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The purpose of this study is to demonstrate the potential of three-dimensional printing technology for the remanufacturing of end-of-life (EoL) composites. This technology will enable the rapid fabrication of environmentally sustainable structures with complex shapes and good mechanical properties. These three-dimensional printed objects will have several application fields, such as street furniture and urban renewal, thus promoting a circular economy model.

For this purpose, a low-cost liquid deposition modeling technology was used to extrude photo-curable and thermally curable composite inks, composed of an acrylate-based resin loaded with different amounts of mechanically recycled glass fiber reinforced composites (GFRCs). Rheological properties of the extruded inks and their printability window and the conversion of cured composites after an ultraviolet light (UV) assisted extrusion were investigated. In addition, tensile properties of composites remanufactured by this UV-assisted technology were studied.

A printability window was found for the three-dimensional printable GFRCs inks. The formulation of the composite printable inks was optimized to obtain high quality printed objects with a high content of recycled GFRCs. Tensile tests also showed promising mechanical properties for printed GFRCs obtained with this approach.

The novelty of this paper consists in the remanufacturing of GFRCs by the three-dimensional printing technology to promote the implementation of a circular economy. This study shows the feasibility of this approach, using mechanically recycled EoL GFRCs, composed of a thermoset polymer matrix, which cannot be melted as in case of thermoplastic-based composites. Objects with complex shapes were three-dimensional printed and presented here as a proof-of-concept.

The purpose of this paper is to solve the problem that the analytic solution model of spatial three-dimensional coordinate measuring system based on dual-position sensitive detector (PSD) is complex and its precision is not high.

A new three-dimensional coordinate measurement algorithm by optimizing back propagation (BP) neural network based on genetic algorithm (GA) is proposed. The mapping relation between three-dimensional coordinates of space points in the world coordinate system and light spot coordinates formed on dual-PSD has been built and applied to the prediction of three-dimensional coordinates of space points.

The average measurement error of three-dimensional coordinates of space points at three-dimensional coordinate measuring system based on dual-PSD based on GA-BP neural network is relatively small. This method does not require considering the lens distortion and the non-linearity of PSD. It has simple structure and high precision and is suitable for three-dimensional coordinate measurement of space points.

A new three-dimensional coordinate measurement algorithm by optimizing BP neural network based on GA is proposed to predict three-dimensional coordinates of space points formed on three-dimensional coordinate measuring system based on dual-PSD.

In part I of this study, a three‐dimensional finite difference iterative solver capable of handling the coupled Navier‐Stokes and energy equations for incompressible viscous flows was described and validated with two‐ and three‐dimensional benchmarks. Part II describes the results of the computational study of two distinct complex geometries: 1) two‐dimensional and three‐dimensional natural convection in cavity whose surface is cooled while two internal blocks are heated; 2) two‐dimensional and three‐dimensional natural convection in the region defined by two interconnected cavities of different sizes which are differentially heated. All computations have been performed for a Prandtl number of 1.0, and different values of the Rayleigh number ranging between 10³ and 10⁶ depending on the problem. In the first problem, three‐dimensional effects in the top region of the cavity trap fluid in vortices near the top of the heated blocks adversely affecting heat transfer in the region while enhancing it in the region between the two heated blocks. In the second problem, the sudden expansion of fluid as it leaves the top cavity and enters the bottom one generates three‐dimensional wakes in the bottom cavity that enhance the convective heat transfer across the system walls near them. These studies tend to suggest that three‐dimensional effects play a very important role in the enhancement of convective heat transfer in complex geometries, especially at higher Rayleigh numbers.

The purpose of this paper is to describe, review, classify and analyze the current challenges in three-dimensional printing processes for combined electrochemical and microfluidic fabrication areas, which include printing devices and sensors in specified areas.

