As a branch of laser cladding technology, laser micro-cladding shows unique local selective processing characteristics. Based on laser micro-cladding technology, this article proposes a new method ...for the in-situ formation of textured surfaces using laser micro-cladding technology. A Ni60/WC/WS2 composite coating was prepared on the cemented carbide substrate using laser micro-cladding technology, and a micro-groove structure was formed in situ. The microstructure, mechanical properties and tribological performance of laser micro-cladding Ni60/WC/WS2 composite coating were studied. The results show that laser micro-cladding technology can effectively prepare periodic controllable micro-textures with micron-sized dimensions, and the thickness of the laser micro-cladding composite coating can reach ∼300 μm. The hardness of composite coating can reach ∼28.48 GPa. The composite coating and micro-texture have a synergistic effect and can effectively improve the tribological properties of the substrate. The LCT sample has the lowest friction coefficient, with an average friction coefficient of ∼0.38. Due to the high hardness of the composite coating, it shows better wear resistance, but the micro-textured edge will cut the steel ball during the friction process, causing the steel ball wear rate of the LCT sample to reach ∼45.86 × 10−5 mm3/Nm. The exploration of laser micro-cladding in-situ forming textured surfaces provides experimental support for the application of cutting tools, brake discs and other mechanical components.
•Micro-textures were prepared on the substrate by laser micro-cladding technology.•Textures and coating have synergistic effect to reduce the friction coefficient.•The coating has high hardness and good wear resistance.•Laser micro-cladding in-situ formed textured surface provide experimental support.
A series of experiments were performed on the fan-shaped water mist interaction with the horizontal under-expanded hydrogen jet flames. The effects of various water mist pressures and horizontal ...release positions were focused on flame length, temperature, and radiant heat flux. The results show that, water mist causes the flame to be tilted and the tilt angle of the flame increases with the water mist pressure, and the horizontal length of the flame is shortened. It is also found that water mist may lead to the radiation and temperature enhancement on the axis and downstream of the action position of water mist and flame, which is closely related to the configuration of water mist. However, this situation disappears and the temperature and radiation decrease with the increase of water mist pressure.
•Effect of fan-shaped water mist on hydrogen jet flames was researched.•Fan-shaped water mist only caused the flame to be tilted.•Flame length was significantly shortened by fan-shaped water mist.•Cooling effect became more pronounced with water mist pressure.
Display omitted
•Cu-PBA: Cu2Fe(CN)6·xH2O crystallites and K2CuFe(CN)6 particles.•Cs+-adsorbed Cu-PBA: the occurrence of Cs2CuFe(CN)6 and K+/Cu2+ release.•GO/CS/Cu-PBA: fully utilized Cu-PBA, ...electrostatic attraction of Cs+ by GO/CS.•The application of GO/CS/Cu-PBA as a bulk aerogel or in a fixed-bed column system.
Efficient removal of 137Cs from various radioactive wastewater and contaminated environment is much meaningful for nuclear energy sustainable development and public health. Herein we used chitosan (CS) to induce the self-assembly of graphene oxide (GO) into a hydrogel (GO/CS) possessing a three-dimensional macroporous structure and produced a type of ternary composite hydrogel/aerogel named GO/CS/Cu-PBA by in situ growing potassium copper hexacyanoferrate(II) (Cu-PBA) nanoparticles onto the GO/CS via simple leaching. The adsorption behaviors of Cs+ by GO, Cu-PBA, and GO/CS/Cu-PBA in various matrice was systematically studied and compared. It was found that the GO/CS/Cu-PBA exhibited satisfactory sorption capacity for Cs+ (64.7 mg/g) and ultrafast kinetics. In addition, a fixed-bed column system could be employed for the cleanup of Cs+ from contaminated groundwater. Further FT-IR, XRD, XPS, and EXAFS analyses clarified the interaction mechanism between Cs+ and GO/CS/Cu-PBA. Highly selective fixation of Cs+ by Cu-PBA was accompanied by the release of K+/Cu2+ and a crystalline phase transition. The adsorption of Cs+ by GO was mainly correlated with the electrostatic attraction by –COO− and C-OH groups. The confinement of Cu-PBA by GO/CS aerogel is of much potential for the practical treatment of cesium-containing radioactive wastewater.
