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In study presented here we focus on the large climate-ice sheet feedbacks on global scales on time scales of 100,000 yrs. We conducted a series of idealised sensitivity experiments under CO2 and solar radiation reduction scenarios with the Globally Resolved Energy Balance - Ice Sheet Model v1.0 (GREB-ISM v1.0), to study the characteristics of five climate-ice sheet feedbacks, including albedo, snowfall, ice latent heat, topography and sea level feedbacks. We analysed the relative importance of each of these feedbacks on the ice sheet growth and on the climate system (surface temperature). The results indicate that the inclusion of ice sheets will delay the response to the external forcing and facilitate the climate cooling in the high latitude and altitude areas in the Northern Hemisphere, but also causes a small amount of warming elsewhere, due to the blocking of atmospheric heat transport. As for individual feedbacks, the albedo feedback is the most dominant positive feedback in favour of ice sheet build-up and cooler climates, whereas snowfall feedback is the greatest negative feedback that reduces the growth of ice sheets. The large ice latent heat required to melt ice allows to maintain ice sheets from one cold seasons to the next and therefore provides a positive feedback for ice sheet growth. The ice sheets impact on the topography is also a positive feedback but with smaller impact than the albedo feedback. The sea level change influences ice sheets by shifting their location, in particular allowing ice sheets growth in the Arctic Ocean, while reducing it over central north Asia.

For uniform size and transparency, polypropylene fiber was chosen. When using PIV, the velocity from suction to pressure side decreases almost linearly between 1.0Q and 1.3Q. It does, however, fall from the suction side and rise until it reaches the pressure surface at 0.7Q. From the leading edge of the blade to the trailing edge, the spanwise velocity nearly increases linearly. With increasing concentration, the velocity increases slightly on the suction side while decreasing on the pressure side, resulting in a small pressure rise. When the external characteristic data of the pumping process is used, the pump exhibits a small elevation of head. When the concentration is increased from 0.5% to 1.0%, the efficiency gradually increases. The efficiency gradually decreases as the concentration increases from 1.0% to 1.5%. To investigate this discrepancy, a high-speed photographic system was used to examine the distribution of fiber particles in the impeller’s channels.

Based on the loss model of pulp pump set up in the I part of this research, an efficient designing method is proposed by taking account of the influences of head reduction by small blade number, leakage loss via tip clearance, and erosion-corrosion wears in pumps separately. Further, a two-stage optimal designing approach was proposed to tackle the oversized design. The pump designing was performed by coupling with a CFD-based optimization procedure. An efficiency increase of near 10 % was achieved on the pump model validated in laboratory. It was proved that performance could be improved by increasing the impeller blade width and enlarging the impeller blade outlet angle. It was further shown that the erosion-corrosion wear in pulp pump was relatively lighter when compared to particle-impingement wear in slurry and sewage pump. Adoption of composite material showed potential in energy-saving in the pumping system.

With growing demand of paper products, the electric consumption in pulp and paper industry is increasing globally where a share of 30 % is attributed to the pulp pumping system. The efficient designing and running of pumping system are critical for energy efficiency. The incomplete information on pulp flows and the oversized designs are the major causes of low efficiency. In the first part of this research, the fiber level models and rheological properties covering a series of unit applications are examined. A loss model of pulp pump is set up by considering different factors influencing pumping performance. The efficiency improvement opportunities in pulp pumping are systematically investigated. The drag-reducing feature at low consistency pulp pumping is highlighted which will be further applied in energy optimized sizing and dimensioning of a pulp pump in the second part of this research.

Centrifugal pump is extensively used in wastewater, pulp, and biomass industries for transporting of particle flows. The motion and distribution of flexible particles are critical for continuous and stable pumping. In this work, a test rig is set up for straw particle flow pumping. A stroboscopic flash is employed to capture the distribution of the straw particle. The pump performance is measured and compared to that of clear water. By increasing the particle concentration, the process from stable pumping to eventually clogging is observed. Firstly, in a wide operation range with 0.1% concentration, the particle is uniformly distributed in the flow passage and the pump is running in a hydrodynamic stable mode where the power increases gradually and is slightly over the pure water circumstance. However, the high efficiency region is shifted to lower flow rate and it becomes narrower as compared to the pure water case. Secondly, at 0.2% and 0.4% concentration, the performance resembles the 0.1% case. But with increasing concentration, the inception of small flocs is observed. In addition, small air bubble is formed near the rotating axis. This subtle change continues until clogging happens. By gradually increasing the concentration of particle, more and more particles are attached to the growing flocs. Finally, the pump runs into mechanical wear between particles and flow passage, and then it is fully clogged. In this condition, the power consumption increases rapidly and the variable frequency drive is used to bring down the shaft speed. The long-term running shows relatively light erosive wear on the surface of impeller and volute by the particles, but no damage is observed.

