High-fidelity 3D Research Articles

Digital technology virtual restoration of the colours and textures of polychrome Bodhidharma statue from the Lingyan Temple, Shandong, China

This work proposes the virtual restoration of the Bodhidharma polychrome sculpture from the Lingyan Temple in China. Based on scientific analyses and simulation experiments, exterior colours and textures were virtually restored by combining 3D scanning and multi-view 3D reconstruction. At the same time, an efficient cultural relics high-fidelity information 3D modelling method was proposed. Colours and textures are essential for polychrome cultural relics, reflecting the historical appearance and technology. Due to long periods of natural ageing and the destruction of environmental factors, the colours and textures of polychrome sculptures are often altered or radically changed, making it difficult for people to appreciate the initial appearance. With the rapid development of digital technology and high-fidelity 3D modelling, virtual reality technology allows us to restore the appearance of cultural relics. This study expands the dimension of cultural relics exhibition, provides new perspectives for archaeology, art history and cultural heritage research, and provides a reference for the virtual restoration and digitalised archive of other cultural relics.

3D printable soft and solvent-free thermoplastic elastomer containing dangling bottlebrush chains.

Polymer networks containing bottlebrush chains are emerging materials with exceptionally soft and highly tunable mechanical properties. However, such materials have not been extensively implemented in functional processing techniques such as three-dimensional (3D) printing. Here, we introduce a new design of soft and solvent-free polydimethylsiloxane (PDMS)-based thermoplastic elastomer which contains dangling and space-filling bottlebrush chains, featuring a yield stress and a rapid recovery after stress removal; both required for high spatial fidelity 3D printing. The developed material is composed of two copolymers; the main building block is a diblock copolymer with linear polystyrene (PS) block and bottlebrush PDMS block (PS-b-bbPDMS) while the second component is PS-b-PDMS-b-PS triblock, self-assembling to a physical network. This design provides independent tunability of each structural parameter on the molecular level, hence, macroscopic control of the materials' mechanical properties. Multiple self-supportive 3D structures with spanning elements are 3D printed at elevated temperatures using a developed material with a low shear modulus of G' = 3.3 kPa containing 3 : 1 molar ratio of diblock to triblock copolymers without the need for volatile solvent, or post-treatment. This 3D printing compatible design opens new opportunities to utilize the distinctive mechanical properties of bottlebrush materials for applications such as soft tissue scaffolds, sensors, actuators, and soft robots.

Mapping 3D Printability of Ionically Cross-Linked Cellulose Nanocrystal Inks: Architecting from Nano- to Macroscale Structures.

Engineering the rheological properties of colloidal inks is one of the main challenges in achieving high-fidelity 3D printing. Herein, we provide a comprehensive study on the rheological behavior of inks based on cellulose nanocrystals (CNCs) in the presence of given salts to enable high-quality 3D printing. The rheological properties of the CNC suspensions are tailored by considering the nature of the electrolyte (i.e., 10 types of salts featuring different ion sizes, charge numbers, and inter- and intra-molecular interactions) at various concentrations (25-100 mM). A high printing fidelity is achieved in a narrow CNC and salt concentration range, significantly depending on the salt type. The structure-property relationship is explored in a "3D-printing" space (2D map), introducing a guideline for researchers active in this field. To further unravel the effect of salt type on morphological properties, CNC aerogels are developed by freeze-drying the printed structures. The results illustrate that enhancing viscoelastic properties render a denser structure featuring smaller pores.

Heterogeneous and Combined Heterogeneous/Homogeneous Combustion Modeling of SOFC Off-Gases.

