Ellipticity Ratio Research Articles

Spectral and Polarization Characteristics of the Light Passing through a Cholesteric Photonic Crystal

Combined optical studies of a cholesteric photonic crystal are performed: the transmission spectra and the rotation of the plane of polarization of light (RPPL) spectra of the crystal are recorded, and the polarization characteristics of the light having passed through the photonic crystal are measured. The RPPL spectra have specific features related to the presence of a photonic quasi-band gap. The photonic density of states and its transformation with the photonic crystal temperature and thickness are determined. The ellipticity (ratio of the minor to the major axis of ellipse) of the light having passed through the sample is maximal at the center of the band gap and decreases when the distance from the band gap increases. At the center of the photonic quasi-band gap, the ellipticity increases with increasing photonic crystal thickness L and decreasing temperature, and it is close to a circular one in samples with L > 5 μm. The results obtained are compared with the existing theories, the analytical expressions derived from the Maxwell equations, and the results of numerical calculations performed by the 4 × 4 Berreman matrix method

Elliptical FRP-Concrete-Steel Double-Skin Tubular Columns under Monotonic Axial Compression

Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a novel form of hollow columns consisting of an outer FRP tube, an inner steel tube, and an annular layer of concrete between the two tubes. Due to the effective confinement of the two tubes, the concrete in hybrid DSTCs is well confined, leading to excellent ductility and strength enhancement. Hybrid DSTCs also have excellent corrosion resistence due to the effective protection of the outer FRP tube. However, existing studies mainly focused on hybrid DSTCs with a circular cross-section. When subjecting to different loads in the two horizontal directions, elliptical columns are preferred as they can provide different bending stiffness and moment capacity around two axes of symmetry without significantly reducing the confining effect of the FRP tube. This paper extends the existing work on circular DSTCs to elliptical DSTCs with a particular focus on four issues: the effect of elliptical aspect ratio (i.e., the ratio of the major axis to the minor axis of the outer elliptical cross-section), the effect of the FRP tube thickness, the effect of void area ratio (i.e., the ratio of the area of concrete void to the area of the outer elliptical section), and the effect of the cross-section of the inner steel tube (i.e., both rectangular and elliptical steel tubes were used). Experimental results show that, the averaged peak stress of the confined concrete in elliptical DSTCs increases with the increase in the elliptical aspect ratio, whereas the elliptical aspect ratio has no obvious effect on the ultimate axial strain; the cross-section shape of the inner steel tube has significant effect on the axial stress-strain behavior of the confined concrete in elliptical DSTCs; elliptical DSTCs with an elliptical steel tube exhibit much better ductility and strength enhancement than those specimens with a rectangular steel tube. A simple stress-strain model of confined concrete was proposed for elliptical DSTCs to account for the effects of the elliptical aspect ratio, the inner void, and the shape of the inner steel tube, which can provide reasonably accurate but conservative predictions.

Study of the nuclear symmetry energy from the rapidity-dependent elliptic flow in heavy-ion collisions around 1 GeV/nucleon regime

The elliptic flow ratio of neutrons versus protons in heavy-ion collisions (HICs) is one of the important probes to constrain the nuclear symmetry energy, however measuring the flow of neutrons with high precision is a great challenge for experimental techniques. In this work, the elliptic flow of protons is studied and it is found that the rapidity at which the sign of v2 changes from negative to positive is sensitive to the density dependence of the symmetry energy. By comparing the existing FOPI experimental data for proton flows to the calculations with the ultrarelativistic quantum molecular dynamics (UrQMD) model, the slope parameter of the nuclear symmetry energy is extracted to be L0=43±20 MeV at 95% confidence level. This is in good agreement with many recent results from investigations of nuclear structure properties and also partly overlaps with the recent result of the ASY-EOS experiment.

Elliptical-spiral elliptical-hole photonic crystal fiber with high birefringence, large nonlinearity, and two zero dispersion.

