Labile organic carbon （LC） and recalcitrant organic carbon （RC） are two major fractions of soil organic carbon （SOC） and play a critical role in organic carbon turnover and sequestration. The aims of this study ...Labile organic carbon （LC） and recalcitrant organic carbon （RC） are two major fractions of soil organic carbon （SOC） and play a critical role in organic carbon turnover and sequestration. The aims of this study were to evaluate the variations of LC and RC in a semi-arid soil （Inner Mongolia, China） under plastic mulch and drip irrigation after the application of organic materials （OMs）, and to explore the effects of OMs from various sources on LC and RC by probing the decomposition characteristics of OMs using in-situ nylon mesh bags burying method. The field experiment included seven treatments, i.e., chicken manure （CM）, sheep manure （SM）, mushroom residue （MR）, maize straw （MS）, fodder grass （FG）, tree leaves （TL） and no OMs as a control （CK）. Soil LC and RC were separated by Huygens D＇s method （particle size-density）, and the average soil mass recovery rate and carbon recovery rate were above 95%, which indicated this method was suitable for carbon pools size analysis. The LC and RC contents significantly （P〈0.01） increased after the application of OMs. Moreover, LC and RC contents were 3.2%-8.6% and 5.0%-9.4% higher in 2016 than in 2015. The applications of CM and SM significantly increased （P〈0,01） LC content and LC/SOC ratio, whereas they were the lowest after the application of TL. However, SOC and RC contents were significantly higher （P〈0.01） after the applications of TL and MS. The correlation analysis indicated the decomposition rate of OMs was positively related with LC content and LC/SOC ratio. In addition, lignin, polyphenol, WOM （total water-soluble organic matter）, WHA （water-soluble humic acid）, HSL （humicdike substance） and HAL （humic acid-like） contents in initial OMs played important roles in SOC and RC. In-situ nylon mesh bags burying experiment indicated the decomposition rates of CM, SM and MS were significantly higher than those of MR, FG, and TL. Furthermore, MS could result in more lignin derivatives, WHA, and HAL polymers in shorter time during the decomposition process. In conclusion, the application of MS in the semi-arid soil under a long-term plastic mulch and drip irrigation condition could not only improve soil fertility, but also enhance soil carbon sequestration.展开更多
As a kind of biological fertilizer sources, green manure can improve soil fertility and the quality of agricultural products. This paper introduced the germplasm resource of green manures in the major provinces in Chi...As a kind of biological fertilizer sources, green manure can improve soil fertility and the quality of agricultural products. This paper introduced the germplasm resource of green manures in the major provinces in China, mainly summarized the characteristics of decomposition and nutrients release of returning green manures to soils, as well as the influence on soil fertility and succeeding crops, with the aim to provide references for rational utilization of green manures and the scientific management of farmland nutrients.展开更多
With nylon mesh bags, the decomposition and nutrients release characteristics of two kinds of green manure crops, February orchid （Orychophragmus violaceus） and Hair Vetch （Vicia villosa Roth）, were investigated i...With nylon mesh bags, the decomposition and nutrients release characteristics of two kinds of green manure crops, February orchid （Orychophragmus violaceus） and Hair Vetch （Vicia villosa Roth）, were investigated in this study. The results showed that these two kinds of green manure crops were decomposed rapidly in the first 14 days, and then decomposed slowly. After 80 days of incubation, the decomposition rates of February orchid and Hair Vetch were 66.92% and 63.12%, respectively. Different nutrients had different release rates from the green manures. Nitrogen （N） and potassium （K） were released rapidly in the initial 7 days, and phosphorus （P） was released steadily in the 80 days of incubation. In the two kinds of green manures, the release rates all ranked as K＇s〉N＇s〉P＇s. The release rates of nutrients, especially P （P〈0.05）, of February orchid were higher than those of Hair Vetch.展开更多
Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the n...Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle(WHTC) urea deposits are urea, cyanuric acid(CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cu β and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cu β, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.展开更多
The effect of rare earth metals(REM)on the characteristics of auto-tempering and decomposition of martensite for low-carbon and low-alloy steels(20SiMn2V and 20SiMn2VRE)was investigated using TEM,dilatometer and micro...The effect of rare earth metals(REM)on the characteristics of auto-tempering and decomposition of martensite for low-carbon and low-alloy steels(20SiMn2V and 20SiMn2VRE)was investigated using TEM,dilatometer and microhardness test.Results show that both ε.and θ carbides,during auto-tempering, may precipitate from the low-carbon martensite matrix at the same time in the 20SiMn2V steel,however,the precipitation of the ε-carbides can be inhibited by the REM contained in the 20SiMn2 VRE steel,resulting in change of the type of precipitated carbides and decrease of the extent of auto-tempering.The“in-situ”ob- servations show that the decomposition of martensite is also inhibited by the REM contained in the 20SiMn2 VRE steel during low temperature tempering.展开更多
