Rotation Of Rods Research Articles

A mixing index for uniformly and gap-graded cohesionless particles influenced by mixing rate and diameter of stirring rods

Soil mechanics, sometimes, deals with the mixing of soil such as in deep mixing of soil and mixing of soil in tunnel boring machines, i.e., earth pressure balance (EPB-TBM) shields. The geometry of mixing apparatus such as size of stirring rods plays an important role to achieve higher degree of mixing. Moreover, the effect of gap-graded particles being mixed on degree of mixture should also be evaluated. It is important to estimate the extent of mixing of the soil to confirm the required performance of such phenomenon.This study aims to propose a simple method to quantify the degree of mixture of solid particles stirred by rotation of rods with varying diameters at different mixing rates. Discrete element method (DEM) is used to simulate the stirring process and evaluate the degree of mixture at each rotation based on the spatial distribution of different types of particles. To reduce complexity in the mixing process of particles, this study focuses on monodispersed (i.e., uniformly graded) and bidispersed (i.e., narrowly gap-graded) spherical particles where inter-particle cohesion is not considered. The DEM results reveal spatial variation of the degree of mixture (dm) in the given volume; however, its mean (dm¯) increases with the rotation number of stirring rods. Besides, dm¯ depends on the size of stirring rods whereas the mixing rate is less sensitive to dm¯ for the non-cohesive sandy particles. The dm¯ of narrowly gap-graded particles cases is slightly on the lower side as compared to that of uniformly graded particles. The results of the DEM simulations are validated through the model test.

DNA double helix, a tiny electromotor.

Flowing fluid past chiral objects has been used for centuries to power rotary motion in man-made machines. By contrast, rotary motion in nanoscale biological or chemical systems is produced by biasing Brownian motion through cyclic chemical reactions. Here we show that a chiral biological molecule, a DNA or RNA duplex rotates unidirectionally at billions of revolutions per minute when an electric field is applied along the duplex, with the rotation direction being determined by the chirality of the duplex. The rotation is found to be powered by the drag force of the electro-osmotic flow, realizing the operating principle of a macroscopic turbine at the nanoscale. The resulting torques are sufficient to power rotation of nanoscale beads and rods, offering an engineering principle for constructing nanoscale systems powered by electric field.

Channel switch based on the transformation of two kinds of topological edge states

In this paper, we have constructed a compound triangular lattice in which the optical quantum spin Hall effects and quantum valley Hall effects can simultaneously occur. Through the rotation of the dielectric rods in the lattice, two complete photonic band gaps with nontrivial topology can be created, one of which is due to the band inversion associated with the pseudospin degree of freedom at point in the first Brillouin zone (BZ) and the other due to the gapping out of Dirac cones associated with the valley degree of freedom at K point in the first BZ. The transformation between the two kinds of topological edge states can be also achieved through the rotation of the dielectric rods. A four-channel structure model is proposed to demonstrate the transformation and to achieve the channel switch of the topological edge states.

Tension-induced phase transformation and anomalous Poisson effect in violet phosphorene

Two-dimensional violet phosphorene (VP) nanosheets are promising semiconductor materials with unique cross structures distinct from those of their allotropes such as black phosphorene and blue phosphorene, but their mechanical behaviors remain almost unexplored. By using the first-principles calculations, in this paper we investigate the mechanical behaviors of monolayer, bilayer, and bulk VP under uniaxial tension. A phase transformation from the open-pore phase to closed-pore phase is observed in VP structures when under a specific tensile strain. It is revealed that the phase transformation is attributed to the competition between the rotation and elongation of sub-nano rods in VP structures during the loading process. Due to the phase transformation, the in-plane Poisson's ratio of monolayer VP can become greater than 1.2, while the bulk VP possesses a negative out-of-plane Poisson's ratio with a magnitude up to -0.3 at a certain strain. These results indicate that Poisson effects in VP are superior to those in any other existing two-dimensional materials. In addition, based on the tensor analysis of elastic constants, a strong mechanical anisotropy is observed in VP structures both before and after the phase transformation. Besides the mechanical properties, the band gap of all VP structures decreases as the applied tensile strain increases, which can eventually transform into the metallic state prior to their fracture. The combination of unique phase transformation, anomalous Poisson effect, strong mechanical anisotropy and tunable electronic properties render VP be a novel nanoscale metamaterial with multifunctional applications.

