Pair Of Parallel Lines Research Articles

Improved relative gain in Nd3+doped GeO2-PbO glass with double waveguides irradiated by femtosecond laser micromachining and decorated with Au nanoparticles

The paper explores the effects of Au nanoparticle (NP) islands deposited by sputtering technique on the surface of Nd3+-doped GeO2-PbO glasses, with double-line waveguides, produced via femtosecond laser processing for photonics. A Ti:sapphire femtosecond laser operating at 800 nm was employed to inscribe the waveguides directly into the glass, 0.7 mm beneath the surface. These waveguides were structured as pairs of parallel lines separated 10 μm. Additional procedures were undertaken to position the waveguides on the glass surface where Au NPs were deposited. Refractive index change of 10−3 at 632 nm was observed in both horizontal and vertical directions. Similar results for the beam quality factors (Mx2 and My2) at 632 nm and 1064 nm indicated x, y-symmetrical guiding. Photoluminescence and relative gain growth were observed due to Au NP islands. The relative gain reached 3.0 dB/cm representing an increase of approximately 450 % when compared to samples without the Au NP islands, and was attributed to the local field growth in their vicinities. This study highlights the potential to change Nd3+-doped GeO2-PbO glasses optical properties with Au nanoparticle islands, opening up new and promising prospects for photonics and 1064 nm optical amplifiers.

Bag Boundaries for Quasispinor Confinement Within Nanolanes on a Graphene Sheet

AbstractThe problem of bag boundary conditions within a field‐theoretic approach is revisited to study confinement of massless Dirac quasispinors in monolayer graphene. While no‐flux bag boundaries have previously been used to model lattice termination sites in graphene nanoribbons, a generalized setting is considered in which the confining boundaries are envisaged as arbitrary straight lines drawn across a graphene sheet and the quasispinor currents are allowed to partially permeate (leak) through such boundaries. Specifically focus is on rectangular nanolanes defined as areas confined between a pair of parallel lines at arbitrary separation on an unbounded lattice. It is shown that such nanolanes exhibit a considerable range of bandgap tunability depending on their widths and armchair, zigzag, or intermediate orientation. The case of nanoribbons can be derived as a special limit from the nanolane model. In this case, certain inconsistencies are clarified in previous implementations of no‐flux bag boundaries and show that the continuum approach reproduces the tight‐binding bandgaps accurately (within just a few percent in relative deviation) even as the nanoribbon width is decreased to just a couple of lattice spacings. This accentuates the proper use of boundary conditions when field‐theoretic approaches are applied to graphene systems.

Effect of Silver Nanoparticles on the Optical Properties of Double Line Waveguides Written by fs Laser in Nd3+-Doped GeO2-PbO Glasses

Nd3+-doped GeO2-PbO glass with silver (Ag) nanoparticles (NPs) are produced with double line waveguides through fs laser processing for photonic applications. A Ti:sapphire fs laser at 800 nm was used to write the waveguides directly into the glass 0.7 mm beneath the surface. This platform is based on pairs of parallel lines with spacing of 10 µm, each pair being formed by two identical written lines but in two different configurations of 4 or 8 separately processed lines, which are coincident. The results of optical microscopy, absorbance measurements, refractive index change, beam quality factor (at 632 and 1064 nm), photoluminescence, propagation losses, and relative gain at 1064 nm are presented. The structural changes in the glass due to the presence of Ag NPs were investigated by Raman spectroscopy. At 632 and 1064 nm, x,y-symmetrical guiding was observed, and for both kinds of overlapping pulses, a refractive index alteration of 10-3 was found in both directions. Photoluminescence growth of ~47% at 1064 nm was observed due to the plasmonic effect of Ag NPs. In dual waveguides containing Ag NPs, the relative gain obtained increased by 40% and 30% for four and eight overlapping lines, respectively, at 600 mW of 808 nm pump power, when compared to waveguides without those metallic NPs. We highlight the resultant positive internal gains of 5.11 and 7.12 dB/cm that showed a growth of ~40% and ~30%, respectively, with respect to the samples without Ag NPs. The increase in photoluminescence and relative gain were related to the local field growth produced by Ag NPs. The present results show that the addition of Ag NPs impacts positively on the optical performance at 1064 nm of double line waveguides processed by fs laser writing in Nd3+-doped GeO2-PbO glass, opening news perspectives for photonics.

