Cylindrical Beam Research Articles

Ultrafast Cylindrical Vector Beams for Improved Energy Feedthrough and Low Roughness Surface Ablation of Metals

The use of ultrafast cylindrical vector vortex beams in laser-matter interactions permits new ablation features to be harnessed from inhomogeneous distributions of polarization and beam geometry. As a consequence, the ablation process can yield higher ablation efficiency compared with conventional Gaussian beams. These beams prevent surface quality degradation during the ablative processes. When processing stainless steel and titanium, the average surface roughness obtained by deploying the cylindrical vector is up to 94% lower than the Gaussian case, and the processing efficiency is 80% higher.

A Variable Clutch Mechanism for Adjustable Stiffness Actuators Based on Bending and Torsion of Prismatic Beams

Today, a major obstacle to developing locomotion mechanisms that are as safe and energy efficient as living organisms has been overcome with the development of actuators with adjustable stiffness. This work presents an innovative clutch mechanism whose stiffness can be adjusted based on the combined bending and torsion of the prismatic beams. In this way, the stiffness of any rotary actuator can be adjusted with the help of this clutch mechanism. The adjustable clutch mechanism consists of elastic prismatic beams placed in any position in the power transmission unit. The stiffness of the clutch mechanism is controlled by varying the active clutch length of these prismatic elastic beams using an additional actuator. This work is a new version developed to solve the mechanical problems observed in our previous studies using elastic cylindrical beams. Cylindrical beams subjected to dynamic bending have a higher risk of cracking on the cylindrical surface over time. The cross-section of cylindrical beams subjected to bending is very narrow at the point furthest from the center, which bears the greatest load in bending. For this reason, it has been observed that the beams break due to micro-cracks on the surfaces of the cylindrical beams in long-term use. However, the rectangular beam proposed as a solution to this mechanical problem is subject to combined torsion and bending, complicating the analytical solution. In this study, the stiffness variation of an adjustable elastic coupling mechanism depending on the coupling length was obtained with a simplified discrete analytical approach. Torsional and bending stiffness of the prismatic beams were calculated separately, and their sum gave the angular stiffness of the actuator. The analytical results obtained using this simple approach are compared with the experimental and finite element analysis results. The results show that the current design can adjust the stiffness over a wide range and the simple analytical approach gives more accurate results as the clutch length increases.

The influence of fracture energy on wooden structural members due to contact explosion

In military operations, sappers must often breach wooden structures. The formulas for determining the destructive explosive loads available in instructions and manuals used by sappers are simplified because they consider only a few variables, such as structure member diameter, whether the wood is dry or damp, or the wood species of the structure. In this study, the destructive explosive loads needed to breach pine, birch and oak members were computed via the finite element method. Static compression tests in three directions were conducted to define the orthotropic constitutive models of those wood species, and the results were used as an input to the numerical models. The damage model for wood considered different levels of energy criteria. The finite element analyses of contact explosion of TNT charges against cylindrical log beams were conducted for selected wood species, and destructive explosive loads were computed for different log diameters. Assuming different energy criteria, the results showed that the traditional approach in military instructions and manuals is higher than the values obtained from the numerical approach, i.e., standard manuals suggest using more explosive than may be needed.

Reduced Plasma Frequency Calculation Based on Particle-in-Cell Simulations

We propose a scheme to calculate the reduced plasma frequency of a cylindrical-shaped electron beam flowing inside of a cylindrical tunnel, based on results obtained from Particle-in-cell (PIC) simulations. In PIC simulations, we modulate the electron beam using two parallel, non-intercepting, closely-spaced grids which are electrically connected together by a single-tone sinusoidal voltage source. The electron energy and the beam current distributions along the length of the tunnel are monitored after the system is operating at steady-state. We build a system matrix describing the beam's dynamics, estimated by fitting a 2x2 matrix that best agrees with the first order differential equations that govern the physics-based system. Results are compared with the theoretical Branch and Mihran model, which is typically used to compute the plasma frequency reduction factor in such systems. Our method shows excellent agreement with the theoretical model, however, it is also general. Our method can be potentially utilized to determine the reduced plasma frequencies of electron beams propagating in differently-shaped beam tunnels, where no theoretical model yet exists, such as the case of a cylindrical or elliptical electron beam propagating inside of a metallic beam tunnel of cylindrical, square, or elliptical cross-section. It can be applied also to electron beams composed of multiple streams.

