Curvature Depth Research Articles

Telemetry system based on fiber-optic gyroscopes

The article presents a telemetry system for monitoring the bit trajectory during well drilling. Fiber-optic closed-loop gyroscopes are the main sensitive element in the telemetry system. The gyroscopes allow determining the azimuth and zenith angles of the well with a high accuracy exceeding most magnetometers. There is no need to use the expensive non-magnetic steels in the body of the telemetry system and non-magnetic drill pipes in the drill string. Fiber-optic closed-loop gyroscopes allow using the telemetry system when drilling near the casing of adjacent wells and magnetized rocks. An inertial navigation system is installed in the developed telemetry system as a measuring unit containing three angular velocity sensors and three accelerometers mounted rigidly. The sequence and results of simulation of a hydraulic link for data transmission from the bottom of the well to the top are described. Pilot tests of the telemetry system were carried out at well No. 450 of the Tatsuksinskoye field. The obtained values of the spatial intensity of the borehole curvature in depth are close in values to the directional survey data for the borehole. The trajectory obtained during the lift is close to the trajectory gathered from directional survey data.

A novel method for finding grasping handles in a clutter using RGBD Gaussian mixture models

AbstractThe paper proposes a novel method to detect graspable handles for picking objects from a confined and cluttered space, such as the bins of a rack in a retail warehouse. The proposed method combines color and depth curvature information to create a Gaussian mixture model that can segment the target object from its background and imposes the geometrical constraints of a two-finger gripper to localize the graspable regions. This helps in overcoming the limitations of a poorly trained deep network object detector and provides a simple and efficient method for grasp pose detection that does not require a priori knowledge about object geometry and can be implemented online with near real-time performance. The efficacy of the proposed approach is demonstrated through simulation as well as real-world experiment.

Effective parametric analysis of machining curvature channel using semicircular curved copper electrode and OHNS steel workpiece through a novel curved EDM process

Electro-discharge machining (EDM) is one of the advanced non-conventional machining techniques used in industries. Most of the EDM research areas are directed towards the linear movement (up-and-down) of the electrode. Through a novel innovation, an innovative way of machining a curvature channel through a semicircular curved copper electrode is possible through curved EDM process. The experimental setup is developed and installed on the Z-axis numerically controlled(ZNC)EDM machine. The oscillating motion of curved electrode on stationary workpiece is obtained by implementing the concept of mechatronics. In this present work, we attempt to investigate the effect of input machining parameters on the output performance characteristics in curved EDM process. During pilot experimentation, critical variables are identified and selected as sparking current, pulse on time, pulse off time and angular sensitivity. Design of Experiment using Taguchi (L9) is used to formulate the planned experiments and to evaluate the effects of input machining characteristics on Material Removal Rate (MRR), Electrode Wear Rate (EWR), Curved Machining Angle (CMA), and Curvature Depth (L). Regression analysis and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) are effectively used to validate the model developed for the curved machining. The results obtained after experimentation predicts that the model can be accepted to optimize the quality machining characteristics in curved EDM process. Geometrical analysis and surface roughness are evaluated for the machined curvature through the advance measuring equipment’s. Scanning Electron Microscopy (SEM) is also used for observing the microstructure at higher magnification of workpiece material before and after machining.

Perception of straightness and parallelism with minimal distance information.

The ability of human observers to judge the straightness and parallelism of extended lines has been a neglected topic of study since von Helmholtz's initial observations 150years ago. He showed that there were significant misperceptions of the straightness of extended lines seen in the peripheral visual field. The present study focused on the perception of extended lines (spanning 90° visual angle) that were directly fixated in the visual environment of a planetarium where there was only minimal information about the distance to the lines. Observers were asked to vary the curvature of 1 or more lines until they appeared to be straight and/or parallel, ignoring any perceived curvature in depth. When the horizon between the ground and the sky was visible, the results showed that observers' judgements of the straightness of a single line were significantly biased away from the veridical, great circle locations, and towards equal elevation settings. Similar biases can be seen in the jet trails of aircraft flying across the sky and in Rogers and Anstis's new moon illusion (Perception, 42(Abstract supplement) 18, 2013, 2016). The biasing effect of the horizon was much smaller when observers were asked to judge the straightness and parallelism of 2 or more extended lines. We interpret the results as showing that, in the absence of adequate distance information, observers tend to perceive the projected lines as lying on an approximately equidistant, hemispherical surface and that their judgements of straightness and parallelism are based on the perceived separation of the lines superimposed on that surface.

Intelligent computer vision system for Sprague-Dawley rat sperm classification using gray-level microscopic images

This paper presents a development of intelligent computer vision system for Sprague-Dawley rat sperm classification. The system is developed to help pathologists and improve the current conventional detection methods and classification of Sprague-Dawley rat sperm. The conventional method tends to result in errors and is also time consuming. Thus, the new computer vision system is developed to overcome these problems and, consequently, produce more accurate results. The system is capable of classifying rat sperm into two groups, namely, normal and abnormal, based on the morphological characteristics of the sperm head. Furthermore, the system has the ability to classify the shapes of abnormal sperms which are banana and hookless shapes. The new system consists of four stages. In the first stage, sperms are segmented using the adaptive fuzzy moving K-means (AFMKM) clustering algorithm. In the second stage, a new automatic cropping algorithm was used to isolate the sperm head and to exclude other details. In the third stage, the feature extraction process was performed, wherein five features namely curvature angle, two flattened angles, curvature depth and number of curvatures are proposed to classify the sperm head of the rat. In the fourth (final) stage, the sperm head is classified using hybrid multilayered perceptron (HMLP) neural network trained with modified recursive prediction error (MRPE) algorithm. The developed system achieved an accuracy rate of 98.7%. Key words: Sprague-Dawley rat sperm, adaptive fuzzy moving K-means clustering algorithm, hybrid multilayered perceptron network, modified recursive prediction error algorithm.

