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Journal articles on the topic 'Planar shape detection'
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1
Oesau, Sven, Florent Lafarge, and Pierre Alliez. "Planar Shape Detection and Regularization in Tandem." Computer Graphics Forum 35, no. 1 (September 28, 2015): 203–15. http://dx.doi.org/10.1111/cgf.12720.
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Takahashi, H., H. Date, S. Kanai, and K. Yasutake. "DETECTION OF INDOOR ATTACHED EQUIPMENT FROM TLS POINT CLOUDS USING PLANAR REGION BOUNDARY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 12, 2020): 495–500. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-495-2020.
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Abstract. Laser scanning technology is useful to create accurate three-dimensional models of indoor environments for applications such as maintenance, inspection, renovation, and simulations. In this paper, a detection method of indoor attached equipment such as windows, lightings, and fire alarms, from TLS point clouds, is proposed. In order to make the method robust against to the lack of points of equipment surface, a footprint of the equipment is used for detection, because the entire or a part of the footprint boundary shapes explicitly appear as the boundary of base surfaces, i.e. walls for windows, and ceilings for lightings and fire alarms. In the method, first, base surface regions are extracted from given TLS point clouds of indoor environments. Then, footprint boundary points are detected from the region boundary points. Finally, target equipment is detected by fitting or voting using given target footprint shapes. The features of our method are footprint boundary point extraction considering occlusions, shape fitting with adaptive parameters based on point intervals, and robust shape detection by voting from multiple footprint boundary candidates. The effectiveness of the proposed method is evaluated using TLS point clouds.
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Xue, Qian, and Xijuan Chen. "Optimization of Planar Array Electrostatic Sensor for Metal Surface Defect Detection." Journal of Physics: Conference Series 2370, no. 1 (November 1, 2022): 012019. http://dx.doi.org/10.1088/1742-6596/2370/1/012019.
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Static electricity is usually generated in the damage area of the metal surface due to contact friction, and the charge distribution density can reflect the size, shape, and relative position of the damage area. Based on this, a planar array electrostatic sensor is designed to detect metal surface defect in this paper, and the shielding method, number of electrodes, electrode shape, and arrangement of the sensor are optimized taking account of the induced charge value, the uniformity of sensitivity and the image correlation coefficient. Different image reconstruction algorithms (e.g. Landweber algorithm, conjugate Gradient algorithm, Tikhonov regularization and primary dual interior point method) are utilized to evaluate the performance of the designed electrostatic sensor. The results demonstrated that the sensor with hexagonal electrode shape, integrated shielding, a new arrangement, a duty cycle of 80%, and a peripheral shielding electrode, has better image quality for all the tested damage models. When using the PDIPA algorithm for image reconstruction, the image correlation coefficient can exceed 0.9.
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Lo, Rong-Chin, and Wen-Hsiang Tsai. "Perspective-transformation-invariant generalized hough transform for perspective planar shape detection and matching." Pattern Recognition 30, no. 3 (March 1997): 383–96. http://dx.doi.org/10.1016/s0031-3203(96)00094-5.
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Zhang, Fang Zhou, Ben Dong Liu, Yu De Wu, and De Sheng Li. "The Simulation Research of Detecting Metal Debris with Different Shape Parameters of Micro Inductance Sensor." Advanced Materials Research 791-793 (September 2013): 861–65. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.861.
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A micro inductance sensor model based on the software of Maxwell to detect the debris in oil is presented. The model is built to study the detecting performance of sensors with different turns and enwinding styles. It can be demonstrated that the planar coil with 15 turns has a better sensitivity to detecting metal debris with about 100 micro meters in size. The solenoid coil with 20 turns has a better performance to detect the micro metal debris. This simulation shows that the detecting performance of a sensor is related to its parameters such as the size, turns, style of enwinding.The optimization of coils for the detection of metal debris with 100 in size is presented at last.
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Zhang, Youzhi, Jinhua Ye, Haomiao Wang, Shuheng Huang, and Haibin Wu. "A Flexible Tactile Sensor with Irregular Planar Shape Based on Uniform Electric Field." Sensors 18, no. 12 (December 15, 2018): 4445. http://dx.doi.org/10.3390/s18124445.
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Tactility is an essential perception for intelligent equipment to acquire external information. It can improve safety and performance during human-machine interactions. Based on the uniqueness theorem of the electrostatic field, a novel flexible film tactile sensor that can detect contact position and be made into any plane shape is proposed in this paper. The tactile sensor included an indium tin oxide (ITO) film, which was uniformly coated on the polyethylene terephthalate (PET) substrate. A specially designed strong conductive line was arranged along the edge of the flexible ITO film, which has weak conductivity. A bias excitation was applied to both ends of the strong conductive line. Through the control of the shape of the strong conductive line, a uniform electric field can be constructed in the whole weak conductive plane. According to the linear relationship between position and potential in the uniform electric field, the coordinate of the contact position can be determined by obtaining the potential of the contact point in the weak conducting plane. The sensor uses a three-layer structure, including an upper conductive layer, an intermediate isolation layer, and a lower conductive layer. A tactile sensor sample was fabricated. The experiment results showed that the principle of the tactile sensor used for the contact position detection is feasible and has certain precision of position detection. The sensor has good flexibility, and can be made into any plane shape, and has only four wires. It is capable of covering large areas of robot arms, and provides safety solutions for most robots.
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Uddin, Shah Mukim, Abkar Sayad, Jianxiong Chan, Efstratios Skafidas, and Patrick Kwan. "Design and Optimisation of Elliptical-Shaped Planar Hall Sensor for Biomedical Applications." Biosensors 12, no. 2 (February 10, 2022): 108. http://dx.doi.org/10.3390/bios12020108.
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The magnetic beads detection-based immunoassay, also called magneto-immunoassay, has potential applications in point-of-care testing (POCT) due to its unique advantage of minimal background interference from the biological sample and associated reagents. While magnetic field detection technologies are well established for numerous applications in the military, as well as in geology, archaeology, mining, spacecraft, and mobile phones, adaptation into magneto-immunoassay is yet to be explored. The magnetic field biosensors under development tend to be multilayered and require an expensive fabrication process. A low-cost and affordable biosensing platform is required for an effective point-of-care diagnosis in a resource-limited environment. Therefore, we evaluated a single-layered magnetic biosensor in this study to overcome this limitation. The shape-induced magnetic anisotropy-based planar hall effect sensor was recently developed to detect a low-level magnetic field, but was not explored for medical application. In this study, the elliptical-shaped planar hall effect (EPHE) sensor was designed, fabricated, characterized, and optimized for the magneto-immunoassay, specifically. Nine sensor variants were designed and fabricated. A customized measurement setup incorporating a lock-in amplifier was used to quantify 4.5 µm magnetic beads in a droplet. The result indicated that the single-domain behaviour of the magnetic film and larger sensing area with a thinner magnetic film had the highest sensitivity. The developed sensor was tested with a range of magnetic bead concentrations, demonstrating a limit of detection of 200 beads/μL. The sensor performance encourages employing magneto-immunoassay towards developing a low-cost POCT device in the future.
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Cielo, P., C. K. Jen, and X. Maldague. "The converging-surface-acoustic-wave technique: anaylsis and applications to nondestructive evaluation." Canadian Journal of Physics 64, no. 9 (September 1, 1986): 1324–29. http://dx.doi.org/10.1139/p86-232.
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Converging surface-acoustic waves (SAW) are generated by irradiating the inspected material with an annular-shaped pulsed laser beam. The converging-SAW pulse arrival is detected by a laser interferometer focused on the center of the annulus, where the converging effect produces a strong amplification of the ultrasonic pulse. This technique can be applied either to the detection of defects or to the characterization of the material by measuring the SAW velocity or attenuation. In this paper we present an analysis of the converging-wave propagation in order to explain some features of the detected signal, such as its shape and amplitude for different positions of the probing beam. A comparison with the signal intensities expected for a diverging as well as a collimated SAW is also presented. Applications of this technique to the characterization of anisotropic materials as well as to the detection of subsurface planar defects are presented and discussed.
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Нургазизов, Н. И., Д. А. Бизяев, А. А. Бухараев, И. В. Русских, and Ю. В. Садчиков. "Использование планарных пермаллоевых микрочастиц для детектирования механических напряжений." Журнал технической физики 89, no. 11 (2019): 1663. http://dx.doi.org/10.21883/jtf.2019.11.48325.113-19.
