Dispersion of solid particles in turbulant flow through pipe expansions

Studies of the effects upon gas-liquid two-phase flows of pipefittings such as expansions, contractions, bends, and valveshave usually concentrated upon pressuredrop correlations andhave not attempted to determine changes in the distributionsof the gas and liquid phases caused by the fitting. However,it is known that such information is important if, for example,flow separators, which divide the gas and liquid phases in avariety of industrial processes, are to function efficiently.It is therefore important to gain an understanding of the influenceupon phase distributions of the common pipe fittings mentionedabove, which will be found in almost any industrial pipeworksystem. As a first step, the dispersion of solid particles carriedby turbulent gas flows through a pipe expansion has been modellednumerically. The commercial fluid-flow code CFDS-FLOW{smalltilde}hDas been used to model the gas flow, together with aneddy interaction model for determination of the motion of thesolid particles. Mean particle velocities and root-mean-squarevalues of the particle velocity fluctuations, as well as particleconcentrations, are evaluated and compared with recent experimentalresults. The influence of different eddy-length and eddy-lifetimespecifications upon the dispersion of particles of various sizesis investigated. It is found that the different eddy characteristicshave little effect on predicted mean particle velocities, whereasfluctuations in particle velocities and particle concentrationare sensitive to the changes made. By comparing the resultswith experimental data, it is possible to draw conclusions aboutthe relative merits of the different eddy specifications.     

Calculation of second Kerr effect virial coefficients of H2S

Second Kerr effect virial coefficients B _K of H₂S have been calculated using our recent molecular tensor theory of B _K for molecules of nonlinear symmetry. After optimization of the intermolecular potential interaction parameters and molecular quadrupole moment for H₂S, the calculated B _K values are seen to agree with the experimental values found in the literature to within 10% over the temperature range of the measured data. The components of the quadrupole moment tensor obtained by optimization are not in good agreement with the one set of calculated values reported in the literature.     

Molecular Organization of Various Collagen Fragments as Revealed by Atomic Force Microscopy and Diffusion‐Ordered NMR Spectroscopy

Heterogeneous mixtures of collagen fragments can be used as nutrition supplement or as key ingredients for ointments with therapeutic relevance in wound healing. Some mixtures of collagen fragments are referred to as collagen hydrolysates owing to the production process with hydrolytic enzymes. Since the precise composition of collagen hydrolysates is generally unknown, it is of interest to analyze samples containing various collagen fragments with appropriate biophysical methods. Any product optimization without a profound knowledge concerning the size and the molecular weight distribution of its components is nearly impossible. It turned out that a combination of AFM methods with NMR techniques is exceptionally suited to examine the size range and the aggregation behavior of the collagen fragments in the hydrolysates of fish, jellyfish, chicken, porcine and bovine collagen. Supported by molecular modeling calculations, the AFM and NMR experiments provide a detailed knowledge about the composition of collagen hydrolysates and collagen ointments. Furthermore, the data allow a correlation between the size of the fragments and their potential bioactivity.     

ON THE HORN EFFECT OF A TYRE/ROAD INTERFACE, PART II: ASYMPTOTIC THEORIES

In Part I, it was shown that boundary element method calculations could successfully be applied to determine sound amplification by a tyre/road geometry. However, the computations are expensive, limited to frequencies below 2500 Hz, and provide little physical insight. In Part II, two supplementary asymptotic approaches are developed; a ray theory for high frequencies and a compact body scattering model for low frequencies. When tested on a representative tyre geometry, these methods are found to have excellent predictive capabilities, at frequencies above 3k Hz and below 300 Hz respectively. Furthermore, the ray theory shows that the neglect of curvature in Ronneberger's wedge model (1989 Workshop on Rolling Noise Generation, Institut fur Technische Akustik, Technische Universitat, Berlin) leads to erroneous amplification levels and interference effects, and the scattering model intriguingly predicts that low frequency amplification increases with belt width independently of the tyre diameter. Lastly, this work confirms the importance of numerical calculations for the intermediate frequencies, where tyre noise is most significant.     

稳态实验考察经模拟道路老化的全配方稀燃Nox捕集催化剂上的Nox还原

Fully formulated lean NOx trap(LNT)catalysts of the type Pt/Rh/BaO/Al2O3 were prepared with and without incorporation of CeO2-ZrO2 in the washcoat,and their NOx reduction behavior was evaluated in steady-state,continuous flow experiments.In the fresh state, the CeO2-ZrO2 addition was found to exert little effect on NOx reduction activity using H2,CO,and NH3 as the reductants.However,after simulated road aging,NOx reduction activity was significantly impaired for the CeO2-ZrO2-free catalyst,whereas the perfo...