Perceived curvature in depth: a test of cue combination models using motion and binocular disparity

Perceived curvature in depth: a test of cue combination models using motion and binocular disparity

Monocular gap stereopsis: manipulation of the outer edge disparity and the shape of the gap

A binocular stimulus that arises when two black frontal plane surfaces located at different depths have a gap between them for one eye but not for the other eye is interesting since the gap is monocular––it has no matching contours in the other eye––and yet binocular processes resolve a depth step effortlessly (Vision Research, 39, 493). In two experiments we investigate the processes and constraints underlying this depth resolution by varying the width of the solid image (the one without the gap) and the shape of the gap. The results show that the processes underlying monocular gap stereopsis can handle a situation in which the images of two surfaces in depth are effectively overlapping for one eye’s view with the other eye seeing between them and that binocular depth is seen even when there is no disparity present. We also show that under ecologically appropriate conditions, depth curvature and warping can result when the monocular gap has a curved or warped edge. Both these experiments imply that the visual system responds to the ambiguity of the stimulus by adopting a minimum slant constraint.

The absence of depth constancy in contour stereograms.

Stereoscopic surfaces constructed from Kanizsa-type illusory contours or explicit luminance contours were tested for three-dimensional (3-D) shape constancy. The curvature of the contours and the apparent viewing distance between the surface and the observer were manipulated. Observers judged which of two surfaces appeared more curved. Experiment 1 allowed eye movements and revealed a bias in 3-D shape judgment with changes in apparent viewing distance, such that surfaces presented far from the observer appeared less curved than surfaces presented close to the observer. The lack of depth constancy was approximately the same for illusory-contour surfaces and for explicit-contour surfaces. Experiment 2 showed that depth constancy for explicit-contour surfaces improved slightly when fixation was required and eye movements were restricted. These experiments suggest that curvature in depth is misperceived, and that illusory-contour surfaces are particularly sensitive to this distortion.

Curvature biases in stereoscopic vision: a nasotemporal asymmetry.

The reliability of curvature judgments for linear elements was studied, with stereograms that contained a binocular arc with curvature in depth, and either a binocular frontoparallel arc or a monocular one, on a background representing a hemiellipsoid. The subjects made about 15% errors on binocular arcs with curvature in depth, and 60%-80% of these occurred when both the hemiellipsoid and the arc were convex, the arc being perceived as concave, by transparency through the hemiellipsoid. There were also about 15%-30% errors on frontoparallel arcs, but spread among all situations, with a small prevalence of concave judgments. Curvature in depth was assigned to the monocular stimuli in more than 60% of the cases. There was a curvature bias when the monocular arcs were on the nasal side, and were viewed against a concave background. Assuming parallel viewing, nasal ingoing arcs were usually perceived as concave, and nasal outgoing arcs usually perceived as convex, in agreement with geometrical likelihood. Nasal-side elements captured by one eye are, in general, those with the highest likelihood of having matching elements in the other eye. Then the observed nasal bias effect suggests that the matching process in stereopsis could be driven from the nasal sides of the projections in the two cerebral hemispheres.

Shape and depth perception from parallel projections of three-dimensional motion.

Parallel projections of dots on the surface of a transparent sphere rotating about a vertical axis provide strong impressions of depth and spherical shape. The hypothesis was tested that these impressions are the result of three perceptual heuristics: (a) The sinusoidal projected velocity function of each dot in the horizontal dimension tends to be perceived as a rotary motion in depth; (b) the projected velocity gradient in the vertical dimension is perceived as curvature in depth; and (c) the simultaneously visible fields of dots moving in opposite directions are perceived as surfaces separated in depth. When each factor was varied independently, all three significantly affected judgments of spherical shape and depth. Similar results were obtained with cylinders. The first factor was more important for shape judgments; the second was generally more important for depth judgments. These results, together with those of earlier studies in which these factors led to similar effects for different stimuli and transformations, suggest that these are general principles applicable to the perception of structure from both rigid and nonrigid motion.

Adaptation of divers to curvature distortion under water.

A diver's face-mask causes ‘ pin-cushion ’ distortion for objects seen under water. The apparent curvature in depth of a straight line was measured for seven divers in air and water before and after a half-hour dive in the sea. Approximately 25 per cent of full adaptation to the optical distortion occurred during the dive, with a corresponding negative after-effect in air. The apparent curvature of the line was also measured for 16 novices and 15 experienced divers both in air and immediately on entering the water. The experienced divers showed some initial adaptation, while the novices showed none. This result suggests that the experienced divers had acquired a ‘ situation-contingent ’ visual response.