Ellipticity Ratio Research Articles

Benefits of final proximal optimisation technique (POT) in provisional stenting

Initial proximal optimisation technique (POT) in provisional stenting improves global malapposition, side-branch (SB) obstruction (SBO) and conservation of arterial circularity. The specific mechanical effects of a final POT sequence concluding the main provisional stenting techniques, on the other hand, are unknown. SynergyTM stents were implanted on fractal coronary bifurcation bench models using the main provisional stenting techniques ( n = 5 per group): kissing-balloon inflation (KBI), snuggle, and rePOT (initial POT + SB inflation + final POT). Final results were quantified on 2D and 3D OCT before and after final POT. Whichever the technique, final POT significantly decreased global malapposition (from 7.6 ± 5.3% to 2.2 ± 2.5%, P < 0.05) and proximal elliptic deformation (from 1.15 ± 0.07 to 1.09 ± 0.04, P < 0.05), without impact on SBO (from 11.5 ± 9.6% to 12.9 ± 10.6%, NS). However, final POT failed to completely correct the elliptic deformation induced by balloon juxtaposition during the KBI and snuggle techniques, with final elliptic ratios of 1.11 ± 0.03 and 1.11 ± 0.04 respectively, significantly higher than with the full rePOT sequence: 1.05 ± 0.02 ( P < 0.05) ( Fig. 1 ). Like initial POT, final POT is mandatary whatever the provisional stenting technique used. However, final POT fails to completely correct all proximal elliptic deformation associated with “kissing-like” techniques, in contrast to results with the rePOT sequence.

Solid phase synthesis and spectroscopic characterization of the active and inactive forms of bacteriophage S21 pinholin protein

The mechanism for the lysis pathway of double-stranded DNA bacteriophages involves a small hole-forming class of membrane proteins, the holins. This study focuses on a poorly characterized class of holins, the pinholin, of which the S21 protein of phage ϕ21 is the prototype. Here we report the first in vitro synthesis of the wildtype form of the S21 pinholin, S2168, and negative-dominant mutant form, S21IRS, both prepared using solid phase peptide synthesis and studied using biophysical techniques. Both forms of the pinholin were labeled with a nitroxide spin label and successfully incorporated into both bicelles and multilamellar vesicles which are membrane mimetic systems. Circular dichroism revealed the two forms were both >80% alpha helical, in agreement with the predictions based on the literature. The molar ellipticity ratio [θ]222/[θ]208 for both forms of the pinholin was 1.4, suggesting a coiled-coil tertiary structure in the bilayer consistent with the proposed oligomerization step in models for the mechanism of hole formation. 31P solid-state NMR spectroscopic data on pinholin indicate a strong interaction of both forms of the pinholin with the membrane headgroups. The 31P NMR data has an axially symmetric line shape which is consistent with lamellar phase proteoliposomes lipid mimetics.

Vibration suppression mechanism research of adjustable elliptical journal bearing under synchronous unbalance load

Abstract A concept of an adjustable elliptical journal bearing with variable elliptical ratio was proposed in order to suppress the vibration amplitude of a rotor under synchronous unbalance load at normal speed operating condition. In numerical simulations, dynamic lubrication program is programmed and it could predict the journal center orbits of the bearing. In experiments, adjustable elliptical journal bearing device and testing system are established. With the elliptical ratios adjusting from 0 to 0.7, journal vibrations are simulated and tested. The results obtained from the experiments are in good agreement with that from the numerical simulations. The results indicate that the effects of vibration suppression are satisfied. The proposed adjustable elliptical journal bearing provides an effective way in forced vibration suppression.

Stability analysis of a rigid rotor supported by two-lobe hydrodynamic journal bearings operating with a non-Newtonian lubricant

In the present work, an investigation has been performed on a rigid rotor supported by two-lobe journal bearings operating with a non-Newtonian lubricant. The governing Reynolds equation for pressure field is solved by using non-linear finite element method. Further to study the dynamic stability of the bearing system, governing equation of motion for the rotor position is solved by fourth order Runge–Kutta method. Bifurcation and Poincaré maps of two-lobe bearings are presented for different values of the non-Newtonian parameter and bearing ellipticity ratio. The numerical results illustrate that the ellipticity of a bearing with a dilatant lubricant improve the stability of the rotordynamic system.

