Gravel lateritic soils are intensively used in road geotechnical engineering. This material is largely representative of engineering soil all around the tropical African Countries [1,2]. Gravel lateritic soils from pa...Gravel lateritic soils are intensively used in road geotechnical engineering. This material is largely representative of engineering soil all around the tropical African Countries [1,2]. Gravel lateritic soils from parts of Burkina Faso and Senegal (West Africa) are used to determine the evolution of the geotechnical parameters from one to ten cycles of modified Proctor compaction. This test procedure is non-common for geotechnical purposes and it was found suitable and finally adopted to describe how these problematic soils behave when submitted to a multi-cyclic set of Modified Proctor compactions (OPM) [3,4]. On another hand, we propose a correlation between the traffic and the cycles of compaction considered as the repeated load. From that, this work shows the generation of active fine particles, the decrease of the CBR index and also the mechanical characteristics (mainly the Young Modulus, E) that contribute at least to the main deformation of the road structure.展开更多
Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cy...Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cycles of injection and production of underground gas storage(UGS)rebuilt from condensate gas reservoir to study the phase characteristics of produced and remaining fluids during multi-cycles of injection and production.Take condensate reservoir gas storage as example,the composition of produced fluid and remaining fluid,phase state of remaining fluid,retrograde condensate saturation and condensate recovery degree in the process of multi-cycles of injection-production were studied through multi-cycle injection-production experiment and phase equilibrium theory simulation.The injected gas could greatly improve the recovery of condensate oil in the gas reservoir,and the condensate oil recovery increased by 42% after 5 cycles of injection and production;the injected gas had significant evaporative and extraction effects on the condensate,especially during the first two cycles;the condensate oil saturation of the formation decreased with the increase of injection-production cycles,and the condensate oil saturation after multi-cycles of injection-production was almost 0;the storage capacity increased by about 7.5% after multi-cycles of injection and production,and the cumulative gas injection volume in the 5 th cycle increased by about 25%compared with that in the 1 st cycle.展开更多
Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.S...Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.Spinel nickel ferrite（NiFe2O4） was prepared and its multi-cycle performance as an oxygen carrier for CLDR was experimentally investigated.X-ray diffraction（XRD） and Laser Raman spectroscopy showed that a pure spinel crystalline phase（NiFe2O4） was obtained by a parallel flow co-precipitating method.NiFe2O4was reduced into Fe-Ni alloy and wustite（FexO） during the CH4 reduction process.Subsequent oxidation of the reduced oxygen carrier was performed with CO2 as an oxidant to form an intermediate state：a mixture of spinel Ni（1-x）Fe（2＋x）O4,Fe（2＋y）O4 and metallic Ni.And CO was generated in parallel during this stage.Approximate 185 mL of CO was generated for 1 g spinel NiFe2O4 in a single cycle.The intermediate oxygen carrier was fully oxidized in the air oxidation stage to form a mixture of Ni（1＋x）Fe（2-x）O4 and Fe2O3.Although the original state of oxygen carrier（NiFe2O4） was not fully regenerated and agglomeration was observed,a good recyclability was shown in 10 successive redox cycles.展开更多
Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and ...Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and interest between OPEC producers and other big oil supplier countries such as the USA and Russia. Forecasting global oil production is significant for all countries for energy strategy planning, although many past forecasts have later been proved to be very seriously incorrect. In this paper,the original generalized Weng model is expanded to a multi-cycle generalized Weng model to better reflect the multi-cycle phenomena caused by political, economic and technological factors. This is used to forecast global oil production based on parameter selection from a large sample, depletion rate of remaining resources, constraints on oil reserves and cycle number determination. This research suggests that the world will reach its peak oil production in 2022, at about 4340×10~6 tonnes. China needs to plan for oil import diversity, a domestic oil production structure based on the supply pattern of large oil suppliers worldwide and the oil demand for China＇s own development.展开更多
Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of...Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.展开更多
An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicin...An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle(20 fs) weak pulse(1013W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68 as and 66 as can be obtained.展开更多
文摘Gravel lateritic soils are intensively used in road geotechnical engineering. This material is largely representative of engineering soil all around the tropical African Countries [1,2]. Gravel lateritic soils from parts of Burkina Faso and Senegal (West Africa) are used to determine the evolution of the geotechnical parameters from one to ten cycles of modified Proctor compaction. This test procedure is non-common for geotechnical purposes and it was found suitable and finally adopted to describe how these problematic soils behave when submitted to a multi-cyclic set of Modified Proctor compactions (OPM) [3,4]. On another hand, we propose a correlation between the traffic and the cycles of compaction considered as the repeated load. From that, this work shows the generation of active fine particles, the decrease of the CBR index and also the mechanical characteristics (mainly the Young Modulus, E) that contribute at least to the main deformation of the road structure.