This paper presents a soft-glass (SF-57) elliptical-spiral photonic crystal fiber with elliptical air holes for achieving high birefringence, large nonlinearity, and tailoring two zero-dispersion wavelengths (ZDWs) in the near-infrared region. A full-vector finite-element method with perfectly matched boundary layer is used to characterize the properties of the photonic crystal fiber for different ellipticity ratios. The designed fiber has a birefringence 4 times higher than the circular-spiral structure. There are two ZDWs at around 1.2 µm and 2.8 µm which can be finely tuned depending on the ellipticity ratios along with a large nonlinearity. Due to the superior guiding properties, the proposed structure can be used for polarization control and broadband supercontinuum generation.

Polynomial decay in $W^{2,\varepsilon}$ estimates for viscosity supersolutions of fully nonlinear elliptic equations

We prove $W^{2,\varepsilon}$ estimates for viscosity supersolutions of fully nonlinear, uniformly elliptic equations where $\varepsilon$ decays polynomially with respect to the ellipticity ratio of the equations. Our result is related to a conjecture of Armstrong-Silvestre-Smart [Comm. Pure Appl. Math. 65 (2012), no. 8, 1169--1184] which predicts a linear decay for $\varepsilon$ with respect to the ellipticity ratio of the equations.

Karadeniz Bölgesi’nden Örneklenen Lüfer Balığının, Pomatomus saltatrix (Linnaeus, 1766) Otolit Şekil Analizi

In this study, otolith shape indices and relationships between otolith shape and otolith length of the bluefish species Pomatomus saltatrix (Linnaeus, 1766), which was sampled from the Samsun offshore of the Blacksea Region were investigated. A total of 166 samples (94♀ and 72♂) were taken from commercial fishermen in two different fishing seasons. Sagittal otoliths of each sample were removed and six different shape index (form factor, roundness, circularity, rectengularity, ellipticity and aspect ratio) were used in analyses. The linear model is preferred for calculating the relationships between otolith shape properties and otolith length. Paired t-test, wilcoxon test, independent t test were used for statistical analysis. The minimum and maximum total lengths and weights of the captured samples are between 13.5-24.8 cm and 22.01-161.19 g, respectively. There is no difference between female and male in terms of total length and weight. When otolith dimensions of female and male were compared, there were no differences in terms of Otolith Length, Otolith Breadth, Otolith Perimeter and Otolith Area (P˃0.05). However, according to left and right otoliths comparisons, there were differences in terms of OB and OP (P˂0.05). Ellipticity was found to have a much stronger relationship with otolith length than the other five parameters (r2˃0.590).

Simulation Effect of Crack Depth and Crack Location on Cylindrical Pressure Vessel

In the present study the problem of calculation of the stress intensity factors (SIF) of semi-elliptical cracks located in the shell and knuckle area of a pressure vessel is numerically solved by 3D Extended finite element method (XEFM) analysis. Crack also will be varied based on crack depth at constant elliptical ratio. The modeling details of the sub-structuring methodology, employed in the analysis, are discussed and the numerical approach is proven to be very efficient for the SIF calculation of pressure vessel semi-elliptical crack. Result of study show that crack with the same geometry, crack located in the shell has more tendency to propagate compare to crack located in the knuckle area. This phenomenon is due to stress at shell is dominated with tensile stress while in the knuckle area, stress is dominated with compressive stress.

An experimental study on vibration suppression of adjustable elliptical journal bearing-rotor system in various vibration states

The working principle of an adjustable elliptical journal bearing was introduced in the previous work, and the physical model has been designed and manufactured. As a continuation of research work, the vibration suppression behavior of the bearing-rotor system in various vibration states are studied experimentally this paper. Two bearing-rotor test rigs are established based on the adjustable bearing. The rigid rotor test rig is built up to study the forced vibration suppression when the rotor is operated at a relatively large unbalance and far lower from the critical speed. The flexible rotor test rig is built up to study the suppression of resonance vibration and the elimination of self-excited vibration. The resonance vibration is tested during the flexible rotor passing through the critical speed. The oil whip self-excited vibration is tested when the flexible rotor is operated near twice of critical speed. Under heavier static load, the forced vibration amplitude of the rigid rotor is suppressed by 50% through increasing the elliptical ratio of the bearings. The suppression effect of forced vibration is up to 60% under lighter static load. During passing through the critical speed, the maximum resonance vibration amplitude of the flexible rotor is suppressed about 30% through decreasing the elliptical ratio of the bearing. When the flexible rotor is operated near twice of the critical speed, the oil whip self-excited vibration is weakened and eliminated eventually through decreasing the elliptical ratio of the bearing.

