Various Ni–Fe/Mg(Al)O alloy catalysts were obtained by calcination of Ni–Fe–Mg–Al hydrotalcite-like compounds, followed by reduction at different temperatures (973–1173 K). The characterizations of ...XRD and STEM-EDX suggest that the resulting Ni–Fe alloy particles are composition-uniform and size-controllable. The alloy composition is little affected by the reduction temperature, whereas the particle size (5.8–8.2 nm) increases with the increase of reduction temperature. This property is ascribed to the homogeneous distribution of nickel and iron species during the catalyst preparation. All of the Ni–Fe/Mg(Al)O alloy catalysts show relatively high and stable activity for CH4–CO2 reforming during 25 h of investigation at 773–1073 K. Particularly, the 973 K-reduced catalyst exhibits higher coke-resistance due to its smaller particle size. Ea-CH4 and CH4-TPSR measurements indicate that Ni–Fe alloying inhibits CH4 dissociation. It is considered that during DRM CH4 is dissociated at the Ni sites and CO2 may be activated at the metal-support interface as well as the Fe sites. Ni–Fe alloying may inhibit CH4 dissociation and/or promote CO2 activation, thus contributing to the suppression of coke deposition.
•Ni–Fe alloy particles are composition-uniform and size-controllable.•Ni–Fe/Mg(Al)O catalysts shows good performance for DRM at 773–1073 K.•The 973 K-reduced catalyst shows higher coke resistance due to small particle size.•Ni–Fe alloying inhibits CH4 dissociation contributing to coke suppression.
This study presents a motion planning method for coordinating multiple mobile robots for collision‐free navigation. A control architecture that uses cloud computing is proposed for the acquisition of ...real‐time robotic data and to coordinate multiple robots in an unstructured environment. The system consists of collision‐free path planning for multiple robots, obstacle avoidance, and navigation control. The path planning method was developed based on the optimal reciprocal collision avoidance (ORCA) algorithm to generate a velocity set of each robot in the system. A laser scanner is used to detect obstacles for each robot. Appropriate obstacle avoidance behaviors are generated using sensory information. A behavior‐fusion control scheme combines obstacle avoidance and collision‐free path planning to coordinate multiple robots. The proposed anti‐collision motion planning method for multiple robots prevents collisions with unexpected obstacles and with other robots in the environment. The experimental results show that multiple mobile robots can navigate to targets that are assigned by the cloud server without colliding with other robots, regardless of whether there are unexpected static or dynamic obstacles in the environment.
To improve simulation accuracy and efficiency of probabilistic fatigue life evaluation for turbine rotor, a decomposed collaborative modeling approach is presented. In this approach, the intelligent ...Kriging modeling (IKM) is firstly proposed by combining the Kriging model (KM) and an intelligent algorithm (named as dynamic multi-island genetic algorithm), to tackle the multi-modality issues for obtaining optimal Kriging parameters. Then, the decomposed collaborative IKM (DCIKM) comes up by fusing the IKM into decomposed collaborative (DC) strategy, to address the high-nonlinearity problems for accelerating simulation efficiency. Moreover, the DCIKM-based probabilistic fatigue life evaluation theory is introduced. The probabilistic fatigue life evaluation of turbine rotor is regarded as case study to verify the presented approach; the evaluation results reveal that the probabilistic fatigue life of turbine rotor is 3296 cycles. The plastic strain range ∆εp and fatigue strength coefficient σf′ are the main affecting factors to fatigue life, whose effect probability are 28% and 22%, respectively. By comparing with direct Monte Carlo method, KM method, IKM method and DC response surface method, the presented DCIKM is validated to hold high efficiency and accuracy in probabilistic fatigue life evaluation.
