Carbon fiber-reinforced polymer (CFRP) easily realizes the integrated manufacturing of components with high specific strength and stiffness, and it has become the preferred material in the aerospace ...field. Grinding is the key approach to realize precision parts and matching the positioning surface for assembly and precision. Hygroscopicity limits the application of flood lubrication in CFRP grinding, and dry grinding leads to large force, surface deterioration, and wheel clogging. To solve the above technical bottleneck, this study explored the grindability and frictional behavior of CNT biological lubricant MQL through grinding experiments and friction-wear tests. Results showed that the CNT biological lubricant reduced the friction coefficient by 53.47% compared with dry condition, showing optimal and durable antifriction characteristics. The new lubrication was beneficial to suppressing the removal of multifiber block debris, tensile fracture, and tensile-shear fracture, with the advantages of tribological properties and material removal behavior, the tangential and normal grinding force, and the specific grinding energy were reduced by 40.41%, 31.46%, and 55.78%, respectively, compared with dry grinding. The proposed method reduced surface roughness and obtained the optimal surface morphology by preventing burrs, fiber pull-out, and resin smearing, and wheel clogging was prevented by temperature reduction and lubricating oil film formation. S
and S
of the CNT biological lubricant were reduced by 8.4% and 7.9%, respectively, compared with dry grinding. This study provides a practical basis for further application of CNT biological lubricant in CFRP grinding.
The effectiveness and cost are always top factors for policy-makers to decide control measures and most measures had no pre-test before implementation. Due to the COVID-19 pandemic, human activities ...are largely restricted in many regions in India since mid-March of 2020, and it is a progressing experiment to testify effectiveness of restricted emissions. In this study, concentrations of six criteria pollutants, PM10, PM2.5, CO, NO2, ozone and SO2 during March 16th to April 14th from 2017 to 2020 in 22 cities covering different regions of India were analysed. Overall, around 43, 31, 10, and 18% decreases in PM2.5, PM10, CO, and NO2 in India were observed during lockdown period compared to previous years. While, there were 17% increase in O3 and negligible changes in SO2. The air quality index (AQI) reduced by 44, 33, 29, 15 and 32% in north, south, east, central and western India, respectively. Correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years, indicating more significant regional transport than previous years. The mean excessive risks of PM reduced by ~52% nationwide due to restricted activities in lockdown period. To eliminate the effects of possible favourable meteorology, the WRF-AERMOD model system was also applied in Delhi-NCR with actual meteorology during the lockdown period and an un-favourable event in early November of 2019 and results show that predicted PM2.5 could increase by only 33% in unfavourable meteorology. This study gives confidence to the regulatory bodies that even during unfavourable meteorology, a significant improvement in air quality could be expected if strict execution of air quality control plans is implemented.
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•The effect of restricted human activities due to the COVID-19 pandemic in India on air quality in 22 cities was estimated.•PM2.5 had maximum reduction in most regions.•Correlation between cities especially in northern and eastern regions improved in 2020 compared to previous years.•The substantial reduction in concentrations resulted in a 4 times reduction in total ER.•PM2.5 could increase due to unfavourable meteorology but the average concentration would still be under CPCB limits.
In this article, I attempt to critically assess Kenneth Waltz’s deployment of the idea of anarchy to erect a ‘scientific theory of international politics’. First, I argue that the formation of a ...concept requires comprehension of the object from the standpoint of historical development, not a narrow reading of it. Second, I subject the thinner abstractions of self-help, balance of power and bandwagoning to the test of history. Third, I argue about mainstream international relations’ disdain for revolutions. I would posit that revolutions are fine templates which store rich agential history of structural transformation, a theme subject to much chagrin by realists of all hues, particularly neorealists. In doing so, I take the Bolshevik Revolution of 1917 as my benchmark. I elucidate that through the occlusion of first and second images, man and state, in the favour of third image, that is, structural anarchy, Waltz tends to ignore the role of agency as a conscious collective which could be best captured by the Bolshevik Revolution. In doing so, I rely on Perry Anderson’s three modes of agency in history. As a corrective to Waltz’s theorization, I make a strong case for class transcending both man and state as an organic category with immense potential of becoming a level of analysis which both acts upon the structure and refracts through it. I finally conclude by saying that anarchy was a condition and not a ‘social relation’ of any sort which could claim to constitute the ‘international’.
