In this study, a new rotor–ball-bearing–casing coupling dynamic model for a practical aero-engine is established. In the coupling system, the rotor and casing systems are modelled using the finite ...element method, support systems are modelled as lumped parameter models, nonlinear factors of ball bearings and faults are included, and four types of supports and connection models are defined to model the complex rotor–support–casing coupling system of the aero-engine. A new numerical integral method that combines the Newmark-β method and the improved Newmark-β method (Zhai method) is used to obtain the system responses. Finally, the new model is verified in three ways: (1) modal experiment based on rotor–ball bearing rig, (2) modal experiment based on rotor–ball-bearing–casing rig, and (3) fault simulations for a certain type of missile turbofan aero-engine vibration. The results show that the proposed model can not only simulate the natural vibration characteristics of the whole aero-engine but also effectively perform nonlinear dynamic simulations of a whole aero-engine with faults.
In order to diagnose effectively the blade–casing rubbing fault, it is very much necessary to simulate the casing vibration correctively and study the casing signals׳ characteristics under ...blade–casing rubbing. In this paper, the casing vibrations in aero-engine resulting from the blade–casing rubbing are simulated. Firstly, an improved aero-engine blade–casing rubbing model is introduced, in which, the effects of the number of blades and changes in the rotor–stator clearance on rubbing forces are considered, the improved rubbing model can simulate rubbing faults for various rubbing conditions, including single-point, multi-point, local-part, and complete-cycle rubbing on the casing and rotor. Secondly, the rubbing model was applied to the rotor–support–casing coupling model, and the casing acceleration responses under rubbing faults are obtained using the time integration approach, which combines the Newmark-β method and an improved Newmark-β method that is a new explicit integral method named the Zhai method. Thirdly, an aero-engine rotor tester with the casings was used to carry out rubbing experiments for single-point rubbing on the casing and complete-cycle rubbing on the rotor, the simulation result was found to agree well with the experimental values, and the improved blade–casing rubbing model was fully verified. Finally, other rubbing faults were simulated for various rubbing conditions and their rubbing characteristics were analyzed.
Abstract
We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 . We combine the relative time delay between the quasar images, Hubble ...Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations. The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias. After unblinding, the inferred distances imply a Hubble constant H0 = 68.8$^{+5.4}_{-5.1}$ km s−1 Mpc−1, assuming a flat Λ cold dark matter cosmology with uniform prior on Ωm in 0.05, 0.5. The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads. Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those. We provide the analysis scripts paired with the publicly available software to facilitate independent analysis (footnote with link to www.h0licow.org). The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics. By combining the likelihoods of the four systems under the same prior, we obtain H0 = 72.5$^{+2.1}_{-2.3}$ km s−1 Mpc−1. This measurement is independent of the distance ladder and other cosmological probes.
The chemical transformation of CO2 not only mitigates the anthropogenic CO2 emission into the Earth’s atmosphere but also produces carbon compounds that can be used as precursors for the production ...of chemicals and fuels. The activation and conversion of CO2 can be achieved on multifunctional catalytic sites available at the metal/oxide interface by taking advantage of the synergy between the metal nanoparticles and oxide support. Herein, we look at the recent progress in mechanistic studies of CO2 hydrogenation to C1 (CO, CH3OH, and CH4) compounds on metal/oxide catalysts. On this basis, we are able to provide a better understanding of the complex reaction network, grasp the capability of manipulating structure and combination of metal and oxide at the interface in tuning selectivity, and identify the key descriptors to control the activity and, in particular, the selectivity of catalysts. Finally, we also discuss challenges and future research opportunities for tuning the selective conversion of CO2 on metal/oxide catalysts.
Direct hydrogen peroxide (H
O
) electrosynthesis via the two-electron oxygen reduction reaction is a sustainable alternative to the traditional energy-intensive anthraquinone technology. However, ...high-performance and scalable electrocatalysts with industrial-relevant production rates remain to be challenging, partially due to insufficient atomic level understanding in catalyst design. Here we utilize theoretical approaches to identify transition-metal single-site catalysts for two-electron oxygen reduction using the *OOH binding energy as a descriptor. The theoretical predictions are then used as guidance to synthesize the desired cobalt single-site catalyst with a O-modified Co-(pyrrolic N)
configuration that can achieve industrial-relevant current densities up to 300 mA cm
with 96-100% Faradaic efficiencies for H
O
production at a record rate of 11,527 mmol h
g
. Here, we show the feasibility and versatility of metal single-site catalyst design using various commercial carbon and cobalt phthalocyanine as starting materials and the high applicability for H
O
electrosynthesis in acidic, neutral and alkaline electrolytes.
The utilization of fossil fuels has enabled an unprecedented era of prosperity and advancement of well-being for human society. However, the associated increase in anthropogenic carbon dioxide (CO2) ...emissions can negatively affect global temperatures and ocean acidity. Moreover, fossil fuels are a limited resource and their depletion will ultimately force one to seek alternative carbon sources to maintain a sustainable economy. Converting CO2 into value-added chemicals and fuels, using renewable energy, is one of the promising approaches in this regard. Major advances in energy-efficient CO2 conversion can potentially alleviate CO2 emissions, reduce the dependence on nonrenewable resources, and minimize the environmental impacts from the portions of fossil fuels displaced. Methanol (CH3OH) is an important chemical feedstock and can be used as a fuel for internal combustion engines and fuel cells, as well as a platform molecule for the production of chemicals and fuels. As one of the promising approaches, thermocatalytic CO2 hydrogenation to CH3OH via heterogeneous catalysis has attracted great attention in the past decades. Major progress has been made in the development of various catalysts including metals, metal oxides, and intermetallic compounds. In addition, efforts are also put forth to define catalyst structures in nanoscale by taking advantage of nanostructured materials, which enables the tuning of the catalyst composition and modulation of surface structures and potentially endows more promising catalytic performance in comparison to the bulk materials prepared by traditional methods. Despite these achievements, significant challenges still exist in developing robust catalysts with good catalytic performance and long-term stability. In this review, we will provide a comprehensive overview of the recent advances in this area, especially focusing on structure–activity relationship, as well as the importance of combining catalytic measurements, in situ characterization, and theoretical studies in understanding reaction mechanisms and identifying key descriptors for designing improved catalysts.
