基于孔口出流模型的实验研究及理论分析

基于孔口出流模型对底部有小孔的圆柱体容器中液体液面高度随时间的变化规律进行了实验研究,并通过计入液体表面张力引起的孔口收缩和流体黏滞力导致的能量损失对实验结果进行了理论分析,与实验结果一致.     

气粒混合物非灰辐射特性合并宽窄谱带K分布模型

气粒混合物辐射问题具有全场性、非灰性、耦合性等特点,准确预估高温燃气/粒子非灰辐射特性是非常重要的。本文将合并宽窄谱带K分布模础(CWNBCK)与离散坐标法(DOM)结合,开展了非灰气粒混合物辐射换热问题的模拟工作,分别验证了一维和三维情况下应用该模型的准确性,给出不同工况下的热流源项、壁面热流或辐射热流等。结果表明:该模型能够给出与SNB模型精度基本相同的结果,考虑其计算效率的提高,可以在工程实际中应用该模型计算非灰气粒混合物辐射换热。     

Brightness Temperature Emitted by Radiometer Calibration Load at Millimeter Wave Band

In this paper, the DVRT (vector radiative transfer theory of densely distributed random discrete scatters) model to calculate the brightness temperature emitted by radiometer calibration load is presented. It takes the multiple scattering of isolation layer into account, which is neglected by the incoherent homogeneous model often used in calibration. Hence, it works much better than incoherent homogeneous model at millimeter wave band. Furthermore, the iteration of DVRT model is presented, and it proves that the incoherent homogeneous model is just the zero-order solution of DVRT model. Some numerical results are provided in the end.     

Palladium‐catalyzed selective decarboxylative coupling reaction versus direct C―H arylation for arylation of heteroaromatics

Conditions for selective palladium‐catalyzed decarboxylative 2‐arylation of 3‐substituted thiophene and furan derivatives bearing an ester at C2 position have been established. By using 2 mol% phosphine‐free Pd(OAc)₂ as the catalyst and a mixture of KOH and K₂CO₃ as the bases, in dimethylacetamide, moderate to good yields of the desired 2‐arylated products were obtained. A range of functional groups such as nitrile, nitro, formyl or acetyl on the aryl bromides was tolerated. This method allows us to employ in some cases more convenient reactants in terms of cost or physical properties (boiling point) for arylations. Copyright © 2013 John Wiley & Sons, Ltd.     

Like‐Charge Attraction: A Combined Electrostatic–Hydrodynamic Approach

Abstract

This article discusses the like‐charge attraction of colloidal spheres close to a charged plate and compares results produced by an electrostatic and a hydrodynamic model with experimental data. Hydrodynamic coupling is shown to be the dominating effect, while the electrostatic influence may often be neglected. Some observations, however, can be explained only by means of a combined electrostatic–hydrodynamic model, which is derived in this work. The combined model is able to predict not only the attractive force between particles of similar charge close to a charged plate but also the change to a purely repulsive force once the sphere‐plate distance is further reduced. This prediction matches qualitatively results of experiments reported in the literature.     

Direct observations of the leaching of a simulated nuclear waste glass in a radiation environment

The durability of the media proposed for the containment of commercial nuclear waste will be affected not only by the differences in groundwater composition that they might encounter but also by the changes that their own irradiation fields will make to these solutions. Experimental results that question the ability of current leaching experiments to predict the stability of nuclear waste composites are presented.     

DARBOUX POLYNOMIALS FOR LOTKA–VOLTERRA SYSTEMS IN THREE DIMENSIONS

We consider Lotka–Volterra systems in three dimensions depending on three real parameters. By using elementary algebraic methods we classify the Darboux polynomials (also known as second integrals) for such systems for various values of the parameters, and give the explicit form of the corresponding cofactors. More precisely, we show that a Darboux polynomial of degree greater than one is reducible. In fact, it is a product of linear Darboux polynomials and first integrals.     

Effect of long-period stacking ordered phase on thermal stability of refined grains in Mg-RE-based alloys

The refined grains in both as-cast Mg-10Y-1Zn-2Zr (WZ101?K, wt.%) and Mg-10Y-1Al (WA101, wt.%) alloys have been found to have superior thermal stability after solution treatment. Plate-shaped, but different polytypes of long-period stacking ordered (LPSO) phases distributed along grain boundaries are considered as the predominant inhibitors of grain growth. Based on the plate-shaped features of the LPSO phases, a modified Zener’s model is established and the predicted limiting grain sizes are in a good agreement with the experimental results. Therefore, this model has strong potential for designing advanced Mg-RE-based alloys with high strength and high creep resistance at high temperatures.     

The electronic origin of unusually large nJFN coupling constants in some fluoroximes

SOPPA(CCSD) calculations show that the FC term is the most important contribution to the through‐space transmission of J_FN coupling constants for the fluoroximes studied in this work. Because of the well‐known behavior of FC term, a new rationalization for the experimental ^TSJ_FN SSCC is presented. It is mainly based on the overlap matrix (S_ij) between fluorine and nitrogen lone pairs obtained from NBO analyses. An expression is proposed to take into account the influence of the electronic density (D_ij) between coupled nuclei as well as the s% character at the site of the coupling nuclei of bonds and non‐bonding electron pairs involved in D_ij. In using this approach, a linear correlation between ^TSJ_FN versus D_ij is obtained. The most important aspect of this rationalization is related to the facility for understanding the behavior of some unusual experimental coupling constants. It is shown that, at least in this case, the electronic origin of the so‐called through‐space coupling is transmitted through to the overlap of orbitals on the coupled atoms, suggesting that, at least for these compounds, instead of through‐space coupling, it should better be dubbed as ‘through overlapping orbital coupling’. Copyright © 2013 John Wiley & Sons, Ltd.     

HCSE method for detection of small carbon–carbon couplings and their signs,comparison with SLAP pulse sequence

Performance of homonuclear coupling sign edited (HCSE) experiment applied to detection of signed carbon–carbon couplings is discussed using a set of already measured samples of nine monosubstituted benzenes. It is shown that coupling sign detection is insensitive to the settings of carbon–carbon polarization transfer delays. The HCSE spectra of ten from the total of 43 measured carbon–carbon couplings were considerably influenced by relaxations and proton–proton strong couplings. These effects are quantitatively discussed. The results of HCSE and SLAP experiments are compared. It is shown that the two methods may complement each other in detection of signed carbon–carbon couplings. Copyright © 2013 John Wiley & Sons, Ltd.