Rapid advancements in science and technology have assured biomaterials and their associated fields towards becoming a multimillion-dollar industry. Biomaterials have been shown as one of the most ...promising materials for biomedical implant development. As such, this article intends to provide a comprehensive review of metal additive manufacturing (metal-AM) processes evolution used in biomedical applications. The most common types of metal-AM methods practised today are Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM) and Laser Engineered Net Shaping (LENS). The present review also covers the application of these metal-AM systems in Ti-6Al-4V-based implants fabrication. The scientific challenges and critical issues towards improving the biomaterial properties so that they are more notable in the biomedical industry are also discussed.
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•Nitrogen-containing volatiles were formed during Oolong tea processing.•Pyrazines were detected in model thermal reaction of l-theanine with d-glucose.•l-Theanine enhanced 2,5-dimethylpyrazine ...production during Oolong tea processing.•The contribution of l-theanine to Oolong tea aroma formation was firstly demonstrated.
l-Theanine, the most abundant amino acid in tea, is widely believed to be associated with the tea taste, however, its contribution to the formation of tea aroma is still unknown. Volatiles were determined and nitrogen-containing compounds formed during manufacturing processes were quantified. Lower levels of total sugar and l-theanine were detected in the Oolong tea product undergoing full fire processing (FFOT) suggesting that l-theanine probably involved in the volatile formation during manufacturing processes. Methylpyrazine and 2,5-dimethylpyrazine, two newly formed compounds in FFOT, together with other volatiles were successfully detected in a model thermal reaction of d-glucose and l-theanine (GT-MTR) but not detectable in thermal reactions with single d-glucose (G-MTR) or l-theanine (T-MTR). The concentration of 2,5-dimethylpyrazine increased significantly by adding additional l-theanine to 2nd roasted tea. Our study demonstrated that l-theanine, at least partly, contributed to the formation of 2,5-dimethylpyrazine, a key roasted peanutty flavor in Oolong tea.
Metal additive manufacturing technologies, such as powder bed fusion process, directed energy deposition (DED) process, sheet lamination process, etc., are one of promising flexible manufacturing ...technologies due to direct fabrication characteristics of a metallic freeform with a three-dimensional shape from computer aided design data. DED processes can create an arbitrary shape on even and uneven substrates through line-by-line deposition of a metallic material. Theses DED processes can easily fabricate a heterogeneous material with desired properties and characteristics via successive and simultaneous depositions of different materials. In addition, a hybrid process combining DED with different manufacturing processes can be conveniently developed. Hence, researches on the DED processes have been steadily increased in recent years. This paper reviewed recent research trends of DED processes and their applications. Principles, key technologies and the state-of-the art related to the development of process and system, the optimization of deposition conditions and the application of DED process were discussed. Finally, future research issues and opportunities of the DED process were identified.
Operation management models have been developed according to changes in society's demands, such as better working conditions, clean production, recyclable and reusable products, and improving social ...conditions. Thus, new challenges in developing sustainable management models, particularly for manufacturing processes, have emerged. Lean Manufacturing and Value Stream Mapping (VSM) have been widely used to develop manufacturing processes without wastes in the production flow. However, current indicators of the VSM tool have not identified the economic, social and environmental factors. This work aims to propose a conceptual method to integrate a new group of sustainability indicators into the VSM tool to assess manufacturing processes. The development of sustainability indicators was performed through analysis of the assessment models of sustainability and sustainability indicators in the period of 2009–2014. The method was applied in three case studies, and the results demonstrated that the proposed method identified different levels of sustainability of manufacturing processes and thus enabled the development of improved scenarios. In this sense, the results contributed to the literature with the proposition of new sustainability indicators related to the manufacturing process. The case studies enabled evaluation of the interaction of a new group of sustainability indicators in different manufacturing processes.
The article investigates the development of a manufacturing route for highly porous titanium foams suitable for craniofacial surgery applications, particularly in cranioplasties. The study focuses on ...the polyurethane replication method for foam production and emphasizes reducing residual gas content, as it significantly affects the mechanical properties and suitability for approval of the foams. Various factors such as starting materials, solvent debinding, heating schedules, and hydrogen atmosphere are analyzed for their impact on residual gas content. It is shown that significant reductions in residual gas content can only be achieved by reworking each step of the process. A combination of initial solvent debinding of the PU template with dimethyl sulphoxide, reduction of suspension additives, use of coarser Gd. 1 powders, and an integrated debinding and sintering process under partial hydrogen atmosphere achieves a significant reduction in residual gas content. This way, the potential for producing titanium foams that comply with relevant standards for craniofacial implants is demonstrated.
Porous titanium‐based structures are developed for their use in patient‐specific cranial cap implants. The study focuses on the polyurethane replication method for foam production and emphasizes reducing residual gas content, as it significantly affects the mechanical properties and suitability for approval of the foams.
