639 research outputs found
Sustainable Manufacturing through Digital Multi-Material 3D Printing
Full text linkThe utilisation of three-dimensional (3D) printing has become a well-established method for fabricating structural components across various materials such as polymers, metals and ceramics. Within this domain, multi-material 3D printing emerges as a pivotal advancement, offering prospects for rapid manufacturing, customised design, and structural innovation. Particularly, the incorporation of recycled materials into multi-material printing holds promise for promoting sustainability and recyclability in manufacturing processes. By leveraging multi-material printing techniques and incorporating recycled materials, this study aims to advance the sustainability agenda within manufacturing practices while concurrently exploring avenues to enhance material performance for practical engineering applications. This study focuses on the multi-material printing of pure polylactic acid (PLA) alongside recycled polylactic acid (rPLA), employing fused deposition modelling (FDM) as a cost-effective 3D printing technique. The research aims to identify the optimal composition for achieving desired material properties by exploring different percentages and layer placements of recycled material in combination with pure PLA. Detailed analysis of the mechanical properties of these 3D printed components was conducted, with the experimental results further validated through analysis of variance. The results of this study emphasis the mechanical advantages associated with the utilisation of multi-material 3D printing techniques. Moreover, the incorporation of both PLA and rPLA materials highlights the potential sustainability benefits inherent in these approaches
HarvOS: Efficient code instrumentation for transiently-powered embedded sensing
Full text linkWe present code instrumentation strategies to allow transiently-powered embedded sensing devices efficiently checkpoint the system's state before energy is exhausted. Our solution, called HarvOS, operates at compile-time with limited developer intervention based on the control-flow graph of a program, while adapting to varying levels of remaining energy and possible program executions at run-time. In addition, the underlying design rationale allows the system to spare the energy-intensive probing of the energy buffer whenever possible. Compared to existing approaches, our evaluation indicates that HarvOS allows transiently-powered devices to complete a given workload with 68% fewer checkpoints, on average. Moreover, our performance in the number of required checkpoints rests only 19% far from that of an "oracle" that represents an ideal solution, yet unfeasible in practice, that knows exactly the last point in time when to checkpoint
supplementary_file – Supplemental material for Cytotoxic effects of Benzodioxane, Naphthalene diimide, Porphyrin and Acetamol derivatives on HeLa cells
No full textSupplemental material, supplementary_file for Cytotoxic effects of Benzodioxane, Naphthalene diimide, Porphyrin and Acetamol derivatives on HeLa cells by Shareni Jeyamogan, Naveed Ahmed Khan, Ayaz Anwar, Muhammad Raza Shah and Ruqaiyyah Siddiqui in SAGE Open Medicine</p
Enhancing Sustainability and Functionality with Recycled Materials in Multi-Material Additive Manufacturing
Full text linkThis study presents a novel multi‐material additive manufacturing (MMAM) strategy by combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to improve both performance and sustainability. Specimens were produced using fused deposition modelling (FDM) with various vPLA: rPLA ratios (33:67, 50:50, and 67:33) and two distinct layering approaches: one with vPLA forming the external layers and rPLA as the core, and a second using the reversed arrangement. Mechanical testing revealed that when vPLA is used as the exterior, printed components exhibit tensile strength and elongation improvements of 10–25% over conventional single‐material prints, while the tensile modulus is largely influenced by the distribution of the two materials. Thermal analysis shows that both vPLA and rPLA begin to degrade at approximately 330°C; however, rPLA demonstrates a higher end‐of‐degradation temperature (461.7°C) and increased residue at elevated temperatures, suggesting improved thermal stability due to enhanced crystallinity. Full‐field strain mapping, corroborated by digital microscopy (DM) and scanning electron microscopy (SEM), revealed that vPLA‐rich regions display more uniform interlayer adhesion with minimal voids or microcracks, whereas rPLA‐dominated areas exhibit greater porosity and a higher propensity for brittle failure. These findings highlight the role of optimal material placement in mitigating the inherent deficiencies of recycled polymers. The integrated approach of combining microstructural assessments with full‐field strain mapping provides a comprehensive view of interlayer bonding and underlying failure mechanisms. Statistical analysis using analysis of variance (ANOVA) confirmed that both layer placement and material ratio have a significant influence on performance, with high effect sizes highlighting the sensitivity of mechanical properties to these parameters. In addition to demonstrating improvements in mechanical and thermal properties, this work addresses a significant gap in the literature by evaluating the combined effect of vPLA and rPLA in a multi-material configuration. The results emphasise that strategic material distribution can effectively counteract some of the limitations typically associated with recycled polymers, while also contributing to reduced dependence on virgin materials. These outcomes support broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within additive manufacturing (AM). Overall, the study establishes a robust foundation for industrial-scale implementations, paving the way for future innovations in eco-efficient FDM processes
