Hasil untuk "Mechanical industries"

Călin Lucian Burcă, Olimpiu Karancsi, Dragoş Vâlsan et al.

The present work aims to investigate the microstructure and mechanical properties of laser beam spot welds in the superalloy Nimonic 80 A. Considering the importance of this innovative process in the manufacturing of engineering components for high-security industries, it is necessary to study the influence of the welding thermal cycle on the microstructure and mechanical properties of welded joints. The rapid heating/cooling, melting, and re-solidification phenomena that occur during welding modify the metallurgical characteristics of the weld compared with the microstructure of the base metal. Because the energy density is high and the process duration is very short, the microstructure obtained after solidification is fine dendritic in the central area of the joint and columnar in the weld–base metal transition zone. For the same reasons, the heat-affected zone (HAZ) is slightly extended. The increase in the size of the crystalline grains in the HAZ is negligible due to the low diffusivity of the nickel-based γ solid solution matrix, which inhibits the rapid migration of grain boundaries during the welding process. Metallographic analyses were performed using optical microscopy and scanning electron microscopy. The microhardness values, 152–168 HV0.05 in the weld and 180–190 HV0.05 in the base metal, together with the tensile–shear strength values (760–780 N/mm²) obtained at room temperature, demonstrate that the proposed welding process is appropriate and feasible for engineering applications involving Nimonic 80A superalloys.

Hanxiao Ma, M Salauddin

The escalating threat of global warming, exacerbated by increasing human activities, presents significant challenges for coastal environments and has led to conflicts between the use of marine space and the conservation of marine resources. A sustainable co-location approach to marine management, aims to restore marine ecosystems, mitigate climate change, and reduce marine spatial conflicts by placing offshore renewable energy (ORE) farms alongside low-trophic aquaculture (LTA). This systematic literature review analyses the strengths and limitations of the co-location method, and the findings suggest a strong potential for its development in offshore areas. The ORE farms and LTA farms can share space, vessels, and wave attenuation effects with each other. The renewable energy farms can supply power and provide anchors for the aquaculture system, while the low-trophic species capture carbon and nutrients in their ambient water. However, this multi-use strategy is still in its early stages and presents significant knowledge gaps that must be addressed before it can be widely implemented on a global scale. Previous field investigations and academic studies have been largely one-dimensional and insufficient. Critical issues in environmental, technical, and socio-economic domains remain unaddressed, underscoring the urgent need for comprehensive solutions.

Muhammad Abdullah Khalid, Afshan Naseem, Mehran Ullah et al.

Sustainability in supply chains, particularly through effective trade-in programs, has become increasingly critical in addressing modern environmental and management challenges posed by short-life-cycle electronic products. Trade-in programs play a pivotal role in enabling sustainable closed-loop supply chains (CLSCs) by promoting product returns and recycling, yet they encounter significant complexities. To address these challenges, this study introduces and empirically validates a novel hybrid decision-making framework combining Cloud Model Theory (CMT), DEMATEL, and MARCOS methods. Initially, expert linguistic assessments are systematically transformed into quantitative cloud parameters, capturing inherent uncertainties and intricate factor interdependencies. The CMT-DEMATEL analysis highlights economic and incentive-driven factors, notably pricing strategies and subsidies, as critical causal influence factors. Subsequently, MARCOS analysis identifies quality considerations, return rates, and real-time inventory systems as top priorities due to their comprehensive impact on sustainability, resilience, and digitalization. The sensitivity analysis then shows that the resilience weight is the most visible leverage: the importance of the inventory system rises or falls in direct proportion to its emphasis. The alignment between these analytical findings and practical industry scenarios underscores the framework’s relevance and utility. This integrated approach provides managers with a robust, actionable guide for optimizing trade-in program performance, effectively bridging key methodological gaps in existing trade-in and CLSC literature.

Tanje Mada Hatsa, Ayele Wondatir Kelile, Ewnetu Getu Beyene et al.

