Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a bacterial disease of citrus and results in peel blemishes rendering fresh fruit unsalable. Xcc is most active in warm, wet Florida summers where tiss...Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a bacterial disease of citrus and results in peel blemishes rendering fresh fruit unsalable. Xcc is most active in warm, wet Florida summers where tissues are infected during periods of active growth. Melanose, caused by Diaporthe citri, is common in citrus producing countries, but, like canker, is only important for fresh market fruit. To control canker and melanose, Florida growers spray trees with copper formulations (Cu), but these sprays are removed by strong rains and intense radiation of Florida summers. A study was undertaken in FL commercial grapefruit groves in 2009 and 2010 to assess the efficiency of a spray combining copper with a specially formulated, hydrating wax (WashGard?) (WG). Using a 21-day spray schedule for the season, fruit were sprayed with WG + Cu, Cu and Control (no spray). Fruit from trees sprayed with WG + Cu had approximately 10 and17% more canker free fruit in 2009 and 2010 respectively compared to trees sprayed with copper alone. Compared to control trees the canker free fruit incidence was increased by ≈10% in 2009 and 57% in 2010. For melanose there was 40% more disease free fruit (treated) over fruit from trees with no treatment in 2009 and approximately 20% more in 2010. Controlling infection with this spray significantly reduces citrus canker and melanose, increasing the percentage of marketable fruit.展开更多
A new droplet collision and coalescence model was presented, a quick-sort method for locating collision partners was also devised and based on theoretical and experimental results, further advancement was made to the ...A new droplet collision and coalescence model was presented, a quick-sort method for locating collision partners was also devised and based on theoretical and experimental results, further advancement was made to the droplet collision outcome. The advantages of the two implementations of smoothed particle hydrodynamics （SPH） method were used to limit the collision of droplets to a given number of nearest droplets and define the probability of coalescence, numerical simulations were carried out for model validation. Results show that the model presented is mesh-independent and less time consuming, it can not only maintains the system momentum conservation perfectly, but not susceptible to initial droplet size distribution as well.展开更多
A formal asymptotics leading from a system of Boltzmann equations for mixtures towards either Vlasov-Navier-Stokes or Vlasov-Stokes equations of incompressible fluids was established by the same authors and Etienne Be...A formal asymptotics leading from a system of Boltzmann equations for mixtures towards either Vlasov-Navier-Stokes or Vlasov-Stokes equations of incompressible fluids was established by the same authors and Etienne Bernard in: A Derivation of the Vlasov-Navier-Stokes Model for Aerosol Flows from Kinetic Theory Commun. Math. Sci., 15: 1703–1741(2017) and A Derivation of the Vlasov-Stokes System for Aerosol Flows from the Kinetic Theory of Binary Gas Mixtures. KRM, 11: 43–69(2018). With the same starting point but with a different scaling, we establish here a formal asymptotics leading to the Vlasov-Euler system of compressible fluids. Explicit formulas for the coupling terms are obtained in two typical situations: for elastic hard spheres on one hand, and for collisions corresponding to the inelastic interaction with a macroscopic dust speck on the other hand.展开更多
The method of reversed-phase high performance liquid chromatography was established for the determination of effective components in OC-CS spray using double wavelength UV detection.The method was utilized under follo...The method of reversed-phase high performance liquid chromatography was established for the determination of effective components in OC-CS spray using double wavelength UV detection.The method was utilized under following conditions:a column of Kromasil C18(250 mm × 4.6 mm,5 μm),mobile phase consisting of methanol/water(80 /20) at a flow rate of 0.8 mL/min,column temperature of 25 ℃,and the UV detection at 227 nm and 300 nm.Three key components in OC-CS spray could be distinguished clearly,including o-chlorobenzalmalononitrile(CS),oleoresin capsicum(OC) and dihydrocapsaicin(DC).This method has the advantages of fast,simple and satisfactory linear relationship between UV absorption and concentration.It may be considered to turn into a standard method for detection of related components in the spray.展开更多
In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-c...In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to explicitly compute all of the fluid and particle degrees of freedom in a numerical simulation of the system. Under such circumstances Lagrangian Particle Tracking (LPT) of a small subset of the particles is used to reduce the computational effort. The purpose of this paper is to compare the LPT with an alternate method that is based on an approximate solution of the conservation equation of particle density in phase space by the method of moments (MOM). Closure is achieved by invoking the assumption that the droplet size distribution is locally lognormal. The resulting coupled transport equations for the local mean and variance of the particle size distribution are then solved in conjunction with the usual equations for the fluid and associated scalar fields. The formalism is applied to the test case of a uniform distribution of droplets placed in a non homogeneous temperature field and stirred with a decaying Taylor vortex. As a benchmark, we perform a direct numerical simulation (DNS) of high resolution that keeps track of all the particles together with the fluid flow.展开更多
文摘Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a bacterial disease of citrus and results in peel blemishes rendering fresh fruit unsalable. Xcc is most active in warm, wet Florida summers where tissues are infected during periods of active growth. Melanose, caused by Diaporthe citri, is common in citrus producing countries, but, like canker, is only important for fresh market fruit. To control canker and melanose, Florida growers spray trees with copper formulations (Cu), but these sprays are removed by strong rains and intense radiation of Florida summers. A study was undertaken in FL commercial grapefruit groves in 2009 and 2010 to assess the efficiency of a spray combining copper with a specially formulated, hydrating wax (WashGard?) (WG). Using a 21-day spray schedule for the season, fruit were sprayed with WG + Cu, Cu and Control (no spray). Fruit from trees sprayed with WG + Cu had approximately 10 and17% more canker free fruit in 2009 and 2010 respectively compared to trees sprayed with copper alone. Compared to control trees the canker free fruit incidence was increased by ≈10% in 2009 and 57% in 2010. For melanose there was 40% more disease free fruit (treated) over fruit from trees with no treatment in 2009 and approximately 20% more in 2010. Controlling infection with this spray significantly reduces citrus canker and melanose, increasing the percentage of marketable fruit.