SPLP: A Certifiably Globally Optimal Solution to the Relative Pose Estimation Problem Using Points and Line Pairs

Estimating the relative pose between two calibrated views with 2D-to-2D correspondences is a fundamental problem in computer vision and 2D perception. In this paper, we present the first certifiably globally optimal solver that can simultaneously incorporate both points and lines as the non-minimal 2D-to-2D correspondences for this problem. Our first contribution is to derive a generalized polynomial-based objective function based on the geometric constraints of orthogonal and parallel line pairs. Built upon it, our second contribution is to reformulate the relative pose estimation problem as a constrained global optimization problem with a unified representation of both point and line pair correspondences. Our third contribution lies in relaxing this non-convex optimization problem to a convex Semi-Definite Program (SDP) using Sum of Squares (SOS) relaxations so as to solve it via Gloptipoly 3 with a reliable guarantee of global optimality. In both synthetic and real experiments, we show that adopting line pairs as supplementary correspondences can greatly improve estimation accuracy, especially in the point-sparse situations, and that our solver, named SPLP (SOS-Point-and-Line-Pair), can outperform other state-of-the-art solvers.

Microstrip sensor and methodology for the determination of complex anisotropic permittivity using perturbation techniques

In this work, a sensor in microstrip technology and a methodology for measuring the real part and the imaginary part of the complex uniaxial permittivity of solid anisotropic samples are presented. The sensor is based on a pair of parallel lines coupled resonators and a cleft arranged in the coupling region which allows to hold the samples under test (SUTs). The proposed methodology relates the change in the even/odd resonance frequency with the real part of the permittivity in the vertical/horizontal direction, and the change in the Q factor of the even/odd mode with the imaginary part of the permittivity in the vertical/horizontal direction. The methodology was successfully verified with the characterization, at 2.43 GHz of anisotropic samples of printed PLA, Diclad 880, and RO4350B using the knowns materials: RT5870, PTFE and RO4003.

Two Separate Circles With Same-Radius: Projective Geometric Properties and Applicability in Camera Calibration

In the domain of computer vision, camera calibration is a key step in recovering the two-dimensional Euclidean structure. Circles are considered important image features similar to points, lines, and conics. In this paper, a novel linear calibration method is proposed using two separate same-radius (SSR) circles as the calibration pattern. We show that the distinct pair of dual circles encodes three lines, two of which are parallel to each other and perpendicular to the remaining line. When any two coplanar or parallel circles degenerate to SSR circles, a solution can be found to recover another pair of parallel lines based on the geometric properties of the SSR circles. Using the vanishing points obtained as the key helper for determining the imaged circular points and the orthogonal vanishing points, we deduce the constraints on the image of the absolute conic (IAC) and then employ it for complete camera calibration. Furthermore, a closed-form solution for the extrinsic parameters can be obtained based on the projective invariance of the conic dual to the circular points. Evaluations based on simulated and real data confirmed the effectiveness and feasibility of the proposed algorithms.

Detection of Vehicles in Multisensor Data via Multibranch Convolutional Neural Networks

Convolutional neural networks, or CNNs, raised the bar for most computer vision problems and have an increasing impact in remote sensing. However, since they usually contain multiple pooling layers, detection of exact borders of small objects at their original resolution remains yet a challenging topic. Additionally, efforts are being made to reduce the amount of training data. In this paper, we investigate the potential of fully convolutional neural networks (FCNs) for individual vehicle detection in combined elevation and optical data using relatively few training samples. By the proposed multibranch CNN, we combine object recognition within a deep learning framework with the object segmentation at a high resolution, for which two CNN branches are employed. Data fusion is accomplished with a pseudo-Siamese approach. The pixelwise classification likelihood, also referred to as heatmap, is harmoniously postprocessed by a vectorization module, which is based on the minimum bounding rectangle (MBR) extraction and allows for delineation of groups of vehicles. Two methods were developed in which MBRs are supported either by pairs of parallel lines or by region growing. Our approach allows efficient training with few training samples, while delivering high-quality detection results and good computational performance. In our detailed evaluation, we investigate the benefits of data fusion and compare our approach to other state-of-the-art networks. Different datasets were used, containing optical images and elevation data, derived either from airborne laser scanning or from photogrammetric reconstruction. The obtained results are very promising with F $_1$ scores up to 97%.

