196746 research outputs found
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Effect of tool revolutionary pitch on heat transfer and material flow in Al/steel friction stir lap welding
No full textThe motion condition of a friction stir welding tool significantly affects weld formation and quality in dissimilar joining between Al alloy and steel owing to its direct effect on thermo-mechanical condition during the process. In this study, a finite element simulation based on the coupled Eulerian–Lagrangian formulation was used to investigate the thermomechanical field evolutions in the friction stir lap welding of Al and steel, focusing on the effect of tool revolutionary pitch on thermal energy generation and material flow. Simulation results indicated that an increasing revolutionary pitch increased the proportion of heat input generated by plastic deformation, exhibiting an approximately linear relationship under the adopted welding parameters. With a fixed revolutionary pitch, a high- parameter-matching of rotational created higher welding temperatures. A lower revolutionary pitch resulted in higher welding temperature, leading to a thicker intermetallic layer at the Al/steel interface. However, a high revolutionary pitch under high-matching parameters significantly weakened the mixing of two materials behind the pin by decreasing material migration from the Al alloy and steel at the pin bottom on the restraining side, due to reduced temperature and increased deformation resistance. A parabolic mathematical correlation between interfacial strength and revolutionary pitch was observed, suggesting that maintaining a revolutionary pitch within the range of 0.4 to 1.2 mm/rev could produce a robust Al/steel lapped interface with joining efficiencies of approximately 91% or higher compared to the Al alloy base metal
Assessing the relevance of energy indicators as sustainability screening metrics for the decarbonisation of industrial heat through electrification
No full textPower generation faces the challenge of reducing its greenhouse gas emissions without shifting the burden to other environmental impacts. Energy and exergy-based environmental indicators have proven to some extent to be effective environmental proxies for the current energy mix but the robustness of this approach has barely been discussed in the frame of energy transition scenarios. Hence, the aim of this study is to analyse their relevance in the context of decarbonisation of industrial heat through electrification. To this end, we investigate the potential relationships between two different energy indicators and environmental indicators using life cycle assessment (Ecoinvent database, 16 environmental indicators, 2 energy indicators) for 28 pairs of energy sources shifting for the production of 1 kWh of electricity. For the reference French case, no similar trends across all sources of energy, for given environmental and energy indicators are found neither between all environmental and energy indicators. The extension to other cases is discussed, leading to the same conclusion. These results highlight the need for a multi-criteria assessment to evaluate the impacts of industrial heat in a context of intensive process electrification, which will be country dependent because of the various strategies in achieving net-zero electricity mix
Injectable Biocompatible RAFT mediated Nitroxide Nanogels:A Robust ROS-Reduction Antioxidant Approach
No full textThis work introduces novel nitroxide-based nanogels (NGs) crafted through controlled RAFT (Reversible Addition Fragmentation chain Transfer) polymerization, showcasing over 85% improved shelf-life compared to native superoxide dismutase (SOD) enzymes. These 30-40 nm NGs hold great promise for injectable delivery, effectively reducing foam cell formation and displaying potent antioxidant behavior against various reactive oxygen species (ROS), revolutionizing antioxidant therapy. Featuring a meticulously designed core-shell structure via precise RAFT polymerization, these NGs mimic SOD enzymatic activity with nitroxide-based antioxidants, providing unprecedented defense against ROS. Combining methacrylated 2,2,6,6-Tetramethyl-4-piperidyl methacrylate (PMA) and Glycidyl methacrylate (GMA) monomers with precisely synthesized nitroxyl radicals results in exceptional properties. Validated through comprehensive analytical methods, these NGs exhibit remarkable stability, halting foam cell formation even at high concentrations, and demonstrate notable biocompatibility. Their ability to protect low density lipoprotein (LDL) from oxidation for up to a month positions them at the forefront of combating cardiovascular diseases, especially atherosclerosis. This study pioneers injectable antioxidant therapy, offering an innovative approach to cardiovascular ailments. Targeting narrow plaques signifies a promising intervention, reshaping cardiovascular disease treatments. It highlights the potential of advanced drug delivery in biomedicine, promising more effective cardiovascular disease treatments
An iterative consumer-centric and technology-driven product innovation strategy based on selective and dynamic consumer attention