Programmable coding photonic topological edge waveguide

In order to obtain reconfigurable topological photonic waveguides, we design a two-dimensional photonic crystal with compound triangular lattice. Through rotating the dielectric rods, we change the topological phase of the lattice and achieve the topological edge states. Through the rotation of rods, we divide the two-dimensional structure space into “0” and “1” blocks made of the topologically trivial and nontrivial lattices, respectively. Through programming the codes of “0” and “1,” we can realize diverse transport pathways of light flow. The controllable light pathways will play important role in the optical circuit. The programmable design results have been demonstrated through the simulations of electromagnetic wave transport.

Pseudospin states and topological phase transitions in two-dimensional photonic crystals made of dielectric materials

Based on the transmission properties of against backscattering and robustness against defects, photonic topological insulators have opened up a novel way to steer the propagation of electromagnetic wave. In order to construct the photonic analogs of the quantum spin Hall effect in an electronic system, we propose a simple two-dimensional photonic crystal made of dielectric materials to realize topologically protected edge states associated with the photonic pseudospin. The photonic crystal comprises a honeycomb array of equilateral-triangle-ring-shaped silicon rods embedded in an air host. By simply rotating the silicon rods around their respective centers by 60°, the band inversion between a twofold degenerated dipolar mode and a twofold degenerated quadrupolar mode is clearly observed in the Brillouin zone center. For the double twofold degenerated states, the chirality of the time-averaged Poynting vector surrounding the unit cell center (i.e., right-hand or left-hand circular polarizations) plays the role of the pseudospin degree of freedom in the present photonic system, and their point group symmetry can be utilized to construct a pseudo-time-reversal symmetry. By utilizing <inline-formula><tex-math id="M2">\begin{document}${{k}} \cdot {{p}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20191962_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20191962_M2.png"/></alternatives></inline-formula> perturbation theory, we develop an effective Hamiltonian for the associated dispersion relation around the Brillouin zone center and calculate the spin Chen number, which indicates that the band inversion leads to a topological phase transition from a trivial to a nontrivial state. With numerical simulations, we unambiguously demonstrate that the unidirectional propagation of pseudospin-dependent edge state along the interface between a topologically nontrivial photonic crystal and a trivial one, and robustness of the edge states against different defects including sharp bend and cavity, regardless of the type of interface. The photonic system proposed by us consists of dielectric materials and the corresponding lattice structure is simple. And without changing the fill ratio or changing the positions of the silicon rods, a simple rotation of the silicon rods can generate the topological phase transition. So the potential applications of the pseudospin-dependent edge states based on our design are expected in more efficient way.

Rotation of intramedullary alignment rods affects distal femoral cutting plane in total knee arthroplasty.

Intramedullary rods are widely used to align the distal femoral cut in total knee arthroplasty. We hypothesised that both coronal (varus/valgus) and sagittal (extension/flexion) cutting plane are affected by rotational changes of intramedullary femoral alignment guides. Distal femoral cuts using intramedullary alignment rods were simulated by means of a computer-aided engineering software in 4°, 6°, 8°, 10°, and 12° of valgus in relation to the femoral anatomical axis and 4° extension, neutral, as well as 4°, 8°, and 12° of flexion in relation to the femoral mechanical axis. This reflects the different angles between anatomical and mechanical axis in coronal and sagittal planes. To assess the influence of rotation of the alignment guide on the effective distal femoral cutting plane, all combinations were simulated with the rod gradually aligned from 40° of external to 40° of internal rotation. Rotational changes of the distal femoral alignment guides affect both the coronal and sagittal cutting planes. When alignment rods are intruded neutrally with regards to sagittal alignment, external rotation causes flexion, while internal rotation causes extension of the sagittal cutting plane. Simultaneously the coronal effect (valgus) decreases resulting in an increased varus of the cutting plane. However, when alignment rods are intruded in extension or flexion partly contradictory effects are observed. Generally the effect increases with the degree of valgus preset, rotation and flexion. As incorrect rotation of intramedullary alignment guides for distal femoral cuts causes significant cutting errors, exact rotational alignment is crucial. Coronal cutting errors in the distal femoral plane might result in overall leg malalignment, asymmetric extension gaps and subsequent sagittal cutting errors.

