3D surface reconstruction based on binocular vision using structured light

A 3D surface reconstruction method using a binocular stereo vision technology and a coded structured light,which combines a gray code with phase-shift has been studied.The accuracy of the 3 D surface reconstruction mainly depends on the decoding of gray code views and phase-shift views.In order to find the boundary accurately,gray code patterns and their inverses are projected onto a human eye plaster model.The period dislocation between the gray code views and the phase-shift views in the course of decoding has been analyzed and a new method has been proposed to solve it.The splicing method is based on feature points.The result of the 3D surface reconstruction shows the accuracy and reliability of our method.

Numerical Simulation of Injection Molding Cooling Process Based on 3D Surface Model

The design of the cooling system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality of design can be improved greatly. At the same time, it is helpful to confirm the cooling system structure and optimize the process conditions. In this paper, the 3D surface model of mold cavity is used to replace the middle-plane model in the simulation by Boundary Element Method, which break the bottleneck of the application of the injection molding simulation softwares base on the middle-plane model. With the improvements of this paper, a practical and commercial simulation software of injection molding cooling process named as HsCAE3D6.0 is developed.

Rainfall-triggered waste dump instability analysis based on surface 3D deformation in physical model test

Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.

CT-scan vs.3D surface scanning of a skull:first considerations regarding reproducibility issues

Three-dimensional surface scanning(3DSS)and multi-detector computed tomography(MDCT)are two techniques that are used in legal medicine for digitalizing objects,a body or body parts such as bones.While these techniques are more and more commonly employed,surprisingly little information is known about the quality rendering of digitalized three-dimensional(3D)models provided by each of them.This paper presents findings related to the measurement precision of 3D models obtained through observation of a study case,where a fractured skull reconstructed by an anthropologist was digitalized using both post-mortem imaging methods.Computed tomography(CT)scans were performed using an 8-row MDCT unit with two different slice thicknesses.The variability of 3D CT models superimposition allowed to assess the reproducibility and robustness of this digitalization technique.Furthermore,two 3D surface scans were done using a professional high resolution 3D digitizer.The comparison of 3D CT-scans with 3D surface scans by superimposition demonstrated several regions with significant differences in topology(average difference between+1.45 and-1.22 mm).When comparing the reproducibility between these two digitalizing techniques,it appeared that MDCT 3D models led in general to greater variability for measurement precision between scanned surfaces.Also,the reproducibility was better achieved with the 3D surface digitizer,showing 3D models with fewer and less pronounced differences(from+0.32 to-0.31 mm).These experiments suggest that MDCT provides less reproducible body models than 3D surface scanning.But further studies must be undertaken in order to corroborate this first impression,and possibly explain the reason for these findings.

Virtual anthropology:a preliminary test of macroscopic observation versus 3D surface scans and computed tomography(CT)scans

Virtual anthropology(VA)is based on applying anthropological methods currently used to analyse bones to 3D models of human remains.While great advances have been made in this endeavour in the past decade,several interrogations concerning how reliable these models are and what their proper use should be remain unanswered.In this research,a fundamental assumption of VA has been investigated:if the way we perceive and apply an anthropological method is truly similar when looking at bones macroscopically and through various 3D media.In order to answer,10 skulls of known age and sex were scanned using a computed tomography(CT)scanner and a 3D surface scanner.Two observers separately applied a defined staging method to eight suture sites on these skulls,first looking at the bone macroscopically,then at the 3D surface scan,and finally on the CT scan.Two rounds of observation were carried out by each observer.Intra-and inter-observer error were evaluated,and two sample t-tests used to evaluate if the different types of medium used yielded significantly different observations.The results show a high degree of inter-observer error,and that data obtained from 3D surface scans differ from macroscopic observation(confidence level 95%,P≤0.05).CT scans,in these settings,yielded results comparable to those obtained through macroscopic observations.These results offer many possibilities for future research,including indications on the kind of anthropological methods and anatomical landmarks that might be reliably transferable to the virtual environment.All current methods used in traditional anthropology should be tested,and if they prove unreliable,new techniques to analyse bones from virtual models should be developed.