In this work, we delve into the realm of quantum chromodynamics (QCD) by calculating twist-4 chiral-even generalized parton distributions (GPDs), within the context of the light-front quark-diquark ...model (LFQDM), focusing specifically on the intriguing case of zero skewness. To shed light on the behavior of twist-4 chiral-even GPDs, we present comprehensive two-dimensional (2-D) and 3-dimensional (3-D) plots, mapping their dependence on the longitudinal momentum fraction (x) and the momentum transfer (t). Furthermore, our research looks into the profound connection between twist-4 chiral-even GPDs and other distribution functions (DFs), including parton distribution functions (PDFs), transverse momentum-dependent parton distributions (TMDs) and generalized transverse-momentum dependent parton distributions (GTMDs). Additionally, our investigation extends to the exploration of related higher twist form factors (FFs), which play a pivotal role in elucidating the internal structure of hadrons. To provide significant insights into the partons spatial distribution, we have also yielded impact parameter GPD plots.
Due to the stringent requirements of carbon emissions, traditional cutting using a large amount of mineral-based metal cutting fluid for lubrication no longer fulfilled the rigorous requirements of ...policies and standards. Nanofluid minimum quantity lubrication has been proven to be a new process to achieve clean manufacturing. However, due to adhesive contact friction, lubricant droplets cannot effectively penetrate the tool and workpiece interface during continuous turning. Changing the microstructure of the rake face of the tool, such as the micro-texture, may provide a geometric channel for the diffusion of the lubricant. However, the effects of micro-texture geometry and arrangement on the film formation and tribological properties of droplets have not been revealed yet. The spreading behavior of minimum quantity lubrication atomized microdroplet on the textured surface was calculated by hydrodynamic modeling. It was proven that the microchannel can effectively store the lubricating medium atomized by compressed air pneumatics. Furthermore, a comparative experiment was conducted on the influence of the texture arrangement on the cutting performance through the turning experiment. Results show that the microgrooves in the direction perpendicular to the main cutting edge obtained the lowest cutting force. The feed force, radial force, and tangential force were reduced by 13.46%, 16.23%, and 6.34%, respectively. Meanwhile, the texture arranged parallel to the cutting edge and crosswise increased the cutting force. The arrangement of the texture perpendicular to the main cutting edge direction obtained the optimal workpiece surface, the smallest chip curling radius, and the smoothest chip surface. Under the optimized texture arrangement, the anti-wear and anti-friction properties of nanofluids in the cutting area are enhanced.
The special mechanical properties of cemented carbide with high strength and hardness will cause complex stress due to excessive force and heat in the process of precision manufacturing, which will ...affect precision retention and endurance limit. Given the health and environmental threat of conventional flood cooling and the harsh processing environment of dry grinding, minimum quantity lubrication (MQL) has become an irreplaceable method to machining cemented carbide. However, the addition of nanoparticles changes the force and heat during grinding, which makes the influence on the residual stress of cemented carbide complicated. Therefore, based on the single abrasive grinding force model, the effective abrasive particle number was obtained by simulating the distribution of abrasive particles on the grinding wheel surface, and the mechanical stress model was established, which was loaded onto the workpiece in iterative attenuation mode. The thermal stress model was established based on the temperature field model. The final residual stress prediction model was obtained by determining whether the grinding process yields results and carrying out stress loading and stress relaxation. Experimental verification of the model was carried out under four different grinding conditions of YG8. The minimum friction coefficient of 0.385 was obtained under nanofluid minimum quantity lubrication (NMQL). In the precision analysis of the model, the minimum error value was 5.9% in the direction perpendicular to the feed direction of the workpiece in the dry grinding condition, which proved that the residual stress model had certain reliability.