We introduce a newly developed global ice sheet model coupled to the Globally Resolved Energy Balance (GREB) climate model for the simulation of global ice sheet evolution on timescales of 100 kyr or longer (GREB-ISM v1.0). Ice sheets and ice shelves are simulated on a global grid, fully interacting with the climate simulation of surface temperature, precipitation, albedo, land–sea mask, topography and sea level. Thus, it is a fully coupled atmosphere, ocean, land and ice sheet model. We test the model in ice sheet stand-alone and fully coupled simulations. The ice sheet model dynamics behave similarly to other hybrid SIA (shallow ice approximation) and SSA (shallow shelf approximation) models, but the West Antarctic Ice Sheet accumulates too much ice using present-day boundary conditions. The coupled model simulations produce global equilibrium ice sheet volumes and calving rates like those observed for present-day boundary conditions. We designed a series of idealized experiments driven by oscillating solar radiation forcing on periods of 20, 50 and 100 kyr in the Northern Hemisphere. These simulations show clear interactions between the climate system and ice sheets, resulting in slow buildup and fast decay of ice-covered areas and global ice volume. The results also show that Northern Hemisphere ice sheets respond more strongly to timescales longer than 100 kyr. The coupling to the atmosphere and sea level leads to climate interactions between the Northern and Southern Hemispheres. The model can run global simulations of 100 kyr d−1 on a desktop computer, allowing the simulation of the whole Quaternary period (2.6 Myr) within 1 month.

A series of composites based on (100-x)wt.%Ce0.9Pr0.1O2-{\delta}-xwt.%Pr0.6Ca0.4FeO3-{\delta} (x = 25, 40 and 50) doped with the cheap and abundant alkaline earth metal Ca2+ at the A-site has been successfully designed and fabricated. The crystal structure, oxygen permeability, phase and CO2 stability were evaluated. The composition of 60wt.%Ce0.9Pr0.1O2-{\delta}-40wt.%Pr0.6Ca0.4FeO3-{\delta}(60CPO-40PCFO) possesses the highest oxygen permeability among three studied composites. At 1000 oC, the oxygen permeation fluxes through the 0.3 mm-thickness 60CPO-40PCFO membranes after porous La0.6Sr0.4CoO3-{\delta} each to 1.00 mL cm-2 min-1 and 0.62 mL cm-2 min-1 under air/He and air/CO2 gradients, respectively. In situ XRD results demonstrated that the 60CPO-40PCFO sample displayed a perfect structural stability in air as well as CO2-containing atmosphere. Thus, low-cost, Co-free and Sr-free 60CPO-40PCFO has high CO2 stability and is economical and environmental friendly since the expensive and volatile element Co was replaced by Fe and Sr was waived since it easily forms carbonates., Comment: 30 pages, 10 figures, 2 tables, post-print of the article published in journal of the european ceramic society (accepted)

Ceramic dual-phase oxygen transport membranes with the composition of 60 wt% Ce0.9Pr0.1O2-δ-40 wt%Pr0.6Sr0.4Fe1-xAlxO3-δ (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0) (60CPO-40PSF1-xAxO) based on 60Ce0.9Pr0.1O2-δ-40Pr0.6Sr0.4FeO3-δ doped Al was successfully synthesized through a modified Pechini method. Crystal structure, surface microtopography and oxygen permeability are investigated systematically. The cell parameters of perovskite phase first increased and then decreased with the increase of Al content, which is related to the radius of the Al3+ and the formation of impurity phase. As x ranges from 0.1 to 0.8, the oxygen permeability of the materials first increases and then decreases, and the maximum value of oxygen permeation rate for 60CPO-40PSF1-xAxO membranes with 0.4 mm thickness at 1000 °C is 1.12 mL min−1 cm−2 when x = 0.4. XRD measurements revealed high temperature stability and CO2-tolerant property of the dual-phase composites. The partial replacement of Fe3+/Fe4+ by Al3+ causes the material not only to exhibit good stability, but also to increase the oxygen permeability of the membranes.

