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Tribology and sustainability
\"This book brings a vision of promoting greener, cleaner, and eco-friendly environment highlighting sustainable solutions in tribology via development of self-lubricating materials, green additives in lubricants, natural fiber reinforced materials and biomimetic approaches. Backed by supporting schematic diagrams, data tables and illustrations for easy understanding, it focusses on the recent advancements in tribology and sustainability. Global sustainability and regional requirements are addressed through chapters on natural composites, green lubricants, biomedical and wind energy systems with a dedicated chapter on Global Sustainability Scenario. Features: Highlights sustainability via new tribological approaches and how such methods are essential. Covers theoretical aspects of various tribological topics concerning mechanical and material designs for energy-efficient systems. Includes practical global sustainability based on the regional requirement of tribological research and sustainable impact. Reviews tribology of green lubricants, green additives, and lightweight materials. Discusses topics related to biomimetics and bio-tribology. This book aims at researchers, professionals and graduate students in Tribology, Surface Engineering, Mechanical Design, Materials Engineering, including Mechanical, Aerospace, Chemical and Environmental Engineering\"-- Provided by publisher.
Book
Adsorption refrigeration technology
\"Gives readers a detailed understanding of adsorption refrigeration technology, with a focus on practical applications and environmental concerns. Systematically covering the technology of adsorption refrigeration, this book provides readers with a technical understanding of the topic as well as detailed information on the state-of-the-art from leading researchers in the field. Introducing readers to background on the development of adsorption refrigeration, the authors also cover the development of adsorbents, various thermodynamic theories, the design of adsorption systems and adsorption refrigeration cycles. The book guides readers through the research process, covering key aspects such as: the principle of adsorption refrigeration; choosing adsorbents according to different characteristics; thermodynamic equations; methods for the design of heat exchangers for adsorbers; and the advanced adsorption cycles needed. It is also valuable as a reference for professionals working in these areas. Covers state-of-the art of adsorption research and technologies for relevant applications, working from adsorption working pairs through to the application of adsorption refrigeration technology for low grade heat recovery. Assesses sustainable alternatives to traditional refrigeration methods, such as the application of adsorption refrigeration systems for solar energy and waste heat Includes a key chapter on the design of adsorption refrigeration systems as a tutorial for readers new to the topic; the calculation models for different components and working processes are also included. Takes real-world examples giving an insight into existing products and installations and enabling readers to apply the knowledge to their own work. Target audience: Academics researching low grade energy utilization and refrigeration; Graduate students of refrigeration and low grade energy utilization; Experienced engineers wanting to renew knowledge of adsorption technology; Engineers working at companies developing adsorption chillers; Graduate students working on thermally driven systems; Advanced undergraduates for the Refrigeration Principle as a part of thermal driven refrigeration technology\"--
eBook
Electro-thermal actuation in percolative ferroelectric polymer nanocomposites
The interconversion between electrical and mechanical energies is pivotal to ferroelectrics to enable their applications in transducers, actuators and sensors. Ferroelectric polymers exhibit a giant electric-field-induced strain (>4.0%), markedly exceeding the actuation strain (≤1.7%) of piezoelectric ceramics and crystals. However, their normalized elastic energy densities remain orders of magnitude smaller than those of piezoelectric ceramics and crystals, severely limiting their practical applications in soft actuators. Here we report the use of electro-thermally induced ferroelectric phase transition in percolative ferroelectric polymer nanocomposites to achieve high strain performance in electric-field-driven actuation materials. We demonstrate a strain of over 8% and an output mechanical energy density of 11.3 J cm−3 at an electric field of 40 MV m−1 in the composite, outperforming the benchmark relaxor single-crystal ferroelectrics. This approach overcomes the trade-off between mechanical modulus and electro-strains in conventional piezoelectric polymer composites and opens up an avenue for high-performance ferroelectric actuators.Piezoelectric actuators play a critical role in precision positioning devices; however, materials with high actuation strain and mechanical energy density are rare. Here a composite of poly(vinylidene fluoride) and TiO2 demonstrates superior performance in these metrics, with the ferroelectric transition driven by Joule heating.
Journal Article
Preparation of porous agro-waste-derived carbon from onion peel for supercapacitor application
Agro-waste-derived porous carbon has received more attention as electrode material for high-performance supercapacitor application due to its diversity and reproducibility. Herein, hierarchical porous carbon was successfully synthesized from most abundant biomass onion peel via double crucible method and it was explored as renewable carbon source for low-cost energy storage device. The supercapacitor electrode exhibits high specific capacitance of 127 Fg−1 at the current density of 0.75 Ag−1 with capacitance retention of 109% after 2000 cycles in three-electrode system. More importantly, its symmetric supercapacitor device exhibits energy density of 13.61 Wh kg−1 at the power density of 200.8 W kg−1 with remarkable electrochemical stability revealing capacitance retention above 100% over 14000 cycles. Our study demonstrates that onion peel-derived carbon is suitable for future low-cost energy storage device.
