Changes In Cross-sectional Shape Research Articles

Hydraulics of Time-Variable Water Surface Slope in Rivers Observed by Satellite Altimetry

The ICESat-2 and SWOT satellite earth observation missions have provided highly accurate water surface slope (WSS) observations in global rivers for the first time. While water surface slope is expected to remain constant in time for approximately uniform flow conditions, we observe time varying water surface slope in many river reaches around the globe in the ICESat-2 record. Here, we investigate the causes of time variability of WSSs using simplified river hydraulic models based on the theory of steady, gradually varied flow. We identify bed slope or cross section shape changes, river confluences, flood waves, and backwater effects from lakes, reservoirs, or the ocean as the main non-uniform hydraulic situations in natural rivers that cause time changes of WSSs. We illustrate these phenomena at selected river sites around the world, using ICESat-2 data and river discharge estimates. The analysis shows that WSS observations from space can provide new insights into river hydraulics and can enable the estimation of river discharge from combined observations of water surface elevation and WSSs at sites with complex hydraulic characteristics.

A global springback compensation method for manufacturing metallic seal ring with complex cross-section and submillimeter precision

The fabrication of complex thin-walled components with irregular cross-sectional geometries often necessitates multi-pass forming processes. The springback phenomena at the microscale level contribute significantly difficulty to the precise control of geometrical accuracy for such components. To achieve submillimeter precision control of micro features in metal seal rings, this research proposed a global springback compensation method to facilitate the attainment of the optimized surfaces of dies. Through the analysis of changes in cross-sectional shape, stress distribution and bending moment in the multiple stages, several partition points were set up to divide the cross-section into four zones. For a partitional control of the manufactured surface, the compensation magnitudes for each segment are determined by iteratively refining the compensation factors using the secant method. The iteration of compensation factors is based on the deviation of dimensions measured by finite element simulation, which greatly saves experimental costs. The experimental results indicate that the predictive dimensional alterations by the global compensation agree with the experimental ones exhibiting a maximum error of less than 3 %. Furthermore, the springback behavior during the unloading and trimming stages coupling caused a dimensional error of 14.9 % for the wave width and 8.3 % for the peak width. Following the application of coupled compensation through two iterations, a distinct decrease in the relative average errors of springback values for both part width and peak width, achieving reductions to 2.4 % and 0.6 %, respectively. Compared to the traditional single springback compensation technique, the global compensation strategy effectively mitigates the out-of-tolerance issues induced by the trimming process.

Precise 3D profile determination of high aspect ratio hole patterns by transmission small-angle X-ray scattering

The etching process of high aspect ratio (HAR) hole patterns on a wafer surface is a key step for fabricating new-generation semiconductor memory devices with vertically stacked structures. As the stacking number of these memory devices increases, it is getting more challenging to maintain the ideal etching profile of HAR holes. Therefore, detailed profile evaluation of these HAR holes is increasingly important. In this study, we have measured 4.2 μm deep holes by transmission small-angle X-ray scattering (T-SAXS) to determine the precise three-dimensional (3D) hole profile. By applying an improved 3D shape model for a hole, we successfully determined a hole profile whose cross-section parallel to the sample surface changes from elliptical to rectangular along its depth. This 3D profile measurement demonstrated that T-SAXS has sufficient sensitivity to evaluate a cross-sectional shape change along the depth of HAR holes.

The Temporal and Spatial Evolution of Magnetohydrodynamic Wave Modes in Sunspots

Through their lifetime, sunspots undergo a change in their area and shape and, as they decay, they fragment into smaller structures. Here, for the first time we analyze the spatial structure of the magnetohydrodynamic (MHD) slow-body and fast-surface modes in the observed umbrae as their cross-sectional shape changes. The proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques were used to analyze 3 and 6 hr Solar Dynamics Observatory/Helioseismic and Magnetic Imager time series of Doppler velocities at the photospheric level of approximately circular and elliptically shaped sunspots. Each time series was divided into equal time intervals to evidence the change in the shape of the sunspots. To identify the physical wave modes, the POD/DMD modes were cross-correlated with a slow-body mode model using the exact shape of the umbra, whereas the shape obtained by applying a threshold level of the mean intensity for every time interval. Our results show that the spatial structure of MHD modes are affected, even by apparently small changes in the umbral shape, especially in the case of the higher-order modes. For the data sets used in our study, the optimal time intervals to consider the influence of the change in the shape on the observed MHD modes is 37–60 minutes. The choice of these intervals is crucial to properly quantify the energy contribution of each wave mode to the power spectrum.

Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional Degeneration.

Tendon degeneration is typically described as an overuse injury with little distinction made between magnitude of load (overload) and number of cycles (overuse). Further, in vivo, animal models of tendon degeneration are mostly overuse models, where tendon damage is caused by a high number of load cycles. As a result, there is a lack of knowledge of how isolated overload leads to degeneration in tendons. A surgical model of synergist ablation (SynAb) overloads the target tendon, plantaris, by ablating its synergist tendon, Achilles. The objective of this study was to evaluate the structural and functional changes that occur following overload of plantaris tendon in a rat SynAb model. Tendon cross-sectional area (CSA) and shape changes were evaluated by longitudinal MR imaging up to 8 weeks postsurgery. Tissue-scale structural changes were evaluated by semiquantified histology and second harmonic generation microscopy. Fibril level changes were evaluated with serial block face scanning electron microscopy (SBF-SEM). Functional changes were evaluated using tension tests at the tissue and microscale using a custom testing system allowing both video and microscopy imaging. At 8 weeks, overloaded plantaris tendons exhibited degenerative changes including increases in CSA, cell density, collagen damage area fraction (DAF), and fibril diameter, and decreases in collagen alignment, modulus, and yield stress. To interpret the differences between overload and overuse in tendon, we introduce a new framework for tendon remodeling and degeneration that differentiates between the inputs of overload and overuse. In summary, isolated overload induces multiscale degenerative structural and functional changes in plantaris tendon.

A novel vibration analytical model for thin-walled box-like long cylindrical structures combining elastic plates and straight and curved beams

This paper proposes a novel analytical model for elastic vibrations of thin-walled box-like long cylindrical structures, commonly observed in railway vehicle carbodies, aircraft, and buses. Here, we focus on railway vehicle carbody, where three-dimensional elastic vibrations are a significant problem for improving ride quality. The carbody is modeled as a box-like structure consisting of elastic plates and beams. The condition to connect those structural members is satisfied by introducing artificial springs at their joints. From observations of some actual carbody's elastic vibration modes, it has already been found that the relative vertical deformation between the roof and floor interacts with lateral deformation of side structures. To express this three-dimensional deformation simply, the authors introduce curved elastic beams as pillars in the side structures in this study; therefore, the newly proposed model is called the curved box model. The free vibration of the curved box model has been investigated in this paper by applying the Ritz method to derive the eigenvalue problem. The modal characteristics (natural frequencies and mode shapes) of elastic vibrations are calculated. The vibration analysis procedure is validated by comparing those results with those obtained from a finite element model. As some numerical examples, the effects of cross-sectional shape changes on the natural frequencies of elastic vibration modes are presented.

THE STRENGTH OF UNDERGROUND HORIZONTAL WORKINGS OF ELLIPTICAL CROSS-SECTION SHAPE SUBJECTED TO ALL-ROUND UNIFORM PRESSURE

The paper presents the results of a study to determine the stress state on the contours of underground workings, the cross-section of which has the form of an ellipse with a fixed value of the large semi-axis. For workings of this type, at different values of the ellipse parameter, the permissible depths of laying and the values of uniform pressure at the points of their contours are determined, at which normal tangential stresses do not exceed the tensile and compressive strength limits of the host rock. Based on the strength condition used in the work, the values of the permissible depths of the workings are calculated for varying values of uniform pressure applied at the points of the workings contours and the specified values of the lateral expansion coefficient of the rock. The permissible values of the stretching uniform pressure at the points of the contours of the elliptical shape of the cross-section with a change in the depth of laying, the specified values of the lateral expansion coefficient of the rock and the ellipse parameter are given. In addition, the paper presents formulas on the basis of which the problem of stress distribution at the points of contours whose cross-section has the shape of an ellipse with a fixed value of the large semi-axis is considered. It is established that when the intensity of the stretching uniform pressure applied at the points of the contours of the workings of an elliptical cross-section shape changes, and the specified values of the ellipse parameter, the depth of the workings and the magnitude of the lateral expansion coefficient of the host rock, sections of the contours on which tensile and compressive stresses act are highlighted. When changing the depths of the workings of the elliptical cross-section shape, sections of contours are identified on which tensile and compressive stresses act at given values of the ellipse parameter, the intensity of the stretching uniform pressure applied to the points of the contours, and the values of the lateral expansion coefficient of the rock.