Abstract Biodiesel is one of the promising biofuels to replace fossil fuels as a primary energy source for machineries and vehicles. It can be produced from various edible and non-edible plants seed oil. Dovyalis caffra is one of the indigenous fruits which contains high amount of non-edible oil (43.05%) in its seed parts. However, there is limited research on Dovyalis caffra non-edible seed oil for production of biodiesel. This research is aimed to produce biodiesel from Dovyalis caffra seed oil. The production process was done by transesterification of oil with methanol using base (NaOH) catalyst and the biodiesel percentage yield result became 96 ± 2.00. Physicochemical characterization (moisture, viscosity, acid value, saponification value, peroxide and free fatty acid) of Dovyalis caffra seed oil was conducted and their values became 0.046 ± 0.99, 42.90 ± 0.19, 0.57 ± 0.51, 193 ± 0.21, 2.7 ± 0.73 and 2.25 ± 1.02, respectively. Also, the physicochemical characterization (acid value, saponification value, iodine value, kinematic viscosity, flash point, pour point, ash content and cross caloric value) of produced biodiesel was conducted and the results indicted with values of 0.42 ± 0.01, 226 ± 0.57, 15.64 ± 2.13, 3.2 ± 0.02, 145, 2, 0.32 ± 0.82 and 10,748.0653, respectively. The results from the experiment shows that Dovyalis caffra seeds have more oil content with good oil quality for biodiesel production, which is a critical issue in the production process of qualified biodiesel.

Mohamed Berradi, Omar Berradi, Youssef El Rhayam et al.

Sarah Shalsi, Kamila Svobodova, Glen Corder et al.

Nat Steinsultz, Pierre Christian, Joel Cofield et al.

Increasingly large amounts of electric supply and load are being deliberately operated or sited on the basis of marginal emissions factor (MEF) models. Validating and calibrating such models is therefore of growing policy importance. This paper uses a natural experiment involving variation in relative changes in wind generation potential at wind farms in the ERCOT power grid to create a benchmark MEF and examine the relative accuracy of several common classes of short term MEF models. This work focuses on MEFs at the level of a few individual generating nodes, a much smaller geographic scale than the Balancing Authority (BA) or load zone. Additionally, the use of wind generation potential as a regressor allows us to factor in wind curtailment, in contrast to previous work. We evaluate multiple prevalent existing MEF models and find that both dispatch and statistical MEF models have a high degree of agreement with the benchmark MEF, while heat rate and average emissions do not. We also find that the emissions reduction benefits of optimizing electricity with MEFs using a geographically granular model instead of a BA-wide model are 1.4, 1.3 and 1.5 times larger for dispatch, statistical and heat rate models, respectively.

Tarikul Islam, Mehedi Hasan Chaion, M. Abdul Jalil et al.

Abstract Natural fiber‐reinforced composites have emerged as a promising alternative in various industries, including automotive, aerospace, construction, and civil engineering, owing to their eco‐friendly nature and favorable mechanical properties. However, challenges such as low thermal stability and high moisture absorption limit their widespread use. To overcome these limitations, surface modifications such as mercerization, benzoylation, silane treatment, and acetylation have been extensively explored. Hybrid composites (HCs), combining natural and synthetic fibers, offer a compelling solution by harnessing the unique properties of both materials. This review comprehensively examines the types of fibers and polymers utilized in HCs, along with various chemical treatments to enhance their properties. Additionally, a detailed analysis of different manufacturing processes for HCs is provided, including hand lay‐up, vacuum‐assisted resin transfer molding, autoclave molding, injection molding, and compression molding. Furthermore, this review highlights recent advancements in HCs and their applications. Significant outcomes include a deeper understanding of the synergistic effects between natural and synthetic fibers, improved mechanical and thermal properties, and enhanced applications in diverse industries. The potential of HCs as a sustainable and high‐performance material solution emphasizes the importance of ongoing research and innovation in this field to overcome existing challenges and unlock new possibilities for composite engineering. Highlights Surface modifications such as mercerization, benzoylation, and silane treatment enhance the properties of natural fibers in composite materials. Hybrid composites (HCs) offer unique advantages by combining natural and synthetic fibers, including improved thermal, mechanical, and damping properties. Various chemical treatments and manufacturing processes contribute to enhancing the properties and applications of HCs. Recent advancements in HCs have led to an improved understanding and utilization of composite engineering across multiple industries. The review discusses challenges, opportunities, and future prospects for HCs, emphasizing the need for ongoing research and innovation in this field.