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The results of the study of changes in the magnetic structure of planar permalloy microparticles under a mechanical stress are presented. The particles were formed on glass substrates and had the square shape in the sample plane. It was shown that uniaxial mechanical stresses can be detected from the images of such particles obtained by magnetic force microscope. The ranges of effectively using of the particles for a detection of the stresses were determined depending on the geometrical sizes of the particle.
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SARKAR, BISWAJIT, LOKENDRA KUMAR SINGH, and DEBRANJAN SARKAR. "A GENETIC ALGORITHM-BASED APPROACH FOR DETECTION OF SIGNIFICANT VERTICES FOR POLYGONAL APPROXIMATION OF DIGITAL CURVES." International Journal of Image and Graphics 04, no. 02 (April 2004): 223–39. http://dx.doi.org/10.1142/s0219467804001385.
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A polygonal approximation captures the essential features of a digital planar curve and yields a compact representation. Those points of the digital curve that carry vital information about the shape of the curve form the vertices of the approximating polygon and are called significant vertices. In this paper, we present a genetic algorithm-based approach to locate a specified number of significant points, such that the approximation error between the original curve and its polygonal version obtained by joining the adjacent significant points is minimized. By using a priori knowledge about the shape of the curve we confine our search to only those points of the curve that have the potential of qualifying as significant points. We also incorporate chromosome differentiation to improve upon the effectiveness of the search in arriving at a near-optimal polygonal approximation. Finally, we show that the proposed method performs remarkably well when evaluated in terms of the metrics available for assessing the goodness of a polygonal approximation algorithm.
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Malihi, Shirin, Mohammad Valadan Zoej, and Michael Hahn. "Large-Scale Accurate Reconstruction of Buildings Employing Point Clouds Generated from UAV Imagery." Remote Sensing 10, no. 7 (July 20, 2018): 1148. http://dx.doi.org/10.3390/rs10071148.
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High-density point clouds are valuable and detailed sources of data for different processes related to photogrammetry. We explore the knowledge-based generation of accurate large-scale three-dimensional (3D) models of buildings employing point clouds derived from UAV-based photogrammetry. A new two-level segmentation approach based on efficient RANdom SAmple Consensus (RANSAC) shape detection is developed to segment potential facades and roofs of the buildings and extract their footprints. In the first level, the cylinder primitive is implemented to trim point clouds and split buildings, and the second level of the segmentation produces planar segments. The efficient RANSAC algorithm is enhanced in sizing up the segments via point-based analyses for both levels of segmentation. Then, planar modelling is carried out employing contextual knowledge through a new constrained least squares method. New evaluation criteria are proposed based on conceptual knowledge. They can examine the abilities of the approach in reconstruction of footprints, 3D models, and planar segments in addition to detection of over/under segmentation. Evaluation of the 3D models proves that the geometrical accuracy of LoD3 is achieved, since the average horizontal and vertical accuracy of the reconstructed vertices of roofs and footprints are better than (0.24, 0.23) m, (0.19, 0.17) m for the first dataset, and (0.35, 0.37) m, (0.28, 0.24) m for the second dataset.
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Liu, Z. "Convex Grouping Impedes Detection of Stereoscopic Depth." Perception 26, no. 1_suppl (August 1997): 242. http://dx.doi.org/10.1068/v970142.
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When two image regions are separated by an occluder, the strength of their perceptual grouping behind the occluder depends in part on the possible smoothness of the hidden contour completions (ie, Gestalt ‘good continuation’). We consider if grouping strength also depends on whether the contour completion is convex or concave. We hypothesised that the stronger the grouping between two such regions, the harder it is to resolve their relative stereoscopic depth; and employed accordingly an objective method of relative depth discrimination. The stimulus was in stereo. A horizontal bar in the centre of the image occluded two pairs of planar regions parallel with the image plane. One pair assumed a convex (oval) shape behind the occluder, the other pair a concave (hourglass) shape. The regions in one pair had a slight depth difference. The task was to detect which pair was not coplanar. The convex grouping impeded detection of stereoscopic relative depth (73% vs 86%, F1,10=8.66, p < 0.02). This held even when the convex completion boundaries were less smooth than the concave ones, a result opposite to predictions by Gestalt ‘good continuation’. In a control experiment, the stimulus was viewed with the ‘occluder’ in the background, so grouping was no longer possible. No difference between the two pairs was found. Our results suggest that convexity, known to play a role in figure/ground segmentation, is also significant in perceptual grouping, and can even win out over ‘good continuation’. We also propose an objective method of depth discrimination to study perceptual grouping in general.
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Peng, F., X. Cai, and W. Tan. "USING COMBINATION OF PLANAR AND HEIGHT FEATURES FOR DETECTING BUILT-UP AREAS FROM HIGH-RESOLUTION STEREO IMAGERY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W7 (September 13, 2017): 857–61. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w7-857-2017.
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Within-class spectral variation and between-class spectral confusion in remotely sensed imagery degrades the performance of built-up area detection when using planar texture, shape, and spectral features. Terrain slope and building height are often used to optimize the results, but extracted from auxiliary data (e.g. LIDAR data, DSM). Moreover, the auxiliary data must be acquired around the same time as image acquisition. Otherwise, built-up area detection accuracy is affected. Stereo imagery incorporates both planar and height information unlike single remotely sensed images. Stereo imagery acquired by many satellites (e.g. Worldview-4, Pleiades-HR, ALOS-PRISM, and ZY-3) can be used as data source of identifying built-up areas. A new method of identifying high-accuracy built-up areas from stereo imagery is achieved by using a combination of planar and height features. The digital surface model (DSM) and digital orthophoto map (DOM) are first generated from stereo images. Then, height values of above-ground objects (e.g. buildings) are calculated from the DSM, and used to obtain raw built-up areas. Other raw built-up areas are obtained from the DOM using Pantex and Gabor, respectively. Final high-accuracy built-up area results are achieved from these raw built-up areas using the decision level fusion. Experimental results show that accurate built-up areas can be achieved from stereo imagery. The height information used in the proposed method is derived from stereo imagery itself, with no need to require auxiliary height data (e.g. LIDAR data). The proposed method is suitable for spaceborne and airborne stereo pairs and triplets.
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Shtain, Z., and S. Filin. "HIERARCHICAL PROXIMITY-BASED OVER-SEGMENTATION OF 3-D POINT CLOUDS FOR EFFICIENT GRAPH FEATURE DETECTION." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences V-2-2020 (August 3, 2020): 273–80. http://dx.doi.org/10.5194/isprs-annals-v-2-2020-273-2020.
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Abstract. Point cloud simplification is empowered by the definition of similarity metrics which we aim to identify homogeneous regions within the point-cloud. Nonetheless, the variety of shapes and clutter in natural scenes, along with the significant resolution variations, occlusions, and noise, contribute to inconsistencies in the geometric properties, thereby making the homogeneity measurement challenging. Thus, the objective of this paper is to develop a point-cloud simplification model by means of data segmentation and to extract information in a better-suited way. The literature shows that most approaches either apply volumetric data strategies and/or resort to simplified planar geometries, which relate to only part of the entities found within a natural scene. To provide a more general strategy, we propose a proximity-based approach that allows an efficient and reliable surface characterization with no limitation on the number or shape of the primitives which in turn, enables detecting free-form objects. To achieve this, a local, computationally efficient and scalable metric is developed, which captures resolution variation and allows for short processing time. Our proposed scheme is demonstrated on datasets featuring a variety of surface types and characteristics. Experiments show high precision rates while exhibiting robustness to the varying resolution, texture, and occlusions that exist within the sets.
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Yang, Jian, Fang-Hong Sun, and Zheng Lu. "Solving the conjugate tooth profile of screw compressor rotors using edge detection method based on Alpha Shape algorithm." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, no. 6 (July 15, 2019): 1217–30. http://dx.doi.org/10.1177/0954408919862718.
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While designing a screw compressor, the design of the rotor profiles is the most important because rotor profiles essentially determine the overall performance of the screw compressor. In the field of rotor design, the mutual solution of male and female rotors is characterized by shortcomings such as complex and error-prone calculation, and unsolvable interference. In this study, an edge detection method based on the Alpha Shape algorithm was proposed to avoid the complex calculation process in the traditional planar meshing theory and quickly obtain the point cloud data with singularity points removed. The results show that, with relatively high accuracy and fast processing speed, this algorithm can extract comparatively desirable edges so as to obtain data of the female (male) rotor profile based on the conjugate male (female) rotor profile. The analytical method and the experimental method were used to compare the data of the conjugate rotors, verifying the correctness of the design, which efficiently and highly accurately overcame the problems in mutual solution of male and female rotors. This method can also be applied to design similar conjugate products such as gears, worms, and milling cutters.