A systematic review of the literature focusing on existing challenges is carried out. Focused toward sensors and devices in electrochemical and microfluidic areas, the challenges are oriented for a discussion exploring the suitability of printing varied geometries in an accurate manner. Classifications on challenges are based on four key categories such as process, material, size and application as the printer designs are mostly based on these parameters.

A key three-dimensional printing process methodologies have their unique advantages compared to conventional printing methods, still having the challenges to be addressed, in terms of parameters such as cost, performance, speed, quality, accuracy and resolution. Three-dimensional printing is yet to be applied for consumer usable products, which will boost the manufacturing sector. To be specific, the resolution of printing in desktop printers needs improvement. Printing scientific products are halted with prototyping stages. Challenges in three-dimensional printing sensors and devices have to be addressed by forming integrated processes.

The research is underway to define an integrated process-based on three-dimensional Printing. The detailed technical details are not shared for scientific output. The literature is focused to define the challenges.

The research can provide ideas to business on innovative designs. Research studies have scope for improvement ideas.

Review is focused on to have an integrated three-dimensional printer combining processes. This is a cost-oriented approach saving much of space reducing complexity.

To date, no other publication reviews the varied three-dimensional printing challenges by classifying according to process, material, size and application aspects. Study on resolution based data is performed and analyzed for improvements. Addressing the challenges will be the solution to identify an integrated process methodology with a cost-effective approach for printing macro/micro/nano objects and devices.

This paper aims to describe a project conducted by the University of Oklahoma Libraries to create a digital collection consisting of three‐dimensional scientific objects.

The University of Oklahoma Libraries developed the following methodology for creating a digital collection of three‐dimensional objects. Digital still photographs of six sides of each object where created. These photographs were then used to create videos that emphasized the most interesting feature on each side of the object. These videos were then imported into CONTENTdm using the picture cube feature to create the digital representation of the three‐dimensional object.

This method was found to be a good method for representing three‐dimensional objects in a two‐dimensional format for inclusion in a digital collection. However, some limitations were encountered. For example, only one interesting feature could be emphasized on each side of the object and the software used to create the digital videos, while easy to use, offered only limited features for enhancing the resulting videos.

This paper demonstrates a cost effective and resource efficient method of implementing a digital collection of three‐dimensional objects that could be further improved through the use of more advanced video creation software.

This paper offers insight into a new way of representing three‐dimensional objects in a digital library. This information will be useful to digital librarians faced with resource and cost constraints who have collections of three‐dimensional physical objects that would be of interest to their user community.

The purpose of this paper is to propose that the three‐dimensional information of obstacles should be identified to allow unmanned aerial vehicles (UAVs) to detect and avoid obstacles existing in their flight path.

First, the approximate outline of obstacles was detected using multi‐scale‐oriented patches (MOPS). At the same time, the spatial coordinates of feature points that exist in the internal outline of the obstacles were calculated through the scale‐invariant feature transform (SIFT) algorithm. Finally, the results from MOPS and the results from the SIFT algorithm were merged to show the three‐dimensional information of the obstacles.

As the method proposed in this paper reconstructs only the approximate outline of obstacles, a quick calculation can be done. Moreover, as the outline information is combined through SIFT feature points, detailed three‐dimensional information pertaining to the obstacles can be obtained.

The proposed approach can be used efficiently in GPS‐denied environments such as certain indoor environments.

For the autonomous flight of small UAVs having a payload limit, this paper suggests a means of forming three‐dimensional information about obstacles with images obtained from a monocular camera.

To introduce a novel numerical calculation procedure for periodically fully developed heat and fluid flow, which can treat three‐dimensional velocity and temperature fields, using a two‐dimensional storage.

The three‐dimensional Navier‐Stokes equation and energy equation have been transformed into quasi‐three‐dimensional forms. An appropriate set of explicit periodic boundary conditions have been obtained for thermally fully developed flow through a general three‐dimensional periodic structure, exploiting the volume averaging theory.

