Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore str...Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace.Coke graphitization was simulated at different heating temperatures from 1100 to 1600℃ at intervals of 100℃.The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method.Results show that the adsorption and desorption curves of graphitized coke have intersection points,and the two curves did not coincide,instead forming a“hysteresis loop.”Based on the hysteresis loop analysis,the porous structure of the graphitized coke mostly appeared in the shape of a“hair follicle.”Furthermore,with an increase in heating temperature,the apparent porosity,specific surface area,total pore volume,and amount of micropores showed good correlation and can divided into three stages:1100-1200,1200-1400,and 1400-1600℃.When the temperature was less than 1400℃,ash migration from the inner part mainly led to changes in the coke pore structure.When the temperature was greater than 1400℃,the pore structure evolution was mainly affected by the coke graphitization degree.The results of scanning electron microscopy,energy dispersive spectrometry,and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400℃ contributed to these changes.展开更多
Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microf...Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.展开更多
BACKGROUND Interdigestive migrating motor complexes(MMC)produce periodic contractions in the gastrointestinal tract,but the exact mechanism of action still remains unclear.Intramuscular interstitial cells of Cajal(ICC...BACKGROUND Interdigestive migrating motor complexes(MMC)produce periodic contractions in the gastrointestinal tract,but the exact mechanism of action still remains unclear.Intramuscular interstitial cells of Cajal(ICC-IM)participate in gastrointestinal hormone and neuromodulation,but the correlation between ICCIM and MMC is also unclear.We found that xiangbinfang granules(XBF)mediated the phase III contraction of MMC.Here,the effects of XBF on gastric antrum motility in W/Wv mice and the effects of ICC-IM on gastric antrum MMC are reported.AIM To observe the effects of ICC-IM on gastric antrum motility and to establish the mechanism of XBF in promoting gastric antrum motility.METHODS The density of c-kit-positive ICC myenteric plexus(ICC-MP)and ICC-IM in the antral muscularis of W/Wv and wild-type(WT)mice was examined by confocal microscopy.The effects of XBF on gastric antrum slow waves in W/Wv and WT mice were recorded by intracellular amplification recording.Micro-strain-gauge force transducers were implanted into the gastric antrum to monitor the MMC and the effect of XBF on gastric antrum motility in conscious W/Wv and WT mice.RESULTS In the gastric antrum of W/Wv mice,c-kit immunoreactivity was significantly reduced,and no ICC-IM network was observed.Spontaneous rhythmic slow waves also appeared in the antrum of W/Wv mice,but the amplitude of the antrum slow wave decreased significantly in W/Wv mice(22.62±2.23 mV vs 2.92±0.52 mV,P<0.0001).MMCs were found in 7 of the 8 WT mice but no complete MMC cycle was found in W/Wv mice.The contractile frequency and amplitude index of the gastric antrum were significantly increased in conscious WT compared to W/Wv mice(frequency,3.53±0.18 cpm vs 1.28±0.12 cpm;amplitude index,23014.26±1798.65 mV·20 min vs 3782.16±407.13 mV·20 min;P<0.0001).XBF depolarized smooth muscle cells of the gastric antrum in WT and W/Wv mice in a dose-dependent manner.Similarly,the gastric antrum motility in WT mice was significantly increased after treatment with XBF 5 mg(P<0.05).Atropine(0.1 mg/kg)blocked the enhancement of XBF in WT and W/Wv mice completely,while tetrodotoxin(0.05 mg/kg)partially inhibited the enhancement by XBF.CONCLUSION ICC-IM participates in the regulation of gastric antrum MMC in mice.XBF induces MMC III-like contractions that enhance gastric antrum motility via ICCIM in mice.展开更多
In order to determine how the subaqueous delta evolution depends on the water and sediment processes in the Yangtze Estuary, the amounts of water and sediment discharged into the estuary were studied. The results show...In order to determine how the subaqueous delta evolution depends on the water and sediment processes in the Yangtze Estuary, the amounts of water and sediment discharged into the estuary were studied. The results show that, during the period from 1950 to 2010, there was no significant change in the annual water discharge, and the multi-annual mean water discharge increased in dry seasons and decreased in flood seasons. However, the annual sediment discharge and the multi-annual mean sediment discharge in flood and dry seasons took on a decreasing trend, and the intra-annual distribution of water and sediment discharges tended to be uniform. The evolution