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Zhang, Wang, Yu, and Zhao. "Research on Four-Point Air Bending Process and Contour Detection Method for JCO Forming Process of LSAW Pipes." Metals 9, no. 8 (August 6, 2019): 859. http://dx.doi.org/10.3390/met9080859.
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Aiming at the forming efficiency and roundness of the longitudinal submerged arc welded (LSAW) pipes in JCO (J-shape to C-shape to O-shape) forming process, this paper proposes a four-point air bending process. Compared with the traditional three-point air bending process, The new process can provide a more uniform bending moment, does not need to crimp the edges of steel sheet, shorten the residual straight segment length, and lengthen the forming length in single pass. The mechanical model is established to analyze the static equilibrium conditions and elastic–plastic deformation. The process is simulated by using the software package ABAQUS, to find the maximum punch spacing, and further determine the formulation principles of other process parameters. In addition, a contour detection method for the LSAW pipes in forming process is proposed based on machine vision (planar-array CCD camera produced by Gray Point Corporation, Vancouver, Canada). This method can not only quickly detect the contour of each pass, but also splice the detected contours together to obtain the overall contour with the given splicing algorithm. According to the measured contour, the bending angle, radius, and roundness can be calculated, to correct the punch reduction in the next pass and improve the forming accuracy of the pipes. Finally, an experimental system is designed to verify the proposed four-point bending JCO forming process and contour detection method. The result shows that the error between the contour detection method and CMM (coordinate measuring machine) is less than 0.5% for the overall contour, the two experimental pipes require 13 and 15 passes respectively, the roundness of pipes are less than 1.1%, which is much better than that of traditional three-point bending JCO forming process.
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Mostert, W., D. I. Pullin, R. Samtaney, and V. Wheatley. "Singularity formation on perturbed planar shock waves." Journal of Fluid Mechanics 846 (May 8, 2018): 536–62. http://dx.doi.org/10.1017/jfm.2018.263.
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We present an analysis that predicts the time to development of a singularity in the shape profile of a spatially periodic perturbed, planar shock wave for ideal gas dynamics. Beginning with a formulation in complex coordinates of Whitham’s approximate model geometrical shock dynamics (GSD), we apply a spectral treatment to derive the asymptotic form for the leading-order behaviour of the shock Fourier coefficients for large mode numbers and time. This is shown to determine a critical time at which the coefficients begin to decay, with respect to mode number, at an algebraic rate with an exponent of $-5/2$, indicating loss of analyticity and the formation of a singularity in the shock geometry. The critical time is found to be inversely proportional to a representative measure of perturbation amplitude $\unicode[STIX]{x1D716}$ with an explicit analytic form for the constant of proportionality in terms of gas and shock parameters. To leading order, the time to singularity formation is dependent only on the first Fourier mode. Comparison with results of numerical solutions to the full GSD equations shows that the predicted critical time somewhat underestimates the time for shock–shock (triple-point) formation, where the latter is obtained by post-processing the numerical GSD results using an edge-detection algorithm. Aspects of the analysis suggest that the appearance of loss of analyticity in the shock surface may be a precursor to the first appearance of shock–shocks, which may account for part of the discrepancy. The frequency of oscillation of the shock perturbation is accurately predicted. In addition, the analysis is extended to the evolution of a perturbed planar, fast magnetohydrodynamic shock for the case when the external magnetic field is aligned parallel to the unperturbed shock. It is found that, for a strong shock, the presence of the magnetic field produces only a higher-order correction to the GSD equations with the result that the time to loss of analyticity is the same as for the gas-dynamic flow. Limitations and improvements for the analysis are discussed, as are comparisons with the analogous appearance of singularity formation in vortex-sheet evolution in an incompressible inviscid fluid.
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Zhai, Lusheng, Zihan Meng, Jie Yang, Hongxin Zhang, and Ningde Jin. "Detection of Interfacial Structures in Inclined Liquid-Liquid Flows Using Parallel-Wire Array Probe and Planar Laser-Induced Fluorescence Methods." Sensors 20, no. 11 (June 2, 2020): 3159. http://dx.doi.org/10.3390/s20113159.
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Flows of two immiscible liquids through inclined pipes are often encountered in industrial processes. The interfacial characteristics in inclined pipes are of significance for understanding the mechanism of flow pattern transition and modeling the flow parameters. This paper developed a novel experimental technique to access the interface characteristics of liquid-liquid flows, during which optical and electrical methods were successfully combined by matching the refractive index and conductivity of the flows. A planar laser-induced fluorescence (PLIF) system was set up with a continuous laser and high-speed camera. Organic and aqueous phases were chosen to match refractive indices. The liquid-liquid interface in the middle of the pipe could be clearly visualized by the PLIF system. Meanwhile, two conductance parallel-wire array probes (CPAPs) were designed to reconstruct the liquid-liquid interfaces at upward and downward pipe cross-sections. The performances of the CPAP were validated using the PLIF results and employed to investigate the liquid-liquid interfacial structures. The interfacial shape and its instability were uncovered using the reconstructed interfaces by the CPAPs.
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Li, Y., J. Fan, Y. Huang, and Z. Chen. "LIDAR-INCORPORATED TRAFFIC SIGN DETECTION FROM VIDEO LOG IMAGES OF MOBILE MAPPING SYSTEM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 6, 2016): 661–68. http://dx.doi.org/10.5194/isprs-archives-xli-b1-661-2016.
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Mobile Mapping System (MMS) simultaneously collects the Lidar points and video log images in a scenario with the laser profiler and digital camera. Besides the textural details of video log images, it also captures the 3D geometric shape of point cloud. It is widely used to survey the street view and roadside transportation infrastructure, such as traffic sign, guardrail, etc., in many transportation agencies. Although many literature on traffic sign detection are available, they only focus on either Lidar or imagery data of traffic sign. Based on the well-calibrated extrinsic parameters of MMS, 3D Lidar points are, the first time, incorporated into 2D video log images to enhance the detection of traffic sign both physically and visually. Based on the local elevation, the 3D pavement area is first located. Within a certain distance and height of the pavement, points of the overhead and roadside traffic signs can be obtained according to the setup specification of traffic signs in different transportation agencies. The 3D candidate planes of traffic signs are then fitted using the RANSAC plane-fitting of those points. By projecting the candidate planes onto the image, Regions of Interest (ROIs) of traffic signs are found physically with the geometric constraints between laser profiling and camera imaging. The Random forest learning of the visual color and shape features of traffic signs is adopted to validate the sign ROIs from the video log images. The sequential occurrence of a traffic sign among consecutive video log images are defined by the geometric constraint of the imaging geometry and GPS movement. Candidate ROIs are predicted in this temporal context to double-check the salient traffic sign among video log images. The proposed algorithm is tested on a diverse set of scenarios on the interstate highway G-4 near Beijing, China under varying lighting conditions and occlusions. Experimental results show the proposed algorithm enhances the rate of detecting traffic signs with the incorporation of the 3D planar constraint of their Lidar points. It is promising for the robust and large-scale survey of most transportation infrastructure with the application of MMS.
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Li, Y., J. Fan, Y. Huang, and Z. Chen. "LIDAR-INCORPORATED TRAFFIC SIGN DETECTION FROM VIDEO LOG IMAGES OF MOBILE MAPPING SYSTEM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 6, 2016): 661–68. http://dx.doi.org/10.5194/isprsarchives-xli-b1-661-2016.