We study the existence of global-in-time classical solutions for the one-dimensional nonisentropic compressible Euler system for a dusty gas with large initial data.Using the characteristic decomposition method propos...We study the existence of global-in-time classical solutions for the one-dimensional nonisentropic compressible Euler system for a dusty gas with large initial data.Using the characteristic decomposition method proposed by Li et al.(Commun Math Phys 267:1–12,2006),we derive a group of characteristic decompositions for the system.Using these characteristic decompositions,we find a sufficient condition on the initial data to ensure the existence of global-in-time classical solutions.展开更多
This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensiona...This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensional(3-D)steady Euler equations can be projected onto the unit sphere and the state of fluid can be characterized by the polar and azimuthal angles.Given a segment smooth curve as a conical-sonic line in the polar-azimuthal angle plane,we construct a classical conical-supersonic solution near the curve under some reasonable assumptions.To overcome the difficulty caused by the parabolic degeneracy,we apply the characteristic decomposition technique to transform the Euler equations into a new degenerate hyperbolic system in a partial hodograph plane.The singular terms are isolated from the highly nonlinear complicated system and then can be handled successfully.We establish a smooth local solution to the new system in a suitable weighted metric space and then express the solution in terms of the original variables.展开更多
In this paper, we establish the existence of four families of simple wave solu- tion for two dimensional compressible full Euler system in the self-similar plane. For the 2 × 2 quasilinear non-reducible hyperboli...In this paper, we establish the existence of four families of simple wave solu- tion for two dimensional compressible full Euler system in the self-similar plane. For the 2 × 2 quasilinear non-reducible hyperbolic system, there not necessarily exists any simple wave solution. We prove the result that there are simple wave solutions for this 4× 4 non- reducible hyperbolic system, its simple wave flow is covered by four straight characteristics λ0 =λ1,λA2, λ3 and the solutions keep constants along these lines. We also investigate the existence of simple wave solution for the isentropic relativistic hydrodynamic system in the self-similar plane.展开更多
In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were...In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were numerically investigated in terms of the distribution of components,temperature,and pressure.The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics.The porosity of the fore-catalytic bed was optimized,and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature.The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.展开更多
In order to construct global solutions to two-dimensional(2 D for short)Riemann problems for nonlinear hyperbolic systems of conservation laws,it is important to study various types of wave interactions.This paper dea...In order to construct global solutions to two-dimensional(2 D for short)Riemann problems for nonlinear hyperbolic systems of conservation laws,it is important to study various types of wave interactions.This paper deals with two types of wave interactions for a 2 D nonlinear wave system with a nonconvex equation of state:Rarefaction wave interaction and shock-rarefaction composite wave interaction.In order to construct solutions to these wave interactions,the authors consider two types of Goursat problems,including standard Goursat problem and discontinuous Goursat problem,for a 2 D selfsimilar nonlinear wave system.Global classical solutions to these Goursat problems are obtained by the method of characteristics.The solutions constructed in the paper may be used as building blocks of solutions of 2 D Riemann problems.展开更多
Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compare...Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compares them with those for the current two-dimensional Riemann problems,to illustrate their worthiness.Two-dimensional Riemann problems are approached via the methodology promoted by Andy Majda in the spirits of modern applied mathematics;that is,simplified model is built via asymptotic analysis,numerical simulation and theoretical analysis.A simplified model called the pressure gradient system is derived from the full Euler system via an asymptotic process.State-of-the-art numerical methods in numerical simulations are used to discern small-scale structures of the solutions,e.g.,semi-hyperbolic patches.Analytical methods are used to establish the validity of the structure revealed in the numerical simulation.The entire process,used in many of Majda's programs,is shown here for the two-dimensional Riemann problems for the compressible Euler systems of conservation laws.展开更多