process from deposition to erosion occurred at the -10 m and -20 m isobaths of the subaqueous delta. The enhanced annual water and sediment discharges had a silting-up effect on the delta, and the effect of sediment was greater than that of water. Based on data analysis, empirical curves were built to present the relationships between the water and sediment discharges over a year or in dry and flood seasons and the erosion/deposition rates in typical regions of the suhaqueous delta, whose evolution followed the pattern of silting in flood seasons and scouring in dry seasons. Notably, the Three Gorges Dam has changed the distribution processes of water and sediment discharges, and the dam's regulating and reserving functions can benefit the subaqueous delta deposition when the annual water and sediment discharges are not affected.展开更多
In this paper, we study the unsteady coupled heat and mass transfer of two-dimensional MHD fluid over a moving oscillatory stretching surface with Soret and Dufour effects. Viscous dissipation effects are adopted in t...In this paper, we study the unsteady coupled heat and mass transfer of two-dimensional MHD fluid over a moving oscillatory stretching surface with Soret and Dufour effects. Viscous dissipation effects are adopted in the energy equation. A uniform magnetic field is applied vertically to the flow direction. The governing equations are reduced to non-linear coupled partial differential equations and solved by means of homotopy analysis method (HAM). The effects of some physical parameters such as magnetic parameter, Dufour number, Soret number, the Prandtl num- ber and the ratio of the oscillation frequency of the sheet to its stretching rate on the flow and heat transfer characteristics are illustrated and analyzed.展开更多
The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of...The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis.Based on the structure stiffness equivalent characteristic,a simple stepped shaft can reflect the entire complex structure model.The existing lubrication model,which does not consider this angle component,is not very precise for journal bearings.Film pressure,misalignment angle,velocity field,oil leakage,and temperature field were calculated and compared in the journal bearing analysis.The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure.A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.展开更多
TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,exce...TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,excellent safety and relatively high specific capacity.Nonetheless,the inferior electronic conductivity and poor ion diffusion coefficients are the biggest bottlenecks that restrict the popular application.Much effort has been focused on resolving these problems toward large-scale applications,and numerous significant advances have been accomplished.In the present work,a comprehensive overview of structure characteristics,electrochemical reaction mechanism and modification strategies of TiO_(2)-based materials was presented.The recent advances of various efficient ways for improving conductivity,Li(Na)storage capacity,rate capability and cycle stability are systematically summarized,including surface engineering,constructing composite and element doping,etc.Constructing TiO_(2)-based materials with novel porous heterogeneous core-shell structures have been regarded as one of the most effective ways to resolve these challenges.Finally,the future research directions and development prospects of TiO_(2)-based anode materials used in the manufacture of high-performance Li(Na)-ion batteries are prospected.This review can provide important comprehension for the construction and optimization of highperformance of TiO_(2)-based anode materials.展开更多
Root-knot nematodes (Meloidogyne spp.) cause major economic damage to numerous crop species around the world. Plant resistance is the most important attribute that is able to suppress invasion by the rootknot nemato...Root-knot nematodes (Meloidogyne spp.) cause major economic damage to numerous crop species around the world. Plant resistance is the most important attribute that is able to suppress invasion by the rootknot nematodes. In the present study, a candidate root-knot nematode resistance gene (Mi) was isolated from the resistant tomato (Lycopersicon esculentum L.) line RN-1. Expression profiling analysis revealed that this gene was expressed specifically in the roots, stems, and leaves, but not in the flowers or fruits. To verify the real function of this candidate gene, both sense and inteference RNA (RNAi) vectors were constructed. We obtained 31 transgenic plants with between one and seven copies of T-DNA inserts of sense Mi from two nematode-susceptible tomato cultivars as assayed by polymerase chain reaction (PCR) and Southern blotting analysis. Reverse transcription-PCR analysis revealed that expression levels of the Mi gene varied in different transgenic plants. Nematode assays showed that the resistance to root-knot nematodes was significantly improved in some transgenic lines compared with untransformed susceptible controls and that the resistance was heritable in selfed progeny. Loss of function via RNAi further confirmed the role of the Mi gene and the original resistant lines became susceptible to root-knot nematodes.展开更多
