Center Of Ellipse Research Articles

Geological characterization of Chandrayaan-2 landing site in the southern high latitudes of the Moon

ISRO's lunar orbiter-lander-rover mission Chandryaan-2 is scheduled to be launched in the mid of 2019. In this contribution, we have carried out detailed geological characterization of the prime landing site (70.9°S, 22.8°E) of the Chandrayaan-2 lander – “Vikram”. The proposed landing site is located amidst the nearside lunar highlands at high southern latitudes, which is ~350 km north of South Pole Aitken (SPA) basin rim. Topography of the region is generally flat and it is largely confined by craters of varying diameter. The majority (94%) of the landing ellipse (~15 × 8 km) is within the boundary of intercrater plains with a slope <15° and yields a crater retention age of ~3.7−0.04+0.03 Ga. Craters (diameter: ~2.28 m to ~1.13 km) consistent with morphologies varying from fresh to degraded are common within the landing ellipse, though the ellipse center is devoid of craters with significant depth. Analysis of the spectral reflectance data suggests that the landing ellipse is dominantly feldspathic/highland material. The estimated average abundance of elements within the landing ellipse are Fe: 4.2 wt%, Mg: 5.4 wt%, Ca: 10 wt%, and Ti: 0.3 wt%. Results indicate that the surface composition might correspond to FAN dominated material. Based on elemental and spectral analysis results, we envisage possible mixing of highland material with ejecta from multiple craters surrounding the landing ellipse and/or SPA basin, resulting in hybridisation of highland regolith. Together, the results provide a contextual framework for in situ investigations at the proposed landing site.

Analysis for center deviation of circular target under perspective projection

PurposeAccurate feature localization is a fundamental problem in computer vision and visual measurement. In a perspective projection model of the camera, the projected center of a spatial circle and the center of the projection ellipse are not identical. This paper aims to show how to locate the real projection center precisely in the perspective projection of a space circle target.Design/methodology/approachBy analyzing the center deviation caused by projection transformation, a novel method is presented to precisely locate the real projection center of a space circle using projective geometry. Solution distribution of the center deviation is analyzed, and the quadratic equation for determining the deviation is derived by locating vanishing points. Finally, the actual projected center of the circular target is achieved by solving the deviation quadratic equations.FindingsThe procedures of the author’s method are simple and easy to implement. Experimental data calculated that maximum deviation occurs at approximately between 3π/10 and 2π/5 of the angle between the projection surface and the space target plane. The absolute reduction in error is about 0.03 pixels; hence, it is very significant for a high-accuracy solution of the position of the space circle target by minimizing systematic measurement error of the perspective projection.Originality/valueThe center deviation caused by the space circle projection transformation is analyzed, and the detailed algorithm steps to locate the real projection center precisely are described.

Elliptical model for surface topography prediction in five-axis flank milling

In five-axis flank milling operations, the intersecting surfaces of different cutting edges create roughness on the milled surfaces that cannot be ignored in situations with strict requirements, especially in aeronautical manufacturing. To focus on motion problems in milling operations, this paper presents a new model that utilizes elliptical paths as cutting edge trajectories on 3D surface topography machined by peripheral milling. First, the cutter parallel axis offset and location angle are considered, which change the location of the ellipse center and intersection point of the cutting edges. Then, through the proposed model, the predicted surface topography is obtained, and the factors that affect the development tendency of roughness are analyzed. Next, the effects of the cutter location position (CLP) geometric parameters, cutter parallel axis offset and curvature on the roughness are evaluated by a numerical simulation. Finally, machining tests are carried out to validate the model predictions, and the results show that the surface topography predictions correspond well with the experimental results.

ClickX: a visualization-based program for preprocessing of serial crystallography data.

Serial crystallography is a powerful technique in structure determination using many small crystals at X-ray free-electron laser or synchrotron radiation facilities. The large diffraction data volumes require high-throughput software to preprocess the raw images for subsequent analysis. ClickX is a program designated for serial crystallography data preprocessing, capable of rapid data sorting for online feedback and peak-finding refinement by parameter optimization. The graphical user interface (GUI) provides convenient access to various operations such as pattern visualization, statistics plotting and parameter tuning. A batch job module is implemented to facilitate large-data-volume processing. A two-step geometry calibration for single-panel detectors is also integrated into the GUI, where the beam center and detector tilting angles are optimized using an ellipse center shifting method first, then all six parameters, including the photon energy and detector distance, are refined together using a residual minimization method. Implemented in Python, ClickX has good portability and extensibility, so that it can be installed, configured and used on any computing platform that provides a Python interface or common data file format. ClickX has been tested in online analysis at the Pohang Accelerator Laboratory X-ray Free-Electron Laser, Korea, and the Linac Coherent Light Source, USA. It has also been applied in post-experimental data analysis. The source code is available via https://github.com/LiuLab-CSRC/ClickX under a GNU General Public License.