Taiyangshan is a poorly studied copper–molybdenum deposit located in the Triassic Western Qinling collisional belt of northwest China. The intrusions exposed in the vicinity of the Taiyangshan ...deposit record episodic magmatism over 20–30millionyears. Pre-mineralization quartz diorite porphyries, which host some of the deposit, were emplaced at 226.6±6.2Ma. Syn-collisional monzonite and quartz monzonite porphyries, which also host mineralization, were emplaced at 218.0±6.1Ma and 215.0±5.8Ma, respectively. Mineralization occurred during the transition from a syn-collisional to a post-collisional setting at ca. 208Ma. A barren post-mineralization granite porphyry marked the end of post-collisional magmatism at 200.7±5.1Ma. The ore-bearing monzonite and quartz monzonite porphyries have a εHf(t) range from −2.0 to +12.5, which is much more variable than that of the slightly older quartz diorite porphyries, with TDM2 of 1.15–1.23Ga corresponding to the positive εHf(t) values and TDM1 of 0.62–0.90Ga corresponding to the negative εHf(t) values. Molybdenite in the Taiyangshan deposit with 27.70 to 38.43ppm Re suggests metal sourced from a mantle–crust mixture or from mafic and ultramafic rocks in the lower crust. The δ34S values obtained for pyrite, chalcopyrite, and molybdenite from the deposit range from +1.3‰ to +4.0‰, +0.2‰ to +1.1‰, and +5.3‰ to +5.9‰, respectively, suggesting a magmatic source for the sulfur. Calculated δ18Ofluid values for magmatic K-feldspar from porphyries (+13.3‰), hydrothermal K-feldspar from stockwork veins related to potassic alteration (+11.6‰), and hydrothermal sericite from quartz–pyrite veins (+8.6 to +10.6‰) indicate the Taiyangshan deposit formed dominantly from magmatic water. Hydrogen isotope values for hydrothermal sericite ranging from −85 to −50‰ may indicate that magma degassing progressively depleted residual liquid in deuterium during the life of the magmatic–hydrothermal system. Alternatively, δD variability may have been caused by a minor amount of mixing with meteoric waters. We propose that the ore-related magma was derived from partial melting of the ancient Mesoproterozoic to Neoproterozoic middle to lower continental crust. This crust was likely metasomatized during earlier subduction, and the crustal magmas may have been contaminated with lithospheric mantle derived magma triggered by MASH (e.g., melting, assimilation, storage, and homogenization) processes during collisional orogeny. In addition, a significant proportion of the metals and sulfur supplied from mafic magma were simultaneously incorporated into the resultant hybrid magmas.
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•Taiyangshan deposit formed in a transition regime from syn-collision to post-collision.•Magma was derived from partial melting of ancient Meso- to Neoproterozoic lower continental crust.•This crust was likely metasomatized during earlier subduction.•Magmas may have been contaminated with lithospheric mantle derived magma triggered by MASH.•The resultant hybrid magmas contribute to its fluid and metal sources.
During acidic pretreatment of renewable lignocellulosic biomass, lignin depolymerization/repolymerization reactions often occur, which intensifies lignin inhibition on cellulose hydrolysis generally ...through lignin-derived inhibitors formation, unproductive binding and physical blockage effect. In order to improve the enzymatic digestibility of dilute acid pretreated hardwood, in this work various additives were compared and their inhibition mitigating effects were examined. It was revealed that 2-naphthol addition reduced the formation of inhibitory derivatives from lignin, thus increasing the enzymatic hydrolysis yield of the whole slurry after dilute acid pretreatment. The addition of phenolic acids largely diminished enzyme binding effect of the insoluble lignin. Moreover, the 2-naphthol-7-sulfonate additive led to the most pronounced mitigation on physical blockage effect of lignin, as XPS and SEM results showed the significant removal of surface lignin. This work revealed the different mechanisms of various additives in mitigating lignin inhibition, and provided a better understanding on utilizing proper additives to improve biomass saccharification for biorefinery applications.
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•Proper additives in pretreatment could effectively mitigate lignin inhibition.•Lignin inhibition of cellulose hydrolysis was evaluated and quantified.•Suppression of lignin depolymerization decreased toxic phenolics formation in WSF.•Lignin physical blockage was notably reduced by preventing lignin repolymerization.•Phenolic acids as green additives mostly diminished enzyme binding to lignin.
The Pacific oyster Crassostrea gigas is an important marine fishery resource, which contains high levels of glycogen that contributes to the flavor and the quality of the oyster. However, little is ...known about the molecular and chemical mechanisms underlying glycogen content differences in Pacific oysters. Using a homogeneous cultured Pacific oyster family, we explored these regulatory networks at the level of the metabolome and the transcriptome.