No full textConsumer attention is a critical factor in driving consumer-centric innovation characterized by selectivity and dynamism. However, existing literature has emphasized the selectivity but overlooked the dynamism vital for frequent iterative innovation. This study addresses the gap by exploring innovation strategies with dynamic consumer attention. We constructed a data-driven agent-based model (ABM) with two decision-making entities: manufacturers and consumers. Aspect-based sentiment analysis (ABSA) results obtained from consumer reviews are used to shape consumer agents with selective and dynamic attention. A comparative experiment, utilizing manufacturers insights based on various consumer-generated knowledge, was devised to evaluate iterative innovation efficacy. The findings highlight benefits of innovation strategies considering consumer attention drivers, especially consumer self-learning and social influence behaviors. Additionally, we identified consumers' observation bias in product attributes exhibits a notable inverted U-shaped effect on new product adoption, and negatively impacting repeat purchases. Moreover, our results show that as technology for new products matures, incremental iteration based on consumer attention becomes the optimal strategy. However, rapid technological advancements or disruptive changes could make attention-focused strategies less reliable. These insights offer valuable implications for manufacturers to optimize product innovation strategies by understanding consumer characteristics, limited innovation resources, and current technological conditions
Novel Approaches on Cheese Feed Preparation:Towards Reducing Additives in Cheese Powder Production
No full textCheese feed is an emulsion-like system that is utilized as spray drying feed during cheese powder production. The basic formulation of cheese feed includes minced natural cheeses of various types, water, and emulsifying salts (ES). The colloidal stability and physicochemical properties of cheese feed are critical factors in achieving the desired characteristics of the resulting cheese powder. Currently, the cheese powder industry relies on the addition of citrate- or phosphate-based ES to produce stable and homogenous cheese feed. However, the growing consumer demand for clean label products and the desire to reduce sodium and phosphate in food products has created a need for new strategies to reduce or eliminate the use of ES in cheese powder production. Therefore, this Ph.D. project aimed to introduce new perspectives and novel approaches to the preparation of cheese feed with the desired characteristics in the absence of ES.Understanding the interactions between ES and caseins is essential for reducing their use in cheese powder. Simplified milk protein systems, which avoid the complexities of cheese, such as pH variations, types, and proteolysis, provide a basis for comprehending and predicting ES behavior. This knowledge is critical for developing strategies to produce clean label cheese powder. Therefore, the first part of Chapter 3 (Paper I) explores the role and interaction of phosphate-based ES in casein systems. The results indicated that calcium, pH, temperature, casein concentration, and ES type and concentration are pivotal factors in these interactions. This complex interplay underscores the importance of using simplified model feed systems to understand the influence of individual factors on the resulting cheese feed. The second part of this chapter (Paper II) discusses the behavior of two different ES-free cheese feed systems prepared solely from Cheddar or Camembert cheeses. This study highlighted the importance of cheese type, insoluble calcium content, and extent of proteolysis on cheese feed stability and yield in the absence of ES. This chapter provides a good overview of the role of ES on casein systems, which is relevant to cheese feed preparation, and how cheese feeds made from different types of cheese respond to the absence of these salts.Chapter 4 investigates the role of pH in the preparation of Cheddar-based cheese feeds. Besides their calcium-chelating ability, the addition of ES in cheese feed preparation increases the feed pH, aiding in protein solubilization. Therefore, the first part of this chapter (Paper III) evaluates the influence of increasing emulsification pH to different levels during cheese feed preparation without the addition of ES. This investigation aims to isolate the specific impact of increasing pH without the addition of ES, which is essential for distinguishing the individual effects of pH adjustment from those of ES in cheese feed preparation. The results indicated that increasing the emulsification pH during cheese feed production had a significant impact on the composition of the cheese feed, primarily due to shifts in mineral balance and protein interactions. These changes correlated with variations in particle size, feed viscosity, and colloidal stability. A noticeable change in trends was observed above emulsification pH of 6. Additionally, Raman spectroscopy detected alterations in protein structure with increased emulsification pH. In the second part of this chapter (Paper IV), a different approach was employed by acidification and re-neutralization of the cheese feed during its preparation to better understand the relationship of pH, calcium solubilization, its reversibility, and feed stability. It was concluded that re-neutralization treatments exhibited reversible calcium solubilization depending on the extent of pre-acidification. Additionally, feed viscosity was predominantly influenced by the final pH, regardless of the acidification history, with lower pH values resulting in increased viscosity, likely due to reduced electrostatic repulsion. The form of calcium upon re-neutralization possibly varied depending on the acidification history. By elucidating the independent effect of pH, Chapter 4 aims to provide a deeper understanding of its influence on mineral balance as well as protein interactions during cheese feed preparation.Finally, Chapter 5 evaluates the potential of using novel processing techniques - namely ohmic heating, pulsed electric