啤酒发酵液冷却过程的流体动力学模拟

为研究啤酒发酵罐内发酵液的动量和热量分布,应用传递过程原理和计算流体动力学(CFD)方法,建立了啤酒发酵后期冷却阶段发酵液动量和热量传递的CFD模型,并进行数值模拟,结果表明:啤酒发酵后期冷却阶段发酵液温度分层严重;流体在发酵罐中产生了分层对流现象,这与一般认为的发酵罐内流体做整体环形对流运动不同。利用CFD方法可以较好地模拟发酵后期冷却阶段发酵液动量和热量的变化过程,所得结果可作为研究啤酒发酵温度控制的基础资料。     

Aerodynamic analysis and CFD simulation of several cellulose evaporative cooling pads used in Mediterranean greenhouses

The present work makes an aerodynamic analysis and computational fluid dynamics (CFD) simulation of the four commercial models of corrugated cellulose evaporative cooling pads that are most widely used in Mediterranean greenhouses. The geometric characteristics of the pads have been determined as well as the volume of water they retain at different flows of water, thus obtaining the mean thickness of the sheet of water which runs down them and their porosity. By means of low velocity wind tunnel experiments, the pressure drop produced by the pads has been recorded at different wind speeds and water flows. In this way it has been possible to obtain the relationship of the permeability and the inertial factor with pad porosity using a cubic type equation. Finally, a CFD simulation with a 3D model has been carried out for both dry pads (Q_w = 0 l s⁻¹ m⁻²) and wet ones (Q_w = 0.256 l s⁻¹ m⁻²), finding good correlation between the simulated and experimental pressure drop, with maximum differences of 9.08% for dry pads and 15.53% for wet ones at an airspeed of 3 m s⁻¹.     

Application of computational fluid dynamics for modeling and designing photobioreactors for microalgae production: A review

The past decade has seen a rapid increase of numerical simulation studies on photobioreactors (PBRs). Developments in computational fluid dynamics (CFD) and the availability of more powerful computers have paved the way for the modeling and designing PRBs, a strategy that was abandoned from the late 1970s until the 1980s because of its complexity. This paper reviews the present status of numerical modeling for PBRs as well the application of CFD in the design of PBR for the mass production of microalgae. Emphasis is on the major breakthroughs in PBR design that may lead to scaling-up. Most simulations have been conducted in bubble column PBRs, which offer many advantages. Their geometry is simple in design with no moving parts, and they are easy to construct and operate. A majority of published simulation studies used two-phase models (air and water) and employed the Eulerian-Eulerian mixture model. CFD models have been vigorously validated by experimental and laboratory studies, with most claiming to have achieved good results. However, current PBR scale-up projects still need to resolve hydrodynamic issues within the PBR, in order to optimize factors for microalgal growth. To create ideal conditions inside the PBR, the main factors that influence microalgal growth such as light intensity and distribution, gas injection and mixing, and hydrodynamics/flow pattern which are the key for design and scale up must be thoroughly understood.The present practice of PBR design using CFD can be considered both an art and a science because of some numerical simulation issues which are yet to be resolved and the complexity of fluid mechanics inside the PBRs. Nonetheless, CFD has proven to be an effective tool in predicting the complex inherent phenomena in the PBRs. The CFD technique has shown to be very promising to successfully design and develop PBRs which can be commercially available for scale-up.     

稀土元素铈(~(141)Ce)在小鼠体内的分布与蓄积动态

采用两种铈剂量的饲料饲喂小鼠 ,利用14 1Ce示踪研究了小鼠在不同时间摄取铈后在脏器中的分布和蓄积动态。结果表明 ,滞留于体内的铈经过再分配而在各脏器组织中均有分布 ,其中眼、骨骼、睾丸、心脏、大脑和脂肪内的蓄积量较高 ,且随剂量或摄入时间的增加而增加 ,表现了明显的选择性蓄积。眼球的蓄积性尤为突出 ,明显高于其它脏器     

2种制备黄河鲤鱼染色体方法的比较及条件优化

以黄河鲤鱼为材料,采用体外肾细胞培养及空气干燥法制作染色体标本,通过对不同培养时间,不同秋水仙素处理时间获得的染色体分裂指数的比对,以期获得最佳的染色体制备条件.结果表明:在秋水仙素浓度及处理时间一定时,培养时间3d后分裂指数最高,为1.46%,且分裂相在前3d逐渐增多,第4d开始减少;同时发现,在培养时间一定时,秋水仙素处理时间为2h时分裂指数最高,为1.49%.因此认为最佳染色体制备条件为:培养时间3d,秋水仙素处理2h;与传统的体内注射PHA短期培养法制备的染色体标本相比,体外肾细胞培养法制备的标本背景清晰,染色后形态可辨,且染色体分散良好,彼此间没有交联,放大后染色体的测量较易完成,可以进行核型分析.     