Comparison of wind turbine blade structural models of different levels of complexity against experimental data

As the design process of a wind turbine blade is highly iterative, one needs to perform the same calculations several times. During that process, the kind of structural model that should be used must be chosen carefully, trying to obtain a good compromise between precision and model setup and computational time. This paper compares four different blade structural models having different levels of complexity. These models are compared to each other and also with experimental results with respect to their abilities to analyze blade cross-sectional properties, natural frequencies, deflection, strains, buckling strength, and composite strength. This comparison shows that even if the 3D shell finite element model is the more precise and is the only one that can manage the regions of the blade where the cross-sectional shape changes quickly, the strength of material based models gives accurate results. Even the simpler model, based on blade shape simplification, gives conservative and accurate results at a very low computational cost.

Accurate measurement of elasticity of the radial artery wall considering changes in cross-sectional shape of artery caused by pushing pressure applied by ultrasound probe

For the early diagnosis of atherosclerosis, our group developed an ultrasound probe that can simultaneously measure blood pressure and vessel diameter at the same position. However, because the developed probe requires the blood vessel to be deformed by pushing to measure the blood pressure, it affects the estimation of the vessel’s elastic modulus. In the present study, we derived a series of equations to estimate the elastic modulus of a blood vessel considering the pushing pressure applied by the ultrasound probe and the resultant deformation of the blood vessel. The validity of the proposed method was verified by numerical calculations, and then the method was applied to in vivo measurements. The proposed method resulted in fewer variations in the elastic modulus estimates with different pushing pressures compared with the conventional method.

Поперечный изгиб заготовки прямоугольного сечения при больших пластических деформациях

The technological operation of bending is widely used in the manufacture of various parts — both rod parts, for example, springs of various types, and shell parts, for example, shells and bottoms of petrochemical apparatuses, ship hulls, automobiles, etc. The maximum plastic strains that arise in this case vary over a wide range and can reach quite large values, significantly exceeding the elastic strains. Regardless of the maximum deformation levels, residual stresses occur in the product, affecting its performance. The study of free three-point bending of a workpiece with a rectangular cross section was carried out at different ratios of the radius of the punch contacting cylindrical surface to the height of the workpiece as well as at different ratios of the width to the height of the workpiece. The workpiece material is low-carbon steel with a real (not approximated) deformation diagram. Stress state, cross-sectional shape change and residual stresses are numerically investigated using the finite element method.

Sensitivity Analysis of Dynamic Response by Change in Excitation Force and Cross-sectional Shape for Damped Vibration of Cantilever Beam

Sensitivity Analysis of Dynamic Response by Change in Excitation Force and Cross-sectional Shape for Damped Vibration of Cantilever Beam

Double diaphragm forming simulation using a global-to-local modelling strategy for detailed defect detection in large structures

A global-to-local modelling strategy is presented based on a sub-modelling approach to predict the formation of macroscale defects in bi-axial non-crimp fabric (NCF) during double diaphragm forming (DDF). A full-scale global simulation is initially performed using a coarse membrane element mesh (5 mm edge length) to locate areas containing potential defects. Refined local simulations are subsequently performed using high a fidelity shell-element mesh (1 mm edge length) to explicitly predict the shape of forming induced defects in these areas, using boundary conditions derived from the global simulation. The methodology is validated by forming a fabric blank over a generic geometry comprising local changes in cross-sectional shape, in order to invoke forming induced defects in a controlled manner. The defective areas predicted by the simulation agree well with the locations observed from the forming experiments, including the shape and length of surface visible defects such as fabric wrinkling and bridging. The CPU time for this two-stage approach is shown to be approximately 13% compared to the CPU time required for the high fidelity full-scale model for the same geometry.

Competing anticlastic and piezoelectric deformation at large deflections

In bending of a purely elastic beam or plate, it is well established that the cross-sectional shape changes character with decreasing bending radius-of-curvature and that the transition can be characterized by the Searle parameter. In a piezoelectric structure, the cross-sectional deformation is affected by the opposite anticlastic and electromechanical bending curvatures. The behavior is consequently more complicated and it is an open question how the cross-sectional shape develops with increasing bending. In this paper, analytical solutions are used to study the cross-sectional deformation of piezoelectric cantilever-actuators taking both anticlastic and electromechanical bending effects into account. We consider unimorph and bimorph actuators. In the case of electrical actuation, as for the purely mechanical case, we find that the Searle parameter is an important parameter characterizing the shape of the cross-section. A load scaling rule gives a criterion for fixed cross-section-deflection for different actuator widths. Using this scaling rule, the Searle parameter is kept unchanged. The analytical results are verified by non-linear finite element analysis using electric potential and mechanical moment as applied loads.