3D Evaluation Method of Cutting Surface Topography of Carbon / Phenolic (C/Ph) Composite

3D evaluation method of cutting surface topography for C/Ph composites was established.The cutting surface was measured by Talyscan 150,using 3D non-contact measurement.Through the results of 2D and 3D roughness evaluating for C/Ph composite and Duralumin,the 2D evaluation method of the cutting surface topography of C/Ph composite loses a lot of information,the characteristics of the surface topography of C/Ph composite can be comprehensively and authentically evaluated only by 3D evaluation method.Furthermore,3D amplitude and spatial parameters were adopted to evaluate the surface.The results show that： the topography of the C/Ph composite is anisotropic,there are more valleys in the machined surface of C/Ph than that of duralumin,and there are not obvious feeding textures for C/Ph,which indicates the machining mechanism is different from the metal.In conclusion,the topography of the C/Ph composite cutting surface is anisotropic;the cutting surface of C/Ph composite needs 3D evaluation method.

Topology optimization of 3D structures with design-dependent loads

Topology optimization of continuum structures with design-dependent loads has long been a challenge. In this paper, the topology optimization of 3D structures subjected to design-dependent loads is investigated. A boundary search scheme is proposed for 3D problems, by means of which the load surface can be identified effectively and efficiently, and the difficulties arising in other approaches can be overcome. The load surfaces are made up of the boundaries of finite elements and the loads can be directly applied to corresponding element nodes, which leads to great convenience in the application of this method. Finally, the effectiveness and efficiency of the proposed method is validated by several numerical examples.

Fast Mesh Reconstruction from Single View Based on GCN and Topology Modification

3D reconstruction based on single view aims to reconstruct the entire 3D shape of an object from one perspective.When existing methods reconstruct the mesh surface of complex objects,the surface details are difficult to predict and the reconstruction visual effect is poor because the mesh representation is not easily integrated into the deep learning framework;the 3D topology is easily limited by predefined templates and inflexible,and unnecessary mesh self-intersections and connections will be generated when reconstructing complex topology,thus destroying the surface details;the training of the reconstruction network is limited by the large amount of information attached to the mesh vertices,and the training time of the reconstructed network is too long.In this paper,we propose a method for fast mesh reconstruction from single view based on Graph Convolutional Network(GCN)and topology modification.We use GCN to ensure the generation of high-quality mesh surfaces and use topology modification to improve the flexibility of the topology.Meanwhile,a feature fusion method is proposed to make full use of the features of each stage of the image hierarchically.We use 3D open dataset ShapeNet to train our network and add a new weight parameter to speed up the training process.Extensive experiments demonstrate that our method can not only reconstruct object meshes on complex topological surfaces,but also has better qualitative and quantitative results.

Arc erosion of AgSnO_2 electrical contacts at different stages of a break operation

Arc erosion studies are conducted on AgSnO2 contact materials at different stages in the break operation. A resistive load arrangement is used with up to 42 V DC at 24 A and a constant contact opening velocity. The arc current is terminated at different stages as the arc is drawn between the contacts enabling a study of the arcing phenomena up to that point. Surface profiling of the contacts is conducted to determine the extent of erosion at the different stages as the arc is drawn. Spectral analysis is also conducted on the arc and then related to the extent of erosion. The results show that particular features occur at different stages as the arc is drawn. As the arc is initially established, it goes through an ＂Arc Generation＂ regime where the arc roots are small and immobile on both the anode and the cathode. Material transfer occurs mainly from anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. As the arc is drawn further and enters the ＂Arc Degeneration＂ regime, the anode undergoes significantly larger erosion than the cathode. Also, both contacts indicate that multiple arc roots have formed, which are highly mobile in the later stages of the discharge. The spectral analysis indicates that Ag and N species are in high concentrations compared to other species. The mechanisms of erosion and deposition are discussed in relation to the species within the arc discharge. For the complete break operation, it is found that the anode undergoes major erosion, and it is thought that the gaseous ions species do not dominate the arc under these conditions of short arcs and voltage 〈42 V to cause cathode erosion.

AFM Analysis of TiN, TiAlN, and TiAlSiN Coatings Prepared by Cathodic Arc Ion Plating

The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP（cathode arc ion plating）, the surface morphologies and phases were analyzed with FESEM（field emission scanning electron microscopy）, and XRD（X-ray diffraction）, respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM（atomic force microscope）. The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN＋TiAlN, TiN＋Si_3N_4＋TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength（102-103 nm）, the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength（〉103 nm）.

