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Correlation between flattening ratio and wear performance of cold sprayed metal matrix composite coatings
No full textCold spray is one of the promising coating deposition techniques for fabricating anti-wear composite coatings. These composite coatings contain an even distribution of the two phases, they are Ti-6Al-4V and Al splats if referring to the current study. With the help of image analysis software (Fiji), the flattening ratio (FR) of Al splats was found to be larger than that of Ti-6Al-4V in different composite coatings. The overall FR is more comprehensively correlated to fracture toughness and wear performance for the entire composite structure, rather than comparing the particular FR of Ti-6Al-4V or Al splats only. The higher the FR of the composite coating, the better its wear performance, but this phenomenon only applies to the same type of composite coating, because different composite coatings respond differently to wear
Lindström theorems in graded model theory
No full textStemming from the works of Petr Hájek on mathematical fuzzy logic, graded model theory has been developed by several authors in the last two decades as an extension of classical model theory that studies the semantics of many-valued predicate logics. In this paper we take the first steps towards an abstract formulation of this model theory. We give a general notion of abstract logic based on many-valued models and prove six Lindström-style characterizations of maximality of first-order logics in terms of metalogical properties such as compactness, abstract completeness, the Löwenheim–Skolem property, the Tarski union property, and the Robinson property, among others. As necessary technical restrictions, we assume that the models are valued on finite MTL-chains and the language has a constant for each truth-value
Scalable fabrication and active site identification of MOF shell-derived nitrogen-doped carbon hollow frameworks for oxygen reduction
No full textNitrogen-doped carbon materials as promising oxygen reduction reaction (ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, high conductivity and low cost. To maximize their catalytic efficiency, rational design of efficient electrocatalysts with rich exposed active sites is highly desired. Besides, due to the complexity of nitrogen species, the identification of active nitrogen sites for ORR remains challenging. Herein, we develop a facile and scalable template method to construct high-concentration nitrogen-doped carbon hollow frameworks (NC), and reveal the effect of different nitrogen species on their ORR activity on basis of experimental analysis and theoretical calculations. The formation mechanism is clearly revealed, including low-pressure vapor superassembly of thin zeolitic imidazolate framework (ZIF-8) shell on ZnO templates, in situ carbonization and template removal. The obtained NC-800 displays better ORR activity compared with other NC-700 and NC-900 samples. Our results indicate that the superior ORR activity of NC-800 is mainly attributed to its content balance of three nitrogen species. The graphitic N and pyrrolic N sites are responsible for lowering the working function, while the pyridinic N and pyrrolic N sites as possible active sites are beneficial for increasing the density of states
Recommender systems based on generative adversarial networks: A problem-driven perspective
No full textRecommender systems (RS) now play a very important role in the online lives of people as they serve as personalized filters for users to find relevant items from a sea of options. Owing to their effectiveness, RS have been widely employed in our daily life. However, despite their empirical successes, these systems still suffer from two limitations: data noise and data sparsity. In recent years, generative adversarial networks (GANs) have garnered increased interest in many fields due to their strong capacity to learn complex real data distributions. Their abilities to enhance RS by tackling the above challenges have also been demonstrated in numerous studies. In general, two lines of research have been conducted, and their common ideas can be summarized as follows: (1) for the data noise issue, adversarial perturbations and adversarial sampling-based training often serve as a solution; (2) for the data sparsity issue, data augmentation—implemented by capturing the distribution of real data under the minimax framework—is the primary coping strategy. To gain a comprehensive understanding of these research efforts, we review the corresponding studies and models, organizing them from a problem-driven perspective. More specifically, we propose a taxonomy of these models, along with their detailed descriptions and advantages. Finally, we elaborate on several open issues and current trends in GAN-based RS
Using resilience assessments to inform the management and conservation of coral reef ecosystems