Deployment dynamics modeling and analysis for mesh reflector antennas considering the motion feasibility

Mesh reflector antennas have been widely used in space satellites for their characteristics of large aperture, low levels of total mass, stowed volume, surface distortion, etc. The antenna turns from a stowed state to a fully deployed configuration and finally forms a required functional surface, and this deployment process affects the performances of antennas on orbit. The dynamic modeling and analysis for the deployment of mesh reflector antennas considering the rigid body rotation of rods, the geometric nonlinearity of the cable net, and the rigid-flexible coupling of the truss and the cable net are presented in this paper. Instead of the previous lumped mass model, the mass of hinges is concentrated on their centroids and the longerons, battens, and diagonals are regarded as homogeneous rods in the study. By this model, the rigid body motion of rods can be well considered in the calculation of kinetic energies rather than be ignored in previous researches. Then, the cable net is discretized into multiple cable elements that are modeled by springs. The slacked and tensioned state of cable elements during deployment are captured by updating the stiffness matrix real-timely. The elastic energy of the cable net is derived by solving systematic equilibrium equations. The dynamic model is established by using Lagrange equation, and then the driving force under the predesigned motion is derived. The “ideal deployment motion” and “feasible deployment motion” are proposed and discussed through several numerical examples. Simulation results match well with experimental data in previous literature.

Stepwise Rotation of Nanometric Building Blocks in the Aragonite Helix of a Pteropod Shell

Aragonite helical fibers in the shell of a pteropod Cavolinia globulosa are shown to consist of single-crystalline rod-like building blocks ∼1 μm long and ∼100–200 nm wide. Although the building blocks of the orthorhombic crystal share similar c-axis orientations along the surface normal, their a and b directions rotate in a stepwise fashion. The crystallographic rotation of the unit rods and the twisted stacking of the fibers along the helical axis form the specific hierarchical architecture of the pteropod shell.

Intraoperative implant rod three-dimensional geometry measured by dual camera system during scoliosis surgery.

Treatment for severe scoliosis is usually attained when the scoliotic spine is deformed and fixed by implant rods. Investigation of the intraoperative changes of implant rod shape in three-dimensions is necessary to understand the biomechanics of scoliosis correction, establish consensus of the treatment, and achieve the optimal outcome. The objective of this study was to measure the intraoperative three-dimensional geometry and deformation of implant rod during scoliosis corrective surgery.A pair of images was obtained intraoperatively by the dual camera system before rotation and after rotation of rods during scoliosis surgery. The three-dimensional implant rod geometry before implantation was measured directly by the surgeon and after surgery using a CT scanner. The images of rods were reconstructed in three-dimensions using quintic polynomial functions. The implant rod deformation was evaluated using the angle between the two three-dimensional tangent vectors measured at the ends of the implant rod.The implant rods at the concave side were significantly deformed during surgery. The highest rod deformation was found after the rotation of rods. The implant curvature regained after the surgical treatment.Careful intraoperative rod maneuver is important to achieve a safe clinical outcome because the intraoperative forces could be higher than the postoperative forces. Continuous scoliosis correction was observed as indicated by the regain of the implant rod curvature after surgery.

Dependency of the photonic band gaps in two-dimensional metallic photonic crystals on the shapes and orientations of rods

Photonic bands in two types of two-dimensional metallic photonic crystals (2-D MPCs), which are composed of dielectric rods embedded into a metallic background (type I MPCs) and metallic rods in a dielectric background (type II MPCs), are investigated theoretically using a method based on the frequency-dependent plane-wave expansion method. We discuss the maximization of the normalized gap width as a function of the rod shapes and orientations. In addition, we study the effect of dielectric constants of the rods and the background on the width of the photonic band gap. Four different shapes of rods-square, circular, diamond, and rectangular-are considered. The numerical results show that the type I MPCs have a higher normalized gap width than the type II MPCs. We observe that the rotation of the noncircular rods in the type I MPCs leads to a slight variation, less than 10%, in the normalized values of the gap width in the two lattice structures. However, rotating the metallic square rods arranged in a square lattice results in doubling of the normalized gap width. The normalized gap width can be tailored by changing the dielectric constant of the rods (background) in type I (type II) MPCs.