Generation of axially splitted ultra-long multiple optical needles/optical tubes using generalized cylindrical vector Bessel Gaussian beam phase modulated by annular Walsh function filter

Based on vector diffraction theory and annular Walsh function filter, axially splitted ultra-long multiple optical needles/optical tubes of electric as well as magnetic field distributions are numerically generated by generalized cylindrical vector Bessel Gaussian beam phase modulated by annular Walsh function filter. This multiple optical structures can be conveniently tailored by properly tuning the initial phase of the Cylindrical vector beam (CVB) and Walsh order of the annular Walsh function filter. Furthermore, the effect of energy flux density (Poynting vector) as well as Spin angular momentum(SAM) distribution in the focal region are theoretically analyzed. We expect that such an axially splitted focal systems could be applicable in optical trapping and manipulation of multiple particles, optical super resolution microscopy etc.

Mechanical Response of Carbon Composite Octet Truss Structures Produced via Axial Lattice Extrusion.

Engineered lattice structures fabricated via additive manufacturing (AM) technologies are of great interest for many applications that require high strength and/or stiffness with minimum mass. This paper studies a novel axial lattice extrusion (ALE) AM technique that greatly enhances mechanical properties of polymeric lattice structures. When the novel ALE process was used to produce 84 mm × 84 mm × 84 mm octet truss lattice samples using fiber reinforced ABS, a total of 219,520 polymer interfaces in the lattice beams were eliminated relative to the conventional 3D printing alternative. Microscopic examination revealed near perfect alignment of the chopped carbon fibers with axes of the cylindrical beams that make up the lattice structure. The greatly enhanced beam quality with fiber reinforcement resulted in excellent mechanical properties. Compression testing yielded an average relative compressive strength of 17.4 MPa and an average modulus of 162.8 MPa. These properties rate very strongly relative to other published work, and indicate that the ALE process shows great potential for fabrication of high-strength, lightweight, large-scale, carbon-fiber composite components. The paper also contributes a modeling approach to finite element analysis (FEA) that captures the highly orthotropic properties of carbon fiber lattice beams. The diagonal shear failure mode predicted via the FEA model was in good agreement with experimentally observed results.

Reconfigurable Vector Vortex Beams Using Spoof Surface Plasmon Ring Resonators

In this article, a spoof surface plasmon (SSP) ring resonator to generate dynamically reconfigurable vortex beams is proposed. According to the phase constant control of the SSP and the harmonic radiation principle, the tunable cylindrical vector vortex beams (VVBs) with different topological charges can be obtained. The tunable system that operates by electronic control would utilize varactors to change the wavenumber of SPP on the ring resonator and realize the reconfigurable VVBs modes at a fixed frequency. All VVBs have excellent orbital angular momentum (OAM) purity (above 90%). Interestingly, the antenna also simultaneously radiates the scalar vortex beams with tunable OAM modes. Both numerical simulations and experimental characterizations confirm the theoretical predictions. Because the designed antenna has the advantages of simple feeding network, easy bias circuit, as well as miniaturization and integration compatibility, we anticipate that the antenna will enable a wide range of applications for future wireless communication and imaging technologies.

Acoustic radiation torque of a cylindrical quasi-Gauss beam on a viscoelastic cylindrical shell near an impedance boundary

This work presents a comprehensive analytical formalism to calculate the acoustic radiation torque acting on a viscoelastic cylindrical shell near an impedance boundary, which is exerted by a cylindrical quasi-Gauss beam with an arbitrary incident angle propagating in an ideal fluid. An analytical expression in finite series form for the acoustic radiation torque is derived by applying the partial-wave series expansion method, the image theory and the translational addition theorem. Numerical computations for a viscoelastic cylindrical polyethylene shell immersed in water are provided, with particular emphasis on the effects of the reflecting coefficient of the interface, the shell-boundary distance, the position of the shell, the incident angle and the beam waist. Changing the relative thickness and the interior fluid medium are also considered. It is shown that the cylindrical shell can be rotated counter-clockwise or clockwise, depending on the beam frequency, the shell size, the reflecting coefficient and the incident angle. The periodical oscillation of acoustic radiation torque is also observed as the shell moves away from the boundary. The results of this study can improve our understanding of the acoustic radiation torque behaviors for viscoelastic particles near the boundary, which is commonly encountered in biomedical ultrasound and fluid dynamics.