闽北天然阔叶林林分材种结构分析及出材率模型

根据闽北天然阔叶林资料,提出编制闽北天然阔叶林的新方法并建立相应材种的出材率模型。以林分平均胸径和平均树高为变量因子,采用联合估计法解决模型不兼容问题并利用免疫进化算法求解模型参数,研制了林分材种出材率模型。经检验,建立的出材率模型能很好地拟合实际情况,可在森林资源调查中推广应用。     

精液中猪细小病毒DNA三种提取方法效果比较

猪精液中含有高浓度的蛋白质,因此提取高纯度DNA较为困难;试验分别用水煮法、异硫氰酸胍法和Trizol法三种方法对连续稀释梯度猪精液提取猪细小病毒DNA,应用Taqman荧光定量PCR技术评价提取效果并加以对比。结果发现Trizol法可以提取出高纯度的DNA,但因Trizol试剂价格昂贵,不适用临床检测;比较另外两种方法,水煮法较异硫氰酸胍抽提法更为有效,是一种迅速、简便、经济、高效的DNA提取方法,适合于临床大量样品的检测。     

不同土壤镉提取方法预测稻米富集镉性能评估

为筛选土壤镉(Cd)有效态提取方法并建立其与稻米Cd污染之间的累积模型,采用大田协同采样方式收集了土壤-水稻140对样品,分别研究了土壤Cd总量及土壤溶液Cd含量和化学浸提(醋酸HAc、复合有机酸、乙二胺四乙酸EDTA、CaCl2)、梯度扩散薄膜(DGT)技术提取的Cd含量与水稻糙米Cd含量的相关性,以评估不同提取方法预测稻米Cd累积模型的可行性。结果表明,研究区所在的长株潭地区存在较为明显的土壤及稻米Cd污染风险,EDTA提取Cd含量与土壤Cd总量显著正相关,模型拟合决定系数R2达到0.908 4,以总量预测稻米Cd污染存在37.2%~39.8%的误判率,0.01 mol·L^-1CaCl2提取的土壤Cd有效态含量存在明显的适用范围限制,在0.04~0.13 mg·kg^-1范围内,效果明显差于其他数据区域,模型决定系数R2仅为0.006。DGT技术能较好地预测稻米对Cd的吸收富集性能,且能区分土壤库供给能力差异对稻米富集Cd的影响,与传统化学浸提方法比较,DGT技术提取的土壤Cd有效态含量与稻米Cd含量具有更好的相关性(R^2=0.585 4,0.900 9),是预测稻米富集Cd较为理想的土壤有效态提取方法。     

捕捉和模拟Windows环境中鼠标和键盘操作的方法

提出在Windows系统范围内,且不影响其它进程的前提下,实现捕捉鼠标和键盘操作及其事后模拟过程的方法;并给出了程序的关键片段.     

Comparison of the performance of traditional advection-dispersion equation and mobile-immobile model for simulating solute transport in heterogeneous soils

The traditional advection-dispersion equation (ADE) and the mobile-immobile model (MIM) are widely used to describe solute transport in heterogeneous porous media. However, the fitness of the two models is case-dependent. In this paper, the transport of conservative, adsorbing and degradable solutes through a 1 m heterogeneous soil column under steady flow condition was simulated by ADE and MIM, and sensitivity analysis was conducted. Results show that MIM tends to prolong the breakthrough process and decrease peak concentration for all three solutes, and tailing and skewness are more pronounced with increasing dispersivity. Breakthrough curves of the adsorbing solute simulated by MIM are less sensitive to the retardation factor compared with the results simulated by ADE. The breakthrough curves of degradable solute obtained by MIM and ADE nearly overlap with a high degradation rate coefficient, indicating that MIM and ADE perform similarly for simulating degradable solute transport when biochemical degradation prevails over the mass exchange between mobile and immobile zones. The results suggest that the physical significance of dispersivity should be carefully considered when MIM is applied to simulate the degradable solute transport and/or ADE is applied to simulate the adsorbing solute transport in highly dispersive soils.     

原子荧光光度法中湿法消解、微波消解前处理法测定土壤中总汞、总砷的比较

采用微波消解对土壤样品进行前处理,同时与湿法消解作比较,采用AFS-930型双道原子荧光光度计测定2种土壤标准物质中总砷、总汞的含量。对2种前处理方法所得的待测液进行5个平行测定,测定值均在其证书标准值范围内,微波消解样品前处理所得的测定结果比湿法消解的更令人满意。