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
基金Supported by the National Natural Science Foundation of China(51974268)the PetroChina Science and Technology Major Project(2015E-4002)China Postdoctoral Science Foundation(2019M663563)。
文摘Based on the differences in production mode and operation process between gas storage and gas reservoir,we established a phase balance test procedure and a theoretical simulation model of phase balance during multi-cycles of injection and production of underground gas storage(UGS)rebuilt from condensate gas reservoir to study the phase characteristics of produced and remaining fluids during multi-cycles of injection and production.Take condensate reservoir gas storage as example,the composition of produced fluid and remaining fluid,phase state of remaining fluid,retrograde condensate saturation and condensate recovery degree in the process of multi-cycles of injection-production were studied through multi-cycle injection-production experiment and phase equilibrium theory simulation.The injected gas could greatly improve the recovery of condensate oil in the gas reservoir,and the condensate oil recovery increased by 42% after 5 cycles of injection and production;the injected gas had significant evaporative and extraction effects on the condensate,especially during the first two cycles;the condensate oil saturation of the formation decreased with the increase of injection-production cycles,and the condensate oil saturation after multi-cycles of injection-production was almost 0;the storage capacity increased by about 7.5% after multi-cycles of injection and production,and the cumulative gas injection volume in the 5 th cycle increased by about 25%compared with that in the 1 st cycle.
基金the financial support by the National Natural Science Foundation of China(51406214 and51406208)supported by the Natural science Foundation of Guangdong Province(2015A030313719)the Science&Technology Research Project of Guangdong Province(2013B050800008)
文摘Chemical looping dry reforming（CLDR） is an innovative technology for CO2 utilization using the chemical looping principle.The CLDR process consists of three stages,i.e.CH4 reduction,CO2 reforming,and air oxidation.Spinel nickel ferrite（NiFe2O4） was prepared and its multi-cycle performance as an oxygen carrier for CLDR was experimentally investigated.X-ray diffraction（XRD） and Laser Raman spectroscopy showed that a pure spinel crystalline phase（NiFe2O4） was obtained by a parallel flow co-precipitating method.NiFe2O4was reduced into Fe-Ni alloy and wustite（FexO） during the CH4 reduction process.Subsequent oxidation of the reduced oxygen carrier was performed with CO2 as an oxidant to form an intermediate state：a mixture of spinel Ni（1-x）Fe（2＋x）O4,Fe（2＋y）O4 and metallic Ni.And CO was generated in parallel during this stage.Approximate 185 mL of CO was generated for 1 g spinel NiFe2O4 in a single cycle.The intermediate oxygen carrier was fully oxidized in the air oxidation stage to form a mixture of Ni（1＋x）Fe（2-x）O4 and Fe2O3.Although the original state of oxygen carrier（NiFe2O4） was not fully regenerated and agglomeration was observed,a good recyclability was shown in 10 successive redox cycles.
基金financial support from the National Natural Science Foundation of China (Grant Nos. 71303258, 71373285, and 71503264)National Social Science Funds of China (13&ZD159)+1 种基金MOE (Ministry of Education in China) Project of Humanities and Social Sciences (13YJC630148, 15YJC630121)Science Foundation of China University of Petroleum, Beijing (ZX20150130)
文摘Low oil prices under the influence of economic structure transformation and slow economic growth have hit the existing markets of traditional big oil suppliers and upgraded the conflict of oil production capacity and interest between OPEC producers and other big oil supplier countries such as the USA and Russia. Forecasting global oil production is significant for all countries for energy strategy planning, although many past forecasts have later been proved to be very seriously incorrect. In this paper,the original generalized Weng model is expanded to a multi-cycle generalized Weng model to better reflect the multi-cycle phenomena caused by political, economic and technological factors. This is used to forecast global oil production based on parameter selection from a large sample, depletion rate of remaining resources, constraints on oil reserves and cycle number determination. This research suggests that the world will reach its peak oil production in 2022, at about 4340×10~6 tonnes. China needs to plan for oil import diversity, a domestic oil production structure based on the supply pattern of large oil suppliers worldwide and the oil demand for China＇s own development.
基金Supported by the Chongqing Technical Innovation and Application&Development Special Project(cstc2020jscx-msxmX0189)。
文摘Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.
基金Supported by the Scientific Research Fund of Liaoning University of Technology of China under Grant No.X201319the Scientific Research Fund of Liaoning Provincial Education Department under Grant No.L2014242
文摘An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle(20 fs) weak pulse(1013W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68 as and 66 as can be obtained.
