Straight Cylinder Research Articles

О стабильности капель катализатора на границе контакта пар-жидкость-кристалл в процессе роста нитевидных нанокристаллов

The paper provides a physical justification for the wettability conditions for a crystalline surface of a limited area by a small-volume catalytic liquid at the end of a growing nanowires (NW) characterized by a contact angle β, which contributes to a fundamental understanding of the nature of the contact angle of catalyst drops at the top of the NW. It is shown that under the conditions of stationary growth of NWs with a transverse singular face, there are only values of the angles β and γ (the angle of inclination of the side surface of the crystal to this face), which correspond to the minimum increment of the free energy of the three-phase system αLVcosβ + αSL = αSVcosγ and determine the stability of the catalyst drop at the top of the NW. With the growth of cylindrical NWs, the conditions of indifferent equilibrium are realized at the drop wetting perimeter. A drop, due to the dissolution of a crystallizing substance or its separation from a liquid solution, can take an equilibrium shape with a contact angle β that does not satisfy the equilibrium contact angle condition θ in the Young equation. A concentric break (rib) at the NW tip should increase the observed wetting angle θ and lead to contact angle hysteresis. The restrictions imposed on the value of the contact angle of a stable catalyst drop at the top of the NW are determined. The catalyst drop will take an equilibrium shape if the hysteresis angle β is in the range θ < β ≤ θ' + γ (θ' is the wetting angle of the NW side walls). For the growth of semiconductor NWs in the form of a straight cylinder, γ = 90° and therefore always β > 90°. It is shown that the direction of displacement of the three-phase line relative to the droplet surface is determined by the growth angle φ0: for the nonwetting growth mode of NWs (with a transverse face) φ0 = β – γ; for the wetting growth mode (with the end surface curved near the three-phase line)

Corrosion Characterization of Friction Stir Weld Dissimilar Aluminium Alloy Joints

The course of contact mix welding is quick acquiring conspicuousness in aviation, marine and car industry because of its benefits as far as mechanical strength, effect and hardness characteristics. There is as yet a requirement for sure fire consideration from the exploration local area to erosion in grating mix welding zones, hence the work introduced here centres around the consumption portrayal of the grinding mix weld divergent aluminium composite. This study looks into friction stir welding under various parametric settings and shows how corrosion happens in a sodium chloride electrolytic media under potentio-dynamic conditions. The friction stir weld joints of dissimilar alloys aluminium are constructed using three sets of parameters. Straight cylinder, taper cylinder, and straight triangular tool profiles; tool rotational speeds of 800, 1000, and 1200 rpm; tool feed rates of 100, 120, and 140 mm/min; and tool offsets of 0.5, 0 mm, and -1.5 mm. The corrosion current (Icorr) reduces as tool rotating speed increases up to 1200 rpm, after which it slightly increases due to the creation of ridges all around the periphery of the friction stir weld area.

Numerical Investigation of Flow Past Bio-Inspired Wavy Leading-Edge Cylinders

A numerical investigation is proposed to explore the flow past a novel wavy circular cylinder as a passive flow control, whose shape is determined by a sinusoidal function applied to its leading edge line, similar to studies with wavy leading-edge airfoils. The latter are motivated by the wavy-shaped tubercles found in the flippers of humpback whales, which are believed to improve their maneuverability. Our attempt is, therefore, to assess the effects of leading-edge waviness now on a simpler and canonical geometry: circular cylinders. The present work relies on iLES simulations conducted with Nektar++ at a Reynolds number of 3900. Besides the straight cylinder, two wavy geometries are assessed, which are determined by a single wavelength of 37.5% for two amplitudes, 3% and 11%, based on the mean diameter of the wavy cylinder. Our results showed that, contrary to what is usually the case with traditional wavy cylinders at similar Reynolds numbers, waviness caused a reduction in the near-wake recirculation length and an increase in the mean near-wake turbulent kinetic energy compared to the straight cylinder. This was followed by a reduction in base pressure (up to about 36%) leading to a rise in lift oscillations and also to a significant increase in the mean drag coefficient of up to about 28%. An attempt to detail the flow phenomena is provided, evidencing the emergence of counter-rotating pairs of streamwise vortices between peaks. It is argued that the differences observed in recirculation length, turbulent kinetic energy, and force coefficients start even prior to the formation of these coherent structures and end up with interactions with the near wake.

