As the number falls,alternatives to the Hagberg–Perten falling number method: A review

This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging.     

Wave dynamics on a thin-liquid film falling down a heated wall

The dynamics of a thin liquid film falling down a uniformly heated wall is studied. The model introduced by Kalliadasis et al. [J. Fluid Mech. 475 (2003) 377] for the same problem is revisited and its deficiencies, namely the prediction of a critical Reynolds number with 20% error, cured. For the energy equation a high-order Galerkin projection in terms of polynomial test functions is developed. It is shown that not only does this more refined formulation correct the critical Reynolds number, but it also gives, with an appropriate expansion close to criticality, the long-wave theory. Bifurcation diagrams for permanent solitary waves are constructed and compared with the solution branches obtained from different models. It is shown that, in all cases, the long-wave theory exhibits limit points and branch multiplicity, while the other models predict the continuing existence of solitary waves. Time-dependent computations show that the free surface and interfacial temperature approach a train of coherent structures that resemble the infinite-domain stationary solitary pulses.     

Terminal velocity of non-spherical particles falling through a Carreau model liquid

A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured.     

微重力落塔电磁悬吊、释放技术研究

论述了微重力落塔电磁悬吊、释放、提升机构的关键技术,电磁释放过程的特性分析以及微重力落塔实际试验的情况。分析说明:悬吊、释放性能的好坏决定了试验落舱的微重力水平,也是微重力落塔试验能否成功的关键技术。     

降膜蒸发过程的数值模拟和传热传质分析

利用CFD软件对逆流降膜蒸发过程进行了实验模拟研究,研究了速度边界层、热边界层和浓度边界层的变化对降膜蒸发传热传质特性的影响规律;通过建立一维逆流降膜蒸发的数学方程编程求解出了对流传热传质的Nu数和Sh数,利用Fluent软件模拟出的实验结果采用回归分析得出了气液流量比Raw、流道的长宽比αL、空气进口无量纲温度θai以及空气进口Re数与Nu数、Sh数之间的无量纲关系式,可为降膜蒸发换热器的设计提供参考。     

PVC型材低温落锤破裂影响因素的分析

从型材内筋壁厚、加工助剂、辅助原料、塑化控制、模具流道等方面分析了PVC型材低温落锤破裂影响因素，并提出了提高PVC型材低温落锤冲击性能的建议。     

氯代邻硝基甲苯精制方法的改进

文章讨论了用精馏和熔融结晶粗制氯代邻硝基甲苯的工艺，以及方法的改进。     

Conjugate heat transfer in turbulent falling liquid films

Heat transfer characteristics for a falling turbulent liquid film flow over a fin are analyzed using the conjugate convection-conduction theory. Numerical results are obtained from a simultaneous solution of the energy equations of the fluid and the fin. Results are presented for the fin temperature distribution, dimensionless heat transfer coefficients, local heat fluxes, and fin efficiencies.     

利用翅片管束外表面降膜反应脱除烟气中SO2的实验研究

A new wet flue gas desulfurization method by reaction across the falling liquid film on the outside surface of axial finned-tube bundle and its principles of removal of SO₂ are presented in this paper.The effects of different styles of tube bundle,and the pitch of tubes,flue gas velocity,gas-liquid ratio and flue gas temperature on desulphurization efficiency and the moisture content of flue gas are studied.The experiment results show that desulphurization effect is better for flue gas at 65℃,4.0m·s^-1 against the tube bundle of 10 rows with relative pitch of staggered rows S₁/d=2.1,S₂/d=1.8.     

降膜传质过程Marangoni效应稳定性分析

通过建立降膜流动传质模型，并考虑液相流动及非线性浓度分布的影响，利用线性微扰理论得到了降膜流动传质过程Marangoni效应发生的理论临界条件.用所建立的降膜流动传质实验装置得出实测传质系数的变化，由此获得Marangoni效应发生的实测临界条件，实测值与理论值基本符合，从而为工业上常见的降膜流动传质过程中Marangoni现象的预测和利用提供了理论依据.