Exploring next generation of IOT devices compatible few mode assisting ring core elliptical cladding optical fiber

In this paper, the design method of few mode elliptical ring core fiber (E-RCF) supporting up to 10 spatial linearly polarized (LP) modes is proposed. With the support of central circular hole, the maximum numbers of modes are generated using finite element method. Optical mode characteristics are optimized in two way; using the geometry properties of the elliptical ring core and radius of central hole region. Further, the mode performance is computed with the function of both ellipticity ratio (ρ) and wavelength. The results show that 10 distinct LP mode is adequately tuned in order to get higher index difference approximation ($$\Delta n_{eff}$$) to reduce the computational complexity. The results show for $$\Delta n_{eff}$$ between the adjacent modes and reported as larger than 18.80 × 10−4 at ρ = 2.5 and larger than 17.30 × 10−4 at the wavelength of 2 μm. The work also describes the E-RCF sustainability in the IoT environment and it promises for better paly upon the user demand with transmitting dense of data.

P3734Feasibility of percutaneous pulmonary valve implantation in the native right ventricle outflow tract from in vivo dynamic regional strain analysis

Abstract Background Patients surgically treated for congenital heart disease (e.g., Tetralogy of Fallot) frequently report long-term dysfunctions (i.e., pulmonary stenosis and/or incompetence) of the native right ventricle outflow tract (RVOT). The efficacy of percutaneous pulmonary valve implantation (PPVI) is recognized worldwide; however, the procedure is only feasible in RVOTs with appropriate size and functional substrate. Accordingly, a three-dimensional (3D) and dynamic assessment of the native RVOT function can be crucial to identify patients who can effectively benefit from PPVI, thus avoiding the risk of device embolization or fracture. Purpose We herein exploited an optical flow-based approach to develop a novel 3D framework for the quantitative in vivo assessment of dimension and dynamic changes of the native RVOT throughout the cardiac cycle. PPVI candidates (n=15) with previous surgery of the native RVOT were enrolled to demonstrate the additional contribution of our 3D patient-tailored analysis to the decision-making process. Methods Contrast-enhanced computed tomography (CT) was performed on a 64-slice dual-source multidetector CT system with retrospective ECG-gating. Multi-phase images of the RVOT were acquired at each 10% increment of the cardiac cycle (slice thickness = 1.5mm, increment = 1mm, pixel spacing = 0.35mm). We implemented a dedicated in-house framework, based on the optical flow tracking algorithm, to dynamically follow three anatomical cross-sections (i.e., proximal, mid and distal) of the native RVOT. The time course of area, perimeter and other relevant parameters (e.g., equivalent radius, elliptical ratio) were extracted and both areal (εA) and longitudinal strain (εlong) were computed on each the RVOT tracked cross-section. Maximum regional strain were calculated between the maximum and minimum value over the cardiac cycle. Dynamic changes in CT-derived variables were assessed using analysis of variance (p<0.05, statistically significant). Results All the enrolled anatomies were successfully analysed, locally pinpointing the in vivo pattern of deformation within each 3D RVOT anatomy (a). Anatomical regional RVOT dimensions (p<0.0001) and changes proved to be significantly different (p≤0.0002) throughout the cardiac cycle. In addition, the dysfunctional RVOT anatomy exhibited an irregular pattern of contraction and dilation: maximum regional strains markedly differed between RVOT regions, e.g., comparing the εA between RVOT mid (22.6%) and distal (46.0%) regions. In vivo tracking of RVOT dynamic changes Conclusions The combination of patient-specific in vivo imaging and bioengineering strategies can improve our understanding of RVOT dysfunctions in congenital patients referred to PPVI. Our optical flow-based and clinically-oriented framework can support the patient selection process and the planning of the percutaneous procedure in order to enhance its efficacy and shorten the operating time while improving the patient safety. Acknowledgement/Funding IRCCS Policlinico San Donato is a clinical research hospital partially funded by the Italian Ministry of Health