Numerical study for the improvement of bead spreading architecture with modified nozzle geometries in additive manufacturing of polymers

Purpose This paper aims to develop a numerical model of bead spreading architecture of a viscous polymer in fused filament fabrication (FFF) process with different nozzle geometry. This paper also focuses on the manufacturing feasibility of the nozzles and 3D printing of the molten beads using the developed nozzles. Design/methodology/approach The flow of a highly viscous polymer from a nozzle, the melt expansion in free space and the deposition of the melt on a moving platform are captured using the FLUENT volume of fluid (VOF) method based computational fluid dynamics code. The free surface motion of the material is captured in VOF, which is governed by the hydrodynamics of the two-phase flow. The phases involved in the numerical model are liquid polymer and air. A laminar, non-Newtonian and non-isothermal flow is assumed. Under such assumptions, the spreading characteristic of the polymer is simulated with different nozzle-exit geometries. The governing equations are solved on a regular stationary grid following a transient algorithm, where the boundary between the polymer and the air is tracked by piecewise linear interface construction (PLIC) to reconstruct the free surface. The prototype nozzles were also manufactured, and the deposition of the molten beads on a flatbed was performed using a commercial 3D printer. The deposited bead cross-sections were examined through optical microscopic examination, and the cross-sectional profiles were compared with those obtained in the numerical simulations. Findings The numerical model successfully predicted the spreading characteristics and the cross-sectional shape of the extruded bead. The cross-sectional shape of the bead varied from elliptical (with circular nozzle) to trapezoidal (with square and star nozzles) where the top and bottom surfaces are significantly flattened (which is desirable to reduce the void spaces in the cross-section). The numerical model yielded a good approximation of the bead cross-section, capturing most of the geometric features of the bead with a reasonable qualitative agreement compared to the experiment. The quantitative comparison of the cross-sectional profiles against experimental observation also indicated a favorable agreement. The significant improvement observed in the bead cross-section with the square and star nozzles is the flattening of the surfaces. Originality/value The developed numerical algorithm attempts to address the fundamental challenge of voids and bonding in the FFF process. It presents a new approach to increase the inter-bead bonding and reduce the inter-bead voids in 3D printing of polymers by modifying the bead cross-sectional shape through the modification of nozzle exit-geometry. The change in bead cross-sectional shape from elliptical (circular) to trapezoidal (square and star) cross-section is supposed to increase the contact surface area and inter-bead bonding while in contact with adjacent beads.

2Pb5-10 Elasticity measurement of radial artery wall considering the change in cross-sectional shape of vessel caused by pushing pressure from ultrasound probe

2Pb5-10 Elasticity measurement of radial artery wall considering the change in cross-sectional shape of vessel caused by pushing pressure from ultrasound probe

The Morphology and Mechanical Properties of PrDyFeCoB Microwires

The PrDyFeCoB microwires, whose diameter and cylindricity are controlled via rotation speed of a cooling cylinder and depend on time of droplet solidification on it, are obtained via extraction of a hanging melt droplet. The variations in cooling mode of a melt droplet lead to a change in cross-sectional shape from completely cylindrical to semicircle, crescent, and almost flat plate one. We found that the cooling mode affects not only the morphology, but also the mechanical properties, which are different for microwires of d-ifferent shapes, and changes the microhardness and Young’s modulus of different surfaces of the same microwire.

Significance of the Microfluidic Flow Inside the Organ of Corti.