A.S. Bhattacharyya, K. Bhattacharyya

Micro-electro-mechanical systems (MEMS) technology has made it possible for the semiconductor industry to construct systems and devices on silicon substrates. Nanocomposite Si-C-N coatings must have reliable characteristics for MEMS as well as in the form of protective coatings for heavy-duty industries like aerospace, automobiles, reactors, etc. Vickers indentation was used to study the fracture response of Si-C-N coatings that were deposited on silicon substrates. Images of the fractured regions which consisted of different types of cracks were analyzed and used for qualitative fracture analysis. The Drucker-Prager (DP) model and subsurface layer distributions were used to evaluate the fractured zones. Microscopic evaluation and supporting image analysis were used to study the growth nature of the coatings.

Chen Wang, Guozheng Peng, Rui Song et al.

Achieving a balance between accuracy and efficiency in target detection applications is an important research topic. To detect abnormal targets on power transmission lines at the power edge, this paper proposes an effective method for reducing the data bit width of the network for floating-point quantization. By performing exponent prealignment and mantissa shifting operations, this method avoids the frequent alignment operations of standard floating-point data, thereby further reducing the exponent and mantissa bit width input into the training process. This enables training low-data-bit width models with low hardware-resource consumption while maintaining accuracy. Experimental tests were conducted on a dataset of real-world images of abnormal targets on transmission lines. The results indicate that while maintaining accuracy at a basic level, the proposed method can significantly reduce the data bit width compared with single-precision data. This suggests that the proposed method has a marked ability to enhance the real-time detection of abnormal targets in transmission circuits. Furthermore, a qualitative analysis indicated that the proposed quantization method is particularly suitable for hardware architectures that integrate storage and computation and exhibit good transferability.

Shrikant Arunrao Thote, Netra Pal Singh

The objective of this review paper is to identify the gap in finding out the direction toward the enhancement of heat transfer and the performance of heat exchangers. Heat exchangers can be found in many applications ranging from engineering devices to household consumer appliances. Heat exchangers must offer a good heat transfer performance apart from saving energy. Heat transfer enhancement techniques help to save energy and cool hot components in the design of electronic and mechanical circuits. However, enhancement in heat transfer takes place at the cost of a bearable increase in friction losses and pressure drop. Therefore, miniature heat exchanger systems and the cost of energy, motivate industries to use energy-saving methods in their design. With aging, the most common problem in heat exchangers is the reduction in heat transfer rate. Numerous studies have proved that placing a disturbance occurs in the fluid flow path and it can help to increase the heat transfer rate in the case of worn-out heat exchangers. For decades, researchers are numerically investigating the effects of various kinds of insert tape to improve the heat transfer operation in the heat exchangers. As heat exchangers form the backbone of many industrial processes, the idea of saving energy with the design of a cost-effective tape insert motivated us to work on this area of research. The paper proposes the new model of heat exchanger with an insert having a trapezoidal cut on both sides of an insert and using the different ratios of twist experimentation that will perform and compare the output with the previous studies by using different fluid or phase change materials as a fluid to maximize the performance of heat transfer rate. Also, it aims to find out the impact on friction factor as well pressure drop in the heat exchanger when there is a change in ratios of twist. This research aims to review the findings of earlier researchers in this area and to utilize the knowledge for improving the heat transfer rate of conventional tubes in our future work.