An Exact Robust Method to Localize a Known Sphere by Means of One Image

In this article we provide a very robust algorithm to compute the position of the center of a sphere with known radius from one image by a calibrated camera. To our knowledge it is the first time that an exact sphere localization formula is published that only uses the (pixel) area and the ellipse center of the sphere image. Other authors either derived an approximation formula or followed the less robust and more time consuming procedure of fitting an ellipse through the detected edge pixels. Our method is analytic and deterministic, making use of the unique positive real tool of a cubic equation. We observe that the proposed area method is significantly more accurate and precise than an ellipse fitting method. Furthermore, we investigate in what conditions for sphere images the proposed exact method is preferable to the robust approximation method. These observations are validated by virtual, synthetic and real experiments.

Image processing and data evaluation algorithms for reproducible optical in-plane permeability characterization by radial flow experiments

Textile permeability is one of the dictating factors in the fabrication of fibre-reinforced polymer composites. However, reproducibility of experimental in-plane permeability characterization is still a challenging task due to the lack of standardized test and evaluation procedures. The paper at hand addresses two major sources for discrepancies when characterizing in-plane permeability through optical observation of radial flow experiments: digital image processing and data evaluation algorithms. A digital image processing strategy is presented, which robustly handles varying lightning conditions, optical properties of the materials under test and image occlusions caused by mechanical elements of the test setup. The strategy is of universal validity and independent of the choice of reinforcing material and impregnating fluid. An experimental analysis compares two approaches for fitting elliptic geometry models to data points detected along the fluid flow front. The study reveals the impact of the fitting strategy on the resulting permeability data and the benefit of forcing the ellipse centre to that of the injection opening. The computation algorithm of Chan and Hwang, widely used for calculating in-plane permeability values from experimental data, is critically discussed. A correction of the algorithm is proposed which avoids a violation of isotropic data characteristics while adding robustness to the data reduction. An experimental analysis compares anisotropic in-plane permeability values obtained with different evaluation algorithms. The study highlights the impact of the computational algorithm on the permeability data and reveals discrepancies of up to 6%, which is considerable compared to the scatter typically reported for in-plane permeability data.

Cultural landscap’s changes of Solyna commune

The main aim of the present work was to analyze the dynamics of settlements from the 2nd half of the 18th century to 2nd half of 20th century in Solyna commune (in polish Solina), in Lesko district, Podkarpackie voivodeship in Eastern Poland. There was analyzed the Solyna commune in terms of the changes of settlements and applied maps together with published historical data for the analysis of changes in its structure. The first was the historical map, in other words the tactical map of «WIG- Military Institute of Geography». Next maps from the «WMS-Web Map Service, Geoportal» were analyzed. Changes in the number of villages and households population dynamics for Greek-catholics, «Latynnykys» and Jews for the year 1785 were evaluated applying ArcGIS 10.3 program. Ukrainian ones were evaluated using ArcGIS program in comparison with the number of Poles and Jews for the year 1939. Ethnic and religious composition from the 2nd half of the 18th century to 2nd half of 20th century and the character of settlements distribution in Solyna commune was evaluated based on the study of spatial distribution of settlements with the use of Spatial Statistics (Spatial Autocorrelation Global Moran's test, Standard Deviational Ellipse and Mean Centre). In 1785 there were 80,55% of Greek-catholics and in 1939 there were 89,82% of Ukrainians in Solyna commune. There was confirmed a similar configuration of Standard Deviation Ellipse and Mean Center for Greek-catholic for the year 1785 and Ukrainians for the year 1939 in Solyna commune. The scale and results of such changes are essential for future research, mainly in terms of the change of traditional village system infrastructure and culture.

