Three-dimensional Image Space Research Articles

Computing Algorithm of Robot Distributed 3D Graphic Simulation System

In view of the shortcomings of current multi-robot path planning strategies, such as high path coupling, long total path, and long waiting time for collision avoidance, as well as the resulting problems of low system robustness and low robot utilization, the paper proposes Multi-robot path planning particle swarm algorithm based on distributed three-dimensional space-time graphics and motion decomposition. We first generate a dynamic temporary obstacle in the time dimension according to the existing path set and the current robot position, and expand it together with the static obstacle into a three-dimensional search graphics space. Secondly, in the three-dimensional image space, the total path movement time is divided into three parameters: movement time, turning time and staying time in place, and using the conditional depth-first search strategy to calculate all the matching parameters from the starting node to the target node the required path collection. The experimental results show that the path of distributed 3D graphics planning by our proposed particle swarm algorithm has the advantages of total length, less running time, system collision-free, and high robustness, which solves the problem of multi-robot systems completing continuous random tasks.

Novel nonlinear reconstruction method with grey-level quantisation units for electron tomography

We report a new computed tomography reconstruction method, named quantisation units reconstruction technique (QURT), applicable to electron and other fields of tomography. Conventional electron tomography methods such as filtered back projection, weighted back projection, simultaneous iterative reconstructed technique, etc. suffer from the ‘missing wedge’ problem due to the limited tilt-angle range. QURT demonstrates improvements to solve this problem by recovering a structural image blurred due to the missing wedge and substantially reconstructs the structure even if the number of projection images is small. QURT reconstructs a cross-section image by arranging grey-level quantisation units (QU pieces) in three-dimensional image space via unique discrete processing. Its viability is confirmed by model simulations and experimental results. An important difference from recently developed methods such as discrete algebraic reconstruction technique (DART), total variation regularisation—DART, and compressed sensing is that prior knowledge of the conditions regarding the specimen or the expected cross-section image is not necessary.

色彩词的文学性研究 - 沈从文小说为中心

This paper attempts to examine the role of color words in Shen Congwen"s literary works from the literary standpoint. Firstly, the use of color words is counted. Then, taking white words, red words and black words as examples, from the perspective of semantic extension, the presentation of literary theme, literary mood and literary atmosphere are carried out. Then, taking color rendering in literature as an example, it illustrates the important role and significance of color words in two-dimensional picture space. Finally, the presentation of literariness is not only reflected in the expansion of semantic connotation, the extension of imaginary pictures, but also in the display of three-dimensional image space. This is achieved in Shen Congwen"s works through the intervention of light, that is, the interaction of light and color. The color words exploit the space of literariness in Shen Congwen"s novels to the greatest extent. They not only enrich the connotation of text semantics, but also realize the presentation of literary pictures above the text through color and composition. Finally, through the harmonization and transformation of color and light, the image space of literature is created, and the three-dimensional presentation of literariness is realized.

Layered manufacturing for medical imaging data

Layered manufacturing techniques have been successfully employed to construct scanned objects from three-dimensional medical image data sets. The printed physical models are useful tools for anatomical exploration, surgical planning, teaching, and related medical applications. Before fabricating scanned objects, we have to first build watertight geometrical representations of the target objects from medical image data sets. Many algorithms had been developed to fulfill this duty. However, some of these methods require extra efforts to resolve ambiguity problems and to fix broken surfaces. Other methods cannot generate legitimate models for layered manufacturing. To alleviate these problems, this article presents a modeling procedure to efficiently create geometrical representations of objects from computerized tomography scan and magnetic resonance imaging data sets. The proposed procedure extracts the iso-surface of the target object from the input data set at the first step. Then it converts the iso-surface into a three-dimensional image and filters this three-dimensional image using morphological operators to remove dangling parts and noises. At the next step, a distance field is computed in the three-dimensional image space to approximate the surface of the target object. Then the proposed procedure smooths the distance field to soothe sharp corners and edges of the target object. Finally, a boundary representation is built from the distance field to model the target object. Compared with conventional modeling techniques, the proposed method possesses the following advantages: (1) it reduces human efforts involved in the geometrical modeling process. (2) It can construct both solid and hollow models for the target object, and wall thickness of the hollow models is adjustable. (3) The resultant boundary representation guarantees to form a watertight solid geometry, which is printable using three-dimensional printers. (4) The proposed procedure allows users to tune the precision of the geometrical model to compromise with the available computational resources.

Sparse Borehole Radar Array Imaging of Orebodies in Three Dimensions

Broadband very high frequency (VHF) borehole radars (BHR) can be used as tactical tools to map orebodies, faults and marker horizons; to identify hazards well in advance of mining and to optimize mine development. In principle, radar profiles and cross-hole scans from fanned arrays of boreholes can be used to synthesize three-dimensional images interferometrically if: borehole trajectories are accurately known; signal-to-noise ratios are adequate; the spatial sampling rate is sufficient; target echoes are well correlated, and if the target space is sufficiently uncluttered to limit the formation of mirages during reconstruction. However, automatic methods of projecting data into three-dimensional image space make stringent demands upon rock homogeneity, translucence and the accuracy of borehole trajectories. These demands can be relaxed by reconstructing objects from parts of geologically plausible 3D primitives such as cylinders, planes and spheres. In this paper we show that a number of useful primitives derive from a common element—a hoop (with semi-circular shell cross-section) of finite radius, centered on the borehole. The parameters defining the hoop’s plane, radius and thickness can be recovered sequentially from borehole radar data to determine the shape of curved 3D reflectors. We show how kinematic mapping can be applied in practice by using data acquired in a Western Australian mine. This survey was shot using [Formula: see text] borehole radars from a fanned array of [Formula: see text] long boreholes. The holes were drilled from a single station at relative angles of [Formula: see text]. Both cross-hole transmission and single-hole reflection surveys were performed. Reflection ranges of [Formula: see text] were achieved in the rocks hosting the deposit. Echo patterns correlated by using kinematic primitives were used to establish the geometry of an arched interface that was located approximately [Formula: see text] above the uppermost edge of the borehole array.

Improved performance of adaptive optics in the visible

A simple tip–tilt adaptive optics system can improve the peak intensity of the corrected image in the infrared by a factor of 2 to 3 compared with that of the uncorrected image. With conventional methods this performance cannot be achieved in the visible unless flexible mirrors are used. A method of improving the peak intensity in the visible by a factor of 8 to 10 compared with that of the uncorrected image by use of a simple tip–tilt mirror is presented. To achieve this improvement, the effective wave aberration, that is, the aberration modulo 2π, is used to obtain tilt and defocus of the turbulent wave front. It is shown that correcting the effective aberration is the equivalent in Fourier space of shift-and-add in image space, that is, moving the brightest speckle to the image center. Christou [ Pub. Astron. Soc. Pac.103, 1040 ( 1991)] has demonstrated the potential of a tip–tilt system when using shift-and-add. Operating in Fourier space rather than in image space offers the advantage of being independent of the type of object to be used for the correction. Additionally, this method is applied to the correction of defocus by determination of the brightest speckle in the three-dimensional image space. Thus the full potential of a rigid-mirror adaptive optics system is demonstrated.