It is well-known that certain fluids are birefringent and when flows are viewed in polarised light interference fringes are observed. The fringes are caused by a phase shift in the light passing through the fluid and are proportional to the integral of the maximum shear strains in the fluid. In order to understand what is happening within the three dimensional flow and overcome the difficulties due to this integration, additional computational or experimental information is needed.
In this work, a commercially available computer code (Fluent) is used for the first time to model the flows. The flow data are then exported to a spreadsheet where the shear rates are integrated across the field and then banded for graphical output. The results from this are then compared to results generated from birefringent flow experiments and the agreement is found to be good since the modelled fringes show the same patterns as those in the experiment. This novel use of computational and experimental techniques together will allow quantitative analysis of three-dimensional flows in the future.
Currently, there are still a lot of empirical variables involved in fitting the computational fringes to the experiment, but the results of this preliminary study show that this is a promising approach to this type of problem. 相似文献
A watermarking technique, with a Computer Generated Hologram (CGH) coding system of the mark, is introduced and tested. The CGH watermarking can be used to authenticate parts of the original image. The hologram of the mark is embedded in the spatial domain by a blind additive embedding technique. The use of holography allows authenticating cuts of the original image, is the major novelty of this paper. The proposed methodology is characterized as an authentication technique, since it does not rely on the original image to decide whether the watermarked image has been altered or not and at the same time it is able to detect and localize any possible malicious change. Asymmetric cryptography is used to hide the hash information in an unambiguous way (non-repudiation property). 相似文献
The aim of this work has been to analyze the problems related to the identification of microporous structure parameters of carbonaceous materials. The new methods for microporous structure parameters identification have been explored with special focus on the influence of the analyzed relative pressure range on the reliability of parameters identification. For that purpose, the adsorption isotherm of nitrogen on active carbon for different ranges of relative pressures p/p0 was analyzed. The conducted research was to provide for an answer to the question of whether the range of the analyzed relative pressures has any effect on the quality of adsorption system parameters identification, as well as what range of the relative pressure permits execution of the reliable identification of microporous structure parameters. 相似文献
By using the discrete Markov chain method, Parrondo’s paradox is studied by means of theoretical analysis and computer simulation, built on the case of game AB played in alternation with modulus M=4. We find that such a case does not have a definite stationary probability distribution and that payoffs of the game depend on the parity of the initial capital. Besides, this paper reveals the phenomenon that “processing in order produces non-deterministic results, while a random process produces deterministic results”. The quantum game method is used in a further study. The results show that the explanation of the game corresponding to a stationary probability distribution is that the probability of the initial capital has reached parity. 相似文献
The temperature profile around the moving solid–liquid interface during non-equilibrium molecular dynamics (MD) simulations of crystallization and melting is examined for HCP Mg and BCC Fe. An evident spike (valley) is found around the solid–liquid interface during solidification (melting). Considering the effect of a non-uniform temperature distribution, it is found that, if the actual interface temperature is adopted to compute the interface mobility, rather than the thermostat temperature (or the mean temperature of the whole system), the kinetic coefficient is approximately a factor of two larger than previous estimates. Although the magnitude of the kinetic coefficient is larger than the previous estimates, the crystalline anisotropies derived in the current work are consistent with earlier calculations. 相似文献
A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the Haasen–Alexander–Sumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process. 相似文献
Various methods achieving importance sampling in ensembles of nonequilibrium trajectories enable one to estimate free energy differences and, by maximum-likelihood post-processing, to reconstruct free energy landscapes. Here, based on Bayes theorem, we propose a more direct method in which a posterior likelihood function is used both to construct the steered dynamics and to infer the contribution to equilibrium of all the sampled states. The method is implemented with two steering schedules. First, using non-autonomous steering, we calculate the migration barrier of the vacancy in Fe-α. Second, using an autonomous scheduling related to metadynamics and equivalent to temperature-accelerated molecular dynamics, we accurately reconstruct the two-dimensional free energy landscape of the 38-atom Lennard-Jones cluster as a function of an orientational bond-order parameter and energy, down to the solid–solid structural transition temperature of the cluster and without maximum-likelihood post-processing. 相似文献
The metastable zone width (MSZW, ΔTm) and induction time (tind) were determined with computer simulation for seeded batch crystallization of potassium sulfate from aqueous solution. The MSZW and induction time determined with simulation showed the same behavior as experimental values reported in the literature; log (ΔTm) increased linearly with an increase in log R (R: cooling rate) and tind decreases in proportion to (ΔT)−n (ΔT: supercooling, n: nucleation order in the secondary rate expression of B=kn(ΔT)n). The secondary nucleation parameters (kn and n) were deduced both from the simulated MSZW and induction times by using the previously proposed model [J. Cryst. Growth, 2010, 312, 548–554]. The secondary nucleation rate calculated with the deduced parameters was in agreement with that calculated with the parameters input for simulation. 相似文献