Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques...Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst(Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 m V superior to that of commercial Pt/C(0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles(Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C,verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.展开更多
In the cloud data centers,how to map virtual machines(VMs) on physical machines(PMs) to reduce the energy consumption is becoming one of the major issues,and the existing VM scheduling schemes are mostly to reduce ene...In the cloud data centers,how to map virtual machines(VMs) on physical machines(PMs) to reduce the energy consumption is becoming one of the major issues,and the existing VM scheduling schemes are mostly to reduce energy consumption by optimizing the utilization of physical servers or network elements.However,the aggressive consolidation of these resources may lead to network performance degradation.In view of this,this paper proposes a two-stage VM scheduling scheme:(1) We propose a static VM placement scheme to minimize the number of activating PMs and network elements to reduce the energy consumption;(2) In the premise of minimizing the migration costs,we propose a dynamic VM migration scheme to minimize the maximum link utilization to improve the network performance.This scheme makes a tradeoff between energy efficiency and network performance.We design a new twostage heuristic algorithm for a solution,and the simulations show that our solution achieves good results.展开更多
Polyvinyl alcohol( PVA) is a water-soluble synthetic polymer that is hard to biodegrade. PVA-degrading microorganisms were previously reported as unitary bacteria and most of them have been identified as aerobes. In t...Polyvinyl alcohol( PVA) is a water-soluble synthetic polymer that is hard to biodegrade. PVA-degrading microorganisms were previously reported as unitary bacteria and most of them have been identified as aerobes. In this work,a microbial community was cultured anaerobically and its degradation performance and biodiversity were analyzed. The microbial community was cultured for more than 40 d,which represents a highly efficient degradation performance with a chemical oxygen demand removal efficiency of 88. 48%. Operational taxonomic unit-based analysis of the sequences revealed a highly diverse community in the reactor. To note,metagenome 16s rDNA sequencing delineated 19 phyla and 41 classes. Specifically, proteobacteria, chlamydiae, bacteroidetes,firmicutes,and planctomycetes play key roles in the biodegradation processes. Moreover,the betaproteobacteria class belonging to the proteobacteria phylum was the predominant bacterial members in this community. Our results demonstrated that anaerobic treatment of PVA wastewater is feasible and confers degradation by a highly diverse microbial community.展开更多
Based on the two existing abrasive water-jet（AWJ） systems, the dia-jet （or pre-jet） and the post-jet, a new type of abrasive water-jet system is put forward, which combines the dia-jet＇s advantage, low operating ...Based on the two existing abrasive water-jet（AWJ） systems, the dia-jet （or pre-jet） and the post-jet, a new type of abrasive water-jet system is put forward, which combines the dia-jet＇s advantage, low operating system pressure, slender stream jet, and more concentrative abrasive in the blended stream, with merits of post-jet, the less sophisticate apparatus, successive supply of abrasives. The theoretic analysis is brought out in detail, and the nozzle system structure is concisely illustrated. Its relevant experiment results are demonstrated, proving that this new system is effective in various aspects, enlarging penetrating capability without raising system pressure, saving machining power supply, lessening energy loss, etc.展开更多
The design and optimization of ship hull forms play a crucial role in enhancing the performance and efficiency of marine vessels.This study focuses on integrating a cylindrical central body part within a conventional ...The design and optimization of ship hull forms play a crucial role in enhancing the performance and efficiency of marine vessels.This study focuses on integrating a cylindrical central body part within a conventional ship hull to explore its impact on hydrodynamic characteristics and overall vessel performance.The research employs hydrodynamical concepts,parametric studies,and optimization algorithms to analyze the design space systematically.The aim of including the cylindrical central body is to investigate its influence on reducing resistance,improving fuel efficiency,and enhancing maneuverability.A new optimization model based on the cylindrical body inclusion in the hull form is developed.The existing generalized reduced gradient(GRG)optimization method is also adopted to determine the accuracy of the proposed methodology.It is revealed that the resistance predicted by the GRG method is much closer to the original result of the parent hull form.A container vessel is taken as a case study example.The new,simplified,approach developed here provides a greater reduction in the resistance values of the case study vessel.Hence,the adoption of a cylindrical hull form in ship design can improve hydrodynamic performance.Although the results from the GRG method and the new scheme agree within the speed range of 0-5 m/s,some deviations are noted.In conclusion,it is observed that although the inclusion of the cylindrical body together with the adoption of the optimum design scheme is capable of improving the resistance performance of a ship,further studies are necessary to understudy the effects of this approach on the other vessel performance metrics.展开更多
Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gil...Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gilts. The experiment was designed as a 2 × 2 factorial arrangement with two sources of dietary proteins（cottonseed meal, CSM vs. soybean meal, SBM） and two levels of CP（12 % vs. 14 %, as-fed basis）. Seventy-two crossbred gilts（89.5 ± 0.9 kg） were allotted to one of four dietary treatments in a randomized complete block design for a period of 28 d. All diets were formulated to be isoenergetic and similar concentrations of standardized ileal digestible essential AA covering the nutrient requirements of pigs.Results： Growth, carcass characteristics and meat quality were not affected by dietary protein source nor crude protein level（P ＆gt; 0.10） except that average daily feed intake was increased by CSM diets（P = 0.03）. Gilts offered reduced protein diets had lower muscle p H45min（P 〈 0.05）. Neither dietary protein source nor crude protein level influenced N deposition. However, reduced protein diets decreased N intake, N excretion, and serum urea nitrogen content, whilst improved N efficiency（P 〈 0.01）. CSM diets increased N intake（P = 0.04）,but did not depress N efficiency. The concentrations of phenylalanine, tryptophan, cysteine and tyrosine（P 〈 0.05） of the longissimus muscle were decreased when gilts offered CSM diets, while muscle intracellular free valine concentration was increased（P = 0.03）. The gilts offered reduced protein diets had greater intracellular concentrations of free methionine, lysine, and total AA in muscle（P 〈 0.05）.Conclusion： These results suggest that CSM could replace SBM as a primary protein source in finishing pig diets in terms of performance, N efficiency, carcass characteristics, and meat quality, but decrease the concentrations of muscle specific AA. Furthermore, the reduced protein diet played an important role in increasing muscle intracellular concentrations of specific free amino acids（FAA）, and in reducing the relative ratios of specific FAA to lysine in longissimus dorsi muscle of pig, whose biological meaning needs further studies.展开更多
In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program...In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program which solves the Reynolds-averaged Navier-Stokes equations was used to find out the mentioned impact and the complicated flow field of transonic compressor-rotors.The CFD method that was used for solving flow field's equation was validated by experimental data of NASA Rotor 67.The results showed that the compressor with curved rotors had higher efficiency,rotor pressure ratio and stable operating range compared to the compressor with un-curved rotors.Using curved rotors mostly had higher impact on the overall stable operating range compared to the other operating parameters.Operating range involves choking point and stall point that were changed separately by using of bended blade.For finding the detailed impact of sweep and lean angle on transonic blades,various forms of lean and sweep angles were exerted to basic rotor.It was found that sweep angles increased overall operating range up to 30%,efficiency up to 2%and pressure ratio up to 1%.Leaning the blades increased the safe operating range,the pressure ratio and efficiency by 14%,4%and 2%respectively.展开更多
基金supported by National Key R&D Program of China (No.2018YFA0108300)the Overseas High-level Talents Plan of China and Guangdong Province+3 种基金the Fundamental Research Funds for the Central Universitiesthe 100 Talents Plan Foundation of Sun Yat-sen Universitythe Program for Guangdong Introducing Innovative and Entrepreneurial Teams (No.2017ZT07C069)the Natinoal Natural Science Foundation of China (Nos.22075321,21821003,21890380 and 21905315)。
文摘Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst(Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 m V superior to that of commercial Pt/C(0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles(Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C,verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.
基金supported by the National Natural Science Foundation of China(61002011)the National High Technology Research and Development Program of China(863 Program)(2013AA013303)+1 种基金the Fundamental Research Funds for the Central Universities(2013RC1104)the Open Fund of the State Key Laboratory of Software Development Environment(SKLSDE-2009KF-2-08)
文摘In the cloud data centers,how to map virtual machines(VMs) on physical machines(PMs) to reduce the energy consumption is becoming one of the major issues,and the existing VM scheduling schemes are mostly to reduce energy consumption by optimizing the utilization of physical servers or network elements.However,the aggressive consolidation of these resources may lead to network performance degradation.In view of this,this paper proposes a two-stage VM scheduling scheme:(1) We propose a static VM placement scheme to minimize the number of activating PMs and network elements to reduce the energy consumption;(2) In the premise of minimizing the migration costs,we propose a dynamic VM migration scheme to minimize the maximum link utilization to improve the network performance.This scheme makes a tradeoff between energy efficiency and network performance.We design a new twostage heuristic algorithm for a solution,and the simulations show that our solution achieves good results.
基金Science and Technology Plan of Henan Province,China(No.132300410080)North China University of Water Resources and Electric Power Postgraduate Education Innovation Program,China(No.YK2015-13)
文摘Polyvinyl alcohol( PVA) is a water-soluble synthetic polymer that is hard to biodegrade. PVA-degrading microorganisms were previously reported as unitary bacteria and most of them have been identified as aerobes. In this work,a microbial community was cultured anaerobically and its degradation performance and biodiversity were analyzed. The microbial community was cultured for more than 40 d,which represents a highly efficient degradation performance with a chemical oxygen demand removal efficiency of 88. 48%. Operational taxonomic unit-based analysis of the sequences revealed a highly diverse community in the reactor. To note,metagenome 16s rDNA sequencing delineated 19 phyla and 41 classes. Specifically, proteobacteria, chlamydiae, bacteroidetes,firmicutes,and planctomycetes play key roles in the biodegradation processes. Moreover,the betaproteobacteria class belonging to the proteobacteria phylum was the predominant bacterial members in this community. Our results demonstrated that anaerobic treatment of PVA wastewater is feasible and confers degradation by a highly diverse microbial community.