Spin-orbit periodic conversion in a gradient-index fiber.

The characteristics of the cylindrical vector beam (CVB) and the cylindrical vector vortex beam (CVVB) in a radial gradient-index (GRIN) fiber are analyzed on the basis of the generalized Huygens-Fresnel principle. The CVB and CVVB exhibit periodic and stable transmission characteristics in the radial GRIN fiber. In the beam with a vortex phase (CVVB), the polarization changes and the spin angular momentum (SAM) is detected at the focal plane of the radial GRIN fiber. A spin-orbit periodic conversion is observed in the radial GRIN fibers. Finally, the SAM expression of partially coherent light is deduced and verified via a simulation.

CyMAD bioreactor: A cyclic magnetic actuation device for magnetically mediated mechanical stimulation of 3D bioprinted hydrogel scaffolds

Mechanical stimulation of bioprinted constructs can enhance the differentiation of cells within these scaffolds, such as driving chondrocytes towards cartilage tissue substitutes. In this study, a holistic approach is presented for designing and engineering a material-specific device based on a magnetic field setup using the Maxwell configuration for a touchless cyclic magnetic stimulation of (bioprinted) hydrogel scaffolds containing magnetic microparticles. We describe the entire development process, from the design of the magnetic field to the construction of the bioreactor and provide an evaluation of the calculation. Finally, an analysis of the distribution and orientation of the particles within the hydrogels and a cytocompatibility test after applying the intended stimulation regime were conducted. As a proof-of-principle, a model system in the shape of a cylindrical bending beam consisting of the established magnetisable bioink based on alginate, methylcellulose and magnetite microparticles (algMC + mag), was used instead of 3D printed, macroporous scaffolds of this material. Requirements for the dimensioning of the force, such as the Young's modulus, were determined experimentally. The magnetic field was calculated using the software Finite Element Method Magnetics (FEMM). The cyclic stimulation of the samples was performed over 14 days with a duration of 3 h per day. The aim was to achieve an elongation of up to 10%. The homogeneous particle distribution in stimulated and non-stimulated samples was proven via μCT and digital image processing (DIP). Even after applying a static magnetic field over 30 min, no structure formation such as chains or agglomeration of the magnetic particles were observed. The deformation behaviour defined as a shifted position of the neutral fibre (centre line of an object) during stimulation was measured via μCT and analysed using DIP. From these data, an elongation of approx. 9% was calculated for day 14. This elongation was achieved for both the stimulated samples and the control group without stimulation, which corresponds to the theoretically calculated value. The cytocompatibility of the bioink, scaffold environment and stimulation approach was demonstrated for bioprinted scaffolds with embedded human mesenchymal stem cells and chondrocytes. These findings proved the suitability and versatility of the bioreactor and the presented approach for stimulation experiments.

Radial disturbance compensation device of cylindrical cantilever beam using embedded piezoelectric ceramics with bending mode

To eliminate the disturbance in all-radial directions of the circular cross-section cantilever beam, this study proposes an embedded piezo-compensator (EPC). Different from cantilever beams with rectangular cross-sections, cantilever beams with circular cross-sections have isotropic stiffness in all-radial directions. This feature makes cylindrical cantilever beams have been widely used in various mechanical structures. However, the current trend towards more compact and more lightweight design in machinery poses a huge challenge to its anti-disturbance ability. Most of the current studies are based on rectangular cantilevers and eliminate the disturbances in one direction. Research on eliminating the disturbances in whole radial direction is rarely reported. Therefore, based on the characteristics of the circular cross-section and piezoelectric materials, an EPC is proposed. The structure and output model of the proposed device are presented and established. Experimental results show that the proposed device can reduce the disturbance by more than 90% in the frequency range from 0 Hz to 600 Hz. At 1000 Hz, it can still reduce disturbance by 69%. With this method, disturbance compensation device can be deployed on the cylindrical cantilever without significant modifications to the original structure, which expands the application in size-sensitive scenarios.

