Points In Three-dimensional Space Research Articles

Investigation of Automotive LiDAR Vision in Rain from Material and Optical Perspectives.

With the emergence of autonomous functions in road vehicles, there has been increased use of Advanced Driver Assistance Systems comprising various sensors to perform automated tasks. Light Detection and Ranging (LiDAR) is one of the most important types of optical sensor, detecting the positions of obstacles by representing them as clusters of points in three-dimensional space. LiDAR performance degrades significantly when a vehicle is driving in the rain as raindrops adhere to the outer surface of the sensor assembly. Performance degradation behaviors include missing points and reduced reflectivity of the points. It was found that the extent of degradation is highly dependent on the interface material properties. This subsequently affects the shapes of the adherent droplets, causing different perturbations to the optical rays. A fundamental investigation is performed on the protective polycarbonate cover of a LiDAR assembly coated with four classes of material-hydrophilic, almost-hydrophobic, hydrophobic, and superhydrophobic. Water droplets are controllably dispensed onto the cover to quantify the signal alteration due to the different droplets of various sizes and shapes. To further understand the effects of droplet motion on LiDAR signals, sliding droplet conditions are simulated using numerical analysis. The results are validated with physical optical tests, using a 905 nm laser source and receiver to mimic the LiDAR detection mechanism. Comprehensive explanations of LiDAR performance degradation in rain are presented from both material and optical perspectives. These can aid component selection and the development of signal-enhancing strategies for the integration of LiDARs into vehicle designs to minimize the impact of rain.

Detection and Evaluation for High-Quality Cardiopulmonary Resuscitation Based on a Three-Dimensional Motion Capture System: A Feasibility Study.

High-quality cardiopulmonary resuscitation (CPR) and training are important for successful revival during out-of-hospital cardiac arrest (OHCA). However, existing training faces challenges in quantifying each aspect. This study aimed to explore the possibility of using a three-dimensional motion capture system to accurately and effectively assess CPR operations, particularly about the non-quantified arm postures, and analyze the relationship among them to guide students to improve their performance. We used a motion capture system (Mars series, Nokov, China) to collect compression data about five cycles, recording dynamic data of each marker point in three-dimensional space following time and calculating depth and arm angles. Most unstably deviated to some extent from the standard, especially for the untrained students. Five data sets for each parameter per individual all revealed statistically significant differences (p < 0.05). The correlation between Angle 1' and Angle 2' for trained (rs = 0.203, p < 0.05) and untrained students (rs = -0.581, p < 0.01) showed a difference. Their performance still needed improvement. When conducting assessments, we should focus on not only the overall performance but also each compression. This study provides a new perspective for quantifying compression parameters, and future efforts should continue to incorporate new parameters and analyze the relationship among them.

Методы кодирования информации на базе трехмерного параллелепипеда на уроках математики

Social informatization requires strong information security measures that would allow companies and individuals to protect their data. Courses in information security may solve this problem. However, methods of coding and encryption can be incorporated in the school curriculum as part of Mathematics and Computer Science. This article introduces an original reliable method of encoding to be integrated with the high school course of Mathematics. The authors used geometric methods of representing points in three-dimensional space bounded by a closed parallelepiped and elementary algebraic operations with matrices. The paper proposes flow and k-gram variants of the matrix method of text encoding and their program implementation in the Python programming language. The encoding methods require no special mathematical training, which makes them teachable to 9–11-graders. By mastering these methods, high-school students can increase their personal information security and develop an algorithmic style of thinking, as well as mathematical skills in general. The article contains some extramural tasks that consolidate practical skills of text coding. The academic and methodological materials make it possible to give the methods of coding and encryption while teaching Mathematics, as well as part of academic disciplines related to information security.

