Corner Orientation Research Articles

Exploring factors affecting the conversion of the coefficient of restitution to equivalent free fall drop height

AbstractThe coefficient of restitution (COR) is used to estimate the equivalent free fall drop height of packaging during handling and transportation. Various experimental studies were designed to explore factors affecting the conversion of the COR to equivalent free fall drop height. These factors include the number of drops, drop height, drop orientation, drop base, temperature and humidity on the COR. The results indicate that the number of drops and drop orientation are the two most influential factors affecting COR values. As the package undergoes more drops, the COR increases. Among the various orientations, the COR is largest for flat drops, followed by edge and corner orientations. Within flat drops, a smaller impact area results in a smaller COR. Manufacturing joints and the flats, edges and corners adjacent to manufacturing joints tend to yield smaller COR values. A COR correction matrix was developed to correct the conventional COR calculation. This matrix allows engineers to refine COR values based on the number of drops and drop orientations in the field. The matrix‐corrected equivalent free fall drop heights demonstrated an average accuracy of 96%. Compared to the conventional COR calculation method, it effectively reduces errors by a factor of 2–3.

Large eddy simulation of incident flows around polygonal cylinders

In this study, we carry out large eddy simulation of incident flow around polygonal cylinders of side number N=5−8 at Reynolds number Re=104. In total, six incidence angles (α) are studied on each cylinder ranging from face to corner orientations, thus covering the entire α spectrum. Special focus is put on the time-mean aerodynamic forces including lift, drag, and vortex shedding frequencies as well as the near wake flow features. It is found that because of y-plane asymmetry of polygonal cross sections at most incidence angles, the flow separation characteristics and hence the induced base pressure distribution and the aerodynamic forces exhibit unique and complex dependence on α and N. While the general inverse relation of drag coefficient and Strouhal number previously proposed from experimental observations at principal orientations still holds at arbitrary α, the variation of the two is found to be non-monotonic on both α and N. We also found that compared to the absolute time mean shear layer length measured from the final separation point, the extent of them stretched to the wake, measured from the cylinder center, is a powerful scaling factor for all the quantities investigated, including the wake characteristic length scales. In particular, the difference between the top and the bottom shear layer (due to geometrical asymmetry at arbitrary α) describes the variation of the non-zero time mean lift coefficient reasonably well, whose sign varies with N non-monotonically.

Numerical Simulation of Cross-Flow Vortex-Induced Vibration of Hexagonal Cylinders with Face and Corner Orientations at Low Reynolds Number

Vortex-induced vibrations (VIV) of hexagonal cylinders at Reynolds number of 1000 and mass ratio of 2 are studied numerically. In the numerical model, the Navier–Stokes equations are solved using finite volume method, and the fluid-structure interaction (FSI) is modelled using Arbitrary Lagrangian Eulerian (ALE) Scheme. The numerical model accounts for the cross-flow vibration of the cylinders, and is validated against published experimental and numerical results. In order to account for different angles of attack, the hexagonal cylinders are studied in the corner and face orientations. The results are compared with the published results of circular and square cylinders. Current results show that within the studied range of reduced velocities (up to 20), unlike circular and square cylinders, no lock-in response is observed in the hexagonal cylinders. The maximum normalized VIV amplitudes of the hexagonal cylinders are 0.45, and are significantly lower than those of circular and square cylinders. Vortex shedding regimes of the corner-oriented hexagons are mostly irregular. However, in the face-oriented hexagons, the shedding modes are more similar to the typical P + S and 2P modes.

Minimal Case Relative Pose Computation Using Ray-Point-Ray Features.

Corners are popular features for relative pose computation with 2D-2D point correspondences. Stable corners may be formed by two 3D rays sharing a common starting point. We call such elements ray-point-ray (RPR) structures. Besides a local invariant keypoint given by the lines' intersection, their reprojection also defines a corner orientation and an inscribed angle in the image plane. The present paper investigates such RPR features, and aims at answering the fundamental question of what additional constraints can be formed from correspondences between RPR features in two views. In particular, we show that knowing the value of the inscribed angle between the two 3D rays poses additional constraints on the relative orientation. Using the latter enables the solution of the relative pose problem with as few as 3 correspondences across the two images. We provide a detailed analysis of all minimal cases distinguishing between 90-degree RPR-structures and structures with an arbitrary, known inscribed angle. We furthermore investigate the special cases of a known directional correspondence and planar motion, the latter being solvable with only a single RPR correspondence. We complete the exposition by outlining an image processing technique for robust RPR-feature extraction. Our results suggest high practicality in man-made environments, where 90-degree RPR-structures naturally occur.

