Development of hull material for high-altitude airship: A parametric study

The development of hull material with ideal properties to meet all the operation requirements has posed the greatest challenge to flying the airship at high altitude for extended periods. Materials developed in our previous study with a laminated structure achieved high strength-to-weight ratio and excellent gas barrier property at a relatively low total weight. To optimize this novel design and obtain a more comprehensive understanding of the laminate properties, a parametric study involving lamination process parameters (temperature and time), and laminate structural parameter (reinforcement fabric construction), was conducted. The effects of lamination parameters on tensile, peel, tear and helium permeability tests were carried out to assess the laminates. It was found that the tensile strength of the laminate is predominantly determined by the fabric reinforcement material properties. The peel and tear strength results showed that increasing the lamination temperature from 185 °C to 200 °C improved respective strength values. Additionally, the analysis of failure modes and tear propagation suggested that laminate samples with progressive failure have better tear resistant property over those with brutal failure. Extremely low helium permeability was achieved, yet the gas barrier property was not affected by the lamination process parameters and fabric type.

Pathogenetic Justification of a New View on the Treatment of Angle-Closure Glaucoma

Purpose. To study the effectiveness of vascular, anti-inflammatory and fibrinolytic therapy, to conduct a comparative assessment with treatment without vascular therapy in patients with angle-closure (ACG) and mixed glaucoma.Methods. A total of 55 patients with angle-closure and mixed glaucoma, mainly with hypermetropic refraction of varying degrees, were examined: 7 people with acute glaucoma attack, 6 people with subacute glaucoma attack (group 1, with anti-inflammatory treatment), 7 people with acute glaucoma attack and 6 people with subacute glaucoma attack (group 2, with vascular treatment), 14 people with chronic angle-closure glaucoma (group 3) and 15 people with mixed glaucoma (group 4). All patients underwent an ophthalmological examination, which included visometry, refractometry, tonometry, computer perimetry, OCT and OCT angiography, and an ELISA analysis to determine cytokines.Results. The administration of the drug Pentoxifylline as a cytokine blocker and antiplatelet agent in ACG contributed, in our opinion, to an improvement in visual acuity, perimetry (MD), an increase in the density of capillaries of the deep vascular plexus at the level of lamina cribrosa in the peripapillary zone (%), i.e. improved blood circulation in the vessels of the optic nerve disc and also contributed to the blockade of cytokines, mainly in the 2-nd group of patients. In our opinion, a personalized approach to the treatment of ACG is to maintain the improvement of blood circulation in the peripapillary zone by prescribing a course of treatment with Pentoxifylline for 6 months after surgery. After phacoemulsification, there was a significant increase in the density of capillaries of the deep peripapillary vascular plexus at the level of lamina cribrosa (p ≤ 0.05) (51.0 ± 3.5 %), and after further treatment with Pentoxifylline, the capillary density continued to increase in 2–4 groups in the next 6 months of follow-up. The thickness of RNFL (Retinal nerve fiber layer, structural parameter) decreased due to a decrease in edema in 1–2 groups, slightly increased in 3–4 groups, in our opinion, due to improved blood circulation. Increased reperfusion in the capillaries of the deep plexus during normalization of IOP in glaucoma patients and further treatment with pentoxifylline indicates the effectiveness of the proposed treatment in addition to surgical treatment. The results obtained emphasize the advantages of the proposed therapy for the treatment of patients with angle-closure and mixed glaucoma.Conclusion. To date, there are no clear recommendations of vascular therapy for the treatment of patients with ACG and mixed glaucoma, which creates the need for its addition to treatment regimens, taking into account the vascular component of ACG and mixed glaucoma.

Analysis of the Electromechanical Characteristics of Power Transformer under Different Residual Fluxes

When the electromagnetic transients occur in a power transformer, an inrush current is generated in its winding. The inrush current not only affects the performance of the transformer windings, but also affects the lifetime of the transformer. Many factors affect the inrush current, the most influential ones among which are the closing phase angle and the residual flux. In this paper, a dry-type transformer simulation model is built to analyze the influence of the inrush current on the performance of transformer windings during no-load reclosing conditions. Firstly, the inrush current was generated in the transformer windings during the no-load reclosing operation under different residual fluxes. Secondly, the field-circuit coupling 3d finite element method is used to analyze the electromagnetic force at different locations of the transformer windings under the influence of different inrush currents. The results of winding structural parameter variations are obtained through electromagnetic-structural coupling simulation, and the electromagnetic forces are used as the input parameter for the structural analysis. Finally, the residual flux is generated by controlling the opening and closing angle of the transformer through the phase-controlled switch, and the winding electromechanical characteristics are tested under different residual fluxes. Finally, comparisons of the test and simulation results are drawn to verify the impact of the closing angle and residual flux on inrush current and the winding deformation during the no-load reclosing conditions.

Individual Tree Structural Parameter Extraction and Volume Table Creation Based on Near-Field LiDAR Data: A Case Study in a Subtropical Planted Forest

Individual tree structural parameters are vital for precision silviculture in planted forests. This study used near-field LiDAR (light detection and ranging) data (i.e., unmanned aerial vehicle laser scanning (ULS) and ground backpack laser scanning (BLS)) to extract individual tree structural parameters and fit volume models in subtropical planted forests in southeastern China. To do this, firstly, the tree height was acquired from ULS data and the diameter at breast height (DBH) was acquired from BLS data by using individual tree segmentation algorithms. Secondly, point clouds of the complete forest canopy were obtained through the combination of ULS and BLS data. Finally, five tree taper models were fitted using the LiDAR-extracted structural parameters of each tree, and then the optimal taper model was selected. Moreover, standard volume models were used to calculate the stand volume; then, standing timber volume tables were created for dawn redwood and poplar. The extraction of individual tree structural parameters exhibited good performance. The volume model had a good performance in calculating the standing volume for dawn redwood and poplar. Our results demonstrate that near-field LiDAR has a strong capability of extracting tree structural parameters and creating volume tables for subtropical planted forests.

Systematically Measuring Ultra-diffuse Galaxies (SMUDGes). II. Expanded Survey Description and the Stripe 82 Catalog

We present 226 large ultra-diffuse galaxy (UDG) candidates (r e > 5.″3, μ 0,g > 24 mag arcsec−2) in the SDSS Stripe 82 region recovered using our improved procedure developed in anticipation of processing the entire Legacy Surveys footprint. The advancements include less constrained structural parameter fitting, expanded wavelet filtering criteria, consideration of Galactic dust, estimates of parameter uncertainties and completeness based on simulated sources, and refinements of our automated candidate classification. We have a sensitivity ∼1 mag fainter in μ 0,g than the largest published catalog of this region. Using our completeness-corrected sample, we find that (1) there is no significant decline in the number of UDG candidates as a function of μ 0,g to the limit of our survey (∼26.5 mag arcsec−2); (2) bluer candidates have smaller Sérsic n; (3) most blue (g–r < 0.45 mag) candidates have μ 0,g ≲ 25 mag arcsec−2 and will fade to populate the UDG red sequence we observe to ∼26.5 mag arcsec−2; (4) any red UDGs that exist significantly below our μ 0,g sensitivity limit are not descendent from blue UDGs in our sample; and (5) candidates with lower μ 0,g tend to smaller n. We anticipate that the final SMUDGes sample will contain ∼30 × as many candidates.