field (PEF) treatment, and ultrasonication - on cheese feed preparation to reduce the need for ES in cheese powder production. The first part of this chapter (Paper V) examines the influence of ohmic heating pre-treatment on Cheddar cheese before cheese feed preparation, aiming to alter the mineral equilibria in the cheese and thereby improve the emulsifying properties of the para-caseins. Ohmic heating increased mineral solubilization from the cheese matrix during the pre-treatment, with higher temperatures exhibiting a synergistic impact due to increased ion mobility. In addition, ohmic heating-treated cheese showed structural weakening, possibly due to colloidal calcium phosphate (CCP) solubilization, which was confirmed by increased porosity observed in confocal imaging. Despite these effects, the overall stability of the prepared cheese feed did not improve, indicating the need for further optimization of the ohmic treatment set-up or combining with other technologies. In the second part of this chapter (Paper VI), a stronger electric field was applied as pre-treatment on cheese by using PEF technology to further investigate the influence of electric field application under non-thermal (<40ºC) conditions. Again, the goal was to induce mineral solubilization through more effective electroporation, thereby improving para-casein functionality in cheese feed. PEF treatment effectively weakened the cheese structure, evidenced by reduced hardness and increased mineral solubilization from the cheese matrix. However, the stability of the cheese feed remained unaffected under the studied PEF parameters. This suggests that optimization through alternative settings, such as different pulse shapes or shorter durations, might enhance mineral solubilization and protein functionality. In conclusion, both methods of electric field application demonstrated potential in promoting mineral solubilization and inducing structural changes in cheese. However, further studies focusing on optimizing treatment methods and parameters are necessary. The final part of this chapter (Paper VII) explores the combined influence of ultrasonication and ohmic heating on Cheddar cheese. These technologies have shown promise in modifying milk protein structure and improving their solubility and emulsifying properties. Hence, the study aimed to incorporate this idea into cheese feed production by investigating their influence on para-casein functionality. The results demonstrated that ultrasonication improved protein-mediated fat stabilization, while subsequent ohmic heating had a less pronounced effect, showing only a slight increase in mineral solubilization compared to the control sample. The findings of this chapter suggest that these novel technologies have the potential to reduce or eliminate the need for ES in cheese powder production.Overall, this thesis offers valuable insights for developing strategies to reduce or eliminate the use of ES in cheese powder manufacturing.<br/
Railway network delay evolution:A heterogeneous graph neural network approach
No full textAccurate delay evolution prediction plays a pivotal role in train rescheduling decision-making for the railway network. Existing studies on delay prediction predominantly centered around predicting delays for each train in the subsequent stations (i.e., following a train-oriented perspective). Furthermore, train operations in the railway network involve different types of entities (stations, trains, etc.), making the current graph/network models with homogenous nodes (i.e., the same kind of nodes) incapable of effectively capturing the interactions between the entities. This paper develops a network-oriented model to investigate the train delay evolution on railway networks, by predicting the delays of running trains in the network after a given time interval. The proposed model combines the GraphSAGE graph neural network (GNN) and the heterogeneous graph neural network (HetGNN) architecture, thus called SAGE-Het, enabling it to capture interactions between heterogeneous nodes (i.e., different types of nodes) based on different edges (e.g., edges between trains, trains, and stations). Additionally, SAGE-Het allows for flexible inputs in contrast to conventional machine learning techniques, whose inputs must meet the consistent dimension requirement (e.g., in the form of rectangular or grid-like arrays). The performance and robustness of the suggested SAGE-Het model are assessed in experiments on the data from two sub-networks of the China railway network. The experimental results demonstrate that SAGE-Het outperforms the existing delay prediction methods and some advanced HetGNNs used for prediction tasks in other domains; SAGE-Het demonstrates excellent scalability, capable of handling various types of nodes; the predictive performances of SAGE-Het under different prediction time horizons (10/20/30 min ahead) all exhibit better performance over other baselines; the accuracies are over 90 % under the permissible 3-minute errors for the three prediction time horizons. Specifically, the impact of train interactions on delay evolution is investigated based on the flexible input characteristic of the proposed model. The results illustrate that train interactions become subtle with the increase of train headways. This finding directly contributes to decision-making in situations where conflict resolution or train-canceling actions are needed.</p
Oxidation-alkaline-enhanced abiotic humification valorizes lignin-rich biogas digestate into artificial humic acids