The heterogeneous (catalytic) and the hetero-/homogeneous (catalytic and gas-phase) combustion processes of solid oxide fuel cell (SOFC) off-gases with compositions typical of a high cell utilization rate are investigated with high-fidelity 2D simulations in a platinum-coated planar channel using detailed hetero-/homogeneous chemistry. The pressures are 1-8 bar; the reactant streams have volumetric H2 and CO contents 0.7-1.5 and 5.3-9.7%, respectively; H2O and CO2 dilutions are ∼40 and ∼50%, respectively; and the global fuel/air equivalence ratio is 0.90. Water inhibits chemically the catalytic oxidation of H2, as it leads to high H(s) surface coverage that favors the recombinative desorption of H(s) to H2. On the other hand, H2O promotes chemically the catalytic oxidation of CO by creating high OH(s) coverage that in turn accelerates the CO consumption. Strong flames are established at the highest H2 content cases and for pressures p ≥ 3 bar. For all cases with vigorous homogeneous combustion, the catalytic and gas-phase reaction pathways coexist and compete with each other for the consumption of H2 and CO. The large H2O content leads to gas-phase production of H2 via the reaction H2O + H = H2 + OH. However, the gas-phase produced H2 is subsequently consumed by the catalytic pathway, such that nearly complete H2 conversion is attained at the reactor outlet. Gaseous chemistry does not affect the reactor lengths required for complete H2 conversion but substantially reduces the corresponding lengths for CO conversion. The H2 emissions decrease with increasing pressure and are in the range 8-110 ppmv, while the CO emissions increase with rising pressure and span the range 0.3-52 ppmv, thus leading to corrected CO emissions (at 15% O2) of less than 15 ppmv. Finally, the peak wall temperatures are largely acceptable in terms of catalyst thermal stability.

Hybrid parallel strategies for the neutron transport code PANDAS-MOC

PANDAS-MOC (Purdue Advanced Neutronics Design and Analysis System with Methods of Characteristics) is being developed to find high fidelity 3D solutions for steady state and transient neutron transport analysis. However, solving such transport problems in a large reactor core could be extremely computationally intensive and memory demanding. Because parallel computing is capable of improving computing efficiency and decreasing memory requirements, three parallel models of PANDAS-MOC are designed using the distributed memory and share memory architectures in this article: a pure message passing interface (MPI) parallel model (PMPI), a segment OpenMP threading hybrid model (SGP), and a whole-code OpenMP threading hybrid model (WCP). Their parallel performances are examined by the C5G7 3D core. For the measured speedup, PMPI model > WCP model > SGP model. The memory consumed by the WCP model is about 60% of that consumed by the PMPI model. This study also demonstrated that the performance of WCP parallelism is limited by the hybrid reduction in the CMFD calculation and omp atomic clause in the MOC sweep. Once they are optimized, the WCP model can outperform the PMPI model.

Motion-corrected 4D-Flow MRI for neurovascular applications

Neurovascular 4D-Flow MRI has emerged as a powerful tool for comprehensive cerebrovascular hemodynamic characterization. Clinical studies in at risk populations such as aging adults indicate hemodynamic markers can be confounded by motion-induced bias. This study develops and characterizes a high fidelity 3D self-navigation approach for retrospective rigid motion correction of neurovascular 4D-Flow data. A 3D radial trajectory with pseudorandom ordering was combined with a multi-resolution low rank regularization approach to enable high spatiotemporal resolution self-navigators from extremely undersampled data. Phantom and volunteer experiments were performed at 3.0T to evaluate the ability to correct for different amounts of induced motions. In addition, the approach was applied to clinical-research exams from ongoing aging studies to characterize performance in the clinical setting. Simulations, phantom and volunteer experiments with motion correction produced images with increased vessel conspicuity, reduced image blurring, and decreased variability in quantitative measures. Clinical exams revealed significant changes in hemodynamic parameters including blood flow rates, flow pulsatility index, and lumen areas after motion correction in probed cerebral arteries (Flow: P<0.001 Lt ICA, P=0.002 Rt ICA, P=0.004 Lt MCA, P=0.004 Rt MCA; Area: P<0.001 Lt ICA, P<0.001 Rt ICA, P=0.004 Lt MCA, P=0.004 Rt MCA; flow pulsatility index: P=0.042 Rt ICA, P=0.002 Lt MCA). Motion induced bias can lead to significant overestimation of hemodynamic markers in cerebral arteries. The proposed method reduces measurement bias from rigid motion in neurovascular 4D-Flow MRI in challenging populations such as aging adults.