Importance of the Reactant-State Potentials of Chromium(V)–Oxo Complexes to Determine the Reactivity in Hydrogen-Atom Transfer Reactions

A new chromium(V)-oxo complex, [CrV(O)(6-COO--py-tacn)]2+ (1; 6-COO--py-tacn = 1-(6-carboxylato-2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), was synthesized and characterized to evaluate the reactivity of CrV(O) complexes in a hydrogen-atom transfer (HAT) reaction by comparing it with that of a previously reported CrV(O) complex, [CrV(O)(6-COO--tpa)]2+ (2; 6-COO--tpa = N, N-bis(2-pyridylmethyl)- N-(6-carboxylato-2-pyridylmethyl)amine). Definitive differences of these two CrV(O) complexes were observed in resonance Raman scatterings of the Cr-O bond (ν = 911 cm-1 for 1 and 951 cm-1 for 2) and the reduction potential (0.73 V vs SCE for 1 and 1.23 V for 2); this difference should be derived from that of the ligand bound at the trans position to the oxo ligand, a tertiary amino group in 1, and a pyridine nitrogen in 2. When we employed 9,10-dihydroanthracene as a substrate, the second-order rate constant ( k) of 1 was 4000 times smaller than that of 2. Plots of normalized k values for both complexes relative to bond dissociation energies (BDEs) of C-H bonds to be cleaved in several substrates showed a pair of parallel lines with slopes of -0.91 for 1 and -0.62 for 2, indicating that the HAT reactions by the two complexes proceed via almost the same transition states. Judging from estimated BDEs of CrIV(OH)/CrV(O) (85-87 kcal mol-1 for 1 and 92-94 kcal mol-1 for 2) and the activation barrier in the HAT reaction of DHA ( Ea = 7.9 kcal mol-1 for 1 and Ea = 4.8 kcal mol-1 for 2), the reactivity of CrV(O) complexes in HAT reactions depends on the energy level of the reactant state rather than the product state.

Geometric Features-Based Parking Slot Detection.

In this paper, we propose a parking slot markings detection method based on the geometric features of parking slots. The proposed system mainly consists of two steps, namely, separating line detection and parking slot entrance detection. First, in the separating line detection stage, we propose a line-clustering method based on the line segment detection (LSD) algorithm. Our detecting and line-clustering algorithm can detect the separating lines that contain a pair of parallel lines with a fixed distance in a bird’s eye view (BEV) image under diverse lighting and ground conditions. Consequently, parking slot candidates are generated by pairing the separating lines according to the width of the parking slots. In the parking slot entrance detection process, we propose a multiview fusion-based learning approach that can increase the number of training samples by performing a perspective transformation on the acquired BEV images. The proposed method was evaluated using 353 BEV images covering diverse parking slot markings. Experiments show that the proposed method can recognize typical perpendicular and parallel rectangular parking slots, and a precision of 97.4% and recall of 96.6% are achieved.

Locating Leaking Buried Pipes Based on Ground Microseismic Records in 3D Space

Pipelines are a safe energy-efficient mode of transporting fluids and gases. However, risks of pipe leaks still exist. Various pipe leak detection methods are in use; some traditional methods rely on acoustic receivers that must be located on the pipe, thereby restricting their implementation. Microseismic monitoring resolves this restriction because the ground rather than the pipe is monitored. However, microseismic monitoring has, thus far, only been applied using 2D methods for pipeline leak detection, and its accuracy is limited. To address this problem, a new 3D leak detection and location method for buried pipelines is proposed. First, using a 3D staggered-grid finite-difference method for acoustic equations, we simulated a microseismic wave field generated by a leaking pipeline, and recorded it with a ground surface geophone array. Then, a generalized cross-correlation technique was used to extract the time difference. Finally, the simulated annealing method was used to obtain the leak location in 3D space. Simulation and field data results show that the proposed method can locate the leakage point and has good anti-noise capability. Accurate 3D leak location requires at least two survey lines. Non-parallel survey lines can locate the approximate plane position of the leakage. Parallel line and orthogonal line pairs can be used to obtain the leak position accurately; the parallel line pair is the most accurate. The proposed method was concluded to be effective and accurate at detecting and locating leakages in buried pipeline networks.

