Air pollution epidemic The lockdown enforced in most cities in China in response to the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulted in the virtual absence of motor vehicle traffic and sharply reduced manufacturing activity for several weeks. Le et al. report some of the anticipated and unanticipated effects that this had on air pollution there, including unexpectedly high levels of particulate matter abundances and severe haze formation in some areas. This natural experiment will help in the assessment of air pollution mitigation strategies. Science, this issue p. 702 The SARS-CoV-2 lockdown dramatically affected air pollution in China. The absence of motor vehicle traffic and suspended manufacturing during the coronavirus disease 2019 (COVID-19) pandemic in China enabled assessment of the efficiency of air pollution mitigation. Up to 90% reduction of certain emissions during the city-lockdown period can be identified from satellite and ground-based observations. Unexpectedly, extreme particulate matter levels simultaneously occurred in northern China. Our synergistic observation analyses and model simulations show that anomalously high humidity promoted aerosol heterogeneous chemistry, along with stagnant airflow and uninterrupted emissions from power plants and petrochemical facilities, contributing to severe haze formation. Also, because of nonlinear production chemistry and titration of ozone in winter, reduced nitrogen oxides resulted in ozone enhancement in urban areas, further increasing the atmospheric oxidizing capacity and facilitating secondary aerosol formation.
Fernando A. Costa Oliveira, Pedro F. Borges, Adriano Coelho
et al.
Microwave (MW) sintering offers a promising alternative to conventional heating in powder metallurgy, providing faster processing, lower energy consumption, and improved microstructural control. In the diamond tool industry—where cost-efficiency and competitiveness are critical—MW–hybrid sintering shows strong potential for producing segments designed for cutting and polishing natural stone and construction materials. This study investigates the effects of sintering temperature, dwell time, and green density on the densification and mechanical properties of metal matrix composite (MMC) segments containing diamond particles. MW sintering reduced the optimum sintering temperature by 90–170 °C when compared to conventional free sintering. Under optimal conditions (57% green density, 820 °C, 5 min dwell), segments achieved ~95% densification and mechanical properties comparable to hot-pressed (HP) samples. Although MW–hybrid sintered matrices exhibited slightly lower Young’s modulus (~15%) and Vickers hardness (~20%), their flexural strength and fracture toughness remained comparable to HP counterparts. Overall, MW hybrid sintering provides a cost-effective, energy-efficient, and scalable route for fabricating high-performance diamond tool segments, supporting both economic viability and sustainable, competitive manufacturing.
The dislocation density in additive-manufactured components significantly influences the local mechanical behavior of crystalline metals. Nanoindentation, renowned for its sensitivity to local mechanical responses and hardness, facilitates the assessment of local dislocation density. This study aimed to analyze the evolution of local dislocation densities in bulk, graded lattice structures (GLSs), and reduced-size GLSs of LPBF SS316L via nanoindentation. Components were fabricated using laser powder bed fusion with 316L stainless steel. The microstructural analysis revealed that the distribution of mechanical deformation across the bodies of the parts was higher in the reduced-size GLS compared to that obtained for the GLS. The simulation of plastic deformation allowed for recognizing that this difference is attributed to the different thermal stresses resulting from the higher rate of thermal excursions to which the scaffold structure was subjected whenever there was a reduction in the reciprocal distance of the struts. Mechanical deformation, identified as the primary factor contributing to dislocation density in additive manufacturing, was significant in both the GLS and reduced-size GLS, for which the dislocation density was incremented by one order of magnitude compared to the bulk material.
Feng Cao, Hossein Najaf Zadeh, Klaudia Świacka
et al.