Advancing Sustainable Manufacturing through Multi-Material Additive Manufacturing
Full text linkBackground: Sustainable engineering focuses on designing and manufacturing products that meet current needs without compromising future generations or the environment, emphasizing waste reduction, resource conservation, and ecological balance. Additive Manufacturing (AM), particularly Multi-Material Additive Manufacturing (MMAM), offers significant potential for sustainability through material efficiency and functional integration. However, MMAM faces challenges including material compatibility, bonding issues, residual stress, and process control complexities.
Objective: This study aims to present a novel MMAM strategy combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to simultaneously improve mechanical performance and enhance sustainability in 3D printed components.
Methods: Components were fabricated using vPLA and rPLA in layered configurations. Mechanical testing (tensile strength, elongation, tensile modulus) was performed. Thermal analysis assessed degradation temperatures and residue. Full-field strain mapping, digital microscopy (DM), and scanning electron microscopy (SEM) were employed to investigate microstructural characteristics, interlayer adhesion, and failure mechanisms.
Results: Mechanical testing revealed that vPLA as the exterior material significantly improved tensile strength and elongation (10–25%) over single-material prints, while tensile modulus depended on material distribution. Thermal analysis indicated both vPLA and rPLA degrade around 330∘C, with rPLA showing higher end-of-degradation temperatures (461.7∘C) and increased residue, suggesting improved thermal stability. Strain mapping, DM, and SEM confirmed that vPLA-rich regions exhibited superior interlayer adhesion with fewer defects, whereas rPLA-dominated areas showed higher porosity and brittle failure.
Conclusion: These findings underscore that strategic material placement in MMAM can effectively mitigate the inherent deficiencies of recycled polymers, reducing reliance on virgin materials. This work contributes to broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within AM, establishing a robust foundation for industrial implementations and future eco-efficient FDM processes
Optimization numbers of labors composition calculation based on probabilistic condition
No full textEstimating a construction project usually based on activity unit price analysis that\ud
consists of materials, manpower and machines. Unit price analysis gives an effective tool for construction management purpose. This effectiveness depends on how accurate the calculation of each variable in the unit price analysis. In a developed country, where standardization is a common condition, the accuracy gives less deviation than in an uncertain condition. The uncertainty occurs due to lack of effective standardizations, which usually happens in a developing country. It gives difficulty in construction project estimating calculation. Based on this problem, a study is attempted to propose a solving technique by using a linear programming method for number of labor composition\ud
optimization. The approach considers uncertainty condition of manpower’s productivity that gives a probabilistic characteristic. By doing so, it could be used to increase competitiveness capabilities and labor selection process
Corrective action recommendation for project cost variance in construction material management
No full textIn construction project operation, often there is a project cost variance in terms of the\ud
material, equipments, manpower, subcontractor, overhead cost, and general condition. Material is the main component in construction projects. Therefore, if the material management is not properly managed it will create a project cost variance. Project cost can be controlled by taking corrective actions towards the cost variance. The objective of this research paper is to identify the main cause of the cost variance and to recommend the corrective actions. The approach to serve that objective is by conducting surveys to high rise building construction projects in order to identify the cause of project cost variance in material purchasing, and by interviewing experts in order to obtain recommendations in taking corrective actions. Method Analysis used in this research is Delphi method. The result of the research shows that the corrective action towards the variance of the material purchasing cost is actually a preventive action (before process
Non-productive activity time measurement as a base for construction workers productivity improvement
No full textA practical system for measuring worker productivity is an essential prerequisite for the\ud
