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Combined with the image explosion source method and LAMBR (LAMB revisied) model, a fast calculation method of wall load of implosion in cylindrical vessels with single explosion source was proposed. The verification results show that the maximum relative errors of the predicted and simulated values of overpressure peak and specific impulse on the structural wall are −13.66% and −17.84% respectively. The predicted overpressure and specific impulse time curves are in good agreement with that obtained by simulation, which can reflect the multimodality of the load at the measuring point under the action of implosion and verify the effectiveness of the method.

A cylindrical combination testing method is proposed in this paper. Three cylindrical mirrors are combined in pairs. By constructing a confocal optical system for interference testing to obtain combined wavefront aberration. The cylindrical surface errors are calculated by the combined wavefront aberration. The source of misalignment error is analyzed in detail and the mathematical model combined with the Chebyshev polynomial coefficients is established. That the misalignment error can be effectively removed by polynomial fitting is proved by simulation.

The change of the surface curvature during the line heating forming process of ship outer plates changes the spatial position of frame lines on the surface, which makes it challenging to locate the position of frame lines during the digital plate-forming inspection. It is necessary to establish the mapping between the frame line data of complex surface shape and the corresponding data in the two-dimensional flattening state with the help of surface flattening algorithms, so as to obtain the spatial position of the frame line data of outer plates in the actual forming state. A Dijkstra-compass intersection-solving algorithm is proposed to achieve surface flattening of ship outer plates. Firstly, the point cloud data of the outer plate shape surface is interpolated and fitted by NURBS to obtain the surface data of the outer plate. Then, the Dijkstra search algorithm is used to find the geodesic, and the frame line curvature is calculated according to the triangular similarity law. Finally, the geodesic line and the middle frame line are expanded, and the surface flattening data is obtained by further expanding the mesh points. This method is used to flatten the cylindrical and circular table surfaces, and the flattening error is less than 3mm compared with theoretical values. The test results show that the proposed method can effectively flatten the three-dimensional surface of the ship’s outer plates, and the deployment accuracy meets the actual use requirements.

Purpose: The present study aimed to analyse the influence of absorptive tinted filter lenses on Contras Sensitivity (CS) in healthy participants under three different environmental conditions. Methods: 10 Healthy qualified volunteers who fulfilled the inclusion/exclusion criteria were recruited: refractive spherical error between +2.00 and -4.00D, refractive cylindrical error less than 1.00 D, Best Corrected Visual Acuity (BCVA) ≥ 1.0 and Low Vision Quality of Life (LVQOF) score ≥ 50. Participants were scheduled for three-session under different environmental conditions where CS was measured with a Pelli-Robson chart with and without five (ML Filters 450, 500, 511, 527 and 550) absorptive tinted filters lenses: 1) indoor, 2) outdoor on a sunny day, 3) outdoor on a rainy day. The filters were always introduced in the same order, from the higher absorption filter (ML Filter 550) to the lower (ML Filter 450). Results between filters and environmental conditions were compared. Results: There was a statistical difference in the CS values obtained with and without a filter in the measurements performed in all environmental conditions (Friedman test: all p < 0.001) with no differences in the pairwise analysis between filters (Wilcoxon test; all ≥ 0.009). There was no statistically difference in the CS values between environmental conditions without filters or with any of the filters (Friedman test: all p ≥ 0.097). Conclusions: The present study found that coloured filter lenses between 450 and 550 nm wavelength absorption had minimal impact on CS in healthy participants.

Explosion tests and numerical simulations are of great significance for the study of submarine and other underwater target damage characteristics. However, the cost of the real ship test is high, the implementation is difficult, and the time cost of the simulation calculation is high, which presents some difficulties in attempting to quickly assess the damage of underwater structures. Currently, the combination of machine learning and numerical simulation has become a more effective means of addressing the aforementioned issues. In this paper, the acoustic-structural arithmetic is employed to realise the non-contact underwater explosion simulation calculation of the reinforced cylindrical shell section. The maximum deflection of the reinforcement bar is extracted as the output parameter from the calculation results. The explosion distance, explosive equivalent, and the thickness of the reinforcement bar are taken as the input parameter. The prediction and analysis are carried out based on the back-propagation neural network algorithm of machine learning. The data generated by the neural network are processed and analysed for the error analysis. The processing and error analysis of the data generated by the neural network revealed that the neural network exhibited a superior prediction effect, establishing an accurate and efficient prediction model for the damage characteristics of underwater exploding cylindrical shells.

Changes in limb volume and shape among transtibial amputees affects socket fit and comfort. The ability to accurately measure residual limb volume and shape and relate it to comfort could contribute to advances in socket design and overall care. This work designed and validated a novel 3D laser scanner that measures the volume and shape of residual limbs. The system was designed to provide accurate and repeatable scans, minimize scan duration, and account for limb motion during scans. The scanner was first validated using a cylindrical body with a known shape. Mean volumetric errors of 0.17% were found under static conditions, corresponding to a radial spatial resolution of 0.1 mm. Limb scans were also performed on a transtibial amputee and yielded a standard deviation of 8.1 ml (0.7%) across five scans, and a 46 ml (4%) change in limb volume when the socket was doffed after 15 minutes of standing.