Integrating a UAV System Based on Pixhawk with a Laser Methane Mini Detector to Study Methane Emissions

This article describes the process of integrating one of the most commonly used laser methane detectors, the Laser Methane mini (LMm), and a multi-rotor unmanned aerial vehicle (UAV) based on the Pixhawk flight controller to create an unmanned aerial system designed to detect methane leakages from the air. The integration is performed via the LaserHub+, a newly developed device which receives data from the laser methane detector, decodes it and transmits it to the flight controller with the protocol used by the ArduPilot platform for laser rangefinders. The user receives a single data array from the UAV flight controller that contains both the values of the methane concentrations measured by the detector, and the co-ordinates of the corresponding measurement points in three-dimensional space. The transmission of data from the UAV is carried out in real time. It is shown in this project that the proposed technical solution (the LaserHub+) has clear advantages over not only similar serial commercial solutions (e.g., the SkyHub complex by SPH Engineering) but also experimental developments described in the scientific literature. The main reason is that LaserHub+ does not require a deep customization of the methane detector or the placement of additional complex devices on board the UAV. Tests using it were carried out in aerial gas surveys of a number of municipal solid waste disposal sites in Russia. The device has a low cost and is easy for the end user to assemble, connect to the UAV and set up. The authors believe that LaserHub+ can be recommended as a mass solution for aerial surveys of methane sources. Information is provided on the approval of LaserHub+ for aerial gas surveys of a number of Russian municipal waste disposal facilities.

A Novel Multi-Projection Correction Method Based on Binocular Vision

In order to improve the accuracy of multi-projection correction fusion, a multi-projection correction method based on binocular vision is proposed. To date, most of the existing methods are based on the single-camera mode, which may lose the depth information of the display wall and may not accurately obtain the details of the geometric structure of the display wall. The proposed method uses the depth information of a binocular camera to build a high-precision 3D display wall model; thus, there is no need to know the specific CAD size of the display wall in advance. Meanwhile, this method can be applied to display walls of any shape. By calibrating the binocular vision camera, the radial and eccentric aberration of the camera can be reduced. The projector projects the encoded structured light stripes, and the high-precision 3D structural information of the projection screen can be reconstructed according to the phase relationship after collecting the deformation stripes on the projection screen with the binocular camera. Thus, the screen-projector sub-pixel-level mapping relationship is established, and a high-precision geometric correction is achieved. In addition, by means of the one-to-one mapping relation between the phase information and the three-dimensional space points, accurate point cloud matching among multiple binocular phase sets could be established, so that such method can be applied to any quantity of projectors. The experimental results based on various special-shaped projection screens show that, comparing to the single-camera-based method, the proposed method improves the geometric correction accuracy of multi-projection stitching by more than 20%. This method also has many advantages, such as strong universality, high measurement accuracy, and rapid measurement speed, which indicate its wide application potential in many different fields.

Three-dimensionally reconfigurable focusing of laser by mechanically tunable metalens doublet with built-in holograms for alignment

Abstract Metalenses have potential to replace various bulky conventional optical elements with ultrathin nanostructure arrays. In particular, active metalenses with reconfigurable focusing capability have attracted considerable interest from the academic and industrial communities. However, their tuning range is currently restricted by limited material properties and fabrication difficulties. Here, a hybrid optical system capable of three-dimensional relocation of a focal spot is proposed and experimentally demonstrated. The system comprises a mechanically actuated passive metalens doublet that can be easily fabricated with commonly available materials and processes. An incident laser can be focused to a desired point in three-dimensional space simply by rotating two metalenses or changing their separation. In addition, exploiting the polarization-multiplexing capability of metasurfaces, a hologram is incorporated to the metalenses to guide rotational and positional alignment of two metasurfaces. The ease of fabrication and alignment provided by this approach could widen its application to many practical fields.

Optimization of vehicle structural parameters considering stability improvement

The main structural parameters that affect vehicle bifurcation characteristics and the safe basin are obtained, with the goal of improving the stability. First, the distribution of the system equilibrium points in three-dimensional space is studied, and the bifurcation characteristics of the front steering angles are obtained. Second, the front steering angle range corresponding to the bifurcation point (FSAR-BP) and the safe basin of the system (SBS) are determined and used as optimization objective functions. Considering the influence of the structural parameters on the FSAR-BP and SBS, a sensitivity analysis of the parameters is performed to establish their importance ranking in terms of their influence on the FSAR-BP and SBS. Third, a non-dominated sorting genetic algorithm II (NSGA-II) is utilized to optimize the parameters, and the competitive Pareto parameter optimization solution sets are obtained. Finally, the three solution sets with better comprehensive performance are selected for comparison with the pre-optimized set in the FSAR-BP and SBS. The results indicate that the optimized FSAR-BP increased by 218.81%, 237.83%, and 267.88%, and the optimized SBS increased by 207.52%, 197.06%, and 173.93%, respectively.