基金supported by the National Key R&D Program of China (2017YFD0201801)the Research Foundation of the Science & Technology Agency of Jilin Province, China (20150203004NY)
文摘Labile organic carbon （LC） and recalcitrant organic carbon （RC） are two major fractions of soil organic carbon （SOC） and play a critical role in organic carbon turnover and sequestration. The aims of this study were to evaluate the variations of LC and RC in a semi-arid soil （Inner Mongolia, China） under plastic mulch and drip irrigation after the application of organic materials （OMs）, and to explore the effects of OMs from various sources on LC and RC by probing the decomposition characteristics of OMs using in-situ nylon mesh bags burying method. The field experiment included seven treatments, i.e., chicken manure （CM）, sheep manure （SM）, mushroom residue （MR）, maize straw （MS）, fodder grass （FG）, tree leaves （TL） and no OMs as a control （CK）. Soil LC and RC were separated by Huygens D＇s method （particle size-density）, and the average soil mass recovery rate and carbon recovery rate were above 95%, which indicated this method was suitable for carbon pools size analysis. The LC and RC contents significantly （P〈0.01） increased after the application of OMs. Moreover, LC and RC contents were 3.2%-8.6% and 5.0%-9.4% higher in 2016 than in 2015. The applications of CM and SM significantly increased （P〈0,01） LC content and LC/SOC ratio, whereas they were the lowest after the application of TL. However, SOC and RC contents were significantly higher （P〈0.01） after the applications of TL and MS. The correlation analysis indicated the decomposition rate of OMs was positively related with LC content and LC/SOC ratio. In addition, lignin, polyphenol, WOM （total water-soluble organic matter）, WHA （water-soluble humic acid）, HSL （humicdike substance） and HAL （humic acid-like） contents in initial OMs played important roles in SOC and RC. In-situ nylon mesh bags burying experiment indicated the decomposition rates of CM, SM and MS were significantly higher than those of MR, FG, and TL. Furthermore, MS could result in more lignin derivatives, WHA, and HAL polymers in shorter time during the decomposition process. In conclusion, the application of MS in the semi-arid soil under a long-term plastic mulch and drip irrigation condition could not only improve soil fertility, but also enhance soil carbon sequestration.
基金Supported by the Natural Science Foundation of Guangxi(2017GXNSFBA198204)the Key Science and Technology Project of Guangxi(Guike AA17204059-9&AA172040459-10)+1 种基金the Planning Project for Scientific Research and Technological Development of Xixiangtang District,Nanning City(2017-2-10309)the Special Fund for the Fundamental Research of Guangxi Academy of Agricultural Sciences(Guinongke 2018YT07&2018YM28)
文摘As a kind of biological fertilizer sources, green manure can improve soil fertility and the quality of agricultural products. This paper introduced the germplasm resource of green manures in the major provinces in China, mainly summarized the characteristics of decomposition and nutrients release of returning green manures to soils, as well as the influence on soil fertility and succeeding crops, with the aim to provide references for rational utilization of green manures and the scientific management of farmland nutrients.
文摘With nylon mesh bags, the decomposition and nutrients release characteristics of two kinds of green manure crops, February orchid （Orychophragmus violaceus） and Hair Vetch （Vicia villosa Roth）, were investigated in this study. The results showed that these two kinds of green manure crops were decomposed rapidly in the first 14 days, and then decomposed slowly. After 80 days of incubation, the decomposition rates of February orchid and Hair Vetch were 66.92% and 63.12%, respectively. Different nutrients had different release rates from the green manures. Nitrogen （N） and potassium （K） were released rapidly in the initial 7 days, and phosphorus （P） was released steadily in the 80 days of incubation. In the two kinds of green manures, the release rates all ranked as K＇s〉N＇s〉P＇s. The release rates of nutrients, especially P （P〈0.05）, of February orchid were higher than those of Hair Vetch.
基金supported by the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2018A10)the Science Fund for Young Scholars of Natural Science Fund in Hebei Province(No.E2019202198)+1 种基金the Science and Technology Research Project of Colleges and Universities in Hebei Province(No.QN2019056)the State Key Laboratory of Engines,Tianjin University(No.K2020-15)。
文摘Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle(WHTC) urea deposits are urea, cyanuric acid(CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cu β and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cu β, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.
