Layer Displacement Research Articles

Seismic performance of indoor substation RC frames with combined base isolation techniques

In order to investigate the seismic performance of indoor RC substations with combined base isolation technique under far-field earthquakes and near-fault earthquakes, a 1/4 scaled three-story RC frame model was prepared for shaking table tests. Three different model configurations were considered, namely the non-isolated model (control model), the mono-isolated model (model with lead rubber bearings), and the combined isolated model (model with lead rubber bearings and viscous dampers). Scaled transformers and GISs were also installed on the model floors to consider the influence of the electrical equipment. Typical far field and near fault seismic waves, in this study the El Centro wave and the ChiChi wave, respectively, up to a PGA of 0.44 g were used as excitations. It was found that LRBs worked desirably for the RC model under the El Centro wave while less effective under the ChiChi wave. The acceleration responses (roof), the inter-story shear force (1F) and the inter-story drift (2F) were reduced by use of the LRBs at most by 21%, 51% and 26%, respectively, with respect to the non-isolated model under the El Centro wave. However, under the ChiChi wave irregular torsional behavior was observed and the isolation layer displacement reached 88% of the limit value. Combined use of LRBs and VDs effectively reduced the seismic responses of the RC model under the ChiChi wave. In particular, the isolation layer displacement was reduced by 15% and the torsional displacement ratio was reduced to less than 1.15, with respect to the model with LRBs only. Considerable equipment-structure interaction was found in the RC indoor substations and increased the acceleration and the displacement responses by up to 21% and 22%, respectively, given the position and mass of the equipment in this study. Besides, the LRBs and VDs were found to be effective to reduce the equipment-structure interaction.

Ferroelastic phase transitions in three new layered perovskites: (3-XC6H5CH2CH2NH3)2[CdCl4] (X = F, Cl, and Br)

Two-dimensional organic-inorganic hybrid ferroelastics with high-temperature reversible phase transitions are very rare and have become one of the research hotspots in the field of ferroelastic materials. Herein, we report three new layered organic-inorganic hybrid perovskites based on halogen-substituted phenethylaminium, (3-XC6H5CH2CH2NH3)2[CdCl4] (X = F (1), Cl (2) and Br (3)). They undergo structural phase transitions at 376/371 K, 436/430 K, and 421/411 K, respectively, between the isomorphic high-temperature phases (space group I4/mmm, Z = 2) and different room-temperature phases with the reduced structural symmetries, i.e., P21/a (Z = 2) in 1, P1¯ (Z = 4) in 2, and P21/a (Z = 4) in 3, respectively. These ferroelastic transitions arise from the order-disorder transition of organic cations together with the synchronous displacement of inorganic layers, accompanying with ferroelastic spontaneous strains of 0.16, 0.13 and 0.12 for 1−3, respectively. By enriching layered perovskite ferroelastics based on halogen-substituted cations, this work provides important clues for exploring new ferroic materials based on hybrid crystals.

Complex-tensor theory of simple smectics

Matter self-assembling into layers generates unique properties, including structures of stacked surfaces, directed transport, and compact area maximization that can be highly functionalized in biology and technology. Smectics represent the paradigm of such lamellar materials — they are a state between fluids and solids, characterized by both orientational and partial positional ordering in one layering direction, making them notoriously difficult to model, particularly in confining geometries. We propose a complex tensor order parameter to describe the local degree of lamellar ordering, layer displacement and orientation of the layers for simple, lamellar smectics. The theory accounts for both dislocations and disclinations, by regularizing singularities within defect cores and so remaining continuous everywhere. The ability to describe disclinations and dislocation allows this theory to simulate arrested configurations and inclusion-induced local ordering. This tensorial theory for simple smectics considerably simplifies numerics, facilitating studies on the mesoscopic structure of topologically complex systems.