No full textClimate change is causing the decline of coral reef ecosystems globally. Recent research highlights the importance of reducing CO emissions in combination with implementing local management actions to support reef health and recovery, particularly actions that protect sites which are more resilient to extreme events. Resilience assessments quantify the ecological, social, and environmental context of reefs through the lens of resilience, i.e., the capacity of a system to absorb or withstand stressors such that the system maintains its structure and functions and has the capacity to adapt to future disturbances and changes. Resilience assessments are an important tool to help marine managers and decision makers anticipate changes, identify areas with high survival prospects, and prioritize management actions to support resilience. While being widely implemented, however, there has not yet been an evaluation of whether resilience assessments have informed coral reef management. Here, we assess the primary and gray literature and input from coral reef managers to map where resilience assessments have been conducted. We explore if and how they have been used to inform management actions and provide recommendations for improving the likelihood that resilience assessments will result in management actions and positive conservation outcomes. These recommendations are applicable to other ecosystems in which resilience assessments are applied and will become increasingly important as climate impacts intensify and reduce the window of opportunity for protecting natural ecosystems
Academic achievement of children in same-sex-parented and different-sex-parented families: a\ua0population-level analysis of linked administrative data from the Netherlands
No full textExistence of Kirillov–Reshetikhin crystals for near adjoint nodes in exceptional types
No full textWe prove that, in types E, F and E, every Kirillov–Reshetikhin module associated with the node adjacent to the adjoint one (near adjoint node) has a crystal pseudobase, by applying the criterion introduced by Kang et al. In order to apply the criterion, we need to prove some statements concerning values of a bilinear form. We achieve this by using the global bases of extremal weight modules
Nonlinear mixing of non-collinear guided waves at a contact interface
No full textWave mixing offers several practical benefits relative to harmonic generation for detecting both distributed and localised damage. An analytical model is proposed for predicting the frequency, mode and direction of propagation of the mixed modes arising from the nonlinear mixing of two incident guided-wave modes at an interface exhibiting contact acoustic nonlinearity. These predictions are validated by a finite-element (FE) analysis involving a unilateral contact law that models both clapping and frictional sliding at the interface. This analysis also provides quantitative insights regarding the optimal interaction angle between the incident waves in the case of shear-horizontal SH modes, and the dependence of the mixed-wave amplitude on the load ratio (i.e. ratio of contact stress to normal stress across the interface due to both incident waves). The non-collinear mixing of guided waves is also investigated experimentally for various values of contact stress and incident stress amplitude, demonstrating the existence of mixed waves, as well as showing that interface mixing leads to a higher amplitude mixed wave than that due to the background material nonlinearity. This higher amplitude combined with great flexibility in the choice of incident wave parameters (frequency, mode and direction) makes wave mixing an attractive practical approach for detecting contact acoustic nonlinearity at crack-like defects and interfaces. Experimentally, the maximum value of mixed-wave amplitude is obtained at the same value of contact stress for the various incident stress amplitudes, whereas the FE model shows a maximum at a unique value of the load ratio. This difference may be a consequence of surface roughness, which is not included in the FE model
Technological assessment of CO2 capture and EOR/EGR/ ECBM-based storage
No full textCarbon capture and CO2-EOR-driven storage provides an efficient way to reduce CO2\ua0emissions into the atmosphere, while allowing the consumption of fossil fuels and securing sufficient energy supply. The scale of carbon capture and storage is still far short of meeting industry-scale demand. Economical large-scale capture techniques, efficient utilization, and geological storage of CO2\ua0provide the best strategy for carbon emission reduction, and CO2-EOR is an inevitable choice and will surely have great prospects in carbon-intensive countries, including China
The interactions of radioactive lead with sulphide minerals
No full textRadionuclides, specifically\ua0210Pb, can be recovered to copper concentrates potentially by associating with copper sulphide surfaces. This presents regulatory and health issues around radionuclide activity in concentrates. It is hypothesised that\ua0210Pb forms a stable PbS species on the copper sulphide surfaces allowing\ua0210Pb to be “carried” through the flotation process. It is the presence of such a species that this paper seeks to confirm. The minerals examined in this study are chalcocite (Cu2S), chalcopyrite (CuFeS2) and pyrite (FeS2) with lead nitrate providing Pb2+\ua0to simulate\ua0210Pb. Thermodynamic modelling and Cyclic Voltammetry studies indicate that PbS does form on the mineral surfaces with Cryogenic X-ray Photoelectron Spectroscopy confirming its presence. The mechanism of PbS formation is via the adsorption of Pb2+\ua0to sulphur-rich regions on the mineral surfaces and subsequent reaction to form PbS. Various oxygen-associated lead species were also detected, forming via the interaction of Pb2+\ua0with mineral oxidation products. Total lead on the mineral surfaces was 9.69 at%, 19.62 at% and 12.62 at% for pyrite, chalcocite and chalcopyrite, respectively. The ratio of lead-sulphur species to lead-oxygen species was 0.27, 0.84 and 1.00 for pyrite, chalcocite and chalcopyrite, respectively. Under flotation conditions, PbS is a stable species, meaning that it likely remains on mineral surfaces throughout the flotation process, facilitating\ua0210Pb recovery to concentrates
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