Mechanism to remove oxide inclusions from molten aluminum by solid fluxes refining method

A novel flux charging method and a crucible quenching method were employed to study the mechanism of solid fluxes refining method regarding the removal of oxide inclusions (Al2O3) from molten aluminum.Electrochemical polishing method was adopted to prepare surfaces of the samples.Through experiments,the morphology of the residual solidified flux in the solidified samples as well as the wetting action of the molten flux during refining were observed for the first time.Three wetting regimes denoted by absorbing regime,engulfing regime and penetration regime correlating with the removal of oxide films (the most typical and common oxide inclusions in molten aluminum) were proposed in terms of different types and distributions of oxide films and different size ratios of the molten flux to oxide films.Particularly,from a thermodynamic point of view,for the first time,the penetration regime provided concrete evidence that the practical oxide inclusions can be wet by molten flux under ambient fluid of molten aluminum.A spreading model was proposed,according to which ingredients and size parameters of practical solid fluxes can be optimized.     

TVD finite point method for two-dimensional conservation equation

A new meshless method, called total variation diminishing (TVD) finite point method (TVDFP), is proposed. The TVDFP method is developed on the least-square procedure which uses a global stencil of grid points and the two-dimensional (2D) TVD procedure for the approximation of fictitious interface directional fluxes. We present the accuracy of the TVDFP method and several 2D test computations.     

Effects of Crop Growth and Development on Land Surface Fluxes

In this study,the Crop Estimation through Resource and Environment Synthesis model (CERES3.0) was coupled into the Biosphere-Atmosphere Transfer Scheme (BATS),which is called BATS_CERES,to represent interactions between the land surface and crop growth processes.The effects of crop growth and development on land surface processes were then studied based on numerical simulations using the land surface models.Six sensitivity experiments by BATS show that the land surface fluxes underwent substantial changes when the leaf area index was changed from 0 to 6 m2 m-2.Numerical experiments for Yucheng and Taoyuan stations reveal that the coupled model could capture not only the responses of crop growth and development to environmental conditions,but also the feedbacks to land surface processes.For quantitative evaluation of the effects of crop growth and development on surface fluxes in China,two numerical experiments were conducted over continental China:one by BATS_CERES and one by the original BATS.Comparison of the two runs shows decreases of leaf area index and fractional vegetation cover when incorporating dynamic crops in land surface simulation,which lead to less canopy interception,vegetation transpiration,total evapotranspiration,top soil moisture,and more soil evaporation,surface runoff,and root zone soil moisture.These changes are accompanied by decreasing latent heat flux and increasing sensible heat flux in the cropland region.In addition,the comparison between the simulations and observations proved that incorporating the crop growth and development process into the land surface model could reduce the systematic biases of the simulated leaf area index and top soil moisture,hence improve the simulation of land surface fluxes.     

冷却速率对连铸保护渣结晶性能的影响

采用 WCT-2型差热分析天平和LEITZ光学显微镜(配有 1350℃高温热台),研究了冷却速率对连铸保护渣结晶性能的影响.研究结果表明:随冷却速率提高,保护渣的结晶温度显著降低,结晶率降低,晶体尺寸减小,晶形也有很大改变.     

Time series of long-term annual fluxes in the streamwater of nine forest catchments from the Swedish environmental monitoring program (PMK 5)

International cooperation has contributed to major declines in SO(2) emission and S deposition during the last two decades in Europe. The chemical recovery from already anthropogenically acidified sites however, has been slow. In the present paper, long-term trends of chemical fluxes from nine selected forested reference catchments were studied, to detect recovery from acidification and leaching of S and base cations (BC). A decline in S deposition resulted in a decreased flux of non-marine sulfate (SO(4)*) in seven of nine streams, with statistically significant changes in four. The two cases with slight increases in SO(4)* flux resulted from increasing water flow. The SO(4)* decrease was followed by a recovery from acidification in terms of increased ANC flux in those sites in southern Sweden that were chronically acidified. The recovery was probably slowed down by leaching of SO(4) from the soil and a decrease in the flux of BC. A better understanding of the processes for leaching of SO(4) and BC is needed in order to quantify the need for further restrictions of sulfur emissions to allow a long term recovery of acidified catchments. The flux calculations available from small catchments such as those in this study, are of value for that understanding.     