The rotary joint is the key device of the marine clutch. Once the seal fails, the power cannot be transmitted. In view of the above problems, this research studies the influence of shape, installation and rotation motion errors on clearance seal. The results show that compared with the absence of roundness error, the roundness error of the shaft will increase the leakage by about 2.5-4.9 %. The cylindrical error of the bushing will reduce the leakage, but it will bring more serious friction, wear and life problems. The existence of radial installation error will increase the leakage, and the larger the radial installation error, the more obvious the flow field extrusion, the higher the unevenness of the pressure field in the whole flow field. The existence of angular installation error will reduce the leakage, but it will cause more serious friction and wear, resulting in a sharp increase in temperature. The leakage increases by about 0.68 % when the radial installation error is 0.1 mm, and the rotary motion error further increases the leakage by about 0.15 %. The above research can provide theoretical support for the structural design and optimization of the rotary joint tin bronze clearance seal.

Computer modelling of technical constructions is increasingly carried out using software that includes more detailed knowledge, which requires an increase in the level as well as an expansion of the scope of the geometric knowledge. A significant part of motion transmission mechanisms are worm drive pairs, for which the separation of the parts dealing with the theoretical and practical problems found in the literature can be experienced in numerous instances. Due to the different technical features, in many cases the helical surfaces are not designed and manufactured in a geometrically correct way, or the best solution is not the compulsory chosen. The geometric model describing the production process of the worm surfaces provides the basis for examining the deviation between the surface mathematically determined by the designer and the surface produced. An integrated mathematical kinematic model was developed for the production geometrical analysis of the elements of cylindrical and conical worm gear drive pairs for machining with a traditional thread grinding machine, which causes a serious pitch fluctuating error among several other problems in the case of machining the conical worm. Modelling of the production process of surfaces and the simultaneous study of the manufacturing errors is basically performed with the toolbox of descriptive geometry, including the use of the projective invariants. Knowing the inheritance of the invariants of projective geometry, the aim was the mathematical generalization of the integrated model and the creation of a projective relationship between the reference surfaces of conical and cylindrical spiral surfaces. As a result, the improved constructive geometric model was created, in which the method of analytically creating the projective geometric relationship between the reference surfaces of conical and cylindrical helicoid surfaces has been described for the first time in this article. This procedure is considered the most important result of the present article. Another significance of the further development presented is that during production of the conical helicoid surface, the thread pitch fluctuation has been eliminated. The results obtained, consisting of an improved geometric model, lead to a new geometry of the technological environment regarding the relative position of the cutting tool and the workpiece as well as the relative motion between them.

Mechanical testing of articular cartilage yields highly variable results, posing challenges for tissue characterization. Many factors cause variability, one is sample geometry. Using in-situ phase-contrast enhanced synchrotron micro-tomographs of cartilage samples while tested in unconfined compression (stress relaxation) our group found high variability in the mechanical response. Since all samples originated from a single bovine knee, they were assumed to share mechanical properties. Microscale tomography images showed geometric irregularities in samples that were not accounted for in the often assumed intended cylindrical shape. We aimed to determine the influence of sample shape on mechanical response in unconfined compression and how sample geometry affects identified mechanical properties. Using a parametric FE model incorporating geometric irregularities in a Design of Experiments approach, results were analysed with 2-way ANOVA. Furthermore, a material parameter fitting was done with multiple segmented sample-specific finite element models simultaneously to assess the influence of sample geometry on material parameters. Results revealed that the average inclined sample surface (4°) caused a 15 % decrease in reaction forces compared to the intended cylinder. Fitting multiple sample-specific geometries simultaneously altered material parameters between −70 to +159 % compared to the average model. Strikingly, initial fibril stiffness and permeability increased by 137 % and 159 %, while the root-mean-square error of the fit was reduced by ∼2/3 compared to using parameters from a cylindrical shape model. In conclusion, minor variability in sample geometry affects property characterization and can account for some of the inter-sample variability in the mechanical data for cartilage.

To evaluate the prevalence and associated factors of steep cornea/keratoconus in the adult Chinese population. The population-based Beijing Eye Study 2011 included 3468 individuals with a mean age of 64.6±9.8 years (range: 50-93 years). A detailed ophthalmic examination was performed including optical low-coherence reflectometry. Steep cornea/keratoconus were defined as an anterior corneal refractive power exceeding 48 diopters. Mean refractive power of the cornea was 43.16±1.45 diopters (range: 36.51 to 48.46 diopters; flattest meridian) and 43.98±1.52 diopters (range: 37.00 to 52.88 diopters; steepest meridian). A steep cornea/keratoconus defined as corneal refractive power of ≥48 diopters and ≥49 diopters was detected in 27 subjects (prevalence rate: 0.9±0.2%) and 6 (0.2± 0.1%) subjects, respectively. Presence of steep cornea/keratoconus was associated with shorter axial length (P<0.001), smaller interpupillary distance (P = 0.038), lower best corrected visual acuity (P = 0.021), higher cylindrical refractive error (P<0.001) and more myopic refractive error (P<0.001). It was not significantly associated with gender, body height, psychic depression, cognitive function, blood concentrations of glucose, lipids, creatinine and C-reactive protein, blood pressure and quality of life score, nor with intraocular pressure, dry eye feeling, and lens thickness. A steep cornea/keratoconus defined as corneal refractive power of 48+ diopters has a prevalence of 0.9±0.2% among Chinese aged 50 years and above. Its prevalence was significantly associated with the ocular parameters of shorter axial length, smaller interpupillary distance, higher cylindrical and myopic refractive error and lower best corrected visual acuity, however, with none of the systemic parameters tested.