Display omitted
•Propose a holistic approach combining demand prediction with system optimization.•Community energy demands are simulated by agent-based modeling approach.•K-means clustering is used ...to generate representative stochastic demand scenarios.•A stochastic programming approach is applied for system optimal design and dispatch.•More than 36% cost savings can be achieved after optimization for case study.
When optimizing the design of integrated energy systems, their energy demands are usually assumed as given input. However, the demand of energy systems may not always be available information or it can be uncertain, particularly for projects at the planning stage. Moreover, the overall energy demand is dependent on the behavior of many individuals, which might change as a result of technical, economic or policy interventions. Therefore, this study proposes a holistic approach to combine the demand modeling with design and dispatch optimization for integrated energy systems. The approach can be decomposed into two stages. Firstly, at demand simulation stage, Agent Based Modeling is adopted to generate uncertain demand scenarios for a case study community and the energy-consuming activities for various types of households living in different kinds of apartments are simulated based on probability models and demographic information. Dozens of demand scenarios are obtained via iterative simulation, and k-means clustering approach is further applied to generate representative stochastic scenarios. Secondly, at system optimization stage, the uncertain demand scenarios are used as input of an established stochastic Mixed Integer Linear Programming model, by which the system design and dispatch strategy can be optimized simultaneously. The case study shows that the obtained optimal solutions can save 36% of annual total cost compared to the business-as-usual baseline scenario.
The hybrid wear system consisting of independent polyether-ether-ketone (PEEK) and polytetrafluoroethylene (PTFE) components sliding together against steel has been proven to improve the tribological ...performance of PEEK without compromising its excellent mechanical properties. In the present work, the effect of the countersurface roughness upon the tribological performance of the hybrid wear system is investigated. In a dual-pin-on-disk tribometer, steel rings with various roughness (Ra = 0.04–0.5) are introduced to PEEK-PTFE/Al2O3-steel (PPAS) hybrid wear systems containing hard nano particles and to PEEK-PTFE/brass-steel (PPBS) hybrid wear systems containing soft micron-scale particles. The morphologies of the worn surfaces demonstrate that the outstanding tribological performance of the hybrid wear system is closely related to the tribo-chemistry and the formation of tribofilms, which jointly depend on the properties of the fillers and on the roughness. The PPAS hybrid wear system is more suitable for low roughness conditions, as the wear debris containing nano-alumina particles will be pressed into the deep processing grooves of the steel surface, thereby hindering the occurrence of the tribo-chemical reaction. By contrast, the PPBS hybrid wear system exhibits good performance under high roughness conditions. With a smooth countersurface, the micron-sized brass particles will deposit onto the worn PTFE surface, and lead to severe abrasive wear on the countersurface, thereby hindering the formation of a transfer film. However, both the PPAS and the PPBS system provide exceptional tribological performance under moderate roughness conditions, due to the formation of high-quality fluorine-based tribofilms on each worn surface with the assistance of tribo-chemistry.
•The roughness and fillers have a combined effect on the tribological properties of the PEEK-PTFE-steel hybrid wear system.•The system containing hard nano-particles exhibits a good tribological performance under low roughness conditions.•The system containing soft micron-sized particles exhibits good performance under moderate-to-high roughness conditions.•The tribological performance are determined by the occurrence of tribo-chemical reactions and the formation of tribofilms.
In this paper we analyze the evolution of China’s growing importance in international scientific collaboration over the past 15 years. Using co-authored publications indexed in Clarivate Analytics’s ...Web of Science Core Collection we develop novel weighted and unweighted centrality measures to quantify China’s emerging role in the global scientific research network. We analyze the networks formed by international co-authorship in three 5-year periods: 2001–2005, 2006–2010, and 2011–2015. This analysis highlights China’s sharp increase in prominence in international scientific collaborations. The analysis of China’s co-authored, highly cited papers also illustrates China’s rising importance in scientific research and collaboration from a different perspective. The impact of multilaterally co-authored papers to the centrality measure is also analyzed both theoretically and empirically. The results show that multilateral collaboration is also a key factor that influences the centrality of a country beyond simply the scale of international co-authorship. We further contextualize our work in a discussion of international scientific collaboration as both a key driver of China’s economy and its emerging perception as a first-world innovator and intellectual power. Finally, we suggest directions for further research including more granular analysis by academic discipline and an alternative investigation based on the fractional counting method.