High stability and oxygen permeability are two prominent requirements for the oxygen transport membrane candidates used as industrialization. Herein, we report several composite membranes based on xwt.%Ce0.9Pr0.1O2(CPO)-(100-x)wt.%Pr0.6Sr0.4Fe0.8Al0.2O3(PSFAO) (x = 50, 60 and 75) prepared via a modified Pechini method. Oxygen permeability test reveals that the 60CPO-40PSFAO composition exhibits the highest oxygen permeability. The oxygen permeation flux through the optimal uncoated 0.33 mm-thickness 60CPO-40PSFAO composite can reach 1.03 mL cm-2 min-1 (over the general requirement value of 1 mL cm-2 min-1) in air/He atmosphere at 1000 {\deg}C. In situ XRD performance confirms the optimal 60CPO-40PSFAO sample shows excellent stability in CO2-containing atmospheres. The 60CPO-40PSFAO membrane still exhibits simultaneously excellent oxygen permeability and phase stability after operating for over 100 h at air/CO2 condition at 1000 {\deg}C, which further indicates that the 60CPO-40PSFAO composite is likely to be used for oxygen supply in CO2 capture, Comment: 29 pages,12 figures, 1 table

By using multisourced data and two sets of sensitivity runs from the coupled general circulation model CESM1.2.0, we investigated the effects of the spring [March, April, and May (MAM)] surface sensible heating over the Tibetan Plateau (SHTP) on the interannual variability of the North Pacific Ocean sea surface temperature (SST) and mixed layer. The results indicated that an above-normal MAM SHTP can generate a Rossby wave downstream and form an anomalous equivalent barotropic anticyclone over the North Pacific, inducing anticyclonic wind stress anomalies. As a result of Ekman transport and Ekman pumping, sea currents converge near 40°N, accompanied by weak downwelling motion. The mixed layer heat budget diagnosis indicates that the net heat fluxes, together with meridional advection anomalies, contributed significantly to changes in the mixed layer temperature (MLT). As a result, the SST anomalies (SSTAs) and MLT anomalies both present a horseshoelike pattern. In addition, the significant warm SSTAs show a maximum in the late spring, but the significant warm MLT anomalies centered under the sea surface (25-m depth) could be sustained until summer, acting like a signal storage for the anomalous spring SHTP. Moreover, the midlatitude ocean–atmosphere interaction provides a positive feedback on the development of the anomalous anticyclone over the North Pacific, since the SSTA pattern could strengthen the oceanic front and induce more active transient eddy activities. The eddy vorticity forcing that is dominant among the total atmospheric forcings tends to produce an equivalent barotropic atmospheric high pressure, which in turn intensifies the initial anomalous anticyclone.

Dense ceramic mixed ionic-electronic conducting membranes (MIECMs) are renowned for their rich and varied properties as admirable candidates in energy industries, such as oxygen separation from air, cathode materials for solid fuel oxide cells (SOFCs) or membrane reactors for partial oxidation of light hydrocarbons. Especially, the MIECMs integrated oxy-fuel combustion is considered to be a promising cost-effective and efficient method for CO2 capture and sequestration. During the oxy-fuel process, high purity oxygen production has been put forward to use OTMs technology instead of the conventional cryogenic technique, which can benefit from low costs and energy consumption and high efficiency. According to the phase numbers, the OTMs can be classified into single phase and composite OTMs. Extensive research activities have been directed towards the single phase perovskite-type oxides due to their high oxygen permeability. However, their industrial practical application was limited since they suffer from deactivation in the presence of CO2 due to alkaline earth carbonates forming on their surfaces. In order to overcome these issues, focus has shifted to the development of dual-phase membranes consisting of an oxygen ion conducting phase and an electron ion conducting phase, which benefit from the contribution of each phase and overcome the limitations of perovskite materials. Dual-phase OTM typically composed of an oxygen conducting phase (OCP) and an electronic conducting phase (ECP), which displays a better structural and mechanical stability comparing with the single phase OTM under reducing atmosphere due to the incorporation of fluorite phase. The first generation dual-phase OTMs are usually made from the fluorite oxides and noble metals, where fluorite oxides are used as the OCP and noble metals are adopted as the ECP. However, the noble metal-containing dual-phase OTM is too expensive. In order to lower the costs, researchers have developd the second generation dual-phase OTMs, which are consisted of fluorite oxides and perovskite oxides. Although the costs have been reduced, reactions between two phases were usually observed in the second generation dual-phase OTMs. Based on the previous findings and driven by the demands for oxy-fuel combustion for CO2 capture, research put forwards to the new CO2-stable dual-phase OTMs without noble metals and alkaline earth elements. Until now, already a large number of CO2-stable dual-phase membrane materials have been explored. However, their CO2 stabilities have been enhanced, but most of their oxygen permeabilities are too low for practical applications. Therefore, continues research efforts have to be made since most of available OTMs materials can′t satisfy the practical applications. In order to enhance the oxygen permeability and/or improve material thermochemical stability of dual-phase OTMs, the large majority of studies focused on tuning the composition through doping, synthesized temperatures, modified the membrane surfaces with coating or development of new synthesis methods. Meanwhile, considerable theoretical efforts have been put into the dual-phase OTMs, a number of models for permeation process such as Bouwmeester model, Xu-Thomson model, and Zhu model et al. are proposed. Up to now, countless publications has been produced in this field. In order to give the guidelines for the development of the dual-phase OTM materials and promote the process of industrialization of the OTMs technology in the oxy-fuel process, we summarize the status of CO2-stable dual-phase mixed conductor oxygen permeable membrane materials. In this review, the oxygen permeability mechanism and research progress of the dual-phase OTM materials are briefly introduced firstly. Subsequently, the influence of the preparation methods, sintering temperatures, ratios of two phases and the composition of the two phases on the oxygen permeability and stability are analyzed systematically. Next, the applications of dual phase MIECM reactor in partial oxidation of methane to syngas (POM), coupling reactions, water decomposition and oxy-fuel combustion are introduced and analyzed. Finally, the existing scientific problems and the possible research directions have been pointed out.