Benefits of final proximal optimization technique (POT) in provisional stenting

AimsInitial proximal optimization technique (POT) in provisional stenting improves global malapposition, side-branch (SB) obstruction (SBO) and conservation of arterial circularity. The specific mechanical effects of a final POT sequence concluding the main provisional stenting techniques, on the other hand, are unknown. Methods and resultsSynergy™ stents were implanted on fractal coronary bifurcation bench models using the main provisional stenting techniques (n = 5 per group): kissing-balloon inflation (KBI), snuggle, and rePOT (initial POT + SB inflation + final POT). Final results were quantified on 2D and 3D OCT before and after final POT. Whichever the technique, final POT significantly decreased global malapposition (from 7.6 ± 5.3% to 2.2 ± 2.5%, p < 0.05) and proximal elliptic deformation (from 1.15 ± 0.07 to 1.09 ± 0.04, p < 0.05), without impact on SBO (from 11.5 ± 9.6% to 12.9 ± 10.6%, NS). However, final POT failed to completely correct the elliptic deformation induced by balloon juxtaposition during the KBI and snuggle techniques, with final elliptic ratios of 1.11 ± 0.03 and 1.11 ± 0.04 respectively, significantly higher than with the complete rePOT sequence: 1.05 ± 0.02 (p < 0.05). ConclusionsLike initial POT, final POT is recommended whatever the provisional stenting technique used. However, final POT fails to completely correct all proximal elliptic deformation associated with “kissing-like” techniques, in contrast to results with the rePOT sequence.

Adsorption equilibrium models: Computation of confidence regions of parameter estimates

Estimation of parameter values of adsorption equilibrium models from available experimental data is a common practice, but the evaluation of parameter uncertainties is not usually performed. Furthermore, adsorption equilibrium models generally present two or more parameters and the uncertainty analysis must be performed with help of confidence regions, allowing for evaluation of parameter correlations. In the present work confidence regions of estimated parameters were determined for Langmuir, Freundlich, Sips and Redlich–Peterson isotherms through the elliptical approximation and the likelihood ratio method, using experimental data related to dyes adsorption from liquid solutions. The effects caused by the number of measurements, the experimental data region and the definition of experimental measurement variance were also evaluated. The results showed that changes of the experimental region can exert large influence on the precision of the estimated parameters when experimental variances are estimated with the minimum value of the least squares objective function, since in this case model performance affects directly the estimated parameter uncertainties. On the other hand, when experimental variances are obtained independently, parameter uncertainties become less dependent on model performance, as expected. It was also observed that the elliptical and likelihood ratio approaches for determination of confidence regions lead to similar results when uncertainties of the parameter estimates are low, even when nonlinear models are considered. Finally, it was shown that the proper evaluation of the experimental uncertainty exerts a major effect on the obtained confidence regions, so that the use of replicates in the experimental grid must certainly be encouraged.

Anisotropic thermal conductivity measurement using a new Asymmetric-Beam Time-Domain Thermoreflectance (AB-TDTR) method.

Anisotropic thermal properties are of both fundamental and practical interests, but remain challenging to characterize using conventional methods. In this work, a new metrology based on asymmetric beam time-domain thermoreflectance (AB-TDTR) is developed to measure three-dimensional anisotropic thermal transport by extending the conventional TDTR technique. Using an elliptical laser beam with controlled elliptical ratio and spot size, the experimental signals can be exploited to be dominantly sensitive to measure thermal conductivity along the cross-plane or any specific in-plane directions. An analytic solution for a multi-layer system is derived for the AB-TDTR signal in response to the periodical pulse, elliptical laser beam, and heating geometry to extract the anisotropic thermal conductivity from experimental measurement. Examples with experimental data are given for various materials with in-plane thermal conductivity from 5 W/m K to 2000 W/m K, including isotropic materials (silicon, boron phosphide, and boron nitride), transversely isotropic materials (graphite, quartz, and sapphire), and transversely anisotropic materials (black phosphorus). Furthermore, a detailed sensitivity analysis is conducted to guide the optimal setting of experimental configurations for different materials. The developed AB-TDTR metrology provides a new approach to accurately measure anisotropic thermal phenomena for rational materials design and thermal applications.