Numerical comparison of thermal and hydraulic performances for heat exchangers having circular and elliptic cross-section

The plain fin and circular tubes are generally used in heat exchangers of cooling systems. Numerous studies aiming at enhancing the thermal and hydraulic performances of this type of heat exchangers by changing the fin geometries are present in literature. In the present study, thermal and hydraulic performances of the heat exchangers with circular and elliptical tube have been compared using computational fluid dynamic method. Initially, the validation and comparison were done for the obtained data of the finned and circular tube design with respect to the performance results of the finned and circular tube design in the literature. The ellipticity ratios for the staggered arrangements of heat exchangers were changed within the range of b/a = 0.307–1.0. Numerical studies were performed with ANSYS-Fluent software within the range of Re = 750–2850 based on the fin spacing. As a result of the numerical validation studies, all analyses were solved by utilizing the SST k-ω turbulence model yielding closer values to the available studies similar to literature. Colburn factor j, friction factor f, JF values being the efficiency index and normalized j*, f* and JF* values were calculated and presented graphically. Moreover, temperature contours and streamline patterns were visually presented to evaluate the flow structures around the six different arrangements and to explain the physical reasons of pressure drop and heat transfer phenomena. The largest values of the Colburn factor j and the friction factor f known respectively as an indicator of heat transfer and a measure of pressure drop were obtained for the circular-tube-design ratio of b/a = 1.0 when compared to the other arrangements. According to the JF values, which is the efficiency index and the integrated outcome of heat transfer and pressure drop, the best result was obtained for the model with the diameter ratio of b/a = 0.307. Variations of the JF values for the arrangements of b/a = 0.333 and b/a = 0.307 depending on Reynolds numbers were found to be significantly close to each other. Finally, it is demonstrated that elliptical cross-section tubes with a better design in terms of lower pressure drop and less separated flow structures can be preferred in heat exchanger applications in order to provide energy saving.

Magnetoelectric Properties of Piezoelectric–Piezomagnetic Composites with Elliptical Nanofibers

Based on the surface/interface theory, the effective magnetoelectric (ME) properties of piezoelectric (PE)–piezomagnetic (PM) composites with elliptical nanofibers are investigated analytically. Using the complex function theory, conformal mapping and the Mori–Tanaka mean-field method, the solutions of magneto-electro-elastic (MEE) fields are obtained, which satisfy both the interface and the single-valued conditions. The closed-form expression of the ME coefficient of the composites shows that the effect of ME coefficient is related to the interface parameters, elliptical aspect ratio, material properties of both fiber and matrix and the fiber volume fraction. Numerical calculation shows that by properly selecting some of these parameters, the effective ME coefficient could be substantially enhanced.

An investigation of influence factor including different tube bundles on inclined elliptical fin-tube heat exchanger

A three-dimensional (3D) computational fluid dynamics (CFD) study is conducted to investigate the influence of tube ellipticity ratio e, tube rotation angle θ and fin spacing H on heat transfer capability. The tube ellipticity ratios range from 0.4 to 1.0 with increments of 0.1. The Reynolds number in the fluid domain varies from 1300 to 2100. The tube rotation angle ranges between 0° and 90°. The performance of heat exchanger is evaluated by non-dimensional parameters Colburn factor j, friction factor f, and Area goodness factor j/f. It can be concluded from this study that when Reynolds number and elliptical ratio are the same, a maximum of Colburn factor j occurs as θ increases, while the friction factor f keeps increasing. Furthermore, the maximum value decreases as the ellipticity ratio increases. The area goodness factor decreases sharply when θ > 45° for heat exchangers with different ellipticity ratios. The study also suggests that the inclined elliptical fin-tube heat exchanger with the tube ellipticity ratio e = 0.6 and rotation angle θ = 30° has the best heat exchange performance and airflow characteristics.