No full textThis study introduces a cost-effective, mild thermal abiotic humification method for producing highly humified artificial humic acids (AHAs) from lignin-rich biogas digestate. Derived from the co-anaerobic digestion of cattle manure-wheat straw, the digestate slurry undergoes an MnO2-KOH-urea-enhanced humification reaction. Key process variables, such as MnO2 dose (0–15 mg/L), KOH dose (0–1 mol/L), urea dose (0–1.2 mol/L), reaction time (30–150 min), and temperature (25–85 °C), were systematically explored to optimize AHA yield, carboxylic acid content, and lignin removal. Optimal conditions, employing 7.69 mg/L of MnO2, 0.57 mol/L of KOH, and 0.63 mol/L of urea at 85 °C for 106 min, resulted in an impressive AHA yield of 32.15%, featuring a significant carboxylic acid content of 3.325 mmol/g. Under these conditions, up to 65% of lignin was effectively removed, accompanied by the release of orthophosphate up to 258 mg/L. The produced AHAs exhibited reduced toxicity, as demonstrated by substantial reductions of 54.13%, 57.14%, and 42.50% in phenols, furfural, and hydroxymethylfurfural, respectively. Notably, the AHAs displayed favorable characteristics, including a lower molecular weight (760.49 g/mol), diminished aromaticity (66.25% reduction), higher humification degree (lower C/N ratio of 8.79), increased oxidation degree (higher O/C ratio of 0.6), and elevated spectral index of humification (higher E4/E6 of 4.58). Analytical techniques, such as FT-IR, XPS, and TGA-MS, revealed chemical resemblance and enhanced functionality of AHAs compared to natural counterparts. Differentiation between AHA, lignin, and humification residues was confirmed through SEM-EDX, ICP-OES, and organic/inorganic carbon analyses. The obtained AHAs exhibit promising characteristics suitable for diverse applications in sustainable agriculture and environmental management
Factors affecting particle characterization of powders used in additive manufacturing
No full textThe present study analyze the effects of sample preparation and data analysis techniques for different experimental methods of metal powder characterization. The aim is to propose a robust strategy for quantifying powder particle size distribution and morphology of relevance for metal additive manufacturing (MAM) processes, in particular for powders with nearly spherical particle shape. Laser diffraction (LD), scanning electron microscopy (SEM) and high-resolution X-ray computed tomography (XCT) are used to analyze three different stainless-steel 316L powders. The results obtained demonstrate that the powder sample itself and the sample preparation, both have a significant effect on the obtained values. For the imaging processing methods, the post-processing route is an important part of the characterization and strongly affects the results. However, proper sample preparation is shown to ease this post-processing. Given the high sphericity of the powders used, it is shown that 2D and 3D methods generally lead to the same result when the 2D data are properly transformed to 3D space. Guidelines to overcome the shortcomings of the different techniques are suggested
Recent advances in the synthesis, photo-/electrocatalytic properties and applications of MXenes/bismuth-related composites
No full textIn recent years, many reviews have been made for MXenes and their derivatives, but a systematic overview specifically dedicated to MXenes/bismuth-related composites (i.e., MXenes/Bi-rcs) is still missing. Here we present the recent progress on the design, synthesis, and photo- /electrocatalytic properties of MXenes/Bi-rcs, as well as their applications, aiming to offer new insights and guidance for their future development. We begin by disclosing the synthesis methods of MXenes/Bi-rcs and highlighting the preparation strategies of MXenes which are an important first step in achieving the MXenes/Bi-rcs. Then, we disclose the photo- /electrocatalytic properties and applications of MXenes/Bi-rcs, with a focus of particular concern on the interplay of Bi element with the functional groups of MXenes and for the mechanisms that account for the enhanced photo- /electroactivity and durability. Finally, we show the promising opportunities of MXenes/Bi-rcs associated with the potential challenges of this emerging research branch
Advancing gasoline vapor recovery in oil depots: Integrating cooling and adsorption technologies
No full textGasoline vapor recovery during fuel distribution is crucial for public health, urban environment quality, and minimizing economic losses from evaporation. This study proposes a gasoline vapor recovery process that integrates multi-stage cooling at partial load operation and dual-vessel pressure swing adsorption with activated carbon. Demonstration in an oil depot achieved a recovery ratio of 0.8 % relative to refueling gasoline, an air pollutant reduction of 99.2 %, and a CO2 equivalent emission reduction of 86.5 %, highlighting significant environmental and economic benefits. An integrated model, validated against field test data, was developed to assess the energetic, exergetic, economic, and environmental performance, focusing on partial-load cooling and load shifting between cooling and adsorption. The Lorenz efficiency ranges from 4.5 % to 19.6 % with current configurations and can reach 25.2 % with stepless capacity control. Exergy analysis revealed an exergetic efficiency of 0.2 %–1.7 %, with major irreversibilities in heat exchangers designed to prevent frosting. Profitability analysis indicated a net present value of 27.6 million CN ¥ (3.88 million USD) and a payback time of 2.3 years. Considering efficiency and economic factors, the gasoline vapor recovery process is optimal at lower cooling temperatures and with smaller pressure swing adsorption configurations for future applications