On-line estimation of the state of traffic based on data sampled by electronic detectors is important for intelligent traffic management and control.Because a nonlinear feature exists in the traffic state,and because particle filters have good characteristics when it comes to solving the nonlinear problem,a genetic resampling particle filter is proposed to estimate the state of freeway traffic.In this paper,a freeway section of the northern third ring road in the city of Beijing in China is considered as the experimental object.By analysing the traffic-state characteristics of the freeway,the traffic is modeled based on the second-order validated macroscopic traffic flow model.In order to solve the particle degeneration issue in the performance of the particle filter,a genetic mechanism is introduced into the resampling process.The realization of a genetic particle filter for freeway traffic-state estimation is discussed in detail,and the filter estimation performance is validated and evaluated by the achieved experimental data. 相似文献
Heat transfer of de-ionized water over in-line and staggered micro-cylinder-groups have been numerically investigated with Reynolds number varying in the range from 25 to 150. A 3-D incompressible numerical model is employed to investigate the vortex distributions and the influences of the vortices on heat transfer characteristics at low Re numbers in micro-cylinder-groups with different geometrical parameters, including micro-cylinder diameters (100, 250 and 500?μm), ratios of pitch to micro-cylinder diameter (1.5, 2 and 2.5) and ratios of micro-cylinder height to diameter (0.5, 1, 1.5 and 2). The vortex distributions, the temperature fields, and the relationships among them are investigated by solving the numerical model with the finite volume method. It is found that the vortex number become more with the increase of pitch ratio and the change of flow rate distribution affects the heat transfer characteristics apparently. Meanwhile, the local heat transfer coefficients nearby the locations of vortices greatly increase due to the boundary layer separation, which further enhance the heat transfer in micro-cylinder-groups. The new correlations which to Nusselt number of de-ionized water over micro-cylinders with Re number varying from 25 to 150 have been proposed considering the differential pressure resistance and the buoyancy effect basing on numerical calculations in this paper. 相似文献
Decline curve analysis (DCA) is a traditional method for production prediction, which is still being used because it works
in many cases and it is relatively simple to apply. However, DCA methods can neither match nor predict the fluctuating oil
production during the early period when applied to entire reservoirs. The change in oil production may be because of variation
in production conditions or the number of injection/production wells. In this study, we focused on the latter problem, change
in the number of production wells. Obviously, there would be a significant oil production boost during a specific time period
if more oil wells are drilled. The traditional DCA approach cannot match the increase in oil production due to the increase
in the number of oil production wells. We have developed a method to match the oil production of entire reservoirs for the
life span by considering the change in the number of production wells. The main idea of this approach came from the concept
of effective wells. We applied this approach in several sandstone oil reservoirs with different permeabilities. The proposed
effective-well model could match the oil production data in different reservoirs, even during the early period of production
when the oil production rate change with time because of the variation in the number of producers. Comparison with the existing
models (exponential, hyperbolic model, and harmonic models) was made and the results showed the proposed approach had the
best fit to the production history in the cases studied. 相似文献
Ternary composites of BiFeO3/graphene nanoplatelet (GNP)/epoxy composites were synthesized and its electromagnetic and microwave absorbing properties were studied; the main absorbing mechanism was illustrated. The phase, microstructure, and microwave absorbing properties were characterized by X-ray diffraction, scanning electron microscope, and vector network analyzer. The results indicated that the BiFeO3 was successfully synthesized and the GNP was uniformly distributed in the composites, and the complex permittivity of BiFeO3/GNP/epoxy composites increased with increasing the GNP content due to the interface polarization and conductance loss. The minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm when the GNP content was 2 wt%, and also the absorbing properties of (BiFeO3+GNP)/epoxy composites can be tailored by the GNP content and composite thickness, which may be used as a kind of absorbing materials with good absorbing performance and low density.
Graphical abstract The reflection loss curves and the simulated matching thickness of GNP-BiFeO3-epoxy composites with 2 wt% GNP content. As can be seen, the minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm, and also the quarter-wavelength matching theory can be used to illustrate the good absorbing properties of GNP-BiFeO3-epoxy composites.
The mean fixation time is often not accurate for describing the timescales of fixation probabilities of evolutionary games taking place on complex networks. We simulate the game dynamics on top of complex network topologies and approximate the fixation time distributions using a mean-field approach. We assume that there are two absorbing states. Numerically, we show that the mean fixation time is sufficient in characterizing the evolutionary timescales when network structures are close to the well-mixing condition. In contrast, the mean fixation time shows large inaccuracies when networks become sparse. The approximation accuracy is determined by the network structure, and hence by the suitability of the mean-field approach. The numerical results show good agreement with the theoretical predictions. 相似文献
In this paper, the trial equation method and the complete discrimination system for polynomial method are applied to retrieve the exact travelling wave solutions of complex Ginzburg–Landau equation. Both the Kerr and power laws of nonlinearity are considered. All the possible exact travelling wave solutions consisting of the rational function-type solutions, solitary wave solutions, triangle function-type periodic solutions and Jacobian elliptic functions solutions are obtained, and some of them are new solutions. In addition, concrete examples are presented to ensure the existence of obtained solutions. Moreover, four types of representative solutions are depicted to present the nature of the obtained solutions. 相似文献