Three Dimensional Metal-Surface Processing Parameter Generation Through Machine Learning-Based Nonlinear Mapping

The accuracy and efficiency of three-dimensional(3D)surface forming,which directly affects the cycle and quality of production,is important in manufacturing.In practice,given the uncertainty of metal plate springback,an error exists between the actual plate and the target surface,which creates a nonlinear mapping from computer aided design models to bending surfaces.Technicians need to reconfigure parameters and process a surface multiple times to delicately control springback,which greatly wastes human and material resources.This study aims to address the springback control problem to improve the efficiency and accuracy of sheet metal forming.A basic computation approach is proposed based on the DeepFit model to calculate the springback value in 3D surface bending.To address the sample data shortage problem,we put forward an advanced approach by combining a deep learning model with case-based reasoning(CBR).Next,a multi-model fused bending parameter generation framework is devised to implement the advanced springback computation approach through surface data preprocessing,CBR-based model matching,convolution neural network-based machining surface generation,and bending parameter generation with a series of model transformations.Moreover,the proposed approaches and the framework are verified by considering saddle surface processing as an example.Overall,this study provides a new idea to improve the accuracy and efficiency of surface processing.

MECHANICAL BEHAVIORS OF SATURATED SAND UNDER COMPLICATED LOADING

The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement. Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space, a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition, and the volume strain of dilatation under drained condition in this paper.

NUMERICAL SIMULATION OF 3-D TURBULENT FLOWS OVER DREDGED TRENCHES

A 3- D free surface flow in open channels based on the Reynolds equations with the k-ε turbulence closure model is presented in this paper. Insted of the 'rigid lid' approximation, the solution of the free surface equation is implemented in the velocity-pressure iterative procedure on the basis of the conventional SIMPLE method. This model was used to compute the flow in rectangular channels with trenches dredged across the bottom. The velocity, eddy viscosity coefficient, turbulent shear stress, turbulent kinetic energy and elevation of the free surface can be obtained. The computed results are in good agreement with previous experimental data.

Three-dimensional Monte Carlo simulation of bulk fin field effect transistor

In this paper, we investigate the performance of the bulk fin field effect transistor （FinFET） through a three- dimensional （3D） full band Monte Carlo simulator with quantum correction. Several scattering mechanisms, such as the acoustic and optical phonon scattering, the ionized impurity scattering, the impact ionization scattering and the surface roughness scattering are considered in our simulator. The effects of the substrate bias and the surface roughness scattering near the Si/SiO2 interface on the performance of bulk FinFET are mainly discussed in our work. Our results show that the on-current of bulk FinFET is sensitive to the surface roughness and that we can reduce the substrate leakage current by modulating the substrate bias voltage.

A clipping algorithm for real-scene 3D models

The development of unmanned aerial vehicle(UAV)oblique photogrammetric technology provides a good foundation for the rapid construction of large-scale and high-definition real-scene 3D models.However,due to the limitations of the modeling process,irrelevant feature data cannot be eliminated in the modeling stage.The built models contain irrelevant features and model distortions caused by errors.At present,most existing clipping algorithms cannot effectively clip real-scene 3D models that are organized as a whole or with levels of detail(LODs).Therefore,this paper proposes a novel algorithm for clipping real-scene 3D models from any perspective based on clipping boundary lines thatfit the surfaces of the models.The results of the clipping experiments for 3D models constructed with oblique UAV images show that this algorithm can effectively clip any part of the 3D models,that the clipping results of each level model closelyfit the corresponding clipping boundary lines,and that the accuracy of the clipping results is very high.Additionally,the time complexity of the algorithm is O(n^(2)).In conclusion,the algorithm proposed in this paper provides correct and effective clipping results for real-scene 3D models with LODs that are constructed with photogrammetric or 3D laser scanning data.

Surface area-volume ratios in insects

Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume （SA/V） ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders （Diptera, Hymenoptera, Lepidoptera, and Coleoptera）. Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 ℃ to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling （residuals of the SA/V - mass2/3 relationship）. Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/Vratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.