This study aimed to assess hematological diseases next-generation sequencing (NGS) panel enhances the diagnosis and classification of myeloid neoplasms (MN) using the 5th edition of the WHO ...Classification of Hematolymphoid Tumors (WHO-HAEM5) and the International Consensus Classification (ICC) of Myeloid Tumors. A cohort of 112 patients diagnosed with MN according to the revised fourth edition of the WHO classification (WHO-HAEM4R) underwent testing with a 141-gene NGS panel for hematological diseases. Ancillary studies were also conducted, including bone marrow cytomorphology and routine cytogenetics. The cases were then reclassified according to WHO-HAEM5 and ICC to assess the practical impact of these 2 classifications. The mutation detection rates were 93% for acute myeloid leukemia (AML), 89% for myelodysplastic syndrome (MDS), 94% for myeloproliferative neoplasm (MPN), and 100% for myelodysplasia/myeloproliferative neoplasm (MDS/MPN) (WHO-HAEM4R). NGS provided subclassified information for 26 and 29 patients with WHO-HAEM5 and ICC, respectively. In MPN, NGS confirmed diagnoses in 16 cases by detecting JAK2, MPL , or CALR mutations, whereas 13 “triple-negative” MPN cases revealed at least 1 mutation. NGS panel testing for hematological diseases improves the diagnosis and classification of MN. When diagnosed with ICC, NGS produces more classification subtype information than WHO-HAEM5.
Display omitted
In this work, we show that selective laser melting (SLM), apart from producing complex structures, can also act as a metallurgical method to modify the Ni/Ti ratio of NiTi shape ...memory alloys, and thus providing a feasible approach to tailor the transformation temperatures and to modify the mechanical performance of NiTi alloys. NiTi samples were fabricated by SLM with a large variation of process parameters, e.g. scanning speed (v) from 400 to 1200 mm s−1, hatch spacing (h) from 40 to 110 μm, and laser power (P) from 60 to 200 W. It is found that the martensite transformation temperature changes monotonously with the respective change of v, h or P. The composition analysis suggests that the different amount of Ni-loss under various SLM process conditions is the main reason for the evolution of transformation temperatures. Most importantly, good mechanical (total elongation >10 %) and functional properties under tensile mode have been obtained despite of the large variation of SLM process parameters and the presence of extensive defects. The good tensile properties and tailorable phase transformation temperatures will provide great potential to make novel NiTi smart structures.
Considering the effects of wall bowing and spatially nonuniform injection, the near-wall flow structures and heat transfer characteristics in transpiration cooling are studied through numerical ...simulations by an in-house thermal lattice Boltzmann solver accelerated by GPGPUs. Results reveal that the development of coolant layer is influenced by local velocity gradients, and a wall blowing ratio of larger than 2%–3% induces the flow separation and unstable coverage of low-temperature layer, and that the coolant injection weakens the surface friction coefficient, while the flow separation facilitates a local increase of the skin friction coefficient downstream the wall. For nonuniform injection, the local increases of mass and momentum with the peak velocity of nonuniform injection is beneficial to the coolant-layer development but the spatial temperature control is unstable, indicating the stable development and coverage of coolant layer are the key factors of the flow and heat transfer in transpiration cooling process.
•A thermal LBM-LES by GPGPUs-acceleration is presented for flow structures and heat transfer in transpiration cooling.•Coolant-layer development, skin-friction-coefficient and thermal performance are investigated under coolant injection.•The stable coolant-layer benefits cooling, and local peak velocity in nonuniform-blowing promotes coolant-coverage.
Abstract
To resolve the issue that conventional rolling bearing fault diagnosis technology are incapable of extracting features adaptively, a one-dimensional residual convolutional recurrent neural ...network (1DRCRNN-LSTM) is proposed to obtain signal characteristics directly from the original signal. Firstly, a train-valid-test paradigm dataset with sample overlap is created by data augmentation and one-hot coding. Secondly, a convolutional neural network (CNN) and a long short-term memory neural network (LSTM) are fused and a residual learning mechanism is introduced to build a network model for the extraction of signal characteristics. Finally, a softmax classification layer is implemented to classify ten types of faults and output diagnostic results. The proposed network model is verified using the Case Western Reserve University (CWRU) Rolling Bearing Dataset and the results show that the 1DRCRNN-LSTM model has a fault diagnosis accuracy of 0.987, which is better than that of multilayer perceptron (MLP) and convolutional neural network and other methods. Meanwhile, through t-sne visualization techniques, it is proved that this method has superior feature extraction and fault diagnosis capabilities.