Integrating pressure sensor control into semi-solid extrusion 3D printing to optimize medicine manufacturing

Semi-solid extrusion (SSE) is a three-dimensional printing (3DP) process that involves the extrusion of a gel or paste-like material via a syringe-based printhead to create the desired object. In pharmaceuticals, SSE 3DP has already been used to manufacture formulations for human clinical studies. To further support its clinical adoption, the use of a pressure sensor may provide information on the printability of the feedstock material in situ and under the exact printing conditions for quality control purposes. This study aimed to integrate a pressure sensor in an SSE pharmaceutical 3D printer for both material characterization and as a process analytical technology (PAT) to monitor the printing process. In this study, three materials of different consistency were tested (soft vaseline, gel-like mass and paste-like mass) under 12 different conditions, by changing flow rate, temperature, or nozzle diameter. The use of a pressure sensor allowed, for the first time, the characterization of rheological properties of the inks, which exhibited temperature-dependent, plastic and viscoelastic behaviours. Controlling critical material attributes and 3D printing process parameters may allow a quality by design (QbD) approach to facilitate a high-fidelity 3D printing process critical for the future of personalized medicine.

Synergizing Exchangeable Fluorophore Labels for Multitarget STED Microscopy.

Investigating the interplay of cellular proteins with optical microscopy requires multitarget labeling. Spectral multiplexing using high-affinity or covalent labels is limited in the number of fluorophores that can be discriminated in a single imaging experiment. Advanced microscopy methods such as STED microscopy additionally demand balanced excitation, depletion, and emission wavelengths for all fluorophores, further reducing multiplexing capabilities. Noncovalent, weak-affinity labels bypass this "spectral barrier" through label exchange and sequential imaging of different targets. Here, we combine exchangeable HaloTag ligands, weak-affinity DNA hybridization, and hydrophophic and protein-peptide interactions to increase labeling flexibility and demonstrate six-target STED microscopy in single cells. We further show that exchangeable labels reduce photobleaching as well as facilitate long acquisition times and multicolor live-cell and high-fidelity 3D STED microscopy. The synergy of different types of exchangeable labels increases the multiplexing capabilities in fluorescence microscopy, and by that, the information content of microscopy images.

Three-Dimensional Numerical Simulation of Grain Growth during Selective Laser Melting of 316L Stainless Steel.

The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental method alone. In this study, we presented a high-fidelity 3D numerical model to address the grain growth mechanisms during the selective laser melting of 316 stainless steel, including two heating modes, i.e., conduction mode and keyhole mode melting. In the numerical model, the powder-scale thermo-fluid dynamics are simulated using the finite volume method with the volume of fluid method. At the same time, the grain structure evolution is sequentially predicted by the cellular automaton method with the predicted temperature field and the as-melted powder bed configuration as input. The simulation results agree well with the experimental data available in the literature. The influence of the process parameters and the keyhole and keyhole-induced void on grain structure formation are addressed in detail. The findings of this study are helpful to the optimization of process parameters for tailoring the microstructure of fabricated parts with expected mechanical properties.

Numerical modelling of green-water overtopping flow striking a pedestrian on the crest of a sloped coastal structure

Some previous research on overtopping flow striking a pedestrian on the crest of coastal structures approximated a standing pedestrian as a cylinder, which may be oversimplified, so this study investigated the hydrodynamic process of overtopping flow striking a realistic pedestrian through both laboratory experiments and numerical simulations. Three postures, i.e., standing, sitting, and lying, were considered. The orientation of the human body was also varied to investigate the influence. The scaled experiments were conducted in a wave flume using a 3D-printed human model. The inline overtopping impact force on the model was collected using a force sensor. The data was used to validate a high-fidelity 3D numerical simulation using OpenFOAM. A good model-data agreement was demonstrated. For the standing posture, the inline force varies with the orientation, due to the change of total impact area. The largest inline forces for the sitting and lying postures are about three and four times greater than that for the standing posture due to increased impact area, respectively.