基金Project supported by the National Natural Science Foundation of China(No.50376054)and the Aerospace Science Foundation(No.03c53021)
文摘A new droplet collision and coalescence model was presented, a quick-sort method for locating collision partners was also devised and based on theoretical and experimental results, further advancement was made to the droplet collision outcome. The advantages of the two implementations of smoothed particle hydrodynamics （SPH） method were used to limit the collision of droplets to a given number of nearest droplets and define the probability of coalescence, numerical simulations were carried out for model validation. Results show that the model presented is mesh-independent and less time consuming, it can not only maintains the system momentum conservation perfectly, but not susceptible to initial droplet size distribution as well.
基金funded by the French "ANR blanche" project Kibord:ANR-13-BS01-0004by Université Sorbonne Paris Cité,in the framework of the "Investissements d’Avenir",convention ANR-11-IDEX-0005the support by the GNFM(research project 2017:"Analisi rigorosa di sistemi di equazione di tipo reazione–diffusione")
文摘A formal asymptotics leading from a system of Boltzmann equations for mixtures towards either Vlasov-Navier-Stokes or Vlasov-Stokes equations of incompressible fluids was established by the same authors and Etienne Bernard in: A Derivation of the Vlasov-Navier-Stokes Model for Aerosol Flows from Kinetic Theory Commun. Math. Sci., 15: 1703–1741(2017) and A Derivation of the Vlasov-Stokes System for Aerosol Flows from the Kinetic Theory of Binary Gas Mixtures. KRM, 11: 43–69(2018). With the same starting point but with a different scaling, we establish here a formal asymptotics leading to the Vlasov-Euler system of compressible fluids. Explicit formulas for the coupling terms are obtained in two typical situations: for elastic hard spheres on one hand, and for collisions corresponding to the inelastic interaction with a macroscopic dust speck on the other hand.
基金Sponsored by the Basic Research Funds of Beijing Institute of Technology (20081642007)
文摘The method of reversed-phase high performance liquid chromatography was established for the determination of effective components in OC-CS spray using double wavelength UV detection.The method was utilized under following conditions:a column of Kromasil C18(250 mm × 4.6 mm,5 μm),mobile phase consisting of methanol/water(80 /20) at a flow rate of 0.8 mL/min,column temperature of 25 ℃,and the UV detection at 227 nm and 300 nm.Three key components in OC-CS spray could be distinguished clearly,including o-chlorobenzalmalononitrile(CS),oleoresin capsicum(OC) and dihydrocapsaicin(DC).This method has the advantages of fast,simple and satisfactory linear relationship between UV absorption and concentration.It may be considered to turn into a standard method for detection of related components in the spray.
文摘In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to explicitly compute all of the fluid and particle degrees of freedom in a numerical simulation of the system. Under such circumstances Lagrangian Particle Tracking (LPT) of a small subset of the particles is used to reduce the computational effort. The purpose of this paper is to compare the LPT with an alternate method that is based on an approximate solution of the conservation equation of particle density in phase space by the method of moments (MOM). Closure is achieved by invoking the assumption that the droplet size distribution is locally lognormal. The resulting coupled transport equations for the local mean and variance of the particle size distribution are then solved in conjunction with the usual equations for the fluid and associated scalar fields. The formalism is applied to the test case of a uniform distribution of droplets placed in a non homogeneous temperature field and stirred with a decaying Taylor vortex. As a benchmark, we perform a direct numerical simulation (DNS) of high resolution that keeps track of all the particles together with the fluid flow.