DOSE DISTRIBUTION ANALYSIS OF PROTON THERAPY FOR MEDULLOBLASTOMA CANCER WITH PHITS 3.24

One of the developments in particle therapy is proton radiation therapy. Meanwhile, a limited number of available proton therapy facilities makes research related to proton therapy difficult. Therefore, there is a need for alternative proton therapy simulations using programs other than those in proton therapy facilities. This research was aimed to simulate medulloblastoma brain cancer which children often experience.The program used in this research was PHITS version 3.24. The human body was modeled with the revised ORNL-MIRD phantom for a 10-year-old child. The therapy scheme was a whole posterior fossa boost of 19.8 Gy. The proton passive scattering was simulated by passing a uniform proton beam through the aperture and compensator with energy variations. The proton pencil beam scanning was simulated with small cylindrical beams with a radius of 0.5 cm, which were adjusted to the planning target volume with layers variations.The total duration to give the prescription dose was 550 seconds with passive scattering and 605 seconds with pencil beam scanning. In passive scattering, the OAR(s) with the most significant percentage of absorbed dose were the skin, cranium, and muscle, i.e., 8.22 ± 0.15 %, 5.51 ± 0.05 % and 1.39 ± 0,04 % respectively to their maximum tolerated dose, while in the pencil beam scanning, the OAR(s) with the most significant percentage of absorbed dose were the skin, cranium, and muscle, i.e., 5.42 ± 0.08 %, 4.43 ± 0.05 % and 0.51 ± 0.05 % respectively to their maximum tolerated dose. Dose distribution in passive scattering was relatively better than in pencil beam scanning in terms of dose homogeneity using dose sampling analysis at some points within the planning target volume.

Optical Vector Vortex Generation by Spherulites with Cylindrical Anisotropy.

Materials with crystalline structures of circular symmetry are rare in nature; however, they are highly desired in optical applications with structured lights, whose characteristics are of cylindrical symmetry. In this work, using a naturally existing circular anisotropy from a spherulite formed by molecular self-assembly, we obtain a cylindrical vector optical vortex beam generation transformed from the spin angular momentum in the wide visible range. The proposed strategy provides promising and broad opportunities for the applications of spherulites in the generation of structured lights and modulations of both the polarization and the angular momentum.

Structural rationalities of tapered hollow cylindrical beams and their use in Japanese traditional bamboo fishing rods

Bamboo has historically been used in Japan as a structural material and for building tools such as fishing rods owing to its remarkable structural properties. In recent years, the materials used for manufacturing fishing rods have changed greatly owing to the development of composite materials; however, the basic slender tapered hollow cylindrical fishing rod design has remained unchanged throughout the long history of fishing. However, the mechanical rationale behind this structural design has not yet been sufficiently verified, and this study clarifies this. The analysis was performed by solving the nonlinear bending equation of a slender tapered cantilever beam with a concentrated load at the tip, which causes large deflection, using the Runge–Kutta method. The deflection curves and bending stresses were obtained, and the structural design to minimize the stresses was explored. Our results may prove useful for bamboo-inspired bionic design and bring to light our ancestors’ deep knowledge of natural materials and their advanced technological capabilities.

Tune shift due to the quadrupolar resistive-wall impedance of an elliptical beam pipe

For a beam pipe with an elliptical cross section, the quadrupolar impedance will be produced. During multibunch operation in a circular accelerator, the complex mode frequency shift is sensitive to the long range wake, which will be further enhanced by the quadrupolar component. In order to get more accurate estimation of the quadrupolar impedance and its induced tune shift, materials outside the beam pipe should be considered and impedance model for multilayer elliptical beam pipe is required. In this paper, the horizontal and vertical quadrupolar impedances, as well as the form factors, are derived for an elliptical beam pipe of infinite thickness. The impedances of a multilayer elliptical beam pipe are expressed as the product of the form factors and the impedances of the multilayer cylindrical beam pipe, in which both the conductivity and the permeability of different layers with finite thickness are considered. On the other hand, the complex incoherent frequency shift due to the quadrupolar impedance is derived from beam oscillation equations, which shows that the direct current (DC) value of the quadrupolar impedance dominates the frequency shift. Numerical studies indicate that the incoherent tune shift due to the quadrupolar resistive-wall impedance is sensitive to the permeability of the magnetic material surrounding the beam pipe. In addition, the occupation of the magnets around the accelerator should be considered when evaluating the incoherent tune shifts. Meanwhile, the metallic coating with constant conductivity on the inner surface of the beam pipe tends to have negligible contribution to the tune shift, in contrary to the distinct contribution found to the coherent tune shift.

Electrostatic tapering for efficient generation of radiation.