We study the vibration modes of a short section in the middle turn of the gerbil cochlea including both longitudinal and radial interstitial fluid spaces between the pillar cells (PC) and the sensory hair cells to determine the role of the interstitial fluid flow within the organ of corti (OoC). Three detailed finite element (FE) models of the cochlear short section (CSS) are studied. In model 1, the CSS is without fluids; model 2 includes the OoC fluid, but not the exterior scalae fluids; and model 3 is the CSS with both scalae and OoC fluids. We find that: (1) the fundamental mode shape of models 1 or 3 is similar to the classical basilar membrane (BM) bending mode that includes pivoting of the arch of corti, and hence determines the low frequency vibrational mode shape of the cochlea in the presence of the cochlear wave. (2) The fundamental mode shape of model 2 is characterized by a cross-sectional shape change similar to the passive response of the cochlea. This mode shape includes a tilting motion of the inner hair cell (IHC) region, a fluid motion within the tunnel of corti (ToC) in the radial direction and along the OoC, and a bulging motion of the reticular lamina (RL) above the outer hair cell (OHC). Each of these motions provides a plausible mode of excitation of the sensory hair cells. (3) The higher vibrational modes of model 1 are similar to the electrically evoked response within the OoC and suggests that the higher vibrational modes are responsible for the active response of the cochlea. We also observed that the fluid flow through the OoC interstitial space is significant, and the model comparison suggests that the OoC fluid contributes to the biphasic BM motion seen in electrical stimulation experiments. The effect of fluid viscosity on cilium deflection was assessed by performing a transient analysis to calculate the cilium shearing gain. The gain values are found to be within the range of experimentally measured values reported by Dallos et al. (1996, The Cochlea, Springer-Verlag, New York).

Determination of indications for the choice of the preparation method of the root canal system with rotation and reciprocation instruments

Compliance with the algorithms of endodontic treatment in most cases ensures the quality of treatment. However, real, long-term and sometimes immediate results that occur in clinical practice are not always successful. In general, the main reason for the unfavorable outcome of dental treatment is an incomplete sanitation of the root canal system. Modern publications by J. F. Siqueira, I. N. Rocas, and D. Ricucci (2019) note that many issues of endodontic treatment are unresolved. It follows that improving the quality of endodontic treatment is still relevant.Aim.To compare two systems of instruments for root canal preparation with different types of rotation.Materials and methods.To identify a tool that will increase the efficiency of root canal preparation, taking into account their anatomy using CBCT, 24 teeth were removed, taken according to orthodontic or pristidintic indications, without previous endodontic treatment. Among them there were 2 incisors, 1 canine, 6 premolars, 15 molars. In total, 60 canals were examined.Results.The shape changes throughout the canal, turning into a round, oval, slit-like, complementing the configuration by the isthmuses between the canals in 13.3% of cases. WaveOne Gold showed a change in cross-sectional shape after preparation, while ProTaper Universal retained a rounded section of 6.67% after preparation of the slit-like channels.Conclusion.Identified priority technique of root canal preparation, allowing to reduce the number of instruments and, as a consequence, the possibility of technological failures in the root canal to reduce machining of the mouth of the channel, retaining dentine playing a major role in the further prosthesis and positive prediction of remote results.

Local corrosion mechanism of SiO2-based refractories caused by slag movement near solid–liquid–gas interface in different slag systems

Abstract Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO−SiO2 slag whose surface tension improves with SiO2 concentration, slag film flows up along four edges under axial Marangoni shear force and wettability. Then, it flows down along four lateral faces under gravity. Corrosion rate at edges is larger than that on lateral faces due to different SiO2 solubilities of ascending and descending flow. Prism cross section shape changes from square to round. For FetO−SiO2 slag whose surface tension reduces with the increase of SiO2 concentration, slag film flows up under the inflence of wettability. Then, it flows down under Marangoni shear force and gravity. Compared to four edges, slag is mainly up and down on four lateral faces due to larger surface tension and size. So, prism cross section shape keeps square.

A silencer incorporated within the thickness of the edge of the door for increasing sound transmission loss.

The present study focuses on a silencer built within the thick portion of a door edge and reports on the results of evaluating silencers by determining sound transmission loss via theoretical analysis and experiments on three types of silencers. The theoretical analysis involved determining the calculated values of sound transmission loss obtained using the transfer matrix method. The change in cross-sectional shape was analyzed by elemental division of the transfer matrix. Using the above, simulations were performed with respect to the optimum shape of the silencer. These theoretical analyses were then compared with the measurement results. Furthermore, the study includes the results of an experiment that attempted to restrain the dip in sound transmission loss by adding a non-woven fabric to the opening of the silencer. In a side branch silencer with an increasing shape wherein the longitudinal cross-section is a linear or an exponential function, the peak of the transmission loss was shifted to the lower frequency side when compared with that in the case of a rectangular side branch silencer. Furthermore, in comparisons between the two, the sound attenuation peak frequency was lower in the case of the exponential shape. The resonance of the side branch was suppressed by adding a non-woven fabric to the opening of the side branch silencer. As a result, the peak and dip of sound attenuation were alleviated, and the sound attenuation characteristics could be adjusted.