In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The i...In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The introduction of CNTs does not change the structure of the Bi_(5) Nb_(3) O_(15) materials,the Bi_(5) Nb_(3) O_(15) particles are decorated on a three-dimensional CNTs network,and the high conductive network promotes transfer of electron/ion and relieve the volume change of Bi_(5) Nb_(3) O_(15).The Bi_(5) Nb_(3) O_(15)@CNTs(8 wt%) electrode shows a superior rate capability with charge(discharge) capacities of 490(898.7),379.1(401.6),311.3(326.9),276.5(285.5) and 243.4(252)mAh·g^(-1) at 50,100,200,300 and 500 mA·g^(-1),respectively.However,the Bi_(5) Nb_(3) O_(15) only shows charge(discharge) capacities of 431(772.6),278.6(309.9),193.1(213.7),160.8(171.1),129.9(139.1) mAh·g^(-1) at the corresponding rates,respectively.The excellent rate capability of Bi_(5) Nb_(3) O_(15)@CNTs can be ascribed to the homogeneous distribution of Bi_(5) Nb_(3) O_(15) particles in the CNTs conductive network and the enhancement of conductivity.Hence,the CNTs modulation can be considered as an effective strategy to enhance electrochemical performances of Bi_(5) Nb_(3) O_(15) materials.展开更多
In order to clarify the mutual effect between bituminite and anthracite in blends during industrial combustion, the influence of particle size and heating rate as well as oxygen concentration in atmosphere was analyze...In order to clarify the mutual effect between bituminite and anthracite in blends during industrial combustion, the influence of particle size and heating rate as well as oxygen concentration in atmosphere was analyzed. The results of non-isothermal thermogravimetric analysis indicated that the combustion behavior of blends was of great difference though blends were prepared with the same volatile content of 20%. The catalysis of bituminite to anthracite changed with the thermal and kinetic condition of combustion reaction, and consequently, blends with different collocations were suitable for various combustion environments. Superior combustion properties of some blends were achieved at high heating rates, while others might react faster under high oxygen-enriched atmosphere. Simultaneously, the volume model and unreacted core model as well as random pore model were introduced to fit the experimental data. The kinetic calculation results showed that the combustion of blends at different heating rates all agreed better with that of random pore model in comparison with the other two models, while the apparent activation energy of samples all decreased with the increase in heating rate. The similarity of functional group structure between bituminite and anthracite is closely related to the accordance in com-bustion stage of bituminite and anthracite in blends.展开更多
Journal misalignment is common in journal bearings. When severe journal misalignment takes place, it affects nearly all aspects of bearing performance. This paper provided a comprehensive analysis of misaligned journa...Journal misalignment is common in journal bearings. When severe journal misalignment takes place, it affects nearly all aspects of bearing performance. This paper provided a comprehensive analysis of misaligned journal bearings based on two different mass-conservative models which appropriately took into account film rupture and reformation. The lubrication characteristics and performance parameters including the cavitation zones, pressure distribution, density distribution, oil leakage, load capacity, moment, and attitude angle were compared with the traditional lubrication model. The results showed that cavitation has great effect on bearing performances, especially when the surface roughness is large. Therefore, it is necessary to consider the effects of journal misalignment alongside inter-asperity cavitation theory in the design and analyses of journal bearings.展开更多