Thermal-Hydraulic Performance and Optimization of Tube Ellipticity in a Plate Fin-And-Tube Heat Exchanger

The flow field inside the heat exchangers is associated with maximum heat transfer and minimum pressure drop. Designing a heat exchanger and employing various techniques to enhance its overall performance has been widely investigated and is still an active research. The application of elliptic tube is an effective alternative to circular tube which can reduce the pressure drop significantly. In this study, numerical simulation and optimization of variable tube ellipticity is studied. The three-dimensional numerical analysis and a multi-objective genetic algorithm (MOGA) with surrogate modeling are performed. Tubes in staggered arrangement in fin-and-tube heat exchanger are investigated for combination of various elliptic ratios and Reynolds numbers. Results show that increasing elliptic ratio increases the friction factor due to increased flow blocking area, however, the effect on the Colburn factor is not significant. Moreover, tube with lower elliptic ratio followed by higher elliptic ratio tube has better thermal-hydraulic performance. To achieve the best overall performance, the Pareto optimal strategy is adopted for which the computational fluid dynamics (CFD) results, artificial neural network (ANN), and MOGA are combined. The tubes elliptic ratio and Reynolds number are the design variables. The objective functions include Colburn factor (j) and friction factor (f). The CFD results are input into ANN model. Once the ANN is computed, it is then used to estimate the model responses as a function of inputs. The final trained ANN is used to drive the MOGA to obtain the Pareto optimal solution. The optimal values of these parameters are finally presented.

An analytical model to study the effect of asperity geometry on forces in ploughing by an elliptical asperity

Abstract An analytical ploughing model is used to compute the forces on a rigid, elliptical, i.e. ellipsoid and elliptic-paraboloid shaped, asperity sliding through a rigid-plastic substrate as a function of its axes size, ellipticity ratio and sliding orientation. The normal force due to the plastic deformation of the substrate and the tangential force due to the shearing of the asperity-substrate interface are calculated from the surface normal vector and the tangent vector along the direction of plastic flow. The elemental forces are integrated over the boundaries of the asperity-substrate contact to obtain the individual force components. In this way, an analytical model to study the effect of asperity geometry on ploughing forces has been developed and compared with the available theories.

Failure mechanisms of wind-induced post-seismic rockfall hazard

The 2008 Mw 7.9 Wenchuan earthquake generated a tremendous number of coseismic landslides and induced dynamic crack propagation in the bedrock of slopes. These processes produced loose material that could be entrained in subsequent landslides potentially triggered by prevailing valley wind in the earthquake-affected area. However, almost nothing is currently known about the influence of wind in triggering rockfall hazard. Therefore, we provide insights into the failure process and mechanics of wind-induced rockfall hazard by means of wind tunnel tests using different rock geometries. First, a 1:1-scale failure process simulation is used to model the aerodynamic instability of different geometries of rock blocks, and results reveal that (i) cubic rocks fail via downwind sliding; (ii) cuboid rocks fail via tailwind toppling or crosswind toppling (the latter only occurs when the unstable rock mass is close to the neighboring wall); and (iii) ellipsoid rocks fail via headwind clockwise rolling. The critical wind speed is inversely proportional to the angle of attack, the aspect ratio, and the ellipticity ratio. Second, a mechanical analysis is performed in terms of aerodynamic coefficients based on 6:1- and 4:1-scale wind pressure measurements, which is beneficial for studying the crucial factors involved in the occurrence of different failure modes. In addition, fast and effective methods to estimate the critical wind speed for sliding and tailwind toppling are developed, respectively.

A proof of the Krylov–Safonov theorem without localization

The Krylov–Safonov theorem says that solutions to non-divergence uniformly elliptic equations with rough coefficients are Hölder continuous. The proof combines a basic measure estimate with delicate localization and covering arguments. Here we give a “global” proof based on convex analysis that avoids the localization and covering arguments. As an application of the technique we prove a estimate where ε decays with the ellipticity ratio of the coefficients at a rate that improves previous results, and is optimal in two dimensions.