Nowadays, advanced manufacturing models, such as the stream-of-variation (SoV) model, have been successfully applied to derive the complex relationships between fixturing, manufacturing, and datum ...errors throughout a multistage machining process. However, the current development of the SoV model is still based on 3-2-1 fixturing schemes, and although some improvements have been done, e.g., N-2-1 fixtures, the effect of general workholding systems, such as bench vices or three-jaw chucks, has not yet been included into the model. This article presents the extension of the SoV model to include fixture and datum errors considering both bench vices and three-jaw chucks as fixturing devices in multistage machining processes. The model includes different workholding configurations, and it is shown how to include the workholding accuracy to estimate part quality. The extended SoV model is validated in a three-stage machining process by both machining experimentation and CAD simulations.
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•First commercialization of bifacial PV modules for terrestrial applications.•Manufacturing of bifacial PV cells and modules in Spain in late 70′s - early 80′s.•Evolution of bifacial ...PV technology throughout the last 30 years.•59 bifacial PV modules manufactured in 1987 have been recovered and tested.•A 3.79 kWp generator has been made up with these modules and it is in operation.
A pioneer experience with the production and first commercialization of bifacial PV modules was developed by ISOFOTON, a Spanish academic spin-off established in 1981. Bifacial modules based on n-PERT cell technology were produced until 1989. 59 modules from that time were recovered from real installations after about 20 years of outdoor exposure. After cleaning and testing, 56 of these modules were connected to the grid at an IES-UPM terrace in Madrid on the 5th May 2021, constituting a 3.79 kW PV generator (nominal power of the frontal side), which is now in routine operation. The good health of these modules translates into yearly Performance Ratios of 88% (referred to the frontal side irradiation) and 81% (referred to the frontal plus rear irradiation). The comparison of the design and features of old and modern bifacial modules allows the evolution of PV technology throughout the last three decades to be appreciated.
Engineering and manufacturing processes and systems designs involve many challenges, such as dynamism, chaotic behaviours, and complexity. Of late, the arrival of big data, high computational speed, ...cloud computing and artificial intelligence techniques (like machine learning and deep learning) has reformed how many engineering and manufacturing professionals approach their work. These technologies offer thrilling innovative ways for engineers and manufacturers to tackle real-life challenges. On the other hand, the field of Artificial Intelligence (AI) is extensive. Several diverse theories, algorithms, and methods are available, which presents a challenge and a barrier in choosing the right AI technique for the appropriate engineering process or manufacturing process and environments. Besides, the pertinent literature is disseminated over various journals, conference proceedings, and research communities. Hence, conducting a systematic survey to scrutinise and classify the existing literature is worthwhile. However, it is challenging, but previous review studies have not adequately addressed AI’s use and advancement in engineering and manufacturing (EM). Besides, some concentrated on single AI models, and others focused on a specific area in EM. This paper presents a comprehensive systematic review of studies on AI and its application in EM. To limit the scope of the current study, we conducted a keyword search in official publisher websites and academic databases, such as Springer, Elsevier, Scopus, Science Publication, Taylor & Francis, Directory of Open Access Journals (DOAJ), Association for Computing Machinery (ACM), Wiley online library, Inderscience and Google scholar. The search results (173 articles) were filtered according to a proposed framework, which resulted in ninety-one (91) relevant research articles. We reviewed the articles based on a proposed taxonomy (the year of publication, the AI algorithm and machine learning task adopted, the application area in EM, the train and test split of data, the error, and accuracy metrics used, the potential benefits). Our assessment using the proposed taxonomy gave a helpful insight into the literature’s anatomy on various AI applications in engineering and manufacturing. Also, we identified opportunities for future research in AI application in the field of EM.
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We describe a swellable microneedle (SMN) consisting of Ca2+ cross-linked alginate, which expands the types of natural polymers available for SMN fabrication. After investigation of ...different fabrication methods, the alginate in situ hydrogel-based SMN with a flat substrate was successfully constructed, whose gelation was triggered by ethylenediaminetetraacetic acid calcium disodium salt and D-(+)-glucono-1,5-lactone. With the addition of polyvinyl alcohol and trehalose, SMN possessed good mechanical properties. The biocompatibility of SMN was demonstrated through the tests of in vitro cytotoxicity and in vivo skin irritation. With the assistance of SMN, the in vitro transdermal delivery efficiencies of drugs were significantly improved throughout 16 h. 3-O-ethyl ascorbic acid (EAA, pH = 4.81) exhibited a cumulative release of up to 83.83 ± 6.30%, which was consistent with zero-order kinetics, while tranexamic acid (TA, pH = 6.90) showed the most significant increase in delivery efficiency, which was consistent with the Higuchi model and Ritger-Peppas model. The SMN remained intact after the 16 h of EAA transdermal delivery, indicating its better suitability for acidic drugs. We believe that this technology has the potential to expand the range of drugs available for transdermal administration as well as the breadth of patient care applications.
The process behaviour of bronze-bonded diamond grinding wheels depends on the selected bond composition and the sintering parameters. Understanding these dependencies is the key to a knowledge-based ...manufacturing process for grinding wheels. In this study, the wear behaviour of different bond compositions and sintering parameters is investigated. It could be shown that the predominant wear mechanism is mainly grain flattening and that it depends on the critical bond strength. Finally, these findings were used to analyse the workpiece quality in dependence of the variously manufactured grinding wheels. This enables a new approach for the production of load adapted grinding wheels.
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