文摘The effect of rare earth metals(REM)on the characteristics of auto-tempering and decomposition of martensite for low-carbon and low-alloy steels(20SiMn2V and 20SiMn2VRE)was investigated using TEM,dilatometer and microhardness test.Results show that both ε.and θ carbides,during auto-tempering, may precipitate from the low-carbon martensite matrix at the same time in the 20SiMn2V steel,however,the precipitation of the ε-carbides can be inhibited by the REM contained in the 20SiMn2 VRE steel,resulting in change of the type of precipitated carbides and decrease of the extent of auto-tempering.The“in-situ”ob- servations show that the decomposition of martensite is also inhibited by the REM contained in the 20SiMn2 VRE steel during low temperature tempering.
基金supported by the National Natural Science Foundation of China(12071278).
文摘We study the existence of global-in-time classical solutions for the one-dimensional nonisentropic compressible Euler system for a dusty gas with large initial data.Using the characteristic decomposition method proposed by Li et al.(Commun Math Phys 267:1–12,2006),we derive a group of characteristic decompositions for the system.Using these characteristic decompositions,we find a sufficient condition on the initial data to ensure the existence of global-in-time classical solutions.
基金the two referees for very helpful comments and suggestions to improve the quality of the paper.This work was partially supported by the Natural Science Foundation of Zhejiang province of China(LY21A010017)the National Natural Science Foundation of China(12071106,12171130).
文摘This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensional(3-D)steady Euler equations can be projected onto the unit sphere and the state of fluid can be characterized by the polar and azimuthal angles.Given a segment smooth curve as a conical-sonic line in the polar-azimuthal angle plane,we construct a classical conical-supersonic solution near the curve under some reasonable assumptions.To overcome the difficulty caused by the parabolic degeneracy,we apply the characteristic decomposition technique to transform the Euler equations into a new degenerate hyperbolic system in a partial hodograph plane.The singular terms are isolated from the highly nonlinear complicated system and then can be handled successfully.We establish a smooth local solution to the new system in a suitable weighted metric space and then express the solution in terms of the original variables.
文摘In this paper, we establish the existence of four families of simple wave solu- tion for two dimensional compressible full Euler system in the self-similar plane. For the 2 × 2 quasilinear non-reducible hyperbolic system, there not necessarily exists any simple wave solution. We prove the result that there are simple wave solutions for this 4× 4 non- reducible hyperbolic system, its simple wave flow is covered by four straight characteristics λ0 =λ1,λA2, λ3 and the solutions keep constants along these lines. We also investigate the existence of simple wave solution for the isentropic relativistic hydrodynamic system in the self-similar plane.
基金supported by the Beijing Natural Science Foundation ( Grant No. 3184064)
文摘In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were numerically investigated in terms of the distribution of components,temperature,and pressure.The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics.The porosity of the fore-catalytic bed was optimized,and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature.The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.
基金supported by the National Natural Science Foundation of China(No.11301326)。
文摘In order to construct global solutions to two-dimensional(2 D for short)Riemann problems for nonlinear hyperbolic systems of conservation laws,it is important to study various types of wave interactions.This paper deals with two types of wave interactions for a 2 D nonlinear wave system with a nonconvex equation of state:Rarefaction wave interaction and shock-rarefaction composite wave interaction.In order to construct solutions to these wave interactions,the authors consider two types of Goursat problems,including standard Goursat problem and discontinuous Goursat problem,for a 2 D selfsimilar nonlinear wave system.Global classical solutions to these Goursat problems are obtained by the method of characteristics.The solutions constructed in the paper may be used as building blocks of solutions of 2 D Riemann problems.
基金supported partially by the National Science Foundation (No.DMS-0603859)
文摘Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compares them with those for the current two-dimensional Riemann problems,to illustrate their worthiness.Two-dimensional Riemann problems are approached via the methodology promoted by Andy Majda in the spirits of modern applied mathematics;that is,simplified model is built via asymptotic analysis,numerical simulation and theoretical analysis.A simplified model called the pressure gradient system is derived from the full Euler system via an asymptotic process.State-of-the-art numerical methods in numerical simulations are used to discern small-scale structures of the solutions,e.g.,semi-hyperbolic patches.Analytical methods are used to establish the validity of the structure revealed in the numerical simulation.The entire process,used in many of Majda's programs,is shown here for the two-dimensional Riemann problems for the compressible Euler systems of conservation laws.