Roozbeh Mofidian, Mojtaba Jahanshahi, Seyed Sharafoddin Hosseini et al.

   Today, dimethyl ether (DME) is changing to ordinarily worn as a superb aerosol propellant and refrigerant for its eco-friendly characteristics. Lately, with the development of novel chemical energy in the coal industries, it has become a fascinating field of research as an alternative green fuel for diesel machines due to the high cetane number. The DME synthesis processes include catalytic dehydrating methanol in an adiabatic fixed-bed reactor. In this study, to investigate the chemical conditions of the methanol dehydration reaction, CFD simulations of the adiabatic reactor have been assessed. The advantage of the work is a sensitivity analysis was run to find the effect of pressure, kinetics, and velocity on the reactor performance. The results showed that using a γ-Al2O3 catalyst with selective mechanical properties and unique surface properties is a convenient choice for DME synthesis. The CFD simulation results also show that the laboratory data such as pressure, energy, and velocity in the adiabatic reactor meet the reaction requirements well, and deliberated a major vision of what happened in the reactor. Also, the graphs of the temperature profile with changes in physical properties pomp that methanol dehydration reaction strongly depends on environmental factors and gives different results under the influence of other conditions.

Leshtayev A. I., Storozhuk I. P., Orlov M. A. et al.

At present, polymer composite materials are widely used in the construction and automotive industries, products for which must meet not only operational, but also aesthetic requirements. Since color is one of the most important design elements, much attention is paid to the coloring of structural composites. There is a fairly wide range of different methods for coloring polymer composites, but each method has both advantages and disadvantages. This article discusses two methods for coloring a hot amine-cured epoxy composition, which is used for the manufacture of composite fiberglass reinforcement: by adding pigment and organic dyes to the epoxy composition. It has been found that organic dyes dissolve in all components of the epoxy composition, but become colorless upon heat treatment. When adding an insoluble dispersed pigment, the color remains unchanged even after the thermal curing of the epoxy matrix. The addition of up to 0.5 mass parts of iron oxide pigment (“red FEPREN TP-303”) to the epoxy binder slightly reduces the mechanical strength of the composite and significantly increases its thermal stability.

John Clifton‐Brown, Astley Hastings, Moritz vonCossel et al.

Abstract Demand for sustainably produced biomass is expected to increase with the need to provide renewable commodities, improve resource security and reduce greenhouse gas emissions in line with COP26 commitments. Studies have demonstrated additional environmental benefits of using perennial biomass crops (PBCs), when produced appropriately, as a feedstock for the growing bioeconomy, including utilisation for bioenergy (with or without carbon capture and storage). PBCs can potentially contribute to Common Agricultural Policy (CAP) (2023–27) objectives provided they are carefully integrated into farming systems and landscapes. Despite significant research and development (R&D) investment over decades in herbaceous and coppiced woody PBCs, deployment has largely stagnated due to social, economic and policy uncertainties. This paper identifies the challenges in creating policies that are acceptable to all actors. Development will need to be informed by measurement, reporting and verification (MRV) of greenhouse gas emissions reductions and other environmental, economic and social metrics. It discusses interlinked issues that must be considered in the expansion of PBC production: (i) available land; (ii) yield potential; (iii) integration into farming systems; (iv) R&D requirements; (v) utilisation options; and (vi) market systems and the socio‐economic environment. It makes policy recommendations that would enable greater PBC deployment: (1) incentivise farmers and land managers through specific policy measures, including carbon pricing, to allocate their less productive and less profitable land for uses which deliver demonstrable greenhouse gas reductions; (2) enable greenhouse gas mitigation markets to develop and offer secure contracts for commercial developers of verifiable low‐carbon bioenergy and bioproducts; (3) support innovation in biomass utilisation value chains; and (4) continue long‐term, strategic R&D and education for positive environmental, economic and social sustainability impacts.

Moritz Breul, Miguel Atienza

Moritz Breul, Thi Xuan Thu Nguyen