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The use of continuous fiber-reinforced filaments improves the mechanical properties obtained with the fused filament fabrication (FFF) process. Yet, there is a lack of simulation tailored tools to assist in the design for additive manufacturing of continuous fiber composites. To build such models, a precise elastic model is required. As the porosity caused by interbead voids remains an important flaw of the process, this paper aims to build an elastic model integrating this aspect.

To study the amount of porosity, which could be a failure initiator, this study proposes a two step periodic homogenization method. The first step concerns the microscopic scale with a unit cell made of fiber and matrix. The second step is at the mesoscopic scale and combines the elastic material of the first step with the interbead voids. The void content has been set as a parameter of the model. The material models predicted with the periodic homogenization were compared with experimental results.

The comparison between periodic homogenization results and tensile test results shows a fair agreement between the experimental results and that of the numerical simulation, whatever the fibers’ orientations are. Moreover, a void content reduction has been observed by increasing the crossing angle from one layer to another. An empiric law giving the porosity according to this crossing angle was created. The model and the law can be further used for design evaluation and optimization of continuous fiber-reinforced FFF.

A new elastic model considering interbead voids and its variation with the crossing angle of the fibers has been built. It can be used in simulation tools to design high performance fused filament fabricated composite parts.

The rapid development and high penetration of digitalization have triggered profound changes in the energy sector. The purpose of this study is to integrate the government digital transformation into the analysis framework and discuss its impact on urban energy efficiency and its realization mechanism.

Using the “Information Benefit Pilot City” (IBC) policy as a quasi-natural experiment, and drawing on data from 285 prefecture-level cities in China from 2008 to 2019, this paper discusses how digital government affects urban energy efficiency by using difference-in-differences (DID).

The results show that digital governance significantly improves energy efficiency, and this conclusion remains reliable even after a series of robustness tests, endogeneity processing and sensitivity analysis. Heterogeneity results show that resource-based, eastern, high economic development level and high urbanization rate city digital government construction are more conducive to improving energy efficiency. The mediating effect shows that the influence mechanism of digital government on energy efficiency mainly includes reducing carbon emission, promoting green technology innovation and attracting talents.

(1) From the perspective of government digital transformation, this study supplements the way to improve energy efficiency and also expands the social dividend of government governance transformation. (2) Through quasi-experimental analysis of IBC policy, this paper solves the problem of difficulty in quantifying the government's digital transformation indicators. (3) The impact heterogeneity and realization mechanism are further discussed and the specific ways of digital government's impact on energy efficiency are revealed.

The purpose of this study is to explore a new assembly process planning and execution mode to realize rapid response, reduce the labor intensity of assembly workers and improve the assembly efficiency and quality.

Based on the related concepts of digital twin, this paper studies the product assembly planning in digital space, the process execution in physical space and the interaction between digital space and physical space. The assembly process planning is simulated and verified in the digital space to generate three-dimensional visual assembly process specification documents, the implementation of the assembly process specification documents in the physical space is monitored and feed back to revise the assembly process and improve the assembly quality.

Digital twin technology enhances the quality and efficiency of assembly process planning and execution system.

It provides a new perspective for assembly process planning and execution, the architecture, connections and data acquisition approaches of the digital twin-driven framework are proposed in this paper, which is of important theoretical values. What is more, a smart assembly workbench is developed, the specific image classification algorithms are presented in detail too, which is of some industrial application values.

The purpose of this study is to investigate the thermoforming process of 3D-printed parts made from polylactic acid (PLA) and explore its application in producing wrist-hand orthoses. These orthoses were 3D printed flat, heated and molded to fit the patient’s hand. The advantages of such an approach include reduced production time and cost.

The study used both experimental and numerical methods to analyze the thermoforming process of PLA parts. Thermal and mechanical characteristics were determined at different temperatures and infill densities. An equivalent material model that considers infill within a print is proposed. Its practical use was proven using a coupled finite-element analysis model. The simulation strategy enabled a comparative analysis of the thermoforming behavior of orthoses with two designs by considering the combined impact of natural convection cooling and imposed structural loads.

The experimental results indicated that at 27°C and 35°C, the tensile specimens exhibited brittle failure irrespective of the infill density, whereas ductile behavior was observed at 45°C, 50°C and 55°C. The thermal conductivity of the material was found to be linearly related to the temperature of the specimen. Orthoses with circular open pockets required more time to complete the thermoforming process than those with hexagonal pockets. Hexagonal cutouts have a lower peak stress owing to the reduced reaction forces, resulting in a smoother thermoforming process.

This study contributes to the existing literature by specifically focusing on the thermoforming process of 3D-printed parts made from PLA. Experimental tests were conducted to gather thermal and mechanical data on specimens with two infill densities, and a finite-element model was developed to address the thermoforming process. These findings were applied to a comparative analysis of 3D-printed thermoformed wrist-hand orthoses that included open pockets with different designs, demonstrating the practical implications of this study’s outcomes.

This study aims to answer the question of how to structure a circular ecosystem for extractive fishing in the Amazon region. It explores possibilities for implementing a circular ecosystem management model in an imperfect market with low technological availability, high informality and limited public assistance.

Qualitative approach was adopted for this paper, with a case study on extractive fishing in the state of Amazonas. Data was collected through 35 interviews and direct observation of the processes of collecting, storing and transporting fish on two routes: Tapauá-Manaus and Manacapuru-Manaus.

Through the data collected, it was possible to observe the importance of an orchestrating agent – such as an association or even a public authority – for the establishment and development of a circular ecosystem for extractive fishing in the region.