Dynamic response of elliptical cylinders undergoing transverse flow-induced vibration

While the flow-induced vibration (FIV) of a circular cylinder has been characterised in considerable detail, the FIV of elliptical cylinders has not received similar attention. This study investigates the dynamic response of elastically-mounted elliptical cylinders with various cross-sectional aspect ratios (or elliptical ratios) in a free stream. The elliptical ratio is defined by ϵ=b∕a, where a and b are the streamwise and cross-flow dimensions, respectively, of the cross section of a cylinder placed at zero incidence angle. The elliptical ratios tested were in the restricted range of 0.67⩽ϵ⩽1.50, which was designed to achieve some but not too large a geometric deviation from a circular cylinder. The fluid–structure system was modelled using a low-friction air-bearing rig in conjunction with a free-surface recirculating water channel facility. This experimental set-up yielded very low mass and damping ratios. The FIV response was characterised as a function of reduced flow velocity. The results showed that the ellipses exhibited different response regimes as ϵ varied. Surprisingly, for the lowest elliptical ratio ϵ=0.67, there existed two separated lock-in regimes. However, for ϵ⩾0.80, lock-in occurred over only a single reduced velocity range that was characterised by different response regimes. As ϵ was increased above unity, lock-in tended to occur at considerably lower reduced velocities than for the circular cylinder case. Moreover, the peak vibration amplitude increased with the elliptical ratio. This means that the body vibration is enhanced, rather than attenuated, as the afterbody is reduced for an ellipse.

Analysis on thermal hydraulic performance of the elliptical tube in the finned-tube heat exchanger by new method

The main objectives were to develop a method for designing an effective finned heat exchanger through changing the configuration to ensure the tubes be streamlined shape. Kinds of inserts including, vortex generator, louver fin, and serrated fin in the heat transfer was used to increase the effect of thermal performance, but also was harmful to the flow characteristics. Consequently, the comprehensive performance was obviously lower than the heat exchangers with no inserts. In order to solve this problem, streamlined tube configuration was adopted in this paper to search a new method to enhance the comprehensive performance by reducing the Karman vortex street effect. Two modified configurations of tube were investigated in this paper. The modified configurations were both made of semicircular tube and semielliptical tube. The simulation was validated by Wang’s experiment and Arafat’s simulation. The numerical data were presented at Reynolds number in the range between 1300 and 2000. Based on the numerical results, the effect of elliptical axis ratio on the thermal hydraulic performance was discussed. The results showed that the comprehensive performance of the modified configurations was greater than that of the circular tube. In addition, the velocity vector, flow streamline and temperature contour of the configurations were displayed. The Karman vortex street effect was adopted to explain the reason of wake region formation. It can be concluded that long and thin section of heat transfer tube, which was coincident with streamlined design, was beneficial to improve the comprehension performance of the heat exchanger.

Analytical and Finite Element Approach for the In-plane Study of Frames of Non-conventional Civil Aircraft

In this paper, we study families of optimal frames of aircraft, as the fuselage cross-section vary, in the preliminary design. A complete closed-form solution of displacements and stresses for a circular arc, already introduced in a previous paper of the authors, is applied to study, in a wide generality, a fuselage cross-section made of tangent circular arcs, connected together in a $${\mathscr {C}}^1$$ -class curve. The closed-form solution is used here for two optimization case studies involving such piece-wise tangent cross-sections. First, we obtain minimum weight configurations of frames under pressurization, and also the effect of a small eccentricity with respect to the perfect circular fuselage is investigated; then, the constraints due to the presence of two floor decks are introduced. Second, the analytic solutions are validated by means of a finite element simulation in Abaqus and, to show the generality of the closed-form solution, the case studies are dedicated to non-conventional aircraft. Finally, we investigate the effects of the ellipticity ratio and the presence of a vertical and horizontal truss by means of finite element beam models.