We introduce a newly developed global ice sheet model coupled to the Globally Resolved Energy Balance (GREB) climate model for the simulation of global ice sheet evolution on time scales of 100 kyr or longer (GREB-ISM v0.3). Ice sheets and ice shelves are simulated on a global grid, fully interacting with the climate simulation of surface temperature, precipitation, albedo, land-sea mask, topography and sea level. Thus, it is a fully coupled atmosphere, ocean, land and ice sheet model. We test the model in ice sheet stand-alone and fully coupled simulations. The ice sheet model dynamics behave similarly to other hybrid SIA (Shallow Ice Approximation) and SSA (Shallow Shelf Approximation) models, but the West Antarctic Ice Sheet accumulates too much ice using present-day boundary conditions. The coupled model simulations produce global equilibrium ice sheet volumes and calving rates similar to observed for present day boundary conditions. We designed a series of idealised experiments driven by oscillating solar radiation forcing on periods of 20 kyr, 50 kyr and 100 kyr in the Northern Hemisphere. These simulations show clear interactions between the climate system and ice sheets, resulting in slow build-up and fast decay of ice-covered areas and global ice volume. The results also show that Northern Hemisphere ice sheets respond more strongly to time scales longer than 100 kyr. The coupling to the atmosphere and sea level leads to climate interactions between the Northern and Southern Hemispheres. The model can run global simulations of 100 kyr per day on a desktop computer, allowing the simulation of the whole Quaternary period (2.6 Myrs) within one month.

Ceramic composite oxygen transport membranes 60 wt%Ce0.9Pr0.1O2−δ–40 wt%Pr0.6Ca0.4Fe1−xCoxO3−δ (0 ≤ x ≤ 1) were synthesized via the Pechini one-pot method. X-ray diffraction patterns indicated that membranes of all compositions maintained the same crystal structure at the room temperature, whereas with the decrease in the Fe/Co ratio, it was more easier to find phase decomposition under Ar environment at an elevated temperature. SEM images demonstrate that the mechanical compatibility of the two phases becomes worse and the grain size gradually increases with the increase in the Co content. Oxygen permeability test results showed that the reduction in the Fe/Co ratio improved the oxygen permeability of the membrane for x ≤ 0.6, while the reduction in the Fe/Co ratio had an adverse impact on the oxygen permeability for x ≥ 0.8. Among all the composition membranes, 60 wt%Ce0.9Pr0.1O2−δ–40 wt%Pr0.6Ca0.4Fe0.4Co0.6O3−δ membrane possessed the highest permeation flux of about 0.85 mL min−1 cm−2 at 1000 °C under air/He atmosphere. The final stability testing indicated that it possessed good stability under air/He, and thereby has potential application prospects in high temperature oxygen consumption industries.