Mathematical modeling for experimental data to investigate the convective heat transfer in non‐Newtonian nanofluid's flow over a thin needle

AbstractThe flow of homogeneous non‐Newtonian nanofluid over a horizontal moving thin needle is studied through experimental data‐based mathematical approach. Experimental data is collected for nanofluids which are prepared by spreading the SiO2, MgO, and TiO2 nanoparticles with correspondingly diameters (20–30 nm, 60–70 nm), (20, 40 nm), and (30, 50 nm) at volume fractions (5%–20%) in ethylene glycol (EG). The rheological power‐law model of viscosity is employed on the current experimental data to govern the co‐relation expression and is further used in heat and mass flow equations. The problem is reduced to ordinary differential equations by employing similarity conversion and then numerically solved. The influence of various volume fractions and diameter of nanoparticles on the distribution of velocity and temperature are discussed through the graphical results. Moreover, velocity and thermal boundary layer thicknesses, momentum and displacement thickness, skin friction coefficient, and Nusselt number are also studied in detail and displayed graphically. The results indicate that enhancing nanoparticle volume fraction causes the decline in velocity profile and rise in temperature profiles. On the contrary, the velocity is amplified and temperature is reduced with enhancing the diameter of the nanoparticle. Newtonian model for nanofluid is not valid in all cases. So, a non‐Newtonian model is applied for nanofluid flow that follows the experimental behavior in the current study. This experimental based model has not investigated before.

DFT＋U calculations on [formula omitted](100) surface: thermodynamic stability and polarity compensation

Employing the DFT+U framework we investigate the thermodynamic stability of U3O8(100) surface. The most stable structure is predicted to gradually turn from the under-stoichiometric 06- to the over-stoichiometric 56-slab as the oxygen chemical potential increases, showing a continuous surface oxidation process. Oxygen atoms are found to always firstly adsorb on the lower oxidized U ions. Due to the polarity compensation, significant modification of surface charge presents on considered terminations, which is transferred via both U-5f and O-2p states, implying the nature of U3O8 as an intermediate state between the Mott–Hubbard and charge-transfer materials. It is also shown that the displacement of the outmost U6O10 layer and the surface energy are strongly related to the redistribution of surface charge. The static effect between charged layers is the major factor which influences the layer displacement. The increase in surface energy is shown to be roughly linearly dependent on the amount of the surface charge transfer.

Seismic demand estimation of isolated buildings with nonlinear bearings subjected to linear response spectra

Response spectrum analysis is a commonly used method for the seismic design of linear structures with fixed bases since the seismic input is normally provided in terms of the response spectrum in many codes. This study proposes a more generalized response spectrum method for the seismic design of three-dimensional isolated structures. Firstly, the theory basis of this method is derived in the framework of the random vibration theory. The equivalent parameters of each bearing are expressed in terms of the statistics of the displacement amplitude. Then, the complex mode theory is introduced into this method to consider the effect of the nonclassical damping resulting from the isolation layer. Finally, an iterative analysis procedure is presented, which combines the equivalent linearization with the complex mode theory. Moreover, the convergence and applicability of this method are discussed in detail. The parameter analyses show that the relative error of the base shear of the superstructure estimated by using this method is within 10% compared with that of the nonlinear time history analysis. In addition, a benchmark base-isolated structure is used as a numerical example to examine the effectiveness of the proposed method. The results show that the iteration is convergent and computationally efficient. The results also show that the maximum relative errors of the predicted isolation layer displacement, the inter-story drift of the bottom floor and the absolute acceleration of the top floor are 9.5%, 3.9% and 18.9%, respectively, by comparing them with the nonlinear time history analysis, while these responses are underestimated by 9.8%, 25.9% and 40.2%, respectively, when using the classical complete quadratic combination (CQC) method that neglects the nonclassical damping effect. Although in this study the proposed approach mainly focuses on isolated structures, in essence, this approach can also be applied to inelastic structures or structures with nonlinear dampers.

Mathematical modeling of changes in density of near-surface ionic layers in semi-infinite metals. Equations for displacements of ionic layers

In this work, we propose a mathematical model for describing the change in the ion density of the near-surface ionic layers of a semi-infinite metal. Through averaging over the subsystem of conduction electrons, we obtain in the adiabatic approximation an effective Hamiltonian of the ionic subsystem of a semi-infinite metal, which models the effect of the "metal–vacuum" separation surface on the structure of the near-surface ionic layers. We calculate the free energy of such a model and, by its minimization, obtain an equation for finding the displacements ξm of the ionic layer m. We show that in the absence of an inhomogeneous distribution of the electronic subsystem ξm≡0.