Fast Location of Table Grapes Picking Point Based on Infrared Tube

This study investigates the low mechanization level of grape picking, and the problems associated with the difficult location of grape picking points in three-dimensional space. A method for rapidly locating the picking points of table grapes based on an infrared tube was proposed in this paper. Firstly, the Otsu algorithm and the maximum connected domain were used to obtain the image of the target grape, which realized the fast recognition and segmentation of the target grape in two-dimensional space. Secondly, a location device for grape-picking points based on an infrared tube was designed, which resolved the technical problem related to the difficulty of locating picking points in three-dimensional space, and realized the accurate positioning of picking points for table grapes. Finally, the experimental results show that the proposed method can quickly and accurately locate the picking points of table grapes in three-dimensional space. The average running time of the proposed algorithm is 0.61 s, and the success rate of location identification is 90.0%. It provides a feasible scheme for the mechanized picking of table grapes.

P-BN48 Utilising spatial geometry to obtain the ideal needle mount for laparoscopic intracorporeal suturing

Abstract Background Intracorporeal suturing is an essential component of any advanced laparoscopic procedure like fundoplication, bypass surgery or common bile duct exploration. Obtaining the appropriate needle mount during suturing can be challenging. Spatial geometry defines points in three-dimensional space. Ergonomics in laparoscopic surgery identifies a manipulation angle of 60o to target as being optimal. This knowledge, in combination with the principles of light reflection can be used to understand needle orientation in laparoscopic suturing. Methods An experiment was designed on a laparoscopic trainer with three participants. Using the principles of spatial geometry and light reflection, four different points were identified on an angle chart and labelled for a right-hand dominant participant as; centre, right off-centre (5.5cm), right lateral (10 cm) and left off-centre (5.5cm). Each participant was instructed to mount the needle at the defined points using light reflection on the needle shaft as a reference guide. Three readings were taken for each position. Mounted angle was defined as the angle between the shaft of needle holder and long axis of the needle. This was measured using a special application and an average value determined for each position. Results The average values for the mounted angle measurements for each spatial position were: Centre(112o), Right off centre(101o), Right lateral (88.8o) and Left off centre (124.6o). Conclusions This study describes a novel and reproducible technique to obtain an ideal needle mount. For a needle mount greater than 100o either the centre position or the left off-centre position should be considered.

On Illumination Vector Quantities Due to Area Light Sources: Comparison of Two Calculation Approaches

ABSTRACT The concept of illumination vector quantities at a given point in three-dimensional space has been proposed since long time ago, but it is mostly described for scenes with point light sources. In real scenes with area light sources, numerical approximations are required to estimate the illumination vector quantities, which can be done by discretising the area into an array of point sources. Two different approaches are proposed in this study; Approach 1 is applicable in the design phase, where the positions of the source and receiver point are exactly known. Approach 2 is applicable during field measurement, based on the obtained cubic illuminances. This study aims to determine the required number of point source elements in the computation and to investigate the difference between both calculation approaches. The proposed concept is demonstrated using a scenario with horizontal, square source and a scenario with vertical, rectangular source, with various luminous intensity distribution patterns, by observing various illumination vector quantities. Grid sensitivity analyses suggest that the largest grid size satisfying the five-to-one approximation rule shall yield quantities that converge within no more than 5% to the final value. For a given size of area source, at a given distance, the differences of illumination vector quantities obtained from both calculation approaches are expected to be approximately the same, regardless the luminous intensity distribution. The estimation of cylindrical illuminance is generally more accurate than that of scalar illuminance.

Numerical Investigation of Effective Thermal Conductivity of Strut-Based Cellular Structures Designed by Spatial Voronoi Tessellation.

Porous materials possess light weight and excellent thermal insulation performance. For disordered porous structures, the number of seed points is an important design parameter which is closely related to the morphology and mean pore size of the structure. Based on the arrangement of points in three-dimensional space, seven kinds of structures were designed by spatial Voronoi tessellation in this paper. The effect of the number of seed points on effective thermal conductivity for Voronoi was studied. Numerical simulation was conducted to research the effects of structural porosity, filling material and structural orientation on the effective thermal conductivity and heat transfer characteristics. The results showed that the effective thermal conductivity is closely related to the porosity and the matrix material. Different number and arrangement of seed points make the structure have different anisotropic performance due to different thermal paths. In addition, required the least number of seed points was obtained for the designation of isotropic random Voronoi.