Overdetermined elliptic problems in onduloid-type domains with general nonlinearities

In this paper, we prove the existence of nontrivial unbounded domains Ω⊂Rn+1,n≥1, bifurcating from the straight cylinder B×R (where B is the unit ball of Rn), such that the overdetermined elliptic problem{Δu+f(u)=0in Ω, u=0on ∂Ω, ∂νu=constanton ∂Ω, has a positive bounded solution. We will prove such result for a very general class of functions f:[0,+∞)→R. Roughly speaking, we only ask that the Dirichlet problem in B admits a nondegenerate solution. The proof uses a local bifurcation argument.

Physical origin of vortex stretching and twisting: Viscous or inertial forces

In this paper, the physical origin of vortex stretching and twisting is theoretically investigated. The effects of inertial and viscous forces are mainly considered and discussed. Two key conditions, i.e., solid walls and three-dimensional (3D) disturbances, are adopted in three typical cases. Among them, the first two cases are straight and curved vortex lines at the initial time without any kind of disturbance. The third case is a straight vortex line at the initial time with introduced 3D natural disturbances. Through experimental observations, numerical simulations, and theoretical analysis in these cases, the first two cases illustrate that the straight or curved vortex lines are still straight or curved at the next time, respectively, regardless of whether solid walls are introduced. However, the third case clearly shows that once natural disturbances are introduced, the straight vortex lines near and at solid walls at the initial time are stretched and twisted mainly by viscous forces, instead of inertial forces, typically demonstrated by the 3D wake transition of a straight circular cylinder and the transition of the laminar boundary layer at a flat plate. Accordingly, based on definitions of generation and enhancement in vortex stretching and twisting, it is confirmed that the viscous forces with two key conditions are the generation mechanism, while the inertial forces alone are the enhancement mechanism.

Quasimodes in the cusp continuum in nonuniform magnetic flux tubes

Context. The study of magnetohydrodynamic (MHD) waves is important both for understanding heating in the solar atmosphere (and in particular the corona) and for solar atmospheric seismology. The analytical investigation of wave mode properties in a cylinder is of particular interest in this domain because many atmospheric structures can be modeled as such in a first approximation. Aims. The aim of this study is to use linearized ideal MHD to investigate quasimodes (global modes that are damped through resonant absorption) with a frequency in the cusp continuum, in a straight cylinder with a circular base and an inhomogeneous layer at its boundary that separates two homogeneous plasma regions inside and outside. We are particularly interested in the damping of these modes, and therefore try to determine their frequency as a function of background parameters. Methods. After linearizing the ideal MHD equations, we found solutions to the second-order differential equation for the perturbed total pressure in the inhomogeneous layer in the form of (1) Frobenius series around the regular singular points that are the Alfvén and cusp resonant positions, and (2) power series around regular points. By connecting these solutions appropriately through the inhomogeneous layer and with the solutions of the homogeneous regions inside and outside the cylinder, we derive a dispersion relation for the frequency of the eigenmodes of the system. Results. From the dispersion relation, it is also possible to find the frequency of quasimodes, even though they are not eigenmodes. As an example, we find the frequency of the slow surface sausage quasimode as a function of the width of the inhomogeneous layer for values of the longitudinal wavenumber relevant for photospheric conditions. The results closely match findings by other authors who studied the resistive slow surface sausage eigenmode. We also discuss the perturbation profiles of the quasimode and the eigenfunctions of continuum modes.

Surface modification of hBN reinforced aluminum alloy Al 2024 through friction stir processing

The focus of this study is to see if Friction Stir Processing can improve the properties of an aluminium alloy with Boron Nitride (BN) particles on the surface. Friction Stir Processing (FSP) is a new surface alteration technique that uses friction to cause plastic deformation, resulting in grain refining and improved mechanical and surface properties. To process 2024 aluminium alloy plates, a straight cylinder tool was used under varying process parameters and to conduct tensile, hardness, wear and impact studies. The findings were evaluated in order to infer the significance of the process parameter and the reinforcement of the metal improvement properties. Friction Stir Processing was effectively processed by reinforcing the Boron Nitride plates and achieved significant changes in the mechanical and surface properties.