Solution of the plane problem of the theory of elasticity on bending of an articulated fixed multilayer panel with a circular axis

This article suggests a method for the solution of the plane problem of the theory of elasticity on the bending of an articulated fixed multilayered panel with a circular axis based on the polynomial approximation of displacements through the thickness of the panel. In contrast to the known solutions of this problem, in this case the coefficients of the approximating polynomials are calculated from the equilibrium conditions and equality of displacements and transverse stresses at the transition across the layer interface and solution of differential equations of equilibrium at several points through the thickness of the layers. Finally, the problem is reduced to the solution of a system of linear equations with respect to the coefficients of approximating polynomials. The validity of the method is confirmed by comparing the results of calculations obtained on its basis and the results obtained with the help of the reference finite element model. The problem is solved in two stages. At the first stage, for a single-layer panel, we investigate the dependence of the polynomial degree on the ratio of the average panel radius to its thickness and the ratio of the transverse shear modulus to the modulus of longitudinal elasticity, which characterize the nonlinearity of displacements. At the second stage, on the example of a three-layered panel, we consider the application of the proposed method for the calculation of multilayered panels. In such case, the results obtained at the first stage are used in selecting the initial degree of polynomials approximating displacements through the thickness of layers. The method proposed in this article makes it possible to obtain an analytical solution without introducing simplifying hypotheses about the nature of displacement of layers and their elastic characteristics in a wide range of variation in geometric dimensions and elastic characteristics of panel layers. This method can be used both for verification of numerical models and for carrying out strength calculations of multilayer panels.

Small atoms fall into bulk from non-close-packed metal surfaces?

Surface rippling has been observed when atoms of X and A are mixed on A substrate surface. The rippling amplitude has been estimated using hard sphere models. We present a gedanken experiment predicting a penetration of small atoms into bulk through the (100) surface. To understand how electronic effects alter this picture, we investigate the surface rippling of X/A(100) from first-principles, assuming X= H to Bi except for noble gases and A= Cu, Ag, and Au. We show that small atoms (such as H, C, N, O and F) attract electrons from the substrate due to the large electronegativity, which prevent them from passing through voids in the (100) surface. Application of machine learning in predicting rippling amplitude also suggests an importance of the electronegativity. The behaviors of small atoms are further explored by studying (i) lateral displacements of the first layer in the A substrate, (ii) a formation of the X dimer above, below, and across the first layer, and (iii) surface adsorption of X atom on the top, bridge, and hollow sites in Cu(100) surface. The present work provides an example to understand when atoms are not hard spheres.

Diagonal compression cyclic testing of unreinforced and reinforced masonry walls

Steel reinforced plasters (SRP) are a traditional strengthening solution of existing masonry structures. SRPs consist of a thin layer of cementitious mortar or concrete (jacket) that incorporates a steel reinforcing mesh tied to a series of steel bent connectors embedded in the underlying masonry. Despite the recent development of more innovative retrofitting methods, SRPs are still widely adopted because of their low costs and effectiveness in terms of improved performance. In the present paper, a comprehensive experimental program on brickwork masonry walls is presented. The results are intended as a contribution to the knowledge of in-plane behavior of masonry strengthened with SRPs. Unreinforced and plastered masonry walls were subjected to cyclic diagonal compression loading under displacement control. Different thicknesses of walls (2 and 3 wythes) and plasters (30 and 50 mm) were selected. The performances of the plastered and non-plastered specimens were analyzed and compared. The results showed that the SRPs increased considerably the performance of the walls in terms of both strength and deformation capacity. The plaster’s thickness had limited effects on the load carrying capacity of the walls, whereas it had a significant effect on their ductility. Finally, the connectors used to tie the steel mesh to the masonry walls played an essential role and avoided large out-of-plane displacements of the plaster layer after its detachment, thus preventing instability phenomena.

Dynamic Damage Quantification of Slab Tracks—Finite Element Models on Winkler Soil and Finite-Element Boundary-Element Models on Continuous Soil

Train passages over intact or damaged slab tracks on different soils were calculated by two methods. The finite element method (FEM) uses a Winkler soil under the track model by adding a thin “soil layer”. The combined finite-element boundary-element method has a continuous soil model that is included by the boundary element method. The basic results are the distributions of the track (rail, track plate, and base layer) displacements along the track for a single axle load. These solutions were superposed to a complete train load and transformed to time histories. The influence of track and soil parameters was analysed. The main interest was the influence of the track damage. A gap between the track plate and base layer of different lengths was studied for changes in amplitudes and widths of deflection. A best fit to measured track displacements was found so that the track damage could be identified and quantified. The FEM model with the Winkler soil cannot be fitted to the amplitude and width with the same soil parameters. Therefore, the FEBEM model is preferable for these railway track problems.