文摘Based on the two existing abrasive water-jet（AWJ） systems, the dia-jet （or pre-jet） and the post-jet, a new type of abrasive water-jet system is put forward, which combines the dia-jet＇s advantage, low operating system pressure, slender stream jet, and more concentrative abrasive in the blended stream, with merits of post-jet, the less sophisticate apparatus, successive supply of abrasives. The theoretic analysis is brought out in detail, and the nozzle system structure is concisely illustrated. Its relevant experiment results are demonstrated, proving that this new system is effective in various aspects, enlarging penetrating capability without raising system pressure, saving machining power supply, lessening energy loss, etc.
文摘The design and optimization of ship hull forms play a crucial role in enhancing the performance and efficiency of marine vessels.This study focuses on integrating a cylindrical central body part within a conventional ship hull to explore its impact on hydrodynamic characteristics and overall vessel performance.The research employs hydrodynamical concepts,parametric studies,and optimization algorithms to analyze the design space systematically.The aim of including the cylindrical central body is to investigate its influence on reducing resistance,improving fuel efficiency,and enhancing maneuverability.A new optimization model based on the cylindrical body inclusion in the hull form is developed.The existing generalized reduced gradient(GRG)optimization method is also adopted to determine the accuracy of the proposed methodology.It is revealed that the resistance predicted by the GRG method is much closer to the original result of the parent hull form.A container vessel is taken as a case study example.The new,simplified,approach developed here provides a greater reduction in the resistance values of the case study vessel.Hence,the adoption of a cylindrical hull form in ship design can improve hydrodynamic performance.Although the results from the GRG method and the new scheme agree within the speed range of 0-5 m/s,some deviations are noted.In conclusion,it is observed that although the inclusion of the cylindrical body together with the adoption of the optimum design scheme is capable of improving the resistance performance of a ship,further studies are necessary to understudy the effects of this approach on the other vessel performance metrics.
基金financially supported by the National Key Basic Research Program of China (2012CB124702, 2013CB127302)National Natural Science Foundation of China (31272452)the National Key Technology R&D Program of China (2011BAD26B01)
文摘Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gilts. The experiment was designed as a 2 × 2 factorial arrangement with two sources of dietary proteins（cottonseed meal, CSM vs. soybean meal, SBM） and two levels of CP（12 % vs. 14 %, as-fed basis）. Seventy-two crossbred gilts（89.5 ± 0.9 kg） were allotted to one of four dietary treatments in a randomized complete block design for a period of 28 d. All diets were formulated to be isoenergetic and similar concentrations of standardized ileal digestible essential AA covering the nutrient requirements of pigs.Results： Growth, carcass characteristics and meat quality were not affected by dietary protein source nor crude protein level（P ＆gt; 0.10） except that average daily feed intake was increased by CSM diets（P = 0.03）. Gilts offered reduced protein diets had lower muscle p H45min（P 〈 0.05）. Neither dietary protein source nor crude protein level influenced N deposition. However, reduced protein diets decreased N intake, N excretion, and serum urea nitrogen content, whilst improved N efficiency（P 〈 0.01）. CSM diets increased N intake（P = 0.04）,but did not depress N efficiency. The concentrations of phenylalanine, tryptophan, cysteine and tyrosine（P 〈 0.05） of the longissimus muscle were decreased when gilts offered CSM diets, while muscle intracellular free valine concentration was increased（P = 0.03）. The gilts offered reduced protein diets had greater intracellular concentrations of free methionine, lysine, and total AA in muscle（P 〈 0.05）.Conclusion： These results suggest that CSM could replace SBM as a primary protein source in finishing pig diets in terms of performance, N efficiency, carcass characteristics, and meat quality, but decrease the concentrations of muscle specific AA. Furthermore, the reduced protein diet played an important role in increasing muscle intracellular concentrations of specific free amino acids（FAA）, and in reducing the relative ratios of specific FAA to lysine in longissimus dorsi muscle of pig, whose biological meaning needs further studies.
文摘In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program which solves the Reynolds-averaged Navier-Stokes equations was used to find out the mentioned impact and the complicated flow field of transonic compressor-rotors.The CFD method that was used for solving flow field's equation was validated by experimental data of NASA Rotor 67.The results showed that the compressor with curved rotors had higher efficiency,rotor pressure ratio and stable operating range compared to the compressor with un-curved rotors.Using curved rotors mostly had higher impact on the overall stable operating range compared to the other operating parameters.Operating range involves choking point and stall point that were changed separately by using of bended blade.For finding the detailed impact of sweep and lean angle on transonic blades,various forms of lean and sweep angles were exerted to basic rotor.It was found that sweep angles increased overall operating range up to 30%,efficiency up to 2%and pressure ratio up to 1%.Leaning the blades increased the safe operating range,the pressure ratio and efficiency by 14%,4%and 2%respectively.