In this work,we construct Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(NLTO-L)composites by a simple ball milled process and post-calcination in air atmosphere to improve the electrochemical performance.The thickness of the LiA...In this work,we construct Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(NLTO-L)composites by a simple ball milled process and post-calcination in air atmosphere to improve the electrochemical performance.The thickness of the LiAlO_(2)coating layer is approximate2 nm.The morphology and particle size of Na_(2)Li_(2)Ti_(6)O_(14)are not dramatically altered after LiAlO_(2)coating.All samples display similar particles with a size range from 150 to 500 nm.The LiAlO_(2)coating can supply fast charge transmission paths with good insertion/extraction dynamics of lithium ions and provide an excellent rate performance and cycle performance of as-prepared Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)anodes.Therefore,LiAlO_(2)coating efficiently enhances the rate performance and cycle performance of Na_(2)Li_(2)Ti_(6)O_(14)anode,even at large current densities.As a result,Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(5 wt%)reveals remarkable rate properties with reversible charge capacity of 238.7,214.7,185.8,168.5 and 139.8 mAh g^(-1)at 50,100,200,300 and 500 mA g^(-1),respectively.Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(5 wt%)also possesses a good cycle performance with a de-lithiation capacity of 166.5 mAh g-1 at 500 mA g^(-1)after 200 cycles.Nonetheless,the corresponding de-lithiation capacity of pure Na_(2)Li_(2)Ti_(6)O_(14)is only 140.1 mAh g^(-1).Consequently,LiAlO_(2)coating is efficeient approach to enhance the electrochemical performances of Na_(2)Li_(2)Ti_(6)O_(14).展开更多
Na_(2)Li_(2)Ti_(6)O_(14) as a reliable anode material is becoming a hopeful candidate for Li-ion battery.Nevertheless,the pristine Na_(2)Li_(2)Ti_(6)O_(14) usually suffer from bad rate performance and poor cycling sta...Na_(2)Li_(2)Ti_(6)O_(14) as a reliable anode material is becoming a hopeful candidate for Li-ion battery.Nevertheless,the pristine Na_(2)Li_(2)Ti_(6)O_(14) usually suffer from bad rate performance and poor cycling stability under high current due to limited diffusion kinetics and poor electrical conductivity.Here,the PPy-coated Na_(2)Li_(2)Ti_(6)O_(14) composites are successfully obtained via the solid-state method and followed by chemical oxidation process in the first time.The results of tests prove that the Na_(2)Li_(2)Ti_(6)O_(14)@PPy composites have better electrochemical performance than the bare Na_(2)Li_(2)Ti_(6)O_(14) because of the excellent electrical conductivity and the special macromolecular architecture of PPy.In particular,the Na_(2) Li_(2) Ti_(6) O_(14) @PPy(4 wt%)exhibits excellent charge capacities of about 223.2,218.0,200.8,184.3 and 172.6 mAh g^(-1) at 50,100,200,300 and500 mA g^(-1),respectively,revealing the best rate capability of all electrode materials.The Na_(2)Li_(2)Ti_(6)O_(14)@PPy(4 wt%)not only has the highest charge capacity under 0.5 mA g^(-1),but also has the highest capacity retention of 85.12%among all samples after 100 loops.Hence,the PPy coating is known as a promising way to improve the electrochemical property of Na_(2)Li_(2)Ti_(6)O_(14).The PPy-coated Na_(2)Li_(2)Ti_(6)O_(14) demonstrates the great prospect as promising negative materials for Li-ion batteries.展开更多
Combustion behavior of single pulverized coals(PCs)and co-combustion characteristics of anthracite(AT)and bituminite(BT)blends with 20 wt.%volatile were studied by thermogravimetric experiments.The results indicated t...Combustion behavior of single pulverized coals(PCs)and co-combustion characteristics of anthracite(AT)and bituminite(BT)blends with 20 wt.%volatile were studied by thermogravimetric experiments.The results indicated that reaction characteristics of PCs were closely related to their functional group structure and consequently,the pyrolysis of PCs with highly active functional groups initiated at lower temperatures.It was also noticed that the discrepancy of functional group structures between AT and BT might impair their interaction during combustion.The early exhaust of BT at low temperatures would possibly lead to an independent combustion of volatile and residual carbon and eventually the inefficient combustion of their blend.However,the mixing of AT and BT with similar functional group structures was more likely to achieve blends with superior combustion property.Simultaneously,non-isothermal kinetic analysis mani-fested that the combustion of blends followed random pore model(RPM),and therefore,the parameters calculated by RPM were more accurate to describe their combustion behavior.The kinetic calculation results showed that the activation energy required for decomposition of blends in early combustion stage was much lower owing to the excellent activity of volatile,while residual carbon with stable aromatic hydrocarbon demanded more energy to initiate its combustion.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51604148,51874171,and 51974154)the Science Foundation for the Talents by University of Science and Technology Liaoning(USTL),China(2019RC11).
