Transverse Pressure Research Articles

Emergent cerebral venous stenting: A valid treatment option for fulminant idiopathic intracranial hypertension

BackgroundFulminant idiopathic intracranial hypertension (FIIH) is characterized by rapid, severe, progressive vision loss and often treated surgically. Cerebral transverse venous stenting (CTVS) is efficacious in IIH patients, but emergent CTVS in FIIH is rarely reported. We present our experience with emergent CTVS in patients with FIIH. MethodsSince 01/2019, an institutional protocol allowed emergent CTVS in FIIH patients with bilateral transverse sinus stenosis and gradient pressure > 15 on digital subtraction angiography (DSA). We retrospectively analyzed a prospective registry of all IIH patients with details of neurological and neuro-ophthalmological assessments before and after treatment, and subjective assessments of headache and tinnitus were made pre-and post-procedure. Results259 IIH patients, including 49 who underwent CTVS, were registered. Among them, five female patients met inclusion criteria for FIIH and underwent emergent CTVS. FIIH patients were younger (18.8 ± 1.64 vs 27.7 ± 4.85, p < 0.01), mean BMI was lower (30.8 ± 10.57 vs 34.6 ± 4.3, p < 0.01), and lumbar puncture opening pressure higher (454 ± vs 361 ± 99.4, p < 0.01) than that of IIH patients. They presented with acute visual loss, severe headache, papilledema, significant bilateral transverse sinus stenosis on CT-venography, and mean dominant side gradient pressure of 26.4 ± 6.2 on DSA. CTVS was performed without significant complications, resulting in remarkable improvement in headache, optical coherence tomography, and visual fields within 1 week. At 1-year follow-up (four patients) and 6-month follow-up (1 patient), there was complete resolution of papilledema and headache, and marked improvement in visual acuity. ConclusionsIn these patients, emergent-CTVS was a safe and effective treatment option for FIIH. Further evaluation is warranted.

Compressive Stress-Strain Behavior of REBCO Coated Conductors and Cables

Rare earth barium copper oxide (REBCO) coated conductor tapes and cables are promising material candidates for constructing high field magnets. In both the magnet constructing stage and operation stage, transverse pressure is exerted on the tapes/cables. Therefore, understanding the mechanical behavior of tapes/cable under transverse pressure and figuring out certain properties, such as modulus and stress limits, will be helpful for magnet design and magnet simulation study. We accomplished these goals by performing compression tests on several commonly used tapes/cables in high field magnets. We found that the mechanical behavior of tape stacks can be characterized in three distinct regimes. In the first regime (<20 MPa), tape stacks underwent flattening and self-relocation. Then in the second regime (20 - 60 MPa), the REBCO tape stack showed a modulus of 3.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 7% GPa, and the Ni-plated REBCO tape stack showed a modulus of 1.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 6% GPa. In the third regime (>60 MPa), the REBCO tape stack and its Ni-plated derivative had a modulus of 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 11% GPa and 4.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 9% GPa respectively. Roebel cable had similar mechanical behavior to the tape stack with three regimes, and the second and third regimes showed a modulus of 3.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 5% GPa and 9.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 11% GPa respectively. The conductor on round core (CORC) cable was more vulnerable to stress, and its fracture stress was around 27 MPa.

Experimental study and simulation analysis of the fracture mechanism in AFRP milling

The finite element model of aramid fiber reinforced polymer (AFRP) was established using the finite element analysis software, and milling simulation analysis was carried out. The influence of cutting speed and tool diameter on cutting force was obtained. Based on the motion law of the milling cutter, a fiber cutting mechanical model was established, and the influence of shear force and transverse pressure on the quality of the fiber section was analyzed. The milling experiment on AFRP specimens was carried out, and the milling appearance and cutting force variation of cutting speeds at 18.850–31.415 m/min and tool diameters of 1 –5 mm were studied. The results show that the diameter of a 5 mm milling cutter has a neater cutting fiber section and fewer burrs than the diameter of a 1 mm milling cutter, but inadequate sharpness can easily cause serious entrance burrs. Due to the influence of the feed motion, the milling tool feeding direction (X direction) is 42.456% higher than the Y direction cutting force, which can easily cause tool fracture. Increasing cutting speed can reduce cutting force to a certain extent and improve cutting quality. Therefore, choosing a large-diameter milling cutter with a large rake angle or relief angle for high-speed cutting can effectively improve the quality of the AFRP milling entrance and section.

