the two defined elliptical cones and the known radius of the SCT, we can uniquely solve the axis equation of the SCT. Finally, because the coordinates of RSCP in the camera coordinate system fulfill both the camera model and the cylindrical equation, these coordinates can be solved and used to obtain the optimal solution of the light-plane equation. The results of simulations and experiments verify that our proposed method has higher accuracy and effectiveness.

Modified Savonius Wind Turbine for Wind Energy Harvesting in Urban Environments

Abstract The flow-induced rotation of the modified Savonius rotor, for which the blade consists of a semicircular profile and an elliptical shape, is studied using a series of unsteady computational fluid dynamics (CFD) simulations. This study first concentrates on the validation of the numerical scheme against Blackwell's experimental data of the conventional rotor. The computed flow physics around the modified rotor with the same diameter is then analyzed and compared with that of the conventional rotor during one rotation cycle. As the result, the modified rotor is outperforming the conventional one but keeping its unique features. The modified rotor offers exceeding performance at a tip speed ratio (TSR) greater than 0.8. The new peak of the power coefficient Cp is reached at TSR = 1.4 which is a typical operating condition of the wind turbine in urban areas. The remarkable finding is that the suppression of the flow separation on the blade is an effective way to improve the rotor's aerodynamic performance. As expected, the additional elliptical profile plays a key role in increasing the positive torque and in preventing the flow separation on the blade, especially at high TSR &amp;gt; 0.8. Finally, this study points to not only advances the fundamental understanding of flow mechanism around the rotor but also proposes a good practical energy harvesting application in urban environments.

Nonideal self-gravity and cosmology: Importance of correlations in the dynamics of the large-scale structures of the Universe

Aims. Inspired by the statistical mechanics of an ensemble of interacting particles (BBGKY hierarchy), we propose to account for small-scale inhomogeneities in self-gravitating astrophysical fluids by deriving a nonideal virial theorem and nonideal Navier-Stokes equations. These equations involve the pair radial distribution function (similar to the two-point correlation function used to characterize the large-scale structures of the Universe), similarly to the interaction energy and equation of state in liquids. Within this framework, small-scale correlations lead to a nonideal amplification of the gravitational interaction energy, whose omission leads to a missing mass problem, for instance, in galaxies and galaxy clusters. Methods. We propose to use a decomposition of the gravitational potential into a near- and far-field component in order to account for the gravitational force and correlations in the thermodynamics properties of the fluid. Based on the nonideal virial theorem, we also propose an extension of the Friedmann equations in the nonideal regime and use numerical simulations to constrain the contribution of these correlations to the expansion and acceleration of the Universe. Results. We estimate that the nonideal amplification factor of the gravitational interaction energy of the baryons lies between 5 and 20, potentially explaining the observed value of the Hubble parameter (since the uncorrelated energy accounts for ∼5%). Within this framework, the acceleration of the expansion emerges naturally because the number of substructures induced by gravitational collapse increases, which in turn increases their contribution to the total gravitational energy. A simple estimate predicts a nonideal deceleration parameter qni ≃ −1; this is potentially the first determination of the observed value based on an intuitively physical argument. We also suggest that small-scale gravitational interactions in bound structures (spiral arms or local clustering) could yield a transition to a viscous regime that can lead to flat rotation curves. This transition could also explain the dichotomy between (Keplerian) low surface brightness elliptical galaxy and (nonkeplerian) spiral galaxy rotation profiles. Overall, our results demonstrate that nonideal effects induced by inhomogeneities must be taken into account, potentially with our formalism, in order to properly determine the gravitational dynamics of galaxies and the large-scale Universe.

Laser Micromachining in Fabrication of Reverse-µEDM Tools for Producing Arrayed Protrusions.

This paper focuses on the fabrication of high-quality novel products using a µEDM process variant called Reverse-µEDM. The tool plate required for the Reverse-µEDM is fabricated using Nd: YAG-based laser beam micromachining (LBµM) at the optimized process parameters. The Grey relation analysis technique is used for optimizing LBµM parameters for producing tool plates with arrayed micro-holes in elliptical and droplet profiles. Titanium sheets of 0.5 mm thickness were used for such micro-holes, which can be used as a Reverse-µEDM tool. The duty cycle (a combination of pulse width and frequency) and current percentage are considered as significant input process parameters for the LBµM affecting the quality of the micro-holes. A duty cycle of 1.25% and a current of 20% were found to be an optimal setting for the fabrication of burr-free shallow striation micro-holes with a minimal dimensional error. Thereafter, analogous protrusions of high dimensional accuracy and minimum deterioration were produced by Reverse-µEDM using the LBµM fabricated tool plates.