Dangerous Situation Detection for Elderly Persons in Restrooms Using Center of Gravity and Ellipse Detection

We developed a restroom danger detection system (RDDS) for detecting dangerous situations and protecting the elderly. Restrooms are particularly dangerous places for elderly persons. Our RDDS detects danger in real time by using image processing and sends an alert to a family member, hospital staff, etc. It comprises four processes: person detection, center of gravity detection, ellipse detection, and danger decision. The human detection process calculates the difference between an image of the empty restroom and one of the restroom when it is occupied (to which a brightness correction has been applied). The difference image is binarized and used for detecting the presence of a person. If a person is detected, the person’s center of gravity and ellipse are detected in the binarized image after it is denoised. The obtained information is used for detecting a dangerous situation. If the dangerous situation continues for 60 seconds, an alert is sent. Testing showed that our system can detect a dangerous situation within 1.5 seconds. This RDDS is one step toward the development of a comprehensive elderly person protection system.

Modelling of Orthogonal Craniofacial Profiles

We present a fully-automatic image processing pipeline to build a set of 2D morphable models of three craniofacial profiles from orthogonal viewpoints, side view, front view and top view, using a set of 3D head surface images. Subjects in this dataset wear a close-fitting latex cap to reveal the overall skull shape. Texture-based 3D pose normalization and facial landmarking are applied to extract the profiles from 3D raw scans. Fully-automatic profile annotation, subdivision and registration methods are used to establish dense correspondence among sagittal profiles. The collection of sagittal profiles in dense correspondence are scaled and aligned using Generalised Procrustes Analysis (GPA), before applying principal component analysis to generate a morphable model. Additionally, we propose a new alternative alignment called the Ellipse Centre Nasion (ECN) method. Our model is used in a case study of craniosynostosis intervention outcome evaluation, and the evaluation reveals that the proposed model achieves state-of-the-art results. We make publicly available both the morphable models and the profile dataset used to construct it.

Design Characteristics of IPMSM With Wide Constant Power Speed Range for EV Traction

This paper presents study of design characteristics with wide constant power speed range (CPSR) for electric vehicle Propulsion. Through analysis of interior permanent magnet synchronous motor (IPMSM) control logic, design characteristic of extending CPSR is proposed. To achieve wide CPSR, center of voltage limit ellipse should be placed at cross point of current limit circle and d-axis. To analyze characteristic of voltage ellipse, four types of representative IPMSM rotor topologies are selected. Through rotor topology analysis, tendency of φ f and L ds parameters which decide center of voltage limit ellipse is analyzed. This paper also considers shifting of voltage limit ellipse center according to change in motor speed. Reflecting the result, this paper focuses on center of voltage limit ellipse position at maximum speed, because central coordinates of high-speed range determine characteristics of CPSR. Through the analysis result, this paper suggests direction of IPMSM design for wide CPSR.

Research on Exact Location Algorithm of Pupil Center Based on Ellipse Fitting

In order to realize the requirement of precise eye tracking in clinical, a pupil center location algorithm based on the least square method is proposed. First, the eye image was captured by the camera under the infrared light, and then the two-valued image was obtained after preprocessing. Use the number of pixels that form the outline which was Extracting from the two-valued image to carry out the rough filtration of the pupil. The ellipse curve was fitting by the randomly select 6 pixels on the filtered contours, and then calculated the variance of distance between the center and the edge of the ellipse. The ellipse center is ellipse center, where the variance of the distance is Minimum. The algorithm has advantage of accurate identification the pupil center when there is white spot interference and squint. Experiments show that the pupil center can be located quickly and real-timely by this algorithm.

Vortex precession in thin elliptical ferromagnetic nanodisks

The magnetostatic energy is calculated for a magnetic vortex in a noncircular elliptical nanodisk. It is well-known that the energy of a vortex in the circular disk is minimized though an ansatz that eliminates the magnetostatic charge at the disk edge. Beginning with this ansatz for the circular disk, a conformal mapping of a circle interior onto the interior of an ellipse results in the magnetization of the elliptical disk. This magnetization in the interior of an ellipse also has no magnetostatic charge at the disk edge also minimizing the magnetostatic energy. As expected the energy has a quadratic dependence on the displacement of the vortex core from the ellipse center, but reflecting the lower symmetry of the ellipse. Through numerical integration of the magnetostatic integral a general expression for the energy is obtained for ellipticity values from 1.0 to about 0.3. Finally a general expression for the gyrotropic frequency as described by the Thiele equation is obtained.