Research on lateral pressure sensing based on Sagnac ring cascaded FBG

In the field of engineering, the deformation and lateral stress in structural health detection have attracted extensive attention to obtain the structural health information of building objects in time. Based on the birefringence effect of polarization maintaining fiber (PMF), a transverse pressure sensor based on Sagnac cascade fiber bragg grating (FBG) was proposed and prepared. The performance of the sensor is analyzed by the combination of the finite element method and experiment. The simulation results show that the cross section of PMF is deformed under the pressure along the fast axis and the slow axis and then modulates the refractive index. The experimental results show that by adding FBG structure, the lateral pressure sensitivity of the sensor is 408.7 pm/N, and the linear fit is 98.3%. The lateral pressure sensitivity of the structure without FBG is 281.7 pm/N, and the linear fit is 99.3%. That is to say, the FBG structure increases the sensitivity of the sensor by 45.1%. The experimental results are in full agreement with the theoretical derivation. The optical fiber lateral pressure sensor proposed in this paper has the characteristics of simple fabrication, low cost, and high repeatability. It plays an important role in the field of structural stress monitoring.

Wrinkling of a normally loaded, spinning, elastic membrane: An asymptotic approximation

This paper revisits recent work on the edge wrinkling experienced by spinning circular membranes loaded by a transverse uniform pressure. The corresponding stability analysis is carried out within the framework of the Föppl–von Kármán nonlinear plate theory. It is shown herein that the effect of rotation of the membrane is similar to an in-plane tension applied on its outer perimeter, an observation that proves to be quite effective in obtaining a tight upper bound for the critical wrinkling load of the problem. Comparisons between the simplified model and direct numerical simulations of the full eigenproblem provide further insight into the accuracy and limitations of the derived results.

Secondary flow and loss mechanisms of variable stator vanes in an annular cascade

Axial compressors with variable stator vanes require annular gaps and radial gaps from the endwalls for smooth adjustment, which induces complex secondary flows such as the penny leakage vortex and tip leakage vortex, leading to a negative impact on the aerodynamic performance. To better understand these mechanisms, numerical investigations were conducted on four different clearance configurations. The results show that the penny leakage vortex moves toward the suction side under the transverse pressure gradient and mixes with the hub corner stall vortex. This causes the corner separation to be further developed, leading to an increase in total pressure loss by 13.6%. However, the tip clearance leakage flow could reduce the transverse pressure gradient, which prevents penny leakage vortex from mixing with low-energy fluid in the corner region. Moreover, the hub corner stall vortex is also replaced by the tip leakage vortex, which effectively suppresses the range of corner separation. Under the comprehensive effects of the penny leakage vortex and the tip leakage vortex, the total pressure loss coefficient is increased only by 7.6%. Therefore, the mixing effect between the penny leakage vortex and low-energy fluid in the corner separation is the main reason for higher loss production of the cascade, and these findings provide theoretical support for the future application of flow control technology to reduce secondary flow loss.

Experimental investigation of nanosecond laser-induced shock waves in water using multiple excitation beams.

Revealing the expansion and interaction dynamics of multiple shock waves induced by a nanosecond laser is important for controlling laser surgery. However, the dynamic evolution of shock waves is a complex and ultrafast process, making it difficult to determine the specific laws. In this study, we conducted an experimental investigation into the formation, propagation, and interaction of underwater shock waves that are induced by nanosecond laser pulses. The effective energy carried by the shock wave is quantified by the Sedov-Taylor model fitting with experimental results. Numerical simulations with an analytic model using the distance between adjacent breakdown locations as input and effective energy as fit parameters provide insights into experimentally not accessible shock wave emission and parameters. A semi-empirical model is used to describe the pressure and temperature behind the shock wave taking into account the effective energy. The results of our analysis demonstrate that shock waves exhibit asymmetry in both their transverse and longitudinal velocity and pressure distributions. In addition, we compared the effect of the distance between adjacent excitation positions on the shock wave emission process. Furthermore, utilizing multi-point excitation offers a flexible approach to delve deeper into the physical mechanisms that cause optical tissue damage in nanosecond laser surgery, leading to a better comprehension of the subject.

The relationship between shear wave velocity in transverse carpal ligament and carpal tunnel pressure: A finite element analysis.