Oysters with the highest and lowest natural glycogen content were selected for differential transcriptome and metabolome analysis. We identified 1888 differentially-expressed genes, seventy-five differentially-abundant metabolites, which are part of twenty-seven signaling pathways that were enriched using an integrated analysis of the interaction between the differentially-expressed genes and the differentially-abundant metabolites. Based on these results, we found that a high expression of carnitine O-palmitoyltransferase 2 (CPT2), indicative of increased fatty acid degradation, is associated with a lower glycogen content. Together, a high level of expression of phosphoenolpyruvate carboxykinase (PEPCK), and high levels of glucogenic amino acids likely underlie the increased glycogen production in high-glycogen oysters. In addition, the higher levels of the glycolytic enzymes hexokinase (HK) and pyruvate kinase (PK), as well as of the TCA cycle enzymes malate dehydrogenase (MDH) and pyruvate carboxylase (PYC), imply that there is a concomitant up-regulation of energy metabolism in high-glycogen oysters. High-glycogen oysters also appeared to have an increased ability to cope with stress, since the levels of the antioxidant glutathione peroxidase enzyme 5 (GPX5) gene were also increased.
Our results suggest that amino acids and free fatty acids are closely related to glycogen content in oysters. In addition, oysters with a high glycogen content have a greater energy production capacity and a greater ability to cope with stress. These findings will not only provide insights into the molecular mechanisms underlying oyster quality, but also promote research into the molecular breeding of oysters.
This paper presents a unique morphological evolution of metal‐organic inverse opals (Pb(NO3)2‐poly(St‐MMA‐AA)) subjected to an electrowetting process. The morphology of the building blocks changes ...from interconnected pores to separated hollow spheres during the electrowetting process, accompanied by an unusual blue‐shift of the stopband position and the decreased wettability of the film. This morphology evolution is attributed to the simultaneous collapse/reconstruction of the metal‐organic frame owing to the partial dissolution of the metal salt and the interfacial assembly of the metal‐organic coordination around the skeleton. The adjustable morphology can be developed as a novel and simple water‐lithography approach for the creation of the photonic crystal pattern.
A unique morphological evolution is demonstrated for metal‐organic inverse opals during an electrowetting process. The building blocks of inverse opals change from the interconnected pore to the separated hollow sphere with respect to electrowetting time, accompanied by a blue‐shift in the reflection bands and the decreased wettability of the film, which provides a facile strategy for the water‐lithography technique.
The creep-fatigue resistance of turbine rotor seriously affects the reliability performance and service lifetime of aircraft engine. Creep-fatigue reliability assessment is an effective measure to ...quantify the uncertain creep-fatigue damage and evaluate the creep-fatigue reliable life for turbine rotor. To improve the modeling accuracy and simulation efficiency of creep-fatigue reliability assessment, a multi-surrogate collaboration approach (MSCA) is proposed by absorbing the strengths of the proposed dynamic neural network surrogate (DNNS) into distributed collaborative strategy. The creep-fatigue reliability assessment of a typical turbine rotor is regarded as one case to estimate the presented MSCA with respect to the fluctuations of multi-physical variables and the variabilities of multi-model parameters. The assessment results reveal that the creep-fatigue reliable life of turbine rotor under reliability degree of 0.998 7 is 629 cycles, and the fatigue strength coefficient and holding creep time play a leading role on creep-fatigue reliable life since their effect probabilities of 27 % and 19 %, respectively. Comparison of various methods (direct Monte Carlo simulation, response surface, neural network surrogate, DNNS) shows that the presented MSCA holds high efficiency and accuracy in creep-fatigue reliability assessment of turbine rotor.
Abstract
The rolling bearing fault detection technology solution can be used to maintain the machinery in advance and avoid downtime and safety accidents. However, the current studies primarily focus ...on utilizing complex algorithms to improve the accuracy of fault diagnosis, while neglecting the influence of extracted features on diagnosis results, resulting in redundancy and conflict among features. To address such an issue, a feature selection method based on compensation distance evaluation technique (CDET) is proposed to optimize the feature set extracted from acoustic emission (AE) signals. Firstly, multiple failure data of the bearing are modeled by the fault simulation experiment platform. Then, the proposed feature selection method is used to evaluate the sensitive features. Finally, hidden markov modelsupport vector machine (HMM-SVM) series model is used to predict works. The experimental results show that the proposed method selects 7 sensitive features from the feature set composed of 13 features and achieve a high accuracy (99.3%).
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