Аналіз поселень ґміни Лютовска від ІІ половини ХVІІІ століття із застосуванням GIS

The study was conducted within the actual area of Lutoviska commune in Bieszczady district, Podkarpackie voivodeship in Eastern Poland. The dynamics of settlements in Lutoviska commune from the 2nd half of the 18th century was discussed. Maps and historical data were analyzed in the ArcGIS 10.3 program. In the study there were presented possibilities of applying the ArcGIS for Desktop 10.3 program. We analyzed the Lutoviska commune in terms of the changes of settlements and used maps for the analysis of changes in its structure. The first of these was the historical map, namely the tactical map of “WIG” in scale 1:100 000 from 1936. Next we analyzed maps from 1965 and 2014, which were prepared applying the “WMS” server. The changes in the number of villages and households were presented. Population dynamics for Greek-Catholics, “Latynnykys” and Jews for the year 1785 and Ukrainians in comparison with the number of Poles and Jews for the year 1939 were shown. Ethnic and religious composition from the 2nd half of the 18th century was evaluated. Based on the study of spatial placement of settlements with the use of Spatial Statistics (Spatial Autocorrelation Global Moran’s test, Standard Deviational Ellipse and Mean Centre) the character of settlements distribution in Lutoviska commune was presented. There was confirmed a similar configuration of Standard Deviation Ellipse and Mean Center for Greek-Catholics-Ukrainians in 1785 and Ukrainians in 1939 in Lutoviska commune. The scale and results of such changes are interesting for future research, mainly in terms of the change of traditional village system infrastructure and culture. Key words: dynamics, village, GIS, Lutoviska commune.

A NEW γ-RAY LOUD, ECLIPSING LOW-MASS X-RAY BINARY

ABSTRACT We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope γ-ray source 3FGL J0427.9–6704. Photometry from OGLE and the SMARTS 1.3 m telescope and spectroscopy from the SOAR telescope have allowed us to classify the system as an eclipsing low-mass X-ray binary (P = 8.8 hr) with a main-sequence donor and a neutron-star accretor. Broad double-peaked H and He emission lines suggest the ongoing presence of an accretion disk. Remarkably, the system shows separate sets of absorption lines associated with the accretion disk and the secondary, and we use their radial velocities to find evidence for a massive (∼1.8–1.9 M ⊙) neutron-star primary. In addition to a total X-ray eclipse with a duration of ∼2200 s observed with NuSTAR, the X-ray light curve also shows properties similar to those observed among known transitional millisecond pulsars: short-term variability, a hard power-law spectrum ( ), and a comparable 0.5–10 keV luminosity ( erg s−1). We find tentative evidence for a partial ( ) γ-ray eclipse at the same phase as the X-ray eclipse, suggesting the γ-ray emission may not be confined to the immediate region of the compact object. The favorable inclination of this binary is promising for future efforts to determine the origin of γ-rays among accreting neutron stars.

INFLUENCE OF RAW IMAGE PREPROCESSING AND OTHER SELECTED PROCESSES ON ACCURACY OF CLOSE-RANGE PHOTOGRAMMETRIC SYSTEMS ACCORDING TO VDI 2634

This paper examines the influence of raw image preprocessing and other selected processes on the accuracy of close-range photogrammetric measurement. The examined processes and features includes: raw image preprocessing, sensor unflatness, distance-dependent lens distortion, extending the input observations (image measurements) by incorporating all RGB colour channels, ellipse centre eccentricity and target detecting. The examination of each effect is carried out experimentally by performing the validation procedure proposed in the German VDI guideline 2634/1. The validation procedure is based on performing standard photogrammetric measurements of high-accurate calibrated measuring lines (multi-scale bars) with known lengths (typical uncertainty = 5 μm at 2 sigma). The comparison of the measured lengths with the known values gives the maximum length measurement error LME, which characterize the accuracy of the validated photogrammetric system. For higher reliability the VDI test field was photographed ten times independently with the same configuration and camera settings. The images were acquired with the metric ALPA 12WA camera. The tests are performed on all ten measurements which gives the possibility to measure the repeatability of the estimated parameters as well. The influences are examined by comparing the quality characteristics of the reference and tested settings.

