刨花板内水分动态扩散系数的研究

推导和分析了求动态扩散系数的计算公式,测试了两种刨花板四种不同厚度试件的动态扩散系数。结果表明,刨花板的吸湿量与加湿时间呈幂函数的关系;动态扩散系数与板内的含水率呈三次或二次的函数关系;通过对吸湿时间(t)和无量纲参教(E~2)线性回归的方法求得平均动态扩散系数;刨花经过高压饱和蒸汽处理后制成的刨花板,其水分动态扩散系数要小于未经蒸汽处理的。     

环境因子对温室茄子光合非稳态性的影响

 采用光合作用测定系统CIRAS-2以2 s的间隔时间采集数据, 对日光温室茄子光合进程进行了瞬态测试, 发现光合的非稳态性。结合光强和CO₂ 浓度的阶梯式处理进行瞬态测试以及瞬态光合进程的回归、相关分析发现, Ci和Ca对Pn非稳态性的作用最大, 其次是Gs、E和PAR, 而T1 和RH的作用很弱; 瞬态Ci与Pn变化呈镜像反式, 为极显著或显著负相关性; 瞬态Gs与Pn未达到显著相关性。     

重力驱动的水滴在土壤毛孔内非稳态运动研究

重力驱动下的水滴入渗是多孔介质特别是土壤中水分运移的一个基本问题,理论研究中常常用毛细管内的液塞(slug)运动来模拟。考虑前端液面的动态接触角效应,建立包含接触角参数的描述液塞非稳态运动过程的动力学模型,并对该模型进行了试验验证。应用该模型,研究多孔介质物理性质如斥水性、毛细管内径和液塞初始长度等参数对液塞运动过程的影响。结果表明:接触角的增加能显著影响毛管内液塞的下落速度,表明斥水性增加将显著降低土壤等多孔介质的导渗率;液塞在大管径毛管中平均速度较大,但能够到达的最终深度较小;相反地,液塞在小管径毛管中的平均下落速度较小,但能到达的最终深度较大。综合得出,在考虑孔隙结构统计分布的基础上,该模型可用于宏观入渗过程的模拟研究。     

A mechanical model for felt in impulse drying: A cellular materials approach. I. Model development and simulation

This paper presents a physically based model of the densification of a felt in the press nip of a paper machine, running at operating conditions similar to those used in impulse drying. The model incorporates the observed features of wet felts compression such as non-linear elasticity and non-recoverable strains that are rate-dependent. A viscoelastoplastic model, based on the cellular solids theory, was developed to describe this behavior. The governing differential equations of the model were established bearing in mind an assembly of modified Maxwell elements combined in series and then arranged in parallel. This approach resulted in a three-dimensional unsteady-state problem, solved by means of an integrator based in the Gear method. The model was used to predict the evolution of thickness, elastic and viscous moduli and apparent density of the material.