A mesh-based model of liver vasculature: implications for improved radiation dosimetry to liver parenchyma for radiopharmaceuticals

PurposeTo develop a model of the internal vasculature of the adult liver and demonstrate its application to the differentiation of radiopharmaceutical decay sites within liver parenchyma from those within organ blood.MethodComputer-generated models of hepatic arterial (HA), hepatic venous (HV), and hepatic portal venous (HPV) vascular trees were algorithmically created within individual lobes of the ICRP adult female and male livers (AFL/AML). For each iteration of the algorithm, pressure, blood flow, and vessel radii within each tree were updated as each new vessel was created and connected to a viable bifurcation site. The vascular networks created inside the AFL/AML were then tetrahedralized for coupling to the PHITS radiation transport code. Specific absorbed fractions (SAF) were computed for monoenergetic alpha particles, electrons, positrons, and photons. Dual-region liver models of the AFL/AML were proposed, and particle-specific SAF values were computed assuming radionuclide decays in blood within two locations: (1) sites within explicitly modeled hepatic vessels, and (2) sites within the hepatic blood pool residing outside these vessels to include the capillaries and blood sinuses. S values for 22 and 10 radionuclides commonly used in radiopharmaceutical therapy and imaging, respectively, were computed using the dual-region liver models and compared to those obtained in the existing single-region liver model.ResultsLiver models with virtual vasculatures of ~ 6000 non-intersecting straight cylinders representing the HA, HPV, and HV circulations were created for the ICRP reference. For alpha emitters and for beta and auger-electron emitters, S values using the single-region models were approximately 11% (AML) to 14% (AFL) and 11% (AML) to 13% (AFL) higher than the S values obtained using the dual-region models, respectively.ConclusionsThe methodology employed in this study has shown improvements in organ parenchymal dosimetry through explicit consideration of blood self-dose for alpha particles (all energies) and for electrons at energies below ~ 100 keV.

Modeling and simulation of creep response of sorghum stems: Towards an understanding of stem geometrical and material variations

Sorghum [ Sorghum bicolor (L.) ] is a tropical grass that often suffers from structural failure (lodging) when subjected to wind, rain, and hail. During lodging, excessive lateral deflection occurs, which inherently correlates with the biomechanical properties of the stem. As such, a fundamental understanding of sorghum's biomechanical behavior is required to mitigate its propensity for lodging. Herein, we perform creep tests to characterize the mechanical behavior of Della genotype sorghum stems and their constituents, i.e., their rind and pith. This study also examines the influence of various testing geometries and boundary conditions on mechanical property characterization. We determine that small geometric irregularities typical of sorghum stems (e.g., from straight circular cylinders) do not affect their mechanical response in an overall engineering strain sense. However, these typical geometric irregularities do lead to nonuniform (localized) stresses and strains, thereby influencing the quantification of certain properties during mechanical testing. We also implement a viscoelastic constitutive model to describe the creep responses of the individual constituents (rind and pith), as to predict the overall biomechanical response of the stems. We find that even though the rind carries most of the load in the stem and itself does not show a significant time-dependent response, an overall time-dependent response of the stem still occurs, arising from viscoelastic effects in the pith.

Influence of tool pin profiles in the strength enhancement of friction stir welded AA5083 and AA5754 alloys

Friction stir welding (FSW) is a well-known technology for joining similar and dissimilar materials. The quality of the weld in FSW is affected by the various process parameters such as tool rotational speed (TRS), tool transverse speed (TTS) and tool pin profiles. This study aims to investigate the effect of three different tool pin profiles on the variation of microstructure and mechanical strength of friction stir welded AA5083 and AA5754 alloys joints. Both of these alloys combinations offer excellent corrosion resistance and formability. As a result, they’re commonly seen in tanks, pressure vessels, shipyards, and trucks. In this work, the FSW methodology focused on varying the TRS of 750, 1000, 1250 and 1500 rpm and TTS as 20, 30, 40 and 50 mm min−1. The surface microstructures of the weldments were analyzed using an optical microscope and scanning electron microscope. Tensile and Microhardness tests were carried out on the weldments to determine the weld strength. Three variety of tool pins, namely straight square, threaded cylinder, and straight cylinder were used for this study. The microstructural and the mechanical properties analysis of the welded samples proved that the straight square tool pin profile is suitable for joining AA5083 and AA5754 alloys. The weldments prepared using a straight square pin profile exhibited good material stream behaviour, uniform spreading of plastic deformation in the weld zone and aided in the reduction of formation of macroscopic defects on the welded zone. Among the process parameters, it was detected that the pin profile displays more impact on tensile strength followed by tool rotation speed and welding speed. According to the findings, the dissimilar weld joint formed at the optimum process parameters had the highest tensile strength of 212 MPa and hardness of 88 HV were: Square Tool Profile, 1250 rpm TRS, and 40 mm min−1 TTS.