We demonstrate the feasibility of electrostatic (dc) tapering such that the net average force of the electromagnetic (ac) field is compensated by a dc field, which at resonance may be interpreted as "direct" energy transfer from the dc to the ac field. This combination persists in all three components of the setup-e-gun, resonant zone, and collector, in each one playing a different role. In equilibrium, the two field components field-emit at the cathode a density modulated cylindrical beam which is accelerated along the e-gun by the dc field; the latter also focuses the e-beam. Radiation confinement perpendicular to the e-beam is ensured by an array of dielectric Bragg-mirrors and an array of metallic hollow electrodes impose synchronous bunches and wave. This double periodic structure ensures the coexistence of dc and ac fields in the same volume. Numerical simulations demonstrate the feasibility of generation of order of 1[W] power at 1 THz from a volume on a scale of few mm^{3} with efficiency of the order of 25%.

Generation and focusing of a second-order vector beam using a subwavelength optical element

This article proposes a new type of subwavelength axicons for creating and focusing second-order vector cylindrical beams. It is also shown that using the proposed subwavelength axicons, it is possible to create focal spots with an energy backflow. The Comsol Multiphysics software is used to simulate the operation of subwavelength axicons with different twist angles. The dependence of the obtained intensity distributions on the angle of twist of the axicon spiral is investigated.

Nonlinear impact on the buckling characteristic of functionally graded nonlocal nanotube via a couple of nonlocal strain gradient theory and a novel higher-order tube theory

The buckling behavior of nonlocal bi-directional functionally graded and imperfect nanotube based on the first-order beam theory and a novel higher-order tube theory is investigated in this paper. The nonlocal strain gradient theory is considered to length-scale impact applying the nonlinear von-Kármán theory using the conservation energy method to derive the nonlocal governing equations and related boundary conditions. Two-dimensional functionally graded (2D-FG) material in both length and radial direction is assumed to model the FG nano-scale tubes. Finally, the nonlinear equations are solved using the generalized differential quadrature method (GDQM) coupled with the iteration technique. Eventually, the calculated results are extracted to study the influence of various parameters, such as the size-effect parameters, FG power indexes parameters, porosity parameters, nonlinear amplitude on the buckling of 2D-FG imperfect nano-scale cylindrical beams and tubes.

Cylindrical wave-based off-axis digital holography with long field of view.

We present a new, to the best of our knowledge, type of off-axis digital holographic imaging method with a long field of view (FOV). In the method, the pre-magnification recording geometry is realized by a cylindrical lens (CL) or cylindrical beam instead of a conventional objective or spherical beam in traditional off-axis digital holography (DH). At the same time, the reference beam is replaced by a divergent cylindrical beam. Theoretical analysis and experiments have justified that, in off-axis DHs, the adoption of the cylindrical beams can realize a one-dimensional pre-magnification of the object beam only in the off-axis direction to satisfy the bandwidth constraint, and at the same time the FOV of the reconstructed image in the orthogonal direction can remain unaffected. In comparison with existing off-axis DHs, this cylindrical wave-based DH (CWDH) method has a distinct advantage in expanding the FOV of the reconstructed image. The FOV feature of the CWDH makes it especially suitable for applications that require a long FOV such as imaging samples in microfluidic channels.

Investigation of the Free Vibrations of Radial Functionally Graded Circular Cylindrical Beams Based on Differential Quadrature Method

In the current research, an effective differential quadrature method (DQM) has been developed to solve natural frequency and vibration modal functions of circular section beams along radial functional gradient. Based on the high-order theory of transverse vibration of circular cross-section beams, lateral displacement equation was reconstructed neglecting circumferential shear stress. Two equations coupled with deflection and rotation angles were derived based on elastic mechanics theory and further simplified into a constant coefficient differential equation with natural frequency as eigenvalue. Then, differential quadrature method was applied to transform the eigenvalue problem of the derived differential equation into a set of algebraic equation eigenvalue problems. Natural frequencies of the free vibrations of cylindrical beams with circular cross-sections were calculated at one time, and corresponding modal functions were solved together. The obtained numerical results indicated that the natural frequencies of functionally graded (FG) circular cylindrical beams obtained using differential quadrature method agreed with the results reported in related literatures. In addition, influences of varying gradient parameters on the modal shapes of circular cylindrical beams were found to be strongly consistent with previous studies. Numerical results further validated the feasibility and accuracy of the developed differential quadrature method in solving the transverse vibration of FG circular cross-section beams.