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The accuracy with which the local and integrated parameters of hydraulic turbines can be predicted depends on a correct choice of the parameters for the computational mathematical model. In the first part of this paper we choose a set of basic parameters (type of computational grid, turbulence model, impeller-stator interface) based the solution of problems for which experimental data are available. In the second part we calculate the energy characteristics of Francis and Kaplan turbines. Features of the calculations and data processing for hydraulic turbines are pointed out and the results of the mathematical model are compared with experimental data. Model results for cavitation and runup tests are shown. The statement of the problem is described and the computational results are compared with experimental data.The accuracy with which the local (speed, pressure in the flow-through section) and integrated (pressure head, power, efficiency) parameters of turbine machinery and, in particular, hydraulic turbines can be predicted depends on the correctness of the parameters chosen for the mathematical design model. In this paper we study the effect of the major parameters of the computational model on the calculated parameters.The effect of the computational grid on the integrated and local parameters of the flow kinematics have been studied for the example of flow calculations in a suction pipe. We have considered a tetrahedral computational grid (289,656 cells), a tetrahedral grid with a prismatic layer (7 prismatic layers) near the wall (858,655 cells), and a hexahedral grid (179,332 cells).Calculations of the flow and losses in the suction pipe using the different grids showed that the latter have a significant effect on the computational results. Figure 1 shows the velocity distributions near the wall of the suction pipe, along with the computational grids that were used. It can be seen that the tetrahedral grid yields a substantially higher boundary layer thickness. The tetrahedral grid with a prismatic layer cannot be used for describing the transition zone of the boundary layer, and in regions with a high velocity gradient, there are numerous highly elongated pyramidal cells (the distance from the center to the boundary with the neighboring cells differs substantially), which has a bad effect on the convergence of the solution and distorts the flow pattern. The hexahedral grid, which is compressed toward the wall, can resolve all the velocity and pressure gradients and the turbulence parameters, as well a provide a correct prediction of frictional losses. During these studies it was found that the velocity profile obtained on the tetrahedral grid with a prismatic layer along the wall differs from those obtained with the hexahedral and tetrahedral grids, as well as from experimental probe data along the flow at the outlet from the suction pipe. An analysis of the solution showed that the tetrahedral grid with prismatic cells near the wall has degenerate cells. The errors induced by low quality interpolation o...

In this article, we consider, based on the super-diamagnetic model, the new problems of Saturn's rings discovered by Cassini, such as: 1) anomalous purity of water ice; 2) Saturn's magnetic field alignment with the planet's rotation axis; 3) "ring rain" of the submicron particles; 4) the deviation in the qualitative composition of the "rain" from the composition of the rings; 5) "dirt" concentrated in the ring gaps; 6) "plateaus" in Saturn's C ring; 7) age of the rings; 8) roll-off in the spectrum of Saturn's rings, and 9) "propellers" in Saturn's A ring. Interpretation of Cassini's observations of spectral roll-off in Saturn's rings in the wavelength range from 100 micrometers to 0.5 mm is given. It was concluded that the substance of the rings could be in the superconducting state. An explanation of the Cassini spectral data is given using the hypothesis of the existence of a superconducting energy gap in the substance of rings.

Purpose Lumbar spinal stenosis (LSS) is a condition affecting several hundreds of thousands of adults in the United States each year and is associated with significant economic burden. The current decision-making practice to determine surgical candidacy for LSS is often subjective and clinician specific. In this study, we hypothesize that the performance of artificial intelligence (AI) methods could prove comparable in terms of prediction accuracy to that of a panel of spine experts. Methods We propose a novel hybrid AI model which computes the probability of spinal surgical recommendations for LSS, based on patient demographic factors, clinical symptom manifestations, and MRI findings. The hybrid model combines a random forest model trained from medical vignette data reviewed by surgeons, with an expert Bayesian network model built from peer-reviewed literature and the expert opinions of a multidisciplinary team in spinal surgery, rehabilitation medicine, interventional and diagnostic radiology. Sets of 400 and 100 medical vignettes reviewed by surgeons were used for training and testing. Results The model demonstrated high predictive accuracy, with a root mean square error (RMSE) between model predictions and ground truth of 0.0964, while the average RMSE between individual doctor's recommendations and ground truth was 0.1940. For dichotomous classification, the AUROC and Cohen's kappa were 0.9266 and 0.6298, while the corresponding average metrics based on individual doctor's recommendations were 0.8412 and 0.5659, respectively. Conclusions Our results suggest that AI can be used to automate the evaluation of surgical candidacy for LSS with performance comparable to a multidisciplinary panel of physicians.

Despite the progress observed in implantology and the rapid evolution of preventive and treatment options employed to treat major dental issues, the number of patients who need prosthetics with removable dentures still remains high, with no decrease trend to be expected soon. Modern dentistry, when dealing with issues related to dentition restoration, makes full use of basic thermoplastic polymers incorporating injection molding technology, whereas the said polymers can boast of such properties as biological inertia, proper aesthetics, strength, flexibility, resistance to external effects, lightness and elasticity. The conventional techniques used for cleaning and disinfecting removable dentures made of thermoplastic polymers fail to be up to the respective advanced requirements – such dentures create environments that are favorable for adhesion and microbial colonization. Aiming to evaluate the effectiveness of the modern means used for cleaning and disinfecting removable denture structures based on thermoplastic polymers, there was a study carried out to investigate the surface of 60 experimental samples of Acry-free ® thermoplastic, including methods of scanning electron microscopy and atomic force microscopy. To analyze the effect that cleaning and disinfecting agents work on the hygienic status of partially removable dentures made of thermoplastics (manufactured for 74 patients suffering from partial adentia), the Ambjornsen E. questionnaire was employed. The developed original set of preventive measures involved thorough oral hygiene activities with a manual toothbrush and mouthwash balms, as well as a consistent use of a special toothbrush and gel paste to take care of the removable dentures, followed with ultrasonic treatment and cleansing with effervescent tablets. The data of scanning electron microscopy and atomic force microscopy showed that using the original set of preventive measures resulted in improved quality of the thermoplastic polymers surface – by 1.1 – 1.5 times, if compared with conventional hygiene and disinfection products. As the data of sociological monitoring reveal, 12 into using the developed preventive measures, over 69% of patients were satisfied with the aesthetic properties of their dentures based on thermoplastics; as for the patients sticking to the practice relying on traditional hygiene and disinfection products, the similar indicator would not exceed 25%. In order to prevent the occurrence of major dental issues, as well as to increase the useful life of dentures made of thermoplastics and used by patients with partial adentia, it is wise to employ an individual approach to the selection of preventive measures that involve specialized extra hygiene products.