МЕТОДИКА РЕШЕНИЯ ОЛИМПИАДНОЙ ГЕОМЕТРИЧЕСКОЙ ЗАДАЧИ

The present work argues that the determination of a geometrical place of an image, equally-spaced from four incoincident points in three-dimensional space, is an important problem in the design and erection of modern architectural and engineering structures. The common issues that the problem is comprised of and essential steps of their resolution are identified. It is revealed that the essence of the problem is the contradiction between necessity of development of three-dimensional objects and two-dimensional ways of obtaining result. The purpose of the present research is to develop a way and a technique of the determination of a geometrical image, equally-spaced from four incoincident points in three-dimensional space. Objectives of the present publication are: 1.&nbsp;To complete the analysis of the developed solution of the Olympics geometrical problem of elevated complexity. 2.&nbsp;To develop a way and a technique of the graphic solution of an engineering geometrical problem of elevated complexity. The analysis of the obtained solution of the Olympics geometrical problem of elevated complexity is made. The following hypotheses are formulated: The hypothesis&nbsp;1. A geometrical place of a required image, equally-spaced from four incoincident points in three-dimensional space A, B, C, D, is point K, which is equally-spaced from set points A, B, C, D if it is the center of the sphere on which all four points A, B, C, and D, non-coincident in three-dimensional space, are located. The hypothesis&nbsp;2. Centre K of sphere with points A, B, C, D is located on the intersection of the middle perpendiculars set to all to all four flat sides of a pyramid, which base points A, B, C, D belong to this spherical surface. Each such middle perpendicular to a flat side of pyramid ABCD is also a geometrical place of points, equally-spaced from three corners of a corresponding side. The current research proves the validity of the hypothesis. The proposed way of the solution of the geometrical problem, consisting in graphic construction of the centers of flat sides of the pyramid, which tops settle down corners locate on sphere, construction of middle perpendiculars to each side through their centers and definitions of a point of intersection of these perpendiculars. On the basis of the proposed way, the methodology of the graphic solution of the engineering geometrical problem is developed. Keywords: point, geometrical place, the analysis, way, technique, algorithm, the complex drawing.

Алгоритмический комплекс для решения задач с квадриками с применением мнимых геометрических образов

The paper is devoted to the consideration of a number of issues related to the creation of an algorithmic complex designed to solve positional and metric problems with quadrics on a projection model . A feature of the complex is the active use of geometric schemes and algorithms involving imaginary geometric images. In the paper has been presented a detailed description of constructive geometric algorithms for constructing of conics, quadrics and associated geometric images in a system of constructive geometric modeling – Simplex. All the discussed algorithms are available for independent repetition by the reader. In the paper have been presented and implemented algorithms for constructing conic from a point, a polar, and three points; constructing conic from two pairs of complex conjugate points and one real point; determination of a point on a quadric’s surface; setting a quadric by nine points in three-dimensional space. A new alternative frame of the quadric has been considered, based on which have been solved problems of constructing a tangent and a normal to the quadric, finding an intersection line of an arbitrary plane with the quadric, and performing polar and inverse transformations with respect to the quadric. Have been proposed algorithms for constructing an autopolar tetrahedron with respect to the quadric, and for constructing a conic from an autopolar triangle and two points. Have been considered problems of determining a collinear transformation in three-dimensional space and control the quadric through it. The implementation of the algorithms considered in the paper allowed conclude that there is an urgent need to develop tools for modeling imaginary conics, without which the complex of solving problems with quadrics cannot be taken for the complete one.

PERFORMING 3D MEASUREMENTS IN A VR ENVIRONMENT

Abstract. In the context of this paper, a virtual reality application that allows each user to perform basic topographic processes on an already created 3D model inside a virtual environment was developed. Specifically, it is an application that allows the user to perform measurements of distances between two points in three-dimensional space and measurement and extraction of the three-dimensional coordinates of any point inside the virtual reality environment. Furthermore, the created application was evaluated in terms of its functionality, its usability and metric accuracy. Before the developing stage a research was done in order to determine which virtual reality system and which game engine is most suitable to use and finally the HTC Vive® virtual reality system and the Unreal Engine 4 game engine were used. Before all that, the concept of the virtual reality science was defined and also the virtual reality technologies in today's world were analyzed.