A Complete Geometric Singular Characterization of the 6/6 Stewart Platform

This paper introduces the three-dimensional (3D) dual Kennedy theorem in statics, and demonstrates its application to characterize the singular configuration of the 6/6 Stewart Platform (6/6 SP). The proposed characterization is articulated as a simple geometric relation that is easy to apply and check. We find two lines that cross four of the six legs of the platform. Each one of these two lines has a parallel line that crosses the remaining two legs. Each pair of parallel lines defines a plane. The 6/6 SP is in a singular position if the intersection of these two planes is perpendicular to the common normal of the remaining two legs. The method developed for the singular characterization is also used for the analysis of the mobility and forces of the SP. Finally, the proposed method is compared to some known singular configurations, such as Hunt's and Fichter's singular configurations and the 3/6 Stewart Platform (3/6 SP) singularity. The relation between the reported characterizations of the 6/6 SP and other reported works is highlighted. Moreover, it is shown that the known 3/6 SP characterization is a special case of the results reported in the paper. Finally, a characterization of a platform that does not appear in the literature, 5/6 SP, is developed based on the new approach to demonstrate its utility.

A Universal Vacant Parking Slot Recognition System Using Sensors Mounted on Off-the-Shelf Vehicles.

An automatic parking system is an essential part of autonomous driving, and it starts by recognizing vacant parking spaces. This paper proposes a method that can recognize various types of parking slot markings in a variety of lighting conditions including daytime, nighttime, and underground. The proposed method can readily be commercialized since it uses only those sensors already mounted on off-the-shelf vehicles: an around-view monitor (AVM) system, ultrasonic sensors, and in-vehicle motion sensors. This method first detects separating lines by extracting parallel line pairs from AVM images. Parking slot candidates are generated by pairing separating lines based on the geometric constraints of the parking slot. These candidates are confirmed by recognizing their entrance positions using line and corner features and classifying their occupancies using ultrasonic sensors. For more reliable recognition, this method uses the separating lines and parking slots not only found in the current image but also found in previous images by tracking their positions using the in-vehicle motion-sensor-based vehicle odometry. The proposed method was quantitatively evaluated using a dataset obtained during the day, night, and underground, and it outperformed previous methods by showing a 95.24% recall and a 97.64% precision.

Rural Road Extraction from High-Resolution Remote Sensing Images Based on Geometric Feature Inference

Road information as a type of basic geographic information is very important for services such as city planning and traffic navigation, as such there is an urgent need for updating road information in a timely manner. Scholars have proposed various methods of extracting roads from remote sensing images, but most of them are not applicable to rural roads with diverse materials, large curvature changes, and a severe shelter problem. In view of these problems, we propose a road extraction method based on geometric feature inference. In this method, we make full use of the linear characteristics of roads, and construct a geometric knowledge base of rural roads using information on selected sample road segments. Based on the knowledge base, we identify the parallel line pairs in images, and further conduct grouping and connection instructed by knowledge reasoning, and finally obtain complete rural roads. The case study in Xiangtan City of China’s Hunan Province validates the performance of the proposed method.

Indoor Manhattan spatial layout recovery from monocular videos via line matching

We present an end-to-end system for structure and motion computation in a Manhattan layout from monocular videos. Unlike most SFM algorithms that rely on point feature matching, only line matches are considered in this work. This may be convenient in indoor environment characterized by extended textureless walls, where point features may be scarce. Our system relies on the notion of “characteristic lines”, which are invariants of two views of the same parallel line pairs on a surface of known orientation. Experiments with indoor video sequences demonstrate the robustness of the proposed system.

Automatic Parking Space Detection and Tracking for Underground and Indoor Environments

Even though many public parking lots are located underground and indoors, most existing automatic parking space detection and tracking methods have difficulty handling such scenarios due to severe illumination and complex obstacle conditions. To overcome this problem, this paper proposes a method that detects and tracks parking spaces in underground and indoor environments by fusing sensors already mounted on mass produced vehicles. The proposed detection method finds parking spaces based on a high-level fusion of two complementary approaches: parking slot marking-based and free space-based. Parking slots are detected by estimating parallel line pairs and free spaces are detected by recognizing the positions of parked vehicles as well as pillars. The proposed tracking method enhances the previous method by considering pillar information. Since pillars degrade parking slot tracking performance, this method estimates a pillar region and utilizes it to remove false edges and to estimate the amount of occlusion.