Rotation and alignment of rods in two-dimensional chaotic flow

We study the dynamics of rod shaped particles in two-dimensional electromagnetically driven fluid flows. Two separate types of flows that exhibit chaotic mixing are compared: one with time-periodic flow and the other with constant forcing but nonperiodic flow. Video particle tracking is used to make accurate simultaneous measurements of the motion and orientation of rods along with the carrier fluid velocity field. These measurements allow a detailed comparison of the motion and orientation of rods with properties of the carrier flow. Measured rod rotation rates are in agreement with predictions for ellipsoidal particles based on the measured velocity gradients at the center of the rods. There is little dependence on length for the rods we studied (up to 53% of the length scale of the forcing). Rods are found to align weakly with the extensional direction of the strain-rate tensor. However, the alignment is much stronger with the direction of Lagrangian stretching defined by the eigenvectors of the Cauchy–Green deformation tensor. A simple model of the stretching process predicts the degree of alignment of rods with the stretching direction.

Optical manipulation and binding of microrods with multiple traps enabled in an inclined dual-fiber system

We present experimental demonstrations of optical manipulation and optical binding of microscopic glass rods using the multiple traps created by a dual-fiber optical trapping system. Trapping, alignment, rotation, and stacking of glass rods were realized. To the best of our knowledge, this is the first time that cylindrical particles are optically trapped and bound by an optical fiber-based system. The optical manipulation of rods is also investigated through numerical simulations, which are used to quantitatively explain the experimental results. The ability of manipulating multiple particles of different shapes, as well as the integrable nature of the fiber-based setup, bestows the system the potential to be used in microfluidic systems for versatile particle manipulations.

Complete mechanical characterization of soft media using nonspherical rods

Hydrogels have been used as substrates for studying the cellular processes by many researchers. The stiffness of such gels was also characterized previously. However, in most of the cases, these soft Poisson's ratio was assumed incompressible and Poisson's ratio is assumed to be one-half. This may not be true in many cases, and might alter the calculation of the stiffness of the gels. In this study, we present equations for the complete characterization of soft media, i.e., calculation of Young's modulus, shear modulus, and Poisson's ratio. The method involves the individual measurement of either the displacement or rotation of cylindrical rods embedded in the soft media, under the application of an external force or torque. Equations involving shear modulus and Poisson's ratio for rotation of the rod and Young's modulus and Poisson's ratio for the displacement of the rod are independently derived. In addition, the displacement and rotation of the rods embedded in an elastic medium, under the application of either a force or a torque, respectively, were also calculated using finite element analysis. These values compared well with the displacements and rotations obtained using closed form equations.

Recrystallization of high-pressure marble (Sivrihisar, Turkey)

In the Sivrihisar Massif, Turkey, the southern margin of a blueschist facies terrane was affected by heating and deformation associated with later regional (Barrovian) metamorphism, creating a recrystallization front that can be observed in calcite microstructures. Calcite marble records a progression from high-pressure (H P) textures in a northern domain to completely recrystallized (greenschist to amphibolite facies) textures in a southern domain, with intermediate stages of partial recrystallization of the H P textures. H P marble is characterized by rod-shaped calcite (aragonite pseudomorphs) arranged in series with the long axis of each grain oblique to compositional layering; obliquity varies from 50° to nearly parallel, but high angles are most common. In a narrow (~ 200 m thick) transition zone that contains partially retrogressed blueschist and eclogite, the H P texture is partially overprinted by chains of small, equant, recrystallized grains that preserve the crystallographic orientation of the pre-existing rod-shaped calcite, as revealed by electron backscatter diffraction analysis; rod-shaped crystals occur locally. In a ~ 100 m thick zone south of the transition zone, all calcite grains are equant but have a crystallographic preferred orientation. Further south in the Barrovian sequence, recrystallized marble contains equant calcite that is randomly oriented. The similarity in fabric elements (foliation, lineation) of the two domains further shows the effect of Barrovian-related processes on the H P domain, including the rotation of the calcite rods during shearing along foliation planes. White mica 40Ar/ 39Ar ages for phengite in H P marble are ~ 88 Ma, and for muscovite in Barrovian marble are ~ 59 Ma, indicating ~ 30 Ma time interval between initial exhumation and cooling of the H P rocks and final cooling of the rocks that were deformed and heated during the later metamorphic event.