Peculiarities of calculating the diameter of the hole for setting the thread-forming part

The effectiveness of technologies is determined by the total technical effect obtained from their implementation. One of the ways to improve technology efficiency indicators is the introduction of assembly-thread-forming processes based on the use of thread-forming fasteners in product designs. Thread-forming screws, pins, bushings are screwed into smooth holes and form a threaded profile by cutting or deformation. The reduction in labor intensity is achieved by eliminating the operation of preliminary threading, and the resulting connections have high operational and technical indicators. In the production of electronic equipment and devices, where, according to technical requirements, the formation of chips is undesirable, thread-extruding screws are used. Despite the advantages of self-tapping screws, their widespread use is restrained by several disadvantages: the strength of the connection using screws is lower than in the connection using a stud or bolt, screws with an increased pitch have unsatisfactory locking performance, with a diameter of more than 10 mm torque instability and thread profile deformation are observed. Improving the quality of threaded joints by ensuring the optimal size of the hole for threading is the topic of this publication. The calculation of the setting diameter for thread-forming parts with a large step has its own characteristics and must be decided taking into account friction, strength and tolerance. The main causes of surface defects in the installation of thread-forming fasteners are those related to geometry - rolling in a filled contour, which leads to an axial displacement of the surface layers of the metal. Determining the optimal value of the diameter of the hole for screwing the thread-forming part, on the one hand, as large as possible, but not more than the permissible value, is the purpose of this work. The nomenclature of thread-forming fastening elements is constantly expanding, while the ratio of the height of the profile to the step is a variable value even within the limits of one standard. Therefore, the calculation method should be universal, taking into account the conditions of friction, strength, tolerances. Thread forming processes are described as plane deformation processes. Physically, the mechanism of plastic deformation of metals is presented in the form of shifts in planes where the tangential stresses have reached their maximum value. For plane deformation, the trajectories of maximum tangential stresses in two orthogonal directions are described by slip lines, or characteristics. The slip line method allows you to calculate contact stresses and deforming forces, fully determine the fields of stresses and velocities in the sections of deformable metal, and also analyze local phenomena, which are usually fundamental in solving technological problems. The characteristics of plane plastic deformation allow you to find a solution using a graphical method. The use of this method allows you to determine the appearance of the slip line field, or its geometric characteristics, which establish the relationship between the maximum tangential stress and normal hydrostatic pressure, i.e., the deforming force, as well as determine the appearance and geometric parameters of the formed profile, the height of which is limited by the permissible amount of overflow of the profile. Analyzing the geometric parameters of the deformation zone of the threaded turn of the part, the diameter of the hole for the thread-forming fastening part was theoretically justified. The methodology of this calculation is implemented in the form of software and mathematics. These recommendations are related to the geometric parameters of the end part of the self-tapping screw. The results of the work will improve the quality of the connection with the thread-forming fastening part due to the optimization of the diameter of the hole of the part. On the basis of solving the problem of the plasticity theory about the immersion of the indenter into the rigid-plastic region and the analysis of the plastic zone in the region of the largest deformations, the geometric parameters and the appearance of the formed profile are established. The method of using sliding lines allows you to calculate and analyze the geometry visually, to observe the change in the shape of the deformable profile from the ratio of the height of the profile to the pitch of the thread, the material and the coefficient of sliding. This visualization allows you to choose a value of filling the profile even greater than one, when a sufficiently large size of the “crater” of the thread does not allow the profile to overflow. This makes it possible to increase the height of the thread profile and the contact area, as well as to expand the tolerance for the hole in the part. As a result, we have an increase in the strength of the connection and the reliability of the assembly process.