Elevated carpal tunnel pressure in carpal tunnel syndrome (CTS) patients is one of the major causes of nerve damage but cannot be measured non-invasively. This study proposed to use shear wave velocity (SWV) in the transverse carpal ligament (TCL) to measure the surrounding carpal tunnel pressure. The relationship between the carpal tunnel pressure and the SWV in the TCL was investigated through a subject-specific carpal tunnel finite element model reconstrued by MRI imaging. Parametric analysis was conducted to study the effect of TCL Young's modulus and carpal tunnel pressure on the TCL SWV. The SWV in TCL was found to be strongly dependent on the carpal tunnel pressure and TCL Young's modulus. The calculated SWV ranged from 8.0m/s to 22.6m/s under a combination of carpal tunnel pressure (0-200mmHg) and TCL Young's modulus (1.1-11MPa). An empirical equation was used to fit the relationship between the SWV in TCL and carpal tunnel pressure, with TCL Young's modulus as a confounding factor. The equation proposed in this study provided an approach to estimate carpal tunnel pressure by measuring the SWV in the TCL for a potential non-invasive diagnosis of CTS and may shed light on the mechanical nerve damage mechanism.

Exact solutions for compact stars in general relativity

Complete, exact, analytic solutions to the spherically symmetric Einstein equations have been constructed. Beginning with the Tolman VII solution we first “complete” the solution by computing an expression for the pressure and subsequently the equation of state. The Tolman VII solution is then extended to include non-zero mass densities at the fluid-vacuum interface. The method developed to construct these solutions is extended to include transverse pressures and charge. Furthermore the quadratic density profile of the Tolman VII type solutions is modified to include quartic density profiles that lead to expressions in terms of Jacobi elliptic integrals. It is shown that, depending on the outer boundary conditions placed on the mass density, the equations of state lead to either a set of polytropes or behaviour that mimics strange quark matter.

New classes of wormhole model in [formula omitted] gravity by assuming conformal motion

The two models of wormhole in f(R,T) gravity using relationship between radial and transverse pressure is discussed in the article. To obtain the wormhole model, we used a separable functional form given by f(R,T)=f1(R)+f2(T). R is the Ricci scalar, and T is the trace of the energy momentum tensor, with f1(R) and f2(T) being arbitrary functions of R and T, respectively. We also explored the possibility of wormhole (WH) solutions by assuming that the spacetime admits conformal killing vectors. Using different values for the coupling parameter γ, we studied the viable solutions and graphically analyzed the various features of these models. It can also be noted that the energy conditions are violated for our anisotropic model and isotropic model violates null energy condition (NEC) for γ = 0,−2,−4 while holds NEC for γ = 2,4. Hence, the anisotropic WH throat is supported by exotic matter and the isotropic by exotic/non-exotic (i.e. γ = 0,−2,−4 & γ = 2,4) although not an interesting model as there is no opening throat.

Applicability of RANS models and pressure drop in edge subchannels for 19-pin wire-wrapped fuel bundle channel in CiADS

The accelerator-driven subcritical system has a strong transmutation ability and high inherent safety, and it is internationally recognized as the most promising long-life nuclear waste disposal device. This study involves the construction of a Visual Hydraulic ExperimentaL Platform (VHELP) for the purpose of evaluating the applicability of Reynolds-averaged Navier–Stokes (RANS) models and analyzing the pressure distribution within the fuel bundle channel of China initiative accelerator-driven system (CiADS). Measurements of thirty differential pressures in edge subchannels within a 19-pin wire-wrapped fuel bundle channel were obtained under different conditions using deionized water. The pressure distribution in the fuel bundle channel at Reynolds numbers of 5000, 7500, 10,000, 12,500, and 15,000 was simulated using Fluent. The results show that RANS models obtained accurate results, and the shear stress transport k-ω model provided the most accurate prediction of the pressure distribution. The difference between the results of the Shear stress transport (SST) k-ω model and experimental data was the smallest, and the maximum difference was ±5.57%. Moreover, the error between the experimental data and numerical results of the axial differential pressure was smaller than that of the transverse differential pressure. The pressure periodicity in axial and transverse directions (one pitch) and a relatively three-dimensional pressure measurements were studied. The static pressure fluctuated and decreased periodically as the z-axis coordinate increased. These results can facilitate research on the cross-flow characteristics of liquid metal-cooled fast reactors.

Assessment of the stiffened panel performance in the OTEC seawater tank design: Parametric study and sensitivity analysis

Ocean thermal energy conversion (OTEC) is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater. Due to the high static and dynamic pressures that are caused by seawater circulation, the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength. The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment. The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS. The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step, in which the axial compression was applied. The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels, and the significance of the stiffener parameters was assessed by using the sensitivity analysis method. As a result, the ultimate strength was reduced by approximately 1.5% for the span-over-bay ratio of 3 and by 7% for the span-over-bay ratio of 6.