For the globalized world economy with intensive international trade, an overview of energy consumption is presented by an embodied energy analysis to track both direct and indirect energy uses based ...on a systems input–output simulation. In 2004, the total amounts of energy embodied in household consumption, government consumption, and investment are 7749, 874, and 2009
Mtoe (million tons of oil equivalent), respectively. The United States is shown as the world’s biggest embodied energy importer (683
Mtoe) and embodied energy surplus receiver (290
Mtoe), in contrast to China as the biggest exporter (662
Mtoe) and deficit receiver (274
Mtoe). Energy embodied in consumption per capita varies from 0.05 (Uganda) to 19.54
toe (Rest of North America). Based on a forecast for 2005–2035, China is to replace the United States as the world’s leading embodied energy consumer in 2027, when its per capita energy consumption will be one quarter of that of the United States.
► We present an overview of global energy profile in terms of embodied energy. ► The US and China are top embodied energy consumers as well as traders in 2004. ► Equality issue is studied by analyzing per capita embodied energy consumption. ► The US remains to be the leading energy consumer until replaced by China in 2027.
Presented in this study is an empirical analysis of embodied carbon dioxide emissions induced by fossil fuel combustion for the world divided into three supra-national coalitions, i.e., G7, BRIC, and ...the rest of the world (ROW), via the application of a multi-region input–output modeling for 2004. Embodied emission intensities for the three coalitions are calculated and compared, with market exchange rate and purchase power parity separately used to investigate the difference between nominal and real production efficiencies. Emissions embodied in different economic activities such as production, consumption, import, and export are calculated and analyzed accordingly, and remarkable carbon trade imbalances associated with G7 (surplus of 1.53 billion tons, or 36% its traded emissions) and BRIC (deficit of 1.37 billion tons, or 51% its traded emissions) and approximate balance with ROW (deficit of 0.16 billion tons, or 3% its traded emissions) are concretely revealed. Carbon leakages associated with industry transfer and international trades are illustrated in terms of impacts on global climate policies. The last but not least, per capita consumption based emissions for G7, BRIC, and ROW are determined as 12.95, 1.53, and 2.22 tons, respectively, and flexible abatement policies as well as equity on per capita entitlement are discussed.
► We compare the embodied CO
2 emissions in 2004 for G7, BRIC, and ROW. ► Emissions embodied in production, consumption, import, and export are investigated. ► Considerable CO
2 trade surplus and deficit are obtained by G7 and BRIC, respectively. ► Per head embodied emissions are 13, 1.5, and 2.2 tons for G7, BRIC, and ROW, respectively.
Abstract Induced pluripotent stem cells (iPSCs) hold great promise as a cell source for regenerative medicine yet its culture, maintenance of pluripotency and induction of differentiation remain ...challenging. Conversely, graphene (G) and graphene oxide (GO) have captured tremendous interests in the fields of materials science, physics, chemistry and nanotechnology. Here we report on that G and GO can support the mouse iPSCs culture and allow for spontaneous differentiation. Intriguingly, G and GO surfaces led to distinct cell proliferation and differentiation characteristics. In comparison with the glass surface, iPSCs cultured on the G surface exhibited similar degrees of cell adhesion and proliferation while iPSCs on the GO surface adhered and proliferated at a faster rate. Moreover, G favorably maintained the iPSCs in the undifferentiated state while GO expedited the differentiation. The iPSCs cultured on both G and GO surfaces spontaneously differentiated into ectodermal and mesodermal lineages without significant disparity, but G suppressed the iPSCs differentiation towards the endodermal lineage whereas GO augmented the endodermal differentiation. These data collectively demonstrated that the different surface properties of G and GO governed the iPSCs behavior and implicate the potentials of graphene-based materials as a platform for iPSCs culture and diverse applications.
As the world is smoothing the transition towards a low-carbon energy structure, natural gas has occupied a critical position in global energy supply. Also, globalization has catalyzed ever-increasing ...indirect energy flows in international trade. In order to present a comprehensive overview of natural gas use in globalized economy, this paper applies the systems multi-regional input-output (MRIO) analysis to track natural gas use from primary suppliers to final consumers via the links by producers in the world economy, supported by typical statistics for the year of 2011. Natural gas embodied in international trade is revealed amounting to 2722.1 bcm, in magnitude up to 90% of total gas extraction for energy use, indicating the intensive relocation of gas use by trade. 83% of traded embodied natural gas is associated with intermediate trade, mainly from leading primary suppliers, including Russia, USA and Western Asia, to dominant final consumers, like USA, EU27 and East Asia. Significant differences are found between direct and embodied natural gas flows. Consumption-based resource efficiency can break the illusion of efficiency improvements, and trade imbalance in terms of gas use can be opposite to the trade imbalance in conventional monetary terms. This paper has constructed a comprehensive analytical framework to trace natural gas flows in globalized economy for the first time, aiming to provide new insights for policy making.
•Global embodied natural gas flows are traced from a systematic perspective.•Major agents in supply chains, net importers and exporters are identified.•83% of traded embodied natural gas is associated with intermediate trade.•Russia, USA and Western Asia are leading source regions.•USA, EU27 and East Asia are dominant final producers and consumers.
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