Oil injection lubrication analysis of a silent chain drive system

Previous investigations on oil lubrication have mainly focused on gear transmission systems. There has been little research on injection lubrication of silent chain drive systems. In this study, a high-fidelity 3D model of a silent chain drive system is established, and the stability of the model is verified through simulation analysis. Using the moving particle semi-implicit (MPS) method, the flow field distribution of the silent chain drive system under the coupling of multiple fields is obtained through co-simulation with RecurDyn and Particleworks. The effects of key parameters, including sprocket speed, injection quantity, lubricant viscosity, and injection angles, on the lubrication performance of the silent chain drive system are investigated. These results provide a reference for future practical application and theoretical research of oil injection lubrication for chain drive systems.

A 2D hydrodynamic model-based method for efficient flood inundation modelling

AbstractEfficient and accurate flood inundation predictions can provide useful information for flood risk mitigation and water resource management. In this paper, we propose a new modelling method, LoHy + , which can be applied to efficiently simulate the spatiotemporal evolution of flood inundation with reasonable accuracy. The method integrates a low-fidelity two-dimensional (2D) hydrodynamic model and a mapping module to estimate water depth in a catchment during floods. The performance of the proposed modelling method was evaluated using a real-world catchment of approximate 2,000 km2, in the Southern Murray–Darling Basin, Australia. The results show that there is a good agreement between flood inundation obtained from the proposed method and that simulated using a high-fidelity 2D hydrodynamic model. The proposed method is much more efficient than the high-fidelity 2D hydrodynamic model, which makes it an alternative method for applications requiring many model runs or long simulation durations. Also, the LoHy+ model has the potential to be applied in flood inundation forecast, flood risk mitigation design water resource management, etc.

Based on Virtual Reality Technology Research on Innovation and Design of Ceramic Painting Products

In order to obtain the complete color point cloud data of traditional ceramic artworks and reconstruct them efficiently, a 3D digital reconstruction method of ceramic painting products based on virtual reality technology was proposed. By the method, the 3D color point cloud data of ceramic works were collected by the camera 3D scanning equipment. The new postprocessing methods such as fusion and repair were investigated and proposed so as to obtain the complete optimized color point cloud information. The high-fidelity 3D mesh model and simplified mesh of ceramic artworks were obtained through the mesh process and the digital display platform was developed by using virtual reality technology. The experiment results showed that the 3D color point cloud data of traditional ceramic artworks were obtained by +5 exposure blend methods on average in the 6 combined modes and point cloud optimization and repair were completed. High-precision color mesh model was generated and digital promotion and publicity were carried out. The proposed 3D reconstruction technology and virtual display method made a positive exploration for the protection, inheritance, and promotion of China’s ceramic artworks and made a new attempt for the digital protection of cultural heritage by using modern science and technology.

Toward Emulating Human Movement: Adopting a Data-Driven Bitmap-Based "Voxel" Multimaterial Workflow to Create a Flexible 3D Printed Neonatal Lower Limb.

It is increasingly common to produce physical anatomical medical models using high-fidelity multiproperty 3D printing to assist doctor-patient communication, presurgical planning, and surgical simulation. Currently, most medical models are created using image thresholding and traditional mesh-based segmentation techniques to produce mono-material boundaries (STL file formats) of anatomical features. Existing medical modeling manufacturing methods restrict shape specification to one material or density, which result in anatomically simple 3D printed medical models with no gradated material qualities. Currently, available high-resolution functionally graded multimaterial 3D printed medical models are rigid and do not represent biomechanical movement. To bypass the identified limitations of current 3D printing medical modeling workflows, we present a bitmap-based "voxel" multimaterial additive manufacturing workflow for the production of highly realistic and flexible anatomical models of the neonatal lower limb using computed tomographic ("CT") data. By interpolating and re-slicing a biomedical volumetric data set at the native 3D printer z resolution of 27 μm and using CT scan attenuation properties (Hounsfield units) to guide material mixing ratios, producing highly realistic models of the neonatal lower limb at a significantly faster rate than other manufacturing methods. The presented medical modeling workflow has considerable potential to improve medical modeling manufacturing methods by translating medical data directly into 3D printing files aiding in anatomical education and surgical simulation practices, especially in neonatal research and clinical training.