INFLUENCE OF RAW IMAGE PREPROCESSING AND OTHER SELECTED PROCESSES ON ACCURACY OF CLOSE-RANGE PHOTOGRAMMETRIC SYSTEMS ACCORDING TO VDI 2634

Abstract. This paper examines the influence of raw image preprocessing and other selected processes on the accuracy of close-range photogrammetric measurement. The examined processes and features includes: raw image preprocessing, sensor unflatness, distance-dependent lens distortion, extending the input observations (image measurements) by incorporating all RGB colour channels, ellipse centre eccentricity and target detecting. The examination of each effect is carried out experimentally by performing the validation procedure proposed in the German VDI guideline 2634/1. The validation procedure is based on performing standard photogrammetric measurements of high-accurate calibrated measuring lines (multi-scale bars) with known lengths (typical uncertainty = 5 μm at 2 sigma). The comparison of the measured lengths with the known values gives the maximum length measurement error LME, which characterize the accuracy of the validated photogrammetric system. For higher reliability the VDI test field was photographed ten times independently with the same configuration and camera settings. The images were acquired with the metric ALPA 12WA camera. The tests are performed on all ten measurements which gives the possibility to measure the repeatability of the estimated parameters as well. The influences are examined by comparing the quality characteristics of the reference and tested settings.

A New Efficient Calibration Method for Binocular Camera

In the vision 3-D measurement field, camera calibration results directly affect the accuracy of measurement. So camera calibration method is hot spot in this field. This paper proposes a new efficient calibration method with binocular camera. First, the method uses an accurate extraction algorithm to extract the ellipse center of calibration target image. Second, the paper presents a automatic matching algorithm based RANSAC (RANSAC SAMPLE CONSENSUS), the automatic matching algorithm is simple, fast, and can complete space calibration feature points matching its image point at once. At the beginning of matching, sort calibration points in the target according to a certain sequence. The sequence of feature points extracted in the calibration image does not correspond with one of the feature points in calibration target, because of the camera distortion. But obtain the correct matching points by the RANSAC algorithm. According to the camera calibration model, use the correct matching points and obtain correct intrinsic and extrinsic parameters of each camera and the relative parameters of two cameras. Finally, through experimental verification, the results show that the calibration method is fast and robust, and has higher calibration accuracy.

Morphological evolution and migration of void in bi-piezoelectric interface based on nonlocal phase field method

This paper reports the result of investigation into the morphological evolution and migration of void in bi-piezoelectric material interface by utilizing nonlocal phase field model and finite element method (FEM), where the small scale effect containing the long-range forces among atoms is considered. The nonlocal elastic strain energy and the nonlocal electric energy around the void are firstly calculated by the finite element method. Then based on the finite difference method (FDM), the thermodynamic equilibrium equation containing the surface energy and anisotropic diffusivity is solved to simulate the morphological evolution and migration of elliptical void in bi-piezoelectric films interface. Results show that the way of load condition plays a significant role in the evolution process, and the boundary of void's long axis gradually collapses toward the center of ellipse. In addition, the evolutionary speed of left boundary gradually decreases with scale effect coefficient growth. This work can provide references for the safety evaluation of piezoelectric materials in micro electro mechanical system.

A method to determine the detector locations of the cone-beam projection of the balls’ centers

In geometric calibration of cone-beam computed tomography (CBCT), sphere-like objects such as balls are widely imaged, the positioning information of which is obtained to determine the unknown geometric parameters. In this process, the accuracy of the detector location of CB projection of the center of the ball, which we call the center projection, is very important, since geometric calibration is sensitive to errors in the positioning information. Currently in almost all the geometric calibration using balls, the center projection is invariably estimated by the center of the support of the projection or the centroid of the intensity values inside the support approximately. Clackdoyle’s work indicates that the center projection is not always at the center of the support or the centroid of the intensity values inside, and has given a quantitative analysis of the maximum errors in evaluating the center projection by the centroid. In this paper, an exact method is proposed to calculate the center projection, utilizing both the detector location of the ellipse center and the two axis lengths of the ellipse. Numerical simulation results have demonstrated the precision and the robustness of the proposed method. Finally there are some comments on this work with non-uniform density balls, as well as the effect by the error occurred in the evaluation for the location of the orthogonal projection of the cone vertex onto the detector.

Constrained Ellipse Fitting with Center on a Line

Fitting an ellipse to given data points is a common optimization task in computer vision problems. However, the possibility of incorporating the prior constraint “the ellipse’s center is located on a given line” into the optimization algorithm has not been examined so far. This problem arises, for example, by fitting an ellipse to data points representing the path of the image positions of an adhesion inside a rotating vessel whose position of the rotational axis in the image is known. Our new method makes use of a constrained algebraic cost function with the incorporated “ellipse center on given line”-prior condition in a global convergent one-dimensional optimization approach. Further advantages of the algorithm are computational efficiency and numerical stability.