Building Descriptors from Local Feature Neighborhoods for Applications in Semi-Dense 3D Reconstruction.

This paper introduces a novel class of descriptors constructed solely from the extraction of a feature set's qualities of location, magnitude and orientation. Oriented Feature Constellations (OFC) descriptors are unlike typical feature descriptors that separate feature extraction from definition, where local underlying pixel information is used to form a unique high-dimensional vector for matching. We use other extracted features within the local neighborhood, or local constellation, to define unique descriptors for matching. This idea is demonstrated by creating a corner orientation extension to Features from Accelerated Segment Test (FAST) corners and use these features to create descriptors, called OFC-FAST. Using a standard two stage matcher to generate dense matches across test image sets, we compare our results with those obtained using Scale Invariant Feature Transform (SIFT) features. OFC-FAST descriptors were able to generate disparity maps of higher densities while using less computational time than the comparison method was able to achieve. We believe that the capability of OFC descriptors to quickly generate higher density disparity maps will be useful for applications in semi-dense 3D reconstruction.

On vortex shedding from a hexagonal cylinder

The unsteady wake behind a hexagonal cylinder in cross-flow is investigated numerically. The time-dependent three-dimensional Navier–Stokes equations are solved for three different Reynolds numbers Re and for two different cylinder orientations. The topology of the vortex shedding depends on the orientation and the Strouhal frequency is generally higher in the wake of a face-oriented cylinder than behind a corner-oriented cylinder. For both orientations a higher Strouhal number St is observed when Re is increased from 100 to 500 whereas St is unaffected by a further increase up to Re=1000. The distinct variation of St with the orientation of the hexagonal cylinder relative to the oncoming flow is opposite of earlier findings for square cylinder wakes which exhibited a higher St with corner orientation than with face orientation.

Estimation of brain activity for perception of aperture problem

Aperture problem is a psychological experiment for analyzing binding mechanism of the spatial recognition in an early stage of visual pathway. In this paper, we measure perceptual rate in the aperture experiments, and discuss the dependency between the perception and various parameters in the experiments. We also record Electroencephalograms(EEG) of subjects who are recognizing the perception. By the elec- troencephalograms(EEG) analysis, we measure reaction latency of visual evoked potential (VEP) and event related potential(ERP) related to visual pathway, and estimate the localized equivalent current dipole(ECD) in the visual pathway. I. INTRODUCTION Aperture problem (1)-(7) is a psychological experiment to analyze binding mechanism of the spatial recognition. A circular aperture that a base bar moves in the background first is displayed at a central coordinate position of a computer display. While the base bar moves to the top right corner orientation from the the lower left side as the starting point, two other circles that a flanking bar moves in the background appear at both ends of the center circle. The flanking bar, however, moves to the upper orientation from the lower side. If a subject perceived that the line joining the base bar and the flanking bar is straight, his/her recognition for orientation of the base bar's movement would be dragged with the flanking bar's movement. The subject would so perceive that the base bar's movement was changed the same upper vertical orientation as the flanking bar. We call the phenomenon per- ception. How will we perceive influence from neighboring other apertures and we depend on an experimental parameters for moving lines? Nishina et al. (2) have already discussed that the perception strongly depends on radius, distance between circles and time scale for displaying the flanking bar (shortly, the display time) by binding mechanism. In human early visual pathway, a binding mechanism performs an important function. In this paper, we affirms Nishina's results and discussed the dependence of the perceptual rate on the display time (5), (6). However, we have simultaneously noticed that the perception rate rather decreases at the display time later than 550ms. We discussed so the dependence of the perceptual rate on the display time by the visual measurement analysis, and in addition we here estimate the localized equivalent current dipole(ECD) in the visual pathway by the electroen- cephalograms(EEG) analysis (8). By two kinds of analyses, we can discuss which localization of the brain relates to the perception, and what mechanism causes the perception in the aperture problem. In the visual measurement analysis, the perceptual recognition rate is calculated with changing radius, distance between circles, display time, and speed of bar. We particularly discuss the influence of the speed of bar to the perceptual rate. Meanwhile, we argue that subjects tend to fail to recognize the perception on the long display time. We then discuss the dependence of the perceptual rate on the speed of bar by trend analysis. In EEG analysis (9)- (11), we measure the visual evoked potential(VEP) and event related potential(ERP) of the perception in order to estimate the localization of the brain activity area with changing radius, distance between circles, display time, and speed of bar. Then, we discuss the relationship between the latency of VEP and ERP by the perception and the localized equivalent current dipole(ECD) in the visual pathway. At the last, we presume which part of the brain relates to VEP and ERP for the perception, and what mechanism causes the perception.