文摘Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace.Coke graphitization was simulated at different heating temperatures from 1100 to 1600℃ at intervals of 100℃.The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method.Results show that the adsorption and desorption curves of graphitized coke have intersection points,and the two curves did not coincide,instead forming a“hysteresis loop.”Based on the hysteresis loop analysis,the porous structure of the graphitized coke mostly appeared in the shape of a“hair follicle.”Furthermore,with an increase in heating temperature,the apparent porosity,specific surface area,total pore volume,and amount of micropores showed good correlation and can divided into three stages:1100-1200,1200-1400,and 1400-1600℃.When the temperature was less than 1400℃,ash migration from the inner part mainly led to changes in the coke pore structure.When the temperature was greater than 1400℃,the pore structure evolution was mainly affected by the coke graphitization degree.The results of scanning electron microscopy,energy dispersive spectrometry,and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400℃ contributed to these changes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304409 and 61705028)the Natural Science Foundation of Chongqing City,China(Grant Nos.csct2013jcyjA4004 and cstc2017jcyjA0893)+1 种基金the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ1500422)the Postgraduate Research Innovation Foundation of Chongqing City,China(Grant No.CYS17240)
文摘Using graphene-covered-microfiber (GCM) as a saturable absorber, the generation and evolution of multiple operation states are proposed and demonstrated in passively mode-locked thulium-doped fiber laser. The microfiber was fabricated using the flame brushing method to an interaction length of - 1.2 cm with a waist diameter of -10 μm. Graphene layers were grown on copper foils by chemical vapor deposition and transferred onto the polydimethylsiloxane (PDMS) to form a PDMS/graphene film, which allowed light-graphene interaction via evanescent field. With the increase of the pump power from 1.25 W to 2.15 W, five different lasing regimes, including continuous-wave, conventional soliton mode-locking, multi- soliton mode-locking, a period of transition, and noise-like mode-locking, were achieved in a fiber ring cavity. To the best of our knowledge, it is the first report of the generation and evolution of multiple operation states by covering graphene on the microfiber in the 2-μ.m region. The results demonstrate that GCM can be a promising method for fabricating all fiber SA, and the switchable operation states can provide more portability in complex application domain.
文摘BACKGROUND Interdigestive migrating motor complexes(MMC)produce periodic contractions in the gastrointestinal tract,but the exact mechanism of action still remains unclear.Intramuscular interstitial cells of Cajal(ICC-IM)participate in gastrointestinal hormone and neuromodulation,but the correlation between ICCIM and MMC is also unclear.We found that xiangbinfang granules(XBF)mediated the phase III contraction of MMC.Here,the effects of XBF on gastric antrum motility in W/Wv mice and the effects of ICC-IM on gastric antrum MMC are reported.AIM To observe the effects of ICC-IM on gastric antrum motility and to establish the mechanism of XBF in promoting gastric antrum motility.METHODS The density of c-kit-positive ICC myenteric plexus(ICC-MP)and ICC-IM in the antral muscularis of W/Wv and wild-type(WT)mice was examined by confocal microscopy.The effects of XBF on gastric antrum slow waves in W/Wv and WT mice were recorded by intracellular amplification recording.Micro-strain-gauge force transducers were implanted into the gastric antrum to monitor the MMC and the effect of XBF on gastric antrum motility in conscious W/Wv and WT mice.RESULTS In the gastric antrum of W/Wv mice,c-kit immunoreactivity was significantly reduced,and no ICC-IM network was observed.Spontaneous rhythmic slow waves also appeared in the antrum of W/Wv mice,but the amplitude of the antrum slow wave decreased significantly in W/Wv mice(22.62±2.23 mV vs 2.92±0.52 mV,P<0.0001).MMCs were found in 7 of the 8 WT mice but no complete MMC cycle was found in W/Wv mice.The contractile frequency and amplitude index of the gastric antrum were significantly increased in conscious WT compared to W/Wv mice(frequency,3.53±0.18 cpm vs 1.28±0.12 cpm;amplitude index,23014.26±1798.65 mV·20 min vs 3782.16±407.13 mV·20 min;P<0.0001).XBF depolarized smooth muscle cells of the gastric antrum in WT and W/Wv mice in a dose-dependent manner.Similarly,the gastric antrum motility in WT mice was significantly increased after treatment with XBF 5 mg(P<0.05).Atropine(0.1 mg/kg)blocked the enhancement of XBF in WT and W/Wv mice completely,while tetrodotoxin(0.05 mg/kg)partially inhibited the enhancement by XBF.CONCLUSION ICC-IM participates in the regulation of gastric antrum MMC in mice.XBF induces MMC III-like contractions that enhance gastric antrum motility via ICCIM in mice.