The dynamics and observability of circularly polarized kink waves

Context. Kink waves are routinely observed in coronal loops. Resonant absorption is a well-accepted mechanism that extracts energy from kink waves. Nonlinear kink waves are know to be affected by the Kelvin-Helmholtz instability. However, all previous numerical studies consider linearly polarized kink waves. Aims. We study the properties of circularly polarized kink waves on straight plasma cylinders, for both standing and propagating waves, and we compare them to the properties of linearly polarized kink waves. Methods. We used the code MPI-AMRVAC to solve the full 3D magnetohydrodynamic equations for a straight magnetic cylinder, excited by both standing and propagating circularly polarized kink (m = 1) modes. Results. The damping due to resonant absorption is independent of the polarization state. The morphology or appearance of the induced resonant flow is different for the two polarizations; however, there are essentially no differences in the forward-modeled Doppler signals. For nonlinear oscillations, the growth rate of small scales is determined by the total energy of the oscillation rather than the perturbation amplitude. We discuss possible implications and seismological relevance.

Rheology of stiff-chain polymer solutions

Theoretical expressions for the intrinsic viscosity, the Huggins coefficient, zero-shear viscosity, and storage and loss moduli for stiff-chain polymer solutions are reviewed. Especially, the mean-field Green function method is explained in detail to consider the intermolecular collision effect on the rheological properties of concentrated stiff-chain polymer solutions, by applying the method to monodisperse and polydisperse straight cylinders and monodisperse fuzzy cylinder models. The theoretical expressions reviewed are compared with experimental results for aqueous solutions of two rigid helical polysaccharides, schizophyllan and xanthan.

Aircraft Pipe Gap Inspection on Raw Point Cloud From a Single View

The pipe is a common part of aviation equipment. The pipe gap is one of the important factors that affect the safety of an aviation equipment system. It is crucial to quickly and accurately measure the gaps among the pipes within the aviation equipment. Due to the complexity of the aviation pipeline system, inspecting the spacing efficiently among different pipes is challenging. In this paper, we propose an effective method to inspect the gaps among aircraft pipes over the raw point data from a single view. First, we design a probe function to extract the information of pipe structures based on the cylinder feature consistency among proximity patches. The probe function is intended to avoid the interference of other structures and also provides an appropriate starting location when extracting the pipe structure information. We then design a growth guidance strategy based on the continuity of pipe axial directions, which can ensure the continuity and accuracy of pipe centerline extraction. Since the curved smooth pipe can be subdivided into many straight cylinders, we devise an adaptive growing method which can ensure the centerline extraction efficiency of multi-curvature aviation pipes. Extensive experiments demonstrate that our algorithm outperforms the state-of-the-art methods in terms of inspection accuracy and efficiency.

Three Crossing Limit Cycles in a 3D-Filippov System Having a T-Singularity

Our starting point is a discontinuous piecewise linear dynamical system in [Formula: see text] with two zones that present a single invisible two-fold straight line and invariant cylinders. We broke the dynamics of this vector field to obtain a new four-parameter piecewise linear vector field with a [Formula: see text]-singularity. For this vector field, we prove that the upper bound of simple crossing limit cycles (simple CLCs) is three, and provide conditions for the existence of 1, 2, or 3 simple CLCs. We also show the occurrence of three distinct bifurcations involving such simple CLCs that are derived from a bifurcation set with two parameters: (i) a Teixeira Singularity bifurcation (TS-bifurcation); (ii) a Fold bifurcation; and (iii) a Cusp bifurcation.

Pulsatile Flow of Copper Suspended Nanofluid Venture Through a Bifurcated Artery

With an aim to investigate the pulsatile flow of blood through a bifurcated artery with mild stenosis in the parent lumen in the manifestation of heat transmission. The blood is treated to be copper suspended nanofluid. The arteries forming bifurcation are assumed to be symmetric about the axis of the parent artery and straight circular cylinders of limited length. The highly nonlinear momentum and energy equations of nanofluid model are simplified by considering the mild stenosis case and a radial coordinate transformation is initiated to map irregular geometry into a rectangular grid. The solution for flow rate, impedance, shear stress are found by using the finite difference scheme in a cylindrical coordinate system. An extensive quantitative analysis has been performed based on numerical computations in order to estimate the effects of pertinent parameters on various physical quantities near the apex by means of their graphical representations so as to validate the applicability of the proposed mathematical model.