Unsaturated quasi-linear flow analysis in V-shaped domains

An explicit, essentially 2D solution for steady unsaturated seepage flow from infinity to a corner, with boundaries kept at constant suction, is obtained for the Kirchhoff potential by the method of separation of variables. A system of coordinates coinciding with the corner boundaries is selected. Distributions of the pressure, stream lines and velocities are derived. Non-existence of steady flows at certain corner orientations, deflection of the incident flow by slanted boundaries and inflection points on the stream lines close to the vertex are discussed. One-dimensional limit for zones far from the trough is examined. Refraction and further collimation of the upper 2D flow in the second underlying porous medium with implications to geotechnical capillary barriers is studied. A vadose zone originated accretion is matched with a saturated ‘wing’, which appears on a slanted bedrock. Mathematically, this matching is done by linking the Dupuit–Forchheimer and quasi-linear models. A tilted water table is shown to entrain the recharging moisture with curvilinear stream lines in the unsaturated zone.

Combined free and forced convection in a corner

A formulation of the three-dimensional combined free and forced convection boundary-layer flow in a corner is derived and discussed in terms of the corner orientation with respect to the buoyancy force. The corner is imagined to be formed by the abutment of two quarter-infinite wedges along a side edge parallel to an incoming uniform stream. Based on this formulation, similarity-type solutions are derived for different boundary-layer regions corresponding to almost planar horizontal corners, the numerical solutions of which are found to be characterized by their non-uniqueness in the corner-layer with a secondary flow exhibiting varying and sometimes complex flow patterns in function of the flow parameters; the most interesting feature is perhaps the existence of two streamwise symmetrically disposed vortices arising in layers immediately adjacent to the corner-layer.

A corner orientation detector

This paper introduces an operator for the detection of the true location and orientation of corners. Its strength in dealing with junctions as well as corners is demonstrated. With this method, corner points are detected as intensity patterns that are anisotropic along several directions. Pixels belonging to the arms of the detected corners are analysed, and a histogram search provides a measure of their dominant orientations. Based on a single derivative scheme proposed by Yang et al. [Structure adaptive anisotropic image filtering, Image and Vision Computing 14 (1996) 135–145] the approach has proved to be insensitive to noise and has been applied to both synthetic and real-life images.

Wavelet transformation for gray-level corner detection

Corners are very attractive features for many applications in computer vision. In this paper, a new gray-level corner detection algorithm based on the wavelet transform is presented. The wavelet transform is used because the evolution across scales of its magnitudes and orientations can be used to characterize localized signals like edges and corners. Most conventional corner detectors detect corners based on the edge detection information. However, these edge detectors perform poorly at corners, adversely affecting their overall performance. To overcome this drawback, we first propose a new edge detector based on the ratio of the inter-scale wavelet transform modulus. This edge detector can correctly detect edges at the corner positions, making accurate corner detection possible. To reduce the number of points required to be processed, we apply the non-minima suppression scheme to the edge image and extract the minima image. Based on the orientation variance, these non-corner edge points are eliminated. In order to locate the corner points, we propose a new corner indicator based on the scale invariant property of the corner orientations. By examining the corner indicator the corner points can be located accurately, as shown by experiments with our algorithm. In addition, since wavelet transform possesses the smoothing effect inherently, our algorithm is insensitive to noise contamination as well.

Corner detection by a cost minimization approach

Corner detection, which is a valuable tool in biological and machine vision systems, is cast as a problem of cost optimization. The cost function is suitably devised to capture different desirable characteristics of corners such as edginess, curvature and region dissimilarity. The geometrical structure of the corner as well as the gray level variation of the image are accounted for in cost factors to evaluate the quality of corner configurations. The cost function is minimized using a simulated annealing algorithm. This approach also provides corner orientations and angles in addition to corner locations. The efficacy of the approach is demonstrated by experimental results.

A performance study for two portable data recorders used to measure package drop heights

AbstractThis study investigated the error in measuring package drop heights using the drop height recorder developed by Dallas Instruments and the environmental data recorder developed by Instrumented Sensor Technology. The shock measuring capabilities of the two recorders were also studied. Drops were made onto the bottom, edge and corner orientations from heights of 18, 24, 30 and 36 inches. The study concluded that the drop height recorder predicts the drop height most accurately and with the least variation using its 'zero‐g' channel. Both recorders show much larger variations in predicted values (up to 30%) when using the recorded acceleration‐time data. The edge and corner orientation drop heights are generally underestimated by both, owing to the inability of the accelerometers to differentiate between partial rotation on impact and vertical travel.