Automatic band detection on pulsed-field gel electrophoresis images

Automatic band detection is important for molecular subtyping on gel images. Automatic band detection has been conducted for many years, but only a few incomplete systems have been proposed. Here, we propose a completely automatic band detection system for pulsed-field gel electrophoresis (PFGE) images. The proposed approach mainly comprises lane segmentation and band extraction. In lane segmentation, we characterized the structural features and the spatial distribution of bands in PFGE images to fit pairs of parallel lines. In band extraction, a polynomial fitting method was used to remove the uneven background in a lane; we then used local gradient information to split the stuck bands and extract all bands in every lane. We compared the results with existing semiautomatic methods based on 20 varied PFGE images. The proposed method was shown to be superior to previous methods in most cases; moreover, the proposed approach is a completely automatic processing method.

Analysis of Gable-Roofed Building Signature in Multiaspect InSAR Data

The spatial resolution of state-of-the-art synthetic aperture radar sensors enables the structure analysis of urban areas. The appearance of buildings in magnitude images in settlements is dominated by the effects of the inherent oblique scene illumination. In urban residential districts, salient pairs of parallel lines of bright magnitude are often caused by direct reflection and double-bounce signal at gable-roofed buildings. In this letter, the magnitude and interferometric phase signature of gable-roofed buildings are discussed to extract reliable building features for reconstruction. The analysis contains signature changes by varying illumination and building geometry. The presented approach is aiming at the reconstruction of gable-roofed buildings by a knowledge-based analysis considering the discussed effects. The reconstruction results are assessed by using a high-resolution LIDAR surface model as ground truth.

Single view based pose estimation from circle or parallel lines

The paper is focused on the problem of pose estimation from a single view in minimum conditions that can be obtained from an image. Under the assumption of known intrinsic parameters, we propose and prove that the pose of the camera can be recovered uniquely in three situations: (i) the image of one circle with discriminable center; (ii) the image of one circle with preassigned world frame; (iii) the image of two general pairs of parallel lines. Compared with previous techniques, the proposed method does not need any 3D measurement of the circle or lines and the required conditions are easily satisfied in many scenarios. Extensive experiments on synthetic and real data are carried out to validate the proposed method.

New Pose-Detection Method for Self-Calibrated Cameras Based on Parallel Lines and Its Application in Visual Control System

In this paper, a new method is proposed to detect the pose of an object with two cameras. First, the intrinsic parameters of the cameras are self-calibrated with two pairs of parallel lines that are orthogonal. Then, the poses of the cameras relative to the parallel lines are deduced, and the rotational transformation between the two cameras is calculated. With the intrinsic parameters and the relative pose of the two cameras, a method is proposed to obtain the poses of a line, plane, and rigid object. Furthermore, a new visual-control method is developed using a pose detection rather than a three-dimensional reconstruction. Experiments are conducted to verify the effectiveness of the proposed method.

On the poisedness of Bojanov–Xu interpolation

In this paper, we consider the bivariate Hermite interpolation introduced by Bojanov and Xu [SIAM J. Numer. Anal. 39(5) (2002) 1780–1793]. The nodes of the interpolation with Π 2 k - δ , where δ = 0 or 1 , are the intersection points of 2 k + 1 distinct rays from the origin with a multiset of k + 1 - δ concentric circles. Parameters are the values and successive radial derivatives, whenever the corresponding circle is multiple. The poisedness of this interpolation was proved only for the set of equidistant rays [Bojanov and Xu, 2002] and its counterparts with other conic sections [Hakopian and Ismail, East J. Approx. 9 (2003) 251–267]. We show that the poisedness of this ( k + 1 - δ ) ( 2 k + 1 ) dimensional Hermite interpolation problem is equivalent to the poisedness of certain 2 k + 1 dimensional Lagrange interpolation problems. Then the poisedness of Bojanov–Xu interpolation for a wide family of sets of rays satisfying some simple conditions is established. Our results hold also with above circles replaced by ellipses, hyperbolas, and pairs of parallel lines. Next a conjecture [Hakopian and Ismail, J. Approx. Theory 116 (2002) 76–99] concerning a poisedness relation between the Bojanov–Xu interpolation, with set of rays symmetric about x -axis, and certain univariate lacunary interpolations is established. At the end the poisedness for a wide class of lacunary interpolations is obtained.