Management of the longwall face advance on the stress-strain state of rock mass

Purpose is to study influence of a longwall face advance on the geomechanical situation in the neighbourhood of a mining site based upon determination of changes in standard and critical subsidence of the immediate roof rocks. Methods. To study a geomechanical situation in the neighbourhood of a mining site the authors have applied software product GeoDenamics Lite developed at Dnipro University of Technology. The software product relies upon a calculation procedure of stress-strain state of rocks by Professor O.V. Savostianov. Expediency of the software selection is based upon the supported control and adaptation of a coal mining technique to changes in geodynamic stress fields in the anisotropic rock-coal medium impacting temporal and spatial changes in the technological parameters. Findings. The basic problems have been singled out connected with certain changes in a longwall face advance. For the first time, an analytical scheme of tangential stresses within the immediate roof rocks has been developed for Lisova mine of SE Lvivvuhillia under the conditions of coal seam mining by means of the paired longwalls which makes it possible to determine both physical and geometrical parameters of standard loads within the formation. Originality. Dependencies of temporal and spatial changes in subsidences and horizontal displacements of rock layers of the immediate roof have been defined being 5.2 m for the upper rock pack and 3.9 m for the lower pack if the longwall longwall face advance is 1.9 up to 4.8 m/day. Both physical and geometrical parameters of the reference pressure have been defined as well as the parameters of lower sandstone pack in the process of the main roof subsidence. Impact of the extra pressure forces on the immediate roof rocks has been analyzed at the moment of critical lowerings of the immediate roof rocks. In this context, standard loading from the overlying formation in addition to tangential stresses in the roof result in rock failure due to vertical cracks above a longwall face. Practical implications. The engineering methods have been developed making it possible to identify impact parameters of a longwall face advance on the geomechanical situation in the neighbourhood of a mining site. In future, it will help forecast changes in the reference pressure around a longwall face while preventing emergency settlement of the powered support.

Structural smoothing on mixed instantaneous phase energy for automatic fault and horizon picking: case study on F3 North Sea

Today, with the development of 3-D studies and the increase in seismic data volume, there is a growing need to expand interpretation techniques for achieving higher speed and accuracy of interpretation tasks. Determining seismic faults and horizons is vital to accomplish the process as one of the essential stages of data interpretation. With the recent development of computational methods in seismic interpretation and their benefits, different approaches have been promoted. The specialist can make the understanding much faster with higher accuracy. In this research, a fully automated dual horizon and fault selection approach in the presence of semi-vertical faults is presented using a structural smoothing condition. Geological faults make it challenging to map sedimentary layers appropriately which is targeted for review in this work. Unlike Image processing techniques that determine the location of faults only, the proposed approach gives the benefit of the estimated fault displacement. In this method, faults are modeled as a displacement vector field. Despite traditional methods (such as similarity and coherence), in this method, the vector field of the estimated fault displacement determines the displacement and its location. This vector field can be used for auto-determination of fault-related layers displacement. As a result, automatic horizon picking in the presence of such faults is possible, thereby simplifying the mapping of sedimentary layers.

Electromagnetic field generated by acoustic wave scattering at a poroelastic inclusion located in a fluid

The study of elastic wave propagation in poroelastic media is of considerable scientific interest because of some effects that do not appear in monophasic elastic or viscoelastic media. In the case of interconnected pores containing a moving fluid in a poroelastic medium, there exist two types of longitudinal waves. In heterogeneous porous media, the energy of elastic oscillations is redistributed due to mutual transformation of elastic waves of different types at the inclusion boundaries. The filtration flow that appears there results in the case of polar fluids in a displacement of electric double layers at the pore boundaries, and, as a consequence, in generation of an electromagnetic field.We consider the problem of the scattering of an elastic wave by a spherical poroelastic inclusion in a fluid. The solution was obtained for sufficiently low frequencies so that the dispersion of the elastic wave on individual grains of the porous media may be neglected and the averaged equations of the mechanics of continuous media (at the so-named mesoscale) may be used. In order to describe the elastic wave propagation, we have used the Pride system of electrokinetic equations. For the solution of our problem, we have applied the decomposition of the potentials of acoustic and electromagnetic waves into spherical harmonics. We have obtained the dependencies of the generated electromagnetic field on the inclusion porosity and the fluid properties in pores. The results were obtained for fully open pore interface at the inclusion boundary.