A VLSI architecture for a half-edge-based corner detector

Corner detection is a low-level feature detection operator that is of great use in image processing applications, for example, optical flow and structure from motion by image correspondence. The detection of corners is a computationally intensive operation. Past implementations of corner detection techniques have been restricted to software. In this paper we propose an efficient very large-scale integration (VLSI) architecture for detection of corners in images. The corner detection technique is based on the half-edge concept and the first directional derivative of Gaussian. Apart from the location of the corner points, the algorithm also computes the corner orientation and the corner angle and outputs the edge map of the image. The symmetrical properties of the masks are utilized to reduce the number of convolutions effectively, from eight to two. Therefore, the number of multiplications required per pixel is reduced from 1800 to 392. Thus, the proposed architecture yields a speed-up factor of 4.6 over conventional convolution architectures. The architecture uses the principles of pipelining and parallelism and can be implemented in VLSI.

An analysis of selected classroom spatial arrangements

The aim of the study was to examine students' preferences concerning eight selected classroom seating arrangements. The subjects stated their preferences for particular arrangements as well as individual seats, which was done in relation to two kinds of teacher: T +, evoking positive feelings, and T -, evoking a negative attitude. Differences among seating arrangements have been analyzed in terms of four criteria: teacher-group inclusion, physical barriers, orientation, and interactional relation between participants. The results show that the arrangements preferred for T + are associated with inclusion or semi-inclusion, lack of barriers, direct or corner orientation, and T-S interactional relation on the one-to-one basis, while the arrangements preferred for T - involve exclusion, presence of barriers, direct orientation, and T-S relation on the one-to-many basis. In contrast to T +, for T - the range of preferred seats is narrower and there is more agreement as to which seat is the best. The choice of a seat involves an optimal combination of distance, orientation, and barriers, and while for T - this indicates a tendency for maximum withdrawal, for T + two opposite tendencies have to be counterbalanced: approach and withdrawal. Either tendency can be affected by factors other than one's positive or negative attitude to T.

Corner detection

Corners are special features in images, and are of great use in computing the optical flow and structure from motion. Conventionally, corners have been defined as the junction point of two straight line edges. Most existing edge detectors perform poorly at corners, mainly because they assume an edge to be an entity having infinite extent, which is violated at the corners. Since, most of the corner detectors are based on existing edge detectors, the performance of such corner detectors is not satisfactory. A corner point can be viewed as the intersection of two half-edges, oriented in 2 different directions, which are not 180° apart. This statement defines both a half-edge and a corner in terms of one another. This definition is the essence of the corner detection strategies presented in this paper. The corner detection algorithms rely on detecting half-edges. A half-edge detector uses information from a single orientation rather than opposing directions. We propose two algorithms for edge detection and corner detection, one is based on the First Directional Derivative of Gaussian and the other is based on the Second Directional Derivative of Gaussian. In addition to the location of the corner points, our algorithms also determine the corner angle and the corner orientation. The efficacy of the detectors has been demonstrated by experimental results for laboratory scenes.

Forced convective heat transfer in the flow along a corner of arbitrary angle

A formulation of the three-dimensional combined free and forced convection boundary-layer flow in a corner is derived and discussed in terms of the corner orientation with respect to the buoyancy force. The corner is imagined to be formed by the abutment of two quarter-infinite wedges along a side edge parallel to an incoming uniform stream. Based on this formulation, similarity-type solutions are derived for different boundary-layer regions corresponding to almost planar horizontal corners, the numerical solutions of which are found to be characterized by their non-uniqueness in the corner-layer with a secondary flow exhibiting varying and sometimes complex flow patterns in function of the flow parameters; the most interesting feature is perhaps the existence of two streamwise symmetrically disposed vortices arising in layers immediately adjacent to the corner-layer.

Crack Formation in Corn Kernels Subject to Impact

ABSTRACT THE formation of internal cracks in corn kernels due to impact loading was investigated for three different levels of moisture content, impact velocity and orienta-tion. The percentage of kernels internally cracked in-creased with an increase in velocity and a decrease in moisture. Side and corner orientations of impact were found to produce the most internal cracks in corn kernels. Analysis of variance studies are discussed.