Mathematical Modeling of Blood Flow Through a Stenosed Bifurcated Artery With Heat Source and Magnetic Effect

The present article illustrates the influence of heat source on MHD blood flow in a branched artery with small obstacle in its main artery by treating blood as micropolar fluid. Artery forming branch is presumed as straight cylinder of restricted length and is symmetric about its axis. The irregular shape of constricted branched artery is changed to a well defined shape by utilizing a adial coordinate transformations. Numerical solution is computed for interested physical quantities such as rate of flow, and shearing stress on one as well as the other sides of the apex.

Nonlinear Aeroelastic Analysis of High-Aspect-Ratio Wings with a Low-Order Propeller Model

A nonlinear aeroelastic analysis framework for high-aspect-ratio wings that includes the aerodynamic effects of propellers is described. The high computational cost required for modeling aerodynamic interaction between the wing and propeller wake is reduced by taking advantage of the relatively slow dynamics of the wing. Consequently, the propeller wake is modeled as a straight vortex cylinder that does not require a computationally expensive wake updating process. By leveraging the smallness of the propeller, an averaged vortex cylinder method is proposed that calculates the induced velocities of the propeller vortex cylinder efficiently without suffering from a numerical singularity and loss of accuracy. The induced velocities are considered in the wing aerodynamic force calculation using an unsteady vortex lattice method. An efficient propeller cylinder coordinate generation method modeling the propeller-attached wing by absolute nodal coordinate formulation with a multibody dynamic theory is also proposed. The developed framework is validated by comparison with other formulations. A static aeroelastic analysis on a low-speed high-aspect-ratio wing demonstrates that the propeller-induced axial velocity causes the deflection change of 5.4%. A nonlinear dynamic result shows that the propeller decreases the vibration amplitude by 6.7% because the propeller-induced axial velocity enhances the aerodynamic damping.

Effect Of Taper Angle On Flow And Stress In Conical Shell Fluid Mixers

Hollow cylindrical flow mixers achieve a homogeneous mixture with less pressure loss and higher momentum. However, the low volume of the mixer due to the hollow creates high pressure effects and mechanical stresses on the mixer. In this study, the stresses formed on the mixer by considering the flow and thermal effects of fluids in a conical cylinder mixer at different temperatures were examined. The effect of taper angle has been studied. In the examinations carried out using the finite element method, a verification study was first made, and solution sensitivity was determined. Water as fluid in standard conditions and common steel properties as cylinder material were used. Plate thickness was chosen to be 1 mm. It seems more appropriate to use a non-conical straight model to achieve thermal equilibrium. The taper angle reduced the velocity of fluid entering the mixer. Stress concentrations were observed at the supports and a lower and decreasing stress distribution was obtained for the conical mixer while it was constant for the straight cylinder in the other regions.

Fluorescence hyperspectral imaging system for analysis and visualization of oil sample composition and thickness.

In this paper, a compact fluorescence hyperspectral imaging system based on a prism-grating-prism (PGP) structure is designed. Its spectrometer spectral range is 400-1000 nm with a spectral resolution of 2.5 nm, and its weight is less than 1.7 kg. The PGP imaging spectrometer combines the technical advantages of prism and grating, by not only using six lenses for imaging and collimation to realize the dual telecentres of object and image but also having a "straight cylinder" structure, which makes the installation and adjustment simple, compact, and stable. By the push-broom method, we obtained the three-dimensional cubic data of different oil products. By normalization processing, minimum noise separation transformation processing, visualization processing, and support vector machine classification processing of different oil fluorescence hyperspectral data, we demonstrate that the fluorescence hyperspectral imaging system can identify different kinds of oil and recognize the oil film thickness. The fluorescence hyperspectral imaging system can be used in oil spill detection, resource exploration, natural disaster monitoring, environmental pollution assessment, and many other fields.

Intramolecular structure and dynamics in computationally designed peptide-based polymers displaying tunable chain stiffness

Polymers assembled using computationally designed coiled coil bundlemers display tunable stiffness via control of interbundlemer covalent connectivity as confirmed using small-angle neutron scattering. Neutron spin echo spectroscopy reveals that rigid rod polymers show a decay rate $\mathrm{\ensuremath{\Gamma}}\ensuremath{\sim}{Q}^{2}$ ($Q$ is the scattering vector) expected of straight cylinders. Semirigid polymers assembled using bundlemers linked via 4-armed organic linker show flexible segmental dynamics at mid-$Q$ and $\mathrm{\ensuremath{\Gamma}}\ensuremath{\sim}{Q}^{2}$ behavior at high Q. The results give insight into linker flexibility-dependent interbundlemer dynamics in the hybrid polymers.