Enhancing the printing accuracy of melt electrowritten fibers deposited on aluminum foils

Melt electrowriting (MEW) is an emerging extrusion-based additive manufacturing technology to process high-fidelity 3D scaffold. To date, the aluminum foil is a commonly-applied substrate to collect the melt electrowritten fibers. However, inaccurate fiber deposition cannot be efficiently avoided when printing on the aluminum foils. In this study, the effects of placing angle of the aluminum foil on the fiber deposition accuracy was investigated. In addition, to eliminate the human error, a planar pattern recognition algorithm was developed to evaluate the fiber deposition accuracy. It was found that the interactions between the fibers and the texture of the aluminum foils would influence the fiber deposition accuracy. The aluminum foil with 45° relative placement angle exhibited the smallest fiber deposition deviation ratio (less than 1.16%), which indicating that reducing the parallelism between the aluminum foil texture and the printed fiber path can significantly improve the printing resolution of MEW scaffold.

Continuing the Legacy of Grant’s Museum: Anatomy Education in the Digital Era

IntroductionIn the 1930s, an innovative adjunct available to anatomy learners was Grant’s Atlas of Anatomy and Grant’s Museum specimens of regional anatomy. With advancements in technology, learning tools used in anatomy education now also include digital reproductions of cadaveric specimens into 3D or interactive formats. Recent pivoting to online teaching and increased reliance on digital resources makes it a natural progression to advance the legacy of Grant's work with an online library of 3D models matching the museum. Realistic digital models are typically produced by either 3D reconstruction from image data, or photogrammetry, both requiring technical skill and time. Recent advances in light technology scanning equipment like the Artec Space Spider claim to produce a high‐fidelity 3D model within a time frame of 2‐3 hours from scan to finished digital model using their bundled software. In an ongoing project creating 3D models from prosections reproducing Grant’s Museum, we aimed to determine the efficiency of digital capture and the final model fidelity using the Artec Space Spider scanner.MethodsTwenty‐seven prosections were created to replicate 38 figures in Grant’s Atlas, ranging from simple geometries such as a lung, to more complex, including the posterior abdominal wall.Scanning &amp; post‐processing: Prosections were scanned using the Artec Space Spider, which captured images at around 7.5 frames per second (0.1 mm resolution). Post‐processing was completed in Artec Studio (Artec Studio 15 Professional x64 15.1.2.60) including alignment, hole‐filling and texture overlay. Early on, it was determined that many models needed digital sculpting, so we engaged expert digital artists using software (Zbrush 2021.6.6) for refinement of the models. The amount of time it took to scan and process each model was calculated to determine efficiency of model development.Fidelity confirmation: Ongoing feedback is being collected from an expert panel of anatomists representing five post‐secondary institutions. These experts are provided finished digital models and feedback is collected on the aspects of texture, lighting, anatomical detail (resolution) and model manipulation (user tools for examining online). This feedback will be finalized in February 2022.ResultsTable 1 depicts the breakdown of scanning and post‐processing time. Forty percent of the models were completed in under 3 hours, and these included prosections with simple geometries. Sixty percent of the models took more than 3 hours to complete, and these included more intricate prosections.ConclusionsWhile the Artec Space Spider may be a great tool to quickly generate anatomical models with simple geometry or features, it may not be ideal for replicating intricate anatomical prosections. Only 40% of scans took less than 3 hours to complete with most moderately complex models and all complex models taking over 3 hours. Much of the time spent on these models was in post‐processing, which was dedicated to filling gaps or refining the details of the models. Our findings suggest that the time:cost ratio may not justify the purchase of such high‐level technology when photogrammetry may result in similar models for relatively less investment.