Piecewise Curve Fitting Based on Least Square Method in 3D Space

Least squares curve fitting is widely used in various neighborhoods, such as industry, agriculture, and economy. The method of piecewise curve fitting is used to deal with some experimental studies with large amounts of data. It can not only be used for plane space points, but also for three-dimensional space points. Firstly, this article introduces the principles of curve fitting and least squares. Secondly, it clarifies the steps based on least square fitting and gives examples of improvements made based on the principle of least square fitting functions by some scientists. Finally, the piecewise curve fitting in the three-dimensional space is obtained using the least squares piecewise curve fitting. It lays a certain theoretical foundation for drawing the laws between data in three-dimensional space.

Camera model and parameter calibration

Each camera has its own model and parameters. Accurate calibration of the camera’s model parameters can effectively prevent distortion effects and ensure image imaging. In this paper, the three-dimensional space points of the camera model are linked with the two-dimensional image points, and the in-plane distortion parameters of the camera are obtained by using the checkerboard calibration method, thereby distorting the image and restoring the image imaging effect.

3DRTE: 3D Rotation Embedding in Temporal Knowledge Graph

Temporal knowledge graph (TKG) embedding has received increasing attention in the academia. However, most existing methods are extensions of traditional translation models. Due to their intrinsic limitations, it is often difficult for such methods to effectively model essential characteristics of TKG, namely three basic relation patterns including symmetry/antisymmetry, inversion, and composition. In this paper, a new 3-Dimensional Rotation Temporal Embedding (3DRTE) method is proposed. Firstly, we selectively fuse temporal and relational features of fact triples by taking advantages of self-attention mechanism in processing sequential information. Then, entities are modelled as points in three-dimensional space, and the relations are interpreted as two isoclinic rotations between entities with Quaternion. Experimental results on several public datasets show that our method obtains state-of-the-art results.

Three-dimensional cellular automaton simulation of austenite grain growth of Fe-1C-1.5Cr alloy steel

A three-dimensional (3D) cellular automaton model describing the austenite grain growth process of Fe-1C-1.5Cr alloy steel is established. This model proposes a discrete representation of the three-dimensional grain boundary curvature, and calculates the 26 neighbor lattice points to the center lattice point in three-dimensional space. The strength of neighbor lattice point’s influence is determined by the distance from the center lattice point. The paper presents the calculation steps of the three-dimensional cellular automaton model and the calculation methods of key parameters such as grain boundary curvature and grain growth speed, and validates the model calculation results. The results show that the model established in this paper can well describe the austenite grain growth process of Fe-1C-1.5Cr alloy steel at different temperatures. The model can be used to study the grain growth process of Fe-1C-1.5Cr alloy steel under three-dimensional conditions.

Deep space exploration orbit design departing from circumlunar orbit of lunar base

A design method for a new kind of deep space mission which departs from a circumlunar orbit of the lunar base is presented in this paper. The difference between this kind of deep space mission and the traditional one is well analyzed. The method of patched conics is employed to divide the mission trajectory into four independent parts. The independent selenocentric segment is designed using a Lambert Problem based method, while the geocentric trajectory from a certain point in three-dimensional space to a fixed excess velocity vector is determined analytically. Then the combination of these segments is optimized via genetic algorithm by minimizing the total velocity increasement. Finally, typically numerical simulations are demonstrated to verify the effectiveness of the proposed method.

Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System

Volumetric display shows promising implications for healthcare related applications as an innovative technology that creates real three-dimensional (3D) image by illuminating points in three-dimensional space to generate volumetric images without image separation. We used eccentric photorefractometry to objectively study ocular performance in a practical environment by evaluating near work-induced refraction shift, accommodative microfluctuations, and pupil size for 38 young adults after viewing anaglyph, and volumetric 3D content for prolonged time. The results of our study demonstrate that participants who performed relative depth estimation task on volumetric 3D content were less likely to experience task-induced myopic refraction shift. For both 3D content types, we observed pupil constriction, that is possibly related to visual fatigue. For anaglyph 3D pupil constriction, onset was observed significantly sooner, compared to volumetric 3D. Overall, sustained work with 3D content, and small disparities or the fully eliminated possibility of accommodation-vergence conflict, not only minimizes near work-induced myopic shift, but also provide beneficial accommodation relaxation that was demonstrated in this study as hypermetropic shift for nearly half of participants.