镁合金活性焊丝TIG焊

选择单一成分的常见化合物作为活性剂,涂敷于焊丝表面形成活性焊丝,并进行TIG填丝焊接试验.结果表明,在镁合金活性焊丝TIG焊接过程中,活性剂仍能起到增加焊接熔深的作用.氯化物活性剂对熔深的增加效果最为明显,熔深较普通焊丝增加最大可达3倍以上.研究发现对镁合金TIG焊熔深增加效果好的活性剂的沸点集中于900℃附近区间.用活性焊丝焊接时熔滴与熔池金属的融合能力变差,填丝性能较普通焊丝相比有所降低.     

304不锈钢A-TIG焊的试验研究

主要研究在304不锈钢焊接时涂敷活性焊剂和未涂敷活性焊剂对焊缝成形的影响。试验结果表明304不锈钢采用A-TIG焊时,涂敷活性焊剂的焊缝熔深显著增加,熔宽有所减小;活性剂使熔池横截面形状发生明显变化,即焊缝上部比较宽、中下部变得很窄,这主要是由表面张力梯度的变化引起的。     

Inverse determination of boundary heat fluxes in a porous enclosure dynamically coupled with thermal transport

The inverse natural convection problem of estimating the heat source profiles in a porous enclosure is proposed in the present work. The physical model for the momentum conservation equation makes use of the Darcy-Brinkman equation, which allows the no-slip boundary condition on a solid wall to be satisfied. An iterative Fletcher-Reeves conjugate gradient method is applied such that the gradient of the cost function is introduced when the appropriate sensitivity and adjoint problems are defined. Particularly, the pressure-based SIMPLE algorithm is adopted to solve the continuum direct, sensitivity and adjoint problems in unification. Effects of thermal Rayleigh number, Darcy number, heat flux profiles, sensor locations and quantity on the accuracy of inverse solutions are investigated with or without the measurement errors. Additionally, the fluid and heat transport structures in the uniform porous layer are analyzed using the streamlines and heatlines, and the heat transfer potential is also explained by the variation of overall Nusselt number. Noise data solutions are regularized by stopping the iterations with the discrepancy principle of Alifanov, before the high frequency components of the random noises are reproduced. The present method solves inverse strong convection problem satisfactorily without any a priori information about the unknown heat flux to be estimated.     

大气隙混合磁悬浮轴承承载力模型的研究

等效磁路法是混合磁悬浮轴承的主要研究方法,然而等效磁路法是基于一系列假设条件提出的,大气隙下这些假设将不再成立,磁路法的应用范围将受到限制,无法对大气隙混合磁悬浮轴承展开研究。因此,需要对大气隙混合磁悬浮轴承承载力模型进行研究,以解决混合磁悬浮轴承在大气隙场合的推广及应用。结合ANSYS有限元分析软件分析在气隙变化时,常规磁路法在混合磁悬浮轴承承载特性分析过程中的适用范围,获得了当气隙增加时磁路法模型计算误差变化规律;针对漏磁这一导致计算误差的影响因数,提出一种混合磁悬浮轴承气隙磁场的漏磁导模型的分析方法,建立基于漏磁导修正的混合磁悬浮轴承承载力理论模型;利用ANSYS有限元分析软件和试验对修正后的混合磁悬浮轴承承载力模型进行了验证。     

基于摩擦学的沙尘环境的研究

针对现代机械产品在沙尘环境中的适应性问题 ,提出了基于摩擦学的沙尘环境分析法 ,并应用此方法进行了实验 ,采用干沉积法收集了西安市 4～ 6月份室外日常降尘以及一次沙尘暴降尘 ;使用感量为 0 1mg的电子天平测量了降尘的沉积通量 ,并用 2 0 0×的FMIII型铁谱显微镜分析了降尘粒子的特征粒径 (粒子二维投影图中的短径 )和形状不规则度 (粒子二维投影图中的长径与短径的比值 )。沉积通量分析的结果表明 :非沙尘暴期间平均沉积通量为 0 5 15 g·m-2 ·day-1,在沙尘暴期间出现最高值 (1 33g·m-2 ·day-1)。降尘粒子的分析结果表明 :不同降尘 (非沙尘暴降尘和沙尘暴降尘 )的特征粒径的平均值在 17μm左右波动 ,90 %的粒子的特征粒径小于 30 μm ;形状不规则度小于 1 5的粒子占 5 0 %～ 6 0 % ,小于 2的占 80 %以上 ,小于 3的占 90 %以上。