Journal Article
Lightweight, Flexible Cellulose-Derived Carbon Aerogel@Reduced Graphene Oxide/PDMS Composites with Outstanding EMI Shielding Performances and Excellent Thermal Conductivities
HighlightsCellulose aerogels were prepared by hydrogen bonding driven self-assembly, gelation and freeze-drying.The skin-core structure of CCA@rGO aerogels can form a perfect three-dimensional bilayer conductive network.Outstanding EMI SE (51 dB) is achieved with 3.05 wt% CCA@rGO, which is 3.9 times higher than that of the co-blended composites.In order to ensure the operational reliability and information security of sophisticated electronic components and to protect human health, efficient electromagnetic interference (EMI) shielding materials are required to attenuate electromagnetic wave energy. In this work, the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide (NaOH)/urea solution, and cellulose aerogels (CA) are prepared by gelation and freeze-drying. Then, the cellulose carbon aerogel@reduced graphene oxide aerogels (CCA@rGO) are prepared by vacuum impregnation, freeze-drying followed by thermal annealing, and finally, the CCA@rGO/polydimethylsiloxane (PDMS) EMI shielding composites are prepared by backfilling with PDMS. Owing to skin-core structure of CCA@rGO, the complete three-dimensional (3D) double-layer conductive network can be successfully constructed. When the loading of CCA@rGO is 3.05 wt%, CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness (EMI SE) of 51 dB, which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites (13 dB) with the same loading of fillers. At this time, the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability (THRI of 178.3 °C) and good thermal conductivity coefficient (λ of 0.65 W m-1 K-1). Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight, flexible EMI shielding composites.Graphic abstract
Journal Article
3D printing for continuous fiber reinforced thermoplastic composites: mechanism and performance
Purpose
Continuous fiber reinforced thermoplastic composites (CFRTPCs) are becoming more significant in industrial applications but are limited by the high cost of molds, the manufacturing boundedness of complex constructions and the inability of special fiber alignment. The purpose of this paper is to put forward a novel three-dimensional (3D) printing process for CFRTPCs to realize the low-cost rapid fabrication of complicated composite components.
Design/methodology/approach
For this purpose, the mechanism of the proposed process, which consists of the thermoplastic polymer melting, the continuous fiber hot-dipping and the impregnated composites extruding, was investigated. A 3D printing equipment for CFRTPCs with a novel composite extrusion head was developed, and some composite samples have been fabricated for several mechanical tests. Moreover, the interface performance was clarified with scanning electron microscopy images.
Findings
The results showed that the flexural strength and the tensile strength of these 10 Wt.% continuous carbon fiber (CCF)/acrylonitrile-butadiene-styrene (ABS) specimens were improved to 127 and 147 MPa, respectively, far greater than the one of ABS parts and close to the one of CCF/ABS (injection molding) with the same fiber content. Moreover, these test results also exposed the very low interlaminar shear strength (only 2.81 MPa) and the inferior interface performance. These results were explained by the weak meso/micro/nano scale interfaces in the 3D printed composite parts.
Originality/value
The 3D printing process for CFRTPCs with its controlled capabilities for the orientation and distribution of fiber has great potential for manufacturing of load-bearing composite parts in the industrial circle.
Journal Article
Applications of Discrete Element Method in the Research of Agricultural Machinery: A Review
As a promising and convenient numerical calculation approach, the discrete element method (DEM) has been increasingly adopted in the research of agricultural machinery. DEM is capable of monitoring and recording the dynamic and mechanical behavior of agricultural materials in the operational process of agricultural machinery, from both a macro-perspective and micro-perspective; which has been a tremendous help for the design and optimization of agricultural machines and their components. This paper reviewed the application research status of DEM in two aspects: First is the DEM model establishment of common agricultural materials such as soil, crop seed, and straw, etc. The other is the simulation of typical operational processes of agricultural machines or their components, such as rotary tillage, subsoiling, soil compaction, furrow opening, seed and fertilizer metering, crop harvesting, and so on. Finally, we evaluate the development prospects of the application of research on the DEM in agricultural machinery, and look forward to promoting its application in the field of the optimization and design of agricultural machinery.