Influences of the cavity leakage flow on shrouded stator performance at different inlet boundary layer shapes

By using the validated numerical method to simulate the annular shrouded stator with the inter-stage seal cavity, the stator aerodynamic performance related to the cavity leakage flow was examined. The current study also indicated the interactions between the leakage flow and the mainstream. Discussions on the developments of secondary flow movement and hub corner separation were conducted, and the performances at different incoming boundary layer shapes were assessed using both the total pressure loss coefficient and the entropy-based loss coefficient. The results indicate that the cavity leakage flow creates a new vortex close to the leading edge of blade and is crucial to the passage vortex development and the concentrated shedding vortex size. At the same time, the cavity leakage flow weakens the transverse deflection of flow near the end wall and strengthens the three-dimensional flow effect. The two loss coefficients for the shrouded stator with seal cavity change little by thickening the boundary layer. The proper boundary layer skew as well as the interacted cavity leakage flow have stronger resistance to the deflection of the passage vortex and the transverse pressure gradient.

On the pressure–deflection relations and instability of carbon-based composite nonlinear pipes

In this paper, for the first time, the nonlinear buckling of curved pipes is investigated for different distributions of single-walled carbon nanotubes (SWCNTs) in the matrix. The curved pipe is subjected to uniformly distributed transverse pressure and experiences uniform temperature rise. Additionally, the pipe is in one-sided contact with an elastic nonlinear medium. Defined thickness-dependent and temperature-dependent material properties of SWCNTs are taken from the results of molecular dynamics (MD) simulations, well-established in the literature on the subject. Five technologically justified types of CNT distributions are considered. Shen’s rule of the mixture is applied to determine the effective properties of CNT-based composites. To avoid determining shear correction factor, the higher-order shear deformation theory is used. The nonlinear components of the Green–Lagrange strain tensor and the principle of virtual displacements are applied to derive the nonlinear system of partial differential equations of motion of the curved pipe. The solution to formulated boundary value problem is obtained by the perturbation technique for both simply-supported and clamped-clamped boundary conditions. The pressure–deflection curves of the curved pipe are obtained and discussed. The investigation of snap-buckling intensity and upper/lower limit load of the curved pipe is presented and new insights for its nonlinear stability are presented. For instance, it is shown that the V-type of CNT distribution profile affects on lower deflection of the curved pipe while the higher deflection exists for the Λ-type profile.

Free vibration response of bidirectional functionally graded rotating micro-disk under mechanical and thermal loading

The present work studies the free vibration response of functionally graded rotating micro-disks subjected to transverse pressure and thermal loading based on the modified couple stress theory. The disk material is considered to be functionally graded along the radial and thickness directions, and its properties are assumed to be temperature-dependent following the Touloukian model. The mathematical formulation is based on an energy functional involving the von Kármán type non-linearity, in which appropriate displacement derivatives and its conjugate stress measures are used to define the strain energy of the micro-disk. The minimum potential energy principle is employed to develop the governing equations for determining the deformed configuration of the micro-disk under combined centrifugal, pressure and thermal loading. Further, the governing equations for free vibratory motion of the micro-disk are derived following Hamilton’s principle and incorporating the tangent stiffness of the deformed micro-disk. The governing equations are discretized and solved employing the Ritz method. The mathematical model is successfully validated with different reduced problems available in the literature. The influence of rotational speed, transverse pressure, thermal loading, size-dependent thickness and volume fraction indices are investigated for a wide range of parametric values. Some illustrative mode shapes along with the contour have also been presented. The present study is first of its kind and the presented results would definitely serve as benchmarks for any further study in this field.

Thermal deflection and snap-buckling analysis of temperature-dependent FGP curved nanotubes via a nonlocal strain gradient theory

Present study deals with the nonlinear analysis of thermally induced deflection and snap-through buckling in functionally graded porous (FGP) curved nanotubes. It is assumed that the curved nanotube is rested on a two-parameter nonlinear elastic foundation. The curved nanotube is subjected to uniformly distributed transverse pressure loading and also uniform temperature rise. Distribution of thermomechanical properties in the thickness of curved nanotubes is radially graded according to a power law function. The even type of porosity distribution patterns is included into the formulation and all properties are considered as temperature dependent. The nonlocal strain gradient and uncoupled thermoelasticity theories are provided to analyze the geometrically nonlinear behaviors of curved nanotubes. The equilibrium equations are obtained based on the high-order shear deformation theory. To capture the large deformations, the von Kármán type of nonlinear kinematic assumptions is included. Two types of immovable boundary conditions are considered which are simply-supported and clamped-clamped. The equilibrium equations are reformulated and transferred into the dimensionless presentation. The closed-form expressions are provided to trace the thermal/mechanical load-deflection paths of curved nanotubes using the two-step perturbation technique. Numerical results of this study are compared with the available data in the literature for the macro-scale curved tubes. After that novel parametric results are provided to discuss the effects of nonlocal and length scale parameters, boundary conditions, porosity coefficient, foundation stiffness, power law exponent, and geometrical parameters.