基金supported by the National Basic Research Program of China(the 973 Program,Grant No.2010CB429002)
文摘In order to determine how the subaqueous delta evolution depends on the water and sediment processes in the Yangtze Estuary, the amounts of water and sediment discharged into the estuary were studied. The results show that, during the period from 1950 to 2010, there was no significant change in the annual water discharge, and the multi-annual mean water discharge increased in dry seasons and decreased in flood seasons. However, the annual sediment discharge and the multi-annual mean sediment discharge in flood and dry seasons took on a decreasing trend, and the intra-annual distribution of water and sediment discharges tended to be uniform. The evolution process from deposition to erosion occurred at the -10 m and -20 m isobaths of the subaqueous delta. The enhanced annual water and sediment discharges had a silting-up effect on the delta, and the effect of sediment was greater than that of water. Based on data analysis, empirical curves were built to present the relationships between the water and sediment discharges over a year or in dry and flood seasons and the erosion/deposition rates in typical regions of the suhaqueous delta, whose evolution followed the pattern of silting in flood seasons and scouring in dry seasons. Notably, the Three Gorges Dam has changed the distribution processes of water and sediment discharges, and the dam's regulating and reserving functions can benefit the subaqueous delta deposition when the annual water and sediment discharges are not affected.
基金supported by the National Natural Science Foundations of China (51076012 and 51276014)
文摘In this paper, we study the unsteady coupled heat and mass transfer of two-dimensional MHD fluid over a moving oscillatory stretching surface with Soret and Dufour effects. Viscous dissipation effects are adopted in the energy equation. A uniform magnetic field is applied vertically to the flow direction. The governing equations are reduced to non-linear coupled partial differential equations and solved by means of homotopy analysis method (HAM). The effects of some physical parameters such as magnetic parameter, Dufour number, Soret number, the Prandtl num- ber and the ratio of the oscillation frequency of the sheet to its stretching rate on the flow and heat transfer characteristics are illustrated and analyzed.
基金Project supported by the National Natural Science Foundation of China (No. 60879002)the Tianjin Support Plan of China(No. 10ZCKFGX03800)
文摘The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis.Based on the structure stiffness equivalent characteristic,a simple stepped shaft can reflect the entire complex structure model.The existing lubrication model,which does not consider this angle component,is not very precise for journal bearings.Film pressure,misalignment angle,velocity field,oil leakage,and temperature field were calculated and compared in the journal bearing analysis.The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure.A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.
基金financially supported by the National Natural Science Foundation of China(No.51774002)the Key Program for International S&T Cooperation Projects of China(No.2017YFE0124300)the“333 Talent Project”of Hebei Province(No.A202005018)。
文摘TiO_(2)-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost,simple composition,easy synthesis,good environmental protection,excellent safety and relatively high specific capacity.Nonetheless,the inferior electronic conductivity and poor ion diffusion coefficients are the biggest bottlenecks that restrict the popular application.Much effort has been focused on resolving these problems toward large-scale applications,and numerous significant advances have been accomplished.In the present work,a comprehensive overview of structure characteristics,electrochemical reaction mechanism and modification strategies of TiO_(2)-based materials was presented.The recent advances of various efficient ways for improving conductivity,Li(Na)storage capacity,rate capability and cycle stability are systematically summarized,including surface engineering,constructing composite and element doping,etc.Constructing TiO_(2)-based materials with novel porous heterogeneous core-shell structures have been regarded as one of the most effective ways to resolve these challenges.Finally,the future research directions and development prospects of TiO_(2)-based anode materials used in the manufacture of high-performance Li(Na)-ion batteries are prospected.This review can provide important comprehension for the construction and optimization of highperformance of TiO_(2)-based anode materials.
基金Supported by the National Natural Science Foundation of China (30370980), Doctorate Program of University of Ministry of Education (20050504028), and National Advanced Technology Research and Development Plan of China (AA212221).
文摘Root-knot nematodes (Meloidogyne spp.) cause major economic damage to numerous crop species around the world. Plant resistance is the most important attribute that is able to suppress invasion by the rootknot nematodes. In the present study, a candidate root-knot nematode resistance gene (Mi) was isolated from the resistant tomato (Lycopersicon esculentum L.) line RN-1. Expression profiling analysis revealed that this gene was expressed specifically in the roots, stems, and leaves, but not in the flowers or fruits. To verify the real function of this candidate gene, both sense and inteference RNA (RNAi) vectors were constructed. We obtained 31 transgenic plants with between one and seven copies of T-DNA inserts of sense Mi from two nematode-susceptible tomato cultivars as assayed by polymerase chain reaction (PCR) and Southern blotting analysis. Reverse transcription-PCR analysis revealed that expression levels of the Mi gene varied in different transgenic plants. Nematode assays showed that the resistance to root-knot nematodes was significantly improved in some transgenic lines compared with untransformed susceptible controls and that the resistance was heritable in selfed progeny. Loss of function via RNAi further confirmed the role of the Mi gene and the original resistant lines became susceptible to root-knot nematodes.
