Experimental results on sediment removal efficiency of vortex chamber type sediment extractors are reported. A geometric configuration of the extractor is identified that is able to remove even the fine sediment (0.055 ? d ? 0.22?mm) from flow with high efficiency. For the purpose of analysis, the experimental data of present study are compiled with the data from other laboratories and the field that were collected previously by other investigators. Since the existing relations are not found to produce satisfactory results, a new relationship is developed for determination of the sediment removal efficiency of the vortex chamber type sediment extractors. 相似文献
The unsteady flow of an Oldroyd-B fluid with fractional derivative model, between two infinite coaxial circular cylinders, is studied by using finite Hankel and Laplace transforms. The motion is produced by the inner cylinder that, at time t = 0+, is subject to a time-dependent longitudinal shear stress. The solutions that have been obtained, presented under series form in terms of the generalized G and R functions, satisfy all imposed initial and boundary conditions. The corresponding solutions for ordinary Oldroyd-B and generalized and ordinary Maxwell and Newtonian fluids, performing the same motion, are obtained as limiting cases of our general solutions. Finally, the influence of the pertinent parameters on the fluid motion, as well as a comparison between models, is shown by graphical illustrations. 相似文献
This research presents a modeling approach to investigate the association of the accident frequency during a snow storm event with road surface conditions, visibility and other influencing factors controlling for traffic exposure. The results have the premise to be applied for evaluating different maintenance strategies using safety as a performance measure. As part of this approach, this research introduces a road surface condition index as a surrogate measure of the commonly used friction measure to capture different road surface conditions. Data from various data sources, such as weather, road condition observations, traffic counts and accidents, are integrated and used to test three event-based models including the Negative Binomial model, the generalized NB model and the zero inflated NB model. These models are compared for their capability to explain differences in accident frequencies between individual snow storms. It was found that the generalized NB model best fits the data, and is most capable of capturing heterogeneity other than excess zeros. Among the main results, it was found that the road surface condition index was statistically significant influencing the accident occurrence. This research is the first showing the empirical relationship between safety and road surface conditions at a disaggregate level (event-based), making it feasible to quantify the safety benefits of alternative maintenance goals and methods. 相似文献
GLAss Spherical Tokamak(GLAST-Ⅲ) is a spherical tokamak with an insulating vacuum vessel that has a unique single-passage capability for incident microwaves.In this work,electron cyclotron resonance heating(ECRH)-assisted plasma pre-ionization in GLAST-Ⅲ is explored for three radio-frequency(RF) polarizations(the O-,X-,and M-modes) at different toroidal-field(TF) strengths and filled gas pressures.The optimum hydrogen pressure is identified for efficient plasma pre-ionization.A comparison of the plasma pre-ionizations initiated by the O-,X-,and M-modes shows prominent differences in the breakdown time,location,and wave absorption.In the case of O-mode polarization,microwave absorption occurs for a relatively shorter duration,resulting in a bell-shaped electron-temperature(T_e) temporal profile.Microwave absorption is dominant in the case of the X-mode,leading to a broader T_e temporal profile.The M-mode discharge contains features of both the X-and O-modes.Efficient plasma pre-ionization is achieved in the X-mode polarization for the intermediate TF strengths(with a central toroidal magnetic field B_0=0.075 T).Traces of the electron-number density show a similar tendency,as revealed by T_e.These results suggest that the X-mode is the best candidate for efficient plasma pre-ionization at low filled gas pressures(~10~(-2) Pa) in small tokamaks. 相似文献
Ni2-xCox(WO4)2 and Ni2-xMnx(WO4)2 (x?=?0.0, 0.50, 1.0, 1.50 and 2.0) nanocomposites have been synthesized by facile hydrothermal method. The synthesized samples have been characterized by powder XRD and Scanning Electron Microscopy to analyze the structure and morphology. Structural analysis has revealed the single phase formation with wolframite monoclinic system for NiWO4 samples. The calculated crystallite size ranges from 6 to 40 nm for the nanocomposites. Magnetic and dielectric parameters have also been studied. Magnetic susceptibility measurements of each sample have been carried out at room temperature (312 K) by using Sherwood magnetometer. A decrease in susceptibility values has been observed by increase in the concentration of manganese or cobalt in nickel tungstate leading to antiferromagnetic behavior. Dielectric measurements in the frequency range of 6 kHz to 1 MHz have been calculated. The analysis showed that dielectric parameters decrease with increase in frequency. 相似文献
This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literature for modeling collision severity. In particular, the research compares three popular multilevel logistic models (i.e., sequential binary logit models, ordered logit models, and multinomial logit models) as well as three data aggregation methods (i.e., occupant based, vehicle based, and collision based). Six years of collision data (2001–2006) from 31 highway routes from across the province of Ontario, Canada were used for this analysis. It was found that a multilevel multinomial logit model has the best fit to the data than the other two models while the results obtained from occupant-based data are more reliable than those from vehicle- and collision-based data. More importantly, while generally consistent in terms of factors that were found to be significant between different models and data aggregation methods, the effect size of each factor differ substantially, which could have significant implications for evaluating the effects of different safety-related policies and countermeasures.