Multiwall Rectangular Plates under Transverse Pressure—A Non-Linear Experimental and Numerical Study

Large deflection of rectangular plates under transverse pressure is described by Föppl-von Kármán equations, which have only approximated solutions. One of these methods is the separation into a small deflection plate and a thin membrane described by a simple third order polynomial expression. The present study presents an analysis to obtain analytical expressions for its coefficients by using the plate's elastic properties and dimensions. To validate the non-linear relationship between the pressure and the lateral displacement of the multiwall plate, a vacuum chamber loading test is used to measure the plate's response, with a large number of plates and length-width combinations. In addition, to further validate the analytical expressions, several finite element analyses (FEA) were performed. It has been found that the polynomial expression fairly describes the measured and calculated deflections. This method allows the prediction of plate deflections under pressure as soon as the elastic properties and the dimensions are known.

Numerical investigation on the ultimate strength behaviour and assessment of continuous hull plate under combined biaxial cyclic loads and lateral pressure

The ultimate strength of continuous hull plate under combined biaxial cyclic loads and lateral pressure is investigated in the present paper by using nonlinear finite element method. Geometric nonlinearity due to large deflection and material nonlinearity induced by kinematic hardening and isotropic hardening are both accounted for. A parametric study is designed and completed to examine the longitudinal ultimate compressive strength behaviours in the cycles on the basis of a large number of load-shortening curves. Effects of series of parameters especially the plate slenderness ratio, transverse cyclic compression, lateral pressure and cycle number are analyzed with details. It is found that the strength characteristic and collapse mode are highly affected by the coupling influence of the mentioned factors as well material behaviours. A dimensionless unified formulation as a function of the decisive factors is empirically proposed to accurately assess the ultimate strength of continuous hull plate in various cycles.

Some aspects of Morris–Thorne wormhole in Scalar–Tensor theory

In this work, we reach the equations of motion of Morris–Thorne wormhole geometry by means of the Einstein Field Equations and Klein–Gordon Equation of Scalar–Tensor Theory. We discuss the anisotropic matter energy distribution. We determine a relation between the radial and the transverse pressures. Hence, we express the anisotropic energy–momentum tensor in terms of one pressure class, by means of that relation. Besides that, we check the isotropic case and show that there is no traversable wormhole (WH), in the zero redshift function situation, if the energy–momentum distribution of the universe is isotropic. In addition, we represent the conditions in order that the Null Energy Condition (NEC) is satisfied in the zero redshift function case, for anisotropic distribution. We also propose a special class of traversable WH shape functions. We will be calling the WHs corresponding to that class of functions as the Yukawa Type WHs. We expressed the NEC for those WHs particularly. Furthermore, we determine the radial and the transverse pressures in zero redshift function situation.

Interaction Behaviors of Longitudinal and Transverse Seismic Waves with Underground Geoengineering Objects

Abstract Main pipelines as long linear objects are vulnerable to dangerous natural and man-made influences. One of the technogenic sources is large-scale explosions, which cause a sharp fluctuations of soil and cause serious damage to underground pipelines. When calculating the strength of pipeline systems, it is assumed that the damage occurs mainly due to additional axial stretching. However, the destruction and damage of pipelines can occur during seismic impacts directed perpendicular to the longitudinal axis of the pipeline. To assess the impact of longitudinal and transverse waves on the underground pipeline during seismic action a software-calculation module is developed. It implements a model of dynamic strength analysis, which allows estimating the magnitude of longitudinal and trans-verse seismic loads on the underground pipeline to establish safe parameters of seismic loads and geometric dimensions of the protected object. The final system of equations of motion of N nodes of a discrete system for a single length of the pipeline is presented as a system of 4N equations of the first order. The efforts on the internal nodes are determined by the strain stresses at the displacement of the nodes of the adjacent rods. The efforts on the nodes of the pipe contour are the diffraction interaction of seismic waves in the soil with the pipe. The system of equations is supplemented by the corresponding initial and boundary conditions. The dependences of the inflow of longitudinal and transverse pressure of explosive seismic pressure on the pipeline are established. The dependences of stresses in the pipeline of the diameter, thickness and type of soil are researched.