基金financially supported by the Key Program for International S&T Cooperation Projects of China (No.2017YFE0124300)the National Natural Science Foundation of China (Nos.U1960107 and 22179019)+2 种基金the "333" Talent Project of Hebei Province (No.A202005018)the Fundamental Research Funds for the Central Universities (No.N2123001)the Natural Science Foundation of Hebei Province of China (No.B2020501003)。
文摘In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The introduction of CNTs does not change the structure of the Bi_(5) Nb_(3) O_(15) materials,the Bi_(5) Nb_(3) O_(15) particles are decorated on a three-dimensional CNTs network,and the high conductive network promotes transfer of electron/ion and relieve the volume change of Bi_(5) Nb_(3) O_(15).The Bi_(5) Nb_(3) O_(15)@CNTs(8 wt%) electrode shows a superior rate capability with charge(discharge) capacities of 490(898.7),379.1(401.6),311.3(326.9),276.5(285.5) and 243.4(252)mAh·g^(-1) at 50,100,200,300 and 500 mA·g^(-1),respectively.However,the Bi_(5) Nb_(3) O_(15) only shows charge(discharge) capacities of 431(772.6),278.6(309.9),193.1(213.7),160.8(171.1),129.9(139.1) mAh·g^(-1) at the corresponding rates,respectively.The excellent rate capability of Bi_(5) Nb_(3) O_(15)@CNTs can be ascribed to the homogeneous distribution of Bi_(5) Nb_(3) O_(15) particles in the CNTs conductive network and the enhancement of conductivity.Hence,the CNTs modulation can be considered as an effective strategy to enhance electrochemical performances of Bi_(5) Nb_(3) O_(15) materials.
基金This work was financially supported by Natural Science and Foundation of Liaoning Province (No. 20170540455)National Natural Science Foundation of China (51504131, 51474124, 51647639).
文摘In order to clarify the mutual effect between bituminite and anthracite in blends during industrial combustion, the influence of particle size and heating rate as well as oxygen concentration in atmosphere was analyzed. The results of non-isothermal thermogravimetric analysis indicated that the combustion behavior of blends was of great difference though blends were prepared with the same volatile content of 20%. The catalysis of bituminite to anthracite changed with the thermal and kinetic condition of combustion reaction, and consequently, blends with different collocations were suitable for various combustion environments. Superior combustion properties of some blends were achieved at high heating rates, while others might react faster under high oxygen-enriched atmosphere. Simultaneously, the volume model and unreacted core model as well as random pore model were introduced to fit the experimental data. The kinetic calculation results showed that the combustion of blends at different heating rates all agreed better with that of random pore model in comparison with the other two models, while the apparent activation energy of samples all decreased with the increase in heating rate. The similarity of functional group structure between bituminite and anthracite is closely related to the accordance in com-bustion stage of bituminite and anthracite in blends.
基金Project supported by the Joint Funds of National Science Foundation of ChinaCivil Aviation Administration Foundation of China(No.U1233201)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20130032130005)
基金Project (No. U1233201) supported by the Joint Funds of National Science Foundation of ChinaCivil Administration Foundation of China
文摘Journal misalignment is common in journal bearings. When severe journal misalignment takes place, it affects nearly all aspects of bearing performance. This paper provided a comprehensive analysis of misaligned journal bearings based on two different mass-conservative models which appropriately took into account film rupture and reformation. The lubrication characteristics and performance parameters including the cavitation zones, pressure distribution, density distribution, oil leakage, load capacity, moment, and attitude angle were compared with the traditional lubrication model. The results showed that cavitation has great effect on bearing performances, especially when the surface roughness is large. Therefore, it is necessary to consider the effects of journal misalignment alongside inter-asperity cavitation theory in the design and analyses of journal bearings.