STEP AP 242 Managed Model-based 3D Engineering:An Application Towards the Automation of Fixture Planning

Fixture design and planning is one of the most important manufacturing activities, playing a pivotal role in deciding the lead time for product development. Fixture design, which affects the part-quality in terms of geometric accuracy and surface finish, can be enhanced by using the product manufacturing information(PMI) stored in the neutral standard for the exchange of product model data(STEP) file, thereby integrating design and manufacturing. The present paper proposes a unique fixture design approach, to extract the geometry information from STEP application protocol(AP) 242 files of computer aided design(CAD) models, for providing automatic suggestions of locator positions and clamping surfaces. Automatic feature extraction software "FiXplan", developed using the programming language C#, is used to extract the part feature, dimension and geometry information. The information from the STEP AP 242 file is deduced using geometric reasoning techniques, which in turn is utilized for fixture planning. The developed software is observed to be adept in identifying the primary, secondary, and tertiary locating faces and locator position configurations of prismatic components. Structural analysis of the prismatic part under different locator positions was performed using commercial finite element method software, ABAQUS, and the optimized locator position was identified on the basis of minimum deformation of the workpiece.The area-ratio(base locator enclosed area(%)/work piece base area(%)) for the ideal locator configuration was observed as 33%. Experiments were conducted on a prismatic workpiece using a specially designed fixture, for different locator configurations. The surface roughness and waviness of the machined surfaces were analysed using an Alicona non-contact optical profilometer. The best surface characteristics were obtained for the surface machined under the ideal locator positions having an area-ratio of 33%, thus validating the predicted numerical results. The efficiency, capability and applicability of the developed software is demonstrated for the finishing operation of a sensor cover – a typical prismatic component having applications in the naval industry, under different locator configurations.The best results were obtained under the proposed ideal locator configuration of area-ratio 33%.

Discontinuous Galerkin Methods for Isogeometric Analysis for Elliptic Equations on Surfaces

We propose a method that combines isogeometric analysis(IGA)with the discontinuous Galerkin(DG)method for solving elliptic equations on 3-dimensional(3D)surfaces consisting of multiple patches.DG ideology is adopted across the patch interfaces to glue the multiple patches,while the traditional IGA,which is very suitable for solving partial differential equations(PDEs)on(3D)surfaces,is employed within each patch.Our method takes advantage of both IGA and the DG method.Firstly,the time-consuming steps in mesh generation process in traditional finite element analysis(FEA)are no longer necessary and refinements,including h-refinement and p-refinement which both maintain the original geometry,can be easily performed by knot insertion and order-elevation(Farin,in Curves and surfaces for CAGD,2002).Secondly,our method can easily handle the cases with non-conforming patches and different degrees across the patches.Moreover,due to the geometric flexibility of IGA basis functions,especially the use of multiple patches,we can get more accurate modeling of more complex surfaces.Thus,the geometrical error is significantly reduced and it is,in particular,eliminated for all conic sections.Finally,this method can be easily formulated and implemented.We generally describe the problem and then present our primal formulation.A new ideology,which directly makes use of the approximation property of the NURBS basis functions on the parametric domain rather than that of the IGA functions on the physical domain(the former is easier to get),is adopted when we perform the theoretical analysis including the boundedness and stability of the primal form,and the error analysis under both the DG norm and the L2 norm.The result of the error analysis shows that our scheme achieves the optimal convergence rate with respect to both the DG norm and the L2 norm.Numerical examples are presented to verify the theoretical result and gauge the good performance of our method.

Network level pavement evaluation with 1 mm 3D survey system

The latest iteration of PaveVision3D Ultra can obtain true 1 mm resolution 3D data at full- lane coverage in all 3 directions at highway speed up to 60 mph. This paper introduces the PaveVision3D Ultra technology for rapid network level pavement survey on approximately 1280 center miles of Oklahoma interstate highways. With sophisticated automated distress analyzer （ADA） software interface, the collected 1 mm 3D data provide Oklahoma Department of Transportation （ODOT） with comprehensive solutions for automated eval- uation of pavement surface including longitudinal profile for roughness, transverse profile for rutting, predicted hydroplaning speed for safety analysis, and cracking and various surface defects for distresses. The pruned exact linear time （PELT） method, an optimal partitioning algorithm, is implemented to identify change points and dynamically deter- mine homogeneous segments so as to assist ODOT effectively using the available 1 mm 3D pavement surface condition data for decision-making. The application of 1 mm 3D laser imaging technology for network survey is unprecedented. This innovative technology allows highway agencies to access its options in using the 1 mm 3D system for its design and management purposes, particularly to meet the data needs for pavement management system （PMS）, pavement ME design and highway performance monitoring system （HPMS）.