Application of a superparametric finite shell element to the calculation of turbine blade vibrations

Determination of the natural frequencies and forms of vibrations of turbine blades with the present level of knowledge is one of the chief problems that have to be solved at the design stage of turbines in order to ensure vibration reliability. Greater possibilities of devising more correct mathematical models of blades and universal methods of investigating their vibrations are opened up in connection with the application of the finite element method.Для расчета колебаний лопаток турбомашин сложной геометрии используют суперпараметрические оболочечные конечные элементы

Monitoring and Quality Control of Diesel Fraction Production Process

In this work the mathematical model of diesel fraction and atmospheric gasoil catalytic dewaxing process has been developed. Also the pattern of applying the created model to solving such problems as monitoring and quality control of diesel fraction production in the catalytic dewaxing process. It has been represented that to meet such challenges, the model should take into consideration thermodynamic and kinetic laws of hydrocarbon conversion on the catalyst surface, and instability factors that are specified by catalyst deactivation. The developed model allows controlling the quality of obtained diesel fraction depending on feed and temperature regime in the reactor. The value of model calculation absolute error does not exceed 2%, which corroborates the adequacy of the model to actual process. The computations using the model have shown that to provide the desired product yield (not less than 40% wt. of overall yield of the unit products) of programmed quality (cold filtering plugging point not higher than minus 34°C for winter diesel fuels and not lower than minus 40°C for arctic ones) at long-time catalyst operation (during 4 years), it is necessary to sustain the reactor temperature at the average level of 19°C higher than when working with fresh catalyst. This must be done to compensate catalyst activity loss due to its deactivation

Ultrabroad-bandwidth multifrequency Raman generation

We report on the modeling of transient stimulated rotational Raman scattering in H2 gas. We predict a multifrequency output, spanning a bandwidth greater than the pump frequency, that may be generated without any significant delay with respect to the pump pulses. The roles of dispersion and transiency are quantified

Assessment of the risk factors for the development and morphological types of posterior subcapsular cataract using optical coherence tomography

Aim. To analyze the risk factors for the development of posterior subcapsular cataract in patients with different morphological changes using anterior segment optical coherence tomography. Materials and methods. A prospective clinical study on the risk factors for posterior subcapsular cataract was conducted during 2020–2022. The study involved 296 patients (512 eyes). The morphological type of the posterior capsule was evaluated using anterior segment optical coherence tomography (AS OCT), Optovue RTVue 100 XR Avanti (Optovue Inc., USA). Results. Significant differences have been found between the first and second types of morphological changes in the posterior lens capsule in diabetes mellitus, long-term steroid use and myopia (χ2 = 68.01, р ≤ 0.0001), as well as between the second and third types of posterior capsule changes in myopia (χ2 = 16.97, р ≤ 0.0001). In the third type of morphological changes in the posterior lens capsule, mainly hereditary risk factors for the development of capsule opacification have been identified, namely, a history of retinitis pigmentosa in 77.8 % of cases, congenital myopia – in 22.2 %. Conclusions. Defining the morphological type of posterior capsule opacities coupled with studying the etiology of the process provide new knowledge concerning the prediction of visual functions and the phacoemulsification technique for posterior subcapsular cataract

Avoiding errors in the diagnosis of polypoidal choroidal vasculopathy in patients with age-related macular degeneration (Part 1)

Background: Poor availability of indocyanine green angiography (ICGA) raises the question of how to improve the diagnosis of polypoidal choroidal vasculopathy (PCV) using alternative imaging modalities, optical coherence tomography (OCT) and OCR angiography (OCTA). Purpose: To optimize the diagnosis of PCV in patients with age-related macular degeneration (AMD) using non-invasive methods, OCT and OCTA. Material and Methods: One hundred and sixty-nine patients (228 eyes) with neovascular AMD underwent OCT and OCTA study as per the proposed algorithm to differentiate between PCV and other types of subretinal neovascularization. Of these, 14 patients (8.28%; 14 eyes) were found to have PCV. Results: Major and additional signs of PCV, secondary neovascularization and activity of the process on OCT were determined. In addition, we determined the signs of PCV on OCTA manu-al and automatic segmentation which will be helpful in accurate differential diagnosis of the disease. On the basis of these data, we developed a step-by-step algorithm of the OCT and OC-TA diagnosis of PCV in patients suspected of the disease, which allows the accurate diagnosis when ICGA is unavailable. Conclusion: Systematic step-by-step interpretation of OCT and OCTA scans allow the reliable differential diagnosis of PCV in patients with exudative AMD

Monitoring and Quality Control of Diesel Fraction Production Process

In this work the mathematical model of diesel fraction and atmospheric gasoil catalytic dewaxing process has been developed. Also the pattern of applying the created model to solving such problems as monitoring and quality control of diesel fraction production in the catalytic dewaxing process. It has been represented that to meet such challenges, the model should take into consideration thermodynamic and kinetic laws of hydrocarbon conversion on the catalyst surface, and instability factors that are specified by catalyst deactivation. The developed model allows controlling the quality of obtained diesel fraction depending on feed and temperature regime in the reactor. The value of model calculation absolute error does not exceed 2%, which corroborates the adequacy of the model to actual process. The computations using the model have shown that to provide the desired product yield (not less than 40% wt. of overall yield of the unit products) of programmed quality (cold filtering plugging point not higher than minus 34°C for winter diesel fuels and not lower than minus 40°C for arctic ones) at long-time catalyst operation (during 4 years), it is necessary to sustain the reactor temperature at the average level of 19°C higher than when working with fresh catalyst. This must be done to compensate catalyst activity loss due to its deactivation