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Mobile Mapping System (MMS) simultaneously collects the Lidar points and video log images in a scenario with the laser profiler and digital camera. Besides the textural details of video log images, it also captures the 3D geometric shape of point cloud. It is widely used to survey the street view and roadside transportation infrastructure, such as traffic sign, guardrail, etc., in many transportation agencies. Although many literature on traffic sign detection are available, they only focus on either Lidar or imagery data of traffic sign. Based on the well-calibrated extrinsic parameters of MMS, 3D Lidar points are, the first time, incorporated into 2D video log images to enhance the detection of traffic sign both physically and visually. Based on the local elevation, the 3D pavement area is first located. Within a certain distance and height of the pavement, points of the overhead and roadside traffic signs can be obtained according to the setup specification of traffic signs in different transportation agencies. The 3D candidate planes of traffic signs are then fitted using the RANSAC plane-fitting of those points. By projecting the candidate planes onto the image, Regions of Interest (ROIs) of traffic signs are found physically with the geometric constraints between laser profiling and camera imaging. The Random forest learning of the visual color and shape features of traffic signs is adopted to validate the sign ROIs from the video log images. The sequential occurrence of a traffic sign among consecutive video log images are defined by the geometric constraint of the imaging geometry and GPS movement. Candidate ROIs are predicted in this temporal context to double-check the salient traffic sign among video log images. The proposed algorithm is tested on a diverse set of scenarios on the interstate highway G-4 near Beijing, China under varying lighting conditions and occlusions. Experimental results show the proposed algorithm enhances the rate of detecting traffic signs with the incorporation of the 3D planar constraint of their Lidar points. It is promising for the robust and large-scale survey of most transportation infrastructure with the application of MMS.
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Kumar, Arjun, and M. V. Kartikeyan. "A Design of a Terahertz Microstrip Bandstop Filter with Defected Ground Structure." Active and Passive Electronic Components 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/192018.
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A planar microstrip terahertz (THz) bandstop filter has been proposed with defected ground structure with high insertion loss (S21) in a stopband of −25.8 dB at 1.436 THz. The parameters of the circuit model have been extracted from the EM simulation results. A dielectric substrate of Benzocyclobutene (BCB) is used to realize a compact bandstop filter using modified hexagonal dumbbell-shape defected ground structure (DB-DGS). In this paper, a defected ground structure topology is used in aλ/4, 50 Ω microstrip line at THz frequency range for compactness. No article has been reported on the microstrip line at terahertz frequency regime using DGS topology. The proposed filter can be used for sensing and detection in biomedical instruments in DNA testing. All the simulations/cosimulations are carried out using a full-wave EM simulator CST V.9 Microwave Studio, HFSS V.10, and Agilent Design Suite (ADS).
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Xu, Y., J. He, S. Tuttas, and U. Stilla. "RECONSTRUCTION OF SCAFFOLDING COMPONENTS FROM PHOTOGRAMMETRIC POINT CLOUDS OF A CONSTRUCTION SITE." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-3/W5 (August 20, 2015): 401–8. http://dx.doi.org/10.5194/isprsannals-ii-3-w5-401-2015.
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This paper presents a data-driven workflow for the detection of scaffolding components from point clouds. The points belonging to the scaffolding components are identified and separated from the main building structures and two basic elements, namely the toeboard and the tube, are reconstructed. The workflow has four main processing steps. Firstly, the raw point clouds are preprocessed by statistical filtering and voxel girding. In the second step, the planar surfaces of the building surface and scaffoldings are extracted via RANSAC and then grouped by their parallelity and distance to separate the building façade. In the third step, the 3D shape descriptor FPFH and random forest classification algorithm are applied to classify the point data of building façades into classes belonging to different elements. Finally, by the use of linear fitting algorithm and matching using SHOT shape descriptor, the tubes and toeboards are reconstructed with their geometric parameters. It is shown that the points belonging to these objects are identified and then reconstructed with cylinder and cuboid models. The final results show that over 60% of the tubes and nearly 90% of the toeboards are reconstructed in the investigated façade, and more than 40% of the reconstructed objects are well rebuilt.
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Wietrzak, Anthony, and Richard M. Lueptow. "Wall shear stress and velocity in a turbulent axisymmetric boundary layer." Journal of Fluid Mechanics 259 (January 25, 1994): 191–218. http://dx.doi.org/10.1017/s0022112094000091.
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Instantaneous streamwise fluctuations of the wall shear stress have been measured using a hot-element probe in a thick axisymmetric turbulent boundary layer on a cylinder aligned parallel to the flow. The measurements were made at a momentum-thickness Reynolds number Rθ = 3050 and a ratio of boundary-layer thickness to cylinder radius of δ/a = 5.7. The ratio of the r.m.s. of the fluctuation to the mean value of the wall shear stress, $\tau_{rms}/\bar{\tau}$, is about 0.32, a value slightly lower than that for recent measurements for flow over a flat plate. The probability density function of the wall shear stress is similar to that for planar wall-bounded flows within experimental error. The power spectral density of the wall shear stress shows that a cylindrical boundary layer contains less energy at lower frequencies and more energy at higher frequencies than other wall-bounded flows. Analysis of simultaneous measurement of the streamwise wall shear stress and the streamwise velocity using VITA and peak detection suggests that transverse curvature has little effect on the near-wall burst–sweep cycle compared to planar wall-bounded flows. The angle of inclination of the structures is similar to that measured for large-scale structures in planar wall-bounded flows. However, measurements of the cross-correlation between the shear stress and the velocity suggest the existence of smaller structures yawed to the axis of the cylinder. The coherence between shear stress and velocity shows a low frequency associated with the inclined structures and a higher frequency associated with the yawed structures. The yawed structures could have an arrowhead or half-arrowhead shape and may be associated with fluid from the outer flow washing over the cylinder.
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Erlandsen, Stanley L., Stephen Olmsted, Paul Walther, Ya Chen, Jim Pawley, Gary Dunny, and Carol L. Wells. "A microbial model for visualization of surface proteins using cryoimmobilization and high-resolution cryo-SEM." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 44–45. http://dx.doi.org/10.1017/s0424820100146060.
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Numerous studies on high resolution visualization of surface membrane proteins have utilized colloidal gold markers in conjunction with SEM, TEM, and by freeze-fracture cytochemistry using conventional or fracture flip methods, but in each case only information on the distribution of the marker complex, and not the actual structure of individual surface protein(s) was obtained.To investigate the detection of individual surface proteins, we have used a microbial model to examine surface proteins involved in conjugation or the transfer of DNA in Enterococcus faecalis. Two surface proteins encoded by the pCF10 plasmid, aggregation substance (Asc10; globular shape) and surface exclusion protein (Sec10; helical shape), mediate the aggregation of donor and recipient cells and prevent aggregation of like donor cells, respectively. Isogenic strains of E. faecalis that constitutively express neither Asc10 or Sec10 (pWM401) or both (pINY1801) were processed by 1) conventional chemical fixation, dehydration, critical point drying with CO2, ion beam sputtering with a discontinuous platinum film (<1 nm), and examination in a Hitachi S-900 FESEM operated at low voltage (<3 keV), or 2) cryoimmobilization of cells by high pressure freezing (Balzers HPM 010), mounting in a Gatan cryoholder followed by etching for 60 minutes at −100°C, cryocoating by planar magnetron sputtering (Balzers MED 010), and examination at −100°C in the S-900 FESEM.
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Le, Tuong Huu, José V. Pardo, and Xiaoping Hu. "4 T-fMRI Study of Nonspatial Shifting of Selective Attention: Cerebellar and Parietal Contributions." Journal of Neurophysiology 79, no. 3 (March 1, 1998): 1535–48. http://dx.doi.org/10.1152/jn.1998.79.3.1535.
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Le, Tuong Huu, José V. Pardo, and Xiaoping Hu. 4 T-fMRI study of nonspatial shifting of selective attention: cerebellar and parietal contributions. J. Neurophysiol. 79: 1535–1548, 1998. Regional blood oxygenation in the cerebellum and posterior cerebral cortices was monitored with functional magnetic resonance imaging (fMRI) at four Tesla while 16 normal subjects performed three tasks with identical visual stimulation: fixation; attention focused upon either stimulus shape or color and sustained during blocks of trials (sustained attention); and rapid, serial shifts in attention between stimulus shape or color within blocks of trials (shifting attention). The stimuli were displayed centrally for 100 ms followed by a central fixation mark for 900 ms. Each stimulus was either a circle or a square displayed in either red or green. Attention shifting required switching between color and shape information after each target detection and occurred on average once every three seconds. Subjects pressed a response key upon detecting the target; reaction time and response accuracy were recorded. Two protocols for T2*-weighted echo-planar imaging were optimized, one with a surface coil for the cerebellum alone and the other with a volume coil for imaging both cerebellum and posterior brain structures (parietal, occipital, and part of temporal cortices). Because fMRI of the cerebellum is particularly susceptible to cardiac and respiratory fluctuations, novel techniques were applied to isolate brain activation signals from physiological noise. Functional activation maps were generated for contrasts of 1) sustained attention to color minus fixation; 2) sustained attention to shape minus fixation; and 3) shifting attention minus sustained attention (to color and shape; i.e., summed across blocks of trials). Consistent with the ease of these tasks, subjects performed with >80% accuracy during both sustained attention and shifting attention. Analysis of variance did not show significant differences in false alarms or true hits across either attentional condition. A subgroup of subjects whose performance data were recorded during ten minutes of continuous practice did not show significant changes over time. Both contrasts between the conditions of sustained attention to color or to shape as compared with the fixation condition showed significant bilateral activation in occipital and inferior temporal regions (Brodmann areas 18, 19, and 37). The anterior medial cerebellum was also significantly activated ipsilateral to the finger used for responding. The principal comparison of interest, the contrast between the condition of shifting attention and the condition of sustained attention produced significant and reproducible activation: lateral cerebellar hemisphere (ansiform lobule: Crus I Anterior and Crus I Posterior; left Crus I Posterior); cerebellar folium; posterior superior parietal lobule (R and L); and cuneus and precuneus (R and L).