Additive manufacturing of hydrogels is a rapidly evolving field due to the unique properties of hydrogels and their potential applications in various sectors. However, the low production rate and coarse resolution of current additive manufacturing methods limit their use. This article proposes a Stencil Additive Manufacturing (SAM) method to produce agarose hydrogel structures with horizontal and vertical resolutions of 500 and 80 μm using a novel SAM printer. Compared to peer methods, the shape fidelity of printed structures was improved and errors resulting from the Barus effect were minimized to 1.7 % and 7.1 %, depending on stencil patterns. Mechanical and thermal properties of agarose hydrogels were investigated by considering chemical crosslinking and agarose concentration, and the gelation and melting temperatures were determined. The analysis of hydrogel microstructures illustrated the change in porosity by regulating agarose concentration and the gelation rate. Static bovine serum albumin binding tests were performed using printed structures with varying concentrations and resolutions to explore the protein adsorption capacity. The results indicated that structure resolutions affect the adsorption capacity dramatically, which was increased from 100.44 to 144.13 mg/ml as resolutions were improved from 500 to 350 µm. Therefore, SAM-printing agarose hydrogels with periodic structures demonstrates potential in applications.
Materials of engineering and construction. Mechanics of materials
D. D. Furszyfer Del Rio, B. Sovacool, A. Foley
et al.
Glass is a material inextricably linked with human civilization. It is also the product of an energy intensive industry. About 75% to 85% of the total energy requirements to produce glass occur when the raw materials are heated in a furnace to more than 1500 °C. During this process, large volumes of emissions arise. The container and flat glass industries, which combined account for 80% of total glass production, emit over 60 million tonne of CO2 per year. However, environmental issues relating to the glass industry are not just limited to the manufacturing stage, but also from raw materials extraction, which impacts local ecosystems and creates other environmental challenges associated with tailing ponds, waste disposal and landfills. This systematic review poses five questions to examine these issues and themes: What alternatives exist to abate the climate effects of glass and thus make the full life cycle of glass more sustainable? What are the key determinants of energy and carbon from glass? What technical innovations have been identified to make glass manufacturing low to zero carbon? What benefits will amass from more carbon-friendly process in glass manufacturing, and what barriers will need tackling? To examine these questions, this study presents the findings of a comprehensive and critical systematic review of 701 studies (and a shorter sample of 375 studies examined in depth). A sociotechnical lens is used to assess glass manufacturing and use across multiple sectors (including buildings, automotive manufacturing, construction, electronics, and renewable energy), and options to decarbonize. The study identifies a number of barriers ranging from financial to infrastructural capacity, along with high potential avenues for future research.
The rise of online marketplaces has raised customer expectations regarding customization and lead time. It poses significant challenges to manufacturing firms and prompts a move from make-to-stock to a more flexible make-to-order system. Compared to make-to-stock settings, make-to-order systems cannot smooth fluctuations in demand using available stock. While viewing dynamic pricing as a useful strategy to balance supply with demand, many manufacturing firms can also create capacity flexibility. In that scenario, system costs could be cut by managing capacity and demand simultaneously. In this paper, we consider a make-to-order production environment with base and surge capacity as well as the ability to adjust product pricing. Our main focus is on operational decision-making, assuming that the base capacity and surge capacity are fixed, but activating the surge capacity incurs a setup cost. Initially, we propose a stochastic control model to reflect this complex decision problem. However, our initial model leads to an intractable dynamic programming problem. To overcome this, we convert the problem to a more tractable diffusion control problem. This approach helps to reveal the conditions under which utilizing flexible capacity is more advantageous than relying solely on fixed capacity. When flexible capacity is advantageous, we provide a solution to the diffusion control problem that can guide optimal capacity and price adjustments. We discover an interesting interplay between capacity adjustment and dynamic pricing. In particular, we find that the price, which aims at reducing congestion, may not monotonically increase with the congestion level when capacity adjustments incur a fixed cost.
Elio Tchoupe Sambou, Daniel Lauwers, Timm Petersen
et al.