Smectic layering: Landau theory for a complex-tensor order parameter

Composed of microscopic layers that stack along one direction while maintaining fluid-like positional disorder within layers, smectics are excellent systems for exploring topology, defects and geometric memory in complex confining geometries. However, the coexistence of crystalline-like characteristics in one direction and fluid-like disorder within layers makes lamellar liquid crystals notoriously difficult to model—especially in the presence of defects and large distortions. Nematic properties of smectics can be comprehensively described by the -tensor; however, lamellar order can exist independent of nematic alignment. To capture the features of the smectic layering alone, we develop a phenomenological Landau theory for a complex-tensor order parameter , which is capable of describing the local degree of lamellar ordering, layer displacement, and orientation of the layers. This theory accounts for both parallel and perpendicular elastic contributions. In addition to resolving the potential ambiguities inherent to complex scalar order parameter models, this model reduces to previously employed models of simple smectics, and opens new possibilities for numerical studies on smectics possessing many defects, within complex geometries and under extreme confinement.

In-Situ/Operando X-Ray CT Characterisation of Lithium-Ion Pouch Cells during Thermal Failure

The safety of concerns of lithium-ion batteries continues to be a prevalent obstacle toward their widespread application from vehicle electrification to space exploration. Aside from the highly oxidising and reducing electrode materials, their safety is compounded by an inherent drawback of poor heat dissipation [1]. High-speed imaging with in-situ/operando X-ray CT has been used extensively to study various lithium-ion battery safety features and failure mechanisms [2][3], including thermal failure [4]. However, these are exclusively using synchrotron X-ray sources which are limited in terms of both access and data recording capabilities: high frame rates require the data collection window to be restricted to a few seconds. During lithium-ion battery failure, there are several changes to a cell structure leading up to thermal runaway (TR) which can take minutes, and as a result are often missed. Here, we present an instrument that simulates thermal failure for lab-based radiography at slower imaging speeds and longer recording lengths, which has been validated by correlative synchrotron measurements. The failure mechanisms within a fully charged (100 % SOC, 4.2 V) commercially available LiCoO2 cathode and graphite anode pouch cell (651628-2C, AA Portable Power Corp) rated at 210 mAh are investigated.Three samples are studied using lab-based radiography at a frame rate of 3.75 fps with a 16.1 µm pixel resolution and, for comparison, an additional three samples are studied using synchrotron X-ray sources at a higher speed of 20,000 fps with a 13.3 µm pixel resolution. For the six samples investigated, the total time taken from a start temperature of 80 °C to TR is approximately 20 minutes and the onset temperatures for TR are recorded within the range of 196 °C to 210 °C. The beginning of the TR event (defined as a sample temperature increase greater than 15 °C s-1), where the effects to the electrode structure are the most catastrophic, lasts for approximately 1 s. Operando radiographic images during this event reveal that the structural displacement of electrode layers begins at the centre of the cell and propagates outwards in a wave-like motion. The electrode displacement, as a result, is quantified by cross-correlating Gabor signals and spatiotemporal mapping [5] in both types of datasets. For the lab-based radiography, data is recorded from the start temperature to TR (lasting approximately 20 minutes), and reactions such as the electrolyte decomposition, ca. 105 °C, and separator melting, ca.130 °C are characterised in the context of electrode deformation and gas evolution. Investigations of pre- and post-failure 3D X-ray CT images further verify the uniformity of the pristine (or pre-failure) cell assembly as well as the estimated post-failure behaviour between samples. Finally, by comparison with correlative synchrotron measurements, the instrument for inducing thermal failure for lab-based X-ray CT is proven to be a viable and more accessible method to investigate thermal failure within a 210 mAh pouch cell. While synchrotron data has a higher-speed imaging advantage, it is limited to only recording the short TR event at a high temporal resolution. Whereas continuous imaging in lab-based radiography has the benefit of measuring the slower architectural changes taking place up to TR, albeit at a marginally lower spatial resolution.

Study on Inlet Flow Field Structure and End-Wall Effect of Axial Flow Pump Impeller under Design Condition

The existing experimental technology cannot accurately and quantitatively measure the flow field structure and the wall boundary layer displacement effect in the axial flow pump. Based on SST k-ω turbulence model, a three-dimensional unsteady numerical simulation of the whole flow field of an axial flow pump was presented at the designed operating point to overcome the weakness of traditional measurement methods in measuring the flow field of the axial flow pump. The flow field structure of the axial flow pump inlet was studied quantitatively and the result was compared with the theoretical design value. It was found that there is an obvious impeller rotation effect and end-wall effect in the flow field of the axial flow pump inlet. The distribution law of the impeller inlet flow field and the crowding coefficient caused by the wall boundary layer were obtained. The pump inlet measurement point in the experiment and calculation domain inlet in the simulation should be kept at a distance of more than 0.5 Ds away from the impeller inlet to eliminate the influence of the impeller rotation effect. Through contrastive analysis, it was found that there is an obvious difference between the calculated value and the design value of the flow field structure due to the end-wall effect. The crowding coefficient should be taken into account when designing an axial flow pump. This study has certain reference significance for further understanding the flow field structure at the inlet of the axial flow pump impeller and improving the design theory of the axial flow pump.