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Dang, Jun-Po, Xiu-Juan Jiang, and Zhen-Hua Tang. "Technique of TiNi-based shape memory alloy thin film coating on optical fibers." Acta Physica Sinica 71, no. 3 (2022): 030701. http://dx.doi.org/10.7498/aps.71.20211437.
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<sec>Intelligent, integrated and cost-effective micro-electro-mechanical system (MEMS) and micro sensors can be developed with TiNi-based memory alloy thin film and optical fibers. Such devices can work in harsh environment, like in deep sea, in space with flammable or explosive objects, or with strong electromagnetic interference; and examples of their possible applications include gas concentration detection in underground mines, dynamic detection of production parameters in oil or gas mining, etc. As TiNi-based memory alloy thin film possesses good biocompatibility, such devices can also be used in intracranial/endocardial pressure test, surgical resection, early cancer assessment, etc. The successful development of the above MEMS and micro sensors involve optical fibers coated with memory alloy films. However, unlike the common planar substrates, optical fiber is of a cylinder with a small diameter, and how to grow good-quality memory alloy film on its surface remains to be explored.</sec><sec>In this work, the silica fibers are coated with TiNi memory alloy films by magnetron sputtering. How to choose the proper operating parameters in the sputtering process, and also the effects of subsequent annealing treatment on the films, are discussed in detail. Uniform thin films are grown on the 125-μm-diameter cylindrical surfaces of optical fibers with our built coating mask device specially designed for fibers. The experiments show that when target-substrate distance, background vacuum degree, Ar gas flow and sputtering time are fixed in the sputtering process, the sputtering power can be optimized, while a higher sputtering pressure results in lower film deposition rate but better surface roughness. The thin film is well crystallized under annealing, and the major martensite B19′ phase and minor austenite B2 phase coexist in the Ti<sub>49.09</sub>Ni<sub>50.91</sub> film. In the experiments, with the optimal operating parameters (sputtering power of 150 W and sputtering pressure of 0.23 Pa), TiNi memory alloy film about 852.2 nm in thickness is grown on the fiber at a deposition rate of 0.118 nm/s, and surface root mean square roughness of the unannealed film is 15.1 nm. Annealing at temperatures of 500, 550 and 600 ℃ are respectively tried, and such a thermal treatment evidently refines the crystalline grains inside the film. Surface root mean square roughness of the film annealed at 600 ℃ is reduced to 6.32 nm.</sec><sec>This work indicates that a glass fiber can be coated with high-quality TiNi-based memory alloy film, and it thus forms a part of the bases of further development of relevant MEMS and micro sensors.</sec>
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Ren, He, and Wei-Feng Sun. "Characterizing Dielectric Permittivity of Nanoscale Dielectric Films by Electrostatic Micro-Probe Technology: Finite Element Simulations." Sensors 19, no. 24 (December 7, 2019): 5405. http://dx.doi.org/10.3390/s19245405.
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Finite element simulations for detecting the dielectric permittivity of planar nanoscale dielectrics by electrostatic probe are performed to explore the microprobe technology of characterizing nanomaterials. The electrostatic force produced by the polarization of nanoscale dielectrics is analyzed by a capacitance gradient between the probe and nano-sample in an electrostatic detection system, in which sample thickness is varied in the range of 1 nm–10 μm, the width (diameter) encompasses from 100 nm to 10 μm, the tilt angle of probe alters between 0° and 20°, and the relative dielectric constant covers 2–1000 to represent a majority of dielectric materials. For dielectric thin films with infinite lateral dimension, the critical diameter is determined, not only by the geometric shape and tilt angle of detecting probe, but also by the thickness of the tested nanofilm. Meanwhile, for the thickness greater than 100 nm, the critical diameter is almost independent on the probe geometry while being primarily dominated by the thickness and dielectric permittivity of nanomaterials, which approximately complies a variation as exponential functions. For nanofilms with a plane size which can be regarded as infinite, a pertaining analytical formalism is established and verified for the film thickness in an ultrathin limit of 10–100 nm, with the probe axis being perpendicular and tilt to film plane, respectively. The present research suggests a general testing scheme for characterizing flat, nanoscale, dielectric materials on metal substrates by means of electrostatic microscopy, which can realize an accurate quantitative analysis of dielectric permittivity.
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Struk, Przemysław. "Analysis of ridges and grooves shape in grating coupler for optimization of integrated optics sensor structures." Photonics Letters of Poland 14, no. 3 (September 30, 2022): 43. http://dx.doi.org/10.4302/plp.v14i3.1151.
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The paper presents a theoretical analysis of a sensor structure based on a planar waveguide and grating coupler designed to determine selected physical properties of blood – hemoglobin concentration and oxidation level. In particular analysis were focused on optimization of selected geometrical properties of grating coupler (shape of ridges and grooves) to obtain maximum efficiency of uncoupling of light from the sensor structure. The analysis were carried out for three type of ridges and grooves shape in grating coupler: rectangular, triangular and sinusoidal. Full Text: PDF ReferencesI. . Singh, A.Weston, A. Kundur, G. Dobie, Haematology Case Studies with Blood Cell Morphology and Pathophysiology; Elsevier: Amsterdam, The Netherlands, (2017). DirectLink P. Jarolim, M. Lahav, SC. Liu, J. Palek, "Effect of hemoglobin oxidation products on the stability of red cell membrane skeletons and the associations of skeletal proteins: correlation with a release of hemin", Blood 76, 10 (1990). CrossRef E. Beutler, J. Waalen, "The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration?", Blood 107, 5 (2006). CrossRef M. Kiroriwal, P. Singal M. Sharma, A. Singal, "Hemoglobin sensor based on external gold-coated photonic crystal fiber", Optics & Laser Technology 149, 107817 (2022). CrossRef A. A. Boiarski, J. R. Busch, B. S. Bhullar, R. W. Ridgway, V. E. Wood, "Integrated optic sensor with macro-flow cell", Proc. SPIE Integrated Optics and Microstructures 1793 (1993). CrossRef L. Cheng, S. Mao, Z. Li, Y. Han and H. Y. Fu, "Grating Couplers on Silicon Photonics: Design Principles, Emerging Trends and Practical Issues", Micromachines 11, 666 (2020). CrossRef P. Struk, "Design of an Integrated Optics Sensor Structure Based on Diamond Waveguide for Hemoglobin Property Detection", Materials 12, 175 (2019). CrossRef P. Struk, "Numerical analysis of integrated photonics structures for hemoglobin sensor application", Phot. Lett. Poland 12, 2 (2020). CrossRef P.V. Lambeck, "Integrated optical sensors for the chemical domain", Meas. Sci. Technol. 17, (2006). CrossRef W. Lukosz, "Integrated optical chemical and direct biochemical sensors", Sens. Actuators B Chem 29 (1995). CrossRef P. Struk, T. Pustelny, K. Gołaszewska,E. Kaminska, M.A. Borysiewicz, M. Ekielski, A. Piotrowska, "Hybrid photonics structures with grating and prism couplers based on ZnO waveguides", Opto-Electron. Rev. 21, (2013). CrossRef P. Struk, "Design of an integrated optics sensor structure for hemoglobin property detection", Proc. SPIE 11204, (2019). CrossRef OptiFDTD Technical Background and Tutorials - Finite Difference Time Domain Photonics Simulation Software, Optiwave Systems Inc. (2008). DirectLink K. Yee, "Cutoff Frequencies of Eccentric Waveguides", IEEE Transactions 14, 3 (1966). CrossRef
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Adalarasu, S. "Analysis on Characteristic Features of L-Mode Guided Wave in Tube Testing." Materials Science Forum 710 (January 2012): 581–87. http://dx.doi.org/10.4028/www.scientific.net/msf.710.581.