Precise electrochemical machining (PECM) is being used increasingly to produce turbine blades (high-pressure compressors) from difficult-to-machine materials such as Inconel. However, the challenges associated with PECM are particularly pronounced for filigree workpieces characterized by high aspect ratios and thin-walled geometries. The need for high-pressure flushing within the working gap to renew the electrolyte poses a dilemma because it induces unwanted deflection in these thin-walled structures. This problem is intensified by the mechanical oscillation of the tool applied to promote flushing efficiency. The superposition of mechanical tool oscillation and turbulent flushing, which exacerbate fluid–structure interaction, has been identified as the essential cause of workpiece deflection. The aim of this paper is to present an experimental setup coupled with numerical methods to better investigate the phenomenon of workpiece deflection during PECM. In the first part of this work, a novel tool system for investigating the phenomenon of workpiece deflection in PECM is presented. The tool system combines typical PECM tool–workpiece arrangements for double-sided machining and a unique electrolytic mask that provides optical access to the working gap, allowing in situ measurements. After validating the tool system by experimental tests, the workpiece deflection is investigated using high-speed imaging. In a next step, analytical studies of the flushing conditions during machining operations are carried out. These investigations are followed by a structural investigation of the workpiece to improve the understanding of the deflection behavior of the workpiece. In addition, the effect on the blade tip caused by the continuously decreasing moment of inertia of the blade due to their thinning during machining is analyzed.
Hajo Groneberg, Sven Oberdiek, Carolin Schulz
et al.
The additive manufacturing technology powder bed fusion of metal with a laser beam (PBF-LB/M) is industrially established for tool-free production of complex and individualized components and products. While the in-processing is based on a layer-by-layer build-up of material, both upstream and downstream process steps (pre-processing and post-processing) are necessary for demand-oriented production. However, there are increasing concerns in the industry about the efficient and economical implementation and validation of the PBF-LB/M. Individual products for mass personalization pose a particular challenge, as they are subject to sophisticated risk management, especially in highly regulated sectors such as medical technology. Additive manufacturing using PBF-LB/M is a suitable technology but a complex one to master in this environment. A structured system for holistic decision-making concerning technical and economic feasibility, as well as quality and risk-oriented process management, is currently not available. In the context of this research, a framework is proposed that demonstrates the essential steps for the systematic implementation and validation of PBF-LB/M in two structured phases. The intention is to make process-related key performance indicators such as part accuracy, surface finish, mechanical properties, and production efficiency controllable and ensure reliable product manufacturing. The framework is then visualized and evaluated using a practice-oriented case study environment.
The real-time, full-field simulation of the tube hydroforming process is crucial for deformation monitoring and the timely prediction of defects. However, this is rather difficult for finite-element simulation due to its time-consuming nature. To overcome this drawback, in this paper, a surrogate model framework was proposed by integrating the finite-element method (FEM) and machine learning (ML), in which the basic methodology involved interrupting the computational workflow of the FEM and reassembling it with ML. Specifically, the displacement field, as the primary unknown quantity to be solved using the FEM, was mapped onto the displacement boundary conditions of the tube component with ML. To this end, the titanium tube material as well as the hydroforming process was investigated, and a fairly accurate FEM model was developed based on the CPB06 yield criterion coupled with a simplified Kim–Tuan hardening model. Numerous FEM simulations were performed by varying the loading conditions to generate the training database for ML. Then, a random forest algorithm was applied and trained to develop the surrogate model, in which the grid search method was employed to obtain the optimal combination of the hyperparameters. Sequentially, the principal strain, the effective strain/stress, as well as the wall thickness was derived according to continuum mechanics theories. Although further improvements were required in certain aspects, the developed FEM-ML surrogate model delivered extraordinary accuracy and instantaneity in reproducing multi-physical fields, especially the displacement field and wall-thickness distribution, manifesting its feasibility in the real-time, full-field simulation and monitoring of deformation states.
The increasing use of renewable energy sources in national electricity networks is challenging because of intermittence, i.e., the fact that the availability of the fuel (e.g., solar irradiance, wind) is volatile. This is a new challenge for the energy sector that has led to much research about energy storage. In the manufacturing sector, dealing with the volatility of demand is not a new problem and is addressed by the application of aggregate production planning techniques. Solving an aggregate production planning problem is about finding the best trade-off because capacity and inventory utilization. This paper explores the application of this technique to energy management problems and explains how it can be used as a complementary solution to energy storage, showing how industrial entities can play an active role in greening the electricity sector, solely through a different planning of their inventory levels.