Application of the finite element method for evaluating the stress distribution in buried damaged polyethylene gas pipes

During the loading process, buried gas pipes can experience severe stresses due to soil- structure interaction, the presence of traffic load, the soil’s column weight, daily and/or seasonal temperature changes and uniform internal pressure. In this research, the finite element method is employed to evaluate the behavior of buried Medium Density Polyethylene (MDPE) pipes which have been subjected to damage at the pipe crown. The modeled pipe damage ranges from a very small circular hole to a large circular hole and elliptic holes with various minor to major diameter ratios, a/b, to simulate circular to crack-shaped defects. The computer simulation and stress analyses were performed using the ANSYS software finite element package. The stress distribution around the defect was determined under the aforementioned mechanical and thermal loading conditions. Then, the maximum values of Von Mises stresses in the damaged buried PE pipes, which were evaluated by finite element solution, were compared with their corresponding reduced strength for safe operation with a life expectancy of fifty years. Based on the results, the maximum Von Mises stress values in the defective buried polyethylene gas pipeline are significantly above the pipe strength limit at 35 °C. The previously mentioned stress values increase with the following factors: temperature increase, increase in circular hole diameter and decrease in elliptic hole diameter ratio (a/b). The maximum stress in the damaged PE pipe is due to the simultaneous loading effects of soil column weight, internal pressure, vehicle wheel load and pipe temperature increase. Additionally, the novel finite element models and stress plots for the buried damaged pipe and the pipe material allowable strength will be used to investigate the correct repair method for the damaged gas pipeline and to choose the best patch arrangement which will assure a safe repair.

Numerical investigation on non-Newtonian fluid flowing in heat exchanger with different elliptic aspect ratios and helical angles

In this paper, the heat transfer and flow performance of the non-Newtonian fluid on the shell side of heat exchanger combined with elliptic tubes and helical baffles were numerically investigated, different helix angles and helical aspect ratios were studied to improve the heat exchanger’s overall performance. An aqueous solution with 3.0% weight fraction of carboxymethyl cellulose (CMC) was selected as the working fluid, which was a kind of non-Newtonian fluid with low viscosity and good stability. The results showed that the increasing aspect ratio improve the heat transfer, but also lead to higher pressure drop. The heat exchanger with aspect ratio between 2.5 and 3.0 has the best heat transfer and flow performance. For the helical angle, both the heat transfer rate and pressure drop increase with the smaller angle. Thermal performance factor (TPF) is taken to evaluate the comprehensive performance, the result showed that when helical angle is 40°, both the TPF and the heat transfer coefficient per pressure drop ho·ΔPo−1 get the most satisfying value.

Numerical study on optical properties of non-circular metamaterial optical fiber

Abstract A non-circular core fiber with a metamaterial cladding using gold is proposed. The mode confinement properties of the disclosed fiber are investigated under various metallic (gold) and dielectric (Al2O3) thickness for different wavelengths and different elliptic ratios of 0.8 μm and 0.9 μm. The parameters like birefringence, confinement loss and dispersion are numerically analyzed theoretically using finite element method (FEM). The overall performance of the proposed fiber is studied and the results show that the fiber exhibits a stable relation between birefringence and confinement loss.

Numerical study on the interaction of a weak shock wave with an elliptic gas cylinder