Journal Article
Stretchable pumps for soft machines
Machines made of soft materials bridge life sciences and engineering
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. Advances in soft materials have led to skin-like sensors and muscle-like actuators for soft robots and wearable devices
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–
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. Flexible or stretchable counterparts of most key mechatronic components have been developed
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,
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, principally using fluidically driven systems
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–
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; other reported mechanisms include electrostatic
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–
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, stimuli-responsive gels
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,
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and thermally responsive materials such as liquid metals
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and shape-memory polymers
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. Despite the widespread use of fluidic actuation, there have been few soft counterparts of pumps or compressors, limiting the portability and autonomy of soft machines
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,
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. Here we describe a class of soft-matter bidirectional pumps based on charge-injection electrohydrodynamics
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. These solid-state pumps are flexible, stretchable, modular, scalable, quiet and rapid. By integrating the pump into a glove, we demonstrate wearable active thermal management. Embedding the pump in an inflatable structure produces a self-contained fluidic ‘muscle’. The stretchable pumps have potential uses in wearable laboratory-on-a-chip and microfluidic sensors, thermally active clothing and autonomous soft robots.
A stretchable polymer pump that uses electric fields to accelerate ions in dielectric liquids can generate flow even when bent into different conformations, offering applications in soft robotics.
Journal Article
A residual denoising and multiscale attention-based weighted domain adaptation network for tunnel boring machine main bearing fault diagnosis
As a critical component of a tunnel boring machine (TBM), the precise condition monitoring and fault analysis of the main bearing is essential to guarantee the safety and efficiency of the TBM cutter drive. Currently, under conditions of strong noise and complex working environments, traditional signal decomposition and machine learning methods struggle to extract weak fault features and achieve high fault classification accuracy. To address these issues, we propose a novel residual denoising and multiscale attention-based weighted domain adaptation network (RDMA-WDAN) for TBM main bearing fault diagnosis. Our approach skillfully designs a deep feature extractor incorporating residual denoising and multiscale attention modules, achieving better domain adaptation despite significant domain interference. The residual denoising component utilizes a convolutional block to extract noise features, removing them via residual connections. Meanwhile, the multiscale attention module uses a 4-branch convolution and 3 pooling strategy-based channel-spatial attention mechanism to extract multiscale features, concentrating on deep fault features. During training, a weighting mechanism is introduced to prioritize domain samples with clear fault features. This optimizes the deep feature extractor to obtain common features, enhancing domain adaptation. A low-speed and heavy-loaded bearing testbed was built, and fault data sets were established to validate the proposed method. Comparative experiments show that in noise domain adaptation tasks, proposed the RDMA–WDAN significantly improves target domain classification accuracy by 42.544%, 23.088%, 43.133%, 16.344%, 5.022%, and 9.233% over dense connection network (DenseNet), squeeze-excitation residual network (SE-ResNet), antinoise multiscale convolutional neural network (ANMSCNN), multiscale attention module-based convolutional neural network (MSAMCNN), domain adaptation network, and hybrid weighted domain adaptation (HWDA). In combined noise and working condition domain adaptation tasks, the RDMA–WDAN improves the accuracy by 45.672%, 23.188%, 43.266%, 16.077%, 5.716%, and 9.678% compared with baseline models.
Journal Article
Graphene aerogel-based phase changing composites for thermal energy storage systems
Phase changing materials (PCM) release or absorb heat in high quantity when there is a variation in phase. PCMs show good energy storage density, restricted operating temperatures and hence find application in various systems like heat pumps, solar power plants, electronic devices, thermal energy storage (TES) systems. Though it has extensive usage in such a diverse range of systems, PCMs have some limitations like poor thermal conductivity, susceptibility to leakage during phase transformations. To overcome these shortcomings, phase changing composites (PCCs) were fabricated. PCCs are an amalgamation of filler material with PCMs to form a composite with those anticipated or desired properties. There are multiple factors like porosity, sealing performance, leaking holding capacity, shape stability, thermal conductivity that should be taken into consideration/account while fabricating PCCs. Having considered such factors, graphene, which has high thermal conductivity (2000–4000 W/m K) and high specific surface area (~ 2630 m2 g−1), acts as a suitable candidate for synthesizing an effective and efficient PCC. In its aerogel form, it is used as a conductive filler or form-stabilizer, to improve the thermal conductivity (~ 5.89 W/m K) and heat transfer of PCMs like reduced graphene oxide. Graphene aerogels, thus, are used in PCM as latent heat storage (LHS) for thermal energy storage systems. Many of the researchers have based their work focus on graphene aerogels in PCMs, significant roles of such PCCs, their advantages and disadvantages; this paper is an effort to elucidate those and provide further insight into TES systems in which LHS is explicitly used in PCMs and their practical aspect.
Journal Article