HRBF-Fusion: Accurate 3D Reconstruction from RGB-D Data Using On-the-fly Implicits

Reconstruction of high-fidelity 3D objects or scenes is a fundamental research problem. Recent advances in RGB-D fusion have demonstrated the potential of producing 3D models from consumer-level RGB-D cameras. However, due to the discrete nature and limited resolution of their surface representations (e.g., point or voxel based), existing approaches suffer from the accumulation of errors in camera tracking and distortion in the reconstruction, which leads to an unsatisfactory 3D reconstruction. In this article, we present a method using on-the-fly implicits of Hermite Radial Basis Functions (HRBFs) as a continuous surface representation for camera tracking in an existing RGB-D fusion framework. Furthermore, curvature estimation and confidence evaluation are coherently derived from the inherent surface properties of the on-the-fly HRBF implicits, which are devoted to a data fusion with better quality. We argue that our continuous but on-the-fly surface representation can effectively mitigate the impact of noise with its robustness and constrain the reconstruction with inherent surface smoothness when being compared with discrete representations. Experimental results on various real-world and synthetic datasets demonstrate that our HRBF-fusion outperforms the state-of-the-art approaches in terms of tracking robustness and reconstruction accuracy.

3DPCTN: Two 3D Local-Object Point-Cloud-Completion Transformer Networks Based on Self-Attention and Multi-Resolution

Acquiring high-fidelity 3D models from real-world scans is challenging. Existing shape completion-methods are incapable of generating details of objects or learning complex point distributions. To address this problem, we propose two transformer-based point-cloud-completion networks and a coarse-to-fine strategy to extract object shape features by way of self-attention (SA) and multi-resolution (MR), respectively. Specifically, in the first stage, the model extracts incomplete point-cloud features based on self-attention and multi-resolution encoders and predicts the missing partial with a set of parametric surface elements. Then, in the second stage, it merges the coarse-grained prediction with the input point cloud by iterative furthest point sampling (IFPS), to obtain a complete but coarse-grained point cloud. Finally, in the third stage, the complete but coarse point-cloud distribution is improved by a point-refiner network based on a point-cloud transformer (PCT). The results from comparison to state-of-the-art methods and ablation experiments on the ShapeNet-Part dataset both verified the effectiveness of our method.

High fidelity 3D mesoscale modeling of concrete with ultrahigh volume fraction of irregular shaped aggregate

High fidelity mesoscale modeling techniques are of vital importance for exploration of mechanical behaviors and failure mechanisms of concrete. This paper presents an innovative approach in construction of 3D mesoscale models of concrete with ultrahigh volume fraction of randomly distributed irregular-shaped aggregate. The new modeling method combines Voronoi diagram-based method with take-and-place strategy. In this method, a database of irregular-shaped aggregate models is built based on computed tomography (CT) scan of real aggregates. Then the geometric models of concrete are constructed with the coarse aggregates generated by shrinking Voronoi cells and the fine aggregates packed through a modified take-and-place procedure. 3D mesoscale models of 50 mm × 50 mm × 50 mm concrete specimens are created by the proposed method and proven to bear a close resemblance to the real ones. Ultrahigh aggregate volume fraction up to 66.2 vol% is achieved in the model following the Fuller gradation. To demonstrate the reliability of the generated models, the results of finite element analysis for the epoxy polymer concrete under uniaxial compression is compared with the experimental data. The simulation well reproduces the mechanical behaviors of the epoxy polymer concrete.

3D Sequencing and Protocols in Head and Neck Reconstructive Surgery: Delivering Predictable Results

The complex nature of head and neck anatomy poses a significant challenge in facial reconstruction, both in functional and aesthetic outcomes. This necessitates that any resection of disease and reconstruction should not only consider the defect, but also the changes in appearance, speech and swallow. High-fidelity 3D planning improves both the outcomes of the resection and the reconstruction. This article presents an up-to-date review of the literature of the role of 3D planning, the stages and requirements of how to sequence head and neck reconstructions, and the future role of 3D planning. We outline the advantages that 3D sequencing affords both the patient and the surgeon, alongside a case report. CPD/Clinical Relevance: The latest advances in oral cancer planning and reconstruction are described and a step-by-step guide to 3D sequencing and planning reconstruction is provided.