The interaction of a weak shock wave with a heavy elliptic gas cylinder is investigated by solving the Eulerian equations in two-dimensional Cartesian coordinates. An interface-capturing algorithm based on the $$\gamma $$ -model and the finite volume weighed essential non-oscillatory scheme is employed to trace the motion of the discontinuous interface. Three gas pairs with different Atwood numbers ranging from 0.21 to 0.91 are considered, including carbon dioxide cylinder in air (air– $$\hbox {CO}_2$$ ), sulfur hexafluoride cylinder in air (air– $$\hbox {SF}_6$$ ), and krypton cylinder in helium (He–Kr). For each gas pair, the elliptic cylinder aspect ratio ranging from 1/4 to 4 is defined as the ratio of streamwise axis length to spanwise axis length. Special attention is given to the aspect ratio effects on wave patterns and circulation. With decreasing aspect ratio, the wave patterns in the interaction are summarized as transmitted shock reflection, regular interaction, and transmitted shock splitting. Based on the scaling law model of Samtaney and Zabusky (J Fluid Mech 269:45–78, 1994), a theoretical approach is developed for predicting the circulation at the time when the fastest shock wave reaches the leeward pole of the gas cylinder (i.e., the primary deposited circulation). For both prolate (i.e., the minor axis of the ellipse is along the streamwise direction) and oblate (i.e., the minor axis of the ellipse is along the spanwise direction) cases, the proposed approach is found to estimate the primary deposited circulation favorably.

Geometric study and simulation of an elliptical rotor profile for Roots vacuum pumps

The rotor profile is one of the key factors for improving the performance of the Roots vacuum pump. A novel elliptical rotor profile consisting of the elliptical arc and its conjugate curve is proposed in this paper. The mathematical model of the elliptical rotor profile is established, and profile equations without incurring undercutting and carryover are derived. The elliptical rotor profile is tested using six Roots rotors, including five new elliptical rotors and one conventional circular arc rotor. Additionally, to assess the performance of the elliptical rotor profile, three-dimensional numerical simulations of the above six Roots rotors are conducted, and then the working process of the Roots vacuum pump is analyzed. The results indicate that all the new designs produce higher flow rate than the traditional circular rotor under the same conditions. As the elliptical axial ratio decreases, the area efficiency of the elliptical rotor increases.

A parametric approach to the probability of plaque rupture based on lumen geometry in coronary arteries using design of experiments

Two-dimensional numerical models of arterial plaque are used to determine the effects of the geometrical characteristics of the lumen on the stress gradient and stress distribution. Three parameters with three levels that form the plaque lumen, stenosis rate by diameter, eccentricity, and ellipticity, were analyzed based on experimental design. A review of 27 cases confirmed that the stress and stress gradient tended to increase with a decreasing stenosis rate by diameter, and the eccentricity and ellipticity ratio also increased. Eccentricity had the greatest influence on the mechanical behavior of the plaque, and it was confirmed that even the same types of plaques varied in magnitude of influence depending on the geometrical characteristics of the lumen.

Improving Efficiency and Birefringence of an All-Dielectric Metasurface Quarter-Wave Plate Using Graphene

Conventional all-dielectric metasurfaces show remarkable properties including high efficiency and tunability of the optical response. However, extreme narrow bandwidth is a limitation that reduce their application in the photonic sensor devices. In this work, an efficient hybrid silicon-graphene metasurface is numerically proposed and designed. Through the sandwiched graphene layer, the structure shows unique quarter-wave properties, tunable through the dimensions of silicon, the Fermi energy of graphene, and an external gate voltage. Dynamic tuning is achieved by reversing the gate voltage: circular polarization state is switched between the right- and the left-handed states by reversing the gate voltage. A 95% polarization conversion ratio and a 96% ellipticity ratio are obtained while converting linearly polarized light into circularly polarized light in the near infrared. Additionally, by integrating graphene with silicon, the Q-factor and the trapped magnetic modes in the silicon are effectively modulated. The structure is compact and has an ultrathin design thickness of ∼0.1 λ, in the telecommunication wavelength. The above properties are essential for integration into photonic sensing devices and for compatibility with the CMOS devices.

Highly efficient birefringent quarter-wave plate based on all-dielectric metasurface and graphene

All-dielectric metasurfaces offer remarkable properties including high efficiency and flexible control of the optical response. However, extreme, narrow bandwidth is a limitation that lowers applicability of these structures in photonic sensing applications. In this work, we numerically design and propose a switchable quarter-wave plate by hybridizing an all-dielectric metasurface with graphene. By using a single layer of graphene between a highly refractive index silicon and a silica substrate, the transmissive resonance is enhanced and broadened. Additionally, integrating graphene with silicon effectively modulates the Q-factor and the trapped magnetic modes in the silicon. A stable birefringence output is obtained and manipulated through the structure dimensions and the Fermi energy of graphene. A 95% polarization conversion ratio is achieved through converting linearly polarized light into circularly polarized light, and a 96% ellipticity ratio is obtained at the resonance wavelength. The structure is compact and has an ultrathin design thickness of 0.1λ, in the telecommunication region. The above properties are essential for integration into photonic sensing devices and the structure has potential for compatibility with the CMOS devices.