Abstract Ultra-thin vapor chamber (UTVC) is an efficient heat transfer element that meets the heat dissipation requirement of miniaturized electronics. In this study, a novel UTVC (0.5 mm thick) with four spiral woven meshes and one bottom mesh composite wick was designed for cooling portable electronic devices. The UTVCs were manufactured using a cost-effective process suitable for mass production. The heat transfer performance of the UTVCs with different filling ratios were tested and the maximum heat transfer capacity of the UTVCs with filling ratios of 90%, 100%, 110% and 120% were 5.10 W, 7.58 W, 6.58 W and 6.33 W, respectively. Furthermore, the maximum heat transfer capacity of the optimal filling ratio UTVC (100%) in five representative placement states: horizontal state, gravity state, anti-gravity state, side state and inverted state were 7.58 W, 9.06 W, 6.33 W, 7.33 W and 7.58 W, respectively. The maximum effective thermal conductivity of the UTVC was found to be about 20900 W/(m·K) in horizontal state and 25200 W/(m·K) in gravity state, which were about 52 times and 63 times higher than that of pure copper, respectively. The proposed novel UTVC is promising for solving the heat dissipation problem of high performance ultra-thin portable electronic devices.
The extremely high costs of manufacturing transglutaminase from animal origin (EC 2.3.2.13) have prompted scientists to search for new sources of this enzyme. Interdisciplinary efforts have been aimed at producing enzymes synthesised by microorganisms which may have a wider scope of use. Transglutaminase is an enzyme that catalyses the formation of isopeptide bonds between proteins. Its cross-linking property is widely used in various processes: to manufacture cheese and other dairy products, in meat processing, to produce edible films and to manufacture bakery products. Transglutaminase has considerable potential to improve the firmness, viscosity, elasticity and water-binding capacity of food products. In 1989, microbial transglutaminase was isolated from Streptoverticillium sp. Its characterisation indicated that this isoform could be extremely useful as a biotechnological tool in the food industry. Currently, enzymatic preparations are used in almost all industrial branches because of their wide variety and low costs associated with their biotechnical production processes. This paper presents an overview of the literature addressing the characteristics and applications of transglutaminase.
Abstract After their first use in electric vehicles (EVs), the residual capacity of traction batteries can make them valuable in other applications. Although reusing EV batteries remains an undeveloped market, second-use applications of EV batteries are in line with circular economy principles and the waste management hierarchy. Although substantial environmental benefits are expected from reusing traction batteries, further efforts are needed in data collection, modelling the life-cycle stages and calculating impact indicators to propose a harmonized and adapted life-cycle assessment (LCA) method. To properly assess the environmental benefits and drawbacks of using repurposed EV batteries in second-use applications, in this article an adapted LCA is proposed based on the comparison of different scenarios from a life-cycle perspective. The key issues for the selected life-cycle stages and the aspects and parameters to be assessed in the analysis are identified and discussed for each stage, including manufacturing, repurposing, reusing and recycling. The proposed method is applied to a specific case study concerning the use of repurposed batteries to increase photovoltaic (PV) self-consumption in a given dwelling. Primary data on the dwelling’s energy requirements and PV production were used to properly assess the energy flows in this specific repurposed scenario: both the literature search performed and the results obtained highlighted the relevance of modelling the system energy using real data, combining the characteristics of both the battery and its application. The LCA results confirmed that the environmental benefits of adopting repurposed batteries to increase PV self-consumption in a house occur under specific conditions and that the benefits are more or less considerable depending on the impact category assessed. Higher environmental benefits refer to impact categories dominated by the manufacturing and repurposing stages. Some of the most relevant parameters (e.g. residual capacity and allocation factor) were tested in a sensitivity analysis. The method can be used in other repurposing application cases if parameters for these cases can be determined by experimental tests, modelling or extracting data from the literature.
