THE DIFFUSION PARAMETER AND HEAT-RELEASE RATE OF PLUMES CAUSED BY THE 1987 FOREST FIRE IN NORTHEAST CHINA

In this paper the meteorological background for the formation of plume from the forest fire in Northeast China on 7—8 May 1987 is stated.The long-range instantaneous diffusion parameters are calculated by using the satellite photograph of the plumes with visible length ranging from 100 to over 500 kin.The results of cal- culation show that the relations between instantaneous diffusion parameter and travel time(up to 60000 sec.) obey the law of linear or 3/2 power.In addition,heat release from the fire on May 7—8 estimated by puff rising formula can meet,in respect to the order of magnitude,the value gained on the field survey.

Influence of Vertical Eddy Diffusivity Parameterization on Daily and Monthly Mean Concentrations of O3 and NOy

Two parameterization schemes for vertical eddy diffusivity were utilized to investigate their impacts on both the daily and monthly mean concentrations of ozone and NOy, which are the major fractions of the sum of all reactive nitrogen species, i.e., NOy=NO＋NO2＋HNO3＋PAN. Simulations indicate that great changes in the vertical diffusivity usually occur within the planetary boundary layer （PBL）. Daily and monthly mean concentrations of NOy are much more sensitive to changes in the vertical diffusivity than those of ozone and ozone and NOy levels only at or in （relatively） clean sites and areas, where long-range transport plays a crucial role, display roughly equivalent sensitivity. The results strongly suggest that a widely-accepted parameterization scheme be selected and the refinement of the model＇s vertical resolution in the PBL be required, even for regional and long-term studies, and ozone only being examined in an effort to judge the model＇s performance be unreliable, and NOy be included for model evaluations.

Energetics of lateral eddy diffusion/advection: Part I. Thermodynamics and energetics of vertical eddy diffusion

Two important nonlinear properties of seawater thermodynamics linked to changes of water density, cab beling and elasticity （compressibility）, are discussed. Eddy diffusion and advection lead to changes in den sity; as a result, gravitational potential energy of the system is changed. Therefore, cabbeling and elasticity play key roles in the energetics of lateral eddy diffusion and advection. Vertical eddy diffusion is one of the key elements in the mechanical energy balance of the global oceans. Vertical eddy diffusion can be con ceptually separated into two steps： stirring and subscale diffusion. Vertical eddy stirring pushes cold/dense water upward and warm/light water downward; thus, gravitational potential energy is increased. During the second steps, water masses from different places mix through subscale diffusion, and water density is increased due to cabbeling. UsingWOA01 climatology and assuming the vertical eddy diffusivity is equal to a constant value of 2x103 pa2/s, the total amount of gravitational potential energy increase due to vertical stirring in the world oceans is estimated at 263 GW. Cabbeling associated with vertical subscale diffusion is a sink of gravitational potential energy, and the total value of energy lost is estimated at 73 GW. Therefore, the net source of gravitational potential energy due to vertical eddy diffusion for the world oceans is estimated at 189 GW.

Analysis and Comparison of Doping Level Effects on a Crystalline Silicon PV Cell under Both Moderate Light Concentration and Normal Illumination Modes

The main purpose of this work is to study doping level effects on a silicon PV cell under both moderate light concentration and normal illumination. This study also aims to compare the doping level effects under the both illumination modes. The results show for both illumination modes that diffusion parameters decrease with increasing doping level. These results are in agreement with the studies of the current and the voltage which showed for the two illumination modes that doping level increase leads to a decrease in current density and an increase in voltage. It also emerges for the two illumination modes and for the doping range 1013 cm-3 - 1016 cm-3, a decrease of maximum power and conversion efficiency. The results also show that decrease of diffusion parameters is faster under moderate concentration in comparison with normal illumination. These results predict a greater variation rate of the current, the voltage, the maximum power and the conversion efficiency under moderate concentration compared to normal illumination. Contrary to diffusion parameters study, the results show higher variation rates of parameters under normal illumination. This is explained by the fact that under moderate concentration, carriers density is close to doping level: the cell is then in high injection condition. Consequently, under moderate concentration, carriers density is less sensitive to doping level variations. The study confirms that carriers density variation with the doping level is weak under the moderate concentration compared to normal illumination.

A New Ensemble HDG Method for Parameterized Convection Diffusion PDEs

A new second order time stepping ensemble hybridizable discontinuous Galerkin method for parameterized convection diffusion PDEs with various initial and boundary conditions,body forces,and time depending coefficients is developed.For ensemble solutions in L_(∞)(0,T;L^(2)(Ω)),a superconvergent rate with respect to the freedom degree of the globally coupled unknowns for all the polynomials of degree k≥0 is established.The results of numerical experiments are consistent with the theoretical findings.

THEORETICAL PREDICTION OF PROEUTECTOID FERRITICTRANSFORMATION IN HYPO-PROEUTECTOID STRUCTRAL STEELS

Proeutectoid ferrite with carbon content xo precipitating from austenite in a multicomponent steel at temperature T is supposed to be equivalent to proeutectoid ferrite with the same carbon content precipitating from austenite in Fe-C binary system at temperature T'.is described as the temperature difference of proeutectiod ferrite formation, and can be calculated from the Fe-X diagrams and the equilibrium temperature A3. By introducing Tf and basing on the thermodynamic model for Fe-C binary alloy, the driving force for phase transformation from austenite to proeutectoid ferrite in multicomponent steels has been successfully calculated. Through the Johnson-Mehl equation and using the data hem known TTT diagrams, the relationship between the chemical composition and the intedecial edenly packeter as well as activation energy for proeutectoid ferrite formation can be calculated. The starting curves of proeutectoid ferritic transformation calculated in this way in some hypo-proeutectoid structural steels agree well with the erperimental data.

Parameter Estimation of S-Shaped Growth Model:A Modified Particle Swarm Algorithm

Parameter estimation plays a critical role for the application and development of S-shaped growth model in the agricultural sciences and others.In this paper,a modified particle swarm optimization algorithm based on the diffusion phenomenon（DPPSO） was employed to estimate the parameters for this model.Under the sense of least squares,the parameter estimation problem of S-shaped growth model,taking the Gompertz and Logistic models for example,is transformed into a multi-dimensional function optimization problem.The results show that the DPPSO algorithm can effectively estimate the parameters of the S-shaped growth model.

An improved prediction model for corner stall in axial compressors with dihedral effect

Corner stall predictions are important and difficult in axial compressors.However,all of the prediction models have proved to be ineffective for advanced compressor blades,which tend to use the combined sweep and dihedral.As for the prediction parameter DL,although it effectively modeled the effects of the adverse pressure gradient and secondary flow,it failed to predict the corner stall of curved blades because the model failed to consider the intersection of the boundary layer at the corner region.In this paper,the shape factor gradientψof the boundary layer at the corner region was investigated by numerically studying specially shaped expansion pipes under different adverse pressure gradients.The improved prediction parameter DJ was presented based on the model of ψ and the circumferential pressure gradient ζ.A comparison of the critical range of the prediction parameters DL and DJ was investigated using the NACA65 cascade database,which was established by a numerical method.Then,the stall criterion was validated according to the experimental results of various test facilities with different blade geometries and experimental conditions.The results show that the improved prediction parameter is able to predict the corner separation/stall flows and is in good agreement with the experimental results for axial compressors with three-dimensional designed blades.