The proposed numerical procedure has been found inexpensive and efficient. Its validity has been proved by comparing the results obtained for a bank of long cylinders in yaw against available experimental data.

Since no explicit sets of periodic boundary conditions of this kind have been reported before, they will be exploited by researchers and practitioners interested in efficient numerical computations of three‐dimensional periodic heat and fluid flows.

The authors set the goal to find the solution of the Eisenhart problem within the framework of three-dimensional trans-Sasakian manifolds. Also, they prove some results of the Ricci solitons, η-Ricci solitons and three-dimensional weakly  symmetric trans-Sasakian manifolds. Finally, they give a nontrivial example of three-dimensional proper trans-Sasakian manifold.

The authors have used the tensorial approach to achieve the goal.

A second-order parallel symmetric tensor on a three-dimensional trans-Sasakian manifold is a constant multiple of the associated Riemannian metric g.

The authors declare that the manuscript is original and it has not been submitted to any other journal for possible publication.

In this paper, the effects of the adhesive and curing agent contents on the tensile strength, bending strength, gas evolution and gas permeability of three-dimensional printed sand molds are studied. A strength model of the three-dimensional printed sand molds is proposed. The multi-material composite sand mold forming test is carried out. In addition, the mesostructure of the sand mold is studied.

The performances of three-dimensional printed sand mold such as tensile strength, bending strength, gas evolution and gas permeability are studied using the standard test methods. The mesostructure of the sand mold is studied by digital core technology.

A sand mold strength model based on the resin adhesive content, curing agent content and sand mold compactness are obtained. Two types of multi-material composite three-dimensional printed sand molds are proposed. An increase in the curing agent content in the sand mold widens the mesoscopic characteristic size distribution of the sand mold, and large-sized mesostructures appear, resulting in a decrease in the sand mold bearing capacity.

Process parameters that affect the performance of three-dimensional printed sand mold are revealed. The sand mold bearing curve provides a reference for the ultimate design of three-dimensional printed sand mold.

The paper deals with experimental work on the performance and mesostructure of multi-material composite three-dimensional printed sand mold with different contents of adhesive and curing agent. That gives a perspective on future designs of sand mold based on these principles.

The purpose of this paper was to investigate the feasibility on design and production of a three-dimensional honeycomb based on selective laser melting (SLM) technique for use in aeronautical application.

Various polyhedrons were investigated using their mechanical property, i.e. strain energy density (SED), by means of finite element (FE) analysis for the suitability of use in aerospace application; the highest SED polyhedron was selected as a candidate polyhedron. From the FE analysis, the truncated octahedron (three-dimensional honeycomb) structure was considered to be the potential candidate. Polyhedron size and beam thickness of the open-cellular three-dimensional honeycomb structure were modelled and analysed to observe how the geometric properties influence the stiffness of the structure. One selected model of open-cellular honeycomb (unit cell size: 2.5 mm and beam thickness: 0.15 mm) was fabricated using SLM. The SLM prototypes were assessed by their mechanical properties, including compressive strength, stiffness and strength per weight ratio. To investigate the feasibility in production of airfoil section sandwich structure, NACA 0016 airfoil section with three-dimensional honeycomb core was constructed and also fabricated using SLM.

According to the result, the three-dimensional honeycomb has elastic modulus of 63.18 MPa and compressive strength of 1.1 MPa, whereas strength per weight ratio is approximately 5.0 × 103 Nm/kg. The FE result presented good agreement to the mechanical testing result. The geometric parameter of the three-dimensional honeycomb structure influences the stiffness, especially the beam thickness, i.e. increase of beam thickness obviously produces the stiffer structure. In addition, the sandwich structure of airfoil was also successfully manufactured.

This work demonstrated the production of sandwich structure of airfoil using SLM for aeronautical engineering. This investigation has shown the potential applications of the three-dimensional structure, e.g. aircraft interior compartment components and structure of unmanned aerial vehicles.