This article examines how the shale oil revolution has shaped the evolution of U.S. crude oil and gasoline prices. It puts the increased production of shale oil into historical perspective, highlights uncertainties about future shale oil production, and cautions against the view that the United States will become the next Saudi Arabia. It then reviews how the ban on U.S. crude oil exports, capacity constraints in refining and transporting crude oil, and the regional fragmentation of the global market for crude oil after 2010 have affected U.S. oil and gasoline prices. In particular, the article discusses the reasons for the persistent wedge between U.S. and global crude oil prices in recent years, explains why domestic oil trading at a discount has not lowered U.S. gasoline prices, and discusses the role of shale oil in causing the 2014 oil price decline. Finally, the article explores the implications of the shale oil revolution for the U.S. economy and explains why increased shale oil production is unlikely to create a boom in oil-intensive U.S. manufacturing industries.
Abstract Due to application-specific tailoring, continuous fiber reinforced plastics (CoFRP) provide an exceptional lightweight potential and are particularly suited for structural components. The use of CoFRP specifically for weight reduction of the automotive car body is the major focus of this feature article. Automotive mass production requires fast and qualified, thus highly automated and material efficient manufacturing technologies. Consequently, CoFRP manufacturing for automotive differs considerably from conventional CoFRP manufacturing for aerospace, particularly in terms of higher throughput with higher investment, but lower operating effort. Furthermore, automotive structures have smaller dimensions with more complex shapes, which makes it more challenging to avoid forming defects and to ensure complete injection. Since manufacturing makes the main difference between automotive and aerospace composite components, this feature article puts emphasis on the process technologies and on the corresponding material behavior and process simulation methods. For a holistic product design of automotive CoFRP components, a simultaneous virtual description and virtual optimization of both manufacturing process and structural capacity is necessary. Production effects must be considered in the part design and, thus, must be reliably predicted by process simulation as well as taken into account in subsequent simulation steps. This feature article therefore evaluates the current state of the art in the continuous virtual representation of CoFRP process chains, including the process steps forming, injection and curing. Furthermore, the integrated optimization along this CAE chain is a key factor for an economic part design and therefore another major subject of this article.
A distribuição de produtos de e-commece apresenta na literatura uma lacuna no que diz respeito a modelos matemáticos que tratem dessa instância sob o enfoque de otimização combinatória de alocação em instalações multicapacitadas. Este estudo tem como objetivo desenvolver um modelo matemático de programação linear inteira, capaz de otimizar a localização e alocação de produtos provenientes de e-commerce. O método, para o desenvolvimento e aplicação do modelo, apoiou-se no estudo de caso de uma empresa que atua na venda de redes de descanso, presente no comércio eletrônico B2C (Business to Consumers). Os principais resultados obtidos foram: uma média de otimização de 39,1% no cenário real da empresa, e a ausência de falhas na geração de relatórios no dia a dia de operação. Conclui-se que o modelo apresentou soluções consistentes e sugere-se que ele possa ser aplicado em instâncias similares, bem como incluído de novas características em estudos futuros.
Production management. Operations management, Production capacity. Manufacturing capacity
Wire electrical discharge machining (WEDM) is widely preferred for machining difficult-to-cut materials like Ti6Al4V. In the present study, current, pulse-off-duration (T<sub>off</sub>), and pulse-on-duration (T<sub>off</sub>) were identified as vital input factors for the WEDM process of Ti6Al4V. Material removal rate (MRR) and surface roughness (SR) were selected as output measures for the study. The experiments were carried out by employing Taguchi’s L9 design at three levels. Empirical models were generated, which give the relationship between the input and output factors of the process. To check the acceptability of the model terms, analysis of variance (ANOVA) was used. The regression mode was observed to be significant for the output measures. For MRR, Toff was recorded as the highly significant factor affecting the response values with 74.95% impact, followed by Ton with 16.39%, and current with 6.56%. In the case of SR, Ton was found to be a highly significant factor with a 50.24% impact, followed by current with 43.99%, and Toff with 1.47%. Further, multi-objective optimization by using the HTS technique was performed. The effect of expanded graphite (EG) nano-powder has been studied on the output factors of MRR and SR. The use of EG nano-powder was found to improve WEDM operations as MRR was increased by 45.35%, and simultaneously, SR was reduced by 36.16%. Lastly, the surface morphology of the machined surface was investigated by employing SEM to understand the effect of EG nano-powder. The results have shown a reduction in surface defects by using EG nano-powder compared to the conventional WEDM process.