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Applications of long range ultrasonic testing are on cylindrical products(pipes and tubes) and planar products(plates and sheets).Guided wave testing using circumferential and longitudinal modes are getting more and more importance as there are huge requirements for testing pipes and tubes in power generators, Chemical plants, steam generators etc.. There will be infinite number of modes with charectestic propagation and wave structure. This propagation characteristic and wave structure plays a major role in deciding its suitability for use in specific application. It is highly essential to use mode control and to understand the generated modes and its characteristics based on which only testing adequacy can be evaluated. In this paper the characteristic features of L-mode generated using a source design parameter for tube testing are explained. The dispersion characteristic of L-mode are discussed using constructed Dispersion Curves, phase and group velocity, its multiple defect detection capability, pulse shape and amplitude dynamics with propagation range and inclination. The details of controlled experiment conducted and the observations are discussed. The derived inferences are explained based on the applicable particle displacement equations and dispersion characteristic equations.
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Chen, Zhe, Lian He Dong, Yan Jun Sun, Yan Bing Leng, Zhen Fang Ma, and Li Wang. "Study on the Fabrication of RPAS Micro-Lens Array for CCD Integration." Key Engineering Materials 552 (May 2013): 174–79. http://dx.doi.org/10.4028/www.scientific.net/kem.552.174.
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The micro-lens array for CCD systems can enhance the utilization efficiency of light energy, then improve its detection sensitivity. This paper firstly researches on the principle of micro-lens array for CCD integration, the lens changing refractive index theory and the mechanism of ionic exchange on glass materials. Then, with reasonable design of the mask and optimization the ionic exchange process parameters, the paper finally produces the Rectangular Plane Arched Shape (RPAS) micro-lens array on the plate glasswith the unit feature size being 22μm x 22μm. The results show that the RPAS micro-lens array’s fill factors could be achieved 93%, and the spectral sensitivity can be improved by 0.3 times. The mask plays a decisive role in micro-lens which is manufactured by ionic exchanged method. The reasonable selection of the mask parameter can eliminate the void that in the circular aperture planar micro-lens array, and enhance the fill factor; in the ionic exchange process, it is easy to obtain the large refractive index by using the ion-pair that have big differences. The ionic exchanged temperature below the glass softening temperature at about 20°C is appropriate.
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Nwosu, D. I., A. S. J. Swamidas, and J. Y. Guigne´. "Dynamic Response of Tubular T-Joints Under the Influence of Propagating Cracks." Journal of Offshore Mechanics and Arctic Engineering 118, no. 1 (February 1, 1996): 71–78. http://dx.doi.org/10.1115/1.2828804.
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This paper presents an analytical study on the vibration response of tubular T-joints for detecting the existence of cracks along their intersections. The ABAQUS finite element program was utilized for carrying out the analysis. Frequency response functions were obtained for a joint with and without cracks. The joint was modeled with 8-node degenerate shell elements having 5 degrees of freedom per node. Line spring elements were used to model the crack. The exact crack configuration (semielliptical shape, Fig. 5(b)), as observed from numerous experimental fatigue crack investigations at the critical location, has been achieved through a mapping function, that allows a crack in a planar element to be mapped on to the tube surface. The natural frequency changes with respect to crack depth show little changes, being 4.82 percent for a 83-percent crack depth for the first mode. On the other hand, significant changes have been observed for bending moment and curvature as a function of crack depth. For an 83-percent chord thickness crack, a 97-percent change in bending moment at points around the crack vicinity, and 34.15 to 78 percent change in bending moments, for those locations far away from the crack location, have been observed. Natural frequency change should be combined with other modal parameters such as “bending moment (or bending strain)” and “curvature” changes for crack detection. The presence of the crack can be detected at locations far away from the crack location using such sensors as strain gages.
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Lambrecht, Armin, Carsten Bolwien, Jochen Erb, Hendrik Fuhr, and Gerd Sulz. "Cylindrical IR-ATR Sensors for Process Analytics." Sensors 20, no. 10 (May 21, 2020): 2917. http://dx.doi.org/10.3390/s20102917.
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Infrared attenuated total reflection (ATR) spectroscopy is a common laboratory technique for the analysis of highly absorbing liquids and solids. However, in a process environment, maintaining a sufficient sample exchange and cleaning of the sensitive surface of the element is a crucial issue. An important industrial application is the measurement of isocyanate concentrations. Isocyanates are necessary for the fabrication of polyurethane materials and are among the chemicals with the highest production volume worldwide. For process applications, narrowband photometers or MEMS spectrometers are more appropriate than the use of bulky FTIR instruments frequently encountered in a laboratory environment. Toluene diisocyanate (TDI) and hexamethylene diisocyanate (HDI) concentrations are measured with a planar ATR photometer setup. Using a miniature Fabry–Perot interferometer (FPI), trace concentrations below 100 ppm (m/m) are detected. By employing an ATR element of the cylindrical shape, sensors can be realized with a smooth surface ideally suited for an automatic cleaning system in a process environment. A laboratory setup with sapphire tubes as ATR elements for incorporation in a liquid flow system is described. Reflection and transmission configurations were investigated. Measurements with acetonitrile as a less toxic substitute showed that with cylindrical ATR sensors’ detection limits for isocyanate concentrations below 100 ppm (m/m) are feasible.
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Kasprian, Gregor J., Michael J. Paldino, Amy R. Mehollin-Ray, Anil Shetty, Jennifer L. Williams, Wesley Lee, and Chris I. Cassady. "Prenatal Imaging of Occipital Encephaloceles." Fetal Diagnosis and Therapy 37, no. 3 (October 29, 2014): 241–48. http://dx.doi.org/10.1159/000366159.
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Introduction: This retrospective study aims to describe systematically the fetal cerebral MR morphology in cases with occipital meningoencephaloceles using standard and advanced fetal MRI techniques. Material and Methods: The 1.5-tesla MR examinations (T1- and T2-weighted imaging, echo planar imaging, EPI, diffusion-weighted imaging, DWI) of 14 fetuses with occipital/parietal meningoencephaloceles were retrospectively analyzed for the classification of anatomic characteristics. A diffusion tensor sequence was performed in 5 cases. Results: In 9/14 cases the occipital lobes were entirely or partially included in the encephalocele sac. Typical features of Chiari III malformation were seen in 6/14 cases. The displaced brain appeared grossly disorganized in 6/14. The brainstem displayed abnormal ‘kinking'/rotation (3/14), a z-shape (1/14) and/or a molar tooth-like configuration of the midbrain (3/14). Tractography revealed the presence and position of sensorimotor tracts in 5/5 and the corpus callosum in 3/5. DWI was helpful in the identification of a displaced brain (in 8/9). EPI visualized the anatomy of draining cerebral veins in 7/9 cases. Clinical (9/14) and MRI (7/14) follow-up data are presented. Discussion: Encephaloceles show a wide range of morphological heterogeneity. Fetal MRI serves as an accurate tool in the visualization of brainstem, white matter pathway and cerebral venous involvement and facilitates the detection of specific underlying syndromes such as ciliopathies.
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Herráez, Borja Javier, and Eduardo Vendrell. "Segmentación de mallas 3d de edificios históricos para levantamiento arquitectónico." Virtual Archaeology Review 9, no. 18 (January 10, 2018): 66. http://dx.doi.org/10.4995/var.2018.5858.
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<p>Advances in three-dimensional (3D) acquisition systems have introduced this technology to more fields of study, such as archaeology or architecture. In the architectural field, scanning a building is one of the first possible steps from which a 3D model can be obtained and can be later used for visualisation and/or feature analysis, thanks to computer-based pattern recognition tools. The automation of these tools allows for temporal savings and has become a strong aid for professionals, so that more and more methods are developed with this objective. In this article, a method for 3D mesh segmentation focused on the representation of historic buildings is proposed. This type of buildings is characterised by having singularities and features in façades, such as doors or windows. The main objective is to recognise these features, understanding them as those parts of the model that differ from the main structure of the building. The idea is to use a recognition algorithm for planar faces that allows users to create a graph showing the connectivity between them, therefore allowing the reflection of the shape of the 3Dmodel. At a later step, this graph is matched against some pre-defined graphs that represent the patterns to look for. Each coincidence between both graphs indicate the position of one of the characteristics sought. The developed method has proved to be effective for feature detection and suitable for inclusion in architectural surveying applications.</p>
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Grzonkowska, Magdalena, Mariusz Baumgart, Mateusz Badura, Marcin Wiśniewski, and Michał Szpinda. "Quantitative anatomy of the fused ossification center of the occipital squama in the human fetus." PLOS ONE 16, no. 2 (February 23, 2021): e0247601. http://dx.doi.org/10.1371/journal.pone.0247601.