基金financially supported by the National Natural Science Foundation of China(No.U1960107)the“333”Talent Project of Hebei Province(No.A202005018)the Fundamental Research Funds for the Central Universities(No N2123001)。
文摘In this work,we construct Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(NLTO-L)composites by a simple ball milled process and post-calcination in air atmosphere to improve the electrochemical performance.The thickness of the LiAlO_(2)coating layer is approximate2 nm.The morphology and particle size of Na_(2)Li_(2)Ti_(6)O_(14)are not dramatically altered after LiAlO_(2)coating.All samples display similar particles with a size range from 150 to 500 nm.The LiAlO_(2)coating can supply fast charge transmission paths with good insertion/extraction dynamics of lithium ions and provide an excellent rate performance and cycle performance of as-prepared Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)anodes.Therefore,LiAlO_(2)coating efficiently enhances the rate performance and cycle performance of Na_(2)Li_(2)Ti_(6)O_(14)anode,even at large current densities.As a result,Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(5 wt%)reveals remarkable rate properties with reversible charge capacity of 238.7,214.7,185.8,168.5 and 139.8 mAh g^(-1)at 50,100,200,300 and 500 mA g^(-1),respectively.Na_(2)Li_(2)Ti_(6)O_(14)@LiAlO_(2)(5 wt%)also possesses a good cycle performance with a de-lithiation capacity of 166.5 mAh g-1 at 500 mA g^(-1)after 200 cycles.Nonetheless,the corresponding de-lithiation capacity of pure Na_(2)Li_(2)Ti_(6)O_(14)is only 140.1 mAh g^(-1).Consequently,LiAlO_(2)coating is efficeient approach to enhance the electrochemical performances of Na_(2)Li_(2)Ti_(6)O_(14).
基金financially supported by the National Natural Science Foundation of China(No.U1960107)the“333”Talent Project of Hebei Province(No.A202005018)the Fundamental Research Funds for the Central Universities(No.N2123001)。
文摘Na_(2)Li_(2)Ti_(6)O_(14) as a reliable anode material is becoming a hopeful candidate for Li-ion battery.Nevertheless,the pristine Na_(2)Li_(2)Ti_(6)O_(14) usually suffer from bad rate performance and poor cycling stability under high current due to limited diffusion kinetics and poor electrical conductivity.Here,the PPy-coated Na_(2)Li_(2)Ti_(6)O_(14) composites are successfully obtained via the solid-state method and followed by chemical oxidation process in the first time.The results of tests prove that the Na_(2)Li_(2)Ti_(6)O_(14)@PPy composites have better electrochemical performance than the bare Na_(2)Li_(2)Ti_(6)O_(14) because of the excellent electrical conductivity and the special macromolecular architecture of PPy.In particular,the Na_(2) Li_(2) Ti_(6) O_(14) @PPy(4 wt%)exhibits excellent charge capacities of about 223.2,218.0,200.8,184.3 and 172.6 mAh g^(-1) at 50,100,200,300 and500 mA g^(-1),respectively,revealing the best rate capability of all electrode materials.The Na_(2)Li_(2)Ti_(6)O_(14)@PPy(4 wt%)not only has the highest charge capacity under 0.5 mA g^(-1),but also has the highest capacity retention of 85.12%among all samples after 100 loops.Hence,the PPy coating is known as a promising way to improve the electrochemical property of Na_(2)Li_(2)Ti_(6)O_(14).The PPy-coated Na_(2)Li_(2)Ti_(6)O_(14) demonstrates the great prospect as promising negative materials for Li-ion batteries.
基金supported by the National Natural Science Foundation of China(51874171,51604148,51974154 and 52074150)Liaoning Provincial Natural Science Foundation Guiding Program of China(2019-ZD-0273).
文摘Combustion behavior of single pulverized coals(PCs)and co-combustion characteristics of anthracite(AT)and bituminite(BT)blends with 20 wt.%volatile were studied by thermogravimetric experiments.The results indicated that reaction characteristics of PCs were closely related to their functional group structure and consequently,the pyrolysis of PCs with highly active functional groups initiated at lower temperatures.It was also noticed that the discrepancy of functional group structures between AT and BT might impair their interaction during combustion.The early exhaust of BT at low temperatures would possibly lead to an independent combustion of volatile and residual carbon and eventually the inefficient combustion of their blend.However,the mixing of AT and BT with similar functional group structures was more likely to achieve blends with superior combustion property.Simultaneously,non-isothermal kinetic analysis mani-fested that the combustion of blends followed random pore model(RPM),and therefore,the parameters calculated by RPM were more accurate to describe their combustion behavior.The kinetic calculation results showed that the activation energy required for decomposition of blends in early combustion stage was much lower owing to the excellent activity of volatile,while residual carbon with stable aromatic hydrocarbon demanded more energy to initiate its combustion.