design of national and regional construction labor productivity improvement programs in Indonesia. It is important, because labor not only constitutes a large part of construction cost, but also susceptible to the influence of construction management. Indonesian construction industry needs a series of productivity indices, which should be designed to allow contractors to compare the performance of their projects with other similar projects, and to analyze different type of construction processes in order to identify problem areas and potential for productivity improvement at the source of problems. Appropriate construction productivity measurement provides the basis for determining trends and levels of productivity as well as the impacts of corrective action. It will assist project owners and construction managers: to manage projects effectively; to detect problems and adverse trends for necessary corrective action; to determine impacts of changed construction methods or conditions; to identify high and low areas of productivity and reasons for the differences; to compare project\ud
performance by region; to compare performance of different contractors; and to provide a means to assess cost effectiveness in construction. This paper discusses the method for measuring standard worker’s performance and productivity rates for improving construction cost estimation, and for assisting the definition of worker/job performance standards. Observations had been conducted in selected road and bridge construction projects at 13 provinces in Indonesia. Data obtained from observation of work processes and time measurements at the various construction sites were evaluated and analyzed to obtain productivity and performance indicators at project, regional and national levels.\ud
Non-productive activity time measurement will then be used as a tool to improve the worker performance by introducing corrective and preventive actions for every non-productive working elemen
House keeping management as a strategy to minimize construction waste in high rise building projects
No full textBuilding design and construction has found many interested parties in nearly all sectors\ud
of the economy of the Indonesia. Various studies in developed countries have indicated that one method of improving construction project performance is by managing the construction waste. Project performance can be improved by reducing the unnecessary costs related to waste disposal and excess materials. However, the issues of construction waste have not been a main concern of construction project stakeholders in Indonesia. The Civil Engineering Department of the University of Indonesia has initiated the study on construction waste management in Indonesia. This paper discusses the results from one of the study, which is on construction waste minimization strategy. The main objective of construction waste minimization strategy is to reduce the amount of waste produced, which will lead to more cost effective project operation. This is based on concept that reduced construction waste can: save project cost, reduce excess materials, improve competitiveness, improve work habit, and improve quality of project environment. Construction waste minimization strategy can be implemented at 4 construction areas, namely project planning, preconstruction, off-site activities\ud
and on-site activities. A case study was conducted on a high-rise building project, which integrates its on-site activities on construction waste minimization into the house-keeping management of the project site. By doing this, the contractor achieve cleaner, more organized & tidier project site. In the on-site activities, improved work productivity, and more cost effective project
Identification of the cause of internal factor problems that influence construction company’s performance in Indonesia
No full textIn improving Indonesia construction companies’ ability to compete, anticipative steps\ud
by determining various improvements and corrections in construction companies are needed to increase the company’s quality performance. Several factors that influence and determine the success of a construction company can be grouped into internal factors, external factors, and market forces. Internal factors in a company are important factors and have the effect of approximately 42% towards the company’s success. Management, equipment, human resources, corporate culture and finance dominate the internal factors’ influence towards the success of a construction company. The research objective discussed in this paper is to identify the cause of the problems arise in a construction\ud
company’s internal factors that influence the company’s success performance as a base to develop an ideal construction company business system in Indonesia. The methods used are literature studies and survey for identifying the cause of the problems and the construction company’s success performance indicators. Analyses used in this research are statistical analysis and cluster analysis. The results show the clusters from the problems arise in internal factors that influence the construction company’s performance, which consists of profitable, growth, sustainable, and competitive
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