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Topic review
Updated time: 12 May 2021
Submitted by: Waleed Ahmed
Definition: Current environmental concerns have led to a search of more environmentally friendly manufacturing methods, thus, natural fibers have gained attention in the 3D printing industry to be used as biofilters along with thermoplastics. The utilization of natural fibers is very convenient as they are easily available, cost-effective, eco-friendly, and biodegradable. Using natural fibers rather than synthetic fibers in the production of the 3D printing filaments will reduces gas emissions associated with the production of the synthetic fibers that would add to the current pollution problem. As a matter of fact, natural fibers have a reinforcing effect on plastics. This review analyzes how the properties of the different types of polymers vary when natural fibers processed to produce filaments for 3D Printing are added. The results of using natural fibers for 3D Printing are presented in this study and appeared to be satisfactory, while a limited number of studies have reported some issues.
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Topic review
Updated time: 07 May 2021
Submitted by: Ansar Kareem
Definition: AA 6061 is an aluminium alloy that has extensive applications due to its superior material characteristics. It is a popular choice of matrix for aluminium matrix composite (AMC) fabrication. Stir casting method is widely for fabricating AA 6061 composites with reinforcements such as SiC, B4C, Al2O3, TiC, other inorganic, organic, hybrid and nanomaterials. An increase in reinforcement content enhances the mechanical and tribological properties of the composites. Hybrid composites show better material properties than single reinforcement composites.
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Topic review
Updated time: 09 Apr 2021
Submitted by: Mika Salmi
Definition: Additive manufacturing (AM, 3D printing) is used in many fields and different industries. In the medical and dental field, every patient is unique and, therefore, AM has significant potential in personalized and customized solutions. This text explores what additive manufacturing processes and materials are utilized in medical and dental applications, especially focusing on processes that are less commonly used. The processes are categorized in ISO/ASTM process classes: powder bed fusion, material extrusion, VAT photopolymerization, material jetting, binder jetting, sheet lamination and directed energy deposition combined with classification of medical applications of AM. Based on the findings, it seems that directed energy deposition is utilized rarely only in implants and sheet lamination rarely for medical models or phantoms. Powder bed fusion, material extrusion and VAT photopolymerization are utilized in all categories. Material jetting is not used for implants and biomanufacturing, and binder jetting is not utilized for tools, instruments and parts for medical devices. The most common materials are thermoplastics, photopolymers and metals such as titanium alloys. If standard terminology of AM would be followed, this would allow a more systematic review of the utilization of different AM processes.
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Topic review
Updated time: 21 Jan 2021
Definition: Advanced oxidation processes (AOPs) are regarded as effective techniques for organic contaminants removal from water and wastewater.
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Topic review
Updated time: 30 Oct 2020
Submitted by: Jose-Luis Molina
Definition: The are thousands of large dams over the globe. The importance of dams is rapidly increasing due to the impact of climate change on increasing hydrological process variability and on water planning and management need. This study tackles a review for the concrete arch-dams’ design process, from a dual sustainability/safety management approach. On one hand, Sustainability is evaluated through a design optimization for dams´ stability and deformation analysis. On the other hand, safety is directly related to the reduction and consequences of failure risk. For that, several scenarios about stability and deformation, identifying desirable and undesirable actions, were estimated. More than 100 specific parameters regarding dam-reservoir-foundation-sediments system and their interactions have been collected. Also, a summary of mathematical modelling was made, and more than 100 references were summarized. The following consecutive steps, required to design engineering (why act), maintenance (when to act) and operations activities (how to act), were evaluated: individuation of hazards, definition of failure potential and estimation of consequences (harm to people, assets and environment). Results show that the area to model the dam–foundation interaction is around 3.0 Hd2, the system-damping ratio and vibration period is 8.5% and 0.39 s. Also, maximum elastic and elasto-plastic displacements are ~0.10–0.20 m. The failure probability for stability is 34%, whereas for deformation it is 29%
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Topic review
Updated time: 22 Jun 2021
Submitted by: Seeram Ramakrishna
Definition: Atomization is an intricate operation involving unstable and complex networks with rupture and fusion of liquid molecules. There are diverse details that typify the spray formation, which are the technique and configuration of the atomization process, dimension and structure of the nozzle, experimental parameters, etc. .
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Topic review
Updated time: 22 Jun 2021
Submitted by: Jongseok Lee
Definition: Wheelchairs are widely used around the world to provide mobility to the elderly and disabled [1]. However, the difficulty to access areas with curbs and stairs using a standard electric-powered wheelchair limits the scope of activities, thereby declining the quality of life of those who depend on electric-powered wheelchairs. Although slopes and elevators are being introduced to promote barrier-free locomotion, it is difficult to implement them in all public facilities. Therefore, climbing up and down the stairs is inevitably a critical issue with respect to user safety. With the increasing interest in the aging population and health welfare around the world, various studies on indoor electric wheelchairs for the elderly and disabled are being conducted.
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Topic review
Updated time: 25 Nov 2020
Submitted by: Nag Jung Choi
Definition: Since the advent of biodiesel as a renewable alternative fuel, it has attracted wide attention from researchers. The raw materials of biodiesel generally produced by transesterification of animal fats, plants, algae or even waste cooking oil, which makes full use of natural resources and alleviates increasingly problematic oil shortages and environmental pollution. Biodiesel can be directly applied to vehicle engines without any modification and will both improve the combustion quality of the engine and reduce the harmful emissions from the engine. This study mainly summarizes the influence of biodiesel applications on diesel engines, including the impact on engine performance, combustion characteristics, emission characteristics, vibration, noise characteristics, and compatibility. In particular, unregulated emissions such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), which are rarely mentioned in other review articles, are also discussed in this study.
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Topic review
Updated time: 30 Mar 2021
Submitted by: Rui Lima
Definition: Blood flow in large arteries or biomedical devices can be treated as a homogenous fluid where its particulate nature can be ignored. However, in reality, blood is a suspension of deformable cells in a viscous fluid plasma. Hence, in microcirculation and microchannels, it is fundamental to take into account the effects of the multiphase properties of the blood and to study the blood flow behaviour at a cellular level. A clear example of the multiphase nature of the blood is the formation of a plasma layer (or cell-free layer) around the walls of the microchannels.
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Topic review
Updated time: 26 Apr 2020
Submitted by: Maher Al-Baghdadi
Definition: Polymer electrolyte membrane (PEM) fuel cell system is an advanced power system for the future that is sustainable, clean and environmental friendly. PEM fuel cells are growing in importance as sources of sustainable energy and will doubtless form part of the changing program of energy resources in the future. PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, reliability, manufacturability and cost-effectiveness. The difficult experimental environment of PEM fuel cell systems has stimulated efforts to develop models that could simulate and predict multi-dimensional coupled transport of reactants, heat and charged species using computational fluid dynamic (CFD) technology. The strength of the CFD numerical approach is in providing detailed insight into the various transport mechanisms and their interaction, and in the possibility of performing parameters sensitivity analyses. The results of CFD analyses are relevant in: conceptual studies of new designs, detailed product development, troubleshooting, and redesign. CFD analysis complements testing and experimentation, by reduces the total effort required in the experiment design and data acquisition. Relevant case studies and recent progress in CFD techniques used in PEM fuel cell development have been presented and analyzed. The CFD models are shown to be able to provide a computer-aided tool for design and optimize future PEM fuel cell with much higher power density, long cell life, and lower cost.
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