The paper makes theoretical contributions by presenting how a circular ecosystem management model could be implemented for an imperfect market in the Global South, as well as contributing to the literature on how the circular economy contributes to mitigate the threat to biodiversity posed by the linear economy.

It contributes to the management practice of structuring circular ecosystems.

The role of public authorities and the collective organization of fishermen as orchestrators connecting the network of actors that develop the extractive fishing ecosystem is fundamental, guaranteeing effective social participation in solving local problems.

The idea of circular ecosystems was applied to imperfect contexts, with high informality, weak institutions and bioeconomy, topics still little explored in the literature.

This study aims to propose the reuse of PA12 (powder) in another AM process, binder jettiinng, which is less sensitive to the chemical and mechanical degradation of the powder after multiple cycles in the laser system.

The experimental process for evaluating the reuse of SLS powders in a subsequent binder jetting process consists of four phases: powder characterization, bonding analysis, mixture testing and mixture characteristics. Analyses were carried out using techniques such as Fourier Transform Infrared Spectroscopy, scanning electron microscopy, thermogravimetric analysis and stress–strain tests for tension and compression. The surface roughness, color, hardness and density of the new mixture were also determined to find physical characteristics. A Taguchi design L8 was used to search for a mixture with the best mechanical strength.

The results indicated that the integration of waste powder PA12 with calcium sulfate hemihydrate (CSH) generates appropriate particle distribution with rounded particles of PA12 that improve powder flowability. The micropores observed with less than 60 µm, facilitated binder and infiltrant penetration on 3D parts. The 60/40 (CSH-PA12) mixture with epoxy resin postprocessing was found to be the best-bonded mixture in mechanical testing, rugosity and hardness results. The new CSH-PA12 mixture resulted lighter and stronger than the CSH powder commonly used in binder jetting technology.

This study adds value to the polymer powder bed fusion process by using its waste in a circular process. The novel reuse of PA12 waste in an established process was achieved in an accessible and economical manner.

In this study, the authors propose a novel digital twinning approach specifically designed for controlling transient thermal systems. The purpose of this study is to harness the combined power of deep learning (DL) and physics-based methods (PBM) to create an active virtual replica of the physical system.

To achieve this goal, we introduce a deep neural network (DNN) as the digital twin and a Finite Element (FE) model as the physical system. This integrated approach is used to address the challenges of controlling an unsteady heat transfer problem with an integrated feedback loop.

The results of our study demonstrate the effectiveness of the proposed digital twinning approach in regulating the maximum temperature within the system under varying and unsteady heat flux conditions. The DNN, trained on stationary data, plays a crucial role in determining the heat transfer coefficients necessary to maintain temperatures below a defined threshold value, such as the material’s melting point. The system is successfully controlled in 1D, 2D and 3D case studies. However, careful evaluations should be conducted if such a training approach, based on steady-state data, is applied to completely different transient heat transfer problems.

The present work represents one of the first examples of a comprehensive digital twinning approach to transient thermal systems, driven by data. One of the noteworthy features of this approach is its robustness. Adopting a training based on dimensionless data, the approach can seamlessly accommodate changes in thermal capacity and thermal conductivity without the need for retraining.

This study aims to explore vocational teachers' perceptions regarding workplace learning that align with students' training models and collaborative teaching involving specialised professionals within the context of industry-university collaboration.

Using a qualitative approach, the study conducted nine semi-structured interviews from three subject areas to better understand how vocational teachers’ work-based learning enhances their pedagogical practice in guiding students’ professional training. Thematic analysis was adopted to identify patterns that emerged from concepts and theories related to coding categories.

The authors identified three key components: vocational teachers’ workplace learning in connection with students’ training models, collaborative teaching with specialised professionals and teachers’ regular interactions with enterprises. The findings demonstrate that vocational teachers’ engagement in workplace learning pertaining to specific subjects provides a valuable avenue for enhancing curriculum design with collaboration with industry experts. This is key for supporting vocational students’ transitions into the workplace and ensuring their knowledge and skills are tailored to the industry-standard practice.

The data are limited to the review of interviews from three vocational subject areas as the representative sector in the study. However, this research implies effective knowledge transfer between workplace settings and vocational institutions, and vocational teachers need to integrate work-based vocational knowledge and skills in a relevant and applicable way across diverse classroom settings.

Fostering collaborative partnerships with local industries and professionals can be a primary way to facilitate authentic learning experiences that are linked to a specific vocational field and bridge the gap between diverse classroom learning and real-world work scenarios.

This study combines contemporary workplace learning theories with the conceptual understanding of vocational teachers’ involvement with industry-specific practice. Connecting teachers’ knowledge to the industry extends the input and collaboration from professionals and field experts to the diverse vocational classrooms.

This study asks whether external auditors enable the transfer of policies to the United Nations organizations that they audit and, if so, what types of policies are transferred.

The empirical research is based on a content analysis of 512 external auditor recommendations from 28 pre- and post-accrual reports of 14 UN bodies.

We find that external auditors do enable policy transfer and that such involvements may, at times, veer into non-neutral policy spaces.

We did not analyze all UN organizations with accruals-based accounting. We also did not engage in a longer longitudinal study.

Our findings raise new questions about international organization accountability, the technocratic and policy-specific influences of external auditors, and open a debate about whether attempted policy transfers can be neutral.

The world’s largest group of international organizations is affiliated with the UN. External auditors help ensure that member-state monies are appropriately utilized. Our study is the first to compare pre- and post-accrual external auditor recommendations for 14 UN bodies. It is also the first to notate and study the attempted policy transfers from external auditors to the audited UN bodies.