To study the influence of fiber particles on the flow field within the passages of an open impeller centrifugal pump, an experiment was performed. The hair fiber was used as solid particle phase in this experiment. After measuring the performance characteristic and PIV data, the flow field in impeller was measured and analyzed. It was shown that at the concentration of 0.1%, a varied distribution of relative velocity from different flow channels was observed. The outlet velocity of the impeller in the second flow channel was obviously higher than that in the first flow channel. The variation of the relative velocity near the hub tended to be consistent at the position of the front plane and the middle plane of the impeller. At 0.2% concentration, the relative velocity at the suction surface of the two channels changes more sharply than the other positions. Within the second channel, it was found that the relative velocity under low flow condition was obviously higher than that under rated and large flow rates. Under different concentrations, the increase of the relative velocity at low flow rate changed intensely compared with the other two conditions. The low velocity zone will be formed near the middle part of the suction surface of the flow channel which gradually decreases with the increase of the flow rate. The external characteristic test shows that the efficiency of the pump and the drag reducing feature increase with the increase of concentration.

The arbitrariness of composite analysis due to criterion of defining positive and negative events is an unsolved problem. To deal with it, a new method based on the covariance and defined as weighted composite analysis was developed in this study. Two ideal cases reveal that the new method can eliminate noise more effectively in small sample size, and has a higher signal to noise ratio than the traditional method in some cases. And a real case on the relationship between ENSO and geopotential height over East Asia in summer indicates that the new method shows some similar features with composite analyses, but can effectually avoid some inappropriate conclusions. It therefore provides an alternative approach to investigate linkages between different variables.

Here we present results from the first phase of the Reduced Complexity Model Intercomparison Project (RCMIP). RCMIP is a systematic examination of reduced complexity climate models (RCMs), which are used to complement and extend the insights from more complex Earth System Models (ESMs), in particular those participating in the Sixth Coupled Model Intercomparison Project (CMIP6). In Phase 1 of RCMIP, with 14 participating models namely ACC2, AR5IR (2 and 3 box versions), CICERO-SCM, ESCIMO, FaIR, GIR, GREB, Hector, Held et al. two layer model, MAGICC, MCE, OSCAR and WASP, we highlight the structural differences across various RCMs and show that RCMs are capable of reproducing global-mean surface air temperature (GSAT) changes of ESMs and historical observations. We find that some RCMs are capable of emulating the GSAT response of CMIP6 models to within a root-mean square error of 0.2 °C (of the same order of magnitude as ESM internal variability) over a range of scenarios. Running the same model configurations for both RCP and SSP scenarios, we see that the SSPs exhibit higher effective radiative forcing throughout the second half of the 21st Century. Comparing our results to the difference between CMIP5 and CMIP6 output, we find that the change in scenario explains approximately 46 % of the increase in higher end projected warming between CMIP5 and CMIP6. This suggests that changes in ESMs from CMIP5 to CMIP6 explain the rest of the increase, hence the higher climate sensitivities of available CMIP6 models may not be having as large an impact on GSAT projections as first anticipated. A second phase of RCMIP will complement RCMIP Phase 1 by exploring probabilistic results and emulation in more depth to provide results available for the IPCC's Sixth Assessment Report author teams.

Developing good performance and low-cost oxygen permeable membranes for CO2 capture based on the oxy-fuel concept is greatly desirable but challenging. Despite tremendous efforts in exploring new CO2-stable dual-phase membranes, its presence is however still far from meeting the industrial requirements. Here we report a series of new Ca-containing CO2-resistant oxygen transporting membranes with composition 60wt.%Ce0.9Ln0.1O2-δ-40wt.%Ln0.6Ca0.4FeO3-δ (CLnO-LnCFO; Ln = La, Pr, Nd, Sm) synthesized via a Pechini one-pot method. Our results indicate all investigated compounds are composed of perovskite and fluorite phases, while the perovskite phases in the CNO-NCFO and CSO-SCFO membranes after sintering generates Ca-rich and Ca-less two kinds of grains with different morphologies, where the Ca-less small perovskite grains block the transport of oxygen ions and eventually result in poor oxygen permeability. Among our investigated CLnO-LnCFO membranes, CPO-PCFO exhibits the highest oxygen permeability and excellent CO2 stability, which were mainly associated with the improvement in crystal symmetry, non-negligible electronic conductivity of fluorite phase and the enhancement in electronic conductivity of perovskite. Our results establish Ca-containing oxides as candidate material platforms for membrane engineering devices that combine CO2 capture and oxygen separation.