Rotational electrophoresis of striped metallic microrods

Analytical models are developed for the translation and rotation of metallic rods in a uniform electric field. The limits of thin and thick electric double layers are considered. These models include the effect of stripes of different metals along the length of the particle. Modeling results are compared to experimental measurements for metallic rods. Experiments demonstrate the increased alignment of particles with increasing field strength and the increase in degree of alignment of thin versus thick electric double layers. The metal rods polarize in the applied field and align parallel to its direction due to torques on the polarized charge. The torque due to polarization has a second-order dependence on the electric field strength. The particles are also shown to have an additional alignment torque component due to nonuniform densities along their length. The orientation distributions of dilute suspensions of particles are also shown to agree well with results predicted by a rotational convective-diffusion equation.

Effect of Photonic Crystal Band Gap on Rotation of Hollow Oval Te Rods in Triangular Lattice

The band structures and field patterns of two-dimensional (2D) triangular photonic crystals with hollow tellurium (Te) rods are calculated using the plane-wave method. Inner-rod and whole-rod rotations are considered to investigate how the rotational and structural symmetries affect E- and H-polarization modes. It is indicated that the H-polarization modes are strongly affected by the shape and interaction between the fields of the rods. In addition, the effect of rotational symmetry on H-polarization modes must be considered when whole rods are rotated. The E-polarization modes for both types of rotations are strongly related to the shape of the rods. Moreover, H-polarization modes determine the absolute photonic band gap (PBG) width when whole rods are rotated, while E-polarization modes determine the absolute PBG width when inner rods are rotated.

Larger absolute photonic band gap in two-dimensional air–silicon structures

We investigate different aspects of the absolute photonic band gap (PBG) formation for two-dimensional photonic crystals, consisting of air rods drilled into silicon. Specifically, square lattices of square and circular rods are considered. The lattice symmetry, shape and orientation of the rods affect the photonic gap parameters. A symmetry reduction by addition of a smaller different shaped rod into the center of the lattice unit cell can produce significantly larger band gap. Combining the symmetry reduction and rotation of the noncircular rods yields the greatest improvements in the size of absolute band gap. We discuss the maximization of the absolute PBG width as a function of lattice parameters and the practical fabrication feasibility of these optimized structures.

Mechanism for the instability of slopes composed of granular materials

The mechanism of instability of slopes composed of granular materials was examined through a tilting-box experiment using an assembly of aluminium rods and direct shear tests. A detailed observation of the experiment and the simple physical model led to the following conclusion. Avalanching of granular materials is triggered by rotation of rods at the slope surface. The force inducing the rotation was caused by the weight of the particles transmitted through contact points. Therefore, the mechanism of avalanching of granular materials was not comparable to the shear mechanism that has been considered to be responsible for the instability of slopes made of granular materials. © 1997 by John Wiley & Sons, Ltd.

Effects of Salts on the Micellization and Gelation of a Triblock Copolymer Studied by Rheology and Light Scattering

The phase behavior and aggregation properties of a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO), with a measured composition (EO)29(PO)40(EO)29, in aqueous solutions containing salt, have been examined using dynamic light scattering, rheological techniques, and sedimentation and viscosity measurements. The copolymer is dissolved as a unimer at low temperatures and forms spherical micelles with increasing temperature. At higher temperatures, a sphere-to-rod transition is seen for the micelles. Two types of gel are formed at higher concentrations of the copolymer. With different inorganic salts, the micellization and gelation properties of the copolymer follow the same type of transitions as the salt-free system, but all transition temperatures are shifted. The spherical micelles thus transform into rod-like micelles at around 38 °C in 1 M KF, which is approximately 36 deg below the transition temperature in the salt-free system. Rod lengths in 1 M KF are between 1000 and 1800 A, at 40 °C. The higher-temperature gel phase is seen at all concentrations down to 0.5 −1 wt %. The elasticity of this gel is due to hindered rotation of rods. Its relaxation time decreases with increasing concentration, indicating that the gel relaxes due to a partial breakdown or dissolution of the rods at the cross points. The strain dependence of this gel suggests that ordered structures of rods are formed at concentrations above 27 wt %. (Less)