Feasibility of constraining the curvature parameter of the symmetry energy using elliptic flow data

A QMD type transport model supplemented by a phase-space coalescence model fitted to FOPI experimental multiplicities of free nucleons and light clusters has been used to study the density dependence of the symmetry energy above the saturation point by a comparison with experimental elliptic flow ratios measured by the FOPI-LAND and ASYEOS collaborations in $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon impact energy. A previous calculation has proven that neutron-to-proton and neutron-to-charged particles elliptic flow ratios probe on average different densities allowing in principle the extraction of both the slope $L$ and curvature $K_{sym}$ parameters of the symmetry energy. Consequently a Gogny interaction inspired potential has been modified to allow independent changes of $L$ and $K_{sym}$. Comparing theoretical predictions with experimental data for neutron-to-proton and neutron-to-charged particles elliptic flow ratios the following constraints have been extracted: $L$=85$\pm$22(exp)$\pm$20(th)$\pm$12(sys) MeV and $K_{sym}$=96$\pm$315(exp)$\pm$170(th)$\pm$166(sys) MeV. Residual model dependence is accounted for in the magnitude of the quoted theoretical error. Systematical uncertainties are generated by the inability of the transport model to reproduce experimental light-cluster-to-proton multiplicity ratios. A value for $L$, free of systematical theoretical uncertainties, can be extracted from the neutron-to-proton elliptic flow ratio alone: $L$=84$\pm$30(exp)$\pm$19(th) MeV. It has also been demonstrated that elliptic flow ratios reach a maximum sensitivity on the $K_{sym}$ parameter in heavy-ion collisions of about 250 MeV/nucleon impact energy, allowing a reduction of the experimental component of uncertainty to about 150 MeV for this parameter.

Analysis of arbitrarily shaped planar cracks in three-dimensional isotropic hygrothermoelastic media

ABSTRACTIn the present article, a planar crack of arbitrary shape embedded in three-dimensional isotropic hygrothermoelastic media is investigated. Based on the general solutions and Hankel transform technique, the fundamental solutions for unit-point and extended displacement discontinuities (EDD; including the displacement discontinuities, moisture concentration discontinuity, and the temperature discontinuity) are derived. The EDD boundary integral equations for an arbitrarily shaped, planar crack in the hygrothermoelastic medium are established in terms of the EDD. Utilizing the boundary integral equation method, the singularities of near-crack front fields are analyzed, and the stress, moisture flux, and heat flux intensity factors are all derived in terms of the EDD. As a special case, the analytical solution for a penny-shaped crack under uniform combined loadings is presented. The EDD boundary element method is proposed for numerical simulation. The numerical result for a penny-shaped crack subjected to uniform mechanical–moisture–thermal loading is compared with the analytical solution to verify the correctness of the proposed method. Two coplanar elliptical cracks subjected to combined loadings are simulated as an application, and the influences of applied loadings and the ellipticity ratio are discussed.

Pre-Procedural Imaging Modalities for Device Size Selection and Adaptive Nature of the Appendage in Patients Undergoing Percutaneous Left Atrial Appendage Closure