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CT-based quantitative analysis of any ossification center in the cranium has not previously been carried out due to the limited availability of human fetal material. Detailed morphometric data on the development of ossification centers in the human fetus may be useful in the early detection of congenital defects. Ossification disorders in the cranium are associated with either a delayed development of ossification centers or their mineralization. These aberrations may result in the formation of accessory skull bones that differ in shape and size, and the incidence of which may be misdiagnosed as, e.g., skull fractures. The study material comprised 37 human fetuses of both sexes (16♂, 21♀) aged 18–30 weeks. Using CT, digital image analysis software, 3D reconstruction and statistical methods, the linear, planar and spatial dimensions of the occipital squama ossification center were measured. The morphometric characteristics of the fused ossification center of the occipital squama show no right—left differences. In relation to gestational age, the ossification center of the occipital squama grows linearly in its right and left vertical diameters, logarithmically in its transverse diameters of both the interparietal and supraoccipital parts and projection surface area, and according to a quadratic function in its volume. The obtained numerical findings of the occipital squama ossification center may be considered age-specific references of relevance in both the estimation of gestational age and the diagnostic process of congenital defects.
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Paula, Ialis C., Fatima N. S. Medeiros, Francisco N. Bezerra, and Daniela M. Ushizima. "Multiscale Corner Detection in Planar Shapes." Journal of Mathematical Imaging and Vision 45, no. 3 (July 3, 2012): 251–63. http://dx.doi.org/10.1007/s10851-012-0365-8.
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Pulina, Silvia, Elena Stanca, Antonella Luglié, Cecilia Teodora Satta, and Bachisio Mario Padedda. "Phytoplankton cell geometric shapes along Mediterranean seasonal environmental variability in natural and artificial lakes." Journal of Plankton Research 44, no. 2 (February 21, 2022): 208–23. http://dx.doi.org/10.1093/plankt/fbac005.
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Abstract In this work, we grouped phytoplankton species according to their cell geometric shape for the first time in lake ecosystems. Field multiannual data were analyzed in order to understand the phytoplankton cell geometric shape distribution along the seasonal environmental variability in two Mediterranean lakes, a shallow natural lake and a deeper artificial lake. We characterized seasonally each lake on the basis of dominant phytoplankton cell geometric shapes, detecting the following common highlights comparing the two ecosystems: a complex and globular geometric shape (Cone + Half Sphere) with high mean volume and low mean surface-to-volume ratio in winter (at the deepest mixing layer); a variety of geometric shapes in spring (at the lowest nutrient concentrations), with a relevant contribution of simple and compact geometric shapes (Sphere and Cube) with low mean volume and high mean surface-to-volume ratio; a simple and elongated geometric shape (Cylinder) in summer (at thermal stratification conditions); a variety of geometric shapes in autumn (at intermediate environmental conditions), when the geometric shapes detected were at similar size. We provide new insights on how phytoplankton cell geometric shapes with similar and different sizes relate to the seasonal environmental variations in lake ecosystems, a topic relatively neglected in literature.
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Polewski, P., W. Yao, and L. Fang. "VERTICAL ORIENTATION CORRECTION OF UAV IMAGE-BASED POINT CLOUDS USING STATISTICAL MODELING OF GABLE ROOF GEOMETRY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 4, 2019): 519–23. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-519-2019.
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<p><strong>Abstract.</strong> Coregistration of point clouds obtained from various sensors is an important part of workflows for automatic building reconstruction from remote sensing data. Many approaches assume a common Z axis between the coordinate systems, and perform coregistration in 2D. While this assumption is usually valid for laser scanning (LS) data, for photogrammetric point clouds the Z axis is in general different from the world Z axis, and requires correction e.g. by manually measured ground control points (GCP). In this paper, we propose a fully automatic, GCP-free procedure for finding the world Z axis in rural areas, based on the relationships of planar surfaces in building gable roofs. Instead of performing direct gable line detection, we derive these lines as theoretical intersections between adjacent roof planes from 3D shape fitting. Each gable roof then casts a vote for both the Z axis direction and sign based on roof convexity constraints, and the votes are aggregated through a non-parametric kernel density estimator model. Experiments on two real world UAV image-based point clouds show that the Z axis recovered by our method leads to high-accuracy planimetric coregistration, with a median distance over 89 as well as 149 matched linear feature pairs (respectively for dataset 1 and 2) lying below 1&thinsp;cm. Our results indicate that a high-quality vertical orientation can be achieved without using any GNSS or IMU hardware, which enables the use of low-cost UAV platforms for suburban and rural mapping tasks.</p>
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Razzell Hollis, Joseph, David Rheingold, Rohit Bhartia, and Luther W. Beegle. "An Optical Model for Quantitative Raman Microspectroscopy." Applied Spectroscopy 74, no. 6 (April 1, 2020): 684–700. http://dx.doi.org/10.1177/0003702819895299.
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Raman spectroscopy is an invaluable technique for identifying compounds by the unique pattern of their molecular vibrations and is capable of quantifying the individual concentrations of those compounds provided that certain parameters about the sample and instrument are known. We demonstrate the development of an optical model to describe the intensity distribution of incident laser photons as they pass through the sample volume, determine the limitations of that volume that may be detected by the spectrometer optics, and account for light absorption by molecules within the sample in order to predict the total Raman intensity that would be obtained from a given, uniform sample such as an aqueous solution. We show that the interplay between the shape and divergence of the laser beam, the position of the focal plane, and the dimensions of the spectrometer slit are essential to explaining experimentally observed trends in deep ultraviolet Raman intensities obtained from both planar and volumetric samples, including highly oriented pyrolytic graphite and binary mixtures of organic nucleotides. This model offers the capability to predict detection limits for organic compounds in different matrices based on the parameters of the spectrometer, and to define the upper/lower limits within which concentration can be reliably determined from Raman intensity for such samples. We discuss the potential to quantify more complex samples, including as solid phase mixtures of organics and minerals, that are investigated by the unique instrument parameters of the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) investigation on the upcoming Mars 2020 rover mission.
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Ye, Jiazhen, Yuki Todo, Zheng Tang, Bin Li, and Yu Zhang. "Artificial Visual System for Orientation Detection." Electronics 11, no. 4 (February 13, 2022): 568. http://dx.doi.org/10.3390/electronics11040568.
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The human visual system is one of the most important components of the nervous system, responsible for visual perception. The research on orientation detection, in which neurons of the visual cortex respond only to a line stimulus in a particular orientation, is an important driving force of computer vision and biological vision. However, the principle underlying orientation detection remains a mystery. In order to solve this mystery, we first propose a completely new mechanism that explains planar orientation detection in a quantitative manner. First, we assume that there are planar orientation-detective neurons which respond only to a particular planar orientation locally and that these neurons detect local planar orientation information based on nonlinear interactions that take place on the dendrites. Then, we propose an implementation of these local planar orientation-detective neurons based on their dendritic computations, use them to extract the local planar orientation information, and infer the global planar orientation information from the local planar orientation information. Furthermore, based on this mechanism, we propose an artificial visual system (AVS) for planar orientation detection and other visual information processing. In order to prove the effectiveness of our mechanism and the AVS, we conducted a series of experiments on rectangular images which included rectangles of various sizes, shapes and positions. Computer simulations show that the mechanism can perfectly perform planar orientation detection regardless of their sizes, shapes and positions in all experiments. Furthermore, we compared the performance of both AVS and a traditional convolution neural network (CNN) on planar orientation detection and found that AVS completely outperformed CNN in planar orientation detection in terms of identification accuracy, noise resistance, computation and learning cost, hardware implementation and reasonability.
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Cózar, J. R., N. Guil, and E. L. Zapata. "Detection of arbitrary planar shapes with 3D pose." Image and Vision Computing 19, no. 14 (December 2001): 1057–70. http://dx.doi.org/10.1016/s0262-8856(01)00066-x.