In this study, the T-even sub-leading twist transverse momentum dependent distributions (TMDs) of proton in the light-front quark-diquark model (LFQDM) have been investigated. We have derived the ...overlap form of the light-front wave functions (LFWFs) for the sub-leading twist proton TMDs by detangling the un-integrated quark-quark correlator for the semi-inclusive deep inelastic scattering (SIDIS). We have obtained the explicit expressions of TMDs for both the cases of the diquark being a scalar or a vector and analyzed their relationships with leading twist TMDs within the same model. Average transverse momenta and average square transverse momenta for the TMDs have been tabulated and compared with the results from the light-front bag model and the light-front constituent quark model (LFCQM). In addition to this, we have also compared our results for the PDF e(x) with the recent CLAS collaboration results.
Transverse momentum dependent parton distributions of proton; T-even sub-leading twist TMDs; light-front quark-diquark model.
Extreme pressure (EP) and antiwear (AW) additives are necessary for boundary lubrication. However, their mechanisms and physical and chemical properties remain unclear. EP and AW additives were ...reviewed to fill gaps in theoretical and industrial applications. Compounds containing chlorine, sulfur, and phosphorus elements were first used in boundary lubrication because of thermal reaction with metal to form film characteristics. First, the mechanisms of traditional EP and AW additives were analyzed, the physical and chemical properties were compared, and properties affecting factors were studied. Traditional EP and AW additives are not environmentally friendly, but nanoparticle EP and AW additives are excellent substitutes. The mechanisms of nanoparticle EP and AW additives were summarized. The influence of nanoparticle structure parameters, concentration, and media polarity on properties was studied. Second, the influence law of non-polar chain length on traditional EP and AW additives was revealed. The improvement interval of traditional EP and AW additives on the performance of the base fluid was determined. The structural advantage of low crystallinity onion-like and multilayer sheet-like low wrinkle effect of nanoparticles was explained. The particle size design principle attached to the surface roughness and size-dependent melting inhibition mechanism was established. The influence of concentration and media polarity on nanoparticle properties was obtained. Finally, the research of minimum amount matching database and mathematical selection model for traditional EP and AW additives and the molecular dynamics analysis of surface-modified nanoparticles and the development of green general-purpose additives based on molecular design are prospected.
Cutting fluid has cooling and lubricating properties and is an important part of the field of metal machining. Owing to harmful additives, base oils with poor biodegradability, defects in processing ...methods, and unreasonable emissions of waste cutting fluids, cutting fluids have serious pollution problems, which pose challenges to global carbon emissions laws and regulations. However, the current research on cutting fluid and its circulating purification technique lacks systematic review papers to provide scientific technical guidance for actual production. In this study, the key scientific issues in the research achievements of eco-friendly cutting fluid and waste fluid treatment are clarified. First, the preparation and mechanism of organic additives are summarized, and the influence of the physical and chemical properties of vegetable base oils on lubricating properties is analyzed. Then, the process characteristics of cutting fluid reduction supply methods are systematically evaluated. Second, the treatment of oil mist and miscellaneous oil, the removal mechanism and approach of microorganisms, and the design principles of integrated recycling equipment are outlined. The conclusion is concluded that the synergistic effect of organic additives, biodegradable vegetable base oils and recycling purification effectively reduces the environmental pollution of cutting fluids. Finally, in view of the limitations of the cutting fluid and its circulating purification technique, the prospects of amino acid additive development, self-adapting jet parameter supply system, matching mechanism between processing conditions and cutting fluid are put forward, which provides the basis and support for the engineering application and development of cutting fluid and its circulating purification.
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