ABSTRACTBackground: This study aimed to compare different pre-procedural left atrial appendage (LAA) imaging modalities and analyze the anatomical adaptation of the LAA to the closure device at 3-month multi-slice computed tomography (MSCT). LAA closure device sizing is crucial to optimize immediate and long-term outcomes.Methods: Patients who underwent percutaneous LAA closure and had pre-procedural transesophageal echocardiography (TEE) and MSCT were identified. Devices used were AmuletTM (Abbott, USA), WatchmanTM, and WatchmanFLXTM (Boston Scientific, USA). LAA ostium and landing zone were measured according to the instructions for use at 2D-TEE, as well as at MSCT and X-ray angiography. Post-procedural MSCT was used to assess LAA ellipticity and closure.Results: A total of 67 patients (44 AmuletTM, 11 WatchmanTM, 12 WatchmanFLXTM) were included. Mean age was 74 ± 7 years, CHA2DS2-VASc-score 3.0 ± 1.6 and HAS-BLED-score 2.7 ± 0.9. Bland-Altman analysis for the maximum LAA diameter at MSCT (CTmax) and TEE (TEEmax) showed a mean difference of +4.8 mm with a limit of agreement (LoA) of 9.6 mm (p < 0.01). Maximum LAA diameters at TEE (TEEmax) and X-ray angiography (XAmax) showed a mean difference of +1.3 mm with LoA of 7.6 mm (p = 0.839). The mean difference between CTmean and TEEmax was +2.1 mm with LoA of 8.4 mm (p < 0.05). In addition, LAA ellipticity ratio decreased from 1.48 to 1.05 while overall LAA area only expanded 3% after device implantation.Conclusion: Of the three imaging modalities, MSCT provides the largest LAA measurements, followed by TEE and angiography. At follow-up MSCT, the elliptical LAA conforms to the circular shape of the closure device; however, overall LAA expansion is only minimal.

An Experimentally Validated Combined Stiffness Formulation for a Finite Domain Considering Volume Fraction, Shape, Orientation, and Location of a Single Inclusion

This work characterizes the stiffness of a finite domain containing one (biaxial ellipsoidal) void due to the combined effect of inclusion’s attributes: (1) size or volume fraction, VF, (2) shape or aspect ratio, AR, (3) angular orientation, and (4) location (position) within the matrix. The values and ranges of these ellipsoidal inclusion attributes are varied according to a matrix developed using design of experiments (DOE). Modified Mori–Tanaka method combined with dual-eigenstrain method (interior and exterior eigenstrain methods) is used to determine the effective stiffness tensor of the composite domain. Employing the numerically calculated normalized axial modulus [Formula: see text] values in SAS/STAT®, a nonlinear mathematical expression of [Formula: see text] as function of the void’s variables is arrived at Stiffness values found from the numerical homogenization scheme are experimentally corroborated using compression tests conducted on 3D-printed ABS cubes having a single ellipsoidal inclusion of various geometric attributes. In addition, finite element simulations were run of said uniaxial compression test cases to further validate the numerical homogenization results. Corroborated findings suggest that while the location of the inclusions in the matrix have no significant effect on normalized modulus [Formula: see text], the void’s volume fraction has the largest effect where it decreases with VF. The effect of the void’s orientation and elliptical aspect ratio are significant. [Formula: see text] increases with AR at angles ranging from 0–[Formula: see text]; at [Formula: see text][Formula: see text] are almost constant with AR, at angles of 60–[Formula: see text] values of [Formula: see text] decrease with AR. As AR approaches unity, the effect of orientation decreases significantly.

Enhancing Mechanical Property of Al7075 by Using Elliptical Cross- Sectioned Spiral Equal-Channel Extrusion: Experimental, Numerical and Optimization Approach

More recently, several studies have been done to improve the mechanical properties of materials. During this period, various methods of SPD (severe plastic deformation (SPD)) have been used to produce Ultra-Fine-Grain (UFG) materials. One of the pioneers in replacing SPD is the elliptical cross-sectional flattened extrusion (ECSEE). In the present study, an optimal combination of the process parameters of the ECSEE method, such as the torsional angle, ellipticity and elliptical diameter ratio, to obtain the maximum effective pressure and minimum punch force, as well as the minimum subsequent error in the cross section of the ABAQUS Software for modeling Numeric done. Due to the design of the central composite test, models of punch force response levels, effective pressure and subsequent error are generated through FE simulation. The simulation results showed that the effective strain was significantly affected by the rotation angle, diameter ratio and channel length. After two ECSEE courses, power ranged from 384 MPa to 340 MPa and its life span was reduced from 15% to 8%. Also, the FEM results indicate that the amount of effective pressure on the surface is greater than the center of the ECSEE pen. The results showed that the torsional angle of 120°, the length of the diameter of 16 and the ratio of the axis to 1.45, the optimal solution give the desired quality characteristics.