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Guerrero-Turrubiates, Jose de Jesus, Ivan Cruz-Aceves, Sergio Ledesma, Juan Manuel Sierra-Hernandez, Jonas Velasco, Juan Gabriel Avina-Cervantes, Maria Susana Avila-Garcia, Horacio Rostro-Gonzalez, and Roberto Rojas-Laguna. "Fast Parabola Detection Using Estimation of Distribution Algorithms." Computational and Mathematical Methods in Medicine 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/6494390.
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This paper presents a new method based on Estimation of Distribution Algorithms (EDAs) to detect parabolic shapes in synthetic and medical images. The method computes a virtual parabola using three random boundary pixels to calculate the constant values of the generic parabola equation. The resulting parabola is evaluated by matching it with the parabolic shape in the input image by using the Hadamard product as fitness function. This proposed method is evaluated in terms of computational time and compared with two implementations of the generalized Hough transform and RANSAC method for parabola detection. Experimental results show that the proposed method outperforms the comparative methods in terms of execution time about93.61%on synthetic images and89%on retinal fundus and human plantar arch images. In addition, experimental results have also shown that the proposed method can be highly suitable for different medical applications.
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Moëll, Mattias K., and Minoru Fujita. "FOURIER TRANSFORM METHODS IN IMAGE ANALYSIS OF COMPRESSION WOOD AT THE CELLULAR LEVEL." IAWA Journal 25, no. 3 (2004): 311–24. http://dx.doi.org/10.1163/22941932-90000368.
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Compression wood affects the overall quality of construction timber and paper quality. We have investigated the microscopic features of lumen shape and tracheid shape for compression wood studies and detection in softwoods. In this paper, we describe a method for directly analyzing tracheid and lumen shape over an entire image. The method uses the Fast Fourier Transform (FFT) and reduces the two-dimensional image data to one-dimensional data, from which lumen and tracheid shape can be evaluated. We illustrate the method by comparison of compression wood images to normal wood images. The results of detecting severe compression wood were successful, while the detection of weak compression wood was not satisfactory.
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Tiang, S. S., M. S. Hathal, N. S. Nik Anwar, M. F. Ain, and M. Z. Abdullah. "Development of a Compact Wide-Slot Antenna for Early Stage Breast Cancer Detection Featuring Circular Array Full-View Geometry." International Journal of Antennas and Propagation 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/309321.
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A novel planar type antenna printed on a high permittivity Rogers’ substrate is proposed for early stage microwave breast cancer detection. The design is based on a p-shaped wide-slot structure with50 Ωmicrostrip feeding circuit to eliminate losses of transmission. The design parameters are optimized resulting in a good reflection coefficient at −10 dB from 4.5 to 10.9 GHz. Imaging result using inhomogeneous breast phantom indicates that the proposed antenna is capable of detecting a 5 mm size cancerous tumor embedded inside the fibroglandular region with dielectric contrast between the target and the surrounding materials ranging from 1.7 : 1 to 3.6 : 1.
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Deraedt, Q., L. Marcélis, F. Loiseau, and B. Elias. "Towards mismatched DNA photoprobes and photoreagents: “elbow-shaped” Ru(ii) complexes." Inorganic Chemistry Frontiers 4, no. 1 (2017): 91–103. http://dx.doi.org/10.1039/c6qi00223d.
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Due to their potentially harmful consequences, the detection of mismatched DNA is a subject of high interest. In order to probe these DNA mismatches, we report new Ru(ii) complexes, bearing “elbow-shaped” extended planar ligands based on an acridine or a phenazine core.
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Westfechtel, Thomas, Kazunori Ohno, Bärbel Mertsching, Ryunosuke Hamada, Daniel Nickchen, Shotaro Kojima, and Satoshi Tadokoro. "Robust stairway-detection and localization method for mobile robots using a graph-based model and competing initializations." International Journal of Robotics Research 37, no. 12 (September 12, 2018): 1463–83. http://dx.doi.org/10.1177/0278364918798039.
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One of the major challenges for mobile robots in human-shaped environments is navigating stairways. This study presents a method for accurately detecting, localizing, and estimating the characteristics of stairways using point cloud data. The main challenge is the wide variety of different structures and shapes of stairways. This challenge is often aggravated by an unfavorable position of the sensor, which leaves large parts of the stairway occluded. This can be further aggravated by sparse point data. We overcome these difficulties by introducing a three-dimensional graph-based stairway-detection method combined with competing initializations. The stairway graph characterizes the general structural design of stairways in a generic way that can be used to describe a large variety of different stairways. By using multiple ways to initialize the graph, we can robustly detect stairways even if parts of the stairway are occluded. Furthermore, by letting the initializations compete against each other, we find the best initialization that accurately describes the measured stairway. The detection algorithm utilizes a plane-based approach. We also investigate different planar segmentation algorithms and experimentally compare them in an application-orientated manner. Our system accurately detects and estimates the stairway parameters with an average error of only [Formula: see text] for a variety of stairways including ascending, descending, and spiral stairways. Our method works robustly with different depth sensors for either small- or large-scale environments and for dense and sparse point cloud data. Despite this generality, our system’s accuracy is higher than most state-of-the-art stairway-detection methods.
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Li, G. X., and Y. F. Li. "Defect Detection Study of Fabric Based on Gabor Filter Algorithm." Materials Science Forum 697-698 (September 2011): 491–94. http://dx.doi.org/10.4028/www.scientific.net/msf.697-698.491.
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This thesis exploits a multichannel Gabor filters detection algorithm. Analysis filtering images from different orientations and scales, then fuses the multichannel data. Finally, a threshold iterative algorithm and mathematical morphology post-processing is used to achieve the fabric defect detection. The experiment selects five types of fabric defect image. Experimental results suggest that this algorithm can effectively identify blob-shaped, linear and planar defect and has well real-time character.
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Fisher, K. A., S. Whitfield, R. E. Thomson, K. Yanagimoto, M. Gustafsson, and J. Clarke. "Scanning tunneling microscopy of planar biomembranes." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 14–15. http://dx.doi.org/10.1017/s0424820100152045.
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The scanning tunneling microscope (STM) is capable of imaging conductive surfaces at atomic resolution. When STMs are used to image biological samples, however, STM resolution is limited to nanometer levels whether samples are hydrated, air-dried, or metal-coated. Lateral resolution is poor due to the nature of biological macromolecules (large Image aspect ratios) as well as to STM tip effects (shape, multiple tips, and tip/sample Interactions). If samples are adsorbed to highly-oriented pyrolytic graphite (HOPG) surfaces and scanned in the topographic (constant current) mode, vertical resolution is also uncertain due to contamination-mediated surface deformation artifacts. Nevertheless, because the STM is capable of detecting sub-Ångstrom displacements in z (e.g. to 0.02 Å in UHV), we have examined the feasibility of using the STM to determine the thickness of planar membranes attached to glass and mica surfaces. Planar membrane monolayers also uniquely provide the opportunity to correlate biochemical and TEM information with STM topographic images.
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Sato, Yoshinobu, and Shinichi Tamura. "Detecting Planar and Curved Symmetries of 3D Shapes from a Range Image." Computer Vision and Image Understanding 64, no. 1 (July 1996): 175–87. http://dx.doi.org/10.1006/cviu.1996.0052.
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Rosero-Montalvo, Paul D., Edison A. Fuentes-Hernández, Manuel E. Morocho-Cayamcela, Luz M. Sierra-Martínez, and Diego H. Peluffo-Ordóñez. "Addressing the Data Acquisition Paradigm in the Early Detection of Pediatric Foot Deformities." Sensors 21, no. 13 (June 28, 2021): 4422. http://dx.doi.org/10.3390/s21134422.
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The analysis of plantar pressure through podometry has allowed analyzing and detecting different types of disorders and treatments in child patients. Early detection of an inadequate distribution of the patient’s weight can prevent serious injuries to the knees and lower spine. In this paper, an embedded system capable of detecting the presence of normal, flat, or arched footprints using resistive pressure sensors was proposed. For this purpose, both hardware- and software-related criteria were studied for an improved data acquisition through signal coupling and filtering processes. Subsequently, learning algorithms allowed us to estimate the type of footprint biomechanics in preschool and school children volunteers. As a result, the proposed algorithm achieved an overall classification accuracy of 97.2%. A flat feet share of 60% was encountered in a sample of 1000 preschool children. Similarly, flat feet were observed in 52% of a sample of 600 school children.