Розподіл напружень у клейовому шарі залежно від форми краю з'єднання

Adhesive lap joints are widely used in many ways of modern technology, particularly in aircraft and aerospace, because to the fact that adhesive joints don't break the integrity of the composite structure. Moreover, adhesive joints ensure the transfer of the loads from the surface of the structure and have low weight, excellent tightness, etc. Mathematical models of the stress-strain state in the adhesive joints are based on the certain hypotheses of the distribution of stresses and displacements in the adhesive layer and in the bearing layers. As a rule, hypotheses about the uniform distribution of shear and normal stresses in the adhesive layer are currently used in articles. The stress state of the joint in the regular area, that is, the area distant from the edge of the adhesive layer, is well described by mathematical models based on these hypotheses. However, in a neighborhood of the edge of the joint, the adhesive layer is in a complex stress state and various factors affect the stress state, including the boundary conditions at the outer edge of the adhesive layer. The research on stresses in a neighborhood of the joint area is carried out in the article. The influence of the stress in the adhesive layer of such designed solutions, such as chamfers on the edges of the bearing layers and glue callus, is shown. The designing solutions, such as the creation of a chamfer on the edge of the bearing layer and the callus of excess glue, can reduce stress at the edge of the joint is also shown in the article. The chamfer in the bearing layer on the side facing the adhesive layer on the one hand allows to reduce the rigidity of the bearing layer, on the other hand to increase the compliance of the adhesive layer. However, the entire space between the outer layers must be filled with adhesive. Thus, the presence of a chamfer and callus of glue significantly reduces the maximum stresses in the adhesive layer, and thereby increases the strength of the structure.

Measurement of the Inner Macular Layers for Monitoring of Glaucoma: Confounding Effects of Age-Related Macular Degeneration

To investigate the confounding effect of nonexudative age-related macular degeneration (AMD), specifically drusen and outer retinal atrophy, on the architecture and automated segmentation of the inner retinal layers as measured with OCT. Observational cross-sectional study. Two hundred sixty-three consecutive eyes with nonexudative AMD were identified through a retrospective chart review. Exclusion criteria were a diagnosis of glaucoma or glaucoma suspect, other retinal pathology affecting the macula, axial length > 26.5 mm or spherical equivalent less than -6 diopters, any other optic nerve or neurologic disorders, or poor image quality. Drusen were automatically segmented on macular OCT B-scans with a publicly available and validated deep learning approach. Automated segmentation of the inner plexiform layer (IPL)/inner nuclear layer (INL) boundary was carried out with the device's proprietary software. Quality of segmentation of the IPL/INL boundary as a function of drusen size and presence of inner retinal layer displacement in the area of macular pathology (drusen or atrophy). One hundred twenty-five eyes (65 patients) met the inclusion criteria. Drusen size varied between 16 and 272 μm (mean, 118 μm). Automated segmentation had a 22% chance of failure if the drusen height was between 145 and 185 μm and was most likely to fail with drusen heights above 185 μm. When drusen height was normalized by total retinal thickness, segmentation failed 36% of the time when the drusen to total retinal thickness ratio was 0.45 or above. Images were likely to show displacement of inner retinal layers with drusen heights above 176 μm and a normalized drusen height ratio of 0.5 or higher. Eighty-seven percent of images with outer retinal atrophy displayed incorrect segmentation. Outer retinal diseases can alter the retinal topography and affect the segmentation accuracy of the inner retinal layers. Large drusen may cause segmentation error and compression of the inner macular layers. Geographic atrophy confounds automated segmentation in a high proportion of eyes. Clinicians should be cognizant of the effects of outer retinal disease on the inner retinal layer measurements when interpreting the results of macular OCT imaging in patients with glaucoma.